EP2674666A2 - Illumination device of a motor vehicle - Google Patents

Abstract

The illumination device (5) has a unit for focusing to light of the illumination device. Dark-colored components (22) of plastic are arranged in the illumination device. The dark-colored components are made of plastic material with heat-conducting additive or with a heat-conductive layer on its side impacted through external radiation. The plastic material is provided as thermoplastic or droplet. The conductive additives are provided as carbon nanotubes, thermally conductive oxides, ceramic or metallic fillers. The thermoplastic plastic is formed as polycarbonate.

Description

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

Various lighting devices for motor vehicles are known from the prior art. These can be designed as headlights or as lights. Headlamps are arranged in the front region of a vehicle and serve in addition to the traffic safety by visualizing the vehicle for other road users in particular the illumination of the area in front of the vehicle, for example in the form of a low beam, long distance or fog light distribution and in the form of certain environmental conditions. and / or driving situations adaptable adaptive light distributions, such as static or dynamic curve light, bad weather light, city light, high street light, motorway light. The lighting devices comprise at least one light source, for example in the form of an incandescent lamp, gas discharge lamp or semiconductor light source, for generating light. Furthermore, they comprise 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 reflection. The reflector may have the shape of an ellipsoid, a paraboloid or any other arithmetically calculated free form. The primary optics can also be formed as a translucent body made of glass or plastic, wherein the bundling of the light then takes place by refraction when entering the body and / or exit from the body and / or by total reflection at outer boundary surfaces of the body.

The lighting devices operate e.g. according to the reflection principle, whereby light emitted by the light source is reflected onto the road ahead of the vehicle to produce a desired light distribution by a primary optic designed as a reflector. However, the lighting devices can also work according to a projection principle, wherein light emitted by the light source is focused after bundling by the primary optics, to produce a desired light distribution by projection optics on the road ahead of the vehicle. The projection optics can be designed as a converging lens or as a reflector, preferably with a paraboloid shape.

Lighting devices comprise a housing, which is preferably made of plastic. The housing has a tightly closed by a translucent cover glass or plastic light exit opening through which the light can leave the illumination device. The cover may have at least partially optically active elements (eg prisms, cylindrical lenses, etc.) (so-called. Lens). But it can also be formed without such optically active elements (so-called. Clear disc).

The actual light-emitting unit of a lighting device is combined to form a light module. This includes the light source, the primary optics and, if present, a secondary optic and a diaphragm arrangement for producing a dimmed 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 else by a plurality of light modules and by superposition of the partial light distributions emitted by them.

Around the light module around a plastic cover frame is often arranged covering the gap between two light modules and covering between a light module and the housing to a visually pleasing design of the lighting device, in particular in the off state, contributes. As a rule, a cover frame surrounds the outer circumference of a projection optical system of a projection module or of a reflector of a reflection module. The cover frames may extend on the inside of the housing along the top, back, bottom and / or side sides. Furthermore, it is conceivable in projection modules that the convergent lens and At least partially, a lens holder, via which the converging lens is attached to the remaining light module, is surrounded by a hollow cylindrical tube made of plastic. Additionally or alternatively, other components may be arranged in plastic inside the housing. Cover frame, tubes or other plastic components in the housing may, 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. For coloring the components, a carbon black-containing paint is preferably used.

In solar radiation through the cover into the interior of the housing of the illumination device may, for example. In a projection module through the projection optics, especially if this is designed as a converging lens, a burning glass effect, which can lead to a local melting of the cover, tubes or other plastic components , This effect is further intensified in the case of dark colored components in that the carbon black usually used for dyeing comprises carbon particles which bring about a strong absorption of the radiation in the entire wavelength range, that is to say also the high-energy IR radiation. This leads to a heating of the components and as a result to a visible change in the surface, deformation or even damage to the component, for example. By the burning of holes.

For example, heat-related damage caused by the heat to counteract an incandescent or halogen lamp in the housing of a lighting device, is from the WO 03/099939 A1 the use of infrared-transmissive plastic material is known, wherein the material is used for producing a headlight housing of a motor vehicle. The material consists of a dark colored, IR-radiation-permeable polymer, which absorbs only partial radiation in the near and mid-infrared range, the remaining radiation is transmitted or reflected through the housing, whereby the heating of the headlight housing can be reduced.

Alternatively, it is also known to use heat shields, as in the 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 cooperation with light-focusing means of the lighting devices. In this case, the appearance of the lighting devices should not be changed if possible, in particular no additional components should be necessary for this.

To solve this problem, it is proposed that the dark-colored components of the illumination device are made at least partially of a plastic with heat-conducting additives and / or with a heat-conducting layer on its side acted upon by radiation from the outside.

With radiation from the outside is meant in particular solar radiation. In general, however, this means radiation that is not affected by the Lighting device itself is generated.

In this case, in particular the infrared radiation is of relevance to radiation from the outside incident on the illumination device. Infrared radiation is defined as an electromagnetic radiation that is adjacent to the visible light with increasing wavelengths, that is, begins at a wavelength of approximately 780 nm. Of particular relevance here is the near infrared (NIR) range, i. a wavelength range of about 780 nm to about 3000 nm. The near infrared range is the wavelength range that leads to a particularly high heating of the components when these beams are absorbed by the components. But even beyond the NIR range, the radiation can lead to their heating when absorbed by the components.

Depending on a position of the sun, high-energy sun rays can hit the light-focusing means of the illumination device at different angles. The sun's rays can be bundled accordingly and meet different components in the lighting device. As a light-focusing means is primarily a converging lens of a projection module of the lighting device into consideration. But it is also conceivable that a curved or curved cover, in particular if it comprises optically active elements, light can focus. Furthermore, it would be conceivable that mirrored components (eg cover frames, tubes, diaphragm elements, etc.) shaped in such a way, in particular bent or arched, are that they focus incident light beams on dark colored components of the illumination device. By the introduction of thermally conductive additives in the Plastic material of the dark colored components or by applying a dark or transparent layer on the plastic material with heat-conducting properties, the heat generated by the infrared fraction of solar rays that are incident from outside into the lighting device on the entire component from the zone of special Warming (hot spot) are derived, whereby the partial strong heating of the component is prevented and thus minimizes damage to the component, but preferably prevented.

In order to prevent the light beams bundled by the light-focusing means locally leading to high temperatures in the components when they hit darkly colored components of the illumination device, these components are made according to the invention from a material with improved thermal conduction properties relative to the plastic material or the plastic material is provided with an additional Layer provided on its surface, which has improved thermal conduction properties. Thus, despite the absorption of the infrared radiation by the dark colored component, only a slight warming of these components by incident and focused light rays instead, which is dissipated, the resulting heat immediately to the other areas of the components. Thereby, a change or damage of the surface of the components, deformation and damage of the entire components can be effectively prevented. At the same time, the affected components continue to be darkened, so that the external appearance of the lighting device remains unchanged compared to conventional lighting devices improved heat conduction. On the provision of metallic or metallized surfaces for dissipation and protection against local heating can be waived.

The infrared radiation of the sun, which is focused by the light-focusing means, can strike, for example, at least part of the cover frame, a tube and / or a trim strip. The corresponding components may be at least partially colored dark, for example, to avoid disturbing reflections, which are caused by from the light module of the lighting device exiting light and / or light of other road users and / or any other extraneous light.

Furthermore, thermosets can be used as plastic material.

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

According to a first embodiment, the plastic components are not simply coated with a particular color, but colored through. Thus, the affected components color practically can not differ from the conventional dark components that are used in known from the prior art lighting devices. In addition, a surface structure of the components is not changed. The lighting device looks like the exterior of the conventional lighting equipment. Heat-conductive additives, such as carbon nanotubes (CNT), thermally conductive oxides (TCO), ceramic or metal fillers or combinations of the abovementioned additives are added to the plastic material. Particularly preferred here is the use of Kohlenstoffnanotubes, since they do not change the mechanical properties of the plastics used or only to a small extent. The manufacturing process of the components can therefore be adapted without much effort. The ceramic or metal fillers used as an alternative increase the weight of the components and are associated with increased wear of the tool during processing, for example in the injection molding process.

According to another preferred embodiment, the dark color of the dark colored components can also be achieved by applying a dark layer, which can be provided wholly or partially. This may also be used with thermally conductive additives, such as, for example, to provide the heat-conducting properties. Carbon nanotubes (CNT), thermal conductive oxides (TCO), ceramic or metal fillers or combinations of the aforementioned additives may be provided. The layer may be, for example, by spraying, printing, knife coating, sputtering, coating but also by the application of a film, e.g. be provided by lamination.

According to a third preferred embodiment, it is also possible to apply to the dark-colored components, which may be produced in a conventional manner or according to one of the aforementioned embodiments, a transparent layer which may be provided wholly or partially. This may also be provided with thermally conductive additives, such as Kohlenstoffnanotubes (CNT), thermal conductive oxides (TCO), ceramic or metal fillers or combinations of the aforementioned additives to achieve the heat-conducting properties. The layer may be, for example, by spraying, printing, knife coating, sputtering, Coating can also be provided by the application of a film, for example by lamination. Particularly preferred is a thin layer consisting of Kohlenstoffnanotubes.

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

Further features and advantages of the present invention will be explained in more detail with reference to the drawing. The single 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 comprises a housing 17, which is preferably made of plastic. Inside the housing 17, a light module is arranged, which is designated in its entirety by the reference numeral 7. The lighting device 5 could also comprise a plurality of light modules, wherein in addition to headlight functions, such as low beam, high beam or fog light, and lighting functions such as flashing light, daytime running lights, position light, etc. may be integrated in the lighting device 5.

The light module 7 has a primary optic formed as a reflector 10, which has an optical axis 11. The reflector 10 preferably has an ellipsoidal shape or a free shape similar to an ellipsoidal shape. In one of its possible focal points, a light source 12 is arranged. The reflector 10 focuses the light emitted by the light source 12. In the FIG. 1 However, the light source 12 may also be formed as at least one semiconductor light source (eg, at least one LED, LED) or as a gas discharge lamp. The reflector 10 may be made of plastic or metal. It is arranged in a holder 14 and can be mounted horizontally and / or vertically adjustable in the housing 17 for generating an adaptive light distribution. In the illustrated example, however, the holder 14 is fixedly connected to the housing 17 of the illumination device 5.

In a light exit direction 16 after the reflector 10 and at a distance therefrom, a projection optics in the form of a collection or projection lens 18 is arranged in the beam path of the light reflected by the reflector 10. The light module 7 is therefore designed as a so-called projection module, the projection lens 18 projecting at least a portion of the light focused by the reflector 10 to generate a desired light distribution on the road ahead of the vehicle. The projection lens 18 is attached via a holding frame 20, which is preferably made of metal, to a front edge of the reflector 10 and thus to the remaining light module 7. The Housing 7 has in the light exit direction 16, a light exit opening 19, which is closed by a transparent cover 15. The cover 15 is made of glass or plastic and may be formed 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 condenser lens 18, so that a gap or gap between the light module 7 and the housing interior is covered and when viewed from the outside through the cover 15 into the interior of the Housing 17 is not visible. The cover frame 22 determined by its design (shape, color, texture, etc.) the aesthetic impression and thus the design of the lighting device 5 quite considerably, especially when the light source 12. It is preferably made of plastic and can be at least partially dark or dyed black. The dark color can, for example, prevent unwanted and disturbing light reflections. In the interior of the housing 17 of the lighting device 5 also other dark colored components made of plastic may be present, however, in FIG. 1 are not explicitly drawn. This could be, for example, a tube surrounding the lens holder 20, in particular dark-colored plastic, a decorative strip made of, in particular, dark-colored plastic or the like.

In the interior of the projection module 7, a diaphragm arrangement 24 may be provided which serves to produce a dimmed light distribution, for example a dipped beam or a fog light. In this case, an upper edge of the diaphragm 24 by the converging lens 18 as Light-dark border projected onto the road in front of the vehicle. The diaphragm 24 shadows reflected light from the reflector 10, which would otherwise reach a region above the light-dark boundary in the light distribution. The diaphragm assembly 24 can be moved in and out of the beam path of the light. In this way, the light distribution between dipped and main beam can be switched.

Depending on a position of the sun relative to the light exit opening 19 of the illumination device 5, sunrays 26 which, inter alia, have high-energy infrared radiation can fall through the cover 15 into the interior of the housing 17 at different angles both when the motor vehicle is moving and when the vehicle is stationary. There, the solar rays 26 can be focused on light focusing means, e.g. in the form of the converging lens 18, meet. A top pulled far back over the converging lens 18 cover 15, as they are often present in modern motor vehicles with flat, windschlüpfrigen fronts, favors this effect yet. In a corresponding embodiment of the cover 15, for example. With a corresponding curvature and / or optically active elements, even the cover 15 itself can act as light focusing means.

Infrared radiation is defined as an electromagnetic radiation that is adjacent to the visible light with increasing wavelengths, ie starts at a wavelength of about 780 nm and goes to about 14000 nm. By absorbing IR radiation through a body, it heats up. The sun's rays 19 are in the light focusing means 10; 15; 18 bundled and can then on the in the Lighting arrangement 5 arranged components 22 of z. B. hit dark colored plastic. When the sun is standing 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, meets a relatively large amount of energy in a spatially limited area on the plastic parts 22. A so-called hot spot 28 is formed. So that this energy in the plastic part 22 does not lead to local heating and as a consequence 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 at least partially made of a plastic with thermally conductive additives and / / or to manufacture with a thermally conductive layer on its side acted upon by radiation from the outside.

The infrared radiation of the sun impinges on the plastic part 22, which due to its own heat-conducting properties or the heat-conducting properties of the additionally mounted on it dark or transparent layer, the selective heating 28 on the entire component 22 and so over a larger area or Distributes a larger volume, so that the heat load of the point 28, on which the sunlight is focused, can be kept sufficiently low. At most, there is a slight heating of the component 22, damage to the component 22 by the absorbed IR radiation is practically excluded. For this purpose, the use of carbon nanotubes is particularly preferred. These can be used either as additives directly in the plastic or in a dark or transparent layer on the plastic part. The use of carbon nanotubes is special preferred because they change the mechanical and processing properties of the plastic only slightly.

In this case, the following variants are conceivable: Basically, the whole cover frame (ADR) consist of carbon nanotubeshaltigem plastic or TCO-containing plastic.

Alternatively, the cover frame may also be only partially formed from a corresponding plastic, wherein the cover is made directly in the production as a two-component component and one of the components consists of a corresponding plastic.

Furthermore, alternatively, the critical region can be made of a plastic which contains TCOs or carbon nanotubes and this further part can be clipped into an opening of the cover frame, for example.

Finally, it can be provided as a further possibility to provide the component or regions of the component with a coating containing TCOs or carbon nanotubes.

Claims (11)

Lighting device (5) of a motor vehicle, wherein the illumination device (5) for light of the illumination device focusing means (10, 15, 18), and in the illumination device (5) dark colored components (22) are arranged made of plastic, characterized in that the dark colored components (22) are at least partially made of a plastic with thermally conductive additives and / or with a heat-conducting layer on its side acted upon by radiation from the outside. Lighting device (5) according to claim 1, characterized in that the plastic of the dark colored components (22) is a thermoplastic or a thermoset, in particular with color pigments. Lighting device (5) according to claim 1 or 2, characterized in that the dark colored components comprise a cover frame (22), a tube and / or a trim strip of the illumination device (5). Lighting device (5) according to one of preceding claims, characterized in that the plastic of the dark colored components (22) thermally conductive additives, in particular Kohlenstoffnanotubes (CNT), thermally conductive oxides (TCO), ceramic or metal fillers or combinations thereof are added. Lighting device (5) according to one of the preceding claims, characterized in that the plastic of the dark colored components (22) at least partially a dark layer comprising heat conductive additives, in particular Kohlenstoffnanotubes (CNT), thermally conductive oxides (TCO), ceramic or metal fillers or Combinations thereof is applied. Lighting device (5) according to one of the preceding claims, characterized in that on the plastic of the dark colored components (22) at least partially a transparent layer comprising heat conductive additives, in particular Kohlenstoffnanotubes (CNT), thermally conductive oxides (TCO), ceramic or metal fillers or Combinations thereof is applied. Lighting device (5) according to any one of claims 5 or 6, characterized in that the dark or transparent layer by printing, spraying, knife coating, sputtering or by applying a film on the plastic of the dark colored components (22) is applied. Lighting device (5) according to one of claims 2 to 7, characterized in that the thermoplastic material is formed as a polycarbonate. Lighting device (5) according to one of the preceding claims, characterized in that the illumination device (5) comprises a light module (7) with a light source (12) and a projection optical system (18). Lighting device (5) according to claim 8, characterized in that the light source (12) comprises at least one semiconductor light source, in particular a light emitting diode. Lighting device (5) according to one of the preceding claims, characterized in that the light-focusing means comprise a projection lens (18), a reflector (10) and / or a curved or curved cover (15) of the illumination device (7).

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