Hitachi, Ltd.

Hitachi Construction Machinery Co., Ltd.

Kunihiko Yoshida

Eiki Izumi

Nobuhiko Ichiki

Shuichi Ichiyama

Kenichi Koshi

A fluid control valve apparatus comprises logic valve means including a valve housing, a first valve member defined in the valve housing, and an axially movable valve body arranged in the first valve chamber, with the valve body including opposite end portions and a conical surface portion brought into contact with the conical surface portion when the valve body is moved in a valve closing direction. First and second hydraulic fluid chambers are defined in the valve housing and communicate with each other when the conical surface portion is out of contact with the valve seat and out of communication when the conical surface portion contacts the valve seat. A first pilot chamber in the valve housing, adjacent one end portion of the valve body, biases the valve body in a closing direction by a first pilot pressure signal. A second valve chamber is defined in the valve housing with an extension of the valve body being formed by extending the other end portion of the valve body through the first hydraulic fluid chamber, and is arranged in the second valve chamber for axial movement. An independent second pilot chamber biases the valve body in an opening direction by a second pilot pressure signal.

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Ibaraki, Japan

Kunihiko Yoshida