22 E-AXLES
electronics. “Taking a motor and putting a transmission
on it isn’t too diffi cult. But one of the biggest challenges
and innovations was in tightly integrating the power
electronics into the same package. That’s where we see
the industry going.”
There are still question marks beyond integration,
however. With a fi nite speed range covered by the electric
motor, e-axle developers essentially have three options:
disengage the motor at high speeds; fi nd a fi xed-ratio
transmission and a motor capable of covering the entire
speed range; or use a multispeed transmission.
GKN’s eTwinsterX concept – currently a working
demonstrator in the advanced prototype stage – uses a
two-speed confi guration, with a conventional shifter fork
mechanism actuated by an electric motor and a dualcone
synchroniser system. However, the eTwinsterX’s
twin clutch packs still have the ability to disengage the
driveshafts when required. Elsewhere, Japanese motor
specialist Nidec has showcased an integrated e-axle design
with an optional clutch mechanism.
These innovations continue to push the functionality
of e-axle units, making them an increasingly attractive
solution, both for hybrids and full EVs. However, there
will always be some applications where the packaging
constraints or the hybridisation strategy requires the
use of alternative layouts.
VehicleDynamicsInternational.com • November/December 2019
GKN’s eTwinsterX uses a twospeed
configuration, with a
conventional shifter fork
mechanism actuated by an
electric motor and a dual-cone
synchroniser system
/VehicleDynamicsInternational.com