Abstract: Disclosed are a hydraulic control system for boom floating of an excavator and a control method thereof. In the hydraulic circuit, a main pump supplies oil to the boom cylinder through a boom reversing valve, and two working ports of the boom reversing valve are connected to a rod cavity and a rodless cavity of the boom cylinder respectively. A rod cavity floating valve and a rodless cavity floating valve are connected to an oil circuit between the rod cavity of the boom cylinder and the boom reversing valve and an oil circuit between the rodless cavity of the boom cylinder and the boom reversing valve respectively. A pilot oil pump and a handle pilot valve are arranged on the pilot oil circuit, an oil inlet of the handle pilot valve is connected to the pilot oil pump.

Abstract: A hydraulic control arrangement for simultaneously supplying at least two hydraulic consumers with predefinable individual pressure medium flow rates includes a hydraulic pump having an adjustable swept volume, and at least two valve arrangements each including a variable metering restrictor and a pressure balance arranged downstream of the variable metering restrictor. Each pressure balance is configured to be acted on in an opening direction by pressure downstream of the respective variable metering restrictor and to be acted on in a closing direction by a highest load pressure or by a pressure derived therefrom. Each valve arrangement is arranged between a pump line, which leads away from the hydraulic pump, and a consumer of the at least two hydraulic consumers. The arrangement further includes an electronic control device, by which the hydraulic pump is actuatable such that it conveys a sum of the predefinable individual pressure medium flow rates.

Abstract: A hydrostatic travel drive includes a hydraulic pump for the purpose of supplying pressure medium to a hydraulic motor of the travel drive that can be coupled to an output, which pump can be coupled to a drive machine. The hydraulic pump has an actuating cylinder with at least one cylinder chamber and a swept volume which can be adjusted via the actuating cylinder, and at least one electrically activatable pressure valve via which the cylinder chamber can be charged with an adjustingly active actuating pressure. The travel drive further includes device via which a pressure of the hydraulic pump can be limited by means of influencing the actuating pressure.

Abstract: A fluid pressure drive device includes a flushing circuit configured to discharge a working fluid from one of the pair of main passages to a tank. The flushing circuit has a low pressure selection valve provided between the pair of main passages and configured to be switched by a pressure difference between the pair of main passages, the low pressure selection valve being configured to select the main passage on the low pressure side; and a flushing passage configured to lead the working fluid passing through the low pressure selection valve to the tank. The flushing passage has a first orifice and a bent portion formed on the downstream side of the first orifice.

Abstract: A work machine includes first and second hydraulic motors, first and second hydraulic pumps provided to supply hydraulic oil in correspondence with the first and second hydraulic motors, respectively, first and second swash plate angle sensors provided in correspondence with swash plates which regulate amounts of delivery by the first and second hydraulic pumps, respectively, the first and second swash plate angle sensors each detecting an angle of the swash plate, a delivery amount setting unit which sets an ideal amount of delivery by the first and second hydraulic pumps, and a command value control unit which corrects a command value for adjusting an angle of the swash plate such that the amount of delivery in accordance with a result of detection by the first and second swash plate angle sensors is set to the ideal amount of delivery.

Abstract: A control device for at least one hydraulic working section (A, B), which can be connected to a pressure supply source (P) and a return flow (T) via a hydraulic supply circuit and to a control valve (34) supplied with a pilot pressure. The device includes an emergency shutdown system (32) having a pilot solenoid valve (16) and an additional valve (14). Both the hydraulic energy flow from the pressure supply source (P) to at least one of the respective working sections (A, B) and the pilot pressure supply to the control valve (34) can be suppressed by the pilot solenoid valve (16) via the additional valve (14).

Abstract: A hydraulic system for a working machine, includes an operation member, an operation valve to change an output pressure of an operation fluid in accordance with operation of the operation member, a hydraulic device to be activated by the operation fluid outputted from the operation valve, a first fluid tube coupling the operation valve to the hydraulic device, and a bleed circuit connected to the first fluid tube and configured to output the operation fluid in the first fluid tube. The first fluid tube includes a first section fluid tube arranged in a section between the operation valve and a coupling portion coupling the first fluid tube to the bleed circuit, and a second section fluid tube arranged in a section between the coupling portion and the hydraulic device, the second section fluid tube having an inner diameter different from an inner diameter of the first section fluid tube.

Abstract: The present invention relates to an electronically controlled valve for a variable displacement pump, a hydraulic pump and a hydraulic pump system with switchable control functions. Multiple control functions of different types of hydraulic pumps can be implemented via one single electronically controlled valve combined with control elements and sensors. The hydraulic pump systems can be easily integrated into the overall application systems for intelligent control.

Abstract: A fluid arrangement for controlling a transmission of a motor vehicle in a hydraulic circuit is disclosed. The fluid arrangement includes a dual clutch including a first sub-clutch and a second sub-clutch, wherein the first sub-clutch is configured to be actuated via a first reversing pump actuator and the second sub-clutch is configured to be actuated via a second reversing pump actuator. The first and second reversing pump actuators each have a first delivery direction and a second delivery direction for delivering a working fluid in the hydraulic circuit. A first gear ratio mechanism with a variable gear ratio for actuating the dual clutch is configured to be actuated via the first delivery direction of the first and second reversing pump actuators a and a second gear ratio mechanism with a variable gear ratio for actuating a consumer arrangement is configured to be actuated via the second delivery direction.

Abstract: A transmission for a propulsion system. The propulsion system includes a power unit, a power transfer system, and a propulsion element. The transmission incorporates a summation, a propulsion output, and a power transfer transmission system, which receives power from the power unit and/or the power transfer system of the propulsion system. The power transfer transmission system includes a propulsion output transmission and a summation transmission, where the propulsion output transmission receives power from the summation transmission and directs the power to the propulsion element. The power transfer transmission system provides for transfer of power between the power transfer system and the summation transmission. The power transfer transmission system includes a power transfer shaft and a power transfer coupler and selectively connects the power transfer shaft to a propulsion outlet shaft, such that power is transferred directly from the power transfer system to the propulsion output transmission.

Abstract: A hydrostatic transmission for a traction drive includes a variable-displacement pump and one or more motors coupled to one another in a closed hydraulic circuit. A braking operation by means of the transmission can be initiated in the traction drive by an electronic control unit if there is a risk of overspeeding of an associated internal combustion engine. The braking operation is initiated if at least two activation thresholds are overshot, of which a first activation threshold is variable whereas the further activation threshold is fixed or variable.

Abstract: A hydraulic system for a work machine includes a tank to store an operation fluid, a hydraulic device to be operated by the operation fluid, a control valve to control the hydraulic device, a first fluid tube connecting the hydraulic device and the control valve, the first fluid tube being to supply the operation fluid from the control valve to the hydraulic device, a second fluid tube branching from the first fluid tube and connected to the tank, a switch valve provided to the second fluid tube, the switch valve being to control a flow rate of the operation fluid, and an oil cooler provided to the second fluid tube between the switch valve and the tank.

Abstract: A hydraulic system of a work machine includes a first hydraulic device to operate in a first operation mode while pressure of hydraulic oil supplied from a hydraulic pump via a first oil passage is equal to or higher than a first pressure threshold. The hydraulic oil in the first oil passage is to be discharged via a second oil passage. A pilot check valve is provided in the second oil passage and has a pilot port to receive a pilot pressure of the hydraulic oil. The pilot check valve is closed to stop discharging the hydraulic oil in the first oil passage through the second oil passage while the pilot pressure is higher than or equal to the second pressure threshold. The pilot check valve is opened while the pilot pressure is less than the second pressure threshold.

Abstract: The present invention relates to a vertical lift type loader comprising a power transmission arrangement with an engine, a hydraulic power system for powering work hydraulics of the loader and a drivetrain power system for powering locomotion of the loader, both being feedable with power from the engine, the hydraulic power system including a power limiter for limiting the power supply of the engine to the hydraulic power system to different power limit values, a determining device for determining an operational state of the loader, and a controller configured to control the power limiter to limit the power supply of the engine to the hydraulic power system to different power limit values, these power limit values being set depending on the operational state of the loader determined by the determining device.

Abstract: The present disclosure relates to a hydraulic system including a variable displacement hydraulic motor for lifting and lowering a load. The hydraulic motor has a high operating speed and a low operating speed. The system also includes an actuator for controlling whether the hydraulic motor is operating at the high or low speed, and a pressure sensor for sensing when a system pressure corresponding to the hydraulic motor exceeds a threshold pressure value. The system further includes a speed control system that controls the actuator such that the hydraulic motor is prevented from operating at the first operating speed when the system pressure exceeds the threshold pressure value.

Abstract: Disclosed are a construction machine such as an excavator having a hydraulic system and a method for controlling the construction machine. The construction machine includes: a hydraulic pump which is operated by a driving source to supply a working fluid; an actuator which operates by being supplied with the working fluid from the hydraulic pump; a spool which controls a flow of the working fluid supplied to the actuator from the hydraulic pump; an operating unit which controls an operation of the actuator; a memory unit which stores at least two operating speed profiles for the actuator; an operating speed selecting unit which selects any one of the at least two operating speed profiles stored in the memory unit; and a control unit which controls a discharge flow rate of the hydraulic pump based on the operating speed profile selected by the operating speed selecting unit.

Abstract: A travel control device is provided with hydraulic pumps of a variable capacity type that are driven by an engine; hydraulic motors that are driven by discharged oil from the hydraulic pumps; traveling devices that are rotation-driven by the hydraulic motors; a travel operation lever that is operated so as to instruct a traveling operation; a first control valve for generating a charged hydraulic pressure by adjusting the discharged oil from a charge pump and a second control valve for generating a capacity control hydraulic pressure in accordance with the operation of the travel operation lever. The first control valve is designed to pressure-adjust and generate a charged hydraulic pressure in accordance with the rotation speed of the engine, and the hydraulic pump is subjected to a variable capacity control process by a capacity control hydraulic pressure that is pressure-adjusted and generated by the second control valve.

Abstract: A hydraulic system of a transmission having a controller and a variable displacement pump. The pump includes an inlet and outlet and is adapted to be driven by a torque-generating mechanism. The system also includes a lube circuit fluidly coupled to the pump. A lube regulator valve is disposed in the lube circuit, such that the lube regulator valve is configured to move between at least a regulated position and an unregulated position. The regulated position corresponds to a regulated pressure in the lube circuit. A pressure switch is fluidly coupled to the lube regulator valve and configured to move between a first position and a second position, where the switch is disposed in electrical communication with the controller. A solenoid is disposed in electrical communication with the controller and is controllably coupled to the pump to alter the displacement of the pump.

Abstract: A hydraulic motor circuit for driving an auger is disclosed. The circuit includes a hydraulic motor that receives oil from an oil supply via a supply line and returns oil to the oil supply via a return line. The circuit further includes a main stage pressure relief valve and a first pilot stage relief valve operable if pressure in the return line exceeds a predetermined value corresponding to an allowable inertia load acting on the motor, opening of the first pilot stage relief valve causing the main stage pressure relief valve to open, allowing flow to be diverted from the return line to the supply line and back to the motor. A control valve is configured to block flow to the first pilot stage relief valve when pressure, in the supply line is greater than pressure in the return line. If pressure in the return line exceeds pressure in the supply line, the control valve shifts open and exposes the first pilot stage relief valve to pressure in the return line.

Abstract: A load based pressure and flow control system including a variable displacement hydraulic motor and a flow control valve coupled with a motor inlet. A motor inlet pressure sensor is interposed between the variable displacement hydraulic motor and the flow control valve, the motor inlet pressure sensor configured to measure a motor inlet pressure at the motor inlet. An output sensor is coupled with a motor output of the variable displacement hydraulic motor and configured to measure an output characteristic of the variable displacement hydraulic motor. A displacement and flow controller of the system is configured to change displacement of the variable displacement hydraulic motor according to a pressure difference across the flow control valve between the measured motor inlet pressure and a hydraulic system pressure, and change a flow rate of hydraulic fluid through the flow control valve according to the measured output characteristic of the hydraulic motor.

Abstract: A working machine control system includes: a split-flow fluid pressure pump configured to discharge a working fluid from a first discharge port and a second discharge port; a communication switching valve configured to be switched by a switch signal when any one of a first operation valve and a second operation valve is switched so as to allow a first neutral passage and a second neutral passage to communicate with each other; a neutral cut valve configured to be switched by the switch signal so as to block communication between a tank and one of the first neutral passage and the second neutral passage for the first operation valve or the second operation valve that is not switched; and a discharge flow rate adjusting device configured to adjust the fluid pressure pump so as to reduce a discharge flow rate thereof when the switch signal is inputted from any one of the first operation valve and the second operation valve.

Abstract: A hybrid or battery type working machine including a hydraulic pump, an electric motor, an electric storage device, and a control device which controls a pump absorption horsepower maximum value in accordance with an amount of electricity stored in the electric storage device. The control device reduces the pump absorption horsepower maximum value by dividing the pump absorption horsepower maximum value into a plurality of regions having different target flow rates, and reduces the pump absorption horsepower maximum value from an old pump absorption horsepower maximum value corresponding to the pump absorption horsepower maximum value which has not yet been reduced to a new pump absorption horsepower maximum value corresponding to the pump absorption horsepower maximum value which has been reduced, so that temporal differences among the regions can increase in a descending order of a target flow rate.

Abstract: A fluid delivery system for an engine is disclosed. The fluid delivery system comprises a pump, a valve module, a motor, and a displacement control module. The pump is operatively coupled with an engine and is adapted to provide a flow of a fluid. The valve module is provided in fluidic communication with the pump to control the flow of the fluid. The motor is provided in fluidic communication with the valve module to receive the flow of the fluid and generate mechanical power. The displacement control module is provided in fluidic communication with the pump and the valve module and is provided downstream of the pump and upstream of the valve module. The displacement control module controls a displacement of the pump for maintaining a constant flow rate of the fluid from the pump based, at least in part, on an engine speed regardless of compressor load.

Abstract: A control device controls a hydraulic cylinder unit having a piston. The device receives a setpoint variable and an actual variable and determines, based on a difference between the setpoint variable and the actual variable, a preliminary manipulated variable for valves of the hydraulic cylinder unit. The setpoint variable and the actual variable relate to a position of the piston or a force applied by the piston. Linearization factors are determined dynamically as a function of the actual position of the piston and working pressures on both sides of the piston and a hydraulic fluid tank/pump. Definitive manipulated variables to control the valves are determined from the preliminary manipulated variable and the linearization factors. With the linearization factors, a ratio of the piston adjustment speed to the difference between the setpoint variable and the actual variable is independent of the actual position of the piston and the working pressures.

Abstract: The invention relates to a hydraulic actuator (1) that can be controlled by a main valve (2) and an auxiliary valve (3). Upstream of the main valve device (2) is a main regulator (7), having a P block (9) and an I block (10). Upstream of the auxiliary valve (3) is an auxiliary regulator (8), having a base block (11) and an I block (12). In a normal mode of operation, the auxiliary valve (3) is deactivated. The main regulator is provided with a main setpoint variable (p*) and a corresponding main actual quantity (p) of the hydraulic actuator (1). The main regulator (7) determines a main actuating variable (s) and predefines the main actuating variable (s) in the main valve device (2). In a special mode of operation, the base block (11) of the auxiliary regulator (8) is provided with an auxiliary setpoint variable (a*) and a corresponding auxiliary actual quantity (p) of the hydraulic actuator (1).

Abstract: An operating state determining unit determines whether a hydraulic cylinder is in operation or not in operation. A discharge pressure reducing unit reduces the discharge pressure of a charge pump. A discharge pressure control unit controls the discharge pressure reducing unit when the hydraulic cylinder in not in operation to reduce the discharge pressure of the charge pump to a low pressure lower than a normal pressure. The normal pressure is the discharge pressure of the charge pump when the hydraulic cylinder is in operation. An accumulator is connected to a charge flowpath. A one-way valve is disposed between the accumulator and the charge pump. The one-way valve allows the flow of hydraulic fluid from the charge pump to the accumulator and prohibits the flow of hydraulic fluid from the accumulator to the charge pump.

Abstract: A debris collection vehicle having an enclosed volume for collecting debris and a hydraulic fan drive system for creating vacuum condition in the enclosed volume is disclosed. In one embodiment, the hydraulic fan system includes a closed loop hydraulic circuit, a variable displacement hydraulic pump disposed within the closed loop circuit, and a hydraulic motor disposed within the closed loop circuit. The hydraulic fan drive system can also include an electronic or hydraulically actuated control valve constructed and arranged to adjust the output of the hydraulic motor via a displacement actuator based on pressure in the closed loop hydraulic circuit.

Abstract: An electric pump includes a pump body, a sensorless brushless motor, and a control portion controlling the motor to perform a constant current control and a constant voltage control to discharge a necessary discharge amount of an operation fluid from the pump body, the control portion controlling the motor to switch from the constant current control to the constant voltage control at a predetermined temperature of the operation fluid and at a predetermined motor applied voltage. The control portion controls the motor to switch from the constant current control to the constant voltage control at a motor applied voltage which is higher than the predetermined motor applied voltage when a temperature of the operation fluid is lower than the predetermined temperature to discharge the necessary discharge amount of the operation fluid from the pump body.

Abstract: A drive system for propelling a power machine over a support surface is disclosed. The drive system includes a hydraulic pressure source and a drive assembly. The drive assembly has a hydraulic motor in fluid communication with the hydraulic pressure source that is switchable between first and second displacement arrangements. A shift valve receives pressurized fluid from the hydraulic pressure source and provides a shift signal to the hydraulic motor to selectively cause the displacement of the hydraulic motor to shift between the first and second displacement arrangements. A sensing device capable of generating a load signal indicative of a load condition provided by the drive assembly is also provided. An electronic controller provides a control signal to the shift valve to control the displacement of the hydraulic motor in response at least in part due to the load signal.

Abstract: A hydraulic control arrangement (1) is described having a directional valve (2), a metering pump unit which has at least two metering pumps (3, 4) which are connected hydraulically in parallel and are operable mechanically in parallel, and a shut-off valve (6) in hydraulic connection between two of the at least two metering pumps (3, 4), a pump connection (P) and a tank connection (T) which are connected to said metering pump unit by way of the directional valve (2), and two working connections (L, R) connected to the directional valve (2), a control input (8) of the shut-off valve (6) being connected to the pump connection (P) by means of a control valve. Such a control arrangement should be operated at a high hydraulic pressure and at the same time it should be made sure that the shut-off valve is actuated only when the required high pressure is available.

Abstract: A vehicle power generation mode control method includes initiating a vehicle power generation mode request; determining whether at least one of the following conditions exists: high engine revolutions per minute is allowed; high voltage or amperage draw is allowed; current fuel level supports power generation mode; and carbon monoxide readings are within acceptable limits; denying requests for engagement of a vehicle transmission if at least one of the conditions exists; and allowing or commanding the vehicle power generation mode.

Abstract: A hydraulic drive system for a construction machine has a travel detection device which detects whether or not the operation mode is a traveling operation and a setting changing device. The setting changing device sets the target differential pressure of load sensing control at an absolute pressure Pa when the operation mode is not a traveling operation, and sets the target differential pressure of the load sensing control at an absolute pressure Pa? rather than the absolute pressure Pa. In this way, in the actuator operation other than traveling, a necessary actuator speed can be obtained and supplied with the necessary maximum flow rate. In addition, during the combined operation, a flow rate in accordance with the opening area ratios of flow control valves can be distributed to actuators different in load pressure from one another; and energy efficiency is enhanced due to less energy loss during traveling operation.

Abstract: A hydrostatic hybrid drive system for road vehicles includes a pump/motor unit (1) connected to the powertrain of the vehicle, controlled by a control unit (5) in a pump or motor operation, and connected to a high-pressure hydraulic accumulator via a first working line (7). The first working line can be closed by a control valve (45) and connected to a low-pressure hydraulic accumulator via a second working line (9). The high-pressure hydraulic accumulator and low-pressure hydraulic accumulator are formed by a double-piston accumulator (11), in which a high-pressure side and a low-pressure side having respective accumulator pistons (15, 17) are formed in an accumulator housing (13). The fluid chambers (23, 25) of the high-pressure side and the low-pressure side are separated by a central housing part (21) through which the common piston rod for both accumulator pistons (15, 17) extends.

Abstract: A hydraulic system has a variable displacement pump that sends fluid from a tank into a supply conduit from which separate open-center control valves convey the fluid to each one of a plurality of hydraulic actuators. The control valves have open-center orifices connected in series between a bypass node and the tank, thereby forming a bypass passage. Pressure at the bypass node controls displacement of the pump. A valve arrangement is connected between an outlet of the pump and the bypass node and is responsive to an amount of fluid flow through the supply conduit to the plurality of hydraulic functions, wherein as the amount of fluid flow increases, the valve arrangement causes fluid flow to the bypass node to decrease. Thus the pressure at the bypass node varies as a function of the operation of the control valves.

Abstract: A controller controls the solenoid-operated variable pressure relief valves that are provided to control, at set pressures that can be electrically commanded, pressure of hydraulic oil fed to an attachment cylinder. The controller is provided with a control logic that is capable of controlling the aforementioned solenoid-operated variable pressure relief valves. The control logic performs the aforementioned calculation by compensating for pressure override characteristics of each solenoid-operated variable pressure relief valve based on input signals related to the set relief pressure for and a relief valve passing flow rate of the solenoid-operated variable pressure relief valve, and outputting to the solenoid-operated variable pressure relief valve command signals related to the adjusted set relief pressure resulting from the compensation of the pressure override characteristics.

Abstract: A fuel vapor purge device includes a canister connected to an internal combustion engine and a fuel tank via a purge passage to adsorb and hold a part of fuel vapor, a switch valve connected to the canister and to an atmosphere, and a pump connected to the switch valve via a pump passage and to the atmosphere via an atmosphere passage. The pump is capable of depressurizing or pressurizing an interior of the fuel tank, and the switch valve switches connection of the canister between with the atmosphere and with the pump. The fuel vapor purge device further includes a seal valve provided in the pump passage to open or close the pump passage depending on a pressure in the atmosphere passage.

Abstract: A hydraulic control system is disclosed for use with a machine. The hydraulic control system may have a tank, a pump, an actuator, and a control valve configured to direct fluid from the pump to the actuator and from the actuator to the tank. The hydraulic control system may also have a pressure sensor to generate a first signal indicative of a pressure differential across the control valve, an operator input device to generate a second signal indicative of a desired movement of the actuator, and a controller. The controller may be configured to make a first determination of an opening amount of the control valve based on the second signal, and to make a second determination based on the first signal of whether the opening amount will result in overspeeding of the actuator. The controller may also be configured to reduce the opening amount based on the second determination.

Abstract: The present disclosure relates to an electronic hydraulic pressure control apparatus and an electronic hydraulic pressure control method using a variable behavior, and more particularly, to an electronic hydraulic pressure control apparatus and an electronic hydraulic pressure control method using a variable behavior which can detect that a user manipulates an electronic joystick of an electronic hydraulic system to positive and negative positions with respect to a neutral point in a preset time period, and vary a behavior (for example, a general behavior or an abrupt operation behavior) according to the detection result, thereby enhancing both comfortableness of an operator and an abrupt operation efficiency in manipulating a construction machine and providing a convenience for an operator.

Abstract: In order to provide a forklift capable of performing an inching control suitable for a specific work and a running operation of the forklift and an inching control method of the forklift, an inching ratio calculating unit calculates an inching ratio, a target engine speed calculating unit calculates a target engine speed, a modulation control unit sets a time constant of the inching ratio in response to a speed difference between the target engine speed and an actual engine speed and outputs a correction inching ratio having the time constant set thereto, a multiplication unit outputs a correction absorption torque obtained by multiplying the correction inching ratio by a target absorption torque, and a HST pump electromagnetic proportional control output current converting unit outputs a current instruction value to a pump capacity setting unit.

Abstract: A hydraulic system for a working machine is provided in which when heavy load fine speed operation work is performed using hydraulic cylinders as hydraulic actuators, and deterioration of fuel consumption can be prevented by reducing energy loss and improving fine speed operability. A center bypass cutoff valve 41 is disposed downstream of a center bypass line 26, and pressure sensors 42, 43, a controller 44, and a solenoid valve 45 provide control such that, when operating means 16 corresponding to a boom cylinder 5 (specific hydraulic actuator) among a plurality of operating means 18-21 is operated to supply a hydraulic fluid to a cylinder chamber 5a of the boom cylinder 5 in a load retaining side, the center bypass cutoff valve 41 is actuated and a fluid delivery pressure of a first hydraulic pump 2 is increased to be higher than a load pressure of the boom cylinder 5.

Abstract: A controller carries out horsepower control to determine a flow rate of a hydraulic pump based on first characteristics and second characteristics, which each define a maximum input setting of the hydraulic pump by a discharge pressure of the hydraulic pump and a flow rate of the hydraulic pump, and based on the discharge pressure. When the discharge pressure is less than a set pressure and when a state where the discharge pressure is equal to or greater than the set pressure has not continued for a set time period, then the controller determines the flow rate based on the first characteristics, and when the state where the discharge pressure is equal to or greater than the set pressure has continued for the set time period, then the controller determines the flow rate based on the second characteristics.

Abstract: A drive system for hydraulically driven working mechanisms of a working machine includes an axial piston pump, the pump capacity and flow direction of which is varied by changing the pivot angle of the axial piston pump. The drive system includes a hydraulic motor connected via a line to the axial piston pump and drivably connected to the working mechanisms, a control unit operated to set the pump capacity of the axial piston pump to zero and a control valve arrangement that is actuated by the control unit to actuate a limiting device such that the pivot angle of the axial piston pump can be mechanically set to zero degrees (0°).

Abstract: A hydraulic fluid flow management system and method includes three subsystems. The first subsystem is an engine mounted hydraulic fluid pump electrically operated flow control proportioning valve combination. The second subsystem is a hydraulic fluid flow distribution manifold assembly. The third subsystem is a computer operated controller and display which governs the operation of the electrically operated flow control proportioning valve combination.

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: A hydrostatic fan drive is operated with a closed circuit and includes a variable-displacement pump with a swept volume that is configured to be adjusted by an adjustment device. The variable-displacement pump is connected by two working lines to a motor that is coupled fixedly in terms of torque to a fan impeller. The fan drive further includes a feed pressure pump and an adjustment pressure line by which the adjustment device is supplied with adjustment pressure medium. A pressure cut-off valve is connected to the adjustment pressure line. The pressure cut-off valve is configured to limit an adjustment pressure, as a function of a high pressure in the working line acting as high-pressure line, to a value such that a certain value of high pressure is not exceeded. The pressure cut-off valve is configured to exhibit pilot control to regulate a working pressure of the variable-displacement pump.

Abstract: A method of controlling a float function of a cylinder 25 having a first side and a second side includes connecting the second side of the cylinder to a reservoir 15; connecting the first side of the cylinder to an output of a pump 20 and to the reservoir; and supplying an amount of flow from a pump less than an amount supplied by the pump under loaded conditions. A three-position directional control valve 30 having a pump port, a reservoir port, a first cylinder port, and a second cylinder port may be provided to effectuate aspects of this method.

Abstract: A hydraulic pump driven by an engine, a hydraulic actuator, and a negative control circuit are provided on an open center hydraulic circuit, for guiding the hydraulic pressure in the center bypass to the hydraulic pump, as a negative control pressure. A negative control pressure control device controls the negative control pressure to an arbitrary value is also provided. The pump characteristic of the hydraulic pump is set such that the discharge flow rate is minimized when the negative control pressure in the negative control circuit is equal to or greater than a first predetermined pressure. Furthermore, an idling detection device that detects whether the hydraulic actuator is in a non-operated state or not is provided. The negative control pressure is forcefully controlled to the first predetermined pressure or higher when the non-operating state is detected.

Abstract: The invention provides a device for extracting energy from a liquid flow. The device has a housing with one or more entry ports through which liquid flow can enter the housing and multiple exit ports through which liquid flow can leave the housing. An air compression chamber is provided along with multiple valve members which are operable to regulate flow of the liquid through the multiple exit ports. The exit ports are arranged in an array inclined in the direction of liquid flow and the valve members are operable to close the exit ports downstream of the liquid flow consecutively as the liquid flow is incident on each exit port, which progressively diverts flow of the liquid towards the air compression chamber and compresses air in the air compression chamber, and to open the exit ports on a return flow of liquid from the air compression chamber.

Abstract: An outdoor power equipment unit comprises a self-propelled mower having a hydraulic traction drive system. When engine load exceeds a predetermined percentage of full load, a controller automatically reduces the stroke of a variable displacement pump in the traction drive system to reduce the ground speed of the mower without the operator having to change the position of the traction pedal. This reduces engine load to enhance continued good cutting performance. At any time, the controller can take the same actions to reduce ground speed if an excessively high temperature in a fluid used in a cooling system on the mower is detected, or if excessive loads on the mower decks of the mower are detected, or both.

Abstract: A load sensing system includes a first assembly of actuators for controlling a first hydraulic function, a pump adapted to supply the actuators with pressurized hydraulic fluid, an electrically controlled valve adapted to control the output pressure of the pump via a hydraulic signal, a first pressure sensor for detecting a load pressure of the first actuator assembly, and a control unit adapted to receive a signal with information about the load pressure detected by the first pressure sensor and to generate a control signal, corresponding to the detected load pressure, to the electrically controlled valve.