Patent ID: 7521849
Filing Date: 2009-04-21
Classification: H01T

Abstract:
1. A spark plug assembly for a spark ignited engine, said assembly comprising: a grounded metallic shell, said shell including a ground electrode; an insulator body disposed at least partially in said shell, said insulator body having an axial length and a central passage extending axially along said length; an electrically conductive center electrode disposed in said central passage of said insulator body, said center electrode having an exposed length terminating in a distal tip, said center electrode having a first predetermined material composition; a sleeve disposed about said exposed length of said center electrode, said sleeve being fabricated from a second predetermined material dissimilar to said first predetermined material of said center electrode, said sleeve having a base end and a free end; and a fixation weld line disposed in a single transverse plane and metallurgically joining said base end of said sleeve to said center electrode, said free end of said sleeve not metallurgically joined to said center electrode so that said sleeve is free to thermally expand and contract unencumbered along its length except at said fixation weld.