US Patent 11695256 Spark plug for internal combustion engine

A spark plug for an internal combustion engine includes insulating glass having a tubular shape, a central electrode including a tip protruding portion, a housing having a tubular shape, and a plug cover provided over an auxiliary combustion chamber. The plug cover is provided with injection holes through which the auxiliary combustion chamber communicates with the exterior. The central electrode includes a base material and a core material disposed inside the base material and having a higher thermal conductivity than the base material. The core material includes a large diameter portion and a small diameter portion continuously formed on a tip side of the large diameter portion. The small diameter portion has a smaller diameter than the large diameter portion, and includes, in a part of the small diameter portion in an axial direction, a small-diameter columnar portion having a constant diameter. At least a part of the small-diameter columnar portion is disposed further on the tip side of the spark plug than a tip of the insulating glass.