Hitachi Construction Machinery Co., Ltd.

Yasuharu Gotou

Kouji Ishikawa

Genroku Sugiyama

Toichi Hirata

Tsuyoshi Nakamura

Tsukasa Toyooka

A hydraulic drive system is provided with a signal guide system for guiding a delivery pressure of a pump as a command pressure via a line and a port, another signal guide system for guiding a pilot pressure of a pilot pump as another command pressure via a line and a port, a tilting control unit for controlling the displacement of the pump by the command pressures guided to the ports, a controller having a command current-setting unit for setting a relationship between a target engine speed and a command current, a target engine speed-indicating unit for an engine, and a solenoid-operated proportional valve for allowing the pilot pressure of the line to pass as is while no drive signal is outputted from the controller but for being reduced in opening to change the pilot pressure to a smaller value when a drive signal is outputted from the controller.

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Ibaraki-ken, Japan

Yasuharu Gotou