| 摘要 |
A spark plug (100) includes an insulator (10) and a metal shell (50) disposed at an outer periphery of the insulator (10). The metal shell (50) includes a shoulder (56). The insulator (10) includes a trunk portion (302) and a leg (310) formed at the tip end side of the trunk portion (302). The shoulder (56) of the metal shell (50) includes a first shoulder (400) and a second shoulder (402) formed at the tip end side of the first shoulder (400). A distance Da between the tip end PA of the second shoulder (402) and the leg (310) and a distance Db between the tip end PB of the trunk portion (302) and the second shoulder (402) satisfy a relationship of Da/Db ‰¥ 1.1. A distance T between the rear end PC of the first shoulder (400) and the tip end PA of the second shoulder (402) and a distance L between the rear end PC of the first shoulder (400) and a tip end face (57) of the metal shell (50) satisfy a relationship of T/L ‰¤ 0.5. |
