Variable vane displacement pump utilizing a control valve and a switching valve

A variable displacement pump comprising:

• a housing including a pump receiving chamber formed within the housing;
• a rotor which is disposed within the pump receiving chamber, and which is rotationally driven;
• a plurality of vanes which are provided on an outer circumference side of the rotor to be projectable from and retractable into the rotor;
• a cam ring which is received within the pump receiving chamber, which receives the rotor and the plurality of vanes therein, which separates a portion between the rotor and an inner circumference side of the cam ring to a plurality of hydraulic fluid chambers, and which is arranged to be moved so that a center of an inner circumference of the cam ring is eccentric with respect to a center of the rotation of the rotor so as to vary an eccentric amount of the center of the inner circumference of the cam ring with respect to the center of the rotation of the rotor;
• side walls disposed on both sides of the cam ring in the axial direction, at least one of the side walls including a suction portion opened in a part of the plurality of the hydraulic fluid chambers, and a discharge portion opened in another part of the plurality of the hydraulic fluid chambers;
• a coil spring which is a first urging member, which is provided within the pump receiving chamber to have a set load, and which is arranged to urge the cam ring in a direction in which the eccentric amount of the cam ring is increased;
• a first control hydraulic chamber which is formed between the pump receiving chamber and the cam ring, to which a hydraulic fluid discharged from the discharge portion is introduced, and whose volume is increased when the cam ring is moved against an urging force of the coil spring;
• a second control hydraulic chamber which is formed between the pump receiving chamber and the cam ring, to which the hydraulic fluid discharged from the discharge portion is introduced from the discharge portion through an introduction passage, and whose volume is increased when the cam ring is moved in a direction identical to a direction of the urging force of the coil spring;
• a switching mechanism which is provided in the introduction passage, the switching mechanism including:
• a switching valve body including an upstream side opening portion which is connected to a portion of the introduction passage that is on a side of the discharge portion, a downstream side opening portion which is connected to a portion of the introduction passage that is on the second control hydraulic chamber, and a switching drain opening portion serving as a drain,
• a valve element which is received within the switching valve body, and which is arranged to switch a connection state between the upstream side opening portion, the downstream side opening portion and the switching drain opening portion, and
• a solenoid which is arranged to drive the valve element by being applied with an current;
• and
• a control mechanism including:
• a control valve body including an introduction passage opening portion which is opened in the downstream side opening portion, a control drain opening portion connected to the drain, and a control hydraulic chamber opening portion connected to the second control hydraulic chamber,
• a spool which is slidably received within the control valve body, and which is arranged to switch a connection state between the introduction passage opening portion, the control drain opening portion, and the control hydraulic chamber opening portion in accordance with an axial position of the spool, and
• a valve spring which is a second urging member which is received within the second axial end portion of the control valve body, and which is arranged to urge the spool toward the first axial end portion of the control valve body.

A variable displacement pump comprising:

• a housing including a pump receiving chamber formed within the housing;
• a pump constituting section which includes a rotor rotationally driven, and a plurality of vanes that are provided on an outer circumference side of the rotor to be projectable from and retractable into the rotor, which is arranged to vary volumes of a plurality of hydraulic fluid chambers in accordance with a rotation, and which is arranged to be rotationally driven, and thereby to discharge a hydraulic fluid introduced from a suction portion to a discharge portion;
• a cam ring which is received within the pump receiving chamber, which receives the pump constituting section on an inner circumference side of the cam ring, which separates a portion between the rotor and the inner circumference side of the cam ring by the plurality of the vanes, and which is arranged to be moved so that a center of an inner circumference of the cam ring is eccentric with respect to a center of the rotation of the rotor so as to vary an eccentric amount of the center of the inner circumference of the cam ring with respect to the center of the rotation of the rotor;
• a coil spring which is a first urging member which is provided within the pump receiving chamber to have a set load, and which is arranged to urge the cam ring in a direction in which the variation amounts of the volumes of the hydraulic fluid chambers opened to the discharge portion are increased;
• a first control hydraulic chamber which is formed between the pump receiving chamber and the cam ring, to which the hydraulic fluid discharged from the discharge portion is introduced, and whose volume is increased when the cam ring is moved against an urging force of the coil spring;
• a second control hydraulic chamber which is formed between the pump receiving chamber and the cam ring, to which the hydraulic pressure discharged from the discharge portion is introduced through an introduction passage connected to the discharge portion, and whose volume is increased when the cam ring is moved in a direction identical to a direction of the urging force of the coil spring;
• a switching valve which is provided in the introduction passage, and which is arranged to switch a first state in which a flow of the hydraulic fluid from the introduction passage to the second control hydraulic chamber is shut off, and in which the hydraulic fluid within the second control hydraulic chamber is discharged, and a second state in which the hydraulic fluid introduced from the introduction passage is introduced into the second control hydraulic chamber;
• and
• a control valve which is provided in the introduction passage between the switching valve and the second control hydraulic chamber, which is arranged to be actuated based on the hydraulic pressure introduced into the first control hydraulic chamber before the variation amounts of the volumes of the hydraulic fluid chambers become minimized by the cam ring, and which is arranged to introduce the hydraulic pressure to the second control hydraulic chamber when the hydraulic pressure introduced from the introduction passage through the switching valve is equal to or smaller than a predetermined pressure, and to discharge the hydraulic fluid within the second control hydraulic chamber in accordance with the hydraulic pressure when the hydraulic pressure introduced from the introduction passage becomes greater than the predetermined pressure.