| 摘要 |
PROBLEM TO BE SOLVED: To provide a spark plug capable of improving reliability as compared with a conventional one by suppressing a stress corrosion crack or the like on a main metal fixture. SOLUTION: The main metal fixture 1 is formed in an approximately cylindrical shape, and a screw part 7 is formed on an outer circumference surface of a tip end side of the main metal fixture 1. A tool engagement part 8 is arranged on an outer circumference part of a rear end side from the screw part 7. A fitting part 9 is provided on a rear end side from the tool engagement part 8, and an insulator 2 formed in an approximately cylindrical shape with a center electrode 3 fitted inside is pressed in and is held on the fitting part 9. An oxide film more than 5 nm thick is formed on an entire surface of the main metal fixture 1. COPYRIGHT: (C)2008,JPO&INPIT
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