| 摘要 |
PROBLEM TO BE SOLVED: To provide a spark plug capable of improving ignitability and flame propagation property, and preventing deterioration of exfoliation resistance or the like caused by forming of oxidized scale. SOLUTION: A rare-metal chip 32 on a ground electrode 27 side is protruded from a tip surface 27s of the ground electrode 27 toward an axis line. The rare-metal chip 32 is resistively welded so as a part of itself to be buried to the ground electrode 27, and satisfies a relation A≥0.25 mm, when a protrusion length from the tip surface 27s is set as A(mm). At a boundary extending in a width direction with the rare-metal chip 32 and the tip surface 27s of the ground electrode 27, an expansion part 51 made of a nickel alloy is provided so as at least to cover a center part of the rare-metal chip 32. By the expansion part 51 having a predetermined volume, oxygen intrusion from a border part D is regulated. COPYRIGHT: (C)2009,JPO&INPIT
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