Method for controlling an automatic transmission by sensing friction element torque capacity

摘要

A method for controlling torque transfer between first and second friction elements in an automatic transmission having a hydraulic band brake servo in which a magnet is fixed to a displaceable piston, and a sensor producing a signal responsive to the sensed intensity of a field produced by the magnet representing the position of the servo piston, producing from the signal an indication of the position of the servo piston, determining a reference threshold servo position corresponding to incipient band brake torque capacity, and reducing pressure in the second friction element when the current servo displacement equals the threshold displacement.