The electric motor that thinks it’s a di
It could happen. Making smarter use of electric motors takes torque vectoring to the next level. By
IGHT NOW it seems like a very long way from the red-blooded performance of Ford’s Focus RS hot hatch to the quiet efficiency of a hybrid city car. But tech innovators GKN say they can help bridge the gap with a new transmission that mixes and matches the best of both worlds.
The starting point is Twinster, GKN’s acclaimed torque vectoring system. It’s a term that’s often sloppily employed, but GKN are very clear about what they mean by torque vectoring: a system to send precise amounts of torque to individual wheels. Using two clutches, Twinster allocates torque between front and rear axles and between the rear wheels. The big benefit on a car such as the RS comes during cornering when an outside wheel will be sped up (rather than an inside wheel being braked, the less energy-efficient solution employed elsewhere).
The new breakthrough, unveiled at the Frankfurt show and available in the early 2020s, is clumsily called eTwinsterX. It’s a compact electric axle that can be used on front-drive, rear-drive or all-wheel-drive cars, on road or off, hybrid or fully electric.
A typical current hybrid has a combustion engine on one axle and an electric motor on the other. There is usually a disconnect system that switches from electric running to combustion-engine running. The single gear ratio between the e-motor and wheels is set up to deliver good launch performance, but as the car’s velocity increases the e-motor runs out of speed and the combustion engine takes over the job.
GKN’s new system works differently. It has two gears, which allows the electric motor to stay engaged at all road speeds, thus requiring less help from the combustion engine. The result is good range, good performance and less pollution.
A lower first gear delivers a good launch and low-end performance in pure electric mode and the second, longer ratio helps with higher speeds.
GKN’s Theo Gassman says: ‘The two-speed system allows you to run the e-machine in or close to its sweet spot, improving overall efficiency for greater range. Combine that with Twinster and you can deliver power from the e-machine to the wheel that has the best grip for another efficiency gain as you’re not wasting energy by using the brakes to slow that wheel down until it regains traction.’
3 TORQUE VECTORING Torque is diverted via Twinster electric axle to wheel or wheels where it’ll be most useful. 1 ELECTRIC MOTOR E-motor is used more e iciently: compact two-gear system allows electric motor to stay in use at higher road speeds. 2...