Abstract: A valve with an inlet, an outlet that is connected to the inlet via a fluid connection, and a valve body which can be brought by displacing it along a displacement direction into a first position, in which the fluid connection is blocked, and a second position, in which the fluid connection is open, wherein the inlet is designed and arranged in such a way that a fluid entering through the inlet exerts a total force on the valve body that at least also acts in a force direction which is perpendicular to the displacement direction when the valve body is in the first position.

Abstract: A hydraulic system for a working machine includes hydraulic actuators actuated with hydraulic fluid delivered from a hydraulic pump, and control valves each of which is shiftable among shift positions to control a flowrate of hydraulic fluid flowing to the corresponding hydraulic actuator. Each control valve includes an input port, an output port, and a flowrate reduction section. When the control valve is shifted to a reduction position, the flowrate reduction section reduces a flowrate of the hydraulic fluid entering the input port and outputs the flowrate-reduced hydraulic fluid to the output port. At least one of the control valves includes a flowrate increase section. When the control valve is shifted to an increase position, the flowrate increase section outputs the hydraulic fluid having entered the input port to the output port at a flowrate larger than that of hydraulic fluid output by the flowrate reduction section.

Abstract: Provided is a hydraulic variable pump set, including a pump body component and an oil supplement component. The pump body component includes a pump body, a first slide valve, and a first control valve. The first slide valve includes a spring end and a pilot cavity. The first control valve is provided with an oil inlet A, an oil inlet B, and an oil outlet T. The pump body includes a variable pump and a variable cylinder. The variable pump includes a swash plate. The variable cylinder includes a rod cavity and a rodless cavity. The variable cylinder is mechanically connected to the spring end and the swash plate. The oil supplement component is in communication with the pilot cavity.

Abstract: A shovel control method includes performing a plane position control or a height control of an end attachment by an operation of one lever. The plane position control is performed while maintaining a height of the end attachment. The height control is performed while maintaining a plane position of the end attachment.

Abstract: A fluid pressure control device includes a switching valve that has a pilot chamber to which the working oil is supplied from the supply passage through the second control valve, and a first relief valve that is provided on the downstream side of the switching valve. The second control valve allows supply of the working oil to the pilot chamber in a case where a flow of the working oil to a tilt cylinder is allowed, and blocks the supply of the working oil to the pilot chamber in a case where the flow of the working oil to the tilt cylinder is blocked. The switching valve allows a flow of the working oil to the first relief valve in a case where the working oil is supplied to the pilot chamber, and blocks the flow of the working oil to the first relief valve in a case where the supply of the working oil to the pilot chamber is blocked.

Abstract: The present disclosure provides, in a first aspect, a pressure-controlled 2-way flow control valve for hydraulic applications, wherein the 2-way flow control valve has applied thereto a first pressure signal in the closing direction of the 2-way flow control valve by means of a first output-side tapping and a second pressure signal in the opening direction by means of an LS pressure reporting duct. A pressure signal corrupting the first or second pressure signal is applied to the 2-way flow control valve in the closing or opening direction by means of a second tapping which is effective at least over part of the control stroke of the 2-way flow control valve.

Abstract: A hydrostatic transmission includes a side having an upstream radial piston motor and a downstream radial piston motor. The motors are connected to each other in series via a connecting line. A flow control valve is configured to discharge pressure medium from the connecting line so that the downstream motor is only engaged in the event of a predetermined amount of slippage of the upstream motor. Each motor has at least two groups of working flanks. Each flank is configured to operatively interact with a high pressure, such that each motor has at least two transmission steps.

Abstract: The present invention relates to a hydraulic control valve for construction machinery that is used to maintain secondary pilot pressure which is formed proportionally to the switching of a switching device so as to be equal to or below a setting pressure of a pilot pump.

Abstract: A pump system includes a closed-loop fluid circuit and an open-loop fluid circuit. The closed-loop fluid circuit includes a motor for rotating a first component connected to the closed-loop fluid circuit. A closed-loop pump drives the motor up to a first maximum rotational speed. The open-loop fluid circuit includes an open-loop pump for driving a second component connected to the open-loop fluid circuit. A control circuit includes a control valve for switching the outflow from the open-loop pump. The control valve selectively connects the open-loop pump to the closed-loop fluid circuit and simultaneously disconnects the open-loop pump from the open-loop fluid circuit. When the open-loop pump is connected to the closed-loop circuit, the closed-loop pump and the open-loop pump drive the motor at a second rotational speed greater than the first maximum rotational speed.

Abstract: A hydrostatic transmission in the shape of a shaft/rotor comprising two hydraulic pumps/motors with adjustable displacement connected in a closed hydraulic system. The displacement of the pumps/motors is adjusted by adjusting the angle of swash plates of the pumps/motors. The control and regulation of the angle of the swash plates is done by transferring a signal by two separate pulse width modulated DC fed pulse trains. The hydrostatic transmission includes oil accumulators connected to the hydraulic pumps/motors.

Abstract: A controller constituting a construction machine includes: a target value computing unit that generates a speed target value of a boom based on a lever manipulating signal; a target value correcting unit that corrects the speed target value; and a command signal output unit that outputs a command signal to a boom driving device based on the corrected speed target value. The target value correcting unit includes: a motion information acquiring unit that acquires motion information on a motion of an arm; a maximum value determining unit that determines based on the motion information a maximum correction value for reducing suppression of a floating motion by a floating motion suppressing unit as the motion of the arm becomes faster; and a correction value regulating unit that corrects the speed target value based on the maximum correction value.

Abstract: A hydraulic system hydraulic system includes a variable displacement pump, and a variable displacement first travel motor selectively fluidly connected to the pump in a closed-loop manner. The system also includes a first switching valve associated with the first travel motor and configured to selectively switch a flow direction of fluid passing through the first travel motor from the pump. The system further includes a variable displacement second travel motor selectively fluidly connected to the pump in a closed-loop manner. The system also includes a second switching valve associated with the second travel motor and configured to selectively switch a flow direction of fluid passing through the second travel motor from the pump.

Abstract: A working machine includes: a first switch operable to set an operation amount; a second switch operable by being pressed; a control unit capable of detecting an operation of the first switch and an operation of the second switch, the control unit outputting a control signal based on the operation amount of the first switch and continuously outputting the control signal when the operation of the first switch is detected after detecting a release of the operation of the second switch under a state where the operation of the second switch is detected; an actuator configured to be activated by a hydraulic operation fluid; a solenoid valve capable of controlling, based on the control signal, a pilot pressure; and a control valve configured to supply, based on the pilot pressure, the hydraulic operation fluid to the actuator.

Abstract: A control valve apparatus includes a second-working-actuator acceleration control valve connected to a first working control valve in parallel. The second-working-actuator acceleration control valve includes pilot chambers receiving a pilot pressure for switching first and second working control valves and a flow channel that guides a pressure fluid of a first pump port to an entrance port side of the second working control valve. The second-working-actuator acceleration control valve is switchable between a first priority position in which a pressure fluid is guided to the first working control valve with a higher priority than the second working control valve and a second priority position in which a pressure fluid is guided to the second working control valve with a higher priority than the first working control valve.

Abstract: A hydraulic system includes a variable-displacement first pump, an over-center variable-displacement first travel motor selectively connected to receive fluid pressurized by the first pump in a closed loop manner, and an over-center variable-displacement second travel motor selectively connected to receive fluid pressurized by the first pump in parallel with the first travel motor in a closed loop manner. The hydraulic system also includes a linear actuator selectively connected to receive fluid pressurized by the first pump in parallel with the first and second travel motors in a closed loop manner.

Abstract: A hydraulic system for a machine is disclosed. The hydraulic system may have a tank configured to hold a supply of fluid, a pump configured to draw fluid from the tank and pressurize the fluid, a first cylinder operatively connected between a first side of a work tool and an undercarriage of the machine, and a second cylinder operatively connected between a second side of the work tool and the undercarriage of the machine. The hydraulic system may also have a first electro-hydraulic valve associated with the first cylinder and configured to selectively regulate a flow of pressurized fluid to the first cylinder independently of the second cylinder, and a second electro-hydraulic valve associated with the second cylinder and configured to selectively regulate a flow of pressurized fluid to the second cylinder independently of the first cylinder.

Abstract: Provided is an electric construction machine capable of avoiding a situation where charging is difficult to achieve due to the exhaustion of a battery device. An electrically-operated hydraulic excavator includes an electric motor, a hydraulic pump that is driven by the electric motor, hydraulic actuators that are driven by hydraulic fluid discharged from the hydraulic pump, and a battery device that serves as an electrical power source for the electric motor. The battery device includes battery systems that each have a plurality of batteries. A selector switch makes it possible to select either one of the battery systems. An arithmetic control section of an inverter device controls connection change switches through battery controllers to change the connections of the battery systems so that electrical power is supplied to the electric motor from either the battery system or the battery system, whichever is selected by the selector switch.

Abstract: A fixed/variable hybrid system has modified constant flow open center hydraulic valves (“fixed/variable valves”), including an open center core, spools, a power core, and a tank galley. A small fixed displacement pump provides fluid at a constant rate to the open center core. A variable displacement piston pump provides fluid directly to the power core as needed. Activation of spools partially restricts the open center core causing an increase in fluid pressure that is communicated to the variable displacement piston pump's load sense signal port, causing the pump to increase fluid flow and pressure to the power core. Activated spools direct pressurized fluid from the power core to the applications through selected hydraulic ports. Activated spools also direct fluid flow from selected hydraulic ports via the tank galley to a hydraulic tank. Pumping the majority of fluid only on an as-needed basis results in significant efficiencies.

Abstract: A method and system for configuring a hydromechanical transmission having a hydraulic pump and a hydraulic motor driven by the hydraulic pump and a pressure-driven actuator employs a particular torque-pressure curve configuration to maximize torque resolution with respect to actuator pressure changes while ensuring that the curve is substantially monotonic in each dimension and at any available motor speed within a predetermined motor speed limit and any available actuator pressure within predetermined actuator pressure limits. The resultant four-dimensional association between actuator pressure, motor speed, primary power source speed and motor torque allows selection of an actuator pressure to provide a desired torque.

Abstract: Systems and methods for associating a load demand with a variable power generation are described. A system includes a renewable variable power generation module including a sensor, the sensor configured to determine an output power capability value for the renewable variable power generation module. The system also includes a load demand module including a response device, the response device configured to receive the output power capability value directly from the renewable variable power generation module and to determine an input power demand value based on the output power capability value.

Abstract: A universal control scheme for mobile hydraulic equipment has switches to activate and/or control any number of different tools or accessories that may be used to configure the equipment. Additionally, a single controller command may be reassigned from one set to another set of hydraulic line pairs. Furthermore, at different times, two separate controller commands may be used to control the same hydraulic line pair. The control scheme also provides for consolidating hydraulic line pair functions to separate for dedicated use those line pairs associated with operating hydraulic cylinders to extend or retract a member and those line pairs used to provide hydraulic fluid for operating tools.

Abstract: A universal control scheme for mobile hydraulic equipment has switches to activate and/or control any number of different tools or accessories that may be used to configure the equipment. Additionally, a single controller command may be reassigned from one set to another set of hydraulic line pairs. Furthermore, at different times, two separate controller commands may be used to control the same hydraulic line pair. The subject invention is also directed to a method for achieving the same.

Abstract: A hydrostatic transaxle is provided for a vehicle having a first axle and a second axle. The hydrostatic transaxle comprises: a hydraulic pump; a first hydraulic motor drivingly connected to the first axle; a closed circuit fluidly connecting the hydraulic pump to the first hydraulic motor; and a fluid-supply switching device shifted between a supply position for supplying fluid from the closed fluid circuit to a second hydraulic motor, which is disposed on the outside of the hydraulic transaxle and is drivingly connected to the second axle, and a supply-stop position for stopping the supply of fluid from the closed fluid circuit to the second hydraulic motor. The first hydraulic motor is variable in displacement, and the hydrostatic transaxle further comprises a linkage system for associating the switching of the fluid-supply switching device between the supply position and the supply-stop position with an operation for changing the displacement of the first hydraulic motor.

Abstract: A hydraulic circuit including a first motor set, and a second motor set for driving vehicle-moving means situated one behind the other. The circuit has first, second, third, and fourth main ducts for feeding the motor sets in parallel. The device includes a selector suitable for taking up a first stable position making the feeding in parallel possible by interconnecting in pairs the feed and discharge main ducts, and for taking up a second stable position in which one of the motor sets is inactive because one of the main ducts is connected to one of main ducts of the other set. Between the stable positions, the selector can take up a temporary position, in which all four main ducts are interconnected. At least while the selector is moving in one direction between its two stable positions, the temporary position is sustained in an intermediate stage during which at least one of the interconnections between the main ducts of the first and second motor sets is constricted.

Abstract: A hydraulic system for utility vehicles is disclosed for prioritized pressure medium supply to internal and external pressure medium consumers (6, 11, 12), which are fed via load sensing spool valves (20, 26), the external pressure medium consumers (11, 12) being supplied with pressure medium via a priority valve (17). In order to improve the work quality of an implement driven by an external pressure medium consumer, the present invention provides that priority can be selectively assigned to the internal (6) or the external (11, 12) pressure medium consumers. It is thus possible for the driver, in order to ensure optimum operation of the utility vehicle in critical situations, to give priority to external pressure medium consumers. In this way during operation of an implement for dispersion of substances, better work quality can be attained, as a reduced supply and thus slower function of the internal power lift are accepted.

Abstract: The operating system for a construction machine gives advice on efficient operation to an operator. A specified state value relating to the operational condition of the construction machine, for example, the hydraulic oil pressure or engine speed, is detected (S101), and the frequency distribution of the state value in prescribed time intervals is calculated (S102). The variable range of the state value is classified into plural regions beforehand, and different target values are pre-set for each these regions. For each region, the frequency distribution is compared with the target value (S104, 106, 108, 110, 112), and as a result of the comparison, a applicable message is selected from the prescribed messages and output (S105, 107, 109, 111, 113). The output message may also be selected according to the combination of the comparison results for the plural state values such as the hydraulic oil pressure and engine speed.

Abstract: A hydrostatic transaxle is provided for a vehicle having a first axle and a second axle. The hydrostatic transaxle comprises: a hydraulic pump; a first hydraulic motor drivingly connected to the first axle; a closed circuit fluidly connecting the hydraulic pump to the first hydraulic motor; and a fluid-supply switching device shifted between a supply position for supplying fluid from the closed fluid circuit to a second hydraulic motor, which is disposed on the outside of the hydraulic transaxle and is drivingly connected to the second axle, and a supply-stop position for stopping the supply of fluid from the closed fluid circuit to the second hydraulic motor. The first hydraulic motor is variable in displacement, and the hydrostatic transaxle further comprises a linkage system for associating the switching of the fluid-supply switching device between the supply position and the supply-stop position with an operation for changing the displacement of the first hydraulic motor.

Abstract: A hydraulic system for use in a work vehicle with a powered implement is disclosed. In one embodiment, the hydraulic system may include a first hydraulic circuit including a first hydraulic pump with a low pressure and low flow output, switch and valve; a second hydraulic circuit including a second hydraulic pump with a high flow and high pressure output, switch and valve; and a third hydraulic circuit including a third hydraulic pump with a high flow and high pressure output, switch and valve. The first, second, and third circuits each include an output selectively combinable with each other by an operator control which controls the switch and valve configurations. The hydraulic system has several configurations.

Abstract: A travel control device enables a crawler type hydraulic excavator to start slowly regardless of the preset speed ratio whenever the manipulation amount of a manual travel control device is small. The travel control device includes left and right travel motors respectively provided with speed changing mechanisms, a high speed shifting valve provided on a high speed signal line for cutting off or transmitting a high speed signal pressure to the speed changing mechanisms, a travel signal detection means for detecting a travel control signal pressure outputted from manual travel control devices. A shutoff valve is provided on the high speed signal line for closing or opening the high speed signal line to keep the speed changing mechanisms in a low speed condition or a high speed condition depending on the magnitude of the travel control signal pressure supplied from the travel signal detection means.

Abstract: A fluid-pressure transmitting apparatus that is capable of securing the operationality of a working machine and braking and preventing against engine stall. The apparatus can switch between a working-machine operating device and a traveling operating device. When a second operating unit is operated during operation of a first operating unit, the pilot pressurized oil outputted from each operating means through first and second pilot-pressure admission passages is admitted to a low-pressure selecting valve. At this time, the pilot pressurized oil is automatically selected through the low-pressure selecting valve to control the delivery capacity of the traveling pump and braking and preventing engine stall and realizing travel at low speed.

Abstract: A fluid control system incorporates an orificing device between each of a plurality of pilot operated control valves in connection with a control device and a resolver. The pilot operated control valves are actuated by the control device to control different functions of a work machine. The actuation of the pilot operated control valves produces pressure flows that are sent to the respective resolver. The orificing devices include a plurality of steps that may be varied in size and shape to dampen the pressure flow to the respective resolver so that independent control for the pilot operated control valves is achieved. Additionally, a precision edge is defined within each of the orificing devices to control the flow of pressurized hydraulic fluid through the respective orificing device and maintain a consistent viscous drag therethrough independent of temperature and oil-viscosity variations.

Abstract: A method for controlling a desired ratio of flow in a system having multiple circuits. The method includes determining a first desired flow in a first circuit and a second desired flow in a second circuit, determining a first actual flow in the first circuit and a second actual flow in the second circuit, comparing the first desired flow to the first actual flow and the second desired flow to the second actual flow, determining a condition of one of the first and second actual flows being less than the respective first and second desired flows, and responsively initiating a command from one of the first and second circuits to the other of the first and second circuits to reduce the actual flow of the other of the first and second circuits to maintain the desired ratio of flow.

Abstract: The present invention includes a hydrostatic transmission system that has a control device that is selectable to send a speed signal to a motor for driving an output at a predetermined speed. A controller is used to automatically permit the selected speed signal in response to a predetermined speed signal and predetermined input from a sensing device indicating that the output is being driven in a forward drive condition. The controller is also used to automatically override the selected speed signal in response to a predetermined speed signal and predetermined input from a sensing device indicating that the output is being driven in a reverse drive condition. This invention allows for the speed of the motor to be changed from a high speed to a low speed when the motor is driving the output in a reverse drive condition to achieve greater efficiency and control of a work machine.

Abstract: A control circuit for a construction machine using a control lever for revolving a boom swing in common with a traveling motor and switching pilot pressure via a switching valve has a switch for supplying a switching signal to the switching valve. A pressure switch detects whether the pilot pressure is output from a remote control valve or not. A switching control circuit switches a position of the switching valve to a position for the boom swing cylinder when the switching signal is output from the switch and holds the position of the switch at the position for the boom swing cylinder when the pilot pressure is detected by the pressure switch, to thereby prevent wrong operation in switching.

Abstract: A method for controlling the storage pressure of a pressurized air store (4) of a closed level control system for a motor vehicle includes a compressor (6), a pressurized air store (4) (which can be filled with air from the atmosphere and which can be discharged into the atmosphere) and at least one air spring (2a to 2d). The air springs (2a to 2d) are connected via the compressor (6) to the pressurized air store (4) so that pressurized air from the air springs (2a to 2d) can be transferred into the pressurized air store (4) and can be transferred in the opposite direction. The storage pressure of the pressurized air store (4) is controlled indirectly via the air quantity in the level control system in that this air quantity is determined. The pressurized air store (4) is filled with air from the atmosphere when the air quantity lies below a lower limit and the pressurized air store (4) is discharged into the atmosphere when the air quantity lies above an upper limit.

Abstract: It is an object of the present invention to provide a control valve which can reduce the number of external lines connected to a hydraulic remote control valve. A control valve 1 for controlling hydraulic cylinders 2,2′ is provided, in one 26 of spool covers, with fluid passages 27,27′, a shuttle valve 28 for selecting higher one of pilot pressures to be transmitted to these fluid passages 27,27′, and a fluid passage 29 for transmitting the pressure selected by the shuttle valve 28. The fluid passages 27,27′ are in communication with pressure fluid ports 25,25′ as connection ports for pilot lines 24a,24c. The control valve 1 is also provided, in the other spool cover 32, with fluid passages 33,33′, a shuttle valve 34 for selecting higher one of pilot pressures to be transmitted to these fluid passages 33,33′, and a fluid passage 35 for transmitting the pressure selected by the shuttle valve 34.

Abstract: A rotational speed of an electric motor 12 is memorized at a memory unit 21 as a set rotational speed for allowing a minimum required volume of brake fluid to be discharged from the pumps in a state where the output hydraulic pressure of the master cylinder is highest, and an energizing duty ratio for the electric motor 12 which is designed so as to rotate the electric motor 12 at the set rotational speed is determined at a duty ratio determining unit 22 in response to an applied voltage detected at a voltage detecting unit 20. A motor control unit 23 controls the energizing of the electric motor 12 from a battery 18 in accordance with the energizing duty ratio determined at the duty ratio determining unit 22.

Abstract: A hydrostatic transmission system for driving a rotatable member includes a differential having an output coupled with the rotatable member, a first hydrostatic drive having an output coupled to a first input of the differential, and a second hydrostatic drive having an output coupled to a second input of the differential. The output of the first hydrostatic drive is rotatable in a first selected direction and at a first selected speed. The output of the second hydrostatic drive is rotatable in a second selected direction and at a second selected speed. A rotational speed and direction of the output of the differential is related to the algebraic sum of the rotational speeds and directions of the outputs of the hydrostatic drives. In one embodiment, the speeds of the first and second drives are maintained above a minimum stable threshold, while operating the rotatable drive at very low or zero speed, by selecting the first direction to be opposite the second direction.

Abstract: A work attachment for a commercial work vehicle such as a skid steer loader has a unique hydraulic circuit that splits hydraulic working flow between two hydraulic functions without the need for electronic solenoids. The commercial work vehicle has hydraulic flow through two hydraulic hoses to the work attachment which can be reversed by the operator of the vehicle to provide two different hydraulic signals. During normal operation, hydraulic working output flow is directed toward a first function, such as the rotary motor of a rotary broom or rotary snow blower. To provide for the second function, the circuit includes a diversion valve that may take the form of a check valve that diverts the flow in response to one of the hydraulic signals (e.g. when flow is reversed). The diversion valve directs flow toward the second hydraulic function such as a hydraulic cylinder for positioning a portion of the attachment (e.g. to effect a selected engaging angle of a rotary broom).

Abstract: When a working implement comes close to a cab during operation, for efficiency, the operation should continue insofar as possible yet it is essential the working implement be prevented from striking the cab. To that end, a pilot pump oil line capable of supplying pilot pressurized oil to a solenoid proportional pressure reducing valve in a state where a control member is not manipulated, is provided in a stick contraction-side pilot oil line. When the working implement enters an interference prevention area, defined around the cab, the stick is automatically moved out so that the operation can continue yet the working element avoids the interference prevention area.

Abstract: A hydraulic system for propelling a vehicle, and with the system arranged with a pump and vehicle drive motors and valves and pilot lines. The operator can select an all-wheel drive or a lesser number of wheel drives. Also, there is a system automatic response to certain conditions of vehicle drive, whereupon the system activates to alter the drive to the various vehicle wheels, including changing from a four-wheel drive mode to a two-wheel drive mode. Further, the operator can override the system's own activation and thereby establish the two-wheel drive mode desired.

Abstract: A tournament oil path constituting apparatus in which while a laminated block is constituted by laminating a number of oil path plates, a number of shuttle valve holes and connection grooves made continuous to the shuttle valve holes are formed at overlap faces of the oil path plates, shuttle valves are integrated to the shuttle valve holes, introductory oil paths communicating with the shuttle valve holes are formed at both of the oil path plates formed with the shuttle valve holes and the oil path plates having match faces on sides of the shuttle valve holes and a high pressure oil is selected by the shuttle valves from pressure oils conducted both of the introductory oil paths and conducted to the connection grooves. The tournament oil path constituting apparatus also including a number of main paths penetrating the number of laminated oil path plates and branch grooves branched from the main paths.

Abstract: The present invention is directed to a hydraulic pressure control device which can overcome problems, such as a shock to an actuator or a pressure boost phenomenon involving a rapid increase in pump delivery pressure, conventionally encountered when a directional control valve is switched. The hydraulic pressure control device is constructed such that first and second connecting ports are connected to a tank when a directional control valve is in its neutral position, one of the first and second connecting ports is cut off from the tank and connected to an actuator and the other is cut off from the tank and closed when the directional control valve has been switched, in accordance with a position to which the directional control valve has been switched, and a maximum pilot pressure selectively taken from between a pressure compensating valve and a pair of check valves is introduced into a pilot line.

Abstract: A drive system for a mobile operating device. The drive system includes a drive motor driving a first variable-delivery hydraulic pump which is in fluid engagement with a first hydraulic motor, the first hydraulic motor being part of a hydraulic travelling drive. A second hydraulic motor drives at least one second variable-delivery hydraulic pump which is in fluid engagement with an operating hydraulic system for implementing device-specific functions.

Abstract: A hydraulic drive system for a vehicle includes a pressurizing circuit and a working circuit. The pressurizing circuit incorporates a pump driven by a prime mover having a nominal horsepower rating. The prime mover is either shut off or idled when the pressure sensed within the pressurizing circuit is within a desired range and run at an optimum high RPM range when the pressure falls below the desired range. At least one accumulator is provided in the pressurizing circuit. The working circuit includes a plurality of motors for driving at least one vehicle wheel and a motor control valve arrangement which isolates one or more motors from the flow of pressurized fluid while deactivated and drives the motors while activated. As vehicle speed increases and drive resistance decreases, the number of motors propelling the vehicle is progressively reduced. A flow control valve alters flow to the motors.

Abstract: An improved pressure-compensated hydraulic system includes a separate valve section which feeds hydraulic fluid from a variable displacement pump to one of several hydraulic actuators. Each valve section has a main valve spool and a pressure compensating poppet. The main valve spool has a metering orifice that controls the flow of fluid to the actuator. The poppets in the valve sections collectively apply a pressure to the pump pressure control input which is a function of the greatest to a load pressure among the hydraulic actuators.

Abstract: A pair of directional control valves 8 and a pair of hold check valves 9 are disposed respectively between a pair of metering notches 6, which are formed in a land 4-1 of a spool 2 and have functions of both flow rate control and direction control, and a pair of actuator ports A, B. Each hold check valve comprises a valve body 90 in the form of a hollow spool having a seat portion 12 formed on an outer periphery and being subject to a pressure developed in an outlet passage 10 communicating with one of the actuator ports to act in the valve-closing direction. Each flow distribution valve comprises a valve body 80 being slidably fitted in the valve body 90 and having a front surface positioned to face an inlet passage 7 communicating with the metering notch and a rear surface positioned to face an control pressure chamber 30 communicating with a signal detecting hydraulic line.

Abstract: In order to accomplish many tasks of a machine efficiently, a motion planning system predetermines the response of the machine to a given set of motion commands. With two or more actuators being driven by a single hydraulic pump, there may not be adequate hydraulic pressure to drive both of the actuators at the speed requested. In order to determine the non-linear response of the actuators and the optimal combination of motions of the moving parts driven by the actuators, a controller for the machine is modeled as a linear dynamic system. The non-linear response of the actuators is modeled using a look-up table that is a function of internal variables of the machine's actuators and hydraulic system. The number of input, or independent, variables that are supplied to the table look-up functions is proportional to the number of actuators being driven by a single pump. Sensors provide data regarding the internal state of each actuator including variables such as spool valve position and cylinder force.

Abstract: The present invention relates to a hydraulic circuit for a hydraulically driven working vehicle which allows the vehicle to travel at an almost constant speed during high-speed traveling, provides a great digging force during working, does not need a charging pressure for preventing cavitation, loses a small amount of energy, and has a simple structure. To this end, the hydraulic circuit has a hydraulic travel pump (2) and a working machine hydraulic pump (4) which are driven by the power of an engine (1) for discharging pressurized oil to a HST travel circuit and a working machine-driving hydraulic circuit, respectively, wherein pressurized oil from the working machine hydraulic pump (4) joins pressurized oil from the hydraulic travel pump (2) to effect high-speed traveling, while pressurized oil from the hydraulic travel pump (2) joins pressurized oil in the working machine hydraulic pump (4) to generate a large digging force to effect digging.

Abstract: An improved pressure-compensated hydraulic system for feeding hydraulic fluid from a variable displacement pump to multiple hydraulic actuators. A separate valve section controls the fluid flow between the pump and a different actuator. Each valve section has a pressure compensating valve with a valve member and poppet within a bore and biased apart by a spring. The poppet acts as a check valve which prevents fluid flow from the actuator through the valve section to the pump when the back pressure from the load exceeds the pump supply pressure. A pressure differential between the load-dependent pressure and the actuator pressure determines a position of the valve member which controls the pressure applied to the pump pressure control input.