Control apparatus for automatic transmission

An apparatus for controlling an automatic transmission that changes speed of an output of an engine mounted on a vehicle through a frictional engaging element, comprising:

• input rotational speed detecting means for detecting an input rotational speed of the automatic transmission;
• output rotational speed detecting means for detecting an output rotational speed of the automatic transmission;
• output rotational speed change amount calculating means for calculating a change amount of the output rotational speed;
• output rotational speed change amount average calculating means for calculating an average of the change amount of the output rotational speed over a predetermined period of an initial inertia phase of shifting;
• vehicle acceleration average calculating means for determining completion of the shifting based on a ratio of the input rotational speed to the output rotational speed and calculating an average of a vehicle acceleration after the completion of the shifting based on the change amount of the output rotational speed, assuming that the change amount of the output rotational speed indicates the vehicle acceleration;
• difference calculating means for calculating a difference between the average of the change amount of the output rotational speed and the average of the vehicle acceleration;
• learning value calculating means for calculating a learning value used for incrementally and decrementally correcting a desired value of transmission torque of the frictional engaging element such that the calculated difference falls within a predetermined range;
• incrementally and decrementally correcting means for incrementally and decrementally correcting the desired value of the transmission torque of the frictional engaging element with the calculated learning value;
• and
• hydraulic supply control means for controlling supply of hydraulic pressure to the frictional engaging element such that it becomes the corrected desired value of the transmission torque.

A method for controlling an automatic transmission that changes speed of an output of an engine mounted on a vehicle through a frictional engaging element, comprising the steps of:

• detecting an input rotational speed of the automatic transmission;
• detecting an output rotational speed of the automatic transmission;
• calculating a change amount of the output rotational speed;
• calculating an average of the change amount of the output rotational speed over a predetermined period of an initial inertia phase of shifting;
• determining completion of the shifting based on a ratio of the input rotational speed to the output rotational speed and calculating an average of a vehicle acceleration after the completion of the shifting based on the change amount of the output rotational speed, assuming that the change amount of the output rotational speed indicates the vehicle acceleration;
• calculating a difference between the average of the change amount of the output rotational speed and the average of the vehicle acceleration;
• calculating a learning value used for incrementally and decrementally correcting a desired value of transmission torque of the frictional engaging element such that the calculated difference falls within a predetermined range;
• incrementally and decrementally correcting the desired value of the transmission torque of the frictional engaging element with the calculated learning value;
• and
• controlling supply of hydraulic pressure to the frictional engaging element such that it becomes the corrected desired value of the transmission torque.