HYDRAULIC DRIVE DEVICE FOR HYDRAULIC EXCAVATOR - HITACHI CONSTRUCTION MACHINERY

Title:

HYDRAULIC DRIVE DEVICE FOR HYDRAULIC EXCAVATOR

Document Type and Number:

WIPO Patent Application WO/2008/075648

Kind Code:

A1

Abstract:

[PROBLEMS] A hydraulic drive device capable of efficiently performing leveling work by utilizing residual energy of pressurized oil in a hydraulic circuit, which energy has not attracted attention from conventional techniques. [MEANS FOR SOLVING PROBLEMS] The hydraulic drive device for a hydraulic excavator has a boom cylinder (1), an arm cylinder (2), a main hydraulic pump (4) for supplying pressurized oil to both the cylinders (1, 2), a directional control valve (7) for boom and directional control valve (8) for arm for respectively controlling the flow of the pressurized oil to both the cylinders (1, 2), and a tank oil path (8c) for connecting the directional control valve (8) for arm to a hydraulic oil tank (6). The hydraulic drive device further has a flow rate control valve (15) capable of selectively closing a tank oil path (8c). When the pressure on the rod side of the arm cylinder (2) rises to a level higher than a preset value while leveling work is performed by using combined operation of boom raising and boom crowding, the flow rate control valve (15) closes the tank oil path (8c) to prevent pressurized oil on the rod side of the arm cylinder (2) from flowing out into the hydraulic oil tank (6) and supply the pressurized oil to the bottom side of the boom cylinder (1).

Inventors:

NAKAMURA KAZUNORI (JP)

Application Number:

PCT/JP2007/074233

Publication Date:

June 26, 2008

Filing Date:

December 17, 2007

Export Citation:

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Assignee:

HITACHI CONSTRUCTION MACHINERY (JP)
NAKAMURA KAZUNORI (JP)

International Classes:

E02F9/22; E02F3/43; F15B11/17; F15B21/14

Foreign References:

JPH035769U	1991-01-21
JPH10331209A	1998-12-15
JP2004346485A	2004-12-09
JP2004346485A	2004-12-09

Other References: