Patent ID: 8565990

Claim:
A method for starting an engine in a hybrid vehicle being driven by an electric machine, the vehicle having a first clutch located between the engine and the starter motor and at least one other clutch disposed between the electric machine and vehicle drive wheels, the at least one other clutch being selectively engageable for facilitating torque transfer between the electric machine and the vehicle drive wheels, the method comprising: initiating operation of a starter motor; reducing the pressure of the first clutch to a second level while the starter motor is operating; detecting engine start; stopping the starter motor; increasing the speed of the engine to approach that of the electric machine; engaging a first clutch connecting the engine to the electric machine; requesting an engine shutdown in response to a reduced engine demand and disengaging the first clutch; requesting an engine start after an engine shutdown is initiated and the engine is still operating in response to an increased engine demand; initiating slip in at least one of the at least one other clutch; and raising the pressure of the first clutch to to facilitate torque transfer from the electric machine to the engine when the slip in the at least one of the at least one other clutch has reached a predetermined level.