ZF and Continental are collaborating to develop and produce hybrid drives for commercial vehicles. ZF will provide the parallel hybrid transmission and Continental will contribute the lithium-ion battery accumulator and system electronics. Production is planned for 2011.
“The parallel hybrid concept can be implemented by utilizing existing vehicle driveline resources,” said Rolf Lutz, Group Executive of the ZF Commercial Vehicle and Special Driveline Technology division.
Continental already uses Li-ion batteries for passenger car volume production applications. The energy-accumulating systems are developed by Continental in Berlin, Germany and by ZF in Friedrichshafen, Germany.
Overall plans include five unique hybrid systems. The firms will work on an energy-accumulating system that can be flexibly integrated in different vehicle concepts to provide an output of 60 kilowatts. This system will be integrated in hybrid drives for light trucks used primarily for deliveries within urban areas. The hybrid system is set up to support the combustion engine during vehicle start-up and at lower speeds (boosting). Two energy-accumulating components providing more than 120 kilowatts total are also planned for city bus applications.
ZF prefers a parallel hybrid where the electric motor and the combustion engine can be actuated in parallel via the transmission, and, if needed, separated by a clutch. The flexible design can be installed in both mild and full hybrids, which use the entire range of hybrid functions: the start-stop function, regeneration of braking energy (recuperation), boosting, and electric starting. Vehicles equipped with full hybrid systems can achieve a 30 percent fuel economy improvement.
The system does not require additional installation space. The hybrid variants based on the parallel hybrid concept transmission, can be integrated into the existing driveline of current ZF manual or automatic transmissions. The additional system weight due to wiring, battery, and the cooling system is offset by downsizing the combustion engine, and omitting the 24 V battery and starter.
As the electric motor also acts as a source for additional power consumption during generator operation, the hybrid transmission system can also be used in municipal vehicles. In current applications, the Power Take Off (PTO) unit permanently requires fuel because it is mechanically connected to the combustion engine. The generator and the hybrid battery in the new system allow for the use of electric PTOs that consume fuel only while being operated (power-on-demand).