Abstract: An axial piston pump controller for an axial piston pump having a fixed valve plate and a variable displacement is provided. The axial piston pump controller is configured to determine a displacement of the axial piston pump, and to calculate a pump displacement control current to be supplied to the axial piston pump to control the displacement of the axial piston pump. Calculating the pump displacement control current comprises calculating a nominal value for the pump displacement control current based on a rotational speed of the axial piston pump, calculating a pump stiffness adjustment factor based on a pump stiffness control map having as inputs: an output pressure of the axial piston pump; and the estimated pump displacement, and calculating the pump displacement control current to be supplied to the axial piston pump based on the nominal value and the pump stiffness adjustment factor.

Abstract: A control system is provided for a power machine that includes a hydraulic charge circuit with a hydraulic charge pump, and a variable displacement drive pump. A signal for control of displacement of the drive pump can be diverted from the hydraulic charge circuit downstream from the pump, including via a flow path that branches from the hydraulic charge circuit from a location upstream of a hydraulic load.

Abstract: The invention relates to a vibrating ram arrangement comprising a hydraulic assembly, a vibrator which is connected to the hydraulic assembly via hydraulic tubes, and a controller which is paired with the hydraulic assembly. The hydraulic assembly has a hydraulic pump which is driven by an internal combustion engine, and the vibrator has imbalances and an adjustable hydraulic engine for driving the imbalances. A hydraulic fluid is conducted through the hydraulic assembly, the hydraulic tubes, and the hydraulic engine in a circuit. A frequency sensor for determining the frequency of the vibrator is connected to the controller, and the controller is designed to control a volumetric flow rate conducted through the circuit dependent on the signal of the frequency sensor. According to the invention, the vibrator has a device, which is independent of the controller, for automatically adjusting a displacement volume of the hydraulic engine dependent on a pressure within the circuit.

Abstract: A hydraulic circuit may be used for controlling a plurality of hydraulic implements. The hydraulic circuit may include a first directional valve, a second directional valve, and a relief valve. A variable displacement pump may be fluidly coupled to the first directional valve, the second directional valve, and the relief valve. The hydraulic circuit may be communicably and operably coupled to a controller, and the controller may be programmed to selectably control the hydraulic circuit between a first operational mode and a second operational mode. Additionally, the controller may be programmed to actuate the first directional valve between an open position and a closed position and to actuate the second directional valve between a first open position, a second open position, a first closed position and a second closed position.

Abstract: The invention relates to a method for changing gear stages in a transmission having a hydrostatic transmission and a downstream manual transmission, and a corresponding transmission arrangement. First, a desire to shift is detected within the manual transmission to change the gear stages. The hydrostatic transmission and the downstream manual transmission are activated to change the gear stage of the downstream transmission. Whether the gear stage to be engaged through a gear stage change was successfully engaged is detected by a detection device, which is connected to an electronic control unit of the transmission arrangement. If the engagement of the gear stage to be engaged is not successful, the original gear stage is reengaged. After the engagement of the original gear stage, the downstream transmission is again activated such that the gear stage to be engaged is engaged.

Abstract: A construction machine includes a condenser 24 for cooling refrigerant for an air conditioner; a fan 21 for cooling the condenser 24 by using forward cooling air produced during normal-rotation drive; other cooled objects such as a radiator 25 and the like disposed under the lee of the forward cooling air with respect to the condenser 24; a refrigerant pressure detector 27 for detecting the pressure of the refrigerant flowing in the condenser 24; and a controller 136 for executing reverse-rotation stop processing for returning the fan 21 to the normal-rotation drive when the pressure P of the air conditioner refrigerant detected by the refrigerant pressure detector 27 reaches a preset normal-rotation return pressure P1 during reverse-rotation drive of the fan 21. Thus, the lowering of the cooling effect of an air conditioner can be suppressed while reducing the burden of cleaning an engine room.

Abstract: Provided is a hybrid construction machine (driving the upper swing structure using a hydraulic motor and an electric motor together) capable of regenerating the energy of the upper swing structure in deceleration or stopping into electric power and using the regenerated electric power for assisting the driving of the upper swing structure, while also being capable of securing satisfactory operational feeling and operation capability even when the electric motor does not operate. When the electric motor is not driven, a controller controls a hydraulic circuit system (specifically, a swing direction/flow rate control valve, a center bypass cut valve and a regulator) so as to increase output torque of the hydraulic motor by an amount corresponding to torque to be compensated for the non-driving of the electric motor compared to cases where the electric motor is driven.

Abstract: A hydraulic linear actuator system known as the “Dynaco Stepper Pump Hydraulics System” is which is an electrically driven hydraulic pump system made of durable materials for use in an electronically controllable hydraulic system comprised of: (a) an electrically driven stepper motor; (b) a hydraulic pump to pressurize a hydraulic fluid; (c) a means to connect the stepper motor to the hydraulic pump; (d) a pressurized reservoir for a quantity of hydraulic fluid; (e) a means to supply pressurized fluid to a hydraulic actuator; (f) the hydraulic actuator with a means to provide linear motion to an object; (g) the means to provide linear motion to an object; (h) a means to return lowered pressurized fluid to the reservoir. An alternative embodiment is further comprised of a controller with a series of feedback signals.

Abstract: In a hydraulic excavator, a hydraulic cylinder drives a boom via a hydraulic fluid discharged from a first hydraulic pump. A first hydraulic circuit connects the first hydraulic pump and the hydraulic cylinder and forms a closed circuit therebetween. A hydraulic motor rotates a revolving upper unit with hydraulic fluid discharged from a second hydraulic pump. A second hydraulic circuit independent from the first hydraulic circuit connects the second hydraulic pump and the hydraulic motor. A motor hydraulic pressure reduction unit reduces the driving hydraulic pressure of the hydraulic motor when a predetermined condition is satisfied. The predetermined condition is a condition in which an operation of the boom operating member to raise the boom and an operation of the rotation operating member to rotate the revolving upper unit are conducted together and an operation amount of the boom operating member is equal to or greater than a predetermined threshold.

Abstract: A hydraulic pump control circuit may include a pressure reducing valve selectively operable to limit the amount of fluid pressure available to an actuator operably coupled to a pump displacement volume adjusting mechanism of a variable displacement pump. The pump may be hydraulically coupled to a motor configured to provide a torque output. The reduced pressure to the actuator limits actuator travel, thereby limiting pump displacement. Accordingly, torque output of the motor may be reduced, thereby improving traction control.

Abstract: A fluid control system including a variable displacement pump having a load system control and configured to operate in an open center mode. A pump control is operable between a first arrangement and a second arrangement. The pump control receives pressurized fluid from a first load sensor pressure in fluid communication with the pump and an actuator return pressure in fluid communication with an actuator configured to operate using pressurized fluid from the system, the pump control providing a selective pump control pressure to the pump load system control. When the system is operating in a standby mode, the pump operates in a first minimized displacement condition. When the system is in a stall mode, the pump operates in a second minimized displacement condition.

Abstract: A travel control device for a work vehicle includes: a hydraulic pump; a plurality of hydraulic motors connected to the hydraulic pump in parallel through a closed-circuit connection, that drive different wheels with pressure oil delivered from the hydraulic pump; a slip detection device that detects a slip occurring at each of the wheels; and a flow control device that reduces, upon detection of a slip occurring at any of the wheels by the slip detection device, a quantity of pressure oil supplied to a hydraulic motor for driving the wheel at which the slip has been detected, among the plurality of hydraulic motors.

Abstract: An agricultural combine has a header height control circuit supplied with hydraulic fluid from a closed center pump. The pump has a variable displacement. The pump displacement is controlled by a control line connected to the pump. The control line is supplied with fluid from the feederhouse lift cylinders that passes through a valve. The valve supplies hydraulic fluid at the feederhouse lift cylinders to the control line of the pump. Upon receiving fluid from the valve the closed center pump rapidly changes its outlet pressure to match the pressure in the feederhouse lift cylinders and thus reduces the response time of the closed center pump.

Abstract: A hydraulic system adapted to recover inertial energy is disclosed. The hydraulic system includes a pump, a variable displacement pump/motor having an input/output shaft, an accumulator, and a valve arrangement. The valve arrangement is operable in: a) a first mode where the variable displacement pump/motor is driven by the pump to rotate the input/output shaft and the load; b) a second mode where the variable displacement pump/motor uses inertial energy from a deceleration of the load to charge the accumulator; and c) a third mode where the variable displacement pump/motor is driven by the accumulator to rotate the input/output shaft and the load. The hydraulic system also includes a controller for controlling operation of the pump, the variable displacement pump/motor and the valve arrangement.

Abstract: A current load rate of an engine 10 is computed and a maximum absorption torque of at least one hydraulic pump 1, 2 is controlled so that the load rate is held at a target value. Engine stalling can be prevented by decreasing the maximum absorption torque of the hydraulic pump under a high-load condition. When an engine output lowers due to environmental changes, the use of poor fuel or other reasons, the maximum absorption torque of the hydraulic pump can be decreased without a lowering of the engine revolution speed. Further, the present invention is adaptable for any kinds of factors causing a lowering of the engine output, such as those factors that cannot be predicted in advance or are difficult to detect by sensors. In addition, because of no necessity of sensors, such as environment sensors, the manufacturing cost can be reduced.

Abstract: Apparatus, system, and method for controlling a desired torque output on a hydromechanical transmission. Controlling torque output of a hydromechanical transmission provides improved operator feel and control. A control module determines a desired torque output and determines a pressure necessary to influence the displacement of the variable displacement pump to output the desired torque output. A pressure-controlling valve applies that amount of pressure to an actuator, which moves in response thereto, to change the displacement of the variable displacement pump. When the motor speed changes, the control module adjusts the pressure applied to the actuator to provide the desired torque output.

Abstract: A main relief valve 13 includes a biasing force altering unit 60, which constitutes, in combination with a gate lock valve 23 and a gate lock lever 24, relief pressure altering means for manually switching the relief pressure of the main relief valve 13 between a first pressure (a standard pressure of 25 MPa, for example) and a second lower pressure for engine start-up (e.g., 3.0 MPa). This allows the main relief valve 13 to return the hydraulic fluid discharged from a hydraulic pump 2 to a tank T in conjunction with an unloading valve 9 when multiple actuators 5a, 5b, . . . are not in operation under the ambient temperature below freezing point. As a result, it is possible to reduce the load on the hydraulic pump during cold engine start-up without compromising the anti-hunting characteristics of the unloading valve, thereby improving the engine start-up performance.

Abstract: The present invention provides a hydraulic drive apparatus which can flexibly be set. The hydraulic drive apparatus which drives a variable displacement hydraulic motor 20 by a pressure oil discharged from a variable displacement hydraulic pump 10 and outputs a driving force of the hydraulic motor 20 to outside. The hydraulic drive apparatus includes torque upper limit setting unit which sets an upper limit of an output torque with respect to the hydraulic motor 20, and control unit which sets a maximum capacity limit value of the hydraulic motor 20 in accordance with the upper limit of the output torque when the upper limit of the output torque is set by the torque upper limit setting unit, and which sets a maximum capacity limit value of the hydraulic pump 10 in accordance with the upper limit of the output torque.

Abstract: A backup system is provided that has a local electric motor and pump for some or all of hydraulic actuators. A local backup hydraulic actuator has two power sources, hydraulic as primary and electrical as backup. During normal operation, the hydraulic actuator receives pressurized fluid from a hydraulic system and the fluid flow to the chambers is controlled by a servo valve. If the hydraulic system fails, the electronic controller detects the failure by observing the signal indicative of the pressure from the pressure sensor, and the controller powers the local hydraulic pump to provide high pressure hydraulic fluid to the hydraulic actuator via the servo valve.

Abstract: The present invention relates to a hydraulic drive system having a pressure-regulated hydraulic pump for the provision of a system pressure and having a secondarily regulated hydraulic motor. In accordance with the invention, a control is provided which sets the desired system pressure during operation in dependence on an operating parameter of the hydraulic motor.

Abstract: A system for controlling a power output is disclosed. The system includes a hydraulic actuator configured to output a first torque and a source of pressurized fluid configured to supply a flow of pressurized fluid to the hydraulic actuator. The system further includes a controller configured to control the flow of pressurized fluid as a function of the first torque, a predetermined torque, and changes to the first torque caused by a load operatively connected to the hydraulic actuator.

Abstract: A method of operating a vehicle with a hydrostatic circuit. The method includes providing a hydrostatic circuit having first and second hydraulic kits that are fluidly connected to one another by first and second fluid lines. A by-pass valve is placed between the first and second hydraulic lines and is controlled in order to actuate the by-pass valve when certain predetermined conditions are present in order to relieve pressure within the hydrostatic circuit.

Abstract: A swing drive system for a construction machine enhances safety for an operator. A swing control means 55A has a lever input amount-torque table 11 and an actual rotating speed-torque table 13. Based on a lever input amount and an actual rotating speed of an electric motor, the tables are used to derive torque values. A minimum value of the torque values is taken as the acceleration torque. The swing control means 55A further has a lever input amount-meter-out restriction area table 15 and an actual rotating speed-relief torque table 119. Based on the lever input amount and the actual rotating speed of the electric motor, a meter-out restriction area is derived from the lever input amount-meter-out restriction area table and the actual rotating speed to calculate a meter-out torque. A minimum value of the meter-out torque and relief torque is taken as the braking torque.

Abstract: An engine lag down suppressing device of construction machinery, comprising a vehicle body controller (13) having a first torque control means and a second torque control means, and a third torque control means. The first torque control means controls a torque control valve (7) to the minimum pump torque (value: Min) according to a target engine rotational speed (Nr) when the operating device (5) in the non-operated state of an continues for a monitoring time (TX1) to suppress an engine lag down after a specified holing time to hold a torque to a low pump torque is passed when the operating device in the non-operated state is operated. The second torque control means controls the torque control valve (7) to hold the minimum pump torque for a specified holding time (Tx2) after the operating device (5) in the non-operated state is operated.

Abstract: A predictive load management system is provided. A power source is operable to generate a power output and has a desired operating range. A transmission has a drive member operably engaged with the power source and a driven member. A control system is operable to receive at least one input indicative of a load on the transmission and to identify a desired load of the transmission based on the at least one input. The control system is also operable to receive at least one input indicative of current power output of the power source. The control system limits the desired transmission load applied to the driven member of the transmission based on the current power output of the power source to thereby prevent the power source from operating outside of the desired operating range.

Abstract: An open circuit system that uses a two-position three-way logic valve that automatically compensates for remote pressure in the system. The system has a pump that sends a pump supply through an orifice to the two-position three-way logic valve. Then depending on the load sense signal, the valve either allows the flow of the pump supply to the compensation relief valve or alternatively, the logic valve prevents the flow from the pump supply. The load sensing signal determines whether the valve will allow flow from the pump supply.

Abstract: Disclosed is a controller for construction equipment, which avoids occurrence of an engine stall even at the time of a heavy load while assuring simultaneous operation of a hydraulic actuator for a working machine and a hydraulic drive motor. The controller is provided with a torque variable control valve for controlling a pump maximum displacement so that a suction torque of a hydraulic pump becomes constant when a discharge oil pressure of the hydraulic pump exceeds a predetermined value; and a servo valve for changing the tilt angle of a cam plate of the hydraulic pump in accordance with an instruction from the torque variable control valve.

Abstract: The present invention provides a hydraulic controller for a variable capacity hydraulic transmission. This hydraulic controller reduces the load of the engine to improve fuel efficiency while maintaining a hydraulic pressure which is necessary for the control of the skew angles of the swash plates of the variable capacity type hydraulic pump and hydraulic motor that are incorporated in the transmission. The hydraulic controller adjusts the hydraulic pressure supplied to the servo cylinders 92 and 96 which are to tilt the pump swash plate 32 and the motor swash plate 38, to a minimum necessary pressure on the basis of the pressure Ph of the oil passage which is at the higher pressure in the hydraulic closed circuit 26.

Abstract: In a hydraulic vehicle drive which has a hydraulic circuit consisting of a variable displacement pump (2) and a hydraulic motor (10), the variable displacement pump (2) is driven by a diesel engine (1). During the braking or overrunning operation of the vehicle, the hydraulic motor becomes the pump and drives the variable displacement pump (2) which acts as a motor on the diesel engine (1) and attempts to accelerate the latter. The braking effect which is intended and obtained thereby involves the risk of the diesel engine (1) reaching impermissibly high rotational speeds. The braking therefore takes place in a controlled manner by a sequence valve (16) being arranged in the line (12) between the hydraulic motor (10) and the variable displacement pump (2). The sequence valve acts on the pivot angle of the variable displacement pump (2) via the pump bypass line (12B).

Abstract: An aircraft flap drive system utilized a variable displacement motor (15) having a fluid pressure actuated device (23) to vary the displacement of the motor. The system includes a displacement control valve (41), and an electrohydraulic control means (55,67,85) operable in response to an electrical input signal (91) to communicate pressurized fluid from a source (11) to the motor. The displacement control valve (41) includes a load sensing arrangement (13,53,49) responsive to an increasing load on the motor to bias the displacement control valve toward a position whereby the motor moves toward its maximum displacement (minimum flow). One result is that the conventional fixed displacement motor, of a particular size and weight, may be replaced by a variable motor which is smaller and lighter.

Abstract: A regenerative adaptive fluid motor control system integrating a load adaptive fluid motor control system and a load adaptive energy regenerating system having a built-in regenerating circuitry containing an energy accumulator. The fluid motor control system includes a variable displacement pump powering a spool valve controlling a fluid motor accumulating a load related energy, such as a kinetic energy of a mass load of the fluid motor or a compressed fluid energy of the fluid motor-cylinder. The load related energy of the fluid motor is regenerated to provide a load adaptive exchange of energy between the fluid motor and the energy accumulator. This load adaptive exchange of energy is combined with a load adaptive primary energy supply for maximizing the over-all energy efficiency and performance potentials of the fluid motor control. The load adaptability is achieved by regulating the exhaust and supply fluid pressure drops across the spool valve.

Abstract: A regenerative adaptive fluid motor control system integrating a load adaptive fluid motor control system and a load adaptive energy regenerating system having an independent regenerating circuitry containing an energy accumulator.The fluid motor control system includes a primary variable displacement pump powering a spool valve controlling a fluid motor accumulating a load related energy, such as a kinetic energy of a mass load of the fluid motor or a compressed fluid energy of the fluid motor-cylinder. The load related energy of the fluid motor is regenerated to provide a load adaptive exchange of energy between the fluid motor and the energy accumulator. This load adaptive exchange of energy is combined with a load adaptive primary energy supply for maximizing the over-all energy efficiency and performance potentials of the fluid motor control. The load adaptability is achieved by regulating the exhaust and supply fluid pressure drops across the spool valve.

Abstract: A regenerative adaptive fluid motor control system integrating a load adaptive fluid motor control system and a load adaptive energy regenerating system having an energy accumulator. The fluid motor control system includes a primary constant displacement pump powering a spool valve controlling a fluid motor accumulating a load related energy, such as a kinetic energy of a mass load of the fluid motor or a compressed fluid energy of the fluid motor-cylinder. The load related energy of the fluid motor is regenerated to provide a load adaptive exchange of energy between the fluid motor and the energy accumulator. This load adaptive exchange of energy is combined with a load adaptive primary energy supply for maximizing the over-all energy efficiency and performance potentials of the fluid motor control. The load adaptability is achieved by regulating the exhaust and supply fluid pressure drops across the spool valve.

Abstract: A regenerative adaptive fluid motor position feedback control system integrating a load adaptive flujid motor position feedback system having an energy accumulator. the fluid motor control system includes a primary variable displacement pump powering a spool valve controlling a fluid motor accumulating a load related energy, such as a kinetic energy of a mass load of the fluid motor or a compressed fluid energy of the fluid motor-cylinder. The load related energy of the fluid motor is regenerated to provide a load adaptive exchange of energy between the fluid motor and the energy accumulator. This load adaptive exchange of energy is combined with a load adaptive primary energy supply for maximizing the over-all energy efficiency and performance potentials of the fluid motor control. The load adaptability is achieved by regulating the exhaust and supply fluid pressure drops across the spool valve.

Abstract: A regenerative adaptive fluid motor output feedback control system integrating a load adaptive fluid motor output feedback control system and a load adaptive energy regenerating system having an energy accumulator. The fluid motor control system includes a primary variable displacement pump powering a spool valve controlling a fluid motor accumulating a load related energy, such as a kinetic energy of a mass load of the fluid motor or a compressed fluid energy of the fluid motor-cylinder. The load related energy of the fluid motor is regenerated to provide a load adaptive exchange of energy between the fluid motor and the energy accumulator. This load adaptive exchange of energy is combined with a load adaptive primary energy supply for maximizing the over-all energy efficiency and performance potentials of the fluid motor control. The load adaptability is achieved by regulating the exhaust and supply fluid pressure drops across the spool valve.

Abstract: A regenerative adaptive fluid motor position feedback control system integrating a load adaptive fluid motor position feedback control system and a load adaptive energy regenerating system having an energy accumulator. The fluid motor control system includes a primary constant displacement pump powering a spool valve controlling a fluid motor accumulating a load related energy, such as a kinetic energy of a mass load of the fluid motor or a compressed fluid energy of the fluid motor-cylinder. The load related energy of the fluid motor is regenerated to provide a load adaptive exchange of energy between the fluid motor and the energy accumulator. This load adaptive exchange of energy is combined with a load adaptive primary energy supply for maximizing the over-all energy efficiency and performance potentials of the fluid motor control. The load adaptability is achieved by regulating the exhaust and supply fluid pressure drops across the spool valve.

Abstract: The invention relates to a hydrostatic transmission having a hydraulic pump (1) and an adjustable hydraulic motor (2) which is connected to first and second working lines (13, 14) of which at least the first (13) leads to the hydraulic pump, and a setting member (40)--for setting the motor displacement volume--is connected with a setting device (4) which upon load operation of the hydrostatic transmission can be acted upon by a setting pressure in a first setting pressure line (44, 57, 43) connected at least to the first working line, and in the case of overrun operation, can be acted upon by the setting pressure in a second setting pressure line (45, 51, 43), connected at least to the second working line. There is a brake valve (6) arranged at least in the second working line downstream of the connection of the second setting pressure line and which upon overrun operation of the hydrostatic transmission the respective working line is restricted.

Abstract: The present invention is directed to a hydro-mechanical or electro-hydro-mechanical control system utilized for positioning a mechanical device. The control system incorporates a control valve for selectively controlling the flow of hydraulic fluid to input ports of a power output transducer in response to a mechanically applied input signal. The power output transducer is then utilized to position a mechanical device. The control system is a closed loop circuit adapted to supply hydraulic fluid at a desired supply pressure to the control valve. The supply pressure is varied in relation to the absolute value of the pressure differential or load pressure exerted across the input ports of the power output transducer. A pressure regulating apparatus is provided for selectively regulating the supply pressure to a value that is nominally equal to the absolute value of the load pressure summed with a preselected supplemental pressure value across the regulating apparatus.

Abstract: The present invention is directed to a hydro-mechanical or electro-hydro-mechanical control system utilized for positioning a mechanical device. The control system incorporates an open-center control valve for selectively controlling the differential pressure applied to and the differential flow between input ports of a power output transducer in response to a mechanically applied rotational inputs. The power output transducer is then utilized to position a mechanical device. The control system is a closed loop circuit adapted to supply hydraulic fluid at a desired supply pressure to the control valve. The supply pressure is varied in relation to the absolute value of the pressure differential or load pressure exerted across the input ports of the power output transducer.

Abstract: The present invention relates to an apparatus for controlling the running speed of a hydraulic motor. A hydraulic motor employable for a construction machine such as a power shovel or the like as a driving power source is constructed such that its rotational speed can be changed to assume either a high speed (low torque) or a low speed (high torque) so as to cope with differences in the running state of the construction machine. The apparatus of the subject invention assures that the running state of the construction machine is determined by not only the running load of a hydraulic motor but also its rotational speed, whereby the construction machine can run smoothly at all times.

Abstract: Paper drive unit instability that includes a variable displacement hydraulic motor (34), a rotary output (48), and a displacement controlling wobbler (36, 40) in the case of an aiding load can be avoided through the use of a double acting hydraulic actuator (42, 44) connected to the wobbler (36, 40) along with a control valve (30) including a single spool (80) connected to the motor (34), and wobbler control pilot valve (62) and to the actuator (42, 44) for a) controlling the speed and direction of rotation of the motor output (48); and b) controlling the actuator (42, 44) to maintain minimum displacement of the motor 34 when an aiding load occurs. System optimization can be achieved by changing the differential pressure setting in response to the available system pressure.

Abstract: The present invention is directed to a hydro-mechanical or electro-hydro-mechanical control system utilized for positioning a mechanical device. The control system incorporates a control valve for selectively controlling the flow of hydraulic fluid to input ports of a power output transducer. The power output transducer is then utilized to position a mechanical device. The control system is a closed loop circuit adapted to supply hydraulic fluid at a desired supply pressure to the control valve. The supply pressure is varied in relation to the absolute value of the pressure differential or load pressure exerted across the input ports of the power output transducer. A pressure regulating apparatus is provided for selectively regulating the supply pressure to a value that is nominally equal to the absolute value of the load pressure summed with a preselected supplemental pressure value across the regulating apparatus.

Abstract: A hydraulic-motor drive circuit system includes an auxiliary hydraulic source connected to one end of an auxiliary line, a low-pressure selector connected to the other end of the auxiliary line and a pair of main lines for causing the other end of the auxiliary line to communicate with one of the main lines on the low pressure side during rotation of a hydraulic motor for driving an inertia load, and a switching control arranged in the auxiliary line for supplying the hydraulic fluid from the auxiliary hydraulic source to the other end of the auxiliary line when the directional control valve is in a neutral position, cutting off the hydraulic fluid from the auxiliary hydraulic source to the other end of the auxiliary line when the directional control valve is in an operative position.

Abstract: In an apparatus for controlling the operation of hydraulic motors having infinitely adjustable eccentricity, wherein a flow-control valve between a pump and a hydraulic motor supplied with pressure medium and a control valve for adjusting the eccentricity of the hydraulic motor as a function of the operating pressure required by the hydraulic motor are provided, in connection with pressure optimization for keeping constant the torque of the hydraulic motor, the hydraulic motor is provided with a regulating device (7,10) which is mechanically connected to the eccentric (3) and transmits an eccentric adjustment outward, wherein this mechanical regulating device (7,10) acts on the flow-control valve (17) in such a way that, as a function of the change in the eccentricity, the flow-control valve (17) controls the pressure-medium quantity supplied to the hydraulic motor in such a way that the speed of the hydraulic motor is kept constant.

Abstract: In order to entirely eliminate pressure drop sensors in a variable displacement hydraulic motor (10), and to change the wobbler angle mechanically rather than hydraulically, the hydraulic motor (10) includes a motor housing (26) having a plurality of hydraulic cylinders (32) and a plurality of hydraulic pistons (34) radially disposed about an axis (36) thereof. A servovalve (40) is provided for controlling the rate and direction of flow of hydraulic fluid to and from the hydraulic cylinders (32), and the wobbler (22) is operatively associated with the hydraulic pistons (34) in a variably angularly positionable manner for varying displacement of the hydraulic motor (10). With this arrangement, the hydraulic motor (10) includes a cam system (22a, 30) for automatically varying the angular positioning of the wobbler (22) relative to the axis (36) of the hydraulic motor (10) responsive to a load-related torque at an output shaft (12) thereof.

Abstract: The problem of energy wastage in power drive units having fixed displacement hydraulic motors is avoided in a system having a variable displacement hydraulic motor (10) without the expense normally associated with such variable displacement systems by a construction which includes a variable displacement hydraulic motor (10) provided with a hydraulic actuator (14). A servo valve (12) is adapted to be connected to a source of hydraulic fluid under pressure and a controller (24) and is connected to the motor (10) for controlling the flow of fluid thereto in response to signals received from the controller (24). A flow limiter (16) is connected between the servo valve (12) and a return to the fluid source. A flow sensor valve (18) is connected across the flow limiter (16) and is responsive to flow therethrough to provide a hydraulic control signal to the actuator (14) to control the displacement of the motor (10).

Abstract: A method and apparatus for controlling the differential hydraulic fluid pressure (.DELTA.P) across a variable displacement hydraulic motor (10) wherein the displacement of the motor is adjusted as a function of the differential fluid pressure across the motor to maintain a near constant differential pressure across the motor when the motor is operating under an opposing load and in an intermediate region of its speed-load torque profile (FIG. 4). In order to minimize the flow requirements of the motor, the displacement of the motor is reduced to minimum when the motor is operating under an aiding load or no load. The method and apparatus are useful in an apparatus for mechanically actuating a device (22) with the variable displacement hydraulic motor (10) driven by hydraulic fluid from a hydraulic power supply (25) such as an aircraft power supply for operating components of the aircraft, e.g. rudder, wing, etc.

Abstract: A bidirectional hydraulic servomotor system includes a variable-displacement motor which may impel or brake movement of a load member that either resists or assits movement by the servomotor, respectively. The direction of load movement is under control of a directional control valve with motor displacement and function (impelling or braking) being effected automatically to achieve controlled load movemement with minimal consumption of hydraulic fluid.

Abstract: Improved control of a hyrostatic drive machine at very small speeds of rotation. The rotation speed control signal in the creep rotation speed region is modified in dependence upon the actual value of the rotation angle and possibly the efficiency characteristic diagram so as to produce a regulated constant torque.

Abstract: An electrohydraulic system for control of a variable output pump includes a microprocessor-based controller receiving inputs from condition sensors coupled to the pump and command inputs from a remote master controller. The controller supplies outputs to an electrohydraulic valve for metering hydraulic fluid to a pump control port and thereby controlling pump operation in any one of a number of preselected and prestored pump control modes. A hydromechanical valve is connected in parallel with the electrohydraulic valve for controlling pump operation in the event of electrical malfunction or failure. Circuitry connected between the pump condition sensors and the control computer prevents aliasing errors due to mismatch between the computer sampling frequency and pump speed. A pump torque sensor measures pump input shaft torque.