Hydraulic control system of automatic transmission for vehicle

摘要

A hydraulic control system of an automatic transmission that precisely control is operating hydraulic pressure supplied to a frictional element during shifting and can eliminate oil leak under a maximum operating hydraulic pressure. The hydraulic control system controls a hydraulic pressure generated by a hydraulic pump to from an operating hydraulic pressure for a frictional element selectively operating at each shift ratio. A hydraulic line is configured such that the operating hydraulic pressure of the frictional element is controlled by a pressure control valve and a switching valve that are controlled by a solenoid valve. An exhaust hydraulic line of the pressure control valve is connected to an exhaust hydraulic line of the switching valve such that the exhaust hydraulic line of the pressure control valve can be controlled by a switching of the switching valve.