Manufacturing method of resistor-incorporated spark plug

Abstract

In a spark plug (100), the resistor composition constituting a resistor (15) contains semiconductive ceramic particles, offering a superior load life characteristic. Also, the value of (α2−α1)/α1>=−0.30, where a value of electric resistance between a terminal (13) and a center electrode (3) is α1 at 20° C. and α2 at 150° C., so that deterioration of the radio frequency noise prevention performance at high temperatures can be effectively suppressed. The resistor composition contains semiconductive ceramic particles whose temperature coefficient of electric resistance shows a positive value, or a negative value of relatively small absolute value, (e.g., TiO2 particles having a rutile type crystalline structure, titanate or zirconate of alkali earth metal elements, titanium suboxide, etc.), or titanium metal. Thus, the invention provides a resistor-incorporated spark plug which is enabled to offer a stable load life characteristic even when a high load acts thereon, and which is unlikely to deteriorate in the radio frequency noise prevention performance even under high temperatures.

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