Abstract: A scroll type machine incorporates a unique system for monitoring the status of a valve which is used to control the capacity of the compressor. The valve functions to open and close a fluid passage between two areas of the compressor for capacity modulation. By monitoring the temperature of the fluid after the valve, it can be determined whether or not the valve is functioning. If the temperature fluctuates, the valve is functioning. If the temperature is constant, the valve is not operating properly. Another embodiment monitors the pressure within the fluid line controlled by the valve.

Abstract: This invention provides the use of a pump to regulate torque in a planetary gear system. The pump is provided with a moveable piston as an end plate. An actuator, attached to the piston, controls the movement of the piston. In one position, the piston is in contact with the internal components of the pump. When the actuator moves the piston, the piston loses contact with the pump, thus allowing a free flow of fluid between the inlet and outlet of the pump. In this configuration, the pump is no longer able to generate the pressure that creates torque in the planetary gear system.

Abstract: The present invention provides the art with a scroll machine which has a plurality of built-in volume ratios along with their respective design pressure ratios. The incorporation of more than one built-in volume ratio allows a single compressor to be optimized for more than one operating condition. The operating envelope for the compressor will determine which of the various built-in volume ratios is going to be selected. Each volume ratio includes a discharge passage extending between one of the pockets of the scroll machine and the discharge chamber. All but the highest volume ration utilize a valve controlling the flow through the discharge passage.

Abstract: A variable displacement compressor has a control valve for controlling the displacement of the compressor. When the pressure in a discharge chamber of the compressor (discharge pressure) is equal to or higher than a first threshold value, a controller executes a limiting control for limiting the discharge pressure. During the limiting control, the controller gradually decreases a duty ratio, which is sent to the control valve, such that the displacement of the compressor is gradually decreased. When the duty ratio is decreased to a reference duty ratio, the controller sets the duty ratio to zero %. As a result, the compressor displacement is minimized and the discharge pressure is lowered. Therefore, the pipes of an external refrigerant circuit does not receive excessive load based on high discharge pressure.

Abstract: A control system for a variable displacement pump. The control system is operably associated with an engine control unit for passively or actively controlling the output of the pump in response to signals from the engine control unit.

Abstract: A high pressure pump and delivery system mating to LNG storage and suited for natural gas powered trucks and buses, but also suitable for other cryogenic liquid fuels. The reciprocating pump is comprised of a liquid pumping portion and a vapor compressing portion, operating in concert so that it is possible to locate the pump above a source of saturated LNG and to reliably supply high pressure LNG. The delivery system provides a method of utilizing both the pumped LNG and the compressed NG in a Diesel type fuel injection system, and also to scavenge NG vapor from the LNG storage container so as to extend it's storage life. While especially useful for trucks and buses, the present invention is not limited thereto, as it is also useful for locomotives, automobiles and other vehicles designed to operate through combustion of natural gas, as well as stationary applications.

Abstract: A safety device limits the pressure in an axial-piston compressor with variable piston displacement. The compressor has as wobble plate or swash plate whose tilt angle can be variably controlled by the pressure differential between the high pressure in the discharge pressure zone and the pressure in the piston-drive chamber. The safety device consists of a valve arranged in a connector channel between the discharge pressure zone and the pressure zone of the piston-drive chamber. When the discharge pressure exceeds a given pressure limit, the safety device responds by allowing an increased flow of pressure medium from the discharge pressure zone to the piston-drive chamber. The influx of pressure medium into the piston-drive chamber causes a reduction of the tilt angle of the swash plate or wobble plate.

Abstract: A variable displacement compressor includes a suction chamber, a discharge chamber, and a crank chamber. The compressor also includes a first path for allowing communication between the crank chamber and the discharge chamber, and a second path for allowing communication between the crank chamber and the suction chamber. Moreover, the compressor includes a valve assembly. The valve assembly includes a valve positioned within the first path, and the valve assembly controls a pressure in the crank clamber by varying a position of the valve. The compressor also includes an orifice mechanism. The orifice mechanism includes a plate having a hole formed therethrough, and an elongated member positioned within the hole. Specifically, the elongated member is movable within the hole, and an annulus of the orifice mechanism is defined between the elongated member and an interior surface of the hole.

Abstract: A method and apparatus for controlling a variable displacement hydraulic pump having a swashplate pivotally attached to the pump. The method and apparatus includes determining a desired swashplate angle as a function of a power limit of the pump, determining an actual swashplate angle, determining a value of discharge pressure of the pump, moving a servo valve spool to a desired position as a function of the desired swashplate angle, the actual swashplate angle and the discharge pressure, and responsively moving the swashplate to the desired swashplate angle position.

Abstract: A cam ring 10 is slidably supported within a pump body 2, and a rotor 20 is rotatably disposed inside the cam ring. The cam ring is eccentric to a rotation shaft 22 of the rotor. The rotor carries a plurality of vanes 18 that can be advanced or retreated, in which a pump chamber 24 is formed in a space between the cam ring and the rotor. The cam ring is formed with the first and second fluid pressure chambers 14 and 16 on both sides thereof, and biased in a direction where the displacement of the pump chamber is at maximum by a spring 26. A control valve 28 is provided in which a differential pressure across a metering orifice is applied on both ends of a spool 32 and a spring 36 is disposed on the side of an end face where a downstream fluid pressure is applied. The fluid pressures of the fluid pressure chambers 14 and 16 are controlled by means of the control valve, whereby the cam ring is swung.

Abstract: In a variable displacement pump, a pressurizing cylinder is provided in an opposite side of the first fluid pressure chamber, holding the cam ring there between, and a piston inserted to the pressurizing cylinder collides with the cam ring. A pressure in an upstream side of both throttle passages comprising the variable throttle passage and the fixed throttle passage provided in the pump discharge side passage is introduced to the first fluid pressure chamber and the oil chamber of the pressurizing cylinder, and a pressure in a downstream side of the both throttle passages is introduced to the second fluid pressure chamber.

Abstract: An fuel injection control unit (an electronic governor 12 and a controller 13) for an engine 1 is capable of performing control in a governor region based on an isochronous characteristic. A working machine controller 18 receives a delivery pressure signal P and controls a regulator 16 such that, when the delivery pressure of a hydraulic pump exceeds a predetermined pressure P1, the displacement of the hydraulic pump does not exceed a value decided in accordance with a preset pump absorption torque curve 20. Also, the working machine controller 18 controls the regulator 16 such that, when the delivery pressure of the hydraulic pump 2 is not higher than the predetermined pressure P1, the displacement of the hydraulic pump is increased as the delivery pressure of the hydraulic pump lowers from the predetermined pressure P1. As a result, even when the governor region is controlled based on the isochronous characteristic, the delivery flow rate of the hydraulic pump is increased as an engine load reduces.

Abstract: In a vane pump, a bottom surface of a suction side low pressure passage is set to be below a bottom surface of a return passage of a flow control valve in a cross portion between the return passage and the low pressure passage.

Abstract: A capacity control system has a valve which closes off the inlet to one or more of the cylinders in a multicylinder compressor. The valve is motivated by fluid at discharge pressure which reacts against a piston to close the inlet. An orifice is positioned in the flow of the fluid at discharge pressure to control the velocity of the piston to reduce impact loading and improve reliability.

Abstract: A variable displacement type compressor has a tiltable swash plate and pistons in cylinder bores. The displacement of the compressor is controlled by changing an inclination angle of the swash plate. A first valve is arranged to open and close the suction passage in response to the pressure in the discharge chamber. The valve element of the first valve is arranged to face the end of the suction passage, and can hermetically close the suction passage when the refrigerant gas is introduced into the pressure chamber from the discharge chamber. The refrigerant gas can be also introduced into the crank chamber when the refrigerant gas is introduced from the discharge chamber into the pressure chamber.

Abstract: A variable displacement vane pump comprises a pump body having inlet and outlet ports, a rotor driven by a drive shaft and co-axially aligned therewith, a plurality of radially extending vanes slidably disposed in the rotor, and a slide pivotally disposed on a pivot in the pump body and having a central axis eccentric to the axis of the rotor. A plurality of fluid chambers are defined by the rotor, vanes, and slide. A spring acts on the slide to urge the slide in one direction. A regulating chamber is configured as a semi-circular cylinder intermediate the pump body and an outer surface of the slide, wherein a pressure regulating valve pressurizes the regulating chamber to pivot the slide against the force of the spring to decrease the volume of the fluid chambers. The slide includes a slide channel formed in a face to channel fluid leakage from the fluid chambers away from the regulating chamber.

Abstract: A scroll type machine incorporates a unique system for monitoring the status of a valve which is used to control the capacity of the compressor. The valve functions to open and close a fluid passage between two areas of the compressor for capacity modulation. By monitoring the temperature of the fluid after the valve, it can be determined whether or not the valve is functioning. If the temperature fluctuates, the valve is functioning. If the temperature is constant, the valve is not operating properly. Another embodiment monitors the pressure within the fluid line controlled by the valve.

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 device for supplying liquids, particularly fuel, has a first drive shaft (32) and a supply pump (30) having at least one supply member (40) coupled to a second drive shaft (36), whereby the first drive shaft (32) drives the second drive shaft (36) via a drive unit (60). The drive unit (60) is preferably a tapered ring drive, which has a first frictional bevel gear (62) connected to the first drive shaft (32) and a second frictional bevel gear (64) connected to the second drive shaft (36), whereby the first and second friction bevel gears (62, 64) roll off one another by a tapered ring (66) disposed between the two bevel gears. The tapered ring (66) is movable for changing the gear ratio of the gear unit (60) as a function of the supply pressure produced by the supply pump (30). In this manner, with a lower supply pressure, a large gear ratio of the gear unit (60) is determined, and with an increased supply pressure, a smaller gear ratio of the gear unit (60) is determined.

Abstract: A variable displacement compressor is operated efficiently by avoiding inefficient conditions. The compressor varies its displacement using a control valve for which an external duty control procedure is performed. A target value for controlling the displacement is determined in accordance with the duty ratio Dt of a drive signal sent to the control valve. If the duty ratio Dt is equal to or greater than a predetermined reference value DJ, the displacement is permitted to be varied corresponding to the duty ratio Dt. If the duty ratio Dt is smaller than the reference value DJ, the variable displacement control through the duty control procedure is suspended. In this case, the compressor is operated with a nullified duty ratio (Dt=0), or a minimum displacement.

Abstract: A variable capacity compressor like a swash plate type where a pressurized fluid is fed to a control pressure chamber such as a swash plate chamber to apply a backpressure to a piston etc. and the backpressure is changed by the capacity control valve, wherein the valve is streamlined and reduced in cost by providing a simple valve such as a two-way solenoid valve as a capacity control valve in a feed path to or discharge path from the control pressure chamber. By controlling the duty ratio of the valve, it is possible to smoothly change the capacity of the compressor. Further, a torque sensor is provided at a drive shaft, and the valve is controlled by a control unit to change the discharge capacity of the compressor in accordance with that detection value.

Abstract: A pump including a pump chamber 18, formed in a pump body 11, between a cam ring 17 and a rotor 15. The cam ring is formed so as to move in a direction whereby the pump capacity of the pump chamber increases and decreases. First and second fluid pressure chambers 33 and 34 are formed at opposite sides of the cam ring 17. The pump has a spool that is axially moved by a difference in fluid pressure between upper and lower stream sides of a metering throttle 50 connected to a discharge side passage 27 of the pump chamber. The spool is part of a control valve 30 that controls fluid pressure in at least the first fluid pressure chamber. An electronic driving unit, for example, a solenoid 60, applies axial thrust to the spool of the control valve.

Abstract: A control valve for installation in a wobbleplate compressor with a changeable working volume is provided with an inlet for a connection to a pressure chamber, a first outlet for connection to a crank chamber, and a second outlet for connection to a suction chamber. A closing element cooperates with the second outlet and is acted upon by a device for controlling the gas mass flow.

Abstract: Scroll compressors (100, 110) may include a movable scroll (20) that is disposed opposite to a fixed scroll (2). At least one compression chamber (32) is defined between the fixed scroll and the movable scroll. A motor (49) drives the movable scroll, so that the movable scroll revolves (orbits) relative to the fixed scroll. The movable scroll includes a front portion (20b) that slidably contacts the fixed scroll. The front portion receives the pressure of the pressurized refrigerant that is disposed within the compression chamber. The movable scroll also includes a rear portion (20a) that slidably contacts a portion (4a) of a compressor housing. The motor is disposed within a motor chamber (45) defined within the compressor housing. A first conduct route (94) communicates discharged refrigerant from a discharge-side region (85) to the motor chamber.

Abstract: The present invention provides the art with a scroll machine which has a plurality of built-in volume ratios along with their respective design pressure ratios. The incorporation of more than one built-in volume ratio allows a single compressor to be optimized for more than one operating condition. The operating envelope for the compressor will determine which of the various built-in volume ratios is going to be selected. Each volume ratio includes a discharge passage extending between one of the pockets of the scroll machine and the discharge chamber. All but the highest volume ration utilize a valve controlling the flow through the discharge passage.

Abstract: A pump includes a cylinder, a piston assembly, a first nozzle, a valve, a controller, a ring and a second nozzle. The cylinder defines first and second chambers and first and second channels for communication between the chambers. The piston assembly is received in the first chamber. The first nozzle defines a channel. The valve is received in the first chamber. The controller defines an axial channel and a radial channel communicated with the axial channel, and is received in the second chamber and linked to the valve through the second channel. The controller is movable between a first position for allowing the valve to seal the second channel and a second position for driving the valve to open the second channel. The ring is mounted on the controller so as to divide the second chamber into a first portion for communication between the first channel and the channel of the first nozzle and a second portion for communication between the second channel and the radial channel of the controller.

Abstract: First and second fluid pressure chambers are formed in both sides of a movement direction of a cam ring swingably placed within a pump body. A spool of a control valve is moved due to a pressure difference between the front and back of a metering orifice. Fluid pressures of the fluid pressure chambers are controlled. The cam ring is swung. Further, a solenoid for giving thrust in an axial direction thereof to the spool of the control valve and electronic control device for controlling driving of the solenoid are provided. The electronic control device has a steering sensor and determines a steering direction based on a signal from the steering sensor and also calculates a steering speed to the steering direction and controls a driving current of the solenoid in response to this steering speed and changes a discharge flow rate of a pump.

Abstract: An auxiliary solenoid controlled variable displacement power steering pump, hydraulic systems incorporating same, and method for improving the efficiency of variable displacement power steering pumps. In one embodiment, a rotor is arranged within a pump body, and a cam fitted on an outer periphery of the rotor and movably arranged within the pump body to form a variable volume pump chamber. The cam is biased towards a position within the pump body to create maximum displacement. A mechanism is provided for forcing the cam into a position of fixed minimum or reduced displacement under certain conditions, such as low engine speed and power steering demand. In a preferred embodiment, the mechanism comprises a solenoid driven connecting rod that is operatively connected to the cam. Activation of the solenoid forces the cam to a position of fixed minimum or reduced displacement.

Abstract: A method and apparatus for controlling a variable displacement hydraulic pump having a swashplate pivotally attached to the pump. The method and apparatus includes determining a desired swashplate angle as a function of a power limit of the pump, determining an actual swashplate angle, determining a value of discharge pressure of the pump, moving a servo valve spool to a desired position as a function of the desired swashplate angle, the actual swashplate angle and the discharge pressure, and responsively moving the swashplate to the desired swashplate angle position.

Abstract: A variable displacement swash plate type compressor which incorporates a conduit formed in the cylinder block to provide fluid communication between a crank chamber and one or more cylinders to eliminate the need for an orifice tube in fluid communication between a discharge chamber and the crank chamber and to increase the flow of refrigerant gas and lubricating oil to the crank chamber under all operating conditions and to increase the internal fluid pressure in the crank chamber.

Abstract: A scroll type machine incorporates a unique system for monitoring the status of a valve which is used to control the capacity of the compressor. The valve functions to open and close a fluid passage between two areas of the compressor for capacity modulation. By monitoring the temperature of the fluid after the valve, it can be determined whether or not the valve is functioning. If the temperature fluctuates, the valve is functioning. If the temperature is constant, the valve is not operating properly. Another embodiment monitors the pressure within the fluid line controlled by the valve.

Abstract: To permit forcedly stopping combining flows of pressure fluid from two hydraulic pumps when a load pressure on a combined-flow-driven actuator in which the flows of pressure fluid are combined together exceeds a predetermined pressure and hence to permit driving the combined-flow-driven actuator with the pressure fluid from only one of the hydraulic pumps, a hydraulic drive system is provided with a flow-combining valve 2 connected to a directional control valve 1 in a first group of directional control valves via a center bypass passage 3, a flow-combining circuit 5 communicating the flow-combining valve 2 and a supply port of a flow-combining directional control valve 4 with each other, and a combined-flow-driven actuator 20 controlled by the flow-combining directional control valve 4, and performs overall power control such that a total value of input torques to the two hydraulic pumps 15,18 does not exceed an output torque from an engine 30.

Abstract: The present invention is directed to a method of reducing cooling capacity in a rotary vane compressor in such a way that the power requirement to drive the rotor is reduced to the same extent (or close to) as capacity is reduced. An economizer port operating in economizing and unloading cycles is located in the compression region at a point after the compression chamber has been closed for the compression and at a point where sufficient both unloading (reducing) and economizing (increasing) capacities are provided. A valve is associated with the economizer port, the valve body being formed from a part of the stator body. A seat of the valve in the closed position is shaped to be contiguous with the wall portion of the stator. In an opened position the valve provides conmumnication between the compression chamber and an external portion of the economizer port.

Abstract: The present invention provides the art with a scroll machine which has a plurality of built-in volume ratios along with their respective design pressure ratios. The incorporation of more than one built-in volume ratio allows a single compressor to be optimized for more than one operating condition. The operating envelope for the compressor will determine which of the various built-in volume ratios is going to be selected. Each volume ratio includes a discharge passage extending between one of the pockets of the scroll machine and the discharge chamber. All but the highest volume ration utilize a valve controlling the flow through the discharge passage.

Abstract: A cam ring 10 is slidably supported within a pump body 2, and a rotor 20 is rotatably disposed inside the cam ring. The cam ring is eccentric to a rotation shaft 22 of the rotor. The rotor carries a plurality of vanes 18 that can be advanced or retreated, in which a pump chamber 24 is formed in a space between the cam ring and the rotor. The cam ring is formed with the first and second fluid pressure chambers 14 and 16 on both sides thereof, and biased in a direction where the displacement of the pump chamber is at maximum by a spring 26. A control valve 28 is provided in which a differential pressure across a metering orifice is applied on both ends of a spool 32 and a spring 36 is disposed on the side of an end face where a downstream fluid pressure is applied. The fluid pressures of the fluid pressure chambers 14 and 16 are controlled by means of the control valve, whereby the cam ring is swung.

Abstract: An improved continuous capacity modulation system for scroll-type compressors is disclosed in which a valve body of a solenoid valve assembly is secured to the inner wall of the hermetic shell and the actuating coil is mounted on the outer surface thereof. The actuating coil includes a plunger/valve member which cooperates with passages provided in the valve body to selectively actuate the capacity modulation arrangement utilizing compressed fluid. The construction offers the advantage that all fluid pressure lines are located within the hermetic shell and thus protected from potential damage, the solenoid coil may be easily changed/replaced to accommodate different available operating voltages and/or malfunction thereof and the system can be easily tested prior to final welding of the outer shell. The actuating coil is controlled by Pulse Width Modulation to reduce the load demand of the compressor during times when load shedding is required.

Abstract: In order to improve a refrigerant compressor apparatus comprising a drive motor, a compressor driven by the drive motor and having several cylinders arranged in a V shape and a compressor shaft bearing eccentrics for driving pistons operating in the respective cylinders in such a manner that as smooth a running as possible can be achieved at any desired V angle it is suggested that the cylinders be arranged at a V angle of less than 90°, that the compressor shaft be mounted with only two bearing sections thereof in corresponding compressor shaft bearings, that the eccentrics be arranged between the bearing sections and that a separate eccentric be provided for each piston and be arranged at a distance from the other, individual eccentrics for the respectively other pistons.

Abstract: An air conditioning system including a compressor, a heating circuit, and a capacity controller. The compressor has a suction port, a discharge port, a driving unit provided within a driving chamber, a first passage and a second passage. The driving unit may decrease compressor output discharge capacity when the pressure within the driving chamber increases. The first passage may connect the discharge port to the driving chamber and the second passage may connect the driving chamber to the suction port. The capacity controller may open the first passage when the refrigerant discharge pressure reaches or exceeds a predetermined set point pressure. By opening the first passage, the high-pressure refrigerant may be released from the discharge port to the driving chamber through the first passage.

Abstract: A scroll compressor assembly includes a first linear drive for driving a first scroll along a first linear axis and a second linear drive for driving the first or second scroll along a second linear axis which is non-parallel to the first linear axis. Relative orbital movement between the first and second scrolls is obtained by controlling the frequency of oscillations of the first linear motor along a first linear axis and the second linear motor along the second linear axis. Further, capacity control is achieved by varying the movement of the first and second linear motors.

Abstract: An air compressor comprises a compressor main body, and a capacity adjusting apparatus connected to an intake side of the compressor main body for adjusting the intake air flow into the compressor main body. The capacity adjusting apparatus is provided in an intake pipe. The intake pipe is adjacent to a discharge pipe of the compressor. A communicating passage is formed in the adjacent portion so as to introduce the compressed air discharged from the discharge pipe into the intake pipe system. The intake pipe is provided with an opening port for limiting the intake air flow into the compressor main body. The capacity adjusting apparatus opens and closes the communicating passage and the opening by means of an intake port switch valve and a discharge ventilating port switch valve which are provided in an end portion of the capacity adjusting apparatus.

Abstract: A power- and moment-regulating system for at least two adjustable hydraulic pumps (10, 11). A hydraulic servo control apparatus (22, 23) continuously adjusts delivery as a function of pressure in a delivery pressure line (16, 17) and pressures in control lines (20, 21). Each servo control apparatus (22, 23) is provided with a moment valve (42, 43) having a valve piston (62) which moves in a valve sleeve (61) forming a valve seat and whose closure force is determined by a measuring spring (46, 47) which is connected to pump actuator (37, 38) and is preloaded depending upon the set delivery rate. The pressure in control line (20, 21) or pressure in control lines of the other hydraulic pump(s) (11, 10) act both on the valve piston (62) and on valve screen (61) of moment valve (42, 43) associated with the given hydraulic pump (10, 11).

Abstract: A pump enable system includes a variable-displacement piston pump having a displacement control device. The displacement control device controls displacement of pistons in the pump based on a position thereof, and a position control system in the pump controls a position of the displacement control device based on a load on the pump. An over-ride system selectively over-rides the position control system such that the displacement control device assumes a position which reduces displacement of the pistons in the pump.

Abstract: A variable displacement type compressor has a tiltable swash plate and pistons in cylinder bores. The displacement of the compressor is controlled by changing an inclination angle of the swash plate. A first valve is arranged to open and close the suction passage in response to the pressure in the discharge chamber. The valve element of the first valve is arranged to face the end of the suction passage, and can hermetically close the suction passage when the refrigerant gas is introduced into the pressure chamber from the discharge chamber. The refrigerant gas can be also introduced into the crank chamber when the refrigerant gas is introduced from the discharge chamber into the pressure chamber.

Abstract: A scroll compressor has a pair of scroll members which compress a fluid as the fluid moves through pockets created by the scroll members. The fluid moves from a suction pressure zone to a discharge pressure zone. A chamber is defined by one of the scroll members. The chamber is in communication with a pocket located between the suction and discharge pressure zone such that an intermediate pressurized fluid is supplied to the chamber through a fluid passageway. The fluid passageway is designed to allow a large flow from the pocket to the chamber and a small flow from the chamber to the pocket. This dual flow capability reduces the pressure pulsation in the chamber. In one embodiment, a capacity control mechanism is associated with the compressor to vary the capacity of the compressor.

Abstract: A variable displacement compressor is operated efficiently by avoiding inefficient conditions. The compressor varies its displacement using a control valve for which an external duty control procedure is performed. A target value for controlling the displacement is determined in accordance with the duty ratio Dt of a drive signal sent to the control valve. If the duty ratio Dt is equal to or greater than a predetermined reference value DJ, the displacement is permitted to be varied corresponding to the duty ratio Dt. If the duty ratio Dt is smaller than the reference value DJ, the variable displacement control through the duty control procedure is suspended. In this case, the compressor is operated with a nullified duty ratio (Dt=0), or a minimum displacement.

Abstract: A control device for a variable displacement pump in which a discharge flow rate of a hydraulic operating fluid is varied by changing a variable element comprises a first negative feedback circuit 24 for controlling a pressure of the hydraulic operating fluid fed from the variable displacement pump, a second negative feedback circuit 24a, and change-over control means 88. The first negative feedback circuit 24 has first pressure detecting means 13 for detecting the pressure of the hydraulic operating fluid, second pressure detecting means 114 for detecting a vent pressure of an electromagnetic relief valve, and a differential pressure calculation circuit 122 for calculating a difference between the pressures detected by the first and second pressure detecting means 13 and 114.

Abstract: A load sensing hydraulic control system for use in a work machine and adaptable for controlling the displacement of a variable displacement hydraulic pump. The control system includes a signal duplicating valve connected in fluid communication with both the pump controller and a fluid pressure source, and a sensor positioned and located for sensing the fluid pressure to the pump controller and outputting a signal to the controller indicative thereof. In response to signals received from the at least one sensor, the controller outputs a representative signal to the signal duplicating valve indicative of the highest pressure sensed by the at least one sensor, the signal duplicating valve being thereafter operable to allow fluid flow to pass therethrough to the pump controller.

Abstract: An air conditioning system 100 may include a compressor 101 having a driving chamber 111, a heating circuit 310 and a controller 203. This system may release high pressure refrigerant from the compressor discharge port 141 into the compressor driving chamber 111 by opening a capacity control valve 181 when the discharge pressure of the refrigerant discharged from the compressor 101 exceeds a predetermined reference value. By increasing the pressure within the driving chamber 111, the compressor discharge capacity can be reduced. As a result, the discharge pressure of the compressor 101 will be reduced by the reduction in the compressor discharge capacity. Further, the controller 203 may decrease the reference value in accordance with a value related to change in the discharge pressure. As a result, the capacity control valve 181 can be opened at an early stage of the increasing of the discharge pressure if the discharge pressure increases rapidly.

Abstract: A control valve for a variable displacement compressor. The control valve has a valve body for regulating gas flow. A bellows actuates the valve body through a first rod in accordance with an operating pressure introduced to a pressure sensing chamber. A solenoid biases the valve body through a second rod with a force based on the level or an electric current supplied to the solenoid. The cross-sectional area of the second rod is no smaller than the cross-sectional area of a valve hole of the control valve.

Abstract: A reciprocating pump having an active feedback system is provided. The reciprocating pump includes a reciprocating pump having a pump chamber with a rod reciprocally movable along a longitudinal axis of the pump chamber, with the rod including a ferromagnetic material. An induction coil disposed around the rod wherein relative axial movement between the inductance coil and the ferromagnetic material of the rod varies the inductance of the induction coil. Also provided is a reciprocating pump having an active feedback system in which the rod has an electrically conductive, diametrically tapered portion. A linear displacement sensor is disposed next to the tapered portion which induces a current in the tapered portion and generates an output voltage proportional to a relative position between the linear displacement sensor and the tapered portion.