Procedure for operating decelerating downshifts with the participation of a form-locking shift element of an automatic transmission comprising a torque converter lockup clutch

摘要

A method of carrying out coasting downshifts that involve an interlocking shifting element in an automatic transmission having a torque converter lockup clutch. At the beginning of the coasting downshift, positive action is taken on the torque. The method including the steps of, at the beginning of the coasting downshift, the torque converter lockup clutch is fully or partially disengaged so that the drive-train is fully or partially decoupled from the drive aggregate, and action upon the torque is carried out in such manner that the engine rotational speed only falls below the turbine rotational speed once the synchronous point for the interlocking shifting element is reached.

主权项

1. A method of carrying out a coasting downshift that involves an interlocking shifting element arranged in an automatic transmission, the automatic transmission further including a torque converter having a disengageable torque converter lockup clutch for adjusting torque transmitted between an engine and the automatic transmission, the method comprising the steps of:
commencing the coasting downshift associated with the interlocking shifting element in order to initiate engagement of the interlocking shifting element, at a beginning of the coasting downshift, either fully or partially disengaging the torque converter lockup clutch for either fully or partially decoupling a driving connection between a drive-train, including the transmission, and the engine and allowing a turbine rotational speed to fall below an engine rotational speed, reaching a synchronous point for the interlocking shifting element, and only once the engine rotational speed falls below the turbine rotational speed and the synchronous point for the interlocking shifting element is reached, then engaging the interlocking shifting element and re-engaging the torque converter lockup clutch to re-couple the driving connection of the engine to the drivetrain.