Pump device and hydraulic circuit system for construction machinery

Abstract

The present invention provides a hydraulic circuit system and a pump device that use a tandem pump, in which two hydraulic pumps capable of independently controlling the flow rates of multiple discharge ports are disposed, and a plurality of switching valves, wherein operability is improved, and mounting characteristics are enhanced by miniaturizing the pump device and reducing the number of hydraulic hoses. To this end, first and second hydraulic pumps 11, 12, which incorporate four pump elements 11a-11d, 12a-12d capable of independently controlling the flow rates of pressurized oil discharged from discharge ports 45a-45d, 46a-46d and are arranged in tandem along the axial direction of a shaft 14 so as to form a tandem pump 30, are such that the discharge ports 45a-45d, 46a-46d are opened in a block surface 13S of a port block 13, which is a shared component, and a manifold block 40, in which switching valves 41a-41d, 42a-42d are mounted and service ports 43, 44 are formed, is coupled to the block surface 13S.

Description

Hydraulic circuit system and pump device for construction machinery

[0001] The present invention relates to a hydraulic circuit system for a construction machine equipped with a pump device capable of independently controlling the flow rates of a plurality of discharge ports, and the pump device.

[0002] Patent Literature 1 (JP-A-2003-102666) describes a pump device called a tandem pump, which has two pumps, a front pump and a rear pump, spaced apart in the axial direction (i.e., arranged in tandem), as a pump device used in the hydraulic circuit system of construction machinery such as hydraulic excavators. In this tandem pump, the front pump and the rear pump are each configured as two-flow piston pumps that generate two discharge flow rates. Furthermore, a port block is interposed between the front pump and the rear pump, and four discharge ports are opened in pairs on different sides of the port block, allowing four discharge flow rates to be extracted.

[0003] Furthermore, Patent Document 2 describes a hydraulic circuit system equipped with a hydraulic pump that can independently control the flow rate of each of four discharge ports. The four discharge ports are connected to four load port oil passages via 16 selector valves, and by switching the selector valves, the number of discharge ports corresponding to the demands of the actuators can be connected to the load port oil passages, thereby supplying the actuators with pressurized oil at a flow rate corresponding to the demands.

[0004] Patent No. 5027878 U.S. Patent Publication No. 2019 / 0211849A1

[0005] The tandem pump described in Patent Document 1 has four discharge ports, each opened in pairs on different sides of a port block located between the front and rear pumps, allowing for four discharge flow rates to be extracted, thereby reducing the size of the port block and the overall size of the tandem pump.However, the front and rear pumps are called split-flow pumps, each equipped with two discharge ports, and it is not possible to control the two discharge flow rates independently.

[0006] The hydraulic circuit system described in Patent Document 2 can extract four discharge flow rates from one pump and control the four discharge flow rates independently. In addition, by switching the switching valve according to the demand of the actuator and changing the number of discharge ports connected to the actuator, it is possible to supply pressure oil to the actuator at a flow rate according to the demand.

[0007] However, in the hydraulic circuit system described in Patent Document 2, one pump has four discharge ports, and in order to extract four discharge flow rates from these four discharge ports, it is necessary to connect the four discharge ports to a switching valve block containing 16 switching valves with four hydraulic hoses. This results in an increase in the size of the pump and a complex hose layout, which reduces the ease of installation on construction machinery.

[0008] This problem becomes particularly noticeable when the number of pumps (discharge ports) is increased to improve operability.

[0009] That is, in construction machinery that drives multiple actuators, such as hydraulic excavators, it is necessary to increase the number of pumps (discharge ports) connected to the actuators in order to improve operability when the actuators are driven, and to achieve this, it is preferable to use multiple hydraulic pumps that can independently control the flow rates of multiple discharge ports, as described in Patent Document 2. For example, if two hydraulic pumps are used as a tandem pump, the number of discharge ports that can independently control the flow rate increases to eight, so the number of discharge ports required for the actuators can be changed in detail and the speed fluctuations of the actuators that accompany switching are also smoothed, leading to improved operability when the actuators are driven.

[0010] However, if two hydraulic pumps described in Patent Document 2 are used in tandem, for example, the number of discharge ports increases to eight, and the number of hydraulic hoses connecting the eight discharge ports to the switching valve also increases to eight, which increases the size of the hydraulic source (pump device) and the hose layout, significantly reducing the mountability of the pump device.

[0011] The object of the present invention is to provide a hydraulic circuit system and pump device for construction machinery that improves operability when driving an actuator and improves mountability on construction machinery by reducing the size of the pump device and hydraulic hoses when the pump device of the hydraulic circuit system is configured using a tandem pump in which two hydraulic pumps that can independently control the flow rate of multiple discharge ports are arranged axially at a distance and multiple switching valves.

[0012] In order to achieve the above object, the present invention provides a hydraulic circuit system for a construction machine comprising a prime mover, a pump device driven by the prime mover, a plurality of actuators driven by pressurized oil discharged from the pump device, and a plurality of directional control valves that control the flow of pressurized oil supplied from the pump device to the plurality of actuators, wherein the pump device comprises a tandem pump having first and second hydraulic pumps arranged at an interval in the axial direction of a shaft that is driven to rotate by the prime mover, and the system comprises a manifold block that is equipped with a plurality of first switching valves and a plurality of second switching valves and that forms a plurality of service ports, the first hydraulic pump includes two or more first pump elements that can independently control the flow of pressurized oil discharged from two or more first discharge ports, and the second hydraulic pump controls the flow of pressurized oil discharged from two or more second discharge ports. and a second pump element that can independently control the flow of pressure oil from the first and second pump elements, the first and second hydraulic pumps being configured as shared components of the first and second hydraulic pumps and having a port block in which the two or more first discharge ports and the two or more second discharge ports open to a side portion thereof, the manifold block being configured to switch the flow direction of pressure oil flowing in from the two or more first and second discharge ports of the port block by the plurality of first and second switching valves and to guide the pressure oil to any of the plurality of service ports, the manifold block being coupled to the side portion of the port block in which the two or more first and second discharge ports open, and the plurality of service ports of the manifold block being connected via a plurality of pipes to a control valve having the plurality of directional control valves housed in a valve housing.

[0013] Furthermore, in order to achieve the above object, the present invention provides a pump device for a construction machine that includes a tandem pump having first and second hydraulic pumps arranged at an interval in the axial direction of a shaft that is driven and rotated by a prime mover, and further includes a manifold block that is equipped with a plurality of first switching valves and a plurality of second switching valves and that has a plurality of service ports formed therein, wherein the first hydraulic pump includes two or more first pump elements that can independently control the flow of pressure oil discharged from two or more first discharge ports, and the second hydraulic pump includes two or more second pump elements that can independently control the flow of pressure oil discharged from two or more second discharge ports. the first and second hydraulic pumps are configured as shared components of the first and second hydraulic pumps and have a port block having the two or more first discharge ports and the two or more second discharge ports opening to a side portion thereof, the manifold block is configured to switch the flow direction of pressure oil flowing in from the two or more first and second discharge ports of the port block by the plurality of first and second switching valves and guide the pressure oil to any of the plurality of service ports, and the manifold block is coupled to the side portion of the port block where the two or more first and second discharge ports open.

[0014] As described above, in the present invention, a tandem pump is formed from two hydraulic pumps, a first hydraulic pump and a second hydraulic pump, and each of the first hydraulic pump and the second hydraulic pump is configured to include two or more first pump elements that can independently control the flow of pressurized oil discharged from two or more first discharge ports and two or more second pump elements that can independently control the flow of pressurized oil discharged from two or more second discharge ports. This makes it possible to increase the number of discharge ports (pump elements) of the pump device, and to increase or decrease the number of discharge ports (number of pump elements) connected to the actuator according to the required flow rate, thereby enabling fine control of the discharge flow rate and improving operability when driving the actuator.

[0015] Furthermore, in a pump device equipped with such a tandem pump, the first discharge port and the second discharge port are opened on the side of the port block configured as a shared component of the first and second hydraulic pumps, and a manifold block equipped with first and second switching valves and having multiple service ports formed thereon is connected to the side of the port block where the first and second discharge ports open. This makes it possible to eliminate all of the numerous hydraulic hoses connecting the discharge ports of the port block to the manifold block, and by reducing the size of the pump device and the number of hydraulic hoses, it is possible to improve the ease of installation on construction machinery.

[0016] According to the present invention, when a pump device of a hydraulic circuit system is constructed using a tandem pump in which two hydraulic pumps that can independently control the flow rate of multiple discharge ports are arranged in tandem, and multiple switching valves, it is possible to improve operability when driving the actuator, and also improve mountability on construction machinery by making the pump device smaller and reducing the hydraulic hoses.

[0017] Fig. 3 is a diagram showing a hydraulic excavator, which is a representative example of a construction machine equipped with a hydraulic circuit system according to a first embodiment of the present invention. Fig. 4 is a diagram showing the circuit configuration of the hydraulic circuit system according to the first embodiment of the present invention. Fig. 5 is a longitudinal sectional view taken along the shaft of a pump device. Fig. 6 is a longitudinal sectional view of the pump device taken along line A-A in Fig. 3. Fig. 7 is a partial sectional top view of the pump device taken along line B-B in Fig. 3. Fig. 8 is a schematic diagram showing a part of an electronically controlled hydraulic pump equipped with pump elements, illustrating the operating principles of first and second hydraulic pumps.

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0019] First Embodiment A first embodiment of the present invention will be described.

[0020] - Construction Machine - Fig. 1 is a diagram showing a hydraulic excavator, which is a typical example of a construction machine equipped with a hydraulic circuit system according to a first embodiment of the present invention.

[0021] The hydraulic excavator 100 shown in FIG. 1 is configured such that an upper rotating body 102 equipped with a cab 102a for an operator is mounted via a rotating device 107 on a lower traveling body 101 equipped with left and right crawler-type traveling devices 108a, 108b.

[0022] A boom 104 of a front work implement 103 is connected to the front of the upper rotating body 102, and the boom 104 is driven by a boom cylinder 1, which is a single-rod hydraulic cylinder. An arm 105 is connected to the tip of the boom 104, and the arm 105 is driven by an arm cylinder 2. A bucket 106, which is a work tool, is connected to the tip of the arm 105, and the bucket 106 is driven by a bucket cylinder 3, which is a work tool cylinder. The swing device 107 is driven by a swing motor 4, and the traveling devices 108a, 108b are driven by left and right traveling motors 5a, 5b.

[0023] -Hydraulic Circuit System- Fig. 2 is a diagram showing the circuit configuration of a hydraulic circuit system according to a first embodiment of the present invention.

[0024] In FIG. 2, the hydraulic circuit system includes an engine 9 as a prime mover, a pump device 10 driven by the engine 9, a plurality of actuators 1 to 5 b (see FIG. 1 for actuators 3 to 5 b) driven by pressurized oil discharged from the pump device 10, a plurality of directional control valves 21 to 29 that control the flow of pressurized oil supplied from the pump device 10 to the plurality of actuators 1 to 5 b, and a plurality of operating lever devices 56 a, 56 b, 56 c, 56 d that switch the plurality of directional control valves 21 to 29 and operate the plurality of actuators 1 to 5 b.

[0025] The pump device 10 includes a tandem pump 30 having first and second hydraulic pumps 11, 12 spaced apart in the axial direction of a shaft 14 driven and rotated by an engine 9, and a manifold block 40 equipped with four first selector valves 41a to 41d that are a plurality of first selector valves and four second selector valves 42a to 42d that are a plurality of second selector valves, and having first and second service ports 43, 44 that are a plurality of service ports. The first and second hydraulic pumps 11, 12 are driven by the engine 9, draw hydraulic oil from a tank 55, and discharge pressurized oil. An electric motor may be used instead of the engine 9.

[0026] Furthermore, the first and second hydraulic pumps 11, 12 each have four first discharge ports 45a to 45d that are two or more first discharge ports and four second discharge ports 46a to 46d that are two or more second discharge ports, and the first hydraulic pump 11 includes four first pump elements 11a to 11d that are two or more first pump elements that can independently control the flow rate of pressure oil discharged from the four first discharge ports 45a to 45d, and the second hydraulic pump 12 includes four second pump elements 12a to 12d that are two or more second pump elements that can independently control the flow rate of pressure oil discharged from the four second discharge ports 46a to 46d. Details of the "pump elements" will be described later.

[0027] The manifold block 40 is configured to switch the flow direction of the pressurized oil flowing in from the first and second discharge ports 45a to 45d, 46a to 46d using the first and second switching valves 41a to 41d, 42a to 42d, and to guide the pressurized oil to either the first or second service port 43, 44.

[0028] The first and second switching valves 41a to 41d, 42a to 42d are electromagnetic switching valves that can be switched between a first position, which is an initial position, and a second position, which is a non-initial position. In the first position, the first switching valves 41a to 41d connect the first discharge ports 45a to 45d to the first service port 43, and in the second position, connect the first discharge ports 45a to 45d to the second service port 44. In the first position, the second switching valves 42a to 42d connect the second discharge ports 46a to 46d to the second service port 44, and in the second position, connect the second discharge ports 46a to 46d to the first service port 43.

[0029] The first and second service ports 43, 44 of the manifold block 40 are connected via first and second pipes 51, 52 to a control valve 20 which houses a plurality of directional control valves 21 to 29 in a valve housing.

[0030] The multiple actuators 1 to 5b are respectively the boom cylinder 1, arm cylinder 2, bucket cylinder 3, swing motor 4, left traveling motor 5a, and right traveling motor 5b shown in FIG. 1, and the multiple directional control valves 21 to 29 are respectively the right traveling directional control valve 21, bucket directional control valve 22, boom I directional control valve 23, boom directional control valve 27, swing directional control valve 25, arm I directional control valve 26, arm II directional control valve 24, spare directional control valve 28, and left traveling directional control valve 29.

[0031] The operating lever device 56a is for the boom 104 and bucket 106, the operating lever device 56b is for the arm 105 and swing device 107, the operating lever device 56c is for the left traveling device 108a, and the operating lever device 56d is for the right traveling device 108b.

[0032] The multiple directional control valves 21-29 are divided into a first valve group 33 including a boom I directional control valve 23 and a boom II directional control valve 27, which are directional control valves for a specific first actuator that is operated relatively frequently, and a second valve group 34 including an arm I directional control valve 26 and an arm II directional control valve 24, which are directional control valves for a specific second actuator that is operated relatively frequently. The control valve 20 has first and second pump ports 31, 32 connected to the first and second valve groups 33, 34, and the first and second pump ports 31, 32 are connected to first and second service ports 43, 44 via first and second pipes 51, 52. The number of first and second service ports 43, 44 and first and second pump ports is two, the same as the number of first and second hydraulic pumps 11, 12 of the tandem pump 30.

[0033] Pressurized oil from the first service port 43 flows through the first pipe 51 and from the pump port 31 into the control valve 20, and is supplied to the right traveling directional control valve 21, bucket directional control valve 22, boom I directional control valve 23, and boom II directional control valve 27 of the first valve group 33. Pressurized oil from the second service port 44 flows through the second pipe 52 and from the pump port 32 into the control valve 20, and is supplied to the swing directional control valve 25, arm I directional control valve 26, arm II directional control valve 24, spare directional control valve 28, and left traveling directional control valve 29 of the second valve group 34.

[0034] The first valve group 33 is configured as an open center circuit in which the directional control valves 21, 22, 23, and 27 are arranged in a center bypass line 33a and the directional control valves 21, 22, 23, and 27 are connected in parallel to one another, and the second valve group 34 is configured as an open center circuit in which the directional control valves 24, 25, 26, 28, and 29 are arranged in a center bypass line 34a and the directional control valves 24, 25, 26, 28, and 29 are connected in parallel to one another.

[0035] The directional control valves 21 to 29 are in a neutral state when the levers of the operating lever devices 56a, 56b, 56c, and 56d are not operated and no command is received from the controller 57, and the pressure oil flowing in from the pump port 32 flows back to the tank 55 through the center bypass lines 33a and 34a. When the levers of the operating lever devices 56a, 56b, 56c, and 56d are operated and a command is generated from the controller 57, the directional control valves 21 to 29 switch from the neutral state, adjust the flow rate distribution of the pressure oil flowing in from the pump ports 31 and 32, and supply the pressure oil to the respective actuators 1 to 5b. Furthermore, when the boom I directional control valve 23 and the boom II directional control valve 27 switch from the neutral state, the pressure oil from these directional control valves 23 and 27 join together and are supplied to the boom cylinder 1. When the arm I directional control valve 26 and the arm II directional control valve 24 are also switched from the neutral state, the pressure oil from these directional control valves 24 , 26 joins together and is supplied to the arm cylinder 2 .

[0036] The controller 57 receives operation signals from the operating lever devices 56a to 56d and sensor signals such as the rotation speed of the engine 9 and the pressure of each part, such as the discharge pressure of the first and second hydraulic pumps 11 and 12, and based on these signals issues commands to the pump controllers 58, 59, the switching valves 41a to 41d, 42a to 42d, and the control valve 20. In response to commands from the controller 57, the pump controllers 58, 59 independently control the discharge flow rates of the first and second pump elements 11a to 11d, 12a to 12d.

[0037] The rotation speed of the engine 9 can be detected, for example, by arranging a rotation sensor such as an encoder on the shaft 14 in the first hydraulic pump 11 or the second hydraulic pump 12. The discharge pressure of the first and second hydraulic pumps 11, 12 can be detected, for example, by connecting a pressure sensor to the pipes 51, 52. The sensor signal of the rotation sensor is used to control the flow rate of the pressurized oil in the first and second pump elements 11a to 11d, 12a to 12d, and the sensor signal of the pressure sensor is used to control the horsepower of the pressurized oil in the first and second pump elements 11a to 11d, 12a to 12d.

[0038] Operation Next, an example of operation when the boom 104 and the arm 105 are operated in the above configuration will be described.

[0039] 2, when the levers of the operating lever devices 56a to 56d are not operated and no command is received from the controller 57, the switching valves 41a to 41d and 42a to 42d are in the positions shown, the four pump elements 11a to 11d in the first hydraulic pump 11 are connected to the first valve group 33, and the four pump elements 12a to 12d in the second hydraulic pump 12 are connected to the second valve group 34. Furthermore, the pump elements 11a to 11d and 12a to 12d discharge zero or a very small amount of fluid. Since the directional control valves 21 to 29 are in a neutral state, the pressure oil flows to the tank 55 through the center bypass lines 33a and 34a.

[0040] When the lever of the operating lever device 56a is operated in the boom drive direction, the boom I directional control valve 23 and the boom II directional control valve 27 are displaced in accordance with the lever operation amount (required flow rate) in response to a command from the controller 57, and the boom cylinder 1 is driven by pressure oil from the first hydraulic pump 11. In addition, the flow rate of the first hydraulic pump 11 also increases in accordance with the lever operation amount in response to a command from the pump controller 58, so that the discharge flow rate of pump element 11a first begins to increase, and when pump element 11a reaches its maximum flow rate, the discharge flow rate of pump element 11b then increases. When pump element 11b reaches its maximum flow rate, the discharge flow rate of pump element 11c increases, and when pump element 11c reaches its maximum flow rate, the discharge flow rate of pump element 11d increases. If the lever operation amount increases further and the required flow rate of the boom cylinder 1 cannot be supplied by the first hydraulic pump 11 alone, the switching valve 42a can be switched to add the flow rate of the pump element 12a, and by switching the switching valves 42a, 42b, 42c, and 42d, the total flow rate of the second hydraulic pump 12 can be added. In other words, all eight pump elements 11a to 11d and 12a to 12d can be connected to the boom cylinder 1, enabling high-speed operation of the boom cylinder 1.

[0041] When the lever of the operating lever device 56b is operated in the arm drive direction, the arm I directional control valve 26 and the arm II directional control valve 24 are displaced in accordance with the lever operation amount in response to a command from the controller 57, and the arm cylinder 2 is driven by pressurized oil from the second hydraulic pump 12. Furthermore, in response to a command from the pump controller 59, the flow rate of the second hydraulic pump 12 also increases in accordance with the lever operation amount, and first the discharge flow rate of pump element 12d begins to increase. When pump element 12d reaches its maximum flow rate, the discharge flow rate of pump element 12c increases. When pump element 12c reaches its maximum flow rate, the discharge flow rate of pump element 12b increases, and when pump element 12b reaches its maximum flow rate, the discharge flow rate of pump element 12c increases. If the lever operation amount further increases and the required flow rate of the arm cylinder 2 cannot be met by the second hydraulic pump 12 alone, the selector valve 41d can be switched to add the flow rate of pump element 11d, and the full flow rate of the first hydraulic pump 11 can be added by switching the selector valves 41d, 41c, 41b, and 41a. That is, all eight pump elements 11a to 11d and 12a to 12d can be connected to the arm cylinder 2, which enables the arm cylinder 2 to operate at high speed.

[0042] When the boom 104 and the arm 105 are operated simultaneously, the lever of the operating lever device 56a is operated in the boom drive direction and the lever of the operating lever device 56b is operated in the arm drive direction, and then the boom I directional control valve 23 and the boom II directional control valve 27 are displaced according to the lever operation amount (required flow rate) in response to a command from the controller 57, and the arm I directional control valve 26 and the arm II directional control valve 24 are displaced. Also, at this time, for example, if the lever of the operating lever device 56a is operated at 20% of its full operation amount and the lever of the operating lever device 56b is operated at 20% of its full operation amount, pump elements 11a, 11b and pump elements 12d, 12c discharge pressure oil, and the boom cylinder 1 is driven by pressure oil from pump elements 11a, 11b, and the arm cylinder 2 is driven by pressure oil from pump elements 12d, 12c. If a demand is input that exceeds the combined maximum flow rate of all eight pump elements 11a to 11d, 12a to 12d, for example, if the lever of operating lever device 56a is input at 100% and the lever of operating lever device 56b is input at 60%, pump elements 11a to 11d, 12a to 12d are allocated in accordance with the ratio of the two (100:60 → 5:3), and boom cylinder 1 is driven by five pump elements 11a, 11b, 11c, 11d, 12a, and arm cylinder 2 is driven by three pump elements 12d, 12c, 12b.

[0043] In this way, the boom cylinder 1 and the arm cylinder 2 are driven independently without the pressure oil supplied from each pump element being divided, so each pump element only needs to supply a flow rate of the minimum pressure required for the boom cylinder 1 and the arm cylinder 2. This eliminates the need to reduce the pressure by throttling the pressure oil with a directional control valve, and it is possible to reduce flow division loss.

[0044] ~Operation principle of first and second hydraulic pumps~ The first pump elements 11a to 11d and the second pump elements 12a to 12d of the first and second hydraulic pumps 11, 12 are each composed of a plurality of cylinder working chambers and solenoid valves that vary the net volume (capacity) of the cylinder working chambers, and the discharge flow rates of the first pump elements 11a to 11d and the second pump elements 12a to 12d are controlled by switching the solenoid valves and changing the net volume of the cylinder working chambers based on commands output from the controller 57 and the pump controllers 58, 59. Hydraulic pumps incorporating such pump elements are sometimes called digital pumps.

[0045] The operating principles of the first hydraulic pump 11 and the second hydraulic pump 12 will be described in detail with reference to Fig. 7. Fig. 7 is a schematic diagram showing a part of an electronically controlled hydraulic pump 200 incorporating multiple pump elements, and the first and second hydraulic pumps 11 and 12 each have a configuration equivalent to that of the hydraulic pump 200.

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

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

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

[0049] The controller 207 corresponds to the pump controllers 58 and 59 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 enter 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, thereby controlling the net volume of the working chamber 202 of each pump element leading to each discharge port 214 via each high-pressure manifold 213 according to the required flow rate.

[0050] The hydraulic pump 200 includes a plurality of cylinders 201 each defining a plurality of working chambers 202 by its inner circumferential surface, and a plurality of pistons 203 that are driven by an eccentric cam 205 provided on a pump shaft 204 and reciprocate within the cylinder 201 to periodically change the volume of the working chambers 202 of the cylinder 201. The hydraulic pump 200 also includes a sensor 206 that 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. The controller 207 determines the current phase of the volume cycle of each working chamber 202 based on the detection information.

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

[0052] The LPV 209 is a normally open solenoid valve that passively opens 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, but is also connected to the controller 207 via an LPV control line 211 and can be selectively closed under active control by the controller 207, placing the working chamber 202 out of fluid communication with the low pressure manifold 210. The LPV 209 may alternatively be a normally closed solenoid valve.

[0053] Each working chamber 202 is further associated with a high-pressure valve (HPV) 212 configured as a pressure-actuated discharge valve. The HPV 212 opens outward from the respective working chamber 202 and is operable to seal a flow path extending from the working chamber 202 to a high-pressure manifold 213. When the HPV 212 is open, the high-pressure manifold 213 connects the working chamber 202 to a 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 passively opens when a pressure differential across the HPV 212 balances the biasing force of a biasing member within 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 an HPV control line 215. Normally, the HPV 212 cannot be opened by the controller 207 against pressure in the high-pressure manifold 213. The HPV 212 may also be open or partially open under the control of the controller 207 when there is pressure in the high-pressure manifold 213 and no pressure in the working chamber 202.

[0054] In the discharge mode, the controller 207 selects a net volumetric flow rate from the working chamber 202 to the high-pressure manifold 213 through the hydraulic pump 200 by actively closing one or more LPVs 209 near the maximum volume 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, creating an active cycle with a net volumetric flow rate for the working chamber 202. Alternatively, the LPV 209 may remain open throughout the entire cycle of the working chamber 202 (or the working chamber 202 may be closed throughout the entire cycle), creating an inactive cycle with no net volumetric flow rate. The controller 207 selects the number and sequence of active and inactive cycles to fill the selected net volumetric flow rate through the working chambers 202 of pump elements connected to the same high-pressure manifold 213 and discharge port 214 and generate flow or torque or power to meet the flow demands of the pump elements.

[0055] The controller 207 is operable to determine for each cycle whether to close or leave the LPV 209 open, selecting between active and inactive cycles, as well as precisely varying the phase at which the LPV 209 and / or HPV 212 closes in response to the changing volume of the working chamber 202, thereby selecting the net volumetric volume from the high pressure manifold 213 to the low pressure manifold 210 or vice versa.

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

[0057] Although 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 each with its own high-pressure manifold 213, discharge port 214, and demand signal.

[0058] More specifically, in the first hydraulic pump 11, four high-pressure manifolds 213 and four discharge ports 214 corresponding to the first discharge ports 45a, 45b, 45c, and 45d are provided, and each high-pressure manifold 213 is connected to the working chamber 202 via a high-pressure valve 209. The same applies to the second hydraulic pump 12.

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

[0060] - Structure of the Pump Device - Next, the structure of the pump device 10 according to this embodiment will be described.

[0061] 3 to 6 are diagrams showing the structure of the pump device 10 in the hydraulic circuit system shown in FIG. 1, with FIG. 3 being a longitudinal cross-sectional view taken along the shaft 14 of the pump device 10, FIG. 4 being a longitudinal cross-sectional view of the pump device 10 taken along line A-A in FIG. 3, FIG. 5 being a partial cross-sectional top view of the pump device 10, and FIG. 6 being a top view of the pump device 10 taken along line B-B in FIG. 3.

[0062] The structure of the pump device 10 in the hydraulic circuit system of this embodiment will be described with reference to FIGS.

[0063] In FIG. 3, as described above, the pump device 10 includes a tandem pump 30 having first and second hydraulic pumps 11, 12 arranged at a distance in the axial direction of the shaft 14, and a manifold block 40 equipped with first switching valves 41 a to 41 d and second switching valves 42 a to 42 d (see FIG. 5) and having first and second service ports 43, 44 (see FIG. 5) formed therein.

[0064] The first and second hydraulic pumps 11, 12 also have a port block 13 configured as a shared component of the first and second hydraulic pumps 11, 12, and the port block 13 has four first discharge ports 45a to 45d and four second discharge ports 46a to 46d opening into a side portion 13S, as shown in Fig. 6. The manifold block 40 is coupled to the side portion 13S (see Figs. 3, 5, and 6) of the port block 13, where the first and second discharge ports 45a to 45d, 46a to 46d open.

[0065] In the illustrated embodiment, the side portion 13S of the port block 13 has a single block surface, and the first and second discharge ports 45a to 45d, 46a to 46d open onto that block surface. However, the side portion 13S of the port block 13 may be formed with multiple stepped surfaces, for example, a first surface and a second surface parallel to the first surface, with the first discharge ports 45a to 45d formed on the first surface and the second discharge ports 46a to 46d formed on the second surface.

[0066] The first hydraulic pump 11 has a casing 48 and two first radial piston pumps 36a, 36b arranged at a distance in the axial direction of the shaft 14a inside the casing 48. The first radial piston pump 36a forms two of the four first pump elements 11a to 11d described above, the first pump elements 11a, 11d, and the first radial piston pump 36b forms the remaining two first pump elements 11b, 11c.

[0067] The second hydraulic pump 12 similarly has a casing 49 and two second radial piston pumps 37a, 37b arranged at a distance from each other on the shaft 14b within the casing 49. The second radial piston pump 37a forms two of the four second pump elements 12a to 12d, the second pump elements 12a, 12d, and the second radial piston pump 37b forms the remaining two second pump elements 12b, 12c.

[0068] The hydraulic oil from the tank 55 is guided via an intake port 47 formed in the port block 13 to the space in the casings 48, 49 where the first radial piston pumps 36a, 36b are located and the space in the casings 48, 49 where the second radial piston pumps 37a, 37b are located.

[0069] The first radial piston pump 36a is mainly composed of a shaft 14a that forms part of the shaft 14, an eccentric cam 15 that rotates integrally with the shaft 14a, a piston 16 that is in sliding contact with the outer peripheral surface of the eccentric cam 15, a cylinder 19 in which the piston 16 reciprocates, and an intake check valve 17a and a discharge check valve 18a that communicate with a cylinder chamber 50 formed by the piston 16 and the cylinder 19. Similarly, the first radial piston pump 36b is mainly composed of the shaft 14a, the eccentric cam 15, the piston 16, the cylinder 19, an intake check valve 17b, and a discharge check valve 18b.

[0070] The second radial piston pump 37a is similarly configured with a shaft 14b, an eccentric cam 15, a piston 16, a cylinder 19, an intake check valve 17c, and a discharge check valve 18c as its main components, and the second radial piston pump 37b is similarly configured with a shaft 14b, an eccentric cam 15, a piston 16, a cylinder 19, an intake check valve 17d, and a discharge check valve 18d as its main components.

[0071] The shaft 14a is rotatably supported by the casing 48 and the port block 13 via bearings, and the shaft 14b is rotatably supported by the casing 49 and the port block 13 via bearings. The shafts 14a and 14b are connected by a coupling 14c to form the shaft 14.

[0072] 4, the first radial piston pump 36a has six piston pumps 60, each consisting of a piston 16 and a cylinder 19, arranged radially at an equal angle relative to the shaft 14a. When the eccentric cam 15 integral with the shaft 14a rotates, the pistons 16 of the piston pumps 60 reciprocate within the cylinder 19, sucking hydraulic oil filling the space within the casing 48 through the suction check valve 17a (see FIG. 3) into the cylinder chamber 50 and discharging it from the discharge check valve 18a. The discharged hydraulic oil passes through internal passages 38a, 38d of the casing 48 and flows into the port block 13 through openings 39a, 39d formed in the end face of the casing 48 on the port block 13 side. The discharged hydraulic oil is then guided to any of the first discharge ports 45a to 45d shown in FIG. 6 (the first discharge ports 45a, 45d in the illustrated embodiment) and discharged from the discharge ports 45a, 45d.

[0073] Although not shown, the first radial piston pump 36b and the second radial piston pumps 37a, 37b are configured in the same manner. However, in the case of the first radial piston pump 37b, the pressure oil discharged from the discharge check valve 18b is led to and discharged from the first discharge ports 45b, 45c shown in Fig. 6. In the case of the first radial piston pump 37a, the pressure oil discharged from the discharge check valve 18c is led to and discharged from the second discharge ports 46a, 46d shown in Fig. 6, and in the case of the second radial piston pump 37b, the pressure oil discharged from the discharge check valve 18d is led to and discharged from the second discharge ports 46b, 46c shown in Fig. 6.

[0074] In FIG. 3, suction check valve 17a is an electromagnetic on / off valve (hereinafter referred to as a solenoid valve). When the solenoid valve is OFF, the valve is always open due to a spring, as shown in suction check valve 17a. Therefore, hydraulic oil drawn into cylinder chamber 50 when piston 16 descends returns through suction check valve 17a to casing 48 when piston 16 ascends, and is not discharged. When piston 16 ascends, turning the solenoid valve ON closes the valve, as shown in suction check valve 17b. Pressurizing cylinder chamber 50 opens discharge check valve 18b, allowing discharge. Furthermore, controlling the ON / OFF timing controls the closing timing of the suction check valve, thereby controlling the discharge flow rate per stroke of piston 16. In this way, by controlling the ON / OFF of the solenoid valve and its ON / OFF timing, it is possible to independently control the flow rate of each piston pump 60.

[0075] In this manner, in this embodiment, a plurality of piston pumps 60 capable of independent flow rate control are used, and the pressurized oil from the plurality of piston pumps 60 is joined together and discharged, and this is called a "pump element."

[0076] In this embodiment, three piston pumps 60 are used for one pump element to reduce pump pulsation, and in the first hydraulic pump 11, four pump elements 11a to 11d are configured from the twelve piston pumps 60 of the first radial piston pumps 36a, 36b, and pressure oil from the pump elements 11a to 11d is discharged from four discharge ports 45a to 45d. Similarly, in the second hydraulic pump 12, four pump elements 12a to 12d are configured from the twelve piston pumps 60 of the second radial piston pumps 37a, 37b, and pressure oil from the pump elements 12a to 12d is discharged from four discharge ports 46a to 46d.

[0077] This will be further explained with reference to FIG.

[0078] In Figure 4, the six piston pumps 60 of the first radial piston pump 36a are indicated clockwise by the reference symbols 60a, 60b, 60c, 60d, 60e, and 60f. The oil discharged from the piston pumps 60a, 60c, and 60e is combined to form the pump element 11a, and the oil discharged from the piston pumps 60b, 60d, and 60f is combined to form the pump element 11d. The combined discharge flow rates flow into the port block 13 from openings 39a and 39d and are directed to the discharge ports 4a and 45d shown in Figure 6. The same is true for the first radial piston pump 36b of the first hydraulic pump 11. The first radial piston pump 36b forms two pump elements 11b and 11c, and the combined discharge flow rates are directed to the discharge ports 45b and 45c shown in Figure 6.

[0079] The second radial piston pumps 37a, 37b of the second hydraulic pump 12 are similar, and the second radial piston pump 37a forms two pump elements 12a, 12d, and the combined discharge flow rates of the two pump elements are led to discharge ports 46a, 46d shown in FIG. 6, while the second radial piston pump 37b forms two pump elements 12b, 12c, and the combined discharge flow rates of the two pump elements are led to discharge ports 46b, 46c shown in FIG. 6.

[0080] In this way, the six piston pumps 60 of each of the two first radial piston pumps 36a, 36b are each divided into two groups, and the pressure oil discharged from each piston pump 60 of each group is joined together to form one of the four pump elements 11a to 11d of the first hydraulic pump 11. Similarly, the six piston pumps 60 of each of the two second radial piston pumps 37a, 37b are each divided into two groups, and the pressure oil discharged from each piston pump 60 of each group is joined together to form one of the four pump elements 12a to 12d of the second hydraulic pump 12.

[0081] 3 and 5, first selector valves 41a to 41d are attached to the side surface of the block body 40a facing the first hydraulic pump 11, and second selector valves 42a to 42d are attached to the side surface of the block body 40a facing the second hydraulic pump 12. Furthermore, two passages 43a and 44a are formed on the outlet sides of the first and second selector valves 41a to 41d and 42a to 42d in the block body 40a (above the first and second selector valves 41a to 41d and 42a to 42d in FIG. 3) that extend parallel to each other and open at opposite end faces of the block body 40a, as shown in FIG. 5, and the first service port 43 is formed at the opening of the passage 43a, and the second service port 44 is formed at the opening of the passage 44a. The first service port 43 and the second service port 44 may be formed by opening the passages 43a and 44a to the upper surface of the block body 40a.

[0082] Furthermore, within the block body 40a of the manifold block 40, there are formed internal passages that guide the pressure oil from the eight discharge ports 45a to 45d and 46a to 46d to the electromagnetic switching valves 41a to 41d and 42a to 42d, respectively, and internal flow paths that guide the pressure oil to either passage 43a or 43b depending on whether or not a command is sent from the controller 57 to the switching valves 41a to 41d and 42a to 42d. These internal passages are configured to form the hydraulic circuit of the manifold block 40 as shown in FIG.

[0083] Effects According to this embodiment, the following effects can be obtained.

[0084] 1. In this embodiment, as described above, when the boom 104 is operated independently, the eight pump elements 11a to 11d, 12a to 12d are sequentially connected to the boom cylinder 1 in accordance with the amount of lever operation (required flow rate), so the number of pump elements (discharge flow rate) can be precisely controlled in accordance with the amount of lever operation, and speed fluctuations in the boom cylinder 1 associated with switching of the discharge ports by the selector valves 41a to 41d, 42a to 42d are smoothed out, improving operability. Also, because all eight pump elements 11a to 11d, 12a to 12d can be connected to the boom cylinder 1, high-speed operation of the boom cylinder 1 is possible, and the amount of work can be secured.

[0085] When the arm 105 is operated independently, the number of pump elements (discharge flow rate) can be precisely controlled according to the lever operation amount, just as in the case of boom operation, improving operability. In addition, high-speed operation of the arm cylinder 2 is possible, ensuring a sufficient amount of work.

[0086] Furthermore, if the switching valves 41a to 41d and 42a to 42d were installed away from the pumps, eight hydraulic hoses would be required to connect the discharge ports 45a to 45d and 46a to 46d to the switching valves 41a to 41d and 42a to 42d, and connecting the eight hydraulic hoses to the discharge ports 45a to 45d and 46a to 46d would reduce mountability due to the space required to pass the hoses, and many other issues would arise, such as an increase in the number of steps required to connect the hoses and the risk of leaks and reliability due to the increased number of hydraulic connections. Furthermore, since it is necessary to increase the distance between the discharge ports 45a to 45d and 46a to 46d in order to connect the eight hydraulic hoses, the port block 13 would become larger, and the pump device 10 itself would also become larger, which would also reduce mountability.

[0087] In this embodiment, the manifold block 40 is connected to the side portion 13S where the eight discharge ports 45a to 45d, 46a to 46d of the port block 13 open, so that all hydraulic hoses connecting the discharge ports 45a to 45d, 46a to 46d to the switching valves 41a to 41d, 42a to 42d can be eliminated, and the pump device 10 can be made smaller and the hydraulic hoses reduced, thereby improving the ease of installation on construction machinery.

[0088] Furthermore, no hose connection work is required, the pump device can be easily installed, and the number of leak points is reduced, improving reliability against leaks.

[0089] In this embodiment, the first hydraulic pump 11 and the second hydraulic pump 12 have four pump elements and four discharge ports, i.e., pump elements 11a to 11d, pump elements 12a to 12d, and discharge ports 45a to 45d, and discharge ports 46a to 46d, respectively, but this is not limited to four. The first hydraulic pump 11 and the second hydraulic pump 12 may have two or more pump elements and discharge ports, such as two, three, or five, and the effects of the present invention can be obtained in terms of operability, energy saving, mountability, etc.

[0090] 2. The control valve 20 is configured so that the boom I directional control valve 23 and the boom II directional control valve 27 are aggregated in the first valve group 33, and the arm I directional control valve 26 and the arm II directional control valve 24 are aggregated in the second valve group 34. Therefore, during combined operation of the boom 104 and the arm 105, the boom cylinder 1 and the arm cylinder 2 are driven independently without dividing the pressurized oil supplied from the connected pump elements, and each pump element only needs to supply the minimum pressure flow rate required for the boom cylinder 1 and the arm cylinder 2. This eliminates the need to throttle and reduce the pressure of the pressurized oil with a directional control valve, reducing division loss and improving energy efficiency.

[0091] 3. Because the number of service ports 43, 44 of the manifold block 40 and the number of pump ports 31, 32 of the control valve 20, which are connected by the pipes 51, 52, are the same as the number of the first and second hydraulic pumps 11, 12 of the tandem pump 30 (two), the manifold block 40 and the control valve 20 can be connected with a minimum number of hoses, which also reduces the number of hoses and improves the ease of installation on construction machinery.

[0092] 4. Within the manifold block 40, the hydraulic circuits are configured such that the first selector valves 41a to 41d, in their first positions (initial positions), connect the first discharge ports 45a to 45d to the first service port 43 and, in their second positions, connect the first discharge ports 45a to 45d to the second service port 44, and the second selector valves 42a to 42d, in their first positions (initial positions), connect the second discharge ports 46a to 46d to the second service port 44 and, in their second positions, connect the second discharge ports 46a to 46d to the first service port 43. Therefore, when pump elements 11a to 11d are connected in sequence to boom cylinder 1 in accordance with the lever operation amount (required flow rate) to supply the discharge flow rate of pump elements 11a to 11d to boom cylinder 1, the discharge flow rate can be supplied without switching over switchover valves 41a to 41d, so no pressure fluctuations due to switching over of switchover valves 41a to 41d occur, and it is possible to smoothly start or accelerate the boom cylinder 1. The same is true when pump elements 42a to 42d are connected in sequence to arm cylinder 2 in accordance with the lever operation amount (required flow rate) to supply the discharge flow rate of pump elements 12a to 12d to arm cylinder 2, and it is possible to smoothly start or accelerate the arm cylinder 2, without pressure fluctuations due to switching over of switchover valves 42a to 42d.

[0093] Furthermore, when the boom cylinder 1 is driven by sequentially connecting the eight pump elements 11a to 11d and 12a to 12d to the boom cylinder 1 in accordance with the lever operation amount, none of the switching valves 41a to 41d and 42a to 42d are switched from the first position until the required flow rate of the boom cylinder 1 can be supplied by the first hydraulic pump 11 alone, and the switching valves 42a to 42d can be switched to the second position when the required flow rate of the boom cylinder 1 can no longer be supplied by the first hydraulic pump 11 alone. The same is true when the eight pump elements 11a to 11d and 12a to 12d are sequentially connected to the arm cylinder 2 in accordance with the lever operation amount to drive the arm cylinder 2, and the switching valves 41a to 41d can be switched to the second position when the required flow rate of the arm cylinder 2 can no longer be supplied by the second hydraulic pump 12 alone. Therefore, the number of times the switching valves 41a to 41d, 42a to 42d are switched when driving the boom cylinder 1 or the arm cylinder 2 can be reduced, and the durability of the switching valves 41a to 41d, 42a to 42d can be improved.

[0094] DESCRIPTION OF SYMBOLS 1...Boom cylinder (specific first actuator) 2...Arm cylinder (specific second actuator) 3...Bucket cylinder 4...Swing motor 1-5b...Multiple actuators 9...Engine 10...Pump device 11...First hydraulic pump 11a-11d...First pump element 12...Second hydraulic pump 12a-12d...Second pump element 13...Port block 14...Shaft 15...Eccentric cam 16...Piston 17a-17d...Suction check valve 18a-18d...Discharge check valve 19...Cylinder 20...Control valve 21...Directional control valve for right travel 22...Directional control valve for bucket 23...Directional control valve for boom I 24...Directional control valve for arm II 25...Directional control valve for swing 26...Directional control valve for arm I 27...Directional control valve for boom I 28...Backup directional control valve 29...Directional control valve for left travel DESCRIPTION OF SYMBOLS 30...Tandem piston 31...First pump port 32...Second pump port 33...First valve group 34...Second valve group 36a, 36b...First radial piston pump 37a, 37b...Second radial piston pump 40...Manifold block 41a to 41d...First switching valve 42a to 42d...Second switching valve 43...First service port 44...Second service port 45a to 45d...First discharge port 46a to 46d...Second discharge port 47...Suction port 48, 49...Casing 50...Cylinder chamber 51...First piping 52...Second piping 55...Tank 56a, 56b, 56c, 56d...Operating lever device 57...Controller 58, 59...Pump controller 60a to 60f...Piston pump 100...Hydraulic excavator 101... Lower traveling body 102... Upper rotating body 108a, 108b... Traveling device

Claims

1. A hydraulic circuit system for a construction machine comprising: a prime mover; a pump device driven by the prime mover; a plurality of actuators driven by pressure oil discharged from the pump device; and a plurality of directional control valves for controlling the flow of pressure oil supplied from the pump device to the plurality of actuators, wherein the pump device comprises a tandem pump having first and second hydraulic pumps arranged at intervals in the axial direction of a shaft driven to rotate by the prime mover, the hydraulic circuit system further comprising a manifold block having a plurality of first switching valves and a plurality of second switching valves mounted thereon and forming a plurality of service ports, the first hydraulic pump includes a plurality of first pump elements capable of independently controlling the flow of pressure oil discharged from a plurality of first discharge ports, the second hydraulic pump includes a plurality of second pump elements capable of independently controlling the flow of pressure oil discharged from a plurality of second discharge ports, the first and second hydraulic pumps are configured as shared components of the first and second hydraulic pumps, and have a port block having the plurality of first discharge ports and the plurality of second discharge ports open to the side, The manifold block is configured to switch the flow direction of pressurized oil flowing in from the first and second discharge ports of the port block using the first and second switching valves, and to guide the pressurized oil to any of the service ports, the manifold block is connected to the side of the port block to which the first and second discharge ports open, and the service ports of the manifold block are connected via a plurality of piping to a control valve which houses the directional control valves within a valve housing. A hydraulic circuit system for a construction machine, characterized in that 2. A hydraulic circuit system for a construction machine as described in claim 1, characterized in that the multiple service ports of the manifold block are connected to multiple pump ports provided on the control valve via the multiple piping, and the number of the multiple service ports and the multiple pump ports is the same as the number of the first and second hydraulic pumps of the tandem pump.

3. A hydraulic circuit system for a construction machine as described in claim 1 or 2, characterized in that: the multiple actuators include a specific first actuator and a specific second actuator which are operated relatively frequently; the multiple directional control valves are divided within the control valve into a first valve group including two directional control valves for the specific first actuator and a second valve group including two directional control valves for the specific second actuator; the multiple service ports include first and second service ports, and the multiple piping includes first and second piping; the control valve has first and second pump ports connected to the first and second valve groups, respectively, and the first and second pump ports are connected to the first and second service ports via the first and second piping.

4. A hydraulic circuit system for a construction machine as described in any one of claims 1 to 3, wherein the plurality of service ports include first and second service ports, the plurality of first and second switching valves are switchable between a first position which is an initial position and a second position which is a non-initial position, the plurality of first switching valves, in the first position, connect the plurality of first discharge ports to the first service port, and in the second position, connect the plurality of first discharge ports to the second service port, and the plurality of second switching valves, in the first position, connect the plurality of second discharge ports to the second service port, and in the second position, connect the plurality of second discharge ports to the first service port.

5. A hydraulic circuit system for construction machinery as described in any one of claims 1 to 4, wherein the plurality of first and second pump elements of the first and second hydraulic pumps are four first and second pump elements, respectively, the plurality of first and second discharge ports are four first and second discharge ports, respectively, and the plurality of first and second switching valves of the manifold block are four first and second switching valves, respectively.

6. A hydraulic circuit system for construction machinery according to any one of claims 1 to 5, characterized in that: the first hydraulic pump has a plurality of first radial piston pumps arranged at intervals in the axial direction of the shaft; each of the two first radial piston pumps has a plurality of piston pumps arranged radially with respect to the shaft, the plurality of piston pumps of the plurality of piston pumps being divided into a plurality of groups, and pressurized oil discharged from each piston pump in each group is joined to form one of the plurality of pump elements of the first hydraulic pump; the second hydraulic pump has a plurality of second radial piston pumps arranged at intervals in the axial direction of the shaft; each of the two second radial piston pumps has a plurality of piston pumps arranged radially with respect to the shaft, the plurality of piston pumps of the plurality of piston pumps being divided into a plurality of groups, and pressurized oil discharged from each piston pump in each group is joined to form one of the plurality of pump elements of the second hydraulic pump.

7. A hydraulic circuit system for a construction machine as described in any one of claims 1 to 6, characterized in that the plurality of first discharge ports are formed on a first surface of the side portion of the port block, and the plurality of second discharge ports are formed on the first surface of the side portion of the port block or on a second surface parallel to the first surface.

8. A pump device for a construction machine equipped with a tandem pump having first and second hydraulic pumps arranged at an interval in the axial direction of a shaft driven and rotated by a prime mover, further comprising a manifold block equipped with a plurality of first switching valves and a plurality of second switching valves and forming a plurality of service ports, the first hydraulic pump contains a plurality of first pump elements capable of independently controlling the flow of pressure oil discharged from a plurality of first discharge ports, the second hydraulic pump contains a plurality of second pump elements capable of independently controlling the flow of pressure oil discharged from a plurality of second discharge ports, the first and second hydraulic pumps are configured as shared components of the first and second hydraulic pumps and have a port block having the plurality of first discharge ports and the plurality of second discharge ports open to a side, the manifold block is configured to switch the flow direction of the pressure oil flowing in from the plurality of first and second discharge ports of the port block by the plurality of first and second switching valves, and to guide the pressure oil to any one of the plurality of service ports, 2. A pump device for a construction machine, comprising: a manifold block coupled to the side of the port block into which the first and second discharge ports open.

9. A pump device for construction machinery as described in claim 8, wherein the plurality of service ports include first and second service ports, the plurality of first and second switching valves are switchable between a first position which is an initial position and a second position which is a non-initial position, the plurality of first switching valves, in the first position, connect the plurality of first discharge ports to the first service port, and in the second position, connect the plurality of first discharge ports to the second service port, and the plurality of second switching valves, in the first position, connect the plurality of second discharge ports to the second service port, and in the second position, connect the plurality of second discharge ports to the first service port.

10. A pump device for construction machinery as described in claim 8 or 9, characterized in that the plurality of first and second pump elements of the first and second hydraulic pumps are four first and second pump elements, respectively, the plurality of first and second discharge ports are four first and second discharge ports, respectively, and the plurality of first and second switching valves of the manifold block are four first and second switching valves, respectively.

11. A pump device for construction machinery according to any one of claims 8 to 10, characterized in that: the first hydraulic pump has a plurality of first radial piston pumps arranged at intervals in the axial direction of the shaft, the plurality of first radial piston pumps each having a plurality of piston pumps arranged radially with respect to the shaft, the plurality of piston pumps being divided into a plurality of groups, and pressurized oil discharged from each piston pump in each group being joined together to form one of the plurality of pump elements of the first hydraulic pump; the second hydraulic pump has a plurality of second radial piston pumps arranged at intervals in the axial direction of the shaft, the plurality of second radial piston pumps each having a plurality of piston pumps arranged radially with respect to the shaft, the plurality of piston pumps being divided into a plurality of groups, and pressurized oil discharged from each piston pump in each group being joined together to form one of the plurality of pump elements of the second hydraulic pump.

12. A pump device for construction machinery as claimed in any one of claims 8 to 11, characterized in that the plurality of first discharge ports are formed on a first surface of the side portion of the port block, and the plurality of second discharge ports are formed on the first surface of the side portion of the port block or on a second surface parallel to the first surface.

13. In the hydraulic circuit system for a construction machine according to any one of claims 1 to 7, the first and second hydraulic pumps each have a pump shaft, and at least three working chambers whose volumes change periodically with the rotation of the pump shaft, each working chamber of the first and second hydraulic pumps has a low pressure valve that controls the flow of pressure oil between the working chamber and a low pressure manifold, and a high pressure valve that controls the flow of pressure oil between the working chamber and the high pressure manifold, the working chambers of the first and second hydraulic pumps form a plurality of pump elements, each pump element has one or more working chambers, and is connected to the high pressure manifold provided in common to the one or more working chambers of each pump element, a controller that 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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