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What is a piston ring?

Cross-section of a cylinder in an internal combustion engineFigure 1. Cross-section of a cylinder in an internal combustion engine

Located between the cylinder and the piston, piston rings are necessary components that allow the engine to operate efficiently. Piston rings have four major functions.

Function1.Compression gas sealing

Compression gas sealing
Piston rings maintain gas compression between the piston and the cylinder wall.
Piston rings seal the cylinder so that combustion gas generated at the time of ignition does not leak into the opening between the piston and the cylinder. If combustion gas leaks, the engine cannot output sufficient power, increasing fuel consumption?not good both in terms of economy and the environment.

Function2.Lubricating oil film control

Lubrication oilFigure 2. Lubrication oil
Piston rings usually make necessary minimum lubricating oil film for preventing scuffing.
Since gas ignition is repeated many times, the piston goes up and down inside the engine at a rate of several thousand times per minute. A small amount of oil is poured over the pistons so they move smoothly, with little friction between metal and metal. Piston rings adjust the amount of oil.

Function3.Heat transfer

Heat transferFigure 3. Heat transfer
Piston rings transfer heat from the piston crown to the cylinder.
When gas ignition takes place, the temperature inside a piston reaches approximately 300 C. If heat accumulates inside the piston, the engine may be damaged. For that reason, it is necessary to release the heat build-up. Piston rings help release this heat.

Function4.Support piston in the cylinder

Receiving force for piston ringFigure 4.Receiving force for piston ring
Piston rings prevent the piston from knocking on the cylinder wall.
If the piston inclines inside the cylinder, it may touch inside parts and cause engine failure as well. Piston rings support pistons to allow for smooth up and down motion.

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