Working machine

Abstract

A working machine includes a working device to attach thereto an attachment which is one of a plurality of attachments to perform work by contacting a target object, and change a posture of the attachment attached thereto including a position of the attachment in an up-down direction, a pressure detector to detect an auxiliary pressure which is a pressure of hydraulic fluid supplied to a hydraulic actuator included in the attachment to drive the attachment, and a controller configured or programmed to perform a posture control to control the working device based on the auxiliary pressure to adjust the posture of the attachment.

Description

BACKGROUND OF THE INVENTION1. Field of the Invention

[0001] The present invention relates to working machines such as skid-steer loaders and compact track loaders, and particularly relates to techniques to perform work using each of various types of attachments attached to a working device including arms and the like.2. Description of the Related Art

[0002] A working machine such as a skid-steer loader or a compact track loader is configured such that a working device including arms and the like has one of various types of attachments attached thereto and that the attached attachment is raised or lowered by the working device to perform work corresponding to the attachment. Some attachments are configured to, for example, perform work while in contact at a predetermined pressure with a target object such as a structure or a natural object including soil and plants. Some attachments of this kind include an actuator to be actuated by power from the working machine to cause the attachment to operate.

[0003] In order to allow the working machine to appropriately perform work using an attachment, for example, the specification of U.S. Pat. No. 11,846,088 discloses an automatic vehicle speed control system to adjust the travel speed of the working machine according to the load on an implement (attachment). A controller of the vehicle speed automatic control system defines the travel speed of the working machine based on creep settings, monitors one or more operating statuses of the implements, and automatically adjusts the travel speed based on the operating status(es). The operating status(es) monitored by the controller includes the pressure in an auxiliary hydraulic circuit for the implement.

[0004] For example, in the case where the height of a target object is not uniform, in some cases, it is necessary to change the posture of the attachment such as the position and the orientation according to variations in height of the target object to appropriately perform work. However, it is difficult for the user of the working machine to manually control the working device to change the posture of the attachment according to variations in height of the target object.SUMMARY OF THE INVENTION

[0005] Example embodiments of the present invention make it possible to improve the work performance of attachments on working machines.

[0006] A working machine according to an example embodiment of the present invention includes a working device to attach thereto an attachment which is one of a plurality of attachments to perform work by contacting a target object, and change a posture of the attachment attached thereto including a position of the attachment in an up-down direction, a pressure detector to detect an auxiliary pressure which is a pressure of hydraulic fluid supplied to a hydraulic actuator included in the attachment to drive the attachment, and a controller configured or programmed to perform a posture control to control the working device based on the auxiliary pressure to adjust the posture of the attachment.

[0007] In an example embodiment of the present invention, the controller may be configured or programmed to perform the posture control when work is being performed by the attachment, and in the posture control, change the posture of the attachment such that the auxiliary pressure falls within an appropriate range.

[0008] In an example embodiment of the present invention, the working machine may further include an input interface to receive input of information indicating the attachment attached to the working device. The controller may be configured or programmed to perform the posture control when the information inputted via the input interface indicates a specific attachment which is one of the plurality of attachments.

[0009] In an example embodiment of the present invention, the controller may be configured or programmed to perform the posture control when the controller is in a predetermined mode in which the controller keeps constant an amount of hydraulic fluid supplied to the hydraulic actuator per unit time.

[0010] In an example embodiment of the present invention, the working machine may further include an input interface to receive input of information indicating the attachment attached to the working device, and a memory and / or a storage to store (i) pieces of information indicating the plurality of attachments attachable to the working device and (ii) pieces of information indicating appropriate ranges of the auxiliary pressure for work defined for the respective plurality of attachments such that (i) the pieces of information and (ii) the pieces of information are associated with each other. The controller may be configured or programmed to read, from the memory and / or the storage, a piece of information indicating an appropriate range that corresponds to the attachment indicated by the information inputted via the input interface, and perform the posture control based on the read piece of information indicating the appropriate range and the auxiliary pressure.

[0011] In an example embodiment of the present invention, the working device may include an arm connected to a machine body of the working machine swingably in the up-down direction, a first actuator to swing the arm, and a hitch connected to a distal portion of the arm to detachably attach the attachment thereto. The controller may be configured or programmed to, in the posture control, control the first actuator based on the auxiliary pressure to swing the arm to adjust the position of the attachment relative to the target object.

[0012] In an example embodiment of the present invention, the controller may be configured or programmed to, when the auxiliary pressure is above an appropriate range, cause the first actuator to swing the arm upward to raise the attachment.

[0013] In an example embodiment of the present invention, the controller may be configured or programmed to, when the auxiliary pressure is below an appropriate range, cause the first actuator to swing the arm downward to lower the attachment.

[0014] In an example embodiment of the present invention, the working device may include an arm connected to a machine body of the working machine swingably in the up-down direction, a first actuator to swing the arm, a hitch connected to a distal portion of the arm swingably in the up-down direction and operable to detachably attach the attachment thereto, and a second actuator to swing the hitch. The controller may be configured or programmed to, in the posture control, cause the first actuator to swing the arm and / or cause the second actuator to swing the hitch to adjust at least one of the position or an orientation of the attachment relative to the target object.

[0015] In an example embodiment of the present invention, a selected one of the plurality of attachments to perform various types of work may be attached to the working device. The working machine may further include an input interface to receive input of information indicating the attachment attached to the working device, and a memory and / or a storage to store (i) pieces of information indicating the plurality of attachments attachable to the working device and (ii) pieces of posture information indicating appropriate ranges of the posture for work defined for the respective plurality of attachments such that (i) the pieces of information and (ii) the pieces of posture information are associated with each other. The controller may be configured or programmed to read, from the memory and / or the storage, one of the pieces of posture information that corresponds to the attachment indicated by the information inputted via the input interface, and perform the posture control based on the read piece of posture information and the auxiliary pressure.

[0016] In an example embodiment of the present invention, the working machine may further include a machine body, a traveling device to cause the machine body to travel, and a speed detector to detect a travel speed of the machine body. The controller may be configured or programmed to not perform the posture control when the travel speed is less than a predetermined value.

[0017] In an example embodiment of the present invention, the working machine may further include a work manual operator to be operated to cause the working device to change the posture of the attachment. The controller may be configured or programmed to not perform the posture control when an operation amount of the work manual operator is greater than a predetermined amount.

[0018] In an example embodiment of the present invention, the working machine may further include a machine body, a traveling device to cause the machine body to travel and to change a traveling state of the machine body, and an input interface to receive input of information indicating the attachment attached to the working device. The controller may be configured or programmed to, based on the attachment indicated by the information inputted via the input interface and based on the auxiliary pressure, selectively perform at least one of the posture control or a travel control to control the traveling device to adjust the traveling state of the machine body.

[0019] In an example embodiment of the present invention, the working machine may further include a memory and / or a storage to store (i) pieces of information indicating the plurality of attachments attachable to the working device and (ii) pieces of information indicating appropriate ranges of the auxiliary pressure for work defined for the respective plurality of attachments such that (i) the pieces of information and (ii) the pieces of information are associated with each other. The controller may be configured to programmed to read, from the memory and / or the storage, a piece of information indicating an appropriate range that corresponds to the attachment indicated by the information inputted via the input interface, and, based on the read piece of information indicating the appropriate range and the auxiliary pressure, selectively perform at least one of the posture control or the travel control.

[0020] In an example embodiment of the present invention, the working machine may further include a memory and / or a storage to store (i) pieces of information indicating the plurality of attachments attachable to the working device and (ii) pieces of posture information indicating appropriate ranges of the posture for work defined for the respective plurality of attachments such that (i) the pieces of information and (ii) the pieces of posture information are associated with each other. The controller may be configured or programmed to read, from the memory and / or the storage, one of the pieces of posture information that corresponds to the attachment indicated by the information inputted via the input interface, and, based on the read piece of posture information and the auxiliary pressure, selectively perform at least one of the posture control or the travel control.

[0021] In an example embodiment of the present invention, the controller may be configured or programmed to perform at least one of the posture control or the travel control when the controller is in a predetermined mode in which the controller keeps constant an amount of hydraulic fluid supplied to the hydraulic actuator per unit time.

[0022] In an example embodiment of the present invention, the working machine may further include a speed detector to detect a travel speed of the machine body. The controller may be configured or programmed to not perform the posture control or the travel control if the travel speed is less than a predetermined value.

[0023] In an example embodiment of the present invention, the working machine may further include a work manual operator to be operated to cause the working device to change the posture of the attachment. The controller may be configured or programmed to not perform the posture control or the travel control when an operation amount of the work manual operator is greater than a predetermined amount.

[0024] In an example embodiment of the present invention, the controller may be configured or programmed to, when the controller is performing at least one of the posture control or the travel control, cause a user interface to output information indicating that the at least one of the posture control or the travel control is being performed.

[0025] The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the example embodiments with reference to the attached drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] A more complete appreciation of example embodiments of the present invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings described below.

[0027] FIG. 1 illustrates an example of a work-related hydraulic circuit of a working machine.

[0028] FIG. 2 illustrates an example of a travel-related hydraulic circuit of a working machine.

[0029] FIG. 3 is a block diagram showing an example of an electrical configuration of a working machine.

[0030] FIG. 4 illustrates an example of a hydraulic circuit to actuate a latch cylinder.

[0031] FIG. 5 illustrates an example of attachment information and control information.

[0032] FIG. 6 illustrates an example of an input screen displaying icons of attachments.

[0033] FIG. 7 is a flowchart showing operation of a working machine of a first example embodiment of the present invention.

[0034] FIG. 8 is a flowchart showing details of posture control in FIG. 7.

[0035] FIG. 9 illustrates an example of a monitor screen of the first example embodiment of the present invention.

[0036] FIG. 10 is a flowchart showing operation of a working machine of a second example embodiment of the present invention.

[0037] FIG. 11 is a flowchart showing details of posture control / travel control in FIG. 10.

[0038] FIG. 12 illustrates an example of a monitor screen of the second example embodiment of the present invention.

[0039] FIG. 13 illustrates another example of a work-related hydraulic circuit of a working machine.

[0040] FIG. 14 illustrates another example of a travel-related hydraulic circuit of a working machine.

[0041] FIG. 15 is a side view of a working vehicle.

[0042] FIG. 16 is an elevational view of a quick hitch.DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

[0043] Example embodiments will now be described with reference to the accompanying drawings, wherein like reference numerals designate corresponding or identical elements throughout the various drawings. The drawings are to be viewed in an orientation in which the reference numerals are viewed correctly.

[0044] Example embodiments of the present invention will now be described with reference to the accompanying drawings as necessary.

[0045] FIG. 15 is a side view of a working machine 1 of the present example embodiment. In the present example embodiment, a compact track loader is illustrated as an example of the working machine 1. However, the working machine according to an example embodiment of the present invention is not limited to a compact track loader, and may be, for example, some other construction machine, agricultural machine, or working machine such as a skid-steer loader, a backhoe, or a tractor. The left direction, right direction, the direction approaching the viewer of FIG. 15, and the direction away from the viewer of FIG. 15 are respectively forward, rearward, left and right directions of the working machine 1. The direction perpendicular to the front-back direction and the up-down direction of the working machine 1 is hereinafter referred to as a machine body width direction.

[0046] The working machine 1 includes a machine body 2, a cabin 3, a working device 4, traveling device(s) 5, and a prime mover 6. The cabin 3 is provided on the machine body 2. The cabin 3 includes a seat 8 therein. The prime mover 6 is provided at a rear portion of the machine body 2. The prime mover 6 is a power source of the working machine 1. In the present example embodiment, the prime mover 6 includes a diesel engine. However, the prime mover 6 may be another internal combustion engine (engine) such as a gasoline engine, and / or may be a motor such as an electric motor.

[0047] The traveling devices 5 are respectively provided on the left and right sides of the machine body 2, support the machine body 2, and cause the machine body 2 to travel. That is, a pair of the left and right traveling devices 5 are provided. The traveling devices 5 include crawler traveling devices. Note that the traveling devices 5 are not limited to crawler traveling devices, and may be wheeled traveling devices including front wheel(s) and rear wheel(s), or may be semi-crawler traveling devices in which the front wheels or the rear wheels are crawler wheels.

[0048] When the left-side traveling device (left traveling device) 5 and the right-side traveling device (right traveling device) 5 are both driven to rotate forward or both driven to rotate reversely, or when one of them is driven to rotate forward and the other is driven to rotate reversely or is stopped, the machine body 2 (working machine 1) travels forward, travels rearward, or turns left or right. Furthermore, as the speed of rotation of the left and right traveling devices 5 changes, the travel speed of the machine body 2 changes, whereas, as the left and right traveling devices 5 stop, the machine body 2 stops. In this way, the traveling devices 5 change the traveling state such as the direction of travel, the travel speed, and the stopping of the machine body 2.

[0049] The working device 4 is provided on the machine body 2. The working device 4 includes arms 10, first links 12, second links 13, lift cylinders 14, tilt cylinders 15, a hitch 16, and an attachment 11. Of these, the arms 10, the first links 12, the second links 13, the lift cylinders 14, and the tilt cylinders 15 are provided on the left and the right of the cabin 3. The left and right arms 10 are connected by a connector.

[0050] The arms 10 are connected to the machine body 2 swingably in the up-down direction relative to the machine body 2. Specifically, the first links 12 and the second links 13 support proximal portions (rear portions) of the arms 10 via shafts such that the arms 10 are swingable in the up-down direction. First ends of the lift cylinders 14 are rotatably connected to the arms 10 via shafts, and opposite second ends of the lift cylinders 14 are rotatably connected to a lower rear portion of the machine body 2 via shafts. The lift cylinders 14 are hydraulic actuators (first actuators) to cause the arms 10 to swing in the up-down direction by extending and retracting.

[0051] The hitch 16 is connected to distal portions of the arms 10 swingably in the up-down direction relative to the distal portion of the arms 10. Specifically, first ends of the tilt cylinders 15 and the distal portions of the arms 10 are respectively rotatably connected to a rear portion of the hitch 16 via shafts. Opposite second ends of the tilt cylinders 15 are rotatably connected to central curved portions of the arms 10 via shafts and brackets. The tilt cylinders 15 are hydraulic actuators (second actuators) to cause the hitch 16 to swing in the up-down direction by extending and retracting. The attachment 11 is attached to the front surface of the hitch 16. The hitch 16 is a linkage to attach and detach the attachment 11 thereto and therefrom.

[0052] FIG. 16 is an elevational view of the quick hitch 16. Specifically, FIG. 16 shows the hitch 16 as seen from the machine body 2 of the working machine 1 in FIG. 15. The hitch 16 includes brackets 30, latching mechanisms 31, a latch cylinder 17, and the like. A pair of the left and right brackets 30 and a pair of the left and right latching mechanisms 31 are provided. The left and right brackets 30 are connected by a beam 39. The distal portions of the left and right arms 10 and the first ends of the left and right tilt cylinders 15 are connected to the left and right brackets 30 via shafts (FIG. 15). The left and right latching mechanisms 31 are respectively provided on the left and right brackets 30.

[0053] Each latching mechanism 31 includes a latch lever 32, a latch pin 33 and the like. An upper portion of the latch lever 32 is rotatably connected to the corresponding bracket 30 via a shaft. The latch pin 33 is held swingably up and down by the bracket 30. A lower end portion of a coil spring 34 is connected to an upper end portion of the latch pin 33 via a shaft, and an upper end portion of the coil spring 34 is connected to a central portion of the latch lever 32 via a shaft.

[0054] The latch cylinder 17 is a hydraulic cylinder (hydraulic actuator) to actuate the latching mechanisms 31 between a latching state and an unlatching state. A first end (distal portion of the rod) of the latch cylinder 17 is rotatably connected to a lower end portion of one of the latch levers 32 via a shaft. An opposite second end (bottom portion of the cylinder case) of the latch cylinder 17 is rotatably connected to a lower end portion of the other the latch levers 32 via a shaft.

[0055] As represented by a solid line in FIG. 16, when the latch cylinder 17 extends with the front surfaces of the brackets 30 abutting a base plate 9 connected to the back surface of the attachment 11, the latch levers 32 rotate to descend, causing the latch pins 33 to be inserted into through-holes 9h in a lower end portion of the base plate 9. With this, the latching mechanisms 31 are brought into a latching state in which the attachment 11 is secured to the brackets 30 (attached to the hitch 16).

[0056] As represented by a dot-dot-dash line in FIG. 16, when the latch cylinder 17 retracts, the latch levers 32 rotate to ascend, allowing the latch pins 33 to be removed from the through-holes 9h of the base plate 9 by the elastic force of the coil springs 34. With this, the latching mechanisms 31 are brought into an unlatching state in which the attachment 11 is not secured to the brackets 30, allowing the attachment 11 to be detached from the hitch 16.

[0057] Since the above-described hitch 16 allows the attachment 11 to be easily replaced with another one, the hitch 16 is called a “quick hitch” or “quick changer”. Note that another actuator such as a hydraulic motor may be used instead of the latch cylinder 17, or an electric actuator such as an electric motor or an electric cylinder may be used instead of the latch cylinder 17.

[0058] When the arms 10 are caused to swing in the up-down direction by the lift cylinders 14 with the attachment 11 attached to the hitch 16 as described above, the attachment 11 is raised or lowered, and the position (height) of the attachment 11 in the up-down direction relative to the machine body 2 and to the target object and the position of the attachment 11 in the front-back direction are changed. When the hitch 16 is caused to swing in the up-down direction by the tilt cylinders 15, the attachment 11 also swings in the up-down direction, and the tilt angle of the attachment 11, i.e., the orientation of the attachment 11 relative to the machine body 2 and the target object, is changed.

[0059] Thus, the working device 4 is a posture changing device to change the posture including the position and the orientation of the attachment 11. Furthermore, with regard to the working device 4, since the arms 10 and the hitch 16 are individually swingable, the working device 4 can, when at least one of the arms 10 or the hitch 16 swing(s) with the attachment 11 attached, change the posture including at least one of the height or the orientation of the attachment 11 relative to the machine body 2 and the target object. The attachment 11 is changed between a work posture in which the working device 4 can perform work on a target object and a non-work posture in which the working device 4 does not perform work. The working machine 1 includes a working unit 4U including the working device 4 and the attachment 11 attached to the working device 4.

[0060] The working device 4 (hitch 16) is operable to attach thereto and detach therefrom each of attachments 11 to perform various types of work, and a selected one of the attachments 11 is attached to the working device (hitch 16). The attachment 11 is a working tool to perform work. The working machine 1 performs work corresponding to the attachment 11 attached to the working device 4.

[0061] Examples of attachments 11 attachable to the working device 4 include follower attachments 11 each of which does not include actuators and each of which operates in a manner that follows the working device 4. For example, follower attachments 11 include buckets and pallet forks that are working tools for earth / cargo handling to carry earth or cargo.

[0062] Examples of attachments 11 attachable to the working device 4 also include drive attachments 11 each of which includes actuator(s) and each of which is to be driven by power from the actuator(s). Examples of drive attachments 11 include contact work attachments 11 to, for example, remove, adjust or destroy a target object in contact therewith such as earth or plants. Examples of contact work attachments 11 include sweepers, snow blowers, snow blades, angle brooms, mowers, plows, skid cutters, breakers, and earth augers. In the example shown in FIG. 15, a sweeper which is a drive, contact work attachment 11 is attached to the working device 4 (hitch 16).

[0063] Examples of the drive attachments 11 also include non-contact work attachments 11 to perform work such as spreading fertilizer or agricultural chemicals without contacting the target object such as earth or crops. Examples of such non-contact work attachments 11 include spreaders.

[0064] In the present example embodiment, the actuator(s) provided in or on the drive attachment 11 is a hydraulic actuator such as a hydraulic motor or a hydraulic cylinder. For example, a hydraulic actuator 27 provided in or on the sweeper (attachment) 11 shown in FIG. 15 is a hydraulic motor which drives the sweeper 11.

[0065] The hydraulic actuator 27 provided in or on the drive attachment 11 is actuated by hydraulic fluid supplied from the working machine 1. As shown in FIG. 15, the machine body 2 of the working machine 1 is provided with AUX port(s) (auxiliary port(s)) 25 at a front portion thereof. The AUX ports 25 allow hydraulic fluid to flow to and from the hydraulic actuator 27. The AUX ports 25 include a first AUX port 25a and a second AUX port 25b. The attachment 11 includes a first hydraulic port and a second hydraulic port. Each port includes a coupler.

[0066] For example, the user or the like connects an external fluid passage 26a including a hose or the like to the first AUX port 25a and to the first hydraulic port of the attachment 11, and connects an external fluid passage 26b to the second hydraulic port of the attachment 11 and to the second AUX port 25b. With this, hydraulic fluid is allowed to flow out (to be supplied) from the working machine 1 to the hydraulic actuator 27 of the attachment 11, and is allowed to flow from the hydraulic actuator 27 into (returns to) the working machine 1. This defines a hydraulic circuit between the working machine 1 and the hydraulic actuator 27, so that the hydraulic actuator 27 can be actuated by hydraulic fluid from the working machine 1 to cause the attachment 11 to perform work. In the example in FIG. 15, the above circuit allows a brush 11b, which is a driven portion of the sweeper, to be driven to rotate by power from the hydraulic actuator 27 and to perform work to remove a target object such as dust on a ground J.

[0067] As described above, the actuators 14, 15 and 27 provided in or on the working device 4 and the attachment 11 are actuated by hydraulic fluid to cause the working device 4 and the attachment 11 to perform work. Note that some attachments are electric-driven attachments including electric actuator(s) such as an electric motor and / or an electric cylinder. Such an electric-driven attachment performs work in the following manner. Electricity from a battery provided in or on the working machine 1 is inputted into an electric actuator via an electric connector and an electric cable in or on the machine body 2, so that the electric actuator is actuated and the attachment is driven by power from the actuator, making it possible to perform work.

[0068] FIG. 1 illustrates a work-related hydraulic circuit 4A included in the working machine 1. This hydraulic circuit 4A causes the working device 4 and the attachment 11 to operate. The working machine 1 includes a pilot pump P1 and a main pump P2. For example, the pilot pump P1 is a fixed displacement hydraulic pump, and the main pump P2 is a variable displacement hydraulic pump.

[0069] The pilot pump P1 is actuated by power from the prime mover 6 to deliver hydraulic fluid stored in a hydraulic fluid tank T to a fluid passage 40. The hydraulic fluid delivered by the pilot pump P1 is pilot fluid to control various hydraulic devices provided in the working machine 1. The pressure of pilot fluid is a pilot pressure.

[0070] The main pump P2 is actuated by power from the prime mover 6 to deliver hydraulic fluid stored in the hydraulic fluid tank T to a main fluid passage 45. The hydraulic fluid delivered by the main pump P2 is used to actuate the lift cylinders 14 and the tilt cylinders 15 of the working device 4, as well as hydraulic device(s) such as the hydraulic actuator 27 provided in or on the attachment 11.

[0071] The working machine 1 includes a plurality of control valves 60A, 60B and 60C. The plurality of control valves 60A, 60B and 60C include a lift control valve 60A, a tilt control valve 60B, and an auxiliary (AUX) control valve 60C. The plurality of control valves 60 are each connected to the main fluid passage 45. The lift control valve 60A controls the flow rate (output) and the supply direction of hydraulic fluid supplied from the main fluid passage 45 to the lift cylinders 14 to actuate the lift cylinders 14. The tilt control valve 60B controls the flow rate (output) and the supply direction of hydraulic fluid supplied from the main fluid passage 45 to the tilt cylinders 15 to actuate the tilt cylinders 15. The AUX control valve 60C controls the flow rate (output) and the supply direction of the hydraulic fluid supplied from the main fluid passage 45 to the hydraulic actuator 27 via the AUX port(s) 25 to actuate the hydraulic actuator 27.

[0072] The lift control valve 60A is connected to the lift cylinders 14 via a plurality of fluid passages 64a and 64b. The lift control valve 60A is a pilot-operated, direct-acting spool three-position switching valve. The lift control valve 60A includes a plurality of work pressure receivers 61a and 61b, and switches between a third position (neutral position) 61c, a first position 61d different from the third position 61c, and a second position 61e different from the third position 61c and the first position 61d depending on the pilot pressure acting on the work pressure receiver(s) 61a and / or 61b. When the lift control valve 60A is in the third position 61c, hydraulic fluid is not supplied from the main fluid passage 45 to the lift cylinders 14.

[0073] When the lift control valve 60A switches to the first position 61d or the second position 61e, hydraulic fluid from the main fluid passage 45 is supplied to the lift cylinders 14 via the lift control valve 60A and the fluid passage 64a or 64b. When the opening of the lift control valve 60A changes according to the pilot pressure while the lift control valve 60A is in the first position 61d or the second position 61e, the flow rate of hydraulic fluid from the main fluid passage 45 to the lift cylinders 14 is changed. Thus, the lift control valve 60A controls the supply direction and the flow rate of hydraulic fluid supplied from the main fluid passage 45 to the lift cylinders 14 according to the pilot pressure acting on the work pressure receiver(s) 61a and / or 61b to cause the lift cylinders 14 to extend or retract.

[0074] More specifically, when the lift control valve 60A switches to the first position 61d, hydraulic fluid from the main fluid passage 45 flows through the lift control valve 60A and the fluid passage 64a and is supplied to the rod-side chambers of the lift cylinders 14. With this, the lift cylinders 14 retract, the arms 10 swing downward, and the attachment 11 attached to the hitch 16 lowers. The hydraulic fluid pushed out of the cap-side chambers of the lift cylinders 14 flows through the fluid passage 64b and is drained from the lift control valve 60A.

[0075] When the lift control valve 60A switches to the second position 61e, hydraulic fluid from the main fluid passage 45 flows through the lift control valve 60A and the fluid passage 64b, and is supplied to the cap-side chambers of the lift cylinders 14. With this, the lift cylinders 14 extend, the arms 10 swing upward, and the attachment 11 attached to the hitch 16 is raised. The hydraulic fluid pushed out from the rod-side chambers of the lift cylinders 14 flows through the fluid passage 64a and is drained from the lift control valve 60A.

[0076] The tilt control valve 60B is connected to the tilt cylinders 15 by a plurality of fluid passages 65a and 65b. The tilt control valve 60B is a pilot-operated, direct-acting spool three-way switching valve. The tilt control valve 60B includes a plurality of work pressure receivers 62a and 62b, and switches between a third position (neutral position) 62c, a first position 62d different from the third position 62c, and a second position 62e different from the third position 62c and the first position 62d, depending on the pilot pressure acting on the work pressure receiver(s) 62a and / or 62b. When the tilt control valve 60B is in the third position 62c, hydraulic fluid is not supplied from the main fluid passage 45 to the tilt cylinders 15.

[0077] The tilt control valve 60B switches to the first position 62d or the second position 62e to allow hydraulic fluid from the main fluid passage 45 to be supplied to the tilt cylinders 15 via the tilt control valve 60B and the fluid passage 65a or 65b. When the opening of the tilt control valve 60B changes according to the pilot pressure while the tilt control valve 60B is in the first position 62d or the second position 62e, the flow rate of hydraulic fluid from the main fluid passage 45 to the tilt cylinders 15 is changed. Thus, the tilt control valve 60B controls the supply direction and the flow rate of hydraulic fluid supplied from the main fluid passage 45 to the tilt cylinders 15 according to the pilot pressure acting on the work pressure receiver(s) 62a and / or 62b to cause the tilt cylinders 15 to extend or retract.

[0078] More specifically, when the tilt control valve 60B switches to the first position 62d, hydraulic fluid from the main fluid passage 45 flows through the tilt control valve 60B and the fluid passage 65b, and is supplied to the cap-side chambers of the tilt cylinders 15. With this, the tilt cylinders 15 extend, the hitch 16 swings downward, the tilt angle of the attachment 11 attached to the hitch 16 decreases, and the orientation is changed such that the front portion of the attachment 11 lowers. The hydraulic fluid pushed out of the rod-side chambers of the tilt cylinders 15 flows through the fluid passage 65b and is drained from the tilt control valve 60B.

[0079] When the tilt control valve 60B switches to the second position 62e, hydraulic fluid from the main fluid passage 45 flows through the tilt control valve 60B and the fluid passage 65a, and is supplied to the rod-side chambers of the tilt cylinders 15. With this, the tilt cylinders 15 retract, the hitch 16 swings upward, the tilt angle of the attachment 11 attached to the hitch 16 increases, and the orientation is changed such that the front portion of the attachment 11 is raised. The hydraulic fluid pushed out from the cap-side chambers of the tilt cylinders 15 flows through the fluid passage 65a and is drained from the tilt control valve 60B.

[0080] The AUX control valve 60C is connected to the AUX ports 25 via a plurality of AUX fluid passages (auxiliary fluid passages) 66a and 66b. Specifically, a first port of the AUX control valve 60C and the first AUX port 25a are connected via the AUX fluid passage 66a, and a second port of the AUX control valve 60C and the second AUX port 25b are connected via the AUX fluid passage 66b. The AUX control valve 60C is a pilot-operated, direct-acting spool three-position switching valve. The AUX control valve 60C includes a plurality of AUX pressure receivers 63a and 63b, and switches between a third position (neutral position) 63c, a first position 63d different from the third position 63c, and a second position 63e different from the third position 63c and the first position 63d, depending on the pilot pressure acting on the AUX pressure receiver(s) 63a and / or 63b.

[0081] When the AUX control valve 60C is in the third position 63c, hydraulic fluid is not supplied to the hydraulic actuator 27 from the main fluid passage 45 via the AUX fluid passage 66a or 66b and the AUX port(s) 25. When the AUX control valve 60C switches to the first position 63d or the second position 63e, hydraulic fluid from the main fluid passage 45 is supplied to the hydraulic actuator 27 via the AUX control valve 60C, the AUX fluid passage 66a or 66b, and the corresponding AUX port 25, and the supply direction of the hydraulic fluid changes.

[0082] More specifically, when the AUX control valve 60C switches to the first position 63d, hydraulic fluid from the main fluid passage 45 is supplied to the hydraulic actuator 27 via the AUX control valve 60C, the AUX fluid passage 66a and the first AUX port 25a, and return fluid from the hydraulic actuator 27 flows through the second AUX port 25b and the AUX fluid passage 66b and is drained from the AUX control valve 60C. When the AUX control valve 60C switches to the second position 63e, hydraulic fluid from the main fluid passage 45 is supplied to the hydraulic actuator 27 via the AUX control valve 60C, the AUX fluid passage 66b and the second AUX port 25b, and return fluid from the hydraulic actuator 27 flows through the first AUX port 25a and the AUX fluid passage 66a and is drained from the AUX control valve 60C.

[0083] When the opening of the AUX control valve 60C changes according to the pilot pressure while the AUX control valve 60C is in the first position 63d or the second position 63e, the flow rate of hydraulic fluid supplied from the main fluid passage 45 to the hydraulic actuator 27 via the corresponding AUX port 25 is changed.

[0084] As described above, the AUX control valve 60C controls the supply direction and the flow rate of hydraulic fluid supplied from the main fluid passage 45 to the hydraulic actuator 27 via the corresponding AUX fluid passage 66a or 66b and the corresponding AUX port 25 according to the pilot pressure acting on the AUX pressure receiver(s) 63a and / or 63b to actuate the hydraulic actuator 27. The AUX control valve 60C, the AUX fluid passages 66a and 66b, and the AUX ports 25 define an auxiliary hydraulic circuit 4B to supply hydraulic fluid to the hydraulic actuator 27 of the attachment 11, and the auxiliary hydraulic circuit 4B is provided in the working machine 1.

[0085] The working machine 1 includes pressure detectors 70a and 70b. The pressure detectors 70a and 70b include pressure sensors. The pressure detector 70a is provided in the AUX fluid passage 66a to detect an AUX pressure (auxiliary pressure) which is the pressure of hydraulic fluid flowing from the AUX control valve 60C through the AUX fluid passage 66a and is supplied to the hydraulic actuator 27 of the attachment 11. The pressure detector 70b is provided in the AUX fluid passage 66b to detect an AUX pressure which is the pressure of hydraulic fluid flowing from the AUX control valve 60C through the AUX fluid passage 66b and is supplied to the hydraulic actuator 27. During work performed by the attachment 11 including the hydraulic actuator 27, the AUX pressure detected by the pressure detector(s) 70a and / or 70b can be regarded as a load on the attachment 11.

[0086] Note that the pressure detectors 70a and 70b also detect the pressure of hydraulic fluid (return fluid) flowing from the hydraulic actuator 27 through the corresponding AUX fluid passage 66a or 66b and returning to the AUX control valve 60C. However, since the pressure is equal to or substantially equal to the atmospheric pressure, the pressure is not regarded as auxiliary pressure by a controller 20.

[0087] The working machine 1 includes a plurality of solenoid valves 76a, 76b, 77a, 77b, 78a and 78b. The plurality of solenoid valves 76a, 76b, 77a, 77b, 78a and 78b are proportional valves in each of which the solenoid is energized and the opening is changed according to a control signal (electric current signal) inputted thereto. The plurality of solenoid valves 76a, 76b, 77a, 77b, 78a and 78b are each connected to fluid passages 40b and 40c branching from the fluid discharge passage 40, and a change in the opening thereof changes the pilot pressure of pilot fluid supplied from the fluid discharge passage 40. Specifically, as the electric current value of the control signal inputted increases, the opening of the plurality of solenoid valves 76a, 76b, 77a, 77b, 78a and 78b increases, allowing pilot fluid from the fluid discharge passage 40 to be outputted with an increased pilot pressure.

[0088] The plurality of solenoid valves 76a, 76b, 77a, 77b, 78a and 78b include lift solenoid valves 76a and 76b, tilt solenoid valves 77a and 77b, and AUX solenoid valves 78a and 78b. The lift solenoid valves 76a and 76b are respectively connected to the work pressure receivers 61a and 61b of the lift control valve 60A via fluid passages. The tilt solenoid valves 77a and 77b are respectively connected to the work pressure receivers 62a and 62b of the tilt control valve 60B via fluid passages. The AUX solenoid valves 78a and 78b are respectively connected to the AUX pressure receivers 63a and 63b of the AUX control valve 60C via fluid passages.

[0089] When the opening of the lift solenoid valve 76a is greater than 0 (zero), pilot fluid from the fluid discharge passage 40 acts on the work pressure receiver 61a from the lift solenoid valve 76a. In so doing, a pilot pressure corresponding to the opening of the lift solenoid valve 76a acts on the work pressure receiver 61a. When the pilot pressure acting on the work pressure receiver 61a is equal to or higher than a predetermined value, the spool of the lift control valve 60A moves, and the lift control valve 60A switches to the first position 61d. With this, the lift cylinders 14 retract and the attachment 11 lowers, and therefore the lift solenoid valve 76a is a solenoid valve to lower the attachment.

[0090] Similarly, when the opening of the lift solenoid valve 76b increases, pilot fluid from the fluid discharge passage 40 acts on the work pressure receiver 61b from the lift solenoid valve 76b, and the lift control valve 60A switches to the second position 61e. With this, the lift cylinders 14 extend and the attachment 11 is raised, and therefore the lift solenoid valve 76b is a solenoid valve to raise the attachment.

[0091] Similarly, when the opening of the tilt solenoid valve 77a increases, pilot fluid from the fluid discharge passage 40 acts on the work pressure receiver 62a from the tilt solenoid valve 77a, and the tilt control valve 60B switches to the first position 62d. With this, the tilt cylinders 15 extend and the tilt angle of the attachment 11 decreases, and therefore the tilt solenoid valve 77a is a solenoid valve to lower the front portion of the attachment. When the opening of the tilt solenoid valve 77b increases, pilot fluid from the fluid discharge passage 40 acts on the work pressure receiver 62b from the tilt solenoid valve 77b, and the tilt control valve 60B switches to the second position 62e. With this, the tilt cylinders 15 retract and the tilt angle of the attachment 11 increases, and therefore the tilt solenoid valve 77b is a solenoid valve to raise the front portion of the attachment.

[0092] Similarly, when the opening of the AUX solenoid valve 78a increases, pilot fluid from the fluid discharge passage 40 acts on the AUX pressure receiver 63a via the AUX solenoid valve 78a, and the AUX control valve 60C switches to the first position 63d. With this, hydraulic fluid is supplied from the AUX control valve 60C to the hydraulic actuator 27 via the AUX fluid passage 66a and the first AUX port 25a. When the opening of the AUX solenoid valve 78b increases, pilot fluid from the fluid discharge passage 40 acts on the AUX pressure receiver 63b via the AUX solenoid valve 78b, and the AUX control valve 60C switches to the second position 63e. With this, hydraulic fluid is supplied from the AUX control valve 60C to the hydraulic actuator 27 via the AUX fluid passage 66b and the second AUX port 25b.

[0093] The plurality of solenoid valves 76a, 76b, 77a, 77b, 78a and 78b change the pilot pressure to act on the corresponding pressure receivers 61a, 61b, 62a, 62b, 63a and 63b according to the control signals inputted thereto to change the flow rate of hydraulic fluid from the corresponding control valves 60A, 60B and 60C to the corresponding actuators 14, 15 and 27.

[0094] The working machine 1 includes a work manual operator (work manual operator unit) 67 and the controller 20. The work manual operator 67 is operable to control the swinging of the arms 10 and the hitch 16. The work manual operator 67 includes a digital joystick. The work manual operator 67 includes a work operating lever 67a and a sensor 67b. The work operating lever 67a is a manual operator (work manual operator) to be operated by the driver of the working machine, and is provided in the vicinity of the seat 8 inside the cabin 3. The work operating lever 67a can be operated not only forward and rearward from a neutral position, but also leftward and rightward from the neutral position.

[0095] The sensor 67b includes at least one of an angle sensor or an electric circuit, detects the operation direction and the operation angle (angle of pivoting) of the work operating lever 67a, and outputs a detection signal (electric signal) corresponding to the operation direction and the operation angle. The controller 20 determines the operation direction and the operation angle of the work operating lever 67a based on the detection signal outputted from the sensor 67b, and calculates the ratio of the operation angle to the maximum angle of pivoting of the work operating lever 67a as the operation amount of the work operating lever 67a.

[0096] The controller 20 then inputs a control signal into the lift solenoid valve 76a or 76b or the tilt solenoid valve 77a or 77b according to the operation direction and the operation amount of the work operating lever 67a to open the solenoid valve. With this, a corresponding one of the lift control valve 60A and the tilt control valve 60B switches to the first position 61d, 62d or the second position 61e, 62e, the lift cylinders 14 or the tilt cylinders 15 extend or retract, the arms 10 or the hitch 16 swing(s) in the corresponding direction, and the position including the height or the orientation (tilt angle) of the attachment 11 attached to the hitch 16 is changed.

[0097] Specifically, when the work operating lever 67a is pivoted forward, the controller 20 inputs a control signal into the lift solenoid valve 76a according to the operation amount of the work operating lever 67 to open the lift solenoid valve 76a. With this, the lift control valve 60A switches to the first position 61d, the lift cylinders 14 retract, the arms 10 swing downward, the attachment 11 lowers, and the height of the attachment 11 decreases. In so doing, the attachment 11 is positioned somewhat forward.

[0098] When the work operating lever 67a is pivoted rearward, the controller 20 inputs a control signal into the lift solenoid valve 76b according to the operation amount of the work operating lever 67a to open the lift solenoid valve 76b. With this, the lift control valve 60A switches to the second position 61e, the lift cylinders 14 extend, the arms 10 swing upward, the attachment 11 is raised, and the height of the attachment 11 increases. In so doing, the attachment 11 is positioned somewhat rearward.

[0099] When the work operating lever 67a is pivoted leftward, the controller 20 inputs a control signal into the tilt solenoid valve 77a according to the operation amount of the work operating lever 67a to open the tilt solenoid valve 77a. With this, the tilt control valve 60B switches to the first position 62d, the tilt cylinders 15 extend, and the hitch 16 swings downward, so that the orientation of the attachment 11 is changed such that the front portion of the attachment 11 lowers.

[0100] When the work operating lever 67a is pivoted rightward, the controller 20 inputs a control signal into the tilt solenoid valve 77b according to the operation amount of the work operating lever 67a to open the tilt solenoid valve 77b. With this, the tilt control valve 60B switches to the second position 62e, the tilt cylinders 15 retract, the hitch 16 swings upward, so that the orientation of the attachment 11 is changed such that the front portion of the attachment 11 is raised.

[0101] Note that when the controller 20 causes the arms 10 to swing, the controller 20 causes the hitch 16 to swing so that the orientation of the attachment 11 is not changed. That is, the controller 20, when causing the arms 10 to swing by inputting a control signal into one of the lift solenoid valves 76a and 76b, the controller 20 also inputs a control signal into a corresponding one of the tilt solenoid valves 77a and 77b that corresponds to the swinging direction of the arms 10 to cause the hitch 16 to swing, thus keeping the orientation of the attachment 11. This eliminates or reduces the likelihood that, when the arms 10 swing, the attachment 11 will tilt and accidentally contact a target object or surrounding objects and be damaged.

[0102] The working machine 1 includes an AUX output switch 73b. The AUX output switch 73b is an operating switch to be operated by the driver. The AUX output switch 73b is turned ON to start supplying hydraulic fluid to the corresponding AUX port 25, and is turned OFF to stop supplying the hydraulic fluid.

[0103] When the controller 20 is in an AUX mode in which the attachment 11 including the hydraulic actuator 27 is allowed to be used with the working machine 1, if the AUX output switch 73b is turned ON, the controller 20 inputs a control signal into one of the AUX solenoid valves 78a and 78b to open the solenoid valve. With this, the AUX control valve 60C switches to the first position 63d or the second position 63e, and hydraulic fluid is supplied from the AUX control valve 60C to the corresponding AUX port 25 via the AUX fluid passage 66a or the AUX fluid passage 66b. In so doing, if the AUX ports 25 and hydraulic ports of the attachment 11 are connected by the external fluid passages 26, hydraulic fluid is supplied from the corresponding AUX port 25 to the hydraulic actuator 27 of the attachment 11 via the corresponding external fluid passage 26 and the like, the hydraulic actuator 27 is actuated, and the attachment 11 is driven.

[0104] When the controller 20 is in the AUX mode, if the AUX output switch 73b is turned OFF, the controller 20 stops inputting the control signal into the AUX solenoid valve 78a or 78b to close the AUX solenoid valve 78a or 78b. With this, the AUX control valve 60C switches to the third position 63c, and the supply of hydraulic fluid from the AUX control valve 60C to the AUX port 25 is stopped. Thus, the supply of hydraulic fluid to the hydraulic actuator 27 of the attachment 11 is also stopped, the hydraulic actuator 27 stops, and the attachment 11 stops.

[0105] The controller 20 inputs a control signal into at least one of the lift solenoid valve 76b or 76b or the tilt solenoid valve 77a or 77b according to the AUX pressure detected by the pressure detectors 70a and 70b to open the solenoid valve(s). With this, the controller 20 switches at least one of the lift control valve 60A or the tilt control valve 60B to the first position or the second position to supply hydraulic fluid to at least one of the lift cylinders 14 or the tilt cylinders 15 to cause the cylinders to extend or retract to cause at least one of the arms 10 or the hitch 16 to swing, thus adjusting at least one of the position or the orientation of the attachment 11. Thus, the controller 20 performs a posture control to control the working device 4 according to the AUX pressure to adjust the posture of the attachment 11.

[0106] The working machine 1 includes a load sensing system (which may be hereinafter simply referred to as “LS system”) 80. The LS system 80 is a hydraulic system to control the flow rate of hydraulic fluid delivered by the variable displacement main pump P2 such that a differential pressure is constant. The differential pressure is obtained by subtracting, from the hydraulic fluid delivery pressure of the main pump P2 which is a variable displacement pump, the maximum of load pressures on the actuators 14, 15 and 27 actuated by hydraulic fluid delivered by the main pump P2.

[0107] The LS system 80 includes a swash plate changing cylinder 81, a flow rate compensation valve 82, and an opening changing cylinder 83. The swash plate changing cylinder 81 adjusts the angle of the swash plate of the main pump P2. The flow rate compensation valve 82 causes a hydraulic pressure to act on the swash plate changing cylinder 81 to actuate the swash plate changing cylinder 81. The opening changing cylinder 83 is actuated by the pilot pressure of pilot fluid from the pilot pump P1 to change the opening of the flow rate compensation valve 82.

[0108] A PLS fluid passage 84 and a PPS fluid passage 85 are connected to the flow rate compensation valve 82. The PLS fluid passage 84 is a fluid passage to transmit a PLS pressure which is the maximum of the load pressures on the actuators 14, 15 and 27 (actuator maximum load pressure). The PPS fluid passage 85 is used to transmit a PPS pressure which is the delivery pressure of the main pump P2. The flow rate compensation valve 82 actuates the swash plate changing cylinder 81 to adjust the angle of the swash plate of the main pump P2 such that the differential pressure, which is obtained by subtracting the PLS pressure from the PPS pressure, is constant. With this, the flow rate of hydraulic fluid delivered by the main pump P2 is controlled, and hydraulic power corresponding to the load applied to the working device 4 and the attachment 11 is outputted from the main pump P2.

[0109] In the present example embodiment, the swash plate of the main pump P2 is pressed by the self-pressure thereof in a direction that increases the flow rate of hydraulic delivered by the main pump P2. The swash plate changing cylinder 81 is operable to cause a force against the self-pressure of the main pump P2 to act on the swash plate. Furthermore, the flow rate compensation valve 82 is operable to control the delivery flow rate of the main pump P2 by adjusting the hydraulic pressure acting on the swash plate changing cylinder 81. Thus, when the hydraulic pressure acting on the swash plate changing cylinder 81 is removed (becomes zero), the angle of the swash plate of the main pump P2 becomes maximum, and the flow rate of hydraulic fluid delivered by the main pump P2 becomes maximum.

[0110] FIG. 2 illustrates a travel-related hydraulic circuit 5A included in the working machine 1. The hydraulic circuit 5A actuates the traveling devices 5 to cause the working machine 1 to travel. The working machine 1 includes travel pumps 50 and travel motors 51.

[0111] Each travel pump 50 is a hydraulic pump to be actuated by power from the prime mover 6. The travel pump 50 is a swash-plate variable displacement axial pump and includes pressure receivers 50a and 50b to receive pilot pressure. The pump pressure receivers 50a and 50b include a forward-travel pump pressure receiver 50a and a rearward-travel pump pressure receiver 50b. The angle of the swash plate of the travel pump 50 is changed according to the pilot pressure acting on the pump pressure receiver(s) 50a and / or 50b. When the angle of the swash plate of the travel pump 50 is changed, the flow rate and the supply direction of the hydraulic fluid delivered by the travel pump 50 change. The travel pumps 50 include a first travel pump 50L corresponding to the first traveling device 5, and a second travel pump 50R corresponding to the second traveling device 5.

[0112] Each travel motor 51 is a hydraulic motor to be actuated by hydraulic fluid delivered by the corresponding travel pump 50. The travel motors 51 include a first travel motor 51L corresponding to the first travel pump 50L, and a second travel motor 51R corresponding to the second travel pump 50R.

[0113] The first travel motor 51L is connected to the first travel pump 50L via a closed loop circuit fluid passage 53a. The first travel motor 51L is actuated by hydraulic fluid supplied from the first travel pump 50L. The first travel motor 51L includes an output shaft 51Lj, and changes the rotation speed of the output shaft 51Lj based on the flow rate of hydraulic fluid delivered by the first travel pump 50L. When the power from the first travel motor 51L is transmitted from the output shaft 51Lj to the drive shaft of the first traveling device 5 via a transmission mechanism, the first traveling device 5 is driven.

[0114] The first travel motor 51L includes a swash plate. When the angle of the swash plate of the first travel motor 51L is changed by a swash plate cylinder 52L, the first travel motor 51L changes the rotation speed stage of the output shaft 51Lj to a first speed stage (low speed stage) or a second speed stage (high speed stage) higher than the first speed stage. Specifically, when the swash plate cylinder 52L retracts, the rotation speed of the output shaft 51Lj of the first travel motor 51L is set to the first speed stage. When the swash plate cylinder 52L extends, the rotation speed of the output shaft 51Lj of the first travel motor 51L is set to the second speed stage.

[0115] The second travel motor 51R is connected to the second travel pump 50R via a closed loop circuit fluid passage 53b. The second travel motor 51R is actuated by hydraulic fluid delivered by the second travel pump 50R to drive the second traveling device 5 via an output shaft 51Rj and the like. When the angle of the swash plate of the second travel motor 51R is changed by a swash plate cylinder 52R, the second travel motor 51R changes the rotation speed stage of the output shaft 51Rj to the first speed stage or the second speed stage. Since the configurations of the second travel motor 51R, the second travel pump 50R, the second traveling device 5 and the swash plate cylinder 52R are respectively the same as the configurations of the first travel motor 51L, the first travel pump 50L, the first traveling device 5 and the swash plate cylinder 52L, detailed description therefor is omitted.

[0116] The working machine 1 includes a plurality of operating valves 54a, 54b, 54c and 54d. Each of the operating valves 54a, 54b, 54c and 54d is a proportional valve in which a solenoid thereof is energized in response to a control signal (electric current signal) inputted thereto and the opening is changed. The plurality of the operating valves 54a, 54b, 54c and 54d are provided in respective four fluid passages 42a, 42b, 42c and 42d connected to the fluid discharge passage 40. Each of them changes the pilot pressure of pilot fluid supplied from the fluid discharge passage 40 according to changes in the opening thereof. Specifically, as the electric current value of the inputted control signal increases, the opening of each of the plurality of operating valves 54a, 54b, 54c and 54d increases, allowing pilot fluid from the fluid discharge passage 40 to be outputted with an increased pilot pressure.

[0117] The first operating valve 54a is connected to the forward-travel pump pressure receiver 50a of the first travel pump 50L via the fluid passage 42a. The second operating valve 54b is connected to the rearward-travel pump pressure receiver 50b of the first travel pump 50L via the fluid passage 42b. The third operating valve 54c is connected to the forward-travel pump pressure receiver 50a of the second travel pump 50R via the fluid passage 42c. The fourth operating valve 54d is connected to the rearward-travel pump pressure receiver 50b of the second travel pump 50R via the fluid passage 42d.

[0118] The working machine 1 includes a travel manual operator (travel manual operator unit) 57. The travel manual operator 57 is operable to operate the travel pumps 50, the travel motors 51, and the traveling devices 5. The travel manual operator 57 includes a digital joystick. The travel manual operator 57 includes a travel operating lever 57a and a sensor 57b. The travel operating lever 57a is a manual operator (travel manual operator) to be operated by the driver, and is provided in the vicinity of the seat 8 inside the cabin 3. The travel operating lever 57a can be operated not only forward, rearward, leftward, and rightward from a neutral position, but also diagonally leftward and forward, diagonally rightward and forward, diagonally leftward and rearward, and diagonally rightward and rearward from the neutral position.

[0119] The sensor 57b includes at least one of an angle sensor or an electric circuit, detects the operation direction and the operation angle of the travel operating lever 57a, and outputs a detection signal corresponding to the operation direction and the operation angle. The controller 20 determines the operation direction and the operation angle of the travel operating lever 57a based on the detection signal outputted from the sensor 57b, and calculates the ratio of the operation angle relative to the maximum angle of pivoting of the travel operating lever 57a as the operation amount of the travel operating lever 57a.

[0120] The controller 20 then, according to the operation direction and the operation amount of the travel operating lever 57a, decides a target value of the travel speed of the machine body 2, a target value of the swash plate angle of the travel pump(s) 50L and 50R, and / or a target value of the pump pressure to be applied to the travel motor(s) 51L and 51R. The controller 20 then inputs a control signal(s) corresponding to the decided target value(s) into at least one of the plurality of operating valves 54a, 54b, 54c and 54d to open the operating valve(s). With this, pilot pressure acts on the pump pressure receiver(s) 50a and / or 50b of the corresponding travel pump(s) 50L and 50R, the angle of the swash plate of the travel pump(s) is changed, and the flow rate and direction of hydraulic fluid delivered by the travel pump(s) are defined or changed. Furthermore, the rotation speed and the rotation direction of the output shaft(s) 51Lj and 51Lj of the corresponding travel motor(s) 51L and 51R are defined or changed, and the travel speed and the travel direction of the traveling device(s) 5 and the machine body 2 (working machine 1) are also defined or changed.

[0121] Specifically, when the travel operating lever 57a is pivoted forward, the controller20 inputs a control signal into the operating valves 54a and 54c according to the operation amount of the travel operating lever 57a to open the operating valves 54a and 54c. With this, the pilot pressures outputted from the operating valves 54a and 54c act on the forward-travel pump pressure receivers 50a of the travel pumps 50L and 50R via the respective fluid passages 42a and 42c. With this, the angle of the swash plates of the travel pumps 50L and 50R is changed, the output shafts 51Lj and 51Rj of the travel motors 51L and 51R rotate forward (rotate to achieve forward travel), the first traveling device 5 and the second traveling device 5 are driven to achieve forward travel, and the working machine 1 travels straight forward at a travel speed corresponding to the operation amount of the travel operating lever 57a.

[0122] When the travel operating lever 57a is pivoted rearward, the controller 20 inputs a control signal into the operating valves 54b and 54d according to the operation amount of the travel operating lever 57a to open the operating valves 54b and 54d. With this, the pilot pressures outputted from the operating valves 54b and 54d act on the rearward-travel pump pressure receivers 50b of the travel pumps 50L and 50R via the respective fluid passages 42b and 42d. With this, the angle of the swash plates of the travel pumps 50L and 50R is changed, the output shafts 51Lj and 51Rj of the travel motors 51L and 51R rotate reversely (rotate to achieve rearward travel), the first traveling device 5 and the second traveling device 5 are driven to achieve rearward travel, and the working machine 1 travels straight rearward at a travel speed corresponding to the operation amount of the travel operating lever 57a.

[0123] When the travel operating lever 57a is pivoted leftward, the controller 20 inputs a control signal into the operating valves 54b and 54c according to the operation amount of the travel operating lever 57a to open the operating valves 54b and 54c. With this, the pilot pressures outputted from the operating valves 54b and 54c act on the rearward-travel pump pressure receiver 50b of the travel pump 50L and the forward-travel pressure receiver 50a of the travel pump 50R via the respective fluid passages 42b and 42c. With this, the angle of the swash plates of the travel pumps 50L and 50R is changed, the output shaft 51Lj of the first travel motor 51L rotates reversely and the first traveling device 5 is driven to achieve rearward travel, the output shaft 51Rj of the second travel motor 51R rotates forward and the second traveling device 5 is driven to achieve forward travel, and the working machine 1 makes a spin turn to the left.

[0124] When the travel operating lever 57a is pivoted rightward, the controller 20 inputs a control signal into the operating valves 54a and 54d according to the operation amount of the travel operating lever 57a to open the operating valves 54a and 54d. With this, the pilot pressures outputted from the operating valves 54a and 54d act on the forward-travel pump pressure receiver 50a of the travel pumps 50L and the rearward-travel pressure receiver 50b of the travel pump 50R via the respective fluid passages 42a and 42d. With this, the angle of the swash plates of the travel pumps 50L and 50R is changed, the output shaft 51Lj of the first travel motor 51L rotates forward, the first traveling device 5 is driven to achieve forward travel, the output shaft 51Rj of the second travel motor 51R rotates reversely, the second traveling device 5 is driven to achieve rearward travel, and the working machine 1 makes a spin turn to the right.

[0125] Furthermore, when the travel operating lever 57a is pivoted diagonally leftward and forward, diagonally rightward and forward, diagonally leftward and rearward, or diagonally rightward and rearward, the controller 20 inputs a control signal into one of or two of the operating valves 54a to 54d according to the direction of pivoting and the operation amount to open the operating valve(s). With this, pilot pressure acts on the pump receivers 50a and / or 50b of the travel pumps 50L and 50R corresponding to the open operating valve(s), the angle of the swash plates of the corresponding travel pumps 50L and 50R is changed, the rotation direction and the rotation speed of the output shafts 51Lj and 51Rj of the corresponding travel motors 51L and 51R are defined, and the working machine 1 makes a pivot turn or a slow turn to the right or to the left while traveling forward or rearward.

[0126] Specifically, when the travel operating lever 57a is pivoted diagonally leftward and forward, the working machine 1 turns left while traveling forward at a travel speed corresponding to the operation direction and the operation amount of the travel operating lever 57a. When the travel operating lever 57a is pivoted diagonally rightward and forward, the working machine 1 turns right while traveling forward at a travel speed corresponding to the operation direction and the operation amount of the travel operating lever 57a. When the travel operating lever 57a is pivoted diagonally leftward and rearward, the working machine 1 turns left while traveling rearward at a travel speed corresponding to the operation direction and the operation amount of the travel operating lever 57a. When the travel operating lever 57a is pivoted diagonally rightward and rearward, the working machine 1 turns right while traveling rearward at a travel speed corresponding to the operation direction and operation amount of the travel operating lever 57a.

[0127] The working machine 1 includes speed-change switching valves 58L and 58R, a speed-change solenoid valve 59, and a speed-change switch 75. The speed-change switching valves 58L and 58R are two-position switching valves. The speed-change switching valve 58L is connected to the swash plate cylinder 52L by a fluid passage, and the speed-change switching valve 58R is connected to the swash plate cylinder 52R by a fluid passage. The speed-change switching valves 58L and 58R are connected to the speed-change solenoid valve 59 via a fluid passage 41. The speed-change solenoid valve 59 is a two-position solenoid switching valve including two positions and a solenoid to be energized in response to a control signal inputted thereto to switch between the positions. The speed-change solenoid valve 59 is connected to the fluid discharge passage 40, and switches the positions of the switching valves 58L and 58R. The speed-change switch 75 is an operating switch to be operated by the driver to input an instruction to switch the speed stage of the rotation speed of the output shafts 51Lj and 51Rj of the travel motor 51 to a first speed stage (low speed stage) or a second speed stage (high speed) higher than the first speed stage.

[0128] Upon receipt of an instruction to switch the speed stage to the first speed stage from the speed-change switch 75, the controller 20 inputs a control signal into the speed-change solenoid valve 59 to switch the speed-change solenoid valve 59 to the first position to block pilot fluid. With this, the pilot fluid from the fluid discharge passage 40 does not act on the pressure receivers of the speed-change switching valves 58L and 58R via the speed-change solenoid valve 59, the speed-change switching valves 58L and 58R are in the first position to block hydraulic fluid, and hydraulic fluid is not supplied from the speed-change switching valves 58L and 58R to the swash plate cylinders 52L and 52R. Thus, the swash plate cylinders 52L and 52R are caused to retract by the elastic force of a spring, and the rotation speed of the output shafts 51Lj and 51Rj of the travel motors 51 is switched to the first speed stage.

[0129] Upon receipt of an instruction to switch the speed stage to the second speed stage from the speed-change switch 75, the controller 20 inputs a control signal into the speed-change solenoid valve 59 to switch the speed-change solenoid valve 59 to the second position to allow pilot fluid to pass therethrough. With this, pilot fluid from the fluid discharge passage 40 acts on the pressure receivers of the speed-change switching valves 58L and 58R via the speed-change solenoid valve 59, the speed-change switching valves 58L and 58R switch to the second position to allow hydraulic fluid to pass therethrough, and hydraulic fluid is supplied from the speed-change switching valves 58L and 58R to the swash plate cylinders 52L and 52R. Thus, the swash plate cylinders 52L and 52R are caused to extend by the hydraulic pressure, and the rotation speed of the output shafts 51Lj and 51Rj of the travel motors 51 is switched to the second speed stage.

[0130] Regardless of whether the speed-change switch 75 is operated or not, the controller 20 may switch the positions of the speed-change solenoid valve 59 to automatically change the second speed stage to the first speed stage (automatic speed reduction) or automatically change the first speed stage to the second speed stage speed (automatic speed increase). In the case where work is performed using a specific attachment 11, the controller 20 switches the speed stage to the first speed stage to perform a low-speed mode (creep mode) in which the travel speed of the working machine 1 is kept at a low speed.

[0131] The working machine 1 includes a plurality of braking actuators 55, a braking solenoid valve 56 and a braking switch 79. The braking actuators 55 are hydraulic cylinders to brake the corresponding travel motors 51L and 51R. The braking solenoid valve 56 is a two-position solenoid switching valve including two positions and a solenoid to be energized in response to a control signal inputted therein to switch between the positions. The braking solenoid valve 56 is connected to the plurality of braking actuators 55 via fluid passages, and is also connected to the main fluid passage 45. The braking switch 79 is a detection switch to detect the depression of a braking pedal provided at the bottom of the seat 8 (FIG. 15). The user depresses the braking pedal to achieve braking.

[0132] When the braking pedal is not depressed, the braking solenoid valve 56 is in the first position to block hydraulic fluid from the main fluid passage 45, and the braking actuators 55 do not brake the rotation of the output shafts 51Lj and 51Rj of the travel motors 51L and 51R. When a detection signal corresponding to the depression of the braking pedal is inputted from the braking switch 79, the controller 20 inputs a control signal into the braking solenoid valve 56 to switch the braking solenoid valve 56 to the second position to allow hydraulic fluid to pass therethrough. With this, the hydraulic fluid from the main fluid passage 45 is supplied to the braking actuators 55 via the braking solenoid valve 56, the braking actuators 55 brake the rotation of the output shafts 51Lj and 51Rj of the travel motors 51L and 51R, the working machine 1 slows down, and the working machine 1 stops.

[0133] When the braking pedal is not depressed and the detection signal is not inputted anymore from the braking switch 79, the controller 20 stops the input of the control signal into the braking solenoid valve 56 to switch the braking solenoid valve 56 to the first position. With this, the hydraulic fluid from the main fluid passage 45 is not supplied to the braking actuators 55 via the braking solenoid valve 56, and the braking actuators 55 do not brake the rotation of the output shafts 51Lj and 51Rj of the travel motors 51L and 51R. The controller 20 may also be configured or programmed to, regardless of whether the braking pedal is depressed or not, switch the position of the braking solenoid valve 56 to brake the rotation of the output shafts 51Lj and 51Rj of the travel motors 51L and 51R and stop the rotation.

[0134] FIG. 3 is a block diagram showing an electrical configuration of the working machine 1. The working machine 1 includes elements shown in FIG. 3. The controller 20 includes a processing circuit including one or more processors. The working machine 1 includes the controller 20 which is configured or programmed to perform various controls relating to the working machine 1. The controller 20 is connected to the other elements shown in FIG. 3 in a communicable manner via in-vehicle network(s) such as CAN, ISOBUS, LIN and / or FlexRay.

[0135] The controller 20 includes at least one of one or more internal memories, analog circuits, digital circuits, and the like. The analog circuits and the digital circuits include one or more processors. The processor(s) included in the controller 20 include, for example, a central processing unit (CPU), a graphics processing unit (GPU), a digital signal processor (DSP), a field programmable gate array (FPGA), an application specific integrated circuit (ASIC) and / or the like.

[0136] The internal memory (memories) of the controller 20 is / are each a volatile or nonvolatile memory which stores software program(s) to be executed by one or more processors and various data. The controller 20 uses a predetermined storage area of the internal memory as a buffer to temporarily store information and data.

[0137] A storing device (memory and / or storage) 21 includes a nonvolatile memory and / or the like. The storing device 21 also stores software program(s) to be executed by one or more processors of the controller 20 and various data. The storing device 21 also stores control data corresponding to various attachments 11.

[0138] The one or more processors of the controller 20 read(s) software program(s) and control data from the internal memory and / or the storing device 21, and perform various processes based on the software program(s) and the control data. The one or more processors of the controller 20 may perform various processes based on a predetermined logic circuit.

[0139] Note that a plurality of physically separated processors of the controller 20 may operate together to perform various processes, and the configuration of the controller 20 is not limited to the above described configuration. In such a case, the plurality of processors are respectively provided in one or more computers which are physically separated from the working machine 1, and are connected in a communicable manner via a network such as a in-vehicle network, LAN, WAN, and / or the Internet.

[0140] The following configuration may be used: the above described software program(s) is / are stored in a storage medium (nonvolatile memory such as HDD, SSD, CD-ROM, DVD-ROM) connected in a communicable manner with the controller 20 and / or in external device(s) such as a server and / or the like connected via the above described network(s), and is / are installed from such storage medium(media) and / or the external device(s) into the internal memory or the storing device 21.

[0141] A user interface 22 is, for example, a terminal device (computer) in the form of a touchscreen or a tablet including a display. The user interface 22 is provided in the vicinity of the seat 8 inside the cabin 3 (FIG. 15). The controller 20 causes the user interface 22 to output (display) various information relating to the working machine 1 stored in the internal memory and / or the storing device 21 to the driver or the like (or to other user(s)).

[0142] The driver or the like of the working machine 1 inputs various information via the user interface 22. For example, information indicating the attachment 11 attached to the working device 4 can be inputted via the user interface 22. The controller 20 causes the internal memory and / or the storing device 21 to store the information inputted via the user interface 22. The user interface 22 functions as an input interface and an output interface. The user interface 22 may include input device(s) such as at least one manual operator, e.g., a button, a switch, a dial, and / or a slider, and / or a microphone, and output device(s) such as a speaker.

[0143] A communicator 24 shown in FIG. 3 includes a communication circuit to wirelessly communicate with external device(s) such as a server, a terminal device and / or a portable device via the Internet, a wireless LAN and / or the like. The portable device is, for example, a smartphone or a tablet. The communicator 24 may include a receiver compliant with a satellite positioning system to receive radio waves from satellites. The communicator 24 also functions as an input interface and an output interface.

[0144] A beacon scanner 23 is a receiver to receive wireless signals compliant with a near field communication standard. Specifically, the beacon scanner 23 receives wireless signals (beacon signals) compliant with Bluetooth (registered trademark) Low Energy which is a near field communication standard. As shown in FIG. 15, the beacon scanner 23 is provided at a front portion of the machine body 2. In the case where a beacon transmitter 19 is provided on the attachment 11 attached to the hitch 16, the beacon scanner 23 receives wireless signals transmitted from the beacon transmitter 19. The beacon scanner 23 is an input interface.

[0145] In the case where the attachment 11 attached to the hitch 16 includes an electric circuit including a processor such as CPU, an electric harness connected to the electric circuit is connected to an AUX connector 28. The AUX connector 28 may communicate in a wired manner with the attachment 11, and functions as an input interface and an output interface.

[0146] An attaching switch 29a, a detaching switch 29b, an accelerator 7, the speed-change switch 75, the braking switch 79, the travel manual operator 57, the work manual operator 67, and an AUX manual operator 73 are provided in the vicinity of the seat 8 inside the cabin 3, and are operated by the driver of the working machine 1.

[0147] The attaching switch 29a is operated to attach the attachment 11 to the hitch 16. The detaching switch 29b is operated to allow the attachment 11 to be detached from the hitch 16. As another example, a single operating switch may be used as an attaching switch and a detaching switch.

[0148] A latch control valve 35 is a three-position solenoid switching valve including three positions and a solenoid to be energized in response to a control signal inputted thereto to switch between the positions, and controls the latch cylinder 17. As shown in FIG. 4, the latch control valve 35 is connected to the latch cylinder 17 by fluid passages and is also connected to the main fluid passage 45. The latch control valve 35 is switchable between (i) a neutral position 35c to block hydraulic fluid from the fluid passage 45, (ii) a first position 35a to allow hydraulic fluid to be supplied to the cap-side chamber of the latch cylinder 17 to cause the latch cylinder 17 to extend, and (iii) a second position 35b to allow hydraulic fluid to be supplied to the rod-side chamber of the latch cylinder 17 to cause the latch cylinder 17 to retract.

[0149] For example, the driver of the working machine 1 operates the work manual operator 67 (FIG. 1) to lower the arms 10 and the hitch 16, and operates the travel manual operator 57 (FIG. 2) to cause the machine body 2 to travel forward very slowly, thus causing the front surface of the bracket 30 of the hitch 16 to contact the base plate 9 (FIG. 16) of the attachment 11 placed on the ground J. Then, when the driver operates the attaching switch 29a, the controller 20 inputs a control signal into the latch control valve 35 to switch the latch control valve 35 from the neutral position 35c to the first position 35a. With this, the latch cylinder 17 extends, the latching mechanisms 31 switch to the latching state, and the attachment 11 is attached (fixed) to the hitch 16.

[0150] The driver, while the working machine 1 is in the stopped state, operates the work manual operator 67 to lower the arms 10 and the hitch 16 to cause the attachment 11 attached to the hitch 16 to contact the ground. Then, when the driver operates the detaching switch 29b, the controller 20 inputs a control signal into the latch control valve 35 to switch the latch control valve 35 from the neutral position 35c to the second position 35b. With this, the latch cylinder 17 retracts, the latching mechanisms 31 switch to the unlatching state, and the attachment 11 is allowed to be detached from the hitch 16. In this state, when the driver operates the travel manual operator 57 to cause the machine body 2 to travel rearward, the attachment 11 is detached from the hitch 16.

[0151] A speed detector 36 shown in FIG. 3 detects the travel speed of the working machine 1 (machine body 2). Specifically, the speed detector 36 includes, for example, rotation speed sensor(s) to detect the rotation speed of the travel motors 51L and 51R (FIG. 2) and a calculator, and the calculator calculates the travel speed based on a detection signal from the rotation speed sensor(s). Note that the calculator may not be provided in the speed detector 36, and the controller 20 may calculate the travel speed based on the detection signal from the rotation speed sensor.

[0152] As another example, the speed detector 36 (or the controller 20) may calculate the travel speed of the working machine 1 based on the operation amount of the travel operating lever 57a detected by the sensor 57b of the travel manual operator 57. Alternatively, the speed detector 36 (or the controller 20) may calculate the position of the machine body 2 at regular intervals based on signals received by the receiver of the communicator 24 from satellites of a satellite positioning system, and calculate the travel speed of the working machine 1 based on time-series position data of the machine body 2. The configuration to detect the travel speed of the working machine 1 is not limited to the above, and a speed detector to detect the travel speed by some other known method may be used.

[0153] An arm position detector 37 and a tilt angle detector 38 include an inertial measurement unit (IMU), a potentiometer, or a sensor such as a gyroscope sensor. The arm position detector 37 detects at least the swinging angle of the arms 10. The controller 20, based on the detection result from the arm position detector 37, detects the position of the distal ends of the arms 10 and the hitch 16 in the up-down direction and in the front-back direction and also detects the position of the attachment 11 attached to the hitch 16 in the up-down direction and in the front-back direction.

[0154] Specifically, the controller 20 detects the position of a work surface 11w (FIG. 15) of the attachment 11 attached to the hitch 16 at least in the up-down direction and the front-back direction, based on the detection result from the arm position detector 37. The work surface 11w is an imaginary surface defined at the contact portion of the attachment 11 that contacts a target object during work, and is a reference surface for the posture of the attachment 11.

[0155] The tilt angle detector 38 detects at least the tilt angle (swinging angle) of the hitch 16. The controller 20 detects the orientation of the hitch 16 and the attachment 11 attached to the hitch 16, based on a detection result from the tilt angle detector 38. Specifically, the controller 20 detects the orientation of the work surface 11w of the attachment 11 attached to the hitch 16 based on the detection result from the tilt angle detector 38.

[0156] In addition to the foregoing pressure detectors 70a and 70b, the working machine 1 includes pressure detectors 49a, 49b, 49c, 49d, 68a, 68b, 68c, and 68d as elements to detect the pressure of hydraulic fluid or pilot fluid. Each of the pressure detectors 49a to 49d and 68a to 68d includes a pressure sensor.

[0157] The pressure detectors 49a, 49b, 49c and 49d are provided in the circuit fluid passages 53a and 53b. The pressure detector 49a detects the pressure of hydraulic fluid acting on a first port 51a of the first travel motor 51L as a first motor pressure. The pressure detector 49b detects the pressure of hydraulic fluid acting on a second port 51b of the first travel motor 51L as a second motor pressure. The pressure detector 49c detects the pressure of hydraulic fluid acting on a third port 51c of the second travel motor 51R as a third motor pressure. The pressure detector 49d detects the pressure of hydraulic fluid acting on a fourth port 51d of the second travel motor 51R as a fourth motor pressure.

[0158] The controller 20 determines the travel direction, the travel speed, whether straight travel is being performed, whether turning is being performed, the turn direction, and the type of turn relating to the working machine 1 based on the first to fourth motor pressures detected by the pressure detectors 49a to 49d. Alternatively, the controller 20 may determine the travel direction, the travel speed, whether straight travel is being performed, whether turning is being performed, the turn direction, and the type of turn relating to the working machine 1 based on the operation direction and on the operation amount of the travel operating lever 57a determined based on a detection signal from the sensor 67b.

[0159] As shown in FIG. 1, the pressure detectors 68a, 68b, 68c and 68d are respectively provided in the fluid passages 64a, 64b, 65a and 65b. The pressure detectors 68a and 68b detect the pressure of hydraulic fluid acting from the lift control valve 60A to the lift cylinders 14 as a lift pressure. The controller 20 refers to the lift pressure and, for example, adjusts the opening of the solenoid valves 76a and 76b. The pressure detectors 68c and 68d detect the pressure of hydraulic fluid acting from the tilt control valve 60B to the tilt cylinders 15 as a tilt pressure. The controller 20 refers to the tilt pressure and, for example, adjusts the opening of the tilt solenoid valves 77a and 77b.

[0160] The accelerator 7 is operable to define and change the rotation speed of the prime mover 6, and includes an acceleration operator and an acceleration sensor. The acceleration operator is, for example, an operation structure (manual operator) such as a lever, a pedal, a dial, or a slider. The acceleration sensor outputs a signal corresponding to the operation position of the acceleration operator. The controller 20 controls the driving of the prime mover 6 and defines and changes the rotation speed of the prime mover 6 based on an acceleration signal outputted from the acceleration sensor.

[0161] The configurations of the speed-change switch 75, the speed-change solenoid valve 59, the braking switch 79, the braking solenoid valve 56, the travel manual operator 57, the operating valves 54a to 54d, the work manual operator 67, the lift solenoid valves 76a and 76b, the tilt solenoid valves 77a and 77b, and the AUX solenoid valves 76a and 76b have been described already. The AUX manual operator 73 is operable to control the supply of hydraulic fluid to the hydraulic actuator 27 of the attachment 11. The AUX manual operator 73 includes, in addition to the foregoing AUX output switch 73b, an AUX mode switch 73a, an AUX steady switch 73c, and an AUX volume switch 73d.

[0162] The AUX mode switch 73a is turned ON to start an AUX mode in which an attachment 11 including a hydraulic actuator 27 is allowed to be used with the working machine 1, and is turned OFF to end the AUX mode. When the AUX mode switch 73a is turned ON to start the AUX mode and then the AUX output switch 73b is turned ON, the controller 20 opens one of the AUX solenoid valves 77a and 77b to allow hydraulic fluid to be supplied from the AUX control valve 60C to the corresponding AUX port 25.

[0163] In so doing, if the first AUX port 25a and the first hydraulic port of the attachment 11 are connected by the external fluid passage 26a and the second hydraulic port of the attachment 11 and the second AUX port 25b are connected by the external fluid passage 26b, (i) hydraulic fluid from the AUX control valve 60C flows through the first AUX port 25a, the external fluid passage 26a, and the first hydraulic port of the attachment 11 and is supplied to the hydraulic actuator 27 of the attachment 11, and (ii) hydraulic fluid discharged from the hydraulic actuator 27 flows through the second hydraulic port of the attachment 11, the external fluid passage 26b, and the second AUX port 25b and returns to the AUX control valve 60C. In some cases, hydraulic fluid from the AUX control valve 60C flows through the second AUX port 25b, the external fluid passage 26b, and the second hydraulic port of the attachment 11 and is supplied to the hydraulic actuator 27, whereas hydraulic fluid from the hydraulic actuator 27 flows through the first hydraulic port of the attachment 11, the external fluid passage 26a, and the first AUX port 25a and returns to the AUX control valve 60C.

[0164] The controller 20 ends the AUX mode when the AUX mode switch 73a is turned OFF after the AUX output switch 73b is turned OFF, the AUX solenoid valves 77a and 77b are closed, and the supply of hydraulic fluid from the AUX control valve 60C to the corresponding AUX port 25 is stopped.

[0165] The AUX steady switch 73c is turned ON to start a steady output mode in which a fluid flow rate (which is the amount of hydraulic fluid supplied per unit time to the hydraulic actuator 27) is kept constant, and is turned OFF to stop the steady output mode. When the AUX steady switch 73c is turned ON while the AUX mode is being performed to supply hydraulic fluid to the hydraulic actuator 27, the controller 20 starts the steady output mode and to maintain the opening of the AUX control valve 60C to keep constant the fluid flow rate of hydraulic fluid supplied to the hydraulic actuator 27. After that, when the AUX steady switch 73c is turned OFF, the controller 20 ends the steady output mode, does not maintain the opening of the AUX control valve 60C anymore, and does not keep constant the fluid flow rate of hydraulic fluid supplied to the hydraulic actuator 27 anymore.

[0166] The AUX volume switch 73d is operated to change the supply amount of hydraulic fluid to the hydraulic actuator 27. The AUX volume switch 73d outputs an electric signal corresponding to the manual operation of a control knob such as a slider operating switch, a dial, or a push button. When the AUX volume switch 73d is operated and an electric signal corresponding to the operation is inputted into the controller 20 when the steady supply mode is not performed, the controller 20 detects the operation position of the AUX volume switch 73d based on the electric signal, and inputs a control signal with an electric current value corresponding to the operation position into the AUX solenoid valves 78a and 78b. With this, the openings of the AUX solenoid valves 78a and 78b are defined and / or changed, the pilot pressure acting on the AUX control valve 60C changes, the opening of the AUX control valve 60C is defined and / or changed, the supply amount of hydraulic fluid from the AUX control valve 60C to the hydraulic actuator 27 is defined and / or changed, and the AUX pressure is also defined and / or changed.

[0167] After the attachment 11 is attached to the hitch 16, the controller 20 identifies the attachment 11. For example, in the case where the attached attachment 11 includes a beacon transmitter 19, a wireless signal including information indicating the attachment 11 is transmitted at regular intervals from the beacon transmitter 19, and therefore the wireless signal is received by the beacon scanner 23. The controller 20 identifies the attached attachment 11 based on the information included in the wireless signal received by the beacon scanner 23. For example, the information transmitted by the beacon transmitter 19 includes identification information of the attachment 11 provided with the beacon transmitter 19. The storing device 21 stores pieces of attachment information indicating a plurality of attachments 11 attachable to the working device 4 and pieces of control information defined for the respective plurality of attachments 11, which are associated with each other.

[0168] FIG. 5 illustrates an example, in the form of a table, of pieces of attachment information of the plurality of attachments 11 attachable to the working device 4 and their corresponding pieces of control information. The pieces of information shown in FIG. 5 are stored in a predetermined storage area of the storing device 21.

[0169] The attachment information shown in FIG. 5 includes identification information (ID), name, icon data, model number, and specifications of a corresponding attachment 11. The specifications include the size of the attachment 11, the position and the orientation of the work surface 11w (FIG. 15) relative to the base plate 9 (FIG. 16) of the attachment 11, the presence or absence of the hydraulic actuator 27, and / or the like. The specifications in the attachment information of an attachment 11 provided with a hydraulic actuator 27 may include specifications information such as the type and / or the capacity of the hydraulic actuator 27.

[0170] The control information includes the default value of a fluid flow rate which is the amount of hydraulic fluid supplied per unit time to the hydraulic actuator 27 in the corresponding attachment 11, an appropriate range of the AUX pressure for work, posture information indicating the appropriate posture range of the attachment 11 for work, a posture change degree to which the posture of the attachment 11 is automatically changed, and / or the like. The posture information includes the range of position and the range of orientation (tilt angle) of the attachment 11 in the vertical direction. The posture change degree includes the degree of change in position of the attachment 11 and the degree of change in orientation of the attachment 11 in the vertical direction.

[0171] Control information for a drive, contact work attachment 11 such as a sweeper includes the default value of the fluid flow rate, the appropriate range of the AUX pressure, posture information, and posture change degree. Since follower attachments 11 such as a bucket and a pallet fork do not need to be supplied with hydraulic fluid, the control information therefor does not include the default value of the fluid flow rate or the appropriate range of the AUX pressure, and also does not include posture information or posture change degree. With regard to non-contact work attachments 11 such as a spreader and holding work attachments 11 such as a grapple, even if the posture (position and / or orientation) is changed during work, the AUX pressure does not change. Therefore, the control information therefor does not include the appropriate range of the AUX pressure, posture information, or posture change degree.

[0172] As another example, attachment information may include at least one of the identification information (ID), name, icon, or model number of the attachment 11, and / or other information such as a nickname and / or the serial number of the attachment 11. The posture information may include the position (height) and the orientation (tilt angle) of the attachment 11 in the vertical direction during work, or may only include the position. At least one of the appropriate range of the AUX pressure or the posture information may be included in the control information.

[0173] The controller 20 reads attachment information and control information corresponding to the information (identification information) about the attachment 11 received from the beacon transmitter 19 from the storing device 21. The controller 20 identifies the type of the attachment 11 and determines whether the attachment 11 includes a hydraulic actuator 27 based on the read attachment information.

[0174] In the case where an electric circuit including a controller such as a CPU is provided in the attachment 11, the controller 20 may, after an electric harness connected to the electric circuit is connected to the AUX connector 28, receive information indicating the attachment 11 transmitted from the controller via the electric harness and the AUX connector 28. The controller 20 may then read control information corresponding to the attachment 11 indicated by the received information from the storing device 21.

[0175] The information transmitted from the beacon transmitter 19 or from the controller of the attachment 11 may include information indicating the attachment 11 and control information corresponding to the attachment 11. In such a case, when the controller 20 receives information from the beacon transmitter 19 or from the controller of the attachment 11, the controller 20 reads information indicating the attachment 11 and control information from the received information. Note that, in addition to or instead of the beacon transmitter 19 and the beacon scanner 23, a transmitter such as a Radio Frequency Identification (RFID) tag may be provided in or on the attachment 11 and a receiver to receive wireless signals issued by the transmitter may be provided in or on the working machine 1.

[0176] Additionally or alternatively, the controller 20 may read from the storing device 21 the data of a plurality of icons C1, C2, C3, C4, C5, C6, and so on indicating respective attachments 11 attachable and detachable to and from the working device 4 and cause the user interface 22 to display the plurality of icons C1, C2, C3, C4, C5, C6, and so on on a predetermined input screen G2 as illustrated in FIG. 6. In the example of FIG. 6, the controller 20 causes the plurality of icons C1, C2, C3, C4, C5, C6, and so on and the pieces of identification information A1, A2, A3, A4, A5, A6, and so on of the attachments 11 corresponding to the plurality of icons C1, C2, C3, C4, C5, C6, and so on to be displayed on the input screen G2.

[0177] The controller 20 may be configured or programmed to, when the driver or the like performs an operation on the user interface 22 to select an icon that represents the attachment 11 attached to the working device 4 from the plurality of icons C1, C2, C3, C4, C5, C6, and so on displayed on the input screen G2, accept the selected icon (icon C3 in FIG. 6) as information indicating the attachment 11 and read the control information for the attachment 11 corresponding to the selected icon from the storing device 21.

[0178] Additionally or alternatively, the following configuration may be used: the driver or the like manually inputs information such as the name of the attachment 11 attached to the working device 4 into the input screen displayed on the user interface 22. The controller 20 may then receive the manually inputted information from the user interface 22, and read the control information corresponding to the information from the storing device 21.

[0179] Additionally or alternatively, the following configuration may be used: an input screen as indicated in FIG. 6 or an input screen for manual input is displayed on a display of an external device such as a smartphone, and information indicating the attachment 11 corresponding to the icon selected by the user via the input screen or manually inputted information indicating the attachment 11 is transmitted from the external device and received by (inputted into) the communicator 24. The controller 20 may then read, from the storing device 21, the control information corresponding to the information indicating the attachment 11 received by the communicator 24.

[0180] The controller 20 is configured or programmed to, in the case where the read control information includes the default value of the fluid flow rate, control the AUX solenoid valves 78a and 78b and the AUX control valve 60C such that hydraulic fluid is supplied to the hydraulic actuator 27 at the default fluid flow rate when the AUX output switch 73b is operated, for example. The controller 20 is also configured or programmed to, in the case where the read control information includes the appropriate range of the AUX pressure, posture information, and / or posture change degree, perform a posture control to control the working device 4 to adjust the posture of the attachment 11 while work is performed by the attachment 11 (at the start of work and / or during work) according to the appropriate range of the AUX pressure, posture information, and posture change degree, and according to the AUX pressure.

[0181] FIG. 7 is a flowchart showing the operation of the working machine 1 of the first example embodiment. The steps in FIG. 7 are repeatedly performed by the controller 20 based on software program(s) stored in the internal memory and / or the storing device 21. The same applies to the steps of flowcharts in other drawings (described later). For convenience, in each flowchart, “attachment” is indicated as “ATT”, and “actuator” is indicated as “ACT”.

[0182] In response to the operation of the attaching switch 29a, the controller 20 actuates the latch cylinder 17 to attach the attachment 11 to the hitch 16 (S1), then acquires input information indicating the attachment 11 inputted thereto from one of the input interfaces 23, 28, 22 and 24, and acquires attachment information and control information corresponding to the attachment 11 indicated by the input information from the storing device 21 (S2). The controller 20 then identifies the attachment 11 based on the acquired attachment information (S3). In so doing, the controller 20 identifies the type of the attachment 11, whether the attachment 11 includes a hydraulic actuator 27, and / or the like.

[0183] In the case where the attachment 11 attached to the hitch 16 is a drive attachment 11, the controller 20 determines that the attached attachment 11 includes a hydraulic actuator 27 (YES at S4). Furthermore, external fluid passages 26 are connected to the AUX ports 25 and the hydraulic ports of the attachment 11 by the driver or the like.

[0184] The controller 20 then starts the AUX mode in response to turning ON of the AUX mode switch 73a, and then starts supplying hydraulic fluid from the AUX control valve 60C to the corresponding AUX port 25 in response to turning ON of the AUX output switch 73b (S5). With this, hydraulic fluid is supplied from the AUX port 25 to the hydraulic actuator 27 of the attachment 11 via the corresponding external fluid passage 26 and the like to actuate the hydraulic actuator 27, so that the attachment 11 is driven. In so doing, the controller 20 actuates the AUX solenoid valves 78a and 78b to define the opening of the AUX control valve 60C such that the fluid flow rate of hydraulic fluid toward the AUX port 25 is the default value indicated by the control information.

[0185] After that, the controller 20, in response to the driver's operation of the work operating lever 67a, controls the opening of the lift solenoid valves 76a and 76b and the tilt solenoid valves 77a and 77b to switch the position of at least one of the lift control valve 60A or the tilt control valve 60B to cause at least one of the lift cylinders 14 or the tilt cylinders 15 to extend or retract to cause at least one of the arms 10 or the hitch 16 to swing, thus setting the attachment 11 in a posture in which work can be performed. The posture of the attachment 11 set here is included in the appropriate posture range for work indicated by the posture information included in the control information for the attachment 11.

[0186] The controller 20 then, in response to the driver's operation of the travel operating lever 57a, controls the opening of the operating valves 54a to 54d to define the angle of the swash plates of the travel pumps 50L and 50R to allow the travel pumps 50L and 50R to deliver hydraulic fluid to rotate the travel motors 51L and 51R to drive the traveling devices 5, thus causing the machine body 2 (working machine 1) to travel. With this, the working machine 1 starts traveling with the attachment 11 performing work. During work, since the rotation speed of the output shafts 51Lj and 51Ri of the travel motors 51L and 51R is set to the first speed stage, the working machine 1 travels in the low-speed mode (creep mode).

[0187] The controller 20 is configured or programmed to, for example, if determining that the posture (position and orientation) of the attachment 11 detected by the arm position detector 37 and the tilt angle detector 38 is within the range of the appropriate posture for work indicated by the posture information, determine that work by the attachment 11 has started (S6).

[0188] Additionally or alternatively, the controller 20 may be configured or programmed to determine that the work by the attachment 11 has started if the controller 20 determines that, while the posture of the attachment 11 is within the range of the appropriate posture for work, the machine body 2 has traveled forward in the low-speed mode based on the detection result(s) from at least one of the speed detector 36 or the pump pressure detectors 49a to 49d. Additionally or alternatively, the controller 20 may be configured or programmed to determine that work by the attachment 11 has started if determining that the AUX pressure detected by the pressure detector(s) 70a and / or 70b is within the appropriate range indicated by the control information.

[0189] After work has started, the controller 20 determines, for example, that the attachment 11 indicated by the input information from the input interface 23, 28, 22 or 24 is a specific attachment (YES at S7), that the steady output mode is currently performed (YES at S8), and that the operation amount of the work operating lever 67a by the driver is less than a predetermined value (YES at S9). In such a case, the controller 20 consults the input information from the beacon scanner 23 or the like and the attachment information acquired from the storing device 21, and determines whether there is a possibility that the attachment 11 will perform work while the working machine 1 is not traveling. In other words, the controller 20 checks the type of the attached attachment 11, and determines whether or not work by the attached attachment 11 can be performed when the working machine 1 is not traveling.

[0190] In the case where there is a possibility that work will be performed by the attachment 11 when the working machine 1 is not traveling (NO at S10), the controller 20 performs a posture control to control the working device 4 according to the AUX pressure to adjust the posture of the attachment 11 (S12). In the case where there is no possibility that work will be performed by the attachment 11 when the working machine is not traveling (YES at S10), the controller 20 consults the travel speed detected by the speed detector 36. Then, if the travel speed is equal to or greater than a predetermined value (YES at S11), the controller 20 performs the posture control (S12).

[0191] In the case where the attachment 11 indicated by the input information from the beacon scanner 23 or the like is not a specific attachment (NO at S7), the controller 20 does not perform the posture control. The specific attachment 11 is an attachment 11 which includes a hydraulic actuator 27 to be actuated by hydraulic fluid supplied from the working machine 1, which performs work on a target object in contact therewith, and which changes in AUX pressure (i.e., load) when the posture thereof is changed by the working device 4 during work.

[0192] In the present example embodiment, examples of the specific attachments 11 include sweepers, snow blowers, snow blades, angle brooms, mowers, plows, skid cutters, breakers, earth augers. Examples of the specific attachments 11 do not include spreaders, grapples, buckets, or pallet forks. The pieces of information indicating the specific attachments 11 are stored in the internal memory of the controller 20 and / or in a predetermined storage area of the storing device 21. The controller 20 reads the stored information and identifies specific attachments 11, and determines whether or not the attachment 11 indicated by the attachment information, i.e., the attachment 11 attached to the hitch 16, is a specific attachment 11.

[0193] The controller 20 may be configured or programmed to determine that the attached attachment 11 is a specific attachment 11 if the control information corresponding to the input information from the beacon scanner 23 or the like includes at least one of the appropriate range of the AUX pressure, the posture information, or the posture change degree (YES at S7). The controller 20 may be configured or programmed to determine that the attached attachment 11 is not a specific attachment 11 if the corresponding control information does not include the appropriate range of the AUX pressure, the posture information, or the posture change degree (NO at S7).

[0194] If the controller 20 is not in the steady output mode (NO at S8), the controller 20 does not perform the posture control. The controller 20 is configured or programmed to perform the posture control if the work operating lever 67a is operated and the operation amount is less than a predetermined value (YES at S9) or if the work operating lever 67a is not operated (YES at S9), but not perform the posture control if the operation amount of the work operating lever 67a is equal to or greater than a predetermined value (NO at S9). That is, when the driver operates the work operating lever 67a to cause the arms 10 or the hitch 16 of the working device 4 to swing, the operation amount of the work operating lever 67a reaches a predetermined value or greater, and therefore the controller 20 does not perform the posture control but causes the arms 10 and / or the hitch 16 to swing to change the posture of the attachment 11 according to the operation direction and the operation amount of the work operating lever 67a.

[0195] In the case where there is no possibility that work will be performed by the attachment 11 when the working machine 1 is not traveling (YES at S10), the controller 20 does not perform the posture control when the travel speed of the working machine 1 is less than a predetermined value (NO at S11). That is, when the working machine 1 is not traveling (travel speed is 0) and when the working machine 1 is moving at very low speed, the posture control is not performed.

[0196] FIG. 8 is a flowchart showing details of the posture control at step S12 of FIG. 7. When work is being performed by a specific attachment 11 on the working machine 1, the controller 20, after starting the posture control, detects the AUX pressure applied to the hydraulic actuator 27 of the attachment 11 (pressure of hydraulic fluid flowing through the AUX fluid passages 66a and 66b) via the pressure detectors 70a and 70b (S21). The controller 20 then compares the detected AUX pressure and the appropriate range included in the control information for the attachment 11.

[0197] If the AUX pressure is above the appropriate range (YES at S22), the controller 20 controls the lift solenoid valve 76b to switch the lift control valve 60A to the second position 61e to cause the lift cylinders 14 to extend to cause the arms 10 to swing upward, thus raising the attachment 11 (S23). In so doing, the controller 20 causes the arms 10 to swing upward by a predetermined angle according to the AUX pressure to raise the attachment 11 by a predetermined displacement.

[0198] For example, at step S23, the controller 20 may determine the electric current value of the control signal to be inputted into the lift solenoid valve 76b and the input time for which the control signal is inputted such that the AUX pressure falls within the appropriate range, according to the difference between the AUX pressure and the upper limit of the appropriate range (first difference) and the difference between the AUX pressure and the lower limit of the appropriate range (second difference). The controller 20 may then input the control signal with the determined electric current value into the lift solenoid valve 76b for the determined input time to actuate the lift control valve 60A and the lift cylinders 14 to cause the arms 10 and the attachment 11 to inch upward. This eliminates or reduces the likelihood that the attachment 11 will be raised to too great an extent.

[0199] That is, the controller 20 is configured or programmed such that, if the load on the attachment 11 increases during work performed by the attachment 11, cause the arms 10 to swing upward to move the attachment 11 in a direction away from the target object, thus adjusting the position of the attachment 11 relative to the target object (i.e., the position (height) of the attachment 11 in the vertical direction). With this, even if the height of the target object changes such that the height increases (such that the target object is raised), the load on the attachment 11 does not become excessive, and the attachment 11 and the hydraulic actuator 27 do not stop because of the overload.

[0200] At step S23, the controller 20 may raise the attachment 11 according to the range of position in the posture information included in the control information corresponding to the attachment 11. For example, the controller 20 determines the electric current value of the control signal inputted into the lift solenoid valve 76b and the input time for which the control signal is inputted such that the position of the attachment 11 (position of the work surface 11w) determined from the detection result from the arm position detector 37 falls within the range of position in the posture information. The controller 20 then inputs the control signal with the determined electric current value into the lift solenoid valve 76b for the determined input time to actuate the lift control valve 60A and the lift cylinders 14, thus causing the arms 10 and the attachment 11 to inch upward.

[0201] At step S23, the controller 20 may determine the control signal inputted into the lift solenoid valve 76b such that the attachment 11 is raised to the degree of change in position included in the control information for the attachment 11. In such a case, even when the attachment 11 is raised to the degree of change in position, the AUX pressure may still not be within the appropriate range, but as long as work is not ended (NO at S13 of FIG. 7), the controller 20 repeats step S8 and subsequent steps to raise the attachment 11 by the amount of change in position at step S23 again. Since step S23 is repeated in this manner, the AUX pressure is brought into the appropriate range.

[0202] On the contrary, if the AUX pressure is below the appropriate range (YES at S24), the controller 20 controls the lift solenoid valve 76a to switch the lift control valve 60A to the first position 61d to cause the lift cylinders 14 to retract to cause the arms 10 to swing downward, thus lowering the attachment 11 (S25). In so doing, the controller 20 causes the arms 10 to swing downward by a predetermined angle according to the AUX pressure to lower the attachment 11 by a predetermined displacement.

[0203] For example, also at step S25, the controller 20 may determine the electric current value of the control signal inputted into the lift solenoid valve 76a and the input time for which the control signal is inputted such that the AUX pressure falls within the appropriate range, according to the difference between the AUX pressure and the upper limit of the appropriate range (first difference) and the difference between the AUX pressure and the lower limit of the appropriate range (second difference). The controller 20 may then input the control signal with the determined electric current value into the lift solenoid valve 76a for the determined input time to actuate the lift control valve 60A and the lift cylinders 14 to cause the arms 10 and the attachment 11 to inch downward.

[0204] That is, the controller 20 is configured or programmed to, if the load on the attachment 11 decreases during work performed by the attachment 11, cause the arms 10 to swing downward to move the attachment 11 in a direction approaching the target object, thus adjusting the position of the attachment 11 relative to the target object. With this, even when the height of the target object changes such that the height decreases (such that the target object is depressed), it is possible to cause the attachment 11 to contact the target object in a workable manner.

[0205] At step S25, the controller 20 may, according to the range of position in the posture information corresponding to the attachment 11, lower the attachment 11 (cause to inch downward) such that the position of the attachment 11 falls within the range of position. The controller 20 may lower the attachment 11 to the degree of change in position corresponding to the attachment 11.

[0206] At steps S23 and S25, the arms 10 swing and therefore the attachment 11 is raised or lowered as well as the orientation of the attachment 11 relative to the target object is changed to some extent. In this regard, the controller 20 causes the hitch 16 to swing as the attachment 11 is raised or lowered (swing in a linked manner with the attachment 11) to adjust the orientation of the attachment 11 (orientation of the work surface 11w) relative to the target object to maintain the relative orientation. In so doing, for example, in the case of a specific attachment 11 such as a sweeper, the work surface 11w is kept parallel to the target object such as the ground J and kept horizontal.

[0207] Specifically, at step S23, the controller 20 determines the electric current value of the control signal inputted into the tilt solenoid valve 77a and the input time for which the control signal is inputted, according to the electric current value of the control signal inputted into the lift solenoid valve 76b. The controller 20 then inputs the control signal with the determined electric current value into the tilt solenoid valve 77a for the determined input time to switch the tilt control valve 60B to the first position 62d to cause the tilt cylinders 15 to extend to cause the hitch 16 to swing such that the hitch 16 inches downward, thus adjusting the orientation of the attachment 11.

[0208] At step S25, the controller 20 determines the electric current value of the control signal inputted into the tilt solenoid valve 77b and the input time for which the control signal is inputted, according to the electric current value of the control signal inputted into the lift solenoid valve 76a. The controller 20 then inputs the control signal with the determined electric current value into the tilt solenoid valve 77b for the determined input time to switch the tilt control valve 60B to the second position 62e to cause the tilt cylinders 15 to retract to cause the hitch 16 to swing such that the hitch 16 inches upward, thus adjusting the orientation of the attachment 11.

[0209] At steps S23 and S25, the controller 20 may, according to the AUX pressure and / or the type or the like of the attachment 11, adjust only the position (position in the up-down direction) of the attachment 11 without adjusting the orientation of the attachment 11, adjust only the orientation of the attachment 11 without adjusting the position of the attachment 11, or adjust both the orientation and the position of the attachment 11. That is, the controller 20 may adjust at least one of the position or the orientation of the attachment 11 in the posture control.

[0210] At steps S23 and S25, the controller 20 may change the orientation of the attachment 11 in a direction away from the target object or in a direction toward the target object in a manner not linked to the position adjustment of the attachment 11. The controller 20 may adjust the orientation of the attachment 11 such that the AUX pressure falls within the appropriate range, and may adjust the orientation of the attachment 11 such that the orientation of the attachment 11 determined from the detection result from the tilt angle detector 38 falls within the range of posture in the posture information. The controller 20 may change the orientation of the attachment 11 to the degree of change in orientation included in the control information for the attachment 11.

[0211] The controller 20 may determine, for each of the plurality of attachments 11 attachable to the working device 4, whether to adjust the position of the attachment 11 and whether to adjust the orientation of the attachment 11 in the posture control, define also the posture information (position range, orientation range) and the posture change degree (degree of change in position, degree of change in orientation), and cause the storing device 21 to store control information including such defined pieces of information.

[0212] The controller 20 may then, at steps S23 and S25 of FIG. 8, using the control information corresponding to the attachment 11, cause the lift cylinders 14 to swing the arms 10 and / or cause the tilt cylinders 15 to swing the hitch 16 based not only on the AUX pressure but also on at least one of the type, the appropriate range, the posture information, or the posture change degree of the attachment 11 to adjust at least one of the position or the orientation of the attachment 11 relative to the target object.

[0213] Additionally or alternatively, at steps S23 and S25, for example, the controller 20 may calculate the first difference between the AUX pressure and the upper limit of the appropriate range and the second difference between the AUX pressure and the lower limit of the appropriate range and, if the smaller one of the above differences is less than a first threshold, cause the hitch 16 to swing to adjust only the orientation of the attachment 11. If the smaller one of the differences is greater than or equal to the first threshold and is less than a second threshold which is greater than the first threshold, the controller 20 may cause the arms 10 to swing to adjust only the position of the attachment 11. If the smaller one of the differences is greater than or equal to the second threshold and is less than a third threshold which is greater than the second threshold, the controller 20 may adjust the position of the attachment 11 and adjust the orientation of the attachment 11 in a manner not linked to the position adjustment. If the smaller one of the differences is greater than or equal to the third threshold, the controller 20 may adjust the position of the attachment 11 and adjust the orientation of the attachment 11 in a manner linked to the position adjustment.

[0214] After step S23 or step S25, the controller 20 ends the posture control and, if work has not ended (NO at S13 of FIG. 7), repeat step S8 and subsequent steps. Also in the case where the AUX pressure is within the appropriate range (NO at S22, and NO at S24 of FIG. 8), the controller 20 ends the posture control, and, if work has not ended (NO at S13 of FIG. 7), repeats step S8 and subsequent steps.

[0215] Note that, for example, when the controller 20 has stopped the supply of hydraulic fluid to the corresponding AUX port 25 (that is, to the hydraulic actuator 27 of the attachment 11) in response to turning OFF of the AUX output switch 73b, the controller 20 determines that work performed by the attachment 11 has ended (YES at S13 of FIG. 7).

[0216] Since the above-described posture control is performed, the working device 4 (arms 10, hitch 16) operates in a manner that does not correspond to the manual operation of the work operating lever 67a, so that the posture of the attachment 11 is changed. In so doing, for the driver of the working machine 1 or the like not to feel uncertainty, the controller 20, during the posture control, causes the user interface 22 to output (display) information indicating that the posture control is being performed.

[0217] FIG. 9 illustrates an example of a monitor screen G1 displayed on the user interface 22. The controller 20 causes the user interface 22 to display the monitor screen G1 while the working machine 1 is in operation. The monitor screen G1 displays pieces of information V1 to V6 indicating the state of the working machine 1 detected by sensors in or on the working machine 1, the current date and time, and pieces of information U1 and U2 indicating the attachment 11 identified by the controller 20. The controller 20 is configured or programmed to, when the controller 20 is performing the posture control of FIG. 8, cause the monitor screen G1 to display a piece of information U3 indicating that the posture control for the attachment 11 is being performed.

[0218] The controller 20 may cause the display of an external device such as a smartphone, instead of the user interface 22, to display (output) the monitor screen G1. In such a case, the controller 20 need only transmit display data of the monitor screen G1 and the foregoing piece of information U3 to the external device via the communicator 24, and cause the display of the external device to display the monitor screen G1 including the piece of information U3.

[0219] FIG. 10 is a flowchart showing operation of a working machine 1 of a second example embodiment. In the second example embodiment, the controller 20 selectively performs at least one of the posture control or a travel control in which the controller 20 controls the traveling devices 5 to adjust the traveling state of the machine body 2, based on the attachment 11 indicated by information inputted via the input interface(s) 23, 28, 22 and / or 24 and based on the AUX pressure (S14).

[0220] In FIG. 10, after start of work, if the controller 20 determines that the attachment 11 is a specific attachment (YES at S7), that the steady output mode is being performed (YES at S8), that the operation amount of the work operating lever 67a is less than a predetermined value (YES at S9), and that there is a possibility that the attachment 11 will perform work while the working machine 1 is not traveling (NO at S10), the controller 20 performs at least one of the posture control or the travel control (S14). If the controller 20 determines that there is no possibility that the attachment 11 will perform work while the working machine 1 is not traveling (YES at S10), if the travel speed is higher than or equal to a predetermined speed (YES at S11), the controller 20 performs at least one of the posture control or the travel control (posture control and / or travel control at S14).

[0221] FIG. 11 is a flowchart showing details of the posture control and / or travel control at step S14 in FIG. 10. The controller 20 detects the AUX pressure applied to the hydraulic actuator 27 of the attachment 11 via the pressure detectors 70a and 70b (S21) and, if the AUX pressure is above the appropriate range (YES at S22), the controller 20 selectively performs at least one of raising the attachment 11 (posture control) or reducing the travel speed of the machine body 2 (travel control) based on the attachment 11 (type of the attachment 11) indicated by the information inputted via the input interface(s) 23, 28, 22 and / or 24 and based on the AUX pressure (S26).

[0222] If the AUX pressure is below the appropriate range (YES at S24), the controller 20 selectively performs at least one of lowering the attachment 11 (posture control) or increasing the travel speed of the machine body 2 (travel control) based on the attachment 11 (type of the attachment 11) indicated by the information inputted via the input interface(s) 23, 28, 22 and / or 24 and based on the AUX pressure (S27).

[0223] In the case where the controller 20 performs the posture control at step S26 or S27, the controller 20 causes the arms 10 to swing upward or downward by a predetermined angle according to the AUX pressure to raise or lower the attachment 11 by a predetermined displacement to adjust the position of the attachment 11. In so doing, the controller 20, for example, may calculate the first difference between the AUX pressure and the upper limit of the appropriate range and the second difference between the AUX pressure and the lower limit of the appropriate range and, if the smaller one of the differences is less than a predetermined threshold, cause the arms 10 to swing without adjusting the travel speed of the machine body 2 to raise or lower the attachment 11 to adjust the position of the attachment 11. The controller 20 may cause the hitch 16 to swing in a manner linked to the swinging of the arms 10 to adjust the orientation of the attachment 11. The adjustment of the position and the orientation of the attachment 11 is similar to those discussed in the first example embodiment.

[0224] At step S26 or S27, if the smaller one of the differences is greater than or equal to the predetermined value, the controller 20 may raise or lower the attachment 11 as well as reducing or increasing the travel speed of the machine body 2. In such a case, the controller 20 reduces or increases the electric current value of the control signals inputted into two of the plurality of operating valves 54a to 54d that are open to change the angle of the swash plates of the travel pumps 50L and 50R to reduce or increase the rotation speed of the output shafts 51Lj and 51Rj of the travel motors 51L and 51R, thus reducing or increasing the travel speed of the traveling devices 5 and the machine body 2. At step S26, the controller 20 may actuate the braking solenoid valve 56 and the braking actuators 55 to brake the rotation of the output shafts 51Lj and 51Rj of the travel motors 51L and 51R to reduce the travel speed of the machine body 2. That is, the controller 20 causes the machine body 2 to travel at a travel speed corresponding to the AUX pressure (load on the attachment 11) instead of a travel speed corresponding to the manual operation of the travel operating lever 57a.

[0225] Alternatively, the controller 20 may be configured or programmed to, at step S26 or S27, if the smaller one of the differences is less than a predetermined value, reduce or increase the travel speed of the machine body 2 without changing the position of the attachment 11 and, if the smaller one of the differences is greater than or equal to the predetermined value, reduce or increase the travel speed of the machine body 2 as well as raising or lowering the attachment 11.

[0226] Alternatively, at step S26 or S27, if the travel speed detected by the speed detector 36 is 0 (zero), i.e., if work is being performed by the attachment 11 while the working machine is in the stopped state, the controller 20 may raise or lower the attachment 11 without adjusting the travel speed of the machine body 2. Alternatively, in such a case, the controller 20 may cause the machine body 2 to travel a predetermined distance in a direction away from the target object (travel rearward) or in a direction toward the target object (travel forward) irrespective of whether to raise or lower the attachment 11 or not.

[0227] When the controller 20 raises or lowers the attachment 11 and reduces or increases the travel speed at steps S26 and S27, the controller 20 may determine the electric current value of the control signal inputted into the lift solenoid valves 76a and 76b and the input time for which the control signal is inputted as well as determining the electric current value of the control signal inputted into the operating valves 54a to 54d such that the AUX pressure falls within the appropriate range. The controller 20 then inputs the determined control signal into the corresponding lift solenoid valve(s) 76a and / or 76b and the operating valve(s) 54a to 54d to raise or lower the attachment 11 such that the attachment 11 inches, and reduce or increase the travel speed of the traveling devices 5 and the machine body 2. In so doing, the controller 20 may determine the electric current value of the control signal inputted into the lift solenoid valves 76a and 76b and the input time for which the control signal inputted and the electric current value of the control signal inputted into the operating valves 54a to 54d and determine the travel speed also in consideration of the position range and the degree of change in the posture information of the attachment 11.

[0228] In the case where the controller 20 only reduces or increases the travel speed at step S26 or S27, the controller 20 determines the electric current value of the control signal inputted into the operating valves 54a to 54d, and inputs the control signal into the operating valve(s) 54a to 54d to reduce or increase the travel speed of the traveling devices 5 and the machine body 2 such that the AUX pressure falls within the appropriate range. At step S26, the controller 20 may, according to the AUX pressure and / or the like, actuate the braking solenoid valve 56 and the braking actuators 55 to brake the rotation of the output shafts 51Lj and 51Rj of the travel motors 51L and 51R to reduce the travel speed of the machine body 2 to 0 (zero) to stop the machine body 2. Furthermore, the controller 20 may, after the machine body 2 stops, change the angle of the swash plates of the travel pumps 50L and 50R via the operating valve 54a to 54d to cause the travel motors 51L and 51R to rotate in the reverse direction to cause the machine body 2 to travel a predetermined distance in the reverse direction.

[0229] The controller 20 may determine, for each of a plurality of attachments 11 attachable to the working device 4, whether to perform the posture control and whether to perform the travel control, and cause the storing device 21 to store control information including such defined pieces of information. The controller 20 may then, at step S26 or S27 of FIG. 11, perform at least one of the posture control or the travel control based on the control information corresponding to the attachment 11.

[0230] After step S26 or step S27, if work has not ended (NO at S13 of FIG. 10), the controller 20 repeats step S8 and subsequent steps. Also in the case where the AUX pressure is within the appropriate range (NO at S22 and NO at S24 of FIG. 11), if work has not ended (NO at S13 of FIG. 10), the controller 20 repeats step S8 and subsequent steps.

[0231] Since the above-described posture control is performed, the working device 4 operates in a manner that does not correspond to the manual operation of the work operating lever 67a, and, since the travel control is performed, the working machine 1 travels in a manner that does not correspond to the manual operation of the travel operating lever 57a and stops, in some cases. To address this, for the driver of the working machine 1 or the like does not feel uncertainty, when the controller 20 is performing at least one of the posture control or the travel control, as shown in, for example, FIG. 12, the controller 20 causes the user interface 22 and / or the like to display information U4 indicating the currently performed control on the monitor screen G1 In the example of FIG. 12, since the controller 20 is performing the posture control and the travel control, the controller 20 causes the information U4, which indicates that the posture control of the attachment 11 and the travel control of the working machine 1 are being performed, to be displayed on the monitor screen G1.

[0232] In the above described example embodiments, the work manual operator 67 and the travel manual operator 57 each include a digital joystick. However, for example, as shown in FIGS. 13 and 14, a pilot-operated hydraulic work manual operator 67 and a pilot-operated hydraulic travel manual operator 57 may be used instead.

[0233] The work manual operator 67 in a work-related hydraulic circuit 4A of another example embodiment shown in FIG. 13 includes a work operating lever 67a and a plurality of pilot valves 89a, 89b, 89c and 89d. The plurality of pilot valves 89a to 89d are connected to a fluid discharge passage 40 and are respectively connected to fluid passages 88a, 88b, 88c and 88d. The fluid passages 88a, 88b, 88c and 88d are respectively connected to corresponding work pressure receivers 61a, 61b, 62a, 62b of the lift control valve 60A and the tilt control valve 60B via high-pressure selection valves 91a, 91b, 91c and 91d. Note that, in FIG. 13, for convenience, a portion of the fluid passages 88a, 88b, 88c and 88d is omitted ((a), (b), (c), (d)).

[0234] The lift solenoid valves 76a and 76b and the tilt solenoid valves 77a and 77b are connected to the corresponding high-pressure selection valves 91a, 91b, 91c and 91d via fluid passages. The high-pressure selection valves 91a, 91b, 91c and 91d each allow the higher one of the hydraulic pressure from the connected pilot valve 89a, 89b, 89c or 89d and the hydraulic pressure from the connected solenoid valve 76a, 76b, 77a or 77b to act on the connected work pressure receiver 61a, 61b, 62a, 62b. The fluid passages 88a to 88d are provided with a solenoid switching valve 87. The solenoid switching valve 87 is a two-position solenoid switching valve, and switchable between a first position to allow passage of pilot fluid and a second position to block pilot fluid. Note that the solenoid switching valve 87 is normally in the first position.

[0235] When the work operating lever 67a is pivoted forward (direction F), the first pilot valve 89a is operated, and, after the pilot pressure of pilot fluid from the fluid discharge passage 40 is changed at the first pilot valve 89a, the pilot fluid passes through the first fluid passage 88a and the solenoid switching valve 87 and the pilot pressure acts on the work pressure receiver 61a of the lift control valve 60A. With this, the lift control valve 60A switches to the first position 61d, the lift cylinders 14 retract, and the arms 10 swing downward.

[0236] When the work operating lever 67a is pivoted rearward (direction B), the second pilot valve 89b is operated, and, after the pilot pressure of pilot fluid from the fluid discharge passage 40 is changed at the second pilot valve 89b, the pilot fluid passes through the second fluid passage 88b and the solenoid switching valve 87 and the pilot pressure acts on the work pressure receiver 61b of the lift control valve 60A. With this, the lift control valve 60A switches to the second position 61e, the lift cylinders 14 extend, and the arms 10 swing upward.

[0237] When the work operating lever 67a is pivoted leftward (direction L), the third pilot valve 89c is operated, and, after the pilot pressure of pilot fluid from the fluid discharge passage 40 is changed at the third pilot valve 89c, the pilot fluid passes through the third fluid passage 88c and the solenoid switching valve 87 and the pilot pressure acts on the work pressure receiver 62a of the tilt control valve 60B. With this, the tilt control valve 60B switches to the first position 62d, the tilt cylinders 15 extend, and the hitch 16 swings downward.

[0238] When the work operating lever 67a is pivoted rightward (direction R), the fourth pilot valve 89d is operated, and, after the pilot pressure of pilot fluid from the pilot fluid discharge passage 40 is changed at the fourth fluid passage 88d, the pilot fluid passes through the fourth fluid passage 88d and the solenoid switching valve 87 and the pilot pressure acts on the work pressure receiver 62b of the tilt control valve 60B. With this, the tilt control valve 60B switches to the second position 62e, the tilt cylinders 15 retract, and the hitch 16 swings upward.

[0239] The controller 20 is configured or programmed such that, when, in the foregoing posture control or the like, actuating at least one of the lift solenoid valves 76a and 76b or the tilt solenoid valves 77a and 77b to switch the position of at least one of the lift control valve 60A or the tilt control valve 60B to cause at least one of the arms 10 or the hitch 16 to swing, the controller 20 inputs a control signal into the solenoid switching valve 87 to switch the solenoid switching valve 87 to the second position. With this, the pilot pressure from the pilot valves 89a to 89d is blocked at the solenoid switching valve 87 and does not act on any of the work pressure receivers 61a, 61b, 62a and 62b of the lift control valve 60A and the tilt control valve 60B.

[0240] The fluid passages 88a, 88b, 88c and 88d are provided with respective pressure detectors 92a, 92b, 92c and 92d. The pressure detectors 92a, 92b, 92c and 92d detect the pilot pressure outputted from the pilot valves 89a, 89b, 89c and 89d. The controller 20 may determine the operation direction and operation amount of the work operating lever 67a based on the pilot pressure detected by the pressure detectors 92a to 92d.

[0241] The travel manual operator 57 in a travel-related hydraulic circuit 5A of another example embodiment of FIG. 14 includes a travel operating lever 57a, a plurality of pilot valves 44a, 44b, 44c and 44d, and a bridge circuit 93. The plurality of pilot valves 44a to 44d are connected to the fluid discharge passage 40 and to the bridge circuit 93. The bridge circuit 93 includes a plurality of shuttle valves 94. Fluid passages 43a, 43b, 43c and 43d are respectively connected to the plurality of shuttle valves 94. The fluid passages 43a, 43b, 43c and 43d are provided with a solenoid switching valve 95. The solenoid switching valve 95 is a two-position solenoid switching valve switchable between a first position to allow passage of pilot fluid, and a second position to block pilot fluid. Note that the solenoid switching valve 95 is normally in the first position. The fluid passages 43a, 43b, 43c and 43d are respectively connected to intermediate portions of fluid passages 42a, 42b, 42c and 42d via high-pressure selection valves 96a, 96b, 96c, and 96d. The high-pressure selection valves 96a, 96b, 96c and 96d each cause the higher one of the hydraulic pressure from the corresponding pilot valve 44a, 44b, 44c or 44d and the hydraulic pressure from the corresponding operating valve 54a, 54b, 54c or 54d to act on the connected pump pressure receiver 50a or 50b.

[0242] When the travel operating lever 57a is pivoted forward (direction F), the first pilot valve 44a is operated, and, after the pilot pressure of the pilot fluid from the fluid discharge passage 40 is changed at the first pilot valve 44a, the pilot fluid passes through the bridge circuit 93, the solenoid switching valve 95, the fluid passages 43a and 43c, and the fluid passages 42a and 42c, and the pilot pressure acts on the forward-travel pump pressure receivers 50a of the travel pumps 50L and 50R. With this, the angle of the swash plates of the travel pumps 50L and 50R is changed, the output shafts 51Lj and 51Rj of the travel motor 51L and 51R rotate in the normal direction, the first traveling device 5 and the second traveling device 5 are driven to travel forward, and the working machine 1 travels straight forward at a travel speed corresponding to the operation amount of the travel operating lever 57a.

[0243] When the travel operating lever 57a is pivoted rearward (direction B), the second pilot valve 44b is operated, and, after the pilot pressure of the pilot fluid from the fluid discharge passage 40 is changed at the second pilot valve 44b, the pilot fluid passes through the bridge circuit 93, the solenoid switching valve 95, the fluid passages 43b and 43d, and the fluid passages 42b and 42d, and the pilot pressure acts on the rearward-travel pump pressure receivers 50b of the travel pumps 50L and 50R. With this, the angle of the swash plates of the travel pumps 50L and 50R is changed, the output shafts 51Lj and 51Rj of the travel motors 51L and 51R rotate in the reverse direction, the first traveling device 5 and the second traveling device 5 are driven to travel rearward, and the working machine 1 travels straight rearward at a travel speed corresponding to the operation amount of the travel operating lever 57a.

[0244] When the travel operating lever 57a is pivoted leftward (direction L), the third pilot valve 44c is operated, and, after the pilot pressure of the pilot fluid from the fluid discharge passage 40 is changed at the third pilot valve 44c, the pilot fluid passes through the bridge circuit 93, the solenoid switching valve 95, the fluid passages 43b and 43c, and the fluid passages 42b and 42c, and the pilot pressure acts on the rearward-travel pump pressure receiver 50b of the travel pump 50L and the forward-travel pressure receiver 50a of the travel pump 50R. With this, the angle of the swash plates of the travel pumps 50L and 50R is changed, the output shaft 51Lj of the first travel motor 51L rotates in the reverse direction, the first traveling device 5 is driven to travel rearward, the output shaft 51Rj of the second travel motor 51R rotates in the normal direction, the second traveling device 5 is driven to travel forward, and the working machine 1 makes a spin turn to the left.

[0245] When the travel operating lever 57a is pivoted rightward (direction R), the fourth pilot valve 44d is operated, and, after the pilot pressure of the pilot fluid from the fluid discharge passage 40 is changed at the fourth pilot valve 44d, the pilot fluid passes through the bridge circuit 93, the solenoid switching valve 95, the fluid passages 43a and 43d, and the fluid passages 42a and 42d, and the pilot pressure acts on the forward-travel pressure receiver 50a of the travel pump 50L and the rearward-travel pump pressure receiver 50b of the travel pump 50R. With this, the angle of the swash plates of the travel pumps 50L and 50R is changed, the output shaft 51Lj of the first travel motor 51L rotates in the normal direction, the first traveling device 5 is driven to travel forward, the output shaft 51Rj of the second travel motor 51R rotates in the reverse direction, the second traveling device 5 is driven to travel rearward, and the working machine 1 performs a spin turn to the right.

[0246] Furthermore, if the travel operating lever 57a is pivoted diagonally leftward and forward, diagonally rightward and forward, diagonally leftward and rearward, or diagonally rightward and rearward, the pilot valve(s) 44a to 44d corresponding to the operation direction and the operation amount are operated, and the pilot pressure acts on the corresponding pump pressure receivers 50a and 50b of the travel pumps 50L and 50R. Then, the angle of the swash plates of the travel pumps 50L and 50R is changed, the rotation direction and rotation speed of the output shafts 51Lj and 51Rj of the travel motors 51L and 51R are determined, and the working machine 1 performs a pivot turn or slowly turns to the left or the right while traveling forward or rearward.

[0247] The fluid passages 43a, 43b, 43c and 43d are provided with respective pressure detectors 48a, 48b, 48c and 48d. The pressure detectors 48a, 48b, 48c 48d respectively detect the pilot pressures acting on the pressure receivers 50a and 50b of the travel pumps 50L and 50R via the connected fluid passages 43a to 43d and 42a to 42d. The controller 20 may be configured or programmed to, based on the pilot pressures detected by the pressure detectors 48a to 48d, determine the operation direction and operation amount of the travel operating lever 57a and also determine the travel direction, the travel speed, whether straight travel is performed, whether turning is performed, the direction of turn, and / or the type of turn, of the working machine 1.

[0248] Working machines 1 of example embodiments described so far include features described in the following items and achieve the following effects.

[0249] (Item 1) A working machine 1 including a working device 4 to attach thereto an attachment 11 which is one of a plurality of attachments 11 to perform work by contacting a target object, and change a posture of the attachment 11 attached thereto including a position of the attachment 11 in an up-down direction, a pressure detector (AUX pressure detector) 70a, 70b to detect an auxiliary pressure which is a pressure of hydraulic fluid supplied to a hydraulic actuator 27 included in the attachment 11 to drive the attachment 11, and a controller 20 configured or programmed to perform a posture control to control the working device 4 based on the auxiliary pressure to adjust the posture of the attachment 11.

[0250] With the configuration according to item 1, even if, for example, the height of the target object is not uniform, the posture of the attachment 11 is adjusted automatically according to the auxiliary pressure which corresponds to the load on the attachment 11, making it possible to cause the posture to follow changes in height of the target object and cause the attachment 11 to perform work appropriately. This makes it possible to improve the work performance of the attachment 11 of the working machine 1.

[0251] (Item 2) The working machine 1 according to item 1, wherein the controller 20 is configured or programmed to perform the posture control when work is being performed by the attachment 11, and in the posture control, change the posture of the attachment 11 such that the auxiliary pressure falls within an appropriate range.

[0252] The configuration according to item 2 makes it possible to appropriately adjust the posture of the attachment 11 and cause the attachment 11 to perform work appropriately by appropriately contacting the target object.

[0253] (Item 3) The working machine 1 according to item 1 or 2, further including an input interface 23, 28, 22, 24 (beacon scanner 23, AUX connector 28, user interface 22, communicator 24) to receive input of information indicating the attachment attached to the working device 4, wherein the controller 20 is configured or programmed to perform the posture control when the information inputted via the input interface 23, 28, 22, 24 indicates a specific attachment 11 which is one of the plurality of attachments 11.

[0254] With the configuration according to item 3, in cases where an attachment 11 for which the posture change by the working device 4 is effective for work performance is attached to the working device 4, the posture of the attachment 11 is adjusted automatically to improve work performance. In cases where an attachment 11 for which the posture change by the working device 4 does not influence work performance is attached to the working device 4, the posture of the attachment 11 is not adjusted automatically, making it possible to reduce the processing load on the controller 20 and perform work efficiently.

[0255] (Item 4) The working machine 1 according to any one of items 1 to 3, wherein the controller 20 is configured or programmed to perform the posture control when the controller 20 is in a predetermined mode (steady output mode) in which the controller 20 keeps constant an amount of hydraulic fluid supplied to the hydraulic actuator 27 per unit time.

[0256] With the configuration according to item 4, it is possible to easily adjust the posture of the attachment 11, because it is not necessary to take into account changes in amount of hydraulic fluid supplied to the hydraulic actuator 27 per unit time. Furthermore, since the user such as the driver of the working machine 1 does not need to perform manual operation for the amount of supply of hydraulic fluid to the hydraulic actuator 27 of the attachment 11 and for the working device 4 to change the posture of the attachment 11, it is possible to reduce the burden on the user.

[0257] (Item 5) The working machine 1 according to any one of items 1 to 4, further including an input interface 23, 28, 22, 24 to receive input of information indicating the attachment 11 attached to the working device 4, and a memory and / or a storage 21 to store (i) pieces of information indicating the plurality of attachments 11 attachable to the working device 4 and (ii) pieces of information indicating appropriate ranges of the auxiliary pressure for work defined for the respective plurality of attachments 11 such that (i) the pieces of information and (ii) the pieces of information are associated with each other, wherein the controller 20 is configured or programmed to read, from the memory and / or the storage 21, a piece of information indicating an appropriate range that corresponds to the attachment 11 indicated by the information inputted via the input interface 23, 28, 22, 24, and perform the posture control based on the read piece of information indicating the appropriate range and the auxiliary pressure.

[0258] With the configuration according to item 5, it is possible to more appropriately adjust the posture of the attachment 11 according to the attachment 11 attached to the working device 4, and further improve work performance.

[0259] (Item 6) The working machine 1 according to any one of items 1 to 5, wherein the working device 4 includes an arm 10 connected to a machine body 2 of the working machine 1 swingably in the up-down direction, a first actuator (lift cylinder) 14 to swing the arm 10, and a hitch 16 connected to a distal portion of the arm 10 to detachably attach the attachment 11 thereto, wherein the controller 20 is configured or programmed to, in the posture control, control the first actuator 14 based on the auxiliary pressure to swing the arm 10 to adjust the position of the attachment 11 relative to the target object.

[0260] With the configuration according to item 6, it is possible to adjust the position of the attachment 11 in the up-down direction (vertical direction) such that the position follows changes in height of the target object.

[0261] (Item 7) The working machine 1 according to item 6, wherein the controller 20 is configured or programmed to, when the auxiliary pressure is above an appropriate range, cause the first actuator 14 to swing the arm 10 upward to raise the attachment 11.

[0262] With the configuration according to item 7, even if the height of the target object changes and increases, the position of the attachment 11 is adjusted such that the attachment 11 is moved (raised) in a direction away from the target object, making it possible to eliminate or reduce the likelihood that the load on the attachment 11 will be excessive and that the excessive load will result in stoppage of the attachment 11 and the hydraulic actuator 27.

[0263] (Item 8) The working machine 1 according to item 6 or 7, wherein the controller 20 is configured or programmed to, when the auxiliary pressure is below an appropriate range, cause the first actuator 14 to swing the arm 10 downward to lower the attachment 11.

[0264] With the configuration according to item 8, even if the height of the target object changes and decreases, the position of the attachment 11 is adjusted such that the attachment 11 is moved (lowered) in a direction toward the target object, making it possible to cause the attachment 11 to contact the target object such that the attachment 11 can perform work and possible to perform work appropriately.

[0265] (Item 9) The working machine according to any one of items 1 to 5, wherein the working device 4 includes an arm 10 connected to a machine body 2 of the working machine 1 swingably in the up-down direction, a first actuator 14 to swing the arm 10, a hitch 16 connected to a distal portion of the arm 10 swingably in the up-down direction and operable to detachably attach the attachment 11 thereto, and a second actuator (tilt cylinder) 15 to swing the hitch 16, wherein the controller 20 is configured or programmed to, in the posture control, cause the first actuator 14 to swing the arm 10 and / or cause the second actuator 15 to swing the hitch 16 to adjust at least one of the position or an orientation of the attachment 11 relative to the target object.

[0266] With the configuration according to item 9, it is possible to appropriately adjust the position in the up-down direction and the orientation of the attachment 11 such that the position and the orientation follow changes in height and surface condition of the target object. It is also possible to more freely adjust the posture of the attachment 11 automatically and possible to adjust the posture more finely.

[0267] (Item 10) The working machine 1 according to any one of items 1 to 9, further including an input interface 23, 28, 22, 24 to receive input of information indicating the attachment 11 attached to the working device 4, and a memory and / or a storage 21 to store (i) pieces of information indicating the plurality of attachments 11 attachable to the working device 4 and (ii) pieces of posture information indicating appropriate ranges of the posture for work defined for the respective plurality of attachments 11 such that (i) the pieces of information and (ii) the pieces of posture information are associated with each other, wherein the controller 20 is configured or programmed to read, from the memory and / or the storage 21, one of the pieces of posture information that corresponds to the attachment 11 indicated by the information inputted via the input interface 23, 28, 22, 24, and perform the posture control based on the read piece of posture information and the auxiliary pressure.

[0268] With the configuration according to item 10, it is possible to more appropriately adjust the posture of the attachment 11 attached to the working device 4 according to the attachment 11, and also possible to further improve work performance.

[0269] (Item 11) The working machine 1 according to any one of items 1 to 10, further including a machine body 2, a traveling device 5 to cause the machine body 2 to travel, and a speed detector 36 to detect a travel speed of the machine body 2, wherein the controller 20 is configured or programmed to not perform the posture control when the travel speed is less than a predetermined value.

[0270] With the configuration according to item 11, it is possible to eliminate or reduce the likelihood that the posture of the attachment 11 will be needlessly adjusted while the working machine 1 is in the stopped state or very slowly traveling state in which the attachment 11 is not performing work, making it possible to reduce an increase in processing load on the controller 20 and a decrease in work performance.

[0271] (Item 12) The working machine 1 according to any one of items 1 to 11, further including a work manual operator (work operating lever) 67a to be operated to cause the working device 4 to change the posture of the attachment 11, wherein the controller 20 is configured or programmed to not perform the posture control when an operation amount of the work manual operator 67a is greater than a predetermined amount.

[0272] With the configuration according to item 12, it is possible to ensure convenience by prioritizing the user's manual operation of the working device 4 over the automatic operation of the working device 4 for the posture control.

[0273] (Item 13) The working machine 1 according to any one of items 1 to 12, further including a machine body 2, a traveling device 5 to cause the machine body 2 to travel and to change a traveling state of the machine body 2, and an input interface 23, 28, 22, 24 to receive input of information indicating the attachment 11 attached to the working device 4, wherein the controller 20 is configured or programmed to, based on the attachment 11 indicated by the information inputted via the input interface 23, 28, 22, 24 and based on the auxiliary pressure, selectively perform at least one of the posture control or a travel control to control the traveling device 5 to adjust the traveling state of the machine body 2.

[0274] With the configuration according to item 13, it is possible to appropriately adjust the auxiliary pressure on the hydraulic actuator 27 of the attachment 11 and the posture of the attachment 11 according to the type of the attachment 11, i.e., the type of work performed by the attachment 11, and according to the load on the attachment 11 to prevent or reduce the overload on the attachment 11 or a lack of contact between the target object and the attachment 11, making it possible to improve the work performance of the attachment 11. It is also possible to more freely adjust the load on the attachment 11 and the contact state of the attachment 11 automatically, and more finely adjust the load and the contact state. Furthermore, since the traveling state is adjusted, the posture of the attachment 11 does not need to be adjusted such that the posture greatly changes, and it is possible to maintain the state of contact between the target object and the attachment 11 during work.

[0275] (Item 14) The working machine 1 according to item 13, further including a memory and / or a storage 21 to store (i) pieces of information indicating the plurality of attachments 11 attachable to the working device 4 and (ii) pieces of information indicating appropriate ranges of the auxiliary pressure for work defined for the respective plurality of attachments 11 such that (i) the pieces of information and (ii) the pieces of information are associated with each other, wherein the controller 20 is configured to programmed to read, from the memory and / or the storage 21, a piece of information indicating an appropriate range that corresponds to the attachment 11 indicated by the information inputted via the input interface 23, 28, 22, 24, and, based on the read piece of information indicating the appropriate range and the auxiliary pressure, selectively perform at least one of the posture control or the travel control.

[0276] With the configuration according to item 14, it is possible to more appropriately adjust the auxiliary pressure and the posture of the attachment 11 and possible to improve the work performance of the attachment 11.

[0277] (Item 15) The working machine 1 according to item 13 or 14, further including a memory and / or a storage 21 to store (i) pieces of information indicating the plurality of attachments 11 attachable to the working device 4 and (ii) pieces of posture information indicating appropriate ranges of the posture for work defined for the respective plurality of attachments 11 such that (i) the pieces of information and (ii) the pieces of posture information are associated with each other, wherein the controller 20 is configured or programmed to read, from the memory and / or the storage 21, one of the pieces of posture information that corresponds to the attachment 11 indicated by the information inputted via the input interface 23, 28, 22, 24, and, based on the read piece of posture information and the auxiliary pressure, selectively perform at least one of the posture control or the travel control.

[0278] With the configuration according to item 15, it is possible to more appropriately adjust the auxiliary pressure and the posture of the attachment 11 and possible to improve the work performance of the attachment 11.

[0279] (Item 16) The working machine 1 according to any one of items 13 to 15, wherein the controller 20 is configured or programmed to perform at least one of the posture control or the travel control when the controller 20 is in a predetermined mode in which the controller 20 keeps constant an amount of hydraulic fluid supplied to the hydraulic actuator 27 per unit time.

[0280] With the configuration according to item 16, it is possible to easily adjust the posture of the attachment 11 and the load on the attachment 11, because it is not necessary to take into account changes in amount of hydraulic fluid supplied to the hydraulic actuator 27 per unit time.

[0281] (Item 17) The working machine 1 according to any one of items 13 to 16, further including a speed detector 36 to detect a travel speed of the machine body 2, wherein the controller 20 is configured or programmed to not perform the posture control or the travel control if the travel speed is less than a predetermined value.

[0282] With the configuration according to item 17, it is possible to eliminate or reduce the likelihood that the posture of the attachment 11 and the traveling state will be needlessly adjusted while the working machine 1 is in the stopped state or very slowly traveling state in which the attachment 11 is not performing work, making it possible to reduce an increase in processing load on the controller 20 and a decrease in work performance.

[0283] (Item 18) The working machine 1 according to any one of items 13 to 17, further including a work manual operator (work operating lever) 67a to be operated to cause the working device 4 to change the posture of the attachment 11, wherein the controller 20 is configured or programmed to not perform the posture control or the travel control when an operation amount of the work manual operator 67a is greater than a predetermined amount.

[0284] With the configuration according to item 18, it is possible to ensure convenience by prioritizing the user's manual operation of the working device 4 over the automatic operation of the working device 4 for the posture control and the automatic adjustment of the raveling state. It is also possible to eliminate or reduce the likelihood that the posture of the attachment 11 and the traveling state will be automatically adjusted in an unintended manner.

[0285] (Item 19) The working machine 1 according to any one of items 13 to 19, wherein the controller 20 is configured or programmed to, when the controller 20 is performing at least one of the posture control or the travel control, cause a user interface 22 to output information indicating that the at least one of the posture control or the travel control is being performed.

[0286] With the configuration according to item 19, even if the working device 4 is actuated under the posture control without responding to the user's manual operation and the posture of the attachment 11 is changed automatically and / or if the traveling state of the working machine 1 is changed automatically under the travel control, it is possible to let the user know that such changes are due to the automatic control at the working machine 1.

[0287] While example embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.

Examples

Embodiment Construction

[0043]Example embodiments will now be described with reference to the accompanying drawings, wherein like reference numerals designate corresponding or identical elements throughout the various drawings. The drawings are to be viewed in an orientation in which the reference numerals are viewed correctly.

[0044]Example embodiments of the present invention will now be described with reference to the accompanying drawings as necessary.

[0045]FIG. 15 is a side view of a working machine 1 of the present example embodiment. In the present example embodiment, a compact track loader is illustrated as an example of the working machine 1. However, the working machine according to an example embodiment of the present invention is not limited to a compact track loader, and may be, for example, some other construction machine, agricultural machine, or working machine such as a skid-steer loader, a backhoe, or a tractor. The left direction, right direction, the direction approaching the viewer of F...

BACKGROUND OF THE INVENTION1. Field of the Invention

[0001] The present invention relates to working machines such as skid-steer loaders and compact track loaders, and particularly relates to techniques to perform work using each of various types of attachments attached to a working device including arms and the like.2. Description of the Related Art

[0002] A working machine such as a skid-steer loader or a compact track loader is configured such that a working device including arms and the like has one of various types of attachments attached thereto and that the attached attachment is raised or lowered by the working device to perform work corresponding to the attachment. Some attachments are configured to, for example, perform work while in contact at a predetermined pressure with a target object such as a structure or a natural object including soil and plants. Some attachments of this kind include an actuator to be actuated by power from the working machine to cause the attachment to operate.

[0003] In order to allow the working machine to appropriately perform work using an attachment, for example, the specification of U.S. Pat. No. 11,846,088 discloses an automatic vehicle speed control system to adjust the travel speed of the working machine according to the load on an implement (attachment). A controller of the vehicle speed automatic control system defines the travel speed of the working machine based on creep settings, monitors one or more operating statuses of the implements, and automatically adjusts the travel speed based on the operating status(es). The operating status(es) monitored by the controller includes the pressure in an auxiliary hydraulic circuit for the implement.

[0004] For example, in the case where the height of a target object is not uniform, in some cases, it is necessary to change the posture of the attachment such as the position and the orientation according to variations in height of the target object to appropriately perform work. However, it is difficult for the user of the working machine to manually control the working device to change the posture of the attachment according to variations in height of the target object.SUMMARY OF THE INVENTION

[0005] Example embodiments of the present invention make it possible to improve the work performance of attachments on working machines.

[0006] A working machine according to an example embodiment of the present invention includes a working device to attach thereto an attachment which is one of a plurality of attachments to perform work by contacting a target object, and change a posture of the attachment attached thereto including a position of the attachment in an up-down direction, a pressure detector to detect an auxiliary pressure which is a pressure of hydraulic fluid supplied to a hydraulic actuator included in the attachment to drive the attachment, and a controller configured or programmed to perform a posture control to control the working device based on the auxiliary pressure to adjust the posture of the attachment.

[0007] In an example embodiment of the present invention, the controller may be configured or programmed to perform the posture control when work is being performed by the attachment, and in the posture control, change the posture of the attachment such that the auxiliary pressure falls within an appropriate range.

[0008] In an example embodiment of the present invention, the working machine may further include an input interface to receive input of information indicating the attachment attached to the working device. The controller may be configured or programmed to perform the posture control when the information inputted via the input interface indicates a specific attachment which is one of the plurality of attachments.

[0009] In an example embodiment of the present invention, the controller may be configured or programmed to perform the posture control when the controller is in a predetermined mode in which the controller keeps constant an amount of hydraulic fluid supplied to the hydraulic actuator per unit time.

[0010] In an example embodiment of the present invention, the working machine may further include an input interface to receive input of information indicating the attachment attached to the working device, and a memory and / or a storage to store (i) pieces of information indicating the plurality of attachments attachable to the working device and (ii) pieces of information indicating appropriate ranges of the auxiliary pressure for work defined for the respective plurality of attachments such that (i) the pieces of information and (ii) the pieces of information are associated with each other. The controller may be configured or programmed to read, from the memory and / or the storage, a piece of information indicating an appropriate range that corresponds to the attachment indicated by the information inputted via the input interface, and perform the posture control based on the read piece of information indicating the appropriate range and the auxiliary pressure.

[0011] In an example embodiment of the present invention, the working device may include an arm connected to a machine body of the working machine swingably in the up-down direction, a first actuator to swing the arm, and a hitch connected to a distal portion of the arm to detachably attach the attachment thereto. The controller may be configured or programmed to, in the posture control, control the first actuator based on the auxiliary pressure to swing the arm to adjust the position of the attachment relative to the target object.

[0012] In an example embodiment of the present invention, the controller may be configured or programmed to, when the auxiliary pressure is above an appropriate range, cause the first actuator to swing the arm upward to raise the attachment.

[0013] In an example embodiment of the present invention, the controller may be configured or programmed to, when the auxiliary pressure is below an appropriate range, cause the first actuator to swing the arm downward to lower the attachment.

[0014] In an example embodiment of the present invention, the working device may include an arm connected to a machine body of the working machine swingably in the up-down direction, a first actuator to swing the arm, a hitch connected to a distal portion of the arm swingably in the up-down direction and operable to detachably attach the attachment thereto, and a second actuator to swing the hitch. The controller may be configured or programmed to, in the posture control, cause the first actuator to swing the arm and / or cause the second actuator to swing the hitch to adjust at least one of the position or an orientation of the attachment relative to the target object.

[0015] In an example embodiment of the present invention, a selected one of the plurality of attachments to perform various types of work may be attached to the working device. The working machine may further include an input interface to receive input of information indicating the attachment attached to the working device, and a memory and / or a storage to store (i) pieces of information indicating the plurality of attachments attachable to the working device and (ii) pieces of posture information indicating appropriate ranges of the posture for work defined for the respective plurality of attachments such that (i) the pieces of information and (ii) the pieces of posture information are associated with each other. The controller may be configured or programmed to read, from the memory and / or the storage, one of the pieces of posture information that corresponds to the attachment indicated by the information inputted via the input interface, and perform the posture control based on the read piece of posture information and the auxiliary pressure.

[0016] In an example embodiment of the present invention, the working machine may further include a machine body, a traveling device to cause the machine body to travel, and a speed detector to detect a travel speed of the machine body. The controller may be configured or programmed to not perform the posture control when the travel speed is less than a predetermined value.

[0017] In an example embodiment of the present invention, the working machine may further include a work manual operator to be operated to cause the working device to change the posture of the attachment. The controller may be configured or programmed to not perform the posture control when an operation amount of the work manual operator is greater than a predetermined amount.

[0018] In an example embodiment of the present invention, the working machine may further include a machine body, a traveling device to cause the machine body to travel and to change a traveling state of the machine body, and an input interface to receive input of information indicating the attachment attached to the working device. The controller may be configured or programmed to, based on the attachment indicated by the information inputted via the input interface and based on the auxiliary pressure, selectively perform at least one of the posture control or a travel control to control the traveling device to adjust the traveling state of the machine body.

[0019] In an example embodiment of the present invention, the working machine may further include a memory and / or a storage to store (i) pieces of information indicating the plurality of attachments attachable to the working device and (ii) pieces of information indicating appropriate ranges of the auxiliary pressure for work defined for the respective plurality of attachments such that (i) the pieces of information and (ii) the pieces of information are associated with each other. The controller may be configured to programmed to read, from the memory and / or the storage, a piece of information indicating an appropriate range that corresponds to the attachment indicated by the information inputted via the input interface, and, based on the read piece of information indicating the appropriate range and the auxiliary pressure, selectively perform at least one of the posture control or the travel control.

[0020] In an example embodiment of the present invention, the working machine may further include a memory and / or a storage to store (i) pieces of information indicating the plurality of attachments attachable to the working device and (ii) pieces of posture information indicating appropriate ranges of the posture for work defined for the respective plurality of attachments such that (i) the pieces of information and (ii) the pieces of posture information are associated with each other. The controller may be configured or programmed to read, from the memory and / or the storage, one of the pieces of posture information that corresponds to the attachment indicated by the information inputted via the input interface, and, based on the read piece of posture information and the auxiliary pressure, selectively perform at least one of the posture control or the travel control.

[0021] In an example embodiment of the present invention, the controller may be configured or programmed to perform at least one of the posture control or the travel control when the controller is in a predetermined mode in which the controller keeps constant an amount of hydraulic fluid supplied to the hydraulic actuator per unit time.

[0022] In an example embodiment of the present invention, the working machine may further include a speed detector to detect a travel speed of the machine body. The controller may be configured or programmed to not perform the posture control or the travel control if the travel speed is less than a predetermined value.

[0023] In an example embodiment of the present invention, the working machine may further include a work manual operator to be operated to cause the working device to change the posture of the attachment. The controller may be configured or programmed to not perform the posture control or the travel control when an operation amount of the work manual operator is greater than a predetermined amount.

[0024] In an example embodiment of the present invention, the controller may be configured or programmed to, when the controller is performing at least one of the posture control or the travel control, cause a user interface to output information indicating that the at least one of the posture control or the travel control is being performed.

[0025] The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the example embodiments with reference to the attached drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] A more complete appreciation of example embodiments of the present invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings described below.

[0027] FIG. 1 illustrates an example of a work-related hydraulic circuit of a working machine.

[0028] FIG. 2 illustrates an example of a travel-related hydraulic circuit of a working machine.

[0029] FIG. 3 is a block diagram showing an example of an electrical configuration of a working machine.

[0030] FIG. 4 illustrates an example of a hydraulic circuit to actuate a latch cylinder.

[0031] FIG. 5 illustrates an example of attachment information and control information.

[0032] FIG. 6 illustrates an example of an input screen displaying icons of attachments.

[0033] FIG. 7 is a flowchart showing operation of a working machine of a first example embodiment of the present invention.

[0034] FIG. 8 is a flowchart showing details of posture control in FIG. 7.

[0035] FIG. 9 illustrates an example of a monitor screen of the first example embodiment of the present invention.

[0036] FIG. 10 is a flowchart showing operation of a working machine of a second example embodiment of the present invention.

[0037] FIG. 11 is a flowchart showing details of posture control / travel control in FIG. 10.

[0038] FIG. 12 illustrates an example of a monitor screen of the second example embodiment of the present invention.

[0039] FIG. 13 illustrates another example of a work-related hydraulic circuit of a working machine.

[0040] FIG. 14 illustrates another example of a travel-related hydraulic circuit of a working machine.

[0041] FIG. 15 is a side view of a working vehicle.

[0042] FIG. 16 is an elevational view of a quick hitch.DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

[0043] Example embodiments will now be described with reference to the accompanying drawings, wherein like reference numerals designate corresponding or identical elements throughout the various drawings. The drawings are to be viewed in an orientation in which the reference numerals are viewed correctly.

[0044] Example embodiments of the present invention will now be described with reference to the accompanying drawings as necessary.

[0045] FIG. 15 is a side view of a working machine 1 of the present example embodiment. In the present example embodiment, a compact track loader is illustrated as an example of the working machine 1. However, the working machine according to an example embodiment of the present invention is not limited to a compact track loader, and may be, for example, some other construction machine, agricultural machine, or working machine such as a skid-steer loader, a backhoe, or a tractor. The left direction, right direction, the direction approaching the viewer of FIG. 15, and the direction away from the viewer of FIG. 15 are respectively forward, rearward, left and right directions of the working machine 1. The direction perpendicular to the front-back direction and the up-down direction of the working machine 1 is hereinafter referred to as a machine body width direction.

[0046] The working machine 1 includes a machine body 2, a cabin 3, a working device 4, traveling device(s) 5, and a prime mover 6. The cabin 3 is provided on the machine body 2. The cabin 3 includes a seat 8 therein. The prime mover 6 is provided at a rear portion of the machine body 2. The prime mover 6 is a power source of the working machine 1. In the present example embodiment, the prime mover 6 includes a diesel engine. However, the prime mover 6 may be another internal combustion engine (engine) such as a gasoline engine, and / or may be a motor such as an electric motor.

[0047] The traveling devices 5 are respectively provided on the left and right sides of the machine body 2, support the machine body 2, and cause the machine body 2 to travel. That is, a pair of the left and right traveling devices 5 are provided. The traveling devices 5 include crawler traveling devices. Note that the traveling devices 5 are not limited to crawler traveling devices, and may be wheeled traveling devices including front wheel(s) and rear wheel(s), or may be semi-crawler traveling devices in which the front wheels or the rear wheels are crawler wheels.

[0048] When the left-side traveling device (left traveling device) 5 and the right-side traveling device (right traveling device) 5 are both driven to rotate forward or both driven to rotate reversely, or when one of them is driven to rotate forward and the other is driven to rotate reversely or is stopped, the machine body 2 (working machine 1) travels forward, travels rearward, or turns left or right. Furthermore, as the speed of rotation of the left and right traveling devices 5 changes, the travel speed of the machine body 2 changes, whereas, as the left and right traveling devices 5 stop, the machine body 2 stops. In this way, the traveling devices 5 change the traveling state such as the direction of travel, the travel speed, and the stopping of the machine body 2.

[0049] The working device 4 is provided on the machine body 2. The working device 4 includes arms 10, first links 12, second links 13, lift cylinders 14, tilt cylinders 15, a hitch 16, and an attachment 11. Of these, the arms 10, the first links 12, the second links 13, the lift cylinders 14, and the tilt cylinders 15 are provided on the left and the right of the cabin 3. The left and right arms 10 are connected by a connector.

[0050] The arms 10 are connected to the machine body 2 swingably in the up-down direction relative to the machine body 2. Specifically, the first links 12 and the second links 13 support proximal portions (rear portions) of the arms 10 via shafts such that the arms 10 are swingable in the up-down direction. First ends of the lift cylinders 14 are rotatably connected to the arms 10 via shafts, and opposite second ends of the lift cylinders 14 are rotatably connected to a lower rear portion of the machine body 2 via shafts. The lift cylinders 14 are hydraulic actuators (first actuators) to cause the arms 10 to swing in the up-down direction by extending and retracting.

[0051] The hitch 16 is connected to distal portions of the arms 10 swingably in the up-down direction relative to the distal portion of the arms 10. Specifically, first ends of the tilt cylinders 15 and the distal portions of the arms 10 are respectively rotatably connected to a rear portion of the hitch 16 via shafts. Opposite second ends of the tilt cylinders 15 are rotatably connected to central curved portions of the arms 10 via shafts and brackets. The tilt cylinders 15 are hydraulic actuators (second actuators) to cause the hitch 16 to swing in the up-down direction by extending and retracting. The attachment 11 is attached to the front surface of the hitch 16. The hitch 16 is a linkage to attach and detach the attachment 11 thereto and therefrom.

[0052] FIG. 16 is an elevational view of the quick hitch 16. Specifically, FIG. 16 shows the hitch 16 as seen from the machine body 2 of the working machine 1 in FIG. 15. The hitch 16 includes brackets 30, latching mechanisms 31, a latch cylinder 17, and the like. A pair of the left and right brackets 30 and a pair of the left and right latching mechanisms 31 are provided. The left and right brackets 30 are connected by a beam 39. The distal portions of the left and right arms 10 and the first ends of the left and right tilt cylinders 15 are connected to the left and right brackets 30 via shafts (FIG. 15). The left and right latching mechanisms 31 are respectively provided on the left and right brackets 30.

[0053] Each latching mechanism 31 includes a latch lever 32, a latch pin 33 and the like. An upper portion of the latch lever 32 is rotatably connected to the corresponding bracket 30 via a shaft. The latch pin 33 is held swingably up and down by the bracket 30. A lower end portion of a coil spring 34 is connected to an upper end portion of the latch pin 33 via a shaft, and an upper end portion of the coil spring 34 is connected to a central portion of the latch lever 32 via a shaft.

[0054] The latch cylinder 17 is a hydraulic cylinder (hydraulic actuator) to actuate the latching mechanisms 31 between a latching state and an unlatching state. A first end (distal portion of the rod) of the latch cylinder 17 is rotatably connected to a lower end portion of one of the latch levers 32 via a shaft. An opposite second end (bottom portion of the cylinder case) of the latch cylinder 17 is rotatably connected to a lower end portion of the other the latch levers 32 via a shaft.

[0055] As represented by a solid line in FIG. 16, when the latch cylinder 17 extends with the front surfaces of the brackets 30 abutting a base plate 9 connected to the back surface of the attachment 11, the latch levers 32 rotate to descend, causing the latch pins 33 to be inserted into through-holes 9h in a lower end portion of the base plate 9. With this, the latching mechanisms 31 are brought into a latching state in which the attachment 11 is secured to the brackets 30 (attached to the hitch 16).

[0056] As represented by a dot-dot-dash line in FIG. 16, when the latch cylinder 17 retracts, the latch levers 32 rotate to ascend, allowing the latch pins 33 to be removed from the through-holes 9h of the base plate 9 by the elastic force of the coil springs 34. With this, the latching mechanisms 31 are brought into an unlatching state in which the attachment 11 is not secured to the brackets 30, allowing the attachment 11 to be detached from the hitch 16.

[0057] Since the above-described hitch 16 allows the attachment 11 to be easily replaced with another one, the hitch 16 is called a “quick hitch” or “quick changer”. Note that another actuator such as a hydraulic motor may be used instead of the latch cylinder 17, or an electric actuator such as an electric motor or an electric cylinder may be used instead of the latch cylinder 17.

[0058] When the arms 10 are caused to swing in the up-down direction by the lift cylinders 14 with the attachment 11 attached to the hitch 16 as described above, the attachment 11 is raised or lowered, and the position (height) of the attachment 11 in the up-down direction relative to the machine body 2 and to the target object and the position of the attachment 11 in the front-back direction are changed. When the hitch 16 is caused to swing in the up-down direction by the tilt cylinders 15, the attachment 11 also swings in the up-down direction, and the tilt angle of the attachment 11, i.e., the orientation of the attachment 11 relative to the machine body 2 and the target object, is changed.

[0059] Thus, the working device 4 is a posture changing device to change the posture including the position and the orientation of the attachment 11. Furthermore, with regard to the working device 4, since the arms 10 and the hitch 16 are individually swingable, the working device 4 can, when at least one of the arms 10 or the hitch 16 swing(s) with the attachment 11 attached, change the posture including at least one of the height or the orientation of the attachment 11 relative to the machine body 2 and the target object. The attachment 11 is changed between a work posture in which the working device 4 can perform work on a target object and a non-work posture in which the working device 4 does not perform work. The working machine 1 includes a working unit 4U including the working device 4 and the attachment 11 attached to the working device 4.

[0060] The working device 4 (hitch 16) is operable to attach thereto and detach therefrom each of attachments 11 to perform various types of work, and a selected one of the attachments 11 is attached to the working device (hitch 16). The attachment 11 is a working tool to perform work. The working machine 1 performs work corresponding to the attachment 11 attached to the working device 4.

[0061] Examples of attachments 11 attachable to the working device 4 include follower attachments 11 each of which does not include actuators and each of which operates in a manner that follows the working device 4. For example, follower attachments 11 include buckets and pallet forks that are working tools for earth / cargo handling to carry earth or cargo.

[0062] Examples of attachments 11 attachable to the working device 4 also include drive attachments 11 each of which includes actuator(s) and each of which is to be driven by power from the actuator(s). Examples of drive attachments 11 include contact work attachments 11 to, for example, remove, adjust or destroy a target object in contact therewith such as earth or plants. Examples of contact work attachments 11 include sweepers, snow blowers, snow blades, angle brooms, mowers, plows, skid cutters, breakers, and earth augers. In the example shown in FIG. 15, a sweeper which is a drive, contact work attachment 11 is attached to the working device 4 (hitch 16).

[0063] Examples of the drive attachments 11 also include non-contact work attachments 11 to perform work such as spreading fertilizer or agricultural chemicals without contacting the target object such as earth or crops. Examples of such non-contact work attachments 11 include spreaders.

[0064] In the present example embodiment, the actuator(s) provided in or on the drive attachment 11 is a hydraulic actuator such as a hydraulic motor or a hydraulic cylinder. For example, a hydraulic actuator 27 provided in or on the sweeper (attachment) 11 shown in FIG. 15 is a hydraulic motor which drives the sweeper 11.

[0065] The hydraulic actuator 27 provided in or on the drive attachment 11 is actuated by hydraulic fluid supplied from the working machine 1. As shown in FIG. 15, the machine body 2 of the working machine 1 is provided with AUX port(s) (auxiliary port(s)) 25 at a front portion thereof. The AUX ports 25 allow hydraulic fluid to flow to and from the hydraulic actuator 27. The AUX ports 25 include a first AUX port 25a and a second AUX port 25b. The attachment 11 includes a first hydraulic port and a second hydraulic port. Each port includes a coupler.

[0066] For example, the user or the like connects an external fluid passage 26a including a hose or the like to the first AUX port 25a and to the first hydraulic port of the attachment 11, and connects an external fluid passage 26b to the second hydraulic port of the attachment 11 and to the second AUX port 25b. With this, hydraulic fluid is allowed to flow out (to be supplied) from the working machine 1 to the hydraulic actuator 27 of the attachment 11, and is allowed to flow from the hydraulic actuator 27 into (returns to) the working machine 1. This defines a hydraulic circuit between the working machine 1 and the hydraulic actuator 27, so that the hydraulic actuator 27 can be actuated by hydraulic fluid from the working machine 1 to cause the attachment 11 to perform work. In the example in FIG. 15, the above circuit allows a brush 11b, which is a driven portion of the sweeper, to be driven to rotate by power from the hydraulic actuator 27 and to perform work to remove a target object such as dust on a ground J.

[0067] As described above, the actuators 14, 15 and 27 provided in or on the working device 4 and the attachment 11 are actuated by hydraulic fluid to cause the working device 4 and the attachment 11 to perform work. Note that some attachments are electric-driven attachments including electric actuator(s) such as an electric motor and / or an electric cylinder. Such an electric-driven attachment performs work in the following manner. Electricity from a battery provided in or on the working machine 1 is inputted into an electric actuator via an electric connector and an electric cable in or on the machine body 2, so that the electric actuator is actuated and the attachment is driven by power from the actuator, making it possible to perform work.

[0068] FIG. 1 illustrates a work-related hydraulic circuit 4A included in the working machine 1. This hydraulic circuit 4A causes the working device 4 and the attachment 11 to operate. The working machine 1 includes a pilot pump P1 and a main pump P2. For example, the pilot pump P1 is a fixed displacement hydraulic pump, and the main pump P2 is a variable displacement hydraulic pump.

[0069] The pilot pump P1 is actuated by power from the prime mover 6 to deliver hydraulic fluid stored in a hydraulic fluid tank T to a fluid passage 40. The hydraulic fluid delivered by the pilot pump P1 is pilot fluid to control various hydraulic devices provided in the working machine 1. The pressure of pilot fluid is a pilot pressure.

[0070] The main pump P2 is actuated by power from the prime mover 6 to deliver hydraulic fluid stored in the hydraulic fluid tank T to a main fluid passage 45. The hydraulic fluid delivered by the main pump P2 is used to actuate the lift cylinders 14 and the tilt cylinders 15 of the working device 4, as well as hydraulic device(s) such as the hydraulic actuator 27 provided in or on the attachment 11.

[0071] The working machine 1 includes a plurality of control valves 60A, 60B and 60C. The plurality of control valves 60A, 60B and 60C include a lift control valve 60A, a tilt control valve 60B, and an auxiliary (AUX) control valve 60C. The plurality of control valves 60 are each connected to the main fluid passage 45. The lift control valve 60A controls the flow rate (output) and the supply direction of hydraulic fluid supplied from the main fluid passage 45 to the lift cylinders 14 to actuate the lift cylinders 14. The tilt control valve 60B controls the flow rate (output) and the supply direction of hydraulic fluid supplied from the main fluid passage 45 to the tilt cylinders 15 to actuate the tilt cylinders 15. The AUX control valve 60C controls the flow rate (output) and the supply direction of the hydraulic fluid supplied from the main fluid passage 45 to the hydraulic actuator 27 via the AUX port(s) 25 to actuate the hydraulic actuator 27.

[0072] The lift control valve 60A is connected to the lift cylinders 14 via a plurality of fluid passages 64a and 64b. The lift control valve 60A is a pilot-operated, direct-acting spool three-position switching valve. The lift control valve 60A includes a plurality of work pressure receivers 61a and 61b, and switches between a third position (neutral position) 61c, a first position 61d different from the third position 61c, and a second position 61e different from the third position 61c and the first position 61d depending on the pilot pressure acting on the work pressure receiver(s) 61a and / or 61b. When the lift control valve 60A is in the third position 61c, hydraulic fluid is not supplied from the main fluid passage 45 to the lift cylinders 14.

[0073] When the lift control valve 60A switches to the first position 61d or the second position 61e, hydraulic fluid from the main fluid passage 45 is supplied to the lift cylinders 14 via the lift control valve 60A and the fluid passage 64a or 64b. When the opening of the lift control valve 60A changes according to the pilot pressure while the lift control valve 60A is in the first position 61d or the second position 61e, the flow rate of hydraulic fluid from the main fluid passage 45 to the lift cylinders 14 is changed. Thus, the lift control valve 60A controls the supply direction and the flow rate of hydraulic fluid supplied from the main fluid passage 45 to the lift cylinders 14 according to the pilot pressure acting on the work pressure receiver(s) 61a and / or 61b to cause the lift cylinders 14 to extend or retract.

[0074] More specifically, when the lift control valve 60A switches to the first position 61d, hydraulic fluid from the main fluid passage 45 flows through the lift control valve 60A and the fluid passage 64a and is supplied to the rod-side chambers of the lift cylinders 14. With this, the lift cylinders 14 retract, the arms 10 swing downward, and the attachment 11 attached to the hitch 16 lowers. The hydraulic fluid pushed out of the cap-side chambers of the lift cylinders 14 flows through the fluid passage 64b and is drained from the lift control valve 60A.

[0075] When the lift control valve 60A switches to the second position 61e, hydraulic fluid from the main fluid passage 45 flows through the lift control valve 60A and the fluid passage 64b, and is supplied to the cap-side chambers of the lift cylinders 14. With this, the lift cylinders 14 extend, the arms 10 swing upward, and the attachment 11 attached to the hitch 16 is raised. The hydraulic fluid pushed out from the rod-side chambers of the lift cylinders 14 flows through the fluid passage 64a and is drained from the lift control valve 60A.

[0076] The tilt control valve 60B is connected to the tilt cylinders 15 by a plurality of fluid passages 65a and 65b. The tilt control valve 60B is a pilot-operated, direct-acting spool three-way switching valve. The tilt control valve 60B includes a plurality of work pressure receivers 62a and 62b, and switches between a third position (neutral position) 62c, a first position 62d different from the third position 62c, and a second position 62e different from the third position 62c and the first position 62d, depending on the pilot pressure acting on the work pressure receiver(s) 62a and / or 62b. When the tilt control valve 60B is in the third position 62c, hydraulic fluid is not supplied from the main fluid passage 45 to the tilt cylinders 15.

[0077] The tilt control valve 60B switches to the first position 62d or the second position 62e to allow hydraulic fluid from the main fluid passage 45 to be supplied to the tilt cylinders 15 via the tilt control valve 60B and the fluid passage 65a or 65b. When the opening of the tilt control valve 60B changes according to the pilot pressure while the tilt control valve 60B is in the first position 62d or the second position 62e, the flow rate of hydraulic fluid from the main fluid passage 45 to the tilt cylinders 15 is changed. Thus, the tilt control valve 60B controls the supply direction and the flow rate of hydraulic fluid supplied from the main fluid passage 45 to the tilt cylinders 15 according to the pilot pressure acting on the work pressure receiver(s) 62a and / or 62b to cause the tilt cylinders 15 to extend or retract.

[0078] More specifically, when the tilt control valve 60B switches to the first position 62d, hydraulic fluid from the main fluid passage 45 flows through the tilt control valve 60B and the fluid passage 65b, and is supplied to the cap-side chambers of the tilt cylinders 15. With this, the tilt cylinders 15 extend, the hitch 16 swings downward, the tilt angle of the attachment 11 attached to the hitch 16 decreases, and the orientation is changed such that the front portion of the attachment 11 lowers. The hydraulic fluid pushed out of the rod-side chambers of the tilt cylinders 15 flows through the fluid passage 65b and is drained from the tilt control valve 60B.

[0079] When the tilt control valve 60B switches to the second position 62e, hydraulic fluid from the main fluid passage 45 flows through the tilt control valve 60B and the fluid passage 65a, and is supplied to the rod-side chambers of the tilt cylinders 15. With this, the tilt cylinders 15 retract, the hitch 16 swings upward, the tilt angle of the attachment 11 attached to the hitch 16 increases, and the orientation is changed such that the front portion of the attachment 11 is raised. The hydraulic fluid pushed out from the cap-side chambers of the tilt cylinders 15 flows through the fluid passage 65a and is drained from the tilt control valve 60B.

[0080] The AUX control valve 60C is connected to the AUX ports 25 via a plurality of AUX fluid passages (auxiliary fluid passages) 66a and 66b. Specifically, a first port of the AUX control valve 60C and the first AUX port 25a are connected via the AUX fluid passage 66a, and a second port of the AUX control valve 60C and the second AUX port 25b are connected via the AUX fluid passage 66b. The AUX control valve 60C is a pilot-operated, direct-acting spool three-position switching valve. The AUX control valve 60C includes a plurality of AUX pressure receivers 63a and 63b, and switches between a third position (neutral position) 63c, a first position 63d different from the third position 63c, and a second position 63e different from the third position 63c and the first position 63d, depending on the pilot pressure acting on the AUX pressure receiver(s) 63a and / or 63b.

[0081] When the AUX control valve 60C is in the third position 63c, hydraulic fluid is not supplied to the hydraulic actuator 27 from the main fluid passage 45 via the AUX fluid passage 66a or 66b and the AUX port(s) 25. When the AUX control valve 60C switches to the first position 63d or the second position 63e, hydraulic fluid from the main fluid passage 45 is supplied to the hydraulic actuator 27 via the AUX control valve 60C, the AUX fluid passage 66a or 66b, and the corresponding AUX port 25, and the supply direction of the hydraulic fluid changes.

[0082] More specifically, when the AUX control valve 60C switches to the first position 63d, hydraulic fluid from the main fluid passage 45 is supplied to the hydraulic actuator 27 via the AUX control valve 60C, the AUX fluid passage 66a and the first AUX port 25a, and return fluid from the hydraulic actuator 27 flows through the second AUX port 25b and the AUX fluid passage 66b and is drained from the AUX control valve 60C. When the AUX control valve 60C switches to the second position 63e, hydraulic fluid from the main fluid passage 45 is supplied to the hydraulic actuator 27 via the AUX control valve 60C, the AUX fluid passage 66b and the second AUX port 25b, and return fluid from the hydraulic actuator 27 flows through the first AUX port 25a and the AUX fluid passage 66a and is drained from the AUX control valve 60C.

[0083] When the opening of the AUX control valve 60C changes according to the pilot pressure while the AUX control valve 60C is in the first position 63d or the second position 63e, the flow rate of hydraulic fluid supplied from the main fluid passage 45 to the hydraulic actuator 27 via the corresponding AUX port 25 is changed.

[0084] As described above, the AUX control valve 60C controls the supply direction and the flow rate of hydraulic fluid supplied from the main fluid passage 45 to the hydraulic actuator 27 via the corresponding AUX fluid passage 66a or 66b and the corresponding AUX port 25 according to the pilot pressure acting on the AUX pressure receiver(s) 63a and / or 63b to actuate the hydraulic actuator 27. The AUX control valve 60C, the AUX fluid passages 66a and 66b, and the AUX ports 25 define an auxiliary hydraulic circuit 4B to supply hydraulic fluid to the hydraulic actuator 27 of the attachment 11, and the auxiliary hydraulic circuit 4B is provided in the working machine 1.

[0085] The working machine 1 includes pressure detectors 70a and 70b. The pressure detectors 70a and 70b include pressure sensors. The pressure detector 70a is provided in the AUX fluid passage 66a to detect an AUX pressure (auxiliary pressure) which is the pressure of hydraulic fluid flowing from the AUX control valve 60C through the AUX fluid passage 66a and is supplied to the hydraulic actuator 27 of the attachment 11. The pressure detector 70b is provided in the AUX fluid passage 66b to detect an AUX pressure which is the pressure of hydraulic fluid flowing from the AUX control valve 60C through the AUX fluid passage 66b and is supplied to the hydraulic actuator 27. During work performed by the attachment 11 including the hydraulic actuator 27, the AUX pressure detected by the pressure detector(s) 70a and / or 70b can be regarded as a load on the attachment 11.

[0086] Note that the pressure detectors 70a and 70b also detect the pressure of hydraulic fluid (return fluid) flowing from the hydraulic actuator 27 through the corresponding AUX fluid passage 66a or 66b and returning to the AUX control valve 60C. However, since the pressure is equal to or substantially equal to the atmospheric pressure, the pressure is not regarded as auxiliary pressure by a controller 20.

[0087] The working machine 1 includes a plurality of solenoid valves 76a, 76b, 77a, 77b, 78a and 78b. The plurality of solenoid valves 76a, 76b, 77a, 77b, 78a and 78b are proportional valves in each of which the solenoid is energized and the opening is changed according to a control signal (electric current signal) inputted thereto. The plurality of solenoid valves 76a, 76b, 77a, 77b, 78a and 78b are each connected to fluid passages 40b and 40c branching from the fluid discharge passage 40, and a change in the opening thereof changes the pilot pressure of pilot fluid supplied from the fluid discharge passage 40. Specifically, as the electric current value of the control signal inputted increases, the opening of the plurality of solenoid valves 76a, 76b, 77a, 77b, 78a and 78b increases, allowing pilot fluid from the fluid discharge passage 40 to be outputted with an increased pilot pressure.

[0088] The plurality of solenoid valves 76a, 76b, 77a, 77b, 78a and 78b include lift solenoid valves 76a and 76b, tilt solenoid valves 77a and 77b, and AUX solenoid valves 78a and 78b. The lift solenoid valves 76a and 76b are respectively connected to the work pressure receivers 61a and 61b of the lift control valve 60A via fluid passages. The tilt solenoid valves 77a and 77b are respectively connected to the work pressure receivers 62a and 62b of the tilt control valve 60B via fluid passages. The AUX solenoid valves 78a and 78b are respectively connected to the AUX pressure receivers 63a and 63b of the AUX control valve 60C via fluid passages.

[0089] When the opening of the lift solenoid valve 76a is greater than 0 (zero), pilot fluid from the fluid discharge passage 40 acts on the work pressure receiver 61a from the lift solenoid valve 76a. In so doing, a pilot pressure corresponding to the opening of the lift solenoid valve 76a acts on the work pressure receiver 61a. When the pilot pressure acting on the work pressure receiver 61a is equal to or higher than a predetermined value, the spool of the lift control valve 60A moves, and the lift control valve 60A switches to the first position 61d. With this, the lift cylinders 14 retract and the attachment 11 lowers, and therefore the lift solenoid valve 76a is a solenoid valve to lower the attachment.

[0090] Similarly, when the opening of the lift solenoid valve 76b increases, pilot fluid from the fluid discharge passage 40 acts on the work pressure receiver 61b from the lift solenoid valve 76b, and the lift control valve 60A switches to the second position 61e. With this, the lift cylinders 14 extend and the attachment 11 is raised, and therefore the lift solenoid valve 76b is a solenoid valve to raise the attachment.

[0091] Similarly, when the opening of the tilt solenoid valve 77a increases, pilot fluid from the fluid discharge passage 40 acts on the work pressure receiver 62a from the tilt solenoid valve 77a, and the tilt control valve 60B switches to the first position 62d. With this, the tilt cylinders 15 extend and the tilt angle of the attachment 11 decreases, and therefore the tilt solenoid valve 77a is a solenoid valve to lower the front portion of the attachment. When the opening of the tilt solenoid valve 77b increases, pilot fluid from the fluid discharge passage 40 acts on the work pressure receiver 62b from the tilt solenoid valve 77b, and the tilt control valve 60B switches to the second position 62e. With this, the tilt cylinders 15 retract and the tilt angle of the attachment 11 increases, and therefore the tilt solenoid valve 77b is a solenoid valve to raise the front portion of the attachment.

[0092] Similarly, when the opening of the AUX solenoid valve 78a increases, pilot fluid from the fluid discharge passage 40 acts on the AUX pressure receiver 63a via the AUX solenoid valve 78a, and the AUX control valve 60C switches to the first position 63d. With this, hydraulic fluid is supplied from the AUX control valve 60C to the hydraulic actuator 27 via the AUX fluid passage 66a and the first AUX port 25a. When the opening of the AUX solenoid valve 78b increases, pilot fluid from the fluid discharge passage 40 acts on the AUX pressure receiver 63b via the AUX solenoid valve 78b, and the AUX control valve 60C switches to the second position 63e. With this, hydraulic fluid is supplied from the AUX control valve 60C to the hydraulic actuator 27 via the AUX fluid passage 66b and the second AUX port 25b.

[0093] The plurality of solenoid valves 76a, 76b, 77a, 77b, 78a and 78b change the pilot pressure to act on the corresponding pressure receivers 61a, 61b, 62a, 62b, 63a and 63b according to the control signals inputted thereto to change the flow rate of hydraulic fluid from the corresponding control valves 60A, 60B and 60C to the corresponding actuators 14, 15 and 27.

[0094] The working machine 1 includes a work manual operator (work manual operator unit) 67 and the controller 20. The work manual operator 67 is operable to control the swinging of the arms 10 and the hitch 16. The work manual operator 67 includes a digital joystick. The work manual operator 67 includes a work operating lever 67a and a sensor 67b. The work operating lever 67a is a manual operator (work manual operator) to be operated by the driver of the working machine, and is provided in the vicinity of the seat 8 inside the cabin 3. The work operating lever 67a can be operated not only forward and rearward from a neutral position, but also leftward and rightward from the neutral position.

[0095] The sensor 67b includes at least one of an angle sensor or an electric circuit, detects the operation direction and the operation angle (angle of pivoting) of the work operating lever 67a, and outputs a detection signal (electric signal) corresponding to the operation direction and the operation angle. The controller 20 determines the operation direction and the operation angle of the work operating lever 67a based on the detection signal outputted from the sensor 67b, and calculates the ratio of the operation angle to the maximum angle of pivoting of the work operating lever 67a as the operation amount of the work operating lever 67a.

[0096] The controller 20 then inputs a control signal into the lift solenoid valve 76a or 76b or the tilt solenoid valve 77a or 77b according to the operation direction and the operation amount of the work operating lever 67a to open the solenoid valve. With this, a corresponding one of the lift control valve 60A and the tilt control valve 60B switches to the first position 61d, 62d or the second position 61e, 62e, the lift cylinders 14 or the tilt cylinders 15 extend or retract, the arms 10 or the hitch 16 swing(s) in the corresponding direction, and the position including the height or the orientation (tilt angle) of the attachment 11 attached to the hitch 16 is changed.

[0097] Specifically, when the work operating lever 67a is pivoted forward, the controller 20 inputs a control signal into the lift solenoid valve 76a according to the operation amount of the work operating lever 67 to open the lift solenoid valve 76a. With this, the lift control valve 60A switches to the first position 61d, the lift cylinders 14 retract, the arms 10 swing downward, the attachment 11 lowers, and the height of the attachment 11 decreases. In so doing, the attachment 11 is positioned somewhat forward.

[0098] When the work operating lever 67a is pivoted rearward, the controller 20 inputs a control signal into the lift solenoid valve 76b according to the operation amount of the work operating lever 67a to open the lift solenoid valve 76b. With this, the lift control valve 60A switches to the second position 61e, the lift cylinders 14 extend, the arms 10 swing upward, the attachment 11 is raised, and the height of the attachment 11 increases. In so doing, the attachment 11 is positioned somewhat rearward.

[0099] When the work operating lever 67a is pivoted leftward, the controller 20 inputs a control signal into the tilt solenoid valve 77a according to the operation amount of the work operating lever 67a to open the tilt solenoid valve 77a. With this, the tilt control valve 60B switches to the first position 62d, the tilt cylinders 15 extend, and the hitch 16 swings downward, so that the orientation of the attachment 11 is changed such that the front portion of the attachment 11 lowers.

[0100] When the work operating lever 67a is pivoted rightward, the controller 20 inputs a control signal into the tilt solenoid valve 77b according to the operation amount of the work operating lever 67a to open the tilt solenoid valve 77b. With this, the tilt control valve 60B switches to the second position 62e, the tilt cylinders 15 retract, the hitch 16 swings upward, so that the orientation of the attachment 11 is changed such that the front portion of the attachment 11 is raised.

[0101] Note that when the controller 20 causes the arms 10 to swing, the controller 20 causes the hitch 16 to swing so that the orientation of the attachment 11 is not changed. That is, the controller 20, when causing the arms 10 to swing by inputting a control signal into one of the lift solenoid valves 76a and 76b, the controller 20 also inputs a control signal into a corresponding one of the tilt solenoid valves 77a and 77b that corresponds to the swinging direction of the arms 10 to cause the hitch 16 to swing, thus keeping the orientation of the attachment 11. This eliminates or reduces the likelihood that, when the arms 10 swing, the attachment 11 will tilt and accidentally contact a target object or surrounding objects and be damaged.

[0102] The working machine 1 includes an AUX output switch 73b. The AUX output switch 73b is an operating switch to be operated by the driver. The AUX output switch 73b is turned ON to start supplying hydraulic fluid to the corresponding AUX port 25, and is turned OFF to stop supplying the hydraulic fluid.

[0103] When the controller 20 is in an AUX mode in which the attachment 11 including the hydraulic actuator 27 is allowed to be used with the working machine 1, if the AUX output switch 73b is turned ON, the controller 20 inputs a control signal into one of the AUX solenoid valves 78a and 78b to open the solenoid valve. With this, the AUX control valve 60C switches to the first position 63d or the second position 63e, and hydraulic fluid is supplied from the AUX control valve 60C to the corresponding AUX port 25 via the AUX fluid passage 66a or the AUX fluid passage 66b. In so doing, if the AUX ports 25 and hydraulic ports of the attachment 11 are connected by the external fluid passages 26, hydraulic fluid is supplied from the corresponding AUX port 25 to the hydraulic actuator 27 of the attachment 11 via the corresponding external fluid passage 26 and the like, the hydraulic actuator 27 is actuated, and the attachment 11 is driven.

[0104] When the controller 20 is in the AUX mode, if the AUX output switch 73b is turned OFF, the controller 20 stops inputting the control signal into the AUX solenoid valve 78a or 78b to close the AUX solenoid valve 78a or 78b. With this, the AUX control valve 60C switches to the third position 63c, and the supply of hydraulic fluid from the AUX control valve 60C to the AUX port 25 is stopped. Thus, the supply of hydraulic fluid to the hydraulic actuator 27 of the attachment 11 is also stopped, the hydraulic actuator 27 stops, and the attachment 11 stops.

[0105] The controller 20 inputs a control signal into at least one of the lift solenoid valve 76b or 76b or the tilt solenoid valve 77a or 77b according to the AUX pressure detected by the pressure detectors 70a and 70b to open the solenoid valve(s). With this, the controller 20 switches at least one of the lift control valve 60A or the tilt control valve 60B to the first position or the second position to supply hydraulic fluid to at least one of the lift cylinders 14 or the tilt cylinders 15 to cause the cylinders to extend or retract to cause at least one of the arms 10 or the hitch 16 to swing, thus adjusting at least one of the position or the orientation of the attachment 11. Thus, the controller 20 performs a posture control to control the working device 4 according to the AUX pressure to adjust the posture of the attachment 11.

[0106] The working machine 1 includes a load sensing system (which may be hereinafter simply referred to as “LS system”) 80. The LS system 80 is a hydraulic system to control the flow rate of hydraulic fluid delivered by the variable displacement main pump P2 such that a differential pressure is constant. The differential pressure is obtained by subtracting, from the hydraulic fluid delivery pressure of the main pump P2 which is a variable displacement pump, the maximum of load pressures on the actuators 14, 15 and 27 actuated by hydraulic fluid delivered by the main pump P2.

[0107] The LS system 80 includes a swash plate changing cylinder 81, a flow rate compensation valve 82, and an opening changing cylinder 83. The swash plate changing cylinder 81 adjusts the angle of the swash plate of the main pump P2. The flow rate compensation valve 82 causes a hydraulic pressure to act on the swash plate changing cylinder 81 to actuate the swash plate changing cylinder 81. The opening changing cylinder 83 is actuated by the pilot pressure of pilot fluid from the pilot pump P1 to change the opening of the flow rate compensation valve 82.

[0108] A PLS fluid passage 84 and a PPS fluid passage 85 are connected to the flow rate compensation valve 82. The PLS fluid passage 84 is a fluid passage to transmit a PLS pressure which is the maximum of the load pressures on the actuators 14, 15 and 27 (actuator maximum load pressure). The PPS fluid passage 85 is used to transmit a PPS pressure which is the delivery pressure of the main pump P2. The flow rate compensation valve 82 actuates the swash plate changing cylinder 81 to adjust the angle of the swash plate of the main pump P2 such that the differential pressure, which is obtained by subtracting the PLS pressure from the PPS pressure, is constant. With this, the flow rate of hydraulic fluid delivered by the main pump P2 is controlled, and hydraulic power corresponding to the load applied to the working device 4 and the attachment 11 is outputted from the main pump P2.

[0109] In the present example embodiment, the swash plate of the main pump P2 is pressed by the self-pressure thereof in a direction that increases the flow rate of hydraulic delivered by the main pump P2. The swash plate changing cylinder 81 is operable to cause a force against the self-pressure of the main pump P2 to act on the swash plate. Furthermore, the flow rate compensation valve 82 is operable to control the delivery flow rate of the main pump P2 by adjusting the hydraulic pressure acting on the swash plate changing cylinder 81. Thus, when the hydraulic pressure acting on the swash plate changing cylinder 81 is removed (becomes zero), the angle of the swash plate of the main pump P2 becomes maximum, and the flow rate of hydraulic fluid delivered by the main pump P2 becomes maximum.

[0110] FIG. 2 illustrates a travel-related hydraulic circuit 5A included in the working machine 1. The hydraulic circuit 5A actuates the traveling devices 5 to cause the working machine 1 to travel. The working machine 1 includes travel pumps 50 and travel motors 51.

[0111] Each travel pump 50 is a hydraulic pump to be actuated by power from the prime mover 6. The travel pump 50 is a swash-plate variable displacement axial pump and includes pressure receivers 50a and 50b to receive pilot pressure. The pump pressure receivers 50a and 50b include a forward-travel pump pressure receiver 50a and a rearward-travel pump pressure receiver 50b. The angle of the swash plate of the travel pump 50 is changed according to the pilot pressure acting on the pump pressure receiver(s) 50a and / or 50b. When the angle of the swash plate of the travel pump 50 is changed, the flow rate and the supply direction of the hydraulic fluid delivered by the travel pump 50 change. The travel pumps 50 include a first travel pump 50L corresponding to the first traveling device 5, and a second travel pump 50R corresponding to the second traveling device 5.

[0112] Each travel motor 51 is a hydraulic motor to be actuated by hydraulic fluid delivered by the corresponding travel pump 50. The travel motors 51 include a first travel motor 51L corresponding to the first travel pump 50L, and a second travel motor 51R corresponding to the second travel pump 50R.

[0113] The first travel motor 51L is connected to the first travel pump 50L via a closed loop circuit fluid passage 53a. The first travel motor 51L is actuated by hydraulic fluid supplied from the first travel pump 50L. The first travel motor 51L includes an output shaft 51Lj, and changes the rotation speed of the output shaft 51Lj based on the flow rate of hydraulic fluid delivered by the first travel pump 50L. When the power from the first travel motor 51L is transmitted from the output shaft 51Lj to the drive shaft of the first traveling device 5 via a transmission mechanism, the first traveling device 5 is driven.

[0114] The first travel motor 51L includes a swash plate. When the angle of the swash plate of the first travel motor 51L is changed by a swash plate cylinder 52L, the first travel motor 51L changes the rotation speed stage of the output shaft 51Lj to a first speed stage (low speed stage) or a second speed stage (high speed stage) higher than the first speed stage. Specifically, when the swash plate cylinder 52L retracts, the rotation speed of the output shaft 51Lj of the first travel motor 51L is set to the first speed stage. When the swash plate cylinder 52L extends, the rotation speed of the output shaft 51Lj of the first travel motor 51L is set to the second speed stage.

[0115] The second travel motor 51R is connected to the second travel pump 50R via a closed loop circuit fluid passage 53b. The second travel motor 51R is actuated by hydraulic fluid delivered by the second travel pump 50R to drive the second traveling device 5 via an output shaft 51Rj and the like. When the angle of the swash plate of the second travel motor 51R is changed by a swash plate cylinder 52R, the second travel motor 51R changes the rotation speed stage of the output shaft 51Rj to the first speed stage or the second speed stage. Since the configurations of the second travel motor 51R, the second travel pump 50R, the second traveling device 5 and the swash plate cylinder 52R are respectively the same as the configurations of the first travel motor 51L, the first travel pump 50L, the first traveling device 5 and the swash plate cylinder 52L, detailed description therefor is omitted.

[0116] The working machine 1 includes a plurality of operating valves 54a, 54b, 54c and 54d. Each of the operating valves 54a, 54b, 54c and 54d is a proportional valve in which a solenoid thereof is energized in response to a control signal (electric current signal) inputted thereto and the opening is changed. The plurality of the operating valves 54a, 54b, 54c and 54d are provided in respective four fluid passages 42a, 42b, 42c and 42d connected to the fluid discharge passage 40. Each of them changes the pilot pressure of pilot fluid supplied from the fluid discharge passage 40 according to changes in the opening thereof. Specifically, as the electric current value of the inputted control signal increases, the opening of each of the plurality of operating valves 54a, 54b, 54c and 54d increases, allowing pilot fluid from the fluid discharge passage 40 to be outputted with an increased pilot pressure.

[0117] The first operating valve 54a is connected to the forward-travel pump pressure receiver 50a of the first travel pump 50L via the fluid passage 42a. The second operating valve 54b is connected to the rearward-travel pump pressure receiver 50b of the first travel pump 50L via the fluid passage 42b. The third operating valve 54c is connected to the forward-travel pump pressure receiver 50a of the second travel pump 50R via the fluid passage 42c. The fourth operating valve 54d is connected to the rearward-travel pump pressure receiver 50b of the second travel pump 50R via the fluid passage 42d.

[0118] The working machine 1 includes a travel manual operator (travel manual operator unit) 57. The travel manual operator 57 is operable to operate the travel pumps 50, the travel motors 51, and the traveling devices 5. The travel manual operator 57 includes a digital joystick. The travel manual operator 57 includes a travel operating lever 57a and a sensor 57b. The travel operating lever 57a is a manual operator (travel manual operator) to be operated by the driver, and is provided in the vicinity of the seat 8 inside the cabin 3. The travel operating lever 57a can be operated not only forward, rearward, leftward, and rightward from a neutral position, but also diagonally leftward and forward, diagonally rightward and forward, diagonally leftward and rearward, and diagonally rightward and rearward from the neutral position.

[0119] The sensor 57b includes at least one of an angle sensor or an electric circuit, detects the operation direction and the operation angle of the travel operating lever 57a, and outputs a detection signal corresponding to the operation direction and the operation angle. The controller 20 determines the operation direction and the operation angle of the travel operating lever 57a based on the detection signal outputted from the sensor 57b, and calculates the ratio of the operation angle relative to the maximum angle of pivoting of the travel operating lever 57a as the operation amount of the travel operating lever 57a.

[0120] The controller 20 then, according to the operation direction and the operation amount of the travel operating lever 57a, decides a target value of the travel speed of the machine body 2, a target value of the swash plate angle of the travel pump(s) 50L and 50R, and / or a target value of the pump pressure to be applied to the travel motor(s) 51L and 51R. The controller 20 then inputs a control signal(s) corresponding to the decided target value(s) into at least one of the plurality of operating valves 54a, 54b, 54c and 54d to open the operating valve(s). With this, pilot pressure acts on the pump pressure receiver(s) 50a and / or 50b of the corresponding travel pump(s) 50L and 50R, the angle of the swash plate of the travel pump(s) is changed, and the flow rate and direction of hydraulic fluid delivered by the travel pump(s) are defined or changed. Furthermore, the rotation speed and the rotation direction of the output shaft(s) 51Lj and 51Lj of the corresponding travel motor(s) 51L and 51R are defined or changed, and the travel speed and the travel direction of the traveling device(s) 5 and the machine body 2 (working machine 1) are also defined or changed.

[0121] Specifically, when the travel operating lever 57a is pivoted forward, the controller20 inputs a control signal into the operating valves 54a and 54c according to the operation amount of the travel operating lever 57a to open the operating valves 54a and 54c. With this, the pilot pressures outputted from the operating valves 54a and 54c act on the forward-travel pump pressure receivers 50a of the travel pumps 50L and 50R via the respective fluid passages 42a and 42c. With this, the angle of the swash plates of the travel pumps 50L and 50R is changed, the output shafts 51Lj and 51Rj of the travel motors 51L and 51R rotate forward (rotate to achieve forward travel), the first traveling device 5 and the second traveling device 5 are driven to achieve forward travel, and the working machine 1 travels straight forward at a travel speed corresponding to the operation amount of the travel operating lever 57a.

[0122] When the travel operating lever 57a is pivoted rearward, the controller 20 inputs a control signal into the operating valves 54b and 54d according to the operation amount of the travel operating lever 57a to open the operating valves 54b and 54d. With this, the pilot pressures outputted from the operating valves 54b and 54d act on the rearward-travel pump pressure receivers 50b of the travel pumps 50L and 50R via the respective fluid passages 42b and 42d. With this, the angle of the swash plates of the travel pumps 50L and 50R is changed, the output shafts 51Lj and 51Rj of the travel motors 51L and 51R rotate reversely (rotate to achieve rearward travel), the first traveling device 5 and the second traveling device 5 are driven to achieve rearward travel, and the working machine 1 travels straight rearward at a travel speed corresponding to the operation amount of the travel operating lever 57a.

[0123] When the travel operating lever 57a is pivoted leftward, the controller 20 inputs a control signal into the operating valves 54b and 54c according to the operation amount of the travel operating lever 57a to open the operating valves 54b and 54c. With this, the pilot pressures outputted from the operating valves 54b and 54c act on the rearward-travel pump pressure receiver 50b of the travel pump 50L and the forward-travel pressure receiver 50a of the travel pump 50R via the respective fluid passages 42b and 42c. With this, the angle of the swash plates of the travel pumps 50L and 50R is changed, the output shaft 51Lj of the first travel motor 51L rotates reversely and the first traveling device 5 is driven to achieve rearward travel, the output shaft 51Rj of the second travel motor 51R rotates forward and the second traveling device 5 is driven to achieve forward travel, and the working machine 1 makes a spin turn to the left.

[0124] When the travel operating lever 57a is pivoted rightward, the controller 20 inputs a control signal into the operating valves 54a and 54d according to the operation amount of the travel operating lever 57a to open the operating valves 54a and 54d. With this, the pilot pressures outputted from the operating valves 54a and 54d act on the forward-travel pump pressure receiver 50a of the travel pumps 50L and the rearward-travel pressure receiver 50b of the travel pump 50R via the respective fluid passages 42a and 42d. With this, the angle of the swash plates of the travel pumps 50L and 50R is changed, the output shaft 51Lj of the first travel motor 51L rotates forward, the first traveling device 5 is driven to achieve forward travel, the output shaft 51Rj of the second travel motor 51R rotates reversely, the second traveling device 5 is driven to achieve rearward travel, and the working machine 1 makes a spin turn to the right.

[0125] Furthermore, when the travel operating lever 57a is pivoted diagonally leftward and forward, diagonally rightward and forward, diagonally leftward and rearward, or diagonally rightward and rearward, the controller 20 inputs a control signal into one of or two of the operating valves 54a to 54d according to the direction of pivoting and the operation amount to open the operating valve(s). With this, pilot pressure acts on the pump receivers 50a and / or 50b of the travel pumps 50L and 50R corresponding to the open operating valve(s), the angle of the swash plates of the corresponding travel pumps 50L and 50R is changed, the rotation direction and the rotation speed of the output shafts 51Lj and 51Rj of the corresponding travel motors 51L and 51R are defined, and the working machine 1 makes a pivot turn or a slow turn to the right or to the left while traveling forward or rearward.

[0126] Specifically, when the travel operating lever 57a is pivoted diagonally leftward and forward, the working machine 1 turns left while traveling forward at a travel speed corresponding to the operation direction and the operation amount of the travel operating lever 57a. When the travel operating lever 57a is pivoted diagonally rightward and forward, the working machine 1 turns right while traveling forward at a travel speed corresponding to the operation direction and the operation amount of the travel operating lever 57a. When the travel operating lever 57a is pivoted diagonally leftward and rearward, the working machine 1 turns left while traveling rearward at a travel speed corresponding to the operation direction and the operation amount of the travel operating lever 57a. When the travel operating lever 57a is pivoted diagonally rightward and rearward, the working machine 1 turns right while traveling rearward at a travel speed corresponding to the operation direction and operation amount of the travel operating lever 57a.

[0127] The working machine 1 includes speed-change switching valves 58L and 58R, a speed-change solenoid valve 59, and a speed-change switch 75. The speed-change switching valves 58L and 58R are two-position switching valves. The speed-change switching valve 58L is connected to the swash plate cylinder 52L by a fluid passage, and the speed-change switching valve 58R is connected to the swash plate cylinder 52R by a fluid passage. The speed-change switching valves 58L and 58R are connected to the speed-change solenoid valve 59 via a fluid passage 41. The speed-change solenoid valve 59 is a two-position solenoid switching valve including two positions and a solenoid to be energized in response to a control signal inputted thereto to switch between the positions. The speed-change solenoid valve 59 is connected to the fluid discharge passage 40, and switches the positions of the switching valves 58L and 58R. The speed-change switch 75 is an operating switch to be operated by the driver to input an instruction to switch the speed stage of the rotation speed of the output shafts 51Lj and 51Rj of the travel motor 51 to a first speed stage (low speed stage) or a second speed stage (high speed) higher than the first speed stage.

[0128] Upon receipt of an instruction to switch the speed stage to the first speed stage from the speed-change switch 75, the controller 20 inputs a control signal into the speed-change solenoid valve 59 to switch the speed-change solenoid valve 59 to the first position to block pilot fluid. With this, the pilot fluid from the fluid discharge passage 40 does not act on the pressure receivers of the speed-change switching valves 58L and 58R via the speed-change solenoid valve 59, the speed-change switching valves 58L and 58R are in the first position to block hydraulic fluid, and hydraulic fluid is not supplied from the speed-change switching valves 58L and 58R to the swash plate cylinders 52L and 52R. Thus, the swash plate cylinders 52L and 52R are caused to retract by the elastic force of a spring, and the rotation speed of the output shafts 51Lj and 51Rj of the travel motors 51 is switched to the first speed stage.

[0129] Upon receipt of an instruction to switch the speed stage to the second speed stage from the speed-change switch 75, the controller 20 inputs a control signal into the speed-change solenoid valve 59 to switch the speed-change solenoid valve 59 to the second position to allow pilot fluid to pass therethrough. With this, pilot fluid from the fluid discharge passage 40 acts on the pressure receivers of the speed-change switching valves 58L and 58R via the speed-change solenoid valve 59, the speed-change switching valves 58L and 58R switch to the second position to allow hydraulic fluid to pass therethrough, and hydraulic fluid is supplied from the speed-change switching valves 58L and 58R to the swash plate cylinders 52L and 52R. Thus, the swash plate cylinders 52L and 52R are caused to extend by the hydraulic pressure, and the rotation speed of the output shafts 51Lj and 51Rj of the travel motors 51 is switched to the second speed stage.

[0130] Regardless of whether the speed-change switch 75 is operated or not, the controller 20 may switch the positions of the speed-change solenoid valve 59 to automatically change the second speed stage to the first speed stage (automatic speed reduction) or automatically change the first speed stage to the second speed stage speed (automatic speed increase). In the case where work is performed using a specific attachment 11, the controller 20 switches the speed stage to the first speed stage to perform a low-speed mode (creep mode) in which the travel speed of the working machine 1 is kept at a low speed.

[0131] The working machine 1 includes a plurality of braking actuators 55, a braking solenoid valve 56 and a braking switch 79. The braking actuators 55 are hydraulic cylinders to brake the corresponding travel motors 51L and 51R. The braking solenoid valve 56 is a two-position solenoid switching valve including two positions and a solenoid to be energized in response to a control signal inputted therein to switch between the positions. The braking solenoid valve 56 is connected to the plurality of braking actuators 55 via fluid passages, and is also connected to the main fluid passage 45. The braking switch 79 is a detection switch to detect the depression of a braking pedal provided at the bottom of the seat 8 (FIG. 15). The user depresses the braking pedal to achieve braking.

[0132] When the braking pedal is not depressed, the braking solenoid valve 56 is in the first position to block hydraulic fluid from the main fluid passage 45, and the braking actuators 55 do not brake the rotation of the output shafts 51Lj and 51Rj of the travel motors 51L and 51R. When a detection signal corresponding to the depression of the braking pedal is inputted from the braking switch 79, the controller 20 inputs a control signal into the braking solenoid valve 56 to switch the braking solenoid valve 56 to the second position to allow hydraulic fluid to pass therethrough. With this, the hydraulic fluid from the main fluid passage 45 is supplied to the braking actuators 55 via the braking solenoid valve 56, the braking actuators 55 brake the rotation of the output shafts 51Lj and 51Rj of the travel motors 51L and 51R, the working machine 1 slows down, and the working machine 1 stops.

[0133] When the braking pedal is not depressed and the detection signal is not inputted anymore from the braking switch 79, the controller 20 stops the input of the control signal into the braking solenoid valve 56 to switch the braking solenoid valve 56 to the first position. With this, the hydraulic fluid from the main fluid passage 45 is not supplied to the braking actuators 55 via the braking solenoid valve 56, and the braking actuators 55 do not brake the rotation of the output shafts 51Lj and 51Rj of the travel motors 51L and 51R. The controller 20 may also be configured or programmed to, regardless of whether the braking pedal is depressed or not, switch the position of the braking solenoid valve 56 to brake the rotation of the output shafts 51Lj and 51Rj of the travel motors 51L and 51R and stop the rotation.

[0134] FIG. 3 is a block diagram showing an electrical configuration of the working machine 1. The working machine 1 includes elements shown in FIG. 3. The controller 20 includes a processing circuit including one or more processors. The working machine 1 includes the controller 20 which is configured or programmed to perform various controls relating to the working machine 1. The controller 20 is connected to the other elements shown in FIG. 3 in a communicable manner via in-vehicle network(s) such as CAN, ISOBUS, LIN and / or FlexRay.

[0135] The controller 20 includes at least one of one or more internal memories, analog circuits, digital circuits, and the like. The analog circuits and the digital circuits include one or more processors. The processor(s) included in the controller 20 include, for example, a central processing unit (CPU), a graphics processing unit (GPU), a digital signal processor (DSP), a field programmable gate array (FPGA), an application specific integrated circuit (ASIC) and / or the like.

[0136] The internal memory (memories) of the controller 20 is / are each a volatile or nonvolatile memory which stores software program(s) to be executed by one or more processors and various data. The controller 20 uses a predetermined storage area of the internal memory as a buffer to temporarily store information and data.

[0137] A storing device (memory and / or storage) 21 includes a nonvolatile memory and / or the like. The storing device 21 also stores software program(s) to be executed by one or more processors of the controller 20 and various data. The storing device 21 also stores control data corresponding to various attachments 11.

[0138] The one or more processors of the controller 20 read(s) software program(s) and control data from the internal memory and / or the storing device 21, and perform various processes based on the software program(s) and the control data. The one or more processors of the controller 20 may perform various processes based on a predetermined logic circuit.

[0139] Note that a plurality of physically separated processors of the controller 20 may operate together to perform various processes, and the configuration of the controller 20 is not limited to the above described configuration. In such a case, the plurality of processors are respectively provided in one or more computers which are physically separated from the working machine 1, and are connected in a communicable manner via a network such as a in-vehicle network, LAN, WAN, and / or the Internet.

[0140] The following configuration may be used: the above described software program(s) is / are stored in a storage medium (nonvolatile memory such as HDD, SSD, CD-ROM, DVD-ROM) connected in a communicable manner with the controller 20 and / or in external device(s) such as a server and / or the like connected via the above described network(s), and is / are installed from such storage medium(media) and / or the external device(s) into the internal memory or the storing device 21.

[0141] A user interface 22 is, for example, a terminal device (computer) in the form of a touchscreen or a tablet including a display. The user interface 22 is provided in the vicinity of the seat 8 inside the cabin 3 (FIG. 15). The controller 20 causes the user interface 22 to output (display) various information relating to the working machine 1 stored in the internal memory and / or the storing device 21 to the driver or the like (or to other user(s)).

[0142] The driver or the like of the working machine 1 inputs various information via the user interface 22. For example, information indicating the attachment 11 attached to the working device 4 can be inputted via the user interface 22. The controller 20 causes the internal memory and / or the storing device 21 to store the information inputted via the user interface 22. The user interface 22 functions as an input interface and an output interface. The user interface 22 may include input device(s) such as at least one manual operator, e.g., a button, a switch, a dial, and / or a slider, and / or a microphone, and output device(s) such as a speaker.

[0143] A communicator 24 shown in FIG. 3 includes a communication circuit to wirelessly communicate with external device(s) such as a server, a terminal device and / or a portable device via the Internet, a wireless LAN and / or the like. The portable device is, for example, a smartphone or a tablet. The communicator 24 may include a receiver compliant with a satellite positioning system to receive radio waves from satellites. The communicator 24 also functions as an input interface and an output interface.

[0144] A beacon scanner 23 is a receiver to receive wireless signals compliant with a near field communication standard. Specifically, the beacon scanner 23 receives wireless signals (beacon signals) compliant with Bluetooth (registered trademark) Low Energy which is a near field communication standard. As shown in FIG. 15, the beacon scanner 23 is provided at a front portion of the machine body 2. In the case where a beacon transmitter 19 is provided on the attachment 11 attached to the hitch 16, the beacon scanner 23 receives wireless signals transmitted from the beacon transmitter 19. The beacon scanner 23 is an input interface.

[0145] In the case where the attachment 11 attached to the hitch 16 includes an electric circuit including a processor such as CPU, an electric harness connected to the electric circuit is connected to an AUX connector 28. The AUX connector 28 may communicate in a wired manner with the attachment 11, and functions as an input interface and an output interface.

[0146] An attaching switch 29a, a detaching switch 29b, an accelerator 7, the speed-change switch 75, the braking switch 79, the travel manual operator 57, the work manual operator 67, and an AUX manual operator 73 are provided in the vicinity of the seat 8 inside the cabin 3, and are operated by the driver of the working machine 1.

[0147] The attaching switch 29a is operated to attach the attachment 11 to the hitch 16. The detaching switch 29b is operated to allow the attachment 11 to be detached from the hitch 16. As another example, a single operating switch may be used as an attaching switch and a detaching switch.

[0148] A latch control valve 35 is a three-position solenoid switching valve including three positions and a solenoid to be energized in response to a control signal inputted thereto to switch between the positions, and controls the latch cylinder 17. As shown in FIG. 4, the latch control valve 35 is connected to the latch cylinder 17 by fluid passages and is also connected to the main fluid passage 45. The latch control valve 35 is switchable between (i) a neutral position 35c to block hydraulic fluid from the fluid passage 45, (ii) a first position 35a to allow hydraulic fluid to be supplied to the cap-side chamber of the latch cylinder 17 to cause the latch cylinder 17 to extend, and (iii) a second position 35b to allow hydraulic fluid to be supplied to the rod-side chamber of the latch cylinder 17 to cause the latch cylinder 17 to retract.

[0149] For example, the driver of the working machine 1 operates the work manual operator 67 (FIG. 1) to lower the arms 10 and the hitch 16, and operates the travel manual operator 57 (FIG. 2) to cause the machine body 2 to travel forward very slowly, thus causing the front surface of the bracket 30 of the hitch 16 to contact the base plate 9 (FIG. 16) of the attachment 11 placed on the ground J. Then, when the driver operates the attaching switch 29a, the controller 20 inputs a control signal into the latch control valve 35 to switch the latch control valve 35 from the neutral position 35c to the first position 35a. With this, the latch cylinder 17 extends, the latching mechanisms 31 switch to the latching state, and the attachment 11 is attached (fixed) to the hitch 16.

[0150] The driver, while the working machine 1 is in the stopped state, operates the work manual operator 67 to lower the arms 10 and the hitch 16 to cause the attachment 11 attached to the hitch 16 to contact the ground. Then, when the driver operates the detaching switch 29b, the controller 20 inputs a control signal into the latch control valve 35 to switch the latch control valve 35 from the neutral position 35c to the second position 35b. With this, the latch cylinder 17 retracts, the latching mechanisms 31 switch to the unlatching state, and the attachment 11 is allowed to be detached from the hitch 16. In this state, when the driver operates the travel manual operator 57 to cause the machine body 2 to travel rearward, the attachment 11 is detached from the hitch 16.

[0151] A speed detector 36 shown in FIG. 3 detects the travel speed of the working machine 1 (machine body 2). Specifically, the speed detector 36 includes, for example, rotation speed sensor(s) to detect the rotation speed of the travel motors 51L and 51R (FIG. 2) and a calculator, and the calculator calculates the travel speed based on a detection signal from the rotation speed sensor(s). Note that the calculator may not be provided in the speed detector 36, and the controller 20 may calculate the travel speed based on the detection signal from the rotation speed sensor.

[0152] As another example, the speed detector 36 (or the controller 20) may calculate the travel speed of the working machine 1 based on the operation amount of the travel operating lever 57a detected by the sensor 57b of the travel manual operator 57. Alternatively, the speed detector 36 (or the controller 20) may calculate the position of the machine body 2 at regular intervals based on signals received by the receiver of the communicator 24 from satellites of a satellite positioning system, and calculate the travel speed of the working machine 1 based on time-series position data of the machine body 2. The configuration to detect the travel speed of the working machine 1 is not limited to the above, and a speed detector to detect the travel speed by some other known method may be used.

[0153] An arm position detector 37 and a tilt angle detector 38 include an inertial measurement unit (IMU), a potentiometer, or a sensor such as a gyroscope sensor. The arm position detector 37 detects at least the swinging angle of the arms 10. The controller 20, based on the detection result from the arm position detector 37, detects the position of the distal ends of the arms 10 and the hitch 16 in the up-down direction and in the front-back direction and also detects the position of the attachment 11 attached to the hitch 16 in the up-down direction and in the front-back direction.

[0154] Specifically, the controller 20 detects the position of a work surface 11w (FIG. 15) of the attachment 11 attached to the hitch 16 at least in the up-down direction and the front-back direction, based on the detection result from the arm position detector 37. The work surface 11w is an imaginary surface defined at the contact portion of the attachment 11 that contacts a target object during work, and is a reference surface for the posture of the attachment 11.

[0155] The tilt angle detector 38 detects at least the tilt angle (swinging angle) of the hitch 16. The controller 20 detects the orientation of the hitch 16 and the attachment 11 attached to the hitch 16, based on a detection result from the tilt angle detector 38. Specifically, the controller 20 detects the orientation of the work surface 11w of the attachment 11 attached to the hitch 16 based on the detection result from the tilt angle detector 38.

[0156] In addition to the foregoing pressure detectors 70a and 70b, the working machine 1 includes pressure detectors 49a, 49b, 49c, 49d, 68a, 68b, 68c, and 68d as elements to detect the pressure of hydraulic fluid or pilot fluid. Each of the pressure detectors 49a to 49d and 68a to 68d includes a pressure sensor.

[0157] The pressure detectors 49a, 49b, 49c and 49d are provided in the circuit fluid passages 53a and 53b. The pressure detector 49a detects the pressure of hydraulic fluid acting on a first port 51a of the first travel motor 51L as a first motor pressure. The pressure detector 49b detects the pressure of hydraulic fluid acting on a second port 51b of the first travel motor 51L as a second motor pressure. The pressure detector 49c detects the pressure of hydraulic fluid acting on a third port 51c of the second travel motor 51R as a third motor pressure. The pressure detector 49d detects the pressure of hydraulic fluid acting on a fourth port 51d of the second travel motor 51R as a fourth motor pressure.

[0158] The controller 20 determines the travel direction, the travel speed, whether straight travel is being performed, whether turning is being performed, the turn direction, and the type of turn relating to the working machine 1 based on the first to fourth motor pressures detected by the pressure detectors 49a to 49d. Alternatively, the controller 20 may determine the travel direction, the travel speed, whether straight travel is being performed, whether turning is being performed, the turn direction, and the type of turn relating to the working machine 1 based on the operation direction and on the operation amount of the travel operating lever 57a determined based on a detection signal from the sensor 67b.

[0159] As shown in FIG. 1, the pressure detectors 68a, 68b, 68c and 68d are respectively provided in the fluid passages 64a, 64b, 65a and 65b. The pressure detectors 68a and 68b detect the pressure of hydraulic fluid acting from the lift control valve 60A to the lift cylinders 14 as a lift pressure. The controller 20 refers to the lift pressure and, for example, adjusts the opening of the solenoid valves 76a and 76b. The pressure detectors 68c and 68d detect the pressure of hydraulic fluid acting from the tilt control valve 60B to the tilt cylinders 15 as a tilt pressure. The controller 20 refers to the tilt pressure and, for example, adjusts the opening of the tilt solenoid valves 77a and 77b.

[0160] The accelerator 7 is operable to define and change the rotation speed of the prime mover 6, and includes an acceleration operator and an acceleration sensor. The acceleration operator is, for example, an operation structure (manual operator) such as a lever, a pedal, a dial, or a slider. The acceleration sensor outputs a signal corresponding to the operation position of the acceleration operator. The controller 20 controls the driving of the prime mover 6 and defines and changes the rotation speed of the prime mover 6 based on an acceleration signal outputted from the acceleration sensor.

[0161] The configurations of the speed-change switch 75, the speed-change solenoid valve 59, the braking switch 79, the braking solenoid valve 56, the travel manual operator 57, the operating valves 54a to 54d, the work manual operator 67, the lift solenoid valves 76a and 76b, the tilt solenoid valves 77a and 77b, and the AUX solenoid valves 76a and 76b have been described already. The AUX manual operator 73 is operable to control the supply of hydraulic fluid to the hydraulic actuator 27 of the attachment 11. The AUX manual operator 73 includes, in addition to the foregoing AUX output switch 73b, an AUX mode switch 73a, an AUX steady switch 73c, and an AUX volume switch 73d.

[0162] The AUX mode switch 73a is turned ON to start an AUX mode in which an attachment 11 including a hydraulic actuator 27 is allowed to be used with the working machine 1, and is turned OFF to end the AUX mode. When the AUX mode switch 73a is turned ON to start the AUX mode and then the AUX output switch 73b is turned ON, the controller 20 opens one of the AUX solenoid valves 77a and 77b to allow hydraulic fluid to be supplied from the AUX control valve 60C to the corresponding AUX port 25.

[0163] In so doing, if the first AUX port 25a and the first hydraulic port of the attachment 11 are connected by the external fluid passage 26a and the second hydraulic port of the attachment 11 and the second AUX port 25b are connected by the external fluid passage 26b, (i) hydraulic fluid from the AUX control valve 60C flows through the first AUX port 25a, the external fluid passage 26a, and the first hydraulic port of the attachment 11 and is supplied to the hydraulic actuator 27 of the attachment 11, and (ii) hydraulic fluid discharged from the hydraulic actuator 27 flows through the second hydraulic port of the attachment 11, the external fluid passage 26b, and the second AUX port 25b and returns to the AUX control valve 60C. In some cases, hydraulic fluid from the AUX control valve 60C flows through the second AUX port 25b, the external fluid passage 26b, and the second hydraulic port of the attachment 11 and is supplied to the hydraulic actuator 27, whereas hydraulic fluid from the hydraulic actuator 27 flows through the first hydraulic port of the attachment 11, the external fluid passage 26a, and the first AUX port 25a and returns to the AUX control valve 60C.

[0164] The controller 20 ends the AUX mode when the AUX mode switch 73a is turned OFF after the AUX output switch 73b is turned OFF, the AUX solenoid valves 77a and 77b are closed, and the supply of hydraulic fluid from the AUX control valve 60C to the corresponding AUX port 25 is stopped.

[0165] The AUX steady switch 73c is turned ON to start a steady output mode in which a fluid flow rate (which is the amount of hydraulic fluid supplied per unit time to the hydraulic actuator 27) is kept constant, and is turned OFF to stop the steady output mode. When the AUX steady switch 73c is turned ON while the AUX mode is being performed to supply hydraulic fluid to the hydraulic actuator 27, the controller 20 starts the steady output mode and to maintain the opening of the AUX control valve 60C to keep constant the fluid flow rate of hydraulic fluid supplied to the hydraulic actuator 27. After that, when the AUX steady switch 73c is turned OFF, the controller 20 ends the steady output mode, does not maintain the opening of the AUX control valve 60C anymore, and does not keep constant the fluid flow rate of hydraulic fluid supplied to the hydraulic actuator 27 anymore.

[0166] The AUX volume switch 73d is operated to change the supply amount of hydraulic fluid to the hydraulic actuator 27. The AUX volume switch 73d outputs an electric signal corresponding to the manual operation of a control knob such as a slider operating switch, a dial, or a push button. When the AUX volume switch 73d is operated and an electric signal corresponding to the operation is inputted into the controller 20 when the steady supply mode is not performed, the controller 20 detects the operation position of the AUX volume switch 73d based on the electric signal, and inputs a control signal with an electric current value corresponding to the operation position into the AUX solenoid valves 78a and 78b. With this, the openings of the AUX solenoid valves 78a and 78b are defined and / or changed, the pilot pressure acting on the AUX control valve 60C changes, the opening of the AUX control valve 60C is defined and / or changed, the supply amount of hydraulic fluid from the AUX control valve 60C to the hydraulic actuator 27 is defined and / or changed, and the AUX pressure is also defined and / or changed.

[0167] After the attachment 11 is attached to the hitch 16, the controller 20 identifies the attachment 11. For example, in the case where the attached attachment 11 includes a beacon transmitter 19, a wireless signal including information indicating the attachment 11 is transmitted at regular intervals from the beacon transmitter 19, and therefore the wireless signal is received by the beacon scanner 23. The controller 20 identifies the attached attachment 11 based on the information included in the wireless signal received by the beacon scanner 23. For example, the information transmitted by the beacon transmitter 19 includes identification information of the attachment 11 provided with the beacon transmitter 19. The storing device 21 stores pieces of attachment information indicating a plurality of attachments 11 attachable to the working device 4 and pieces of control information defined for the respective plurality of attachments 11, which are associated with each other.

[0168] FIG. 5 illustrates an example, in the form of a table, of pieces of attachment information of the plurality of attachments 11 attachable to the working device 4 and their corresponding pieces of control information. The pieces of information shown in FIG. 5 are stored in a predetermined storage area of the storing device 21.

[0169] The attachment information shown in FIG. 5 includes identification information (ID), name, icon data, model number, and specifications of a corresponding attachment 11. The specifications include the size of the attachment 11, the position and the orientation of the work surface 11w (FIG. 15) relative to the base plate 9 (FIG. 16) of the attachment 11, the presence or absence of the hydraulic actuator 27, and / or the like. The specifications in the attachment information of an attachment 11 provided with a hydraulic actuator 27 may include specifications information such as the type and / or the capacity of the hydraulic actuator 27.

[0170] The control information includes the default value of a fluid flow rate which is the amount of hydraulic fluid supplied per unit time to the hydraulic actuator 27 in the corresponding attachment 11, an appropriate range of the AUX pressure for work, posture information indicating the appropriate posture range of the attachment 11 for work, a posture change degree to which the posture of the attachment 11 is automatically changed, and / or the like. The posture information includes the range of position and the range of orientation (tilt angle) of the attachment 11 in the vertical direction. The posture change degree includes the degree of change in position of the attachment 11 and the degree of change in orientation of the attachment 11 in the vertical direction.

[0171] Control information for a drive, contact work attachment 11 such as a sweeper includes the default value of the fluid flow rate, the appropriate range of the AUX pressure, posture information, and posture change degree. Since follower attachments 11 such as a bucket and a pallet fork do not need to be supplied with hydraulic fluid, the control information therefor does not include the default value of the fluid flow rate or the appropriate range of the AUX pressure, and also does not include posture information or posture change degree. With regard to non-contact work attachments 11 such as a spreader and holding work attachments 11 such as a grapple, even if the posture (position and / or orientation) is changed during work, the AUX pressure does not change. Therefore, the control information therefor does not include the appropriate range of the AUX pressure, posture information, or posture change degree.

[0172] As another example, attachment information may include at least one of the identification information (ID), name, icon, or model number of the attachment 11, and / or other information such as a nickname and / or the serial number of the attachment 11. The posture information may include the position (height) and the orientation (tilt angle) of the attachment 11 in the vertical direction during work, or may only include the position. At least one of the appropriate range of the AUX pressure or the posture information may be included in the control information.

[0173] The controller 20 reads attachment information and control information corresponding to the information (identification information) about the attachment 11 received from the beacon transmitter 19 from the storing device 21. The controller 20 identifies the type of the attachment 11 and determines whether the attachment 11 includes a hydraulic actuator 27 based on the read attachment information.

[0174] In the case where an electric circuit including a controller such as a CPU is provided in the attachment 11, the controller 20 may, after an electric harness connected to the electric circuit is connected to the AUX connector 28, receive information indicating the attachment 11 transmitted from the controller via the electric harness and the AUX connector 28. The controller 20 may then read control information corresponding to the attachment 11 indicated by the received information from the storing device 21.

[0175] The information transmitted from the beacon transmitter 19 or from the controller of the attachment 11 may include information indicating the attachment 11 and control information corresponding to the attachment 11. In such a case, when the controller 20 receives information from the beacon transmitter 19 or from the controller of the attachment 11, the controller 20 reads information indicating the attachment 11 and control information from the received information. Note that, in addition to or instead of the beacon transmitter 19 and the beacon scanner 23, a transmitter such as a Radio Frequency Identification (RFID) tag may be provided in or on the attachment 11 and a receiver to receive wireless signals issued by the transmitter may be provided in or on the working machine 1.

[0176] Additionally or alternatively, the controller 20 may read from the storing device 21 the data of a plurality of icons C1, C2, C3, C4, C5, C6, and so on indicating respective attachments 11 attachable and detachable to and from the working device 4 and cause the user interface 22 to display the plurality of icons C1, C2, C3, C4, C5, C6, and so on on a predetermined input screen G2 as illustrated in FIG. 6. In the example of FIG. 6, the controller 20 causes the plurality of icons C1, C2, C3, C4, C5, C6, and so on and the pieces of identification information A1, A2, A3, A4, A5, A6, and so on of the attachments 11 corresponding to the plurality of icons C1, C2, C3, C4, C5, C6, and so on to be displayed on the input screen G2.

[0177] The controller 20 may be configured or programmed to, when the driver or the like performs an operation on the user interface 22 to select an icon that represents the attachment 11 attached to the working device 4 from the plurality of icons C1, C2, C3, C4, C5, C6, and so on displayed on the input screen G2, accept the selected icon (icon C3 in FIG. 6) as information indicating the attachment 11 and read the control information for the attachment 11 corresponding to the selected icon from the storing device 21.

[0178] Additionally or alternatively, the following configuration may be used: the driver or the like manually inputs information such as the name of the attachment 11 attached to the working device 4 into the input screen displayed on the user interface 22. The controller 20 may then receive the manually inputted information from the user interface 22, and read the control information corresponding to the information from the storing device 21.

[0179] Additionally or alternatively, the following configuration may be used: an input screen as indicated in FIG. 6 or an input screen for manual input is displayed on a display of an external device such as a smartphone, and information indicating the attachment 11 corresponding to the icon selected by the user via the input screen or manually inputted information indicating the attachment 11 is transmitted from the external device and received by (inputted into) the communicator 24. The controller 20 may then read, from the storing device 21, the control information corresponding to the information indicating the attachment 11 received by the communicator 24.

[0180] The controller 20 is configured or programmed to, in the case where the read control information includes the default value of the fluid flow rate, control the AUX solenoid valves 78a and 78b and the AUX control valve 60C such that hydraulic fluid is supplied to the hydraulic actuator 27 at the default fluid flow rate when the AUX output switch 73b is operated, for example. The controller 20 is also configured or programmed to, in the case where the read control information includes the appropriate range of the AUX pressure, posture information, and / or posture change degree, perform a posture control to control the working device 4 to adjust the posture of the attachment 11 while work is performed by the attachment 11 (at the start of work and / or during work) according to the appropriate range of the AUX pressure, posture information, and posture change degree, and according to the AUX pressure.

[0181] FIG. 7 is a flowchart showing the operation of the working machine 1 of the first example embodiment. The steps in FIG. 7 are repeatedly performed by the controller 20 based on software program(s) stored in the internal memory and / or the storing device 21. The same applies to the steps of flowcharts in other drawings (described later). For convenience, in each flowchart, “attachment” is indicated as “ATT”, and “actuator” is indicated as “ACT”.

[0182] In response to the operation of the attaching switch 29a, the controller 20 actuates the latch cylinder 17 to attach the attachment 11 to the hitch 16 (S1), then acquires input information indicating the attachment 11 inputted thereto from one of the input interfaces 23, 28, 22 and 24, and acquires attachment information and control information corresponding to the attachment 11 indicated by the input information from the storing device 21 (S2). The controller 20 then identifies the attachment 11 based on the acquired attachment information (S3). In so doing, the controller 20 identifies the type of the attachment 11, whether the attachment 11 includes a hydraulic actuator 27, and / or the like.

[0183] In the case where the attachment 11 attached to the hitch 16 is a drive attachment 11, the controller 20 determines that the attached attachment 11 includes a hydraulic actuator 27 (YES at S4). Furthermore, external fluid passages 26 are connected to the AUX ports 25 and the hydraulic ports of the attachment 11 by the driver or the like.

[0184] The controller 20 then starts the AUX mode in response to turning ON of the AUX mode switch 73a, and then starts supplying hydraulic fluid from the AUX control valve 60C to the corresponding AUX port 25 in response to turning ON of the AUX output switch 73b (S5). With this, hydraulic fluid is supplied from the AUX port 25 to the hydraulic actuator 27 of the attachment 11 via the corresponding external fluid passage 26 and the like to actuate the hydraulic actuator 27, so that the attachment 11 is driven. In so doing, the controller 20 actuates the AUX solenoid valves 78a and 78b to define the opening of the AUX control valve 60C such that the fluid flow rate of hydraulic fluid toward the AUX port 25 is the default value indicated by the control information.

[0185] After that, the controller 20, in response to the driver's operation of the work operating lever 67a, controls the opening of the lift solenoid valves 76a and 76b and the tilt solenoid valves 77a and 77b to switch the position of at least one of the lift control valve 60A or the tilt control valve 60B to cause at least one of the lift cylinders 14 or the tilt cylinders 15 to extend or retract to cause at least one of the arms 10 or the hitch 16 to swing, thus setting the attachment 11 in a posture in which work can be performed. The posture of the attachment 11 set here is included in the appropriate posture range for work indicated by the posture information included in the control information for the attachment 11.

[0186] The controller 20 then, in response to the driver's operation of the travel operating lever 57a, controls the opening of the operating valves 54a to 54d to define the angle of the swash plates of the travel pumps 50L and 50R to allow the travel pumps 50L and 50R to deliver hydraulic fluid to rotate the travel motors 51L and 51R to drive the traveling devices 5, thus causing the machine body 2 (working machine 1) to travel. With this, the working machine 1 starts traveling with the attachment 11 performing work. During work, since the rotation speed of the output shafts 51Lj and 51Ri of the travel motors 51L and 51R is set to the first speed stage, the working machine 1 travels in the low-speed mode (creep mode).

[0187] The controller 20 is configured or programmed to, for example, if determining that the posture (position and orientation) of the attachment 11 detected by the arm position detector 37 and the tilt angle detector 38 is within the range of the appropriate posture for work indicated by the posture information, determine that work by the attachment 11 has started (S6).

[0188] Additionally or alternatively, the controller 20 may be configured or programmed to determine that the work by the attachment 11 has started if the controller 20 determines that, while the posture of the attachment 11 is within the range of the appropriate posture for work, the machine body 2 has traveled forward in the low-speed mode based on the detection result(s) from at least one of the speed detector 36 or the pump pressure detectors 49a to 49d. Additionally or alternatively, the controller 20 may be configured or programmed to determine that work by the attachment 11 has started if determining that the AUX pressure detected by the pressure detector(s) 70a and / or 70b is within the appropriate range indicated by the control information.

[0189] After work has started, the controller 20 determines, for example, that the attachment 11 indicated by the input information from the input interface 23, 28, 22 or 24 is a specific attachment (YES at S7), that the steady output mode is currently performed (YES at S8), and that the operation amount of the work operating lever 67a by the driver is less than a predetermined value (YES at S9). In such a case, the controller 20 consults the input information from the beacon scanner 23 or the like and the attachment information acquired from the storing device 21, and determines whether there is a possibility that the attachment 11 will perform work while the working machine 1 is not traveling. In other words, the controller 20 checks the type of the attached attachment 11, and determines whether or not work by the attached attachment 11 can be performed when the working machine 1 is not traveling.

[0190] In the case where there is a possibility that work will be performed by the attachment 11 when the working machine 1 is not traveling (NO at S10), the controller 20 performs a posture control to control the working device 4 according to the AUX pressure to adjust the posture of the attachment 11 (S12). In the case where there is no possibility that work will be performed by the attachment 11 when the working machine is not traveling (YES at S10), the controller 20 consults the travel speed detected by the speed detector 36. Then, if the travel speed is equal to or greater than a predetermined value (YES at S11), the controller 20 performs the posture control (S12).

[0191] In the case where the attachment 11 indicated by the input information from the beacon scanner 23 or the like is not a specific attachment (NO at S7), the controller 20 does not perform the posture control. The specific attachment 11 is an attachment 11 which includes a hydraulic actuator 27 to be actuated by hydraulic fluid supplied from the working machine 1, which performs work on a target object in contact therewith, and which changes in AUX pressure (i.e., load) when the posture thereof is changed by the working device 4 during work.

[0192] In the present example embodiment, examples of the specific attachments 11 include sweepers, snow blowers, snow blades, angle brooms, mowers, plows, skid cutters, breakers, earth augers. Examples of the specific attachments 11 do not include spreaders, grapples, buckets, or pallet forks. The pieces of information indicating the specific attachments 11 are stored in the internal memory of the controller 20 and / or in a predetermined storage area of the storing device 21. The controller 20 reads the stored information and identifies specific attachments 11, and determines whether or not the attachment 11 indicated by the attachment information, i.e., the attachment 11 attached to the hitch 16, is a specific attachment 11.

[0193] The controller 20 may be configured or programmed to determine that the attached attachment 11 is a specific attachment 11 if the control information corresponding to the input information from the beacon scanner 23 or the like includes at least one of the appropriate range of the AUX pressure, the posture information, or the posture change degree (YES at S7). The controller 20 may be configured or programmed to determine that the attached attachment 11 is not a specific attachment 11 if the corresponding control information does not include the appropriate range of the AUX pressure, the posture information, or the posture change degree (NO at S7).

[0194] If the controller 20 is not in the steady output mode (NO at S8), the controller 20 does not perform the posture control. The controller 20 is configured or programmed to perform the posture control if the work operating lever 67a is operated and the operation amount is less than a predetermined value (YES at S9) or if the work operating lever 67a is not operated (YES at S9), but not perform the posture control if the operation amount of the work operating lever 67a is equal to or greater than a predetermined value (NO at S9). That is, when the driver operates the work operating lever 67a to cause the arms 10 or the hitch 16 of the working device 4 to swing, the operation amount of the work operating lever 67a reaches a predetermined value or greater, and therefore the controller 20 does not perform the posture control but causes the arms 10 and / or the hitch 16 to swing to change the posture of the attachment 11 according to the operation direction and the operation amount of the work operating lever 67a.

[0195] In the case where there is no possibility that work will be performed by the attachment 11 when the working machine 1 is not traveling (YES at S10), the controller 20 does not perform the posture control when the travel speed of the working machine 1 is less than a predetermined value (NO at S11). That is, when the working machine 1 is not traveling (travel speed is 0) and when the working machine 1 is moving at very low speed, the posture control is not performed.

[0196] FIG. 8 is a flowchart showing details of the posture control at step S12 of FIG. 7. When work is being performed by a specific attachment 11 on the working machine 1, the controller 20, after starting the posture control, detects the AUX pressure applied to the hydraulic actuator 27 of the attachment 11 (pressure of hydraulic fluid flowing through the AUX fluid passages 66a and 66b) via the pressure detectors 70a and 70b (S21). The controller 20 then compares the detected AUX pressure and the appropriate range included in the control information for the attachment 11.

[0197] If the AUX pressure is above the appropriate range (YES at S22), the controller 20 controls the lift solenoid valve 76b to switch the lift control valve 60A to the second position 61e to cause the lift cylinders 14 to extend to cause the arms 10 to swing upward, thus raising the attachment 11 (S23). In so doing, the controller 20 causes the arms 10 to swing upward by a predetermined angle according to the AUX pressure to raise the attachment 11 by a predetermined displacement.

[0198] For example, at step S23, the controller 20 may determine the electric current value of the control signal to be inputted into the lift solenoid valve 76b and the input time for which the control signal is inputted such that the AUX pressure falls within the appropriate range, according to the difference between the AUX pressure and the upper limit of the appropriate range (first difference) and the difference between the AUX pressure and the lower limit of the appropriate range (second difference). The controller 20 may then input the control signal with the determined electric current value into the lift solenoid valve 76b for the determined input time to actuate the lift control valve 60A and the lift cylinders 14 to cause the arms 10 and the attachment 11 to inch upward. This eliminates or reduces the likelihood that the attachment 11 will be raised to too great an extent.

[0199] That is, the controller 20 is configured or programmed such that, if the load on the attachment 11 increases during work performed by the attachment 11, cause the arms 10 to swing upward to move the attachment 11 in a direction away from the target object, thus adjusting the position of the attachment 11 relative to the target object (i.e., the position (height) of the attachment 11 in the vertical direction). With this, even if the height of the target object changes such that the height increases (such that the target object is raised), the load on the attachment 11 does not become excessive, and the attachment 11 and the hydraulic actuator 27 do not stop because of the overload.

[0200] At step S23, the controller 20 may raise the attachment 11 according to the range of position in the posture information included in the control information corresponding to the attachment 11. For example, the controller 20 determines the electric current value of the control signal inputted into the lift solenoid valve 76b and the input time for which the control signal is inputted such that the position of the attachment 11 (position of the work surface 11w) determined from the detection result from the arm position detector 37 falls within the range of position in the posture information. The controller 20 then inputs the control signal with the determined electric current value into the lift solenoid valve 76b for the determined input time to actuate the lift control valve 60A and the lift cylinders 14, thus causing the arms 10 and the attachment 11 to inch upward.

[0201] At step S23, the controller 20 may determine the control signal inputted into the lift solenoid valve 76b such that the attachment 11 is raised to the degree of change in position included in the control information for the attachment 11. In such a case, even when the attachment 11 is raised to the degree of change in position, the AUX pressure may still not be within the appropriate range, but as long as work is not ended (NO at S13 of FIG. 7), the controller 20 repeats step S8 and subsequent steps to raise the attachment 11 by the amount of change in position at step S23 again. Since step S23 is repeated in this manner, the AUX pressure is brought into the appropriate range.

[0202] On the contrary, if the AUX pressure is below the appropriate range (YES at S24), the controller 20 controls the lift solenoid valve 76a to switch the lift control valve 60A to the first position 61d to cause the lift cylinders 14 to retract to cause the arms 10 to swing downward, thus lowering the attachment 11 (S25). In so doing, the controller 20 causes the arms 10 to swing downward by a predetermined angle according to the AUX pressure to lower the attachment 11 by a predetermined displacement.

[0203] For example, also at step S25, the controller 20 may determine the electric current value of the control signal inputted into the lift solenoid valve 76a and the input time for which the control signal is inputted such that the AUX pressure falls within the appropriate range, according to the difference between the AUX pressure and the upper limit of the appropriate range (first difference) and the difference between the AUX pressure and the lower limit of the appropriate range (second difference). The controller 20 may then input the control signal with the determined electric current value into the lift solenoid valve 76a for the determined input time to actuate the lift control valve 60A and the lift cylinders 14 to cause the arms 10 and the attachment 11 to inch downward.

[0204] That is, the controller 20 is configured or programmed to, if the load on the attachment 11 decreases during work performed by the attachment 11, cause the arms 10 to swing downward to move the attachment 11 in a direction approaching the target object, thus adjusting the position of the attachment 11 relative to the target object. With this, even when the height of the target object changes such that the height decreases (such that the target object is depressed), it is possible to cause the attachment 11 to contact the target object in a workable manner.

[0205] At step S25, the controller 20 may, according to the range of position in the posture information corresponding to the attachment 11, lower the attachment 11 (cause to inch downward) such that the position of the attachment 11 falls within the range of position. The controller 20 may lower the attachment 11 to the degree of change in position corresponding to the attachment 11.

[0206] At steps S23 and S25, the arms 10 swing and therefore the attachment 11 is raised or lowered as well as the orientation of the attachment 11 relative to the target object is changed to some extent. In this regard, the controller 20 causes the hitch 16 to swing as the attachment 11 is raised or lowered (swing in a linked manner with the attachment 11) to adjust the orientation of the attachment 11 (orientation of the work surface 11w) relative to the target object to maintain the relative orientation. In so doing, for example, in the case of a specific attachment 11 such as a sweeper, the work surface 11w is kept parallel to the target object such as the ground J and kept horizontal.

[0207] Specifically, at step S23, the controller 20 determines the electric current value of the control signal inputted into the tilt solenoid valve 77a and the input time for which the control signal is inputted, according to the electric current value of the control signal inputted into the lift solenoid valve 76b. The controller 20 then inputs the control signal with the determined electric current value into the tilt solenoid valve 77a for the determined input time to switch the tilt control valve 60B to the first position 62d to cause the tilt cylinders 15 to extend to cause the hitch 16 to swing such that the hitch 16 inches downward, thus adjusting the orientation of the attachment 11.

[0208] At step S25, the controller 20 determines the electric current value of the control signal inputted into the tilt solenoid valve 77b and the input time for which the control signal is inputted, according to the electric current value of the control signal inputted into the lift solenoid valve 76a. The controller 20 then inputs the control signal with the determined electric current value into the tilt solenoid valve 77b for the determined input time to switch the tilt control valve 60B to the second position 62e to cause the tilt cylinders 15 to retract to cause the hitch 16 to swing such that the hitch 16 inches upward, thus adjusting the orientation of the attachment 11.

[0209] At steps S23 and S25, the controller 20 may, according to the AUX pressure and / or the type or the like of the attachment 11, adjust only the position (position in the up-down direction) of the attachment 11 without adjusting the orientation of the attachment 11, adjust only the orientation of the attachment 11 without adjusting the position of the attachment 11, or adjust both the orientation and the position of the attachment 11. That is, the controller 20 may adjust at least one of the position or the orientation of the attachment 11 in the posture control.

[0210] At steps S23 and S25, the controller 20 may change the orientation of the attachment 11 in a direction away from the target object or in a direction toward the target object in a manner not linked to the position adjustment of the attachment 11. The controller 20 may adjust the orientation of the attachment 11 such that the AUX pressure falls within the appropriate range, and may adjust the orientation of the attachment 11 such that the orientation of the attachment 11 determined from the detection result from the tilt angle detector 38 falls within the range of posture in the posture information. The controller 20 may change the orientation of the attachment 11 to the degree of change in orientation included in the control information for the attachment 11.

[0211] The controller 20 may determine, for each of the plurality of attachments 11 attachable to the working device 4, whether to adjust the position of the attachment 11 and whether to adjust the orientation of the attachment 11 in the posture control, define also the posture information (position range, orientation range) and the posture change degree (degree of change in position, degree of change in orientation), and cause the storing device 21 to store control information including such defined pieces of information.

[0212] The controller 20 may then, at steps S23 and S25 of FIG. 8, using the control information corresponding to the attachment 11, cause the lift cylinders 14 to swing the arms 10 and / or cause the tilt cylinders 15 to swing the hitch 16 based not only on the AUX pressure but also on at least one of the type, the appropriate range, the posture information, or the posture change degree of the attachment 11 to adjust at least one of the position or the orientation of the attachment 11 relative to the target object.

[0213] Additionally or alternatively, at steps S23 and S25, for example, the controller 20 may calculate the first difference between the AUX pressure and the upper limit of the appropriate range and the second difference between the AUX pressure and the lower limit of the appropriate range and, if the smaller one of the above differences is less than a first threshold, cause the hitch 16 to swing to adjust only the orientation of the attachment 11. If the smaller one of the differences is greater than or equal to the first threshold and is less than a second threshold which is greater than the first threshold, the controller 20 may cause the arms 10 to swing to adjust only the position of the attachment 11. If the smaller one of the differences is greater than or equal to the second threshold and is less than a third threshold which is greater than the second threshold, the controller 20 may adjust the position of the attachment 11 and adjust the orientation of the attachment 11 in a manner not linked to the position adjustment. If the smaller one of the differences is greater than or equal to the third threshold, the controller 20 may adjust the position of the attachment 11 and adjust the orientation of the attachment 11 in a manner linked to the position adjustment.

[0214] After step S23 or step S25, the controller 20 ends the posture control and, if work has not ended (NO at S13 of FIG. 7), repeat step S8 and subsequent steps. Also in the case where the AUX pressure is within the appropriate range (NO at S22, and NO at S24 of FIG. 8), the controller 20 ends the posture control, and, if work has not ended (NO at S13 of FIG. 7), repeats step S8 and subsequent steps.

[0215] Note that, for example, when the controller 20 has stopped the supply of hydraulic fluid to the corresponding AUX port 25 (that is, to the hydraulic actuator 27 of the attachment 11) in response to turning OFF of the AUX output switch 73b, the controller 20 determines that work performed by the attachment 11 has ended (YES at S13 of FIG. 7).

[0216] Since the above-described posture control is performed, the working device 4 (arms 10, hitch 16) operates in a manner that does not correspond to the manual operation of the work operating lever 67a, so that the posture of the attachment 11 is changed. In so doing, for the driver of the working machine 1 or the like not to feel uncertainty, the controller 20, during the posture control, causes the user interface 22 to output (display) information indicating that the posture control is being performed.

[0217] FIG. 9 illustrates an example of a monitor screen G1 displayed on the user interface 22. The controller 20 causes the user interface 22 to display the monitor screen G1 while the working machine 1 is in operation. The monitor screen G1 displays pieces of information V1 to V6 indicating the state of the working machine 1 detected by sensors in or on the working machine 1, the current date and time, and pieces of information U1 and U2 indicating the attachment 11 identified by the controller 20. The controller 20 is configured or programmed to, when the controller 20 is performing the posture control of FIG. 8, cause the monitor screen G1 to display a piece of information U3 indicating that the posture control for the attachment 11 is being performed.

[0218] The controller 20 may cause the display of an external device such as a smartphone, instead of the user interface 22, to display (output) the monitor screen G1. In such a case, the controller 20 need only transmit display data of the monitor screen G1 and the foregoing piece of information U3 to the external device via the communicator 24, and cause the display of the external device to display the monitor screen G1 including the piece of information U3.

[0219] FIG. 10 is a flowchart showing operation of a working machine 1 of a second example embodiment. In the second example embodiment, the controller 20 selectively performs at least one of the posture control or a travel control in which the controller 20 controls the traveling devices 5 to adjust the traveling state of the machine body 2, based on the attachment 11 indicated by information inputted via the input interface(s) 23, 28, 22 and / or 24 and based on the AUX pressure (S14).

[0220] In FIG. 10, after start of work, if the controller 20 determines that the attachment 11 is a specific attachment (YES at S7), that the steady output mode is being performed (YES at S8), that the operation amount of the work operating lever 67a is less than a predetermined value (YES at S9), and that there is a possibility that the attachment 11 will perform work while the working machine 1 is not traveling (NO at S10), the controller 20 performs at least one of the posture control or the travel control (S14). If the controller 20 determines that there is no possibility that the attachment 11 will perform work while the working machine 1 is not traveling (YES at S10), if the travel speed is higher than or equal to a predetermined speed (YES at S11), the controller 20 performs at least one of the posture control or the travel control (posture control and / or travel control at S14).

[0221] FIG. 11 is a flowchart showing details of the posture control and / or travel control at step S14 in FIG. 10. The controller 20 detects the AUX pressure applied to the hydraulic actuator 27 of the attachment 11 via the pressure detectors 70a and 70b (S21) and, if the AUX pressure is above the appropriate range (YES at S22), the controller 20 selectively performs at least one of raising the attachment 11 (posture control) or reducing the travel speed of the machine body 2 (travel control) based on the attachment 11 (type of the attachment 11) indicated by the information inputted via the input interface(s) 23, 28, 22 and / or 24 and based on the AUX pressure (S26).

[0222] If the AUX pressure is below the appropriate range (YES at S24), the controller 20 selectively performs at least one of lowering the attachment 11 (posture control) or increasing the travel speed of the machine body 2 (travel control) based on the attachment 11 (type of the attachment 11) indicated by the information inputted via the input interface(s) 23, 28, 22 and / or 24 and based on the AUX pressure (S27).

[0223] In the case where the controller 20 performs the posture control at step S26 or S27, the controller 20 causes the arms 10 to swing upward or downward by a predetermined angle according to the AUX pressure to raise or lower the attachment 11 by a predetermined displacement to adjust the position of the attachment 11. In so doing, the controller 20, for example, may calculate the first difference between the AUX pressure and the upper limit of the appropriate range and the second difference between the AUX pressure and the lower limit of the appropriate range and, if the smaller one of the differences is less than a predetermined threshold, cause the arms 10 to swing without adjusting the travel speed of the machine body 2 to raise or lower the attachment 11 to adjust the position of the attachment 11. The controller 20 may cause the hitch 16 to swing in a manner linked to the swinging of the arms 10 to adjust the orientation of the attachment 11. The adjustment of the position and the orientation of the attachment 11 is similar to those discussed in the first example embodiment.

[0224] At step S26 or S27, if the smaller one of the differences is greater than or equal to the predetermined value, the controller 20 may raise or lower the attachment 11 as well as reducing or increasing the travel speed of the machine body 2. In such a case, the controller 20 reduces or increases the electric current value of the control signals inputted into two of the plurality of operating valves 54a to 54d that are open to change the angle of the swash plates of the travel pumps 50L and 50R to reduce or increase the rotation speed of the output shafts 51Lj and 51Rj of the travel motors 51L and 51R, thus reducing or increasing the travel speed of the traveling devices 5 and the machine body 2. At step S26, the controller 20 may actuate the braking solenoid valve 56 and the braking actuators 55 to brake the rotation of the output shafts 51Lj and 51Rj of the travel motors 51L and 51R to reduce the travel speed of the machine body 2. That is, the controller 20 causes the machine body 2 to travel at a travel speed corresponding to the AUX pressure (load on the attachment 11) instead of a travel speed corresponding to the manual operation of the travel operating lever 57a.

[0225] Alternatively, the controller 20 may be configured or programmed to, at step S26 or S27, if the smaller one of the differences is less than a predetermined value, reduce or increase the travel speed of the machine body 2 without changing the position of the attachment 11 and, if the smaller one of the differences is greater than or equal to the predetermined value, reduce or increase the travel speed of the machine body 2 as well as raising or lowering the attachment 11.

[0226] Alternatively, at step S26 or S27, if the travel speed detected by the speed detector 36 is 0 (zero), i.e., if work is being performed by the attachment 11 while the working machine is in the stopped state, the controller 20 may raise or lower the attachment 11 without adjusting the travel speed of the machine body 2. Alternatively, in such a case, the controller 20 may cause the machine body 2 to travel a predetermined distance in a direction away from the target object (travel rearward) or in a direction toward the target object (travel forward) irrespective of whether to raise or lower the attachment 11 or not.

[0227] When the controller 20 raises or lowers the attachment 11 and reduces or increases the travel speed at steps S26 and S27, the controller 20 may determine the electric current value of the control signal inputted into the lift solenoid valves 76a and 76b and the input time for which the control signal is inputted as well as determining the electric current value of the control signal inputted into the operating valves 54a to 54d such that the AUX pressure falls within the appropriate range. The controller 20 then inputs the determined control signal into the corresponding lift solenoid valve(s) 76a and / or 76b and the operating valve(s) 54a to 54d to raise or lower the attachment 11 such that the attachment 11 inches, and reduce or increase the travel speed of the traveling devices 5 and the machine body 2. In so doing, the controller 20 may determine the electric current value of the control signal inputted into the lift solenoid valves 76a and 76b and the input time for which the control signal inputted and the electric current value of the control signal inputted into the operating valves 54a to 54d and determine the travel speed also in consideration of the position range and the degree of change in the posture information of the attachment 11.

[0228] In the case where the controller 20 only reduces or increases the travel speed at step S26 or S27, the controller 20 determines the electric current value of the control signal inputted into the operating valves 54a to 54d, and inputs the control signal into the operating valve(s) 54a to 54d to reduce or increase the travel speed of the traveling devices 5 and the machine body 2 such that the AUX pressure falls within the appropriate range. At step S26, the controller 20 may, according to the AUX pressure and / or the like, actuate the braking solenoid valve 56 and the braking actuators 55 to brake the rotation of the output shafts 51Lj and 51Rj of the travel motors 51L and 51R to reduce the travel speed of the machine body 2 to 0 (zero) to stop the machine body 2. Furthermore, the controller 20 may, after the machine body 2 stops, change the angle of the swash plates of the travel pumps 50L and 50R via the operating valve 54a to 54d to cause the travel motors 51L and 51R to rotate in the reverse direction to cause the machine body 2 to travel a predetermined distance in the reverse direction.

[0229] The controller 20 may determine, for each of a plurality of attachments 11 attachable to the working device 4, whether to perform the posture control and whether to perform the travel control, and cause the storing device 21 to store control information including such defined pieces of information. The controller 20 may then, at step S26 or S27 of FIG. 11, perform at least one of the posture control or the travel control based on the control information corresponding to the attachment 11.

[0230] After step S26 or step S27, if work has not ended (NO at S13 of FIG. 10), the controller 20 repeats step S8 and subsequent steps. Also in the case where the AUX pressure is within the appropriate range (NO at S22 and NO at S24 of FIG. 11), if work has not ended (NO at S13 of FIG. 10), the controller 20 repeats step S8 and subsequent steps.

[0231] Since the above-described posture control is performed, the working device 4 operates in a manner that does not correspond to the manual operation of the work operating lever 67a, and, since the travel control is performed, the working machine 1 travels in a manner that does not correspond to the manual operation of the travel operating lever 57a and stops, in some cases. To address this, for the driver of the working machine 1 or the like does not feel uncertainty, when the controller 20 is performing at least one of the posture control or the travel control, as shown in, for example, FIG. 12, the controller 20 causes the user interface 22 and / or the like to display information U4 indicating the currently performed control on the monitor screen G1 In the example of FIG. 12, since the controller 20 is performing the posture control and the travel control, the controller 20 causes the information U4, which indicates that the posture control of the attachment 11 and the travel control of the working machine 1 are being performed, to be displayed on the monitor screen G1.

[0232] In the above described example embodiments, the work manual operator 67 and the travel manual operator 57 each include a digital joystick. However, for example, as shown in FIGS. 13 and 14, a pilot-operated hydraulic work manual operator 67 and a pilot-operated hydraulic travel manual operator 57 may be used instead.

[0233] The work manual operator 67 in a work-related hydraulic circuit 4A of another example embodiment shown in FIG. 13 includes a work operating lever 67a and a plurality of pilot valves 89a, 89b, 89c and 89d. The plurality of pilot valves 89a to 89d are connected to a fluid discharge passage 40 and are respectively connected to fluid passages 88a, 88b, 88c and 88d. The fluid passages 88a, 88b, 88c and 88d are respectively connected to corresponding work pressure receivers 61a, 61b, 62a, 62b of the lift control valve 60A and the tilt control valve 60B via high-pressure selection valves 91a, 91b, 91c and 91d. Note that, in FIG. 13, for convenience, a portion of the fluid passages 88a, 88b, 88c and 88d is omitted ((a), (b), (c), (d)).

[0234] The lift solenoid valves 76a and 76b and the tilt solenoid valves 77a and 77b are connected to the corresponding high-pressure selection valves 91a, 91b, 91c and 91d via fluid passages. The high-pressure selection valves 91a, 91b, 91c and 91d each allow the higher one of the hydraulic pressure from the connected pilot valve 89a, 89b, 89c or 89d and the hydraulic pressure from the connected solenoid valve 76a, 76b, 77a or 77b to act on the connected work pressure receiver 61a, 61b, 62a, 62b. The fluid passages 88a to 88d are provided with a solenoid switching valve 87. The solenoid switching valve 87 is a two-position solenoid switching valve, and switchable between a first position to allow passage of pilot fluid and a second position to block pilot fluid. Note that the solenoid switching valve 87 is normally in the first position.

[0235] When the work operating lever 67a is pivoted forward (direction F), the first pilot valve 89a is operated, and, after the pilot pressure of pilot fluid from the fluid discharge passage 40 is changed at the first pilot valve 89a, the pilot fluid passes through the first fluid passage 88a and the solenoid switching valve 87 and the pilot pressure acts on the work pressure receiver 61a of the lift control valve 60A. With this, the lift control valve 60A switches to the first position 61d, the lift cylinders 14 retract, and the arms 10 swing downward.

[0236] When the work operating lever 67a is pivoted rearward (direction B), the second pilot valve 89b is operated, and, after the pilot pressure of pilot fluid from the fluid discharge passage 40 is changed at the second pilot valve 89b, the pilot fluid passes through the second fluid passage 88b and the solenoid switching valve 87 and the pilot pressure acts on the work pressure receiver 61b of the lift control valve 60A. With this, the lift control valve 60A switches to the second position 61e, the lift cylinders 14 extend, and the arms 10 swing upward.

[0237] When the work operating lever 67a is pivoted leftward (direction L), the third pilot valve 89c is operated, and, after the pilot pressure of pilot fluid from the fluid discharge passage 40 is changed at the third pilot valve 89c, the pilot fluid passes through the third fluid passage 88c and the solenoid switching valve 87 and the pilot pressure acts on the work pressure receiver 62a of the tilt control valve 60B. With this, the tilt control valve 60B switches to the first position 62d, the tilt cylinders 15 extend, and the hitch 16 swings downward.

[0238] When the work operating lever 67a is pivoted rightward (direction R), the fourth pilot valve 89d is operated, and, after the pilot pressure of pilot fluid from the pilot fluid discharge passage 40 is changed at the fourth fluid passage 88d, the pilot fluid passes through the fourth fluid passage 88d and the solenoid switching valve 87 and the pilot pressure acts on the work pressure receiver 62b of the tilt control valve 60B. With this, the tilt control valve 60B switches to the second position 62e, the tilt cylinders 15 retract, and the hitch 16 swings upward.

[0239] The controller 20 is configured or programmed such that, when, in the foregoing posture control or the like, actuating at least one of the lift solenoid valves 76a and 76b or the tilt solenoid valves 77a and 77b to switch the position of at least one of the lift control valve 60A or the tilt control valve 60B to cause at least one of the arms 10 or the hitch 16 to swing, the controller 20 inputs a control signal into the solenoid switching valve 87 to switch the solenoid switching valve 87 to the second position. With this, the pilot pressure from the pilot valves 89a to 89d is blocked at the solenoid switching valve 87 and does not act on any of the work pressure receivers 61a, 61b, 62a and 62b of the lift control valve 60A and the tilt control valve 60B.

[0240] The fluid passages 88a, 88b, 88c and 88d are provided with respective pressure detectors 92a, 92b, 92c and 92d. The pressure detectors 92a, 92b, 92c and 92d detect the pilot pressure outputted from the pilot valves 89a, 89b, 89c and 89d. The controller 20 may determine the operation direction and operation amount of the work operating lever 67a based on the pilot pressure detected by the pressure detectors 92a to 92d.

[0241] The travel manual operator 57 in a travel-related hydraulic circuit 5A of another example embodiment of FIG. 14 includes a travel operating lever 57a, a plurality of pilot valves 44a, 44b, 44c and 44d, and a bridge circuit 93. The plurality of pilot valves 44a to 44d are connected to the fluid discharge passage 40 and to the bridge circuit 93. The bridge circuit 93 includes a plurality of shuttle valves 94. Fluid passages 43a, 43b, 43c and 43d are respectively connected to the plurality of shuttle valves 94. The fluid passages 43a, 43b, 43c and 43d are provided with a solenoid switching valve 95. The solenoid switching valve 95 is a two-position solenoid switching valve switchable between a first position to allow passage of pilot fluid, and a second position to block pilot fluid. Note that the solenoid switching valve 95 is normally in the first position. The fluid passages 43a, 43b, 43c and 43d are respectively connected to intermediate portions of fluid passages 42a, 42b, 42c and 42d via high-pressure selection valves 96a, 96b, 96c, and 96d. The high-pressure selection valves 96a, 96b, 96c and 96d each cause the higher one of the hydraulic pressure from the corresponding pilot valve 44a, 44b, 44c or 44d and the hydraulic pressure from the corresponding operating valve 54a, 54b, 54c or 54d to act on the connected pump pressure receiver 50a or 50b.

[0242] When the travel operating lever 57a is pivoted forward (direction F), the first pilot valve 44a is operated, and, after the pilot pressure of the pilot fluid from the fluid discharge passage 40 is changed at the first pilot valve 44a, the pilot fluid passes through the bridge circuit 93, the solenoid switching valve 95, the fluid passages 43a and 43c, and the fluid passages 42a and 42c, and the pilot pressure acts on the forward-travel pump pressure receivers 50a of the travel pumps 50L and 50R. With this, the angle of the swash plates of the travel pumps 50L and 50R is changed, the output shafts 51Lj and 51Rj of the travel motor 51L and 51R rotate in the normal direction, the first traveling device 5 and the second traveling device 5 are driven to travel forward, and the working machine 1 travels straight forward at a travel speed corresponding to the operation amount of the travel operating lever 57a.

[0243] When the travel operating lever 57a is pivoted rearward (direction B), the second pilot valve 44b is operated, and, after the pilot pressure of the pilot fluid from the fluid discharge passage 40 is changed at the second pilot valve 44b, the pilot fluid passes through the bridge circuit 93, the solenoid switching valve 95, the fluid passages 43b and 43d, and the fluid passages 42b and 42d, and the pilot pressure acts on the rearward-travel pump pressure receivers 50b of the travel pumps 50L and 50R. With this, the angle of the swash plates of the travel pumps 50L and 50R is changed, the output shafts 51Lj and 51Rj of the travel motors 51L and 51R rotate in the reverse direction, the first traveling device 5 and the second traveling device 5 are driven to travel rearward, and the working machine 1 travels straight rearward at a travel speed corresponding to the operation amount of the travel operating lever 57a.

[0244] When the travel operating lever 57a is pivoted leftward (direction L), the third pilot valve 44c is operated, and, after the pilot pressure of the pilot fluid from the fluid discharge passage 40 is changed at the third pilot valve 44c, the pilot fluid passes through the bridge circuit 93, the solenoid switching valve 95, the fluid passages 43b and 43c, and the fluid passages 42b and 42c, and the pilot pressure acts on the rearward-travel pump pressure receiver 50b of the travel pump 50L and the forward-travel pressure receiver 50a of the travel pump 50R. With this, the angle of the swash plates of the travel pumps 50L and 50R is changed, the output shaft 51Lj of the first travel motor 51L rotates in the reverse direction, the first traveling device 5 is driven to travel rearward, the output shaft 51Rj of the second travel motor 51R rotates in the normal direction, the second traveling device 5 is driven to travel forward, and the working machine 1 makes a spin turn to the left.

[0245] When the travel operating lever 57a is pivoted rightward (direction R), the fourth pilot valve 44d is operated, and, after the pilot pressure of the pilot fluid from the fluid discharge passage 40 is changed at the fourth pilot valve 44d, the pilot fluid passes through the bridge circuit 93, the solenoid switching valve 95, the fluid passages 43a and 43d, and the fluid passages 42a and 42d, and the pilot pressure acts on the forward-travel pressure receiver 50a of the travel pump 50L and the rearward-travel pump pressure receiver 50b of the travel pump 50R. With this, the angle of the swash plates of the travel pumps 50L and 50R is changed, the output shaft 51Lj of the first travel motor 51L rotates in the normal direction, the first traveling device 5 is driven to travel forward, the output shaft 51Rj of the second travel motor 51R rotates in the reverse direction, the second traveling device 5 is driven to travel rearward, and the working machine 1 performs a spin turn to the right.

[0246] Furthermore, if the travel operating lever 57a is pivoted diagonally leftward and forward, diagonally rightward and forward, diagonally leftward and rearward, or diagonally rightward and rearward, the pilot valve(s) 44a to 44d corresponding to the operation direction and the operation amount are operated, and the pilot pressure acts on the corresponding pump pressure receivers 50a and 50b of the travel pumps 50L and 50R. Then, the angle of the swash plates of the travel pumps 50L and 50R is changed, the rotation direction and rotation speed of the output shafts 51Lj and 51Rj of the travel motors 51L and 51R are determined, and the working machine 1 performs a pivot turn or slowly turns to the left or the right while traveling forward or rearward.

[0247] The fluid passages 43a, 43b, 43c and 43d are provided with respective pressure detectors 48a, 48b, 48c and 48d. The pressure detectors 48a, 48b, 48c 48d respectively detect the pilot pressures acting on the pressure receivers 50a and 50b of the travel pumps 50L and 50R via the connected fluid passages 43a to 43d and 42a to 42d. The controller 20 may be configured or programmed to, based on the pilot pressures detected by the pressure detectors 48a to 48d, determine the operation direction and operation amount of the travel operating lever 57a and also determine the travel direction, the travel speed, whether straight travel is performed, whether turning is performed, the direction of turn, and / or the type of turn, of the working machine 1.

[0248] Working machines 1 of example embodiments described so far include features described in the following items and achieve the following effects.

[0249] (Item 1) A working machine 1 including a working device 4 to attach thereto an attachment 11 which is one of a plurality of attachments 11 to perform work by contacting a target object, and change a posture of the attachment 11 attached thereto including a position of the attachment 11 in an up-down direction, a pressure detector (AUX pressure detector) 70a, 70b to detect an auxiliary pressure which is a pressure of hydraulic fluid supplied to a hydraulic actuator 27 included in the attachment 11 to drive the attachment 11, and a controller 20 configured or programmed to perform a posture control to control the working device 4 based on the auxiliary pressure to adjust the posture of the attachment 11.

[0250] With the configuration according to item 1, even if, for example, the height of the target object is not uniform, the posture of the attachment 11 is adjusted automatically according to the auxiliary pressure which corresponds to the load on the attachment 11, making it possible to cause the posture to follow changes in height of the target object and cause the attachment 11 to perform work appropriately. This makes it possible to improve the work performance of the attachment 11 of the working machine 1.

[0251] (Item 2) The working machine 1 according to item 1, wherein the controller 20 is configured or programmed to perform the posture control when work is being performed by the attachment 11, and in the posture control, change the posture of the attachment 11 such that the auxiliary pressure falls within an appropriate range.

[0252] The configuration according to item 2 makes it possible to appropriately adjust the posture of the attachment 11 and cause the attachment 11 to perform work appropriately by appropriately contacting the target object.

[0253] (Item 3) The working machine 1 according to item 1 or 2, further including an input interface 23, 28, 22, 24 (beacon scanner 23, AUX connector 28, user interface 22, communicator 24) to receive input of information indicating the attachment attached to the working device 4, wherein the controller 20 is configured or programmed to perform the posture control when the information inputted via the input interface 23, 28, 22, 24 indicates a specific attachment 11 which is one of the plurality of attachments 11.

[0254] With the configuration according to item 3, in cases where an attachment 11 for which the posture change by the working device 4 is effective for work performance is attached to the working device 4, the posture of the attachment 11 is adjusted automatically to improve work performance. In cases where an attachment 11 for which the posture change by the working device 4 does not influence work performance is attached to the working device 4, the posture of the attachment 11 is not adjusted automatically, making it possible to reduce the processing load on the controller 20 and perform work efficiently.

[0255] (Item 4) The working machine 1 according to any one of items 1 to 3, wherein the controller 20 is configured or programmed to perform the posture control when the controller 20 is in a predetermined mode (steady output mode) in which the controller 20 keeps constant an amount of hydraulic fluid supplied to the hydraulic actuator 27 per unit time.

[0256] With the configuration according to item 4, it is possible to easily adjust the posture of the attachment 11, because it is not necessary to take into account changes in amount of hydraulic fluid supplied to the hydraulic actuator 27 per unit time. Furthermore, since the user such as the driver of the working machine 1 does not need to perform manual operation for the amount of supply of hydraulic fluid to the hydraulic actuator 27 of the attachment 11 and for the working device 4 to change the posture of the attachment 11, it is possible to reduce the burden on the user.

[0257] (Item 5) The working machine 1 according to any one of items 1 to 4, further including an input interface 23, 28, 22, 24 to receive input of information indicating the attachment 11 attached to the working device 4, and a memory and / or a storage 21 to store (i) pieces of information indicating the plurality of attachments 11 attachable to the working device 4 and (ii) pieces of information indicating appropriate ranges of the auxiliary pressure for work defined for the respective plurality of attachments 11 such that (i) the pieces of information and (ii) the pieces of information are associated with each other, wherein the controller 20 is configured or programmed to read, from the memory and / or the storage 21, a piece of information indicating an appropriate range that corresponds to the attachment 11 indicated by the information inputted via the input interface 23, 28, 22, 24, and perform the posture control based on the read piece of information indicating the appropriate range and the auxiliary pressure.

[0258] With the configuration according to item 5, it is possible to more appropriately adjust the posture of the attachment 11 according to the attachment 11 attached to the working device 4, and further improve work performance.

[0259] (Item 6) The working machine 1 according to any one of items 1 to 5, wherein the working device 4 includes an arm 10 connected to a machine body 2 of the working machine 1 swingably in the up-down direction, a first actuator (lift cylinder) 14 to swing the arm 10, and a hitch 16 connected to a distal portion of the arm 10 to detachably attach the attachment 11 thereto, wherein the controller 20 is configured or programmed to, in the posture control, control the first actuator 14 based on the auxiliary pressure to swing the arm 10 to adjust the position of the attachment 11 relative to the target object.

[0260] With the configuration according to item 6, it is possible to adjust the position of the attachment 11 in the up-down direction (vertical direction) such that the position follows changes in height of the target object.

[0261] (Item 7) The working machine 1 according to item 6, wherein the controller 20 is configured or programmed to, when the auxiliary pressure is above an appropriate range, cause the first actuator 14 to swing the arm 10 upward to raise the attachment 11.

[0262] With the configuration according to item 7, even if the height of the target object changes and increases, the position of the attachment 11 is adjusted such that the attachment 11 is moved (raised) in a direction away from the target object, making it possible to eliminate or reduce the likelihood that the load on the attachment 11 will be excessive and that the excessive load will result in stoppage of the attachment 11 and the hydraulic actuator 27.

[0263] (Item 8) The working machine 1 according to item 6 or 7, wherein the controller 20 is configured or programmed to, when the auxiliary pressure is below an appropriate range, cause the first actuator 14 to swing the arm 10 downward to lower the attachment 11.

[0264] With the configuration according to item 8, even if the height of the target object changes and decreases, the position of the attachment 11 is adjusted such that the attachment 11 is moved (lowered) in a direction toward the target object, making it possible to cause the attachment 11 to contact the target object such that the attachment 11 can perform work and possible to perform work appropriately.

[0265] (Item 9) The working machine according to any one of items 1 to 5, wherein the working device 4 includes an arm 10 connected to a machine body 2 of the working machine 1 swingably in the up-down direction, a first actuator 14 to swing the arm 10, a hitch 16 connected to a distal portion of the arm 10 swingably in the up-down direction and operable to detachably attach the attachment 11 thereto, and a second actuator (tilt cylinder) 15 to swing the hitch 16, wherein the controller 20 is configured or programmed to, in the posture control, cause the first actuator 14 to swing the arm 10 and / or cause the second actuator 15 to swing the hitch 16 to adjust at least one of the position or an orientation of the attachment 11 relative to the target object.

[0266] With the configuration according to item 9, it is possible to appropriately adjust the position in the up-down direction and the orientation of the attachment 11 such that the position and the orientation follow changes in height and surface condition of the target object. It is also possible to more freely adjust the posture of the attachment 11 automatically and possible to adjust the posture more finely.

[0267] (Item 10) The working machine 1 according to any one of items 1 to 9, further including an input interface 23, 28, 22, 24 to receive input of information indicating the attachment 11 attached to the working device 4, and a memory and / or a storage 21 to store (i) pieces of information indicating the plurality of attachments 11 attachable to the working device 4 and (ii) pieces of posture information indicating appropriate ranges of the posture for work defined for the respective plurality of attachments 11 such that (i) the pieces of information and (ii) the pieces of posture information are associated with each other, wherein the controller 20 is configured or programmed to read, from the memory and / or the storage 21, one of the pieces of posture information that corresponds to the attachment 11 indicated by the information inputted via the input interface 23, 28, 22, 24, and perform the posture control based on the read piece of posture information and the auxiliary pressure.

[0268] With the configuration according to item 10, it is possible to more appropriately adjust the posture of the attachment 11 attached to the working device 4 according to the attachment 11, and also possible to further improve work performance.

[0269] (Item 11) The working machine 1 according to any one of items 1 to 10, further including a machine body 2, a traveling device 5 to cause the machine body 2 to travel, and a speed detector 36 to detect a travel speed of the machine body 2, wherein the controller 20 is configured or programmed to not perform the posture control when the travel speed is less than a predetermined value.

[0270] With the configuration according to item 11, it is possible to eliminate or reduce the likelihood that the posture of the attachment 11 will be needlessly adjusted while the working machine 1 is in the stopped state or very slowly traveling state in which the attachment 11 is not performing work, making it possible to reduce an increase in processing load on the controller 20 and a decrease in work performance.

[0271] (Item 12) The working machine 1 according to any one of items 1 to 11, further including a work manual operator (work operating lever) 67a to be operated to cause the working device 4 to change the posture of the attachment 11, wherein the controller 20 is configured or programmed to not perform the posture control when an operation amount of the work manual operator 67a is greater than a predetermined amount.

[0272] With the configuration according to item 12, it is possible to ensure convenience by prioritizing the user's manual operation of the working device 4 over the automatic operation of the working device 4 for the posture control.

[0273] (Item 13) The working machine 1 according to any one of items 1 to 12, further including a machine body 2, a traveling device 5 to cause the machine body 2 to travel and to change a traveling state of the machine body 2, and an input interface 23, 28, 22, 24 to receive input of information indicating the attachment 11 attached to the working device 4, wherein the controller 20 is configured or programmed to, based on the attachment 11 indicated by the information inputted via the input interface 23, 28, 22, 24 and based on the auxiliary pressure, selectively perform at least one of the posture control or a travel control to control the traveling device 5 to adjust the traveling state of the machine body 2.

[0274] With the configuration according to item 13, it is possible to appropriately adjust the auxiliary pressure on the hydraulic actuator 27 of the attachment 11 and the posture of the attachment 11 according to the type of the attachment 11, i.e., the type of work performed by the attachment 11, and according to the load on the attachment 11 to prevent or reduce the overload on the attachment 11 or a lack of contact between the target object and the attachment 11, making it possible to improve the work performance of the attachment 11. It is also possible to more freely adjust the load on the attachment 11 and the contact state of the attachment 11 automatically, and more finely adjust the load and the contact state. Furthermore, since the traveling state is adjusted, the posture of the attachment 11 does not need to be adjusted such that the posture greatly changes, and it is possible to maintain the state of contact between the target object and the attachment 11 during work.

[0275] (Item 14) The working machine 1 according to item 13, further including a memory and / or a storage 21 to store (i) pieces of information indicating the plurality of attachments 11 attachable to the working device 4 and (ii) pieces of information indicating appropriate ranges of the auxiliary pressure for work defined for the respective plurality of attachments 11 such that (i) the pieces of information and (ii) the pieces of information are associated with each other, wherein the controller 20 is configured to programmed to read, from the memory and / or the storage 21, a piece of information indicating an appropriate range that corresponds to the attachment 11 indicated by the information inputted via the input interface 23, 28, 22, 24, and, based on the read piece of information indicating the appropriate range and the auxiliary pressure, selectively perform at least one of the posture control or the travel control.

[0276] With the configuration according to item 14, it is possible to more appropriately adjust the auxiliary pressure and the posture of the attachment 11 and possible to improve the work performance of the attachment 11.

[0277] (Item 15) The working machine 1 according to item 13 or 14, further including a memory and / or a storage 21 to store (i) pieces of information indicating the plurality of attachments 11 attachable to the working device 4 and (ii) pieces of posture information indicating appropriate ranges of the posture for work defined for the respective plurality of attachments 11 such that (i) the pieces of information and (ii) the pieces of posture information are associated with each other, wherein the controller 20 is configured or programmed to read, from the memory and / or the storage 21, one of the pieces of posture information that corresponds to the attachment 11 indicated by the information inputted via the input interface 23, 28, 22, 24, and, based on the read piece of posture information and the auxiliary pressure, selectively perform at least one of the posture control or the travel control.

[0278] With the configuration according to item 15, it is possible to more appropriately adjust the auxiliary pressure and the posture of the attachment 11 and possible to improve the work performance of the attachment 11.

[0279] (Item 16) The working machine 1 according to any one of items 13 to 15, wherein the controller 20 is configured or programmed to perform at least one of the posture control or the travel control when the controller 20 is in a predetermined mode in which the controller 20 keeps constant an amount of hydraulic fluid supplied to the hydraulic actuator 27 per unit time.

[0280] With the configuration according to item 16, it is possible to easily adjust the posture of the attachment 11 and the load on the attachment 11, because it is not necessary to take into account changes in amount of hydraulic fluid supplied to the hydraulic actuator 27 per unit time.

[0281] (Item 17) The working machine 1 according to any one of items 13 to 16, further including a speed detector 36 to detect a travel speed of the machine body 2, wherein the controller 20 is configured or programmed to not perform the posture control or the travel control if the travel speed is less than a predetermined value.

[0282] With the configuration according to item 17, it is possible to eliminate or reduce the likelihood that the posture of the attachment 11 and the traveling state will be needlessly adjusted while the working machine 1 is in the stopped state or very slowly traveling state in which the attachment 11 is not performing work, making it possible to reduce an increase in processing load on the controller 20 and a decrease in work performance.

[0283] (Item 18) The working machine 1 according to any one of items 13 to 17, further including a work manual operator (work operating lever) 67a to be operated to cause the working device 4 to change the posture of the attachment 11, wherein the controller 20 is configured or programmed to not perform the posture control or the travel control when an operation amount of the work manual operator 67a is greater than a predetermined amount.

[0284] With the configuration according to item 18, it is possible to ensure convenience by prioritizing the user's manual operation of the working device 4 over the automatic operation of the working device 4 for the posture control and the automatic adjustment of the raveling state. It is also possible to eliminate or reduce the likelihood that the posture of the attachment 11 and the traveling state will be automatically adjusted in an unintended manner.

[0285] (Item 19) The working machine 1 according to any one of items 13 to 19, wherein the controller 20 is configured or programmed to, when the controller 20 is performing at least one of the posture control or the travel control, cause a user interface 22 to output information indicating that the at least one of the posture control or the travel control is being performed.

[0286] With the configuration according to item 19, even if the working device 4 is actuated under the posture control without responding to the user's manual operation and the posture of the attachment 11 is changed automatically and / or if the traveling state of the working machine 1 is changed automatically under the travel control, it is possible to let the user know that such changes are due to the automatic control at the working machine 1.

[0287] While example embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.

Examples

Embodiment Construction

[0043]Example embodiments will now be described with reference to the accompanying drawings, wherein like reference numerals designate corresponding or identical elements throughout the various drawings. The drawings are to be viewed in an orientation in which the reference numerals are viewed correctly.

[0044]Example embodiments of the present invention will now be described with reference to the accompanying drawings as necessary.

[0045]FIG. 15 is a side view of a working machine 1 of the present example embodiment. In the present example embodiment, a compact track loader is illustrated as an example of the working machine 1. However, the working machine according to an example embodiment of the present invention is not limited to a compact track loader, and may be, for example, some other construction machine, agricultural machine, or working machine such as a skid-steer loader, a backhoe, or a tractor. The left direction, right direction, the direction approaching the viewer of F...

Claims

1. A working machine comprising:a working device to:attach thereto an attachment which is one of a plurality of attachments to perform work by contacting a target object; andchange a posture of the attachment attached thereto including a position of the attachment in an up-down direction;a pressure detector to detect an auxiliary pressure which is a pressure of hydraulic fluid supplied to a hydraulic actuator included in the attachment to drive the attachment; anda controller configured or programmed to perform a posture control to control the working device based on the auxiliary pressure to adjust the posture of the attachment.

2. The working machine according to claim 1, wherein the controller is configured or programmed to:perform the posture control when work is being performed by the attachment; andin the posture control, change the posture of the attachment such that the auxiliary pressure falls within an appropriate range.

3. The working machine according to claim 1, further comprising:an input interface to receive input of information indicating the attachment attached to the working device; whereinthe controller is configured or programmed to perform the posture control when the information inputted via the input interface indicates a specific attachment which is one of the plurality of attachments.

4. The working machine according to claim 1, wherein the controller is configured or programmed to perform the posture control when the controller is in a predetermined mode in which the controller keeps constant an amount of hydraulic fluid supplied to the hydraulic actuator per unit time.

5. The working machine according to claim 1, further comprising:an input interface to receive input of information indicating the attachment attached to the working device; anda memory and / or a storage to store (i) pieces of information indicating the plurality of attachments attachable to the working device and (ii) pieces of information indicating appropriate ranges of the auxiliary pressure for work defined for the respective plurality of attachments such that (i) the pieces of information and (ii) the pieces of information are associated with each other; whereinthe controller is configured or programmed to read, from the memory and / or the storage, a piece of information indicating an appropriate range that corresponds to the attachment indicated by the information inputted via the input interface, and perform the posture control based on the read piece of information indicating the appropriate range and the auxiliary pressure.

6. The working machine according to claim 1, whereinthe working device includes:an arm connected to a machine body of the working machine swingably in the up-down direction;a first actuator to swing the arm; anda hitch connected to a distal portion of the arm to detachably attach the attachment thereto; whereinthe controller is configured or programmed to, in the posture control, control the first actuator based on the auxiliary pressure to swing the arm to adjust the position of the attachment relative to the target object.

7. The working machine according to claim 6, wherein the controller is configured or programmed to, when the auxiliary pressure is above an appropriate range, cause the first actuator to swing the arm upward to raise the attachment.

8. The working machine according to claim 6, wherein the controller is configured or programmed to, when the auxiliary pressure is below an appropriate range, cause the first actuator to swing the arm downward to lower the attachment.

9. The working machine according to claim 1, whereinthe working device includes:an arm connected to a machine body of the working machine swingably in the up-down direction;a first actuator to swing the arm;a hitch connected to a distal portion of the arm swingably in the up-down direction and operable to detachably attach the attachment thereto; anda second actuator to swing the hitch; whereinthe controller is configured or programmed to, in the posture control, cause the first actuator to swing the arm and / or cause the second actuator to swing the hitch to adjust at least one of the position or an orientation of the attachment relative to the target object.

10. The working machine according to claim 1, further comprising:an input interface to receive input of information indicating the attachment attached to the working device; anda memory and / or a storage to store (i) pieces of information indicating the plurality of attachments attachable to the working device and (ii) pieces of posture information indicating appropriate ranges of the posture for work defined for the respective plurality of attachments such that (i) the pieces of information and (ii) the pieces of posture information are associated with each other; whereinthe controller is configured or programmed to read, from the memory and / or the storage, one of the pieces of posture information that corresponds to the attachment indicated by the information inputted via the input interface, and perform the posture control based on the read piece of posture information and the auxiliary pressure.

11. The working machine according to claim 1, further comprising:a machine body;a traveling device to cause the machine body to travel; anda speed detector to detect a travel speed of the machine body; whereinthe controller is configured or programmed to not perform the posture control when the travel speed is less than a predetermined value.

12. The working machine according to claim 1, further comprising a work manual operator to be operated to cause the working device to change the posture of the attachment; whereinthe controller is configured or programmed to not perform the posture control when an operation amount of the work manual operator is greater than a predetermined amount.

13. The working machine according to claim 1, further comprising:a machine body;a traveling device to cause the machine body to travel and to change a traveling state of the machine body; andan input interface to receive input of information indicating the attachment attached to the working device; whereinthe controller is configured or programmed to, based on the attachment indicated by the information inputted via the input interface and based on the auxiliary pressure, selectively perform at least one of the posture control or a travel control to control the traveling device to adjust the traveling state of the machine body.

14. The working machine according to claim 13, further comprising a memory and / or a storage to store (i) pieces of information indicating the plurality of attachments attachable to the working device and (ii) pieces of information indicating appropriate ranges of the auxiliary pressure for work defined for the respective plurality of attachments such that (i) the pieces of information and (ii) the pieces of information are associated with each other; whereinthe controller is configured to programmed to read, from the memory and / or the storage, a piece of information indicating an appropriate range that corresponds to the attachment indicated by the information inputted via the input interface, and, based on the read piece of information indicating the appropriate range and the auxiliary pressure, selectively perform at least one of the posture control or the travel control.

15. The working machine according to claim 13, further comprising a memory and / or a storage to store (i) pieces of information indicating the plurality of attachments attachable to the working device and (ii) pieces of posture information indicating appropriate ranges of the posture for work defined for the respective plurality of attachments such that (i) the pieces of information and (ii) the pieces of posture information are associated with each other; whereinthe controller is configured or programmed to read, from the memory and / or the storage, one of the pieces of posture information that corresponds to the attachment indicated by the information inputted via the input interface, and, based on the read piece of posture information and the auxiliary pressure, selectively perform at least one of the posture control or the travel control.

16. The working machine according to claim 13, wherein the controller is configured or programmed to perform at least one of the posture control or the travel control when the controller is in a predetermined mode in which the controller keeps constant an amount of hydraulic fluid supplied to the hydraulic actuator per unit time.

17. The working machine according to claim 13, further comprising a speed detector to detect a travel speed of the machine body; whereinthe controller is configured or programmed to not perform the posture control or the travel control if the travel speed is less than a predetermined value.

18. The working machine according to claim 13, further comprising a work manual operator to be operated to cause the working device to change the posture of the attachment; whereinthe controller is configured or programmed to not perform the posture control or the travel control when an operation amount of the work manual operator is greater than a predetermined amount.

19. The working machine according to claim 13, wherein the controller is configured or programmed to, when the controller is performing at least one of the posture control or the travel control, cause a user interface to output information indicating that the at least one of the posture control or the travel control is being performed.

Images