| 摘要 |
PURPOSE:To provide a center electrode excellent in heat radiation and further prevented from damage by stress deformation by preventing a cavity from its generation between a core member and an external member in the case of extrusion-molding the center electrode, in manufacture of the center electrode of a spark plug having a compound structure of comprising the core member and the external member. CONSTITUTION:By setting a top angle theta in the point end of a cone-shaped core member 14 and in the bottom of a hole part of the same-shaped external member 15 to a relation where 80 deg.<=theta<=120 deg. a cavity is prevented from being generated between the core member 14 and the external member 15 even in extrusion-molding a center electrode. Since a diameter of the core member 14 in the point end of the center electrode can be decreased, the core member of internally sealed high heat conductive material can be placed to approach the point end of the center electrode without decreasing also strength, and heat radiation can be improved. |
