An alternative to the combustion-only engine is the fuel-saving and efficient hybrid drive which is compatible with the way in which individual transport is used today. Furthermore, it provides an ideal intermediate stage on the way to the emission-free fuel-cell vehicle.
Using the latest near-series research vehicles, Mercedes-Benz – supported and complemented by BMW and General Motors, its equal research partners – is helping drive forward the development of innovative hybrid-drive systems in order to make a series-production implementation of this fuel-saving and more environmentally compatible drive technology available as soon as possible.
In principle, a vehicle with fuel-cell stacks, an electric motor and an additional traction battery also belongs to the category of hybrid vehicles.
The basic principle of a hybrid drive never varies. Two energy accumulators, battery and fuel tank, are joined together with a combustion engine and one or more electric power units. This combination permits a number of variants:
1) The parallel hybrid has been found to be a good, and particularly energy-efficient concept for use in passenger cars. In the parallel hybrid, the combustion engine and the electric motor are connected to the drive train. Both of them can drive the vehicle together, either by one axle or, in all-wheel drive operation, by separate axles.
2) In the case of the serial hybrid, which is used principally in the commercial vehicle sector, the entire output of the combustion engine is converted into electricity (by means of a generator). This is used to run a powerful electric motor which drives one or more axles.
3) A split hybrid is a combination of the two preceding set-ups. It allows the output of the combustion engine to be transferred both to the drive axle and to a generator.
4) In a mild hybrid, most of the work is done by the combustion engine but it switches off whenever it is not in use. The relatively small electric motor, which serves as a starter and an acceleration booster, relieves the strain on the combustion engine in stop-and-go traffic and is also used to recover kinetic energy.
The two-mode hybrid drive is an innovative Mercedes-Benz development with two electric motors and an intelligent switching program. This latest hybrid generation, which was developed with the principal goal of providing a powerful and compact drive system, uses a split hybrid concept – an intelligent synthesis of the serial and parallel hybrids. The patented two-mode hybrid also differs from the familiar single-mode systems in that it requires significantly smaller electric motors and can therefore be implemented in a much more compact package.
Thanks to its two-mode operation, the system also offers the advantage of reduced fuel consumption at the highest possible performance levels, particularly in the long-distance driving cycle. It also displays superior traction performance.
