Hydraulic system for work machine and control method for hydraulic system for work machine

Abstract

The present invention reduces oscillation of a movable member (21) smoothly.　A hydraulic system (S) of a work machine (1) comprises: a work device (20) having a movable member (21) and a hydraulic cylinder (22); an electromagnetic proportional valve (70); and a control device (80). The control device (80) is provided with: a first calculation unit (86) that calculates a first electric current value (I1) for decelerating the angular speed (ω) of the movable member (21); a second calculation unit (87) that calculates a second electric current value (I2) for reducing the supply flow rate of a hydraulic oil to the hydraulic cylinder (22); and an electric current limiting unit (88) that corrects an electric current to be supplied to the electromagnetic proportional valve (70) by using the second electric current value (I2) when a determination distance (H), which is an operation length (L) from a present operation position to a stroke end (E) of the hydraulic cylinder (22), is longer than a first threshold (T1) but not longer than a second threshold (T2), and corrects the electric current to be supplied to the electromagnetic proportional valve (70) by selecting one of the first electric current value (I1) and the second electric current value (I2) when the determination distance (H) is not longer than the first threshold (T1).

Description

[Technical Field]

[0001] The present invention relates to a hydraulic system for a work machine and a control method for a hydraulic system for a work machine. [Background technology]

[0002] BACKGROUND ART An electronic cushion control device for a hydraulic cylinder disclosed in Patent Document 1 is known.

[0003] The electronic cushion control device for a hydraulic cylinder in Patent Document 1 includes a hydraulic cylinder having a cylinder body and a piston that slides within the cylinder body, for driving a work attachment of a construction machine, a supply / discharge amount adjustment means for changing the amount of hydraulic oil supplied to and discharged from the hydraulic cylinder, and a controller that electrically controls the operation of the supply / discharge amount adjustment means, and the controller operates the supply / discharge amount adjustment means to adjust the amount of hydraulic oil supplied to and discharged from the hydraulic cylinder, thereby performing cushion control to decelerate the piston as it approaches the stroke end of the cylinder body. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2010-261521 Summary of the Invention [Problem to be solved by the invention]

[0005] In the electronic cushion control device for a hydraulic cylinder described in Patent Document 1, a stroke end detection section within the controller (control unit) detects that the stroke end is approaching based on the boom's rotation angle, and when the detection information from the stroke end detection section is input to an operation control section within the control unit, it activates an electromagnetic proportional valve to decelerate the piston rod and slowly stop it.

[0006] However, when the piston rod is decelerated near the stroke end, as in the invention disclosed in Patent Document 1, the piston rod may not be decelerated sufficiently, or the hydraulic cylinder may be decelerated too much, resulting in a step in the operating speed.

[0007] In view of the above problems, the present invention has an object to provide a hydraulic system for a work machine and a control method for a hydraulic system for a work machine that can smoothly decelerate the swing of a movable member. [Means for solving the problem]

[0008] A hydraulic system for a work machine according to one aspect of the present invention includes a work device having a movable member and a hydraulic cylinder that oscillates the movable member, an electromagnetic proportional valve that can change the flow rate of hydraulic oil supplied to the hydraulic cylinder, and a control device that controls the flow rate of hydraulic oil supplied to the hydraulic cylinder to be equal to or less than a predetermined flow rate by controlling the current supplied to the electromagnetic proportional valve, wherein the control device includes a first calculation unit that calculates a first current value, which is a current value of a current supplied to the electromagnetic proportional valve to control the electromagnetic proportional valve so as to decelerate the angular velocity of the movable member as the operating length of the hydraulic cylinder approaches the stroke end of the hydraulic cylinder, and a second calculation unit that calculates a second current value, which is a current value of a current supplied to the electromagnetic proportional valve to control the electromagnetic proportional valve so as to decelerate the angular velocity of the movable member as the operating length of the hydraulic cylinder approaches the stroke end of the hydraulic cylinder. and a current limiting unit that corrects the current supplied to the electromagnetic proportional valve by the second current value when a judgment distance, which is an operating length from the current operating position of the hydraulic cylinder to the stroke end, is longer than a first threshold value and is equal to or shorter than a second threshold value that is set to a value longer than the first threshold value, and that corrects the current supplied to the electromagnetic proportional valve by selecting either the first current value or the second current value when the judgment distance is equal to or shorter than the first threshold value.

[0009] The first calculation unit may be configured not to calculate the first current value when the determination distance is longer than the first threshold, and the second calculation unit may be configured not to calculate the second current value when the determination distance is longer than the second threshold.

[0010] The first current value when the determination distance is the first threshold value may be a current value corresponding to a reference angular velocity that is the minimum value of the angular velocity when the flow rate of the hydraulic oil supplied to the hydraulic cylinder is the predetermined flow rate, and the first current value when the determination distance is zero may be a current value corresponding to a predetermined terminal angular velocity that is smaller than the reference angular velocity.

[0011] The second current value when the determination distance is the second threshold value may be a current value that supplies hydraulic oil to the hydraulic cylinder at a flow rate substantially equal to the predetermined flow rate.

[0012] When the determination distance is equal to or less than the first threshold value, the current limiting unit may select, from the first current value and the second current value, the current value that results in a smaller flow rate of hydraulic oil supplied to the hydraulic cylinder.

[0013] When the determination distance is equal to or less than the first threshold value, the current limiting unit may correct the current supplied to the proportional solenoid valve by the first current value.

[0014] The hydraulic system of the work machine may include a first operating device that outputs an operation signal to the control device, and the control device may have a definition unit that defines, based on the operation signal, a current to be supplied to the electromagnetic proportional valve within a range equal to or less than a reference current value at which the opening of the electromagnetic proportional valve is maximized and the flow rate of hydraulic oil supplied to the hydraulic cylinder becomes the predetermined flow rate, and the current limiting unit may correct the current value defined by the definition unit using the first current value or the second current value.

[0015] The hydraulic system of the work machine may include an operable second operating device, an operating valve that controls the flow rate of pilot oil discharged in response to operation of the second operating device, a directional control valve that changes its switching position using pilot oil supplied from the operating valve and changes the flow rate of working oil supplied to the hydraulic cylinder to control the hydraulic cylinder, and a connecting oil passage that connects the directional control valve and the hydraulic cylinder, and the electromagnetic proportional valve is provided in the connecting oil passage, changes its opening in response to a current supplied from the control device, and changes the flow rate of working oil supplied from the directional control valve to the hydraulic cylinder to be equal to or less than the predetermined flow rate.

[0016] A control method for a hydraulic system of a work machine according to one aspect of the present invention is a control method for a hydraulic system of a work machine including a work device having a movable member and a hydraulic cylinder that oscillates the movable member, and an electromagnetic proportional valve that is capable of changing a flow rate of hydraulic oil supplied to the hydraulic cylinder, the control method controlling the flow rate of hydraulic oil supplied to the hydraulic cylinder to be equal to or less than a predetermined flow rate by controlling the current supplied to the electromagnetic proportional valve, the control method including a first step of calculating a first current value that is a current value of a current supplied to the electromagnetic proportional valve to control the electromagnetic proportional valve so as to decelerate the angular velocity of the movable member as the operating length of the hydraulic cylinder approaches a stroke end of the hydraulic cylinder; a second step of calculating a second current value, which is the current value of the current to be supplied to the electromagnetic proportional valve, in order to control the electromagnetic proportional valve so as to reduce the flow rate of hydraulic oil supplied to the hydraulic cylinder as the stroke end is approached; and a third step of correcting the current to be supplied to the electromagnetic proportional valve by the second current value when a judgment distance, which is the operating length from the current operating position of the hydraulic cylinder to the stroke end, is longer than a first threshold value and is equal to or less than a second threshold value that is set to a value longer than the first threshold value, and correcting the current to be supplied to the electromagnetic proportional valve by either the first current value or the second current value, whichever reduces the flow rate of hydraulic oil supplied to the hydraulic cylinder, when the judgment distance is equal to or less than the first threshold value. [Effects of the Invention]

[0017] According to the hydraulic system for a work machine and the method for controlling the hydraulic system for a work machine of the present invention, the swinging of the movable member is smoothly decelerated. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a schematic side view of a work machine according to a first embodiment. [Figure 2] FIG. 2 is a diagram showing a hydraulic system of the work machine in the first embodiment. [Figure 3] 5 is a diagram showing the relationship between the operation amount of the first operating device and the supply current in the first embodiment. FIG. [Figure 4] FIG. 3 is a diagram illustrating the operating length of a hydraulic cylinder in the first embodiment. [Figure 5] FIG. 4 is a diagram showing an example of the relationship between the operating length of the hydraulic cylinder and the angle of the movable member in the first embodiment. [Figure 6] FIG. 4 is a diagram showing the relationship between the angle and angular velocity of the movable member when a reference current value is supplied to the proportional solenoid valve in the first embodiment. [Figure 7] FIG. 4 is a diagram showing an example of the relationship between the angle of the movable member and the limited angular velocity in the first embodiment. [Figure 8] FIG. 4 is a diagram showing an example of the relationship between the angle of the movable member and a first current value in the first embodiment. [Figure 9] 5 is a diagram showing an example of the relationship between the angle of the movable member and a second current value in the first embodiment. FIG. [Figure 10] FIG. 4 is a diagram showing a comparison between a first current value and a second current value in the first embodiment. [Figure 11] 5 is a flowchart illustrating a series of steps in cushion control in the first embodiment. [Figure 12] FIG. 6 is a diagram showing a hydraulic system of a work machine in a second embodiment. [Figure 13] FIG. 10 is a diagram showing a comparison between a first current value and a second current value in a modified example of the second embodiment. [Figure 14]10 is a flowchart illustrating a series of steps in cushion control in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings as appropriate.

[0020] [First embodiment] 1 is a schematic side view of a work machine 1 in a first embodiment. In this embodiment, the work machine 1 is exemplified by a backhoe, which is a swivel work machine.

[0021] As shown in Fig. 1, the work machine 1 includes a traveling body 1A and a work device 20 mounted on the traveling body 1A. The traveling body 1A includes a traveling device 3 and a machine body (swivel base) 2 mounted on the traveling device 3. The machine body 2 is equipped with a driver's seat 6 where a driver sits.

[0022] Hereinafter, the direction in which the driver seated in the driver's seat 6 of the work machine 1 faces (the direction of arrow A1 in FIG. 1) will be referred to as the forward direction, and the opposite direction (the direction of arrow A2 in FIG. 1) will be referred to as the rearward direction. Also, the left side of the driver (the front side in FIG. 1) will be referred to as the left side, and the right side of the driver (the back side in FIG. 1) will be referred to as the right side. Note that the direction perpendicular to the fore-and-aft direction K1 of the machine body 2 may be referred to as the machine body width direction (width direction).

[0023] As shown in Fig. 1, the traveling device 3 is a device that supports the machine body 2 so that it can travel. The traveling device 3 is driven by a traveling motor 11 that is configured by a hydraulic motor (hydraulic actuator), an electric motor, or the like. Note that, although a crawler-type traveling device 3 is used in this embodiment, this is not limiting, and a wheel-type traveling device 3 or the like may also be used.

[0024] The machine body 2 is supported on the traveling device 3 via a swivel bearing 8 so as to be rotatable about a swivel axis X1. The swivel axis X1 is an axis that passes through the center of the swivel bearing 8 and extends in the vertical direction.

[0025] The aircraft body 2 is equipped with a prime mover 5. The prime mover 5 is a diesel engine. The prime mover 5 may be a gasoline engine or an electric motor, or may be a hybrid type having an engine and an electric motor.

[0026] The machine body 2 has, at its front, a support bracket 15 that supports a boom device 30 (described below), and a swing bracket 16. The support bracket 15 is provided so as to protrude forward from the machine body 2. The swing bracket 16 is attached to the front portion of the support bracket 15 (the portion that protrudes from the machine body 2) via a swing shaft so as to be swingable about a vertical axis (an axis extending in the up-down direction). Therefore, the swing bracket 16 can rotate in the width direction of the machine body (horizontally around the swing shaft).

[0027] The working device 20 has a movable member 21 and a hydraulic cylinder 22 that swings the movable member 21. The hydraulic cylinder 22 is linearly driven to extend or contract by the supplied hydraulic oil, swinging the movable member 21 around the rotation axis. The hydraulic cylinder 22 has a cylindrical cylinder portion 22A and a piston rod 22B one end of which is inserted slidably into the cylinder portion 22A.

[0028] As shown in FIG. 1, in this embodiment, the work apparatus 20 includes a boom apparatus 30, an arm apparatus 40, a work implement apparatus 50, and a dozer apparatus 60.

[0029] The boom device 30 has a boom 31, which is a movable member 21, and a boom cylinder 32, which is a hydraulic cylinder 22. The boom 31 has a base 31A supported by the first pivot portion 17 of the swing bracket 16 so as to be swingable (rotatable) about a horizontal axis (rotation axis) 35 extending in the width direction of the machine body, a tip end 31B that swingably supports an arm 41, and an intermediate portion 31C provided between the base 31A and the tip end 31B. The intermediate portion 31C is elongated along the longitudinal direction and bent downward halfway. A lower bracket 33 is provided on one side (lower portion) of the bent portion of the intermediate portion 31C, and an upper bracket 34 is provided on the other side (upper portion) of the bent portion of the intermediate portion 31C.

[0030] The boom cylinder 32 can swing the boom 31 by extending or retracting. The boom cylinder 32 includes a cylindrical cylinder portion 32A and a piston rod 32B having one end slidably inserted into the cylinder portion 32A. The base end of the cylinder portion 32A is supported by the second pivot portion 18 of the swing bracket 16 so as to be swingable about a horizontal shaft 36. The tip end of the piston rod 32B is supported by the lower bracket 33 so as to be swingable about a horizontal shaft 37.

[0031] The boom cylinder 32 is disposed on the side of the boom 31 that faces the arm 41 when the arm 41 swings in the arm crowding direction D3. In other words, the boom cylinder 32 is provided at the lower part of the front side of the boom 31.

[0032] Therefore, the boom cylinder 32 (hydraulic cylinder 22) can swing the boom 31 (movable member 21) around the horizontal axis (rotation axis) 35. That is, as shown in Fig. 1, the boom 31 can swing upward in a boom-raising direction D1 and downward in a boom-lowering direction D2.

[0033] In this embodiment, the boom cylinder 32 can swing the boom 31 in a boom-raising direction D1 by extending it, and can swing the boom 31 in a boom-lowering direction D2 by retracting it.

[0034] The arm device 40 has an arm 41 which is the movable member 21, and an arm cylinder 42 which is the hydraulic cylinder 22. The arm 41 is elongated in the longitudinal direction. A base end of the arm 41 is supported by the tip 31B of the boom 31 so as to be able to swing freely around a horizontal shaft (rotation shaft) 43. An upper bracket 44 is provided on the upper surface side of the base end of the arm 41.

[0035] The arm cylinder 42 can swing the arm 41 by extending or retracting. The arm cylinder 42 includes a cylindrical cylinder portion 42A and a piston rod 42B having one end slidably inserted into the cylinder portion 42A. The base end of the cylinder portion 42A is supported by the upper bracket 34 of the boom 31 so as to be swingable about the horizontal shaft 38. The tip end of the piston rod 42B is supported by the upper bracket 44 so as to be swingable about the horizontal shaft 46.

[0036] Therefore, the arm cylinder 42 (hydraulic cylinder 22) can swing the arm 41 (movable member 21) around the horizontal axis (rotation axis) 43. Therefore, the arm device 40 (arm 41) can freely swing upward or downward (forward or backward). In other words, as shown in FIG. 1 , the arm 41 can swing in an arm crowding direction D3 in which it approaches the boom 31, and in an arm dumping direction D4 in which it moves away from the boom 31.

[0037] In this embodiment, the arm cylinder 42 can swing the arm 41 in the arm crowding direction D3 by extending it, and can swing the arm 41 in the arm dumping direction D4 by contracting it.

[0038] The implement device 50 has an implement 51 which is the movable member 21, and an implement cylinder 52 which is the hydraulic cylinder 22. In this embodiment, the implement 51 is a bucket, and the implement cylinder 52 is a bucket cylinder. The bucket 51 is supported at the tip of the arm 41 so as to be able to swing freely around a pivot (rotational axis) 57. A link mechanism 53 is provided between the bucket 51 and the tip of the arm 41. The bucket 51 has a bucket body 51a which is a part that scoops up earth and sand, etc., and a mounting bracket 51b which is attached to the arm 41 and the link mechanism 53.

[0039] The bucket cylinder 52 can swing the bucket 51 by extending or contracting. The bucket cylinder 52 includes a cylindrical cylinder portion 52A and a piston rod 52B having one end slidably inserted into the cylinder portion 52A. The base end of the cylinder portion 52A is supported by the upper bracket 44 of the arm 41 so as to be swingable about a horizontal shaft 48. The tip end of the piston rod 52B is supported by the link mechanism 53 so as to be swingable about a horizontal shaft 56.

[0040] Therefore, the bucket cylinder 52 (hydraulic cylinder 22) can swing the bucket 51 (movable member 21) around the pivot (rotation axis) 57. As a result, the bucket 51 can perform a crowding operation (scooping operation) and a dumping operation toward the tip of the arm 41. That is, as shown in FIG. 1 , the bucket 51 can swing in a bucket crowding direction (work implement crowding direction) D5, which is a direction in which the tip of the bucket 51 approaches the boom 31 (arm 41), and a bucket dumping direction (work implement dumping direction) D6, which is a direction in which the tip of the bucket 51 moves away from the boom 31 (arm 41). The crowding operation (scooping operation) is, for example, an operation for scooping up earth and sand. Furthermore, the dumping operation is, for example, an operation for dropping (discharging) the scooped up earth and sand.

[0041] In this embodiment, the work implement 51 is a bucket, but instead of or in addition to a bucket, other work implements (hydraulic attachments) that can be driven by a hydraulic actuator can be attached to the work machine 1. Examples of other work implements include a hydraulic breaker, hydraulic crusher, angle broom, earth auger, pallet fork, sweeper, mower, snow blower, etc.

[0042] The dozer device 60 has a dozer 61 which is a movable member 21, and a dozer cylinder 62 which is a hydraulic cylinder 22. The base end of the dozer 61 is pivotally supported on the frame (track frame) of the traveling device 3 so as to be able to swing up and down around a swing shaft (rotation shaft) 63.

[0043] The dozer cylinder 62 can swing the dozer 61 by extending or contracting. The dozer cylinder 62 has a cylindrical cylinder portion 62A and a piston rod 62B whose one end is slidably inserted into the cylinder portion 62A. The base end of the cylinder portion 62A is supported so as to be able to swing above the dozer 61 on the track frame of the traveling device 3. The tip end of the piston rod 62B is supported so as to be able to swing midway through the dozer 61.

[0044] Therefore, the dozer cylinder 62 (hydraulic cylinder 22) can swing the dozer 61 around the swing shaft 63. Therefore, the dozer device 60 (dozer 61) can swing freely upward or downward. That is, as shown in Fig. 1, the dozer 61 can swing upward in a dozer-raising direction D7 and downward in a dozer-lowering direction D8.

[0045] In this embodiment, the dozer cylinder 62 can swing the dozer 61 in a dozer-raising direction D7 by contracting, and can swing the dozer 61 in a dozer-lowering direction D8 by extending.

[0046] Furthermore, in this embodiment, the working device 20 has been described as including the boom device 30, the arm device 40, the implement device 50, and the dozer device 60, but the working device 20 is not limited to the boom device 30, the arm device 40, the implement device 50, and the dozer device 60 as long as it has the movable member 21 and the hydraulic cylinder 22. For example, the working device 20 may include a swing device having a swing bracket 16. In such a case, the swing device is composed of the swing bracket 16 as the movable member 21 and a swing cylinder (not shown) as the hydraulic cylinder 22. The swing cylinder is provided inside the machine body 2, and swings the swing bracket 16 in the width direction of the machine body by extending and contracting.

[0047] 2 is a diagram showing the hydraulic system S of the work machine 1 in the first embodiment. As shown in FIG. 2, the hydraulic system S of the work machine 1 includes an electromagnetic proportional valve 70, a control device 80, and a first operating device 90.

[0048] The electromagnetic proportional valve 70 is a switching valve that can change the flow rate of hydraulic oil supplied to the hydraulic cylinder 22. More specifically, the electromagnetic proportional valve 70 changes its switching position using an electric current supplied from the control device 80 to change the flow direction (supply direction) and flow rate of hydraulic oil supplied to the hydraulic cylinder 22. In this embodiment, the electromagnetic proportional valve 70 is a direct-acting solenoid valve that controls the flow of hydraulic oil by moving a direct-acting spool (hereinafter simply referred to as the spool) using solenoids 70a, 70b. The spool can be switched to switching positions: a first position 70A, a second position 70B, and a third position (neutral position) 70C.

[0049] The solenoids 70a, 70b can be switched between energized and de-energized states depending on the magnitude of the current (current value I) supplied thereto. Of the solenoids 70a, 70b, the first solenoid 70a is provided on one end side of the spool, and the second solenoid 70b is provided on the other end of the spool. The strength of excitation is changed depending on the supplied current value I, and the position of the spool is continuously changed between a first position 70A, a second position 70B, and a third position 70C. This allows the solenoid proportional valve 70 to continuously change the flow rate (output) of hydraulic oil supplied from the hydraulic pump P to the hydraulic cylinder 22, and to switch the supply direction of the hydraulic oil.

[0050] In the following explanation, an example will be given in which, when current is supplied to the first solenoid 70a but not to the second solenoid 70b, the spool switching position switches to the first position 70A and the hydraulic cylinder 22 contracts, and when current is not supplied to the first solenoid 70a but is supplied to the second solenoid 70b, the spool switching position switches to the second position 70B and the hydraulic cylinder 22 extends.

[0051] In addition, the solenoids 70a, 70b may change the position of the spool in stages between the first position 70A, the second position 70B, and the third position 70C depending on the current value I of the supplied current. In such a case, the electromagnetic proportional valve 70 can change in stages the flow rate (output) of the hydraulic oil supplied from the hydraulic pump P to the hydraulic cylinder 22 and switch the supply direction of the hydraulic oil.

[0052] Furthermore, the electromagnetic proportional valve 70 is not limited to the configuration described above, and may be, for example, an electromagnetic three-position switching valve incorporating a solenoid valve and in which the position of a spool is switched by hydraulic oil (pilot oil) supplied from a pump (not shown) different from the hydraulic pump P. Furthermore, the electromagnetic proportional valve 70 is not limited to a configuration incorporating a solenoid valve, and may be configured with a direct-acting spool (directional switching valve) and a solenoid valve configured separately. Furthermore, the electromagnetic proportional valve 70 is not limited to a three-position switching valve, and may be a two-position switching valve, a four-position switching valve, or the like.

[0053] 2, in this embodiment, the electromagnetic proportional valve 70 includes a boom control valve 71, an arm control valve 72, a bucket control valve 73, and a dozer control valve 74. The boom control valve 71, the arm control valve 72, the bucket control valve 73, and the dozer control valve 74 are connected to the boom cylinder 32, the arm cylinder 42, the bucket cylinder 52, and the dozer cylinder 62, respectively, via oil passages. In addition, a hydraulic pump P that discharges hydraulic oil is connected to the boom control valve 71, the arm control valve 72, the bucket control valve 73, and the dozer control valve 74, respectively, via oil passages.

[0054] The control device 80 controls the current supplied to the solenoids 70a and 70b of the electromagnetic proportional valves 70 (the boom control valve 71, the arm control valve 72, the bucket control valve 73, and the dozer control valve 74).

[0055] The control device 80 is a device configured with electric and electronic circuits, programs stored in a CPU, an MPU, etc. The control device 80 controls various devices of the work implement 1. The control device 80 can control the work implement 20 based on the operation of the first operating device 90. Specifically, the control device 80 controls the magnitude of the current (current value I) supplied to the solenoids 70a, 70b of the boom control valve 71, the arm control valve 72, the bucket control valve 73, and the dozer control valve 74 based on the operation of the first operating device 90, thereby controlling the switching operation of each of these control valves. In this way, the control device 80 can control the operation of the boom 31, the arm 4, the bucket 51, and the dozer implement 60. Furthermore, as shown in FIG. 2 , the control device 80 has a memory unit 81. The memory unit 81 is a non-volatile memory or the like, and stores various information related to the control of the control device 80.

[0056] The first operating device 90 is an operating tool for operating the working device 20. The first operating device 90 is composed of a lever or the like that is held by the driver when operating the device, and is provided near the driver's seat 6. The first operating device 90 is connected to the control device 80, and outputs an operating signal to the control device 80 that indicates the direction and amount of operation.

[0057] As shown in Fig. 2, the first operating device 90 includes operating devices 91L and 91R and a dozer operating device 91D. Each of the operating devices 91L and 91R has an operating lever 92a and a position sensor 92b. The operating lever 92a is freely swingable forward, backward, right, and left from a neutral position, and the position sensor 92b detects the swing direction and swing amount (operation amount) of the operating lever 92a from the neutral position of forward, backward, right, and left. The operating lever 92a outputs an electric signal (operation signal) indicating the swing direction and swing amount detected by the position sensor 92b to the control device 80.

[0058] The dozer operation device 91D has an operation lever 93a and a position sensor 93b. The operation lever 93a can be freely swung forward and backward from a neutral position, and the position sensor 93b detects the direction and amount of swing (operation amount) of the operation lever 93a from the neutral position forward and backward. The operation lever 93a outputs an electric signal (operation signal) indicating the direction and amount of swing detected by the position sensor 93b to the control device 80.

[0059] The following describes the control of the working device 20 by the control device 80 based on the operation of the first operating device 90. The control device 80 controls the current supplied to the electromagnetic proportional valve 70 to keep the flow rate of the hydraulic oil supplied to the hydraulic cylinder 22 at or below a predetermined flow rate. Specifically, the control device 80 controls the current supplied to the electromagnetic proportional valve 70 (supply current) to be within a range equal to or below a predetermined reference current value IB.

[0060] As shown in FIG. 2 , the control device 80 has a definition unit 82 that defines a supply current based on an operation signal output from the first operation device 90. The definition unit 82 defines the magnitude of the current (current value I) to be supplied to the electromagnetic proportional valve 70 corresponding to the operation target indicated by the operation signal, based on the operation signal and a control map pre-stored in the storage unit 81 or a predetermined arithmetic expression, within a range equal to or less than a reference current value IB (I≦IB). In this embodiment, the definition unit 82 defines the magnitude of the current within a range equal to or greater than a minimum current value IA and equal to or less than a reference current value IB (IA≦I≦IB). The minimum current value IA is the minimum current value I that can adjust the aperture of the electromagnetic proportional valve 70. The reference current value IB is the magnitude of the current (maximum current value) when the aperture of the electromagnetic proportional valve 70 is maximized. When a current equal to the reference current value IB is supplied, the electromagnetic proportional valve 70 supplies hydraulic oil to the hydraulic cylinder 22 at a maximum flow rate (predetermined flow rate).

[0061] 3 shows an example of the relationship between the operation amount of the first operating device 90 and the supply current in the first embodiment. When the first operating device 90 is near the neutral position, that is, when the operation amount is less than the first operating amount G1, the definition unit 82 defines the supply current as zero.

[0062] Furthermore, when the operation amount of the first operating device 90 is equal to or greater than the first operating amount G1 and equal to or less than the second operating amount G2, the definition unit 82 changes the supply current in proportion to the operation amount of the first operating device 90 or in a correspondence (correlation) close to a proportional relationship.

[0063] 2, the definition unit 82 includes a boom control unit 82a, an arm control unit 82b, a bucket control unit 82c, and a dozer control unit 82d. The boom control unit 82a defines the current (supply current) to be supplied to the boom control valve 71 based on an operation signal output from a position sensor 92b of the control device 91R. As a result, the control device 80 supplies the defined supply current to the first solenoid 70a and the second solenoid 70b of the boom control valve 71, thereby switching the boom control valve 71.

[0064] The arm control section 82b defines the current (supply current) to be supplied to the arm control valve 72 based on the operation signal output from the position sensor 92b of the operating device 91L. As a result, the control device 80 supplies the defined supply current to the first solenoid 70a and the second solenoid 70b of the arm control valve 72, thereby switching the arm control valve 72.

[0065] The bucket control unit 82c defines the current (supply current) to be supplied to the bucket control valve 73 based on an operation signal output from the operation lever 92a of the operation device 91R. As a result, the control device 80 supplies the defined supply current to the first solenoid 70a and the second solenoid 70b of the bucket control valve 73, thereby switching the bucket control valve 73.

[0066] The dozer control section 82d defines the current (supply current) to be supplied to the dozer control valve 74 based on the operation signal output from the operation lever 93a of the dozer operation device 91D. As a result, the control device 80 supplies the defined supply current to the first solenoid 70a and the second solenoid 70b of the dozer control valve 74, thereby switching the dozer control valve 74.

[0067] The control device 80 can perform cushion control to decelerate the piston rod 22B when the hydraulic cylinder 22 approaches the stroke end (terminal end) E. When the hydraulic cylinder 22 approaches the stroke end E, the control device 80 performs cushion control by limiting the magnitude of the current (current value I) supplied to the electromagnetic proportional valve 70 to reduce the hydraulic oil supplied to the hydraulic cylinder 22. Specifically, in the cushion control, the control device 80 reduces the hydraulic oil supplied to the hydraulic cylinder 22 by limiting the current supplied to the electromagnetic proportional valve 70 based on a judgment distance H, which is the operating length L from the current operating position of the hydraulic cylinder 22 to the stroke end E.

[0068] FIG. 4 is a diagram illustrating the operating length L of the hydraulic cylinder 22 in the first embodiment. The hydraulic cylinder 22 retracts to a first stroke end E1 and extends to a second stroke end E2. That is, in the example shown in FIG. 4, the operating length L of the hydraulic cylinder 22 extends from a minimum operating length L1 when the hydraulic cylinder 22 is fully retracted (first stroke end E1) to a maximum operating length L2 when the hydraulic cylinder 22 is fully extended (second stroke end E2). In the following description, the operating length L when the hydraulic cylinder 22 is in the center between the first stroke end E1 and the second stroke end E2 (neutral position N) is referred to as a central operating length L3. The minimum operating length L1, maximum operating length L2, and central operating length L3 vary for each hydraulic cylinder 22 depending on its shape, structure, etc.

[0069] In this embodiment, the control device 80 performs cushioning control based on the judgment distance H by converting the operating length L into a swing angle (angle) θ of the movable member 21. Note that the control device 80 only needs to be able to perform cushioning control based on the judgment distance H, and may be configured to perform cushioning control by calculating the operating length L of the hydraulic cylinder 22 from various sensors without converting it into the swing angle θ, or may be configured to convert the judgment distance H into the operating position of the hydraulic cylinder 22 and perform cushioning control based on the operating position.

[0070] The control device 80 performs cushion control on at least one of the work devices 20 included in the work machine 1. In this embodiment, an example will be described in which the control device 80 performs cushion control on the boom device 30, the arm device 40, the implement device 50, and the dozer device 60.

[0071] As shown in FIG. 2, the hydraulic system S of the work machine 1 is equipped with an angle detection device 95 that detects the swing angle θ of the movable member 21. The angle detection device 95 detects the swing angle θ of the movable member 21 around the rotation axis thereof, and outputs an electric signal (detection signal) indicative of the detected swing angle θ to the control device 80. The angle detection device 95 is configured with, for example, a potentiometer. Note that the angle detection device 95 may be any angle sensor capable of detecting the swing angle θ of the movable member 21, and may also be another angle sensor such as an inertial measurement unit (IMU). Alternatively, the swing angle θ may be detected using a cylinder stroke sensor that detects the operating length L of the hydraulic cylinder 22.

[0072] In this embodiment, the angle detection device 95 includes a boom angle sensor 95a that detects the swing angle θa (swing position) of the boom 31, an arm angle sensor 95b that detects the swing angle θb (swing position) of the arm 41, a work tool angle sensor (bucket angle sensor) 95c that detects the swing angle θc (swing position) of the bucket 51 around the pivot 57 relative to the tip of the arm 41, and a dozer angle sensor 95d that detects the swing angle θd (swing position) of the dozer 61.

[0073] The following provides a detailed description of the cushion control of the control device 80. As shown in FIG.

[0074] The angle calculation unit 85 acquires the detection signal detected by the angle detection device 95 and calculates the swing angle θ of the movable member 21. The angle calculation unit 85 calculates the swing angle θ based on a map or an arithmetic expression stored in advance in the storage unit 81.

[0075] Fig. 5 is a diagram showing an example of the relationship between the operating length L of the hydraulic cylinder 22 and the swing angle θ of the movable member 21 in the first embodiment. As shown in Fig. 5, the operating length L of the hydraulic cylinder 22 increases approximately in proportion to the swing angle θ of the movable member 21. As shown in Fig. 5, the swing angle θ of the movable member 21 corresponding to the minimum operating length L1 is the minimum angle θ1, the swing angle θ of the movable member 21 corresponding to the central operating length L3 is the central angle θ3, and the swing angle θ of the movable member 21 corresponding to the maximum operating length L2 is the maximum angle θ2.

[0076] Therefore, the control device 80 can determine that the hydraulic cylinder 22 is approaching the first stroke end E1 based on a change in the difference between the actual swing angle θ of the movable member 21 calculated by the angle calculation unit 85 and the minimum angle θ1. The control device 80 can also determine that the hydraulic cylinder 22 is approaching the second stroke end E2 based on a change in the difference between the actual swing angle θ of the movable member 21 calculated by the angle calculation unit 85 and the maximum angle θ2.

[0077] The relationship between the operating length L of the hydraulic cylinder 22 and the swing angle θ of the movable member 21 shown in FIG. 5 is an example, and is defined by different calculation formulas depending on the structure of the working device 20 including the movable member 21 and the hydraulic cylinder 22.

[0078] Furthermore, the angle calculation unit 85 calculates the actual angular velocity ω (actual angular velocity ωr) of the movable member 21 per predetermined time based on the calculated swing angle θ of the movable member 21.

[0079] Next, the relationship between the oscillation angle θ and the angular velocity ω of the movable member 21 when a reference current value IB is supplied to the electromagnetic proportional valve 70 will be described. FIG. 6 shows the relationship between the oscillation angle θ and the angular velocity ω of the movable member 21 when a reference current value IB is supplied to the electromagnetic proportional valve 70 in the first embodiment. In the graph of FIG. 6, the horizontal axis represents the oscillation angle θ of the movable member 21, and the vertical axis represents the angular velocity ω of the movable member 21. As described above, the reference current value IB is the current value I that maximizes the opening of the electromagnetic proportional valve 70, and therefore the angular velocity ω shown in FIG. 6 is the maximum angular velocity (maximum angular velocity) ωmax at the oscillation position of the movable member 21 corresponding to each oscillation angle θ. In the example of FIG. 6, the maximum angular velocity ωmax at the minimum angle θ1 and the maximum angular velocity ωmax at the maximum angle θ2 are equal, but there are also cases where the two are different.

[0080] As described above, the hydraulic cylinder 22 is linearly driven to extend or retract by the supplied hydraulic oil, thereby swinging the movable member 21 around the rotation axis 27. Therefore, as shown in Fig. 6, the maximum angular velocity ωmax at each swing angle θ changes in a downwardly convex curve with respect to the swing angle θ. Specifically, as the swing angle θ of the hydraulic cylinder 22 decreases from the central angle θ3 to the minimum angle θ1, the maximum angular velocity ωmax gradually increases and then suddenly increases. Furthermore, as the swing angle θ of the hydraulic cylinder 22 increases from the central angle θ3 to the maximum angle θ2, the maximum angular velocity ωmax gradually increases and then suddenly increases.

[0081] In the following description, when the flow rate of hydraulic oil supplied to the hydraulic cylinder 22 is constant at a predetermined flow rate, the minimum value of the angular velocity ω within the range of oscillation angles θ1 to θ2 is referred to as the "reference angular velocity ωB." In the example shown in Fig. 6, the reference angular velocity ωB is the angular velocity when the oscillation angle θ of the movable member 21 is the central angle θ3. Note that the oscillation position at which the angular velocity ω has the minimum value is not necessarily the position corresponding to the central angle θ3.

[0082] The first calculation unit 86 calculates a first current value I1, which is the current value I of the current supplied to the electromagnetic proportional valve 70 to control the electromagnetic proportional valve 70 to decelerate the angular velocity ω of the movable member 21 as the operating length L of the hydraulic cylinder 22 approaches the stroke end E of the hydraulic cylinder 22. The first calculation unit 86 calculates the first current value I1 when the determination distance H is equal to or less than a first threshold value T1, and does not calculate the first current value I1 when the determination distance H is longer than the first threshold value T1.

[0083] Specifically, when a determination distance H, which is the length to the stroke end E of the hydraulic cylinder 22, is equal to or shorter than a first threshold value T1, the first calculation unit 86 calculates a limit angular velocity ωL that decreases as the determination distance H approaches zero to limit the angular velocity ω of the movable member 21. The first threshold value T1 is an arbitrary value that is set based on the distance required to appropriately decelerate the hydraulic cylinder 22 near the stroke end E when a reference current value IB is supplied to the solenoid proportional valve 70. It is preferable to set the first threshold value T1 to as small (shortest) a value as possible within a range in which appropriate cushioning performance is obtained so as not to impair the operability of the working device 20.

[0084] The limit angular velocity ωL is the target angular velocity ω when performing cushion control, and when the judgment distance H is less than or equal to the first threshold value T1, it decreases as the hydraulic cylinder 22 approaches the stroke end E, and is defined as an angular velocity ω that can sufficiently decelerate the linear drive of the hydraulic cylinder 22 when the hydraulic cylinder 22 reaches the stroke end E.

[0085] 7 is a diagram showing an example of the relationship between the oscillation angle θ of the movable member 21 and the limit angular velocity ωL in the first embodiment. As shown in Fig. 7, the limit angular velocity ωL is defined in the range from the reference angular velocity ωB to the terminal angular velocity ωE. The limit angular velocity ωL decreases approximately proportionally as the oscillation angle θ of the movable member 21 decreases from a first determination angle θ11 (described later) to the minimum angle θ1, and decreases approximately proportionally as the oscillation angle θ of the movable member 21 increases from a second determination angle θ21 (described later) to the maximum angle θ2.

[0086] 7 is merely an example. For example, the limit angular velocity ωL may decrease in a curved manner as the swing angle θ of the movable member 21 decreases from the first judgment angle θ11 to the minimum angle θ1. Alternatively, the limit angular velocity ωL may decrease in a curved manner as the swing angle θ of the movable member 21 increases from the second judgment angle θ21 to the maximum angle θ2. The relationship between the swing angle θ of the movable member 21 and the limit angular velocity ωL may be defined differently depending on the controlled object (working device 20) of the cushion control by the control device 80. In this embodiment, the value of the first threshold T1 is set to the same value at the stroke end E on the minimum angle θ1 side and the stroke end E on the maximum angle θ2 side, but this is not limiting and different values ​​may be set.

[0087] As shown in Fig. 5, when the judgment distance H is the first threshold value T1, the operating length L is a first judgment length L11 on the first stroke end E1 side and a second judgment length L21 on the second stroke end E2 side. As shown in Fig. 5, the oscillation angle θ of the movable member 21 corresponding to the first judgment length L11 is a first judgment angle θ11, and the oscillation angle θ of the movable member 21 corresponding to the second judgment length L21 is a second judgment angle θ21. The limit angular velocity ωL when the oscillation angle θ of the movable member 21 is the first judgment angle θ11 and the second judgment angle θ21 is the reference angular velocity ωB.

[0088] Furthermore, the terminal angular velocity ωE is the angular velocity ω when the hydraulic cylinder 22 reaches the stroke end E, and is an angular velocity ω at which the linear drive of the hydraulic cylinder 22 can be sufficiently decelerated. In other words, the terminal angular velocity ωE is the limit angular velocity ωL when the swing angle θ of the movable member 21 is the minimum angle θ1 or the maximum angle θ2. The terminal angular velocity ωE is a predetermined angular velocity ω that is smaller than the reference angular velocity ωB. In this embodiment, the terminal angular velocity ωE is defined to be zero. Note that the terminal angular velocity ωE is not limited to zero as long as it is an angular velocity ω at which the linear drive of the hydraulic cylinder 22 can be sufficiently decelerated and an angular velocity ω at which the shock when the hydraulic cylinder 22 reaches the stroke end E can be reduced.

[0089] Therefore, the reference angular velocity ωB decreases from the reference angular velocity ωB to the terminal angular velocity ωE as the swing angle θ of the movable member 21 decreases from the first judgment angle θ11 to the minimum angle θ1. Furthermore, the reference angular velocity ωB decreases from the reference angular velocity ωB to the terminal angular velocity ωE as the swing angle θ of the movable member 21 increases from the second judgment angle θ21 to the maximum angle θ2.

[0090] Furthermore, the first calculation unit 86 calculates a first current value I1 corresponding to the limit angular velocity ωL based on the actual angular velocity ωr calculated by the angle calculation unit 85 and the current (current value I) supplied by the control device 80 to the solenoid proportional valve 70. For example, the first calculation unit 86 calculates the first current value I1 corresponding to the limit angular velocity ωL by feedback control (PID control), feedforward control, or the like. Note that the first calculation unit 86 only needs to be able to calculate the first current value I1, and may be configured to calculate the first current value I1 corresponding to the limit angular velocity ωL based on an arithmetic expression or a calculation map stored in the storage unit 81.

[0091] In this embodiment, as the supply current increases, the flow rate of hydraulic oil supplied from the electromagnetic proportional valve 70 to the hydraulic cylinder 22 increases, and the angular velocity ω increases. Conversely, as the supply current decreases, the flow rate of hydraulic oil supplied from the electromagnetic proportional valve 70 to the hydraulic cylinder 22 decreases, and the angular velocity ω decreases.

[0092] FIG. 8 is a diagram showing an example of the relationship between the swing angle θ of the movable member 21 and the first current value I1 in the first embodiment. When the judgment distance H is the first threshold value T1, that is, when the swing angle θ of the movable member 21 is the first judgment angle θ11 or the second judgment angle θ21, the first current value I1 corresponds to the reference angular velocity ωB. As described above, when a current of the reference current value IB is supplied to the solenoid proportional valve 70, the maximum angular velocity ωmax (reference angular velocity ωB) when the swing angle θ of the movable member 21 is the central angle θ3 is the minimum value. Therefore, when the swing angle θ of the movable member 21 is the first judgment angle θ11 or the second judgment angle θ21, the first current value I1 (starting current value Is) is less than the reference current value IB (Is <IB)。

[0093] As shown in Fig. 8, as the determination distance H decreases from the first threshold T1 to zero, the first current value I1 decreases to a magnitude (first terminal current value Ie) corresponding to the terminal angular velocity ωE. In other words, when the determination distance H is zero, the first current value I1 is a current value corresponding to a predetermined terminal angular velocity ωE that is smaller than the reference angular velocity ωB, and the first current value I1 is defined in a range equal to or greater than the first terminal current value Ie and equal to or less than the initial current value Is (Ie ≦ I1 ≦ Is). More specifically, as shown in Fig. 8, when the oscillation angle θ of the movable member 21 decreases from the first determination angle θ11, the first current value I1 gradually decreases and then rapidly decreases in a curved manner as the oscillation angle θ of the movable member 21 decreases, and reaches the first terminal current value Ie when the oscillation angle θ reaches the minimum angle θ1. In this embodiment, when current is supplied to the first solenoid 70a but not to the second solenoid 70b, the spool switching position switches to the first position 70A and the hydraulic cylinder 22 contracts, so when the swing angle θ of the movable member 21 is equal to or less than the first judgment angle θ11, the first current value I1 is the current value I supplied to the first solenoid 70a.

[0094] 8, when the swing angle θ of the movable member 21 increases from the second judgment angle θ21, the first current value I1 gradually decreases and then rapidly decreases along a curve as the swing angle θ of the movable member 21 increases, and reaches the first terminal current value Ie when the swing angle θ reaches the maximum angle θ2. In this embodiment, when no current is supplied to the first solenoid 70a but current is supplied to the second solenoid 70b, the switching position of the spool switches to the second position 70B and the hydraulic cylinder 22 extends. Therefore, when the swing angle θ of the movable member 21 is equal to or greater than the second judgment angle θ21, the first current value I1 is the current value I supplied to the second solenoid 70b.

[0095] The first threshold value T1 and the terminal angular velocity ωE may be values ​​pre-stored in the memory unit 81 and may be changeable by operating an operation unit (not shown) provided in the work machine 1 or a terminal (such as a display device, PC, or smartphone) communicatively connected to the control device 80.

[0096] The second calculation unit 87 calculates a second current value I2, which is the current value I of the current supplied to the solenoid proportional valve 70, in order to control the solenoid proportional valve 70 to reduce the flow rate of hydraulic oil supplied to the hydraulic cylinder 22 as the operating length L of the hydraulic cylinder 22 approaches the stroke end E of the hydraulic cylinder 22. The second current value I2 is a current value that reduces the flow rate of hydraulic oil supplied to the hydraulic cylinder 22 from a predetermined flow rate as the judgment distance H approaches zero, thereby limiting the operating speed of the hydraulic cylinder 22.

[0097] Specifically, the second calculation unit 87 calculates the second current value I2 when the determination distance H is equal to or less than the second threshold value T2, and does not calculate the second current value I2 when the determination distance H is longer than the second threshold value T2. The second threshold value T2 is defined as a value longer than the first threshold value T1.

[0098] When the judgment distance H is the second threshold value T2, the motion length L is, as shown in FIG. 5, a third judgment length L12 on the first stroke end E1 side and a fourth judgment length L22 on the second stroke end E2 side.

[0099] 5, the oscillation angle θ of the movable member 21 corresponding to the third judgment length L12 is the third judgment angle θ12, and the oscillation angle θ of the movable member 21 corresponding to the fourth judgment length L22 is the fourth judgment angle θ22. In other words, the second calculation unit 87 calculates the second current value I2 when the oscillation angle θ of the movable member 21 is equal to or smaller than the third judgment angle θ12 and when it is equal to or larger than the fourth judgment angle θ22.

[0100] The second current value I2 is equal to or less than the reference current value IB and decreases as the determination distance H approaches zero. The second calculation unit 87 calculates the second current value I2 corresponding to the swing angle θ of the movable member 21 based on a calculation formula or calculation map stored in the storage unit 81. FIG. 9 is a diagram showing an example of the relationship between the swing angle θ of the movable member 21 and the second current value I2 in the first embodiment. As shown in FIG. 9, the second current value I2 is defined to be in the range equal to or greater than the second terminal current value IE and equal to or less than the reference current value IB (IE≦I2≦IB).

[0101] Note that the relationship between the swing angle θ of the movable member 21 shown in FIG. 9 and the second current value I2 is merely an example. As the swing angle θ of the movable member 21 decreases from the third determination angle θ12 to the minimum angle θ1, the second current value I2 decreases, and as the swing angle θ of the movable member 21 increases from the fourth determination angle θ22 to the maximum angle θ2, the second current value I2 decreases. The relationship is not limited to the example in FIG. 9. For example, the second current value I2 may increase or decrease in a curve according to the increase or decrease of the swing angle θ of the movable member 21. Also, the relationship between the swing angle θ of the movable member 21 and the second current value I2 may be defined differently according to the control target (working device 20) of the cushion control of the control device 80.

[0102] When the determination distance H is the second threshold value T2, that is, when the swing angle θ of the movable member 21 is the third determination angle θ12 or the fourth determination angle θ22, the second current value I2 is the same value as the reference current value IB. Also, the second current value I2 when the determination distance H is zero is the second terminal current value IE. Note that the second current value I2 when the determination distance H is the second threshold value T2 may be the current value I that supplies the hydraulic cylinder 22 with hydraulic oil having a flow rate substantially equivalent to a predetermined flow rate, and does not necessarily have to match the reference current value IB. That is, the second current value I2 when the determination distance H is the second threshold value T2 may be defined as a current value I higher than the reference current value IB in order to reliably supply the hydraulic cylinder 22 with a predetermined flow rate of hydraulic oil.

[0103] As shown in FIG. 9, as the determination distance H decreases from the second threshold value T2 to zero, the second current value I2 decreases substantially proportionally from the reference current value IB to the second terminal current value IE. The second terminal current value IE is defined as a current value I larger than the first terminal current value Ie (Ie < IE). Note that the second current value I2 when the determination distance H is zero may be less than or equal to the reference current value IB, and its magnitude is not particularly limited.

[0104] In this embodiment, when current is supplied to the first solenoid 70a but not to the second solenoid 70b, the spool switching position switches to the first position 70A and the hydraulic cylinder 22 contracts, so when the swing angle θ of the movable member 21 is less than or equal to the third judgment angle θ12, the second current value I2 is the current value I supplied to the first solenoid 70a.

[0105] In addition, in this embodiment, when current is not supplied to the first solenoid 70a but is supplied to the second solenoid 70b, the spool switching position switches to the second position 70B and the hydraulic cylinder 22 extends, so when the swing angle θ of the movable member 21 is equal to or greater than the fourth judgment angle θ22, the second current value I2 is the current value I supplied to the second solenoid 70b.

[0106] The second threshold value T2 may be a value pre-stored in the memory unit 81 and may be changeable by operating an operating tool provided on the work machine 1 or a terminal (display device, PC, smartphone, etc.) connected to the control device 80 so as to be able to communicate with the work machine 1.

[0107] 10 is a diagram showing a comparison between the first current value I1 and the second current value I2 in the first embodiment. In Fig. 10, the first current value I1 is indicated by a dashed line, and the second current value I2 is indicated by a dashed double-dashed line. The current value I of the supply current is indicated by a solid line, and for convenience of illustration, the first current value I1 and the second current value I2 are offset from each other.

[0108] When the determination distance H is longer than the first threshold value T1 and is equal to or smaller than the second threshold value T2, the current limiting unit 88 corrects the current supplied to the electromagnetic proportional valve 70 by the second current value I2. When the determination distance H is equal to or smaller than the first threshold value T1, the current limiting unit 88 selects and corrects the current supplied to the electromagnetic proportional valve 70 from either the first current value I1 or the second current value I2. In this embodiment, the current limiting unit 88 limits the supply current by correcting the supply current defined by the definition unit 82 by the first current value I1 or the second current value I2. In this embodiment, in order to perform cushion control for the boom apparatus 30, the arm apparatus 40, the implement apparatus 50, and the dozer apparatus 60, the current limiting unit 88 corrects the supply current defined by the boom control unit 82a, the arm control unit 82b, the bucket control unit 82c, and the dozer control unit 82d.

[0109] 10, when the judgment distance H is longer than the first threshold T1 and equal to or less than the second threshold T2, i.e., when the swing angle θ of the movable member 21 is equal to or less than the third judgment angle θ12 and exceeds the first judgment angle θ11, or when the swing angle θ is equal to or greater than the fourth judgment angle θ22 and less than the second judgment angle θ21, the current limiting unit 88 selects the second current value I2. Furthermore, when the supply current defined by the definition unit 82 exceeds the selected second current value I2 (selected current value Ic), the current limiting unit 88 corrects the supply current by the second current value I2.

[0110] 10, when the judgment distance H is equal to or smaller than the first threshold value T1, i.e., when the swing angle θ of the movable member 21 is equal to or smaller than the first judgment angle θ11, or when the swing angle θ is equal to or larger than the second judgment angle θ21, the current limiting unit 88 selects the current value I that provides the smaller flow rate of hydraulic oil to be supplied to the hydraulic cylinder 22 from the first current value I1 calculated by the first calculation unit 86 and the second current value I2 calculated by the second calculation unit 87. Furthermore, when the supply current defined by the definition unit 82 exceeds the selected current value I (selected current value Ic), the current limiting unit 88 corrects the supply current by the selected current value Ic.

[0111] For this reason, for example, in a state in which the first operating device 90 is operated and the definition unit 82 defines the reference current value IB as the supply current, when the hydraulic cylinder 22 approaches the stroke end E and the judgment distance H reaches the second threshold value T2, the supply current is first corrected by the second current value I2 and gradually decreases from the reference current value IB. Furthermore, when the hydraulic cylinder 22 further approaches the stroke end E and the judgment distance H reaches the first threshold value T1, the supply current is corrected by the selected current value Ic, which is the smaller of the first current value I1 and the second current value I2.

[0112] As a result, when correction is made using only the first current value I1, a sudden change in the current value from the reference current value IB to the starting current value Is may occur, but by correcting in advance using the second current value I2, it is possible to suppress the sudden change in the current value and reduce the current value I. This makes it possible to smoothly decelerate the swing speed of the movable member 21 when the hydraulic cylinder 22 approaches the stroke end E.

[0113] In the present embodiment, the current limiting unit 88 selects either the first current value I1 or the second current value I2 as the current value I in the section where the determination distance H decreases from the second threshold value T2 to zero, but the selection method is not limited to the above. For example, when the determination distance H is longer than the first threshold value T1 and equal to or less than the second threshold value T2, the second current value I2 may be selected, and when the determination distance H is equal to or less than the first threshold value T1, the first current value I1 may be selected.

[0114] The supply current limitation in cushion control will be described below with reference to Fig. 11. Fig. 11 is a flowchart illustrating a series of steps in cushion control in the first embodiment. First, the definition unit 82 acquires an electric signal (operation signal) representing the swing direction and swing amount from the first operating device 90 (S1), and defines the supply current of the operation target based on the acquired operation signal (S2).

[0115] Next, the angle calculation unit 85 calculates the swing angle θ and the actual angular velocity ωr of the movable member 21 (S3).

[0116] Next, the current limiting unit 88 determines whether the determination distance H is equal to or less than the second threshold value T2 (S4).

[0117] When the current limiting unit 88 determines that the determination distance H is equal to or less than the second threshold value T2 (S4, Yes), the second calculation unit 87 calculates the second current value I2 (S5, second step).

[0118] Next, the current limiting unit 88 determines whether the determination distance H exceeds the first threshold value T1 (S6).

[0119] If the current limiting unit 88 determines that the judgment distance H exceeds the first threshold value T1 (S6, Yes), the current limiting unit 88 selects the second current value I2 calculated by the second calculation unit 87 as the selected current value Ic (S7).

[0120] If the current limiting unit 88 determines that the judgment distance H does not exceed the first threshold value T1 (S6, No), the first calculation unit 86 calculates the limited angular velocity ωL and calculates the first current value I1 corresponding to the limited angular velocity ωL (S8, first step).

[0121] Next, the current limiting unit 88 selects, as the selected current value Ic, the current value I that provides a smaller flow rate of hydraulic oil to be supplied to the hydraulic cylinder 22, from the first current value I1 calculated by the first calculation unit 86 and the second current value I2 calculated by the second calculation unit 87 (S9). In this embodiment, the current limiting unit 88 selects, as the selected current value Ic, the smaller current value I from the first current value I1 and the second current value I2.

[0122] When the current limiting unit 88 selects the selected current value Ic (S7 or S9), it determines whether the supply current defined by the defining unit 82 exceeds the selected current value Ic (S10).

[0123] When the current limiting unit 88 determines that the current value I of the supply current exceeds the selected current value Ic (S10, Yes), it corrects the current value I of the supply current to the selected current value Ic (S11). Next, the control device 80 supplies the corrected supply current to the solenoid proportional valve 70 (S12). S7 and S9 to S12 are referred to as the third step.

[0124] On the other hand, if the current limiting unit 88 determines that the judgment distance H is not less than the second threshold value T2 (S4, No), and if it determines that the current value I of the supply current does not exceed the selected current value Ic (S10, No), the control device 80 supplies the supply current defined by the definition unit 82 to the electromagnetic proportional valve 70 without correcting it with the selected current value Ic (S13).

[0125] The hydraulic system S of the working machine 1 described above comprises a working device 20 having a movable member 21 and a hydraulic cylinder 22 that oscillates the movable member 21, an electromagnetic proportional valve 70 that can change the flow rate of hydraulic oil supplied to the hydraulic cylinder 22, and a control device 80 that controls the flow rate of hydraulic oil supplied to the hydraulic cylinder 22 to be equal to or less than a predetermined flow rate by controlling the current supplied to the electromagnetic proportional valve 70, and the control device 80 comprises a first calculation unit 86 that calculates a first current value I1, which is a current value I of a current to be supplied to the electromagnetic proportional valve 70 in order to control the electromagnetic proportional valve 70 so as to decelerate the angular velocity ω of the movable member 21 as the operating length L of the hydraulic cylinder 22 approaches the stroke end E of the hydraulic cylinder 22, The hydraulic cylinder 22 includes a second calculation unit 87 that calculates a second current value I2, which is the current value I of the current supplied to the electromagnetic proportional valve 70, in order to control the electromagnetic proportional valve 70 so as to reduce the flow rate of hydraulic oil supplied to the hydraulic cylinder 22 as the stroke end E is approached; and a current limiting unit 88 that corrects the current supplied to the electromagnetic proportional valve 70 by the second current value I2 when a judgment distance H, which is the operating length L from the current operating position of the hydraulic cylinder 22 to the stroke end E, is longer than a first threshold value T1 and is equal to or shorter than a second threshold value T2 that is set to a value longer than the first threshold value T1, and corrects the current supplied to the electromagnetic proportional valve 70 by selecting either the first current value I1 or the second current value I2 when the judgment distance H is equal to or shorter than the first threshold value T1.

[0126] According to the above configuration, when the hydraulic cylinder 22 approaches the stroke end E, the flow rate of the hydraulic oil supplied to the hydraulic cylinder 22 can be gradually reduced, and the oscillation of the movable member 21 can be smoothly decelerated.

[0127] Furthermore, the first calculation unit 86 does not calculate the first current value I1 when the judgment distance H is longer than the first threshold value T1, and the second calculation unit 87 does not calculate the second current value I2 when the judgment distance H is longer than the second threshold value T2.

[0128] According to the above configuration, the current limiting unit 88 gradually reduces the flow rate of hydraulic oil supplied to the hydraulic cylinder 22 from a predetermined flow rate by limiting the current in order from the second current value I2 as the hydraulic cylinder 22 approaches the stroke end E, thereby enabling the oscillation of the movable member 21 to be decelerated more smoothly.

[0129] Furthermore, when the judgment distance H is the first threshold value T1, the first current value I1 is the current value I corresponding to the reference angular velocity ωB, which is the minimum value of the angular velocity ω when the flow rate of the hydraulic oil supplied to the hydraulic cylinder 22 is a predetermined flow rate, and when the judgment distance H is zero, the first current value I1 is the current value I corresponding to a predetermined terminal angular velocity ωE that is smaller than the reference angular velocity ωB.

[0130] According to the above configuration, deceleration can be started when the determination distance H reaches the first threshold value T1, that is, from the beginning when the hydraulic cylinder 22 approaches the stroke end E. As a result, by limiting the current supplied by the current control unit to the solenoid proportional valve 70, the hydraulic cylinder 22 can be decelerated more reliably.

[0131] Furthermore, the second current value I2 when the determination distance H is the second threshold value T2 is the current value I that supplies hydraulic oil to the hydraulic cylinder 22 at a flow rate that is substantially the same as the predetermined flow rate.

[0132] According to the above configuration, when the hydraulic cylinder 22 approaches the stroke end E and the judgment distance H becomes the second threshold value T2, the flow rate of the hydraulic oil supplied to the hydraulic cylinder 22 can be gradually reduced from a predetermined flow rate, and the oscillation of the movable member 21 can be decelerated more smoothly.

[0133] In addition, when the judgment distance H is less than or equal to the first threshold value T1, the current limiting unit 88 selects the current value I between the first current value I1 and the second current value I2, whichever current value provides the lower flow rate of hydraulic oil supplied to the hydraulic cylinder 22.

[0134] According to the above configuration, when the hydraulic cylinder 22 approaches the stroke end E, the flow rate of the hydraulic oil supplied to the hydraulic cylinder 22 can be reliably reduced, and the oscillation of the movable member 21 can be decelerated more smoothly.

[0135] Furthermore, when the determination distance H is equal to or smaller than the first threshold value T1, the current limiting unit 88 corrects the current supplied to the proportional solenoid valve 70 by the first current value I1.

[0136] According to the above configuration, as the hydraulic cylinder 22 approaches the stroke end E, the current value is corrected by switching from the second current value I2 to the first current value I1, thereby achieving smooth deceleration of the movable member 21 in accordance with the angular velocity ω near the stroke end E.

[0137] In addition, the hydraulic system S of the work machine 1 is equipped with a first operating device 90 that outputs an operating signal to the control device 80, and the control device 80 has a definition unit 82 that defines the current to be supplied to the electromagnetic proportional valve 70 based on the operating signal within a range equal to or less than a reference current value IB at which the opening of the electromagnetic proportional valve 70 is maximized and the flow rate of the hydraulic oil supplied to the hydraulic cylinder 22 becomes a predetermined flow rate, and a current limiting unit 88 corrects the current value I defined by the definition unit 82 using the first current value I1 or the second current value I2.

[0138] According to the above configuration, when the hydraulic cylinder 22 is controlled by an operation signal, as the hydraulic cylinder 22 approaches the stroke end E, the flow rate of the hydraulic oil supplied to the hydraulic cylinder 22 can be gradually reduced by supplying the first current value I1 or the second current value I2 to the electromagnetic proportional valve 70. This allows the oscillation of the movable member 21 to be smoothly decelerated.

[0139] Further, a control method for a hydraulic system S of a work machine 1 includes a work device 20 having a movable member 21 and a hydraulic cylinder 22 that oscillates the movable member 21, and an electromagnetic proportional valve 70 that can change the flow rate of hydraulic oil supplied to the hydraulic cylinder 22, and the control method controls the flow rate of hydraulic oil supplied to the hydraulic cylinder 22 to be equal to or less than a predetermined flow rate by controlling the current supplied to the electromagnetic proportional valve 70, the control method including a first step of calculating a first current value I1, which is a current value I of a current supplied to the electromagnetic proportional valve 70 in order to control the electromagnetic proportional valve 70 to decelerate the angular velocity ω of the movable member 21 as the operating length L of the hydraulic cylinder 22 approaches a stroke end E of the hydraulic cylinder 22; a second step of calculating a second current value I2, which is the current value I of the current supplied to the electromagnetic proportional valve 70, in order to control the electromagnetic proportional valve 70 so as to reduce the flow rate of the hydraulic oil supplied to the hydraulic cylinder 22 as the hydraulic cylinder approaches a stroke end E of 2; and a third step of correcting the current supplied to the electromagnetic proportional valve 70 by the second current value I2 when a judgment distance H, which is the operating length L from the current operating position of the hydraulic cylinder 22 to the stroke end E, is longer than a first threshold value T1 and is equal to or shorter than a second threshold value T2 that is set to a value longer than the first threshold value T1, and correcting the current supplied to the electromagnetic proportional valve 70 by either the first current value I1 or the second current value I2, whichever reduces the flow rate of the hydraulic oil supplied to the hydraulic cylinder 22, when the judgment distance H is equal to or shorter than the first threshold value T1.

[0140] According to the above configuration, when the hydraulic cylinder 22 approaches the stroke end E, the flow rate of the hydraulic oil supplied to the hydraulic cylinder 22 can be gradually reduced, and the oscillation of the movable member 21 can be smoothly decelerated.

[0141] [Second embodiment] 12 shows another embodiment (second embodiment) of the hydraulic system S of the work machine 1. The following description of the hydraulic system S of the work machine 1 of the second embodiment will focus on configurations that differ from those of the above-described embodiment (first embodiment), and configurations that are common to the first embodiment will be assigned the same reference numerals and will not be described in detail. In the first embodiment, an example was described in which the electromagnetic proportional valve 70 includes a boom control valve 71, an arm control valve 72, a bucket control valve 73, and a dozer control valve 74, in other words, the boom control valve 71, the arm control valve 72, the bucket control valve 73, and the dozer control valve 74 are electromagnetic proportional valves 70. However, in the second embodiment, the boom control valve 171, the arm control valve 172, the bucket control valve 173, and the dozer control valve 174 are directional control valves 170 that change their switching positions and change the flow rate of hydraulic oil supplied to the hydraulic cylinder 22 to control the hydraulic cylinder 22, and the electromagnetic proportional valve 160 is separate from the directional control valve 170.

[0142] 12, the hydraulic system S of the work machine 1 includes a second operating device 190, a pilot valve 191, a directional control valve 170, and a connecting oil passage 175. The second operating device 190 is an operable operating tool. The second operating device 190 is composed of, for example, an operating lever, a pedal, etc., arranged around the driver's seat 6.

[0143] The pilot valve 191 controls the flow rate of the pilot oil to be discharged in accordance with the operation of the second operating device 190. The pilot valve 191 is a valve that can change the pressure (pilot pressure) of the pilot oil to be output in accordance with the operation direction and amount of the second operating device 190, and outputs the pilot pressure to the directional control valve 170.

[0144] The directional control valve 170 is a direct-acting spool-type switching valve, and its switching position can be changed by hydraulic oil supplied from a pilot valve 191. The directional control valve 170 moves its spool in proportion to the flow rate of hydraulic oil supplied from the pilot valve 191, and supplies an amount of hydraulic oil proportional to the amount of movement of the spool to the hydraulic cylinder 22 to be operated. The spool can be switched to switching positions of a first position 170A, a second position 170B, and a third position (neutral position) 170C. Note that the directional control valve 170 is not limited to a three-position switching valve, and may be a two-position switching valve, a four-position switching valve, or the like. Furthermore, the operation of the work implement 20 in response to the switching position of the directional control valve 170 (boom control valve 171, arm control valve 172, bucket control valve 173, and dozer control valve 174) is the same as when the boom control valve 71, arm control valve 72, bucket control valve 73, and dozer control valve 74 in the first embodiment are electromagnetic proportional valves 160, and therefore a detailed explanation will be omitted.

[0145] The connection oil passage 175 is an oil passage that connects the direction switching valve 170 and the hydraulic cylinder 22. One end of the connection oil passage 175 is connected to the supply and discharge ports 170a, 170b of the direction switching valve 170, and the other end of the connection oil passage 175 is connected to the hydraulic cylinder 22. In detail, the connection oil passage 175 includes a first connection oil passage 175a that connects the first supply and discharge port 170a of the direction switching valve 170 and the first port (port on the piston rod 22B side) 22b of the hydraulic cylinder 22, and a second connection oil passage 175b that connects the second supply and discharge port 170b of the direction switching valve 170 and the second port (port on the cylinder section 22A side) 22a of the hydraulic cylinder 22.

[0146] That is, by operating the direction switching valve 170, it is possible to cause the hydraulic oil to flow from the direction switching valve 170 toward the first connecting oil passage 175a, or to cause the hydraulic oil to flow from the direction switching valve 170 toward the second connecting oil passage 175b. More specifically, when the switching position of the direction switching valve 170 is changed and the flow rate of the hydraulic oil flowing through the first connecting oil passage 175a increases, the hydraulic cylinder 22 contracts. On the other hand, when the switching position of the direction switching valve 170 is changed and the flow rate of the hydraulic oil flowing through the second connecting oil passage 175b increases, the hydraulic cylinder 22 extends.

[0147] 12, in the second embodiment, the electromagnetic proportional valve 160 is provided in the connecting oil passage 175. In this embodiment, the control device 80 performs cushion control at both the first stroke end E1 and the second stroke end E2, and therefore the electromagnetic proportional valve 160 is provided in both the first connecting oil passage 175a and the second connecting oil passage 175b. Note that, when cushion control is performed at either the first stroke end E1 or the second stroke end E2, it is sufficient that the electromagnetic proportional valve 160 is provided in either the first connecting oil passage 175a or the second connecting oil passage 175b.

[0148] The electromagnetic proportional valve 160 is a switching valve that can change the flow rate of the hydraulic oil supplied to the hydraulic cylinder 22. More specifically, the electromagnetic proportional valve 160 is an opening adjustment valve that changes the amount of hydraulic oil supplied from the directional control valve 170 to the hydraulic cylinder 22 midway.

[0149] 12, the solenoid proportional valve 160 is biased by a spring in a direction to switch to the suppression position, and is switched to the suppression position by demagnetizing the solenoid 160a, and is switched to the supply position by exciting the solenoid 160a with a supply current supplied from the control device 80. In other words, as the supply current increases, the flow rate of hydraulic oil supplied from the directional control valve 170 to the hydraulic cylinder 22 increases, and the angular velocity ω increases.

[0150] The supply current that the control device 80 supplies to the electromagnetic proportional valve 160 is defined in advance as a reference current value IB. In this embodiment, the reference current value IB is a current value I that maximizes the opening of the electromagnetic proportional valve 160.

[0151] In the second embodiment, as in the first embodiment, when the judgment distance H approaches zero, the current limiting unit 88 selects either the first current value I1 or the second current value I2, and corrects the current value I (reference current value IB) of the predefined supply current with the selected current value I, thereby limiting the current supplied to the electromagnetic proportional valve 160 so as to reduce the flow rate of the hydraulic oil supplied to the hydraulic cylinder 22 from a predetermined flow rate.

[0152] In the above-described embodiment, for example, a detection sensor may be provided to detect the amount of operation of second operating device 190, and cushion control may be performed only when the amount of operation is equal to or greater than a predetermined amount. Also, a pressure sensor to detect the pressure of the hydraulic oil may be provided in the oil passage connecting pilot valve 191 and directional control valve 170, or in connection oil passage 175, and cushion control may be performed only when the pressure of the hydraulic oil (pilot oil) is equal to or greater than a predetermined amount.

[0153] Furthermore, in the above-described embodiment, an example was given of a configuration in which the electromagnetic proportional valve 160 is switched to the suppression position by demagnetizing the solenoid 160a, and is switched to the supply position by receiving a supply current from the control device 80 and exciting the solenoid 160a. However, as a modified example, the electromagnetic proportional valve 160 may be configured to be switched to the supply position by demagnetizing the solenoid 160a, and is switched to the suppression position by receiving a supply current from the control device 80 and exciting the solenoid 160a.

[0154] In this modified example, when the supply current increases, the flow rate of the hydraulic oil supplied from the directional control valve 170 to the hydraulic cylinder 22 decreases, and the angular velocity ω decreases.

[0155] Therefore, in this modified example, the relationship between the swing angle θ of the movable member 21, the first current value I1 calculated by the first calculation unit 86, and the second current value I2 calculated by the second calculation unit 87 is as shown in Fig. 13. In Fig. 13, the first current value I1 is represented by a dashed dotted line, and the second current value I2 is represented by a dashed two-dotted line. Furthermore, the current value I of the supply current is represented by a solid line, and for convenience of illustration, it is shifted from the first current value I1 and the second current value I2.

[0156] 13, as the determination distance H decreases from the first threshold T1 to zero, the first current value I1 increases to a magnitude (first terminal current value Ie) corresponding to the terminal angular velocity ωE. That is, when the swing angle θ of the movable member 21 is equal to or smaller than the first determination angle θ11, the first current value I1 increases as the swing angle θ of the movable member 21 decreases, and becomes the first terminal current value Ie when the swing angle θ of the movable member 21 reaches the minimum angle θ1. When the swing angle θ of the movable member 21 is equal to or larger than the second determination angle θ21, the first current value I1 increases as the swing angle θ of the movable member 21 increases, and becomes the first terminal current value Ie when the swing angle θ of the movable member 21 reaches the maximum angle θ2.

[0157] 13, as the determination distance H decreases from the second threshold T2 to zero, the second current value I2 increases substantially proportionally from the reference current value IB to the second terminal current value IE. That is, when the pivot angle θ of the movable member 21 is equal to or smaller than the third determination angle θ12, the second current value I2 increases as the pivot angle θ of the movable member 21 decreases, and becomes the second terminal current value IE when the pivot angle θ of the movable member 21 reaches the minimum angle θ1. When the pivot angle θ of the movable member 21 is equal to or larger than the fourth determination angle θ22, the second current value I2 increases as the pivot angle θ of the movable member 21 increases, and becomes the second terminal current value IE when the pivot angle θ of the movable member 21 reaches the maximum angle θ2.

[0158] The limitation of the supply current in the cushion control will be described below with reference to Fig. 14. Fig. 14 is a flowchart illustrating a series of steps in the cushion control in the second embodiment. First, the angle calculation unit 85 calculates the swing angle θ and the actual angular velocity ωr of the movable member 21 based on the detection signal detected by the angle detection device 95 (S21).

[0159] Next, the current limiting unit 88 determines whether the determination distance H is equal to or less than the second threshold value T2 (S22).

[0160] When the current limiting unit 88 determines that the determination distance H is equal to or less than the second threshold value T2 (S22, Yes), the second calculation unit 87 calculates the second current value I2 (S23, second step).

[0161] Next, the current limiting unit 88 determines whether the determination distance H exceeds the first threshold value T1 (S24).

[0162] If the current limiting unit 88 determines that the judgment distance H exceeds the first threshold value T1 (S24, Yes), the current limiting unit 88 selects the second current value I2 calculated by the second calculation unit 87 as the selected current value Ic (S25).

[0163] If the current limiting unit 88 determines that the judgment distance H does not exceed the first threshold value T1 (S24, No), the first calculation unit 86 calculates the limited angular velocity ωL and the first current value I1 corresponding to the limited angular velocity ωL (S26, first step).

[0164] Next, the current limiting unit 88 selects, as the selected current value Ic, the current value I that results in a smaller flow rate of hydraulic oil supplied to the hydraulic cylinder 22 from the first current value I1 calculated by the first calculation unit 86 and the second current value I2 calculated by the second calculation unit 87 (S27). In the second embodiment, the current limiting unit 88 selects the smaller current value I from the first current value I1 calculated by the first calculation unit 86 and the second current value I2 calculated by the second calculation unit 87. Note that in the case of the modified example shown in FIG. 13 , the current limiting unit 88 selects the larger current value I from the first current value I1 calculated by the first calculation unit 86 and the second current value I2 calculated by the second calculation unit 87.

[0165] When the current limiting unit 88 selects the selected current value Ic (S25 or S27), it corrects the current value I of the supply current with the selected current value Ic (S28), and the control device 80 supplies the corrected supply current to the electromagnetic proportional valve 160 (S29).

[0166] On the other hand, if the current limiting unit 88 determines that the judgment distance H is not equal to or less than the second threshold value T2 (S22, No), the control device 80 supplies the current of the reference current value IB to the solenoid proportional valve 70 without correcting it with the selected current value Ic (S30). Note that S25 and S27 to S29 are referred to as the third step.

[0167] The hydraulic system S of the work machine 1 also includes an operable second operating device 190, a pilot valve 191 that controls the flow rate of the pilot oil discharged in accordance with the operation of the second operating device 190, a directional control valve 170 that changes its switching position using the pilot oil supplied from the pilot valve 191, changes the flow rate of the hydraulic oil supplied to the hydraulic cylinder 22, and controls the hydraulic cylinder 22, and a connecting oil passage 175 that connects the directional control valve 170 and the hydraulic cylinder 22, and the electromagnetic proportional valve 160 is provided in the connecting oil passage 175, changes its opening in accordance with the current supplied from the control device 80, and changes the flow rate of the hydraulic oil supplied from the directional control valve 170 to the hydraulic cylinder 22 to a predetermined flow rate or less.

[0168] According to the above configuration, when the hydraulic cylinder 22 is controlled by pilot oil, as the hydraulic cylinder 22 approaches the stroke end E, the flow rate of the hydraulic oil flowing through the connecting oil passage 175 is reduced, thereby smoothly slowing down the oscillation of the movable member 21.

[0169] Although one embodiment of the present invention has been described above, the embodiment disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0170] 1 Work equipment 20 Work equipment 21 Movable parts 22 Hydraulic cylinder 70 Solenoid proportional valve 80 Control device 82 Definition part 86 1st calculation section 87 2nd calculation section 88 Current limiter 90 1st operating device 160 Solenoid proportional valve 170 Directional valve 175 Connecting oil passage 190 Second operating device 191 Pilot valve E Stroke End H Judgment distance I Current value I1 First current value I2 Second current value IB Reference current value (maximum current value) S Hydraulic System T1 First threshold T2 Second threshold ω angular velocity ωr Actual angular velocity ωB Reference angular velocity ωE Terminal angular velocity ωL Limit angular velocity

Claims

1. a working device having a movable member and a hydraulic cylinder for swinging the movable member; an electromagnetic proportional valve capable of changing the flow rate of hydraulic oil supplied to the hydraulic cylinder; a control device that controls the flow rate of the hydraulic oil supplied to the hydraulic cylinder to be equal to or less than a predetermined flow rate by controlling the current supplied to the electromagnetic proportional valve; Equipped with The control device a first calculation unit that calculates a first current value, which is a current value of a current to be supplied to the electromagnetic proportional valve in order to control the electromagnetic proportional valve so as to decelerate the angular velocity of the movable member as the operating length of the hydraulic cylinder approaches a stroke end of the hydraulic cylinder; a second calculation unit that calculates a second current value, which is a current value of a current supplied to the electromagnetic proportional valve in order to control the electromagnetic proportional valve so as to reduce a flow rate of hydraulic oil supplied to the hydraulic cylinder as the operating length of the hydraulic cylinder approaches a stroke end of the hydraulic cylinder; a current limiting unit that corrects the current supplied to the electromagnetic proportional valve by the second current value when a determination distance, which is an operating length from a current operating position of the hydraulic cylinder to a stroke end, is longer than a first threshold value and is equal to or shorter than a second threshold value that is set to a value longer than the first threshold value, and that corrects the current supplied to the electromagnetic proportional valve by selecting either the first current value or the second current value when the determination distance is equal to or shorter than the first threshold value; A hydraulic system of a work implement having:

2. the first calculation unit does not calculate the first current value when the determination distance is longer than the first threshold value; The hydraulic system for a work machine according to claim 1 , wherein the second calculation unit does not calculate the second current value when the determination distance is longer than the second threshold value.

3. the first current value when the determination distance is the first threshold value is a current value corresponding to a reference angular velocity that is a minimum value of the angular velocity when a flow rate of hydraulic oil supplied to the hydraulic cylinder is the predetermined flow rate, The hydraulic system for a work machine according to claim 1 , wherein the first current value when the determination distance is zero is a current value corresponding to a predetermined terminal angular velocity that is smaller than the reference angular velocity.

4. The hydraulic system for a work machine according to claim 1 , wherein the second current value when the determination distance is the second threshold value is a current value that supplies hydraulic oil to the hydraulic cylinder at a flow rate substantially equal to the predetermined flow rate.

5. 2. The hydraulic system of claim 1, wherein the current limiting unit selects, when the determination distance is equal to or less than the first threshold value, the current value that provides a lower flow rate of hydraulic oil to be supplied to the hydraulic cylinder, between the first current value and the second current value.

6. The hydraulic system for a work machine according to claim 1 , wherein the current limiting unit corrects the current supplied to the electromagnetic proportional valve by the first current value when the determination distance is equal to or less than the first threshold value.

7. a first operating device that outputs an operating signal to the control device; the control device has a definition unit that defines, based on the operation signal, a current to be supplied to the electromagnetic proportional valve within a range equal to or less than a reference current value at which the electromagnetic proportional valve has a maximum opening and the flow rate of the hydraulic oil supplied to the hydraulic cylinder becomes the predetermined flow rate, The hydraulic system for a work machine according to any one of claims 1 to 6, wherein the current limiting unit corrects the current value defined by the defining unit using the first current value or the second current value.

8. an operable second operating device; an operating valve that controls the flow rate of the pilot oil to be discharged in response to operation of the second operating device; a directional control valve that changes a switching position by using pilot oil supplied from the operation valve and changes the flow rate of working oil supplied to the hydraulic cylinder to control the hydraulic cylinder; a connecting oil passage connecting the directional control valve and the hydraulic cylinder; Equipped with The hydraulic system for a work machine according to any one of claims 1 to 6, wherein the electromagnetic proportional valve is provided in the connecting oil passage, changes its opening in response to the current supplied from the control device, and changes the flow rate of the hydraulic oil supplied from the directional control valve to the hydraulic cylinder to be equal to or less than the predetermined flow rate.

9. A control method for a hydraulic system of a work machine including a work device having a movable member and a hydraulic cylinder that oscillates the movable member, and an electromagnetic proportional valve that can change a flow rate of hydraulic oil supplied to the hydraulic cylinder, the method controlling a current supplied to the electromagnetic proportional valve to control the flow rate of hydraulic oil supplied to the hydraulic cylinder to be equal to or less than a predetermined flow rate, a first step of calculating a first current value, which is a current value of a current supplied to the electromagnetic proportional valve to control the electromagnetic proportional valve so as to decelerate the angular velocity of the movable member as the operating length of the hydraulic cylinder approaches a stroke end of the hydraulic cylinder; a second step of calculating a second current value, which is a current value of a current supplied to the electromagnetic proportional valve to control the electromagnetic proportional valve so as to reduce the flow rate of hydraulic oil supplied to the hydraulic cylinder as the operating length of the hydraulic cylinder approaches a stroke end of the hydraulic cylinder; a third step of correcting the current supplied to the electromagnetic proportional valve by the second current value when a determined distance, which is an operating length from a current operating position of the hydraulic cylinder to a stroke end, is longer than a first threshold value and is equal to or shorter than a second threshold value set to a value longer than the first threshold value, and correcting the current supplied to the electromagnetic proportional valve by the first current value or the second current value, whichever results in a smaller flow rate of hydraulic oil supplied to the hydraulic cylinder, when the determined distance is equal to or shorter than the first threshold value; A method for controlling a hydraulic system of a work machine having the same.

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