Hydraulic drive system of construction machine

Abstract

To provide a hydraulic drive system of a construction machine capable of reducing splitting pressure loss in simultaneously driving a plurality of hydraulic actuators, and improving energy efficiency.SOLUTION: First selector valves V11-V14 can be switched to a first position for supplying all of pressure oil discharged from first pump elements P11-P14 to a second control valve group G2 and a second position for supplying a part of the pressure oil discharged from the first pump elements P11-P14 to a first control valve group G1 and supplying the remaining pressure oil to a third control valve group G3, and second selector valves V21-V24 can be switched to a first position for supplying all of the pressure oil discharged from second pump elements P21-P24 to the first control valve group G1 and a second position for supplying a part of the pressure oil discharged from the second pump elements P21-P24 to a second control valve group G2 and supplying the remaining pressure oil to a third control valve group G3.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a hydraulic drive system for construction machinery, and in particular to a hydraulic drive system for construction machinery such as a hydraulic excavator which is equipped with a pump device containing multiple pump elements capable of independently controlling the flow rate of pressurized oil discharged from multiple discharge ports, and which supplies the pressurized oil discharged from this pump device to multiple directional control valves to drive multiple hydraulic actuators. [Background technology]

[0002] In recent years, energy conservation has become an important development topic for construction machinery such as hydraulic excavators. Improving the fuel efficiency of hydraulic drive systems is essential to saving energy in construction machinery, and various hydraulic drive systems have been proposed to date. Patent documents 1, 2, and 3 are examples of documents disclosing such conventional technology.

[0003] Patent Document 1 discloses a hydraulic drive system equipped with three hydraulic pumps and a control valve composed of three valve groups, with a directional control valve for the boom and a directional control valve for the arm arranged in each of the three valve groups, enabling the combined operation of boom raising and arm crowding to be performed without the need for a throttle, and also enabling arm crowding operations to be performed in the same way as if a regeneration circuit with a throttle were provided.

[0004] Patent document 2 discloses a hydraulic drive system equipped with a pump device containing four pump elements that can independently control the flow rate of pressurized oil discharged from four discharge ports, the four discharge ports being connected to four load port oil passages via 16 switching valves, and three hydraulic actuators being connected in parallel to one of the four load port oil passages via three directional control valves.

[0005] Patent document 3 discloses a hydraulic drive system that includes a pump device containing two pump elements that can independently control the flow rate of pressurized oil discharged from two discharge ports, and connects two actuators in parallel to the two discharge ports via two open center type directional control valves, enabling pressurized oil to be supplied to the two actuators from each discharge port. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5572586 [Patent Document 2] WO2008 / 009950 publication [Patent Document 3] WO2020 / 053577 publication Summary of the Invention [Problem to be solved by the invention]

[0007] The hydraulic drive system described in Patent Document 1 arranges a directional control valve for the boom and a directional control valve for the arm in each of the three valve groups, so that the combined operation of boom raising and arm crowding can be performed without providing a throttle, reducing pressure loss caused by providing a throttle and improving pump efficiency. However, when performing a combined operation including the boom and arm, both the directional control valves for the boom and the arm in each of the three valve groups switch in conjunction with each other, so that a shunt pressure loss occurs due to throttling the directional control valve on the low-pressure actuator side in the same valve group, and energy efficiency decreases.

[0008] In the hydraulic drive system described in Patent Document 2, three actuators are connected in parallel to one of four load port oil passages via three directional control valves. Therefore, when performing a combined operation in which two or more of the three actuators are driven simultaneously, a diversion pressure loss occurs due to throttling the directional control valve on the low-pressure actuator side, resulting in reduced energy efficiency.

[0009] The hydraulic drive system described in Patent Document 3 is similar, and since two actuators are connected in parallel to each of the two discharge ports of the pump device via two directional control valves, when a combined operation is performed in which two actuators are driven simultaneously, a diversion pressure loss occurs due to throttling the directional control valve on the low-pressure actuator side, resulting in reduced energy efficiency.

[0010] The object of the present invention is to provide a hydraulic drive system for construction machinery that can reduce branch pressure loss when driving multiple hydraulic actuators simultaneously and improve energy efficiency in a hydraulic drive system equipped with a pump device containing multiple pump elements that can independently control the flow rate of pressurized oil discharged from multiple discharge ports. [Means for solving the problem]

[0011] In order to achieve the above object, the present invention provides a construction machine comprising: a plurality of hydraulic pumps; a plurality of hydraulic actuators driven by pressure oil discharged from the plurality of hydraulic pumps; a plurality of directional control valves for controlling the flow of pressure oil supplied from the plurality of hydraulic pumps to the plurality of hydraulic actuators; and a plurality of operating devices for generating operating signals for driving the plurality of hydraulic actuators, wherein the plurality of directional control valves are divided into a first control valve group, a second control valve group, and a third control valve group, and the plurality of hydraulic actuators include a boom cylinder for driving a boom, an arm cylinder for driving an arm, a work tool cylinder for driving a work tool, and a swing motor for driving a swing body, wherein the first control valve group includes a first boom directional control valve and a first arm directional control valve, the second control valve group includes a second boom directional control valve and a second arm directional control valve, and the third control valve group includes a third boom directional control valve and a third arm directional control valve, and a work tool directional control valve and a swing directional control valve are included in different control valve groups among the first control valve group, the second control valve group, and the third control valve group. In the hydraulic drive system, the plurality of hydraulic pumps include a first hydraulic pump containing a plurality of first pump elements each capable of independently controlling a discharge flow rate, and a second hydraulic pump containing a plurality of second pump elements each capable of independently controlling a discharge flow rate, and further includes a plurality of first switching valves connected to the plurality of first pump elements of the first hydraulic pump and switching connections between the plurality of first pump elements and the first control valve group, the second control valve group, and the third control valve group, and a plurality of second pump elements connected to the plurality of second hydraulic pump and switching connections between the plurality of second pump elements and the plurality of first switching valves. The first hydraulic pump further includes a plurality of second switching valves for switching connections between the first control valve group, the second control valve group, and the third control valve group, and the plurality of first switching valves include at least one first switching valve configured to be switched between a first position in which all of the pressure oil discharged from the first pump element is supplied to the second control valve group and a second position in which all of the pressure oil discharged from the first pump element is supplied to one of the first control valve group and the third control valve group, for each of a plurality of first pump elements of the first hydraulic pump, and the plurality of second switching valves includeFor each of the second pump elements of the second hydraulic pump, at least one second switching valve is configured to be switched between a first position in which all of the pressure oil discharged from the second pump element is supplied to the first control valve group, and a second position in which all of the pressure oil discharged from the second pump element is supplied to one of the second control valve group and the third control valve group.

[0012] In the present invention configured in this manner, the multiple directional control valves are divided into a first control valve group, a second control valve group, and a third control valve group, and a boom directional control valve and an arm directional control valve are included in each of the first control valve group, the second control valve group, and the third control valve group. Then, the multiple first switching valves and the multiple second switching valves are provided as described above, and each of the multiple first switching valves and the multiple second switching valves can be switched to a first position and a second position. By this, during combined operations including the arm and the boom, the multiple first pump elements and the multiple second pump elements can be distributed and connected to the boom directional control valves and the arm directional control valves of the different control valve groups of the first control valve group, the second control valve group, and the third control valve group, and pressure oil can be supplied to the boom directional control valves and the arm directional control valves of the different control valve groups. This reduces the frequency of operations in which both the boom directional control valve and the arm directional control valve in the same control valve group are switched to supply pressurized oil, reducing the branch pressure loss that occurs when the directional control valve on the low-pressure actuator side in the same control valve group is throttled, thereby improving energy efficiency. Effect of the Invention

[0013] According to the present invention, it is possible to reduce the branch pressure loss when driving a plurality of hydraulic actuators simultaneously, and to improve energy efficiency. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a side view of a hydraulic excavator according to an embodiment of the present invention. [Diagram 2] 1 is a diagram showing a hydraulic drive system according to a first embodiment of the present invention. [Diagram 3] FIG. 2 is an enlarged view showing a circuit configuration of four first switching valves and four second switching valves. [Figure 4] FIG. 4 is a functional block diagram showing the processing contents of a controller. [Diagram 5] FIG. 13 is a diagram showing a table for calculating a required flow rate of a boom cylinder, a required flow rate of an arm cylinder, a required flow rate of a bucket cylinder, and a required flow rate of a swing motor based on operation signals of left and right operating devices. [Figure 6] 10 is a flowchart showing a calculation logic for the number of allocated pump elements in a requested pump element number / allocated pump element number calculation unit. [Figure 7A] 5 is a flowchart showing the calculation contents of a directional control valve command, a switching valve command, and a pump command calculation unit. [Figure 7B] 5 is a flowchart showing the calculation contents of a directional control valve command, a switching valve command, and a pump command calculation unit. [Figure 8] FIG. 13 is a diagram showing a control valve group priority order map used for allocating the numbers of pump elements, which is set for the first to third boom directional control valves and the first to third arm directional control valves. [Figure 9] FIG. 13 is a diagram showing an operation pattern map for explaining a further operation example of the present embodiment. [Figure 10] FIG. 4 is a diagram showing a hydraulic drive system for a construction machine according to a second embodiment of the present invention. [Figure 11] FIG. 11 is a diagram showing a hydraulic drive system for a construction machine according to a third embodiment of the present invention. [Figure 12] FIG. 2 is a schematic diagram showing a part of an electronically controlled hydraulic pump equipped with a pump element, illustrating the operating principle of the first and second hydraulic pumps. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, a hydraulic excavator will be taken as an example of a construction machine according to an embodiment of the present invention and described with reference to the drawings.

[0016] <First embodiment> ~Construction machinery~ FIG. 1 is a side view of a hydraulic excavator in one embodiment of the present invention.

[0017] In Fig. 1, the hydraulic excavator comprises a lower traveling body 101, an upper rotating body 102, and a front device 103. The lower traveling body 101 has left and right crawler-type traveling devices 104a, 104b, and is driven by left and right traveling motors 105a, 105b. The upper rotating body 102 is mounted on the lower traveling body 101 so as to be rotatable, and is driven by a swing motor 106a. The front device 103 is attached to the front of the upper rotating body 102 so as to be rotatable in the vertical direction. In addition, the front device 103 is a multi-joint structure including a boom 107 attached to the front of the upper rotating body 102 so as to be rotatable in the vertical direction, an arm 108 attached to the end of the boom 107 so as to be rotatable in the vertical and front-to-rear directions, and a bucket 109 which is a work tool attached to the end of the arm 108 so as to be rotatable in the vertical and front-to-rear directions, and the boom 107 rotates in the vertical direction by the extension and contraction of a boom cylinder 107a, the arm 108 rotates in the vertical and front-to-rear directions by the extension and contraction of an arm cylinder 108a, and the bucket 109 rotates in the vertical and front-to-rear directions by the extension and contraction of a bucket cylinder 109a which is a work tool cylinder.

[0018] The upper rotating body 102 is equipped with an engine room 110 and a cabin 111. The cabin 111 forms a cab inside, and the cab is equipped with a driver's seat (not shown) where an operator sits, left and right operation devices 115a, 115b (see FIG. 2) that generate operation signals for driving the upper rotating body 102, the boom 107, the arm 108, and the bucket 109 (multiple driven bodies), and left and right operation devices 116a, 116b (see FIG. 2) that are provided in the center of the floor in front of the driver's seat and generate operation signals for driving the left and right traveling devices 104a, 104b (multiple driven bodies).

[0019] In this specification, "left", "right", "front" and "rear" refer to directions seen by an operator seated in the driver's seat.

[0020] ~Hydraulic drive system~ FIG. 2 is a diagram showing a hydraulic drive system according to a first embodiment of the present invention.

[0021] The hydraulic drive system of this embodiment includes a prime mover 1, a first hydraulic pump 14 and a second hydraulic pump 15 which are multiple hydraulic pumps driven by the prime mover 1, multiple hydraulic actuators 105a, 105b, 106a, 107a, 108a, 109a driven by pressurized oil discharged from the first hydraulic pump 14 and the second hydraulic pump 15, multiple open center type directional control valves 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27 which control the flow of pressurized oil supplied from the first and second hydraulic pumps 14, 15 to the multiple hydraulic actuators 105a-109a, and multiple operating devices 115a, 115b, 116a, 116b which generate operating signals for driving the multiple hydraulic actuators 105a-109a.

[0022] The prime mover 1 is, for example, a diesel engine, but may also be an electric motor.

[0023] The plurality of hydraulic actuators 105a to 109a include the above-mentioned left and right travel motors 105a, 105b, swing motor 106a, boom cylinder 107a, arm cylinder 108a, and bucket cylinder 109a.

[0024] The directional control valves 17-27 are divided into a first control valve group G1, a second control valve group G2, and a third control valve group G3. The directional control valves 17-27 are formed as spool valves in one control block.

[0025] The first control valve group G1 includes a first boom directional control valve 19 and a first arm directional control valve 20, the second control valve group G2 includes a second boom directional control valve 23 and a second arm directional control valve 22, and the third control valve group G3 includes a third boom directional control valve 27 and a third arm directional control valve 26, and different control valve groups (the first control valve group G1 and the second control valve group G2) among the first control valve group G1, the second control valve group G2 and the third control valve group G3 include the bucket directional control valve 18 and the swing directional control valve 21, which are implement directional control valves.

[0026] The first control valve group G1 also includes a left travel direction control valve 17 for the left travel motor 105a, and the second control valve group G2 includes a spare directional control valve 24 for the spare hydraulic cylinder 112 and a right travel direction control valve 25 for the right travel motor 105b.

[0027] The first hydraulic pump 14 has four first discharge ports 14a, 14b, 14c, 14d, and includes four first pump elements P11, P12, P13, P14 that are a plurality of first pump elements that can independently control the flow rate of the pressure oil discharged from the four first discharge ports 14a, 14b, 14c, 14d. The second hydraulic pump 15 has four second discharge ports 15a, 15b, 15c, 15d, and includes four second pump elements P21, P22, P23, P24 that are a plurality of second pump elements that can independently control the flow rate of the pressure oil discharged from the four second discharge ports 15a, 15b, 15c, 15d.

[0028] In addition, the hydraulic drive system of this embodiment further includes four first switching valves V11, V12, V13, V14 which are a plurality of first switching valves connected to the first pump elements P11-P14 of the first hydraulic pump 14 and switch the connections between the first pump elements P11-P14 and the first control valve group G1, the second control valve group G2, and the third control valve group G3, and four second switching valves V21, V22, V23, V24 which are a plurality of second switching valves connected to the second pump elements P21-P24 of the second hydraulic pump 15 and switch the connections between the second pump elements P21-P24 and the first control valve group G1, the second control valve group G2, and the third control valve group G3.

[0029] In addition, the hydraulic drive system of this embodiment is equipped with a controller 28 that controls the four first pump elements P11-P14 and the four second pump elements P21-P24, the multiple directional control valves 17-27, the four first switching valves V11-V14 and the four second switching valves V21-V24 based on operation signals from operating devices 115a-116b.

[0030] The first pump elements P11-P14 and the second pump elements P21-P24 each have a built-in solenoid valve that can vary its own capacity, and can discharge pressure oil at a required flow rate by switching the solenoid valve based on a discharge flow rate command output from the controller 28. These pump elements are also called digital pumps, and their specific configurations will be described later.

[0031] The multiple directional control valves 17-27 are electromagnetic control valves that operate based on control valve commands output from a controller 28, and the first switching valves V11-V14 and the second switching valves V21-V24 are also electromagnetic switching valves that operate based on switching valve commands output from the controller 28.

[0032] The multiple first switching valves V11-V14 include at least one first switching valve V11-V14 configured to be switched between a first position where all of the pressure oil discharged from the first pump elements P11-P14 is supplied to the second control valve group G2 and a second position where all of the pressure oil discharged from the first pump elements P11-P14 is supplied to one of the first control valve group G1 and the third control valve group G3, for each of the multiple first pump elements P11-P14 of the first hydraulic pump 14; The multiple second switching valves V21-V24 include at least one second switching valve V21-V24 configured for each of the multiple second pump elements P21-P24 of the second hydraulic pump 15 to be switched between a first position in which all of the pressurized oil discharged from the second pump elements P21-P24 is supplied to the first control valve group G1, and a second position in which all of the pressurized oil discharged from the second pump elements P21-P24 is supplied to one of the second control valve group G2 and the third control valve group G3.

[0033] Further, some P13, P14 of the multiple first pump elements P11-P14 of the first hydraulic pump 14 are connected to either the second control valve group G2 other than the third control valve group G3 or the first control valve group G1 via at least one switching valve V13, V14, and other parts P11, P12 of the multiple first pump elements P11-P14 of the first hydraulic pump 14 are connected to either the second control valve group G2 other than the first control valve group G1 or the third control valve group G3 via at least one switching valve V11, V12, Some P21, P22 of the multiple second pump elements P21-P24 of the second hydraulic pump 15 are connected to either the first control valve group G1 other than the third control valve group G3 or the second control valve group G2 via at least one switching valve V21, V22, and the other parts P23, P24 of the multiple second pump elements P21-P24 of the second hydraulic pump 15 are connected to either the first control valve group G1 other than the second control valve group G2 or the third control valve group G3 via at least one switching valve V23, V24.

[0034] The circuit configuration relating to the first switching valves V11 to V14 and the second switching valves V21 to V24 will be described in detail below.

[0035] FIG. 3 is an enlarged view showing a circuit configuration relating to the first switching valves V11 to V14 and the second switching valves V21 to V24.

[0036] The first switching valves V11 to V14 are arranged in a first switching valve block 30 having three output ports 34, 36, 38, and the second switching valves V21 to V24 are arranged in a second switching valve block 31 having three output ports 41, 43, 45.

[0037] The first switching valves V11 to V14 can distribute the discharge oil of the first pump elements P11 to P14 of the first hydraulic pump 14 to the three output ports 34, 36, and 38 by switching their respective switching positions according to switching valve commands from the controller .

[0038] More specifically, when the first switching valves V11-V14 are in the first position, which is the initial position shown in the figure, a hydraulic path Sa1 is formed in which pressurized oil discharged from the first pump elements P11-P14 flows to the output port 34 via the junction oil path 33, and when the first switching valves V11-V14 are switched from the shown position to the second position, a hydraulic path Sa2 is formed in which the pressurized oil discharged from the first pump elements P13, P14 flows to the output port 36 via the junction oil path 35, and a hydraulic path Sa3 is formed in which the pressurized oil discharged from the first pump elements P11, P12 flows to the output port 38 via the junction oil path 37.

[0039] Similarly, the oil discharged from the second pump elements P21 to P24 of the second hydraulic pump 15 can be divided into three output ports 41, 43, and 45 by switching the second switching valves V21 to V24 using switching valve commands from the controller .

[0040] More specifically, when the second switching valves V21-V24 are in the first position, which is the initial position shown in the figure, a hydraulic path Sb2 is formed in which the pressurized oil discharged from the second pump elements P21-P24 flows to the output port 43 via the junction oil path 42, and when the second switching valves V21-V24 are switched from the shown position to the second position, a hydraulic path Sb1 is formed in which the pressurized oil discharged from the second pump elements P21, P22 flows to the output port 41 via the junction oil path 40, and a hydraulic path Sb3 is formed in which the pressurized oil discharged from the second pump elements P23, P24 flows to the output port 45 via the junction oil path 44.

[0041] The pressurized oil flowing out from the output ports 36, 43 is supplied to the first control valve group G1, the pressurized oil flowing out from the output ports 34, 41 is supplied to the second control valve group G2, and the pressurized oil flowing out from the output ports 38, 45 is supplied to the second control valve group G3.

[0042] In this manner, the four first switching valves V11-V14 can be switched between a first position in which all of the pressure oil discharged from the four first pump elements P11-P14 of the first hydraulic pump 14 is supplied to the second control valve group G2, and a second position in which a portion of the pressure oil discharged from the four first pump elements P11-P14 is supplied to the first control valve group G1, and the remaining pressure oil discharged from the four first pump elements P11-P14 is supplied to the third control valve group G3. The four second switching valves V21-V24 are switchable between a first position in which all of the pressurized oil discharged from the four second pump elements P21-P24 of the second hydraulic pump 15 is supplied to the first control valve group G1, and a second position in which a portion of the pressurized oil discharged from the four second pump elements P21-P24 is supplied to the second control valve group G2, and the remainder of the pressurized oil discharged from the four second pump elements P21-P24 is supplied to the third control valve group G3.

[0043] As a result, the first control valve group G1 can be connected to the first pump elements P13, P14 and the second pump elements P21-P24, the second control valve group G2 can be connected to the first pump elements P11-P14 and the second pump elements P21-P24, and the third control valve group G3 can be connected to the first pump elements P11, P12 and the second pump elements P23, P24.

[0044] ~Operation principle of the first and second hydraulic pumps~ The first pump elements P11-P14 and the second pump elements P21-P24 of the first and second hydraulic pumps 14, 15 are each composed of a plurality of cylinder working chambers and solenoid valves that vary their net volumes (capacities), and the discharge flow rates of the first pump elements P11-P14 and the second pump elements P21-P24 are controlled by switching the solenoid valves based on commands output from the controller 28 and changing the net volumes of the cylinder working chambers. A hydraulic pump incorporating such pump elements is sometimes called a digital pump.

[0045] The details of the operating principles of the first hydraulic pump 14 and the second hydraulic pump 15 will be explained using Fig. 12. Fig. 12 is a schematic diagram showing a part of an electronically controlled hydraulic pump 200 that contains multiple pump elements, and the first and second hydraulic pumps 14, 15 each have the same configuration as the hydraulic pump 200.

[0046] The hydraulic pump 200 has a pump shaft 204 and at least three cylinder working chambers (hereinafter simply referred to as working chambers) 202 whose volumes change periodically as the pump shaft 204 rotates.

[0047] The hydraulic pump 200 also has a low pressure valve 209 that controls the flow of pressurized oil between a low pressure manifold 201 connected to a tank port 216 and the working chamber 202, and a high pressure valve 212 that controls the flow of pressurized oil between a high pressure manifold 213 connected to a discharge port 214 and the working chamber 202.

[0048] The hydraulic pump 200 forms a plurality of pump elements by means of working chambers 202, and each pump element has one or more working chambers 202 (typically multiple working chambers 202) and is connected to the aforementioned high-pressure manifold 213 which is common to the multiple working chambers 202 of each pump element.

[0049] The controller 207 corresponds to the controller 28 shown in Figure 2, and actively controls at least the low-pressure valve in phase correlation with the volume cycle of the working chamber 202, thereby determining whether each working chamber 202 will perform an active cycle in which a net volume of the working chamber 202 is formed between the low-pressure manifold 210 and the high-pressure manifold 213, or an inactive cycle in which a net volume of the working chamber 202 is not formed between the low-pressure manifold 210 and the high-pressure manifold 213, and thereby controlling the net volume of the working chamber 202 of each pump element leading to each discharge port 214 via each high-pressure manifold 213 according to the required flow rate.

[0050] The hydraulic pump 200 includes a plurality of cylinders 201 which define a plurality of working chambers 202 by their inner circumferential surfaces, and a plurality of pistons 203 which are driven by an eccentric cam 205 provided on a pump shaft 204 and reciprocate within the cylinders 201 to periodically change the volume of the working chambers 202 of the cylinders 201. The hydraulic pump 200 also includes a sensor 206 which detects the angular position and / or rotational speed of the shaft 204 at that time, and sends the detection information of the sensor 206 to a controller 207 via a signal line 208, and the controller 207 determines the current phase of the volume cycle of each working chamber 202 based on the detection information.

[0051] The working chambers 202 are each associated with a low pressure valve (LPV) 209 configured as an electronically actuated face-sealing poppet valve that is operable to selectively close the flow path from the working chambers 202 to a low pressure manifold 210. The low pressure manifold 210 may thereby connect one or more, or all, of the working chambers 202 associated with each pump element to a tank port 216.

[0052] The LPV 209 is a normally open solenoid valve that is passively open during the intake stroke when the pressure in the working chamber 202 is equal to or less than the pressure in the low pressure manifold 210, placing the working chamber 202 in fluid communication with the low pressure manifold 210, while the LPV 209 is connected to the controller 207 via an LPV control line 211 and can be selectively closed under active control by the controller 207, placing the working chamber 202 out of fluid communication with the low pressure manifold 210. The LPV 209 may alternatively be a normally closed solenoid valve.

[0053] Each of the working chambers 202 is further associated with a high pressure valve (HPV) 212 configured as a pressure actuated discharge valve. The HPV 212 opens outwardly from the respective working chamber 202 and is operable to seal a flow passage extending from the working chamber 202 to the high pressure manifold 213. When the HPV 212 is open, the high pressure manifold 213 connects the working chamber 202 to the discharge port 214, allowing pressurized oil to flow from the working chamber 202 to the discharge port 214. The HPV 212 functions as a normally closed pressure relief check valve that opens passively in balance with the biasing force of a biasing member within the HPV 212 due to a pressure differential across the HPV 212. In some embodiments, the HPV 212 also functions as a normally closed electromagnetic check valve that, once opened by the pressure within the working chamber 202, is selectively held open by the controller 207 via the HPV control line 215. Typically, the HPV 212 cannot be opened by the controller 207 against pressure in the high pressure manifold 213. The HPV 212 may also be open or partially open under the control of the controller 207 when there is pressure in the high pressure manifold 213 and no pressure in the working chamber 202.

[0054] In the discharge mode, the controller 207 selects a net volumetric flow rate from the working chamber 202 to the high pressure manifold 213 by the hydraulic pump 200 by actively closing one or more LPVs 209 near a maximum volumetric point in the volumetric cycle of the associated working chamber 202 to close the flow path to the low pressure manifold 210, thereby allowing hydraulic fluid to flow through the associated HPV 212 (but without actively opening the HPV 212) on the subsequent contraction stroke, resulting in a useful cycle with a net volumetric flow rate of the working chamber 202. Alternatively, the LPV 209 may be left open throughout the entire cycle of the working chamber 202 (or the working chamber 202 may be closed throughout the entire cycle), resulting in a non-useful cycle with no net volumetric flow rate. The controller 207 selects the number and sequence of useful and non-useful cycles to generate flow or generate shaft torque or power to meet the selected net volumetric flow rate of the working chamber 202 of the pump element connected to the same high pressure manifold 213 and discharge port 214, and to meet the flow rate demand of the pump element.

[0055] The controller 207 is operable not only to decide for each cycle whether to close or leave the LPV 209 open, selecting between active and inactive cycles, but also to precisely vary the phase at which the LPV 209 and / or HPV 212 are closed in relation to the changing volume of the working chamber 202, thereby selecting the net volumetric amount from the high pressure manifold 213 to the low pressure manifold 210 or vice versa.

[0056] The arrows on the manifolds 210, 213 indicate the flow of hydraulic fluid in pump mode, with the flow being reversed in motor mode.

[0057] While the illustrated example shows all working chambers 202 connected to the same high pressure manifold 213 and discharge port 214, typically the hydraulic pump 200 further comprises working chambers 202 forming one or more separate pump elements having their own high pressure manifold 213, discharge port 214, and demand signal.

[0058] More specifically, in the first hydraulic pump 14, four high-pressure manifolds 213 and four discharge ports 214 corresponding to the first discharge ports 14a, 14b, 14c, and 14d are provided, and each high-pressure manifold 213 is connected to the working chamber 202 via a high-pressure valve 209. The same is true for the second hydraulic pump 15.

[0059] The demand signal may be expressed in any suitable units. As an example, the demand signal is expressed as a "volume change rate Fd," which is the maximum possible volume change per revolution of the pump shaft 204. The target flow rate is expressed as the product of the volume change rate Fd and the rotational speed of the pump shaft 204.

[0060] ~Controller~ The processing contents of the controller 28 will now be described.

[0061] FIG. 4 is a functional block diagram showing the processing contents of the controller 28. As shown in FIG.

[0062] The controller 28 has a requested pump element number / allocated pump element number calculation unit 28a, and a directional control valve command / switching valve command / pump command calculation unit 28b.

[0063] The processing functions of the requested pump element number / allocated pump element number calculation unit 28a and the directional control valve command / switching valve command / pump command calculation unit 28b will be described in detail below.

[0064] <Requested pump element number / allocated pump element number calculation unit 28a> <<Overview of calculation processing>> The required pump element number / allocated pump element number calculation unit 28a (hereinafter sometimes simply referred to as the calculation unit 28a) calculates a required pump element number as a required flow rate of the multiple hydraulic actuators 105a-109a including the boom cylinder 107a, the arm cylinder 108a, the bucket cylinder 109a, and the swing motor 106 corresponding to the operation signals based on the operation signals generated by the multiple operating devices 115a-116b, and calculates a first allocated pump element number for each hydraulic actuator based on the required pump element number.

[0065] At this time, the calculation unit 28a corrects the required number of pump elements so that the total number of pump elements falls within the range of 8, which is the total number of pump elements of the multiple first pump elements P11 to P14 and the multiple second pump elements P21 to P24, and sets this corrected required number of pump elements as the first assigned number of pump elements for each hydraulic actuator.

[0066] <<Details of calculation process - required flow rate and required number of pump elements>> FIG. 5 is a diagram showing a table for calculating the required flow rate of the boom cylinder 107a (hereinafter referred to as the required flow rate of the boom), the required flow rate of the arm cylinder 108a (hereinafter referred to as the required flow rate of the arm), the required flow rate of the bucket cylinder 109a (hereinafter referred to as the required flow rate of the bucket), and the required flow rate of the swing motor 106a (hereinafter referred to as the required flow rate for swing) based on the operation signals of the operating devices 115a, 115b.

[0067] The controller 28 stores a required flow rate calculation table as shown in FIG. 5, and a required pump element number / allocated pump element number calculation unit 28a calculates the required flow rate from the operation signal using the table.

[0068] Each of the operating devices 115a, 115b is configured to generate an operating signal for driving two hydraulic actuators with one operating lever.

[0069] That is, when the operation lever of the left operation device 115a is operated in the left-right direction, an operation signal for driving the arm cylinder 108a is generated, and when the operation lever of the left operation device 115a is operated in the front-back direction, an operation signal for driving the swing motor 106a is generated. Operation of the operation lever of the operation device 115a in the left-right direction corresponds to operation in the arm dump direction and the arm cloud direction, respectively, and operation of the operation lever of the operation device 115a in the front-back direction corresponds to operation in the swing right direction and the swing left direction, respectively.

[0070] When the operation lever of the right operation device 115b is operated in the left-right direction, an operation signal for driving the bucket cylinder 109a is generated, and when the operation lever of the right operation device 115b is operated in the front-rear direction, an operation signal for driving the boom cylinder 107a is generated. Operation of the operation lever of the operation device 115b in the left-right direction corresponds to operation in the bucket cloud direction and the bucket dump direction, respectively, and operation of the operation lever of the operation device 115b in the up-down direction corresponds to operation in the boom lowering direction and the boom raising direction, respectively.

[0071] The boom table shown in FIG. 5 has set thereon a boom required flow characteristic DF1 when the operating lever of the operating device 115b is operated in the forward / backward direction, the arm table has set thereon an arm required flow characteristic DF2 when the operating lever of the operating device 115a is operated in the left / right direction, the bucket table has set thereon a bucket required flow characteristic DF3 when the operating lever of the operating device 115b is operated in the left / right direction, and the swing table has set thereon a swing required flow characteristic DF4 when the operating lever of the operating device 115a is operated in the forward / backward direction.

[0072] The horizontal axis of Figure 5 indicates the lever operation amount as a percentage of the full lever operation amount, and the vertical axis indicates the required flow rate as the number of pump elements, the first pump elements P11-P14 and the second pump elements P21-P24 of the first hydraulic pump 14 and the second hydraulic pump.

[0073] The maximum required flow rate of the boom and arm tables is 8, which is the same as the total number of pump elements of the first pump elements P11-P14 and the second pump elements P21-P24, and the maximum required flow rate of the bucket and swing tables is 6, which is less than the total number of pump elements. In each of the boom, arm, bucket and swing tables, the required flow rate characteristics DF1-DF4 are set so that the required flow rate increases as the lever operation amount increases. By setting the required flow rate characteristics DF1-DF4 in this manner, the required pump element number is calculated based on the operation signals generated by the multiple operation devices 115a-116b as the required flow rate of the hydraulic actuator corresponding to the operation signals, with the maximum pump element number being the number of pump elements that does not exceed the total number of pump elements of the first pump elements P11-P14 and the second pump elements P21-P24. At this time, if a fraction after the decimal point occurs, the required pump element number is calculated as a value including the first decimal point, rounded off to the second decimal point.

[0074] The controller 28 stores a similar table for the operation signals of the operation devices 116a and 116b for traveling, and the required pump element number / allocated pump element number calculation unit 28a uses the table to calculate the required flow rate (required pump element number) from the operation signals. The explanation of the travel table will be omitted.

[0075] <<Details of calculation process - Number of 1st assigned pump elements>> The requested number of pump elements / allocated number of pump elements calculation unit 28a calculates the requested flow rate (requested number of pump elements) using the calculation logic described below.

[0076] As an operation example, assume that the operation lever of the operation device 115b is operated in the boom raising direction with an operation amount of 80%, while being operated in the bucket cloud direction perpendicular to the boom raising direction with an operation amount of 40%, and furthermore, the operation lever of the operation device 115a is operated in the arm cloud direction with an operation amount of 80%. In this operation example, the required pump element number of the boom is 6.4, the required pump element number of the arm is 6.4, and the required pump element number of the bucket is 1.6, so the total required pump element number is greater than 8. Therefore, it is necessary to calculate the allocated pump element number by correcting the required pump element number so that the total pump element number is 8 or less.

[0077] FIG. 6 is a flowchart showing the calculation logic of the number of allocated pump elements in the requested pump element number / allocated pump element number calculation unit 28a.

[0078] First, the calculation unit 28a calculates the required number of pump elements for the boom cylinder 107a (hereinafter referred to as the required number of pump elements for the boom), the required number of pump elements for the arm cylinder 108a (hereinafter referred to as the required number of pump elements for the arm), the required number of pump elements for the bucket cylinder 109a (hereinafter referred to as the required number of pump elements for the bucket), and the required number of pump elements for the swing motor 106a (hereinafter referred to as the required number of pump elements for swing) using the table shown in Fig. 5, and expresses them as a = the required number of pump elements for the boom, b = the required number of pump elements for the arm, c = the required number of pump elements for the bucket, and d = the required number of pump elements for swing (step S100). In the above operation example, it can be expressed as (a, b, c) = (6.4, 6.4, 1.6).

[0079] Next, the calculation unit 28a assigns the number of pump elements to each actuator in the following procedure, and sets the number as a first assigned number of pump elements.

[0080] First, the calculation unit 28a expresses the rounded up values ​​of the requested numbers of pump elements as a', b', c', and d' (step S110). In this operation example, (a', b', c') = (7, 7, 2).

[0081] Next, it is determined whether the sum of the required pump element numbers a', b', c', d' is 8 or less (step S120), and if No, a correction calculation is performed so that the sum of a, b, c, d is within the range of 8, and the first decimal place is rounded off and the resulting value is replaced with the new required pump element numbers a', b', c', d' (step S130). In this operation example, since a'+b'+c'=7+7+2=16, and the sum of a, b, c, d is not 8 or less, a correction calculation is performed so that the sum is within the range of 8, and the first decimal place is rounded off and the value is replaced with the new required pump element numbers a', b', c', d', thereby obtaining (a', b', c')=(4, 4, 1).

[0082] Next, the calculation unit 28a again determines whether the total of the required pump element numbers a', b', c', d' is 8 or less (step S140), and reduces the maximum value of a', b', c', d' by one. If there are two or more maximum values, the pump element numbers are reduced by one in the order of boom, arm, bucket, and swing, and the reduced pump element numbers are defined again as a', b', c', d' (step S150). In this operation example, (a', b', c') = (4, 4, 1), and the total is 9, so the maximum value of a', b', c' is reduced by one. In this operation example, a' = 4, b' = 4, and there are two or more maximum values, so the number of pump elements of the boom is reduced by one in the above order, and as a result, (a', b', c') = (3, 4, 1) is obtained.

[0083] Finally, the calculation unit 28a compares the values ​​of the same symbols (a, b, c, d) and (a', b', c', d'), selects the smaller of the two values, and sets the smaller requested pump element number as the first allocated pump element number (step S160). In this operation example, (a, b, c) = (6.4, 6.4, 1.6), and (a', b', c') = (3, 4, 1), so (a', b', c) = (3, 4, 1) is set as the first allocated pump element number.

[0084] <Directional control valve command / switching valve command / pump command calculation unit 28b> <<Overview of calculation processing>> A directional control valve command, switching valve command, and pump command calculation unit 28b (hereinafter, sometimes simply referred to as calculation unit 28b) calculates the second allocated number of pump elements for each directional control valve based on the first allocated number of pump elements for each hydraulic actuator.

[0085] At this time, the calculation unit 28b presets priorities for allocating the numbers of pump elements to the first, second and third boom directional control valves 19, 23, 27 as priorities of the control valve groups, allocates the numbers of pump elements to the first, second and third boom directional control valves 19, 23, 27 and the first, second and third arm directional control valves 20, 22, 26 in accordance with the priorities, and calculates the second allocated number of pump elements for each directional control valve.

[0086] The priority of the control valve groups which allocate the numbers of pump elements to the first, second and third boom directional control valves 19, 23 and 27 is, for example, the first control valve group G1, the second control valve group G2 and the third control valve group G3, as indicated by "Boom 1", "Boom 2" and "Boom 3" for the boom directional control valves 19, 23 and 27 in FIG. 2 (see FIG. 8), and the priority of the control valve groups which allocate the numbers of pump elements to the first, second and third arm directional control valves 20, 22 and 26 is, for example, the second control valve group G2, the first control valve group G1 and the third control valve group G3, as indicated by "Arm 2", "Arm 1" and "Arm 3" for the arm directional control valves 20, 22 and 26 in FIG. 2.

[0087] Moreover, the calculation unit 28b calculates the second allocated number of pump elements in the following procedure.

[0088] 1. The number of pumps is assigned to the bucket directional control valve 18 and the swing directional control valve 21 with the highest priority, which is set as the second assigned number of pump elements.

[0089] 2. Within the same control valve group, when the number of pump elements is assigned to one of the first, second and third boom directional control valves 19, 23 and 27 and one of the arm directional control valves of the first, second and third arm directional control valves 20, 22 and 26, and the number of pump elements assigned to the boom directional control valve is the same as the number of pump elements assigned to the arm directional control valve, the allocation of the number of pump elements to the boom directional control valve is withdrawn and the number of pump elements is assigned to the boom directional control valve of the control valve group with the next highest priority, making it the second allocated number of pump elements.

[0090] 3. If the number of pump elements assigned to the boom directional control valve and the number of pump elements assigned to the arm directional control valve are not the same, the allocation of the number of pump elements to the boom directional control valve or the arm directional control valve whichever has the fewer number of allocated pump elements shall be withdrawn, and the number of pump elements to the directional control valve with the next highest priority shall be assigned as the second allocated number of pump elements.

[0091] Furthermore, the calculation unit 28b switches and controls the directional control valve to which the second allocated pump element number is assigned, and controls the multiple first switching valves V11-V14 and the multiple second switching valves V21-V24 and the multiple first pump elements P11-P14 and the multiple second pump elements P21-P24 so that the flow rate of the second allocated pump element number is supplied to the directional control valve to which the second allocated pump element number is assigned.

[0092] <<Details of the calculation process>> 7A and 7B are flowcharts showing the calculation contents of the directional control valve command / switching valve command / pump command calculation unit 28b. Fig. 8 is a diagram showing a control valve group priority order map used for allocating the numbers of pump elements set for the first to third boom directional control valves 19, 23, 27 and the first to third arm directional control valves 20, 22, 26.

[0093] The calculation result of the first assigned pump element numbers in this operation example is (a', b', c) = (3, 4, 1), and as the assigned pump element numbers of the hydraulic actuators, 3 pump elements are assigned to the boom cylinder 107a, 4 pump elements are assigned to the arm cylinder 108a, and 1 pump element is assigned to the bucket cylinder 109a.

[0094] First, when the hydraulic actuator to which the pump element number is assigned includes bucket cylinder 109a or swing motor 106, since the relevant directional control valve is only bucket directional control valve 18 or swing direction control valve 21, calculation unit 28b assigns the pump element number to bucket directional control valve 18 or swing direction control valve 21 with the highest priority, and sets it as the second assigned pump element number (step S200). In this operation example, since pump element number 1 is assigned to bucket cylinder 109a, pump element number 1 is assigned to bucket directional control valve 18 with the highest priority, and sets it as the second assigned pump element number.

[0095] Next, the calculation unit 28b sets the number of pump elements allocated to the remaining boom and arm as a new number of pump elements allocated X, and reads the number of pump elements Y that can be allocated to each of the control valve groups G1, G2, and G3 (step S210). At this time, if the number of pump elements was allocated to the bucket direction control valve 18 or the swing direction control valve 21 in step S200, the corresponding control valve group G1 or G2 is excluded from the control valve group for which the number of pump elements Y that can be allocated is read.

[0096] In this embodiment, G1 can be connected to the first pump elements P13, P14 and the second pump elements P21-P24, and G2 can be connected to the first pump elements P11-P14 and the second pump elements P21-P24. Therefore, G3 can be connected to the first pump elements P11, P12 and the second pump elements P23, P24, so the number of pump elements that can be assigned to G1 is 6, the number of pump elements that can be assigned to G2 is 6, and the number of pump elements that can be assigned to G3 is 4.

[0097] Also, in this operation example, since the bucket directional control valve 18 is assigned the pump element number 1, G1 is excluded from the control valve group that reads the assignable pump element number Y, and the assignable pump element number 6 of G2 and the assignable pump element number 4 of G3 are read.

[0098] Next, the calculation unit 28b sets the number of processing times i=1 (step S220), and assigns the smaller of the number of assigned pump elements X and the number of allocatable pump elements, min(X,Y), to each of the boom and arm for the control valve group with the i-th priority in the priority map of Fig. 8, and sets it as the second number of assigned pump elements. Also, the remaining number of assigned pump elements X is updated to X-min(X,Y) (step S230). If the remaining number of assigned pump elements X does not become a value of 0 or less in the first processing with i=1, the same processing is repeated three times by sequentially setting i=2, i=3 (steps S240→S250→S230→S240).

[0099] In this embodiment, in the priority order map of FIG. 8, the priority order is set for the boom cylinder 107a as follows: G1 is set to 1, G2 is set to 2, and G3 is set to 3, and the priority order is set for the arm cylinder 108a as follows: G2 is set to 1, G1 is set to 2, and G3 is set to 3.

[0100] In this operation example, since G1 with priority 1 for the boom is excluded from the control valve group into which the number of allocatable pump elements Y is read, G2 with priority 2 becomes priority 1, and the second boom directional control valve 23 of G2 is assigned the number of pump elements 3, which is the smaller of the number of allocated pump elements X=3 and the number of allocatable pump elements Y=6. Also, the second arm directional control valve 22 of G2 with priority 1 for the arm is assigned the number of pump elements 4, which is the smaller of the number of allocated pump elements X=4 and the number of allocatable pump elements Y=6, and this is set as the second number of allocated pump elements, and the number of allocated pump elements of the remaining boom and arm is set as the new remaining number of allocated pump elements X(=X-min(X,Y) (step S230).

[0101] In addition, in this operation example, the remaining new number of allocated pump elements X for the boom is X-min(X,Y) = 3-3 = 0, and the remaining new number of allocated pump elements X for the arm is X-min(X,Y) = 3-4 = -1, so proceed to the next step after the first processing.

[0102] Next, the calculation unit 28b sets the number of processing times as i=1 (step S260), and judges whether or not multiple directional control valves are used in the same control valve group (step S270). If the judgment is Yes, it judges whether or not the allocated pump element numbers of the multiple directional control valves used in the same control valve group are the same (step S280), and if Yes, it cancels the allocation of the pump element number of the boom directional control valve, moves to the directional control valve with the next priority and allocates the pump element number to it, setting it as the second allocated pump element number (step S290).

[0103] On the other hand, if the determination in step S280 is No, the calculation unit 28b cancels the allocated pump element number of the boom directional control valve or the arm directional control valve, whichever has the fewer, and moves to the directional control valve with the next priority and allocates the pump element number to set it as the second allocated pump element number (step S300).Then, the calculation unit 28b determines whether i is i≧2 (step S310), and if No, it increments i by 1 and repeats the same process (steps S320, S270 to S310), and if Yes, it proceeds to the next process.

[0104] In this operation example, the second boom directional control valve 23 of G2 is assigned the pump element number 3, and the second arm directional control valve 22 of the same G2 is assigned the pump element number 4, and multiple directional control valves are used in the same control valve group. Therefore, the determination in step S270 is Yes, and the process proceeds to step S280. Since the assigned pump element numbers of the second boom directional control valve 23 and the second arm directional control valve 22 used in the same control valve group G2 are different, 3 and 4, the determination in step S280 is No, and the process proceeds to step S300. In step S300, the boom directional control valve with the smaller assigned pump element number (the second boom directional control valve 23) moves to the third boom directional control valve 27 of G3, which is the next-ranked directional control valve, and the third boom directional control valve 27 is assigned the pump element number 3, making it the second assigned pump element number.

[0105] Furthermore, in the second processing for i=2, since multiple directional control valves are not used in the same control valve group, the result of step S270 is No, and the process proceeds to the next processing.

[0106] As a result, in this operation example, the pump element number 1 is ultimately assigned to the bucket directional control valve 18 of G1, the pump element number 4 is assigned to the second arm directional control valve 22 of G2, and the pump element number 3 is assigned to the third boom directional control valve 27 of G3.

[0107] Next, the calculation unit 28b generates and outputs control valve commands to switch the directional control valves in the first control valve group G1, the second control valve group G2, and the third control valve group G3 to which the numbers of pump elements are assigned as described above (step S330).

[0108] Next, the calculation unit 28b is connected to the control valve group to which the directional control valve to which the pump element number is assigned belongs, selects a pump element and a switching valve that supply the flow rate of the assigned pump element number to that control valve group, calculates the target discharge volume of the selected pump element and whether or not the selected switching valve needs to be switched, and generates and outputs corresponding pump commands and switching valve commands (step S340).

[0109] The pump element and switching valve connected to the control valve group may be selected according to predetermined rules depending on the type of hydraulic actuator driven by the directional control valve (e.g., boom cylinder or arm cylinder), the type of control valve group to which the directional control valve belongs (G1, G2, or G3), whether the operation is independent or combined, etc. Once the pump element and switching valve are selected, the necessity for switching the switching valve connected to the control valve group is also automatically determined. At this time, it is preferable to determine the above rules so that the operation frequency of the switching valve is reduced as much as possible.

[0110] In this operation example, the pump element and the switching valve are selected according to a predetermined rule, for example, in the following order, and it is determined whether or not the switching valve needs to be switched.

[0111] G3 3rd boom directional control valve 27 (2nd assigned pump element number 3) Connecting pump elements: P11, P12, P24 Switching valves to be connected: V11, V12, V24 First arm directional control valve 20 of G2 (number of second assigned pump elements: 4) Connecting pump elements: P21, P22, P13, P14 Switching valves to be connected: V21, V22, V13, V14 Bucket directional control valve 18 of G1 (number of second assigned pump elements: 1) Connecting pump element: P23 Connecting switching valve: V23 Switching valves that need to be switched from the initial position: V11, V12, V24, V21, V22 In this embodiment, the maximum discharge amount of the pump element is, for example, 120 L / min, and the target discharge amount of the pump element is calculated by the following formula.

[0112] Target discharge rate = (Number of second allocated pump elements x Maximum discharge rate) / Number of pump elements In the above example operation, the target discharge amount is calculated as follows.

[0113] Pump elements P11, P12, P24: Target discharge amount=(3×120L / min) / 3=120L / min Pump elements P21, P22, P13, P14: Target discharge amount=(4×120L / min) / 4=120L / min Pump element P23: Target discharge amount=(1×120L / min) / 1=120L / min That is, in this operation example, since the assigned pump element numbers of all directional control valves are integers, the assigned pump element number and the number of pumps are the same value, and the average discharge amount is calculated as 120 L / min, which is the same value as the maximum discharge amount. If the assigned pump element number is a value including a fraction after the decimal point, the number of pumps is a value larger than the second assigned pump element number, and the target discharge amount is calculated as the average discharge amount smaller than the maximum discharge amount (see operation examples 2 and 3 described later).

[0114] In the above explanation based on the flowcharts shown in Figures 6, 7A, and 7B, explanations related to the left and right traveling motors 105a, 105b have been omitted. However, for the left and right traveling motors 105a, 105b, like the bucket cylinder 109a, there are only one corresponding directional control valve each, the left traveling direction control valve 17 and the right traveling direction control valve 25, so it is sufficient to carry out the same processing as for the bucket cylinder 109a.

[0115] ~Operation~ FIG. 9 is a diagram showing an operation pattern map for explaining a further operation example of this embodiment.

[0116] In the motion pattern map shown in Figure 9, the first column on the left shows the types of "motion": "single motion" of the boom or arm, "two-combined motion" of the boom and arm, and "three-combined motion" of the boom, arm, and bucket.

[0117] In addition, the second column from the left shows the "lever operation amount" of the operating device, the "requested pump element number: requested flow rate" determined by the lever operation amount, and the first allocated pump element number, and the requested pump element number and the first allocated pump element number are values ​​calculated by calculation unit 28a.

[0118] The third column from the left shows the directional control valves to which the number of pump elements is assigned and the second assigned number of pump elements for each of the control valve groups G1, G2, and G3, and the second assigned number of pump elements is a value calculated by the calculation unit 28b.

[0119] In addition, the fourth and fifth columns from the left show the control valve groups G1, G2, G3 connected to the first and second switching valves V11, V12, V13, V14 and the second switching valves V21, V22, V23, V24, respectively, in comparison with the case where the operating lever in the top row is not operated. In the case where the operating lever is not operated in the top row, the first switching valves V11 to V14 and the second switching valves V21 to V24 are in the initial position (first position), and in the rows below, the symbols of the control valve groups different from the control valve groups G1, G2, G3 in the case where the operating lever is not operated indicate the switching valves switched from the initial position to the second position.

[0120] In the sixth and seventh columns from the left, for each of the first pump elements P11, P12, P13, and P14 and the second pump elements P21, P22, P23, and P24, pump elements that supply flow rates corresponding to the number of assigned pump elements to the control valve group are indicated with circles and crosses in comparison with the case where the topmost operating lever is not operated. Crosses indicate pump elements that do not discharge pressure oil, and circles indicate pump elements that discharge pressure oil.

[0121] Whether or not the above-mentioned switching valve is switched and whether or not the pump element is discharging pressure oil are the results of calculations made by the calculation unit 28b.

[0122] Below, we will explain the operation examples of the operation pattern map shown in Figure 9, including a two-component operation with a boom lever operation amount of 20% and an arm lever operation amount of 100% (operation example 1), a three-component operation with a boom lever operation amount of 10%, an arm lever operation amount of 10% and a bucket lever operation amount of 10% (operation example 2), and a three-component operation with a boom lever operation amount of 60%, an arm lever operation amount of 10% and a bucket lever operation amount of 10% (operation example 3).

[0123] <Example 1> Two combined movements: boom 20%, arm 100% This operation example is when the operating lever of the operating device 115b is operated in the boom raising direction, and the operating lever of the operating device 115a is operated in the arm crowding direction, and the ratio of the lever operation amount at that time to full operation is 20% for boom and 100% for arm.

[0124] The controller 28, which has received the operation signals from the operating devices 115b, 115a, calculates, in step S100 of the flowchart shown in FIG. 6 in the calculation unit 28a, the required number of pump elements a of the boom and the required number of pump elements of the arm according to the respective lever operation amounts using the boom and arm tables shown in FIG. 5 as follows:

[0125] (a,b)=(1.6,8) Next, in step S110, values ​​a' and b' obtained by rounding up a and b are calculated as follows.

[0126] (a',b')=(2,8) In this case, the total required number of pump elements is 10, which is more than the number of pump elements 8, so in steps S130 and S140, the sum of a' and b' is corrected to be within the range of 8, and the following values ​​a' and b' are calculated.

[0127] (a',b')=(1,7) Next, in step S160, the values ​​of the same symbols (a, b) and (a', b') are compared, and the smaller value is selected, thereby obtaining the following first allocated pump element numbers a', b'.

[0128] (a',b')=(1,7) Next, in steps S200 to S315 of the flowchart shown in Figures 7A and 7B of the calculation unit 28b, the controller 28 allocates pump element numbers to the directional control valves of the boom and arm based on the first allocated pump element number (a', b') = (1, 7) as follows, and obtains the second allocated pump element number.

[0129] G1 first boom directional control valve 19: Number of pump elements 1 G2 second arm directional control valve 22: Number of pump elements: 5 G3 third arm directional control valve 26: pump element number 2 Next, the controller 28 uses the numbers of pump elements assigned to the directional control valves 19, 22, and 26, selects pump elements and switching valves in the following order according to predetermined rules, and determines whether or not the switching valves need to be switched.

[0130] G1 1st boom directional control valve 19 (2nd assigned pump element number 1) Connecting pump element: P21 Connecting switching valve: V21 G2 second arm directional control valve 22 (number of second assigned pump elements: 5) Connecting pump elements: P11~P14, P22 Connected switching valves: V11~V14, V22 G3 third arm directional control valve 26 (second allocation pump element number 2) Connecting pump elements: P23, P24 Switching valve to be connected: V23, V24 Switching valves that need to be switched from the initial position: V22, V23, V24 Furthermore, if the maximum discharge amount of the pump element is set to 120 L / min as described above, the target discharge amount of the pump element is calculated as follows.

[0131] Pump element P21: Target discharge amount=(0.6×120L / min) / 1=72L / min Pump elements P11 to P14, P22: Target discharge amount=(5×120L / min) / 5=120L / min Pump elements P23, P24: Target discharge amount=(2×120L / min) / 2=120L / min Next, in steps S330 and S340 of the flowchart shown in FIG. 7B of the calculation unit 28b, the controller 28 generates and outputs control valve commands to switch the first boom direction control valve 19, the second arm direction control valve 22, and the third arm direction control valve 26, switching valve commands to switch the switching valves V22, V23, and V24 from the initial positions to the second positions, and pump commands to cause pump element P21, pump elements P11-P14, P22, pump elements P23, and P24 to discharge the above-mentioned target discharge amounts.

[0132] As a result, even if the required number of pump elements (required flow rate) according to the lever operation amount is greater than the actual number of pump elements, eight, the boom and arm can be driven without incurring the branch pressure loss that occurs when throttling the directional control valve on the low-pressure actuator side in the same control valve group.

[0133] <Example 2> Three combined movements: boom 10%, arm 10%, bucket 10% This operation example is for a case in which the operating lever of the operating device 115b is operated in the boom raising direction and bucket crowding direction, and the operating lever of the operating device 115a is operated in the arm crowding direction, with the ratio of the lever operation amount at that time to full operation being boom 10%, arm 10%, and bucket 10%.

[0134] In step S100 of the flow chart shown in Fig. 6, the controller 28 receives the operation signals from the operation devices 115b and 115a and calculates the required number of pump elements a for the boom, the required number of pump elements b for the arm, and the required number of pump elements c for the bucket according to the respective lever operation amounts using the tables for the boom, arm, and bucket shown in Fig. 5 as follows:

[0135] (a,b,c)=(0.8.0.8,0.6) Next, in step S110, values ​​a', b', and c' obtained by rounding up a, b, and c are calculated as follows.

[0136] (a',b',c')=(1,1,1) In this case, the total required number of pump elements is 3, which is less than the number of pump elements 8, so in step S160, the values ​​of the same symbols (a, b, c) and (a', b', c') are compared and the smaller value is selected, obtaining the following first allocated pump element numbers a', b', c'.

[0137] (a',b',c')=(0.8.0.8,0.6) Next, in steps S200 to S320 of the flowchart shown in Figures 7A and 7B of the calculation unit 28b, the controller 28 assigns pump element numbers to the directional control valves of the boom, arm, and bucket based on (a', b', c') = (0.8.0.8, 0.6) as follows, and obtains a second assigned pump element number.

[0138] G1 bucket directional control valve 18: Number of pump elements 0.6 G2 second arm directional control valve 22: pump element number 0.8 G3 3rd boom directional control valve 27: pump element number 0.8 Next, the controller 28 uses the number of pump elements assigned to the directional control valves 18, 22, and 27, selects pump elements and switching valves in the following order according to predetermined rules, and determines whether or not the switching valve needs to be switched.

[0139] Bucket directional control valve 18 of G1 (number of second allocated pump elements 0.6) Connecting pump element: P21 Connecting switching valve: V21 G2 second arm directional control valve 22 (second allocation pump element number 0.8) Connecting pump element: P12 Connected switching valve: V12 G3 3rd boom directional control valve 27 (2nd assigned pump element number 0.8) Connecting pump element: P11 Connected switching valve: V11 Switching valve that needs to be switched from the initial position: V11 Furthermore, if the maximum discharge amount of the pump element is 120 L / min as described above, the target discharge amount of the pump element is calculated as follows.

[0140] Pump element P21: Target discharge amount=(0.6×120L / min) / 1=72L / min Pump element P12: Target discharge amount=(0.8×120L / min) / 1=96L / min Pump element P11: Target discharge amount=(0.8×120L / min) / 1=96L / min Next, in steps S330 and S340 of the flowchart shown in FIG. 7B of the calculation unit 28b, the controller 28 generates and outputs control valve commands to switch the bucket directional control valve 18, the second arm directional control valve 22, and the third arm directional control valve 26, a switching valve command to switch the switching valve V11 from the initial position to the second position, and pump commands to cause the pump elements P21, P12, and P11 to discharge the above-mentioned target discharge amounts.

[0141] This makes it possible to drive the boom, arm, and bucket without the branch pressure loss that occurs when throttling the directional control valve on the low-pressure actuator side in the same control valve group.

[0142] <Example 3> Three combined movements: boom 60%, arm 10%, bucket 10% This operation example is when the operating lever of the operating device 115b is operated in the boom raising direction and bucket crowding direction, and the operating lever of the operating device 115a is operated in the arm crowding direction, and the ratio of the lever operation amount to full operation at that time is boom 60%, arm 10%, and bucket 10%.

[0143] In step S100 of the flow chart shown in Fig. 6, the controller 28 receives the operation signals from the operation devices 115b and 115a and calculates the required number of pump elements a for the boom, the required number of pump elements b for the arm, and the required number of pump elements c for the bucket according to the respective lever operation amounts using the tables for the boom, arm, and bucket shown in Fig. 5 as follows:

[0144] (a,b,c)=(4.8.0.8,0.6) Next, in step S110, values ​​a', b', and c' obtained by rounding up a, b, and c are calculated as follows.

[0145] (a',b',c')=(5,1,1) In this case, the total required number of pump elements is 7, which is less than the number of pump elements 8, so in step S160, the values ​​of the same symbols (a, b, c) and (a', b', c') are compared and the smaller value is selected, obtaining the following first allocated pump element numbers a', b', c'.

[0146] (a',b',c')=(4.8.0.8,0.6) Next, in steps S200 to S315 of the flowchart shown in Figures 7A and 7B of the calculation unit 28b, the controller 28 assigns pump element numbers to the directional control valves of the boom, arm, and bucket based on (a', b', c') = (4.8.0.8, 0.6) as follows, and a second assigned pump element number is obtained.

[0147] G1 bucket directional control valve 18: Number of pump elements 0.6 G3 3rd boom directional control valve 27: Number of pump elements 4 G2 second arm directional control valve 22: pump element number 0.8 G2 second boom directional control valve 23: pump element number 0.8 Next, the controller 28 uses the numbers of pump elements assigned to the directional control valves 18, 22, 23, and 27, selects pump elements and switching valves in the following order according to predetermined rules, and determines whether or not the switching valves need to be switched.

[0148] Bucket directional control valve 18 of G1 (number of second allocated pump elements 0.6) Connecting pump element: P21 Connecting switching valve: V21 G3 3rd boom directional control valve 27 (2nd assigned pump element number 4) Connecting pump elements: P11, P12, P23, P24 Connected switching valves: V11, V12, V23, V24 G2 second arm directional control valve 22 (second allocation pump element number 0.8) Connecting pump element: P13 Connected switching valve: V13 G2 second boom directional control valve 23 (second allocation pump element number 0.8) Connecting pump element: P14 Connecting switching valve: V14 Switching valves that need to be switched from the initial position: V11, V12, V23, V24 Furthermore, if the maximum discharge amount of the pump element is 120 L / min as described above, the target discharge amount of the pump element is calculated as follows.

[0149] Pump element P21: Target discharge amount=(0.6×120L / min) / 1=72L / min Pump elements P11, P12, P23, P24: Target discharge amount=(4×120L / min) / 4=120L / min Pump element P13: Target discharge amount=(0.8×120L / min) / 1=96L / min Pump element P14: Target discharge amount=(0.8×120L / min) / 1=96L / min Next, in steps S330 and S340 of the flowchart shown in FIG. 7B of the calculation unit 28b, controller 28 generates and outputs control valve commands to switch bucket directional control valve 18, second arm directional control valve 22, second boom directional control valve 23, and third boom directional control valve 27, switching valve commands to switch switching valves V11, V12, V23, and V24 from the initial positions to the second positions, and pump commands to cause pump element P21, pump elements P11, P12, P23, P24, pump element P13, and pump element P14 to discharge the above-mentioned target discharge amounts.

[0150] This reduces the branch pressure loss that occurs when throttling the directional control valve on the low-pressure actuator side in the same control valve group, making it possible to drive the boom, arm, and bucket.

[0151] ~Effects~ According to this embodiment, the following effects can be obtained.

[0152] 1. By making it possible to switch each of the first switching valves V11-V14 and the second switching valves V21-V24 between the first and second positions, the multiple first pump elements P11-P14 and the multiple second pump elements P21-P24 can be connected to the first control valve group G1, the second control valve group G2, and the third control valve group G3. Therefore, during combined operations including the arm and the boom, the multiple first pump elements P11-P14 and the multiple second pump elements P21-P24 can be distributed and connected to the boom directional control valves and arm directional control valves of different control valve groups in the first control valve group G1, the second control valve group G2, and the third control valve group G3, and pressurized oil can be supplied to the boom directional control valves and arm directional control valves of the different control valve groups. This reduces the frequency of operations in which both the boom directional control valve and the arm directional control valve in the same control valve group are switched to supply pressurized oil, reducing the branch pressure loss when throttling the directional control valve on the low-pressure actuator side in the same control valve group, and improving energy efficiency.

[0153] 2. By making it possible to switch each of the first switching valves V11-V14 and the second switching valves V21-V24 between the first and second positions, it is possible to supply pressurized oil discharged from the first pump elements P11-P14 not only to the second control valve group G2 but also to the first control valve group G1 and the third control valve group G3, and it is possible to supply pressurized oil discharged from the second pump elements P21-P24 not only to the first control valve group G1 but also to the second control valve group G2 and the third control valve group G3.Therefore, it is possible to supply pressurized oil from the first pump elements P11-P14 and the second pump elements P21-P24 to the three control valve groups G1, G2, G3 with the same number of switching valves V11-V14; V21-V24 as the first pump elements P11-P14 and the second pump elements P21-P24. This allows the size of the first switching valve block 30 and the second switching valve block 31 to be reduced, making it easier to secure space for mounting a hydraulic drive system equipped with such switching valve blocks 30, 31 inside a construction machine, and improving the mountability of the hydraulic drive system.

[0154] 3. By making it possible to switch each of the first switching valves V11-V14 and the second switching valves V21-V24 between the first position and the second position, the multiple first pump elements P11-P14 and the multiple second pump elements P21-P24 can be connected to the first control valve group G1, the second control valve group G2, and the third control valve group G3. Therefore, when the four pump elements P11-P14 of the first hydraulic pump 14 are connected to the second control valve group G2 according to the amount of lever operation to supply pressurized oil to the second arm directional control valve 22 and drive the arm cylinder 108a, the first switching valves V11-V14 can be maintained in the first position, which is the initial position. Similarly, when the four pump elements P21-P24 of the second hydraulic pump 15 are connected to the first control valve group G1 in accordance with the lever operation amount to supply pressure oil to the first boom direction control valve 19 and drive the boom cylinder 107a, the second switching valves V21-V24 may be held in the first position, which is the initial position. This makes it possible to reduce the number of times the switching valves 41a-41d, 42a-42d are switched when driving the arm cylinder 108a or boom cylinder 107a, and improve the durability of the switching valves 41a-41d, 42a-42d.

[0155] 4. As the first hydraulic pump and the second hydraulic pump, hydraulic pumps containing multiple first pump elements and second pump elements, each of which can have its discharge flow rate independently controlled, are used. Therefore, the discharge flow rate can be finely controlled by increasing or decreasing the number of discharge ports (the number of pump elements) connected to the actuator depending on the required flow rate, thereby improving operability.

[0156] <Second embodiment> FIG. 10 is a diagram showing a hydraulic drive system for a construction machine according to the second embodiment of the present invention.

[0157] The hydraulic drive system of this embodiment differs from the hydraulic drive system of the first embodiment shown in Figure 2 in that the swing direction control valve 21, which was included in control valve group G2 in the first embodiment, is included in control valve group G3, and a second spare directional control valve is included in control valve group G3.

[0158] Even when the hydraulic drive system is configured in this manner, the same effects as those of the first embodiment can be obtained.

[0159] <Third embodiment> FIG. 11 is a diagram showing a hydraulic drive system for a construction machine according to the third embodiment of the present invention.

[0160] The hydraulic drive system of this embodiment differs from the hydraulic drive system of the first embodiment shown in Figure 2 in that, while in the first embodiment, the first hydraulic pump 14 and the second hydraulic pump 15 are configured to include four first pump elements P11, P12, P13, P14 and four second pump elements P21, P22, P23, P24, respectively, in this embodiment, the first hydraulic pump 14 and the second hydraulic pump 15 are configured to include five first pump elements P11, P12, P13, P14, P15 and five second pump elements P21, P22, P23, P24, P25, respectively. In addition, as the number of first pump elements and second pump elements increases from four to five, the number of first and second switching valves connected to the five first pump elements P11, P12, P13, P14, P15 and the five second pump elements P21, P22, P23, P24, P25 also increases to five first switching valves V11, V12, V13, V14, V15 and five second switching valves V21, V22, V23, V24, V25.

[0161] In the hydraulic drive system configured in this manner, similar to the first embodiment, the effects of improving energy efficiency by reducing branch pressure loss and improving the mountability of the hydraulic drive system are obtained, and since the number of first pump elements and second pump elements is increased from four to five, the discharge flow rate can be controlled more finely and operability can be improved. [Explanation of symbols]

[0162] 102 Upper rotating body 107 Boom 108 Arm 109 Bucket 106a Swivel motor 107a Boom cylinder 108a Arm cylinder 109a Bucket cylinder 105a~109a Multiple hydraulic actuators 115a,115b Operating device 116a,116b Operating device 1 Prime mover 14 First hydraulic pump 15 No. 2 hydraulic pump 18 Bucket directional control valve 19 First boom directional control valve 20 First arm directional control valve 21 Swing directional control valve 22 Second arm directional control valve 23 No. 2 boom directional control valve 26 Third arm directional control valve 27 Third boom directional control valve 17~27 Multiple directional control valves 28 Controller 28a Required pump element number / allocated pump element number calculation section 28b Directional control valve command, switching valve command, pump command calculation unit 30 First switching valve block 31 Second switching valve block G1 First control valve group G2 Second control valve group G3 3rd control valve group P11, P12, P13, P14 First pump element P21, P22, P23, P24 Second pump element V11, V12, V13, V14 First switching valve V21, V22, V23, V24 Second switching valve P11, P12, P13, P14, P15 First pump element P21, P22, P23, P24, P25 Second pump element V11, V12, V13, V14, V15 First switching valve V21, V22, V23, V24, V25 Second switching valve

Claims

1. A plurality of hydraulic pumps; a plurality of hydraulic actuators driven by pressure oil discharged from the plurality of hydraulic pumps; a plurality of directional control valves for controlling the flow of pressure oil supplied from the plurality of hydraulic pumps to the plurality of hydraulic actuators; a plurality of operating devices that generate operation signals for driving the plurality of hydraulic actuators; The plurality of directional control valves are divided into a first control valve group, a second control valve group, and a third control valve group, The plurality of hydraulic actuators include a boom cylinder that drives a boom, an arm cylinder that drives an arm, a work tool cylinder that drives a work tool, and a rotation motor that drives a rotating body, In a hydraulic drive system for a construction machine, the first control valve group includes a first boom directional control valve and a first arm directional control valve, the second control valve group includes a second boom directional control valve and a second arm directional control valve, the third control valve group includes a third boom directional control valve and a third arm directional control valve, and a work tool directional control valve and a swing directional control valve are included in different control valve groups among the first control valve group, the second control valve group, and the third control valve group, The plurality of hydraulic pumps include a first hydraulic pump including a plurality of first pump elements each capable of independently controlling a discharge flow rate, and a second hydraulic pump including a plurality of second pump elements each capable of independently controlling a discharge flow rate, a plurality of first switching valves connected to a plurality of first pump elements of the first hydraulic pump and switching connections between the plurality of first pump elements and the first control valve group, the second control valve group, and the third control valve group; a plurality of second switching valves connected to a plurality of second pump elements of the second hydraulic pump and switching connections between the plurality of second pump elements and the first control valve group, the second control valve group, and the third control valve group; the plurality of first switching valves include at least one first switching valve configured to be switched, for each of a plurality of first pump elements of the first hydraulic pump, between a first position in which all of the pressure oil discharged from the first pump element is supplied to the second control valve group and a second position in which all of the pressure oil discharged from the first pump element is supplied to one of the first control valve group and the third control valve group, A hydraulic drive system for a construction machine, characterized in that the multiple second switching valves include at least one second switching valve configured for each of the multiple second pump elements of the second hydraulic pump to be switched between a first position in which all of the pressurized oil discharged from the second pump element is supplied to the first control valve group, and a second position in which all of the pressurized oil discharged from the second pump element is supplied to one of the second control valve group and the third control valve group.

2. 2. The hydraulic drive system for a construction machine according to claim 1, A portion of the plurality of first pump elements of the first hydraulic pump is connected to either the second control valve group other than the third control valve group or the first control valve group via at least one switching valve, and another portion of the plurality of first pump elements of the first hydraulic pump is connected to either the second control valve group other than the first control valve group or the third control valve group via at least one switching valve, A hydraulic drive system for a construction machine, characterized in that some of the multiple second pump elements of the second hydraulic pump are connected to either the first control valve group other than the third control valve group or the second control valve group via at least one switching valve, and other parts of the multiple second pump elements of the second hydraulic pump are connected to either the first control valve group other than the second control valve group or the third control valve group via at least one switching valve.

3. The hydraulic drive system for a construction machine according to claim 1 or 2, a controller that controls the first pump elements, the second pump elements, the directional control valves, the first switching valves, and the second switching valves based on operation signals generated by the operation devices; The controller Calculating a required number of pump elements as a required flow rate of the plurality of hydraulic actuators including the boom cylinder, the arm cylinder, the work tool cylinder, and the swing motor corresponding to the operation signals based on the operation signals generated by the plurality of operation devices; Calculating a first allocated number of pump elements for each hydraulic actuator based on the requested number of pump elements; calculating a second allocated number of pump elements for each directional control valve based on the first allocated number of pump elements for each hydraulic actuator; A hydraulic drive system for a construction machine, characterized in that a directional control valve to which the second allocated pump element number is assigned is switched and controlled, and the plurality of first switching valves and the plurality of second switching valves and the plurality of first pump elements and the plurality of second pump elements are controlled so that a flow rate of the second allocated pump element number is supplied to the directional control valve to which the second allocated pump element number is assigned.

4. 4. The hydraulic drive system for a construction machine according to claim 3, The controller a first allocated number of pump elements for each hydraulic actuator, the first allocated number of pump elements being set to a first number of pump elements for each hydraulic actuator, the first allocated number of pump elements being set to a first number of pump elements for each hydraulic actuator, and the first allocated number of pump elements being set to a first number of pump elements for each hydraulic actuator.

5. 4. The hydraulic drive system for a construction machine according to claim 3, The controller a first assigned number of pump elements for each of the first, second, and third boom directional control valves and the first, second, and third arm directional control valves is determined in advance as a priority order of a control valve group, a number of pump elements is allocated to the first, second, and third boom directional control valves and the first, second, and third arm directional control valves in accordance with the priority order, and a second assigned number of pump elements for each of the directional control valves is calculated.

6. 6. The hydraulic drive system for a construction machine according to claim 5, a first control valve group for allocating pump element numbers to the first, second and third boom directional control valves, in the order of first control valve group, second control valve group, and third control valve group; and a second control valve group for allocating pump element numbers to the first, second and third arm directional control valves, in the order of second control valve group, first control valve group, and third control valve group.

7. 6. The hydraulic drive system for a construction machine according to claim 5, The controller The number of pumps is assigned to the work tool direction control valve and the swing direction control valve with the highest priority, and set as the second assigned number of pump elements; a second allocated number of pump elements is assigned to the boom directional control valve of a control valve group having a next priority, if the number of pump elements assigned to the boom directional control valve is the same as the number of pump elements assigned to the arm directional control valve, and the allocation of the number of pump elements to the boom directional control valve of a control valve group having a next priority is cancelled, and a second allocated number of pump elements is assigned to the boom directional control valve of a control valve group having a next priority, if the number of pump elements assigned to the boom directional control valve is not the same as the number of pump elements assigned to the arm directional control valve,

8. In the hydraulic drive system for a construction machine according to any one of claims 1 to 7, the first hydraulic pump and the second hydraulic pump each include four pump elements; A hydraulic drive system for a construction machine, wherein each of the first plurality of switching valves and the second plurality of switching valve groups includes four switching valves.

9. In the hydraulic drive system for a construction machine according to any one of claims 1 to 8, the first hydraulic pump and the second hydraulic pump each include five pump elements; 2. A hydraulic drive system for a construction machine, wherein each of the plurality of first switching valves and the plurality of second switching valves includes five switching valves.

10. In the hydraulic drive system for a construction machine according to any one of claims 1 to 9, A hydraulic drive system for a construction machine, wherein the plurality of directional control valves are a plurality of open center type directional control valves.

11. In the hydraulic drive system for a construction machine according to any one of claims 1 to 10, 13. A hydraulic drive system for a construction machine, comprising: a work implement directional control valve included in the first control valve group; and a swing directional control valve included in the second control valve group.

12. In the hydraulic drive system for a construction machine according to any one of claims 1 to 10, 13. A hydraulic drive system for a construction machine, comprising: a work implement directional control valve included in the first control valve group; and a swing directional control valve included in the third control valve group.

13. In the hydraulic drive system for a construction machine according to any one of claims 1 to 12, 1. A hydraulic drive system for a construction machine, comprising: a work tool that is a bucket; a work tool cylinder that is a bucket cylinder; and a work tool directional control valve that is a bucket directional control valve.

14. In the hydraulic drive system for a construction machine according to any one of claims 1 to 13, the first and second hydraulic pumps each have a pump shaft; and The pump has at least three working chambers whose volumes change periodically with rotation of the pump shaft, Each working chamber of the first and second hydraulic pumps is a low pressure valve for controlling the flow of pressure oil between the working chamber and a low pressure manifold; a high-pressure valve for controlling the flow of pressure oil between the working chamber and a high-pressure manifold; The working chambers of the first and second hydraulic pumps form a plurality of pump elements, each pump element having one or more working chambers, and connected to the high-pressure manifold provided in common to the one or more working chambers of each pump element; The controller actively controls at least the low-pressure valve in phase correlation with the volume cycle of the working chamber, thereby determining, for each volume cycle of the working chamber, whether each working chamber will perform an effective cycle in which a net displacement volume of pressurized oil is formed between the low-pressure manifold and the high-pressure manifold, or an ineffective cycle in which a net displacement volume of pressurized oil is not formed between the low-pressure manifold and the high-pressure manifold, and controls the net displacement volume of the working chamber of each pump element leading to each of the discharge ports via each of the high-pressure manifolds in accordance with the respective required flow rates of pressurized oil.

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