Lamp module for a motor vehicle

Abstract

The invention concerns a lamp module (10). comprising a primary optical device including light sources (16) generating a beam of light (18) propagating along an X axis, a light guide extending along a longitudinal axis Y perpendicular to the X axis, and a projecting lens (40) arranged downstream an emitting surface (30) of the light guide. In a cross-section along a plane normal to the Y axis, the projection of the emitting surface is as a curve. At each point, the tangent of the curve forms an angle a with a Z axis that is perpendicular to the X and Y axes, defined by the equation: where : • n is the refractive index of the material of the light guide and • θ the extreme viewing angle, with respect to the X axis, of the ray of light emitted at the point considered by the emitting surface of the light guide as it exits the output surface (44).

Description

[0001] The invention relates to the domain of the automotive industry, and particularly to a motor vehicle lamp module.

[0002] In particular, the invention relates to an LED lighting unit using a light guide that conforms to a light distribution standard for a vehicle lamp such as a headlight, auxiliary headlight, spot light, tail light, signal lamp, traffic lamp, or other vehicle lamp using the same.

[0003] A conventional LED lighting unit mounted in vehicle lamps usually includes a primary optical device comprising plurality of LEDs, a light guide arranged downstream the primary optical device comprising an incident surface configured to receive the rays of the beam of light generated by the LEDs, and a lens arranged downstream the emitting surface of the light guide.

[0004] The plurality of LEDs have an optical axis located in a direction towards or corresponding with a light-emission direction of the associated vehicle lamp. Therefore, the conventional LED lighting unit illuminates in a direction corresponding to the light-emission direction via the lens located in front of the light guide.

[0005] However, new vehicle lighting systems do not only focus the optical output increasing the driving comfort and traffic safety, but also on appearance. Modern point and planar light sources, especially LED and OLED sources, have opened a new chapter for new stylistic options of car designers. In particular, there is an increasing trend to add a variety of esthetic and functional effects.

[0006] The above conventional, "flat" light modules lack a sense of depth, making them highly suitable for applications that are essentially 2-dimensional, but are unable to provide 3-dimensional effects.

[0007] To obtain these kinds of effects, the shape of the lens can be altered and given different shapes, for example forming a cavity. However, because each of the plurality of LEDs possesses characteristics of an approximately point light source, the light propagated by the emitting surface of the light guide forms a light distribution which scatters each projection image of a plurality of point light sources on the front lens. This results in an irregularity of brightness, and thus a non-homogenous overall projected light.

[0008] To improve the overall homogeneity of the projected light, it is known to use of a light guide of increased thickness or having both of its faces have a rough surface (also called "grained surface"). However, it is sought to reduce the overall volume of the lamp modules and therefore thick light guides are thus undesirable. Moreover, applying a rough surface on a thin light guide is usually not possible.

[0009] Another solution that allows to keep the thickness of the light guide to a minimum consists in shaping its emitting surface such that it includes a plurality of pillow-shaped projections of small size. However, this solution makes the manufacturing of the light guide complex, and thus costly.

[0010] As a result, there is exists a need to provide a lighting unit that allows for 3-dimensional effects with a good homogeneity of the projected light, that is both thin and less costly to manufacture than the existing solutions.

[0011] To that end, the invention concerns a lamp module for a motor vehicle comprising: a primary optical device, comprising at least one light source, generating a beam of light consisting of a plurality of rays of light, said beam of light propagating essentially along an X axis, a light guide, arranged downstream of the primary optical device, extending along a longitudinal axis Y that is substantially perpendicular to the X axis, comprising an incident surface configured to receive the rays of the beam of light generated by the primary optical device and a body configured to guide said beam of light towards an emitting surface of the light guide, an optical element arranged downstream of the emitting surface of the light guide, comprising an input surface configured to receive the rays of the beam of light emitted by the emitting surface of the light guide and an output surface, characterized in that the emitting surface of the light guide is a freeform surface, wherein, in a cross-section along a plane normal to the Y axis the projection of the freeform surface is as a curve defined as a series of points, wherein at each point of the curve, the tangent of the curve forms an angle α with a Z axis that is perpendicular to the X and Y axes, defined by the equation : α = tan − 1 sin θ n − cos θ where : n is the refractive index of the material of the light guide and θ the extreme viewing angle, with respect to the X axis. of the ray of light emitted at the point considered by the emitting surface of the light guide as it exits the output surface, with

[0012] The term "extreme viewing angle" should be understood as the angle is the maximum required angle where the light has to be directed. Said angle is measured with respect to X axis. The extreme viewing angle is best described as how far a viewer to either side of the lamp module can move and still see the signal emitted by the lamp module. This angle is usually set as a requirement by car manufacturers.

[0013] Owing to the fact that the emitting surface of the light guide is a freeform surface and has a shape that follows the above-mentioned equation, the light will be uniformly distributed with a similar brightness level in dynamic directions. "Dynamic directions" refer to varying viewing angles of the lamp when it is assembled in a vehicle. These angles are determined by the customer according to styling preferences or aesthetic considerations for the vehicle or the lamp as perceived by the end user.

[0014] In particular, all the flanges of the lens which delimit the cavity are homogenously lit, whilst keeping the thickness light guide to a minimum. There is also no need for the faces of the light guide to have a rough, grained surface. Finally, a smooth freeform shape is much simpler, and thus cost-effective, to manufacture than a shape that includes plurality of pillow-shaped protrusions.

[0015] Preferably, the freeform surface is a concave surface.

[0016] According to a preferred embodiment, to further simplify its manufacturing, the light guide is made in one piece.

[0017] Advantageously, to focus the light beam and obtain the desired lighting effect, the optical element is a projection lens.

[0018] Preferably, in order to obtain at three-dimension lighting effect, the optical element forms a cavity extending along the X axis extending from a surface perpendicular to the X axis.

[0019] To further enhance the three-dimension lighting effect, the cavity has a cross-section having a general shape of a U in a plane perpendicular to the Y axis.

[0020] Preferably, the light guide is made of transparent thermoplastic polymer, for example polycarbonate of polymethylmethacrylate, which is material that is easily manufactured, light and allows for a good propagation of the light.

[0021] Preferably, the optical element is made of transparent thermoplastic polymer, for example polycarbonate of polymethylmethacrylate, which is material that is easily manufactured, light and allows for a good focus of the light.

[0022] According to a particular embodiment, the primary optical device comprises several light sources arranged substantially on a same horizontal plane.

[0023] Preferably, the primary optical device comprises several light sources, the light sources being light-emitting diodes. The use of LEDs reduces the size and energy consumption of the primary optical device.

[0024] According to a particular embodiment, the primary optical device comprises multiple light condensing structures, for example having an ovoidal shape, mounted downstream of the light sources.

[0025] According to a particular embodiment, the lamp is a rear lamp, a front lamp, or a signal lamp.Brief description of the Figures

[0026] The invention will be better understood upon reading the following description, which is given only as an example and is made with reference to the attached drawings in which: Figure 1 is a perspective view of a lamp module according to an embodiment of the invention; Figure 2 is a perspective view of a lamp module of Figure 1 according to another angle; Figure 3 is a perspective view of a lamp module of Figure 1 according to another angle; Figure 4 is a partial cross-section of the lamp module of Figure 1 along plane IV-IV; Figure 5 is a cross-section of the lamp module of Figure 1 along plane IV-IV; Figure 6 is a view of a detail of Figure 5. Detailed Description

[0027] With reference to Figures 1 to 4, a motor vehicle lamp module 10 according to an embodiment of the invention, which is destined to be mounted in a motor vehicle, for example a car. On the figures, only a part of bodywork panel 12 of the car is shown.

[0028] The vehicle lamp module 10 extends along an axis Y and has an overall rectilinear shape.

[0029] The lamp of the module 10 may be a rear lamp, a front lamp, or a signal lamp. For example, it can be a headlight, auxiliary headlight, spot light, tail light, signal lamp, traffic lamp, or other vehicle lamp using the same.

[0030] The lamp module 10 comprises a primary optical device 14, comprising at least one light source 16. In this particular embodiment, the primary optical device 14 comprises several light sources 16 arranged substantially on a same horizontal plane.

[0031] The light sources 16 generate a beam of light 18 consisting of a plurality of rays of light 20. The beam of light 18 propagates essentially along a general direction, or X axis, which preferably coincides with an optical axis X of the lamp module. The individual rays of light 20, however, do not necessarily individually propagate along an X axis. The X axis can for example be parallel to the axis along which the vehicle is being driven when the light module corresponds to a front or a rear lamp. The X axis is here determined by the purpose and function of the light module 10.

[0032] Here, the light sources 16 are light-emitting diodes (LEDs). They could also be Organic Light-Emitting Diodes (OLEDs).

[0033] Since the LEDs 16 emit substantially in a half-space limited by the plane in which they are positioned, the average lighting direction X is typically perpendicular to the LED plane.

[0034] The primary optical device 14 comprises multiple light-condensing structures 22, for example having an ovoidal shape, mounted downstream of the light sources 16.

[0035] The light-condensing structures 22 are arranged in rows in the same way as the light sources 16. As can be seen on Figure 2, each light-condensing structure 22 is associated to a pair of two LEDs 16. In an alternative embodiment (not shown), a light condensing structure could be associated with a single LED 16.

[0036] The lamp module 10 also comprises a light guide 24, arranged downstream of the primary optical device 16, extending along a longitudinal axis Y that is substantially perpendicular to the X axis.

[0037] In this particular embodiment, the light guide 24 is made in one piece. The light guide 24 is preferably made of a transparent thermoplastic polymer, such as polycarbonate (PA) or polymethyl methacrylate (PMMA). It could also be made of other transparent materials, depending in particular on the desired refractive index.

[0038] As can be seen on Figure 5, the light guide 24 comprises an incident surface 26 configured to receive the rays 20 of the beam of light 18 generated by the primary optical device 14.

[0039] The incident surface 26 is shaped like a cavity, so as to create an optical element whose focus receives the light from the light sources 16. The cavity has a surface section that is convex when considering the direction towards which the light rays 20 are propagated, which is from left to right on the Figures.

[0040] The light guide 24 also comprises a body 28 configured to guide the beam of light 18 towards an emitting surface 30 of the light guide 24. More particularly, the body 28 is delimited by two parallel surfaces 32, as can be seen on Figure 4. These sides are substantially normal to the Y axis.

[0041] The emitting surface 30 of the light guide is a freeform surface, when considering the direction towards which the light rays 20 are propagated, which is from left to right on the Figures. For example, the emitting surface 30 forms a concave surface, which will be defined in detail later on.

[0042] The lamp module 10 also comprises an optical element 40 arranged downstream of the emitting surface of the light guide 24. It comprises an input surface 42 configured to receive the rays 20 of the beam of light emitted by the emitting surface 30 of the light guide. II also comprises an output surface 44.

[0043] As can be best seen on Figures 5 and 6, in a cross-section along a plane normal to the Y axis, the projection of the freeform surface 30 is as a curve defined as a series of points.

[0044] At each point of the curve, the tangent of the curve forms an angle α with a Z axis that is perpendicular to the X and Y axes, defined by the equation : α = tan − 1 sin θ n − cos θ where : n is the refractive index of the material of the light guide 24 and θ the extreme viewing angle, with respect to the X axis, of the ray of light 35 emitted at the point considered by the emitting surface 30 of the light guide as it exits the output surface 44.

[0045] These angles are represented on Figure 5. The term "extreme viewing angle" should be understood as the angle is the maximum required angle where the ray of light has to be directed. Said angle is measured with respect to X axis. The extreme viewing angle is best described as how far a viewer to either side of the lamp module 10 can move and still see the signal emitted by the lamp module 10. This angle is usually set as a requirement by car manufacturers.

[0046] For example, as can be seen on Figures 5 and 6, a particular ray of light 35 exits the freeform surface 30 at a particular point P of the surface.

[0047] In this particular case, this ray of light 35 is the furthest ray of light away from the X axis that can be seen from the right side of the light module 10 (here corresponding to the top of the Figures), in the case of a headlamp, but this can apply to any other ray of light exiting any random point of the surface 30.

[0048] This ray of light 35 hits the optical element 40 on its input surface 42, goes through the optical element 40 and exits it at its output surface 44. The extreme viewing angle θ is represented as the angle formed between the ray of light 35 and the axis X.

[0049] Optical element 40 is a projection lens. Projection lens 40 is preferably made of a transparent thermoplastic polymer, such as polycarbonate (PA) or polymethyl methacrylate (PMMA). It could also be made of other transparent materials, depending in particular on the desired refractive index.

[0050] As can be seen on Figures 4 to 6, the lens 40 forms a cavity 46 extending along the X axis, extending from a surface perpendicular to the X axis. As shown on Figures 1 and 4, the cavity 46 protrudes from the bodywork panel 12 in the direction X.

[0051] In this particular embodiment, the cavity 46 has a cross-section having a general shape of a U in a plane perpendicular to the Y axis (XZ plane on the Figures). However, other shapes can be considered, such as a V shape.

[0052] Preferably, the cavity 46 is delimited by a rear wall 48 and a pair of side walls 50, such that the rear wall 48 is directly facing the emitting surface 30 of the light guide.

[0053] In this example, as shown on Figures 5 and 6, in the XZ plane, the rear wall 48 forms the base of the U shape, and the side walls 50 form the branches of the U. It should be noted that, as shown on the Figures, the side walls 50 are not necessarily parallel.

[0054] The distance between the side walls 50 of the cavity 46 preferably is larger than the width of the light guide 24 along the direction Z. In other words, the light guide 24 could fit within the cavity 46.

[0055] The invention is not limited to the presented embodiments and other embodiments will clearly appear to the skilled person. Any combination of the aforementioned embodiments or variants is for example explicitly envisioned.References list:

[0056] 10 : Vehicle lamp module 12 : Bodywork panel 14 : Primary optical device 16 : Light sources (LEDs) 18 : Beam of light 20 : Rays of light 22 : Light-condensing structures 24 : Light guide 26 : Incident surface of the light guide 28 : Body of the light guide 30 : Emitting surface of the light guide 32 : Parallel surfaces of the light guide body 35 : Extreme ray of light 40 : Optical element (lens) 42 : Input surface of the optical element 44 : Output surface of the optical element 46 : Cavity of the optical element 48 : Rear wall of the cavity 50 : Side walls of the cavity

Claims

1. A lamp module (10) for a motor vehicle comprising : - a primary optical device (14), comprising at least one light source (16), generating a beam of light (18) consisting of a plurality of rays of light (20), said beam of light (18) propagating essentially along an X axis, - a light guide (24), arranged downstream of the primary optical device (14), extending along a longitudinal axis Y that is substantially perpendicular to the X axis, comprising an incident surface (26) configured to receive the rays (20) of the beam of light (18) generated by the primary optical device (14) and a body (28) configured to guide said beam of light (18) towards an emitting surface (30) of the light guide, - an optical element (40) arranged downstream of the emitting surface (30) of the light guide (24), comprising an input surface (42) configured to receive the rays (20) of the beam of light (18) emitted by the emitting surface (30) of the light guide and an output surface (44), characterized in that the emitting surface (30) of the light guide is a freeform surface, wherein, in a cross-section along a plane normal to the Y axis the projection of the freeform surface is as a curve defined as a series of points, wherein at each point (P) of the curve, the tangent of the curve forms an angle α with a Z axis that is perpendicular to the X and Y axes, defined by the equation : α = tan − 1 sin θ n − cos θ where : n is the refractive index of the material of the light guide (24) and θ the extreme viewing angle, with respect to the X axis. of the ray of light (35) emitted at the point (P) considered by the emitting surface (30) of the light guide as it exits the output surface (44).

2. The lamp module (10) according to claim 1, wherein the emitting surface (30) of the light guide is a concave surface.

3. The lamp module (10) according to claim 1 or 2, wherein the light guide (24) is made in one piece.

4. The lamp module (10) according to any one of the preceding claims, wherein the optical element (40) is a projection lens.

5. The lamp module (10) according to any one of the preceding claims, wherein the optical element (40) forms a cavity (46) extending along the X axis extending from a surface perpendicular to the X axis.

6. The lamp module (10) according to claim 5, wherein the cavity (46) has a cross-section having a general shape of a U in a plane perpendicular to the Y axis.

7. The lamp module (10) according to any one of the preceding claims, wherein the light guide (24) is made of transparent thermoplastic polymer, for example polycarbonate of polymethylmethacrylate.

8. The lamp module (10) according to any one of the preceding claims, wherein the optical element (40) is made of transparent thermoplastic polymer, for example polycarbonate of polymethylmethacrylate.

9. The lamp module (10) according to any one of the preceding claims, wherein the primary optical device (14) comprises several light sources (16) arranged substantially on a same horizontal plane.

10. The lamp module (10) according to any one of the preceding claims, wherein the primary optical device (14) comprises several light sources, the light sources (16) being light-emitting diodes.

11. The lamp module (10) according to any one of the preceding claims, wherein the primary optical device (14) comprises multiple light condensing structures (22), for example having an ovoidal shape, mounted downstream of the light sources (16).

12. The lamp module (10) according to any one of the preceding claims, wherein the lamp is a rear lamp, a front lamp, or a signal lamp.

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