The air ring, also known as the compression ring, is used to ensure the sealing between the piston and the cylinder, and to prevent the high-temperature and high-pressure gas in the cylinder from entering the crankcase; And transfer most of the heat from the piston head to the cylinder wall, avoiding overheating of the piston. The sealing effect of the gas ring is generally related to the number of gas rings, the gasoline engine generally uses 2 air rings, and the diesel engine generally uses 3 gas rings.