The forces acting on the piston ring include gas pressure, the elastic force of the ring itself, the inertial force of the ring's reciprocating motion, and the frictional force between the ring and the cylinder as well as the ring groove, etc. Due to the action of these forces, the ring will generate basic motions such as axial motion, radial motion and rotary motion.

In addition, due to its movement characteristics, the piston ring is accompanied by irregular movement, which inevitably leads to floating and axial vibration caused by axial irregular movement, radial irregular movement and vibration, and twisting movement, etc. These irregular movements often prevent the piston rings from functioning properly. When designing piston rings, it is necessary to give full play to the favorable movement and control the unfavorable aspects.

Thermal conductivity

The high heat generated by combustion is transferred to the cylinder wall through the piston rings, thus playing a role in cooling the piston. The heat dissipated to the cylinder wall through the piston rings can generally reach 30 to 40% of the heat borne by the top of the piston.

Air tightness

The first function of the piston ring is to maintain the seal between the piston and the cylinder wall and control the air leakage to the minimum. This function is mainly undertaken by the gas ring, that is, under any operating conditions of the engine, the leakage of compressed air and gas must be controlled to the minimum to improve thermal efficiency. Prevent seizing between the cylinder and the piston or between the cylinder and the ring due to air leakage; Prevent malfunctions caused by the deterioration of lubricating oil, etc.

Oil control

The second function of the piston rings is to properly scrape off the lubricating oil adhering to the cylinder wall and maintain a normal fuel consumption. When too much lubricating oil is supplied, it will be sucked into the combustion chamber, increasing fuel consumption. Moreover, due to the carbon deposits produced by combustion, it has a very bad impact on engine performance.

Supportability

Because the piston is slightly smaller than the inner diameter of the cylinder, if there are no piston rings, the piston will be unstable in the cylinder and cannot move freely. Meanwhile, the ring also needs to prevent the piston from coming into direct contact with the cylinder and play a supporting role. Therefore, the piston rings move up and down in the cylinder, and their sliding surfaces are all borne by the rings.

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