| 摘要 |
PROBLEM TO BE SOLVED: To provide a spark plug for internal combustion engines excelling in ignitability without increasing the requested voltage. SOLUTION: The spark plug 1 for internal combustion engines includes a mounting bracket 2, an insulating insulator 3, a central electrode 4, and a grounding electrode 5. The grounding electrode 5 has a grounding base metal 50 fixed to the mounting bracket 2 and a protrusion 52 mounted on the opposite surface 61 which is a surface in the central electrode (4) side of the grounding base metal 50 and disposed opposite to the central electrode 4. A receding surface 510 having a shape gradually moving towards the tip of the plug as it goes outwards in the cross-section perpendicular to the grounding base metal 50 in the axial direction of the spark plug 1 is provided at both sides of the junction of the protrusion 52 in the grounding base metal 50. The grounding base metal 50 has a corner part 54 at which the receding surface 510 intersects with the rear surface 53 of the base metal opposite to the central electrode 4 in the grounding base metal 50. COPYRIGHT: (C)2009,JPO&INPIT
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