| 摘要 |
<P>PROBLEM TO BE SOLVED: To effectively restrain flashover between a terminal electrode and a main metal fitting in a spark plug having the terminal electrode whose head is exposed from a rear end of an insulator. <P>SOLUTION: A spark plug 1 comprises an electric insulator 2 having a shaft hole 4 extending in a direction of an axial line CL1, and a terminal electrode 6 inserted in the rear end of the shaft hole 4 on its tip side and having a head 6H exposed from a rear end of the electric insulator 2 on its rear end side. Also, a collar part 6F swollen outward in a radial direction is provided at the tip of the head 6H in the direction of the axial line CL1, and a tip face of the collar part 6F is in contact with a rear end face of the electric insulator 2. A convex-shaped curve face part 6W is provided between a tip face and an outer periphery of the collar part 6F. When a curvature radius of the curve face part 6W is represented as R1 (mm) on a cross section including the axial line CL1, R1≥0.15 is satisfied. <P>COPYRIGHT: (C)2013,JPO&INPIT |
