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| Valve (Image credit: rexresearch.com) |
Valve is a device to close and open a passage in motor vehicle engines. Two valves are used for each cylinder - An inlet or intake valve and an exhaust valve. Fuel is admitted to the cylinder by the inlet valve, and the burnt gases escape from the exhaust valve. When closed, the valve must seal the combustion space tightly. The valves are usually made of Austenitic stainless steel which is a corrosion and heat resisting material. Exhaust valve is usually made of silchrome steel which is an alloy of silicon and chromium with unusual resistance to heat. Inlet valve being subjected to less heat is usually made of nickel chromium alloy steel. The valves used in modern passenger car engines are termed as poppet or mushroom valves.
Valve mechanism:
Valves are operated by cams mounted on a camshaft. The camshaft gets motion from crankshaft. As the camshaft turns the cam operates the valves. According to the location of the valves, the valve mechanism are of two types:
- Valve mechanism for operating the valve in engine block ( Straight poppet valve)
- Valve mechanism for operating the valve in cylinder head ( Overhead poppet valve)