| 摘要 |
In a semi-creeping discharge type spark plug, a cylindrical metal shell and an insulator are provided, the latter of which has an axial bore and placed within the metal shell so that a front end of the insulator extends beyond the metal shell. A center electrode is placed within the axial bore of the insulator so that a front end surface edge of the center electrode retracts by 0.1~0.6 mm behind from a front end surface of the insulator. A ground electrode, one end of which is connected to a front end of the metal shell, and the other end of which is bent to oppose an outer surface of the insulator so as to form an air-gap therebetween while permitting creeping spark discharges running along said front end surface of said insulator. A foward edge portion of a front end surface of the ground electrode extends by 0.0~1.0 mm forward from the front end surface of the insulator.
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