Abstract: A pump control assembly for controlling a variable displacement hydraulic pump includes a spool mounted within a valve block. The spool is configured to move between a first and a second position within the valve block so as to selectively control the displacement of the attached pump. The pump control assembly further includes first and second chambers that each apply a force to opposite ends of the spool. The first chamber is positioned at a first end of the spool in fluid communication with a pump output port. The second chamber is positioned at a second end of the spool and in fluid communication with a hydraulic tank port and a proportional pressure reducing valve. The second chamber also includes a piston and first and second springs positioned on either side of the piston.

Abstract: The present disclosure relates to an adjusting device for adjusting the swash plate of an axial piston machine comprising an adjusting piston, which is connected to the swash plate of the axial piston machine via an adjusting lever, and a regulator for adjusting the adjusting pressure acting on the adjusting piston in dependence on a control force acting on a control piston of the regulator, wherein the adjusting piston is connected to the control piston via a feedback spring. In accordance with the present disclosure the feedback spring is at least partly received in a pot-shaped recess of the control piston.

Abstract: An electronic board includes a board, and includes on the board: a power input part inputting power output from an in-vehicle power supply; a drive circuit driving a drive source; a controller controlling driving of the drive source performed by the drive circuit; and a drive command signal input part inputting a drive command signal transmitted from outside. The electronic board further includes on the board: a drive command signal detection circuit capable of detecting the drive command signal, and controlling whether to supply the power input to the power input part to the controller based on whether the drive command signal is detected.

Abstract: In an output control of a hybrid-type engine generator equipped with a load output demand detecting unit, a load output demand increase/decrease determination unit and an output control unit, a configuration is adopted whereby load output demand from (output required by) the load is detected, increase/decrease of the detected load output demand is determined, discharge power from the battery is added to generated power output of the engine generator unit when detected load output demand is determined to be increasing, and output of the engine generator unit is controlled so as to use some generated power output of the engine generator unit as charge power of the battery when detected load output demand is determined to be decreasing.

Abstract: Disclosed are a compressor control method, control apparatus and control system. The method includes: receiving a cylinder switching instruction, and detecting operating parameters of a compressor; determining whether a cylinder switching operation is completed according to the operating parameters of the compressor; and after it is determined that the cylinder switching operation is completed, performing torque compensation.

Abstract: A working machine includes a prime mover, a traveling pump to be driven by the prime mover to output operation fluid, a traveling motor to be driven by the operation fluid outputted from the traveling pump and to change a motor speed between a first speed and a second speed higher than the first speed, a machine body on which the prime mover, the traveling pump, and the traveling motor are arranged, a traveling switching valve to be switched between a first state allowing the traveling motor to rotate at the first speed and a second state allowing the traveling motor to rotate at the second speed, and a controller to reduce a revolving speed of the prime mover based on a traveling condition of the machine body in switching the traveling switching valve between an accelerating state to switch the traveling switching valve from the first state to the second state and a decelerating state to switch the traveling switching valve from the second state to the first state.

Abstract: A hydrostatic positive displacement machine has an adjustable swept volume, and has a lifting element, a rotor with positive displacement elements supported on the lifting element, and a hydraulic adjusting device that adjusts the swept volume and includes an adjusting piston that is mounted in or on a cylinder, is movable axially rectilinearly in relation to the cylinder, and is adjacent to a pressurizable adjusting chamber. A bearing gap is formed between a circular-cylindrical bearing surface of the adjusting piston and a circular-cylindrical bearing surface of the cylinder. The adjusting piston is mounted hydrostatically, wherein at least three pressure pockets are distributed uniformly in a row over the circumference of a bearing surface. Pressure fluid flows into each pressure pocket via a fixed throttle, which is assigned only to the respective pressure pocket, and flows out of each pressure pocket via the bearing gap.

Abstract: A displacement adjusting device of a swash plate pump includes: a tilting piston slidably inserted in a housing's accommodating hole, the tilting piston pressing the swash plate pump's swash plate; a sleeve forming a control pressure chamber between the sleeve and tilting piston, the sleeve including a pump port, tank port, and output port; a spool slidably held by the sleeve, the spool switching whether to bring output port into communication with one of the pump port and tank port or block the output port from the pump and tank port; a tilting spring urging the tilting piston and spool away from each other; and a solenoid including a rod that presses the spool from an opposite side to tilting spring. In the sleeve, reaction force chamber and communication passage are formed. The communication passage being a passage through which the control pressure chamber communicates with reaction force chamber.

Abstract: In one aspect, a method for adjusting torque limits for a work vehicle may include controlling, with a computing device, an operation of an engine of the work vehicle such that a torque output of the engine is maintained at or below a baseline engine torque limit. The method may also include receiving, with the computing device, an input associated with a current hydraulic power requirement of a hydraulic system of the work vehicle, and adjusting, with the computing device, a torque limit for the engine from the baseline engine torque limit to an adjusted engine torque limit based on the current hydraulic power requirement of the hydraulic system. In addition, the method may include controlling, with the computing device, the operation of the engine such that the torque output of the engine is maintained at or below the adjusted engine torque limit.

Abstract: A hydraulic control apparatus is provided including: an electromagnetic valve that has an input port communicating with a supply destination unit of oil and a control port that is switched between communication and disconnection by resultant force of a hydraulic pressure of the supply destination unit and electromagnetic force; a variable displacement pump which has a suction port communicating with a supply source of the oil, an ejection port communicating with the supply destination unit, and a control chamber communicating with the control port and rotates in accordance with drive of the supply destination unit, in which an amount of the oil ejected to the supply destination unit through the ejection port changes in accordance with a pressure in the control chamber; and a control unit that controls a value of a necessary current that is caused to flow through the electromagnetic valve.

Abstract: A pump control assembly for controlling a variable displacement hydraulic pump includes a spool mounted within a valve block. The spool is configured to move between a first and a second position within the valve block so as to selectively control the displacement of the attached pump. The pump control assembly further includes first and second chambers that each apply a force to opposite ends of the spool. The first chamber is positioned at a first end of the spool in fluid communication with a pump output port. The second chamber is positioned at a second end of the spool and in fluid communication with a hydraulic tank port and a proportional pressure reducing valve. The second chamber also includes a piston and first and second springs positioned on either side of the piston.

Abstract: A construction machine includes a hydraulic cylinder configured to drive an attachment, a hydraulic circuit configured to supply hydraulic oil to the hydraulic cylinder, an input device that is operated by an operator, and a controller configured to control the hydraulic circuit in at least one of a first control mode where the attachment is caused to generate a force corresponding to an operation amount of the input device and a second control mode where the attachment is driven at a velocity corresponding to the operation amount of the input device.

Abstract: A work machine including a specific actuator that supplies hydraulic fluid from a plurality of hydraulic pumps includes: first and second hydraulic pumps communicating with a first hydraulic actuator; a first control valve returning hydraulic fluid delivered by the first hydraulic pump to a tank; and a load detection section that detects a load on the first hydraulic actuator. A control valve drive section drives the first control valve such that a communication area between the first hydraulic pump and the tank is enlarged corresponding to an increase in the load on the first hydraulic actuator; and a flow rate control section, during supply of the hydraulic fluid from the first and second hydraulic pumps to the first hydraulic actuator, controls to reduce a delivery flow rate of the first hydraulic pump corresponding to an increase in the load on the first hydraulic actuator.

Abstract: A compact wheel loader having a hydrostatic transmission and two modes of operation. In a normal mode, a demand lever is used to set the engine speed, and displacement of the swash plate of the hydraulic pump of the transmission is set by a hydraulic pilot pressure (Ps) that increases with engine speed, so that the transmission ratio automatically decreases as the engine speed increased. In a creeper mode, the engine is set to operate at a high speed to meet the demand of powered implements of the loader, and the wheel speed is controlled by the demand lever setting the transmission ratio by varying the hydraulic pilot pressure (Ps).

Abstract: Error detection and correction decoding apparatus performs single error correction-double error detection (SEC-DED) or double error correction-triple error detection (DEC-TED) depending on whether the data input contains a single-bit error or a multiple-bit error, to reduce power consumption and latency in case of single-bit errors and to provide powerful error correction in case of multiple-bit errors.

Abstract: A hydraulic power control system includes an engine driving a variable displacement pump. The variable displacement pump is fluidly connected to a first passageway and a second passageway, and has a selectively variable displacement that is adjustable in response to a pump displacement command signal. A hydraulic motor fluidly connected to the first and second passageways operates by a flow of hydraulic fluid originating from the pump. A controller receives an engine speed signal and adjusts pump displacement based on the engine speed signal to reduce the rotation speed of the pump when an overrun condition is present.

Abstract: A regulating valve, in particular an electroproportional pivot-angle regulator for a variable-displacement pump, includes a piston bore formed in a valve housing and a regulating piston guided in the piston bore. The regulating piston is configured to be actuated in an adjusting direction via an actuator, in particular via a lifting magnet. The regulating piston is acted upon in the opposite direction by a spring force of a counterspring. The counterspring is supported via a spring plate on a supporting spring which is supported on the valve housing. The spring plate is tensioned between the supporting spring and an adjusting device by which the spring plate is configured to be displaced in relation to the valve housing in or opposite to the adjusting direction.

Abstract: A work vehicle includes a fluid circuit to operate at least one implement for performing work, the fluid circuit having at least a first operating mode and a second operating mode. The first operating mode is configured to operate within a first predetermined flow rate range within a first predetermined fluid pressure level range. The second operating mode is configured to operate within a second predetermined flow rate range and within a second predetermined fluid pressure level range. In response to the fluid circuit operating within the second operating mode, a maximum pressure value of the second predetermined fluid pressure level range is greater than a maximum pressure value of the first predetermined fluid pressure level range, and a maximum value of the second predetermined flow level range is less than a maximum value of the first predetermined flow level range.

Abstract: There is provided a working machine which is capable of vehicle speed control through accelerator pedal operation even during execution of work under a condition where engine rotational speed is maintained constant. The working machine has the normal mode for exercising vehicle speed control by controlling engine rotational speed on the basis of the amount of depression of the accelerator pedal and by controlling the swash plate of the EST pump on the basis of the engine rotational speed, and the attachment mode for exercising vehicle speed control by controlling the swash plate of the HST pump on the basis of the amount of depression of the accelerator pedal irrespective of engine rotational speed.

Abstract: A control system for a variable displacement hydraulic motor. A movable element is movable to adjust the operating displacement of hydraulic fluid through the motor. A positioning actuator moves the movable element between first and second positions to cause maximum and minimum operating displacement of the motor. A range limiting actuator positions a movable stop in a desired position, such that the movable stop interengages the movable element to cause motor displacement between the maximum and minimum operating displacements. The control system thus operates the motor in at least three modes: maximum operating displacement; minimum operating displacement; and an intermediate operating displacement.

Abstract: In a pump housing of a motor-vehicle hydraulic assembly, on which at least two inlet-valve openings, at least two outlet-valve openings, at least one high-pressure control valve opening and at least one switchover-valve opening and a pressure-sensor connection are formed. The at least two inlet-valve openings are arranged in a first row, the at least two outlet-valve openings are arranged in a following second row, the pressure sensor connection is arranged in a further following third row, and the at least one high-pressure control valve opening and the at least one switchover valve opening are arranged in a further following fourth row. There are also five embodiments of arrangements of connecting lines and holes in a pump housing for the short connection of the valve openings and connections, and one embodiment with respect to the use of the pump housing according to one of the six embodiments.

Abstract: A control system for a variable displacement hydraulic pump is disclosed. The control system utilizes two flow control valves to provide a flow of hydraulic fluid to two control actuators. The control actuators create opposing moments on the pump swashplate to control swashplate orientation and pump displacement.

Abstract: An arrangement for a hydraulic eccentric adjustment for setting a predetermined displacement volume in a hydrostatic motor and, in particular a radial piston motor (1). The arrangement has an adjustment device which, to position an eccentric element (2), can be acted upon with pressure medium via a shuttle valve (5) such that at least one actuating piston (19), of an adjustment cylinder (3) that can be acted upon on both opposed sides is provided, as the adjustment device. A first pressure chamber (7) of the cylinder is connected to a first supply line (9), for setting a smaller displacement volume while a second opposed pressure chamber (8) is connected to a second supply line (10), for setting a larger displacement volume. The two supply lines (9, 10) are connected to one another by a connecting line (11).

Abstract: A method for controlling an automated clutch, which comprises a hydraulic clutch actuating system having a hydrostatic actuator, the pressure of which is detected. The method includes using the pressure of the hydrostatic actuator to adapt the characteristic curve of the clutch.

Abstract: A variable displacement pump includes: a rotor mounted in a body; a cam ring mounted radially outside of the rotor, and arranged to move with a change in an eccentricity of the cam ring with respect to the rotor, wherein change of the eccentricity causes a change in a specific discharge rate; and an electromagnetic actuator arranged to actuate the cam ring for regulating the eccentricity. During control of operation of the electromagnetic actuator, a first response is set slower than a second response, wherein the first response is a response of movement of the cam ring to a change of an input signal in a direction to request a decrease in the specific discharge rate, and the second response is a response of movement of the cam ring to a change of the input signal in a direction to request an increase in the specific discharge rate.

Abstract: A hydraulic motor unit according to the present invention includes an electric motor having an electric motor main body that is electrically controlled, an electric motor case that accommodates the electric motor main body and an electric motor main body output shaft that is rotated around an axis line thereof by the electric motor main body, the electric motor case being detachably mounted to the motor housing, wherein mounting of the electric motor to the motor housing causes the electric motor main body output shaft to be operatively connected to the first end of the control shaft so that the control shaft is rotated around the axis line in accordance with rotation of the electric motor main body output shaft.

Abstract: A hydraulic system includes an engine driven adjustable hydraulic pump which supplies fluid to a hydraulic consumer, and an electronic control unit. The adjustable pump includes flow controller for controlling a pressure difference between the consumer and the adjustable pump to a pre-determined control pressure difference. The flow controller includes an actuator controlled by the control unit, through which the pressure difference can be controlled. The electronic control unit receives an engine speed signal and controls the actuator to control the pressure difference, in order to make power delivery of the adjustable pump conform to the operating conditions of a vehicle.

Abstract: A control for a variable displacement pump disposed in a hydraulic system obtains a requested signal from a manual control device and provides a command signal to a valve operating to adjust a displacement setting of the variable displacement pump. The control provides the command signal based on the requested signal, and scales the requested signal based on a sensed or calculated load of the system.

Abstract: An open center hydraulic system that includes a variable displacement pump having an inlet, an outlet and a sensing port, the pump configured to provide reduced fluid flow in response to a predetermined fluid pressure differential between the outlet and the sensing port. A first fluid circuit and a second fluid circuit each serve as signal lines with the pump sensing port. During operation of the second fluid circuit, reduced fluid flow from the pump outlet is achieved as a result of the sum of induced fluid pressure reductions of respective controlled pressure reduction devices approaching the predetermined pump fluid pressure differential.

Abstract: An electric actuator of the present invention includes a hydraulic fluid supply device and an actuator actuated in response to an input of hydraulic fluid from a variable-volume pump. The hydraulic fluid supply device includes an adjustable-speed motor, the variable-volume pump which is driven by the adjustable-speed motor and ejects hydraulic fluid, an electric motor control unit which controls the adjustable-speed motor so as to achieve an intended rotation speed, and a pump control unit which controls the variable-volume pump so that the ejection volume of the variable-volume pump decreases with an increase in the ejection pressure of the variable-volume pump.

Abstract: A hydrostatic pump (1) with a variable displacement volume can be operated in a closed circuit and is driven by a drive engine (2), in particular by an internal combustion engine. To control the displacement of the pump (1), a control device (4) is provided which can be actuated as a function of the speed-dependent control pressure which is a function of the speed of the drive engine (2). To improve the control characteristics of the pump, a switchover device (35) is provided, by which the pump (1) can be switched between a speed-dependent displacement control by the speed-dependent control pressure and a volume flow-dependent delivery control, in which the control device (4) of the pump (1) can be controlled as a function of the actuation of an actuator mechanism (28).

Abstract: A hydraulic motor 11 is switched to a high-speed mode when pressure oil is supplied to a pressure chamber 23 of a tilt piston 17 based on the transmission of a speed signal to a high-low speed switching valve 18, and the hydraulic motor 11 is switched to a low-speed mode when pressure oil is discharged from the pressure chamber 23 of the tilt piston 17. A first braking purpose speed changing mechanism 13 operates so as to discharge pressure oil from the pressure chamber 23 of the tilt piston 17 when the pressure of pressure oil between a counterbalance valve 15 and a direction changeover valve 103 becomes equal to a tank pressure. Therefore, it is possible to provide a variable hydraulic motor driving device which is capable of preventing braking operation from being excessively long and also capable of preventing a large shock from occurring at a time of stoppage due to a large braking force generated from an early stage of braking operation.

Abstract: A simplified method for calibrating a variable-displacement hydraulic PTO system on an agricultural windrower when powering a header wherein the variable-displacement pump is operated at maximum flow capacity while the engine is operated at a pre-determined speed and a flow balance valve is adjusted to achieved a pre-determined cutterbar speed. Operation of the cutterbar at the pre-determined speed allows sufficient hydraulic fluid flow through the remaining parallel fluid circuit to power the remaining equipment, typically a reel, on the header. Controls for managing pump displacement and engine speed as well as indication of cutterbar speed are typically available on the windrower tractor thereby eliminating the need for additional diagnostic equipment and making the method suitable for use in the field.

Abstract: A valve assembly (2) forming a bridge circuit and a hydraulic actuator comprising at least one valve assembly (2) are disclosed. The valve assembly (2) is fluidly connectable between a fluid source (3) and a fluid drain (4). The valve assembly (2) comprises a first valve (8) fluidly connected between the fluid source (3) and a first diagonal point (12) of the bridge circuit, a second valve (9) fluidly connected between the fluid source (3) and a second diagonal point (13) of the bridge circuit, a third valve (10) fluidly connected between the first diagonal point (12) and the fluid drain (4), and a fourth valve (11) fluidly connected between the second diagonal point (13) and the fluid drain (4). The valves (8, 9, 10, 11) are such that in the case of a power cut off, flows of fluid away from the diagonal points (12, 13) are prevented.

Abstract: The invention provides a control system for a working vehicle, which can realize higher work performance and better fuel economy in a compatible way. A controller 10 includes table 10a, 10b and tables 10e, 10f for deciding maximum pump absorption torques and engine output torques based on an engine revolution speed, and selectors 10c, 10g for switching over the decided maximum pump absorption torques and engine output torques depending on a work performance mode or a fuel economy mode is selected. A pump absorption torque characteristic for the fuel economy mode is set so as to provide a relative small maximum pump absorption torques TB in a high revolution range, and an engine output characteristic for the fuel economy mode is set so as to provide a relatively small engine output torque in the high revolution range.

Abstract: Method and arrangement for controlling a work vehicle that includes a hydraulic system (22) having at least one pump (18,180) and at least one actuator (4,5,8,9,10) operatively driven by hydraulic fluid delivered from the pump and at least a first pump (18) is a variable displacement pump. The system (22) is of the load-sensing type in that pump displacement is controlled by a pilot pressure representing a load exerted on the system. The arrangement includes means (63) for reducing the pilot pressure delivered to the first pump (18) so that the first pump displacement is regulated down when there is a need for limiting hydraulic power consumption.

Abstract: A servo drive includes a hydraulic cylinder. The hydraulic cylinder comprises a piston that is mounted in the cylinder and that delimits two working chambers. Relief lines connected to the working chambers via control orifices may aid the definition of the right and left end positions of the piston. The control orifices are exposed by the piston in its respective end positions, thus relieving the pressure in the active working chamber. An end stop, which may be predetermined by the position of the control orifices may be formed by the pressure relief that occurs at the relevant location in the working chamber. Such measure can relieve the pressure in the hydraulic pump, for instance in end stop positions.

Abstract: A fluid pressure actuator includes an output cylinder, a fluid pressure pump, an electric motor, a first output cylinder passage, a second output cylinder passage, a return passage and a swash plate control cylinder. The output cylinder includes a first output cylinder chamber, a second output cylinder chamber and an output piston arranged between the first output cylinder chamber and the second output cylinder chamber. The fluid pressure pump includes a first supply and discharge port, a second supply and discharge port and a swash plate for changing displacement of the fluid pressure pump. The electric motor drives the fluid pressure pump. The first output cylinder passage connects the first output cylinder chamber and the first supply and discharge port. The second output cylinder passage connects the second output cylinder chamber and the second supply and discharge port. The return passage is connected to an accumulator for accumulating working fluid leaked from the fluid pressure pump.

Abstract: A control apparatus is provided for a hydrostatic transmission to simulate a gear drive on a tractor. The hydrostatic transmission has a swashplate that is angularly movable to a plurality of positions, and a proportional valve that provides a control pressure to a servo piston to control the hydrostatic transmission swashplate position. A transmission control lever may be moved to a plurality of positions, each position providing a different voltage signal to a microcontroller. The microcontroller receives and converts a voltage signal to a coil current to actuate the proportional valve.

Abstract: An improved rotary spool control system for a closed hydrostatic circuit and method to use the same. The control spool utilizes metering of the spool notches and specifically the metering of the servo drain notch wherein the drain notch is of irregular cross sectional shape. Because of the metering and irregular cross sectional shape, this spool is able to provide an aggressive response while still having smooth linear control. The method of creating the feedback control includes displacing pressurized fluid through the hydrostatic circuit rotating the control spool to create an error signal removing the error signal with a control sleeve and metering the servo piston drain with the irregularly shaped metering porting notch.

Abstract: With respect to a method of controlling a pump flow rate of a hydraulic pump, a method having a small flow rate command value is selected between a pressure feedback control for controlling the pump flow rate based on a set pressure (a cutoff pressure) and a pump pressure, and, an ordinary control for controlling the pump flow rate based on operation information, and in a case that the pressure feedback control is selected, a flow rate increasing control for increasing the flow rate command value after the case with the passage of time is performed.

Abstract: A motion converting section (31) and a translation bar (33) of a feedback mechanism (30) are provided between a lateral side of a swash plate (21) and a control sleeve (26) of a regulator (24). When the swash plate (21) is in a neutral position, the motion converting section (31) is located in an initial position (F—F) at one end of axial direction along an axis line (O—O) passing through a tilting center (C) of tilting motions, and, when the swash plate (21) is driven to tilt in a forward or reverse direction, displaced to the other end of axial direction along the axis line (O—O) to convert a tilting motion of the swash plate (21) into an axial displacement. Through the translation bar (33), the axial displacement is transmitted to the control sleeve (26) of the regulator (24) as an axial displacement.

Abstract: A variable capacity hydraulic machine has a rotating group located within a casing and a control housing secured to the casing to extend across and seal an opening in the casing. The control housing accommodates a control circuit and a pair of sensors to sense change in parameters associated with the rotating group. One of the sensors is positioned adjacent the barrel on the rotating group to sense rotational speed and the other senses displacement of the swashplate. The control housing accommodates a control valve and accumulator to supply fluid to the control valve.

Abstract: An improved rotary spool control system for a closed hydrostatic circuit and method to use the same. The control spool utilizes metering of the spool notches and specifically the metering of the servo drain notch wherein the drain notch is of irregular cross sectional shape. Because of the metering and irregular cross sectional shape, this spool is able to provide an aggressive response while still having smooth linear control. The method of creating the feedback control includes displacing pressurized fluid through the hydrostatic circuit rotating the control spool to create an error signal removing the error signal with a control sleeve and metering the servo piston drain with the irregularly shaped metering porting notch.

Abstract: Control valves are respectively provided in a pair of variable displacement hydraulic pumps. If an ultra low speed travel signal is issued in response to an ultra-low-speed switch turned on, one of the control valves is fixed to a neutral position by a solenoid valve. And a displacement amount of a travel motor is fixed at a maximum displacement by another solenoid valve. In this way, an upper limit for motor rotation speed is significantly reduced. As a result, it is possible to realize the ultra low speed travel with maximum operation of an accelerator pedal, without the need for subtle operation of the accelerator pedal.

Abstract: The speed control apparatus for a hydraulic actuator includes a hydraulic source, an actuator connected with the hydraulic source and driven based on a supply of an operation oil, a direction switching valve which is switchably installed in a flow path between the hydraulic source and the actuator, an inclination piston which is installed between a parallel flow path in parallel connected with a flow path in a supply side of the actuator and the actuator for thereby controlling an inclination angle of an inclination plate of the actuator, a multi-step adjusting inclination piston which is driven when an operation oil is supplied, and adjusts an inclination angle of an inclination plate of the actuator based on multiple steps, and a multi-step adjusting control valve which is switchably installed in a flow path between the parallel flow path and the multi-step adjusting inclination piston, controls an operation oil supplied to the multi-step adjusting inclination piston, and adjusts a speed of the actuator.

Abstract: A control device apparatus for a proportionally adjustable hydraulic pump of a closed hydraulic circuit, including an axial piston pump adjustable from a zero position in two pivoting directions, with an electro hydraulic valve configuration for the activation of a piston of the hydraulic pump from both sides and with a feedback device, connected to the piston and whereby the angular pivoting position of the piston can be fed back to the valve configuration as a control signal, the valve configuration having a valve for each pivoting direction of the piston, and the feedback device comprising two mechanical feeler elements, each connected to one of the valves and in sliding engagement with the piston in such a way that the feeler elements are actuated when it leaves the zero position.

Abstract: The speed control apparatus for a hydraulic actuator includes a hydraulic source, an actuator connected with the hydraulic source and driven based on a supply of an operation oil, a direction switching valve which is switchably installed in a flow path between the hydraulic source and the actuator, an inclination piston which is installed between a parallel flow path in parallel connected with a flow path in a supply side of the actuator and the actuator for thereby controlling an inclination angle of an inclination plate of the actuator, a multi-step adjusting inclination piston which is driven when an operation oil is supplied, and adjusts an inclination angle of an inclination plate of the actuator based on multiple steps, and a multi-step adjusting control valve which is switchably installed in a flow path between the parallel flow path and the multi-step adjusting inclination piston, controls an operation oil supplied to the multi-step adjusting inclination piston, and adjusts a speed of the actuator.

Abstract: An adjusting device (1) for adjusting the swash plate (12) of an axial piston engine (1) with a swash-plate construction has an actuating piston (18) which acts on the swash plate (12) of the axial piston engine (1); and a control value (19). The control valve (19) is used to regulate the actuating pressure which is present in an actuating volume (45) and which is acting on the actuating piston (18), in accordance with a control force acting on a valve piston (20) of the control valve (19). The actuating piston (18) is structurally separate from the control valve (19) and the actuating piston (18) is connected to the valve piston (20) of the control valve (19) by a readjusting spring (34) that opposes the control force.

Abstract: When the load acting on a fluid motor (25) increases, a changeover valve (61) starts to be changed over toward a low-speed position L, but at this time an additional pilot fluid whose pressure is determined by the amount of fluid flowing into or out of a second passage (68) through first and second notches functions as a pressure regulator for a spool (65), and lowers the pressure within the second passage (68) without lowering the pressure within a high pressure-side main circuit (28), thereby tilting a swash plate (26) from a position of high-speed rotation to a position of low-speed rotation.