Abstract: A variable displacement pump includes a control valve formed with a high-pressure chamber for introducing therein high-pressure fluid on the upstream side of a metering orifice, a pressure chamber for introducing therein pressure fluid on the downstream side of the metering orifice, a low-pressure chamber arranged between the high-pressure and pressure chambers for introducing therein low-pressure fluid, and a communication passage for providing fluid communication between one of the high-pressure and low-pressure chambers and a first fluid-pressure chamber of the pump.

Abstract: A variable displacement pump includes a rear cover and side plate arranged on both sides of a cam ring and making slide contact with the cam ring. The rear cover has an end face on the side of the cam ring, which is formed with a suction port. A seal member is arranged in a chamber formed between a pump housing and the cam ring and for dividing the chamber into two portions that define first and second working chambers. A connection groove and terminal groove are formed in the end face of the rear cover to provide fluid communication between the suction port and the second working chamber.

Abstract: Within a cam ring (8), a rotor having a plurality of vanes (27) is eccentrically disposed. A metering orifice (136) is provided halfway on a discharge passage (135) of pressure fluid discharged from the pump, and a control valve is activated due to a pressure difference between the upstream and downstream sides of the metering orifice (136). A fluid pressure of the first fluid pressure chamber (21) is controlled by activation of the control valve (123). The second fluid pressure chamber (22) is shut off from the control valve (123) to introduce a pressure on the suction side at any time. To return the cam ring (8) in a direction of expanding a pump chamber (11), an internal pressure of the cam ring (8) is applied in the return direction.

Abstract: A variable displacement pump has a cam ring, a rotor, a plurality of vanes, a pressure plate and a rear body. The cam ring is accommodated within a pump body. The rotor rotates within the cam ring. The plurality of vanes are inserted retractably into slits formed at regular intervals circumferentially in the rotor. The pressure plate and the rear body carry the cam ring and the rotor. A circular groove communicating to a back pressure inlet bore on a bottom portion of the slits is formed in a suction area on a face of the rear body on a side of the rotor. The groove is communicated via a communication passage to a passage between a power steering gear and a tank T to introduce a working oil after used in the power steering gear.

Abstract: Within a cam ring (8), a rotor having a plurality of vanes (27) is eccentrically disposed. A metering orifice (136) is provided halfway on a discharge passage (135) of pressure fluid discharged from the pump, and a control valve is activated due to a pressure difference between the upstream and downstream sides of the metering orifice (136). A fluid pressure of the first fluid pressure chamber (21) is controlled by activation of the control valve (123). The second fluid pressure chamber (22) is shut off from the control valve (123) to introduce a pressure on the suction side at any time. To return the cam ring (8) in a direction of expanding a pump chamber (11), an internal pressure of the cam ring (8) is applied in the return direction.

Abstract: Within a cam ring (8), a rotor having a plurality of vanes (27) is eccentrically disposed. A metering orifice (136) is provided halfway on a discharge passage (135) of pressure fluid discharged from the pump, and a control valve is activated due to a pressure difference between the upstream and downstream sides of the metering orifice (136). A fluid pressure of the first fluid pressure chamber (21) is controlled by activation of the control valve (123). The second fluid pressure chamber (22) is shut off from the control valve (123) to introduce a pressure on the suction side at any time. To return the cam ring (8) in a direction of expanding a pump chamber (11), an internal pressure of the cam ring (8) is applied in the return direction.

Abstract: A variable displacement pump has a cam ring, a rotor, a plurality of vanes, a pressure plate and a rear body. The cam ring is accommodated within a pump body. The rotor rotates within the cam ring. The plurality of vanes are inserted retractably into slits formed at regular intervals circumferentially in the rotor. The pressure plate and the rear body carry the cam ring and the rotor. A circular groove communicating to a back pressure inlet bore on a bottom portion of the slits is formed in a suction area on a face of the rear body on a side of the rotor. The groove is communicated via a communication passage to a passage between a power steering gear and a tank T to introduce a working oil after used in the power steering gear.

Abstract: A variable displacement pump includes a control valve formed with a high-pressure chamber for introducing therein high-pressure fluid on the upstream side of a metering orifice, a pressure chamber for introducing therein pressure fluid on the downstream side of the metering orifice, a low-pressure chamber arranged between the high-pressure and pressure chambers for introducing therein low-pressure fluid, and a communication passage for providing fluid communication between one of the high-pressure and low-pressure chambers and a first fluid-pressure chamber of the pump.

Abstract: A variable displacement pump includes a rear cover and side plate arranged on both sides of a cam ring and making slide contact with the cam ring. The rear cover has an end face on the side of the cam ring, which is formed with a suction port. A seal member is arranged in a chamber formed between a pump housing and the cam ring and for dividing the chamber into two portions that define first and second working chambers. A connection groove and terminal groove are formed in the end face of the rear cover to provide fluid communication between the suction port and the second working chamber.

Abstract: A first fluid pressure chamber 21 is provided in one of the swing directions of a cam ring 8 and a second fluid pressure chamber 22 is provided in the other direction, with a spring 17 for urging the cam ring 8 toward the second fluid pressure chamber 22. Within the cam ring 8, a rotor having a plurality of vanes 27 is eccentrically disposed. A metering orifice 136 is provided halfway on a discharge passage 135 of pressure fluid discharged from the pump, and a control vale is activated due to a pressure difference between the upstream and downstream sides of the metering orifice 136. A fluid pressure of the first fluid pressure chamber 21 is controlled by activation of the control valve 123. The second fluid pressure chamber 22 is shut off from the control valve 123 to introduce a pressure on the suction side at any time.

Abstract: A variable displacement pump has a cam ring, a rotor, a plurality of vanes, a pressure plate and a rear body. The cam ring is accommodated within a pump body. The rotor rotates within the cam ring. The plurality of vanes are inserted retractably into slits formed at regular intervals circumferentially in the rotor. The pressure plate and the rear body carry the cam ring and the rotor. A circular groove communicating to a back pressure inlet bore on a bottom portion of the slits is formed in a suction area on a face of the rear body on a side of the rotor. The groove is communicated via a communication passage to a passage between a power steering gear and a tank T to introduce a working oil after used in the power steering gear.

Abstract: First and second fluid pressure chambers 43 and 44 are formed on both sides of a swingable cam ring 27. A control valve 40 for controlling a swing of the cam ring is provided. To operate the control valve, a variable metering throttle 61 is provided in the middle of a discharge path. The variable metering throttle 61 is formed with a communicating channel 62 which is formed in the side surface of one side of the cam ring in the axial direction, and communicates with a discharge-side hollow 33 being formed in a pressure plate 30 which faces the side surface, and a small hole 63 which is bored in the pressure plate 30 while facing a part of the communicating channel, and of which the opening area is varied with the side edge 62a of the communicating channel of the cam ring 27 when the cam ring swings.

Abstract: A variable displacement pump includes pump bodies, a cam ring, first and second fluid pressure chambers, a rotor, a driving shaft, a pump chamber, a compression coil spring, a metering restrictor portion, and a control valve. A plunger damper is formed to incorporate the compression coil spring such that a distal end of the plunger damper abuts against a side portion of the cam ring in the second fluid pressure chamber. A small hole constituting the metering restrictor portion is formed at such a position that it is opened/closed by a slidable motion of the plunger damper during a swing motion of the cam ring, and such that it is partitioned from the second fluid pressure chamber, so that an opening area of the small hole changes in an interlocking manner to the swing motion of the cam ring.

Abstract: A flow control valve which exhibits a so-called drooping response is provided which causes the flow rate supplied to a hydraulic instrument to be reduced as a discharge flow from a pump increases. A union is inserted into and fixedly connected to a bore which receives a spool valve, and is formed with an orifice. A sleeve having an outer diameter which varies in its axial direction is fitted around the union, thereby defining a restricted passage on the outside of the sleeve which restricts the passage of a hydraulic fluid. A pressure differential between the upstream and the downstream side of the restricted passage is effective to slide the sleeve, thereby reducing the opening of the orifice to reduce the flow rate supplied to the hydraulic instrument in a gradual manner.

Abstract: A flow control valve which exhibits a drooping response, namely, having a response which causes the flow rate supplied to a hydraulic instrument to be reduced as the discharge flow from a pump increases is disclosed. A spool valve is received in a bore, in which a union is disposed and secured. An orifice is formed in the union, and a sleeve is fitted around the union. A restriction which limits the passage of hydraulic fluid therethrough is formed on the external surface of the sleeve. A pressure differential between the upstream and the downstream side of the restriction is effective to cause a sliding movement of the sleeve to thereby reduce the area of the orifice, thus gradually decreasing the flow rate supplied to the hydraulic instrument.

Abstract: A flow control valve comprises an orifice which is formed in a supply passage of hydraulic fluid, and a spool valve for feeding part of hydraulic fluid supplied through the supply passage to a branch passage in response to a pressure differential across the orifice. A switching valve which switches a fluid circuit is assembled with the flow control valve. The switching valve comprises drive means which is directly and mechanically coupled to the spool valve for forcibly causing a displacement of the spool valve to open the branch passage while closing the supply passage. Hydraulic fluid is normally supplied through the supply passage, but when the drive means is actuated, hydraulic fluid can be supplied only to the branch passage.