Hitachi Construction Machinery Co., Ltd.

Ryou Yagisawa

Masatoshi Hoshino

Yasutaka Tsuruga

Seiji Hijikata

Shou Furukawa

Provided is a work machine including a flow control valve serving as a flow control mechanism that controls a flow rate of pressurized fluid from a hydraulic pump to a hydraulic actuator via a first control valve. A controller of the work machine, when the pressurized fluid is supplied to the hydraulic actuator from only an accumulator, drives a second control valve such that a meter-in side of the hydraulic actuator and the accumulator are connected to each other, drives the first control valve such that a meter-out side of the hydraulic actuator and a tank are connected to each other, and drives the flow rate control mechanism such that a flow of the pressurized fluid from the hydraulic pump to the hydraulic actuator via the first control valve is interrupted.

Work machine

An object of the present invention is to provide a construction machine that is equipped with a pressure accumulating device, which accumulates the return oil of an actuator, and that is capable of adjusting the operation speed of the actuator according to the revolution speed of a prime mover. For this purpose, in a construction machine including a prime mover, a revolution speed setting device that sets a revolution speed of the prime mover, an actuator, a pressure accumulating device that can supply and discharge a hydraulic fluid to and from the actuator, a first control valve disposed on a hydraulic fluid line that connects the pressure accumulating device and the actuator to each other, an operation device that gives an instruction for operation of the actuator, and a controller that is inputted with an operation signal of the operation device and outputs a control signal to the first control valve, the controller controls the first control valve according to an operation amount of the operation device and the revolution speed set by the revolution speed setting device.

Construction machine

The present invention provides a construction machine equipped with a pressure accumulation device that accumulates return oil from an actuator, and that can implement both improvement in fuel efficiency with enhancement in workability. To achieve the foregoing, a controller sets an actuator upper limit output power that is an upper limit for an output power of the actuator according to a work mode selected by a work mode selection device, and controls a first control valve and a second control valve such that a sum of an output power of a hydraulic pump and an output power of the pressure accumulation device does not exceed the actuator upper limit output power.

A work machine includes a hydraulic pump that is driven by an engine and delivers a pressurized fluid, a hydraulic actuator that is operated by the pressurized fluid delivered by the hydraulic pump, a hydraulic accumulator device that accumulates the pressurized fluid discharged from the hydraulic actuator, a differential pressure control valve that is disposed between the hydraulic actuator and the hydraulic accumulator device and generates a differential pressure across the differential pressure control valve between a pressure of the hydraulic actuator and a pressure of the hydraulic accumulator device, a pressure sensor that senses the pressure of the hydraulic accumulator device, and a controller that controls the differential pressure control valve on the basis of a sensing result of the pressure sensor. The controller controls the differential pressure control valve in such a manner that the differential pressure across the differential pressure control valve reduces according to a rise in the pressure of the hydraulic accumulator device sensed by the pressure sensor.

Provided is a work machine capable of achieving both low fuel consumption and ensuring of workability. The work machine is configured to, in a state where an output of an engine or hydraulic pump has increased to an increase threshold (S: Yes) with the rotational speed being at a first rotational speed (S: Yes), raise the rotational speed from the first rotational speed to a second rotational speed (S); in a process of raising the rotational speed to the second rotational speed, output, to a regulator, a signal instructing reduction in the discharge rate (S) so as to keep the output of the engine or hydraulic pump constant; and after the rotational speed has reached the second rotational speed, output, to the regulator, a signal instructing increase in the discharge rate (S) so as to make the output of the engine or hydraulic pump have a value corresponding to a request load.

Growing community of inventors

Tsuchiura, Japan

Ryou Yagisawa