| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a spark plug that can improve breakage resistance of a ground electrode by increasing a cross-sectional area of the ground electrode without changing an area of a front end surface of a metal fitting body. <P>SOLUTION: A spark plug is configured so that one end of a ground electrode 9 is welded to a front end surface 7a of a cylindrical metal fitting body 7. The spark plug satisfies the following equations (1) and (2). That is, K≥1.1 A ...(1); and K≥(D-d)/2 ...(2), where A is a thickness of a part of the front end surface at which a radial thickness is a minimum, d is a maximum inner diameter of the front end surface, D is a minimum outer diameter of the front end surface, and K is a thickness of a part of the front end surface to which the ground electrode is welded. <P>COPYRIGHT: (C)2013,JPO&INPIT |
