JPH10215106A - On-vehicle antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enlarge external load impedance and to reduce the attenuation of signals by making stray capacitance generated in a signal route for transmitting antenna output from the base end of an antenna element be small. SOLUTION: In a projected state, a linear conductive line 40 is extended from the base end of the antenna element 22 and passed through a ground metal fitting 16 and a connection metal fitting 42 is provided on the tip. A power feeding metal fitting 44 is provided on a cylindrical base 12 corresponding to the position of the connection metal fitting 42 and an electronic circuit 34 is disposed near it and connected by a short conductive line 50. The connection metal fitting 42 and the power feeding metal fitting 44 are at positions not facing the ground metal fitting 16 and the stray capacitance generated between them is small. Also, the linear conductive line 40 passed through the ground metal fitting 16 is in a long distance from the ground metal fitting 16, a facing area is small and the generated stray capacitance is extremely small. Thus, the large external load impedance is obtained and the attenuation of the signals is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicular antenna apparatus for reducing stray capacitance generated in a signal path for transmitting an antenna output from a base end of an antenna element.

[0002]

2. Description of the Related Art FIG.
This will be described with reference to FIG. FIG. 3 is a longitudinal sectional view of a main part of an example of a conventional vehicle-mounted motor drive antenna device. In FIG. 3, a cylindrical base 12 protruding from a base body 10 is provided.
Is passed through a hole 14 a formed in the body 14. The tubular base 12 is located on the back side of the body 14.
A grounding metal fitting 16 is fitted around the outer periphery of the vehicle body 14.
The holding member 18 is fitted on the outer periphery of the cylindrical base 12 on the front side of the above, and a top nut 20 is screwed to the tip of the cylindrical base 12. By screwing the top nut 20, the vehicle body 14 is clamped by the earth metal fitting 16 and the clamping member 18, and the cylindrical base 12 is fixed to the vehicle body 14. In addition, the grounding fitting 16 is cut into the vehicle body 14 and is electrically connected.

An antenna element 22 is inserted into the cylindrical base 12 so as to protrude in the axial direction and to be housed. The movement of the antenna element 22 in the protruding direction is restricted by an appropriate protruding length, so that the antenna element 22 is prevented from coming off in the protruding direction. Then, the distal end of the rack cord 24 is appropriately connected to the base end side of the antenna element. A pinion gear connected to the motor is meshed with the rack of the rack cord 24, and the protrusion and storage of the antenna element 22 are controlled by forward and reverse rotation of the motor. Further, a connection fitting 26 made of a conductive material is integrally provided on the base end side of the antenna element 22 and is electrically connected to the base end of the antenna element 22.

A power supply fitting 28 made of a conductive material is disposed on the inner peripheral wall of the tubular base 12 in correspondence with the position of the connection fitting 26 when the antenna element 22 protrudes. The connection fitting 26 and the power supply fitting 28 are elastically connected by a spring member 30 having conductivity, and are electrically connected. The spring member 30 may be provided on either the connection fitting 26 or the power supply fitting 28. Then, the center conductor of the coaxial cable 32 is connected to the power supply fitting 28, and the antenna output is provided to an electronic circuit 34 such as an amplifier circuit or a matching circuit provided on the base body 10.

[0005]

In the conventional vehicle-mounted motor-driven antenna device as described above, when the antenna element 22 is in the protruding state, the connection fitting 26 is located at the position facing the grounding fitting 16, and the power supply fitting 28 is also connected to the ground. It is arranged on the cylindrical base 12 at a position facing the metal fitting 16. In addition, the distance between the grounding metal member 16 and the power supply metal member 28 is short and the area facing the metal member 16 is large, so that the stray capacitance generated therebetween is large. Therefore, there is a problem that a signal received by the antenna element 22 is greatly attenuated by a small external load impedance caused by a large stray capacitance.

A coaxial cable 3 for transmitting an antenna output to an electronic circuit 34 disposed apart from the power supply fitting 28.
According to 2, the longer the transmission path, the more the signal is attenuated.

[0007] Such a problem is caused by the antenna element 22
If the protrusion length is long, the level of the received signal is large, so that even if it is attenuated, no practical problem occurs. However, if the protruding length of the antenna element 22 is reduced, especially for AM band signals, the level of the received signal becomes smaller and the antenna output impedance becomes larger, and the antenna output impedance becomes larger due to the magnitude of the external load impedance. Greatly depends on the amount of attenuation.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks of the conventional antenna device, and has as its object to provide a vehicle-mounted antenna device in which stray capacitance is reduced and external load impedance is increased. I do.

[0009]

In order to achieve the above object, an on-vehicle antenna device according to the present invention has an antenna element which is inserted into a cylindrical base so as to protrude in the axial direction and can be housed, and the cylindrical base is attached to a vehicle body. Through a hole formed in the body, a grounding fitting is inserted into the outer periphery of the cylindrical base on the back side of the vehicle body, and a holding member is inserted and inserted into the outer periphery of the cylindrical base on the front side of the vehicle body. An in-vehicle antenna device in which a top nut is screwed into a tip portion of a cylindrical base, and the body nut is held by the holding member with a holding member to fix the cylindrical base to the body body. In the above, in a state where the antenna element protrudes from the vehicle body, a linear conductive wire is passed through the grounding metal from a base end of the antenna element. At the same time, the connecting metal is fixed to the cylindrical base so as to be movable in the axial direction and electrically connected to the linear conductive wire at a position where the connecting metal does not face the grounding metal. A power supply fitting made of a conductive material is disposed on the inner peripheral wall of the cylindrical base in such a manner that the connection fitting and the power supply fitting are elastically connected to each other to be electrically connected.

An electronic circuit for amplifying or matching the antenna output may be provided near the power supply fitting so that the antenna output is supplied to the electronic circuit through a short signal path from the power supply fitting. good.

Further, the antenna element, the linear conductive wire and the connection fitting, or a constituent member of the connection fitting may be integrally formed of an insulating resin.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a longitudinal sectional view of a main part of one embodiment of an on-vehicle antenna device of the present invention. FIG.
FIG. 3 is an enlarged vertical sectional view of the antenna element and the connection fitting. In FIGS. 1 and 2, the same or equivalent members as those in FIG. 3 are denoted by the same reference numerals, and redundant description will be omitted.

In FIG. 1, a cylindrical base 12 projects from a base body 10 and is fixed to a hole 14a of a vehicle body 14 by screwing a top nut 20 by a grounding member 16 and a holding member 18 as shown in FIG. Is the same as the conventional structure shown in FIG.

The vehicle-mounted antenna device of the present invention differs from the conventional device shown in FIG. 3 in the following structure. First, when the antenna element 22 is in the protruding state, the length of the linear conductive wire 40 extending from the base end of the antenna element 22 is set to penetrate the grounding bracket 16, and the end is connected to a position not facing the grounding bracket 16. The metal fitting 42 is electrically connected to be integrated with the antenna element 22.
A power supply fitting 44 is disposed on the inner peripheral wall of the cylindrical base 12 in correspondence with the position of the connection fitting 42, and
The spring members 46 having conductivity provided on the outer periphery of the second 2 are provided.
And are electrically connected. This power supply fitting 44
Near the base body 10 and the electronic circuit housing case 4
8, the electronic circuit 34 is housed therein, and the electronic circuit 34 is electrically connected to the power supply fitting 44 by a short conductive line 50 as a signal path.

Next, a structure in which the antenna element 22 and the connection fitting 42 are integrated will be described with reference to FIG. A linear conductive wire 40 extends from the base end of the antenna element 22 formed of a helical coil, and a connection base 60 formed of a conductive material is electrically connected to the end thereof by soldering or the like. Then, the outer diameter of the antenna element 22 and the outer periphery of the connection base 60 are fixed to a mold to form an insulating resin pipe 62 by insert molding, and these are integrated. Then, the antenna cover 64 made of insulating resin is entirely covered on the integrated antenna element 22. A large-diameter portion is provided on the outer periphery of the axially intermediate portion of the antenna cover 64, and is set so as not to pass through the top nut 20 so as to be prevented from falling off. A bottomed hole is formed in the lower end surface of the connection base 60 so that the rack cord 2
The first and second holders 66 and 68 are inserted while holding the front end of the fourth holder 4 and engaging with each other. Then, a fixing nut member 70 made of a conductive material is screwed to the lower end of the connection base 60 so that the first and second holders 66 and 68 do not come out of the bottomed holes. The outer diameter of the fixing nut member 70 is substantially the same as the antenna cover 64. Further, a joint pipe 72 made of a conductive material is fitted over the lower end portion of the antenna cover 64 and the outer periphery of the fixed nut member 70, and is further caulked, so that the antenna cover 64 and the fixed nut member 70 are connected and fixed. . On the outer periphery of the joint pipe 72, spring members 46 made of a conductive material having elasticity are provided by welding. Here, the connection base 60, the fixed nut member 70 and the joint pipe 7
Reference numeral 2 denotes an electrical connection, and these constitute a connection fitting 42.

In this configuration, when the antenna element 22 is in the protruding state as shown in FIG. 1, the connection fittings 42 and the power supply fittings 44 are not at positions corresponding to the grounding fittings 16 and the stray capacitance generated in the connection fittings 42 and the power supply fittings 44. Is significantly smaller than the case corresponding to the grounding metal fitting 16 shown in FIG. Since the diameter of the linear conductive wire 40 penetrating the ground metal 16 is small, the distance between the straight conductive wire 40 and the ground metal 16 is long, and the area facing the ground metal 16 is small. Extremely small. Furthermore, the stray capacitance is small as the conductive line 50 from the power supply fitting 44 to the electronic circuit 34 is short. Therefore, the total stray capacitance generated in the signal path from the base end of the antenna element 22 to the electronic circuit 34 is small. As a result, a large external load impedance is obtained, the attenuation of the received signal is small, and the signal is transmitted to the electronic circuit 34 at a higher level.

In the above embodiment, the connection fitting 42 is composed of a plurality of members, but it is a matter of course that the construction is not limited to this. Further, in the embodiment, the antenna element 22 and the connection base 60 are integrated by the insulating resin pipe 62 and the antenna cover 64 is further covered, but the antenna element 22 and the connection fitting 42 are integrated, and Any structure may be used as long as it can move inside the base 12 in the axial direction. And the electronic circuit 3
4 for disposing the base 4 near the power supply fitting 44.
Although the electronic circuit housing 48 is provided separately from the electronic circuit housing 0, the electronic circuit 34 is provided on the base body 10 and the power supply fitting 44 is provided.
May be connected by a coaxial cable or the like with little attenuation. Further, in the embodiment, the wire forming the antenna element 22 is extended along the axis at the base end to form the linear conductive wire 4.
Although it is set to 0, it may be formed of a conductive wire separate from the antenna element 22 or a rod-shaped body made of a conductive material. Further, the above embodiment has been described assuming that the present invention is applied to a vehicle-mounted motor drive antenna device.
The present invention can be applied to any antenna device having another structure as long as it is a protruding and retractable antenna device having a cylindrical base 12 fixed to a vehicle body 14 using a grounding member 16 or the like. For example, the antenna element may be manually pulled out and pushed in.

[0018]

As described above, the vehicle-mounted antenna device according to the present invention is constituted, so that the following special effects can be obtained.

According to the first aspect of the present invention, the grounding metal is penetrated by a linear conductive wire extending from the base end of the antenna element in a protruding state, and the connecting metal fitting is located at a position not facing the grounding metal. As a result, the stray capacitance generated in the connection fittings and the corresponding power supply fittings is significantly smaller than that provided at the position facing the conventional grounding fittings. In addition, since the linear conductive wire penetrating the grounding metal has a long distance to the grounding metal and a small corresponding area,
The stray capacitance is extremely small. Therefore, compared to the past,
The total stray capacitance becomes small, and the external load impedance becomes large. As a result, the received signal is output with small attenuation.

In the vehicle-mounted antenna device according to the second aspect, the electronic circuit is arranged near the power supply fitting and is electrically connected through a short signal path, so that the antenna output between the power supply fitting and the electronic circuit is reduced. Attenuation can be reduced.

In the vehicle-mounted antenna device according to the third aspect of the present invention, the antenna element and the connection fitting or a component thereof are integrally formed of an insulating resin, so that the antenna element can be easily attached to a cylindrical base or the like.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a main part of one embodiment of a vehicle-mounted antenna device according to the present invention.

FIG. 2 is an enlarged vertical sectional view of an antenna element and a connection fitting.

FIG. 3 is a longitudinal sectional view of a main part of an example of a conventional vehicle-mounted motor drive antenna device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 Cylindrical base 14 Body body 14a hole 16 Grounding member 18 Clamping member 20 Top nut 22 Antenna element 26, 42 Connection fitting 28, 44 Power supply fitting 30, 46 Spring member 34 Electronic circuit 40 Linear conductive wire 50 Conductive line 60 Connection base Table 62 Insulating resin pipe 64 Antenna cover 70 Fixed nut member 72 Joint pipe

Claims (3)

[Claims] 1. An antenna element is inserted into a cylindrical base so as to protrude and be housed in an axial direction, and penetrates the cylindrical base through a hole formed in a vehicle body. A grounding fitting is inserted into the outer periphery, a holding member is inserted into the outer periphery of the cylindrical base on the front side of the vehicle body, and a top nut is screwed into a tip end of the cylindrical base. In a vehicle-mounted antenna device for fixing the cylindrical base to the vehicle body by holding the vehicle body with a grounding member and a holding member, a base end of the antenna element may be provided in a state where the antenna element protrudes from the vehicle body. A straight conductive wire is extended to a length that penetrates the grounding metal from above, and at a position where the straight conductive wire does not face the grounding metal. In addition, a connection fitting is fixed and electrically connected to the cylindrical base so as to be movable in the axial direction, and a power supply fitting made of a conductive material is disposed on the inner peripheral wall of the cylindrical base corresponding to the connection fitting at this position. An in-vehicle antenna device, wherein the connection fitting and the power supply fitting are elastically connected to each other for electrical connection. 2. An on-vehicle antenna device according to claim 1, further comprising: an electronic circuit for amplifying or matching an antenna output in the vicinity of the power supply fitting, and a short signal path from the power supply fitting to the electronic circuit. An in-vehicle antenna device configured to receive an antenna output. 3. The on-vehicle antenna device according to claim 1, wherein the antenna element, the linear conductive wire and the connecting member or a component of the connecting member are integrally formed of an insulating resin. Antenna device.