Hitachi Construction Machinery Co., Ltd.

Jun Okamura

Kazuo Takiguchi

Yoshifumi Takimoto

Hiromasa Takahashi

Mitsuhiro Yoshimoto

Takeshi Kobayashi

Chinori Iio

Masakazu Andou

An object of the invention of the present application is to provide a hydraulic system that is capable of causing a control pressure outputted from a solenoid valve to follow a control request value quickly at the time the solenoid valve starts to be driven. To achieve the object, in the hydraulic system including a solenoid valve that generates a control pressure for operating a control valve, an operation device that is operated to input a control request value as a request value for the control pressure, and a controller configured to set a control target value as a target value for the control pressure depending on the control request value and drive the solenoid valve with the control target value, the controller sets the control target value such that the control target value becomes a maximum output pressure in a usage range of the solenoid valve at the time of starting to drive the solenoid valve and becomes gradually closer to the control request value as time elapses after having reached the maximum output pressure.

Hydraulic system

There is provided a hydraulic drive device for a working machine with which a number of times of maintenance can be reduced. A controller () opens a first on-off valve (), closes a second on-off valve (), switches a first directional switching valve () to a first position (A), and switches a second directional switching valve () to a third position (C), thereby pressure oil from a hydraulic pump () is supplied from the first on-off valve to an actuator () through the first directional switching valve. When history data of the first on-off valve is determined to satisfy a prescribed condition, the controller closes the first on-off valve, opens the second on-off valve, switches the first directional switching valve to a second position (B), and switches the second directional switching valve to a fourth position (D), thereby pressure oil from the hydraulic pump is supplied from the second on-off valve to the actuator through the second directional switching valve. For example, the controller determines that the prescribed condition is satisfied when an operation number of times of the first on-off valve reaches a first prescribed value.

Hydraulic drive device for working machine

A main spool () has a throttle passage () that, when the main spool () moves to an axial other side against a first return spring () in a main spool insertion hole (), communicates a pilot pressure chamber () with a first tank port () and limits a flow amount of hydraulic oil to be discharged to the first tank port () from the pilot pressure chamber (). When the main spool () moves to the axial other side along the main spool insertion hole (), the throttle passage () communicates the pilot pressure chamber () with the first tank port () before a state where a first pump port () is communicated with an output port () and a state where the output port () is blocked from the first tank port ().

Pressure reducing valve unit

Growing community of inventors

Ibaraki, Japan

Jun Okamura