LIGHTING DEVICE FOR A MOTOR VEHICLE

Abstract

A lighting device for a motor vehicle, having at least one light guide, which is formed planar, and having at least one illuminant. Light rays from the illuminant can be coupled or are coupled into the light guide via a light incoupling surface assigned to the light guide. Incoupled light rays are deflected via at least one light outcoupling structure of the light guide in the direction of at least one light outcoupling surface of the light guide and are again outcoupled from the light guide via the light outcoupling surface. The invention proposes that a rear surface of the light guide, which surface is opposite to the light outcoupling surface, is provided at least over a majority of its planar extent with a facet-like surface structure, which forms the light outcoupling structure of the light guide and formed of a plurality of irregularly formed facet surfaces.

Claims

1. A lighting device for a motor vehicle, the lighting device comprising: at least one light guide that is formed planar; at least one illuminant, wherein light rays from the illuminant are adapted to be coupled into the light guide via a light incoupling surface assigned to the light guide; and at least one light outcoupling structure, wherein incoupled light rays are deflected via the at least one light outcoupling structure of the light guide in a direction of at least one light outcoupling surface of the light guide and is adapted to be again outcoupled or are outcoupled from the light guide via the light outcoupling surface; and a rear surface of the light guide, the rear surface being opposite the light outcoupling surface, is provided at least over a majority of its planar extent with a facet-like surface structure, which forms the light outcoupling structure of the light guide and is formed of a plurality of irregularly formed facet surfaces.

2. The lighting device according to claim 1, wherein the facet-like surface structure is a macrostructuring.

3. The lighting device according to claim 1, wherein each of the facet surfaces has a microstructuring.

4. The lighting device according to claim 3, wherein the microstructuring has a periodicity in a range from 50 ?m to 500 ?m in at least one spatial direction.

5. The lighting device according to claim 1, further comprising a plurality of illuminants and at least one control unit for controlling the illuminants, wherein the illuminants are controlled independently of one another, and wherein the illuminants are controlled and are arranged relative to the positions and/or orientations of the facet surfaces in such a way that at least one light function with a perceptible sparkle is produced in a specific viewing position by the light rays emitted by the illuminants and deflected at the light outcoupling structure.

6. The lighting device according to claim 1, wherein the light guide is flat.

7. The lighting device according to claim 1, wherein there is at least one second light guide, into which light rays from at least one second illuminant is coupled via a light incoupling surface assigned to the second light guide and is outcoupled again via at least one light outcoupling surface of the second light guide, wherein the illuminants facing the light incoupling surfaces of the light guides are arranged on a common circuit board and the light outcoupling surfaces of the light guides point at least in sections in the same light emission direction.

8. The lighting device according to claim 7, wherein the second light guide is also formed planar, wherein one edge side of the light guide serves as its light incoupling surface and another edge side of the light guide serves as its light outcoupling surface.

9. The lighting device according to claim 7, wherein the second light guide is designed rod-shaped, wherein one end face of the second light guide serves as its light incoupling surface and another end face of the second light guide serves as its light outcoupling surface.

10. The lighting device according to claim 1, wherein one light guide is oriented with its planar extent perpendicular to a planar extent of the circuit board and the second light guide is oriented parallel to the planar extent of the circuit board, wherein the second light guide has a deflection slope arranged in the region of its light incoupling surface.

11. A motor vehicle comprising at least one lighting device according to claim 1.

12. The lighting device according to claim 1, wherein the lighting device is a rear light of the motor vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

[0032] FIG. 1 is a lighting device in cross section, according to an example;

[0033] FIG. 2 is a depiction of the lighting device according to view II of FIG. 1 against the light emission direction;

[0034] FIG. 3 is a view of a rear side of the lighting device according to view III of FIG. 1, but only partially and with the light guide exposed;

[0035] FIG. 4 is a sectional view according to sectional line IV through the detail section D from FIG. 3;

[0036] FIG. 4a is a view of the detail section D according to view IVa from FIG. 4;

[0037] FIG. 5 is a sectional view of a lighting device according to an example;

[0038] FIG. 6 is a depiction of the lighting device against a light emission direction according to view VI from FIG. 5; and

[0039] FIG. 7 is the rear view of a motor vehicle with lighting devices of the invention.

DETAILED DESCRIPTION

[0040] A lighting device 1 is shown in these figures, which has a housing 18 (indicated by a dashed line) which is provided with an opening, closed by a lens 19, in the light emission direction LA.

[0041] A light guide 1a is accommodated in housing 18. Light guide 1a is preferably made of a transparent plastic. The plastic may be colored red. It can be made of PMMA (polymethyl methacrylate) or PC (polycarbonate), for example.

[0042] Light guide 1a is formed planar and therefore is a planar light guide. Light guide 1a therefore has a planar extent F1 that is several times greater than a thickness d1 of light guide 1a. Furthermore, it should also be noted that light guide 1a is flat. It is therefore not curved or bent when viewed in its cross section (cf. FIG. 1)

[0043] As can be seen further from the figures, light guide 1a has a light incoupling surface 10, which is used to couple light from an illuminant 15. Light incoupling surface 10 is formed by a lower edge surface of light guide 1a.

[0044] In the example, there are multiple illuminants 15, which are preferably designed as light-emitting diodes (LEDs) and are mounted next to each other in a row on a circuit board 16.

[0045] Illuminants 15 can be individually controlled via a control unit 17. Control unit 17 can be part of lighting device 1. However, it is also conceivable that control unit 17 is present as a separate component. Control unit 17 can in turn be connected to a data bus (for example, a CAN bus) in terms of signaling. The signal connection of lighting device 1, for example, to the driver assistance systems of a motor vehicle can be realized in this way.

[0046] Light guide 1a has a rear surface 12, which is opposite a front light outcoupling surface 11.

[0047] Furthermore, it is indicated by a dashed line in the figures that rear surface 12 or at least a majority of rear surface 12 is provided with a facet-like surface structure S, which serves as a light outcoupling structure and will be explained in more detail later.

[0048] Light guide 1a is surrounded by a frame-like panel 13. Frame-like panel 13 is designed light-tight and covers light guide 1a at the rear, on its laterally outer sides, and on its upper side. At the front, therefore, in the light emission direction LA, a window-like opening 14 is left free by frame-like panel 13.

[0049] Generated light rays from illuminants 15, which are coupled into light guide 1a at the edge via light incoupling surface 10, are deflected at the facet-like surface structure S in the direction of light outcoupling surface 11 and then emerge from light outcoupling surface 11 into the surroundings.

[0050] As can be seen in particular in FIGS. 2 and 3, the facet-like surface structure S is formed macroscopically and formed of a plurality of facet surfaces 120. Facet surfaces 120 are formed in particular by a combination of rectangular and/or triangular surfaces. Facet surfaces 120 can have different sizes. Preferably, facet surfaces 120 each have a longitudinal extent in a range of more than one millimeter in at least one spatial direction (spatial longitudinal direction X, spatial transverse direction Y, and/or spatial vertical direction Z). Particularly preferably, the longitudinal extent of each facet surface 120 in at least one spatial direction is in a range from about one millimeter to about ten millimeters. The individual facet surfaces 120 each have a microstructuring (will be explained later), wherein the normals of neighboring facet surfaces are oriented differently. Edges 120a, which have the smallest possible radius, are formed between adjacent facet surfaces 120. The orientation of the normals on one facet surface 120 differs from the orientation of the normals of all neighboring facet surfaces 120. A discontinuous deflection of the incoupled light rays falling on facet surfaces 120 and thus an intended sparkle effect are achieved hereby in a simple and cost-effective way. A sparkle effect occurs when a viewer changes from a first viewing position to a second viewing position.

[0051] However, it is also conceivable that a sparkle effect can be achieved if a viewer adopts a fixed viewing position looking at lighting device 1 opposite to the light emission direction LA. It is necessary for this that one or more of the illuminants 15 are activated in succession and thus switched on. For this purpose, control unit 17 can also contain a random generator with which one or more of the illuminants 15 can be randomly selected and activated.

[0052] It is possible that front light outcoupling surface 11 is provided with patterns or coatings to achieve additional lighting effects. The inner surfaces of the frame-like panel 13, said surfaces facing light guide 1a, can also be provided with coatings (preferably reflective).

[0053] FIGS. 3, 4, and 4a show a detail section D of light guide 1a without frame-like panel 13 for a better representation.

[0054] It is particularly clear from FIGS. 4 and 4a that each of the facet surfaces 120 is in turn provided with a microstructuring MS. The microstructuring MS has in at least one spatial direction X, Y, Z a periodicity with a magnitude of preferably about 50 ?m to about 500 ?m, particularly preferably about 100 ?m. In other words, the microstructuring MS in the example comprises a plurality of microstructures which have a sawtooth shape in cross section and which are repeated at least in one spatial direction X, Y, Z at a distance of about 50 ?m to about 500 ?m, particularly preferably of about 100 ?m. In this regard, the microstructurings MS of neighboring facet surfaces 120 are oriented differently, so that again different light outcoupling directions LA1, LA2, LA3, . . . , LAn result (cf. FIG. 4a). The aforementioned sparkle effect can be optimized by the additional microstructuring MS.

[0055] Returning to FIG. 1, it is conceivable that light guide 1a can have an additional edge outcoupling element on one or more of its edge surfaces (for example, on the edge surface opposite light incoupling surface 10 at the edge). Such an edge outcoupling element can be arranged at least partially on an edge surface of light guide 1a and designed to additionally deflect light rays, coupled into light guide 1a, via light incoupling surface 10 in a predetermined angular range and to outcouple them again from light guide 1a. Preferably, such an additional edge outcoupling element is integrally connected to the respective edge surface. The predetermined angular range can include a surface normal of light outcoupling surface 11. In this case, the predetermined angular range can preferably lie in a cone with an opening angle of no more than 160? around the surface normal of light outcoupling surface 11. The cross section of such an edge outcoupling element can be designed triangular (in the form of a roof edge) and/or free-form.

[0056] Lighting device 1a can be supplemented in particular with directional light outcoupling with such an edge outcoupling element, which can increase the effectiveness of lighting device 1a.

[0057] A further example of a lighting device 2 is illustrated in FIGS. 5 and 6.

[0058] Lighting device 2 has a first light guide 1a and a second light guide 1b. First light guide 1a is designed in the same way as light guide 1a of the first example. In other words, it is also formed planar with a planar extent F1 and a thickness d1. Further, a rear surface 12 of light guide 1a is provided with a facet-like surface structure S (as already described).

[0059] Light guide 1a is in turn framed by a frame-like panel 13, which leaves open a window-like opening 14 of a light outcoupling surface 11a at the front.

[0060] Second light guide 1b is also formed planar, with a planar extent F2 and a thickness d2, wherein the planar extent F2 is several times greater than the thickness d2. The two light guides 1a, 1b are arranged with their planar extents F1, F2 at right angles to each other. The second light guide 1b is also made of a plastic (for example, PMMA or PC). The two light guides 1a, 1b can be connected to each other in one piece (materially bonded) using an injection molding process.

[0061] A circuit board 16, which carries illuminants 15a and 15b, is arranged below the light guide assembly formed of light guides 1a and 1b. Illuminants 15a, 15b are again preferably designed as LEDs. In this example, circuit board 16 therefore serves as a common circuit board for holding illuminants 15a, 15b.

[0062] In each case, multiple illuminants 15b arranged next to each other in a row are assigned to second light guide 1b and multiple illuminants 15a arranged next to each other in a row are assigned to first light guide 1a. In other words, light rays L2 from illuminants 15b are coupled into second light guide 1b via a first light incoupling surface 10b, deflected via a deflection slope 10c, and finally outcoupled via a light outcoupling surface 11b of second light guide 1b in the direction of a light emission direction LA of lighting device 2.

[0063] Light rays L1 from illuminants 15a, in contrast, are incoupled via a light incoupling surface 10a of second light guide 1b, perpendicular to a planar extent F2 of second light guide 1b, thus first entering second light guide 1b, passing through it, and then entering first light guide 1a. In this light guide, they are deflected in the direction of light outcoupling surface 11a with the aid of the facet-like surface structure S and outcoupled from it within window-like opening 14.

[0064] In the shown mounting position of lighting device 2, circuit board 16, which is jointly assigned to light guides 1a, 1b, is oriented horizontally with its planar extent F3. In this case, second light guide 1b is oriented with its planar extent F2 parallel to planar extent F3 of common circuit board 16. First light guide 1a is oriented with its planar extent F1 at a right angle to planar extent F3 of common circuit board 16.

[0065] The aforementioned components are in turn accommodated in a common housing 20. In the light emission direction LA, a light exit opening of housing 20 is closed by a lens 21. Lighting device 2 (like lighting device 1) is preferably designed as a rear light for a motor vehicle.

[0066] Further, it should be pointed out that light outcoupling surfaces 11a and 11b point in the same light emission direction LA or at least in sections in the same light emission direction LA. In other words, light outcoupling surfaces 11a, 11b of light guides 1a, 1b are oriented, at least in sections, such that their imaginary surface normals point in the same light ray direction LA.

[0067] It is clear from FIG. 6 that light guides 1a and 1b have the same or at least approximately the same width b. For the sake of clarity, housing 20 is no longer shown here.

[0068] It can be seen from this figure that, due to the planar design of second light guide 1b as well, its light outcoupling surface 11b is also designed strip-like or line-like.

[0069] Thus, for example, it is conceivable that the light function of a taillight is realized by illuminants 15a in conjunction with first light guide 1a. The light function of a brake light or a direction indicator as well can be realized by illuminants 15b in conjunction with second light guide 1b.

[0070] For this purpose, illuminants 15a and 15b can be suitably selected in terms of the type of light they emit. It is also conceivable to design illuminants 15a, 15b as so-called RGB light-emitting diodes. These are capable of emitting light in any color.

[0071] Deviating from the example, it is also conceivable to design second light guide 1b not planar but rod-shaped. The image as shown in FIG. 6 (light outcoupling surfaces 11b are indicated by dashed lines) can then result with an exemplary use of multiple rod-shaped light guides 1b, each of which has a square light outcoupling surface 11b, for example.

[0072] Finally, a panel 22 should also be mentioned, into which second light guide 1b is introduced with its light outcoupling surface 11b.

[0073] Illuminants 15a, 15b are each arranged perpendicular to the plane of the drawing in a row, preferably along the entire or almost the entire width b of lighting device 2 (see FIGS. 5 and 6).

[0074] In this example as well, there is a control unit 17, which is connected to circuit board 16 in terms of signals. Illuminants 15a and 15b can be controlled separately from one another with the aid of control unit 17. In particular, illuminants 15a can be controlled individually or in groups independently of one another in such a way that a sparkle effect can also be created for an observer in a fixed viewing position.

[0075] Finally, a motor vehicle K is shown in a rear view in FIG. 7. The motor vehicle K is equipped with lighting devices 1 (or 2) of the invention, which in the present case are designed as rear lights.

[0076] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.