| 摘要 |
PROBLEM TO BE SOLVED: To provide a spark plug for an internal combustion engine capable of preventing degradation of ignitability by suppressing inflow inhibition of an air-fuel mixture into a spark discharge gap, and capable of improving durability by improving bonding strength of noble metal chips. SOLUTION: At a ground electrode 27 formed of an inner layer 27A made of a copper alloy and an outer layer 27B made of a nickel alloy, the noble metal chip 32 for the ground electrode is installed so as to be opposed to the noble metal chip 31 for the center electrode. Basically, at the tip part beyond a bent part of the ground electrode 27 formed in a cross-sectional circular shape, a flat face F1 is formed, and the noble metal chip 32 is joined thereto via a pedestal part 51. In a cross section of the ground electrode 27 visually recognized from the tip face side along the axis line CL1, when the shortest distance between the flat face F1 and the inner layer 27A is A, and a distance between the farthest point from the center electrode 5 in the inner layer 27A and the farthest point from the center electrode 5 in the outer layer 27B is B (mm), A/B≤0.7 is satisfied. COPYRIGHT: (C)2009,JPO&INPIT
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