What Are The Common Types Of Spark Plugs?

According to calorific value, there are cold type and hot type; According to the electrode material, there are nickel alloy, silver alloy and platinum alloy; If it is more professional, the types of spark plugs are generally as follows:
1. Quasi-type spark plug: Its insulator skirt is slightly shrunk into the end face of the housing, and the side electrode is outside the end face of the housing, which is the most widely used type.
2. Spark plug with protruding edge: The insulator skirt 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 reduce the temperature, so it is not easy to cause hot ignition, so the thermal adaptation range is wide.
3. Electrode type spark plug: Its electrode is very thin, characterized by strong spark and good ignition ability. It can also ensure that the engine can start quickly and reliably in severe cold season, with a wide thermal range and can meet various purposes.
4. Seat type spark plug: Its shell and screw-in thread are made into a cone, so it can maintain good sealing without gasket, thus reducing the volume of spark plug, which is more beneficial to engine design.
5. Pole type spark plug: The side electrode is generally two or more. The advantage is reliable ignition, and the gap does not need to be adjusted frequently. Therefore, it is often used in some gasoline engines where the electrode is easy to ablate and the spark plug gap cannot be adjusted frequently.
6. Surface spark plug: That is, surface gap type. It is the coldest type of spark plug. The gap between its central electrode and the end face of the shell is concentric.
7. Standard and protruding spark plugs
The standard spark plug is a single-side electrode spark plug whose insulator skirt end is slightly lower than the threaded end of the housing. It uses the traditional ignition end structure that is most widely used in side-mounted valve engines. In order to distinguish it from the later "prominent type", this structure is called "standard type".
Protrusive spark plugs were originally designed for overhead valve engines. Its insulator skirt protrudes from the threaded end face of the shell and extends into the combustion chamber. It absorbs more heat in the combustion mixture, and has a higher working temperature at rest speed to avoid contamination; At high speed, because the valve is overhead, the inhaled air flow aims at the insulator skirt and cools it, so that the maximum temperature is not increased much, so the thermal range is large. The protruding spark plug is not suitable for the side-mounted valve engine because of the many bends in the inlet and the little cooling effect of the air flow on the insulator skirt.
8. Single-pole and multi-pole spark plugs
The traditional single-pole spark plug has an obvious defect, that is, the side electrode covers the center electrode. When high-voltage discharge occurs between the two poles, the mixture at the spark gap will absorb the spark heat and be activated by ionization to form a "fire core". The place where the fire core is formed is generally close to the side electrode, and the heat will be absorbed by the side electrode more, that is, the "flame suppression effect" of the electrode, which reduces the spark energy and reduces the fire jump performance.
Thus, in the 1920s, three-pole spark plugs appeared. Compared with single side electrode, the spark gap of multiple side electrodes is composed of the section of multiple side electrodes (punched into a circular hole) and the cylindrical surface of the central electrode. This side-mounted spark gap eliminates the defect that the side electrode covers the central electrode, and increases the "accessibility" of the spark. The spark energy is large, and it is easier to penetrate into the cylinder, which helps to improve the combustion condition of the mixture and reduce exhaust emissions. Because the multiple side poles provide multiple ignition channels, the service life is extended and the ignition reliability is improved. It must be pointed out here that the instant of discharge can only be the flashover of one channel, and it is impossible to flashover of multiple poles at the same time. The discharge process of high-speed photography proves this point.
The suffix letters (letters after the calorific value number) D, J and Q in the domestic spark plug model indicate the two side pole, three side pole and four side pole respectively.
9. Nickel base alloy and copper core electrode spark plug
The most basic requirements for the electrode extending into the combustion chamber are ablation resistance (electrical and chemical corrosion) and good thermal conductivity. With the development of material science and technology, electrode materials have experienced the evolution of iron, nickel, nickel-based alloys, nickel-copper composites and precious metals. Nickel base alloys are the most commonly used nowadays. Generally, the thermal conductivity of pure metal is better than that of alloy, but the chemical corrosion reaction of pure metal (such as nickel) to combustion gas and solid deposits formed is more sensitive than that of alloy. Therefore, the electrode material is made of nickel base and added with elements such as chromium, manganese and silicon. Chromium improves the resistance to electric corrosion, while manganese and silicon improve the resistance to chemical corrosion, especially the resistance to sulfur oxide with great harm.
10. Ordinary and resistance spark plugs
As a spark discharge generator, spark plug is a broadband continuous electromagnetic radiation interference source. In order to suppress the strong interference of electromagnetic radiation on the radio electric field caused by fire jump, protect radio communication and prevent the misoperation of on-board electronic devices, countries around the world have accelerated the development of resistance spark plugs since the 1960s. China has also issued a series of mandatory national standards for electromagnetic compatibility, which strictly limits the radio interference characteristics of vehicle devices driven by spark plug ignition engines, so the demand for resistive spark plugs has also increased significantly. There is no big difference between the resistance type spark plug and the ordinary type in structure, just changing the conductor sealant in the insulation body to the resistance sealant.