Patent ID: 6109162
Filing Date: 2000-08-29
Classification: F15B,Y10T

Abstract:
A fluid control valve system for controlling the flow of hydraulic fluid supplied to and discharged out of an actuator having first and second actuator ports, comprising:a valve housing formed with a hole having a center axis to have an inner wall portion with a peripheral surface, said valve housing having first and second pressure ports having hydraulic fluid supplied therethrough, first and second return ports having said hydraulic fluid discharged therethrough, and first and second work ports respectively being held in communication with said first and second actuator ports of said actuator and having hydraulic fluid supplied and discharged therethrough;a valve spool axially movably received in said hole of said valve housing and formed with an axial through bore axially extending and open at its axial ends, said valve spool having an outer wall portion formed with first to third land portions axially spaced apart from each other to form a first groove between said first and second land portions and a second groove between said second and third land portions, said first and second grooves being axially spaced apart from each other and open at their outer surfaces thereof to define in combination with said peripheral surface of said inner wall portion of said valve housing first and second groove chambers respectively held in fluid communication with said first and second work ports of said valve housing and being able to be brought selectively into fluid communication with said first pressure port and said first return port, and said first pressure port and said second return port, of said valve housing;valve spool operating means including a force motor, a piston rod driven to be axially reciprocated by said force motor and having an axially intermediate portion axially extending in said hole of said valve housing, a stop flange firmly connected to said axially intermediate portion and facing said force motor, and a fixed piston firmly connected to the axial end of said axially intermediate portion remotest from said force motor, said piston rod having said valve spool slidably received on said axially intermediate portion between said stop flange and said fixed piston to form a pressure sensing chamber between said valve spool and said fixed piston in said hole of said valve housing, said pressure sensing chamber being held in communication with said second pressure port of said valve housing; andresiliently urging means for resiliently urging said valve spool toward said fixed piston of said valve spool operating means along said center axis of said valve housing,said valve spool being urged by the hydraulic pressure of the hydraulic fluid in said pressure sensing chamber and said resiliently urging means to assume operation positions consisting of:normal operation positions where the hydraulic fluid is supplied to said pressure sensing chamber to give the hydraulic pressure to the hydraulic fluid of said pressure sensing chamber, said hydraulic pressure in said pressure sensing chamber having said valve spool urged toward said stop flange against said resiliently urging means to have said valve spool brought into contact with said stop flange, said valve spool being reciprocated by said force motor with said piston rod to have said first pressure port and said first return port, and said first pressure port and said second return port selectively held in communication with said first and second actuator ports of said actuator respectively through said first and second work ports of said valve housing; andan abnormal operation position where the hydraulic pressure in said pressure sensing chamber is reduced until said resiliently urging means starts to urge and axially move said valve spool toward said fixed piston, said second pressure port being held out of communication with said first and second actuator ports of said actuator.