Control device for work machinery and work machinery equipped therewith

Abstract

To provide a control device for a work machine capable of suppressing a decrease in work efficiency caused by an increase in the load on one actuator in work in which two actuators are operated simultaneously, and a work machine equipped with the same.SOLUTION: By using a target flow rate of hydraulic oil to a first actuator 11 according to a first operation and a target flow rate of hydraulic oil to a second actuator 12 according to a second operation, a controller 50 of a control device calculates a target value of an output-related value regarding an output of a pump 10, and performs ratio control when the target value exceeds an upper limit value. Ratio control is a control that adjusts the output-related value below the upper limit value by making a correction to reduce the target flow rate to a large load actuator, and increases the ratio of the target flow rate to a small load actuator to the target flow rate to the large load actuator compared to before modification when one of the first actuator 11 and the second actuator 12 is the large load actuator with a relatively large load and the other is the small load actuator with a relatively small load.SELECTED DRAWING: Figure 5

Description

[[Technical Field]]

[0001] The present disclosure relates to a control device for a work machine and a work machine including the same. [[Background Art]]

[0002] A work machine such as a hydraulic excavator includes a lower traveling body, an upper rotating body rotatably supported by the lower traveling body, and a work device supported by the upper rotating body, and performs various works such as excavation work. The work device includes a boom rotatably supported by the upper rotating body, an arm rotatably supported at a tip end of the boom, and a bucket rotatably supported at a tip end of the arm. The work machine includes a plurality of actuators for moving the work device. The plurality of actuators include a boom cylinder that rotates the boom, an arm cylinder that rotates the arm, and a bucket cylinder that rotates the bucket. Each of these actuators operates by being supplied with hydraulic oil discharged from a pump (for example, Patent Document 1).

[0003] In this work machine, for example, when lever operations are simultaneously input to two operation levers, a controller determines a target flow rate of hydraulic oil to be supplied to an actuator corresponding to each lever operation according to an operation amount of the lever operation, and determines a discharge amount of hydraulic oil from the pump such that the target flow rate of hydraulic oil is supplied to each of the two actuators. That is, the controller distributes the hydraulic oil from the pump to the two actuators at a ratio determined according to lever operation amounts of the two lever operations.

[0004] The pump is driven by a drive source such as an engine to discharge hydraulic oil. The output of the pump is proportional to the product of a pump pressure (discharge pressure of the pump) and the discharge amount of the pump. If the output of the pump exceeds an upper output limit value of the engine, engine stall may occur or the engine rotation speed may decrease. Therefore, the controller of the work machine performs PQ control, which is control for increasing or decreasing the discharge amount of the pump according to the pump pressure so that the output of the pump does not exceed the upper output limit value of the engine. [[Prior Art Documents]] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-230109 [Overview of the project] [Problems that the invention aims to solve]

[0006] Incidentally, in the operation of simultaneously operating two actuators by applying lever operation to two operating levers at the same time, if one of these is a high-load actuator with a relatively large load and the other is a low-load actuator with a relatively small load, the work efficiency may decrease for the following reasons. That is, when the load (operating pressure) of the high-load actuator increases, the pump pressure also increases, so the pump discharge volume is limited to a small value by PQ control. As a result, the operating speed of the high-load actuator decreases. In this case, the operator may apply an operation to the operating lever to activate the low-load actuator in order to reduce the load on the high-load actuator (hereinafter sometimes referred to as a load relief operation). However, in a situation where the pump discharge volume is limited to a small value due to the large load on the high-load actuator, not only the flow rate of hydraulic fluid supplied to the high-load actuator but also the flow rate of hydraulic fluid supplied to the low-load actuator decreases. In this case, even if the operator performs the load relief operation, the operation of the low-load actuator becomes slow, and it is necessary to keep the low-load actuator operating for a long time in order to reduce the load on the high-load actuator, and as a result, the work efficiency decreases.

[0007] The present disclosure aims to provide a control device for a work machine and a work machine equipped with the same, which can suppress the decrease in work efficiency caused by an increased load on one of the actuators during work in which two actuators are operated simultaneously. [Means for solving the problem]

[0008] The control device for the provided work machine comprises a pump that discharges hydraulic fluid, a first actuator that operates when supplied with the hydraulic fluid, a second actuator that operates when supplied with the hydraulic fluid, an operating device that provides a first operation and a second operation, and a controller that calculates a target value for output-related values ​​relating to the output of the pump using a target flow rate of the hydraulic fluid to the first actuator in accordance with the first operation and a target flow rate of the hydraulic fluid to the second actuator in accordance with the second operation, and performs ratio control when the target value exceeds an upper limit, wherein the ratio control is a control that, when one of the first actuator and the second actuator is a heavy-load actuator with a relatively large load and the other is a light-load actuator with a relatively small load, adjusts the output-related values ​​to be below the upper limit by making a correction to reduce the target flow rate to the heavy-load actuator, while increasing the ratio of the target flow rate to the light-load actuator to the target flow rate to the heavy-load actuator compared to before the correction.

[0009] In this control system, the controller performs the ratio control described above when the target value of the pump output-related value exceeds the upper limit, thereby allowing the low-load actuator to be operated preferentially. This suppresses the decrease in work efficiency caused by the increased load on one actuator when operating two actuators simultaneously. Specifically, it works as follows: In this ratio control, when the pump output-related value is brought below the upper limit, a modification is made to reduce the target flow rate to the high-load actuator so that the ratio of the target flow rate to the low-load actuator to the target flow rate to the high-load actuator (target flow rate to the low-load actuator / target flow rate to the high-load actuator) becomes larger than before the modification. This makes it possible to operate the low-load actuator preferentially over the high-load actuator, and suppresses the decrease in the operating speed of the low-load actuator, compared to a modification that reduces the target flow rate to the high-load actuator and the target flow rate to the low-load actuator while maintaining the ratio of target flow rates determined by the lever operation amount of the two levers. Therefore, when an operator performs a load relief operation, that is, an operation to activate a small-load actuator to reduce the load on a large-load actuator, the slow operation of the small-load actuator can be suppressed. As a result, the time required to reduce the load on the large-load actuator and resolve the slow operation of the large-load actuator can be shortened compared to conventional methods. Thus, this control device can suppress the decrease in work efficiency caused by the high load on the large-load actuator when operating two actuators simultaneously.

[0010] Preferably, the controller performs ratio control so that the output-related value is adjusted to the upper limit. In this configuration, the controller adjusts the actual pump output to the upper limit of the pump output that is permissible at that time, thereby ensuring a larger flow rate of hydraulic fluid supplied to the low-load actuator and more effectively suppressing the slowing down of the low-load actuator's operation. This makes it possible to more effectively suppress the decrease in work efficiency.

[0011] It is preferable that the controller performs the ratio control such that the amount by which the target flow rate to the heavy-load actuator is reduced is greater when the load on the heavy-load actuator is greater than when the load on the heavy-load actuator is small. In this configuration, the amount by which the target flow rate to the heavy-load actuator is reduced is determined according to the load on the heavy-load actuator, making it easier to ensure the flow rate of hydraulic fluid supplied to the light-load actuator. Specifically, it is as follows: As described above, the output of the pump is proportional to the product of the pump pressure and the pump discharge rate, and the pump pressure increases as the load on the heavy-load actuator increases. Therefore, in order to limit the pump output-related values ​​to below the upper limit, it is necessary to reduce the pump discharge rate as the load on the heavy-load actuator increases. Thus, in this configuration, the controller performs the ratio control such that the amount by which the target flow rate to the heavy-load actuator is reduced is greater when the load on the heavy-load actuator is large than when the load on the heavy-load actuator is small. As a result, even when the load on the heavy-load actuator increases and the pump discharge rate decreases, it becomes easier to limit the pump output-related values ​​to below the upper limit without increasing the amount by which the target flow rate to the light-load actuator is reduced. As a result, it becomes easier to ensure a sufficient flow rate of hydraulic fluid supplied to the low-load actuator, and the slow operation of the low-load actuator can be suppressed.

[0012] Preferably, the controller performs ratio control such that the target flow rate to the small load actuator is not reduced when the load of the small load actuator is within a predetermined range, and the target flow rate to the small load actuator is reduced in accordance with the load of the small load actuator when the load of the small load actuator is greater than the predetermined range. In this configuration, when the load of the small load actuator is relatively small and within a predetermined range, the target flow rate to the small load actuator is not reduced and is maintained at the target flow rate corresponding to the manipulated amount, thereby effectively suppressing a decrease in the operating speed of the small load actuator. On the other hand, when the load of the small load actuator becomes greater than the predetermined range, not only is the target flow rate to the large load actuator reduced, but the target flow rate to the small load actuator is also reduced in accordance with the load of the small load actuator, thereby reliably preventing the pump output-related values ​​from exceeding the upper limit.

[0013] The control device may further include a first flow regulator that adjusts the flow rate of the hydraulic fluid supplied to the first actuator to the target flow rate to the first actuator based on a command from the controller, and a second flow regulator that adjusts the flow rate of the hydraulic fluid supplied to the second actuator to the target flow rate to the second actuator based on a command from the controller.

[0014] Preferably, the low-load actuator is an actuator capable of operating in a manner that reduces the load on the high-load actuator.

[0015] The provided work machine is equipped with the control device described above. This work machine can suppress the decrease in work efficiency caused by the increased load on one of the actuators when operating two actuators simultaneously. [Effects of the Invention]

[0016] According to this disclosure, a control device for a work machine and a work machine equipped therewith are provided that can suppress a decrease in work efficiency caused by an increased load on one of the actuators during work in which two actuators are operated simultaneously. [Brief explanation of the drawing]

[0017] [Figure 1] This is a side view showing an example of a work machine equipped with a control device according to an embodiment of the present disclosure. [Figure 2] This figure shows the aforementioned control device. [Figure 3] This figure shows the positional relationship between the bucket and the soil during the excavation work performed by the aforementioned work machine. [Figure 4] This flowchart shows an example of calculation processing performed by the controller of the aforementioned control device. [Figure 5] A flowchart shows an example of the calculation process performed by the aforementioned controller. [Figure 6] This is a correspondence relationship used for ratio control by the aforementioned controller, showing the correspondence between the lever operation amount and the target flow rate (target speed). [Figure 7] This is a correspondence used for ratio control by the controller, and shows the correspondence between a target speed (target flow rate) and a valve opening degree. [Figure 8] This is a correspondence used for ratio control by the controller, and shows the correspondence between a load of an actuator and a control rate. MODE FOR CARRYING OUT THE INVENTION

[0018] Embodiments of the present disclosure will be described with reference to the drawings. FIG. 1 is a side view showing a work machine 100 according to the present embodiment. This work machine 100 is a hydraulic excavator. As shown in FIG. 1, the work machine 100 includes a lower traveling structure 1 capable of traveling on the ground G, an upper revolving structure 2 supported by the lower traveling structure 1 so as to be revolvable about a vertically oriented revolving central axis Z, and a working device 3 supported by the upper revolving structure 2. "Front" and "rear" in the drawings are directions based on the orientation of the upper revolving structure 2.

[0019] The lower traveling structure 1 includes a pair of crawler traveling devices and a lower frame connecting these traveling devices. The upper revolving structure 2 includes an upper frame rotatably supported by the lower frame, a cabin supported at a front portion of the upper frame, and a counterweight supported at a rear portion of the upper frame. In the present embodiment, the working device 3 includes a boom 4, an arm 5, and a distal attachment, and the distal attachment is a bucket 6. However, the distal attachment may be another distal attachment such as a fork, a grapple, a breaker, or a crusher.

[0020] The boom 4 is rotatably supported on the upper frame of the upper slewing body 2. The boom 4 has a base end, which is attached to the upper frame so as to be rotatable in the boom raising direction and boom lowering direction about a horizontal axis, and a boom tip end, which is the tip end on the opposite side. The boom raising direction is the direction in which the boom tip end moves away from the ground G, and the boom lowering direction is the opposite direction to the boom raising direction, which is the direction in which the boom tip end moves towards the ground G.

[0021] The arm 5 is rotatably supported by the boom 4. The arm 5 has an arm base end, which is attached to the tip of the boom so as to be rotatable in the arm pulling direction and the arm pushing direction about a horizontal axis, and an arm tip end, which is the tip end on the opposite side. The arm pulling direction is the direction in which the arm tip end approaches the lower traveling body 1, and the arm pushing direction is the opposite direction to the arm pulling direction, and is the direction in which the arm tip end moves away from the lower traveling body 1.

[0022] The bucket 6 is rotatably supported by the arm 5. The bucket 6 has a bucket base end 61, which is attached to the end of the arm so as to be rotatable in the bucket pulling direction and the bucket pushing direction about a horizontal axis, and a bucket tip end 62, which is the end on the opposite side. The bucket pulling direction is the direction in which the bucket tip end approaches the lower traveling body 1 when the bucket 6 performs an excavation operation, as shown in Figure 1, for example, and the bucket pushing direction is the opposite direction of rotation to the bucket pulling direction, and is the direction in which the bucket tip end moves away from the lower traveling body 1.

[0023] The bucket 6 has a bucket body 6A including a bucket base end 61, and a plurality of teeth 6B (a plurality of claws). The bucket body 6A constitutes the container portion of the bucket 6 and has a storage space that is capable of holding soil and sand. The bucket body 6A has an inner surface that defines the storage space. The plurality of teeth 6B constitute the bucket tip 62 of the bucket 6 and are fixed to the tip of the bucket body 6A so as to be aligned along the width direction of the bucket body 6A. The width direction of the bucket body 6A is parallel to the horizontal axis and is the left-right direction. Each of the plurality of teeth 6B protrudes from the tip of the bucket body 6A in a direction perpendicular to the width direction.

[0024] The work machine 100 can perform various tasks at the work site. These various tasks include, for example, excavation work, soil holding and rotating work, soil removal work, and return rotation work. Excavation work is the work of excavating the target to be excavated, such as the ground G or embankment, by moving the bucket 6 along the target to be excavated, and holding the soil in the bucket 6. Soil holding and rotating work is the work of moving the bucket 6, which holds the soil, to a point directly above the destination for soil removal, such as the bed of a dump truck, by rotating the upper rotating body 2 while the bucket 6 rises. Soil holding and rotating work is sometimes called lifting and rotating work. Soil removal work is the work of releasing the soil held in the bucket 6, which has been moved to directly above the bed of the truck, and letting it fall onto the truck bed, and then loading the soil onto the truck bed. Return rotation work is the work of moving the bucket 6 to the location of the excavation target by lowering the bucket 6 while rotating the upper rotating body 2 after the soil removal work.

[0025] Figure 2 shows a control device 101 according to this embodiment. The work machine 100 includes the control device 101. As shown in Figure 2, the control device 101 includes a pump 10, a plurality of actuators, an operating device 20, a plurality of flow regulators, a plurality of detectors, and a controller 50.

[0026] Pump 10 is a hydraulic pump that discharges hydraulic fluid when driven by a power source such as an engine (not shown in the figure). Pump 10 is a variable displacement hydraulic pump that can change its pump capacity according to a pump capacity command (tilt capacity command in Figure 2) input from the controller 50. In addition to pump 10, the control device 101 may also be equipped with another hydraulic pump.

[0027] As shown in Figures 1 and 2, the multiple actuators include a boom cylinder 11, an arm cylinder 12, a bucket cylinder 13, and a slewing motor 14. In this embodiment, each of the multiple actuators is a hydraulic actuator that operates by hydraulic pressure. That is, the boom cylinder 11, arm cylinder 12, and bucket cylinder 13 are hydraulic cylinders that extend and retract in response to the supply of hydraulic fluid discharged by the pump 10, and the slewing motor 14 is a hydraulic motor that operates in response to the supply of hydraulic fluid discharged by the pump 10. Note that in Figure 2, only the boom cylinder 11 and arm cylinder 12 are shown among the multiple actuators, and the bucket cylinder 13 and slewing motor 14 are not shown. The boom cylinder 11 is an example of a first actuator in this disclosure, and the arm cylinder 12 is an example of a second actuator in this disclosure.

[0028] The boom cylinder 11 rotates the boom 4 as the boom cylinder 11 extends and retracts. The base end of the boom cylinder 11 is rotatably attached to the upper slewing body 2, and the tip end of the boom cylinder 11 is rotatably attached to the boom 4. When the boom cylinder 11 extends, the boom 4 rotates in the boom-up direction, and when the boom cylinder 11 retracts, the boom 4 rotates in the boom-down direction.

[0029] The arm cylinder 12 rotates the arm 5 as the arm cylinder 12 extends and retracts. The base end of the arm cylinder 12 is rotatably attached to the boom 4, and the tip end of the arm cylinder 12 is rotatably attached to the arm 5. When the arm cylinder 12 extends, the arm 5 rotates in the arm-pulling direction, and when the arm cylinder 12 retracts, the arm 5 rotates in the arm-pushing direction.

[0030] The bucket cylinder 13 rotates the bucket 6 as it extends and retracts. The base end of the bucket cylinder 13 is rotatably attached to the arm 5, and the tip of the bucket cylinder 13 is rotatably attached to the bucket 6. When the bucket cylinder 13 extends, the bucket 6 rotates in the bucket-pulling direction, and when the bucket cylinder 13 retracts, the bucket 6 rotates in the bucket-pushing direction.

[0031] The slewing motor 14 rotates the upper slewing body 2 relative to the lower traveling body 1. The slewing motor 14 is connected to the upper slewing body 2 via a reduction gear (not shown). The slewing motor 14 rotates in a direction corresponding to the direction of hydraulic fluid supply, thereby rotating the upper slewing body 2 in a leftward or rightward direction.

[0032] The operating device 20 receives an operation from an operator to operate the work machine 100 and inputs an operation signal (lever command in Figure 2) corresponding to that operation to the controller 50. In this embodiment, the operating device 20 includes a boom operator 21, an arm operator 22, a bucket operator, and a slewing operator. In Figure 2, only the boom operator 21 and the arm operator 22 are shown, and the bucket operator and slewing operator are not shown.

[0033] The boom operator 21 includes a boom operation lever 21A to which the operator applies boom operation, and an output unit 21B that outputs a boom operation signal corresponding to the boom operation to the controller 50. The boom operation is either a boom raising operation or a boom lowering operation. A boom raising operation is an operation performed by the operator to move the boom 4 in the boom raising direction. A boom lowering operation is an operation performed by the operator to move the boom 4 in the boom lowering direction. When a boom raising operation is applied to the boom operation lever 21A, the output unit 21B inputs a boom operation signal (boom raising operation signal) corresponding to the boom raising operation to the controller 50. This boom raising operation signal includes information regarding the amount of the boom raising operation. When a boom lowering operation is applied to the boom operation lever 21A, the output unit 21B inputs a boom operation signal (boom lowering operation signal) corresponding to the boom lowering operation to the controller 50. This boom lowering operation signal includes information regarding the amount of the boom lowering operation.

[0034] The arm operator 22 includes an arm operation lever 22A to which an arm operation is input by an operator, and an output unit 22B that outputs an arm operation signal corresponding to the arm operation to the controller 50. The arm operation is either an arm pull operation or an arm push operation. An arm pull operation is an operation by an operator to move the arm 5 in the arm pull direction. An arm push operation is an operation by an operator to move the arm 5 in the arm push direction. When an arm pull operation is input to the arm operation lever 22A, the output unit 22B inputs an arm operation signal (arm pull operation signal) corresponding to the arm pull operation to the controller 50. This arm pull operation signal includes information about the amount of the arm pull operation. When an arm push operation is input to the arm operation lever 22A, the output unit 21B inputs an arm operation signal (arm push operation signal) corresponding to the arm push operation to the controller 50. This arm push operation signal includes information about the amount of the arm push operation.

[0035] Similarly, the bucket operator includes a bucket operation lever to which the operator controls the bucket, and an output device that outputs a bucket operation signal corresponding to the bucket operation to the controller 50. The bucket operation is either a bucket pulling operation or a bucket pushing operation. The slewing operator includes a slewing operation lever to which the operator controls the slewing operation, and an output device that outputs a slewing operation signal corresponding to the slewing operation to the controller 50. The slewing operation is either a right slewing operation or a left slewing operation.

[0036] The lever structure may be such that a single operating lever combines the functions of multiple operating levers. For example, a right-side operating lever located to the front right of the operator's seat may function as a boom operating lever 21A when operated in the forward / backward direction and as a bucket operating lever when operated in the left / right direction. Similarly, a left-side operating lever located to the front left of the operator's seat may function as an arm operating lever 22A when operated in the forward / backward direction and as a slewing operating lever when operated in the left / right direction.

[0037] Each of the multiple flow regulators adjusts the flow rate and direction of the hydraulic fluid supplied to the actuator corresponding to the flow regulator, based on control commands input from the controller 50. The multiple flow regulators include a boom flow regulator 31, an arm flow regulator 32, a bucket flow regulator, and a slewing flow regulator. In Figure 2, only the boom flow regulator 31 and the arm flow regulator 32 are shown, while the bucket flow regulator and slewing flow regulator are omitted.

[0038] The boom flow regulator 31 adjusts the flow rate and direction of the hydraulic fluid supplied to the boom cylinder 11 based on a boom control command (opening command in Figure 2) input from the controller 50. The boom control command is either a boom raising control command or a boom lowering control command. The boom flow regulator 31 is an example of a first flow regulator in this disclosure.

[0039] The arm flow regulator 32 adjusts the flow rate and direction of the hydraulic fluid supplied to the arm cylinder 12 based on arm control commands (opening commands in Figure 2) input from the controller 50. The arm control commands are either arm pull control commands or arm push control commands. The arm flow regulator 32 is an example of a second flow regulator in this disclosure.

[0040] The bucket flow regulator adjusts the flow rate and direction of the hydraulic fluid supplied to the bucket cylinder 13 based on bucket control commands input from the controller 50. The bucket control command is either a bucket pull control command or a bucket push control command.

[0041] The swivel flow regulator adjusts the flow rate and direction of the hydraulic fluid supplied to the swivel motor 14 based on the swivel control command input from the controller 50. The swivel control command is either a right swivel control command or a left swivel control command.

[0042] Each of the multiple flow regulators only needs to have the function of adjusting the direction and flow rate of the hydraulic fluid supplied to the actuator corresponding to the flow regulator, based on control commands input from the controller 50, and the specific configuration is not particularly limited. Therefore, each of the multiple flow regulators can employ various configurations capable of realizing the above function. For example, each of the multiple flow regulators may include a control valve and an electromagnetic proportional valve. Specifically, this is as follows.

[0043] The boom flow regulator 31 may include a boom control valve 31A and a pair of solenoid proportional valves 31B. The boom control valve 31A is interposed between the pump 10 and the boom cylinder 11. The boom control valve 31A has a pair of pilot ports. The pair of pilot ports includes a boom-raising pilot port and a boom-down pilot port. The pair of solenoid proportional valves 31B includes a boom-raising solenoid proportional valve 31B and a boom-down solenoid proportional valve 31B. The boom-raising solenoid proportional valve 31B is interposed between a pilot pump (not shown) and the boom-raising pilot port of the boom control valve 31A. The boom-down solenoid proportional valve 31B is interposed between the pilot pump and the boom-down pilot port of the boom control valve 31A.

[0044] When the controller 50 inputs a boom-raising control command to the boom-raising electromagnetic proportional valve 31B, the boom-raising electromagnetic proportional valve 31B outputs a secondary pressure obtained by reducing the hydraulic pressure of the pilot pump to a size corresponding to the boom-raising control command. When the output secondary pressure (pilot pressure) is input to the boom-raising pilot port of the boom control valve 31A, the spool of the boom control valve 31A is displaced according to the magnitude of the pilot pressure, and the size of the opening of the oil passage in the boom control valve 31A (valve opening) is adjusted. As a result, hydraulic fluid at a flow rate corresponding to the boom-raising control command is supplied to the head side chamber of the boom cylinder 11, and the hydraulic fluid in the rod side chamber of the boom cylinder 11 is discharged, causing the boom cylinder 11 to extend and the boom 4 to rotate in the boom-raising direction.

[0045] When the controller 50 inputs a boom-down control command to the boom-down electromagnetic proportional valve 31B, the boom-down electromagnetic proportional valve 31B outputs a secondary pressure obtained by reducing the hydraulic pressure of the pilot pump to a size corresponding to the boom-down control command. When the output secondary pressure (pilot pressure) is input to the boom-down pilot port of the boom control valve 31A, the spool of the boom control valve 31A is displaced according to the magnitude of the pilot pressure, and the size of the opening of the oil passage in the boom control valve 31A (valve opening) is adjusted. As a result, hydraulic fluid at a flow rate corresponding to the boom-down control command is supplied to the rod-side chamber of the boom cylinder 11, and the hydraulic fluid in the head-side chamber of the boom cylinder 11 is discharged, causing the boom cylinder 11 to contract and the boom 4 to rotate in the boom-down direction.

[0046] Similarly, the arm flow regulator 32 may include an arm control valve 32A and a pair of solenoid proportional valves 32B. The arm control valve 32A is interposed between the pump 10 and the arm cylinder 12. The arm control valve 32A has a pair of pilot ports. The pair of pilot ports includes an arm pull pilot port and an arm push pilot port. The pair of solenoid proportional valves 32B includes an arm pull solenoid proportional valve 32B and an arm push solenoid proportional valve 32B. The arm pull solenoid proportional valve 32B is interposed between the pilot pump and the arm pull pilot port of the arm control valve 32A. The arm push solenoid proportional valve 32B is interposed between the pilot pump and the arm push pilot port of the arm control valve 32A.

[0047] When the controller 50 inputs an arm-pull control command to the arm-pull electromagnetic proportional valve 32B, the arm-pull electromagnetic proportional valve 32B outputs a secondary pressure obtained by reducing the hydraulic pressure of the pilot pump to a size corresponding to the arm-pull control command. When the output secondary pressure (pilot pressure) is input to the arm-pull pilot port of the arm control valve 32A, the spool of the arm control valve 32A is displaced according to the magnitude of the pilot pressure, and the size of the opening of the oil passage in the arm control valve 32A (valve opening) is adjusted. As a result, hydraulic fluid at a flow rate corresponding to the arm-pull control command is supplied to the head side chamber of the arm cylinder 12, and the hydraulic fluid in the rod side chamber of the arm cylinder 12 is discharged, causing the arm cylinder 12 to extend and the arm 5 to rotate in the arm-pull direction.

[0048] When the controller 50 inputs an arm-pushing control command to the arm-pushing solenoid proportional valve 32B, the arm-pushing solenoid proportional valve 32B outputs a secondary pressure obtained by reducing the hydraulic pressure of the pilot pump to a size corresponding to the arm-pushing control command. When the output secondary pressure (pilot pressure) is input to the arm-pushing pilot port of the arm-control valve 32A, the spool of the arm-control valve 32A is displaced according to the magnitude of the pilot pressure, and the size of the opening of the oil passage in the arm-control valve 32A (valve opening) is adjusted. As a result, hydraulic fluid at a flow rate corresponding to the arm-pushing control command is supplied to the rod-side chamber of the arm cylinder 12, and the hydraulic fluid in the head-side chamber of the arm cylinder 12 is discharged, causing the arm cylinder 12 to contract and the arm 5 to rotate in the arm-pushing direction.

[0049] Similarly, the bucket flow regulator may include a bucket control valve and a pair of solenoid proportional valves. The bucket control valve is interposed between the pump 10 and the bucket cylinder 13. The slewing flow regulator may include a slewing control valve and a pair of solenoid proportional valves. The slewing control valve is interposed between the pump 10 and the slewing motor 14. The basic configuration and function of the bucket flow regulator and the slewing flow regulator are the same as those of the boom flow regulator 31 described above. Therefore, a detailed explanation of these is omitted.

[0050] The multiple detectors include a pump pressure sensor 41 that detects the pump pressure, which is the discharge pressure of the pump 10; a boom pressure sensor 42 that detects the meter-in pressure of the boom cylinder 11; and an arm pressure sensor 43 that detects the meter-in pressure of the arm cylinder 12. The multiple detectors may further include a bucket pressure sensor that detects the meter-in pressure of the bucket cylinder 13, and may further include a slewing pressure sensor that detects the meter-in pressure of the slewing motor 14. Each of the multiple detectors inputs information about the detection result to the controller 50.

[0051] The pump pressure sensor 41 is positioned to detect the pump pressure, the boom pressure sensor 42 is positioned to detect the meter-in pressure of the boom cylinder 11, and the arm pressure sensor 43 is positioned to detect the meter-in pressure of the arm cylinder 12. In the specific example shown in Figure 2, the pump pressure sensor 41 is positioned upstream of the multiple flow regulators in the line through which the hydraulic fluid is discharged from the pump 10, the boom pressure sensor 42 is positioned in the line connecting the boom flow regulator 31 and the boom cylinder 11, and the arm pressure sensor 43 is positioned in the line connecting the arm flow regulator 32 and the arm cylinder 12.

[0052] The controller 50 includes, for example, a computer that includes an arithmetic processing unit and memory. The controller 50 controls the operation of the work machine 100.

[0053] The controller 50 calculates target values ​​for output-related values ​​related to the output of the pump 10 using the pump pressure, the boom target flow rate which is the target flow rate of hydraulic fluid to the boom cylinder 11 determined according to the amount of boom operation, and the arm target flow rate which is the target flow rate of hydraulic fluid to the arm cylinder 12 determined according to the amount of arm operation. If these target values ​​exceed the upper limit, the controller performs ratio control as described later. Note that boom operation is an example of the first operation in this disclosure, and boom cylinder 11 is an example of the first actuator in this disclosure. Arm operation is an example of the second operation in this disclosure, and arm cylinder 12 is an example of the second actuator in this disclosure. Furthermore, boom cylinder 11 is an example of a low-load actuator, and arm cylinder 12 is an example of a high-load actuator.

[0054] The ratio control described above is a control that, when one of the boom cylinder 11 and the arm cylinder 12 is a high-load actuator with a relatively large load and the other is a low-load actuator with a relatively small load, adjusts the output-related values ​​to be below the upper limit by making a modification to reduce the target flow rate to the high-load actuator, thereby increasing the ratio of the target flow rate to the low-load actuator to the target flow rate to the high-load actuator compared to before the modification.

[0055] The advantages of this ratio control will be explained with reference to the specific examples shown in Figures 1 and 3. Figure 1 shows the state in which the work machine 100 is performing excavation work. Figure 3 shows the positional relationship between the bucket 6 and the soil during excavation work.

[0056] During excavation, the bucket 6 is displaced in the following order, as shown in Figure 1, for example: starting position P1, the position at the start of the excavation; mid-stage position P2, the position in the middle of the excavation; and final position P3, the position at the end of the excavation. In this excavation, the operator displaces the bucket 6 in the following order by applying arm pulling operation to the arm operation lever 22A and boom operation to the boom operation lever 21A. In this excavation, the boom operation applied to the boom operation lever 21A may be either a boom lowering operation or a boom raising operation. That is, the boom lowering operation and boom raising operation are appropriately selected by the operator according to the stage of the excavation to ensure that the bucket 6 is at a height suitable for excavating soil. Note that during the excavation, bucket operation may also be applied to the bucket operation lever.

[0057] When excavation work is being carried out, of the boom cylinder 11 and arm cylinder 12, the arm cylinder 12 corresponds to a heavy load actuator with a relatively large load, while the boom cylinder 11 corresponds to a light load actuator with a relatively small load.

[0058] In this excavation operation, for example, as shown in the left diagram of Figure 3, if the bucket 6 penetrates too deep into the ground, the resistance when the arm 5 performs the arm-pulling operation in the direction indicated by arrow D1 becomes very large, and the operating pressure (load) when extending the arm cylinder 12 becomes very high. As the pump pressure increases along with the operating pressure of the arm cylinder 12, the discharge rate of the pump 10 is limited so that the output of the pump 10 does not exceed the upper limit of the output. Specifically, the controller 50 inputs a pump capacity command to the regulator of the pump 10 to limit the capacity of the pump 10 so that the output of the pump 10, which is proportional to the product of the discharge pressure (pump pressure) and the discharge rate of the pump 10, does not exceed the upper limit of the output. This prevents the output of the pump 10 from exceeding the upper limit of the output, but since the discharge rate of the pump 10 is limited to a small value, the speed of the arm-pulling operation decreases, and the operation of the boom 4 also decreases. Therefore, even if the operator applies the maximum arm-pulling force to the arm operating lever 22A, it takes a very long time for the arm cylinder 12 to extend, and the arm-pulling operation hardly progresses.

[0059] In the situation described above, the operator performs the following load relief operation to reduce the resistance to the arm pulling motion and the operating pressure (load) when extending the arm cylinder 12. Specifically, the load relief operation in this embodiment is a boom-raising operation applied to the boom operation lever 21A so that the bucket 6 rises slightly in the direction of arrow D2 from the position shown in the left diagram of Figure 3 to the position shown in the center diagram of Figure 3. When this load relief operation (boom-raising operation) is applied to the boom operation lever 21A, the boom 4 rotates in the boom-raising direction, reducing the depth to which the bucket 6 penetrates the ground. As a result, the resistance to the arm pulling motion is reduced, and the operating pressure (load) when extending the arm cylinder 12 is also reduced, so the pump pressure decreases, and it becomes unnecessary to limit the discharge amount of the pump 10 to a small value. As a result, a decrease in the speed of the arm pulling motion can be avoided. In this case, the boom cylinder 11 (an example of a low-load actuator) is an actuator that can operate to reduce the load on the arm cylinder 12 (an example of a high-load actuator).

[0060] However, as mentioned above, when the discharge rate of pump 10 is limited, not only does the speed of the arm pulling operation decrease significantly, but the speed of the boom raising operation also decreases significantly. Therefore, even if the operator applies a boom raising operation as a load relief operation to the boom operation lever 21A, the speed of the boom raising operation becomes very slow, and it takes a very long time for the bucket 6 to rise from the position shown in the left diagram of Figure 3 to the position shown in the center diagram of Figure 3.

[0061] Therefore, the controller 50 of the control device 101 according to this embodiment prioritizes the operation of the boom cylinder 11 by performing the ratio control described above in the above-mentioned situation, thereby suppressing the decrease in work efficiency caused by the increased operating pressure (load) of the arm cylinder 12 during excavation work.

[0062] In other words, in this ratio control, when the output-related value of the pump 10 is reduced to below the upper limit, the correction is not made to reduce the arm target flow rate and boom target flow rate while maintaining the ratio of the target flow rate determined according to the amount of boom operation and the amount of arm pulling operation, but rather the arm target flow rate is reduced so that the ratio of the boom target flow rate to the arm target flow rate (boom target flow rate / arm target flow rate) becomes larger than before the correction. This makes it possible to operate the boom cylinder 11 preferentially over the arm cylinder 12, and makes it possible to suppress the decrease in the operating speed of the boom cylinder 11. Therefore, when the operator applies a load relief operation to reduce the operating pressure (load) of the arm cylinder 12, i.e., a boom raising operation, to the boom operation lever 21A, it is possible to suppress the slowing down of the operation of the boom cylinder 11. As a result, the time required to reduce the operating pressure (load) of the arm cylinder 12 and resolve the slowing down of the arm cylinder 12, specifically the time required for the bucket 6 to rise from the position shown in the left diagram of Figure 3 to the position shown in the center diagram of Figure 3, can be shortened compared to the conventional method. As a result, the resistance when the arm 5 performs an arm-pulling motion in the direction indicated by arrow D1 in the right-hand diagram of Figure 3 decreases in a relatively short time. Therefore, this control device 101 can suppress the decrease in work efficiency caused by the increased operating pressure (load) of the arm cylinder 12 during excavation work in which the arm cylinder 12 and boom cylinder 11 are operated simultaneously.

[0063] Below, an example of calculation processing by the controller 50 will be explained with reference to the flowcharts shown in Figures 4 and 5.

[0064] When excavation work begins at the work site, the controller 50 performs the processing from step S11 onwards as shown in Figures 4 and 5. The controller 50 can determine that excavation work has begun, for example, as follows: For example, if the operator makes a predetermined start input for the start of excavation work to an input device (not shown), this input device inputs a signal corresponding to this start input to the controller 50, and the controller 50 can determine that excavation work has begun based on the signal input from the input device. Also, if the control device 101 of the work machine 100 is equipped with a detector that detects information for determining the work to be performed by the work machine 100, the controller 50 can determine that excavation work has begun using the detection signal input from this detector. This detector may be, for example, a posture detector that detects the posture of the work device 3, including the posture of the boom 4 and the posture of the arm 5, or an image detector that detects an image of the work site including an image of the work device 3.

[0065] In step S11, the controller 50 obtains information (lever operation information) from the operating device 20 regarding the operation that the operator gives to one or more operating levers of the operating device 20. In an excavation operation as shown in Figure 1, the operator gives an arm pull operation to the arm operating lever 22A and a boom operation (boom raise operation or boom lower operation) to the boom operating lever 21A so that the arm 5 performs an arm pull operation and the boom 4 performs a boom raise operation or boom lower operation. Therefore, in an excavation operation as shown in Figure 1, the controller 50 receives an arm pull operation signal from the arm operating device 22 of the operating device 20 and a boom operation signal (boom raise operation signal or boom lower operation signal) from the boom operating device 21 of the operating device 20. In addition, when a bucket operation is given to the bucket operating lever during the excavation operation, the controller 50 receives a bucket operation signal from the bucket operating device of the operating device 20.

[0066] In step S12, the controller 50 calculates the target flow rate. Figure 6 shows the correspondence (map) between the lever operation amount and the target flow rate (target speed). The controller 50 can calculate the target flow rate using, for example, a pre-set correspondence as shown in Figure 6. The flow rate of hydraulic fluid supplied to actuators such as the boom cylinder 11 and arm cylinder 12 correlates with the operating speed of the actuators. Therefore, in step S12, the controller 50 may calculate the target flow rate to the actuators, or it may calculate the target operating speed of the actuators. The controller 50 can convert the target speed to a target flow rate using a pre-stored relational expression. The controller 50 can also convert the target speed to a target flow rate using a pre-stored relational expression.

[0067] Specifically, for example, the controller 50 stores in advance a map for the boom (for example, a map like the one shown in Figure 6) that defines the correspondence between the amount of boom operation (lever operation) and the target boom flow rate. The controller 50 also stores in advance a map for the arm (for example, a map like the one shown in Figure 6) that defines the correspondence between the amount of arm operation (lever operation) and the target arm flow rate. The target boom flow rate is the target flow rate of hydraulic fluid to the boom cylinder 11, which is determined according to the amount of boom operation, and the target arm flow rate is the target flow rate of hydraulic fluid to the arm cylinder 12, which is determined according to the amount of arm pulling operation. In excavation work, when an arm pulling operation is applied to the arm operation lever 22A and a boom operation is applied to the boom operation lever 21A, the controller 50 calculates the target boom flow rate (Qtgt1) using the boom operation signal input from the boom operator 21 and the boom map, and calculates the target arm flow rate (Qtgt2) using the arm pulling operation signal input from the arm operator 22 and the arm map.

[0068] In step S13, the controller 50 calculates the target discharge rate (Qpump) of the pump 10. If the operating device 20 is only provided with arm pulling operation and boom operation, the target discharge rate (Qpump) is the sum of the boom target flow rate (Qtgt1) and the arm target flow rate (Qtgt2) (Qpump = Qtgt1 + Qtgt2). If the operating device 20 is provided with arm pulling operation, boom operation and one or more other operations (e.g., bucket operation), the target discharge rate (Qpump) is the sum of the boom target flow rate (Qtgt1), the arm target flow rate (Qtgt2), and other target flow rates corresponding to the other operations.

[0069] In step S14, the controller 50 determines whether the target discharge rate (Qpump) is less than or equal to the maximum dischargeable flow rate (Qspec). The maximum dischargeable flow rate (Qspec) is the maximum flow rate that the pump 10 can discharge. Specifically, for example, if the drive source for driving the pump 10 is an engine, the maximum dischargeable flow rate (Qspec) is the maximum flow rate that the pump 10 can discharge at the engine speed at that time.

[0070] If the target discharge rate (Qpump) exceeds the maximum dischargeable flow rate (Qspec) (NO in step S14), in step S15, the controller 50 corrects the multiple target flow rates included in the target discharge rate (Qpump) so that the target discharge rate (Qpump) does not exceed the maximum dischargeable flow rate (Qspec). Specifically, the controller 50 corrects the multiple target flow rates, including the boom target flow rate (Qtgt1) and the arm target flow rate (Qtgt2), using the following equations (1) and (2) so that the target discharge rate (Qpump) becomes equal to the maximum dischargeable flow rate (Qspec).

[0071] Qtgt1'=Qspec×Qtgt1 / Qpump ···(1) Qtgt2'=Qspec×Qtgt2 / Qpump ···(2) In equation (1) above, "Qtgt1'" is the corrected target flow rate of the boom, and in equation (2) above, "Qtgt2'" is the corrected target flow rate of the arm.

[0072] The ratio of the uncorrected arm target flow rate to the uncorrected boom target flow rate (Qtgt1 / Qtgt2) is the same as the ratio of the corrected arm target flow rate to the corrected boom target flow rate (Qtgt1' / Qtgt2'). When the boom target flow rate (Qtgt1) and arm target flow rate (Qtgt2) are corrected using the above equations (1) and (2), the target discharge rate (Qpump) is the sum of the corrected boom target flow rate (Qtgt1') and the corrected arm target flow rate (Qtgt2') (Qpump = Qtgt1' + Qtgt2'). If the target discharge rate (Qpump) includes the other target flow rates, the corrected other target flow rates are calculated in the same way as the boom target flow rate (Qtgt1).

[0073] If the target discharge rate (Qpump) is less than or equal to the maximum dischargeable flow rate (Qspec) (YES in step S14), the controller 50 performs the process in step S16.

[0074] In step S16, the controller 50 obtains the pump pressure (Ppump) from the pump pressure sensor 41.

[0075] In step S17, the controller 50 acquires the meter-in pressure (M / I pressure) of the actuator. Specifically, the controller 50 acquires the meter-in pressure (Pmi1) of the boom cylinder 11 from the boom pressure sensor 42 and the meter-in pressure (Pmi2) of the arm cylinder 12 from the arm pressure sensor 43.

[0076] In step S18, the controller 50 calculates the target output (Lpump) of the pump 10 using, for example, the following equation (3).

[0077] Lpump=Ppump×Qpump / 60 (3) In equation (3) above, "Ppump" is the pump pressure, and "Qpump" is the target discharge volume of pump 10.

[0078] In step S19, the controller 50 calculates the target output of the actuator. Specifically, the controller 50 calculates the target output (Ltgt1) of the boom cylinder 11 using, for example, equation (4), and calculates the target output (Ltgt2) of the arm cylinder 12 using equation (5).

[0079] Ltgt1=Pmi1×Qtgt1 / 60 (4) Ltgt2=Pmi2×Qtgt2 / 60 ···(5) In equation (4) above, "Pmi1" is the meter-in pressure of the boom cylinder 11, and "Qtgt1" is the boom target flow rate. In equation (5) above, "Pmi2" is the meter-in pressure of the arm cylinder 12, and "Qtgt2" is the arm target flow rate. Note that in step S15, if the boom target flow rate (Qtgt1) is corrected to the boom target flow rate (Qtgt1') and the arm target flow rate (Qtgt2) is corrected to the arm target flow rate (Qtgt2'), the controller 50 calculates the target output (Ltgt1) by replacing "Qtgt1" with "Qtgt1'" in equation (4) above, and calculates the target output (Ltgt2) by replacing "Qtgt2" with "Qtgt2'" in equation (5) above.

[0080] In step S20, the controller 50 calculates the upper limit (Qlimit) of the discharge volume of the pump 10 using, for example, the following equation (6).

[0081] Qlimit=(Llimit / Ppump)×60 ···(6) In equation (6) above, "Llimit" is the upper limit of the engine output that can be used by pump 10 at that time, and "Ppump" is the pump pressure.

[0082] In step S21, the controller 50 determines whether the target discharge rate (Qpump) of the pump 10 exceeds the upper limit (Qlimit) of the pump 10's discharge rate. The discharge rate of the pump 10 is an example of an output-related value relating to the pump's output in this disclosure, and the target discharge rate (Qpump) of the pump 10 is an example of a target value for an output-related value in this disclosure.

[0083] If the target discharge rate (Qpump) is less than or equal to the upper limit of the discharge rate of pump 10 (Qlimit) (NO in step S21), the controller 50 determines the opening size of the oil passage in the flow regulator (valve opening) (step S27). Figure 7 shows a preset correspondence (map) between the target flow rate (target speed) and the valve opening. The controller 50 can determine the valve opening using the target flow rate and the correspondence shown in Figure 7.

[0084] Specifically, for example, the controller 50 pre-stores a map for the boom (as shown in Figure 7) that defines the correspondence between the boom target flow rate (Qtgt1) and the opening size of the oil passage (valve opening) in the boom control valve 31A of the boom flow regulator 31. The controller 50 also pre-stores a map for the arm (as shown in Figure 7) that defines the correspondence between the arm target flow rate (Qtgt2) and the opening size of the oil passage (valve opening) in the arm control valve 32A of the arm flow regulator 32. The controller 50 uses the boom target flow rate (Qtgt1) and the boom map shown in Figure 7 to calculate the valve opening (Atgt1), which is the opening size of the oil passage in the boom control valve 31A, and uses the arm target flow rate (Qtgt2) and the arm map shown in Figure 7 to calculate the valve opening (Atgt2), which is the opening size of the oil passage in the arm control valve 32A.

[0085] In step S28, the controller 50 inputs a pump capacity command to the regulator of the pump 10 to adjust the capacity of the pump 10 to the target discharge rate (Qpump). The controller 50 also inputs a control command corresponding to the valve opening to the flow regulator. Specifically, the controller 50 inputs a control command (boom raising control command or boom lowering control command) corresponding to the valve opening determined in step S27 to the solenoid proportional valve 31B of the boom flow regulator 31. The controller 50 also inputs an arm pulling control command, which is a control command corresponding to the valve opening determined in step S27, to the solenoid proportional valve 32B of the arm flow regulator 32.

[0086] On the other hand, if the target value of the output-related value exceeds the upper limit, that is, if the target discharge rate (Qpump) exceeds the upper limit of the discharge rate of the pump 10 (Qlimit) (YES in step S21), the controller 50 performs the following ratio control.

[0087] In step S22, the controller 50 adjusts the target discharge rate (Qpump) to the upper limit (Qlimit) of the discharge rate of the pump 10.

[0088] In step S23, the controller 50 calculates the differential pressure, which is the difference between the pump pressure and the meter-in pressure (M / I pressure). This differential pressure is an example of a value that represents the load on the actuator. As the load on the actuator increases, the differential pressure decreases. That is, as the load on the actuator increases, the meter-in pressure of the actuator increases and approaches the pump pressure.

[0089] Specifically, in step S23, the controller 50 calculates the boom differential pressure (Pdif1), which is the difference between the pump pressure (Ppump) obtained from the pump pressure sensor 41 and the meter-in pressure (Pmi1) of the boom cylinder 11 obtained from the boom pressure sensor 42 (Pdif1 = Ppump - Pmi1). The controller 50 also calculates the arm differential pressure (Pdif2), which is the difference between the pump pressure (Ppump) and the meter-in pressure (Pmi2) of the arm cylinder 12 obtained from the arm pressure sensor 43 (Pdif2 = Ppump - Pmi2). The boom differential pressure (Pdif1) is an example of a value representing the load of the boom cylinder 11, and the arm differential pressure (Pdif2) is an example of a value representing the load of the arm cylinder 12.

[0090] In step S24, the controller 50 determines the PQ control ratio. The PQ control ratio is a value used in ratio control to limit the output of the pump 10 to below the upper limit of the output, and represents the degree to which the target flow rate of hydraulic fluid to the actuator is reduced. Figure 8 is an example of a map showing the relationship between the differential pressure representing the load on the actuator and the PQ control ratio. In the map of Figure 8, when the differential pressure is Pa or less, the PQ control ratio is at its maximum value, when the differential pressure is Pb or greater, the PQ control ratio is at its minimum value, and the PQ control ratio decreases as the differential pressure increases from Pa to Pb. The maximum value may be set to, for example, "1", and the minimum value may be set to, for example, "0", but the setting of the maximum and minimum values ​​is not limited to the above specific example. In this embodiment, as will be described later, the larger the PQ control ratio, the greater the amount by which the target flow rate of hydraulic fluid to the actuator is reduced. By using such a map showing the relationship between differential pressure and the PQ control ratio, the controller 50 can perform ratio control so that the amount by which the target flow rate to the actuator is reduced is greater when the load on the actuator is large compared to when the load on the actuator is small.

[0091] Specifically, in step S24, the controller 50 uses the boom differential pressure (Pdif1) and the map shown in Figure 8 to determine the boom PQ control ratio (PQratio1), which is a PQ control ratio representing the degree to which the boom target flow rate (Qtgt1) is reduced. Similarly, the controller 50 uses the arm differential pressure (Pdif2) and the map shown in Figure 8 to determine the arm PQ control ratio (PQratio2), which is a PQ control ratio representing the degree to which the arm target flow rate is reduced.

[0092] In excavation work, as shown in Figure 1, the arm is pulled back so that the bucket 6 moves in the order of starting position P1, middle position P2, and final position P3 with at least a portion of the bucket 6 positioned in the ground. Therefore, the resistance when performing this arm pulling operation tends to be large. In this excavation work, for example, as shown in the left diagram of Figure 3, if the bucket 6 goes too deep into the ground, the resistance when the arm 5 pulls back in the direction indicated by arrow D1 becomes very large, and the operating pressure (load) when extending the arm cylinder 12 becomes very high. In the situation shown in the left diagram of Figure 3, the arm differential pressure (Pdif2) becomes, for example, Pa or less, while the boom differential pressure (Pdif1) becomes, for example, Pb or more. Therefore, in the situation shown in the left diagram of Figure 3, the controller 50 sets the arm PQ control ratio (PQratio2) to the maximum value (for example, "1") and the boom PQ control ratio (PQratio1) to the minimum value (for example, "0").

[0093] In step S25, the controller 50 calculates an output correction value (Ldif1) using the target output of the pump 10 (Lpump), the upper limit of the engine output (Llimit), the boom PQ control ratio (PQratio1), and, for example, the following equation (7). Similarly, the controller 50 calculates an output correction value (Ldif2) using the target output of the pump 10 (Lpump), the upper limit of the engine output (Llimit), the arm PQ control ratio (PQratio2), and, for example, the following equation (8).

[0094] Ldif1=(Lpump-Llimit)×PQratio1 ···(7) Ldif2=(Lpump-Llimit)×PQratio2 ···(8) The output correction value (Ldif1) is the value to be subtracted from the target output (Ltgt1) of the boom cylinder 11, and the output correction value (Ldif2) is the value to be subtracted from the target output (Ltgt2) of the arm cylinder 12.

[0095] In step S26, the controller 50 modifies the target flow rate of hydraulic fluid to the actuator. Specifically, the controller 50 calculates the modified boom target flow rate (Qtgt1) using the target output (Ltgt1) of the boom cylinder 11, the output correction value (Ldif1), the meter-in pressure (Pmi1) of the boom cylinder 11, and the following equation (9). Similarly, the controller 50 calculates the modified arm target flow rate (Qtgt2) using the target output (Ltgt2) of the arm cylinder 12, the output correction value (Ldif2), the meter-in pressure (Pmi2) of the arm cylinder 12, and the following equation (10).

[0096] Qtgt1=((Ltgt1-Ldif1) / Pmi1)×60 ···(9) Qtgt2=((Ltgt2-Ldif2) / Pmi2)×60 ···(10) As described above, when the boom PQ control ratio (PQratio1) is set to "0" and the arm PQ control ratio (PQratio2) is set to "1", the output correction value (Ldif1) becomes zero. In this case, the boom target flow rate, which is the target flow rate to the boom cylinder 11, is not reduced, and only the arm target flow rate, which is the target flow rate to the arm cylinder 12, is reduced.

[0097] In other words, this ratio control allows the ratio of the boom target flow rate to the arm target flow rate (boom target flow rate / arm target flow rate) to be increased compared to before the modification, while adjusting the output-related values ​​to be below the upper limit value by making a modification to reduce the arm target flow rate to the arm cylinder 12 (an example of a high-load actuator).

[0098] In step S27, the controller 50 determines the opening size (valve opening) of the oil passage in the flow regulator. Specifically, the controller 50 uses the boom target flow rate (Qtgt1) calculated in step S26 and the boom map shown in Figure 7 to calculate the valve opening (Atgt1), which is the opening size of the oil passage in the boom control valve 31A. Then, using the arm target flow rate calculated in step S26, i.e., the modified arm target flow rate (Qtgt2), and the arm map shown in Figure 7, the controller 50 calculates the valve opening (Atgt2), which is the opening size of the oil passage in the arm control valve 32A.

[0099] In step S28, the controller 50 inputs a pump capacity command to the regulator of the pump 10 to limit the capacity of the pump 10. Specifically, the controller 50 inputs a pump capacity command to the regulator of the pump 10 to limit the capacity of the pump 10 so that the discharge amount of the pump 10 is adjusted to the target discharge amount (Qpump) corrected in step S22, i.e., the upper limit (Qlimit) of the discharge amount of the pump 10. The controller 50 also inputs a control command corresponding to the valve opening to the flow regulator. Specifically, the controller 50 inputs a control command (boom raising control command or boom lowering control command) corresponding to the valve opening determined in step S27 to the solenoid proportional valve 31B of the boom flow regulator 31. The controller 50 also inputs an arm pulling control command, which is a control command corresponding to the valve opening determined in step S27, to the solenoid proportional valve 32B of the arm flow regulator 32.

[0100] In this control device 101, ratio control as shown in steps S22 to S28 above is performed to reduce the target flow rate of the arm cylinder 10 (an example of an output-related value) to below the upper limit. This is done so that the ratio of the target flow rate of the boom cylinder 11 (an example of a low-load actuator) to the target flow rate of the arm cylinder 12 (an example of a high-load actuator) (target boom flow rate / target arm flow rate) becomes larger than before the modification. This makes it possible to operate the boom cylinder 11 preferentially over the arm cylinder 12, thereby suppressing a decrease in the operating speed of the boom cylinder 11. Therefore, this control device 101 can suppress a decrease in work efficiency caused by the increased load on the arm cylinder 12 during excavation work in which the boom cylinder 11 and arm cylinder 12 are operated simultaneously.

[0101] Furthermore, in this embodiment, the controller 50 performs the ratio control so that the discharge amount of the pump 10 is adjusted to the upper limit. That is, the controller 50 adjusts the actual output of the pump 10 to the upper limit of the output of the pump 10 that is permissible at that time, so that a larger flow rate of hydraulic fluid is secured to the boom cylinder 11, and the slowing down of the operation of the boom cylinder 11 can be suppressed more effectively. As a result, the decrease in work efficiency can be suppressed more effectively.

[0102] Furthermore, in this embodiment, the controller 50 performs the ratio control such that the amount by which the arm target flow rate is reduced is greater when the load on the arm cylinder 12 is greater than when the load on the arm cylinder 12 is small. Since the amount by which the arm target flow rate is reduced is determined according to the load on the arm cylinder 12 in this way, it becomes easier to secure the flow rate of hydraulic fluid supplied to the boom cylinder 11.

[0103] Furthermore, in this embodiment, the controller 50 controls the ratio such that the boom target flow rate is not reduced when the load on the boom cylinder 11 is within a predetermined range, specifically, when the differential pressure between the pump pressure and the meter-in pressure of the boom cylinder 11 is greater than or equal to Pb in the graph of Figure 8, and when the load on the boom cylinder 11 is greater than the predetermined range, specifically, when the differential pressure is less than Pb in the graph of Figure 8, the boom target flow rate is reduced according to the load on the boom cylinder 11.Therefore, when the load on the boom cylinder 11 is within the predetermined range and relatively small, the boom target flow rate is maintained at a level corresponding to the amount of boom operation without being reduced.This effectively suppresses a decrease in the operating speed of the boom cylinder 11.On the other hand, when the load on the boom cylinder 11 becomes greater than the predetermined range, not only is the arm target flow rate reduced, but the boom target flow rate is also reduced according to the load on the boom cylinder 11, thereby reliably preventing the output-related values ​​of the pump 10 from exceeding the upper limit. In this embodiment, the controller 50 can perform ratio control such that the amount by which the boom target flow rate is reduced is greater when the load on the boom cylinder 11 is greater than when the load on the boom cylinder 11 is small.

[0104] [Differentiation] Although a control device for a work machine according to the embodiments of this disclosure has been described above, this disclosure is not limited to the embodiments described above and includes, for example, the following modifications.

[0105] (A) Regarding the PQ control ratio In the above embodiment, the controller 50 determines the PQ control ratio using the map shown in Figure 8 and the differential pressure between the pump pressure and the meter-in pressure of the actuator. However, the method for determining the PQ control ratio is not limited to the above embodiment. The controller 50 may set the boom PQ control ratio to a preset value, or the arm PQ control ratio to a preset value. Furthermore, the controller 50 may set the boom PQ control ratio based on an input value entered by the operator into the input device 60 shown in Figure 2, or the arm PQ control ratio based on an input value entered by the operator into the input device 60. In any of these cases, the arm PQ control ratio is set to a value greater than the boom PQ control ratio (specifically, one example is when the boom PQ control ratio is set to "0.5" and the arm PQ control ratio is set to "0.8").

[0106] In these variations, the controller 50 may calculate the corrected boom target flow rate and the corrected arm target flow rate, for example, as follows: The controller 50 may calculate the corrected boom target flow rate using, for example, the following equation (11), and calculate the corrected arm target flow rate using, for example, the following equation (12).

[0107] Revised boom target flow rate = Total provisional target flow rate × Revised boom target flow rate / Total revised target flow rate ... (11) Revised arm target flow rate = total provisional target flow rate × revised arm target flow rate / total revised target flow rate ... (12) Here, in equations (11) and (12), the "provisional target flow rate total" is the sum of target flow rates calculated so that the output of pump 10 reaches its upper limit, while maintaining the ratio of the boom target flow rate, which is determined according to the amount of boom operation, and the arm target flow rate, which is determined according to the amount of arm operation. The "boom modified target flow rate" in equation (11) is calculated using the following equation (13), and the "arm modified target flow rate" in equation (12) is calculated using the following equation (14).

[0108] Boom modified target flow rate = Provisional boom target flow rate + Boom PQ excluded flow rate ... (13) Arm modified target flow rate = Provisional arm target flow rate + Arm PQ excluded flow rate ... (14) Here, the "provisional boom target flow rate" in equation (13) is the target flow rate for the boom cylinder out of the total provisional target flow rate, and the "provisional arm target flow rate" in equation (14) is the target flow rate for the arm cylinder out of the total provisional target flow rate. The "boom PQ excluded flow rate" in equation (13) is calculated using the following equation (15), and the "arm PQ excluded flow rate" in equation (14) is calculated using the following equation (16).

[0109] Boom PQ exclusion flow rate = (Boom required target flow rate - Provisional boom target flow rate) × (1 - Boom PQ control rate) ... (15) Arm PQ exclusion flow rate = (Arm required target flow rate - Provisional arm target flow rate) × (1 - Arm PQ control rate) ... (16) Here, the "boom target flow rate" in equation (15) is the boom target flow rate determined according to the amount of boom operation, and the "arm target flow rate" in equation (16) is the arm target flow rate determined according to the amount of arm operation.

[0110] (B) In the embodiment described above with reference to Figures 4 and 5, if the sum of the boom PQ control rate and the arm PQ control rate determined in step S24 of Figure 5 is "1", the controller 50 may modify the boom target flow rate and the arm target flow rate by performing the processing in steps S25 and S26 of Figure 5. If the sum of the boom PQ control rate and the arm PQ control rate is not "1", the boom target flow rate and the arm target flow rate may be modified using equations (11) to (16) in the modified example described above.

[0111] (C) The controller may perform the ratio control so that the target flow rate to the small load actuator is not reduced regardless of the magnitude of the load on the small load actuator. In this case, in the ratio control, the target flow rate to the small load actuator is not reduced and is maintained at a value determined according to the operation given to the operating device, so that the decrease in the operating speed of the small load actuator can be suppressed more effectively when an operation to activate the small load actuator is given to the operating device.

[0112] (D) Output-related values In the above embodiment, the output-related value relating to the pump output is the discharge rate of the pump 10, and the target value of the output-related value is the target discharge rate of the pump 10. However, the output-related value relating to the pump output in this disclosure may be, for example, the output of the pump, and in this case, the target value of the output-related value in this disclosure may be, for example, the target output of the pump.

[0113] (E) Regarding the first operation, the second operation, and the load relief operation In the above embodiment, the first operation is boom operation, the second operation is arm pulling operation, and the load relief operation is boom raising operation. However, the first operation, second operation, and load relief operation in this disclosure are not limited to the boom operation, arm pulling operation, and boom raising operation in the above embodiment, but include various operations such as boom operation, arm operation, bucket operation, and slewing operation that an operator can give to the operating device 20. Specifically, for example, in the case of work to push soil forward, the first operation is boom operation, the second operation is arm pushing operation, the load relief operation is boom raising operation, the heavy load actuator is the arm cylinder 12, and the light load actuator is the boom cylinder 11. When the operating pressure (load) when retracting the arm cylinder 12 becomes very high, the boom raising operation is performed as a load relief operation. [Explanation of symbols]

[0114] 10: Pump 11: Boom cylinder (an example of a first actuator) 12: Arm cylinder (an example of a second actuator) 20: Operating device 31: Boom flow regulator (an example of a first flow regulator) 32: Arm flow regulator (an example of a second flow regulator) 50: Controller 100: Working machinery 101: Control device

Claims

1. A pump that discharges hydraulic fluid, A boom cylinder that operates when the aforementioned hydraulic fluid is supplied to it, and rotates the boom of the work machine, The arm cylinder, which is operated by the supply of the aforementioned hydraulic fluid and rotates the arm of the work machine, An operating device that provides boom operation for moving the boom in the boom-raising direction or boom-lower direction, and arm operation for moving the arm in the arm-pulling direction or arm-pushing direction, Equipped with a controller, The aforementioned controller, Using the target flow rate of the hydraulic fluid to the boom cylinder in response to the boom operation and the target flow rate of the hydraulic fluid to the arm cylinder in response to the arm operation, a target value for the output-related value related to the pump's output is calculated. Determine whether the aforementioned target value exceeds the upper limit, If one of the boom cylinder and the arm cylinder is a high-load actuator with a relatively large load and the other is a low-load actuator with a relatively small load, and the target value is less than or equal to the upper limit, control is performed so as not to change the ratio of the target flow rate to the low-load actuator to the target flow rate to the high-load actuator. The system is configured to perform ratio control when the target value exceeds the upper limit. The ratio control is a control device for a work machine, wherein, when one of the boom cylinder and the arm cylinder is the high-load actuator and the other is the low-load actuator, the control adjusts the output-related values ​​to be below the upper limit by making a modification to reduce the target flow rate to the high-load actuator, thereby increasing the ratio of the target flow rate to the low-load actuator to the target flow rate to the high-load actuator compared to before the modification.

2. The control device for a work machine according to claim 1, wherein the controller performs the ratio control so that the output-related value is adjusted to the upper limit value.

3. The control device for a work machine according to claim 1, wherein the controller performs the ratio control such that the amount by which the target flow rate to the heavy load actuator is reduced is greater when the load on the heavy load actuator is greater than when the load on the heavy load actuator is small.

4. The control device for a work machine according to claim 1, wherein the controller performs ratio control such that the target flow rate to the small load actuator is not reduced when the load of the small load actuator is within a predetermined range, and the target flow rate to the small load actuator is reduced in accordance with the load of the small load actuator when the load of the small load actuator is greater than the predetermined range.

5. A first flow regulator adjusts the flow rate of the hydraulic fluid supplied to the boom cylinder to the target flow rate to the boom cylinder based on a command from the controller, A control device for a work machine according to claim 1, further comprising: a second flow regulator that adjusts the flow rate of the hydraulic fluid supplied to the arm cylinder to the target flow rate to the arm cylinder based on a command from the controller.

6. The control device for a work machine according to claim 1, wherein the low-load actuator is an actuator capable of operating in such a way as to reduce the load on the high-load actuator.

7. A work machine equipped with a control device according to any one of claims 1 to 6.

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