Patent ID: 7104925

Claim:
An automatic transmission comprising: plural friction engagement elements for defining plural shift stages by combinations of engagement and disengagement of the plural friction engagement elements; means for controlling the engagement and disengagement of the plural friction engagement elements by controlling an oil pressure to be supplied via plural controlled solenoid valves; means for switching to a learning mode for learning a standby oil pressure value; means for memorizing a condition for verifying a controlled value; and means for determining the standby oil pressure value based on an input value defined by at least a turbine rotational speed, the means for determining the standby oil pressure value activated by switching to the learning mode, wherein the standby oil pressure determining means under the learning mode during a vehicle stationary condition increases an oil pressure of the friction engagement element for setting the standby oil pressure value by a predetermined step pressure Δpj by the controlling means while a transmission input shaft rotational speed has been maintained and performs a standby oil pressure setting for shifting the friction engagement element to an engagement side, performs a standby oil pressure value verifying process for recognizing whether a controlled value Ij is within a predetermined range corresponding to the predetermined step pressure Δpj memorized by the memorizing means when a change of the input value due to decrease of the turbine rotational speed satisfies a predetermined condition; learns the controlled value Ij when the controlled value Ij is within the predetermined range corresponding to the step pressure Δpj, and sets a step pressure Δpj+1 larger than the step pressure Δpj and performs the standby oil pressure setting and the standby oil pressure value verifying process again when the controlled value Ij is beyond the predetermined range corresponding to the step pressure Δpj.