Patent ID: 8545200
Filing Date: 2013-10-01
Classification: F04C

Abstract:
1. A variable displacement oil pump comprising: a rotor configured to be rotationally driven by an internal combustion engine; a plurality of vanes movable out from and into an outer circumferential portion of the rotor; a cam ring configured to: a housing configured to receive the cam ring therein, and including: a biasing member configured to bias the cam ring in a direction that enlarges the eccentricity between the rotation center of the rotor and the center of the inner circumferential surface of the cam ring; a contact surface configured to become in contact with an outer circumferential surface of the cam ring by means of a biasing force applied to the cam ring by the biasing member, wherein a distance between the swing fulcrum and the contact surface is shorter than a distance between the swing fulcrum and a portion at which the cam ring is biased by the biasing member; a control chamber separately formed by the contact surface and the swing fulcrum of the cam ring on an outer circumference of the cam ring when the contact surface is in contact with the outer circumferential surface of the cam ring, and configured to cause the cam ring to swing against the biasing force of the biasing member by a pressure introduced from the discharge portion to the control chamber; and a choking portion formed on the outer circumferential surface of the cam ring and configured to maintain a pressure of the control chamber even when the cam ring swings.