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Pneumatic valve springs are metal bellows filled with compressed air [1] used as an alternative to the metal wire springs used to close valves in high-speed internal combustion engines. This system was introduced in Formula One in 1986 with the Renault EF-Type.
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. Renault's pneumatic valve technology replaced steel springs with light weight compressed air 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. Pneumatic 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 would normally reside, becomes the cylinder, and the retainer assembly becomes the piston. Pressurized air (nitrogen) 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. 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 springs gave Renault an advantage with its turbocharged engines, often said to be one of the most powerful. However, reliability and poor handling of their chassis kept the cars from success until 1989, when Renault provided Williams with a new V10 engine 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 and Honda. Ducati uses a desmodromic design.
While pneumatic valve springs have become standard in Formula One engines, a number of manufacturers have been researching computer-controlled electromagnetic valve actuation (EVA) using no camshaft, to reduce moving parts while improving valve control. In particular, Renault and Freevalve (under supervision of Koenigsegg) are two companies interested in developing the technology for production road vehicles.
The camshaft is a rotating object— usually made of metal— that contains pointed cams, which converts rotational motion to reciprocal motion. Camshafts are used in internal combustion engines, mechanically controlled ignition systems and early electric motor speed controllers. Camshafts in automobiles are made from steel or cast iron, and are a key factor in determining the RPM range of an engine's power band.
A four-strokeengine is an internal combustion (IC) engine in which the piston completes four separate strokes while turning the crankshaft. A stroke refers to the full travel of the piston along the cylinder, in either direction. The four separate strokes are termed:
An actuator is a component of a machine that is responsible for moving and controlling a mechanism or system, for example by opening a valve. In simple terms, it is a "mover".
A desmodromic valve is a reciprocating engine poppet valve that is positively closed by a cam and leverage system, rather than by a more conventional spring.
The Wärtsilä RT-flex96C is a two-stroke turbocharged low-speed diesel engine designed by the Finnish manufacturer Wärtsilä. It is designed for large container ships that run on heavy fuel oil. Its largest 14-cylinder version is 13.5 metres (44 ft) high, 26.59 m (87 ft) long, weighs over 2,300 tons, and produces 80,080 kW (107,390 hp). The engine is the largest reciprocating engine in the world.
In internal combustion engines, variable valve timing (VVT) is the process of altering the timing of a valve lift event, and is often used to improve performance, fuel economy or emissions. It is increasingly being used in combination with variable valve lift systems. There are many ways in which this can be achieved, ranging from mechanical devices to electro-hydraulic and camless systems. Increasingly strict emissions regulations are causing many automotive manufacturers to use VVT systems.
A tappet is most commonly a component in an internal combustion engine which converts the rotating motion of the camshaft into linear motion of the valves, either directly or indirectly.
Valve float is an adverse condition which can occur at high engine speeds when the poppet valves in an internal combustion engine valvetrain do not properly follow the closure phase of the cam lobe profile. This reduces engine efficiency and performance. There is also a significant risk of severe engine damage due to valve spring damage, and/or pistons contacting the valves, and/or catastrophic lifter and cam lobe failure, especially with roller lifters.
In a piston engine, the valve timing is the precise timing of the opening and closing of the valves. In an internal combustion engine those are usually poppet valves and in a steam engine they are usually slide valves or piston valves.
A camless or free-valve piston engine is an engine that has poppet valves operated by means of electromagnetic, hydraulic, or pneumatic actuators instead of conventional cams. Actuators can be used to both open and close valves, or to open valves closed by springs or other means.
Pneumatic cylinders are mechanical devices which use the power of compressed gas to produce a force in a reciprocating linear motion.
A valvetrain or valve train 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 into the combustion chamber, while the exhaust valves control the flow of spent exhaust gasses out of the combustion chamber once combustion is completed.
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 small clearance between the valve and its rocker or cam follower. This space prevents the parts from binding as they expand with the engine's heat, but can also lead to noisy operation and increased wear as the parts rattle against one another until they reach operating temperature. The hydraulic lifter was designed to compensate for this small tolerance, allowing the valve train to operate with zero clearance—leading to quieter operation, longer engine life, and eliminating the need for periodic adjustment of valve clearance.
A pneumatic circuit is an interconnected set of components that convert compressed gas into mechanical work. In the normal sense of the term, the circuit must include a compressor or compressor-fed tank.
A control valve is a valve used to control fluid flow by varying the size of the flow passage as directed by a signal from a controller. This enables the direct control of flow rate and the consequential control of process quantities such as pressure, temperature, and liquid level.
A valve actuator is the mechanism for opening and closing a valve. Manually operated valves require someone in attendance to adjust them using a direct or geared mechanism attached to the valve stem. Power-operated actuators, using gas pressure, hydraulic pressure or electricity, allow a valve to be adjusted remotely, or allow rapid operation of large valves. Power-operated valve actuators may be the final elements of an automatic control loop which automatically regulates some flow, level or other process. Actuators may be only to open and close the valve, or may allow intermediate positioning; some valve actuators include switches or other ways to remotely indicate the position of the valve.
An angle seat piston valve is a pneumatically-controlled valve with a piston actuator providing linear actuation to lift a seal off its seat. The seat is set at an angle to provide the maximum possible flow when unseated. Angle seat piston valves are particularly suited to applications where high temperatures and large flow rates are required, such as steam or water. When used in reverse some models of angle seat piston valve will eliminate water hammer when operated.
Jacobs Vehicle Systems, Inc. is an American company that engineers, develops and manufacturers commercial vehicle retarding and valve actuation technologies. The company produces light-duty, medium-duty, and heavy-duty engine brakes, recreational vehicle exhaust brakes, aftermarket parts and tune-up kits to heavy-duty diesel engine manufacturers in its domestic market in America, as well as in Asia and Europe. The company was incorporated in 1990 and is based in Bloomfield, Connecticut. Jacobs Vehicle Systems, Inc. operates as a subsidiary of Altra Industrial Motion Corporation. On 9th February 2022, Cummins, Inc. announced an agreement to acquire Jacobs Vehicle Systems from Altra.
A bash valve is a valve within a piston engine, used to control the admission of the working fluid. They are directly actuated valves, operated by contact between the piston and the valve tip.
The Maybach VL I was an Otto cycle V-12 engine, made from 1924 in Germany. The airship LZ 126 was powered by five VL I engines which emphasised reliability and low fuel consumption.