Patent ID: 6310430
Filing Date: 2001-10-30
Classification: H01T

Abstract:
A spark plug for attachment to a cylinder head, comprising:a metallic shell including a tip-end side having an open tip end and a tail-end side having an open tail end, the metallic shell having an attachment screw portion peripherally formed at the tip-end side thereof;a ground electrode attached onto the tip-end side of the metallic shell;an insulator including an axial through-hole formed therein and a tail end portion having a tail end, the insulator disposed within the metallic shell such that the tail end portion of the insulator substantially projects from the tail end of the metallic shell;a center electrode having a tip end and being disposed within the through-hole and facing the ground electrode to define a spark discharge gap therebetween; anda metallic terminal having a tail end and being disposed within the through-hole of the insulator such that the tail end of the metallic terminal is set back from the tail end of the insulator into the through-hole, the metallic terminal being electrically connected with the center electrode, wherein the metallic terminal and the tail end of the metallic shell are separated with a distance for preventing an electrical discharge therebetween, and wherein, when A represents a distance between the tail end of the insulator and the tail end of the metallic terminal disposed within the through-hole, and B represents a length of the tail end portion of the insulator projecting from the tail end of the metallic shell along the axial direction of the through-hole of the insulator, a length of (A+B) is at least 20 mm.