Hydraulic control system for working machine

Abstract

Problem: In a hydraulic control system including a prime mover, a plurality of variable displacement hydraulic pumps driven by the prime mover, and a plurality of hydraulic actuators driving the hydraulic pumps as hydraulic sources, merging of discharge oil of the hydraulic pumps is reduced so as to reduce a reduction in efficiency and operability caused by the merging. Solution: A controller (10) is provided to control the pump displacement of the hydraulic pumps (P1, P2) and the rotational speed of the prime mover (M), and the controller (10) is equipped with: a reference pump flow rate setting unit (61) that sets a reference pump flow rate; a target pump flow rate setting unit (64) that sets a target pump flow rate for each hydraulic pump (P1, P2) in accordance with the operation of the manipulator; and a pump flow rate control unit (65) that maximizes the pump displacement of any hydraulic pump (P1, P2) and increases the rotational speed of the prime mover (M) when the target pump flow rate of the hydraulic pump (P1, P2) exceeds the reference pump flow rate, thereby increasing the pump flow rate to be greater than the reference pump flow rate.

Description

Technical Field

[0001] The present invention relates to the technical field of hydraulic control systems used in working machines such as hydraulic excavators. Background Art

[0002] Typically, a working machine such as a hydraulic excavator is equipped with a prime mover such as an engine or an electric motor, a plurality of hydraulic pumps driven by the prime mover, and a plurality of hydraulic actuators using the hydraulic pumps as hydraulic sources. In such a hydraulic system, in the case of a large-flow hydraulic actuator (where the hydraulic actuator requires hydraulic oil supplied from a plurality of hydraulic pumps), or in the case of a compound operation (where the plurality of hydraulic actuators are operated simultaneously), the hydraulic oil from the plurality of hydraulic pumps may be merged to supply the hydraulic actuator, but in this case, the hydraulic interference caused by the merging may result in reduced efficiency or deterioration of operability. For example, when hydraulic oil from two hydraulic pumps is fed to a hydraulic actuator at different load pressures, efficiency is reduced because the discharge pressure of the two hydraulic pumps needs to be increased to the pressure of the hydraulic actuator on the high load side in order to avoid the hydraulic oil from flowing to the hydraulic actuator on the low load side.

[0003] On the other hand, there is a known technology as a technology for improving operability during compound operations, which determines the priority of the hydraulic oil supply order from the first hydraulic pump and the second hydraulic pump (front pump, rear pump) to each hydraulic actuator according to the combination of hydraulic actuators operating simultaneously, thereby independently controlling the hydraulic oil supply timing and the hydraulic oil supply amount (for example, refer to patent document 1).

[0004] There is also a technology that provides: a variable displacement first hydraulic pump, which is driven by an engine and supplies hydraulic oil to a first hydraulic actuator; a second hydraulic pump and a third hydraulic pump, which are driven by the engine via a continuously variable transmission and supply hydraulic oil to the second hydraulic actuator and the third hydraulic actuator, respectively; and a controller that changes the displacement of the first hydraulic pump and the speed ratio of each continuously variable transmission according to an operating amount (for example, see patent document 2).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: JPH 08-23768A

[0008] Patent Document 2: P 2016-205451A Summary of the invention

[0009] Problems to be solved by the present invention

[0010] However, the invention of Patent Document 1 is configured to supply hydraulic oil from both the first hydraulic pump and the second hydraulic pump to any hydraulic actuator that is operated simultaneously during a compound operation, and for a bucket cylinder that is supplied with hydraulic oil only from the first hydraulic pump during a single operation, hydraulic oil is supplied from the second hydraulic pump or from both the first hydraulic pump and the second hydraulic pump during the compound operation. In addition, for the boom cylinder and the arm cylinder that are large-flow hydraulic actuators, hydraulic oil is supplied from both the first hydraulic pump and the second hydraulic pump when the supply flow exceeds half of the maximum flow during the single operation. In other words, in Patent Document 1, the confluence of the discharge oil of the first hydraulic pump and the second hydraulic pump is frequently performed. Therefore, although it is impossible to avoid the reduction in efficiency and operability caused by the confluence, there is a problem that a circuit for supplying confluence oil to a hydraulic actuator that is not a large-flow actuator is required, and the circuit becomes complicated.

[0011] On the other hand, the invention of Patent Document 2 is constructed so that basically one hydraulic pump is used as the hydraulic supply source for one or two hydraulic actuators, that is, each hydraulic pump is individually constructed to be able to supply the maximum supply flow rate for one or two hydraulic actuators. For this purpose, a large-displacement hydraulic pump is required, and there are disadvantageous problems in terms of cost and space, which are problems to be solved by the present invention.

[0012] Means of solving the problem

[0013] In view of the above-mentioned reality, the present invention is designed to solve these problems. The invention described in claim 1 relates to a hydraulic control system for a working machine, wherein the hydraulic control system includes: a prime mover; a plurality of variable displacement hydraulic pumps, which are driven by the prime mover; a plurality of hydraulic actuators, which drive at least one of the hydraulic pumps as a hydraulic source; an operating member for each hydraulic actuator, which is operated to drive each hydraulic actuator; and a plurality of control valves, which control the supply of hydraulic oil from the hydraulic pump to each hydraulic actuator, and the hydraulic control system is equipped with a control device to control the actuation of the control valve, the pump displacement of the hydraulic pump and the rotational speed of the prime mover; wherein the control device includes: a reference pump flow setting member, when the pump displacement of the hydraulic pump is a maximum value and the rotational speed of the prime mover is pre-set At a reference speed, the reference pump flow setting component sets the pump flow of the hydraulic pump to a reference pump flow; a target pump flow setting component, according to the operation of the operating component for each hydraulic actuator, sets the target pump flow of each hydraulic pump within a range within which the pump flow of each hydraulic pump does not exceed a preset maximum pump flow; and a pump flow control component, when the target pump flow of any one of the hydraulic pumps set by the target pump flow setting component exceeds the reference pump flow, the pump flow control component maximizes the pump displacement of the one of the hydraulic pumps and increases the speed of the prime mover to greater than the reference speed, thereby increasing the pump flow of the one of the hydraulic pumps to greater than the reference pump flow.

[0014] The invention described in claim 2, wherein in claim 1, a first hydraulic pump and a second hydraulic pump as the hydraulic pump are included, and a large-flow hydraulic actuator as the hydraulic actuator is included, and hydraulic oil is supplied from both the first hydraulic pump and the second hydraulic pump to the large-flow hydraulic actuator when the maximum flow is supplied; a controller controls any one of the first hydraulic pump and the second hydraulic pump as a main pump, and supplies hydraulic oil only from the main pump until the flow supplied to the large-flow hydraulic actuator reaches a set flow, and when the operating component for the large-flow hydraulic actuator is operated alone, the set flow is set to exceed the reference flow, and when the flow exceeds the set flow, the hydraulic oil is supplied from both the first hydraulic pump and the second hydraulic pump; and according to the supply flow from the main pump to the large-flow hydraulic actuator, the target pump flow setting component sets the target pump flow of the main pump to exceed the reference pump flow.

[0015] The invention described in claim 3, wherein in claim 2, a first large-flow hydraulic actuator using the first hydraulic pump as the main pump is included, and a second large-flow hydraulic actuator using the second hydraulic pump as the main pump is included; when the operating components for the first large-flow hydraulic actuator and the second large-flow hydraulic actuator are operated simultaneously, the controller controls to supply the hydraulic oil from each main pump to the first large-flow hydraulic actuator and the second large-flow hydraulic actuator respectively; and according to the operation amount of the operating components for the first large-flow hydraulic actuator and the second large-flow hydraulic actuator, the target pump flow setting component sets the target pump flow of the first hydraulic pump and the second hydraulic pump for each hydraulic pump.

[0016] The invention described in claim 4, wherein in claim 1, the working machine includes: a traveling body, the traveling body having a left traveling body and a right traveling body; a working device, the working device being installed on the traveling body; a first hydraulic pump and a second hydraulic pump, the first hydraulic pump and the second hydraulic pump serving as the hydraulic pumps; a left traveling motor and a right traveling motor, the left traveling motor and the right traveling motor serving as the hydraulic actuators and driving the left traveling body and the right traveling body respectively; and a plurality of working hydraulic actuators, the plurality of working hydraulic actuators driving the working device; when the left traveling motor and the right traveling motor and the operating component for the working hydraulic actuator are operated simultaneously, the controller controls the control valve to supply the hydraulic oil from the first hydraulic pump to the left traveling hydraulic motor and the right traveling hydraulic motor, and to supply the hydraulic oil from the second hydraulic pump to the working hydraulic actuator; and the target pump flow setting component sets the target pump flow of the second hydraulic pump to be greater than the reference pump flow.

[0017] Effects of the Invention

[0018] According to the invention described in claim 1, it is possible to reduce the reduction in efficiency and operability and the complexity of the circuit caused by the confluence, and it is not necessary to provide a large-displacement hydraulic pump.

[0019] According to the invention described in claim 2, even for a large flow rate hydraulic actuator that is supplied with hydraulic oil from both the first hydraulic pump and the second hydraulic pump at the time of maximum flow rate supply, the frequency of confluence can be reduced.

[0020] According to the invention described in claim 3, when the first large-flow hydraulic actuator and the second large-flow hydraulic actuator are driven simultaneously, even if the large-flow hydraulic actuator is supplied with hydraulic oil from both the first hydraulic pump and the second hydraulic pump at the time of maximum flow supply, the confluence of the discharge oil of the first hydraulic pump and the second hydraulic pump can be eliminated.

[0021] According to the invention described in claim 4, hydraulic oil can be supplied to the left and right travel motors and the working hydraulic actuator independently without causing hydraulic interference with each other, and the flow rate supplied to the working hydraulic actuator can be greater than the reference pump flow rate, which can help improve working efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 1 is a hydraulic circuit diagram illustrating the first embodiment.

[0023] Figure 2 It is a side view of a hydraulic excavator.

[0024] Figure 3 is a block diagram illustrating the input / output of the controller.

[0025] Figure 4 It is a table diagram illustrating a setting example of a target pump flow rate.

[0026] Figure 5 It is a diagram illustrating the relationship between the operation amount of the manipulator, the target supply flow from the first hydraulic pump and the second hydraulic pump to the boom cylinder, the opening area of ​​the boom flow control valve and the opening area of ​​the supply valve channel for the boom reversing valve when the boom manipulator is operated alone.

[0027] Figure 6 2 is a hydraulic circuit diagram illustrating a second embodiment. DETAILED DESCRIPTION

[0028] Embodiments of the present invention will be described below with reference to the accompanying drawings.

[0029] first, Figure 1 FIG. 1 is a hydraulic circuit diagram illustrating a first embodiment of a hydraulic control system for a hydraulic excavator embodying the present invention. Figure 1 , M represents a prime mover; P1 and P2 represent variable displacement hydraulic pumps driven by the prime movers, respectively; P1a and P2a represent variable displacement members that change the displacement of the hydraulic pumps P1 and P2, respectively, based on control signals sent from a controller 10 mentioned later; 3 represents an oil tank; 4 represents a left travel motor; 5 represents a right travel motor; 6 represents a boom cylinder; 7 represents a slewing device motor; 8 represents an arm cylinder; and 9 represents a bucket cylinder. The left travel motor 4, the right travel motor 5, the boom cylinder 6, the slewing device motor 7, the arm cylinder 8, and the bucket cylinder 9 are hydraulic actuators that use the hydraulic pumps P1 and P2 as hydraulic supply sources. Among these hydraulic actuators, the boom cylinder 6 and the arm cylinder 8 are hydraulic actuators that use the two hydraulic pumps P1 and P2 as hydraulic supply sources, and correspond to the large flow hydraulic actuators of the present invention. Furthermore, in the present embodiment, an electric motor driven by power from a battery (not shown) is used as the prime mover M, and the drive shafts of the hydraulic pumps P1 and P2 are connected to the output shaft of the electric motor.

[0030] It should be noted that the hydraulic excavator 1 is an example of a working machine of the present invention, and Figure 2 As shown, the hydraulic excavator is constructed to include: a lower traveling body 71 having a left traveling body and a right traveling body driven by a left traveling motor 4 and a right traveling motor 5, respectively; an upper swinging body 72 pivotally supported by the lower traveling body 71 and pivotally driven by a slewing device motor 7; and a front working machine 73 mounted on the upper slewing device body 72. The front working machine 73 is constructed to include: a boom 74 vertically freely supported on the upper slewing device body 72 and driven by a boom cylinder 6; a dipper arm 75 swingably axially supported on the tip of the boom 74 and driven by a dipper arm cylinder 8; and a bucket 76 mounted on the tip of the dipper arm 75 and driven by a bucket cylinder 9. The lower traveling body 71 and the upper swinging body 72 constitute the traveling body of the present invention. Furthermore, the front working machine 73 corresponds to the working device of the present invention, and the boom cylinder 6 , the arm cylinder 8 , and the bucket cylinder 9 correspond to the working hydraulic actuator of the present invention.

[0031] The hydraulic pump P1 is connected to the pump line C via the straight travel valve 11 at the first position X mentioned later, and is connected to the left travel switching valve 13. In addition, the hydraulic pump P2 is connected to the pump line D, and is connected to the right travel switching valve 14 at the first position X via the straight travel valve 11.

[0032] The straight travel valve 11 is a two-position switching valve that switches to a first position X and a second position Y based on a control signal output from the controller 10. When the straight travel valve 11 is located at the first position X, the discharge oil of the hydraulic pump P1 is supplied to the pump line C and the left travel reversing valve 13, and the discharge oil of the hydraulic pump P2 is supplied to the pump line D and the right travel reversing valve 14. In addition, when the straight travel valve 11 is located at the second position Y, the discharge oil of the hydraulic pump P1 is supplied to both the left travel reversing valve 13 and the right travel reversing valve 14, and the discharge oil of the hydraulic pump P2 is supplied to both the pump lines C and D. Then, when only the left travel manipulator and the right travel manipulator (not shown) are operated, or when only other hydraulic actuator manipulators (boom, swing device, bucket manipulator, not shown) other than the travel manipulator are operated, the controller 10 controls the straight travel valve 11 to be located at the first position X. On the other hand, when both the left and right traveling operators are operated to perform straight travel and the other hydraulic actuator operators are operated at the same time, a control signal is output to switch the straight travel valve 11 to the second position Y. Therefore, when only the left and right traveling operators are operated and the straight travel valve 11 is located at the first position X, the discharge oil of the hydraulic pumps P1 and P2 is supplied to the left and right traveling motors 4 and 5 via the left and right traveling reversing valves 13 and 14, respectively. On the other hand, if the left and right traveling operators are operated simultaneously with the other hydraulic actuator operators, the discharge flow rate of the hydraulic pump P1 may be distributed only by both the left and right traveling motors 4 and 5 so that the supply flow rates to both the traveling motors 4 and 5 are equal, and the discharge flow rate of the hydraulic pump P2 may be supplied to the other hydraulic actuators. In the following description, unless otherwise specifically excluded, it will be explained that when the straight travel valve 11 is located at the first position X, that is, the discharge oil of the hydraulic pump P1 is supplied to the pump line C and the left travel reversing valve 13, and the discharge oil of the hydraulic pump P2 is supplied to the pump line D and the right travel reversing valve 14. In addition, the manipulators for left and right travel, boom, swing, arm, and bucket correspond to the operating members of the present invention.

[0033] The left travel switching valve 13 and the right travel switching valve 14 are closed center slide valves for switching the supply flow rate and the discharge flow rate for the left travel motor 4 and the right travel motor 5 and switching the supply direction and the discharge direction, and include a valve connected to the left travel forward side proportional solenoid valve 47a, the left travel reverse side proportional solenoid valve 47b, the right travel forward side proportional solenoid valve 48a, and the right travel reverse side proportional solenoid valve 48b (such as Figure 3The forward side pilot ports 13a, 14a and the reverse side pilot ports 13b, 14b of the control valve 10 are used to output the pilot pressure based on the control signal output from the controller 10. In addition, when the pilot pressure is not input to the forward side pilot ports 13a, 14a and the reverse side pilot ports 13b, 14b, the left travel switching valve 13 and the right travel switching valve 14 are positioned at the neutral position N, in which the supply and discharge of the left travel motor 4 and the right travel motor 5 are not controlled. When the pilot pressure is input to the forward pilot ports 13a, 14a, the left travel reversing valve 13 and the right travel reversing valve 14 are switched to the forward side operating position X to open the supply valve channels 13e, 14e, thereby supplying the discharge oil of the hydraulic pumps P1, P2 to the forward side ports 4a, 5a of the left travel motor 4 and the right travel motor 5, and at the same time open the discharge valve channels 13f, 14f, thereby allowing the discharge oil from the reverse ports 4b, 5b to flow to the oil tank 3. In addition, when the pilot pressure is input to the reverse pilot ports 13b, 14b, the left travel reversing valve 13 and the right travel reversing valve 14 are switched to the reverse side operating position Y to open the supply valve channels 13e, 14e, thereby supplying the discharge oil of the hydraulic pumps P1, P2 to the reverse ports 4b, 5b of the left travel motor 4 and the right travel motor 5, and at the same time open the discharge valve channels 13f, 14f, thereby allowing the discharge oil from the forward side ports 4a, 5a to flow to the oil tank 3. When located at the forward side operation position X and the reverse side operation position Y, the supply flow rate and the discharge flow rate of the left traveling motor 4 and the right traveling motor 5 are controlled by the opening area of ​​the supply valve passages 13e, 14e and the discharge valve passages 13f, 14f, and the opening area is controlled to increase or decrease according to the valve core movement position moved with the increase or decrease of the pilot pressure input from the traveling proportional solenoid valve to the forward pilot port 13a, 14a or the reverse pilot port 13b, 14b. Then, the controller 10 controls the left traveling forward side proportional solenoid valve 47a, the left traveling reverse side proportional solenoid valve 47b, the right traveling forward side proportional solenoid valve 48a, and the right traveling reverse side proportional solenoid valve 48b to output the pilot pressure which increases or decreases according to the operation amount of the traveling manipulator when the left traveling manipulator and the right traveling manipulator are operated, so that the left traveling motor 4 and the right traveling motor 5 can be driven at a speed corresponding to the operation amount of the traveling manipulator.

[0034] On the other hand, a boom main-side supply oil passage 17, an arm sub-side supply oil passage 18, and a bucket supply oil passage 19 are branched out in parallel with each other from a pump line C connected to the hydraulic pump P1, and a boom sub-side supply oil passage 20, a swing device supply oil passage 21, and an arm main-side supply oil passage 22 are branched out in parallel with each other from a pump line D connected to the hydraulic pump P2. The boom main-side oil supply passage 17 and the boom sub-side supply oil passage 20 are oil passages that connect the hydraulic pumps P1 and P2 to a pump port 23p of a boom reversing valve 23 described later, and the arm main-side supply oil passage 22 and the arm sub-side supply oil passage 18 are oil passages that connect the hydraulic pumps P2 and P1 to a pump port 25p of an arm reversing valve 25, respectively. The swing supply oil passage 21 is an oil passage connecting the hydraulic pump P2 to the pump port 24 p of the swing switch valve 24 , and the bucket supply oil passage 19 is an oil passage connecting the hydraulic pump P1 to the pump port 26 p of the bucket switch valve 26 .

[0035] The arm secondary side supply oil passage 18 is equipped with an arm flow control valve 28, which controls the supply flow from the hydraulic pump P1 to the arm reversing valve 25. In addition, the boom secondary side supply oil passage 20 is equipped with an arm flow control valve 29 to control the supply flow from the hydraulic pump P2 to the boom reversing valve 23. The arm flow control valve 28 and the boom flow control valve 29 are controlled by a pilot flow proportional solenoid valve 45 and a flow proportional solenoid valve 46 (such as Figure 3 The lifting valve is operated by a lifting valve (shown in FIG. 1 ), which is operated based on a control signal output from the controller 10 to control the flow rate. It has a backflow prevention function that allows oil to flow from the hydraulic pumps P1 and P2 to the arm reversing valve 25 and the boom reversing valve 23, but prevents backflow.

[0036] On the other hand, in the boom main side supply oil passage 17, the bucket supply oil passage 19, the swing device supply oil passage 21, and the arm main side supply oil passage 22, the flow control valves described above (such as the arm flow control valve 28 and the boom flow control valve 29) are not provided, and the flow from the hydraulic pump P1 or the hydraulic pump P2 is supplied to the boom reversing valve 23, the bucket reversing valve 26, the swing device reversing valve 24, and the arm reversing valve 25 without controlling the flow. In addition, check valves 30 are provided in the boom main side supply oil passage 17, the bucket supply oil passage 19, the swing device supply oil passage 21, and the arm main side supply oil passage 22, respectively, and oil is allowed to flow from the hydraulic pumps P1 and P2 to the boom reversing valve 23, the bucket reversing valve 26, the swing device reversing valve 24, and the arm reversing valve 25, but backflow is prevented.

[0037] Therefore, the pump port 23p on the boom reversing valve 23 can be simultaneously supplied with hydraulic oil from the hydraulic pump P1 via the boom main-side oil supply passage 17 and hydraulic oil from the hydraulic pump P2 via the boom sub-side oil supply passage 20. In addition, the hydraulic oil from the hydraulic pump P2 is supplied to the boom reversing valve 23 in a state of flow rate controlled by the boom flow control valve 29 provided in the boom sub-side oil supply passage 20 (including a cut-off state). The pump port 25p of the arm reversing valve 25 is simultaneously supplied with hydraulic oil from the hydraulic pump P2 via the arm main-side oil supply passage 22 and hydraulic oil from the hydraulic pump P1 via the arm sub-side oil supply passage 18, and the hydraulic oil from the hydraulic pump P1 is supplied to the arm reversing valve 25 in a state of flow rate controlled by the arm flow control valve 28 provided in the arm sub-side oil supply passage 18 (including a cut-off state).

[0038] Next, a description is provided about the boom reversing valve, the swing device reversing valve, the arm reversing valve, and the bucket reversing valves 23 to 26.

[0039] First, a description is provided of the swing device reversing valve 24 and the bucket reversing valve 26 to which hydraulic oil is supplied from any of the hydraulic pumps P1 and P2. The swing device reversing valve 24 is a closed central slide valve for controlling the supply flow rate and discharge flow rate of the swing device motor 7 and switching the supply direction and discharge direction thereof. The swing device reversing valve 24 includes: a left swing device pilot port 24a and a right swing device pilot port 24b, which are connected to the left swing device proportional solenoid valve 44a and the right swing device proportional solenoid valve 44b ( Figure 324a and 24b), for outputting a pilot pressure based on a control signal output from the controller 10; a pump port 24p connected to the swing device supply oil passage 21; a tank port 24t connected to the tank line T of the tank 3; a first actuator port 24c connected to the left swing device port 7a on the swing device motor 7; and a second actuator port 24d connected to the right swing device port 7b on the swing device motor 7. In addition, when the pilot pressure is not input to both the left swing device pilot port 24a and the right swing device pilot port 24b, the swing device reversing valve 24 is positioned at a neutral position N, in which the supply and discharge of the swing device motor 7 are not controlled. When the pilot pressure is input to the left swing device pilot port 24a, the valve 24 is switched to the left swing device operating position X to open the supply valve passage 24e from the pump port 24p to the first actuator port 24c, and to open the discharge valve passage 24f from the second actuator port 24d to the tank port 24t. In addition, when the pilot pressure is input to the right swing device pilot port 24b, the valve 24 is configured to switch to the right swing device operating position Y to open the supply valve passage 24e from the pump port 24p to the second actuator port 24d, and to open the discharge valve passage 24f from the first actuator port 24c to the tank port 24t. When the valve 24 is positioned at the left swing device operating position X or the right swing device operating position Y, the supply flow and the discharge flow for the swing device motor 7 will be controlled by the opening area of ​​the supply valve channel 24e and the discharge valve channel 24f, and the opening area is controlled to increase or decrease according to the valve core movement position that moves with the increase or decrease of the pilot pressure output from the left swing device proportional solenoid valve 42a and the right swing device proportional solenoid valve 42b to the left swing device pilot port 24a and the right swing device pilot port 24b.

[0040] The bucket switching valve 26 is a closed central slide valve for controlling the supply flow rate and discharge flow rate of the bucket cylinder 9 and switching the supply direction and discharge direction thereof. The valve 26 has an extension side pilot port 26a and a retraction side pilot port 26b, the extension side pilot port and the retraction side pilot port are respectively connected to the bucket extension side proportional solenoid valve 44a and the retraction side proportional solenoid valve 44b (such as Figure 31 ), for outputting a pilot pressure based on a control signal output from the controller 10; a pump port 26p connected to the bucket supply oil passage 19; a tank port 26t connected to the tank line T; a first actuator port 26c connected to the head side port 9a on the bucket cylinder 9; and a second actuator port 26d connected to the rod side port 9b on the bucket cylinder 9. The structure of the bucket reversing valve 26 is the same as that of the swing device reversing valve 24 mentioned above. When the valve 26 is switched from the neutral position N to the extension side operation position X or the retraction side operation position Y, the valve 26 is configured to open the supply valve passage 26e from the pump port 26p to the actuator port 26c or 26d, and to open the discharge valve passage 26f from the actuator port 26d or 26c to the tank port 26t, and to control the supply flow rate and the discharge flow rate according to the opening area of ​​the supply valve passage 26e and the discharge valve passage 26f of the bucket cylinder 9. The opening area is controlled to increase or decrease according to the spool movement position moved with the increase or decrease of the pilot pressure output from the bucket extension side proportional solenoid valve 44a, the retraction side proportional solenoid valve 44b.

[0041] Next, an explanation is provided about the boom reversing valve 23 and the arm reversing valve 25 to which hydraulic oil is supplied from both the first hydraulic pump P1 and the second hydraulic pump P2. The bucket reversing valve 25 is a closed central slide valve for controlling the supply flow rate and the discharge flow rate of the arm cylinder 10 and switching the supply direction and the discharge direction thereof. The valve 25 has an extension side pilot port 25a and a retraction side pilot port 25b, which are respectively connected to the extension side proportional solenoid valve 43a and the retraction side proportional solenoid valve 43b (such as Figure 325a and 25b), for outputting a pilot pressure based on a control signal output from the controller 10; a pump port 25p, which is connected to the boom main-side supply oil passage 22 and the boom sub-side supply oil passage 18; a tank port 25t, which is connected to the tank line T; a first actuator port 25c, which is connected to the head-side port 8a of the boom cylinder 8; and a second actuator port 25d, which is connected to the rod-side port 8b of the boom cylinder 8. When the pilot pressure is not input to the extension-side pilot port 25a and the retraction-side pilot port 25b, the boom reversing valve 25 is positioned at a neutral position N, in which the supply and discharge of the boom cylinder 8 are not controlled. When the pilot pressure is input to the extension-side pilot port 25a, the valve 25 is configured to switch to the extension-side operation position X to open the supply valve passage 25e from the pump port 25p to the first actuator port 25c, and to open the discharge valve passage 25f from the second actuator port 25d to the tank port 25t. When the pilot pressure is input to the retract-side pilot port 25b, the valve 25 is configured to switch to the retract-side operation position Y to open the supply valve passage 25e from the pump port 25p to the second actuator port 25d, and to open the discharge valve passage 25f from the first actuator port 25c to the tank port 25t. The opening areas of the supply valve passage 25e and the discharge valve passage 25f are controlled to increase or decrease according to the spool movement position moved by the pilot pressure output from the boom extension-side proportional solenoid valve 43a and the retract-side proportional solenoid valve 43b, and the discharge flow rate from the boom cylinder 8 is controlled by the opening area of ​​the discharge valve passage 25f. When the arm flow control valve 28 closes the arm secondary side supply oil passage 18, the supply flow to the arm cylinder 8 is controlled by the opening area of ​​the supply valve passage 25e on the arm reversing valve 25. When the arm flow control valve 28 opens the arm secondary side supply oil passage 18, the supply flow to the arm cylinder 8 is controlled by the opening area of ​​the arm flow control valve 28 and the opening area of ​​the supply valve passage 25e of the arm reversing valve 25.

[0042] The boom switching valve 23 is a closed central slide valve for controlling the supply flow and discharge flow of the boom cylinder 6 and switching the supply direction and discharge direction thereof. The valve 23 has an extension side pilot port 23a and a retraction side pilot port 23b, the extension side pilot port and the retraction side pilot port are respectively connected to the boom extension side proportional solenoid valve 41a and the retraction side proportional solenoid valve 41b (such as Figure 323a, 23b, 23c, 23cb ... The opening areas of the supply valve passage 23e and the discharge valve passage 23f are controlled to increase or decrease according to the spool movement position moved by the pilot pressure output from the boom extension side proportional solenoid valve 41a and the retraction side proportional solenoid valve 41b, and the discharge flow rate from the boom cylinder 6 is controlled by the opening area of ​​the discharge valve passage 23f. When the boom flow control valve 29 closes the boom secondary side supply oil passage 20, the supply flow rate to the boom cylinder 6 is controlled by the opening area of ​​the supply valve passage 23e of the boom reversing valve 23. When the boom flow control valve 29 opens the boom secondary side supply oil passage 20, the supply flow rate to the boom cylinder 6 is controlled by the opening area of ​​the boom flow control valve 29 and the opening area of ​​the supply valve passage 23e on the boom reversing valve 23.

[0043] It should be noted that the straight travel valve 11, the left travel reversing valve 13 and the right travel reversing valve 14, the boom reversing valve, the slewing device reversing valve, the dipper arm reversing valve, the bucket reversing valves 23 to 26, the boom flow control valve 28, and the dipper arm flow control valve 29 correspond to the control valves of the present invention.

[0044] In addition, in the present embodiment, as described above, the hydraulic pumps P1, P2 correspond to the pumps of the present invention or the first and second hydraulic pumps, and the boom cylinder 6 and the arm cylinder 8 are hydraulic actuators corresponding to the large-flow hydraulic actuator of the present invention or the first and second large-flow hydraulic actuators, and both the first and second hydraulic pumps of the present invention are used as hydraulic supply sources. In addition, the main pump of the present invention is a hydraulic pump to which the main side supply oil channel (boom main side supply oil channel 17, arm main side supply oil channel 22) is connected. In the present embodiment, the main pump of the boom cylinder 6 is the hydraulic pump P1, and the main pump of the arm cylinder 8 is the hydraulic pump P2.

[0045] like Figure 3As shown in the block diagram of FIG. 1 , the controller 10 (corresponding to the control member in the present invention) is connected on the input side to: a boom operation detection member 50 for detecting the operation direction and operation amount of the boom manipulator, a slewing device operation detection member 51 for detecting the operation direction and operation amount of the slewing device manipulator, an arm operation detection member 52 for detecting the operation direction and operation amount of the dipper arm manipulator, a bucket operation detection member 53 for detecting the operation direction and operation amount of the bucket manipulator, and a travel manipulator for detecting the operation direction and operation amount of the bucket operation detection member 54. The travel operation detection member 54, and a plurality of pressure sensors (not shown in the figure) for detecting the discharge pressure of the hydraulic pumps P1 and P2 and the load pressure of each hydraulic actuator (the boom cylinder 6, the slewing device motor 7, the arm cylinder 8, the bucket cylinder 9, and the left travel motor 4 and the right travel motor 5); and connected on the output side to: the boom reversing valve, the slewing device reversing valve, the arm reversing valve and the bucket reversing valves 23 to 26, the boom extension side proportional solenoid valve 41a and the retraction side proportional solenoid valve 41b, the slewing device left reversing valve 41a, and the retracting side proportional solenoid valve 41b. The swing side proportional solenoid valve 42a and the right swing side proportional solenoid valve 42b, the boom extension side proportional solenoid valve 43a and the retraction side proportional solenoid valve 43b, the bucket extension side proportional solenoid valve 44a and the retraction side proportional solenoid valve 44b, the left travel forward proportional solenoid valve 47a and the reverse proportional solenoid valve 47b, the right travel forward proportional solenoid valve 48a and the reverse proportional solenoid valve 48b, the boom flow control proportional solenoid valve 45 (which outputs a pilot pressure to the boom flow control valve 28 provided on the boom secondary side supply oil passage 18), the boom The flow control proportional solenoid valve 46 (which outputs pilot pressure to the boom flow control valve 29 provided on the boom secondary side supply oil passage 20), the straight travel valve 11, and the variable displacement devices P1a, P2a of the hydraulic pumps P1, P2 (which output pilot pressure to the pilot ports 23a, 23b to 26a, 26b, 13a, 13b, 14a, 14b of the boom reversing valve, the swing device reversing valve, the arm reversing valve, the bucket reversing valve 23 to 26 and the left travel reversing valve 13 and the right travel reversing valve 14, respectively). The controller 10 can freely control the input / output of the prime mover control device. In addition, the controller 10 includes various setting units and control units, such as a reference pump flow rate setting unit (corresponding to the reference pump flow rate setting means of the present invention) 61, a target supply flow rate setting unit 62, a supply flow rate control unit 63, a target pump flow rate setting unit (corresponding to the target pump flow rate setting means of the present invention) 64, and a pump flow rate control unit (including a pump displacement control unit 65a and a prime mover speed control unit 65b, corresponding to the pump flow rate control means of the present invention) 65. These setting units and control units are configured to perform oil supply and discharge control for each of the hydraulic actuators 4 to 9, displacement control for the hydraulic pumps P1 and P2, and speed control for the prime mover M, etc.

[0046] Next, control performed by each setting unit, the control units 61 to 65 , of the controller 10 will be described.

[0047] First, in the reference pump flow rate setting unit 61, when the pump displacement of the hydraulic pumps P1 and P2 is the maximum value and the rotation speed of the prime mover M is the preset reference rotation speed Ns, the controller 10 sets the pump flow rates of the hydraulic pumps P1 and P2 to the reference pump flow rate Ls. In this case, during the normal operation of the hydraulic excavator, the use speed range of the prime mover M is preset, and the reference rotation speed Ns is set to a speed that is less than the maximum rotation speed Nm within the use speed range. The reference pump flow rate Ls is integrated into the reference pump flow rate setting unit 61 as a control parameter, and can be changed, for example, using a monitoring device (not shown) arranged in the cab of the hydraulic excavator 1.

[0048] In addition, when the displacements of the hydraulic pumps P1 and P2 are maximum and the rotation speed of the prime mover M is the maximum rotation speed Nm, the pump flow rates of the hydraulic pumps P1 and P2 are set to the maximum pump flow rate Lm of each of the hydraulic pumps P1 and P2.

[0049] In addition, when detection signals are input from the corresponding operation detection components 50 to 54 of the slave arm, slewing device, dipper arm, bucket and travel, the controller 10 sets the target supply flow of each hydraulic actuator in the target supply flow setting unit 62, and sets the target pump flow Lt of the hydraulic pumps P1 and P2 in the target pump flow setting unit 64.

[0050] The target supply flow rate setting unit 62 sets the target supply flow rate supplied from each hydraulic pump P1, P2 to each hydraulic actuator according to the combination of the hydraulic actuator being operated and the operation amount of each manipulator. In this case, the sum of the target supply flow rates supplied from each hydraulic pump P1 and P2 is set so that the pump flow rates of the hydraulic pumps P1 and P2 are distributed to each hydraulic actuator according to the manipulator operation amount of each hydraulic actuator with the hydraulic pumps P1 and P2 as the hydraulic supply sources within a range not exceeding the maximum pump flow rate Lm of each hydraulic pump P1 and P2.

[0051] In addition, the target pump flow rate setting unit 64 sets the target pump flow rate Lt of each hydraulic pump P1 and P2 based on the sum of the target supply flow rates to each hydraulic actuator carried by each hydraulic pump P1 and P2, respectively. In this case, the target pump flow rate Lt of each hydraulic pump P1, P2 is set not to exceed the preset maximum pump flow rate Lm of each hydraulic pump P1, P2.

[0052] In addition, in the supply flow control unit 63, the controller 10 outputs a control signal to each of the solenoid proportional valves 41a, 41b to 44a, 44b, 47a, 47b to 48a, 48b, 45, 46 to output a pilot pressure for an opening area, and calculates the opening areas of the boom reversing valve, the slewing device reversing valve, the arm reversing valve, the bucket reversing valve 23 to 26, the left travel reversing valve 13 and the right travel reversing valve 14 corresponding to the target supply flow, so that the target supply flow set by the target supply flow setting unit 62 is supplied from each hydraulic pump P1, P2 to each hydraulic actuator.

[0053] In addition, the controller 10 controls the pump displacements of the hydraulic pumps P1 and P2 and the speed of the prime mover M in the pump flow control unit 65 (including a pump displacement control unit 65a that controls the pump displacements of the hydraulic pumps P1 and P2, and a prime mover speed control unit 65b that outputs a control signal to the prime mover controller 60 to control the speed of the prime mover M) so that the pump flow rates of the hydraulic pumps P1 and P2 are equal to the target pump flow rate Lt set by the target pump flow rate setting unit 64. In this case, when the target pump flow rates Lt of both the hydraulic pumps P1 and P2 set in the target pump flow rate setting unit 64 are less than or equal to the reference pump flow rate Ls, the pump flow control unit 65 controls the speed of the prime mover M to the reference speed Ns, and controls the pump displacements so that the pump flow rates of the hydraulic pumps P1 and P2 are equal to the target pump flow rates Lt. On the other hand, when the target pump flow rate Lt of either hydraulic pump P1 or P2 exceeds the reference pump flow rate Ls, the pump displacement of either hydraulic pump P1 or P2 is maximized, and the rotation speed of the prime mover M is increased to be greater than the reference rotation speed Ns having the maximum rotation speed Nm as the upper limit, so that the pump flow rate Lt of either hydraulic pump P1 or P2 is controlled to be the target pump flow rate Lt exceeding the reference pump flow rate Ls. Furthermore, by adjusting the pump displacement according to the increased rotation speed of the prime mover M, any other hydraulic pump of the hydraulic pumps P2 and P1 is controlled to be equal to the target pump flow rate Lt.

[0054] Next, control performed by the controller 10 will be described in detail.

[0055] For example, when the maximum pump displacement of the hydraulic pumps P1 and P2 is set to 125cc / rev and the reference rotation speed Ns of the prime mover M is set to 1600rpm, the reference pump flow rate Ls is set to 200L / m. In addition, if the maximum rotation speed Nm within the normal use rotation speed range of the prime mover M is set to 2400rpm, the maximum pump flow rate Lm of the hydraulic pumps P1, P2 is set to 300L / m.

[0056] Figure 4The table shows an example of the target pump flow Lt of the hydraulic pumps P1 and P2 set when operating the manipulator for each hydraulic actuator when the reference pump flow Ls is set to 200 L / m and the maximum pump flow Lm is set to 300 L / m as described above. "A" to "F" in the table are the target pump flow Lt when the left travel manipulator, the right travel manipulator, the boom manipulator, the arm manipulator, the bucket manipulator, and the swing device manipulator are separately and completely operated, respectively, and "G" is the target pump flow Lt when the left and right travel manipulators, the boom manipulator, the arm manipulator, and the bucket manipulator are fully operated at the same time. In addition, the straight travel valve 11 is controlled to be located at the first position X in the case of "A" to "F", and to be located at the second position in the case of "G".

[0057] Here, in the present embodiment, the reference pump flow rate Ls is set to the same flow rate as the maximum supply flow rate to each of the left traveling motor 4 and the right traveling motor 5. The maximum supply flow rates to the left traveling motor 4 and the right traveling motor 5 are set to the maximum value of the supply flow rates to the left traveling motor 4 and the right traveling motor 5 so that no turning occurs when the hydraulic excavator 1 is driven in a straight line. Then, the reference pump flow rate Ls is set to the maximum supply flow rate to the traveling motor 4 and the traveling motor 5, and the target pump flow rate Lt when the left traveling manipulator and the right traveling manipulator are fully operated is set to the reference pump flow rate Ls (200 L / m), as shown in FIG. Figure 4 As shown in “A” in FIG. 1 , the maximum supply flow rates from the hydraulic pumps P1 and P2 to the left motor 4 and the right motor 5 can be equally supplied only when the left and right traveling manipulators are fully operated at the same time.

[0058] Furthermore, an example of the target pump flow rates Lt of the hydraulic pumps P1 and P2 when the boom manipulator and the arm manipulator are operated individually is as follows: Figure 4 As described above, the boom cylinder 6 and the arm cylinder 8 are large-flow hydraulic actuators that use both hydraulic pumps P1 and P2 as hydraulic sources, and when the boom manipulator and the arm manipulator are operated individually, the target supply flow rate and the target pump flow rate Lt are set separately for the hydraulic pumps P1 and P2. Regarding the control in this case, based on Figure 5The arm cylinder 8 is described as an example because the case of the boom cylinder 6 is the same as that of the arm cylinder 8. The controller 10 does not set the target supply flow rate (which is zero) from the hydraulic pump P1 connected to the arm secondary side supply oil passage 18, but sets only the target supply flow rate from the hydraulic pump (main pump) P2 connected to the arm primary side supply oil passage 22 to increase as the operation amount of the manipulator increases, sets the opening area of ​​the supply valve passage 25e of the arm reversing valve 25 to increase as the operation amount of the manipulator increases, and controls the arm flow control valve 28 to close. On the other hand, when the operation amount of the manipulator exceeds the set value D, the target supply flow rates from both the hydraulic pumps P2 and P1 are set, and the arm flow control valve 28 is controlled to open in addition to the supply valve passage 25e of the arm reversing valve 25. When the operation amount of the manipulator is 100% in the fully operated state, the set value D of the operation amount of the manipulator is set to a value exceeding 50% of the operation amount (for example, 70% to 90% of the operation amount), and the target supply flow rate is set to the set flow rate Ld when the operation amount of the manipulator is the set value D, and the set flow rate Ld is set to a maximum pump flow rate Lm close to the reference pump flow rate Ls of the hydraulic pump P2. Therefore, if the flow rate supplied to the boom cylinder 8 is lower than the set flow rate Ld set to exceed the reference pump flow rate Ls, the flow rate to the boom cylinder 8 is supplied with only the hydraulic oil from the hydraulic pump P2, and if the flow rate exceeds the set flow rate Ld, the supply flow rate to the boom cylinder 8 is supplied with the hydraulic oil from both the hydraulic pumps P1 and P2. In addition, the controller 10 sets the target pump flow rates Lt of the hydraulic pumps P2, P1 so that the target supply flow rates can be supplied, but in this case, according to the target supply flow rate, the target pump flow rate Lt of the hydraulic pump P2 is set to exceed the reference pump flow rate Ls. Then, by setting the target supply flow and the target pump flow Lt in this manner, when the operation amount of the manipulator exceeds the set value D, that is, when the supply flow to the boom cylinder 8 exceeds the set flow Ld set to exceed the reference pump flow Ls, the hydraulic oil from both the hydraulic pumps P2 and P1 merge and are supplied to the boom cylinder 8, so that the frequency of performing the merging can be reduced.

[0059] On the other hand, when the boom manipulator and the arm manipulator are operated simultaneously, that is, when the boom cylinder 6 and the arm cylinder 8, which are large-flow hydraulic actuators, are driven simultaneously, the controller 10 calculates the distribution flow rates to the boom cylinder 6 and the arm cylinder 8 according to the operation amount of the manipulators, sets the target supply flow rate so that the distribution flow rate is supplied to the boom cylinder 6 and the arm cylinder 8 only from the main hydraulic pumps P1 and P2, respectively, and further sets the target pump flow rate Lt according to the target supply flow rate. That is, the target supply flow rate from the hydraulic pump P1 is set only for the boom cylinder 6, and the target pump flow rate Lt of the hydraulic pump P1 is set according to the target supply flow rate to the boom cylinder 6; and the target supply flow rate from the hydraulic pump P2 is set only for the arm cylinder 8, and the target pump flow rate Lt of the hydraulic pump P2 is set according to the target supply flow rate to the arm cylinder 8. Then, the boom reversing valve 23 and the arm reversing valve 25 are controlled to open the supply valve passages 23e, 25e according to the opening area according to the target supply flow rate, and the boom flow control valve 29 and the arm flow control valve 28 are controlled to be closed. In addition, the pump displacement control of the hydraulic pumps P1 and P2 and the speed control of the prime mover M are performed so that the pump flow rates of the hydraulic pumps P1 and P2 are respectively equal to the target pump flow rate Lt. In this way, when the boom cylinder 6 and the arm cylinder 8 are driven simultaneously, even a large flow hydraulic actuator that is supplied with hydraulic oil from the hydraulic pumps P1 and P2 at the time of maximum flow supply can eliminate the confluence of the discharge oil of the hydraulic pumps P1 and P2.

[0060] Furthermore, an example of the target pump flow rate Lt of the hydraulic pump P1 when the bucket manipulator alone is fully operated is as follows: Figure 4 As shown in "E" of FIG. 1 , the target pump flow rate Lt is set to be greater than the reference pump flow rate Ls of the hydraulic pump P1. This enables a flow rate exceeding the reference pump flow rate Ls to be supplied to the bucket cylinder 9 when the bucket operating tool is fully operated alone, and even for the bucket cylinder 9 that has only one hydraulic pump P1 as a hydraulic supply source, the supply flow rate can be increased without increasing the displacement of the hydraulic pump P1, thereby improving the working efficiency.

[0061] Furthermore, an example of the target pump flow rates Lt of the hydraulic pumps P1 and P2 when the left and right traveling operators and the boom operator, the arm operator, and the bucket operator are fully operated at the same time is as follows: Figure 4 As shown in "G" of FIG. 1 , in this case, as described above, the straight travel valve 11 is controlled to be located in the second position Y, so that the left travel motor 4 and the right travel motor 5 are supplied with hydraulic oil from the hydraulic pump P1, and the boom cylinder 6, the arm cylinder 8, and the bucket cylinder 9 are supplied with hydraulic oil from the hydraulic pump P2. Then, in this case, by setting the target pump flow rate Lt of the hydraulic pump P2 to be greater than the reference pump flow rate Ls, as shown in FIG. Figure 4As shown in "G" of FIG. 1 , the supply flow rate to the boom cylinder 6, the arm cylinder 8 and the bucket cylinder 9 can be increased, which can help improve working efficiency.

[0062] In the present embodiment configured as described, the hydraulic control system of the hydraulic excavator 1 is constructed to include: a prime mover M; a plurality of variable displacement hydraulic pumps P1, P2, which are driven by the prime mover M; and a plurality of hydraulic actuators 4 to 9 (left travel motor 4 and right travel motor 5, boom cylinder 6, swing device motor 7, arm cylinder 8, bucket cylinder 9), which drive at least one of the hydraulic pumps P1, P2 as a hydraulic source; a plurality of hydraulic actuators for each hydraulic actuator (left travel manipulator and right travel manipulator) The invention relates to an operating component (a forward manipulator, a boom manipulator, a slewing device manipulator, an arm manipulator, and a bucket manipulator) which is operated to drive each hydraulic actuator 4 to 9; and a plurality of control valves (a straight travel valve 11, a left travel reversing valve 13 and a right travel reversing valve 14, a boom reversing valve, a slewing device reversing valve, an arm reversing valve, a bucket reversing valve 23 to 26, a boom flow control valve 28, and an arm flow control valve 29) which control the supply of hydraulic oil from the hydraulic pumps P1 and P2 to each hydraulic actuator 4 to 9. Furthermore, when the controller 10 is equipped to control the operation of the control valve, the pump displacement of the hydraulic pumps P1, P2, and the rotation speed of the prime mover M, the controller 10 includes: a reference pump flow rate setting unit 61 that sets the reference pump flow rate Ls as the pump flow rate of the hydraulic pumps P1, P2 when the pump displacement of the hydraulic pumps P1, P2 is the maximum value and the rotation speed of the prime mover M is the preset reference rotation speed Ns; and a target pump flow rate setting unit 64 that sets the target pump flow rate Ls of the hydraulic pumps P1 and P2 for each of the hydraulic pumps according to the operation of the operating member for each of the hydraulic actuators. The target pump flow Lt of each hydraulic pump in P2 is set within a range within which the pump flow of each hydraulic pump in hydraulic pumps P1 and P2 does not exceed the preset maximum pump flow Lm; and a pump flow control section 65, when the target pump flow of any hydraulic pump P1 or P2 set by the target pump flow setting unit 64 exceeds the reference pump flow Ls, the pump flow control section maximizes the pump displacement of any hydraulic pump P1 or P2, and makes the speed of the prime mover greater than the reference speed Ns, thereby increasing the pump flow of the hydraulic pump P1 or P2 to greater than the reference pump flow Ls.

[0063] However, by controlling the reference pump flow rate setting unit 61, the target pump flow rate setting unit 64, and the pump flow rate control unit 65 provided in the controller 10, when the pump displacement is the maximum value and the rotation speed of the prime mover M is the reference rotation speed Ns, the pump flow rate of the hydraulic pump P1 or P2 as the hydraulic source of the hydraulic actuator operated by the manipulator can be increased to be greater than the reference pump flow rate Ls, so that the need and frequency of the discharge oil confluence of the hydraulic pumps P1 and P2 can be reliably reduced to ensure the flow rate supplied to the operated hydraulic actuator, thereby reducing efficiency, operability, and complexity of the circuit caused by the confluence. In addition, since this configuration increases the pump flow of the hydraulic pumps P1 and P2 to be greater than the reference pump flow rate Ls by increasing the rotation speed of the prime mover M to be greater than the reference rotation speed Ns, it is not necessary to equip a large-displacement hydraulic pump.

[0064] In addition, in the present embodiment, although the hydraulic pumps P1 and P2 (the first hydraulic pump and the second hydraulic pump) are provided as hydraulic pumps, the boom cylinder 6 and the arm cylinder 8 (high flow hydraulic actuators) are provided as hydraulic actuators, and are supplied with hydraulic oil from both the hydraulic pumps P1 and P2 at the time of maximum flow supply. On the other hand, when the boom manipulator and the arm manipulator are independently operated, the controller 10 controls one of the hydraulic pumps P1 and P2 as a main pump to supply hydraulic oil only from the main pump until the supply flow to the boom cylinder 6 and the arm cylinder 8 reaches the set flow Ld set to exceed the reference pump flow Ls, and when the set flow Ld is exceeded, the controller controls the hydraulic oil supplied from the two hydraulic pumps P1, P2; and the target pump flow setting unit 64 sets the target pump flow Lt of the main pump to exceed the reference pump flow Ls according to the supply flow from the main pump to the boom cylinder 6 and the arm cylinder 8. This means that only when the flow supplied to the boom cylinder 6 and the boom cylinder 8 exceeds the set flow Ld which is set to exceed the reference pump flow Ls, the hydraulic oil from both hydraulic pumps P1 and P2 will merge and be supplied to the boom cylinder 6 and the boom cylinder 8, so that even when hydraulic oil is supplied from both hydraulic pumps P1 and P2 to the large-flow hydraulic actuator at the maximum flow rate, the frequency of merging can be reduced.

[0065] In addition, in the present embodiment, the boom cylinder 6 uses the hydraulic pump P1 as the main pump, and the arm cylinder 8 uses the hydraulic pump P2 as the main pump. However, when the boom manipulator and the arm manipulator are operated simultaneously, the controller 10 controls the supply of hydraulic oil only from the main pump to the boom cylinder 6 and the arm cylinder 8, and the target pump flow setting unit 64 sets the target pump flow Lt of the hydraulic pumps P1 and P2 for the hydraulic pumps according to the operation amount of the boom manipulator and the arm manipulator. Therefore, when the boom cylinder 6 and the arm cylinder 8 are driven simultaneously, even a large flow hydraulic actuator that uses both the hydraulic pumps P1 and P2 as the hydraulic oil source at the time of maximum flow supply can eliminate the confluence of the discharge oil of the hydraulic pumps P1 and P2.

[0066] In addition, the hydraulic excavator 1 includes a traveling body (a lower traveling body 71 and an upper slewing device body 72) including a left traveling body and a right traveling body, and a working device (a front working machine 73) mounted on the traveling body; and the hydraulic excavator includes a hydraulic pump P1 and a hydraulic pump P2 as hydraulic pumps, and a left traveling motor 4 and a right traveling motor 5 as hydraulic actuators driving the left traveling body and the right traveling body, respectively. On the one hand, the hydraulic excavator includes a boom cylinder 6, an arm cylinder 8, and a bucket cylinder 9 as a plurality of working hydraulic actuators driving the working device. On the other hand, when the left and right travel manipulators, the boom manipulator, the arm manipulator, and the bucket manipulator are operated simultaneously, the controller 10 controls the straight travel valve 11 to supply hydraulic oil from the hydraulic pump P1 to the left and right travel motors 4 and 5, and to supply hydraulic oil from the hydraulic pump P2 to the boom cylinder 6, the arm cylinder 8, and the bucket cylinder 9, and the target pump flow rate setting unit 64 sets the target pump flow rate Lt of the hydraulic pump P2 to be greater than the reference pump flow rate Ls. Therefore, it is possible to independently supply hydraulic oil to the left and right travel motors 4 and 5 and the working hydraulic actuators (the boom cylinder 6, the arm cylinder 8, the bucket cylinder 9) without hydraulic interference with each other, and by setting the target pump flow rate Lt of the hydraulic pump P2 to be greater than the reference pump flow rate Ls, the supply flow rate to the working hydraulic actuator can be increased, which helps to improve working efficiency.

[0067] The following will refer to Figure 6 A second embodiment of the present invention is described. In the second embodiment, the same components as those of the first embodiment are given the same reference numerals, and description is omitted.

[0068] In the second embodiment, three hydraulic pumps P1, P2, and P3 are provided as hydraulic pumps driven by the prime mover M. In addition, as in the first embodiment, the hydraulic pump P1 is connected to the pump line C via the straight travel valve 11 located in the first position, and is connected to the left travel reversing valve 13. In addition, the hydraulic pump P2 is connected to the pump line D, and is connected to the right travel reversing valve 14 via the straight travel valve 11 located in the first position X. On the other hand, the hydraulic pump P3 is connected to the boom main side supply oil passage 17.

[0069] From the pump line C connected to the hydraulic pump P1, the arm sub-side supply oil passage 18 and the bucket supply oil passage 19 are branched in parallel with each other, and from the pump line D connected to the hydraulic pump P2, the boom sub-side supply oil passage 20, the swing device supply oil passage 21, and the arm main-side supply oil passage 22 are branched in parallel with each other. As in the first embodiment, the arm sub-side supply oil passage 18 and the boom sub-side supply oil passage 20 are respectively provided with an arm flow control valve 28 and a boom flow control valve 29.

[0070] The hydraulic oil from the hydraulic pump P3 is supplied via the boom main-side supply oil passage 17 and the hydraulic oil from the hydraulic pump P2 is supplied via the boom sub-side supply oil passage 20 to the pump port 23p of the boom reversing valve 23, and in a state (including a cut-off state) where the flow rate is controlled by the boom flow control valve 29 provided in the boom sub-side supply oil passage 20, the hydraulic oil from the hydraulic pump P2 is supplied to the boom reversing valve 23. In addition, the hydraulic oil from the hydraulic pump P2 is supplied via the arm main-side supply oil passage 22 and the hydraulic oil from the hydraulic pump P1 is supplied via the arm sub-side supply oil passage 18 to the pump port 25p of the boom reversing valve 25, and in a state (including a cut-off state) where the flow rate is controlled by the arm flow control valve 28 provided in the arm sub-side supply oil passage 18, the hydraulic oil from the hydraulic pump P1 is supplied to the arm reversing valve 25. In addition, the hydraulic oil from the hydraulic pump P1 is supplied to the pump port 26p of the bucket switching valve 26 via the bucket supply oil passage 19, and the hydraulic oil from the hydraulic pump P2 is supplied to the pump port 24p of the swing device switching valve 24 via the swing device supply oil passage 21. The boom switching valve, the swing device switching valve, the arm switching valve, the bucket switching valves 23 to 26, and the boom flow control valve 29 and the arm flow control valve 28 are the same as those of the first embodiment.

[0071] Also, in the second embodiment, as in the first embodiment, the oil supply and discharge control of each hydraulic actuator 4 to 9, the displacement control of the hydraulic pumps P1, P2, P3, the rotation speed control of the prime mover M, etc. are performed by the controller 10, but in the second embodiment, the hydraulic pump P3 is only the hydraulic supply source of the boom cylinder 6. Then, when the boom manipulator, the arm manipulator, and the bucket manipulator are operated simultaneously, that is, the so-called front triplex operation, the controller 10 controls to close the boom flow control valve 29 and the arm flow control valve 28, respectively. Therefore, during the front triplex operation, hydraulic oil is supplied only from the hydraulic pump P3 to the boom cylinder 6, hydraulic oil is supplied only from the hydraulic pump P2 to the arm cylinder 8, and hydraulic oil is supplied only from the hydraulic pump P1 to the bucket cylinder 9, so that hydraulic oil can be supplied to the boom cylinder 6, the arm cylinder 8, and the bucket cylinder 9 in independent circuits without causing hydraulic interference with each other. In this case, according to the operation amount of the boom manipulator, the boom manipulator and the bucket manipulator, the pump flow of the hydraulic pumps P3, P2, and P1 can be controlled to increase or decrease through the pump displacement control and speed control of the prime mover M, so that the pump flow of each of the hydraulic pumps P3, P2 and P1 can be a flow corresponding to the operation amount of the manipulators of the boom cylinder 6, the boom cylinder 8 and the bucket cylinder 9.

[0072] It should be noted that the present invention is not limited to the first and second embodiments described above, and for example, when setting the target pump flow rate of each hydraulic pump, it may be configured to set the upper limit to the sum of the target pump flows of all hydraulic pumps. In this case, the upper limit of the sum of the target pump flows may be arbitrarily set within the range not exceeding the sum of the maximum pump flows of each hydraulic pump. In addition, in the above embodiments, an electric motor is used as a prime mover, but the present invention can be implemented even if an engine is used as a prime mover.

[0073] In addition, the present invention can obviously be implemented in various working machines having a plurality of hydraulic pumps driven by a prime mover, and is not limited to a hydraulic excavator.

[0074] Industrial Applicability

[0075] The present invention can be used in a hydraulic control system of a working machine such as a hydraulic excavator.

Claims

1. A hydraulic control system for a working machine, characterized in that: The hydraulic control system includes: a prime mover; a plurality of variable displacement hydraulic pumps driven by the prime mover; a plurality of hydraulic actuators driving at least one of the hydraulic pumps as a hydraulic source; an operating member for each hydraulic actuator, the operating member being operated to drive each hydraulic actuator; and a plurality of control valves controlling the supply of hydraulic oil from the hydraulic pump to each hydraulic actuator. and the hydraulic control system is provided with control means for controlling the actuation of the control valve, the pump displacement of the hydraulic pump and the rotational speed of the prime mover; The control device comprises: a reference pump flow rate setting means for setting the pump flow rate of the hydraulic pump to a reference pump flow rate when the pump displacement of the hydraulic pump is a maximum value and the rotation speed of the prime mover is a preset reference rotation speed; a target pump flow rate setting member that sets, for each hydraulic pump, a target pump flow rate of each hydraulic pump within a range within which the pump flow rate of each hydraulic pump does not exceed a preset maximum pump flow rate, according to an operation of the operating member for each hydraulic actuator; and a pump flow control member which, when the target pump flow of any one of the hydraulic pumps set by the target pump flow setting member exceeds the reference pump flow, maximizes the pump displacement of the one of the hydraulic pumps and increases the rotational speed of the prime mover to be greater than the reference rotational speed, thereby increasing the pump flow of the one of the hydraulic pumps to be greater than the reference pump flow.

2. The hydraulic control system in the working machine according to claim 1, characterized in that: A first hydraulic pump and a second hydraulic pump as the hydraulic pumps are included, and a large-flow hydraulic actuator as the hydraulic actuator is included, and hydraulic oil is supplied from both the first hydraulic pump and the second hydraulic pump to the large-flow hydraulic actuator at a maximum flow supply; a controller controlling any one of the first hydraulic pump and the second hydraulic pump as a main pump and supplying hydraulic oil only from the main pump until a flow rate supplied to the large-flow hydraulic actuator reaches a set flow rate, the set flow rate being set to exceed the reference pump flow rate when the operating member for the large-flow hydraulic actuator is operated alone, and supplying the hydraulic oil from both the first hydraulic pump and the second hydraulic pump when the flow rate exceeds the set flow rate; and The target pump flow rate setting means sets the target pump flow rate of the main pump to exceed the reference pump flow rate according to the supply flow rate from the main pump to the large-flow rate hydraulic actuator.

3. The hydraulic control system in the working machine according to claim 2, characterized in that: A first high-flow hydraulic actuator using the first hydraulic pump as the main pump is included, and a second high-flow hydraulic actuator using the second hydraulic pump as the main pump is included; when the operating members for the first and second large-flow hydraulic actuators are operated simultaneously, the controller controls to supply the hydraulic oil from each main pump to the first and second large-flow hydraulic actuators, respectively; and The target pump flow rate setting member sets the target pump flow rates of the first hydraulic pump and the second hydraulic pump for each hydraulic pump according to the operation amount of the operation member for the first large flow rate hydraulic actuator and the second large flow rate hydraulic actuator.

4. The hydraulic control system in the working machine according to claim 1, characterized in that: The working machine includes: a traveling body, the traveling body having a left traveling body and a right traveling body; a working device, the working device being mounted on the traveling body; a first hydraulic pump and a second hydraulic pump, the first hydraulic pump and the second hydraulic pump serving as the hydraulic pumps; a left traveling motor and a right traveling motor, the left traveling motor and the right traveling motor serving as the hydraulic actuators and driving the left traveling body and the right traveling body, respectively; and a plurality of working hydraulic actuators, the plurality of working hydraulic actuators driving the working device; When the left and right traveling motors and the operating member for the working hydraulic actuator are operated simultaneously, the controller controls the control valve to supply the hydraulic oil from the first hydraulic pump to the left and right traveling hydraulic motors and to supply the hydraulic oil from the second hydraulic pump to the working hydraulic actuator; and The target pump flow rate setting means sets the target pump flow rate of the second hydraulic pump to be greater than the reference pump flow rate.

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