WO2010122951A1

WO2010122951A1 - Hydraulic drive device

Info

Publication number: WO2010122951A1
Application number: PCT/JP2010/056793
Authority: WO
Inventors: 和巳伊藤
Original assignee: カヤバ工業株式会社
Priority date: 2009-04-23
Filing date: 2010-04-09
Publication date: 2010-10-28
Also published as: CN101970880B; KR101233541B1; JP5188444B2; CN101970880A; KR20100137480A; JP2010255244A

Abstract

A hydraulic drive device (100) comprises a variable displacement main piston pump (20) and a variable displacement sub piston pump (50) which are rotationally driven through a common drive shaft (25, 55). The hydraulic drive device (100) is provided with: main hydraulic actuators (7, 8) for gradually reducing the discharge capacity of the main piston pump (20) according to rises in the discharge pressures (P1, P2) of the main piston pump (20); and a sub hydraulic actuator (10) for switching the discharge capacity of the sub piston pump (50) in two stages according to a rise in the discharge pressure (P3) of the sub piston pump (50). The configuration enables the capacity of the main piston pump (20) to be fine-adjusted and prevents the load on the pumps of the hydraulic drive device (100) from excessively increasing.

Description

Hydraulic drive

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

JP 2003-221842 A issued by the Japan Patent Office in 2003 discloses a hydraulic excavator equipped with a hydraulic drive device including three variable displacement hydraulic pumps driven by a common engine. Of the three hydraulic pumps, the discharge hydraulic oil of the first hydraulic pump and the second hydraulic pump is used for excavating the soil and moving the excavator, and the discharge hydraulic oil of the third hydraulic pump is used for the boom and operation. Used for chamber rotation.

This hydraulic drive unit has a structure that is complicated and high in manufacturing cost because the discharge capacity of three variable displacement hydraulic pumps is continuously adjusted according to the discharge pressure of each hydraulic pump. was there.
Accordingly, an object of the present invention is to provide a hydraulic drive device capable of adjusting a drive load of a pump under a simple structure.
In order to achieve the above object, the present invention provides a hydraulic drive apparatus including a variable displacement type main piston pump and a variable displacement type sub piston pump that are rotationally driven via a common drive shaft. A main hydraulic actuator that continuously decreases the discharge capacity of the main piston pump in response to an increase in the discharge pressure of the pump, and a discharge capacity of the sub-piston pump in accordance with the discharge pressure of the sub-piston pump. And a sub-hydraulic actuator that switches between them.
The details of the invention as well as other features and advantages are set forth in the following description of the specification and illustrated in the accompanying drawings.

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

FIG. Referring to FIG. 1, a hydraulic drive device 100 mounted on a hydraulic excavator includes a first pump 1, a second pump 2, and a third pump 3 that are driven by a common internal combustion engine 4.
The hydraulic excavator is a traveling device using left and right crawlers, a drilling device that excavates the ground by driving buckets, arms, booms, etc., a turning device that turns the excavating device and the cab relative to the vehicle body, earth and sand in the traveling direction, etc. The hydraulic drive device 100 is driven by supplying pressurized hydraulic oil to these devices.
The pressurized hydraulic oil discharged from the first pump 1 is supplied to a hydraulic motor that drives the left and right crawlers via the first pump passage 11. The pressurized hydraulic oil discharged from the second pump 2 is supplied to a 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 that drives the swivel device and the hydraulic cylinder that drives the earth discharging plate through the third pump passage 13.
FIG. 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 a sub piston pump 50. The main piston pump 20 and the sub piston pump 50 are coaxially configured on a shaft 25 driven by the internal combustion engine 4.
The main piston pump 20 is a two-flow type variable displacement swash plate type piston pump having two discharge ports.
The main piston pump 20 is accommodated in a space formed by a main casing 21 and a cover 22 fixed to the main casing 21. The main piston pump 20 includes 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 cover 22 via a bearing 32, and an intermediate portion of the shaft 25 is supported by the main casing 21 via a bearing 31. The other end of the shaft 25 protruding from the main casing 21 to the outside is the FIG. The rotational torque of the internal combustion engine 4 shown in FIG.
In the main cylinder block 23, an even number of main cylinders 26 are arranged in parallel with the central axis O of the shaft 25 at a constant interval on substantially the same circumference centering on the central axis O.
A main piston 28 is inserted into each main cylinder 26. A main volume chamber 27 facing one end of the main piston 28 is defined inside the main cylinder 26. The other end of the main piston 28 protrudes from the main cylinder block 23 and comes into sliding contact with the main swash plate 24 via a shoe 29.
A spring 48 that presses the shoe 29 toward the main swash plate 24 is housed inside the main cylinder block 23.
When the main cylinder block 23 rotates, the main piston 28 slidably contacting the main swash plate 24 via the shoe 29 rotates together with the main cylinder block 23 and reciprocates in the direction of the central axis O to expand and contract the main volume chamber 27. To do.
A cylinder port 33 or a 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 swash plate 24. This end surface 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 circumferences of different radii around the central axis O. As a result, a cylinder port 33 communicating with half of the cylinders 26 and a cylinder port 34 communicating with the remaining half of the cylinders 26 are opened at the end surface of the main cylinder block 23.
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 where the main volume chamber 27 expands. The two discharge ports include 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 discharge port of the first pump 1 has a FIG. 1 is connected to the discharge port of the second pump 2 in FIG. 2 is connected. FIG. 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 reciprocates in the main cylinder 26 one time. In the suction stroke in which the main volume chamber 27 expands, the hydraulic oil is sucked into the main volume chamber 27 from the suction port of the valve plate 30 through the cylinder ports 33 and 34. In the discharge stroke in which the main volume chamber 27 of the main cylinder 26 contracts, the hydraulic oil is discharged from the main volume chamber 27 to the two discharge ports of the valve plate 30 via the cylinder port 33 or 34 and the first pump passage 11. And supplied to the second pump passage 12.
With the above structure of the main piston pump 20, hydraulic oil is supplied to the first pump passage 11 and the second pump passage 12 individually.
The main swash plate 24 is supported via a bearing 41 so as to be tiltable with respect to 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 swash plate 24 in the direction of increasing the tilt angle. The spring 35 always urges the main swash plate 24 in the direction of increasing the tilt angle, and the spring 36 moves the main swash plate 24 in the direction of increasing the tilt angle when the tilt angle of the main swash plate 24 falls below a predetermined angle. Energize. It is also possible to support the main swash plate 24 with a single spring instead of the

springs

35 and 36.
Again 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.
Again FIG. 2, the first main hydraulic actuator 7 and the second main hydraulic actuator 8 are slidably inserted into the

cylinders

37 and 38 formed coaxially with the main casing 21 and the

cylinders

37 and 38. And a stepped plunger 42. The main casing 21 is formed with a hydraulic chamber 43 that exerts pressure on the step portion of the stepped plunger 42 and a hydraulic chamber 44 that exerts pressure on the tip portion 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 that exerts pressure on the stepped plunger 42 constitutes the first main hydraulic actuator 7, and the hydraulic chamber 43 that exerts pressure on the stepped plunger 42 constitutes the second main hydraulic actuator 8.
Again FIG. Referring to FIG. 1, the discharge pressure P <b> 1 of the first pump 1 is guided to the hydraulic chamber 44 of the first main hydraulic actuator 7. When the pressure guided to 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 becomes smaller. 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 in the hydraulic chamber 43 increases, the stepped plunger 42 is displaced, and the main swash plate 24 is driven in a direction in which the tilt angle becomes smaller. 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 defined by the piston in the cylinder. The auxiliary hydraulic actuator 9 is the same as FIG. The discharge pressure P3 of the third pump 3 normally acts on the hydraulic chamber 9A of the auxiliary hydraulic actuator 9 (not shown in 2). When the pressure in the hydraulic chamber 9A increases, the piston in the auxiliary hydraulic actuator 9 displaces the main swash plate 24 in the direction in which the tilt angle becomes smaller, that is, in the direction in which the discharge capacity of the main piston pump 20 decreases.
The discharge pressure P3 of the third pump 3 is guided to the hydraulic chamber 9B of the auxiliary hydraulic actuator 9 via 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 direction of decreasing the discharge pressure of the main piston pump 20 stops. Accordingly, the displacement of the main swash plate 24 in the direction of decreasing the tilt angle is also stopped.
As described above, the main swash 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 as the main swash plate 24. The pressing force exerted and the elastic support force of the

springs

35 and 36 that support the main swash plate 24 in the opposite direction are held at an arbitrary position. Therefore, the discharge capacity of the main piston pump 20 changes steplessly according to the pressure of the actuator 7-9.
Again FIG. Referring to FIG. 2, the sub-piston pump 50 constituting the third pump 3 is a one-flow type variable displacement swash plate type piston pump having one discharge port.
The sub piston pump 50 is housed in a space formed by the sub casing 51 fixed to the main casing 21 and the main casing 21. The sub piston pump 50 includes 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 sub casing 51 via a bearing 62. The other end of the shaft 55 is supported on the main casing 21 via a bearing 61. The shaft 55 is configured integrally with the shaft 25 on the same axis, and rotates integrally with the shaft 25.
A plurality of sub-cylinders 56 parallel to the central axis O are formed in the sub-cylinder block 53 on a circumference centered on the central axis O at regular intervals.
A sub piston 58 is inserted into each sub cylinder 56. A sub volume chamber 57 that faces one end of the sub piston 58 is defined inside the sub cylinder 56. The other end of the sub piston 58 protrudes from the sub cylinder block 53 and is in sliding contact with the sub swash plate 54 via a shoe 59.
A spring 65 for pressing the shoe 59 toward the sub swash plate 54 is accommodated inside the sub cylinder block 53.
When the sub cylinder block 53 makes one rotation, each sub piston 58 reciprocates in the sub cylinder 56 one time. The sub piston 58 slidably contacting the sub swash plate 54 via the shoe 59 reciprocates in the direction of the central axis O while expanding integrally with the sub cylinder block 53 to expand and contract the sub volume chamber 57.
A cylinder port 63 communicating with the sub volume chamber 57 is opened at the end surface of the sub cylinder block 53 located on the opposite side of the sub swash 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 where the sub volume chamber 57 expands. 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 rate and pressure of the hydraulic oil in the third pump passage 13 can be controlled independently from the flow rates and pressures of the hydraulic oil in the first pump passage 11 and the second pump passage 12.
The sub swash plate 54 is supported by the sub casing 51 through a pair of ball bearings in a state in which the 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 a hydraulic chamber 68 is defined therebetween.
The third pump passage 13 is connected to the hydraulic chamber 68 via the pilot switching valve 5.
Again FIG. Referring to FIG. 1, the third pump passage 13 is connected to a hydraulic motor that drives the turning device and a hydraulic cylinder that drives the earth discharging plate, and the auxiliary hydraulic actuator 9 is connected to the main swash plate 24 in the direction of decreasing the tilt angle. Connected to the hydraulic chamber 9A. The third pump passage 13 is further connected to the hydraulic chamber 9B for operating the auxiliary hydraulic actuator 9 in the direction of increasing the tilt angle of the main swash plate 24 and the hydraulic chamber 68 of the sub hydraulic actuator 10 via the pilot switching valve 5. Is done. The sub hydraulic actuator 10 drives the sub swash plate 54 in the direction of decreasing the tilt angle by supplying pressure to the hydraulic chamber 68. The pilot switching valve 5 drives the auxiliary hydraulic actuator 9 in the direction of increasing the tilt angle of the main swash plate 24. A drive position A for supplying the discharge pressure P3 of the third pump 3 to the hydraulic chamber 9B formed in the auxiliary hydraulic actuator 9 and the hydraulic chamber 68 of the sub hydraulic actuator 10 via the third pump passage 13; And a drain position B for releasing the hydraulic chamber to the drain passage 14.
The pilot switching valve 5 is urged toward the drain position B by the elastic force of the return spring 6. Further, the discharge pressure P3 of the third pump 3 from the third pump passage 13 acts as a pilot pressure in the opposite direction to the return spring 6, that is, toward the drive position A.
When the discharge pressure P3 of the third pump 3 is low, the pilot switching valve 5 is located at the drain position B, and the sub swash plate 54 of the third pump 3 is held at the maximum tilt angle position. For example, by decentering the tilting axis of the sub swash plate 54 with respect to the shaft 55, a moment is generated by the pressing force applied by the sub piston 58 to the sub swash plate 54, and the sub swash plate 54 is maximized without using a spring. The tilt angle position can be held.
When the discharge pressure P3 of the third pump 3 exceeds the elastic force of the return spring 6, the pilot switching valve 5 is switched to the drive position A. As a result, the plunger 67 rotates the sub swash plate 54 to the minimum tilt angle position by the discharge pressure P3 of the third pump 3 supplied to the hydraulic chamber 68. As a result, the third pump 3 reduces the discharge flow rate. In this way, the discharge capacity of the third pump 3 is switched between the maximum capacity and the minimum capacity in accordance with the position of the pilot switching valve 5.
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 swash plate 24 of the auxiliary hydraulic actuator 9. While the pilot switching valve 5 is in the drain position B, the hydraulic chamber 9B that increases the tilt angle of the main swash plate 24 of the auxiliary hydraulic actuator 9 is open to the drain. Therefore, in this state, a force in the direction of decreasing the tilt angle based on the discharge pressure P3 of the third pump 3 acts on the main swash plate 24 via the auxiliary hydraulic actuator 9.
On the other hand, when switching to the drive position A, the discharge pressure P3 of the third pump 3 also acts on the hydraulic chamber 9B that increases the tilt angle of the main swash plate 24 of the auxiliary hydraulic actuator 9. As a result, the auxiliary hydraulic actuator 9 stops displacement in the direction of decreasing the tilt angle of the main swash plate 24.
In this way, in this hydraulic drive device, as the discharge pressure P3 of the third pump 3 increases, the tilt angle of the main swash plate 24 and the tilt angle of the sub swash plate 54 decrease, and the hydraulic drive device as a whole. Balance the discharge capacity. On the other hand, when the discharge pressure P3 of the third pump 3 exceeds a certain pressure, the decrease in the tilt angle of the main swash plate 24 stops. The sub swash plate 54 is held at the minimum tilt angle position as it is.
The elastic restoring force of the return spring 6 is configured to be manually adjustable. By setting the elastic restoring force of the return spring 6 large, the discharge pressure P3 of the third pump 3 at which the switching valve 5 switches from the drain position B to the driving position A can be set high.
During 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 first pump 1 is supplied to a hydraulic motor that drives the left and right crawlers through the first pump passage 11. The discharge hydraulic oil of the second pump 2 is supplied to each hydraulic cylinder that drives the excavator through the second pump passage 12. The discharge hydraulic oil of the third pump 3 is supplied through the third pump passage 13 to a hydraulic motor that drives the swivel device and a hydraulic cylinder that drives the earth discharging plate.
The flow rate of the hydraulic oil supplied to each device is adjusted by an operator operating a control valve, and the excavator travels, excavates the ground, and transports earth and sand.
The main piston pump 20, which is used as both the first pump 1 and the second pump 2, has the urging force of the

springs

35 and 36, the discharge pressure P1 of the first pump 1 guided to the first main hydraulic actuator 7, and the second main The tilt angle of the main swash plate 24 is set at a position where the total pressure of the discharge pressure P2 of the second pump 2 guided to the hydraulic actuator 8 and the discharge pressure P3 of the third pump 3 guided to the auxiliary hydraulic actuator 9 is balanced. Hold. When any one of the discharge pressures P1, P2, and P3 is increased, the main swash plate 24 is tilted to a position where the driving force of the swash plate 24 and the urging force of the

springs

35 and 36 due to the increased pressure are balanced. The displacement of the main piston 28 per one rotation is reduced. As the displacement of the main piston 28 decreases, the discharge capacity of the main piston pump 20 gradually decreases. As a result, the output of the internal combustion engine 4 is kept within a certain range.
The sub piston pump 50 constituting the third pump 3 changes the tilt angle of the sub swash plate 54, that is, the discharge capacity of the third pump 3 in two steps according to the discharge pressure P3.
For example, when the swing device of the hydraulic excavator starts a swing operation, or when the swing device presses the bucket of the excavator against an object by turning, the discharge pressure P3 of the third pump 3 exceeds a predetermined pressure. As the valve rises, the switching valve 5 switches 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, the driving load of the third pump 3 can be prevented from rising excessively.
The discharge pressure P3 of the third pump 3 is also led to the hydraulic chamber 9A of the auxiliary hydraulic actuator 9. The pressure in the hydraulic chamber 9B acts in a direction that reduces the tilt angle of the main swash plate 24 of the main piston pump 20, that is, a direction that reduces the driving load of the first pump 1 and the second pump 2.
That is, when the discharge pressure P3 of the third pump 3 increases, the first pump 1, the second pump 2, and the third pump 3 all change the tilt angle in the direction of decreasing the discharge capacity. The load on the internal combustion engine 4 can be prevented from being stopped due to an excessive load.
When the discharge pressure P3 of the third pump 3 rises above a certain pressure, the switching valve 5 is switched, and the third pump is also provided to the hydraulic chamber 9B that increases the tilt angle of the main swash plate 24 of the auxiliary hydraulic actuator 9. 3 discharge pressure P3 is supplied. As a result, the operation of the auxiliary hydraulic actuator 9 in the direction of decreasing the tilt angle of the main swash plate 24 is stopped, and the decrease of the tilt angle of the main swash plate 24 is also stopped.
In this way, the main swash plate according to the discharge pressures P1 and P2 of the first pump 1 and the second pump 2 constituted by the main piston pump 20 and the discharge pressure P3 of the third pump 3 constituted by the sub-piston pump 50. The tilt angle of 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 between the maximum tilt angle position and the minimum tilt angle position in accordance with the discharge pressure P3. By switching the discharge capacity on / off, it is possible to prevent the drive load of the internal combustion engine 4 from becoming excessive. That is, it is possible to prevent an overload of the internal combustion engine 4 with a simple configuration while maintaining a fine adjustment function of the discharge capacity of the main piston pump 20.
Since the sub piston pump 50 switches the tilt angle of the sub swash plate 54 on and off, the support structure of the sub swash plate 54 is simplified and the sub swash plate 54 is urged in the direction of increasing the tilt angle. Can be omitted. Such a structure of the sub-piston pump 50 is preferable for reducing the manufacturing cost of the hydraulic drive device.
FIG. 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 are denoted by the same reference numerals, and detailed description thereof is omitted.
In this embodiment, the priority valve 16 and the low pressure relief valve 17 are arranged in series in the third pump passage 13 through which the third pump 3 constituting the sub-piston pump 50 discharges hydraulic oil. The third pump passage 13 branches into the pump passage 18 and the pump passage 19 via the priority valve 16. The priority valve 16 supplies the pump passage 18 with priority, and supplies excess hydraulic oil to the pump passage 19. Further, the excess hydraulic oil returns to the suction side of the third pump 3 through the low pressure relief valve 17. According to this embodiment, hydraulic oil can be supplied from the third pump 3 to the two

pump passages

18 and 19.
Regarding the above explanation, the contents of Japanese Patent Application No. 2009-105219 in Japan, whose application date is April 23, 2009, are incorporated herein by reference.
Although the present invention has been described through several specific embodiments, the present invention is not limited to the above embodiments. Those skilled in the art can make various modifications or changes to these embodiments within the scope of the claims.
For example, although the working oil is used as the working fluid in each of the above embodiments, a working fluid such as a water-soluble alternative liquid may be used instead of the working oil.

As described above, the hydraulic drive device according to the present invention is suitable for hydraulic supply for running, working, and turning of a hydraulic excavator, but is not limited to this, and can be applied to hydraulic supply devices for all construction machines and work vehicles. is there.
The exclusive properties or features encompassed by embodiments of the invention are claimed as follows.

Claims

In a hydraulic drive device (100) comprising a variable displacement main piston pump (20) and a variable displacement sub-piston pump (50) that are rotationally driven via a common drive shaft (25, 55):
A main hydraulic actuator (7, 8) for gradually decreasing the discharge capacity of the main piston pump (20) in response to an increase in the discharge pressure (P1, P2) of the main piston pump (20);
A sub hydraulic actuator (10) that switches the discharge capacity of the sub piston pump (50) between two set capacities in response to an increase in the discharge pressure (P3) of the sub piston pump (50);
Is provided.
The hydraulic actuator (100) according to claim 1, wherein the auxiliary actuator (9) gradually reduces the discharge capacity of the main piston pump (20) in response to an increase in the discharge pressure (P3) of the sub-piston pump (50). Is further provided.
The hydraulic drive device (100) according to claim 2, wherein the auxiliary actuator (9) includes a capacity decreasing hydraulic chamber (9A) for reducing a discharge capacity of the main piston pump (20), and the main piston pump (20). ), And a discharge pressure (P3) of the sub-piston pump (50) is constantly supplied to the volume reduction hydraulic chamber (9A). The hydraulic drive device (100) further includes a switching valve (5) for supplying the discharge pressure (P3) of the sub-piston pump (50) to the capacity increasing hydraulic chamber (9B).
The hydraulic drive device (100) according to claim 3, wherein the switching valve (5) is driven selectively with a drain position (B) applied in accordance with a discharge pressure (P3) of the sub-piston pump (50). Position (A), and at the drain position (B), the capacity increasing hydraulic chamber (9B) and the sub hydraulic actuator (10) are opened to the drain, and at the driving position (A), the capacity is increased. The discharge pressure (P3) of the sub piston pump (50) is supplied to the increased hydraulic chamber (9B) and the sub hydraulic actuator (10).
The hydraulic drive device (100) according to any one of claims 1 to 4, wherein the main piston pump (20) includes a main cylinder block (23) driven by an internal combustion engine (4), and the main cylinder block (23). When a plurality of main cylinders (26) are formed, the main piston (28) accommodated in each main cylinder (26), and the main piston (28) are arranged in a main volume chamber (26) in the main cylinder (26). 27), a main swash plate (24) for expanding and contracting the main volume chamber (27) by reciprocating the main piston (28) according to the rotation of the main cylinder block (23), A spring (35, 36) for urging the main swash plate (24) in a direction in which the tilt angle of the main swash plate (24) increases, and the main actuator The data (7, 8) is configured to drive the main swash plate (24) in a direction in which the tilt angle of the main swash plate (24) decreases, and the sub-piston pump (50) includes the internal combustion engine. The sub-cylinder block (53) driven by (4) and the sub-cylinder block (21) are formed with a plurality of sub-cylinders (56), and the sub-pistons housed in each sub-cylinder (56) (58), the sub-piston (58) defines a sub-volume chamber (57) in the sub-cylinder (56), and the sub-piston (58) according to the rotation of the sub-cylinder block (53). A sub swash plate (54) that reciprocates the sub volume chamber (57), and the sub hydraulic actuator (10) has a direction in which the tilt angle of the sub swash plate (54) decreases. To the sub Configured to drive plate (54).