SPARK PLUG

A spark plug comprising a solid, electrically and thermally conductive housing (1) with a connecting means and in the inner c avity whereof a gasproof ceramic insulator (2), with a central el ectrode (9), is placed, and the protruding tip thereof, has at le ast one ring-shaped auxiliary electrode (4, 5) provided on the ex tended portion of the ceramic insulator forming a spark gap with the one end of the housing (1) and with the central electrode (9) . The peripheral edges of the auxiliary ring-shaped el ectrode (4 , 5) are thickened. There are at least two auxiliary ring-shaped electrodes (4, 5) and their inner or outer collars (12) project i n the same direction. The auxiliary ring-shaped electrodes (4, 5) are made of titanium nitride (TiN) formed of layers shaped into the surface of a truncated cone having thicker upper and lower pe ripheral edges conforming to the narrowing tip of the cylindrical ceramic insulator (2).