GKN, the world’s leading
supplier of automotive driveline components and systems, has produced the
industry’s first two-speed eAxle. This new technology has already entered
production on the BMW i8 plug-in hybrid sports car.
According to a press release
issued by GKN, 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.
The 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
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 27kg and measures less than 325mm by 562mm by 313mm,
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
11,400rpm, GKN’s precise software control of the eMotor and the
synchro-actuation achieves a smooth gearshift in all conditions.
GKN Automotive CEO Andrew
Reynolds-Smith said that 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, ” he said,
Theodor Gassmann, GKN
Driveline’s Vice President Product Technoloy eDrive Systems, said: “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.”
“Gear shifts are completely transparent to the
driver,” said Gassmann. “The smooth electromechanically actuated shift between
the synchronised ratios has enabled our eAxle to set new benchmarks for comfort
and NVH. The eAxle combines superior efficiency of 97% with high gear shift
comfort and low gear noise. And yet the shift mechanism is a proven technology
with components already in series production, providing a robust and
cost-effective solution,” he added.
“By drawing on all the
expertise and knowledge within GKN’s global engineering network, we were able
to take the eAxle from concept to production in just 24 months,” said Gassmann.
“Going forward, pairing electric powertrains with multi-speed transmissions is
enabling GKN to supply downsized eDrive modules for future hybrid and electric
vehicles. The technology also enables more radical future eMotor downsizing
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