GB2563619A - Surface treating method for a body panel component of a vehicle - Google Patents

Abstract

A body panel component 51 of a vehicle comprises a first surface 26 and a second surface 28 respectively comprising a first coating layer 52 providing a first reflectivity and a second coating layer 54 providing a second reflectivity, wherein the first and second reflectivities are substantially matched, preferably for incident electromagnetic radiation of a predetermined frequency greater than 76 GHz. The second surface coating layers may comprise a reflective layer that is preferably a metallic or pearlescent paint comprising reflective particles or may comprise a self-supporting film. The second surface coating layer may include a primer coating layer, a colour coating layer and a protective coating layer. The overall thickness of the component is preferably an odd integer multiple of one quarter of an effective wavelength of incident electromagnetic radiation. The component may be a bumper panel component (4, 6, figure 1). An antenna installation comprises the body panel component and a radar antenna 2. In a method of surface treating a body panel component of a vehicle, a reflective layer may be added as a fluid medium.

Description

SURFACE TREATING METHOD FOR A BODY PANEL COMPONENT OF A VEHICLE

TECHNICAL FIELD

The present disclosure relates to a surface treating method for a body panel component of a vehicle. Aspects of the invention relate to a surface treating method, a body panel component, to an antenna installation and to a vehicle.

BACKGROUND

Modern vehicles are equipped with a range of sensors or other sensing components and advanced driver assistance systems (ADAS). These sensors, components and ADAS increasingly use radar technology to identify objects and understand the vehicle’s environment. As such, radar antennas are conveniently fitted around a perimeter of the vehicle to monitor the areas of the vehicle which are less visible to the driver. These antennas are commonly positioned behind the body panel components of the vehicle.

However, whilst offering many advantages, radar systems can be challenging to implement effectively. For example, their installation behind a body panel component, such as a bumper panel, can mean that radar energy is reflected by the bumper panel in such a manner that it reduces the ability of the radar system to deduce range data for distant objects.

At least in certain embodiments, the present invention has been devised to mitigate or overcome at least some of the above-mentioned problems.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide a surface treating method, a body panel component, an antenna installation and a vehicle as claimed in the appended claims.

According to an aspect of the present invention there is provided a surface treating method for a body panel component of a vehicle, the body panel component comprising first and second opposing surfaces, wherein the first surface has one or more first surface coating layers that provide a first reflectivity, the surface treating method including: adding one or more second surface coating layers to at least a portion of the second surface of the body panel component, thereby providing a second reflectivity that substantially matches the first reflectivity provided by the first surface coating layers.

Incident electromagnetic radiation (for example, but not limited to, radio frequency (RF) radiation from an automotive radar) is reflected internally from the first surface of the body panel component and the second surface of the body panel component. By providing a second reflectivity that substantially matches the first reflectivity the combined intensity of the internally reflected radiation can be reduced. As such, the invention is advantageously able to minimise the attenuation loss of incident electromagnetic radiation and the body panel component may be better suited for use concealing an antenna that transmits/receives object detection and ranging signals, such as radar signals. Generally, radar processing algorithms produce warnings at a predetermined “time to collision”. Thus, providing a greater range increases the reliability of the warning because the threat becomes visible earlier.

For the sake of clarity it is understood that by ‘adding’ one or more second surface coating layers to at least a portion of the second surface of the body panel component, it is intended to mean ‘adding’, ‘administering’, ‘spreading’ or otherwise ‘applying’ one or more second surface coating layers either directly onto the second surface or onto another surface coating layer, previously applied or otherwise joined to the second surface, to ‘cover’ or ‘coat’ the underlying layers and/or surface.

Optionally, one or more of the second surface coating layers are added to a selected zone of the second surface.

Optionally, one or more of the second surface coating layers are added to substantially the entirety of the second surface.

In an embodiment, the second surface coating layers include a reflective layer having a reflectivity of at least 20%.

Additionally, the reflective layer may comprise reflective particles, which may be metallic or ‘mica’ i.e. silicate, particles.

In an embodiment, the reflective layer is a metallic paint or a pearlescent paint.

Optionally, the reflective layer is added to a selected zone of the second surface.

Optionally, the reflective layer is added as a fluid medium.

Optionally, the reflective layer is added as a self-supporting film.

In an embodiment, the second surface coating layers comprise one or more of a colour coating layer, a primer coating layer, and a protective coating layer.

In an embodiment, the first surface coating layers comprise a primer coating layer, a colour coating layer and a protective coating layer.

Including a protective coating layer, also known as a gloss coating layer, on a patch of the first and/or second surface can also help reduce the adherence of dirt that could also degrade the radar performance. The primer coating layer is equally known as a primer coat and the colour coating layer may commonly be referred to as a base coat layer.

Additionally, one of the primer coating layer, the colour coating layer and the protective coating layer may be a reflective layer having a reflectivity of at least 20%.

Additionally, the colour coating layer may be the reflective layer.

In an embodiment, one or more of the first surface coating layers are added to the first surface contemporaneously with the addition of one or more respective second surface coating layers that are added to the second surface.

In an embodiment, the second surface coating layers are the same as the first surface coating layers.

The second reflectivity may, for example, substantially match the first reflectivity for incident electromagnetic radiation of a predetermined frequency.

In an embodiment, the predetermined frequency is greater than 76GHz.

Additionally, the predetermined frequency may be less than 79GHz.

Optionally, the first and second opposing surfaces of the body panel component are substantially parallel.

According to another aspect of the present invention there is provided a body panel component of a vehicle, the body panel component comprising first and second opposing surfaces, the first surface bearing one or more first surface coating layers that provide a first reflectivity and the second surface bearing one or more second surface coating layers that provide a second reflectivity, wherein the second reflectivity substantially matches the first reflectivity.

Note that preferred and/or optional features of the previously described aspect of the invention may also relate to this aspect of the invention.

Optionally, one or more of the second surface coating layers coat substantially the entirety of the second surface.

Optionally, one or more of the second surface coating layers coat a selected zone of the second surface.

Optionally, the second surface coating layers include a reflective layer having a reflectivity of at least 20%.

Optionally, the reflective layer of the second surface coating layers comprises reflective particles.

Optionally, the reflective layer of the second surface coating layers is a metallic paint or a pearlescent paint.

Optionally, the reflective layer coats a selected zone of the second surface.

Optionally, the reflective layer of the second surface coating layers comprises a self-supporting film.

Optionally, the second surface coating layers include one or more of a primer coating layer, a colour coating layer and a protective coating layer.

Optionally, the first surface coating layers includes a primer coating layer, a colour coating layer and a protective coating layer.

Optionally, one of the primer coating layer, the colour coating layer and the protective coating layer is a reflective layer having a reflectivity of at least 20%.

Optionally, the colour coating layer is the reflective layer.

Optionally, the first surface coating layers are the same as the second surface coating layers.

Optionally, the second reflectivity substantially matches the first reflectivity for incident electromagnetic radiation of a predetermined frequency. The predetermined frequency may be greater than 76GHz. The predetermined frequency may be less than 79GHz.

In an embodiment, an overall thickness of the body panel component is tuned to an effective wavelength of incident electromagnetic radiation. A tuned body panel component has a thickness which is selected to ensure that incident electromagnetic radiation is reflected from the first surface in anti-phase with incident electromagnetic radiation that is reflected from the second surface, for an optimal angle of incidence. Optionally, the optimal angle of incidence is normal to the first and/or second surface.

Optionally, the overall thickness of the body panel component is an odd integer multiple of one quarter of the effective wavelength of the incident electromagnetic radiation.

In an embodiment, the first and second opposing surfaces of the body panel component are substantially parallel.

Optionally, the body panel component of the vehicle is a bumper panel component.

According to another aspect of the present invention there is provided an antenna installation of a vehicle, the antenna installation comprising the body panel component as described in a previous aspect of the invention and a radar antenna.

Optionally, the radar antenna is configured to transmit a radar signal and the body panel component is arranged to at least partially conceal the radar antenna, such that, a radar signal transmitted from the radar antenna travels through the body panel component before radiating outward.

According to another aspect of the present invention there is provided a vehicle comprising the body panel component as described in a previous aspect of the invention, or the antenna installation as described in another previous aspect of the invention.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows schematically a vehicle including a body panel component in accordance with an embodiment of the present invention;

Figures 2(a) and 2(b) show the functional operation of an advanced driver assistance system of the vehicle shown in Figure 1;

Figure 3 shows schematically a signal processing system configured to control the advanced driver assistance system shown in Figure 2;

Figure 4 illustrates thin-plate interference effects as a transmitted signal passes through a body panel component;

Figure 5 is a graph that plots attenuation loss against the thickness of a body panel component

Figure 6 illustrates the thin-plate interference effects when the thickness of the body panel component is tuned to the transmitted signals;

Figure 7 illustrates the presence of high reflectivity surface coatings on a body panel component and their effect on thin-plate interference;

Figure 8 shows an antenna installation within a vehicle and signal transmission from the antenna through a cross section of a body panel component in accordance with an embodiment of the present invention;

Figure 9 identifies the parameters of the body panel component and antenna installation which may be varied to tune the body panel component of Figure 8 and minimise attenuation loss; and

Figure 10 illustrates a surface treating method of a body panel component in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION

Certain embodiments of the present invention relate to an antenna installation within a vehicle, wherein a body panel component of the vehicle is used to conceal the antenna that transmits and/or receives object detection and ranging signals which generate data for use by an advanced driver assistance system of the vehicle. The body panel component may, for example, be any suitable body panel component which combines with other body panel components to form the exterior bodywork of the vehicle. In contrast to the prior art, the body panel component is suitably treated to provide substantially matching reflectivity between its opposing interior and exterior surfaces. The thickness of the body panel component may be tuned or optimised to the effective wavelength of the antenna signals. Matching the reflectivity and selecting the appropriate thickness optimises the body panel component for use concealing the antenna.

Figure 1 shows a vehicle 1 equipped with antennas 2, mounted behind a front bumper 4 body panel component and a rear bumper 6 body panel component of the vehicle 1. The antennas 2 are able to transmit and receive signals, for example radar signals, that can be used to determine the proximity and relative velocity of objects within the vehicle’s environment. Signals received at the antennas 2 are fed to an electronic control unit (ECU) 8 of the vehicle 1 where they provide data which informs the operation of an ADAS of the vehicle 1. Accordingly, the ECU 8 connects to one or more in-vehicle modules, such as a visual display unit (VDU) 10 or a braking system 12, which may be activated in response to a detected object. Optionally, the VDU is comprised within an infotainment system or Human Machine Interface (HMI) of the vehicle. Alternatively, the ECU 8 may communicate with additional ECUs of the vehicle which are configured to arbitrate between data collected from various sensors, including the antennas 2, to determine an appropriate response.

Figures 2(a) and 2(b) illustrate a vehicle 1, of the type shown in Figure 1, situated in various common driving scenarios. In Figure 2(a), the vehicle 1 is shown driving along a road in a first lane 14 with a second vehicle 16 in an adjacent lane. A portion of the second vehicle 16 is alongside the vehicle 1, such that a front bumper 18 of the second vehicle 16 is alongside the rear bumper 6 of the vehicle 1. The driver of the vehicle 1 may be unable to see the second vehicle 16; given its position in a blind spot of the vehicle 1.

However, in use, the antennas 2 transmit signals, for example radar signals, some of which are incident upon the second vehicle 16 and are reflected by the surface of the second vehicle 16 back at the antennas 2. The antennas 2 receive the reflected signals and transfer the reflected signals to the ECU 8 which is able to determine the proximity of the second vehicle 16.

As a result, an ADAS operated by the ECU 8 may be able to inform the driver of the presence of the second vehicle 16 and improve the driver’s situational awareness. For example, the ECU 8 may command the VDU 10 to indicate the presence of the second vehicle 16 by illuminating a symbol on the dashboard and/or producing an audible alert.

In Figure 2(b) the vehicle 1 is shown approaching a second vehicle 16 which is moving at a slower speed. The antennas 2 at the front bumper 4 transmit signals, for example radar signals, and receive reflected signals from the second vehicle 16 to determine the relative proximity and velocity of the second vehicle 16. This information can be used to operate an ADAS of the vehicle 1. The ADAS may control the brakes and/or issue a warning to change the speed or direction of the vehicle 1 if, for example, the second vehicle 16 suddenly starts braking.

Figure 3 illustrates a signal processing system 20 which generates object detection and ranging data which may be used to operate the ADAS of the vehicle 1 shown in the previous figures. For example, the ECU 8 may utilise the antennas 2 to transmit signals 22 and receive reflected signals 24 from the second vehicle 16 or other objects. The reflected signals 24 are delivered back to the ECU 8 which compares the transmitted signals 22 to the reflected signals 24 in order to determine the proximity of the second vehicle 16 or other objects and their relative velocities.

The proximity may be determined by processing the signal information in one or more methods including, but not limited to, time-of-flight measurement or frequency modulation methods. The velocity of the body may be determined, for example, by monitoring changes in proximity measurements with time or by using the Doppler shift principle to analyse the change in frequency between the transmitted and reflected signals 22, 24.

The ECU 8 is further connected to one or more in-vehicle modules, such as the VDU 10 or the braking system 12, which can be used to alert the driver to the detected body and/or slow the vehicle. For example, the ECU 8 may process the signal information and identify an object. In response, the ECU 8 may send a command signal that operates the braking system 12 to slow the vehicle 1.

It should be noted at this point that the implementation shown in Figure 3 depicts one way in which such a system may be embodied, although other arrangements are possible. However, the principle issue is that the ECU 8 provides the functionality of controlling one or more antennas 2, interpreting the signals 22, 24 and providing useful data that can inform the control of further systems of the vehicle 1.

Figure 4 shows a cross section of an antenna installation comprising an antenna 2 and a body panel component 24 of a vehicle 1. The body panel component 24 conceals the antenna 2 which transmits/receives signals for object detection and ranging. For example, the antenna 2 may send radar signals used to generate data for use in an advanced driver assistance system as described previously. In the embodiment of Figure 4, the antenna 2 transmits/receives radar signals at frequencies between 76 -81 GHz, in accordance with the usable bandwidth defined by the European and US legislators, for example the Federal Communications Commission (FCC). One of a plurality of transmitted signals 22 is shown emerging from the antenna 2.

The body panel component 24 may, for example, take the form of the rear bumper panel 6 of the vehicle 1, as shown in Figure 1. Typically this would be fabricated from a plastics material such as polycarbonates, polypropylenes, polyamides or blends thereof. Typically, the body panel component 24 is 2 to 4mm thick to minimise its contribution to the vehicle weight, however, other thicknesses are envisaged.

The body panel component 24 includes a first, exterior surface 26 and an opposing second, interior surface 28. The interior surface 28 of the body panel component 24 faces an interior frame of the vehicle 1 and the exterior surface 26 faces the external environment. Note that the interior frame of the vehicle is not shown here, although its presence is implied, particularly by virtue of the fact that the antenna would be mounted to the frame. The interior surface 28 and the exterior surface 26 may be substantially parallel and the distance between them corresponds to the thickness of the body panel component 24.

The antenna 2 is mounted behind the body panel component 24 such that the antenna 2 is concealed from the external environment and it faces the interior surface 28 of the body panel component 24. In this manner, the body panel component 24 protects the antenna 2 from damaging impacts and adverse weather conditions.

However, the resultant arrangement may be detrimental to the effectiveness of the antenna 2. In some circumstances these body panel components 24 have been observed to cause significant attenuation loss as the signals pass therethrough and may considerably reduce the range and accuracy of the associated signal processing system 20.

These installation issues will now be described in more detail, with reference to Figures 4 to 7. The wavelengths and amplitudes of the signals shown in the subsequent figures are for illustrative purposes only and are not intended to be actual representations of the signals. 1. Attenuation losses due to thin-plate interference.

Figure 4 illustrates a typical installation of an antenna 2 behind a body panel component 24. The thin nature of the body panel component 24 makes it susceptible to thin-plate interference as the transmitted signal 22 travels from the antenna 2, through the body panel component 24 from which it radiates outward.

Initially, the transmitted signal 22 travels towards the interior surface 28 of the body panel component 24. Upon incidence with the interior surface 28, the transmitted signal 22 is partially reflected, producing an internal reflection shown by the first internally reflected signal 30.

Such an internal reflection arises due to the change in medium between the material of the body panel component 24 and the surrounding air. The body panel component 24 may, for example, be comprised of plastic with greater density and a larger refractive index and dielectric constant than air. This causes some of the transmitted signal’s energy to be reflected from the interior surface 28, at the air-plastic interface.

The remaining energy of the transmitted signal 22 continues through the thickness of the body panel component 24 to the exterior surface 26. As the transmitted signal 22 travels to the exterior surface 26 there are small absorption losses within the thickness of the body panel component 24 which transfer energy as heat.

At the exterior surface 26 there is a second plastic-air interface. Consequently, the transmitted signal 22 is partially reflected upon incidence with the exterior surface 26, producing a second internally reflected signal 32.

The second internally reflected signal travels back through the thickness of the body panel component 24 and emerges through the interior surface 28 towards the interior frame of the vehicle 1.

The vast majority of the transmitted signal’s energy passes outside of the body panel component 24. However, the first and second internally reflected signals 30, 32 combine to produce reflection loss of the transmitted signal 22. The reflection loss reduces the intensity of the transmitted signal 22 and can affect various characteristics of the system, such as the effective range and accuracy of the antenna 2. 2. Attenuation loss variation with the thickness of the body panel component.

The attenuation loss varies with the thickness of the body panel component 24 and is considered to be attributable to absorption losses within the thickness of the material and reflection losses as described above.

Figure 5 plots the transmitted signal’s attenuation loss, on the y-axis, against the thickness of the body panel component 24, on the x-axis, for an angle of incidence of approximately zero, i.e. normal incidence. The results are shown for a normal angle of incidence because an appropriate choice of polarisation of the radiation can cause the reflectivity to drop off as the angle of incidence increases, reaching zero at approximately 45 degrees for some materials, due to Brewster’s effect, as would be understood by a skilled person.

The attenuation loss is shown by the dashed line 36 and is formed by the combination of the absorption losses, shown by the solid line 38, and the reflection losses.

The graph shows that attenuation losses due to absorption, hereinafter referred to as absorption losses, increase as the thickness of the body panel component 24 increases. In addition, the attenuation losses due to reflection, hereinafter referred to as reflection losses, vary in a predictable manner with the thickness of the body panel component 24.

Figure 5 shows minimal reflection loss, at specific thicknesses of the body panel component 24, for example at maxima 40, 42, 44. At these maxima 40, 42, 44 the first and second internally reflected signals 30, 32 combine destructively and cancel out with no internal reflection. Similarly, maximum reflection loss is shown for thicknesses, for example at minima 46, 48, 50, that produce first and second internally reflected signals 30, 32 that combine to augment each other with a maximum intensity of internal reflection.

The internally reflected signals 30, 32 combine destructively when they travel towards the interior frame in anti-phase and combine to augment each other when they travel in-phase. Thus, the relative reflection loss is dictated by the phase difference between the first internally reflected signal 30 and the second internally reflected signal 32.

Returning to Figure 4, phase difference between the first and second internally reflected signals 30, 32 is introduced for two reasons. Upon reflection, there is a halfwavelength phase shift of the internally reflected signals 30, 32 due to the change in refractive index and dielectric constant at the interface. Additionally, the second internally reflected signal 32 travels the additional distance from the interior surface 28 to the exterior surface 26 and then back from the exterior surface 26 to the interior surface 28 before it emerges back towards the interior frame of the vehicle 1, that is, the space, chamber or void located between the interior frame and the body panel component 24.

The additional distance introduces phase difference and the amount of phase difference depends on the division of the additional distance travelled by the transmitted signal’s effective wavelength (λθ).

The effective wavelength, (λθ), of the transmitted signal 22 depends on the refractive index of the body panel component 24, as shown. For example, the radar signals that are used in collision avoidance systems are typically emitted at a frequency of 77 GHz. This corresponds to an effective wavelength of approximately 3.9mm in air. However, the body panel components 24 are typically formed from materials that have a higher density and dielectric constant, such as plastics, in which the effective wavelength is proportionately shorter. The plastics have a dielectric constant of approximately 2.5, leading to an effective wavelength in the body panel component 24 of 1.56mm, reducing the effective wavelength of the transmitted signal 22 within the body panel component 24.

Bearing this understanding in mind, Figure 6 illustrates a ‘tuned’ or Optimised’ body panel component 24, wherein the thickness of the body panel component 24 is selected to minimise reflection loss and produce the maxima 40, 42, 44 shown in Figure 5.

Here, the first and second internally reflected signals 30, 32 are shown in anti-phase because the distance travelled by the second internally reflected signal 32 is equal to three and a half effective wavelengths of the transmitted signal 22 (3.5λθ). Comparing this with Figure 4, it will be appreciated that the two internally reflected signals 30, 32 are in anti-phase and they cancel out with no reflection loss. In this instance the thickness of the body panel component 24 is ‘tuned’ or ‘optimised’ to the transmitted signal 22.

The above discussion relates to thin plate interference issues that affect signal transmission through a body panel component. The interference effects have been illustrated to describe how the combined intensity of the internally reflected signals varies between a maximum and a minimum with the thickness of the body panel component.

The subsequent discussion will now explore the increase in the reflection loss when the exterior surface of the body panel component 24 bears one or more high reflectivity surface coating layers. This issue detrimentally affects existing antenna installations.

Figure 7 is similar to Figure 6, but shows the body panel component 24 with an exterior surface 26 that bears one or more high reflectivity surface coating layers 52, such as a metallic paint layer, and an interior surface 28 that does not. The surface coating layers 52 are featured to enhance the visual appearance of the body panel component 24 and provide protection from adverse environmental conditions.

Typically, one of the surface coating layers 52 is a base coat layer which provides the visual properties of colour to the finish of the vehicle 1 and may consist of metallic paint. Metallic paints contain metallic particles that are highly reflective and give a perception of quality that makes them a popular choice.

The base coat layer will typically only be applied to the exterior surface 26 of the body panel component 24 and not the interior surface 28 because the interior surface 28 is rarely visible and does not affect the customer’s perception of the vehicle 1.

Accordingly, cost deterrents, that include the cost of surface coating layers and the machinery used to apply them, discourage equivalent treatments.

As a result, the reflectivity of the exterior surface 26 greatly exceeds the reflectivity of the interior surface 28 and Figure 7 illustrates the resulting impact on the attenuation losses.

The intensity of the second internally reflected signal 32 is much greater than the intensity of the first internally reflected signal 30. In Figure 7 this is illustrated by the relative amplitudes and it is apparent that the combined amplitude of the internal reflections 30, 32 will always be non-zero, producing reflection losses regardless of the phase difference.

The differences in reflectivity also mask the ability for destructive combinations of the first and second internally reflected signals 30, 32 that have been described in relation to Figure 6. This helps to explain the lack of appreciation of these problems in the prior art.

Embodiments of the present invention aim to mitigate at least some of the above mentioned problems by proposing an alternative surface treating method for the body panel components and producing a body panel component which is more suitable for concealing an antenna installation of a vehicle.

Figure 8 illustrates an antenna installation within a vehicle in accordance with the present invention. It shows a cross-section of an antenna 2 and an embodiment of a body panel component 51 of the present invention. It should be noted at this point that the body panel component 51 is substantially similar to the body panel component 24 described previously. For the sake of clarity, the subsequent discussion will focus on the differences and the same reference numerals will be used where appropriate.

The body panel component 51 can be considered as a body panel component 24 that bears one or more surface coating layers 52, 54 on its interior and exterior surfaces 28, 26 following a surface treating method.

For example, the body panel component 51 of the present invention may bear surface coating layers 52, 54 that include an electrocoat layer, a primer coat layer, a colour coat layer and a protective coat layer. Such a combination of layers is typical on a so-called ‘A’ surface of a vehicle.

The electrocoat layer is the innermost layer and is commonly adhered to both interior and exterior surfaces 28, 26 of the body panel component 51 to provide electrical insulation.

The primer coat layer is usually a paint of neutral colour, held on the electrocoat layer by adhesion to cover small defects in the underlying surface and provide a smooth surface that supports the base coat layer.

The colour coat layer or base coat layer provides colour to the finish of the vehicle 1 as described previously and commonly consists of metallic paint. Consequently, the base coat layer is a reflective layer, typically with reflectivity greater than 20% and more commonly with reflectivity greater than 30%, which significantly increases the reflectivity of the interior and exterior surfaces 28, 26 of the body panel component 51 and provides a desirable finish.

The protective coat layer is the outermost layer which adheres to the base coat layer. The protective coat layer is a relatively thick layer and may consist of a clear resin with no pigments, also known as a clear coat layer. The clear coat layer provides a glossy finish and protects the underlying components and layers from scratches and ultraviolet light.

The surface coating layers 54, 52 combine to alter the reflectivity of the interior and exterior surfaces 28, 26. Accordingly, a first reflectivity of the transmitted signal 22 is produced at the exterior surface 26 and a second reflectivity of the transmitted signal 22 is produced at the interior surface 28. In the present invention, the body panel component 51 is characterised in that the first reflectivity and the second reflectivity substantially match.

The first reflectivity is a ratio of the intensity of the second internally reflected signal 32 to the intensity of the transmitted signal 22 and the second reflectivity is a ratio of the intensity of the first internally reflected signal 30 to the intensity of the transmitted signal 22.

As a result, with substantially matching first and second reflectivities, the first and second internally reflected signals 30, 32 are produced with substantially the same intensity, shown in Figure 8 as amplitude. In practice it may be difficult to achieve an exact match of reflectivity, however, for minimum attenuation loss they should match as closely as possible. For example, the reflectivities may substantially match if they are within 5%.

However, the highly reflective surface coating layers 54, 52 increase the intensities of the internally reflected signals 30, 32 and hence the body panel component 51 may optionally be ‘tuned’ to maximise the cancellation. Tuning the body panel component 51 aims to achieve desirable phase difference between the first and second internally reflected signals 30, 32 and minimise the reflection loss.

In Figure 8 the thickness of the body panel component 51 corresponds to the effective wavelength (λθ) of the transmitted signal 22 such that the body panel component 51 has a ‘tuned’ thickness and the first and second internally reflected signals 30, 32 travel in approximate anti-phase. When necessary, the ‘tuned’ thickness may also incorporate the thickness of the surface coating layers 52, 54.

Figure 9 is used to illustrate how the body panel component 51 can be ‘tuned’ to achieve desirable phase difference. It shows the transmitted signal 22, incident upon the interior surface 28 at angle of incidence, ‘0/, and incident upon the surface the exterior surface 26 at second angle of incidence, ‘θ2’, following refraction through the thickness, ‘t’, of the body panel component 51. The first internally reflected signal 30 is produced at the interior surface 28 and the second internally reflected signal 32 is produced at the exterior surface 26.

To closely achieve anti-phase between the first and second internally reflected signals 30, 32 and minimise reflection losses, the overall thickness of the body panel component 51 and, when necessary, the surface coating layers 52, 54 should be:

Where, ‘n’ is any odd integer number, (1, 3, 5, 7...).

In this manner, the second internally reflected signal 32 travels further than the first internally reflected signal 30 and emerges through the interior surface 28 as though it has travelled an additional distance, approximately equal to an odd integer multiple of half of the effective wavelength of the transmitted signal 22 The distance travelled ‘D’ can be approximated by:

As a result, the first and second internally reflected signals 30, 32 should travel in approximate anti-phase, minimising the attenuation loss. Optionally, anti-phase may occur for a desired optimal angle of incidence ‘0/ of the transmitted signal 22 upon the interior surface 28. The position of the antenna 2 relative to the body panel component 24 may be selected to ensure that the optimal angle of incidence ‘0/ corresponds to an optimum angle for detecting external objects.

Matching the first and second reflectivities and tuning the body panel component 51 in this manner optimises it for use concealing the antenna 2. However, it should be noted that a body panel component 51 which has not been tuned to the transmitted signal 22 could still reduce the attenuation to acceptable levels.

There are various surface coating layer arrangements which are capable of achieving substantially matching reflectivity as will now be discussed.

The reflectivity of each surface coating layer may be approximated, for example, by thickness measurements; where the change in reflectivity with thickness is known and a specific thickness corresponds to a certain reflectivity. Similarly, a standardised coating process may be suitably calibrated to ensure the thickness of each surface coating layer and hence the overall reflectivity.

In the embodiment of the invention shown in Figure 8, the interior surface 28 bears matching surface coating layers 54 to the surface coating layers 52 of the exterior surface 26. The composition of each surface coating layer 52, 54 is the same, the method of application is equivalent and the thickness of each layer matches according to paint depth gauge measurements.

In this manner, radar signals reflected from the interior surface 28 are reflected with the same intensity as those reflected from the exterior surface 26. The overall thickness of the body panel component 51 is also ‘tuned; to the effective wavelength (λθ) of the transmitted signal 22.

In another embodiment of the invention, the same advantages may be realised when the exterior surface 26 is substantially covered in the combination of surface coating layers 52 described, but only targeted zones of the interior surface 28 bear the same combination of surface coating layers 54. The targeted zones may be areas through which the transmitted signal 22 is known to pass. In such cases, the interior surface coating layers 54 would provide matching reflectivities between the targeted zones and the exterior surface 26 of the body panel component 51. This may prove to be a more economical method of production as less coating products would be required. As a further example, the interior surface 28 may be substantially covered by a primer coating layer, but only bear the reflective base coat layer at the targeted zones.

In one sense, a perfect match between the surface coating layers of the interior and exterior surfaces 28, 26 would be desirable to minimise the reflection loss. However, the metallic paint is the main contributor to the reflectivity of the surface and it may be the case that acceptable matching of the first and second reflectivities can be achieved when the exterior surface 26 bears the complete combination of surface coating layers 52 but the interior surface 28 only bears a metallic paint layer. The reflectivity of batches of metallic paint should match, within acceptable tolerances, when the same metallic paint layer is used on both the interior and exterior surfaces 28, 26.

The surface coating layers may also take different forms between the interior and exterior surfaces 28, 26. For example, a highly reflective patch of film may be adhered to the interior surface 28 that provides a second reflectivity that substantially matches the first reflectivity of the combination of surface coating layers 52 on the exterior surface 26. That patch may be applied over a large area of the interior surface 28, or in targeted zones, as mentioned above. One benefit of this approach is that the painting process for the body panel component would be unaffected, and a patch could be applied to the interior surface of the component during the vehicle assembly stage or subsequent to fitting an antenna 2 to the vehicle.

In the prior art, the body panel components are generally produced in automated processes which could be adapted to treat a body panel component with surface coating layers in a manner in accordance with the invention.

Accordingly, another aspect of the invention relates to a surface treatment method applied to the body panel component of Figure 8 to produce the body panel component 51. The surface treatment method is arranged to provide substantially matching reflectivity between interior and exterior opposing surfaces 28, 26 of the body panel component 51 and a tuned overall thickness.

Figure 10 describes a detailed embodiment of a surface treating method 60 of the present invention. The surface treating method 60 is designed to accommodate the established surface treatment techniques wherever possible and apply the surface coating layers 52, 54 in a precise manner. The surface coating layers 52, 54 are applied contemporaneously to the interior and exterior surfaces 28, 26.

Quality control in this process may be reliant on thickness measurements, by paint depth gauges, or suitable calibration that ensures sufficient coverage of the body panel component 51 without incurring excessive costs. As a result, the processes are ideally carried out by automated machinery in ‘clean’ environments that maximise the control of the processes and ensure that each layer is within a specified thickness tolerance.

At step 62, the body panel component 51 has been formed in a suitable manufacturing process and is suitably supported ready for surface treatment. For example, the body panel component 51 may be assembled with other body panel components to form the exterior bodywork of the vehicle 1 or the body panel component 51 may be supported on a frame structure alongside other components that are awaiting surface treatment. The body panel component 51 has been pressure washed, degreased and made corrosion resistant by dipping in a phosphate coat. The phosphate coat further provides a bonding layer for an electrocoat layer, which has been applied by another dipping process to insulate the body panel component 51.

In step 62, the electrocoat layer is abrasion treated by sand blasting to roughen the interior and exterior surfaces 28, 26 and prepare the body panel component 51 for the surface treatment.

With the body panel component 51 suitably prepared, it moves to the primer coat station, in step 64, where robotic arms spray a primer coat layer, as a thin vapour, coating the interior surface 28 of the body panel component 51.

Similarly, in step 66, robotic arms spray the primer coat layer over the exterior surfaces 26 of the body panel component 51. In this manner, the primer coat layer substantially covers the entirety of the interior and exterior surfaces 28, 26 of the body panel component 51. However, in some embodiments it may be appropriate that the primer coat layer only coats a targeted portion or zone of the interior and exterior surfaces 28, 26 of the body panel component 51, as discussed later.

The spray of thin vapour is controlled by a closed loop control process that monitors fluid flow rate and uses a mechanical gear pump to control fluid flow. In this manner, the thickness of the primer coat layer is tightly controlled and may be selectively chosen between 5-40 microns thick.

In step 68, the body panel component 51 is moved to cure in an oven which typically heats the body panel component 51 for 30 minutes at 180°C. The oven curing process ensures sufficient density and consistency throughout the primer coat layers, whilst eliminating the risk of condensate contamination. It should be noted that the curing times and temperatures prescribed for the various processes of the surface treating method 60 are generally sufficient when applying surface treatments to a body panel component. However, the parameters are susceptible to change with the specific surface coating layers used.

Once the primer coat layer has cured, the interior and exterior surfaces 28, 26 of the body panel component 51 are wiped down to remove any debris and the body panel component 51 is moved to the base coat station.

In step 70, the base coat layer is applied to the interior surface 28 of the body panel component 51. Robotic arms are supplied with the preferred choice of base coat layer, for example a verbier silver paint, and paint over the interior surface 28 of the body panel component 51.

Another set of exterior robotic arms repeat this process for the exterior surface 26 in step 72. Paint atomisation and controlled flow are essential to ensure that the metallic particles of the paint are scattered evenly across the surfaces 26, 28 of the body panel component 51. Metallic particle concentrations significantly increase the reflectivity of the underlying surface and achieving even distribution is an important aspect of the process.

As indicated previously, the base coat layer may only coat a targeted portion or zone of the interior and/or exterior surfaces 26, 28 of the body panel component 24 and need not coat the entirety of the surfaces 26, 28.

The resultant base coat layer is typically 10-40 microns thick. The thickness tolerances of the base coat layer are much smaller than the other layers since the base coat layer has the greatest influence over the surface’s reflectivity.

The body panel component 51 is subsequently moved to cure in an oven in step 74. The base coat layer is cured at a lower temperature than the primer coat layer, typically at 125°C for 30 minutes.

Touch-up repair may be necessary between the applications of each surface coating layer to ensure maximum uniformity across each layer. Dust contamination or physical damage are the major reasons for touch-up repair which involves removal and reapplication of the surface coating layers 52, 54 in these isolated areas. The surface coating layers 52, 54 are cured in these areas by a localised infrared cure.

In step 76, the body panel component 51 is positioned at a clear coat station and another set of robotic arms spray a clear coat layer over the entirety of the interior surface 28, in this embodiment, of the body panel component 51. However, in some embodiments it may be appropriate that the clear coat layer only coats a targeted portion or zone of the interior surface 28 of the body panel component 51.

External robotic arms then spray the clear coat layer over the exterior surface 26 of the body panel component 51 in step 78. In this manner, the surface coating layers 54 applied to the interior surface 28 of the body panel component 51 substantially match those applied to the exterior surface 26 (at least in the targeted portion or zone). The clear coat layer is typically the thickest layer as it must protect the underlying layers from scratches and UV light. Accordingly, the clear coat layer is typically 35-110 microns thick.

The clear coat layer is cured for 30 minutes at 180°C in an oven during step 80. Once the clear coat layer has cured, the surface treatment of the body panel component 51 is complete and the body panel component 51 is passed on for inspection in step 82.

The surface treating method should be suitably calibrated such that the thickness of each surface coating layer 52, 54 can be accurately predicted and controlled as well as the overall reflectivity produced at each of the interior and exterior surfaces 28, 26. Thickness measurements 84 may be taken between processes as a further guarantee.

It is noted that the steps of the surface treating method 60 described are merely by way of example only and are not intended to limit the features of the body panel component 51 and/or the surface treating method 60. As such, it is understood that the processes involved may be altered, reordered, added and removed as will be appreciated by the person skilled in the art.

In another embodiment, the body panel component 51 may have previously been treated such that the exterior surface 26 bears several surface coating layers 52 and the interior surface does not, as in Figure 7.

In such a case, the invention relates to the application of at least one surface coating layer to the interior surface 28 of the body panel component 51, such that the reflectivity of the interior surface 28 substantially matches the reflectivity of the exterior surface 26 and the overall thickness is tuned to the effective wavelength of the transmitted signals 22.

In other embodiments of the surface treating method, the person skilled in the art will appreciate that one or more of the surface coating layers may only be applied to targeted zones of the interior surface 28 and/or exterior surface 26 of the body panel component 51.

In further embodiments of the surface treating method, any range of surface coating layers may be applied to the body panel component 51, including liquid paints and powder coats or even film elements and solid panels. For example, one of the surface coating layers may take the form of a self-supporting film panel that is secured to the interior surface 28 of the body panel component 51, by adhesive means, to match the reflectivity of the interior surface 28 to that of the exterior surface 26. This may provide a more cost effective means of achieving the matching reflectivity.

Many modifications may be made to the above examples without departing from the scope of the present invention as defined in the accompanying claims.

Claims (39)

1. A surface treating method for a body panel component of a vehicle, the body panel component comprising first and second opposing surfaces, wherein the first surface has one or more first surface coating layers that provide a first reflectivity, the surface treating method including: adding one or more second surface coating layers to at least a portion of the second surface of the body panel component, thereby providing a second reflectivity that substantially matches the first reflectivity provided by the first surface coating layers.

2. The surface treating method of Claim 1, wherein one or more of the second surface coating layers are added to substantially the entirety of the second surface.

3. The surface treating method of Claim 1 or 2, wherein one or more of the second surface coating layers are added to a selected zone of the second surface.

4. The surface treating method of Claims 1 to 3, wherein the second surface coating layers include a reflective layer having a reflectivity of at least 20%.

5. The surface treating method of Claim 4, wherein the reflective layer comprises reflective particles.

6. The surface treating method of Claim 5, wherein the reflective layer is a metallic paint or a pearlescent paint.

7. The surface treating method of Claims 4 to 6, wherein the reflective layer is added to a selected zone of the second surface.

8. The surface treating method of Claims 4 to 7, wherein the reflective layer is added as a fluid medium.

9. The surface treating method of Claims 4 to 7, wherein the reflective layer is added as a self-supporting film.

10. The surface treating method of Claims 4 to 9, wherein the one or more second surface coating layers include one or more of a colour coating layer, a primer coating layer, and a protective coating layer.

11. The surface treating method of Claims 1 to 10, wherein the first surface coating layers comprise a primer coating layer, a colour coating layer and a protective coating layer.

12. The surface treating method of Claim 11, wherein one of the primer coating layer, the colour coating layer and the protective coating layer is a reflective layer having a reflectivity of at least 20%.

13. The surface treating method of Claim 12, wherein the colour coating layer is the reflective layer.

14. The surface treating method of Claims 1 to 13, wherein one or more of the first surface coating layers are added to the first surface contemporaneously with the addition of one or more respective second surface coating layers that are added to the second surface.

15. The surface treating method of any preceding claim, wherein the second surface coating layers are the same as the first surface coating layers.

16. The surface treating method of any preceding claim, wherein the second reflectivity substantially matches the first reflectivity for incident electromagnetic radiation of a predetermined frequency.

17. The surface treating method of Claim 16, wherein the predetermined frequency is greater than 76GHz.

18. The surface treating method of any preceding claim, wherein the first and second opposing surfaces of the body panel component are substantially parallel.

19. A body panel component of a vehicle, the body panel component comprising first and second opposing surfaces, the first surface bearing one or more first surface coating layers that provide a first reflectivity and the second surface bearing one or more second surface coating layers that provide a second reflectivity, wherein the second reflectivity substantially matches the first reflectivity.

20. The body panel component of Claim 19, wherein one or more of the second surface coating layers coat substantially the entirety of the second surface.

21. The body panel component of Claim 19 or 20, wherein one or more of the second surface coating layers coat a selected zone of the second surface.

22. The body panel component of Claims 19 to 21, wherein the second surface coating layers include a reflective layer having a reflectivity of at least 20%.

23. The body panel component of Claim 22, wherein the reflective layer of the second surface coating layers comprises reflective particles.

24. The body panel component of Claim 23, wherein the reflective layer of the second surface coating layers is a metallic paint or a pearlescent paint.

25. The body panel component of Claim 24, wherein the reflective layer coats a selected zone of the second surface.

26. The body panel component of Claims 22 to 25, wherein the reflective layer of the second surface coating layers comprises a self-supporting film.

27. The body panel component of Claims 19 to 26, wherein the second surface coating layers include one or more of a primer coating layer, a colour coating layer and a protective coating layer.

28. The body panel component of Claims 19 to 27, wherein the first surface coating layers includes a primer coating layer, a colour coating layer and a protective coating layer.

29. The body panel component of Claim 28, wherein one of the primer coating layer, the colour coating layer and the protective coating layer is a reflective layer having a reflectivity of at least 20%.

30. The body panel component of Claim 29, wherein the colour coating layer is the reflective layer.

31. The body panel component of Claims 19 to 30, wherein the first surface coating layers are the same as the second surface coating layers.

32. The body panel component of Claims 19 to 31, wherein the second reflectivity substantially matches the first reflectivity for incident electromagnetic radiation of a predetermined frequency.

33. The body panel component of Claim 32, wherein the predetermined frequency is greater than 76GHz.

34. The body panel component of Claims 19 to 33, wherein an overall thickness of the body panel component is tuned to an effective wavelength of incident electromagnetic radiation.

35. The body panel component of Claim 34, wherein the overall thickness of the body panel component is an odd integer multiple of one quarter of the effective wavelength of the incident electromagnetic radiation.

36. The body panel component of Claims 19 to 35, wherein the first and second opposing surfaces of the body panel component are substantially parallel.

37. The body panel component of Claims 19 to 36, wherein the body panel component of the vehicle is a bumper panel component.

38. An antenna installation of a vehicle, the antenna installation comprising the body panel component of any one of Claims 19 to 37 and a radar antenna.

39. A vehicle comprising the body panel component of any of claims 19 to 37, or the antenna installation of Claim 38.