Spark plug having a multi-layered electrode

摘要

A spark plug has a central electrode, an insulator, a metal shell and a ground electrode. The insulator is provided exterior to the central electrode. The metal shell is provided exterior to the insulator. The ground electrode opposes the central electrode. At least one of the central electrode and the ground electrode has a multi-layered structure comprising a core and a high heat conducting layer that covers at least part of the outermost surface of the core. An inner layer of the core is more heat conductive than the outermost layer of the core that is in contact with high heat conducting layer.