Hydraulic control system

摘要

PCT No. PCT/JP97/02713 Sec. 371 Date Feb. 10, 1998 Sec. 102(e) Date Feb. 10, 1998 PCT Filed Aug. 5, 1997 PCT Pub. No. WO98/06949 PCT Pub. Date Feb. 19, 1998In a hydraulic control system including a valve device B for controlling a hydraulic fluid supplied from a hydraulic pump A to a hydraulic cylinder C, the valve device comprises a spool 16 slidably fitted into a valve body 1, and a non-leak valve 27 for controlling communication of an actuator passage 19. The non-leak valve comprises a main valve section 40 including a seat valve 41 provided in the valve body, and a pilot control section 60 including a pilot poppet valve 61 provided in an end cover 31. The seat valve is controlled in proportion to an opening of the pilot poppet valve, and a relief valve 55 for preventing the hydraulic cylinder from being subject to an overload is built in the seat valve. The non-leak valve thus fulfills a load holding function and an overload relief function. By arranging the non-leak valve and the spool in two lines, the valve device can be made more compact.