摘要 |
A spark plug includes a metal shell, an insulator coaxially disposed within the metal shell, and a center electrode coaxially disposed in the insulator. The metal shell has a substantially cylindrical base portion, and the base portion has a lower surface with a recess formed therein. A bimetallic groun d electrode is affixed to the lower surface of the base portion at the recess thereof. The ground electrode has a central core formed of a first thermally conductive metal which may include copper, and an external sheath surroundin g the core, the sheath being made of a second metal which includes nickel. The recess in the lower surface of the metal shell is preferred to be provided a s an annular groove extending therearound. The present invention also encompasses a methods of making a spark plug, including a step of placing a ground electrode adjacent a lower surface of a spark plug shell, aligned wit h a recess thereof, such that a tip end of ground electrode enters into the recess. Another step in the method involves welding the ground electrode to the spark plug shell.
|