【Anatomy of spark plugs】The composition of automobile spark plugs

Generally speaking, automobile spark plugs mainly consist of the following parts.
Put them on a line↓ (do not produce manufacturing conditions, only show the order of parts and appearance)
Put them together↓ (not to better show the order of parts and appearance)
Vertical laser cutting of finished car spark plugs, plus installation tips, that’s it.
Look at the basic elements and characteristics of each part from top to bottom:
Metal material terminal – also known as wiring nut, high pressure connector, etc. The most common method today is the fusion of metal material terminals and metal material screws, and the alloy screws are immediately independent. However, the initial spark plugs, especially motorcycle spark plugs, fully considered the inconsistency of the terminals, and designed the terminal post as a detachable type. . The metal material terminal is connected to the ignition coil, and the high voltage is introduced into the spark plug.
Aluminium oxide ceramic insulator – Aluminium oxide is a milky white solid with a chemical formula of Al2O3 and a melting point of 2054°C. Automobile spark plugs usually use 95% Al2O3 aluminum oxide, that is, 95 porcelain. The higher the Al2O3 composition, the better the performance, but the more complicated the processing technology, the higher the cost. The key performance characteristics of alumina ceramics are high strength (HRA87 can still maintain HRA82 at 760 ° C and 1200 ° C), good wear resistance, heat resistance, and can be used at a high temperature of 1600 ° C for a long time. It has strong corrosion resistance and maintains good insulating properties. The insulation performance at high frequency is particularly prominent, and each mm thickness can bear the working pressure of more than 8000V. The disadvantages of alumina ceramics are low ductility, poor thermal shock resistance, and can not withstand large changes in ambient temperature. The surface of the spark plug porcelain insulator connection end (package printing end) is glazed to resist environmental pollution. The spark plug stipulates that the insulator has good heat transfer, high insulating layer characteristic impedance, high organic chemical compressive strength and high impact toughness, but this is different from the insulating layer material. At present, this kind of alumina ceramics with a small amount of other materials is the only material choice for spark plug insulators.
Plastic Case – Also known as the case. shell. It is usually made of high carbon steel, which has good heat transfer and high strength. To avoid rust and corrosion. Avoid interacting and bonding with the cylinder head under continuous high temperature. If there is no bite, the surface of the casing will be hot-dip galvanized chromium, nickel, titanium and other anti-corrosion coatings.
Resistors – 99.99% of automotive spark plugs on the market at this stage are all resistors. The specific goal of the resistor is to prevent the high voltage electromagnetic wave from the spark plug from affecting the normal operation of other power circuit parts of the car. For car manufacturers, the EMC test of automotive electronic products is likely to fail. But the car is 20 years old. Motorcycles with low power consumption have low regulations on this matter, so the early car spark plugs. Nowadays, more and more motorcycle spark plugs cannot have a resistor body. Another goal of the resistance is to reduce the amount of current when the spark plug is charged and discharged, thereby reducing the erosion of the electrode of the spark plug by the amount of charge and discharge current. For the above reasons, aside from unique requirements, automotive spark plug manufacturers are not currently able or willing to manufacture automotive spark plugs without a resistor body. The market does not use automotive spark plugs without a resistor body. In turn, a driver or auto mechanic who pretends to master the spark plug asks the merchant: Does your spark plug have a resistor? It’s as if you were asking a phone buyer these days: this new phone isn’t single-core, is it? The spark plug with a resistor will make a slight moisturizing sound on the spark plug equipment, while the spark plug without a resistor will make a very loud popping sound, which is a small thunder, that is, the gas is heated and expanded after being penetrated. sound.
Outer seals – also known as gaskets, are usually made of steel or copper. After installing and tightening the spark plug, the outer sealing ring is flat, and the outer sealing ring has two functions: 1. Sealing, filling the gap between the spark plug and the engine block; 2. Heat transfer, transferring the heat of the spark plug to the engine block.
Whether the spark plug is installed properly can be distinguished according to the appearance of the outer sealing ring.
If the spark plug is installed too loosely, it is very likely that the spark plug is not sealed, the driving is weak, the idle speed is jittery, the thermal adjustment is invalid (damages the spark plug), and common failures are likely to occur. When the spark plug is installed too tightly, it is very likely that the external thread will be deformed, it is very easy to break (the pottery is destroyed), it cannot be disassembled, the thermal adjustment is invalid (the spark plug is damaged), and it is very prone to abnormalities.
The conical spark plug has no outer sealing ring, and the spherical surface of the spark plug closely matches the conical surface of the spark plug hole to meet the sealing heat transfer.
The original spark plug uses the outer sealing ring, and the cone seat spark plug without the sealing ring cannot be used, and vice versa.
Inner sealing ring – usually steel. The inner sealing ring in the finished spark plug has two functions: 1. Sealing, filling the gap between the porcelain insulator and the alloy shell tightly, so as to achieve the standard mark of no leakage; 2. Heat transfer, according to the inner sealing ring, the heat of the porcelain insulator is transferred to the metal shell. The inner sealing ring can be imagined as the silicone ring in the thermal insulation cup, which has the effect of sealing and avoiding heat dissipation.
Insulator Skirt – Also known as Insulator Nose. Porcelain head. Because the heat transfer of alumina ceramics is not as good as that of metal materials, the heat of the spark plug can be adjusted according to the length of the insulator skirt.
Center Electrode – The center electrode of the nickel spark plug consists of an internal structure copper core electrode. The outside is encapsulated with nickel, and the center electrode of the iridium spark plug is composed of a copper core electrode with an internal structure. Externally encapsulated nickel. Welded iridium with electric welding on the tip. Internal structure copper core electrode. The method of encapsulating nickel outside, also known as nickel-copper, because copper has good heat rejection and poor oxidation resistance, nickel has good oxidation resistance and is worse than copper in heat rejection. This type of construction can improve heat rejection and antioxidant capacity. Especially at the tip of the nickel electrode, iridium or platinum can be welded by electric welding, which can improve the performance of the spark plug and the heat resistance of the electrode.
Side electrode – The side electrode is connected to the plastic casing and is the negative stage. When the spark plug is working, the high-voltage line penetrates the mixture of natural gas according to the center electrode, causing a flame, and the current flows from the center electrode to the side electrode, and then according to the spark plug casing. The engine oil pan reaches the grounding device, the negative stage of the rechargeable battery.
Gas Chamber – Also known as the hot chamber, the area between the insulator skirt and the outer shell is the gas chamber, where the mixture of hot and cold gas continues to exchange.

Post time: Mar-10-2022