Radio wave transmission cover

Abstract

To provide a technique capable of more favorably suppressing erroneous detection or sensitivity deterioration due to a reflection wave from a radome or a bumper than before.SOLUTION: Radio wave transmission covers (2, 6) are provided on a front side of a transmission / reception unit (7) included in a radio wave radar device (4) so as to transmit radio waves emitted from the transmission / reception unit. The radio wave transmission cover includes a reflection suppression unit (10) that suppresses reflection of the radio waves to the transmission / reception unit. The reflection suppression unit has a configuration in which a plurality of conical parts (21) having a hollow conical shape opening toward the transmission / reception unit are arranged.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a radio wave transparent cover that is provided on the front side of a transmitter / receiver unit included in a radio wave radar device and is configured to transmit radio waves emitted from the transmitter / receiver unit. [Background technology]

[0002] For example, if the radome of a radar device is shaped parallel to the antenna surface, the radar device may experience false detection due to the antenna receiving the reflected waves reflected by the radome, which may result in a decrease in sensitivity. Therefore, various technologies have been proposed to cancel out the reflected waves by changing the shape of the radome and prevent the antenna from receiving the reflected waves.

[0003] For example, the radome described in Patent Document 1 is a single-layer dielectric plate radome that has a convex shape with a vertex on one side of the plane that includes the periphery for mounting to the antenna. The convex shape is, for example, a quadrangular pyramid, a cone, or a dome. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5334238 Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure has been made in consideration of the circumstances exemplified above, etc. That is, the present disclosure provides a technique that can effectively suppress false detection or reduction in sensitivity due to waves reflected from, for example, a radome or a bumper. [Means for solving the problem]

[0006] The radio wave transparent cover (2, 6) according to claim 1 is provided on the front side of a transmitter / receiver (7) provided in a radio wave radar device (4) so ​​as to transmit radio waves emitted from the transmitter / receiver, a reflection suppression unit (10) that suppresses reflection of the radio wave to the transmitting / receiving unit, The reflection suppressing section has a configuration in which a plurality of cone sections (21) each having a hollow cone shape that opens toward the transmitting / receiving section side are arranged.

[0007] Radio waves emitted from a transmitter / receiver provided in a radio wave radar device pass through a radio wave transparent cover provided on the front side of the transmitter / receiver. In this case, a radio wave transparent cover having such a configuration effectively suppresses the reflection of radio waves back to the transmitter / receiver by using a reflection suppression unit having a configuration in which multiple hollow cone-shaped cone portions that open toward the transmitter / receiver. Therefore, a radio wave transparent cover having such a configuration effectively suppresses false detection or sensitivity reduction due to waves reflected by the radio wave transparent cover.

[0008] In addition, in each section of the application documents, each element may be assigned a reference symbol in parentheses. However, such reference symbols merely indicate an example of the correspondence between the element and the specific means described in the embodiments below. Therefore, the present disclosure is not limited in any way by the above-mentioned reference symbols. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view showing the appearance of a vehicle to which a radio wave transmission cover according to the present disclosure is applied; [Figure 2] 2 is an enlarged cross-sectional view showing the periphery of a radio wave transmitting region shown in FIG. 1. FIG. [Figure 3] 3 is an enlarged cross-sectional view showing an example of the configuration of the reflection suppressing section shown in FIG. 2. FIG. [Figure 4] 4 is an enlarged front view of a portion of the first layer shown in FIG. 3. FIG. [Figure 5]FIG. 5 is an enlarged perspective view of one of the plurality of cone portions shown in FIGS. 3 and 4. [Figure 6] FIG. 8 is a conceptual diagram for explaining the angle of incidence on the horizontal axis in FIG. [Figure 7] 1 is a graph showing the relationship between the angle of incidence and the reflection coefficient on a dielectric surface. [Figure 8] FIG. 4 is a conceptual diagram showing how radio waves are reflected on the first layer shown in FIG. 3. [Figure 9] 4 is a graph showing the effect of the reflection suppressing unit shown in FIG. 3. [Figure 10] 4 is a graph showing the effect of the reflection suppressing unit shown in FIG. 3. [Figure 11] 4 is a graph showing the effect of the reflection suppressing unit shown in FIG. 3. [Figure 12] 4 is a cross-sectional view schematically showing the configuration of the reflection suppressing section according to the first embodiment shown in FIG. 3. FIG. [Figure 13] 13 is a cross-sectional view schematically showing the configuration of a modified example of the reflection suppressing section according to the first embodiment shown in FIG. 12. FIG. [Figure 14] 13 is a cross-sectional view schematically showing the configuration of another modified example of the reflection suppressing section according to the first embodiment shown in FIG. 12. FIG. [Figure 15] 13 is a cross-sectional view schematically showing the configuration of yet another modified example of the reflection suppressing section according to the first embodiment shown in FIG. 12. FIG. [Figure 16] FIG. 10 is a cross-sectional view schematically showing the configuration of a reflection suppressing section according to a second embodiment of the present disclosure. [Figure 17] 17 is a cross-sectional view schematically showing the configuration of a modified example of the reflection suppressing section according to the second embodiment shown in FIG. 16. FIG. [Figure 18] 17 is a cross-sectional view schematically showing the configuration of another modified example of the reflection suppressing section according to the second embodiment shown in FIG. 16. FIG. [Figure 19] 17 is a cross-sectional view schematically showing the configuration of yet another modified example of the reflection suppressing section according to the second embodiment shown in FIG. 16. FIG. [Figure 20]17 is a cross-sectional view schematically showing the configuration of yet another modified example of the reflection suppressing section according to the second embodiment shown in FIG. 16. FIG. [Figure 21] 17 is a cross-sectional view schematically showing the configuration of yet another modified example of the reflection suppressing section according to the second embodiment shown in FIG. 16. FIG. [Figure 22] FIG. 10 is an enlarged front view showing the configuration of a reflection suppressing section according to a third embodiment of the present disclosure. [Figure 23] 23 is a cross-sectional view taken along the line XXIII-XXIII in FIG. 22. [Figure 24] FIG. 10 is a perspective view showing the appearance of a vehicle to which a configuration according to one modification of the present disclosure is applied. [Figure 25] FIG. 25 is an enlarged cross-sectional view of the radio wave radar device shown in FIG. 24 and its surroundings. [Figure 26] FIG. 26 is a cross-sectional view schematically showing the configuration of the reflection suppressing section shown in FIG. 25. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Embodiment) Hereinafter, exemplary embodiments and specific examples (i.e., examples and modified examples) of the present disclosure will be described with reference to the drawings as appropriate. Note that identical or equivalent parts among multiple embodiments and specific examples are designated by the same reference numerals. Therefore, with regard to components having the same reference numerals as components in previously described embodiments, etc., the explanations in the previously described embodiments, etc. may be appropriately incorporated into subsequent embodiments, etc., unless there is a technical contradiction or a special additional explanation.

[0011] (First embodiment: configuration) 1, a vehicle 1 to which the present disclosure is applied is an automobile that travels on public roads and includes a box-shaped body 1 A. Bumpers 2 serving as radio wave transparent covers according to the present disclosure are attached to the front and rear ends of the body 1 A.

[0012] As shown in Fig. 2, the bumper 2 is formed of a second layer 12 made of a material that is transmissive to radio waves (e.g., synthetic resin) and a first layer 11 made of a material that partially reflects radio waves (e.g., metallic paint; strictly speaking, the paint on the vehicle 1 is made of multiple layers, but for simplicity, the first layer 11 is made of a single layer of a high-dielectric-constant material). A radio wave transmissive region 3 is provided in at least a portion of the bumper 2. To avoid cluttering the illustration, the first layer 11 and the second layer 12 are shown as flat in Fig. 2, but as will be described in detail later, the first layer 11 and the second layer 12 have a shape or structure that suppresses reflection of radio waves. The radio wave transmissive region 3 is configured to effectively transmit radio waves emitted from a radio wave radar device 4 disposed inside the bumper 2.

[0013] Referring to FIG. 2 , the radio wave radar device 4 is provided on the inside, i.e., rear side, of the bumper 2. For ease of illustration and explanation, in this embodiment, the portion of the bumper 2 facing the radio wave radar device 4 is shown as a macroscopically flat plate. However, as will be described later, the present disclosure is not limited to this form. The term "macroscopically flat plate-like" refers to a generally flat appearance, specifically, a planar imaginary cover surface Vc. The imaginary cover surface Vc is an imaginary surface passing through the center between a first imaginary surface passing through the innermost position of the bumper 2, i.e., the position on the radio wave radar device 4 side, and a second imaginary surface passing through the outermost position of the bumper 2, i.e., the position on the exterior space side.

[0014] The first imaginary surface, the imaginary cover surface Vc, and the second imaginary surface are offset in this order by a predetermined value along the thickness direction of the macroscopic bumper 2. Twice this predetermined value corresponds to the macroscopic thickness of the bumper 2. The "macroscopic thickness of the bumper 2" refers to the thickness of the plate material when the bumper 2 is considered to be a plate material of a constant thickness, ignoring uneven shapes that may be formed on the inner and outer surfaces. The imaginary cover surface Vc is an imaginary surface that passes through the center position of the plate material in the thickness direction.

[0015] The radio wave radar device 4 includes a casing 5, a radome 6, and a transmitter / receiver 7. The casing 5, also called a lower case, is a bathtub-shaped box-like member that opens on one side and is made of a material that is opaque to radio waves (for example, a metal such as aluminum). The radome 6 is a plate-like member that is provided to close the opening in the casing 5 and is made of a material that allows radio waves to pass through easily (for example, a synthetic resin).

[0016] The transmitter / receiver 7 has a configuration as a circuit board on which an antenna 8 and the like are formed, and is supported by the casing 5 so as to be disposed opposite the radome 6. In this embodiment, the radio wave radar device 4 is configured to operate at an operating frequency of 76 to 81 GHz, for example. The radio wave radar device 4 is held within the bumper 2 in an orientation such that the radome 6 faces the bumper 2.

[0017] In FIG. 2 , the transmission / reception direction D1 is a direction parallel to the direction in which the radiation wave Wd, which is the radio wave emitted from the radio wave radar device 4, propagates through space, specifically, a direction parallel to the directional center axis of the radiation wave Wd. For ease of illustration and explanation, in this embodiment, the transmission / reception direction D1 is shown as being normal to the virtual cover surface Vc, i.e., the incident angle of the radiation wave Wd with respect to the virtual cover surface Vc is 0 degrees. However, as will be described later, the present disclosure is not limited to this configuration. Any direction perpendicular to the transmission / reception direction D1, i.e., a direction parallel to the virtual cover surface Vc, is referred to as the creeping direction D2. The transmission / reception direction D1 and the creeping direction D2 are shown in FIG. 2 and in the following figures, which will be described later, so as to be consistent with each other.

[0018] In this way, the bumper 2 as a radio wave transmission cover is provided on the front side of the transmitter / receiver 7 so as to transmit the radiated waves Wd, which are radio waves emitted from the transmitter / receiver 7 provided in the radio wave radar device 4. At least a part of the radio wave transmission area 3 of the bumper 2, which is the area through which the radiated waves Wd pass, is provided with a reflection suppression part 10.

[0019] The reflection suppression unit 10 has a structure that suppresses reflection of the radiated wave Wd toward the transceiver unit 7, i.e., the generation of internally reflected waves Wr. The internally reflected waves Wr are radio waves caused by the radiated wave Wd that propagate toward the transceiver unit 7 without passing through the bumper 2, and are typically waves reflected by the bumper 2. In this embodiment, as will be described later, the first layer 11 and the second layer 12 of the reflection suppression unit 10, which has a two-layer structure, are each formed from a dielectric material having a relative dielectric constant of 2 to 20. Note that, as will be described later, when the reflection suppression unit 10 is formed from three or more layers, each of the three or more layers is formed from a dielectric material having a relative dielectric constant of 2 to 20. Similarly, when the reflection suppression unit 10 has a single-layer structure, the reflection suppression unit 10 of this single-layer structure is formed from a dielectric material having a relative dielectric constant of 2 to 20.

[0020] 3, the reflection suppressing unit 10 according to this embodiment has a laminated structure of two dielectric layers, a first layer 11 and a second layer 12. The first layer 11 is thinner than the second layer 12 and is made of a material with a high dielectric constant. Specifically, in this embodiment, the first layer 11 is made of a dielectric material with a relative dielectric constant of 5.5 and a thickness t1 of 0.1 mm (i.e., approximately 0.026 times the wavelength). On the other hand, the second layer 12 is made of a dielectric material with a relative dielectric constant of 2.5 and a thickness t2 of 1.7 mm (i.e., approximately 0.44 times the wavelength).

[0021] As shown in Figures 3 and 4, the first layer 11 has a configuration in which a plurality of cone portions 21, each having a hollow cone shape that opens toward the propagation direction of the internally reflected wave Wr (i.e., toward the transmitter / receiver 7), are arranged two-dimensionally in the surface direction D2. In this embodiment, as shown in Figures 4 and 5, the cone portion 21 is formed in a triangular pyramid shape having an apex 22 and a triangular bottom 23. The apex 22 may have an angular shape, or may have a shape with a flat portion or a rounded shape. The bottom 23 is formed in an equilateral triangular shape in the surface direction D2.

[0022] The pyramidal portions 21, each having a triangular pyramidal shape with an equilateral triangular base, are closely packed in the surface direction D2 so that the arrangement period P is 0.25 to 1.5 times the wavelength of the radiation wave Wd. As shown in Fig. 4, the arrangement period P is the distance between adjacent apexes 22 in a first surface direction D21, which is parallel to one side of the equilateral triangle at the bottom 23, within the surface direction D2. Note that, within the surface direction D2, a direction perpendicular to the first surface direction D21 is referred to as a second surface direction D22, and a direction along which the radius of a circle centered at a certain point extends is referred to as a radial direction D23.

[0023] 5, the cone size S, which corresponds to the size of the bottom portion 23, is the length of one side of the equilateral triangle at the bottom of the hollow cone shape, and in this embodiment is set to be 0.25 to 1.5 times the wavelength of the radiated wave Wd. Specifically, for example, when the cone size S is 1.15 times the wavelength of the radiated wave Wd, it is approximately 4.5 mm. As shown in FIGS. 3 and 4, the multiple cone portions 21 arranged two-dimensionally in the surface direction D2 are formed so that the cone sizes S are uniform.

[0024] 3, inner cone surface 24, which is the inner surface of cone portion 21, i.e., the surface on the opening side, is inclined with respect to transmission / reception direction D1 or creeping direction D2 so that the reflection coefficient of radio waves is less than -6 dB. Specifically, the inclination angle θc of inner cone surface 24 with respect to imaginary cover surface Vc can be set to 30 to 75 degrees. More specifically, for example, when height H of cone portion 21 is 1.83 mm (i.e., approximately 0.47 times the wavelength), it is preferable that inclination angle θc is approximately 50 degrees.

[0025] As described above, the first layer 11 is formed of a plate or film material with a predetermined thickness t1 and has a structure in which multiple cone portions 21 of a predetermined size are closely packed and arranged two-dimensionally in the surface direction D2. Therefore, the thickness direction defining the thickness t1 of the first layer 11 is inclined by 90-θc degrees with respect to the bumper thickness direction, which is perpendicular to the imaginary cover surface Vc. The thickness direction defining the thickness t2 of the second layer 12 is also inclined. Therefore, the second layer 12 has a recess 31 that opens in the same direction as the cone portion 21 at a position corresponding to the cone portion 21 in the surface direction D2. The recess inner surface 32, which is the surface of the recess 31, is formed as an inclined surface along the inner cone surface 24. As such, in this embodiment, hollow cone shapes are provided in both the first layer 11 and the second layer 12.

[0026] (First embodiment: effect) The effects achieved by the configuration of this embodiment will be described below along with the mechanism by which they are achieved. The radiated waves Wd, which are radio waves radiated from the transmitter / receiver 7 provided in the radio wave radar device 4, pass through the radio wave transmission area 3 in the bumper 2, which serves as a radio wave transmission cover provided on the front side of the transmitter / receiver 7. The radio wave transmission area 3 is configured as a plate-like dielectric material.

[0027] It is generally known that when a radio wave having a plane of polarization perpendicular to a dielectric surface is incident at a large incident angle, the amount of reflection is greatly reduced. Figures 6 and 7 are diagrams for explaining the general nature of radio wave reflection when a radiated wave Wd is incident on an incident surface X, which is a dielectric surface. As is well known, the incident angle θd of the radiated wave Wd is defined based on the normal L to the incident surface X. In other words, when the radiated wave Wd is incident perpendicularly to the incident surface X, the incident angle θd is 0 degrees.

[0028] As shown in FIG. 7, the reflection coefficient decreases significantly when the incident angle θd is between 30 and 60 degrees compared to when it is 0 degrees. This tendency is observed up to an incident angle θd of approximately 75 degrees. For this reason, as shown in FIG. 3, the reflection suppression unit 10 has a structure including multiple cone portions 21, each having an inner cone surface 24 inclined relative to the imaginary cover surface Vc. In this structure, the incident angle θd relative to the inner cone surface 24 corresponds to the inclination angle θc of the inner cone surface 24 relative to the imaginary cover surface Vc. In this way, by making the dielectric surface that reflects the radiated wave Wd an inclined surface like the inner cone surface 24, the reflection coefficient is reduced, thereby making it possible to effectively suppress the internally reflected wave Wr.

[0029] FIG. 8 schematically illustrates how radio waves are reflected by the inner conical surface 24. As shown in FIG. 8, a portion of the radiated wave Wd incident on the inner conical surface 24 passes through the first layer 11 and becomes a transmitted wave Wt that is radiated toward the vehicle exterior space, while the remaining portion is reflected by the inner conical surface 24 and becomes a primary internally reflected wave Wr1. The propagation direction of the primary internally reflected wave Wr1 intersects the transmission / reception direction D1. Furthermore, the propagation direction of the secondary internally reflected wave Wr2, which is a wave that is re-reflected from the primary internally reflected wave Wr1 by the inner conical surface 24, also intersects the transmission / reception direction D1. Thus, with this configuration, the propagation direction of most of the reflected waves intersects the transmission / reception direction D1, thereby effectively suppressing the internally reflected wave Wr traveling toward the transceiver unit 7 along the transmission / reception direction D1.

[0030] FIG. 9 is a graph showing a comparison of the reflection coefficients of the examples and comparative examples. FIG. 10 is a graph showing a comparison of the transmission coefficients of the examples and comparative examples. In the figure, the plots of the examples indicated by black circles represent the case of the dielectric plate having the structure shown in FIG. 3, and the plots of the comparative examples indicated by white circles represent the case of the dielectric plate having a flat, single-layer structure of uniform thickness. Since methods for measuring the reflection coefficient and transmission coefficient were well known at the time of filing this application, detailed explanations will be omitted in this specification. As shown in FIGS. 9 and 10, it was confirmed that the configuration according to this embodiment can obtain better reflection coefficients and transmission coefficients than conventional plate materials of uniform thickness.

[0031] 11 shows the radiation pattern of the radiated wave Wd. In FIG. 11, the dotted line shows the radiation pattern of the antenna 8 alone, the solid line shows the radiation pattern of the transmitted wave Wt that has passed through the reflection suppression unit 10 according to this embodiment, and the dashed line shows the radiation pattern of the comparative example, that is, the transmitted wave Wt that has passed through a dielectric plate with a flat single-layer structure. As shown in FIG. 11, in the comparative example, the signal strength decreased in the azimuth range of -15 to +15 degrees, which is a range that is significantly affected by reflection. In contrast, according to this embodiment, no such decrease in signal strength was observed, and a radiation pattern similar to that obtained when only the antenna 8 was used was obtained.

[0032] As described above, in this embodiment, the reflection of radio waves toward the transceiver 7 is effectively suppressed by the reflection suppression unit 10 having a configuration in which a plurality of cone sections 21, each having a hollow cone shape that opens toward the transceiver 7, are arranged. Specifically, according to this embodiment, it is possible to effectively suppress false detection or sensitivity reduction caused by internally reflected waves Wr by reducing the reflection coefficient using the inclined surface and controlling the propagation direction of the reflected waves. Furthermore, by optimizing the shape and arrangement period P of the cone sections 21, it is possible to even more effectively suppress the internally reflected waves Wr heading toward the transceiver 7.

[0033] Therefore, according to this embodiment, it is possible to effectively suppress false detection or a decrease in sensitivity due to the internally reflected waves Wr, which are waves reflected from the bumper 2. In particular, it is possible to improve the transmittance and reduce the reflectance simply by providing a predetermined structure, without changing the material of the bumper 2 serving as a radio wave transparent cover.

[0034] (First embodiment: modified example) As shown in Fig. 12, the above embodiment has a configuration in which a first layer 11 having a cone portion 21 is formed on a second layer 12. Such a configuration can be realized, for example, in the form of the second layer 12 serving as a support layer constituting the main body portion of the bumper 2 shown in Fig. 2, and the first layer 11 serving as a coating layer formed on this support layer. In the above embodiment, a recess 31 is formed in the second layer 12, thereby providing a hollow cone shape in both the first layer 11 and the second layer 12.

[0035] In contrast, in the configuration according to the modified example shown in FIG. 13, the inner surface, i.e., the bottom surface, of the second layer 12 is a smooth surface without any recesses 31. That is, in this modified example, the second layer 12 has a configuration in which solid cones are arranged two-dimensionally. Even with this modified example, the cone portion 21 is provided in the first layer 11 on the high-dielectric-constant side of the two-layer laminated structure made up of the first layer 11 and the second layer 12, and the inner cone surface 24, which is the inner surface, is made into an inclined surface, thereby achieving the same reflection reduction effect as in the above embodiment. Note that in this case, the thickness direction of the second layer 12 is along (i.e., parallel to) the transmission / reception direction D1.

[0036] Fig. 14 shows a configuration in which the positional relationship between the first layer 11 and the second layer 12 in the transmitting and receiving direction D1, i.e., the front and back, is reversed from the configuration shown in Fig. 12. Similarly, Fig. 15 shows a configuration in which the positional relationship between the first layer 11 and the second layer 12 in the transmitting and receiving direction D1 is reversed from the configuration shown in Fig. 13. These configurations can also achieve the same reflection reduction effect as the above embodiment.

[0037] Second Embodiment In this embodiment, the reflection suppressing section 10 has a three-layer structure made up of a first layer 11 to a third layer 13. That is, the configuration shown in Fig. 16 is obtained by adding a third layer 13 to the outside of the first layer 11 in addition to the configuration shown in Fig. 12. Similarly, the configuration shown in Fig. 17 is obtained by adding a third layer 13 to the outside of the first layer 11 in addition to the configuration shown in Fig. 13. The third layer 13 is provided as a dielectric layer having a lower dielectric constant than the first layer 11.

[0038] Such a configuration can be realized, for example, in the form of a second layer 12 as a support layer constituting the main body portion of the bumper 2 shown in Fig. 2, a first layer 11 as a coating layer formed on this support layer, and a third layer 13 as a protective layer formed on this coating layer. Even with such a configuration, the same reflection-reducing effect as in the above embodiment can be achieved. Note that, as shown in Figs. 18 and 19, the outer surface, i.e., the top surface, of the third layer 13 may be a smooth surface without any irregularities.

[0039] In the configurations shown in Figures 20 and 21, the third layer 13 is a high-dielectric layer bonded to the second layer 12 and is made of a material with a higher dielectric constant than the second layer 12. That is, the configuration shown in Figure 20 is the same as the configuration shown in Figure 13, except that a third layer 13 of a constant thickness is added to the inner surface of the smooth second layer 12. Similarly, the configuration shown in Figure 21 is the same as the configuration shown in Figure 15, except that a third layer 13 of a constant thickness is added to the outer surface of the smooth second layer 12. In these examples, the second layer 12 with a low dielectric constant is sandwiched between the first layer 11 and third layer 13 with a high dielectric constant. Such configurations can also achieve the same reflection reduction effect as the above embodiment.

[0040] As described above in detail, the configuration according to the present disclosure has the cone portion 21 provided in at least one of the layers of the reflection suppression unit 10 having a laminated structure of multiple dielectric layers. This makes it possible to effectively suppress the internal reflection wave Wr heading toward the transmitter / receiver 7, thereby effectively suppressing erroneous detection or reduced sensitivity due to the internal reflection wave Wr.

[0041] (Third embodiment) In each of the above embodiments, the cone size S of the cone portion 21 and the arrangement period P of the cone portion 21 are uniform in the surface direction D2. In contrast, in this embodiment, the cone size S and the arrangement period P are non-uniform.

[0042] 22, the reflection suppressing unit 10 has an inner region 40, a first outer region 41, and a second outer region 42. The first outer region 41, the inner region 40, and the second outer region 42 are arranged in this order along the first creeping direction D21. That is, the inner region 40 is provided at a position sandwiched between the first outer region 41 and the second outer region 42. In other words, the first outer region 41 and the second outer region 42 are disposed outside the inner region 40 in the creeping direction D2.

[0043] The inner region 40 has cone portions 21 of different sizes than those in the first outer region 41 and the second outer region 42. That is, the cone portions 21 are formed in the inner region 40 so that the cone size S is larger than those in the first outer region 41 and the second outer region 42. Furthermore, the cone portions 21 are formed in the inner region 40 so that the arrangement period P is larger than those in the first outer region 41 and the second outer region 42.

[0044] That is, the inner arrangement period P0, which is the arrangement period P in the inner region 40, is set to be larger than the first outer arrangement period P1, which is the arrangement period P in the first outer region 41, and the second outer arrangement period P2, which is the arrangement period P in the second outer region 42. With this configuration, it is possible to satisfactorily achieve a reflection reduction effect that corresponds to the directional characteristics.

[0045] In the configuration examples shown in FIGS. 22 and 23, the size of the cone portions 21 in the inner region 40 is uniform. The same is true for the first outer region 41 and the second outer region 42. The size of the cone portions 21 in the first outer region 41 is the same as that in the second outer region 42. Furthermore, the first outer arrangement period P1 is the same as that in the second outer region 42. However, this embodiment is not limited to this example.

[0046] Therefore, for example, the sizes of the cone portions 21 may be distributed in the inner region 40, the first outer region 41, and the second outer region 42. That is, for example, the sizes of the cone portions 21 in the inner region 40 may become smaller as they move outward from the center position in the surface direction D2 of the inner region 40. Here, "moving outward from the center position" means moving from the center position in the first surface direction D21, the second surface direction D22, or the radial direction D23. As a result, the inner arrangement period P0 may also have a distribution.

[0047] The size of the cone portions 21 may be different between the first outer region 41 and the second outer region 42. Furthermore, a distribution in the size of the cone portions 21 may be provided in the first outer region 41 or the second outer region 42. Specifically, for example, in the first outer region 41 or the second outer region 42, the cone portions 21 may become smaller with increasing distance from the inner region 40. This allows the first outer arrangement period P1 and the second outer arrangement period P2 to also have a distribution.

[0048] (Other variations) The present disclosure is not limited to the above-described embodiments and specific examples. Therefore, the above-described embodiments and the like can be modified as appropriate. Representative modifications will be described below. In the following description of the modifications, differences from the above-described embodiments and the like will be mainly described. Furthermore, the same reference numerals are used for parts that are identical or equivalent to each other in the above-described embodiments and the following modifications. Therefore, in the following description of the modifications, the explanations in the above-described embodiments and the like can be used as appropriate for components that have the same reference numerals as the above-described embodiments and the like, unless there is a technical contradiction or special additional explanation.

[0049] The present disclosure is not limited to the specific application targets and device configurations shown in the above embodiments. For example, the application targets of the present disclosure are not limited to automobiles running on public roads. Furthermore, there are no particular limitations on the type of automobile.

[0050] As described above, in the above embodiment, for the sake of simplicity of illustration and description, the imaginary cover surface Vc is assumed to be planar. However, the present disclosure is not limited to such an embodiment. That is, the radio wave transmission area 3 is not limited to being macroscopically flat, but may also be macroscopically curved. That is, the imaginary cover surface Vc may also be curved.

[0051] The radio wave transparent region 3 may be provided in a portion of the bumper 2 or over the entire bumper 2. Similarly, the reflection suppression section 10 may be provided in a portion of the radio wave transparent region 3 or over the entire bumper 2. The first layer 11 may have a single-layer structure or a multi-layer structure. The same applies to the second layer 12 and the third layer 13. Furthermore, the reflection suppression section 10 may be provided with further additional layers, such as a fourth layer or a fifth layer.

[0052] The shape of the cone portion 21 is not limited to a triangular pyramid, but may be an N-sided pyramid having a base 23 of any shape, or may be a cone. N is an integer of 3 or greater. When N=4, i.e., a square pyramid, the cone size S is the length of one side of the square shape of the base 23. When N≧5, the cone size S is the diameter of the circumscribing circle. When it is a cone, the cone size S is the diameter.

[0053] In each of the above embodiments, an example has been shown in which the radio wave transparent cover according to the present disclosure is the bumper 2, but the present disclosure is not limited to such an embodiment. That is, for example, the radio wave transparent cover according to the present disclosure may be a radome 6. The appearance of the vehicle 1 in this case is shown in FIG. 24 .

[0054] In the configuration according to this modified example shown in FIG. 24, the bumper 2 may be provided with the radio wave transparent region 3 shown in FIG. 1, as in the above embodiment. That is, this modified example and the above embodiment may be combined with each other. In this modified example, as shown in FIG. 25, the reflection suppressing portion 10 may be provided in at least a part of the radome 6. As shown in FIG. 26, the reflection suppressing portion 10 in such a radome 6 may have a single-layer structure consisting of only the first layer 11 in the above embodiment. Furthermore, for example, the radio wave transparent cover according to the present disclosure may be a vehicle part other than the bumper 2 (for example, an emblem attached to the front grille).

[0055] In the above description, multiple components that were formed seamlessly and integrally with each other may be formed by bonding separate members together. Similarly, multiple components that were formed by bonding separate members together may be formed seamlessly and integrally with each other. Furthermore, in the above description, multiple components that were formed from the same material may be formed from different materials. Similarly, multiple components that were formed from different materials may be formed from the same material.

[0056] It goes without saying that the elements constituting the above-described embodiments are not necessarily essential unless expressly stated as essential or clearly considered essential in principle. Furthermore, when numerical values ​​such as the number, value, amount, and range of components are mentioned, the present disclosure is not limited to those specific numbers unless expressly stated as essential or clearly limited to a specific number in principle. Similarly, when the shape, direction, positional relationship, etc. of components are mentioned, the present disclosure is not limited to those shapes, directions, positional relationships, etc. unless expressly stated as essential or clearly limited to a specific shape, direction, positional relationship, etc. in principle.

[0057] The modified examples are not limited to the above examples. That is, for example, all or part of one of the multiple embodiments and all or part of another may be combined with each other as long as there is no technical contradiction. Similarly, all or part of one of the multiple modified examples and all or part of another may be combined with each other as long as there is no technical contradiction.

[0058] (Disclosure perspective) As is clear from the above description of the embodiments and modifications, this specification discloses at least the following matters.

[0059] [First viewpoint] A radio wave transparent cover (2, 6) is provided on the front side of a transmitter / receiver (7) provided in a radio wave radar device (4) so ​​as to transmit radio waves emitted from the transmitter / receiver, a reflection suppression unit (10) that suppresses reflection of the radio wave to the transmitting / receiving unit, The reflection suppression unit has a configuration in which a plurality of cone portions (21) each having a hollow cone shape that opens toward the transmitting / receiving unit side are arranged. Radio wave transparent cover. [Second viewpoint] It has a laminated structure of multiple dielectric layers, The cone portion is provided in at least one of the plurality of layers. The radio wave transparent cover according to the first aspect. [Third Perspective] the anti-reflection portion is formed of a dielectric material having a relative dielectric constant of 2 to 20; The radio wave transparent cover according to the first or second aspect. [Fourth viewpoint] The inner cone surface (24) of the cone portion, which is the surface of the cone portion facing the transmitting / receiving portion, is inclined so that the reflection coefficient of the radio wave is less than −6 dB. The radio wave transmission cover according to any one of the first to third aspects. [Fifth viewpoint] The inclination angle of the inner conical surface is 30 to 75 degrees. The radio wave transparent cover according to the fourth aspect. [Sixth viewpoint] The size (S) of the bottom (23) of the cone portion is 0.25 to 1.5 times the wavelength of the radio wave. The radio wave transmission cover according to any one of the first to fifth aspects. [Seventh viewpoint] The size is non-uniform. A radio wave transparent cover according to a sixth aspect. [Eighth viewpoint] The arrangement period of the cone portions is 0.25 to 1.5 times the wavelength of the radio wave. The radio wave transmission cover according to any one of the first to seventh aspects. [Ninth viewpoint] The arrangement period is non-uniform. The radio wave transmission cover according to the eighth aspect. [10th viewpoint] The hollow cone-shaped shape is a triangular pyramid. The radio wave transmission cover according to any one of the first to ninth aspects. [Explanation of symbols]

[0060] 1 vehicle 2 Bumper (radio wave transmission cover in the embodiment) 3 Radio wave transmission area 4. Radio radar equipment 6 Radome (Radio wave transparent cover in modified form) 7 Transmitter / Receiver 10 Reflection suppressor 21 Cone 23 Bottom 24 Medial pyramidal surface

Claims

1. A radio wave transparent cover (2, 6) is provided on the front side of a transmitter / receiver (7) provided in a radio wave radar device (4) so ​​as to transmit radio waves emitted from the transmitter / receiver, a reflection suppression unit (10) that suppresses reflection of the radio wave to the transmitting / receiving unit, The reflection suppression unit has a configuration in which a plurality of cone portions (21) each having a hollow cone shape that opens toward the transmitting / receiving unit side are arranged. Radio wave transparent cover.

2. It has a laminated structure of multiple dielectric layers, The cone portion is provided in at least one of the plurality of layers. The radio wave transparent cover according to claim 1 .

3. The anti-reflection portion is formed of a dielectric material having a relative dielectric constant of 2 to 20. The radio wave transparent cover according to claim 1 .

4. The inner cone surface (24) of the cone portion, which is the surface of the transmitting / receiving portion side, is inclined so that the reflection coefficient of the radio wave is less than −6 dB. The radio wave transparent cover according to claim 1 .

5. The inclination angle (θc) of the inner conical surface is 30 to 75 degrees. The radio wave transmission cover according to claim 4.

6. The size (S) of the base (23) of the cone portion is 0.25 to 1.5 times the wavelength of the radio wave. The radio wave transparent cover according to claim 1 .

7. The size is non-uniform. The radio wave transmission cover according to claim 6.

8. The arrangement period of the cone portions is 0.25 to 1.5 times the wavelength of the radio wave. The radio wave transparent cover according to claim 1 .

9. The arrangement period is non-uniform. The radio wave transparent cover according to claim 8.

10. The hollow cone-shaped shape is a triangular pyramid. The radio wave transparent cover according to claim 1 .

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