| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a miniaturized spark plug excelling in vibration resisting performance and resistor load life characteristics by enhancing adhesiveness between a resistor and a conductive glass seal layer. Ž<P>SOLUTION: A center electrode 13 and the resistor 18 arranged in a through-hole 16 of an insulator 12 are joined by the conductive glass seal layer 19 provided between them. The diameter D of the conductive glass seal layer 19 joined to the resistor 18 is 1.9-3.3 mm (1.9 mm≤D≤3.3 mm). A joint surface 23 of the conductive glass seal layer 19 joined to the resistor 18 is formed in bowl shape, and Sa/S1 obtained based on a surface area Sa of the joint surface 23 and a cross-sectional area S1 of the conductive glass seal layer 19 is 1.1 or more (Sa/S≥1.1). Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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