| 摘要 |
PROBLEM TO BE SOLVED: To provide a spark plug in an internal combustion engine capable of preventing reduction in thermal value and eliminating a crack in an insulator. SOLUTION: The spark plug in the internal combustion engine has a central electrode 2, a cylindrical insulator 3 internally retaining the central electrode 2, and a cylindrical mounting tool 4 internally retaining the insulator 3. The central electrode 2 has a locking unit 22 for determining the axial direction of the central electrode 2 with respect to the insulator 3. The insulator 3 has a locking receiver 32 for receiving the locking unit 22 of the central electrode 2 on the inner wall 311 of an axial hole 31 to pass through the central electrode 2. The inner wall 311 of the axial hole 31 is provided with a parallel portion 34 formed in parallel to the outer side of the central electrode 2 at the farther extremity than the locking receiver 32, and is provided with an expanding radius 35 with a larger clearance to the outer side of the central electrode 2 than to the parallel portion 34 is formed in between the parallel portion 34 and the locking receiver 32. COPYRIGHT: (C)2009,JPO&INPIT
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