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The function of the spark plug is to introduce the high-voltage electricity (above 10,000 volts) generated by the ignition coil into the engine cylinder, and generate a spark between the gaps between the electrodes of the spark plug to ignite the mixture. The working environment of spark plugs is extremely harsh. Take the spark plug of an ordinary four-stroke gasoline engine as an example. During the intake stroke, the temperature is only 60°C and the pressure is 90KPa; when igniting and burning, the temperature will instantly rise to 3000°C and the pressure will reach 4000KPa; The alternating frequency of this rapid cooling and rapid heating is very high, which cannot be handled by ordinary materials, and the insulation performance must be guaranteed, so the material requirements for the spark plug are also very strict. The spark plug is small, but its construction is not simple. It has two major parts: an insulator and a metal shell: the metal shell is threaded for screwing into the cylinder; an insulator is installed in the shell, which runs through a center electrode, and there is a wiring nut on the upper end of the center electrode, which is connected from the The high-voltage wire coming from the distribution board; the ground electrode is welded on the lower end face of the casing, and there is a gap of 0.6-1.0 mm between the center electrode and the ground electrode. When the high-voltage power enters the ground through this gap, sparks will burst to ignite the mixture. .