Automatic transmission and method for controlling same

A control method for an automatic transmission that is mounted on a vehicle and includes a first friction engagement element and a second friction engagement element, the first friction engagement element being engaged when a first gear position is realized and disengaged when a second gear position is realized, and the second friction engagement element being engaged when the second gear position is realized and disengaged when the first gear position is realized, the control method comprising:

• determining whether or not a current state is a state in which the automatic transmission does not perform shift, the state involving a predetermined vehicle operation state and an engaged state of one of the friction engagement elements;
• determining that learning is permitted if it is determined that the current state is the state in which the shift is not performed;
• causing the one of friction engagement elements to slip by decreasing an instructional pressure for the one of the friction engagement elements if it is determined that the learning is permitted;
• and
• learning an engagement start pressure of the other one of the friction engagement elements based on a change in a differential rotation of the one of the friction engagement elements, or in a parameter that changes in accordance with the differential rotation of the one of the friction engagement elements, at a time when an instructional pressure for the other one of the friction engagement elements is increased.

An automatic transmission mounted on a vehicle, comprising:

• a first friction engagement element that is engaged when a first gear position is realized, and is disengaged when a second gear position is realized;
• a second friction engagement element that is engaged when the second gear position is realized, and is disengaged when the first gear position is realized;
• shift determination means for determining whether or not a current state is a state in which the automatic transmission does not perform shift, the state involving a predetermined vehicle operation state and an engaged state of one of the friction engagement elements;
• learning permission determination means for determining that learning is permitted if the shift determination means determines that the current state is the state in which the shift is not performed;
• and
• learning control means for, if the learning permission determination means determines that the learning is permitted, causing the one of the friction engagement elements to slip by decreasing an instructional pressure for the one of the friction engagement elements, and learning an engagement start pressure of the other one of the friction engagement elements based on a change in a differential rotation of the one of the friction engagement elements, or in a parameter that changes in accordance with the differential rotation of the one of the friction engagement elements, at a time when an instructional pressure for the other one of the friction engagement elements is increased.