Provided is a work machine that can operate a front work implement at a speed according to an operator's lever operation while securing the accuracy of work by machine control. A hydraulic excavator 1 includes a controller 20 that sets a target surface for a bucket 10 and controls the operation of a front work implement 1B in such a manner that the bucket does not penetrate to below the target surface. The controller sets a speed correction region on an upper side of the target surface, varies a width R of the speed correction region in accordance with an operation amount of an operation device 15A or 15C, and controls the operation of the front work implement in such a manner that the work tool does not penetrate into the speed correction region.

A servovalve system comprising a pilot stage valve in communication with an hydraulic stage valve, the hydraulic stage valve comprising a valve member movably mounted in a valve chamber to selectively meter fluid flow in a flow path from an upstream inlet port to a downstream outlet port and at least two variable-sized orifices disposed in the flow path between the inlet and outlet ports, an upstream pressure sensor, a downstream pressure sensor, a fluid temperature sensor, a position sensor sensing a linear position of the valve member, a controller that receives input from the upstream pressure sensor, the downstream pressure sensor, the fluid temperature sensor and the position sensor; and the controller configured to provide a control signal to the pilot stage valve as a function of the input from the upstream pressure sensor, the downstream pressure sensor, the fluid temperature sensor and the position sensor.

A hydraulic machine includes an actuator, a tank, a directional control valve disposed between the actuator and the tank, and an adjustable return check valve disposed between the directional control valve and the tank. The directional control valve includes an attachment actuator directional control valve disposed between an attachment actuator of the actuator and the tank and a swing actuator directional control valve disposed between a swing actuator of the actuator and the tank. The adjustable return check valve allows fluid to flow from the attachment actuator directional control valve toward the tank while applying the low back pressure but blocks a flow, and allows fluid to flow from the swing actuator directional control valve toward the tank while applying the high back pressure but blocks a reverse flow.

A hydraulic pump control apparatus for construction equipment includes a first hydraulic pump; a first hydraulic actuator driven by the hydraulic oil of the first hydraulic pump; a first control valve installed on the fluid channel of the first hydraulic pump; a second hydraulic pump connected, to a power take-off apparatus of an engine; a second hydraulic actuator driven by the hydraulic oil of the second hydraulic pump; a second control valve installed on the fluid channel of the second hydraulic pump; a pressure sensor that detects the pressure of the second hydraulic pump; a regulator that controls the amount of oil discharged from the first hydraulic pump; and a controller that computes a horse power value using the detected pressure value of the second hydraulic pump and the amount of oil discharged from the second hydraulic pump and inputs a control signal to the regulator to discharge an amount of oil that corresponds to the difference between the maximum working horse power value of the engine and the computed horse power value of the second hydraulic pump.

A work machine includes: a hydraulic actuator that is driven by a hydraulic fluid from a hydraulic pump; an open-center directional control valve that is arranged on a center bypass line, and controls a flow of the hydraulic fluid to be supplied to the hydraulic actuator; a CB cut valve arranged between a directional control valve and a hydraulic working fluid tank on the center bypass line; and a machine controller that controls an opening of the CB cut valve. The machine controller restricts the opening of the CB cut valve when operation on the hydraulic actuator is in a fine operation state in which the operation on the hydraulic actuator is within a predetermined range representing a region of fine operation, and the fine operation state is continued longer than a predetermined period, and fully opens the CB cut valve otherwise.

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 control system of a hybrid construction machine includes fluid pressure pumps, a regeneration motor, a rotating electric motor coupled to the regeneration motor, a storage battery configured to store electric power generated by the rotating electric motor, an assist pump provided coaxially to the regeneration motor to be driven by the rotating electric motor, the assist pump being configured to supply a working fluid to a fluid pressure actuator, and load adjusting units configured to change a load of the assist pump in accordance with a state of the storage battery.

The present invention provides a work machine including a steering device that is very responsive to switching operations. The work machine includes: a proportional solenoid valve for outputting a first pilot pressure oil with a pressure responding to a steering signal; a solenoid valve for outputting a second pilot pressure oil with a predetermined pressure while the steering signal is outputted from the steering device; a switching valve capable of switching to a first state of outputting the first pilot pressure oil to a directional control valve and a second state of outputting the second pilot pressure oil to the directional control valve, while the first pilot pressure oil is outputted from the proportional solenoid valve and the second pilot pressure oil is outputted from the solenoid valve in parallel; and a controller to switch the switching valve from the first state to the second state in a case where a malfunction is detected in a main circuit ranging from the steering device to the directional control valve via the proportional solenoid valve and the switching valve of the first state.

A bi-directional pump connected to a motor by a pair of supply/discharge lines; a regulator changes the bi-directional pump tilting angle; and a controller controls the regulator based on a turning signal outputted from a turning operation valve. At the turning acceleration, at which the signal increases, the controller calculates a motor flow rate passing through the motor and an instruction flow rate determined based on the turning signal. If the instruction flow rate is greater than a reference flow rate obtained by adding a predetermined value to the motor flow rate, the controller controls the regulator so the bi-directional pump tilting angle is adjusted to a tilting angle realizing the reference flow rate. If the instruction flow rate is not greater than the reference flow rate, the controller controls the regulator so the bi-directional pump tilting angle is adjusted to a tilting angle realizing the instruction flow rate.

A hydraulic control device that reduces the loss of the power of a pump in combined operation of boom lowering and arm pushing. A controller performs single control of increasing capacity of a first pump in accordance with increase in an operation amount of a boom operation member, in a single operation of the boom lowering. On the other hand, the controller restricts the capacity of the first pump compared to capacity in the single control, during a restriction control period when the combined operation of boom lowering and arm pushing is detected, and the operation amount of the boom operation member is a prescribed operation amount or more.