| 摘要 |
The present invention suppresses deformation of a protrusion and a seat in a crimping step, and secures favorable airtightness. This spark plug (1) is provided with an insulator (2) and primary fitting (3). The primary fitting (3) has: a crimping section (19); a seat (16) equipped with a tapered surface (31); a screw (15) having a screw diameter of no greater than M12; and a protrusion (20). The insulator (2) has a locking section (14) locked to the protrusion (20), and is affixed to the primary fitting (3) in the state of being sandwiched between the crimping section (19) and the protrusion (20). When the surface area of the tapered surface (31) is SB (mm2), the length of the seat outer peripheral surface (32) extending from the back end of the tapered surface (31) of the seat (16) is LB (mm), the surface area of the locked surface (33) of the protrusion (20) locked by the locking section (14) is SC (mm2), and the length of the protrusion inner peripheral surface extending from the tip of the locked surface (33) to the tip side of the protrusion (20) is LC (mm), the following are satisfied: SB/SC >= 3.5; SB/LB <= 12.0; and SC/LC <= 12.0. |
