| 摘要 |
A spark plug includes a chip made of iridium. The distance E between the chip and a copper core of a core rod of the center electrode is not greater than 3.5 mm. The core rod has a diameter D1 of 1.4 mm to 2.6 mm. The ratio of a chip diameter D2 to the core rod diameter D1, or D2/D1, is not greater than 0.50.
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