| 摘要 |
<p>A spark plug (100) includes an electrode (30) wherein a plurality of fusion regions (60) is formed by melting each other a circular noble metal tip (70) having a diameter of not less than 2 mm and a base material disposed around an outer periphery of the noble metal tip (70). In a particular tip cross section, a total length of portions passing the fusion region (60) on the circumference of a circle A concentric to an outline of the noble metal tip (70) and having a diameter of 90% length of the noble metal tip (70) is not less than 30% of the length of the circumference of the concentric circle A, and a total length of portions on which a circumference of a concentric circle B having the same diameter as that of the outline passes is not less than 30% of the length of the circumference of the circle B.</p> |
