| 摘要 |
PURPOSE: A hydraulic control system of an automatic transmission is provided to reduce the shift shock due to an orifice by controlling line pressure of pressure control valves independently controlled by solenoid valves, to make speed change to respective speed ranges in the neutral state, and to reduce the operation shock of clutches and a brake at a high speed travel. CONSTITUTION: An automatic transmission supplies line pressure to a forward/backward pressure pipeline by the manipulation of a manual valve(210). Speed change is performed by selectively supplying line pressure to three clutch devices(310,320,330) and two brake devices(340,350). Three pressure control valves(230,240,250) are independently controlled by three solenoid valves(260,270,280) switched on/off depending on vehicle speed and throttle valve opening degree to open and close a path. Line pressures supplied from respective pressure control valves are selectively supplied to respective clutch devices and brake devices by changing a path by plural control valves(360,370,380,390). In speed change from a second speed to a third speed, from a third speed to a fourth speed, from a fourth speed to a third speed, and from a third speed to a second speed, line pressures are supplied to an operation part and a non-operation part of the first brake device or released from the operation part and non-operation part. Therefore, shift shock is reduced.
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