| 摘要 |
PROBLEM TO BE SOLVED: To provide a spark plug capable of preventing a lateral spark by arranging the inner peripheral surface of a main metal fitting and the outer peripheral surface of an insulator so as to be shifted from a concentric circle. SOLUTION: On a flat plane including the top end face 57 of a main metal fitting 50 of the spark plug 100, a line passing through the center Q of a grounding electrode 30 jointed on the top end face 57 of the main metal fitting 50, and an axial line P of the main metal fitting 50 is denoted by Y-Y. On the line Y-Y, a distance between the outer peripheral face 14 of an insulator 10 and an inner peripheral face side circle L of the top end face 57 of the main metal fitting 50 at the grounding electrode 30 side of the axial line P is denoted by A, and a distance between the outer peripheral face 14 of an insulator 10 and an inner peripheral face side circle L of the top end face 57 of the main metal fitting 50 at a side opposite to the grounding electrode 30 from the axial line P is denoted by B. On these conditions, the axial line P of the main metal fitting 50 and an axial line O of the insulator 10 are arranged so as to be shifted from each other and fixed so that a relation A>B is satisfied. COPYRIGHT: (C)2007,JPO&INPIT
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