Automotive Engineering - October 2022 - 8

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The Inside Story on Ignition Coils
I
n an interview with SAE's Automotive Engineering, Robert Nordstrom, Principal Engineer, Wells Vehicle Electronics,
discusses the research and development and advanced materials, manufacturing and testing expertise Wells leverages
to assure the maximum level of performance, durability and reliability is engineered into the more than one million
ignition coils the company manufactures annually.
AE: Describe some of the sophisticated testing processes
you've installed more recently to assure reliability on ignition
coils. You've adopted the use of finite element
analysis (FEA) for example, correct?
Nordstrom: Yes, we've developed
with our parent company,
NGK, some extremely
stringent testing requirements.
And from their
knowledge of spark plugs to
that whole area of the engine,
they're very well versed
in that. So, together, we
worked with NGK to develop
strong reliability testing and
accelerated life testing. The
typical life test that maybe
somebody would be employing
is to create a replica
spark gap and [test with]
that. We're actually utilizing
some other techniques that
achieve a high-voltage situation
for a longer period of
time, as opposed to whenever
a spark plug flashes
over, that happens in a very
short duration. What we're
trying to do is to extend that
high-voltage time period,
which puts the materials in a high-voltage environment for
a longer period.
I guess the best analogy I can give: you take a hammer
and a nail and you hit it once, it might go in a certain distance.
But now, instead of hitting it with a hammer, you hit
it with a hundred-pound weight. So, now it drives the nail
all the way. It's a longer duration - it's more energy into
that place.
AE: Testing an ignition coil for thermal shock also is critical?
Nordstrom: Absolutely. We do a variety of thermal shock
testings with numerous chambers. We go from a hot to a
cold chamber - that's kind of the older method; it's like a
mechanical system. And now, there are high-performance
thermal shock chambers that exchange the air much more
quickly, so there are fewer mechanical moving parts. We
can get thermal transfer rates of greater than 20 degrees
C per minute.
That's really moving heat in and out of the components
8 October 2022
very quickly. And the reason we're doing that is to check
the stress levels inside of the ignition coil to ensure that
the dissimilar materials - steel, copper and plastic, and
epoxy - all of those things are [thermally] moving at different
rates and the last
thing you want to have on an
ignition coil is a crack.
AE: Wells even molds its
own plastic parts?
Nordstrom: That's correct.
We mold our own plastic
parts here; we mold our own
bobbins and we mold our
housings, injection molding
with high grade DuPont resins.
We're molding Rynite;
PET is a very common polymer
used in high-voltage, so
we're using that, utilizing
glass-filled polymers.
Porosity in plastic parts is
pretty important - that way,
we can control that quality.
We've been molding some
ignition coil components
since the '90s.
Robert Nordstrom, Principal Engineer, Wells Vehicle Electronics.
AE: You said Wells manufactures
in excess of one million
coils a year. How many varieties does that include?
Nordstrom: We're making probably around 60 different
types; we manufacture all our coils in North America. Most
OEMs now are doing coil-on-plug (COP). I think the big
question is whether they put an ignition module on that
coil or they put it on the ECU.
AE: What's been one of the most significant things you've
seen change in terms of manufacture and testing of ignition
coils?
Nordstrom: I think one of the biggest changes I've noted is
OEMs getting away from pencil coils. They seem to have
been going away from that and back into more of a coilon-plug
(COP) layout. You can get a lot of energy out of a
COP. You can get a lot more winding in there, you can get
a lot more steel.
For more information, navigate to:
https://wellsengineeredproducts.com/ignitioncoils/
AUTOMOTIVE ENGINEERING

https://wellsengineeredproducts.com/ignitioncoils/

Automotive Engineering - October 2022

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