| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a spark plug having a protrusion made of same material as that of a ground electrode in which heat dissipation performance of the protrusion is improved and as a result, wear resistance is improved. <P>SOLUTION: The spark plug 1 includes a center electrode 5 of bar shape extending in an axis CL1 direction, an insulator 2 of nearly cylindrical shape installed at the outer circumference of the center electrode 5, a body fitting 3 of nearly cylindrical shape installed at the outer circumference of the insulator 2, and a ground electrode 27 which extends from the tip part 26 of the body fitting 3 and of which tip part forms a spark discharge gap 35 between the tip part of the center electrode 5. A protrusion 28 which projects to the center electrode 5 side at the tip part of the ground electrode 27 and forms the spark discharge gap 35 between the tip part of the center electrode 5 is formed of the same material as that of the ground electrode 27. Further, at least the average crystal particle size of the protrusion 28 is 20μm or more and 200μm or less. <P>COPYRIGHT: (C)2010,JPO&INPIT</p> |
