The drive unit (1) uses a combustion engine (3) and an electric motor (5), used individually or in conjunction for driving a common drive shaft, during different time intervals. The rotor of the electric motor is coupled to the engine crankshaft for acting as a flywheel mass, with the surface of the rotor facing the transmission acting as a coupling surface of a friction clutch between the crankshaft and the transmission. The stator of the electric motor is mounted on the engine, with dissipation of heat via a common cooling system.
