EP3502556A1

EP3502556A1 - Automotive lighting device

Info

Publication number: EP3502556A1
Application number: EP17382887.2A
Authority: EP
Inventors: Alvaro Andres; Carlos Gomez; Maria-Del-Pilar MEDINA; Borja MARTINEZ; Jesus TALLON
Original assignee: Valeo Iluminacion SA
Current assignee: Valeo Iluminacion SA
Priority date: 2017-12-22
Filing date: 2017-12-22
Publication date: 2019-06-26

Abstract

This invention is related to a lighting device (1) comprising a housing (2), a light source (3), an internal support (4), an external heatsink (5) and a thermally conductive link (6). The internal support (4) is located inside the housing and in thermal connection with the light source (3). The external heatsink (5) is located at least partially outside the housing (2). The thermally conductive link (6) is in thermal contact with the internal support (4) and with the external heatsink (5). The thermally conductive link (6) is flexible and has a thermal conductivity greater than 100 W/m·K.

Description

TECHNICAL FIELD

This invention is related to the field of heat dissipation in automotive lighting devices.

STATE OF THE ART

Light sources generate a big amount of heat which needs to be dissipated, so that the operation of said light sources is not jeopardized. This issue is even more important when light sources are light emitting diodes (LEDs), since temperature has a big impact on the operational properties of said light sources.
Heatsinks with heaters are known to solve this problem. A heatsink is located in thermal contact with the light source, and this heatsink is provided with heaters, which dissipate the heat coming from the heatsink, so that air surrounding the heater is heated and then wasted.
These heatsinks may be located inside or outside the lighting device. Heatsinks which are located inside the lighting device provides better heat dissipation, since they may be in a more direct contact with the light source to be cooled. However, as they dissipate heat into a closed atmosphere, air is becoming hotter and hotter, and cooling turns out to be less efficient.
Another option is arranging the heater outside the lighting device, but heat transfer is more difficult. Heat pipes are usually used, such as in document US 2008/247177 A1 . A lighting element connected to a heat pipe is less versatile, since heat pipes do not usually allow a free movement of the associated element.

DESCRIPTION OF THE INVENTION

The invention provides a solution for reusing the wasted air in order to optimise heat dissipation by means of an automotive lighting device according to claim 1. Preferred embodiments of the invention are defined in dependent claims.
In an inventive aspect, the invention provides an automotive lighting device comprising

a housing;
a light source;
an internal support, located inside the housing and in thermal connection with the light source;
an external heatsink, located at least partially outside the housing; and
a thermally conductive link, which is in thermal contact with the internal support and with the external heatsink, wherein the thermally conductive link is flexible and has a thermal conductivity greater than 100 W/m·K.

In this document, the fact that an element is "flexible" should be understood as the property of this element of bending to make contact between opposite ends of this element without suffering a plastic deformation. The person skilled in the art knows this concept because it is used to distinguish between a "flexible" printed circuit board from a standard printed circuit board.
This automotive lighting device provides an alternative way of dissipating heat in a lighting device, with a simple and small system, thus saving maintenance cost and space.
In some particular embodiments, the thermally conductive link is made of a material with a thermal conductivity greater than 360 W/m·K.
Choosing such a conductive material for the thermally conductive link ensures that dissipated heat is enough for keeping the lighting elements in operative conditions.
In some particular embodiments, the thermally conductive link is made of a material comprising carbon.
The main advantage of such an automotive lighting device is the fact that a great amount of heat may be dissipated by using a simple an inexpensive system.
In some particular embodiments, the material comprising carbon is at least one of graphite, graphene or carbon nanotubes.
The main advantage of such an automotive lighting device is the fact that a great amount of heat may be dissipated without using heavy systems.
In some particular embodiments, the thermally conductive link further comprises a cover. In further particular embodiments, the cover is made of silicone.
This cover made out of a flexible material such as silicone is useful for following the movements of the thermally conductive link.
In some particular embodiments, the automotive lighting device further comprises auxiliary plates which are in thermal contact with the internal support and with the conductive link.
These auxiliary plates contribute to dissipate heat between the light sources and the external heatsink. Further, they may be used to improve the stiffness of the conductive link when they are in physical contact with said conductive link.
In some particular embodiments, the internal support is a PCB. This arrangement is very common in an automotive lighting device, where semiconductor light sources are arranged on a PCB and this PCB dissipates heat generated in the semiconductor light source to the heatsink.

BRIEF DESCRIPTION OF THE DRAWINGS

To complete the description and in order to provide for a better understanding of the invention, a set of drawings is provided. Said drawings form an integral part of the description and illustrate an embodiment of the invention, which should not be interpreted as restricting the scope of the invention, but just as an example of how the invention can be carried out. The drawings comprise the following figures:

Figures 1 a and 1 b show an automotive lighting device according to the invention in two different operation positions.
Figure 2 shows an alternative embodiment of an automotive lighting device according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 a shows an automotive lighting device according to the invention in a first operation position. This automotive lighting device comprises

a housing 2;
a light source 3;
an internal PCB 4, located inside the housing and in thermal connection with the light source 3;
an external heatsink 5, located at least partially outside the housing 2; and
a thermally conductive link 6, which is in thermal contact with the internal PCB 4 and with the external heatsink 5.

The thermally conductive link 6 is flexible and has a thermal conductivity greater than 360 W/m·K.
In this case, the thermally conductive link 6 is made of graphite, although other materials comprising carbon, such as graphene or carbon nanotubes may be used in different embodiments.
The thermally conductive link 6 is fixed to the internal PCB 4 by means of contact pressure, screws or glue and to the external heatsink 5 by means of contact pressure, screws or glue. This arrangement allows three-dimensional regulation of the light source 3, because the flexible conductive link 6 absorbs the linear movement in the three spatial directions, so that the external heatsink 5 may not move and be still connected to the internal PCB 4 by means of the flexible conductive link 6.
This automotive lighting device further comprises some auxiliary plates 8 which are in thermal contact with the internal PCB 4 and with the conductive link 6. These auxiliary plates contribute to dissipate heat between the light sources 3 and the external heatsink 5. Further, they improve the stiffness of the conductive link 6.
Figure 1b shows an automotive lighting device according to the invention in a different operation position. The internal PCB 4 containing the light sources 3 has been moved according to the direction of the arrow, either because the internal PCB 4 where the light source 3 is installed has been adjusted or because it has moved due to a cornering light functionality. The flexible conductive link 6, due to its flexibility properties, is able to remain in thermal contact both with the internal PCB 4 and with the external heatsink 5, thus providing heat dissipation despite the movement of the light sources 3.
Although this figure shows a rotation according to Z-axis, different devices may be used to provide a rotation in X-axis and/or Y-axis, since the conductive link 6 may also absorb these movements.
Figure 2 shows an alternative embodiment of some of the elements of an automotive lighting device 1 according to the invention.
In this case, the thermally conductive link 6 is made out of metal and comprises a cover 7. This conductive link 6 is more ductile, although, depending on the metal used, it may have a lower thermal conductivity than in the previous case.
In this case, the cover 7 is made of silicone, which ensures good protection and may bear high temperatures.
Figure 3 shows an embodiment of an automotive lighting device 1 according to the invention installed in an automotive vehicle 100.

Claims

Automotive lighting device (1) comprising
a housing (2);
a light source (3);
an internal support (4), located inside the housing and in thermal connection with the light source (3);
an external heatsink (5), located at least partially outside the housing (2); and
a thermally conductive link (6), which is in thermal contact with the internal support (4) and with the external heatsink (5), wherein the thermally conductive link (6) is flexible and has a thermal conductivity greater than 100 W/m·K.
Automotive lighting device (1) according to claim 1, wherein the thermally conductive link (6) is made of a material with a thermal conductivity greater than 360 W/m·K.
Automotive lighting device (1) according to claim 2, wherein the thermally conductive link (6) is made of a material comprising carbon.
Automotive lighting device (1) according to claim 3, wherein the material comprising carbon is at least one of graphite, graphene or carbon nanotubes.
Automotive lighting device (1) according to any of the preceding claims, wherein the thermally conductive link (6) further comprises a cover (7).
Automotive lighting device (1) according to claim 5, wherein the cover (7) is made of silicone.
Automotive lighting device (1) according to any of the preceding claims, further comprising auxiliary plates (8) which are in thermal contact with the internal support (4) and with the conductive link (6).
Automotive lighting device (1) according to any of the preceding claims, wherein the internal support is a PCB.