| 摘要 |
PROBLEM TO BE SOLVED: To provide a spark plug for internal combustion engine of simple configuration that can ensure stabilized ignitability, regardless of the mounting orientation to an internal combustion engine.SOLUTION: A spark plug 1 has a housing 2, an insulator 3, a center electrode 4, a ground electrode 5 and a tip protrusion 22, and the tip protrusion has a wind guide surface 221. When viewing from the plug axis direction, following relations are satisfied; b≥-67.8×(a/D)+27.4, b≤-123.7×(a/D)+64.5, -0.4≤(a/D)≤0.4, 0°<b≤90°, where (a) is the distance between the intersection of a straight line L connecting the center of the standing portion 51 of the ground electrode 5 and the center point C of the center electrode, and a straight line M that is the extension line of the wind guide surface, b is the angle formed by the straight lines L and M, and D is the diameter of the housing. When viewing from the plug axis direction, following relation is satisfied for the angle &thetas; of 0-30°; 0.8≤r/R≤1, where r is the distance between the central axis and the outer side of the ground cross-section, and R is the distance between the central axis and the outer corner in the protrusion cross-section. |
