EP2674666B1 - Illumination device of a motor vehicle - Google Patents

Description

The present invention relates to a lighting device of a motor vehicle, wherein the lighting device has focusing means for the light of the lighting device, and dark-colored components made of plastic are arranged in the lighting device.

Various types of lighting devices for motor vehicles are known from the prior art. These can be in the form of headlights or lights. Headlights are arranged in the front area of a vehicle and, in addition to ensuring road safety by making the vehicle visible to other road users, are used in particular to illuminate the area in front of the vehicle, e.g. in the form of a low beam, high beam or fog light distribution and in the form of adaptive light distributions that can be adapted to certain environmental and/or driving situations, such as static or dynamic cornering lights, bad weather lights, city lights, country road lights, motorway lights. The lighting devices include at least one light source, e.g. in the form of an incandescent lamp, Gas discharge lamp or semiconductor light source, for generating light. They also include at least one primary optics for bundling the generated light. The primary optics can be designed as a reflector (concave mirror), which reflects the light by means of conventional mirroring. The reflector can have the shape of an ellipsoid, a paraboloid or any other arithmetically calculated free form. However, the primary optics can also be designed as a transparent body made of glass or plastic, the bundling of the light then taking place by refraction when entering the body and/or exiting the body and/or by total reflection at the outer boundary surfaces of the body.

The lighting devices work, for example, according to the reflection principle, with light emitted by the light source being reflected onto the roadway in front of the vehicle by primary optics designed as a reflector in order to produce a desired light distribution. However, the lighting devices can also work according to a projection principle, with light emitted by the light source, after being concentrated by the primary optics, being imaged by a projection optics on the roadway in front of the vehicle in order to produce a desired light distribution. The projection optics can be designed as a converging lens or as a reflector, preferably with a paraboloid shape.

Lighting devices include a housing that is preferably made of plastic. The housing has a light exit opening which is tightly sealed by a translucent cover plate made of glass or plastic and through which the light can leave the lighting device. The cover plate can have optically active elements (e.g. prisms, cylindrical lenses, etc.) at least in certain areas (so-called diffuser). However, it can also be designed without such optically effective elements (so-called clear pane).

The actual light-emitting unit of a lighting device is combined into a light module. This includes the light source, the primary optics and - if present - a secondary optics and a diaphragm arrangement for generating a shielded light distribution. A light module is arranged either alone or together with other light modules in the housing of a lighting device. A desired light distribution can be generated by a single light module or by a plurality of light modules and by superimposing the partial light distributions emitted by them.

A cover frame made of plastic is often arranged around the light module, which covers gaps between two light modules and between a light module and the housing and contributes to a visually appealing design of the lighting device, particularly when it is switched off. As a rule, a cover frame surrounds the outer circumference of a projection optics of a projection module or of a reflector of a reflection module. The cover frames can extend on the inside of the housing along the top, the back, the bottom and/or the lateral sides. Furthermore, in the case of projection modules, it is conceivable that the converging lens and at least partially also a lens holder, via which the converging lens is attached to the rest of the light module, are surrounded by a hollow-cylindrical tube made of plastic. Additionally or alternatively, inside the Housing also be arranged other components made of plastic. Cover frames, tubes or other plastic components in the housing can, for example, be mirrored. It is also known to color these cover frames, tubes or other components dark, preferably black, for example in order to avoid unwanted and uncontrollable reflection of light on them. The dark colored cover frames, tubes or other plastic components have a matt or glossy surface. A paint containing carbon black is preferably used to color the components.

When the sun shines through the cover plate into the interior of the housing of the lighting device, a burning glass effect can occur, for example in a projection module, due to the projection optics, especially if this is designed as a converging lens, which can lead to local melting of the cover frames, tubes or other plastic components. In the case of dark-colored components, this effect is intensified by the fact that the soot usually used for coloring includes carbon particles that cause strong absorption of the radiation in the entire wavelength range, including the high-energy IR radiation. This leads to heating of the components and, as a result, to a visible change in the surface, deformation or even damage to the component, e.g. by burning holes.

So reveals the JP 2008 277237 A a lighting device of a motor vehicle, the lighting device having focusing means and dark-colored components made of plastic being arranged in the lighting device, the dark-colored Components are at least partially made of a plastic with thermally conductive additives and / or with a thermally conductive layer on their exposed to radiation from the outside side.

For example, to counteract heat-related damage caused by the heat generated by an incandescent or halogen lamp in the housing of a lighting device WO 03/099939 A1 the use of infrared-transparent plastic material is known, the material being used to produce a headlight housing of a motor vehicle. The material consists of a dark-colored, IR-radiation-permeable polymer that only partially absorbs radiation in the near and mid-infrared range, the remaining radiation is transmitted or reflected through the housing, which can reduce the heating of the headlight housing.

Alternatively, it is also known to use heat shields, as shown in EP 1 150 065 B1 is provided.

The object of the invention is to prevent aesthetic and functional impairments of the known lighting devices due to solar radiation in conjunction with light-focusing means of the lighting devices. If possible, the appearance of the lighting devices should not be changed, and in particular no additional components should be necessary for this.

To solve this problem, a lighting device with the features of claim 1 is proposed.

It is provided that the dark-colored components of the lighting device comprise a cover frame and are made at least in regions from a plastic with thermally conductive additives and with a thermally conductive layer on the side exposed to radiation from the outside, the layer being at least partially a dark layer comprising thermally conductive additives and/or at least partially a transparent layer comprising thermally conductive additives.

External radiation means, in particular, solar radiation. In general, however, this refers to radiation that is not generated by the lighting device itself.

In this case, of the radiation incident on the lighting device from the outside, infrared radiation is particularly relevant. Infrared radiation is defined as electromagnetic radiation that borders on visible light with increasing wavelengths, i.e. starting at a wavelength of approx. 780 nm. The near infrared range (NIR: near IR) is particularly relevant here, i.e. a wavelength range from around 780 nm to around 3000 nm. The near infrared range is the wavelength range that leads to particularly strong heating of the components when these rays are absorbed by the components. But even beyond the NIR range, the radiation can lead to heating when absorbed by the components.

Depending on the position of the sun, high-energy sunbeams can strike the light-focusing means of the lighting device at different angles. The sun's rays can be bundled accordingly and hit different components in the lighting device. A converging lens of a projection module of the lighting device is primarily considered as the light-focusing means. But it is also conceivable that a curved or arched Cover plate, especially if it includes optically effective elements, light can have a focusing effect. It would also be conceivable for mirrored components (eg cover frames, tubes, screen elements, etc.) to be shaped, in particular bent or arched, in such a way that they focus incident light rays on dark-colored components of the lighting device. By introducing thermally conductive additives into the plastic material of the dark-colored components and by applying a dark or transparent layer to the plastic material with thermally conductive properties, the heat generated by the infrared portion of the sun's rays that strike the lighting device from outside can be dissipated onto the entire component from the zone of special heating (hotspot), which prevents the partial strong heating of the component and thus at least minimizes, but preferably prevents, damage to the component.

In order to prevent the light beams bundled by the light-focusing means from causing local high temperatures in the components when they strike dark-colored components of the lighting device, these components are made, according to the invention, from a material with improved thermal conductivity properties compared to the plastic material, and the plastic material is provided with an additional layer on its surface, which has improved thermal conductivity properties. Despite the absorption of the infrared radiation by the dark-colored components, these components are only slightly heated by incident and focused light rays, which immediately dissipates the heat generated to the other areas of the components. This can change or damage the surface of the components, deformation and damage to the complete components can be effectively prevented. At the same time, the affected components are still colored dark, so that the external appearance of the lighting device remains unchanged compared to conventional lighting devices. The provision of metallic or metalized surfaces for dissipation and protection against local heating can be dispensed with.

The infrared radiation from the sun bundled by the light-focusing means can, for example, impinge on at least part of the cover frame, a tube and/or a decorative strip. The corresponding components can be at least partially dark in color in order to avoid, for example, disruptive reflections caused by light emerging from the light module of the lighting device and/or light from other road users and/or any other extraneous light.

Thermosetting plastics can also be used as the plastic material.

The dark-colored components of the lighting device are preferably colored black or at least approximately black.

According to a first embodiment, the plastic components are not simply coated with a specific color, but colored throughout. This means that the affected components cannot differ in terms of color from the conventional dark components that are used in lighting devices known from the prior art. In addition, one Surface structure of the components not changed. The lighting device looks like the conventional lighting devices from the outside. In this case, thermally conductive additives such as carbon nanotubes (CNT), thermally conductive oxides (TCO), ceramic or metal fillers or combinations of the aforementioned additives are added to the plastic material. The use of carbon nanotubes is particularly preferred here, since these do not change the mechanical properties of the plastics used, or do so only to a small extent. The manufacturing process of the components can therefore be adapted without great effort. The alternatively used ceramic or metal fillers increase the weight of the components and are associated with increased tool wear during processing, for example in the injection molding process.

Furthermore, it is provided that the dark-colored components are manufactured with a thermally conductive layer on their side exposed to external radiation. The dark color of the dark-colored components can be achieved by applying a dark layer, which can be provided in whole or in part. To achieve the thermally conductive properties, this is also provided with thermally conductive additives, such as carbon nanotubes (CNT), thermally conductive oxides (thermally conductive oxides, TCO), ceramic or metal fillers or combinations of the aforementioned additives. The layer can be provided, for example, by spraying, printing, squeegeeing, sputtering, coating, but also by applying a film, e.g. by lamination.

Alternatively or in addition to the dark layer, the dark colored components, a transparent layer, which can be provided in whole or in part, can be applied. To achieve the thermally conductive properties, this is also provided with thermally conductive additives, such as carbon nanotubes (CNT), thermally conductive oxides (thermally conductive oxides, TCO), ceramic or metal fillers or combinations of the aforementioned additives. The layer can be provided, for example, by spraying, printing, squeegeeing, sputtering, coating, but also by applying a film, for example by lamination. It is particularly preferably a thin layer consisting of carbon nanotubes.

The light source advantageously comprises at least one semiconductor light source, in particular a light-emitting diode. The lighting device according to the invention effectively prevents impairments of such lighting devices equipped with semiconductor light sources. The invention is particularly advantageous in the case of lighting devices with a projection module, since the projection optics (for example the converging lens) captures a particularly large amount of sunlight and focuses it onto visible (dark-colored) components of the lighting device. Even in such a case, the invention effectively prevents damage to or destruction of the components.

Further features and advantages of the present invention are explained in more detail below with reference to the drawing. The only figure shows a schematic representation of a lighting device according to the invention in longitudinal section.

A lighting device 5 for motor vehicles according to the invention shown in a longitudinal section in the figure is designed as a headlight. The headlight 5 includes a housing 17 which is preferably made of plastic. A light module is arranged inside the housing 17 and is denoted by the reference numeral 7 in its entirety. The lighting device 5 could also include several light modules, in which case, in addition to headlight functions such as low beam, high beam or fog light, lighting functions such as turn signals, daytime running lights, position lights, etc. can also be integrated in the lighting device 5 .

The light module 7 has primary optics designed as a reflector 10 and having an optical axis 11 . The reflector 10 preferably has an ellipsoid shape or a free form similar to an ellipsoid shape. A light source 12 is arranged in one of its possible focal points. The reflector 10 bundles the light emitted by the light source 12 . In the figure 1 The light source 12 shown is a halogen lamp. However, the light source 12 can also be designed as at least one semiconductor light source (for example at least one light-emitting diode, LED) or as a gas discharge lamp. The reflector 10 can be made of plastic or metal. It is arranged in a holder 14 and can be mounted in the housing 17 so that it can be adjusted horizontally and/or vertically in order to generate an adaptive light distribution. In the example shown, however, the holder 14 is firmly connected to the housing 17 of the lighting device 5 .

In a light exit direction 16 after the reflector 10 and at a distance from it, in the beam path of the light reflected by the reflector 10, there is a projection optics in Form a converging or projection lens 18 arranged. The light module 7 is therefore designed as a so-called projection module, with the projection lens 18 projecting at least part of the light bundled by the reflector 10 to generate a desired light distribution onto the roadway in front of the vehicle. The projection lens 18 is fastened to a front edge of the reflector 10 and thus to the rest of the light module 7 via a holding frame 20 which is preferably made of metal. The housing 7 has a light exit opening 19 in the light exit direction 16 which is closed with a translucent cover plate 15 . The cover plate 15 consists of glass or plastic and can be designed with or without optically active elements, in particular scattering elements.

At least one cover frame 22 is arranged around the outer circumference of the projection module 7, in particular along the outer circumference of the converging lens 18, so that a gap or spacing between the light module 7 and the interior of the housing is covered and cannot be seen when looking from the outside through the cover pane 15 into the interior of the housing 17. The design (shape, color, surface quality, etc.) of the cover frame 22 determines the aesthetic impression and thus the design of the lighting device 5 to a large extent, especially when the light source 12 is switched off. It is made of plastic and can be colored at least partially dark or black. The dark color can, for example, prevent unwanted and disturbing light reflections. Inside the housing 17 of the lighting device 5, there can also be other dark-colored plastic components, which, however, figure 1 are not explicitly marked. It could be, for example, a die The tube surrounding the lens holder 20 may be made of, in particular, dark-colored plastic, a decorative strip made of, in particular, dark-colored plastic, or the like.

A diaphragm arrangement 24 can be provided inside the projection module 7, which is used to generate a shielded light distribution, e.g. a low beam or a fog light. In this case, an upper edge of the screen 24 is projected through the converging lens 18 as a light-dark boundary onto the roadway in front of the vehicle. The screen 24 shades off light reflected by the reflector 10, which would otherwise reach an area above the light-dark boundary in the light distribution. The aperture assembly 24 can be moved in and out of the light path. In this way, the light distribution can be switched between low beam and high beam.

Depending on the position of the sun relative to the light exit opening 19 of the lighting device 5, the sun's rays 26, which include high-energy infrared radiation, can fall through the cover pane 15 into the interior of the housing 17 at different angles, both when the motor vehicle is moving and stationary. There, the sun's rays 26 can hit light-focusing means, for example in the form of the converging lens 18 . A covering pane 15 pulled far back over the converging lens 18 at the top, as is often the case in modern motor vehicles with flat, streamlined fronts, further promotes this effect. With a corresponding configuration of the cover plate 15, for example with a corresponding curvature and/or optically active elements, the cover plate 15 itself can even be used as a light-focusing means act.

Infrared radiation is defined as electromagnetic radiation that borders on visible light with increasing wavelengths, i.e. starting at a wavelength of around 780 nm and going up to around 14000 nm. Absorption of IR radiation by a body causes it to heat up. The sun's rays 19 are focused in the light means 10; 15; 18 bundled and can then on the arranged in the lighting assembly 5 components 22 from z. B. dark colored plastic. When the sun is so that the sun's rays through the light focusing means 10; 15; 18 on the z. B. dark-colored plastic parts 22 are focused, a relatively large amount of energy hits the plastic parts 22 in a spatially limited area. A so-called hotspot 28 arises. So that this energy does not lead to local heating in the plastic part 22 and consequently to a change in the surface, damage or even destruction of the plastic part 22, the present invention proposes that the dark plastic part 22 be manufactured at least in areas from a plastic with heat-conducting additives and with a heat-conducting layer on the side exposed to radiation from the outside, the layer being at least in areas a dark layer comprising heat-conducting additives and/or at least in areas a transparent layer comprising heat-conducting additives.

The infrared radiation from the sun hits the plastic part 22, which due to its own thermally conductive properties and the thermally conductive properties of the dark or transparent layer additionally applied to it, distributes the selective heating 28 to the entire component 22 and thus over a larger area or a larger volume, so that the heat load on the point 28 on which the sunlight is focused can be kept sufficiently low. At most, the component 22 heats up slightly, but damage to the component 22 by the absorbed IR radiation is practically impossible. For this purpose, the use of carbon nanotubes is particularly preferred. These can either be used directly in the plastic as additives or applied to the plastic part in a dark or transparent layer. The use of carbon nanotubes is particularly preferred, since these change the mechanical and processing properties of the plastic only slightly.

The following variants are conceivable: In principle, the entire cover frame (ADR) can consist of plastic containing carbon nanotubes or plastic containing TCO.

Alternatively, the cover frame can also only be formed in sections from a corresponding plastic, with the cover frame being produced directly during production as a two-component part and one of the components being made of a corresponding plastic.

Furthermore, as an alternative, the critical area can be made of a plastic that contains TCOs or carbon nanotubes, and this further part can be clipped into an opening in the cover frame, for example.

Finally, as a further possibility, provision can be made for the component or areas of the component to be provided with a coating containing TCOs or carbon nanotubes.

Claims (9)

1. Lighting device (5) of a motor vehicle, the lighting device (5) having means (10, 15, 18) for focusing light of the lighting device, and having dark-colored components (22) which are made of plastics material and are arranged in the lighting device (5), characterized in that the dark-colored components (22) comprise a cover frame (22) and are produced, at least in regions, from a plastics material having thermally conductive additives, specifically carbon nanotubes (CNT), thermally conductive oxides (TCO), ceramic or metal fillers or combinations thereof, and are produced having a thermally conductive layer on their side exposed to radiation from the outside, the layer being, at least in regions, a dark layer comprising thermally conductive additives, specifically carbon nanotubes (CNT), thermally conductive oxides (TCO), ceramic fillers or combinations thereof, and/or being, at least in regions, a transparent layer comprising thermally conductive additives, specifically carbon nanotubes (CNT), thermally conductive oxides (TCO), ceramic or metal fillers or combinations thereof.
2. Lighting device (5) according to claim 1, characterized in that the plastics material of the dark-colored components (22) is a thermoplastic or a thermoset, in particular having color pigments.
3. Lighting device (5) according to either claim 1 or claim 2, characterized in that the dark-colored components also comprise a tube and/or a decorative strip of the lighting device (5).
4. Lighting device (5) according to any of the preceding claims, characterized in that the dark layer, which is applied, at least in regions, to the plastics material of the dark-colored components (22) and comprises thermally conductive additives, also comprises metal fillers.
5. Lighting device (5) according to any of claims 1 to 4, characterized in that the dark or transparent layer is applied by printing, spraying, blade coating, sputtering or by applying a film to the plastics material of the dark-colored components (22).
6. Lighting device (5) according to any of claims 2 to 5, characterized in that the thermoplastic material is designed as a polycarbonate.
7. Lighting device (5) according to any of the preceding claims, characterized in that the lighting device (5) comprises a light module (7) having a light source (12) and a projection optics (18).
8. Lighting device (5) according to claim 7, characterized in that the light source (12) comprises at least one semiconductor light source, in particular a light-emitting diode.
9. Lighting device (5) according to any of the preceding claims, characterized in that the light-focusing means comprise a projection lens (18), a reflector (10) and/or a bent or curved cover disk (15) of the lighting device (7) .

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