Design of a ceramic glow plug
The heating coil of a ceramic glow plug has an especially high melting point. It is also sheathed in silicon nitrite, an extremely rugged ceramic material.
The combination of the heating coil and ceramic sheath enable higher temperatures and extremely short preheating times due to excellent thermal conductivity.
The combination of the heating coil and ceramic sheath enable higher temperatures and extremely short preheating times due to excellent thermal conductivity. Also, ceramic glow plugs have a more compact design. This is important, because there is very little free space in today’s engines.
Heating coil
Like metal rod glow plugs, conventional ceramic glow plugs also have a metal heating coil. However, their melting point is especially high, which enables higher glow temperatures and faster heating.
Ceramic liner
The heating coil or heating element of a ceramic glow plug is encased by a highly-resistant ceramic material: silicon nitrite. It protects the coil from the high temperatures and vibrations and is also an outstanding heat conductor, so the heat which arises is quickly released in the combustion chamber.
Regulating coil
Metal control coils, like those used in self-regulating glow plugs, increase their electrical resistance as temperatures increase. In this way, the current flow is minimised and the glow plug is protected from overheating.
Central electrode
The battery voltage reaches the coils through the central electrode.
Insulator
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.
Connecting bolt
The battery voltage is applied at the current connection.
Metal case
Exploded drawing of a ceramic glow plug
SRC and NHTC
In an SRC (Self Regulating Ceramic) glow plug the heating element is made of ceramic with a sintered metal heating coil. An HTC (High Temperature Ceramic) or NHTC (New High Temperature Ceramic) glow plug has a heating element and a heater made of ceramic.
