A hydraulic driving apparatus that drives a plurality of driving subjects and regenerates energy thereof. This hydraulic driving apparatus includes: a first pump motor; a second pump motor that is switchable between a state of moving a first driving subject by hydraulic oil discharged from the first pump motor and a state of being operated as a pump by means of energy of the first driving subject; a first pump motor line that couples the first and second pump motors with each other; a first accumulator connected to the first pump motor line; a regeneration subject hydraulic actuator that moves a second driving subject; a second accumulator that receives hydraulic oil from the regeneration subject hydraulic actuator; a second pump motor line that couples the second accumulator with the first pump motor; and a pressure release changeover valve that opens/closes the second pump motor line.

An excavator includes a lower travelling body; an upper turning body mounted on the lower travelling body; a hydraulic pump installed in the upper turning body; a travelling hydraulic motor that is a variable displacement type motor configured to move the lower travelling body by being driven by hydraulic oil discharged by the hydraulic pump; and a control device configured to control a motor capacity of the travelling hydraulic motor so as to be switchable between a plurality of levels. The control device switches the motor capacity to a low rotation setting upon detecting that an operation for changing a travelling direction of the lower travelling body is performed.

A hydraulic machine, such as a revolving excavator work machine, including a travel-purpose hydraulic motor whose capacity is switchable, in which a work accuracy is obtained by avoiding that a hydraulic motor mainly used for work travel in a large-capacity setting state is affected by an increased traveling speed resulting from a small-capacity setting state of a hydraulic motor. A control device for the hydraulic machine, in driving each of a plurality of hydraulic actuators, corrects a target value for a ratio of a supply flow rate to a required flow rate for each hydraulic actuator in accordance with a change in the engine rotation number and further corrects the target value for the ratio of the supply flow rate to the required flow rate for each hydraulic actuator in accordance with switching of the capacity of the travel-purpose hydraulic motor included in the plurality of hydraulic actuators.

A pump having a fluid driver disposed within the interior volume of the pump and to a method of delivering fluid from an inlet of the pump to an outlet of the pump using the fluid driver. The fluid driver includes a variable-speed and/or a variable torque prime mover and a fluid displacement assembly. The pump can be used in a fluid pumping system to provide fluid to an actuator that is operated by the fluid. At least one of a speed and a torque of the pump is controlled so as to adjust at least one of a flow and a pressure in the fluid pumping system to a desired set point, without the aid of another flow control device.

A control device for suppressing engine load fluctuation according to main pump circuit conditions, wherein an assist torque calculation task includes a target engine torque calculation task separating smooth torque components from main pump load torque and setting a minimum value of either smooth torque component or engine setting torque as target engine torque, and a subtractor calculating target assist torque based on a difference between the main pump load torque and the target engine torque, the assist torque calculation task controlling a capacity of an assist pump based on the target assist torque and controlling switching between an assist mode and a charge mode.

A valve assembly and a hydraulic circuit including the valve assembly are provided. The valve assembly comprises a hydraulically actuated valve configured to be biased from a first control position to a second control position by a hydraulic pressure applied to a first fluid port of the hydraulically actuated valve. A first switching threshold pressure required to switch the hydraulically actuated valve to its second control position when applied to the first fluid port of the hydraulically actuated valve in its first control position differs from a second switching threshold pressure required to keep the hydraulically actuated valve in its second control position when applied to the first fluid port of the hydraulically actuated valve in its second control position.

A hydraulic driving apparatus that drives a plurality of driving subjects and regenerates energy thereof. This hydraulic driving apparatus includes: a first pump motor; a second pump motor that is switchable between a state of moving a first driving subject by hydraulic oil discharged from the first pump motor and a state of being operated as a pump by means of energy of the first driving subject; a first pump motor line that couples the first and second pump motors with each other; a first accumulator connected to the first pump motor line; a regeneration subject hydraulic actuator that moves a second driving subject; a second accumulator that receives hydraulic oil from the regeneration subject hydraulic actuator; a second pump motor line that couples the second accumulator with the first pump motor; and a pressure release changeover valve that opens/closes the second pump motor line.

A hydraulic system includes: a high-pressure line; a pump configured to supply pressurized hydraulic fluid to the high-pressure line; a variable displacement hydraulic machine connected by a fluid connection to the high-pressure line for rotationally driving the rotatable load; an electronic control unit; an energy storing device connected to the high-pressure line and configured to communicate with the high-pressure line by receiving energy from the high-pressure line and/or supplying energy to the high-pressure line; and a first detector configured to detect the amount of energy stored in the energy storing device and to transmit a signal indicating said amount of energy stored to the electronic control unit. The electronic control unit is configured to control the volume flow intake of the variable displacement hydraulic machine dependent on a target output of the variable displacement hydraulic machine and on the detected amount of energy stored in the energy storing device.

To provide construction machinery capable of more efficiently utilizing the energy of return hydraulic oil from a hydraulic actuator. The present invention is provided with: an engine 11; a hydraulic pump 12 that is driven by the engine 11; a hydraulic actuator 17 that is driven by fluid discharged from the hydraulic pump 13; a discharge pressure sensor 12d that detects the discharge pressure from the hydraulic pump 13; a hydraulic regenerative motor 18 that is driven by the return hydraulic oil from the hydraulic actuator 17; a flow meter 18e that detects the flow rate of the return hydraulic oil; a flow dividing valve 50 that controls the rate of inflow to the hydraulic regenerative motor 18; a controller 15 that controls the flow dividing valve 50 according to the discharge pressure detected by the discharge pressure sensor 12d and the flow rate detected by the flow meter 18e; a regenerative generator 19 that generates electric power by being driven by the power of the hydraulic regenerative motor 18; and a motor generator 13 that assists drive of the engine 11 by the electric power supplied from the regenerative generator 19.

A control system for hybrid construction machine includes: an operation valve for operating a boom; a variable displacement type fluid pressure motor; a distribution mechanism adapted to adjust a flow to be distributed to the fluid pressure motor; a motor generator adapted to be rotated integrally with the fluid pressure motor; a variable displacement type assist pump adapted to be rotated integrally with the motor generator; a distribution mechanism control unit adapted to control the distribution mechanism; a tilt angle control unit adapted to control tilt angles of the fluid pressure motor and the assist pump; and a motor generator control unit adapted to maintain a rotation speed of the motor generator at a target rotation speed. The target rotation speed at the time of boom regeneration control is set to higher than the target rotation speed in a case where only an assist control is carried out.