Pneumatic Valve Springs
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Pneumatic valve springs are metal
bellows A bellows or pair of bellows is a device constructed to furnish a strong blast of air. The simplest type consists of a flexible bag comprising a pair of rigid boards with handles joined by flexible leather sides enclosing an approximately airtig ...
filled with compressed air used as an alternative to the metal wire springs used to close
valve A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or Slurry, slurries) by opening, closing, or partially obstructing various passageways. Valves are technically Pip ...
s in high-speed
internal combustion engine An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal comb ...
s. This system was introduced in
Formula One Formula One (F1) is the highest class of worldwide racing for open-wheel single-seater formula Auto racing, racing cars sanctioned by the Fédération Internationale de l'Automobile (FIA). The FIA Formula One World Championship has been one ...
in 1986 with the Renault EF-Type.


Concept

Racing engines often fail at high rotational speeds because mechanical springs are unable to retract the valves quickly enough to provide clearance for the
piston A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder (engine), cylinder a ...
. Renault's pneumatic valve technology replaced steel springs with light weight
compressed air Compressed air is air kept under a pressure that is greater than atmospheric pressure. Compressed air in vehicle tires and shock absorbers are commonly used for improved traction and reduced vibration. Compressed air is an important medium for t ...
bellows. These could retract valves more quickly and reduce the possibility of piston-valve interference, as long as pressure could be maintained. Additionally, the amount of seat tension required to keep a coil sprung valve under control results in greater peak lift loading. This results in added stress to the entire
valvetrain A valvetrain is a mechanical system that controls the operation of the intake and exhaust valves in an internal combustion engine. The intake valves control the flow of air/fuel mixture (or air alone for direct-injected engines) into the combu ...
.
Pneumatic Pneumatics (from Greek 'wind, breath') is the use of gas or pressurized air in mechanical systems. Pneumatic systems used in Industrial sector, industry are commonly powered by compressed air or compressed inert gases. A centrally located a ...
systems sharing a common reservoir of pressure retain a more static level of force, controlling the valve effectively without any attendant peak lift load increase. The actuation mechanism is simply a piston and cylinder, similar to a small pneumatic ram. The ''tappet bore'' where a
hydraulic tappet A hydraulic tappet, also known as a hydraulic valve lifter or hydraulic lash adjuster, is a device for maintaining zero valve clearance in an internal combustion engine. Conventional solid valve lifters require regular adjusting to maintain a ...
would normally reside becomes the cylinder, and the retainer assembly becomes the piston. Pressurized air (
nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...
) is pumped into this cylinder which then causes the piston/retainer to rise to the top of cylinder, causing the valve to form an airtight seal with the seat. The compressed gas then becomes the spring, so to speak, but does not have the same traits as springs do at elevated
rpm Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or r⋅min−1) is a unit of rotational speed (or rotational frequency) for rotating machines. One revolution per minute is equivalent to hertz. Standards ISO 80000-3:2019 def ...
. A small light spring is sometimes fitted between the piston and retainer so that when the system is switched off the spring forces the piston down against the bottom of the bore, thus forcing the retainer upwards. This ensures that no crown-to-valve contact occurs when shut down.


Pneumatic valve technology in racing

Pneumatic valve springs gave
Renault Renault S.A., commonly referred to as Groupe Renault ( , , , also known as the Renault Group in English), is a French Multinational corporation, multinational Automotive industry, automobile manufacturer established in 1899. The company curr ...
an advantage with its
turbocharged In an internal combustion engine, a turbocharger (also known as a turbo or a turbosupercharger) is a forced induction device that is powered by the flow of exhaust gases. It uses this energy to compress the intake air, forcing more air into the ...
engines, often said to be one of the most powerful. However, reliability and poor handling of their
chassis A chassis (, ; plural ''chassis'' from French châssis ) is the load-bearing framework of a manufactured object, which structurally supports the object in its construction and function. An example of a chassis is a vehicle frame, the underpart ...
kept the cars from success until 1989, when Renault provided Williams with a new
V10 engine A V10 engine is a ten- cylinder piston engine where two banks of five cylinders are arranged in a V configuration around a common crankshaft. V10 engines are much less common than V8 and V12 engines. Several V10 diesel engines have been pro ...
that began a winning streak. Pneumatic valve springs are also found in several Moto GP motorcycle engines, debuting in 2002 with the Aprilia RS Cube. In 2005, Team Roberts was the first to use pneumatic valves full-time in their uncompetitive KTM powered bike. Today, almost all of the MotoGP teams use pneumatic valve technology on their bikes, including Yamaha,
Suzuki is a Japanese multinational mobility manufacturer headquartered in Hamamatsu, Shizuoka Prefecture, Shizuoka. It manufactures automobiles, motorcycles, all-terrain vehicles (ATVs), outboard motor, outboard marine engines, wheelchairs and a va ...
and
Honda commonly known as just Honda, is a Japanese multinational corporation, multinational Conglomerate (company), conglomerate automotive manufacturer headquartered in Minato, Tokyo, Japan. Founded in October 1946 by Soichiro Honda, Honda has bee ...
.
Ducati Ducati Motor Holding S.p.A () is an Italian motorcycle manufacturing company headquartered in Bologna, Italy. History Barely a month after the official liberation of Italy in 1944, SIATA announced its intention to sell this engine, called ...
uses a desmodromic design.


See also

* 4-stroke cycle engine valves * Helical camshaft


Notes

{{Automotive engine , collapsed Engine valves Springs (mechanical)