1. Steel shell: the lower part of the steel shell is thin thread, which is used to fit with the spark plug hole of the cylinder head, and the upper part is provided with outer six-square nut, which is used to install the spark plug sleeve, so as to tighten or screw out the spark plug [3].

2. The metal rod is the central electrode. The lower end of the metal rod is in contact with the upper end of the central electrode through the conductor glass, and the upper end of the metal rod is equipped with a wiring nut [3].

3. There is a high alumina ceramic insulator between the steel shell and the central electrode to insulate the central electrode when it is energized [3].

4. The bottom part of the steel shell is provided with a bent side electrode [3].

Spark plug mechanism drawing

Spark plug mechanism drawing

5. The middle of the outer steel case has a copper washer 


Under the action of high voltage, the air between the center electrode and the side electrode of the spark plug will rapidly ionize, forming positively charged ions and negatively charged free electrons. When the voltage between the electrodes reaches a certain value, the number of ions and electrons in the gas increases like an avalanche, so that the air loses its insulation, and the gap forms a discharge channel, and the phenomenon of "breakdown" occurs. At this point, the gas forms luminaries, or sparks. As it heats up and expands, it makes a "pop" sound. The temperature of this spark can reach 2000 ~ 3000℃, which is sufficient to ignite the mixture in the cylinder combustion chamber