Patent ID: 9004882
Filing Date: 2015-04-14
Classification: F04C

Abstract:
1. A variable displacement pump comprising: a rotor driven by an internal combustion engine; a plurality of vanes provided in an outer circumference portion of the rotor, and arranged to be moved in a radially inward direction of the rotor and in a radially outward direction of the rotor; a cam ring which receives the rotor and the vanes therein, which separates a plurality of hydraulic chambers with the rotor and the vanes, and which is arranged to be moved to vary an eccentric amount with respect to a center of a rotation of the rotor, and thereby to increase or decrease volumes of the hydraulic chambers at the rotation of the rotor; a housing which receives the cam ring therein, and which includes a suction portion that is formed in an inner side surface of the housing, that is opened to the hydraulic chambers whose the volumes are increased when the cam ring is moved to one side to be eccentric, and a discharge portion that is formed in the inner side surface of the housing, that is opened to the hydraulic chambers whose the volumes are decreased when the cam ring is moved to the one side to be eccentric; a first urging member arranged to urge the cam ring in a direction to increase the eccentric amount of the cam ring with respect to the center of the rotation of the rotor; a second urging member arranged to urge the cam ring in a direction to decrease the eccentric amount of the cam ring by an urging force smaller than an urging force of the first urging member when the eccentric amount of the cam ring is equal to or greater than a predetermined amount, and arranged so as not to apply the urging force to the cam ring to store the urging force when the eccentric amount of the cam ring is smaller than the predetermined amount; a control hydraulic chamber arranged to receive a discharge pressure, and thereby to move the cam ring against the urging force of the first urging member; and a hydraulic pressure introduction section configured to introduce the discharge pressure to the control hydraulic chamber when the discharge pressure becomes greater than a predetermined pressure which is in a range in which the cam ring is movable with respect to a resultant force of the urging force of the first urging member and the urging force of the second urging member, and in which the cam ring is not movable only with respect to the urging force of the first urging member.