Abstract: The present disclosure is directed to a hydrostatic transmission apparatus including a pump, a first motor, and a second motor having two elementary motors, each of them and the first motor having feed/discharge first and second enclosures. In work mode and in road mode the second enclosure of the first elementary motor of the second motor and the first enclosure of the first motor are connected together in series, the second enclosure of the first motor being connected to the second port of the pump and the second enclosure of the second elementary motor of the second motor is connected to the second port of the pump. In work mode, the first enclosure of each of the two elementary motors of the third motor is connected to the first port of the pump.

Abstract: A hydraulic fan circuit is provided. The hydraulic fan circuit includes a tank, a motor having a fluid inlet and a fluid outlet and a pump to draw fluid at a low pressure from the tank and discharge the fluid at elevated pressures to the motor via the fluid inlet. The hydraulic fan circuit further includes a directional control valve disposed between the fluid outlet of the motor and the tank. The directional control valve is operable to move between a flow blocking position and a flow passing position. Further, the directional control valve is configured to reduce a positive speed of the motor below a lowest positive speed attainable through control of pump output. Furthermore, the hydraulic fan circuit includes a pressure control circuit configured to provide a pilot fluid flow at varying pressure to move the directional control valve.

Abstract: A hybrid construction machine drives the upper swing structure using a hydraulic motor and an electric motor together and is 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 hydraulic motor for driving the upper swing structure. The opening area characteristics of a meter-out restrictor and a bleed-off restrictor of a swing directional control valve are set to become larger than for construction machines driving the upper swing structure with the hydraulic motor alone. Torque of the electric motor is controlled so that the total sum of the actual torque occurring in the hydraulic and electric motors in deceleration or acceleration of the hydraulic motor equals the torque occurring when the opening area of the meter-out restrictor or the bleed-off restrictor is set at the prescribed opening area.

Abstract: The present disclosure is related to a drive system for a ground engaging member of a machine. The drive system includes first and second hydraulic motors that are disposed parallel to each other. The drive system also include first and second brake valves that are configured to regulate flow of fluid through the first and second hydraulic motors in order to selectively perform braking. The first hydraulic motor is in fluid communication with a first input line and a first output line. The second hydraulic motor is in fluid communication with a second input line and a second output line. A first connection line is configured to fluidly communicate the first input line with the second input line to equalize pressure therebetween. A second connection line is configured to fluidly communicate the first output line with the second output line to equalize pressure therebetween.

Abstract: A hydrostatic travel drive has a variable displacement pump, two hydraulic motors arranged in series and supplied with pressure medium in a closed hydraulic circuit by the variable displacement pump, and a flow control valve, via which a pressure medium volume flow flows from a line segment between the two hydraulic motors to a pressure sink. The flow control valve is integrated into a housing of a first of the two hydraulic motors.

Abstract: A system for providing pressurized hydraulic fluid includes an engine driven main pump and an electrical motor driven auxiliary pump. The auxiliary pump provides hydraulic fluid at line pressure to shift control subsystems during a vehicle launch while the main pump provides hydraulic fluid to cooler or lubrication subsystems during the vehicle launch. A pressure regulation valve regulates the pressure of the hydraulic fluid from the main pump. Once the main pump reaches a critical speed, the main pump provides hydraulic fluid at line pressure to the hydraulic control system and the auxiliary pump is turned off.

Abstract: Disclosed is a swing relief energy regeneration apparatus in which working oil relieved into a hydraulic tank is stored in a pressure accumulator during swing and deceleration to recycle the stored pressure.

Abstract: The present disclosure provides embodiments directed towards a system for the control of hydraulic output by a hydraulic power source. In one embodiment, a system is provided. The system includes a hydraulic supply system having a drive, a hydraulic pump coupled to the drive, a first hydraulic output configured to supply a first flow of a hydraulic fluid from the hydraulic pump to a hydraulic lift, a second hydraulic output configured to supply a second flow of the hydraulic fluid from the hydraulic pump to a first hydraulic tool, and a controller configured to adjust a speed of the drive in response to a feedback indicative of a first load by the hydraulic lift, a second load by the first hydraulic tool, or a combination thereof.

Abstract: A hydrostatic travel drive includes a hydraulic pump that is arranged in a hydraulic circuit with two pairs of hydraulic motors. To prevent a pressure build-up between the hydraulic motors of a hydraulic motor pair on steering while stationary, a valve device is configured to set a pressure relief to a working line or to low pressure. A mobile device includes the hydrostatic travel drive.

Abstract: A vehicle automatic transmission of a multistage type includes multiple engagement elements having an engagement state switched by an oil pressure to selectively establish a plurality of shift stages based on a combination of engagement and release of the multiple engagement elements according to an oil pressure supplied from a hydraulic circuit, each of the shift stages being established by engagement of two or more engagement elements of the multiple engagement elements, at least one of the multiple engagement elements being a normally closed engagement element engaged when no oil pressure is supplied from the hydraulic circuit, and the normally closed engagement element being a meshing engagement element.

Abstract: A construction machine includes: a work device; an operation device which receives a manipulation; a hydraulic unit including a hydraulic motor; an electric unit including an electric motor and an energy storage unit; a control device which makes the electric power of the energy storage unit assist the hydraulic unit upon the manipulation for the drive side, and makes the electric motor generate regenerative electric power unit upon the manipulation for the regeneration side; and a power-discharge command unit which issues a discharge command for the energy storage unit. Upon receiving the discharge command, the control device operates the electric motor to lower a voltage of the energy storage unit upon the manipulation for the drive side, and makes only the hydraulic unit decelerate or stop the work device upon the manipulation for the regeneration side.

Abstract: A shuttle valve connects a second flowpath and a drain flowpath when the hydraulic pressure in a first flowpath is greater than the hydraulic pressure in the second flowpath. The shuttle valve connects the first flowpath and the drain flowpath when the hydraulic pressure in a second flowpath is greater than the hydraulic pressure in the first flowpath. The ratio between the pressure receiving area of a first pressure section and the pressure receiving area of a second pressure section is the same as the ratio between the pressure receiving area of a first chamber side and the pressure receiving area of a second chamber side of a cylinder rod.

Abstract: A control device for a hybrid construction machine includes a discharge pressure introduction passage that leads a discharge pressure from a variable volume pump to a regulator, and a load pressure introduction passage that leads one of a maximum load pressure of respective actuators and a load pressure of a hydraulic motor to the regulator. A controller, having determined that the actuators are in an inoperative condition on the basis of a detection result from an operating condition detector, excites a solenoid of a solenoid pilot control valve such that a discharge oil from the variable volume pump is led to the hydraulic motor, and controls the regulator such that a differential pressure between the discharge pressure of the variable volume pump and the load pressure of the hydraulic motor is kept constant.

Abstract: Provided is a load sensing system for controlling a discharge pressure of the hydraulic pump so as to render a differential pressure obtained by subtracting a maximum load pressure among the hydraulic actuators from a discharge pressure of the hydraulic pump to be a constant pressure, and there are provided: a first load pressure flow passage which introduces load pressures of the hydraulic actuators to be outputted to a PLS transmission line which transmits the maximum load pressure among the hydraulic actuators at the time of activating the hydraulic actuators; and a second load pressure flow passage which is a flow path for introducing the load pressures of the hydraulic actuators to be outputted to the PLS transmission line during operation after activations of the hydraulic actuators, and wherein a flow rate of the pressure oil therein is reduced than that in the first load pressure flow passage.

Abstract: An implement pose control system and method is provided for a machine. The system and method include determining an actual implement pose having a first actual angle component relative to the first implement rotational axis and a second actual angle component relative to the second implement rotational axis. A desired implement pose may be determined that has first and second desired angle components relative to the first and second implement rotational axes. First and second axis errors may be determined, and the first and second actuators may be automatically operated in response to the error signals.

Abstract: A work machine includes a swing hydraulic motor and a swing electric motor for driving an upper swing structure. A capacitor supplies electricity to the swing electric motor and an operating device outputs through one operation, an operating signal for concurrently operating the swing hydraulic motor and the swing electric motor. A main controller switches between a hydraulic-alone drive mode and an electric-alone drive mode, the hydraulic-alone drive mode being a mode to drive only the swing hydraulic motor selected from the swing hydraulic motor and the swing electric motor when the operating device is operated, the electric-alone drive mode being a mode to drive only the swing electric motor selected from the swing hydraulic motor and the swing electric motor when the operating is operated. Therefore, the actuator that malfunctions can easily be specified among the plurality of mounted actuators.

Abstract: An independent metering valve (IMV) assembly is disclosed that includes a metering stem including an inlet. The IMV assembly also includes a hydro-mechanical control valve in communication with a fluid source and the inlet. The control valve also including a spool with a closed end and an open end. The control valve includes a biasing member that biases the control valve or spool towards an open position thereby establishing communication between the fluid source and the inlet. The control valve also including a load signal line providing communication between an outlet of the control valve upstream of the inlet and the closed end of the spool. Wherein high pressure in the load signal line allowing the control valve to move towards a closed position thereby overcoming bias of the biasing member and reducing flow to the inlet during a high pressure condition.

Abstract: Construction machinery that can achieve a great fuel reduction effect through an efficient use of recovered energy is provided. The Construction machinery includes at least two actuators 7 and 8, a main pump 3 that generates hydraulic energy for driving the actuators 7 and 8, flow control means 4 disposed between the main pump 3 and the actuators 7 and 8, an additional energy generating means 11 that generates energy to be added to the hydraulic energy, and a control means 20 that reduces hydraulic energy generated by the main pump 3 when the additional energy generating means 11 generates energy. The construction machinery further comprises changeover means 12d, 12e, and 12f that selectively change a location at which the energy from the additional energy generating means 11 is to be added according to the actuators 7 and 8. The control means 20 changes a reduction rate of the hydraulic energy generated by the main pump 3 depending on a specific actuator 7 or 8 to which the energy is to be added.

Abstract: This disclosure is directed towards a hydraulic system for providing auxiliary drive to a powertrain (11) and a hydraulic circuit (12) by storing and releasing hydraulic fluid using an accumulator (29). A hydraulic drive system (10) comprises an engine (14), a hydraulic machine (22) operably connected to the engine (14), a pump (17), an accumulator (29) and at least one valve (20, 27). The pump (17) is driven by the engine (14) and is configured to control a hydraulic circuit (12). The accumulator (29) is fluidly connected to the hydraulic circuit (21) and the hydraulic machine (22). In one instance, the at least one valve (20, 27) is operable to direct pressurised fluid from at least one of the hydraulic machine (22) and the pump (17) to charge the accumulator (29). Alternatively, the at least one valve (20, 27) is operable to direct pressurised fluid from the accumulator (29) to at least one of the hydraulic machine (22) and the hydraulic circuit (21).

Abstract: A walk behind aerator hydrostatic traction drive system includes left and right rear wheel hydrostatic motors driving left and right rear wheels positioned forwardly of a coring head, and a front wheel hydrostatic motor driving a single steerable front wheel carried in a pivotal yoke. The pivotal yoke is coupled to a handle assembly attached to a neck extending upwardly and forwardly for pivoting the single steerable front wheel about a vertical pivot axis. A check valve is connected in parallel to the front wheel hydrostatic motor. The check valve opens if the walk behind aerator moves in a forward direction and the handle assembly is turned to pivot the single steerable front wheel and the front wheel rotates more than each rear wheel, or if the walk behind aerator moves in a reverse direction.

Abstract: The present disclosure relates to an apparatus for controlling/regulating the travel speed of a utility vehicle comprising at least one drive motor, at least one hydraulic pump, at least one control slide valve, at least one hydraulic travel motor, at least one further hydraulic drive, as well as at least one controller. In accordance with the present disclosure, the travel speed of the at least one hydraulic travel motor is controlled/regulated via at least the speed of the drive motor, while the at least one further hydraulic drive does not provide any drive power.

Abstract: The pressure supply unit has a pressure generating aggregate (10), which generates a supply pressure (PL) for the intermittent operation of a power screwdriver (11). So as to allow also a tensioning cylinder unit (33) to be operated alternatively to the power screwdriver (11), which requires higher pressure, a pressure intensifier (30) is provided which is included in a separate module (31) and generates high pressure (PH) from the supply pressure (PL). The reversal of the pressure intensifier (30) for carrying out strokes is achieved by the same stroke switch valve (20) which otherwise performs the reversal of the power screwdriver (11).

Abstract: A lock valve switching section switches a lock valve from a locked state to a released state when a lock member is switched from a locked position to a release position. An erroneous operation monitoring section maintains the lock valve in the released state when the pilot pressure is equal to or more than a predetermined pressure when elapsed time, which is from a point in time where the lock member is switched from the locked position to the release position, is equal to or more than the predetermined time. The erroneous operation monitoring section switches the lock valve to the locked state when the pilot pressure is equal to or more than the predetermined pressure when the elapsed time is less than the predetermined time.

Abstract: A hydraulic control system for a machine is disclosed. The hydraulic control system may have a tank, a pump configured to draw fluid from the tank and pressurize the fluid, an actuator, and a control valve configured to direct fluid from the pump to the actuator and from the actuator to the tank to move the actuator. The hydraulic system may also have a main relief valve movable away from a closed position to pass pressurized fluid to the tank when a pressure of the fluid directed to the actuator exceeds a first threshold pressure, and a controller in communication with the pump. The controller may be configured to selectively reduce a displacement of the pump after the main relief valve has moved away from the closed position when the pressure of the fluid directed to the actuator exceeds a second threshold pressure.

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: An assembly (10) forming part of a regenerative drive system for a motor lorry. The motor lorry has a driven train that is operatively associated with the assembly (10) so as to cause operation of the assembly (10) to store energy, or alternatively to be driven by the assembly (10) by depletion of energy stored by the assembly (10). The assembly (10) includes a variable angled swash plate pump/motor (11) that is drivingly associated with the drive train and the motor lorry. The assembly (10) includes a clutch (13) that is engaged when the motor lorry is de-accelerating, to cause the pump/motor (11) to be driven.

Abstract: A control for an excavator of the type having a plurality of hydraulic cylinders for moving excavator components such that digging is accomplished at a worksite with an excavator bucket or other excavator implement, includes a plurality of hydraulic control valves, each of which is associated with a respective one of the hydraulic cylinders for controlling the application of hydraulic fluid pressure to the respective one of the hydraulic cylinders, and a plurality of manually actuated joystick valves for supplying hydraulic fluid pressure to the respective hydraulic control valves to control the movement of the hydraulic cylinders. The control includes a sensor arrangement for sensing the position of one or more excavator components.

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 hydraulic system includes a power source, a fluid displacement assembly, a plurality of actuators, a plurality of control valves and an electronic control unit. The fluid displacement assembly is coupled to the power source. The plurality of actuators is in selective fluid communication with the fluid displacement assembly. The plurality of control valves is adapted to provide selective fluid communication between the fluid displacement assembly and the plurality of actuators. The electronic control unit is adapted to actuate the plurality of control valves, the electronic control unit receives a rotational speed of the power source, determines a firing frequency of the power source based on the rotational speed, selects a frequency of the pulse width modulation signal for the plurality of control valves based on the firing frequency of the power source, and actuates the plurality of control valves in accordance with the frequency of the pulse width modulation signal.

Abstract: The present disclosure provides an oil pressure system for a wheel loader with an improved raising process of a boom, thereby, especially, decreasing impact generated when the boom approaches a maximum height during loading work.

Abstract: A control apparatus for a working vehicle includes a travel circuit HC1 formed through a closed circuit connection of a variable displacement hydraulic pump driven by an engine and a variable displacement hydraulic motor, a work circuit HC2 that includes a work hydraulic pump driven by the engine and a work hydraulic actuator that operates by pressure oil from the work hydraulic pump, a relief valve that relieves high pressure oil of the travel circuit HC1, a rotation speed control unit that controls the engine rotation speed in correspondence to an accelerator pedal operation amount, a state detection unit that detects a vehicle state of high load travel and high load work, and a speed limitation unit that reduces an engine rotation speed upper limit when the vehicle state of high load travel and high load work is detected.

Abstract: An energy recycling system is disclosed. When a construction apparatus performs a combined operation of a boom down operation and an arm out operation, hydraulic energy returned in the boom down operation is recycled for the arm out operation by the energy recycling system.

Abstract: A turning control apparatus includes a turning body and a hydraulic motor to turn the turning body. A high-pressure relief circuit relieves hydraulic pressure of a first hydraulic line at a first relief pressure, the first hydraulic line supplying an operating oil to drive the hydraulic motor. A hunting reduction circuit relieves a hydraulic pressure of a second hydraulic line at a pressure lower than the first relief pressure, the second hydraulic line being connected to a deceleration-side hydraulic port from which the operating oil is discharged when the hydraulic motor is being driven. The hunting reduction circuit connected to the deceleration-side hydraulic port is caused to open before an operation lever to operate turning of the turning body returns to a neutral position.

Abstract: A hydraulic system for a self-propelled agricultural working machine includes a variable displacement pump driven by an internal combustion engine (1) and supplies a plurality of hydraulic circuits, a swept volume of which is changeable via an adjustment mechanism, and supplies pressure medium via at least one pressure line to a hydraulic motor. The hydraulic motor drives a radiator fan. An output of the radiator fan is reduced, at least temporarily, in the event of a drop in pressure for which the variable displacement pump cannot compensate.

Abstract: An automatic transmission for a hybrid vehicle comprising a first hydraulic pressure supply source driven with an internal combustion engine; a second hydraulic pressure supply source driven independently of the first supply source; and a regulator valve regulating hydraulic pressure produced by the supply sources. A first oil passage supplying line pressure regulated by the regulator valve to a hydraulic servo operating a friction engagement element; a second oil passage supplying hydraulic pressure discharged from the regulator valve to a lubricated portion via an oil cooler; and a thud oil passage merged with the second oil passage at a point downstream of the oil cooler supplying the hydraulic pressure of the second supply source to the lubricated portion. A first reverse flow prevention mechanism is disposed between the oil cooler and the merging point to prevent reverse flow of hydraulic pressure.

Abstract: An exemplary hydraulic system includes a plurality of digital valves, each valve fluidly connectable to a corresponding hydraulic load. The digitals valves are operable to fluidly connect the corresponding hydraulic load to a pressure source. The hydraulic system further includes a digital controller operably connected to the plurality of digital valves. The digital controller is configured to assign a priority level so that it is associated with each of a plurality of hydraulic loads, and to formulate a pulse width modulated control signal based on the assigned priority levels. The digital controller transmits the control signal to the plurality of digital valves for controlling the operation of the valves.

Abstract: The present invention relates to a process for the production of hydraulic energy by direct osmosis from two saline solutions having different concentrations made to pass through one or more modules of semipermeable membranes having a double inlet and outlet port, originally designed to execute the process of inverse osmosis, without a requirement to realise any technical modification to said modules of membranes. In this manner, an osmotic potential is produced in the membranes creating a current of solution having a pressure sufficient to produce hydraulic energy. A further object of the present invention is the installation designed to produce hydraulic energy according to the stated procedure and the use thereof, together with a desalination plant and a tertiary waste water treatment plant comprising the installation to produce hydraulic energy.

Abstract: A construction machine includes: a work device; an operation device which receives a manipulation; a hydraulic unit including a hydraulic motor; an electric unit including an electric motor and an energy storage unit; a control device which makes the electric power of the energy storage unit assist the hydraulic unit upon the manipulation for the drive side, and makes the electric motor generate regenerative electric power unit upon the manipulation for the regeneration side; and a power-discharge command unit which issues a discharge command for the energy storage unit. Upon receiving the discharge command, the control device operates the electric motor to lower a voltage of the energy storage unit upon the manipulation for the drive side, and makes only the hydraulic unit decelerate or stop the work device upon the manipulation for the regeneration side.

Abstract: When the actuator drive torque of a hydraulic pump is lower than a switching torque ?0, a controller closes a solenoid switching valve and makes a rotary electric machine function as a generator. With the increase in the actuator drive torque, the controller controls a pressure compensated flow control valve so that the flow rate of hydraulic fluid supplied from the hydraulic pump to a rotary hydraulic device decreases. When the actuator drive torque is higher than the switching torque, the controller opens the solenoid switching valve, makes the rotary electric machine function as an electric motor, and controls the pressure compensated flow control valve so that the hydraulic fluid discharged by the hydraulic pump is not supplied to the rotary hydraulic device. Consequently, shocks due to flow rate fluctuation are prevented when operational states of the rotary hydraulic device and the rotary electric machine are switched.

Abstract: A hydraulic system is disclosed. The hydraulic system may have a plurality of pumps with unidirectional functionality and being variable displacement, a common discharge passage connected to the plurality of pumps, and a common intake passage connected to the plurality of pumps. The hydraulic system may also have at least one actuator connected in closed-loop manner to the common discharge and common intake passages, and a switching valve associated with the at least one actuator and disposed between the at least one actuator and the common discharge and intake passages. The hydraulic system may additionally have at least one isolation valve configured to selectively isolate a portion of the common discharge passage and a portion of the common intake passage associated with one pump of the plurality of pumps from another pump of the plurality of pumps.

Abstract: A hydraulic system includes a first pump, a first actuator fluidly connected to the first pump via a first closed-loop circuit, a second pump, and a second actuator fluidly connected to the second pump via a second closed-loop circuit. The system also includes a third pump, a third actuator fluidly connected to the third pump via a third closed-loop circuit, a fourth pump, and a fourth actuator fluidly connected to the fourth pump via a fourth closed-loop circuit. The system further includes a first combining valve configured to combine fluid from the first and second circuits, a second combining valve configured to combine fluid from the second and third circuits, and a third combining valve configured to combine fluid from the third and fourth circuits. The system also includes a fourth combining valve configured to combine fluid from the first and fourth circuits.

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 large hydraulic excavator permits an easy change from a machine mode corresponding to a backhoe excavator to a machine mode corresponding to a loader excavator, and vice versa. A hydraulic circuit is provided with hydraulic pumps and directional control valves, solenoid valves for controlling the hydraulic pumps and the directional control valves, and a controller for controlling the solenoid valves in accordance with operation of control lever devices and control pedal devices. The controller performs its control in a backhoe mode or loader mode selectively instructed by a mode instruction unit. Control of the solenoid valves in the backhoe mode makes the hydraulic circuit function as a backhoe hydraulic drive circuit, while control in the loader mode makes the hydraulic circuit function as a loader hydraulic drive circuit.

Abstract: A drive train of a vehicle has a drive motor and a traction drive driven by the drive motor. A hydraulic work system has at least one hydraulic pump driven by the drive motor. To deliver torque into the drive train and/or to absorb torque from the drive train, the drive train is provided with an additional hydraulic machine which can be placed in communication with a hydraulic pressure accumulator and/or a tank and can be operated as a pump and a motor in the same direction of rotation. The hydraulic machine has an inlet connection and an outlet connection and a switching valve device is provided to control the connection of the inlet connection and the outlet connection with the pressure accumulator or the tank.

Abstract: Fail-safe methods for utilizing an over-center pump/motor in a hydraulic hybrid vehicle are disclosed. A high-pressure fluid shutoff valve and an optional electrically or manually operated valve are additionally provided as means to ensure disconnection of the high pressure source in the event of a failure. Displacement stroke position and pressure differentials across the pump/motor are continually monitored. On detection of various modes of failure or irregularity in control of displacement, actions are taken including any of: the high pressure and low pressure accumulators are shut off automatically or manually, a check valve between the high and low pressure ports of the pump/motor is activated, and a small amount of pressurized fluid is released from the high pressure circuit to depressurize the captive fluid. Safe startup and shutdown procedures are also specified.

Abstract: In an attachment control apparatus for a hydraulic excavator having a hydraulic circuit that includes a hydraulic pump, a plurality of actuators having a breaker which is an attachment actuator, and a plurality of flow control valves having an attachment flow control valve that is switched by operation pilot pressure from a control pedal device to supply delivery fluid of the hydraulic pump to the attachment actuator, if the control pedal device is operated in a state where an attachment mode is not selected by an attachment selection device, the movement of the attachment actuator is limited. Thus, failure and reduced life of the attachment and other hydraulic devices can be prevented in the event that an operator has forgotten to switch from a normal mode to an attachment mode and has operated the attachment.

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 method and control system for operating a transmission includes a transmission control module determining a transmission sensor signal and a transmission pressure sensor offset prior to starting a vehicle engine and an engine start initiator starting the vehicle engine. The transmission control module controls a transmission function in response the transmission pressure sensor offset and the pressure sensor signal.

Abstract: A pump control device for a construction machine includes a pump regulator, a pump pressure detector, a travelling operation detector, a working operation detector, and a controller instructing the pump flow rate depending on the pump pressure to the pump regulator. The controller stores first and second P-Q characteristics as a horsepower characteristic and instructs the pump flow rate to the pump regulator, based on the first P-Q characteristic when a travelling operation is detected, and based on the second P-Q characteristic when a working operation is detected. The second P-Q characteristic is equal to the first P-Q characteristic in a low-pressure region while is one giving a low characteristic relatively to the first P-Q characteristic so as to increase a horsepower difference as the pump pressure increases, in intermediate-pressure and high-pressure regions.

Abstract: A hydraulic control system for a machine is disclosed. The hydraulic control system may have a hydraulic circuit, a pump configured to supply pressurized fluid, and a first sensor configured to generate a first signal indicative of a pressure of the hydraulic circuit. The hydraulic circuit may also have a first fluid actuator fluidly connected to receive pressurized fluid from the hydraulic circuit, a second sensor configured to generate a second signal indicative of a velocity of the first fluid actuator, and a controller in communication with the first and second sensors. The controller may be configured to receive an input indicative of a desired flow rate for the first fluid actuator, to determine an actual flow rate of the first fluid actuator based on the second signal, and to determine a stall condition of the first fluid actuator based on the desired flow rate, the actual flow rate, and the first signal.