Patent ID: 7816874

Claim:
A vehicle driving system comprising: an electric motor driven by an electric power supply mounted in a vehicle, the electric motor being adapted so as to use a reduction gear to supply driving force to wheels different from wheels driven by an engine; control means for controlling the driving of the electric motor by controlling electric power supplied from the power supply mounted in the vehicle to the electric motor; and means for outputting information on a rotating speed of the electric motor; wherein, the rotating speed information output means is also rotating speed estimation means that estimates the rotating speed of the electric motor from an induced voltage thereof; in accordance with input information including the rotating speed of the electric motor estimated by the rotating speed estimation means, the control means controls the electric power to be supplied from the vehicle-mounted power supply to the electric motor; the electric motor includes a field coil; and the rotating speed estimation means estimates a first motor-induced voltage constant Ek from a field current flowing through the field coil, the rotating speed estimation means estimating the rotating speed of the electric motor by using the estimated first motor-induced voltage constant Ek.