Patent ID: 7586246
Filing Date: 2009-09-08
Classification: H01T

Abstract:
1. A spark plug comprising: a hollow cylindrical metal shell; a center electrode retained in said metal shell to be insulated from said metal shell; and a ground electrode having a portion facing a tip of said center electrode through a spark gap, said ground electrode being joined to said metal shell through a weld, so that a portion of said metal shell is sunk into and embedded in said ground electrode, the weld extending from an end surface of said metal shell to an inner peripheral surface of said metal shell, wherein the weld is formed by melting said ground electrode and the end surface of said metal shell and sinking a portion of the end surface of said metal shell into said ground electrode in a longitudinal direction of said metal shell, and wherein a ratio of a sinking depth of said metal shell in said ground electrode to a thickness of a major body of said ground electrode is within a range of 0.2 to 0.7, and wherein said metal shell has a rounded corner formed between the inner peripheral surface and the end surface of said metal shell, said rounded corner being joined to said ground electrode through the weld, and wherein the inner peripheral surface of said metal shell faces said center electrode.