| 摘要 |
PROBLEM TO BE SOLVED: To provide a spark plug using a chip made of iridium (Ir) and having high performance and a long life without causing abnormal wear or uneven wear of the chip. SOLUTION: This spark plug is so structured that the distance E from the chip 31 to a copper core 23 of a core rod is set not greater than 3.5 mm; the diameter of the core rod 21 is set to 1.4 mm to 2.6 mm; and the ratio D2/D1 of a chip diameter D2 to the core rod diameter D1 is set not greater than 0.50. COPYRIGHT: (C)2007,JPO&INPIT
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