Radome for vehicle-mounted radar device and vehicle-mounted radar structure

Abstract

To provide a radome which exhibits practical snow melting capability as a radome for a vehicle-mounted radar device while suppressing attenuation of an electromagnetic wave emitted by the vehicle-mounted radar device within an acceptable range.SOLUTION: A radome 1 for a vehicle-mounted radar device is provided, having a base body 2 comprising an electromagnetic wave transparent base material 3 and a heater wire 41 stacked on an inner surface of the base material 3 and wired along an in-plane direction of the base material 3. Linear portions 411 of the heater wire 41 are juxtaposed in a spaced-apart manner in the in-plane direction of the base material 3 within an electromagnetic wave irradiated area R of the base material 3. The linear portions 411 of the heater wire 41 in the electromagnetic wave radiated area R of the base material 3 is set to occupy area corresponding to 1-24%, inclusive, of the electromagnetic wave irradiated area R.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a radome for an on-vehicle radar device provided on the front side of the on-vehicle radar device, and more particularly to a radome for an on-vehicle radar device having a snow melting function and an on-vehicle radar structure including this radome. [Background technology]

[0002] Conventionally, there are radomes for vehicle-mounted radar devices having a snow-melting function, such as those disclosed in Patent Documents 1 and 2, which can suppress attenuation during transmission of millimeter waves while exerting the snow-melting function. This radome has a decorative main body part having millimeter-wave transparency and a linear heater wire, and the heater wire has multiple straight parts extending parallel to each other, and is configured by connecting the ends of adjacent straight parts with arc-shaped folded parts. Some of the multiple straight parts of the heater wire are arranged within the millimeter-wave irradiation area, and the area ratio of all the straight parts in the millimeter-wave irradiation area is set to 10% or less so that the attenuation of millimeter waves is the allowable value of 2.5 dB or less.

[0003] Furthermore, Patent Documents 1 and 2 disclose that when the straight portion of the heater wire is parallel to the polarization plane of the millimeter wave, the millimeter wave may come into surface contact with the straight portion of the heater wire, hindering transmission and attenuating the millimeter wave, and that by arranging the straight portion of the heater wire perpendicular to the polarization plane of the millimeter wave, the area of ​​contact between the millimeter wave and the straight portion of the heater wire can be minimized, minimizing the amount of millimeter wave whose transmission is hindered and minimizing the attenuation of the millimeter wave. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-66705 A [Patent Document 2] JP 2018-66706 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, in the radomes of Patent Documents 1 and 2, it is possible to suppress the amount of attenuation of millimeter waves by setting the area ratio of the straight portion of the heater wire to the millimeter wave irradiation region to 10% or less. However, since the amount of heater wire required to exhibit a practical snow melting function as a radome for an on-vehicle radar device is not disclosed, if the area ratio of the straight portion of the heater wire to the millimeter wave irradiation region is set to an arbitrary area ratio of 10% or less, there are cases in which a practical snow melting function cannot be exhibited. Therefore, there is a demand for a radome with a structure that can exhibit a practical snow melting function as a radome for an on-vehicle radar device while suppressing the attenuation of the electromagnetic waves irradiated by the on-vehicle radar device.

[0006] The present invention has been proposed in consideration of the above-mentioned problems, and aims to provide a radome for an on-board radar device and an on-board radar structure that can suppress the attenuation of the electromagnetic waves radiated by the on-board radar device within an acceptable range while providing a practical snow-melting function as a radome for an on-board radar device. [Means for solving the problem]

[0007] The radome for an on-vehicle radar device of the present invention comprises an electromagnetic wave transparent substrate and a base body having heater wires arranged in a layered manner on the inner surface of the substrate and wired in the surface direction of the substrate, in which the straight portions of the heater wires are arranged in parallel with intervals in the surface direction of the substrate in the electromagnetic wave irradiation region of the substrate, and the surface occupancy rate of the straight portions of the heater wires in the electromagnetic wave irradiation region of the substrate is set to 1% or more and 24% or less.Furthermore, the radome for an on-vehicle radar device of the present invention comprises an electromagnetic wave transparent substrate and a base body having heater wires arranged in a layered manner on the inner surface of the substrate, which is on the vehicle center side in front of the on-vehicle radar device arranged on the vehicle center side, and wired in the surface direction of the substrate, in which the straight portions of the heater wires are arranged in parallel with intervals in the surface direction of the substrate in the electromagnetic wave irradiation region of the substrate, the straight portions of the heater wires are arranged in parallel so as to extend substantially perpendicular to the plane of polarization of the linearly polarized electromagnetic waves irradiated by the on-vehicle radar device,The surface occupancy rate of the straight line portion of the heater wire in the electromagnetic wave irradiation region of the substrate is set to 1% or more and 24% or less, the heater wire and an electromagnetic wave permeable insulating film constitute a heater sheet, the heater sheet is laminated and fixed on the inner surface side of the substrate, the heater wire is wired, and a refractive index defined based on the complex dielectric constant of the substrate and a refractive index defined based on the complex dielectric constant of the insulating film are matched or close to each other. The insulating film is welded to be fixed to the base material. It is characterized by: The radome for an on-vehicle radar device of the present invention has an electromagnetic wave transparent base material, and a base body including heater wires arranged in a laminated manner on the inner surface side of the base material, which is the center side of the vehicle and in front of the on-vehicle radar device arranged on the center side of the vehicle, and wired in a surface direction of the base material, in an electromagnetic wave irradiation area of ​​the base material, straight portions of the heater wires are arranged in parallel with intervals in the surface direction of the base material, the straight portions of the heater wires are arranged in parallel with each other so as to extend approximately perpendicularly to the polarization plane of the linearly polarized electromagnetic wave irradiated by the on-vehicle radar device, and the surface occupancy rate of the straight portions of the heater wires in the electromagnetic wave irradiation area of ​​the base material is The dielectric constant is set to be 1% or more and 24% or less, the heater sheet is composed of the heater wire and an electromagnetic wave permeable insulating film, the heater sheet is laminated and fixed to the inner surface side of the base material to wire the heater wire, the refractive index defined based on the complex dielectric constant of the base material and the refractive index defined based on the complex dielectric constant of the insulating film match or are close to each other, and the insulating film is fixed to the base material via an adhesive layer whose refractive indexes defined based on the complex dielectric constant of the base material and the insulating film match or are close to each other. According to this, by setting the surface occupancy rate of the straight portion of the heater wire in the electromagnetic wave irradiation region of the substrate to 1% or more, the temperature of the outer surface of the substrate can be kept above 0°C even when the environmental temperature is -5°C and the vehicle is traveling at a speed of 100km / h. Therefore, the attenuation of the electromagnetic waves irradiated by the vehicle-mounted radar device can be suppressed within the required allowable range, and a practical snow-melting function can be achieved as a radome for the vehicle-mounted radar device.

[0008] The radome for an automotive radar device of the present invention is characterized in that the straight portions of the heater wire are arranged in parallel so as to extend approximately perpendicular to the polarization plane of the linearly polarized electromagnetic wave irradiated by the automotive radar device, and the surface occupancy rate of the straight portions of the heater wire in the electromagnetic wave irradiation area of ​​the substrate is set to be 1% or more and 24% or less. This allows the radome for an automotive radar device to exhibit a practical snow-melting function, while ensuring that the transmittance of the base material for the electromagnetic waves emitted by the automotive radar device is -1.5 dB or higher, and suppressing the attenuation of the electromagnetic waves within a high allowable range that is sufficient for practical use.

[0009] The radome for an automotive radar device of the present invention is characterized in that the straight portions of the heater wire are arranged in parallel so as to extend approximately perpendicular to the polarization plane of the linearly polarized electromagnetic wave irradiated by the automotive radar device, and the surface occupancy rate of the straight portions of the heater wire in the electromagnetic wave irradiation area of ​​the substrate is set to be 3% or more and 20% or less. With this, even when the environmental temperature is -15°C and the vehicle is traveling at 100km / h, the temperature of the outer surface of the base material can be kept above 0°C, and snow can be reliably melted on the radome for the on-vehicle radar device even in a more severe cold environment. In addition, the transmittance of the base material for the electromagnetic waves irradiated by the on-vehicle radar device can be guaranteed to be -1.0dB or higher, and the attenuation of the electromagnetic waves can be suppressed within a very high allowable range that is sufficient for practical use. Furthermore, it is also suitable as a radome configured such that the straight portions of the heater wires are arranged in parallel so as to extend approximately perpendicular to the polarization plane of the linearly polarized electromagnetic wave irradiated by the vehicle-mounted radar device, and the surface occupancy rate of the straight portions of the heater wires in the electromagnetic wave irradiation area of ​​the substrate is set to 1% or more and 20% or less.It is also suitable as a radome configured such that the straight portions of the heater wires are arranged in parallel so as to extend approximately perpendicular to the polarization plane of the linearly polarized electromagnetic wave irradiated by the vehicle-mounted radar device, and the surface occupancy rate of the straight portions of the heater wires in the electromagnetic wave irradiation area of ​​the substrate is set to 3% or more and 24% or less.

[0010] The radome for an automotive radar device of the present invention is characterized in that the straight portions of the heater wire are arranged in parallel so as to extend approximately perpendicular to the polarization plane of the linearly polarized electromagnetic wave irradiated by the automotive radar device, and the surface occupancy rate of the straight portions of the heater wire in the electromagnetic wave irradiation area of ​​the substrate is set to be 3% or more and 7.5% or less. With this, even when the environmental temperature is -15°C and the vehicle is traveling at 100km / h, the temperature of the outer surface of the base material can be kept above 0°C, and snow can be reliably melted on the radome for the vehicle-mounted radar device even in a more severe cold environment. In addition, the transmittance of the base material against the electromagnetic waves irradiated by the vehicle-mounted radar device can be guaranteed to be -0.35dB or higher, ensuring an extremely high electromagnetic wave transmittance.

[0011] The radome for an automotive radar device of the present invention is characterized in that the straight portions of the heater wire are arranged in parallel to extend approximately parallel to the polarization plane of the linearly polarized electromagnetic wave irradiated by the automotive radar device, and the surface occupancy rate of the straight portions of the heater wire in the electromagnetic wave irradiation area of ​​the substrate is set to be 1% or more and 16% or less.Furthermore, the radome for an on-vehicle radar device of the present invention has an electromagnetic wave permeable base material, and a base body including a heater wire arranged in a laminated manner on the inner surface side of the base material, which is the center side of the vehicle and in front of the on-vehicle radar device arranged on the center side of the vehicle, and wired in a surface direction of the base material, in which straight lines of the heater wire are arranged in parallel with a space in the surface direction of the base material in an electromagnetic wave irradiation area of ​​the base material, the straight lines of the heater wire are arranged in parallel so as to extend approximately parallel to the polarization plane of the linearly polarized electromagnetic wave irradiated by the on-vehicle radar device, the surface occupancy rate of the straight lines of the heater wire in the electromagnetic wave irradiation area of ​​the base material is set to 1% or more and 16% or less, the heater wire and an electromagnetic wave permeable insulating film form a heater sheet, the heater sheet is arranged in a laminated manner on the inner surface side of the base material and fixed thereto, a refractive index defined based on the complex dielectric constant of the base material and a refractive index defined based on the complex dielectric constant of the insulating film are matched or close to each other, and the insulating film is welded to fix the insulating film to the base material. The radome for an on-vehicle radar device of the present invention has an electromagnetic wave transparent base material, and a base body including heater wires arranged in a laminated manner on the inner surface side of the base material, which is the center side of the vehicle and in front of the on-vehicle radar device arranged on the center side of the vehicle, and wired in a surface direction of the base material, wherein straight portions of the heater wires are arranged in parallel with intervals in the surface direction of the base material in an electromagnetic wave irradiation area of ​​the base material, the straight portions of the heater wires are arranged in parallel with each other so as to extend approximately parallel to the polarization plane of the linearly polarized electromagnetic wave irradiated by the on-vehicle radar device, and the surface occupancy rate of the straight portions of the heater wires in the electromagnetic wave irradiation area of ​​the base material is 1 % or more and 16% or less, a heater sheet is formed of the heater wire and an electromagnetic wave permeable insulating film, the heater sheet is laminated and fixed to the inner surface side of the base material to wire the heater wire, a refractive index defined based on the complex dielectric constant of the base material and a refractive index defined based on the complex dielectric constant of the insulating film match or are close to each other, and the insulating film is fixed to the base material via an adhesive layer whose refractive indexes defined based on the complex dielectric constant of the base material and the insulating film match or are close to each other. This allows the radome for an automotive radar device to exhibit a practical snow-melting function, while ensuring that the transmittance of the base material for the electromagnetic waves emitted by the automotive radar device is -1.5 dB or higher, and suppressing the attenuation of the electromagnetic waves within a high allowable range that is sufficient for practical use.

[0012] The radome for an automotive radar device of the present invention is characterized in that the straight portions of the heater wire are arranged in parallel to extend approximately parallel to the polarization plane of the linearly polarized electromagnetic wave irradiated by the automotive radar device, and the surface occupancy rate of the straight portions of the heater wire in the electromagnetic wave irradiation area of ​​the substrate is set to be 3% or more and 13% or less. With this, even when the environmental temperature is -15°C and the vehicle is traveling at 100km / h, the temperature of the outer surface of the base material can be kept above 0°C, and snow can be reliably melted on the radome for the on-vehicle radar device even in a more severe cold environment. In addition, the transmittance of the base material for the electromagnetic waves irradiated by the on-vehicle radar device can be guaranteed to be -1.0dB or higher, and the attenuation of the electromagnetic waves can be suppressed within a very high allowable range that is sufficient for practical use. Furthermore, the straight portions of the heater wire are arranged in parallel so as to extend approximately parallel to the polarization plane of the linearly polarized electromagnetic wave irradiated by the vehicle-mounted radar device, and the surface occupancy rate of the straight portions of the heater wire in the electromagnetic wave irradiation area of ​​the substrate is set to 1% or more and 13% or less. Also, the straight portions of the heater wire are arranged in parallel so as to extend approximately parallel to the polarization plane of the linearly polarized electromagnetic wave irradiated by the vehicle-mounted radar device, and the surface occupancy rate of the straight portions of the heater wire in the electromagnetic wave irradiation area of ​​the substrate is set to 3% or more and 16% or less.

[0013] The radome for an automotive radar device of the present invention is characterized in that the heater wire is wired in a meandering manner by folding back and forth, the directions of currents flowing in adjacent straight portions of the heater wire are approximately anti-parallel to each other, and at least four straight portions of the heater wire are arranged side by side with similar pitches in the electromagnetic wave irradiation area of ​​the substrate. According to this, the directions of the currents flowing through the straight portions of the adjacent heater wires are made anti-parallel to each other, so that the electromagnetic waves radiated from the adjacent heater wires are in opposite phases, and the electromagnetic radiation from the heater wires can be cancelled out, resulting in better electromagnetic wave transmission performance. Also, by arranging at least four heater wires in parallel at a pitch that approximates the straight portions of the heater wires in the electromagnetic wave irradiation area of ​​the substrate, the temperature distribution in the entire electromagnetic wave irradiation area of ​​the substrate can be made more uniform, preventing the occurrence of localized areas with low temperatures when the heater wire is heated, and more reliably melting snow can be performed over the entire electromagnetic wave irradiation area of ​​the substrate.

[0014] The radome for an automotive radar device of the present invention is characterized in that the heater wire is wired in a meandering manner by folding back, the directions of currents flowing in adjacent straight portions of the heater wire are approximately anti-parallel to each other, the straight portions of the heater wire within the electromagnetic wave irradiation area and the straight portions of the heater wire outside the electromagnetic wave irradiation area adjacent to each other are provided at a pitch that is approximate to the pitch between the straight portions of the heater wire within the electromagnetic wave irradiation area, and the straight portions of the heater wire outside the electromagnetic wave irradiation area are extended for a length equal to or longer than the length within the electromagnetic wave irradiation area of ​​the straight portions of the heater wire in the adjacent electromagnetic wave irradiation areas. According to this, the directions of the currents flowing through the straight portions of the adjacent heater wires are made anti-parallel to each other, so that the electromagnetic waves radiated from the adjacent heater wires are in opposite phases, and the electromagnetic radiation from the heater wires can be cancelled out, and a better electromagnetic wave transmission performance can be obtained. Also, by providing the straight portions of the heater wire outside the electromagnetic wave irradiation area adjacent to the straight portions of the heater wire inside the electromagnetic wave irradiation area at a pitch that is close to the pitch between the straight portions of the heater wire inside the electromagnetic wave irradiation area, and extending the straight portions of the heater wire outside the electromagnetic wave irradiation area by a length equal to or longer than the length of the straight portions of the heater wire inside the adjacent electromagnetic wave irradiation area in the electromagnetic wave irradiation area, the electromagnetic radiation from the straight portions of the heater wire inside the electromagnetic wave irradiation area located near the periphery of the electromagnetic wave irradiation area can be cancelled out with high certainty, regardless of whether the straight portions juxtaposed inside the electromagnetic wave irradiation area are an even number or an odd number, and a better electromagnetic wave transmission performance can be obtained.

[0015] The vehicle-mounted radar structure of the present invention is characterized by comprising: the radome for the vehicle-mounted radar device of the present invention; and an vehicle-mounted radar device that irradiates the radome for the vehicle-mounted radar device with linearly polarized electromagnetic waves. This makes it possible to obtain an on-vehicle radar structure that exhibits the effects of the radome for an on-vehicle radar device of the present invention. Effect of the Invention

[0016] According to the present invention, it is possible to suppress the attenuation of the electromagnetic waves emitted by the vehicle-mounted radar device within an acceptable range, while providing a practical snow-melting function as a radome for the vehicle-mounted radar device. [Brief description of the drawings]

[0017] [Figure 1] FIG. 2A is a front view of a radome for an automotive radar device according to an embodiment of the present invention, and FIG. [Diagram 2] Enlarged cross-sectional view taken along line AA in Figure 1. [Diagram 3] Enlarged cross-sectional view of FIG. 1 taken along line B-B. [Figure 4] 1 is an explanatory diagram of an on-vehicle radar structure including a radome for an on-vehicle radar device according to an embodiment; [Diagram 5] FIG. 11 is a cross-sectional view illustrating a modified example of the radome for the vehicle-mounted radar device according to the embodiment. [Figure 6] FIG. 4 is a schematic diagram of a measuring device for an example experiment in which the relationship between the surface occupancy rate of a heater wire in an electromagnetic wave irradiation area and the electromagnetic wave transmittance is measured. [Figure 7] (a) is a schematic diagram illustrating the state in which an electromagnetic wave is irradiated onto a sample used in an experimental example with the polarization plane of linear polarization perpendicular to the straight part of the heater wire of the sample, and (b) is a schematic diagram illustrating the state in which an electromagnetic wave is irradiated onto a sample used in an experimental example with the polarization plane of linear polarization parallel to the straight part of the heater wire of the sample. [Figure 8] 13 is a graph of an experimental example showing the relationship between the surface occupancy of the heater wire and the electromagnetic wave transmittance when the polarization plane of linearly polarized electromagnetic waves is irradiated perpendicularly to the straight portion of the heater wire and when the polarization plane is parallel to the straight portion of the heater wire. [Figure 9] 13 is a graph of an experimental example showing the relationship between the surface occupancy rate of the heater wire and the outer surface temperature of the sample when the environmental temperature is -5°C and when the environmental temperature is -15°C. [Figure 10] 13 is a graph of an experimental example showing the relationship between the surface occupancy rate of the heater wire, the electromagnetic wave transmittance, and the outer surface temperature of a sample when the polarization plane of linearly polarized electromagnetic waves is perpendicular to the straight portion of the heater wire and the sample is irradiated with the linearly polarized electromagnetic waves. [Figure 11] 13 is a graph of an experimental example showing the relationship between the surface occupancy rate of the heater wire, the electromagnetic wave transmittance, and the outer surface temperature of a sample when the polarization plane of linearly polarized electromagnetic waves is parallel to the straight portion of the heater wire and the sample is irradiated with the linearly polarized electromagnetic waves. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] [Radome for vehicle-mounted radar device according to embodiment] 1 to 3, a radome 1 for an on-vehicle radar device according to an embodiment of the present invention is composed of an electromagnetic wave transparent base material 3 and a base body 2 including a heater wire 41 arranged in a layered manner on the inner surface side of the base material 3, in other words, on the center side of the vehicle, and wired in the surface direction of the base material 3. The base material 3 can be made of any suitable material within the scope of the present invention, such as synthetic resin, glass, ceramics, etc., but is preferably made of insulating synthetic resin.

[0019] The radome 1 in the illustrated example is a bumper cover attached to the bumper of a vehicle, and the base material 3 is formed of an insulating synthetic resin. When the base material 3 is made of an insulating synthetic resin, the material may be any appropriate material within an applicable range, and may be, for example, one of acrylic resins such as acrylonitrile-butadiene-styrene copolymer (ABS), polypropylene (PP), polymethyl methacrylate (PMMA), polycarbonate (PC), polyethylene terephthalate (PET), polyethylene (PE), acrylonitrile-styrene copolymer (AS), polystyrene (PS), cycloolefin polymer (COP), acrylonitrile-styrene-acrylate copolymer (ASA), acrylonitrile-ethylenepropyl rubber-styrene copolymer (AES), or the like, either alone or in combination of two or more thereof, and may contain additives.

[0020] The heater wire 41 in this embodiment constitutes a part of the heater sheet 4, and the heater sheet 4 is composed of the heater wire 41 and an electromagnetic wave-transmitting insulating film 42. The heater wire 41 in the illustrated example is provided so as to be entirely embedded in the planar insulating film 42, or so as to be exposed on the back side of the planar insulating film 42. The heater wire 41 can be made of an appropriate conductive material that can be applied, such as nichrome wire, iron chromium, copper, silver, carbon fiber, or a transparent conductive film such as an ITO film. The insulating film 42 can be made of an insulating material that has appropriate electromagnetic wave transmittance, and is preferably formed of an insulating synthetic resin such as polycarbonate (PC), polyethylene (PE), polypropylene (PP, OPP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyvinyl chloride (PVC), polystyrene (PS), acrylic (AC), or polyether ether ketone (PEEK).

[0021] In addition, the heater sheet 4 can be configured as appropriate within the applicable range other than the preferred configuration example in which the heater wire 41 is embedded in the planar insulating film 42. For example, it is also preferred that the heater wire 41 is fixed to the back side or inner side of the insulating film 42 located on the vehicle center side, and further, it is also preferred that the heater wire 41 is fixed to the back side or inner side of the insulating film 42 located on the vehicle center side, and a protective film is laminated and fixed to the insulating film 42 so as to cover the heater wire 41 from the back side.

[0022] Both ends of the heater wire 41 are electrically connected to and mechanically fixed to the connector 6 at the bottom of the radome 1 for the vehicle-mounted radar device in the illustrated example, and power is supplied to the heater wire 41 via the connector 6 and an electric cable (not shown) connected to it, causing the heater wire 41 to generate heat.

[0023] The heater wire 41 is formed by wiring in a continuous manner so as to meander and fold back in the direction in which the back surface 31 of the base material 3 expands or along the back surface 31, and the straight portions 411 of the heater wire 41 are arranged in parallel at intervals in the electromagnetic wave irradiation region R of the base material 3 or along the back surface 31, and the directions of currents flowing through the straight portions 411 of adjacent heater wires 41 are set to be approximately anti-parallel or anti-parallel to each other. By setting the directions of currents flowing through the straight portions 411 of adjacent heater wires 41 to be approximately anti-parallel or anti-parallel to each other, the electromagnetic waves radiated from the straight portions 411 of the adjacent heater wires 41 have opposite phases, and the electromagnetic radiation from the straight portions 411 of the heater wires 41 is cancelled out, making it possible to obtain better electromagnetic wave transmission performance. In this embodiment, at least four straight portions 411 of the heater wire 41 are arranged side by side at an approximate pitch P in the electromagnetic wave irradiation region R of the substrate 3, and in the illustrated example, four straight portions 411 of the heater wire 41 are arranged side by side at an approximate pitch P in the electromagnetic wave irradiation region R of the substrate 3.

[0024] Furthermore, in this embodiment, the straight line portions 411m of the heater wire 41 in the electromagnetic wave irradiation region R of the base material 3 and the straight line portions 411n of the heater wire 41 outside the electromagnetic wave irradiation region R adjacent to each other are provided at a pitch P that is approximate to the pitch P of the straight line portions 411-411 of the heater wire 41 in the electromagnetic wave irradiation region R, and the straight line portions 411n of the heater wire 41 outside the electromagnetic wave irradiation region R are extended so as to be approximately anti-parallel to each other and with a length equal to or longer than the length of the straight line portions 411m of the heater wire 41 in the adjacent electromagnetic wave irradiation region R in the electromagnetic wave irradiation region R. In the illustrated example, the pitch P between the straight portions 411m and 411n of the heater wire 41 is set to be approximate to the pitch P between the straight portions 411-411 of the heater wire 41 in the electromagnetic wave irradiation region R, the straight portion 411n of the heater wire 41 extends approximately anti-parallel to the straight portion 411m with approximately the same length, and the straight portion 411n extends outside the electromagnetic wave irradiation region R so as to be approximately anti-parallel to the straight portion 411m with a length exceeding the length of the straight portion 411m in the electromagnetic wave irradiation region R. Note that the approximation of the approximate pitch P between the straight portions 411-411 of the heater wire 41 including the straight portions 411m-411n in this embodiment means that, when the minimum pitch Pmin, the maximum pitch Pmax, and the intermediate pitch Pmid are the minimum pitch Pmin and the maximum pitch Pmax, the minimum pitch Pmin / intermediate pitch Pmid is 0.80 or more and the maximum pitch Pmax / intermediate pitch Pmid is 1.2 or less.

[0025] Furthermore, in the radome 1 for an on-vehicle radar device of this embodiment, the heater wire 41 is provided such that the surface occupancy rate of the straight portion 411 of the heater wire 41 in the electromagnetic wave irradiation region R of the substrate 3 is set to be 1% or more and 24% or less.

[0026] In the present embodiment, in the case of an on-vehicle radar structure in which the straight portions 411 of the heater wire 41 are arranged in parallel so as to extend substantially perpendicular or perpendicular to the polarization plane of the linearly polarized electromagnetic wave irradiated by the on-vehicle radar device 10 described later, it is preferable to set the surface occupancy rate of the straight portions 411 of the heater wire 41 in the electromagnetic wave irradiation region R of the substrate 3 to be 1% or more and 24% or less. As an example of this configuration, when the pitch P between the straight portions 411 of the heater wire 41 is 7.0 mm, the line width W of the straight portions 411 is 0.07 mm to 1.68 mm. More preferably, the surface occupancy rate of the straight line portions 411 of the heater wire 41 in the electromagnetic wave irradiation region R of the substrate 3 is set to 1% or more and 20% or less, or the surface occupancy rate of the straight line portions 411 of the heater wire 41 in the electromagnetic wave irradiation region R of the substrate 3 is set to 3% or more and 24% or less, or the surface occupancy rate of the straight line portions 411 of the heater wire 41 in the electromagnetic wave irradiation region R of the substrate 3 is set to 3% or more and 20% or less. As an example of the surface occupancy rate of the straight line portions 411 of the heater wire 41 in the electromagnetic wave irradiation region R of the substrate 3 being set to 3% or more and 20% or less, when the pitch P between the straight line portions 411 of the heater wire 41 is 7.0 mm, the line width W of the straight line portions 411 is 0.21 to 1.40 mm.

[0027] In the present embodiment, in the case of an on-vehicle radar structure in which the straight portions 411 of the heater wire 41 are arranged so as to extend substantially parallel or parallel to the polarization plane of the linearly polarized electromagnetic wave irradiated by the on-vehicle radar device 10 described later, it is preferable to set the surface occupancy rate of the straight portions 411 of the heater wire 41 in the electromagnetic wave irradiation region R of the substrate 3 to be 1% or more and 16% or less. As an example of this configuration, when the pitch P between the straight portions 411 of the heater wire 41 is 7.0 mm, the line width W of the straight portions 411 is set to 0.07 to 1.12 mm. More preferably, the surface occupancy rate of the straight line portions 411 of the heater wire 41 in the electromagnetic wave irradiation region R of the substrate 3 is set to 1% or more and 13% or less, or the surface occupancy rate of the straight line portions 411 of the heater wire 41 in the electromagnetic wave irradiation region R of the substrate 3 is set to 3% or more and 16% or less, or the surface occupancy rate of the straight line portions 411 of the heater wire 41 in the electromagnetic wave irradiation region R of the substrate 3 is set to 3% or more and 13% or less. As an example of the surface occupancy rate of the straight line portions 411 of the heater wire 41 in the electromagnetic wave irradiation region R of the substrate 3 being set to 3% or more and 13% or less, when the pitch P between the straight line portions 411 of the heater wire 41 is 7.0 mm, the line width W of the straight line portions 411 is 0.21 to 0.91 mm.

[0028] From the viewpoint of improving the electromagnetic wave transmission performance, it is preferable to use insulating film 42, or insulating film 42 and the protective film when a protective film is laminated and fixed to insulating film 42, whose refractive index n defined based on the complex dielectric constant matches that of substrate 3, or whose refractive index n is approximately the same or close to that of substrate 3. It is preferable that the numerical range of the refractive index n between substrate 3 and insulating film 42, the refractive index n between substrate 3 and protective film, and the refractive index n between insulating film 42 and protective film be such that the difference between the respective refractive indexes is within a range of 0 to 10%.

[0029] Here, the refractive index n is a quantity defined by the real part εr' of the relative dielectric constant and the imaginary part εr" of the relative dielectric constant as shown in Equation 1. From the viewpoint of transparency, it is preferable to use materials for the base material 3, insulating film 42, and protective film, each of which has a dielectric loss tangent tan δ of 0.1 or less, which is defined by Equation 2 from the ratio of the imaginary part to the real part at the applicable frequency. It is also preferable to set the magnitude of the real part of the relative dielectric constant to 3 or less. By setting the magnitudes of the dielectric loss tangent and the real part of the non-dielectric constant to these numerical values ​​or less, it is possible to ensure the reflectance and reduction of internal loss required for the radome.

[0030]

number

[0031]

number

[0032] The heater sheet 4 in this embodiment is fixed to the inner surface or rear surface of the substrate 3 via an adhesive layer 5. The adhesive layer 5 is made of an appropriate electromagnetic wave-transmitting insulating material, and can be formed of, for example, an adhesive such as methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, or ethyl methacrylate, or a double-sided tape made of an acrylic or silicone adhesive and a core material such as PET, polypropylene, or acrylic foam, or a double-sided tape with only an adhesive without a core material. Note that, instead of a configuration in which the heater sheet 4 is fixed to the substrate 3 via the adhesive layer 5, a configuration in which the heater sheet 4 and the insulating film 42 are welded to be fixed to the substrate 3 is also preferable.

[0033] From the viewpoint of improving the transmission performance of electromagnetic waves, it is preferable to use a material for the adhesive layer 5, which has a refractive index n defined based on the complex dielectric constant and which matches with the base material 3 and the insulating film 42, or with the base material 3, the insulating film 42, and the protective film, or has a refractive index n that is approximately the same or close to each other. It is preferable that the difference between the refractive indexes n of the adhesive layer 5 and the base material 3 when they are close to each other, the refractive index n of the adhesive layer 5 and the insulating film 42 when they are close to each other, and the refractive index n of the adhesive layer 5 and the protective film when they are close to each other is within a range of 0 to 10%. Note that these refractive indices n are also amounts defined by the real part εr' of the relative dielectric constant and the imaginary part εr" of the relative dielectric constant as Formula 1. In addition, from the viewpoint of transmission, it is preferable to use a material for the adhesive layer 5, which has a dielectric loss tangent tanδ of 0.1 or less, which is defined by the ratio of the imaginary part and the real part at the applicable frequency as Formula 2. It is also preferable that the magnitude of the real part of the relative dielectric constant is 3 or less.

[0034] 4, the radome 1 for the vehicle-mounted radar device is disposed in front of the vehicle-mounted radar device 10 disposed on the center side of the vehicle and attached to the vehicle to form an on-vehicle radar structure. The vehicle-mounted radar device 10 irradiates linearly polarized electromagnetic waves to the radome 1 for the vehicle-mounted radar device. The wavelength or frequency of the electromagnetic waves irradiated by the vehicle-mounted radar device 10 is appropriate as needed, and may be, for example, millimeter waves in the 76 / 77 GHz band from 76.0 to 77.0 GHz or 76 / 79 GHz band from 76.0 to 79.0 GHz.

[0035] In the illustrated example, the radome 1 for the vehicle-mounted radar device is a bumper cover, but the radome for the vehicle-mounted radar device of the present invention can be configured with an appropriate vehicle-mounted component such as an emblem-shaped radome. In addition, the base 2 of the radome 1 for the vehicle-mounted radar device can be additionally arranged in the normal direction of the substrate 3 as necessary, and in a bumper cover or an emblem-shaped radome, for example, it is preferable to arrange the heater sheet 4 on the inner surface or back surface of the substrate 3 on the vehicle center side and fix the electromagnetic wave-transmitting rear substrate 71 by adhesion or welding, or to arrange the electromagnetic wave-transmitting decorative layer 72 and the transparent substrate 73 on the outer surface or front surface of the substrate 3 on the vehicle outer surface side and fix the substrate 3 by adhesion or welding (see FIG. 5).

[0036] In this case, it is preferable that the difference between the refractive index of the rear substrate 71 and the refractive index of the substrate 3, the insulating film 42 of the heater sheet 4, or the insulating film 42 and the protective film, and the adhesive layer 5 in the case where the adhesive layer 5 is interposed, is within the range of 0 to 10%. Also, it is preferable that the difference between the refractive index of the transparent substrate 73 and the refractive index of the substrate 3, the insulating film 42 of the heater sheet 4, or the insulating film 42 and the protective film, and the adhesive layer 5 in the case where the adhesive layer 5 is interposed, is within the range of 0 to 10%. In addition, it is preferable to use a material for the rear substrate 71 and the transparent substrate 73, which has a dielectric loss tangent tan δ defined as Formula 2 of 0.1 or less, and further, it is preferable to set the magnitude of the real part of the relative dielectric constant to 3 or less. In addition, the configuration of the electromagnetic wave transparent decorative layer is appropriate within the scope of the purpose of the present invention, and it is possible to use, for example, a decorative layer composed of a discontinuous metal film and a colored part that are divided into islands by cracks and have integral visibility, a decorative layer composed of only a discontinuous metal film, etc.

[0037] According to the radome 1 for an on-vehicle radar device of this embodiment, by setting the surface occupancy rate of the straight portion 411 of the heater wire 41 in the electromagnetic wave irradiation region R of the substrate 3 to 1% or more, the temperature of the outer surface of the substrate 3 can be kept above 0°C even when the environmental temperature is -5°C and the vehicle is traveling at a speed of 100km / h. Therefore, the radome 1 for an on-vehicle radar device can exhibit a practical snow melting function while suppressing the attenuation of the electromagnetic waves irradiated by the on-vehicle radar device 10 within a required allowable range.

[0038] Furthermore, when the straight portions 411 of the heater wire 41 are arranged in parallel so as to extend approximately perpendicular to the polarization plane of the linearly polarized electromagnetic wave irradiated by the vehicle-mounted radar device 10, and the surface occupancy rate of the straight portions 411 of the heater wire 41 in the electromagnetic wave irradiation area R of the substrate 3 is set to 1% or more and 24% or less, the radome 1 for the vehicle-mounted radar device can exhibit a practical snow-melting function, and the transmittance of the substrate 2 to the electromagnetic wave irradiated by the vehicle-mounted radar device 10 can be guaranteed to be -1.5dB or more, and the attenuation of the electromagnetic wave can be suppressed within a high allowable range that is sufficient for practical use.

[0039] In addition, when the straight portions 411 of the heater wire 41 are arranged in parallel so as to extend substantially perpendicularly to the plane of polarization of the linearly polarized electromagnetic wave irradiated by the vehicle-mounted radar device 10, and the surface occupancy rate of the straight portions 411 of the heater wire 41 in the electromagnetic wave irradiation region R of the substrate 3 is set to 3% or more and 20% or less, even when the environmental temperature is -15°C and the vehicle is traveling at a speed of 100 km / h, the temperature of the outer surface of the substrate 3 can be kept above 0°C, and snow can be reliably melted on the radome 1 for the vehicle-mounted radar device even in a more severe cold environment. In addition, the transmittance of the substrate 2 to the electromagnetic wave irradiated by the vehicle-mounted radar device 10 can be guaranteed to be -1.0 dB or more, and the attenuation of the electromagnetic wave can be suppressed within a very high allowable range that is sufficient for practical use.

[0040] Furthermore, when the straight portions 411 of the heater wire 41 are arranged in parallel so as to extend approximately parallel to the polarization plane of the linearly polarized electromagnetic wave irradiated by the vehicle-mounted radar device 10, and the surface occupancy rate of the straight portions 411 of the heater wire 41 in the electromagnetic wave irradiation area R of the substrate 3 is set to 1% or more and 16% or less, the radome 1 for the vehicle-mounted radar device can exhibit a practical snow-melting function, and the transmittance of the substrate 2 to the electromagnetic wave irradiated by the vehicle-mounted radar device 10 can be guaranteed to be -1.5dB or more, and the attenuation of the electromagnetic wave can be suppressed within a high allowable range that is sufficient for practical use.

[0041] In addition, when the straight line portions 411 of the heater wire 41 are arranged so as to extend substantially parallel to the plane of polarization of the linearly polarized electromagnetic wave irradiated by the vehicle-mounted radar device 10, and the surface occupancy rate of the straight line portions 411 of the heater wire 41 in the electromagnetic wave irradiation region R of the substrate 3 is set to 3% to 13%, the temperature of the outer surface of the substrate 3 can be kept above 0°C even when the environmental temperature is -15°C and the vehicle is traveling at a speed of 100 km / h, and snow can be reliably melted on the radome 1 for the vehicle-mounted radar device even in a more severe cold environment. In addition, the transmittance of the substrate 2 to the electromagnetic wave irradiated by the vehicle-mounted radar device 10 can be guaranteed to be -1.0 dB or more, and the attenuation of the electromagnetic wave can be suppressed within a very high allowable range that is sufficient for practical use.

[0042] Furthermore, according to the radome 1 for an in-vehicle radar device, the directions of currents flowing through the straight portions 411 of adjacent heater wires 41 are made anti-parallel to each other, so that the electromagnetic waves radiated from adjacent heater wires are in opposite phase, and the electromagnetic radiation from the heater wires 41 can be cancelled out, thereby obtaining better electromagnetic wave transmission performance. Furthermore, by arranging at least four straight portions 411 of the heater wires 41 in parallel with each other at a similar pitch in the electromagnetic wave irradiation region R of the base material 3, the temperature distribution in the entire electromagnetic wave irradiation region R of the base material 3 can be made more uniform, and the occurrence of localized regions with low temperatures when the heater wires are heated can be prevented, and snow can be melted more reliably over the entire electromagnetic wave irradiation region R of the base material 3.

[0043] Furthermore, by providing the straight line portion 411m of the heater wire 41 in the electromagnetic wave irradiation region R and the straight line portion 411n of the heater wire 41 outside the electromagnetic wave irradiation region R adjacent to each other at a pitch similar to the mutual pitch of the straight line portions 411·411 of the heater wire 41 in the electromagnetic wave irradiation region R, and extending the straight line portion 411n of the heater wire 41 outside the electromagnetic wave irradiation region R by a length equal to or longer than the length of the straight line portion 411m of the heater wire 41 in the adjacent electromagnetic wave irradiation region R within the electromagnetic wave irradiation region R, it is possible to cancel out the electromagnetic radiation of the straight line portion 411m of the heater wire 41 in the electromagnetic wave irradiation region R located in the vicinity of the periphery of the electromagnetic wave irradiation region R with high certainty, regardless of whether the straight line portions 411 juxtaposed within the electromagnetic wave irradiation region R are an even number or an odd number, and it is possible to obtain even better electromagnetic wave transmission performance.

[0044] [Experimental example regarding surface occupancy rate of heater wire, electromagnetic wave transmittance, and snow melting performance] As a sample corresponding to the base of the radome for an on-vehicle radar device of the present invention and the base 2 of the radome 1 for an on-vehicle radar device of the above embodiment, a sample 20 shown in Fig. 6 and Fig. 7 was prepared, and an experiment to verify the electromagnetic wave transmittance and an experiment to verify the snow melting property were carried out using the sample 20. The sample 20 is composed of a base material 21 corresponding to the base material 3, a heater sheet 22 corresponding to the heater sheet 4, and a double-sided tape 23 corresponding to the adhesive layer 5, and the double-sided tape 23 and the heater sheet 22 are laminated in this order on the back side or inner side of the base material 21 on the side irradiated with electromagnetic waves, and the heater sheet 22 is fixed to the base material 21 via the double-sided tape 23.

[0045] The substrate 21 is a flat plate having a thickness of 2.2 mm, the double-sided tape 23 is a planar plate having a thickness of 0.1 mm, and the heater sheet 22 is a planar plate having a thickness of 0.1 mm, and the total thickness of the approximately planar sample in which these are laminated is 2.4 mm. The substrate 21 is a resin plate made of ABS resin, and more specifically, it is made of heat-resistant ABS resin (MTH-2) made by Nippon A&L Co., Ltd. The complex dielectric constant ε' of this ABS (MTH-2) for electromagnetic waves (millimeter waves) in the 76 / 77 GHz band at room temperature (about 25°C) is 2.656, and the dielectric tangent tanδ is 0.0065.

[0046] The heater sheet 22 is configured such that the heater wire 221 is embedded in the insulating film 222 so that the heater wire 221 and its terminal 2212 are exposed on the back side of the insulating film 222. The insulating film 222 is a polyimide film, and the heater wire 221 is a copper wire (resistivity 1.69×10 -8 The dielectric constant ε' of the polyimide film that is the insulating film 222 is 3.247 and the dielectric tangent tanδ is 0.0054 for electromagnetic waves (millimeter waves) in the 76 / 77 GHz band at room temperature (approximately 25°C). The heater wire 221 is formed so as to extend continuously, meandering and folded back along the insulating film 222, and the straight portions 2211 are arranged in parallel at intervals along the insulating film 222. The pitch P between the straight portions 2211 of the heater wire 221 of the sample 20 is 7.0 mm, and the pitch P between all of the straight portions 2211 is the same.

[0047] The double-sided tape 23 is made of an acrylic adhesive without a core material, and has a complex dielectric constant ε' of 2.513 and a dielectric tangent tan δ of 0.0139 for electromagnetic waves (millimeter waves) in the 76 / 77 GHz band at room temperature (approximately 25° C.).

[0048] The measurement of the experiment to verify the electromagnetic wave transmittance using the sample 20 was carried out using a Quality Automobile Radome Tester (QAR) manufactured by ROHDE & SCHWARZ as a measuring device. In the schematic diagram of this measuring device in Fig. 6, 101 is an electromagnetic wave transmitting unit, 102 is a receiving unit, and 103 is an evaluation device. The electromagnetic wave transmitted from the electromagnetic wave transmitting unit 101 used in the measurement is a millimeter wave in the 76 / 77 GHz band. EW is the propagation direction of the millimeter wave.

[0049] Then, electromagnetic waves were irradiated from the electromagnetic wave emitting unit 101 to the sample 20 so that R shown in Figure 7 was the electromagnetic wave irradiation area, and measurements were made of the electromagnetic wave transmittance when the electromagnetic waves were irradiated so that the polarization plane LP of the linearly polarized millimeter wave in the 76 / 77 GHz band was perpendicular to the straight portion 2211 of the heater wire 221 of the sample 20 (see Figure 7(a)), and also when the electromagnetic waves were irradiated so that the polarization plane LP of the linearly polarized millimeter wave in the 76 / 77 GHz band was parallel to the straight portion 2211 of the heater wire 221 of the sample 20 (see Figure 7(b)).

[0050] In measuring the electromagnetic wave transmittance, for both the case where the polarization plane LP is perpendicular to the straight line portion 2211 and the case where the polarization plane LP is parallel to the straight line portion 2211, the line width W of the straight line portion 2211 was changed while maintaining the pitch of 7.0 mm to change the occupancy rate of the heater wire 221 or its straight line portion 2211 in the entire area of ​​the electromagnetic wave irradiation region R, and the measurement was performed without passing electricity through the heater wire 221. The measurement results are shown in FIG.

[0051] 8, when the allowable value of the electromagnetic wave transmission attenuation of the sample 20 corresponding to the base of the radome for an in-vehicle radar device is set to -1.5 dB or more, in a structure in which the polarization plane LP of the linearly polarized electromagnetic wave is irradiated perpendicularly to the straight portion 2211 of the heater wire 221, it can be seen that this can be achieved by setting the surface occupancy rate of the straight portion 2211 of the heater wire 221 in the electromagnetic wave irradiation region R of the substrate 21 to 24% or less. Also, in a structure in which the polarization plane LP of the linearly polarized electromagnetic wave is irradiated parallel to the straight portion 2211 of the heater wire 221, it can be seen that a similar allowable value can be achieved by setting the surface occupancy rate of the straight portion 2211 of the heater wire 221 in the electromagnetic wave irradiation region R of the substrate 21 to 16% or less.

[0052] Furthermore, it is found that when the allowable value of the electromagnetic wave transmission attenuation of the sample 20 corresponding to the base of the radome for an on-vehicle radar device is set to -1.0 dB or more, in a structure in which the polarization plane LP of the linearly polarized electromagnetic wave is irradiated perpendicularly to the straight portion 2211 of the heater wire 221, this can be achieved by setting the surface occupancy rate of the straight portion 2211 of the heater wire 221 in the electromagnetic wave irradiation region R of the substrate 21 to 20% or less. Also, in a structure in which the polarization plane LP of the linearly polarized electromagnetic wave is irradiated parallel to the straight portion 2211 of the heater wire 221, it is found that a similar allowable value can be achieved by setting the surface occupancy rate of the straight portion 2211 of the heater wire 221 in the electromagnetic wave irradiation region R of the substrate 21 to 13% or less.

[0053] Furthermore, in a structure in which the polarization plane LP of the linearly polarized electromagnetic wave is irradiated perpendicularly to the straight portion 2211 of the heater wire 221, it is found that when the surface occupancy rate of the straight portion 2211 of the heater wire 221 in the electromagnetic wave irradiation region R of the substrate 21 is 10% or less, the electromagnetic wave transmittance is -0.4 dB or more, and when the surface occupancy rate of the straight portion 2211 of the heater wire 221 in the electromagnetic wave irradiation region R of the substrate 21 is 7.5% or less, the electromagnetic wave transmittance is -0.35 dB or more, which is an extremely high electromagnetic wave transmittance.

[0054] In an experiment to verify the snow melting property using sample 20, sample 20 was placed in front of the vehicle with the vehicle traveling direction facing forward, and the heater wire 221 of sample 20 was energized with an input voltage of 10V, and the vehicle speed was set to 100km / h. While maintaining the pitch of 7.0mm, the line width W of the straight portion 2211 was changed to change the occupancy rate of the heater wire 221 or its straight portion 2211 in the entire area of ​​the electromagnetic wave irradiation region R, and experiments were performed at environmental temperatures of -5°C and -15°C. The measurement results are shown in FIG.

[0055] 9, when the environmental temperature is -5°C and the vehicle is traveling at 100km / h, it is possible to make the temperature of the outer surface (front surface in the vehicle traveling direction) of the substrate 21 exceed 0°C by setting the surface occupancy rate of the straight portion 2211 of the heater wire 221 in the electromagnetic wave irradiation region R of the substrate 21 to 1% or more. It is also possible to make the temperature of the outer surface (front surface in the vehicle traveling direction) of the substrate 21 exceed 0°C by setting the surface occupancy rate of the straight portion 2211 of the heater wire 221 in the electromagnetic wave irradiation region R of the substrate 21 to 3% or more when the environmental temperature is -15°C and the vehicle is traveling at 100km / h.

[0056] 10 shows the relationship between the surface occupancy rate of the heater wire 221, the electromagnetic wave transmittance, and the outer surface temperature of the sample 20 when the sample 20 is irradiated with the polarization plane LP of the linearly polarized electromagnetic wave perpendicular to the straight portion 2211 of the heater wire 221. In a structure in which the polarization plane LP of the linearly polarized electromagnetic wave is irradiated perpendicular to the straight portion 2211 of the heater wire 221, from the viewpoint of achieving a practical snow melting function while satisfying the required electromagnetic wave transmittance, the lower limit of the surface occupancy rate of the heater wire 221 or its straight portion 2211 is preferably 1% or more, more preferably 3% or more, and the upper limit is preferably 24% or less, more preferably 20% or less. Furthermore, in order to obtain an extremely excellent electromagnetic wave transmittance, the upper limit of the surface occupancy rate of the heater wire 221 or its straight portion 2211 is more preferably 10% or less, and even more preferably 7.5% or less.

[0057] 11 shows the relationship between the surface occupancy rate of the heater wire 221, the electromagnetic wave transmittance, and the outer surface temperature of the sample 20 when the sample 20 is irradiated with the polarization plane LP of the linearly polarized electromagnetic wave parallel to the straight portion 2211 of the heater wire 221. In a structure in which the polarization plane LP of the linearly polarized electromagnetic wave is irradiated parallel to the straight portion 2211 of the heater wire 221, from the viewpoint of achieving a practical snow melting function while satisfying the required electromagnetic wave transmittance, the lower limit of the surface occupancy rate of the heater wire 221 or its straight portion 2211 is preferably 1% or more, more preferably 3% or more, and the upper limit is preferably 16% or less, more preferably 13% or less.

[0058] [Scope of the invention disclosed herein] The inventions disclosed in this specification include, in addition to the inventions and embodiments listed as inventions, those specified by changing partial contents of these to other contents disclosed in this specification, those specified by adding other contents disclosed in this specification to these contents, or those specified by deleting partial contents of these to the extent that partial effects can be obtained, and specifying them as a higher-level concept. The inventions disclosed in this specification also include the following modified examples and added contents.

[0059] For example, the radome for an automotive radar device of the present invention appropriately includes one having an electromagnetic wave transparent substrate and a base body having a heater wire laminated on the inner surface of the substrate and wired in the surface direction of the substrate, and also includes a radome having a structure in which the heater wire is laminated on the inner surface of the substrate and directly fixed thereto without using a heater sheet 4. [Industrial Applicability]

[0060] The present invention can be used as a radome for an on-vehicle radar device and an on-vehicle radar structure. [Explanation of symbols]

[0061] 1...Radome for on-vehicle radar device 2...Base 3...Substrate 31...Rear surface 4...Heater sheet 41...Heater wire 411, 411m, 411n...Straight section 42...Insulating film 5...Adhesive layer 6...Connector 71...Rear substrate 72...Decorative layer 73...Transparent member 10...On-vehicle radar device 20...Sample 21...Substrate 22...Heater sheet 221...Heater wire 2211...Straight section 2212...Terminal 222...Insulating film 23...Double-sided tape 101...Electromagnetic wave transmitter 102...Receiver 103...Evaluation device R...Electromagnetic wave irradiation area P...Pitch between straight sections of heater wire W...Width of straight section of heater wire EW...Propagation direction of millimeter wave LP...Polarization plane (polarization direction) of linearly polarized wave

Claims

1. The vehicle radar device includes a base body including an electromagnetic wave-transmitting base material and a heater wire arranged on an inner surface of the base material on the vehicle center side, which is in front of an on-vehicle radar device arranged on the vehicle center side, and wired in a surface direction of the base material, In an electromagnetic wave irradiation region of the substrate, straight portions of the heater wire are arranged in parallel at intervals in a surface direction of the substrate, the straight portions of the heater wires are arranged in parallel so as to extend substantially perpendicular to the plane of polarization of the linearly polarized electromagnetic waves irradiated by the on-vehicle radar device, The surface occupancy rate of the straight line portion of the heater wire in the electromagnetic wave irradiation region of the substrate is set to 1% or more and 24% or less, The heater wire and an electromagnetic wave-transmitting insulating film constitute a heater sheet, The heater sheet is laminated and fixed to the inner surface of the base material, thereby wiring the heater wire, a refractive index defined based on the complex dielectric constant of the base material and a refractive index defined based on the complex dielectric constant of the insulating film are matched or close to each other, A radome for an automotive radar device, characterized in that the insulating film is fixed to the substrate via an adhesive layer whose refractive index, defined based on a complex dielectric constant, matches or is close to that of the substrate and the insulating film.

2. 2. The radome for an on-vehicle radar device according to claim 1, wherein a surface occupancy rate of the straight portions of the heater wire in the electromagnetic wave irradiation region of the base material is set to 3% or more and 20% or less.

3. 3. The radome for an on-vehicle radar device according to claim 2, wherein a surface occupancy rate of the straight portions of the heater wire in the electromagnetic wave irradiation region of the base material is set to 3% or more and 7.5% or less.

4. The vehicle radar device includes a base body including an electromagnetic wave-transmitting base material and a heater wire arranged on an inner surface of the base material on the vehicle center side, which is in front of an on-vehicle radar device arranged on the vehicle center side, and wired in a surface direction of the base material, In an electromagnetic wave irradiation region of the substrate, straight portions of the heater wire are arranged in parallel at intervals in a surface direction of the substrate, the straight portions of the heater wires are arranged in parallel so as to extend substantially parallel to the plane of polarization of the linearly polarized electromagnetic waves irradiated by the vehicle-mounted radar device, The surface occupancy rate of the straight line portion of the heater wire in the electromagnetic wave irradiation region of the substrate is set to 1% or more and 16% or less, The heater wire and an electromagnetic wave-transmitting insulating film constitute a heater sheet, The heater sheet is laminated and fixed to the inner surface of the base material, thereby wiring the heater wire, a refractive index defined based on the complex dielectric constant of the base material and a refractive index defined based on the complex dielectric constant of the insulating film are matched or close to each other, A radome for an automotive radar device, characterized in that the insulating film is fixed to the substrate via an adhesive layer whose refractive index, defined based on a complex dielectric constant, matches or is close to that of the substrate and the insulating film.

5. 5. The radome for an on-vehicle radar device according to claim 4, wherein a surface occupancy rate of the straight portions of the heater wire in the electromagnetic wave irradiation region of the base material is set to 3% or more and 13% or less.

6. A radome for an on-vehicle radar device according to any one of claims 1 to 5, An on-vehicle radar structure comprising an on-vehicle radar device that irradiates a linearly polarized electromagnetic wave onto the radome for the on-vehicle radar device.

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