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Variable displacement vane pump

Variable displacement vane pump description/claims

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.

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.

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.

• Provisional Patent
• Utility Patent

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