| 摘要 |
<p>A spark plug includes a metal shell, an insulator, a center electrode, and a ground electrode. The metal shell has a threaded portion with an outer diameter of equal to or less than 10 mm, or equal to 12 mm for installing the spark plug in an internal combustion engine. The dimensional parameters in the structure of the spark plug, such as a clearance X between the center electrode and the insulator, a surface-creeping distance Y outside the metal shell, a protruding length Y1 of the insulator, an air pocket size Z, and a surface-creeping distance W inside the metal shell satisfy the dimensional relationships defined through experimental investigation in the invention. The structure ensures a high capability of the spark plug to ignite the air-fuel mixture even when the insulator thereof is fouled with carbon. <IMAGE></p> |
