A motor-generator (27) is connected mechanically to an engine (21) and a hydraulic pump (23). The hydraulic pump (23) delivers pressurized oil to cylinders (12D) to (12F) in a working mechanism (12), a traveling hydraulic motor (25) and a revolving hydraulic motor (26). The revolving hydraulic motor (26) drives a revolving device (3) in cooperation with a revolving electric motor (33). An HCU (36) reduces outputs of the revolving electric motor (33), the revolving hydraulic motor (26), the boom cylinder (12D) and the like such that a ratio of a revolving speed of an upper revolving structure (4) and a movement speed of raising a boom (12A) is held to a ratio in a normal mode (NMODE) at the time of performing a compound movement of a revolving movement and a boom-raising movement in a low speed mode (LSMODE).

An intermittent air discharge apparatus has a main valve and a pilot valve, the main valve being switched between a discharge state and a discharge stop state. The pilot valve is switched between an air-supply state to supply air to a pilot chamber for air-discharge, and an air-supply stop state. When the pilot valve is switched to the air-supply state, an exhaust passage communicates with the pilot chamber for air-discharge. When the pilot valve is switched to the air-supply state, a supply or exhaust passage allows an air supply passage to communicate with the pilot chamber for air-discharge and a pilot chamber for stopping air-supply; when the pilot valve is switched to the air-supply stop state, communication with the air supply passage is blocked. A flow rate of air from the pilot chamber for air-discharge is set by the exhaust passage, and a flow rate of air from the pilot chamber for stopping air-supply is set by the supply or exhaust passage.

A control valve is provided for construction equipment having a holding valve which prevents the natural lowering of an operation apparatus due to the dead weight of the operation apparatus when an actuator is in a neutral position. A control valve for construction equipment according to the present invention includes: a valve body in which a supply path in communication with a pump path, through which a hydraulic fluid is supplied from a hydraulic pump, and actuator ports connected to an actuator are formed; a spool which is embedded in the valve body so as to be switchable; a holding valve having a holding poppet which is formed at the actuator port of any one of the actuator ports, and an auxiliary spool which is connected to a back pressure chamber of the holding poppet and releases the held load of the actuator at the time of switching; a control valve provided in the valve body; a pilot pressure control valve, embedded in the holding valve so as to be switchable, which applies or blocks a pilot pressure applied to switch the auxiliary spool on or off through a path when the pilot pressure control valve is switched on or off by means of the pressure of the hydraulic fluid which is drained from the back pressure chamber of the holding poppet at the time of switching the auxiliary spool on or off.

The present invention relates to a hydraulic valve arrangement for controlling/regulating at least one hydraulic consumer of a mobile machine, with a summation interconnection of at least two hydraulic valves and at least one consumer interconnection of hydraulic valves, wherein the outputs of the summation interconnection are hydraulically connected with the inputs of the consumer interconnection, wherein at least one backflow valve is provided in the consumer interconnection. According to the invention, the at least one backflow valve for throttling a consumer return volume flow opens or closes in dependence on a consumer inflow pressure and comprises at least one main piston arranged in a bushing and at least two further pistons arranged in a lid separate from the bushing.

An independent metering valve circuit includes an actuator, a set of independent metering valves, an independent metering valve pre-compensator, an inverse resolver, and a signal conditioning element. The set of independent metering valves are fluidly coupled to the actuator and configured to independently control a flow of a hydraulic fluid to the actuator. The independent metering valve pre-compensator is configured to control the flow of the hydraulic fluid to the set of independent metering valves. The inverse resolver is configured to receive a first pressure signal from the independent metering valve circuit and a second pressure signal from a load-sense hydraulic system and output a third pressure signal. The signal conditioning element is configured to receive the third pressure signal and output a forth pressure signal configured to control a pump fluidly coupled to the load-sense hydraulic system and the independent metering valve circuit.

A power unit with manual override control for a hydraulic system having an initial state and at least one operational state is provided, comprising: a tank for storing hydraulic fluid that moves between a first chamber and a second chamber of a hydraulic cylinder; a pump that routes the hydraulic fluid in and out of the tank; a first relief valve; a first solenoid valve configured to shift between a plurality of positions based on the at least one operational state of the hydraulic system; a first check valve connected to the first solenoid valve; a manual override control unit comprising: a second check valve; and a second solenoid valve configured to shift between a plurality of positions based on activation of a manual override control, wherein the activation of the manual override control returns the hydraulic system from the at least one operational state to the initial state.

Presented is a system and method to control hydraulic fluid flow, more specifically throttle hydraulic fluid flow, to achieve actuator deceleration rates greater than the maximum deceleration rate of an electrically driven pump. Electric machines and electric machine inverters generally have a maximum torque and current limit beyond which they cannot be operated at. To decelerate a large inertia load for example, high electric machine torque and inverter current are required to provide the braking torque, opposing the fluid flow and pressure generated by the load and hydraulic system.

According to the present invention, a hydraulic system of construction equipment is implemented as a close center system, which converts an input signal of an electric or hydraulic joystick into a speed signal of a work apparatus, and controls a speed of the work apparatus regardless of an external load condition, thereby minimizing fatigue of a worker to improve work efficiency, improving a work apparatus operation ability of an unskilled person, and patterning standardized work to implement automation of construction equipment.

An actuator controller for actuating an actuator which can be operated fluidically, having a feed line for an inflow of the working fluid to an actuator connector and having a discharge line for an outflow of the working fluid to a fluid outlet, wherein the feed line is assigned a feed line valve and the discharge line is assigned a discharge valve, which valves are configured in each case to influence a volumetric fluid flow at the actuator connector, and having a control device for actuation of the feed line valve and the discharge valve. A throughflow sensor is arranged in a line section between the discharge valve and the fluid outlet, which throughflow sensor is configured for determining a volumetric fluid flow in the discharge line and for providing a throughflow signal.

An excavator includes a hydraulic oil holding circuit that is provided in an oil passage between a bottom-side oil chamber of a boom cylinder and a control valve and is closed when the boom is not lowered, and a controller. The controller releases a closed state of the hydraulic oil holding circuit when the excavator is in a predetermined unstable state, and controls a released state so that an acting velocity in a lowering direction of the boom becomes less than or equal to a predetermined reference.