POWERTRAIN CONTROL METHOD AND SYSTEM

摘要

The invention concerns a method of operating a motor vehicle powertrain comprising an infinitely variable transmission and an engine. The transmission comprises a rotary transmission input coupled to the engine, a rotary transmission output coupled to the vehicle wheels, a variator which provides a continuously variable ratio (the "variator ratio"), and gearing for coupling the variator between the engine and the transmission output in such a manner that the ratio of transmission output speed to transmission input speed (the "reciprocal transmission ratio") is a function of the variator ratio. The available range of variator ratios maps onto both forward and reverse reciprocal transmission ratios, and at a particular variator ratio (the "geared neutral ratio") the transmission output is stationary despite its being coupled through the transmission to the rotating transmission input. Tthe comprises sustaining engine speed in a range of low reciprocal transmission ratios containing and extending to either side of geared neutral, by applying a drive torque demand to the engine even while the powertrain is operating in overrun.