| 摘要 |
A spark plug is disclosed, in which a center electrode has, at the end thereof which forms a spark discharge gap, a noble metal chip which has a straight rod portion of 1.0 mm or less in diameter and 0.2 mm or more in length; width of coverage K of a ground electrode on which a rectangular noble metal chip is welded satisfies a relation of -d<=K<=0.5 mm (where, d represents the diameter of the end face of the center electrode); and width w of a portion of the discharge plane 111A which falls within a range corresponded to the axial extension of the end face 22B of the noble metal chip 22 provided on the center electrode 2 satisfies a relation of w<2.1-K (in mm), where K is the foregoing width of coverage.
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