Ceramic spark plug insulator, spark plug, and use of a glaze on a spark plug insulator

A ceramic spark plug insulator, comprising:

• an insulator head oriented in a direction of an electrical connection area;
• a combustion chamber-side insulator root;
• and
• a transition area between the insulator root situated in the combustion chamber and an insulator area situated outside the combustion chamber, the transition area including a root fillet which has a first surface area directed toward an outer side of the spark plug insulator and has a first length LA defined in an axial direction of the spark plug insulator, the first surface area including a glaze.

A spark plug for an internal combustion engine, comprising:

• a metallic housing;
• a center electrode;
• at least one ground electrode, which is situated on the housing;
• and
• a ceramic spark plug insulator for separating the center electrode from the ground electrode, the ceramic spark plug insulator including an insulator head oriented in a direction of an electrical connection area, a combustion chamber-side insulator root, and a transition area between the insulator root situated in the combustion chamber and an insulator area situated outside the combustion chamber, the transition area including a root fillet which has a first surface area directed toward an outer side of the spark plug insulator and has a first length LA defined in an axial direction of the spark plug insulator, the first surface area including a glaze.