JP2010255244A - Hydraulic drive device for working machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic drive device for a working machine, capable of simplifying a structure and adjusting the driving load of a pump. <P>SOLUTION: The hydraulic drive device 100 includes a main piston pump 20 and a sub-piston pump 50 which are driven by a common engine 4. In the main piston pump 20, the tilt angle of a main tile plate 24 is continuously changed over according to its discharge pressures P1 and P2 to finely adjust its discharge capacity. In the sub piston pump 50, the tilt angle of a sub tile plate 54 is changed over between two positions according to its discharge pressure P3 to adjust its discharge capacity in two stages. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a hydraulic drive device mounted on a working machine such as a hydraulic excavator.

  Conventionally, as this type of hydraulic drive device, Patent Document 1 includes first, second, and third hydraulic pumps that are driven by a common engine, and is discharged from the first and second hydraulic pumps. A hydraulic excavator excavator is driven by hydraulic oil, and a hydraulic excavator turning device is driven by hydraulic oil discharged from a third hydraulic pump.

JP 2003-221842 A

  However, in such a conventional hydraulic drive device, the discharge capacity for each of the first, second and third hydraulic pumps is continuously adjusted according to the discharge pressure of each hydraulic pump. Therefore, there is a problem that the structure is complicated and the cost of the product is increased.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a hydraulic drive device for a working machine that can simplify the structure and adjust the drive load of the pump.

  The present invention is a hydraulic drive device including a main piston pump and a sub-piston pump driven by a common engine, and the main piston pump includes a main cylinder block that is driven to rotate by the engine, and the main cylinder block. A main swash plate that reciprocates the main piston so as to expand and contract the main volume chamber with rotation, a spring that urges the main swash plate in a direction to increase its tilt angle, and a main against the spring The main hydraulic actuator that moves the swash plate in a direction that reduces the tilt angle, and the main hydraulic actuator continuously switches the tilt angle of the main swash plate as the discharge pressure of the main piston pump increases. Main discharge capacity adjusting means for gradually decreasing the discharge capacity of the main piston pump. The piston pump is composed of a sub-cylinder block that is rotationally driven by the engine, a sub-swash plate that reciprocates the sub-piston so as to expand and contract the sub-volume chamber as the sub-cylinder block rotates, and a pressing force received from the sub-piston. The sub hydraulic actuator that moves the sub swash plate against it, and the sub hydraulic actuator switches the tilt angle of the sub swash plate to two positions according to the discharge pressure of the sub piston pump, and the discharge capacity of the sub piston pump is a predetermined value And a sub discharge capacity adjusting means for reducing the sub discharge capacity.

  According to the present invention, the main piston pump continuously switches the tilt angle of the main swash plate according to its discharge pressure, and its discharge capacity is finely adjusted, while the sub-piston pump responds to its discharge pressure. The tilt angle of the sub-swash plate is switched depending on the position, and the discharge capacity is adjusted in two stages, so that it is possible to prevent the engine drive load from becoming excessive, and to prevent engine stall and the like.

  Since the sub-piston pump has a structure in which the tilt angle of the sub-swash plate is switched by position, the structure for supporting the sub-swash plate to be tilted is simplified, and the direction in which the tilt angle of the sub-swash plate is increased This eliminates the need for a spring or the like that biases the product, thus reducing the cost of the product.

The hydraulic-pressure circuit diagram of the hydraulic-pressure drive device which shows embodiment of this invention. Sectional drawing of a hydraulic-pressure drive device similarly. The hydraulic-pressure circuit diagram of the hydraulic-pressure drive device which shows other embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a hydraulic circuit diagram showing a hydraulic drive device 100 mounted on a hydraulic excavator as a work machine.

  A hydraulic excavator (not shown) includes a traveling device that travels with left and right crawlers, a drilling device that excavates with a bucket, an arm, a boom, and the like, a swiveling device that rotates the excavator and a cab with respect to the vehicle body, and earth and sand in the traveling direction. These are driven by the pressurized hydraulic fluid supplied from the hydraulic pressure driving device 100.

  The hydraulic pressure driving device 100 includes a first pump 1, a second pump 2, and a third pump 3 that are driven by a common engine 4.

  The hydraulic fluid (oil) discharged from the first pump 1 and the second pump 2 is supplied to a hydraulic motor (not shown) that drives the left and right crawlers through the first and second pump passages 11 and 12, respectively. And supplied to each hydraulic cylinder (not shown) for driving the excavator.

  For example, a working fluid such as a water-soluble alternative solution may be used as the working fluid instead of oil.

  The hydraulic fluid discharged from the third pump 3 is supplied to a hydraulic motor (not shown) that drives the swivel device through the third pump passage 13, and at the same time, a hydraulic cylinder (not shown) that drives the dozer. ).

  FIG. 2 is a cross-sectional view of the hydraulic drive device 100. In the hydraulic pressure driving device 100, the main piston pump 20 and the sub piston pump 50 are provided coaxially.

  The main piston pump 20 is a two-flow type variable displacement swash plate type piston pump having two discharge ports, and constitutes a first pump 1 and a second pump 2.

  In the main piston pump 20, a main cylinder block 23 and a main swash plate 24 are accommodated in an internal space formed by a main casing 21 and a cover 22.

  The main cylinder block 23 is rotationally driven via a shaft 25. One end of the shaft 25 is supported by the cover 22 via the bearing 32, and the middle thereof is supported by the main casing 21 via the bearing 31. The rotation of the shaft 25 is transmitted from the engine 4 (not shown) to one end of the shaft 25 that projects outward from the main casing 21.

  In the main cylinder block 23, an even number of cylinders 26 are arranged in parallel with the rotation axis O and arranged at regular intervals on the substantially same circumference around the rotation axis O.

  A main piston 28 is inserted into each cylinder 26, and a main volume chamber 27 is defined between them. One end side of each main piston 28 protrudes from the main cylinder block 23 and is supported via a shoe 29 in contact with the main swash plate 24.

  A spring 48 is compressed inside the main cylinder block 23, and an elastic restoring force of the spring 48 is transmitted to each shoe 29, and each shoe 29 is pressed against the main swash plate 24.

  When the main cylinder block 23 rotates, each main piston 28 reciprocates between the main swash plate 24 and expands / contracts the main volume chamber 27 of the cylinder 26.

  Cylinder ports 33 and 34 communicating with the main volume chambers 27 are opened at the end surface of the main cylinder block 23. The cylinder ports 33 and 34 are alternately arranged on different radii around the rotation axis O.

  A valve plate 30 is provided in the main casing 21 so that the end face of the main cylinder block 23 is in sliding contact therewith. The valve plate 30 is opened with one suction port and two discharge ports (not shown). As the main cylinder block 23 rotates, the cylinder ports 33 and 34 communicate with each other to control the suction and discharge of hydraulic oil into the main volume chambers 27. The two discharge ports communicate with the first and second pump passages 11 and 12. The first and second pump passages 11 and 12 are formed in the main casing 21.

  Each main piston 28 reciprocates the cylinder 26 once per rotation of the main cylinder block 23. In the suction stroke in which the main volume chamber 27 of the cylinder 26 is expanded, 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 cylinder 26 contracts, hydraulic oil is discharged from the main volume chamber 27 to the first and second pump passages 11 and 12 through the two discharge ports of the valve plate 30 from the cylinder ports 33 and 34. To do. Thereby, in the 1st, 2nd pump channel | paths 11 and 12, the flow of the hydraulic fluid mutually independent arises, and the flow volume and pressure of hydraulic fluid can be set separately.

  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, and the main swash plate 24 is urged by the springs 35 and 36 in a direction that maximizes the tilt angle. The spring 35 always urges the main swash plate 24, and the spring 36 urges the main swash plate 24 in a range where the tilt angle of the main swash plate 24 is within a predetermined value. The main swash plate 24 may be provided with a single spring.

  The main piston pump 20 includes first, second and third (for cooperation) main hydraulic actuators 7, 8, and 9 as main discharge capacity adjusting means for adjusting the discharge capacity (pump displacement). Thus, the main swash plate 24 is moved against the springs 35 and 36.

  As the first and second main hydraulic actuators 7 and 8, cylinder portions 37 and 38 that are coaxially formed in the main casing 21, and a stepped plunger 42 that is slidably inserted into the cylinder portions 37 and 38. The hydraulic chambers 43 and 44 are defined between the two.

  As shown in 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 pressure chamber 44 rises, the plunger 42 moves to drive the main swash plate 24 in a direction in which the tilt angle decreases, and the discharge capacity of the main piston pump 20 is continuously adjusted.

  As shown in FIG. 1, the discharge pressure P2 of the second pump 2 is guided to the hydraulic chamber 43 of the second hydraulic actuator 8, and when this pressure P2 rises, the stepped plunger 42 moves, and the main diagonal The plate 24 is driven in a direction in which the tilt angle becomes smaller, and the discharge capacity of the main piston pump 20 is continuously adjusted.

  As the third (cooperating) main hydraulic pressure actuator 9, a cylinder portion not shown in FIG. 2, a plunger slidably inserted into the cylinder portion, a hydraulic pressure chamber defined between the two, Is provided.

  As shown in FIG. 1, the discharge pressure P3 of the third pump 3 is guided to the hydraulic chamber of the third (cooperating) main hydraulic actuator 9 via the switching valve 5, and when this pressure P3 rises, The plunger moves to drive the main swash plate 24 in a direction in which the tilt angle becomes smaller, and the discharge capacity of the main piston pump 20 is adjusted stepwise.

  The sub-piston pump 50 is a one-flow type variable displacement swash plate type piston pump having one discharge port, and constitutes the sub-piston pump 50.

  In the sub piston pump 50, a sub cylinder block 53 and a sub swash plate 54 are accommodated in an internal space formed by the sub casing 51 and the main casing 21.

  The sub cylinder block 53 is rotationally driven via a shaft 55. One end of the shaft 55 is supported by the sub casing 51 via a bearing 62, and the other end is supported by the main casing 21 via a bearing 61. The shaft 55 is connected coaxially with the shaft 25 and rotates together with the shaft 25.

  In the sub-cylinder block 53, a plurality of cylinders 56 are arranged in parallel with the rotation axis O and arranged on the substantially same circumference with the rotation axis O as a center at a predetermined interval.

  A sub piston 58 is inserted into each cylinder 56, and a sub volume chamber 57 is defined between them. One end side of each sub-piston 58 protrudes from the sub-cylinder block 53 and is supported via a shoe 59 in contact with the sub-swash plate 54.

  Inside the sub cylinder block 53, a spring 65 is compressed and interposed. The elastic restoring force of the spring 65 is transmitted to each shoe 59, and each shoe 59 is pressed against the sub swash plate 54.

  When the sub cylinder block 53 rotates, each sub piston 58 reciprocates between the sub swash plate 54 and expands / contracts the sub volume chamber 57 of the cylinder 56.

  A cylinder port 63 communicating with each sub volume chamber 57 is opened at the end surface of the sub cylinder block 53.

  In the sub casing 51, a valve plate 60 for slidingly contacting the end surface of the sub cylinder block 53 is interposed. One suction port and one discharge port 64 (not shown) are opened in the valve plate 60, respectively. As the sub-cylinder block 53 rotates, the cylinder ports 63 communicate with each other to control the suction and discharge of hydraulic oil into the sub-volume chambers 57. The discharge port communicates with the third pump passage 13. The third pump passage 13 is formed in the main casing 21.

  Each sub-piston 58 reciprocates the cylinder 56 once per rotation of the sub-cylinder block 53. In the suction stroke in which the main volume chamber 27 of the cylinder 56 is expanded, the hydraulic oil is sucked from the suction port of the valve plate 60 into the sub volume chamber 57 through the cylinder port 63. In the discharge stroke in which the sub volume chamber 57 contracts, the hydraulic oil is discharged from the sub volume chamber 57 to the third pump passage 13 from the cylinder port 63 through the discharge port of the valve plate 60. Thereby, in the third pump passage 13, the flow of hydraulic oil independent of the first and second pump passages 11 and 12 is generated, and the flow rate and pressure of the hydraulic oil can be individually set.

  The sub swash plate 54 is supported to be tiltable with respect to the sub casing 51 via a pair of ball bearings (not shown).

  The sub-piston pump 50 includes a sub-hydraulic actuator 10 as sub-discharge capacity adjusting means for adjusting the discharge capacity (pump displacement), and thereby the sub-swash plate 54 against the pressing force received from each sub-piston 58. Is to move.

  The sub-hydraulic actuator 10 includes a cylinder portion 66 formed at the bottom of the sub-casing 51 and a plunger 67 that is slidably inserted into the cylinder portion 66, and a hydraulic chamber 68 is defined therebetween. Is done. A spring 69 is interposed between the bottom of the cylinder portion 66 and the plunger 67.

  As shown in FIG. 1, the discharge pressure P <b> 3 of the third pump 3 is guided to the hydraulic chamber 68 of the sub hydraulic actuator 10 via the switching valve 5. When the pressure guided to the hydraulic pressure chamber 68 rises, the plunger 67 moves and drives the main swash plate 24 in a direction in which the tilt angle becomes smaller.

  The switching valve 5 has a drive position a for guiding the discharge pressure P3 of the third pump 3 to the third and fourth hydraulic actuators 9 and 10 via the third pump passage 13 and a drain passage 14 for these. And a drain position b for guiding pressure.

  The pilot type switching valve 5 is urged to the drain position b by the elastic restoring force of the return spring 6, and the discharge pressure P3 of the third pump 3 generated in the third pump passage 13 is guided as the pilot pressure.

  The switching valve 5 switches from the drain position b to the driving position a against the elastic restoring force of the return spring 6 when the pilot pressure P3 guided thereby rises above a predetermined value.

  The elastic restoring force of the return spring 6 is manually adjusted. By adjusting the elastic restoring force of the return spring 6 to be high, the pilot pressure P3 at which the switching valve 5 is switched from the drain position b to the driving position a is increased.

  Next, the operation of the embodiment of the present invention configured as described above will be described.

  During operation of the hydraulic excavator, the engine 4 drives the first pump 1, the second pump 2, and the third pump 3.

  The hydraulic fluid discharged from the first pump 1 and the second pump 2 is supplied to a hydraulic motor that drives the left and right crawlers through the first and second pump passages 11 and 12, respectively, and drives the excavator. Is supplied to each hydraulic cylinder.

  The hydraulic fluid discharged from the third pump 3 is supplied through the third pump passage 13 to a hydraulic motor that drives the swivel device, and also to a hydraulic cylinder that drives the dozer.

  The flow rate of the hydraulic fluid supplied to each device is adjusted through a control valve (not shown) operated by an operator, and the excavator travels, excavates the ground, and transports the earth and sand.

  The main piston pump 20 constituting the first pump 1 and the second pump 2 has a main swash plate 24 whose tilt angle is the urging force of the springs 35 and 36 and the first, second and third (for cooperation) main liquids. The driving force by the discharge pressures P1, P2, and P3 of the first pump 1, the second pump 2, and the third pump 3 led to the pressure actuators 7, 8, and 9, respectively, is adjusted to a balanced position. When one of the discharge pressures P1, P2, and P3 of the first pump 1, the second pump 2, and the third pump 3 rises, the main swash plate is in a position where the driving force by this pressure and the biasing force of the springs 35 and 36 are balanced. 24 tilts to reduce the displacement of the shaft 25 per revolution. As a result, as the driving load of the main piston pump 20 increases, the discharge capacity of the main piston pump 20 gradually decreases, and the output of the engine 4 is maintained within a predetermined range.

  In the sub-piston pump 50 constituting the third pump 3, the tilt angle of the sub-swash plate 54 is switched at two positions according to the discharge pressure P3, and the discharge capacity is switched in two stages.

  When the discharge pressure P3 of the third pump 3 is below a predetermined value, the switching valve 5 is in the drain position b, and the drain pressure is guided to the sub hydraulic actuator 10 so that the sub swash plate 54 is as shown in FIG. At the maximum tilt angle.

  When the discharge pressure P3 of the third pump 3 rises exceeding a predetermined value, the switching valve 5 is switched from the drain position b to the drive position a, and the discharge pressure P3 is guided to the sub hydraulic pressure actuator 10, thereby The swash plate 54 is switched to the minimum tilt angle.

  Thus, the discharge capacity of the third pump 3 is switched in two stages according to the discharge pressure P3 of the third pump 3, so that, for example, when the swing device of the hydraulic excavator starts the swing operation or when the swing device rotates. When the bucket of the excavator is pressed against the object, the sub swash plate 54 is quickly switched from the maximum tilt angle to the minimum tilt angle as the discharge pressure P3 of the third pump 3 rises above a predetermined value. Thus, an increase in the driving load of the third pump 3 can be suppressed.

  At this time, as described above, as the discharge pressure P3 of the third pump 3 rises above a predetermined value, the discharge pressure P3 is also guided to the third (linkage) main hydraulic actuator 9. The main swash plate 24 of the main piston pump 20 reduces the tilt angle according to the discharge pressure P3, and the driving load of the first pump 1 and the second pump 2 is reduced.

  Thus, as the discharge pressure P3 of the third pump 3 rises above a predetermined value, the switching valve 5 is switched from the drain position b to the drive position a, and the first pump 1, the second pump 2, the third pump 3 By reducing the discharge capacity of the pump 3 in a stepwise manner, the driving load of the engine 4 is reduced with good responsiveness, and engine stall or the like can be prevented.

In the present embodiment, the hydraulic drive device 100 includes a main piston pump 20 and a sub-piston pump 50 that are driven by a common engine 4.
The main piston pump 20 includes a main cylinder block 23 that is rotationally driven by the engine 4, and a main swash plate 24 that reciprocates the main piston 28 so as to expand and contract the main volume chamber 27 as the main cylinder block 23 rotates. The main swash plate 24 is biased in the direction of increasing the tilt angle, and the main swash plate 24 is moved in the direction of decreasing the tilt angle against the springs 35, 36. As the discharge pressures P1 and P2 of the hydraulic pressure actuators 7 and 8 and the main piston pump 20 rise, the main hydraulic pressure actuators 7 and 8 continuously switch the tilt angle of the main swash plate 24, and the main piston pump Main discharge capacity adjusting means for gradually reducing the discharge capacity of the sub piston pump 50. The sub cylinder block 53 that is rotationally driven by the gin 4, the sub swash plate 54 that reciprocates the sub piston 58 so as to expand and contract the sub volume chamber 57 with the rotation of the sub cylinder block 53, and the sub piston 58. The sub hydraulic actuator 10 moves the sub swash plate 54 against the pressing force, and the sub hydraulic actuator 10 switches the tilt angle of the sub swash plate 54 to two positions according to the discharge pressure P3 of the sub piston pump 50. Sub-discharge capacity adjusting means for reducing the discharge capacity of the sub-piston pump 50 to a predetermined value.

  Based on the above configuration, the main piston pump 20 is continuously switched in tilt angle of the main swash plate 24 in accordance with the discharge pressures P1 and P2, and its discharge capacity is finely adjusted. The tilt angle of the sub-swash plate 54 is switched between two positions according to the discharge pressure P3, and the discharge capacity is adjusted in two stages, so that the driving load of the engine 4 can be prevented from being excessive, Etc. can be prevented.

  Since the sub-piston pump 50 has a configuration in which the tilt angle of the sub-swash plate 54 is switched at two positions, the structure for supporting the sub-swash plate 54 so as to be tilted is simplified, and the sub-swash plate 54 is tilted. A spring or the like that biases the angle in the increasing direction is not necessary, and the cost of the product can be reduced.

  In the present embodiment, the sub discharge capacity adjusting means includes a switching valve 5 that switches the hydraulic pressure guided to the sub hydraulic actuator 10 in accordance with the pilot pressure, and the switching valve 5 is connected to the sub hydraulic actuator 10. It has a drive position a for guiding the discharge pressure P3 of the piston pump 50 and a drain position b for guiding the drain pressure to the sub hydraulic pressure actuator 10, and the discharge pressure P3 of the sub piston pump 50 guided as a pilot pressure exceeds a predetermined value. The drive position a is switched to the drain position b as the position rises.

  Based on the above configuration, the sub-piston pump 50 is operated by switching the drain position b to the drive position a and operating the sub-hydraulic actuator 10 as the discharge pressure P3 of the sub-piston pump 50 increases beyond a predetermined value. The discharge capacity of 50 is adjusted stepwise with good responsiveness, and it is possible to prevent the drive load of the engine 4 from becoming excessive, and to prevent engine stalls and the like.

  In the present embodiment, a third (cooperating) main hydraulic pressure actuator 9 that changes the discharge capacity of the main piston pump 20 is provided, and the main hydraulic pressure actuator 9 and the sub hydraulic pressure actuator 10 are connected via the switching valve 5. The drain pressure and the discharge pressure P3 of the sub piston pump 50 are selectively guided.

  Based on the above configuration, when the discharge pressure P3 of the sub-piston pump 50 increases beyond a predetermined value, the drain position b is switched to the drive position a, and the sub hydraulic actuator 10 and the main hydraulic actuator 9 are operated. As a result, the discharge capacities of the sub-piston pump 50 and the main piston pump 20 are adjusted in stages, and it is possible to prevent the driving load of the engine 4 from becoming excessive, and to prevent engine stall and the like.

  Next, another embodiment shown in FIG. 3 will be described. This basically has the same configuration as that of the embodiment of FIG. 1, and only different portions will be described. In addition, the same code | symbol is attached | subjected to the same structure part as the said embodiment.

  A priority valve 16 and a low pressure relief valve 17 are interposed in series in the third pump passage 13 that guides the hydraulic fluid discharged from the third pump 3 (sub-piston pump 50). The third pump passage 13 is branched into a pump passage 18 through which a working fluid having a discharge pressure P3 is led through a priority valve 16 and a pump passage 19 through which a working fluid having a flow rate controlled by the priority valve 16 is led. Thereby, the two pump passages 18 and 19 are taken out from the third pump 3.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

DESCRIPTION OF SYMBOLS 1 1st pump 2 2nd pump 3 3rd pump 4 Engine 5 Switching valve 7 1st main hydraulic pressure actuator 8 2nd main hydraulic pressure actuator 9 3rd (for cooperation) main hydraulic pressure actuator 10 Sub hydraulic pressure actuator 11 First pump passage 12 Second pump passage 13 Third pump passage 14 Drain passage 20 Main piston pump 23 Main cylinder block 24 Main swash plate 27 Main volume chamber 28 Main piston 35, 36 Spring 50 Sub piston pump 53 Sub cylinder block 54 Sub swash plate 57 Sub volume chamber 58 Sub piston 100 Hydraulic drive unit

Claims (3)

A hydraulic drive device comprising a main piston pump and a sub-piston pump driven by a common engine,
The main piston pump is
A main cylinder block rotationally driven by the engine;
A main swash plate that reciprocates the main piston so as to expand and contract the main volume chamber with the rotation of the main cylinder block;
A spring for urging the main swash plate in a direction to increase its tilt angle;
A main hydraulic actuator that moves the main swash plate in a direction that reduces the tilt angle against the spring;
Main discharge capacity adjusting means for gradually decreasing the discharge capacity of the main piston pump by the main hydraulic actuator continuously switching the tilt angle of the main swash plate as the discharge pressure of the main piston pump increases. And comprising
The sub-piston pump is
A sub-cylinder block that is rotationally driven by the engine;
A sub-swash plate that reciprocates the sub-piston so as to expand and contract the sub-volume chamber with the rotation of the sub-cylinder block;
A sub hydraulic actuator that moves the sub swash plate against the pressing force received from each of the sub pistons;
A sub discharge capacity adjusting means for causing the sub hydraulic pressure actuator to switch the tilt angle of the sub swash plate to two positions in accordance with the discharge pressure of the sub piston pump to reduce the discharge capacity of the sub piston pump to a predetermined value; A hydraulic drive device for a working machine, comprising: The sub-discharge capacity adjusting means is
A switching valve for switching the hydraulic pressure guided to the sub hydraulic actuator according to the pilot pressure;
This switching valve
A drive position for guiding the discharge pressure of the sub piston pump to the sub hydraulic actuator;
A drain position for guiding the drain pressure to the sub hydraulic actuator,
2. The hydraulic pressure of the working machine according to claim 1, wherein the hydraulic pressure of the working machine is switched from the driving position to the drain position in response to an increase in discharge pressure of the sub-piston pump guided as a pilot pressure exceeding a predetermined value. Drive device. A main hydraulic actuator for cooperation that changes the discharge capacity of the main piston pump;
3. A configuration in which a drain pressure and a discharge pressure of the sub piston pump are selectively guided to the main hydraulic pressure actuator and the sub hydraulic pressure actuator via the switching valve. The hydraulic drive device of the working machine as described in 2.

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