Vehicle-mounted radar device

Abstract

To provide a technique capable of more excellently suppressing deterioration of transmission / reception signal quality (that is, amplitude and angle measurement error) of a radar due to a reflected wave from a bumper than before.SOLUTION: An on-vehicle radar device (2) mounted on a vehicle (1) includes a radome (22) and a reflection suppression layer (24). The radome is a member surrounding a transmission / reception part (23) for transmitting / receiving a radar wave, and is installed in a bumper (12) of a vehicle. The reflection suppression layer is provided between the bumper and the radome so as to suppress reflection of the radar wave from the bumper to the transceiver. The reflection suppression layer has a plurality of metal wires (242) and is provided at a position separated from the rear surface (14) of the bumper.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an on-vehicle radar device mounted on a vehicle. [Background technology]

[0002] When a radar device is mounted on the rear side of a structure that easily reflects radar waves, such as a bumper cover, in a vehicle, it is required to effectively suppress the reflection of radar waves inside the vehicle and increase the transmittance of radar waves to the outside of the vehicle using a simple configuration.In this regard, Patent Document 1 describes a technology for suppressing the reflection of radar waves by installing a frequency selective plate that has the function of passing radar waves in a predetermined frequency band and blocking the passage of radio waves of frequencies other than the predetermined frequency band.

[0003] Specifically, the radar device described in Patent Document 1 includes an antenna unit and a radome. The antenna unit transmits and receives radar waves. The radome is a cylindrical member with a bottom that is arranged to cover the antenna unit, and at least its bottom is configured as a transmission part made of a dielectric material, and is arranged so that radar waves transmitted from the antenna unit pass through the transmission part and are transmitted to the outside of the radar device. The radar device is mounted on the back side of a top layer structural member such as a bumper cover. A frequency selective surface is provided on the back side of the top layer structural member. The radar device is arranged so that the frequency selective surface is sandwiched on both sides between the top layer structural member and the transmission part of the radome. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-145777 Summary of the Invention [Problem to be solved by the invention]

[0005] In a structure in which a frequency selective plate is sandwiched between a bumper cover and a radome, as in the radar device described in Patent Document 1, if the frequency selective plate is in close contact with them, the metal pattern on the frequency selective plate must be changed if the reflection characteristics of the bumper cover change. There is also a concern that the adhesive layer may increase loss. The present invention has been made in consideration of the above-mentioned circumstances. Specifically, the present invention provides a technology that can, for example, better suppress the degradation of radar transmission and reception signal quality (i.e., amplitude and angle measurement error) due to waves reflected from the bumper than in the past, without affecting the design of the bumper. [Means for solving the problem]

[0006] The on-board radar device (2) mounted on a vehicle (1) according to claim 1 comprises: a radome (22) that is installed in a bumper (12) of the vehicle and surrounds a transmitting / receiving unit (23) that transmits and receives radar waves; a reflection suppressing layer (24) provided between the bumper and the radome to suppress reflection of the radar wave from the bumper to the transmitter / receiver; Equipped with The reflection-suppressing layer is a plurality of metal wirings (242); It is provided at a position spaced apart from the rear surface (14) of the bumper.

[0007] In this configuration, the reflection suppressing layer having metal wiring is disposed between the rear surface of the bumper and the transmitter / receiver, and is provided at a position spaced apart from the rear surface of the bumper, thereby making it possible to more effectively suppress the degradation of the radar's transmitted and received signal quality (i.e., amplitude and angle measurement error) caused by waves reflected from the bumper, without affecting the design of the bumper.

[0008] In addition, in each section of the application documents, each element may be given a reference symbol in parentheses. However, such reference symbol merely indicates an example of the correspondence between the element and the specific means described in the embodiment described below. Therefore, the present invention 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 equipped with an on-vehicle radar device according to an embodiment of the present invention; [Figure 2] 2 is a cross-sectional view showing an example of the arrangement of the on-vehicle radar device shown in FIG. 1 with a bumper. [Figure 3] 3 is a diagram showing an example of the configuration of metal wiring in the reflection suppressing layer shown in FIG. 2. FIG. [Figure 4] 2 is a cross-sectional view showing an example of the arrangement of a bumper, a radar, and a reflection suppressing layer of the on-vehicle radar device shown in FIG. 1. FIG. [Figure 5] 10 is a graph showing changes in the reflection characteristics of radar waves caused by providing an anti-reflection layer and changing the gap between the anti-reflection layer and the bumper. [Figure 6] 10 is a graph showing changes in reflection characteristics at an incident angle of 0° when the gap between the antireflection layer and the bumper is changed. [Figure 7] 10 is a graph showing the change in transmission characteristics at an incident angle of 0° when the gap between the antireflection layer and the bumper is changed. [Figure 8] 10 is a graph showing changes in the frequency characteristics of the reflected wave at an incident angle of 0° when the gap between the antireflection layer and the bumper is changed. [Figure 9] 10 is a graph showing changes in the frequency characteristics of the reflected wave at an incident angle of 0° when the gap between the antireflection layer and the bumper is changed. [Figure 10] 10 is a graph showing changes in the intensity and peak frequency of the reflected wave at an incident angle of 0° when the gap between the antireflection layer and the bumper is changed. [Figure 11] 2 is a cross-sectional view showing an example of the arrangement of the on-vehicle radar device shown in FIG. 1 with a bumper. [Figure 12] 2 is a cross-sectional view showing an example of the arrangement of the on-vehicle radar device shown in FIG. 1 with a bumper. [Figure 13] 2 is a cross-sectional view showing an example of a mounting structure of the on-vehicle radar device shown in FIG. 1 to a bumper. [Figure 14] FIG. 14 is a cross-sectional side view taken along the line XIV-XIV in FIG. 13. [Figure 15] 2 is a cross-sectional view showing an example of a mounting structure of the on-vehicle radar device shown in FIG. 1 to a bumper. [Figure 16] 2 is an exploded rear view showing an example of a mounting structure for the vehicle-mounted radar device shown in FIG. 1 relative to a bumper. FIG. [Figure 17] FIG. 17 is a diagram showing a cross-sectional configuration of the mounting structure shown in FIG. 16. [Figure 18] FIG. 18 is a diagram showing a cross-sectional configuration in which a part of the mounting structure shown in FIG. 17 is modified. DETAILED DESCRIPTION OF THE INVENTION

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

[0011] Referring to FIG. 1, a vehicle 1 is equipped with an on-board radar device 2. The vehicle 1, which is an application of the present invention, is an automobile that travels on public roads and has a box-shaped body 11. Bumper covers 12 are attached to the front and rear ends of the body 11. The bumper cover 12 is the outermost structural member that constitutes the bumper and is formed mainly from a base material and a paint film. The on-board radar device 2 is installed inside the bumper, i.e., inside the bumper cover 12, and is configured to detect objects around the vehicle 1 by transmitting and receiving radar waves in the millimeter wave or submillimeter wave band.

[0012] 2, the bumper cover 12 has a bumper cover front surface 13, which is the outer surface facing the space outside the vehicle 1, and a bumper cover back surface 14 on the back side thereof. The on-board radar device 2 is provided to face the bumper cover back surface 14. That is, the on-board radar device 2 transmits radar waves toward the bumper cover back surface 14, which then pass through the bumper cover 12 and propagate into the space outside the bumper cover front surface 13.

[0013] For the sake of simplicity of illustration and explanation, the portion of the bumper cover 12 facing the on-board radar device 2 is shown as a macroscopically flat plate in Fig. 2, but the present invention is not limited to this form. "Macroscopically flat plate-like" means that the appearance is generally flat, and more specifically, that the bumper cover front surface 13 and the bumper cover back surface 14 are planar and parallel to each other. This also applies to the other drawings described below.

[0014] The radar main body 21 constituting the main body of the on-vehicle radar device 2 includes a radome 22 and a transmitter / receiver 23. In addition to the radar main body 21, the on-vehicle radar device 2 further includes a reflection suppressing layer 24. As shown in Fig. 4, the on-vehicle radar device 2 may further include an air gap forming material 25. The reflection suppressing layer 24 and the air gap forming material 25 will be described later.

[0015] Referring again to Figure 2, the radar main body 21 is disposed so that the radome 22 is spaced apart from the rear surface 14 of the bumper cover in the direction of transmission and reception of radar waves. The "transmission and reception direction of radar waves" is typically the vertical direction in Figure 2. The radome 22 is a cover-like member that surrounds the transmitter / receiver unit 23, and is formed in a box shape from synthetic resin, which is a dielectric. The transmitter / receiver unit 23 includes an antenna 231 and is configured to transmit and receive radar waves.

[0016] The reflection suppressing layer 24 is provided between the bumper cover 12 and the radome 22 so as to suppress reflection of radar waves from the bumper cover 12 to the transmitter / receiver 23. Specifically, in the configuration example shown in FIG. 2 , the reflection suppressing layer 24 is fixed to the bumper cover 12 at the rear surface 14 of the bumper cover. A gap is provided between the reflection suppressing layer 24 and the radome 22 in the transmission and reception direction of the radar waves. As shown in FIG. 3 , the reflection suppressing layer 24 includes a dielectric layer 241 and a plurality of metal wirings 242 supported by the dielectric layer 241. In this embodiment, the plurality of metal wirings 242 are formed in a mesh shape that is symmetrical in the vertical and horizontal directions so as to accommodate both horizontally polarized waves and vertically polarized waves.

[0017] 2, the reflection suppressing layer 24 is bonded to the bumper cover rear surface 14 via a bonding layer made of double-sided tape or the like (not shown). Therefore, the reflection suppressing layer 24 is provided at a position separated from the bumper cover rear surface 14 by a distance equivalent to the thickness of the bonding layer. In this configuration example, the distance between the bumper cover rear surface 14 and the reflection suppressing layer 24 in the transmission and reception direction of the radar wave is determined by the thickness of the bonding layer.

[0018] 4, the distance between the bumper cover rear surface 14 and the reflection suppressing layer 24 can be adjusted by the thickness of the gap-forming material 25 sandwiched between them. As a result, a gap G formed by an air layer is provided between the bumper cover rear surface 14 and the reflection suppressing layer 24. When the width of the gap G, that is, the distance from the bumper cover rear surface 14 to the reflection suppressing layer 24, is defined as dg, changes in the reflection characteristics due to changes in dg will be explained below using experimental results and computer simulation results.

[0019] FIG. 5 is a graph showing the experimental results of the reflection peak frequency. The "reflection peak frequency" is the frequency at which the frequency characteristics of the radar wave transmitted from the transmitter / receiver 23 and reflected from the bumper cover 12 exhibit a minimum value. The frequency of the radar wave in the experiment was 76.5 GHz. In addition, the target value is indicated by a diamond plot in the graph. The target value is a suitable characteristic value that is expected to be achieved in an actual product, and in this specific example, the reflection intensity is -15 dB or less at 76 to 77 GHz.

[0020] The solid "before countermeasure" curve in Fig. 5 shows the experimental results when only the bumper cover 12 was used without the reflection suppressing layer 24. The curve for dg = 0.1 mm shows the experimental results when the rear surface 14 of the bumper cover and the reflection suppressing layer 24 were joined with 0.1 mm-thick double-sided tape in the configuration example shown in Fig. 2. The curve for dg = 1.9 mm shows the experimental results when the width of the gap G was adjusted using the gap-forming material 25 so that dg = 1.9 mm in the configuration example shown in Fig. 4.

[0021] Generally, the phase of the reflection coefficient is reversed when light is incident from a medium with a low dielectric constant to a medium with a high dielectric constant. Therefore, the reflected wave at the boundary between the reflection suppressing layer 24 and the gap G and the reflected wave at the rear surface 14 of the bumper cover are in a phase-reversed relationship and cancel each other out when the path length difference is an integer multiple of the wavelength, i.e., when the width dg of the gap G is an integer multiple of half the wavelength. Therefore, when n is an integer greater than or equal to 0, equivalent performance can be obtained for multiple values ​​of n that satisfy dg = n × (λ / 2), where λ is the wavelength of the radar wave.

[0022] In this regard, in the experimental results shown in FIG. 5, when dg = 0.1 mm, although the reflection intensity at 76 to 77 GHz is reduced compared to that before the countermeasure, it does not reach the target value. The reflection peak frequency in this case is around 74 GHz. On the other hand, when dg = 1.9 mm, the reflection peak frequency shifts to around 76 GHz on the high-frequency side, and the reflection intensity is reduced to the extent that it satisfies the target value. Here, the value of λ / 2 is approximately 1.96 mm, and the difference Δdg = 1.8 mm between dg = 0.1 mm and dg = 1.9 mm is << 1.96 mm.

[0023] FIGS. 6 to 10 show the results of computer simulations with the radar wave frequency set to 76.5 GHz. FIG. 6 shows the change in the intensity of the reflected wave when the width dg of the gap G is changed. FIG. 7 shows the change in the transmission intensity when the width dg of the gap G is changed. In FIGS. 6 and 7, the value of the width dg of the gap G is shown as a normalized value indicating how many times the wavelength λ of the radar wave it is.

[0024] As shown in FIGS. 6 and 7, it was confirmed that there is a point where equivalent transmission and reflection performance can be obtained at a position where the value of the width dg of the gap G is separated by 0.5λ. Also, when the target value of the reflection intensity is set to -15 dB or less and the target value of the transmission intensity is set to -1.2 dB or more, it was confirmed that good transmission and reflection performance can be obtained within the range satisfying the following formula (1). Here, n is an integer of 0 or more, 0 ≦ offset < kλ, k is a value sufficiently smaller than 0.5 and typically about 0.1. However, when n = 0, offset > 0. dg = n×(λ / 2) ± offset ··· (1)

[0025] Figure 8 shows the results of comparing the frequency characteristics of reflected waves for four different offsets: dg = 0 mm, 0.1 mm, 1.9 mm, and 2 mm. As shown in Figure 8, it can be seen that the characteristics of the pair dg = 0 mm and dg = 1.9 mm, and the pair dg = 0.1 mm and dg = 2 mm are close to each other. This is because the spacing is close to λ / 2, or approximately 1.96 mm. For example, in equation (1) above, when n = 0 and offset = 0.1 mm, dg = 0.1 mm, and when n = 1 and offset = 0.1 mm, dg = 2.06 mm, which is approximately 2 mm.

[0026] Figure 9 shows the change in the frequency characteristics of the reflected wave when the value of dg is changed in 0.1 mm increments from 0 mm to 2 mm. As shown in Figure 9, a typical change in the frequency characteristics can be seen in the first order, i.e., the first significant reflection peak frequency seen from the low frequency side, which occurs in the range of approximately 40 to 60 GHz, gradually shifting to lower frequencies as the value of dg moves from 0 mm to 2 mm. Here, we focused on the high-order reflection peak frequency near 100 GHz and discovered that by widening the width dg of the gap, or air gap G, we could pull it to near 77 GHz.

[0027] Figure 10 shows the change in reflection peak frequency and reflection intensity in the range of 70 to 100 GHz when the dg value is changed in 0.1 mm increments from 0 mm to 2 mm. In the figure, the open diamond plots indicate the first-order reflection peak frequencies, and the open square plots indicate higher-order reflection peak frequencies. The thin dotted line along the plot of higher-order reflection peak frequencies indicates the regression line of a linear function, and the regression equation is shown above it. The solid line plots indicate the reflection intensity.

[0028] As mentioned above, increasing the gap distance dg shifts the reflection peak frequency to the lower frequency side. The slope of the regression line α is ≒ -1.2 mmGHz / 0.1 mm. The method for calculating the gap width dg, i.e., the gap G, which corrects the error from the target value of the reflection peak frequency, is shown below. In the formula below, f0 is the reflection peak frequency when dg = 0, and f target is the target value of the reflection peak frequency, and ferr is the error between the target value and the reflection peak frequency.

number

number

[0029] For example, if the reflection peak frequency is at 75 GHz with dg = 0 mm, it is possible to reproduce the same reflection peak frequency at 75 GHz with dg = 1.96 mm. On the other hand, if you want to raise the reflection peak frequency to around 76 GHz, it is recommended to set dg to around 1.86 mm (i.e., Δdg = -0.1 mm). Similarly, if the reflection peak frequency is at 77 GHz, it is possible to reproduce the same reflection peak frequency at 77 GHz with dg = 1.96 mm. On the other hand, if you want to lower the reflection peak frequency to around 76 GHz, it is recommended to set dg to around 2.06 mm (i.e., Δdg = +0.1 mm).

[0030] As described above, in this embodiment, the reflection suppression layer 24 having the metal wiring 242 is disposed between the bumper cover rear surface 14 and the transceiver 23, and is provided at a position spaced apart from the bumper cover rear surface 14. This allows the gap to be adjusted to favorably adjust the reflection characteristics. Specifically, the reflection suppression layer 24 is disposed at a distance from the bumper cover rear surface 14 that is approximately an integer multiple of half the wavelength of the radar wave. More specifically, the reflection suppression layer 24 is disposed so that the distance dg from the bumper cover rear surface 14 to the reflection suppression layer 24 satisfies the above formula (1).

[0031] This makes it possible to, for example, shift the reflection peak frequency to a higher frequency, which was previously difficult. This also makes it possible to use the same reflection suppressing layer 24 for multiple vehicle models. Furthermore, for example, when there is variation in the thickness of the bumper cover body 121, which is the base material of the bumper cover 12, it is possible to set the reflection peak frequency to a desired value by adjusting the distance dg. This embodiment is also applicable to curved bumpers in which an unintended gap occurs between the bumper cover 12 and the reflection suppressing layer 24. Therefore, according to this embodiment, it is possible to more effectively suppress erroneous detection or reduced sensitivity due to reflected waves from the bumper cover 12 than in the past, while not affecting the design of the bumper cover 12.

[0032] To provide a desired gap between the reflection suppression layer 24 and the bumper cover 12, i.e., the bumper cover rear surface 14, without tightly contacting them, the reflection suppression layer 24 may be provided on the radome 22, as shown in FIG. 11 . In this case, the reflection suppression layer 24 may be fixed to the radome 22 using, for example, an adhesive or double-sided tape. In such a configuration, although the position of the radar main body 21 is restricted, it is possible to reduce the size of the reflection suppression layer 24 required to accommodate a desired field of view, thereby achieving cost reduction. Alternatively, for example, as shown in FIG. 12 , the reflection suppression layer 24 may be configured not to be fixed to either the bumper cover rear surface 14 or the radome 22. In such a configuration, the degree of freedom in arranging the radar main body 21 and the reflection suppression layer 24 is improved. Specific examples of these configurations will be described below.

[0033] (Example 1) 13 and 14 show a specific example of positioning the reflection suppression layer 24 at a desired position in the configuration shown in Fig. 11 in which the reflection suppression layer 24 is attached to the radar main body 21, i.e., the radome 22. Note that in Figs. 13 and 14, the bumper cover 12 has a bumper cover main body 121 made of synthetic resin and a coating film 122 with a relatively high dielectric constant formed on the outer surface of the bumper cover main body 121, but the bumper cover 12 shown in Fig. 2 etc. can also be configured in a similar manner.

[0034] In this example, an engagement protrusion 243 is provided on the outer edge of the reflection suppression layer 24. The engagement protrusion 243 may be formed, for example, as a triangular prism-shaped protrusion extending across substantially the entire width of the reflection suppression layer 24. The radar onboard structure 300 according to this example is configured to position the reflection suppression layer 24 using the engagement protrusion 243 and a bracket 301 integrated with the bumper cover 12.

[0035] The radar mounting structure 300 mounts the radar main body 21, to which the reflection suppression layer 24 is fixed, to a bracket 301 using a sensor mounting plate 302 and radar fixing screws 303. That is, the bracket 301 is configured so that the radar main body 21 and the reflection suppression layer 24 can be detachably mounted to the bumper. The sensor mounting plate 302 is integrated with the radar main body 21 on the surface of the radar main body 21 opposite to the surface to which the reflection suppression layer 24 is fixed.

[0036] The bracket 301 is formed in a generally U-shape and has a pair of bracket side plates 311 and a bracket bottom plate 312 provided therebetween. The bracket side plates 311 and the bracket bottom plate 312 are molded seamlessly as a single piece from synthetic resin. The bracket 301 may be integrated with the bumper cover main body 121 afterward by a joining means such as adhesion or welding, or may be molded seamlessly as a single piece with the bumper cover main body 121.

[0037] The bracket 301 is configured so that the distance between the bumper cover rear surface 14 and the reflection suppressing layer 24 can be set to a predetermined distance. Specifically, in this example, as shown in Fig. 14 , an engagement groove 313 is formed in the bracket bottom plate 312, which is a groove for positioning and arranging the reflection suppressing layer 24 by engaging with an engagement protrusion 243 provided on the reflection suppressing layer 24.

[0038] In this specific example, a plurality of engagement grooves 313 are provided corresponding to a plurality of different values ​​of the integer n that satisfy the above formula (1). Specifically, the engagement grooves 313 are disposed at a position corresponding to n=1, a position corresponding to n=2, ... Here, by changing the offset value between the plurality of engagement grooves 313 with different values ​​of n, it is possible to change the reflection characteristics (i.e., reflection peak frequency) depending on which engagement groove 313 is selected.

[0039] (Example 2) A specific example of positioning the reflection suppression layer 24 at a desired position in the configuration shown in FIG. 12 in which the reflection suppression layer 24 is not fixed to either the bumper cover rear surface 14 or the radar main body 21, i.e., the radome 22, is shown with reference to FIG. 15 . In this specific example, the bracket 301 is also formed in a substantially U-shape. However, in this specific example, the engaging protrusion 243 on the reflection suppression layer 24 and the engaging groove 313 that engages with it, as shown in FIGS. 13 and 14 , are not provided. Note that, as will be described later, the engaging protrusion 243 can also be provided on the reflection suppression layer 24 in this specific example, but the position can be different from the position shown in FIG. 14 .

[0040] Meanwhile, in this specific example, the bracket side plates 311 are provided with slots 314 into which the reflection suppressing layer 24 is inserted to position and arrange the layer. The slots 314 are formed in the shape of grooves that open toward the space between the pair of bracket side plates 311. The slots 314 are provided in both of the pair of bracket side plates 311. In other words, the pair of slots 314 are formed to face each other.

[0041] In this specific example, multiple pairs of slots 314 are provided corresponding to multiple different values ​​of the integer n that satisfy the above formula (1). Specifically, the slots 314 are arranged at a position corresponding to n=1, a position corresponding to n=2, and so on. Here, by changing the offset value between multiple pairs of slots 314 with different values ​​of n, it is possible to change the reflection characteristics (i.e., reflection peak frequency) depending on which slot 314 is selected.

[0042] (Example 3) 16 and 17 show a specific example in which the reflection suppression layer 24 is positioned at a desired position while being fixed separately from the fixing of the radar main body 21, similar to the above-described specific example 2. In this specific example, the bracket 301 has a pair of radar fixing parts 315 and a reflection suppression layer fixing part 316 provided therebetween.

[0043] The radar fixing portion 315 is formed so as to protrude from the bumper cover rear surface 14. The radar fixing portion 315 is provided with a radar fixing hole 317, which is a screw hole for fixing the radar main body 21. The reflection suppressing layer fixing portion 316 is formed in a plate or block shape extending along the bumper cover rear surface 14. The reflection suppressing layer fixing portion 316 is provided with a reflection suppressing layer fixing hole 318, which is a screw hole used to attach the reflection suppressing layer 24. The reflection suppressing layer fixing portion 316 is provided with a window-frame-shaped flange portion 319. The flange portion 319 is formed in a thin plate shape protruding inward from the radar fixing portion 315 and the reflection suppressing layer fixing portion 316.

[0044] The sensor mounting plate 302 is formed with a first screw insertion hole 321, which is a through hole for inserting the radar fixing screw 303. Then, the sensor mounting plate 302 is brought into contact with the radar fixing portion 315, and the radar fixing hole 317 is aligned with the first screw insertion hole 321, and the radar fixing screw 303 is screwed into the radar fixing hole 317, thereby mounting the radar main body 21 to the bracket 301.

[0045] Before mounting the radar main body 21 on the bracket 301, the reflection suppression layer 24 is mounted on the bracket 301 using a reflection suppression layer fixing plate 340, which is a plate-shaped member. This makes it possible to position the radar main body 21 and the reflection suppression layer 24 separately and independently.

[0046] The reflection suppressing layer fixing plate 340 has a pair of bracket fixing portions 341 and a reflection suppressing layer pressing portion 342 provided between them, and is formed seamlessly as a single piece from the same material. The pair of bracket fixing portions 341 are formed in the shape of flat plates and are provided parallel to each other. The reflection suppressing layer pressing portion 342 is formed in the shape of a window frame with an opening 343 on the inside.

[0047] The bracket fixing portion 341 is provided with a second screw insertion hole 344, which is a through-hole. The second screw insertion hole 344 is formed so that a reflection suppression layer fixing screw 345 for fixing the reflection suppression layer fixing plate 340 to the bracket 301 can be inserted therethrough. Then, as shown in FIG. 17 , the flange portion 319, the gap-forming material 25, the reflection suppression layer 24, and the reflection suppression layer pressing portion 342 are stacked in this order, and the reflection suppression layer fixing hole 318 and the second screw insertion hole 344 are aligned and the reflection suppression layer fixing screw 345 is screwed in, thereby attaching the reflection suppression layer 24 to the bracket 301.

[0048] In this configuration, it is possible to adjust the gap dimension between the bumper cover rear surface 14 and the reflection suppressing layer 24 by adjusting the total thickness of the flange portion 319 and the gap-forming material 25. In other words, it is possible to easily adjust the reflection peak frequency by adjusting the thickness of the gap-forming material 25, which is a spacer.

[0049] 18, the flange portion 319 can be omitted. That is, in the configuration example shown in FIG. 18, the reflection suppressing layer 24 and the gap-forming material 25 are stacked together and pressed against the bumper cover rear surface 14 by the reflection suppressing layer fixing plate 340. Even with this configuration, it is possible to easily adjust the reflection peak frequency by adjusting the thickness of the gap-forming material 25.

[0050] (Variation) The present invention 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.

[0051] The present invention is not limited to the specific application targets and device configurations shown in the above embodiments. For example, the application targets of the present invention are not limited to automobiles running on public roads. Furthermore, there are no particular limitations on the type of automobile.

[0052] The configuration of the reflection suppressing layer 24 is not limited to the above specific example. That is, in the above embodiment, the plurality of metal wirings 242 are formed in a mesh pattern to accommodate both horizontally polarized waves and vertically polarized waves, but the present invention is not limited to such an embodiment. Specifically, for example, if the transceiver 23 includes a horizontally polarized antenna 231, the plurality of metal wirings 242 are arranged parallel to one another and extend in the horizontal direction.

[0053] The metal wiring 242 may also function as an electric heating wire heater, which allows the reflection suppressing layer 24 to be used as an antifreeze heater to prevent condensation around the in-vehicle radar device 2.

[0054] Alternatively, for example, the configuration of the reflection suppression layer 24 may be the same as that of the frequency selective surfaces disclosed in Japanese Patent Application Laid-Open No. 2016-145777 and Japanese Patent Application Laid-Open No. 2018-19136.

[0055] The fixing structure and positioning structure of the reflection suppressing layer 24 are not limited to the above specific examples. That is, for example, the bracket 301 may be a separate structure rather than being integrated with the bumper cover 12. There are also no particular limitations on the detailed configuration of the bracket 301.

[0056] Specific Example 1 shown in Figures 13 and 14 and Specific Example 2 shown in Figure 15 may be combined with each other. That is, for example, the slot portion 314 shown in Figure 15 may be a groove that engages with the engaging protrusions 243 provided on both ends of the reflection suppressing layer 24.

[0057] 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.

[0058] It goes without saying that the elements constituting the above-described embodiments are not necessarily essential unless they are particularly clearly stated as essential or are considered to be clearly essential in principle. Furthermore, when numerical values ​​such as the number, value, amount, range, etc. of components are mentioned, the present invention is not limited to those specific numbers unless they are particularly clearly stated as essential or are clearly limited to specific numbers in principle. Similarly, when the shape, direction, positional relationship, etc. of components are mentioned, the present invention is not limited to those shapes, directions, positional relationship, etc. unless they are particularly clearly stated as essential or are clearly limited to specific shapes, directions, positional relationship, etc. in principle.

[0059] The variations are not limited to the above examples. For example, all or part of one of the multiple specific examples may be combined with all or part of another of the multiple specific examples, provided that no technical inconsistency exists. Similarly, all or part of one of the multiple variations may be combined with all or part of another of the multiple variations, provided that no technical inconsistency exists. [Explanation of symbols]

[0060] 1 vehicle 2. On-board radar equipment 12 Bumper 14 Back of bumper 21 Radar body 22 Radome 23 Transmitter / Receiver 24 Reflection suppression layer 242 Metal wiring G void

Claims

1. An on-board radar device (2) mounted on a vehicle (1), a radome (22) that is installed in a bumper (12) of the vehicle and surrounds a transmitting / receiving unit (23) that transmits and receives radar waves; a reflection suppressing layer (24) provided between the bumper and the radome so as to suppress reflection of the radar wave from the bumper to the transmitting / receiving unit; Equipped with The reflection-suppressing layer is a plurality of metal wirings (242); provided at a position spaced apart from the rear surface (14) of the bumper; Automotive radar equipment.

2. the reflection suppressing layer is disposed at a distance from the rear surface that is close to an integer multiple of half the wavelength of the radar wave; The on-vehicle radar device according to claim 1 .

3. an air gap (G) is provided between the rear surface and the reflection suppressing layer; The on-vehicle radar device according to claim 1 .

4. The reflection suppressing layer is provided on the surface of the radome. The on-vehicle radar device according to claim 1 .

5. a bracket (301) for detachably attaching the radar body (21) including the transmitting / receiving unit and the radome and the reflection suppressing layer to the bumper; the bracket is configured so that the distance from the rear surface to the reflection suppressing layer can be set to a predetermined distance. The on-vehicle radar device according to claim 1 .

6. A slot (314) for inserting and positioning the reflection suppressing layer is further provided, The slot portion is When the distance from the rear surface to the reflection suppressing layer is dg and the wavelength of the radar wave is λ, the following equation (1) is satisfied: dg=n×(λ / 2)±offset...(1) A plurality of values ​​are provided corresponding to different values ​​of the integer n that satisfy the above. The on-vehicle radar device according to claim 1 .

7. an engagement groove (313) that is a groove for positioning and arranging the reflection suppressing layer by engaging with the reflection suppressing layer, The engagement groove is When the distance from the rear surface to the reflection suppressing layer is dg and the wavelength of the radar wave is λ, the following equation (1) is satisfied: dg=n×(λ / 2)±offset...(1) A plurality of values ​​are provided corresponding to different values ​​of the integer n that satisfy the above. The on-vehicle radar device according to claim 1 .

8. The metal wiring functions as an electric wire heater. The on-vehicle radar device according to claim 1 .

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