Patent ID: 6621198
Filing Date: 2003-09-16
Classification: H01T

Abstract:
A spark plug comprising:a center electrode; an insulator shell holding the center electrode; a ground electrode fixed at the insulator shell and facing the center electrode across a discharge gap; a tip comprised of an iridium alloy essentially consisting of iridium bonded to at least one of said center electrode and said ground electrode at facing portions of said electrodes; and a stress relieving layer arranged between the tip and a tip bonding portion of the at least one of the center electrode and ground electrode to which the tip is bonded, wherein the tip bonding portion is comprised of an iron-based alloy, and the relieving layer is comprised of an alloy including platinum having a coefficient of linear expansion between that of the iridium alloy and said iron-based alloy and having a Young's modulus of elasticity smaller than said iridium alloy and said iron-based alloy.