EP4082076A1

EP4082076A1 - Radome for motor vehicle comprising a decorative pattern

Info

Publication number: EP4082076A1
Application number: EP20833910.1A
Authority: EP
Inventors: Elise Dubost; Alaeddine LANDOULSI; Frédéric STABLO
Original assignee: Plastic Omnium SE
Current assignee: Plastic Omnium SE
Priority date: 2019-12-24
Filing date: 2020-12-23
Publication date: 2022-11-02
Also published as: US20230039346A1; CN113036423A; WO2021130295A1; FR3105608A1; CN213043058U; FR3105608B1

Abstract

The invention relates to a radome (4) for a motor vehicle, comprising a main body (8) comprising at least one zone transparent to the waves emitted by the wave-emitting element and intended to be traversed by said waves, the zone comprising a face (14) comprising an alternation of first parts (10) covered by at least one layer of paint and second parts (12) not covered by the layer of paint, the first and second parts (10, 12) forming at least one decorative pattern (6) and being arranged in such a way as to make the decorative pattern (6) transparent to the waves emitted by the wave-emitting element.

Description

Title of the invention: Radome for a motor vehicle comprising a decorative pattern The invention relates to motor vehicles equipped with wave-emitting members and more particularly the protection devices configured to protect these wave-emitting members from motor vehicle.

More and more motor vehicles have body parts on which are mounted members emitting waves. These wave emission devices are, for example, one or more ACC type radars according to the English expression “Adaptive Cruise Control” emitting radio waves.

Such wave-emitting devices are masked and protected, for example from bad weather, by protective devices commonly called "radomes". In the remainder of the description, the term “radome” is used as a synonym for “protection device”.

These radomes are intended to be crossed by the waves emitted by the transmitting device (s), so they must be transparent to them. By "transparent to the waves emitted by a wave-emitting member" is meant the capacity of a material traversed by an incident wave flow to transmit a fraction greater than 90% of the wave flow passing through it.

To obtain such transparency, the thickness of the region intended to be placed in front of a radar is chosen from a set of pairs of attenuation and reflection values of the radar waves / thickness of the region. This set of couples is obtained for example by measurements and calculations of attenuation and reflection of the waves as a function of the thickness, and also as a function of parameters such as the dielectric properties of the materials used for the manufacture of the part, the varnish or the paint applied to the surface of the part, in particular the different layers and their different thicknesses which make it possible to obtain a paint for automotive application, such as the primer, the base and the varnish. The use of these protection devices may have an aesthetic vocation, as is for example described in application FR 3 070 547 A1 in which the radome comprises luminous means diffusing light through the radome so as to form a pattern. on the surface of the latter, pattern visible from the outside of a vehicle on which the radome is mounted. The latter is therefore partly transparent to visible light. The term “transparent to visible light” is understood to mean that it is at least transparent or translucent to any light radiation. exhibiting a wavelength included in the visible spectrum, that is to say between approximately 380 and 780 nm.

The decorative pattern can be achieved by covering certain areas with paint opaque to visible light, other areas not being covered by this paint, the lighting of the radome making it possible to reveal the decorative motif (area through which the light passes if the pattern is formed by areas through which light passes or does not pass if the pattern is formed by areas through which light does not pass).

However, it is possible that the paint used, for example to obtain a high-quality visual rendering, is not transparent to the waves emitted by a wave-emitting device. This poses a problem because certain paints cannot therefore be used to paint a radome.

In addition, and even when using paints transparent to the waves emitted by a wave-emitting device, it is possible that the presence of an alternation of areas covered or not by said paint disturbs the passage of the waves. Indeed, the waves emitted by the wave-emitting member (s) will pass through areas comprising layers of paint (for example primer then base then varnish) and areas not comprising said layers. These layers of paint, especially the primer, influence the passage of waves. The waves therefore pass through different zones influencing them to a greater or lesser extent depending on whether or not these zones are covered with one or more layers of paint. This leads to heterogeneity in the passage of waves through the radome and consequently to a decrease in the performance of the wave-emitting member (s). This heterogeneity, even if the overall signal has an attenuation and a reflection which remain weak, in particular complicates the detection of obstacles, making the signal less easily usable.

The object of the invention is in particular to provide a radome making it possible to solve simply this problem of disturbance of the propagation of the waves while maintaining a radome having an optimal visual appearance. To this end, the invention relates to a radome for a motor vehicle comprising a main body comprising at least one zone transparent to the waves emitted by the wave-emitting member and intended to be traversed by said waves, the zone comprising a face comprising an alternation of first parts covered by at least one layer of paint and second parts not covered by said layer of paint, the first and second parts forming at least one decorative pattern and being arranged so as to make the decorative pattern transparent to waves emitted by the wave-emitting device. Thus, one chooses to have the different areas covered or not with one or more layers of paint so as to avoid a disturbance in the passage of waves through the radome. It is therefore the parameters determined during the production of the first and second parts which make it possible to obtain this facilitated passage.

The radome according to the invention can also include at least one of the characteristics below:

- the first parts form bands with a width equal to (N * l) / 4, N being a non-zero natural whole number and l being equal to the emission wavelength of the emission member d 'waves,

- the second parts form bands with a width of less than h / 4 separated from each other by the first parts,

- the second parts form bands with a width greater than h / 4 separated from each other by the first parts,

- the distance between two first consecutive parts is constant,

- the first parts and the second parts are rectilinear bands parallel to each other,

- the first parts and the second parts extend at least partly in a direction perpendicular to a plane in which propagate the waves emitted by the wave-emitting member,

- all the first parts are all the same width and all the second parts are all the same width,

- which the second parts are transparent to visible light,

- the radome comprises a light guide facing the decorative pattern and arranged to diffuse visible light through the second parts, preferably comprising a bundle of optical fibers,

- a maximum thickness of the radome being less than or equal to 6 mm

- which the main body (8) is made of a material chosen from polymethyl methacrylate, polycarbonate, polypropylene, a polyamide, a copolyester, acrylonitrile butadiene styrene, acrylonitrile styrene acrylate, styrene acrylonitrile, a mixture of acrylonitrile styrene acrylate and polycarbonate, a mixture of polycarbonate and polyethylene terephthalate, and

- the first parts are covered with at least one layer of primer, one base layer and one layer of varnish.

Brief description of the figures The invention will be better understood on reading the description which will follow, given solely by way of example and made with reference to the appended drawings in which:

[Fig. 1] Figure 1 is a perspective view of a body panel comprising a radome according to the invention;

[Fig. 2] Figure 2 is a front view of the radome comprising a decorative pattern;

[Fig. 3] Figure 3 is a sectional view of the radome according to the invention;

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

[Fig. 5] Figure 5 is a sectional view of a portion of the decorative pattern.

detailed description

Reference is now made to Figure 1 which illustrates a body panel 2, here a front bumper, comprising a protection device configured to protect at least one wave-emitting member.

The protection device, also called radome 4, protects a wave-emitting member (not shown) in position on the front face of a motor vehicle behind the radome 4. In what follows, we will describe the example. a radar placed behind the radome 4 on the front face of a vehicle. Those skilled in the art will understand that depending on its function, the radar can be mounted in another position of the vehicle, for example on the rear face, on the side faces or on the roof. The number of wave-emitting organs can also vary.

The radome 4 is at least in part intended to be traversed by the waves emitted by the wave emitter.

Therefore, it must be at least partly transparent to these waves, at least at the level of an area transparent to the waves. As explained above, the term “transparent to the waves emitted by a wave-emitting member” is understood to mean the capacity of a material traversed by an incident wave flow to transmit a fraction greater than 90% of the wave flow. crossing it. To allow this, a main body 8 of the radome 4 can be made of a material chosen from PMMA (polymethyl methacrylate), polycarbonate, polypropylene, a polyamide, a copolyester, acrylonitrile butadiene styrene, acrylonitrile. styrene acrylate, styrene acrylonitrile, a mixture of acrylonitrile styrene acrylate and polycarbonate, a mixture of polycarbonate and polyethylene terephthalate.

The radome 4 comprises at least one decorative pattern 6. This decorative pattern 6 is produced by the presence, on the main body 8 of the radome 4, of an alternation of first parts 10 covered by at least one layer of paint and of seconds. parts 12 not covered by said layer or layers of paint, for example by a paint which does not allow the waves emitted by the wave-emitting member to pass. For example, the first parts 10 can be covered with a primer, a base and a varnish not covering the second parts 12. The number of paint layers can be different. This does not mean that the second parts 12 are not covered with paint. It is for example possible that the latter are covered with a layer of varnish (preferably transparent to visible light as will be explained later), sharing or not this layer of paint with the first parts 10. The face covered by the paint layer (s) may be the internal face 14 of the main body 8 as shown in FIG. 3 or the external face of the radome 4.

The first parts 10 and the second parts 12 are arranged so as to allow a homogeneous passage of the waves over the whole of the decorative pattern 6. In other words, the decorative pattern is transparent to these waves as a whole and does not disturb the passage of waves, not generating additional heterogeneity to the signal.

In what follows, we will describe a decorative pattern 6 according to the invention placed opposite a radar transmitting at a frequency between 75 and 81 GHz. In order to allow optimal passage of the waves, it is possible to arrange for the first parts to form bands with a width L equal to (N * l) / 4, N being a non-zero natural number and l being equal at the emission wavelength of the wave-emitting member. In other words, the first parts 10 are of a width which cannot be less than h / 4 and can be equal to a multiple of l / 4, within the limit of what it is possible to achieve over the length. of the radome 4. The selection of a width of the first parts 10 from among the possibilities resulting from the aforementioned formula makes it possible to optimize and homogenize the passage of the waves emitted by a radar.

According to a first variant shown in Figures 4 and 5, it is possible that the second parts 12 form bands of a width I less than h / 4 separated from each other by the first parts 10. The narrowness of the second parts 12 allows radars to be very precise. In other words, and when it will be necessary for a radar, by virtue of its function, to collect data as accurately as possible, the second parts 12 form bands of width less than 1/4, the reduction of the width allowing the radar to gain in precision.

Conversely, and with the aim of obtaining a backlit decorative motif 6 as will be explained below (with second parts 12 transparent to the light visible), it is possible that the width of the second parts 12 is greater than 1/4. This is possible in particular when the function of the radar does not require it to have the finest possible precision. It is even possible that the second parts 12 have a width I equal to or greater than the width L of the first parts 10. It is therefore possible to seek a compromise between the precision of the radar and the aesthetic appearance by dimensioning the second parts 12 of adequately.

Preferably, the spacing between two first consecutive parts 10 is constant. This ensures optimal wave passage.

Even more preferably, the first parts 10 and the second parts 12 form rectilinear bands parallel to each other. This makes it possible to facilitate the passage of the waves emitted by a radar. However, it is possible that they form wavy or curved bands (it is then possible to have a constant spacing as described above).

In order to facilitate the passage of the waves emitted by a radar, it is possible the first parts 10 and the second parts 12 extend at least partly in a direction perpendicular to a plane in which propagate the waves emitted by a radar. In other words, the wave-emitting member emits waves propagating in a given plane (traditional radars have unidirectional polarization), conventionally (but not necessarily) in a horizontal plane for a motor vehicle radar. . In this case, the first parts 10 and the second parts 12 are vertical. In the case of non-rectilinear bands, they may extend partly in a direction perpendicular to a plane in which the waves emitted by a radar propagate.

It is also possible that all of the first parts 10 are all of the same width and all of the second parts 12 are all of the same width. There is therefore repetition of a preferential pattern, for example for the passage of waves. It is alternatively possible to vary the thicknesses of the first parts 10 (while respecting the formula (N ^* 1) / 4) as well as those of the second parts 12.

In general, the arrangement of the lines forming the decorative pattern 6 can vary depending on the frequency of emission of the wave-emitting member and the desired result by respecting the formula set out above.

The realization of the second parts 12 may aim to achieve a backlit pattern as explained above. The second parts 12 can therefore also be transparent to visible light (just like the possible layer or layers of paint covering these parts). The term “transparent to visible light” is understood to mean that it is at least transparent or translucent to any light radiation. exhibiting a wavelength included in the visible spectrum, that is to say between approximately 380 and 780 nm.

It is therefore possible to place, opposite the decorative pattern 6, a diffusing light guide arranged so as to diffuse visible light through the second parts 12. By this is meant that the light-emitting surface is formed. by a side face of the light guide. As a result, the light emerges from the diffusing light guide in a substantially radial direction and the distributed light flux is approximately constant at any point on the exit surface of the diffusing part of the diffusing light guide. The light diffused by the latter comes from at least one light source which can for example consist of a plurality of light-emitting diodes (LEDs), the light source being able to be deported (ie located outside the zone crossed by the waves and also advantageously outside areas impacted by small shocks, such as “parking” shocks).

The diffusing light guide can be formed by a plurality of optical fibers. Optical fibers are plastic. They can also be made of glass. They can be arranged in a sheet. It is possible to obtain radial light output by treating the optical fibers by sandblasting or by laser scraping in order to deteriorate the surface of the latter.

The attenuation by a sheet of optical fibers of the radar waves was measured with equipment certified for the control of the electromagnetic transparency of radomes. For example, a measurement was made for optical fibers made of PMMA, with a diameter of 500 µm, and woven with a polyester yarn. The web thus woven, 1 mm thick, was placed between two sheets of polycarbonate 3 mm thick each. In the 76 to 77 GHz band (ACC radar emission range), the attenuation due to the two polycarbonate plates alone (without a layer of optical fibers), measured in transmission ("one way", in one direction only. across all three layers), is 1.39 dB. At these same frequencies, the entire fiber optic web and the two polycarbonate sheets have an attenuation of 0.65 dB. The overall attenuation (measured one-way) is below the car manufacturers specification for a radome (eg 1.5dB). The measurements show that the fiber optic web is transparent to electromagnetic waves at 77 GHz and that the attenuation is due to the thickness of the two polycarbonate plates.

The attenuation can be improved by adjusting the thicknesses of the two polycarbonate plates. Such a light guide therefore does not disturb the operation of a radar. Alternatively, the diffusing light guide can be made of transparent plastic extruded polycarbonate 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 the standard. ISO 62. The presence of a diffusing light guide makes it possible to illuminate the decorative motif 6. It is possible to replace the above light guide by any light source known to those skilled in the art and being suitable for allow backlighting of the decorative pattern 6.

In order to ensure transparency to waves, it is also advantageous to limit the maximum thickness of radome 4 (main body 8 + paint layer (s)), less than or equal to 6 mm.

Concerning the production of the decorative pattern 6, it is possible to paint the whole of the radome 4 (for example the external face of the radome 4 visible from the outside of a motor vehicle on which the body panel 2 is mounted) then to remove the desired paint layer (s) by laser scraping to form the second parts 12. Depending on the desired result, especially in the case of a backlit pattern, the amount of paint scraped (for making the second parts 12) can vary.

The invention is not limited to the embodiments presented and other embodiments will be apparent to those skilled in the art.

It is in particular possible to create a decorative pattern by means other than those described above.

It is also possible to use materials other than those mentioned above and having the same properties as the latter, in particular wave transparency.

Reference list

2: body panel 4: radome 6: decorative pattern

8: main body 10: first parts 12: second parts 14: internal face of the radome L: width of the first parts 10 I: width of the second parts 12

Claims

[Claim 1] Radome (4) for a motor vehicle, characterized in that it comprises a main body (8) comprising at least one area transparent to the waves emitted by the wave-emitting member and intended to be traversed by said waves, the zone comprising a face (14) comprising an alternation of first parts (10) covered by at least one layer of paint and of second parts (12) not covered by said layer of paint, the first and second parts (10 , 12) forming at least one decorative pattern (6) and being arranged so as to make the decorative pattern (6) transparent to the waves emitted by the wave-emitting member.

[Claim 2] A radome (4) according to claim 1, wherein the first parts (10) form bands of a width (L) equal to (N ^* l) / 4, N being a non-zero natural number and l being equal to the emission wavelength of the wave emitting member.

[Claim 3] A radome (4) according to claim 2, wherein the second parts (12) form bands of a width (I) less than h / 4 separated from each other by the first parts (10).

[Claim 4] A radome (4) according to claim 2, wherein the second parts (12) form bands of a width (I) greater than h / 4 separated from each other by the first parts (10).

[Claim 5] A radome (4) according to any one of the preceding claims, in which the spacing between two consecutive first parts (10) is constant.

[Claim 6] A radome (4) according to claim 5, wherein the first parts (10) and the second parts (12) are rectilinear bands parallel to each other.

[Claim 7] A radome (4) according to any preceding claim, wherein the first parts (10) and the second parts (12) extend at least in part in a direction perpendicular to a plane in which propagate the waves emitted by the wave-emitting device.

[Claim 8] A radome (4) according to any preceding claim, wherein all of the first parts (10) are all of the same width and all of the second parts (12) are all of the same width.

[Claim 9] A radome (4) according to any preceding claim, wherein the second portions (12) are transparent to visible light.

[Claim 10] A radome (4) according to claim 4, wherein the radome (4) comprises a light guide facing the decorative pattern (6) and arranged to diffuse visible light through the second parts (12), comprising preferably a bundle of optical fibers.

[Claim 11] Radome (4) according to any one of the preceding claims, a maximum thickness of the radome (4) being less than or equal to 6 mm.

[Claim 12] Radome (4) according to any one of the preceding claims, wherein the main body (8) is made of a material selected from polymethyl methacrylate, polycarbonate, polypropylene, polyamide, copolyester, acrylonitrile butadiene styrene, acrylonitrile styrene acrylate, styrene acrylonitrile, a mixture of acrylonitrile styrene acrylate and polycarbonate, a mixture of polycarbonate and polyethylene terephthalate.

[Claim 13] A radome (4) according to any preceding claim, wherein the first parts (10) are covered with at least one primer coat, one base coat and one coat of varnish.