| 摘要 |
PROBLEM TO BE SOLVED: To provide a spark plug for internal combustion engine of simple configuration which can ensure stable ignitability regardless of the mounting position with respect to an internal combustion engine.SOLUTION: A spark plug 1 for internal combustion engine has a housing 2, an insulator 3, a central electrode 4, a ground electrode 5 and a tip protrusion 22. The tip protrusion 22 has an air guide face 221. When viewed from the axial direction of a plug, following relations are satisfied entirely; b≥-67.8×(a/D)+27.4, b≤-123.7×(a/D)+64.5, -0.4≤(a/D)≤0.4, 0°<b≤90°, where L is a straight line connecting the center of the standing part 51 of the ground electrode 5 in the circumferential direction of the plug and the center point C of the central electrode 4, M is a straight line of the extension of the air guide face 221, a (separating side from the standing part 51 is positive) is the distance between the intersection A of the straight lines L, M and the center point C of the central electrode 4, b is the angle formed by the straight lines L, M, and D is the diameter of the housing. |
