| 摘要 |
<P>PROBLEM TO BE SOLVED: To precisely form an insulation object by surely preventing deformation and breakage of a support pin. <P>SOLUTION: The spark plug includes an insulator 2 which contains a shaft hole 4 extending in an axial line CL1 direction, holds a central electrode 5 on the tip end side in the shaft hole 4, and holds a terminal electrode 6 on the rear end side in the shaft hole 4. A manufacturing step for the insulator 2 includes a pressure molding step in which material powder PM is compressed to mold a molding CP1 containing a non-penetration hole HL which is to be the shaft hole 4, a support pin inserting step for inserting a rod-like support pin 61 from the rear end side of the molding CP1, and a grinding step in which the outer peripheral surface of the molding CP1 into which the support pin 61 is inserted is ground to provide an insulation body intermediate body IP which is an insulation body form. During the pressure molding step, the molding CP1 is so formed that a maximum ground part MG whose grinding amount is maximum during the grinding step is present in the range 2L/3 from the rear end of the molding CP1, where L is the length of the molding CP1 along the axial line CL1. <P>COPYRIGHT: (C)2013,JPO&INPIT |
