Patent ID: 7204786

Claim:
A hydraulic pressure characteristic value setting method for an automatic transmission that includes a control portion and a plurality of friction engaging elements, wherein the control portion controls the plurality of friction engaging elements to be engaged or disengaged by controlling hydraulic pressure applied to the plurality of friction engaging elements so as to achieve a plurality of transmission ratio in accordance with combinations of engagement and disengagement of the plurality of friction engaging elements, the hydraulic pressure characteristic value setting method comprising steps of: disengaging one of the plurality of friction engaging elements; transmitting turbine rotation to one side of the disengaged friction engaging elements; securing other side of the disengaged friction engaging elements; detecting variations of speed of the turbine rotation by means of a turbine rotation sensor; executing a learning of a hydraulic pressure characteristic value in accordance with at least the variations of speed of turbine rotations when the disengaged friction engaging element starts to be engaged, and disengaging the engaged friction engaging element when a predetermined guard condition has been fulfilled.