HYDRAULIC DRIVE DEVICE - HITACHI CONSTRUCTION MACHINERY

Title:

HYDRAULIC DRIVE DEVICE

Document Type and Number:

WIPO Patent Application WO/2001/051820

Kind Code:

A1

Abstract:

A hydraulic drive device having target compensation pressure differences for pressure compensating valves (21a, 21b) set by a pressure difference between a pump delivery pressure and the maximum load pressure and a target LS pressure difference set as a variable value dependent upon the number of rotations of an engine (1), wherein a fixed throttle (32) and a signal pressure variable relief valve (33) are disposed in a maximum load pressure line (35), and a relief set pressure P¿LMAX'? is set to be P¿LMAX'?=P¿R? - P¿GR? + $g(a) ($g(a) is a value smaller than P¿GR?) where the target LS pressure difference is R¿GR? and the set pressure of a main relief valve (30) is P¿R?, whereby, in the combined operation where a plurality of actuators are driven simultaneously, even if a load pressure of any one of the actuators reaches the set pressure of the main relief valve, the pressure compensating valves will not close, the other actuators do not increase their speeds, and thus an excellent combined controllability can be obtained.

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Inventors:

TSURUGA YASUTAKA (JP)
KANAI TAKASHI (JP)
KAWAMOTO JUNYA (JP)
HAMAMOTO SATOSHI (JP)
OKAZAKI YASUHARU (JP)
NAGAO YUKIAKI (JP)

Application Number:

PCT/JP2001/000057

Publication Date:

July 19, 2001

Filing Date:

January 10, 2001

Export Citation:

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Assignee:

HITACHI CONSTRUCTION MACHINERY (JP)
TSURUGA YASUTAKA (JP)
KANAI TAKASHI (JP)
KAWAMOTO JUNYA (JP)
HAMAMOTO SATOSHI (JP)
OKAZAKI YASUHARU (JP)
NAGAO YUKIAKI (JP)

International Classes:

E02F9/22; F15B11/00; F15B11/16; (IPC1-7): F15B11/00; E02F9/22

Foreign References:

EP0877168A1	1998-11-11
JPH04119205A	1992-04-20

Other References: