Control system and control method for working machinery

Abstract

To supply the required flow rate of hydraulic fluid to each of multiple actuators. [Solution] The control system for the work machine comprises a pump that discharges hydraulic fluid, a plurality of actuators driven by the hydraulic fluid discharged from the pump, a plurality of actuator circuits connected to each of the plurality of actuators through which the hydraulic fluid supplied to the actuators flows, a plurality of meter-in valves that adjust the flow rate supplied to each of the plurality of actuator circuits, a pressure compensation mechanism having a plurality of pressure compensation valves connected to each of the plurality of meter-in valves to compensate for the differential pressure across the meter-in valves, and a controller. The controller calculates a required flow rate that indicates a target value for the flow rate of hydraulic fluid supplied to the actuator circuits, and controls the opening area of ​​the meter-in valves so that the required flow rate of hydraulic fluid is supplied to the actuator circuits based on the characteristics of the pressure compensation mechanism.

Description

Technical Field

[0001] The present disclosure relates to a control system for a work machine and a method for controlling a work machine.

Background Art

[0002] [[ID=1,1]] In the technical field related to work machines, a hydraulic circuit that supplies discharge pressure oil from one hydraulic pump to a plurality of hydraulic actuators, as disclosed in Patent Document 1, is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When simultaneously operating a plurality of actuators of a work machine, a technique capable of supplying hydraulic oil with a required flow rate to each of the plurality of actuators is desired.

[0005] An object of the present disclosure is to supply hydraulic oil with a required flow rate to each of a plurality of actuators.

Means for Solving the Problems

[0006] A control system for a working machine is provided, comprising: a pump for discharging hydraulic fluid; a plurality of actuators driven by the hydraulic fluid discharged from the pump; a plurality of actuator circuits connected to each of the plurality of actuators, through which the hydraulic fluid supplied to the actuators flows; a plurality of meter-in valves for adjusting the flow rate supplied to each of the plurality of actuator circuits; a pressure compensation mechanism having a plurality of pressure compensation valves connected to each of the plurality of meter-in valves for compensating the differential pressure across the meter-in valves; and a controller. The controller calculates a required flow rate indicating a target value for the flow rate of hydraulic fluid supplied to the actuator circuits, and controls the opening area of ​​the meter-in valves so that the required flow rate of hydraulic fluid is supplied to the actuator circuits based on the characteristics of the pressure compensation mechanism. [Effects of the Invention]

[0007] According to this disclosure, a required flow rate of hydraulic fluid is supplied to each of the multiple actuators. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a side view showing a work machine according to the first embodiment. [Figure 2] Figure 2 shows the cab of the work machine according to the first embodiment. [Figure 3] Figure 3 is a schematic diagram showing the control system of a work machine according to the first embodiment. [Figure 4] Figure 4 is a hardware configuration diagram showing the controller according to the first embodiment. [Figure 5] Figure 5 is a functional block diagram showing the controller according to the first embodiment. [Figure 6] Figure 6 illustrates a method for calculating the required flow rate of an actuator according to the first embodiment. [Figure 7] Figure 7 is a schematic diagram showing the control system of a work machine according to the second embodiment. [Figure 8] Figure 8 is a functional block diagram showing a controller according to the third embodiment. [Figure 9] Figure 9 is a flowchart showing a control method for a work machine according to the third embodiment. [Figure 10] Figure 10 is a flowchart showing the control method for a work machine according to the third embodiment. [Figure 11] Figure 11 is a schematic diagram showing the control system of a work machine according to the fourth embodiment. [Modes for carrying out the invention]

[0009] [First Embodiment] The first embodiment will be described.

[0010] <Working machinery> Figure 1 is a side view showing a work machine 1 according to the first embodiment. The work machine 1 operates at a work site. Examples of work machines 1 include a hydraulic excavator, a wheel loader, and a bulldozer. In this embodiment, the work machine 1 is a hydraulic excavator. The work machine 1 comprises a traveling body 2, a slewing body 3, a work machine 4, a slewing motor 5, a work machine cylinder 6, a controller 7, an operating device 8, and a monitor 9.

[0011] The running body 2 supports the rotating body 3. The running body 2 has a pair of tracks 2A. The working machine 1 moves as the tracks 2A rotate.

[0012] The slewing body 3 is positioned above the traveling body 2. The slewing body 3 is rotatably supported by the traveling body 2. The slewing body 3 has a cab 10. The operator of the work machine 1 is seated in the cab 10. The control device 8 and monitor 9 are located in the cab 10.

[0013] The work implement 4 is rotatably mounted on the slewing body 3. The work implement 4 includes a boom 4A, an arm 4B, and a bucket 4C. The boom 4A is rotatably connected to the front of the slewing body 3. The arm 4B is rotatably connected to the tip of the boom 4A. The bucket 4C is rotatably connected to the tip of the arm 4B.

[0014] The slewing motor 5 slews the slewing body 3 supported by the traveling body 2. The slewing motor 5 is a hydraulic motor driven by hydraulic oil. The slewing motor 5 is an example of an actuator driven by hydraulic oil.

[0015] The work implement cylinder 6 operates the work implement 4 attached to the slewing body 3. The work implement cylinder 6 is a hydraulic cylinder driven by hydraulic oil. The work implement cylinder 6 is an example of an actuator driven by hydraulic oil. The work implement cylinder 6 has a cylinder tube, a piston movable inside the cylinder tube, and a rod fixed to the piston. The piston partitions the inside of the cylinder tube into a head chamber and a bottom chamber. When hydraulic oil flows into the head chamber and flows out from the bottom chamber, the work implement cylinder 6 contracts. When hydraulic oil flows into the bottom chamber and flows out from the head chamber, the work implement cylinder 6 extends. The work implement cylinder 6 includes a boom cylinder 6A, an arm cylinder 6B, and a bucket cylinder 6C.

[0016] The boom cylinder 6A operates the boom 4A. The base end portion of the cylinder tube of the boom cylinder 6A is connected to the slewing body 3, and the tip end portion of the rod of the boom cylinder 6A is connected to the boom 4A. The operation of the boom 4A includes a raising operation and a lowering operation. When hydraulic oil flows into the bottom chamber of the boom cylinder 6A and the boom cylinder 6A extends, the boom 4A performs a raising operation. When hydraulic oil flows into the head chamber of the boom cylinder 6A and the boom cylinder 6A contracts, the boom 4A performs a lowering operation.

[0017] The arm cylinder 6B operates the arm 4B. The base end portion of the cylinder tube of the arm cylinder 6B is connected to the boom 4A, and the tip end portion of the rod of the arm cylinder 6B is connected to the arm 4B. The operation of the arm 4B includes an excavation operation and a dumping operation. When hydraulic oil flows into the bottom chamber of the arm cylinder 6B and the arm cylinder 6B extends, the arm 4B performs an excavation operation. When hydraulic oil flows into the head chamber of the arm cylinder 6B and the arm cylinder 6B contracts, the arm 4B performs a dumping operation.

[0018] Bucket cylinder 6C operates bucket 4C. The base end of the cylinder tube of bucket cylinder 6C is connected to arm 4B, and the tip of the rod of bucket cylinder 6C is connected to bucket 4C via a link mechanism. The operation of bucket 4C includes digging and dumping operations. When hydraulic fluid flows into the bottom chamber of bucket cylinder 6C and bucket cylinder 6C extends, bucket 4C performs the digging operation. When hydraulic fluid flows into the head chamber of bucket cylinder 6C and bucket cylinder 6C retracts, bucket 4C performs the dumping operation.

[0019] <Cab> Figure 2 shows the cab 10 of the work machine 1 according to the first embodiment. As shown in Figure 2, the operating device 8 and monitor 9 are located in the cab 10. The operating device 8 is operated to operate at least one of the traveling body 2, the rotating body 3, and the work machine 4. The operating device 8 is operated by an operator seated in the cab 10. The operating device 8 includes a plurality of levers. The operator can operate the operating device 8 while seated in the driver's seat 11 located in the cab 10.

[0020] The operating device 8 includes a left work lever 8A and a right work lever 8B, which are operated to operate the slewing body 3 and the work implement 4; a left travel lever 8C and a right travel lever 8D, which are operated to operate the traveling body 2; and a left foot pedal 8E and a right foot pedal 8F.

[0021] When the left work lever 8A is operated in the forward / backward direction, the arm 4B performs a dumping or digging operation. When the left work lever 8A is operated in the left / right direction, the slewing body 3 performs a left or right slewing operation. When the right work lever 8B is operated in the left / right direction, the bucket 4C performs an digging or dumping operation. When the right work lever 8B is operated in the forward / backward direction, the boom 4A performs a lowering or raising operation. Alternatively, when the left work lever 8A is operated in the forward / backward direction, the slewing body 3 may perform a right or left slewing operation. When the left work lever 8A is operated in the left / right direction, the arm 4B may perform a dumping or digging operation.

[0022] When the left travel lever 8C is operated in the forward or backward direction, the left track 2A of the vehicle 2 moves forward or backward. When the right travel lever 8D is operated in the forward or backward direction, the right track 2A of the vehicle 2 moves forward or backward.

[0023] The left foot pedal 8E is linked to the left travel lever 8C. The right foot pedal 8F is linked to the right travel lever 8D. By operating the left foot pedal 8E and the right foot pedal 8F, the vehicle 2 may move forward or backward.

[0024] Monitor 9 is positioned to the right and in front of the driver's seat 11. Monitor 9 includes a display device 9A and an input device 9B. Display device 9A displays display data. Display device 9A provides display data to the operator seated in the cab 10. An example of display device 9A is a flat panel display such as a liquid crystal display or an organic EL display. Input device 9B is operated by the operator seated in the cab 10. Input device 9B generates input data when operated by the operator. An example of input device 9B is a touch panel, a button switch, and a computer keyboard.

[0025] <Manipulation amount> The operating device 8 is operated to operate the actuators of the work machine 1. The actuators include a slewing motor 5 and a work machine cylinder 6. As described above, the operating device 8 includes a left work lever 8A and a right work lever 8B which are operated to operate the slewing body 3 and the work machine 4. When the operating device 8 is operated, an operating signal (electrical signal) is generated. The operating signal of the operating device 8 is transmitted to the controller 7. The operating signal of the operating device 8 includes the operating amount of the operating device 8. The operating amount may be considered as the signal strength of the operating signal. The operating amount may be considered as the operating angle (tilting angle) of the left work lever 8A and the right work lever 8B. The controller 7 controls the actuators based on the operating amount of the operating device 8.

[0026] In this embodiment, the operation signal (operated quantity) is generated by operating the operating device 8, but the operation signal may be generated by, for example, the controller 7. The operator may not operate the operating device 8, and the controller 7 may automatically generate the operation signal. The operation signal may be generated by a controller other than the controller 7. The other controller may be located outside the work machine 1. The operation signal may be transmitted from the controller located outside the work machine 1 to the controller 7 mounted on the work machine 1. The operating device 8 may be located outside the work machine 1. The work machine 1 may be remotely controlled by a remote control device located outside the work machine 1. When the work machine 1 is remotely controlled by a remote control device, a remote controller connected to the remote control device may generate the operation signal. The operation signal generated by the remote controller may be transmitted to the controller 7 mounted on the work machine 1.

[0027] In the following description, the amount of manipulation required to operate the boom cylinder 6A will be appropriately referred to as the boom maneuver. The amount of manipulation required to operate the arm cylinder 6B will be appropriately referred to as the arm maneuver. The amount of manipulation required to operate the bucket cylinder 6C will be appropriately referred to as the bucket maneuver. The amount of manipulation required to operate the slewing motor 5 will be appropriately referred to as the slewing maneuver.

[0028] The boom control amount is the control amount for boom cylinder 6A. The arm control amount is the control amount for arm cylinder 6B. The bucket control amount is the control amount for bucket cylinder 6C. The slewing control amount is the control amount for slewing motor 5.

[0029] In the following explanation, when the manipulated amount is zero, that is, when the operating device 8 for operating a certain actuator is not being operated, the manipulated amount is considered to be 0%. When the manipulated amount is at its maximum, that is, in the so-called full lever state, the manipulated amount is considered to be 100%.

[0030] <Compound operation> The operating device 8 may be operated so that at least two of the multiple actuators of the work machine 1 operate simultaneously. For example, the operating device 8 may be operated so that the boom cylinder 6A and the arm cylinder 6B operate simultaneously. For example, the operating device 8 may be operated so that the boom cylinder 6A, the arm cylinder 6B, and the bucket cylinder 6C operate simultaneously. For example, the operating device 8 may be operated so that the boom cylinder 6A, the arm cylinder 6B, and the slewing motor 5 operate simultaneously. In the following description, operating the operating device 8 so that at least two actuators operate simultaneously will be referred to as a compound operation as appropriate. Also, the operation of at least two actuators simultaneously will be referred to as a compound operation as appropriate.

[0031] Furthermore, operating the control device 8 so that only one of the multiple actuators of the work machine 1 operates is appropriately referred to as "single-actuator operation." Single-actuator operation includes boom single-actuator operation, in which the control device 8 is operated so that only the boom cylinder 6A operates; arm single-actuator operation, in which the control device 8 is operated so that only the arm cylinder 6B operates; bucket single-actuator operation, in which the control device 8 is operated so that only the bucket cylinder 6C operates; and slewing single-actuator operation, in which the control device 8 is operated so that only the slewing motor 5 operates.

[0032] <Control System> Figure 3 is a schematic diagram showing the control system 13 of the work machine 1 according to the first embodiment. The control system 13 includes a hydraulic system (hydraulic circuit) that operates using hydraulic fluid. As shown in Figure 3, the control system 13 includes a controller 7, an operating device 8, a power source 14, a pump 15, a tank 16, a relief circuit 35, a relief valve 36, a meter-in valve 17, a pressure compensation mechanism 23, an actuator circuit pressure sensor 18, a pump circuit 19, a suction circuit 20, a meter-in circuit 22, an actuator circuit 21, and a plurality of actuators. Figure 3 is a simplified illustration of the control system 13. In Figure 3, the boom cylinder 6A and the arm cylinder 6B of the work machine cylinder 6 are shown as actuators driven by hydraulic fluid.

[0033] Power source 14 is the power source for the work machine 1. A diesel engine is given as an example of power source 14. However, power source 14 may also be an electric motor. Power source 14 is connected to pump 15. Power source 14 drives pump 15.

[0034] Pump 15 is a hydraulic pump that discharges hydraulic fluid. Pump 15 discharges hydraulic fluid that is supplied to the actuators of the work machine 1. The actuators include a slewing motor 5 and a work machine cylinder 6. In this embodiment, the hydraulic fluid discharged from pump 15 is distributed to each of the multiple actuators. Each of the multiple actuators is driven by the hydraulic fluid discharged from the pump. Pump 15 draws in hydraulic fluid contained in tank 16 via suction circuit 20. Pump 15 discharges the hydraulic fluid drawn in from tank 16 to pump circuit 19. Pump 15 is a swashplate variable displacement pump. The capacity [cc / rev] of pump 15 is changed by changing the angle of the swashplate of pump 15.

[0035] The meter-in valve 17 adjusts the flow rate of hydraulic fluid supplied to each of the multiple actuator circuits 21. The meter-in valve 17 includes a directional control valve that controls the flow rate and direction of the hydraulic fluid supplied from the pump 15 to the actuators of the work machine 1. Multiple meter-in valves 17 are provided to control the flow rate of hydraulic fluid supplied from the pump 15 to each of the multiple actuators. In one embodiment, the meter-in valve 17 includes a first meter-in valve 17A that controls the flow rate of hydraulic fluid supplied from the pump 15 to the boom cylinder 6A, and a second meter-in valve 17B that controls the flow rate of hydraulic fluid supplied from the pump 15 to the arm cylinder 6B.

[0036] The pump circuit 19 connects the pump 15 to the meter-in valve 17. The pump circuit 19 connects the pump 15 to the first meter-in valve 17A and to the second meter-in valve 17B. In this embodiment, the hydraulic fluid discharged from the pump 15 is distributed to the first meter-in valve 17A and the second meter-in valve 17B.

[0037] The relief circuit 35 is connected to the pump circuit 19. A relief valve 36 is located in the relief circuit 35. The relief valve 36 closes when the pressure in the pump circuit 19 is below a predetermined receipt pressure. The relief valve 36 opens when the pressure in the pump circuit 19 reaches a predetermined cracking pressure. When the relief valve 36 opens, at least some of the hydraulic fluid from the pump circuit 19 is discharged to the tank 16 via the relief circuit 35.

[0038] The meter-in circuit 22 connects the meter-in valve 17 and the pressure compensation mechanism 23. Multiple meter-in circuits 22 are provided so as to be connected to each of the multiple actuators via the pressure compensation mechanism 23. In one embodiment, the meter-in circuit 22 includes a first meter-in circuit 22A that connects a first meter-in valve 17A to the pressure compensation mechanism 23, and a second meter-in circuit 22B that connects a second meter-in valve 17B to the pressure compensation mechanism 23.

[0039] The pressure compensation mechanism 23 compensates for the differential pressure across the meter-in valve 17. The pressure compensation mechanism 23 has a plurality of pressure compensation valves 24 connected to each of the plurality of meter-in valves 17. In this embodiment, the pressure compensation valves 24 include a first pressure compensation valve 24A connected to the first meter-in valve 17A via a first meter-in circuit 22A, and a second pressure compensation valve 24B connected to the second meter-in valve 17B via a second meter-in circuit 22B.

[0040] The pressure compensation valve 24 has a self-pressure receiving port 26 and a maximum pressure receiving port 27. In the example shown in Figure 3, the self-pressure receiving port 26 of the first pressure compensation valve 24A is located on the right side of the first pressure compensation valve 24A. The maximum pressure receiving port 27 of the first pressure compensation valve 24A is located on the left side of the first pressure compensation valve 24A. The self-pressure receiving port 26 of the second pressure compensation valve 24B is located on the left side of the second pressure compensation valve 24B. The maximum pressure receiving port 27 of the second pressure compensation valve 24B is located on the right side of the second pressure compensation valve 24B.

[0041] The pressure compensation mechanism 23 includes a first compensation circuit 23A, a second compensation circuit 23B, a third compensation circuit 23C, and a shuttle valve 25.

[0042] The first compensation circuit 23A connects the self-pressure receiving port 26 of the first pressure compensation valve 24A to the shuttle valve 25. The first compensation circuit 23A merges with the first meter-in circuit 22A. At least a portion of the hydraulic fluid flowing through the first meter-in circuit 22A flows into the first compensation circuit 23A.

[0043] The second compensation circuit 23B connects the self-pressure receiving port 26 of the second pressure compensation valve 24B to the shuttle valve 25. The second compensation circuit 23B merges with the second meter-in circuit 22B. At least a portion of the hydraulic fluid flowing through the second meter-in circuit 22B flows into the second compensation circuit 23B.

[0044] The third compensation circuit 23C connects the shuttle valve 25 to the highest pressure receiving port 27 of the first pressure compensation valve 24A and the highest pressure receiving port 27 of the second pressure compensation valve 24B, respectively. The hydraulic fluid with the higher pressure between the first compensation circuit 23A (first meter-in circuit 22A) and the second compensation circuit 23B (second meter-in circuit 22B) flows into the third compensation circuit 23C via the shuttle valve 25.

[0045] The shuttle valve 25 operates so that the hydraulic fluid with the higher pressure between the first compensation circuit 23A (first meter-in circuit 22A) and the second compensation circuit 23B (second meter-in circuit 22B) flows into the third compensation circuit 23C.

[0046] The actuator circuit 21 is connected to each of the multiple actuators. The hydraulic fluid supplied to the actuators flows through the actuator circuit 21. The actuator circuit 21 connects the pressure compensation mechanism 23 to the actuators. In this embodiment, the actuator circuit 21 includes a first actuator circuit 21A that connects a first pressure compensation valve 24A to a boom cylinder 6A, and a second actuator circuit 21B that connects a second pressure compensation valve 24B to an arm cylinder 6B.

[0047] The actuator circuit pressure sensor 18 detects the load pressure acting on the actuator. The actuator circuit pressure sensor 18 detects the pressure of the hydraulic fluid in the actuator circuit 21 between the pressure compensation mechanism 23 and the actuator. Multiple actuator circuit pressure sensors 18 are provided to detect the pressure of each of the multiple actuator circuits 21. In this embodiment, the actuator circuit pressure sensor 18 includes a first actuator circuit pressure sensor 18A that detects the pressure of the first actuator circuit 21A (the load pressure of the boom cylinder 6A) and a second actuator circuit pressure sensor 18B that detects the pressure of the second actuator circuit 21B (the load pressure of the arm cylinder 6B). The first actuator circuit pressure sensor 18A detects the pressure of the first actuator circuit 21A between the first pressure compensation valve 24A and the boom cylinder 6A. The second actuator circuit pressure sensor 18B detects the pressure of the second actuator circuit 21B between the second pressure compensation valve 24B and the arm cylinder 6B. The detection data from the actuator circuit pressure sensor 18 is transmitted to the controller 7.

[0048] In the following description, it is assumed that the operating device 8 is operated in combination so that the boom cylinder 6A and the arm cylinder 6B operate simultaneously. Furthermore, the load pressure of the boom cylinder 6A and the load pressure of the arm cylinder 6B are different. The load pressure of the boom cylinder 6A is assumed to be higher than the load pressure of the arm cylinder 6B. The boom cylinder 6A is the high-pressure side, and the arm cylinder 6B is the low-pressure side.

[0049] Furthermore, in the following explanation, the target value of the flow rate of the hydraulic fluid discharged from pump 15 will be appropriately referred to as the pump target flow rate Qt_p. The pressure of the hydraulic fluid discharged from pump 15 will be appropriately referred to as the pump pressure P_p. The differential pressure across the first meter-in valve 17A on the high-pressure side will be appropriately referred to as the differential pressure ΔPvt_H. The differential pressure across the second meter-in valve 17B on the low-pressure side will be appropriately referred to as the differential pressure ΔPvt_L. The pressure of the first meter-in circuit 22A on the high-pressure side will be appropriately referred to as the meter-in pressure Pm_H. The pressure of the second meter-in circuit 22B on the low-pressure side will be appropriately referred to as the meter-in pressure Pm_L. The pressure of the first actuator circuit 21A on the high-pressure side will be appropriately referred to as the actuator circuit pressure P_H. The pressure of the second actuator circuit 21B on the low-pressure side will be appropriately referred to as the actuator circuit pressure P_L. The target flow rate of the hydraulic fluid supplied to the first actuator circuit 21A (boom cylinder 6A) is appropriately referred to as the required flow rate Qt_H. The target flow rate of the hydraulic fluid supplied to the second actuator circuit 21B (arm cylinder 6B) is appropriately referred to as the required flow rate Qt_L.

[0050] <Pressure compensation mechanism> The pressure compensation mechanism 23 compensates for the differential pressure across the meter-in valve 17. In a circuit without the pressure compensation mechanism 23, if the opening areas of the multiple meter-in valves 17 (17A, 17B) are the same, the hydraulic characteristics will be such that the hydraulic fluid is more likely to flow to the actuator circuit 21 with lower pressure than to the actuator circuit 21 with higher pressure. If the opening areas of the first meter-in valve 17A and the second meter-in valve 17B are the same, and the first actuator circuit 21A is at a higher pressure than the second actuator circuit 21B, then in a circuit without the pressure compensation mechanism 23, the hydraulic characteristics will be such that the hydraulic fluid is more likely to flow to the second actuator circuit 21B with lower pressure than to the first actuator circuit 21A with higher pressure.

[0051] As described above, the shuttle valve 25 operates so that the hydraulic fluid with the higher pressure between the first compensation circuit 23A (first meter-in circuit 22A) and the second compensation circuit 23B (second meter-in circuit 22B) flows into the third compensation circuit 23C. If the meter-in pressure Pm_H is higher than the meter-in pressure Pm_L, at least a portion of the hydraulic fluid from the first meter-in circuit 22A flows into the third compensation circuit 23C. The meter-in pressure Pm_H acts on the highest pressure receiving port 27 of the first pressure compensation valve 24A and the highest pressure receiving port 27 of the second pressure compensation valve 24B. The meter-in pressure Pm_H acts on the self-pressure receiving port 26 of the first pressure compensation valve 24A, and the meter-in pressure Pm_L acts on the self-pressure receiving port 26 of the second pressure compensation valve 24B.

[0052] In the second pressure compensation valve 24B, the meter-in pressure Pm_H acts on the highest pressure-receiving port 27 and the meter-in pressure Pm_L acts on the self-pressure-receiving port 26, so the spool of the second pressure compensation valve 24B moves to the left in Figure 3. That is, the opening area of ​​the second pressure compensation valve 24B becomes smaller. When the opening area of ​​the second pressure compensation valve 24B becomes smaller, the pressure loss of the second pressure compensation valve 24B increases, and the meter-in pressure Pm_L increases. As a result, the opening area of ​​the second pressure compensation valve 24B is adjusted so that the meter-in pressure Pm_L acting on the self-pressure-receiving port 26 of the second pressure compensation valve 24B is equal to the meter-in pressure Pm_H acting on the highest pressure-receiving port 27 of the second pressure compensation valve 24B. As a result, the differential pressure across the first meter-in valve 17A and the differential pressure across the second meter-in valve 17B become equivalent pressures. Therefore, if the opening area of ​​the first meter-in valve 17A and the opening area of ​​the second meter-in valve 17B are the same, the flow rate passing through the first meter-in valve 17A and the flow rate passing through the second meter-in valve 17B will be distributed equally.

[0053] The examples described above assume that the pressure-receiving area A1 of the self-pressure-receiving port 26 and the pressure-receiving area A2 of the maximum pressure-receiving port 27 of the pressure compensation mechanism 23 are of equal size. On the other hand, generally, the pressure compensation mechanism 23 has dimensional characteristics in which there is a difference between the pressure-receiving area A1 of the self-pressure-receiving port 26 and the pressure-receiving area A2 of the maximum pressure-receiving port 27. When the pressure-receiving area A2 of the maximum pressure-receiving port 27 is smaller than the pressure-receiving area A1 of the self-pressure-receiving port 26, the second pressure compensation valve 24B balances the meter-in pressure Pm_L to be lower than the meter-in pressure Pm_H. As a result, the differential pressure across the second meter-in valve 17B becomes larger than the differential pressure across the first meter-in valve 17A. Therefore, if the opening area of ​​the first meter-in valve 17A and the opening area of ​​the second meter-in valve 17B are the same, the flow rate passing through the second meter-in valve 17B will be greater than the flow rate passing through the first meter-in valve 17A.

[0054] <Controller> Figure 4 is a hardware configuration diagram showing a controller 7 according to the first embodiment. The controller 7 includes a computer 12. The computer 12 has a processor 12A such as a CPU (Central Processing Unit), a main memory 12B including non-volatile memory such as ROM (Read Only Memory) and volatile memory such as RAM (Random Access Memory), a storage 12C, an input / output interface 12D including input / output circuits, and a communication interface 12E including communication circuits. The functions of the controller 7 are stored in the storage 12C as a computer program 12F. The processor 12A reads the computer program 12F from the storage 12C, loads it into the main memory 12B, and executes processing according to the computer program 12F. The computer program 12F may be distributed to the computer 12 via a network.

[0055] Figure 5 is a functional block diagram showing the controller 7 according to the first embodiment. The controller 7 outputs control commands to control at least the pump 15 and the meter-in valve 17. An operating device 8 and an actuator circuit pressure sensor 18 are connected to the controller 7.

[0056] The controller 7 has multiple functional units. The functions of the controller 7's functional units are performed by the processor 12A. The controller 7's functional units include an actuator circuit pressure acquisition unit 70, an operation amount acquisition unit 71, a maximum load pressure circuit determination unit 72, an actuator requested flow rate calculation unit 73, a high-pressure meter-in pressure calculation unit 74, a pump pressure calculation unit 75, a low-pressure meter-in pressure calculation unit 76, a high-pressure meter-in opening area calculation unit 77, a low-pressure meter-in opening area calculation unit 78, a meter-in valve control unit 79, a pump target flow rate calculation unit 80, and a pump control unit 81.

[0057] The actuator circuit pressure acquisition unit 70 acquires the actuator circuit pressure (P_H, P_L). The actuator circuit pressure is detected by the actuator circuit pressure sensor 18. The actuator circuit pressure acquisition unit 70 acquires the detection data from the actuator circuit pressure sensor 18. The actuator circuit pressure acquisition unit 70 acquires the actuator circuit pressure P_H from the first actuator circuit pressure sensor 18A and the actuator circuit pressure P_L from the second actuator circuit pressure sensor 18B.

[0058] The manipulated amount acquisition unit 71 acquires the operation signal of the operating device 8. The operation signal of the operating device 8 includes the manipulated amount of the operating device 8. When the operating device 8 is operated in a combined manner, the manipulated amount acquisition unit 71 acquires a combined manipulated amount that indicates the manipulated amount of the operating device 8 that operates multiple actuators simultaneously.

[0059] The maximum load pressure circuit determination unit 72 determines, based on the detection data from the actuator circuit pressure sensor 18, the high-pressure side actuator circuit 21, which is the actuator circuit 21 with the highest pressure, and the low-pressure side actuator circuit 21, which is an actuator circuit 21 other than the high-pressure side actuator circuit, from among the multiple actuator circuits 21 connected to each of the multiple actuators that operate simultaneously (compound operation). In this embodiment, the high-pressure side actuator circuit is the first actuator circuit 21A, and the low-pressure side actuator circuit is the second actuator circuit 21B.

[0060] The actuator flow rate calculation unit 73 calculates the required flow rate (Qt_H, Qt_L), which indicates the target value of the flow rate of the hydraulic fluid supplied to the actuator circuit 21. The actuator flow rate calculation unit 73 calculates the required flow rate (Qt_H, Qt_L) based on the amount of operation of the operating device 8.

[0061] Figure 6 illustrates a method for calculating the required flow rate of an actuator according to the first embodiment. Figure 6 illustrates a method for calculating the required flow rate of each of the four actuators (actuator A, actuator B, actuator C, and actuator D). The amount of operation of the operating device 8 for operating actuator A is referred to as the lever A operation amount, the amount of operation of the operating device 8 for operating actuator B is referred to as the lever B operation amount, the amount of operation of the operating device 8 for operating actuator C is referred to as the lever C operation amount, and the amount of operation of the operating device 8 for operating actuator D is referred to as the lever D operation amount.

[0062] For example, the actuator flow rate calculation unit 73 calculates the required flow rate when actuators A, B, C, and D are each operated on a single axis. The required flow rate during single-axis operation may be a value proportional to the amount of operation. The actuator flow rate calculation unit 73 calculates the final required flow rates for actuators A, B, C, and D based on the ratio of the required flow rates during single-axis operation, so that the sum of the required flow rates for actuators A, B, C, and D does not exceed the pump upper limit flow rate.

[0063] The high-pressure meter-in pressure calculation unit 74 calculates the meter-in pressure Pm_H on the high-pressure side. The high-pressure meter-in pressure calculation unit 74 calculates the meter-in pressure Pm_H based on the characteristics of the pressure compensation mechanism 23 and the actuator circuit pressure P_H detected by the first actuator circuit pressure sensor 18A. The pressure compensation mechanism 23 has an opening characteristic in which the opening area of ​​the first pressure compensation valve 24A connected to the first actuator circuit 21A is always at its maximum (fully open) when the first actuator circuit 21A is at its maximum pressure. The differential pressure ΔPc across the first pressure compensation valve 24A when the opening area of ​​the first pressure compensation valve 24A is at its maximum is known data that can be determined in advance, for example, by preliminary experiments or simulations. The high-pressure meter-in pressure calculation unit 74 calculates the meter-in pressure Pm_H based on the actuator circuit pressure P_H detected by the first actuator circuit pressure sensor 18A and the known data differential pressure ΔPc across the first pressure compensation valve 24A. The meter-in pressure Pm_H is the sum of the actuator circuit pressure P_H and the differential pressure ΔPc. That is, the high-pressure meter-in pressure calculation unit 74 calculates the meter-in pressure Pm_H by performing the following equation (1).

[0064] Pm_H = P_H + ΔPc …(1)

[0065] The pump pressure calculation unit 75 calculates the pump pressure P_p, which indicates the pressure of the hydraulic fluid discharged from the pump 15. A target differential pressure ΔPvt_H is set in advance, which indicates a target value of the differential pressure across the first meter-in valve 17A connected to the high-pressure side first actuator circuit 21A. For example, the first meter-in valve 17A is controlled so that the target differential pressure ΔPtv_H is generated when hydraulic fluid at a required flow rate Qt_H flows through the first meter-in valve 17A. Based on the target differential pressure ΔPtv_H, the fuel consumption of the power source 14 and the operating state of the hydraulic system change. The target differential pressure ΔPtv_H is a constant value predetermined based on the fuel consumption of the power source 14 and the target operating state of the hydraulic system. The pump pressure calculation unit 75 calculates the pump pressure P_p based on the meter-in pressure Pm_H and the target differential pressure ΔPtv_H. The pump pressure P_p is the sum of the meter-in pressure Pm_H and the target differential pressure ΔPtv_H. In other words, the pump pressure calculation unit 75 calculates the pump pressure P_p by performing the following equation (2).

[0066] P_p = Pm_H + ΔPtv_H …(2)

[0067] The low-pressure meter-in pressure calculation unit 76 calculates the meter-in pressure Pm_L on the low-pressure side. The low-pressure meter-in pressure calculation unit 76 calculates the meter-in pressure Pm_L based on the characteristics of the pressure compensation mechanism 23 and the meter-in pressure Pm_H on the high-pressure side. The characteristics of the pressure compensation mechanism 23 include the ratio of the pressure-receiving area A1 of the self-pressure-receiving port 26 of the second pressure compensation valve 24B to the pressure-receiving area A2 of the maximum pressure-receiving port 27 of the second pressure compensation valve 24B. The low-pressure meter-in pressure calculation unit 76 calculates the meter-in pressure Pm_L on the low-pressure side by calculating the following equation (3).

[0068] Pm_L = A2 / A1 × Pm_H …(3)

[0069] Furthermore, the low-pressure meter-in pressure calculation unit 76 calculates the differential pressure ΔPvt_L across the second meter-in valve 17B on the low-pressure side based on the pump pressure P_p and the meter-in pressure Pm_L on the low-pressure side. The low-pressure meter-in pressure calculation unit 76 calculates the differential pressure ΔPvt_L across the low-pressure side by performing the following calculation using equation (4).

[0070] ΔPvt_L = P_p - Pm_L …(4)

[0071] The high-pressure meter-in opening area calculation unit 77 calculates the opening area Avt_H of the first meter-in valve 17A based on the required flow rate Qt_H and the differential pressure ΔPvt_H. The high-pressure meter-in opening area calculation unit 77 calculates the opening area Avt_H of the first meter-in valve 17A based on the following equation (5). In equation (5), C is the flow rate constant.

[0072] Avt_H=Qt_H / (C√ΔPvt_H) …(5)

[0073] The low-pressure meter-in opening area calculation unit 78 calculates the opening area Avt_L of the second meter-in valve 17B based on the required flow rate Qt_L and the differential pressure ΔPvt_L. The low-pressure meter-in opening area calculation unit 78 calculates the opening area Avt_L of the second meter-in valve 17B based on the following equation (6). In equation (6), C is the flow rate constant.

[0074] Avt_L=Qt_L / (C√ΔPvt_L) …(6)

[0075] The meter-in valve control unit 79 controls the first meter-in valve 17A so that its opening area becomes opening area Avt_H. The meter-in valve control unit 79 controls the second meter-in valve 17B so that its opening area becomes opening area Avt_L.

[0076] The pump target flow rate calculation unit 80 calculates the pump target flow rate Qt_p, which indicates the target value of the flow rate of the hydraulic fluid discharged from the pump 15. The pump target flow rate calculation unit 80 determines the pump target flow rate Qt_p as the sum of the required flow rates (Qt_H, Qt_L) of the multiple actuator circuits 21. That is, the pump target flow rate calculation unit 80 calculates the pump target flow rate Qt_p based on the following equation (7).

[0077] Qt_p = Qt_H + Qt_L …(7)

[0078] The pump control unit 81 controls the swash plate of the pump 15 so that the pump 15 discharges hydraulic fluid at a target flow rate Qt_p.

[0079] <Effects> As described above, the controller 7 calculates a required flow rate, which indicates a target value for the flow rate of the hydraulic fluid supplied to the actuator circuit 21, and controls the opening area of ​​the meter-in valve 17 so that the required flow rate of hydraulic fluid is supplied to the actuator circuit 21, based on the characteristics of the pressure compensation mechanism 23. According to this embodiment, the required flow rate of hydraulic fluid is supplied to each of the multiple actuators.

[0080] The controller 7 determines the first actuator circuit 21A, which is the actuator circuit with the highest pressure, and the second actuator circuit 21B, which is other than the first actuator circuit 21A, from among the multiple actuator circuits 21 connected to each of the multiple actuators operating simultaneously. The controller 7 sets a target differential pressure ΔPvt_H, which indicates the target value of the differential pressure across the first meter-in valve 17A connected to the first actuator circuit 21A. Based on the target differential pressure ΔPvt_H, the controller 7 controls the opening area Avt_H of the first meter-in valve 17A so that the required flow rate Qt_H of hydraulic fluid is supplied to the first actuator circuit 21A. Based on the characteristics of the pressure compensation mechanism 23, the controller 7 calculates the differential pressure ΔPvt_L across the second meter-in valve 17B connected to the second actuator circuit 21B. Based on the differential pressure ΔPvt_L of the second meter-in valve 17B, the controller 7 controls the opening area Avt_L of the second meter-in valve 17B so that the required flow rate Qt_L of hydraulic fluid is supplied to the second actuator circuit 21B. Here, by controlling the pump 15 to discharge the sum of the requested flow rate Qt_H and the requested flow rate Qt_L as the pump target flow rate Qt_p, the first actuator circuit 21A and the second actuator circuit 21B are each distributed with the requested flow rates Qt_H and Qt_L, respectively, and each actuator can achieve the intended operation.

[0081] <If the actuator circuit pressure sensor is malfunctioning> An abnormality may occur in the actuator circuit pressure sensor 18. If an abnormality occurs in the actuator circuit pressure sensor 18, it may become difficult to calculate the differential pressure ΔPvt_L across the second meter-in valve 17B. The controller 7 can detect an abnormality in the actuator circuit pressure sensor 18. When the actuator circuit pressure sensor 18 is normal, the value of the detection data of the actuator circuit pressure sensor 18 will be within a predetermined normal range. When the actuator circuit pressure sensor 18 is abnormal, the value of the detection data of the actuator circuit pressure sensor 18 will be outside the normal range. Based on the value of the detection data of the actuator circuit pressure sensor 18, the controller 7 can determine whether or not the actuator circuit pressure sensor 18 is abnormal. If the detection data of the actuator circuit pressure sensor 18 includes a voltage value, and the normal range of the voltage value of the actuator circuit pressure sensor 18 is, for example, 0.5V or more and 4.5V or less, and the voltage value output from the actuator circuit pressure sensor 18 is, for example, 0.3V or less or 4.7V or more, the controller 7 can determine that the actuator circuit pressure sensor 18 is abnormal.

[0082] If the controller 7 detects an abnormality in the actuator circuit pressure sensor 18, it may control the opening area Avt_L of the second meter-in valve 17B based on a predetermined target differential pressure ΔPvt_H and the required flow rate Qt_L of the second actuator circuit 21B. The controller 7 may also calculate the opening area Avt_L of the second meter-in valve 17B by calculating the following equation (8). In equation (8), C is the flow rate constant.

[0083] Avt_L=Qt_L / (C√ΔPvt_H) …(8)

[0084] [Second Embodiment] A second embodiment will now be described. In the following description, components that are the same as or equivalent to those in the above-described embodiment will be denoted by the same reference numerals, and the descriptions of those components will be simplified or omitted.

[0085] Figure 7 is a schematic diagram showing the control system 13 of the work machine 1 according to the second embodiment. In the second embodiment, the control system 13 includes a pump pressure sensor 30 that detects the pressure of the pump circuit 19 through which the hydraulic fluid flowing into the first meter-in valve 17A on the high-pressure side flows, and a meter-in pressure sensor 31 that detects the pressure of the meter-in circuit 22 through which the hydraulic fluid flowing out from the meter-in valve 17 flows. The meter-in pressure sensor 31 includes a first meter-in pressure sensor 31A that detects the pressure of the first meter-in circuit 22A through which the hydraulic fluid flowing out from the first meter-in valve 17A on the high-pressure side flows, and a second meter-in pressure sensor 31B that detects the pressure of the second meter-in circuit 22B through which the hydraulic fluid flowing out from the second meter-in valve 17B on the low-pressure side flows.

[0086] The pump pressure sensor 30 detects the pump pressure P_p. The first meter-in pressure sensor 31A detects the meter-in pressure Pm_H. The second meter-in pressure sensor 31B detects the meter-in pressure Pm_L. The controller 7 may calculate the differential pressure ΔPvt_H across the high-pressure side first meter-in valve 17A and the differential pressure ΔPvt_L across the low-pressure side second meter-in valve 17B based on the detection data from the pump pressure sensor 30, the detection data from the first meter-in pressure sensor 31A, and the detection data from the second meter-in pressure sensor 31B.

[0087] Alternatively, the controller 7 may use a preset target differential pressure ΔPtv_H for the differential pressure ΔPvt_H across the first meter-in valve 17A on the high-pressure side, similar to the first embodiment. It may then calculate the pump pressure P_p using the detection data from the first meter-in pressure sensor 31A and the above-mentioned equation (2), and calculate the differential pressure ΔPvt_L across the second meter-in valve 17B on the low-pressure side based on that value and the detection value from the second meter-in pressure sensor 31B.

[0088] [Third Embodiment] A third embodiment will now be described. In the following description, components that are the same as or equivalent to those in the embodiments described above will be denoted by the same reference numerals, and the descriptions of those components will be simplified or omitted.

[0089] Figure 8 is a functional block diagram showing a controller 7 according to the third embodiment. In the third embodiment, the controller 7 includes a data acquisition unit 83, a switching unit 84, a first control unit 91, and a second control unit 92.

[0090] Note that the first control unit 91 and the second control unit 92 may be separate controllers (hardware). The first control unit 91 performs the first control. The second control unit 92 performs the second control. In this embodiment, the first control by the first control unit 91 and the second control by the second control unit 92 are switched based on the state of the work machine 1.

[0091] The controller 7 is connected to an operating device 8, a monitor 9 including an input device 9B, an actuator circuit pressure sensor 18, and a rotation sensor 32. The rotation sensor 32 detects the rotation state of the rotation body 3. The rotation state of the rotation body 3 includes whether or not it is rotating, the rotation angle of the rotation body 3 relative to the vehicle 2, and the rotation speed of the rotation body 3 relative to the vehicle 2. Examples of rotation sensors 32 include a rotation speed pickup sensor and an inertial measurement unit (IMU).

[0092] The data acquisition unit 83 acquires input data from the input device 9B. The data acquisition unit 83 acquires detection data from the actuator circuit pressure sensor 18 and detection data from the rotation sensor 32.

[0093] The first control unit 91 controls the opening area of ​​the meter-in valve 17 so that, according to the first embodiment described above, a required flow rate Qt_L and a required flow rate Qt_H of hydraulic fluid are supplied to a plurality of actuator circuits 21 connected to each of the plurality of actuators that operate simultaneously.

[0094] The second control unit 92 controls the opening area of ​​the meter-in valves 17 (17A, 17B) so that, among the multiple actuator circuits 21 connected to each of the multiple actuators operating simultaneously, the second actuator circuit 21B with low pressure is supplied with hydraulic fluid at a target flow rate Qt_Lr which is greater than the required flow rate Qt_L, and the first actuator circuit 21A with high pressure is supplied with hydraulic fluid at a target flow rate Qt_Hr which is less than the required flow rate Qt_H.

[0095] The switching unit 84 switches between the control of the meter-in valve 17 by the first control unit 91 and the control of the meter-in valve 17 by the second control unit 92 based on the state of the work machine 1. The switching unit 84 outputs a switching command to switch from the control of the meter-in valve 17 by the first control unit 91 and the control of the meter-in valve 17 by the second control unit 92 to the other.

[0096] The status of the work machine 1 includes its operating state or setting state. The controller 7 acquires setting data to set the status of the work machine 1. Examples of setting data include an automatic operation mode in which the work machine 1 operates autonomously without operator intervention, and a manual operation mode in which the work machine 1 operates based on operator input.

[0097] The setting data may be input to the controller 7 from, for example, the input device 9B. Based on the setting data, the switching unit 84 switches between the control of the meter-in valve 17 by the first control unit 91 and the control of the meter-in valve 17 by the second control unit 92.

[0098] Similar to the first embodiment described above, multiple actuator circuit pressure sensors 18 are provided to detect the pressure of each of the multiple actuator circuits 21. The second control unit 92 compares the pressures of the multiple actuator circuits 21 connected to each of the multiple actuators operating simultaneously, based on the detection data from the actuator circuit pressure sensors 18. By comparing the pressures of the multiple actuator circuits 21 connected to each of the multiple actuators operating simultaneously, the second control unit 92 can distinguish between actuator circuits 21 with high pressure and actuator circuits 21 with low pressure.

[0099] Similar to the controller 7 described in the first embodiment above, the second control unit 92 can determine from among the multiple actuator circuits 21 connected to each of the multiple actuators operating simultaneously which are the actuator circuit 21 with the highest pressure, which is the high-pressure side first actuator circuit 21A, and the actuator circuit 21 other than the high-pressure side second actuator circuit 21B, which is the low-pressure side second actuator circuit. The second control unit 92 can set a target differential pressure ΔPvt_H which indicates a target value for the differential pressure across the high-pressure side first meter-in valve 17A connected to the high-pressure side first actuator circuit 21A. The second control unit 92 can calculate the differential pressure ΔPvt_L across the low-pressure side second meter-in valve 17B connected to the low-pressure side second actuator circuit 21B.

[0100] The second control unit 92 can control the meter-in valve 17 using either the first or second calculation method described below.

[0101] (1st method) The second control unit 92 controls the opening area Avt_H of the first meter-in valve 17A on the high-pressure side based on the target differential pressure ΔPvt_H, so that the first actuator circuit 21A on the high-pressure side is supplied with hydraulic fluid at a target flow rate Qt_Hr.

[0102] The second control unit 92 controls the opening area Avt_L of the second meter-in valve 17B on the low-pressure side, based on the differential pressure ΔPvt_L across the second meter-in valve 17B, so that the second actuator circuit 21B on the low-pressure side is supplied with hydraulic fluid at a target flow rate Qt_Lr.

[0103] The second control unit 92 determines the first actuator circuit 21A with the highest pressure and the second actuator circuit 21B other than the first actuator circuit 21A from among the multiple actuator circuits 21 connected to each of the multiple actuators operating simultaneously, sets a target differential pressure ΔPvt_H indicating the target value of the differential pressure across the first meter-in valve 17A, and controls the opening area Avt_H of the first meter-in valve 17A based on the target differential pressure ΔPvt_H so that hydraulic fluid at a target flow rate Qt_Hr is supplied to the first actuator circuit 21A. Based on the characteristics of the pressure compensation mechanism 23, it calculates the differential pressure ΔPvt_L across the second meter-in valve 17B, and controls the opening area Avt_L of the second meter-in valve 17B based on the differential pressure ΔPvt_L so that hydraulic fluid at a target flow rate Qt_Lr is supplied to the second actuator circuit 21B. Specifically, the second control unit 92 calculates the opening area Avt_H of the first meter-in valve 17A on the high-pressure side based on equation (9) below, and calculates the opening area Avt_L of the second meter-in valve 17B on the low-pressure side based on equation (10) below. In equations (9) and (10), C is the flow rate constant.

[0104] Avt_H=Qt_Hr / (C√ΔPvt_H) …(9) Avt_L=Qt_Lr / (C√ΔPvt_L) …(10)

[0105] (Second method) The second control unit 92 controls the opening area Avt_H of the first meter-in valve 17A on the high-pressure side and the opening area Avt_L of the second meter-in valve 17B on the low-pressure side so that the ratio of the opening area Avt_H of the first meter-in valve 17A on the high-pressure side to the opening area Avt_L of the second meter-in valve 17B on the low-pressure side is the same as the ratio of the required flow rate Qt_H of the first actuator circuit 21A to the required flow rate Qt_L of the second actuator circuit 21B.

[0106] In other words, the second control unit 92 sets target differential pressure ΔPvt_H for both the differential pressure across the first meter-in valve 17A on the high-pressure side and the differential pressure across the second meter-in valve 17B on the low-pressure side, and calculates the opening area Avt_H of the first meter-in valve 17A on the high-pressure side and the opening area Avt_L of the second meter-in valve 17B on the low-pressure side using the required flow rates Qt_H and Qt_L for both the high-pressure side circuit and the low-pressure side circuit, respectively. In other words, the second control unit 92 calculates the opening area Avt_H of the first meter-in valve 17A on the high-pressure side based on equation (11) below, and calculates the opening area Avt_L of the second meter-in valve 17B on the low-pressure side based on equation (12) below. In equations (11) and (12), C is the flow rate constant.

[0107] Avt_H=Qt_H / (C√ΔPvt_H) …(11) Avt_L=Qt_L / (C√ΔPvt_H) …(12)

[0108] In either the first or second calculation method, when each meter-in valve is controlled to achieve the opening areas Avt_H and Avt_L calculated by the calculation method of the second control unit 92, the second actuator circuit 21B, which has low pressure, is supplied with hydraulic fluid at a target flow rate Qt_Lr that is greater than the required flow rate Qt_L, and the first actuator circuit 21A, which has high pressure, is supplied with hydraulic fluid at a target flow rate Qt_Hr that is less than the required flow rate Qt_H.

[0109] The switching unit 84 outputs a switching command so that the meter-in valve 17 is controlled by the first control unit 91 if the maximum pressure among the pressures of the multiple actuator circuits 21 connected to each of the multiple actuators operating simultaneously is less than a predetermined set value. The switching unit 84 outputs a switching command so that the meter-in valve 17 is controlled by the second control unit 92 if the maximum pressure is equal to or greater than the set value.

[0110] The second control unit 92 can control the meter-in valve 17 using the first or second calculation method described above.

[0111] When the maximum pressure is below the first setpoint, the controller 7 controls the opening area Avt_H (opening area Avt_L) of the meter-in valve 17 so that the flow rate of the hydraulic fluid supplied to the actuator circuit 21 becomes the required flow rate Qt_H (required flow rate Qt_L). In other words, when the maximum pressure is below the first setpoint, the controller 7 determines the opening area Avt_H (opening area Avt_L) of the meter-in valve 17 to the opening area calculated by the first control unit 91.

[0112] When the maximum pressure exceeds the first set value, the controller 7 controls the opening area Avt_H (opening area Avt_L) of the meter-in valve 17 so that the flow rate of the hydraulic fluid supplied to the actuator circuit 21 approaches the target flow rate Qt_Hr (target flow rate Qt_Lr) as it approaches the second set value, which is greater than the first set value. In other words, when the maximum pressure exceeds the first set value, the controller 7 changes the opening area of ​​the meter-in valve 17 from the opening area calculated by the first control unit 91 to the opening area calculated by the second control unit 92 as it approaches the second set value, which is greater than the first set value.

[0113] When the maximum pressure exceeds the second setpoint, the controller 7 controls the opening area Avt_H (opening area Avt_L) of the meter-in valve 17 so that the flow rate of the hydraulic fluid supplied to the actuator circuit 21 becomes the target flow rate Qt_Hr (target flow rate Qt_Lr). In other words, when the maximum pressure exceeds the second setpoint, the controller 7 controls the opening area of ​​the meter-in valve 17 to the opening area calculated by the second control unit 92.

[0114] As described above, the second control unit 92 controls the opening areas (Avt_H, Avt_L) of the meter-in valves 17 (17A, 17B) so that, among the multiple actuator circuits 21 connected to each of the multiple actuators operating simultaneously, the second actuator circuit 21B with the lowest pressure is supplied with hydraulic fluid at a target flow rate Qt_Lr which is greater than the required flow rate Qt_L, and the first actuator circuit 21A with the highest pressure is supplied with hydraulic fluid at a target flow rate Qt_Hr which is less than the required flow rate Qt_H. For example, when supplying hydraulic fluid to the second actuator circuit 21B, if the maximum pressure and the first set value are the same value, the second actuator circuit 21B is supplied with hydraulic fluid at a flow rate equivalent to the required flow rate Qt_L. If the maximum pressure significantly exceeds the first set value and the maximum pressure exceeds the second set value, the second actuator circuit 21B is supplied with hydraulic fluid at a flow rate close to the target flow rate Qt_Lr. The same applies when supplying hydraulic fluid to the first actuator circuit 21A.

[0115] The switching unit 84 determines whether the actuators are prone to vibration when multiple actuators are operating simultaneously. If it determines that the actuators are not prone to vibration, the switching unit 84 outputs a switching command so that the meter-in valve 17 is controlled by the first control unit 91. If it determines that the actuators are prone to vibration, the switching unit 84 outputs a switching command so that the meter-in valve 17 is controlled by the second control unit 92.

[0116] The fact that the actuator is prone to vibration includes the fact that the actuator operates at a high speed. The fact that the actuator operates at a high speed includes the fact that the flow rate of the hydraulic fluid supplied to the actuator is high.

[0117] The fact that the actuator is prone to vibration includes the fact that the operating speed of the actuator fluctuates greatly. The fact that the operating speed of the actuator fluctuates greatly includes the fact that the flow rate of the hydraulic fluid supplied to the actuator fluctuates greatly.

[0118] The controller 7 determines that the actuator is prone to vibration if the flow rate (required flow rate) of the hydraulic fluid supplied to the actuator is equal to or greater than a predetermined first threshold. The second control unit 92 may also determine that the actuator is even more prone to vibration if the fluctuation amount of the flow rate (required flow rate) of the hydraulic fluid supplied to the actuator is equal to or greater than a predetermined second threshold.

[0119] The controller 7 controls the opening area Avt_H (opening area Avt_L) of the meter-in valve 17 so that the flow rate supplied to the actuator circuit 21 approaches the target flow rate Qt_Hr (target flow rate Qt_Lr) from the required flow rate Qt_H (required flow rate Qt_L) as the degree to which the actuator is prone to vibration increases.

[0120] In other words, if the degree to which the actuator is prone to vibration is less than or equal to the first set value, the controller 7 controls the opening area of ​​the meter-in valve 17 to the opening area calculated by the first control unit 91. If the degree to which the actuator is prone to vibration exceeds the first set value, the controller 7 changes the opening area of ​​the meter-in valve 17 from the opening area calculated by the first control unit 91 to the opening area calculated by the second control unit 92 as it approaches the second set value, which is greater than the first set value. If the degree to which the actuator is prone to vibration exceeds the second set value, the controller 7 controls the opening area of ​​the meter-in valve 17 to the opening area calculated by the second control unit 92.

[0121] For example, when supplying hydraulic fluid to the second actuator circuit 21B, if the required flow rate Qt_L and the first threshold are the same value, the second actuator circuit 21B will be supplied with hydraulic fluid at a flow rate equivalent to the required flow rate Qt_L. If the required flow rate Qt_L significantly exceeds the first threshold and exceeds the second threshold, the second actuator circuit 21B will be supplied with hydraulic fluid at a flow rate close to the target flow rate Qt_Lr. The same applies when supplying hydraulic fluid to the first actuator circuit 21A.

[0122] Similar to the second embodiment described above, if differential pressure sensors (pump pressure sensor 30 and second meter-in pressure sensor 31B) are provided to detect the differential pressure ΔPvt_L across the second meter-in valve 17B on the low-pressure side, the second control unit 92 may obtain the differential pressure ΔPvt_L across the second meter-in valve on the low-pressure side from the detection data of the pump pressure sensor 30 and the detection data of the second meter-in pressure sensor 31B.

[0123] Similar to the second embodiment described above, if a pump pressure sensor 30 for detecting the pressure of the pump circuit 19, a first meter-in pressure sensor 31A for detecting the pressure of the first meter-in circuit 22A, and a second meter-in pressure sensor 31B for detecting the pressure of the second meter-in circuit 22B are provided, the second control unit 92 may calculate the differential pressure ΔPvt_L across the low-pressure second meter-in valve 17B based on the detection data from the pump pressure sensor 30, the detection data from the first meter-in pressure sensor 31A, and the detection data from the second meter-in pressure sensor 31B.

[0124] The second control unit 92 may calculate the differential pressure ΔPvt_H across the first meter-in valve 17A on the high-pressure side and the differential pressure ΔPvt_L across the second meter-in valve 17B on the low-pressure side based on the detection data of the first meter-in pressure sensor 31A, the detection data of the second meter-in pressure sensor 31B, and the target flow rate Qt_Lr of the second actuator circuit 21B on the low-pressure side.

[0125] The second control unit 92 may use a preset target differential pressure ΔPtv_H for the differential pressure ΔPvt_H across the first meter-in valve 17A on the high-pressure side, similar to the first embodiment. It may then calculate the pump pressure P_p using the detection data from the first meter-in pressure sensor 31A and the above-mentioned equation (2), and calculate the differential pressure ΔPvt_L across the second meter-in valve 17B on the low-pressure side based on that value and the detection value from the second meter-in pressure sensor 31B.

[0126] If the first control unit 91 detects an abnormality in the actuator circuit pressure sensor 18, it may control the opening area Avt_L of the second meter-in valve 17B on the low-pressure side based on the target differential pressure ΔPvt_H of the first meter-in valve 17A on the high-pressure side and the required flow rate Qt_L of the second actuator circuit 21B on the low-pressure side.

[0127] Next, an example of a control method for the second control unit 92 will be described. This will describe a control method for the work machine 1 when the operating device 8 is operated in a combined manner so that multiple work machine cylinders 6 operate simultaneously, and at least one work machine cylinder 6 reaches the stroke end. The stroke end refers to the end position of the movable range of the rod of the work machine cylinder 6. That is, the stroke end refers to the position of the rod when the work machine cylinder 6 is most retracted or when the rod is most extended.

[0128] For example, when the operating device 8 is operated in combination so that the boom cylinder 6A and the arm cylinder 6B operate simultaneously, if the boom cylinder 6A reaches the stroke end, the boom cylinder 6A can no longer move, so the pump pressure P_p rises above the crack pressure of the relief valve 36, and most of the pump discharge flow rate is relieved to the tank 16. If the combined operation of the operating device 8 is not released and hydraulic fluid continues to be supplied to the boom cylinder 6A even though the boom cylinder 6A has reached the stroke end and can no longer move, most of the pump discharge will be relieved to the tank 16, so almost no pump discharge flow rate will be supplied to the arm cylinder 6B, the operating speed of the arm cylinder 6B will decrease, and as a result, the work efficiency will decrease. Therefore, when the boom cylinder 6A has reached the stroke end and can no longer move, the second control unit 92 outputs a control command to suppress the pressure increase of the pump pressure P_p by greatly reducing the flow rate of hydraulic fluid supplied to the boom cylinder 6A, so as not to reduce the flow rate of hydraulic fluid supplied to the arm cylinder 6B.

[0129] In this embodiment, the second control unit 92 determines whether a high-load combined operation state is in which the load pressure of at least one actuator is equal to or greater than a pressure threshold when the operating device 8 is being operated in a combined manner so that multiple actuators are operating simultaneously. The second control unit 92 determines that the actuator whose load pressure is equal to or greater than the pressure threshold is a high-load actuator that has reached its stroke end and is no longer able to move. The second control unit 92 outputs a control command to reduce the flow rate of hydraulic fluid supplied to the high-load actuator. The second control unit 92 intervenes and controls the meter-in valve 17 to reduce the flow rate of hydraulic fluid supplied to the high-load actuator.

[0130] Figure 9 is a flowchart showing the control method for the work machine 1 according to the third embodiment. Below, we will describe the control method when the boom cylinder 6A reaches the stroke end, in a case where the operating device 8 is operated in combination so that the boom cylinder 6A and the arm cylinder 6B operate simultaneously.

[0131] The second control unit 92 acquires the load pressure of the work machine cylinder 6. That is, the second control unit 92 acquires the detection data of the actuator circuit pressure sensor 18. In this embodiment, the second control unit 92 acquires the detection data of the first actuator circuit pressure sensor 18A and the second actuator circuit pressure sensor 18B (step SB1).

[0132] The second control unit 92 acquires the combined operating amount of the operating device 8, which is operated in combination so that the boom cylinder 6A and the arm cylinder 6B operate simultaneously (step SB2).

[0133] The second control unit 92 determines whether a high-load combined operation state is in which the load pressure of at least one of the work equipment cylinders 6 of the boom cylinder 6A and the arm cylinder 6B is equal to or greater than a predetermined pressure threshold, while the operating device 8 is operated so that the boom cylinder 6A and the arm cylinder 6B are operating simultaneously. The pressure threshold is a predetermined value (step SB3).

[0134] In step SB3, if it is determined, for example, that the load pressure of the boom cylinder 6A is equal to or greater than a predetermined pressure threshold (step SB3: Yes), the second control unit 92 intervenes to control one or both of the first meter-in valve 17A and the second meter-in valve 17B so as to suppress the flow rate of the hydraulic fluid supplied to the boom cylinder 6A (step SB4).

[0135] Intervention control of the meter-in valve 17 means that, while the operating device 8 is being operated, the meter-in valve 17 outputs an operating command different from the control command determined based on the operating amount.

[0136] The second control unit 92 outputs a control command to intervene and control one or both of the first meter-in valve 17A and the second meter-in valve 17B so as to reduce the flow rate of hydraulic fluid supplied to the boom cylinder 6A, which is a high-load actuator. That is, the second control unit 92 outputs a control command to either reduce the opening area of ​​the first meter-in valve 17A or increase the opening of the second meter-in valve 17B. The second control unit 92 may also output a control command to reduce the opening area of ​​the first meter-in valve 17A and increase the opening of the second meter-in valve 17B at the same time.

[0137] If the second control unit 92 determines in step SB3 that a high-load combined operation state is in place, it outputs a control command to reduce the flow rate of hydraulic fluid supplied to the boom cylinder 6A, based on the load pressure of the boom cylinder 6A, which is a high-load actuator, and the arm control amount that operates the arm cylinder 6B, which is a low-load actuator whose load pressure is below the pressure threshold. Specifically, the second control unit 92 reduces the flow rate of hydraulic fluid supplied to the boom cylinder 6A as the arm operation amount increases. When the arm operation amount is large, a large flow rate of hydraulic fluid should be supplied to the arm cylinder 6B, so the opening area of ​​the first meter-in valve 17A is made sufficiently small so that the flow rate of hydraulic fluid supplied to the arm cylinder 6B increases.

[0138] If the second control unit 92 determines in step SB3 that a high-load combined operation state is in place, it outputs a control command to reduce the flow rate of hydraulic fluid supplied to the boom cylinder 6A, based on the boom operation amount that operates the boom cylinder 6A, which is a high-load actuator, and the load pressure of the arm cylinder 6B, which is a low-load actuator whose load pressure is below a pressure threshold. Specifically, the second control unit 92 reduces the flow rate of hydraulic fluid supplied to the boom cylinder 6A as the boom operation amount decreases. After the boom cylinder 6A reaches the stroke end, if the boom operation amount decreases, the flow rate of hydraulic fluid to be supplied to the boom cylinder 6A does not need to be large, so the opening area of ​​the first meter-in valve 17A is made sufficiently small so that the flow rate of hydraulic fluid supplied to the boom cylinder 6A is reduced.

[0139] If the second control unit 92 determines in step SB3 that a high-load combined operation state is in effect, it outputs a control command to increase the flow rate of hydraulic fluid supplied to the arm cylinder 6B, which is a low-load actuator whose load pressure is below the pressure threshold. The second control unit 92 outputs a control command to intervene and control the second meter-in valve 17B so that the flow rate of hydraulic fluid supplied to the arm cylinder 6B, which is a low-load actuator, increases. In other words, the second control unit 92 outputs a control command to increase the opening area of ​​the second meter-in valve 17B.

[0140] If the second control unit 92 determines in step SB3 that a high-load combined operation state is in place, it outputs a control command to increase the flow rate of hydraulic fluid supplied to the arm cylinder 6B, based on the load pressure of the boom cylinder 6A, which is a high-load actuator whose load pressure is above a pressure threshold, and the arm operation amount that operates the arm cylinder 6B, which is a low-load actuator. Specifically, the second control unit 92 increases the flow rate of hydraulic fluid supplied to the arm cylinder 6B as the arm operation amount increases. When the arm operation amount is large, a large flow rate of hydraulic fluid should be supplied to the arm cylinder 6B, so the opening area of ​​the second meter-in valve 17B is increased to increase the flow rate of hydraulic fluid supplied to the arm cylinder 6B.

[0141] If it is determined in step SB3 that the high-load combined operation state is not present (step SB3: No), the meter-in valve 17 is controlled based on the combined operation amount and correlation data (step SB5).

[0142] Next, we will explain how to control the work machine 1 when the slewing body 3 is unable to rotate, even though the operating device 8 is operated in combination to operate the slewing motor 5 and the work machine cylinder 6 simultaneously. For example, due to contact between the slewing body 3 and an object, or contact between the work machine 4 and an object, a situation may arise where the slewing body 3 cannot rotate even though the operating device 8 is operated to allow the slewing body 3 to rotate.

[0143] The second control unit 92 determines that the slewing body 3 is in a high-load combined operation state if it determines that the load pressure of the slewing motor 5 is equal to or greater than the pressure threshold, the amount of operation required to rotate the slewing body 3 is equal to or greater than the operation amount threshold, and the slewing speed of the slewing body 3 is less than the speed threshold, and that these conditions have persisted for a specified period of time. The pressure threshold, operation amount threshold, and speed threshold are all predetermined values.

[0144] In other words, if the load pressure of the slewing motor 5 is above the pressure threshold, the amount of operation required to rotate the slewing body 3 is above the operation amount threshold, and the slewing speed of the slewing body 3 is below the speed threshold, and this condition persists for a specified time, the second control unit 92 determines that a situation has occurred where the slewing body 3 cannot rotate despite the operation device 8 being operated to rotate the slewing body 3, and determines that the slewing body 3 is in a high-load combined operation state.

[0145] Furthermore, as described above, the second control unit 92 determines that the work implement 4 is in a high-load combined operation state if the load pressure of the work implement cylinder 6 is equal to or greater than the pressure threshold.

[0146] The second control unit 92 changes the pressure threshold based on the rotation state of the slewing body 3. Specifically, the second control unit 92 changes the pressure threshold based on the detection data of the rotation sensor 32. When the slewing body 3 is stopped and the work implement 4 is operating, the second control unit 92 sets the pressure threshold for the work implement cylinder 6 to a first value, and when the slewing body 3 is rotating and the work implement 4 is operating, the second control unit 92 sets the pressure threshold for the work implement cylinder 6 to a second value which is smaller than the first value.

[0147] When the working implement 4 is operating while the slewing body 3 is stopped, the working implement 4 may be performing heavy-load operations such as excavation. If the pressure threshold is set to a low value when the working implement 4 is performing heavy-load operations, it may be determined that a high-load combined operation state is occurring even though the working implement cylinder 6 has not reached the stroke end (even though the working implement cylinder 6 is operating normally), and the meter-in valve 17 may intervene to reduce the flow rate of hydraulic fluid supplied to the working implement cylinder 6. As a result, work efficiency may decrease. Therefore, when the working implement 4 is operating while the slewing body 3 is stopped, the pressure threshold for the working implement cylinder 6 is set to a high first value.

[0148] When the working implement 4 is operating while the slewing body 3 is slewing, the working implement 4 may simply be moving in the air without performing any work. When the working implement 4 is moving in the air, it is preferable to set the pressure threshold to a low value so that when the working implement cylinder 6 reaches the end of its stroke, it is immediately determined that the working implement cylinder 6 is in a high-load combined operation state. That is, when the working implement 4 is moving in the air, it is preferable that when the working implement cylinder 6 reaches the end of its stroke, the amount of hydraulic fluid supplied to the working implement cylinder 6 is immediately reduced and the amount of hydraulic fluid supplied to the slewing motor 5 is increased. By increasing the amount of hydraulic fluid supplied to the slewing motor 5, the decrease in the slewing speed of the slewing body 3 is suppressed, and thus the decrease in work efficiency is suppressed. For this reason, when the working implement 4 is operating while the slewing body 3 is slewing, the pressure threshold for the working implement cylinder 6 is set to a low second value.

[0149] Figure 10 is a flowchart showing the control method for the work machine 1 according to the third embodiment. The second control unit 92 acquires the load pressure of the work machine cylinder 6 and the load pressure of the swing motor 5. That is, the second control unit 92 acquires the detection data of the actuator circuit pressure sensor 18 (step SC1).

[0150] The second control unit 92 acquires the combined operating amount of the operating device 8, which has been operated in combination so that multiple actuators operate simultaneously (step SC2).

[0151] The second control unit 92 acquires the rotation state of the rotating body 3. That is, the second control unit 92 acquires the detection data of the rotation sensor 32 (step SC3). Based on the detection data of the rotation sensor 32, the second control unit 92 determines whether or not the rotating body 3 is rotating. Alternatively, the second control unit 92 may determine whether or not the rotating body 3 is rotating based on the amount of rotation operation (step SC4).

[0152] If it is determined in step SC4 that the rotating body 3 is rotating (step SC4: Yes), the second control unit 92 sets the pressure threshold to the first value (step SC5). If it is determined in step SC4 that the rotating body 3 is not rotating (step SC4: No), the second control unit 92 sets the pressure threshold to the second value (step SC6).

[0153] The second control unit 92 determines whether the slewing body 3 is in a high-load combined operation state. That is, the second control unit 92 determines whether the load pressure of the slewing motor 5 is equal to or greater than the pressure threshold, the amount of slewing operation to rotate the slewing body 3 is equal to or greater than the operation amount threshold, and the slewing speed of the slewing body 3 is less than the speed threshold, and whether this state has continued for a specified time (step SC7).

[0154] In step SC7, if it is determined that the slewing body 3 is in a high-load combined operation state (step SC7: Yes), the second control unit 92 intervenes to control the fourth meter-in valve 17D, which controls the flow rate of hydraulic fluid supplied to the slewing motor 5. The second control unit 92 outputs a control command to intervene and control the fourth meter-in valve connected to the slewing motor 5 so that the flow rate of hydraulic fluid supplied to the slewing motor 5 decreases. That is, the second control unit 92 outputs a control command so that the opening area of ​​the fourth meter-in valve becomes smaller (step SC9).

[0155] In step SC7, if it is determined that the slewing body 3 is not in a high-load combined operation state (step SC7: No), the second control unit 92 determines whether the work implement 4 is in a high-load combined operation state. That is, the second control unit 92 determines whether the load pressure of the work implement cylinder 6 is above a pressure threshold (step SC8).

[0156] In step SC8, if it is determined that the work equipment cylinder 6 is in a high-load combined operation state (step SC8: Yes), the second control unit 92 intervenes to control the meter-in valve 17, which controls the flow rate of hydraulic fluid supplied to the work equipment cylinder 6. For example, if it is determined that the boom cylinder 6A is in a high-load combined operation state, the second control unit 92 outputs a control command to intervene and control the first meter-in valve 17A so that the flow rate of hydraulic fluid supplied to the boom cylinder 6A decreases. That is, the second control unit 92 outputs a control command so that the opening area of ​​the first meter-in valve 17A becomes smaller (step SC9).

[0157] If it is determined in step SC8 that the high-load combined operation state is not present (step SC8: No), the meter-in valve 17 is controlled based on the combined operation amount and correlation data (step SC10).

[0158] [Fourth Embodiment] A fourth embodiment will now be described. In the following description, components that are the same as or equivalent to those in the embodiments described above will be denoted by the same reference numerals, and their descriptions will be simplified or omitted. In the first to third embodiments described above, the operation during combined operation by two actuators was explained. In the fourth embodiment, the operation during combined operation by three or more actuators will be explained.

[0159] Figure 11 is a schematic diagram showing the control system of the work machine 1 according to the fourth embodiment. As shown in Figure 11, the actuator includes a boom cylinder 6A, an arm cylinder 6B, a bucket cylinder 6C, and a slewing motor 5. The meter-in valve 17 includes a first meter-in valve 17A that controls the flow rate of hydraulic fluid supplied to the boom cylinder 6A, a second meter-in valve 17B that controls the flow rate of hydraulic fluid supplied to the arm cylinder 6B, a third meter-in valve 17C that controls the flow rate of hydraulic fluid supplied to the bucket cylinder 6C, and a fourth meter-in valve 17D that controls the flow rate of hydraulic fluid supplied to the slewing motor 5.

[0160] The pressure compensation valve 24 includes a first pressure compensation valve 24A connected to a first meter-in valve 17A via a first meter-in circuit 22A, a second pressure compensation valve 24B connected to a second meter-in valve 17B via a second meter-in circuit 22B, a third pressure compensation valve 24C connected to a third meter-in valve 17C via a third meter-in circuit 22C, and a fourth pressure compensation valve 24D connected to a fourth meter-in valve 17D via a fourth meter-in circuit 22D.

[0161] The first pressure compensation valve 24A is connected to the boom cylinder 6A via the first actuator circuit 21A. The second pressure compensation valve 24B is connected to the arm cylinder 6B via the second actuator circuit 21B. The third pressure compensation valve 24C is connected to the bucket cylinder 6C via the third actuator circuit 21C. The fourth pressure compensation valve 24D is connected to the slewing motor 5 via the fourth actuator circuit 21D.

[0162] The actuator circuit pressure sensor 18 includes a first actuator circuit pressure sensor 18A for detecting the pressure of the first actuator circuit 21A, a second actuator circuit pressure sensor 18B for detecting the pressure of the second actuator circuit 21B, a third actuator circuit pressure sensor 18C for detecting the pressure of the third actuator circuit 21C, and a fourth actuator circuit pressure sensor 18D for detecting the pressure of the fourth actuator circuit 21D.

[0163] The first compensation circuit 23A and the first meter-in circuit 22A merge, the second compensation circuit 23B and the second meter-in circuit 22B merge, the third compensation circuit 23C and the third meter-in circuit 22C merge, and the fourth compensation circuit 23D and the fourth meter-in circuit 22D merge. The fifth compensation circuit 23M is connected to the respective highest pressure receiving ports 27 of the multiple pressure compensation valves 24.

[0164] The fifth compensation circuit 23M is connected to the self-pressure-receiving port 26 of the pressure compensation valve 24 via a check valve 28. The check valve 28 includes a first check valve 28A positioned between the self-pressure-receiving port 26 of the first pressure compensation valve 24A and the fifth compensation circuit 23M, a second check valve 28B positioned between the self-pressure-receiving port 26 of the second pressure compensation valve 24B and the fifth compensation circuit 23M, a third check valve 28C positioned between the self-pressure-receiving port 26 of the third pressure compensation valve 24C and the fifth compensation circuit 23M, and a fourth check valve 28D positioned between the self-pressure-receiving port 26 of the fourth pressure compensation valve 24D and the fifth compensation circuit 23M.

[0165] As shown in Figure 11, a check valve 28 may be used instead of the shuttle valve.

[0166] In the first to third embodiments described above, the magnitude of the load pressure of two actuator circuits was detected, and the control method for the meter-in valves 17 of the high-pressure side circuit and the low-pressure side circuit was explained. However, in the fourth embodiment, when three or more actuators are operated simultaneously, the meter-in valve 17 of the circuit with the highest pressure is calculated and controlled using the method described as "high pressure" in the first to third embodiments, and all the meter-in valves 17 of the other circuits are calculated and controlled using the method described as "low pressure" in the first to third embodiments. [Explanation of Symbols]

[0167] 1...Work machine, 2...Traction unit, 2A...Tracks, 3...Slewing unit, 4...Work machine, 4A...Boom, 4B...Arm, 4C...Bucket, 5...Slewing motor, 6...Work machine cylinder, 6A...Boom cylinder, 6B...Arm cylinder, 6C...Bucket cylinder, 7...Controller, 8...Operating device, 8A...Left work lever, 8B...Right work lever, 8C...Left travel lever, 8D...Right travel lever, 8E...Left foot pedal, 8F...Right foot pedal, 9...Monitor, 9A...Display device, 9B...Input device, 10...Cab, 11...Driver's seat, 12...Computer, 12A...Processor, 12B... Main memory, 12C...Storage, 12D...Input / Output interface, 12E...Communication interface, 12F...Computer program, 13...Control system, 14...Power source, 15...Pump, 16...Tank, 17...Meter-in valve, 17A...First meter-in valve, 17B...Second meter-in valve, 17C...Third meter-in valve, 17D...Fourth meter-in valve, 18...Actuator circuit pressure sensor, 18A...First actuator circuit pressure sensor, 18B...Second actuator circuit pressure sensor, 18C...Third actuator circuit pressure sensor, 18D...Fourth actuator circuit pressure Sensor, 19... Pump circuit, 20... Suction circuit, 21... Actuator circuit, 21A... First actuator circuit, 21B... Second actuator circuit, 21C... Third actuator circuit, 21D... Fourth actuator circuit, 22... Meter-in circuit, 22A... First meter-in circuit, 22B... Second meter-in circuit, 22C... Third meter-in circuit, 22D... Fourth meter-in circuit, 23... Pressure compensation mechanism, 23A... First compensation circuit, 23B... Second compensation circuit, 23C... Third compensation circuit, 23D... Fourth compensation circuit, 23M... Fifth compensation circuit, 24... Pressure compensation valve, 24A... First pressure compensation valve , 24B...2nd pressure compensation valve, 24C...3rd pressure compensation valve, 24D...4th pressure compensation valve, 25...Shuttle valve, 26...Self-pressure receiving port, 27...Maximum pressure receiving port, 28...Check valve, 28A...1st check valve, 28B...2nd check valve, 28C...3rd check valve, 28D...4th check valve, 30...Pump pressure sensor, 31...Meter-in pressure sensor, 31A...1st meter-in pressure sensor, 31B...2nd meter-in pressure sensor, 32...Swivel sensor, 35...Relief circuit, 36...Relief valve, 70...Actuator circuit pressure acquisition unit, 71...Operation amount acquisition unit, 72...Maximum load pressure circuit determination unit,73...Actuator required flow rate calculation unit, 74...High pressure meter-in pressure calculation unit, 75...Pump pressure calculation unit, 76...Low pressure meter-in pressure calculation unit, 77...High pressure meter-in opening area calculation unit, 78...Low pressure meter-in opening area calculation unit, 79...Meter-in valve control unit, 80...Pump target flow rate calculation unit, 81...Pump control unit, 83...Data acquisition unit, 84...Switching unit, 91...First control unit, 92...Second control unit, Qt_p...Pump target flow rate, P_p...Pump pressure, ΔPc...Pressure difference between front and rear, ΔPvt_H...Pressure difference between front and rear, ΔPvt_L...Pressure difference between front and rear, Pm_H...Meter-in pressure, Pm_L...Meter-in pressure, P_H...Actuator circuit pressure, P_L...Actuator circuit pressure, Qt_H...Required flow rate, Qt_L...Required flow rate, Qt_Hr...Target flow rate, Qt_Lr...Target flow rate, Avt_H...Opening area, Avt_L...Opening area. ,

Claims

1. A pump that discharges hydraulic fluid, A plurality of actuators driven by the hydraulic fluid discharged from the pump, Multiple actuator circuits, each connected to a plurality of actuators and through which hydraulic fluid supplied to the actuators flows, Multiple meter-in valves for adjusting the flow rate of hydraulic fluid supplied to each of the multiple actuator circuits, A pressure compensation mechanism having a plurality of pressure compensation valves connected to each of the plurality of meter-in valves, which compensates for the differential pressure across the meter-in valves, Equipped with a controller, The aforementioned controller, The required flow rate, which indicates the target value of the flow rate of the hydraulic fluid supplied to the actuator circuit, is calculated. Based on the characteristics of the pressure compensation mechanism, the opening area of ​​the meter-in valve is controlled so that the required flow rate of hydraulic fluid is supplied to the actuator circuit. Control system for industrial machinery.

2. The characteristics of the pressure compensation mechanism include, when the opening areas of the multiple meter-in valves are the same, hydraulic characteristics that allow hydraulic fluid to flow more easily to the actuator circuit with lower pressure than to the actuator circuit with higher pressure. A control system for a work machine according to claim 1.

3. The system includes multiple actuator circuit pressure sensors that detect the pressure of each of the multiple actuator circuits, The aforementioned controller, The actuator circuit with the highest pressure is determined from among the multiple actuator circuits connected to each of the multiple actuators operating simultaneously. The opening area of ​​meter-in valves other than those in the actuator circuit with the highest pressure is controlled based on the differential pressure across the meter-in valve of the actuator circuit with the highest pressure. A control system for a work machine according to claim 1.

4. The system includes multiple actuator circuit pressure sensors that detect the pressure of each of the multiple actuator circuits, The aforementioned controller, Based on the detection data from the actuator circuit pressure sensor, the high-pressure side actuator circuit, which is the actuator circuit with the highest pressure, and the low-pressure side actuator circuit, which is an actuator circuit other than the high-pressure side actuator circuit, are determined from among the multiple actuator circuits connected to each of the multiple actuators that operate simultaneously. A target differential pressure is set, which indicates the target value of the differential pressure across the high-pressure side meter-in valve, which is a meter-in valve connected to the high-pressure side actuator circuit. Based on the target differential pressure, the opening area of ​​the high-pressure side meter-in valve is controlled so that the required flow rate of hydraulic fluid is supplied to the high-pressure side actuator circuit. Based on the characteristics of the pressure compensation mechanism, the differential pressure across the low-pressure side meter-in valve, which is a meter-in valve connected to the low-pressure side actuator circuit, is calculated. The opening area of ​​the low-pressure side meter-in valve is controlled based on the differential pressure across the low-pressure side meter-in valve so that the required flow rate of hydraulic fluid is supplied to the low-pressure side actuator circuit. A control system for a work machine according to claim 1.

5. The system includes a differential pressure sensor that detects the differential pressure across the low-pressure side meter-in valve, The aforementioned controller, The differential pressure across the low-pressure side meter-in valve is obtained from the differential pressure sensor. A control system for a work machine according to claim 4.

6. A pump pressure sensor that detects the pressure in the pump circuit through which the hydraulic fluid flowing into the high-pressure side meter-in valve flows, A first meter-in pressure sensor detects the pressure in the first meter-in circuit through which the hydraulic fluid flowing out from the high-pressure side meter-in valve flows, The system includes a second meter-in pressure sensor that detects the pressure in a second meter-in circuit through which the hydraulic fluid flowing out from the low-pressure side meter-in valve flows, The aforementioned controller, Based on the detection data from the pump pressure sensor, the detection data from the first meter-in pressure sensor, and the detection data from the second meter-in pressure sensor, the differential pressure across the low-pressure side meter-in valve is calculated. A control system for a work machine according to claim 4.

7. A first meter-in pressure sensor detects the pressure in the first meter-in circuit through which the hydraulic fluid flowing out from the high-pressure side meter-in valve flows, The system includes a second meter-in pressure sensor that detects the pressure in a second meter-in circuit through which the hydraulic fluid flowing out from the low-pressure side meter-in valve flows, The aforementioned controller, Based on the detection data from the first meter-in pressure sensor and the pump circuit pressure calculated from the target differential pressure indicating the target value of the differential pressure across the high-pressure side meter-in valve, the differential pressure across the low-pressure side meter-in valve is calculated. A control system for a work machine according to claim 4.

8. The actuator circuit pressure sensor includes a high-pressure side actuator circuit pressure sensor for detecting the pressure of the high-pressure side actuator circuit and a low-pressure side actuator circuit pressure sensor for detecting the pressure of the low-pressure side actuator circuit. The aforementioned controller, Based on the detection data from the high-pressure side actuator circuit pressure sensor, the detection data from the low-pressure side actuator circuit pressure sensor, and the dimensional characteristics of the pressure compensation mechanism, the differential pressure across the low-pressure side meter-in valve is calculated. A control system for a work machine according to claim 4.

9. The aforementioned controller, If an abnormality is detected in the actuator circuit pressure sensor, Based on the target differential pressure and the required flow rate of the low-pressure side actuator circuit, the opening area of ​​the low-pressure side meter-in valve is controlled. A control system for a work machine according to claim 4.

10. The aforementioned controller, A first control that controls the opening area of ​​the meter-in valve so that the required flow rate of hydraulic fluid is supplied to multiple actuator circuits connected to each of the multiple actuators that operate simultaneously, A second control is performed to control the opening area of ​​the meter-in valve such that, among the multiple actuator circuits connected to each of the multiple actuators operating simultaneously, the actuator circuit with the lowest pressure is supplied with a target flow rate of hydraulic fluid greater than the required flow rate, and the actuator circuit with the highest pressure is supplied with a target flow rate of hydraulic fluid less than the required flow rate. The first control and the second control are switched based on the state of the work machine. A control system for a work machine according to claim 1.

11. The system includes multiple actuator circuit pressure sensors that detect the pressure of each of the multiple actuator circuits, The second control is, This includes comparing the pressures of multiple actuator circuits connected to each of the multiple actuators operating simultaneously, based on the detection data from the actuator circuit pressure sensor, to distinguish between actuator circuits with high pressure and actuator circuits with low pressure. A control system for a work machine according to claim 10.

12. The second control is, Based on the detection data from the actuator circuit pressure sensor, the high-pressure side actuator circuit, which is the actuator circuit with the highest pressure, and the low-pressure side actuator circuit, which is an actuator circuit other than the high-pressure side actuator circuit, are determined from among the multiple actuator circuits connected to each of the multiple actuators that operate simultaneously. Setting a target differential pressure that indicates a target value of the differential pressure across the high-pressure side meter-in valve, which is a meter-in valve connected to the high-pressure side actuator circuit, The opening area of ​​the high-pressure side meter-in valve is controlled based on the target differential pressure so that the target flow rate of hydraulic fluid is supplied to the high-pressure side actuator circuit. To obtain the differential pressure across the low-pressure side meter-in valve, which is a meter-in valve connected to the low-pressure side actuator circuit, This includes controlling the opening area of ​​the low-pressure side meter-in valve based on the differential pressure across the low-pressure side meter-in valve so that a target flow rate of hydraulic fluid is supplied to the low-pressure side actuator circuit, A control system for a work machine according to claim 11.

13. The system includes a differential pressure sensor that detects the differential pressure across the low-pressure side meter-in valve, The aforementioned controller, The differential pressure across the low-pressure side meter-in valve is obtained from the differential pressure sensor. A control system for a work machine according to claim 12.

14. A pump pressure sensor that detects the pressure in the pump circuit through which the hydraulic fluid flowing into the high-pressure side meter-in valve flows, A first meter-in pressure sensor detects the pressure in the first meter-in circuit through which the hydraulic fluid flowing out from the high-pressure side meter-in valve flows, The system includes a second meter-in pressure sensor that detects the pressure in a second meter-in circuit through which the hydraulic fluid flowing out from the low-pressure side meter-in valve flows, The second control is, This includes calculating the differential pressure across the low-pressure side meter-in valve based on the detection data from the pump pressure sensor, the detection data from the first meter-in pressure sensor, and the detection data from the second meter-in pressure sensor. A control system for a work machine according to claim 12.

15. A first meter-in pressure sensor detects the pressure in the first meter-in circuit through which the hydraulic fluid flowing out from the high-pressure side meter-in valve flows, The system includes a second meter-in pressure sensor that detects the pressure in a second meter-in circuit through which the hydraulic fluid flowing out from the low-pressure side meter-in valve flows, The second control is, This includes calculating the differential pressure across the low-pressure side meter-in valve based on the detection data from the first meter-in pressure sensor and the pump circuit pressure calculated from the target differential pressure indicating the target value of the differential pressure across the high-pressure side meter-in valve. A control system for a work machine according to claim 12.

16. The system includes multiple actuator circuit pressure sensors that detect the pressure of each of the multiple actuator circuits, The actuator circuit pressure sensor includes a high-pressure side actuator circuit pressure sensor for detecting the pressure of the high-pressure side actuator circuit and a low-pressure side actuator circuit pressure sensor for detecting the pressure of the low-pressure side actuator circuit. The second control is, This includes calculating the differential pressure across the low-pressure meter-in valve based on the detection data from the high-pressure side actuator circuit pressure sensor, the detection data from the low-pressure side actuator circuit pressure sensor, and the dimensional characteristics of the pressure compensation mechanism. A control system for a work machine according to claim 12.

17. The system includes multiple actuator circuit pressure sensors that detect the pressure of each of the multiple actuator circuits, The first control is, This includes setting a target differential pressure that indicates a target value of the differential pressure across the high-pressure side meter-in valve, which is a meter-in valve connected to the high-pressure side actuator circuit, If an abnormality is detected in the actuator circuit pressure sensor, Based on the target differential pressure and the required flow rate of the low-pressure side actuator circuit, the opening area of ​​the low-pressure side meter-in valve is controlled. A control system for a work machine according to claim 12.

18. The system includes multiple actuator circuit pressure sensors that detect the pressure of each of the multiple actuator circuits, The first control is, Based on the detection data from the actuator circuit pressure sensor, the high-pressure side actuator circuit, which is the actuator circuit with the highest pressure, and the low-pressure side actuator circuit, which is an actuator circuit other than the high-pressure side actuator circuit, are determined from among the multiple actuator circuits connected to each of the multiple actuators that operate simultaneously. Setting a target differential pressure that indicates a target value of the differential pressure across the high-pressure side meter-in valve, which is a meter-in valve connected to the high-pressure side actuator circuit, The opening area of ​​the high-pressure side meter-in valve is controlled based on the target differential pressure so that the required flow rate of hydraulic fluid is supplied to the high-pressure side actuator circuit. Based on the characteristics of the pressure compensation mechanism, the differential pressure across the low-pressure side meter-in valve, which is a meter-in valve connected to the low-pressure side actuator circuit, is obtained. This includes controlling the opening area of ​​the low-pressure side meter-in valve based on the differential pressure across the low-pressure side meter-in valve so that the required flow rate of hydraulic fluid is supplied to the low-pressure side actuator circuit, The second control is, Based on the detection data from the actuator circuit pressure sensor, the high-pressure side actuator circuit, which is the actuator circuit with the highest pressure, and the low-pressure side actuator circuit, which is an actuator circuit other than the high-pressure side actuator circuit, are determined from among the multiple actuator circuits connected to each of the multiple actuators that operate simultaneously. This includes controlling the opening areas of the high-pressure side meter-in valve and the low-pressure side meter-in valve so that the ratio of the opening area of ​​the high-pressure side meter-in valve to the opening area of ​​the low-pressure side meter-in valve is the same as the ratio of the required flow rate of the high-pressure side actuator circuit to the required flow rate of the low-pressure side actuator circuit. A control system for a work machine according to claim 10.

19. The second control is, Setting a target differential pressure that indicates a target value of the differential pressure across the high-pressure side meter-in valve, which is a meter-in valve connected to the high-pressure side actuator circuit, This includes controlling the opening area of ​​the high-pressure side meter-in valve and the low-pressure side meter-in valve based on the target differential pressure and the required flow rate, A control system for a work machine according to claim 18.

20. The system includes multiple actuator circuit pressure sensors that detect the pressure of each of the multiple actuator circuits, The aforementioned controller, If the highest pressure among the pressures of the multiple actuator circuits connected to each of the multiple actuators operating simultaneously is less than a predetermined set value, the first control controls the meter-in valve. If the aforementioned maximum pressure is equal to or greater than the set value, the meter-in valve is controlled by the second control. A control system for a work machine according to claim 10.

21. The system includes multiple actuator circuit pressure sensors that detect the pressure of each of the multiple actuator circuits, The aforementioned controller, If the maximum pressure is less than or equal to the first set value, the opening area of ​​the meter-in valve is determined to be the opening area calculated by the first control. If the maximum pressure exceeds the first set value, the opening area of ​​the meter-in valve is changed from the opening area calculated by the first control to the opening area calculated by the second control as it approaches a second set value which is greater than the first set value. If the maximum pressure exceeds the second set value, the opening area of ​​the meter-in valve is controlled to be the opening area calculated by the second control. A control system for a work machine according to claim 20.

22. The aforementioned controller, When multiple actuators are operating simultaneously, it is determined whether the actuators are in a state where they are prone to vibration. If it is determined that the actuator is in a state where it is less likely to vibrate, the meter-in valve is controlled by the first control. If it is determined that the actuator is prone to vibration, the second control controls the meter-in valve. A control system for a work machine according to claim 10.

23. The aforementioned controller, When multiple actuators are operating simultaneously, it is determined whether the actuators are in a state where they are prone to vibration. If the degree to which the actuator is prone to vibration is less than or equal to a first set value, the opening area of ​​the meter-in valve is controlled to the opening area calculated by the first control. If the degree to which the actuator is prone to vibration exceeds the first set value, the opening area of ​​the meter-in valve is changed from the opening area calculated by the first control to the opening area calculated by the second control as it approaches a second set value which is greater than the first set value. If the degree to which the actuator is prone to vibration exceeds the second set value, the opening area of ​​the meter-in valve is controlled to the opening area calculated by the second control. A control system for a work machine according to claim 10.

24. The aforementioned controller, Obtain setting data to set the status of the work machine, Based on the aforementioned setting data, the first control and the second control are switched. A control system for a work machine according to claim 10.

25. The aforementioned controller, The sum of the required flow rates of multiple actuator circuits is determined as the target flow rate of the hydraulic fluid discharged from the pump. A control system for a work machine according to claim 1.

26. The aforementioned work machine is The car body and, A work machine rotatably mounted on the vehicle body, The work machine has a plurality of actuators for operating the work machine, A control system for a work machine according to claim 1.

27. A pump that discharges hydraulic fluid, A plurality of actuators driven by the hydraulic fluid discharged from the pump, Multiple actuator circuits, each connected to a plurality of actuators and through which hydraulic fluid supplied to the actuators flows, Multiple meter-in valves that adjust the flow rate supplied to each of the multiple actuator circuits, A pressure compensation mechanism having a plurality of pressure compensation valves connected to each of the plurality of meter-in valves, which compensates for the differential pressure across the meter-in valves, A control method for a work machine comprising a controller, The aforementioned controller The required flow rate, which indicates the target value of the flow rate of the hydraulic fluid supplied to the actuator circuit, is calculated. Based on the characteristics of the pressure compensation mechanism, the opening area of ​​the meter-in valve is controlled so that the required flow rate of hydraulic fluid is supplied to the actuator circuit. A method for controlling industrial machinery.

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