Patent ID: 7673714

Claim:
A hybrid vehicle propulsion system comprising: an internal combustion engine; a torque converter including a lockup clutch, the torque converter having an input and an output, the input coupled to the internal combustion engine; an electric energy conversion device coupled downstream of the torque converter output; and a control system for adjusting torque output of the hybrid propulsion system including: when unassisted engagement of the lockup clutch is available based on a required torque capacity of the lockup clutch, engaging the lockup clutch without assistance from the electric energy conversion device to lock up the torque converter, and when unassisted engagement of the lockup clutch is unavailable based on the required torque capacity of the lockup clutch, engaging the lockup clutch to lock up the torque converter with assistance from the electric energy conversion device by increasing torque output of the electric energy conversion device during the torque converter lockup clutch engagement.