Spark plug and a method of producing the same

摘要

Reliability in connection between a chip and a base material (at least one of the central electrode and the ground electrode) of a spark plug is improved by forming a plurality of welding layers at connection between the chip and the base material in a distance increasing direction from the central electrode with overlap. With respect to section along the connection surface the sum of the sectional area of the first weld layer and the second weld layer at the overlap portion between the first and second weld layers is equal to or greater than 1.4 times the sectional are of the chip. A stress releasing layer of which linear expansion coefficient is between those of the chip and the base material may be provided between the chip and the base material for welding.