Lighting device for vehicles

Abstract

Lighting device for vehicles comprising a planar light guide (1) - two opposite flat surfaces (4) for total reflection of light coupled into the planar light guide (1), - a light coupling surface (8) for coupling light to a light coupling side (3) of the planar light guide (1), - a light output surface (6) for coupling out the coupled light at a light output side (5) of the planar light guide (1), wherein the light output surface (6) forms a narrow side connecting the opposite flat sides (4), - that each light coupling surface (8) is assigned a light source (2) and that the light coupling surface (8) is uneven, that the light coupling surface (8) has a central coupling section (12) arranged in the main emission direction (H) in front of the light source (2) and an outer coupling section (13) adjacent to it, wherein the central coupling section (12) and the outer coupling section (13) are shaped such that a first partial light beam (L1) of the light source (2) incident on the central coupling section (12) strikes a central area (14) of a partial area (16, 16') of the light coupling surface (6) arranged in the main emission direction (H) in front of the light coupling surface (8) and that a second partial light beam (L2) of the light source (2) incident on the outer coupling section (13) strikes an outer area (15, 15', 15") of the same partial area adjacent to the central area (14). (16, 16') hits,characterized in that the central coupling section (12) is shaped such that the first partial light beam (L1) is expanded in the extension direction (R) of the planar light guide (1) and / or in the extension direction of the light output surface (6), so that the central area (14) of the partial surface (16, 16') is stretched in the extension direction (R) of the light output surface (6) and / or that the first partial light beam (L1) is expanded in the direction of its plane (E) extending perpendicular to the flat sides (4) and to the light output surface (6), so that the central area 14 of the partial surface (16, 16') is stretched perpendicular to the extension direction (R) of the light output surface (6), wherein only light rays of the first partial light beam (L1) are emitted from the central area (14) of the partial surface (16, 16') and from the outer area (15, 15', 15") of the Partial area (16,16') where only light rays from the second partial light beam (L2) can be extracted.

Description

[0001] The invention relates to a lighting device for vehicles according to the preamble of claim 1.

[0002] From DE 10 2008 048 765 A1, a lighting device for vehicles is known, comprising a planar light guide with opposing flat sides and a plurality of light sources. The light sources are arranged on a light-input side of the planar light guide. Each light source is associated with a flat light-input surface at which the light emitted by the light source is coupled into the planar light guide. The coupled-in light is totally reflected at the opposite flat sides and coupled out at a light-output side of the planar light guide in the direction of a light-output surface designed as a narrow side. The light is coupled into the planar light guide in an undirected manner via the flat light-input surface, resulting in brightness differences at the narrow light-output surface.Particularly in the main emission direction in front of the light source in the area of ​​one of its optical axis, relatively high brightness values ​​result, which leads to a non-homogeneous illumination of the light output surface.

[0003] From DE 10 2007 057 399 A1, a generic lighting device for vehicles is known, comprising a planar light guide and a plurality of light sources, in which the light coupling surfaces assigned to each light source are spherical, i.e., not flat. This allows a point-like bright illumination of a light coupling surface in the main direction of emission directly in front of the light source to be attenuated. However, the photometric efficiency is impaired because, due to the frequent total internal reflection of the coupled light at the opposite flat surfaces, stray light is generated, which is lost for the required light distribution of the lighting device.

[0004] From US patent 2012 / 0033441A1, a lighting device for vehicles is known, comprising a planar light guide with a light coupling surface and a light coupling surface, and parallel flat sides for total internal reflection of the coupled light. An annular lens is associated with the light coupling surface and is arranged within a recess in the light guide associated with the light source. The recess has flat walls, to the edge of which a central coupling section of the light guide is attached. The flat walls form an outer coupling section of the light coupling surface of the light guide.In conjunction with the lens, the central coupling section leads to a parallelization of the coupled light towards a central area of ​​a light output area, while the outer coupling section, in conjunction with the lens, leads to a parallel light guidance within the light guide and output at an outer area of ​​the light output area.

[0005] From DE 10 2010 005 806 A1, a lighting device for vehicles is known, comprising a planar light guide with a light coupling surface and a light coupling surface and the same connecting flat sides. The light coupling surface has a partially cylindrical coupling section, wherein a first partial light beam entering through a central coupling section is scattered relatively broadly, so that it superimposes at the light coupling surface with a second partial light beam coupled in through an outer coupling section. The second partial light beam is essentially parallelized by paraboloidally shaped total internal reflection surfaces and thus does not intersect a central area of ​​a light coupling surface where a portion of the first partial light beam is coupled out.

[0006] The object of the present invention is therefore to further develop a lighting device for vehicles with a planar light guide in such a way that homogeneous illumination at a light output surface of the planar light guide is achieved in a cost-effective and simple manner, while achieving the highest possible photometric efficiency.

[0007] To solve this problem, the invention has the features of claim 1.

[0008] According to the invention, a light coupling surface of the lighting device has, on the one hand, a central coupling section and, on the other hand, an outer coupling section. The central coupling section is shaped such that a first partial beam of light from a light source striking it is directed into a central area of ​​a partial surface of the light coupling surface located in front of the light coupling surface in the main emission direction. The outer coupling section is shaped such that a second partial beam of light from the light source striking it strikes an outer area of ​​the partial surface adjacent to the central area. The light from the light source coupled into the light coupling surface is thus focused and controlled in the direction of the light coupling surface, resulting in high photometric efficiency.The portion of the light-emitting surface positioned in front of the light-in coupling surface in the main emission direction is illuminated homogeneously or uniformly. The central coupling section shapes the first partial beam of light emitted by the light source at a relatively small opening angle, and the outer coupling section shapes or directs the second partial beam of light emitted by the light source at a relatively large opening angle. The central coupling section and / or the outer coupling section can be formed as a freeform surface.

[0009] According to the invention, the central coupling section of the light coupling surface is shaped such that the first partial light beam is expanded in the direction of extension of the planar light guide and / or in the direction of extension of the light coupling surface, so that the central area of ​​the partial surfaces is elongated in the direction of extension of the light coupling surface. This is achieved by different orientations of the light rays of the first partial light beam in a plane perpendicular to the flat sides and in a plane in the direction of the flat sides. Advantageously, this allows the formation of central areas of the partial surface that follow the contour of the light coupling surface, e.g., rectangular, from which the first partial light beam is coupled out. The light rays of the first partial light beam can, for example, have a larger opening angle in the direction of the flat sides than in the direction perpendicular to the flat sides.The illumination of the light output surface can therefore be adapted to the elongated geometries of the light output surface. If the first partial light beam is spread out perpendicular to the direction of extension of the light output surface, it can be adapted to different thicknesses of the planar light guide.

[0010] According to a preferred embodiment of the invention, the central and outer regions of the partial surface extend over the light coupling surface located behind it in the main emission direction. The partial surface is bounded by edges of the light coupling surface that extend to the adjacent flat sides of the light coupling surface. Furthermore, the central region, from which the first partial light beam is coupled out, is separated from the outer region, from which the second partial light beam is coupled out, by a transition section or a boundary line. The transition section and the boundary line extend essentially transversely to the extent of the flat sides. If a transition section is present, the central and outer coupling sections of the light coupling surface are designed such that a smooth transition occurs between the central and outer regions at the light coupling surface.In this transition section, light rays from the first and second partial light beams are coupled out. If a boundary line is present, the central and / or outer coupling section is shaped such that the central area is discretely separated from the outer area, without creating areas on the light-coupling side where light rays from the first and second partial light beams are coupled out. Both with a transition section and with a discrete boundary line, the light-coupling surface is homogeneously illuminated along its length. Corresponding transition sections or boundary lines are also provided between adjacent partial areas of the light-coupling surface, to which separate light sources are assigned at the rear in the main emission direction.

[0011] According to a preferred embodiment of the invention, the outer coupling section is shaped such that the second partial light beam is focused in a plane perpendicular to the flat sides and to the light output surface. Advantageously, this reduces the number of total internal reflections at the flat sides, thus decreasing scattering losses.

[0012] In a further development of the invention, the outer coupling section is arranged on both sides of the central coupling section. Furthermore, a collecting section extends on a side of the outer coupling section facing away from the central coupling section, at which light rays of the second partial light beam are totally reflected towards the outer region of the partial light surface. Advantageously, this prevents the light rays of the second partial light beam from being totally reflected at the flat surfaces, thus further reducing scattering losses. The central coupling section ensures that the light rays of the first partial light beam are not totally reflected at the flat surfaces of the planar light guide, but are directed directly towards the light output surface.

[0013] According to a further development of the invention, a parabolic shape of the collecting section can ensure that the light rays of the second partial beam are directed in a parallel direction towards the light output surface. Alternatively, by designing the collecting section and / or the outer coupling section, the second partial beam can be scattered at a scattering angle relative to a plane perpendicular to the flat surfaces and the light output surface, with limiting rays of the second partial beam striking the edges of the light output surface. In this way, total internal reflection at the flat surfaces is also avoided, so that scattering losses are low and homogeneous illumination is provided at the outer area of ​​the partial surface.

[0014] According to a further development of the invention, the light coupling surface has a plurality of diffusing lenses by means of which the first and second partial light beams are coupled out in a predetermined solid angle range to generate a light distribution.

[0015] An embodiment of the invention is explained in more detail below with reference to the drawings.

[0016] They show: Fig. 1. A perspective rear view of a lighting device from an oblique angle above, Fig. 2 an enlarged perspective view of a light coupling surface of a planar light guide of the lighting device , Fig. 3 a perspective front view of the lighting device with areas of the light output surface shown, which either output a partial beam of light formed by a central coupling section or by an outer coupling section of the light input surface, Fig. 4 a section through the planar light guide in its plane of extension with light rays drawn in, Fig. 5 a view of the lighting device from a narrow side with parallel light rays shown and Fig. 6 A view of an alternative lighting device from a narrow side with scattered light rays shown.

[0017] A lighting device according to the invention for vehicles can be used in the front or rear area to generate a taillight, brake light or daytime running light function.

[0018] The lighting device essentially consists of a planar light guide 1 and a plurality of light sources 2 arranged on a light coupling side 3 of the planar light guide 1. The light sources 2 are designed as semiconductor-based light sources, preferably as LED light sources.

[0019] The planar light guide 1 has opposing flat sides 4, which in the present embodiment are planar. In the main emission direction H, the flat sides 4 define a light output surface 6 at the front of a light output side 5. A first partial light beam L1 and a second partial light beam L2, each emitted by the light sources 2, are coupled out of this surface 6 with homogeneous illumination according to a predetermined light distribution. To couple out the partial light beams L1 and L2 within a solid angle to generate a predetermined light distribution, the light output surface 5 has a plurality of diverting lenses 7, which are preferably pincushion-shaped.

[0020] The planar optical fiber 1 has, on its light-input side 3, a plurality of light-input surfaces 8 spaced apart from one another in its direction R, to which a parabolic collecting section 9 is attached on both sides. The collecting section 9 is formed as a cutout on the light-input side 3 of the planar optical fiber 1. The collecting section 9 has the same thickness d as the lateral narrow sides 10 of the planar optical fiber 1, which connect an outer collecting section 9' to a lateral edge 11, between which the light-output surface 8 runs.

[0021] The light coupling surface 8 is uneven. Each light coupling surface 8 is assigned a light source 2, with the light coupling surface 8 being arranged in front of the corresponding light source 2 in the main emission direction H.

[0022] The light coupling surface 8 has, on the one hand, a central coupling section 12 and, on the other hand, outer coupling sections 13 adjoining the central coupling section 12 on both sides.

[0023] The central coupling section 12 couples the first partial light beam L1 of the light source 2 assigned to the light coupling surface 8 into the planar light guide 1, and the outer coupling section 13 couples the second partial light beam L2 of the same light source 2 into the planar light guide 1. The central coupling section 12 and the outer coupling section 13 are shaped such that the partial light beams L1 and L2 are focused.

[0024] As especially from Fig. As can be seen in Figure 3, the first partial light beam L1 is directed by means of the central coupling section 12 such that, in the main emission direction H, a central area 14 of a partial surface 16 of the light coupling surface 6, which is arranged in the main emission direction in front of the light coupling surface 8, intersects the light coupling surface 8. The central coupling section 12 is shaped such that light rays of the first partial light beam L1 are oriented in different directions. Thus, the first partial light beam L1 can have an opening angle in the extension direction R of the light coupling surface 6 that is larger than an opening angle in a plane E that is perpendicular to the flat sides 4 and perpendicular to the light coupling surface 6. In this way, the central area 14 of the partial surface 16 is elongated and / or rectangular in the extension direction R of the light coupling surface 6.

[0025] Light rays of the first partial light beam L1 are refracted at the central coupling section 12 in such a way that they hit the light output coupling surface 6 directly, without total reflection of the light rays occurring at the opposite flat surfaces 4 of the planar light guide 1.

[0026] The second partial light beam L2, coupled in via the outer coupling section 13, hits an outer area 15 of the partial surface 16, which is directly adjacent to the central area 14 of the same.

[0027] The second partial light beam L2 coupled into the outer coupling section 13 is totally reflected at the collecting section 9, 9' in the direction of the outer areas 15 of the partial surface 16, without any further total reflection of the same occurring at the flat sides 4.

[0028] Since the collecting section 9, 9' is parabolic, the light rays of the second partial light beam L2 are totally reflected parallel to the flat surfaces 4 in the direction of the outer area 15, see. Fig. 5. As from Fig. As can be seen in Figure 3, one collecting section 9 reflects the second partial light beam L2 towards a first outer area 15', and another opposite collecting section 9, which is assigned to the same light coupling surface 8, reflects the second partial light beam L2 towards a second outer area 15" of the partial surface 16. Thus, there is no overlap of the respective partial light beams L1, L2 within the planar light guide 1.

[0029] As from the Fig. 3 and Fig. As can be seen in Figure 4, the central area 14 is separated from the adjacent outer areas 15, 15', 15" of the same sub-area 16 by a boundary line G. The first partial light beam L1 strikes exclusively the central area 14 of the sub-area 16. The second partial light beam L2 strikes exclusively the outer areas 15, 15', 15" of the same sub-area 16. Thus, a discrete transition occurs at the boundary line G between differently shaped partial light beams L1 and L2, formed by a light coupling surface 8. During the transition from the central area 14 to the outer areas 15' and 15" respectively, there are no differences in brightness, so the sub-area 16 of the light coupling surface 6 assigned to the light source 2 is homogeneously illuminated. The same applies to the transition from the sub-area 16 to an adjacent sub-area 16', to which a different, preferably adjacent, light coupling surface 8 is assigned.

[0030] As from Fig. As can be seen in Figure 3, the central area 14 and the outer area 15, 15', 15" are bounded by edges 17 running in the direction R of extension of the light coupling surface 6 and by the boundary line G or boundary lines G of adjacent sub-areas 16'. This transition is not discernible, since the central area 14 and the outer areas 15', 15" each have the same brightness values ​​across their area.

[0031] As from Fig. As can be seen in Figure 5, the light rays of the second partial light beam L2 run parallel between the light coupling surface 8 and the light coupling surface 6 of the planar light guide 1. This is caused in particular by the parabolic shape of the collecting section 9, 9'.

[0032] According to an alternative embodiment of the invention Fig.6 The outer coupling section 13 and / or the collecting section 9 can be shaped such that the second partial light beam L2 is scattered at a scattering angle α in the plane E, such that limiting rays 18 of the second partial light beam L2 strike the edge 17 of the partial surface 16 or the light output surface 6. In this configuration, total internal reflection does not occur at the flat sides 4 of the second partial light beam L2. Advantageously, this can result in a homogenized illumination of the light output surface depending on the thickness d of the light guide 1 at the light output side 5. Particularly with relatively thick light guides, the area of ​​the light output surface 6 near the edges 17 can thus exhibit the same brightness values ​​as the central area of ​​the light output surface 6. This ensures adaptation to different thicknesses d of the planar light guide 1.According to an embodiment of the invention (not shown), instead of discrete boundary lines G between the central region 14 and the adjacent outer region 15', 15" a transition section can be provided, which is illuminated by the light rays of the first partial light beam L1 and the second partial light beam L2. In this way, a continuous, rather than an abrupt, transition of the partial light beams L1, L2 is created between the central region 14 and the adjacent outer regions 15. In the transition section, the same brightness is generated by the superposition of light rays from the first partial light beam L1 and the second partial light beam L2 as in the central region 14 and the outer region 15', 15", where only light rays from the first partial light beam L1 and the second partial light beam L2, respectively, contribute to the illumination.

[0033] The thickness d of the planar light guide 1 can be in a range between 5 mm and 20 mm. The planar light guide 1 is preferably manufactured from a crystal-clear plastic material by injection molding. The light coupling surface 6 is integrally connected to the planar light guide 1.

Claims

[1] Lighting device for vehicles comprising a planar light guide (1) - two opposite flat surfaces (4) for total reflection of light coupled into the planar light guide (1), - a light coupling surface (8) for coupling light to a light coupling side (3) of the planar light guide (1), - a light output surface (6) for coupling out the coupled light at a light output side (5) of the planar light guide (1), wherein the light output surface (6) forms a narrow side connecting the opposite flat sides (4), - that each light coupling surface (8) is assigned a light source (2) and that the light coupling surface (8) is uneven, that the light coupling surface (8) has a central coupling section (12) arranged in the main emission direction (H) in front of the light source (2) and an outer coupling section (13) adjacent to it, wherein the central coupling section (12) and the outer coupling section (13) are shaped such that a first partial light beam (L1) of the light source (2) incident on the central coupling section (12) strikes a central area (14) of a partial area (16, 16') of the light coupling surface (6) arranged in the main emission direction (H) in front of the light coupling surface (8) and that a second partial light beam (L2) of the light source (2) incident on the outer coupling section (13) strikes an outer area (15, 15', 15") of the same partial area adjacent to the central area (14). (16, 16') hits, characterized by, that the central coupling section (12) is shaped such that the first partial light beam (L1) is expanded in the extension direction (R) of the planar light guide (1) and / or in the extension direction of the light output surface (6), so that the central area (14) of the partial surface (16, 16') is stretched in the extension direction (R) of the light output surface (6) and / or that the first partial light beam (L1) is expanded in the direction of its plane (E) extending perpendicular to the flat sides (4) and to the light output surface (6), so that the central area 14 of the partial surface (16, 16') is stretched perpendicular to the extension direction (R) of the light output surface (6), wherein only light rays of the first partial light beam (L1) are emitted from the central area (14) of the partial surface (16, 16') and from the outer area (15, 15', 15") of the Partial area (16,16') can be decoupled exclusively from light rays of the second partial light beam (L2). [2] Lighting device according to claim 1, characterized by , that the central area (14) and the outer area (15, 15', 15") of the same sub-area (16, 16') of the light coupling surface (6) are bounded by edges (17) of the same and that the central area (14) and the outer area (15, 15', 15") of the sub-areas (16, 16') are separated from each other by a boundary line (G), whereby on one side only the first partial light beam (L1) is emitted and on the other side only the second partial light beam (L2) is emitted. [3] Lighting device according to claim 1 or 2, characterized by , that the outer coupling section (13) is designed such that the second partial light beam (L2) is focused in a plane (E) perpendicular to the flat sides (4) and to the light coupling surface (6). [4] Lighting device according to any one of claims 1 to 3, characterized by, that the outer coupling section (13) connects to the central coupling section (12) on both sides of the same, and that on a side of the outer coupling section (13) facing away from the central coupling section (12) a collecting section (9, 9') cut in the planar light guide (1) is connected, at which light rays of the second partial light beam (L2) are totally reflected in the direction of the outer area (15, 15', 15") of the partial area (16, 16'). [5] Lighting device according to any one of claims 1 to 4, characterized by, that the outer coupling section (13) and / or the collecting section (9, 9') are shaped such that the second partial light beam (L2) is directed directly onto the outer area (15, 15', 15") of the partial surface (16, 16') without total internal reflection of light rays of the second partial light beam (L2) at the flat sides (4) and that the central coupling section (12) is shaped such that the first partial light beam (L1) is directed directly onto the central area (14) of the partial surface (6, 16') without total internal reflection of light rays of the first partial light beam (L1) at the flat sides (4). [6] Lighting device according to claim 5, characterized by, that the second partial light beam (L2) is scattered parallel to flat surfaces (4) or at a scattering angle (cc) in the plane (E) perpendicular to the flat surfaces (4), that boundary rays (18) of the second partial light beam (L2) meet the edges (17) of the light coupling surface (6). [7] Lighting device according to any one of claims 1 to 6, characterized by , that the central area (14) and / or the outer area (15, 15', 15") of the sub-area (16, 16') are rectangular or square in shape. [8] Lighting device according to any one of claims 1 to 7, characterized by , that the light output surface (6) has a plurality of diverting lenses (7) for directing the first partial light beam (L1) and the second partial light beam (L2) in a solid angle area to generate a predetermined light distribution.

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