| 摘要 |
PROBLEM TO BE SOLVED: To enhance accuracy of coaxiality between a center electrode and a noble metal chip, in a spark plug with the noble metal chip jointed to a grounding electrode. SOLUTION: A shoulder part 41b in contact with a tip surface 13d of the grounding electrode 13 is formed on a bending punch 41 for pressing the grounding electrode 13 in forming a predetermined spark gap G. Movement of the tip surface 13d of the grounding electrode 13 toward the shoulder part 41 in forming the predetermined spark gap G is restricted by the shoulder part 41b. Thereby, the position in a direction perpendicular to a center electrode axis Z1 of the noble metal chip 14 is restricted by the shoulder part 41b. By setting the position of the shoulder part 41b for each spark plug, the accuracy of coaxiality between the center electrode 12 and the metal chip 14 can be enhanced. COPYRIGHT: (C)2005,JPO&NCIPI |
