Title:
VARIABLE DISPLACEMENT VANE PUMP
Kind Code:
A1


Abstract:
A variable displacement vane pump includes a drive shaft; a rotor formed with slots; vanes received by the slots; a cam ring which can become eccentric and cooperates with the rotor and vanes to define pump chambers; suction and discharge ports opened to the pump chambers; a sealing member dividing a space on an outer circumferential surface of the cam ring into first and second fluid pressure chambers; a metering orifice formed on a discharge passage connected with the discharge port; and a pressure control section adapted to control a pressure which is introduced into the first or second fluid pressure chamber. The pressure control section includes a high pressure chamber into which an upstream pressure of metering orifice is introduced, a medium pressure chamber into which a downstream pressure of metering orifice is introduced, and a low pressure chamber connected with a reservoir tank. The vane pump further includes a relief valve adapted to drain the downstream pressure of metering orifice to the reservoir tank; and a variable metering mechanism configured to narrow an area of the metering orifice at least when the relief valve is opened.



Inventors:
Yamamuro, Shigeaki (Zushi-shi, JP)
Application Number:
12/191695
Publication Date:
02/19/2009
Filing Date:
08/14/2008
Assignee:
HITACHI, LTD.
Primary Class:
International Classes:
F04B49/00
View Patent Images:
Related US Applications:



Primary Examiner:
LETTMAN, BRYAN MATTHEW
Attorney, Agent or Firm:
FOLEY & LARDNER LLP (WASHINGTON, DC, US)
Claims:
What is claimed is:

1. A variable displacement vane pump comprising: a pump body; a drive shaft supported rotatably by the pump body; a rotor disposed inside the pump body and adapted to be rotatably driven by the drive shaft, the rotor being formed with a plurality of slots spaced from each other in a circumferential direction of the rotor; a plurality of vanes received by the slots so as to be movable out from the slots and into the slots; a cam ring formed in an annular shape and disposed inside the pump body to permit the cam ring to become eccentric relative to the drive shaft, the cam ring cooperating with the rotor and the vanes to define a plurality of pump chambers on an inner circumferential side of the cam ring; a first plate member and a second plate member disposed on axially both sides of the cam ring; a suction port provided on a side of at least one of the first plate member and the second plate member and opened to at least one of the plurality of pump chambers; a discharge port provided on a side of at least one of the first plate member and the second plate member and opened to at least one of the plurality of pump chambers; a sealing member provided on an outer circumferential side of the cam ring, the sealing member dividing a space on an outer circumferential surface of the cam ring into a first fluid pressure chamber and a second fluid pressure chamber, wherein a flow rate of working fluid discharged from the discharge port is increased when the cam ring moves to the first fluid pressure chamber, wherein the flow rate of working fluid discharged from the discharge port is decreased when the cam ring moves to the second fluid pressure chamber; a metering orifice formed on a discharge passage connected with the discharge port; a pressure control section adapted to control a pressure which is introduced into the first fluid pressure chamber or the second fluid pressure chamber, the pressure control section comprising a high pressure chamber into which an upstream pressure of the metering orifice is introduced, a medium pressure chamber into which a downstream pressure of the metering orifice is introduced, and a low pressure chamber connected with a reservoir tank for storing working fluid; a relief valve provided between a downstream side of the metering orifice and the reservoir tank, the relief valve being adapted to be opened by receiving a pressure greater than or equal to a predetermined level and thereby to drain the downstream pressure of the metering orifice to the reservoir tank; and a variable metering mechanism configured to narrow a cross-sectional area of opening portion of the metering orifice at least when the relief valve is opened.

2. The variable displacement vane pump as claimed in claim 1, wherein the cam ring is adapted to swing so as to gradually block the opening portion of the metering orifice, the variable metering mechanism being achieved by the metering orifice and the cam ring; and the metering orifice comprises the opening portion formed in an axial end surface of the first plate member or the second plate member.

3. The variable displacement vane pump as claimed in claim 2, wherein the variable metering mechanism is configured to gradually narrow the opening portion of the metering orifice after the cam ring has swung to its position having a predetermined angle.

4. The variable displacement vane pump as claimed in claim 2, wherein a circumferential width of the opening portion of the metering orifice is greater than a radial width thereof.

5. The variable displacement vane pump as claimed in claim 4, wherein the opening portion of the metering orifice is formed in an elliptical shape or a slot shape.

6. The variable displacement vane pump as claimed in claim 4, wherein the metering orifice comprises a plurality of holes.

7. The variable displacement vane pump as claimed in claim 2, further comprising a pilot orifice provided on a passage connecting the discharge port with the high pressure chamber.

8. The variable displacement vane pump as claimed in claim 2, further comprising a damper orifice provided on a passage connecting the metering orifice with the medium pressure chamber.

9. The variable displacement vane pump as claimed in claim 1, wherein the variable displacement vane pump further comprises a piston adapted to move in response to a swing of the cam ring; and the metering orifice is formed in the piston.

10. The variable displacement vane pump as claimed in claim 1, wherein the variable metering mechanism is configured to vary the area of opening portion of the metering orifice on the basis of a downstream pressure of the relief valve.

11. The variable displacement vane pump as claimed in claim 10, wherein the variable metering mechanism is achieved by a spool adapted to controllably vary the area of opening portion of the metering orifice by moving relative to the metering orifice.

12. A variable displacement vane pump comprising: a pump body; a drive shaft supported rotatably by the pump body; a rotor disposed inside the pump body and adapted to be rotatably driven by the drive shaft, the rotor being formed with a plurality of slots spaced from each other in a circumferential direction of the rotor; a plurality of vanes received by the slots so as to be movable out from the slots and into the slots; a cam ring formed in an annular shape and disposed inside the pump body to permit the cam ring to become eccentric relative to the drive shaft, the cam ring cooperating with the rotor and the vanes to define a plurality of pump chambers on an inner circumferential side of the cam ring; a first plate member and a second plate member disposed on axially both sides of the cam ring; a suction port provided on a side of at least one of the first plate member and the second plate member and opened to at least one of the plurality of pump chambers; a discharge port provided on a side of at least one of the first plate member and the second plate member and opened to at least one of the plurality of pump chambers; a sealing member provided on an outer circumferential side of the cam ring, the sealing member dividing a space on an outer circumferential surface of the cam ring into a first fluid pressure chamber and a second fluid pressure chamber, wherein a flow rate of working fluid discharged from the discharge port is increased when the cam ring moves to the first fluid pressure chamber, wherein the flow rate of working fluid discharged from the discharge port is decreased when the cam ring moves to the second fluid pressure chamber; a metering orifice formed on a discharge passage connected with the discharge port; a pressure control section adapted to control a pressure which is introduced into the first fluid pressure chamber or the second fluid pressure chamber, the pressure control section comprising a high pressure chamber into which an upstream pressure of the metering orifice is introduced, a medium pressure chamber into which a downstream pressure of the metering orifice is introduced, and a low pressure chamber connected with a reservoir tank for storing working fluid; a relief valve provided between a downstream side of the metering orifice and the reservoir tank, the relief valve being adapted to be opened by receiving a pressure greater than or equal to a predetermined level and thereby to drain the downstream pressure of the metering orifice into the reservoir tank; and a variable metering mechanism configured to narrow a cross-sectional area of opening portion of the metering orifice when a discharge pressure on a downstream side of the discharge port is higher than or equal to a predetermined pressure.

13. The variable displacement vane pump as claimed in claim 12, wherein the variable metering mechanism is achieved by a fluid-pressure sensor adapted to sense the pressure discharged from the discharge port and an electromagnetic valve adapted to be opened based on a sensed signal of the fluid-pressure sensor.

14. The variable displacement vane pump as claimed in claim 12, wherein the variable metering mechanism is achieved by a spool adapted to controllably vary the area of opening portion of the metering orifice by moving relative to the metering orifice.

15. A variable displacement vane pump comprising: a pump body; a drive shaft supported rotatably by the pump body; a rotor disposed inside the pump body and adapted to be rotatably driven by the drive shaft, the rotor being formed with a plurality of slots spaced from each other in a circumferential direction of the rotor; a plurality of vanes received by the slots so as to be movable out from the slots and into the slots; a cam ring formed in an annular shape and disposed inside the pump body to permit the cam ring to become eccentric relative to the drive shaft, the cam ring cooperating with the rotor and the vanes to define a plurality of pump chambers on an inner circumferential side of the cam ring; a first plate member and a second plate member disposed on axially both sides of the cam ring; a suction port provided on a side of at least one of the first plate member and the second plate member and opened to at least one of the plurality of pump chambers; a discharge port provided on a side of at least one of the first plate member and the second plate member and opened to at least one of the plurality of pump chambers; a sealing member provided on an outer circumferential side of the cam ring, the sealing member dividing a space on an outer circumferential surface of the cam ring into a first fluid pressure chamber and a second fluid pressure chamber, wherein a flow rate of working fluid discharged from the discharge port is increased when the cam ring moves to the first fluid pressure chamber, wherein the flow rate of working fluid discharged from the discharge port is decreased when the cam ring moves to the second fluid pressure chamber; a metering orifice formed on a discharge passage connected with the discharge port; a pressure control section adapted to control a pressure which is introduced into the first fluid pressure chamber or the second fluid pressure chamber, the pressure control section comprising a high pressure chamber into which an upstream pressure of the metering orifice is introduced, a medium pressure chamber into which a downstream pressure of the metering orifice is introduced, and a low pressure chamber connected with a reservoir tank for storing working fluid; a relief valve provided between a downstream side of the metering orifice and the reservoir tank, the relief valve being adapted to be opened by receiving a pressure greater than or equal to a predetermined level and thereby to drain the downstream pressure of the metering orifice into the reservoir tank; and a variable metering mechanism configured to narrow a cross-sectional area of opening portion of the metering orifice to a larger extent as the eccentricity of the cam ring becomes smaller when the relief valve is open.

16. The variable displacement vane pump as claimed in claim 15, wherein the cam ring is adapted to swing so as to gradually block the opening portion of the metering orifice, the variable metering mechanism being achieved by the metering orifice and the cam ring; and the metering orifice comprises the opening portion formed in an axial end surface of the first plate member or the second plate member.

17. The variable displacement vane pump as claimed in claim 15, wherein the variable metering mechanism is configured to gradually narrow the opening portion of the metering orifice after the cam ring has swung to its position having a predetermined angle.

18. The variable displacement vane pump as claimed in claim 15, further comprising a pilot orifice provided on a passage connecting the discharge port with the high pressure chamber.

19. A variable displacement vane pump comprising: a pump body; a drive shaft supported rotatably by the pump body; a rotor disposed inside the pump body and adapted to be rotatably driven by the drive shaft, the rotor being formed with a plurality of slots spaced from each other in a circumferential direction of the rotor; a plurality of vanes received by the slots so as to be movable out from the slots and into the slots; a cam ring formed in an annular shape and disposed inside the pump body to permit the cam ring to become eccentric relative to the drive shaft, the cam ring cooperating with the rotor and the vanes to define a plurality of pump chambers on an inner circumferential side of the cam ring; a first plate member and a second plate member disposed on axially both sides of the cam ring; a suction port provided on a side of at least one of the first plate member and the second plate member and opened to at least one of the plurality of pump chambers; a discharge port provided on a side of at least one of the first plate member and the second plate member and opened to at least one of the plurality of pump chambers; a sealing member provided on an outer circumferential side of the cam ring, the sealing member dividing a space on an outer circumferential surface of the cam ring into a first fluid pressure chamber and a second fluid pressure chamber, wherein a flow rate of working fluid discharged from the discharge port is increased when the cam ring moves to the first fluid pressure chamber, wherein the flow rate of working fluid discharged from the discharge port is decreased when the cam ring moves to the second fluid pressure chamber; a metering orifice formed on a discharge passage connected with the discharge port; a pressure control section adapted to control a pressure which is introduced into the first fluid pressure chamber or the second fluid pressure chamber, the pressure control section comprising a high pressure chamber into which an upstream pressure of the metering orifice is introduced, a medium pressure chamber into which a downstream pressure of the metering orifice is introduced, and a low pressure chamber connected with a reservoir tank for storing working fluid; a fluid-pressure sensor adapted to sense a pressure discharged from the discharge port; a relief valve adapted to drain the downstream pressure of the metering orifice to the reservoir tank, and a pressure-using device adapted to use a pressure supplied from the discharge port; and a variable metering mechanism configured to narrow a cross-sectional area of flow passage of the metering orifice on the basis of an output signal of the fluid-pressure sensor.

20. The variable displacement vane pump as claimed in claim 19, wherein the variable metering mechanism is achieved by an electromagnetic valve adapted to be opened based on the output signal of the fluid-pressure sensor.

Description:

BACKGROUND OF THE INVENTION

The present invention relates to a variable displacement vane pump, more particularly to a variable displacement vane pump for a power steering apparatus.

Japanese Patent Application Publication No. 2003-21076 discloses a previously-proposed variable displacement vane pump. In this technique, the variable displacement vane pump includes a relief valve installed inside a control valve. This relief valve serves to release a discharge-side pressure into a reservoir tank when the discharge-side pressure becomes higher than or equal to a predetermined pressure.

SUMMARY OF THE INVENTION

However, in the above technique, in the case of trying to enhance a fuel economy by reducing a relief amount of working fluid from the relief valve by means of a narrowing of a pilot orifice, the relief valve itself is vibrated due to a vibration of working fluid caused when the working fluid passes through the pilot orifice. If the relief amount is reduced by use of a damper orifice instead of the pilot orifice in order to avoid this vibration, the working fluid leaks from an annular portion of the control valve.

Accordingly, a pressure difference of valve is reduced so that a control flow rate under a high pressure state is increased. Thereby, a pump workload is increased so as to cancel out an effect of reducing the fuel consumption which is obtained by the reduction of relief amount of working fluid. There has been such a problem.

It is therefore an object of the present invention to provide a variable displacement vane pump devised to reduce the relief amount and to suppress the increase in pump workload so as to enhance the fuel economy.

According to one aspect of the present invention, there is provided a variable displacement vane pump comprising: a pump body; a drive shaft supported rotatably by the pump body; a rotor disposed inside the pump body and adapted to be rotatably driven by the drive shaft, the rotor being formed with a plurality of slots spaced from each other in a circumferential direction of the rotor; a plurality of vanes received by the slots so as to be movable out from the slots and into the slots; a cam ring formed in an annular shape and disposed inside the pump body to permit the cam ring to become eccentric relative to the drive shaft, the cam ring cooperating with the rotor and the vanes to define a plurality of pump chambers on an inner circumferential side of the cam ring; a first plate member and a second plate member disposed on axially both sides of the cam ring; a suction port provided on a side of at least one of the first plate member and the second plate member and opened to at least one of the plurality of pump chambers; a discharge port provided on a side of at least one of the first plate member and the second plate member and opened to at least one of the plurality of pump chambers; a sealing member provided on an outer circumferential side of the cam ring, the sealing member dividing a space on an outer circumferential surface of the cam ring into a first fluid pressure chamber and a second fluid pressure chamber, wherein a flow rate of working fluid discharged from the discharge port is increased when the cam ring moves to the first fluid pressure chamber, wherein the flow rate of working fluid discharged from the discharge port is decreased when the cam ring moves to the second fluid pressure chamber; a metering orifice formed on a discharge passage connected with the discharge port; a pressure control section adapted to control a pressure which is introduced into the first fluid pressure chamber or the second fluid pressure chamber, the pressure control section comprising a high pressure chamber into which an upstream pressure of the metering orifice is introduced, a medium pressure chamber into which a downstream pressure of the metering orifice is introduced, and a low pressure chamber connected with a reservoir tank for storing working fluid; a relief valve provided between a downstream side of the metering orifice and the reservoir tank, the relief valve being adapted to be opened by receiving a pressure greater than or equal to a predetermined level and thereby to drain the downstream pressure of the metering orifice to the reservoir tank; and a variable metering mechanism configured to narrow a cross-sectional area of opening portion of the metering orifice at least when the relief valve is opened.

According to another aspect of the present invention, there is provided a variable displacement vane pump comprising: a pump body; a drive shaft supported rotatably by the pump body; a rotor disposed inside the pump body and adapted to be rotatably driven by the drive shaft, the rotor being formed with a plurality of slots spaced from each other in a circumferential direction of the rotor; a plurality of vanes received by the slots so as to be movable out from the slots and into the slots; a cam ring formed in an annular shape and disposed inside the pump body to permit the cam ring to become eccentric relative to the drive shaft, the cam ring cooperating with the rotor and the vanes to define a plurality of pump chambers on an inner circumferential side of the cam ring; a first plate member and a second plate member disposed on axially both sides of the cam ring; a suction port provided on a side of at least one of the first plate member and the second plate member and opened to at least one of the plurality of pump chambers; a discharge port provided on a side of at least one of the first plate member and the second plate member and opened to at least one of the plurality of pump chambers; a sealing member provided on an outer circumferential side of the cam ring, the sealing member dividing a space on an outer circumferential surface of the cam ring into a first fluid pressure chamber and a second fluid pressure chamber, wherein a flow rate of working fluid discharged from the discharge port is increased when the cam ring moves to the first fluid pressure chamber, wherein the flow rate of working fluid discharged from the discharge port is decreased when the cam ring moves to the second fluid pressure chamber; a metering orifice formed on a discharge passage connected with the discharge port; a pressure control section adapted to control a pressure which is introduced into the first fluid pressure chamber or the second fluid pressure chamber, the pressure control section comprising a high pressure chamber into which an upstream pressure of the metering orifice is introduced, a medium pressure chamber into which a downstream pressure of the metering orifice is introduced, and a low pressure chamber connected with a reservoir tank for storing working fluid; a relief valve provided between a downstream side of the metering orifice and the reservoir tank, the relief valve being adapted to be opened by receiving a pressure greater than or equal to a predetermined level and thereby to drain the downstream pressure of the metering orifice into the reservoir tank; and a variable metering mechanism configured to narrow a cross-sectional area of opening portion of the metering orifice when a discharge pressure on a downstream side of the discharge port is higher than or equal to a predetermined pressure.

According to still another aspect of the present invention, there is provided a variable displacement vane pump comprising: a pump body; a drive shaft supported rotatably by the pump body; a rotor disposed inside the pump body and adapted to be rotatably driven by the drive shaft, the rotor being formed with a plurality of slots spaced from each other in a circumferential direction of the rotor; a plurality of vanes received by the slots so as to be movable out from the slots and into the slots; a cam ring formed in an annular shape and disposed inside the pump body to permit the cam ring to become eccentric relative to the drive shaft, the cam ring cooperating with the rotor and the vanes to define a plurality of pump chambers on an inner circumferential side of the cam ring; a first plate member and a second plate member disposed on axially both sides of the cam ring; a suction port provided on a side of at least one of the first plate member and the second plate member and opened to at least one of the plurality of pump chambers; a discharge port provided on a side of at least one of the first plate member and the second plate member and opened to at least one of the plurality of pump chambers; a sealing member provided on an outer circumferential side of the cam ring, the sealing member dividing a space on an outer circumferential surface of the cam ring into a first fluid pressure chamber and a second fluid pressure chamber, wherein a flow rate of working fluid discharged from the discharge port is increased when the cam ring moves to the first fluid pressure chamber, wherein the flow rate of working fluid discharged from the discharge port is decreased when the cam ring moves to the second fluid pressure chamber; a metering orifice formed on a discharge passage connected with the discharge port; a pressure control section adapted to control a pressure which is introduced into the first fluid pressure chamber or the second fluid pressure chamber, the pressure control section comprising a high pressure chamber into which an upstream pressure of the metering orifice is introduced, a medium pressure chamber into which a downstream pressure of the metering orifice is introduced, and a low pressure chamber connected with a reservoir tank for storing working fluid; a relief valve provided between a downstream side of the metering orifice and the reservoir tank, the relief valve being adapted to be opened by receiving a pressure greater than or equal to a predetermined level and thereby to drain the downstream pressure of the metering orifice into the reservoir tank; and a variable metering mechanism configured to narrow a cross-sectional area of opening portion of the metering orifice to a larger extent as the eccentricity of the cam ring becomes smaller when the relief valve is open.

According to still another aspect of the present invention, there is provided a variable displacement vane pump comprising: a pump body; a drive shaft supported rotatably by the pump body; a rotor disposed inside the pump body and adapted to be rotatably driven by the drive shaft, the rotor being formed with a plurality of slots spaced from each other in a circumferential direction of the rotor; a plurality of vanes received by the slots so as to be movable out from the slots and into the slots; a cam ring formed in an annular shape and disposed inside the pump body to permit the cam ring to become eccentric relative to the drive shaft, the cam ring cooperating with the rotor and the vanes to define a plurality of pump chambers on an inner circumferential side of the cam ring; a first plate member and a second plate member disposed on axially both sides of the cam ring; a suction port provided on a side of at least one of the first plate member and the second plate member and opened to at least one of the plurality of pump chambers; a discharge port provided on a side of at least one of the first plate member and the second plate member and opened to at least one of the plurality of pump chambers; a sealing member provided on an outer circumferential side of the cam ring, the sealing member dividing a space on an outer circumferential surface of the cam ring into a first fluid pressure chamber and a second fluid pressure chamber, wherein a flow rate of working fluid discharged from the discharge port is increased when the cam ring moves to the first fluid pressure chamber, wherein the flow rate of working fluid discharged from the discharge port is decreased when the cam ring moves to the second fluid pressure chamber; a metering orifice formed on a discharge passage connected with the discharge port; a pressure control section adapted to control a pressure which is introduced into the first fluid pressure chamber or the second fluid pressure chamber, the pressure control section comprising a high pressure chamber into which an upstream pressure of the metering orifice is introduced, a medium pressure chamber into which a downstream pressure of the metering orifice is introduced, and a low pressure chamber connected with a reservoir tank for storing working fluid; a fluid-pressure sensor adapted to sense a pressure discharged from the discharge port; a relief valve adapted to drain the downstream pressure of the metering orifice to the reservoir tank, and a pressure-using device adapted to use a pressure supplied from the discharge port; and a variable metering mechanism configured to narrow a cross-sectional area of flow passage of the metering orifice on the basis of an output signal of the fluid-pressure sensor.

The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a vane pump in a first embodiment according to the present invention, taken in an axial direction of the vane pump.

FIG. 2 is a cross-sectional view of the vane pump in the first embodiment, taken in a radial direction of the vane pump (at maximum swing position).

FIG. 3 is an enlarged cross-sectional view near a variable metering mechanism.

FIG. 4 is a view showing the relation between an opening area of metering orifice and a swing amount of cam ring.

FIG. 5 is a view showing an example in which a minimum secured area of the metering orifice is provided as a separate hole.

FIG. 6 is an enlarged view of FIG. 5.

FIG. 7 is a view showing an example in which the metering orifice is provided as a plurality of round holes.

FIG. 8 is a view showing an example in which a damper orifice is provided outside a first housing.

FIG. 9 is a view showing an example in which a piston adapted to move in and out in response to the swing of cam ring is formed with the metering orifice.

FIG. 10 is a cross-sectional view of a vane pump in a second embodiment according to the present invention, taken in an axial direction of the vane pump.

FIG. 11 is a cross-sectional view of the vane pump in the second embodiment, taken in a radial direction of the vane pump.

FIG. 12 is a view showing an example in which a spool is provided as an electromagnetic valve in the second embodiment.

FIG. 13 is a view showing an example in which a relief valve is provided outside a housing in the second embodiment.

FIG. 14 is a view showing an example in which a shape of the spool is changed in a manner that the spool is operated by use of a drain pressure produced at a downstream side of the relief valve in the second embodiment.

FIG. 15 is an enlarged view of FIG. 14.

DETAILED DESCRIPTION OF THE INVENTION

Reference will hereinafter be made to the drawings in order to facilitate a better understanding of the present invention. Variable displacement vane pumps according to the present invention will be explained below based on embodiments of the present invention, referring to the drawings.

First Embodiment

[Overview Structure of Vane Pump]

A first embodiment according to the present invention will now be explained. FIG. 1 is a cross-sectional view of a vane pump 1 in the first embodiment, taken in an axial direction of the vane pump 1. FIG. 2 is a cross-sectional view of the vane pump 1, taken in a radial direction of the vane pump 1. FIG. 2 shows the state where a cam ring 4 has moved to its most negative position relative to y-axis (maximum eccentricity amount). In FIG. 2, Oc denotes a center of the cam ring 4, and OR denotes a center of a drive shaft 2.

X-axis is defined as the axial direction of the drive shaft 2, and a positive direction of x-axis is defined as a direction in which the drive shaft 2 is inserted into first and second housings 11 and 12. Moreover, y-axis is defined as an axial direction of a spring 91 (see FIG. 2) for regulating a swing (oscillation) of the cam ring 4. A negative direction of y-axis is defined as a direction in which the spring 91 biases or urges the cam ring 4. Z-axis is defined as an axis orthogonal to x-axis and y-axis, and a positive direction of z-axis is defined as a direction toward an inlet port IN.

The vane pump 1 includes the drive shaft 2, a rotor 3, the cam ring 4, an adapter ring 5 and a pump body 10. The drive shaft 2 is connected through a pulley with an engine. The drive shaft 2 is supported rotatably by the pump body 10, and rotates integrally with the rotor 3.

An outer circumferential portion of the rotor 3 is formed with a plurality of slots 31 as axial grooves. The plurality of slots 31 are given radially in the rotor 3, and are spaced from each other in the circumferential direction of rotor 3. A vane 32 is inserted into or received by each slot 31 to allow the vane 32 to rise and fall in the radial direction of rotor 3. That is, each vane 32 can move in the outward and inward directions of the slot 31. Each slot 31 is continuously connected with a back pressure chamber 33 which is provided at a radially-inner end of the slot 31 and which is supplied with a fluid pressure. This fluid pressure biases or urges the vane 32 outwardly in the radial direction.

The pump body 10 includes a first housing 11 and a second housing 12 (corresponding to a first plate member according to the present invention). The first housing 11 is shaped like a cup having its bottom (11a) and is opening in the positive direction of x-axis. A pressure plate 6 (corresponding to a second plate member according to the present invention) in the form of a circular disc is disposed on the bottom portion 11a of first housing 11. That is, the first housing 11 accommodates the pressure plate 6 on the bottom portion 11a. The first housing 11 includes a pump element receiving portion 11b at an inner circumferential portion of first housing 11. The pump element receiving portion 11b accommodates or receives the adapter ring 5, cam ring 4 and rotor 3 which are located adjacent to the pressure plate 6 in the positive direction of x-axis.

The second housing 12 fluid-tightly abuts on the adapter ring 5, cam ring 4 and rotor 3 from the positive side of x-axis. The adapter ring 5, cam ring 4 and rotor 3 are supported by the pressure plate 6 and the second housing 12 so as to be sandwiched between the pressure plate 6 and the second housing 12.

A suction port 62 and a discharge port 63 are provided in an x-axis positive side surface 61 of the pressure plate 6. Similarly, a suction port 121 and a discharge port 122 are provided in an x-axis negative side surface 120 of the second housing 12. The suction ports 62 and 121 are connected with the inlet port IN. The discharge ports 63 and 122 are connected with an outlet port OUT. The suction and discharge ports 62, 63, 121 and 122 function to supply and discharge the working fluid to (from) a pump chamber B formed between the rotor 3 and the cam ring 4. The inlet port IN is connected through a fluid passage 7a with a control valve 7.

The adapter ring 5 is a substantially elliptical annular member having a major axis along the y-axis and a miner axis along the z-axis. The outer circumferential side (i.e., radially outer side) of the adapter ring 5 is surrounded by the inner circumferential surface of the first housing 11, and the inner circumferential side (i.e., radially inner side) of the adapter ring 5 surrounds or accommodates the cam ring 4. The adapter ring 5 is restrained by a pin 40 from rotating relative to the first housing 11, namely so as not to rotate within the first housing 11 at the time of driving operation of the vane pump 1.

The cam ring 4 is an annular member having a substantially complete roundness (i.e., almost perfect circle). An outer diameter of cam ring 4 is substantially equal to the miner axis of elliptic bore of the adapter ring 5. Since the cam ring 4 is received inside the substantially elliptical adapter ring 5, a fluid pressure chamber “A” is formed between an inner circumferential surface 53 of the adapter ring 5 and an outer circumferential surface of the cam ring 4. The cam ring 4 can be swung in the direction of y-axis within the adapter ring 5.

As shown in FIG. 2, a sealing member 50 is provided in a z-axis-positive-directional end portion of the inner circumferential surface 53 of adapter ring 5. On the other hand, the adapter ring 5 is formed with a supporting surface N at a z-axis-negative-directional end portion. Specifically, the sealing member 50 is located in the most advanced position of the inner circumferential surface 53 of adapter ring 5 in the positive direction of z-axis, and the supporting surface N is located in the most advanced position of the inner circumferential surface 53 of adapter ring 5 in the negative direction of z-axis. The cam ring 4 is swingable about a swing fulcrum given on the supporting surface N. The cam ring 4 is in contact with the supporting surface N and is swingably supported on the supporting surface N of the adapter ring 5 in the negative direction of z-axis.

A pin (a second sealing member) 40 is provided in the supporting surface N. The pin 40 and the sealing member 50 cooperate with each other to divide the fluid pressure chamber “A” defined by the cam ring 4 and the adapter ring 5 into a first fluid pressure chamber A1 and a second fluid pressure chamber A2. That is, since the first fluid pressure chamber A1 is separated from the second fluid pressure chamber A2 by means of the pin 40 and sealing member 50; the first fluid pressure chamber A1 is formed on the y-axis negative side, and the second fluid pressure chamber A2 is formed on the y-axis positive side.

Since the cam ring 4 swings by rolling on the supporting surface N, volumetric capacities of the respective fluid pressure chambers A1 and A2 are varied. As shown in FIG. 2, the supporting surface N is in parallel with ξ-axis which is defined by rotating y-axis about an origin point of the coordinate system in a counterclockwise direction of FIG. 2. That is, the supporting surface N is inclined in the z-axis positive direction, and thereby a y-axis positive side of the supporting surface N is located at a more positive position of z-axis than a y-axis negative side of the supporting surface N. Accordingly, the cam ring 4 has a tendency to swing in the y-axis negative direction because of the inclined supporting surface N.

An outer diameter of the rotor 3 is smaller than a diameter of an inner circumference (surface) 41 of cam ring 4. The rotor 3 is disposed within a central bore of the cam ring 4. The rotor 3 is arranged so as to prevent the outer circumference of rotor 3 from abutting on the inner circumference 41 of cam ring 4 even when the swing movement of cam ring 4 varies a relative position between the rotor 3 and cam ring 4.

When the cam ring 4 has moved to its swing position farthest in the y-axis negative direction, a distance (radial interval of a pump chamber By−) L between the inner circumference 41 of cam ring 4 and the outer circumference of rotor 3 becomes maximum on the y-axis negative side. On the other hand, when the am ring 4 has moved to its swing position farthest in the y-axis positive direction, the distance L becomes maximum on the y-axis positive side.

Each vane 32 is designed to have a radial length larger than a maximum value of the distance (radial interval) L. Hence, each vane 32 remains in the state where a radially inner portion of vane 32 has been inserted or received in the corresponding slot 31 and a radially outer portion of vane 32 is in contact with the inner circumference 41 of cam ring 4, regardless of the relative position between the rotor 3 and cam ring 4. Accordingly, the back pressure is always applied from each back pressure chamber 33 to the corresponding vane 32 so that the vane 32 is fluid-tightly in contact with the inner circumference 41 of cam ring 4.

Therefore, a space between the rotor 3 and cam ring 4 is divided into pump chambers B by the vanes 32 which are disposed adjacent to each other in the circumferential direction of the cam ring 4 and rotor 3. Each pump chamber B formed by the adjacent vanes 32 is always kept fluid-tight. That is, the cam ring 4 cooperates with the rotor 3 and vanes 32 to define the pump chambers B on the inner circumferential side of cam ring 4. A volume of each pump chamber B varies in accordance with the rotation of the rotor 3 in the case where the cam ring 4 and the rotor 3 are positioned in the eccentric relation to each other as a result of the swing of cam ring 4.

The suction ports 62 and 121 and the discharge ports 63 and 122 which are provided respectively in the pressure plate 6 and the second housing 12 as mentioned above are formed along the outer circumference of rotor 3. The suction ports 62 and 121 are open to a region (some chambers) of the plurality of pump chambers B in which the volume of pump chamber B increases with the rotation of rotor 3, as shown in FIG. 2. Moreover, the discharge ports 63 and 122 are open to a region (some chambers) of the plurality of pump chambers B in which the volume of pump chamber B decreases with the rotation of rotor 3. The supply and discharge of the working fluid are performed through these ports 62, 63, 121 and 122 by the variation in volume of each pump chamber B.

The adapter ring 5 has a radial through-hole 51 at an end portion thereof in the y-axis positive direction. Moreover, the first housing 11 has a plug-member insertion hole 114 at an end portion thereof in the y-axis positive direction. A plug member 90 shaped like a cup having its bottom is inserted in the plug-member insertion hole 114, and serves to keep the first and second housings 11 and 12 fluid-tightly against an external thereof.

A spring 91 is installed radially inside an inner circumference of the plug member 90 (i.e., is installed in an inside bore of plug member 90) and is expandable and compressible in the y-axis direction. The spring 91 extends through the radial through-hole 51 of adapter ring 5, and abuts on the cam ring 4. Thereby, the spring 91 biases or urges the cam ring 4 in the y-axis negative direction.

The spring 91 biases the cam ring 4 in the y-axis negative direction, namely, in the direction causing an amount of swing movement of cam ring 4 to become maximum (maximum eccentricity). This biasing force of spring 91 serves to stabilize the swing position of cam ring 4 at the time of start-up of vane pump 1 during which the fluid pressure is unstable. That is, the spring 91 serves to stabilize the flow rate of working fluid to be discharged at the time of start-up of vane pump 1.

[Control Valve]

The control valve 7 (corresponding to a pressure control section according to the present invention) is a mechanical valve adapted to be driven based on discharge and suction pressures. The first housing 11 is formed with a valve installation hole 115 located in a z-axis positive portion of first housing 11. The control valve 7 is received or installed in the valve installation hole 115. This control valve 7 includes a spool 71 and a spring 72. Radially inside the spool 71 formed in a tubular shape having its bottom, a relief valve 80 is installed.

(Spool)

The spool 71 is a hollow cylindrical (tubular) member having one closed end, namely its bottom portion 71a. The bottom portion 71a is located at an end portion of the spool 71 in the y-axis negative direction. At another end portion of the spool 71 in the y-axis positive direction, namely at an opening portion 71b of the spool 71; the spring 72 biases the spool 71 in the y-axis negative direction. Moreover, an outer circumference of the spool 71 includes a sealing portion 71c which is fluid-tightly in contact with an inner circumferential surface of the valve installation hole 115.

The opening portion 71b is also fluid-tightly in contact with the inner circumferential surface of the valve installation hole 115. Hence, the spool 71 divides the valve installation hole 115 into three compartments, namely, a high pressure chamber CH, a medium pressure chamber CM and a low pressure chamber CL which are sealed against one another. The high pressure chamber CH is formed on the y-axis negative side of the spool 71. The medium pressure chamber CM is formed on the y-axis positive side of the spool 71. The low pressure chamber CL is formed on the outer circumferential surface of the spool 71 and between the sealing portion 71c and the opening portion 71b (i.e., spool 71's outer peripheral area surrounded by the sealing portion 71c, the opening portion 71b and the first housing 11).

The valve installation hole 115 is connected through a fluid passage 113 and a through-hole 52 with the first fluid pressure chamber A1. The first housing 11 is formed with this fluid passage 113. The through-hole 52 is a radial through-hole provided in the adapter ring 5. The sealing portion 71c of spool 71 is located at its position closing the fluid passage 113 when the spring 72 is not compressed.

Therefore, when the spool 71 moves in the y-axis positive direction, the fluid passage 113 is communicated (or linked) with the high pressure chamber CH so that a high pressure is introduced into the first fluid pressure chamber A1. On the other hand, when the spool 71 moves in the y-axis negative direction, the fluid passage 113 is communicated with the low pressure chamber CL so that a low pressure is introduced into the first fluid pressure chamber A1.

A y-axis negative portion of the high pressure chamber CH is connected through a pilot orifice 300 and a fluid passage 21 with the discharge ports 63 and 122. The low pressure chamber CL is connected through the fluid passage 7a with the inlet port IN. This fluid passage 7a is provided at a more positive position than the sealing portion 71c relative to y-axis, and hence is not connected with the high pressure chamber CH.

The medium pressure chamber CM is connected through a fluid passage 116 and a damper orifice 200 with the second fluid pressure chamber A2. Moreover, the second fluid pressure chamber A2 is connected through a metering orifice 110 with a discharge passage 22 and the discharge ports 63 and 122. The metering orifice 110 is provided in the pressure plate 6. Accordingly, the fluid pressures of the high pressure chamber CH and medium pressure chamber CM correspond respectively to an upstream (fluid) pressure and a downstream pressure of the metering orifice 110. A pressure difference between the upstream pressure and the downstream pressure is proportional to a flow rate (flow quantity) of the metering orifice 110.

[Swing of Cam Ring]

A control fluid pressure of the control valve 7 is introduced through the fluid passage 113 and through-hole 52 into the first fluid pressure chamber A1. Moreover, the downstream pressure of the metering orifice 110 is introduced in the second fluid pressure chamber A2.

In accordance with an increase of the discharge pressure; the fluid pressure difference of the metering orifice 110 becomes greater, so that the pressure difference between the high pressure chamber CH connected to the upstream side of the metering orifice 110 and the medium pressure chamber CM connected to the downstream side of the metering orifice 110 also becomes greater. This pressure difference moves the spool 71 of control valve 7 in the y-axis positive direction against the biasing force of the spring 72. Thereby, the first fluid pressure chamber A1 is communicated with the high pressure chamber CH so that a high pressure Ph is introduced into the first fluid pressure chamber A1.

Meanwhile, the downstream pressure of the metering orifice 110 is introduced in the second fluid pressure chamber A2 communicating with the medium pressure chamber CM. Thereby, the pressure difference between the first and second fluid pressure chambers A1 and A2 is caused (becomes greater). This pressure difference swings the cam ring 4 in the y-axis positive direction against the biasing force of the spring 91.

As a result, the pump chamber By− located on the y-axis negative side is reduced, so that a quantity of working fluid which is pushed (squeezed) into the discharge ports 63 and 122 is reduced. Meanwhile, a pump chamber By+ located on the y-axis positive side is enlarged, so that a quantity of working fluid which is put back (brought back) to the suction ports 62 and 121 is increased. Thus, a pump discharge rate (discharge quantity) is reduced, and thereby the pressure difference of the metering orifice 110 is reduced so as to reduce the pressure difference between the high pressure chamber CH and the medium pressure chamber CM.

Accordingly, the spool 71 becomes incapable of resisting the biasing force of the spring 72, and thereby moves in the y-axis negative direction. Then, the communication between the first fluid pressure chamber A1 and the high pressure chamber CH is blocked so that the fluid pressure of the first fluid pressure chamber A1 is lowered. Accordingly, the pressure difference between the first fluid pressure chamber A1 and the second fluid pressure chamber A2 is reduced, and the y-axis positive directional force caused by this pressure difference becomes balanced (or matched) with the biasing force of spring 91. Thereby, the swing of the cam ring 4 is stopped.

As explained above, the pressure difference of the metering orifice 110 and the biasing forces of springs 72 and 91 function to adjust the position of cam ring 4 so as to always maintain a constant discharge rate (discharge quantity). In the case that an opening area of the metering orifice 110 is small, the pressure difference becomes large. In the case that the opening area of the metering orifice 110 is large, the pressure difference becomes small.

(Relief Valve)

The relief valve 80 includes a valve body 81, a valve seat 82, a valve ball 83 and a spring 84. One end of the spring 84 is fixedly connected with the bottom portion 71a of the spool 71. The spring 84 biases or urges the valve body 81 in the y-axis positive direction. Thereby, the valve body 81 is in contact with the valve ball 83, and biases the valve seat 82 in the y-axis positive direction through this valve ball 83.

An outer circumferential surface of a y-axis positive-directional end portion 81a of the valve body 81 is fluid-tightly in contact with an inner circumferential surface of the spool 71. Hence, the valve body 81 cooperates with the inner circumference of the spool 71 to define a first fluid chamber D1. The spool 71 is formed with a first radial hole 71d provided from the outer circumference of the spool 71. The first radial hole 71d connects the inner circumferential surface of spool 71 with the outer circumferential surface of spool 71 to communicate an inside space of spool 71 to an outside space of spool 71.

When the spring 84 of relief valve 80 is under its most expanded state (i.e., when the spring 84 has expanded to a greatest extent), the first radial hole 71d is located at a more negative position relative to y-axis than the end portion 81a of the valve body 81. At this time, the first radial hole 71d communicates the low pressure chamber CL with the first fluid chamber D1. When the valve body 81 moves in the y-axis negative direction, the first radial hole 71d is closed.

The valve seat 82 includes a through-hole 82a formed in the y-axis direction. At a y-axis negative side of this through-hole 82a, the through-hole 82a is closed or blocked by the valve ball 83 provided between the through-hole 82a and the valve body 81. A y-axis positive portion of the valve seat 82 faces the medium pressure chamber CM. The outer circumference of the valve seat 82 is fixed to the inner circumference of the spool 71 by means of press fitting, and thereby a second fluid chamber D2 is formed between the valve body 81 and the valve seat 82.

Since the through-hole 82a is provided in the valve seat 82 in the y-axis direction, a medium pressure Pm is applied through the through-hole 82a to the valve ball 83 in the y-axis negative direction. When the medium pressure Pm within the medium pressure chamber CM increases, the valve ball 83 is pressed in the y-axis negative direction against the biasing force of spring 84. Thereby, the valve ball 83 is detached (moves apart) from the through-hole 82a, so that the medium pressure chamber CM is communicated with the low pressure chamber CL. Thus, a relief state is achieved, in which the medium pressure Pm is drained through the fluid passage 7a to the inlet port IN.

(Swing of Cam Ring at the Time of Relief)

Since the fluid passage 116 and damper orifice 200 are provided upstream of the medium pressure chamber CM, the fluid pressure of medium pressure chamber CM is reduced at the time of the relief state. Thereby, the pressure difference between the medium pressure chamber CM and the high pressure chamber CH becomes larger so that the spool 71 moves in the y-axis positive direction by resisting against the biasing force of spring 72.

Then, the first fluid pressure chamber A1 is made to communicate with the high pressure chamber CH. Because of this high pressure, the cam ring 4 is swung in the y-axis positive direction, so that the discharge flow rate is reduced. Because of the reduction of discharge flow rate, the pressure difference of the metering orifice 110 is reduced so that the pressure difference between the medium pressure chamber CM and the high pressure chamber CH is reduced. Thereby, the pressure Ph of high pressure chamber CH becomes unable to resist the biasing force of spring 72, so that the spool 71 moves in the y-axis negative direction.

Thereby, the communication between the high pressure chamber CH and the first fluid pressure chamber A1 is blocked, and the pressure of the first fluid pressure chamber A1 is lowered. At this time, the y-axis positive-directional force which is applied from the first fluid pressure chamber A1 to the cam ring 4 is reduced so that the swing of cam ring 4 stops. Thus, the discharge flow rate is reduced.

Thereby, the pressure difference between upstream and downstream sides of the metering orifice 110 is also reduced. That is, the enlargement of this pressure difference between the upstream and downstream sides is corrected, so that the pump discharge flow rate is maintained to a predetermined flow rate. Therefore, under the relief state, a surplus flow rate (quantity) is reduced by means of the swing of cam ring 4 so as to improve an efficiency.

(Metering Orifice)

FIG. 3 is an enlarged cross-sectional view near a variable metering (throttling) mechanism 100. The metering orifice 110 is a long (and narrow) hole formed long in the circumferential direction of vane pump 1. An opening area of the metering orifice 110 is varied by the y-axis-directional swing of the cam ring 4.

The long hole defining the metering orifice 110 is designed to cause a major (longer) axis of the metering orifice 110 to deviate slightly from the z-axis direction. That is, the major axis of the metering orifice 110 is inclined from a cam ring 4's tangent which is perpendicular to an imaginary line passing through a center point of the major axis of metering orifice 110 and the center Oc of cam ring 4. A portion 111 of a z-axis negative-directional end portion of the metering orifice 110 is not closed by the cam ring 4 even when the cam ring 4 swings in the y-axis positive direction to its greatest extent, as shown in FIG. 3. Hence, the metering orifice 110 is always open to the second fluid pressure chamber A2 at least by the minimum secured area 111. That is, the minimum secured area 111 which is not blocked by the cam ring 4 always communicates with the second fluid pressure chamber A2.

When the cam ring 4 swings in the y-axis positive direction, the opening portion of the metering orifice 110 is partly closed by the cam ring 4 to reduce the opening area of metering orifice 110. When the cam ring 4 reaches its position farthest in the y-axis positive direction, the metering orifice 110 is closed except only one portion (minimum secured area 111). This variable metering mechanism 100 adapted to vary the area of flow passage is achieved by the metering orifice 110 and the cam ring 4.

Since the opening portion of the metering orifice 110 is provided in the shape of a long narrow hole (elliptical slot) elongated in the circumferential direction of cam ring 4, the metering orifice 110 is gradually closed after the cam ring 4 has swung by a predetermined angle. Therefore, the metering orifice 110 is not closed or narrowed down at the time of a non-relief state where the discharge flow rate is constant. Thereby, it is suppressed that the discharge-rate control is influenced by the variation of the pressure difference between upstream and downstream sides of the metering orifice 110. Thereby, a tuning of the discharge-rate control is made easy to conduct.

Moreover, since the opening portion of the metering orifice 110 is shaped like a long hole having the greater circumferential width than the radial width thereof as mentioned above, the opening area of the metering orifice 110 can be reduced rapidly relative to an amount (displacement) of swing of the cam ring 4.

[Fluid Pressure Supply to First and Second Fluid Pressure Chambers]

The discharge pressure is restricted by the pilot orifice 300 provided on the fluid passage 21, and then is supplied to the high pressure chamber CH so as to urge the spool 71 in the y-axis positive direction. Thereby, the spool 71 moves in the y-axis positive direction so that the high pressure chamber CH is communicated with the fluid passage 113. Accordingly, the pressure Ph of high pressure chamber CH is introduced into the first fluid pressure chamber A1. The discharge pressure is also introduced to the discharge passage 22, and then is introduced into the second fluid pressure chamber A2 by being restricted by the metering orifice 110, as shown in FIG. 2.

Since the fluid pressure of second fluid pressure chamber A2 is supplied to a fluid-pressure available pathway (connected to a pressure-using device) provided outside the vane pump 1, the orifice pressure-difference occurs in proportion to the flow rate of the metering orifice 110. Thereby, the medium pressure Pm of medium pressure chamber CM located downstream of the metering orifice 110 becomes lower than the pressure Ph of high pressure chamber CH located upstream of the metering orifice 110. Accordingly, the second fluid pressure chamber A2 is made to have a lower pressure than that of the first fluid pressure chamber A1 so that the cam ring 4 swings in the y-axis positive direction.

When the cam ring 4 swings; the pump discharge flow rate decreases, and the flow-rate pressure difference of the metering orifice 110 is lowered. Thereby, the pressure difference between the high pressure chamber CH and the medium pressure chamber CM is reduced so that the biasing force of spring 72 moves the spool 71 in the y-axis direction. Thereby, the pressure to be supplied to the first fluid pressure chamber A1 is reduced, so that the swing of cam ring 4 is stopped. Thus, the predetermined discharge flow rate is attained.

The outer circumferential side of cam ring 4 receives the pressures of first and second fluid pressure chambers A1 and A2, and the inner circumferential side of cam ring 4 receives the discharge pressure in the y-axis negative direction and also in the z-axis negative direction. The swing of cam ring 4 is stopped at a position striking a balance among these pressures.

In the case that the discharge rate decreases, because of the reduction of pressure difference of the metering orifice 110, the pressure Ph within high pressure chamber CH is also reduced. Thereby, the spool 71 is moved in the y-axis negative direction by the biasing force of spring 72 so that the low pressure chamber CL is communicated with the fluid passage 113. Thereby, a low pressure Pl is introduced into the first fluid pressure chamber A1, so that the first fluid pressure chamber A1 becomes lower in fluid pressure than the second fluid pressure chamber A2. Accordingly, the cam ring 4 returns in the y-axis negative direction. Thus, the pressure difference of the metering orifice 110 becomes constant to attain or maintain the predetermined flow rate.

[Reduction of Discharge Flow Rate During Relief State]

FIG. 4 is a view showing a relation between the opening area of metering orifice 110 and the swing amount of cam ring 4 (the position of cam ring 4 by its swing motion). In the case where the swing amount of cam ring 4 is within a normal use range; the metering orifice 110 is not closed by the cam ring 4, namely, the opening area of metering orifice 110 remains constant in its fully open condition. Accordingly, the discharge flow rate is maintained at a constant flow rate, by means of the movement of spool 71, the swing of cam ring 4 and the pressure difference of metering orifice 110.

In the case of relief state where the pressure of medium pressure chamber CM is drained through the relief valve 80 and the fluid passage 7a to the inlet port IN, the pressure of medium pressure chamber CM is reduced because of the existence of the fluid passage 7a and the pilot orifice 300.

Thereby, the pressure Ph of high pressure chamber CH becomes higher than the pressure Pm of medium pressure chamber CM, so that the pressure P1 of first fluid pressure chamber A1 communicating with the high pressure chamber CH becomes higher than the pressure P2 of the second fluid pressure chamber A2 communicating with the medium pressure chamber CM. Accordingly, the cam ring 4 swings in the y-axis positive direction, so that the discharge rate is reduced. Here, under the relief state, the swing amount (i.e., displacement in the y-axis positive direction) of cam ring 4 is further enlarged as mentioned above.

Since the cam ring 4 moves in the y-axis positive direction, the opening area of metering orifice 110 is reduced. Since the opening area of metering orifice 110 is reduced, the pressure difference between the both sides of metering orifice 110 is increased. Accordingly, the pressure difference between the high pressure chamber CH and the medium pressure chamber CM is also increased. Hence, the spool 71 moves in the y-axis positive direction so that the high pressure chamber CH is communicated with the first fluid pressure chamber A1. Since the pressure P1 of first fluid pressure chamber A1 rises, the cam ring 4 further swings in the y-axis positive direction so that the discharge flow rate is further reduced.

As explained above, at the time of relief state, the surplus quantity of working fluid which is drained from the medium pressure chamber CM to the inlet port IN is reduced by restricting the flow rate to the medium pressure chamber CM. Thus, the drain quantity of working fluid is reduced during the relief state so as to enhance fuel economy.

In this embodiment, the swing of cam ring 4 varies the cross sectional area of flow passage (the opening area of metering orifice 110), and thereby the drain quantity of working fluid is reduced. Therefore, the drain quantity of working fluid is linked to the variation of cross sectional area of flow passage with the use of simple structure.

Moreover, by providing the pilot orifice 300, the cam ring 4 is made easy to move in the y-axis positive direction so that the opening area of metering orifice 110 is made easy to be narrowed or reduced. Thereby, the drain quantity of working fluid is further reduced at the time of relief. At that time, the relief state can be accurately judged or recognized by detecting the y-axis positive-directional movement (position) of cam ring 4.

In case that the pilot orifice 300 is more narrowed down, it is conceivable that the pressure Pm of medium pressure chamber CM becomes further easy to be reduced at the time of relief state, and thereby the swing amount of cam ring 4 is made greater to further reduce the surplus flow rate. However in such a case, there is a fear that a vibration of valve ball 83 under the relief state fluctuates the pressure Pm of medium pressure chamber CM so as to also vibrate the spool 71 and cam ring 4. Thereby, there is a fear that a vibration of the discharge pressure is caused.

Therefore, in this embodiment according to the present invention, the structure is employed which lessens the metering orifice 110 at the time of relief state. According to this structure, the lessening (narrowing-down) of the pilot orifice 300 can be set relatively moderately. In this embodiment, the surplus flow rate is reduced without causing the vibration of fluid pressure.

Moreover, by providing the damper orifice 200; a vibration of spool 71 which is caused due to the discharge pressure is suppressed, and also the fluid-pressure vibration at the time of relief state is suppressed so that the control valve 7 operates stably resulting in a stable swing of cam ring 4.

[Structures and Effects According to First Embodiment]

(1) The variable displacement vane pump in the first embodiment includes the metering orifice 110 formed on the discharge passage 22 connected with the discharge ports 63 and 122; the control valve 7 adapted to control the pressure which is introduced into the first fluid pressure chamber A1 or the second fluid pressure chamber A2, wherein the control valve 7 includes the high pressure chamber CH into which the upstream pressure of the metering orifice 110 is introduced, the medium pressure chamber CM into which the downstream pressure of the metering orifice 110 is introduced, and the low pressure chamber CL connected with the reservoir tank RSV for storing working fluid; the relief valve 80 provided between the downstream side of metering orifice 110 and the reservoir tank RSV, wherein the relief valve 80 is adapted to be opened by receiving a pressure greater than or equal to a predetermined level and thereby to drain the downstream pressure of the metering orifice 110 to the reservoir tank RSV; and the variable metering mechanism 100 configured to narrow the cross-sectional area of opening portion (flow passage) of the metering orifice 110 at least when the relief valve 80 is opened.

Accordingly, it becomes possible that the flow rate is reduced by the metering orifice 110 at the time of relief so that the cam ring 4 is swung. Thereby, the surplus fluid quantity to be drained from the medium pressure chamber CM to the inlet port IN is reduced. Thus, the surplus flow rate can be stably reduced without generating the fluid-pressure vibration. Therefore, the increase in pump workload can be suppressed while reducing the relief amount, and thereby the fuel economy is enhanced.

(2) The cam ring 4 is adapted to swing so as to gradually block the opening portion of the metering orifice 110, and hence the variable metering mechanism 100 is achieved by the metering orifice 110 and the cam ring 4. Further, the opening portion of metering orifice 110 is formed in the axial end surface of the first plate member 12 or the second plate member 6. Accordingly, the reduction of drain flow rate of working fluid can be linked to the variation of cross sectional area of the flow passage under the relief state, with the use of simple structure.

(3) The variable metering mechanism 100 is configured to gradually narrow the opening portion of the metering orifice 110 after the cam ring 4 has swung to its position having a predetermined angle. Accordingly, the metering orifice 110 is not blocked or narrowed at the time of non-relief state where the discharge flow rate is constant. Thereby, it is suppressed that the discharge-rate control is influenced by the variation of the pressure difference between upstream and downstream sides of the metering orifice 110. Thereby, the tuning of the discharge-rate control can be made easy to perform.

(4) The circumferential width of opening portion of the metering orifice 110 is greater than the radial width thereof. Accordingly, the area of the metering orifice 110 can be narrowed sharply for the swing amount of the cam ring 4 so as to greatly reduce the surplus flow rate.

(5) The opening portion of the metering orifice 110 is formed in an elliptical shape or a slot shape. Accordingly, the area of the metering orifice 110 can be narrowed sharply for the swing amount of the cam ring 4 so as to greatly reduce the surplus flow rate.

(6) The variable displacement vane pump further includes a pilot orifice 300 provided on the passage connecting the discharge ports 63 and 122 with the high pressure chamber CH. Accordingly, the relief state can be accurately judged based on the swing motion of cam ring 4.

(7) The variable displacement vane pump further includes the damper orifice 200 provided on the passage connecting the metering orifice 110 with the medium pressure chamber CM. Accordingly, the stability of control valve 7 can be improved at the time of relief.

Other modified examples according to the first embodiment will be explained below.

[First Modified Example According to First Embodiment]

FIGS. 5 and 6 show an example in which the minimum secured area 111 of metering orifice 110 is provided as a separate hole (another hole). Although the major axis of the metering orifice 110 (i.e., the longer axis of cross-section of metering orifice 110) is inclined from the z-axis in the above-mentioned example of the first embodiment, the metering orifice 110 in the first modified example of the first embodiment is formed as a long hole (slot) having its major axis parallel to the z-axis. In the first modified example, the hole (another hole) formed separately on the y-axis positive side of the metering orifice 110 serves as the minimum secured area 111.

The metering orifice 110 is completely closed when the cam ring 4 reaches its most positive swing position relative to y-axis, namely is completely closed at the position of an alternate long and two short dashes line of FIG. 6. On the other hand, the minimum secured area 111 is located at a position which is not closed irrespective of the swing position of cam ring 4. Therefore, the major (longer) axis of metering orifice 110 is provided in parallel with the z-axis so that a manufacturing processing of the metering orifice 110 can be simplified.

[Second Modified Example According to First Embodiment]

FIG. 7 shows an example in which the metering orifice 110 is provided as a plurality of holes each having a substantially complete roundness. Accordingly, a sufficient opening area can be ensured as well as ensuring a stiffness near the opening portion of metering orifice 110.

[Third Modified Example According to First Embodiment]

FIG. 8 shows an example further modifying the above-explained first modified example in such a manner that the damper orifice 200 is provided outside the adapter ring 5. In the third modified example, a fluid passage 23 connecting the second fluid pressure chamber A2 with the medium pressure chamber CM is provided outside the first housing 11, and this fluid passage 23 is formed with the damper orifice 200.

[Fourth Modified Example According to First Embodiment]

FIG. 9 shows an example in which a piston 92 adapted to move in and out in response to the swing of cam ring 4 is provided, and this piston 92 is formed with the metering orifice 110. The piston 92 is located on the y-axis negative side of the plug member 90 and on the y-axis positive side of the cam ring 4. The piston 92 is a circular tubular (hollow cylindrical) member having its bottom. The bottom portion of piston 92 abuts on the cam ring 4 in the y-axis negative direction.

An outer circumferential surface of piston 92 is inserted into the plug-member insertion hole 114 slidably and fluid-tightly. Thereby, the piston 92 cooperates with the plug member 90 to define a third fluid chamber D3. An inner circumference of the plug member 90 is formed with an opening portion 22a of the discharge passage 22 communicating with the discharge ports 63 and 122. Thereby, the discharge pressure is introduced into the third fluid chamber D3, and cooperates with the spring 91 to bias the piston 92 in the y-axis negative direction. Accordingly, the cam ring 4 is biased in the y-axis negative direction through the piston 92 by means of the biasing force of spring 91 and the pressure of the third fluid chamber D3.

A tubular portion of the piston 92 is formed with small (through-)holes each of which communicates an inner circumferential surface of piston 92 with an outer circumferential surface of piston 92. These small holes are used as the metering orifice 110. The piston 92 is pressed by the cam ring 4 in the y-axis positive direction in accordance with the y-axis positive-directional swing of cam ring 4, and thereby moves in the y-axis positive direction against the pressures of spring 91 and third fluid chamber D3.

When the piston 92 moves in the y-axis positive direction, the piston 92 is deeply inserted (buried) into the plug-member insertion hole 114. Thereby, the metering orifice 110 is closed by (the inner surface of) the plug-member insertion hole 114. In such a way, the variable metering mechanism 100 is constructed in the fourth modified example. Accordingly, the drain quantity of working fluid is reduced at the time of relief state in the similar manner as the not-modified example of the first embodiment. In this fourth modified example, since the metering orifice 110 is closed by the plug-member insertion hole 114, a leakage in the metering orifice 110 becomes relatively low so that an accuracy in the quantity metering (reduction) control is enhanced.

(8) The variable displacement vane pump according to the first embodiment further includes the piston 92 adapted to move in response to the swing of cam ring 4; and the metering orifice 110 is formed in the piston 92. Accordingly, the leakage of the metering orifice 110 becomes relatively small so that the accuracy in quantity metering (reduction) control can be enhanced.

Second Embodiment

A second embodiment according to the present invention will now be explained. A basic structure of the second embodiment is similar as the first embodiment. Although the opening portion provided on the discharge passage 22 is used as the metering orifice 110 in the first embodiment, a spool 400 adapted to vary an area of flow passage corresponds to the metering orifice 110, in the second embodiment, as a different point from the first embodiment.

FIG. 10 is a cross-sectional view of vane pump 1 according to the second embodiment, taken in the axial direction of vane pump 1. FIG. 11 is a cross-sectional view of the vane pump 1, taken in the radial direction of vane pump 1. Since the cross section of FIG. 11 is different from the cross section (FIG. 2) taken in the axial direction in the first embodiment, only a part of the control valve 7 is shown in FIG. 11. The first housing 11 is formed with a spool installation hole 117 located in parallel with the valve installation hole 115 for the control valve 7. The spool 400 is installed or received in this spool installation hole 117.

The spool 400 includes step portions 423 and 425 at both end portions of spool 400 in the y-axis direction. The spool 400 further includes a recess portion 424 in a substantially center portion of spool 400. This recess portion 424 is formed in the entire outer circumference (i.e., all-around) of spool 400. Moreover, sealing portions 421 and 422 are provided to the outer circumferential surface of spool 400 on y-axis directional both sides of the recess portion 424. Accordingly, the spool installation hole 117 is divided into three compartments, namely, a first spool fluid chamber 411, a second spool fluid chamber 412 and a third spool fluid chamber 413 which are sealed fluid-tightly against one another.

A spring 401 is provided in the first spool fluid chamber 411. One end of spring 401 is engaged with the step portion 423 located at the y-axis negative portion of the spool 400, and another end of spring 401 is fixed to a y-axis negative end portion of the spool installation hole 117. Thereby, the spool 400 is biased in the y-axis positive direction. The first spool fluid chamber 411 is connected with the inlet port IN, and thereby the suction pressure is introduced into the first spool fluid chamber 411. The first spool fluid chamber 411 is also connected through the fluid passage 7a with the low pressure chamber CL of the control valve 7.

The second spool fluid chamber 412 and third spool fluid chamber 413 are connected with the outlet port OUT. Thereby, the discharge pressure is introduced into the second spool fluid chamber 412 and third spool fluid chamber 413 so that the spool 400 is biased in the y-axis negative direction. The outlet port OUT is connected with the discharge ports 63 and 122 and the medium pressure chamber CM through fluid passages (not shown).

The second fluid pressure chamber A2 is connected through a fluid passage 24 with the spool installation hole 117. An opening portion 24a of the fluid passage 24 which is open to the spool installation hole 117 is provided to overlap with the recess portion 424 in the z-axis direction under a normal state where a sufficient pressure difference is not applied to the spool 400. Specifically, y-axis directional positions of both ends of opening portion 24a are same as y-axis directional positions of both ends of recess portion 424 under the normal state. Accordingly, the fluid passage 24 is connected through the recess portion 424 with the outlet port OUT, under the normal state.

When the discharge pressure becomes higher and reaches the relief pressure, the spool 400 moves in the y-axis negative direction against the biasing force of spring 401. Thereby, the opening portion 24a is gradually closed or narrowed by the sealing portion 422 of spool 400 which is located on the y-axis positive side of the recess portion 424. Accordingly, the area of flow passage between the second fluid pressure chamber A2 and the outlet port OUT is reduce (corresponding to the narrowing of metering orifice 110 in the first embodiment), so that the (some) pressure difference between the second fluid pressure chamber A2 and the outlet port OUT is caused. This pressure difference moves the control valve 7, so that the pressure Ph of high pressure chamber CH is introduced into the first fluid pressure chamber A1.

Thereby, the cam ring is swung in the y-axis positive direction, so that the discharge rate (discharge quantity) and the discharge pressure are reduced. Accordingly, the surplus discharge pressure at the time of relief is reduced in the similar manner as the first embodiment. The biasing force of spring 401 is adjusted to allow the narrowing of the opening portion 24a to start when the discharge pressure becomes greater than or equal to a predetermined value. Hence, in this second embodiment, the variable metering mechanism 100 is constructed by use of a convenient structure. Moreover, the surplus flow rate is cut reliably at the time of relief pressure.

[Structures and Effects According to Second Embodiment]

(1) The variable displacement vane pump in the second embodiment includes the variable metering mechanism 100 configured to narrow the cross-sectional area of opening portion (flow passage) of the metering orifice 24a when the discharge pressure on the downstream side of the discharge ports 63 and 122 is higher than or equal to a predetermined pressure. Accordingly, the similar effects as in the first embodiment can be obtained.

(2) The variable metering mechanism 100 is achieved by the spool 400 adapted to controllably vary the opening area of the metering orifice 24a by moving relative to the metering orifice 24a. Accordingly, the variable metering mechanism 100 can be simply constructed.

Other modified examples according to the second embodiment will be explained below.

[First Modified Example According to Second Embodiment]

FIG. 12 show an example in which the spool 400 is provided as an electromagnetic (solenoid) valve. In the above-explained non-modified example of the second embodiment, the spool 400 is a mechanical valve adapted to move based on the discharge pressure. On the other hand, in a first modified example of the second embodiment, the spool 400 is constructed by the electromagnetic valve and is connected with an electromagnetic actuator 500. Moreover, there is provided a pressure sensor 510 for sensing the pressure of the outlet port OUT. The electromagnetic actuator 500 is driven based on the sensed values of pressure sensor 510, and thereby narrows or blocks the opening portion 24a (corresponding to the metering orifice 110 in the first embodiment, i.e., corresponding to the metering orifice according to the present invention). Thus, the variable metering mechanism 100 is achieved.

(Structures and Effects According to First Modified Example of Second Embodiment)

(3) The variable metering mechanism 100 is achieved by the fluid-pressure sensor 510 adapted to sense the discharge pressure, and the electromagnetic valve adapted to be opened based on the sensed signal of the fluid-pressure sensor 510. Accordingly, a freedom degree in design and tuning accuracy can be enhanced since the area of flow passage is varied by moving the spool 400 electromagnetically.

[Second Modified Example According to Second Embodiment]

FIG. 13 shows an example further modifying the above-explained first modified example of second embodiment in such a manner that the relief valve 80 is provided outside the housing 11. In a second modified example of the second embodiment, the relief valve 80 is connected through a fluid passage 27 with the second spool fluid chamber 412 of spool 400 and the medium pressure chamber CM. The relief valve 80 is also connected with a reservoir tank RSV. This relief valve 80 only permits a flow from the fluid passage 27 toward the reservoir tank RSV, namely, permits the flow in only one direction.

The second spool fluid chamber 412 of spool 400 is connected through a fluid passage 26 with the discharge ports 63 and 122. Moreover, the first spool fluid chamber 411 is connected through a fluid passage 28 with the inlet port IN.

Since the relief valve 80 is located outside the control valve 7 and there is no orifice between the medium pressure chamber CM and the fluid passage 27; the reduction of pressure of medium pressure chamber CM due to a narrow shape of orifice is not caused at the time of relief state. Thereby, the swing of cam ring 4 is suppressed.

In the second modified example of the second embodiment, when the sensed value of pressure sensor 510 reaches the relief pressure, the electromagnetic actuator 500 is driven to move the spool 400 and thereby narrow the fluid passage 27 (corresponding to the narrowing of metering orifice 110 in the first embodiment). Thereby, the cam ring 4 is swung so that the surplus flow quantity is reduced. Therefore, it is not necessary to operate the control valve 7 by using the discharge pressure under the relief state. Thus, the problem regarding the vibration of control valve 7 is also avoided.

[Third Modified Example According to Second Embodiment]

FIGS. 14 and 15 show an example in which the shape of the spool 400 is changed in a manner that the spool 400 is operated by use of a drain pressure produced at a downstream side of the relief valve 80. In a third modified example of the second embodiment, a fluid passage 30 is provided at the y-axis negative side (end) of the spool 400, as shown in FIG. 15. Through this fluid passage 30, the spool 400 is connected with the downstream side of the relief valve 80. The spring 401 is provided within the third spool fluid chamber 413, and biases the spool 400 in the y-axis negative direction.

In this third modified example, the spool 400 forms a fourth spool fluid chamber 414 within the spool installation hole 117, in addition to the first to third spool fluid chambers 411 to 413. Hence, a volume of the first spool fluid chamber 411 is smaller than that of the non-modified example of the second embodiment.

The fourth spool fluid chamber 414 is located between the first and second spool fluid chambers 411 and 412, and is connected through a fluid passage 29 with the inlet port IN. Moreover, the fourth spool fluid chamber 414 is connected with the third spool fluid chamber 413 through a shaft-center hole 430 formed in a shaft center portion of the spool 400, so that the suction pressure is introduced into the third spool fluid chamber 413.

Accordingly, when the downstream pressure of the relief valve 80 becomes high, the spool 400 moves in the y-axis positive direction against the biasing force so that the opening area of the opening portion 24a of fluid passage 24 is reduced. Thus, in the similar manner as the non-modified example of the second embodiment, the surplus discharge pressure is reduced at the time of relief, and the variable metering mechanism 100 is constructed by use of a convenient structure. Furthermore, since the spool 400 is driven by using the downstream-side pressure of relief valve 80, the relief state is more accurately judged or recognized.

(Structures and Effects According to Third Modified Example of Second Embodiment)

(4) The variable metering mechanism 100 is configured to vary the area of the opening portion (fluid passage) on the basis of the downstream pressure of relief valve 80. Accordingly, the relief state can be more accurately caught.

(5) The variable metering mechanism 100 is achieved by the spool 400 adapted to controllably vary the opening area by moving in and out. Accordingly, the variable metering mechanism 100 can be simply constructed.

Other Embodiments

Although the invention has been described above with reference to certain embodiments of the invention, the invention is not limited to the embodiments described above. Modifications and variations of the embodiments described above will occur to those skilled in the art in light of the above teachings.

This application is based on prior Japanese Patent Application No. 2007-212854 filed on Aug. 17, 2007. The entire contents of this Japanese Patent Application are hereby incorporated by reference.

The scope of the invention is defined with reference to the following claims.