Vehicle assembly comprising a radar sensor

Abstract

One aspect of the invention relates to a vehicle assembly (1) contained in a vehicle, the vehicle assembly comprising: - a radar sensor (10) configured to emit and / or receive associated radar waves (R1); and - a protective panel (20) comprising a support layer (22) provided with a first face (22A) and a second face (22B), the second face being provided with a coating layer (24), the coating layer comprising a structure formed of a plurality of patterns (25), each pattern extending between a free end (25A) and a base (25B), the base being formed at the second face, one section (S) of each pattern being defined parallel to the second face, and for each pattern, the section being variable between a minimum section value at the free end of the pattern and a maximum section value at the base of the pattern.

Description

Vehicle assembly including a radar sensor TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention generally relates to vehicle equipment equipped with a radar sensor.

[0002] In particular, the invention relates to a vehicle assembly included in a vehicle and comprising a radar sensor. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] A large majority of motor vehicles today are equipped with advanced driver assistance systems (ADAS, for "Advanced Driver Assistance Systems" according to the commonly used acronym). These driver assistance systems are, for example, safety and driver assistance systems to avoid potentially dangerous situations that could lead to an accident.

[0004] These driving assistance systems are based in particular on the use of detection systems equipped, for example, with radar sensors.

[0005] Weather conditions can significantly impede the proper functioning of driver assistance systems. For example, snow can cause the detection system to become blinded, and thus cause the driver assistance system to malfunction.

[0006] It is then known to install systems, such as defrosting systems, to allow the area facing the detection system to be maintained at a relatively high temperature to ensure the proper functioning of the detection system (and therefore of the driving assistance system).

[0007] However, the defrosting phenomenon causes water droplets to form on the surface. The presence of these water droplets also disrupts the detection system because the water partially absorbs the waves used for detection. This therefore affects the performance of the detection system, and therefore the effectiveness of the driver assistance system in assisting the driver.

[0008] The present invention then proposes a vehicle assembly making it possible to improve the propagation and detection of radar waves emitted and received by a radar sensor included in a driving assistance system in order to attenuate, or even eliminate, the reflections of these radar waves.

[0009] One aspect of the invention thus relates to a vehicle assembly included in a vehicle, said vehicle assembly comprising:- a radar sensor configured to emit and / or receive associated radar waves, the radar waves propagating towards a protective panel, and- the protective panel comprising at least one support layer, the support layer comprising a first face and a second face, opposite the first face, the second face being provided with a coating layer, said coating layer comprising a structure formed of a plurality of patterns, each pattern extending between a free end and a base, the base being formed at the second face of the support layer, a section of each pattern being defined parallel to the second face, and for each pattern,the section being variable between a minimum section value at the free end of the pattern and a maximum section value at the base of the pattern.,

[0010] Thus, advantageously according to the invention, the presence of this plurality of patterns in the coating layer makes it possible to introduce a refractive index gradient between the value of the index of the protective panel and that of the external environment. The progressive and successive evolution of the refractive index in the protective panel then makes the interface “invisible” for the radar wave, which propagates without being reflected. The signal-to-noise ratio associated with the radar sensor is therefore considerably improved, because the parasitic reflections are eliminated (or greatly reduced so that they do not reduce the signal-to-noise ratio associated with the radar sensor).

[0011] In addition, the formed coating layer has a low surface energy due to the structure with the different patterns used (and the variation in the section of each pattern). This results in a strong repulsion of water molecules.

[0012] Thus, advantageously, the structure of the coating layer according to the invention (with the different patterns) makes it possible to obtain a surface substantially reproducing a so-called "Lotus" effect (with a contact angle at the interface greater than 150°). In other words, the patterned structure of the coating layer makes it possible to confer a superhydrophobic character on the surface of the protective panel. This then improves the detection of radar waves by the radar sensor because the water droplets do not remain in the detection field of the radar sensor. The radar waves are therefore not absorbed, which improves the efficiency of the radar sensor.

[0013] In addition to the characteristics which have just been mentioned in the preceding paragraph, the vehicle assembly according to the invention may have one or more additional characteristics from among the following, considered individually or according to all technically possible combinations:

[0014] - two adjacent patterns of the plurality of patterns are spaced apart by a distance less than a characteristic distance associated with the base of the pattern;

[0015] - each pattern of the plurality of patterns has a height less than one tenth of a wavelength of the radar waves;

[0016] - the coating layer comprises a polymer material;

[0017] - the coating layer comprises polyurethane;

[0018] - the patterns of the plurality of patterns are equally distributed on the second face;

[0019] - the patterns of the plurality of patterns are randomly distributed on the second face;

[0020] - each pattern has a pyramidal, trapezoidal or conical shape;

[0021] - the first face of the support layer is provided with another coating layer, said other coating layer comprising another structure formed of a plurality of other patterns, each other pattern extending between another free end and another base, the other base being formed at the first face of the support layer, another section of each other pattern being defined parallel to the first face, and for each other pattern, the other section being variable between another minimum section value at the other free end of the pattern and another maximum section value at the other base of the pattern;

[0022] - the protective panel is positioned at a distance from the radar sensor, the first face of said protective panel being positioned opposite the radar sensor;

[0023] - the radar sensor is integrated into the support layer of the protective panel; and

[0024] - the radar sensor is a millimeter wave or hyperfrequency or microwave radar sensor. BRIEF DESCRIPTION OF THE FIGURES

[0025] Other features and advantages of the invention will become apparent upon reading the description, which can be read in conjunction with the figures. These figures are presented for information purposes only and in no way limit the invention.

[0026] Larepresents a schematic view of a first example of embodiment of a vehicle assembly, included in a vehicle, in accordance with the invention,

[0027] It schematically represents the propagation of a radar wave emitted by a radar sensor included in the vehicle assembly of the,

[0028] Larepresente, schematically, a second example of embodiment of a vehicle assembly in accordance with the invention,

[0029] La represents, schematically, another example of embodiment of a protection panel included in the vehicle assembly according to the invention, and

[0030] It schematically represents a third example of an embodiment of a vehicle assembly in accordance with the invention.

[0031] For clarity, identical or similar elements are identified by identical reference signs throughout the figures. DETAILED DESCRIPTION

[0032] The present invention aims to provide a vehicle assembly making it possible to improve the operation and efficiency of driver assistance systems in a vehicle. It aims more particularly to improve the propagation and detection of radar waves emitted and received by a radar sensor included in a driver assistance system in order to attenuate, or even eliminate, the reflections of these radar waves and therefore to improve (i.e. to reduce) a signal-to-noise ratio associated with the radar sensor.

[0033] In the present description, the vehicle 2 considered is a motor vehicle. By “motor vehicle” is meant any type of motorized vehicle. In the following, the two terminologies “vehicle” and “motor vehicle” are used to describe the vehicle 2 concerned by the present invention.

[0034] The figure represents a vehicle assembly 1 of a motor vehicle 2. As can be seen in this figure as well as in figures 2, 3 and 5, the vehicle assembly 1; 5 comprises a radar sensor 10 and a protection panel 20.

[0035] The radar sensor 10 is configured to transmit and receive radar waves R1.

[0036] In practice, the radar sensor 10 is a millimeter wave radar sensor (with frequencies between 24 Gigahertz (GHz) and 300 GHz). Alternatively, the radar sensor is a microwave radar sensor (with frequencies between 300 Megahertz (MHz) and 81 GHz). Alternatively, the radar sensor is a microwave radar sensor (between 1 GHz and 300 GHz).

[0037] Preferably in the present invention, the radar sensor 10 operates at a radar frequency between 76 GHz and 81 GHz. The radar waves R1 are for example emitted on a frequency band between 100 MHz and 3 GHz. Thus, in a preferred example, if the sensor operates at a radar frequency of 77 GHz with a frequency band of 1 GHz, the radar sensor 10 operates on a frequency band of 76.5 GHz to 77.5 GHz. The radar waves R1 are thus emitted on the frequency range 76.5 GHz to 77.5 GHz, then corresponding to a range Δ1 of wavelengths λ between 3.87 millimeters (mm) and 3.92 mm.

[0038] In another embodiment, if the radar sensor 10 operates at a radar frequency of 78.5 GHz with a frequency band of 5 GHz, the radar sensor 10 operates on a frequency band of 76 GHZ to 81 GHz. In this case, the radar waves R1 are thus emitted on the frequency range 76 GHZ to 81 GHz, corresponding to a range Δ1 of wavelengths λ between 3.701 mm and 3.945 mm.

[0039] As can be seen in the figure, the emitted radar waves R1 arrive with an angle of incidence θ on the protection panel 20.

[0040] In an exemplary embodiment, the angle of incidence θ is between 0° and + / -30 degrees (°). The field of view FOV associated with the radar sensor 10 thus varies between -30° and +30°. The center of the field of view FOV corresponds to an angle of 0° relative to a longitudinal axis of the vehicle 2. This longitudinal axis of the vehicle 2 is also called the “axis of the vehicle”.

[0041] In another exemplary embodiment, the field of view FOV associated with the radar sensor 10 can vary between -90° and +45°. The center of the field of view FOV is, in this case, an angle of -45° relative to the axis of the vehicle 2. The angle of incidence θ of the radar waves R1 on the protection panel 20 is close to 0°. In such an example, the vehicle assembly 1 is then positioned at approximately 45° from the axis of the vehicle 2.

[0042] The radar sensor 10 is configured to scan the external environment of the motor vehicle 2, by emitting radar waves R1. The radar sensor 10 does not constitute the heart of the invention here. It is therefore not described in detail in the following.

[0043] Essentially, as shown in Figures 1, 2 and 5, the radar sensor 10 comprises:

[0044] - at least one transmitting antenna 100 configured to transmit primary radar waves R1, and

[0045] - at least two receiving antennas 101 configured to receive secondary radar waves R2.

[0046] In practice, the radar sensor 10 also comprises at least one transmitter 103 configured to generate the primary radar waves R1. It also comprises at least one receiver 104 configured to process the secondary radar waves R2 received in return.

[0047] In an exemplary embodiment, a single electronic component can be used to implement both transmission and reception functions. The vehicle assembly then comprises one or more transmitters / receivers (also called "transceivers" according to the commonly used Anglo-Saxon term).

[0048] In practice, the transmitter 103 generates primary radar waves R1 which are subsequently emitted by the transmitting antenna 100, which when they encounter an object 3 (here a pedestrian in the non-limiting example illustrated in the) in the external environment of the motor vehicle 2 are reflected on this object 3. The radar waves thus reflected are waves transmitted in return to the radar sensor 10. These are the secondary radar waves R2 received by the receiving antennas 101. They correspond to the radar waves retransmitted in the direction of the radar sensor 10.

[0049] In an exemplary embodiment, the primary radar waves R1 and the secondary radar waves R2 are radio frequency waves.

[0050] Alternatively (not shown), the radar sensor may include a plurality of transmitters and a plurality of receivers.

[0051] In practice, the transmitting antenna 100 (also called antenna 100 in the present description), is configured to transmit the primary radar waves R1 generated by the transmitter 103. The receiving antennas 101 (also called antennas 101 in the following) are configured to receive the secondary radar waves R2 and communicate them to the receiver 104 which subsequently processes them. There is a phase shift between the secondary radar waves R2 received by the receiving antennas 101 which makes it possible to deduce therefrom the position of the object 3 relative to the motor vehicle 2, object 3 which is located in the external environment of the motor vehicle 2.

[0052] In practice, the antennas 100, 101 are for example so-called “patchantennas” (or “patchantennas” according to the commonly used terminology of Anglo-Saxon origin). Alternatively, the antennas may be so-called “slotantennas” (or “slotantennas” according to the commonly used terminology of Anglo-Saxon origin).

[0053] In practice here, the antennas 100, 101, the transmitter 103 and the receiver 104 are arranged on a printed circuit board 105. The printed circuit board is for example a rigid printed circuit board also called PCBA (for "PrintedCircuitBoardAssembly" according to the terminology of commonly used Anglo-Saxon origin). Alternatively, the printed circuit board may be a flexible printed circuit board (or "Flexboard" according to the terminology of commonly used Anglo-Saxon origin).

[0054] The radar sensor 10 further comprises an electronic control unit 106 configured to control the transmitter 103 and the receiver 104.

[0055] As can be seen in Figures 1, 2, 3 and 5, the vehicle assembly 1; 5 also includes the protective panel 20.

[0056] This protective panel 20 corresponds for example here to an outlet window of a lighting device (not shown) of the motor vehicle 2. This lighting device is for example a headlight or a rear light of the motor vehicle 2. As a variant, the protective panel 20 may be a part of the bumper of the motor vehicle 2. More particularly, the protective panel 20 may for example correspond to the central front bumper panel of the motor vehicle 2. As a further variant, the protective panel 20 may correspond to a radome for the radar sensor 10. In practice, the protective panel 20 forms an outer layer of the vehicle assembly 1; 5, that is to say a layer which is directly in contact with the external environment of the motor vehicle 2.

[0057] Whatever the use considered, the protective panel 20 is particularly suitable for protecting the radar sensor 10.

[0058] In the embodiment shown in Figures 1, 2 and 5, the protective panel 20 is positioned opposite the radar sensor 10.

[0059] The protective panel 20 has an equivalent refractive index n eq on the wavelength scale λ of the wavelength range Δ1 introduced previously. As will be explained below, this equivalent refractive index n eq is variable due in particular to the optical design of a coating layer 24 described below.

[0060] As shown in Figures 1, 2, 3 and 5, the protective panel 20 here comprises a support layer 22 and a coating layer 24.

[0061] The support layer 22 comprises a first face 22A and a second face 22B, opposite the first face 22A. The second face 22B is for example here directed towards the outside of the motor vehicle 2 (that is to say it is in direct contact with the air outside the motor vehicle 2).

[0062] The support layer 22 comprises, for example, a polymer material. Alternatively, this layer comprises a glass or ceramic material.

[0063] Preferably, the support layer 22 comprises polycarbonate (commonly known by the acronym PC). Alternatively, the support layer may comprise polyethylene terephthalate (more commonly known by the acronym PET). Alternatively, the support layer may comprise an optically transparent adhesive (or OCA for “Optical Clear Adhesive” according to the terminology of commonly used Anglo-Saxon origin). Alternatively, the support layer may comprise polyurethane (commonly known by the acronym PU).

[0064] Generally, the support layer 22 comprises a dielectric material. Such a material is advantageous because it is non-conductive and therefore allows radar waves R1 to pass through (unlike a conductive material).

[0065] The support layer 22 has a thickness of less than 8 millimeters (mm). Preferably, this thickness is between 2 and 3 mm.

[0066] The support layer 22 has a refractive index noted n1.

[0067] According to a first exemplary embodiment visible in Figures 1, 2 and 5, the layer 22 forms the part of the protective panel 20 positioned directly opposite the radar sensor 10 and at a distance from the latter. Thus, the first face 22A is directly opposite the radar sensor 10.

[0068] The distance between the first face 22A of the support layer 22 and the radar sensor 10 (for example a face of the radar sensor 10 directly opposite the protective panel 20) is for example less than 15 mm. Preferably, it is between 2 and 10 mm. This then makes it possible to avoid the formation of condensation between the radar sensor and the protective panel. This also makes it possible to avoid the deposition of dust and impurities between the radar sensor and the protective panel, and therefore to maintain good detection quality for the radar sensor.

[0069] According to a second example embodiment visible on the, the radar sensor 10 is integrated into the support layer 22. In other words, the radar sensor 10 is here an integral part of the protection panel 20. More particularly, the transmitting antenna 100 and the receiving antennas 101 are encapsulated in the support layer 22.

[0070] This arrangement is particularly advantageous because it makes it possible to reduce the overall size of the vehicle assembly 1. In particular, it makes it possible to reduce the space required behind the protection panel (which is here less than 100 millimeters (mm), more particularly of the order of 80mm). In addition, in this case, the manufacture of the vehicle assembly 1 is facilitated. Indeed, the molding of the radar sensor 10 directly in the protection panel 20 is easier to implement.

[0071] This arrangement also reduces the overall weight of the vehicle assembly by eliminating the need for a radar sensor mount. This also increases the accuracy of the radar sensor.

[0072] As can be seen in Figures 1 to 5, the protective panel 20 also comprises the covering layer 24; 27. This covering layer 24 is formed on the second face 22B of the support layer 22. The covering layer 24 is therefore in direct contact with the air outside the motor vehicle 2.

[0073] Advantageously according to the invention, the coating layer 24 comprises a structure formed from a plurality of patterns 25, 26; 28. This plurality of patterns 25, 26 then forms a texturing of the support layer 22 (and more particularly of the second face 22B of the support layer 22).

[0074] As can be seen in Figures 1 to 5, each pattern 25, 26; 28 extends between a free end 25A, 26A; 28A and a base 25B, 26B; 28B. The base 25B, 26B of each pattern 25, 26 is formed at the second face 22B of the support layer 22.

[0075] The coating layer 24 comprises, for example, a polymer material. Preferably, the coating layer 24 comprises polyurethane. The use of polyurethane is particularly advantageous because it makes it possible to reinforce this coating layer. Indeed, the use of polyurethane makes it possible to give the coating layer (and therefore the protective panel) excellent mechanical strength, great durability and high abrasion resistance. In particular, such a coating layer is more resistant, in particular to external weather conditions for example. Such a coating layer also degrades very little over time.

[0076] Alternatively, the coating layer may comprise polycarbonate. Further alternatively, the coating layer may comprise polyethylene terephthalate (PET). Further alternatively, the coating layer may comprise an optically clear adhesive (OCA).

[0077] Generally, the coating layer 24 comprises a dielectric material. Such a material is advantageous because it is non-conductive and therefore allows radar waves R1 to pass through (unlike a conductive material).

[0078] Thus, when the radar waves R1 are emitted by the radar sensor 10, they first encounter the support layer 22 and then the coating layer 24 (with the patterns 25, 26).

[0079] In practice, this coating layer 24 is for example formed by overmolding on the support layer 22. For example, a mold adapted to form the plurality of patterns 25, 26 is used for overmolding this coating layer 24 on the support layer 22.

[0080] As can be seen in Figures 1 to 5, a section S of each pattern 25 is defined parallel to the second face 22B of the support layer 22. In other words, the section S of each pattern 25 corresponds to an intersection between a plane parallel to the second face 22B of the support layer 22 and the pattern 25, 26 concerned.

[0081] Advantageously according to the invention, for each pattern 25, 26, the section S is variable between a minimum value of section S min at the free end 25A, 26A of the pattern 25, 26 and a maximum value of section S maxat the base 25B, 26B of the pattern 25, 26. In other words, the section S of each pattern 25, 26 varies between the maximum value of section S max at base level 25B, 26B and the minimum value of section S min at the free end 25A, 26A. This then implies an evolution in the shape of each pattern 25, 26 with a section S which reduces from the base 25B, 26B towards the free end 25A, 26A.

[0082] Here, each pattern 25 has, for example, a pyramidal shape (figures 1 to 3 and 5). As a variant (shown in the), each pattern 26 may have a trapezoidal shape (corresponding to a truncated pyramidal shape). As a further variant (not shown), each pattern may have a conical shape.

[0083] This evolution of the section S of each pattern 25, 26 (and therefore of the shape of each pattern 25, 26) makes it possible to obtain an evolution of the refractive index in the coating layer 24. The use of the patterns then makes it possible to obtain a gradient of refractive indices in the protective panel 20, which results in a progressive transition from one medium to the other for the propagation of the radar waves. This then makes it possible to avoid Fresnel reflections which would occur at the level of the faces of the protective panel 20.

[0084] Indeed, as shown in the figure, when a radar wave R1 is emitted by the radar sensor 10, it propagates to the protection panel 20. When this radar wave R1 arrives, for example with an angle of incidence θ, at an interface between the protection panel 20 and the external medium (of refractive index n ext), the radar wave R1 undergoes reflection (reflected wave R11) and refraction. The reflection phenomenon causes disturbances at the radar sensor, namely in particular an attenuation of the signal-to-noise ratio. This reflection phenomenon is notably due to the significant difference in index between the index associated with the protective panel and that of the external environment (for example, here air, with a refractive index close to 1).

[0085] Advantageously according to the invention, the presence of the coating layer provided with the plurality of patterns makes it possible to introduce a refractive index gradient between the value of the index of the protective panel and that of the external environment. The progressive evolution of the refractive index in the layer then makes the interface “invisible” for the radar wave, which propagates without being reflected (here the reflections are therefore eliminated at the level of the face of the support layer provided with the coating layer, that is to say at the level of the second face of the support layer). The signal-to-noise ratio associated with the radar sensor 10 is therefore considerably improved, because the parasitic reflections are eliminated (or greatly reduced so that they do not reduce the signal-to-noise ratio associated with the radar sensor).

[0086] Whatever the shape of each pattern 25, 26, it is possible to define a characteristic distance associated with the base 25B, 26B of the pattern 25, 26 (at the level of the second face 22 of the support layer 22). This characteristic distance corresponds for example to the side of the regular polygon in the case of a regular pyramidal shape. It can also be the diameter of the base circle in the case of a cone of revolution.

[0087] Here, this characteristic distance is, for example, less than 0.5 mm. This characteristic distance is in practice very small compared to the wavelengths λ of the Δ1 wavelength range introduced previously. For example, in the case where the wavelength λ is 4 mm for a frequency of 77 GHz, the characteristic distance is approximately equal to one tenth of the wavelength λ of the radar waves.

[0088] For example, in the case of a radar wave emitted with a frequency between 76 GHz and 81 GHz, that is to say with a wavelength of the order of 4 mm, the characteristic distance associated with each pattern 25 is less than 400 micrometers (µm).

[0089] Advantageously, two adjacent patterns of the plurality of patterns 25, 26 are spaced apart by a distance d1. This distance d1 corresponds to the distance, at the level of the second face 22B, between two adjacent patterns 25, 26.

[0090] In practice here, this distance d1 is less than the characteristic distance associated with the base of each pattern 25, 26. More particularly, this distance d1 is between 0 and 1. The case where this distance d1 is close to 0, this means that the patterns 25 are contiguous (or joined), as is for example represented in figures 1, 2 and 5.

[0091] It is possible to define a quantity T0 quantifying the spacing between two adjacent patterns 25, 26 by the following formula: . According to the conditions stated previously on the distance d1 separating two adjacent patterns, this quantity T0 is between 0 and 1.

[0092] Furthermore, each pattern 25, 26 has a height h (visible in Figures 2 to 4). This height h is less than one tenth of the wavelength of the radar waves.

[0093] For example, in the case of a radar wave emitted with a frequency between 76 GHz and 81 GHz, that is to say with a wavelength of the order of 4 mm, the height h of each pattern 25, 26 is less than 400 micrometers (µm). Preferably, this height h is greater than 20 µm.

[0094] With regard to the arrangement of the patterns 25, 26 of the plurality of patterns on the second face 22B, the patterns 25, 26 are equally distributed on the second face 22B. This then means that the patterns 25, 26 are regularly distributed on the second face 22B. These patterns therefore form a regular paving of the second face 22B of the support layer 22. In this case, the patterns 25, 26 therefore form a network of patterns with a network pitch Λ (equal to d1+a with the notations introduced previously).

[0095] Alternatively, the plurality of patterns are randomly distributed on the second side of the support layer.

[0096] The coating layer 24 has a refractive index n2. This refractive index n2 is variable. It depends in particular here on the patterns 25, 26 of the plurality of patterns and on the spacing between these patterns 25, 26 (quantified by the distance d1 introduced previously).

[0097] It is then possible to define a local refractive index in the coating layer 24 (also called equivalent refractive index n eq ). This equivalent refractive index n eq is given by the following formula:

[0098] , with n ext the refractive index of the medium external to the protective panel 20, n2 the refractive index of the coating layer 24 and T0 the quantity quantifying the spacing between two adjacent patterns 25.

[0099] Thus, advantageously according to the invention, the presence of this plurality of patterns in the coating layer makes it possible to introduce a refractive index gradient between the value of the index of the protective panel and that of the external environment. The progressive and successive evolution of the refractive index in the protective panel then makes the interface “invisible” for the radar wave, which propagates without being reflected. The signal-to-noise ratio associated with the radar sensor is therefore considerably improved, because the parasitic reflections are eliminated (or greatly reduced so that they do not reduce the signal-to-noise ratio associated with the radar sensor).

[0100] In other words, the range of radar wave detection is improved.

[0101] In addition, the formed coating layer has a low surface energy due to the structure with the different patterns used (and the variation in the section of each pattern). This results in a strong repulsion of water molecules.

[0102] Furthermore, this patterned structure (along with the refractive index gradient) also increases the surface roughness, resulting in reduced surface wettability.

[0103] Thus, advantageously, the structure of the coating layer according to the invention (with the different patterns) makes it possible to obtain a surface substantially reproducing a so-called "Lotus" effect (with a contact angle at the interface greater than 150°). In other words, the patterned structure of the coating layer makes it possible to confer a superhydrophobic character on the surface of the protective panel. This then improves the detection of radar waves by the radar sensor because the water droplets do not remain in the detection field of the radar sensor. The radar waves are therefore not absorbed, which improves the efficiency of the radar sensor.

[0104] In an exemplary embodiment shown in the, the protective panel 20 of the vehicle assembly 5 may comprise another coating layer 27. This other coating layer 27 is here formed on the first face 22A of the support layer 22.

[0105] In a similar manner to the coating layer 24 described previously, the other coating layer 27 comprises a structure formed from a plurality of other patterns 28. This plurality of other patterns 28 then forms a texturing of the support layer 22 (and more particularly of the first face 22A of the support layer 22).

[0106] The other patterns 28 have characteristics similar to those presented previously concerning patterns 25, 26.

[0107] In an exemplary embodiment, the patterns 25, 26 formed on the second face 22B and the other patterns 28 formed on the first face 22A are identical.

[0108] In another exemplary embodiment, the patterns 25, 26 and the other patterns 28 are different (for example in shape, or in spacing distance d1, or even in materials).

[0109] This other embodiment is particularly advantageous because the effects conferred by the structure with the plurality of patterns on the second face 22B of the support layer 22 are also observed on the opposite face (i.e. the first face 22A) of the support layer 22. Thus, as indicated previously for the coating layer 24, the presence of this plurality of other patterns in the other coating layer makes it possible to introduce a refractive index gradient between the value of the index of the protective panel and that of the external environment (on the opposite face). The progressive and successive evolution of the refractive index in the protective panel then makes the interface “invisible” for the radar wave, which propagates without being reflected.The signal-to-noise ratio associated with the radar sensor is therefore considerably improved, because stray reflections are eliminated (or greatly reduced so that they do not reduce the signal-to-noise ratio associated with the radar sensor).

[0110] In addition, as previously indicated, the structure in other patterns of the other coating layer makes it possible to confer a superhydrophobic character to this other face of the protective panel.

Claims

Vehicle assembly (1; 5) included in a vehicle (2), said vehicle assembly (1;5) comprising:- a radar sensor (10) configured to emit and / or receive associated radar waves (R1), the radar waves (R1) propagating towards a protective panel (20), and- the protective panel (20) comprising at least one support layer (22), the support layer (22) comprising a first face (22A) and a second face (22B), opposite the first face (22A), the second face (22B) being provided with a coating layer (24), said coating layer (24) comprising a structure formed of a plurality of patterns (25, 26), each pattern (25, 26) extending between a free end (25A, 26A) and a base (25B, 26B), the base (25B, 26B) being formed at the second face (22B) of the support layer (22), a section (S) of each pattern (25, 26) being defined parallel to the second face (22B), and for each pattern (25, 26), the section (S) being variable between a minimum value (S; min) of section at the free end (25A, 26A) of the pattern (25, 26) and a maximum value (S max ) of section at the base (25B, 26B) of the pattern (25, 26). Vehicle assembly (1; 5) according to claim 1, wherein two adjacent patterns (25, 26) of the plurality of patterns are spaced apart by a distance (d1) less than a characteristic distance (a) associated with the base (25B, 26B) of the pattern (25, 26). Vehicle assembly (1; 5) according to claim 1 or 2, wherein each pattern (25, 26) of the plurality of patterns has a height (h) less than one tenth of a wavelength of the radar waves. Vehicle assembly (1; 5) according to any one of claims 1 to 3, wherein the coating layer (24) comprises a polymeric material. Vehicle assembly (1; 5) according to any one of claims 1 to 4, wherein the coating layer (24) comprises polyurethane. Vehicle assembly (1; 5) according to any one of claims 1 to 5, wherein the patterns (25, 26) of the plurality of patterns are equally distributed on the second face (22B). Vehicle assembly (1; 5) according to any one of claims 1 to 5, wherein the patterns (25, 26) of the plurality of patterns are randomly distributed on the second face (22B). Vehicle assembly (1; 5) according to any one of claims 1 to 7, in which each pattern (25, 26) has a pyramidal, or trapezoidal or conical shape. Vehicle assembly (1; 5) according to any one of claims 1 to 8, wherein the first face (22A) of the support layer (22) is provided with a further covering layer (27), said further covering layer (27) comprising a further structure formed of a plurality of further patterns (28), each further pattern (28) extending between a further free end (28A) and a further base (28B), the further base (28B) being formed at the first face (22A) of the support layer (22), a further section (S') of each further pattern (28) being defined parallel to the first face (22A), and for each further pattern (28), the further section (S') being variable between a further minimum section value at the other free end (28A) of the pattern (28) and a further maximum section value at the other base (28B) of the pattern (28). Vehicle assembly (1) according to any one of claims 1 to 9, wherein the protective panel (20) is positioned at a distance from the radar sensor (10), the first face (22A) of said protective panel (20) being positioned opposite the radar sensor (10). Vehicle assembly (5) according to any one of claims 1 to 9, wherein the radar sensor (10) is integrated into the support layer (22) of the protective panel (20). Vehicle assembly (1; 5) according to any one of claims 1 to 11, wherein the radar sensor (10) is a millimeter wave or hyperfrequency or microwave radar sensor.

Images