German company ZF and Auburn Hills, Mich.-based Continental have finalized a strategic alliance to develop and produce hybrid drives for commercial vehicles. ZF, as the systems supplier, will provide the parallel hybrid transmission, while Continental will provide the lithium-ion battery accumulator, and system electronics. In addition to pure hybrid technology (transmission, electric motor, and power electronics), ZF is responsible for system integration and controls.
"The parallel hybrid concept can be implemented by utilizing existing vehicle driveline resources,” said Rolf Lutz, group executive of the Commercial Vehicle and Special Driveline Technology division for ZF.
"With the latest generation of powerful lithium-ion batteries, we create the very prerequisites for electrically assisted driving of hybrid buses and trucks," added Jörg Grotendorst, head of the Business Unit Hybrid Electric Vehicles for the Powertrain Division at Continental. “This allows for additional CO2 reductions in city driving.”
The cooperation stipulates that Continental—already using Li-ion batteries for passenger car volume production applications—further develops the battery technology with ZF, with volume production scheduled for 2011. The energy-accumulating systems are developed by Continental in Berlin, Germany, and by ZF in Friedrichshafen, Germany.
Plans include an energy-accumulating system that can be flexibly integrated in different vehicle concepts to provide an output of 60 kilowatts—more powerful than those used in the passenger car sector. 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).
In this new commercial system, ZF prefers the concept of 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. In this context, vehicles equipped with full hybrid systems can achieve a 30 percent fuel economy improvement.
In addition 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 by omitting the 24 V battery, and starter.
As the electric motor also acts as a source for additional power consumption during generator operation, this hybrid transmission system is also a great option for municipal vehicles. In current applications, the Power Take Off (PTO) unit permanently requires fuel because it is mechanically connected to the combustion engine. The powerful generator and the hybrid battery in this new system allow for the use of electric PTOs that consume fuel only while being operated (power-on-demand).
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