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: A controller 28 calculates a required pump element number of hydraulic actuators 105a-109a on the basis of an operation signal, calculates an allocation pump element number of each of the hydraulic actuators 105a-109a on the basis of the required pump element number as a first allocation pump element number, selects a direction control valve relating to the first allocation pump element number on the basis of the first allocation pump element number, and boom priority and arm priority, calculates an allocation pump element number of the selected direction control valve as a second allocation pump element number, and controls the selected direction control valve, the first selector valves V11-V14 and the second selector valves V21-V24, and the first pump elements P11-P14 and the second pump elements P21-P24.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 hydraulic system 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, the plurality of directional control valves being divided into a first control valve group, a second control valve group, and a third control valve group, the plurality of hydraulic actuators including 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, the first control valve group including a first boom directional control valve and a first arm directional control valve, the second control valve group including a second boom directional control valve and a second arm directional control valve, the third control valve group including 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 provided in different control valve groups among the first control valve group, the second control valve group, and the third control valve group. In a hydraulic drive system for a construction machine including a valve, the multiple hydraulic pumps include a first hydraulic pump containing multiple first pump elements each capable of independently controlling a discharge flow rate, and a second hydraulic pump containing multiple second pump elements each capable of independently controlling a discharge flow rate, and a controller is provided that controls the multiple first pump elements and the multiple second pump elements and the multiple directional control valves based on operation signals generated by the multiple operation devices, and the controller calculates required pump element numbers for each of the multiple hydraulic actuators, including a required pump element number for the boom cylinder, a required pump element number for the arm cylinder, a required pump element number for the work tool cylinder, and a required pump element number for the swing motor, as required flow rates for the multiple hydraulic actuators, based on the operation signals generated by the multiple operation devices, and allocates pump element numbers to each of the multiple hydraulic actuators based on the required pump element numbers for each of the multiple hydraulic actuators, thereby allocating the number of pump elements for the boom cylinder, the number of pump elements for the arm cylinder,The allocated pump element numbers of each of the plurality of hydraulic actuators, including the allocated pump element number of the implement cylinder and the allocated pump element number of the swing motor, are calculated as a first allocated pump element number, and a boom priority order of the first to third control valve groups for allocating the first allocated pump element number of the boom cylinder to the first to third boom directional control valves and an arm priority order of the first to third control valve groups for allocating the first allocated pump element number of the arm cylinder to the first to third arm directional control valves are set in advance, and a directional control valve related to the first allocated pump element number is selected based on the first allocated pump element number, the boom priority order, and the arm priority order, and a pump element number is allocated to the selected directional control valve, thereby calculating the allocated pump element number of the selected directional control valve as a second allocated pump element number, controlling a switching position of the selected directional control valve, and controlling the plurality of first pump elements and the plurality of second pump elements so that a flow rate of pressure oil of the second allocated pump element number is supplied to the selected directional control valve.

[0012] In the present invention configured in this manner, the allocated pump element number of each of the multiple hydraulic actuators is calculated as a first allocated pump element number based on the required pump element number of each of the multiple hydraulic actuators, and the allocated pump element number of a selected directional control valve is calculated as a second allocated pump element number based on the first allocated pump element number, the boom priority order, and the arm priority order, and the selected directional control valve is switched and controlled, thereby reducing 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 division pressure loss that occurs when the directional control valve on the low-pressure actuator side in the same control valve group is throttled, and 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 logic of a directional control valve command, switching valve command, and pump command calculation unit. [Figure 7B] 5 is a flowchart showing the calculation logic of a directional control valve command, switching valve command, and pump command calculation unit. [Figure 8] 1 is a control valve group priority map showing boom priority and arm priority of three control valve groups used when allocating the number of pump elements to the first to third boom directional control valves and the first to third arm directional control valves in the first embodiment. [Figure 9] FIG. 11 is a diagram showing an operation pattern map for explaining an operation example of the present embodiment. [Figure 10] As a comparative example, this figure shows an operation pattern map in the hydraulic drive system of Patent Document 1 (Patent Publication No. 5572586) when the hydraulic actuator is driven with the same lever operation amount as in FIG. [Figure 11] FIG. 4 is a diagram showing a hydraulic drive system for a construction machine according to a second embodiment of the present invention. [Figure 12]13 is a boom-arm directional control valve priority map showing the priority of three control valve groups used when allocating the numbers of pump elements to the first to third boom directional control valves and the first to third arm directional control valves in the second embodiment. [Figure 13] FIG. 11 is a diagram showing an operation pattern map for explaining an operation example of the second embodiment. [Figure 14] FIG. 11 is a diagram showing a hydraulic drive system for a construction machine according to a third embodiment of the present invention. [Figure 15] 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 to 109a, multiple operating devices 115a, 115b, 116a, 116b which generate operating signals for driving the multiple hydraulic actuators 105a to 109a, and a pressure sensor 120 which detects the pressure of the pressurized oil supplied to the rod side of the boom cylinder 107a.

[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, 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 a bucket directional control valve 18 and a swing directional control valve 21. In the following, the first boom directional control valve 19, the second boom directional control valve 23 and the third boom directional control valve 27 will be simply referred to as the boom directional control valve 19, the boom directional control valve 23 and the boom directional control valve 27, respectively, and the first arm directional control valve 20, the second arm directional control valve 22 and the third arm directional control valve 26 will be simply referred to as the arm directional control valve 20, the arm directional control valve 22 and the arm directional control valve 26.

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

[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 is equipped with four first switching valves V11, V12, V13, V14 which are connected to the first pump elements P11-P14 of the first hydraulic pump 14 and serve as a plurality of first switching valves for switching the connection 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 connected to the second pump elements P21-P24 of the second hydraulic pump 15 and serve as a plurality of second switching valves for switching the connection 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] Furthermore, the hydraulic drive system of this embodiment is equipped with a controller 28 that controls the four first pump elements P11-P14 of the first hydraulic pump 14 and the four second pump elements P21-P24 of the second hydraulic pump 15, as well as a plurality of 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 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.

[0031] FIG. 3 is an enlarged view showing the circuit configuration of the first switching valves V11 to V14 and the second switching valves V21 to V24.

[0032] 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.

[0033] When the first switching valves V11-V14 are in the first position, which is the initial position shown in the figure, the pressurized oil discharged from the first pump elements P11-P14 flows to the output port 34 via the junction oil passage 33, and when the first switching valves V11-V14 are switched from the shown position to the second position, the pressurized oil discharged from the first pump elements P13, P14 flows to the output port 36 via the junction oil passage 35, and the pressurized oil discharged from the first pump elements P11, P12 flows to the output port 38 via the junction oil passage 37.

[0034] When the second switching valves V21-V24 are in the first position, which is the initial position shown in the figure, the pressurized oil discharged from the second pump elements P21-P24 flows to the output port 43 via the junction oil passage 42, and when the second switching valves V21-V24 are switched from the shown position to the second position, the pressurized oil discharged from the second pump elements P21, P22 flows to the output port 41 via the junction oil passage 40, and the pressurized oil discharged from the second pump elements P23, P24 flows to the output port 45 via the junction oil passage 44.

[0035] 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.

[0036] In this way, 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.

[0037] ~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.

[0038] The details of the operating principles of the first hydraulic pump 14 and the second hydraulic pump 15 will be explained using Fig. 15. Fig. 15 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 and 15 each have the same configuration as the hydraulic pump 200.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] The arrows on the manifolds 210, 213 indicate the flow of hydraulic fluid in pump mode, with the flow being reversed in motor mode.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] ~Controller~ The processing contents of the controller 28 will now be described.

[0054] FIG. 4 is a functional block diagram showing the processing contents of the controller 28. As shown in FIG.

[0055] 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.

[0056] The controller 28 performs the following calculations in a requested pump element number / allocated pump element number calculation section 28a and a directional control valve command / switching valve command / pump command calculation section 28b.

[0057] First, in a required pump element number / allocated pump element number calculation unit 28a (hereinafter sometimes simply referred to as calculation unit 28a), the controller 28 calculates the required pump element numbers of each of the multiple hydraulic actuators 105a-109a, including the required pump element number of the boom cylinder 107a, the required pump element number of the arm cylinder 108a, the required pump element number of the bucket cylinder 109a, and the required pump element number of the swing motor 106a, as the required flow rates of the multiple hydraulic actuators 105a-109a, based on operation signals generated by the multiple operating devices 115a-116b.

[0058] In addition, in the calculation unit 28a, the controller 28 calculates the number of pump elements allocated to each of the multiple hydraulic actuators 105a-109a, including the number of pump elements allocated to the boom cylinder 107a, the number of pump elements allocated to the arm cylinder 108a, the number of pump elements allocated to the bucket cylinder 109a, and the number of pump elements allocated to the swing motor 106a, as a first allocated pump element number by assigning the number of pump elements to each of the multiple hydraulic actuators 105a-109a based on the required number of pump elements of each of the multiple hydraulic actuators 105a-109a.

[0059] Next, in a directional control valve command / switching valve command / pump command calculation unit 28b (hereinafter sometimes simply referred to as calculation unit 28b), the controller 28 presets boom priorities of the first to third control valve groups G1, G2, G3 for allocating the first allocated pump element number of the boom cylinder 107a to the first to third boom directional control valves 19, 23, 27, and arm priorities of the first to third control valve groups G1, G2, G3 for allocating the first allocated pump element number of the arm cylinder 108a to the first to third arm directional control valves 20, 22, 26, and selects a directional control valve related to the first allocated pump element number based on the first allocated pump element number, the boom priority order, and the arm priority order, and allocates a pump element number to the selected directional control valve, thereby calculating the allocated pump element number of the selected directional control valve as the second allocated pump element number.

[0060] In addition, the controller 28 switches and controls the selected directional control valve, and also controls the first switching valves V11-V14 and the second switching valves V21-V24 and the first pump elements P11-P14 and the second pump elements P21-P24 so that the flow rate of pressurized oil corresponding to the second assigned number of pump elements is supplied to the selected directional control valve.

[0061] 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.

[0062] <Requested pump element number / allocated pump element number calculation unit 28a> 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.

[0063] 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.

[0064] Each of the operating devices 115a, 115b is configured to generate an operating signal for driving two hydraulic actuators with one operating lever.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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, which indicates 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.

[0069] The maximum required flow rate of the boom and arm tables is eight pump elements, 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 four pump elements, which is less than the above. 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, 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, as the required flow rate of the hydraulic actuator corresponding to the operation signals.

[0070] 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.

[0071] The requested number of pump elements / allocated number of pump elements calculation unit 28a calculates the requested flow rate (requested number of pump elements) based on the concept described below.

[0072] As an operation example, a case will be cited in which 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 thereto with an operation amount of 40%, and further 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, using the table shown in Fig. 5, the required pump element number of the boom is calculated to be 6.4, the required pump element number of the arm is calculated to be 6.4, and the required pump element number of the bucket is calculated to be 1.6, and the total required pump element number is greater than 8. Therefore, the required pump element number is corrected so that the total pump element number is 8 or less, and the assigned pump element number is calculated.

[0073] 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.

[0074] 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, (a, b, c) = (6.4, 6.4, 1.6).

[0075] 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.

[0076] First, the calculation unit 28a rounds up the requested pump element numbers and expresses the values ​​as a', b', c', and d' (step S110). In this operation example, (a', b', c')=(7, 7, 2).

[0077] Next, it is determined whether the total of the required pump element numbers a', b', c', d' is 8 or less (step S120), and if No, the maximum value of the required pump element numbers a', b', c', d' is reduced by one (step S150). If there are two or more maximum values, the order of priority is determined in advance, for example, boom, arm, bucket, and swing, and the number of pump elements is reduced by one in that order, and the reduced number of pump elements is defined again as a', b', c', d' (step S150). In this operation example, (a', b', c') = (7, 7, 2), and a' + b' + c' = 7 + 7 + 2 = 16, so the total of a, b, c, d is not 8 or less, and a' = 7, b' = 7, and there are two or more maximum values, so the number of pump elements of the boom is reduced by one in accordance with the order of priority, and as a result, (a', b', c') = (6, 7, 2) is obtained. This calculation is repeated until the total number of pump elements becomes 8 or less, and finally (a', b', c') = (3, 3, 2).

[0078] 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, since (a, b, c) = (6.4, 6.4, 1.6) and (a', b', c') = (3, 3, 2), (a', b', c) = (3, 3, 1.6) is obtained as the first allocated pump element number. That is, the pump element number 3 is assigned to the boom cylinder 107a, the pump element number 3 is assigned to the arm cylinder 108a, and the pump element number 1.6 is assigned to the bucket cylinder 109a.

[0079] <Directional control valve command / switching valve command / pump command calculation unit 28b> The calculation unit 28b calculates the second allocated number of pump elements in the following procedure.

[0080] 1. When the operation signal includes a boom lowering operation signal and the boom lowering is due to the free fall of the boom 107 in the air, the number of pump elements (second allocated pump element number) allocated to the boom directional control valves 19, 23, 27 is set to 0. At this time, the controller 28 inputs the detection value of the pressure sensor 120, and if the detection value is equal to or lower than a predetermined pressure, it determines that the boom lowering is due to the free fall of the boom 107 in the air. When the boom 107 free falls in the air, the pressure on the rod side of the boom cylinder 107a drops to a value close to the tank pressure due to the pump action of the boom cylinder 107a. As the above-mentioned predetermined pressure, the upper limit value of the pressure range close to the tank pressure is set.

[0081] 2. The number of pumps is allocated to the bucket directional control valve 18 and the swing directional control valve 21 with the highest priority, which is set as the second allocated number of pump elements.

[0082] 3. Based on the boom priority order and the arm priority order, pump element numbers are assigned to the boom directional control valve and the arm directional control valve of the control valve group with the highest priority order, and if pump element numbers are assigned to the boom directional control valve and the arm directional control valve in the same control valve group and 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 the same, the allocation of the pump element number to one of the boom directional control valve and the arm directional control valve is withdrawn, and a pump element number is assigned to the directional control valve of the control valve group with the next highest priority order, which becomes the second allocated pump element number.

[0083] 4. 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 assigned pump elements is withdrawn, and the number of pump elements is assigned to the directional control valve of the directional control valve group with the next highest priority, which becomes the second assigned number of pump elements.

[0084] 7A and 7B are flowcharts showing the calculation logic of the directional control valve command / switching valve command / pump command calculation unit 28b. Fig. 8 is a boom / arm directional control valve priority map showing the boom priority and arm priority of the control valve groups G1, G2, G3 used when allocating the numbers of pump elements to the first to third boom directional control valves 19, 23, 27 and the first to third arm directional control valves 20, 22, 26.

[0085] The calculation result of the first assigned pump element numbers in the above-mentioned operation example is (a', b', c) = (3, 3, 1.6), and the pump element number 3 is assigned to the boom cylinder 107a, the pump element number 3 is assigned to the arm cylinder 108a, and the pump element number 1.6 is assigned to the bucket cylinder 109a.

[0086] The calculation unit 28b first determines, when the hydraulic actuator to which the pump element number is assigned includes the boom cylinder 107a, based on the detection value of the pressure sensor 120, whether the boom movement is boom lowering due to free fall in the air, and if it is boom lowering due to free fall, sets the pump element number (second assigned pump element number) assigned to the boom direction control valves 19, 23, 27 to 0 (step S200).

[0087] In this operation example, the operation lever is operated in the boom-raising direction, not in the boom-lowering direction, so the number of pump elements allocated to the boom direction control valves 19, 23, 27 (second allocated pump element number) remains at three.

[0088] In addition, when the hydraulic actuator to which the pump element number is assigned includes the bucket cylinder 109a or the swing motor 106a, the calculation unit 28b assigns the pump element number to the corresponding directional control valve, that is, the bucket directional control valve 18 or the swing directional control valve 21, with top priority, and sets this as the second assigned pump element number (step S205).

[0089] In this operation example, since the bucket cylinder 109a is assigned the pump element number 1.6, the bucket directional control valve 18 is assigned the pump element number 1.6 with the highest priority, which becomes the second assigned pump element number.

[0090] 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 S205, 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.

[0091] In this embodiment, G1 can be connected to the first pump elements P13, P14 and the second pump elements P21-P24, G2 can be connected to the first pump elements P11-P14 and the second pump elements P21-P24, and G3 can be connected to the first pump elements P11, P12 and the second pump elements P23, P24. Therefore, 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.

[0092] 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.

[0093] 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 Y, min(X,Y), to the control valve group with the i-th priority in the priority map of Fig. 8 for each of the boom and arm, 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 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).

[0094] In this embodiment, in the priority map of FIG. 8, the priorities for the boom are set in the order of G3=1, G1=2, G2=3, and the priorities for the arm are set in the order of G3=1, G2=2, G3=3.

[0095] In this operation example, since G3, which has the first priority order for the boom and arm, is not excluded from the control valve group that reads the number of allocatable pump elements Y in step S210, 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=4, is assigned to the third boom directional control valve 27 of G3, and 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=4, is also assigned to the third arm directional control valve 26 of G3. Next, the number of allocated pump elements for the remaining boom and arm is updated to the new remaining number of allocated pump elements X(=X-min(X,Y)) (step S230).

[0096] In addition, in this operation example, the number of remaining newly allocated pump elements X of the boom is X-min(X,Y) = 3-3 = 0, and the number of remaining newly allocated pump elements X of the arm is also X-min(X,Y) = 3-3 = 0, so proceed to the next step after the first processing.

[0097] Next, the calculation unit 28b sets the number of processing times as i=1 (step S260), and judges whether multiple directional control valves are used in the same control valve group (step S270). If the judgment is Yes, it judges whether the assigned 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 assignment of the pump element number of the boom directional control valve, moves to the control valve group of the next priority, and assigns the boom directional control valve pump element number of that control valve group, which becomes the second assigned pump element number (step S290).

[0098] On the other hand, if the determination in step S280 is No, the calculation unit 28b cancels the assigned pump element number of the boom directional control valve or the arm directional control valve, whichever has the smaller number, and moves to the control valve group with the next higher priority and assigns the pump element number to the directional control valve of that control valve group, setting it as the second assigned pump element number (step S300).Then, the calculation unit 28b determines whether i is i≧2 (step S310), and if No, increments i by 1 and repeats the same process (steps S320, S270 to S310), and if Yes, proceeds to the next process.

[0099] In this operation example, the third boom directional control valve 27 of G3 is assigned the pump element number 3, and the third arm directional control valve 26 of the same G3 is assigned the pump element number 3, and multiple directional control valves are used in the same control valve group G3. Therefore, the determination in step S270 is Yes, and the process proceeds to step S280. Since the assigned pump element numbers of the third boom directional control valve 27 and the third arm directional control valve 26 used in the same control valve group G3 are the same at 3, the determination in step S280 is Yes, and the process proceeds to step S290. Then, in step S290, the allocation of the pump element number of the third boom directional control valve 27 in step S230 is cancelled, and the process moves to the control valve group of the next priority. At this time, the control valve group of the next priority is G1, but the bucket directional control valve 18 is already used in G1, and G1 has been excluded in step S210, so the process moves to G2 of the third priority, and the pump element number 3 is assigned to the boom directional control valve 23 of G2, making it the second assigned pump element number (step S290).

[0100] 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.

[0101] As a result, in this operation example, the bucket direction control valve 18 of G1 is ultimately assigned the pump element number of 1.6, the boom direction control valve 23 of G2 is assigned the pump element number of 3, and the third boom direction control valve 27 of G3 is assigned the pump element number of 3.

[0102] 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).

[0103] In addition, 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, and selects a switching valve corresponding to the pump element that supplies 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 a pump command and a switching valve command (step S340).

[0104] 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, it is determined whether or not the switching valve connected to the control valve group needs to be switched. 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.

[0105] 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.

[0106] G3 third arm directional control valve 26 (second allocation pump element number 3) Connecting pump elements: P11, P12, P24 Switching valves to be connected: V11, V12, V24 Boom directional control valve 23 of G2 (number of second assigned pump elements: 3) Connecting pump elements: P21, P22, P13 Switching valves to be connected: V21, V22, V13 G1 bucket directional control valve 18 (number of second allocated pump elements 1.6) Connecting pump elements: P14, P23 Switching valve to be connected: V14, V23 Switching valves that need to be switched from the initial position: V11, V12, V24, V21, V22 Furthermore, if the maximum discharge amount of the pump element is, for example, 120 L / min, the target discharge amount of the pump element is calculated by the following formula.

[0107] 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.

[0108] Pump elements P11, P12, P24: Target discharge amount=(3×120L / min) / 3=120L / min Pump elements P21, P22, P13: Target discharge amount=(3×120L / min) / 3=120L / min Pump elements P14, P23: Target discharge amount=(1.6×120L / min) / 2=96L / min That is, in this operation example, the assigned pump element numbers of the boom and arm directional control valves are integers, so the assigned pump element number and the number of pumps used are the same value, and the average discharge volume is calculated as 120 L / min, the same value as the maximum discharge volume. The assigned pump element number of the bucket directional control valve 18 is 1.6, a value that includes a fraction after the decimal point, so the number of pumps used is a value larger than the second assigned pump element number, and the target discharge volume is calculated as 96 L / min, an average discharge volume that is smaller than the maximum discharge volume.

[0109] 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 25 and the right traveling direction control valve 17, so it is sufficient to carry out the same processing as for the bucket cylinder 109a.

[0110] ~Operation~ 9 is a diagram showing an operation pattern map for explaining further operation examples of this embodiment. This operation pattern map shows the following three operation examples.

[0111] Motion example 1: Three combined motions: rotation, boom lift, and bucket crowding Operation example 2: Three combined operations of boom lift, arm cloud, and bucket cloud Operation example 3: Combined operation of rotation and boom lowering The following explains each step in order.

[0112] <Example 1> This operation example is when the operating lever of the operating device 115b is operated in the boom-raising direction with an operating amount of 39%, while being operated in the bucket cloud direction perpendicular to that with an operating amount of 20%, and further the operating lever of the operating device 115a is operated in the rotation direction with an operating amount of 5%.

[0113] 6, the calculation unit 28a calculates that the number of required pump elements for the boom is 3.1, the number of required pump elements for the bucket is 0.8, and the number of required pump elements for swing is 0.2. This can be expressed as (a, c, d) = (3.1, 0.8, 0.2). Next, in step S110, the calculation unit 28a rounds up the required pump element numbers 3.1, 0.8, and 0.2, respectively, to (a', c', d') = (4.1.1). In this case, since a'+c'+d'=6 and the sum is less than 8, the calculation unit 28a judges in step S120 as positive, and in step S160, the values ​​of the same symbols (a, c, d) and (a', c', d') are compared, the smaller of the respective values ​​is selected, and the first assigned pump element numbers are set to (a, c, d)=(3.1, 0.8, 0.2), respectively. That is, the pump element number 3.1 is assigned to the boom cylinder 107a, the pump element number 0.8 is assigned to the bucket cylinder 109a, and the pump element number 0.2 is assigned to the swing motor 106a.

[0114] Upon receiving the above calculation results of the calculation unit 28a, in step S205 of FIG. 7A, the calculation unit 28b assigns the pump element number of 0.8 to the bucket direction control valve 18 of G1 as the second assigned pump element number, and assigns the pump element number of 0.2 to the swing direction control valve 21 of G2 as the second assigned pump element number.

[0115] In addition, in step S210, the calculation unit 28b sets the remaining allocated pump element number, which is the first allocated pump element number of 3.1 for the boom, as the new allocated pump element number X, and reads 4 as the allocable pump element number Y for G3, which is a control valve group other than G1, to which the pump element number of 0.8 is assigned to the bucket directional control valve 18, and G2, to which the pump element number of 0.2 is assigned to the swing directional control valve 21.

[0116] Furthermore, in step S230, the calculation unit 28b assigns 3.1, which is the smaller value of X and Y, as the second allocated pump element number to the third boom directional control valve 27 of G3, which has priority order 1 for the boom in the priority order map of FIG.

[0117] Next, in step S270 of Fig. 7B, the calculation unit 28b judges whether multiple directional control valves are used in the same control valve group. In this operation example, since multiple directional control valves are not used in the same control valve group, the judgment is denied and the above-mentioned second assigned pump element number is confirmed. That is, the pump element number 0.8 is assigned to the bucket directional control valve 18 of G1, the pump element number 0.2 is assigned to the swing directional control valve 21 of G2, and the pump element number 3.1 is assigned to the boom directional control valve 27 of G3.

[0118] Next, in step S330, the calculation unit 28b generates and outputs switching commands for the bucket direction control valve 18, the swing direction control valve 21, and the boom direction control valve 27.

[0119] Moreover, in step S340, a pump element and a switching valve are selected as shown in the operation pattern of FIG. 9, a target discharge amount of the pump element is calculated, and the switching valve is switched.

[0120] Specifically, for the control valve groups G1, G2, and G3, the pump elements and switching valves are selected as follows.

[0121] G1:P22 V22 G2:P13 V13 G3: P11, P12, P23, P24 V11, V12, V23, V24 The maximum discharge flow rate of one pump element is 112.5 L / min, and the target flow rates of the selected pump elements are as follows:

[0122] P11, P12, P23, P24: 87.5L / min (boom) P13: 20L / min (turning) P22: 100L / min (bucket) The switching valves that switch from the initial position are as follows.

[0123] V11, V12, V23, V24 FIG. 10 is a diagram showing, as a comparative example, an operation pattern map in the hydraulic drive system of Patent Document 1 (Patent Publication No. 5572586) when the hydraulic actuator is driven with the same lever operation amount as in FIG.

[0124] As shown in Figure 10, in the comparative example, when the three combined operations of swing, boom raising, and bucket crowding are performed with the same lever operation amount as in operation example 1, the boom direction control valve and bucket direction control valve are used in control valve group G1, and the boom direction control valve and swing direction control valve are used in control valve group G3, so that diversion occurs between the boom direction control valve and bucket direction control valve of G1, and between the boom direction control valve and swing direction control valve of G3, and energy efficiency decreases due to diversion pressure loss.

[0125] In contrast, in this embodiment, the directional control valves 18, 21, and 27 are distributed to the control valve groups G1, G2, and G3, respectively, so that no branching occurs as in the comparative example, and energy efficiency can be improved. <Example 2> This operation example is when the operating lever of the operating device 115b is operated in the boom raising direction with an operating amount of 2%, while being operated in the bucket cloud direction perpendicular to that with an operating amount of 9%, and further the operating lever of the operating device 115a is operated in the arm cloud direction with an operating amount of 73%.

[0126] 6, the calculation unit 28a calculates that the required pump element numbers for the boom are 0.17, the required pump element numbers for the bucket are 0.35, and the required pump element numbers for the arm are 5.8. This can be expressed as (a, b, c) = (0.17, 5.8, 0.35). Next, in step S110, the calculation unit 28a rounds up the required pump element numbers 0.17, 5.8, and 0.35, respectively, to (a', c', d') = (1.6.1). In this case, since a'+c'+d'=8 and the sum is less than 8, the calculation unit 28a judges in step S120 as positive, and in step S160, the values ​​of the same symbols (a, b, c) and (a', b', c') are compared, the smaller of the respective values ​​is selected, and the first assigned pump element numbers are set to (a, b, c)=(0.17, 5.8, 0.35), respectively. That is, the pump element number 0.17 is assigned to the boom cylinder 107a, the pump element number 5.8 is assigned to the arm cylinder 108a, and the pump element number 0.35 is assigned to the bucket cylinder 109a.

[0127] Upon receiving the above calculation result of the calculation unit 28a, the calculation unit 28b assigns the pump element number of 0.35 to the bucket directional control valve 18 of G1 as the second assigned pump element number in step S205 of FIG. 7A.

[0128] Furthermore, in step S210, the calculation unit 28b sets the remaining allocated pump element numbers as the new allocated pump element numbers X, which are the first allocated pump element number for the boom, 0.17, and the first allocated pump element number for the arm, 5.8, and reads 6 and 4, respectively, as the allocatable pump element numbers Y for G2 and G3, which are control valve groups other than G1, to which the bucket directional control valve 18 is assigned the pump element number of 0.35.

[0129] Furthermore, in step S230, the calculation unit 28b assigns 0.17, which is the smaller of X(0.17) and Y(4), as the second assigned pump element number to the third boom directional control valve 27 of G3 with priority order 1 for the boom in the priority order map of Fig. 8. Also, since the assignable pump element number Y to the third arm directional control valve 26 of G3 with priority order 1 for the arm is 4, the calculation unit 28b assigns 4, which is the smaller of X(5.8) and Y(4), as the second assigned pump element number to the third arm directional control valve 26, and assigns the pump element number 1.8, which is the difference (5.8-4=1.8) between the assigned pump element number X of 5.8 and the assignable pump element number Y of 4, to the arm directional control valve 22 of G2 with priority order 2 for the arm.

[0130] Next, in step S270 of Fig. 7B, the calculation unit 28b judges whether a plurality of directional control valves are used in the same control valve group. In this operation example, since the pump element number 0.17 is assigned to the boom directional control valve 27 of G3 and the pump element number 4 is assigned to the arm directional control valve 26, the pump element number 0.17 of the boom directional control valve 27, which has a smaller assigned pump element number, is moved to the boom directional control valve 19 of G1, which has a priority order 2, according to the priority order map of Fig. 8. In step S270 of Fig. 7B, the calculation unit 28b again judges whether a plurality of directional control valves are used in the same control valve group. In this operation example, since the pump element number 0.35 is assigned to the bucket directional control valve 18 in G1, the pump element number 0.17 of the boom directional control valve 19 is again moved to the boom directional control valve 23 of G2, which has a priority order 3, according to the priority order map of Fig. 8, and the boom directional control valve 23 is assigned the pump element number 0.17.

[0131] As a result, ultimately, the bucket directional control valve 18 of G1 is assigned a pump element number of 0.35, the arm directional control valve 22 of G2 is assigned a pump element number of 1.8, the boom directional control valve 23 of G2 is assigned a pump element number of 0.17, and the arm directional control valve 26 of G3 is assigned a pump element number of 4.

[0132] Next, in step S330, the calculation unit 28b generates and outputs switching commands for the bucket direction control valve 18, the arm direction control valve 22, the boom direction control valve 23, and the arm direction control valve 26.

[0133] Moreover, in step S340, a pump element and a switching valve are selected as shown in the operation pattern of FIG. 9, a target discharge amount of the pump element is calculated, and the switching valve is switched.

[0134] Specifically, for the control valve groups G1, G2, and G3, the pump elements and switching valves are selected as follows.

[0135] G1:P22 V22 G2: P13, P14, P21 V13, V14, V21 G3: P11, P12, P23, P24 V11, V12, V23, V24 The maximum discharge flow rate of one pump element is 112.5 L / min, and the target flow rates of the selected pump elements are as follows:

[0136] P11, P12, P13, P14, P23, P24: 110L / min (arm) P21: 20L / min (boom) P22: 40L / min (bucket) The switching valves that switch from the initial position are as follows.

[0137] V11, V12, V21, V23, V24 In the comparative example shown in Figure 10, in the case of the three combined operations of boom raising, arm crowding, and bucket crowding, the boom directional control valve, arm directional control valve, and bucket directional control valve are used in control valve group G1, and the boom directional control valve and arm directional control valve are used in control valve group G2, so that diversion occurs between G1 and G2, and in G1 in particular, diversion occurs at the three directional control valves, the boom directional control valve, arm directional control valve, and bucket directional control valve, resulting in large diversion pressure loss and reduced energy efficiency.

[0138] In contrast, in this embodiment, as shown in FIG. 9, only two directional control valves in the control valve group G2 divide the flow, so that the pressure loss in the divided flow is smaller than in the comparative example, and energy efficiency can be improved. <Example 3> This operation example is when the operating lever of the operating device 115b is operated in the boom lowering direction with an operating amount of 50%, and the operating lever of the operating device 115a is operated in the rotation direction with an operating amount of 90%, and the boom is lowered as a free fall in the air.

[0139] In step S100 of Fig. 6, the calculation unit 28a calculates that the number of pump elements required for the boom is 4, and the number of pump elements required for the swing is 3.6. This can be expressed as (a, d) = (4, 3.6). Next, in step S110, the calculation unit 28a rounds up the required pump element numbers 4 and 3.6, respectively, to (a', d') = (4.4). In this case, since a' + d' = 8, and the total is 8 or less, the calculation unit 28a judges in step S120 as positive, and in step S160, the calculation unit 28a compares the values ​​of the same symbols (a, d) and (a', d') to select the smaller of the two values, and sets (a, d) = (4, 3.6) as the first assigned pump element numbers. That is, the pump element number 4 is assigned to the boom cylinder 107a, and the pump element number 3.6 is assigned to the swing motor 106a.

[0140] Upon receiving the above calculation result of the calculation unit 28a, the calculation unit 28b assigns the pump element number 3.6 to the swing direction control valve 21 of G2 as the second assigned pump element number in step S205 of FIG. 7A.

[0141] Furthermore, in this operation example, the boom lowering is a free fall in the air, and the detection value of the pressure sensor 120 is below a predetermined pressure, so in step S200, the calculation unit 28b determines that the boom lowering operation is due to a free fall in the air based on the detection value of the pressure sensor 120, and sets the number of pump elements to be assigned to the boom direction control valves 19, 23, 27 to 0.

[0142] As a result, the pump element number of 3.6 is finally assigned to the swing direction control valve 21 of G2 as the second assigned pump element number.

[0143] Next, the calculation unit 28b generates and outputs a switching command for the swing direction control valve 21 in step S330.

[0144] Moreover, in step S340, a pump element and a switching valve are selected as shown in the operation pattern of FIG. 9, a target discharge amount of the pump element is calculated, and the switching valve is switched.

[0145] Specifically, for the control valve group G2, the pump elements and switching valves selected are as follows:

[0146] G2: P11, P12, P13, P14 V11, V12, V13, V14 The maximum discharge flow rate of one pump element is 112.5 L / min, and the target flow rate of the pump element is selected as follows:

[0147] P11, P12, P13, P14: 101L / min (rotation) There is no switching valve that switches from the initial position.

[0148] In the comparative example shown in Figure 10, when the two combined operations of rotation and boom lowering (free fall) are performed, the maximum discharge flow rate of one pump is 300 L / min and the total discharge flow rate of the three pumps is 900 L / min, but the maximum flow rate of pressurized oil that can be supplied to the rotation direction control valve is 300 L / min.

[0149] In this embodiment, the flow rate of pressure oil supplied to the swing direction control valve 21 is 404 L / min with four pump elements, and the swing speed can be increased compared to the comparative example, thereby improving the work efficiency. Also, in this embodiment, a maximum of six pump elements P11, P12, P13, P14, P21, and P22 can be connected to the control valve group G2, and when six pump elements are connected to the control valve group G2, the swing speed can be further increased and the work efficiency can be improved.

[0150] <Second embodiment> FIG. 11 is a diagram showing a hydraulic drive system according to the second embodiment of the present invention.

[0151] In FIG. 11, the hydraulic drive system of this embodiment differs from the hydraulic drive system of the first embodiment in the arrangement of the directional control valves.

[0152] That is, in the hydraulic drive system of the first embodiment shown in Figure 2, the rotation direction control valve 21 is arranged in the second control valve group G2, but in this embodiment, the rotation direction control valve 21 is arranged in the third control valve group G3.

[0153] FIG. 12 is a boom-arm directional control valve priority map showing the priority of the control valve groups G1, G2, G3 used when allocating the number of pump elements to the first to third boom directional control valves 19, 23, 27 and the first to third arm directional control valves 20, 22, 26 in this embodiment.

[0154] In the priority map of Figure 12, for the boom, the priorities are set in the order of G2 1, G1 2, G3 3, and for the arm, the priorities are set in the order of G2 1, G3 2, G1 3.

[0155] The configuration other than the above is the same as that of the first embodiment.

[0156] Fig. 13 is a diagram showing an operation pattern map for explaining an operation example of this embodiment. This operation pattern map corresponds to operation example 2 of the three combined operations of boom raising, arm crowding, and bucket crowding shown in Fig. 9 of the first embodiment, in which the operation lever of the operation device 115b is operated with an operation amount of 2% in the boom raising direction, while being operated with an operation amount of 9% in the bucket crowding direction perpendicular thereto, and further, the operation lever of the operation device 115a is operated with an operation amount of 73% in the arm crowding direction.

[0157] Calculation unit 28a shown in Fig. 4 performs the same processes as in the first embodiment in steps S100 to S160 in Fig. 6, and calculates (a, b, c) = (0.17, 5.8, 0.35) as the first allocated pump element numbers. That is, the pump element number 0.17 is assigned to boom cylinder 107a, the pump element number 5.8 is assigned to arm cylinder 108a, and the pump element number 0.35 is assigned to bucket cylinder 109a.

[0158] Upon receiving the above calculation result of the calculation unit 28a, the calculation unit 28b assigns the pump element number of 0.35 to the bucket directional control valve 18 of G1 as the second assigned pump element number in step S205 of FIG. 7A.

[0159] Furthermore, in step S210, the calculation unit 28b sets the remaining allocated pump element numbers as the new allocated pump element numbers X, which are the first allocated pump element number for the boom, 0.17, and the first allocated pump element number for the arm, 5.8, and reads 6 and 4, respectively, as the allocatable pump element numbers Y for G2 and G3, which are control valve groups other than G1, to which the bucket directional control valve 18 is assigned the pump element number of 0.35.

[0160] Furthermore, in step S230, the calculation unit 28b assigns 0.17, which is the smaller of X(0.17) and Y(6), to the boom directional control valve 23 of G2 with priority level 1 for the boom in the priority map of FIG. 8, as the second allocated pump element number, and assigns 5.8, which is the smaller of X(5.8) and Y(6), to the arm directional control valve 22 of G2 with priority level 1 for the arm, as the second allocated pump element number.

[0161] Next, in step S270 of Fig. 7B, the calculation unit 28b determines whether multiple directional control valves are used in the same control valve group. In this operation example, since the pump element number 0.17 is assigned to the boom directional control valve 27 of G2 and the pump element number 5.8 is assigned to the arm directional control valve 26, the pump element number 0.17 of the boom directional control valve 27 with the smallest assigned pump element number is moved to the boom directional control valve 27 of G3 with priority 2 according to the priority map of Fig. 8.

[0162] As a result, ultimately, the bucket directional control valve 18 of G1 is assigned a pump element number of 0.35, the arm directional control valve 22 of G2 is assigned a pump element number of 5.8, and the boom directional control valve 27 of G3 is assigned a pump element number of 0.17.

[0163] Next, in step S330, the calculation unit 28b generates and outputs switching commands for the bucket direction control valve 18, the arm direction control valve 22, the boom direction control valve 23, and the arm direction control valve 26.

[0164] Moreover, in step S340, a pump element and a switching valve are selected as shown in the operation pattern of FIG. 9, a target discharge amount of the pump element is calculated, and the switching valve is switched.

[0165] Specifically, for the control valve groups G1, G2, and G3, the pump elements and switching valves are selected as follows.

[0166] G1:P23 V23 G2: P11, P12, P13, P14, P21, P22 V11, V12, V13, V14, V21, V22 G3:P24 V24 The maximum discharge flow rate of one pump element is 112.5 L / min, and the target flow rates of the selected pump elements are as follows:

[0167] P11, P12, P13, P14, P21, P22: 110L / min (arm) P23: 40L / min (bucket) P24: 20L / min (boom) The switching valves that switch from the initial position are as follows.

[0168] V21, V23, V24 As mentioned above, in the comparative example shown in Figure 10, in the case of the three combined operations of boom raising, arm crowding, and bucket crowding, the boom directional control valve, arm directional control valve, and bucket directional control valve are used in control valve group G1, and the boom directional control valve and arm directional control valve are used in control valve group G2, so that diversion occurs in G1 and G2, and in G1 in particular, diversion occurs at the three directional control valves, the boom directional control valve, arm directional control valve, and bucket directional control valve, resulting in large diversion pressure loss and reduced energy efficiency.

[0169] In contrast, in this embodiment, the directional control valves 18, 21, and 27 are distributed to the control valve groups G1, G2, and G3, respectively, so that no branching occurs as in the comparative example, and the branching that occurred in the second embodiment is also avoided, improving energy efficiency. <Third embodiment> FIG. 14 is a diagram showing a hydraulic drive system for a construction machine according to the third embodiment of the present invention.

[0170] 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.

[0171] 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]

[0172] 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 controller that controls the first pump elements, the second pump elements, and the directional control valves based on operation signals generated by the operation devices; The controller Calculating the required pump element numbers of the plurality of hydraulic actuators, including the required pump element number of the boom cylinder, the required pump element number of the arm cylinder, the required pump element number of the implement cylinder, and the required pump element number of the swing motor, as the required flow rates of the plurality of hydraulic actuators based on the operation signals generated by the plurality of operation devices; By allocating a number of pump elements to each of the plurality of hydraulic actuators based on the number of required pump elements of each of the plurality of hydraulic actuators, the number of allocated pump elements of each of the plurality of hydraulic actuators, including the number of allocated pump elements of the boom cylinder, the number of allocated pump elements of the arm cylinder, the number of allocated pump elements of the work tool cylinder, and the number of allocated pump elements of the swing motor, is calculated as a first allocated pump element number; a boom priority order of the first to third control valve groups for allocating the first allocated pump element number of the boom cylinder to the first to third boom directional control valves, and an arm priority order of the first to third control valve groups for allocating the first allocated pump element number of the arm cylinder to the first to third arm directional control valves are set in advance, a directional control valve related to the first allocated pump element number is selected based on the first allocated pump element number, the boom priority order, and the arm priority order, and a pump element number is allocated to the selected directional control valve, thereby calculating the allocated pump element number of the selected directional control valve as a second allocated pump element number; A hydraulic drive system for a construction machine, characterized in that the switching position of the selected directional control valve is controlled, and the multiple first pump elements and the multiple second pump elements are controlled so that a flow rate of pressurized oil corresponding to the second assigned number of pump elements is supplied to the selected directional control valve.

2. 2. The hydraulic drive system for a construction machine according to claim 1, the boom priority order preset in the controller is the third control valve group, the first control valve group, and the second control valve group in that order; 1. A hydraulic drive system for a construction machine, comprising: a first control valve group for controlling a first arm of a construction machine; a second control valve group for controlling a second arm of the construction machine;

3. The hydraulic drive system for a construction machine according to claim 1 or 2, the boom priority order preset in the controller is the second control valve group, the first control valve group, and the third control valve group in that order; 1. A hydraulic drive system for a construction machine, comprising: a first control valve group and a second control valve group, the first control valve group being arranged in that order of arm priority;

4. In the hydraulic drive system for a construction machine according to any one of claims 1 to 3, The controller A hydraulic drive system for a construction machine, characterized in that the first allocated number of pump elements for each of the multiple hydraulic actuators is calculated by correcting the required number of pump elements so that the total number of required pump elements falls within the range of the total number of pump elements of the multiple first pump elements and the multiple second pump elements.

5. In the hydraulic drive system for a construction machine according to any one of claims 1 to 4, The controller a first allocated pump element number for the work tool cylinder and the swing motor, respectively, being assigned with top priority to the work tool direction control valve and the swing direction control valve, and a second allocated pump element number for the work tool direction control valve and the swing direction control valve being calculated.

6. In the hydraulic drive system for a construction machine according to any one of claims 1 to 5, The hydraulic drive system for construction machinery is characterized in that the operation signal includes an operation signal instructing boom lowering, and if the boom lowering is due to a free fall of the boom in the air, the controller sets the number of second assigned pump elements assigned to the first to third boom directional control valves to 0.

7. In the hydraulic drive system for a construction machine according to any one of claims 1 to 6, The controller assigning pump element numbers to the boom directional control valves and the arm directional control valves of the control valve groups with the highest priorities based on the boom priority order and the arm priority order; When the number of pump elements is assigned to a boom directional control valve and an arm directional control valve in the same control valve group, 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 assignment of the number of pump elements to one of the boom directional control valve and the arm directional control valve is cancelled, and a number of pump elements is assigned to the directional control valve of the control valve group with the next priority, as the second assigned number of pump elements; a second assigned number of pump elements is allocated to the directional control valve of the control valve group having the next priority, which is determined as the second assigned number of pump elements.

8. In the hydraulic drive system for a construction machine according to any one of claims 1 to 7, 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 first hydraulic pump and the second hydraulic pump each include four pump elements; 2. A hydraulic drive system for a construction machine, wherein each of the first plurality of switching valves and the second plurality of switching valves includes four switching valves.

9. In the hydraulic drive system for a construction machine according to any one of claims 1 to 8, 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 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, 1. A hydraulic drive system for a construction machine, comprising: a work tool comprising a bucket; a work tool cylinder comprising a bucket cylinder; and a work tool directional control valve comprising a bucket directional control valve.

12. In the hydraulic drive system for a construction machine according to any one of claims 1 to 11, the first and second hydraulic pumps each having a pump shaft; 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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