Headlight with condensation protection device

Abstract

The invention relates to a headlight (1), comprising a headlight housing (10) having a light exit opening (12) closed off by a covering sheet (11), at least one LED light source (21) arranged in at least one light module (20), positioned in the headlight housing (10), for producing a predefined light distribution in front of the headlight (1), and an anti-condensation protection device (30) having at least one air channel (40) for guiding air (41) and having at least one radiation emitter (60), wherein the at least one air channel (40) has an air entry opening (42) and at least one air exit opening (43) and the air exit opening (43) preferably faces the covering sheet (11), and the air (41) guided in the air channel (40) is heatable by the thermal radiation generated by the radiation emitter (60). The at least one radiation emitter (60) is arranged within the air channel (40) in the region of the air entry opening (42), wherein the air channel (40) is produced from a wall material (45) that reflects infrared radiation and is nontransmissive to light, and the air channel (40), between the air entry opening (42) and the air exit opening (43), has at least one curved longitudinal axis section (50) having a radius (51) of curvature and an angle (52) of curvature.

Description

[0001] The invention relates to a headlight, in particular a motor vehicle headlight, having the features of the preamble of independent claim 1.

[0002] Headlights, particularly those of motor vehicles, are often subject to the undesirable formation of water droplets or films and / or the formation of ice films, which can occur in adverse weather conditions, for example during rain, snowfall, fog or ice mist, due to the deposition of excess moisture from the air as a result of condensation or the formation of frost.

[0003] Generally, condensation, or dew, refers to the water that forms on the cool surface of an object when air or gas containing water vapor cools below the dew point. Condensation on technical objects, such as on cover panes or inside the housings of vehicle headlights, is referred to as dew or fogging.

[0004] Various designs of headlight trace heaters that serve as condensation protection are already known from the prior art. For example, document EP 0 859 188 A2 relates to a headlight condensation protection device in which the waste heat from a conventional quartz bulb base of a low beam lamp and / or a high beam lamp, which typically reaches temperatures of up to 900°C during operation, is directed by means of a reflector toward the cover plate of the headlight housing, heating it and thus ensuring a condensation-free cover plate or condensation-free surfaces in the headlight housing.For modern vehicle headlights, whose light modules have at least one light source for emitting the light to generate the light distribution, which is designed as a semiconductor light source, preferably as a light-emitting diode (LED), this conventional variant of the trace heating of the headlight housing is no longer sufficient due to the insufficient waste heat of the energy-saving light sources, such as light-emitting diodes.

[0005] Document DE 10 2011 084 114 A1 relates to a conventional motor vehicle headlight with a headlight housing and a light exit opening closed by a cover plate. A light module for generating a predetermined light distribution in front of the vehicle is located within the housing. Furthermore, a fan device including a heating element with a connecting tubular air duct is arranged within the housing, with the heating element being integrated within the fan device. The heating element can be designed, for example, as a heating sleeve that surrounds the air duct from the outside, as a heating conductor, heating coil, heating band, heating mat, or heating register. The fan device serves to circulate heated air within the headlight housing, thus ensuring condensate-free surfaces in the headlight housing.The disadvantage of this design is at least that the fan device, for example in the form of an axial fan with integrated heating elements, is structurally complex and also results in increased operating and maintenance costs during operation.

[0006] Furthermore, document DE 10 2004 025 623 A1 discloses a headlight for a motor vehicle in which a light-emitting diode array serves as the main light source. However, since modern white light-emitting diodes—in contrast to conventional headlights with previously common halogen light sources—generate virtually no infrared heat in the light cone, which could be used to defrost or de-ice the headlight cover, this headlight is provided with a separate heat-conducting agent as headlight condensation protection. The heat-conducting agent serves to exchange heat generated on the back of the luminous surfaces of the light-emitting diode array with an air flow inside the headlight. For this purpose, the heat-conducting agent is equipped with air conducting means and is preferably designed as a heat sink with cooling fins, wherein the spaces between the cooling fins form air conduction channels.The cooling fins are arranged parallel to the airflow, which conducts the waste heat from the LEDs to the headlight cover. Since the heat source of the LEDs is not adjustable, it is proposed to additionally provide a heat exchanger so that the heat exchanger can either add heat to the airflow or, conversely, extract heat from it.

[0007] The disadvantage of this design is that the heat dissipation from the LEDs is usually too low to ensure sufficient heating of the headlight cover in extreme weather conditions such as snowfall or fog, or at particularly low temperatures. Furthermore, the required heat conduction elements and an additional heat exchanger for regulating the airflow temperature are complex and expensive.

[0008] Modern LED headlights are designed to minimize the amount of waste heat generated by the LEDs. During operation, an airflow in direct contact with a heat sink, typically located on the back of the LED's illuminated surfaces, can typically reach temperatures of up to 80°C to 100°C. However, the airflow has already cooled significantly on its way to the cover. Therefore, previously known concepts for quickly defrosting and defrosting cover screens or for preventing unwanted condensation on vehicles are unsuitable for LED headlights.

[0009] The device for defrosting a lighting unit disclosed in document DE 10 2012 005 874 A1 is also complex because it describes a plurality of light-emitting diodes arranged with their rear sides on the outside of an air duct located in the interior of a vehicle headlight. The air duct extends from the rear of a reflector through the reflector towards the headlight cover plate. Waste heat from the engine compartment of the motor vehicle, which is conveyed by a fan located in the engine compartment through the air duct into the interior of the vehicle headlight, is further heated by the waste heat generated on the rear sides of the light-emitting diodes attached to the outside of the air duct. To improve air flow towards the cover plate, the air duct has a nozzle at its front free end, which is oriented towards the cover plate.

[0010] A disadvantage of this design is the considerable construction effort required to arrange the air duct so that it extends through the reflector and forms a connection between the interior of the vehicle headlight and the engine compartment without disrupting the desired light distribution of the reflector. Another disadvantage is that this defrosting device for the headlight only becomes effective when the operating temperature of the internal combustion engine in the engine compartment reaches correspondingly high values, for example, over 100°C. Even with this complex device, rapid defrosting and defrosting of the vehicle headlight cover plates is not possible.

[0011] Furthermore, DE 10 2013 001287 A1 shows a headlight with features of the headlight mentioned above.

[0012] The present invention aims to provide a headlight with a condensation protection device for trace heating the headlight, which avoids the disadvantages of the prior art described above. The condensation protection device should ensure the shortest possible defrosting time for the cover lenses of the headlight equipped with it. Furthermore, the condensation protection device should be simple in design, integrated inside the vehicle headlight, and be cost-effective and as maintenance-free as possible during ongoing heating operation.

[0013] According to the invention, these objects are achieved in a generic headlight having the features of the characterizing part of claim 1. Advantageous embodiments and further developments of the invention are set forth in the subclaims and the description.

[0014] The invention further provides a motor vehicle having at least one headlight with a dew forming device.

[0015] In a headlight according to the invention, the air duct of the anti-condensation device is expediently designed such that, when thermal radiation in the form of infrared radiation is fed in by the radiation emitter arranged within the air duct, the escape of visible light at the at least one air outlet opening is prevented. This is ensured by at least one curved longitudinal axis section between the air inlet opening, at which the radiation emitter is arranged, and the air outlet opening. The at least one air duct can have one or more curved sections. The air duct is shaped such that visible thermal radiation components of the radiation emitter are correspondingly reflected or totally reflected on the inner surfaces of the curved longitudinal axis sections of the air duct. Furthermore, the air duct is made of an infrared-reflecting and opaque wall material.

[0016] To define what is understood in the context of this application by the term curvature or a curved longitudinal axis section: The curvature of a plane curve is the change in direction when passing through the curve. The curvature of a straight line is zero everywhere because its direction does not change. A circle (arc) with radius r has the same curvature everywhere because its direction changes equally everywhere. The smaller the radius of the circle, the greater its curvature. The size of the circle serves as a measure of the curvature of the curve. 1 r = Δ φ Δ s , the ratio of the central angle or angle of curvature to the length of a circular arc. The central angle or angle of curvature is equal to the exterior angle between the tangents to the circle at the endpoints of the arc-shaped curve segment. To define the curvature of any curve at a point, consider a curve segment of length Δ s,which contains the point in question and whose tangents at the endpoints are at an angle Δ φ This means that the curvature κ at the point is κ = Δ φ Δ s defined. If the curvature at a point is non-zero, then the inverse of the curvature is called the radius of curvature. If the curvature at a point is infinite, then the radius of curvature at that point is zero, and the curve "bends" or forms a break point. A break point is therefore a point at which a curve significantly changes its curvature and, consequently, its direction. The corners of a rectangle, for example, are such break points.

[0017] In the extreme case, a curved longitudinal axis section of the air duct is also understood to mean such a bending point of the air duct for a radius of curvature = 0 (zero). An air duct of an anti-condensation device according to the invention can thus be understood to have one or more bending points. Thus, an air duct consisting of two or more straight air duct sections whose longitudinal axes have one or more bending points in the form of an open polygonal line is also encompassed by the invention.

[0018] The cross-section of the air duct is not subject to any design restrictions. The air duct can have a square, rectangular, triangular, circular, or elliptical cross-section, for example, in sections or throughout. Therefore, depending on the requirements and space requirements of the headlight, the air duct can be at least partially shaft-shaped (angular) or tubular (round). Furthermore, within the scope of the invention, the air duct can, for example, branch into a Y-shape and have two or more air outlet openings, from each of which heated air radiates to heat the cover plate. Likewise, several air inlets can lead to a common air outlet opening of the air duct.The at least one air outlet opening is preferably directed towards the cover plate of the headlight or at least oriented such that the heated air flowing out of the at least one air outlet opening is directed as directly as possible towards the cover plate.

[0019] As is well known to those skilled in the art, a light module has at least one light source for emitting the light to generate the light distribution, which here is designed as a light-emitting diode (LED). To generate the desired light distribution, the light module has, for example, primary optics, for example in the form of a reflector and / or a TIR (Total Internal Reflection) attachment optic, for bundling the light emitted by the semiconductor light source. In addition, the light module can also have secondary optics, for example in the form of a converging lens, in the beam path of the emitted light, wherein the secondary optics projects the bundled light onto the road in front of the vehicle to generate the light distribution.If the light distribution is a dimmed light distribution, for example in the form of dipped beam or fog light, a diaphragm arrangement can be provided in the light module between the primary optics and the secondary optics, the upper edge of which (in the case of a vertical diaphragm arrangement) or the front edge of which (in the case of a horizontal diaphragm arrangement) is projected as a light-dark boundary onto the road in front of the vehicle.

[0020] In general, the assignment of terms with regard to a location or orientation, such as "horizontal", "vertical", "in the horizontal direction", "in the vertical direction", "top", "bottom", "front", "below", "above" etc., is chosen merely for simplification and these terms may refer to the representation in the drawings, but not necessarily to an actual position of use or installation position of the anti-condensation device or the air duct in relation to the headlight or its headlight housing.

[0021] In an advantageous variant of the invention, in a headlight, the air duct between the air inlet opening and the air outlet opening can have a first curved longitudinal axis section and, spaced from this in the longitudinal axis direction of the air duct, at least one further, second curved longitudinal axis section. By an extended design of the air duct, the heated air can be guided as close as possible to the sections of the headlight housing to be heated. Likewise, it is possible within the scope of the invention to design the air duct in a manner comparable to a heat exchanger such that heated air can accumulate within the air duct and the heated air within the air duct has a higher temperature than when the air exits from at least the air outlet opening of the air duct.Thus, the air duct can act as a heat accumulator, similar to a radiator, and heat the ambient air inside the headlight housing.

[0022] In a further development of the invention, the radii of curvature and the angles of curvature of the first curved longitudinal axis section and of the at least second curved longitudinal axis section can each be the same in a headlight. In this embodiment, standardized air duct sections can advantageously be joined together in order to position the air duct as close to the sections of the headlight housing to be heated as possible and in the most space-saving manner.

[0023] In an alternative embodiment, in a headlight according to the invention, the radii of curvature and / or the angles of curvature of the first curved longitudinal axis section and of the at least second curved longitudinal axis section can be different. This embodiment offers the advantage of being able to install a space-saving air duct within the headlight housing using individually designed air duct sections that are joined together.

[0024] It may be particularly advantageous if, in a headlight according to the invention, the angle of curvature of at least one curved longitudinal axis section of the air duct is between 50° and 130°, preferably between 60° and 120°, particularly preferably between 70° and 110°. The stated angles of curvature are to be understood as being measured relative to a longitudinal axis direction of a straight section of the air duct.

[0025] Depending on the orientation and installation position of the air duct in relation to the headlight housing, such a straight length section of the air duct can, for example, point upwards in the vertical axial direction, with the air inlet opening together with the radiation emitter being located at the lower end of this vertically aligned air duct.

[0026] With respect to this assumed vertical reference axis, a first curved longitudinal axis section can, for example, be curved between 50° and 130° relative to the vertical axis direction. If the angle of curvature is selected to be greater than 90° in this case and, for example, 120° relative to the vertical axis direction, the free end of the air duct with its air outlet opening points diagonally downward. Thus, in the area of ​​the curved longitudinal axis section, according to this assumed installation position of the air duct, a highest section is formed in which the heated air will accumulate before flowing downward to the air outlet opening due to convection flow—or, in the case of the use of an additional fan, due to the set forced flow.This circumstance can be advantageously exploited, for example, by forming an air collection chamber at such a section of the air duct that is located highest in relation to the respective installation position. This chamber is connected to the air duct and in which the heated air can accumulate. As already mentioned at the beginning, this conceivable design variant can also serve – comparable to a heat exchanger – to allow heated air to accumulate within the air duct, and the heated air within the air duct has a higher temperature than when the air exits from at least the air outlet opening of the air duct.

[0027] In a further advantageous embodiment of the invention, the radius of curvature of at least one curved longitudinal axis section of the air duct in a headlight can be from 0 mm to 100 mm, preferably from 1 mm to 80 mm. Depending on the embodiment, longitudinal axis sections of the air duct can also be used that have a bend, i.e., a curvature with a radius of curvature of 0 mm.

[0028] In a headlight according to the invention, the air duct can expediently be made of a wall material selected from the group consisting of: sheet steel, aluminum, aluminum alloys, metal matrix composite material, plastic, temperature-resistant plastic and / or a plastic composite material.

[0029] Examples of suitable wall materials include the following temperature-resistant plastics: PI polyimide, PEEK polyetheretherketone, PPS polyphenylene sulfide, PA polyamide, PBT polybutylene terephthalate, and PET polyethylene terephthalate. Thus, materials that are already established for the production of headlights, particularly automotive headlights, can be advantageously used to manufacture the air duct.

[0030] The embodiment of a headlight according to the invention in which the radiation emitter is an infrared radiator, preferably a quartz radiator, a halogen radiator or an infrared lamp, can be particularly advantageous.

[0031] Particularly inexpensive, common infrared heaters can be used as radiation emitters. In a quartz heater, a heating resistor through which an electric current flows is usually located in a quartz tube filled with inert gas. This means that the temperature of the heating wire can be set higher than in a conventional heater. A halogen heater is usually more efficient than a quartz heater. Halogen heaters are also used, among other things, for cooking purposes under ceramic hobs. Infrared lamps (also called red light lamps or heat lamps) are lamps that emit predominantly invisible heat radiation. For this purpose, a filter, usually red, can be built into the infrared lamp to filter out the remaining (non-red) visible light. The light sources used can also contain these filters directly in their glass casing.In addition to the (still visible) red light component, the emitted radiation then mainly includes so-called near infrared radiation (NIR).

[0032] A particularly economical and cost-effective variant of the invention is provided with a headlight in which the radiation emitter is a halogen lamp. For example, standardized H11 halogen lamps or comparable lamps can be used as the radiation emitter. This has the advantage that these are common spare parts that can be obtained quickly and inexpensively. Depending on the headlight design, it is thus possible for anyone to replace a radiation emitter in the form of a halogen lamp quickly and easily.

[0033] According to the invention, the air duct is provided on its inner surfaces with a visible light-absorbing, light-shading coating, wherein the light-shading coating is preferably dark, particularly preferably deep black.

[0034] Suitable light-shading coating materials can be obtained, for example, from ACM Coatings GmbH, a subsidiary of Acktar Ltd. Acktar (see https: / / www.acm-coatings.de / ). Such light-absorbing coatings can be used, for example, in the form of direct coatings. Coatings in the form of foils or films can also be used. These are deep-black coated foils and films, with or without an adhesive layer, which can also be used to coat larger surface areas. Depending on the coating material used, excellent absorption values ​​can be achieved with such light-absorbing foils. For example, such foils can exhibit a hemispherical reflection of less than 1% at wavelengths from 10 nm to 10,000 nm.

[0035] In a further advantageous variant of the invention, the anti-condensation device for a headlight can further comprise a fan, which is connected to the air duct. A fan offers the advantage that the heated air flowing out of the air duct can be directed particularly effectively to corresponding sections of the cover plate for defrosting due to the forced flow caused by the fan. This is particularly advantageous for larger headlight housings, for example, those of trucks, in order to quickly and effectively heat the correspondingly larger volumes within the headlight housing.

[0036] In a further development of the invention, the fan blower in a headlight can be integrated into the air duct. Depending on the design, the fan blower can be arranged entirely or at least partially within the air duct. The fan blower is preferably arranged near the radiation emitter in order to transport the heated air away from the radiation emitter as quickly as possible within the air duct.

[0037] It can be advantageous if, in a headlight according to the invention, the air outlet opening of the air duct is designed as a diffuser for even air distribution. The exit velocity of the air from the air outlet opening is evened out or slowed down by the use of a diffuser. Thus, in this design, the air space within the headlight housing is heated as evenly as possible.

[0038] Within the scope of the invention, a motor vehicle with at least one headlight according to the invention is also specified.

[0039] Further details, features, and advantages of the invention will become apparent from the following explanation of exemplary embodiments schematically illustrated in the drawings. The drawings show: Fig. 1 in a partially cut-out oblique view from the front, a headlight according to the invention with a dew protection device; Fig. 2 in schematic sketches possible variants of air ducts with a curved ( Fig. 2a ) or bent ( Fig. 2b ) Longitudinal intercept; Fig. 3 a further embodiment of a headlight according to the invention in a cut-away side view with a condensation protection device with a double-bent air duct in the installed position within a headlight housing; Fig. 4 a next embodiment of a headlight according to the invention in a cut-away side view with an anti-condensation device with a double-curved air duct in the installed position within a headlight housing; Fig. 5 a further embodiment of a headlight according to the invention in a cut-away side view with a forked, doubly curved air duct of an anti-condensation device in the installed position within the headlight housing; Fig. 6 in schematic sketches possible variants of air ducts with a curved ( Fig. 6a ) or bent ( Fig. 6b ) Longitudinal axis section, wherein the air outlet opening is shaped in the form of a diffuser.

[0040] Fig. 1 shows a first headlight 1 according to the invention with an anti-condensation device 30. This is a headlight 1 for a motor vehicle. The headlight 1 has a headlight housing 10 together with a cover plate 11, which in a manner known per se closes off a light exit opening 12, which, when the headlight 1 is installed in the motor vehicle, points forward in the direction of travel towards a roadway. Inside the headlight housing 10 there is a light module 20 with several LED light sources 21. The headlight 1 is equipped with an anti-condensation device 30, which has an air duct 40 for guiding air 41. The direction of air flow within the air duct 40 is symbolized here by an arrow 41. The air duct 40 shown here is essentially vertical orSlightly inclined upwards, it is mounted within the headlight housing 10 and has an air inlet opening 42 at its lower end in the installed position and an air outlet opening 43 at its upper, curved end. The longitudinal axis direction of the straight length section of the air duct 40 is designated by the reference numeral 44 to identify the longitudinal axis of the air duct 10. The air duct 10 is made of a wall material 45, for example, a temperature-resistant plastic made of polybutylene terephthalate (PBT for short). An inner surface 46 of the air duct 40 is provided with a light-shading coating 70, which largely absorbs visible light and prevents unwanted light reflection.

[0041] At the upper end of the air duct 40, a curved longitudinal axis section 50 adjoins the straight longitudinal axis section 44 of the air duct 10. The air outlet opening 43 is thus oriented essentially horizontally toward the upper edge of the cover plate 11. An angle of curvature 52 between the straight longitudinal axis section 44 of the air duct 10 and the curved longitudinal axis section 50 is slightly greater than 90°.

[0042] A radiation emitter 60, which is designed here as a cost-effective halogen lamp 65, is arranged at the lower end of the air duct 40 in the region of the air inlet opening 42. During operation of the radiation emitter 60, the heated air rises in the direction of arrow 41 within the air duct 40 from bottom to top and leaves the air duct 40 after the curved longitudinal axis section 50 through the air outlet opening 43. In Fig. 1 A convection flow is sketched in dashed lines, after which the heated air flows in the interior of the headlight housing 10 along the inside of the cover plate 11, is cooled there, and at the lower edge of the headlight housing 10 again passes through the air inlet opening 42 into the air duct 40. In the air duct 40, the air is again heated by the radiation emitter 60 and rises again upwards in the direction of arrow 43.

[0043] Fig. 2 shows in schematic sketches possible variants of air ducts 40 with a curved ( Fig. 2a ) or a bent ( Fig. 2b ) Longitudinal section. The air ducts 40 shown here purely schematically are possible alternatives for installation, for example, in the Fig. 1 headlight 1 shown.

[0044] In Fig. 2a The curved longitudinal axis section 50, which borders the upper end of the straight longitudinal axis section 44 of the air duct 40, has a radius of curvature 51 and an angle of curvature 52. The radius of curvature 51 is, for example, 10 mm here—assuming an overall length of the air duct 40 of approximately 100 mm. The angle of curvature 52 of the curved longitudinal axis section 50 relative to the axial direction 44 of the straight longitudinal axis section of the air duct 40 is, for example, 120° here. The air outlet opening 43 thus points obliquely downward in the installed position of the air duct 40. A halogen lamp 65 serves as the radiation emitter 60 here.

[0045] In Fig. 2b The air duct 40 has a bend, i.e., a curved longitudinal axis section 55 with a radius of curvature 56 equal to zero or 0 mm. This bend is located between the lower straight longitudinal axis section 44 and the longitudinal axis section 44 of the air duct 40 adjoining it at an angle of curvature 57, or in this case, at an angle of bend 57. The selected angle of curvature 57, or in this case, the angle of bend 57, is, for example, 110°. The lower straight longitudinal axis section 44 is oriented slightly obliquely upwards here. The upper or second straight longitudinal axis section 44 is oriented essentially horizontally here. The air outlet opening 43 thus points approximately horizontally into a headlight housing (not shown) in the installed position of the air duct 40. An infrared radiator 61 serves as the radiation emitter 60 here.

[0046] Fig. 3 shows a further embodiment of a headlight 1 according to the invention with an anti-condensation device 30 and a double-bent air duct 40 in the installed position within a headlight housing 10. The first curved longitudinal axis section 50 forms a bending point with a radius of curvature 51 of 0 mm and a curvature angle 52 of approximately 110°. The second curved longitudinal axis section 55 of the air duct 40 forms a bending point with a radius of curvature 56 of 0 mm and a curvature angle 57 of approximately 90°. The heated air flows out of the air outlet opening 43, here obliquely upward in the direction of arrow 41.

[0047] Fig. 4 shows a further embodiment of a headlight 1 according to the invention with an anti-condensation device 30 and a double-curved air duct 40 in the installed position within a headlight housing 10. The first curved longitudinal axis section 50 has a radius of curvature 51 of 10 mm and an angle of curvature 52 of approximately 110°. The second curved longitudinal axis section 55 of the air duct 40 has a radius of curvature 56 of 15 mm and an angle of curvature 57 of approximately 90°. The heated air flows obliquely upward from the air outlet opening 43 in the direction of arrow 41. In the region of the second curved longitudinal axis section 55, a fan 80 is additionally provided to improve convection.

[0048] Fig. 5 shows a further embodiment of a headlight 1 according to the invention with a bifurcated, doubly curved air duct 40 of a condensation protection device 30 in the installed position within the headlight housing 10. The air duct 40 has two spaced-apart air outlet openings 43 at its opposite ends, which blow preheated air 41 into the interior of the headlight housing 10 at the upper and lower edges of the headlight housing 10. A radiation emitter 60 is located approximately centrally within the air duct 40.

[0049] Fig. 6 shows in schematic sketches possible variants of air ducts 40 with a curved ( Fig. 6a ) or a bent ( Fig. 6b ) Longitudinal section. In contrast to the Figuren 2a und 2b Unlike the air ducts shown, the air ducts 40 sketched here each have an air outlet opening 43 shaped like a diffuser 75. The exit velocity of the preheated air is reduced and evened out by the diffuser 75 in a conventional manner. The use of such air ducts 40 achieves particularly gentle and uniform heating of the interior of the headlight housing 10. LISTE DER BEZUGSZEICHEN

[0050] 1Headlight for a motor vehicle 10Headlight housing 11Cover lens 12Light exit opening 20Light module 21LED light source 30Dew condensation protection device 40Air duct 41Air, symbolized by an air flow (in the direction of the arrow) 42Air inlet opening of the air duct 43Air outlet opening of the air duct 44Longitudinal axis of the air duct or longitudinal axis direction 45Wall material of the air duct 46Inner surface of the air duct 50(First) curved longitudinal axis section of the air duct 51Radius of curvature 52Angle of curvature 55(Second) curved longitudinal axis section of the air duct 56Radius of curvature 57Angle of curvature 60Radiation emitter 61Infrared radiator 65Halogen lamp 70Coating on the inner surface of the air duct 75Diffuser 80Fan blower

Claims

1. Headlamp (1), in particular a motor vehicle headlamp, comprising a headlamp housing (10) with a light exit opening (12) closed by a cover lens (11), at least one LED light source (21) which is arranged in at least one light module (20) positioned in the headlamp housing (10) for generating a predetermined light distribution in front of the headlamp (1), and a dew protection device (30) arranged in the headlight housing (10) and having at least one air duct (40) for guiding air (41) and having at least one radiation emitter (60), the at least one air duct (40) having an air inlet opening (42) and at least one air outlet opening (43), and the at least one air outlet opening (43) preferably facing the cover lens (11), and the air (41) guided in the air duct (40) can be heated with the heat radiation generated by the radiation emitter (60), wherein the at least one radiation emitter (60) is arranged within the air duct (40) in the region of the air inlet opening (42), the air duct (40) being made of a wall material (45) which reflects infrared radiation and is opaque, and the air duct (40) having, between the air inlet opening (42) and the at least one air outlet opening (43), at least one curved longitudinal axis section (50) with a radius of curvature (51) and an angle of curvature (52), characterized in that the air duct (40) is equipped on its inner surfaces (46) with a visible light-absorbing, light-shadowing coating (70), the light-shadowing coating (70) preferably being dark, particularly preferably jet black.

2. Headlamp (1) according to claim 1, wherein the air duct (40) has a first curved longitudinal axis section (50) between the air inlet opening (42) and the at least one air outlet opening (43) and at least one further, second curved longitudinal axis section (55) spaced therefrom in the longitudinal axis direction (44) of the air duct (40).

3. Headlamp (1) according to claim 2, wherein the radii of curvature (51, 56) and the angles of curvature (52, 57) of the first curved longitudinal axis section (50) and of the at least second curved longitudinal axis section (55) are in each case the same.

4. Headlamp (1) according to claim 2, wherein the radii of curvature (51, 56) and / or the angles of curvature (52, 57) of the first curved longitudinal axis section (50) and of the at least second curved longitudinal axis section (55) are different.

5. Headlamp (1) according to one of claims 1 to 4, wherein the angle of curvature (52, 57) of the at least one curved longitudinal axis section (50, 55) of the air duct (40) is between 50° and 130°, preferably between 60° and 120°, particularly preferably between 70° and 110°.

6. Headlamp (1) according to any one of claims 1 to 5, wherein the radius of curvature (51, 56) of the at least one curved longitudinal axis portion (50, 55) of the air duct (40) is from 0 mm to 100 mm, preferably from 1 mm to 80 mm.

7. Headlamp (1) according to any one of claims 1 to 6, wherein the air duct (40) is made of a wall material (45) selected from the group consisting of: Sheet steel, aluminum, aluminum alloys, metal matrix composite material, plastic, temperature resistant plastic, plastic composite material.

8. Headlamp (1) according to one of claims 1 to 7, wherein the radiation emitter (60) is an infrared emitter (61), preferably a quartz emitter, a halogen emitter or an infrared lamp.

9. Headlamp (1) according to any one of claims 1 to 8, wherein the radiation emitter (60) is a halogen illuminant (65).

10. Headlamp (1) according to any one of claims 1 to 9, wherein the anti-condensation device (30) further comprises a fan blower (80), which fan blower (80) is connected to the air duct (40).

11. Headlamp (1) according to claim 10, wherein the fan blower (80) is integrated in the air duct (40).

12. Headlamp (1) according to any one of claims 1 to 11, wherein the air outlet opening (43) of the air duct (40) is designed as a diffuser (75) for uniform air distribution.

13. Motor vehicle with at least one headlamp (1) according to one of claims 1 to 12.

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