| 摘要 |
PROBLEM TO BE SOLVED: To provide a technology for a spark plug which can attain both roles of accepting spark discharge made to flow from a proper discharge gap in order to restrain cutoff of the spark discharge, and effecting surface discharge for burning off carbon adhered on the surface of an insulator. SOLUTION: For the spark plug provided with a center electrode, a main grounding electrode 7 extended further inward into a combustion chamber than a tip 2a of the center electrode and forming a proper discharge gap against the tip 2a of the center electrode, and an auxiliary grounding electrode 8 extended further inward into the combustion chamber than the tip 2a of the center electrode and forming an auxiliary discharge gap in a space with the tip 2a of the center electrode for accepting spark discharge made to flow from the proper discharge gap, a protruded part 8b is provided at a middle part of the auxiliary grounding electrode 8 for effecting surface discharge through carbon adhered on the surface of an end face 3a of an insulator 3. COPYRIGHT: (C)2008,JPO&INPIT
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