Patent ID: 8337361

Claim:
A method for controlling a speed ratio upshift in a multiple gear ratio automatic transmission for a vehicle powertrain having an engine for developing transmission input torque and two torque establishing couplings for effecting a gear ratio upshift in a torque flow path from the engine to a transmission torque output shaft, a first of the torque establishing couplings being an on-coming friction coupling, a second of the torque establishing elements being an off-going coupling, the upshift being characterized by a torque phase followed by an inertia phase, the method comprising: increasing torque capacity of the friction coupling at a controlled rate during the torque phase as torque of the off-going torque establishing coupling is reduced and maintained in a locked state; increasing transmission input torque during the torque phase at a controlled rate before start of the inertia phase; decreasing transmission input torque at a controlled rate during the inertia phase; and decreasing torque capacity of the friction coupling at a controlled rate during the inertia phase, whereby a smooth transition is effected in a torque transfer from a transmission torque input shaft to the transmission torque output shaft.