Patent ID: 6120256
Filing Date: 2000-09-19
Classification: F04C

Abstract:
A variable displacement pump comprising:a rotor having vanes and rotatable in a pump body;a cam ring fitted on an outer circumferential surface of said rotor to form a pump chamber together with said rotor and arranged to be movable and displaceable in said pump body;first and second fluid pressure chambers formed on two sides of an outer circumferential surface of said cam ring between said cam ring and said pump body to guide therein a fluid pressure corresponding to a flow rate of a pressure fluid discharged from said pump chamber, thereby moving and displacing said cam ring; anda pump suction opening and a pump discharge opening formed in side plate members, that form said pump chamber together with said rotor and said cam ring, to oppose pump suction and discharge sides, respectively, of said pump chamber, whereinnotches are formed by notching in a starting or terminal end portion, in a rotor rotating direction, of said pump suction opening and said pump discharge opening to have a substantially V-letter shape, andat least one of said notches is formed to change a timing at which either one of said pump suction opening and said pump discharge opening communicates with a pressure chamber formed between said vanes in accordance with swing and displacement of said cam ring.