| 摘要 |
<P>PROBLEM TO BE SOLVED: To more reliably prevent dropout of a chip, and maintain an effect for improving ignitability for a long time by restraining spark discharge between a melting section and a center electrode. <P>SOLUTION: A spark plug 1 comprises a center electrode 5, an electrical insulator 2 provided on an outer periphery of the center electrode 5, a main body metal fitting 3 provided on an outer periphery of the electric insulator 2, a ground electrode 27 arranged at a tip of the main body metal fitting 3, and a chip 28 whose one end is jointed to the tip of the ground electrode 27. The chip 28 is jointed to the ground electrode 27 via a melting section 30 formed by resistance-welding, and the tip of the center electrode 5 is opposed to the other end face of the chip 28. A main component of metal constituting the chip 28 is identical to a main component of metal constituting the ground electrode 27. The chip 28 has a swollen part 28P with a largest outside diameter on the other end rather than one end. When the outside diameter of the swollen part 28P is designated as A (mm) and the outside diameter of the melting section 30 is designated as B (mm), A>B is satisfied. <P>COPYRIGHT: (C)2012,JPO&INPIT |
