JP2000104674A - Variable displacement vane pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the driving loss of a variable displacement vane pump. SOLUTION: This variable displacement vane pump 1 changes pump delivery by moving a cam ring 70 by means of differential pressure before and after a back pressure orifice 17. Where, a first delivery side back pressure chamber 3 and a second delivery side back pressure chamber 4 are divided to be contracted at the back of each vane pushed in a rotor 50. The back pressure orifice 17 is provided in the course of a first back pressure escape passage 15 for flowing out a working fluid from the first delivery side back pressure chamber 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, as a variable displacement vane pump of this type, for example, disclosed in Japanese Patent Application Laid-Open No. 4-272489, a pump ring surrounding each vane is eccentric with respect to a rotor shaft center. The discharge flow rate is increased. By reducing the flow rate of the hydraulic oil returned from the vane pump to the tank in this manner, wasteful energy consumption is reduced.

As a control mechanism for adjusting the pump discharge flow rate of the vane pump, a discharge side back pressure chamber which contracts behind each vane pushed into the rotor, a back pressure release passage through which a working fluid flows out from the discharge side back pressure chamber. And a back pressure restrictor interposed in the middle of the back pressure release passage. The cam ring is moved by the differential pressure across the back pressure restrictor to change the pump discharge amount.

[0004] Since the flow rate of hydraulic oil flowing through the back pressure relief passage is smaller than the discharge flow rate of the vane pump, the drive loss of the vane pump can be suppressed as compared with a structure in which a throttle is interposed in the pump discharge passage.

[0005]

However, in such a conventional variable displacement vane pump, when the function of preventing the vane from separating from the cam ring and the function of controlling the flow rate of hydraulic oil are both compatible, the back pressure is reduced. May be set too high, which may accelerate wear of the vane tip.

The present invention has been made in view of the above problems, and has as its object to reduce the drive loss of a variable displacement vane pump.

[0007]

According to a first aspect of the present invention, a plurality of vanes slidably protruding from a rotating rotor, a cam ring which slidably contacts an outer peripheral end of each vane to define a pump chamber, A discharge-side back-pressure chamber that contracts behind each vane pushed into the rotor, a back-pressure relief passage that allows working fluid to flow out of the discharge-side back pressure chamber, and a back-pressure throttle that is interposed in the middle of the back-pressure relief passage. The present invention is applied to a variable displacement vane pump having a variable displacement mechanism that moves a cam ring by a differential pressure across a back pressure restrictor to change a pump discharge amount.

The discharge side back pressure chamber is divided into a plurality of parts, and a plurality of back pressure relief passages for allowing the working fluid to flow out from each discharge side back pressure chamber are provided, and a variable displacement mechanism is driven in one of the back pressure relief passages. A back pressure restrictor is provided to perform the operation.

[0009]

According to the first aspect of the present invention, as the pump rotational speed increases, the flow rate of the working fluid flowing out of each discharge side back pressure chamber through each back pressure release passage increases, and The differential pressure across the iris increases. When the differential pressure across the back pressure throttle rises, the variable displacement mechanism moves the cam ring to change the pump discharge.

Since the back pressure restrictor is structured to be interposed in one of the plurality of back pressure relief passages, the driving of the vane pump is performed without imparting resistance to the working fluid flowing through the other back pressure relief passages. Loss can be reduced. That is, by dividing the discharge side back pressure chamber into a plurality, the flow rate of the working fluid flowing through one back pressure relief passage can be reduced, and wasteful energy consumption can be reduced accordingly.

Further, the back pressure of the vane at the discharge port facing the portion where separation of the vane is unlikely to occur can be set low, and wear of the vane tip can be suppressed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a vane pump provided as a hydraulic pressure source of a power steering device mounted on a vehicle will be described below with reference to the accompanying drawings.

As shown in FIG. 1, the vane pump 1 includes a rotor 50 rotatably housed in a casing, a plurality of vanes 20 slidably projecting from the rotor 50, and a cam ring 70 surrounding each vane 20. Is composed mainly of.

Rotation from the engine is transmitted to the rotor 50 via a drive shaft (not shown), a pulley, a belt, and the like.
Rotate counterclockwise as indicated by the arrow in the figure. Each vane 20 slides its outer peripheral end against the inner peripheral surface of the cam ring 70 while moving in and out of the rotating rotor 50 in the radial direction to expand and contract the pump chamber.

A suction port 30 and a discharge port 40 are opened in the valve plate 10 defining the side of the pump chamber. The suction port 30 and the discharge port 40 are each curved and open along the outer periphery of the rotor 50. Hydraulic oil is sucked from the suction port 30 into the pump chamber that expands between the vanes 20 as the rotor 50 rotates, and hydraulic oil is discharged to the discharge port 40 from the pump chamber that contracts between the vanes 20. The suction port 30 is connected to the tank 12 through the suction passage 11.
The discharge port 40 communicates with a hydraulic cylinder of a power steering device (not shown) via the pump discharge passage 13.

As a variable displacement mechanism for changing the pump discharge flow rate, an adapter ring 90 for rotatably accommodating the cam ring 70 is provided.
Is rotatably supported by the adapter ring 90 via the.
The cross section of the inner peripheral surface of the cam ring 70 is formed in a substantially circular shape, and the pump discharge flow rate becomes zero when the center Oc of the cam ring 70 is on the axis Op of the rotor 50 as shown in the figure. As the amount of eccentricity of the cam ring center Oc with respect to the rotor axis Op increases, the displacement of the pump increases, and the pump discharge flow rate increases.

A pair of first cam pressure chambers 7 and second cam pressure chambers 8 are defined with a cam ring 70 interposed therebetween. A seal member 22 that is in contact with the outer peripheral upper portion of the cam ring 70 is interposed at the upper inner peripheral portion of the adapter ring 90, and the first cam pressure chamber 7
And the second cam pressure chamber 8 is sealed. The drive pressure guided to the first cam pressure chamber 7 and the second cam pressure chamber 8 causes the adapter ring 90 to rotate clockwise against the spring 25, so that the eccentric amount of the cam ring center Oc with respect to the rotor shaft Op is small. That is, the pump discharge flow rate is reduced.

Eight slits 51 are formed radially on the rotor 50 to slidably fit the eight vanes 20, and three slits 51 are provided between the inner end of each slit 51 and the valve plate 10. Back pressure chambers 2, 3, and 4 are defined. Each back pressure chamber 2,
Each vane 20 is slit 5 by the pressure guided to 3, 4
1 is pushed out in the radial direction.

The suction-side back pressure chamber 2 is located behind each of the vanes 20 facing the suction port 41, and its volume increases as the rotor 50 rotates. Hydraulic oil flows into the suction side back pressure chamber 2 from a passage 14 branched from the pump discharge passage 13.

The first and second discharge side back pressure chambers 3 and 4 are located behind each vane 20 facing the discharge port 42, and the volume thereof decreases as the rotor 50 rotates. First and second back pressure relief passages 15 and 16 connecting the first and second discharge side back pressure chambers 3 and 4 and the pump discharge passage 13 are provided. Hydraulic oil discharged from the first and second discharge side back pressure chambers 3 and 4 flows out to the pump discharge passage 13 through the first and second back pressure relief passages 15 and 16.

First discharge side back pressure chamber 3 and pump discharge passage 13
In the middle of the first back pressure relief passage 15 connecting the
Is interposed. A first back pressure relief passage 15 upstream of the back pressure restrictor 17 communicates with the first cam pressure chamber 7 through a passage 18, and a first back pressure relief passage 15 downstream of the back pressure restrictor 17.
Is connected to the second cam pressure chamber 8 through the passage 19. That is, the cam ring 70 rotates rightward in FIG. 1 against the spring 25 due to the differential pressure across the back pressure throttle 17.

Second discharge side back pressure chamber 4 and pump discharge passage 13
In the middle of the second back pressure relief passage 16 connecting the
Is interposed.

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

As the pump speed increases, the amount of hydraulic oil flowing from the first discharge side back pressure chamber 3 to the pump discharge passage 13 increases, and the differential pressure across the back pressure throttle 17 increases.

While the vane pump 1 is stopped and the pump rotation speed rises to a predetermined value, the cam ring 70 is positioned on the left side by the urging force of the spring 25 and the rotor shaft Op
Is maintained at a state where the eccentric amount of the cam ring center Oc is maximized, and the amount of hydraulic oil flowing through the pump discharge passage increases as the rotation speed of the rotor 50 increases. Thus, the pump discharge pressure is sufficiently increased from the time of low-speed running of the vehicle, and the hydraulic assist force required for the power steering device can be secured.

When the differential pressure across the back pressure throttle 17 rises above a predetermined value in the operating region where the pump rotation speed rises above a predetermined value, the cam ring 70 counterclockwise resists the urging force of the spring 25. The pump rotates in the circumferential direction, and the displacement of the pump decreases. By automatically adjusting the position of the cam ring 70 and controlling the pump discharge amount, the flow rate of the working oil returned from the vane pump 1 to the tank 12 is reduced, thereby reducing unnecessary energy consumption.

The back pressure throttle 17 flows through the second back pressure relief passage 16 because it is interposed in the first back pressure relief passage 15 connecting the first discharge side back pressure chamber 3 and the pump discharge passage 13. The drive loss of the vane pump 1 can be suppressed without imparting resistance to the hydraulic oil. That is, by providing the first and second discharge side back pressure chambers 3 and 4 separately, the flow rate of the working oil flowing through the back pressure restrictor 17 can be reduced, and wasteful energy consumption can be reduced accordingly.

Further, as another embodiment, the first back pressure chamber is disposed in a pressure transition process portion where the separation of the vane is apt to occur, so that the second back pressure chamber facing the portion where the separation of the vane is unlikely to occur. It is possible to set the back pressure of the room low,
The pressing force of the vane is reduced, and the wear at the tip of the vane can be suppressed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a vane pump according to an embodiment of the present invention.

[Description of Signs] 1 Vane pump 3 First discharge side back pressure chamber 4 Second discharge side back pressure chamber 7 First cam pressure chamber 8 Second cam pressure chamber 10 Valve plate 13 Pump discharge passage 15 First back pressure relief passage 16 Second back pressure relief passage 17 Back pressure restrictor 20 Vane 30 Suction port 40 Discharge port 50 Rotor 70 Cam ring

Claims (1)

[Claims] A plurality of vanes slidably projecting from a rotating rotor; a cam ring defining an outer peripheral end of each of the vanes in sliding contact with each other to define a pump chamber; and a plurality of vanes pushed into the rotor. A discharge-side back-pressure chamber that contracts behind, a back-pressure relief passage for allowing a working fluid to flow out of the discharge-side back-pressure chamber, a back-pressure restriction interposed in the middle of the back-pressure release path, and the back-pressure restriction And a variable displacement mechanism that moves the cam ring by the front-rear differential pressure to change the pump discharge amount, wherein the discharge-side back pressure chamber is divided into a plurality of sections, and A variable displacement type comprising: a plurality of the back pressure relief passages for allowing a working fluid to flow out; and the back pressure restrictor for driving the variable displacement mechanism is interposed in one of the back pressure relief passages. Vane Pom .