Hydraulic system of work machine, and work machine

Abstract

To achieve both suppression of engine stall and workability.SOLUTION: A hydraulic system of a work machine comprises: an engine; a variable-capacity first hydraulic pump that is driven by the engine to deliver hydraulic oil; a first hydraulic actuator to be driven by hydraulic oil delivered by the first hydraulic pump; a variable-capacity second hydraulic pump that is driven by the engine to deliver hydraulic oil and that is different from the first hydraulic pump; a second hydraulic actuator to be driven by hydraulic oil delivered by the second hydraulic pump; a first restrictor to restrict an output of the first hydraulic pump based on a load on the engine; and a second restrictor to restrict an output of the second hydraulic pump based on a load on the engine. The first restrictor is to change an output restriction of the first hydraulic pump based on predetermined priority information about the first and second hydraulic actuators and / or the second restrictor is to change an output restriction of the second hydraulic pump based on the priority information.SELECTED DRAWING: Figure 6

Description

[Technical Field]

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

[0002] The hydraulic system of the work machine disclosed in Patent Document 1 includes a prime mover, a hydraulic actuator, a control valve that controls the operation of the hydraulic actuator, a first hydraulic pump that is driven by the power of the prime mover and discharges pilot oil for switching the control valve, a second hydraulic pump with a variable capacity that is driven by the power of the prime mover and discharges hydraulic oil for operating the hydraulic actuator, a first oil passage through which the maximum load pressure when the hydraulic actuator is operating can act, a second oil passage through which the discharge pressure of hydraulic oil from the second hydraulic pump can act, a hydraulic control unit that controls the second hydraulic pump to set an LS (load sensing) differential pressure that is the pressure difference between the discharge pressure of the second hydraulic pump and the maximum load pressure, a third oil passage through which the first hydraulic pump discharges pilot oil, a fourth oil passage branching from the third oil passage, a solenoid valve that changes the pilot pressure, which is the pressure of the pilot oil that flows through the fourth oil passage and acts on the hydraulic control unit, and a control device that controls the operation of the solenoid valve to adjust the pilot pressure, and the control device changes the LS differential pressure according to the load acting on the prime mover.

[0003] In addition, the hydraulic system of the work machine disclosed in Patent Document 1 includes a travel pump that is operated by the power of the prime mover, an operating valve that controls the travel pump with pilot oil discharged from a first hydraulic pump, and an operating valve that is provided in a third oil passage and changes the pilot pressure of the pilot oil supplied from the first hydraulic pump to the operating valve, and the control device controls the operating valve in accordance with the load acting on the prime mover and reduces the pilot pressure acting on the operating valve. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-025934 Summary of the Invention [Problem to be solved by the invention]

[0005] In the hydraulic system of the work machine of Patent Document 1, stalling of the prime mover can be suppressed by changing the output of the second hydraulic pump and the travel pump according to the load on the prime mover, but more precise horsepower control is required.

[0006] The present invention has been made to solve the problems of the conventional technology, and has an object to provide a hydraulic system for a work machine that can suppress stalling of the prime mover while also achieving good workability. [Means for solving the problem]

[0007] A hydraulic system of a work machine according to one aspect of the present invention includes a prime mover, a first hydraulic pump of variable displacement driven by power of the prime mover and discharging hydraulic oil, a first hydraulic actuator driven by the hydraulic oil discharged by the first hydraulic pump, a second hydraulic pump of variable displacement different from the first hydraulic pump, driven by power of the prime mover and discharging hydraulic oil, a second hydraulic actuator driven by the hydraulic oil discharged by the second hydraulic pump, a first limiting unit that limits the output of the first hydraulic pump in accordance with the load of the prime mover, and a second limiting unit that limits the output of the second hydraulic pump in accordance with the load of the prime mover, wherein the first limiting unit changes the output limit of the first hydraulic pump in accordance with predetermined priority information between the first hydraulic actuator and the second hydraulic actuator, and / or the second limiting unit changes the output limit of the second hydraulic pump in accordance with the priority information.

[0008] A work machine according to one aspect of the present invention includes the hydraulic system of the work machine, a vehicle body, a traveling device, and a work device. [Effects of the Invention]

[0009] According to the hydraulic system for the work machine and the work machine described above, it is possible to suppress stalling of the prime mover while also improving workability. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a side view showing a track loader as an example of a work machine. [Figure 2] FIG. [Figure 3] FIG. 2 is a diagram showing a hydraulic circuit for a traveling system in the hydraulic system (hydraulic circuit) of the work machine. [Figure 4] FIG. 2 is a diagram showing a hydraulic circuit for a working system in a hydraulic system (hydraulic circuit) of a working machine. [Figure 5] FIG. 2 is a diagram showing an example of a traveling system line. [Figure 6] FIG. 2 is a diagram showing an example of a work line. [Figure 7] FIG. 10 is a diagram showing an example of a second correction value. [Figure 8] FIG. 10 is a diagram showing an example of a first correction value. [Figure 9] FIG. 10 is a diagram illustrating an example of a third correction value. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] Fig. 1 is a side view showing a track loader as an example of a work machine 1. Note that Fig. 1 shows a compact track loader as an example of the work machine 1, but the work machine 1 according to the present invention is not limited to a compact track loader and may be, for example, another type of loader work machine such as a skid steer loader. Furthermore, the work machine 1 may be a work machine 1 other than a loader work machine.

[0013] As shown in Figure 1, the work machine 1 comprises a machine body 2, a cabin 3, a traveling device 4, and a work device 5. In the embodiment of the present invention, the direction in which an operator seated in the driver's seat 3a of the work machine 1 faces (the left side in Figure 1) is referred to as the forward direction, and the opposite direction (the right side in Figure 1) is referred to as the rearward direction. The left side of the operator (the front side in Figure 1) is referred to as the left side, and the right side of the operator (the back side in Figure 1) is referred to as the right side. The horizontal direction, which is perpendicular to the front-to-rear direction, is referred to as the machine body width direction.

[0014] The machine body 2 supports various devices of the work machine 1, such as the cabin 3 and the work implement 5. The machine body 2 is equipped with, for example, a prime mover 6. The prime mover 6 is a power source that generates power. The prime mover 6 is an internal combustion engine (engine) such as a diesel engine or a gasoline engine, an electric motor, or the like.

[0015] The cabin 3 is mounted on the aircraft body 2. The cabin 3 is provided with a driver's seat 3a.

[0016] The traveling devices 4 support the machine body 2 and allow the machine body 2 to travel. The traveling devices 4 include a first traveling device 4L provided on the left side of the machine body 2 and a second traveling device 4R provided on the right side of the machine body 2. In this embodiment, the first traveling device 4L and the second traveling device 4R are of a crawler type. Note that the traveling device 4 is not limited to the crawler type shown in FIG. 1, and may be a semi-crawler type or a wheel type having front and rear wheels.

[0017] The work implement 5 is provided on the machine body 2. The work implement 5 has an attachment 30, a connecting device 10, a boom 11, a lift link 12, a control link 13, a boom cylinder 14, and a front cylinder 15.

[0018] The attachment 30 is a work tool such as a bucket, and can be attached to and detached from the connecting device 10. Examples of attachments 30 other than buckets include earth augers, angle brooms, crushers, grapples, cold planers, sweepers, skid cutters, skid graders, stump grinders, snow blowers, snow pushers, spreaders, dozer blades, trenchers, breakers, pallet forks, hopper brooms, mowers, rippers, loader booms, and rotary tillers.

[0019] In the following description, an attachment 30 that has a hydraulic actuator (hydraulic cylinder, hydraulic motor, etc.) and is driven by supplied hydraulic oil, such as an earth auger or angle broom, may be referred to as a "first attachment," and an attachment 30 that does not have a hydraulic actuator and is not driven by hydraulic oil, such as a bucket, may be referred to as a "second attachment."

[0020] The connecting device 10 is a device to which any of the attachments 30 can be attached and detached, and is provided on the boom 11. The connecting device 10 is, for example, a device for attaching and detaching the attachment 30. The operator of the work machine 1 can easily change the attachment 30 using the coupling device 10.

[0021] The boom 11, lift link 12, control link 13, boom cylinder 14, and front cylinder 15 are provided on the left and right sides of the cabin 3. The left and right booms 11 are connected to each other at their front midpoints by a connector. A hydraulic oil output port (power output port) and a hydraulic oil input port are provided at the front of the left boom 11 to connect to the hydraulic actuator of the first attachment.

[0022] The lift link 12 and the control link 13 support the base (rear) of the boom 11 via a shaft so that the boom 11 can swing up and down.

[0023] One end of the boom cylinder 14 is rotatably connected to the boom 11 via a shaft, and the other end of the boom cylinder 14 is rotatably connected to the rear lower part of the machine body 2 via a shaft. The boom cylinder 14 raises and lowers the boom 11 by extending and retracting.

[0024] One end of the front cylinder 15 is rotatably connected to the boom 11 via a shaft, and the other end of the front cylinder 15 is rotatably connected to the connecting device 10 via a shaft. The front cylinder 15 swings the attachment 30 (connecting device 10) by extending and retracting.

[0025] 2 is a configuration diagram of the work machine 1. The work machine 1 includes a control device 21, a storage device 22, a user interface 23, a plurality of operation members 24, a plurality of detection devices 25, and the like.

[0026] The control device 21 is a processing circuit including one or more processors. The control device 21 is a controller for the work machine 1 and performs various controls related to the work machine 1. The control device 21 is communicably connected to multiple devices mounted on the work machine 1 via an in-vehicle network such as CAN, ISOBUS, LIN, or FlexRay.

[0027] The control device 21 includes one or more memories, various analog circuits, various digital circuits, etc. The one or more memories store (memorize) software programs and various data to be executed by one or more processors. Specifically, among the one or more memories possessed by the control device 21, the memory (internal memory) is composed of volatile or non-volatile memory. The control device 21 uses, for example, a predetermined storage area of ​​the memory composed of volatile memory as a buffer for temporarily storing information and data.

[0028] Furthermore, a storage device 22 (non-volatile memory) is communicatively connected to the control device 21, and the storage device 22 is provided outside the control device 21. The memory and storage device 22 store software programs and control data for the control device 21 to control the operation of each part.

[0029] The control device 21 can use one or more processors to read software programs and control data from the storage device 22 and execute various processes based on the software programs and control data. Note that the control device 21 may also use one or more processors to execute various processes based on predetermined logic circuits.

[0030] The processor may be, for example, a central processing unit (CPU), a graphics processing unit (GPU), a digital signal processor (DSP), a field programmable gate array (FPGA), or an application specific integrated circuit (ASIC).

[0031] The control device 21 may execute various processes by having multiple physically separated processors cooperate with each other, and the configuration is not limited to the configuration described above. In such a case, the multiple processors are mounted on one or more computers that are physically separated from the work machine 1, and these processors are connected to each other so as to be able to communicate with each other via a network such as an in-vehicle network, a LAN, a WAN, or the Internet.

[0032] In addition, the software program may be stored in a recording medium (non-volatile memory such as HDD, SSD, CD-ROM, DVD-ROM, etc.) communicatively connected to the control device 21, or in an external server device connected via the above-mentioned network, and installed from there into the above-mentioned memory.

[0033] The user interface 23 is configured, for example, by a touch panel. Alternatively, the user interface 23 may be configured with an input device and an output device separately. good.

[0034] The multiple operating members 24 are pedals, switches, levers, dials, etc. that are operated by the operator of the work machine 1. The multiple operating members 24 are connected to the control device 21 and output operation signals to the control device 21. The control device 21 controls each device provided in the work machine 1 based on the operation signals output from the multiple operating members 24. The multiple operating members 24 include a rotation speed operating device 24a that operates the target rotation speed of the prime mover 6, and an attachment / detachment operating device 24b that attaches and detaches the attachment 30 to and from the coupling device 10. To explain the operating member 24 using the rotation speed operating device 24a as an example, the rotation speed operating device 24a may be an accelerator lever that is supported so as to be able to swing, an accelerator pedal that is supported so as to be able to swing, an accelerator volume that is supported so as to be able to rotate, an accelerator slider that is supported so as to be able to slide, etc.

[0035] The user interface 23 and the plurality of operating members 24 are installed in the vicinity of the driver's seat 3a of the cabin 3 so as to be operable.

[0036] The multiple detection devices 25 are devices that detect the state of each device provided in the work machine 1. For example, the multiple detection devices 25 include a rotation speed detection device 25a that detects the actual rotation speed (prime motor rotation speed) of the prime mover 6, an oil temperature detection device 25b that detects the temperature of the hydraulic oil, and the like.

[0037] The hydraulic system S (hydraulic circuit) provided in the work machine 1 will be described below with reference to Figures 3 and 4. Figure 3 is a diagram showing the hydraulic circuit of the traveling system in the hydraulic system S of the work machine 1. Figure 4 is a diagram showing the hydraulic circuit of the work system in the hydraulic system S of the work machine 1. The hydraulic system S of the traveling system of the work machine 1 is a system that operates the traveling device 4. Furthermore, the hydraulic system S of the work system of the work machine 1 is a system that operates the work device 5. As shown in Figures 3 and 4, the hydraulic system S of the work machine 1 is equipped with a main pump 40 (second hydraulic pump) and a pilot pump 44.

[0038] The main pump 40 is a variable displacement hydraulic pump (swash plate type variable displacement axial pump) that is driven by the power of the prime mover 6 to discharge hydraulic oil. The main pump 40 is connected between a main oil passage 41 and an intake oil passage 42 that is connected to a hydraulic oil tank T, and is capable of discharging hydraulic oil stored in the hydraulic oil tank T to the main oil passage 41. The main pump 40 changes the amount of hydraulic oil discharged by changing the angle of the swash plate (swash plate angle). In particular, the main pump 40 supplies hydraulic oil to a hydraulic system S of the working system.

[0039] The pilot pump 44 is operated by the power of the prime mover 6 and discharges hydraulic oil. The pilot pump 44 is configured by a fixed displacement gear pump. Specifically, the pilot pump 44 is connected between the hydraulic oil tank T and a discharge oil passage 45, and is capable of discharging the hydraulic oil stored in the hydraulic oil tank T to the discharge oil passage 45. In particular, the pilot pump 44 discharges hydraulic oil that is mainly used to control the work machine 1.

[0040] In the following description, the hydraulic oil discharged from the pilot pump 44 that is used for control purposes will be referred to as pilot oil, and the pressure of the pilot oil will be referred to as pilot pressure.

[0041] 3, the hydraulic circuit of the travel system includes a first hydraulic pump 51 (travel pump) and a first hydraulic actuator 52. The travel pump 51 is a variable displacement hydraulic pump (swash plate type variable displacement axial pump) that is driven by power from the prime mover 6 to discharge hydraulic oil. In this embodiment, the travel pump 51 includes a first travel pump 51L and a second travel pump 51R.

[0042] The travel pump 51 has a forward pressure receiving portion 51a and a reverse pressure receiving portion 51b on which a pilot pressure acts. The angle of the swash plate of the travel pump 51 is changed according to the pilot pressure acting on the forward pressure receiving portion 51a and the reverse pressure receiving portion 51b. By changing the angle of the swash plate, the travel pump 51 can change the discharge amount (output) of the hydraulic oil supplied from the discharge oil passage 45 and the discharge direction of the hydraulic oil.

[0043] The first hydraulic actuator 52 is a hydraulic device that is driven by the hydraulic oil discharged by the travel pump 51. The first hydraulic actuator 52 is also a hydraulic device that drives the travel device 4, and is, for example, a motor (travel motor 52) that operates by the hydraulic oil discharged from the travel pump 51 and transmits power to the drive shaft of the travel device 4.

[0044] The travel motor 52 can change its rotation speed (number of rotations) between a first speed (predetermined low-speed range) that is a low speed and a second speed (predetermined high-speed range) that is faster than the first speed. The travel motor 52 can change its rotation speed by changing the angle of the swash plate. In this embodiment, the travel motor 52 includes a first travel motor 52L and a second travel motor 52R.

[0045] The first travel motor 52L is driven by hydraulic oil discharged from the first travel pump 51L and transmits power to the drive shaft of the first travel device 4L. The first travel motor 52L is connected to the first travel pump 51L by a circulation oil passage 53a, and hydraulic oil is supplied to the first travel motor 52L from the first travel pump 51L via this circulation oil passage 53a. The rotational speed (number of rotations) of the first travel motor 52L can be changed based on the flow rate of hydraulic oil supplied from the first travel pump 51L.

[0046] The second travel motor 52R is driven by hydraulic oil discharged from the second travel pump 51R and transmits power to the drive shaft of the second travel device 4R. The second travel motor 52R is connected to the second travel pump 51R by a circulation oil passage 53b, and hydraulic oil is supplied to the second travel motor 52R from the second travel pump 51R via this circulation oil passage 53b. The rotational speed (number of revolutions) of the second travel motor 52R can be changed based on the flow rate of hydraulic oil supplied from the second travel pump 51R.

[0047] 3, the circulation oil passages 53a and 53b are provided with travel relief valves 54. The travel relief valves 54 discharge the hydraulic oil flowing through the circulation oil passages 53a and 53b into the hydraulic oil tank T when the work implement 1 performs work such as pushing earth using a bucket.

[0048] Below, a detailed description will be given of operations relating to the travel of the work machine 1, that is, operations (travel operations) of the travel device 4. As shown in Fig. 3, the hydraulic system S of the work machine 1 is provided with a first operating device 55 (travel operating device).

[0049] The travel operation device 55 is a device that controls the drive of the travel motor 52. In this embodiment, the travel operation device 55 changes the hydraulic oil discharged by the travel pump 51 in response to operation to control the drive of the travel motor 52. The travel operation device 55 changes the pilot pressure acting on the pressure receiving portions 51a, 51b in response to operation, and is able to change the angle of the swash plate of the travel pump 51. The travel operation device 55 includes a first operation member 56 (travel operation member) and a plurality of first operation valves 57 (travel operation valves).

[0050] The travel operating member 56 includes an operating lever 56a (travel lever) that swings left and right or forward and backward.

[0051] The multiple travel operation valves 57 are valves that are operated by operation of the travel operation member 56. Specifically, the multiple travel operation valves 57 are connected to the discharge oil passage 45 and can change the pressure (pilot pressure) of pilot oil, which is hydraulic oil supplied from the discharge oil passage 45. The multiple travel operation valves 57 support the travel lever 56a and are operated by the travel lever 56a. The multiple travel operation valves 57 change their opening depending on the direction and amount of operation of the travel lever 56a, and the pressure of the pilot oil that is output changes. The multiple travel operation valves 57 are connected to the travel pump 51 by the travel oil passage 58 and apply the pressure of the pilot oil (pilot pressure) to pressure receiving portions 51a, 51b of the travel pump 51 via the travel oil passage 58.

[0052] In the above example, the multiple travel operation valves 57 support the travel lever 56a and are physically operated by operating the travel lever 56a, but the travel operation device 55 only needs to change the hydraulic oil discharged from the travel pump 51 in response to the operation and operate the travel motor 52. For example, a detection sensor may be provided to detect the amount and direction of operation of the travel operation member 56 (e.g., the travel lever 56a), and the control device 21 may electrically operate the multiple travel operation valves 57 based on the detection results of the detection sensor.

[0053] 3, the hydraulic system S of the work machine 1 includes a hydraulic cylinder 60 (switching cylinder) that changes the angle of the swash plate of the traveling motor 52, and a speed switching valve 61 that changes the hydraulic oil supplied to the switching cylinder 60. In this embodiment, the speed switching valve 61 includes a first switching valve 61a and a second switching valve 61b.

[0054] The first switching valve 61a is connected to the switching cylinder 60 via an oil passage, and changes the amount of hydraulic oil supplied to the switching cylinder 60. The first switching valve 61a is, for example, a two-position switching valve that can be switched between a first position and a second position. When the first switching valve 61a is in the first position, The supply of hydraulic oil to the cylinder 60 is stopped, causing the switching cylinder 60 to contract. Furthermore, the first switching valve 61a in the second position supplies hydraulic oil to the switching cylinder 60, causing the switching cylinder 60 to expand.

[0055] The second switching valve 61b is connected to the pressure-receiving portion of the first switching valve 61a via an oil passage, and changes the pilot pressure acting on the pressure-receiving portion to change the switching position of the first switching valve 61a. The second switching valve 61b is a two-position switching valve that can be switched between a first position and a second position by excitation. When the second switching valve 61b is in the first position, pilot oil is applied to the pressure-receiving portion of the first switching valve 61a, switching the first switching valve 61a to the first position. On the other hand, when the second switching valve 61b is in the first position, pilot oil is not applied to the pressure-receiving portion of the first switching valve 61a, switching the first switching valve 61a to the second position.

[0056] The second selector valve 61b is operated by a speed changer 24c included in the multiple operating members 24. Specifically, the control device 21 acquires an operation signal from the speed changer 24c and outputs a control signal (for example, voltage, current, etc.) to the second selector valve 61b in accordance with the operation of the speed changer 24c, thereby changing the switch position of the second selector valve 61b. This allows the travel motor 52 to switch between a first speed and a second speed in accordance with the operation of the speed changer 24c.

[0057] As shown in Fig. 4, the hydraulic circuit of the working system includes a control valve unit 71 and a second hydraulic actuator C. The second hydraulic actuator C is a hydraulic device that is driven by hydraulic oil discharged from the main pump 40. The second hydraulic actuator C is a hydraulic device that drives the working implement 5, and is, for example, the boom cylinder 14 and the front cylinder 15 that are actuated by hydraulic oil discharged from the main pump 40. If the attachment 30 attached to the connecting device 10 is an attachment 30 that is driven by hydraulic oil, the hydraulic actuator (hydraulic cylinder, hydraulic motor, etc., hereinafter referred to as the standby actuator) that the attachment 30 has is the second hydraulic actuator C.

[0058] The control valve unit 71 allows the hydraulic oil supplied from the main pump 40 via the main oil passage 41 to flow to the second hydraulic actuator C. The control valve unit 71 also discharges the hydraulic oil (return oil) discharged from the second hydraulic actuator C to the hydraulic oil tank T. The control valve unit 71 controls the supply direction and supply amount of the hydraulic oil to the second hydraulic actuator C.

[0059] Specifically, the control valve unit 71 includes control valves 71a, 71b, and 71c corresponding to the second hydraulic actuators C (e.g., the boom cylinder 14, the front cylinder 15, and the backup actuator). Each of the control valves 71a, 71b, and 71c is switchable between a neutral position, a first position, and a second position. Each of the control valves 71a, 71b, and 71c is held in the neutral position by the elastic force of a spring. In this embodiment, the switching position of each of the control valves 71a, 71b, and 71c is changed in accordance with the pilot pressure acting on the pressure-receiving portion.

[0060] Below, a detailed description will be given of operations related to work by the work machine 1, that is, operations (work operations) of the work device 5. As shown in Fig. 4, the hydraulic system S of the work machine 1 is provided with a second operating device 65 (work operating device).

[0061] The work operating device 65 is a device that operates the drive of the second hydraulic actuators C. In this embodiment, the work operating device 65 controls each of the control valves 71a, 71b, 71c in response to operation, changes the hydraulic oil discharged by the main pump 40, and operates the drive of each of the second hydraulic actuators C. The work operating device 65 changes the pilot pressure acting on the pressure-receiving portions of each of the control valves 71a, 71b, 71c in response to operation, and is able to change the positions of the control valves 71a, 71b, 71c. The work operating device 65 includes a second operating member 66 (work operating member) and a plurality of second operating valves 67 (work operating valves).

[0062] The work operation member 66 includes an operation lever 66a (work lever) that swings left and right or forward and backward, and an operation switch 66b (backup switch). The backup switch 66b is configured, for example, as a seesaw-type switch that can swing freely, a slide-type switch that can slide freely, or a push-type switch that can be pressed freely.

[0063] The plurality of work operation valves 67 are valves that are actuated by the operation of the work operation members 66. The plurality of work operation valves 67 are connected to the discharge oil passage 45 and can change the pressure (pilot pressure) of the pilot oil supplied from the discharge oil passage 45. Of the plurality of work operation valves 67, the work operation valves 67 connected to the control valves 71a, 71b support the work lever 66a and are operated by the work lever 66a. These work operation valves 67 change their opening depending on the direction and amount of operation of the work lever 66a, and the pressure of the pilot oil they output changes. Furthermore, the work operation valves 67 are connected to the control valves 71a, 71b by work oil passages 68, respectively, and the pressure of the pilot oil (pilot pressure) acts on the pressure receiving parts of the control valves 71a, 71b via the work oil passages 68.

[0064] Of the multiple work operation valves 67, the work operation valve 67 corresponding to the control valve 71c is an electromagnetic proportional valve operated by a standby switch 66b. The control device 21 acquires an operation signal from the standby switch 66b and outputs a control signal to the work operation valve 67 in accordance with the operation of the standby switch 66b, thereby changing the position of the work operation valve 67. The work operation valve 67 changes its opening in accordance with the control signal, and the pressure of the pilot oil it outputs changes. Furthermore, each work operation valve 67 is connected to the control valve 71c by a work oil passage 68, and the pressure of the pilot oil (pilot pressure) acts on the pressure-receiving portion of the control valve 71c via the work oil passage 68.

[0065] In the above example, a case has been described in which the multiple work operation valves 67 support the work lever 66a and are physically operated by operating the work lever 66a, but the work operation device 65 only needs to be able to change the hydraulic oil output from the control valve unit 71 in accordance with the operation and operate the drive of the second hydraulic actuator C. For example, a detection sensor may be provided to detect the amount and direction of operation of the work operation member 66 (e.g., the work lever 66a), and the control device 21 may electrically operate the work operation valves 67 corresponding to the control valves 71a, 71b based on the detection results of the detection sensor.

[0066] The hydraulic system S of the work machine 1 can limit (reduce) the output of the travel pump 51 and the main pump 40 in accordance with the load on the prime mover 6, thereby preventing the prime mover 6 from stalling (engine stall). That is, the hydraulic system S of the work machine 1 of this embodiment performs control (anti-stall control) to prevent engine stall by limiting the horsepower consumption (torque consumption) of the prime mover 6 in both the hydraulic system S of the travel system and the hydraulic system S of the work system. As shown in FIG. 2, the hydraulic system S of the work machine 1 includes a first limiting unit 21a and a second limiting unit 21b. The hydraulic system S of the work machine 1 also includes a load calculating unit 21c.

[0067] The first limiting unit 21a limits the output of the travel pump 51 in accordance with the load on the prime mover 6. The second limiting unit 21b limits the output of the main pump 40 in accordance with the load on the prime mover 6. In other words, the first limiting unit 21a performs anti-stall control (first anti-stall control) of the hydraulic system S of the travel system, and the second limiting unit 21b performs anti-stall control (second anti-stall control) of the hydraulic system S of the work system. The first limiting unit 21a and the second limiting unit 21b are, for example, software programs implemented in the control device 21.

[0068] The load calculation unit 21c calculates the load of the prime mover 6. The load calculation unit 21c calculates a drop rotation speed, which is the difference between the target rotation speed of the prime mover 6 and the actual rotation speed of the prime mover 6, as the load of the prime mover 6. The load calculation unit 21c is, for example, a software program implemented in the control device 21. The load calculation unit 21c calculates the drop rotation speed based on the difference between the target rotation speed of the prime mover 6 operated by the rotation speed operation device 24a and the actual rotation speed of the prime mover 6 detected by the rotation speed detection device 25a (target rotation speed - actual rotation speed). The first limiting unit 21a and the second limiting unit 21b perform anti-stall control based on the load of the prime mover 6 calculated by the load calculation unit 21c.

[0069] Furthermore, the first limiting unit 21a changes the output limit of the travel pump 51 in accordance with predetermined priority information between the travel motor 52 and the second hydraulic actuator C, and / or the second limiting unit 21b changes the output limit of the main pump 40 in accordance with the priority information. Below, an example will be described in which, of the first limiting unit 21a and the second limiting unit 21b, the first limiting unit 21a does not change the output limit of the travel pump 51 in accordance with the priority information, and the second limiting unit 21b changes the output limit of the main pump 40 in accordance with the priority information.

[0070] The priority information is the priority regarding the driving of the traveling motor 52 and the second hydraulic actuator C. The priority information is information that defines the priority of allocation of horsepower consumed to drive the traveling motor 52 and the second hydraulic actuator C (horsepower consumption of the prime mover 6). The second limiting unit 21b acquires priority information based on, for example, the operation of the traveling operation device 55. Based on the priority information, the second limiting unit 21b changes the output limit so that the output of the main pump 40 is more restricted when the traveling motor 52 is being operated than when the traveling motor 52 is not being operated.

[0071] Specifically, the second restriction unit 21b acquires first priority information when the travel operation device 55 is not being operated, and acquires second priority information when the travel operation device 55 is being operated. Therefore, the second restriction unit 21b acquires either the first priority information or the second priority information as priority information, and when one of the information is acquired, the other information is not acquired. The second priority information has a higher priority for driving the travel motor 52 than the first priority information.

[0072] The control device 21 has a flag setting unit 21d that sets a flag (first priority flag) corresponding to priority information based on the operation of the travel operation device 55, and the second restriction unit 21b refers to the first priority flag set by the flag setting unit 21d. The second restriction unit 21b acquires the first priority information when the referenced first priority flag is off. Furthermore, the second restriction unit 21b acquires the second priority information when the first priority flag is on.

[0073] Flag setting unit 21d is, for example, a software program implemented in control device 21. Flag setting unit 21d acquires the operation state of travel operation device 55 based on, for example, the pilot pressure of pilot oil output from travel operation valve 57. In this case, pressure sensor 25c (first operating pressure sensor) that detects the pilot pressure of pilot oil acting on each of pressure receiving portions 51a, 51b is provided in travel oil line 58, and flag setting unit 21d acquires the operation state of travel operation device 55 based on the detection signal detected by first operating pressure sensor 25c. For example, if the pilot pressure detected by first operating pressure sensor 25c is equal to or greater than a predetermined value, flag setting unit 21d determines that travel operation device 55 is being operated and turns on a first priority flag. On the other hand, if the pilot pressure detected by first operating pressure sensor 25c is less than the predetermined value, flag setting unit 21d determines that travel operation device 55 is not being operated and turns off the first priority flag.

[0074] It should be noted that flag setting unit 21d may simply set the first priority flag to on or off based on the operation of travel operation device 55, and the method of acquiring the operation state of travel operation device 55 may be other than the pilot pressure detected by first operating pressure sensor 25c. For example, if a detection sensor is provided that detects the amount and direction of operation of travel operation member 56, the operation state of travel operation device 55 may be acquired based on the detection result detected by that detection sensor.

[0075] The first limiting unit 21a and the first anti-stall control will be described in detail below. As the first anti-stall control, the first limiting unit 21a changes the pilot pressure (primary pressure) of the pilot oil supplied to the travel operation valve 57 and reduces the output of the travel pump 51, thereby limiting the horsepower consumed by the prime mover 6 by the travel pump 51.

[0076] 3, the hydraulic system S of the work machine 1 includes an operating valve 80 that is provided in the discharge oil passage 45 and is capable of changing the pilot pressure of the pilot oil that operates the travel pump 51. The first restriction unit 21a controls the opening of the operating valve 80 to change the pilot pressure (primary pressure) of the pilot oil that is supplied from the discharge oil passage 45 to the travel operation device 55 (plurality of travel operation valves 57).

[0077] The actuating valve 80 is provided in the discharge oil passage 45, between a branch point 45a of the oil passage connected to the travel operation valve 57 and the oil passage connected to the work operation valve 67 side, and the travel operation valve 57. The control device 21 (first restriction unit 21a) outputs a control signal (for example, voltage, current, etc.) to the actuating valve 80, and the actuating valve 80 is actuated by the control signal to change its opening, thereby changing the pilot pressure (primary pressure) of the pilot oil supplied from the discharge oil passage 45 to the travel operation device 55. Below, we will explain the case where the control signal output by the control device 21 to the actuating valve 80 is a current, and the current value output as the control signal will be referred to as the "first command current value." The electromagnetic proportional valve that constitutes the actuating valve 80 can increase its opening in proportion to the magnitude of the first command current value. do.

[0078] That is, the primary pressure is changed according to the control signal output from the first limiting unit 21a to the actuated valve 80. In the present embodiment, the first limiting unit 21a outputs a first command current value to the actuated valve 80, and therefore the primary pressure is changed according to the magnitude of the first command current value. Specifically, as the first command current value increases, the opening of the actuated valve 80 increases, and the primary pressure increases. On the other hand, as the first command current value decreases, the opening of the actuated valve 80 decreases, and the primary pressure decreases.

[0079] Therefore, there is a proportional or nearly proportional correspondence (correlation) between the first command current value and the primary pressure. Therefore, by changing the first command current value, the first limiting unit 21a can change the target pressure of the pilot pressure (primary pressure) of the pilot oil supplied to the multiple travel operation valves 57.

[0080] First limiting unit 21a defines a first command current value based on the actual rotation speed of prime mover 6 detected by rotation speed detection device 25a and the drop rotation speed calculated by load calculation unit 21c. First limiting unit 21a obtains a first control map pre-stored in storage device 22 and references a traveling system line L1 defined in the first control map. First limiting unit 21a obtains a first command current value corresponding to the actual rotation speed in the referenced traveling system line L1.

[0081] FIG. 5 is a diagram showing an example of a travel system line L1 in which a control signal (target pressure of the primary pressure) is set based on the actual rotation speed of the prime mover 6. The travel system line L1 is a function in which the first limiting unit 21a defines the control signal based on the actual rotation speed of the prime mover 6. The travel system line L1 is derived based on the results of a previous experiment or simulation. In the travel system line L1 shown in FIG. 5, the first command current value increases as the actual rotation speed of the prime mover 6 increases. That is, as the actual rotation speed of the prime mover 6 increases, the first command current value output by the first limiting unit 21a to the actuated valve 80 increases, thereby increasing the primary pressure, and thereby increasing the output of the travel pump 51. On the other hand, as the actual rotation speed of the prime mover 6 decreases, the first command current value output by the first limiting unit 21a to the actuated valve 80 decreases, thereby decreasing the primary pressure, and thereby decreasing the output of the travel pump 51. The example shown in FIG. 5 is a control map (anti-stall map) showing an example of the travel system line L1. The traveling line L1 includes a first traveling line L1a and a third traveling line L1c. In Fig. 5, the first traveling line L1a is indicated by a solid line, and the third traveling line L1c is indicated by a two-dot chain line.

[0082] As described above, there is a corresponding relationship, such as a proportional relationship, between the magnitude of the first command current value, which is the control signal output from the first limiting unit 21a to the operating valve 80, and the target pressure of the primary pressure. In other words, the traveling system line L1 shown in FIG. 5 can be rephrased as a line that defines the target pressure of the primary pressure corresponding to the control signal (first command current value) based on the actual rotation speed of the prime mover 6. For this reason, in FIG. 5, the vertical axis can be referred to as the "control signal (first command current value)" or the "primary pressure (target pressure)."

[0083] The first running system line L1a is a line that sets a control signal (first command current value) corresponding to the target pressure of the primary pressure based on the actual rotation speed when the load acting on the prime mover 6 is less than a predetermined value (for example, the drop rotation speed is less than a first threshold value). In other words, the first running system line L1a is a no-load characteristic line that is adopted when the load on the prime mover 6 is less than a predetermined value. Note that the first threshold value is a predetermined value that is stored in advance in the storage device 22, but may be changeable as appropriate by operating the user interface 23.

[0084] The third running system line L1c is a line that sets a control signal (first command current value) corresponding to the target pressure of the primary pressure based on the actual rotation speed when the load acting on the prime mover 6 is equal to or greater than a predetermined value (for example, the drop rotation speed is equal to or greater than a first threshold value). In other words, the third running system line L1c is a drop characteristic line that is adopted when a running load equal to or greater than a predetermined value occurs.

[0085] The third running system line L1c is a line that sets a first command current value that is greater than the first command current value of the first running system line L1a at the same actual rotation speed. The third running system line L1c is provided corresponding to the actual rotation speed of the prime mover 6, and exists for each actual rotation speed. Therefore, when the drop rotation speed transitions from a state where it is less than the first threshold value to a state where it is equal to or greater than the first threshold value, the first limiting unit 21a refers to the third running system line L1c that passes through the first command current value output to the operating valve 80 and the actual rotation speed.

[0086] The second limiting unit 21b and the second anti-stall control will be described in detail below. In the second anti-stall control, the second limiting unit 21b limits the output of the main pump 40 in accordance with the load on the prime mover 6 as well as the drive state of the second hydraulic actuator C. As described above, unlike the second limiting unit 21b, in the first anti-stall control, the first limiting unit 21a limits the output of the travel pump 51 in accordance with the load on the prime mover 6, regardless of the drive state of the travel motor 52. As the second anti-stall control, the second limiting unit 21b changes the angle of the swash plate of the main pump 40 to reduce the output of the main pump 40, thereby limiting the horsepower consumed by the main pump 40. Specifically, the second limiting unit 21b controls the main pump 40 to control the pressure difference between the discharge pressure of the main pump 40 and the maximum load pressure when the second hydraulic actuator C is operating to a predetermined pressure difference (set pressure) based on the load on the prime mover 6.

[0087] 4, the hydraulic system S of the work machine 1 is equipped with a load sensing system 90 that controls the pressure difference between the discharge pressure of the main pump 40 and the maximum load pressure when the second hydraulic actuator C is operating to a set pressure, and the second restriction unit 21b controls the set pressure to limit the output of the main pump 40. The load sensing system 90 has a PLS oil passage 91, a PPS oil passage 92, a hydraulic control unit 93, and a setting change unit 94.

[0088] The PLS oil line 91 is connected to each of the control valves 71a, 71b, and 71c. The PLS oil line 91 is an oil line for detecting the load pressure, which is the pressure of hydraulic oil applied to each of the control valves 71a, 71b, and 71c when each of the control valves 71a, 71b, and 71c is in operation. The PLS oil line 91 can be acted upon by the PLS signal pressure, which is the highest load pressure among the load pressures of each of the control valves 71a, 71b, and 71c. In other words, the PLS oil line 91 can be acted upon by the highest load pressure when each of the second hydraulic actuators C is in operation.

[0089] The PPS oil passage 92 is connected to the discharge port of the main pump 40. A PPS signal pressure, which is the pressure (discharge pressure) of the hydraulic oil discharged from the main pump 40, can act on the PPS oil passage 92. That is, the discharge pressure of the hydraulic oil from the main pump 40 can act on the PPS oil passage 92.

[0090] The hydraulic control unit 93 includes a flow compensation valve 93a and a swash plate adjusting unit 93b. The flow compensation valve 93a controls the operation of the swash plate adjusting unit 93b based on the PLS signal pressure and the PPS signal pressure. The flow compensation valve 93a is a control valve connected to the PLS oil passage 91 and the PPS oil passage 92. The flow compensation valve 93a controls the operation of the swash plate adjusting unit 93b by changing its opening and changing the hydraulic oil supplied to the swash plate adjusting unit 93b. The flow compensation valve 93a is biased in a predetermined direction by the elastic force of a spring, and changes its opening so that the pressure difference between the PPS signal pressure and the PLS signal pressure (also referred to as differential pressure, or LS differential pressure) becomes a set pressure.

[0091] The swash plate variable unit 93b changes the angle of the swash plate of the main pump 40. The swash plate variable unit 93b is, for example, a hydraulic cylinder. The swash plate variable unit 93b is connected to the swash plate of the main pump 40 and expands and contracts in response to the hydraulic oil supplied from the flow rate compensation valve 93a, thereby changing the angle of the swash plate of the main pump 40.

[0092] The setting change unit 94 can change the set pressure. The setting change unit 94 has a solenoid valve 94a and a hydraulic cylinder (changing cylinder 94b). The solenoid valve 94a is an electromagnetic proportional valve that controls the changing cylinder 94b. The solenoid valve 94a is connected to the discharge oil passage 45, and more specifically, is connected to an oil passage that branches off from at least a portion of the discharge oil passage 45 between the branch point 45a and the pilot pump 44. In the following description, the pressure of the hydraulic oil supplied from the solenoid valve 94a to the changing cylinder 94b may be referred to as the "changing pressure."

[0093] The change cylinder 94b acts on the flow rate compensation valve 93a to change the opening of the flow rate compensation valve 93a, thereby changing the set pressure. The change cylinder 94b is connected to the flow rate compensation valve 93a, and expands and contracts according to the pressure (change pressure) of the hydraulic oil supplied from the solenoid valve 94a, moving the flow rate compensation valve 93a against the elastic force of the spring. This changes the set pressure of the flow rate compensation valve 93a, and changes the flow rate and pressure of the hydraulic oil supplied from the flow rate compensation valve 93a to the swash plate change unit 93b. Therefore, the swash plate change unit 93b expands and contracts according to this change, and the angle of the swash plate of the main pump 40 is changed. In this embodiment, as the change pressure increases, As the change pressure decreases, the change cylinder 94b expands and the set pressure is changed to a lower value. On the other hand, as the change pressure decreases, the change cylinder 94b contracts and the set pressure is changed to a higher value.

[0094] The control device 21 (second limiting unit 21b) outputs a control signal (for example, voltage, current, etc.) to the solenoid valve 94a, and the solenoid valve 94a operates in response to the control signal to change the opening degree, thereby changing the pressure. Below, we will explain the case where the control signal output by the control device 21 to the solenoid valve 94a is a current, and the current value output as the control signal will be referred to as the "second command current value." The solenoid proportional valve that constitutes the solenoid valve 94a can increase the opening degree in proportion to the magnitude of the second command current value.

[0095] That is, the adjusted pressure is changed according to the control signal output from the second limiting unit 21b to the solenoid valve 94a. In this embodiment, the second limiting unit 21b outputs the second command current value to the solenoid valve 94a, and therefore the adjusted pressure is changed according to the magnitude of the second command current value. Specifically, as the second command current value increases, the opening of the solenoid valve 94a increases, and the adjusted pressure increases. On the other hand, as the second command current value decreases, the opening of the solenoid valve 94a decreases, and the adjusted pressure decreases.

[0096] Therefore, there is a proportional or nearly proportional correspondence (correlation) between the second command current value and the changed pressure, and the second limiting unit 21b can change the set pressure and limit the output of the main pump 40 by changing the second command current value output to the solenoid valve 94a.

[0097] The second limiting unit 21b defines a second command current value based on the actual rotation speed of the prime mover 6 detected by the rotation speed detection device 25a and the drop rotation speed calculated by the load calculation unit 21c. The second limiting unit 21b acquires a second control map pre-stored in the storage device 22 and refers to the working system line L2 defined in the second control map. The second limiting unit 21b acquires a second command current value corresponding to the actual rotation speed in the working system line L2 that has been referenced.

[0098] FIG. 6 shows an example of the working system line L2 that sets the second control signal (target pressure of the adjusted pressure) based on the actual rotation speed of the prime mover 6. The working system line L2 is a function that defines the control signal by the second limiting unit 21b based on the actual rotation speed of the prime mover 6. The working system line L2 is derived based on the results of a previous experiment or simulation. The example shown in FIG. 6 is a control map (anti-stall map) that shows an example of the working system line L2. In the working system line L2 shown in FIG. 6, the second command current value decreases as the actual rotation speed of the prime mover 6 increases. That is, as the actual rotation speed of the prime mover 6 increases, the second limiting unit 21b reduces the second command current value output to the solenoid valve 94a, thereby increasing the set pressure, and thereby increasing the output of the main pump 40. On the other hand, as the actual rotation speed of the prime mover 6 decreases, the second limiting unit 21b increases the second command current value output to the solenoid valve 94a, thereby decreasing the set pressure, and thereby decreasing the output of the main pump 40. The work line L2 includes a first work line L2a, a second work line L2b, and a third work line L2c. In Fig. 6, the first work line L2a is indicated by a solid line, the second work line L2b is indicated by a dashed line, and the third work line L2c is indicated by a dashed line.

[0099] As described above, there is a corresponding relationship, such as a proportional relationship, between the magnitude of the second command current value, which is the control signal output from the second limiting unit 21b to the solenoid valve 94a, and the target pressure of the changed pressure. In other words, the work system line L2 shown in Fig. 6 can be rephrased as a line that defines the target pressure of the changed pressure corresponding to the control signal (second command current value) based on the actual rotation speed of the prime mover 6. For this reason, in Fig. 6, the vertical axis can be referred to as the "control signal (second command current value)" or the "changed pressure (target pressure)."

[0100] The first work system line L2a is a line that sets a control signal (second command current value) corresponding to the target pressure of the changed pressure based on the actual rotation speed when the load acting on the prime mover 6 is less than a predetermined value (for example, the drop rotation speed is less than a second threshold value). In particular, the second limiting unit 21b refers to the first work system line L2a when the load acting on the prime mover 6 is less than a predetermined value and first priority information has been acquired. In other words, the first work system line L2a is a no-load characteristic line that is adopted when the load on the prime mover 6 is less than a predetermined value and the travel operating device 55 is not being operated. The second threshold value is, for example, a predetermined value that is the same as the first threshold value, and is stored in the storage device 22. Although the value is stored in advance, it may be possible to change it as needed by operating the user interface 23.

[0101] The second work system line L2b is a line that sets a control signal (second command current value) corresponding to the target pressure of the changed pressure based on the actual rotation speed when the load acting on the prime mover 6 is less than a predetermined value (for example, the drop rotation speed is less than a second threshold value). In particular, the second limiting unit 21b refers to the second work system line L2b when the load acting on the prime mover 6 is less than a predetermined value and second priority information has been acquired. In other words, the second work system line L2b is a no-load characteristic line that is adopted when the load on the prime mover 6 is less than a predetermined value and the travel operating device 55 is being operated.

[0102] The second work system line L2b is a line that can set a second command current value equal to or greater than the second command current value of the first work system line L2a at the same actual rotation speed. As shown in FIG. 6, the second work system line L2b matches the first work system line L2a when the actual rotation speed is below a predetermined value (e.g., idling rotation speed), and has a larger second command current value than the first work system line L2a when the actual rotation speed is equal to or greater than the predetermined value. As a result, when the drop rotation speed is less than the second threshold value and the actual rotation speed is equal to or greater than the predetermined value, the second limiting unit 21b sets a larger second command current value corresponding to the same actual rotation speed when the second priority information is acquired than when the first priority information is acquired, and the second limiting unit 21b more effectively limits the output of the main pump 40.

[0103] In the example shown in Figure 6, the second work system line L2b coincides with the first work system line L2a in the range where the actual rotation speed is less than the idling rotation speed, but the second work system line L2b only needs to be able to set a second command current value that is equal to or greater than the second command current value of the first work system line L2a, and the specified value is not limited to the idling rotation speed, and the specified value may be zero, and the second command current value may be greater than that of the first work system line L2a in the range where the actual rotation speed is equal to or greater than zero.

[0104] The third work system line L2c is a line that sets a control signal (second command current value) corresponding to the target pressure of the changed pressure based on the actual rotational speed when the load acting on the prime mover 6 is equal to or greater than a predetermined value (for example, the drop rotational speed is equal to or greater than a second threshold value). In other words, the third work system line L2c is a drop characteristic line that is adopted when a traveling load equal to or greater than a predetermined value occurs. When the drop rotational speed is equal to or greater than a predetermined value, the second limiting unit 21b refers to the third work system line L2c and acquires the second command current value corresponding to the actual rotational speed in the third work system line L2c.

[0105] The third work system line L2c is a line for setting a second command current value that is greater than the second command current values ​​of the first work system line L2a and the second work system line L2b at the same actual rotation speed. The third work system line L2c is provided corresponding to the actual rotation speed of the prime mover 6, and exists for each actual rotation speed.

[0106] Therefore, when the drop rotational speed transitions from a state where it is less than the second threshold to a state where it is equal to or greater than the second threshold, the second limiting unit 21b references the third work system line L2c, which intersects with the first work system line L2a or the second work system line L2b that it is referencing at the current actual rotational speed. In other words, the second limiting unit 21b references the third work system line L2c, which passes through the second command current value output to the solenoid valve 94a and the actual rotational speed. That is, since the second work system line L2b can have a second command current value equal to or greater than the second command current value of the first work system line L2a at the same actual rotational speed, the third work system line L2c, referenced by the second limiting unit 21b that has acquired second priority information, can have a second command current value equal to or greater than the third work system line L2c that it references when it has acquired first priority information.

[0107] As a result, even when the drop rotation speed is equal to or greater than the second threshold, second limiting unit 21b can limit the output of main pump 40 more when second priority information is acquired than when first priority information is acquired. As a result, second limiting unit 21b limits the output of main pump 40 more when travel operation device 55 is operated than when travel operation device 55 is not operated.

[0108] Furthermore, when the drive of the traveling motor 52 is being operated, the second limiting unit 21b acquires the drive state of the traveling motor 52 and changes the output limit so that the output of the main pump 40 is limited more when the output of the traveling motor 52 is large than when the output of the traveling motor 52 is small. The second limiting unit 21b corrects the second command current value acquired from the referenced work line L2 using a correction value (second correction value) defined according to the output of the travel motor 52, and changes the set pressure, thereby changing the output limit of the main pump 40.

[0109] The second correction value is defined in accordance with the output of the traveling motor 52. In this embodiment, the second limiting unit 21b corrects the second command current value by multiplying the second command current value by the second correction value. In other words, the second correction value is a correction coefficient (gain) for correcting the second command current value. FIG. 7 is a diagram showing an example of the second correction value. As shown in FIG. 7, there is, for example, a proportional or nearly proportional correspondence (correlation) between the second correction value and the magnitude of the output of the traveling motor 52. Note that the second correction value is not limited to the example shown in FIG. 7. It is sufficient that the second correction value is defined so as to limit the output of the main pump 40 more when the output of the traveling motor 52 is large than when the output of the traveling motor 52 is small.

[0110] The second limiting unit 21b obtains the output of the traveling motor 52 based on the detection results of the multiple detecting devices 25 provided in the work machine 1, and the second correction value corresponds to the output of the traveling motor 52. For example, the second limiting unit 21b obtains the actual rotation speed of the traveling motor 52 (actual motor rotation speed) as the output of the traveling motor 52. In such a case, the second limiting unit 21b obtains the actual motor rotation speed based on the detection results of a rotation sensor 25d that is included in the multiple detecting devices 25 and detects the actual motor rotation speed.

[0111] The rotation sensor 25d is connected to the control device 21 and outputs a detected signal (detection signal) to the control device 21. In this embodiment, the traveling motor 52 includes a first traveling motor 52L and a second traveling motor 52R, and therefore the rotation sensor 25d is attached to each of the first traveling motor 52L and the second traveling motor 52R.

[0112] In this embodiment, the second limiting unit 21b performs calculations on the actual rotation speed of the travel motor 52 without distinguishing between the rotation speed during forward rotation and the rotation speed during reverse rotation, and adopts the sum of the actual motor rotation speeds n1 of the first travel motor 52L and the second travel motor 52R as the actual rotation speed of the travel motor 52. The second correction value is defined corresponding to the actual motor rotation speed adopted as the output of the travel motor 52, and is defined to increase as the actual motor rotation speed increases.

[0113] In addition, the actual motor rotation speed adopted by the second limiting unit 21b as the output of the traveling motor 52 is not limited to the sum of the actual motor rotation speeds n1 of the first traveling motor 52L and the second traveling motor 52R, and the higher rotation speed n1 may be adopted as the actual rotation speed of the traveling motor 52.

[0114] Furthermore, in the above example, the second limiting unit 21b acquires the actual motor rotation speed as the output of the travel motor 52, and the second correction value is defined corresponding to the actual motor rotation speed. However, the second limiting unit 21b may acquire information other than the actual motor rotation speed as the output of the travel motor 52, and correct the second command current value by a second correction value based on the acquired information. For example, the second limiting unit 21b may acquire the effective pressure P1 of the travel pump 51, and use the effective pressure P1 as the travel motor 52.

[0115] 3, the circulation oil passages 53a, 53b are provided with a pair of pressure sensors 25e (travel pressure sensors) that detect either the discharge pressure P1o or the suction pressure P1i of the hydraulic oil discharged by the travel pump 51. The second restriction unit 21b calculates the effective pressure P1 based on the difference (P1o-P1i) between the discharge pressure P1o of the travel pump 51 and the suction pressure P1i of the travel pump 51. Note that if the suction pressure P1i is substantially zero, the suction pressure P1i may be ignored.

[0116] Furthermore, the second limiting unit 21b may acquire the traveling speed (vehicle speed) of the work implement 1 and use this vehicle speed as the travel motor 52. Specifically, the second limiting unit 21b acquires the vehicle speed calculated by the control device 21 based on the detection result of the rotation sensor 25d. Furthermore, if the multiple detecting devices 25 include a position detecting device that detects the current position (machine position) of the work implement 1 using a satellite positioning system or the like, the control device 21 may calculate the vehicle speed based on the machine position detected by the position detecting device instead of the rotation sensor 25d, and the second limiting unit 21b may acquire this vehicle speed.

[0117] The second limiting unit 21b may also acquire the horsepower consumption of the travel pump 51 and use the horsepower consumption as the output of the travel motor 52. Since the travel pump 51 includes a travel pump 51L and a second travel pump 51R, the second restriction unit 21b adopts the total horsepower consumption of the travel pump 51 as the horsepower consumption of the travel pump 51, which is the sum of the horsepower consumption of the first travel pump 51L and the horsepower consumption of the second travel pump 51R.

[0118] The second limiting unit 21b calculates the consumed horsepower H1 based on the discharge pressure P1o of the hydraulic oil discharged by each travel pump 51 and the flow rate Q1 of the hydraulic oil. Specifically, the second limiting unit 21b can calculate the consumed horsepower H1 using the following formula (1) based on the effective pressure P1 of each travel pump 51 based on the discharge pressure P1o, the flow rate Q1 of the hydraulic oil, and the efficiency η1.

[0119] Consumption horsepower H1 = (effective pressure P1 × flow rate Q1) / (60 × η1) Equation (1) The efficiency η1 is a predetermined value that includes losses in power transmission from the prime mover 6 to each travel pump 51, and is stored in the storage device 22 in advance.

[0120] The second limiting unit 21b can calculate the flow rate Q1 of the hydraulic oil discharged from each travel pump 51 based on the displacement volume q1 of each travel motor 52 and the actual motor rotation speed n1 of each travel motor 52 using the following equation (2).

[0121] Flow rate Q1 = displacement volume q1 × actual motor rotation speed n1 / 1000 Formula (2) In this embodiment, the travel motor 52 changes the angle of the swash plate using the switching cylinder 60 and the speed switching valve 61 to switch between the first speed and the second speed, so the second limiting unit 21b calculates the displacement q1 based on operation information of the speed change operating device 24c (information related to the operation of switching between the first speed and the second speed) and a predetermined table pre-stored in the storage device 22. The table associates each speed with the displacement q1.

[0122] The method for calculating the displacement volume q1 is not limited to the above example, and the second limiting unit 21b may calculate the displacement volume q1 of each travel motor 52 based on the angle of the swash plate of each travel motor 52. In such a case, each travel motor 52 is provided with an angle sensor 25f (first swash plate angle sensor) that detects (measures) the angle of the swash plate of that travel motor 52, and the second limiting unit 21b calculates the displacement volume q1 based on the detection result of the first swash plate angle sensor 25f and a predetermined function or the like that is pre-stored in the storage device 22.

[0123] Furthermore, in the above example, a case has been described in which the second limiting unit 21b calculates the flow rate Q1 of hydraulic oil discharged from each travel pump 51 based on the actual motor rotation speed n1, but the second limiting unit 21b may calculate the flow rate Q1 based on the actual rotation speed n2 of the power input to the travel pump 51 from the prime mover 6 (first input actual rotation speed) instead of the actual motor rotation speed n1. In such a case, the second limiting unit 21b can calculate the flow rate Q1 of hydraulic oil discharged from each travel pump 51 based on the displacement volume q2 of each travel pump 51 and each first input actual rotation speed n2 using the following equation (3):

[0124] Flow rate Q1 = Displacement volume q2 × First input actual rotation speed n2 / 1000 Formula (3) In this embodiment, the second limiting unit 21b calculates the displacement volume q2 of each travel pump 51 based on the angle of the swash plate of each travel pump 51. Each travel pump 51 is provided with an angle sensor 25g (second swash plate angle sensor) that detects (measures) the angle of the swash plate of that travel pump 51, and the second limiting unit 21b calculates the displacement volume q2 based on the detection result of the second swash plate angle sensor 25g and a predetermined function or the like that is pre-stored in the storage device 22. The second limiting unit 21b also calculates the first actual input rotation speed n2 based on the actual rotation speed of the prime mover 6 detected by the rotation speed detection device 25a and a predetermined function or the like that is pre-stored in the storage device 22.

[0125] Furthermore, although the case has been described in which the second limiting unit 21b acquires the horsepower consumption of the travel pump 51 as the output of the travel motor 52, the second limiting unit 21b may acquire the torque consumption as the output of the travel motor 52 instead of the horsepower consumption. The second limiting unit 21b calculates the horsepower consumption of each travel pump 51 using the calculation method described above, and calculates the torque consumption of each travel pump 51 by subtracting the first input actual rotation speed n2, etc. from each horsepower consumption based on a predetermined function, etc., stored in advance in the storage device 22. The second limiting unit 21b calculates the torque consumption of each travel pump 51 by subtracting the first input actual rotation speed n2, etc., from each horsepower consumption based on a predetermined function, etc., stored in advance in the storage device 22. The total value of the torque consumption of the first motor 52 is obtained as the output of the travel motor 52.

[0126] In the above example, the second limiting unit 21b corrects the second command current value by multiplying the second command current value by the second correction value, but the method of correcting the second command current value using the second correction value is not limited to multiplication. Depending on how the second correction value is defined, the second command current value may be corrected by dividing, adding, or subtracting the second correction value from the second command current value, and the correction method is not limited to the above method. Furthermore, the second limiting unit 21b may correct the second command current value using a predetermined function instead of the second correction value.

[0127] Next, an example will be described in which the first limiting unit 21a changes the output limit of the travel pump 51 in accordance with the priority information. Note that when the first limiting unit 21a changes the output limit of the travel pump 51 in accordance with the priority information, the second limiting unit 21b may or may not also limit the output of the main pump 40 in accordance with the priority information. When the second limiting unit 21b does not limit the output of the main pump 40 in accordance with the priority information, it does not acquire priority information and acquires the first work system line L2a when the load acting on the prime mover 6 is less than a predetermined value.

[0128] When the first limiting unit 21a changes the output limit of the travel pump 51 in accordance with the priority information, the first limiting unit 21a acquires the priority information based on the operation of the work operation device 65. Based on the priority information, the first limiting unit 21a changes the output limit so as to limit the output of the travel pump 51 more when the drive of the second hydraulic actuator C is being operated than when the drive of the second hydraulic actuator C is not being operated.

[0129] Specifically, the first restriction unit 21a acquires the third priority information when the work operation device 65 is not being operated, and acquires the fourth priority information when the work operation device 65 is being operated. Therefore, the first restriction unit 21a acquires either the third priority information or the fourth priority information as the priority information, and when one of the information is acquired, the other is not acquired. The fourth priority information has a higher priority for driving the second hydraulic actuator C than the third priority information.

[0130] The first limiting unit 21a refers to the second priority flag set by the flag setting unit 21d, and acquires the third priority information when the second priority flag is off. Also, the first limiting unit 21a acquires the fourth priority information when the first priority flag is on.

[0131] The flag setting unit 21d acquires the operation state of the work lever 66a of the work operation device 65, for example, based on the pilot pressure of the pilot oil output from the work operation valve 67. In such a case, a pressure sensor 25h (second operation pressure sensor) that detects the pilot pressure of the pilot oil flowing through each work oil line 68 is provided, and the flag setting unit 21d acquires the operation state of the work operation device 65 based on the detection signal detected by the second operation pressure sensor 25h. For example, if the pilot pressure detected by the second operation pressure sensor 25h is equal to or greater than a predetermined value, the flag setting unit 21d determines that the work lever 66a is being operated, and if it is less than the predetermined value, the flag setting unit 21d determines that the work lever 66a is not being operated.

[0132] Furthermore, based on the operation signal of the auxiliary switch 66b, the flag setting unit 21d acquires the operation state of the auxiliary switch 66b of the work operation device 65. Therefore, when the flag setting unit 21d determines that at least one of the work lever 66a and the auxiliary switch 66b has been operated, it turns on the second priority flag, and when it determines that neither has been operated, it turns off the second priority flag.

[0133] The flag setting unit 21d only needs to set the second priority flag on or off based on the operation of the work operation device 65, and the method of acquiring the operation state of the work operation device 65 is not limited to the example described above, and may be acquired by other methods. For example, if a detection sensor is provided that detects the amount and direction of operation of the work lever 66a, the operation state of the work lever 66a may be acquired based on the detection results detected by the detection sensor.

[0134] The first limiting unit 21a, which changes the output limit of the travel pump 51 in accordance with the priority information, acquires a different travel system line L1 in accordance with the priority information when the load acting on the prime mover 6 is less than a predetermined value. Specifically, when the load acting on the prime mover 6 is less than a predetermined value, the first limiting unit 21a refers to the first travel system line L1a when the third priority information has been acquired, and refers to the second travel system line L1b included in the travel system line L1 when the fourth priority information has been acquired.

[0135] The second traveling system line L1b is a line that sets a control signal (first command current value) corresponding to the target pressure of the primary pressure based on the actual rotation speed when the load acting on the prime mover 6 is less than a predetermined value (the drop rotation speed is less than the first threshold value). In such a case, the first traveling system line L1a is a no-load characteristic line that is used when the load on the prime mover 6 is less than a predetermined value and the work operation device 65 is not being operated, and the second traveling system line L1b is a no-load characteristic line that is used when the load on the prime mover 6 is less than a predetermined value and the work operation device 65 is being operated.

[0136] The second traveling system line L1b is a line for which a first command current value equal to or less than the first command current value of the first traveling system line L1a can be set at the same actual rotation speed. In FIG. 5, the second traveling system line L1b is indicated by a dashed line. As shown in FIG. 5, the second traveling system line L1b matches the first traveling system line L1a when the actual rotation speed is below a predetermined value (e.g., idling rotation speed), and has a smaller first command current value than the first traveling system line L1a when the actual rotation speed is equal to or greater than the predetermined value. As a result, when the drop rotation speed is below the predetermined value, the first limiting unit 21a can reduce the first command current value corresponding to the same actual rotation speed when the fourth priority information is acquired compared to when the third priority information is acquired, and the first limiting unit 21a can more effectively limit the output of the traveling pump 51.

[0137] In the example shown in FIG. 5, the second driving system line L1b coincides with the first driving system line L1a in a range where the actual rotation speed is less than the idling rotation speed. However, the second driving system line L1b may have a first command current value that is equal to or less than the first command current value of the first driving system line L1a, and the predetermined value is not limited to the idling rotation speed. The predetermined value may be zero, and the first command current value may be smaller than that of the first driving system line L1a in a range where the actual rotation speed is equal to or greater than zero.

[0138] As described above, when the drop rotational speed transitions from a state where it is less than the first threshold to a state where it is equal to or greater than the first threshold, the first limiting unit 21a references the third running system line L1c, which intersects with the first running system line L1a or the second running system line L1b that it is referencing at the current actual rotational speed. In other words, the first limiting unit 21a references the third running system line L1c, which passes through the first command current value output to the actuated valve 80 and the actual rotational speed. That is, because the second running system line L1b can set a first command current value equal to or less than the first command current value of the first running system line L1a at the same actual rotational speed, the third running system line L1c, referenced by the first limiting unit 21a that has acquired the fourth priority information, can set a first command current value equal to or less than the third running system line L1c that it references when it has acquired the third priority information.

[0139] As a result, even when the drop rotation speed is equal to or greater than the first threshold value, the first limiting unit 21a can limit the output of the travel pump 51 more when the fourth priority information has been acquired than when the third priority information has been acquired. As a result, the above-described first limiting unit 21a limits the output of the travel pump 51 more when the work operating device 65 is being operated than when the work operating device 65 is not being operated.

[0140] Furthermore, when the drive of the second hydraulic actuator C is being operated, the first limiting unit 21a may acquire the drive state of the second hydraulic actuator C, and change the output limit so that the output of the travel pump 51 is more restricted when the output of the second hydraulic actuator C is large than when the output of the second hydraulic actuator C is small. The first limiting unit 21a corrects the first command current value acquired from the referenced travel system line L1 by a correction value (first correction value) defined in accordance with the output of the second hydraulic actuator C, and changes the primary pressure, thereby changing the output limit of the travel pump 51.

[0141] The first correction value is defined in accordance with the output of the second hydraulic actuator C, and in this embodiment, the first limiting unit 21a corrects the first command current value by multiplying the first correction value by the first correction value. In other words, the first correction value is a correction coefficient (gain) for correcting the first command current value. FIG. 8 is a diagram showing an example of the first correction value. As shown in FIG. 8, there is, for example, a proportional or nearly proportional correspondence (correlation) between the first correction value and the magnitude of the output of the second hydraulic actuator C. Note that the first correction value is not limited to the example shown in FIG. 8, and may be defined to limit the output of the travel pump 51 more when the output of the second hydraulic actuator C is large than when the output of the second hydraulic actuator C is small. It would be good if it was done.

[0142] The first limiting unit 21a acquires the output of the second hydraulic actuator C based on the detection results of a plurality of detecting devices 25 provided in the work machine 1, and the first correction value corresponds to the output of the second hydraulic actuator C. For example, the first limiting unit 21a may acquire the effective pressure P2 of the main pump 40 and use the effective pressure P2 as the pressure for the second hydraulic actuator C.

[0143] 3, a pressure sensor 25i (discharge pressure sensor) is provided in the main oil passage 41 to detect a discharge pressure 25i of the hydraulic oil discharged by the main pump 40, and a pressure sensor 25j (suction pressure sensor) is provided in the suction oil passage 42 to detect a suction pressure P2i of the hydraulic oil sucked by the main pump 40. The first restrictor 21a calculates the effective pressure P2 based on the difference (P2o-P2i) between the discharge pressure P2o and the suction pressure P2i. Note that if the suction pressure P2i is substantially zero, the suction pressure P2i may be ignored, and in such a case, the suction pressure sensor 25j need not be provided in the main oil passage 41 and the suction oil passage 42.

[0144] Furthermore, the first limiting unit 21a may obtain the horsepower consumption of the main pump 40 and use the horsepower consumption as the output of the second hydraulic actuator C. The first limiting unit 21a calculates the horsepower consumption H2 based on the discharge pressure P2o of the hydraulic oil discharged by the main pump 40 and the flow rate Q2 of the hydraulic oil. Specifically, the first limiting unit 21a can calculate the horsepower consumption H2 using the following equation (4) based on the effective pressure P2 of the main pump 40 based on the discharge pressure P2o, the flow rate Q2 of the hydraulic oil, and the efficiency η2.

[0145] Consumption horsepower H2 = (effective pressure P2 × flow rate Q2) / (60 × η2) Equation (4) The efficiency η2 is a predetermined value that includes a loss in power transmission from the prime mover 6 to the main pump 40, and is stored in the storage device 22 in advance.

[0146] The first restriction unit 21a can calculate the flow rate Q2 of hydraulic oil discharged by the main pump 40 based on the actual rotational speed n3 (second input actual rotational speed) of the power input from the prime mover 6 to the main pump 40 using the following equation (5).

[0147] Flow rate Q2 = displacement volume q3 × second input actual rotation speed n3 / 1000 Equation (5) In this embodiment, the first limiting unit 21a calculates the displacement volume q3 of each main pump 40 based on the angle of the swash plate of the main pump 40. The main pump 40 is provided with an angle sensor 25k (third swash plate angle sensor) that detects (measures) the angle of the swash plate of the main pump 40, and the first limiting unit 21a calculates the displacement volume q3 based on the detection result of the third swash plate angle sensor 25k and a predetermined function or the like pre-stored in the storage device 22. The first limiting unit 21a also calculates the first actual input rotation speed n2 based on the actual rotation speed of the prime mover 6 detected by the rotation speed detection device 25a and a predetermined function or the like pre-stored in the storage device 22.

[0148] Furthermore, although the above description has been given of the case where the first limiting unit 21a obtains the horsepower consumption of the main pump 40 as the output of the second hydraulic actuator C, the first limiting unit 21a may obtain the consumed torque instead of the consumed horsepower as the output of the second hydraulic actuator C. The first limiting unit 21a calculates the horsepower consumption of the main pump 40 using the calculation method described above, and calculates the torque consumption of the main pump 40 by subtracting the second input actual rotation speed n3, etc. from each consumed horsepower based on a predetermined function, etc., stored in advance in the storage device 22. The first limiting unit 21a obtains the sum of the calculated torque consumptions of the main pump 40 as the output of the second hydraulic actuator C.

[0149] In the above example, the first limiting unit 21a corrects the first command current value by multiplying the first command current value by the first correction value, but the method of correcting the first command current value using the first correction value is not limited to multiplication. Depending on how the first correction value is defined, the first command current value may be corrected by dividing, adding, or subtracting the first correction value from the first command current value, and the correction method is not limited to the above method. Furthermore, the first limiting unit 21a may correct the first command current value using a predetermined function instead of the first correction value.

[0150] In the above example, the flag setting unit 21d is configured to set the driving operation device 55 and the work operation. In the above description, a flag corresponding to the priority information is set based on the operation of the travel operation device 65, and the first limiting unit 21a and the second limiting unit 21b acquire the priority information based on the flag. However, the priority information does not have to correspond to the operation of the travel operation device 55 or the operation of the work operation device 65. For example, the priority information may be configured so that the worker can manually operate the operation tool 24d. In this embodiment, the operation tool 24d is an operation switch included in the multiple operation members 24, and receives an operation to select the priority information.

[0151] When both the first limiting unit 21a and the second limiting unit 21b change the output limit based on the priority information, the operating device 24d accepts a selection operation from among first to fourth priority information. For example, the operating device 24d accepts a selection operation from among a "traveling priority mode" in which the second priority information and the third priority information are selected and priority is given to driving the traveling motor 52, a "neutral mode" in which the first priority information and the third priority information are selected and neither is prioritized, and a "working priority mode" in which the first priority information and the fourth priority information are selected and priority is given to driving the second hydraulic actuator C.

[0152] If the second limiting unit 21b changes the output limit based on the priority information and the first limiting unit 21a does not change the output limit based on the priority information, the operating device 24d accepts a selection operation of either the first or second priority information. In this case, the operating device 24d accepts a selection operation between a "traveling priority mode" in which the second priority information is selected and priority is given to driving the traveling motor 52, and a "neutral mode" in which the first priority information is selected and priority is not given to driving the traveling motor 52.

[0153] Furthermore, when the first limiting unit 21a changes the output limit based on the priority information and the second limiting unit 21b does not change the output limit based on the priority information, the operating device 24d accepts a selection operation of either the third or fourth priority information. In such a case, the operating device 24d accepts a selection operation between a "neutral mode" in which the third priority information is selected and no priority is given to driving the second hydraulic actuator C, and a "work priority mode" in which the fourth priority information is selected and priority is given to driving the second hydraulic actuator C.

[0154] The flag setting unit 21d acquires an operation signal from the operating tool 24d and sets a flag in accordance with the operation of the operating tool 24d. The flag setting unit 21d turns on a flag corresponding to priority information that has been selected and operated by the operating tool 24d, and turns off a flag corresponding to priority information that has not been selected and operated.

[0155] Furthermore, the flag setting unit 21d may set the first priority flag based on, for example, the speed change (first speed, second speed) of the traveling motor 52, without depending on the operation of the traveling operation device 55. For example, the flag setting unit 21d acquires operation information of the speed change operation device 24c, and turns off the first priority flag when the traveling motor 52 has been shifted to the first speed, and turns on the first priority flag when the traveling motor 52 has been shifted to the second speed.

[0156] The first limiting unit 21a may also change the output limit of the travel pump 51 depending on the attachment 30 attached to the coupling device 10. For example, the first limiting unit 21a changes the output limit to limit the output of the travel pump 51 when the attachment 30 attached to the coupling device 10 is a first attachment that consumes a large amount of hydraulic oil for driving (a consumed flow rate) compared to when the attachment 30 attached to the coupling device 10 is a first attachment that consumes a small amount of hydraulic oil. For this reason, the first limiting unit 21a changes the output limit to limit the output of the travel pump 51 when the attachment 30 attached to the coupling device 10 is the first attachment compared to when the attachment 30 is a second attachment. The first limiting unit 21a corrects the referenced first command current value acquired from the travel system line L1 by a correction value (third correction value) defined depending on the attached attachment 30, and changes the primary pressure to change the output limit of the travel pump 51.

[0157] Specifically, the hydraulic system S of the work machine 1 includes an identification unit 21e that identifies the attachment 30 attached to the coupling device 10, and the first limiting unit 21a changes the output limit based on the attachment 30 identified by the identification unit 21e. The identification unit 21e is, for example, a software program implemented in the control device 21. The identification unit 21e identifies the attachment 30 attached to the coupling device 10 based on information input via the user interface 23. In other words, the identification unit 21e identifies the attachment 30 attached to the coupling device 10 based on the worker's manual operation to select the attachment 30. In this case, when the attachment 30 is attached to the connecting device 10, the user interface 23 displays an attachment list including a plurality of pieces of attachment 30 information indicating each of a plurality of attachments 30 that can be attached to the connecting device 10, and the identification unit 21e identifies the attachment 30 attached to the connecting device 10 from any of the attachment 30 information selected from the attachment list by the user interface 23.

[0158] The storage device 22 stores, in table format, the correspondence between the identification information (attachment ID) of the attachment 30 and the third correction value. The attachment ID of the attachment 30 and the third correction value are associated with each other and stored in a predetermined storage area of ​​the storage device 22. Note that other control data than the third correction value, such as the hydraulic pressure level or hydraulic oil to be output to the attachment 30, may be associated with the attachment ID and stored in the storage device 22.

[0159] The third correction value is defined corresponding to the attachment 30, and in this embodiment, the first limiting unit 21a corrects the first command current value by multiplying the first command current value by the third correction value. In other words, the third correction value is a correction coefficient (gain) for correcting the first command current value. FIG. 9 is a diagram showing an example of the third correction value. The third correction value is defined according to the consumption flow rate of hydraulic oil required for driving each actuator, and is defined so that the value for a first attachment with a high consumption flow rate is larger than that for a first attachment with a low consumption flow rate.

[0160] In this embodiment, the third correction value corresponding to the second attachment that does not have a hydraulic actuator and is not driven by hydraulic oil is "1," and the first limiting unit 21a does not actually correct the first command current value. Also, in the example described above, a case has been described in which a third correction value is defined for each actuator, but it is sufficient for at least the first limiting unit 21a to change the output limit of the travel pump 51 based on the attached attachment 30, and the third correction value may be defined in association with, for example, the type of attachment 30 or the work content.

[0161] Furthermore, in the above example, the case has been described where the worker operates the user interface 23 to manually select the attached attachment 30, but the identification unit 21e may also be able to automatically identify the attached attachment 30. For example, if the attachment 30 is provided with a transmitter (beacon) that periodically emits a wireless signal including an attachment ID, and the work machine 1 is equipped with a receiver that receives the wireless signal emitted from the beacon, the identification unit 21e will automatically identify the attached attachment 30 based on the wireless signal.

[0162] In the above example, the first limiting unit 21a corrects the first command current value by multiplying the first command current value by the third correction value, but the method of correcting the first command current value using the third correction value is not limited to multiplication. Depending on how the third correction value is defined, the first command current value may be corrected by dividing, adding, or subtracting the first correction value from the first command current value, and the correction method is not limited to the above method. Furthermore, the first limiting unit 21a may correct the first command current value using a predetermined function instead of the third correction value.

[0163] A preferred embodiment of the present invention provides a hydraulic system S for a work machine 1 and the work machine 1 described in the following items. (Item 1) a first hydraulic pump 51 having a variable displacement that is driven by the power of the prime mover 6 and discharges hydraulic oil; a first hydraulic actuator 52 that is driven by the hydraulic oil discharged by the first hydraulic pump 51; a second hydraulic pump 40 that is driven by the power of the prime mover 6 and discharges hydraulic oil and has a variable displacement different from that of the first hydraulic pump 51; a second hydraulic actuator C that is driven by the hydraulic oil discharged by the second hydraulic pump 40; a first limiting unit 21a that limits the output of the first hydraulic pump 51 in accordance with the load of the prime mover 6; and a second limiting unit 21b that limits the output of the second hydraulic pump 40 in accordance with the load of the prime mover 6. The hydraulic system S of the work machine 1 changes the output limit of the first hydraulic pump 51 in accordance with priority information, and / or the second limiting unit 21b changes the output limit of the second hydraulic pump 40 in accordance with the priority information.

[0164] According to the hydraulic system S of the work machine 1 relating to item 1, the output limitation of the first hydraulic pump 51 according to the load on the prime mover 6 and the output limitation of the second hydraulic pump 40 can be appropriately balanced according to the priority information. (Item 2) The hydraulic system S of the work machine 1 described in item 1, wherein the first limiting unit 21a limits the output of the first hydraulic pump 51 in accordance with the load on the prime mover 6, regardless of the drive state of the first hydraulic actuator 52, and the second limiting unit 21b limits the output of the second hydraulic pump 40 in accordance with the drive state of the second hydraulic actuator C in addition to the load on the prime mover 6.

[0165] According to the hydraulic system S of the work machine 1 related to item 2, the first limiting unit 21a and the second limiting unit 21b limit the output of the hydraulic pump based on different conditions, while the second limiting unit 21b can appropriately balance the output of the second hydraulic pump 40 in accordance with the priority information. Therefore, in the hydraulic system S of the work machine 1, the workability of the first hydraulic actuator 52 or the second hydraulic actuator C can be improved in accordance with the priority information while suppressing stall of the prime mover 6. (Item 3) The hydraulic system S of the work machine 1 described in item 2, wherein the first limiting unit 21a limits the output of the first hydraulic pump 51 according to a drop rotation speed, which is the difference between the target rotation speed of the prime mover 6 and the actual rotation speed of the prime mover 6.

[0166] According to the hydraulic system S of the work machine 1 relating to item 3, by adopting a drop rotation speed as the load of the prime mover 6, the first limiting unit 21a can limit the output of the first hydraulic pump 51 by relatively simple calculation processing. (Item 4) The hydraulic system S of the work machine 1 described in item 2 or 3, wherein the second restriction unit 21b controls the second hydraulic pump 40 to control the pressure difference between the discharge pressure of the second hydraulic pump 40 and the maximum load pressure during operation of the second hydraulic actuator C to a predetermined pressure difference based on the load of the prime mover 6.

[0167] According to the hydraulic system S of the work machine 1 related to item 4, the driving state of the second hydraulic actuator C can be taken into consideration and the horsepower control of the second hydraulic pump 40 can be performed appropriately. (Item 5) The hydraulic system S of the work machine 1 described in any one of items 2 to 4 includes a first operating device 55 that operates the drive of the first hydraulic actuator 52, and the second limiting unit 21b acquires the priority information based on the operation of the first operating device 55 and changes the output limit so as to limit the output of the second hydraulic pump 40 more when the drive of the first hydraulic actuator 52 is operated than when the drive of the first hydraulic actuator 52 is not operated.

[0168] According to the hydraulic system S of the work machine 1 related to item 5, the priority information can be accurately defined based on the operation of the first operating device 55, i.e., the operator's intention to drive the first hydraulic actuator 52. In other words, the second limiting unit 21b can instantly reflect the operator's intention in the output limit without requiring any operation other than the operation of the first operating device 55. (Item 6) The hydraulic system S of the work machine 1 described in item 5, wherein the second limiting unit 21b acquires the drive status of the first hydraulic actuator 52 when the drive of the first hydraulic actuator 52 is being operated, and changes the output limit so as to limit the output of the second hydraulic pump 40 more when the output of the first hydraulic actuator 52 is large than when the output of the first hydraulic actuator 52 is small.

[0169] According to the hydraulic system S of the work machine 1 related to item 6, the second limiting section 21b can more appropriately limit the output in accordance with the magnitude of the output of the first hydraulic actuator 52. (Item 7) The hydraulic system S of the work machine 1 described in any one of items 2 to 6 includes a second operating device 65 that operates the drive of the second hydraulic actuator C, and the first limiting unit 21a acquires the priority information based on the operation of the second operating device 65 and changes the output limit so as to limit the output of the first hydraulic pump 51 more when the drive of the second hydraulic actuator C is operated than when the drive of the second hydraulic actuator C is not operated.

[0170] According to the hydraulic system S of the work machine 1 related to item 7, the priority information can be accurately defined based on the operation of the second operating device 65, i.e., the operator's intention to drive the second hydraulic actuator C. In other words, the first limiting unit 21a can instantly reflect the operator's intention in the output limit without requiring any operation other than the operation of the second operating device 65. (Item 8) The hydraulic system S of the work machine 1 described in item 7, wherein when the drive of the second hydraulic actuator C is being operated, the first limiting unit 21a acquires the drive state of the second hydraulic actuator C and changes the output limit so as to limit the output of the first hydraulic pump 51 more when the output of the second hydraulic actuator C is large than when the output of the second hydraulic actuator C is small.

[0171] According to the hydraulic system S of the work machine 1 related to item 8, the first limiting section 21a can limit the output more appropriately in accordance with the magnitude of the output of the second hydraulic actuator C. (Item 9) 5. The hydraulic system S of the work machine 1 according to any one of items 2 to 4, further comprising an operating tool 24d that accepts an operation for the priority information.

[0172] According to the hydraulic system S of the work machine 1 relating to item 9, the priority information does not change frequently unless it is changed by operating the operating tool 24d. Therefore, it is possible to prevent the priority information from frequently fluctuating (changing) while the worker is operating the work machine 1. (Item 10) The hydraulic system S of the work implement 1 described in any one of items 1 to 9, wherein the first hydraulic actuator 52 drives a traveling device 4 that supports a vehicle body and causes the vehicle body to travel, and the second hydraulic actuator C drives a work device 5 provided on the vehicle body.

[0173] According to the hydraulic system S of the work machine 1 relating to item 10, it is possible to appropriately change the output balance between the drive of the traveling system and the drive of the working system while suppressing stall of the prime mover 6. (Item 11) A work machine (1) comprising the hydraulic system (S) of the work machine (1) according to any one of items (1) to (10), the machine body (2), the traveling device (4), and the work device (5).

[0174] According to the work machine 1 according to item 11, it is possible to realize a work machine 1 that exhibits the unique effects described above. (Item 12) The work implement 1 described in item 11, wherein the work device 5 has a connecting device 10 to which any one of a plurality of attachments 30 can be attached and detached, and the first limiting section 21a changes the output limit of the first hydraulic pump 51 depending on the attachment 30 attached to the connecting device 10.

[0175] According to the work machine 1 relating to item 12, the output limit of the first hydraulic pump 51 by the first limiting section 21a can be changed taking into account the work content of the attachment 30, so that stalling of the prime mover 6 can be suppressed while improving the workability of the attachment 30. (Item 13) The work machine 1 described in item 12, wherein the multiple attachments 30 include a first attachment driven by hydraulic oil discharged by the second hydraulic pump 40, and the first restricting unit 21a changes the output restriction so as to restrict the output of the first hydraulic pump 51 when the attachment 30 attached to the connecting device 10 is a first attachment requiring a large flow rate of hydraulic oil for driving, rather than when the attachment 30 is a first attachment requiring a small flow rate of hydraulic oil for driving.

[0176] According to the work machine 1 according to item 13, the flow of hydraulic oil required for the work performed by the attachment 30 is Since the output of the first hydraulic pump 51 is limited depending on the amount, stalling of the prime mover 6 can be suppressed and the workability of the attachment 30 can be improved. (Item 14) The work machine 1 described in item 12, wherein the multiple attachments 30 include a first attachment that is driven by hydraulic oil discharged by the second hydraulic pump 40 and a second attachment that is not driven by hydraulic oil discharged by the second hydraulic pump 40, and the first limiting unit 21a changes the output limit to limit the output of the first hydraulic pump 51 when the attachment 30 attached to the connecting device 10 is the first attachment more than when the attachment 30 is the second attachment.

[0177] According to the work implement 1 related to item 14, the output limit of the first hydraulic pump 51 is changed in accordance with the configuration of the attachment 30, thereby improving operability when the attachment 30 is the first attachment. As a result, it is possible to appropriately balance the drive of the work implement 5 and the drive of the traveling device 4 while suppressing stalling of the prime mover 6.

[0178] Although the present invention has been described above, the embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. 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]

[0179] 1: Work equipment 2: Aircraft 4: Running gear 5: Work equipment 6: Prime mover 10: Quick hitch 21a: First restriction section 21b: Second restriction part 24d: Operating tool 30: Attachment (work tool) 40: Second hydraulic pump (main pump) 51: First hydraulic pump (travel pump) 52: First hydraulic actuator (travel motor) 55: First operating device (travel operating device) 65:Second operating device (work operating device) C: Second hydraulic actuator S: Hydraulic system

Claims

1. The prime mover and a variable displacement first hydraulic pump that is driven by power of the prime mover and discharges hydraulic oil; a first hydraulic actuator driven by hydraulic oil discharged from the first hydraulic pump; a second hydraulic pump that is driven by the power of the prime mover to discharge hydraulic oil and has a variable displacement different from that of the first hydraulic pump; a second hydraulic actuator driven by hydraulic oil discharged from the second hydraulic pump; a first limiting unit that limits the output of the first hydraulic pump in accordance with a load on the prime mover; a second limiting unit that limits the output of the second hydraulic pump in accordance with a load on the prime mover; Equipped with A hydraulic system for a work machine, wherein the first limiting unit changes the output limit of the first hydraulic pump in accordance with predetermined priority information between the first hydraulic actuator and the second hydraulic actuator, and / or the second limiting unit changes the output limit of the second hydraulic pump in accordance with the priority information.

2. the first limiting unit limits the output of the first hydraulic pump in accordance with the load of the prime mover, regardless of the driving state of the first hydraulic actuator; The hydraulic system for a work machine according to claim 1 , wherein the second limiting unit limits the output of the second hydraulic pump in accordance with the driving state of the second hydraulic actuator in addition to the load on the prime mover.

3. 3. The hydraulic system for a work machine according to claim 2, wherein the first limiting unit limits the output of the first hydraulic pump in accordance with a drop rotation speed, which is the difference between a target rotation speed of the prime mover and an actual rotation speed of the prime mover.

4. 3. The hydraulic system for a work machine according to claim 2, wherein the second limiting unit controls the second hydraulic pump to control the pressure difference between the discharge pressure of the second hydraulic pump and the maximum load pressure during operation of the second hydraulic actuator to a predetermined pressure difference based on the load of the prime mover.

5. a first operating device that operates the drive of the first hydraulic actuator; 3. The hydraulic system of claim 2, wherein the second limiting unit acquires the priority information based on the operation of the first operating device, and changes the output limit so as to limit the output of the second hydraulic pump more when the drive of the first hydraulic actuator is being operated than when the drive of the first hydraulic actuator is not being operated.

6. 6. The hydraulic system of claim 5, wherein the second limiting unit, when the drive of the first hydraulic actuator is being operated, acquires the drive state of the first hydraulic actuator, and changes the output limit so as to limit the output of the second hydraulic pump more when the output of the first hydraulic actuator is large than when the output of the first hydraulic actuator is small.

7. a second operating device that operates the drive of the second hydraulic actuator; 3. The hydraulic system of claim 2, wherein the first limiting unit acquires the priority information based on the operation of the second operating device, and changes the output limit so as to limit the output of the first hydraulic pump more when the second hydraulic actuator is being operated than when the second hydraulic actuator is not being operated.

8. The first limiting unit, when the drive of the second hydraulic actuator is being operated, acquires a drive state of the second hydraulic actuator, and is configured to limit the first hydraulic pump more when the output of the second hydraulic actuator is large than when the output of the second hydraulic actuator is small.

8. The hydraulic system for a work machine according to claim 7, wherein the output limit is changed so as to limit the output of the pump.

9. The hydraulic system for a work machine according to claim 2 , further comprising an operating tool that accepts an operation for the priority information.

10. the first hydraulic actuator drives a traveling device that supports a vehicle body and causes the vehicle body to travel; 10. The hydraulic system for a work machine according to claim 1, wherein the second hydraulic actuator drives a work device provided on the vehicle body.

11. a hydraulic system for a work machine according to claim 10; The vehicle body; The traveling device; The working device; A work machine equipped with the above.

12. The working device has a connecting device to which any one of a plurality of attachments can be attached or detached, The work machine according to claim 11, wherein the first limiting unit changes the output limit of the first hydraulic pump depending on the attachment attached to the connecting device.

13. the plurality of attachments include a first attachment driven by hydraulic oil discharged by the second hydraulic pump, 13. The work machine according to claim 12, wherein the first restriction unit changes the output restriction so as to restrict the output of the first hydraulic pump when the attachment attached to the coupling device is a first attachment requiring a large flow rate of hydraulic oil for driving, rather than when the first attachment is a first attachment requiring a small flow rate of hydraulic oil for driving.

14. the plurality of attachments include a first attachment that is driven by hydraulic oil discharged by the second hydraulic pump and a second attachment that is not driven by hydraulic oil discharged by the second hydraulic pump, 13. The work machine according to claim 12, wherein the first limiting unit changes the output limit so as to limit the output of the first hydraulic pump more when the attachment attached to the coupling device is the first attachment than when the attachment is the second attachment.

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