| 摘要 |
PROBLEM TO BE SOLVED: To improve dirt resistance and to hardly generate channeling by forming an erosion suppressing layer on the surface of the tip section of an insulator, and suppressing the erosion of the surface of the tip section of the insulator caused by a creeping spark discharge. SOLUTION: One or more kinds of Fe, Cr, Cu are included as insulator erosion suppressing components at least in the ignition faces 2b, 4a of the central electrode 2 and ground electrode 4 of a spark plug. When the spark plug is fitted to an internal combustion engine and the engine is operated at a high speed or a high load of a fixed value, an erosion suppressing layer 30 including the insulator erosion suppressing components is formed on the surface of the tip section of an insulator 3 as a spark discharge occurs. The surface of the tip section of the insulator 3 is protected by the erosion suppressing layer 30 during the creep discharge caused by flying sparks in a second gap g2, and the progress of channeling is prevented or suppressed effectively. The erosion suppressing layer 30 is mainly made of an oxide compound containing Cr, Cu as cation components preferably.
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