Hydraulic system for work equipment

Abstract

To improve accuracy of control of travel speed when a work machine is caused to travel at a speed slower than usual.SOLUTION: A hydraulic system for a work machine comprises: an engine; a traveling device driving the work machine; a traveling motor capable of transmitting power to the traveling device; a variable capacity traveling pump driven by power from the engine to supply hydraulic oil to the traveling motor; a first operation member for operating the traveling device; a second operation member for switching between a first mode for driving the work machine and a second mode for driving the work machine at a speed slower than that in the first mode; a control device for controlling drive of at least one of the engine and the traveling pump based on operation states of the first operation member and the second operation member; and an adjustment mechanism for adjusting an angle of a swash plate the traveling pump has. In the first mode, the control device controls drive of the engine based on the operation state of the first operation member, and in the second mode, the control device changes the angle of the swash plate of the traveling pump using the adjustment mechanism based on the operation state of the first operation member.SELECTED DRAWING: Figure 11

Description

[Technical field]

[0001] The present invention relates to a hydraulic system for a work machine such as a skid steer loader or a compact track loader, and to a work machine equipped with this hydraulic system. [Background technology]

[0002] Conventionally, there is known a work machine equipped with a load sensing system that controls the amount of hydraulic oil discharged from a hydraulic pump according to the work load. For example, the work machine disclosed in Patent Document 1 includes a first hydraulic pump that discharges pilot oil for switching a control valve that controls the operation of a hydraulic actuator, a second hydraulic pump that discharges hydraulic oil for operating the hydraulic actuator, a first oil passage through which the maximum load pressure during operation of the hydraulic actuator can act, a second oil passage through which the discharge pressure of the hydraulic oil from the second hydraulic pump can act, a third oil passage through which the pilot oil is discharged from the first hydraulic pump, and a hydraulic control unit that controls the second hydraulic pump.

[0003] The hydraulic control unit controls the amount of hydraulic oil discharged from the second hydraulic pump so that the differential pressure between the maximum load pressure acting on the first oil line and the discharge pressure of the second hydraulic pump acting on the second oil line is constant. The hydraulic control unit also controls the horsepower of the first hydraulic pump by controlling the amount of hydraulic oil discharged from the second hydraulic pump based on the differential pressure between the first pressure of the pilot oil taken out from the first outlet in the third oil line and the second pressure of the pilot oil taken out from the second outlet, thereby reducing horsepower loss. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-125560 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a hydraulic system for a work machine that can improve the accuracy of control of the travel speed when the work machine is traveled at a speed slower than normal. [Means for solving the problem]

[0006] The technical means of the present invention for solving the above technical problems are as follows. The hydraulic system of the working machine of the present invention comprises a prime mover, a traveling device for traveling the working machine, a traveling motor capable of transmitting power to the traveling device, a variable capacity traveling pump driven by power of the prime mover to supply hydraulic oil to the traveling motor, a first operating member for operating the traveling device, a second operating member for switching between a first mode for traveling the working machine and a second mode for traveling the working machine at a speed slower than the first mode, a control device for controlling the drive of at least one of the prime mover and the traveling pump based on the operating states of the first operating member and the second operating member, and an adjustment mechanism for adjusting the angle of a swash plate of the traveling pump, wherein in the first mode, the control device controls the drive of the prime mover based on the operating state of the first operating member, and in the second mode, changes the angle of the swash plate of the traveling pump by the adjustment mechanism based on the operating state of the first operating member.

[0007] In one aspect of the present invention, the hydraulic system of the work machine includes a hydraulic pump driven by power of the prime mover and discharging pilot oil for adjusting the angle of a swash plate of the travel pump, and an operating valve connected to an oil passage through which the pilot oil discharged from the hydraulic pump flows and applying a pilot pressure, which is the pressure of the pilot oil, to a pressure receiving section of the travel pump depending on an operating state of the first operating member, the adjustment mechanism having a pressure change unit that changes the pilot pressure acting on the operating valve, and the control device may change the pilot pressure using the pressure change unit based on the operating state of the first operating member.

[0008] In one aspect of the present invention, the adjustment mechanism may have an operating valve that applies a pilot pressure, which is the pressure of the pilot oil, to a pressure-receiving portion of the travel pump, and the control device may change the pilot pressure by controlling the opening of the operating valve based on the operating state of the first operating member.

[0009] In one aspect of the present invention, the adjustment mechanism includes an operating valve that applies a pilot pressure, which is the pressure of the pilot oil, to a pressure receiving portion of the travel pump in accordance with an operating state of the first operating member, and a pressure change unit that changes the pilot pressure acting on the pressure receiving portion of the travel pump from the operating valve, and the control device may change the pilot pressure using the pressure change unit based on the operating state of the first operating member.

[0010] In one aspect of the present invention, the adjustment mechanism includes a hydraulic regulator that changes the angle of a swash plate of the travel pump, and an operating valve that can be switched between a neutral position in which the pilot oil is not supplied, a first position in which the pilot oil is supplied in a first direction, and a second position in which the pilot oil is supplied in a second direction for the hydraulic regulator, and the control device may change the pilot pressure, which is the pressure of the pilot oil, by changing the operating state of the operating valve based on the operating state of the first operating member.

[0011] In one aspect of the present invention, the first operating member includes an accelerator member capable of setting the rotation speed of the prime mover in the first mode, and the control device may control the drive of the prime mover in the first mode to match the rotation speed of the prime mover to the rotation speed set by the accelerator member, and in the second mode, change the angle of the swash plate of the travel pump using the adjustment mechanism based on the operating state of the accelerator member to adjust the rotation speed of the travel motor and the travel speed of the travel device.

[0012] In one aspect of the present invention, the first operating member includes a speed adjusting member capable of adjusting the rotation speed of the traveling motor in the second mode, and the control device, in the second mode, changes the angle of the swash plate of the traveling pump using the adjustment mechanism based on the operation state of the speed adjusting member to adjust the rotation speed of the traveling motor and the traveling speed of the traveling device, and when the accelerator member is operated, changes the angle of the swash plate of the traveling pump using the adjustment mechanism based on the operation amount of the accelerator member to adjust the rotation speed of the traveling motor and the traveling speed of the traveling device so that they are faster than the rotation speed of the traveling motor and the traveling speed adjusted based on the operation state of the speed adjusting member.

[0013] In one aspect of the present invention, the first operating member includes a travel operating member capable of adjusting the rotation speed of the traveling motor in the first mode and the second mode, and the control device adjusts the rotation speed of the traveling motor and the traveling speed of the traveling device by changing the angle of the swash plate of the traveling pump using the adjustment mechanism in accordance with the amount of operation of the travel operating member in the first mode and the second mode, and may adjust the rotation speed of the traveling motor and the traveling speed of the traveling device in the second mode in accordance with the amount of operation of the travel operating member to be slower than the rotation speed of the traveling motor and the traveling speed of the traveling device in the first mode in accordance with the same amount of operation of the travel operating member.

[0014] In one aspect of the present invention, the first operating member includes an accelerator member capable of setting the rotation speed of the prime mover in the first mode, and a travel operation member capable of adjusting the rotation speed of the traveling motor in the first mode and the second mode, and the control device controls the drive of the prime mover in the first mode to match the rotation speed of the prime mover to the rotation speed set by the accelerator member, and in the second mode, changes the angle of the swash plate of the travel pump using the adjustment mechanism based on the operation amount of the travel operation member to adjust the rotation speed of the travel motor and the travel speed of the traveling device, and when the accelerator member is operated while the operation amount of the travel operation member is constant, changes the angle of the swash plate of the travel pump using the adjustment mechanism based on the operation amount of the accelerator member without changing the rotation speed of the prime mover, to adjust the rotation speed of the travel motor and the travel speed of the traveling device.

[0015] In one aspect of the present invention, the first operating member includes a first accelerator member and a second accelerator member capable of setting the rotation speed of the prime mover in the first mode, and a travel operation member capable of adjusting the rotation speed of the traveling motor in the first mode and the second mode, and the control device controls the drive of the prime mover in the first mode to match the rotation speed of the prime mover to the rotation speed set by either the first accelerator member or the second accelerator member, and in the second mode, when the operation amount of the first accelerator member is equal to or greater than a certain amount, sets an adjustment range of the rotation speed of the traveling motor and the traveling speed of the traveling device in accordance with the operation amount of the second accelerator member, and changes the angle of the swash plate of the traveling pump using the adjustment mechanism in accordance with the operation amount of the travel operation member to adjust the rotation speed of the traveling motor and the traveling speed of the traveling device within the set adjustment range.

[0016] In one aspect of the present invention, the first operating member includes the first accelerator member and the second accelerator member, and a speed adjustment member capable of adjusting the rotation speed of the traveling motor in the second mode, and the control device, in the second mode, changes the angle of the swash plate of the traveling pump using the adjustment mechanism based on the operation state of the speed adjustment member to adjust the rotation speed of the traveling motor and the traveling speed of the traveling device, and when the second accelerator member is operated when the operation amount of the first accelerator member is equal to or greater than a certain amount, changes the angle of the swash plate of the traveling pump using the adjustment mechanism to adjust the rotation speed of the traveling motor and the traveling speed of the traveling device based on the operation amount of the second accelerator member, and may adjust the rotation speed of the traveling motor and the traveling speed of the traveling device, which are different from the rotation speed of the traveling motor and the traveling speed of the traveling device adjusted based on the operation state of the speed adjustment member, based on the operation amount of the second accelerator member. Effect of the Invention

[0017] According to the present invention, it is possible to provide a hydraulic system for a work machine that can improve the accuracy of control of the travel speed when the work machine is caused to travel at a speed slower than normal. [Brief description of the drawings]

[0018] [Figure 1A] 1 is an overall view of a hydraulic system for a work system of a work machine according to a first embodiment. [Figure 1B] FIG. 2 is an enlarged view of the periphery of a hydraulic control unit in the first embodiment. [Figure 2A] FIG. 4 is a graph showing the relationship between the engine speed, the LS differential pressure, and the pump discharge amount in the first embodiment. [Figure 2B] FIG. 4 is a diagram showing, in a table form, the relationship among the engine speed, the LS differential pressure, and the pump discharge amount in the first embodiment. [Diagram 3] FIG. 5 is an overall view of a hydraulic system for a work train of a work machine according to a second embodiment. [Figure 4A] FIG. 11 is a graph showing the relationship between the engine speed, the LS differential pressure, and the pump discharge amount in the second embodiment. [Figure 4B]FIG. 11 is a diagram showing, in the form of a table, the relationship among the engine speed, the LS differential pressure, and the pump discharge amount in the second embodiment. [Diagram 5] FIG. 11 is a graph showing the relationship between the engine speed, the LS differential pressure, and the pump discharge amount in the third embodiment. [Figure 6] FIG. 11 is a diagram showing, in the form of a table, the relationship among the engine speed, the LS differential pressure, and the pump discharge amount in the third embodiment. [Figure 7A] FIG. 11 is a diagram showing a first modified example of a hydraulic control section. [Figure 7B] FIG. 13 is a diagram showing a second modified example of the hydraulic control section. [Figure 7C] FIG. 13 is a diagram showing a third modified example of the hydraulic control section. [Figure 8A] FIG. 13 is a diagram showing a fourth modified example of the hydraulic control section. [Figure 8B] FIG. 13 is a diagram showing a fifth modified example of the hydraulic control section. [Figure 9A] FIG. 13 is a diagram showing a sixth modified example of the hydraulic control section. [Figure 9B] FIG. 13 is a diagram showing a seventh modified example of the hydraulic control section. [Figure 9C] FIG. 13 is a diagram showing an eighth modified example of the hydraulic control section. [Figure 9D] FIG. 13 is a diagram showing a ninth modified example of the hydraulic control section. [Figure 10A] FIG. 13 is a diagram showing a main part of a hydraulic system for a working train of a working machine according to a fourth embodiment. [Figure 10B] FIG. 13 is a graph showing the relationship between the secondary pressure of the control valve and the operation amount of the operating member in the fourth embodiment. [Figure 10C] 13 is a graph showing another relationship between the secondary pressure of the control valve and the operation amount of the operating member according to the fourth embodiment. FIG. [Figure 11] FIG. 13 is an overall view of a hydraulic system for a traveling system of a work machine according to a fifth embodiment. [Figure 12A] FIG. 13 is a graph showing the relationship between the operation amount of an accelerator member and a primary traveling pressure in the fifth embodiment. [Figure 12B] FIG. 13 is a graph showing another relationship between the operation amount of the accelerator member and the primary traveling pressure in the fifth embodiment. [Figure 13]FIG. 13 is a diagram showing a main part of a hydraulic system for a traveling train of a work machine according to a sixth embodiment. [Figure 14A] FIG. 13 is a graph showing the relationship between the operation amount of a joystick and the secondary pressure for traveling in the sixth embodiment. [Figure 14B] 13 is a graph showing the relationship between the operation amount of a joystick and the discharge amount of a traveling pump. FIG. [Figure 14C] 11 is a graph showing the relationship between the operation amount of a joystick and the rotation speed of a traveling motor. FIG. [Figure 15] 13A and 13B are diagrams illustrating a modified example of the speed adjustment mechanism. [Figure 16A] FIG. 23 is a table showing the relationship between engine speed and LS differential pressure in the seventh embodiment. [Figure 16B] FIG. 23 is a table showing the relationship between the engine speed and the traveling primary pressure and secondary pressure in the seventh embodiment. [Figure 17] FIG. 23 is a diagram showing the relationship between the operation amount of the operating member, the engine speed, and the proportional valve current in the seventh embodiment. [Figure 18] FIG. 13 is an overall view of a hydraulic system for a traveling system of a work machine according to an eighth embodiment. [Figure 19] FIG. 23 is a graph showing the relationship between engine speed and primary traveling pressure in the eighth embodiment. [Figure 20A] FIG. 13 is a diagram showing a main part of a hydraulic system for a traveling train of a work machine according to a ninth embodiment. [Figure 20B] FIG. 13 is a diagram showing another example of the hydraulic system of the traveling system of the work machine according to the ninth embodiment. [Figure 21] FIG. 23 is a graph showing the relationship between the engine speed and a first correction coefficient in the tenth embodiment. [Figure 22] 4A and 4B are diagrams illustrating an example of a joystick operation direction and a command value. [Figure 23] FIG. 4 is a diagram showing the relationship between a command value and an operating current value. [Figure 24] FIG. 1 is a side view of a working machine according to an embodiment of the present invention. [Diagram 25] 1 is a side view showing an internal structure of a body of a work machine according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of a hydraulic system for a work machine and a work machine equipped with this hydraulic system according to the present invention will be described with reference to the drawings as appropriate. [Overall configuration of the work machine] FIG. 24 is a side view of the working machine 1 according to the embodiment of the present invention. The working machine 1 includes a machine body 2 and a carrier. The vehicle includes a bin 3, a working device 4, and a traveling device 5. In this embodiment, a compact track loader is shown as an example of the working machine 1, but the working machine according to the present invention is not limited to a compact track loader and may be, for example, a tractor, a skid steer loader, a backhoe, etc.

[0020] A cabin 3 is mounted on the machine body 2. A driver's seat 8 is provided inside the cabin 3. The front side of a driver seated in the driver's seat of the work machine 18 (the left side in FIG. 24) is the front, the rear side of the driver (the right side in FIG. 24) is the rear, the left side of the driver (the near side in FIG. 24) is the left side, and the right side of the driver (the far side in FIG. 24) is the right side. Fig. 25 is a side view showing the internal structure of the machine body 2 of the work machine 1. As shown in Fig. 25, the cabin 3 is connected to the machine body 2 by a connecting shaft 6 or the like, and is rotatable upward around the connecting shaft 6.

[0021] Hydraulic pumps P1, P2 and a prime mover 32 are mounted inside the aircraft body 2. The prime mover 32 is composed of an engine (diesel engine, gasoline engine) that is an internal combustion engine driven by petroleum-based fuel. As another example, the prime mover 32 may be composed of an electric motor driven by electricity. In this embodiment, the following description will be given assuming that the prime mover 32 is the engine 32.

[0022] 24, the working implement 4 is attached to the machine body 2. The working implement 4 has a boom 10, a working tool 11, a lift link 12, a control link 13, a boom cylinder 14, and a bucket cylinder 15. The boom 10 is provided on the right and left sides of the cabin 3 so as to be able to swing up and down. The work implement 11 is, for example, a bucket. The bucket 11 is provided on the tip (front end) of the boom 10 so as to be able to swing up and down. A lift link 12 and a control link 13 support the base (rear) of the boom 10.

[0023] The front portions of the left and right booms 10 are connected to each other by a connecting pipe of an irregular shape, and the base portions (rear portions) of the left and right booms 10 are connected to each other by a connecting pipe of a circular shape. The lift link 12, the control link 13, and the boom cylinder 14 are provided on the left and right sides of the machine body 2 so as to correspond to the left and right booms 10, respectively. The lift link 12 is provided vertically at the rear of the base of each boom 10. An upper portion of this lift link 12 is pivoted rotatably about a horizontal axis via a pivot shaft 16 (first pivot shaft) near the rear of the base of each boom 10. A lower portion of the lift link 12 is pivoted rotatably about a horizontal axis via a pivot shaft 17 (second pivot shaft) near the rear of the aircraft body 2. The second pivot shaft 17 is provided below the first pivot shaft 16.

[0024] An upper portion of the boom cylinder 14 is pivoted rotatably about a horizontal axis via a pivot shaft 18 (third pivot shaft). The third pivot shaft 18 is the base of each boom 10 and is provided at the front of the base. A lower portion of the boom cylinder 14 is pivoted rotatably about a horizontal axis via a pivot shaft 19 (fourth pivot shaft). The fourth pivot shaft 19 is provided below the third pivot shaft 18, toward the lower rear portion of the machine body 2.

[0025] The control link 13 is provided in front of the lift link 12. One end of the control link 13 is pivoted to be rotatable about a horizontal axis via a pivot shaft 20 (fifth pivot shaft). The fifth pivot shaft 20 is provided on the aircraft body 2 at a position corresponding to the front of the lift link 12. The other end of the control link 13 is pivoted to be rotatable about a horizontal axis via a pivot shaft 21 (sixth pivot shaft). The sixth pivot shaft 21 is provided on the boom 10 in front of and above the second pivot shaft 17.

[0026] As the boom cylinder 14 extends and retracts, the boom 10 swings up and down about the first pivot shaft 16 while the base of the boom 10 is supported by the lift link 12 and the control link 13, and the tip of the boom 10 moves up and down. The control link 13 swings up and down about the fifth pivot shaft 20 in conjunction with the up and down swing of the boom 10. The lift link 12 swings back and forth about the second pivot shaft 17 in conjunction with the up and down swing of the control link 13.

[0027] Instead of the bucket 11, another working tool can be attached to the front of the boom 10. The other working tool can be, for example, a spare attachment such as a hydraulic crusher, a hydraulic breaker, an angle broom, an earth auger, a pallet fork, a sweeper, a mower, or a snow blower. A hydraulic take-off (not shown) is provided at the front of the left boom 10. The hydraulic take-off connects a hydraulic actuator (not shown) equipped on the spare attachment to piping (not shown) such as a hydraulic pipe provided on the boom 10. The hydraulic take-off and the hydraulic actuator of the spare attachment are connected by a separate hydraulic pipe. The hydraulic oil supplied to the hydraulic take-off passes through this separate hydraulic pipe and is supplied to the hydraulic actuator.

[0028] The bucket cylinders 15 are disposed near the front of each boom 10. By extending and contracting the bucket cylinders 15, the bucket 11 swings up and down. The traveling devices 5 are provided on the outside of the machine body 2. In this embodiment, the left and right traveling devices 5 are each made of a crawler type (including a semi-crawler type) traveling device. Note that instead of the traveling devices 5, a wheel type traveling device having front and rear wheels may be used. The boom 10 swings up and down as the boom cylinder 14 expands and contracts, and the bucket 11 swings up and down as the bucket cylinder 15 expands and contracts.

[0029] [First embodiment] FIG. 1A is a diagram showing a hydraulic system 30A of a work system of a work machine 1 of a first embodiment. 1A, the hydraulic system 30A includes a first hydraulic pump P1 and a second hydraulic pump P2. The first hydraulic pump P1 is a hydraulic pump driven by the power of the engine 32. The first hydraulic pump P1 is capable of discharging hydraulic oil stored in the hydraulic oil tank 22. The first hydraulic pump P1 is configured by a fixed displacement gear pump whose discharge flow rate varies according to the rotation speed of the engine 32.

[0030] The second hydraulic pump P2 is a pump driven by the power of the engine 32 and is a hydraulic pump installed at a position different from that of the first hydraulic pump P1. The second hydraulic pump P2 is configured as a swash plate type variable displacement axial pump. The second hydraulic pump P2 is capable of discharging hydraulic oil stored in the hydraulic oil tank 22. The second hydraulic pump P2 discharges hydraulic oil for operating hydraulic actuators (such as the boom cylinder 14, the bucket cylinder 15, the hydraulic actuators provided on the auxiliary attachment, and the hydraulic actuators provided on the traveling device 5) for performing work on the work machine 1. The first hydraulic pump P1 discharges pilot oil for switching control valves (such as the control valve 56 in FIG. 1) that control the operation of hydraulic equipment (such as hydraulic valves and hydraulic actuators) provided on the work machine 1.

[0031] The hydraulic system 30A is a hydraulic system that operates the boom 10, bucket 11, auxiliary attachment, etc., and includes a plurality of control valves 56. The plurality of control valves 56 are provided in an oil passage 39 that is connected to a discharge port of the second hydraulic pump P2. The plurality of control valves 56 are a boom control valve 56A, a bucket control valve 56B, and an auxiliary control valve 56C. The boom control valve 56A is a valve for controlling the operation of the boom cylinder 14. The bucket control valve 56B is a valve for controlling the operation of the bucket cylinder 15. The auxiliary control valve 56C is a valve for controlling the operation of a hydraulic actuator provided in the auxiliary attachment.

[0032] The boom 10 and the bucket 11 can be operated by an operating member 58, such as a lever type, provided around the driver's seat 8. The operating member 58 is included in the operating device (work operating device) 52. The operating member 58 is supported so as to be tiltable from a neutral position in the forward, backward, left, right, left diagonally forward, left diagonally rearward, right diagonally forward, and right diagonally rearward directions. By tilting the operating member 58 in any direction, a plurality of operating valves 59 (operating valve 59A, operating valve 59B, operating valve 59C, operating valve 59D) provided at the bottom of the operating member 58 can be operated. The plurality of operating valves 59 are connected to an oil passage (third oil passage) 40 connected to the first hydraulic pump P1, and hydraulic oil from the first hydraulic pump P1 can be supplied to the operating valves 59.

[0033] When the operating member 58 is tilted forward, the lowering operating valve 59A is operated and a pilot pressure is output from the lowering operating valve 59A. This pilot pressure acts on the pressure receiving portion of the boom control valve 56A, causing the boom 10 to lower. When the operating member 58 is tilted rearward, the lifting operating valve 59B is operated and a pilot pressure is output from the lifting operating valve 59B. This pilot pressure acts on the pressure receiving portion of the boom control valve 56A, causing the boom 10 to lift.

[0034] When operating member 58 is tilted to the right, operating valve 59C for bucket dump is operated and pilot oil acts on the pressure receiving portion of bucket control valve 56B. As a result, bucket control valve 56B operates in a direction that extends bucket cylinder 15, and bucket 11 is dumped at a speed proportional to the amount of tilt of operating member 58.

[0035] When operating member 58 is tilted to the left, operating valve 59D for the bucket scoop is operated, and pilot oil acts on the pressure receiving portion of bucket control valve 56B. As a result, bucket control valve 56B operates in a direction to contract bucket cylinder 15, and bucket 11 performs a scooping operation at a speed proportional to the amount of tilt of operating member 58.

[0036] The auxiliary attachment can be operated using an operation switch 24 provided around the driver's seat 8. The operation switch 24 is configured, for example, as a seesaw-type switch that can be swung freely, a slide-type switch that can be slid freely, or a push-type switch that can be pressed freely. An electric signal corresponding to the operation of the operation switch 24 is input to the control device 25.

[0037] The control device 25 is composed of semiconductors such as a CPU, an MPU, or a memory, and electric and electronic circuits. The control device 25 outputs a command (electrical signal) according to the amount of operation of the operation switch 24 to the first solenoid valve 60A and the second solenoid valve 60B. The first solenoid valve 60A and the second solenoid valve 60B open in response to the command output from the control device 25, i.e., in response to the amount of operation of the switch 24. As a result, pilot oil is supplied to the spare control valve 56C connected to the first solenoid valve 60A and the second solenoid valve 60B, and the spare actuator of the spare attachment is operated by the hydraulic oil supplied from the spare control valve 56C.

[0038] The hydraulic system 30A is equipped with a load sensing system that controls the discharge amount of the second hydraulic pump P2 in accordance with the work performed by the work machine 1. The load sensing system is equipped with a first oil passage 70, a second oil passage 71, and a hydraulic control unit 75. The hydraulic control unit 75 includes a flow compensation valve 72, a swash plate variable unit 73, an opening degree change unit 76, and a solenoid valve 81.

[0039] The first oil passage 70 (also referred to as the "PLS oil passage") is connected to each of the control valves 56A, 56B, 56C and the flow compensation valve 72. The first oil passage 70 is an oil passage for detecting the load pressure, which is the pressure of the hydraulic oil applied to each of the control valves 56A, 56B, 56C when each of the control valves 56A, 56B, 56C is in operation. The first oil passage 70 transmits the PLS signal pressure, which is the maximum load pressure among the load pressures of each of the control valves 56A, 56B, 56C, to the flow compensation valve 72. In other words, the maximum load pressure during operation of the hydraulic actuators 14, 15, etc. can act on the first oil passage 70.

[0040] The second oil passage 71 (also referred to as the "PPS oil passage") is connected to the discharge port of the second hydraulic pump P2 and a flow compensation valve 72. The second oil passage 71 transmits a PPS signal pressure, which is the pressure (discharge pressure) of the hydraulic oil discharged from the second hydraulic pump P2, to the flow compensation valve 72. That is, the discharge pressure of the hydraulic oil from the second hydraulic pump P2 can act on the second oil passage 71. The second hydraulic pump P2 discharges hydraulic oil to the oil passages 71 and 39 depending on the opening states of the spools of the control valves 56A, 56B, and 56C.

[0041] FIG. 1B is an enlarged view of the periphery of a hydraulic control unit 75 of the hydraulic system 30A. The swash plate variable part 73 is composed of, for example, a hydraulic cylinder. The swash plate variable part 73 has a piston 73A, a housing part 73B that houses the piston 73A, and a rod (moving part) 73C connected to the piston 73A. One end of the rod 73C is connected to the piston 73A, and the other end of the rod 73C is connected to the swash plate of the second hydraulic pump P2. When hydraulic oil is supplied from the flow compensation valve 72 into the housing part 73B on the bottom side of the swash plate variable part 73, the piston 73A moves, the rod 73C expands and contracts, and the angle of the swash plate of the second hydraulic pump P2 can be changed. That is, the swash plate variable part 73 changes the angle of the swash plate of the second hydraulic pump P2. The hydraulic oil supplied into the housing part 73B is discharged to the tank 22 from an oil passage (not shown) connected to, for example, the top side of the housing part 73 (the rod 73C side with respect to the piston 73A).

[0042] The flow rate compensation valve 72 is a control valve, and is connected to the first oil passage 70 and the second oil passage 71. The flow rate compensation valve 72 is a control valve that can control the operation of the swash plate control unit 73 based on the PLS signal pressure and the PPS signal pressure. The flow rate compensation valve 72 sets the opening of the supply port of hydraulic oil to the swash plate control unit 73 so as to keep the LS differential pressure (=PPS signal pressure-PLS signal pressure), which is the pressure difference between the PPS signal pressure and the PLS signal pressure, constant. The flow rate compensation valve 72 supplies hydraulic oil to the swash plate control unit 73 according to the set opening to apply hydraulic pressure, thereby moving a piston 73A of the swash plate control unit 73 and extending or retracting a rod 73C.

[0043] According to the load sensing system as described above, the angle of the swash plate of the second hydraulic pump P2 is changed by the flow compensation valve 72 and the swash plate control unit 73, etc., so that the LS differential pressure, which is the pressure difference between the PPS signal pressure and the PLS signal pressure, is constant, and the amount of hydraulic oil discharged from the second hydraulic pump P2 is adjusted. The hydraulic system 30A is equipped with a horsepower control circuit. The horsepower control circuit includes a hydraulic control unit 75. The hydraulic control unit 75 is also operated by the pilot oil discharged from the first hydraulic pump P1, and controls the second hydraulic pump P2 so as to keep the LS differential pressure constant.

[0044] Pilot oil discharged from the first hydraulic pump P1 flows through the third oil passage 40. A solenoid valve 81 is provided in a fourth oil passage 41 branching off from the third oil passage 40. The solenoid valve 81 is configured, for example, as a solenoid proportional valve, a pilot check valve, or a variable relief valve. In the example of FIG. 1, the solenoid valve 81 is configured as a solenoid proportional valve. The opening degree of the solenoid valve 81 can be arbitrarily changed by exciting a solenoid or the like provided in the solenoid valve 81. The operation of the variable solenoid valve 81 (change in opening degree) is electrically controlled by the control device 25.

[0045] A filter 49 is provided in a midway portion of the third oil passage 40 on the upstream side (first hydraulic pump P1 side) of the fourth oil passage 41. A relief valve (reference number omitted) is provided in an oil passage (reference number omitted) that branches from a portion of the third oil passage 40 on the upstream side of the filter 49 and leads to the tank 22.

[0046] The pilot oil discharged from the first hydraulic pump P1 to the third oil passage 40 flows through the filter 49, the fourth oil passage 41, and the solenoid valve 81 to the opening degree change unit 76. The solenoid valve 81 controls the flow rate of the pilot oil that reaches the opening degree change unit 76 through the fourth oil passage 41 by changing the opening degree. This changes the opening of the solenoid valve 81 to adjust the pilot pressure applied to the opening change unit 76. More specifically, as the opening of the solenoid valve 81 decreases, the flow rate of pilot oil flowing to the opening change unit 76 decreases, and the pilot pressure acting on the opening change unit 76 increases. The filter 49 also increases the pilot pressure acting on the opening change unit 76 from the oil passages 40, 41.

[0047] In this way, the solenoid valve 81 adjusts the pilot pressure of the pilot oil that operates the opening change unit 76. In addition, by changing the opening of the solenoid valve 81, a pilot differential pressure (pressure difference of pilot oil; PA-Pi) is generated between a first pressure Pi of the pilot oil flowing into the solenoid valve 81 and a second pressure PA of the pilot oil flowing out of the solenoid valve 81, among the pilot oil flowing through the fourth oil passage 41, and the pilot differential pressure changes.

[0048] The opening degree changing unit 76 is composed of, for example, a hydraulic cylinder. The opening degree changing unit 76 has a piston 76A, a housing portion 76B that houses the piston 76A, and a rod 76C connected to the piston 76A. One end of the rod 76C is connected to the piston 76A, and the other end of the rod 76C is connected to the flow compensation valve 72. The fourth oil passage 41 is connected to the bottom side of the housing portion 76B (the side opposite to the rod 76C).

[0049] The piston 76A moves in the housing portion 76B due to the pilot pressure (second pressure PA) of the pilot oil flowing from the fourth oil passage 41 into the bottom side (opposite side to the rod 76C) of the housing portion 76B. In detail, when the pilot pressure of the pilot oil flowing from the fourth oil passage 41 into the housing portion 76B becomes small, the piston 76A moves in a direction to contract the rod 76C (direction away from the flow compensation valve 72). When the pilot pressure of the pilot oil flowing from the fourth oil passage 41 into the housing portion 76B becomes large, the piston 76A moves in a direction to extend the rod 76C (direction approaching the flow compensation valve 72). The extension and contraction of the rod 76C changes the opening of the flow compensation valve 72. That is, the opening change unit 76 operates according to the pilot pressure adjusted by the solenoid valve 81 to change the opening of the flow compensation valve 72. The pilot oil in the accommodation portion 76B of the opening degree changing portion 76 is discharged from a discharge oil passage 41A connected to the rod 76C side of the accommodation portion 76B.

[0050] The flow rate compensation valve 72 has its opening set so that the LS differential pressure, which is the pressure difference between the PLS signal pressure and the PPS signal pressure, is constant, and its opening is also changed in response to the movement of a piston 76A of an opening changer 76. By changing the opening of the flow rate compensation valve 72, the flow rate and pressure of the hydraulic oil supplied from the flow rate compensation valve 72 to the swash plate control unit 73 are also changed.

[0051] When the opening degree changing unit 76 is not in operation, a spool (not shown) built into the flow compensation valve (control valve) 72 is biased in a predetermined direction by a spring 72A, and the opening degree of the flow compensation valve 72 is set so that the LS differential pressure is constant. When the opening degree changing unit 76 is operated and the rod 76C expands and contracts, the spool of the flow compensation valve 72 moves against the elastic force of the spring 72A, and the opening degree of the flow compensation valve 72 is changed. As a result, the flow rate and pressure of the hydraulic oil supplied from the flow compensation valve 72 to the swash plate control unit 73 are changed, and in response to the change, the piston 73A of the swash plate control unit 73 moves, the rod 73C expands and contracts, and the angle of the swash plate of the second hydraulic pump P2 is changed.

[0052] 1A also controls the hydraulic control section 75 and the second hydraulic pump P2 by controlling the operation of the solenoid valve 81, and changes the LS differential pressure kept constant by the flow rate compensation valve 72. The change in the LS differential pressure will be described in detail below.

[0053] A first measuring device 82 that measures the rotation speed of the engine 32 is connected to the control device 25. Hereinafter, the rotation speed of the engine 32 will be simply referred to as the "engine rotation speed", and the measurement value of the first measuring device 82 will be referred to as the actual rotation speed. A control signal (current signal) is output to the solenoid valve 81 according to the rotation speed (actual rotation speed) to control the opening of the solenoid valve 81. A pilot pressure (second pressure PA) acting on the opening change unit 76 is changed according to the opening of the solenoid valve 81, and the opening of the flow rate compensation valve 72 is changed by the opening change unit 76. Then, according to the change in the opening of the flow rate compensation valve 72, the pressure of the hydraulic oil acting on the swash plate variable unit 73 from the flow rate compensation valve 72 is changed, and the angle of the swash plate of the second hydraulic pump P2 is changed by the swash plate variable unit 73, and the flow rate of the hydraulic oil discharged by the second hydraulic pump P2 is changed. As a result, the LS differential pressure, which is the differential pressure (pressure difference) between the PLS signal pressure acting on the first oil passage 70 and the PPS signal pressure acting on the second oil passage 71, is changed. The changed LS differential pressure is kept constant by the flow rate compensation valve 72 and the like.

[0054] Fig. 2A is a graph showing the relationship between the engine speed, LS differential pressure, and pump discharge volume of the work machine 1. Fig. 2B is a table showing the same relationship as Fig. 2A. In Figs. 2A and 2B, the pump discharge volume refers to the discharge volume of hydraulic oil from the second hydraulic pump P2 when the opening area of ​​the spool of the control valve 56 (boom control valve 56A, bucket control valve 56B, auxiliary control valve 56C) is kept constant (maximum).

[0055] The relationship among the engine speed, the LS differential pressure, and the pump discharge amount shown in Fig. 2A and Fig. 2B is derived based on, for example, the results of experiments or simulations performed in advance. Data indicating the relationship is stored in the storage unit 26 provided in the control device 25. The data indicating the relationship may be, for example, graph data as shown in Fig. 2A, table data as shown in Fig. 2B, or function data for calculating the LS differential pressure from the actual speed of the engine 32. That is, the relationship among the engine speed, the LS differential pressure, and the pump discharge amount may be in any format as long as the data is capable of calculating the corresponding LS differential pressure from the actual speed of the engine 32. Hereinafter, for convenience of explanation, the relationship among the engine speed, the LS differential pressure, and the pump discharge amount shown in Fig. 2A and Fig. 2B is referred to as a control map.

[0056] The control line L1 shown by a dashed line in Fig. 2A represents the change in the LS differential pressure according to the engine speed, and corresponds to the one-to-one relationship between the engine speed and the LS differential pressure shown in Fig. 2B. Moreover, the thick solid line shown in Fig. 2A represents the change in the pump discharge rate according to the engine speed, and corresponds to the one-to-one relationship between the engine speed and the pump discharge rate shown in Fig. 2B.

[0057] The first control line L1 in the control map of Fig. 2A or the first and second columns from the left in the control map of Fig. 2B show the change in the LS differential pressure when the engine speed changes from the idling speed (1200 rpm) to the maximum speed (2600 rpm). Note that idling refers to a state in which the engine speed is suppressed to a low level in the work machine 1. In the first control line L1 in Fig. 2A and Fig. 2B, the LS differential pressure also increases as the engine speed increases.

[0058] When the control device 25 acquires the actual rotation speed of the engine 32 measured by the first measuring device 82 from the first measuring device 82, the control device 25 sets the LS differential pressure corresponding to the actual rotation speed based on the control map of FIG. 2A or FIG. 2B. Then, the control device 25 outputs a control signal corresponding to the set LS differential pressure to the solenoid valve 81, and changes the opening of the solenoid valve 81. The control signal corresponding to the LS differential pressure set by the control device 25 may be generated by the control device 25 based on an arithmetic expression or control data previously stored in the storage unit 26. When the opening of the solenoid valve 81 is changed according to the control signal from the control device 25 as described above, the pilot pressure (second pressure PA) acting on the opening change unit 76 is changed, and the second hydraulic pump P2 is controlled by the opening change unit 76, the flow rate compensation valve 72, and the swash plate variable unit 73, to realize the LS differential pressure corresponding to the control signal. That is, the control device 25 changes the LS differential pressure by the hydraulic control unit 75 based on the actual rotation speed of the engine 32 measured by the first measuring device 82.

[0059] By changing the LS differential pressure in this manner, the angle of the swash plate of the second hydraulic pump P2 is changed, and the amount of hydraulic oil discharged from the second hydraulic pump P2 is adjusted. That is, the output of the second hydraulic pump P2 is adjusted in conjunction with the drive of the engine 32 of the work machine 1. This makes it possible to improve the accuracy of horsepower control of the work system of the work machine 1, and maximize the output of the second hydraulic pump P2 within the controllable horsepower range.

[0060] Furthermore, the control device 25 controls the opening of the solenoid valve 81, thereby changing the pilot pressure (second pressure PA) acting on the opening change unit 76, and the LS differential pressure is changed by the opening change unit 76 and the swash plate variable unit 73, thereby adjusting the output of the second hydraulic pump P2. This increases the degree of freedom in adjusting the output of the second hydraulic pump P2, and can further improve the accuracy of horsepower control of the work system of the work machine 1.

[0061] As another example, the control device 25 may change the LS differential pressure based on the actual rotation speed and the target engine rotation speed of the engine 32. The target engine rotation speed can be set by operating the accelerator member 84 (FIG. 1).

[0062] The accelerator member 84 includes a first accelerator member 84a and a second accelerator member 84b. The accelerator members 84a and 84b are provided near the driver's seat 8 and connected to the control device 25. The first accelerator member 84a is a dial-type operating member having a rotatable knob. The driver (operator) can set a target engine speed by gripping and turning the knob of the first accelerator member 84a. The second accelerator member 84b is a pedal-type operating member having a swingable depression portion. The driver can also set a target engine speed by depressing the depression portion of the second accelerator member 84b.

[0063] The operation amount of the accelerator members 84a, 84b is detected by, for example, a potentiometer or the like, and input to the control device 25. The control device 25 adopts the larger of the target engine speed set by the first accelerator member 84a (referred to as the first target engine speed) and the target engine speed set by the second accelerator member 84b (referred to as the second target engine speed). For example, when the first target engine speed is 1300 rpm and the second target engine speed is 2200 rpm, the control device 25 sets the second target engine speed set by the second accelerator member 84b as the target engine speed EP2, and controls the driving of the engine 32 based on the target engine speed EP2.

[0064] At this time, when the actual rotation speed EP1 of the engine 32 measured by the first measuring device 82 is equal to or higher than the target engine rotation speed EP2 (actual rotation speed EP1≧target engine rotation speed EP2), the control device 25 sets the LS differential pressure based on the first control line L1 in FIG. 2A and the actual rotation speed EP1, and outputs a control signal according to the LS differential pressure to the solenoid valve 81. In other words, when the actual rotation speed EP1 of the engine 32 is equal to or higher than the target engine rotation speed EP2, the control device 25 changes the LS differential pressure according to the actual rotation speed EP1 of the engine 32.

[0065] On the other hand, when the actual rotation speed EP1 of the engine 32 measured by the first measuring device 82 is lower than the target engine rotation speed EP2 (actual rotation speed EP1<target engine rotation speed EP2), or when the actual rotation speed EP1 is lower than the rotation speed obtained by subtracting a predetermined value A1 from the target engine rotation speed EP2 (actual rotation speed EP1<target engine rotation speed EP2-predetermined value A1, for example, A1=100 rpm), the control device 25 calculates a second control line L2 by shifting the first control line L1 in a direction in which the LS differential pressure decreases, as shown in FIG. 2A. Then, the control device 25 sets the LS differential pressure based on the second control line L2 and the actual rotation speed EP1, and outputs a control signal according to the LS differential pressure to the solenoid valve 81. That is, when the actual rotation speed EP1 of the engine 32 falls below the target engine rotation speed EP2, the control device 25 reduces the LS differential pressure. Note that the pump discharge amount shown by the thick solid line in FIG. 2A corresponds to the first control line L1, and does not correspond to the second control line L2.

[0066] The control device 25 calculates the second control line L2 based on, for example, the following formula (1). Second control line L2 = First control line L1 x e 2 [Constant × maximum load factor (load factor - constant, 0)]...(1)

[0067] In formula (1), the "load rate" is the load rate of the engine 32, and the "maximum load rate" is the maximum load rate of the engine 32. The load rate of the engine 32 is the ratio (proportion) of the output of the engine 32 when the equipment mounted on the work implement 1 (the work implement 4 or the travelling device 5) is operating (operating load state) to the output of the engine 32 when the equipment is not operating (unloaded state). The output of the engine 32 is the amount of work obtained by multiplying the torque of the engine 32 by the rotation speed of the engine 32 (unit: kW or PS (horsepower)). The torque of the engine 32 is detected by a torque sensor (not shown). When the "load rate-constant" in formula (1) is a negative value, the value of the "maximum load rate (load rate-constant)" is set to zero.

[0068] For example, when the hydraulic actuators of the working implement 4 (the boom cylinder 14, the bucket cylinder 15, and the hydraulic actuators of the auxiliary attachment) and the traveling implement 5 are stopped, the control device 25 determines that the engine 32 is in an unloaded state. Then, the control device 25 calculates the output of the engine 32 at this time and records the calculated value as the output of the engine 32 in the unloaded state. The control device 25 may calculate and record this output of the engine 32 in the unloaded state at a predetermined cycle. As another example, the output of the engine 32 in the unloaded state may be set in advance and stored in the memory unit 26.

[0069] Furthermore, when at least one of the hydraulic actuator of the working device 4 and the traveling device 5 is operated, the control device 25 determines that the engine 32 is in an operating load state. The control device 25 then calculates the output of the engine 32 at a predetermined cycle, and sets the calculated value as the output of the engine 32 in the operating load state. Furthermore, each time the control device 25 calculates the output of the engine 32 in the operating load state, it calculates the ratio of the output of the engine 32 in the operating load state to the output of the engine 32 in the no-load state that has already been recorded, as the load factor of the engine 32, and records the load factor. Furthermore, the control device 25 detects the maximum load factor among the recorded load factors of the engine 32.

[0070] As another example, the control device 25 may calculate the second control line L2 based on the following equation (2). Second control line L2 = First control line L1 x e 2 -(α × ΔE ) (2) In formula (2), "ΔE" is the difference between the target engine speed and the actual engine speed (speed difference ΔE = target engine speed EP2 - actual engine speed EP1). "α" is a coefficient that changes depending on whether the work machine 1 is in a traveling priority mode in which traveling is prioritized, or a work priority mode in which work by the work machine 1 is prioritized. The coefficient α in the work priority mode is smaller than the coefficient α in the traveling priority mode. The traveling priority mode and the work priority mode can be switched between by operating a switch or the like provided around the driver's seat. In addition, between the traveling priority mode and the work priority mode, a slight traveling priority mode in which traveling is slightly prioritized over work, and a slight work priority mode in which work is slightly prioritized over traveling may be provided, and the coefficient α may be changed for each of these four modes.

[0071] As another example, when the actual rotation speed of the engine 32 is slightly decreased (e.g., less than a few revolutions) from the target engine rotation speed, the control device 25 may calculate the second control line L2 by adopting the following formula (3) or formula (4) instead of the above formula (2). Second control line L2 = First control line L1 x e 2 -(α × ΔE 2 ) · · · (3) Second control line L2 = First control line L1 x e 2 -{α × maximum load factor (ΔE-constant, 0)) (4)

[0072] In the above example, when the actual rotation speed of the engine 32 falls below the target engine rotation speed, the control device 25 calculates the second control line L2 by shifting the first control line L1 in the direction of decreasing the LS differential pressure. However, instead, the second control line L2 may be set in advance and stored in the memory unit 26.

[0073] As described above, when the actual rotation speed of the engine 32 falls below the target engine rotation speed, the control device 25 changes the LS differential pressure based on the second control line L2 and the actual rotation speed, so that even if some load is applied to the engine 32 and the actual rotation speed falls, the amount of hydraulic oil discharged from the second hydraulic pump P2 can be reduced in accordance with the load. Also, the control device 25 calculates the second control line L2 in accordance with the load or rotation speed of the engine 32, so that the amount of hydraulic oil discharged from the second hydraulic pump P2 can be reduced in accordance with the load of the engine 32. As a result of these, it is possible to improve the accuracy of the horsepower control of the working system of the working machine 1.

[0074] As another example, the control device 25 may change the LS differential pressure based on the difference between the target engine speed and the actual speed (speed difference ΔE). In this case, the control device 25 first obtains the speed difference (ΔE) between the target engine speed set by the accelerator member 84 and the actual speed measured by the first measuring device 82. Next, the control device 25 shifts the first control line L1 in a direction in which the LS differential pressure decreases according to the speed difference ΔE. At this time, the control device 25 increases the shift amount of the first control line L1 as the speed difference ΔE increases. In addition, the control device 25 multiplies a predetermined constant A (pressure, unit: MPa) by the speed difference ΔE to obtain the shift amount (shift amount=A×ΔE). Next, the control device 25 calculates the second control line L2 by shifting the first control line L1 by the obtained shift amount in a direction in which the LS differential pressure decreases. The control device 25 then sets the LS differential pressure based on the second control line L2 and the actual rotation speed of the engine 32, and outputs to the solenoid valve 81 a control signal corresponding to the LS differential pressure.

[0075] According to the above, even if the actual engine speed falls below the target engine speed due to the load on the engine 32, the amount of hydraulic oil discharged from the second hydraulic pump P2 can be reduced according to the amount of fall (difference in speed ΔE). As a result, it is possible to accurately control the horsepower of the work system of the work machine 1 according to the load on the engine 32. As another example, the second control line L2 corresponding to each shift amount may be set in advance and stored in the storage unit .

[0076] Furthermore, the control device 25 may change the LS differential pressure based on the amount of fuel injected into the engine 32. In this case, the control device 25 calculates the amount of fuel injected from an injector (not shown) when controlling the operation of the engine 32. The calculation of the injection amount is performed based on various conditions such as the target engine speed, the actual speed, or the crank angle input to the control device 25, but the specific calculation method is similar to that of known techniques and therefore will not be described. Note that, in the case where the engine 32 is a diesel engine, the fuel injection amount refers to the amount of fuel injected (main injection amount) for generating the output of the engine 32, and is not a post-injection amount for performing DPF regeneration (particle combustion) or the like.

[0077] After calculating the fuel injection amount, the control device 25 judges whether the injection amount is greater than a predetermined injection threshold. The injection threshold is set to a value greater than a standard injection amount determined according to the engine speed. When the calculated fuel injection amount is greater than the injection threshold, the control device 25 shifts the first control line L1 in a direction that decreases the LS differential pressure to calculate the second control line L2. The control device 25 then sets the LS differential pressure based on the second control line L2 and the actual speed of the engine 32, and outputs a control signal according to the LS differential pressure to the solenoid valve 81. In this way, even if the load on the engine 32 is large and the fuel injection amount becomes greater than the injection threshold, The amount of hydraulic oil discharged from the second hydraulic pump P2 can be reduced. As a result, the horsepower of the work system of the work machine 1 can be controlled with high accuracy in accordance with the load on the engine 32.

[0078] The solenoid valve 81 may change the LS differential pressure based on the load factor of the engine 32. In this case, the control device 25 calculates the load factor of the engine 32 as described above, and determines whether the load factor is greater than a predetermined threshold value. Here, when the load factor of the engine 32 is greater than the threshold value, the control device 25 shifts the first control line L1 in a direction in which the LS differential pressure decreases to calculate the second control line L2. Then, the control device 25 sets the LS differential pressure based on the second control line L2 and the actual rotation speed of the engine 32, and outputs a control signal according to the LS differential pressure to the solenoid valve 81. According to this, even if the load of the engine 32 is large and the load factor increases, the discharge amount of the hydraulic oil from the second hydraulic pump P2 can be reduced. As a result, it is possible to perform horsepower control with high accuracy according to the load of the engine 32.

[0079] Furthermore, as the temperature of at least one of the hydraulic oil (including pilot oil) provided in the work machine 1, the cooling water for cooling various devices mounted on the work machine 1, and the engine oil in the engine 32 increases, the control device 25 may increase the shift amount of the first control line L1 to calculate the second control line L2. Then, the control device 25 may set an LS differential pressure based on the second control line L2 and the actual rotation speed of the engine 32, and realize the LS differential pressure by the hydraulic control unit 75.

[0080] The control device 25 may change the LS differential pressure based on the temperature of at least one of the hydraulic oil, the cooling water, and the engine oil provided in the work machine 1. A second measuring device 83 (FIG. 1) that measures the temperature of the fluid flowing through a flow path provided in the work machine 1 is connected to the control device 25. The second measuring device 83 measures the temperature of at least one of the hydraulic oil flowing through an oil path provided in the work machine 1, the cooling water for cooling devices such as the engine 32 flowing through a water path, and the engine oil flowing through an oil path provided in the engine 32. When the control device 25 acquires the temperature of the fluid measured by the second measuring device 83, it executes at least one of a first determination for determining whether or not the temperature of the fluid is equal to or lower than a corresponding predetermined lower threshold value, and a second determination for determining whether or not the temperature of the fluid is equal to or higher than a corresponding predetermined upper threshold value.

[0081] The above lower limit threshold and upper limit threshold are predetermined temperatures of the fluid that are set to determine whether the heat balance of the work machine 1 is good or not based on the temperature of the fluid. For example, when the temperature of the hydraulic oil or the engine oil is -20°C or lower, the control device 25 determines that the heat balance is not good because the viscosity of the hydraulic oil or the engine oil is high. Also, when the temperature of the hydraulic oil or the engine oil is 60°C or higher, the control device 25 determines that the heat balance is not good.

[0082] As described above, the control device 25 acquires the temperature of the fluid (at least one of the hydraulic oil, the cooling water, and the engine oil) measured by the second measuring device 83, compares the temperature of the fluid with the upper threshold or the lower threshold, and judges whether the heat balance of the working machine 1 is good or not based on the comparison result. If the heat balance is not good, that is, if the temperature of the fluid is equal to or lower than the lower threshold, or if the temperature of the fluid is equal to or higher than the upper threshold, the control device 25 shifts the first control line L1 in a direction in which the LS differential pressure decreases, and calculates the second control line L2. At this time, the control device 25 may calculate the second control line L2 by increasing the shift amount of the first control line L1 as the difference between the temperature of the fluid and the upper threshold or the lower threshold increases. After calculating the second control line L2, the control device 25 sets the LS differential pressure based on the second control line L2 and the actual rotation speed of the engine 32, and outputs a control signal according to the LS differential pressure to the solenoid valve 81 to realize the LS differential pressure.

[0083] According to the above, it is possible to reduce the amount of hydraulic oil discharged from the second hydraulic pump P2 when the heat balance of the work machine 1 is not good. As a result, it is possible to accurately control the horsepower of the work system of the work machine 1 according to the load of the engine 32, and it is also possible to induce the work machine 1 to have a good heat balance.

[0084] [Second embodiment] 3 is a diagram showing a hydraulic system 30B of a work machine 1 according to a second embodiment. In the second embodiment, a description of the same configuration as in the first embodiment will be omitted. In a hydraulic system 30B of a second embodiment shown in FIG. 3, a command member 88 that commands a change in the LS differential pressure is connected to the control device 25. The command member 88 is an operation switch provided near the driver's seat 8. When the command member 88 is turned on, an electric signal that commands a change in the LS differential pressure is issued from an electric circuit that links with the command member 88, and the electric signal (hereinafter simply referred to as a "change command") is input to the control device 25. When the command member 88 is not turned on, that is, when it is in an off operation state, a command to change the LS differential pressure is not issued, and the change command is not input to the control device 25.

[0085] Fig. 4A is a graph showing the relationship between the engine speed, the LS differential pressure, and the pump discharge rate in accordance with the presence or absence of a command to change the LS differential pressure in the work machine 1. Fig. 4B is a table showing the same relationship as Fig. 4A. The control maps shown in Figs. 4A and 4B are stored in advance in the memory unit 26.

[0086] 4A and 4B, when a command to change the LS differential pressure is not input from the command member 88 to the control device 25 (no change command), the relationship between the engine speed, the LS differential pressure, and the pump discharge volume (control line L1 shown by a dashed line in FIG. 4A, the first to third columns from the left in FIG. 4B) is the same as the relationship between the engine speed, the LS differential pressure, and the pump discharge volume shown in FIG. 2A and 2B. When a command to change the LS differential pressure is input from the command member 88 to the control device 25 (with change command), the LS differential pressure and the pump discharge volume corresponding to the engine speed are higher than when there is no change command (control line L1 shown by a dashed line in FIG. 4A, the first, fourth, and fifth columns from the left in FIG. 4B).

[0087] The control device 25 sets the LS differential pressure based on the presence or absence of a change command from the command member 88, the actual rotation speed of the engine 32 measured by the first measuring device 82, and the control map shown in Fig. 4A or 4B, and outputs a control signal corresponding to the LS differential pressure to the solenoid valve 81. As a result, the opening degree of the solenoid valve 81 is changed in response to the control signal, and the LS differential pressure corresponding to the control signal is realized. In other words, when there is a change command for the LS differential pressure from the command member 88, the LS differential pressure is changed in response to the actual rotation speed of the engine 32 measured by the first measuring device 82.

[0088] 4A and 4B, the control device 25 sets the LS differential pressure when there is a command to change the LS differential pressure from the command member 88 to a value larger than the LS differential pressure when there is no such command to change the LS differential pressure. That is, when there is a command to change the LS differential pressure from the command member 88, the LS differential pressure is higher than when there is no such command to change the LS differential pressure.

[0089] According to the above, for example, when the operator of the work machine 1 wishes to operate the attachment of the work implement 4, i.e., the hydraulic actuators (boom cylinder 14, bucket cylinder 15, hydraulic actuators of the auxiliary attachment) faster than usual, the LS differential pressure increases and the discharge amount of hydraulic oil from the second hydraulic pump P2 increases by turning on the command member 88. As a result, the work machine 1 enters the high-speed mode, making it possible to operate the hydraulic actuators of the work implement 4 quickly.

[0090] [Third embodiment] In the third embodiment, the accelerator member 84 also serves as a command member. That is, by operating at least one of a first accelerator member 84a and a second accelerator member 84b included in the accelerator member 84, it is possible to set the rotation speed of the engine 32 and to issue a command to change the LS differential pressure. The configuration of the hydraulic system of the work machine 1 in the third embodiment is similar to the configuration of the hydraulic system 30A in the first embodiment shown in Fig. 1, and therefore a description thereof will be omitted.

[0091] For example, when at least one of the first accelerator member 84a and the second accelerator member 84b is operated, a predetermined electric signal is input from an electric circuit (not shown) linked to the accelerator member to the control device 25. Based on the electric signal, the control device 25 sets a target engine speed and determines that a command to change the LS differential pressure has been issued.

[0092] When both accelerator members 84a and 84b are operated, the control device 25 sets the first target engine speed based on an electric signal input in response to the operation of the first accelerator member 84a, and sets the second target engine speed based on an electric signal input in response to the operation of the second accelerator member 84b. Then, the control device 25 adopts the larger of the first target engine speed and the second target engine speed as the target engine speed. Furthermore, the control device 25 controls the driving of the engine 32 based on the adopted target engine speed and the actual speed of the engine 32 so that the speed of the engine 32 matches the target engine speed. Furthermore, the control device 25 sets the LS differential pressure (the change value of the LS differential pressure) based on the speed not adopted as the target engine speed, i.e., the smaller speed, of the first target engine speed and the second target engine speed.

[0093] For example, the first accelerator member 84a is operated to a maximum amount or a predetermined amount slightly less than the maximum amount, the first target engine speed is set to the maximum amount or a value slightly less than the maximum amount, and the second accelerator member 84b is operated an amount less than the amount of operation of the first accelerator member 84a, the second target engine speed is set to a value smaller than the first target engine speed. In this case, the control device 25 adopts the first target engine speed as the target engine speed, and sets the LS differential pressure based on the second target engine speed.

[0094] Conversely, the second accelerator member 84b is operated to the maximum amount or a predetermined amount slightly less than the maximum amount, the second target engine speed is set to the maximum amount or a value slightly less than the maximum amount, and the first accelerator member 84a is operated an amount less than the amount of operation of the second accelerator member 84b, the first target engine speed is set to a value smaller than the second target engine speed. In this case, the control device 25 adopts the second target engine speed as the target engine speed and sets the LS differential pressure based on the first target engine speed.

[0095] Fig. 5 is a graph showing the relationship between the operation amount of one of the first accelerator member 84a and the second accelerator member 84b, the LS differential pressure, and the pump discharge amount when the operation amount of the other accelerator member is at a maximum or a predetermined amount or more. Fig. 6 is a table showing the same relationship as Fig. 5. The control maps shown in Figs. 5 and 6 are stored in advance in the memory unit 26.

[0096] In the control maps shown in Figs. 5 and 6, when the operation amount of one of the first accelerator member 84a and the second accelerator member 84b is equal to or less than a small predetermined amount (10%) (slightly more than 0%) and the operation amount of the other accelerator member is equal to or greater than the maximum (100%) or a large predetermined amount (90%) (slightly less than 100%), the LS differential pressure is the minimum value of 1.50 MPa. As shown in the first embodiment (Figs. 2A, 2B) and the second embodiment (Figs. 4A, 4B), this minimum value of the LS differential pressure (1.50 MPa) is the same as the LS differential pressure (1.50 MPa) when the engine speed is at the maximum value (2600 rpm) (in the second embodiment, when there is no change command and the engine speed is at the maximum value). In other words, when the operation amount of one accelerator member is equal to or less than a small predetermined amount (10%) and the operation amount of the other accelerator member is equal to or greater than a large predetermined amount (90%), the LS differential pressure is equal to or less than a small predetermined amount (100%). Even if the LS pressure is not set to the minimum value, if the operation amount of the other accelerator member is equal to or greater than a predetermined maximum or larger amount, the LS pressure difference is set to the minimum value.

[0097] 5 and 6, the LS differential pressure increases as the operation amount of one accelerator member increases. When the operation amount of one accelerator member reaches or exceeds a predetermined amount (90%), which is slightly less than 100%, the LS differential pressure becomes a maximum value of 1.80 MPa.

[0098] The control device 25 sets the LS differential pressure based on the operation amount of either the first accelerator member 84a or the second accelerator member 84b, whichever has the smaller operation amount (including 0% operation amount), and the control map of Fig. 5 or 6, and outputs a control signal corresponding to the LS differential pressure to the solenoid valve 81. As a result, the opening degree of the solenoid valve 81 is changed based on the control signal, and the LS differential pressure corresponding to the control signal is realized.

[0099] That is, when the operator of the working machine 1 operates both the first accelerator member 84a and the second accelerator member 84b, the rotation speed of the engine 32 can be changed according to the operation of one of the accelerator members with a larger operation amount, thereby controlling the travel speed of the working machine 1. Also, the LS differential pressure can be changed according to the operation of the other accelerator member with a smaller operation amount, thereby changing the discharge amount of hydraulic oil from the second hydraulic pump P2. In particular, by the operator operating both the first accelerator member 84a and the second accelerator member 84b with a large operation amount, the LS differential pressure can be increased, thereby increasing the discharge amount of hydraulic oil from the second hydraulic pump P2. As a result, the horsepower control of the working machine 1 can be performed with high accuracy according to the operation state of the accelerator members 84, 84a, 84b.

[0100] [Modification of hydraulic control unit] 7A is a diagram showing a first modified example of the hydraulic control unit. The hydraulic control unit 75A shown in FIG. 7A includes a throttle unit 101, an electromagnetic valve 102, and an opening change unit 103 (second opening change unit) in addition to the flow compensation valve 72, the swash plate variable unit 73, and the opening change unit 76 (first opening change unit). The fourth oil passage branching from the third oil passage 40 includes the first branch oil passage 41, the second branch oil passage 41B, and the third branch oil passage 41C. The third transmission oil passage 41C is also connected to the first connection point (branch point) 43 between the third oil passage 40 and the first branch oil passage 41. The second transmission oil passage 41B is connected to the second connection point (branch point) 44 located downstream of the connection point 43 (opposite side to the first hydraulic pump P1). The end of the first branch oil passage 41 (the end opposite to the first connection part 43) is connected to the bottom side of the accommodation part 76B of the opening change unit 76. The tip end of the second transmission oil passage 41B (the end opposite to the second connection portion 44) is connected to the rod 76C side of the accommodation portion 76B.

[0101] The throttle portion 101 is provided between the first connection point 43 and the second connection point 44 of the third oil passage 40. The throttle portion 101 reduces the flow rate of the pilot oil flowing through the third oil passage 40. The solenoid valve 102 is composed of an electromagnetic proportional valve, a variable relief valve, an electromagnetic switching valve, an electromagnetic throttle valve, or the like. The solenoid valve 102 is provided in a midway portion of the third branch oil passage 41C.

[0102] The opening degree change unit 103 is composed of a hydraulic cylinder. The opening degree change unit 103 has a piston 103A, a housing portion 103B that houses the piston 103A, and a rod 103C that moves with the movement of the piston 103A. The tip end (the end opposite to the first connection portion 43) of the third branch oil passage 41C is connected to the bottom side (the side opposite to the rod 76C) of the housing portion 103B. The rod 103C is connected to the flow compensation valve 72. The piston 103A can be moved by the pressure of pilot oil discharged from the solenoid valve 102 to the third branch oil passage 41C.

[0103] When the pressure of the pilot oil discharged from the solenoid valve 102 to the third branch oil passage 41C on the piston 103A side increases, the piston 103A moves in a direction to extend the rod 103C (flow rate When the pressure of the pilot oil discharged from the solenoid valve 102 to the third branch oil passage 41C on the piston 103A side decreases, the piston 103A moves in a direction that contracts the rod 103C (a direction away from the flow rate compensation valve 72).

[0104] The control device 25 controls the opening degree of the solenoid valve 102. For example, when the command member 88 is in the OFF operating state, the solenoid valve 102 is in a fully closed state. When the command member 88 is turned ON, the control device 25 inputs a control signal (electrical signal) to the solenoid valve 102 to bring the solenoid valve 102 to a fully open state. Note that when the command member 88 is in the OFF operating state, the control device 25 may input a fully closed control signal to the solenoid valve 102 to bring the solenoid valve 102 to a fully closed state.

[0105] When the solenoid valve 102 is in a fully closed state, the pilot oil discharged from the first hydraulic pump P1 to the third oil passage 40 flows through the first branch oil passage 41 and into the accommodation portion 76B on the bottom side of the piston 76A of the opening degree change portion 76. In this manner, the pilot pressure of the pilot oil flowing into the opening degree change portion 76 is set by the throttle portion 101. The opening degree change portion 76 expands and contracts the rod 76C by the pilot pressure acting from the first branch oil passage 41, thereby setting the opening degree of the flow rate compensation valve 72.

[0106] When the solenoid valve 102 is in the fully open state, pilot oil discharged from the first hydraulic pump P1 to the third oil passage 40 flows through the third branch oil passage 41C, passes through the solenoid valve 102, and flows into the accommodation portion 103B on the bottom side of the piston 103A of the opening degree change portion 103. The opening degree of the solenoid valve 102 is changed by the control device 25, thereby changing the pilot pressure of the pilot oil flowing into the opening degree change portion 103. The opening degree change portion 103 expands and contracts the rod 103C by the pilot pressure acting from the third branch oil passage 41C, thereby changing the opening degree of the flow rate compensation valve 72.

[0107] As another example, the control device 25 may control the opening degree of the solenoid valve 102 depending on the operation state of the accelerator member 84. For example, when the operation amount (depression amount) of the second accelerator member 84b is 0% (the second accelerator member 84b is not operated), the control device 25 fully closes the solenoid valve 102. Also, when the second accelerator member 84b is operated, the control device 25 increases the opening degree of the solenoid valve 102 as the operation amount of the second accelerator member 84b increases.

[0108] When the second accelerator member 84b is not operated, the solenoid valve 102 is fully closed, and the pilot pressure acting on the opening degree change unit 76 is set by the throttle unit 101. When the second accelerator member 84b is operated, the solenoid valve 102 opens, and the pilot pressure acting on the cylinder unit 103 increases. In addition, as the amount of operation of the second accelerator member 84b increases, the opening of the solenoid valve 102 increases, and the pilot pressure acting on the opening degree change unit 103 also increases.

[0109] For example, when the operation amount of the second accelerator member 84b is other than 0%, the control device 25 sets a pilot pressure acting on the opening degree changing unit 103 based on the operation amount of the second accelerator member 84b and the control map shown in Figure 5 or 6, and inputs a control signal (electrical signal) corresponding to the pilot pressure to the solenoid valve 102 to adjust the opening of the solenoid valve 102. As a result, the pilot pressure acting on the opening degree changing unit 103 is changed, and the opening degree changing unit 103 changes the opening of the flow rate compensation valve 72.

[0110] As in the case of the second accelerator member 84b described above, the control device 25 may adjust the opening of the solenoid valve 102 and change the pilot pressure acting on the opening degree change unit 103 in accordance with the operating state of the first accelerator member 84a. FIG. 7B is a diagram showing a second modified example of the hydraulic control unit. In the hydraulic control unit 75B shown in FIG. A solenoid switching valve 106 and a throttle section 110 are provided in a middle portion of the third branch oil passage 41C. The solenoid switching valve 106 is provided on the first connection point 43 side of the throttle section 110. The solenoid switching valve 106 is configured, for example, as a two-position switching valve that can be switched between a first position 106a and a second position 106b.

[0111] The control device 25 inputs a control signal (electrical signal) to the solenoid switching valve 106 to switch the position of the solenoid switching valve 106. For example, when the command member 88 is in the OFF operating state, the solenoid switching valve 106 is in the first position 106a as shown in Fig. 7B. When the command member 88 is turned ON, the control device 25 inputs a control signal to the solenoid switching valve 106 to switch the solenoid switching valve 106 to the second position 106b. Note that when the command member 88 is in the OFF operating state, the control device 25 may input a control signal to the solenoid switching valve 106 to switch the solenoid switching valve 106 to the first position 106a.

[0112] When the solenoid switching valve 106 is switched to the first position 106a, even if the pilot oil discharged from the first hydraulic pump P1 to the third oil passage 40 flows into the third branch oil passage 41C, it cannot pass through the solenoid switching valve 106 and does not flow to the opening degree change unit 103. However, the pilot oil discharged from the first hydraulic pump P1 to the third oil passage 40 flows through the first branch oil passage 41 and flows into the accommodation portion 76B on the bottom side of the piston 76A of the opening degree change unit 76. In this way, the pilot pressure of the pilot oil flowing into the opening degree change unit 76 is set by the throttle unit 101. Therefore, the opening degree change unit 76 expands and contracts the rod 76C by the pilot pressure acting from the first branch oil passage 41 to set the opening degree of the flow compensation valve 72.

[0113] When the solenoid switching valve 106 is switched to the second position 106b, the pilot oil discharged from the first hydraulic pump P1 to the third oil passage 40 flows through the third branch oil passage 41C, and passes through the solenoid switching valve 106 and the throttle section 110 before flowing into the opening change section 103. The pilot pressure of the pilot oil flowing into the opening change section 103 in this manner is set by the throttle section 101. For this reason, the opening change section 103 expands and contracts the rod 103C by the pilot pressure acting from the third branch oil passage 41C, thereby changing the opening of the flow rate compensation valve 72 to a larger value.

[0114] The above-mentioned hydraulic control units 75A and 75B can also be used to change the opening of the flow compensation valve 72. Then, in response to the change in the opening of the flow compensation valve 72, the flow rate and pressure of the hydraulic oil supplied from the flow compensation valve 72 to the swash plate variable unit 73 can be changed, and the angle of the swash plate of the second hydraulic pump P2 can be changed by the swash plate variable unit 73, thereby changing the discharge amount of the hydraulic oil from the second hydraulic pump P2. As a result, it is possible to change the operating speed of the hydraulic actuators (cylinders 14, 15, etc.). Also, it is possible to improve the accuracy of the horsepower control of the working system of the working machine 1 by changing the LS differential pressure, which is the pressure difference between the PPS signal pressure and the PLS signal pressure.

[0115] As another example, in the hydraulic control unit 75A, 75B shown in FIG. 7A or FIG. 7B, the solenoid valve 81 shown in FIG. 1B, etc. may be connected to the first branch oil passage 41, and the opening of the solenoid valve 81 may be adjusted by the control device 25 to control the operation of the opening change unit 76.

[0116] FIG. 7C is a diagram showing a third modified example of the hydraulic control unit. In the hydraulic control unit 75C shown in FIG. 7C, a solenoid valve 81 is provided in the first branch oil passage 41. A second branch oil passage 41B is connected to the second connection point (branch point) 44 of the third oil passage 40. A solenoid valve 74 is provided in a fifth oil passage 85 for supplying hydraulic oil from the flow compensation valve 72 to the swash plate control unit 73. The control device 25 inputs a control signal (current signal) to the solenoid valve 81 or the solenoid valve 74 to change the opening degree of the solenoid valves 81 and 74, thereby changing the flow rate and pressure of the hydraulic oil supplied from the flow compensation valve 72 to the swash plate control unit 73, and changing the angle of the swash plate of the second hydraulic pump P2. By changing the angle of the swash plate of the second hydraulic pump P2, the discharge amount of the hydraulic oil from the second hydraulic pump P2 is changed, and the LS differential pressure, which is the differential pressure between the PPS signal pressure and the PLS signal pressure, is also changed. That is, the control device 25 changes the opening degree of the solenoid valves 81 and 74 to change the LS differential pressure.

[0117] FIG. 8A is a diagram showing a fourth modified example of the hydraulic control unit. The hydraulic control unit 75D shown in FIG. 8A includes a solenoid valve 181A consisting of a variable throttle valve whose throttle area can be electrically changed. The solenoid valve 181A is provided between the first connection point 43 and the second connection point 44 of the third oil passage 40. The solenoid valve 181A increases or decreases the flow rate of pilot oil flowing through the third oil passage 40. The control device 25 electrically changes the opening of the solenoid valve 181A, so that a pilot differential pressure (PA-Po) is generated between the pilot pressure (second pressure PA) acting from the first branch oil passage 41 to the inside of the accommodation portion 76B on the bottom side of the opening degree change portion 76 and the pilot pressure (third pressure Po) acting on the second branch oil passage 41B and the inside of the accommodation portion 76B on the rod 76C side of the opening degree change portion 76, and the pilot differential pressure changes. This change in pilot differential pressure causes the piston 76A of the opening degree changer 76 to move and the rod 76C to expand and contract, thereby setting or changing the opening degree of the flow rate compensation valve 72. In detail, as the control device 25 reduces the opening degree of the solenoid valve 181A, the first pilot differential pressure increases, and the opening degree changer 76 increases the opening degree of the flow rate compensation valve 72.

[0118] FIG. 8B is a diagram showing a fifth modified example of the hydraulic control unit. The hydraulic control unit 75E shown in FIG. 8B includes a solenoid valve 181B consisting of a variable throttle valve whose throttle area can be electrically changed. A fourth oil passage branched from the third oil passage 40 includes a first branch oil passage 41, a second branch oil passage 41B, and a bypass oil passage 41D. The solenoid valve 181B is connected to the bypass oil passage 41D. A first end of the bypass oil passage 41D is connected between the throttle section 101 in the third oil passage 40 and the first hydraulic pump P1. A second end of the bypass oil passage 41D is connected to the second connection section 44 of the third oil passage 40. The solenoid valve 181B increases or decreases the flow rate of pilot oil flowing through the bypass oil passage 41D.

[0119] The control device 25 electrically changes the opening degree of the solenoid valve 181B. As a result, a pilot pressure difference (Pi-Po) is generated between the first pressure Pi, which is the pressure of the pilot oil discharged from the first hydraulic pump P1, and the pilot pressure (third pressure Po) acting on a part of the bypass oil passage 41D and the second branch oil passage 41B downstream (the opposite side to the first hydraulic pump P1) of the solenoid valve 181B and the throttle unit 101, and the pilot pressure difference changes.

[0120] Due to the change in the pilot pressure difference, a pilot pressure difference (PA-Po) is generated in the pilot pressure (second pressure PA) acting from the first branch oil passage 41 into the accommodation portion 76B on the bottom side of the opening degree change portion 76, and in the pilot pressure (third pressure Po) acting in the second branch oil passage 41B and the accommodation portion 76B on the rod 76C side of the opening degree change portion 76, and the pilot pressure difference changes. As a result, the piston 76A of the opening degree change portion 76 moves, the rod 76C expands and contracts, and the opening of the flow rate compensation valve 72 is set or changed.

[0121] In detail, as the control device 25 reduces the opening of the solenoid valve 181B, the pilot pressure difference (Pi-Po) between the first pressure Pi and the third pressure Po described above increases, and the pilot pressure difference (PA-Po) between the second pressure PA and the third pressure Po also increases, causing the opening change unit 76 to increase the opening of the flow compensation valve 72.

[0122] The control device 25 can change the LS differential pressure by controlling the openings of the above-mentioned solenoid valves 181A and 181B in accordance with the rotation speed of the engine 32 and the like.

[0123] Fig. 9A is a diagram showing a sixth modified example of the hydraulic control section. In a hydraulic control section 75F shown in Fig. 9A, instead of the solenoid valve 181B shown in Fig. 8B, a solenoid valve 182 consisting of a solenoid switching valve and a throttle section 183 are provided in the bypass oil passage 41D. The throttle section 183 reduces the flow rate of pilot oil flowing through the bypass oil passage 41D. In this example, the throttle section 183 is provided upstream of the solenoid valve 182 (on the first hydraulic pump P1 side), but the throttle section 183 is provided downstream of the solenoid valve 182. 3 may be provided.

[0124] The solenoid valve 182 is electrically switched between a first position 182a and a second position 182b by the control device 25. For example, when the control device 25 does not input a control signal to the solenoid valve 182, the solenoid valve 182 is in a state switched to the first position 182a by the elastic force of the spring. At this time, all of the pilot oil discharged from the first hydraulic pump P1 to the third oil passage 40 passes through the throttle section 101, and the flow rate of the pilot oil flowing through the oil passage 40 is throttled by the throttle section 101. For this reason, a pilot pressure difference (Pi-Po) is generated between the pilot pressure (first pressure Pi) of the pilot oil flowing through the oil passage 41 upstream of the throttle section 101 and the pilot pressure (third pressure Po) of the pilot oil flowing through the oil passage 41B downstream of the throttle section 101, and the pilot pressure difference becomes large.

[0125] When the control device 25 inputs a control signal to the solenoid valve 182, the solenoid valve 182 is switched to the second position 182b. At this time, a part of the pilot oil discharged from the first hydraulic pump P1 to the third oil passage 40 passes through the throttle section 101, and the flow rate of the part of the pilot oil is throttled by the throttle section 101. In addition, the other part of the pilot oil discharged from the first hydraulic pump P1 to the third oil passage 40 flows through the bypass oil passage 41D and passes through the throttle section 183 and the solenoid valve 182, and the flow rate of the other part of the pilot oil is throttled by the throttle section 183. For this reason, a pilot differential pressure (Pi-Po) is generated between the pilot pressure (first pressure Pi) of the pilot oil flowing through the oil passage 41 and the pilot pressure (third pressure Po) of the pilot oil flowing through the oil passage 41B, and the pilot differential pressure becomes small.

[0126] Due to the change in the pilot pressure difference, a pilot pressure (second pressure PA) acting from the first branch oil passage 41 into the accommodation portion 76B on the bottom side of the opening degree change portion 76 and a pilot pressure (third pressure Po) acting from the second branch oil passage 41B and into the accommodation portion 76B on the rod 76C side of the opening degree change portion 76 also generate a pilot pressure difference (PA-Po), and the pilot pressure difference (PA-Po) changes in the same manner as the pilot pressure difference (Pi-Po) described above. As a result, the piston 76A of the opening degree change portion 76 moves, the rod 76C expands and contracts, and the opening degree of the flow compensation valve 72 is set or changed. Then, the swash plate variable portion 73 operates according to the opening degree of the flow compensation valve 72, the angle of the swash plate of the second hydraulic pump P2 is changed, and the output and the LS differential pressure of the second hydraulic pump P2 are changed.

[0127] Fig. 9B is a diagram showing a seventh modified example of the hydraulic control unit. In hydraulic control unit 75G shown in Fig. 9B, a throttle unit 184 is provided in oil passage 182c inside second position 182b of solenoid valve 182, instead of throttle unit 183 shown in Fig. 9A. Throttle unit 184 reduces the flow rate of pilot oil flowing through internal oil passage 182c.

[0128] In this way, even if the throttle unit 184 is provided in the internal oil passage 182c of the solenoid valve 182, the control device 25 switches the solenoid valve 182 to the first position 182a or the second position 182b, whereby the throttle units 101, 184 throttle the flow rate of the pilot oil flowing through the oil passages 40, 41D, 182c, and the pilot differential pressure acting on the opening degree change unit 76 changes, and the opening degree change unit 76 operates in response to the change in the pilot differential pressure, and the opening degree of the flow rate compensation valve 72 is set or changed. Then, the swash plate variable unit 73 operates in response to the opening degree of the flow rate compensation valve 72, and the angle of the swash plate of the second hydraulic pump P2 is changed, and the output and the LS differential pressure of the second hydraulic pump P2 are changed.

[0129] The control device 25 can change the LS differential pressure by controlling the position of the above-mentioned solenoid valve 182 in accordance with the rotation speed of the engine 32 and the like. Fig. 9C is a diagram showing an eighth modified example of the hydraulic control unit. In the hydraulic control unit 75H shown in Fig. 9C, a solenoid valve 185 consisting of a solenoid proportional valve that can be switched between three positions is provided instead of the solenoid valve 182 shown in Fig. 9A and Fig. 9B.

[0130] The solenoid valve 185 is electrically switched to a first position 185a, a second position 185b, and a third position 185c by the control device 25. The internal oil passages 185d, 185e, and 185f of the positions 185a, 185c, and 185c are provided with throttle sections 184a, 184b, and 184c, respectively. The throttle sections 184a, 184b, and 184c reduce the flow rate of the pilot oil flowing through the corresponding internal oil passages 185d, 185e, and 185f. The opening area of ​​the throttle section 184a is smaller than the opening area of ​​the throttle section 184b. The opening area of ​​the throttle section 184c is larger than the opening area of ​​the throttle section 184b.

[0131] When the control device 25 switches the solenoid valve 185 to any one of the first position 185a, the second position 185b, and the third position 185c, the flow rate of the pilot oil flowing through the oil passages 40, 41D, 185d, 185e, and 185f is throttled by the throttle unit 101 and the throttle units 184a, 184b, and 184c provided at each position. As a result, a pilot pressure difference is generated between the pilot pressure (first pressure Pi) of the pilot oil flowing through a part of the oil passages 40 and 41D upstream of the throttle units 101, 184a, 184b, and 184c and the pilot pressure (third pressure Po) of the pilot oil flowing through the second branch oil passage 41B, and the pilot pressure difference changes.

[0132] A pilot pressure difference is also generated between the pilot pressure (second pressure PA) acting from the first branch oil passage 41 into the accommodation portion 76B of the opening degree changing portion 76 and the pilot pressure (third pressure Po) acting between the second branch oil passage 41B and the accommodation portion 76B of the opening degree changing portion 76, and the pilot pressure difference changes. Then, the opening degree changing portion 76 operates in response to the pilot pressure difference, and the opening degree of the flow rate compensation valve 72 is set or changed.

[0133] Fig. 9D is a diagram showing a ninth modification of the hydraulic control unit. In hydraulic control unit 75I shown in Fig. 9D, solenoid valve 186 made of a solenoid proportional valve switchable to three positions is provided instead of solenoid valve 185 shown in Fig. 9C.

[0134] The solenoid valve 186 is electrically switched to a first position 186a, a second position 186b, and a third position 186c by the control device 25. The internal oil passages 186e, 186f in the second position 186c and the third position 186c are provided with throttle sections 184b, 184c, respectively. The throttle sections 184b, 184c reduce the flow rate of the pilot oil flowing through the corresponding internal oil passages 186e, 186f. The opening area of ​​the throttle section 184c is larger than the opening area of ​​the throttle section 184b.

[0135] For example, when the control device 25 does not input a control signal to the solenoid valve 186, the solenoid valve 186 is switched to the first position 186 due to the elastic force of the spring, and pilot oil that has flowed into the bypass oil passage 41D cannot pass through the solenoid valve 186. When the control device 25 inputs a control signal to the solenoid valve 186, the solenoid valve 186 is switched to the second position 186b or the third position 186c, and the pilot oil that has flowed into the bypass oil passage 41D passes through the second position 186b or the third position 186c of the solenoid valve 186.

[0136] In this manner, when the pilot oil passes through the second position 186b or the third position 186c, the throttling sections 101, 184b, 184c throttle the flow rate of the pilot oil flowing through the oil passages 40, 41D, and a pilot differential pressure is generated between the pilot pressure (first pressure Pi) of the pilot oil flowing through a portion of the oil passages 40, 41D upstream of the throttling sections 101, 184b, 184c and the pilot pressure (third pressure Po) of the pilot oil flowing through the second branch oil passage 41B, and the pilot differential pressure changes.

[0137] In addition, the pilot pressure (second pressure PA) acting from the first branch oil passage 41 to the inside of the accommodation portion 76B of the opening degree change portion 76 and the pilot pressure (second pressure PA) acting from the second branch oil passage 41B and the inside of the accommodation portion 76B of the opening degree change portion 76 are A pilot pressure difference (Pi-Po) also occurs in the pilot pressure (third pressure Po) that is generated by the second hydraulic pump P2, and the pilot pressure difference changes. In response to the change in the pilot pressure difference (Pi-Po), an opening changer 76 operates to set or change the opening of the flow rate compensation valve 72. In response to the opening of the flow rate compensation valve 72, a swash plate control unit 73 operates to change the angle of the swash plate of the second hydraulic pump P2, and the LS differential pressure also changes.

[0138] When either of the above-mentioned hydraulic control units 75H, 75I is used, when a command to change the LS differential pressure is issued by the command members 88, 84, the control device 25 may switch the solenoid valves 185, 186 to the first positions 185a, 186a to change the LS differential pressure to an increased value. In the modified examples shown in FIG. 7A, FIG. 7B, FIG. 8B, and FIG. 9A to FIG. 9D, the discharge flow rate of the pilot oil from the first hydraulic pump P1 changes according to the actual rotation speed of the engine 32, so the differential pressure between the pilot pressure acting on the upstream side of the throttle unit 101 and the pilot pressure acting on the downstream side also changes. Therefore, the LS differential pressure can be set hydraulically (mechanically) without setting a control parameter for the LS differential pressure according to the rotation speed of the engine 32. In addition, when the load of the engine 32 increases, the LS differential pressure that is automatically set hydraulically can be reduced by the solenoid valves 181B, 182, 185, and 186. In other words, when the load of the engine 32 increases, the solenoid valves 181B, 182, 185, and 186 are opened to divert a part of the pilot oil discharged from the first hydraulic pump P1, thereby reducing the flow rate of the pilot oil flowing through the throttle unit 101, thereby reducing the pilot differential pressure acting on the opening degree change unit 76 relative to the discharge amount of the pilot oil by the first hydraulic pump P1.

[0139] When the viscosity of the hydraulic oil changes due to the type of hydraulic oil used in the work machine 1, the hydraulic oil temperature, etc., the discharge amount of the hydraulic oil from the second hydraulic pump P2 changes, and the LS differential pressure also changes. (The higher the viscosity of the hydraulic oil, the larger the LS differential pressure.) Therefore, when the second hydraulic pump P2 is to discharge a determined flow rate of hydraulic oil, it is necessary to set the LS differential pressure according to the viscosity of the hydraulic oil, and in the hydraulic circuit shown in FIG. 1A, it is necessary to add a sensor that detects the viscosity of the hydraulic oil, etc., or to perform complex control. In contrast, in the hydraulic circuits shown in FIGS. 7A, 7B, 8B, and 9A to 9D, when the viscosity of the hydraulic oil is high, the pilot differential pressure of the pilot oil increases between the upstream and downstream sides of the throttle units 101, 181A or the solenoid valves 102, 185, 186, and the LS differential pressure increases. Therefore, the LS differential pressure can be changed as described above without adding a sensor that detects the viscosity of the hydraulic oil, etc., or performing complex control that takes the viscosity into consideration.

[0140] In the above-described embodiment, the hydraulic control unit 75, 75A to 75I increases the discharge amount of hydraulic oil from the second hydraulic pump P2, thereby improving (increasing) the operating speed of the hydraulic actuator. However, in addition to this, the operating speed of the hydraulic actuator may be improved by, for example, operating members 58, 84 and a control valve 56D as shown in FIG. 10A.

[0141] [Fourth embodiment] 10A is a diagram showing a main part of a hydraulic system 30C of a work system of a work machine 1 of a fourth embodiment. In the hydraulic system 30C, an operating member 58, an accelerator member 84, and a control valve 56D are connected to a control device 25. The operating member 58 is a lever for operating the boom 10, the bucket 11, or an auxiliary attachment, or the like. The amount of operation of the operating member 58 is detected by, for example, a potentiometer, and input to the control device 25.

[0142] The control valve 56D is a three-position change-over valve, and has a pair of electrically driven solenoid parts 56e and a pair of hydraulically movable pressure receiving parts 56f. The control device 25 controls the drive of the solenoid parts 56e in response to the amount of operation of the operating member 58, and switches the position of the control valve 56D. The hydraulic actuator connected to the control valve 56D controls the boom cylinder 14, the bucket The attachment may be a hydraulic actuator such as a hydraulic cylinder 15 or a hydraulic actuator provided on a spare attachment.

[0143] Fig. 10B is a graph showing the relationship between the secondary pressure of the control valve 56D (the pressure of the hydraulic oil discharged from the control valve 56D to the hydraulic actuators 14, 15, etc.), the amount of movement of the spool of the control valve 56, and the amount of operation of the operating members 58, 84b. Fig. 10C is a table showing the same relationship as Fig. 10B. Note that in Fig. 10B, the vertical axis shows both the secondary pressure of the control valve 56D and the amount of movement of the spool of the control valve 56D, and each is shown as a percentage with the maximum being 100%.

[0144] 10B and 10C, when the operation amount (depression amount) of second accelerator member 84b is 10% or less, controller 25 outputs a control signal to at least one of solenoid units 56e so that the amount of movement of the spool of control valve 56D is 80% even if operating member 58 is operated to the maximum (full stroke 100%). In other words, when the operation amount of second accelerator member 84b is smaller than the threshold value, controller 25 sets the opening area of ​​the spool of control valve 56D, which corresponds to the large operation amount (85 to 100%) near the maximum of operating member 58, to a value somewhat smaller than the maximum (80%).

[0145] On the other hand, when the amount of operation of second accelerator member 84b is 90% or more, a control signal is output to at least one of solenoid units 56e so that the amount of movement of the spool of control valve 56D becomes the maximum (full stroke) 100% when the amount of operation of operating member 58 exceeds 85%. In other words, when the amount of operation of second accelerator member 84b is greater than the threshold value, controller 25 maximizes (100%) the opening area of ​​the spool of control valve 56D, which corresponds to the large amount of operation (85 to 100%) of operating member 58 near the maximum.

[0146] As described above, by interlocking the amount of operation of the second accelerator member 84b with the amount of operation of the operating member 58, when the amount of operation of the second accelerator member 84b is large, the hydraulic actuators 14, 15, etc. can be operated quickly. When the amount of operation of the second accelerator member 84b is small, the hydraulic actuators 14, 15, etc. can be operated at a standard speed.

[0147] 10B and 10C, the operation amount of the second accelerator member 84b is shown as a percentage based on the maximum operation amount, but the operation amount of the second accelerator member 84b may be expressed based on a predetermined operation amount other than the maximum operation amount (e.g., 80%). Also, the first accelerator member 84a may be used instead of the second accelerator member 84b, and the first accelerator member 84a, the operating member 58, and the control valve 56D may be linked to change the operating speed of the hydraulic actuators 14, 15, etc.

[0148] Furthermore, the above-mentioned operating valves 59 (operating valves 59A, 59B, 59C, and 59D) may be configured with solenoid valves, and the pilot pressure output from the operating valves 59 may be changed according to the amount of operation of the operating member 58. In this case, when the control device 25 acquires the amount of operation of the operating member 58, it sets the opening degree of the operating valve (solenoid valve) 59 based on the amount of operation, and outputs a control signal according to the opening degree to the operating valve 59. This allows the opening degree of the operating valve 59 to be set to an opening degree according to the amount of operation of the operating member 58.

[0149] [Fifth embodiment] Fig. 11 is a diagram showing a hydraulic system 30D of the traveling system of a work machine 1 according to a fifth embodiment. The fifth embodiment is applicable to any of the first to fourth embodiments described above. That is, the hydraulic system 30D of the traveling system can be combined with any of the hydraulic systems 30A to 30C of the work system and the hydraulic control units 75, 75A to 75I described above. (The same applies to the other hydraulic systems 30E to 30G of the traveling system described later.) In the explanation of the fifth embodiment, explanations of configurations similar to those of the above-mentioned embodiments will be omitted.

[0150] 11 is capable of driving the traveling device 5. The hydraulic system 30D also includes a first traveling pump 53L, a second traveling pump 53R, a first traveling motor 36L, and a second traveling motor 36R.

[0151] The first travel pump 53L and the second travel pump 53R are hydraulic pumps driven by the power of the engine 32. Specifically, the first travel pump 53L and the second travel pump 53R are swash plate type variable displacement axial pumps driven by the power of the engine 32. The first travel pump 53L and the second travel pump 53R have pressure receiving parts 53a and 53b on which pilot pressure acts, and the angle of the swash plate of the travel pumps 53L and 53R is changed by the pilot pressure acting on the pressure receiving parts 53a and 53b. By changing the angle of the swash plate, the output (discharge amount of hydraulic oil) and the discharge direction of the hydraulic oil of the first travel pump 53L and the second travel pump 53R can be changed.

[0152] The first travel pump 53L and the first travel motor 36L are connected by a circulation oil passage 57h, and the hydraulic oil discharged by the first travel pump 53L is supplied to the first travel motor 36L. The second travel pump 53R and the second travel motor 36R are connected by a circulation oil passage 57i, and the hydraulic oil discharged by the second travel pump 53R is supplied to the second travel motor 36R.

[0153] The first traveling motor 36L is a hydraulic motor that transmits power to the drive shaft of the traveling device 5 provided on the left side of the machine body 2. The first traveling motor 36L can be rotated by hydraulic oil discharged from the first traveling pump 53L, and the rotation speed (number of rotations) can be changed by the flow rate of the hydraulic oil. A swash plate switching cylinder 37L is connected to the first traveling motor 36L, and the rotation speed (number of rotations) of the first traveling motor 36L can also be changed by extending or retracting the swash plate switching cylinder 37L to one side or the other side. That is, when the swash plate switching cylinder 37L is contracted, the rotation speed of the first traveling motor 36L is set to a low speed range (first speed), and when the swash plate switching cylinder 37L is extended, the rotation speed of the first traveling motor 36L is set to a high speed range (second speed). That is, the rotation speed of the first traveling motor 36L can be changed between a first speed, which is a low speed side, and a second speed, which is a high speed side.

[0154] The second traveling motor 36R is a hydraulic motor that transmits power to the drive shaft of the traveling device 5 provided on the right side of the machine body 2. The second traveling motor 36R can be rotated by hydraulic oil discharged from the second traveling pump 53R, and the rotation speed (number of rotations) can be changed by the flow rate of the hydraulic oil. A swash plate switching cylinder 37R is connected to the second traveling motor 36R, and the rotation speed (number of rotations) of the second traveling motor 36R can also be changed by extending or retracting the swash plate switching cylinder 37R to one side or the other side. That is, when the swash plate switching cylinder 37R is contracted, the rotation speed of the second traveling motor 36R is set to a low speed range (first speed), and when the swash plate switching cylinder 37R is extended, the rotation speed of the second traveling motor 36R is set to a high speed range (second speed). That is, the rotation speed of the second traveling motor 36R can be changed between a first speed, which is a low speed side, and a second speed, which is a high speed side.

[0155] The hydraulic system 30D also includes a travel switching valve 34. The travel switching valve 34 can be switched between a first state in which the rotational speeds of the travel motors 36L, 36R are set to a first speed, and a second state in which the rotational speeds are set to a second speed. The travel switching valve 34 includes first switching valves 71L, 71R and a second switching valve 172.

[0156] The first switching valve 71L is connected to the swash plate switching cylinder 37L of the first traveling motor 36L via an oil passage, and is a two-position switching valve that can be switched between a first position 71La and a second position 71Lb. When the first switching valve 71L is switched to the first position 71La, When the first switching valve 71La is switched to the second position 71L2b, the swash plate switching cylinder 37L is extended.

[0157] The first switching valve 71R is connected to the swash plate switching cylinder 37R of the second traveling motor 36R via an oil passage and is a two-position switching valve that can be switched to a first position 71Ra and a second position 71Rb. When the first switching valve 71R is switched to the first position 71Ra, it contracts the swash plate switching cylinder 37R. When the first switching valve 71R is switched to the second position 71Rb, it extends the swash plate switching cylinder 37R.

[0158] The second switching valve 172 is an electromagnetic valve that switches the first switching valve 71L and the first switching valve 71R, and is a two-position switching valve that can be switched between a first position 172a and a second position 172b when excited. The second switching valve 172, the first switching valve 71L, and the first switching valve 71R are connected by an oil passage 41. When the second switching valve 172 is switched to the first position 172a, the second switching valve 172 switches the first switching valve 71L and the first switching valve 71R to the first positions 71La and 71Ra. When the second switching valve 172 is switched to the second position 172b, the second switching valve 172 switches the first switching valve 71L and the first switching valve 71R to the second positions 71La and 71Rb.

[0159] When the second switching valve 172 is in the first position 172a, the first switching valve 71L is in the first position 71La, and the first switching valve 71R is in the first position 71Ra, the travel switching valve 34 is in the first state and the rotation speed of the travel motors 36L, 36R is set to the first speed. When the second switching valve 172 is in the second position 172b, the first switching valve 71L is in the second position 71La, and the first switching valve 71R is in the second position 71Ra, the travel switching valve 34 is in the second state and the rotation speed of the travel motors 36L, 36R is set to the second speed. In other words, the travel switching valve 34 can switch the travel motors 36L, 36R between the first speed, which is the low speed side, and the second speed, which is the high speed side.

[0160] The travel motors 36L, 36R can be switched to the first speed or the second speed by the speed change member 61. The speed change member 61 is composed of a push switch or the like that can be operated by the driver of the work machine 1, and is connected to the control device 25. By performing a predetermined operation with the speed change member 61, it is possible to execute an increase in speed by switching the rotation speed of the travel motors 36L, 36R from the first speed (first state) to the second speed (second state). In addition, by performing another predetermined operation with the speed change member 61, it is possible to execute a decrease in speed by switching the rotation speed of the travel motors 36L, 36R from the second speed (second state) to the first speed (first state).

[0161] The control device 25 switches the state of the travel switching valve 34 based on the operation state of the shifting member 61. For example, when the rotation speed of the travel motors 36L, 36R is set to the first speed and a predetermined operation is performed on the shifting member 61, a second speed command (a command to set the travel switching valve 34 to the second state) indicating that the rotation speed of the travel motors 36L, 36R is to be increased to the second speed is output from an electric circuit interlocked with the shifting member 61 to the control device 25. Also, when the rotation speed of the travel motors 36L, 36R is set to the second speed and a predetermined operation is performed on the shifting member 61, a first speed command (a command to set the travel switching valve 34 to the first state) indicating that the rotation speed of the travel motors 36L, 36R is to be decreased to the first speed is output from an electric circuit interlocked with the shifting member 61 to the control device 25.

[0162] The speed-changing member 61 may be an operation switch that can hold an ON operation state and an OFF operation state. In this case, when the speed-changing member 61 is in the OFF operation state, a command to hold the rotation speed of the traveling motors 36L, 36R at a first speed is output to the control device 25. When the speed-changing member 61 is in the ON operation state, a command to hold the rotation speed of the traveling motors 36L, 36R at a second speed is output to the control device 25.

[0163] When the control device 25 receives a command (first speed command) to switch the traveling switching valve 34 to the first state, it switches the traveling switching valve 34 to the first state by demagnetizing the solenoid of the second switching valve 172. When the control device 25 receives a command (second speed command) to switch the traveling switching valve 34 to the second state, it magnetizes the solenoid of the second switching valve 172 to switch the traveling switching valve 34 to the second state.

[0164] The hydraulic system 30D includes a first hydraulic pump P1, a second hydraulic pump P2, and a travel operation device (hereinafter simply referred to as the "operation device") 54. The first hydraulic pump P1 and the second hydraulic pump P2 are the same as the first hydraulic pump P1 and the second hydraulic pump P2 of the above-described embodiment. The hydraulic system 30D of the travel system is connected to an oil passage 40a (FIG. 11, etc.) branched from a branch point 48 (FIGS. 11 and 1, etc.) of the third oil passage 40 from which the first hydraulic pump P1 discharges pilot oil. (The same is true for the hydraulic systems 30E to 30G of the other travel systems described later.)

[0165] The operating device 54 is a device that operates the first travel pump 53L and the second travel pump 53R, and is capable of changing the angle of the swash plates (swash plate angle) of the travel pumps 53L, 53R. The operating device 54 includes a travel operating member (first operating member; hereinafter, simply referred to as the “operating member”) 159 formed of an operating lever or the like, and a plurality of operating valves 55.

[0166] The operating member 159 is supported by the operating valve 55, and can be swung (tilted) in the left-right direction (body width direction of the work machine 1) or the front-rear direction. That is, with respect to the neutral position N as a reference, the operating member 159 can be swung to the right and left from the neutral position N, and can also be swung forward and backward from the neutral position N. In other words, the operating member 159 can be swung in at least four directions with respect to the neutral position N. For ease of explanation, both the forward and rearward directions, i.e., the front-rear direction, are referred to as the first direction. Also, both the right and left directions, i.e., the left-right direction, are sometimes referred to as the second direction.

[0167] Further, the multiple operation valves 55 are commonly operated, i.e., by a single operation member 159. The multiple operation valves 55 operate based on the oscillation of the operation member 159. A discharge oil passage 40 is connected to the multiple operation valves 55, and hydraulic oil (pilot oil) from the first hydraulic pump P1 can be supplied via the discharge oil passage 40. The multiple operation valves 55 are operation valve 55A, operation valve 55B, operation valve 55C, and operation valve 55D.

[0168] When the operating member 159 is swung forward (one side) in the front-rear direction (first direction), i.e., when the operating member 159 is operated forward, the operating valve 55A changes the pressure of the hydraulic oil to be output in accordance with the forward operation amount (operation) of the operating member 159. When the operating member 159 is swung backward (the other side) in the front-rear direction (first direction), i.e., when the operating member 159 is operated backward, the operating valve 55B changes the pressure of the hydraulic oil to be output in accordance with the backward operation amount (operation) of the operating member 159. When the operating member 159 is swung rightward (one side) in the left-right direction (second direction), i.e., when the operating member 159 is operated rightward, the operating valve 55C changes the pressure of the hydraulic oil to be output in accordance with the right operation amount (operation) of the operating member 159. When the operating member 159 is swung to the left (the other) of the left-right directions (second directions), i.e., when the operating member 159 is operated to the left, the operating valve 55D changes the pressure of the hydraulic oil output in accordance with the left operation amount (operation) of the operating member 159.

[0169] The multiple operation valves 55 and the travel pumps 53L, 53R are connected by the travel oil passage 45. In other words, the travel pumps 53L, 53R are hydraulic devices that can be operated by the hydraulic oil output from the operation valves 55 (operation valve 55A, operation valve 55B, operation valve 55C, operation valve 55D). The travel oil passage 45 includes a first travel oil passage 45a, a second travel oil passage 45b, a third travel oil passage 45c, a fourth travel oil passage 45d, and a fifth travel oil passage 45e. The second travel oil passage 45b is an oil passage connected to the pressure receiving portion 53b of the travel pump 53L. The third travel oil passage 45c is an oil passage connected to the pressure receiving portion 53a of the travel pump 53R. The fourth travel oil passage 45d is an oil passage connected to the pressure receiving portion 53b of the travel pump 53R. The fifth travel oil passage 45e is an oil passage connecting the operation valve 55, the first travel oil passage 45a, the second travel oil passage 45b, the third travel oil passage 45c, and the fourth travel oil passage 45d.

[0170] When the operating member 159 is swung forward (in the direction of arrow A1 in FIG. 11), the operating valve 55A is operated and pilot pressure is output from the operating valve 55A. This pilot pressure acts on the pressure receiving portion 53a of the first traveling pump 53L via the first traveling oil passage 45a, and also acts on the pressure receiving portion 53a of the second traveling pump 53R via the third traveling oil passage 45c. This changes the swash plate angle of the first traveling pump 53L and the second traveling pump 53R, and the first traveling motor 36L and the second traveling motor 36R rotate forward (forward rotation), causing the work machine 1 to move straight forward.

[0171] Furthermore, when the operating member 159 is swung backward (in the direction of arrow A2 in FIG. 11), the operating valve 55B is operated and pilot pressure is output from the operating valve 55B. This pilot pressure acts on the pressure receiving portion 53b of the first traveling pump 53L via the second traveling oil passage 45b, and also acts on the pressure receiving portion 53b of the second traveling pump 53R via the fourth traveling oil passage 45d. This changes the swash plate angle of the first traveling pump 53L and the second traveling pump 53R, and the first traveling motor 36L and the second traveling motor 36R rotate in the reverse direction (reverse rotation), causing the work machine 1 to move straight backward.

[0172] Furthermore, when the operating member 159 is swung to the right (in the direction of arrow A3 in FIG. 11), the operating valve 55C is operated and pilot pressure is output from the operating valve 55C. This pilot pressure acts on the pressure receiving portion 53a of the first traveling pump 53L via the first traveling oil passage 45a, and also acts on the pressure receiving portion 53b of the second traveling pump 53R via the fourth traveling oil passage 45d. This changes the swash plate angles of the first traveling pump 53L and the second traveling pump 53R, causing the first traveling motor 36L to rotate forward and the second traveling motor 36R to rotate reversely, causing the work machine 1 to swing to the right.

[0173] Furthermore, when the operating member 159 is swung to the left (in the direction of arrow A4 in FIG. 11), the operating valve 55D is operated and pilot pressure is output from the operating valve 55D. This pilot pressure acts on the pressure receiving portion 53a of the second traveling pump 53R via the third traveling oil passage 45c, and also acts on the pressure receiving portion 53b of the first traveling pump 53L via the second traveling oil passage 45b. This changes the swash plate angles of the first traveling pump 53L and the second traveling pump 53R, causing the first traveling motor 36L to rotate in the reverse direction and the second traveling motor 36R to rotate in the forward direction, causing the work machine 1 to swing to the left.

[0174] In addition, when the operating member 159 is swung diagonally, the rotation direction and rotation speed of the first traveling motor 36L and the second traveling motor 36R are determined by the differential pressure of the pilot pressure acting on the pressure receiving portion 53a and the pressure receiving portion 53b, and the work machine 1 turns right or left while moving forward or backward.

[0175] That is, when the operating member 159 is swung diagonally forward to the left, the work machine 1 turns left while moving forward at a speed corresponding to the swing angle of the operating member 159. When the operating member 159 is swung diagonally forward to the right, the work machine 1 turns right while moving forward at a speed corresponding to the swing angle of the operating member 159. When the operating member 159 is swung diagonally backward to the left, the work machine 1 turns left while moving backward at a speed corresponding to the swing angle of the operating member 159. When the operating member 159 is swung diagonally backward to the right, the work machine 1 turns right while moving backward at a speed corresponding to the swing angle of the operating member 159.

[0176] The control device 25 is connected to the accelerator members 84a and 84b and the first measuring device 82. The control device 25 acquires the operation amount of the accelerator members 84a and 84b, and outputs the operation amount of the accelerator members 84a and 84b to the first measuring device 82. The control device 25 then sets a target engine speed based on the amount of operation of the accelerator members 84a, 84b, and controls the operation of the engine 32 while checking the actual engine speed of the engine 32 so as to realize the target engine speed.

[0177] The hydraulic system 30D includes a speed adjustment mechanism (adjustment mechanism) 200. The speed adjustment mechanism 200 adjusts the angle of the swash plate of the travel pumps 53L, 53R by changing the pilot pressure acting on at least the pressure receiving portions 53a, 53b of the travel pumps 53L, 53R, and makes the speed (vehicle speed) of the work machine 1 faster than a predetermined speed (set speed).

[0178] The speed adjustment mechanism 200 has a pressure changing unit 201. The pressure changing unit 201 is composed of, for example, an electromagnetic proportional valve (solenoid valve, operating valve) provided in the third oil passage 40. The control device 25 inputs a control signal to the pressure changing unit 201 to change the opening degree of the pressure changing unit 201, thereby changing the primary pressure (which is the pilot pressure of the pilot oil flowing from the third oil passage 40 to the operating valve 55, and is also called the traveling primary pressure) acting on the operating valve 55 from the third oil passage 40.

[0179] In addition, the control device 25 can switch between a first mode (normal mode) in which the work machine 1 runs normally, and a second mode (creep mode) in which the work machine 1 runs at a low speed by limiting the vehicle speed of the work machine 1 to a low speed. Switching between the first mode and the second mode can be performed by operating an operation switch 202 (second operation member) provided near the driver's seat 8, for example.

[0180] 12A is a graph showing the relationship between the operation amount of accelerator member 84 and the traveling primary pressure which is the primary pressure of operation valve 55 (or the traveling secondary pressure which is the secondary pressure of operation valve 55). Control map data showing the relationship shown in FIG. 12A is stored in advance in storage unit 26. Control device 25 changes the opening degree of pressure change unit 201 based on the control map shown in FIG. 12A, thereby changing the traveling primary pressure acting on operation valve 55.

[0181] Specifically, for example, in the first mode (normal mode), the control device 25 inputs a control signal to the pressure changing unit 201 so that the primary traveling pressure is constant regardless of the amount of operation of the accelerator member 84 (first accelerator member 84a or first accelerator member 84b; first operating member), as shown by control line L10 in FIG. 12A. In the first mode (normal mode), the rotation speed of the prime mover 32 can be set by operating the accelerator member 84. That is, in the first mode, the control device 25 sets the rotation speed of the engine 32 based on the operating state of the accelerator member 84, and controls the drive of the engine 32 so that the actual rotation speed of the prime mover 32 matches the set rotation speed.

[0182] When the second mode (creep mode) is selected by the operation switch 202, the control device 25 sets the primary pressure of the operating valve 55 to a value lower than the pressure set by the control line L10, as shown by the control line L11 in Fig. 12A. Then, based on the control line L11, the control device 25 inputs a control signal to the pressure changing unit 201 so that the primary pressure of the operating valve 55 increases as the amount of operation of the accelerator member 84 (first accelerator member 84a or first accelerator member 84b) increases. Note that the control line L11 shown in Fig. 12A is just an example.

[0183] As described above, in the second mode (creep mode), the opening degree of the pressure change unit 201, the primary pressure acting on the operating valve 55, and the pilot pressure acting on the pressure receiving units 53a, 53b of the travel pumps 53L, 53R can be changed according to the amount of operation of the accelerator member 84. Also, the angle of the swash plates of the travel pumps 53L, 53R, the discharge amount of hydraulic oil from the travel pumps 53L, 53R, and the rotation speed of the travel motors 36L, 36R can be changed.

[0184] That is, in the second mode, the control device 25 controls the working machine 1 in response to the operation amount of the accelerator member 84. It is possible to control the drive of the travel pumps 53L, 53R that discharge hydraulic oil for operating the travel motors 36L, 36R, which are actuators of the travel system, and it is also possible to control the drive of the travel motors 36L, 36R. As a result, it is possible to improve the accuracy of the horsepower control and the vehicle speed (travel speed) control of the travel system of the work machine 1.

[0185] In particular, in the second mode, as the operation amount of the accelerator member 84 increases, the opening degree of the pressure change unit 201 increases, and the primary pressure acting on the operation valve 55 also increases, so that the pilot pressure acting on the pressure receiving units 53a, 53b of the travel pumps 53L, 53R can be changed to be larger. Then, the angle of the swash plate of the travel pumps 53L, 53R can be changed to increase the discharge amount of hydraulic oil from the travel pumps 53L, 53R, and the rotation speed of the travel motors 36L, 36R can be increased to increase the vehicle speed of the work machine 1. As described above, in the second mode, the control device 25 changes the angle of the swash plate of the travel pumps 53L, 53R based on the operation state (operation amount) of the accelerator member 84, without changing the rotation speed of the engine 32, to change the rotation speed of the travel motors 36L, 36R and the travel speed of the work machine 1 (travel device 5).

[0186] Also, in the second mode, the control device 25 may change the angle of the swash plates of the travel pumps 53L, 53R using the speed adjustment mechanism 200 based on the operation state of the speed adjustment member 86 and the accelerator member 84 (the first accelerator member 84a or the second accelerator member 84b) to adjust the rotation speed of the travel motors 36L, 36R and the travel speed of the travel device 5. In this case, the control device 25 first changes the angle of the swash plates of the travel pumps 53L, 53R using the speed adjustment mechanism 200 based on the operation state of the speed adjustment member 86 to adjust the rotation speed of the travel motors 36L, 36R and the travel speed of the travel device 5. When the accelerator member 84 is operated, the angle of the swash plates of the traveling pumps 53L, 53R is changed by the speed adjustment mechanism 200 based on the amount of operation of the accelerator member 84 so that the rotation speed of the traveling motors 36L, 36R and the traveling speed of the traveling device 5 are faster than those adjusted based on the operating state of the speed adjustment member 86.

[0187] Also, in the second mode, the control device 25 may change the adjustment range of the primary pressure of the operating valve 55 by shifting (translating) the control line L11 (FIG. 12A) in the vertical axis direction in accordance with the operation state of the speed adjusting member 86. The speed adjusting member 86 is composed of a volume switch or the like that temporarily adjusts (changes) the vehicle speed of the work machine 1 with an adjustment range smaller than that of the accelerator member 84 and the speed change member 61, and is operated by the driver of the work machine 1. The control device 25 detects the operation state of the speed adjusting member 86 based on an electrical signal input from an electrical circuit (not shown) that links with the speed adjusting member 86 in accordance with the operation state of the speed adjusting member 86.

[0188] Specifically, for example, the speed adjustment member 86 is operated to set an adjustment range of the vehicle speed of the work machine 1 and the primary pressure (traveling primary pressure) of the operating valve 55. Then, the control line L11 in FIG. 12A is shifted in the vertical axis direction according to the adjustment range set by the speed adjustment member 86. More specifically, in the second mode, when the first stage at which the vehicle speed is the slowest is set by the speed adjustment member 86, the control device 25 corrects the data of the control line L11 in FIG. 12A to calculate data of the control line L11a obtained by shifting the control line L11 downward. Also, when the Nth stage (N is an integer of 2 or more) at which the vehicle speed is the fastest is set by the speed adjustment member 86, the control device 25 corrects the data of the control line L11 to calculate data of the control line L11b obtained by shifting the control line L11 upward.

[0189] Thereafter, the control device 25 inputs a control signal to the pressure changing unit 201 based on the corrected control lines L11a, 11b and the operation amount of the accelerator member 84 (first accelerator member 84a or first accelerator member 84b), and changes the primary pressure of the operating valve 55. When the adjustment stage of the vehicle speed is set (or changed) by the speed adjusting member 86, the control device 25 changes the rotation speed of the engine 32 in accordance with the adjustment stage.

[0190] As another example, in the second mode, when the amount of operation of accelerator member 84 is equal to or greater than a threshold (for example, the amount of operation of first accelerator member 84a or second accelerator member 84b is equal to or greater than 80%), when the adjustment stage of the vehicle speed is changed by speed adjustment member 86, controller 25 may correct the data of control line L11 according to the changed adjustment stage as described above, and calculate data of the corrected control line. In this case, controller 25 inputs a control signal to pressure change unit 201 based on the corrected control line and the amount of operation of accelerator member 84, and changes the primary pressure of operating valve 55.

[0191] When the amount of operation of the accelerator member 84 is less than a threshold value (for example, the amount of operation of the first accelerator member 84a or the second accelerator member 84b is less than 80%), the control device 25 does not correct the data of the control line L11 even if the adjustment stage of the vehicle speed is changed by the speed adjustment member 86. In this case, the control device 25 inputs a control signal corresponding to the primary pressure corresponding to the amount of operation of the accelerator member 84 of 0% out of the primary pressures of the operating valve 55 shown by the control line L11 to the pressure changing unit 201, and realizes the primary pressure of the operating valve 55. The control device 25 also changes the rotation speed of the engine 32 based on the amount of operation of the accelerator member 84 or the adjustment stage of the vehicle speed set by the speed adjustment member 86.

[0192] The control line L10 may also be corrected by the control device 25 in accordance with the adjustment level of the vehicle speed by the speed adjusting member 86 and the operation amount of the accelerator member 84, like the above-mentioned control line L11. In the second mode, the control line L11c shown in FIG. 1 ~L11c 10 In this way, the control device 25 may change the primary pressure of the operating valve 55 in response to the amount of operation of the accelerator member 84.

[0193] In the relationship between the operation amount of the accelerator member 84 and the traveling primary pressure (or secondary pressure) shown in the graph of FIG. 12B, the operation amount when the accelerator member 84 is operated to the maximum is set to 100%. 1 ~L11c 10The data of the control lines L11c and L10 are stored in advance in the storage unit 26. 1 ~L11c 10 Data for at least one of the control lines may be stored in advance in the storage unit 26, and the control device 25 may calculate data for the remaining control lines based on the data for that control line.

[0194] In this case, the control device 25 adjusts the control line L11c in accordance with the adjustment level of the vehicle speed set by the speed adjustment member 86. 1 ~L11c 10 Specifically, for example, the speed of the work machine 1 is configured to be adjustable in 10 stages by the speed adjustment member 86. The control line L11c becomes larger as the number of adjustment stages set by the speed adjustment member 86 increases, such as the first stage being the slowest vehicle speed, the second stage being the next slowest vehicle speed, ..., the tenth stage being the fastest vehicle speed. 1 , L11c 2 , , L11c 10 In this way, the control device 25 sets the control line L11c having a large inclination. 1 ~L11c 10 will be adopted.

[0195] In detail, for example, when the vehicle speed is set to the first stage, which is the slowest, by the speed adjusting member 86, the control device 25 sets the control line L11c 1 For example, when the 10th stage, which is the fastest vehicle speed, is set, the control device 25 uses the control line L11c. 10 The control device 25 adopts the data of any one of the control lines L11c 1 ~L11c 10 Based on the amount of operation of the accelerator member 84, a control signal is input to a pressure changing section (proportional valve) 201, and the primary pressure of the operating valve 55 is changed.

[0196] In this way, by operating the speed adjusting member 86, the control device 25 controls the control line L11c 1 ~L11c 10That is, the control device 25 selects either the primary travel pressure, which is the primary pressure of the operating valve 55 (or the secondary travel pressure, which is the secondary pressure of the operating valve 55), and in turn the angle of the swash plates of the traveling pumps 53L and 53R, the rotation speed of the traveling motors 36L and 36R, and the traveling speed of the traveling device 5. Then, by operating the accelerator member 84, the control device 25 determines whether the operation amount and the selected control line L11c are in a range where the accelerator member 84 can be adjusted. 1 ~L11c 10 Based on this, the primary traveling pressure and the like are adjusted in the above adjustment stage.

[0197] In addition, when the accelerator member 84 is operated by a predetermined amount or more, the control device 25 determines whether the operation amount and the selected control line L11c 1 ~L11c 10 Based on this, the primary traveling pressure and the like are changed to increase in the corresponding adjustment stage. That is, in the second mode (creep mode), the speed adjustment member 86 is operated to set the adjustment stage of the vehicle speed of the work machine 1, and the accelerator member 84 is operated to change the vehicle speed and the like of the work machine 1 in the set adjustment stage.

[0198] In the first mode, the control device 25 employs the control line L10, and inputs a control signal to the pressure change unit (proportional valve) 201 so that the primary pressure of the operating valve 55 becomes a constant pressure indicated by the control line L10, regardless of the amount of operation of the accelerator member 84. 1 ~L11c 10 The primary pressure of the operating valve 55 that is set based on this is equal to the primary pressure (constant pressure) of the operating valve 55 indicated by the control line L10 of the first mode when the operation amount of the accelerator member 84 is 100%.

[0199] As another example, the control device 25 may change the control lines L10 and L11 in FIG. 12A or the control line L11c in FIG. 12B in response to the load (load factor, etc.) of the engine 32 or the difference between the actual engine speed and the target engine speed of the engine 32. 1 ~L11c 10 In addition, a correction may be performed to shift the value in the vertical axis direction.

[0200] Also, for example, when the operation amount of the first accelerator member 84a out of the first accelerator member 84a and the second accelerator member 84b is less than a predetermined amount (e.g., 80%), the control device 25 sets the control lines L10, L11, L11c 1 ~L11c 10 The primary pressure of the operating valve 55 may be set based on either one of the above and the operation amount of the first accelerator member 84a. When the operation amount of the first accelerator member 84a is equal to or greater than a predetermined amount, the control device 25 sets the control lines L10, L11, L11c. 1 ~L11c 10 The primary pressure of the operating valve 55 may be set based on either of the above and the amount of operation of the second accelerator member 84b.

[0201] In the above-described embodiment, the primary pressure acting on the operating valve 55 is changed in the second mode (creep mode). However, instead of this, the secondary pressure (also called the traveling secondary pressure), which is the pressure of the pilot oil discharged from the operating valve 55, may be changed. In this case, the control data shown in Figs. 12A to 12C can be used. In addition, it is preferable that the operating device 54 is configured by a joystick or the like capable of outputting an electric signal according to the operating state.

[0202] [Sixth embodiment] 13 is a diagram showing a main part of a hydraulic system 30E of a traveling system of a work machine 1 of a sixth embodiment. An operating device 54 of the hydraulic system 30E has an operating member (travel operating member) 159 for operating the traveling of the work machine 1, and operation valves 55a, 55b, 55c, and 55d. The operating member 159 is made up of a joystick, and has an operating unit 159a and an electric circuit 159b that operates in conjunction with the operating unit 159a. Hereinafter, for convenience, the operating member 159 made up of a joystick will be referred to as a joystick 159.

[0203] The operation unit 159a of the joystick 159 can be swung left and right (aircraft body width direction) or forward and backward. The electric circuit 159b inputs an operation signal (electrical signal) according to the operation amount and operation direction of the operation unit 159a to the control device 25. The control device 25 detects the operation amount and operation direction of the joystick 159 (operation unit 159a) based on the operation signal input from the electric circuit 159b.

[0204] The operating valves 55a to 55d are electromagnetic proportional valves (solenoid valves). The operating valves 55a to 55d are provided in the middle of the travel oil passage 45 (45a to 45d) connected to the third oil passage 40. More specifically, the operating valve 55a is connected to the middle of the first travel oil passage 45a. One end of the first travel oil passage 45a is connected to the third oil passage 40, and the other end of the first travel oil passage 45a is connected to the pressure receiving portion 53a of the travel pump 53L. The operating valve 55b is connected to the middle of the second travel oil passage 45b. One end of the second travel oil passage 45b is connected to the third oil passage 40, and the other end of the second travel oil passage 45b is connected to the pressure receiving portion 53b of the travel pump 53L.

[0205] The operating valve 55c is connected to a middle portion of the third traveling oil passage 45c. One end of the third traveling oil passage 45c is connected to the third oil passage 40, and the other end of the third traveling oil passage 45c is connected to the pressure receiving portion 53a of the traveling pump 53R. The operating valve 55d is connected to a middle portion of the fourth traveling oil passage 45d. One end of the fourth traveling oil passage 45d is connected to the third oil passage 40, and the other end of the fourth traveling oil passage 45d is connected to the pressure receiving portion 53b of the traveling pump 53R.

[0206] When the operating unit 159a is operated to swing forward, the control device 25 outputs a control signal to the operating valves 55a and 55c to swing the swash plates of the travel pumps 53L and 53R in the forward rotation (forward) direction. When the operating unit 159a is operated to swing backward, the control device 25 outputs a control signal to the operating valves 55b and 55d to swing the swash plates of the travel pumps 53L and 53R in the reverse (reverse) direction. When the operating unit 159a is operated to swing rightward, the control device 25 outputs a control signal to the operating valves 55a and 55d to swing the swash plate of the first travel pump 53L in the forward rotation direction and swing the swash plate of the second travel pump 53R in the reverse direction. Furthermore, when the operating unit 159a is operated to swing to the left, the control device 25 outputs a control signal to the operating valves 55b and 55c, causing the swash plate of the first traveling pump 53L to swing in the reverse direction and the swash plate of the second traveling pump 53R to swing in the forward direction.

[0207] The operating valves 55a to 55d also function as pressure changing units included in the speed adjustment mechanism 200. The control device 25 changes the secondary pressures (traveling secondary pressures) of the operating valves 55a to 55d by changing the opening degrees of the operating valves 55a to 55d in accordance with the amount of operation of the joystick 159. 14A is a graph showing the relationship between the operation amount of the joystick 159 and the traveling secondary pressure. A control map showing the relationship shown in FIG.

[0208] When the first mode (normal mode) is selected by the operation switch 202 (FIG. 13), the control device 25 sets the secondary pressure of the operation valves 55a-55d based on the control line L20 shown in FIG. 14A and the operation amount of the joystick 159, and outputs control signals to the operation valves 55a-55d to realize the secondary pressure. That is, in the first mode, the control device 25 increases the opening of the operation valves 55a-55d as the operation amount of the joystick 159 increases, thereby increasing the secondary pressure output from the operation valves 55a-55d. Note that in the first mode, the control device 25 does not change the inclination of the control line L20, etc., regardless of the operation amount of the accelerator member 84.

[0209] On the other hand, when the second mode (creep mode) is selected by the operation switch 202, the control device 25 sets the secondary pressure of the operation valves 55a-55d based on one of the control lines L21-L23 shown in FIG. 14A and the operation amount of the joystick 159, and outputs a control signal to the operation valves 55a-55d to realize the secondary pressure. That is, the control device 25 sets the secondary pressure of the operation valves 55a-55d to a value lower than the pressure set based on the control line L20 used in the first mode. The control device 25 also changes the secondary pressure output from the operation valves 55a-55d in accordance with the operation amount of the joystick 159.

[0210] When the joystick 159 is operated to its maximum, the amount of joystick 159 operation is 10 0%. Furthermore, when the first accelerator member 84a of the accelerator member 84 is operated to the maximum, the operation amount of the first accelerator member 84a also becomes 100%, and when the second accelerator member 84b is operated to the maximum, the operation amount of the second accelerator member 84b also becomes 100%.

[0211] For example, in the second mode, the speed adjustment stage corresponding to the control line L21 in FIG. 14A is selected by operating the speed change member 61 (FIG. 11) or the like (or the speed adjustment member 86). When the first accelerator member 84a is operated by a certain amount (80%) or more, and the operation amount of the second accelerator member 84b is less than 10%, the control device 25 sets the secondary pressure of the operating valves 55a to 55d based on the control line L21 and the operation amount of the joystick 159. When the operation amount of the second accelerator member 84b is less than 10% to 90%, the control device 25 sets the secondary pressure of the operating valves 55a to 55d based on the control line L22 and the operation amount of the joystick 159. When the operation amount of the second accelerator member 84b is 90% or more, the control device 25 sets the secondary pressure of the operating valves 55a to 55d based on the control line L23 and the operation amount of the joystick 159.

[0212] The secondary pressures of the operating valves 55a-55d, which are set based on the control lines L21-L23 in the second mode, are smaller than the secondary pressures of the operating valves 55a-55d, which are set based on the control line L20 in the first mode. When the joystick 159 is operated by an amount equal to or greater than a predetermined amount, the secondary pressures of the operating valves 55a-55d are set higher in the order of the control line L21, the control line L22, and the control line L23.

[0213] When the control device 25 sets the secondary pressure of the operating valves 55a to 55d based on any one of the control lines L21 to L23 and the amount of operation of the joystick 159 as described above, it outputs a control signal to the operating valves 55a to 55d to control the opening degree of the operating valves 55a to 55d so as to realize the secondary pressure.

[0214] According to the above, in the second mode (creep mode), as the operation amount of the joystick (travel operation member) 159 increases, the secondary pressure output from the operation valves 55a to 55d increases, so that it is possible to change the pilot pressure acting on the pressure receiving parts 53a and 53b of the travel pumps 53L and 53R to increase the vehicle speed of the work machine 1. That is, the control device 25 makes the rotation speed of the travel motors 36L and 36R and the travel speed of the travel device 5, which are adjusted in the second mode according to the operation amount of the joystick 159, slower than the rotation speed of the travel motors 36L and 36R and the travel speed of the travel device 5, which are adjusted in the first mode according to the same operation amount of the travel operation member. In addition, the control device 25 controls the travel pumps 53L and 53R according to the operation amount of the joystick 159, so that it is possible to improve the accuracy of the horsepower control and the vehicle speed control of the travel system of the work machine 1.

[0215] In the second mode, when the first accelerator member 84a is operated to a certain amount or more and the second accelerator member 84b is operated to a predetermined amount, the control device 25 selects one of the control lines L21 to L22. That is, the control device 25 sets an adjustment stage within a range in which the traveling secondary pressure, which is the secondary pressure of the operating valves 55a to 55d (and thus the angle of the swash plates of the traveling pumps 53L and 53R, the rotation speed of the traveling motors 36L and 36R, and the traveling speed of the traveling device 5) can be adjusted. Then, the control device 25 adjusts the traveling secondary pressure and the like based on the operation state of the joystick 159 and the selected control line. When the joystick 159 is operated to a certain amount or more, the control device 25 changes the traveling secondary pressure to be increased in the adjustment stage based on the operation amount of the joystick 159 and the selected control line.

[0216] As described above, by operating the joystick 159 after operating the accelerator members 84a, 84b, the secondary traveling pressure is adjusted, and the angle of the swash plates of the traveling pumps 53L, 53R, the rotation speed of the traveling motors 36L, 36R, and the traveling speed of the traveling device 5 are also adjusted, thereby changing the vehicle speed of the work machine 1. Also, as shown by the control lines L21-L23 in FIG. 14A, the adjustment range of the secondary traveling pressure by the joystick 159 is smaller than the adjustment range of the secondary traveling pressure by the second accelerator member 84b, so that by operating the second accelerator member 84b to set the adjustment range of the vehicle speed of the work machine 1, and then operating the joystick 159, the vehicle speed of the work machine 1 can be adjusted within an adjustment range smaller than that of the second accelerator member 84b.

[0217] Also, the vehicle speed of the work machine 1 corresponding to the amount of operation of the joystick 159 in the second mode can be made slower than the vehicle speed of the work machine 1 corresponding to the amount of operation of the joystick 159 in the first mode. Furthermore, the degree of the reduction in the vehicle speed of the work machine 1 can be set by operating the second accelerator member 84b.

[0218] In the above embodiment, in the second mode, the control device 25 adopts one of the control lines L21 to L23 depending on the amount of operation of the accelerator member 84. However, in addition to this, for example, the control device 25 may adopt one of the control lines L21 to L23 depending on the adjustment stage of the vehicle speed set by the speed adjustment member 86.

[0219] Specifically, for example, when the first stage, which is the slowest vehicle speed, is set by the speed adjusting member 86, the control device 25 adopts the control line L21. When the Nth stage (N is a natural number equal to or greater than 3) is set, which is the fastest vehicle speed, the control device 25 adopts the control line L23. When the NMth stage (M is a natural number equal to or greater than 1 and less than N, preferably M=N / 2), which is intermediate between the first stage and the Nth stage, is set, the control device 25 adopts the control line L22.

[0220] In the embodiment described above, the pilot pressure (primary pressure or secondary pressure of the operating valves 55a to 55d) of the traveling system of the work machine 1 is changed according to the amount of operation of the joystick 159, but the discharge amount of hydraulic oil from the traveling pumps 53L, 53R or the rotation speed of the traveling motors 36L, 36R (FIG. 11) may be changed according to the amount of operation of an electrical operating member such as the joystick 159. An embodiment in this case will be described below. In the following, the joystick 159 is adopted as an example of an electrical operating member.

[0221] Fig. 14B is a graph showing the relationship between the operation amount of the joystick 159 and the discharge amount of hydraulic oil from the travel pumps 53L, 53R. Fig. 14C is a graph showing the relationship between the operation amount of the joystick 159 and the rotation speed of the travel motors 36L, 36R. The control map showing the relationship shown in Fig. 14B or the control map showing the relationship shown in Fig. 14C is stored in advance in the memory unit 26 of the control device 25.

[0222] When the operation switch 202 is switched to the first mode (normal mode), the control device 25 employs the control lines L20b and L20c. When the operation switch 202 is switched to the second mode (creep mode), the control device 25 employs one of the control lines L21b to L23b or one of the control lines L21c to L23c.

[0223] For example, the speed adjustment stage corresponding to the control lines L21b and L21c is selected by the shift member 61, and the first accelerator member 84a is operated by a certain amount (80%) or more. In this case, when the operation amount of the second accelerator member 84b is less than 10%, the control device 25 adopts the control lines L21b and L21c. When the operation amount of the second accelerator member 84b is 10% to less than 90%, the control device 25 adopts the control lines L22b and L22c. When the second accelerator member 84b is 90% or more, the control device 25 adopts the control lines L23b and L23c. As another example, when the second accelerator member 84b is 90% or more, the control device 25 may adopt not only the control lines L23b and L23c but also the control line L20. The solenoid valves 181B, 182, 185, and 186 can be used to lower the control line L20.

[0224] As described above, when the control device 25 adopts any one of the control lines L20b to L23b, L20c to L23c, it sets the discharge volume of the travel pumps 53L, 53R or the rotation speed of the travel motors 36L, 36R based on the control line and the operation amount of the joystick 159, and outputs a control signal to the operating valves 55a to 55d to realize the discharge volume or rotation speed.

[0225] As another example, the control device 25 may set the secondary pressure of the operating valves 55a-55d, the discharge amount of hydraulic oil from the travel pumps 53L, 53R, or the rotation speed of the travel motors 36L, 36R based on the following arithmetic expressions (5)-(7). Equations (5)-(7) are arithmetic expressions used when the operation switch 202 is switched to the second mode, the operation amount of the first accelerator member 84a is equal to or greater than a threshold value (e.g., 80% or more), the operation amount of the second accelerator member 84b is equal to or greater than 10%, and the speed adjustment member 86 is set to the first stage as the vehicle speed adjustment stage.

[0226] Equation (5) is as follows. Secondary pressure of the operating valves 55a to 55d=(Secondary pressure of the operating valves 55a to 55d corresponding to the operation amount of the joystick 159 on the control line L21 in FIG. 14A)×[1+constant×(operation amount (%) of the second accelerator member 84b−10%))] (5)

[0227] When the control device 25 calculates the secondary pressure of the operating valves 55a to 55d based on the above formula (5), the control device 25 compares the calculated value with the secondary pressure (set value) of the operating valves 55a to 55d corresponding to the operation amount of the joystick 159 set based on the control line L21 of Fig. 14A. If the calculated value of the secondary pressure of the operating valves 55a to 55d is greater than the set value, the control device 25 controls the aperture of the operating valves 55a to 55d so as to realize the calculated value (secondary pressure of the operating valves 55a to 55d). On the other hand, if the calculated value of the secondary pressure of the operating valves 55a to 55d is equal to or less than the set value, the control device 25 controls the aperture of the operating valves 55a to 55d so as to realize the set value (secondary pressure of the operating valves 55a to 55d).

[0228] Equation (6) is as follows. Discharge amount of hydraulic oil from the travel pumps 53L, 53R=(Discharge amount of the travel pumps 53L, 53R corresponding to the operation amount of the joystick 159 on the control line L21 in FIG. 14B)×[1+Constant×(Operation amount of the second accelerator member 84b (%)−10%))] (6)

[0229] When the control device 25 calculates the discharge amount of the hydraulic oil from the travel pumps 53L, 53R based on the above formula (6), the control device 25 compares the calculated value with the discharge amount (set value) of the travel pumps 53L, 53R corresponding to the operation amount of the joystick 159 set based on the control line L21 of FIG. 14B. If the calculated value of the discharge amount of the travel pumps 53L, 53R is greater than the set value, the control device 25 controls the opening degree of the operation valves 55a to 55d so as to realize the calculated value (discharge amount of the travel pumps 53L, 53R). On the other hand, if the calculated value of the discharge amount of the travel pumps 53L, 53R is equal to or less than the set value, the control device 25 controls the opening degree of the operation valves 55a to 55d so as to realize the set value (discharge amount of the travel pumps 53L, 53R).

[0230] In addition, the opening degrees of the operating valves 55a to 55d corresponding to the discharge volumes of the travel pumps 53L, 53R, or control data indicating the control signals that the control device 25 inputs to the operating valves 55a to 55d to realize those opening degrees, are pre-stored in the memory unit 26.

[0231] Equation (7) is as follows. Rotational speed of the travel motors 36L, 36R=(Rotational speed of the travel motors 36L, 36R corresponding to the operation amount of the joystick 159 on the control line L21 in FIG. 14C)×[1+Constant×(Operation amount (%) of the second accelerator member 84b−10%))] (7)

[0232] When the control device 25 calculates the rotation speeds of the traveling motors 36L, 36R based on the above formula (7), the control device 25 compares the calculated value with the rotation speeds (set value) of the traveling motors 36L, 36R corresponding to the operation amount of the joystick 159 set based on the control line L21 in Fig. 14C. If the calculated value of the rotation speeds of the traveling motors 36L, 36R is greater than the set value, the control device 25 controls the openings of the operation valves 55a to 55d so as to realize the calculated value (rotation speeds of the traveling motors 36L, 36R). On the other hand, if the calculated value of the rotation speeds of the traveling motors 36L, 36R is equal to or less than the set value, the control device 25 controls the openings of the operation valves 55a to 55d so as to realize the set value (rotation speeds of the traveling motors 36L, 36R).

[0233] In addition, the opening degrees of the operating valves 55a to 55d corresponding to the rotation speeds of the travel motors 36L, 36R, or control data indicating the control signals that the control device 25 inputs to the operating valves 55a to 55d to realize those opening degrees, are pre-stored in the memory unit 26. When the operation switch 202 is switched to the first mode, the control device 25 applies the control lines L20, L20b, and L20c in the above equations (5) to (7).

[0234] In addition, when the operation switch 202 is switched to the second mode and the speed adjustment member 86 is set to the second or higher adjustment stage of the vehicle speed, the control device 25 applies one of the control lines L21 to L23, L21b to L23b, or L21c to L23c in the above equations (5) to (7) depending on the adjustment stage.

[0235] As another example, in the case where the working implement 11 (FIG. 24) is replaceable in the working machine 1, the control device 25 may detect the type of working implement 11 attached to the working machine 1 by a detection device such as a sensor, and change the constant (correction coefficient) of at least one of the above-mentioned equations (5) to (7) according to the type of the working implement 11. Also, instead of the joystick 159, another electrical operating member that outputs an electric signal according to the operating state may be used, or another operating member that outputs a hydraulic signal according to the operating state may be used.

[0236] In addition, the control device 25 may perform corrections to shift the control lines L20 to L23, L20b to L23b, and L20c to L23c in Figures 14A to 14C in the vertical axis direction depending on the load on the engine 32 (such as the load rate) or the difference between the actual rotation speed of the engine 32 and the target engine rotation speed.

[0237] In addition, for example, when the amount of operation of the first accelerator member 84a is less than a predetermined amount (such as 80%), the control device 25 may adopt any one of the control lines L20-L23, L20b-L23b, or L20c-L23c depending on the amount of operation of the first accelerator member 84a, and set the secondary pressure of the operating valves 55a-55d, the discharge volume of the travel pumps 53L, 53R, or the rotation speed of the travel motors 36L, 36R based on the control line and the amount of operation of the joystick 159.

[0238] In addition, for example, when the amount of operation of the first accelerator member 84a is equal to or greater than a predetermined amount, the control device 25 may adopt any one of the control lines L20-L23, L20b-L23b, or L20c-L23c in accordance with the amount of operation of the second accelerator member 84b, and set the secondary pressure of the operating valves 55a-55d, the discharge volume of the travel pumps 53L, 53R, or the rotation speed of the travel motors 36L, 36R based on the control line and the amount of operation of the joystick 159.

[0239] Also, for example, in the second mode, when the joystick (travel operation member) 159 is operated, the control device 25 changes the angle of the swash plate of the travel pumps 53L, 53R by the speed adjustment mechanism 200 based on the operation amount of the joystick 159 to adjust the rotation speed of the travel motors 36L, 36R and the traveling speed of the traveling device 5. When the operation amount of the joystick 159 is constant, that is, when the speed adjustment mechanism 200 is adjusting the rotation speed of the travel motors 36L, 36R and the traveling speed of the traveling device 5 to be constant based on the operation amount of the joystick 159, when the accelerator member 84 (the first accelerator member 84a or the second accelerator member 84b) is operated, the speed adjustment mechanism 200 changes the angle of the swash plate of the travel pumps 53L, 53R based on the operation amount of the accelerator member 84 without changing the rotation speed of the engine 32, and the rotation speed of the travel motors 36L, 36R and the traveling speed of the traveling device 5 may be changed (re-adjusted).

[0240] Also, for example, in the second mode, the control device 25 may change the angle of the swash plate of the travel pumps 53L, 53R using the speed adjustment mechanism 200 based on the operation state of the speed adjustment member 86 to adjust the rotation speed of the travel motors 36L, 36R and the traveling speed of the travel device 5, and then, when the operation amount of the first accelerator member 84a is equal to or greater than a certain amount and the second accelerator member 84b is operated, change the angle of the swash plate of the travel pumps 53L, 53R using the speed adjustment mechanism 200 based on the operation amount 84b of the second accelerator member to adjust the rotation speed of the travel motors 36L, 36R and the traveling speed of the travel device 5. In this case, the control device 25 adjusts the rotation speed of the travel motors 36L, 36R and the traveling speed of the travel device 5, which are different from the rotation speed of the travel motors 36L, 36R and the traveling speed of the travel device 5 adjusted based on the operation state of the speed adjustment member 86, based on the operation amount of the second accelerator member 84b.

[0241] 14A, the controller 25 selects a speed adjustment stage corresponding to one of the control lines L21-L23 based on the operation state of the speed adjustment member 86. When the first accelerator member 84a is operated a certain amount (80%) or more and the second accelerator member 84b is further operated, the controller 25 shifts the selected control line L21-L23 in the vertical axis direction based on the operation amount of the second accelerator member 84b. At this time, the controller 25 shifts the selected control line L21-L23 in the vertical axis direction so that it does not overlap with the other control lines L21-L23.

[0242] As a result, the rotation speed of the traveling motors 36L, 36R and the traveling speed of the traveling device 5, which are different from those adjusted based on the operating state of the speed adjustment member 86, are adjusted by the control device 25 based on the operation amount of the second accelerator member 84b. In addition, the control device 25 may input a control signal to all, any one, or any two or more of the operating valves 55a-55d based on the secondary pressure of the operating valves 55a-55d, the discharge volume of the travel pumps 53L, 53R, or the rotation speed of the travel motors 36L, 36R set as described above, to control the opening degree of the operating valves.

[0243] In the sixth embodiment described above, the secondary pressures of the operating valves 55a to 55d and the like are changed in the second mode (creep mode), but other than this, the pilot pressure acting on the pressure receiving portions 53a and 53b of the travel pumps 53L and 53R, the angles of the swash plates of the travel pumps 53L and 53R and the travel motors 36L and 36R, or the rotation speeds of the travel motors 36L and 36R may be changed using valves other than the operating valves 55a to 55d. Also, the travel pumps 53L and 53R or the travel motors 36L and 36R may be controlled.

[0244] Fig. 15 is a diagram showing a modified example of the speed adjustment mechanism 200. In the speed adjustment mechanism 200 shown in Fig. 15, a pressure change unit 201A is connected to a branch oil passage 51 branched from each of the travel oil passages 45a to 45d. The pressure change unit 201A is composed of, for example, a variable relief (solenoid valve) valve. The travel oil passages 45a to 45d are connected to operation valves (solenoid proportional valves) 55a to 55d as shown in Fig. 13.

[0245] The control device 25 uses the control map shown in FIG. 12A and the operation amount of the accelerator member 84. Based on this, the opening degree of the pressure changing unit 201A is changed to change the pilot pressure acting on the travel oil passages 45a to 45d. Specifically, when the operation switch 202 is switched to the first mode (normal mode), the control device 25 fixes the opening degree of the pressure changing unit 201A to full open or a predetermined opening degree based on the control line L10 in Fig. 12A regardless of the operation amount of the accelerator member 84, and keeps the pilot pressure (secondary pressure of the operation valves 55a to 55d) acting on the travel oil passages 45a to 45d constant.

[0246] On the other hand, when the second mode (creep mode) is selected by the operation switch 202, the control device 25 sets the opening degree of the pressure changer 201A to be lower than the opening degree of the pressure changer 201A when the control line L10 is used, based on the control line L11 in Fig. 12A and the operation amount of the accelerator member 84, thereby lowering the pilot pressure (secondary pressure of the operation valves 55a-55d) acting on the travel oil passages 45a-45d compared to the first mode. Also, the control device 25 increases the opening degree of the pressure changer 201A so that the pilot pressure acting on the travel oil passages 45a-45d increases as the operation amount of the accelerator member 84 increases.

[0247] That is, in the second mode (creep mode), as the operation amount of the accelerator member 84 increases, the opening degree of the pressure change unit 201A increases, so that the pilot pressure acting on the pressure receiving parts 53a, 53b of the travel pumps 53L, 53R can be changed to increase. Then, by changing the angle of the swash plate of the travel pumps 53L, 53R, the discharge amount of hydraulic oil from the travel pumps 53L, 53R can be increased, the rotation speed of the travel motors 36L, 36R can be increased, and the vehicle speed (travel speed) of the work machine 1 can be increased.

[0248] 12A is used in combination with the pressure changing unit 201A in Fig. 15, the control map shown in Fig. 12A may be used in combination with the control device 25 to change the control line L10 in accordance with the load on the engine 32 or the difference between the actual engine speed and the target engine speed of the engine 32. In addition, as the load on the engine 32, for example, the opening degree of the throttle valve detected by a sensor or the like, or the load factor of the engine 32 may be used.

[0249] Then, if the load of the engine 32 is equal to or greater than a first threshold, the control device 25 may shift the control line L10 downward (in the pressure decreasing direction) to set the secondary pressure of the operating valves 55a to 55d low. Alternatively, if the difference between the actual engine speed and the target engine speed of the engine 32 is equal to or greater than a second threshold, the control device 25 may shift the control line L10 downward to set the secondary pressure of the operating valves 55a to 55d low. In these cases, the control device 25 may shift the control line L10 in the direction of change of the secondary pressure of the operating valves 55a to 55d in conjunction with anti-stall control that prevents the engine 32 from stalling.

[0250] Alternatively, the control device 25 may obtain a new control line by shifting the control line L10 in Fig. 12A in the vertical axis direction according to the load on the engine 32 or the difference between the actual rotation speed and the target engine rotation speed of the engine 32 through PID control or PI control. Moreover, not only the control line L10 but also the control line L11 of the second mode may be shifted in the vertical axis direction in the same manner as above. Furthermore, the secondary pressure of the operating valves 55A to 55D in FIG. 11 (pilot pressure acting on the pressure receiving portions 53a, 53b of the travel pumps 53L, 53R) may be changed by using the pressure change portion 201A in FIG. 15 and the control map in FIG. 12A in combination.

[0251] [Seventh embodiment] Fig. 16A is a diagram showing in a table the relationship between engine speed and LS differential pressure in the seventh embodiment. As the hydraulic system in the seventh embodiment, any one of the working hydraulic systems 30A to 30C in Figs. 1, 3, and 10A, or any one of the traveling hydraulic systems 30D, 30E in Figs. 11 and 13 can be applied. Also, the speed adjustment mechanism 200 shown in Fig. 15 can be applied.

[0252] In the seventh embodiment, the control device 25 controls the operation of the engine 32 to execute auto idle control that suppresses the actual rotation speed of the engine 32. In detail, for example, in the auto idle control, the control device 25 adjusts the actual rotation speed of the engine 32 to match a predetermined target engine rotation speed during auto idle control or to be equal to or lower than the target engine rotation speed during auto idle control.

[0253] Triggers for starting auto idle control include, for example, when the work operating member 58 or the travel operating member 159 has not been operated for a certain period of time or more, when the supply of pilot oil to the operating devices 52, 54 has been cut off by an unload valve (not shown) (hydraulic lock state), when a parking switch (not shown) that commands the operation of a braking device (not shown) is operated, or when an operating switch that commands the execution of auto idle control is operated.

[0254] If any of the operating members 58, 159, 84 is operated while the auto idle control is being performed, the control device 25 stops the auto idle control and returns to the normal state. In the normal state, the control device 25 controls the rotation speed of the engine 32 so that it matches the set rotation speed of the engine 32 set by, for example, any of the hand operating members 86, 159, 84 that can be operated by the driver's hand or the accelerator member 84.

[0255] Furthermore, the control device 25 sets and changes the LS differential pressure in conjunction with the auto idle control. For example, when the auto idle control is not being executed (normal operation), the control device 25 sets the LS differential pressure according to the engine speed (actual speed), as shown in the first and second columns from the left in Fig. 16A. Then, the control device 25 realizes the set LS differential pressure by the hydraulic control units 75, 75A to 75C.

[0256] Furthermore, when the auto idle control is being executed, the control device 25 sets the LS differential pressure to a fixed value (e.g., 1.5 MPa) even if the engine speed (actual speed) changes, as shown in the first and third columns from the left in Fig. 16A. This fixed value of the LS differential pressure is the same as the LS differential pressure that is set when the engine speed (actual speed) is at its maximum, as explained in the first embodiment and the like (see control line L1 in Fig. 2A, Fig. 2B, and the like).

[0257] That is, when the auto idle control is being performed, the control device 25 sets a large predetermined differential pressure (third column from the left in FIG. 16A) that is equal to or greater than a predetermined differential pressure (second column from the left in FIG. 16A) according to the engine speed (actual speed) as the LS differential pressure, and fixes the LS differential pressure even if the engine speed changes. Then, the control device 25 realizes and maintains the set LS differential pressure (fixed value) by the hydraulic control units 75, 75A to 75C.

[0258] According to the above, even if the auto idle control is executed and the actual rotation speed of the engine 32 drops, a pressure (the LS differential pressure in the third column from the left in FIG. 16A) equal to or higher than a predetermined pressure corresponding to the actual rotation speed (the LS differential pressure in the second column from the left in FIG. 16A) is set as the LS differential pressure, and the LS differential pressure is realized. Therefore, when the operating member 58 is operated, the hydraulic actuators 14, 15, etc. can be quickly operated to instantly perform work by the working device 4 in accordance with the operating state of the joystick 159, and the accuracy of horsepower control of the working system of the working machine 1 can be improved.

[0259] In addition, while the auto idle control is being executed, a predetermined pressure corresponding to the maximum rotation speed of the engine 32 (the LS differential pressure in the bottom row, second column from the left in FIG. 16A) is set as the LS differential pressure, and by realizing this LS differential pressure, the hydraulic actuators 14, 15 and the working device 4 can be operated more quickly in response to the operation of the operating member 58.

[0260] As another example, when the control device 25 is executing the auto idle control, the control device 25 may set the LS differential pressure corresponding to the rotation speed (target engine rotation speed) of the engine 32 set by the accelerator member 84. This makes it possible to set a pressure equal to or higher than a predetermined pressure corresponding to the actual rotation speed of the engine 32 as the LS differential pressure.

[0261] The control device 25 may change the primary pressure or secondary pressure (traveling primary pressure / secondary pressure) of the operating valve 55 (operating valves 55A to 55D in FIG. 11 or operating valves 55a to 55d in FIG. 13) in conjunction with the auto-idle control. The relationship between the engine speed and the traveling primary pressure / secondary pressure in this case is shown in the table of FIG. 16B. In the example shown in FIG. 16B, when auto idle control is not being executed (normal operation), the control device 25 sets the traveling primary pressure and secondary pressure according to the engine speed (actual speed), as shown in the first and second columns of FIG. 16B.

[0262] Furthermore, when the auto idle control is being executed, the control device 25 sets the primary pressure or secondary pressure of the operating valve 55 to a fixed value (e.g., 2.6 MPa) even if the engine speed (actual speed) changes, as shown in the first and third columns from the left in Fig. 16B. This fixed value of the primary pressure or secondary pressure of the operating valve 55 is the same as the primary pressure or secondary pressure (2.6 MPa) of the operating valve 55 set when the engine speed (actual speed) is at its maximum (2600 rpm) (see the bottom panel in the second column from the left in Fig. 16B).

[0263] That is, when the control device 25 is executing the auto idle control, the control device 25 sets the primary pressure or secondary pressure (pilot pressure) of the operating valves 55a to 55d to a predetermined pressure equal to or greater than a predetermined pressure according to the engine speed by the pressure changing units (201, 201A, 55a to 55d) described above, and fixes (maintains) the pressure even if the engine speed changes. Then, the control device 25 realizes and maintains the set primary pressure or secondary pressure (fixed value) by the pressure changing units (201, 201A, 55a to 55d).

[0264] According to the above, even if the auto idle control is executed and the actual rotation speed of the engine 32 drops, a pressure (the pressure in the third row from the left in FIG. 16B) equal to or higher than a predetermined pressure (the pressure in the second row from the left in FIG. 16B) corresponding to the actual rotation speed is set as the primary pressure or secondary pressure of the operating valve 55, and the primary pressure or secondary pressure is realized. Therefore, when the joystick 159 is operated, the travel pumps 53L, 53R and the travel motors 36L, 36R are quickly operated (responded), and the working machine 1 can be instantly traveled by the traveling device 5 according to the operation state of the joystick 159. This makes it possible to improve the accuracy of the horsepower control of the traveling system of the working machine 1.

[0265] In addition, while auto idle control is being executed, a predetermined pressure (the pressure in the bottom row, second column from the left in FIG. 16B) corresponding to the maximum rotation speed of the engine 32 is set as the primary pressure or secondary pressure of the operating valve 55, and the primary pressure or secondary pressure is realized, whereby the traveling pumps 53L, 53R, the traveling motors 36L, 36R, the traveling device 5, etc. can be operated more quickly in response to the operation of the joystick 159.

[0266] As another example, when the control device 25 is executing the auto idle control, the control device 25 may set the primary pressure or secondary pressure of the operating valve 55 corresponding to the rotation speed (target engine rotation speed) of the engine 32 set by the accelerator member 84. This makes it possible to set a pressure equal to or higher than a predetermined pressure corresponding to the actual rotation speed of the engine 32 as the primary pressure or secondary pressure of the operating valve 55. Also, the primary pressure or secondary pressure of the operating valve 55 may be changed using the actuated valve 167 (FIG. 18) instead of the pressure changing units 201, 201A, 55a to 55d.

[0267] The control device 25 changes the primary pressure of the operating valve 55 by changing the control signal (current value) input to the pressure changing units (201, 201A, 55a to 55d) described above. 13, the operating valve 55 may be configured with electromagnetic proportional valves 55a-55d, and the controller 25 may change the secondary pressure of the electromagnetic proportional valves 55a-55d by, for example, changing a control signal (applied current value) input to the electromagnetic proportional valves 55a-55d. Alternatively, as shown in FIG 15, the pressure changing unit 201A provided in the travel oil passages 45a-45d may be configured with an adjustable relief valve, and the controller 25 may change the secondary pressure of the electromagnetic proportional valves 55a-55d by changing a control signal input to the adjustable relief valve 201A.

[0268] Furthermore, when changing the primary traveling pressure or the secondary traveling pressure (pilot pressure) by the solenoid proportional valve (pressure changing unit 201, 201A, 55a to 55d) according to the operation amount of the operating member 159, 84, 58 for traveling, the control device 25 may change the current value (control signal) input to the solenoid proportional valve (201, 201A, 55a to 55d) during execution of the auto idle control and during normal operation when the auto idle control is not executed. As an example of this case, the relationship between the operation amount of the joystick 159, the engine speed, and the current input to the solenoid proportional valve 201 is shown in a graph in FIG. 17. Note that the horizontal axis in FIG. 17 indicates time.

[0269] As shown in Fig. 17, when the joystick 159 is operated (amount of operation>0%) at time t1 while auto idle control is being executed (AI is executed), thereafter (to the right of time t1 on the horizontal axis in Fig. 17), the control device 25 sets the current to be input to the solenoid proportional valve 201 as shown by the two-dot chain line in Fig. 17 according to the amount of operation of the joystick 159 shown by the dotted line in Fig. 17. That is, when the joystick 159 is operated while auto idle control is being executed, the current value (two-dot chain line in Fig. 17) input from the control device 25 to the solenoid proportional valve 201 becomes steeper than the current value (dashed line in Fig. 17) input from the control device 25 to the solenoid proportional valve 201 when the joystick 159 is operated during normal operation when auto idle control is not being executed.

[0270] For this reason, the input current from the control device 25 to the solenoid proportional valve 201 when the joystick 159 is operated during execution of auto idle control (two-dot chain line in FIG. 17) coincides with the current value corresponding to the amount of operation of the joystick 159 more quickly than the input current from the control device 25 to the solenoid proportional valve 201 when the joystick 159 is operated normally (dashed line in FIG. 17). Accordingly, the primary pressure or secondary pressure of the operating valve 55 when the joystick 159 is operated during execution of auto idle control coincides with the pressure corresponding to the amount of operation of the joystick 159 more quickly than the primary pressure or secondary pressure of the operating valve 55 when the joystick 159 is operated normally.

[0271] According to the above, even if the auto idle control is executed and the actual rotation speed of the engine 32 drops, when the joystick 159 is operated, the travel pumps 53L, 53R and the travel motors 36L, 36R can be made to react quickly, and the work machine 1 can be made to travel instantly by the travel device 5 in accordance with the operation state of the joystick 159. This makes it possible to improve the accuracy of the horsepower control of the travel system of the work machine 1.

[0272] Furthermore, when the joystick 159 is operated while auto idle control is being executed, the control device 25 may apply a high voltage to the solenoid proportional valve 201 and input a current value corresponding to the amount of operation of the joystick 159 to the solenoid proportional valve 201. As a result, the travel pumps 53L, 53R and the travel motors 36L, 36R are controlled by a pilot pressure corresponding to the amount of operation of the joystick 159, and the work machine 1 can quickly return to the normal state from the auto idle state.

[0273] In addition, when the joystick 159 is operated during normal operation when the auto idle control is not being performed, the input current (dashed line in FIG. 17) from the control device 25 to the solenoid proportional valve 201 is The timing at which the current value coincides with the amount of operation of the joystick 159 is almost the same as the timing at which the actual rotation speed of the engine 32 (not shown in FIG. 17) coincides with the rotation speed corresponding to the amount of operation of the joystick 159 when the joystick 159 is operated under normal conditions.

[0274] In addition, the input current from the control device 25 to the solenoid proportional valve 201 when the joystick 159 is operated to its maximum (100%) during execution of auto idle control and the input current from the control device 25 to the proportional valve 201 when the joystick 159 is operated to its maximum (100%) under normal conditions may be set to the same value.

[0275] In the above embodiment, an example has been described in which the primary pressure of the operating valve 55 is changed by the electromagnetic proportional valve 201 in accordance with the amount of operation of the operating member 159 for traveling, but the present invention is not limited to this. For example, an electromagnetic proportional valve may be provided that changes the primary pressure (pilot pressure of the inflowing pilot oil) or secondary pressure (pilot pressure of the outflowing pilot oil) of the control valve 56 in accordance with the amount of operation of the operating member 58 for work (FIG. 1, etc.). In this case, the primary pressure or secondary pressure of the control valve 56 may be set or changed by applying, for example, the control map shown in FIG. 17.

[0276] In the first embodiment shown in Figures 1A to 2B, the coefficient α of equation (2) for calculating the second control line L2 (Figure 2A) is changed between the travel priority mode and the work priority mode of the work machine 1. In addition to this, the coefficient α of equation (2) may be changed, for example, in conjunction with the operating valve 167 shown in Figure 18.

[0277] [Eighth embodiment] Fig. 18 is an overall view of a hydraulic system 30F of a traveling system of a work machine 1 of an eighth embodiment. The hydraulic system 30F shown in Fig. 18 is provided with an operating valve 167 instead of the pressure change unit 201 of the speed adjustment mechanism 200 shown in Fig. 11. The rest of the configuration of the hydraulic system 30F is the same as that of the hydraulic system 30E shown in Fig. 11. The operating valve 167 is made up of an electromagnetic proportional valve (solenoid valve) and is provided in the third oil passage 40. The operating valve 167 is a valve for preventing engine stall of the work machine 1 (also called an anti-stall valve), and changes the pilot pressure of the pilot oil acting on the operating valves 55 (55A to 55D) (the primary pressure of the operating valves 55, i.e., the traveling primary pressure).

[0278] The control device 25 executes control to prevent the engine 32 from stopping unintentionally (engine stall), that is, anti-stall control, by controlling the opening of the operating valve 167. In the anti-stall control, for example, when a drop rotation speed, which is the difference between a target engine rotation speed set by the accelerator member 84 and an actual rotation speed of the engine 32 detected by the first measuring device 82, is equal to or greater than a threshold value, the control device 25 prevents engine stall by reducing the output (the force when discharging hydraulic oil) of the travel pumps 53L, 53R.

[0279] The operating valve 167 is provided in the third oil passage 40 through which the pilot oil flows, and changes the pilot pressure acting on the pressure receiving parts 53a, 53b of the travel pumps 53L, 53R by changing the opening degree thereof by the control device 25. The control device 25 changes the opening degree of the operating valve 167 by changing a control signal (which may be a current signal or a voltage signal) input to the operating valve 167.

[0280] By changing the opening degree of the operating valve 167, the pilot pressure (travel primary pressure) acting on the operating valve 55 (55A to 55D) from the operating valve 167 is changed, and the pilot pressure acting on the pressure receiving parts 53a and 53b of the travel pumps 53L and 53R is also changed. Then, the angle of the swash plate of the travel pumps 53L and 53R is changed, and the discharge amount of the hydraulic oil from the travel pumps 53L and 53R is changed. The rotation speed of the travel motors 36L, 36R is also changed. That is, the control device 25 changes the travel primary pressure by changing the opening of the operating valve 167, and controls the discharge amount of hydraulic oil from the travel pumps 53L, 53R and the output of the travel motors 36L, 36R. This makes it possible to prevent engine stall in the work machine 1 and improve the accuracy of horsepower control of the travel system.

[0281] In addition, by combining the hydraulic system 30F of the traveling system shown in FIG. 18 with the hydraulic system 30A-30C of the working system shown in FIG. 1A, FIG. 1B, FIG. 3, or FIG. 7A-FIG. 10A, the control device 25 changes the opening of the operating valve 167, so that the pilot pressure acting on the third oil passage 40 is changed, and the pilot pressure acting on the other oil passages 41, 41B, 41C, 41D, or the oil passage 41A connected to the third oil passage 40 is also changed. That is, the pilot pressure for operating the opening change unit 76 is changed. Therefore, the operating states of the opening change unit 76, the flow rate compensation valve 72, and the swash plate variable unit 73 are changed, and the angle of the swash plate of the second hydraulic pump P2, the output of the second hydraulic pump P2 (the amount of hydraulic oil discharged from the second hydraulic pump P2), and the LS differential pressure are changed in response to the change. In this way, the control device 25 can also change the LS differential pressure by controlling the operation of the operating valve (solenoid valve) 167, thereby improving the accuracy of the horsepower control of the work system of the work machine 1.

[0282] Furthermore, by combining hydraulic systems 30D, 30E of the traveling system shown in Figure 11, Figure 13 or Figure 15 with hydraulic systems 30A to 30C of the work system shown in Figure 1A, Figure 1B, Figure 3 or Figures 7A to 10A, the control device 25 can change the LS differential pressure by controlling the operation of solenoid valves 201, 55a to 55d, 201A, thereby improving the accuracy of horsepower control of the work system of the work machine 1.

[0283] FIG. 19 is a graph showing the relationship between the engine speed and the primary traveling pressure in the eighth embodiment. The data of the control map showing the relationship in FIG. 19 is stored in advance in the memory unit 26 of the control device 25. The primary traveling pressure is the pilot pressure of the pilot oil from the operating valve 167 to the operating device 54 in the third oil passage 40. In other words, the primary traveling pressure is the primary pressure of the pilot oil acting on the multiple operating valves 55A, 55B, 55C, and 55D provided in the operating member 159 that performs the traveling operation of the work machine 1. The multiple control lines L80A, L80B, and L80C shown in FIG. 19 are control data used by the control device 25 to set the primary traveling pressure.

[0284] For example, when the drop rotation speed, which is the difference between the target engine rotation speed and the actual rotation speed of the engine 32, is less than a predetermined threshold value during execution of the anti-stall control, the control device 25 sets the primary traveling pressure based on the control line L80C and the actual rotation speed. In detail, as shown by the thin dotted line in FIG. 19, the primary traveling pressure is set at the intersection of the rotation speed (actual rotation speed) of the engine 32 and the control line L80. The control line L80C is shifted toward a higher primary traveling pressure (upward in FIG. 19) compared to the control line L80A. For this reason, when the control device 25 employs the control line L80C, ​​the primary traveling pressure is set higher than when the control lines L80A and L80B are employed.

[0285] On the other hand, when the drop rotation speed of the engine 32 is equal to or higher than the threshold value during execution of anti-stall control, the control device 25 sets the primary traveling pressure based on either the control line L80A or the control line L80B and the actual rotation speed of the engine 32. Compared to the control line L80A, the control line L80B is shifted toward a side where the primary traveling pressure is lower (downward in FIG. 19). For this reason, when the control device 25 employs the control line L80B, the primary traveling pressure is set lower than when the control lines L80A and L80C are employed.

[0286] For example, if the drop speed of the engine 32 is equal to or greater than the threshold and is equal to or greater than a predetermined value that is greater than the threshold, the control device 25 performs the following operation based on the control line L80B and the actual speed of the engine 32: If the drop rotation speed of the engine 32 is equal to or higher than the threshold value and is lower than a predetermined value, the control device 25 sets the primary traveling pressure based on the control line L80A and the actual rotation speed of the engine 32.

[0287] As another example, the controller 25 may employ one of the control lines L80A, L80B, L80C based on a variable other than the drop rotation rate. For example, when the work machine 1 is in the travel priority mode, the control device 25 employs the control line L80A regardless of the drop rotation speed, and employs the largest coefficient candidate value among a plurality of different coefficient candidate values ​​stored in advance as the coefficient α in the equations (2) to (4) shown in the first embodiment. Also, when the work machine 1 is in the work priority mode, the control device 25 employs the control line L80B regardless of the drop rotation speed, and employs the smallest coefficient candidate value as the coefficient α.

[0288] Furthermore, between the traveling priority mode and the work priority mode, a slight traveling priority mode in which traveling is given a slight priority over work, and a slight work priority mode in which work is given a slight priority over traveling, may be provided. In this case, when the work machine 1 is in the slight traveling priority mode, the control device 25 adopts the control line L90A and adopts as the coefficient α a coefficient candidate value that is smaller than the coefficient candidate value adopted in the traveling priority mode and larger than the coefficient candidate value adopted in the work priority mode. Also, when the work machine 1 is in the slight work priority mode, the control device 25 adopts the control line L80B and adopts as the coefficient α a coefficient candidate value that is smaller than the coefficient candidate value adopted in the slight traveling priority mode and larger than the coefficient candidate value adopted in the work priority mode.

[0289] As described above, the control lines L80A and L80B are adopted and the coefficient α is changed regardless of the drop rotation speed depending on the execution state of the mode indicating whether the working machine 1 is to prioritize traveling or working. Therefore, the control device 25 can calculate the second control line L2 (FIG. 2A) based on any one of the above-mentioned formulas (2) to (4) and the coefficient α. Then, when the actual rotation speed of the engine 32 is lower than the target engine rotation speed, or when the actual rotation speed is lower than the rotation speed obtained by subtracting a predetermined value from the target engine rotation speed, the control device 25 can set or change the LS differential pressure based on the second control line L2 and the actual rotation speed of the engine 32.

[0290] That is, the control device 25 can set or change the LS differential pressure according to the priority status of the traveling and work of the work machine 1 and the actual rotation speed of the engine 32, and can change the discharge amount of hydraulic oil from the second hydraulic pump P2 according to the LS differential pressure. Also, the control device 25 can set the traveling primary pressure based on the control lines L80A, L80B, L80C and the actual rotation speed of the engine 32, and can change the discharge amount of hydraulic oil from the traveling pumps 53L, 53R according to the traveling primary pressure. Furthermore, as a result of these, it is possible to improve the accuracy of the horsepower control of the working system and traveling system of the work machine 1.

[0291] [Ninth embodiment] Fig. 20A is a diagram showing a main part of a hydraulic system 30G of a traveling system of a work machine 1 of a ninth embodiment. The hydraulic system 30G includes operation valves 155L, 155R and hydraulic regulators 156L, 156R as an operating device 54A for traveling and an adjustment mechanism 200. In addition to the components shown in Fig. 20A, the hydraulic system 30G is provided with components of the traveling system of the work machine 1, such as the control device 25 and traveling motors 36L, 36R described above (not shown in Fig. 20A).

[0292] The hydraulic regulators 156L, 156R have a supply chamber 157 to which hydraulic oil can be supplied, and a piston rod 158 provided in the supply chamber 157. The piston rod 158 of the hydraulic regulator 156L is connected to the swash plate of the first travel pump 53L. The piston rod 158 of the hydraulic regulator 156R is connected to the swash plate of the second travel pump 53R. The angle of the swash plate of each of the travel pumps 53L, 53R is changed by the operation (linear movement) of the piston rod 158 of each of the hydraulic regulators 156L, 156r.

[0293] The operating valve 155L is an electromagnetic proportional valve (solenoid valve) that operates the hydraulic regulator 156L and can be switched between a first position 155a, a second position 155b, and a neutral position 155c. The position of the operating valve 155L is changed by the spool of the operating valve 155L moving based on a control signal output from the control device 25. A first port of the operating valve 155L and a supply chamber 157 of the hydraulic regulator 156L are connected by a first travel oil passage 145a. A second port of the operating valve 155L and a supply chamber 157 of the hydraulic regulator 156L are connected by a second travel oil passage 145b.

[0294] The operating valve 155R is an electromagnetic proportional valve (solenoid valve) that operates the hydraulic regulator 156R and can be switched between a first position 155a, a second position 155b, and a neutral position 155c. The position of the operating valve 155R is changed by the spool of the operating valve 155R moving based on a control signal output from the control device 25. A first port of the operating valve 155R and a supply chamber 157 of the hydraulic regulator 156R are connected by a fourth travel oil passage 145d. A second port of the operating valve 155R and a supply chamber 157 of the hydraulic regulator 156R are connected by a third travel oil passage 145c.

[0295] The operating valves 155L and 155R are switched from the neutral position 155c to the first position 155a and the second position 155b based on a control signal input from the control device 25 (not shown in FIG. 20). The control device 25 inputs a control signal to the operating valves 155L and 155R to switch the operating valves 155L and 155R to the first position 155a. This causes the swash plates of the first traveling pump 53L and the second traveling pump 53R to swing in the forward rotation direction, allowing the first traveling pump 53L and the second traveling pump 53R to rotate forward.

[0296] In addition, the control device 25 outputs a control signal to the operating valve 155L and the operating valve 155R to switch the operating valve 155L and the operating valve 155R to the second position 155b. This causes the swash plates of the first traveling pump 53L and the second traveling pump 53R to swing in the reverse direction, allowing the first traveling pump 53L and the second traveling pump 53R to rotate in reverse. In addition, the control device 25 outputs control signals to the operating valve 155L and the operating valve 155R to switch the operating valve 155L to the first position 155a and switch the operating valve 155R to the second position 155b. This causes the swash plate of the first traveling pump 53L to swing in the forward rotation direction, allowing the first traveling pump 53L to rotate forward, and causes the swash plate of the second traveling pump 53R to swing in the reverse rotation direction, allowing the second traveling pump 53R to rotate in reverse.

[0297] Furthermore, the control device 25 outputs a control signal to the operating valve 155L and the operating valve 155R to switch the operating valve 155L to the second position 155b and switch the operating valve 155R to the first position 155a. As a result, the swash plate of the first traveling pump 53L swings in the reverse direction, allowing the first traveling pump 53L to rotate in reverse, and the swash plate of the second traveling pump 53R swings in the forward direction, allowing the second traveling pump 53R to rotate forward.

[0298] The control device 25 outputs a control signal to the operating valves 155L, 155R to change the opening of the operating valves 155L, 155R in the first position 155a or the second position 155b. The control device 25 changes the position or opening of the operating valves 155L, 155R based on the operating state of the operating members 159, 84 to change the pilot pressure acting on the travel oil passages 145a-145d, that is, the pressure of the pilot oil for adjusting the angle of the swash plate of the travel pumps 53L, 53R. The hydraulic oil discharged from the travel pumps 53L, 53R is supplied to the travel motors 36L, 36R described above, respectively. Even when the above-mentioned operating valves (solenoid valves) 155L, 155R are used, the pilot pressure (i.e., the primary traveling pressure and the secondary traveling pressure) of the pilot oil flowing in and out of the operating valves 155L, 155R can be changed as shown in Figures 12A, 12B, and 14 to change the angle of the swash plates of the traveling pumps 53L, 53R and to change the direction and speed of rotation of the traveling motors 36L, 36R.

[0299] As another example, as shown in FIG. 20B, a pressure change unit 201 may be provided in the third oil passage 40 through which the pilot oil is discharged from the first hydraulic pump P1. In this case, the control device 25 may change the pressure of the pilot oil (pilot pressure acting on the travel oil passages 145a-145d) for adjusting the angle of the swash plate of the travel pumps 53L, 53R by changing the position or opening of the operation valves 155L, 155R or the opening of the pressure change unit 201 based on the operation state of the operation members 159, 84. In this way, by using the operation valves 155L, 155R in combination with the pressure change unit 201, the angle of the swash plate of the travel pumps 53L, 53R and the rotation direction and rotation speed of the travel motors 36L, 36R can be changed in a finer change range, and the accuracy of the speed control of the travel device 5 and the work machine 1 can be improved.

[0300] In addition, by combining the hydraulic system 30G of the traveling system shown in FIG. 20A with the hydraulic systems 30A to 30C of the working system shown in FIG. 1A, FIG. 1B, FIG. 3, or FIG. 7A to FIG. 10A, the control device 25 changes the positions of the electromagnetic proportional valves 155L and 155R, so that the pilot pressure acting on the third oil passage 40 is changed, and the pilot pressure acting on the other oil passages 41, 41B, 41C, 41D, or the oil passage 41A connected to the third oil passage 40 is also changed. Therefore, the pilot pressure for operating the opening degree changer 76 is changed, and the operating states of the opening degree changer 76, the flow rate compensation valve 72, and the swash plate variable unit 73 are changed, and the angle of the swash plate of the second hydraulic pump P2, the output of the second hydraulic pump P2, and the LS differential pressure are changed according to the change. In this way, the control device 25 can change the LS differential pressure by controlling the operation of the electromagnetic proportional valves (solenoid valves) 155L and 155R as well, thereby improving the accuracy of the horsepower control of the working system of the working machine 1.

[0301] In the above-described seventh embodiment (FIGS. 16A to 17), the control device 25 may calculate the target engine speed during auto idle control based on the set speed of the engine 32, which is set by, for example, any one of the hand operating members 86, 159, 84 that can be operated by the driver's hand, the reference speed stored in the memory unit 26, and the following equation (8). Target engine speed during auto idle control = (set speed - reference speed) × coefficient + reference speed (8)

[0302] Specifically, for example, if the reference speed is 1000 rpm, the set speed is 1500 rpm, and the coefficient is 0.5, then based on equation (8), the target engine speed during auto idle control will be 1250 rpm (=(1500-1000)×0.5+1000). Also, for example, if the reference speed is 1000 rpm, the set speed is 2000 rpm, and the coefficient is 0.5, then based on equation (8), the target engine speed during auto idle control will be 1500 rpm (=(2000-1000)×0.5+1000).

[0303] The coefficient in formula (8) may be set to any value. For example, when the work machine 1 is used in a cold region, the coefficient may be set to a value greater than 0.5 to increase the target engine speed during auto idle control. Also, when the temperature of the cooling water or hydraulic oil provided in the work machine 1 becomes higher than a threshold value, the coefficient may be set to a value less than 0.5 to decrease the target engine speed during auto idle control.

[0304] Also, for example, the lowest engine speed that can be set by the hand operating members 86, 159, 84 or the accelerator member 84 (the speed generally called "idling speed") may be set as the reference speed in equation (8). In addition, the target engine revolution during auto idle control can be calculated using a calculation formula or method other than formula (8). You may set a number.

[0305] When the operating members 58, 159 are operated during auto idle control, the control device 25 ends the auto idle control and returns to the normal state. Then, based on the target engine speed set by the accelerator member 84 and the actual engine speed of the engine 32 measured by the first measuring device 82, the control device 25 executes drive control of the engine 32, changes the LS differential pressure, changes the control lines of various control maps, or changes the primary or secondary traveling pressure.

[0306] Furthermore, after the operation of the operating members 58, 159, the control device 25 may keep the LS differential pressure at a fixed value until the actual rotation speed of the engine 32 reaches the target engine rotation speed, that is, until the engine rotation speed (actual rotation speed) rises and becomes constant, as shown by the thick solid line in Fig. 17. As a result, when auto idle control is being executed before the operation of the operating members 58, 159, the actual rotation speed of the engine 32 can be made to match the target engine rotation speed more quickly than when the operation of the operating members 58, 159 was under normal conditions.

[0307] In the seventh embodiment, as the current input from the control device 25 to the solenoid proportional valve 201 increases, the traveling pressure (primary pressure and secondary pressure of the operation valve 55) also increases, so the input current to the solenoid proportional valve 201 and the traveling pressure are in a proportional relationship, but as another example, the input current to the solenoid proportional valve 201 and the traveling pressure may be in an inversely proportional relationship. In this case, the control device 25 may control the input current to the solenoid proportional valve 201 so that the traveling pressure becomes a desired pressure.

[0308] [Tenth embodiment] The above-described auto-idle control and anti-stall control may be linked in the work machine 1. This case will be described below as a tenth embodiment. Fig. 21 is a graph showing the relationship between the engine speed and the first correction coefficient in the tenth embodiment. The configuration of the hydraulic system of the work machine 1 in the tenth embodiment is the same as the configuration of the hydraulic systems 30E, 30G shown in Fig. 13 or Fig. 20, for example. The control map shown in Fig. 21 is used by the control device 25 in place of the control map shown in Fig. 19. Data of the control map showing the relationship shown in Fig. 21 is stored in advance in the memory unit 26 of the control device 25.

[0309] The first correction coefficient is a correction value used to control the travel pumps 53L, 53R while anti-stall control is being executed in the work machine 1. More specifically, the first correction coefficient is a current correction value for correcting a current value input to the operation valves 55a-55d (FIG. 13) or the operation valves 155L, 155R (FIG. 20) consisting of solenoid proportional valves while anti-stall control is being executed. Control lines L90A, L90B, L90C shown in FIG. 21 are control data for determining the first correction coefficient according to the actual rotation speed of the engine 32.

[0310] For example, when both anti-stall control and auto-idle control are being executed in the work machine 1, or when only anti-stall control is being executed and the drop rotation speed of the engine 32 is less than the threshold value, the control device 25 sets the first correction coefficient based on the control line L90C and the actual rotation speed. Compared to the control line L90A, the control line L90C is shifted to the side where the first correction coefficient is higher (upward in FIG. 21). For this reason, when the control device 25 employs the control line L90C, the first correction coefficient is set higher than when the control lines L90A and L90B are employed.

[0311] On the other hand, when only the anti-stall control out of the anti-stall control and the auto-idle control is executed and the drop rotation speed of the engine 32 is equal to or higher than the threshold value, the control device 25 sets the first correction coefficient based on either the control line L90A or the control line L90B and the actual rotation speed of the engine 32. Compared to the control line L90A, the control line L90B is shifted to the side where the first correction coefficient is lower (downward in FIG. 21). For this reason, when the control device 25 employs the control line L90B, the first correction coefficient is set lower than when the control lines L90A and L90C are employed.

[0312] For example, when the drop speed of the engine 32 is equal to or greater than the threshold and equal to or greater than a predetermined value that is greater than the threshold, the control device 25 sets the first correction coefficient based on the control line L90B and the actual speed of the engine 32. When the drop speed of the engine 32 is equal to or greater than the threshold and less than the predetermined value, the control device 25 sets the first correction coefficient based on the control line L90A and the actual speed of the engine 32.

[0313] Fig. 22 is a diagram showing an example of the operation direction and command value of the joystick 159. The directions parallel to the arrows shown in Fig. 22 show examples of the operation direction of the joystick 159. The two numerical values ​​(%) in parentheses shown near the tip and base of each arrow represent the operation direction, operation amount, and command value of the joystick 159.

[0314] The command value of the joystick 159 is a command value for controlling the travel pumps 53L, 53R by the operating valves (electromagnetic proportional valves) 55a to 55d, 155L, 155R. More specifically, the value (%) on the left side of the parentheses is a command value for controlling the first travel pump 53L, and the value (%) on the right side of the parentheses is a command value for controlling the second travel pump 53R. In addition, a plus (+) command value (positive value) indicates forward rotation of the travel pumps 53L, 53R, and a minus (-) command value (negative value) indicates reverse rotation of the travel pumps 53L, 53R.

[0315] For example, (0%, 0%) indicates that the joystick 159 is in a neutral position (unoperated state), the operation amount is "0" (none), and the command value for controlling the traveling pumps 53L and 53R is "0" (none). Also, for example, (+100%, +100%) indicates that the operation direction of the joystick 159 is forward, the operation amount is the maximum 100%, and the command value for controlling the first traveling pump 53L and the command value for controlling the second traveling pump 53R are both 100% of forward rotation. In other words, for example, when the joystick 159 is operated to the maximum right, (+100%, -100%) indicates that the operation amount is the maximum 100%, the command value for the first traveling pump 53L is 100% of forward rotation, and the command value for the second traveling pump 53R is 100% of reverse rotation.

[0316] When the joystick 159 is swung in any direction, an electric signal corresponding to the operation state is input from the joystick 159 (electric circuit 159b in FIG. 13) to the control device 25. The control device 25 detects the operation direction, operation amount, and command value of the joystick 159 based on the electric signal.

[0317] Fig. 23 is a diagram showing the relationship between a command value and an operating current value. A control map showing the relationship shown in Fig. 23 is stored in advance in storage unit 26 of control device 25. Control device 25 detects a command value based on an electric signal input from joystick 159, and then sets operating current values ​​to be input to operating valves (electromagnetic proportional valves) 55a to 55d, 155L, and 155R, respectively, based on the command value and the control map shown in Fig. 23.

[0318] When anti-stall control is not being performed, the control device 25 sets an operating current value and inputs the operating current value as a control signal to the operating valves 55a to 55d, 155L, and 155R, thereby controlling the travel pumps 53L, 53R via the operating valves 55a to 55d, 155L, and 155R. Furthermore, when anti-stall control is being performed, the control device 25 sets the operating current value as described above, and also sets a first correction coefficient based on the control map shown in Fig. 21 and the actual rotation speed of the engine 32. Then, the control device 25 corrects the operating current value with the first correction coefficient. The anti-stall current value is calculated by correcting the operating current value. At this time, for example, the control device 25 multiplies the operating current value by a first correction coefficient (0.4 to 1) to obtain a current value as the anti-stall current value. The anti-stall current value calculated in this manner is equal to or less than the operating current value.

[0319] Furthermore, when both anti-stall control and auto-idle control are being executed before the joystick 159 is operated, the control device 25 sets the first correction coefficient based on the control line L90C shown in Fig. 21 and the actual rotation speed of the engine 32. Therefore, when the joystick 159 is operated, the control device 25 sets the operation current value, and then corrects the operation current value with the first correction coefficient based on the control line L90C etc. to obtain the anti-stall current value. The anti-stall current value obtained in this manner is equal to or greater than the anti-stall current value (the product of the first correction coefficient based on either the control line L90A or L90B and the operation current value) when only the anti-stall control is being executed and the drop rotation speed is equal to or greater than the threshold value before the joystick 159 is operated.

[0320] Furthermore, when anti-stall control is being executed, the control device 25 inputs the anti-stall current value as a control signal to the operating valves (electromagnetic proportional valves) 55a to 55d, 155L, and 155R, and controls the travel pumps 53L, 53R via the operating valves 55a to 55d, 155L, and 155R. As described above, as the operating current value or anti-stall current value input from the control device 25 to the operating valves 55a-55d, 155L, 155R becomes higher, the secondary pressure for traveling increases and the amount of hydraulic oil discharged from the traveling pumps 53L, 53R increases.

[0321] As another example, the control device 25 may input a current value according to the target engine speed or the actual speed of the engine 32 to the control valves 55a-55d, 155L, and 155R by PID control or PI control. In this case, for example, the control device 25 may obtain the current value to be input to the control valves 55a-55d, 155L, and 155R by multiplying the set operation current value or anti-stall current value by a coefficient (control gain) used in PID control.

[0322] When the joystick 159 is operated to stop the auto-idle control while both the anti-stall control and the auto-idle control are being executed, the control device 25 increases the rotation speed of the engine 32 according to the operation state (operation direction and operation amount) of the joystick 159. At this time, the target engine rotation speed set by the control device 25 according to the operation direction and operation amount of the joystick 159 may be corrected by a first correction coefficient set based on the control line L90C (FIG. 21) and the actual rotation speed of the engine 32.

[0323] Furthermore, when the joystick 159 is operated while both the anti-stall control and the auto-idle control are being executed, the control device 25 increases the rotation speed of the engine 32 according to the operation state of the joystick 159. At this time, the control device 25 may set the traveling secondary pressure (secondary pressure of the operating valves 55a to 55d, 155L, 155R), the discharge amount (discharge amount of hydraulic oil) of the traveling pumps 53L, 53R, or the rotation speed of the traveling motors 36L, 36R based on the following equations (9) to (11).

[0324] Traveling secondary pressure=(Secondary pressure of the operating valves 55a to 55d corresponding to the operation amount of the joystick 159 on the control line L20 in FIG. 14A × [1 + constant × (target engine speed / actual engine speed)] (9) Discharge amount of the travel pumps 53L, 53R=(Discharge amount of the travel pumps 53L, 53R corresponding to the operation amount of the joystick 159 on the control line L20 in FIG. 14B × [1 + constant × (target engine speed / actual speed)] (10) The number of revolutions of the traveling motors 36L and 36R = (the control line L20 in FIG. 14C and the joystick 1 The rotation speed of the travel motors 36L and 36R corresponding to the operation amount of 59 × [1 + constant × (target engine rotation speed / actual rotation speed)] (11)

[0325] The control device 25 sets the travel secondary pressure, the discharge volume of the travel pumps 53L, 53R, or the rotation speed of the travel motors 36L, 36R based on the above equations (9) to (11), and then controls the opening degree of the operating valves 55a to 55d, 155L, 155R to realize these.

[0326] 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 the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0327] 1: Work equipment 14: Boom cylinder (hydraulic actuator) 15: Bucket cylinder (hydraulic actuator) 25: Control device 30A~30G: Hydraulic system for work equipment 32: Prime mover 40: No. 3 oil road 41: 4th oilway, 1st branch oilway 41B: 2nd branch oilway 41C: 3rd branch oil line 41D: Bypass oil passage 56, 56A, 56B, 56C, 56D: Control valve 70: No. 1 oil road 71: 2nd oil road 72: Flow compensation valve 73: Variable swash plate 75, 75A~75I: Hydraulic control section 76: Opening degree change section 81: Solenoid valve 82: 1st measuring device 83:Second measuring device 84: Accelerator parts (command parts) 84a: First accelerator member (command member) 84b: Second accelerator member (command member) 88: Command component 102: Solenoid valve 103: Opening degree change unit 181A, 181B: Solenoid valve 182, 185, 186: Solenoid valves 201, 201A Pressure change part (solenoid valve) 55a~55d, 155L, 155R Control valve (solenoid valve) P1: First hydraulic pump P2: Second hydraulic pump

Claims

1. The prime mover, A traveling device for traveling the work machine; A traveling motor capable of transmitting power to the traveling device; a variable displacement travel pump that is driven by the power of the prime mover to supply hydraulic oil to the travel motor; A first operating member for operating the traveling device; a second operating member that switches between a first mode in which the working machine travels and a second mode in which the working machine travels at a speed slower than that in the first mode; a control device that controls the drive of at least one of the prime mover and the travel pump based on an operation state of the first operating member and the second operating member; An adjustment mechanism for adjusting the angle of a swash plate of the traveling pump, The control device includes: In the first mode, the driving of the prime mover is controlled based on an operation state of the first operating member, In the second mode, the adjustment mechanism changes the angle of the swash plate of the travel pump based on the operation state of the first operating member.

2. a hydraulic pump that is driven by the power of the prime mover and discharges pilot oil for adjusting the angle of the swash plate of the traveling pump; an operating valve that is connected to an oil passage through which the pilot oil discharged from the hydraulic pump flows and applies a pilot pressure, which is the pressure of the pilot oil, to a pressure receiving portion of the travel pump in accordance with an operating state of the first operating member; The adjustment mechanism has a pressure changing unit that changes the pilot pressure acting on the operation valve, The hydraulic system for a work machine according to claim 1 , wherein the control device changes the pilot pressure by the pressure changing unit based on an operation state of the first operating member.

3. a hydraulic pump that is driven by the power of the prime mover and discharges pilot oil for adjusting the angle of the swash plate of the traveling pump; The adjustment mechanism has an operating valve that applies a pilot pressure, which is the pressure of the pilot oil, to a pressure receiving portion of the travel pump, The hydraulic system for a work machine according to claim 1 , wherein the control device changes the pilot pressure by controlling an opening degree of the operating valve based on an operating state of the first operating member.

4. a hydraulic pump that is driven by the power of the prime mover and discharges pilot oil for adjusting the angle of the swash plate of the traveling pump; The adjustment mechanism includes: an operating valve that applies a pilot pressure, which is the pressure of the pilot oil, to a pressure receiving portion of the travel pump in accordance with an operating state of the first operating member; a pressure changing unit that changes the pilot pressure acting on a pressure receiving portion of the travel pump from the operation valve, The hydraulic system for a work machine according to claim 1 , wherein the control device changes the pilot pressure by the pressure changing unit based on an operation state of the first operating member.

5. a hydraulic pump that is driven by the power of the prime mover and discharges pilot oil for adjusting the angle of the swash plate of the traveling pump; The adjustment mechanism includes: A hydraulic regulator for changing an angle of a swash plate of the traveling pump; an operation valve that can be switched to a neutral position in which the pilot oil is not supplied to the hydraulic regulator, a first position in which the pilot oil is supplied in a first direction, and a second position in which the pilot oil is supplied in a second direction, 2. The hydraulic system for a work machine according to claim 1, wherein the control device changes a pilot pressure, which is the pressure of the pilot oil, by changing an actuation state of the operating valve based on an operating state of the first operating member.

6. the first operating member includes an accelerator member capable of setting a rotation speed of the prime mover in the first mode, The control device includes: In the first mode, the driving of the prime mover is controlled to make the rotation speed of the prime mover coincide with the rotation speed set by the accelerator member; A hydraulic system for a work machine as described in any one of claims 1 to 5, wherein in the second mode, the adjustment mechanism changes the angle of the swash plate of the travel pump based on the operation state of the accelerator member to adjust the rotation speed of the travel motor and the travel speed of the travel device.

7. the first operating member includes a speed adjusting member capable of adjusting a rotation speed of the traveling motor in the second mode, In the second mode, the control device The angle of the swash plate of the traveling pump is changed by the adjustment mechanism based on the operation state of the speed adjustment member, thereby adjusting the rotation speed of the traveling motor and the traveling speed of the traveling device; 7. A hydraulic system for a work machine as described in claim 6, wherein when the accelerator member is operated, the angle of the swash plate of the travel pump is changed by the adjustment mechanism based on the amount of operation of the accelerator member, so that the rotation speed of the travel motor and the traveling speed of the traveling device are faster than the rotation speed of the travel motor and the traveling speed of the traveling device adjusted based on the operation state of the speed adjustment member.

8. the first operation member includes a travel operation member capable of adjusting a rotation speed of the travel motor in the first mode and the second mode, In the first mode and the second mode, the control device changes an angle of the swash plate of the travel pump by the adjustment mechanism in accordance with an operation amount of the travel operation member to adjust the rotation speed of the travel motor and the travel speed of the travel device, A work machine according to any one of claims 1 to 5, wherein the rotation speed of the travel motor and the travel speed of the travel device, which are adjusted in the second mode in response to the operation amount of the travel operating member, are slower than the rotation speed of the travel motor and the travel speed of the travel device, which are adjusted in the first mode in response to the same operation amount of the travel operating member.

9. The first operating member is an accelerator member capable of setting a rotation speed of the prime mover in the first mode; a travel operation member capable of adjusting a rotation speed of the travel motor in the first mode and the second mode, The control device includes: In the first mode, the driving of the prime mover is controlled to make the rotation speed of the prime mover coincide with the rotation speed set by the accelerator member; 6. The hydraulic system for a work machine according to claim 1, wherein in the second mode, the adjustment mechanism changes the angle of the swash plate of the travel pump based on the amount of operation of the travel operating member to adjust the rotation speed of the travel motor and the travel speed of the travel device, and when the accelerator member is operated while the amount of operation of the travel operating member is constant, the adjustment mechanism changes the angle of the swash plate of the travel pump based on the amount of operation of the accelerator member without changing the rotation speed of the prime mover to adjust the rotation speed of the travel motor and the travel speed of the travel device. 。

10. The first operating member is a first accelerator member and a second accelerator member capable of setting a rotation speed of the prime mover in the first mode; a travel operation member capable of adjusting a rotation speed of the travel motor in the first mode and the second mode, The control device includes: In the first mode, the driving of the prime mover is controlled to make the rotation speed of the prime mover coincide with the rotation speed set by either the first accelerator member or the second accelerator member, A hydraulic system for a work machine as described in any one of claims 1 to 5, wherein, in the second mode, when the amount of operation of the first accelerator member is equal to or greater than a certain amount, an adjustment range of the rotation speed of the travel motor and the traveling speed of the travel device is set in accordance with the amount of operation of the second accelerator member, and the angle of the swash plate of the travel pump is changed by the adjustment mechanism in accordance with the amount of operation of the travel operating member, thereby adjusting the rotation speed of the travel motor and the traveling speed of the travel device within the set adjustment range.

11. The first operating member is a first accelerator member and a second accelerator member capable of setting a rotation speed of the prime mover in the first mode; a speed adjusting member capable of adjusting a rotation speed of the traveling motor in the second mode, In the second mode, the control device The angle of the swash plate of the traveling pump is changed by the adjustment mechanism based on the operation state of the speed adjustment member, thereby adjusting the rotation speed of the traveling motor and the traveling speed of the traveling device; When the second accelerator member is operated while the operation amount of the first accelerator member is equal to or greater than a certain amount, the angle of the swash plate of the traveling pump is changed by the adjustment mechanism based on the operation amount of the second accelerator member, thereby adjusting the rotation speed of the traveling motor and the traveling speed of the traveling device; A hydraulic system for a work machine as described in any one of claims 1 to 5, wherein the rotation speed of the travel motor and the traveling speed of the travel device, which are different from those adjusted based on the operation state of the speed adjustment member, are adjusted based on the operation amount of the second accelerator member.

Images