Elliptical lighting module without screen emitting a low beam and headlamp comprising the same

The present invention relates to a lighting module and a headlamp of a motor vehicle lighting.

The present invention relates more particularly to a lighting module for a motor vehicle headlight producing a kind of cut-off light beam, comprising, arranged from back to front overall along a longitudinal horizontal optical axis, a reflector of the elliptical type which delimits a volume of reflection for light rays and comprises a substantially elliptical reflection surface, at least one light source which is arranged in the vicinity of a first focus of the reflector, and a convergent lens, the focal plane is arranged in the vicinity of second focus of the reflector.

The projectors of the elliptical type or projectors optical image reproduction, are two in known particularly for producing a lighting beam with cutoff.

Means illuminating beam to cut an illumination beam which has a directional limit or cut-off, above which the emitted light intensity is low.

The functions of low lights, fog lights and codes are examples of cut lighting beams, according to European legislation.

Generally, in a projector elliptical, the cut is performed by means of a cover, which is formed of a vertical plate of suitable profile, which is interposed axially between the elliptical reflector and the convergent lens, and which is arranged in the vicinity of second focus of the reflector.

The cache is used to mask the light rays from the light source and reflected by the reflector towards the lower part of the focal plane of the convergent lens, and which would, in the absence of cache, emitted by the projector over the cut.

A disadvantage of this type of projector is an important part of the light energy emitted by the source is dissipated in the back of the cover. Furthermore, this type of module provides a dual function, namely the "road" and "code" function function.

One solution to this problem is disclosed in US Patent 4,914,747.

In this document is described a lighting module for a motor vehicle headlight producing a kind of cut-off light beam, comprising, arranged from back to front overall along a longitudinal horizontal optical axis, two reflectors of the elliptical type each defines a volume of reflection for light rays and each of which comprises a substantially elliptical reflection surface, two light sources which are arranged respectively in the vicinity of a first focus of each reflector, and a convergent lens, the focal plane is arranged vicinity of the second focus of the first reflector, said first reflector comprising a horizontal flat reflection surface, the upper face of which is reflective, which delimits vertically downwards the volume of reflection of the beam emitted by the first light source and having an edge of front end, said cut-off edge, which is arranged near the second focus of the reflector, so as to form the cutoff in the lighting beam.

According to this prior art, the first light source formed of a filament has a lower cap ensuring a single beam upwardly emitted by this source. The first elliptical reflector associated therewith can be designed in an optimized manner according to this first source to populate the function code.

Against by the second light source, also a filament, can emit as much upwards as downwards. If the second elliptical reflector associated therewith can be designed in an optimized way depending on the second power source to complete the route function, there is an upper beam defined by the choice of this second light source and reflecting from the first reflector defined as to it by the choice of the first light source. If this beam once thought involved in road function, this function can be optimized as dependent on criteria relating to the function code, in terms of the first reflector.

This results in an uncontrolled and random layout efficiency or at least require extensive testing to achieve the desired functions.

The invention solves this technical problem and to do this, it proposes a lighting module for a motor vehicle headlight producing a lighting beam with cut-off type, comprising, arranged from back to front overall along a horizontal optical axis longitudinal, two reflectors of the elliptical type, each of which delimits a reflection volume for light rays and each of which comprises a substantially elliptical reflection surface, two light sources which are arranged respectively in the vicinity of a first focus of each reflector, and a lens convergent, the focal plane is arranged in the vicinity of the second focus of the first reflector, said first reflector comprising a horizontal flat reflection surface, the upper face of which is reflective, which delimits vertically downwards the volume of reflection of the beam emitted by the first light source and comprising a front end edge, said cut-off edge, which is arranged near the second focus of the reflector, this flat surface of the first reflector being arranged in a horizontal plane passing overall through the foci of the first reflector, wherein that the second light source is arranged to emit a light beam only towards the second reflector, at least one light source consisting of a light emitting diode.

Thus, each light source emits in a half volume of limited reflection by the elliptical reflector corresponding, independently. This allows to control their function and radiation easily and accurately.

With the lighting module according to the invention, most of the light generated from each source is used in the light beam produced by the module, in order to achieve the dual function of lighting associated regulatory, preferably the "road "and the" code "..

According to a preferred embodiment, this arrangement consists in that the two light sources are separated by an opaque shroud.

Preferably, the second focal points of the first and second elliptical reflectors are substantially coincident.

Advantageously, said horizontal flat reflection surface, the upper face of which is reflective, consists of a transparent part having a reflective coating.

This characteristic limits the hole or dead area of ​​light corresponding to the image of the thickness of this reflecting surface by the light beam reflected by the first reflector to the thickness of said reflective coating can be achieved by a vacuum deposition for example aluminum which is of a thickness between approximately 500 nm and approximately a few micrometers, the order of magnitude of some visible wavelengths.

Moreover, this transparent part also has an optical function with respect to the optical beam reflected by the second reflector. Indeed, it is crossed by the beam.

To limit the optical losses at this crossing, preferably, said transparent part comprises a spherical lower face centered on the second focus of the second elliptical reflector.

Thus the light rays emitted by reflection on the second reflector are normal to said bottom face.

Preferably, the substantially elliptical surface of the first reflector is formed by an arc part substantially of revolution, around the longitudinal optical axis, and in that this angular sector extends vertically above the flat surface of the reflector .

Preferably, the substantially elliptical surface of the second reflector is formed by an arc part substantially of revolution about an axis of said revolution.

And preferably, the optical axis of the first reflector and the axis of revolution of the second reflector intersect.

According to other characteristics of the invention:<ul><li>the flat surface of the reflector may extend longitudinally rearwardly from its cut-off edge, at least to the vicinity of the first focus of the reflector;</li><li>the light source associated with the first reflector is arranged in the module so that its light diffusion axis is substantially perpendicular to the planar surface of said reflector;</li><li>the flat surface of the cut-off edge of the first reflector has a curved profile, in the horizontal plane, so as to generally follow the curvature of the focal plane of the lens.</li></ul>

The invention also relates to a projector for a motor vehicle lighting comprising at least one lighting module as previously specified and for a dual lighting function.

Preferably, this double feature includes the lighting function mode "code" and the lighting function mode "route".

Other features and advantages of the invention will become apparent from reading the following detailed description for the understanding of which is made to the attached drawings among which:<ul><li>Figure 1 is a vertical sectional view which schematically shows a preferred embodiment of the lighting module according to the invention;</li><li>Figure 2 is a perspective view showing part of this preferred embodiment of the lighting module according to the invention;</li><li>Figure 3 is a top view that schematically shows the light module of Figure 1;</li><li>Figure 4 is a side view which schematically illustrates the light path in the light module of Figure 1; </li><li>Figure 5 is a view similar to that of Figure 2 which shows a second embodiment of the lighting module according to the invention;</li><li>Figure 6 is a view similar to that of Figure 2 which shows an alternative embodiment of the lighting module of Figure 1 having a plurality of light emitting diodes;</li><li>Figure 7 is a front view which schematically shows a vehicle lighting projector comprising light source module according to the invention and performing a regulatory dipped lighting beam;</li><li>Figure 8 is a schematic perspective view of the lighting module shown in Figure 1;</li><li>Figure 9 is a schematic representation of an image of the projection of the light beam emitted by the module, according to a first module of the mode of operation according to the invention</li><li>Figure 10 is a schematic representation of an image of the projection of the light beam emitted by the module, a second module according to the operating mode according to the invention.</li></ul>

schematically shown in Figure 1 a lighting unit 10 which is constructed according to the teachings of the invention.

Conventionally, the illumination module 10 comprises, arranged from back to front along a longitudinal horizontal optical axis AA, a first reflector 12 of the elliptical type, a first light source 14 which is arranged in the vicinity of a first focus F1 the first reflector 12 and a lens 16 whose focal plane is arranged in the vicinity of the second focus F2 of the first reflector 12.

The first reflector 12 and the lens 16 form a part of the optical system of the lighting module 10.

The optical axis AA defined here, not limited, a horizontal longitudinal direction and a rear direction forward, which corresponds to an orientation from left to right in the figures. The optical axis A is for example substantially parallel to the longitudinal axis of a vehicle (not shown) equipped with the lighting module 10.

In the following description, are not limited to, use a vertical orientation which corresponds to a downward direction in FIG 1.

The converging lens 16 is here a part of revolution around the longitudinal optical axis AA. The lens 16 comprises, vis-a-vis the first reflector 12, a transverse inlet surface 17 to the light rays.

According to the embodiment shown here, the first reflector 12 has an elliptical surface 18 which is in the form of an angular sector part substantially of revolution, and which extends into the half space above a horizontal axial plane passing through the longitudinal optical axis AA.

The internal face 20 of the elliptical surface 18 is reflective.

It is noted that the elliptical surface 18 may not be perfectly elliptical and may have several specific profiles designed to optimize the light distribution in the light beam produced by the module 10, according to the "code" Lighting function performed by the Module 10. This therefore implies that the reflector is not perfectly revolution.

According to the teachings of the invention, the first reflector 12 has a horizontal flat surface 22 whose upper face 24 is reflective.

The first reflector 12 delimits a volume of reflection for light rays emitted by the first source 14, that is a volume in which the light rays are emitted and in which light rays are reflected. This volume of reflection is delimited in its upper part, by the internal reflection face 20 of the elliptical surface 18, and vertically downward by the reflecting face 24 of the flat surface 22.

The flat surface 22 extends here in a horizontal axial plane.

Figures 2 to 7 only represent the first reflector 12, the lens 16 and the planar surface 22.

The flat surface 22 is bounded at the rear, at its intersection with the elliptical surface 18, by an elliptical edge 26, and at the front by a longitudinal front end edge 28. It can be provided alternatively as planar surface 22 is bounded at the rear by a line segment perpendicular to the axis a and passing in the immediate vicinity of the source 14, in front of the latter.

The front end edge 28 of the flat surface 22 is arranged near the second focus F2 of the reflector 12, so as to form a sufficiently sharp cutoff in the lighting beam produced by the light module 10.

In the following description, so we will designate that the front end edge 28 by "cutoff edge 28".

The focal plane of the lens 16 in a horizontal plane passing through the focus F2 of the lens 16, form a curved profile, concave forward. According to the embodiment, the curved shape of the profile is more or less complex, and can be likened to a first approximation to a circular arc. Therefore, preferably, the cut-off edge 28 has a curved profile, in the horizontal plane, so as to generally follow the profile of the focal plane of the lens 16.

According to the embodiment shown here, the reflective planar surface 22 comprises a rear section 30, semi-ellipsoidal, which is delimited by the elliptical edge 26, and by the diameter 32 of the front edge 34 of the semi-circular elliptical surface 18.

The reflective planar surface 22 comprises a front section 36 generally isosceles trapezoidal, which is delimited by the diameter 32 of the elliptical surface 18, by two lateral edges 38, 40, and the cut-off edge 28.

According to the embodiment shown here, the transverse width of the front section 36 increases progressively towards the front, so that the transverse width of the cut-off edge 28 is substantially equal to the diameter of the entrance surface of the lens 16.

According to an alternative embodiment as shown in Figure 3, the flat surface 22 may comprise only a front portion 36, which extends axially rearward from the cutoff edge 28 up to a predetermined point in the optical axis a between the first F1 and second F2 foci of the reflector 12.

Advantageously, the light source 14 is scheduled to issue its light energy in less than a "half space" located above the flat surface 22, and to transmit its light energy towards the internal face 20 of the elliptical surface 18.

Advantageously, the light source 14 is a light emitting diode 44 encapsulated.

is defined here as light emitting diode 44, the junction that produces light energy as well as the globe, or the capsule, light diffusion, which surrounds the upper part of the junction.

Conventionally, the light emitting diode 44 is mounted on a circuit board support 42, which is shown in Figure 4, and which is arranged here in parallel under the flat surface 22.

The light emitting diode 44 has an axis of light scattering BB which is here substantially perpendicular to the planar surface 22.

The LED 44 emits the light energy within a solid angle generally centered about its axis BB of light diffusion, and less than 180 degrees.

This arrangement allows the diode 44 to emit most of its light energy towards the internal face 20 of the elliptical surface 18.

The principle of operation of the illumination module 10 according to the invention is as follows.

It is assumed that the light source 14 is of small extent around a point coincident with the first focus F1 of the elliptical reflector 18.

At first, we consider the light rays emitted by the light source 14 which pass above the cut-off edge 28, and which will be designated by primary rays R1.

As the light source 14 is arranged at the first focus F1 of the elliptical reflector 18, most of the primary rays R1 emitted by the source 14, after being reflected on the internal face 20 of the elliptical surface 18, is returned to the second focus F2 of the reflector 18 or in the vicinity thereof.

These primary light rays R1 form, the focus F2 of the lens 16, a concentrated light image that is projected at the front of the lighting module 10 by the lens 16 according to a direction substantially parallel to the longitudinal axis AA but facing downwards.

Secondly, we consider the light rays R2 emitted by the source 14 which would pass below the cutoff edge 28, if there were not the flat surface 22, and which will be designated by secondary rays R2.

These secondary light rays R2 are reflected by the inner face 20 of the elliptical surface 18 to the flat reflecting surface 22, so that they are reflected a second time towards the front.

At the second reflection, the secondary light rays R2 are transmitted to the upper part of the inlet surface 17 of the lens 16. Therefore, due to its convergence properties, the lens 16 deviates the secondary light rays R2 to the bottom. R2 secondary light rays are emitted under the cutoff in the lighting beam, in the same area as that in which are emitted rays R1.

More place of reflection on the flat surface 22 of a secondary light ray R2 is close to the cutoff edge 28, so close to the focal plane of the lens 16, over the direction of this secondary light ray R2, the output of the lens 16, is close to a direction parallel to the longitudinal axis AA.

An advantage of the lighting module 10 of the invention is that its optical system 11 does not obscure a significant portion of light rays emitted by the source 14, as is the case in conventional lighting module comprising a cover .

The reflective flat surface 22 can "fold" the images of the light source 14 are reflected by the elliptical surface 18 of the reflector 12 at the second focus F2 of the reflector 12.

Indeed, in the absence of the flat surface 22, some of the images should overlap the edge formed by the cut-off edge 28, in a vertical plane generated by the cut-off edge 28. Each image would then comprise an upper portion situated over well cutoff edge 28 and a lower portion located below the cutoff edge 28. Thanks to the flat reflecting surface 22, the lower portion of each image is reflected upward, as if the bottom portion was folded over the upper portion, so that these image portions are superimposed above the cutoff edge 28, in the vertical plane generated by the cut-off edge 28.

The "fold" formed by the "folding" of images contributes to forming a sharp cutoff in the lighting beam projected by the lens 16.

The light source module 10 according to the invention also has particular advantages in the context of using a light emitting diode 44 as the light source 14 in an illumination module.

Indeed, the image of the virtual source corresponding to a diode is generally round and diffuse.

To make a cut in a lighting beam from a light source module using a light source and a Fresnel lens, or using a light source and a reflector of the complex surface type, it is necessary to align the edges of images of the light source on the measurement screen used to validate the statutory illumination beam.

When the light source is a filament, its virtual image has overall the shape of a rectangle, so it is relatively easy to achieve a clean cut by aligning the edges of the rectangles.

When the light source is a diode, it is much more difficult to achieve a clean break by aligning the corresponding images of round forms.

This difficulty could be overcome by using a diaphragm with the diode, but would then lose a significant amount of light energy produced by the diode.

The light source module 10 according to the invention produces a clean cut with a diode 44, because it projects on the front image of an edge of the optical system 11, i.e. the image of the edge cut 28.

The shape of the cutoff in the lighting beam is therefore determined by the profile of the cut-off edge 28, in a projection on a vertical transverse plane.

Another difficulty for the embodiment of a lighting module from a diode due to the fact that the distribution of light energy in the light beam emitted by the diode is not homogeneous. Therefore, it is very difficult to achieve a homogeneous illumination beam from direct images of the diode.

The illumination module 10 according to the invention overcomes this difficulty by exploiting a property of elliptical illumination modules which is "mixing" the images of the light source at the second focus F2 of the reflector 12, which improves the uniformity of lighting beam produced.

One advantage of the illumination module 10 of the invention is that it exploits the property of encapsulated diodes 44 of emitting overall in a half space, which can capture more than eighty percent of the luminous flux emitted by the diode 44, whereas in an elliptical projector traditional code, it captures less than fifty percent of the light flux.

According to a first embodiment, which is shown schematically in Figures 2 to 4, the lighting module 10 is made by an assembly of discrete elements.

The light source module 10 includes, for example, an element 18 forming the elliptical portion of the reflector 12, an element 22 forming the flat surface of the reflector 12, and an element 16 forming the lens.

The inner surface of the elliptical portion 18 and the upper face of the flat surface 22 are for example coated with a reflective material.

In the case where the light source 14 is a light emitting diode 44, in view of the low heat dissipation of this type of source, relative to the lamps, it is possible to produce the discrete elements in the form of polymer parts assembled by example by interlocking.

The lens 16 may be a Fresnel lens.

According to another embodiment of the invention, which is shown schematically in Figure 5, the optical system 11 of the lighting module 10 is made in a single full optical part, of transparent material, for example PMMA (polymethyl methyl).

Full optical piece is made for example by molding or by machining.

To allow the reflection of light rays emitted by the source 14 into the volume of reflection delimited by the reflector 12, the outer surface of the elliptical portion 18 of the reflector 12 and the outer surface, here below, the planar surface 22 of the reflector 12 are coated with a reflective material.

For some portions of the reflector 12, the total reflection properties can be used in a medium of index greater than air to cause reflection of light rays in the volume of reflection delimited by the reflector 12, without using a reflective material. These reflector portions 12 will then have a slightly different form from that of a pure ellipsoid.

According to this second embodiment, the light rays which are emitted by the light source 14 propagate within the material constituting the optical system 11 of the lighting module 10, and then they come out of the optical system 11 from the front side of the converging lens 16.

The fact that the light rays propagate within a material, in the second embodiment, while the light rays propagate in the air, in the first embodiment, has no influence noticeable on the principle of operation of the illumination module 10 according to the invention.

Advantageously, the reflective planar surface 22 includes a cavity of complementary shape to the capsule of the light emitting diode 44.

For example, if the capsule of the diode 44 has a hemispherical shape, the cavity is substantially hemispherical.

In a variant of this second embodiment, the reflector 12 is made of a single piece of transparent material, which is separate from the part forming the convergent lens 16.

According to an alternative embodiment of the invention, which is shown in Figure 6, the light source 14 can be realized by means of several light emitting diodes 44.

Note that the light emitting diodes 44 must be very close to each other, so that they are generally arranged at the first focus F1 of the reflector 12.

For example, according to Figure 6, two diodes 44 are aligned, preferably in a direction perpendicular to the longitudinal optical axis AA.

The resulting light source 14 is then equivalent to a light source extended in width because the illumination beams produced by each light emitting diode 44 overlap.

This arrangement of LEDs 44 allows to broaden the light beam produced by the illumination module 10.

Advantageously, to perform a function of regulatory lighting, to cut, for example a lighting function "code" is performed by a vehicle headlight of several identical illumination modules 10 operating simultaneously.

The light source module 10 are arranged in parallel, ie that their optical axes AA are substantially mutually parallel.

Thus, the light beams produced by each of the lighting modules 10 are superimposed on the front of the vehicle so as to form the cut to regulatory lighting beam.

For example, there is shown in Figure 7 a projector 46 of the vehicle which performs a code function, which uses four identical illumination modules 10.

As the passing illumination beam must have a cutoff portion having an inclined by a determined angle, for example fifteen degrees, two light source module 48 of the projector 46 are rotated fifteen degrees about their longitudinal optical axis AA, so as to produce an illumination beam having an inclined cut-off of fifteen degrees relative to a horizontal plane.

The other two lighting modules 50 form an illumination beam having a horizontal cutoff.

The superposition of the light beams produced by the four light source module 10 then forms a regulatory lighting beam having a horizontal portion and an inclined portion of fifteen degrees.

According to an alternative embodiment (not shown) of the invention, the light source 14 may be formed by the free end of a fiber optic bundle.

A disadvantage of optical fibers is that they form a light source comprising a bright core and a dark ring, due to the cladding surrounding the core of the fiber.

This type of light source, when used in a vehicle lighting projector using such a reflector of the complex surface type, so as in the illumination beam, images as pixels surrounded by an area dark, due to the sheath.

One advantage of the illumination module 10 of the invention is that it mixes all the images of the light source 14 at the second focus F2 of the reflector 12 so that is not found in the illumination beam pixels of the optical fiber.

Now back to Figure 1, associated with Figure 8. In addition to what has already been described in detail above, in order to fulfill a dual function, namely the "code" function but also the "road" function, the module according to the invention, intended to equip a motor vehicle headlamp of lighting, also comprises arranged from back to front overall along the longitudinal optical horizontal axis AA, a second reflector 12 'of the elliptical type which delimits a volume reflection for light rays and comprises a substantially elliptical reflection surface 18 ', 20', a second light source 14 'which is arranged in the vicinity of a first focus F1' of the second reflector 12 '. This second light source 14 is arranged to emit a single light beam downwards.

The second reflector 18 'and the second light source 14' may be similar to the first reflector 18 and the first light source 14. They can submit all relevant features already mentioned above, without the latter are explicitly included here.

To do this, the two light sources 14, 14 'to selectively control which are preferably two light emitting diodes or two sets of light emitting diodes are separated by an opaque shroud 60 which optionally may contain a heater and control circuitry.

As already discussed above, the substantially elliptical surface of the first reflector 12 is formed by an arc part substantially of revolution, around the longitudinal optical axis AA, and this angular sector extends vertically above the planar surface 22 of the reflector.

The substantially elliptical surface of the second reflector is, in turn, formed by an angular sector part substantially of revolution, about its axis of revolution said A'-A 'and, preferably, the optical axis AA of the first reflector and axis of revolution A'- A 'of the second reflector intersect.

The second elliptical reflector 12 'is arranged to have its second substantially focus merged with the second focus F2 of the first reflector 12. The optical axis A of the first reflector and the revolution axis A'-A' of the second reflector is thus cut substantially in the second focus F2.

The horizontal flat reflection surface 22, the upper face 24 is reflective, consists of a transparent member 22 'carrying a reflective coating on its upper face and forming the reflective top surface 24. Advantageously, the transparent member 22' has a spherical lower surface 22A substantially centered on the second focus F2. Its lateral surface 22B facing the lens 16 is in turn preferably defined by a ruled surface defined by straight vertical plane connecting the upper edge 34 of the first reflector 12 at the second focus F2.

Preferably, this transparent member 22 'is made of PMMA (polymethyl methacrylate) and the reflective coating consists of a vacuum deposition of aluminum.

The optical operation of the module has already been stated above as regards the first elliptical reflector 12 with its reflective surface 22 associated in particular with reference to Figure 4.

To summarize, with reference to Figure 1, during operation of the first light source 14, most of the primary radiation emitted by the source 14, after being reflected on the internal face 20 of the elliptical surface 18, is returned to the second focus F2 of the reflector 18 or in the vicinity thereof. The secondary light beams are reflected by the inner face 20 of the elliptical surface 18 to the flat reflecting surface 22, so that they are reflected a second time towards the front, this reflective surface 22 operating according to a "collapsing".

An image I1 of the projection of the light beam emitted by the module, the output of the lens 16, is shown schematically in Figure 9. This first module function is particularly "code" mode of a motor vehicle headlight.

During the simultaneous switching of the second light source 14 ', the majority of the primary rays R1' emitted by the source 14 ', after being reflected on the internal face 20 of the elliptical surface 18, is returned to the second focus F2 or in the vicinity thereof. These rays normal to the bottom surface 22A of the transparent member 22 'through it without optical loss, the losses incurred by glass near the reflection surface 22A, and are then returned by the lens 16 above the axis AA .

An image of the projection of the light beam emitted by the module, the output of the lens 16, is shown schematically in Figure 10. A picture I2 there is an adjunct to the previous image I1. This second module function corresponds in particular to "road" mode of a motor vehicle headlight.

Given the transparency of the part 22 'and of the reduced and non-visible thickness of the reflective coating 24, the two images I1 and I2 in question are contiguous to the eye and form a single light beam.