Abstract: To provide a hydraulic drive system for a work machine capable of securing a favorable operability in the case where hydraulic fluid discharged from a hydraulic actuator is regenerated for driving other hydraulic actuator.

Abstract: The Construction machinery includes at least two actuators, a main pump that generates hydraulic energy for driving the actuators, control valves disposed between the main pump and the actuators, a hydraulic pump motor driven by the generator motor that generates energy to be added to the hydraulic energy, and a controller that reduces hydraulic energy generated by the main pump when the hydraulic pump motor driven by the generator-motor generates energy. The construction machinery further comprises changeover valves that selectively change a location at which the energy from the hydraulic pump motor driven by the generator-motor is to be added according to the actuators. The controller changes a reduction rate of the hydraulic energy generated by the main pump depending on a specific actuator to which the energy is to be added.

Abstract: A hydraulic energy regeneration system for a work machine for boosting a pressure of a return hydraulic fluid of a hydraulic cylinder and regenerating the hydraulic fluid, prevents a bottom pressure from reaching an overload relief set pressure and suppresses a changeover shock to ensure favorable operability.

Abstract: Provided is a hydraulic fluid energy recovery system for a work machine equipped with a hydraulic pump, a hydraulic actuator for driving the work machine, an operating device for operating the hydraulic actuator, and a regenerating device for recovering a return fluid flowing back from the hydraulic actuator.

Abstract: Provided is a construction machine allowing regeneration of a return hydraulic fluid at the time of both a boom raising operation and a boom lowering operation with a small number of valves, making it possible to secure a satisfactory operability at the time of both the boom raising operation and the boom lowering operation.

Abstract: The hydraulic fluid energy recovery apparatus includes a fluid communication line for holding a bottom-side hydraulic fluid chamber and a rod-side hydraulic fluid chamber of a hydraulic cylinder in fluid communication with each other, a fluid communication valve connected to the fluid communication line for adjusting the pressure and/or flow rate of a hydraulic fluid passing through the fluid communication line in a manner that allows for adjustment of a degree of opening of the fluid communication valve, first pressure detecting means for detecting a signal indicative of pressure at the bottom-side hydraulic fluid chamber of the hydraulic cylinder, an amount-of-operation detecting means for detecting an amount of operation of the operating means, and a control device for capturing the signal of pressure at the bottom-side hydraulic fluid chamber of the hydraulic cylinder detected by the first pressure detecting means.

Abstract: Regeneration control is exercised and energy saving is realized even when an abnormality occurs to pressure sensors for hydraulic actuators.

Abstract: A controller sets a target flow rate of a regenerative hydraulic motor at zero or a low flow rate within an extent in which hydraulic pressure in a regeneration hydraulic line does not become negative pressure when a detected pressure PS detected by a pressure sensor is lower than a first set value previously set by overload relief valves, sets the target flow rate of the regenerative hydraulic motor at a value corresponding to the detected pressure when the detected pressure is higher than or equal to the first set value, and controls the revolution speed of a generator/motor in such a manner that a flow rate through the regenerative hydraulic motor equals the target flow rate. With such features, excellent operability equivalent to that in the conventional technology can be secured.

Abstract: The invention provides a construction machine in which the load torque at the time of engine start-up can be reduced even when the engine stops against the will of the operator. A hydraulic excavator includes a control device (35) having a pump displacement control section (37) and an unload control section (38). The pump displacement control section (37) makes the displacement of a hydraulic pump (16) variable to a minimum displacement by controlling a regulator device (20) when the speed of an engine (14) detected by a speed sensor (41) becomes equal to or less than a preset low speed N3 at the time of driving of the engine (14). The unload control section (40) controls an unloading valve (24) to the open position at the time of start-up of the engine (14).

Abstract: A hydraulic system for construction machinery is capable of suppressing irregularity in the operation of the front structure not intended by the operator, and includes a regeneration motor adapted to be driven by return fluid from a bottom port of a boom cylinder; a regeneration electric motor converting rotary power into electric energy; return fluid control valves controlling the flow of the return fluid according to a pilot pressure related to an operation of a boom control lever; and a malfunction prevention device adapted to be activated by pressure fluctuation caused by malfunction of a solenoid valve for the return fluid control valve that interrupts the delivery of a pilot secondary pressure from the solenoid valve to the corresponding return fluid control valve.

Abstract: Energy regeneration system does not affect operation of a hydraulic actuator except when a relief valve is operating, by connecting an actuator hydraulic line to a regeneration hydraulic motor with a small pressure loss during regeneration, and ensures holding pressure when the energy cannot be regenerated. A first valve device disposed between actuator hydraulic lines and a regeneration hydraulic motor, has a throttle passage capable of increasing pressure in the higher pressure side actuator hydraulic line to a set pressure of the relief valves. A second valve device disposed in parallel with the first valve device between the actuator hydraulic lines and the regeneration hydraulic motor, is switched from a close to an open position by pressure between the first valve device and the regeneration hydraulic motor when pressure between the first valve device and the regeneration hydraulic motor increases to approach the set pressure of the swing relief valve.

Abstract: A hydraulic drive system 100A for a work machine includes: a boom cylinder 4; an arm cylinder 8; a hydraulic pump device 51; a control valve 5; a regenerative device 61; a first operation device 41; a second operation device 42; a sensor device 71; and a controller 27. The sensor device 71 includes at least one of pressure sensors 23, 24, 25, and 26. The controller 27 includes an abnormality detection part 142 and a first control part. The abnormality detection part 142 determines whether or not the sensor device 71 is abnormal. If the sensor device 71 is abnormal, the first control part controls the regenerative device 61 such that the hydraulic fluid returning from the boom cylinder 4 is not supplied to the arm cylinder 8 even if the values measured by the sensor device 71 satisfy regenerative conditions.

Abstract: A hydraulic fluid energy regeneration apparatus of a work machine includes: a regeneration hydraulic motor driven by a return hydraulic fluid; a first hydraulic pump mechanically connected to the regeneration hydraulic motor; a second hydraulic pump that delivers a hydraulic fluid for driving a hydraulic actuator; a confluence line that causes the hydraulic fluid delivered from the first hydraulic pump to join the hydraulic fluid delivered from the second hydraulic pump; a first adjuster configured to adjust the flow rate of the hydraulic fluid of the first hydraulic pump; and a second adjuster configured to adjust the delivery flow rate of the second hydraulic pump.

Abstract: A hydraulic fluid energy regeneration system for a work machine capable of securely maintaining a brake pressure even when a solenoid valve or the like is erroneously rendered open by an electrical failure is provided.

Abstract: Disclosed is a hydraulic drive system capable of improving the fuel efficiency of a work machine by reducing the pressure loss and drag loss of a hydraulic pump. There are provided an electric motor M; a third pump P3 driven by the electric motor; a third pump hydraulic line L3 to which the delivered hydraulic fluid from the third pump is supplied; a third directional control valve V4 provided in the third pump hydraulic line, switch-operated by an arm operation device 19, and controlling the flow rate of the hydraulic fluid supplied to the arm cylinder 8 from the third hydraulic pump; and a controller 18 drive-controlling the electric motor, wherein the controller drives the third pump by the electric motor when a swing/arm combined operation is detected by pilot pressure sensors S6, S7, S10, S11.

Abstract: When hydraulic fluid discharged from a hydraulic actuator is to be recovered for driving a different hydraulic actuator, the recovery frequency is increased to achieve further energy saving. To this end, a pressure increasing circuit 36 is provided in which a communication pressure increasing valve 12 is disposed in a communication passage 26 that connects a bottom side line 23 of and a rod side line 24 a boom cylinder 4. A recovery control valve 11 is controlled such that, when a first operation unit 5 is operated in a boom lowering direction (own weight falling direction of the boom) and a second operation unit 6 is operated simultaneously, only if the pressure at the bottom side of the boom cylinder 4 is higher than the pressure at the arm cylinder side that is a recovery destination of hydraulic fluid, the recovery control valve 11 is opened to recover the flow rate discharged from the bottom side of the boom cylinder 4 to the arm cylinder side.

Abstract: The construction machine includes: a control valve that switchingly supplies hydraulic fluid from a hydraulic pump to a hydraulic actuator; a control valve drive device that supplies pilot secondary hydraulic fluid to the control valve in accordance with an operation of an operation lever device; a pilot hydraulic pump that supplies pilot primary hydraulic fluid to the control valve drive device; a pressure accumulation device that recovers return hydraulic fluid returned from the hydraulic actuator. The construction machine further includes: a check valve provided in a line between the pilot hydraulic pump and the control valve drive device; a pressure reducing valve that supplied the hydraulic fluid accumulated in the pressure accumulation device; a flow rate reduction device; and a controller that controls the flow rate reduction device in accordance with the pressure in the line between the check valve and the control valve drive device.

Abstract: Provided is a hydraulic drive system for a work machine configured with a single solenoid proportional valve for a regeneration circuit, wherein substantially the same actuator speed can be secured irrespective of whether or not hydraulic fluid discharged from a hydraulic actuator is regenerated for driving of another hydraulic actuator.

Abstract: To provide a hydraulic drive system for a work machine capable of securing a favorable operability in the case where hydraulic fluid discharged from a hydraulic actuator is regenerated for driving other hydraulic actuator.

Abstract: The Construction machinery includes at least two actuators, a main pump that generates hydraulic energy for driving the actuators, control valves disposed between the main pump and the actuators, a hydraulic pump motor driven by the generator motor that generates energy to be added to the hydraulic energy, and a controller that reduces hydraulic energy generated by the main pump when the hydraulic pump motor driven by the generator-motor generates energy. The construction machinery further comprises changeover valves that selectively change a location at which the energy from the hydraulic pump motor driven by the generator-motor is to be added according to the actuators. The controller changes a reduction rate of the hydraulic energy generated by the main pump depending on a specific actuator to which the energy is to be added.