Patent ID: 6849995
Filing Date: 2005-02-01
Classification: H01T

Abstract:
1. A spark plug comprising a rodlike center electrode ( 3 ), a rodlike insulator ( 2 ) surrounding said center electrode ( 3 ) and having a protrusion ( 2 e ) at a central portion thereof, a metallic shell ( 1 ) assuming an open-ended, tubular shape and surrounding said insulator ( 2 ), and a ground electrode ( 4 ), a first end of said ground electrode ( 4 ) being joined to said metallic shell ( 1 ) and a second end of said ground electrode ( 4 ) facing said center electrode ( 3 ) to thereby define a spark discharge gap (g), and characterized in that: an insulator insertion hole ( two protrusions ( an inside diameter of said insulator insertion hole (