Patent ID: 9219350
Filing Date: 2015-12-22
Classification: H01T

Abstract:
1. A spark plug for an internal combustion engine, the spark plug comprising: a tubular housing: a tubular insulator retained in the housing; a center electrode secured in the insulator with a distal end portion of the center electrode protruding outside the insulator; and a ground electrode provided at a distal end of the housing, the ground electrode having a distal end portion that faces the distal end portion of the center electrode in an axial direction of the spark plug through a spark gap formed therebetween, wherein the housing has a seat portion formed on an inner periphery thereof, the seat portion having a seat surface that faces proximalward, the insulator has a distal portion, a proximal portion that has a larger outer diameter than the distal portion, and a shoulder formed on an outer periphery of the insulator between the distal and proximal portions, the shoulder being arranged to seat on the seat surface of the seat portion of the housing, the spark plug further comprises an annular packing that is interposed between the seat surface of the seat portion of the housing and the shoulder of the insulator, and wherein on an inner peripheral surface of the seat portion of the housing which faces an outer peripheral surface of the distal portion of the shoulder, there are formed a plurality of uneven portions that are arranged in a circumferential direction of the spark plug, each of the uneven portions consisting of a protrusion and a recess that adjoin each other in the circumferential direction.