Title:
HYDRAULIC DRIVING UNIT
Document Type and Number:
WIPO Patent Application WO/1989/009343
Kind Code:
A1
Abstract:
A hydraulic driving unit having at least one hydraulic pump (1), a plurality of hydraulic actuators (2, 3) adapted to be driven by the pressure oil discharged from the hydraulic pump, tanks (4) into which the return oil from the hydraulic actuators is discharged, flow rate control valve means (14, 18) provided in the hydraulic actuators and including first main variable throttle means (23A, 23B) for controlling the flow rate of the pressure oil supplied from the hydraulic pump to the hydraulic actuators, and second main variable throttle means (24A, 24B) for controlling the flow rate of the return oil discharged from the hydraulic actuators to the tanks, a pump control means (22) for controlling the discharge rate of the hydraulic pump normally in response to a difference between the discharge pressure of the hydraulic pump and a maximum load pressure of the hydraulic actuators so that the discharge pressure of the pump becomes higher than the maximum load pressure by a certain quantity, and first pressure compensation control means (15, 19) adapted to be operated with a value, which is determined by the difference between the discharge pressure of the pump and the maximum load pressure, as a target compensation differential pressure and control the pressure compensation of the first main variable throttle means in the flow rate control valve means, wherein the hydraulic driving unit further includes second pressure compensation control means (16, 20) adapted to be operated with a value, which is determined by a longitudinal differential pressure of the first main variable throttle means (23A, 23B), as a target compensation differential pressure and control the second main variable throttle means (24A, 24B) in the flow rate control valve means (14, 18).
Inventors:
HIRATA TOICHI (JP)
TANAKA HIDEAKI (JP)
SUGIYAMA GENROKU (JP)
NOZAWA YUSAKU (JP)
TANAKA HIDEAKI (JP)
SUGIYAMA GENROKU (JP)
NOZAWA YUSAKU (JP)
Application Number:
PCT/JP1989/000302
Publication Date:
October 05, 1989
Filing Date:
March 22, 1989
Export Citation:
Assignee:
HITACHI CONSTRUCTION MACHINERY (JP)
International Classes:
E02F9/22; F15B11/00; F15B11/16; F15B13/04; (IPC1-7): F15B11/00; F15B11/16
Foreign References:
| JPS59197603A | 1984-11-09 |
Other References:
See also references of EP 0362409A4
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