Patent ID: 8095284

Claim:
An automatic transmission comprising: a planetary gear; a plurality of frictional engagement elements, a plurality of gear positions being realized by switching engagement/disengagement states of the plurality of frictional engagement elements and at least one of the plurality of frictional engagement elements being a variable capacity frictional engagement element that comprises a first hydraulic chamber and a second hydraulic chamber and has an engagement capacity that can be modified by modifying a supply of a working oil pressure to the first hydraulic chamber and the second hydraulic chamber; a pressure regulator valve that regulates the working oil pressure supplied to the variable capacity frictional engagement element from a source pressure; a first oil passage that connects the pressure regulator valve to the first hydraulic chamber; a second oil passage that connects the pressure regulator valve to the second hydraulic chamber; a switch valve provided in the second oil passage to switch a communication state of the second oil passage; a switch valve control unit that uses the switch valve to set the second oil passage in a non-communicative state during a shift from a first gear position in which the variable capacity frictional engagement element is disengaged to a second gear position in which the variable capacity frictional engagement element is engaged, whereby oil pressure is supplied from the pressure regulator valve to the first hydraulic chamber alone; a learning control unit that corrects the working oil pressure such that a dynamic characteristic during a shift approaches a target dynamic characteristic; and a failure determining unit that determines whether or not a constantly open failure, in which the switch valve remains in communication with the second oil passage, has occurred on the basis of a parameter representing the dynamic characteristic during the shift from the first gear position to the second gear position, wherein the failure determining unit begins the constantly open failure determination after the working oil pressure supplied to the variable capacity frictional engagement element has been corrected by the learning control unit.