| 摘要 |
PROBLEM TO BE SOLVED: To improve a spark plug's carbon burning-down effect. SOLUTION: In a spark plug, carbon is ionized by a leakage current caused before starting of capacitive discharge and burned by a leakage current caused during an inductive discharge period by arranging a boundary portion 33 between the body portion 31 of a center electrode 30 and a fining portion 32 in an insulator 20. In addition, providing a thin protruded portion 42 on a grounded electrode 40 increases electric intensity in a discharge gap 50, which makes lower a discharge voltage, and further suppresses coil discharge energy during capacitive discharge. This increases inductive discharge energy and extends an inductive discharge period, thereby improving carbon burning-down effect. COPYRIGHT: (C)2004,JPO
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