| 摘要 |
<p>According to the invention, it is provided a spark plug capable of increasing a welding strength between a leading end of a metal shell and a base end of a ground electrode to prevent fracture of a welded part due to vibrations and the like even when reducing a diameter of the metal shell. The spark plug 100 satisfies a relation of S2 ‰§ S wherein S2 is a sectional area of the welded part between the metal shell 11 and the ground electrode 14, the sectional area S2 being cut off by a plane including a leading end surface of the metal shell 11, and S is a sectional area of the ground electrode 14, the sectional area S being cut off by a plane passing to the most leading end of a boundary in the axial direction between the ground electrode 14 and the welded part and perpendicular to the axial direction.</p> |
