JPS62279279A - Hydraulic pump device - Google Patents

Abstract

PURPOSE:To obtain the small-sized and inexpensive hydraulic pump having the desired characteristics by allowing a pilot folow passage to communicate selectively to two control valves set by spring means by a selector valve. CONSTITUTION:The captioned device is constituted of a variable capacity type hydraulic pump A, control valve B set by the first spring 65 and the second spring 67, and a selector valve C. When the communication between the first chamber R1, second chamber R2, and a pilot flow passage 29 is controlled by the selector valve C, the angle of a swash plate 23 can be varied by varying the set pressure by the both springs 65 and 67. A number of characteristics can be obtained according to the relation of magnitude of the set pressure, and only one large hydraulic pump becomes necessary.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a hydraulic pump device for supplying pressure fluid to hydraulic actuators such as various hydraulic cylinders and hydraulic motors. In particular, the present invention relates to a hydraulic pump device that is equipped with a single variable displacement hydraulic pump, a control valve, and a switching valve, and is capable of performing large-volume discharge and small-volume discharge necessary for a hydraulic actuator.

[Prior art]

This type of hydraulic pump device was conventionally used in Japanese Patent Publication No. 60-531.
No. 94 G trowel has been proposed. The hydraulic pump devices proposed in the publication include a variable displacement hydraulic pump that can have a maximum, intermediate, or zero discharge volume, and a variable displacement hydraulic pump that operates at low pressure to maximize its discharge volume. a first control valve that provides the necessary hydraulic pressure to switch from to intermediate, and a second control valve that operates at high pressure to provide the variable displacement hydraulic pump with the necessary hydraulic pressure to switch its discharge amount to zero; A switching valve is provided that switches and connects a pilot flow path branched from a discharge flow path of the variable displacement hydraulic pump to the first control valve or the first and second control valves. Therefore, in the hydraulic pump device, if the pilot flow path is connected only to the first control valve using the switching valve, the discharge amount is maximized in the low pressure region until the first control valve operates, and The discharge amount is set to be intermediate in the high pressure region after the first control valve operates. On the other hand, if the pilot flow path is connected to the first and second control valves using a switching valve, the discharge amount will be maximized in the low pressure region until the first control valve operates, and the first control valve will operate. The discharge amount is set to be intermediate in the high pressure region until the rear second control valve is activated, and the discharge amount is set to zero in the high pressure region after the second control valve is activated. (Refer to the characteristic diagram in Fig. 4) (Problem to be solved by the invention) The above-mentioned conventional hydraulic pump device has a single variable displacement hydraulic pump with first and second control valves and a switching valve. Although it has the advantage of being able to stably obtain low-pressure, large-capacity and high-pressure, small-capacity discharges because it is a compact structure constructed by combining them, it does not have the advantage of being able to stably discharge low-pressure, large-capacity and high-pressure, small-capacity discharges.

(Each characteristic as shown in C1 cannot be obtained.

In addition, each characteristic of FIG. 3 (al, (bl, (C1) is
A hydraulic pump with a large discharge volume and a relief valve attached to it,
Although this can be achieved with a device equipped with a hydraulic pump with a small discharge volume and a relief valve attached to it, this device requires two large and expensive hydraulic pumps, which increases the size and cost of the device. High is unavoidable.

[Means for solving problems]

The present invention has been made to provide a small and inexpensive hydraulic pump device that can obtain the characteristics shown in FIG. a variable control element that defines the variable control element, a pressing body that is provided on the back of the variable control element and presses the variable control element toward a maximum position, and a pressing body that is disposed on the front of the variable control element and is movable opposite to the pressing body. A plunger is provided at the back of the plunger and is moved by hydraulic pressure applied to an action chamber formed at the back of the plunger, and the plunger is provided at the back of the plunger so as to be movable in the same direction as the plunger. a push rod that integrally has a piston that can come into contact with the plunger at its tip and forms a liquid chamber at its rear end; this push rod is pushed toward the plunger by pressurized liquid supplied to the liquid chamber; an adjusting body that integrally has a stopper part that can come into contact with a part of the push rod when the push rod is moved, and can adjust the amount of movement of the push rod toward the plunger, and A variable displacement hydraulic pump whose discharge amount is variable, and a valve body which receives the hydraulic pressure of the first outflow passage on one side and receives a spring force from the first spring means on the other side, When the hydraulic pressure in the first outflow passage is less than the first pressure set by the first spring means, the communication passage communicating with the working chamber is connected to the discharge passage, and the hydraulic pressure in the first outflow passage is is equal to or higher than the first pressure, a first valve that shuts off the communication flow path from the discharge flow path and connects it to the first outflow path and a second outflow path that is connected to the liquid chamber equalize the hydraulic pressure. a valve body receiving a spring force from a second spring means on one side and a valve body receiving a spring force from a second spring means on the other side; The communication flow path is blocked from the second outflow path and connected to the discharge flow path, and when the liquid pressure in the second outflow path is equal to or higher than the second pressure, the communication flow path is shut off from the discharge flow path. a control valve including a second valve connected to the second outflow path; a control valve that connects a pilot flow path branched from the discharge flow path of the hydraulic pump to the first outflow path or the second outflow path; A feature of the present invention is that it includes a switching valve that connects the passage or the first outflow passage to the discharge passage.

[Action of the invention]

In the liquid pump device according to the present invention, when the variable displacement hydraulic pump is operated with the viroft flow path connected to the first outflow path and the second outflow path connected to the discharge flow path using the switching valve, A part of the discharged liquid from the discharge passage of the hydraulic pump is introduced into the first outflow passage through the pilot passage. Accordingly, when the liquid pressure in the first outflow path is less than the first pressure P1 set by the first spring means, the first valve of the control valve connects the communication flow path communicating with the working chamber to the discharge flow path. Therefore, the discharge liquid is not supplied to the action chamber, the variable control element of the hydraulic pump is held at the maximum position by the pressing body, and the discharge rate of the hydraulic pump is maintained at the maximum discharge rate Q1. By the way, when the liquid pressure in the first outflow path becomes equal to or higher than the first pressure P1, the first valve of the control valve cuts off the communication flow path communicating with the action chamber from the discharge flow path and connects it to the first outflow path. The discharge liquid introduced into the first outflow path is supplied to the action chamber, and the plunger pushes the variable control element against the pushing body. Therefore, the discharge amount of the hydraulic pump decreases to a minimum.

In addition, when the variable displacement hydraulic pump is operated with the pyro throat flow path connected to the second outflow path and the first outflow path connected to the discharge flow path using the switching valve, the same hydraulic pump A part of the discharged liquid is introduced from the discharge passage into the second outlet passage through the viroft passage, flows into the liquid chamber from the second outlet passage, and is directed toward the plunger until the push rod comes into contact with the stop flange of the adjustment body. and push it a predetermined amount. Therefore, the plunger and the variable control element are pushed by a predetermined amount by the push rod against the pressing body, and the discharge amount of the hydraulic pump is set to an intermediate discharge amount Q2, which is decreased by a predetermined amount from the maximum discharge amount Q1.

Therefore, when the liquid pressure in the second outflow path is less than the second pressure P2 set by the second spring means, the second valve of the control valve blocks the communication flow path communicating with the action chamber from the second outflow path. Since the pump is connected to the discharge flow path, no discharge liquid is supplied to the action chamber, and the variable control element of the hydraulic pump is held at an intermediate position by the cooperative action of the pressing body and the push rod.
The discharge amount of the hydraulic pump is maintained at intermediate discharge IQ2. By the way, when the liquid pressure in the second outflow path becomes equal to or higher than the second pressure P2, the second valve of the control valve cuts off the communication flow path communicating with the action chamber from the discharge flow path and connects it to the second outflow path. The discharge liquid introduced into the second outflow path is supplied to the action chamber, and the plunger pushes the variable control element against the pushing body. Therefore, the discharge amount of the hydraulic pump decreases to a minimum.

〔Effect of the invention〕

As is clear from the above description, in the hydraulic pump device according to the present invention, the first pressure P1 set by the first spring means is lower than the second pressure P2 set by the second spring means. , each characteristic 1. shown in Figure 3 fa). II can be obtained, and by making the first pressure P1 and the second pressure P2 the same, each characteristic shown in FIG.

11a can be obtained, and by further increasing the first pressure P1 to the second pressure P2, the characteristics Ib and nb shown in FIG. 3 tc+ can be obtained.

In addition, the hydraulic pump device according to the present invention is composed of one variable displacement hydraulic pump, a control valve, and a switching valve, and requires only one large and expensive hydraulic pump, so it has similar characteristics. Compared to a device that can obtain a high discharge volume, that is, a hydraulic pump with a large discharge volume and a relief valve installed therein, and a hydraulic pump with a small discharge volume and a relief valve installed therein, It is possible to reduce the size and weight of the device, and also to significantly reduce costs.

〔Example〕

An embodiment of the present invention will be briefly described below with reference to the drawings.

1 and 2 show a hydraulic pump device according to the present invention, which consists of a variable displacement hydraulic pump A, a control valve B and a switching valve C assembled to the liquid pump A. It is configured.

The variable displacement hydraulic pump A is a swash plate type piston pump, and a side plate 12 is provided on one side of the hollow housing body 11.
is fixed. A main shaft 15 is rotatably supported inside the housing body 11 via bearings 13 and 14, and a cylinder block 17 is rotatably supported on the main shaft 15 via a spline portion 16 formed in an intermediate portion. ing.

A large number of pistons 18 are provided in the cylinder block 17 so as to be able to reciprocate with a predetermined stroke. Shoes 22 supported by retainers 21 are attached to the spherical tips of the pistons 18. Piston 18 is connected to swash plate 23. Further, a valve plate 24 is provided on the Fi12 side of the cylinder block 17.
The valve plate 24 is integrally assembled to the side plate 12. In addition, the valve plate 24
is provided with a suction boat 25 and a discharge boat 26, a suction passage 27 communicates with the suction boat 25, a discharge passage 28 communicates with the discharge boat 26, and a discharge passage 28 communicates with the discharge boat 26.
A pilot flow path 29 is provided to branch from.

On the other hand, the swash plate 23 is swingable around the trunnion shaft 31 within a certain angle of inclination.
A spring 32 interposed between the back of the housing body 11 and the inner surface of the housing main body 11 always pushes the inclination angle toward the maximum position (the position shown in the figure), and a plunger 33 is located at the front of the spring 32. It is provided. The plunger 33 is movably assembled (movable in the axial direction) in opposition to the spring 32 on a guide 34 provided by discharging into the housing body 11 from the side plate 12, and is attached to the swash plate 23 at the tip. They are in contact with each other and form an action chamber RO at the back. The plunger 33 is pushed by hydraulic pressure applied to the action chamber RO through the communication channel 36, and is also pushed by a push rod 37 provided at the back of the plunger 33.

The push rod 37 is attached to the side plate 12 coaxially with the plunger 33, is movable in the same direction as the plunger 33, and can come into contact with the plunger 33 at its tip. This push rod 37 has a piston 38 integrally at its rear end, and a plunger 33 of the piston 38
A first chamber R1 communicating with the flow path 41 is formed on one side, and a second chamber R2 communicating with the flow path 42 is formed on the other side.

Further, the amount of movement of the push rod 37 toward the plunger 33 can be adjusted by an adjustment bolt 43 attached to the side plate 12 so as to be movable forward and backward. The adjustment port 43 integrally has a stopper part 44 that can come into contact with the piston 38 at its inner end, and can be adjusted forward or backward from the outside. It is also possible to push against the swash plate 23
It is also possible to adjust the oblique angle of about 1 at maximum.

The control valve B is connected to the working chamber R0 of the hydraulic pump A, the first
It is a valve that controls the supply and discharge of pressurized liquid to the chamber R1 and the second chamber R2, and the valve body 46 has large diameter holes 47 and 48 on both sides so that the valve body 50 can be slid in the axial direction. A passage 52 connected to a discharge passage 51 connected to the housing main body 11 communicating with the reservoir, and a passage 53 connected to the communication passage 36 are provided with an insertion hole 49 for accommodating the reservoir. 54
and a flow path 55 connected to the flow path 41 and the flow path 42, respectively.
- 56 are provided successively from the center of the insertion hole 49 on both sides at intervals in the axial direction.

The valve body 50 has a land portion 57 in the center that disconnects communication between the flow path 52 and the flow paths 53 and 54, and the land portion 5
On both sides of 7, there are land portions 58 that cut off communication between the flow path 53 and the flow paths 52 and 55, and land portions 59 that cut off communication between the flow path 54 and the flow paths 52 and 56, respectively. is the flow path 55 and the communication hole 61 (hole provided in the valve body 50)
A first working surface 62 is formed on which the pressure applied through the valve acts, and a second working surface 64 is formed at the right end on which the pressure applied through the flow path 56 and the through hole 63 (hole provided in the valve body 50) acts. It is formed. Further, the valve body 50 contacts a first spring 65 housed in the large-diameter hole 48 via a spring receiver 66, and abuts a second spring 67 housed in the large-diameter hole 47 via a spring receiver 68. In the illustrated position, the flow path 53 and the flow path 55 are cut off, the flow path 54 and the flow path 56 are cut off, and both the flow paths 53 and 54 are communicated with the flow path 52. The first spring 65 is for setting the opening pressure (the first pressure PL at which the flow path 53 is cut off from communication with the flow path 52 and communicated with the flow path 55) due to the rightward movement of the valve body 50. The opening pressure can be adjusted as desired by moving the plug 71 screwed into the valve body 46 back and forth. The second spring 67 is activated by the opening pressure caused by the leftward movement of the valve body 50 (a second
This is for setting the pressure P2), and the opening pressure can be arbitrarily adjusted by moving a plug 72 screwed into the valve body 46 back and forth. In addition, in this example,
The opening pressure P2 by the second spring 67 is set higher than the opening pressure P1 by the first spring 65.

The switching valve C is a four-bottom, two-position electromagnetic switching valve, and its valve body 73 is provided with an insertion hole 75 for accommodating a valve body 74 slidably in the axial direction. 46
an inlet passage 77 that communicates with the pilot passage 29 of the hydraulic pump A through a through passage 76 provided in the flow passage 5 of the control valve B;
5 and 56, respectively.
8.79 and a flow path 81 connected to the flow path 52 of control valve B.
- 82 are provided successively on both sides from the center of the insertion hole 75 at intervals in the axial direction and direction.

The valve body 74 has a land portion 83 that disconnects communication between the outflow path 78 and the inflow path 77 and flow path 81, and also has a land portion 84 that disconnects communication between the outflow path 79 and the inflow path 77 and flow path 82, respectively. It has a spring receiver 85 at the left end.
The spring 86 is in contact with the spring 86 through the spring receiver 87 at the right end, and the inflow path 77 is connected to the outflow path 78 in the illustrated position, and the outflow path 79 is connected to the flow path 8.
It is connected to 2. Further, the valve body 74 is adapted to be pushed to the right from the illustrated position by energizing an electromagnetic device 89 disposed on one side of the valve body 73, and when moved to the right, the valve body 74 closes the inflow path. 77 is communicated with the outflow path 79 and the outflow path 78 is connected with the flow path 81. Note that when the valve body 74 moves to the right, both the outflow passages 78 and 79 are temporarily cut off from the inflow passage 77 and both the flow passages 81 and 82.

In this embodiment configured as described above, if the electromagnetic device 89 of the switching valve C is not energized, the working chamber RO of the hydraulic pump A is connected to the flow path 36. The first chamber R1 communicates with the discharge flow path 51 through the flow paths 53, 54, and 52, and the first chamber R1 is connected to the flow path 41. Channel 55.
Outflow channel 78. The second chamber R2 communicates with the pilot flow path 29 through the inflow path 77 and the through flow path 76, and the second chamber R2 is connected to the flow path 42. Channel 5
6. Outflow channel 79. Channels 82 and 81. It communicates with the discharge flow path 51 through the flow path 52 . Therefore, when the main shaft 15 is driven in this state and the piston 18 is reciprocated to operate the pump, a part of the discharged liquid in the discharge passage 28 flows from the pilot passage 29 to the first chamber R1 and the push rod 37 The adjustment bolt 43 is moved back until it abuts the stopper part 44 of the adjustment bolt 43, and the pressure in the flow path 55 (discharge pressure)
1 and acts on the first working surface 62 of the valve body 50. Therefore, when the discharge pressure of the discharge passage 28 acting on the first action surface 62 is less than the opening pressure 21 caused by the first spring 65,
Since the land portion 58 of the valve body 50 continues to block communication between the flow path 55 and the flow path 53, the action chamber R.

No discharge liquid is supplied to the swash plate 23, the inclination angle of the swash plate 23 is maintained at the maximum as shown in the figure by the spring force of the spring 32, and the discharge amount of the hydraulic pump A is maintained at the maximum discharge NQ1. By the way, when the discharge pressure of the discharge passage 28 becomes equal to or higher than the opening pressure 21 caused by the first spring 65, the valve body 50 of the control valve B moves to the right against the spring force of the first spring 65, and the land portion 58 blocks the flow path 53 from the flow path 52 and communicates with the flow path 55, and the land portion 57 blocks the flow path 54 from the flow path 52, so that the discharged liquid introduced into the flow path 55 flows through the flow path. 53 and is supplied to the action chamber RO through the communication channel 36,
The plunger 33 pushes the swash plate 23 against the spring force of the spring 32 in a direction that reduces the angle of inclination. Therefore, the discharge amount of the hydraulic pump A decreases to the minimum, that is, zero.

Note that when the discharge pressure of the discharge passage 28 becomes less than the opening pressure 21 caused by the first spring 65 due to a decrease in the discharge amount, the control valve B
returns to the state shown, and the action chamber R.

The liquid in the communication channel 36. Since the flow is discharged through the flow paths 53, 54, and 52° discharge flow path 51, the swash plate 23 and the plunger 33 are returned to the illustrated state by the spring force of the spring 32, and the discharge amount of the hydraulic pump A becomes the maximum discharge amount Q1 again. become. (See Fig. 3 (Characteristic line ■)) Also, when the electromagnetic device 89 is energized to switch the switching valve C from the state shown in the figure, the valve body 74 moves to the right in the switching valve C, causing the flow to flow through the outflow path 78. The outflow path 79 is disconnected from the flow path 82 and communicated with the inflow path 77. Therefore, the working chamber RO of the hydraulic pump A is communicated with the discharge flow path 51. Although this does not change, the first chamber R1 communicates with the discharge passage 51 through the flow passage 41.flow passage 55.outflow passage 78.flow passage 81°flow passage 52, and the second chamber R2 communicates with the discharge passage 51 through the flow passage 41. 56.Outflow path 79.It communicates with the pilot flow path 29 through the inflow path 77 and the through flow path 76. Therefore, a part of the discharged liquid in the discharge flow path 28 is transferred from the viroft flow path 29 to the second
It flows into the chamber R2 and advances the push rod 37 until it comes into contact with the stopper part 44 of the adjustment bolt 43, and the pressure in the flow path 56 (discharge pressure) passes through the through hole 63 and pushes the valve body 5.
0 on the second operating surface 64. When the push rod 37 moves forward, the plunger 33 is moved by the push rod 37.
Since the swash plate 23 is pushed by a predetermined amount against the spring force of the spring 32, the discharge amount of the hydraulic pump A is set to an intermediate discharge amount Q2 which is decreased by a predetermined amount from the maximum discharge amount Q1. However, the second
When the discharge pressure of the discharge passage 28 acting on the working surface 64 is less than the opening pressure 22 caused by the second spring 67, the land portion 59 of the valve body 50 continues to block communication between the passage 56 and the passage 54. No discharge liquid is supplied to the action chamber Ro, and the swash plate 2
3 is held at an intermediate position where the inclination angle is decreased by a predetermined amount from the maximum position by the spring force of the spring 32 and the cooperative action of the push rod 37, and the discharge amount of the hydraulic pump A is the intermediate discharge amount Q2.
will be maintained. By the way, when the discharge pressure of the discharge passage 28 becomes equal to or higher than the opening pressure 22 caused by the second spring 67, the control valve B
The valve body 50 moves to the left against the spring force of the second spring 67, and the land portion 59 blocks the flow path 54 from the flow path 52 and communicates with the flow path 56, and the land portion 57 closes the flow path. In order to block the passage 53 from the passage 52, the discharged liquid introduced into the passage 56 is supplied to the action chamber Ro through the passage 54 and the communication passage 36, and the plunger 33 resists the spring force of the spring 32. The swash plate 23 is pushed in a direction to decrease the inclination angle. Therefore, the discharge amount of the hydraulic pump A decreases to the minimum, that is, zero. (See Figure 3 (characteristic line n of al))
When the electromagnetic device 89 is de-energized, the switching valve C is switched to the illustrated state.

By the way, in the present embodiment described above, the first spring 65
If the spring force of is adjusted by the plug 71 to be the same as the spring force of the second spring 67, the opening pressure P1 due to the first spring 65 and the opening pressure P2 due to the second spring 67 in the control valve B are made the same. By switching the switching valve C, the discharge amount can be controlled as shown by the characteristic line 1a or Ila in FIG. At the same time, if the spring force of the second spring 67 is adjusted by the plug 72 to make the spring force of the first spring 65 larger than the spring force of the second spring 67, the opening pressure P1 of the first spring 65 in the control valve B is increased.
can be made higher than the opening pressure P2 by the second spring 67, and the discharge amount can be controlled as shown by the characteristic line rb or ■b in Fig. 3(C) by switching the switching valve C. becomes.

In addition, in the present embodiment described above, (al,
(bl, two different discharge pressure-discharge rate characteristics shown at +01 (1, n or Ia, Ila or I
b, nb) are one variable displacement hydraulic pump A, the same hydraulic pump A, and the working chamber Ro of the same hydraulic pump A.

Control valve B that controls the supply and discharge of pressurized liquid to the first chamber R1 and the second chamber R2
and the switching valve C. Therefore, a device that can obtain similar characteristics, that is, a hydraulic pump with a large discharge amount (discharge iQ
1 hydraulic pump), a relief valve provided therein (valve with relief pressure P1), and a hydraulic pump with a small discharge volume (discharge volume Q
Compared to a device consisting of a hydraulic pump (2) and a relief valve (valve with relief pressure P2) installed therein, the device can be made smaller and lighter, and it is also possible to significantly reduce costs. can.

[Modified example]

In the above embodiment, the first . The present invention was carried out by connecting the flow path 41 communicating with the chamber R1 to the flow path 55 of the control valve B, but instead of connecting the flow path 41 to the flow path 55, as shown in FIG. Substantially the same operation as in the above embodiment can be obtained even if it is connected directly into the housing body 11. Therefore, as shown in FIG.
If a switching valve is interposed between the flow path 2 and the flow path 56, which operates when the internal pressure of the flow path 56 is equal to or higher than the third pressure P3 (which can be adjusted as needed), and connects both the flow paths 42 and 56, Figure 6(a).

(bl, (Each characteristic shown in C1 can be obtained.

Further, in the above embodiment, the valve body 50 is used as a control valve.
The control valve B has a relatively simple structure (the first valve has a first action surface 62 and a second action surface 64 at one end and the other end, and a first spring 65 and a second spring 67). The valve body 50 serves as both the valve body and the valve body of the second valve), but
As the control valve, it is also possible to employ a control valve that separately includes a valve body of a first valve and a valve body of a second valve.

Furthermore, in the above embodiment, a switching valve C whose operating method is an electromagnetic type was adopted as the switching valve, but instead of the switching valve C, the operating method may be a manual type, a mechanical type, a pilot hydraulic type, or an electromagnetic type. It is also possible to employ a switching valve.

Further, in the above embodiment, the swash plate type piston pump A was employed as the variable displacement hydraulic pump, but it is also possible to employ a variable displacement vane pump in place of the hydraulic pump A. In the case of variable displacement vane pumps,
The cam ring is a variable control element, and a plunger substantially the same as the plunger 33 of the above embodiment may be brought into contact with this cam ring.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of a hydraulic pump device according to the present invention, FIG. 2 is a diagram showing the device shown in FIG. 1 with symbols, and FIG. 3 is a hydraulic pump device according to the present invention. The discharge pressure-discharge rate characteristic diagram obtained by
A discharge pressure-discharge rate characteristic diagram obtained by the device proposed in Publication No. 3194, FIG. 5 is a sectional view of a main part showing a modification of the hydraulic pump device according to the present invention, and FIG. It is a discharge pressure-discharge amount characteristic diagram obtained by the shown apparatus. Explanation of symbols 23...Swash plate (variable control element), 28...Discharge channel, 29...Pilot channel, 32...Spring (pressing body), 33...Plunger, 36...・Communication channel, 37
...Push rod, 38...Piston, 43...
・Adjustment bolt (adjustment body), 44...stopper part, 50
... Valve body, 51... Discharge flow path, 65... First spring (means), 67... Second spring (means), 78...
(1st) Outflow path, 79... (2nd) Outflow path, A...
- Variable displacement hydraulic pump, B...control valve, C...switching valve, RO...action chamber, R2...second chamber (liquid chamber).

Claims (1)

[Scope of Claims] A variable control element that regulates the discharge amount, a pressing body that is provided at the back of the variable control element and presses the variable control element toward a maximum position, and a pressing body that is provided at the front of the variable control element. a plunger that is movably provided opposite to the pressing body and that abuts the variable control element at its tip and is pushed by hydraulic pressure applied to an action chamber formed at the back; a push rod that is movable in the same direction as the push rod, has an integral piston that can come into contact with the plunger at its tip and forms a liquid chamber at its rear end; an adjusting body that integrally has a stopper portion that can come into contact with a portion of the push rod when pushed toward the plunger by the liquid, and is capable of adjusting the amount of movement of the push rod toward the plunger; A variable displacement hydraulic pump whose discharge amount is changed by changing the position of the variable control element; one side receives the hydraulic pressure of the first outflow path, and the other side receives the spring force from the first spring means. a valve body that receives the valve body, and connects a communication flow path communicating with the working chamber to a discharge flow path when the hydraulic pressure in the first outflow path is less than a first pressure set by the first spring means; Further, when the liquid pressure in the first outflow path is equal to or higher than the first pressure, a first valve is configured to cut off the communication flow path from the discharge flow path and connect the communication flow path to the first outflow path, and a first valve is connected to the liquid chamber. The valve body receives the hydraulic pressure of the second outflow passage on one side and receives the spring force from the second spring means on the other side, and the hydraulic pressure of the second outflow passage is set by the second spring means. When the pressure is less than the second pressure, the communication flow path is shut off from the second outflow path and connected to the discharge flow path, and when the liquid pressure in the second outflow path is equal to or higher than the second pressure, the communication flow path is a control valve including a second valve that blocks a passage from a discharge passage and connects it to the second outflow passage; and a control valve that connects a pilot passage branched from the discharge passage of the hydraulic pump to the first outflow passage or the second outflow passage. A hydraulic pump device comprising a switching valve that connects the second outflow path or the first outflow path to the discharge path.