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ZF Designed 2-speed EV transmissions for EVs

July 29,2019

ZF on Tuesday unveiled a new two-speed transmission. Dedicated for electric vehicles, ZF believes its technology can improve a vehicle's efficiency without taking up an unnecessarily large amount of space, which would only work against the new transmission's efforts. Its new 140 Kw 2-speed drive unit for electric cars (scalable up to 250 kW), which consists of an electric motor, 2-speed transmission and power electronics - all integrated into a compact drive unit.

This new two-speed unit is programmed to shift at about 43 miles per hour, but that shift position isn't set in stone. It can work with a car's other systems to, for example, choose when to shift based on local maps and topography. It could also shift into a more range-minded gear based on its distance from the next EV charger to help alleviate range anxiety.

By implementing this second gear, which can provide a ratio more suited to efficiency, ZF claims its transmission can boost range by up to 5 percent when compared with a single-speed unit. Automakers could pair this with a smaller battery, reducing curb weight while maintaining range, or it could use the same battery for additional range.

ZF believes there's use for a two-speed transmission beyond efficiency, too. By tweaking the gear ratios, ZF could instead create a transmission gearing that boosts an electric car's top speed - a notable sticking point for some EVs, which have rev-limited top speeds in exchange for better low-speed performance.

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Bert Hellwig, Head of System House at ZF’s E-Mobility division said:

“For electric vehicles in everyday use, it is important to obtain as much range as possible from each battery charge. Every percent of improvement in energy conversion efficiency translates into two percent more range.” To increase the performance rating of the new electric axle drive system, ZF leveraged its expertise in systems to develop a new electric motor with a maximum power rating of 140 kW paired with a two-stage shift element. “Bringing together our know-how in relation to electric motors, gearboxes, and power electronics ensures that we achieve the best possible range from each battery charge”.


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