INNOVATION IN LUBRICANTS CAN HELP REDUCE FAILURES OF EV COMPONENTS
by Natasha Christou Digital Marketing ConsultantPure electric vehicles house an electric motor and a battery
pack – combined, these move a vehicle forwards. Rolling bearings, which are commonly used in all types of
land-based vehicles are now prone to suffer from electro erosion (or electrical discharge) than ever
before. This is due to the increased adoption of electric vehicles.
As
such, with the increased frequency in modern power transmission systems,
there’s bound to be an increase of components getting damaged by electric
erosion; with the current trend of new vehicles supporting higher voltages – be
it from higher capacity battery packs or high-powered motors – there’s now an
even greater risk of such issues from occurring.
For
more than 20 years, the tribology experts at Kluber
Lubrication have been researching into the use of ionic liquids (salt in a liquid state)
for innovative lubricant concepts. This modern concept turns the lubricant into
a “lightning conductor” to prevent harmful potentials from forming. In addition
to the vehicle-relevant data like speed, smooth operation and extended service
life, these new-gen lubricants also address the issue of electric conductivity.
What can electro erosion damage?
The
rolling bearings of electric motors and other electric components can develop
electro erosion caused by an undesirable passage of current through the contact
zone between the rolling element and the raceway. Therefore, the heat that’s
generated locally melts the surface. From that, several micro-metre sized
pittings are formed. Both types, tend to damage the lead to the generation of
undesirable bearing noise at first, which finally leads to premature failures.
The
problem can be solved by several design approaches, for example, by insulating
the inner and outer rings or using ceramic rolling elements. The problem with
these measures is that they don’t always bring success, despite the high costs’
manufacturers have to incur. A simpler, yet more promising approach, is to use
a lubricant of low impedance to dissipate the currents generated.
Another
property of lubricants is that they’re insulators. How? Because they block the
passage of electric currents that they increase a voltage build-up in bearings
components made of metal. Traditional solutions involve the use of black
lubricants based on graphite and carbon, which, on the one hand, can also
prevent parasitic currents.
On
the other hand, they contain black, solid graphite particles which impede
smooth running. As such particles are displaced from the friction point over
time and are subject to change by the mechanical load, electroconductivity of
these greases decreases continuously.
Innovative lubricants
There
are advantages of making the lubricant conductive by adding ionic liquids to
dissipate, which can see it replacing ‘black lubricants’. Especially
high-frequency EDM (Electric Discharge Machining) currents can be neutralised
by suitable lubricant designs.
Currently,
this solution is offered by Kluber; they own three patents for using ionic
liquids in lubricant formulations. One of these patents implies their use of
base oil, the other two patents refer to the use of additives.
The outlook of ionic liquids
Colliding
with strong partners within the industry, Kluber Lubrication is currently
working on further optimising the conductivity of lubricants while still
maintaining their tribological performance by means of ionic liquids. In case
of a very high level of energy passage, it is not yet possible at this stage to
solve the problem of undesirable current passage merely by means of a
lubricant.
This,
however, would be highly desirable for the industry, because it could reduce
the size of the bearings. An interesting approach is the combination of
insulating bearings and additional discharge elements containing
electroconductive lubricants.
With
them being a design element, lubricants are a crucial factor when it comes to
efficiency and reliability of mechanical components. Research on continuous
development by the likes of Kluber Lubrication is the key to extending the
service life of components and increasing both energy efficiency and
sustainability.
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Created on Apr 21st 2020 07:18. Viewed 351 times.