Spark plug for internal combustion engine and method of manufacturing spark plug

摘要

A spark plug includes 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 an annular ground electrode fixed to a distal end of the housing. The housing has, at the distal end thereof, a small-inner diameter portion that has a smaller inner diameter than other portions of the housing. The annular ground electrode is arranged on a distal end surface of the small-inner diameter portion of the housing so that an inner circumferential surface of the ground electrode faces an outer circumferential surface of the distal end portion of the center electrode through a spark gap formed therebetween. The outer diameter of the ground electrode is less than the outer diameter of the distal end surface of the small-inner diameter portion of the housing.

主权项

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; anda ground electrode having an annular overall shape and fixed to a distal end of the housing,whereinthe housing has, at the distal end thereof, a small-inner diameter portion that has a smaller inner diameter than other portions of the housing,the ground electrode is arranged on a distal end surface of the small-inner diameter portion of the housing so that: the ground electrode protrudes distalward from the distal end surface of the small-inner diameter portion of the housing; and an annular inner circumferential surface of the ground electrode radially faces an annular outer circumferential surface of the distal end portion of the center electrode through a spark gap formed therebetween, and an outer diameter of the ground electrode is less than an outer diameter of the distal end surface of the small-inner diameter portion of the housing.