Directional control valve with flow distribution valves

摘要

PCT No. PCT/JP98/00197 Sec. 371 Date Sep. 17, 1998 Sec. 102(e) Date Sep. 17, 1998 PCT Filed Jan. 20, 1998 PCT Pub. No. WO98/31940 PCT Pub. Date Jul. 23, 1998A pair of directional control valves 8 and a pair of hold check valves 9 are disposed respectively between a pair of metering notches 6, which are formed in a land 4-1 of a spool 2 and have functions of both flow rate control and direction control, and a pair of actuator ports A, B. Each hold check valve comprises a valve body 90 in the form of a hollow spool having a seat portion 12 formed on an outer periphery and being subject to a pressure developed in an outlet passage 10 communicating with one of the actuator ports to act in the valve-closing direction. Each flow distribution valve comprises a valve body 80 being slidably fitted in the valve body 90 and having a front surface positioned to face an inlet passage 7 communicating with the metering notch and a rear surface positioned to face an control pressure chamber 30 communicating with a signal detecting hydraulic line. The valve body 90 has a shape to maintain a balance between forces produced by a pressure in the control pressure chamber and acting upon the valve body. A slit 21 having a variable dead zone X2 is formed between the valve body 80 and the valve body 90 for detecting and introducing a pressure between an outlet portion of the flow distribution valve and an inlet portion of the hold check valve to the control pressure chamber. The casing structure and device construction of a directional control valve with postpositional type flow distribution valves are thereby simplified.