Hydraulic control system of a 4-speed automatic transmission for vehicle

摘要

The present invention is directed to a hydraulic pressure control system of an automatic transmission for a vehicle includes a damper clutch control part (A) for controlling a damper clutch (4) to increase power train efficiency, a pressure regulating part for regulating line pressure generated from a hydraulic pump (10), and a shift control part (B) for selectively supplying hydraulic pressure regulated at the pressure regulating part to friction members for applying more than one of the friction members in accordance with each speed ratio. The shift control part includes a manual valve (16) responsive to a shift lever, a shift control valve (18), controlled by two solenoid valves (S1, S2), for selectively feeding second, third and fourth speed control pressures, a first pressure regulating valve (22) for feeding drive pressure fed from the manual valve to one of the friction members, a first-to-second speed shift valve (30) which is controlled by the second speed control pressure to feed drive pressure to another friction member, a second pressure regulating valve (23) for feeding the second speed control pressure to another friction member, and a second-to-third/fourth-to-third speed shift valve (40) controlled by the second speed control pressure to feed drive pressure to another fiction member.