HYDRAULIC DRIVING DEVICE

Japanese Patent JP3816893

B2

PROBLEM TO BE SOLVED: To provide a hydraulic driving device capable of utilizing pressure oil on a holding side of a first hydraulic cylinder to increase speed of a second hydraulic cylinder when performing composite operation of the first and second hydraulic cylinders.
SOLUTION: This hydraulic driving device is provided with a main hydraulic pump 21, a boom cylinder 6 and an arm cylinder 7, a direction control valve 23 for boom and a direction control valve 24 for arm, an operation device 25 for boom and an operation device 26 for arm, and a pressure oil supply means for supplying pressure oil in a rod side chamber 6b of the boom cylinder 6 to the upstream side of the direction control valve 24 for arm when bottom pressure of the arm cylinder 7 becomes high pressure exceeding a predetermined pressure. The pressure oil supply means includes a confluence change-over valve 44 which is provided in a tank passage 42 capable of communicating with the rod side chamber 6b of the boom cylinder 6 and holds a communicating passage 40 connecting the tank passage 42 with the upstream side of the direction control valve 24 for arm in a condition in which pressure oil can be supplied to the upstream side of the direction control valve 24 for arm when bottom pressure of the arm cylinder 7 exceeds a predetermined pressure.

Koji Ishikawa
Yusuke Kajita
Kazunori Nakamura
Genroku Sugiyama
Hideo Karasawa

JP2003113323A

August 30, 2006

April 17, 2003

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Hitachi Construction Machinery Co., Ltd.

E02F9/22; F15B11/17; F15B21/14; (IPC1-7): E02F9/22; F15B11/17; F15B21/14

JP2002339907A
JP55119838A
JP8219121A
JP2003120604A
JP200231104A

Kenjiro Take
Ichiro Suzuki
Hirohiro Ichimura
Kazunori Satake

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