Design of a metal glow plug

The interior of a metal rod glow plug has only a few, yet very powerful and resistant components
The interior of the glow tube is filled with an extremely compressed, special magnesium oxide which has good insulating properties

The self-regulating quick-start glow plug (SRM glow plug) is amongst the most frequently used glow plug types. It is comprised of the following components.

Heating coil

The heating coil of a self-regulating quick-start glow plug is made of metal. As soon as the glow plug is supplied with current it begins to glow and thereby heats up its surroundings. By using different wire diameters or lengths for the construction of heating coils, the heating behaviour changes, thus influencing how quickly the glow plug glows.

Insulating filler

The inside of the glow tube is filled with an extremely compact, special powder: magnesium oxide. Magnesium oxide is electrically insulating and is an outstanding heat conductor. The insulation filling fulfils two important functions: It protects the coils from impact and vibrations and guarantees an optimal transmission of the produced heat.

Heating tube

The heating tube of a metal rod glow plug is made of a heat-resistant alloy. In combination with the insulation filling, it ensures that the coils inside are not subjected to the combustion and shockwaves resulting from combustion without protection..

Regulating coil

The control coil is welded to the current-carrying central electrode and the heating coil. As the temperature increases, the electrical resistance of the control coil also increases. In this manner, it reduces the current flow to the heating coil depending on the temperature. .

Central electrode

The battery voltage reaches the coils through the central electrode.

Thread

The thread of a high-quality glow plug is always rolled and never cut. This way, damage to the glow plug bore in the cylinder head is prevented.

Connection

The battery voltage is applied at the current connection.

Exploded drawing of a metal rod glow plug

The interior of a metal rod glow plug has only a few, yet very powerful and resistant components

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