| 摘要 |
PROBLEM TO BE SOLVED: To improve an insertion property of a boot part of an ignition coil by lessening a difference in dimension between a terminal electrode and an electric porcelain of a spark plug. SOLUTION: The spark plug is provided with a metal fitting 10, an electric porcelain 2 fixed inside the metal fitting 10, a center electrode fixed inside an axis hole 21 of the electric porcelain 20, a grounding electrode 40 opposing an end part 30a of the center electrode 30 through a spark discharge gap 50, and a terminal electrode 80 with one end part 80a conducted with the other end 30b of the center electrode 30 inside the electric porcelain 20 and the other end part 80b inserted into and fixed to the inside of the electric porcelain 20 in a state protruded from the other end part 20b of the electric porcelain, a difference in absolute values of a diameter B mm at a region of the electric porcelain 20 protruding from the other end part 10b of the metal fitting 10 and and that A mm of a maximum-diameter part of the terminal electrode 80 at a region protruding from the other end part 20b of the electric porcelain 20 being 0.6 mm or less. COPYRIGHT: (C)2005,JPO&NCIPI
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