| 摘要 |
PROBLEM TO BE SOLVED: To improve the welding strength between a ground electrode and a main metal fitting.SOLUTION: The spark plug comprises: a rod-like center electrode extending in the axial direction; an insulator which has an axial hole extending in the axial direction and holds the center electrode in the axial hole; a main metal fitting which holds a part of the insulator by surrounding in the circumferential direction; and a ground electrode whose base end is welded to the main metal fitting. The main metal fitting and the ground electrode are joined through a melting section formed by melting both the ground electrode and the main metal fitting by welding. Where the thickness of a portion whose thickness is smallest among the thicknesses of the melting section in the axial direction is determined as A, the length of the boundary of melting on the ground electrode side which is the boundary between the melting section and the ground electrode in a cross section parallel to the axis line including the center line of the ground electrode is determined as B, and the thickness of the ground electrode is determined as C. Conditions A≥0.2 mm and B>C are satisfied. |
