SPARK PLUG FOR INTERNAL COMBUSTION ENGINE

摘要

A spark plug for an internal combustion engine has a housing, an insulator, a center electrode, a ground electrode, and a tip projecting portion. The tip projecting portion has an air guiding surface. In the spark plug, when viewed from a plug axial direction, a straight line that connects the center, in the plug circumferential direction, of the erect portion of the ground electrode and a center point of the center electrode is a straight line. An extension line of the air guiding surface is a straight line. A distance between an intersection, between the straight line and the straight line, and the center point of the center electrode is a (positive towards the side moving away from the erect portion. An angle formed by the straight line and the straight line is b. A diameter of the housing is D. At this time, all of b≧−67.8×(a/D)+27.4, b≦123.7×(a/D)+64.5, −0.4≦(a/D)≦0.4, and 0°

主权项

1. A spark plug for an internal combustion engine comprising:
a cylindrical housing having an axial direction; a cylindrical insulator that is held inside the housing; a center electrode that is held inside the insulator so that a tip portion projects outwards; a ground electrode that projects from a tip portion of the housing towards a tip side of the housing along the axial direction and forms a spark discharge gap between the ground electrode and the center electrode; and a tip projecting portion that projects from the tip portion of the housing towards the tip side, at a position differing from that of the ground electrode wherein the tip projecting portion has a flat air guiding surface that faces the ground electrode side in a plug circumferential direction, and when viewed from a plug axial direction, when a straight line that connects the center, in the plug circumferential direction, of the erect portion of the ground electrode standing erect from the housing and a center point of the center electrode is a straight line, an extension line of the air guiding surface is a straight line, a distance between an intersection, between the straight line L and the straight line, and the center point of the center electrode is a, an angle formed by the straight line and the straight line M is b, a diameter of the housing is D, and the distance a is positive towards the side receding from the erect portion of the ground electrode and negative towards the side approaching the erect portion, all of expression to expression below are satisfied:
b≧−67.8×(a/D)+27.4   (1)b≦−123.7×(a/D)+64.5 (2)−0.4(a/D)≦0.4   (3)0°≦190°  (4)