Radar device, and vehicle lamp

Abstract

To prevent an increase in transmission loss when using a radar device with a shielding member.SOLUTION: A shielding member provided herein is used in a radar device and comprises: a flat first portion made of a foamed resin; a second portion made of a non-foamed resin and arranged to surround the first portion so as to abut the side face of the first portion; and a third portion made of a non-foamed resin and arranged to abut one face and the other face of the first portion.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a radar device.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2021-099313 (Patent Document 1) describes a vehicle lamp having a lamp unit, a millimeter-wave radar unit having an antenna, and a shielding member made of a foamed resin that covers at least a part of the front surface of the millimeter-wave radar unit provided with the antenna. By configuring the shielding member using a foamed resin, it is possible to reduce the transmission loss of the millimeter waves transmitted and received by the millimeter-wave radar unit.

[0003] By the way, when the shielding member is configured using a foamed resin, moisture in the air or the like may enter the air bubbles of the foamed resin during use, resulting in an increase in transmission loss and a possible deterioration in the performance of the radar device.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] One of the objectives of the specific aspect according to the present disclosure is to prevent an increase in transmission loss when using a radar device having a shielding member.

Means for Solving the Problems

[0006] [1] The shielding member according to one aspect of the present disclosure is a shielding member used in a radar device, a flat plate-shaped first part made of a foamed resin, and It is arranged to surround the first part so as to be in contact with the side surface of the first part, and includes a second part made of a non-foamed resin, It is arranged to be in contact with each of one surface and the other surface of the first part, and includes a third part made of a non-foamed resin, and is a shielding member. [2] A radar device according to one aspect of the present disclosure is the shielding member described in 1 above, a radar wave transmitter arranged with a gap provided between it and the shielding member, and is a radar device.

[0007] According to the above configuration, an increase in transmission loss when using a radar device having a shielding member can be prevented.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0009] FIG. 1 is a diagram schematically showing the internal structure of a vehicle lamp according to an embodiment. The vehicle lamp 10 is mounted on a vehicle and is used for irradiating light around the vehicle, and is, for example, a headlamp. FIG. 1 schematically shows a cross-section in a horizontal plane (or a plane parallel to the road surface) when the vehicle lamp 10 (left headlamp) mounted on the left front of the vehicle is viewed from above.

[0010] The vehicle lamp 10 includes a base 11, a transparent cover 12 held by the base 11, a headlamp unit 14, a millimeter-wave radar unit (radar wave transmitter) 15, a light-emitting unit 16, a shielding member 18, and an extension 19. The shielding member 18 is a kind of extension member for making the millimeter-wave radar unit 15 difficult to be visually recognized from the outside. The base 11 and the transparent cover 12 constitute a housing, and the headlamp unit 14, the millimeter-wave radar unit 15, the light-emitting unit 16, the shielding member 18, and the extension 19 are provided in this housing. In this embodiment, a radar device is constituted including the radar unit 15 and the shielding member 18.

[0011] The headlamp unit 14 is configured to have a light source such as an LED (Light Emitting Diode) and a lens or a reflector for distributing and irradiating the light from the light source. The headlamp unit 14 irradiates the irradiation light LB of the low beam (passing beam) and the high beam (driving beam) in the forward direction of the vehicle.

[0012] The millimeter-wave radar unit 15 has a transmission / reception surface provided with a transmission / reception antenna for millimeter waves (radar waves) on its front surface. In this specification, the transmission / reception surface of the millimeter-wave radar unit 15 (the front surface of the millimeter-wave radar unit 15) is also referred to as the antenna surface.

[0013] Specifically, the millimeter-wave radar unit 15 has a transmission antenna and a reception antenna on its transmission / reception surface (electromagnetic wave radiation surface). The millimeter-wave radar unit 15 radiates millimeter waves (radar waves), which are electromagnetic waves, from the transmission antenna, and receives the reflected waves reflected by the object by the reception antenna. By performing signal processing using the received reflected waves, the distance, angle, and speed between the object and the millimeter-wave radar unit 15 can be detected. In the millimeter-wave radar unit 15, for example, millimeter waves in the 76 - 81 GHz band, particularly millimeter waves in the 79 GHz band are used, but it is not limited to this frequency band. Also, the antenna may have both functions of transmission and reception.

[0014] The light-emitting unit 16 includes a light guide body 16b composed of a light source 16a and at least one light guide member that guides the light from the light source 16a. The light-emitting unit 16 functions as, for example, DRL (Daytime Running Lights) or a turn lamp. The light source 16a has, for example, an LED, an incandescent bulb, etc., and supplies the light to the light guide body 16b.

[0015] The millimeter-wave radar unit 15 is arranged such that the normal direction of the antenna surface is inclined in the outer direction of the vehicle (i.e., the left direction in the case of the left headlamp) relative to the optical axis of the headlamp unit 14.

[0016] The shielding member 18 is arranged with a gap from the antenna surface of the millimeter-wave radar unit 15. Further, at least one extension 19 is provided in the lamp housing. The extension 19 is a design component provided to reflect light, or guide light, or make internal structures, etc. difficult to visually recognize from the outside.

[0017] In addition, in FIG. 1, the shielding member 18 is provided in the housing together with the millimeter-wave radar unit 15. However, it may also be a radar device provided with the millimeter-wave radar unit 15 in a separate housing composed of a separate base from the base 11 and the shielding member 18. In this case, the shielding member 18 constitutes the exterior of the vehicle, similar to the transparent cover 12 in FIG. 1.

[0018] FIG. 2(A) is a schematic cross-sectional view for explaining the arrangement of the millimeter-wave radar unit 15 and the shielding member 18. FIG. 2(B) is a schematic plan view of the millimeter-wave radar unit 15 and the shielding member 18 as viewed from the shielding member 18 side. Note that the cross-sectional view in FIG. 2(A) corresponds to the cross-section in the direction of line A-A shown in FIG. 2(B).

[0019] As shown in FIGS. 2(A) and 2(B), the shielding member 18 is configured, for example, as a flat plate with a substantially constant thickness, and one surface thereof is arranged to face the antenna surface of the millimeter-wave radar unit 15. The shielding member 18 is preferably arranged so as to be perpendicular to the central axis or the reference axis of the radiation pattern of the antenna. Here, the radiation pattern of the antenna refers to the angular distribution of the electromagnetic wave intensity transmitted from the antenna surface of the millimeter-wave radar unit 15. Generally, the normal direction of the antenna surface has the maximum intensity, and the electromagnetic wave intensity decreases as the angle from the normal direction increases. The angle at which the intensity becomes -3 dB from the maximum intensity is called the half-value width of the antenna pattern, and is, for example, 80°.

[0020] The shielding member 18 includes a flat plate-shaped first portion 18a made of a foamed resin and a second portion 18b made of a non-foamed resin. The first portion 18a is arranged at the center of the shielding member 18 in a plan view. The second portion 18b is provided so as to be in contact with the side surface of the first portion 18a, and is arranged in an annular shape surrounding the first portion 18a in a plan view.

[0021] Also, as shown in the partial enlarged view in FIG. 3, on both the one surface and the other surface of the first portion 18a, third portions 18c are provided which are arranged so as to be in contact with the respective one surface and the other surface. These third portions 18c are made of a non-foamed resin in the same manner as the second portion 18b. In the present embodiment, the second portion 18b and each of the third portions 18c are integrally formed. Thereby, the first portion 18a is in a state where its periphery is entirely sealed with the non-foamed resin.

[0022] The shielding member 18 can have a thickness of about 2.9 mm, for example. Also, each of the third portions 18c can have a thickness of 100 μm or less (a thickness smaller than that of the first portion 18a). In the present embodiment, the combined thickness of the first portion 18b and each of the third portions 18c is 2.9 mm, and the thickness of the second portion 18b is also 2.9 mm. That is, the shielding member 18 has a substantially uniform thickness as a whole.

[0023] In addition, in the present embodiment, the second portion 18b and the third portion 18c are made of a non-foamed resin using the same material. Further, the first portion 18a is made of a foamed resin obtained by mixing bubbles into the same material as the constituent materials of the second portion 18b and the third portion 18c.

[0024] Here, the "foamed resin" and "non-foamed resin" in the present embodiment will be described. The "foamed resin" is a resin in which gas (foaming gas) generated by a chemical reaction (chemical reaction) or physical change is mixed and formed with a polymer or oligomer as a raw material. Specifically, for example, it refers to a resin in which bubbles are mixed into a transparent resin such as polycarbonate, acrylic, polyimide, or epoxy by enclosing carbon dioxide gas or the like. Since the foamed resin can reduce the dielectric constant by enclosing gas in the resin, it is possible to greatly reduce the influence on electromagnetic waves. The bubble ratio (the ratio of bubbles in the total volume) of the foamed resin is preferably 50% or more. The "non-foamed resin" refers to a resin in which the above-described active foaming molding is not performed and no bubbles are provided. Note that a resin in which a small amount of unintentional bubbles are mixed in manufacturing corresponds to a "non-foamed resin" rather than a "foamed resin" in the present embodiment.

[0025] As an example, the dielectric constant and the attenuation amount at an incident angle of 0° were measured for the shielding member of the example having the configuration according to the present embodiment and the shielding member of the comparative example made of a foamed resin. In the example, a shielding member was prepared with the combined thickness of the first portion 18a and each third portion 18c being 2.9 mm and each third portion 18c being 100 μm as described above. In the comparative example, a shielding member was prepared by forming a flat plate of foamed resin with a thickness of 2.9 mm. As the resin, polycarbonate was used in both the example and the comparative example. In the comparative example, the initial dielectric constant was 1.658 and the attenuation amount was 0.035 dB, but after the water wetting test, the dielectric constant changed to 1.631 and the attenuation amount changed to 0.65 dB. In the example, the dielectric constant was 1.83 and the attenuation amount was 0.11 dB, without change before and after the water wetting test.

[0026] Referring back to Fig. 2(A), the arrangement of the millimeter-wave radar unit and the shielding member will be described in detail. As shown in Fig. 2(A), the shielding member 18 has a boundary 18d between the first part 18a and the second part 18b. This boundary 18d is annular (rectangular) as shown in Fig. 2(B) in a plan view. In the present embodiment, this boundary 18d is provided at a position where the incident angle of the millimeter waves radiated from the millimeter-wave radar unit 15 to the shielding member 18 is 60° at least in the A-A cross section. The position where the incident angle is 60° means, for example, when the entire surface of the shielding member 18 facing the millimeter-wave radar unit 15 is the antenna surface, as shown in the figure, it is the position where the angle formed by the line connecting the outer edge of the antenna surface and the boundary 18d and the normal line of the surface of the shielding member 18 facing the antenna surface is 60°. That is, in the present embodiment, the first part 18a is arranged corresponding to the range where the incident angle of the millimeter waves is 0° or more and 60° or less (relatively small range), and the second part 18b is arranged corresponding to the range where the incident angle of the millimeter waves is greater than 60° (relatively large incident angle range).

[0027] In consideration of errors during manufacturing, etc., it is preferable to provide the boundary 18d within a range of ±5° with respect to the preferred value of the incident angle (60° in the above example).

[0028] Fig. 4 is a diagram showing a calculation example of the attenuation amount due to the incident angle of millimeter waves on the shielding member. This calculation example is calculated using the Fresnel formula under the conditions of a frequency of 76.5 GHz, horizontal polarization, a dielectric constant of 2.7, and a dielectric loss tangent of 0.01. As shown in the calculation example, in the case of a plate thickness of 2.4 mm where the attenuation amount is the smallest at a normal incidence with an incident angle of 0°, when the incident angle is 80°, the attenuation amount becomes a large value exceeding 4 dB. When the plate thickness is 2.9 mm, the attenuation amount at normal incidence is -1.4 dB, which is a large attenuation amount.

[0029] Here, it is known that when the dielectric constant of the shielding member is reduced by using a foamed resin, the attenuation amount is less affected even at a large incident angle. Therefore, for the shielding member, a non-foamed resin with a plate thickness of 2.9 mm is used to form the portion (the above-described second portion 18b) exceeding an incident angle of 60°, and the portion within an incident angle of 60° (the above-described first portion 18a) is formed of a foamed resin, so that it is possible to reduce the attenuation amount for the entire measurement range (field of view: FOV) of the shielding member 18.

[0030] In addition, in order to make the overall thickness of the shielding member 18 uniform at 2.9 mm, it is necessary to determine the dielectric constant of the foamed resin so that the attenuation amount is minimized when the plate thickness of the first portion 18a, which is the foamed resin portion, is 2.9 mm. Since the dielectric constant of the foamed resin can be expressed by the following relational expression, by using this relational expression, the dielectric constant can be determined so as to minimize the transmission loss. Dielectric constant of the foamed resin = (1 / (plate thickness / wavelength of the millimeter-wave radar)) 2

[0031] For example, when the plate thickness is 2.9 mm and the wavelength of the millimeter-wave radar is 3.92 mm (corresponding to 76.5 GHz), if the foaming ratio is set so that the dielectric constant of the foamed resin portion is 1.83, an optimal foamed resin can be obtained with a plate thickness of 2.9 mm.

[0032] In addition, since the third portion 18c, which is a skin layer, is formed on both one surface and the other surface of the first portion 18a formed of the foamed resin, holes that absorb moisture are not formed on one surface and the other surface of the first portion 18a. Further, since the second portion 18b is formed around (the side surface) of the first portion 18a, moisture absorption from the side surface of the first portion 18a can also be suppressed. Note that the formation of the second portion 18b and the third portion 18c on one surface, the other surface, and the periphery of the first portion 18a can be realized, for example, by insert molding.

[0033] FIG. 5 is a diagram showing the measurement results of the transmission loss in the shielding member of the embodiment. Here, a shielding member of the embodiment was used in which the combined plate thickness of the first portion 18a and each third portion 18c was 2.9 mm, and the plate thickness of the second portion 18b was also 2.9 mm. The shielding member of this embodiment has a dielectric constant of 1.83 and a dielectric tangent of 0.002 at the portion where the first portion 18a and each third portion 18c are combined, and a dielectric constant of 2.7 and a dielectric tangent of 0.01 at the second portion 18c.

[0034] As shown by the characteristic line a in the figure, when the shielding member of the embodiment is irradiated with millimeter waves from the millimeter wave radar unit 15 with respect to the first portion 18a (including the third portion 18), in the range where the incident angle is 0 or more and 65° or less, the attenuation amount is lower than that of the second portion 18b shown by the characteristic line b. On the other hand, in the range where the incident angle exceeds 65°, the second portion 18b has a lower attenuation amount than the first portion 18a. Based on the results of the attenuation amount due to such an incident angle, in this embodiment, the boundary 18d between the first portion 18a and the second portion 18b can be determined at a position where the incident angle is 65°. When considering the manufacturing error as described above, the boundary 18d can be determined in the range of 65° ± 5°.

[0035] According to the above-described embodiments and examples, since measures against moisture absorption are taken when using the foamed resin, it is possible to prevent an increase in transmission loss as a whole of the shielding member in various devices such as a radar device and a vehicle lamp using the same. Further, since the shielding member has a simple flat plate-like structure as a whole, it is also possible to improve the strength of the shielding member.

[0036] Note that the present disclosure is not limited to the content of the above-described embodiments, and various modifications can be made and implemented within the scope of the gist of the present disclosure. For example, the specific numerical conditions and the like given in the examples are examples for facilitating the understanding of the present disclosure, and do not limit the scope of application of the present disclosure to those conditions. Specifically, for example, the method of determining the position of the above-described boundary 18d (corresponding to an incident angle of 60° as an example in the embodiment) is an example, and the suitable value can vary according to various conditions such as the materials and thicknesses of the foamed resin and non-foamed resin used to form the shielding member 18. That is, in the same manner as shown in an example in FIG. 5, the range of the incident angle in which the transmission loss in the foamed resin is smaller than the transmission loss in the non-foamed resin may be obtained, and based on this, the boundary 18d between the first part 18a and the second part 18b may be determined.

[0037] In addition, in the above-described embodiment, a headlamp is cited as an example of a vehicle lamp, but it is not limited thereto, and the vehicle lamp may be a tail lamp, a backlight, or the like. Further, although a housing of a vehicle lamp is cited as an example of a place where the radar device is installed, it is not limited thereto, and the radar device can be installed at any place.

Explanation of Reference Numerals

[0038] 10: Vehicle lamp, 11: Base body, 12: Transparent cover, 14: Headlamp unit, 15: Millimeter-wave radar unit, 16: Light-emitting unit, 18: Shielding member, 18a: First part, 18b: Second part, 18c: Third part, 18d: Boundary

Claims

1. A shielding member used in a radar device, a flat first part made of a foamed resin, a second part made of a non-foamed resin, which is arranged to surround the first part so as to be in contact with the side surface of the first part, a third part made of a non-foamed resin, which is arranged to be in contact with each of one surface and the other surface of the first part, The shielding member includes.

2. The shielding member according to claim 1, wherein the combined thickness of the first part and the third part is substantially the same as the thickness of the second part. The shielding member according to claim 1.

3. The shielding member according to claim 1, wherein the second part and the third part are integrally formed. The shielding member according to claim 1.

4. The shielding member according to claim 1, wherein the thickness of the third part is smaller than the thickness of the first part. The shielding member according to claim 1.

5. The shielding member according to claim 1, wherein the second part and the third part are made of the same material. The shielding member according to claim 1.

6. The shielding member according to claim 1, wherein the first part is made of a foamed resin in which bubbles are mixed in the same material as the constituent materials of the second part and the third part. The shielding member according to claim 1.

7. A radar device including the shielding member according to claim 1, and a radar wave transmitter arranged with a gap provided between the shielding member and the shielding member. The radar device includes.

8. In the radar device according to claim 7, the first part of the shielding member is arranged in a range where the incident angle of the radar wave is relatively small, and the second part is arranged in a range where the incident angle is relatively large. The radar device according to claim 7.

9. In the radar device according to claim 8, the boundary between the first part and the second part is determined based on the range of the incident angle at which the transmission loss in the foamed resin is smaller than the transmission loss in the non-foamed resin. The radar device according to claim 8.

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