Reflector, low beam module and automobile headlight comprising the reflector and process of modification of working surface for the reflector

Abstract

A reflector (2) for a low beam module for an automobile headlight, a low beam module and an automobile headlight comprising the reflector (2) and a process for creating a working surface (4) for the reflector (2). The reflector (2) comprises a working surface (4) for reflecting light from a light source (1) of the low beam module towards a lens (3) of the low beam module, and the working surface (4) is provided with a reflective section (5) and a cut-off line section (6). The cut-off line section (6) has a lower reflectance than the reflective section (5), wherein the cut-off line section (6) is for creating a cut-off line (7) for reducing dazzling of oncoming drivers in the light beam emitted by the low beam module when in operation. The reflective section can be created by metallic coating of base material of the reflector.

Description

[0001] Reflector, low beam module and automobile headlight comprising the reflector and process of modification of working surface for the reflector

[0002] Technical field

[0003] The present invention relates to automotive lighting. More specifically it relates to a reflector for a low beam module and its adaptation to provide an asymmetrical output beam with a cut-off line in order to prevent dazzling of oncoming drivers.

[0004] Background of the Invention

[0005] Automobile headlights generally comprise multiple lighting modules for performing various illumination functions. These modules usually include a high beam module, which a driver can use to illuminate the road far ahead when there is no traffic in front of the driver in either direction, and a low beam module (also called dipped or passing beam module), which drivers use when there is other traffic in front of them. The low beam module can provide an asymmetrical light beam, which shines further ahead in the driver’s own lane than in the opposite lane, i.e., the light falls farther ahead in the right lane than in the left lane in right-hand traffic.

[0006] A know way of providing this asymmetrical beam is to provide a shading element in front of the low beam’s light source, lens or reflector. The shading elements blocks a part of the light beam produced by the light source so there is a shaded area on the road corresponding to the shape and position of the shading element. The element is said to provide a cut-off line or asymmetrical cut-off line, i.e., the boundary between illuminated and shaded area is closer to the vehicle on one side of the road than on the other. An example of headlight with such a low beam module is disclosed in document JP2003168307A. One disadvantage of using such a shading element is in the need to provide a different shading element with different shape and position for different countries having different legislation defining how a low beam light beam needs to look. Different position of the shading element might thus require a significant change in the construction of a headlight. Providing an alternative way of providing a low beam cut-off pattern would therefore be advantageous.

[0007] Summary of the Invention

[0008] The shortcomings of the solutions known in the prior art are to some extent eliminated by a reflector for a low beam module for an automobile headlight. The reflector comprises a working surface for reflecting light from a light source of the low beam module towards a lens of the low beam module. The working surface is provided with a reflective section and a cut-off line section, wherein the cut-off line section has a lower reflectance than the reflective section. This difference in reflectance can be achieved especially by coating of at least one of the sections, e.g., by providing the reflective section with a high- reflectance metallic coating. The cut-off line section is for creating a cut-off line in the light beam emitted by the low beam module when in operation, the cut-off line serving for reducing dazzling of oncoming drivers. The shape, size and location of the cut-off line section can have impact on the shape and location of the cut-off line in the resulting beam, or more precisely in an illumination pattern it provides on a road surface, where the cutoff line can delimit a boundary between light and dark areas of the road.

[0009] The cut-off line section is preferably adjacent to the top or bottom edge of the working surface, or of the reflective section. Preferably, it is placed asymmetrically in horizontal direction, i.e., to the left or to the right when viewed from area in front of a vehicle equipped with the module with the reflector. It can have for example a substantially trapezoidal shape.

[0010] The reflector is preferably a freeform optical element. E.g., the shape of the working surface and / or its reflective section and / or the cut-off line section can be provided by a computer-aided design based on the desired optical function. E.g., the working surface is designed to reflect light towards a projection lens of the module. The working surface, especially the cut-off line section where there is a cut-out or opening in the reflective section (e.g., in a reflective coating), can be designed to provide a shaded area in the opposite traffic lane when the reflected light beam is directed by the lens in the module.

[0011] The cut-off line for reducing or preventing the dazzling of oncoming drivers can be partially based on legislative requirements, usually specific for a certain country or region. Brightness of illumination in the opposite traffic lane at certain distance(s) in front of the vehicle equipped with the low beam module can be defined, shape of the cut-off line can be defined etc. The resulting light beam, outputted by the low beam module, can then by asymmetrical, such that the cut-off line gets closer to the vehicle on the opposite lane. E.g., in right-handed traffic, the right side of the road and the area to the right of the road is illuminated more (more brightly and / or farther) than the left side of the road and the area farther to the left. The provided cut-off line can thus be a relatively sharp boundary between an illuminated area of the road (closer to the vehicle) and non-illuminated area (farther away) and this boundary can be tilted, bent or shifted at the dividing line(s) between the traffic lanes or close to the dividing line(s). These requirements as well as other requirements such as aesthetic considerations can then have impact on a specific shape of the cut-off line section on the working surface, e.g., as defined by a skilled person with a computer-aided-design software.

[0012] The cut-off line section can be uncoated, e.g., it can be a non-coated surface of the reflector, e.g., made of plastic. It can also be coated by an additional light absorbing material, e.g., a black coating. The reflective section is preferably coated with a reflective coating but in can also be formed from a reflective material without further coating. The cut-off section is then provided with a treatment or coating for lowering reflectance.

[0013] Providing the cut-off line for low beam function by the cut-off line section of the reflector can be advantageous because it removes the need for a separate shading element, holder for such an element etc. The module and the final headlight can then be cheaper, lighter, smaller etc. Different modules or headlights for different markets with different legal requirements for the low beam function can then be provided by changing the shape of the reflective section and the cut-off line section. Other components can remain the same, e.g., the reflector can have the same overall shape for any possible cut-off line shape, with the same mounting means, space requirements etc. The reflector can e.g., be made in the same injection molding device regardless of the required cut-off line shape since only the coating has to be changed, e.g., a mask for covering the cut-off line section before coating can have a different shape or the coating is machined-off in a differently shaped part of the working surface. Producing headlights for different markets or for customers requiring differently shaped cut-off lines is thus cheaper and easier.

[0014] In other words, the shape of the reflective section and the cut-off line section of the working surface defines the shape of the cut-off line when the reflector is used in a headlight (module), usually after the reflected light passes through one or more lenses. Boundary of the reflective section on one of its sides, e.g., at the bottom of the section, defines the cut-off line - boundary between illuminated and non-illuminated parts of the road. This boundary, defining the shape of the cut-off line section, can then be the only thing that needs to be changed when a different shape of the light-dark boundary in the resulting light beam pattern is required for any reason.

[0015] The reflectance of the reflective section, i.e., the proportion of the light falling on the section, which is reflected and not absorbed or let through, is preferably at least 80 %. More preferably it is at least 85 %, e.g., at least 90 %. The higher the reflectance, the better the efficiency of the resulting module can be, e.g., less energy is needed to provide the same illumination intensity.

[0016] The reflectance of the cut-off line section is advantageously at most 10 %, more advantageously at most 5 %, e.g., at most 4 %. The rest of the light falling on this section can be absorbed or can pass through the section into the reflector (e.g., it can be absorbed inside of or behind the reflector or on its back surface or it can be even utilized after passing through the reflector for a different illumination function). When the cut-off line section reflectance is lower, the contrast of the cut-off line in the resulting pattern is higher, e.g., less light can be directed to the area of the road which is supposed to be unilluminated when the low beam function is used. The reflectance can be affected by a material of the surface of the section, by its roughness, by a coating etc.

[0017] The reflectance of the reflective section can advantageously be at least 20 times higher than the reflectance of the cut-off line section. More advantageously it is at least 24 times or at least 30 times higher. A sufficient contrast of the cut-off line can then be achieved, which can have an impact on aesthetics of the light beam pattern, on complying with legal requirements etc. Generally, even reflectance just, e.g., at least 5 times higher on the reflective section than on the cut-off line section, is possible. A reflectance ratio of at least 10:1 is however more preferable and the ratio of at least 20:1 , as given above, is even more suitable with respect to illumination effectivity and contrast between the shaded and illuminated areas of the road.

[0018] The reflective section can comprise a reflective coating and the cut-off line section can then be a cut-out in the reflective coating. A coating, e.g., a metallic coating, can be a practical and relatively cheap way of creating a high-reflection surface. Not applying the coating to certain areas of the working surface, or removing the coating from these areas, can then be sufficient to provide a desired contrast between illuminated and nonilluminated parts of the road.

[0019] The working surface can have a bottom edge for being oriented downwards when installed in a headlight of a vehicle wherein the cut-off line section is adjacent to the bottom edge. Since a projection used in the low beam module generally flips the passing light beam over, the bottom area, where part of light is not reflected thanks to the cut-off line section, is farther in front of the vehicle and thus creates the shaded area, especially in the opposite lane, where oncoming traffic is expected. Similarly the cut-off line section can be more to the right when the shaded area is to be on the left (opposite lane in right- handed traffic) and can be more to the left for left-handed traffic. It is however also possible to design the projection lens and other potential optical elements such that the image (light beam) is not flipped over and the cut-off line area can then be adjacent to the top edge instead of the bottom one.

[0020] The cut-off line section can be located off-centre of the bottom edge, in order to provide asymmetrical cut-off line, which is generally required for low beam lights.

[0021] The reflector can especially be made from a transparent or black material. These materials are specifically suitable when the cut-off line section does not receive any coating, i.e., if the reflector material itself needs to have low enough reflectance. Transparent material lets the light through, so it is not reflected, or only a small part of it is reflected. A surface treatment can then have an impact on how much of the light is reflected. A black material can absorb light, so it is also not reflected, or more precisely only a small part of it is reflected while most is absorbed. The cut-off line section can then be an exposed part of the reflector material. This simplifies the manufacture of the reflector, and the resulting module or headlight can thus be cheaper.

[0022] The reflective section is advantageously made of metal, especially of metallic coating. Chromium and / or aluminium and / or silver or their alloys are examples of suitable materials.

[0023] Cut-off line section can cover for example from 5 to 15 % of the working surface. The area mainly depends on shape of the desired light beam pattern.

[0024] The shortcomings of the solutions known in the prior art are to some extent also eliminated by a low beam module for an automobile headlight comprising at least one light source, a lens, such as a projection lens, and the reflector according to the invention. The working surface of the reflector is for reflecting light from the light source towards the lens, e.g., a projection lens. The lens then directs light out of the module, and it can have an impact on shape of the emitted light beam, its homogeneity etc.

[0025] The light source is preferably LED or multiple LEDs. It can be placed under the reflector, partially inside of it, but also above it or to the side of the reflector. Further optical elements can be placed between the light source and the reflector and / or between the reflector and the projection lens and / or in front of the projection lens. The reflector and / or the projection lens are preferably freeform optical elements. E.g., the shape of the lens can be provided by a computer-aided design based on the desired optical function. The lens can be designed to direct the light from the reflector towards the road with a sufficient homogeneity etc.

[0026] The shortcomings of the solutions known in the prior art are to some extent also eliminated by an automobile headlight which comprises the low beam module according to the invention.

[0027] The reflector according to the invention can be made using a process of modification of working surface for the reflector during which the part of the working surface of the reflector for forming the cut-off line section is covered by a mask. The mask preserves the value of reflectance on that part while the rest of the working surface is covered by a more reflective coating. More reflective coating meaning more reflective than the material of the reflector, such that the coated reflection surface of the final reflector has higher reflectivity than the cut-off line surface which was masked during coating. The difference in reflectance is capable to create a cut-off line for preventing dazzling of oncoming drivers in the light beam emitted by a low beam module comprising the reflector, when it is in operation.

[0028] More generally, a process of modification of a reflector working surface can be used to transform a more generic reflector into the reflector according to the invention. In this process, the working surface is divided in two parts - one for forming a reflective section and the other for forming a cut-off line section. The reflectance of one of the sections is then modified to make the reflectance of the cut-off line section lower than that of the reflective section. It is possible to increase reflectance of the reflective section, decrease reflectance of the cut-off line section, or to do both. The difference in reflectance after this modification is capable to create a cut-off line for preventing dazzling of oncoming drivers in the light beam emitted by a low beam module comprising the reflector, when it is in operation. This capability of the cut-off line section is given mainly by its shape, position, and the lower reflectance. The function and advantages of the cutoff line formed by the reflector itself was described in more detail above.

[0029] During the reflectance modification, the cut-off line section can be covered by a mask, e.g., a tape, for preserving the value of reflectance on that part of the working surface while the rest of the working surface is covered by a more reflective coating, e.g., a metallic coating. The mask can then be removed. The desired reflectance difference, e.g., as described above for the reflector according to the invention, is thus achieved by increasing the reflectance of the reflective section and leaving the base material unchanged on the cut-off line section. The cut-off line section can alternatively be further treated to decrease its reflectance so that it’s lower than that of the base material.

[0030] In an alternative way of the reflectance modification, the working surface is covered by a more reflective coating and the coating is then removed from the cut-off line section with laser beam machining. A different kind of machining can also be used. It is again possible to treat the base material uncovered on the cut-off line section to further increase the reflectance difference between the two sections. Description of drawings

[0031] A summary of the invention is further described by means of exemplary embodiments thereof, which are described with reference to the accompanying drawings, in which:

[0032] Fig 1 . Shows a schematical drawing of a front view of an example of the low beam module according to the invention, specifically its reflector and light source, wherein the cut-off line section is located on the lower left side of the working surface;

[0033] Fig 2. Shows a schematical drawing of a side view of the module from fig. 1 , wherein a projection lens is placed in front of the reflector;

[0034] Fig 3. Shows a schematical drawing of a road in front of a vehicle provided with the low beam module, wherein the cut-off line delimiting a boundary between illuminated and dark area of the road is marked by dashed line, wherein the module used is intended for right-hand traffic; and

[0035] Fig 4. Shows a schematical flowchart of an exemplary process of modification of working surface for the reflector.

[0036] Exemplary Embodiments of the Invention

[0037] The invention will be further described by means of exemplary embodiments with reference to the respective drawings.

[0038] An embodiment of the reflector 2 for a low beam module is shown in fig. 1. The reflector 2 is preferably a freeform reflector 2, i.e., different parts of its working surface 4 can be individually adapted by their shape and inclination to reflect light into a desired direction towards a lens 3 of the module. In the depicted embodiment, the projection surface is substantially parabolical, in some embodiments it can be exactly parabolical, but it can also have any different shape configured for reflecting light towards the lens 3. In the exemplary embodiment, the reflector 2 has a bottom wall, which is substantially flat and has an opening for the light from the module’s light source 1, and a back wall, which is curved, and which comprises the working surface 4 on its inner side.

[0039] The working surface 4 has a reflective section 5. Preferably, the reflective section 5 is made of a reflective coating, e.g., a metallic coating. The coating is the part of the surface which reflects the light while the non-coated part of the surface has lower reflectance, preferably much lower, e.g., at least 20 times lower than the reflective section 5. In some embodiments, the part of the working surface 4 without the reflective section 5 can be coated by a different lower-reflectance material, e.g., a black coating for absorbing light. In some embodiments the reflective section 5 can be made of the underlying reflector 2 material, and the less reflective part of the surface can then be provided with a light-absorbing coating or paint.

[0040] The reflective section 5 is shaped such that it partially delimits a cut-out portion which forms a cut-off line section 6 of the working surface 4. The cut-off line section 6 is shaped and located such that after being shaped and / or directed by the lens 3 and optionally other lens or optical elements included in the module or the headlight, the light beam from the reflector 2 forms a cut-off line 7 for low beam light function, i.e., for preventing or limiting dazzling or blinding of oncoming traffic. Such a cut-off line 7 for right-handed traffic is depicted in fig. 3. Light beam with such a cut-off line 7 basically shines farther ahead in front of the vehicle having the low beam module in its own lane (the right lane for righthanded traffic) than in the opposite lane. An exact shape of the low beam light beam is defined by legislation, it can for example be defined, how far ahead and how brightly the module can illuminate the opposite traffic lane. The corresponding shape for the cut-off line section 6 on the working surface 4 for a specific projection lens 3 can be for example obtained by a computer simulation. In the exemplary embodiment, the projection lens 3 flips the light beam (i.e., the image of the projection surface) over, so the cut-off line section 6 is located on the bottom left of the reflective section 5, adjacent to a bottom edge of the working surface 4 and also a bottom edge of the reflective section 5, and the resulting shaded cut-off line 7 area on the road is on the right and on the top (i.e., farther away from the vehicle).

[0041] In the exemplary embodiment in fig. 1 , the cut-off line section 6 has a substantially trapezoidal shape, in different embodiments it can be different based on shape of the working surface 4, geometry of the projection lens 3 and the legislative requirements for a low-beam function. E.g., it can be substantially rectangular, elliptical or triangular etc. The cut-off line section 6 can extend higher on the working surface 4 in order to decrease the illumination distance of the opposite lane, it can be wider to provide a wider shaded area, it can be on the right side of the surface for a left-handed traffic application, it can be on the top of the reflective section 5 if the projection lens 3 does not flip the image or is complemented by more lens, etc.

[0042] The reflective section 5 can have a reflectance of at least 80 %, i.e., at least 80 % of the incoming light is reflected. Commonly used metallic coatings known in the art generally provide reflectance of approximately 83 %, e.g., when aluminum is used. Preferably, the reflectance is at least 90 %, which can for example be achieved by using silver coating. Chromium and / or aluminum and / or silver can for example be used as the metal. The coating can be for example made by applying a mask on the cut-off line section 6, coating the surface by any known method (e.g., vacuum metalizing, or electroplating) and removing the mask. It can also be made by metallizing the whole working surface 4 and then removing the coating on the required cut-off line section 6, e.g., using a laser.

[0043] The cut-off line section 6 can have reflectance lower than or equal to 10 %, preferably lower than or equal to 5 %. The higher the reflectance of the reflective section 5, the higher the reflectance of the cut-off line section 6 can be while providing a sufficient contrast between the cut-off line 7 shaded area of the road and the illuminated area. Brightness of the illumination can then be determined by the light sources 1 used. The ratio between the reflectance of the reflective section 5 and the cut-off line section 6 is preferably at least 10:1 , more preferably at least 20:1 , e.g., at least 24:1. In the exemplary embodiments shown in figs. 1 and 2, a metallic coating with reflectance of 86 % is used while the cut-off line section 6 (non-coated black polycarbonate) has a reflectance of 4 %, so the ratio is 21.5:1. An advantageous ratio of over 30:1 can be achieved by using reflective coating with reflectance over 90 % and lowering the cut-off line section 6 reflectance under 3 %.

[0044] The cut off-line section 6 of the working surface 4 can be made from the underlying material of the reflector 2. The material of the reflector 2 is then preferably black or transparent, such that it absorbs the light that is not supposed to be reflected towards the projection lens 3, or it lets the light through. Polycarbonate or polycarbonate with black pigment can for example be used for the reflector 2. An exemplary embodiment of the low beam module for an automobile headlight according to the invention comprises a light source 1, a reflector 2, e.g., as described above, and a projection lens 3, as depicted in example in fig. 1. The module further includes other components such as a frame for holding the components, e.g., a lens 3 holder and / or reflector 2 holder, a casing for encapsulating the other components and for attaching the module to the headlight, electrical connections, cover lens, heat sink, etc. The light source 1 is for example a LED or an array of LEDs, in the depicted embodiments, the LED is attached to the reflector 2.

[0045] The projection lens 3 is preferably a freeform lens, i.e., lens with individual parts of surface individually shaped to provide the desired optical function. It can be a substantially converging lens, configured by its shape and location for directing the light from the reflector 2 towards the road ahead. Focal point of the projection lens 3 can be substantially at the reflector’s 2 reflective section 5.

[0046] The low beam module can be a part of an automobile headlight, i.e., a lamp for the front of an automobile. The headlight can comprise additional light modules, such as a high beam module, turn signal module, fog light, daytime running light etc. In can further comprise a headlight casing for holding all the modules together and for mounting to the automobile, it can comprise actuators for adjusting the modules, electrical connections for powering the modules, cover lens, etc.

[0047] The reflector 2 can be made for example by injection molding from a polycarbonate or other suitable polymer, such as PMMA. A mask can then be provided and applied on the part of the working surface 4 which corresponds to the cut-off line section 6 on the final reflector 2. The mask thus has a shape corresponding to the shape of the cut-off line section 6. When the mask is attached to the working surface 4, the working surface 4 is coated with a reflective coating, especially a metallic coating. The material under the mask is protected from receiving the coating during this process. The reflective section 5 is thus created. The mask is then removed. The cut-off line section 6 can then optionally receive an additional surface treatment for lowering reflectance, e.g., it can receive a non- reflective coating. It is also possible to provide such a surface treatment to the whole working surface 4 before applying the mask and the reflective coating. The process for modification of the working surface 4 of the reflector 2 is indicated by the flowchart in fig. 4. Alternatively, instead of providing the mask, the whole working surface 4 can be provided with the reflective coating. The area for forming the cut-off line section 6 can then be treated by a coating-removing process, e.g., the coating can be removed using a laser, or it can be provided with a non-reflective coating. Non-reflective coating can be any coating with lower reflectance than the reflective coating, preferably at least 20 times lower.

[0048] List of reference numbers

[0049] 1 - Light source

[0050] 2 - Reflector

[0051] 3 - Lens

[0052] 4 - Working surface

[0053] 5 - Reflective section

[0054] 6 - Cut-off line section

[0055] 7 - Cut-off line

Claims

CLAIMS1 . A reflector (2) for a low beam module for an automobile headlight, the reflector (2) comprising a working surface (4) for reflecting light from a light source (1 ) of the low beam module towards a lens (3) of the low beam module, wherein the working surface (4) is provided with a reflective section (5), characterized in that the working surface (4) further comprises a cut-off line section (6), wherein the cut-off line section (6) has a lower reflectance than the reflective section (5), wherein the cut-off line section (6) is for creating a cut-off line (7) for reducing dazzling of oncoming drivers in the light beam emitted by the low beam module when in operation.

2. The reflector (2) according to claim 1 wherein the reflectance of the reflective section (5) is at least 80 %.

3. The reflector (2) according to any of the preceding claims wherein the reflectance of the cut-off line section (6) is at most 10 %.

4. The reflector (2) according to any of the preceding claims wherein the reflectance of the reflective section (5) is at least 20 times higher than the reflectance of the cut-off line section (6).

5. The reflector (2) according to any of the preceding claims wherein the reflective section (5) comprises a reflective coating and the cut-off line section (6) is a cutout in the reflective coating.

6. The reflector (2) according to any of the preceding claims wherein the working surface (4) has a bottom edge for being oriented downwards when installed in a headlight of a vehicle wherein the cut-off line section (6) is adjacent to the bottom edge.

7. The reflector (2) according to claim 6 wherein the cut-off line section (6) is located off centre of the bottom edge.

8. The reflector (2) according to any of the preceding claims wherein the reflector (2) is made from a transparent or black material.

9. The reflector (2) according to claim 8 wherein the cut-off line section (6) is an exposed part of the reflector (2) material.

10. The reflector (2) according to any of the preceding claims wherein the reflective section (5) is made of metal.1 1 .The reflector (2) according to any of the preceding claims wherein the cut-off line section (6) covers from 5 to 15 % of the working surface (4).

12. A low beam module for an automobile headlight comprising at least one light source (1 ), and a lens (3) characterized in that it further comprises the reflector (2) according to any of the preceding claims.

13. An automobile headlight characterized in that it comprises the low beam module according to claim 12.

14. A process of modification of a reflector working surface (4) for the reflector (2) according to any of claims 1 to 12 characterized in that the working surface (4) is divided into a reflective section (5) and a cut-off line section (6), and the reflectance of one of the sections is modified to make the reflectance of the cut-off line section (6) lower than the reflectance of the reflective section (5), so the difference in reflectance is capable to create a cut-off line (7) for preventing dazzling of oncoming drivers in the light beam emitted by a low beam module comprising the reflector (2), when it is in operation.

15. The process according to claim 14 wherein during the reflectance modification, the cut-off line section (6) is covered by a mask for preserving the value of reflectance on that part while the rest of the working surface (4) is covered by a more reflective coating.

16. The process according to claim 14 wherein during the reflectance modification, the working surface (4) is covered by a more reflective coating and the coating is then removed from the cut-off line section (6) with laser beam machining.

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