| 摘要 |
PROBLEM TO BE SOLVED: To provide a spark plug capable of reducing the diameter thereof, and of preventing occurrence of looseness by being influenced by torque in attaching it to an engine and of preventing its attachment to the engine from becoming difficult by the bulge of a screw part for attachment to the engine. SOLUTION: The thread part 6 is formed on a circumferential surface of a main fitting 1 on the tip side relative to a bearing surface 5. A fitting part 7 is formed on the front end side of the thread part 6. The fitting part 7 radially fits and holds an insulating insulator 2 thereto by pressing it therein. A second thread part 9 is formed on a circumferential surface on a further front end side relative to the fitting part 7. The second thread part 9 is formed to be screwable to a threaded hole equivalent to the screw part 6. The outer diameter of the circumferential surface of the fitting part 7 is formed to be set smaller than the bottom diameters of the thread part 6 and the second thread part 9. COPYRIGHT: (C)2008,JPO&INPIT
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