| 摘要 |
PROBLEM TO BE SOLVED: To achieve further longer life of a spark plug for an internal combustion engine by suppressing elevation of a discharge voltage in the case consumption of an electrode progresses. SOLUTION: A noble metal chip 31 of the center electrode is constituted of a plate-shaped part 31a and a leg part 31b. At this time, the leg part 31b is extended and installed in the axial direction from the peripheral part of the plate part 31a, and the cross sectional area of a cross sectional face along the diameter direction of the leg part 31b is made smaller compared with the cross sectional area of the plate part 31a. On the other hand, an engagement part 32a with a smaller diameter is integrally formed at the tip of an electrode base material 32, and so that the outside face of the engaging part 32a and the inside face of the leg part 31b are made to be contacted, the noble metal chip 31 is welded and fixed against the electrode base material 32 at a fusing part 33 of the tip outer edge part of that leg part 31b. COPYRIGHT: (C)2007,JPO&INPIT
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