WO2009081252A1

WO2009081252A1 - Covering structure for vehicle-mounted radar device

Info

Publication number: WO2009081252A1
Application number: PCT/IB2008/003503
Authority: WO
Inventors: Tomoya Kawasaki
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2007-12-26
Filing date: 2008-12-16
Publication date: 2009-07-02
Also published as: JP2009156705A

Abstract

A covering structure for a vehicle-mounted radar device includes a radar device (1) mounted on a vehicle (3), and a vehicle outer plate (2) that is disposed on the outer side of the radar device (1) with respect to the vehicle (3). The radar device is mounted on the vehicle (3) such that a beam axis (A) of the radar device is angled with respect to a line perpendicular to the vehicle outer plate within a range of 10° to 42°.

Description

COVERING STRUCTURE FOR VEHICLE-MOUNTED RADAR DEVICE

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The invention relates to a covering structure for a vehicle-mounted radar device, and more specifically, relates to a covering structure that includes an outer plate of a vehicle and a vehicle-mounted radar device that is disposed on the inner side of the outer plate of the vehicle.

2. Description of the Related Art

[0002] Japanese Patent Application Publication No. 2001-228238 (JP-A-2001-228238) describes a directional axis correction device that corrects a directional axis of electromagnetic waves (millimeter waves) radiated from an antenna of a vehicle-mounted radar device using a cover (radome) provided for the radar device. More specifically, in the directional axis correction device, the thickness of the radome is varied (in other words, an inclination of the outer surface of the radome is made different from an inclination of the inner surface of the radome) so as to correct the directional axis of the electromagnetic waves.

[0003] The vehicle-mounted radar device is normally provided on the inner side of an outer plate (for example, a bumper) of a vehicle, and the electromagnetic waves are radiated from the radar device to the outside of the vehicle through the outer plate. The radar device according to the related art is typically disposed to face forward with respect to the vehicle, and performs the monitoring in a front direction of the vehicle. Therefore, the radar device is disposed in a manner such that a beam axis of the radar device is perpendicular to the surface of the outer plate.

[0004] On the other hand, the radar device may be disposed to face diagonally forward with respect to the vehicle in order to avoid an intersection collision at, for example, a collision at an intersection of crossroads. If the radar device is diagonally disposed with respect to the forward direction of the vehicle, the beam axis of the radar device is diagonal with respect to the surface of the outer plate. In this case, the beam axis of the radar device is not perpendicular to the surface of the outer plate, which can prevent the radar device from achieving desired detection performance. In order to avoid this, it is one of the options to set the orientation of the outer plate to be diagonal in accordance with the orientation of the radar device that is diagonally disposed with respect to the forward direction of the vehicle. However, this significantly influences the design of the vehicle, and therefore, it is desirable to avoid changing the orientation of the outer plate.

SUMMARY OF THE INVENTION

[0005] The invention provides a covering structure for a vehicle-mounted radar device in which the radar device is disposed diagonally with respect to an outer plate of a vehicle, while suppressing degradation in performance of the radar device.

[0006] A first aspect of the invention relates to a covering structure for a vehicle-mounted radar device. The covering structure for the vehicle-mounted radar device includes a radar device mounted on a vehicle, and a vehicle outer plate disposed on the outer side of the radar device with respect to the vehicle. The radar device is mounted on the vehicle so that a beam axis of the radar device is angled with respect to a line perpendicular to the vehicle outer plate within a range of 10° to 42°.

[0007] In the aforementioned configuration, the mounting angle of the radar device with respect to the outer plate is set within the suitable range, and therefore, it is possible to suppress degradation in the angle detection performance of the radar device caused when the mounting angle of the radar device is too large. Further, it is also possible to suppress degradation of radio wave transmission-attenuation properties of the radar device caused when the mounting angle of the radar device is too small. Accordingly, it is possible to suppress degradation in the radar device even when the radar device is diagonally disposed with respect to the vehicle outer plate.

[0008] In the aforementioned configuration, a thickness of the vehicle outer plate may be varied depending on directions of radiation of a radar wave from the radar device.

[0009] Further, in the aforementioned configuration, the thickness of the vehicle outer plate may be set so that variation in a path length of the radar wave in the vehicle outer plate in the directions of radiation of the radar wave from the radar device is smaller as compared to the case where the thickness of the vehicle outer plate is constant.

[0010] In the aforementioned configuration, it is possible to adjust the path length of the radar wave in the vehicle outer plate by changing the thickness of the vehicle outer plate. This makes it possible to make the path length in each of the radiation directions substantially constant, and therefore, it is possible to further improve the angle detection performance of the radar device.

[0011] In the aforementioned configuration, a permittivity of the vehicle outer plate may be varied depending on the directions of radiation of the radar wave from the radar device.

[0012] In the aforementioned configuration, the permittivity of the vehicle outer plate may be set so that variation in the number of waves of the radar wave in the vehicle outer plate depending on the directions of radiation of the radar wave from the radar device is smaller as compared to the case where the thickness of the vehicle outer plate is constant.

[0013] In the aforementioned configuration, it is possible to adjust the number of waves of the radar wave in the vehicle outer plate by changing the permittivity of the vehicle outer plate. This makes it possible to make the number of wavelength in the vehicle outer plate in each of the radiation directions substantially constant, and therefore, it is possible to further improve the angle detection performance of the radar device.

[0014] In the aforementioned configuration, the radar device may be mounted on the vehicle so that the beam axis is directed diagonally forward with respect to the vehicle. Further, in the aforementioned configuration, the radar device may be mounted on the vehicle so that the beam axis is directed diagonally rearward with respect to the vehicle.

[0015] In the aforementioned configuration, it is possible to detect, using the radar device, an object existing diagonally in front of or diagonally at the rear of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The foregoing and further features and advantages of the invention will become apparent from the following description of example embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements and wherein:

FIG. 1 shows how radar devices are disposed in a vehicle that includes a covering structure according to a first embodiment;

FIG. 2 shows a detailed configuration of the covering structure according to the first embodiment;

FIGS. 3 A to 3E are diagrams, each showing a relation between a mounting angle α and an angle error;

FIG. 4 shows a relation between the mounting angle α, a maximum difference of the angle error, and an attenuation amount;

FIG. 5 shows a relation between a radiation angle and a path length in an outer panel for each mounting angle;

FIG. 6 shows a detailed configuration of a covering structure according to a second embodiment;

FIG. 7 shows the relation between the radiation angle and the path length in the outer panel according to the second embodiment; and

FIG. 8 shows a covering structure according to a modification example of the second embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

[0017] Hereinafter, a covering structure for a vehicle-mounted radar device according to a first embodiment of the invention will be described. FIG. 1 shows how the radar devices are disposed in a vehicle that includes the covering structure according to the first embodiment. As shown in FIG. 1, the covering structure according to the first embodiment includes radar devices Ia, Ib, and an outer plate 2. The covering structure according to the first embodiment suppresses degradation in performance of the radar devices Ia, Ib when the radar devices Ia, Ib are diagonally mounted on a vehicle 3 with respect to the front side of the vehicle 3 in order to perform the monitoring in a diagonally front direction of the vehicle 3. Each portion of the covering structure will be hereinafter described in detail.

[0018] The radar devices Ia, Ib are mounted on the vehicle 3 and detect an obstacle (for example, another vehicle) existing around the vehicle 3. In the first embodiment, in consideration of intersection collisions, such as a collision at an intersection of crossroads, the radar devices Ia, Ib are provided to detect the obstacle existing diagonally in front of the vehicle 3. A millimeter wave radar is typically employed as each of the radar devices Ia, Ib. As shown in FIG. 1, each of the radar devices Ia, Ib is mounted in the vehicle 3, facing diagonally forward with respect to the vehicle 3. In other words, each of the radar devices Ia, Ib is mounted in the vehicle 3 in a manner such that a beam axis A of each of the radar devices Ia, Ib is angled with respect to the forward direction of the vehicle 3. More specifically, the radar device Ia that is mounted in a right front portion of the vehicle 3 is mounted so that the beam axis A of the radar device Ia is directed diagonally forward right with respect to the vehicle 3, and the radar device Ib that is mounted in a left front portion of the vehicle 3 is mounted so that the beam axis A of the radar device Ib is directed diagonally forward left with respect to the vehicle 3. The hatched regions in FIG. 1 each indicate a range of detection (range of monitoring) of each of the radar devices Ia, Ib. It should be noted that, in this specification, when the radar devices Ia, Ib need not be particularly distinguished, one of the radar devices Ia, Ib will be representatively referred to as the "radar device 1".

[0019] The first embodiment will be described on the assumption that the radar device 1 is mounted in a front portion of the vehicle 3. However, the invention is not limited to this configuration, and the radar device 1 may be mounted in any portion of the vehicle 3. For example, the radar device 1 may be mounted in a side portion or a rear portion of the vehicle 3. Further, the radar device 1 may be mounted in a manner such that the beam axis A is directed diagonally rearward with respect to the vehicle 3. [0020] The outer plate 2 forms a part of a vehicle body, and is provided on the outer side of the radar device 1 with respect to the vehicle 3. In the first embodiment, the outer plate 2 is a bumper of the vehicle 3. The outer plate 2 may be made of any material as long as the material transmits electromagnetic waves radiated from the radar device 1. The "outer plate" according to the first embodiment is a member that forms a part of the vehicle body, and is different from an antenna cover (radome) provided for the radar device 1. However, the radar device 1 may be configured without the antenna cover.

[0021] FIG. 2 shows a detailed configuration of the covering structure according to the first embodiment. FIG. 2 shows how the radar device 1 and the outer plate 2 are disposed in a top view of the vehicle 3. In FIG. 2, an angle formed between the beam axis A of the radar device 1 and a normal to a surface of the outer plate 2 is referred to as an "mounting angle (α)" (of the radar device 1 with respect to the outer plate 2). The normal is taken at the intersection point between the beam axis A of the radar device 1 and the surface of the outer plate 2 (that is, an outer surface of the outer plate 2 with respect to the vehicle 3). As shown in FIG. 1, if the radar device 1 is mounted in the vehicle 3 in a manner such that the radar device 1 is diagonally disposed with respect to the forward direction of the vehicle 3, in view of the design of the vehicle 3, it is difficult to configure the outer plate 2 so that the beam axis A of the radar device 1 is perpendicular (that is, α=0°) to the surface of the outer plate 2, and normally, the direction of the beam axis A is not perpendicular to the surface of the outer plate 2. In FIG. 2, an angle β is a field of view (in a horizontal direction) that indicates the range of detection by the radar device 1. The field-of-view angle β typically ranges from 20° to 40°. In the first embodiment, the detection range of the radar device 1 will be described on the assumption that the outer plate 2 is a flat plate. However, in general, the outer plate 2 of an actual vehicle is curved, and therefore, the outer plate 2 according to the invention may be curved. Further, in the first embodiment, the thickness of the outer plate 2 is constant.

[0022] As shown in FIG. 2, if the mounting angle α is not 0°, accuracy of angle detection by the radar device 1 (hereinafter referred to as the "angle detection accuracy") may vary, compared to the case where the mounting angle α is 0°. More specifically, when the mounting angle α is 0°, the outer plate 2 is symmetrically disposed with respect to the beam axis A from the viewpoint of the radar device 1. However, when the mounting angle α is not 0°, the outer plate 2 is asymmetrically disposed with respect to the beam axis A. Therefore, a path length of the radar wave (millimeter wave) in the outer plate 2 differs on both sides of the beam axis A of the radar device 1. For example, as shown in FIG. 2, a path length Ll differs from a path length L2, the path length Ll being a path length of the radar wave in the outer plate 2 in a radiation direction in which the distance between the outer plate 2 and the radar device 1 is the shortest within the detection range of the radar device 1 , the path length L2 being a path length of the radar wave in the outer plate 2 in a radiation direction in which the distance between the outer plate 2 and the radar device 1 is the longest within the detection range of the radar device 1. More specifically, the path length Ll is shorter than the path length L2. Therefore, when the mounting angle α is not 0°, the angle detection accuracy of the radar device 1 (that is, angle detection performance of the radar device 1) varies due to a difference in the path lengths in different radiation directions.

[0023] Further, when the mounting angle α is not 0°, the amount of attenuation of waves received by the radar device 1 varies depending on the radiation directions, compared to the case where the mounting angle α is 0°. More specifically, when the mounting angle α is not 0°, the outer plate 2 is asymmetrically disposed with respect to the beam axis A of the radar device 1. Therefore, an angle of incidence at which a millimeter wave radiated from the radar device 1 is incident on the outer plate 2 varies on both sides of the beam axis A. For example, as shown in FIG. 2, an angle of incidence θl differs from an angle of incidence Θ2. The angle of incidence θl is an angle at which a millimeter wave is incident on the outer plate 2 in the radiation direction in which the distance between the outer plate 2 and the radar device 1 is the shortest within the detection range of the radar device 1. Further, the angle of incidence Θ2 is an angle at which a millimeter wave is incident on the outer plate 2 in the radiation direction in which the distance between the outer plate 2 and the radar device 1 is the longest within the detection range of the radar device 1. More specifically, the angle of incidence θl is smaller than the angle of incidence Θ2. Therefore, the amount of attenuation of waves received by the radar device 1 (that is, radio wave transmission-attenuation properties) varies depending on the radiation directions due to the difference in the angles of incidence as described above.

[0024] As described above, when the mounting angle α is not 0°, performance of the radar device 1 varies from that of the radar device 1 when the mounting angle α is 0°. FIGS. 3A to 3E show how the angle detection performance (angle error) of the radar device 1 is changed when the mounting angle α is changed. In FIG. 3, a vertical axis indicates an angular error (that is, the difference between the actual value of the angle to be detected and the detected value of the angle), and a horizontal axis indicates a radiation angle (that is, an angle at which radio waves are radiated when the direction of the beam axis is set to 0°). Further, FIG. 3A is a diagram showing a case where the mounting angle α=0°, and FIG. 3 B is a diagram showing a case where the mounting angle α=10°. FIG. 3C is a diagram showing a case where the mounting angle α=20°, and FIG. 3D is a diagram showing a case where the mounting angle α=35°. FIG. 3E is a diagram showing a case where the mounting angle α=50°. The dotted lines in FIGS. 3A to 3E each roughly indicate a permissible range of angle error, and in the first embodiment, the permissible range of angle error is assumed to be ± 0.5°, except for the region around the radiation angle of 0°. As shown in FIG. 3, the angle error fluctuates in such a manner that the angle error repeatedly increases and decreases as the radiation angle changes. The fluctuation is especially large when the mounting angle α is 20° or larger.

[0025] FIG. 4 shows a relation between the mounting angle α, a maximum difference of the angle error, and the attenuation amount. In FIG. 4, the vertical axis indicates the maximum difference and the attenuation amount, and the horizontal axis indicates the mounting angle α. The "maximum difference" in this specification means the difference between a maximum positive value and a minimum negative value of the angle error shown in FIG. 3. The graph (a) shown in FIG. 4 shows the relation between the mounting angle α and the maximum difference of the angle error. As is obvious from FIGS. 3 A to 3E and the graph (a) shown in FIG. 4, if the mounting angle α is within the range of 0°<α<20°, the maximum difference is 0.5° or below. Further, if the mounting angle α is within the range of 0°<α<35°, the maximum difference is 1.0° or below. If the mounting angle α is 50°, the maximum difference is 1.0° or above. Therefore, from FIGS. 3 A to 3E and the graph (a) shown in FIG. 4, it can be seen that the difference between the maximum positive value and the minimum negative value of the angle error (that is, the maximum difference) tends to increase as the mounting angle α increases. This is because the path length of the radar wave in the outer plate 2 differs on both sides of the beam axis A, and such path length difference increases as the mounting angle α increases.

[0026] On the other hand, a graph (b) shown in FIG. 4 indicates the relation between the mounting angle α and the attenuation amount. The graph (b) shown in FIG. 4 shows that the attenuation amount tends to decrease as the mounting angle α is increased. It is conceivable that this is because an influence of the component of millimeter waves reflected on the outer plate 2 is reduced as the mounting angle α is increased. More specifically, it is conceivable that as the mounting angle α becomes closer to 0°, the component of millimeter waves reflected on the outer plate 2 that is received by the radar device 1 (reflected wave) increases, and the amount of attenuation of waves received by the radar device 1 is therefore increased.

[0027] As is obvious from the graph (a) and the graph (b) shown in FIG. 4, the mounting angle α is desirably within the intermediate range in the diagram shown in FIG. 4, in consideration of both of the angle error and the attenuation amount. In the first embodiment, the mounting angle α is set within the range of 10° to 42°, due to the following reason. If the mounting angle α is set to 10° or larger, it is possible to reduce the attenuation amount as compared to the case where the mounting angle α is 0°. If the mounting angle α is set to 10°, the maximum difference of the angle error is minimized. It is estimated based on the graph (a) in FIG. 4 that the maximum difference of the angle error is 1.0° when the mounting angle α is approximately 42°. Therefore, if the mounting angle α is set to 42° or smaller, the maximum difference of the angle difference is 1.0° or smaller. However, the invention is not limited to the configuration described herein, and may be configured so that the mounting angle α is set within the range of 10° to 35°. In this configuration, the maximum difference of the angle error is limited to around 0.6° at a maximum, and the attenuation amount is limited to around 1.5 [dB] at a maximum.

[0028] As described above, according to the first embodiment, the mounting angle α of the radar device 1 with respect to the outer plate 2 of the vehicle 3 is set within the range of 10° to 42°. This makes it possible to mount the radar device 1 on the vehicle 3 in a manner such that the radar device 1 is diagonal with respect to the outer plate 2, while minimizing the angle error and the attenuation amount of the radar device 1. In other words, according to the first embodiment, it is possible to suppress the degradation in performance of the radar device 1 when the radar device is mounted on the vehicle 3 so that the radar device is diagonal with respect to the vehicle 3 and the outer plate 2. However, the invention is not limited to the aforementioned configuration, and may be configured so that the mounting angle α is set within the range of 10° to 35°.

[0029] A covering structure for a vehicle-mounted radar device according to a second embodiment of the invention will be hereinafter described. In the first embodiment, the performance degradation of the radar device is suppressed by optimizing the mounting angle of the radar device with respect to the outer plate. By contrast, according to the second embodiment, performance degradation of the radar device is further suppressed by modifying the configuration of the outer plate, in addition to the mounting angle of the radar device.

[0030] FIG. 5 shows the relation between the radiation angle and the path length in the outer plate for each mounting angle. In FIG. 5, the vertical axis indicates the path length (which is expressed on the assumption that the length corresponding to a half wavelength of a radar wave is 1), and the horizontal axis indicates the radiation angle (which is expressed on the assumption that the radiation angle is 0° in the direction of the beam axis). Generally, the path length of the radar wave in the outer plate 2 is desirably set equal to an integral multiple of a half wavelength of a radar wave, because, if the path length is equal to an integral multiple of a half wavelength of the radar wave, the influence of radio waves reflected on the outer plate 2 is reduced. In FIG. 5, the thickness of the outer plate 2 is set to 3.6 [mm] so that the path length in the outer plate 2 at the radiation angle 0° is equal to an integral multiple of a half wavelength of a radar wave when the mounting angle α of the radar device 1 with respect to the outer plate 2 is 0°.

[0031] The graph (a) shown in FIG. 5 shows a relation between the radiation angle and the path length in the outer plate when the mounting angle α is 0° (α=0°), and the graph (b) shown in FIG. 5 shows the above relation when the mounting angle α is 10° (α=10°). Further, the graph (c) shows the above relation when the mounting angle α is 20° (α=20°), and the graph (d) indicates the above relation when the mounting angle α is 35° (α=35°). The graph (e) indicates the above relation when the mounting angle α is 50° (α=50°). As is obvious from the graph (a) to the graph (e), even when the thickness is set to a thickness that is optimal when the mounting angle α is 0° (α=0°) (in FIG. 5, the thickness is 3.00 times a half wavelength of a radar wave), the path length is deviated from an integral multiple of a half wavelength of a radar wave as the mounting angle α increases. Further, as the mounting angle α increases, variation (difference) in the path length depending on the radiation directions (radiation angles) also increases. As described in the first embodiment, the angle detection performance is deteriorated due to such variation in the path length.

[0032] According to the second embodiment, the thickness of the outer plate 2 is varied depending on the radiation directions (radiation angles) so as to minimize the variation in the path length in the outer plate 2 even when the radiation angle varies. FIG. 6 shows the detailed configuration of the covering structure according to the second embodiment, and shows how the radar device 1 and the outer plate 2 are disposed in a top view of the vehicle 3.

[0033] As shown in FIG. 6, the outer plate 2 according to the second embodiment is not a flat plate, and configured in a manner such that the thickness varies depending on the radiation directions of the radar device 1. Specifically, the outer plate 2 is configured so that the closer a portion of the outer plate 2 is to the radar device 1 , the greater the thickness of the portion of the outer plate 2 is. More specifically, the thickness of the outer plate 2 is set so that the path length in each radiation direction is made substantially constant (in other words, the variation in the path length in the different radiation directions becomes smaller, compared to the case where the thickness of the outer plate 2 is constant). Further, the thickness of the outer plate 2 is set so that the path length in each radiation direction is equal to an integral multiple of a half wavelength of a radar wave. In this way, if the thickness of the outer plate 2 is varied such that the path length is made substantially constant in the different radiation directions, the variation in the path length in the different radiation directions is reduced, thus, the angle detection performance of the radar device 1 is improved. Further, if the path length in each radiation direction is set to an integral multiple of a half wavelength of a radar wave, the influence of radio waves reflected on the outer plate 2 is reduced, and thus, the amount of attenuation of waves received by the radar device 1 is further reduced. The thickness of the outer plate 2 may be varied only in a portion that corresponds to a radiation range in which the radar device 1 radiates radio waves, and may be constant in other portions of the outer plate 2 than the portion that corresponds to the radiation range. [0034] FIG. 7 shows a relation between the radiation angle and the path length in the outer plate according to the second embodiment. In FIG. 7, the vertical axis indicates the path length (which is expressed on the assumption that the path length corresponding to a half wavelength of a radar wave is 1), and the horizontal axis indicates the radiation angle. The graph (a) shown in FIG. 7 shows the relation between the radiation angle and the path length according to the second embodiment. In FIG 7, the mounting angle α of the radar device 1 with respect to the outer plate 2 is 25° (α=25°). The graph (b) shown in FIG. 7 is identical with the graph (c) shown in FIG. 5. As is obvious from the graph (a) shown in FIG. 7, according to the second embodiment, if the thickness of the outer plate 2 is varied, the path length in the outer plate 2 is substantially equal to an integral multiple of a half wavelength of a radar wave (3.00 times, in FIG. 7) even when the radiation angle varies, and it is possible to reduce the variation in the path length in the different radiation directions, compared to the case where the thickness of the outer plate 2 is constant, which is indicated by the graph (b).

[0035] The covering structure according to the second embodiment is the same as the covering structure according to the first embodiment, except for the feature that the thickness of the outer plate 2 is varied depending on the radiation directions. Therefore, also in the case shown in FIG. 6, the mounting angle α of the radar device 1 is set within the range of 10° to 42°.

[0036] As described above, according to the second embodiment, it is possible to make the path length in the outer plate 2 substantially constant in the different radiation directions by varying the thickness of the outer plate 2. Thus, this makes it possible to improve the angle detection performance and the radio wave transmission-attenuation properties of the radar device 1.

[0037] FIG. 8 shows the covering structure according to a modification example of the second embodiment. In the second embodiment, the thickness of the outer plate 2 is continuously varied. However, as shown in FIG. 8, the thickness of the outer plate 2 may be varied stepwise. Further, the outer plate 2 exemplified in the second embodiment or the modification example of the second embodiment may be integrally formed, or may be formed by bonding another member to a flat outer plate 2.

[0038] According to the second embodiment, the thickness of the outer plate 2 is varied depending on the radiation directions. However, the invention is not limited to this configuration, and the permittivity of the outer plate 2 may be varied depending on the radiation directions so that the number of waves of the radar wave in the outer plate 2 is made close to a constant number (in other words, a variation in the number of waves depending on the different radiation directions is reduced, compared to the case where the thickness of the outer plate is constant). Further, the permittivity of the outer plate 2 may be varied depending on the radiation directions so that the path length of the radar wave in the outer plate 2 is equal to an integral multiple of a half wavelength of a radar wave. With this configuration, it is possible to achieve the effect similar to the effect achieved in the case where the thickness of the outer plate 2 is varied. In other words, with this configuration, it is possible to further improve the angle detection performance and the radio wave transmission-attenuation properties of the radar device 1. If the permittivity of the outer plate 2 is varied, the outer plate 2 may be made by combining a plurality of members that have different permittivities (in this case, the permittivity varies stepwise), or may be made so that the permittivity continuously varies.

[0039] As described above, the invention may be employed as, for example, the covering structure for the vehicle-mounted radar device in order to, for example, dispose the radar device diagonally with respect to the outer plate of the vehicle, while suppressing performance degradation of the radar device.

Claims

1. A covering structure for a vehicle-mounted radar device, comprising: a radar device mounted on a vehicle; and a vehicle outer plate disposed on an outer side of the radar device with respect to the vehicle, wherein the radar device is mounted on the vehicle such that a beam axis of the radar device is angled with respect to a line perpendicular to the vehicle outer plate within a range of 10° to 42°.

2. The covering structure according to claim 1, wherein a thickness of the vehicle outer plate is varied depending on directions of radiation of a radar wave from the radar device.

3. The covering structure according to claim 2, wherein the thickness of the vehicle outer plate is set so that a variation in a path length of the radar wave in the vehicle outer plate depending on the directions of radiation of the radar wave from the radar device is smaller as compared to a case where the thickness of the vehicle outer plate is constant.

4. The covering structure according to claim 1, wherein a permittivity of the vehicle outer plate is varied depending on the directions of radiation of the radar wave from the radar device.

5. The covering structure according to claim 4, wherein the permittivity of the vehicle outer plate is set so that variation in a number of waves of the radar wave in the vehicle outer plate depending on the directions of radiation of the radar wave from the radar device is smaller as compared to a case where the thickness of the vehicle outer plate is constant.

6. The covering structure according to claim 1, wherein the radar device is mounted on the vehicle such that the beam axis is directed diagonally forward with respect to the vehicle.

7. The covering structure according to claim 1, wherein the radar device is mounted on the vehicle so that the beam axis is directed diagonally rearward with respect to the vehicle.

8. The covering structure according to claim 1, wherein the radar device is mounted on the vehicle so that the beam axis is angled with respect to a normal to an outer surface of the vehicle outer plate within the range of 10° to 42°.

9. The covering structure according to claim 2, wherein the thickness of the vehicle outer plate is set to decrease as an angle of incidence at which the radar wave from the radar device is incident on the vehicle outer plate increases.

10. The covering structure according to claim 2, wherein the thickness of the vehicle outer plate is set to decrease stepwise as an angle of incidence at which the radar wave from the radar device is incident on the vehicle outer plate increases.

11. The covering structure according to claim 2, wherein the thickness of the vehicle outer plate is set so that a path length of the radar wave in the vehicle outer plate in each of the directions of radiation of the radar wave from the radar device is equal to an integral multiple of a half wavelength of the radar wave.