Hydraulic driving device and work machine equipped with the same

Abstract

To suppress an impact of pump flow rate control on work accuracy in a hydraulic driving device.SOLUTION: A hydraulic driving device includes: a variable capacity type hydraulic pump 40B; first and second actuators 48 and 44 for receiving supply of working fluid from the hydraulic pump 40B; first and second operation devices 68 and 64 to which first and second operations are given for the first and second actuators 48 and 44 respectively; and a controller 80 for performing pump flow rate control. The pump flow rate control includes increasing a pump flow rate accompanying an increase in first and second operation amounts respectively, and slowing down the reaction of the pump flow rate for a change in the first operation amount to a greater degree as the second operation amount is smaller in the combined operations in which the first operation and the second operation are given.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a hydraulic drive system and a work machine equipped with the same. [Background technology]

[0002] A known hydraulic drive system for a work machine such as a hydraulic excavator includes a variable displacement hydraulic pump, multiple actuators, and a controller. The multiple actuators are actuated by hydraulic fluid supplied from the hydraulic pump to move movable parts of the work machine. The controller controls the pump flow rate of the hydraulic pump according to the operating state, i.e., performs pump flow rate control.

[0003] For example, Patent Document 1 discloses a hydraulic drive system for operating a hydraulic excavator, the system including first and second hydraulic pumps, each of which is a variable displacement hydraulic pump; a plurality of hydraulic actuators, each of which can be connected to at least one of the first and second pumps; and a controller for controlling the pump flow rate, which is the discharge flow rate of the first and second pumps. The plurality of actuators include a boom cylinder, an arm cylinder, and an option cylinder, of which the arm cylinder and option cylinder are connected to a common second hydraulic pump. The controller performs so-called positive control, which increases the pump flow rate of the first or second hydraulic pump as the operation applied to operate each of the plurality of hydraulic actuators increases. Specifically, the controller controls to increase the pump flow rate of the second hydraulic pump as the arm operation and option operation corresponding to the arm cylinder and the option cylinder, respectively, connected to the second hydraulic pump increase. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-249849 Summary of the Invention [Problem to be solved by the invention]

[0005] In a device in which multiple hydraulic actuators are connected to a common variable displacement hydraulic pump and the pump flow rate is controlled based on the operation of the multiple hydraulic actuators, there is a risk that the operating speed of some of the hydraulic actuators may suddenly change during combined operations in which the multiple hydraulic actuators are operated simultaneously, affecting the accuracy of the work. For example, in a case in which an arm cylinder and an optional actuator are connected to a common hydraulic pump and the optional actuator changes the attitude of the bucket relative to the arm, if an optional operation is performed on the optional actuator to adjust the attitude of the bucket while the arm operation is suppressed (for example, while half-lever operation is being performed) to adjust the operating speed of the arm cylinder for an operation to slowly move the cutting edge of the bucket of the hydraulic excavator along a target work surface (for example, horizontal pulling), the flow rate of the hydraulic pump is increased by the position control (specifically, the capacity of the hydraulic pump is increased) in response to an increase in the optional operation amount, which is the amount of the optional operation, and this may suddenly change the operating speed of the arm cylinder, affecting the accuracy of the work.

[0006] Regarding combined operation for simultaneously moving both the arm cylinder and the optional cylinder, Patent Document 1 discloses a control that cuts off the supply of hydraulic oil from the second hydraulic pump to the optional cylinder and supplies hydraulic oil to the optional cylinder from the first hydraulic pump, which is separate from the second hydraulic pump. However, this control is intended to suppress changes in the flow rate of hydraulic oil supplied to the arm cylinder depending on the magnitude of the load on the optional cylinder, and does not suggest any means for solving the problems specific to so-called positive control. Furthermore, the technology described in Patent Document 1 is based on the premise of special equipment including a confluent oil passage and a confluent switching valve for supplying hydraulic oil from both the first and second hydraulic pumps to the arm cylinder, and cannot be applied to other equipment. [Means for solving the problem]

[0007] An object of the present invention is to provide a hydraulic drive system in which hydraulic oil is supplied to first and second actuators from a common hydraulic pump, and which is capable of effectively suppressing the impact of control of the pump flow rate, which is performed based on the operation of the first actuator, on the accuracy of work performed by the second actuator, and a work machine equipped with the hydraulic drive system.

[0008] What is provided is a hydraulic drive system for hydraulically moving a movable part of a work machine, the hydraulic drive system comprising: a variable displacement hydraulic pump, a first actuator that receives a supply of hydraulic oil from the hydraulic pump to move a first part of the work machine, a second actuator that receives a supply of hydraulic oil from the hydraulic pump to move a second part of the work machine, a first operating device to which a first operation for specifying an operating speed of the first actuator is given, a second operating device to which a second operation for specifying an operating speed of the second actuator is given, and a controller that performs pump flow rate control to increase a pump flow rate that is a discharge flow rate of the hydraulic pump in accordance with an increase in a first operating amount that is the amount of the first operation and an increase in a second operating amount that is the amount of the second operation. The pump flow rate control includes, during a combined operation in which the first operation and the second operation are given to the first operating device and the second operating device, respectively, slowing the response of the pump flow rate to a greater degree as the second operating amount is smaller.

[0009] The controller can suppress the effect of a change in the first operation amount on the accuracy of work performed by the second operation, even though the controller performs the pump flow rate control (e.g., positive control) that increases the pump flow rate, which is the discharge flow rate of the hydraulic pump, in response to an increase in the first operation amount and an increase in the second operation amount. Specifically, when the second operation amount is small, that is, when the operator is performing work that requires delicate adjustment of the operating speed of the second actuator by suppressing the second operation amount (e.g., a half-lever operation), the controller significantly slows down the response of the pump flow rate to a change in the first operation amount, thereby suppressing a sudden change in the pump flow rate and therefore a sudden change in the operating speed of the second actuator that occurs in response to a change in the first operation amount, thereby reducing the effect of a change in the first operation amount on the accuracy of work performed by the second actuator. On the other hand, when the second operation amount is large, that is, when the operator increases the second operation amount (for example, by operating the lever fully) to request high-speed operation of the second actuator and therefore precise speed adjustment is not required, the degree to which the pump flow rate slows down in response to changes in the first operation amount can be reduced, thereby making it possible to quickly provide the operating speed of the first actuator that the operator requests through the first operation.

[0010] Note that "slowing the response of the pump flow rate to a change in the first manipulated variable" is not intended to be limited to slowing both an increase in the pump flow rate in response to an increase in the first manipulated variable and a decrease in the pump flow rate in response to a decrease in the first manipulated variable, but also includes a mode of slowing only one of the increase or decrease. For example, even by the former mode, i.e., the mode of slowing only the increase in the pump flow rate in response to an increase in the first manipulated variable, it is possible to suppress a sudden increase in the operating speed of the second actuator that accompanies an increase in the pump flow rate, thereby reducing the impact on operation accuracy.

[0011] Preferably, the controller is configured to determine a second operation flow rate change gain that increases as the second operation amount increases, based on the second operation amount, and to increase the time rate of change of the pump flow rate with respect to a change in the first operation amount as the second operation flow rate change gain increases. The controller can slow the response of the pump flow rate to a change in the first operation amount by a simple calculation and control operation of determining the second operation flow rate change gain.

[0012] When the second operation includes an operation in a first direction and an operation in a second direction different from the first direction, the controller may be configured to increase the degree to which the response of the pump flow rate is slowed down in response to the second operation amount in the second direction compared to the degree to which the response of the pump flow rate is slowed down in response to the second operation amount in the first direction. This makes it possible to change the responsiveness of the pump flow rate to a change in the first operation amount depending on the direction of the second operation (the first direction or the second direction).

[0013] For example, if the second actuator is a hydraulic cylinder that can be extended and contracted by piston movement, and the pressure-receiving area of ​​the piston for extending the hydraulic cylinder is larger than the pressure-receiving area of ​​the piston for retracting the hydraulic cylinder, it is preferable that the operation in the first direction is an operation for extending the hydraulic cylinder and the operation in the second direction is an operation for retracting the hydraulic cylinder. In such a hydraulic cylinder, the speed of the extension operation corresponding to the flow rate of hydraulic oil supplied is lower than the speed of the retraction operation. Therefore, even if the flow rate of hydraulic oil supplied is the same, the retraction operation of the second actuator is more sensitive to the operation in the second direction than the retraction operation of the second actuator to the operation in the first direction. Therefore, by slowing the latter response to a greater degree than the former response, the responsiveness of the pump flow rate to changes in the second operation amount can be equalized for the operations in the first and second directions.

[0014] Specifically, the controller is preferably configured to determine a second flow rate change gain during operation that increases as the second operation amount increases based on the second operation amount, to increase the time rate of change of the pump flow rate with respect to the change in the first operation amount as the second operation amount increases, and to determine the second flow rate change gain during operation corresponding to the second operation amount in the second direction to be a smaller gain than the second flow rate change gain during operation corresponding to the second operation amount in the first direction.

[0015] The hydraulic drive system may further include a third actuator that receives a supply of hydraulic oil from the hydraulic pump to move a third part of the work machine, and a third operating device to which a third operation is applied to specify an operating speed of the third actuator. In this aspect, the controller may be configured to increase the pump flow rate in accordance with an increase in the first operating amount, an increase in the second operating amount, and an increase in a third operating amount that is the amount of the third operation, and to slow down the response of the pump flow rate to a change in the first operating amount to a greater extent as the second operating amount is smaller and to a greater extent as the third operating amount is smaller, during a combined operation in which the first operation, the second operation, and the third operation are simultaneously applied to the first operating device, the second operating device, and the third operating device, respectively. The controller can slow down the response of the pump flow rate to a change in the first operating amount even when a suppressed operation is performed on not only the second actuator but also the third actuator, that is, when the third operating amount is kept small and it is inferred that the operating speed of the third actuator is being adjusted, thereby suppressing the effect of the change in the first operating amount on the accuracy of work performed by the third actuator.

[0016] In this case, similarly to the second operation variable, it is preferable that the controller determines a third operation flow rate change gain that increases as the third operation variable increases based on the magnitude of the third operation variable, and is configured to increase the time rate of change of the pump flow rate in response to a change in the first operation variable as the second operation flow rate change gain and the third operation flow rate change gain become larger.

[0017] When determining the third operation flow rate change gain in addition to the second operation flow rate change gain in this way, the controller can determine the time rate of change of the pump flow rate based on both gains. For example, the controller may be configured to determine a final gain based on the sum of the second operation flow rate change gain and the third operation flow rate change gain, and to increase the time rate of change of the pump flow rate in response to a change in the first operation as the final gain is larger.

[0018] A work machine to which the hydraulic drive system is well applied includes, for example, a machine body, a work arm attached to the machine body, and a work member attached to the tip of the work arm. The work arm operates to move the work member, the first actuator is a hydraulic actuator that moves the work member relative to the work arm, and the second actuator is a hydraulic actuator that moves the work arm. In this work machine, when the second manipulated variable is small, that is, when the second actuator moves the work arm at a low speed to move the work member at a low speed, by slowing down the response of the pump flow rate to changes in the first manipulated variable, it is possible to prevent a sudden change in the movement speed of the work member due to a change in the first manipulated variable, which can adversely affect the accuracy of the movement of the work member by the second actuator.

[0019] A work machine to which the hydraulic drive system further comprising the third actuator is suitably applied comprises, for example, a lower traveling body, an upper rotating body rotatably mounted on the lower traveling body, a work arm attached to the upper rotating body, and a work member attached to the tip of the work arm, wherein the work arm operates to move the work member, the first actuator is a hydraulic actuator that moves the work member relative to the work arm, the second actuator is a hydraulic actuator that moves the work arm, and the third actuator is a hydraulic actuator that rotates the upper rotating body relative to the lower traveling body. In this work machine, when at least one of the second operation amount and the third operation amount is small, that is, when the second actuator moves the work arm at a low speed to move the work member at a low speed, or when the third actuator rotates the upper rotating body at a low speed to move the work member at a low speed, the pump flow rate is made to slow down the response of the pump flow rate to a change in the first operation amount, thereby preventing a sudden change in the movement speed of the work member by the second actuator or the third actuator due to a change in the first operation amount, which can adversely affect the accuracy of the movement of the work member by the second actuator or the third actuator. [Effects of the Invention]

[0020] As described above, according to the present invention, it is possible to provide a hydraulic drive system in which hydraulic oil is supplied to first and second actuators from a common hydraulic pump, and which is capable of effectively suppressing the impact of control of the pump flow rate, which is performed based on the operation of the first actuator, on the accuracy of work performed by the second actuator, and a work machine equipped with the same. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a side view of a work machine according to an embodiment of the present invention. [Figure 2]FIG. 2 is a side view showing a bucket attached to the tip of the arm of the work machine and an actuator for moving the bucket. [Figure 3] FIG. 2 is a circuit diagram showing a hydraulic drive system mounted on the work machine. [Figure 4] FIG. 2 is a block diagram showing the configuration of a controller that controls the movement of the hydraulic circuit. [Figure 5] 10 is a graph showing the relationship between each manipulated variable and the target pump flow rate for each operation, which is stored in the storage unit of the controller. [Figure 6] 10 is a graph showing a relationship between an arm operation amount and a flow rate change gain during arm operation, the relationship being stored in a memory unit of the controller. [Figure 7] 10 is a graph showing a relationship between a swing operation amount and a swing operation flow rate change gain, which is stored in a memory unit of the controller. [Figure 8] 4 is a flowchart showing a process executed by the controller. [Figure 9] 4 is a time chart showing an example of a boom-raising operation amount and a change over time in a first pump flow rate controlled in response thereto. [Figure 10] 6 is a time chart showing an example of temporal changes in an arm retraction operation amount, a bucket swing operation amount, and a second pump flow rate controlled in response to these. DETAILED DESCRIPTION OF THE INVENTION

[0022] A preferred embodiment of the present invention will now be described with reference to the drawings.

[0023] 1 shows a hydraulic excavator 10, which is a work machine according to the embodiment. The hydraulic excavator 10 includes a lower traveling body 12, an upper rotating body 14, a working arm 16, and a working member.

[0024] The lower traveling body 12 includes a traveling frame and a pair of crawlers disposed on both the left and right sides of the traveling frame. The pair of crawlers are driven so that the entire lower traveling body 12 travels on the ground.

[0025] The upper rotating body 14 is rotatably mounted on the undercarriage 12 and, together with the undercarriage 12, constitutes the body of the hydraulic excavator 10. The upper rotating body 14 includes a rotating frame 20, a cab 22, and a machine room 24. The rotating frame 20 is rotatably connected to the traveling frame of the undercarriage 12 via a swing bearing (not shown). The cab 22 is mounted on the front of the rotating frame 20 and allows an operator to perform operations for operating the hydraulic excavator 10 from within the cab 22. The machine room 24 houses the engine 18, multiple hydraulic devices, and other devices shown in FIG. 3. Of the multiple hydraulic devices, those shown in FIG. 3 will be described in detail later.

[0026] In this embodiment, the working member is a bucket 30, which is attached to the tip of the working arm 16. The working arm 16 is attached to the upper rotating body 14 so as to enable working arm operation. The working arm operation is an operation of moving the bucket 30 relative to the upper rotating body 14, i.e., an operation of changing the relative position of the bucket 30 with respect to the upper rotating body 14.

[0027] In this embodiment, the working arm 16 includes a boom 26 and an arm 28. The boom 26 is connected to the upper rotating body 14 to enable a hoisting operation, specifically, a vertical rotation. Specifically, the boom 26 has a base end and a tip end on the opposite side, and the base end is connected to an appropriate position on the upper rotating body 14 via a support shaft, i.e., a boom foot pin 11. The boom foot pin 11 extends in the working arm width direction, which is parallel to the left-right direction of the upper rotating body 14, and allows the boom 26 to rotate up and down relative to the upper rotating body 14, i.e., a hoisting operation, about the boom foot pin 11. The arm 28 has a base end and a tip end on the opposite side, and the base end is connected to the tip end of the boom 26 via a support shaft, i.e., an arm connecting pin 21. The arm connecting pin 21 extends in the working arm width direction and allows the arm 28 to rotate up and down relative to the boom 26 about the arm connecting pin 21. By the rotation of the boom 26 and the arm 28, the bucket 30 is moved relative to the upper rotating body 14 on a work operation plane which is a vertical plane including the boom 26 and the arm 28.

[0028] 2, the bucket 30 is connected to the tip of the work arm 16, in this embodiment, the tip of the arm 28, via a bucket holding member 33. The bucket mounting member 33 is interposed between the bucket 30 and the arm 28 and holds the bucket 30 so that the bucket 30 can perform bucket opening / closing operations and bucket swing operations relative to the work arm 16.

[0029] The bucket opening and closing operation is a vertical rotation relative to the working arm 16, more specifically, a rotation about an axis extending in the width direction of the working arm, a so-called pitch movement, and is a rotation along the working movement plane (a plane parallel to the paper surface in FIG. 2). Of the bucket opening and closing operations, the closing operation (counterclockwise rotation in FIG. 2) is an operation for excavating with the bucket 30, and the opening operation (clockwise rotation in FIG. 2) is an operation for discharging soil from the bucket 30.

[0030] The bucket swinging motion is a lateral rotation relative to the working arm 16, more specifically, a rotation about a bucket swing axis Xb parallel to the working motion plane (a plane parallel to the paper surface in FIG. 2), a so-called yaw motion, and is a rotation perpendicular to the working motion plane. The bucket swinging motion changes the orientation of the bucket 30 relative to the arm 28 during excavation work or ground leveling work, thereby reducing the movement resistance that the bucket 30 receives from the object to be excavated and improving the smoothness of the construction surface.

[0031] The bucket holding member 33 is connected to the tip of the arm 28 via a bucket pin 31. The bucket pin 31 extends in the width direction of the working arm, and allows the bucket holding member 33, and further the bucket 30 held thereby, to rotate about the central axis of the bucket pin 31 relative to the arm 28, i.e., allows the bucket 30 to perform the bucket opening and closing operation.

[0032] As shown in FIG. 2, the bucket 30 has a bucket base 30c, multiple claws 30a, a bottom surface 30b, and a ground-contacting wall surface 30f. The bucket base 30c is connected to the bucket holding member 33 so as to be rotatable relative to the bucket holding member 33 about the bucket pivot axis Xb. As a result, the bucket holding member 33 holds the bucket 30 so as to allow the bucket 30 to perform the bucket pivoting operation with respect to the arm 28. The ground-contacting wall surface 30f is a surface that is disposed along a target work surface St in a horizontal towing operation as shown in FIG. 2, and is located on the opposite side of the bottom surface 30b from the bucket base 30c (the lower side in FIG. 2). The bucket pivot axis Xb extends in a direction substantially parallel to the normal to the ground-contacting wall surface 30f. The multiple claws 30a protrude in the same direction from the tip edge of the open end of the bucket 30, i.e., the tip of the bucket body portion that forms the soil storage section of the bucket 30, along the contact wall surface 30f.

[0033] The hydraulic excavator 10 is equipped with a hydraulic drive system shown in Fig. 3. The hydraulic drive system is a device for hydraulically moving movable parts of the hydraulic excavator 10, and includes a first pump 40A, a second pump 40B, a plurality of hydraulic actuators, a plurality of control valves, a plurality of operating devices, a plurality of pressure sensors, and a controller 80.

[0034] Each of the first and second pumps 40A, 40B is a variable displacement hydraulic pump. That is, the first pump displacement and the second pump displacement, which are the pump displacements of the first and second pumps 40A, 40B, can be adjusted. The first and second pumps 40A, 40B are driven by the engine 18 and thereby discharge hydraulic oil from a tank independently of each other. Each of the first and second pumps 40A, 40B includes a pump body and a regulator, and the regulator operates to change the displacement of the pump body (first pump displacement and second pump displacement) by receiving a pump displacement command signal from the controller 80. In this embodiment, the second pump 40B of the first and second pumps 40A, 40B corresponds to the "hydraulic pump" of the hydraulic drive system according to the present invention.

[0035] The plurality of hydraulic actuators are driven by receiving a supply of hydraulic oil from the first pump 40A or the second pump 40B, and move movable parts corresponding to the plurality of hydraulic actuators in the hydraulic excavator 10. Specifically, the plurality of hydraulic actuators include a plurality of hydraulic motors and a plurality of hydraulic cylinders. The plurality of hydraulic motors include a pair of travel motors (not shown), a swing motor 41, and a bucket swing motor 48, and the plurality of hydraulic cylinders include a boom cylinder 42, an arm cylinder 44, and a bucket cylinder 46.

[0036] The pair of travel motors respectively move the pair of crawlers on the undercarriage 12, thereby causing the undercarriage 12 to perform the travelling operation. Each of the pair of travel motors is configured by a hydraulic motor having a motor body and an output shaft, the motor body is connected to the travel frame, and the output shaft is connected to the corresponding one of the pair of crawlers.

[0037] The swing motor 41 causes the upper swing body 14 to perform a swing operation, i.e., an operation of swinging relative to the lower traveling body 12. The swing motor 41 is configured by a hydraulic motor having a motor body and an output shaft, and the motor body is fixed to the lower traveling body 12, and the output shaft is connected to the upper swing body 14 via a drive transmission mechanism.

[0038] Each of the hydraulic cylinders includes a cylinder body, a piston mounted in the cylinder body, and a piston rod that moves integrally with the piston. When the piston moves within the cylinder body, the entire hydraulic cylinder can extend and retract.

[0039] The boom cylinder 42 causes the boom 26 to perform the hoisting operation, i.e., to rotate up and down relative to the undercarriage 12. The boom cylinder 42, which is a hydraulic cylinder, is connected to the undercarriage 12 and the boom 26 so that the boom 26 performs the hoisting operation relative to the undercarriage 12 by its extension and contraction. Specifically, the extension operation of the boom cylinder 42 causes the boom 26 to perform an upward boom-raising operation (rotation in the clockwise direction in FIG. 1), and the contraction operation of the boom cylinder 42 causes the boom 26 to perform a downward boom-lowering operation (rotation in the counterclockwise direction in FIG. 1).

[0040] The arm cylinder 44 rotates the arm 28 in the vertical direction relative to the boom 26. The arm cylinder 44, which is a hydraulic cylinder, is connected to the boom 26 and the arm 28 so that the arm 28 rotates in the vertical direction relative to the boom 26 when it extends or retracts. Specifically, the extending operation of the arm cylinder 44 causes the arm 28 to perform an arm-pushing operation, and the retracting operation of the arm cylinder 44 causes the arm 28 to perform an arm-pushing operation. The arm-pushing operation is the rotation of the arm 28 in a direction in which the bucket 30 approaches the boom 26 (counterclockwise rotation in FIG. 1), and the arm-pushing operation is the rotation of the arm 28 in a direction in which the bucket 30 moves away from the boom 26 (clockwise rotation in FIG. 1).

[0041] The bucket cylinder 46 causes the bucket 30 to perform the bucket opening and closing operation, i.e., to rotate in the pitch direction relative to the arm 28. The bucket cylinder 46, which is the hydraulic cylinder, is connected to the arm 28 and is also connected to the bucket 30 via the bucket link mechanism 32 so that the bucket 30 performs the bucket opening and closing operation relative to the arm 28 by its extension and contraction operation. Specifically, the extension operation of the bucket cylinder 46 causes the bucket 30 to perform a closing operation (rotation in the counterclockwise direction in FIG. 2), and the contraction operation of the bucket cylinder 46 causes the bucket 30 to perform an opening operation (rotation in the clockwise direction in FIG. 2).

[0042] The bucket link mechanism 32 is a parallel link mechanism as shown in Fig. 2, and converts the extension and contraction movement of the bucket and cylinder 46 into the bucket opening and closing movement of the bucket 30. The bucket link mechanism 32 is composed of a first link member 34A, a second link member 34B, the bucket holding member 33, and the end, i.e., the tip, of the arm 28 shown in Fig. 2. The first link member 34A has a bucket-side end (the lower end in the position shown in Fig. 2) and a cylinder-side end (the upper end in Fig. 2) on the opposite side, and the bucket-side end is rotatably connected to the bucket holding member 33 via a first link pin 35A that is parallel to the bucket pin 31 at a position offset from the bucket pin 31 toward the back side of the arm 28 (the left side in Fig. 2). The second link member 34B has an arm-side end (the right end in the attitude shown in FIG. 2) and a cylinder-side end (the left end in FIG. 2) on the opposite side thereof, and the arm-side end is rotatably connected to the arm 28 via a second link pin 35B that is parallel to the bucket pin 31 at a position that is offset from the bucket pin 31 toward the base end of the arm 28 (the upper side in FIG. 2). The bucket-side ends of the first and second link members 34A, 34B are both rotatably connected to the tip end of the bucket cylinder 46, i.e., the rod-side end, via a third link pin 35C that is parallel to the bucket pin 31.

[0043] The bucket rotation motor 48 causes the bucket 30 to perform the bucket rotation operation, i.e., rotation in the yaw direction relative to the bucket holding member 33. The bucket rotation motor 48 is configured by a hydraulic motor as shown in FIG. 2 and has a motor body and an output shaft. The motor body is fixed to the bucket holding member 33, and the output shaft is connected to the bucket base 30c of the bucket 30. The center of the output shaft corresponds to the bucket rotation axis Xb, which is the central axis of the bucket rotation operation. The bucket rotation motor 48, together with the bucket holding member 33, constitutes an optional device (tiltrotator) for causing the bucket 30 to perform the bucket rotation operation in addition to the bucket opening and closing operation.

[0044] In this embodiment, the bucket swing motor 48 corresponds to a first actuator that receives a supply of hydraulic oil from the second pump 40B to move the bucket 30, which is a first part of the hydraulic excavator 10; the arm cylinder 44 corresponds to a second actuator that receives a supply of hydraulic oil from the second pump 40B to move the arm 28, which is a second part of the hydraulic excavator 10; and the swing motor 41 corresponds to a third actuator that receives a supply of hydraulic oil from the second pump 40B to move the upper swing body 14, which is a third part of the hydraulic excavator 10.

[0045] The plurality of control valves are hydraulic pilot-type directional control valves respectively interposed between the first pump 40A or the second pump 40B and the plurality of actuators, and perform a valve opening operation to change the direction and flow rate of the supply of hydraulic oil from the first pump 40A or the second pump 40B to each of the plurality of actuators in response to the pilot pressure applied to the directional control valve.

[0046] 3, namely, a swing control valve 51, a boom control valve 52, a boom-raising acceleration control valve 53, an arm control valve 54, an arm-pushing acceleration control valve 55, and a bucket swing control valve 58. Of these control valves 51, 52 to 55, 58, the boom control valve 52 and the arm-pushing acceleration control valve 55 are connected to the first pump 40A, and the swing control valve 51, the boom-raising acceleration control valve 53, the arm control valve 54, and the bucket swing control valve 58 are connected to the second pump 40B.

[0047] A first center bypass line CL1 and a second center bypass line CL2 leading to a tank are connected to the discharge ports of the first and second pumps 40A, 40B, respectively, and the boom control valve 52 and the arm pull acceleration control valve 55 are arranged along the first center bypass line CL1, and the swing control valve 51, the boom raise acceleration control valve 53, the arm control valve 54, and the bucket swing control valve 58 are arranged along the second center bypass line CL2. A first parallel supply line PL1 and a second parallel supply line PL2 branch off from the first center bypass line CL1 and the second center bypass line CL2, respectively, to form hydraulic oil supply paths.

[0048] The swing control valve 51 is interposed between the second pump 40B and the swing motor 41. The swing control valve 51 has a right swing pilot port 51a shown in FIG. 3 and a left swing pilot port (not shown) on the opposite side. When pilot pressure is not supplied to either the right swing pilot port 51a or the left swing pilot port, the swing control valve 51 maintains a neutral state and fully opens the second center bypass line CL2, while preventing the hydraulic oil discharged from the second pump 40B from being supplied to the swing motor 41, thereby stopping the swing motor 41. On the other hand, when pilot pressure, i.e., swing pilot pressure (right swing pilot pressure or left swing pilot pressure), is supplied to either the right swing pilot port 51a or the left swing pilot port, the swing control valve 51 opens in a direction corresponding to the pilot port to which the swing pilot pressure is supplied at an opening corresponding to the magnitude of the swing pilot pressure, forming a supply oil path that allows hydraulic oil to be supplied to the swing motor 41 through the second parallel supply line PL2. As a result, the swing motor 41 rotates so as to swing the upper swing body 14 in a direction (right swing direction or left swing direction) corresponding to the opening direction of the swing control valve 51 at a speed corresponding to the magnitude of the swing pilot pressure.

[0049] The boom control valve 52 is interposed between the first pump 40A and the boom cylinder 42. The boom control valve 52 has a boom-raising pilot port 52a shown in FIG. 3 and a boom-lowering pilot port (not shown) on the opposite side. When pilot pressure is not supplied to either the boom-raising pilot port 52a or the boom-lowering pilot port, the boom control valve 52 maintains a neutral state, fully opens the first center bypass line CL1, and blocks communication between the first pump 40A and the boom cylinder 42. On the other hand, when pilot pressure, i.e., boom pilot pressure (boom-raising pilot pressure or boom-lowering pilot pressure), is supplied to either the boom-raising pilot port 52a or the boom-lowering pilot port, the boom control valve 52 opens to an opening degree corresponding to the magnitude of the boom pilot pressure in a direction corresponding to the pilot port to which the boom pilot pressure is supplied, thereby forming an oil supply path that allows hydraulic oil to be supplied to the boom cylinder 42 via the first parallel supply line PL1. As a result, the boom cylinder 42 extends and retracts to raise and lower the boom 26 in a direction corresponding to the opening direction of the boom control valve 52 (boom-up direction or boom-down direction) at a speed corresponding to the magnitude of the boom pilot pressure.

[0050] The boom-raising acceleration control valve 53 is a control valve for accelerating the boom-raising operation and is interposed between the second pump 40B and the boom cylinder 42. The boom-raising acceleration control valve 53 has a boom-raising acceleration pilot port 53a shown in FIG. 3, and when the pilot pressure supplied to the boom-raising acceleration pilot port 53a is equal to or lower than a certain level (including when no pilot pressure is supplied), the boom-raising acceleration control valve 53 maintains a neutral state, fully opens the second center bypass line CL2, and blocks communication between the second pump 40B and the boom cylinder 42. On the other hand, when a pilot pressure (boom-raising acceleration pilot pressure) equal to or higher than a certain level is supplied to the boom-raising acceleration pilot port 53a, the boom-raising acceleration control valve 53 opens to an opening corresponding to the magnitude of the boom-raising acceleration pilot pressure, forming an oil supply path that allows hydraulic oil to be supplied to the boom cylinder 42 via the first parallel supply line PL1 in addition to the hydraulic oil supplied from the boom control valve 52 to the boom cylinder 42 (i.e., the hydraulic oil flows together). As a result, the speed of the boom raising operation caused by the extension operation of the boom cylinder 42 is increased by an amount corresponding to the magnitude of the boom raising acceleration pilot pressure.

[0051] The arm control valve 54 is interposed between the second pump 40B and the arm cylinder 44. The arm control valve 54 has an arm pull pilot port 54a shown in FIG. 3 and an arm push pilot port (not shown) on the opposite side. When pilot pressure is not supplied to either the arm pull pilot port 54a or the arm push pilot port, the arm control valve 54 maintains a neutral state and fully opens the second center bypass line CL2 while blocking communication between the second pump 40B and the arm cylinder 44. On the other hand, when pilot pressure, i.e., arm pilot pressure (arm pull pilot pressure or arm push pilot pressure), is supplied to either the arm pull pilot port 54a or the arm push pilot port, the arm control valve 54 opens to an opening degree corresponding to the magnitude of the arm pilot pressure in a direction corresponding to the pilot port to which the arm pilot pressure is supplied, and forms a supply oil path that allows hydraulic oil to be supplied to the arm cylinder 44 through the second parallel supply line PL2. As a result, the arm cylinder 44 expands and contracts to rotate the arm 28 in a direction corresponding to the opening direction of the arm control valve 54 (arm pulling direction or arm pushing direction) at a speed corresponding to the magnitude of the arm pilot pressure.

[0052] The arm pull acceleration control valve 55 is a control valve for accelerating the arm pull operation, and is interposed between the first pump 40A and the arm cylinder 44. The arm pull acceleration control valve 55 has an arm pull acceleration pilot port 55a shown in Fig. 3, and when the pilot pressure supplied to the arm pull acceleration pilot port 55a is equal to or lower than a certain level (including when no pilot pressure is supplied), the arm pull acceleration control valve 55 maintains a neutral state, fully opens the first center bypass line CL1, and blocks communication between the first pump 40A and the arm cylinder 44. On the other hand, when a pilot pressure (arm pull acceleration pilot pressure) equal to or higher than a certain level is supplied to the arm pull acceleration pilot port 55a, the arm pull acceleration control valve 55 opens at an opening corresponding to the magnitude of the arm pull acceleration pilot pressure, and forms a supply oil path that allows hydraulic oil to be supplied to the arm cylinder 44 via the first parallel supply line PL1 in addition to the hydraulic oil supplied from the arm control valve 54 to the arm cylinder 44 (i.e., the flows join together). As a result, the speed of the arm pulling operation caused by the extension operation of the arm cylinder 44 is increased by an amount corresponding to the magnitude of the arm pulling acceleration pilot pressure.

[0053] The bucket swing control valve 58 is interposed between the second pump 40B and the bucket swing motor 48. The bucket swing control valve 58 has a bucket right swing pilot port 58a shown in FIG. 3 and a bucket left swing pilot port (not shown) on the opposite side. When pilot pressure is not supplied to either the bucket right swing pilot port 58a or the bucket left swing pilot port, the bucket swing control valve 58 maintains a neutral state and fully opens the second center bypass line CL2, while preventing the hydraulic oil discharged from the second pump 40B from being supplied to the bucket swing motor 48, thereby stopping the bucket swing motor 48. On the other hand, when pilot pressure, i.e., bucket swing pilot pressure (bucket right swing pilot pressure or bucket left swing pilot pressure), is supplied to either the bucket right swing pilot port 58a or the bucket left swing pilot port, the bucket swing control valve 58 opens in a direction corresponding to the pilot port to which the bucket swing pilot pressure is supplied, by an opening degree corresponding to the magnitude of the bucket swing pilot pressure, and forms a supply oil path that allows hydraulic oil to be supplied to the bucket swing motor 48 via the second parallel supply line PL2. As a result, the bucket swing motor 48 rotates to cause the bucket 30 to perform the bucket swing operation in a direction (bucket right swing direction or bucket left swing direction) corresponding to the valve opening direction of the bucket swing control valve 58, at a speed corresponding to the magnitude of the bucket swing pilot pressure.

[0054] Although not shown in Fig. 3, the plurality of control valves further include a pair of travel control valves and a bucket control valve. The pair of travel control valves are respectively interposed between the pair of travel motors and a hydraulic source that supplies hydraulic oil thereto, and the bucket control valve is interposed between the bucket cylinder 46 and a hydraulic source that supplies hydraulic oil thereto. The hydraulic sources for the pair of travel motors and the bucket cylinder 46 may be either the first or second pumps 40A, 40B shown in Fig. 3, or may be hydraulic pumps other than the first and second pumps 40A, 40B.

[0055] The plurality of operating devices are provided corresponding to the plurality of actuators, respectively, and allow operations for specifying the operating speeds of the respective actuators to be applied to the respective operating devices. Furthermore, each of the plurality of operating devices is configured to supply a pilot pressure of a magnitude corresponding to an operation amount, which is the amount of the operation, to a pilot port of a hydraulic actuator corresponding to the corresponding operating device among the plurality of hydraulic actuators.

[0056] In the example shown in FIG. 3 , the source of the pilot pressure, i.e., the pilot hydraulic source, is a pilot pump 40C, which, like the first and second pumps 40A and 40B, is driven by the engine 18 and discharges hydraulic oil for supplying the pilot pressure. Each of the multiple operating devices includes an operating member and a pilot valve. The operation can be applied to the operating member by an operator in the operator's cab 22. The operating member is, for example, a rotatable operating lever. In this case, the operation is an action of rotating the operating lever, and the amount of operation is the angle by which the operating lever rotates from a neutral position. The pilot valve is interposed between the pilot pump 40C, which is the pilot hydraulic source, and a corresponding actuator, which is a hydraulic actuator among the multiple hydraulic actuators that corresponds to the operating device, and opens so that a pilot pressure corresponding to the operation is applied to the corresponding actuator.

[0057] The plurality of operating devices include operating devices respectively corresponding to the hydraulic actuators shown in Fig. 3. Specifically, the plurality of operating devices include a swing operating device 61, a boom operating device 62, an arm operating device 64, and a bucket swing operating device 68 respectively corresponding to the swing motor 41, the boom cylinder 42, the arm cylinder 44, and the bucket swing motor 48.

[0058] The swing operation device 61 includes a swing lever, which is the operation lever, and a swing pilot valve, which is the pilot valve. An operator can apply a swing operation to the swing lever. The swing operation is an operation for specifying the operating speed of the swing motor 41 and therefore the swing speed of the upper swing body 14, and is a right swing operation for specifying the right swing speed of the upper swing body 14, or a left swing operation, which is an operation in the opposite direction to the right swing operation, for specifying the left swing speed of the upper swing body 14. When the right swing operation is applied to the swing lever, the swing pilot valve opens so that a right swing pilot pressure of a magnitude corresponding to the right swing operation amount, which is the amount of the right swing operation, is applied to the right swing pilot port 51a of the swing control valve 51. Conversely, when the left rotation operation is applied to the rotation lever, the rotation pilot valve opens so that a left rotation pilot pressure of a magnitude corresponding to the amount of left rotation operation, which is the amount of the left rotation operation, is applied to the left rotation pilot port of the rotation control valve 51.

[0059] The boom operation device 62 includes a boom lever serving as the operation lever and a boom pilot valve serving as the pilot valve. An operator can apply boom operation to the boom lever. The boom operation is an operation for specifying the extension / retraction speed of the boom cylinder 42 and, therefore, the speed of the boom hoisting operation of the boom 26, and can be a boom-raising operation for specifying the speed of the boom-raising operation, or a boom-lowering operation that is an operation in the opposite direction to the boom-raising operation for specifying the speed of the boom-lowering operation. When the boom-raising operation is applied to the boom lever, the boom pilot valve opens so that boom-raising pilot pressure of a magnitude corresponding to the boom-raising operation amount, which is the amount of the boom-raising operation, is applied to the boom-raising pilot port 52a and the boom-raising acceleration pilot port 53a of the boom control valve 52 and the boom-raising acceleration control valve 53. As described above, the boom-raising acceleration control valve 53 opens only when the pilot pressure applied to the boom-raising acceleration pilot port 53a, i.e., the boom-raising acceleration pilot pressure, is equal to or higher than a certain level (i.e., only when the boom-raising pilot pressure is equal to or higher than a certain level), and therefore the boom-raising operation is accelerated by opening the boom-raising acceleration control valve 53 only when the boom-raising operation amount is equal to or higher than a certain level, i.e., when the boom lever is operated greatly in the direction of the boom-raising operation. Conversely, when the boom-lowering operation is applied to the boom lever, the boom pilot valve opens so that a boom-lowering pilot pressure of a magnitude corresponding to the boom-lowering operation amount, which is the amount of the boom-lowering operation, is applied to the boom-lowering pilot port of the boom control valve 52.

[0060] The arm operating device 64 includes an arm lever serving as the operating lever and an arm pilot valve serving as the pilot valve. An operator can apply an arm operation to the arm lever. The arm operation is an operation for specifying the extension / retraction speed of the arm cylinder 44 and therefore the rotation speed of the arm 28, and is an arm pulling operation for specifying the speed of the arm pulling operation, or an arm pushing operation that is an operation in the opposite direction to the arm pulling operation for specifying the speed of the arm pushing operation. When the arm pulling operation is applied to the arm lever, the arm pilot valve opens so that an arm pulling pilot pressure of a magnitude corresponding to the arm pulling operation amount, which is the amount of the arm pulling operation, is applied to the arm pulling pilot port 54a and the arm pulling acceleration pilot port 55a of the arm control valve 54 and the arm pulling acceleration control valve 55. As described above, the arm pull acceleration control valve 55 opens only when the pilot pressure applied to the arm pull acceleration pilot port 53a, i.e., the arm pull acceleration pilot pressure, is equal to or greater than a certain level (i.e., when the arm pull pilot pressure is equal to or greater than a certain level), and therefore, only when the arm pull operation amount is equal to or greater than a certain level, i.e., when the arm lever is operated greatly in the direction of the arm pull operation, the arm pull operation is accelerated by opening the arm pull acceleration control valve 55. Conversely, when the arm push operation is applied to the arm lever, the arm pilot valve opens so that an arm push pilot pressure of a magnitude corresponding to the arm push operation amount, which is the amount of the arm push operation, is applied to the arm push pilot port of the arm control valve 54.

[0061] The bucket swing operation device 68 includes a bucket swing lever which is the operation lever, and a bucket swing pilot valve which is the pilot valve. An operator can apply a bucket swing operation to the bucket swing lever. The bucket swing operation is an operation for specifying the rotation speed of the bucket swing motor 48 and, by extension, the speed of the bucket swing operation of the bucket 30, and is a bucket right swing operation for specifying the bucket right swing speed of the bucket 30, or a bucket left swing operation which is an operation in the opposite direction to the bucket right swing operation and specifies the bucket left swing speed of the bucket 30. When the bucket right swing operation is applied to the bucket swing lever, the bucket swing pilot valve opens so that a bucket right swing pilot pressure of a magnitude corresponding to a bucket right swing operation amount, which is the amount of the bucket right swing operation, is applied to the bucket right swing pilot port 58a of the bucket swing control valve 58. Conversely, when the bucket left swing operation is applied to the bucket swing lever, the bucket swing pilot valve opens so that bucket left swing pilot pressure of a magnitude corresponding to the bucket left swing operation amount, which is the amount of the bucket left swing operation, is applied to the bucket left swing pilot port of the bucket swing control valve 58.

[0062] Although not shown in FIG. 3 , the multiple operation devices further include a travel operation device and a bucket operation device. The travel operation device is given an operation for specifying the rotational speed of the pair of travel motors and thus the operating speed of each of the pair of crawlers, i.e., a travel operation, and the travel operation device operates to allow a pilot pressure corresponding to the travel operation to be supplied to the pair of travel control valves. The bucket operation device is given an operation for specifying the extension / retraction speed of the bucket cylinder 46 and thus the speed of the bucket opening / closing operation of the bucket 30, i.e., a bucket opening / closing operation, and the bucket operation device operates to allow a pilot pressure corresponding to the bucket opening / closing operation to be supplied to the bucket control valve.

[0063] In this embodiment, the bucket rotation operation device 68 corresponds to a first operation device to which the bucket rotation operation, which is a first operation for specifying the rotation speed of the bucket rotation motor 48, which is the first actuator, is given, the arm operation device 64 corresponds to a second operation device to which the arm operation, which is a second operation for specifying the extension / retraction speed (operation speed) of the arm cylinder 44, which is the second actuator, is given, and the rotation operation device 61 corresponds to a third operation device to which the rotation operation, which is a third operation for specifying the rotation speed (operation speed) of the rotation motor 41, which is the third actuator, is given.

[0064] The multiple pressure sensors each detect pressure at a specific position in the hydraulic circuit shown in Fig. 3. Each of the multiple pressure sensors generates a pressure detection signal corresponding to the detected pressure and inputs the signal to the controller 80. The multiple pressure sensors include pressure sensors respectively corresponding to the operating devices shown in Fig. 3, i.e., first pump pressure sensor 70A, second pump pressure sensor 70B, right rotation pilot pressure sensor 71A, left rotation pilot pressure sensor 71B, boom-raising pilot pressure sensor 72A, boom-lowering pilot pressure sensor 72B, arm-pushing pilot pressure sensor 74A, arm-pushing pilot pressure sensor 74B, bucket-right-rotation pilot pressure sensor 78A, and bucket-left-rotation pilot pressure sensor 78B shown in Fig. 4.

[0065] The first pump pressure sensor 70A detects the pressure of the hydraulic oil discharged by the first pump 40A, i.e., a first pump pressure Pp1 which is the discharge pressure of the first pump 40A. Similarly, the second pump pressure sensor 70B detects the pressure of the hydraulic oil discharged by the second pump 40B, i.e., a second pump pressure Pp2 which is the discharge pressure of the second pump 40B.

[0066] The right turn pilot pressure sensor 71A detects the pilot pressure input from the swing operation device 61 to the right turn pilot port 51a of the swing control valve 51, i.e., the right turn pilot pressure Psr. Similarly, the left turn pilot pressure sensor 71B detects the pilot pressure input from the swing operation device 61 to the left turn pilot port of the swing control valve 51, i.e., the left turn pilot pressure Psl.

[0067] The boom-raising pilot pressure sensor 72A detects the pilot pressure input from the boom operating device 62 to the boom-raising pilot port 52a of the boom control valve 52 and the boom-raising acceleration pilot port 53a of the boom-raising acceleration control valve 53, i.e., boom-raising pilot pressure Pbr. Of these, the boom-raising pilot pressure Pbr input to the boom-raising acceleration pilot port 53a functions as a boom-raising acceleration pilot pressure. On the other hand, the boom-lowering pilot pressure sensor 72B detects the pilot pressure input from the boom operating device 62 to the boom-lowering pilot port of the boom control valve 52, i.e., boom-lowering pilot pressure Pbl.

[0068] The arm pulling pilot pressure sensor 74A detects the pilot pressure input from the arm operating device 64 to the arm pulling pilot port 54a of the arm control valve 54 and the arm pulling acceleration pilot port 55a of the arm pulling acceleration control valve 55, i.e., arm pulling pilot pressure Pac. Of these, the arm pulling pilot pressure Pac input to the arm pulling acceleration pilot port 55a functions as an arm pulling acceleration pilot pressure. On the other hand, the arm pushing pilot pressure sensor 74B detects the pilot pressure input from the arm operating device 64 to the arm pushing pilot port of the arm control valve 54, i.e., arm pushing pilot pressure Pad.

[0069] The bucket right rotation pilot pressure sensor 78A detects the pilot pressure input from the bucket rotation operating device 68 to the bucket right rotation pilot port 58a of the bucket rotation control valve 58, i.e., the bucket right rotation pilot pressure Ptr. Similarly, the bucket left rotation pilot pressure sensor 78B detects the pilot pressure input from the bucket rotation operating device 68 to the bucket right rotation pilot port 58a of the bucket rotation control valve 58, i.e., the bucket right rotation pilot pressure Ptr.

[0070] Although not shown in Fig. 4, the multiple pressure sensors include pilot pressure sensors corresponding to operation devices not shown in Fig. 3, specifically, a pair of travel pilot pressure sensors and a bucket opening / closing pilot pressure sensor. The pair of travel pilot pressure sensors detect pilot pressures input from the travel operation devices not shown to the pair of travel control valves, i.e., travel pilot pressures. Similarly, the bucket opening / closing pilot pressure sensor detects pilot pressures input from the bucket opening / closing operation devices not shown to the bucket control valves, i.e., bucket opening / closing pilot pressures.

[0071] Each of the pilot pressure sensors described above functions as an operation detector that detects the direction (e.g., arm pull or arm push) of the operation (e.g., the arm operation) applied to each of the multiple operating devices and the operation amount (e.g., arm pull operation amount or arm push operation amount), which is the amount of operation.

[0072] The controller 80 controls the first pump flow rate F1 and the second pump flow rate F2, i.e., pump flow rate control, based on pressure detection signals input from the plurality of pressure sensors. The first pump flow rate F1 is the flow rate of hydraulic oil discharged from the first pump 40A, and the second pump flow rate F2 is the flow rate of hydraulic oil discharged from the second pump 40B. The controller 80 performs the pump flow rate control by manipulating the first and second pump capacities of the first and second pumps 40A, 40B.

[0073] The controller 80 is configured by, for example, a computer mounted on the hydraulic excavator 10, and includes a storage unit 82 and an arithmetic unit 84 shown in Fig. 4. The storage unit 82 stores data necessary for executing the pump flow rate control and data calculated during control execution. The arithmetic unit 84 generates a first pump displacement command signal and a second pump displacement command signal, which are the pump displacement command signals for the first and second pumps 40A, 40B, respectively, based on the data stored in the storage unit 82 and detection signals input from the outside, and inputs the first and second pump displacement command signals to the regulators of the first and second pumps 40A, 40B, respectively.

[0074] As the pump displacement control, the controller 80 according to this embodiment performs the following positive control and horsepower control.

[0075] The positive control is a control for manipulating the first and second pump capacities so as to increase the pump flow rate (the first pump flow rate F1 or the second pump flow rate F2) of the hydraulic pump related to the operation, out of the first pump 40A and the second pump 40B, as the amount of operation applied to each of the plurality of operating devices, i.e., the operation amount, increases. Specifically, for the positive control, the controller 80 performs the following operations.

[0076] (1) Acquisition of each operation amount The controller 80 acquires an operation amount L, which is the amount of operation applied to each of the plurality of operation devices, from the detection signals input from each of the plurality of pilot pressure sensors, i.e., pilot pressure detection signals. For example, the calculation unit 84 of the controller 80 calculates an arm pull operation amount Lac, which is the amount of the arm pull operation of the arm operation applied to the arm operating device 64, based on the arm pull pilot pressure detection signal input from the arm pull pilot pressure sensor 74A.

[0077] (2) Calculation of target pump flow rate by operation The controller 80 calculates an operation-specific target pump flow rate Ft based on the operation amount L acquired for each of the plurality of operation devices. The operation-specific target pump flow rate Ft is a target pump flow rate calculated for each of the plurality of operation devices, and is calculated so as to increase as the operation amount L of the operation device increases.

[0078] In order to determine the operation-specific target pump flow rate Ft, the memory unit 82 of the controller 80 stores pre-prepared target pump flow rate data (maps, tables, relational expressions, etc.) regarding the relationship between the operation amount L and the operation-specific target pump flow rate Ft, and the calculation unit 84 calculates the operation-specific target pump flow rate Ft corresponding to the operations given to the plurality of operating devices, based on the target pump flow rate data.

[0079] 5 shows an example of a relationship that is set between the manipulated variable L and the operation-specific target pump flow rate Ft. In this example, when the manipulated variable L is in a range that is less than a first operation threshold L1, the operation-specific target pump flow rate Ft is set to a minimum flow rate Ftmin, when the manipulated variable L is in a range that is equal to or greater than the first operation threshold L1 and less than a second operation threshold L2 (>L1), the operation-specific target pump flow rate Ft is set so that the operation-specific target pump flow rate Ft increases from the minimum flow rate Ftmin to a maximum flow rate Ftmax (>Ftmin) as the manipulated variable L increases, and when the manipulated variable L is in a range that is equal to or greater than the second operation threshold L2, the operation-specific target pump flow rate Ft is set to the maximum flow rate Ftmax.

[0080] The relationship between the manipulated variable L and the operation-specific target pump flow rate Ft is not limited to the example shown in Fig. 5. For example, the relationship may be such that the operation-specific target pump flow rate Ft increases in a curved manner (rather than linearly as shown in Fig. 5) as the manipulated variable L increases. Furthermore, the relationship may be common to the multiple operating devices, or a different relationship may be set for each operating device. For example, the relationship between the arm operating variable La and the corresponding operation-specific target pump flow rate Ft may be the same as or different from the relationship between the swing operating variable Ls and the corresponding operation-specific target pump flow rate Ft.

[0081] (3) Calculation of target pump flow rate for PC The controller 80 calculates a target pump flow rate for PC, which is a final target pump flow rate for positive control, for each of the first and second pumps 40A, 40B based on the operation-specific target pump flow rate Ft determined for each of the multiple operating devices.

[0082] Specifically, the target pump flow rate for PC of the first pump 40A is calculated based on the target pump flow rate for each operation Ft corresponding to the operation amount L of the operation given to the hydraulic actuator among the plurality of hydraulic actuators that basically receives hydraulic oil supply from the first pump 40A.

[0083] In the example shown in FIG. 3, the target pump flow rate for PC of the first pump 40A is calculated (for example, to a flow rate equivalent to the operation-specific target pump flow rate Ft corresponding to the boom-raising operation amount Lbr) based on the boom operation amount Lb, which is the operation amount (boom-raising operation or boom-lowering operation) applied to the boom cylinder 42 of the multiple hydraulic actuators.

[0084] On the other hand, the target pump flow rate for PC of the second pump 40B is calculated based on the sum of the operation-specific target pump flow rates Ft corresponding to the operation amounts L of operations applied to the hydraulic actuators (the bucket swing motor 48, the arm cylinder 44, and the swing motor 41 in the example shown in FIG. 3) among the plurality of hydraulic actuators that basically receive a supply of hydraulic oil from the second pump 40B. For example, during a so-called combined operation in which an arm operation (arm pulling operation or arm pushing operation) is applied to the arm operating device 64 and at the same time a swing operation (right swing operation or left swing operation) is applied to the swing operation device 61, the target pump flow rate for PC of the second pump 40B is calculated based on the sum of the arm operation amount La which is the amount of the arm operation and the swing operation amount Ls which is the amount of the swing operation.

[0085] More specifically, the PC target pump flow rate of the second pump 40B may be set to a value equal to the sum of the operation-specific target pump flow rates Ft, or may be set to a flow rate smaller than the sum. As an example of the latter, the PC target pump flow rate may be set to any of (i) a value obtained by subtracting a certain flow rate value from the sum, (ii) a value obtained by multiplying the sum by a coefficient less than 1, or (iii) a value equal to the sum of flow rate values ​​obtained by multiplying each of the operation-specific target pump flow rates by a coefficient less than 1.

[0086] (4) Flow rate change suppression control during bucket swing operation As a feature of this device, when a bucket rotation operation is applied to bucket rotation operation device 68, which corresponds to the "first operation device" in this embodiment, controller 80 executes the following flow rate change suppression control.

[0087] First, of the operating devices related to the control of the second pump flow rate F2, specifically, the bucket swing operation device 68, the arm operation device 64, and the swing operation device 61, which correspond to the first, second, and third operation devices, respectively, when operation is being applied only to the bucket swing operation device 68, in other words, when only the bucket swing operation of the bucket swing operation (first operation), the arm operation (second operation), and the swing operation (third operation) is being performed, the controller 80 calculates the target pump flow rate for PC as usual so as to immediately (i.e., without any intentional delay) increase or decrease the target pump flow rate for PC in response to an increase or decrease in the bucket swing operation amount Lbt, which is the operation amount of the bucket swing operation.

[0088] In contrast, during a combined operation in which at least one of the arm operation (second operation) and the swing operation (third operation) is applied in addition to the bucket swing operation (first operation), the controller 80 executes the flow rate change suppression control. The flow rate change suppression control is control that slows the response of the PC target pump flow rate to a change in the bucket swing operation amount Lbt to a greater extent as the amount of the second operation and / or third operation (the arm operation and / or the swing operation) applied in addition to the bucket swing operation, which is the first operation, i.e., the second operation amount and / or the third operation amount (the arm operation amount La and / or the swing operation amount Ls) becomes smaller. In other words, the controller 80 executes control to reduce the responsiveness of the PC target pump flow rate to a degree corresponding to the arm operation amount La and the swing operation amount Ls, rather than immediately increasing or decreasing the PC target pump flow rate in response to an increase or decrease in the bucket swing operation amount Lbt.

[0089] In this embodiment, in order to perform the flow rate change suppression control, the controller 80 determines an arm operation flow rate change gain Ga and a swing operation flow rate change gain Gs, respectively, based on the arm operation amount La and the swing operation amount Ls, as shown in Figures 6 and 7. These flow rate change gains Ga and Gs are values ​​corresponding to the rate of change per unit time of the target pump flow rate for PC, i.e., the rate of change over time, and therefore, the smaller the flow rate change gains Ga and Gs, the more control is executed to dampen the increase or decrease in the target pump flow rate for PC in response to an increase or decrease in the arm operation amount La and the swing operation amount Ls.

[0090] In the example shown by the solid line in Figure 6, (i) when the arm operation amount La is in a range below a first arm operation threshold La1, the flow rate change gain Ga during arm operation is set to a minimum gain Gamin, (ii) when the arm operation amount La is in a range above the first arm operation threshold La1 and below a second arm operation threshold La2 (>La1), the flow rate change gain Ga during arm operation is set so that the flow rate change gain Ga during arm operation increases from the minimum gain Gamin to a maximum gain Gamax (>Gamin) as the arm operation amount La increases, and (iii) when the arm operation amount La is in a range above the second arm operation threshold La2, the flow rate change gain Ga during arm operation is set to the maximum gain Gamax.

[0091] 6 may be common to both the arm pulling operation and the arm pushing operation, or may be applied to only one and a different characteristic may be given to the other. In this embodiment, even for the same arm operation amount La, the characteristics of both are set so that the flow rate change gain during arm operation Ga (hereinafter referred to as "flow rate change gain during arm pushing operation Gad") corresponding to the arm pushing operation amount Lad is smaller than the flow rate change gain during arm operation Ga (hereinafter referred to as "flow rate change gain during arm pulling operation Gac") corresponding to the arm pulling operation amount Lac. The reason for this is that in the arm cylinder 44 which is a hydraulic cylinder, the pressure-receiving area of ​​the piston in the head-side chamber to which hydraulic oil is supplied during the extension operation is larger than the pressure-receiving area of ​​the piston in the rod-side chamber to which hydraulic oil is supplied during the retraction operation, and therefore the speed of the extension operation corresponding to the flow rate of hydraulic oil supplied is slower than the speed of the retraction operation. That is, the arm cylinder 44 causes the arm 28 to perform the arm-pushing operation by extending the arm cylinder 44, and conversely causes the arm 28 to perform the arm-pushing operation by retracting the arm cylinder 44, so even if the supply flow rate of hydraulic oil is the same, the response of the retracting operation of the arm cylinder 44 to the arm-pushing operation is more sensitive than the response of the extending operation of the arm cylinder 44 to the arm-pushing operation. Therefore, by making the degree of slowing down the response of the target pump flow rate for PC to the arm-pushing operation amount Lad greater than the degree of slowing down the response of the target pump flow rate for PC to the arm-pushing operation amount Lad, it is possible to equalize the responsiveness of the target pump flow rate for PC to changes in the arm operation amount Lac for the arm-pushing operation and the arm-pushing operation.

[0092] Various characteristics can be set to make the arm pushing operation flow rate change gain Gad smaller than the arm pulling operation flow rate change gain Gac. For example, when the characteristic of the arm pulling operation flow rate change gain Gac is the characteristic shown by the solid line in Fig. 6, the characteristic of the arm pushing operation flow rate change gain Gad can be set to, for example, the characteristics shown by the two-dot chain lines 91, 92, and 93 in Fig. 6. The characteristic shown by the two-dot chain line 91 has a gradient smaller than the gradient of the characteristic shown by the solid line in Fig. 6 in the operation range from the first arm operation threshold La1 to the second arm operation threshold La2. In the characteristic shown by the two-dot chain line 92, the arm operation amount La for the arm operation flow rate change gain Ga to rise from the minimum gain Gamin is larger than the first arm operation threshold La1 (i.e., the range in which the minimum gain Gamin is maintained is larger than the characteristic shown by the solid line). In the characteristic indicated by the two-dot chain line 93, the portion corresponding to the operation range from the first arm operation threshold La1 to the second arm operation threshold La2 is a curve that bulges downward compared to the characteristic indicated by the solid line in Figure 6.

[0093] Similar to the example shown by the solid line in Figure 6, in the example shown in Figure 7, (i) when the turning operation amount Ls is in the range where it is less than the first turning operation threshold Ls1, the flow rate change gain Gs during the turning operation is set to the minimum gain Gsmin, (ii) when the turning operation amount Ls is in the range where it is equal to or greater than the first turning operation threshold Ls1 and less than the second turning operation threshold Ls2 (>Ls1), the flow rate change gain Gs during the turning operation is set so that the flow rate change gain Gs during the turning operation increases from the minimum gain Gsmin to the maximum gain Gsmax (>Gsmin) as the turning operation amount Ls increases, and (iii) when the turning operation amount Ls is in the range where it is equal to or greater than the second turning operation threshold Ls2, the flow rate change gain Gs during the turning operation is set to the maximum gain Gsmax.

[0094] The relationships between the arm operation amount La and the swing operation amount Ls and the flow rate change gains Ga and Gs are not limited to the examples shown in Figures 6 and 7. For example, the relationships may be such that the flow rate change gains Ga and Gs increase in a curved manner (rather than linearly as shown in Figures 6 and 7) as the operation amounts La and Ls increase. Furthermore, the relationships shown in Figures 6 and 7 may be the same as each other or may be different from each other.

[0095] The storage unit 82 of the controller 80 stores flow rate change gain data, which is data on the relationship between the operation amount and the flow rate change gain, in the form of a map, table, relational expression, or other format, as shown in Figures 6 and 7. The calculation unit 84 of the controller 80 calculates an arm operation flow rate change gain Ga and a swing operation flow rate change gain Gs corresponding to the current arm operation amount La and swing operation amount Ls, respectively, based on the flow rate change gain data, and determines the amount of change in the target pump flow rate for PC relative to the amount of change in the bucket swing operation amount Lbt, based on the elapsed time from when the bucket swing operation amount Lbt started to increase or decrease and the flow rate change gains Ga and Gs. In other words, the larger the flow rate change gains Ga and Gs, the faster the change in the target pump flow rate for PC is made to follow the change in the bucket swing operation amount Lbt (i.e., the smaller the flow rate change gains Ga and Gs, the slower the change in the target pump flow rate for PC is made to follow the change in the bucket swing operation amount Lbt).

[0096] When both the arm operation and the swing operation are being performed simultaneously in addition to the bucket swing operation, a final gain, which is a flow rate change gain that is ultimately applied to the flow rate change suppression control, is determined based on both the arm operation flow rate change gain Ga and the swing operation flow rate change gain Gs. A specific method for determining the final flow rate change gain is not limited. The final flow rate change gain is preferably determined based on the sum of both flow rate change gains Ga and Gs. Alternatively, the final flow rate change gain may be set to the smaller of the flow rate change gains Ga and Gs so as to prioritize the more suppressed operation (the operation with a smaller amount of operation) of the second and third operations (the arm operation and the swing operation in this embodiment), or may be determined based on the average value of both flow rate change gains Ga and Gs.

[0097] On the other hand, the horsepower control is a control that limits the first and second pump flow rates so as to prevent the pump horsepower, which is the horsepower required to drive the first and second pumps 40A, 40B, from exceeding an upper limit horsepower determined based on the engine speed. Specifically, for the horsepower control, the controller 80 calculates a target pump flow rate for HPC (for horsepower control) based on the first and second pump pressures Pp1, Pp2 detected by the first and second pump pressure sensors 70A, 70B to keep the pump horsepower below the upper limit horsepower, compares the calculated target pump flow rate for PC with the target pump flow rate for HPC and selects the smaller target pump flow rate as the final target pump flow rate, and generates a first pump displacement command signal and a second pump displacement command signal to realize the first and second pump displacements, respectively, to obtain the selected final target pump flow rates and inputs them to the regulators of the first and second pumps 40A, 40B.

[0098] Fig. 8 shows the process for controlling the second pump flow rate, which is performed by the controller 80. The process shown in Fig. 8 is repeated at a fixed control cycle.

[0099] The controller 80 determines whether or not the operations related to the control of the second pump flow rate F2, that is, the arm operation, the swing operation, and the bucket operation, which correspond to the second operation, the third operation, and the first operation in this embodiment, are being performed among the operations related to the multiple hydraulic actuators (steps S10, S12, S14).

[0100] When the controller 80 determines that at least one of the arm operation and the swing operation is being performed (YES in step S10 or YES in step S12) but that the bucket swing operation is not being performed (NO in step S14), it calculates a target pump flow rate for PC to perform normal positive control without suppressing flow rate changes (i.e., without suppressing the time rate of change of the second pump flow rate) (step S18). Similarly, when it determines that neither the arm operation nor the swing operation is being performed (NO in steps S10 and S12) but only the bucket swing operation is being performed (YES in step S14), it also calculates a target pump flow rate for PC to perform normal positive control (step S18). Therefore, in these cases, control is performed to increase or decrease the target pump flow rate for PC immediately (i.e., without any intentional delay) in response to increases or decreases in the amount of arm operation, the amount of swing operation, and the amount of bucket swing operation.

[0101] On the other hand, when at least one of the arm operation and the swing operation is being performed (YES in either step S10 or S12), if it is determined that the bucket swing operation is being performed (YES in step S16), the controller 80 determines a flow rate change gain for executing the flow rate change suppression control (step S20). For example, when the arm operation (arm pull operation or arm push operation) is being performed, the controller 80 determines an arm operation flow rate change gain Ga corresponding to an arm pull operation amount Lac or an arm push operation amount Lad. When the swing operation (right swing operation or left swing operation) is being performed, the controller 80 determines a swing operation flow rate change gain Gs corresponding to a right swing operation amount Lsr or a left swing operation amount Lsl. Furthermore, when both the arm operation and the swing operation are being performed, the controller 80 determines a final gain, which is a final flow rate change gain, based on both the arm operation flow rate change gain Ga and the swing operation flow rate change gain Gs.

[0102] Based on the flow rate change gain determined in this manner, the controller 80 further calculates a target pump flow rate for PC for executing the flow rate change suppression control (step S22). This calculation includes the flow rate change gain and the elapsed time from the start of change in the bucket swing operation amount as factors, and the smaller the flow rate change gain, the smaller the calculated target pump flow rate for PC will be, with a smaller time rate of change of the target pump flow rate for PC in response to changes in the bucket swing operation amount (i.e., a slower response).

[0103] Next, the controller 80 compares the target pump flow rate for PC calculated in step S18 or step S22 with the target pump flow rate for HPC for horsepower control to limit the pump horsepower to an upper limit horsepower or less (step S24). If the target pump flow rate for PC is equal to or less than the target pump flow rate for HPC (YES in step S24), the controller 80 calculates a second pump displacement, which is the pump displacement of the second pump 40B required to achieve the target pump flow rate, based on the target pump flow rate for PC and the engine speed, and generates a pump displacement command for achieving the second pump displacement and inputs it to the regulator of the second pump 40B (step S26). This executes normal control or positive control including the flow rate change suppression control. On the other hand, if the target pump flow rate for PC exceeds the target pump flow rate for HPC (NO in step S24), the controller 80 generates a pump displacement command corresponding to the target pump flow rate for HPC and inputs it to the regulator of the second pump 40B (step S28). As a result, horsepower control is executed to limit the pump horsepower to the upper limit horsepower or less regardless of the amount of operation.

[0104] The positive control (positive control including the flow rate change suppression control) performed as described above makes it possible to reduce the effect that an increase or decrease in the pump flow rate due to an increase or decrease in the first operation amount has on the speed adjustment in work in which the second operation and / or the third operation is suppressed and adjustment of the operating speed of the second actuator and / or the third actuator is important. Specifically, this control is particularly effective in work, such as horizontal pulling work, in which the bucket 30, which is a working member, is moved along a predetermined target work surface (for example, the target work surface St shown in FIG. 2), by at least one of an arm pulling operation or an arm pushing operation by the arm cylinder 44, which is the second actuator, and a swing operation by the swing motor 41, which is the third actuator. In such work, it is required to accurately move the bucket 30 along the target work surface while suppressing the movement speed of the bucket 30 by an operation that suppresses at least one of the arm operation amount and the swing operation amount (so-called half-lever operation), but if, for example, a bucket swing operation, which is the first operation, is performed to change the direction of the bucket 30 during the work and the second pump flow rate is increased by the positive control in instantaneous response to an increase in the bucket swing operation amount, the movement speed of the bucket 30 could change suddenly, which could significantly affect the accuracy of the work. In contrast, with the above-mentioned control, when the arm operation amount or the swing operation amount is small, the response of the second pump flow rate to changes in the bucket swing operation amount is slowed down, that is, the increase or decrease is delayed, thereby effectively suppressing the effect of the bucket swing operation on the accuracy of the work. On the other hand, when the work is completed or the like and the arm operating device 66 or the swing operating device 61 is operated to a large extent, that is, when the amount of arm operation or the amount of swing operation is large and it can be considered that the need for precise speed adjustment is low, the second pump flow rate can be made to quickly respond to changes in the amount of bucket swing operation, thereby quickly providing a pump flow rate that matches the requirements of each operation, as with a normal positive control, and preventing a decrease in work efficiency due to the slowdown in response.

[0105] 9 and 10 show an example of control of the first pump flow rate F1 and an example of control of the second pump flow rate F2 performed by the controller 80, respectively.

[0106] 9, when a boom-raising operation with a boom-raising operation amount Lbr1 is performed at time t1 for boom cylinder 42 that receives a supply of hydraulic oil from first pump 40A among the multiple hydraulic actuators, the first pump flow rate F1 is increased quickly, that is, at the maximum time change rate, from the minimum flow rate F1min by an amount corresponding to the boom-raising operation amount Lbr1 (to pump flow rate F11 in FIG. 9), as in normal positive control. This allows the first pump flow rate F1 (the pump flow rate F11) that corresponds to the speed request of the operator performing the boom-raising operation to be quickly provided.

[0107] On the other hand, as shown in Fig. 10, with respect to the arm cylinder 44 among the plurality of hydraulic actuators that receives a supply of hydraulic oil from the second pump 40B, when an arm pulling operation is performed at time t2 with an operation amount Lac2, that is, an operation with a relatively small arm pulling operation amount Lac (for example, a half-lever operation), the second pump flow rate F2 is quickly increased from the minimum flow rate F2min by an amount corresponding to the arm pulling operation amount Lac2 (to a pump flow rate F22 in Fig. 9), as in the normal positive control. Thereafter, when the arm pulling operation is performed further deeply at time t3 and the arm pulling operation amount Lac is increased from the operation amount Lac2 to an even larger operation amount Lac3 (for example, a full-lever operation), the second pump flow rate F2 is further quickly increased to a pump flow rate F23 (>F22).

[0108] On the other hand, if the bucket swing operation is further performed during the arm retraction operation, as in the normal positive control, the second pump flow rate F2 is further increased from the pump flow rate corresponding to the arm retraction operation amount Lac (the pump flow rate F22 or the pump flow rate F23), but the time change rate of the increase in the second pump flow rate F2 (responsiveness to the bucket swing operation amount Lbt) varies depending on the arm retraction operation amount Lac.

[0109] Specifically, during period T2 (the period from time t2 to time t3) when the arm swing operation amount Lac is relatively small (the operation amount Lac2), when the bucket swing operation is performed at time t21 and the bucket swing operation amount Lbt is increased to the operation amount Lbt4, the second pump flow rate F2 is further increased from the flow rate F22 by an amount corresponding to the operation amount Lbt4. However, because the arm operation flow rate change gain Ga corresponding to the operation amount Lac2 is small, the time change rate of the increase (the slope in the lower graph in FIG. 10 ) is small. Therefore, the second pump flow rate F2 increases gradually in accordance with the bucket swing operation. Similarly, when the bucket swing operation is released at time t22 within period T2 (i.e., the bucket swing operation lever is returned to the neutral position), the second pump flow rate F2 is also returned to the flow rate F22 before the increase. However, because the arm operation flow rate change gain Ga is small, the second pump flow rate F2 gradually decreases to the second pump flow rate F22. Such a slower response (increase / decrease) of the second pump flow rate F2 to an increase / decrease in the bucket rotation operation amount Lbt gives the operator some leeway to deal with an increase / decrease in the second pump flow rate F2 resulting from the bucket rotation operation, thereby making it possible to maintain a high level of accuracy in the work performed by the arm pulling operation (for example, horizontal pulling work) regardless of the bucket rotation operation.

[0110] In contrast, during period T3 (the period after time t3) when the arm pull operation amount Lac is the large operation amount Lac3, when the bucket swing operation is performed at time t31 and the bucket swing operation amount Lbt is increased to the operation amount Lbt4, the same as in period T2, the second pump flow rate F2 is further increased from the flow rate F23. However, because the arm operation flow rate change gain Ga corresponding to the operation amount Lac3 is large, the time change rate of the increase is large, and therefore the second pump flow rate F2 increases quickly as the bucket swing operation amount Lbt increases. Similarly, the second pump flow rate F2 decreases quickly as the bucket swing operation amount Lbt decreases from time t32. This rapid response (increase / decrease) of the second pump flow rate F2 to the increase / decrease in the bucket swing operation amount Lbt makes it possible to quickly provide a bucket swing operation that meets the request of the operator performing the bucket swing operation, thereby preventing a decrease in work efficiency. This also applies to the case where the bucket swing operation is performed independently during the period T1 (the period up to time t2) when the arm pulling operation is not performed.

[0111] 10, control is performed to slow down both the increase in the second pump flow rate F2 in response to an increase in the bucket swing operation amount Lbt, which is the first operation amount, and the decrease in the second pump flow rate F2 in response to a decrease in the bucket swing operation amount Lbt, but control may be performed to slow down only one of the increase or decrease. For example, even by using the former mode, i.e., the mode in which only the increase in the second pump flow rate F2 in response to an increase in the bucket swing operation amount Lbt, it is possible to suppress a sudden increase in the operating speed of the bucket swing motor 48 that accompanies an increase in the second pump flow rate F2 (i.e., a sudden increase in the speed of the bucket swing operation), and thereby reduce the impact on work accuracy.

[0112] The present invention is not limited to the above-described embodiment, but includes the following aspects, for example.

[0113] (Regarding the first to third actuators and the first to third operations) The first to third actuators in the present invention are not limited to the bucket swing motor 48, the arm cylinder 44, and the swing motor 41 according to the above embodiment, and therefore the first to third operations are not limited to the bucket swing operation, the arm operation, and the swing operation. The first actuator may be a hydraulic actuator included in an optional device other than the optional device (so-called tiltrotator) including the bucket swing motor 48, such as an opening / closing cylinder that opens and closes a pair of crushing blades of a crusher, or it may be a hydraulic actuator other than the hydraulic actuator included in the optional device, such as the bucket cylinder 46 or the boom cylinder 42 according to the above embodiment. In either case, the present invention can be effectively applied, particularly to work that requires moving a movable part at a low speed by suppressing the second operation amount (or the third operation amount).

[0114] In the present invention, the third actuator and the corresponding third operation device that affect the flow rate change gain are optional elements. For example, in the above-described embodiment, the flow rate change gain may be determined based only on the arm operation amount La, regardless of the swing operation amount Ls. In other words, the swing motor 41 and the swing operation device 61 according to the above-described embodiment do not necessarily correspond to the third actuator according to the present invention.

[0115] (Regarding slow response of pump flow rate) In the present invention, the method for slowing the response of the pump flow rate to an increase or decrease in the first manipulated variable is not limited to setting a flow rate change gain as described above. For example, control may be performed such that the timing at which the pump flow rate starts to change is delayed as the second manipulated variable (or the third manipulated variable) increases. Alternatively, flow rate change suppression control may be performed such that the time rate of change of the pump flow rate gradually increases over time after the first manipulated variable starts to increase or decrease.

[0116] (Regarding the first to third operating devices) The first to third operating devices according to the present invention are not limited to those that output pilot pressures corresponding to the amount of operation, as in the operating devices according to the above-described embodiments. Each of the first to third operating devices according to the present invention may be, for example, an electric lever device, i.e., a device that generates and outputs an electric signal (operation signal) corresponding to the direction and magnitude (operation amount) of an operation applied to an operating lever. In this case, an operation detector for detecting each of the first to third operations is an operation detection element (e.g., a potentiometer that detects the rotation angle of the lever) built into the electric lever device, and the pilot pressure sensor is not necessarily required. Furthermore, the controller 80 can input appropriate command signals to solenoid valves (e.g., electromagnetic proportional pressure reducing valves) interposed between the plurality of control valves and the pilot hydraulic source, thereby controlling the opening of each of the plurality of control valves at an opening corresponding to the operation signals output from the electric lever device and controlling the pump flow rate based on the operation signals.

[0117] Furthermore, at least some of the multiple operating devices may be provided outside the work machine rather than inside the work machine (for example, the operator's cab 22 of the hydraulic excavator 10) to form a remote control device. For example, at least some of the multiple operating devices may be formed by the electric lever device and have a function of transmitting an operating signal, and the controller may have a function of receiving the operating signal.

[0118] (Regarding pump flow control) The pump flow rate control according to the present invention is sufficient as long as it includes at least control (e.g., positive control) that increases or decreases the pump flow rate in response to an increase or decrease in the manipulated variable, and other control (e.g., horsepower control according to the above-described embodiment) may be performed as desired. For example, the horsepower control may be omitted, or control other than horsepower (e.g., load sensing control) may be performed in addition to the positive control. Furthermore, if a work machine is equipped with multiple hydraulic pumps (e.g., the first and second pumps 40A, 40B according to the above-described embodiment), the pump flow rate control according to the present invention may be applied to each of two or more of the multiple hydraulic pumps.

[0119] (About work machines) The work machine to which the hydraulic drive system according to the present invention is applied is not limited to the hydraulic excavator 10. The present invention can also be applied to, for example, the lifting and lowering of a suspended load and the raising and lowering of a jib in a hydraulic crane, the operation of a blade in a bulldozer, and the movement of a gondola in an aerial work vehicle. [Explanation of symbols]

[0120] 10. Hydraulic excavator 12 Undercarriage 14 Upper rotating body (third section) 16 Working Arm 18 Engine 26 Boom 28 Arm (second part) 30 Bucket (working part) 40B Second pump (variable displacement hydraulic pump) 41 Swing motor (third actuator) 44 Arm cylinder (second actuator) 48 Bucket rotation motor (first actuator) 61 Swing operation device (third operation device) 64 Arm operating device (second operating device) 68 Bucket rotation operation device (first operation device) 80 Controller

Claims

1. A hydraulic drive device for hydraulically moving a movable part of a work machine, A variable displacement hydraulic pump; a first actuator that receives hydraulic oil from the hydraulic pump and moves a first part of the work machine; a second actuator that receives hydraulic oil from the hydraulic pump and moves a second part of the work machine; a first operating device to which a first operation for specifying an operating speed of the first actuator is applied; a second operating device to which a second operation is given for specifying an operating speed of the second actuator; a controller that performs pump flow rate control that operates the displacement of the hydraulic pump so as to increase a pump flow rate that is a discharge flow rate of the hydraulic pump in accordance with an increase in a first operation amount that is an amount of the first operation and an increase in a second operation amount that is an amount of the second operation, The pump flow rate control includes, during a combined operation in which the first operation and the second operation are applied to the first operating device and the second operating device, respectively, slowing the response of the pump flow rate to a change in the first operating amount to a greater extent as the second operating amount is smaller.

2. 2. The hydraulic drive system according to claim 1, wherein the controller determines a second operation flow rate change gain that increases as the second operation amount increases based on the second operation amount, and increases a time rate of change of the pump flow rate with respect to a change in the first operation amount as the second operation flow rate change gain increases.

3. 2. The hydraulic drive system according to claim 1, wherein the second operation includes an operation in a first direction and an operation in a second direction different from the first direction, and the controller increases the degree to which the response of the pump flow rate is slowed down in response to the second operation amount in the second direction compared to the degree to which the response of the pump flow rate is slowed down in response to the second operation amount in the first direction.

4. 4. The hydraulic drive system according to claim 3, wherein the controller determines a second during-operation flow rate change gain that increases as the second operation amount increases based on the second operation amount, increases a time rate of change of the pump flow rate with respect to a change in the first operation amount as the second operation amount increases, and determines the second during-operation flow rate change gain corresponding to the second operation amount in the second direction to be a gain smaller than the second during-operation flow rate change gain corresponding to the second operation amount in the first direction.

5. 4. The hydraulic drive system according to claim 3, wherein the second actuator is a hydraulic cylinder that can be extended and contracted by movement of a piston, a pressure-receiving area of ​​the piston for extending the hydraulic cylinder is larger than a pressure-receiving area of ​​the piston for contracting the hydraulic cylinder, the operation in the first direction is an operation for extending the hydraulic cylinder, and the operation in the second direction is an operation for contracting the hydraulic cylinder.

6. The hydraulic drive system according to claim 1, a third actuator that receives a supply of hydraulic oil from the hydraulic pump and moves a third part of the work machine; and a third operating device to which a third operation is given for specifying an operating speed of the third actuator, wherein the controller increases the pump flow rate in accordance with each of an increase in the first operating amount, an increase in the second operating amount, and an increase in a third operating amount that is the amount of the third operation, and during a combined operation in which the first operation, the second operation, and the third operation are simultaneously given to the first operating device, the second operating device, and the third operating device, respectively, the controller slows down the response of the pump flow rate to a change in the first operating amount to a greater extent as the second operating amount is smaller and to a greater extent as the third operating amount is smaller.

7. 7. The hydraulic drive system according to claim 6, wherein the controller determines a third during-operation flow rate change gain that increases as the third operation amount increases based on the magnitude of the third operation amount, and increases a time rate of change of the pump flow rate in response to a change in the first operation amount as the second during-operation flow rate change gain and the third during-operation flow rate change gain become larger.

8. 8. The hydraulic drive system according to claim 7, wherein the controller determines a final gain based on the sum of the second operation flow rate change gain and the third operation flow rate change gain, and increases a time rate of change of the pump flow rate in response to a change in the first operation as the final gain increases.

9. 2. A hydraulic drive system according to claim 1, wherein the work machine comprises a machine body, a work arm attached to the machine body, and a work member attached to the tip of the work arm, the work arm operates to move the work member, the first actuator is a hydraulic actuator that moves the work member relative to the work arm, and the second actuator is a hydraulic actuator that moves the work arm.

10. 7. A hydraulic drive system according to claim 6, wherein the work machine comprises a lower traveling body, an upper rotating body rotatably mounted on the lower traveling body, a work arm attached to the upper rotating body, and a work member attached to the tip of the work arm, the work arm operates to move the work member, the first actuator is a hydraulic actuator that moves the work member relative to the work arm, the second actuator is a hydraulic actuator that moves the work arm, and the third actuator is a hydraulic actuator that rotates the upper rotating body relative to the lower traveling body.

11. A work machine, The hydraulic drive system according to claim 1; The aircraft and a working arm attached to the machine body; a working member attached to the tip of the working arm, the working arm operating to move the working member; A work machine wherein the first actuator is a hydraulic actuator that moves the work member relative to the work arm, and the second actuator is a hydraulic actuator that moves the work arm.

12. A work machine, The hydraulic drive system according to claim 6; a lower running body; an upper rotating body rotatably mounted on the lower traveling body; A working arm attached to the upper rotating body; a working member attached to the tip of the working arm, the working arm operating to move the working member; a hydraulic actuator for moving the working member relative to the working arm, a hydraulic actuator for moving the working arm, and a hydraulic actuator for rotating the upper rotating body relative to the lower traveling body.

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