AUTOMATIC TRANSMISSION

摘要

An automatic transmission is provided to improve the detection accuracy with respect to a failure of a switching valve by using a parameter when a first gear shift stage is changed into a second gear shift stage. A friction coupling component includes a first hydraulic pressure room(37) and a second hydraulic pressure room(38) to which an operational hydraulic pressure is applied for operating the friction coupling component. A surge valve(39) controls the operational hydraulic pressure applied to the friction coupling component having the first hydraulic pressure room and the second hydraulic pressure room. A switching valve(41) switches a communication state of a fluid channel between the surge valve and the first and second hydraulic pressure rooms. A transmission gear controller blocks the second hydraulic pressure from the surge valve and controls the surge valve to supply the operational hydraulic pressure to the first hydraulic pressure room when a first gear shift stage is changed to a second gear shift stage. An abnormal state determination unit determines an abnormal state of the surge valve based on a parameter when the first gear shift stage is changed into the second gear shift stage.