JPS62102606A - Antenna system for automobile - Google Patents

Abstract

PURPOSE:To effectively detect a current induced in a car body from a broadcast wave and to send it to an on-vehicle receiver by providing an outer metallic member and an antenna wire arranged prolongedly along the car body incorporatedly while electric insulation is kept. CONSTITUTION:A metallic side lace 32 is arranged prolongedly along the car body while being electrically insulated from a roof panel 36 and a header inner panel 38 by a resin-made space 34. Further, a resin part 40 formed incorporatedly with the lace 32 along the lengthwise direction is provided to one side ridge of the lace 32, the antenna wire 42 is imbedded in the resin part 40 and positioned and fixed surely in a range depending on the carrier frequency of a broadcast wave. Thus, it is possible to make the lace 32 as nearly a half wavelength for a lower band in the VHF band, nearly one wavelength for a high band and as nearly 2-4 wavelengths for the UHF band thereby causing the surface current to be easily concentrated. That is, the current induced on the car body by the broadcast wave is detected effectively and sent to the on-vehicle receiver.

Description

[Detailed Description of the Invention] [Industrial Application Field 1] The present invention is an antenna device for an automobile, particularly an antenna device for effectively detecting broadcast waves received on the body of an automobile and supplying a detection signal to various receivers mounted on the automobile. This invention relates to an improved automotive antenna device.

[Prior Art] A conventional general antenna device is known as a pole antenna, and although the antenna protruding from the car body exhibits favorable performance in terms of reception characteristics, it is always treated as a nuisance in terms of car body design. It was my destiny to become

In addition, such pole antennas are susceptible to breakage, bending, and other damage even in actual use, and are subject to mischief or theft.Furthermore, they have the problem of generating unpleasant wind noise when driving at high speeds. has,
There were many requests to somehow remove this.

In particular, in recent years, as the frequency bands of broadcast waves or communication waves received inside cars have expanded, it has become necessary to install multiple antennas for each frequency band, which has changed the aesthetic concept of the car's exterior. There are problems in that the antennas are destroyed without any cost, and that the reception performance of these various antennas is significantly degraded due to mutual electrical interference between them.

In the past, several efforts have been made to remove or hide the above-mentioned ball antenna so that it cannot be seen from the outside, and for example, pasting a thin antenna wire on the rear windshield has been put into practical use.

In addition, as a means of solving this problem, it has been proposed to detect surface current induced in the vehicle body itself by broadcast waves. At first glance, utilizing the current flowing through the car body seems to be the most reliable and efficient method, but previous experiments have continued to show results that completely contradict these expectations.

The first reason why it was not possible to use general car body surface currents due to broadcast waves is that the surface current values were not as large as expected, and conventional surface currents were mainly targeted at the car body ceiling panels. However, even with this, it was not possible to obtain a detection IB power at a level sufficient for full use.

The second reason is that a very large proportion of noise is mixed into the surface current, and such noise is mainly generated from the engine's ignition system and battery charging regulator system, and when the engine is active. As long as the vehicle was in use, these noises leaked into the vehicle body, making it impossible to receive clear broadcast waves that could be used for practical measurements.

Even under such disadvantageous conditions, several proposals have been made in the past. Japanese Patent Publication No. 53-22 as a conventional antenna device that utilizes the current induced in the car body by broadcast waves.
418 is known, in which an electrical insulator is formed in a current concentration area of the vehicle body, and the current across the insulator is directly detected by a sensor.

It is certainly suggested that this conventional device can provide a practically usable detection signal with an excellent S/N ratio, but its pickup structure requires a cutout in a part of the vehicle body, etc. It was impossible to apply this method to ordinary mass-produced automobiles.

Another conventional device is known from Japanese Utility Model Publication No. 53-34826, which proposes an antenna that uses a pickup coil to detect the current flowing through the pillar of a vehicle. Although this conventional device was useful in showing the direction of development in which the antenna is built into the vehicle body, it is actually impractical to provide a pickup coil near the pillar and perpendicular to the longitudinal direction of the pillar. Such a pickup arrangement could not provide a practical antenna output and was thought to be nothing more than an idea.

[Problems to be Solved by the Invention] Problems of the Prior Art As described above, antenna devices for detecting current induced in a vehicle body by broadcast waves have not always been successful in the past.

In particular, in the past, the main problem with the prior art was a pickup structure that could effectively detect the current induced by broadcast waves flowing through the vehicle body, and a practical S.
The pickup arrangement for obtaining the N ratio has not been properly resolved, and rather, various experimental results point to the fact that antenna devices that utilize vehicle body current may not be usable in principle.

Purpose of the Invention The present invention has been made in view of the above-mentioned problems, and provides an improved small car antenna that can effectively detect the current induced in the car body by broadcast waves and transmit it to a receiver mounted on the car. The purpose is to provide equipment.

[Means and effects for solving the problem] In order to achieve the above object, the present invention disposes an antenna wire close to the peripheral edge of the vehicle body. The present invention is characterized in that it is provided with an antenna device for detection.

That is, it includes an exterior metallic member extending along the vehicle body while being electrically insulated from the vehicle body frame, and an antenna wire that is integrally and insulated in proximity to the metallic member. The present invention is characterized in that the received signal picked up by the antenna wire is supplied to various receivers mounted on the vehicle.

Examples of the exterior metal parts include side moldings, roof retainers, and other front window moldings. The density of high frequency surface current induced on the surface of the sexual member is increased.

The metallic member has a longitudinal length, for example, in a lower band (1 to 3c) of the VHF band in the TV band.
It is possible to make it approximately equal to about half a wavelength for h), about 1 wavelength for high bands (4 to 11 channels), and about 2 to 4 wavelengths for UHF bands, and these bands In this case, the surface current becomes more concentrated, and highly sensitive reception is performed.

Conventional antenna devices were mainly intended to receive AM waves due to the background of the times, or because of this, the wavelength of the broadcast waves that were used to detect the car body current was too large, resulting in poor reception characteristics. The present inventors focused on this frequency dependence, and by setting the broadcast wave to be received to 50) 1112 or more in the FM frequency band or higher in the normal case, the present inventors This made it possible to receive signals from the vehicle body current extremely effectively, which was previously thought to be impossible.

In addition, in the present invention, we have focused on the fact that the current value of such high-frequency car body current has significantly different distribution characteristics in each part of the car body, and we have developed side moldings and roof retainer,
Other items selected include front window molding.

Further, in the present invention, in order to reliably detect the raw high-frequency current with the above-mentioned frequency characteristics, the antenna wire is separated from the edge of the metal member by 12X10-3C/f (m>(c
= speed of light, f = carrier frequency), and by adjusting the length of wire 4 and O according to the reception band, efficient reception can be achieved.

[Example] Hereinafter, a preferred example of the automotive antenna device according to the present invention will be described based on the drawings.

5 to 10 explain the steps for determining the most efficient antenna installation position by examining the distribution characteristics of high-frequency current.

FIG. 5 shows that when an external radio wave W such as a broadcast wave passes through a car body B made of a metal conductor, a surface current ■ corresponding to the strength of the electromagnetic wave is induced in each part of the car body. Of these radio waves, only the frequency bands used for FM waves, television waves, etc. of 50 Hllz or higher, which belong to relatively high frequency bands, are targeted.

The present invention is characterized in that the induced current distribution of the vehicle body is measured in such a specific high frequency band, and the pickup is installed in a portion where the surface current density is high and there is little noise.

In order to know the surface current I fi, computer simulations and actual current intensity measurements are performed at each point. A probe was used to measure the surface current by moving the probe across the entire surface of the vehicle, changing direction at each point.

FIG. 6 shows a schematic configuration of such a probe P, in which a loop coil 12 is fixed inside a case 10 made of a conductor in order to avoid mixing of radio waves from the outside. An opening 10a is provided in the opening 10a, and a part of the loop coil 12 is exposed to the outside through this opening 10a, and the exposed portion of the loop coil 12 is brought close to the surface of the vehicle body B to transfer the magnetic flux generated from the vehicle surface current to the loop coil. 12. A portion of the loop coil 12 is connected to the case 10 by a shorting wire 14, and is also connected to an output end 16 or a core wire 20 of a coaxial cable 18. Also, a part of the loop coil 12 has a capacitor 2.
Two of them are provided, and the frequency of the loop coil 12 can be made to resonate with the desired frequency to be measured, thereby increasing the pickup efficiency.

As described above, by moving the probe P along the surface of the vehicle body B and rotating its angle at each measurement point, it is possible to accurately determine the surface current distribution and its direction on the vehicle body surface. In FIG. 6, the output of the probe P is amplified by a high frequency voltage amplifier 24, and the output voltage is measured by a high frequency voltage measuring device 26. This coil output voltage is read by the meter indication value of the measuring device 26, and the voltage corresponding to this meter indication value is recorded by the XY recorder 28 as a surface current distribution in each part of the vehicle body. The XY recorder 28 has a potentiometer 30
A signal indicating each position of the vehicle body is input from the sensor, making it possible to know the high-frequency surface current at each position.

FIG. 7 shows the deviation angle θ between the high-frequency surface current I and the loop coil 12 of the pickup. As shown in Figure 8, the maximum voltage is obtained when θ is O, that is, when the surface current I and the loop coil 12 of the pickup are parallel, and the maximum voltage is obtained by rotating the probe P at each measurement point. This allows you to know the direction of the surface galvanic work when it is applied.

Figures 9 and 10 show the magnitude and direction of the high-frequency surface current generated in each part of the vehicle body at a frequency of 80) IHz, which was determined from both the measurement results using the probe P and the computer simulation. 9
As is clear from the figure, the magnitude of the surface current exhibits a distribution in which the density is high along the edges of the flat plate portion of the vehicle body, and the density is extremely low in the central portion of the flat plate portion.

Furthermore, as shown in the direction of the current in FIG. 10, it is understood that each current is concentrated in a direction parallel to the edge of the vehicle body or along a connecting portion of each plane portion.

In Figure 9, if we consider the current distribution induced in the metal parts of the car body along the chain line A that runs longitudinally through the car body, we can see that the surface current value decreases as the distance from the end or edge of the car body decreases. Considering the current drop range of 6 decibels or less that can obtain a high sensitivity,
It can be recognized that extremely good sensitivity can be obtained if the value is within the range.

Furthermore, in the present invention, the antenna wire is extended and arranged at the edge of the outer surface of the vehicle body B, such as the side molding, roof retainer, or front wind molding, in a state where it is electrically insulated. In order to obtain extremely good sensitivity, it is preferable to set the installation range from the edge to a range that depends on the carrier frequency of the broadcast wave.

Therefore, in the present invention, for example, for a carrier frequency of 80 MHz, the antenna wire is placed 4 to 5 cm from the periphery of the vehicle body.
A practically sufficient antenna device can be obtained by arranging the antenna device within the range.

It has become clear from computer simulation results and various experimental results that this practical separation distance depends on the carrier frequency, and it has been recognized that the practical separation distance decreases as the frequency increases.

Therefore, based on the above-mentioned practical separation distance of 4.5 cm at the carrier frequency of 80) IHz, which is inversely proportional to the frequency, the installation range of the high-frequency pickup from the flat metal edge of the vehicle body is set to 12 x 10'c/f ( m) If provided within
= carrier frequency).

In the present invention, since the separation distance actually depends on the frequency, for example, when the carrier frequency is 100) IHz, it is sufficient to provide the antenna wire within 3.6 cm from the edge of the vehicle body, and the carrier frequency f is As the number of antenna wires increases, the installation position of the antenna wire will be limited to an area extremely close to the edge.

FIG. 1 shows an embodiment in which the present invention is applied to a side molding of a vehicle body.

In the figure, a metal side molding 32 is extended along the vehicle body while being electrically insulated from a roof panel 36 and a header inner panel 38 by a resin spacer 34, A side glass 52 is connected to 38 via a weather strip 50. A resin part 40 integrally molded with the side molding 32 along the longitudinal direction is provided at one edge of the side molding 32, and an antenna wire 42 is embedded in this resin part 40 to transmit broadcast waves. The position is reliably fixed within a range dependent on the carrier frequency.

The side molding 32 has a longitudinal length T, for example.
The lower band (1 to 3 Ch) of the VHF band in the V band
) for approximately half a wavelength, for high bands (4 to 11 channels) to approximately 1 wavelength, and for UHF bands to approximately 2 to 4 wavelengths, and in these bands the surface current It becomes easier to concentrate, and highly sensitive reception is performed.

Therefore, the antenna wire 42 and the resin part 40 can be molded simultaneously during molding and painting of the side molding 32, thereby eliminating the hassle of vehicle assembly.

Further, the antenna wire 42 is disposed close to the edge of the side molding 32 in an insulated state, and the magnetic flux induced from the high-frequency surface current flowing to the edge is reliably captured by the antenna wire 42 and is induced in the vehicle body. This makes it possible to detect currents with high sensitivity.

In FIG. 2, an antenna wire 42 is attached to the edge of the side molding 32.
Fig. 3 shows the state in which the antenna wire and the coaxial cable are connected.

That is, in the resin portion 40, one end of the antenna wire 42 is in an open state, and the other end is connected to the core wire of the coaxial cable 44. The jacket conductor of the coaxial cable 44 is attached to the vehicle body frame by a bracket 46, and the coaxial cable 44 itself is guided into the vehicle body through a service hole 48 provided in the vehicle body frame on the back side of the side molding 32.

This coaxial cable 44 is connected to an on-vehicle receiver (not shown), and the received signal is processed by a circuit section that includes a preamplifier and the like.

FIG. 4 shows the reception sensitivity characteristics of the antenna wire of this embodiment, and curve a indicates that the length of the antenna wire 42 is 1.
The curve shows the sensitivity characteristic at 800 mm, and the curve shows the sensitivity characteristic at 900 mm. As is clear from this characteristic curve, good reception can be achieved by adjusting the length of the antenna wire 42 according to the reception band.

As described above, the embodiment of the present invention has an antenna wire that can be integrally molded when molding and painting an exterior vehicle member, so there is no difficulty in mounting it on the vehicle. In addition, it is inexpensive because it can be formed as a part of the vehicle component, and the reception band can be easily adjusted by adjusting the length of the antenna wire, so installation does not require detailed adjustments. has advantages.

[Effects of the Invention] As described above, the present invention includes an exterior metallic member extending along the vehicle body while being electrically insulated from the vehicle body frame, and an insulating state integrally extending between the metallic portions. By including the antenna wire and the antenna wire arranged in close proximity to each other, it is possible to obtain an antenna device for an automobile that has good reception sensitivity characteristics and is easy to attach to a vehicle.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of an embodiment of the automotive antenna device according to the present invention applied to a side molding, Fig. 2 is an external view showing the antenna wire arranged on the side molding, and Fig. 3 is an antenna. Fig. 4 is an explanatory diagram of the connection state between the wire and the coaxial cable; Fig. 4 is a diagram showing the antenna reception sensitivity characteristics according to this embodiment; Fig. 5 is an explanatory diagram showing the surface current ■ generated on the car body due to external waves W; The figure is an explanatory diagram of a probe and its processing circuit for determining the distribution of vehicle surface current using a high-frequency pickup probe. Figure 7 is an explanatory diagram showing the state of electromagnetic coupling between the surface current ■ and the pickup loop antenna. Figure 8 is an explanatory diagram showing the directivity characteristics of the loop antenna in Fig. 7, Fig. 9 is an explanatory diagram showing the distribution characteristics of the surface current intensity,
Figure 0 is an explanatory diagram showing the direction of surface current. 32... Side molding 34... Spacer 36... Roof panel 38... Header inner panel 40... Resin part 42... Antenna wire 44... Coaxial cable 48... Service hole.

Claims (2)

[Claims] (1) In an automotive antenna device that detects high-frequency surface current induced in a vehicle body by broadcast waves and flowing concentrated around the periphery of the vehicle body, the antenna device is arranged to extend along the vehicle body while being electrically insulated from the vehicle body frame. Exterior metal members;
An antenna for an automobile, comprising: an antenna wire disposed in close proximity to the metal member in an integrally insulated state; and a received signal picked up by the antenna wire is supplied to various receivers mounted on the vehicle. Device. (2) In the device according to claim (1), one end of the antenna wire is open and the other end is connected to a coaxial cable laid inside the vehicle interior through a service hole provided in the vehicle body frame. An antenna device for an automobile characterized by the following.