| 摘要 |
PURPOSE: A spark plug is provided to improve an efficiency by removing an additional electrode gap checking process and preventing a carbon from being deposited. CONSTITUTION: In the device, a central electrode(1), insulated by an insulating member(3), induces high voltage which is generated at an ignition coil. And a housing(4), protecing the insulating member, is screwed to a cylinder head. An insulating rod(6) which surrounds the central electrode(1) can move up and down along the guide of the housing(4) and the insulating member(3). The bottom end of the insulating rod(6) is located at the electrode gap(t) between the central electrode(1) and an earth electrode(2). When the insulating rod(6) moves upward by compressing pressure in the cylinder, the insulating rod(6) releases the discharging portions of the central electrode(1) and the earth electrode(2) from the insulation state. A helical spring (7) supports the insulating rod(6) with the elastic restitution force to return the same to its original position.
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