Verfahren zum Herunterschalten eines automatischen Getriebes.

摘要

A power-on clutch-to-clutch downshift control is initiated by partially releasing an off-going torque transmitting device (C1,C2,C4) to permit an increase in the transmission input speed. At the same time, an on-coming torque transmitting device (C1,B1) is filled in preparation for engagement. When the slip across the on-coming device is near zero, the on-coming device pressure is progressively increased while the off-going clutch pressure is controlled to maintain the near-zero on-coming slip speed condition. When the on-coming device develops significant capacity, a tie-up develops between the on-coming and off-going devices, causing a drop in output shaft (30) acceleration. The drop is detected and used to release the off-going device, the shift being complete when the on-coming device is fully engaged. Engine (12) torque controls are employed to ensure a smooth output torque transition at the end of the shift.