Patent ID: 8292781

Claim:
A method of operating a motor vehicle powertrain comprising an infinitely variable transmission and an engine, the transmission comprising 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 transmission input and 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, that the available range of variator ratios maps onto both forward and reverse reciprocal transmission ratios, and that 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, the method being characterised in that it comprises sustaining engine speed where engine speed is not sustainable by torque from the transmission alone, in a low range of 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.