Patent ID: 9160146
Filing Date: 2015-10-13
Classification: H01T

Abstract:
1. A spark plug comprising: an electrode that includes a noble metal tip and a base material, wherein the noble metal tip is formed in a circular cross-sectional shape and contains a noble metal, the base material is disposed around an outer periphery of the noble metal tip, the noble metal tip is welded to the base material to form a fusion region extending from the base material to the noble metal tip, the noble metal tip has a diameter of not less than 2 mm, in a cross section perpendicular to a central axis CL1 of the noble metal tip and passing a point closest to the central axis CL1 in the fusion region, the fusion region includes a plurality of central fusion portions formed at an inner side with respect to a circumference of a circle A concentric to an outline of the noble metal tip, the concentric circle A having a diameter corresponding to a length of 90% of the diameter of the noble metal tip, a concentric circle B is a circle concentric to the outline of the noble metal tip and having the same diameter as the noble metal, a total of lengths on the concentric circle A passing through the fusion region is not less than 30% of the length of the circumference thereof, and a total of lengths on the concentric circle B passing through the fusion region is not less than 30% of the length of the circumference thereof, and in the fusion region, a content ratio of a metal constituting the noble metal tip in a portion overlapping the circumference of the concentric circle B in the cross section is not more than 10 mass %.