Spark plug with surface discharge gap

摘要

A spark plug with surface discharge gap has a spark plug housing (10), an insulating element (15) which is enclosed by the spark plug housing (10) over a longitudinal section and a central electrode (21) which rests in the insulating element and protrudes freely at the end sides, the surface discharge gap being formed between the central electrode (21) and an annular earthing electrode (14), located at the combustion space-side end of the spark plug housing (10), along a surface discharge path (30) on the surface of the insulating element (15). In order to realise a spark plug with a high degree of efficiency and a low firing voltage requirement, the insulating element (15) is produced from an aluminium oxide ceramic with dielectric strength which is greater than or equal to 25 kV/mm and the arrangement and design of the electrodes (14, 21) and of the free end of the insulating body (15) is such that the length of the surface discharge path (30) which is formed is approximately 2-5 mm. The thickness of the wall of the insulating element (15) is dimensioned to be approximately 0.8-1.2 mm at the exit point out of the spark plug housing (10), (Fig. 1). <IMAGE>