Hitachi Construction Machinery Co., Ltd.

Yukihiko Sugiyama

Takashi Yagyu

Yasuo Tanaka

Masami Ochiai

Yoshinori Furuno

Yutaka Watanabe

Tsutomu Udagawa

Kazuo Takiguchi

Mitsuo Aihara

Akira Hashimoto

Katsumi Ueno

Takashi Yagyuu

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

Measurement and display of load of excavating blasted ground

Apparatus for diagnosing failure of hydraulic pump for work machine

A system for the estimation of residual service time of a work vehicle includes an arithmetic and logic unit which is inputted with an engine speed and a speed difference from a controller for an engine, with a signal, which indicates whether or not at least one of several control levers has been operated, from a lever position detector, and also with a residual fuel quantity in a fuel tank from a converting device. The residual fuel quantity is determined at intervals of about 1 hour at the arithmetic and logic unit. Upon an elapse of each short period of time, a quantity of fuel consumed during said short time, said quantity being obtained based on a difference in engine speed, is subtracted from the residual fuel quantity, whereby a calculated residual fuel quantity is obtained. A quantity of fuel consumed from a preceding residual fuel quantity measurement period to a current residual fuel quantity measurement period is divided by the calculated residual fuel quantity to obtain a value. The residual fuel quantity is then divided by this value to compute a residual service time, which is then displayed on a display.

System for estimating residual service time of work vehicle

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Tsuchiura, Japan

Yukihiko Sugiyama