The spark plug (spark plugs), commonly known as fire mouth, its role is the high-voltage pulse voltage wire (wire-burner) sent discharging air breakdown between the electrodes of the spark plug, spark ignition in this cylinder in the mixed gas. The basic conditions for high-performance engine: a high energy spark stable, uniformly mixed air-fuel mixture, a high compression ratio. The fuel
1. The action of the spark plug
using internal combustion engines used in cars are generally gasoline and diesel. In the Chinese car market, gasoline accounted for a large proportion. Gasoline engines and diesel engines are not the same, due to the high ignition gasoline (about 400 degrees), thus requiring the use of forced ignition ignite the mixture. By spark discharge phenomenon between the electrodes, a gasoline engine by a timely mixed gas combusting fuel and thus producing power, but it is difficult as a fuel autoignition gasoline even in a high temperature environment, in order to make it necessary to use a combustion timely “fire” to ignite. Here that is the role of spark ignition “spark plug” of.
2. The operating principle of the spark plug
The quality of the overall performance of the engine spark plug is completely dependent on the good or bad spark flashed determined. We tend to engine than as a “heart of the car,” but more than that can spark plug as the “engine of the heart.”
● spark
applying a high voltage generated by the ignition means between the center electrode and the ground electrode of the spark plug, whereby the insulated state between the electrodes is destroyed generating a current, generating spark discharge. Spark energy determine whether the compressed mixed gas firing broke out. Discharge phenomenon is in a very short period of time (about a thousandth of seconds) to complete, and extremely complex. The action of the spark plug is between the electrodes must be within a predetermined period of time effective to produce a strong spark, to become the starting point of the combustion gas mixture.
● ignition
is ignited by a spark caused by the spark discharge between the electrodes of the particles of the active combustion, chemical reaction (acid), and thermal effect, and ultimately the flame kernel is formed. The thermal energy so that the mixture gas around the active, and ultimately the flame kernel is formed in the combustion itself as the center to the periphery of expanding. But if the anti-inflammatory effect electrode is larger than the effect of the flame kernel, the flame kernel will result in the disappearance leads to flame (heat-absorbing electrode that due to the elimination of the flame effect). Further, if the spark gap is wide, the flame kernel becomes larger, fire extinction effect is also reduced, indeed ensure ignition. When the spark gap is too wide, a large discharge voltage is required, thus exceeding the performance limit of the coil, but can not be discharged.
Therefore, we can plug ignition process can be divided into four steps: an ignition coil high voltage across the spark plug electrodes, dielectric breakdown between the electrodes of the high pressure spark is generated; 2 arc after high-temperature heating gas mixture generated flame kernel; 3. the flame kernel becomes larger, the spark plug electrode structure can affect this process, thus affecting the performance of a spark plug ignition; 4. flame core temperature rises to when the mixture is ignited air-fuel mixture ignition. .
3 internal configuration of a spark plug
The spark plug is composed of the following parts: 1, wire nuts; 2, the center electrode; 3, a ground electrode; 4, metal shell body; 5, an insulator. A ground electrode of the spark plug on the connection with the metal casing, the connection to the engine block through the cylinder head screw. The main functions of the insulator spacer and the center electrode a metal housing. Wire nuts on the spark plug is in contact with the high voltage winding portion, the current through wire nuts and the central electrode, dielectric breakdown between the center electrode and the ground electrode spark to ignite the mixture in the cylinder.
4. The spark plug of the type
the high and low calorific value according to points, a cold and hot type type; according to points electrode material, nickel alloy, silver alloy, platinum alloy and the like; if more professional look, the spark plug of the type generally are summarized as follows: [ 123]
1, the quasi-type spark plug: a skirt portion which is slightly retracted into the insulator housing end, outside the housing end side electrode, is the most widely used one.
2, spark plug projecting rim body: an insulator long skirt, projecting outside the housing end. It has an endothermic large, good dirt capacity, etc., and can be directly cooled by the intake air temperature is lowered, and thus is less likely to cause ignition hot, so hot adapt to a wide range.
3-electrode type spark plug: its very fine electrode, characterized by a strong spark ignition capability is good, in the cold season to ensure that the engine can be started quickly and reliably, a wide range of heat, to meet a variety use.
4, Block type spark plug: its housing and screwed into threads are tapered, and therefore the gasket can not maintain a good seal, thereby reducing the volume of the spark plug, the engine is more advantageous.
5, polarity type spark plug: two-side electrode is generally two or more, the advantage of reliable ignition, do not require frequent adjustment of the gap, it is easy and ablation electrodes of the spark plug gap adjustment can not always Some gasoline engines often used.
6, surface flashover type spark plug: the gap along the surface, which is the most cold type spark plug, the gap between the housing and the end face of the center electrode are concentric.
In addition, in order to suppress radio interference automotive ignition system, but also the production of the shielded resistor type and a spark plug. Resistive type spark plug is a spark plug with a built-in resistance 5-10kΩ, the spark plug is shielded with a metal housing shielding the entire spark plug is sealed. Shielded spark plug can not only prevent radio interference, it may also be used for waterproofing, explosion-proof case.
5. The electrode type spark plug
After a hundred years of development, traditional standard spark plugs have been developed a variety of electrode types. The spark plug of a conventional standard one-sided electrode type development sided electrode protrudes from one side up to the development electrode side electrode.
6. The spark plug unilateral
The conventional one-side electrode of the spark plug a flame kernel is located in the center electrode and the side electrode between, more heat is absorbed thereby suppressing side electrode increases the flame kernel, i.e., “quenching action” clear. This reduces the flashover performance of this type of spark plug.
7. Multi-side spark plug
In the 1920s, began a three-pole side of the spark plug, the ground electrode is located three central electrodes around the spark plug electrode is eliminated unilateral center electrode side is blocked by the electrode disadvantage, weakened “quenching action” spark energy larger, have better flashover properties. Here must be clear that, although a plurality of multi-electrode spark plug ground electrode, but only a transient current in the spark by the spark plug ground electrode flashover single, multi-electrode does not occur simultaneously flashover situation
[ 123] 
8. the material of the spark plug
in the process of developing a spark plug incorporated in a variety of rare metals, to provide good heat dissipation capacity, chemical resistance, resistance to electrical corrosion, flashover performance and work performance stability. First we look at the central electrode of the spark plug. A central electrode material undergoes iron, nickel, nickel-based alloys, nickel – copper and a noble metal composite material evolution several conditions.
engines are now mainstream enhanced power turbocharged, direct injection technology or power, compression ratio, the maximum speed are rising. To meet the high-speed, High compression ratio, power demand soaring “three-high” gasoline engines, the spark plug electrode material is further upgraded to use a high melting point of platinum (melting point 1772 deg.] C), iridium (melting point of 2410 ± 40 ℃) as the spark plug electrode material.
Such a spark plug using a noble metal having a high chemical resistance, has made substantial progress in life. Projecting the noble metal spark plug has several advantages:
1 high corrosion resistance so that the ignition electrode is unchanged for a long gap, the gap stabilizing ignition, engine running smoothly, without correcting the engine ignition gap. Data show that the use of platinum spark plugs engine after 160,000 km running, the ignition gap increases only 0.05mm.
2. Since the noble metal electrode has a fine point discharge effect, and therefore easier to ignition, the engine can be run smoothly at low speed conditions.
3. Ultrafine electrode weakened quenching action and the heat absorbing electrode, so that the flame kernel is formed more easily ignite the mixture, so that more complete combustion and lower emissions.
9. The spark plug condition checking
a spark plug firing conditions other than the sealed special test equipment, the following method may be adopted to check .
(1) on the vehicle inspection method
A, the touch method: starting the engine, so that idling touch the plug insulating ceramic parts, such as the temperature rises very soon, indicating that the normal spark plugs, antiIt is not normal.
b, the short-circuit method: starting the engine, so that it idle, then the spark plug with a screwdriver on the cylinder by a short circuit, and listen to the sound of the engine speed changes, changes in sound speed and clear, indicating that the spark plug normal, otherwise unusual.
c, flashover method: Unscrew the spark plug on the cylinder block, with a high-voltage test fire, without spark or weak spark, the spark plug show leakage or inoperative.
(2) the concept of color method
Remove the spark plug was observed, such as russet or rust, showed a spark plug normal; such as stains oil, showed that the spark plug gap disorder or excessive oil, high-voltage short or open; the black smoke was indicative of the spark plug or the wrong type of hot and cold air mixture concentrated, channeling oil; as sediments between the electrode tip, when the oily deposit, described independent cylinder channeling oil to the spark plug, when the black deposits, spark plug fouling and bypass instructions, when gray deposit, is covering the electrode lead additives in gasoline misfire; if severe erosion, such as scar from the top, black burst pattern, melting of the electrode, the spark plug showed damage.
