The function of the spark plug is to introduce tens of thousands volts of high-voltage electricity into the combustion chamber and generate electric spark to ignite the mixture, and the ignition system and fuel supply system cooperate with the engine to work, to a great extent, to determine the performance of the engine.
The main part of the spark plug is the insulator, shell, screw and electrode wiring. Insulators must have good insulation and thermal conductivity, high mechanical strength, can withstand high temperature thermal shock and chemical corrosion, the material is usually 95% alumina ceramic. Shell is a steel parts, the function is to fix the spark plug on the cylinder head. Shell hexagonal thread size has been incorporated into the ISO international standards. The spark plug electrode includes a center electrode and a side electrode with a spark gap therebetween. The size of the gap directly affects the engine start, power, work stability and economy. Reasonable gap and ignition voltage. Electrode materials must have good resistance to electrical erosion (spark erosion) and corrosion (chemical - hot corrosion), and should have good thermal conductivity. Between the center electrode and the wiring screw conductor glass sealant, it is necessary to be able to conduct electricity, but also to withstand the high pressure mixture of combustion, while ensuring its sealing.