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Title:
HYDRAULIC PUMP DISPLACEMENT CONTROL DEVICE
Document Type and Number:
Japanese Patent JPH10184556
Kind Code:
A
Abstract:

To control pump discharge in the same way as before the generation of a failure even in case of the failure being generated to an electric system in a hydraulic pump displacement control device performing electromagnetic proportional control of a pump discharge by electrohydraulic servo mechanism using a solenoid proportional control valve.

A shaft 4j of a solenoid 4c of a control valve 4 and a shaft 4k of a spool 4b are separated, and an input switching control chamber 4n is provided at a part where the end faces of the shafts 4j, 4k are positioned. The diameter of the shaft 4j is made larger than that of the shaft 4k, and a command pressure port 4p is formed at a casing part of the input switching control chamber 4n. A horsepower control piston 4q is arranged in series to a spring 4d on the opposite side of the solenoid 4c, and a horsepower control spring 4r is provided in such a way as to support the piston 4q. A horsepower control chamber 4t is formed at a part where the piston 4q is positioned and a horsepower control oil pressure port 4u for taking in delivery pressure of a hydraulic pump 1 is formed at a casing 4s of the horsepower control chamber 4t.


Inventors:
SOU HARUKI
GOTO YASUHARU
KOKUBU HARUO
YUASA KAZUMASA
NAKAMURA SHIGETAKA
MOTOSAWA YUKIHIRO
SAKAIRI TETSUYA
Application Number:
JP34091796A
Publication Date:
July 14, 1998
Filing Date:
December 20, 1996
Export Citation:
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Assignee:
HITACHI CONSTRUCTION MACHINERY
International Classes:
F15B9/09; F04B49/06; F15B13/044; (IPC1-7): F04B49/06; F15B13/044
Attorney, Agent or Firm:
Kasuga



 
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