Truck & Off-Highway Engineering - December 2021 - 22

DEVELOPING
EV-specific lubes
LUBRICANTS FEATURE
These characteristics include dynamic
viscosity, or how easily the fluid flows;
density, or the weight of fluid in a given
volume; specific heat capacity, or how
much heat the fluid can store; and thermal
conductivity, or how easily heat
travels through the fluid. A properly
formulated e-fluid that balances each of
these characteristics can deliver significant
benefits. For example, if an e-fluid
can help an e-motor run cooler during
peak times of operation, the e-motor
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" EVs are increasingly
having their own
standards for
lubricants instead
of just borrowing
standards from the
ICE industry. "
will operate more efficiently.
Additionally, an e-fluid's ability to prevent
extreme temperatures can better
protect the entirety of the driveline.
NVH is another critical consideration.
An e-DCT may experience clutch shuddering,
gear and bearing noises, torque
ripple and electrical whining, all of which
detract from the overall driving experience.
To combat NVH, it's important to
use the proper driveline fluid formulation
that provides enhanced friction performance.
(For more on lubricant " tuning "
for EVs, see www.sae.org/news/2021/10/
retuning-lubricants-for-ev-duty).
Lower-viscosity lubricants and oils
are just as popular in EV transmissions
as they are in traditional ICE hardware;
thinner fluids mean less resistance to
moving parts. Manufacturers must find
the right balance between this demand
and all others.
Ultimately, what does this mean for
lubricants and lubricant manufacturers?
It means that EVs are increasingly having
their own standards for lubricants
instead of just borrowing standards
from the ICE industry. As transmission
designs for EV and hybrid vehicles
evolve, manufacturers are developing
specialized e-fluids for a range of etransmissions.
As the market continues
to move in the direction of higher EV
adoption, e-fluids will become more
critical to the function and reliability of
these vehicles.
Dr. Michael Gahagan, technology manager
of driveline at Lubrizol, wrote this article for
Truck & Off-Highway Engineering. His most
recent SAE Technical Paper on this topic
can be found at www.sae.org/publications/
technical-papers/content/2017-01-2358/.
22 December 2021
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TRUCK & OFF-HIGHWAY ENGINEERING

http://www.sae.org/news/2021/10/retuning-lubricants-for-ev-duty http://info.hotims.com/79458-705 http://www.sae.org/publications/technical-papers/content/2017-01-2358/

Truck & Off-Highway Engineering - December 2021

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