August 2006 / Hybrid Belt for Automatic Transmissions

The application

The continuously variable transmission (CVT) combines driving dynamics with fuel efficiency. An electronic ratio control unit makes it possible to comfortably „cruise” in the automatic mode as well as to intervene manually in the selection of the gear ratio. Various driving strategies are possible, including adaptive strategies.
 

The problem
 

Friction drives with metallic elements and oil lubrication are predominant in vehicles with medium motorization; toroidal transmissions currently under development are targeted at high-performance upper-class cars. Both designs based upon steel-to-steel contact must get along with low friction coefficients with oil lubrication. 
 

Pumps create considerable pressures and volume flows for the generation of downforce, lubrication and cooling, thus reducing the efficiency of the system. The effort and costs required by the system are excessively high for compact class cars; and continuously variable automatic transmissions are hardly available at present.
 

The solution
 

As an alternative there is the dry hybrid belt with all the advantages of a CVT, high frictional forces and low losses in the peripherals.
 

The advantages

Maximum riding comfort without interruption of traction
Sporty driving style with acceleration-otimized strategy
Fuel economy and emission reduction thanks to increased efficiency

The structure