The working principle of a spark plug is that the insulation skirt of a standard spark plug is slightly shrunk into the end face of the housing, and the side electrode is outside the end face of the housing, making it the most widely used type. The insulation skirt of the edge protruding spark plug is longer and protrudes beyond the end face of the housing. It has the advantages of large heat absorption and good anti fouling ability, and can be directly cooled by the intake air to lower the temperature, so it is not easy to cause hot ignition, so the thermal adaptation range is wide.

Spark plugs are key components of engines, consisting of a steel shell, central electrode, insulator, and side electrode. The lower part of the steel shell has a fine thread, which is used to fit with the spark plug hole in the cylinder head. The upper part has an outer hexagonal nut, which is used to fit the spark plug sleeve to tighten or unscrew the spark plug. The central electrode is a metal rod, with the lower end in contact with the upper end of the central electrode through a conductor glass body. The upper end of the metal rod is equipped with a wiring nut. There is a high alumina ceramic insulator between the steel shell and the central electrode, which insulates the central electrode when energized. The bottom part of the steel shell is equipped with curved side electrodes. There is a copper washer in the middle of the outer part of the steel shell.