WO2019038107A1

WO2019038107A1 - Back-illuminated radome

Info

Publication number: WO2019038107A1
Application number: PCT/EP2018/071784
Authority: WO
Inventors: Issam KHAYAT; Gilles MOULIN; Georges FRAPPA
Original assignee: Compagnie Plastic Omnium
Priority date: 2017-08-25
Filing date: 2018-08-10
Publication date: 2019-02-28
Also published as: EP3673536A1; FR3070547A1; MA49936A

Abstract

The device (1) for protecting a motor vehicle radar comprises a body (21) formed of a material transparent to radar waves and light, a support (23) opaque to light and transparent to radar waves. It further comprises a diffusing light guide (27) arranged between the support (23) and the body (21), and the diffusing light guide (27) is connected to a light source (29).

Description

RETRO-ILLUMINATED DECORATION RADOME

The present invention relates to the field of motor vehicles equipped with radar, and more particularly, the field of devices for masking and protecting such a radar, also called "radomes".

The device according to the invention applies in particular to the radars arranged in the front or rear bumper of the vehicles, for example of the ACC type.

For security reasons in particular, it is known to equip motor vehicles radar, for example ACC type, according to the English expression "Adaptive Cruise Control". Such a radar serves in particular to regulate the speed of vehicles according to the traffic and / or obstacles on the road. The radar detects the speed and the distance of the object preceding the carrier vehicle, so as to maintain in particular a safety distance between the vehicles.

ACC radars are mounted on the front or rear of vehicles, usually between the bars of the grid, which may be a cooling grid.

To hide these radars for aesthetic reasons, and / or to protect them from external aggressions (rain, ice, frost, mud, insects, leaves ...), it is known to use a radome, ie a protection piece with a plastic cover positioned in front of the radar.

Such a plastic cover lets the radar waves pass with as little attenuation as possible so as not to disturb the operation of the radar itself.

It has already been proposed in US2014 / 0218263, a decorated radome consisting of two plastic plates. In this radome, a decorative metal layer was deposited in vapor phase on one of the plates, so as to represent a decorative pattern. This mode of decoration has the disadvantage of being visible only when the vehicle is illuminated, especially in the light of day.

Also known from the application FR3046387 a decoration system consisting of a body member comprising a body made of a transparent material and disposed on a support forming part of the vehicle body, one side is covered with a semi decorative coating -Transparent (translucent paint, metallic deposit or translucent film). A light guide connected to a light source is disposed between the support and the body of the body member. The semi-transparent coating filters light from the light guide and reveals a graphic pattern.

The invention aims to overcome the disadvantage of the decorated radome of the state of the art by providing a backlit radome. Such a solution does not exist for the moment because it is difficult to associate a radome with retro-illumination, because the radome has a number of constraints, difficult to reconcile with the backlighting. Indeed, the radome must be made in one or more material (s) transparent to the radar waves. In addition, it must have a constant thickness, depending on the frequency of the radar to maintain the best transparency to the waves (about 6 mm for a frequency of 77 GHz). In addition, the radome must not contain any metallic element other than indium, gold or tin. Indeed, the other metallic elements prevent the transmission of waves in the thickness. Finally, the radome must have a low geometry variation, so as not to diffract the waves.

For this purpose, the subject of the invention is a device for protecting a motor vehicle radar, comprising a body formed of a material that is transparent to radar waves and to light, a medium that is opaque to light and transparent to radar waves. . The device comprises a diffusing light guide disposed between the support and the body. The light guide is connected to a light source.

By optical guide or light guide is meant here a transparent or translucent piece having a higher refractive index than the ambient air, inside which light rays move in a controlled manner in a common general direction from a first end of the guide having an entrance surface near which are disposed one or more light sources, to an exit surface from which the light rays emerge. The propagation of the light inside the light guide is done by successive internal reflections of the light rays on the faces of the light guide called internal reflection faces. The exit surface may be formed by the face or section opposite to the entrance face or alternatively by a side face of the light guide.

In the present description, and in a manner known to those skilled in the art, the term "diffusing light guide" means a light guide in which the exit surface of the light is formed by a lateral face of said light guide. This surface, which occupies all or part of the surface of the light guide, is generally substantially parallel to the general direction of progression of the light in the light guide. Thus, for a diffusing light guide of circular cross section, such as an optical fiber, the light emerges from the light guide in a substantially radial direction.

The diffusing light guide therefore makes it possible to distribute a substantially constant luminous flux at any point on the exit surface of the diffusing portion of the guide. The effect of style obtained with the help of the diffusing light guide is to create a luminous halo distributed in a regular way all along the part of the radome on which he is disposed.

The protection device may further comprise one or more of the following features, taken alone or in combination.

- The protective device further comprises between the light guide and the body, a semitransparent coating in light and transparent to radar waves. The decorative coating is backlit, which reinforces the effect of style provided by the decorative coating.

- The protection device further comprises between the light guide and the body, a coating opaque to light and transparent to radar waves. Thus, the edges of the decor are illuminated by a halo matching the shape of the decor.

- The total thickness of the protection device is constant and less than or equal to 6 mm. This makes it possible to maintain a good transparency to the radar waves.

- The decorative coating has a metallic appearance. Its appearance is thus in harmony with the usual aesthetic appearance of a motor vehicle.

- The decorative coating is obtained by color or texturing.

- The decorative coating is obtained by a technique known to those skilled in the art, such as the hot stamping technique (printing during which a film is pressed against a surface), or by overmolding a film metallized (for example by prior deposition of a thin layer of coating which gives a metallic appearance, layer of the order of 0.5 μηη), or by application of chromatic paint, or by the technique of vapor deposition ("Physical Vapor Deposition", PVD), metals such as indium, gold or tin. The use of these techniques and materials makes it possible to give the radome a metallized appearance, even though the metallic elements generally disturb the transmission of the radar waves. Another advantage of these different techniques is to be able to obtain a very thin thickness and to ensure the transparency of the coating to the light when it is activated while allowing to conceal the light source by reflection of the ambient light when it is off.

- The body and the support each have on their inner face at least one rib or groove of complementary shape to one another. These complementary shapes can be used to sandwich the decorative coating and / or the light guide.

- The carrier has one or more transmission ports for the light guide, allowing it to pass from the outer face of the support to the inner face of the support.

- The light guide is formed by one or more optical fiber (s). Fibers optics have a better adaptation to forms, for example curved or constituted by a prominence, than draping (thermoforming with a positive mold, in which the mold rests on the material so that it matches its shape, which can generate folds , freezing marks and variations in thickness). In addition, the luminance is higher with optical fibers (1600 candela per square meter (cd.m ^"2 for an area of 10 x 400 mm) than with flat light guides with a luminance of about 200 cd .m ^"2. the use of optical fibers allows, with a light source of the same intensity, to produce an element of brighter decor. traditionally, it is considered that the appearance plane of a radome is very important to obtain the radome function In a light guide constituted by optical fibers, the thickness of the latter is not homogeneous (cylinders placed side by side) and the surfaces are not smooth. therefore not natural to use optical fibers as a light guide in a radome, because it could be assumed that the optical fibers would attenuate the radar waves.However, the presence of heterogeneous materials may have different behaviors and different thicknesses erentes could suggest that the radome with such a light guide would not have a homogeneous behavior. The inventors have shown that optical fibers have attenuation of radar waves compatible with the requirements of car manufacturers. Optionally, the optical fibers are arranged in sheets or in strands.

The light guide consists of one or more plastic film (s), for example extruded polycarbonate transparent films having a light transmission greater than or equal to 90% according to the ISO 13468-2 standard, and a refractive index of 1.584 according to ISO 62.

The light guide is adapted to be connected to a light source located outside an area facing a transmission zone of the radar. This arrangement makes it possible to avoid disturbing the operation of the radar.

The support and the body are in poly (methyl methacrylate) (PMMA), opaque for the support and transparent for the body.

The support is made of ASA (Acrylonitrile styrene acrylate) or ABS-PC (Acrylonitrile Butadiene Styrene / Polycarbonate). The body is made of polycarbonate.

The opaque support is a light and radar-transparent part, preferably obtained by injection, on which a resin opaque to light and transparent to radar waves has been poured or over-injected. The opaque resin may be polyurethane. The invention also relates to a method of assembling the protection device comprising the steps of:

- installation of the light guide on the inner face of the support,

- Fixing the body and the support, optionally by gluing.

The assembly method may further comprise one or more of the following steps, taken alone or in combination.

depositing the decorative coating on the internal face of the body, preferably before the installation of the light guide,

encapsulation in a resin of the light guide on the inner face of the support, manufacture of the opaque support by injection of a transparent part to the light and the radar waves and application, on the external face of this part, of a resin opaque to light and transparent to radar waves, preferably after the installation steps of the light guide and deposition of the decorative coating.

The opaque material which fills the back of the assembly consisting of the transparent piece, the decorative coating and the light guide can be cast at a lower temperature and pressure than the temperature at which the transparent material is injected. Thus, by coating the support with the opaque resin after installation of the light guide and deposition of the decorative coating, the transparent part is not damaged and the positioning and the optical quality of the light guides and the decorative coating are maintained. Coating the substrate with the opaque resin after installation of the light guide and depositing the decorative coating simplifies the assembly process because it avoids the manufacture of two pieces separately, which must then be mounted with two other elements (coating of decor and light guide.

We will now present an embodiment of the invention given by way of non-limiting example and with reference to the appended figures in which:

FIG. 1 is a schematic representation of the positioning of a radome of the state of the art with respect to the radar,

FIG. 2 is a front view of a radome according to one embodiment of the invention, installed on a grid of a motor vehicle,

FIG. 3 is a perspective view of three-quarter left inclined of the radome of FIG. 2, represented in front of a radar,

FIG. 4 is an exploded perspective view of three-quarter left inclined of the radome of FIG. 2;

FIG. 5 is a left view in section of a detail of the radome of the figure 2,

Figures 6a and 6b are each a front view of the radome of Figure 2, respectively off and on.

As illustrated in FIG. 1, the radome 1 according to the state of the art is intended to be placed in front of the radar 2. The radome 1 comprises at least one transmission zone 3 able to be traversed by the waves 4 of the radar 2 The transmission zone 3 is formed of a material transparent to the radar waves. The radome 1 is adapted to be fixed on a bumper of a motor vehicle, in front of the radar.

Figure 2 shows a radome 1 according to the invention, placed in front of the gate 6 of a motor vehicle. The grid 6 comprises bars 7. The grid 6 has two zones 7bis backlit. The two black vertical lines 9 represent the lateral limits of the radome 1 on the grid 6.

FIG. 3 shows the radome 1 according to one embodiment of the invention, independently of the gate 6. The radome 1 is placed in front of the radar 2 and the waves 4 of the radar 2 are transmitted in the transmission zone 3 of the radome 1 The contour 8 of the transmission zone 3 of the radar waves 4 is represented by interrupted black lines. Radome 1 has a decorative coating 10 opaque to light and transparent to radar waves. In the example of Figure 3, the decorative coating has the form of bars 11 similar to the bars 7 of the grid, in continuity of which they are placed. Thus, the grid has the same appearance in the zone with radome as in the zone without radome.

Figure 4 is an exploded view of the radome 1 of Figure 2. The radome 1 comprises a body 21 formed of a material transparent to radar waves and light. It also comprises a support 23, opaque to light and transparent to the radar waves, placed behind the body 21. The body 21 and the support 23 both have grooves and ribs, visible in FIG. 5, arranged in crenellations, which are complementary according to the illustrated example. The support 23 comprises in its periphery, here represented on a vertical line located near its left edge, transmission orifices 25 for a diffusing light guide 27. The light guide 27 passes through this orifice 25 of the outer face 30 from the support 23 to its inner face 28. The light guide 27 is stretched and held taut on the inner face 28 of the support 23, with unrepresented fasteners fixed to the support 23, and located outside the area of transmission whose contour 8 is represented on the body 21. The inset figure shows a light guide 27 connected to a light source 29. The light source is not visible in the main figure. It is located behind the support 23, at the level of the transmission orifices 25. The light source is remote, that is to say it is not located opposite the transmission zone 3 radar waves, to avoid disrupting its operation.

In this embodiment, the light guide 27 is formed by a plurality of optical fibers. The optical fibers are plastic. They can also be made of glass. The optical fibers may be arranged in a sheet or in a strand.

The attenuation by a sheet of optical fibers of the radar waves was measured with a certified equipment for the control of the electromagnetic transparency of the radomes. In this example, the optical fibers were polymethacrylate (PMMA), and they were woven with polyester yarn. The optical fibers each had a diameter of 500 μηη. The web thus woven, 1 mm thick, was placed between two polycarbonate sheets 3 mm thick each. In the 76 to 77 GHz band, the attenuation due to the two polycarbonate plates alone (without an optical fiber mat), measured in one-way transmission (one way through the three thicknesses), is 1, 39 dB. At these same frequencies, the whole of the optical fiber ply and the two polycarbonate plates has an attenuation of 0.65 dB. The attenuation of the set (measured in one way) is below the specification of the car manufacturers for a radome (for example 1, 5 dB). The measurements show that the fiber optic layer is transparent to electromagnetic waves at 77 GHz and that the attenuation is due to the thickness of the two polycarbonate plates. Attenuation can be improved by adjusting the thicknesses of the two polycarbonate plates. Such a light guide does not disturb the operation of the radar itself.

In another embodiment, not shown, the light guide consists of extruded polycarbonate transparent plastic films having a light transmission greater than or equal to 90% according to ISO 13468-2, and a refractive index of 1, 584 according to ISO 62.

These light guides are diffusing, that is to say that the exit surface of the light is formed by a lateral face of the light guide. As a result, the light emerges from the light guide in a substantially radial direction and the distributed light flux is substantially constant at any point on the exit surface of the diffusing portion of the guide.

In this embodiment, the light guide 27 extends substantially the entire length of the inner face 28 of the support 23, from the transmission orifice 25, so as to create a luminous halo distributed in a regular manner over the entire length of the radome 1.

The opaque decor coating is disposed between the light guide 27 and the body 21.

In this embodiment, the light source is constituted by a plurality of light-emitting diodes (LEDs or LEDs).

In the embodiment of FIG. 4, the support 23 is made of poly (methyl methacrylate) (PMMA), as is the body 21. Preferably, the support 23 is black in color. In another embodiment, the support 23 is made of polyurethane and the body 21 is made of polycarbonate.

The decorative coating 10 is generally designed to have a metallized appearance. It can be obtained by the technique of hot stamping ("hot stamping"). Overmolding of a metallized film can also be used, or chromatic paint. Finally, the technique of vapor deposition ("Physical Vapor Deposition", PVD) can also be used. Metals such as indium, gold or tin can thus be deposited.

The assembly of the various components of the radome of FIG. 3 is represented in FIG. 5. First of all, the body 21 is decorated using one of the techniques mentioned above. The decorative coating 10 is deposited on the ribs 29 or the grooves 31 located on the internal face 33 of the body 21. The support 23 has on its inner face 28 complementary portions 35 and 37 respectively of the groove 31 and the rib 29 of the body 21. The light guide 27 is positioned on the support 23. The light guide 27 can be secured to the support 23 by encapsulation in a resin. The complementary parts of the body 21 and support 23 are then brought together. In the embodiment of Figure 5, the two parts are assembled by gluing. A glue point 39 is shown between the inner face 33 of the body 21 and the inner face 28 of the support 23.

FIG. 6a shows the front view of the radome 1 of FIG. 3 when it is off. The bars 11 of the decorative coating are visible thanks to their metallized appearance. Figure 6b shows the appearance of the same radome 1 when the light source 29 is on. The light diffuses from the diffusing surface of the optical fiber and illuminates the bars 11, reinforcing the pattern and making it visible when the vehicle is not lit. Thus, the part of the grid in front of which the radome is located may have the same luminous appearance as the rest of the grid, namely the zones 7a visible in FIG.

The invention is not limited to the embodiments presented and other embodiments will become apparent to those skilled in the art. For example, the optical fiber is not necessarily PMMA but may be polycarbonate or glass. The diameter of the optical fiber may be between 250 μηη and 1 mm.

Claims

claims

1. Device (1) for protecting a radar (2) of a motor vehicle, comprising a body (21) formed of a material transparent to the waves (4) radar (2) and to light, a support (23) opaque to light and transparent to radar waves (4), characterized in that it comprises a diffusing light guide (27) disposed between the support (23) and the body (21), said diffusing light guide (27) being connected to a light source (29).

2. Device (1) for protecting a radar (2) of a motor vehicle according to the preceding claim, which further comprises between the light guide (27) and the body (21), a decorative coating (10) semi -Transparent to light and transparent to radar waves (4).

3. Device (1) for protecting a radar (2) of a motor vehicle according to the preceding claim, the decorative coating (10) being obtained by the hot stamping technique, or by overmolding a metallized film or by application of chromatic paint, or by the technique of physical vapor deposition (PVD), metals such as indium, gold or tin.

4. Device (1) for protecting a radar (2) of a motor vehicle according to any one of the preceding claims, the total thickness of the device (1) of protection being constant, and less than or equal to 6 mm.

5. Device (1) for protecting a radar (2) of a motor vehicle according to any one of the preceding claims, the body (21) and the support (23) each having on their inner face (28, 33) to least one rib (29, 35) or a groove (31, 37) of complementary shape to one another.

6. Device (1) for protecting a motor vehicle radar according to any one of the preceding claims, wherein the light guide (27) consists of one or more plastic film (s).

7. Device (1) for protecting a motor vehicle radar according to any one of the preceding claims, wherein the light guide is formed by one or more optical fiber (s).

8. A method of assembling the device (1) for protection according to any one of the preceding claims, comprising the steps of:

- Installation of the light guide (27) on the inner face (28) of the support (23), - fixing the body (21) and the support (23), optionally by gluing.

9. Assembly method according to the preceding claim, further comprising a step of depositing the decorative coating (10) on the inner face (33) of the body (21), preferably before installation of the light guide (27).

10. The assembly method according to claim 8 or 9, further comprising a step of encapsulation in a resin of the light guide (27) on the inner face (28) of the support (23).

11. An assembly method according to any one of claims 8 to 10, further comprising a step of manufacturing the opaque support (23) by injecting a piece (23) transparent to light and radar waves and applying, on the outer surface (30) of this piece (23), a resin opaque to light and transparent to radar waves, preferably after the steps of installing the light guide (27) and deposition of the decorative coating (10). ).