OPTICAL ELEMENT INTENDED TO MODIFY THE DISTRIBUTION OF A LIGHT BEAM, FOR VEHICLE HEADLIGHT

AUTOMOTIVE

TECHNICAL AREA

The field of the present invention is that of equipment for motor vehicles and, more particularly, that of light projectors for these motor vehicles.

STATE OF THE ART

Motor vehicle headlamps generally comprise an elliptical reflector in which are arranged a light source, a cut-off strip allowing various phases of concealment of the light beam and an optical lens diffusing the light beam created on the road.

The cut-off bar is electrically actuated by an actuator to move, on command, between at least two angular positions in which it more or less obscures the light beam. This makes it possible to limit the range of the headlamp, for example to that of the dipped beam headlamps, called the low beam position, so as not to dazzle drivers traveling in the opposite direction, or to that of the high beam headlights, called the high beam position, in which it does not there is no occultation. This technology is commonly used with projectors comprising a high power light source, such as halogen or xenon lamp projectors, for which the loss of light power due to the interception of the flux by the strip is not really harmful. .

The technology of automobile headlamps currently tends to the use of light sources constituted by diodes.

light-emitting diodes known as LED (or LED for "Light-Emitting Diode" in English) for their reduced cost and their better lifespan. On the other hand, the light power emitted by these devices remains for the moment still limited and it is necessary to use it as well as possible. It is therefore desirable to be able to do without the cut-off cover which, in the low beam position, absorbs substantially half of the emitted luminous flux.

Document FR 3 028 002 proposes the use of a mobile reflecting surface. Thanks to its mobility, this reflective surface makes it possible to redirect the light beam to form, as desired, high beams or low beams, without having to cut and, therefore, without losing part of the power of the emitted light beam. .

However, this reflecting surface is exposed to external radiation, in particular solar radiation. It can therefore heat up by focusing the external radiation on said reflecting surface. This reflecting surface can be carried by a plastic support which can therefore be damaged by heating at the level of the reflecting surface.

DISCLOSURE OF THE INVENTION

The object of the present invention is to alleviate these drawbacks by providing an optical element resistant to heat.

To this end, the invention relates to an optical element intended to modify a distribution of light beams for a motor vehicle headlight.

According to the invention, the optical element comprises a resin body having a functional surface covered with a reflecting coating capable of reflecting the light beams, the reflecting coating comprising:

- a layer of copper covering at least the functional surface,

- a layer of nickel covering the copper layer,

a chromium layer covering the nickel layer.

Thus, thanks to the copper layer, the heating produced at the functional surface can be dissipated by the copper layer.

According to one embodiment, the optical element further comprises a nickel plating layer between the functional surface and the copper layer.

According to one variant, the optical element comprises a plating layer comprising a mixture of nickel and copper between the functional surface and the copper layer.

The plating layer allows good adhesion of the reflective coating to the resin body.

According to another embodiment, the layer of nickel comprises:

- a semi-glossy nickel sublayer covering the copper layer,

- a high sulfur nickel sublayer covering the semi-bright nickel sublayer,

- a shiny nickel sublayer covering the high sulfur nickel sublayer,

- a matte nickel sublayer covering the shiny nickel sublayer.

According to a first embodiment, the functional surface has a semi-elliptical shape.

According to a second embodiment, the functional surface has a planar shape.

The invention also relates to a headlight for a motor vehicle comprising at least one reflector and at least one light source capable of emitting at least one light beam, the reflector having the shape of a portion of a half-ellipsoid extending above. a plane of symmetry of the ellipsoid, the light source being positioned on an axis of symmetry of the ellipsoid.

According to the invention, the headlight further comprises an optical element as described above, the optical element being arranged to be movable to modify a distribution of the light beam emitted by the light source and reflected by the reflector.

In addition, the light source is disposed substantially at a first focal point of the ellipsoid, the reflector being able to reflect the light beam (s) towards a second focal point of the ellipsoid, the functional surface of the optical element being disposed at the second. hearth.

Furthermore, the projector comprises a drive module configured to change the position of the optical element between at least a first position of the optical element and a second position of the optical element, the first position of the optical element. making it possible to form a beam in the form of dipped beams at the outlet of the headlamp, the second position of the optical element making it possible to form a beam in the form of high beams at the outlet of the headlamp.

The invention also relates to a method of manufacturing an optical element intended to modify a distribution of light beams as described above.

According to the invention, the method comprises the following steps:

- a step of forming a resin body having a functional surface;

a first step of covering at least part of the functional surface with a layer of copper;

- a second step of covering the copper layer with a nickel layer;

- a third step of covering the layer of nickel with a layer of chromium.

According to one embodiment, the method further comprises a step of covering with a nickel plating preceding the first covering step.

According to one variant, the method further comprises a step of covering with a plating comprising a mixture of nickel and copper preceding the first covering step.

According to another embodiment, the second covering step comprises:

- a first sub-step of covering a semi-gloss nickel sublayer on the copper layer;

a second sub-step of covering a nickel sublayer with a high sulfur content on the semi-bright nickel sublayer;

a third sub-step of covering a sublayer of shiny nickel on the sublayer of nickel with a high sulfur content;

a fourth sub-step of covering a matte nickel sublayer on the shiny nickel sublayer.

BRIEF DESCRIPTION OF THE FIGURES

The invention, with its characteristics and advantages, will emerge more clearly on reading the description given with reference to the appended drawings in which:

- Figure 1 shows a profile view of the headlight for a motor vehicle according to one embodiment,

- Figure 2 shows a perspective view of the optical element according to one embodiment,

- Figure 3 shows a cross section of the reflective coating on the body according to one embodiment,

- Figure 4 shows a cross section of the reflective coating on the body according to another embodiment.

DETAILED DESCRIPTION

FIG. 1 represents a headlight 13 for a motor vehicle.

The projector comprises at least one reflector 14 and at least one light source 15 capable of emitting at least one light beam 17.

In the remainder of the description, the term “light beam” will be used in the singular. But, it will be understood that this term can also mean “light beams” in the plural.

The reflector 14 has the shape of a portion of a semi-ellipsoid extending above a plane of symmetry 16 of the ellipsoid. The light source 15 is positioned on an axis of symmetry of the ellipsoid. The light source may include at least one LED diode that emits at a solid angle of 2p steradians so that all of the light beam emitted by the light source is reflected by the reflector.

The projector 13 further comprises an optical element 1 arranged to move to modify a distribution of the light beam 18 emitted by the light source 15 and reflected by the reflector 14.

Advantageously, the light source 15 is disposed substantially at a first focal point of the ellipsoid. The reflector 14 is then able to reflect the light beam 17 towards a second focal point of the ellipsoid.

The projector can also include a lens 18 disposed on the path of the light beam 17 after said light beam 17 has been reflected on the reflector 14 then cut and / or reflected by the optical element 1. Preferably, the lens 18 is convergent. .

Advantageously, the projector 13 comprises a drive module 16 configured to modify the position of the optical element 1 between at least a first position of the optical element 1 and a second position of the optical element 1. The first position of optical element 1

makes it possible to form a beam in the form of dipped beams at the outlet of the headlight 13. The second position of the optical element 1 makes it possible to form a beam in the form of high beams at the outlet of the headlamp 13.

The optical element 1 intended to modify a distribution of light beams is shown in FIG. 2.

The optical element 1 comprises a resin body 2 having a functional surface 3 covered with a reflecting coating 4 capable of reflecting the light beam.

In a nonlimiting manner, the resin can be polyphthalamide (PPA) reinforced with glass fibers (PPA GF25-40%). This resin has excellent thermal properties and high mechanical strength. It is also resistant to fatigue.

Preferably, the resin can be reinforced PPA (PPA MR 30%). This resin has excellent thermal properties, good mechanical strength and very good dimensional stability. PPA MR 30% is preferred for its dimensional stability. Indeed, the successive coatings tend to amplify any defects in appearance.

Advantageously, the functional surface 3 of the optical element 1 is disposed substantially at the second focal point of the ellipsoid.

The functional surface 3 can have a semi-elliptical shape or a planar shape.

The semi-elliptical shape of the functional surface 3 may correspond to a concave semi-elliptical shape located outside the focal plane of the ellipsoid, between the lens 18 and the focal plane, allowing reflection of the light source 15 to achieve a distribution. Subdued additional light, above the traffic light to increase the visibility of vertical traffic signs.

The reflective coating 4 comprises (figure 3):

- a copper layer 5 covering, at least in part, the functional surface 3,

- a layer of nickel 6 covering the layer of copper 5, and

- a layer of chromium 7 covering the layer of nickel 6.

The copper layer 5 corresponds to a heat conductive layer. Said copper layer 5 makes it possible to dissipate the heat produced by heating at the level of the functional surface 3 by the external radiation 19. It also has good resistance to high temperatures and to temperature changes. The copper has good adhesion with the material of the resin body 2 and the nickel layer 6. The copper layer 5 further provides good elasticity to the reflective coating 4.

If the projector 13 includes a converging lens 18, heating of the functional surface 3 caused by the convergence of the external radiation 19 on said functional surface 3 can be dissipated by the copper layer 5. Thus, heating is not localized to the place where the external radiation 19 converges. This prevents destruction of the resin body 2.

In a nonlimiting manner, the copper layer 5 has a thickness of between 15 μm and 25 μm, preferably 20 μm.

The nickel layer 6 makes it possible to resist the corrosion of the reflective coating 4. It also has good resistance to climatic cycles.

The chromium layer 7 makes it possible to provide hardness to the reflective coating 4 as well as a gloss.

In a nonlimiting manner, the chromium layer has a thickness of between 0.1 μm and 1 μm, preferably 0.25 μm.

According to one embodiment, the reflective coating further comprises a cladding layer 8 between the functional surface 3 and the copper layer 5.

The plating layer 8 can be made of nickel or comprise a mixture of nickel and copper.

In a nonlimiting manner, the plating layer comprises from 50% to 70% copper and from 50% to 30% nickel. Preferably, the plating layer comprises about 60% copper and 40% nickel.

The plating layer 8 improves the adhesion of the copper layer 5 to the resin body 2.

In a limiting manner, the cladding layer has a thickness of between 0.5 μm and 1.5 μm, preferably 1 μm.

According to another embodiment (FIG. 4), the nickel layer 6 comprises:

- a semi-gloss nickel sublayer 9 covering the copper layer 5,

- a nickel sub-layer with a high sulfur content 10 covering the semi-gloss nickel sub-layer 9,

- a shiny nickel sublayer 11 covering the high sulfur nickel sublayer 10,

- a matte nickel sublayer 12 covering the shiny nickel sublayer 11.

The semi-gloss nickel sub-layer 9 provides good adhesion of the copper layer 5 with the nickel layer 6. It also provides good corrosion resistance of the reflective coating 4.

In a non-limiting manner, the semi-gloss nickel sublayer 9 has a low sulfur content of between 0.002% and 0.005% by mass.

In a nonlimiting manner, the semi-gloss nickel sublayer 9 has a thickness of between 10 μm and 20 μm, preferably 15 μm.

The high sulfur nickel sub-layer 10 allows good adhesion of the semi-gloss nickel sub-layer 9 and the bright nickel sub-layer 11.

In a non-limiting manner, the high sulfur content nickel sublayer 10 has a sulfur content of between 0.1% and 0.25% by mass. The term "high content" for "high sulfur nickel" means that the nickel includes a sulfur content ranging from 0.1% to 0.25% by mass.

In a non-limiting manner, the high sulfur content nickel sublayer 10 has a thickness between 1.5 µm and 2.5 µm.

The bright nickel undercoat 11 provides a good gloss of the reflective coating 4 and an improvement in the hardness of the reflective coating 4.

In a nonlimiting manner, the shiny nickel sublayer 11 has a thickness of between 5 μm and 15 μm, preferably 10 μm.

The matte nickel underlayer 12 provides the reflective coating 4 with a shiny surface identical to a mirror.

In a nonlimiting manner, the matte nickel sublayer 12 has a thickness of between 5 μm and 15 μm, preferably 10 μm.

The terms "semi-gloss", "gloss" and "mat" can be related by a relationship between diffuse reflection and specular reflection (reflectivity). A reflection can be said to be diffuse when an incident ray is reflected in a large number of directions, while a reflection is said to be specular when an incident ray is reflected in one direction.

Thus, the term "mat" can mean that diffuse reflection is more important than specular reflection. Light energy reflected by

diffusion is therefore greater than the light energy reflected in a specular manner.

The term "bright" can mean that specular reflection is more important than diffuse reflection. The specularly reflected light energy is therefore greater than the scattered reflected light energy.

The term "semi-gloss" follows from these definitions. It can therefore mean that the specular reflection is substantially as great or significantly less than the diffuse reflection. The specularly reflected light energy is therefore substantially equal to or substantially less than the light energy reflected by scattering.

In a nonlimiting manner, a glossy surface has a reflectivity (specular reflection) of between 50% and 100%, a semi-glossy surface of between 20% and 50% and a matt surface of less than 20%.

The optical element 1 can be manufactured by a manufacturing process which comprises the following steps:

- a step of forming a resin body 2 having a functional surface 3;

a first step of covering at least part of the functional surface 3 with a layer of copper 5;

- a second step of covering the copper layer 5 with a nickel layer 6;

- a third step of covering the layer of nickel 6 with a layer of chromium 7.

The step of forming the resin body 2 can be carried out by molding the resin or by 3D printing.

The first recovery step can be carried out chemical copper plating.

The second recovery step can be carried out by electrolytic deposits.

The third recovery step can be carried out by electrolytic deposition.

According to one embodiment, the method comprises a step of covering with a nickel plating 8 or a mixture of nickel and copper preceding the first covering step.

The step of covering with a plating 8 can be carried out by electrolytic deposition.

According to another embodiment, the second covering step comprises:

- a first sub-step of covering a semi-gloss nickel sublayer 9 on the copper layer 5;

- a second sub-step of covering a sub-layer of nickel with a high sulfur content 10 on the sub-layer of semi-bright nickel

9;

a third sub-step of covering a sublayer of shiny nickel 11 on the sublayer of nickel with a high sulfur content 10;

- a fourth sub-step of covering a matte nickel sublayer 12 on the shiny nickel sublayer 11.

Each of the sub-steps can be implemented by electrolytic deposition.

The first covering sub-step may comprise depositing a layer of matt nickel and polishing the layer of matt nickel.

The third covering sub-step may comprise depositing a layer of matt nickel and dipping the layer of matt nickel in a bath containing brightening additives.

The present description details various embodiments with reference to figures and / or technical characteristics. Those skilled in the art will understand that the various technical characteristics of the various embodiments can be combined with one another to obtain other embodiments, unless the reverse is explicitly mentioned or these technical characteristics are incompatible.

CLAIMS

1. Optical element intended to modify a distribution of light beams for a motor vehicle headlight,

characterized in that it comprises a resin body (2) having a functional surface (3) covered with a reflecting coating (4) capable of reflecting the light beams, the reflecting coating (4) comprising:

- a copper layer (5) covering, at least in part, the functional surface (3),

- a layer of nickel (6) covering the layer of copper (5),

- a chromium layer (7) covering the nickel layer (6).

2. Optical element according to claim 1,

characterized in that it further comprises a plating layer (8) of nickel between the functional surface (3) and the copper layer (5).

3. Optical element according to claim 1,

characterized in that it further comprises a plating layer (8) comprising a mixture of nickel and copper between the functional surface (3) and the copper layer (5).

4. Optical element according to any one of claims 1 to 3, characterized in that the nickel layer (6) comprises:

- a semi-gloss nickel sublayer (9) covering the copper layer (5),

- a nickel sub-layer with a high sulfur content (10) covering the semi-gloss nickel sub-layer (9),

- a shiny nickel sublayer (11) covering the high sulfur nickel sublayer (10),

- a matte nickel sublayer (12) covering the shiny nickel sublayer (11).

5. Optical element according to any one of claims 1 to 4, characterized in that the functional surface (3) has a semi-elliptical shape.

6. Optical element according to any one of claims 1 to 4, characterized in that the functional surface (3) has a planar shape.

7. Headlight for a motor vehicle comprising at least one reflector (14) and at least one light source (15) capable of emitting at least one light beam, the reflector (14) having the shape of a portion of a half-ellipsoid s 'extending above a plane of symmetry (16) of the ellipsoid, the light source (15) being positioned on an axis of symmetry of the ellipsoid,

characterized in that it further comprises an optical element (1) according to any one of claims 1 to 6, the optical element (1) being arranged movably to modify a distribution of the light beam (18) emitted by the light source (15) and reflected by the reflector (14).

8. A projector according to claim 7,

characterized in that the light source (15) is arranged substantially at a first focal point of the ellipsoid, the reflector (14) being able to reflect the light beam (s) towards a second focal point of the ellipsoid, the functional surface (3 ) of the optical element (1) being disposed at the second focus.

9. A projector according to any one of claims 7 or 8, characterized in that it comprises a drive module (16) configured to modify the position of the optical element (1) between at least a first position of the 'optical element (1) and a second position of the optical element (1), the first position of the optical element (1) making it possible to form a beam in the form of dipped beams at the outlet of the headlamp (13), the second position of the optical element (1) making it possible to form a beam in the form of high beams at the outlet of the headlight (13).

10. A method of manufacturing an optical element (1) intended to modify a distribution of light beams according to any one of claims 1 to 6,

characterized in that it comprises the following steps:

- a step of forming a resin body (2) having a functional surface (3);

- a first step of covering at least part of the functional surface (3) with a layer of copper (5);

- a second step of covering the copper layer (5) with a nickel layer (6);

- a third step of covering the layer of nickel (6) with a layer of chromium (7).

11. The method of claim 10,

characterized in that it further comprises a step of covering with a nickel plating (8) preceding the first covering step.

12. The method of claim 10,

characterized in that it comprises in a covering step with a plating (8) comprising a mixture of nickel and copper preceding the first covering step.

13. Method according to any one of claims 10 to 12,

characterized in that the second covering step comprises:

- a first sub-step of covering a semi-gloss nickel sublayer (9) on the copper layer (5),

- a second sub-step of covering a nickel sublayer with a high sulfur content (10) on the semi-gloss nickel sublayer (9),

- a third sub-step of covering a sublayer of shiny nickel (11) on the sublayer of nickel with a high sulfur content (10), a fourth sub-step of covering a sublayer of matt nickel (12) on the shiny nickel sublayer (11).