November 10, 2014

GKN produces world's first two-speed eAxle for Hybrids and EVs

GKN has produced the industry's first two-speed eAxle. The technology has entered production on the BMW i8 plug-in hybrid sports car.

"GKN's customers aren't just looking to make their next car more efficient; they want to create new driving experiences. Our expertise in driveline
efficiency, torque vectoring and electric drive systems is enabling automakers to connect drivers to the road in new ways. We are developing the systems that are helping bring a new generation of electric drive vehicles to life," said Andrew Reynolds-Smith, CEO, GKN Automotive.

Theodor Gassmann, GKN Drivelines Director of eDrive systems development, added, "Being the first Tier One to deliver a two-speed eAxle demonstrates GKN’s leadership in electric drive technologies and hybrid driveline systems. Two-speed eAxles will help manufacturers enhance hybrid and electric drivetrains and support the trend to downsize eMotors to reduce weight and cost. With the technology proven in a high-performance vehicle with high levels of refinement, significant savings in CO2 are possible."

Giving the electric motor an additional gear ratio improves acceleration and pure electric range, benefiting both driving dynamics and CO2 emissions. GKN's two-speed eAxle also enables the motor and all its associated systems to be downsized, reducing mass and further increasing efficiency.

eAxle technology enables automakers to produce 'axle-split hybrids'. A conventional or hybridised engine provides the primary power to either the front or rear wheels, with the other axle driven by an eAxle module. The technology responds intelligently to deliver an instant high-torque all-wheel drive experience, a useful pure electric range or a refined, efficient parallel hybrid mode. No other hybrid architecture offers such a strong combination of efficiency, traction, dynamics and packaging.

Until now electric and axle-split hybrid vehicles have used single-speed transmissions. Using a fixed ratio limits electric drives in terms of either acceleration or top speed as they must disconnect at certain speeds to prevent the motor overspinning. GKN's two-speed eAxle is the first to enable the electric drive to boost the vehicle’s performance across its entire speed range.

Designing the two-speed eAxle for a high-performance sports car application placed tight packaging requirements on GKN's development team. To achieve high torque density in a package that weighs just 27 kg and measures less than 325 mm by 562 mm by 313 mm, some remarkable design decisions were made.

To make the system narrower, the shift mechanism sits on the input shaft instead of the intermediate shaft in the middle of the transmission. Even with the input shaft spinning at up to 11,400 rpm, GKN's precise software control of the eMotor and the synchro-actuation achieves a smooth gearshift in all conditions.


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