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Characteristics of Aln Insulator Spark Plug
Published November 23, 1995 by Associazione Tecnica Dell'Automobile in Italy
Regarding a spark plug performance, the car manufacturers principally have a carbon fouling and a pre-ignition problem. The improvement in thermal conductivity of a spark plug make it possible to improve the carbon fouling resistance, and the anti pre-ignition properties. We tried to use AlN (aluminum nitride) as a spark plug insulator.
Three types of AlN based ceramics are used which in turn have 80, 170, and 220 W/mK in thermal conductivity. Further, Al2O3 (aluminum oxide) based ceramics is used which has 27 W/mK in thermal conductivity. These ceramics are applied to a spark plug insulator to estimate characteristics of the spark plug.
It is found that the carbon fouling property depends on a nose length of the insulator irrespective of the thermal conductivity. It is also found that when AlN based ceramics are used, the pre-ignition resistant property has remarkably improved compared to Al2O3 insulator. Regarding the pre- ignition resistant property, no significant difference has been perceived among AlN based ceramics of different thermal conductivity. This is mainly because the heat conduction path is predominated by metallic parts such as the metal shell and the packing or the like except for the spark plug insulator itself.