PRODUCTS & SERVICES
New age fl uid testing
Drivetrain electrification is
a real challenge for lubricant,
the one component that touches
every part of the transmission. Welldesigned
lubricants can unlock new
engineering ideas, although it’s
often hard to correlate laboratory
performance with real-world use.
Still, next-generation lubricants could
support a wide range of hardware,
from transmissions hybridized with
e-motors to new, dedicated hybrid
transmissions and full e-drive
solutions. Fluid compatibility and
electrical and cooling properties
will have to supplement core friction
performance and parts protection.
Determining fluid and additive needs
will be essential for controlling risk.
“Unfortunately, current industry
tests aren’t always wholly relevant to
or predictive of lubricant performance
in EVs,” says Dr Harald Maelger,
senior OEM relationship manager
at Afton Chemical. “Avoiding the
pitfalls requires close partnerships
with additive and lubricant suppliers,
New lubricants are tested extensively through fi ve phases before they are allowed to enter production
so OEMs can really benefit from nonstandard
testing to bridge the gap
between laboratory, rig and road.”
Afton Chemical is at the forefront
of EV fluid testing, with recent
advances in three areas: friction
durability with thermal stress; gas
and liquid phase compatibility;
and electrical property changes in
ageing fluid. Tests are specifically
designed to correlate with field
performance to generate robust,
reliable fluid recommendations.
Unsurprisingly, Afton examined
friction durability first. “The FVA’s
recent GK test round robin was
worrying. The same reference fluid,
168 // January 2020 // www.electrichybridvehicletechnology.com
under identical conditions, showed
friction failure anywhere between
3,500 and 9,300 cycles,” says Dr
Susie Hurley, senior adviser in ATF
R&D at Afton Chemical. “This raises
a red flag: fluids meeting OEM
specifications on one test rig might
not meet them on another, making
it even harder to translate results
into the real world. Standard testing
also overlooks the role of heat, as
found in a hybrid transmission.”
Afton’s own HEV friction durability
test combined dedicated friction
apparatus with a thermal loop to
simulate cooling stresses. Results
showed an antagonistic e ect,
limiting e ective fluid life more than
anticipated. “We wanted a reliable
indicator of field performance, so we
tested used as well as new clutch
plates,” Hurley says. “Plate analysis
showed that fluid formulation is
paramount, but that if problems do
occur, shorter oil drain intervals are
e ective at restoring performance.”
Sensitive e-motor components
also demand lubricant compatibility.
“Our initial recommendation was
to extend the standard copper
corrosion test and also measure
end-of-test copper in oil,” says
Hurley. “Screening tests revealed
that some commercial fluids are
especially aggressive in the gas
phase, which is important given the
higher temperatures associated with
e-motors. We worked very closely
with an OEM to develop a simple
screener test that correlates to
problems experienced in the field.”
Fluid conductivity is a third focus.
“Naturally, OEMs want to know what
the right tests and the right limits
are,” says Dr Maelger. Again, Afton
moved away from the standard DC
conductivity tests to field-based
assessment. “Hybrid taxis being
rare, we used taxis with conventional
step ATs to obtain real-world used
lubricant samples. They were taken
at intervals and tested for suitability
in hybrid transmissions. This allowed
real-world evaluation with everything
present except the e-motor.
“Fluid conductivity increased only
slightly overall; there was a balance
between the increase from iron wear
particles and the natural decrease
seen in ageing fluids; and the used
lubricant still had a solid all-round
performance reserve.”
The rapid pace of e-mobility
development continues to generate
questions. “Our additive chemistry
has the advantage of inherent
thermal stability and excellent
friction characteristics, but we
are never satisfied. We’re always
looking for new ways to assess
real-world component and additive
interactions,” says Dr Maelger.
“Our ability to develop robust,
reliable lubricant tests that predict
how fluids age in service will prove
every bit as important for our
OEM partners as their nextgeneration
hardware.”
Partnering on new, more targeted tests for electrified transmission
fluids can better predict real-world lubricant performance
Afton conducted a copper corrosion test, using an ATF used by a large
OEM, in which the wiring was destroyed by the lubricant vapour
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To learn more about Afton Chemical,
visit: www.magupdate.co.uk/PEHV
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