A plurality of traveling wheels are supported via expandable/contractible tubular support members to a vehicle body frame. A hydraulic operation type vehicle height adjustment mechanism provided for each one of the traveling wheels, the vehicle height adjustment mechanism being capable of switching a relative height of the traveling wheel relative to the vehicle body frame within a predetermined length range by expanding/contracting the support member by a hydraulic cylinder. There are provided a hydraulic control valve capable of controlling feeding state of work oil to each one of the plurality of hydraulic cylinders, a controlling section for controlling an operation of the hydraulic control valve to bring the vehicle body to a target state via vehicle height adjustment by the hydraulic cylinder in response to a change in the posture of the vehicle body and a plurality of accumulators connected oil chambers of the respective plurality of hydraulic cylinders.

A regeneration control hydraulic system for an excavator, including at least one hydraulic pump, an actuator, a regeneration oil path, and a regeneration cut-off oil path. The regeneration oil path is configured to send a return oil as a regeneration oil to a cavity having a negative pressure of the actuator. The regeneration oil path is provided with a regeneration valve and a first control valve. The first control valve is configured to control the regeneration oil to enter the cavity having the negative pressure of the actuator when a working device of the excavator retracts inwards, or to control the oil to be discharged from the actuator to the regeneration cut-off oil path when the working device swings outwards. The regeneration cut-off oil path is configured to send the regeneration oil passing through the regeneration valve or the oil discharged from the actuator to other destinations.

The available power surge capacity of a battery is detected. The available steady state regeneration energy capacity of the battery is also detected. The available battery generation power, available from an electric motor, is detected as well. The generation power available from the electric motor is applied to regenerate (or recharge) the battery based upon the available power surge capacity, and the available steady state capacity of the battery.

A hydraulic system includes a first electric machine connected to a first hydraulic machine and a second electric machine connected to a second hydraulic machine. An output side of the second hydraulic machine is connected to an input side of the first hydraulic machine. A hydraulic consumer is hydraulically coupled to an output side of the first hydraulic machine via a supply line and is powered by the first hydraulic machine. A return line hydraulically couples the hydraulic consumer to an input side of the first hydraulic machine. The second hydraulic machine provides a flow of hydraulic fluid to the input side of the first hydraulic machine if a requested flow from the first hydraulic machine exceeds a flow of the return line and recuperates energy if the requested flow from the first hydraulic machine is lower than the flow of the return line.

Method for controlling a hydraulic system for a working machine, the system including a first electric machine connected to a first hydraulic machine the first hydraulic machine including an input side and an output side a second electric machine connected to a second hydraulic machine the second hydraulic machine including a high-pressure side and a low-pressure side the high-pressure side connected to the input side; a hydraulic consumer coupled to the output side via a supply line and configured to be powered by the first hydraulic machine; a first return line hydraulically coupling the hydraulic consumer to the input side and to the high-pressure side; wherein the method includes detecting a return flow from the hydraulic consumer through the first return line; and controlling the second hydraulic machine to maintain a pressure in the first return line at a pressure level higher than a predetermined minimum pressure level.

An energy recuperation system for construction equipment includes an actuator driving upward and downward operations of a work unit; an accumulator connected to the actuator; and a controller determining a predicted downward mode associated with the downward operation of the work unit, regulating a dischargeable lowest limit pressure of the accumulator to a target pressure corresponding to the predicted downward mode, and charging the accumulator having the dischargeable lowest limit pressure regulated to the target pressure with pressurized oil discharged from the actuator during the downward operation of the work unit to recuperate energy, and an energy recuperation method.

A fluid circuit includes a pressure fluid source configured to supply pressure fluid, multiple actuators connected to the pressure fluid source , a direction switching valve configured to switch a supply destination of the pressure fluid supplied from the pressure fluid source , and a discharge amount control mechanism configured to control the output pressure of the pressure fluid source such that a pressure difference ΔP between the output pressure of the pressure fluid source and the maximum load pressure of the load pressures of the multiple actuators reaches a target value ΔPt. The fluid circuit further includes an accumulator configured to accumulate part of return fluid from the actuators.

The invention relates to a hydraulic device for a hydraulic system (12). The hydraulic device includes a chamber arrangement including at least one high-pressure chamber for connection to a high-pressure side of the hydraulic system, and at least one low-pressure chamber for connection to a low-pressure side of the hydraulic system; and a movable member arranged to reciprocate at least partly inside the chamber arrangement in response to pressure variations within the at least one high-pressure chamber and within the at least one low-pressure chamber. The chamber arrangement further includes at least one tank chamber for connection to a tank-pressure side of the hydraulic system.

A fluid pressure circuit includes a directional switching valve arranged between a fixed displacement pump and a fluid pressure actuator and configured to switch a flow passage for a pressurized fluid, an accumulator arranged in a branch flow passage branched from a connection flow passage that connects the fluid pressure actuator and the directional switching valve, an accumulator flow control valve arranged between the connection flow passage and the accumulator, and a pump flow control valve arranged between the fluid pressure actuator and the fixed displacement pump and configured to variably divert a flow rate of the pressurized fluid discharged from the fixed displacement pump into a first system including the tank and a second system including the fluid pressure actuator.

A hydraulic system for a working machine includes a first electric machine connected to a first hydraulic machine; a second electric machine connected to a second hydraulic machine, an output side of the second hydraulic machine being connected to an input side of the first hydraulic machine; at least one hydraulic consumer hydraulically coupled to an output side of the first hydraulic machine via a supply line and configured to be powered by the first hydraulic machine; and a valve arrangement arranged between the hydraulic consumer and the first and second hydraulic machines, wherein the valve arrangement is configured to control a return flow of hydraulic fluid from the hydraulic consumer to either the input side of the first hydraulic machine or an input side of the second hydraulic machine based on a requested output pressure from the first hydraulic machine.