There is this simple formula
which is not only dominant but also respected among automobile engineers. The
formula says that “Less friction + less weight = less fuel consumption” which
in turn also means fewer CO2 emissions. This formula is a dominant theme today
in the development departments of automotive manufacturers and their suppliers.
It has long ceased being all about grand savings and has instead become a
matter of highly detailed work, since every saved gram of CO2 counts in the
final analysis. This was stated in a press release issued by ContiTech.
This is one of the reasons why the timing belt
in the timing assembly has gained significantly in importance once again in
recent years. Volkswagen is again fitting belts instead of chains in the Golf
VII and Audi A1. And other manufacturers too are increasingly designing their
new engines for high-tech drive belts made from rubber and plastic, because
they know that belts have distinct advantages over chains in reducing fuel
consumption and CO2 emissions from combustion engines.
According to FEV GmbH, an
independent engine designer, the belt drive lowers fuel consumption compared to
the chain, and therefore reduces CO2 emissions. In a 1.6 litre gasoline engine,
for example, the belt drive reduces fuel consumption by more than 1pc and saves
up to 1.5 grams of CO2 per kilometre. "Belt drives are lighter and run a
lot more quietly too. Belts don't tend to lengthen either," says Hermann
Schulte, head of Timing Belt Development at the ContiTech Power Transmission
Group. "A significant advantage, because a lengthening chain alters the
engine timing. As a result, consumption increases and performance drops.
Emissions levels are quickly exceeded." In endurance tests, a belt
lengthened by just 0.1% after 240,000 kilometers of service life – the figure
was five times greater with a chain.
Many large automotive manufacturers in Europe
are now making use of the benefits of timing belts in their engines and this
number is growing. ContiTech supplies dry-running timing belts to manufacturers
including Audi, Volkswagen, Volvo, Ford, Opel, and PSA. It's not only camshafts
that are controlled by timing belts, but injection systems and oil pumps too.
ContiTech developers are already considering whether to use a timing belt to
drive balance shafts as well and therefore make spur gears superfluous. And
their focus is on unconventional yet safe solutions, such as the
"Since the start of 2013,
the ContiTech Power Transmission Group has been part of the group of series
production suppliers for these applications. Timing belts are already in use
for oil pump and timing drives in the newer Ford, PSA, and Volkswagen
engines," says Ralf Berger, head of Key Account Management and Application
Engineering at the ContiTech Power Transmission Group.
What was previously
unthinkable is today running along without a hitch in series production. To
achieve this, ContiTech has adapted the elastomer, the fabric, and the cord to
the new environment. In addition to polyamide and aramid fabric with a Duralon
coating containing Teflon, an ultra-durable rubber compound made from ACN-HNBR
(hydrogenated acrylonitrile butadiene rubber), as well as E-glass and K-glass,
is also being used for high length stability. Because of these special
components, even impurities in the oil cannot harm the belt, whereas simple
soot particles in the oil can destroy chains.
The advantage of the timing
belt in oil is that it has a narrower construction than the dry-running version
and it is even quieter. In the case of a crankshaft pulley with 19 teeth, no
noise can be detected, even with the engine operating under full load, because
the oil not only reduces friction, it absorbs sound as well. This is important
for the simple reason that the increasingly popular downsized engines generally
run less smoothly. Here is where a belt can help minimize vibration and make
driving a pleasant experience despite the use of environmentally friendly technology.
Benchmark trials also
demonstrate that belts today have at least the same and often even better
properties than chain drives with their hydraulic tensioners and plastic
guides. This is why developers are no longer concentrating on durability – this
has long been a given. In on-road tests, the belts still ran without a hitch
even after 300,000 kilometers.
The question today is one of
making the belts even narrower – every millimetre counts, because installation
space in vehicles is becoming ever tighter. "This is where the belt has
another advantage. The engine designer has more flexibility in designing the
belt drive than with a chain," says Hermann Schulte. The aim is to reduce
belts for the camshaft drive in the next generation of engines from today's 16
– 20 mm width to 14, 12 or even 10 mm. Belts for oil pump drives currently
measure just 9 mm – and so are as narrow as a chain.
Yet when it comes to the issue of reducing
weight, it is not enough to consider the belt alone. Tensioners, idlers, and
toothed pulleys are critical too. This is why developers at the joint venture
company ContiTech-INA are already working on drives that can make do with
simpler, and therefore lighter, tensioning systems. Or even none at all. In
this way more grams can be saved and the CO2 emissions ultimately reduced even
further. Vehicle manufacturers are backing this trend with their development
commissions and in so doing reveal their confidence in ContiTech's many years
of experience in the field of drives.
The many advantages offered by modern timing
belts, including their long service life, reduced friction and reduced noise,
will again expand the market share of timing belts. Experts estimate that it
will include at least two thirds of European vehicles in 2015 and over 70% in
2017. The share of belts running in oil will more than double from today's 8%
to over 20%. A development that will benefit the environment and motorist
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