Spark plug

A spark plug comprising an inner conductor, a center electrode connected with the inner conductor, an insulator surrounding the inner conductor and having a front end and a rear end, a spark plug body surrounding the insulator and having a front end and a rear end, and a ground electrode connected with the front end of the spark plug body;

• the front end of the spark plug body projects over the front end of the insulator;
• the insulator has at its front end a surface region lying between center electrode and the spark plug body, which surface region forms an insulating section preventing a sliding spark between the center electrode and the spark plug body;
• at the front end of the spark plug body a seal seat is provided, cooperating with the front end of the insulator;
• at the front end of the insulator a recess is arranged, open towards the front end of the spark plug body, into which recess the center electrode projects and forms an air spark gap with the ground electrode;
• through the recess an annular intermediate space is formed between the insulator and the center electrode;
• and
• wherein a surface of the recess, viewed in a longitudinal section through the spark plug, runs in an at least partially curved manner between the center electrode and the end of the spark plug body projecting over the front end of the insulator, and has an overall length of 5 mm or more, measured in the longitudinal section along the curved surface of the recess, so that the recess forms with its surface, facing the center electrode, an insulating section preventing a sliding spark between the center electrode and the spark plug body.