Truck & Off-Highway Engineering - October 2022 - 21

ELECTRIFICATION FEATURE
eAxles gain TRACTION
ZF's eBeam axle is scalable for both light- and
medium-duty applications with an output of up to 350 kW.
OEMs are developing and testing axles with integrated electric powertrains to
electrify trucks of all sizes.
by Matt Wolfe
D
evelopment of electrified drivelines is rapidly
ramping up at OEMs and Tier 1 suppliers. With
a wide variety of vehicles suddenly in need of
electrified drivelines capable of matching or
surpassing the capabilities of the existing ICE powertrains,
suppliers are providing an array of solutions
to meet customer needs.
For the electrification of light- and medium-duty
trucks, one of the technologies rapidly gaining interest
is electric axle or eAxle. An eAxle is a traditional axle
housing and differential incorporating an electric motor,
an inverter and a thermal-management system. Most
eAxles also are equipped with a multi-speed transmission
for high- and low-torque demands. While the basic
concept is similar across the industry, suppliers are taking
varying approaches to put these axles on the roads
depending on their target vehicle segment, required
power output and desired vehicle range.
The benefit of an eAxle from the OEM standpoint is
that they offer the capability to electrify new and legacy
chassis with minimal engineering changes, which in
turn provides a shorter lead time to bring such a vehicle
to market. The scalability of eAxles also enables suppliers
to develop a single design that can be easily adapted
for use in light- and heavy-duty applications. The
following is a look at several companies currently developing
and testing eAxles for existing and future trucks.
ZF's scalable design
ZF recently demonstrated a prototype truck eAxle at
its Next Generation Mobility event at M1 Concourse in
TRUCK & OFF-HIGHWAY ENGINEERING
Pontiac, Michigan. ZF's unit is a solid axle with an integrated electric
motor, inverter and transmission. It is scalable for 400V and 800V
architectures, with a power output range of 180 to 350 kW. Max
torque output reportedly is 15,000 Nm (11,063 lb-ft). ZF states that
an integrated inverter-in-transmission housing is an option and that
customers have a choice of various differentials. Rear-wheel steering
also is available.
The axle is designed to be packaged into legacy and future chassis
as a complete unit so that OEMs can upfit vehicles with very few engineering
changes. ZF packaged a prototype version of its eAxle into
a current-generation Chevrolet Silverado 2500, which was used as a
demonstrator for SAE Media and other journalists. The eAxle in the
demonstrator was rated at 300 kW and 10,200 Nm (7,376 ft-lb).
The batteries powering the demo vehicle were supplied by CATL.
They operate in an 800V architecture and also can operate with a
400V system. In the demo vehicle, there were four battery packs positioned
under the floor and two more in the bed. ZF noted that this
would not be the production configuration and the battery placement
was purely for prototype purposes. Each pack had a rated capacity
of 35 kWh for a system total of 210 kWh.
From inside the cabin and behind the wheel, the axle's operation
was quiet and seamless. Though the motor, inverter and other components
do add unsprung weight, handling was not adversely affected
in a noticeable manner, even combined with the additional
weight of the battery packs. Though SAE Media did not get to drive
the demo truck with a trailer or a load, the benefits in instant torque
when towing or hauling would be a welcome attribute.
It's clear that the acceleration capabilities of ZF's eAxle aren't meant
to pin occupants in their seats. Rather, it is designed to match the hauling
capabilities of today's current crop of light- and medium-duty diesel
powertrains. The company did not give specific towing ratings for
this prototype, but it expects that a production eAxle fitted to a similar
October 2022 21
ZF
Truck & Off-Highway Engineering - October 2022

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