Patent ID: 7267631

Claim:
An automatic transmission having a start-up clutch assembly comprising: a transmission housing; an input drive shaft continuously operatively connected to a motor shaft of an engine adapted to transfer torque from the engine to said transmission; an output drive shaft operatively coupled to a vehicle drive shaft; an input planetary gear assembly having a sun gear, a ring gear, and a plurality of planet gears disposed therebetween, said ring gear operatively connected to said input drive shaft; an output planetary gear assembly operatively coupled to said input planetary gear assembly and said output drive shaft, said output planetary gear assembly including a double planetary gear set that has a first sun gear, a first planetary gear operatively supported by a first planet arm, a second sun gear, a second planetary gear held by a second planet arm and an output ring gear, said input planetary gear assembly and said output planetary gear assembly adapted to provide a plurality of selectively operable gear ratios between said input drive shaft and said output drive shaft; and a start-up clutch operatively disposed between said transmission housing and said sun gear and adapted to allow said sun gear to freely rotate when said start-up clutch is disengaged so that no torque is transferred from said input planetary gear assembly to said output planetary gear assembly, said start-up clutch further adapted to engage and hold said sun gear stationary so that torque is fully transferred from said input planetary gear assembly to said output planetary gear assembly, and said start-up clutch further adapted to provide a varying and controllable slipping interaction between said disengaged and engaged positions at vehicle start-up, thereby providing said vehicle with a smooth transition from stationary to moving; wherein prior to initializing vehicle start-up, torque and rotation of said input drive shaft provided by the motor shaft of the engine is coupled directly to said ring gear so that speed of said ring gear is substantially the same as speed of the motor shaft.