Patent ID: 9670925
Date: 2017-06-06
CPC Classifications: F04B,F04C

Claim:
1. A variable displacement pump used in an internal combustion engine, the variable displacement pump comprising: a pump constituting section arranged to vary volumes of a plurality of hydraulic fluid chambers by being driven by the internal combustion engine, and thereby to discharge oil sucked from a suction portion, from a discharge portion; a cam ring accommodating the pump constituting section, and movable to vary variation amounts of the volumes of the hydraulic fluid chambers which are opened to the discharge portion; an urging mechanism including two spring members being provided with spring loads respectively, and applying an urging force to the cam ring toward a direction such that the variation amounts of the volumes of the hydraulic fluid chambers opened to the discharge portion are varied, and the urging force by the urging mechanism changing in a stepwise manner when the variation amount of the volume of a hydraulic fluid chamber is a predetermined amount; a first control chamber arranged to receive the oil discharged from the discharge portion, and thereby to apply, to the cam ring, a force in a direction in which the variation amounts of the volumes of the hydraulic fluid chambers which are opened to the discharge portion become small; a second control chamber arranged to receive the oil discharged from the discharge portion, and thereby to apply, to the cam ring, a force in a direction in which the variation amounts of the volumes of the hydraulic fluid chambers which are opened to the discharge portion becomes large, the force acting on the second control chamber being smaller than the force acting on the first control chamber; an electromagnetic switching valve arranged to connect the second control chamber and the discharge portion in an energized state, and to connect the second control chamber and a low pressure portion in a deenergized state; and a control valve actuated by pressure of oil discharged from the discharge portion, and arranged to decrease the pressure within the second control chamber when the pressure of oil discharged from the discharge portion becomes equal to or greater than a predetermined pressure.