British firm makes a multi-speed EV gearbox

August 12, 2010 § Leave a comment

British transmission firm Zeroshift has announced its clutchless multi-speed gearbox for electric vehicles. This unit with ‘seamless’ ratio changes has a damper inside the gear hubs in place of a clutch, and paired interlocking rings in place of a conventional manual’s synchromesh, and is said to increase the operating  efficiency of an EV – its range and battery life expectancy – by 10%. Zeroshift says that the compact, lightweight transmission could enable the downsizing of motors as well.

The flow of torque remains uninterrupted during gearshifts, and the different gearing allows for longer operation at peak efficiency, an improvement over the single-speed gearboxes currently fitted in electric vehicles.

“The benefits of Zeroshift’s transmission would be greatest for electric delivery vehicles where the compromises in efficiency are greatest,” says Bill Martin, Zeroshift’s MD. “To be able to pull away fully laden on hills requires low gearing, but the motor then runs too fast and too inefficiently on the highway.”

“Until now, none of the transmission alternatives provided a satisfactory option for EVs,” Martin explains. “Conventional manual transmissions interrupt the drive to the wheels during gear shifting and require a clutch, adding cost and bulk to the tightly packaged powertrain of an EV. Conventional automatic transmissions also add bulk and introduce a 10 percent efficiency loss, wiping out the potential motor efficiency benefits.”

Zeroshift says that is is working with ‘several vehicle manufacturers’ as well as with consultancy firms on potential applications of its technology in passenger cars, buses and medium-duty hybrid trucks.


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