| 摘要 |
PROBLEM TO BE SOLVED: To provide a spark plug capable of improving combustion efficiency of an internal combustion engine.SOLUTION: When a length between a base point P3 and a base point P4 along an X axis direction is defined as A, a length along a Y axis direction from a straight line connecting the base point P3 and the base point P4 to a base point P7 is defined as B, an average curvature radius of a first curve part is defined as r1, an average curvature radius of a second curve part is defined as r2, an average curvature radius of a third curve part is defined as R1, and an average curvature radius of a fourth curve part is defined as R2, a cross sectional shape of an intermediate part 460 of a ground electrode 40 in a spark plug 100 satisfies B>(A/2), R1>r1, and R2>r2. |
