Lighting device for a motor vehicle
View Patent ↗The invention relates to a lighting device for a motor vehicle. Said lighting device comprises a light source ( 1; 96 ) for emitting electromagnetic radiation, in particular light which is visible to the human eye, and a reflector ( 70; 81; 90 ) for focusing the emitted light. The light source ( 1; 96 ) is fastened on the reflector ( 70; 81; 90 ) at least indirectly in a defined position relative to a reflective surface of said reflector. In order firstly to make heat transfer from the reflector ( 70; 81; 90 ) to the light source ( 1; 96 ) more difficult and secondly to enable EMC shielding by virtue of an electrical contact between the light source ( 1; 96 ) and the reflector ( 70; 81; 90 ), the invention proposes that a material ( 72 ) with poor thermal conductivity is arranged between the reflector ( 70; 81; 90 ) and the light source ( 1; 96 ) for thermally insulating the light source ( 1; 96 ) from the reflector ( 70; 81; 90 ). Preferably, the material ( 72 ) has a thermal conductivity λ of less than 2 W/mK and a relative permittivity (ε r ) of greater than 1.
1. A lighting device for a motor vehicle, comprising a light source for emitting electromagnetic radiation, in particular light which is visible to the human eye, and a reflector for focusing the emitted light, the light source being fastened to the reflector at least indirectly in a defined position relative to a reflective surface of said reflector, wherein a material with poor thermal conductivity is arranged between the reflector and the light source for thermally insulating the light source from the reflector.
2. The lighting device as claimed in claim 1 , wherein the light source is a gas discharge lamp with a starting device in the form of an integral part of the gas discharge lamp, and wherein the material with poor thermal conductivity is arranged between the starting device of the gas discharge lamp and a rear wall of the reflector.
3. The lighting device as claimed in claim 2 , wherein the starting device has a housing, at least regions of which are metallic, at least regions of the rear wall of the reflector are electrically conductive, and metallic regions of the starting device housing are electrically conductively connected to electrically conductive regions of the reflector rear wall, the electrically conductive connection having an increasingly better conductivity for electrical signals the higher the signal frequencies are.
4. The lighting device as claimed in claim 3 , wherein the material with poor thermal conductivity has a thermal conductivity λ of less than 2 W/mK.
5. The lighting device as claimed in claim 4 , wherein the material with poor thermal conductivity has a thermal conductivity λ of less than 1 W/mK.
6. The lighting device as claimed in claim 5 , wherein the material with poor thermal conductivity has a thermal conductivity λ of less than 0.1 W/mK.
7. The lighting device as claimed in to claim 6 , wherein a capacitive coupling is formed between the metallic regions of the starting device housing and the electrically conductive regions of the reflector rear wall.
8. The lighting device as claimed in to claim 7 , wherein the material with poor thermal conductivity has a relative permittivity (ε r ) of greater than 1.
9. The lighting device as claimed in claim 8 , wherein the material with poor thermal conductivity has a relative permittivity (ε r ) of greater than 2.
10. The lighting device as claimed in claim 9 , wherein the material with poor thermal conductivity has a relative permittivity (ε r ) of greater than 5.
11. The lighting device as claimed in to claim 10 , wherein the starting device housing is designed in such a way that at least regions of a housing wall, which is directed toward the reflector rear wall, are spaced apart from one another and run equidistantly with respect to the reflector rear wall, the material with poor thermal conductivity being arranged within the region in which the housing wall and the reflector rear wall are equidistant with respect to one another, in the gap between the housing wall and the reflector rear wall.
12. The lighting device as claimed in to claim 11 , wherein the material with poor thermal conductivity is in the form of air.
13. The lighting device as claimed in to claim 11 , wherein the material with poor thermal conductivity is in the form of a ceramic material.
14. The lighting device as claimed in to claim 11 , wherein the material with poor thermal conductivity is in the form of a plastic.
15. The lighting device as claimed in claim 14 , wherein the material with poor thermal conductivity is in the form of polyethylene naphthalate.
16. The lighting device as claimed in to claim 11 , wherein the material with poor thermal conductivity is in the form of yttrium-stabilized zirconium oxide.