Antenna device

An antenna device that can suitably be provided on the exterior of a vehicle is provided with low cost. An antenna case includes a top cover and a bottom plate joined with each other. The top cover stores an antenna module that receives a signal and a packing member provided at the joining part between the top cover and the bottom plate to keep the antenna case tightly sealed. The antenna case has a notch positioned at the joining part through which a signal line is externally extended, and the packing member integrally forms a base part that covers the entire surface of the antenna module and a gasket part that covers the outer periphery of the signal line connected to the antenna module in the position of the notch.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a GPS receiving antenna device that receives a GPS signal transmitted from a GPS satellite.

2. Description of the Related Art

In recent years, a system to receive signal waves transmitted from multiple artificial satellites that orbit around the earth by a receiver and detect the present position of the receiver based on information included in the received signal waves has come into widespread use. The system is generally called GPS (Global Positioning System) in countries including Japan and the United States of America and typically uses the GPS satellites controlled by the U.S. Department of Defense, while there are similar systems such as Galileo in Europe and Glonass in the Russian Federation. Herein, the positioning system using artificial satellites, the artificial satellites for the positioning system, signal waves transmitted from the artificial satellites, and receivers receiving the signal waves will be referred to as GPS, GPS satellites, GPS signals, and GPS receivers, respectively for ease of representation.

The GPS allows the present position of a moving body to be detected highly accurately and almost in real time, and therefore the system is primarily used for measuring the present position of a moving body such as an automobile, an airplane, and a mobile telephone using a receiver provided in the moving body.

Today, GPS receivers suitable for automobiles, in other words, vehicle GPS receivers have rapidly come into widespread use. When such a GPS receiver is provided in an automobile, an antenna device for receiving a GPS signal is provided on the exterior of the automobile such as on the roof.

As shown inFIG. 7, a conventional antenna device100includes an antenna case103having a top cover101and a bottom plate102joined with each other, an antenna module104stored in the top cover101, and a packing member105provided at the joining part between the top cover101and the bottom plate102for keeping the antenna case103tightly sealed, and a signal line106connected to the antenna module104.

The antenna module104includes an antenna element110having an antenna for receiving a GPS signal transmitted from a GPS satellite, and a circuit board111having a circuit for carrying out various kinds of signal processing such as signal amplification to the GPS signal received at the antenna element110. The antenna element110and the circuit board111are joined with each other for example with a length of double-faced adhesive tape.

The circuit board111is connected with a signal line113for extracting the GPS signal to the outside of the antenna case103. The circuit board111is provided with a shield case114for shielding the circuit on its main surface opposite to the side of the antenna element110. The signal line113is externally extended through a notch101aformed in the top cover101, and a gasket115is attached in a position corresponding to the notch101a.

In the antenna device100, the antenna module104and the packing member105are stored in the internal space of the top cover101, while the top cover101and the bottom plate102are integrally joined by securing four screws120.

The bottom plate102has two recesses120a(only one of which is shown inFIG. 7) and a permanent magnet (not shown) is provided in each of the recesses120a. These permanent magnets are provided to fix the GPS receiving antenna100on the roof of the automobile by the magnetic attraction. At the main surface of the bottom plate102facing the outside, a thin aluminum name plate121having the model number and the name of the GPS receiving antenna100and the like inscribed thereon is provided. A transparent resin sheet122to protect the automobile roof against damage is attached over the nameplate121and about on the entire main surface (see Japanese Patent Laid-Open No. 2001-68912).

Now, the conventional antenna100having the structure described above is produced by assembling 16 parts altogether. In recent years, there has been a demand for reduced cost in the field of such GPS receiving antennas, and therefore the number of parts has been reduced or the assembling process has been simplified for the purpose of reducing the product cost.

SUMMARY OF THE INVENTION

The invention has been made in view of the above described circumstances associated with the conventional technique, and it is an object of the invention to provide an antenna device that allows the number of parts to be reduced and the assembling process to be simplified.

An antenna according to the invention is an antenna device receiving a signal transmitted from a satellite and includes an antenna case having a top cover and a bottom plate joined with each other, an antenna module stored in the top cover for receiving the signal, a packing member provided at a joining part between the top cover and the bottom plate for keeping the antenna case tightly sealed, and a signal line connected to the antenna module. The antenna case has a notch positioned at the joining part for externally extending the signal line, and the packing member has a base part covering the entire surface of the antenna module and a gasket part covering the outer periphery of the signal line in the position of the notch. The packing member and the gasket part are integrally formed.

The antenna device as described above according to the invention includes the packing member that has the base part and the gasket part integrally formed. Therefore, as compared to the conventional antenna that keeps the joining part tightly sealed by the two members, the number of parts may be reduced. In addition, in this way, the assembly process may be simplified and the product cost may be reduced.

The antenna device according to the invention includes the packing member having the base part and the gasket part integrally formed, and therefore as compared to the conventional GPS receiving antenna that keeps the joining part tightly sealed by the two members, the number of parts may be reduced. In addition, in this way, the assembly process may be simplified and the product cost may be reduced.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the invention will be described in detail in conjunction with the accompanying drawings. In the following description, an antenna device10shown inFIG. 1will be described as an application of the invention.

As shown inFIG. 1, the GPS receiving antenna device10includes an antenna case13having a top cover11and a bottom plate12joined with each other, an antenna module14stored in the top cover11, a packing member15provided at the joining part between the top cover11and the bottom plate12to keep the antenna case13tightly sealed, and a signal line16connected to the antenna module14.

The antenna module14has an antenna element20having an antenna receiving a GPS signal transmitted from a GPS satellite, a circuit board21for carrying out various kinds of signal processing including signal amplification to the GPS signal received by the antenna element20. The antenna element20and the circuit board21are joined by a length of double-faced adhesive tape22or the like.

The circuit board21is connected with the signal line16used to extract GPS signals to the outside of the antenna case13. The circuit board21is provided with a shield case24at its main surface opposite to the side of the antenna element20for shielding the circuit. The signal line16is externally extended through a notch11aformed in the top cover11.

In the antenna device10, while the antenna module14and the packing member15are stored in the internal space of the top cover11, the top cover11and the bottom plate12are engaged with each other to be integrally joined. The packing member15is for example made of a resin material such as EPDM rubber and includes a base part15acovering the entire surface of the antenna module14and a gasket part15bcovering the outer periphery of the signal line16in the position of the notch11aformed in the top cover11as shown inFIG. 2. The base part15ahas a recess15fthat positions the antenna module14and has an outer shape that substantially covers the entire bottom surface of the antenna module14.

The packing member15is held between the top cover11and the bottom plate12as they are joined and keeps them tightly sealed at the joining part. The gasket part15bis formed as it is raised upright from the base part15ain the position corresponding to the notch11aof the top cover11and has a hole15din the center through which the signal line16is inserted. The gasket part15ais provided with a notch15cto divide the gasket part15bin the direction from about the upper center of the gasket part15bto the base part15a.

The signal line16is inserted from the notch15cto the hole15dof the gasket part15b. An extended recess15eabuts against the lower side of the signal line to form a waterproof structure and is exposed to the outside from the notch11ain the top cover11to form a part of the surface of the antenna main body. Protrusions15gare provided at the lower surface of the base part15aand exposed from the bottom surface of the antenna main body through the bottom plate12and a resin sheet31. The protrusions15gserve to prevent the antenna main body from slipping when the antenna main body is placed on the roof of the automobile.

As shown inFIG. 3, the top cover11has a storing part11dsurrounded by a wall part11eto store the box-shaped antenna module14. In the storing part11d,projecting members11babutting against the antenna module are provided in four locations at the inner wall of the top of the top cover11and integrally with the inner wall of the top cover11. The four locations are close to the four corners of the antenna element20.

In a gasket receiving part11c,a part of a wall part11eand a wall part11fare arranged in two rows in the direction of the length of the signal line16, and the circular projections15hof the gasket part15bare inserted into a groove11idefined by the wall parts11eand11fand the outer wall surface of the top cover11.

As shown inFIG. 4, a single recess12ais formed in the center of the bottom plate12, and a permanent magnet30is provided in the recess12a.The permanent magnet30is provided to securely fix the antenna device10to the roof of the automobile by the magnetic attraction. The protrusion15gof the packing member15is inserted to a hole12b.The resin sheet31to protect the roof of the automobile against damages is provided on the main surface of the bottom plate12facing the outer side substantially along the entire surface. The resin sheet31has the model number, name and the like of the antenna device10printed thereon.

The antenna device10having the above-described structure is made of ten parts altogether.

Herein, the top cover11is provided with engagement parts40having a shape as shown inFIGS. 3 and 5in four locations at the edge on the side to be joined with the bottom plate12. The bottom plate12is provided with claws50having a shape as shown inFIGS. 3 and 6in positions corresponding to the positions of the engagement parts40in the top cover11.

As shown inFIGS. 3 and 5, the engagement part40has a shape corresponding to the outer shape of the claw50formed at the bottom plate12and is made of a recess40adepressed from the inner wall surface of the top cover11in the same thickness and length as those of the claws50and an engagement member40bhaving a raised shape with an inclined part40cabout in the center of the recess40a.

As shown inFIGS. 4 and 6, the claw50projects outwardly from the edge of the bottom plate12by a prescribed thickness and has an upright part50aformed integrally from the bottom plate12to stand upright. In the center of the upright part50a,a hole50blarge enough for the engagement member40bof the engagement part40to engage is formed.

In the antenna device10, the engagement parts40and the claws50having the above-described structure form a fitting part that joins the top cover11and the bottom plate12. More specifically, the top cover11and the bottom plate12are joined with each other as the upright part50aof the claw50is fitted into the recess40aof the engagement part40while the engagement member40bis engaged with the hole50b. The engagement member40bhas the inclined part40c, and therefore the engagement part40and the claw50can easily be engaged. In the GPS receiving antenna10, while the top cover11and the bottom plate12are joined, the packing member15is slightly compressed by the top cover11and the bottom plate12. Therefore, the compressed packing member15generates force to urge the top cover11and the bottom plate12away from each other. In this way, in the antenna device10, the top cover11and the bottom plate12can surely be fitted with each other.

During the assembly of the antenna device10, the signal line16is pressed into the gasket part15bfrom the notch15cfor inserting the signal line16to the upper part of the gasket part15b,and the antenna module14and the packing member15are stored in the top cover11. At the time, the signal line16is externally extended from the notch11a,and the bottom plate12is fitted with the top cover11in this state. Then, the permanent magnet30is fitted into the recess12aof the bottom plate12, and the resin sheet31is attached to the bottom plate12. In this way, the antenna device10is completed. The notch15celiminates the necessity of inserting the signal line16into the hole of the gasket part15b,which can further improve the productivity.

In the antenna device10as described above, the fitting parts are fitted so that the top cover11and the bottom plate12are joined with each other. Therefore, as compared to the conventional antenna device having the top cover and the bottom plate joined by securing a number of screws, the number of parts can be reduced. In this way, the assembly process can be simplified, so that the product cost can be reduced. Since the screws for joining are not necessary, a boss part and a rib part to secure the screws are not necessary in the antenna case, and the space for the boss part and the rib part can be saved to reduce the size of the device as a whole.

Note that in the foregoing, the top cover11and the bottom plate12are provided with the four engagement parts40and the four claws50, respectively by way of illustration, but an arbitrary number of such fitting parts40,50may be provided. As long as sufficient joining strength is provided, for example only two pairs of fitting parts40,50may be provided.

In the foregoing description, the top cover11and the bottom plate12are provided with the engagement parts40and the claws50, respectively by way of illustration, but the top cover11may be provided with a part in a shape corresponding to the claw50, and the bottom plate12may be provided with a part in a shape corresponding to the engagement part40.

The GPS receiving antenna10in the above-described structure includes the packing member15having the integrally formed base part15aand gasket part15b.Therefore, as compared to the conventional GPS receiving antenna that keeps the joining part tightly sealed by the two members, the number of parts may be reduced. In addition, in this way, the assembly process may be simplified and the operability may be improved, so that the product cost may be reduced.