Motor vehicle radar cover with decorative pattern

Abstract

The present invention relates to a radar dome (4) for a motor vehicle, comprising a body (8) including at least one region that is transparent to and intended to be penetrated by waves emitted by a wave emitting member, the region including a surface (14) comprising alternations of a first portion (10) covered by at least one layer of coating and a second portion (12) not covered by the coating layer, the first and second portions (10, 12) forming at least one decorative pattern (6) and arranged such that the decorative pattern (6) is transparent to waves emitted by the wave emitting member.

Description

TECHNICAL FIELD

[0001] The present invention relates to motor vehicles equipped with a wave-emitting member, and more particularly to a protective device designed to protect the wave-emitting member of these motor vehicles. BACKGROUND

[0002] Increasingly, automobiles have bodywork parts fitted with a wave-emitting member, such as one or more ACC-type radars (i.e. the acronym for the English term "adaptive cruise") that emit radio waves.

[0003] Such wave-emitting members are generally shielded and protected from, for example, adverse weather, by a protective device commonly referred to as a "radar cover". In the following description, the term "radar cover" is used as a synonym for "protective device".

[0004] These radar covers are intended to be traversed by the waves emitted by the one or more emitting members, and thus they must be transparent to these waves. By "transparent to the waves emitted by the wave-emitting member" is meant the ability of the material traversed by the incident wave flow to enable more than 90% of the wave flow to pass through itself.

[0005] The use of these protective devices can have an aesthetic significance, as described for example in French application FR 3070 547 Al, in which the radar cover comprises a light-emitting device that diffuses light through the radar cover to form a pattern on the surface of the radar cover, which is visible from outside the vehicle on which the radar cover is installed. The radar cover is thus partially transparent to visible light. By "transparent to visible light" is meant that it is at least transparent or translucent to any light radiation having a wavelength in the visible spectrum, i.e. approximately between 380 and 780 nm.

[0006] A decorative pattern can be achieved by covering certain areas with a paint that is opaque to visible light, while other areas are not covered by this paint, and the illumination of the radar cover reveals the decorative pattern (if the pattern is formed by areas through which light passes, it is the areas through which light passes; if the pattern is formed by areas through which light cannot pass, it is the areas through which light cannot pass).

[0007] However, the paint used to obtain a high-quality visual effect, for example, can be opaque to the waves emitted by the wave-emitting member. This poses a problem in that certain paints cannot therefore be used to draw the radar cover.

[0008] In addition, even if a paint that is transparent to the waves emitted by the wave-emitting member is used, it is possible that the passage of the waves is disturbed by the presence of alternation of covered and uncovered zones by the paint. Indeed, the waves emitted by the wave-emitting member will pass through zones comprising paint layers (for example a primer, then a base paint, then a varnish) and zones not comprising these paint layers. These paint layers, especially the primer, will affect the passage of the waves. Thus, the different zones through which the waves pass affect their passage more or less, depending on whether these zones are covered by one or more paint layers. This leads to a non-uniformity of the passage of the waves through the radome and thus to a deterioration of the performance of the wave-emitting member. This non-uniformity complicates the detection of obstacles, making the signal difficult to exploit, even if the attenuation and reflection of the entire signal remains weak. SUMMARY

[0009] The object of the application is in particular to provide a radome that makes it possible to simply solve the problem of disturbance of the propagation of the waves, while preserving a radome with an optimal visual appearance.

[0010] To this end, the subject of the application is a radome for a motor vehicle comprising a main body comprising at least one zone that is transparent to the waves emitted by a wave-emitting member and through which the waves pass, the zone comprising a face comprising an alternation of first portions covered by at least one layer of paint and second portions not covered by the layer of paint, the first portions and the second portions forming at least one decorative pattern and being arranged so as to make the decorative pattern transparent to the waves emitted by the wave-emitting member.

[0011] Thus, by choosing the arrangement of the different zones covered or not covered by one or more layers of paint, it is possible to avoid the waves being disturbed in their passage through the radome. It is thus a parameter determined during the manufacture of the first portions and the second portions that allows this facilitated passage to be obtained.

[0012] The radome according to the application can also comprise at least one of the following characteristics:

[0013] - the first portions form bands of width (N*λ) / 4, with N being a non-zero natural integer, λ being equal to the wavelength of the waves emitted by the wave-emitting member;

[0014] - the second portions form bands of width less than λ / 4, separated from one another by the first portions;

[0015] - the second portions form bands of width greater than λ / 4, separated from one another by the first portions;

[0016] - the spacing between two adjacent first portions is constant;

[0017] - the first portions and the second portions are parallel straight lines to one another;

[0018] - the first portions and the second portions extend at least partly in a direction perpendicular to the plane of propagation of the waves emitted by the wave-emitting member;

[0019] - all the first portions have the same width and all the second portions have the same width;

[0020] - the second portions are transparent to visible light;

[0021] - the radome comprises a light guide facing the decorative pattern, arranged to diffuse the visible light through the second portions, and preferably comprises a bundle of optical fibres;

[0022] - the radome has a maximum thickness less than or equal to 6 mm;

[0023] - the main body (8) is made of a material selected from the group consisting of polymethyl methacrylate, polycarbonate, polypropylene, polyamide, copolyester, acrylonitrile-butadiene-styrene, acrylonitrile-styrene-acrylate, styrene-acrylonitrile, acrylonitrile-acrylic acid-styrene ester and mixtures of polycarbonate and polyethylene terephthalate;

[0024] - the first portions are covered by at least one layer of primer, one layer of base paint and one layer of varnish. BRIEF DESCRIPTION OF DRAWINGS

[0025] The application will be better understood by reading the following description, given only as an example and with reference to the attached drawings in which:

[0026] Figure 1 is a perspective view of a body panel comprising a radome according to the application;

[0027] Figure 2 is a front view of a radome comprising a decorative pattern;

[0028] Figure 3 is a cross-sectional view of a radome according to the application;

[0029] Figure 4 is a front view of a portion of the decorative pattern; and

[0030] Figure 5 is a cross-sectional view of a portion of the decorative pattern. DETAILED DESCRIPTION

[0031] Reference is now made to Figure 1 which shows a body panel 2, here a front bumper, comprising a protective device configured to protect at least one member for emitting waves.

[0032] This protection device, also called radome 4, protects the wave-emitting members (not shown) located on the front surface of the motor vehicle behind the radome 4. In what follows, the example described is a radar placed behind the radome 4 on the front face of the vehicle. The skilled person will understand that, depending on the function of the radar, the latter can be installed in another location of the vehicle, for example on the rear, on the side or on the roof. The number of wave-emitting members can also vary.

[0033] The radome 4 is designed to be at least partially crossed by the waves emitted by the wave-emitting members.

[0034] It must therefore be at least partially transparent to these waves, at least in the areas that are transparent to the waves. As mentioned previously, "transparent to the waves emitted by the wave-emitting members" means the ability of the material crossed by the incident wave flow to enable more than 90% of the wave flow to cross itself. To do this, the body 8 of the radome 4 can be made of a material chosen from the following list: PMMA (polymethyl methacrylate), polycarbonate, polypropylene, polyamide, copolyester, acrylonitrile-butadiene-styrene, acrylonitrile-styrene-acrylate, acrylonitrile-styrene, a mixture of acrylonitrile-styrene-acrylate and polycarbonate, a mixture of polycarbonate and polyethylene terephthalate.

[0035] The radome 4 comprises at least one decorative pattern 6. This decorative pattern 6 is created by the alternate presence of first portions 10 and second portions 12 on the body 8 of the radome 4, said first portions 10 being covered by at least one layer of paint and said second portions 12 not being covered by said one or more layers of paint, for example by a paint that does not allow the waves emitted by the wave-emitting members to cross. For example, the first portions 10 can be covered with a primer, a base paint and a varnish, while the second portions 12 are not covered. The number of layers of paint can vary. This does not mean that the second portions 12 are not covered by paint. For example, these second portions can be covered with a layer of varnish (preferably transparent to visible light, as described below) and can or can not share this layer of paint with the first portions 10.

[0036] The surface covered by one or more layers of paint can be the internal face 14 of the body 8 as shown in Figure 3 or the external face of the radome 4.

[0037] The first portions 10 and the second portions 12 are arranged to allow the waves to pass uniformly over the entire decorative pattern 6. In other words, the decorative pattern is transparent to these waves as a whole and does not interfere with the passage of the waves, does not create additional non-uniformities to the signal.

[0038] In what follows, a decorative pattern 6 according to the application will be described, which is placed opposite a radar emitting frequencies between 75 and 81 GHz.

[0039] To allow the best passage of the waves, it can be ensured that the first portions form bands of width L equal to (N*λ) / 4, with N being a non-zero natural integer and λ being equal to the wavelength of the waves emitted by the wave-emitting means. In other words, the width of the first portions 10 cannot be less than λ / 4 and can be equal to a multiple of λ / 4 within the range that can be achieved over the length of the radome 4. The width of the first portions 10 is chosen according to the possibilities resulting from the above formula, so that the passage of the waves emitted by the radar can be optimized and homogenized.

[0040] According to Figure 4 and Figure 5 According to a first variant, illustrated in Figs. 1 and 2, the second portions 12 can form bands of width I less than λ / 4, these bands being separated from each other by the first portions 10. The narrowness of the second portions 12 enables the radar to be very precise. In other words, when the radar needs to collect data as precisely as possible in order to fulfil its function, the second portions 12 form bands of width less than λ / 4, the reduction in width allowing the radar to gain in precision.

[0041] Conversely, in order to obtain a backlit decorative pattern 6 as described later (the second portions 12 being transparent to visible light), the width of the second portions 12 can be greater than λ / 4. This is especially possible when the function of the radar does not require it to have as high a precision as possible. The width I of the second portions 12 can even be equal to or greater than the width L of the first portions 10.

[0042] Thus, by appropriately determining the dimensions of the second portions 12, it is possible to seek a compromise between the precision of the radar and the aesthetic appearance.

[0043] Preferably, the spacing between two adjacent first portions 10 is constant. This ensures the best passage of the waves.

[0044] Even more preferably, the first portions 10 and the second portions 12 form straight lines parallel to each other. This makes the passage of the waves emitted by the radar easier. However, they can also form undulating or curved bands (which can then have a constant spacing as described above).

[0045] In order to facilitate the passage of the waves emitted by the radar, the first portions 10 and the second portions 12 can extend at least partly in a direction perpendicular to the plane of propagation of the waves emitted by the radar. In other words, the wave-emitting means emits waves that propagate in a given plane (conventionally, but not necessarily, in the horizontal plane for a radar of a motor vehicle). In this case, the first portions 10 and the second portions 12 are vertical. In the case of non-straight bands, the non-straight bands can extend partly in a direction perpendicular to the plane of propagation of the waves emitted by the radar.

[0046] All first portions 10 can have the same width and all second portions 12 also have the same width. Thus, for example, a pattern which is preferred for the passage of the waves can be repeated. Alternatively, the widths of the first portions 10 can also be made different (but satisfying the formula (N*λ) / 4) or the widths of the second portions 12 can be made different.

[0047] In general, while satisfying the above formula, the arrangement of the lines forming the decorative pattern 6 can vary depending on the emission frequency of the wave-emitting member and the desired result.

[0048] The purpose of providing the second portions 12 can be to create a backlight pattern as described above. Thus, the second portions 12 can also be transparent to visible light (just like the paint layer covering these portions). By "transparent to visible light" is meant that it is at least transparent or translucent to any light radiation having a wavelength in the visible spectrum (i.e. between approximately 380 and 780 nm).

[0049] Thus, a scattering light guide can be arranged opposite the decorative pattern 6, which is arranged to diffuse the visible light through the second portions 12. This means that the side faces of the light guide form the output surface of the light. Thus, the light exits the scattering light guide in a substantially radial direction and the light flux distributed is substantially constant at all points of the output surface of the scattering portion of the scattering light guide. The light scattered by the scattering light guide comes from at least one light source, which can for example consist of a plurality of light-emitting diodes (LEDs), which can be offset (i.e. located outside the area crossed by the waves and also advantageously outside the area affected by a small impact such as a parking collision).

[0050] The scattering light guide can be formed by a plurality of optical fibers. The optical fibers are made of plastic. They can also be made of glass. They can be arranged in a sheet-like manner. The radial light output can be obtained by sandblasting the optical fibers or by laser skiving to deteriorate the surface of the optical fibers.

[0051] In order to control the electromagnetic transparency of the radome, the attenuation produced by the sheet of optical fibers to the radar waves was measured with certified equipment. For example, PMMA optical fibers with a diameter of 500 pm and braided with polyester threads were measured. A 1 mm thick sheet thus braided was placed between two polycarbonate sheets each 3 mm thick.

[0052] In the 76 to 77 GHz band (emission range of ACC radars), the attenuation due to the two polycarbonate sheets alone (without the optical fiber sheet) is 1.39 dB, measured in transmission (‘one way’, across the three thicknesses in only one direction). At these same frequencies, the attenuation of the optical fiber sheet and the two polycarbonate sheets as a whole is 0.65 dB. The overall attenuation (measured in one way) is lower than the values specified in the radar cover specifications of car manufacturers (e.g. 1.5 dB). The measurements show that the optical fiber sheet is transparent to electromagnetic waves of 77 GHz and that the attenuation is due to the thickness of the two polycarbonate sheets.

[0053] The attenuation can be improved by adjusting the thickness of the two polycarbonate sheets. Thus, this light guide does not interfere with the operation of the radar.

[0054] Alternatively, the diffusing light guide can be made of a transparent plastic film formed by extrusion of polycarbonate, 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.

[0055] The presence of the diffusing light guide makes it possible to illuminate the decorative pattern 6. Any light source known to the person skilled in the art and capable of providing backlighting for the decorative pattern 6 can be used instead of the light guide described above.

[0056] To ensure transparency to the waves, it is also advantageous to limit the maximum thickness of the radar cover 4 (body 8 + one or more layers of paint) to less than or equal to 6 mm.

[0057] As regards the manufacture of the decorative pattern 6, it is possible to spray the entire radar cover 4 (for example the outer surface of the radar cover 4 visible from the outside of the car on which the body panel 2 is mounted) and then remove the desired layer or layers of paint by laser ablation to form the second portion 12. The amount of paint removed (to achieve the second portion 12) can vary depending on the result desired, in particular in the case of a backlit pattern.

[0058] The application is not limited to the embodiments described above and other implementations will be conceivable to the person skilled in the art.

[0059] In particular, the decorative pattern can be produced by means other than those described above.

[0060] Other materials can also be used, other than those described above but having the same properties, in particular transparency to the waves.

[0061] List of reference signs

[0062] 2: body panel

[0063] 4: radar cover

[0064] 6: decorative pattern

[0065] 8: main body

[0066] 10: first portion

[0067] 12: second portion

[0068] 14: inner face of the radome

[0069] L: width of the first portion 10

[0070] l: width of the second portion 12

Claims

1. A radome (4) for a motor vehicle, characterized in that It comprises a body (8) comprising at least one area transparent to the waves emitted by the wave-emitting means and crossed by said waves, the area comprising a face (14) comprising alternations of first portions (10) covered by at least one layer of paint and second portions (12) not covered by said layer of paint, said first and second portions (10, 12) forming at least one decorative pattern (6) and being arranged so that the decorative pattern (6) is transparent to the waves emitted by the wave-emitting means, wherein said first portions (10) form bands of width (L) equal to (N*λ) / 4, with N being a non-zero natural integer and λ being equal to the emission wavelength of the wave-emitting means.

2. The radome (4) of claim 1, wherein, Said second portions (12) form bands of width (1) less than λ / 4, these bands being separated from one another by said first portions (10).

3. The radome (4) of claim 1, wherein, Said second portions (12) form bands of width (1) greater than λ / 4, these bands being separated from one another by said first portions (10).

4. The radome (4) according to any one of claims 1 to 3, wherein, The spacing between two adjacent first portions (10) is constant.

5. The radome (4) as claimed in claim 4, wherein, Said first portions (10) and said second portions (12) are rectilinear strips parallel to one another.

6. The radome (4) according to any one of claims 1 to 3, wherein, Said first portions (10) and said second portions (12) extend at least partially in a direction perpendicular to the plane of propagation of the waves emitted by the wave-emitting means.

7. The radome (4) according to any one of claims 1 to 3, wherein, All the first portions (10) have the same width and all the second portions (12) have the same width.

8. The radome (4) according to any one of claims 1 to 3, wherein, Said second portions (12) are transparent to visible light.

9. The radome (4) as claimed in claim 3, wherein, Said radome (4) comprises a light guide facing said decorative pattern (6), said light guide being arranged to diffuse visible light through said second portions (12).

10. The radome (4) of any one of claims 1 to 3, the maximum thickness of said radome (4) being less than or equal to 6 mm.

11. The radome (4) as claimed in any of claims 1 to 3, wherein, Said body (8) is made of a material chosen from the following: polymethyl methacrylate, polycarbonate, polypropylene, polyamide, copolyester, acrylonitrile-butadiene-styrene, acrylonitrile-styrene-acrylate, styrene-acrylonitrile, acrylonitrile-styrene-acrylate and mixtures of polycarbonate and polyethylene terephthalate.

12. The radome (4) as claimed in any of claims 1 to 3, wherein, Said first portions (10) are covered by at least one layer of primer, one layer of base paint and one layer of varnish. Said first portions (10) are covered by at least one layer of primer, one layer of base paint and one layer of varnish.

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