JP2002349450A - Variable displacement vane pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable displacement vane pump capable of responsively reducing a pump discharge flow rate when a relief valve is opened. SOLUTION: The variable displacement vane pump has a first cam driving pressure chamber 11 contracted with an increase of pump displacement, a second cam driving pressure chamber 12 contracted with a decrease of the pump displacement, a control valve 31 changing over driving pressure of a cam ring 3 with an increase of the pump discharge flow rate, and the relief valve 41 releasing pump discharge pressure as it rises exceeding a prescribed value, wherein, in response to the opening of the relief valve 41, the control valve 31 guides the pump discharge pressure into the first cam driving pressure chamber 11 and further releases the pump discharge pressure guided into the second cam driving pressure chamber 12, thereby improving drive responsiveness of the cam ring 3 when the relief valve 41 is opened.

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 used for, for example, a vehicle power steering device.

[0002]

2. Description of the Related Art Conventionally, as a variable displacement vane pump of this type, for example, those disclosed in Japanese Patent Application Laid-Open No. 2000-291570 and those disclosed in Japanese Patent Application Laid-Open No. 2000-161249 have disclosed cam rings surrounding each vane. A first cam drive pressure chamber and a second cam drive pressure chamber are provided on both sides of the pump, and the cam ring is eccentric with respect to the rotor axis to increase the pump discharge flow rate. A control valve that switches the driving pressure of the cam ring as the pump discharge flow increases increases the pump discharge flow when the rotor rotates at a high speed to reduce unnecessary energy consumption due to unnecessary hydraulic oil discharge. are doing.

The vane pump disclosed in Japanese Patent Application Laid-Open No. 2000-291570 is provided with a relief valve for releasing the pump discharge pressure as the pump discharge pressure rises to a predetermined value or more, and responds to the opening operation of the relief valve. Accordingly, the control valve drives the cam ring in a direction to reduce the displacement of the pump, and also reduces the energy consumption by reducing the pump discharge flow rate when the relief valve is opened.

[0004]

However, in such a conventional variable displacement vane pump, the control valve switches only the pressure of the first cam driving pressure chamber in response to the opening operation of the relief valve. Since the pump discharge pressure is always guided to the second cam drive pressure chamber, the operation response of the cam ring is low, and there is a problem that the pump discharge flow rate cannot be reduced with good response even when the relief valve is opened. .

In addition, since a throttle is not interposed in a passage connecting the valve drive pressure chamber to which the relief valve is connected and the discharge passage, the pressure in the valve drive pressure chamber is reduced in response in response to the opening operation of the relief valve. Therefore, there has been a problem that control responsiveness of the pump discharge pressure cannot be enhanced.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide a variable displacement vane pump capable of reducing a pump discharge flow rate with good response when a relief valve is opened.

[0007]

According to a first aspect of the present invention, a plurality of vanes slidably protrude from the outer periphery of a rotating rotor;
A cam ring that slidably contacts the outer peripheral end of each vane to define a pump chamber, a first cam drive pressure chamber that contracts as the pump displacement increases, and contracts as the pump displacement decreases. A second cam drive pressure chamber, a control valve for switching the drive pressure of the cam ring as the pump discharge flow rate increases, and a relief valve for releasing the pump discharge pressure as the pump discharge pressure rises above a predetermined value. In response to the opening operation of the relief valve, the control valve guides the pump discharge pressure to the first cam drive pressure chamber and releases the pressure of the second cam drive pressure chamber. .

According to a second aspect of the present invention, in the first aspect, a flow rate detection throttle interposed in a discharge passage through which a working fluid discharged from the pump chamber flows, and a pressure upstream of the flow rate detection throttle as a drive pressure of the control valve. A first valve driving pressure chamber into which the pressure is guided, and a second valve driving pressure chamber into which a pressure downstream of the flow detection throttle is guided as the driving pressure of the control valve. The relief valve releases pressure in the second valve driving pressure chamber as it rises, and a relief upstream throttle is interposed in a passage connecting the second valve driving pressure chamber and the discharge passage downstream of the flow rate detection throttle. It is characterized by having done.

According to a third aspect of the present invention, in the first or second aspect, the control valve has a hollow structure, and a relief valve is interposed inside the control valve.

[0010]

According to the first aspect of the invention, the control valve lowers the pressure of the second cam driving pressure chamber in response to the opening operation of the relief valve, whereby the operation responsiveness of the movement of the cam ring can be improved. In addition, the pump discharge flow rate can be reduced responsively, the control responsiveness of the pump discharge pressure can be increased, the energy consumption due to unnecessary discharge of hydraulic oil can be reduced, and the rise in hydraulic oil temperature can be suppressed.

When the displacement of the pump is reduced when the relief valve is opened, the flow rate of the hydraulic oil passing through the relief valve is reduced, so that the override characteristics are improved and noise is reduced.

According to the second aspect of the present invention, by providing the relief upstream throttle on the upstream side of the second valve driving pressure chamber, the amount of hydraulic oil released from the discharge passage via the relief valve when the relief valve is opened is reduced. However, with the opening of the relief valve, the pressure in the second valve driving pressure chamber is quickly reduced, the operation responsiveness of the cam ring swinging rightward is enhanced, and the control responsiveness of the pump discharge pressure is enhanced.

[0013] According to the third aspect of the present invention, the passage length for releasing the hydraulic oil in the second valve driving pressure chamber to the tank side with the opening of the relief valve can be shortened, and the control response of the pump discharge pressure can be improved.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a variable displacement 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. A variable displacement mechanism for changing the displacement of the vane pump has already been proposed by the present applicant in Japanese Patent Application Laid-Open No. 2000-161249.

As shown in FIG. 1, the vane pump 1 defines a pump chamber by slidingly contacting a plurality of vanes 2 slidably projecting from the outer periphery of a rotating rotor 9 and the outer peripheral end of each vane 2. And a working oil sucked into the pump chamber from the suction port 4 with the rotation of the rotor 9 and discharged to the discharge port 5.

As a variable displacement mechanism, the cam ring 3 is provided inside the adapter ring 6 so as to be swingable with the pin 7 as a fulcrum. With the cam ring 3 pressed against the left side of the adapter ring 6 by the urging force of the return spring 8 as shown in the figure, the amount of eccentricity of the cam ring 3 with respect to the axis of the rotor 9 is maximized, and the displacement of the pump is maximized. As the cam ring 3 swings rightward in the drawing against the return spring 8, the rotor 9
The amount of eccentricity of the cam ring 3 with respect to the shaft center becomes small, and the displacement of the pump decreases. The biasing force of the return spring 8 is applied to the plunger 22 and the feedback pin 23.
Through the cam ring 3.

As a mechanism for driving the cam ring 3, a first cam driving pressure chamber 11 and a second cam driving pressure chamber 12 are provided on both sides of the cam ring 3 between the cam ring 3 and the adapter ring 6. As the cam ring 3 swings rightward to reduce the displacement of the pump, the first cam drive pressure chamber 11 expands and the second cam drive pressure chamber 12 contracts. The cam ring 3 is held at a swing position where the pressure of the first cam driving pressure chamber 11 and the second cam driving pressure chamber 12 and the urging force of the return spring 8 are balanced.

A flow detection throttle 21 for passing hydraulic oil from the discharge port 5 is provided, and the pressure in the first cam drive pressure chamber 11 and the pressure in the second cam drive pressure chamber 12 are switched according to the differential pressure across the flow detection throttle 21. And a control valve 31.

The spool-shaped control valve 31 is slidably housed in a spool hole of the housing 10, and a first valve driving pressure chamber 32 and a second valve driving pressure chamber 33 are formed at both ends thereof. The first valve driving pressure chamber 32 communicates the passage 14 with the discharge passage 15 on the upstream side of the flow detection throttle 21. The second valve driving pressure chamber 33 communicates with the discharge passage 16 downstream of the flow detection throttle 21. Thereby, the pressure before and after the flow rate detection throttle 21 is guided to the first valve driving pressure chamber 32 and the second valve driving pressure chamber 33, respectively.

When the differential pressure across the flow rate detection throttle 21 is smaller than a predetermined value, the control valve 31 is in the closed position where it has moved to the leftmost side as shown in FIG. When the control valve 31 is in this closed position, the tank pressure is guided to the first cam drive pressure chamber 11 via the suction passage 19 and the like, and the flow rate detection is guided to the second cam drive pressure chamber 12 via the throttle 13. The pressure on the upstream side of the throttle 21 is maintained. This places the cam ring 3 on the left side to maximize pump displacement.

As the differential pressure across the flow detection throttle 21 rises above a predetermined value, the control valve 31
4 moves to the right against the urging force of 4, and the upstream pressure of the flow rate detection throttle 21 is guided to the first cam drive pressure chamber 11 via the passage 14, the first valve drive pressure chamber 32, and the throttle 35, Notch 36 and suction passage 19 are provided in second cam drive pressure chamber 12.
The tank pressure is led through the above.

That is, the control valve 31 is connected to the spring 34
When it moves to the right against the urging force, the pressure guided to the first cam drive pressure chamber 11 is switched from the tank pressure to the pump discharge pressure, and the pressure guided to the second cam drive pressure chamber 12 is changed from the pump discharge pressure to the pump discharge pressure. The pressure is switched to the tank pressure, and this pressure difference causes the cam ring 3 to swing to the right where the displacement of the pump decreases.

As the cam ring 3 swings rightward, the movement of the cam ring 3 is transmitted to the plunger 22 via the feedback pin 23, and the opening area of the flow rate detection throttle 21 is reduced by the plunger 22.

The gist of the present invention is that the vane pump 1 is provided with a relief valve 41, and the relief valve 41 is opened when the pressure of the second valve driving pressure chamber 33 of the control valve 31 rises above a predetermined value. Speak
The second valve driving pressure chamber 33 communicates with the tank. In response to the opening operation of the relief valve 41, the control valve 31
Is displaced to the left, the pump discharge pressure guided to the first cam drive pressure chamber 11 and the pump discharge pressure guided to the second cam drive pressure chamber 12 is released to the suction passage 19, and the cam ring 3 is displaced to the right to move the pump The discharge flow rate is reduced.

The second valve driving pressure chamber 33 and the flow detection throttle 2
A relief upstream-side throttle 17 is interposed in a passage connecting the discharge passage 16 downstream of 1. Thereby, the pump discharge pressure downstream of the flow rate detection throttle 21 is always guided to the second valve drive pressure chamber 33 via the relief upstream throttle 17.

The control valve 31 having a hollow structure is formed in a bottomed cylindrical shape, and has a shaft hole 37 opened in the second valve driving pressure chamber 33.
The relief valve 41 is slidably housed in the shaft hole 37. A cylindrical valve seat 42 is attached to the open end of the shaft hole 37, and the second valve driving pressure chamber 33 communicates with the suction passage 19 on the tank side through the hole of the valve seat 42. The relief valve 41 is a valve seat 42
Is pressed by the urging force of the relief spring 43. When the pressure in the second valve driving pressure chamber 33 rises to a predetermined value or more, the relief valve 41 separates from the valve seat 42 against the relief spring 43, and releases the pressure in the second valve driving pressure chamber 33 through the suction passage 19. To the tank side.

Next, the operation of the variable displacement vane pump 1 will be described.

Hydraulic oil sucked into the pump chamber from the suction port 4 with the rotation of the rotor 9 is discharged to the discharge port 5, and is discharged to the discharge passage 15, the flow detection throttle 21, and the discharge passage 16.
Through the power steering device.

When the differential pressure across the flow detection throttle 21 is smaller than a predetermined value when the vane pump 1 is rotating at a low speed, the control valve 31 is in the closed position as shown in FIG. At the same time, the pressure on the upstream side of the flow rate detection throttle 21 guided to the second cam drive pressure chamber 12 is maintained.
As a result, the cam ring 3 is held at the maximum eccentric position, and the pump discharge amount increases in proportion to the pump rotation speed.
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 flow rate detection throttle 21 rises above a predetermined value and the vane pump 1 rotates at a high speed, the control valve 31
Moves to the right against the urging force of the spring 34, the upstream pressure of the flow detection throttle 21 is guided to the first cam driving pressure chamber 11, and the notch 36 is moved to the second cam driving pressure chamber 12.
The tank pressure is led via. Accordingly, the cam ring 3 swings according to the pressure difference between the first cam drive pressure chamber 11 and the second cam drive pressure chamber 12 as the rotation speed of the vane pump 1 increases, and the eccentric amount of the cam ring 3 decreases. At the same time, the control plunger 21 following the cam ring 3 gradually reduces the opening area of the flow rate detection throttle 21. Such a reduction in the opening area of the flow detection throttle 21 and the cam ring 3
As shown in FIG. 2, the effect of reducing the amount of eccentricity
It is possible to obtain a drooping characteristic in which the pump discharge flow rate Q decreases with an increase in the pump rotation speed N at no load. In this way, during high-speed running of a vehicle in which the pump rotation speed (engine rotation speed) is high, the hydraulic assist force of the power steering device does not need to be excessive, energy consumption due to unnecessary discharge of hydraulic oil is reduced, and hydraulic oil temperature is reduced. Can be suppressed.

When the load applied to the power steering device is small and the pump discharge pressure is lower than a predetermined value, the relief valve 41 is seated on the valve seat 42 by the urging force of the relief spring 43 and is guided to the second valve driving pressure chamber 33. Hold the discharge pressure.

On the other hand, when the load applied to the power steering device increases and the pump discharge pressure rises above a predetermined value, the relief valve 41 separates from the valve seat 42 against the urging force of the relief spring 43, and the second valve is driven. The pump discharge pressure guided to the pressure chamber 33 through the relief upstream throttle 17 is released to the tank side via the suction passage 19. As the pressure in the second valve driving pressure chamber 33 decreases in this manner, the control valve 31 moves rightward against the urging force of the spring 34 and moves to the second cam driving pressure chamber 12 via the notch 36 via the notch 36. Pressure is guided. Thus, the second cam driving pressure chamber 1
As the pump discharge pressure guided to 1 is released, the cam ring 3 swings rightward to reduce the displacement of the pump, and the pump discharge flow rate and pump discharge pressure decrease.

In this way, in response to the opening operation of the relief valve 41, the control valve 31 moves the second cam drive pressure chamber 12
, The operation responsiveness of the cam ring 3 swinging rightward is increased, the pump discharge pressure is reduced with good response, the energy consumption due to unnecessary discharge of hydraulic oil is reduced, and the hydraulic oil temperature is reduced. The rise can be suppressed.

By providing a relief upstream throttle 17 on the upstream side of the second valve driving pressure chamber 33, the relief valve 4 is connected to the relief valve 4 when the relief valve 41 is opened.
Although the amount of hydraulic oil released via the first valve 1 is reduced, the second valve driving pressure chamber 33 is opened with the opening of the relief valve 41.
, The operation responsiveness of the cam ring 3 swinging rightward when the relief valve 41 is opened is increased, and the control responsiveness of the pump discharge pressure is enhanced.

When the relief valve 41 is opened, the displacement of the pump is reduced.
Since the flow rate of the hydraulic oil passing through is reduced, the override characteristics are improved and noise is reduced.

With the structure in which the relief valve 41 is housed inside the control valve 31, the length of the passage connecting the second valve driving pressure chamber 33 and the suction passage 19 on the tank side is shortened, and with the opening of the relief valve 41. The speed at which the pressure in the second valve driving pressure chamber 33 decreases can be increased, and the control response of the pump discharge pressure can be improved.

As another embodiment, a drain passage may be formed in the housing to communicate the second valve driving pressure chamber with the tank side, and a relief valve may be interposed in the drain passage.

It is apparent that the present invention is not limited to the above-described embodiment, but can be variously modified within the scope of the technical idea.

[Brief description of the drawings]

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

FIG. 2 is a characteristic diagram showing a relationship between a pump rotation speed and a pump discharge flow rate.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 vane pump 2 vane 3 cam ring 4 suction port 5 discharge port 9 rotor 11 first cam drive pressure chamber 12 second cam drive pressure chamber 16 discharge passage 17 relief upstream-side restrictor 21 flow detection restrictor 23 feedback pin 31 control valve 32 first valve Drive pressure chamber 33 Second valve drive pressure chamber 41 Relief valve 43 Relief spring

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Jun Inoue 2-4-1 Hamamatsucho, Minato-ku, Tokyo World Trade Center Building Kayaba Industry Co., Ltd. (72) Inventor Masumi Hayashi 2-chome Hamamatsucho, Minato-ku, Tokyo No. 1 World Trade Center Building F-term in Kayaba Industry Co., Ltd. (Reference) 3H040 AA03 BB01 BB11 CC22 DD11 DD23 DD33 DD37 3H044 AA02 BB05 CC19 CC22 DD03 DD10 DD13 DD24 DD35

Claims (3)

[Claims] 1. A plurality of vanes slidably protruding from the outer periphery of a rotating rotor, a cam ring which slidably contacts an outer peripheral end of each vane to define a pump chamber, and a pump displacement increases. A first cam drive pressure chamber that contracts and contracts; a second cam drive pressure chamber that contracts as the displacement of the pump decreases; a control valve that switches the drive pressure of the cam ring as the pump discharge flow rate increases; A relief valve for releasing the pump discharge pressure as the pump discharge pressure rises above a predetermined value, and the control valve guides the pump discharge pressure to the first cam drive pressure chamber in response to the opening operation of the relief valve. A variable displacement vane pump wherein the pressure in the second cam drive pressure chamber is released. 2. A flow detection throttle interposed in a discharge passage through which a working fluid discharged from the pump chamber flows, and a first valve driving pressure to which a pressure upstream of the flow detection restriction is introduced as a driving pressure of the control valve. A second valve driving pressure chamber into which a pressure downstream of the flow detection throttle is introduced as a driving pressure of the control valve, and as the pressure of the second valve driving pressure chamber increases to a predetermined value or more. The relief valve is configured to release the pressure of the second valve drive pressure chamber, and a relief upstream throttle is interposed in a passage connecting the second valve drive pressure chamber and the discharge passage downstream of the flow rate detection throttle. The variable displacement vane pump according to claim 1. 3. The variable displacement vane pump according to claim 1, wherein the control valve has a hollow structure, and the relief valve is provided inside the control valve.