Abstract: A working machine comprises an operation member for operating a hydraulic device via a control valve. An oscillation calculator acquires a specific value corresponding to a feature representing oscillation of the operation member when the feature appears in variation of an control signal output according to an operation amount of the operation member within one of a sequence of predetermined periods, and calculates an evaluation value representing a degree of oscillation of the operation member by adding up the specific value or values obtained within one or more of the predetermined periods. A control signal generator generates a control signal for controlling the control valve based on the operation signal. The control signal generator decreases a value of the control signal per a unit value of the operation signal as the evaluation value gradually increases with the elapse of one or more of the sequence of the predetermined periods.

Abstract: A battery powered driver for propelling a wheeled ground surface modifying machine includes at least one wheel contacting a ground surface, a battery powered electric motor, control circuitry configured to manage delivery of electrical battery power to the electric motor to control a sped of the driver, at least one pedal attached to a pedal axle and tiltable in each of a forward and rearward direction with respect to the pedal axle, and at least one pedal tilt sensor configured to output one or more signals to the control circuitry indicating a degree of tilt of the at least one pedal.

Abstract: In a vehicle with aerial work platform, while not receiving an operation instruction to move down the work platform from the rise and fall operating device, when moving down of the work platform is detected based on the detecting result of the rise and fall position detecting device, the rise and fall control device controls the first switching valve to switch so that the bottom-side oil chamber is connected to the hydraulic pump and controls the second switching valve to switch to the first state so as to make oil pressure in the bottom-side oil chamber be kept by the second switching valve and the check valve. Then, the rise and fall hydraulic cylinder is stopped to be contracted.

Abstract: A prime mover and a plurality of hydraulic actuators, a hydraulic machine having a rotatable shaft in driven engagement with the prime mover and comprising a plurality of working chambers, a hydraulic circuit extending between a group of one or more working chambers of the hydraulic machine and one or more of the hydraulic actuators, each working chamber of the hydraulic machine comprising a low-pressure valve which regulates the flow of hydraulic fluid between the working chamber and a low-pressure manifold and a high-pressure valve which regulates the flow of hydraulic fluid between the working chamber and a high-pressure manifold.

Abstract: An auxiliary power supply device supplies electric power to an encoder when supply of electric power of a control device is cut off, and includes: a backup power source for supplying backup electric power to the encoder when supply of electric power of the control device is cut off; an auxiliary power source for supplying electric power to the encoder when the backup power source is removed; a remaining capacity determination unit for determining the remaining capacity of the auxiliary power source; a display unit for displaying an indication that the remaining capacity is insufficient when the remaining capacity determined by the remaining capacity determination unit is lower than a threshold; and a switch for actuating the display unit.

Abstract: A hydraulic system, comprising: a hydraulic pump, a hydraulic load, and an electric machine. The electric machine working as an electric generator and mechanically coupled with said hydraulic pump. A low-pressure fluid tank and a valve assembly comprising one or more valves selectively fluidly connecting the hydraulic load with the low-pressure fluid tank.

Abstract: A shovel includes a hydraulic pump, multiple hydraulic actuators, a center bypass oil passage supplied with hydraulic oil discharged from the hydraulic pump, multiple directional control valves, and a bleed-off valve. The directional control valves are arranged in tandem in the center bypass oil passage and configured to supply the hydraulic actuators with the hydraulic oil from the center bypass oil passage. At least a directional control valve other than the most downstream directional control valve in the center bypass oil passage among the directional control valves opens the center bypass oil passage. The bleed-off valve is connected to part of the center bypass oil passage upstream of at least one of the directional control valves.

Abstract: In a drive unit which has an axial piston pump and an electronic control unit, the axial piston pump is pivoted with a method in which pressure-reducing valves which act in opposition to one another are suddenly energized. Since in this respect no orifices are provided in the adjustment device, a so-called initiation jump of the excited current gives rise to a sudden reduction in the assigned actuating pressure or the actuating pressure difference formed therefrom. Then, a zero crossover jump of the excited current or of the excited currents is carried out in order to overcome the centering spring and therefore ensure a continuous zero crossover of the axial piston pump. Furthermore, a hydrostatic traction drive includes such a drive unit.

Abstract: A drive control arrangement, for driving of consumers of a mobile working machine with a Diesel engine, includes a Diesel engine controller, vehicle controller, and interface. The engine controller is configured to actuate the Diesel engine via a first control signal. The vehicle controller is configured to (i) control the consumers via at least one second control signal, (ii) transfer a power demand, via the interface, to the engine controller, and (iii) receive feedback, via the interface, with reference to an available power from the Diesel engine. The interface is configured such that the power demand includes a value for a mechanical power and at least one speed interval value. When the engine is delivering a power according to the value of the power demand and/or with reference to the feedback, the engine controller is further configured to control a speed of the engine in a speed interval with reference to the at least one speed interval value.

Abstract: A control apparatus of a transmission includes the transmission that is configured to perform shifting operation with use of a control pressure derived from an actuating oil to be supplied to a hydraulic pressure unit. The control apparatus includes a hydraulic pressure supply source, a switcher, a control pressure adjusting valve, an abnormality detector, and a controller. The controller is configured to control the shifting operation of the transmission to keep a revolution speed of an engine, in an abnormal period in which an abnormality of the switcher is detected by the abnormality detector, at a value that is equal to or greater than an abnormal lower limit value. The abnormal lower limit value is higher than a normal lower limit value in a normal period. The normal period is prior to the detection of abnormality of the switcher by the abnormality detector.

Abstract: A control arrangement for use in a drive arrangement of a vehicle includes an engine, a hydrostatic transmission, a load sensing means configured to detect a load on the engine, and an engine speed controller for controlling the engine. The arrangement further includes a pressure control means configured to act on a pressure in the hydrostatic transmission and a drive controller. The load sensing means generates a first signal, and based on the first signal, the drive controller generates a second signal for the engine speed controller and the pressure control means.

Abstract: The present disclosure relates to a control device and a control method for a construction machine. The control device and the control method for the construction machine according to the exemplary embodiment of the present disclosure may adjust an engine revolutions per minute (rpm) according to a load applied to the construction machine, thereby controlling an output of equipment. In the control device and the control method for the construction machine according to the exemplary embodiment of the present disclosure, an output of a pump is increased at an appropriate time, so that good operation performance may be maintained, and in the case of an operation pattern, in which a load is low, the engine rpm is adjusted to be decreased, thereby improving fuel efficiency.

Abstract: A hydrostatic propulsion drive for a vehicle is disclosed including an electronic control unit and a hydrostatic transmission having a hydraulic pump with an adjustable swept volume and a hydraulic motor with an adjustable swept volume, the hydraulic pump being arranged in a closed hydraulic circuit. The swept volumes of the hydraulic pump and the hydraulic motor are changeable in accordance with a correction factor which is stored in a characteristic diagram and is dependent on the rotational speed and the drive torque of the hydraulic motor, the operating pressure at the hydraulic motor being increased if the correction factor is used. Due to the increased operating pressure, flow-induced pressure drops are reduced by way of volumetric flows, and leakage flows via gaps between moving parts of the hydraulic pump and the hydraulic motor are kept large enough to avoid excessive friction and loss of efficiency.

Abstract: A method of deactivating an underwater hydraulic device includes providing a hydraulic device operable under water, the device having a hydraulic cylinder with a pushrod and a piston. The device is lowered below a water surface with a hose reel that is located at the water surface area such as on a marine vessel. The hose reel includes first and second hydraulic hoses that connect to the cylinder on opposing sides of the piston. Fluid flow in the first and second hydraulic hoses is continuously monitored. The ratio of the volume of fluid flowing into the cylinder from one side of the piston to the volume of fluid flowing into the cylinder from the other side of the cylinder is continuously calculated with a computer or controller. The hydraulic device is deactivated if the ratio varies from a preset value.

Abstract: A hydrostatic transmission with which a braking operation is realized in which at least one traction motor which acts as a pump is supported via a closed circuit on an adjustable axial piston pump which acts as a motor, and which in turn is supported on an internal combustion engine. Since overspeeding of the latter should be avoided, pilot control is performed with a rotational speed that is subcritical for the internal combustion engine, and thereafter closed-loop control is performed with a closed-loop controller which outputs a corrective value in a manner dependent on the rotational speed deviation between the present rotational speed and the maximum and thus ideal rotational speed of the internal combustion engine.

Abstract: A speed change control apparatus for a work vehicle includes a hydraulic continuously variable speed transmission that performs speed change on power input from an engine by changing a trunnion shaft angle based on a depressing amount of a speed change pedal and outputs the power, a pedal position detector that detects a pedal position responsive to the depressing amount of the speed change pedal, and a control unit that controls a number of revolutions of the engine and the trunnion shaft angle of the hydraulic continuously variable speed transmission based on a detection value of the pedal position detector. The control unit performs control so that the trunnion shaft angle is maximized at a second pedal position set to a position shallower than a first pedal position at which the number of revolutions of the engine is maximized by a depressing operation of the speed change pedal.

Abstract: The present disclosure relates to an apparatus for controlling a hydraulic pump for a construction machine. The apparatus for controlling the hydraulic pump for the construction machine according to the present disclosure includes: a hydraulic pump control device configured to generate first and second pump commands for controlling first and second hydraulic pumps so that the first and second hydraulic pumps generate pump torque corresponding to a request value; and a torque controller configured to generate first and second corrected pump commands, which are the corrected first and second pump commands, by a torque inclination map generated by reflecting a dynamic characteristic of an engine, and to provide the first and second corrected pump commands to the first and second hydraulic pumps.

Abstract: The present disclosure relates to a boom driving system for a hybrid excavator and a control method therefor, and more particularly, to a boom driving system for a hybrid excavator, which drives a hydraulic pump motor so as to move a boom upward and downward, and collects regenerative power of the boom using an electric motor so as to improve fuel efficiency, and a control method for the boom driving system. Provided in exemplary embodiments of the present disclosure is a boom driving system for a hybrid excavator and a control method therefor, which may allow an electric motor generator to normally produce electricity by allowing retraction speed and force of the boom actuator to be controlled to a target speed when a boom is moved downward.

Abstract: A hybrid work vehicle includes a work device, a traveling drive device, a lever operation quantity detection unit, an engagement state detection unit, a pedal operation quantity detection unit, a travel state detection unit, and an engine control unit. The engine control unit controls an engine rotation rate based upon at least either the lever operation quantity or the pedal operation quantity in correspondence to either the engaged state or the non-engaged state and either the traveling state or the non-traveling state.

Abstract: A forklift equipped with a variable displacement traveling hydraulic pump driven by an engine, a hydraulic motor that forms a closed circuit with the traveling hydraulic pump therebetween and is driven by hydraulic oil discharged from the traveling hydraulic pump, and driving wheels driven by the hydraulic motor, when an accelerator opening detected by an accelerator opening sensor is reduced, the accelerator opening detected by the accelerator opening sensor and a target maximum absorption torque of the traveling hydraulic pump are given to a table on which a setting value calculated in advance depending on the accelerator opening, and the target maximum absorption torque of the traveling hydraulic pump or a vehicle speed of the forklift is described to calculate the setting value, and the accelerator opening detected by the accelerator opening sensor is corrected using the obtained setting value to calculate a corrected accelerator opening.

Abstract: A method is provided for controlling a hydraulic cylinder in a work machine, which hydraulic cylinder is arranged to move an implement that is subjected to a load, with the hydraulic cylinder being controlled by a hydraulic machine. The method includes detecting that a lifting movement of the implement is to be initiated, and attaining a basic speed of the hydraulic machine before lifting takes place.

Abstract: An inexpensive engine assist device capable of performing stable energy regeneration from an accumulator and a working machine on which the engine assist device is mounted are provided. A variable capacity type main pump and a variable capacity type assist pump are directly connected to an engine. A return pressure oil flowing out from a fluid pressure actuator is temporarily accumulated by a sub-accumulator and is supplied to an inlet of the assist pump, and the assist pump pressurizes the return fluid pressure oil and supplies the return fluid pressure oil to a main accumulator. A controller calculates and controls an assist pump swash plate angle, and assist starting torque or charge starting torque, and introduces a pressure-accumulated fluid discharged from the main accumulator to the inlet of the assist pump or introduces a pressurized fluid discharged from an outlet of the assist pump into the main accumulator.

Abstract: An engine control apparatus for controlling an engine which drives a hydraulic pump to discharge operation oil, the engine control apparatus includes: a pump driving power limit unit configured to limit pump driving power, which is power used to drive the hydraulic pump, based on pressure of the operation oil discharged by the hydraulic pump when in a state in which a part of the operation oil discharged by the hydraulic pump is released because pressure of the operation oil discharged by the hydraulic pump has become equal to or higher than preset relief pressure; and an engine output control unit configured to control output of the engine so that target speed, which is speed of the engine set as a target, becomes equal to or higher than a value of a point of time when limiting of the pump driving power is started.

Abstract: A control system for controlling speed of an engine of a work machine having a hydrostatic transmission is disclosed. The control system may include a power source and a hydrostatic transmission operatively coupled to the power source. The control system may also include a controller capable of receiving information from the power source and the transmission and actively controlling an engine speed of the work machine to reduce the engine speed below a threshold value to emulate an engine lug during a stall condition.

Abstract: The present disclosure relates to a hybrid excavator boom actuating system and to a method for controlling the same. The boom actuating system comprises: an electric motor serving as a motor or a generator; an ultra capacitor for storing electricity generated by the electric motor; a hydraulic pump motor driven by the electric motor to supply hydraulic fluid to a boom; a boom control valve which has a closed circuit for selectively connecting or disconnecting an outlet line and an inlet line of the hydraulic pump motor to or from a head or a rod side of the boom; a main pump driven by the engine to supply hydraulic fluid to a bucket, a travel motor or an arm; a motor bypass valve connected to the outlet line and the inlet line to interconnect the outlet line and the inlet line or disconnect the outlet line from the inlet line; and a controller for controlling the electric motor, the hydraulic pump motor, the boom control valve and the motor bypass valve.

Abstract: An outlet port of a hydraulic pump/motor and a bottom chamber of a lift cylinder are connected to each other by a hydraulic fluid passage. A hydraulic fluid passage that is connected to a hydraulic fluid tank is formed to branch off the hydraulic fluid passage. A flow control valve controls the hydraulic fluid delivered from the lift cylinder when the fork is lowered, thereby regulating the flow rate of hydraulic fluid supplied to the hydraulic pump/motor and the flow rate of hydraulic fluid supplied to the hydraulic fluid tank. If regenerative operation can be performed, the flow control valve is closed and hydraulic fluid is delivered to the hydraulic pump/motor. If regenerative operation cannot be performed, the flow control valve is opened and hydraulic fluid is delivered to the hydraulic fluid tank. In either case, the fork can be lowered at an instructed speed.

Abstract: Method of controlling multiple variable displacement hydraulic pumps determined relative to operator commands. If non-second-pump-dominated command, a respective adjusted displacement request is determined based upon the lesser of the operator requested torque limited displacement and an adjusted torque limited displacement that calculated based upon and the torque limited displacement of the respective pump and a scaling factor calculated based upon the first relief valve set pressure and respective pump pressure. If second-pump-dominated command, the set pressure of a relief valve associated with one of the pumps is instead utilized in calculating the scaling factor in the above strategy.

Abstract: In situ density and compressibility of a fluid sample are determined for a fluid sample collected downhole. The density and compressibility of the fluid sample is determined by measuring a distance to a piston contained within the sample chamber using an external magnetic field sensor that senses a magnetic field emanating from a magnetic provided on the piston internal to the sample chamber. The testing is performed quickly and at the surface in a noninvasive fashion (i.e., without opening the sample chamber).

Abstract: Disclosed is a system for driving a boom of a hybrid excavator, and a method for controlling the same. The system comprises: an electric motor; a capacitor for storing electricity generated by the electric motor; a hydraulic pump motor driven by the electric motor to supply working oil to a boom; a boom control valve having a closed circuit selectively connecting/disconnecting a discharge line and an inlet line of the hydraulic pump motor to/from a head or a load of the boom; a main pump arranged separately from the motor to supply working oil; a boom-assisting valve connecting discharge lines of the main pump and the hydraulic pump motor to combine discharged working oil; and a control unit controlling the electric motor, the hydraulic pump motor, and the boom control valve. The system minimizes energy loss during excavation, ensures performance of the boom, and recovers regenerative energy from the boom.

Abstract: An exhaust gas temperature raising processing system, which increases a load acting on an engine to raise the exhaust gas temperature, includes an electric assist motor connected to the engine and an inverter for adjusting a torque of the electric assist motor. It also includes a main controller having a first determination unit for determining whether or not an actuator control valve is in a non-feed state and a second determination unit for determining whether or not clogging has occurred on a filter of an exhaust gas purification system. When the non-feed state is determined by the first determination unit and clogging is determined to have occurred on the filter by the second determination unit, the main controller drives the electric assist motor to generate electric power such that a load acting on the engine is increased.

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 method for operating a working machine provided with a power source providing power and a plurality of power consuming systems connected to the power source includes the steps of providing a model predicting a power demanded by at least one of the power consuming systems, detecting at least one operational parameter indicative of a power demand, using the detected operational parameter in the prediction model, and balancing a provided power to the demanded power according to the prediction model.

Abstract: Provided is a hydraulic engine that generates power using oil pressure, the hydraulic engine including: a hydraulic power unit including a hydraulic tube comprising a hollow portion having an opened front end and being filled with a fluid, an amplitude amplification device that is disposed at the rear side of the hydraulic tube, an oscillator that is disposed at the rear side of the amplitude amplification device so as to be deformed and increases and decreases a pressure within the hydraulic tube, and an oscillator head that is attached to a front end of the oscillator.

Abstract: A device (1) for driving working equipment (2) which can be connected to an agricultural commercial vehicle. The commercial vehicle has a combustion engine (6) and a generator (9) which can be driven by the combustion engine (6). The commercial vehicle and/or the working equipment (2) have at least a hydraulic pump (5), for the supply of a hydraulic working circuit (3), and a mechanical connection (4), for driving the working equipment (2). At least one hydraulic pump (5) and/or the mechanical connection (4) can be driven electrically and/or mechanically, and can be driven with a controllable rotational speed by way of the power branching.

Abstract: A method of controlling a pump for a hybrid transmission includes commanding a first line pressure of the transmission and deriving a first torque value—an open-loop torque value—from the first line pressure command, and commanding the pump to operate at the first torque value. The method monitors actual speed of the pump and derives a second torque value—a closed-loop torque value—therefrom. A third torque value is derived from the first and second torque values, and the pump commanded to operate at the third torque value. A first speed value may be derived from the first line pressure command, and the second torque value derived from the difference between the monitored and the first speed values. Deriving the third torque value may include a substantially-linear combination of the first and second torque values.

Abstract: Provided is a hybrid construction machine including: a hydraulic actuator; a hydraulic pump which discharges hydraulic fluid for driving the hydraulic actuator; a generator-motor which performs an electric generator action of generating electric power and an electric motor action of generating motive power; an engine connected to the hydraulic pump and the motor-generator; an electrical storage device; and a controller which causes the generator-motor to perform the electric generator action and charge the electrical storage device and causes the generator-motor to perform the electric motor action by electric power discharged from the electrical storage device to assist the engine. The controller causes the generator-motor to start the electric generator action when an engine output becomes equal to or greater than a predetermined engine lower limit output, and controls the electric generator action to keep the engine output no lower than the engine lower limit output.

Abstract: A system architecture for use on mobile hydraulic equipment. The system architecture includes a power system that includes an electrical generator, power supply electronics in electrical communication with the electrical generator, an electrical storage medium in electrical communication with the electrical generator and in parallel with the power supply electronics, and an electrical power bus for distributing power from the power system to a first component control system. The first component control system includes first drive electronics and at least a first electro hydrostatic actuator. The system architecture also includes a main controller. The power system is in data communication and electrical communication with the main controller, and the first component control system is in data communication with the main controller.

Abstract: A walking machine that includes a chassis with an operator interface, a main controller in data communication with the operator interface, at least two leg members operatively connected to the chassis, and a power system in data communication and electrical communication with the main controller. Each leg member includes a leg control system that includes a leg microcontroller in data communication with the main controller and at least a first electro hydrostatic actuator in electrical communication with the leg microcontroller. The power system includes an electrical generator, power supply electronics in electrical communication with the electrical generator, an electrical storage medium in electrical communication with the electrical generator and in parallel with the power supply electronics, and an electrical power bus for distributing power from the power system to the leg control systems.

Abstract: A shovel includes a boom cylinder that drives a boom and an arm cylinder that drives an arm. A hydraulic pump supplies operating oil to the boom cylinder and the arm cylinder. An engine is connected to the hydraulic pump and equipped with a supercharger. The engine is controlled to maintain a revolution speed within a certain definite range. A controller controls a rotating speed of the supercharger. The controller performs a process of increasing the rotating speed of the supercharger so as to increase a supercharging pressure generated by the supercharger before a hydraulic load is applied to the engine.

Abstract: Pneumatic actuator apparatuses with expandable chambers, and methods of using same. In some embodiments, the apparatuses are self-contained and/or self-inflating.

Abstract: A work vehicle includes an engine, an idling stop execution portion, a determination portion, a counting portion, and an idling stop time period adjustment portion. The engine can rotate in a first idling state and a second idling state in which the engine rotates at the number of rotations higher than a prescribed number of rotations. The idling stop execution portion performs an idling stop operation for stopping the engine. The determination portion determines whether or not stop has been made from the second idling state. The counting portion counts the number of times of stop of the engine from the second idling state. An idling stop time period adjustment portion makes a prescribed time period of the second idling state longer than a current time period, when the number of times of stop of the engine is equal to or greater than the prescribed number of times.

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 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 method of controlling a pump and motor system having at least one of a variable displacement pump and a variable displacement motor. The method may comprise providing an engine drivingly coupled to a primary load and a secondary load, the secondary load being driven by the pump and motor system. The method may also comprise sensing a change in engine speed in response to a change in the primary load. The method may further comprise changing the engine speed to compensate for the primary load change. The method may further comprise changing a displacement of the at least one variable displacement pump and the variable displacement motor to maintain a constant secondary load.

Abstract: A hydraulic-pressure control device includes: a regulator (182) including a housing (200), a control piston (204) in the housing (200); an input chamber (212) at a rear of the control piston (204) and an output chamber (214) in front of the control piston (204); and an input-hydraulic-pressure control device (56,184) which controls hydraulic pressure in the input chamber (212) to move the control piston (204) forward or backward to raise or reduce hydraulic pressure in the output chamber (214).

Abstract: A device for the investigation of an object uses a microwave transmitter, a microwave receiver, a control device and a contrast medium. The microwave transmitter and the microwave receiver are controlled by the control device. In one embodiment, the following steps may be implemented: introduction of the contrast medium into the object under investigation; transmission of a microwave signal into the object under investigation by the microwave transmitter; scattering of the microwave signal by the object under investigation and by the contrast medium; and/or reception of the scattered microwave signal by the microwave receiver.

Abstract: The hydraulic torque converter with a temperature automatic regulator of dynamic liquid includes hydraulic torque converter and radiator. A temperature control valve is also included to reflect the temperature of the dynamic liquid. The hydraulic torque converter is provided with dynamic liquid outlet tube and dynamic liquid inlet tube. The dynamic liquid inlet tube and dynamic liquid outlet tube are connected with radiator. The temperature control valve is mounted at the end of dynamic liquid inlet tube and dynamic liquid outlet tube near the hydraulic torque converter.

Abstract: A method for overpressure control in a hydraulic system having multiple hydraulic pumps, with each hydraulic pump being connected by a respective hydraulic circuit for actuating a single respective hydraulic actuator, includes actuating a first variable displacement hydraulic pump, the first hydraulic pump being fluidly linked by a first hydraulic circuit to a first hydraulic actuator for powering the first hydraulic actuator. Upon detecting a pressure that exceeds a predetermined threshold pressure, the flow rate of the first hydraulic pump is electronically modified to a second flow rate lower than the first flow rate whereby the pressure in the first hydraulic circuit is reduced to a pressure that is below the predetermined threshold pressure.

Abstract: The invention addresses the problem of avoiding insufficient flow being supplied to the hydraulic actuator and speed becoming insufficient during light loads in hydraulic machinery such as hydraulic shovels when the engine rotation speed is set low during normal work. The solution is to increase the discharge flow of the hydraulic pump (2) by increasing the rotation speed of the engine (1) above the target rotation speed set by the engine rotation speed-setting means (14) when the hydraulic pump (2) discharge pressure is at the light load pump discharge pressure, the hydraulic pump (2) inclination angle is at the maximum inclination angle, and the negative control signal pressure is at the signal pressure when the hydraulic actuator-operating means (7) is at full operation.

Abstract: A hydraulic control device for a forklift includes a hydraulic pump, a single electric motor for driving the hydraulic pump, an outflow control mechanism provided between a lift cylinder and the hydraulic pump, a flow control valve provided between the outflow control mechanism and a draining portion, and a controller. When a lowering operation of a fork and either forward or rearward mast tilting operations of a mast are performed at the same time, the controller controls the electric motor based on a target speed of the hydraulic pump. The flow control valve controls the flow rate of hydraulic fluid from the lift cylinder to the hydraulic pump and the flow rate from the lift cylinder to the draining portion in accordance with the difference between the actual rotation speed of the hydraulic pump and the target rotation speed of the hydraulic pump.

Abstract: A hydraulic drive system for a hydraulic working machine sets a delivery pressure at a preset value upon raising a temperature of exhaust gas to a temperature needed for combustion of particulate matter by increasing a load to be applied to an engine. In a non-operation state, a variable restrictor is controlled by a controller and a delivery pressure control valve to increase a delivery pressure of a variable displacement hydraulic pump, so that the load is increased to raise the temperature of exhaust gas to the temperature needed for the particulate matter combustion. At this time, the controller controls the delivery pressure control valve such that a delivery pressure to be detected by a delivery pressure sensor will conform with a preset reference delivery pressure. The reference delivery pressure is set to a minimum pressure that can provide the exhaust gas with combustion heat.