| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a spark plug for an internal combustion engine capable of improving ignitability and a lifetime while maintaining the resistance to carbon fouling, and the attachment structure thereof. <P>SOLUTION: A spark plug 1 includes a housing 2, an insulator 3, a center electrode 4, a main ground electrode 51, a first sub ground electrode 52, and a second sub ground electrode 53. The first sub ground electrode 52 and the second sub ground electrode 53 are disposed facing one another. When Hc represents the protrusion length of the center electrode 4, Gm represents the size of a main gap 61, Hs1 represents the protrusion length of the first sub ground electrode 52, Hs2 represents the protrusion length of the second sub ground electrode 53, Gs1 represents the plug radial direction length of a first sub gap 62, Gs2 represents the plug radial direction length of a second sub gap 63, and Gg represents the plug radial direction distance between the outer circumference angle part 311 and the inner circumference angle part 312 of an insulator tip 31, the following conditions are satisfied: Hs1<Hc+Gm, Gm<Gs1+Gg, Gm<Gs2+Gg, Hs2≥Hs1, and Hc<Hs2. <P>COPYRIGHT: (C)2013,JPO&INPIT |
