1. Field of the Invention
The invention concerns a drive system with a drive motor, especially an internal combustion engine of a motor vehicle, and an electric machine.
2. Description of the Related Art
Drive systems of motor vehicles with internal combustion engine are traditionally equipped with two electric machines. One electric machine serves as a generator for power supply (dynamo), another one for starting the engine (starter).
Moreover, a motor vehicle has a battery, which takes on the function of a chemical accumulator of the energy produced in the dynamo. The energy stored in the battery is used for starting the motor vehicle, and also for operating electrical consumers.
Electric machines, internal combustion engine, and battery are attuned to each other for the particular application. The battery in drive systems of conventional motor vehicles is supposed to provide high currents, in order to accomplish the high starting power required in internal combustion engine. Furthermore, it must provide electrical energy for the electrical consumers, especially when the dynamo is not operated.
Traditionally, a lead/sulfuric acid storage battery is used in the motor vehicle (see Robert Bosch GmbH, "Automotive Engineering Handbook," VDI Verlag, Dusseldorf, 1991, p. 763ff.). This is characterized by high number of cycles and high reliability, while at the same time it is economical in cost. The known motor vehicle drive systems with lead/sulfuric acid battery have the disadvantage, however, of being limited in their power and energy density.