| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a spark plug capable of restraining horizontal jump and the like of discharge by improving an anti-fouling property. <P>SOLUTION: A spark plug has a center electrode extending in an axial line direction, a cylindrical insulator provided on an outer periphery of the center electrode, and a cylindrical main body metal fitting provided on an outer periphery of the insulator. The insulator has one or more grooves opened outward in a radial direction from the center electrode at its tip. Total of volumes occupied by a space of a groove portion from the tip of the insulator to a bottom of the groove is 1/9 or more and 1 or less to a volume of the insulator at a portion from the tip of the insulator to the bottom of the groove. <P>COPYRIGHT: (C)2013,JPO&INPIT |
