| 摘要 |
PROBLEM TO BE SOLVED: To provide a spark plug for an internal combustion engine having a long life, and capable of enhancing ignitability and adjusting a spark discharge gap easily, and to provide a method of manufacturing the same.SOLUTION: A spark plug 1 for an internal combustion engine has a cylindrical housing 2, a cylindrical insulator 3 held on the inside of the housing 2, a center electrode 4 held on the inside of the insulator 3, and projecting to the tip side of the insulator 3, and an annular ground electrode 5 to be fixed to the tip side of the housing 2. The housing 2 has, at the tip thereof, a diameter reduction part 21 having the inner diameter D4 smaller than that at other part. The ground electrode 5 is arranged to project above the apical surface 211 of the diameter reduction part 21, and to face the outer peripheral surface 41 of the center electrode 4. The outer diameter D1 of the ground electrode 5 is smaller than the outer diameter D0 of the apical surface 211 of the diameter reduction part 21.SELECTED DRAWING: Figure 4 |
