ILMA Compoundings December 2016 - 19

THE EVOLUTION OF... TRANSMISSIONS

and South Asia. The OEM offers CVT options on its compact
and mid-size vehicles and says CVTs can increase fuel economy
by 5 percent.
Toyota has recently introduced CVTs in North America and its
"7-speed" CVTi-S is designed to feel more like a conventional
automatic in operation, with discrete stepped shift points
programmed into the car's acceleration and deceleration
curves. The CVTi-S mimics the familiar characteristics of geared
automatics by creating a sense of positive shift engagement.
Toyota expects most future growth to come from the North
American and Chinese markets.
Reports suggest that the focus of Subaru/Fuji Heavy will remain
in North America. Their Lineartronic chain CVT has replaced
automatic transmissions in more than 90 percent of their
vehicles, including those in hybrid electric vehicles. The system,
which the company says allows the engine to operate at lower
speeds for longer than conventional automatic transmission
systems, reportedly delivers better fuel economy plus a
smoother ride and a quieter engine.
Lastly, Hyundai is expanding its use of CVTs beyond its home
market into China. The Kappa CVT was developed by Hyundai
and has been optimized to provide efficiency via an ultra-flat
torque converter specifically for its Kappa engine. The company
has also developed an eco-friendly hybrid electric vehicle CVT.

Shear stability is even more important for CVTF than for
conventional ATF because of the high-pressure pumps that
are used in CVT applications. In addition to these specific
requirements, CVTF must also offer advanced wear protection -
particularly to control fatigue and sliding wear.
The requirements don't stop there. CVTF must also provide
extended anti-shudder durability to enable aggressively slipping
torque converter clutch operation, used by some designs for
added fuel efficiency, without reducing steel-on-steel friction.
They must also deliver good oxidation stability, air release
capability and paper-on-steel friction.
Getting the right balance between all of these critical
characteristics is a rewarding challenge for fluid formulators.
In Infineum's view, advances in CVT hardware technology
provide fertile ground to develop ultra-advanced fluids. This
means formulation expertise will be increasingly important so
that technology can be customized for optimum hardware
performance in belt or chain CVT applications.

Post is North America specialties market manager for Infineum USA
LP. He may be reached at 908-474-2323 or Ed.Post@Infineum.com.
More information from Infineum on the evolution of transmissions
can be found at www.infineuminsight.com.

CVTs Rely on the Fluid
More than any other transmission, a CVT relies on the
performance of the fluid for its successful operation. As new
CVT designs with unique lubrication requirements come onto
the drawing board, the transmission fluid has become an integral
part of the design.
To understand why a conventional automatic transmission
fluid (ATF) is not suitable for use in a CVT, it is important to
understand how the CVT functions. The heart of a CVT consists
of a variator with two pulleys, each built up of two conical,
adjustable sheaves, around which a steel push belt or chain is
looped. The torque is transmitted by the steel-on-steel frictional
force generated between the pulley and the belt or chain. With
high steel-on-steel friction, it is essential to minimize wear
between these elements. CVT fluids (CVTF) deliver high steelon-steel friction to allow CVTs to be used in the highest torque
applications. A conventional ATF delivers low steel-on-steel
friction, which can lead to belt slippage, wear and severe damage
to the pulley and the belt or chain.

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UNINAP® naphthenic base oils
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Compoundings December 2016 * 19 * Vol. 66 No. 12

Linking Customer's Needs with Refiner's Quality

http://www.infineuminsight.com http://www.unisource-energy.com

ILMA Compoundings December 2016

Table of Contents for the Digital Edition of ILMA Compoundings December 2016