Antenna device and door mirror device

Abstract

To obtain good antenna characteristics regardless of the internal shape of a door mirror device, and to easily install an antenna device.SOLUTION: An antenna device 10 includes an antenna element and a bracket 200 to which the antenna element is fixedly attached as a film antenna 100. The bracket 200 to which the film antenna 100 having the antenna element is attached is provided between an outer cover and an inner cover of a door mirror device.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an antenna device and a door mirror device.

Background Art

[0002] Conventionally, an antenna device incorporated in a door mirror device of a vehicle is known. For example, a vehicle antenna in which an antenna element is attached inside an enclosure as an outer cover of a door mirror is known (see Patent Document 1). Also, an antenna device in which a film antenna is disposed on an inner cover of a door mirror device is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the shapes of conventional vehicle antennas and antenna devices depend on the shapes of outer covers and inner covers, and good antenna characteristics cannot be obtained depending on the bending angle (degree of bending) of the antenna element. For example, when a film antenna including an antenna element is attached and installed on the inner covers of various door mirror devices, the bending angle of the film antenna changes according to the shape of each inner cover. Therefore, the antenna characteristics of the film antenna in each door mirror device also change and are not stable.

[0005] Also, when mounting an antenna device on a door mirror device where no antenna is installed, it is necessary to change the shape of the conventional parts (such as the inner cover) at the mounting destination, resulting in man-hours and costs associated with the change.

[0006] An object of the present invention is to obtain good antenna characteristics and easily install an antenna device regardless of the internal shape of a door mirror device.

Means for Solving the Problems

[0007] To solve the above problems, the antenna device of the present invention includes: an antenna element; a bracket to which the antenna element is fixedly attached, and the bracket to which the antenna element is attached is provided between an outer cover and an inner cover of the door mirror device.

Effects of the Invention

[0008] According to the present invention, good antenna characteristics can be obtained regardless of the internal shape of the door mirror device, and the antenna device can be easily installed.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention and the first and second modification examples will be described in detail in order with reference to the accompanying drawings. However, the scope of the invention is not limited to the illustrated examples.

[0011] (Embodiment) With reference to FIGS. 1 to 9, embodiments of the present invention will be described. First, with reference to FIGS. 1 to 4, the device configuration of the present embodiment will be described. FIG. 1 is an external perspective view showing the door mirror device 1 of the present embodiment. FIG. 2 is a perspective view showing the internal configuration of the door mirror device 1. FIG. 3 is a perspective view showing the antenna device 10. FIG. 4 is a top view showing the film antenna 100 and the cable 310. FIG. 5 is a perspective view showing the bracket 200.

[0012] As shown in FIG. 1, the door mirror device 1 is installed on the front seat door of a vehicle such as an automobile. The door mirror device 1 includes a mirror 2a, a turn light 2b, a cable 2c, and outer covers 3a and 3b. The mirror 2a is a rearview mirror of the vehicle, and the angle of the mirror surface can be adjusted by a motor (not shown) or the like. The turn light 2b is a direction indicator light. The cable 2c is a cable having one end connected to an antenna or the like inside the door mirror device 1 and the other end connected to a receiver or the like inside the vehicle.

[0013] The outer covers 3a and 3b are covers provided outside the door mirror device 1, and are made of, for example, a resin having radio wave permeability. The outer cover 3a is an outer cover provided on the upper (zenith direction) side. The outer cover 3b is an outer cover provided on the lower (nadir (ground) direction) side.

[0014] The antenna device 10 of the present embodiment is installed inside the door mirror device 1. Specifically, the antenna device 10 is provided inside the outer covers 3a and 3b. Therefore, the vehicle user cannot visually recognize the antenna device 10 from the outside. The antenna device 10 is, for example, an antenna device for cellular communication as a wireless communication method. The cellular communication is assumed to be communication in the frequency bands of 3G (Generation), 4G, and 5G (including Sub6). The frequency band of the cellular communication is approximately 617 [MHz] to 6 [GHz]. However, the wireless communication method of the antenna device 10 is not limited to cellular communication.

[0015] Fig. 2 shows the internal configuration of the door mirror device 1 with the outer cover 3a removed. As shown in Fig. 2, the door mirror device 1 further includes an inner cover 4, antennas 5a, 5b, and 5c, and an antenna device 10.

[0016] The inner cover 4 is a cover made of resin or the like provided further inside the outer covers 3a and 3b. The inner cover 4 has built-in actuators such as motors and components such as cables (both not shown).

[0017] The antenna 5a is an antenna for transmitting and receiving Wi-Fi (registered trademark) radio waves disposed on the inner cover 2a1 of the inner part of the mirror 2a. The antenna 5b is an antenna for transmitting and receiving Bluetooth (registered trademark) radio waves disposed on the inner cover 4. The antenna 5c is a patch antenna for receiving GNSS (Global Navigation Satellite System) radio waves disposed on a bracket 200 described later.

[0018] The antenna device 10 is mounted on the inner cover 4 by means of the screw 4a provided on the inner cover 4. More precisely, the antenna device 10 is mounted on the inner cover 2a1 by tightening the screw 4a for attaching the inner cover 4 to the inner cover 2a1 together. In this way, the antenna device 10 is provided between the outer covers 3a, 3b and the inner cover 4. However, the method of attaching the antenna device 10 to the inner cover 2a1 is not limited to tightening with the screw 4a.

[0019] As shown in FIG. 3, the antenna device 10 includes a film antenna 100, a bracket 200, a cable 310, and a cable cover 320. The film antenna 100 is a planar antenna body of the antenna device 10. The bracket 200 fixes and supports the film antenna 100 at a predetermined bending angle (degree of bending) formed in advance.

[0020] The cable 310 is a coaxial cable, one end of which is electrically connected to the film antenna 100, and the other end of which is electrically connected to a receiver provided inside the vehicle. The cable cover 320 is a substantially rectangular parallelepiped-shaped cover made of resin or the like that covers the tip of the cable 310 connected to the film antenna 100. The cable cover 320 sandwiches and protects the film antenna 100 and the cable 310 from the front and back by screwing through the hole portions H1 of the two cover portions.

[0021] FIG. 4 shows the film antenna 100 and the cable 310 in a state where the antenna device 10 is removed from the bracket 200 and flattened and the cable cover 320 is removed. The film antenna 100 has an antenna element 110 and a film 120. The antenna element 110 has a radiating element 111, a GND (Ground) portion 112, and a resistor R1.

[0022] The antenna element 110 is a planar dipole antenna element made of metal such as copper foil. However, the antenna element 110 is not limited to a dipole antenna.

[0023] The radiating element 111 is an antenna element that receives radio waves and conducts an antenna current. The GND part 112 is an antenna element that is grounded. The film 120 is a single film made of an insulating (dielectric) resin such as polyimide, and is laminated (stacked) on the back surface of the antenna element 110 to cover the antenna element 110 from below. The film 120 holds (supports) and protects the antenna element 110. The film antenna 100 is bendable. Also, a resist (not shown) is formed on the upper layer (surface) of the antenna element 110 and the film 120.

[0024] A power supply point P1 is provided near the gap portion between the radiating element 111 and the GND part 112. The power supply point P1 is electrically connected to the inner conductor of the cable 310 by soldering or the like. The GND part 112 is electrically connected to the outer conductor of the cable 310 by soldering or the like. The resistor R1 is electrically connected to the radiating element 111 and the GND part 112. The resistor R1 is a detection resistor for detecting whether the antenna device 10 is electrically connected to the cable 310.

[0025] As shown in FIG. 5, the bracket 200 is assumed to be an integral resin molded product made of a resin such as ABS (Acrylonitrile Butadiene Styrene) resin as a dielectric. The bracket 200 has a bracket body 210, a notch portion 220, a mounting portion 230, a base portion 240, and a C-shaped portion 250. The bracket body 210 is a flat plate of the main body of the bracket 200. The bracket body 210 has a relatively small predetermined bending angle as will be described later. For this reason, the bending angle of the film antenna 100 attached to the bracket 200 is fixed by the bending angle of the bracket 200. However, the bending angle of the bracket 200 is not limited to the bending angle in FIG. 5.

[0026] The cutout portion 220 is a rectangular cutout portion in the bracket main body 210. A cable cover 320 that stores the tip portion of the cable 310 is inserted into the cutout portion 220. The film antenna 100 is attached to the bracket 200 by, for example, being attached to the bracket main body 210 with double-sided tape.

[0027] The bracket body 210 (bracket 200) as a dielectric has a wavelength shortening effect according to its dielectric constant. Therefore, by increasing the dielectric constant of the bracket 200, the length of the antenna element 110 of the attached film antenna 100 can be shortened. Based on a rough estimate from the frequency fluctuation measured in the ABS resin bracket 200, the antenna element 110 can be reduced in size by about 10%.

[0028] The mounting portion 230 extends to the upper left side of the bracket main body 210 in the figure, and has a hole through which the screw 4a is inserted. The mounting portion 230 is a portion that mounts the bracket 200 to the inner cover 2a1 by threading the screw 4a through the hole. The base portion 240 extends from the back side of the bracket main body 210 to the left in the figure, and is a base portion on which the antenna 5c is installed. The C-shaped portion 250 is a C-shaped recess that extends from the back side of the bracket main body 210 downward in the figure. The C-shaped portion 250 is fitted into a protrusion (not shown) of the outer cover 3b.

[0029] The bracket 200 is firmly attached to the inner cover 2a1 and the outer cover 3b by the screw 4a of the attachment portion 230 being threadedly engaged and the C-shaped portion 250 being fitted thereto.

[0030] When the antenna device 10 is mounted inside the door mirror device 1, a bracket 200 is used to fix and stabilize the bending angle. For this reason, the bracket 200 does not need to have high bending strength (ease of bending), but it does need to have high impact strength, and therefore ABS resin is used.

[0031] On the other hand, when attaching a film antenna or film antenna 100 for a conventional door mirror device, since it is bent when attaching to the attachment destination, high bending strength is required, so polyimide or the like is used for the film or film 120. For this reason, the impact strength of the bracket 200 is higher than the impact strength of the film 120. Also, the bending strength of the bracket 200 is lower than the bending strength of the film 120. The materials, shapes, and thicknesses of the bracket 200 and the film 120 are set to satisfy these conditions.

[0032] Next, with reference to FIGS. 6 to 9, the antenna characteristics of the antenna device 10 will be described. FIG. 6 is a diagram showing the frequency characteristics of the VSWR (Voltage Standing Wave Ratio) of the antenna device 10. FIG. 7 is a schematic diagram of the antenna devices 10, 10A, and 10B. FIG. 8 is a diagram showing the frequency characteristics of the average gain of the antenna devices 10, 10A, and 10B. FIG. 9 is a diagram showing the frequency characteristics of the VSWR of the antenna device 10 with / without the bracket 200.

[0033] As shown in FIG. 6, the VSWR of the antenna device 10 with respect to the frequency [GHz] was measured. The VSWR of the antenna device 10 is low in the frequency band of cellular communication, indicating that resonance is achieved.

[0034] Next, the antenna characteristics of the antenna device 10 compared with other antenna devices will be described. As shown in FIG. 7, in addition to the antenna device 10, consider antenna devices 10A and 10B in which the bending angle of the bracket 200 in the antenna device 10 is changed. In FIG. 7, the detailed parts of the antenna devices 10, 10A, and 10B are omitted from the illustration. However, as the bracket 200, one without the attachment portion 230, the base portion 240, and the C-shaped portion 250 was used.

[0035] The antenna devices 10, 10A, and 10B have different bending angles of the bracket 200 from each other. The bending angle of the antenna device 10 < the bending angle of the antenna device 10A < the bending angle of the antenna device 10B.

[0036] FIG. 8 shows the average gain [dBi] of the antenna devices 10, 10A, and 10B versus frequency [GHz] and the frequency bands for cellular communication. The average gain [dBi] is the average value of the gain [dBi] of the antenna devices 10, 10A, and 10B at elevation angles of 0 to 30° (0°, 10°, 20°, and 30°). The elevation angles are defined as 0° in the horizontal direction when the antenna devices 10, 10A, and 10B (bracket 200) are erected as shown in FIG. 7. The gain [dBi] at each elevation angle is the average value of the gain around 360° in the horizontal direction (horizontal direction) centered on the antenna devices 10, 10A, and 10B in FIG. 7.

[0037] As shown in Fig. 8, the larger the bending angle of bracket 200 of an antenna device, the lower the average gain [dBi] in the cellular communication frequency band, and the more deteriorated the antenna characteristics. Note that the frequency band of approximately 1 to approximately 1.4 [GHz] in Fig. 8 is outside the cellular communication frequency band, so the average gain [dBi] of antenna devices 10, 10A, and 10B was not measured.

[0038] For this reason, the larger the bending angle, the more the average gain of the film antenna 100 deteriorates. Therefore, when the film antenna 100 is attached inside door mirror devices with various internal structures, the average gain of the film antenna 100 changes depending on the bending angle, and in some cases the required average gain cannot be obtained.

[0039] However, even if the antenna device 10 is attached to door mirror devices with various internal structures, the bending angle of the film antenna 100 is fixed (maintained) by the bracket 200. Therefore, even if the antenna device 10 is attached to the various door mirror devices, a high average gain can be obtained.

[0040] 9, the VSWR was measured for frequency [GHz] for the antenna device 10 and the film antenna 100 as the antenna device 10 without the bracket 200. Fig. 9 shows that adding the bracket 200 to the film antenna 100 to create the antenna device 10 causes a frequency shift in the VSWR to the lower frequency side.

[0041] To lower the frequency, it is usually necessary to lengthen the antenna pattern of the antenna element 110. However, this can be compensated for by the resin (dielectric constant) of the bracket 200, so the antenna device 10 can remain small without lengthening the pattern length of the antenna element 110.

[0042] As described above, according to this embodiment, the antenna device 10 includes the antenna element 110 and the bracket 200 to which the antenna element 110 is fixedly attached. The bracket 200 to which the antenna element 110 is attached is provided between the outer covers 3a, 3b and the inner covers 2a1, 4 of the door mirror device 1. The door mirror device 1 includes the antenna device 10, the outer covers 3a, 3b, and the inner covers 2a1, 4.

[0043] Therefore, the bending angle of the antenna element 110 is fixed and stabilized by the bracket 200, so good antenna characteristics can be obtained regardless of the internal shape of the door mirror device 1. Furthermore, the antenna element 110 attached to the bracket 200 does not bend, and the bracket 200 does not require changing the internal configuration of the door mirror device 1, so the antenna device 10 can be easily installed in the door mirror device 1.

[0044] The antenna element 110 is a copper foil as a conductive foil. The antenna device 10 includes a film 120 that holds the antenna element 110. The film antenna 100, which includes the antenna element 110 and the film 120, is attached to a bracket 200. Therefore, the antenna element 110 can be easily attached to the bracket 200.

[0045] The bracket 200 is made of ABS resin as a dielectric material, and therefore the antenna element 110 and the antenna device 10 can be made smaller due to the wavelength shortening effect of the dielectric material.

[0046] Furthermore, the bracket 200 has a shape with a predetermined bending angle, so that the desired antenna characteristics can be obtained by forming the bracket 200 at a bending angle that will achieve the desired antenna characteristics.

[0047] (First Modification) A first modification of the above embodiment will be described with reference to Fig. 10. Fig. 10 is a schematic perspective view showing an antenna device 20 of this modification.

[0048] The antenna device 10 of the above embodiment is configured to include one film antenna 100. The antenna device 20 of this modified example is configured to include a plurality of antennas.

[0049] As shown in Fig. 10, the antenna device 20 includes a film antenna 100, 500 and a bracket 400. In the modified example, parts that are the same as those in the device configuration of the above-described embodiment are given the same reference numerals, and their description will be omitted. Also, in Fig. 10, detailed parts such as the antenna patterns of the antenna elements of the film antennas 100, 500 of the antenna device 20 and the mounting portion of the bracket 400 are not shown.

[0050] The film antenna 500 is a film antenna with a similar configuration to the film antenna 100, but is a film antenna for Wi-Fi as a wireless communication method. Wi-Fi frequency bands include the 2.4 GHz band and the 5 GHz band. The film antenna 500 is smaller than the film antenna 100.

[0051] Bracket 400 is an integral resin molded product similar to bracket 200. Bracket 400 has antenna mounting portions 411, 412 and a connecting portion 413. Antenna mounting portion 411 is a flat plate portion for mounting film antenna 100. Antenna mounting portion 412 is a flat plate portion for mounting film antenna 500. Connecting portion 413 is a connecting portion that connects antenna mounting portion 411 and antenna mounting portion 412.

[0052] As described above, according to this modification example, antenna device 20 includes two antenna elements (film antennas 100, 500). Film antennas 100, 500 are attached to bracket 400. Therefore, antenna devices of different multiple wireless communication systems can be mounted in door mirror device 1 with space saving. Note that the antenna devices attached to bracket 400 may be of the same wireless communication system.

[0053] (Second Modification Example) Referring to FIG. 11, a second modification example of the above-described embodiment will be described. FIG. 11 is a perspective view showing antenna device 30 of this modification example.

[0054] Antenna device 10 of the above-described embodiment had a configuration in which film antenna 100 was mounted on bracket 200. Antenna device 30 of this modification example has a configuration in which an antenna element is directly mounted on a bracket.

[0055] As shown in FIG. 11, antenna device 30 includes antenna element 600 and bracket 200. In this modification example, parts similar to the device configuration of the above-described embodiment are denoted by the same reference numerals, and the description thereof is omitted. Also, in FIG. 11, illustration of detailed parts such as the antenna pattern of the antenna element of antenna device 30 and mounting portion 230 of bracket 200 is omitted.

[0056] The antenna element 600 is an antenna element for cellular communication and has, for example, the same antenna pattern as the antenna element 110. Further, the antenna element 600 is a sheet metal antenna made of a metal such as SPTE (Steel Plate Tin Electrolytic) and is not covered with a film or the like. The antenna element 600 is directly attached onto the bracket 200 using a double-sided tape or the like. Therefore, the bending angle of the antenna element 600 is formed and fixed (maintained) in advance so as to correspond to the bending angle of the bracket 200.

[0057] As described above, according to this modification example, the antenna element 110 is directly attached to the bracket 200. Therefore, the manufacturing process of the antenna device 30 can be simplified, and the manufacturing cost can also be reduced.

[0058] Note that the descriptions in the above embodiments and modification examples are examples of the antenna device and the door mirror device according to the present invention and are not limited thereto. For example, a configuration in which at least two of the above embodiments and modification examples are appropriately combined may be used.

[0059] Also, in the above embodiments and modification examples, the frequency bands of the antenna devices 10, 20, and 30 are configured to be the frequency bands of cellular communication (and Wi-Fi), but the present invention is not limited thereto, and other wireless communication system frequency bands may be used.

[0060] In addition, regarding the detailed configurations and detailed operations of the antenna devices 10, 20, and 30 and the door mirror device 1 in the above embodiments, they can be appropriately changed without departing from the spirit of the present invention.

Description of Reference Numerals

[0061] 1 Door mirror device 2a Mirror 2b Turn light 2c, 310 Cable 3a, 3b Outer cover 2a1, 4 Inner cover 4a Screw 5a, 5b, 5c antennas 10, 10A, 10B, 20, 30 antenna devices 100, 500 film antennas 110, 600 antenna elements 111 radiation elements 112 GND part R1 resistor H1 hole part P1 feeding point 200, 400 brackets 210 bracket body 220 notch part 230 mounting part 240 base part 250 C-shaped part 320 cable cover 411, 412 antenna mounting parts 413 connection part

Claims

1. An antenna element, a bracket to which the antenna element is fixedly attached, and the antenna device comprises: The bracket to which the antenna element is attached is provided between an outer cover and an inner cover of a door mirror device.

2. The antenna element is a conductive foil, a film for holding the antenna element is provided, and The film antenna having the antenna element and the film is attached to the bracket. The antenna device according to claim 1.

3. The antenna element is directly attached to the bracket. The antenna device according to claim 1.

4. There are a plurality of the antenna elements, and The plurality of antenna elements are attached to the bracket. The antenna device according to claim 1.

5. The bracket is a dielectric. The antenna device according to claim 1.

6. The bracket has a shape with a predetermined bending angle. The antenna device according to claim 1.

7. An antenna device according to any one of claims 1 to 6, the outer cover, and the inner cover, and a door mirror device comprising the same.

Images