Spark plug, commonly known as flame nozzle, is used to discharge the pulse high-voltage electricity sent by the high-voltage wire (flame nozzle wire), breakdown the air between the two electrodes of the spark plug, and generate an electric spark to ignite the mixed gas in the cylinder. The main types include: standard type spark plugs, edge protruding spark plugs, electrode type spark plugs, seat type spark plugs, pole type spark plugs, surface jumping spark plugs, etc.

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.