JPH0612848B2 - Car antenna device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an antenna device for an automobile, and more particularly, to effectively detect a broadcast wave received by a vehicle body of an automobile and supply a detection signal to various receivers mounted on the vehicle. The present invention relates to an improved vehicle antenna device.

[Prior Art] An antenna device is indispensable for a vehicle in order to reliably receive various broadcast waves, for example, broadcast communication waves of radio, television, telephone, etc., by a receiver provided in the vehicle. This kind of antenna device is extremely important for transmitting and receiving citizen's band radio waves that communicate with other stations,
It will play a major role in the standard equipped communication functions of automobiles in the future.

The conventional general antenna device is known as a pole antenna, and the antenna protruding from the vehicle body shows preferable performance in terms of its reception characteristics, but it has the fate that it is always treated as an obstacle in terms of vehicle body design. Was.

Further, such a pole antenna has various problems such as breaking, bending, etc. even in actual use, being a target of mischief or theft, and generating an unpleasant wind noise at high speed. In the past, however, there have been many requests to somehow remove this.

In particular, as the frequency band of broadcast waves or communication waves received inside a car expands as in recent years, it is necessary to install multiple antennas according to each frequency band, which destroys the aesthetic concept of the appearance of the car. In addition, there is a problem that the reception performance of these various antennas is significantly deteriorated due to mutual electrical interference between these various antennas.

In the past, some efforts have been made to remove the above-mentioned pole antenna or conceal it so that it cannot be seen from the outside. For example, attaching an antenna thin wire to a rear windshield has been put into practical use.

As another conventional solution, it has been proposed to detect the surface current induced in the vehicle body itself by broadcast waves. The use of such a current flowing through the vehicle body is considered to be the most reliable and efficient method at first glance, but conventional experiments have continued to show results that completely violate such expectations.

The first reason that the surface current induced by a general broadcast wave on the vehicle body cannot be used is that the surface current value is not as large as expected, and conventional surface current is mainly applied to the ceiling plate of the vehicle body. Although it was the target, even with this, it was not possible to obtain a detection output of a level sufficient for sufficient use.

A second conventional problem is that noise is mixed into the surface electricity at an extremely large rate. Such noise is mainly generated from the ignition system of the engine and the regulator system for battery charging, and the engine is operating. As long as these noises leaked to the car body, it was impossible to perform a clear broadcast wave reception action that could be practically used.

Even under such disadvantageous conditions, some proposals have been made in the past. As a conventional antenna device that utilizes the current induced in the vehicle body by broadcast waves, Japanese Patent Publication No. 53-22
418 is known, and an electrical insulating portion is formed in a current concentrating portion of a vehicle body, and a current between both ends of the insulating portion is directly detected by a sensor. Although it has been suggested that this conventional device can obtain a practical detection signal having an excellent SN ratio, its pickup structure requires a notch in a part of the vehicle body, which is quite normal. It was impossible to apply it to mass-produced automobiles.

Japanese Utility Model Publication No. 53-34826 is known as another conventional device, and an antenna has been proposed in which a pickup coil detects a current flowing through a pillar of a vehicle. This conventional device was useful for indicating the development direction of incorporating the antenna in the vehicle body, but in practice, it is not practical to provide a pickup coil orthogonal to the longitudinal direction in the vicinity of the pillar, In addition, such a pickup arrangement could not obtain a practical antenna output, and was considered to be a mere idea.

[Problems to be Solved by the Invention] Problems of Prior Art As described above, conventionally, the antenna device for detecting the current induced in the vehicle body by the broadcast wave has not always been successful.

Particularly, in the related art, a pickup structure and a practicable S for effectively detecting the current induced by the broadcast wave flowing in the vehicle body, which is the above-mentioned major problem of the related art.
The arrangement of the pickup for obtaining the N ratio has not been properly solved, and rather various experimental results have pointed out that the antenna device utilizing the vehicle body current could not be used in principle.

OBJECT OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object thereof is to effectively detect a current induced in a vehicle body by a broadcast wave and transmit it to a vehicle-mounted receiver. Another object of the present invention is to provide an improved antenna device for a small vehicle, which can be easily mounted on the vehicle body and can obtain a high output.

[Means for Solving the Problems] In order to achieve the above object, the present invention is an antenna device for detecting a high frequency surface current of a predetermined frequency or higher by causing a loop antenna of a high frequency pickup to face a peripheral portion of a vehicle body. The outer side of the loop antenna is protected by a case, and an opening is provided in the case along the longitudinal direction of the loop antenna facing the peripheral edge of the vehicle body, and at the front end of the opening. A high-frequency wave is provided in which the peripheral edge of the vehicle body is positioned and guided, and one side of the loop antenna is supported at the rear end portion of the opening so that the peripheral edge portion of the vehicle body and the loop antenna are correctly opposed to each other. It is characterized by including a pickup.

The antenna device in the past was mainly intended to receive AM waves from the background of the times, but for this reason, an antenna for detecting a vehicle body current receives good reception because the wavelength of the target broadcast wave is too large. The result is that the characteristics cannot be obtained, and the inventors of the present invention pay attention to this frequency dependence and set the broadcast wave to be received in the present invention to FM.
By setting the frequency to 50MHz or higher in the normal case of the frequency band or higher, it has become possible to effectively receive from the vehicle body current, which was previously impossible.

Further, in the present invention, attention is paid to the fact that the current value of such a high-frequency vehicle body current also has a distribution characteristic that is remarkably different in each part of the vehicle body, and it is difficult to pick up noise and the density of the current induced by the broadcast wave is high. A high-frequency pickup is provided, and the vicinity of the peripheral edge of the vehicle body is selected as an installation location that satisfies such conditions.

Further, the pickup is a loop antenna for electromagnetically detecting the magnetic flux generated by the vehicle body current, whereby an efficient detection action is obtained.

[Embodiment] A preferred embodiment of an automobile antenna device according to the present invention will be described below with reference to the drawings.

7 to 15 illustrate the steps for investigating the distribution characteristics of the high frequency current and obtaining the most efficient antenna installation position.

FIG. 7 shows that when an external radio wave W such as a broadcast wave passes through a vehicle body B made of a metal conductor, a surface current I corresponding to the strength of the electromagnetic wave is induced in each part of the vehicle body. In the example, only the frequency band used for FM waves of 50 MHz or more, television waves, etc., which belong to a relatively high frequency band, of these radio waves are targeted.

Then, in such a specific high frequency band, the induced current distribution of the vehicle body is measured, and the pickup is installed in a portion where the surface current density is high and noise is small.

In order to know the surface current distribution, a computer simulation and measurement of the actual current intensity are performed, and in this embodiment, a probe based on the same principle as a high-frequency pickup provided in a desired vehicle body part described later. Was used, and the surface current was measured by moving this probe over the entire surface of the vehicle body while changing the direction at each point.

FIG. 8 shows a schematic structure of a probe P produced on the basis of a principle similar to that of a high-frequency pickup to be described later, and a case 10 made of a conductor is provided in order to avoid mixing of radio waves from the outside. Loop coil 12 inside
Is fixed, an opening 10a is provided in a part of the case 10, a part of the loop coil 12 is exposed to the outside through the opening 10a, and an exposed portion of the loop coil 12 is brought close to the surface of the vehicle body B. The magnetic flux generated from the vehicle body surface current is detected by the loop coil 12. A part of the loop coil 12 is connected to the case 10 by a short-circuit wire 14, and the output end 16 has a core wire 20 of a coaxial cable 18.
It is connected to the. Further, a capacitor 22 is provided in a part of the loop coil 12, so that the frequency of the loop coil 12 can resonate to a desired measured frequency and the pickup efficiency can be increased.

As described above, by moving the probe P along the surface of the vehicle body B and rotating the angle at each measurement point, it becomes possible to accurately obtain the surface current distribution on the vehicle body surface and its direction. In FIG. 8, the output of the probe P is amplified by the high frequency voltage amplifier 24, and the output voltage is measured by the high frequency voltage measuring device 26. The coil output voltage is read by the meter indication value of the measuring device 26, and the voltage corresponding to the meter indication value is recorded by the XY recorder 28 as the surface current distribution in each part of the vehicle body. A signal indicating each position of the vehicle body is input from the potentiometer 30 to the XY recorder 28, and the high frequency surface current at each position can be known.

FIG. 9 shows the declination θ between the high frequency surface current I and the loop coil 12 of the pickup. As shown in the figure, the magnetic flux φ due to the current I is linked to the loop coil 12 so that the detected voltage is applied to the loop coil 12. V is generated and the tenth
As shown in the figure, when θ is 0, that is, when the surface current I and the loop coil 12 of the pickup are parallel to each other, the maximum voltage is obtained, and the probe P is rotated at each measurement point to obtain the maximum voltage. You can know the direction.

11 and 12 show the magnitude and direction of the high frequency surface current generated in each part of the vehicle body at the frequency of 80 MHz obtained from both the measurement result by the probe P and the simulation by the computer, as shown in FIG. As is clear from the above, the distribution of the surface current has a high density along the edge of the plane part of the vehicle body and an extremely low density in the central part of the flat plate part.

Further, it is understood that each current is concentrated in the direction parallel to the edge portion of the vehicle body or the direction along the connecting portion of each flat surface portion as shown in the direction of the current in FIG.

In FIG. 11, when the current distribution induced in the metal part of the vehicle body is examined in detail along the chain line that longitudinally extends through the vehicle body, the distribution characteristics as shown in FIGS. 13 to 15 are obtained.

FIG. 13 shows the surface current distribution along the trunk lid from the vertical cut lines A to B. As is clear from the figure, the largest current flows at both end positions, and from both ends toward the center of the lid. Shows the distribution characteristic that the current value decreases.

Therefore, from FIG. 13, regarding the trunk lid, if a high frequency pickup is arranged in the vicinity of the peripheral portion thereof, it becomes possible to detect the intensively flowing current in the vicinity of the peripheral portion.

Similarly, FIG. 14 shows the distribution along the ceiling plate of the vehicle body, and FIG. 15 shows the current distribution along the engine lid of the vehicle body. It is understood that the largest current flows at both ends and the current value decreases toward the center.

Therefore, in the present embodiment, it is understood that the broadcast wave can be picked up with good sensitivity in the vicinity of the peripheral edge of each part of the vehicle body.

Of course, the installation position of the high-frequency pickup is not limited to the above-mentioned lids or ceiling plates, but can be similarly applied to pillars and fenders.

Further, in the present embodiment, the high-frequency pickup is installed in the vicinity of the peripheral edge of each vehicle body, for example, in the longitudinal direction of the loop antenna along the peripheral edge, in order to obtain extremely good sensitivity in practice. In addition, it is preferable to set the pickup installation range from the edge to a range depending on the carrier frequency of the broadcast wave.

The distribution characteristics of Figs. 13 to 15 are the currents of the vehicle body with respect to the FM broadcasting frequency of 80MHz, and the surface current value decreases as described above according to the distance from each vehicle body end or edge, and actually good sensitivity is obtained. Considering the current drop range of 6 dB or less that can obtain
It is understood that extremely good sensitivity is obtained within cm.

Therefore, in this embodiment, if the high frequency pickup is arranged within 4.5 cm from the peripheral portion of the vehicle body for the carrier frequency of 80 MHz, a practically sufficient antenna device can be obtained.

Then, it was clarified that this practical separation distance depends on the carrier frequency by computer simulation results and various experimental results, and it was confirmed that the practical separation distance decreases as the frequency increases.

Therefore, since the practical separation distance of 4.5 cm at the carrier frequency of 80 MHz described above is inversely proportional to the frequency, the installation range of the high frequency pickup from the metal flat edge of the vehicle body is 12 × 10 ^{−3 in} this embodiment. If it is set within c / f (m), a good reception effect can be obtained according to each carrier frequency (in the above formula, c = speed of light, f =
Carrier frequency).

As described above, according to the present embodiment, the high frequency pickup is provided close to the edge of each metal vehicle body, and is preferably provided within the above-mentioned separation distance from the edge, thereby obtaining a good receiving action. To be

In the present embodiment, since the separation distance actually depends on the frequency, for example, at a carrier frequency of 100 MHz, a high frequency pickup should be provided within 3.6 cm from the edge of the vehicle body, and as the carrier frequency f increases. The installation position of the high frequency pickup is limited to a narrow area very close to the edge.

FIG. 1 is an external view showing a preferred embodiment of a high frequency pickup of an antenna device for an automobile according to the present invention.
The figure is a schematic vertical cross-sectional view of a state where the peripheral portion of the vehicle body faces the loop antenna. The high frequency pickup 38 includes a loop antenna 42 inside the cases 32 and 34 for detecting a high frequency surface current, and a circuit unit 58 connected to the loop antenna 42 for matching / amplifying a detection signal. Is formed, and is arranged close to the peripheral portion of the vehicle body.

The high-frequency detection signal processed by the circuit unit 58 is taken out from the coaxial cable 60 and processed by the same circuit as that used in the surface current distribution measurement described above. The circuit section 58 is supplied with power and signals for controlling the circuit from a cable 62.

The loop antenna 42 is composed of a single-turn antenna, and has a structure in which an insulating coating is applied to the coil so as to be arranged in a state of being electrically insulated from and closely contacted with the peripheral portion of the vehicle body, and the coil is pressed against the peripheral portion of the vehicle body. The magnetic flux generated from the surface current can be more strongly linked to the loop antenna 42.

In the embodiment, the one case 32 is made of synthetic resin to protect the loop antenna 42, and the other case 34 is made of a metal plate and is integrally provided with the one case 32 to protect the circuit portion 58. ing. That is, since the one case 32 is made of synthetic resin, the magnetic flux generated in the peripheral portion of the vehicle body can be detected in a wide range, and the other case 34 is made of metal.
4 is connected to the shield layer of the coaxial cable 60 and functions as an electrostatic shield wall, so that the influence of noise on the circuit portion 58 is removed.

What is characteristic of the present invention is that the opening 36 is provided along the longitudinal direction of the loop antenna 42 facing the vehicle body peripheral edge of the one case 32, and the vehicle body is formed at the front end of the opening 36. Position and guide the periphery,
That is, one side of the loop antenna 42 is supported at the rear end of the opening 36.

In this embodiment, as shown in FIG.
The front end side facing the peripheral edge of the vehicle body is thickened, and a first opening 36a having a rectangular cross section is formed at the front end of the case 32 along the longitudinal direction of the loop antenna 42. Further, a second opening 36b is formed at the rear end of the first opening 36a so that the longitudinal side of the loop antenna 42 can be exposed to the side of the first opening 36a.

As described above, in the present embodiment, the first and second openings 36a and 36b communicating with each other are provided, and the peripheral portion of the vehicle body and the loop antenna 42 are positioned and arranged at correct positions, respectively. And

That is, when the loop antenna 42 of the high frequency pickup 38 is housed in the case 32, its current detection side is inserted and positioned in the second opening 36b of the case 32. In this positioning state, as described above, the width of the opening 36b is set to be substantially equal to the diameter of the loop antenna 42, so that the opening 36b can firmly hold the loop antenna 42 on the upper and lower surfaces. Therefore, the vertical movement of the loop antenna 42 due to the vibration of the vehicle body is restricted by the opening 36b, and the undesirable vibration can be effectively prevented.

The high frequency pickup 38 is mounted on the vehicle body so that the peripheral portion of the inner plate member 44 connected to the inner plate of the vehicle body is inserted into the first opening portion 36a provided so as to be connected to the opening portion 36b. It is possible to correctly guide the arrangement of the peripheral portion and the loop antenna 42 at the time of insertion to a desired position, or a position where they face each other in the normal case.

Therefore, if a high frequency pickup in which the loop antenna 42 is positioned inside is mounted on a predetermined peripheral portion of the vehicle body, the peripheral portion of the vehicle body is guided to the exposed side of the loop antenna 42 by the first opening portion 36a, and the peripheral edge of the loop antenna 42 and the peripheral portion thereof. It is possible to face the section very easily.

High-frequency pickup 3 positioned as described above
Although not shown, 8 is positioned and fixed to the vehicle body by an adjustable mounting bracket.

As described above, according to the present embodiment, the inner plate member 44 is attached to the loop antenna 42 by utilizing the opening 36 provided in the case 32.
High-frequency pickup 3
8 can be easily attached to the vehicle body. Further, the inner plate member 44 and the loop antenna 42 can be brought into close contact with each other as much as possible, and the high frequency surface current induced in the vehicle body can be efficiently detected.

3 and 4 show another embodiment. In addition, this embodiment has a configuration similar to that of the above-described embodiment, and the members corresponding to those of the above-described embodiment are shown by adding reference numeral 100. The present embodiment is characterized in that even if the plate thickness of the inner plate member 144 changes, the opening gap for sandwiching the inner plate member 144 can be easily adjusted.

That is, a plurality of guide pieces 46-1 and 46- are provided in the first opening 136a having a rectangular cross section provided on the front end side of the case 132.
2, 46-3 are detachably provided along the longitudinal direction of the upper and lower walls, respectively. Then, the inner plate member 144 is guided by the guide groove 48 formed between the facing surfaces of the guide pieces 46 in the vertical direction, and is positioned so as to face the loop antenna 142. Therefore, the inner plate member 14
Even if the plate thickness of 4 changes, it can be easily dealt with by sharing the case 132 only by replacing the guide piece 46.

Further, the guide piece 46 is made of the same material as the case 132, so that the adjacent guide pieces 46-1, 46-2, 46
It is possible to reduce the weight of the space formed between the −3 and −3.

5 and 6 show still another embodiment.
The embodiment in FIG. 5 is similar to the construction of the first embodiment described above, and the embodiment in FIG. 6 is similar to the construction of the other embodiments described above. Therefore, the members corresponding to those in the above-described embodiment are shown in the 200s in the case of FIG. 5 and in the 300s in the sixth case. In these embodiments, the inner plate member is positioned and guided through the cushioning material in the opening, and the elasticity of the cushioning material prevents vibration of the inner plate member.

That is, the first opening 236a and the inner plate member 2 of FIG.
A cushioning material 50 is provided between the adhesive layer 44 and 44. A cushioning material 52 is provided between the guide groove 348 and the inner plate member 344 of FIG. These cushioning members 50 and 52 are made of an elastic body such as a rubber plate, and are attached so that the cushioning members 50 and 52 sandwich the inner plate members 244 and 344 in the vertical direction. Therefore, even if the vehicle body vibrates, it can be absorbed by the cushioning materials 50 and 52, and in FIG. 5, the inner plate member 244 may cause mutual interference at the first opening 236 a of the case 232. In addition, in FIG. 6, the inner plate member 344 does not generate an abnormal sound due to mutual interference in the guide groove 348 of the guide piece 346. Furthermore, the positional relationship between the end surfaces of the inner plate members 244 and 344 and the loop antennas 242 and 342 is also secured, and stable output can be obtained. Although rubber plates are used as the cushioning members 50 and 52 in the above description, if a ferrite rubber plate mixed with magnetic powder is used, the cross magnetic flux on the loop surface is further increased and the pickup output is increased. There is also a merit that the value will increase.

As described above, according to the present invention, the surface current flowing in the peripheral portion of the vehicle body is electromagnetically detected by the high frequency pickup,
It is possible to reliably perform reception in the high frequency band without exposing the antenna device to the outside at all, which is extremely useful as an automobile antenna.

[Effects of the Invention] As described above, according to the present invention, the high frequency surface current generated at a specific portion of the vehicle body, particularly at the peripheral portion of the vehicle body is used for the broadcast wave in the relatively high frequency band, for example, the FM frequency band or higher. Since the broadcast wave receiving antenna is formed by using the broadcast antenna, it is possible to perform a high-density, low-noise, high-quality detection action for the broadcast wave, and a pickup with the peripheral portion of the vehicle body and the loop antenna facing each other. It is possible to obtain an automobile antenna device which can be easily attached and which can obtain a high output.

[Brief description of drawings]

FIG. 1 is an external view of a high frequency pickup of an automobile antenna device according to the present invention, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG. 3 is an external view of a high frequency pickup showing another embodiment. FIG. 4 is a sectional view taken along the line IV-IV in FIG. 3, FIGS. 5 and 6 are longitudinal sectional views of a high frequency pickup showing still another embodiment, and FIG. 7 is a surface current I generated in a vehicle body B by an external wave W. FIG. 8 is an explanatory view of a probe and its processing circuit for knowing the distribution of the vehicle body surface current by using the same probe as the high frequency pickup used in the present invention, and FIG. 9 is the surface current I and the pickup. FIG. 10 is an explanatory view showing an electromagnetic coupling state with a loop antenna, FIG. 10 is an explanatory view showing a directional characteristic of the loop antenna in FIG. 9, FIG. 11 is an explanatory view showing a distribution characteristic of surface current intensity, and FIG. 12 is a surface. Current direction Illustration showing, the 13,1
4 and 15 are characteristic diagrams showing the vehicle body surface current distribution along the longitudinal section line of the vehicle body in FIG. 11, respectively. 32, 34 ... Case 36 ... Opening 38 ... High-frequency pickup 42 ... Loop antenna 44 ... Inner plate member 46 ... Guide piece 48 ... Guide groove 50, 52 ... Cushioning material

Claims (3)

[Claims] 1. A high frequency pickup including a case having a built-in loop antenna, wherein the loop antenna is closely arranged along a longitudinal direction of a vehicle body peripheral portion and is induced in the vehicle body by broadcast waves and concentrated on the vehicle body peripheral portion. Detecting a high-frequency surface current flowing through the case, the case is provided with an opening along the longitudinal direction of the loop antenna facing the vehicle body peripheral portion, and the vehicle body peripheral portion is positioned and guided at the front end of the opening,
An antenna device for an automobile, characterized in that one side of a loop attenuator is supported at a rear end of the opening so that the peripheral portion of the vehicle body and the loop antenna are correctly opposed to each other. 2. The apparatus according to claim 1, wherein guide pieces are detachably provided on the upper and lower walls of the front end of the opening along the longitudinal direction of the opening, and the facing surfaces of the guide pieces are opposed to each other. An antenna device for an automobile, characterized in that a guide groove is formed between the guide grooves and the peripheral edge of the vehicle body is positioned and guided in the guide groove. 3. The apparatus according to claim 1 or 2, wherein a cushioning material is provided between a front end portion of the opening and a vehicle body peripheral edge portion, and the vehicle body peripheral edge portion is covered by the cushioning material. An automobile antenna device characterized by being sandwiched.