JP6279377B2 - Vehicle antenna device - Google Patents

Description

  The present invention relates to a vehicle antenna device, and more particularly to a vehicle antenna device capable of reducing the height of an antenna device capable of receiving FM broadcast and AM broadcast.

  As a vehicle antenna device, one that can receive FM broadcast and AM broadcast is generally used. As a vehicle antenna device, a rod antenna, a film antenna, a glass antenna, or the like is used. Recently, there is a small and low-profile antenna device such as a so-called shark fin antenna. As the antenna length, a rod antenna or the like is configured to have a quarter wavelength length in the FM wave band. Further, in the vehicular antenna device, there is a helical antenna that is configured to be short by winding the antenna element in a helical shape because the height protruding from the vehicle roof is limited due to external projection restriction. However, in the AM wave band, since the antenna length is much shorter than the wavelength, the reception sensitivity is significantly lowered. For this reason, a device capable of reducing the height of the antenna device by attaching a top load portion of a metal body to the open end side of the antenna element so as to have a capacitance has been developed. For example, the antenna device of Patent Document 1 is of the shark fin antenna type, and an antenna coil provided with a top load portion obtained by processing a metal plate at the open end of the antenna coil is disclosed.

International Publication No. 2008/062746

  A vehicle antenna device is usually provided with an antenna cover. However, in an antenna device having a top load portion, the top load portion is theoretically arranged at the top. This is because the antenna performance is improved when the top load portion is separated from the antenna base and the vehicle roof which are the ground plane. On the other hand, further reduction in the height of the antenna device has been demanded due to external projection restrictions and design requirements. Therefore, it has been required to improve the antenna characteristics by increasing the height of the top load portion in millimeters while reducing the height of the antenna device.

  In view of such circumstances, the present invention intends to provide a vehicular antenna device capable of improving antenna characteristics even when the height is lowered.

  In order to achieve the above-described object of the present invention, a vehicle antenna device according to the present invention includes an antenna cover that defines the outer shape of the vehicle antenna device, an antenna element covered inside the antenna cover, and an open end of the antenna element. A top load portion made of conductive resin, and an intervening portion having a higher conductivity than the top load portion, connecting the antenna element and the top load portion between the antenna element and the top load portion. Are provided.

  Here, the top load portion may be any one that is integrally molded from the partial surface of the antenna cover to the inside.

  Further, the antenna cover may include an inner cover and an outer cover that covers the inner cover, and the top load portion may be integrally formed from a partial surface of the inner cover to the inside.

  Moreover, the top load part should just be shape | molded by block shape.

  Further, the antenna element is composed of a helical antenna element, the top load part has a groove part into which the open end of the helical antenna element is fitted, and the interposition part only needs to be disposed in the groove part.

  The antenna element may be formed by arranging an antenna pattern on a substrate, the top load portion may have a groove portion into which the substrate is fitted, and the interposition portion may be arranged in the groove portion.

  Moreover, the interposition part should just be provided so that a contact surface with a top load part may become a surface contact.

  The vehicle antenna device of the present invention has an advantage that the antenna performance is improved even if the height is lowered.

FIG. 1 is a schematic view for explaining a vehicular antenna apparatus of the present invention. FIG. 2 is a schematic bottom view for explaining a connection portion between the antenna element and the top load portion of the vehicle antenna device of the present invention. FIG. 3 is a schematic diagram for explaining another example of the vehicle antenna device of the present invention. FIG. 4 is a schematic cross-sectional side view for explaining the configuration when the antenna cover of the vehicle antenna device of the present invention is divided into an inner cover and an outer cover. FIG. 5 is a graph for explaining the antenna gain performance of the vehicle antenna device of the present invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described together with illustrated examples. 1A and 1B are schematic views for explaining a vehicle antenna device of the present invention. FIG. 1A is a side sectional view, and FIG. 1B is a bb sectional view thereof. As illustrated, the vehicle antenna device of the present invention mainly includes an antenna cover 10, an antenna element 20, a top load part 30, and an interposition part 40.

  The antenna cover 10 defines the outer shape of the vehicle antenna device. This is made of a non-conductive member such as ABS resin. The antenna cover 10 is not limited to a single one. For example, the antenna cover 10 may be divided into an inner cover and an outer cover that covers the inner cover. The antenna cover 10 is closed at the opening by the antenna base 1. For example, a circuit board 2 is mounted on the antenna base 1. Further, an antenna element 20 described later is also supported by the antenna base 1 as necessary. The antenna base 1 may be a conductive base or a resin base.

  The antenna element 20 is covered with the antenna cover 10. The antenna element 20 is configured to receive FM broadcast and AM broadcast, for example. Specifically, for example, any antenna having an antenna length such as ¼ of the frequency of the FM wave band may be used. Moreover, it is comprised so that it may function as a capacitive antenna with the top load part 30 mentioned later. In other words, the antenna length of the antenna element 20 is made to correspond to the FM wave band, and the top load unit 30 is used to form a capacitive antenna corresponding to the AM wave band. As the antenna element, various existing antenna elements such as a helical shape, a meander shape, and a space filling curve shape can be used. In the example of illustration, the example of the helical antenna element was shown. The antenna element may include not only a radiating element but also a coil for adjusting an inductor.

  The top load part 30 is made of a conductive resin. Here, the conductive resin refers to a synthetic resin having electrical conductivity. Specifically, the top load portion 30 is preferably made of a material having high conductivity, for example, a conductive grade of PB2N1 PP compound resin by Daicel Polymer Co., Ltd. can be used. The top load portion 30 is connected to the open end side of the antenna element 20. By connecting the top load unit 30 to the open end side of the antenna element 20, the antenna element 20 can receive FM broadcasts and can receive AM broadcasts as a capacitive antenna. In the vehicle antenna device of the present invention, the top load portion 30 is made of a conductive resin. For example, by pouring the conductive resin into the antenna cover 10, the top load portion 30 can be easily aligned with the upper end of the antenna cover 10. The top load portion 30 can be formed in a different shape. Therefore, it is possible to arrange the top load portion at a position that is as high as possible as compared with a conventional top load portion obtained by processing a metal plate.

  Furthermore, the top load portion 30 may be integrally formed from a partial surface of the antenna cover 10 to the inside as in the illustrated example. Specifically, a part of the top portion of the antenna cover 10 is constituted by the top load portion 30, and the top load portion 30 is also formed inside. Since the top load portion 30 of the vehicle antenna device of the present invention is made of resin, it can be formed integrally with the antenna cover 10 made of resin. Therefore, there is no worry that water, dust, etc. enter from the outside through the joint. In the vehicle antenna device of the present invention, the top load portion 30 can be arranged at a higher position by the thickness of the antenna cover by integrally molding the top load portion 30 with the antenna cover 10 in this way. As a result, it is possible to further improve the antenna characteristics.

  Moreover, the top load part 30 should just be shape | molded in the block shape like the example of illustration unlike what processed the metal plate. That is, the top load portion 30 is not formed only on the surface side, but is formed as a lump filled up to the inside. The thickness of the conductive resin is a large parameter for the electrical performance, and a thicker one is more advantageous for reducing the resistance value of the top load portion. Therefore, the resistance of the top load portion 30 can be reduced by forming the block shape. Note that the vehicle antenna device of the present invention is not limited to the block-shaped top load portion, and may have a hollow shape such as an umbrella.

  In the vehicular antenna device of the present invention, the capacity of the top load portion can be increased as compared with a conventional metal plate processed, so that the same capacity can be reduced compared to the metal plate. It becomes. Therefore, as a result, the number of turns and the length of the antenna element such as the coil can be increased, and the antenna performance can be improved.

  The interposition part 40 is interposed between the antenna element 20 and the top load part 30. The antenna element 20 and the top load part 30 are connected by the interposition part 40. In the top load portion 30 made of a conductive resin, even if the antenna element 20 is brought into contact as it is, it may not be in an electrically conductive state. Therefore, in the vehicle antenna device of the present invention, the antenna element 20 and the top load portion 30 are connected using the interposition portion 40. Here, the interposition part 40 has higher conductivity than the top load part 30. For example, a conductive metal such as copper, a conductive rubber, a conductive adhesive, or the like may be used. And the interposition part 40 should just be fixed with a certain amount of area to the top load part 30 side. That is, the interposition part 40 is provided for the purpose of increasing the contact area with the top load part 30. More specifically, for example, the interposition part 40 may be electrically attached to the top load part 30 so as to have an area of about 10 mm square or more. Further, since the contact area of the interposition part 40 only needs to be increased, it is not necessary to have a plate shape, and if it is a rod shape, the diameter may be increased to increase the contact area. Furthermore, when an interposition part is comprised like a screw hole, it becomes possible to increase a surface area further by the part of a screw groove. By increasing the contact area between the top load part 30 and the interposition part 40, the contact resistance between the antenna element 20 and the top load part 30 is reduced, and the antenna characteristics can be improved. In the illustrated example, the intervening portion is provided separately from the antenna element. However, the present invention is not limited to this, and the open end of the antenna element is processed to increase the contact area like the intervening portion. Thus, the interposition part may be formed integrally with the antenna element.

  Here, the connection portion between the antenna element 20 and the top load portion 30 will be described more specifically with reference to FIG. FIG. 2 is a schematic bottom view for explaining a connection portion between the antenna element and the top load portion of the vehicle antenna device of the present invention. In the figure, the same reference numerals as those in FIG. 1 denote the same parts. FIG. 2 is a view of the top load portion 30 as viewed from the antenna base side. As illustrated, in the vehicle antenna device of the present invention, an interposition part 40 is disposed between the antenna element 20 and the top load part 30. In addition, as the antenna element 20, the conducting wire of the predetermined | prescribed diameter was shown like the open end part of a helical antenna element, for example. As in the illustrated example, the interposition part 40 is provided such that the contact surface with the top load part 30 is in surface contact in order to increase the contact area with the top load part 30. Specifically, as shown in the drawing, for example, a groove portion 31 is provided in the top load portion 30, and the interposition portion 40 is disposed in the entire groove portion 31. Thereby, the contact area of the top load part 30 and the interposition part 40 becomes large. The open end of the antenna element 20 is connected so as to fit into the groove 31. Thereby, the antenna element 20 and the top load part 30 are reliably electrically connected, and the antenna characteristics are improved.

  Next, another example of the connecting portion will be described with reference to FIG. In FIG. 1 and FIG. 2, the example which used the helical antenna element as an antenna element was shown concretely. In FIG. 3, an antenna element using a substrate will be described. 3A and 3B are schematic views for explaining another example of the vehicle antenna device of the present invention. FIG. 3A is a side sectional view, and FIG. 3B is a bb sectional view thereof. In the figure, the same reference numerals as those in FIG. 1 denote the same parts. In the illustrated example, the antenna pattern 22 is arranged on the substrate 21 as the antenna element. As illustrated, the top load part 30 has a groove part 32 into which the substrate 21 is fitted. And the interposition part 40 is arrange | positioned at this groove part. The contact area between the top load part 30 and the interposition part 40 is increased by disposing the interposition part 40 in surface contact with the entirety of the groove part 32. An open end of the antenna pattern 22 is disposed in a portion of the substrate 21 that fits into the groove portion 32, and the land portion 23 is configured to be in electrical contact with the interposition portion 40. That is, a land portion 23 from which a resist film or the like is peeled is provided at a contact portion between the open end of the antenna pattern 22 and the interposition portion 40. Thereby, the land part 23 and the interposition part 40 surface-contact, and a contact area becomes large. Further, when the antenna element is constituted by a double-sided board, it is possible to further increase the contact area by providing land portions on both sides. Moreover, the open end of the antenna pattern 22 may be configured by a leaf spring-like member. The antenna pattern 22 and the top load part 30 are more reliably connected via the interposition part 40 by fitting in a state where tension is applied in the groove part 32 by the leaf spring-like member.

  Thus, in the vehicle antenna device of the present invention, various antenna elements can be applied, such as those in which a conductive wire such as a helical antenna element is wound, or those in which an antenna pattern is arranged using a substrate. It is. Any antenna element may be used as long as the top load part is connected to the open end side of the antenna element via the interposition part.

  Next, the case where the antenna cover is divided into an inner cover and an outer cover covering the inner cover will be described. FIG. 4 is a schematic cross-sectional side view for explaining the configuration when the antenna cover of the vehicle antenna device of the present invention is divided into an inner cover and an outer cover. In the figure, the same reference numerals as those in FIG. 1 denote the same parts. In the illustrated example, only the antenna cover and the top load portion are mainly shown, and the other configurations are not shown. In the vehicle antenna device of the present invention, the antenna cover and the top load portion are both made of resin, and therefore can be integrally formed. However, since they are different types of resins, there is a possibility that joints may be visible in appearance. In addition, paint smears may occur between the conductive resin and the ABS resin. Therefore, as shown in the drawing, the antenna cover 10 is composed of an inner cover 11 and an outer cover 12 that covers it. Then, the top load portion 30 is integrally formed from a partial surface of the inner cover 11 to the inside. The inner cover 11 configured in this way is covered with an outer cover 12. Thereby, there is no possibility that joints can be seen and smears are not generated.

  The antenna gain performance of the vehicle antenna device of the present invention will be described with reference to FIG. 5A and 5B are graphs for explaining the antenna gain performance of the vehicle antenna device of the present invention. FIG. 5A is an antenna gain characteristic of FM horizontal polarization, and FIG. 5B is FM vertical polarization. Antenna gain characteristics, FIG. 5C shows AM received power. In the figure, the black line is the characteristic of the vehicle antenna device of the present invention, and the gray line is the characteristic when using a top load portion obtained by processing a conventional metal plate for comparison. As shown in the figure, the FM antenna gain was improved by about 0.3-0.4 dB on average, and the AM antenna gain was improved by about 0.2 dB. This is due to the fact that the top load portion can be arranged at a high position by the thickness of the antenna cover.

  Note that the vehicle antenna device of the present invention is not limited to the illustrated examples described above, and it is needless to say that various modifications can be made without departing from the scope of the present invention. For example, in the illustrated example, an example of a low profile antenna such as a so-called shark fin antenna is shown, but the present invention is not limited to this, and a pole antenna such as a rod antenna can be applied. That is, a top load portion made of a conductive resin may be connected to the open end of the pole antenna via an interposition portion having a higher conductivity than the top load portion.

DESCRIPTION OF SYMBOLS 1 Antenna base 2 Circuit board 10 Antenna cover 11 Inner cover 12 Outer cover 20 Antenna element 21 Board | substrate 22 Antenna pattern 23 Land part 30 Top load part 31, 32 Groove part 40 Interposition part

Claims (7)

An antenna device for a vehicle, the vehicle antenna device comprising:
An antenna cover for defining the outer shape of the vehicle antenna device;
An antenna element covered inside the antenna cover;
Connected to the open end side of the antenna element, a top load portion made of conductive resin,
The antenna element and the top load part are interposed between the antenna element and the top load part, and the intermediate part having higher conductivity than the top load part,
A vehicle antenna apparatus comprising:   The vehicle antenna device according to claim 1, wherein the top load portion is integrally formed from a partial surface of the antenna cover to an inside thereof. The vehicle antenna device according to claim 1, wherein the antenna cover includes an inner cover and an outer cover that covers the inner cover.
The vehicular antenna device, wherein the top load portion is integrally formed from a partial surface of the inner cover to the inside.   4. The vehicle antenna device according to claim 1, wherein the top load portion is formed in a block shape. 5. The vehicle antenna device according to any one of claims 1 to 4, wherein the antenna element is a helical antenna element.
The top load part has a groove part into which an open end of the helical antenna element is fitted,
The interposition part is disposed in the groove part.
A vehicle antenna device characterized by the above. The vehicle antenna device according to any one of claims 1 to 4, wherein the antenna element has an antenna pattern disposed on a substrate.
The top load part has a groove part into which the substrate is fitted,
The interposition part is disposed in the groove part.
A vehicle antenna device characterized by the above.   The vehicle antenna device according to any one of claims 1 to 6, wherein the interposition portion is provided such that a contact surface with the top load portion is in surface contact.