Patent ID: 6849829

Claim:
A sheathed-element glow plug for starting a thermal combustion process, comprising: a housing capable of being sealingly mounted in a wall of a combustion chamber; and a ceramic heating element that is accommodated in the housing and that extends into the combustion chamber, wherein: the ceramic heating element includes a heating conductor that is connectible to a voltage source and has an electrical resistance, and an electrically conductive cross-section of the heating conductor is smaller in a region of a tip of the ceramic heating element than in an electrically conductive cross-section in a region of a body of the ceramic heating element, and the tip of the ceramic heating element has a frustoconical shape, wherein the end of the frustoconical-shaped tip includes a hemispherical segment, a first diameter of the tip of the ceramic heating element being smaller than a second diameter of the body of the ceramic heating element.