JP2008141481A - Rearview mirror having built-in etc, antenna arrangement configuration and antenna arrangement method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rearview mirror having a built-in ETC which can be attached on various kinds of cars without interrupting usual transmission/reception of radio waves by an antenna. <P>SOLUTION: A conductive base member 7 to which a stay 16 of a car rearview mirror is engaged via a base end portion 16c is fixed on the windshield of the car. The antenna has an arrangement configuration in which a plurality of dipole antennas 11a-11d for performing radio communications with each of road-side devices installed on a gate of an express way are arranged near the base member 7. The antennas 11a-11d are each arranged so as to be vertical symmetry in a vehicle width direction centered at the base member 7. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is an ETC (Electronic Toll Collection) built-in inner mirror mounted on a vehicle such as an automobile, an antenna arrangement configuration preferably used for the ETC built-in inner mirror, and preferably used for the ETC built-in inner mirror. The present invention relates to an antenna arrangement method.

Conventionally, an ETC (automatic toll collection system) which is one of so-called DSRC (Dedicated Short-Range Communication) systems has been used.
As an example of this, radio waves including data such as billing information (usually in the 5.8 GHz band) between an ETC in-vehicle antenna mounted on an automobile (vehicle) and a roadside device provided in a highway gate or the like. Some radio waves are used).

  By the way, a so-called ETC built-in inner mirror in which an in-vehicle antenna for ETC is integrated with the inner mirror has been developed (see Patent Document 1). As shown in FIG. 6A, in this type of ETC built-in inner mirror 50, an ETC in-vehicle antenna 51 is accommodated in an antenna case 55 provided in the vicinity of the inner mirror 58 with respect to the windshield 2 of the automobile. Has been. In addition, a conductive base member 7 (inner mirror mounting button) to which the stay 56 of the inner mirror 58 is engaged at the base end portion (antenna holding portion 55) is fixed to the windshield 2.

  The ETC in-vehicle antenna 51 includes two (plural) dipole antennas 11 and 11 (antennas), and the dipole antennas 11 and 11 are orthogonal to each other on a rectangular substrate 52 made of a dielectric. It is arranged. Each dipole antenna 11, 11 is connected to an inner conductor 18 a of a coaxial cable 18 connected to a high-frequency power source, and the two dipole antennas 11, 11 are connected to each other in a plane perpendicular to the traveling direction of radio waves. Circularly polarized waves whose direction of the electric field rotates with a period equal to the excitation frequency of the radio wave are radiated.

  In the ETC built-in inner mirror 50, as shown in FIG. 6B, a radio wave is transmitted from the front direction of the automobile 3 to the roadside device 6 from the ETC in-vehicle antenna 51, and is transmitted from the roadside device 6. Is received by the ETC in-vehicle antenna 51. In this case, when the angle formed between the direction substantially perpendicular to the surface of the windshield 2 and the direction perpendicular to the road surface 5 (vertical direction) is a predetermined angle, specifically about 22.5 °, the automobile 3 is The directivity (a specific direction in which radio waves are selectively received or a specific direction in which radio waves are selectively emitted) of the in-vehicle antenna 51 for ETC when it is at a predetermined position under the gate is the direction facing the roadside unit 6 and is optimal. A simple transmission / reception state is realized. Further, since the roadside machine 6 is installed at a substantially central position in the road width direction at a gate of an expressway or the like, the ETC built-in inner mirror 50 has a vehicle width of the automobile 3 as shown in FIG. It is desirable that radio waves are transmitted and received from the center position in the direction toward the front.

  By the way, recently, in order to be able to mount the ETC built-in inner mirror as described above in various types of vehicles, it is strongly demanded to reduce the size and to save the space of the mounting portion on the windshield of the vehicle. .

As one of the best methods for realizing such versatility, in the ETC built-in inner mirror 50 shown in FIG. 6A, the dipole antennas 11 and 11 are arranged in the vicinity of the base member 7 described above. For example, the antenna case 55 that accommodates the base member 7 and the in-vehicle antenna 51 for ETC can be downsized and the installation space can be reduced.
JP 2006-197429 A

  However, as shown in FIGS. 5A and 5B, when the dipole antennas 11 and 11 are arranged in the vicinity of the conductive base member 7, radio waves are absorbed and reflected by the base member 7, and the ETC. The directivity of the on-vehicle antenna 51, that is, the radiation direction of the radio wave becomes asymmetrical in the vehicle width direction (see FIG. 3B), and it is difficult to properly transmit and receive radio waves with the roadside device 6 and the like. There was a case. In FIGS. 5 (a) and 5 (b), the antenna holding portion 15 'is in front of the vehicle with the bottom member 12' engaged with the base member 7 fixed to the vehicle windshield. Mounted on glass. The dipole antennas 11 and 11 are arranged in a standing state on a dielectric substrate 13 ′ provided in the antenna holding portion 15 ′ and orthogonal to each other so as to radiate circularly polarized waves.

  On the other hand, as with a so-called phased array antenna, for example, means for controlling the directivity of the antenna by changing the phase of the current supplied to each of the two antennas can be considered. In this case, however, the adjustment of the phase of the current is possible. There is a problem that becomes complicated.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an ETC built-in inner mirror that can be attached to various vehicles without hindering normal transmission and reception of radio waves by an antenna, An object of the present invention is to provide an antenna arrangement configuration preferably used for an ETC built-in inner mirror and an antenna arrangement method preferably used for the ETC built-in inner mirror.

  In order to solve the above problems, the invention according to claim 1 is characterized in that a conductive base member to which a stay of an inner mirror of a vehicle is engaged at a base end is fixed to a windshield of the vehicle, In an antenna arrangement configuration in which a plurality of antennas that perform wireless communication with a communication terminal outside the vehicle are arranged in the vicinity of the base member, the antennas are arranged symmetrically in the vehicle width direction with the base member as a center. It is a summary.

  According to this configuration, the antennas are arranged symmetrically in the vehicle width direction about the base member, so that the radio waves radiated from the antennas are absorbed and reflected symmetrically in the vehicle width direction by the base member. The electric lines of force formed near the base member by the antenna are symmetrical in the vehicle width direction about the base member. As a result, radio waves are transmitted and received by the antennas from the center position in the vehicle width direction of the vehicle toward the front.

  According to a second aspect of the present invention, in the antenna arrangement configuration according to the first aspect, the base member is a flat plate member formed in a planar view shape, and each antenna is a dipole antenna. Then, the gist of the invention is that circular polarization is radiated by a pair of antennas that are arranged such that the length direction thereof extends along each side of the base member and is orthogonal to each other.

  According to this configuration, the directivity by the plurality of dipole antennas surrounding the base member having a rectangular shape in plan view is a direction directed forward from the center position in the vehicle width direction of the vehicle. Further, since circularly polarized waves are radiated by a pair of antennas orthogonal to each other, a highly directional and highly sensitive antenna suitable for DSRC (narrow band communication) can be realized.

  According to a third aspect of the present invention, there is provided an inner mirror engaged with a conductive base member fixed to a windshield of a vehicle at a base end portion of the stay, a vicinity of the base member, and an outside of the vehicle. An ETC that includes a plurality of antennas that perform wireless communication with a communication terminal and a power supply module that feeds power to each of the antennas, and that transmits and receives radio waves to and from roadside devices provided at highway gates and the like. (Automatic fee collection system) A built-in inner mirror, wherein each antenna is arranged according to the arrangement configuration of the antenna according to claim 1 or 2.

  According to this configuration, the antennas are arranged symmetrically in the vehicle width direction about the base member, so that the radio waves radiated from the antennas are absorbed and reflected symmetrically in the vehicle width direction by the base member. The electric lines of force formed in the vicinity of the base member by the antenna are symmetrical in the vehicle width direction with the base member as the center. As a result, radio waves are transmitted and received by the antennas from the center position in the vehicle width direction of the vehicle toward the front. As a result, the communication state with the communication terminal outside the vehicle such as a roadside device provided at the gate of the expressway is optimized. Also, in this case, the effect of absorbing and reflecting the radiated radio waves of each antenna by the base member is equalized in the vehicle width direction regardless of the phase of the current supplied to each antenna. Is a direction facing the front of the vehicle with the base member as the center. In addition, since each antenna is arranged in the vicinity of the base member, a plurality of antennas can be accommodated in a small space, the size of the ETC built-in inner mirror can be reduced, and the mounting portion of the vehicle windshield can be saved. Space saving is realized, and the ETC built-in inner mirror can be mounted on various vehicle types without depending on the size of the mounting portion.

  According to a fourth aspect of the present invention, a conductive base member to which a stay of an inner mirror of a vehicle is engaged at a base end is fixed to a windshield of the vehicle, and communication outside the vehicle is performed in the vicinity of the base member. A gist of an antenna arrangement method for arranging a plurality of antennas for wireless communication with a terminal, wherein the antennas are arranged symmetrically in a vehicle width direction with the base member as a center.

  According to this configuration, the plurality of antennas are arranged so as to be symmetrical in the vehicle width direction with the base member as the center, so that radio waves radiated from each antenna are absorbed symmetrically in the vehicle width direction by the base member. The electric lines of force that are reflected and formed in the vicinity of the base member by the respective antennas are symmetrical in the vehicle width direction with the base member as the center.

  According to a fifth aspect of the present invention, in the antenna arrangement method according to the fourth aspect, the base member is a flat plate member formed in a planar view shape, and each antenna is a dipole antenna. Then, the gist is to arrange the length direction along each side of the base member.

  According to this configuration, the directivity by the plurality of dipole antennas surrounding the base member having a rectangular shape in plan view can be set to the direction facing the front direction from the center position in the vehicle width direction of the vehicle.

  According to the present invention, an ETC built-in inner mirror that can be mounted on various vehicles without hindering normal transmission and reception of radio waves by the antenna, an antenna arrangement configuration preferably used for the ETC built-in inner mirror, and the built-in ETC An antenna arrangement method that is preferably used for the inner mirror can be provided.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described with reference to the drawings.
The inner mirror with built-in ETC according to the present embodiment is obtained by integrating a plurality of dipole antennas as in-vehicle antennas for an ETC (automatic toll collection system) on an inner mirror of an automobile (vehicle).

  As shown in FIG. 1, the ETC built-in inner mirror 10 includes an antenna holding portion 15 attached to a windshield 2 of an automobile, and a roadside machine held by the antenna holding portion 15 and provided at a gate of an expressway or the like. 4 (plural) dipole antennas 11a to 11d as ETC in-vehicle antennas that transmit and receive radio waves between them.

  The antenna holding portion 15 includes a rectangular columnar bottom member 12 fixed to the windshield 2 by being engaged with a conductive base member 7 attached (fixed) to the windshield 2 with an adhesive or the like. And a holding unit body 13 having a substantially quadrangular pyramid shape, which is integrated with the bottom member 12 and holds the dipole antennas 11a to 11d in an upright state. The base member 7 shown in FIG. 1 is a flat plate member formed in a square shape in plan view, and is formed of a metal such as copper or iron. The base member 7 is slidably engaged with a slide groove 12a formed in the bottom member 12 of the antenna holding portion 15 (see FIGS. 2A and 2B).

  As shown in FIGS. 2A and 2B, the dipole antennas 11a to 11d are arranged on the dielectric substrate 13a (see FIG. 1) provided on the holding unit main body 13 in the length direction. Are arranged in a standing state along the sides of the bottom member 12 and the base member 7. Referring to FIG. 2B, the dipole antennas 11 a to 11 d are arranged so as to be symmetric with respect to the vehicle width direction around the base member 7. Each of the dipole antennas 11a to 11d takes the form of a so-called half-wave dipole antenna in which transmission lines 11a ', 11a' to 11d 'and 11d' each having a quarter wavelength are widened to the left and right. Then, high frequency power is supplied to the two pairs of dipole antennas 11a, 11b, 11c, and 11d orthogonal to each other via the coaxial cable 18, and circularly polarized waves are radiated from the pair of dipole antennas 11a and 11b and the dipole antennas 11c and 11d, respectively. It has come to be.

  Returning to FIG. 1, the ETC built-in inner mirror 10 includes an inner mirror device 14 provided with an inner mirror 14a for rearward viewing, and supports the inner mirror device 14 with a tip portion 16a, and a joint ball 16b at a central portion. In addition, a stay 16 in which the support direction of the inner mirror device 14 is variable and the base end portion 16 c is integrated with the holding portion main body 13 of the antenna holding portion 15 is further provided. The stay 16 can freely change the rear viewing state by the inner mirror 14a. The inner mirror device 14 is hollowed to form a housing portion 14b for housing a circuit board or the like, and the power feeding module 17 constituting a part of the ETC built-in inner mirror 10 is provided in the housing portion 14b. Contained. Power is supplied to the power supply module 17 from a battery unit of the automobile via a power supply cable (not shown), and is electrically connected to the dipole antennas 11 a to 11 d via a coaxial cable 18.

The ETC built-in inner mirror 10 of the present embodiment is configured as described above and has the following effects.
The dipole antennas 11a to 11d (ETC in-vehicle antennas) are arranged symmetrically in the vehicle width direction with the conductive base member 7 as the center. For this reason, the radio waves radiated from the dipole antennas 11a to 11d are absorbed and reflected symmetrically in the vehicle width direction by the base member 7, and the electric force formed in the vicinity of the base member 7 by the dipole antennas 11a to 11d. As shown in FIG. 3A, the line is symmetrical in the vehicle width direction with the base member 7 as the center.

  Here, FIGS. 3A and 3I show a quarter period from the state in which the maximum current flows through the upper and lower dipole antennas 11a and 11c (one period T indicates the period of the high-frequency current flowing through the antenna). 3 (a) and (ii) show the state of the electric lines of force after the elapse of 3/4 cycle from the state where the maximum current flows through the upper and lower dipole antennas 11a and 11c, respectively. Show.

  FIG. 3B shows a state of electric lines of force in the prior art in which one dipole antenna 11e is arranged above the base member 7 and one dipole antenna 11f is arranged on the left side. ) (I) shows the state of the electric lines of force after ¼ period has elapsed from the state where the maximum current flows through the upper dipole antenna 11e, and FIGS. 3B and (ii) show the state of the upper dipole antenna 11a. The state of the electric lines of force after the lapse of 3/4 period from the state where the maximum current flows is shown. Thereby, the following effects can be obtained.

  (1) The dipole antennas 11a to 11d transmit and receive radio waves from the center position in the vehicle width direction of the vehicle toward the front. As a result, the state of communication with a communication terminal outside the vehicle such as a roadside device provided at a highway gate or the like is optimized. Further, in this case, the absorption / reflection effect of the radiated radio waves of the dipole antennas 11a to 11d by the base member 7 is equalized in the vehicle width direction without depending on the phase of the current supplied to the dipole antennas 11a to 11d. . For this reason, the directivity of the dipole antennas 11a to 11d is always the direction toward the front of the vehicle around the base member 7, that is, the direction toward the front from the center position in the vehicle width direction of the vehicle. In addition, since circularly polarized waves are radiated by the pair of dipole antennas 11a and 11b and the dipole antennas 11c and 11d orthogonal to each other, a highly directional and sensitive antenna suitable for DSRC (narrow band communication) is realized. become.

  (2) Each of the dipole antennas 11 a to 11 d is disposed in the vicinity of the base member 7. For this reason, the dipole antennas 11a to 11d are accommodated in a small space, the size of the ETC built-in inner mirror 10 can be reduced, and the space for the attachment portion on the windshield of the vehicle can be saved. It can be mounted on a variety of vehicles without depending on the size of the vehicle. The above embodiment may be modified as follows.

  In the embodiment described above, the dipole antennas 11a to 11d are arranged in a standing state on the dielectric substrate 13a so that the length directions of the dipole antennas 11a to 11d are along the sides of the base member 7 that is rectangular in plan view. That is, one dipole antenna is provided on each side of the base member 7. However, the present invention is not limited to this, and any structure may be used as long as it is bilaterally symmetric in the vehicle width direction around the base member 7. For example, as shown in FIG. Dipole antennas 102 and 103 may be disposed on the right side and the right side, respectively. In this case, the amount of power supplied to one dipole antenna 101 is equal to the total amount of power supplied to the two dipole antennas 102 and 103.

  -In above-mentioned embodiment, the vehicle-mounted antenna for ETC was comprised with the some dipole antenna 11a-11d. However, the present invention is not limited to this, and in the present invention, the ETC in-vehicle antenna may be composed of other types of antennas such as a monopole antenna, a slot antenna, a loop antenna, and the like.

The partial cross section figure of the ETC built-in inner mirror concerning the embodiment of the present invention. (A) is a perspective view of the antenna holding part of the ETC built-in inner mirror concerning the embodiment of the present invention, and (b) is a top view of the antenna holding part. (A) is a top view which shows the electric force line by the dipole antenna concerning embodiment of this invention, (b) is a top view which shows the electric force line by the dipole antenna concerning a prior art (in this figure, each dipole) Only the electric lines of force generated from the antenna are shown). The top view of the antenna holding part of the ETC built-in inner mirror concerning the modification of this invention. (A) is a perspective view of the antenna holding part of the ETC built-in inner mirror concerning a prior art, (b) is a top view of the antenna holding part. (A) is a cross-sectional view showing a general structure of an ETC built-in inner mirror, and (b) is a transmission / reception of radio waves between the ETC built-in inner mirror and a roadside device provided at a gate of an expressway. The side view which shows the state which has been broken, (c) is a front view which shows the state.

Explanation of symbols

  2 ... windshield, 3 ... automobile (vehicle), 7 ... base member, 10 ... inner mirror with built-in ETC, 11a, 11b, 11c, 11d ... dipole antenna, 14a ... inner mirror, 16 ... stay, 16c ... base end, 17: Power supply module.

Claims (5)

A conductive base member to which the stay of the inner mirror of the vehicle is engaged at the base end is fixed to the windshield of the vehicle,
In the arrangement configuration of the antenna in which a plurality of antennas that perform wireless communication with a communication terminal outside the vehicle are arranged in the vicinity of the base member,
The antenna arrangement configuration, wherein the antennas are arranged symmetrically in the vehicle width direction with the base member as a center. The antenna arrangement according to claim 1,
The base member is a flat plate member formed in a square shape in plan view, and each antenna is a dipole antenna, and the length direction thereof is arranged along each side of the base member. In addition, an antenna arrangement configuration in which circularly polarized waves are radiated by a pair of antennas orthogonal to each other. An inner mirror engaged at a base end portion of a stay with a conductive base member fixed to a windshield of the vehicle;
A plurality of antennas arranged in the vicinity of the base member and performing wireless communication with a communication terminal outside the vehicle;
An inner mirror with a built-in ETC (automatic toll collection system) that is configured to transmit and receive radio waves to and from a roadside device provided at a highway gate or the like. ,
An inner mirror with built-in ETC, wherein the antennas are arranged according to the arrangement configuration of the antennas according to claim 1 or 2. A conductive base member to which the stay of the inner mirror of the vehicle is engaged at the base end is fixed to the windshield of the vehicle,
In the vicinity of the base member, there is an antenna arrangement method for arranging a plurality of antennas for performing wireless communication with a communication terminal outside the vehicle,
An antenna arrangement method, wherein the antennas are arranged symmetrically in the vehicle width direction with the base member as a center. The antenna arrangement method according to claim 4,
The base member is a flat plate member formed in a square shape in plan view, and each antenna is a dipole antenna, and its length direction is arranged along each side of the base member. Antenna placement method.

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