JPH09177663A - Variable capacity pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To narrow the inclination of a swash plate when discharge pressure comes to have a predetermined value or more. SOLUTION: A variable capacity pump P has a swash plate 18. The discharging volume of hydraulic oil discharged from the variable capacity pump P is adjusted in accordance with the inclination of the swash plate 18. The inclination of the swash plate 18 is adjusted by an adjusting cylinder 41. The adjusting cylinder 41 consists of a first adjusting piston 43, a second adjusting piston 44 connected to the swash plate 18, a spring 46 interposed between the first and second adjusting pistons 43, 44, and a regulating part T1 for regulating the movement of the first adjusting pin 43, etc. The left-directional movement of the first adjusting piston 43 in line with discharging pressure, etc., results in the left-directional movement of the second adjusting piston 44 and a spring 46 as well, widening the inclination of the sash plate 18. Abutting the first adjusting piston 43 to the regulating part T1 maximizes the inclination of the swash plate 18. Then, no first adjusting piston 43 is moved by the regulating part T1 even if the discharging pressure of the hydraulic oil is elevated, narrowing the inclination of the swash plate 18 in accordance with the return moment of the swash plate 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable displacement pump.

[0002]

2. Description of the Related Art Conventionally, as a technique of this kind, Japanese Patent Laid-Open No. 57-
A variable displacement pump disclosed in Japanese Patent No. 167501 has been proposed.

As shown in FIG. 6, the hydraulic oil discharged from the variable pump 71 passes through a throttle valve 72 and a hydraulic cylinder 73.
Is discharged. The oil pressures on the upstream side and the downstream side of the throttle valve 72 act on the spool 75 of the flow rate control valve 74 as pilot pressures, and the flow rate control valve 74 controls the variable pump 71 so that the pressure difference between the upstream side and the downstream side is constant. To control. That is, the flow rate control valve 74 controls the discharge amount control unit 71 a of the variable pump 71 to control the discharge amount of the variable pump 71.

A branch passage 76 is provided upstream of the throttle valve 72.
And a surge pressure absorption valve 77 is connected to the branch passage 76. The surge pressure absorbing valve 77 connects the branch passage 76 and the drain 78 to each other when the hydraulic pressure in the branch passage 76 becomes equal to or higher than a predetermined value, and reduces the pressure of the hydraulic oil discharged from the variable pump 71. Let This predetermined value is set by the pilot relief valve 79.

That is, when the pressure of the hydraulic oil discharged from the variable pump 71 exceeds a predetermined value, the surge pressure absorption valve 77 operates to reduce the discharge amount of the hydraulic oil discharged from the variable pump 71.

[0006]

However, when the pressure of the working oil discharged from the variable pump 71 becomes equal to or higher than a predetermined pressure value by using two control valves, the surge pressure absorption valve 77 and the pilot relief valve 79. Surge pressure absorption valve 7
Since the pressure of the hydraulic oil discharged from the variable pump 71 is lowered by operating the valve 7, there is a problem that the structure becomes complicated and the cost becomes high.

Further, since the surge pressure absorption valve 75 and the pilot relief valve 79 are usually separate from the pump main body, the installation space for installing these valves 75, 79 and each pump main body is wide. There's a problem.

The present invention has been made in order to solve the above-mentioned problems, and its purpose is to make the inclination angle of the swash plate the maximum inclination angle when the discharge pressure of the hydraulic oil becomes a predetermined value or more with a simple structure. It is an object of the present invention to provide a variable displacement pump that does not discharge a predetermined amount or more of hydraulic oil by controlling below.

[0009]

In order to solve the above-mentioned problems, the invention according to claim 1 is characterized in that the pump main body comprises a pump portion having a swash plate and an actuator connected to the swash plate. In the variable displacement pump, the portion discharges hydraulic oil by the relative rotation of the operating body with respect to the swash plate, and the discharge capacity of the hydraulic oil discharged from the pump portion is adjusted according to the inclination angle of the swash plate. The pump main body adjusts the inclination angle of the swash plate according to the discharge pressure of the hydraulic oil discharged from the pump section, and when the discharge pressure exceeds a predetermined value, the swash plate returns according to the return moment. The gist of the present invention is to provide an angle adjusting mechanism for adjusting the inclination angle of the plate to a maximum inclination angle or less.

According to a second aspect of the present invention, in the first aspect of the present invention, the angle adjusting mechanism includes a first adjusting piston that moves according to a discharge pressure of hydraulic oil discharged from the pump section, and the swash plate. A second adjusting piston connected,
A biasing member having one end connected to the first adjusting piston and the other end connected to the second adjusting piston, and a first member provided between the first adjusting piston and the second adjusting piston.
The gist of the present invention is to have a regulating portion that regulates the movement of the adjusting piston.

A third aspect of the present invention is summarized in that, in the second aspect of the invention, a hydraulic cylinder mechanism is provided between the first adjusting piston and the second adjusting piston.

According to a fourth aspect of the present invention, in the first to third aspects of the present invention, the pump main body is provided with a throttle valve in a discharge passage through which hydraulic oil discharged from the pump portion passes, and the throttle valve is provided. The gist of the invention is that a spool is moved according to the differential pressure between the upstream side and the downstream side of the valve, and a flow rate control valve that adjusts the flow rate of the hydraulic oil introduced into the angle adjusting mechanism based on the movement of the spool is provided. And

Therefore, according to the first aspect of the invention, in the variable displacement pump, the amount of hydraulic oil discharged from the pump portion is adjusted based on the inclination angle of the swash plate. The inclination angle of the swash plate is adjusted by the angle adjusting mechanism. In this case, the angle adjusting mechanism adjusts the inclination angle to the maximum inclination angle or less according to the return moment on the swash plate side when the discharge pressure becomes equal to or higher than the predetermined value.

According to the second aspect of the invention, when the first adjusting piston moves according to the discharge pressure, the second adjusting piston is pressed by the biasing means, and the second adjusting piston presses the swash plate, Increase the tilt angle of the plate. Then, when the first adjusting piston comes into contact with the restricting portion and the swash plate is tilted to the maximum tilt angle, the return moment on the swash plate side increases, and the swash plate causes the second adjusting piston to be in the pressing direction of the first adjusting piston. Press in the opposite direction. Then, the second adjusting piston presses the biasing means in accordance with the pressing, and the tilt angle of the swash plate decreases. Therefore, when the discharge pressure exceeds a predetermined value, the tilt angle of the swash plate becomes less than the maximum tilt angle.

According to the third aspect of the invention, the urging means can be assisted and the urging effect can be enhanced by the cylinder mechanism provided between the first adjusting piston and the second adjusting piston.

According to the fourth aspect of the invention, the flow rate control valve holds the differential pressure upstream and downstream of the throttle valve constant by driving the spool based on the differential pressure upstream and downstream of the throttle valve. Therefore, the amount of hydraulic oil discharged from the variable displacement pump can be controlled more accurately.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a variable displacement pump P. The main body (pump main body) Pa of the variable displacement pump P also functions as a swash plate guide 1
And an end cover 2 and the like, and a suction port 3 and a discharge port 4 are formed on a side portion of the end cover 2. A suction pipe 5 for sucking hydraulic oil into the variable displacement pump P is connected to the suction port 3, and a discharge pipe 6 for discharging hydraulic oil from the variable displacement pump P is connected to the discharge port 4. The suction pipe 5 is connected to a hydraulic tank 7 (see FIG. 2), and the discharge pipe 6 is connected to, for example, a hydraulic cylinder 8 (see FIG. 2) as a hydraulic device.

A drive shaft 11 is rotatably supported between the swash plate guide 1 and the end cover 2 via a pair of bearings 12 and 13. A cylinder block 15 which is in sliding contact with the end cover 2 is fixed to the spline portion 14 of the drive shaft 11, and is provided so as to be rotatable integrally with the drive shaft 11. The drive shaft 11 is connected to an output shaft K of a power take-off device (PTO) connected to the engine, and is rotated with the rotation of the output shaft K.

The cylinder block 15 is formed with a plurality of cylinder bores 16 extending in parallel with the drive shaft 11, and the center of which is located on the same circumference with the drive shaft 11 as the center. . The cylinder bore 1
A piston 19 that is constantly pressed by a swash plate 18 via a shoe 17 is accommodated in the inside of the unit 6 such that the piston 19 can reciprocate. In this case, the shoe 17 is formed with a circumferential groove 17a having a substantially arcuate cross section. That is, the spherical portion 20 formed at the tip of the piston 19 and the circumferential groove 17a contact each other, and the spherical portion 20 is rotatably provided along the circumferential groove 17a. In this case, the cylinder bore 16 and the piston 19 form an operating body.

A housing hole 22 is formed in the front portion of the center of the cylinder block 15, and a pressing member 23 is fitted in the housing hole 22 so as to be rotatable integrally with the cylinder block 15 and slidable in the axial direction. There is. The pressing member 23 is urged toward the swash plate 18 by a spring 24 arranged in the accommodation hole 22.

In this case, when the drive shaft 11 rotates together with the output shaft K of the power takeoff device, the cylinder block 1
5 rotates with the drive shaft 11. Then, each piston 19 housed in each cylinder bore 16 also rotates together with the cylinder block 15. During this rotation, the piston 19 rotates along the shoe 17. Therefore, for example, when the swash plate 18 is inclined, the piston 19 reciprocates in the cylinder block 15. In this case, the hydraulic oil is sucked when the piston 19 moves in the direction away from the bottom surface 16a of the cylinder bore 16 (leftward in FIG. 1). That is, the piston 19 is the bottom surface 16 of the cylinder bore 16.
The process of moving in the direction away from a is a suction process.
When the piston 19 moves toward the bottom surface 16a of the cylinder bore 16 (in the right direction in FIG. 1), hydraulic oil is discharged. That is, the piston 19 becomes the cylinder bore 16
The step of moving the bottom surface 16a toward the bottom surface 16a is a discharging step. At the time of this rotation, one of all pistons 19 is in the suction process,
One of the pistons 19 is in the discharge process. Therefore, when the drive shaft 11 rotates, the hydraulic oil is continuously sucked from the suction pipe 5 and discharged from the discharge pipe 6. Further, as the rotation speed of the drive shaft 11 increases, the reciprocating motion of the piston 19 becomes faster.
Therefore, the amount of hydraulic oil discharged by each piston 19 increases.

In this embodiment, the drive shaft 11, the cylinder block 15, the cylinder bore 16, the swash plate 18, the piston 19 and the like constitute the pump portion 26 shown in FIG. In this case, as the rotation speed of the drive shaft 11 increases, the reciprocating motion of the piston 19 becomes faster.
Therefore, the amount of hydraulic oil discharged from the pump unit 26 increases. That is, the pump body Pa includes the pump portion 26.

An angle adjusting mechanism 31 for adjusting the angle of the swash plate 18 and a switching valve 32 for supplying / discharging hydraulic oil to / from the angle adjusting mechanism 31 are provided below the end cover 2. The switching valve 32 is located on the side of the end cover 2, the angle adjusting mechanism 31 is located inside of the switching valve 32, and when it is turned on, hydraulic oil is supplied to the angle adjusting mechanism 31, and when it is turned off, the angle is adjusted. The hydraulic oil on the adjusting mechanism 31 side is discharged to the drain 32a.

The switching valve 32 comprises a first housing hole 33 formed in the end cover 2, a spool 34 housed in the first housing hole 33, and the like. A branch passage 35 for communicating a part of the hydraulic oil discharged by the piston 19 is communicated with the first storage hole 33. In addition, the drain passage 3 for discharging the hydraulic oil to the drain 32a is provided in the first storage hole 33.
6 is communicated. The spool 34 has a central passage 3
7 and drain passages 37a and 37b are formed. The central passage 37 extends in the axial direction of the spool 34 and communicates with the first storage hole 33. Also, the extraction passages 37a, 3
7b is formed in a direction orthogonal to the central passage 37. That is, the first passage is formed in the central passage 37 and the passage 37a.
The passage 38 is formed, and the central passage 37 and the extraction passage 37b are formed.
The second passage 39 is formed at. The first passage 38 is a passage for supplying hydraulic oil to the angle adjusting mechanism 31 side, and is communicated with the branch passage 35 at the time of turning on. The second passage 39 is a passage for discharging the hydraulic oil from the angle adjusting mechanism 31, and is communicated with the drain passage 36 when it is off. The position of the spool 34 of the switching valve 32 is switched by the solenoid 40. That is, the solenoid 4
According to the operation of 0, the switching valve 32 is turned on / off.

The angle adjusting mechanism 31 comprises a hydraulic cylinder (hereinafter referred to as "adjusting cylinder") 41 for adjusting the angle. The adjustment cylinder 41 includes a second accommodation hole 42 formed in the end cover 2, a first adjustment piston 43 and a second adjustment piston 44 accommodated in the second accommodation hole 42, and the like.
The second storage hole 42 is connected to the first storage hole 33 by the communication passage 42a.
Has been communicated with. Further, a cylindrical collar 42b is fitted on the swash plate 18 side of the second storage hole 42, and the collar 42b
A second adjusting piston 44 is slidably provided in the inside of b. Further, the first adjusting piston 43 is adapted to slide on the right side of the second housing hole 42 in which the collar 42b is not fitted. In this case, the first adjusting piston 4 of the collar 42b
The end portion on the 3 side is a regulation portion T1 that regulates the movement of the first adjustment piston 43. That is, in FIG.
The end portion on the right side of b is the regulation portion T1.

A groove 45 having a circular cross section is formed in the first adjusting piston 43, and the second adjusting piston 44 is inserted into the groove 45. A spring 46 is housed between the bottom surface 45 a of the groove 45 and the side surface 44 a of the second adjusting piston 44. That is, the first adjusting piston 43 is pressed by the hydraulic oil supplied from the switching valve 32. Further, the edge surface portion of the recessed groove 45 serves as a locking portion T2 and comes into contact with the regulation portion T1. That is, in FIG. 1, the left end portion of the first adjusting piston 43 is the regulating portion T2.

The second adjusting piston 44 has a base end portion which is tapered. The tip of the swash plate 18 is connected to the tip of the second adjusting piston 44 via a steel ball X. In this case, when the switching valve 32 is turned on, the hydraulic oil flows from the branch passage 35 to the angle adjusting mechanism 31 side via the first passage 38 of the spool 34. That is, the hydraulic oil flows into the second storage hole 42.

Then, the hydraulic oil presses the first adjusting piston 43. Then, the first adjusting piston 43 presses the second adjusting piston 44 via the spring 46. The second adjusting piston 44 presses the swash plate 18 via the steel ball X based on the pressing of the first adjusting piston 43, and the swash plate 18 is inclined.

When the switching valve 32 is turned off, the second passage 3
9 and the drain passage 36 communicate with each other. In this case, the hydraulic oil in the second storage hole 42 is discharged to the drain 32a (see FIG. 2) via the second passage 39 and the drain passage 36.

Next, the hydraulic circuit in the variable displacement pump P will be described. FIG. 2 shows the variable displacement pump P.
3 is a circuit diagram showing the hydraulic circuit of FIG. The variable displacement pump P is
A pump unit 26, a switching valve unit 32, a throttle valve unit 47 as a throttle valve, and a flow rate control valve unit 48 as a flow rate control valve are provided. The throttle valve portion 47 and the flow control valve portion 48 are not shown in FIG. 1 because they are formed in a cross section different from the cross section shown in FIG.

The pump portion 26 communicates with the discharge port 4 through a main passage 49 as a discharge passage. A throttle valve portion 47 is formed in the main passage 49. That is, the hydraulic oil from the pump portion 26 flows to the discharge port 4 via the main passage 49 and is supplied to the hydraulic cylinder 8 via the discharge pipe 6. Further, in the main passage 49, the branch passage 35 is connected downstream of the throttle valve portion 47, and the flow passage control valve portion 48 is connected to the branch passage 35.

The flow rate control valve portion 48 is connected to the drain 48a via a drain passage 50, and is connected to the switching valve portion 32 via a hydraulic passage 51. A first passage 53 and a second passage 54 are formed in the spool 52 of the flow rate control valve portion 48. The first passage 53 is a passage that communicates with the hydraulic passage 51 and allows the working oil to flow to the switching valve 32 side. The second passage 54 communicates with the drain passage 50 to transfer the hydraulic oil to the drain 48.
It is a passage for discharging to a.

The oil pressure on the upstream side of the throttle valve portion 47 acts as pilot pressure on one end (the right end in FIG. 2) of the spool 52 of the flow control valve portion 48, and the other end (the left end in FIG. 2)
The hydraulic pressure on the downstream side of the throttle valve portion 47 acts as pilot pressure. That is, the spool 52 moves based on the difference (differential pressure) between the upstream and downstream hydraulic pressures that increases with an increase in the flow rate, and the flow rate of the hydraulic oil is controlled so that the differential pressure becomes constant.

The switching valve 32 is connected to the drain 32a via a drain passage 36, and is connected to the adjusting cylinder 41 via the communication passage 42a. A first passage 38 and a second passage 39 are formed in the spool 34 of the switching valve 32. The first passage 38 is a passage for flowing the working oil from the flow control valve portion 48 to the adjusting cylinder 41 side, and the second passage 39 is the drain for the working oil from the adjusting cylinder 41 to the drain 32a.
It is a passage for flowing into.

The adjusting cylinder 41 is provided with the first adjusting piston 43, the second adjusting piston 44, the spring 46, the restricting portion T1 and the like, based on the hydraulic oil introduced through the flow control valve portion 48. The first and second adjusting pistons 4
3, 44 are driven, and the pump unit 26 is driven.

Next, the operation and effect of the variable displacement pump configured as described above will be described. As shown in FIGS. 1 and 2, when the pump portion 26 is driven by the rotation of the output shaft K of the power takeoff device, the hydraulic oil in the hydraulic tank 7 is pumped through the suction pipe 5 and the suction port 3. Supplied within. Then, the pump unit 26 discharges the hydraulic oil to the main passage 49. The hydraulic oil discharged into the main passage 49 is supplied to the hydraulic cylinder 8 via the throttle valve portion 47.

Normally, when operating the cylinder 8, the switching valve portion 32 is turned on. When the switching valve unit 32 is turned on, that is, the hydraulic passage 51 is passed through the first passage 38 of the spool 34.
And the communication passage 42 a communicate with each other, and a part of the hydraulic oil discharged from the pump portion 26 is flowed through the branch passage 35 to the flow control valve portion 4.
8 and the switching valve section 32, and further, the adjustment cylinder 41
Introduced to. That is, when the cylinder 8 is operated, the switching valve 32 is turned on and a part of the hydraulic oil supplied to the hydraulic cylinder 8 is introduced into the adjustment cylinder 41.

In FIG. 1, hydraulic oil is supplied to the adjusting cylinder 41.
Is introduced into the first adjusting piston 43, the first adjusting piston 43 is pressed by the hydraulic oil and moves leftward (moves leftward). Then, the first adjusting piston 43 presses the second adjusting piston 44 via the spring 46. That is, the second adjusting piston 44 moves leftward together with the first adjusting piston 43. In this case, a pressing force F that presses the swash plate 18 is generated in the second adjusting piston 44, and the swash plate 18 is
The connecting part is pressed in the direction of increasing the tilt angle, that is, to the left. In this case, the swash plate 18, the pressing moment M ₁ is applied by the pressing force F.

On the other hand, when the output shaft K rotates and the variable displacement pump P is driven to discharge, the rotation center of the swash plate 18 is eccentrically attached to the low pressure side piston 19 side. Has a return moment M ₀ . The return moment M ₀ is a moment generated by the hydraulic oil discharged by the action of each piston 19, that is, the hydraulic oil discharged from the pump portion 26, and is represented by the following equation (S1).

M ₀ = (π / 4) · d ² · (Z / 2) · e · R ₁ (S1) (d is the diameter of the piston 19, Z is the number of pistons 19, e
Is the amount of eccentricity of the swash plate 18, and R ₁ is the discharge pressure of the hydraulic oil discharged from the pump section 26. In addition, these d, Z, e,
Each value of R1 is preset in the variable displacement pump P. Since the pressing moment M ₁ due to the pressing of the cylinder 41 is larger than the return moment M _0, when hydraulic oil is supplied from the switching valve 32 to the adjusting cylinder 41, the swash plate 18 tilts and tilts according to the pressing moment M _1. The angle increases.

Further, when the pressure in the circuit rises due to, for example, the load of the cylinder 8, the first and second adjusting pistons 43 and 44 move leftward based on the pressure, and the first and second adjusting pistons 43 and 44 move to the left.
The adjusting piston 43 eventually comes into contact with the restriction portion T1.
At this time, the inclination angle of the swash plate 18 becomes maximum. That is, the inclination angle of the swash plate 18 becomes the maximum inclination angle.

From this state, when the discharge pressure of the hydraulic oil from the pump portion 26 further rises, the return moment M ₀
Becomes larger than the pressing moment M ₁ .
Then, the return moment M ₀ resists the pressing force of the spring 46, and the inclination angle of the swash plate 18 decreases in accordance with the return moment M ₀ , that is, the connecting portion of the second adjusting piston 44 inclines to the right. . At this time, the first adjusting piston 43 is pressed leftward in the drawing by the hydraulic oil in the second storage hole 42, but its movement is restricted by the collar 42b, and only the second adjusting piston 44 is Spring 4
Overcome the force of 6 and move to the right in the figure. Therefore, for example, even if the load increases and the discharge pressure increases, the discharge flow rate of the hydraulic oil discharged from the pump unit 26 decreases.

According to this embodiment, the following (a) to
It has the effect shown in (e). (A) According to the above embodiment, the first adjustment piston 43
Comes into contact with the regulating portion T1, that is, when the tilt angle of the swash plate 18 reaches the maximum tilt angle, the first adjusting piston 43 does not press the second adjusting piston 44 via the spring 46, and thus the second adjusting piston 44 is not pressed. The movement of the piston 44 in the direction of increasing the inclination angle of the swash plate 18 is stopped, and when the discharge pressure increases thereafter, the swash plate 18 follows the return moment M ₀ .
The second adjusting piston 44 is pushed against the pushing moment M ₁ . That is, the swash plate 18 tilts in the direction in which the tilt angle decreases in accordance with the return moment M ₀ , and the tilt angle of the swash plate 18 decreases. Therefore, the hydraulic fluid of a predetermined discharge amount or more is not discharged from the variable displacement pump P from the pump portion 18.

Therefore, when the discharge pressure increases, the hydraulic oil of a predetermined discharge amount or more is not discharged from the pump portion 26, and the capacity of the variable displacement pump P decreases, so that the engine overload can be prevented. Further, since the hydraulic oil of a predetermined discharge amount or more is not discharged and the capacity of the variable displacement pump P is reduced, the structure of the power take-out device can be simplified. For example, the power takeoff device may not be provided with a clutch for transmitting the rotation of the engine to the output shaft K.

(B) Since the adjusting cylinder 41 is provided in the variable displacement pump P, the installation place of the variable displacement pump P can be reduced. Therefore, the installation space of the variable displacement pump P can be made advantageous.

(C) A spring 46 is provided between the first adjusting piston 43 and the second adjusting piston 44, and the regulating portion T1 is formed between the first adjusting piston 43 and the second adjusting piston 44. Thus, the angle adjusting mechanism 31 can be easily configured so that the tilt angle of the swash plate 18 is equal to or less than the maximum tilt angle when the discharge pressure becomes equal to or higher than the predetermined value. That is, the angle adjusting mechanism 31 can be configured with a simple configuration. Further, the maximum tilt angle can be easily changed by changing the position of the restricting portion T1.

(D) As shown in FIG. 3, when the tilt angle of the swash plate 18 reaches the maximum tilt angle and the discharge amount of the hydraulic oil reaches a predetermined discharge amount, the return moment M of the swash plate 18 is eventually reached.
_{With 0} , the inclination angle of the swash plate 18 decreases, and the amount of hydraulic oil discharged decreases. The degree of decrease in the discharge amount of the hydraulic oil when the hydraulic oil decreases depends on the spring constant of the spring 46. Therefore, by using the springs 46 having different spring constants, the degree of decrease in the discharge amount of the hydraulic oil can be easily adjusted. For example, by using the spring 46 having a large spring constant, the degree of decrease of the hydraulic oil can be reduced as shown by the imaginary line (L1). Further, by using the spring 46 having a small spring constant, the virtual line (L
As shown in 2), the degree of decrease in hydraulic oil can be increased.

Further, by appropriately changing the initial load applied to the spring 46 in advance, the discharge pressure reaching the maximum inclination angle can be appropriately changed as shown by the dotted line in FIG.
(E) Since the flow rate control valve unit 48 that keeps the differential pressure upstream and downstream of the throttle valve unit 47 constant is provided, the variable displacement pump P can be controlled more accurately.

The present invention is not limited to the above-mentioned embodiment, and can be carried out as follows with appropriate changes without departing from the spirit of the invention. (1) In the above embodiment, as shown in FIGS. 4 and 5, it may be applied to a variable displacement pump P provided with a hydraulic cylinder mechanism 62 in an adjusting cylinder 61 as an angle adjusting mechanism.

That is, the concave groove 4 of the first adjusting piston 43.
A central shaft portion 64 extending in the axial direction is provided at the central position of 5. The central shaft portion 64 is formed with a through hole 65 penetrating in the axial direction thereof. An insertion hole 66 is formed on the first adjusting piston 43 side of the second adjusting piston 44,
The central shaft portion 64 is inserted. Normally, the central shaft portion 6
A space portion 67 is formed between 4 and the insertion hole 66. In this case, the central shaft portion 64 and the insertion hole 66 constitute the hydraulic cylinder mechanism 62.

In this adjusting cylinder 61, the switching valve 3
When hydraulic oil is supplied from the second side, the adjustment cylinder 41
Similarly, the hydraulic oil presses the first adjusting piston 43, and the first adjusting piston 43 presses the second adjusting piston 44 via the spring 46. At this time, the hydraulic oil is introduced into the space 67 through the through hole 65. That is, the hydraulic oil is
The hydraulic oil directly presses the second adjusting piston 44 by being introduced into. Therefore, the second adjusting piston 44 can more quickly incline the swash plate 18 in the direction in which the inclination angle increases.

After the tilt angle of the swash plate 18 reaches the maximum tilt angle, the return moment M ₀ of the swash plate 18 is changed to the spring 4.
6 and the pressure of the hydraulic oil introduced into the space 65. That is, the return moment M _{0 is transferred} to the spring 4
6 and the hydraulic cylinder mechanism 62. Therefore, the hydraulic cylinder mechanism 62 assists the spring force of the spring 46, and
It is possible to enhance the effect of biasing by. Therefore, for example, the spring 46 having a small spring force can be used, and the spring 46 can be downsized.

(2) In the above embodiment, the drive shaft 1
The swash plate 18 side may rotate with 1 and the actuation body may not rotate, so that the actuation body may rotate relative to the swash plate 18.

(3) In the above embodiment, the switching valve 3
2 and the variable displacement pump P not provided with the flow rate control valve portion 48 may be applied. (4) In the above-described embodiment, the variable displacement pump P can be used for a dust collecting vehicle or an injection molding machine.

The technical ideas other than the claims that can be understood from the above-described embodiment will be described below along with their effects. (1) The variable displacement pump according to any one of claims 1 to 4, wherein the actuating body rotates relative to the swash plate when the actuating body rotates together with the drive shaft 11. According to this variable displacement pump, the hydraulic oil can be easily discharged from the pump unit 26 in accordance with the rotation of the operating body.

[0056]

As described above in detail, according to the first aspect of the present invention, the angle adjusting mechanism causes the tilt angle of the swash plate to be equal to or less than the maximum tilt angle when the discharge pressure becomes equal to or higher than a predetermined value. Is controlled to reduce the capacity of the variable displacement pump, so that, for example, the load on the engine or the like that drives the variable displacement pump can be reduced.

According to the second aspect of the invention, the biasing member is interposed between the first adjusting piston and the second adjusting piston, and the first adjusting piston is provided between the first adjusting piston and the second adjusting piston. By providing a regulation part that regulates the movement of the piston, when the discharge pressure easily exceeds a predetermined value,
It is possible to configure an angle adjusting mechanism in which the tilt angle of the swash plate is equal to or less than the maximum tilt angle.

According to the third aspect of the invention, the urging means can be assisted by the cylinder mechanism provided between the first adjusting piston and the second adjusting piston to enhance the effect of the urging. .

According to the fourth aspect of the invention, the flow rate control valve holds the differential pressure upstream and downstream of the throttle valve constant by driving the spool based on the differential pressure upstream and downstream of the throttle valve. Therefore, the discharge amount of the hydraulic oil discharged from the variable displacement pump can be controlled more accurately.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a variable displacement pump.

FIG. 2 is a circuit diagram showing a hydraulic circuit of a variable displacement pump.

FIG. 3 is an explanatory diagram showing a discharge amount and a discharge pressure.

FIG. 4 is a sectional view showing a variable displacement pump according to another example.

FIG. 5 is a circuit diagram showing a hydraulic circuit of a variable displacement pump according to another example.

FIG. 6 is a circuit diagram showing a conventional hydraulic circuit for adjusting the flow rate of hydraulic oil.

[Explanation of symbols]

16 ... Cylinder bores that constitute the operating body, 18 ... Swash plate, 2
6 ... Pump part, 19 ... Piston forming the operating body, 31
... angle adjusting mechanism, 32 ... switching valve portion as switching valve, 34
... Spool, 41 ... Adjusting cylinder as an angle adjusting mechanism, 43 ... First adjusting piston, 44 ... Second adjusting piston, 46 ... Spring as biasing member, 47 ... Throttle valve portion as throttle valve, 48 ... Flow rate adjusting Flow control valve part as a valve,
61 ... Adjusting cylinder as an angle adjusting mechanism, 62 ... Hydraulic cylinder mechanism, T1 ... Regulator, P ... Variable displacement pump, P
a ... Pump body.

Claims (4)

[Claims] 1. A pump body includes a pump portion having a swash plate and an operating body connected to the swash plate, and the pump portion discharges hydraulic oil by rotating the operating body relative to the swash plate. In addition, in the variable displacement pump in which the discharge capacity of the hydraulic oil discharged from the pump section is adjusted according to the inclination angle of the swash plate, the pump body has a gradient according to the discharge pressure of the hydraulic oil discharged from the pump section. While adjusting the inclination angle of the board,
A variable displacement pump provided with an angle adjusting mechanism for adjusting the tilt angle of the swash plate to a maximum tilt angle or less according to the return moment on the swash plate side when the discharge pressure exceeds a predetermined value. 2. The angle adjusting mechanism includes a first adjusting piston that moves according to a discharge pressure of hydraulic oil discharged from the pump unit, a second adjusting piston connected to the swash plate, and one end of the first adjusting piston. A biasing member that is connected to the adjusting piston and has the other end connected to the second adjusting piston, and a restriction that restricts movement of the first adjusting piston provided between the first adjusting piston and the second adjusting piston. The variable displacement pump according to claim 1, further comprising: 3. The variable displacement pump according to claim 2, wherein a hydraulic cylinder mechanism is provided between the first adjusting piston and the second adjusting piston. 4. The pump main body is provided with a throttle valve in a discharge passage through which hydraulic oil discharged from the pump portion passes, and a spool moves according to a differential pressure between the upstream side and the downstream side of the throttle valve. The variable displacement pump according to any one of claims 1 to 3, further comprising a flow rate control valve for controlling a flow rate of the hydraulic oil introduced into the angle control mechanism based on movement of the spool.