Control system and control method for working machinery

Abstract

To suppress the occurrence of cavitation. [Solution] The control system for the work machine comprises a hydraulic pump that discharges hydraulic fluid, a meter-in valve that adjusts the hydraulic fluid discharged from the hydraulic pump, a hydraulic actuator to which the hydraulic fluid adjusted by the meter-in valve is supplied via a meter-in passage, and a controller. The controller acquires the supply flow rate, which indicates the flow rate of hydraulic fluid supplied to the hydraulic actuator, and if it determines that a pressure decrease state is occurring where the pressure in the meter-in passage decreases, it calculates a compensation flow rate to be added to the supply flow rate in order to suppress the pressure decrease in the meter-in passage, and controls at least one of the opening area of ​​the meter-in valve and the hydraulic pump based on the supply flow rate and the compensation flow rate.

Description

[Technical Field]

[0001] This disclosure relates to a control system for a work machine and a control method for a work machine. [Background technology]

[0002] In the technical field of work machinery, a hydraulic excavator equipped with a work machine having a boom, an arm, and a bucket is known, as disclosed in Patent Document 1. In Patent Document 1, the hydraulic excavator is equipped with a hydraulic drive circuit that controls the hydraulic actuator operating speed corresponding to the flow rate of pressurized oil discharged from the hydraulic actuator to be greater than the hydraulic actuator operating speed corresponding to the flow rate of pressurized oil supplied to the hydraulic actuator. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2013-249900 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] If cavitation occurs inside a hydraulic actuator, where air bubbles are formed in the hydraulic fluid, it can lead to malfunction of the hydraulic actuator.

[0005] This disclosure aims to suppress the occurrence of cavitation. [Means for solving the problem]

[0006] A control system for a work machine is provided, comprising a hydraulic pump for discharging hydraulic fluid, a meter-in valve for adjusting the hydraulic fluid discharged from the hydraulic pump, a hydraulic actuator to which the hydraulic fluid adjusted by the meter-in valve is supplied via a meter-in passage, and a controller. The controller obtains a supply flow rate indicating the flow rate of hydraulic fluid supplied to the hydraulic actuator, and if it determines that a pressure drop condition occurs where the pressure in the meter-in passage decreases, it calculates a compensation flow rate to be added to the supply flow rate to suppress the pressure drop in the meter-in passage, and controls at least one of the opening area of ​​the meter-in valve and the hydraulic pump based on the supply flow rate and the compensation flow rate. [Effects of the Invention]

[0007] According to this disclosure, the occurrence of cavitation is suppressed. [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 is a schematic diagram showing the control system of a work machine according to the first embodiment. [Figure 3] Figure 3 is a hardware configuration diagram showing the controller according to the first embodiment. [Figure 4] Figure 4 is a functional block diagram showing the controller according to the first embodiment. [Figure 5] Figure 5 is a schematic diagram showing the work machine cylinder according to the first embodiment. [Figure 6] Figure 6 is a diagram illustrating the load state according to the first embodiment. [Figure 7] Figure 7 shows an example of the meter-in pressure and the rate of change of the meter-in pressure over time detected by the meter-in pressure sensor according to the first embodiment. [Figure 8] Figure 8 is a diagram illustrating the corrected pump flow rate according to the first embodiment. [Figure 9] Figure 9 is a flowchart showing the control method for a work machine according to the first embodiment. [Figure 10] Figure 10 is a timing chart showing a control method for a working machine according to the first embodiment. [Figure 11] Figure 11 is a flowchart showing a control method for a working machine when the meter-in pressure sensor according to the first embodiment is abnormal. [Figure 12] Figure 12 is a functional block diagram showing a controller according to the second embodiment. [Figure 13] Figure 13 is a flowchart showing a control method for a working machine according to the second embodiment. [Figure 14] Figure 14 is a flowchart showing a control method for a working machine when the operating speed sensor according to the second embodiment is abnormal.

Mode for Carrying Out the Invention

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

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

[0011] The traveling body 2 supports the revolving body 3. The traveling body 2 has a pair of crawlers 2A. One crawler 2A is disposed on the left side of the traveling body 2. The other crawler 2A is disposed on the right side of the traveling body 2. The working machine 1 travels by rotation of the crawlers 2A.

[0012] The revolving body 3 is the vehicle body of the working machine

[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 travel motor 9 moves the vehicle 2. The travel motor 9 rotates the tracks 2A of the vehicle 2. The travel motor 9 includes a left travel motor that rotates the left track 2A and a right travel motor that rotates the right track 2A. The vehicle 2 moves as the tracks 2A rotate. The travel motor 9 is a hydraulic motor driven by hydraulic fluid. The travel motor 9 is an example of a hydraulic actuator driven by hydraulic fluid.

[0015] The slewing motor 5 rotates the slewing body 3, which is supported by the traveling body 2. The slewing body 3 includes the slewing motor 5. The slewing motor 5 is a hydraulic motor driven by hydraulic fluid. The slewing motor 5 is an example of a hydraulic actuator driven by hydraulic fluid.

[0016] 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 fluid. The work implement cylinder 6 is an example of a hydraulic actuator driven by hydraulic fluid. The work implement cylinder 6 has a cylinder tube 61, a piston 62 that is movable inside the cylinder tube 61, and a rod 63 fixed to the piston 62 (see Figure 2). The work implement cylinder 6 includes a boom cylinder 6A, an arm cylinder 6B, and a bucket cylinder 6C.

[0017] The boom cylinder 6A operates the boom 4A. The base end of the cylinder tube of the boom cylinder 6A is connected to the slewing body 3, and the tip of the rod of the boom cylinder 6A is connected to the boom 4A. The operation of the boom 4A includes raising and lowering movements. When hydraulic fluid flows into the bottom chamber of the boom cylinder 6A and the boom cylinder 6A extends, the boom 4A is raised. When hydraulic fluid flows into the head chamber of the boom cylinder 6A and the boom cylinder 6A retracts, the boom 4A is lowered.

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

[0019] 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.

[0020] The control device 8 is located in the cab. The control device 8 is operated by an operator seated in the cab. The operator can operate the control device 8 while seated in the driver's seat located in the cab. The control device 8 includes a number of levers. The control device 8 is operated to operate the hydraulic actuator of the work machine 1. The control device 8 is operated to operate at least one of the traveling body 2, the slewing body 3, and the work machine 4.

[0021] When the operating device 8 is operated, an operating signal (electrical signal) is generated to operate the hydraulic actuator of the work machine 1. The operating signal from the operating device 8 is transmitted to the controller 7. The operating signal from the operating device 8 includes the amount of operation of the operating device 8. The amount of operation may be considered as the signal strength of the operating signal. If the operating device 8 includes a lever, the amount of operation may be considered as the operating angle (tilting angle) of the lever. The controller 7 controls the hydraulic actuator based on the amount of operation of the operating device 8.

[0022] 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.

[0023] <Control System> Figure 2 is a schematic diagram showing the control system 10 of the work machine 1 according to the first embodiment. The control system 10 includes a hydraulic circuit (hydraulic system) that operates using hydraulic fluid. Hereinafter, the hydraulic actuator will be assumed to be the work machine cylinder 6.

[0024] As shown in Figure 2, the control system 10 includes a work machine cylinder 6, a controller 7, an operating device 8, a power source 11, a hydraulic pump 12, a tank 13, a meter-in valve 14, a meter-out valve 15, a meter-in pressure sensor 16, an operating speed sensor 17, a suction passage 18, a pump passage 19, a meter-in passage 20, a meter-out passage 21, and a tank passage 22.

[0025] The work implement cylinder 6 is a hydraulic cylinder. The work implement cylinder 6 has a cylinder tube 61, a piston 62, and a rod 63. The piston 62 is movable inside the cylinder tube 61. The rod 63 is fixed to one end face of the piston 62 and moves together with the piston 62. The piston 62 divides the internal space of the cylinder tube 61 into a head chamber 64 and a bottom chamber 65. When the work implement cylinder 6 is retracted, the volume of the head chamber 64 increases. When the work implement cylinder 6 is extended, the volume of the bottom chamber 65 increases. The work implement cylinder 6 is retracted as hydraulic fluid flows into the head chamber 64 and hydraulic fluid flows out of the bottom chamber 65. The work implement cylinder 6 is extended as hydraulic fluid flows into the bottom chamber 65 and hydraulic fluid flows out of the head chamber 64.

[0026] Power source 11 is the power source for the work machine 1. A diesel engine is given as an example of power source 11. However, power source 11 may also be an electric motor. Power source 11 is connected to the hydraulic pump 12. Power source 11 drives the hydraulic pump 12.

[0027] The suction passage 18 connects the tank 13 and the hydraulic pump 12. The pump passage 19 connects the hydraulic pump 12 and the meter-in valve 14. The meter-in passage 20 connects the meter-in valve 14 and the work machine cylinder 6. The meter-out passage 21 connects the work machine cylinder 6 and the meter-out valve 15. The tank passage 22 connects the meter-out valve 15 and the tank 13. In the example shown in Figure 2, the meter-in passage 20 is connected to the head chamber 64 of the work machine cylinder 6. The meter-out passage 21 is connected to the bottom chamber 65 of the work machine cylinder 6.

[0028] The hydraulic pump 12 discharges hydraulic fluid. The hydraulic fluid discharged from the hydraulic pump 12 is supplied to the work machine cylinder 6. The hydraulic pump 12 is a swashplate type variable displacement pump. The capacity [cc / rev] of the hydraulic pump 12 is changed by changing the angle of the swashplate of the hydraulic pump 12. The hydraulic pump 12 draws in hydraulic fluid contained in the tank 13 through the suction passage 18. The hydraulic pump 12 discharges the hydraulic fluid drawn in from the tank 13 into the pump passage 19.

[0029] The meter-in valve 14 adjusts the hydraulic fluid discharged from the hydraulic pump 12. The meter-in valve 14 controls the flow rate of hydraulic fluid supplied from the hydraulic pump 12 to the work machine cylinder 6. The hydraulic fluid adjusted by the meter-in valve 14 is supplied to the work machine cylinder 6 via the meter-in passage 20. By adjusting the opening area of ​​the meter-in valve 14, the flow rate of hydraulic fluid supplied to the work machine cylinder 6 is adjusted. By controlling the flow rate of hydraulic fluid supplied to the work machine cylinder 6, the operating speed (cylinder speed) of the work machine cylinder 6 is controlled.

[0030] The meter-out valve 15 adjusts the hydraulic fluid discharged from the work machine cylinder 6. The meter-out valve 15 controls the flow rate of hydraulic fluid discharged from the work machine cylinder 6 to the tank 13. By adjusting the opening area of ​​the meter-out valve 15, the flow rate of hydraulic fluid discharged from the work machine cylinder 6 is adjusted. By controlling the flow rate of hydraulic fluid discharged from the work machine cylinder 6, the operating speed (cylinder speed) of the work machine cylinder 6 is controlled.

[0031] The meter-in pressure sensor 16 detects the meter-in pressure p, which indicates the pressure of the hydraulic fluid supplied to the work machine cylinder 6. The meter-in pressure sensor 16 also detects the pressure in the meter-in passage 20 between the meter-in valve 14 and the work machine cylinder 6. The meter-in pressure p indicates the pressure in the meter-in passage 20 between the meter-in valve 14 and the work machine cylinder 6. The meter-in pressure p can be considered as the load pressure applied to the work machine cylinder 6. The detection data from the meter-in pressure sensor 16 is transmitted to the controller 7.

[0032] The operating speed sensor 17 detects the operating speed of the work machine cylinder 6. The operating speed of the work machine cylinder 6 is the cylinder speed, which indicates the movement speed of the piston 62 (rod 63) of the work machine cylinder 6. An example of the operating speed sensor 17 is a cylinder stroke sensor capable of detecting the distance or speed of movement of the piston 62 (rod 63) relative to the cylinder tube 61. The operating speed sensor 17 may also include an inertial measurement unit (IMU) attached to the work machine 4. The inertial sensor can detect the operating speed, operating acceleration, or operating angular velocity of the work machine 4. The operating speed of the work machine cylinder 6 may be calculated based on the detection data of the inertial sensor. The operating speed sensor 17 may also include a camera attached to the slewing body 3. The operating speed of the work machine cylinder 6 may be calculated by image processing of image data of the work machine 4 or work machine cylinder 6 captured by the camera. The detection data of the operating speed sensor 17 is transmitted to the controller 7.

[0033] <Controller> Figure 3 is a hardware configuration diagram showing a controller 7 according to the first embodiment. The controller 7 includes a computer 25. The computer 25 has a processor 25A such as a CPU (Central Processing Unit), a main memory 25B including non-volatile memory such as ROM (Read Only Memory) and volatile memory such as RAM (Random Access Memory), a storage 25C, an input / output interface 25D including input / output circuits, and a communication interface 25E including communication circuits. The functions of the controller 7 are stored in the storage 25C as a computer program 25F. The processor 25A reads the computer program 25F from the storage 25C, loads it into the main memory 25B, and executes processing according to the computer program 25F. The computer program 25F may be distributed to the computer 25 via a network.

[0034] Figure 4 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 hydraulic pump 12 and the meter-in valve 14. The controller 7 has a plurality of functional units. The functions of the functional units of the controller 7 are performed by the processor 25A. The functional units of the controller 7 include a target operating speed calculation unit 71, a target pump flow rate calculation unit 72, a pressure reduction state determination unit 73, a corrected pump flow rate calculation unit 74, and a control unit 75.

[0035] The target operating speed calculation unit 71 calculates the target operating speed (target cylinder speed) of the work machine cylinder 6. The target operating speed calculation unit 71 calculates the target operating speed of the work machine cylinder 6 based on the manipulated variable, which indicates the value of the operation signal for operating the work machine cylinder 6. The operation signal is generated when the operator operates the operating device 8. The target operating speed calculation unit 71 calculates the target operating speed of the work machine cylinder 6 based on the manipulated variable of the operating device 8. The target operating speed may be a value proportional to the manipulated variable of the operating device 8. If a first correlation data showing the relationship between the manipulated variable of the operating device 8 and the target operating speed is predetermined, the target operating speed calculation unit 71 may determine the target operating speed by inputting the manipulated variable of the operating device 8 into the first correlation data.

[0036] The target pump flow rate calculation unit 72 calculates a target supply flow rate, which indicates a target value for the flow rate of hydraulic fluid supplied to the work machine cylinder 6, based on the target operating speed of the work machine cylinder 6 calculated by the target operating speed calculation unit 71. In this embodiment, the target supply flow rate of hydraulic fluid supplied to the work machine cylinder 6 includes a target pump flow rate, which indicates a target value for the flow rate of hydraulic fluid discharged from the hydraulic pump 12. In the following description, the target supply flow rate of hydraulic fluid supplied to the work machine cylinder 6 will be referred to as the target pump flow rate as appropriate. In the first embodiment, the supply flow rate, which indicates the flow rate of hydraulic fluid supplied to the work machine cylinder 6, includes the target pump flow rate.

[0037] The target operating speed of the work machine cylinder 6 and the target pump flow rate correspond one-to-one. The target pump flow rate calculation unit 72 calculates the target pump flow rate of the hydraulic pump 12 based on the target operating speed of the work machine cylinder 6. The target pump flow rate may be a value proportional to the target operating speed. If a second correlation data showing the relationship between the target operating speed and the target pump flow rate is predetermined, the target pump flow rate calculation unit 72 may determine the target pump flow rate by inputting the target operating speed into the second correlation data. The target pump flow rate calculation unit 72 may also calculate the target pump flow rate based on the operating amount of the operating device 8.

[0038] Figure 5 is a schematic diagram showing the work machine cylinder 6 according to the first embodiment. The hydraulic fluid discharged from the hydraulic pump 12 and passing through the meter-in valve 14 flows into the work machine cylinder 6 via the meter-in passage 20. The supply flow rate Q from the meter-in passage 20 in The hydraulic fluid flows into the work machine cylinder 6. The flow of hydraulic fluid into the work machine cylinder 6 via the meter-in passage 20 causes the piston 62 to move. The piston 62 moves at a speed V. If the pressure-receiving area of ​​the piston 62 is A, the consumption flow rate, which indicates the change in the volume of hydraulic fluid per unit time in the chamber into which the hydraulic fluid flows in the work machine cylinder 6 (in this embodiment, the head chamber 64), is expressed as [pressure-receiving area A] × [movement speed V]. For the operation of the work machine cylinder 6, it can be considered that a flow rate of hydraulic fluid equal to the product AV of the movement speed V and the pressure-receiving area A is consumed in the work machine cylinder 6. In addition, as the hydraulic fluid flows into the work machine cylinder 6 via the meter-in passage 20 and the piston 62 moves, the volume W of the chamber of the work machine cylinder 6 connected to the meter-in passage 20 (head chamber 64 or bottom chamber 65) changes. The pressure in the chamber of the work machine cylinder 6 connected to the meter-in passage 20 (head chamber 64 or bottom chamber 65) is the meter-in pressure p, which is detected by the meter-in pressure sensor 16.

[0039] Figure 6 is a diagram illustrating the load conditions according to the embodiment. Figure 6 shows the state in which the arm 4B is performing a dumping operation. The load conditions when the arm 4B is performing a dumping operation will be described below, but the load conditions when the arm 4B is performing an excavation operation, when the boom 4A is performing an raising and lowering operation, and when the bucket 4C is performing an excavation and dumping operation are similar.

[0040] When arm 4B performs a dumping operation, arm cylinder 6B retracts. When arm 4B is dumped, hydraulic fluid is supplied from the meter-in passage 20 to the head chamber 64 of arm cylinder 6B. The piston 62 of arm cylinder 6B moves in the direction indicated by arrow Ya. When arm 4B performs a dumping operation, arm 4B moves along arm trajectory H. In the example shown in Figure 6, arm 4B starts the dumping operation from a position above the bottom dead center Hn of arm trajectory H and close to the slewing body 3, passes the bottom dead center Hn, and then rotates to a position above the bottom dead center Hn and farther from the slewing body 3. In the range Ha of arm trajectory H that is closer to the slewing body 3 than the bottom dead center Hn, the direction of the load on arm cylinder 6B is the same forward direction as the dumping operation of arm 4B. In the range Hb of arm trajectory H that is farther from the slewing body 3 than the bottom dead center Hn, the direction of the load on arm cylinder 6B is the opposite direction to the dumping operation of arm 4B.

[0041] In range Ha, the arm 4B rotates to bottom dead center Hn due to its own weight. Due to its own weight, the arm 4B may rotate at a higher operating speed than the target operating speed determined based on the operating amount of the operating device 8. If the arm 4B rotates at an operating speed higher than the target operating speed, even if hydraulic fluid is being discharged from the hydraulic pump 12, the flow rate of hydraulic fluid supplied from the meter-in passage 20 to the arm cylinder 6B may become insufficient, and the pressure in the meter-in passage 20 and the head chamber 64 may drop sharply. If the situation of insufficient hydraulic fluid being supplied from the hydraulic pump 12 to the head chamber 64 of the arm cylinder 6B continues, the head chamber 64 may become negatively pressurized, and cavitation may occur in the head chamber 64, where air bubbles are generated in the hydraulic fluid.

[0042] In this embodiment, the pressure reduction state determination unit 73 determines whether or not a pressure reduction state occurs based on the meter-in pressure p detected by the meter-in pressure sensor 16. The pressure reduction state determination unit 73 determines that a pressure reduction state occurs when the meter-in pressure p decreases. Meter-in pressure p and supply flow rate Q in The following relationship (1) holds between the consumption flow rate AV and the volume W of the head chamber 64 connected to the meter-in flow path 20. In equation (1), K is the bulk modulus and t is time.

[0043]

number

[0044] As shown in equation (1), the supply flow rate Q in If the supply flow rate Q is less than the consumption flow rate AV, the time rate of change of the meter-in pressure p becomes negative, and the meter-in pressure p decreases. The pressure reduction state determination unit 73 determines when the meter-in pressure p decreases, that is, when the time rate of change of the meter-in pressure p becomes negative, the supply flow rate Q in If it is determined that the flow rate AV is less than the consumption rate AV, it is determined that the head chamber 64 is in a pressure-reduced state.

[0045] Figure 7 shows an example of the meter-in pressure p and the rate of change of the meter-in pressure p detected by the meter-in pressure sensor 16 according to the first embodiment. In the graph shown in Figure 7, the horizontal axis is time, and the vertical axis is the meter-in pressure and the rate of change of the meter-in pressure over time. As shown in section Ca of Figure 7, when the meter-in pressure p decreases, that is, when the rate of change of the meter-in pressure Va becomes negative, the pressure reduction state determination unit 73 determines that the arm cylinder 6B is in a pressure reduction state.

[0046] The corrected pump flow rate calculation unit 74 calculates the supply flow rate Q in If the pressure reduction state determination unit 73 determines that the pressure reduction state is less than the consumption flow rate AV, it calculates the corrected pump flow rate by adding the compensation flow rate to the target pump flow rate.

[0047] Figure 8 is a diagram illustrating the corrected pump flow rate according to the first embodiment. In Figure 8, line Lp1 shows the target pump flow rate calculated by the target pump flow rate calculation unit 72. Line Lp2 shows the corrected pump flow rate calculated by the corrected pump flow rate calculation unit 74. As described above, the target pump flow rate is calculated based on the operating amount of the operating device 8 or the target operating speed of the work machine cylinder 6.

[0048] If a pressure decrease is detected, the corrected pump flow rate calculation unit 74 adds a compensation flow rate to the target pump flow rate. By supplying the hydraulic fluid at the corrected pump flow rate (the target pump flow rate plus the compensation flow rate) to the work machine cylinder 6, a rapid decrease in pressure in the work machine cylinder 6 is suppressed, preventing a negative pressure state. In other words, the supply flow rate Q supplied to the head chamber 64 is equal to the compensation flow rate. in As this increases, the occurrence of cavitation is suppressed.

[0049] In this embodiment, the compensation pump flow rate calculation unit 74 calculates the compensation flow rate based on the rate of change of meter-in pressure p over time, Va, when the meter-in pressure p decreases. The compensation pump flow rate calculation unit 74 calculates the compensation flow rate by multiplying the rate of change of time Va by an adjustment gain. The adjustment gain is a predetermined value. The larger the absolute value of the rate of change of time Va, the greater the compensation flow rate. That is, the more rapidly the meter-in pressure p decreases, the greater the compensation flow rate. The adjustment gain may be a fixed value (constant value). The adjustment gain may be a variable value. If the adjustment gain is a variable value, the compensation flow rate is changed when the adjustment gain is changed.

[0050] If the adjustment gain is a variable value, the compensation pump flow rate calculation unit 74 may change the adjustment gain based on the amount manipulated by the operating device 8. The compensation pump flow rate calculation unit 74 may increase the adjustment gain as the amount manipulated by the operating device 8 increases. In other words, the compensation flow rate may increase as the amount manipulated by the operating device 8 increases.

[0051] If the adjustment gain is a variable value, the compensation pump flow rate calculation unit 74 may change the adjustment gain based on the detection data of the operating speed sensor 17. The operating speed sensor 17 detects the actual operating speed (actual operating speed) of the work machine cylinder 6. The compensation pump flow rate calculation unit 74 may change the adjustment gain based on the actual operating speed of the work machine cylinder 6 detected by the operating speed sensor 17. The compensation pump flow rate calculation unit 74 may increase the adjustment gain as the actual operating speed of the work machine cylinder 6 increases. That is, the higher the actual operating speed of the work machine cylinder 6, the larger the compensation flow rate may be. In the case of a work machine 1 that does not have an operating speed sensor 17, or if the operating speed sensor 17 fails, the actual operating speed of the work machine cylinder 6 may be an estimated value of the operating speed calculated from the target supply flow rate (target pump flow rate).

[0052] The control unit 75 controls the hydraulic pump 12 so that it discharges hydraulic fluid at a corrected pump flow rate. The control unit 75 controls the hydraulic pump 12 so that it discharges hydraulic fluid at a corrected pump flow rate that is greater than the target pump flow rate. The control unit 75 controls the angle of the swash plate of the hydraulic pump 12. By adjusting the angle of the swash plate of the hydraulic pump 12 so that the capacity of the hydraulic pump 12 is increased, hydraulic fluid at a corrected pump flow rate that is greater than the target pump flow rate is discharged from the hydraulic pump 12.

[0053] Furthermore, when the control unit 75 adds the compensation flow rate to the target pump flow rate, it controls the meter-in valve 14 so that the opening area of ​​the meter-in valve 14 becomes larger. Since a compensation pump flow rate greater than the target pump flow rate is discharged from the hydraulic pump 12, the control unit 75 increases the opening area of ​​the meter-in valve 14 in accordance with the compensation pump flow rate so that the hydraulic fluid of the compensation pump flow rate can pass through the meter-in valve 14. The control unit 75 controls the meter-in valve 14 so that its opening area becomes larger than the opening area of ​​the meter-in valve 14 determined based on the target pump flow rate.

[0054] <Control Method> Figure 9 is a flowchart showing the control method for the work machine 1 according to the first embodiment. The target operating speed calculation unit 71 calculates the target operating speed of the work machine cylinder 6 based on the amount of operation of the operating device 8 (step SA1).

[0055] The target pump flow rate calculation unit 72 calculates a target pump flow rate, which indicates the target value of the flow rate of the hydraulic fluid discharged from the hydraulic pump 12, based on the target operating speed of the work machine cylinder 6 calculated by the target operating speed calculation unit 71 (step SA2).

[0056] The pressure reduction state determination unit 73 determines the supply flow rate Q based on the meter-in pressure p detected by the meter-in pressure sensor 16. in Determine whether the pressure reduction is less than the consumption flow rate AV (Step SA3).

[0057] In step SA3, if it is determined that the working machine cylinder 6 is in a pressure-reducing state (step SA3: Yes), the corrected pump flow rate calculation unit 74 calculates the corrected pump flow rate based on the rate of change of meter-in pressure p over time Va when the meter-in pressure p decreases. The corrected pump flow rate calculation unit 74 calculates the compensation flow rate by multiplying the rate of change of meter-in pressure p over time Va by the adjustment gain. The corrected pump flow rate calculation unit 74 calculates the corrected pump flow rate by adding the compensation flow rate to the target pump flow rate calculated in step SA2 (step SA4).

[0058] The control unit 75 controls the hydraulic pump 12 based on the corrected pump flow rate calculated in step SA4. The control unit 75 controls the hydraulic pump 12 so that the corrected pump flow rate of hydraulic fluid is discharged from the hydraulic pump 12. The control unit 75 controls the angle of the swash plate of the hydraulic pump 12 so that the corrected pump flow rate of hydraulic fluid is discharged from the hydraulic pump 12 (step SA5).

[0059] Furthermore, the control unit 75 controls the meter-in valve 14 based on the corrected pump flow rate. The control unit 75 controls the opening area of ​​the meter-in valve 14 in accordance with the corrected pump flow rate. The control unit 75 controls the meter-in valve 14 so that its opening area is larger than the opening area of ​​the meter-in valve 14 determined based on the target pump flow rate (step SA6).

[0060] In step SA3, if it is determined that the work machine cylinder 6 does not enter a pressure reduction state (step SA3: No), the control unit 75 controls the hydraulic pump 12 based on the target pump flow rate calculated in step SA2. The control unit 75 controls the hydraulic pump 12 so that the target pump flow rate of hydraulic fluid is discharged from the hydraulic pump 12. The control unit 75 controls the angle of the swash plate of the hydraulic pump 12 so that the target pump flow rate of hydraulic fluid is discharged from the hydraulic pump 12 (step SA7).

[0061] Furthermore, the control unit 75 controls the meter-in valve 14 based on the target pump flow rate. The control unit 75 controls the opening area of ​​the meter-in valve 14 in accordance with the target pump flow rate so that the hydraulic fluid at the target pump flow rate can pass through the meter-in valve 14 (step SA8).

[0062] Figure 10 is a timing chart showing the control method of the work machine 1 according to the first embodiment. Figure 10 is a timing chart when the arm 4B, which was described with reference to Figure 6, performs a dumping operation. In the multiple graphs shown in Figure 10, the horizontal axis is time, and the vertical axes are the operating speed of the arm cylinder 6B, the hydraulic fluid pressure, the rate of change of the meter-in pressure over time, the compensation flow rate, the pump flow rate, the opening area of ​​the meter-in valve 14, and the opening area of ​​the meter-out valve 15, respectively.

[0063] In Figure 10, time t1 follows time 0, time t2 follows time t1, time t3 follows time t2, and time t4 follows time t3. As explained with reference to Figure 6, at time 0, arm 4B is positioned above the bottom dead center Hn of arm trajectory H and close to the rotating body 3. Operation of the operating device 8 begins at time t1. From time t1 to time t4, arm 4B rotates within range Ha. At time t4, arm 4B reaches the bottom dead center Hn.

[0064] Line La indicates the target operating speed of arm cylinder 6B, line Lb indicates the actual operating speed of arm cylinder 6B, and line Lc indicates the operating speed of arm cylinder 6B corresponding to the target pump flow rate.

[0065] Line Ld indicates the meter-in pressure, which represents the pressure of the hydraulic fluid flowing into the arm cylinder 6B, and line Le indicates the meter-out pressure, which represents the pressure of the hydraulic fluid flowing out of the arm cylinder 6B. Line Lf indicates the meter-in pressure for the comparative example. The meter-in pressure for the comparative example is the meter-in pressure when the hydraulic pump 12 discharges hydraulic fluid at the target pump flow rate even in a negative pressure state.

[0066] Line Lg indicates the rate of change of the meter-in pressure over time. Line Lh indicates the compensation flow rate. Line Li indicates the target pump flow rate. Line Lj indicates the correction pump flow rate. Line Lk indicates the opening area of ​​the meter-in valve 14 matched to the target pump flow rate. Line Ll indicates the opening area of ​​the meter-in valve 14 matched to the correction pump flow rate. Line Lm indicates the opening area of ​​the meter-out valve 15.

[0067] At time t1, when the operation of the control device 8 is initiated, the target operating speed and target pump flow rate increase, and the opening area of ​​the meter-in valve 14 increases. The period from time t1 to time t2 is the period immediately following the start of the dump operation of the arm 4B, and the operating speed of the arm cylinder 6B is accelerated by the hydraulic fluid supplied from the meter-in passage 20 to the head chamber 64.

[0068] As shown by line Lb and line Lc, between time point t1 and time point t2, the operating speed corresponding to the target pump flow rate exceeds the actual operating speed. The fact that the operating speed corresponding to the target pump flow rate exceeds the actual operating speed means that the supply flow rate Q in exceeds the consumption flow rate AV.

[0069] During the period from time point t2 to time point t3, due to the action of the self-weight of the arm 4B, the speed of the arm 4B performing the damping operation accelerates, and the operating speed of the arm cylinder 6B accelerates. Between time point t2 and time point t3, the actual operating speed exceeds the operating speed corresponding to the target pump flow rate. The fact that the actual operating speed exceeds the operating speed corresponding to the target pump flow rate means that the consumption flow rate AV exceeds the supply flow rate Q in . That is, between time point t2 and time point t3, the work implement cylinder 6 is in a pressure reduction state. The decrease in the meter-in pressure p starts from time point t2. When the meter-in pressure p decreases, a compensation flow rate is calculated. By adding the calculated compensation flow rate to the target pump flow rate, a corrected pump flow rate is calculated. Between time point t2 and time point t3, the hydraulic oil of the corrected pump flow rate is discharged from the hydraulic pump 12. Also, in accordance with the corrected pump flow rate, the opening area of the meter-in valve 14 becomes larger than the opening area of the meter-in valve 14 determined based on the target pump flow rate.

[0070] When the arm 4B approaches the bottom dead point Hn after passing time point t3, the decrease in the meter-in pressure p ends. The compensation flow rate becomes zero, and the target pump flow rate and the corrected pump flow rate coincide.

[0071] The target opening area of ​​the meter-out valve 15 may be calculated based on the target operating speed of the work machine cylinder 6. The controller 7 may control the opening area of ​​the meter-out valve 15 based on the target operating speed of the work machine cylinder 6. The target opening area of ​​the meter-out valve 15 may be a value proportional to the target operating speed. If a third correlation data showing the relationship between the target operating speed and the target opening area of ​​the meter-out valve 15 is predetermined, the target opening area of ​​the meter-out valve 15 may be determined by inputting the target operating speed into the second correlation data. The target opening area of ​​the meter-out valve 15 may also be calculated based on the amount of operation of the operating device 8.

[0072] As shown by line Lf, if the hydraulic pump 12 discharges hydraulic fluid at the target pump flow rate even when the pressure decreases, the meter-in pressure in the comparative example decreases rapidly between time points t1 and t2, and then falls into a negative pressure state. As shown by line Ld, when the pressure decreases, the hydraulic pump 12 discharges hydraulic fluid at a corrected pump flow rate that is greater than the target pump flow rate, so the decrease in the meter-in pressure in the embodiment is suppressed between time points t1 and t2. In other words, the occurrence of a negative pressure state is suppressed.

[0073] <Control when the meter-in pressure sensor is malfunctioning> As described above, in this embodiment, the compensation flow rate is calculated based on the time rate of change Va of the meter-in pressure p detected by the meter-in pressure sensor 16. The control method for the work machine 1 when the meter-in pressure sensor 16 is abnormal will be described below.

[0074] Figure 11 is a flowchart showing the control method for the work machine 1 when the meter-in pressure sensor 16 according to the first embodiment is malfunctioning. When the meter-in pressure sensor 16 is malfunctioning, the correction pump flow rate calculation unit 74 cannot calculate the correction pump flow rate.

[0075] The corrected pump flow rate calculation unit 74 detects an abnormality in the meter-in pressure sensor 16 (step SB1).

[0076] If the meter-in pressure sensor 16 is malfunctioning, the detected data value from the meter-in pressure sensor 16 may become excessively low or excessively high. The corrected pump flow rate calculation unit 74 can determine that the meter-in pressure sensor 16 is malfunctioning if the detected data value from the meter-in pressure sensor 16 is below a predetermined first threshold, or if the detected data value from the meter-in pressure sensor 16 is above a predetermined second threshold. The second threshold is a value greater than the first threshold.

[0077] If the meter-in pressure sensor 16 is abnormal, the compensation pump flow rate calculation unit 74 does not calculate the compensation pump flow rate. If the meter-in pressure sensor 16 is abnormal, the compensation pump flow rate calculation unit 74 sets the compensation flow rate to zero. The control unit 75 controls the hydraulic pump 12 based on the target pump flow rate. That is, if the meter-in pressure sensor 16 is abnormal, the control unit 75 controls the hydraulic pump 12 so that even if cavitation occurs in the work machine cylinder 6, or if cavitation occurs simultaneously with a malfunction of the work machine cylinder 6 caused by cavitation, the hydraulic pump 12 discharges hydraulic fluid at the target pump flow rate so that the work machine cylinder 6 can operate to the minimum extent in response to the operation signal of the operating device 8 (step SB2).

[0078] Furthermore, the control unit 75 controls the meter-in valve 14 based on the target pump flow rate. The control unit 75 controls the opening area of ​​the meter-in valve 14 in accordance with the target pump flow rate (step SB3).

[0079] <Effects> As described above, according to the embodiment, the supply flow rate Q in If it is determined that the pressure reduction is less than the consumption flow rate AV, a compensation flow rate is added to the target pump flow rate calculated based on the operating amount of the operating device 8, and hydraulic fluid at a corrected pump flow rate greater than the target pump flow rate is discharged from the hydraulic pump 12. As a result of the discharge of hydraulic fluid at the corrected pump flow rate from the hydraulic pump 12, the supply flow rate Q of hydraulic fluid supplied from the meter-in passage 20 to the head chamber 64 of the arm cylinder 6B is increased. inAs this increases, a rapid pressure drop in the head chamber 64 is suppressed, and a negative pressure state is prevented. Since a negative pressure state in the head chamber 64 is prevented, cavitation in the head chamber 64 is suppressed. Since cavitation is suppressed, malfunctions of the arm cylinder 6B are prevented.

[0080] [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.

[0081] In the first embodiment described above, the compensation flow rate is calculated based on the rate of change Va of the meter-in pressure p when the meter-in pressure p decreases. In the second embodiment, the supply flow rate Q in This section explains an example where the compensation flow rate is calculated based on the difference between the consumption flow rate and the AV flow rate.

[0082] Figure 12 is a functional block diagram showing the controller 7 according to the second embodiment. Similar to the first embodiment described above, the controller 7 includes a target operating speed calculation unit 71, a target pump flow rate calculation unit 72, a pressure reduction state determination unit 73, a corrected pump flow rate calculation unit 74, and a control unit 75. In the second embodiment, the controller 7 includes a supply flow rate calculation unit 76 and a consumption flow rate calculation unit 77.

[0083] The supply flow rate calculation unit 76 determines the supply flow rate Q, which indicates the flow rate of hydraulic fluid supplied to the work machine cylinder 6, based on the target operating speed of the work machine cylinder 6 calculated by the target operating speed calculation unit 71. in The following are calculated: the target operating speed of the work implement cylinder 6 and the supply flow rate Q flowing into the work implement cylinder 6. in This corresponds one-to-one. The supply flow rate calculation unit 76 calculates the supply flow rate Q that flows into the work machine cylinder 6 via the meter-in flow path 20, based on the target operating speed of the work machine cylinder 6. in Calculate the supply flow rate Q. in This may be a value proportional to the target operating speed. Target operating speed and supply flow rate Q inIf a third correlation data showing the relationship is predetermined, the supply flow rate calculation unit 76 inputs the target operating speed into the third correlation data, thereby calculating the supply flow rate Q in The supply flow rate calculation unit 76 determines the supply flow rate Q based on the amount of operation of the operating device 8. in You may calculate this.

[0084] The supply flow rate calculation unit 76 calculates the supply flow rate Q based on the capacity of the hydraulic pump 12 and the rotational speed of the hydraulic pump 12. in The capacity of the hydraulic pump 12 is detected, for example, by a swash plate sensor that detects the angle of the swash plate of the hydraulic pump 12. The rotational speed of the hydraulic pump 12 is detected, for example, by a rotational speed sensor that detects the rotational speed of the power source 11. The supply flow rate calculation unit 76 calculates the supply flow rate Q based on the estimated value of the opening area of ​​the meter-in valve 14 and the differential pressure across the meter-in valve 14. in You may calculate this.

[0085] The consumption flow rate calculation unit 77 calculates the consumption flow rate AV, which indicates the flow rate of hydraulic fluid consumed for the operation of the work machine cylinder 6. Based on the actual operating speed of the work machine cylinder 6 detected by the operating speed sensor 17 and the pressure-receiving area of ​​the work machine cylinder 6, the consumption flow rate calculation unit 77 calculates the consumption flow rate AV, which indicates the change in the volume of hydraulic fluid per unit time on the hydraulic fluid inlet side of the work machine cylinder 6.

[0086] The consumption flow rate calculation unit 77 calculates the consumption flow rate AV based on the pressure-receiving area A of the piston 62 and the movement speed V of the piston 62. The pressure-receiving area A is known data derived from the design data or specifications data of the work machine cylinder 6. The movement speed V of the piston 62 is the operating speed of the work machine cylinder 6 and is detected by the operating speed sensor 17. The consumption flow rate calculation unit 77 can calculate the consumption flow rate AV of the hydraulic fluid of the work machine cylinder 6 by multiplying the pressure-receiving area A, which is known data, by the movement speed V of the piston 62 detected by the operating speed sensor 17.

[0087] The pressure reduction state determination unit 73 determines the supply flow rate Q calculated by the supply flow rate calculation unit 76. inThe pressure reduction state determination unit 73 determines whether the pressure reduction state is less than the consumption flow rate AV calculated by the consumption flow rate calculation unit 77. in Based on the flow balance, which shows the difference between the current flow rate and the consumption flow rate AV, it is determined whether or not a pressure reduction condition occurs. The corrected pump flow rate calculation unit 74 calculates the compensation flow rate based on the flow balance.

[0088] Figure 13 is a flowchart showing the control method for the work machine 1 according to the second embodiment. The target operating speed calculation unit 71 calculates the target operating speed of the work machine cylinder 6 based on the amount of operation of the operating device 8 (step SC1).

[0089] The target pump flow rate calculation unit 72 calculates a target pump flow rate, which indicates the target value of the flow rate of the hydraulic fluid discharged from the hydraulic pump 12, based on the target operating speed of the work machine cylinder 6 calculated by the target operating speed calculation unit 71 (step SC2).

[0090] The supply flow rate calculation unit 76 determines the supply flow rate Q, which indicates the flow rate of hydraulic fluid supplied to the work machine cylinder 6, based on the target operating speed of the work machine cylinder 6 calculated by the target operating speed calculation unit 71. in Calculate (Step SC3).

[0091] The consumption flow rate calculation unit 77 calculates the consumption flow rate AV, which represents the change in the volume of hydraulic fluid per unit time in the chamber (head chamber 64 in this embodiment) into which the hydraulic fluid of the work machine cylinder 6 flows, based on the known data of the pressure-receiving area A and the movement speed V of the piston 62 detected by the operating speed sensor 17 (step SC4).

[0092] The pressure reduction state determination unit 73 determines the supply flow rate Q in Determine whether the pressure reduction is less than the consumption flow rate AV (step SC5).

[0093] In step SC5, if it is determined that the working machine cylinder 6 is in a pressure-reducing state (step SC5: Yes), the corrected pump flow rate calculation unit 74 calculates the supply flow rate Q inWhen the supply flow rate Q is smaller than the consumption flow rate AV, in Based on the difference ΔQ between the target pump flow rate and the consumption flow rate AV, the compensation flow rate is calculated. The compensation pump flow rate calculation unit 74 calculates the compensation flow rate by multiplying the difference ΔQ by the adjustment gain. The compensation pump flow rate calculation unit 74 calculates the compensation pump flow rate by adding the compensation flow rate to the target pump flow rate calculated in step SC2 (step SC6).

[0094] The adjustment gain may be a fixed value (constant value). The adjustment gain may also be a variable value. If the adjustment gain is a variable value, changing the adjustment gain will change the compensated flow rate.

[0095] If the adjustment gain is a variable value, the compensation pump flow rate calculation unit 74 may change the adjustment gain based on the amount manipulated by the operating device 8. The compensation pump flow rate calculation unit 74 may increase the adjustment gain as the amount manipulated by the operating device 8 increases. In other words, the compensation flow rate may increase as the amount manipulated by the operating device 8 increases.

[0096] If the adjustment gain is a variable value, the compensation pump flow rate calculation unit 74 may change the adjustment gain based on the operating speed of the work machine cylinder 6 (movement speed V of the piston 62) detected by the operating speed sensor 17. The compensation pump flow rate calculation unit 74 may increase the adjustment gain as the actual operating speed of the work machine cylinder 6 increases. In other words, the compensation flow rate may increase as the actual operating speed of the work machine cylinder 6 increases.

[0097] The control unit 75 controls the hydraulic pump 12 based on the corrected pump flow rate calculated in step SC6. The control unit 75 controls the hydraulic pump 12 so that the corrected pump flow rate of hydraulic fluid is discharged from the hydraulic pump 12. The control unit 75 controls the angle of the swash plate of the hydraulic pump 12 so that the corrected pump flow rate of hydraulic fluid is discharged from the hydraulic pump 12 (step SC7).

[0098] Furthermore, the control unit 75 controls the meter-in valve 14 based on the corrected pump flow rate. The control unit 75 controls the opening area of ​​the meter-in valve 14 in accordance with the corrected pump flow rate. The control unit 75 controls the meter-in valve 14 so that its opening area is larger than the opening area of ​​the meter-in valve 14 determined based on the target pump flow rate (step SC8).

[0099] In step SC5, if it is determined that the work machine cylinder 6 does not enter a pressure reduction state (step SC5: No), the control unit 75 controls the hydraulic pump 12 based on the target pump flow rate calculated in step SC2. The control unit 75 controls the hydraulic pump 12 so that the target pump flow rate of hydraulic fluid is discharged from the hydraulic pump 12. The control unit 75 controls the angle of the swash plate of the hydraulic pump 12 so that the target pump flow rate of hydraulic fluid is discharged from the hydraulic pump 12 (step SC9).

[0100] Furthermore, the control unit 75 controls the meter-in valve 14 based on the target pump flow rate. The control unit 75 controls the opening area of ​​the meter-in valve 14 in accordance with the target pump flow rate so that the hydraulic fluid at the target pump flow rate can pass through the meter-in valve 14 (step SC10).

[0101] As explained above, in the second embodiment as well, the supply flow rate Q in If it is determined that the pressure reduction is less than the consumption flow rate AV, the hydraulic pump 12 discharges a corrected flow rate of hydraulic fluid that is greater than the target flow rate. The discharge of the corrected flow rate of hydraulic fluid from the hydraulic pump 12 increases the supply flow rate Q of hydraulic fluid supplied from the meter-in passage 20 to the head chamber 64 of the arm cylinder 6B. in As this increases, a rapid pressure drop in the head chamber 64 is suppressed, and a negative pressure state is prevented. Since a negative pressure state in the head chamber 64 is prevented, cavitation in the head chamber 64 is suppressed. Since cavitation is suppressed, malfunctions of the arm cylinder 6B are prevented.

[0102] <Control when the operating speed sensor is malfunctioning> As described above, in the second embodiment, the compensation flow rate is calculated based on the consumption flow rate AV. The consumption flow rate AV is calculated based on the movement speed V detected by the operating speed sensor 17. The control method for the work machine 1 when the operating speed sensor 17 is malfunctioning will be described below.

[0103] Figure 14 is a flowchart showing the control method for the work machine 1 when the operating speed sensor 17 according to the second embodiment is malfunctioning. When the operating speed sensor 17 is malfunctioning, the correction pump flow rate calculation unit 74 cannot calculate the correction pump flow rate.

[0104] The corrected pump flow rate calculation unit 74 detects an abnormality in the operating speed sensor 17 (step SD1).

[0105] If the operating speed sensor 17 is malfunctioning, the detected data value from the operating speed sensor 17 may become excessively low or excessively high. The corrected pump flow rate calculation unit 74 can determine that the operating speed sensor 17 is malfunctioning if the detected data value from the operating speed sensor 17 is below a predetermined first threshold, or if the detected data value from the operating speed sensor 17 is above a predetermined second threshold. The second threshold is a value greater than the first threshold.

[0106] If the operating speed sensor 17 is abnormal, the corrected pump flow rate calculation unit 74 does not calculate the corrected pump flow rate. If the operating speed sensor 17 is abnormal, the corrected pump flow rate calculation unit 74 sets the compensation flow rate to zero. The control unit 75 controls the hydraulic pump 12 based on the target pump flow rate. That is, if the operating speed sensor 17 is abnormal, the control unit 75 controls the hydraulic pump 12 so that even if cavitation occurs in the work machine cylinder 6, or if cavitation occurs simultaneously with a malfunction of the work machine cylinder 6 caused by cavitation, the hydraulic pump 12 discharges hydraulic fluid at the target pump flow rate so that the work machine cylinder 6 can operate to the minimum extent in response to the operation signal of the operating device 8 (step SD2).

[0107] Furthermore, the control unit 75 controls the meter-in valve 14 based on the target pump flow rate. The control unit 75 controls the opening area of ​​the meter-in valve 14 in accordance with the target pump flow rate (step SD3).

[0108] <Other Embodiments> In the above-described embodiment, the control method for when the arm 4B is performing a dumping operation was explained, but the control methods for when the arm 4B is performing an excavation operation, when the boom 4A is performing an raising and lowering operation, and when the bucket 4C is performing an excavation operation and a dumping operation are the same. [Explanation of symbols]

[0109] 1...Work machine, 2...Traction unit, 2A...Track, 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, 61...Cylinder tube, 62...Piston, 63...Rod, 64...Head chamber, 65...Bottom chamber, 7...Controller, 8...Operating device, 9...Traction motor, 10...Control system, 11...Power source, 12...Hydraulic pump, 13...Tank, 14...Meter-in valve, 15...Meter-out valve, 16...Meter-in pressure Sensor, 17...Operating speed sensor, 18...Suction channel, 19...Pump channel, 20...Meter-in channel, 21...Meter-out channel, 22...Tank channel, 25...Computer, 25A...Processor, 25B...Main memory, 25C...Storage, 25D...Input / output interface, 25E...Communication interface, 25F...Computer program, 71...Target operating speed calculation unit, 72...Target pump flow rate calculation unit, 73...Pressure reduction state determination unit, 74...Corrected pump flow rate calculation unit, 75...Control unit, 76...Supply flow rate calculation unit, 77...Consumption flow rate calculation unit.

Claims

1. A hydraulic pump that discharges hydraulic fluid, A meter-in valve for adjusting the hydraulic fluid discharged from the hydraulic pump, A hydraulic actuator to which the hydraulic fluid adjusted by the meter-in valve is supplied via a meter-in passage, Equipped with a controller, The aforementioned controller, The supply flow rate, which indicates the flow rate of the hydraulic fluid supplied to the hydraulic actuator, is obtained. If it is determined that the pressure in the meter-in channel is in a pressure-reducing state, a compensation flow rate to be added to the supply flow rate is calculated to suppress the pressure drop in the meter-in channel. Based on the supply flow rate and the compensation flow rate, the opening area of ​​the meter-in valve and at least one of the hydraulic pump are controlled. Control system for industrial machinery.

2. The aforementioned controller, The target operating speed of the hydraulic actuator is obtained, Based on the target operating speed, the supply flow rate is calculated. A control system for a work machine according to claim 1.

3. The system includes a meter-in pressure sensor that detects the meter-in pressure, which indicates the pressure in the meter-in flow path. The aforementioned controller, Based on the meter-in pressure, it is determined whether or not the pressure decrease state occurs. Based on the meter-in pressure, the compensation flow rate is calculated. A control system for a work machine according to claim 1.

4. The aforementioned controller, Based on the rate of change over time of the meter-in pressure, it is determined whether or not the pressure decreases. A control system for a work machine according to claim 3.

5. The aforementioned controller, Based on the rate of change over time of the meter-in pressure, the compensation flow rate is calculated. A control system for a work machine according to claim 3.

6. The aforementioned controller, The compensation flow rate is calculated by multiplying the aforementioned rate of change over time by the adjustment gain. A control system for a work machine according to claim 5.

7. The aforementioned controller, If the meter-in pressure sensor is abnormal, the compensation flow rate is set to zero. A control system for a work machine according to claim 3.

8. The hydraulic actuator is equipped with an operating speed sensor for detecting the actual operating speed, The aforementioned controller, Based on the actual operating speed and the pressure-receiving area of ​​the hydraulic actuator, the consumption flow rate, which represents the change in the volume of hydraulic fluid per unit time on the hydraulic fluid inlet side of the hydraulic actuator, is calculated. Based on the flow balance showing the difference between the supply flow rate and the consumption flow rate, it is determined whether or not the pressure reduction state occurs. Based on the flow rate balance, the compensation flow rate is calculated. A control system for a work machine according to claim 1.

9. The aforementioned controller, The compensation flow rate is calculated based on the difference between the supply flow rate and the consumption flow rate when the supply flow rate is smaller than the consumption flow rate. A control system for a work machine according to claim 8.

10. The aforementioned controller, The difference between the supply flow rate and the consumption flow rate is multiplied by an adjustment gain to calculate the compensation flow rate. A control system for a work machine according to claim 9.

11. The aforementioned controller, If the operating speed sensor is abnormal, the compensation flow rate is set to zero. A control system for a work machine according to claim 8.

12. The aforementioned controller, Based on the control quantity indicating the value of the operation signal for operating the hydraulic actuator, the target operating speed of the hydraulic actuator is calculated. Based on the aforementioned manipulated amount, the adjustment gain is changed. A control system for a work machine according to claim 6 or claim 10.

13. The aforementioned controller, The larger the manipulated amount, the greater the adjustment gain. A control system for a work machine according to claim 12.

14. The hydraulic actuator is equipped with an operating speed sensor for detecting the actual operating speed, The aforementioned controller, Based on the actual operating speed, the adjustment gain is changed. A control system for a work machine according to claim 6 or claim 10.

15. The aforementioned controller, The higher the actual operating speed, the larger the adjustment gain. A control system for a work machine according to claim 14.

16. The system includes a meter-out valve that controls the flow rate of hydraulic fluid discharged from the hydraulic actuator to a tank, The aforementioned controller, Based on the target operating speed of the hydraulic actuator, the opening area of ​​the meter-out valve is controlled. A control system for a work machine according to claim 8.

17. The aforementioned work machine has a boom connected to the vehicle body and an arm connected to the boom, The hydraulic actuator is an arm cylinder that moves the arm. A control system for a work machine according to claim 1.

18. A hydraulic pump that discharges hydraulic fluid, A meter-in valve for adjusting the hydraulic fluid discharged from the hydraulic pump, A hydraulic actuator to which the hydraulic fluid adjusted by the meter-in valve is supplied via a meter-in passage, A control method for a work machine comprising a controller, The aforementioned controller, The supply flow rate, which indicates the flow rate of the hydraulic fluid supplied to the hydraulic actuator, is obtained. If it is determined that the pressure in the meter-in channel is in a pressure-reducing state, a compensation flow rate to be added to the supply flow rate is calculated to suppress the pressure drop in the meter-in channel. Based on the supply flow rate and the compensation flow rate, the opening area of ​​the meter-in valve and at least one of the hydraulic pump are controlled. A method for controlling industrial machinery.

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