Title:
CONTROL DEVICE FOR VARIABLE DISPLACEMENT PUMP
Document Type and Number:
Japanese Patent JPS5923103
Kind Code:
A
Abstract:
PURPOSE:To effectively utilize an output in the case that pressure loss in a circuit is large, by raising a relief cut-off set pressure when a specific hydraulic actuator of a power shavel is in operation. CONSTITUTION:When a travel selector valve is in its neutral position and a travel pressure Pa is nearly zero, a selector valve 18 is in a position A and a discharge pressure Pp is supplied to pressure receiving sections 15a and 15b. Accordingly, when the discharge pressure Pp becomes equal to or higher than a relief cut-off set pressure PR1 during unoperation of a travel motor, a control valve 15 is switched to a position B, and thereby to communicate a cylinder chamber 9a with a tank and to move a servo piston 9 to its left end. As a result, a discharge flow Q of a pump 2 is reduced to a minimum value QR. On the other hand, when the travel selector valve is in its operational position, and the travel pressure Pa is increased from the nearly zero value, the selector valve 18 is switched to a position B, and the discharge pressure Pp is supplied to the pressure receiving section 15a, while not being applied to the pressure receiving section 15b. Accordingly, when the discharge pressure Pp becomes equal to or higher than a relief cut-off set pressure PR2, which is higher than the set pressure PR1, during operation of the motor, the control valve 15 is switched to the position B, and therefore the discharge flow Q reaches the minimum value QR.
Inventors:
UNO KEIICHIROU
ICHIYAMA SHIYUUICHI
AOYANAGI YUKIO
KANEHARA MASAKI
ICHIYAMA SHIYUUICHI
AOYANAGI YUKIO
KANEHARA MASAKI
Application Number:
JP13117182A
Publication Date:
February 06, 1984
Filing Date:
July 29, 1982
Export Citation:
Assignee:
HITACHI CONSTRUCTION MACHINERY
International Classes:
F15B11/17; F04B49/00; F04B49/08; F15B11/16; (IPC1-7): F04B49/08; F15B11/16
Domestic Patent References:
| JP56501133Y |
Attorney, Agent or Firm:
Junnosuke Nakamura