Hitachi Construction Machinery Co., Ltd.

Kazuo Takiguchi

Tsutomu Udagawa

Tsukasa Toyooka

Masami Ochiai

Eiji Egawa

Makoto Sugaya

Akira Nakayama

Mitsuo Aihara

Yukihiko Sugiyama

Jun Okamura

Yoshifumi Takimoto

Tsuyoshi Nakamura

Hiromasa Takahashi

Takashi Yagyu

Kensuke Sato

Mitsuhiro Yoshimoto

Katsumi Ueno

Takashi Yagyuu

Takeshi Kobayashi

Kensuke Satou

Hideo Sorata

Masakazu Andou

Chinori Iio

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

A travel control device for a work vehicle includes: a hydraulic pump; a plurality of hydraulic motors connected to the hydraulic pump in parallel through a closed-circuit connection, that drive different wheels with pressure oil delivered from the hydraulic pump; a slip detection device that detects a slip occurring at each of the wheels; and a flow control device that reduces, upon detection of a slip occurring at any of the wheels by the slip detection device, a quantity of pressure oil supplied to a hydraulic motor for driving the wheel at which the slip has been detected, among the plurality of hydraulic motors.

Travel control device for work vehicle and work vehicle

A hydro-static transmission travel system for a working machine enables the working machine to travel over a range from low speed to high speed with a simplified circuit arrangement. By referring to a machine traveling speed (vehicle speed) based on a detected signal from a rotation sensor, a controller computes respective target tilting amounts of hydraulic motorsand controls the tilting amount for the hydraulic motors and a clutch. Depending on whether the traveling speed exceeds a setting speed as a reference boundary, the controller selectively switches over a drive mode between low-speed four-wheel drive, in which travel unitsare both driven, and high-speed two-wheel drive, in which the front-wheel side hydraulic motoris controlled to zero displacement and only the rear-wheel side travel unitis driven.

HST travel system for working machine

A hydraulic drive system comprises directional flow control valves (-) for selectively supplying a hydraulic fluid from a first hydraulic pump (), inflow control valves (-) disposed respectively in branch lines (A-C) branched from a supply line () for supplying a hydraulic fluid delivered from a second hydraulic pump () to rod pushing-side chambers (A,A,A,A) of hydraulic cylinders, a bypass flow control valve () disposed in a line () connecting the supply line () and a reservoir (), and a controller () for computing control variables corresponding to operation command signals from control levers () and controlling the inflow control valves (-) and the bypass flow control valve () in accordance with the computed control variables. Thus, the number of flow control valves and the length of piping required for their connection can be reduced, and a total pressure loss can be further reduced.

Hydraulic driving system of construction machinery

The control valve apparatus holds a seat valve member in a position seated on a valve seat to thereby prevent a backward flow even if the pressure in the inlet chamber side becomes lower than the pressure in the outlet chamber side. With a pilot control valve member is in a closed state, when the pressure in the inlet chamber is higher, a pressurized medium is introduced to the control pressure chamber via a first valve unit and is cut off from the outlet chamber by a second valve unit. When the pressure in the outlet chamber is higher, the pressurized medium is introduced to the control pressure chamber via the second valve unit and is cut off from the outlet chamber by the first valve unit.

Control valve apparatus and pressure circuit

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Moriya, Japan

Kazuo Takiguchi