Vehicle component, sensor assembly, motor vehicle, and method and foil kit for improving the transmission of a vehicle

Abstract

The invention relates to a vehicle component (4) comprising a carrier component (6) made of a polymeric material, the carrier component having a first surface (7) and a second surface (8) substantially parallel to the first surface, a first coating (9) applied on the first surface (7) of the carrier component (6), and a second coating (9) applied on the second surface (8) of the carrier component (6). A first coating (10) which is applied to the second surface (8) of the carrier part (6) and has a first reflectance R1 for electromagnetic waves (5) of a predetermined frequency spectrum, in particular radar waves (5a, 5b), and a second coating (10) which is applied to the second surface (8) of the carrier part (6) and has a second reflectance R2 for electromagnetic waves (5) of a predetermined frequency spectrum. In this case, the second reflectance R2 is adapted to the first reflectance R1, such that the carrier part (6), the first coating (9) and the second coating (10) form a resonator (11) for the electromagnetic waves (5). The invention further relates to a sensor assembly, a motor vehicle and a method for improving the transmittance of a vehicle component.

Description

[0001] The invention relates to a vehicle component comprising a support component, a sensor assembly comprising a vehicle chassis, at least one emitter and a detector arranged at the vehicle chassis, and a vehicle component arranged in the region of the emitter and / or the detector, a motor vehicle having at least one radar-based distance sensor, and a method and a foil set for improving the transmittance to electromagnetic waves of a predetermined frequency, in particular radar waves.

[0002] DE 10 2009 029 763 A1 discloses a body plastic component for a motor vehicle, which has a carrier with a plastic base body. A paint, in particular a paint having at least two effect paint layers, can be applied to the base body. The body plastic component has a radiation attenuation effect in the radar frequency range between 75 GHz and 85 GHz, at least in the radar transparent band, with a value of less than 3 dB in the case of a single pass.

[0003] It is an object of the present invention to describe an alternative, preferably particularly simply constructed vehicle component, a sensor arrangement and a method for producing the same which contribute to the transmission of electromagnetic waves, in particular radar waves, of a predetermined frequency through the vehicle component in a manner that is as loss-free as possible.

[0004] According to a first aspect of the present disclosure, a vehicle component is described. The vehicle component comprises:

[0005] a support component made of a polymer material, the support component having a first surface and a second surface substantially parallel to the first surface;

[0006] a first coating applied to the first surface of the support component, the first coating having a first reflectivity R1 for electromagnetic waves of a predetermined spectrum, in particular radar waves; and

[0007] A second coating is applied to at least one section of the second surface of the support component, the second coating having a second reflectivity R2 for electromagnetic waves of a predetermined spectrum, wherein the second reflectivity R2 is adapted to the first reflectivity R1, so that the support component, the first coating and the second coating constitute a resonator for the electromagnetic waves.

[0008] The first coating can be a lacquer layer or a painted or pigmented plastic foil. The plastic foil can be pigmented with effect pigments, for example. The foil is generally self-adhesive and can be easily bonded to the corresponding vehicle component.

[0009] The inventors have learned, among other things, that by applying an additional reflective layer on a second surface of the vehicle component (e.g. a crash buffer), in particular on the back side of a support component painted or foiled on the front side, a resonator for electromagnetic waves, in particular radar waves, can be formed, and this can lead to an increased transmittance or reduced reflectivity of the vehicle component for electromagnetic waves in a predetermined spectrum or in a range around a given operating frequency or center frequency. To this end, the reflectivity R2 of the coating is adapted to the reflectivity R1 of the first coating of the first surface, for example for a given operating frequency or center frequency or the entire spectrum.

[0010] In at least one embodiment, the vehicle component has a transmittance of more than 50 percent, preferably more than 80 percent, for example in a range between 60 and 100 GHz, in particular between 75 and 85 GHz. This spectrum is used, among other things, for radar-based collision avoidance and / or adaptive cruise control.

[0011] In at least one embodiment, the support part can be made of a plastic material and have a thickness in the range of 1.5 to 5 mm. Such a material thickness achieves the rigidity required in vehicle construction and is at the same time in the order of magnitude of the wavelength of the radar waves.

[0012] In at least one embodiment, the first coating has an effect paint layer with effect pigments, which has a thickness of, for example, between 12 and 20 μm. Together with other paint layers, such as a primer and base paint layer located therebelow and a clearcoat layer located thereon, the first coating has a total thickness of between 80 and 130 μm. Such paint layers and paint layer thicknesses achieve the desired appearance in vehicle construction and have a reflectivity that allows a resonator construction to be achieved.

[0013] In at least one embodiment, the second coating has the same structure as the first coating.By applying the reverse lacquer layer, the equivalence of the two coatings can be ensured particularly easily, for example by also applying the same lacquer with the same thickness to the second side of the vehicle component.

[0014] In at least one embodiment, the second coating comprises a thin metallized plastic or metal foil which is bonded to the back of the vehicle component. Such a vehicle component can be produced particularly simply and cost-effectively by bonding foil sections with the desired reflectivity. In this case, the use of a preferably self-adhesive foil also allows simple retrofitting of existing vehicle components, for example after determining the reflectivity of a paint layer present on the first surface.

[0015] Such a vehicle component is particularly suitable for manufacturing a sensor assembly, wherein at least one transmitter for emitting electromagnetic waves of a predetermined frequency, in particular radar waves, and at least one detector arranged to detect electromagnetic waves of a predetermined frequency, in particular reflected radar waves, are arranged on the vehicle chassis, and the transmitter and the detector are covered by the vehicle component.

[0016] Such a vehicle component or such a sensor arrangement is suitable in particular for use in a motor vehicle having a radar-based sensor.

[0017] According to another aspect of the present disclosure, a method for improving the transmittance of a vehicle component to electromagnetic waves of a predetermined frequency, especially radar waves, is disclosed. The method comprises the following steps:

[0018] determining the reflectivity of a first coating of a first surface of a vehicle component, in particular a paint layer applied on an outer side of the vehicle component; and

[0019] A second coating is applied to at least a section of a second surface of the vehicle component which is arranged opposite the first surface, wherein the reflectivity of the second coating is matched to the reflectivity of the first coating.

[0020] According to another aspect of the disclosure, a foil set for improving the transmittance of electromagnetic waves, especially radar waves, of a predetermined frequency is disclosed. The foil set comprises a plurality of self-adhesive sections of a metal foil or a metallized plastic foil, wherein the sections differ in their reflectivity and optionally in their thickness. Such a foil set is advantageous for manufacturing a vehicle component or a sensor assembly of the above-mentioned type in a simple manner, especially by selecting foil sections with appropriate physical properties.

[0021] Further designs and advantages of the disclosed invention are disclosed in the subsequent description of exemplary embodiments and in the appended claims.

[0022] The present invention will be described in detail below with reference to the accompanying drawings with the aid of different embodiments.

[0023] Figure 1 A schematic diagram showing a sensor assembly;

[0024] Figure 2 shows a cross section through a vehicle component according to a design of the present disclosure;

[0025] Figures 3A to 4B shows different samples used to determine the transmittance and reflectance of coated polymer materials;

[0026] Figures 5A to 7B shows the measurement scheme for samples coated in different ways; and

[0027] Figure 8The steps of a method for improving the transmittance of a vehicle component are schematically shown.

[0028] The vehicle components described below are particularly suitable for covering radar-based sensors. For example, radar-based distance sensors are increasingly being installed in motor vehicles to prevent accidents, improve driving comfort and ultimately enable autonomous vehicles. Other applications are also possible, for example, radar-based sensors are used to detect seeds or liquids in commercial vehicles such as trucks or agricultural machinery. In order to protect the radar wave transmitters and detectors required for this purpose from environmental influences and / or so that the design of the front of the vehicle does not cause aerodynamic or aesthetic negative effects, radar-based sensors are usually arranged behind vehicle components or covers formed from polymer materials (for example in the form of integrated bumpers of motor vehicles or collision buffers in the lining of commercial vehicles).

[0029] The polymer materials used to produce such vehicle components have only a relatively low reflectivity and a low absorption of radar waves. However, for aesthetic reasons, such vehicle components are generally provided with a lacquer layer or a lacquered, preferably self-adhesive plastic foil or a pigmented, preferably self-adhesive plastic foil, which corresponds to the lacquer layer of the rest of the vehicle. Such plastic foils or lacquer layers, in particular containing metallic effect pigments, have a higher reflectivity and therefore hinder the emission and reception of reflected radar waves.

[0030] Figure 1 A schematic cross section through a sensor arrangement 4 of a motor vehicle (not shown in the remainder), in particular a passenger car or a truck, is shown.

[0031] The sensor assembly 1 comprises a part of the vehicle chassis 2, a radar-based sensor 3 in the form of a distance sensor, and a vehicle component 4 covering the distance sensor 3. This part of the chassis 2 is, for example, the front part of the vehicle made of a metal material. In the illustrated embodiment, the vehicle component 4 is a crash buffer in the form of an integrated bumper made essentially of a polymer material, in particular a plastic material. Alternatively, the vehicle component 4 can also be a simple covering component for the radar-based sensor. Such a covering is also called a radome.

[0032] The distance sensor 3 includes a transmitter 3a for emitting electromagnetic waves 5 of a predetermined spectrum. The spectrum is a continuous frequency range here, such as a frequency range between a maximum frequency and a minimum frequency or a region with a predetermined bandwidth around a given frequency. The transmitter 3a especially emits radar waves 5a in a spectrum between 70 and 80 GHz. Such electromagnetic radar waves 5a are reflected by the vehicle or other obstacles traveling ahead and are transmitted back to the detector 3b of the distance sensor 3 as reflected electromagnetic radar waves 5b. Here, the electromagnetic wave 5 passes through the vehicle component 4 twice. In another embodiment, the transmitter and the detector can also be the same component.

[0033] Although the vehicle component 4 typically has a complex rounded shape, it has surfaces that are substantially parallel to one another, at least in the region where the radar waves 5a or 5b penetrate the vehicle component 4. Figure 1 If the outer surface on the right in the middle is painted with effect paint or bonded with a foil containing effect pigments, a large part of the emitted radar waves 5a and reflected radar waves 5b are reflected by the vehicle component 4, so that the signal-to-noise ratio of the distance sensor 3 is significantly reduced. In particular, the part of the emitted radar waves reflected back inwards can interfere with the sensor or even completely saturate the sensor.

[0034] Figure 2 Show according to Figure 1 An enlarged partial view of a vehicle component 4. It should be noted that Figure 2 The illustrations in FIG. 4 are for illustration purposes only and do not represent the actual scale of the vehicle component 4 .

[0035] according to Figure 2 The vehicle component 4 has a support part 6 with two surfaces 7 and 8 that are parallel to each other. In the embodiment shown, Figure 2 Surface 7 on the middle right diverges Figure 2 The second surface 8 which is arranged opposite to the distance sensor 3 and which is not shown in the figure faces the distance sensor 3. Therefore, the first surface 7 is typically the outer side of the vehicle component 4 and the second surface 8 is the inner side of the vehicle component 4.

[0036] A first coating 9 is arranged on the first surface 7. The first coating is, for example, a paint layer or foil 12 comprising a plurality of effect pigments 13. The effect pigments 13 provide, in particular, aesthetically attractive effects of the paint layer 12 (e.g., metallic effects, brightness changes and / or color changes (farbflop), actual glittering effects). The effect pigments 13 are, for example, metallic effect pigments in the form of microscopic aluminum flakes with a thickness of less than 1 μm. Such aluminum flakes can be prepared, for example, by sheet rolling of small aluminum balls and introduced into a suitable carrier paint. In addition to metallic effect pigments, non-metallic effect pigments are also known. Such effect pigments are based on flaky substrates, such as, for example, natural or synthetic mica, talc, SiO2 Thin sheet, Al 2 O 3 Flakes, glass flakes, iron oxide flakes, graphite flakes completely coated with one or more metal oxides. A conductive primer is often also used for the paint layer 12, which reflects another part of the electromagnetic radiation. Without further measures, the coating 12 and in particular the effect pigments 13 contained therein and the primer significantly increase the reflectivity of the first coating 9. As a result, a large proportion of the electromagnetic waves 5 that strike the vehicle component 4 can be reflected.

[0037] In order to reduce or completely prevent this effect, a second coating 10 is arranged on the second surface 8. In this embodiment, the second layer 10 is, for example, an adhesive foil, in particular a self-adhesive metal foil or a metallized plastic foil 14. When using a metallized plastic foil 14, a controlled shift of the resonance frequency can also be achieved by controlling its thickness.

[0038] like Figure 2 As shown in , the second coating 10 does not necessarily cover the entire second surface 8 of the vehicle component 4. It is sufficient that the second coating 10 is arranged at least in the section 15 of the second surface 8 that should be penetrated by the electromagnetic waves 5, that is, for example, in the area of ​​the vehicle component 4 located behind the distance sensor 3. Alternatively, the second coating 10 can also cover the entire second surface 8.

[0039] The second coating 10 is adapted in its reflectivity exactly to the reflectivity of the first coating 9. The first coating 9, the support part 6 and the second coating 10 thus together form a resonator 11.

[0040] If the resonator 11 is adapted in its dimensions to the frequency of the electromagnetic wave 5, the resonator 11 as a whole has a reflectivity which is significantly reduced in relation to the reflectivity of the individual layers 9 and 14. In other words, the electromagnetic wave 5 can penetrate the vehicle component 4 substantially unimpeded. In other words, in the resonance region, the vehicle component 4 is substantially transparent to the electromagnetic wave 5.

[0041] In this embodiment, the support part 6 made of polymer material has a thickness D of, for example, 2 to 3 mm. The first layer 9 or the second coating 10 has a thickness of about 20 μm and has a reflectivity of about 10 to 20 percent for a frequency of 70 to 80 GHz, which is typical for radar-based distance sensors. This corresponds to a wavelength of about 4.28 to 3.75 mm in air. Therefore, a thickness D of the support part 6 of about 2 mm corresponds approximately to half the wavelength of the electromagnetic wave 5.

[0042] The resonator 11 essentially forms a relatively weak Fabry-Perot interferometer, for example with a resonator quality factor of less than 100, in particular less than 20, for example 15 or 10. In this case, for the resonator quality factor Q and the resonance frequency f0 and bandwidth Δf applies is:

[0043]

[0044] The transmission maximum can be found at multiples of the half wavelength λ:

[0045]

[0046] Here, n is the refractive index of the material used, and m is a positive natural number.

[0047] The transmission T of the Fabry-Perot interferometer depends, among other things, on the first reflectivity R1 of the first coating 9 and the second reflectivity R2 of the second coating 10. When the absorption losses are neglected, the following applies for the maximum transmission of the resonator in the resonance case:

[0048]

[0049] Above or below the resonance frequency, the transmittance T decreases accordingly. The maximum value of the transmittance T reaches 100 percent of the theoretical value when the two surfaces 7 and 8 of the support part 6 have the same reflectivity for the electromagnetic waves 5 used by the distance sensor 3, that is, when R1=R2. In addition, in practice, the actual transmittance T is reduced due to absorption losses, for example, absorption losses of the polymer material of the support part 6 and other components of the coatings 9 and 10. However, such losses are small enough in practice and do not significantly affect the functionality of the distance sensor 3.

[0050] One possibility of adapting the reflectivities R1 and R2 of the coatings 9 and 10 to one another is to first determine the reflectivity R1 of the coating 12. To this end, the vehicle component 4 painted on one side can first be measured. Then, for example, a foil can be selected from metallized plastic foils 14 of different thicknesses in some cases, whose reflectivity R2 is close to the reflectivity R1 of the first coating 9. Optionally, a desired resonance range shift in some cases can be achieved by selecting its thickness. The selected foil 14 is then glued to the back side 8 of the carrier component 6.

[0051] For this purpose, for example, a foil set with multiple foil sections with different physical properties can be used. These foil sections can for example be arranged and marked in a matrix form, wherein the foil sections in a column have different reflectivities and the same thickness, and the foil sections in a row have the same reflectivity and different thicknesses.

[0052] One possibility for adapting the reflectivities R1 and R2 of the coatings 9 and 10 to one another is to provide the carrier part 6 with a similar paint layer on both sides. As mentioned above, the painting is carried out only in the region 15 of the sensor 3 or over the entire surface.

[0053] In order to ensure the above effects, a total of five different samples were prepared. Figures 3A to 4B The structures of four of the five samples are shown in Figure .

[0054] Sample 0F0R consists of a plastic plate not shown in the figure, which is not coated on both sides. The plastic plate is a 3 mm thick polycarbonate plate with electromagnetic properties similar to plastics such as those used in crash buffers, and is available under the trade name

[0055] according to Figure 3A Sample 2F0R has not only a single-sided, single-layer paint layer 12, which has a thickness of about 13 μm on the first surface 7. Such a thickness is typical for painted motor vehicle parts 4. The paint used contains aluminum pigments in a concentration of about 18% by mass in the solid paint (18% PMC aluminum effect pigments), which corresponds to a very high pigmentation of the metallic paint layer of a motor vehicle. This sample was used, among other things, to demonstrate the reflection or transmission behavior of a conventional vehicle part 4 that is painted only on one side.

[0056] according to Figure 3B The sample 2F2R of FIG. 1 was coated on both sides with a single layer of lacquer 12 with a thickness of approximately 13 μm. For this purpose, the two surfaces 7 and 8 of the carrier part 6 were painted with the same vehicle paint comprising metallic effect pigments 13 .

[0057] Figure 4A and 4B Two further samples 4F0R and 4F4R are shown, whose surfaces 7 and 8 are provided with a double lacquer layer 12 with a total thickness of about 27 μm. Figure 4A In the sample 4F0R of Figure 4B In sample 4F4R, the first surface 7 and the second surface 8 were painted in the same manner.

[0058] exist Figure 5A and 5B In the figure, firstly as a percentage value or as a corresponding signal reduction in decibels, the uncoated plastic plate according to sample 0F0R and the uncoated plastic plate according to sample 0F0R are shown. Figure 3A The transmittance or reflectivity of the plastic plate 2F0R coated on one side. Figure 5A As can be seen in Figure 1, uncoated plastic material has a reflectivity of 0 to 20 percent and a transmittance of approximately 75 to 95 percent in the relevant spectrum between 60 and 90 GHz. The minimum reflectivity is in the spectrum below 65 GHz, which is typically not used by radar sensors. Values ​​below 100 percent can be explained in particular by absorption caused by the plastic material.

[0059] By applying a single layer of lacquer 12, as in Figure 3A As shown in FIG. 1 , the minimum of the reflection is shifted to about 83 GHz. In contrast, the maximum is located in the range between 64 and 77 GHz, with a reflectivity of about 30 to 40 percent, while the transmittance decreases to about 55 to 65 percent.

[0060] exist Fig. 6A and 6B In, according to Figure 3A and 3B The transmission behavior or reflection behavior measured by the two samples 2F0R and 2F2R is opposite to each other. Fig. 6A and 6B As can be seen in the figure, the transmittance has a maximum value of more than 85 percent at a frequency of 77 GHz. Correspondingly, the reflection at this frequency has a minimum value of close to 0 percent (-24 dB). Therefore, the vehicle component 4 causes practically no interfering reflections in the spectrum typical for radar sensors. In addition, the transmitted signal proportion is significantly increased, so that the signal-to-noise ratio is significantly improved.

[0061] Among other things, Fig. 6A As can be seen from the figure, there is a continuous frequency range in which the reflection of the double-coated sample 2F2R is significantly less than the reflection minimum of the single-coated sample 2F0R. Equivalently, the transmission is significantly higher in this area. In this shaded area between 74 and 79 GHz, radar-based distance sensors can operate reliably.

[0062] exist Fig. 7A and 7B It is shown that according to Figure 4A and 4B Corresponding measurement results of samples 4F0R and 4F4R. As can be seen therein, due to the doubling of the paint layer 12, the transmission maximum or reflection minimum is shifted to lower operating frequencies, especially in the region of 72 GHz. Although the reflectivity of the double paint layer is significantly increased, the reflection minimum in the 72 GHz range is only a few percent and is therefore also suitable for radar-based distance sensors 3. In addition, the reflected signal ratio of sample 4F4R, which is painted on both sides, is lower with approximately -14 dB (e.g. 10 dB) than the reflected signal ratio of sample 4F0R, which is only painted on one side, with approximately -4 dB.

[0063] Will Figures 6A to 7B Taken together, it can be seen that the resonance frequency of the vehicle component 4 can be matched to the frequency of the electromagnetic waves 5 used, in particular the radar waves 5a and 5b, by matching the thickness of the paint layer 12. The thickness D of the carrier component 6 is used as a further optimization parameter.

[0064] When the reflectivity R2 of the second coating 10 is selected to be slightly less than the reflectivity R1 of the first coating 9 to at least partially compensate for the absorption caused by the support component 6, the reflectivity or transmittance of the coated vehicle component 4 can be further optimized. For example, the reflectivity R2 of the second coating 10 is about 80 to 99 percent, preferably 90 to 98 percent, for example 95 percent of the reflectivity R1 of the first coating 9.

[0065] Figure 8 The steps of a method for improving the transmittance of a vehicle component 4 are schematically shown.

[0066] like Figure 8 As shown in FIG. 1 , in a first step S1 , the reflectivity R1 of the first coating 9 is first determined.

[0067] As described above, this can be done by measuring the vehicle component 4 that has been painted on one side or based on knowledge of the relevant parameters for production (especially the transmission behavior, reflection behavior and absorption behavior of the materials used, the carrier component 6 and the thickness of the first coating 9). In this case, the reflectivity R1 of the vehicle component 4 can be obtained by a corresponding theoretical model or with the help of a known measurement series. Finally, it is also possible to detect only the parameters for painting without explicitly detecting the first reflectivity R1.

[0068] In a further step S2 , a second coating 10 is applied to the oppositely arranged surface 8 , wherein the reflectivity R2 of the second coating 10 is selected such that it substantially corresponds to the first reflectivity R1 .

[0069] As already explained above, this can be done by gluing corresponding foil sections to the second surface 8 (in particular a self-adhesive metallized plastic foil 14) or by painting at least one section 15 of the second surface 8. If essentially the same parameters (such as the layer thickness of the paint layer) are selected for the painting, an explicit determination of the reflectivity can be omitted in practice, since the reflection type of such a paint layer 12 is substantially uniform.

[0070] List of Reference Numerals

[0071] 1Sensor assembly

[0072] 2 Chassis

[0073] 3D Distance Sensor

[0074] 3a Transmitter

[0075] 3b Detector

[0076] 4 Vehicle Parts

[0077] 5Electromagnetic waves

[0078] 5a (Emitted) Radar Wave

[0079] 5b (Reflected) radar wave

[0080] 6 Bracket parts

[0081] 7 First Surface

[0082] 8 Second Surface

[0083] 9. First coating

[0084] 10 Second coating

[0085] 11Resonator

[0086] 12 coats of paint

[0087] 13 Effect pigments

[0088] 14Metalized plastic foil

[0089] 15 Section (of the second surface 8)

[0090] S1, S2 Method Steps

[0091] D Thickness of bracket part

Claims

1. Vehicle parts (4), including: A support component (6) made of a polymer material, the support component having a first surface (7) and a second surface (8) substantially parallel to the first surface; a first coating (9) applied to the first surface (7) of the support component (6), the first coating having a first reflectivity R1 for electromagnetic waves (5), in particular radar waves (5a, 5b), of a predetermined spectrum; as well as A second coating (10) is applied to at least one section (15) of the second surface (8) of the support component (6), the second coating having a second reflectivity R2 for electromagnetic waves (5) of a predetermined spectrum, wherein the second reflectivity R2 is adapted to the first reflectivity R1, so that the support component (6), the first coating (9) and the second coating (10) constitute a resonator (11) for the electromagnetic waves (5). 2 . The vehicle component ( 4 ) according to claim 1 , wherein the first reflectivity R1 and the second reflectivity R2 differ in value from one another by at most 20 percent, preferably by less than 10 percent.

3. The vehicle component (4) according to claim 1 or 2, wherein the predetermined frequency spectrum lies in a range between 60 and 100 GHz, in particular between 75 and 85 GHz.

4. The vehicle component (4) according to at least one of claims 1 to 3, wherein the vehicle component (4) has a transmittance greater than 50 percent, preferably greater than 80 percent and / or a reflectivity less than 10 percent, preferably less than 5 percent for the predetermined spectrum.

5. The vehicle component (4) according to at least one of claims 1 to 4, wherein the bracket component (6) has a thickness (D) in the range between 1.5 and 5.0 mm, in particular in the range between 1.85 and 2.15 mm or 3.70 and 4.3 mm. 6 . The vehicle component ( 4 ) according to claim 1 , wherein the first coating ( 9 ) is a lacquer layer or a painted or pigmented plastic foil.

7. The vehicle component (4) according to at least one of claims 1 to 6, wherein the first coating (9) and / or the second coating (10) has a thickness in the range between 80 and 130 μm. 8 . The vehicle component ( 4 ) according to claim 1 , wherein the first coating ( 9 ) contains effect pigments ( 13 ), in particular metallic effect pigments.

9. The vehicle component (4) according to at least one of claims 1 to 8, wherein the second coating (10) has substantially the same structure, composition and thickness as the first coating (9). 10 . The vehicle component ( 4 ) according to claim 1 , wherein the second coating ( 10 ) comprises a metal foil or a metallized plastic foil ( 14 ). 11 . The vehicle component ( 4 ) according to claim 1 , wherein the vehicle component is designed as a crash buffer and / or as a cover for a sensor assembly.

12. A sensor assembly (1), comprising: - vehicle chassis (2); at least one transmitter (3a) arranged on the vehicle chassis (2) for emitting electromagnetic waves (5), in particular radar waves (5a), of a predetermined spectrum; - at least one detector (3b) arranged at the vehicle chassis (2) for detecting electromagnetic waves (5), in particular reflected radar waves (5b), in the predetermined spectrum; and A vehicle component (4) according to any one of claims 1 to 11, arranged in the region of the emitter (3a) and / or detector (3b).

13. A motor vehicle having at least one radar-based sensor, in particular a distance sensor (3), wherein the radar-based sensor is arranged behind a vehicle component (4) according to any one of claims 1 to 11, and wherein the first coating (9) of the vehicle component (4) has a paint layer (12) applied to the outer side of the vehicle and the second coating of the vehicle component (4) faces the radar-based sensor.

14. A method for improving the transmittance of a vehicle component (4) for electromagnetic waves (5), in particular radar waves (5a, 5b), of a predetermined spectrum, the method comprising: - determining (S1) the reflectivity R1 of a first coating (9) of a first surface, in particular a paint layer or a pigmented or painted plastic foil (12) applied to the outer side of the vehicle component (4); as well as - applying (S2) a second coating (10) in at least one section (15) of a second surface (8) of the vehicle component (4) arranged opposite the first surface (7), wherein the reflectivity R2 of the second coating (10) is matched to the reflectivity R1 of the first coating (9).

15. The method according to claim 14, wherein the determining step (S1) comprises: - determining the layer thickness of the first coating (9); and / or - measuring the reflectivity R1 of a first coating (9) applied on a support component (6) of the vehicle component (4).

16. The method according to claim 14 or 15, wherein the applying step (S2) comprises: - painting the second surface (8), in particular the at least one section (15) of the inner side of the vehicle component (4), in particular using a paint having effect pigments (13); and / or - bonding a self-adhesive metal foil or metallized plastic foil (14) to the at least one section (15).

17. A foil set for improving the transmittance for electromagnetic waves (5), in particular radar waves (5a, 5b), of a predetermined spectrum, wherein the foil set comprises a plurality of self-adhesive sections of a metal foil or a metallized plastic foil (14), wherein the sections differ in their reflectivity and optionally in their thickness.

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