NGK glow plugs viewed in detail

Modern sheathed type glow plugs essentially consists of the plug element, the heating rod with heating and control coil as well as connection bolts. Glow plugs draw their electrical energy from the battery. The controls are provided by an electronic glow-control unit. 

The basic principle of modern sheathed type glow plugs is the combination of the heating and control coil to form a joint resistance element. The heating coil together with the glow pencil forms the heating zone. The control coil has the property that its resistance increases with increasing temperature and it therefore limits current and temperature.

Detail sheathed type glow plug

The heating and control coil are electrically connected in series and welded to each other. Both coils have positive, but differently high temperature resistances. The control coil has the higher coefficient, the heating coil a lower coefficient.

Special features:

The heating up times and glow temperatures of the plugs can be changed through varying lengths, diameters and wire thicknesses of heating and control coils and adjusted to the respective engine type!

The whole coil is packed in a compacted, electrically insulating ceramic power (magnesium oxide) with a very high heat conductivity. The powder is highly pressed together during mechanical compaction, so that the coil sits absolutely firmly. It is so stable that the wires of the heating and control coils permanently withstand all vibrations.

Detail ceramic glow plug

Ceramic glow plugs are equipped with a special heating coil, which has a particularly high melting point. This is enclosed in the new ceramic material silicon nitrite.

Significance:

Silicon nitrite is a particularly good heat conductor, so that the preheating time is very short. 

Further advantages:

The material can also withstand rapid heating for long periods of time!

The ceramic glow plug is more heat resistant and long-lasting than a sheathed type glow plug!