Abstract: In a variable displacement oil pump, a drain chamber 36 partitioned with respect to first and second control oil chambers 31, 32 and which serves to generate a biasing force in a concentric direction based on a pump drain pressure directly introduced from a drain port 22a is interposed between first control oil chamber 31 which serves to generate a biasing force in the concentric direction in which a volume variation quantity of a plurality of pump chambers PR for a cam ring 15 based on a control pressure as a main gallery pressure introduced from an internal combustion engine and second control oil chamber 32 which serves to generate the biasing force in an eccentric direction in which the volume variation quantity of the plurality of pump chambers PR is increased for cam ring 15 based on the control pressure.

Abstract: An oil pump includes first and second control chambers, a biasing mechanism, and a changeover mechanism. The changeover mechanism connects the first control chamber with a drain portion when a valving element is in a first position, introduces a discharge pressure into the first and second control chambers when the valving element reaches a second position, and drains oil of the second control chamber to the drain portion and introduces the discharge pressure into the first control chamber when the valving element reaches a third position. The changeover mechanism changes from the first position to the second position, when the discharge pressure becomes higher than a pressure level at which the cam ring can move against a set load of the biasing mechanism, and is lower than a pressure level at which a biasing force of the biasing mechanism is increased in a stepwise manner.

Abstract: A variable displacement pump includes: side walls provided on both sides of the cam ring in an axial direction; and an introduction passage which is formed on one of the separation walls across which the hydraulic chambers pass when the hydraulic chambers are moved from the suction portion to the discharge portion, which is arranged to shut off a connection between one of the hydraulic chambers and the control hydraulic chamber by an axial end surface of the cam ring when the cam ring is in a maximum eccentric state, and which is arranged to connect the one of the hydraulic chambers and the control hydraulic chamber by a movement of the cam ring in the direction to decrease the eccentric amount of the cam ring, and thereby to introduce the discharge pressure within the control hydraulic chamber to the one of the hydraulic chambers.

Abstract: A variable displacement pump includes: a first control oil chamber which moves a cam ring toward a direction against a biasing force of a biasing member when a discharge pressure is introduced thereinto; a second control oil chamber which acts a hydraulic pressure upon the cam ring by cooperating with the biasing force of the biasing member when hydraulic oil is introduced thereinto; a switching mechanism which switches between one state in which hydraulic oil whose pressure is decreased than a discharge pressure is introduced to the second control oil chamber from the discharge section and another state in which hydraulic oil is discharged from the second control oil chamber; and a control mechanism operated before an eccentricity of the cam ring becomes a minimum and which discharges a greater amount of hydraulic oil within the second control oil chamber as the discharge pressure becomes larger.

Abstract: A vane pump in which oil is drawn from at least one side, in an axial direction, of a cam ring and is discharged from at least the one side, in the axial direction, of the cam ring, the vane pump including: a portion defined by a groove formed on an inner circumference surface of the cam ring, the groove extending along a circumferential direction of the inner circumference surface and arranged in a position including a middle of an axial direction width on the inner circumference surface in an oil suction section or an oil discharge section of the cam ring, the groove being formed so that a depth of the groove is constantly shallower from a mid-point, in the circumferential direction, of the groove to both ends of the groove.

Abstract: A vane pump includes a rotor including a first annular groove and a second annular groove. The rotor further includes a cylindrical portion projecting axially from a radial inner side of the first annular groove and fitting over a drive shaft, and a slide contact portion formed on a radial inner side of the second annular groove. The cylindrical portion is slidably received in a bearing hole formed in a first side wall of a housing, whereas the slide contact portion abuts slidably on an inside wall surface of a second side wall of the housing. There is further formed, in the first annular groove, a recessed portion making a pressure receiving area of one of the first and second annular grooves greater than a pressure receiving area of the other of the first and second annular grooves.

Abstract: A variable displacement pump includes: a first urging member arranged to urge the cam ring in a direction to increase the eccentric amount; a second urging member arranged to urge the cam ring in a direction to decrease the eccentric 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 where the cam ring is movable against a resultant force of the urging forces of the first and second urging members, and where the cam ring is not movable only against the urging force of the first urging member.

Abstract: A vane pump in which oil is drawn from at least one side, in an axial direction, of a cam ring and is discharged from at least the one side, in the axial direction, of the cam ring, the vane pump including: a portion defined by a groove formed on an inner circumference surface of the cam ring, the groove extending along a circumferential direction of the inner circumference surface and arranged in a position including a middle of an axial direction width on the inner circumference surface in an oil suction section or an oil discharge section of the cam ring, the groove being formed so that a depth of the groove is constantly shallower from a mid-point, in the circumferential direction, of the groove to both ends of the groove.

Abstract: A variable displacement oil pump includes: a switching mechanism arranged to switch a state in which the hydraulic fluid is introduced to the second control hydraulic chamber through a connection passage, and a state in which the hydraulic fluid is discharged from the second control hydraulic chamber through the connection passage; and a control mechanism arranged to be actuated before the eccentric amount of the cam ring becomes minimum, and arranged to vary an opening area of the connection passage as the discharge pressure is increased, and to vary an opening area of a discharge passage arranged to discharge the hydraulic fluid within the second control hydraulic chamber, in a direction opposite to a direction of a variation of the opening area of the introduction passage.

Abstract: A variable displacement pump including a control mechanism shiftable between first and second states, when the control mechanism is in the first state, the spool is in an initial position in which fluid communication between an introduction port and the remaining ports is restrained, fluid communication between a first control port and a drain port is allowed, and fluid communication between a second control port and the drain port is restrained, and when the control mechanism is shifted to the second state in accordance with increase in fluid pressure discharged, the spool is in an operating position in which the fluid communication between the introduction port and the first control port is allowed, the fluid communication between the first control port and the drain port is restrained, and the fluid communication between the second control port and the drain port is allowed.

Abstract: A variable displacement pump includes: a control mechanism arranged to be actuated based on a hydraulic pressure introduced into the introduction passage before the eccentric amount is minimized, and arranged to introduce the hydraulic pressure through a throttling to the second control hydraulic chamber when the hydraulic pressure introduced from the introduction passage 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; and a switching mechanism arranged to switch between a state in which the hydraulic fluid introduced into the introduction passage is introduced to the control mechanism, and a state in which the hydraulic fluid introduced into the introduction passage is discharged from the control mechanism.

Abstract: A variable displacement pump includes a pump structural member configured to change volumes of a plurality of working chambers by rotation of a rotor, so as to introduce oil through an inlet port into the working chambers and to discharge the oil through a discharge port, and further configured to oscillate a cam ring by a discharge pressure introduced into a control oil chamber. A first coil spring is provided to force the cam ring in a direction for increasing of a rate of change of the working-chamber volume. A second coil spring is provided to force the cam ring in a direction for decreasing of the rate of change of the working-chamber volume. The first and second coil springs are laid out on both sides of an arm portion of the cam ring in a manner so as to be opposed to each other.

Abstract: A variable displacement pump includes: a first control oil chamber which moves a cam ring toward a direction against a biasing force of a biasing member when a discharge pressure is introduced thereinto; a second control oil chamber which acts a hydraulic pressure upon the cam ring by cooperating with the biasing force of the biasing member when hydraulic oil is introduced thereinto; a switching mechanism which switches between one state in which hydraulic oil whose pressure is decreased than a discharge pressure is introduced to the second control oil chamber from the discharge section and another state in which hydraulic oil is discharged from the second control oil chamber; and a control mechanism operated before an eccentricity of the cam ring becomes a minimum and which discharges a greater amount of hydraulic oil within the second control oil chamber as the discharge pressure becomes larger.

Abstract: An oil pump includes first and second control chambers, a biasing mechanism, and a changeover mechanism. The changeover mechanism connects the first control chamber with a drain portion when a valving element is in a first position, introduces a discharge pressure into the first and second control chambers when the valving element reaches a second position, and drains oil of the second control chamber to the drain portion and introduces the discharge pressure into the first control chamber when the valving element reaches a third position. The changeover mechanism changes from the first position to the second position, when the discharge pressure becomes higher than a pressure level at which the cam ring can move against a set load of the biasing mechanism, and is lower than a pressure level at which a biasing force of the biasing mechanism is increased in a stepwise manner.

Abstract: A variable displacement pump includes: side walls provided on both sides of the cam ring in an axial direction; and an introduction passage which is formed on one of the separation walls across which the hydraulic chambers pass when the hydraulic chambers are moved from the suction portion to the discharge portion, which is arranged to shut off a connection between one of the hydraulic chambers and the control hydraulic chamber by an axial end surface of the cam ring when the cam ring is in a maximum eccentric state, and which is arranged to connect the one of the hydraulic chambers and the control hydraulic chamber by a movement of the cam ring in the direction to decrease the eccentric amount of the cam ring, and thereby to introduce the discharge pressure within the control hydraulic chamber to the one of the hydraulic chambers.

Abstract: Fluid inlet and outlet portions are provided for introducing and discharging a hydraulic fluid. The fluid outlet portion includes a plurality of outlet ports. A drive shaft is provided that rotates about its axis. A plurality of volume variable pump chambers are arranged about the drive shaft and rotated by the same. The pump chambers are arranged between the fluid inlet and outlet portions for compressing the hydraulic fluid from the fluid inlet portion before discharging the same from the fluid outlet portion. The pump chambers are exposed to the outlet ports separately one after another when the pump chambers are rotated by the drive shaft. A discharge rate varying mechanism is provided that varies a fluid discharge rate of each of the outlet ports by varying the amount of the fluid led to the outlet ports.

Abstract: A variable displacement pump includes: a first urging member arranged to urge the cam ring in a direction to increase the eccentric amount; a second urging member arranged to urge the cam ring in a direction to decrease the eccentric 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 where the cam ring is movable against a resultant force of the urging forces of the first and second urging members, and where the cam ring is not movable only against the urging force of the first urging member.

Abstract: An oil pump includes: a valve receiving hole including; a first port connected with the suction port, a second port connected with the switching port, a third port connected with the discharge port, and a discharge pressure introduction port arranged to receive the discharge pressure, a valve element arranged to switch a first state in which the second port and the third port are connected, and a second state in which the first port and the second port are connected; and an urging member arranged to urge the valve element toward the first end side, the pressure receiving area of the valve element and the urging force of the urging member being set so that the oil pump is switched from the first state to the second state when the pressure within the hydraulic fluid chambers to which the switching port is opened is a negative pressure.

Abstract: A variable displacement pump includes: a pump section arranged to be driven by an internal combustion engine, and to discharge a lubricant introduced from an induction portion to a plurality of hydraulic chambers, through a discharge portion, by volume variations of the hydraulic chambers; a variable mechanism arranged to move a movable member by using the discharge pressure of the lubricant, and to vary volumes of the hydraulic chambers which are opened to the discharge portion; and an urging section arranged to urge the movable member in a direction to increase quantities of the volume variations of the hydraulic chambers, the urging section having a spring constant which increases as a movement distance of the movable member in a direction to decrease the quantities of the volume variations of the hydraulic chambers increases.

Abstract: In a variable displacement vane pump employing a cam ring, a pump rotor, and a plurality of vanes, each slidably fitted into the rotor, a biasing member is provided to force the cam ring in a direction that a geometric center of an inner peripheral surface of the cam ring and a rotation center of the rotor are spaced apart from each other. A force, by which the cam ring can be oscillated against the biasing member in accordance with a buildup of a pressure in a pump discharge portion, acts on the inner peripheral surface of the cam ring.