Variable displacement pump

摘要

A variable displacement pump includes: a first control oil chamber which moves a cam ring toward a direction against a biasing force of a biasing member when a discharge pressure is introduced thereinto; a second control oil chamber which acts a hydraulic pressure upon the cam ring by cooperating with the biasing force of the biasing member when hydraulic oil is introduced thereinto; a switching mechanism which switches between one state in which hydraulic oil whose pressure is decreased than a discharge pressure is introduced to the second control oil chamber from the discharge section and another state in which hydraulic oil is discharged from the second control oil chamber; and a control mechanism operated before an eccentricity of the cam ring becomes a minimum and which discharges a greater amount of hydraulic oil within the second control oil chamber as the discharge pressure becomes larger.

主权项

1. A variable displacement pump comprising:
a rotationally driven rotor; a plurality of vanes provided in an outer periphery of the rotor and arranged to be moved in a radially inward direction and to be moved in a radially outward direction; a cam ring in an inside of which the rotor and the vanes are housed, in an inner part of which a plurality of pump chambers are formed, and configured to be moved to vary an eccentricity of the cam ring with respect to a rotary center of the rotor; a housing including:
a suction section formed on at least one side surface of the cam ring and opened to one of the pump chambers whose volume is increased when the cam ring is eccentrically moved toward one direction with respect to the rotary center of the rotor; anda discharge section opened to one of the pump chambers whose volume is decreased when the cam ring is eccentrically moved toward another direction with respect to the rotary center of the rotor; a biasing member configured to bias the cam ring toward the one direction toward which the eccentricity of the cam ring with respect to the rotary center of the rotor becomes large; a first control oil chamber configured to move the cam ring toward the other direction against a biasing force of the biasing member when a discharge pressure is introduced into the first control oil chamber; a second control oil chamber configured to act a hydraulic pressure upon the cam ring by cooperating with the biasing force of the biasing member when hydraulic oil is introduced into the second control oil chamber; a switching mechanism configured to switch between a first state in which hydraulic oil whose pressure is decreased with respect to a discharge pressure is introduced to the second control oil chamber from the discharge section and a second state in which hydraulic oil is discharged from the second control oil chamber; and a control mechanism configured to discharge hydraulic oil within the second control oil chamber as the discharge pressure becomes larger and to adjust the pressure within the second control oil chamber in a pressure decrease direction when the switching mechanism introduces hydraulic oil whose pressure is decreased with respect to the discharge pressure to the second control oil chamber during a high revolution of the pump.