ZF develops off-the-shelf plug-in auto
Eight-speed auto incorporates electric motor for higher speeds and longer EV rangeGerman driveline specialist ZF has developed a new eight-speed automatic transmission with an integrated electric motor that has plug-in hybrid applications in mind.
In a discipline where it is more common to see CVT transmissions as the conduit for delivering reciprocating engine power, ZF says the new modular hybrid auto transmission has the potential to offer full-EV operation over longer periods at higher speeds and is able to reduce fuel consumption, depending on the size of the vehicle's battery pack, by as much as 70 per cent.
The transmission is based on ZF's 8HP gearbox, substituting the conventional torque converter with an 83kW/250Nm permanent-field synchronous electric motor that fits into the same space in the transmission housing. The electric motor also acts as a generator to send power to the batteries on braking or deceleration. While the technology is not new in itself, it's a breakthrough for car manufacturers having the supplier provide a motor/generator unit fully integrated with a conventional epicyclic auto transmission.
The combination is claimed to allow maximum pure-electric operation up to speeds approaching 120km/h and a range of around 31 kilometers. That's somewhat slower than the maximum EV speed of the Porsche Panamera S e-Hybrid, but 50 per cent longer range.
Two dampers within the transmission help reduce high-load torsional vibrations within the combustion engine at low rpm.
ZF is working on tailor-made applications for the new hybrid systems, including various electric-motor outputs as well as a full-hybrid module with an integrated separating clutch for full EV operation.
According to Dr. Stefan Sommer, who is CEO of ZF Friedrichshafen AG, "Electrifying the driveline is an essential means for ZF to further increase efficiency and significantly reduce emissions. As plug-in hybrid vehicles become more prolific, consumers are exposed to the performance capability of hybrid technology in general, for which we expect demand to increase for a long time, and our plug-in hybrid transmission in particular. It makes individual mobility more environmentally friendly, more dynamic, and also more sustainable, and is completely suitable for everyday use at the same time."
The new ZF transmission will make its first appearance on the upcoming BMW X5 xDrive40e plug-in hybrid.
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