JP6919752B2 - How to set the thickness of the radio wave transmissive cover and the detection device - Google Patents

Description

The present invention relates to a method of setting a plate thickness of a radio wave transmissive cover arranged in a radio wave path of a radio wave radar device, and a detection device including the radio wave radar device and the radio wave transmissive cover.

Recent automobiles are equipped with a millimeter-wave radar device (hereinafter referred to as a radar device) that detects the distance between the automobile and the surrounding automobiles and obstacles. Such a radar device is mounted on the rear side of an emblem provided on the front surface of an automobile or on the rear side of a front grill (see, for example, Patent Document 1). The emblem or the like in this case functions as a radio wave transmissive cover (hereinafter referred to as a cover) through which millimeter waves are transmitted. Conventionally, by setting the plate thickness of the cover to a constant thickness that is an integral multiple of 1/2 the wavelength of the radio wave (millimeter wave) of the radar device, attenuation when the radio wave passes through the cover is suppressed and the radar device is detected. I am trying to improve the accuracy.

Japanese Unexamined Patent Publication No. 2016-80479

By the way, in such a conventional cover, the plate thickness is set to a constant thickness as described above. In this case, for radio waves that are incident at an incident angle of 0 degrees with respect to the cover, that is, radio waves that are vertically incident, the attenuation when passing through the cover can be effectively reduced, but the detection range by the radar device is limited. If an attempt is made to widen the angle, the incident angle becomes large, and the amount of attenuation when the radio wave passes through the cover becomes large. As a result, it is difficult to improve the detection accuracy of the radar device on the wide-angle side.

An object of the present invention is a method for setting a thickness of a radio wave transmissive cover capable of widening the detection range by a radio wave radar device, and a method for setting a wide angle of a detection range by a radio wave radar device and a radio wave radar device. The purpose is to provide a detection device provided with a radio wave transmission cover.

The method of setting the plate thickness of the radio wave transmissive cover for achieving the above object is a method of setting the plate thickness of the radio wave transmissive cover arranged in the radio wave path of the radio wave radar device, and each position of the cover. The following (Equation 1) to (Equation 8) are established between the incident angle of the radio wave from the radio wave radar device at the position, the plate thickness of the cover, and the attenuation amount of the radio wave. Based on the above, the amount of attenuation of the radio wave, which changes periodically according to the thickness of the cover, is set to be the minimum value.

According to the same method, the plate thickness at each position of the cover, that is, the plate thickness at each incident angle changes periodically according to the plate thickness of the cover based on the above (Equation 1) to (Equation 8). The amount of radio wave attenuation is set to the minimum value. Therefore, the attenuation of the radio wave can be appropriately suppressed even in the region where the incident angle of the radio wave is large.

In the method of setting the thickness of the radio wave transmissive cover, when the thickness of the cover at the reference position where the incident angle of the radio wave is 0 degrees is set as the reference plate thickness, the cover is placed at a position around the reference position. It is preferable to set the plate thickness to the plate thickness closest to the reference plate thickness among the plate thicknesses of the cover corresponding to the plurality of minimum values of the attenuation amount of the radio wave.

According to this method, it is possible to prevent the plate thickness of the cover from being significantly different depending on the position. Therefore, the shape of the cover can be simplified.
The method of setting the thickness of the radio wave transmitting cover for achieving the above object is a method of setting the thickness of the radio wave transmitting cover arranged in the radio wave path of the radio wave radar device, and the thickness of the radio wave transmitting cover is set on the back surface of the cover. A plurality of vertical surface portions through which the radio waves are vertically incident are formed, and the thickness of the cover in each normal direction of the vertical surface portions is an integral multiple of 1/2 of the wavelength of the radio waves. Set the plate thickness at each position.

According to this method, radio waves are vertically incident on each vertical surface portion formed on the back surface of the cover, and the thickness of the cover in the normal direction of each vertical surface portion is 1 / of the wavelength of the radio wave. It is an integral multiple of 2. Therefore, the attenuation of the radio wave can be appropriately suppressed even in the region where the incident angle of the radio wave is large.

The detection device for achieving the above object is a detection device including a radio wave radar device and a radio wave transmissive cover arranged in the radio wave path of the radio wave radar device, and the plate thickness at each position of the cover. Is based on the following (Equation 1) to (Equation 8) established between the incident angle of the radio wave from the radio wave radar device at the position, the plate thickness of the cover, and the attenuation amount of the radio wave. , The amount of attenuation of the radio wave, which changes periodically according to the thickness of the cover, is set to be the minimum value.

In the detection device, when the plate thickness at the reference position where the incident angle of the radio wave on the cover is 0 degrees is set as the reference plate thickness, the plate thickness of the cover at the position around the reference position is the plate thickness of the radio wave. It is preferable that the cover thickness is set to be the closest to the reference plate thickness among the plate thicknesses corresponding to the plurality of minimum values of the attenuation amount.

According to the present invention, the detection range of the radio wave radar device can be widened.

The figure for demonstrating each position P1 to P15 on the cover about 1st Embodiment of the radio wave transmission cover and the plate thickness setting method of the radio wave transmission cover. An enlarged cross-sectional view showing an enlarged portion A of FIG. A graph showing the relationship between the cover plate thickness and the reciprocating millimeter wave attenuation amount for each incident angle. The graph which shows the relationship between the incident angle of the radio wave and the reciprocating millimeter wave attenuation amount in the cover of 1st Embodiment. A graph showing the relationship between the incident angle of radio waves and the amount of reciprocating millimeter-wave attenuation in a conventional cover with a constant plate thickness. The figure which shows an example of the reflection mode of the radio wave in the cover of 2nd Embodiment. The figure which shows an example of the reflection mode of the radio wave in the cover of the comparative example. The figure which shows the incident mode of the radio wave in the cover of 3rd Embodiment.

<First Embodiment>
Hereinafter, the first embodiment which embodies the method of setting the thickness of the radio wave transmitting cover and the radio wave transmitting cover will be described with reference to FIGS. 1 to 5.

First, the basic configuration of the radio wave transmissive cover (hereinafter, cover 10) will be described with reference to FIGS. 1 and 2. In addition, in FIG. 1 and FIG. 2, the scale of each member is appropriately changed and shown in order to make each member a recognizable size.

The cover 10 is an emblem attached to an opening of a front grill provided on the front surface of the automobile. The cover 10 is arranged in front of the traveling direction of the radio wave (millimeter wave) from the millimeter wave radar device 90, and is arranged in the path of the radio wave of the millimeter wave radar device 90. The wavelength λ of the radio wave of the millimeter wave radar device 90 of the present embodiment is, for example, 2.4 mm.

The cover 10 has a transparent member 20 that constitutes the surface of the cover 10. The transparent member 20 of the present embodiment is made of a polyester-based copolymer polycarbonate having excellent impact resistance, weather resistance, and water absorption resistance.

As shown in FIG. 2, on the back surface of the transparent member 20, the decorative layer 30 and the relaxation member 40 are provided in this order from the front side. The decorative layer 30 has a colored layer 31, a metal layer 32, and a corrosion prevention layer 33 in this order from the front side.

The colored layer 31 is printed on the back surface of the transparent member 20, and exhibits, for example, black.
The metal layer 32 is made of a metal material such as indium, and is vapor-deposited on the back surface of the colored layer 31 and the back surface of the transparent member 20 where the colored layer 31 is not printed. The metal layer 32 has a film thickness of about 20 nm.

In the present embodiment, the background region 10a of the cover 10 is formed by the portion provided with the colored layer 31. Further, the character region 10b (in this case, "1") of the cover 10 is formed by the portion where the colored layer 31 is not provided, that is, the portion where the metal layer 32 is exposed via the transparent member 20.

The corrosion prevention layer 33 is for suppressing the corrosion of the metal layer 32, and is made of, for example, an acrylic or urethane resin material. The corrosion prevention layer 33 has a film thickness of about several tens of μm.

The relaxation member 40 is for relaxing the heat transfer to the transparent member 20 side at the time of insert molding of the base material 60 described later, and is made of, for example, a polyamide resin. The thickness of the relaxation member 40 is preferably in the range of, for example, 0.1 mm to 1.0 mm. If thermal damage to the transparent member 20 and the decorative layer 30 does not pose a problem during molding of the base material 60, the relaxation member 40 may be omitted.

A base material 60 made of AES (acrylonitrile / ethylene / styrene copolymer) resin is provided on the back surface of the relaxation member 40.
In the present embodiment, the front side member 50 is composed of the transparent member 20, the decorative layer 30, and the relaxation member 40.

In the present embodiment, the plate thickness d of the cover 10 is a reference plate thickness dP0 that is an integral multiple of 1/2 of the wavelength λ of the radio wave at the reference position where the incident angle θ of the radio wave from the millimeter wave radar device 90 is 0 degree. Is set to. In the present embodiment, the reference plate thickness dP0 is set to 6.0 mm, which is five times the wavelength λ of 1/2 (1.2 mm in the present embodiment). The incident angle θ of the radio wave is an angle formed by the normal line orthogonal to the tangent plane at each position of the cover 10 and the traveling direction of the radio wave.

Further, at a position around the reference position, the plate thickness d of the cover 10 is gradually changed to be thicker than the reference plate thickness dP0 as the distance from the reference position increases.
Here, the incident angle θ of the radio wave from the millimeter wave radar device 90 at each position of the cover 10, the plate thickness d of the cover 10, and the reciprocating millimeter wave attenuation which is the amount of attenuation when the radio wave reciprocates in the cover 10. The following (Equation 1) to (Equation 8) are established between the amount (hereinafter referred to as the amount of radio wave attenuation) (see "Antenna Engineering Handbook 1st. Edt. Chapter 32, McGraw-Hill Book Company").

FIG. 3 shows, as an example, the relationship between the plate thickness d of the cover 10 and the amount of radio wave attenuation when the incident angles θ are 0 °, 30 °, and 45 °, respectively. In the present embodiment, the amount of radio wave attenuation is calculated by substituting a value into the plate thickness d in increments of 0.01 mm with the incident angle θ fixed.

As shown by the solid line in the figure, when the incident angle θ is 0 °, the amount of radio wave attenuation is the minimum value when the plate thickness d is 6.0 mm, 7.2 mm, and 8.4 mm, respectively.
As shown by the broken line in the figure, when the incident angle θ is 30 °, the plate thickness d is larger than 6.0 mm and smaller than 6.5 mm, d1, larger than 7.0 mm, and larger than 7.5 mm. At a small d3, the amount of radio wave attenuation becomes a minimum value.

As shown by the alternate long and short dash line in the figure, when the incident angle θ is 45 °, the plate thickness d is larger than 6.5 mm and smaller than 7.0 mm, and larger than 7.5 mm and more than 8.0 mm. At d4, which is also small, the amount of radio wave attenuation is the minimum value.

Therefore, in the present embodiment, the plate thickness d at each position of the cover 10, that is, the plate thickness d at each incident angle θ is determined by the plate thickness d of the cover 10 based on the above (Equation 1) to (Equation 8). The amount of radio wave attenuation that changes periodically according to the above is set to the minimum value.

As described above, there are a plurality of plate thicknesses in which the amount of radio wave attenuation is the minimum value. Therefore, in the present embodiment, the plate thickness d of the cover 10 is set to the plate thickness d closest to the reference plate thickness dP0 among the plate thicknesses of the cover 10 corresponding to the plurality of minimum values of the attenuation of the radio waves. ing.

That is, as shown by the broken line in FIG. 3, in the present embodiment, the plate thickness d is set to d1 which is closer to 6.0 mm than d3 at the position where the incident angle θ is 30 °.
Further, as shown by the alternate long and short dash line in FIG. 3, in the present embodiment, the plate thickness d is set to d2, which is closer to 6.0 mm than d4, at the position where the incident angle θ is 45 °.

In the present embodiment, as shown by the alternate long and short dash line in FIG. 1, the plate thickness d at each position Px (in this case, x = 1 to 15), which is the intersection of the virtual grids on the cover 10, is calculated by the method described above. At the same time, the plate thickness d between two adjacent points (for example, between P1 and P2 and between P1 and P6) is calculated by polynomial interpolation.

According to such a method, as shown in FIG. 4, the amount of radio wave attenuation is about 2 dB or less even in the region where the incident angle θ of the radio wave is 20 ° to 45 °.
On the other hand, as shown in FIG. 5, in the case of the conventional cover having a constant plate thickness, when the incident angle θ of the radio wave becomes larger than 20 °, the attenuation amount of the radio wave becomes larger than 2 dB. In particular, in a region where the incident angle θ of the radio wave is 30 ° or more, the amount of attenuation of the radio wave increases significantly from 3 dB to 6 dB as the incident angle θ increases.

According to the method for setting the thickness of the radio wave transmitting cover and the radio wave transmitting cover according to the present embodiment described above, the following effects can be obtained.
(1) The plate thickness d at each position of the cover 10 is established between the incident angle θ of the radio wave from the millimeter wave radar device 90 at that position, the plate thickness d of the cover 10, and the attenuation amount of the radio wave. Based on the above (Equation 1) to (Equation 8), the amount of attenuation of the radio wave, which changes periodically according to the plate thickness d of the cover 10, is set to be the minimum value.

According to such a method, the plate thickness d at each position of the cover 10, that is, the plate thickness d at each incident angle θ is changed to the plate thickness d of the cover 10 based on the above (Equation 1) to (Equation 8). The amount of radio wave attenuation that changes periodically accordingly is set to be the minimum value. Therefore, the attenuation of the radio wave can be appropriately suppressed even in the region where the incident angle θ of the radio wave is large. Therefore, the detection range of the millimeter-wave radar device 90 can be widened.

(2) When the plate thickness d at the reference position where the incident angle θ of the radio wave on the cover 10 is 0 degrees is defined as the reference plate thickness dP0, the plate thickness d of the cover 10 at a position around the reference position is defined as the reference plate thickness d. Of the plate thicknesses of the cover 10 corresponding to the plurality of minimum values of the radio wave attenuation, the plate thickness d closest to the reference plate thickness dP0 is set.

According to such a method, it is possible to prevent the plate thickness d of the cover 10 from being significantly different depending on the position. Therefore, the shape of the cover 10 can be simplified.
(3) The plate thickness d of the cover 10 is set to a reference plate thickness dP0 which is an integral multiple of 1/2 of the wavelength λ of the radio wave at the reference position where the incident angle θ of the radio wave from the millimeter wave radar device 90 is 0 degree. At the same time, the position around the reference position is gradually changed so that the thickness becomes thicker than the reference plate thickness dP0 as the distance from the reference position increases.

According to such a configuration, the same effect as the above effect (1) can be obtained.
<Second Embodiment>
Hereinafter, the second embodiment will be described with reference to FIGS. 6 and 7, focusing on the differences from the first embodiment.

As shown in the cover 10 of the comparative example shown in FIG. 7, a part of the radio wave from the millimeter wave radar device 90 is reflected at the interface 70 between the base material 60 and the front side member 50, and the reflected wave is reflected by the millimeter wave radar device 90. Noise may increase due to detection by the detection unit 91. This is one of the factors that deteriorate the detection accuracy of the millimeter wave radar device 90.

As shown in FIG. 6, in the cover 110 of the present embodiment, the thickness of the base material 60 is reduced at the central portion and thickened at the peripheral portion so that the interface 70 between the base material 60 and the front side member 50 is formed. A small curvature portion 71 having a partially reduced curvature is provided.

According to such a cover 110, the incident angle when the radio wave is incident on the small curvature portion 71 provided at the interface 70 between the base material 60 and the front side member 50 and the reflection angle when the radio wave is reflected on the small curvature portion 71. Will increase respectively. Therefore, it is possible to prevent the reflected wave from the small curvature portion 71 from being detected by the detection unit 91 of the millimeter wave radar device 90.

According to the method for setting the thickness of the radio wave transmitting cover and the radio wave transmitting cover according to the above-described embodiment, in addition to the effects (1) to (3) of the first embodiment, the following action effects are newly shown. Will be obtained.

(4) A small curvature portion 71 having a partially reduced curvature is provided at the interface 70 between the base material 60 and the front side member 50.
According to such a configuration, since the above-mentioned action is obtained, deterioration of the detection accuracy of the millimeter wave radar device 90 can be suppressed without changing the shape of the back surface of the cover 110.

<Third Embodiment>
Hereinafter, the third embodiment will be described with reference to FIG.
As shown in FIG. 8, in the cover 210 of the present embodiment, a plurality of vertical surface portions 211 to 213 in which radio waves from the millimeter wave radar device 90 are vertically incident are formed on the back surface thereof. Although not shown, the cover 210 of the present embodiment also has a base material and a front side member in the same manner as in the first embodiment and the second embodiment.

The vertical surface portion 211 located at the center in the width direction is a portion in which the incident angle θ in the first embodiment corresponds to the range of 0 ° to 20 °.
The pair of vertical surface portions 212 are provided on the outer sides of the vertical surface portions 211 in the width direction, respectively, and are portions corresponding to the positions where the incident angle θ in the first embodiment is 30 °.

The pair of vertical surface portions 213 are provided on the outer sides of the pair of vertical surface portions 212 in the width direction, respectively, and are portions where the incident angle θ in the first embodiment corresponds to 45 °.
The plate thickness d at each position of the cover 210 is set so that the thickness of the cover 210 in the normal direction of each of the vertical surface portions 211 to 213 is an integral multiple of 1/2 of the wavelength of the radio wave.

According to the method for setting the thickness of the radio wave transmitting cover and the radio wave transmitting cover according to the present embodiment described above, the following effects can be obtained.
(5) A plurality of vertical surface portions 211 in which the radio waves are vertically incident are formed on the back surface of the cover 210, and the thickness of the cover 210 in each normal direction of the vertical surface portions 211 is 1/2 of the wavelength of the radio waves. The plate thickness of the cover 210 was set so as to be an integral multiple.

According to such a method, the radio waves are vertically incident on the vertical surface portions 211 to 213 formed on the back surface of the cover 210, and the cover 210 in each normal direction of the vertical surface portions 211 to 213. The thickness is an integral multiple of 1/2 the wavelength of the radio wave. Therefore, the attenuation of the radio wave can be appropriately suppressed even in the region where the incident angle of the radio wave is large.

<Modification example>
The above embodiment can be changed as follows, for example.
-In the above embodiment, the radio wave transmitting cover according to the present invention is embodied as an emblem of an automobile, but the present invention can also be embodied as another component such as a front grill.

-In the first embodiment, the plate thickness d may be set to d3 at a position where the incident angle θ is 30 °. Further, the plate thickness d may be set to d4 at a position where the incident angle θ is 45 °.

In the first embodiment, the plate thickness d of the cover 10 is set so that the attenuation amount of the radio wave, which changes periodically according to the plate thickness d of the cover 10, is the minimum value. It can be made thicker by about 0.1 mm or thinner than the thickness d by about 0.1 mm. Even in this case, the attenuation of the radio wave can be suppressed in the region where the incident angle θ of the radio wave is larger than that of the conventional cover in which the plate thickness d is constant.

-The layer structure of the front member 50 can be changed as appropriate.
(Additional notes on means for solving problems)
The means for solving the above-mentioned problems include the following (Appendix 1), which is a technical idea that can be grasped from the above-described embodiment and its modification.

(Appendix 1)
In the radio wave transmissive cover arranged in the radio wave path of the radio wave radar device, the cover has a base material having a back surface on which radio waves from the radio wave radar device are incident and a side surface of the base material opposite to the back surface. A radio wave transmitting cover having a front side member provided on the surface, and a small curvature portion having a partially reduced curvature is provided at an interface between the base material and the front side member.

10, 110, 210 ... Cover (radio wave transmissive cover), 10a ... Background area, 10b ... Character area, 20 ... Transparent member, 30 ... Decorative layer, 31 ... Colored layer, 32 ... Metal layer, 33 ... Corrosion prevention layer , 40 ... relaxation member, 50 ... front side member, 60 ... base material, 70 ... interface, 71 ... small curvature portion, 90 ... millimeter wave radar device (radio wave radar device), 91 ... detection unit, 211-213 ... vertical surface portion.

Claims (5)

It is a radio wave transmissive cover arranged in the radio wave path of the radio wave radar device , and the thickness of the radio wave transmissive cover differs depending on the position on the back surface of the radio wave transmissive cover in which the incident angle of the radio wave from the radio wave radar device differs depending on the position on the back surface of the radio wave transmissive cover. How to set
The following thicknesses of the cover at a plurality of positions separated from each other are established between the incident angle of the radio wave from the radio wave radar device at the position, the plate thickness of the cover, and the attenuation amount of the radio wave. Based on (Equation 1) to (Equation 8), the attenuation of the radio wave, which changes periodically according to the thickness of the cover, is set to be the minimum value, and each of the plurality of positions is set. The plate thickness of the portion between two adjacent positions is set to a size calculated by polynomial interpolation based on the plate thickness of the two positions .

How to set the thickness of the radio wave transmission cover. When the plate thickness at the reference position where the incident angle of the radio wave on the cover is 0 degrees among the plurality of positions is used as the reference plate thickness.
The plate thickness of the cover at a position around the reference position among the plurality of positions is closest to the reference plate thickness among the plate thicknesses of the cover corresponding to the plurality of minimum values of the attenuation of the radio wave. Set to plate thickness,
The method for setting the thickness of the radio wave transmitting cover according to claim 1. It is a method of setting the thickness of the radio wave transmissive cover placed in the radio wave path of the radio wave radar device.
A plurality of separate positions of definitive on the back surface of the cover, a plurality of vertical surface portion radio wave from the radio wave radar is incident perpendicularly is formed to protrude,
The normal directions of the vertical planes are different from each other.
Before SL set the thickness of each position of the cover so that the thickness of the cover in the normal direction of each of the vertical surface portion is a half of an integral multiple of the wavelength of radio wave,
How to set the thickness of the radio wave transmission cover. A detection device provided with a radio wave radar device and a radio wave transmissive cover arranged in the radio wave path of the radio wave radar device.
The incident angle of the radio wave from the radio wave radar device differs depending on the position on the back surface of the radio wave transmissive cover.
The plate thicknesses at a plurality of positions apart from each other in the cover are as follows, which are established between the incident angle of the radio wave from the radio wave radar device at the position, the plate thickness of the cover, and the attenuation amount of the radio wave. Based on (Equation 1) to (Equation 8), the amount of attenuation of the radio wave, which changes periodically according to the thickness of the cover, is set to be the minimum value, and among the plurality of positions. The plate thickness of the portion between two positions adjacent to each other is set to a size calculated by polyphonic complementation based on the plate thickness of the two positions .

Detection device. When the plate thickness at the reference position where the incident angle of the radio wave on the cover is 0 degrees among the plurality of positions is used as the reference plate thickness.
The plate thickness of the cover at a position around the reference position among the plurality of positions is the closest to the reference plate thickness among the plate thicknesses of the cover corresponding to the plurality of minimum values of the attenuation of the radio wave. It is set to the plate thickness,
The detection device according to claim 4.

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