According to the calorific value, there are cold type and hot type, according to the electrode material, there are nickel alloy, silver alloy and platinum alloy, etc., if more professional, the types of spark plugs are generally as follows:
1. Quasi-type spark plug: the skirt of the insulator is slightly retracted into the end face of the shell, and the side electrode is outside the end face of the shell, which is the most widely used.
2. Spark plug with protruding edge: the skirt of the insulator is long, protruding beyond the end face of the shell. It has the advantages of high heat absorption, good anti-fouling ability, and can be directly cooled by the intake air to reduce the temperature, so it is not easy to cause hot spots, so it has a wide range of thermal adaptation.
3. Electrode spark plug: its electrode is very thin, characterized by strong sparks, good ignition ability, and can ensure that the engine can start quickly and reliably in the severe cold season, with a wide thermal range, which can meet a variety of purposes.
4. Seated spark plug: The housing and screw-in threads are made into a cone, so that a good seal can be maintained without gaskets, thereby reducing the volume of the spark plug and making it more beneficial to the design of the engine.
5. Polar spark plug: the side electrodes are generally two or more than two, the advantage is that the ignition is reliable, and the gap does not need to be adjusted frequently, so it is often used in some gasoline engines where the electrode is easy to ablation and the spark plug gap cannot be adjusted frequently.
6. Surface skip type spark plug: that is, the gap type along the surface, it is the coldest type of spark plug, and the gap between the central electrode and the end face of the shell is concentric.
7. Standard and prominent spark plugs
The standard spark plug is a single-sided electrode spark plug with the insulator skirt end slightly below the screw end of the housing, and it uses the traditional ignition end construction of the side-mounted valve engine, which is the most widely used. In order to distinguish it from the "protruding type" that appeared later, this structure is called the "standard type".
The protruding spark plug was originally designed for use with overhead valve engines. Its insulator skirt protrudes from the screw end face of the shell and protrudes into the combustion chamber. It absorbs more heat in the combustion mixture, and has a higher working temperature at the speed to avoid fouling; at high speed, due to the overhead valve, the inhaled air flow is aligned with the skirt of the insulator and cools it, so that the maximum temperature is not increased much, so the thermal range is larger. Prominent spark plugs are not suitable for side-valve engines due to the many bends in the intake tract and the little effect of the airflow on cooling the insulator skirt.
8. Unilateral pole and multi-side pole spark plugs
One obvious flaw of conventional single-sided pole spark plugs is that the side electrode covers the center electrode. When a high-voltage discharge is made between the two poles, the gas mixture at the spark gap will absorb the heat of the spark and form a "fire core" due to the activation of ionization. The place where the fire core is formed is generally close to the side electrode, and the heat will be absorbed more by the side electrode, that is, the "flame suppression" of the electrode, which reduces the spark energy and reduces the flashover performance.