Backlit radome incorporating a de-icing device

Description

[0001] The invention relates to the field of motor vehicles equipped with radar, and more particularly, to the field of devices for masking and protecting such radar, also called "radomes".

[0002] The device according to the invention is particularly applicable to radars located in the front or rear bumper of vehicles, for example of the ACC type.

[0003] For safety reasons, it is common practice to equip motor vehicles with radar systems, such as ACC (Adaptive Cruise Control). Such radar is used, in particular, to regulate vehicle speed based on traffic conditions and / or obstacles on the road. The radar detects the speed and distance of the object in front of the vehicle, in order to maintain a safe distance between vehicles.

[0004] ACC radars are mounted on the front or rear of vehicles, usually between the bars of the grille, which may be a cooling grille, but also on other body parts such as wings, for example for cyclist detection.

[0005] 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, that is to say a piece, or protective device including a plastic cover positioned in front of the radar.

[0006] Such a plastic cover allows radar waves to pass through with as little attenuation as possible so as not to disrupt the operation of the radar itself.

[0007] In order to enhance the aesthetic effect produced by bodywork elements, it has been proposed to place a light source behind the surface of the radome so as to create a light effect in front of the radar when the light source is activated.

[0008] Thus, when the optical system is off, the appearance of the radome is determined by the coating on the outer layer of the body panel. Conversely, when the optical system is on, the radome appears as a luminous surface.

[0009] By activating the lighting system, it is also possible to display special patterns such as a manufacturer's logo, or special figurative elements that remain invisible when the vehicle is illuminated by daylight.

[0010] We know from the applicant's application WO2019 / 038107, a decorated radome composed of a support opaque to light and transparent to radar waves and a body transparent to radar waves and to light, between which is arranged a diffusing light guide.

[0011] However, radar systems can experience disruptions in their normal operation due to the presence of ice, snow, or frost when temperatures are below 10 degrees Celsius, as vehicle movement negatively affects temperature. Therefore, frost deposits can be observed even at above-freezing temperatures. A layer of frost interferes with the normal transmission of electromagnetic waves and introduces errors in the measurement of external physical parameters.

[0012] To prevent frost build-up, which not only renders the assistance system unusable, but can also generate false alarms, a de-icing system is planned for the radome.

[0013] Such a defrosting system traditionally consists of a heating element made of conductive wires capable of converting electrical energy into thermal energy through the Joule effect. Two connecting plates at each end of the heating element supply it with an electric current. The entire assembly is positioned on a body panel and near a sensor. The thermal energy thus released allows for localized defrosting of the panel if a layer of frost has formed. To avoid interfering with the transmission of electromagnetic waves, the heating element must be positioned according to a specific geometry, referred to below as a "serpentine" configuration.For clarity of explanation, a heating track positioned in a "serpentine" is defined as follows: a heating track in a serpentine pattern follows a boustrophedon path, namely a path which describes parallel segments with 180° turns between two segments which alternately rotate in one direction, then in the opposite direction with a constant distance between two parallel segments.

[0014] By extension, a serpentine track refers to a track configured to allow the passage of electromagnetic waves of a radar frequency range.

[0015] Indeed, the precise positioning of the heating track is crucial to prevent it from obstructing the passage of electromagnetic waves. Specifically, the parallelism between the different segments of the heating tracks and the spacing between them must be maintained with extreme precision. Each electromagnetic wave frequency will correspond to an optimal heating track positioning configuration to ensure that the heating track is transparent to the passage of that electromagnetic wave.

[0016] The invention aims in particular to provide a radome decorated by backlighting, however allowing optimized operation of the radar, even in temperature conditions where a layer of ice, snow or frost could have formed on the radome, in particular at temperatures below 10 degrees Celsius.

[0017] A device for protecting a motor vehicle radar is known from application DE102015004204. This device comprises a body transparent to radar waves and light, a surface light guide through which and from which light is transmitted, also transparent to radar waves, a support opaque to light and transparent to radar waves, and an electrically conductive heating track positioned on a surface of the transparent body. In this device, light exits the light guide through an exit surface substantially perpendicular to the outer surface of the device. The exit surface is a small area of ​​the light guide, corresponding substantially to its thickness and oriented laterally with respect to the device. In order to illuminate the radome uniformly, the light passing through the light guide is reflected onto a reflective surface arranged to deflect the light outwards from the radar protection device.This device has a complex structure, requiring the assembly of numerous components and the optimization of their orientation relative to others to achieve adequate lighting. Therefore, there is a need for a protective device offering the aforementioned advantages but simpler and less expensive to manufacture.

[0018] Application DE102016007119 describes a radar protection device comprising a similar light guide in which light is emitted from a small area of ​​the light guide and reflected back onto a reflective surface. This device has the same drawbacks as described above.

[0019] To this end, the invention relates to a device for protecting a motor vehicle radar, comprising: a body made of a material transparent to radar waves and light, a surface illuminating element transparent to radar waves, and a support opaque to light and transparent to radar waves. The protective device also includes an electrically conductive heating track positioned on a surface of the body. Advantageously, the surface lighting element is configured so that light is emitted by the surface lighting element. In this text, we An object is considered to emit light, as opposed to "reflect," when light exits the object, meaning that the light has passed through its interior. Light reflected by an object is not emitted by the object because, in the case of reflection, the light always remains external to the object. The surface lighting element is advantageously configured to emit light directly towards an external surface of the body, from a face of the surface lighting element having the largest surface area of ​​the surface lighting element, located opposite the external surface of the body.

[0020] This solution thus provides a backlit, decorated radome compatible with radar operation at temperatures below 10 degrees Celsius, even in conditions where ice, snow, or frost might have formed on the radome. In this radome, the surface illuminating element directly and uniformly illuminates the radome, without requiring an intermediate component. This radome is simpler and less expensive to manufacture.

[0021] Therefore, the radome according to the invention can also be fitted to vehicles classified as levels 4 and 5 in the International Organization of Motor Vehicle Manufacturers (OICA) classification. These are vehicles capable of moving without a driver under certain conditions for level 4, and under all conditions for level 5. Indeed, in these vehicles, the radome's de-icing function is necessary.

[0022] Because the heating element is positioned on a transparent surface of the body, defrosting is more efficient as the heating element is closer to the frosted surface, which corresponds to the outer surface of the transparent body.

[0023] The absorbance of a medium measures its ability to absorb the electromagnetic wave passing through it. The transmission (or transmittance) of a medium is defined as the inverse of the absorbance. It is therefore the fraction of the flux passing through the medium. Transparency refers to visible light. Thus, a material is transparent to light when a fraction of visible light passes through it.

[0024] For the purposes of this invention, "transparent to radar waves" means a material that allows radar waves to pass through it. The thickness of the radar-transparent material will depend on its dielectric characteristics (permittivity and Tan Delta) and the operating frequency of the radar.

[0025] Non-exhaustively, the material transparent to light and radar waves can be chosen from a thermoplastic or a thermoset, for example polycarbonate, polyamide, polypropylene, polymethyl methacrylate, copolyester, acrylonitrile butadiene styrene, acrylonitrile styrene acrylate, styrene acrilonitrile, a mixture of acrylonitrile styrene acrylate and polycarbonate, a mixture of polycarbonate and polyethylene terephthalate, an epoxy resin, a polyurethane.

[0026] A "surface illuminating element" is defined as a thin product, where the thickness is very small compared to the length and width, such as an illuminating fabric or film. The thickness of a surface illuminating element is typically around 1 mm. A surface illuminating element conforms to the shape of the object on whose surface it is placed. The surface illuminating element can diffuse light uniformly, thus providing even illumination of the radome.

[0027] Advantageously, the light is diffused by the surface lighting element. "Light diffusion" refers to its transmission in multiple directions. This mode of light transmission allows for a virtually constant luminous flux to be distributed at every point on the output surface of the lighting element. The resulting aesthetic effect is the creation of a luminous halo distributed evenly along the entire length of the radome on which it is placed.

[0028] Depending on other optional features of the radar protection device, taken alone or in combination: The surface illuminating element is an illuminating fabric. In this description, "illuminating fabric" generally refers to a set of natural and / or synthetic fibers comprising optical fibers combined with the fabric's mesh. These optical fibers are typically connected to a light source, such as one or more diodes. These optical fibers can be illuminated from one or both of their ends, which act as feed points, to illuminate the corresponding piece of fabric. In these illuminating fabrics, the optical fibers generally constitute the weft and / or warp yarns and may be combined with conventional natural or synthetic fibers, such as polyester, provided they are transparent to radar waves.

[0029] One advantage of luminous fabric is its ease of customization, allowing for variations in light colors and / or patterns. Furthermore, the ability to use a remote light source is a significant benefit, as it enables the lighting system, which is typically very expensive, to be located in an area that would be undamaged in a crash and / or easily accessible. Finally, luminous fabric offers good radar transparency. The surface illuminating element is an illuminating film. The illuminating film produces and diffuses its own light. Using an illuminating film therefore simplifies the manufacture of the radar protection device because there is no need for a remote light source, a light guide, and / or an additional reflective surface. The device also includes a decorative coating or surface texture. The heating track includes a connection section located outside the radar's emission cone. This ensures that the connection section does not interfere with the radar's operation. The body includes a light-opaque area. The connection section can thus be concealed behind this opaque area of ​​the transparent material. The heating track includes a heating element that extends over an intersection surface between the body and the radar's emission cone.This will result in homogeneous and complete de-icing of the portion of the radome located within the emission cone. The surface illuminating element extends over at least part of the intersection surface between the support and the radar emission cone. The surface illuminating element is fixed within a depression in the support. At least the entire width of the depression in the support is contained within the radar emission cone. The depression in the support extends over part of the intersection surface between the support and the cone, and the total thickness of the surface illuminating element, also called the "illuminating foil," and the support at the depression is identical to the thickness of the support in portions of the support outside the depression. This ensures a constant total thickness within the emission cone, thus maintaining good transparency to radar waves. The heating track is positioned on an internal surface of the body.In this description, the term "internal" refers to a part of a component or an element located towards the inside of the vehicle, in this case, facing the radar, while the term "external" refers to a part of a component or an element located towards the outside of the vehicle, opposite the radar. Compared to mounting on an external surface of the transparent body, this solution protects the heating element and is more durable. This extends the lifespan of the decorated radome. Furthermore, this solution is more aesthetically pleasing because the heating element has raised bumps that, if positioned on an external surface of the body, would detract from the radome's appearance. The surface lighting element is fixed to an external surface of the support.This configuration protects the surface illuminator and allows it to be positioned within the radar cone, even when the heating element is itself located on the internal surface of the body. Indeed, it is impractical to place the heating element and the surface illuminator on the same surface. The decorative coating or surface texture is located on an external surface of the body. Thus, the heating element and the decorative coating can coexist in the area illuminated by the surface illuminator. The body, made of a material transparent to radar waves and light, and the support, opaque to light and transparent to radar waves, are two separate parts. Brief description of the figures

[0030] The invention will be better understood upon reading the following description, given solely by way of example and made with reference to the accompanying drawings in which: [ Fig. 1 ] there figure 1; Fig. 2 ] there figure 2 ; Fig. 3 ] there figures 3 ; And [ Fig. 4 ] there figure 4 These are schematic top-section views of a radar and a radome according to embodiments of the invention, the radomes being shown in exploded view. Fig. 5 ] there figure 5 is a schematic top view in section of the radar and radome of the figure 2 , in assembly. [ Fig. 6 ] there figure 6 is a perspective top view of a radar and radome according to an embodiment of the invention. Detailed description

[0031] We have represented on the figure 1A protective device for a motor vehicle radar according to a first embodiment of the invention, designated by general reference numeral 1. This radome 1 is shown with the radar 3 it protects. The radome 1 comprises a body 5 made of a material transparent to radar waves and light, and a support 7 opaque to light and transparent to radar waves. The body 5 and the support 7 are two separate parts. The radome 1 also comprises a surface illuminating element 9 and an electrically conductive heating track 11. The surface illuminating element 9 emits light directly onto the external surface 27 of the body 5, from a face 33 of the surface illuminating element 9 having the largest surface area of ​​the surface illuminating element 9, which is located opposite the external surface 27 of the body 5. More precisely, the light is diffused by the surface illuminating element 9.The surface illuminating element 9 is a thin product, in which the thickness e is very small compared to the length L and the width I. The surface 33 of the surface illuminating element 9 is its largest surface, defined by the length L and the width I of the surface illuminating element 9. In this description, the terms "width" and "length" of an object (here the surface illuminating element) refer to the width and length of the object's largest surface. The thickness e is the smallest dimension of the object. The heating track 11 is positioned on an internal surface 13 of the body 5. The radome 1 also includes a decorative coating 15. This is also shown on the figure. figure 1A radar emission cone 17 3. In this embodiment, the surface illuminating element 9 is fixed to an external surface 19 of the support 7, within a depression 21 of the support 7. Furthermore, the surface illuminating element 9 extends over an intersection surface 23 between the support 7 and the radar emission cone 17 3. In this embodiment, the heating track 11 extends over an intersection surface 25 between the body 5 and the radar emission cone 17 3. Like the surface illuminating element 9, in this embodiment, the decorative coating 15 is located on an external surface 19 of the support 7. In this embodiment, the decorative coating 15 is located outside the radar emission cone 17. Therefore, it is not necessary for the coating 15 to be transparent to radar waves.

[0032] In other embodiments, the same numerical references designate similar elements. These embodiments differ from the embodiment of the figure 1 in that: In the mode of implementation of figures 2 And 5 , the decorative coating 15 is located on an external surface 27 of the body 5.

[0033] The same applies to the method of implementation of the figure 3 Furthermore, in this embodiment, the heating track 11 is positioned on an external surface 27 of the body 5.

[0034] The method of implementation of the figure 4 includes two types of decorative coatings 15. One is positioned as in the embodiment of the figure 1 The other is positioned on the external surface 27 of body 5, on an intersection surface 31 between body 5 and the emission cone 17 of radar 3.

[0035] By referring to the figure 6The heating track 11 is shown positioned and fixed to a surface of the body 5. This heating track 11 comprises a connection portion 11c and a heating element, here in the form of a coil, for defrosting 11s. The coiled defrosting portion 11s of the heating track 11 is positioned in an arrangement compatible with the passage of electromagnetic waves through the body 5. In the example described, the coiled defrosting portion 11s of the heating track 11 follows a boustrophedon path. The coiled portion 11s of the heating track 11 is a good thermal conductor and is transparent to radar waves and light. In this example, it comprises a metal wire with a diameter of less than 100 µm. The metal wire was deposited onto the body by 3D printing. The metal wire could also have been deposited by ultrasound onto a film chemically compatible with the material of the transparent body, the film itself being deposited onto the body during overmolding.The heating element 11s could also be based on conductive inks, metallic nanowires (copper, silver, or any other metal offering good thermal conductivity and radio wave transparency), or carbon nanotubes. In this case, the design is not serpentine; it is a conductive heating system powered by two busbars on either side of this heating zone. The design of these systems also allows for transparency at the radar frequency.

[0036] The heating portion 11s of the heating track 11 extends over an intersection surface 25 between the body 5 and the radar emission cone 17. The connecting portion 11c of the heating track 11 is located outside the radar emission cone 17. A decorative coating, not shown, is deposited on the external surface 19 of the support 7. The decorative coating could also be on an internal 29 or external 27 surface of the body 5. It can be located inside or outside an intersection surface with the radar cone 17. If it is located inside the radar cone 17, it must be transparent to radar waves, as described, for example, in the applicant's application WO2019 / 038107. Thus, it could be laser-etched. The decoration could also be a surface texture. Body 5 has two opaque areas to light, not shown, behind which the connection parts 11c of the heating track 11 are concealed.

[0037] In all the embodiments shown, the surface lighting element 9 is a luminous fabric.

[0038] Furthermore, although the illuminating element in the embodiments shown extends over the entire intersection surface between the support and the radar emission cone, it could also extend over only a portion of this area. In this case, the total thickness of the illuminating element and the support at the depression will advantageously be identical to the thickness of the support in portions outside the depression. This will maintain a constant total thickness within the emission cone, thus preserving good transparency to radar waves. Any other configuration that maintains a constant radome thickness within the radar emission cone can also be implemented.

[0039] The invention is not limited to the embodiments shown and other embodiments will be obvious to a person skilled in the art.

[0040] In particular, it is possible to use as a surface lighting element any element known to a person skilled in the art and having the required qualities, namely suitable dimensions (very small thickness compared to the length and width), a capacity to diffuse light and transparency to radar waves, for example a luminous film.

[0041] Instead of a decorative coating, it is also possible to use a surface texture.

[0042] The lighting element could be fixed in another location on the radome, allowing light to be diffused outwards from the radome, and allowing the heating track to be positioned on the body. List of references

[0043] 1: radome, 3: radar, 5: body transparent to radar waves and light, 7: support opaque to light and transparent to radar waves, 9: surface illuminating element, 11: heating track, 11c: connecting part of the heating track, 11s: serpentine part of the heating track, 13: internal surface of body 5, 15: decorative coating, 17: radar emission cone, 19: external surface of the support, 21: depression in the support, 23: intersection surface between the support and the radar emission cone, 25: intersection surface between the body and the radar emission cone, 27: external surface of body 5, 29: internal surface of body 5, 31: intersection surface between body 5 and the radar emission cone, 33: surface of the surface illuminating element, e: thickness of the illuminating element surface L: length of the surface lighting element, I: width of the surface lighting element.

Claims

1. A device (1) for protecting a motor vehicle radar (3), comprising: - a body (5) made of a material transparent to radar waves and light, - a surface lighting element (9) transparent to radar waves, configured so that light is emitted by the surface lighting element (9), - a support (7) that is opaque to light and transparent to radar waves, - an electrically conductive heating track (11) positioned on a surface (13) of the body (5), characterized in that the surface lighting element (9) is configured to emit light directly toward an outer surface (27) of the body (5), from a face (33) of the surface lighting element having the largest surface area of the surface lighting element (9), facing the outer surface (27) of the body (5).

2. A device (1) according to the preceding claim, wherein the surface lighting element (9) is a luminous fabric or film.

3. A device (1) according to any one of the preceding claims, which further comprises a decorative coating (15) or a surface texture.

4. A device (1) according to any of the preceding claims, wherein the heating track (11) comprises a connection portion (11c) that is located outside a radar (3) emission cone (17).

5. A device (1) according to any of the preceding claims, wherein the body (5) comprises a light-opaque zone.

6. A device (1) according to any one of the preceding claims, wherein the heating track (11) comprises a heating portion (11s) that extends over an intersection surface (25) between the body (5) and the emission cone (17) of the radar (3).

7. A device (1) according to any one of the preceding claims, wherein the surface lighting element (9) extends over at least a portion of an intersection surface (23) between the support (7) and the emission cone (17) of the radar (3).

8. A device (1) according to any one of the preceding claims, wherein the surface lighting element (9) is secured in a recess (21) of the support (7).

9. A device (1) according to any one of the preceding claims, wherein the heating track (11) is positioned on an inner surface (13) of the body (5).

10. A device (1) according to the preceding claim, wherein the surface lighting element (9) is secured to an outer surface (19) of the support (7).

11. A device (1) according to the preceding claim and claim 3, wherein the decorative coating (15) or surface texture is located on an outer surface (27) of the body (5).

12. A device (1) according to any one of the preceding claims, wherein the body (5), formed of a material transparent to radar waves and light, and the support (7), which is opaque to light and transparent to radar waves, are two separate parts.