Variable displacement pump
View Patent ↗Within a cam ring ( 8 ), a rotor having a plurality of vanes ( 27 ) is eccentrically disposed. A metering orifice ( 136 ) is provided halfway on a discharge passage ( 135 ) of pressure fluid discharged from the pump, and a control valve is activated due to a pressure difference between the upstream and downstream sides of the metering orifice ( 136 ). A fluid pressure of the first fluid pressure chamber ( 21 ) is controlled by activation of the control valve ( 123 ). The second fluid pressure chamber ( 22 ) is shut off from the control valve ( 123 ) to introduce a pressure on the suction side at any time. To return the cam ring ( 8 ) in a direction of expanding a pump chamber ( 11 ), an internal pressure of the cam ring ( 8 ) is applied in the return direction.
1. A variable displacement pump comprising:
a cam ring carried swingably between plates on both sides;
a first fluid pressure chamber formed in one of the swing directions of the cam ring;
a second fluid pressure chamber provided in the other swing direction of the cam ring;
urging means for urging the cam ring toward the first fluid pressure chamber, disposed on a side of the second fluid pressure chamber;
a rotor eccentrically disposed within the cam ring and having a plurality of vanes on an outer circumference thereof;
a metering orifice disposed halfway on a discharge passage of a pressure fluid discharged from a pump; and
a control valve activated by a pressure difference between upstream and downstream sides of the metering orifice,
wherein a fluid pressure in at least one of the first and second fluid pressure chambers is controlled by activation of the control valve to swing the cam ring;
wherein a discharge opening for discharging a pressure fluid from a pump chamber is disposed on one of the plates for carrying the cam ring;
wherein a first seal ring surrounding a drive shaft for driving the rotor and a second seal ring on an outer circumference of the first seal ring, surrounding a wider region than a region where the discharge opening is disposed are provided on a rear face of the other plate; and
wherein an inlet passage for introducing a discharge pressure is formed in an area between the first and second seal rings.
2. The variable displacement pump according to claim 1 ,
wherein the first and second seal rings are made of resin;
wherein the first and second seal rings communicate to seal grooves to which the seal rings are fitted;
wherein concave portions, which are deeper than the seal grooves, are formed to introduce a discharge pressure thereinto.