EP2634861A1

EP2634861A1 - Film antenna device

Info

Publication number: EP2634861A1
Application number: EP13157120.0A
Authority: EP
Inventors: Yoshiaki Imano; Kenichi Kamada
Original assignee: Mitsumi Electric Co Ltd
Current assignee: Mitsumi Electric Co Ltd
Priority date: 2012-02-29
Filing date: 2013-02-28
Publication date: 2013-09-04
Anticipated expiration: 2033-02-28
Also published as: JP5929314B2; JP2013179510A; EP2634861B1

Abstract

A film antenna device which is attached to an attachment object, including a film antenna unit which includes a film including a bonding surface on one side and an antenna element formed on the film; a circuit board unit which is electrically connected to the antenna element; a bonding member including a first and a second bonding surfaces wherein the first bonding surface is bonded to the circuit board unit and the second bonding surface is bonded to an end portion of the film antenna unit; and a case unit which houses the circuit board unit, the bonding member and the end portion of the film antenna unit, wherein the case unit includes a top case and a bottom case, and the bottom case includes a film antenna supporting unit which pushes the film antenna unit against the bonding member.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a film antenna device including film antenna units wherein antenna elements are formed on films.

2. Description of Related Art

Conventionally, there is known a film antenna which is attached to a vehicle and receives electric wave such as DAB (Digital Audio Broadcast) (see Japanese Patent Application Laid Open Publication No. 2000-295023 , for example). In such film antenna, antenna elements in a predetermined strip shape are formed on a surface of the film and feed terminals are connected to the antenna elements. Such film antenna is attached to a window inner surface of a vehicle to be used.
There is also known a film antenna device including a film antenna unit and a circuit board unit which has an electronic circuit that amplifies a signal received by the film antenna unit (see Japanese Patent Application Laid Open Publication No. 2000-196327 , for example). The circuit board is housed in a case unit. The case unit is separate from the circuit board unit and includes metal springy contact terminals connected to the circuit board unit, and a double-faced tape is attached to a flat part around the contact terminals. The circuit board unit is electrically connected to the antenna elements by peeling a release paper of the double-faced tape and attaching the case unit to the film antenna unit so that the contact terminals contact with terminals of the antenna elements in the film antenna unit.
However, in the conventional film antenna devices, there is possibility of bad electrical contact between the antenna elements in the film antenna unit and the contact terminals connected to the circuit board unit caused by the double-faced tape being peeled off due to the deterioration with age after the film antenna device is manufactured by connecting the case unit to the film antenna unit.
An object of the present invention is to prevent a bad electrical connection between a film antenna unit and a circuit board unit.

SUMMARY OF THE INVENTION

In order to achieve the above object, according to the first aspect of a preferred embodiment of the present invention, there is provided a film antenna device which is attached to an attachment object, including a film antenna unit which includes a film including a bonding surface on one side and an antenna element formed on the film, a circuit board unit which is electrically connected to the antenna element of the film antenna unit, a bonding member which includes a first and a second bonding surfaces wherein the first bonding surface is bonded to the circuit board unit and the second bonding surface is bonded to an end portion of the film antenna unit, and a case unit which houses the circuit board unit, the bonding member and the end portion of the film antenna unit, wherein the case unit includes a top case and a bottom case which joins with the top case, and the bottom case includes a film antenna supporting unit which pushes the film antenna unit against the bonding member.
According to the present invention, the bad electrical connection between the film antenna unit and the circuit board unit can be avoided.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, advantages and features of the present invention will become more fully understood from the detailed description given hereinafter and the appended drawings which are given by way of illustration only, and thus are not intended as a definition of the limits of the present invention, and wherein:

FIG. 1 is a plan view of a film antenna device in an embodiment of the present invention;
FIG. 2 is an exploded view of a film antenna device seen from above;
FIG. 3 is an exploded view of a film antenna device seen from below;
FIG. 4 is a plan view of a circuit board unit to which the film antenna unit is attached; and
FIG. 5 is a partially sectional view of a film antenna device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, an embodiment of the present invention will be described in detail on the basis of the drawings. However, the present invention is not limited to the illustrated examples.
With reference to FIGS. 1 to 3, a device configuration of a film antenna device 1 of the embodiment will be described. FIG. 1 is a plan view of the film antenna device of the embodiment. FIG. 2 is an exploded view of the film antenna device 1 seen from above. FIG. 3 is an exploded view of the film antenna device 1 seen from below.
The film antenna device 1 of the embodiment is to be attached to an inner surface of a window (window glass) of a mobile object such as a vehicle. The film antenna device 1 is an antenna device which receives electric wave of DAB. However, the film antenna device 1 is not limited to this antenna device and may receive and send electric waves of other communication systems.
As shown in FIG. 1, the film antenna device 1 of the embodiment includes film antenna units 10A and 10B, a case unit 20, a cable 50 and pull- tabs 60A and 60B.
The film antenna units 10A and 10B are bands of film antennas. The film antenna unit 10A includes a film 11A and an antenna element 12A. The film 11A is a band of a film member which is transparent, for example. Since the film 11A is transparent, external visibility through a window glass by a crew is less disturbed even when the film antenna unit 10A is attached to the window glass of a vehicle. The film 11A is made of a PET (Polyethylene Terephthalate) material. A bonding agent (adhesive) is applied to a surface of the film 11A which is to be attached to the window glass and a peeling film (not shown in the drawing) is applied on the bonding agent. The bonding agent on the film 11A is approximately 0.03 [mm] thick, for example.
The antenna element 12A is configured by including a copper wire as a metal wire, for example. The diameter of the copper wire of the antenna element 12A is 0.1 mm, for example. In the manufacturing, the antenna element 12A is embedded in one surface of the film 11A, for example. The antenna element 12A protrudes from the film 11A for 0. 03 to 0.07 [mm], for example. The flat surface of the film 11A which is opposite to the surface in which the antenna element 12A is embedded is attached to the attachment surface of the window glass. This is to avoid air bubbles due to the protruding part of the antenna element 12A when the film antenna unit 10A is attached to the window glass. The antenna element 12A includes an end portion 12A1 which does not contact with the film 11A. Also, the antenna element 12A except for the end portion 12A1 is coated with an insulator such as enamel.
The film antenna unit 10B includes a film 11B and an antenna element 12B. The antenna element 12B includes an end portion 12B1. The configuration of the film antenna unit 10B is same as the configuration of the film antenna unit 10A. The antenna units 10A and 10B are disposed so that the longitudinal directions of the antenna elements 12A and 12B lie on a straight line centering the case unit 20.
The case unit 20 is a case of molded resin and the shape thereof is a nearly rectangular box shape with round shape corners. The case unit 20 houses end portions of the film antenna units 10A and 10B, a circuit board unit 30 and a bonding member 40 which will be mentioned later and an end of the cable 50.
The cable 50 is a coaxial cable. One end of the cable 50 is connected to the circuit board unit 30 in the case unit 20 and the other end of the cable 50 is connected to a connector 51. The cable 50 is connected to a DAB receiver or such like via the connector 51.
The pull- tabs 60A and 60B are members to peal off the peeling films (not shown in the drawings) attached to the bonding surfaces of the film antenna units 10A and 10B respectively, and the pull- tabs 60A and 60B are bonded to the peeling films strongly.
Next, the inner configuration of the case unit 20 will be described with reference to FIGS. 2 and 3. As shown in FIGS. 2 and 3, the case unit 20 houses the circuit board unit 30, the bonding member 40, an end of the cable 50 and end portions 13A and 13B of the film antenna units 10A and 10B. The end portion 13A is the end portion of the film antenna unit 10A which is housed in the case unit 20. The end portion 13B is the end portion of the film antenna unit 10B which is housed in the case unit 20.
The case unit 20 includes a top case 20a, a bottom case 20b and male threads 20c.
The top case 20a is the upper case (cover) (the upper side is the side opposite to the window glass side of a vehicle) of the case unit 20. The top case 20a includes a cover main body 21a, protruding parts 22a, female threads 23a, a cable supporting part 24a and ribs 25a.
The cover main body 21a is the main body of the top case 20a and is a nearly rectangular box shape which is bottomless. The protruding parts 22a are provided on the two facing lateral surfaces of the top case 20a and the function thereof is to push down the film antenna units 10A and 10B. The female thread parts 23a are provided inside the top case 20a and the male threads 20c are threaded into the female thread parts 23a.
The cable supporting part 24a is provided on a lateral surface of the top case 20a and supports the cable 50 by sandwiching the cable 50 with the cable supporting part 24b. The ribs 25a are provided inside the top case 20a and support the circuit board unit 30 by setting the height of the circuit board unit 30.
The bottom case 20b is the lower case (cover) (the lower side is the window glass side of a vehicle) of the case unit 20 and joins with the top case 20a. The bottom case 20b includes a cover main body 21b, film antenna guide parts 22b, hole parts 23b, a cable supporting part 24b, a film antenna supporting unit 25b and concave parts 26b.
The cover main body 21b is the main body of the bottom case 20b. The film antenna guide parts 22b are provided at positions corresponding to the protruding parts 22a and curved so as to gradually guide the film antenna units 10A and 10B downward from the film antenna supporting unit 25b. The hole parts 23b are through-holes, which are formed in the cover main body 21b, for the male threads 20c.
The cable supporting part 24b is provided on a lateral surface of the bottom case 20b and supports the cable 50 by sandwiching the cable 50 with the cable supporting part 24a. The film antenna supporting unit 25b is a flat surface part disposed at a position corresponding to the bonding member 40, and the function thereof is to push the end portions 13A and 13B of the film antenna units 10A and 10B against the bonding member 40. That is, the end portions 13A and 13B of the film antenna units 10A and 10B are sandwiched between the bonding member 40 and the film antenna supporting unit 25b to be fixed. The film antenna supporting unit 25b includes flat surface parts 25d and 25e. The flat surface part 25d is a flat surface part to which the bonding member 40 is bonded. The flat surface parts 25e are flat surface parts to which the end portions 13A and 13B of the film antenna units 10A and 10B are bonded and the flat surface parts 25e push the end portions 13A and 13B against the bonding member 40.
The concave parts 26b are concave parts to place convex parts of after-mentioned soldering parts 60 in which the end portions 12A1 and 12B1 of the antenna elements 12A and 12B of the film antenna units 10A and 10B are soldered to the circuit board unit 30.
The circuit board unit 30 is electrically connected to the antenna elements 12A and 12B of the film antenna units 10A and 10B and includes an electronic circuit, such as an amplifying circuit, which amplifies a signal received by the film antenna units 10A and 10B and outputs the signal to the cable 50. The circuit board unit 30 includes a board main body 31, hole parts 32, a bonding member mounted section 33 and antenna element connecting parts 34.
The board main body 31 is a PWB (Printed Wiring Board) which includes electronic circuit components and a track pattern. The hole parts 32 are through-holes, which are formed in the board main body 31, for the male threads 20c. The bonding member mounted section 33 is a flat surface on which the bonding member 40 is to be mounted by bonding. The bonding member mounted section 33 includes flat surface parts 33a and 33b. The flat surface part 33a is bonded to the bonding member 40 and located at a position corresponding to the flat surface part 25d. The flat surface parts 33b are bonded to the bonding member 40 and located at positions corresponding to the flat surface parts 25e. The antenna element connecting parts 34 include conductive parts connected to the circuit elements of the board main body 31. The antenna element connecting parts 34 are not bonded to the bonding member 40 and the antenna element connecting parts 34 connect the antenna elements 12A and 12B to the board main body 31 electrically by soldering the end portions 12A1 and 12B1 thereto.
The bonding member 40 is a bonding member such as a double-faced tape which bonds the end portions of the film antenna units 10A and 10B to the circuit board unit 30. The bonding member 40 includes a film antenna bonding part 41 and hole parts 42. The film antenna bonding part 41 is the main body of the bonding member 40 and is a bonding member, such as a double-faced tape, wherein a bonding agent (adhesive) is applied on both surfaces of the base body. The base body is formed of nonwoven fabric whose horizontal to vertical strength difference is small, for example. The base body is 0.1 to 0.15 [mm] thick, for example. In the bonding member 40, one bonding surface is bonded to the bonding member mounted section 33 and the other bonding surface is bonded to the end portions 13A and 13B of the film antenna units 10A and 10B and the film antenna supporting unit 25b.
The hole parts 42 are formed in the film antenna bonding part 41 for soldering the end portions 12A1 and 12B1 of the antenna elements 12A and 12B of the film antenna units 10A and 10B to the antenna element connecting parts 34 of the circuit board unit 30. The hole parts 42 are located at positions corresponding to the antenna element connecting parts 34. It is preferable that the bonding member 40 is inelastic. The bonding strength of the bonding member 40 is equal to or more than 10N/20mm, for example.
Next, the manufacturing method of the film antenna device 1 will be described with reference to FIGS. 4 and 5. FIG. 4 is a plan view of the circuit board unit 30 to which the film antenna units 10A and 10B are attached. FIG. 5 is a partially sectional view of the film antenna device 1.
As shown in FIG. 4, in the circuit board unit 30 to which an inner conductor and an outer conductor of the cable 50 are soldered to be electrically connected, one bonding surface of the bonding member 40 is bonded to the bonding member mounted section 33. Then, the film antenna units 10A and 10B are disposed so that the end portions 12A1 and 12B1 of the antenna elements 12A and 12B are located at the two hole parts 42, and the end portions 13A and 13B are bonded to the other bonding surface of the bonding member 40. The end portions 12A1 and 12Bl of the antenna elements 12A and 12B are soldered to the antenna element connecting parts 34 via the hole parts 42 to form convex soldering parts 60.
In conventional film antenna devices, contact terminals of a case unit cannot be soldered to terminals of antenna elements of film antenna units. This is because the films are made of PET material and the antenna elements are made of silver paste, and thus the films will melt away if soldering is performed to connect the contact terminals of the case unit to the terminals of the antenna elements. However, in the film antenna device 1, soldering is possible because the end portions 12A1 and 12B1 are not in contact with the films 11A and 11B.
The soldering parts 60 are disposed in the concave parts 26b, and the end portions 13A and 13B of the film antenna units 10A and 10B are disposed on the film antenna guide parts 22b and the film antenna supporting unit 25b. The circuit board unit 30 to which the film antenna units 10A and 10B are attached is bonded to the bottom case 20b by bonding the bonding surface 40a of the bonding member 40 exposed at a position corresponding to the flat surface part 33a to the flat surface part 25d and by bonding the bonding surfaces of the end portions 13A and 13B of the films 11A and 11B of the film antenna units 10A and 10B to the flat surface parts 25e and the film antenna guide parts 22b.
Then, the top case 20a is joined with the bottom case 20b and the male threads 20c are threaded to the female thread parts 23a via the hole parts 23b and 32. Due to such threading, the film antenna units 10A and 10B are firmly fixed to the circuit board unit 30 and the case unit 20 by the soldering at the soldering parts 60, the bonding by the bonding member 40, and the pressing by the film antenna supporting unit 25b against the bonding member 40. Thus, the film antenna units 10A and 10B do not come off from the circuit board unit 30 and the case unit 20 even when there is a mechanical tension stress due to attachment, handling and such like.
Further, as shown in FIG. 5, a bonding member 70 is attached to the downside of the cover main body 21b of the bottom case 20b. The bonding member 70 is a bonding member such as a double-faced tape.
When the film antenna device 1 is attached to a window glass 80 of a vehicle as an attachment object, the bonding member 70 is bonded to the window glass 80 and peeling films of the film antenna units 10A and 10B are peeled away so that the bonding surfaces are bonded to the window glass 80.
The film antenna units 10A and 10B are guided to the window glass 80 side (the downside) by the film antenna guide parts 22b and forcibly pushed down to the window glass 80 side by the protruding parts 22a.
As described above, according to the embodiment, in the film antenna device 1, one bonding surface of the bonding member 40 is bonded to the circuit board unit 30, the other bonding surface of the bonding member 40 is bonded to the end portions 13A and 13B of the film antenna units 10A and 10B, the bottom case 20b is bonded to the bonding surfaces of the film antenna units 10A and 10B and to the bonding surface of the bonding member 40 on the window glass 80 side, and the film antenna units 10A and 10B are pressed against the bonding member 40 by the film antenna supporting unit 25b. Thus, the film antenna units 10A and 10B are firmly fixed to the circuit board unit 30 and to the case unit 20 by being bonded by the bonding member 40 and pressed by the film antenna supporting unit 25b. Thereby, bad electrical connection between the film antenna units 10A and 10B and the circuit board unit 30 is prevented. Further, the film antenna device 1 can be attached to the window glass 80 easily since the film antenna units 10A and 10B and the circuit board unit 30 can be formed in an integrated type and there is no need for careful attachment of a power feeding part of the film antenna units 10A and 10B.
In addition, the film antenna supporting unit 25b of the bottom case 20b is bonded to the bonding surfaces of the film antenna units 10A and 10B at the flat surface parts 25e and bonded to the bonding surface of the bonding member 40 on the window glass 80 side at the flat surface part 25d. Thus, the film antenna units 10A and 10B can be firmly fixed to the bottom case 20b and the bonding member 40.
Also, the bottom case 20b includes the film antenna guide parts 22b which guide the film antenna units 10A and 10B to the window glass 80 side. Therefore, it is possible to guide the film antenna units 10A and 10B to the window glass 80 side easily and avoid gaps between the film antenna units 10A and 10B and the window glass 80 in which dust is gathered. Thus, the film antenna units 10A and 10B can be prevented from peeling off from the window glass 80.
The top case 20a includes the protruding parts 22a which push down the film antenna units 10A and 10B to the window glass 80 side. Therefore, it is possible to push down the film antenna units 10A and 10B to the window glass 80 side easily and avoid gaps between the film antenna units 10A and 10B and the window glass 80 in which dust is gathered. Thus, the film antenna units 10A and 10B can be prevented from peeling off from the window glass 80.
The antenna elements 12A and 12B include the end portions 12A1 and 12B1 which do not contact with the films 11A and 11B, respectively, and the end portions 12A1 and 12B1 are electrically connected to the antenna element connecting parts 34 of the circuit board unit 30 by soldering. Thus, it is possible to further avoid bad electrical connection between the film antenna units 10A and 10B and the circuit board unit 30.
The antenna elements 12A and 12B are copper wires. Thus, it is possible to easily expose and solder the end portions 12A1 and 12B1 of the antenna elements 12A and 12B which do not contact with the films 11A and 11B.
The bottom case 20b includes the concave parts 26b to place the soldering parts 60. Thus, the circuit board unit 30 to which the film antenna units 10A and 10B are soldered can be firmly bonded to the film antenna supporting unit 25b of the case unit 20.
Though the present invention made by the inventors has been specifically described on the basis of the embodiment, the present invention is not limited to the above embodiment and various changes can be made within the scope of the invention.
The scope of the present invention includes the scope of the invention described in claims and the equivalent thereof.
According to one aspect of the preferred embodiments of the present invention, there is provided a film antenna device which is attached to an attachment object, including a film antenna unit which includes a film including a bonding surface on one side and an antenna element formed on the film, a circuit board unit which is electrically connected to the antenna element of the film antenna unit, a bonding member which includes a first and a second bonding surfaces wherein the first bonding surface is bonded to the circuit board unit and the second bonding surface is bonded to an end portion of the film antenna unit, and a case unit which houses the circuit board unit, the bonding member and the end portion of the film antenna unit, wherein the case unit includes a top case and a bottom case which joins with the top case, and the bottom case includes a film antenna supporting unit which pushes the film antenna unit against the bonding member.
Preferably, the film antenna supporting unit of the bottom case is bonded to the bonding surface of the film antenna unit and to the second bonding surface of the bonding member.
Preferably, the bottom case includes a film antenna guide part which guides the film antenna unit toward the attachment object.
Preferably, the top case includes a protruding part which pushes down the film antenna unit toward the attachment object.
Preferably, the antenna element includes an end portion which does not contact with the film, the circuit board unit includes an antenna element connecting part which is not bonded to the bonding member and to which the antenna element is electrically connected, and the end portion of the antenna element is electrically connected to the antenna element connecting part by soldering.
Preferably, the antenna element is a metal wire.
Preferably, the bottom case includes a concave part to place a soldering part which is formed by the soldering.

Claims

A film antenna device which is attached to an attachment object, comprising:
a film antenna unit which includes a film including a bonding surface on one side and an antenna element formed on the film;

a circuit board unit which is electrically connected to the antenna element of the film antenna unit;

a bonding member which includes a first and a second bonding surfaces wherein the first bonding surface is bonded to the circuit board unit and the second bonding surface is bonded to the film antenna unit; and

a case unit which houses the circuit board unit, the bonding member and an end portion of the film antenna unit,

wherein

the case unit includes a top case and a bottom case which joins with the top case, and

the bottom case includes a film antenna supporting unit which pushes the film antenna unit against the bonding member.
The film antenna device according to claim 1, wherein the film antenna supporting unit of the bottom case is bonded to the bonding surface of the film antenna unit and to the second bonding surface of the bonding member.
The film antenna device according to claim 1 or 2, wherein the bottom case includes a film antenna guide part which guides the film antenna unit toward the attachment object.
The film antenna device according to any one of claims 1 to 3, wherein the top case includes a protruding part which pushes down the film antenna unit toward the attachment object.
The film antenna device according to any one of claims 1 to 4, wherein
the antenna element includes an end portion which does not contact with the film,
the circuit board unit includes an antenna element connecting part which is not bonded to the bonding member and to which the antenna element is electrically connected, and
the end portion of the antenna element is electrically connected to the antenna element connecting part by soldering.
The film antenna device according to claim 5, wherein the antenna element is a metal wire.
The film antenna device according to claim 5 or 6, wherein the bottom case includes a concave part to place a soldering part which is formed by the soldering.