KR101233541B1 - Hydraulic driving apparatus - Google Patents

Abstract

The hydraulic drive device 100 includes a variable displacement main piston pump 20 and a variable displacement sub piston pump 50 that are rotationally driven through common drive shafts 25 and 55. The discharge pressures of the main hydraulic actuators 7 and 8 and the sub piston pump 50 reducing the discharge capacity of the main piston pump 20 as the discharge pressures P1 and P2 of the main piston pump 20 rise. By providing the subhydraulic actuator 10 which switches the discharge capacity of the sub piston pump 50 in two stages in accordance with the rise of P3), the hydraulic drive device ( To prevent excessive increase in the pump load of 100).

Description

Hydraulic Drive Unit {HYDRAULIC DRIVING APPARATUS}

The present invention relates to a hydraulic drive device mounted on a construction machine such as a hydraulic excavator or a work vehicle.

JP2003-221842A, issued in 2003 by the Japanese Patent Office, discloses a hydraulic excavator provided with a hydraulic drive device comprising three variable displacement hydraulic pumps driven by a common engine. Among the three hydraulic pumps, the discharge hydraulic oil of the first hydraulic pump and the second hydraulic pump is used for excavation of the soil and movement of the hydraulic excavator, and the discharge hydraulic oil of the third hydraulic pump is used for turning the boom and the operating room.

This hydraulic drive device has a problem that the structure is complicated and the manufacturing cost is high because of the structure of continuously adjusting the discharge capacities of the three variable displacement hydraulic pumps in accordance with the discharge pressure of each hydraulic pump.

It is therefore an object of the present invention to provide a hydraulic drive device capable of adjusting the drive load of a pump based on a simple structure.

In order to achieve the above object, this invention is a hydraulic drive provided with the variable displacement main piston pump and the variable displacement sub piston pump which are rotationally driven through a common drive shaft, and raises the discharge pressure of the said main piston pump. A main hydraulic actuator for continuously reducing the discharge capacity of the main piston pump, and a sub hydraulic actuator for switching the discharge capacity of the sub piston pump between two set capacities according to the discharge pressure of the sub piston pump. Doing.

The details and other features and advantages of the present invention will be set forth in the accompanying drawings and described in the description below.

1 is a hydraulic circuit diagram of a hydraulic drive device according to the present invention.
2 is a longitudinal sectional view of a hydraulic drive device;
3 is a hydraulic circuit diagram of a hydraulic drive apparatus according to another embodiment of the present invention.

Referring to FIG. 1 of the drawings, the hydraulic drive device 100 mounted on the hydraulic excavator includes a first pump 1, a second pump 2, and a third pump driven by a common internal combustion engine 4. 3) is provided.

Hydraulic excavators extrude traveling equipment by left and right crawlers, an excavation device for driving the bucket, arms, booms, and the like to excavate the ground, a turning device for turning the excavator or steering wheel with respect to the vehicle body, and extrusion of earth and sand in the traveling direction. And a hydraulic plate 100, and the hydraulic drive device 100 supplies pressurized hydraulic oil to these devices to drive them.

The pressurized hydraulic oil from which the first pump 1 is discharged is supplied to a hydraulic motor that drives the right and left crawlers through the first pump passage 11. The pressurized hydraulic oil from which the second pump 2 is discharged is supplied to the plurality of hydraulic cylinders that drive the excavator through the second pump passage 12.

The hydraulic oil discharged from the third pump 3 is supplied to the hydraulic motor for driving the turning device and the hydraulic cylinder for driving the top plate through the third pump passage 13.

Referring to FIG. 2, the first pump 1 and the second pump 2 are constituted by a main piston pump 20. The third pump 3 is constituted by the sub piston pump 50. The main piston pump 20 and the sub piston pump 50 are configured coaxially on a shaft 25 driven by the internal combustion engine 4.

The main piston pump 20 is a 2-flow type variable displacement inclined piston pump having two discharge ports.

The main piston pump 20 is housed in a space formed by the main casing 21 and the cover 22 fixed to the main casing 21. The main piston pump 20 has a main cylinder block 23 and a main swash plate 24.

The main cylinder block 23 is fixed to the shaft 25 and rotates integrally with the shaft 25. One end of the shaft 25 is supported by the bearing 32 on the cover 22, and the intermediate portion of the shaft 25 is supported by the bearing 31 on the main casing 21. Rotational torque of the internal combustion engine 4 shown in FIG. 1 is input to and at one end thereof projecting outward from the main casing 21 of the shaft 25.

An even number of main cylinders 26 are arranged in the main cylinder block 23 at regular intervals on approximately the same circumference around the center axis O in parallel with the center axis O of the shaft 25.

The main piston 28 is inserted into each main cylinder 26. Inside the main cylinder 26, a main volume chamber 27 facing one end of the main piston 28 is partitioned. One end thereof on the main piston 28 protrudes from the main cylinder block 23 and is in sliding contact with the main inclined plate 24 via the shoe 29.

Inside the main cylinder block 23, a spring 48 for pressing the shoe 29 toward the main inclined plate 24 is housed.

When the main cylinder block 23 rotates, the main piston 28, which is in sliding contact with the main inclined plate 24 through the shoe 29, rotates integrally with the main cylinder block 23 while reciprocating in the direction of the central axis O. The main volume chamber 27 is expanded and contracted.

The cylinder port 33 or the cylinder port 34 communicating with the main volume chamber 27 is opened at the end surface of the main cylinder block 23 located on the opposite side of the main inclined plate 24. This end face of the main cylinder block 23 is in sliding contact with the valve plate 30 supported by the main casing 21.

The cylinder port 33 and the cylinder port 34 are alternately formed on the circumference of another radius centering on the central axis O. As shown in FIG. As a result, the cylinder port 33 which communicates with the half cylinder 26 and the cylinder port 34 which communicates with the remaining half cylinder 26 are opened in the end surface of the main cylinder block 23. As shown in FIG.

The valve plate 30 is formed with one suction port and two discharge ports. The suction port communicates with both the cylinder port 33 and the cylinder port 34 in the rotation angle region of the main cylinder block 23 in which the main volume chamber 27 is enlarged. The two discharge ports consist of a discharge port communicating with the cylinder port 33 and a discharge port communicating with the cylinder port 34 in the rotation angle region of the main cylinder block 23 in which the main volume chamber 27 is reduced. .

The discharge port communicating with the cylinder port 33, the main cylinder 26 having the cylinder port 33, and the main piston 28 inserted into the main cylinder 26 constitute the first pump 1. The discharge port communicating with the cylinder port 34, the main cylinder 26 having the cylinder port 34, and the main piston 28 inserted into the main cylinder 26 constitute the second pump 1.

The first pump passage 11 shown in FIG. 1 is connected to the discharge port of the first pump 1, and the second pump passage 12 shown in FIG. 1 is connected to the discharge port of the second pump 2. do. Although not shown in FIG. 2, the first pump passage 11 and the second pump passage 12 are formed through the main casing 21.

When the main cylinder block 23 rotates once, each main piston 28 moves back and forth inside the main cylinder 26. In the suction stroke in which the main volume chamber 27 is expanded, hydraulic oil is sucked into the main volume chamber 27 through the cylinder ports 33 and 34 from the suction port of the valve plate 30. In the discharge stroke in which the main volume chamber 27 of the main cylinder 26 is contracted, hydraulic oil is discharged from the main volume chamber 27 to the two discharge ports of the valve plate 30 through the cylinder ports 33 and 34. And the first pump passage 11 and the second pump passage 12.

Due to the above structure of the main piston pump 20, the hydraulic oil is supplied to the first pump passage 11 and the second pump passage 12 separately.

The main inclined plate 24 is supported by the bearing 41 so as to be able to be tilted against the cover 22.

Springs 35 and 36 are interposed between the main swash plate 24 and the main casing 21. The springs 35 and 36 urge the main inclined plate 24 in the tilt angle increasing direction. The spring 35 always biases the main swash plate 24 in the direction of the tilt angle increase, and the spring 36 tilts the main swash plate 24 when the tilt angle of the main swash plate 24 falls below a predetermined angle. Tighten in the direction of increase. It is also possible to support the main ramp 24 by a single spring instead of the springs 35 and 36.

Referring again to FIG. 1, the discharge capacity of the main piston pump 20 is adjusted by the first main hydraulic actuator 7, the second main hydraulic actuator 8, and the auxiliary hydraulic actuator 9.

Referring back to FIG. 2, the first main hydraulic actuator 7 and the second main hydraulic actuator 8 include cylinders 37 and 38 coaxially formed on the main casing 21 and cylinders 37 and 38. It is provided with a stepped plunger 42 which is slidably inserted into. The main casing 21 is provided with a hydraulic chamber 43 for applying pressure to the stepped portion of the stepped plunger 42 and a hydraulic chamber 44 for applying pressure to the tip of the stepped plunger 42.

The stepped plunger 42 is common to the first main hydraulic actuator 7 and the second main actuator 8. The hydraulic chamber 44 which presses the stepped plunger 42 constitutes the first main hydraulic actuator 7, and the hydraulic chamber 43 which presses the stepped plunger 42 presses the second main hydraulic actuator ( 8) Configure.

Referring again to FIG. 1, the discharge pressure P1 of the first pump 1 is induced in the hydraulic chamber 44 of the first main hydraulic actuator 7. When the pressure induced in the hydraulic chamber 44 rises, the stepped plunger 42 is displaced, and the main swash plate 24 is driven in a direction in which the tilt angle is small. As a result, the discharge capacity of the main piston pump 20 is reduced.

The discharge pressure P2 of the second pump 2 is guided to the hydraulic chamber 43 of the second main hydraulic actuator 8. When the pressure of the hydraulic chamber 43 rises, the stepped plunger 42 is displaced, and the main inclined plate 24 is driven in a direction in which the tilt angle is reduced. As a result, the discharge capacity of the main piston pump 20 is reduced.

The auxiliary hydraulic actuator 9 includes a cylinder, a piston slidably inserted into the cylinder, and hydraulic chambers 9A and 9B partitioned by the piston in the cylinder. In addition, the auxiliary hydraulic actuator 9 is not shown in FIG.

The discharge pressure P3 of the third pump 3 always acts on the hydraulic chamber 9A of the auxiliary hydraulic actuator 9. When the pressure in the hydraulic chamber 9A rises, the piston in the auxiliary hydraulic actuator 9 displaces the main inclined plate 24 in the direction of decreasing the tilt angle, that is, in the direction of decreasing the discharge capacity of the main piston pump 20. .

In the hydraulic chamber 9B of the auxiliary hydraulic actuator 9, the discharge pressure P3 of the third pump 3 is guided through the switching valve 5. When the discharge pressure P3 of the third pump 3 acts on the hydraulic chamber 9B, the displacement of the piston in the discharge pressure reduction direction of the main piston pump 20 is stopped. In connection with this, the displacement of the main inclination plate 24 in the tilt direction reduction direction also stops.

As described above, the main inclined plate 24 that determines the discharge capacity of the main piston pump 20 includes the first main hydraulic actuator 7, the second main hydraulic actuator 8, and the auxiliary hydraulic actuator 9. The pressure applied to the main inclined plate 24 and the elastic support force of the springs 35 and 36 supporting the main inclined plate 24 in the reverse direction are maintained at an arbitrary position. Therefore, the discharge capacity of the main piston pump 20 changes steplessly in accordance with the pressures of the actuators 7-9.

Referring again to FIG. 2, the sub piston pump 50 constituting the third pump 3 is a variable flow type inclined plate piston pump of one flow type having one discharge port.

The sub piston pump 50 is housed in a space formed by the sub casing 51 and the main casing 21 fixed to the main casing 21. The sub piston pump 50 has a sub cylinder block 53 and a sub swash plate 54.

The sub cylinder block 53 is fixed to the shaft 55 and rotates integrally with the shaft 55. One end of the shaft 55 is supported by the bearing 62 in the sub casing 51. Already one end of the shaft 55 is supported via a bearing 61 on the main casing 21. The shaft 55 is integrally formed coaxially with the shaft 25 and rotates integrally with the shaft 25.

In the sub-cylinder block 53, a plurality of sub-cylinders 56 parallel to the central axis O are formed at regular intervals on the circumference having the central axis O as the center.

The sub piston 58 is inserted into each sub cylinder 56. Inside the sub cylinder 56, a sub volume chamber 57 facing one end of the sub piston 58 is partitioned. Already one end of the sub piston 58 protrudes from the sub cylinder block 53, and makes sliding contact with the sub inclined plate 54 through the shoe 59.

Inside the sub cylinder block 53, a spring 65 for pressing the shoe 59 toward the sub inclined plate 54 is accommodated.

When the sub cylinder block 53 rotates once, each sub piston 58 moves one reciprocation in the sub cylinder 56. The sub piston 58 in sliding contact with the sub inclined plate 54 via the shoe 59 is reciprocated in the direction of the central axis O while integrally rotating with the sub cylinder block 53 to expand the sub volume chamber 57. Contraction.

The cylinder port 63 which communicates with the sub volume chamber 57 is opened in the end surface of the sub cylinder block 53 located in the opposite side to the sub inclination plate 54.

This end surface of the sub cylinder block 53 is in sliding contact with the valve plate 60 supported by the main casing 21 in the sub casing 51. One suction port and one discharge port 64 are formed in the valve plate 60. The suction port communicates with the cylinder port 63 in the rotation angle region of the sub cylinder block 53 in which the sub volume chamber 57 is enlarged. The discharge port 64 communicates with the cylinder port 63 in the rotation angle region of the sub cylinder block 53 in which the sub volume chamber 57 is reduced.

The discharge port 64 is connected to the third pump passage 13. The third pump passage 13 is formed through the main casing 21. Therefore, the flow volume and the pressure of the hydraulic fluid of the 3rd pump channel | path 13 can be controlled independently from the flow volume and the pressure of the hydraulic fluid of the 1st pump channel | path 11 and the 2nd pump channel | path 12.

The sub inclination plate 54 is supported by the sub casing 51 by a pair of ball bearings so that a tilt angle can be changed.

The sub-hydraulic actuator 10 includes a cylinder 66 formed at the bottom of the sub-casing 51 and a plunger 67 slidably inserted into the cylinder 66, and the hydraulic chamber 68 therebetween. It is partitioned.

The third pump passage 13 is connected to the hydraulic chamber 68 via the pilot switching valve 5.

Referring again to FIG. 1, the third pump passage 13 is connected to a hydraulic motor for driving the turning device and a hydraulic cylinder for driving the top plate, and the auxiliary hydraulic actuator 9 is attached to the main slope plate 24. It is connected to 9 A of hydraulic chambers which operate in each reduction direction. The third pump passage 13 further includes a hydraulic chamber 9B for operating the auxiliary hydraulic actuator 9 in the tilt angle increasing direction of the main inclined plate 24 through the pilot switching valve 5, and the subhydraulic actuator ( 10 is connected to the hydraulic chamber 68. The sub hydraulic actuator 10 drives the sub swash plate 54 in the tilt angle reduction direction by supplying pressure to the hydraulic chamber 68.

The pilot switching valve 5 includes the hydraulic chamber 9B formed in the auxiliary hydraulic actuator 9 which drives the auxiliary hydraulic actuator 9 in the direction of increasing the tilt angle of the main inclined plate 24 and the sub hydraulic actuator 10. The drive position A which supplies the discharge pressure P3 of the 3rd pump 3 to the hydraulic chamber 68 via the 3rd pump channel | path 13, and the drain position B which releases these hydraulic chambers to the drain channel | path 14. Has

The pilot switching valve 5 is urged toward the drain position B by the elastic force of the return spring 6. In addition, the discharge pressure P3 of the third pump 3 from the third pump passage 13 acts as a pilot pressure in the reverse direction to the return spring 6, that is, toward the drive position A. FIG.

When the discharge pressure P3 of the 3rd pump 3 is low, the pilot switching valve 5 is located in the drain position B, and the sub swash plate 54 of the 3rd pump 3 is hold | maintained at the maximum tilt angle position. . For example, by eccentric the light axis of the sub-slope plate 54 with respect to the shaft 55, the moment is generated by the pressure applied to the sub-piston 58 to the sub-slope plate 54, without using the spring The inclined plate 54 can be kept at the maximum tilt angle position.

When the discharge pressure P3 of the 3rd pump 3 exceeds the elastic force of the return spring 6, the pilot switching valve 5 will switch to drive position A. FIG. As a result, the plunger 67 rotates the sub inclination plate 54 to the minimum tilt angle position at the discharge pressure P3 of the third pump 3 supplied to the hydraulic chamber 68. As a result, the third pump 3 lowers the discharge flow rate. In this manner, depending on the position of the pilot switching valve 5, the discharge capacity of the third pump 3 is switched between the maximum capacity and the minimum capacity.

On the other hand, the discharge pressure P3 of the third pump 3 always acts on the pressure chamber that reduces the tilt angle of the main inclined plate 24 of the auxiliary hydraulic actuator 9. In addition, while the pilot switching valve 5 is in the drain position B, the hydraulic chamber 9B which increases the tilt angle of the main inclination plate 24 of the auxiliary hydraulic actuator 9 is open to the drain. Therefore, in this state, the main tilt plate 24 acts on the tilt angle reducing direction based on the discharge pressure P3 of the third pump 3 via the auxiliary hydraulic actuator 9.

On the other hand, when switching to the drive position A, the discharge pressure P3 of the 3rd pump 3 also acts on the hydraulic chamber 9B which increases the tilt angle of the main inclination plate 24 of the auxiliary hydraulic actuator 9. As a result, the auxiliary hydraulic actuator 9 stops the displacement in the direction of decreasing the tilt angle of the main inclined plate 24.

In this way, in this hydraulic drive device, as the discharge pressure P3 of the third pump 3 increases, the warp angle of the main inclination plate 24 and the warp angle of the sub inclination plate 54 are reduced, so that Balance the discharge capacity. On the other hand, when the discharge pressure P3 of the 3rd pump 3 exceeds a fixed pressure, the decrease of the tilt angle of the main inclination plate 24 will stop. The sub swash plate 54 is kept at the minimum tilt angle position as it is.

The elastic restoring force of the return spring 6 is comprised so that adjustment is possible by manual. By setting the elastic restoring force of the return spring 6 large, the discharge pressure P3 of the 3rd pump 3 with which the switching valve 5 switches from the drain position B to the drive position A can be set high.

During the operation of the hydraulic excavator, the first pump 1, the second pump 2, and the third pump 3 are driven by the rotational torque of the internal combustion engine 4.

The discharge hydraulic oil of the 1st pump 1 is supplied to the hydraulic motor which drives a crawler on either side through the 1st pump channel | path 11. As shown in FIG. The discharge hydraulic oil of the second pump 2 is supplied to each hydraulic cylinder that drives the excavator by the second pump passage 12. The discharge hydraulic oil of the 3rd pump 3 is supplied to the hydraulic motor which drives a turning device, and the hydraulic cylinder which drives a top plate through the 3rd pump channel 13.

The flow rate of the hydraulic oil supplied to each apparatus is adjusted by an operator operating a control valve, and traveling of a hydraulic excavator, excavation of the ground, and conveyance of earth and sand are performed.

The main piston pump 20 which combines the 1st pump 1 and the 2nd pump 2 is the 1st pump guide | induced by the auxiliary force of the springs 35 and 36, and the 1st main hydraulic actuator 7 ( Discharge pressure P1 of 1), discharge pressure P2 of second pump 2 guided to second main hydraulic actuator 8, and discharge pressure P3 of third pump 3 guided to auxiliary hydraulic actuator 9; The tilt angle of the main swash plate 24 is maintained at a position where the total pressure is balanced. If any one of the discharge pressures P1, P2, P3 rises, the main inclination plate 24 will be warped in a position where the driving force of the inclination plate 24 and the subordinate force of the springs 35 and 36 are balanced by the rising pressure, The pushing volume of the main piston 28 per one revolution of 25 is reduced. With the decrease in the pushing volume of the main piston 28, the discharge capacity of the main piston pump 20 is gradually reduced. As a result, the output of the internal combustion engine 4 is maintained in a certain range.

The sub piston pump 50 constituting the third pump 3 changes the tilt angle of the sub inclined plate 54, that is, the discharge capacity of the third pump 3, in two stages according to the discharge pressure P3.

For example, when the turning device of the hydraulic excavator starts turning operation, or when the turning device pushes the bucket of the excavator to the object by turning, the discharge pressure P3 of the third pump 3 exceeds the predetermined pressure. As it rises, the switching valve 5 is switched to the drive position A, and the sub swash plate 54 quickly changes the tilt angle from the maximum tilt angle position to the minimum tilt angle position. As a result, it is possible to prevent the drive load of the third pump 3 from excessively rising.

The discharge pressure P3 of the third pump 3 is also induced in the hydraulic chamber 9A of the auxiliary hydraulic actuator 9. The pressure of the hydraulic chamber 9A is a direction for reducing the tilt angle of the main inclined plate 24 of the main piston pump 20, that is, a direction for reducing the driving loads of the first pump 1 and the second pump 2. Acts as.

That is, when the discharge pressure P3 of the 3rd pump 3 rises, the 1st pump 1, the 2nd pump 2, and the 3rd pump 3 all have a tilt angle also in the direction which reduces a discharge capacity. Since the load of the internal combustion engine 4 is responsively reduced, the operation stop of the internal combustion engine 4 by an overload can be prevented because it changes.

In addition, when the discharge pressure P3 of the third pump 3 rises above the predetermined pressure, the switching valve 5 is switched and the hydraulic chamber which increases the tilt angle of the main inclined plate 24 of the auxiliary hydraulic actuator 9 ( Also to 9B), the discharge pressure P3 of the 3rd pump 3 is supplied. As a result, the operation in the direction of decreasing the tilt angle of the main tilt plate 24 of the auxiliary hydraulic actuator 9 is stopped, and the decrease of the tilt angle of the main tilt plate 24 is also stopped.

In this way, the discharge pressures P1, P2 of the first pump 1 and the second pump 2 that the main piston pump 20 constitutes, and the third pump 3 that the sub piston pump 50 constitutes According to the discharge pressure P3, the tilt angle of the main swash plate 24 changes continuously. Therefore, the discharge capacity of the main piston pump 20 is finely adjusted according to the discharge pressure of these pumps 1-3. On the other hand, the third pump 3 switches the tilt angle of the sub swash plate 54 on / off between the maximum tilt angle position and the minimum tilt angle position in accordance with the discharge pressure P3. By switching on / off of the discharge capacity, it is possible to prevent the drive load of the internal combustion engine 4 from becoming excessive. That is, prevention of the overload of the internal combustion engine 4 can be implemented by the simple structure, maintaining the fine adjustment function of the discharge capacity of the main piston pump 20. FIG.

Since the sub piston pump 50 switches on / off the tilt angle of the sub inclination plate 54, the supporting structure of the sub inclination plate 54 is simplified, and the sub inclination plate 54 is urged in the increase in the tilt angle. Spring can be omitted. Such a structure of the sub piston pump 50 is preferable at the point of reducing the manufacturing cost of a hydraulic drive apparatus.

A second embodiment of the present invention will be described with reference to FIG.

In the description of this embodiment, the same components as those in the first embodiment will be denoted by the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, the priity valve 16 and the low pressure relief valve 17 are serially connected to the third pump passage 13 through which the third pump 3 constituting the sub piston pump 50 discharges the hydraulic oil. Post it. The third pump passage 13 is branched into the pump passage 18 and the pump passage 19 through the priority valve 16. Priority valve 16 preferentially supplies pump passage 18, and supplies excess hydraulic oil to pump passage 19. The surplus hydraulic fluid is also returned to the suction side of the third pump 3 via the low pressure relief valve 17. According to this embodiment, the hydraulic oil can be supplied from the third pump 3 to the two pump passages 18 and 19.

In connection with the above description, the content of patent application 2009-105219 in Japan which makes April 23, 2009 the filing date is incorporated here by reference.

As mentioned above, although this invention was demonstrated through several specific Example, this invention is not limited to each said Example. Those skilled in the art can make various modifications or changes to these embodiments within the scope of the claims.

For example, although the hydraulic fluid is used for the working fluid in each of the above embodiments, it is also possible to use working fluid such as a water-soluble substitute liquid instead of the working oil.

As described above, the hydraulic drive device according to the present invention is suitable for hydraulic supply for traveling, working and turning hydraulic excavators, but is not limited thereto, and can be applied to hydraulic supply devices for all construction machinery and work vehicles.

Exclusive properties or features included in the embodiments of the present invention are claimed as follows.

Claims (5)

As a hydraulic drive device 100 having a variable displacement main piston pump 20 and a variable displacement sub piston pump 50 which are rotationally driven through common drive shafts 25 and 55,
Main hydraulic actuators 7 and 8 for decreasing the discharge capacity of the main piston pump 20 in accordance with the increase in the discharge pressures P1 and P2 of the main piston pump 20;
Sub hydraulic actuator 10 for switching the discharge capacity of the sub-piston pump 50 between two set capacities as the discharge pressure P3 of the sub-piston pump 50 rises.
Hydraulic drive device having a. The method of claim 1,
And an auxiliary actuator (9) for decreasing the discharge capacity of the main piston pump (20) as the discharge pressure (P3) of the sub piston pump (50) rises. The method of claim 2,
The auxiliary actuator 9 has a capacity reducing hydraulic chamber 9A for reducing the discharge capacity of the main piston pump 20 and a capacity increasing hydraulic chamber for acting in an increasing direction of the discharge capacity of the main piston pump 20. 9B, the discharge pressure P3 of the sub piston pump 50 is always supplied to the capacity reducing hydraulic chamber 9A, while the hydraulic drive device 100 is provided with the sub piston pump 50. And a switching valve (5) for supplying the discharge pressure (P3) of the gas to the capacity increasing hydraulic chamber (9B). The method of claim 3,
The switching valve 5 has a drain position B and a drive position A which are selectively applied according to the discharge pressure P3 of the sub-piston pump 50. In the drain position B, The capacity increasing hydraulic chamber 9B and the sub-hydraulic actuator 10 are opened to the drain, and in the driving position A, the capacity increase hydraulic chamber 9B and the sub-hydraulic actuator 10 are connected to the sub-piston pump ( A hydraulic drive device configured to supply a discharge pressure P3 of 50). 5. The method according to any one of claims 1 to 4,
The main piston pump 20 includes a main cylinder block 23 driven by an internal combustion engine 4, a main inclination plate 24, and springs 35 and 36.
The main cylinder block 23 is formed with a plurality of main cylinders 26,
Each of the plurality of main cylinders 26 is equipped with a main piston 28 for partitioning the main volume chamber 27,
The main inclined plate 24 expands and contracts the main volume chamber 27 by reciprocating the main piston 28 in accordance with the rotation of the main cylinder block 23.
The springs 35 and 36 bias the main inclined plate 24 in a direction in which the tilt angle of the main inclined plate 24 increases,
The main hydraulic actuators 7 and 8 are configured to drive the main inclined plate 24 in a direction in which the tilt angle of the main inclined plate 24 is reduced,
The sub piston pump 50 includes a sub cylinder block 53 driven by the internal combustion engine 4 and a sub inclination plate 54,
A plurality of sub cylinders 56 are formed in the sub cylinder block 53,
Each of the plurality of sub cylinders 56 is equipped with a sub piston 58 for partitioning the sub volume chamber 57,
The sub inclined plate 54 expands and contracts the sub volume chamber 57 by reciprocating the sub piston 58 in accordance with the rotation of the sub cylinder block 53,
The sub hydraulic actuator (10) is configured to drive the sub inclined plate (54) in a direction in which the tilt angle of the sub inclined plate (54) is reduced.

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