Antenna device

Abstract

To provide an antenna apparatus capable of reducing abnormal noise generated due to collision between an antenna element and a case (enclosure) without increasing the time required, cost, and weight.SOLUTION: An antenna apparatus includes: one or two or more antenna elements 11A, 11B; an enclosure 20 having a wall body 22 mounted thereon with the antenna elements jointed on an inner surface; and a printed board with the antenna elements mounted by connecting leg parts of the antenna elements to one surface, the printed board being stored inside the enclosure 20. On the inner surface of the wall body of the enclosure, a plurality of presser pieces 23a-23h for holding the antenna elements with the wall body of the enclosure are formed at predetermined intervals. In each of the plurality of presser pieces, a size and an interval are set so that a difference in amount of deflection between the wall body and the antenna element when the enclosure vibrates is equal to or smaller than a predetermined value (e.g., 0.01 mm).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an antenna device having an antenna element mounted on a printed circuit board, and relates to a technique that is effective when applied to, for example, an antenna device mounted on a vehicle. [Background technology]

[0002] Since antenna devices that are installed in vehicles and transmit and receive wireless communication signals in a specified frequency band are required to be small, devices that mount an antenna element on a printed circuit board or base plate on which electronic components such as amplifiers and filters are mounted have been put into practical use. Meanwhile, in the automotive field, the number of cars with quieter engine noise has been increasing in recent years due to the shift to hybrid and electric vehicles, and measures to reduce abnormal noise generated by products are urgently needed to maintain a comfortable interior space in the vehicle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 7-29920 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventionally, in vehicle-mounted antenna devices, the antenna element has been fixed to the case mainly by using fixing parts such as double-sided tape or screws. On the other hand, there are also methods that do not use fixing parts, such as adhesive bonding or heat welding, but in any case, from the viewpoint of the effects of contraction / expansion due to the ambient temperature environment, the precision of the parts, and the deflection of the parts due to vibration, the antenna element has been fixed to the case by the above method after taking noise reduction measures such as applying sound-absorbing tape to the antenna element.

[0005] Furthermore, fixing methods using adhesives or heat welding require time for hardening and cooling after the process, which lengthens the time required to complete the product. Furthermore, adhesives have the problem of their adhesive strength deteriorating due to environmental changes, and fixing methods that use heat, such as heat welding, cannot be used on cases made of thermosetting resin, which limits the material options available. On the other hand, to address the abnormal noise that occurs when parts collide with each other due to deflection of parts caused by vibration, measures such as changing to a more rigid material or making the parts thicker in order to increase their rigidity may be taken, but in such cases there are issues such as increased part costs and increased product weight.

[0006] Incidentally, Patent Document 1 describes a device for avoiding a decrease in adhesive strength due to aging in a method of fixing an antenna element with double-sided tape. The device in Patent Document 1 is configured such that four support parts (support pieces) that contact the sides of the rectangular antenna element are provided on the power supply board, and the antenna element is fixed and supported from the outside by elastic force. According to this device, although lateral vibration of the antenna element can be suppressed, it is difficult to suppress vertical vibration with only the four support parts, and it is not possible to sufficiently prevent the antenna element from hitting the power supply board and generating abnormal noise.

[0007] This invention has been made with an eye on the above-mentioned problems, and its purpose is to provide an antenna device that can reduce abnormal noise caused by the antenna element hitting the case (housing) without increasing the time required to complete the product, increasing costs, or increasing weight. Another object of the present invention is to provide an antenna device that allows for a wider range of options for case materials. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides An antenna device comprising: one or more antenna elements; a housing having a wall on which the antenna elements are attached with the walls joined to the inner surface; and a printed circuit board on one surface of which the legs of the antenna elements are connected, the printed circuit board being mounted, the printed circuit board being housed inside the housing; a plurality of pressing pieces are formed on the inner surface of the wall of the housing at predetermined intervals to sandwich the antenna element between the wall and the housing; The size of each of the multiple pressure pieces and the spacing between them are set so that the difference between the amount of deflection of the wall body and the amount of deflection of the antenna element when the housing vibrates is less than a predetermined value (e.g., 0.01 mm).

[0009] With an antenna device having the above-described configuration, even if a gap occurs between the antenna element and the wall of the housing (case) and they collide with each other, no abnormal noise will be generated, or even if a noise is generated, it can be reduced to a very small level that cannot be heard. Furthermore, since the antenna element is fixed to the case by sandwiching it between the wall and the retaining piece that is integral with the wall of the housing (case), there is no need for any fixing parts. This does not lead to an increase in cost or weight, and since adhesives or heat welding are not used, the time required to complete the product can be shortened. Another advantage is that since heat welding is not used, there is a wider range of case material options available. [Effects of the Invention]

[0010] The antenna device according to the present invention can reduce noise caused by the antenna element hitting the case without increasing the time required to complete the product, costs, or weight, and also has the effect of broadening the options for case materials. [Brief explanation of the drawings]

[0011] [Figure 1]1A is a perspective view showing a main part (a case in which an antenna element is mounted) of an embodiment of an antenna device to which the present invention is applied, and FIG. 1B is a cross-sectional view showing the cross-sectional structure taken along line BB in FIG. 1A. [Figure 2] 10 is a graph showing the amount of gap (amount of deflection of antenna element-amount of deflection of case wall) between the antenna element and the wall of the case when the interval between the pressing pieces is changed in the antenna device of the embodiment. [Figure 3] FIG. 2 is a perspective view showing the antenna device of the embodiment with the case removed. [Figure 4] 4 is a cross-sectional view of the antenna device showing a cross-sectional structure taken along line IV-IV in FIG. 3. [Figure 5] 1A is a bottom view showing the state in which the case and the ground substrate are joined together, and FIG. 1B is a perspective view showing the state in which the case and the ground substrate are joined together. [Figure 6] FIG. 10 is a perspective view showing a modified example of the antenna device of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Fig. 1(A) shows a perspective view of the main part of an embodiment of an antenna device according to the present invention. In the following description, the upper left side of the antenna device shown in Fig. 1(A) will be referred to as the front end side, and the lower right side will be referred to as the rear end side. The antenna device of this embodiment is composed of a case (housing) with one open side, a circuit board on which a pair of antenna elements are mounted and housed within the case, and a flat bracket joined to the open side of the case to close the opening. Figure 1(A) shows a perspective view of the internal configuration of case 20. Figure 1(B) shows a cross-sectional structure taken along line BB in Figure 1(A).

[0013] As shown in FIG. 1(A), the case 20 is made of synthetic resin and has a frame body 21 that forms a rectangular recess, and a wall body 22 that is formed integrally with the frame body 21 and covers one of the openings, and a bulge portion 21a is formed on one side of the frame body 21 to correspond to the connector described below. The inner surface of the wall 22 is formed with a plurality of pressing pieces 23 that constitute fixing means with a snap-fit ​​structure for fixing the pair of antenna elements 11A, 11B made of conductive metal plates inside the case.

[0014] Although not particularly limited, in the antenna device of this embodiment, the two antenna elements 11A and 11B have symmetrical shapes and are formed to receive signals (radio waves) in the same frequency band. Each of the antenna elements 11A and 11B is made of a plate-like member and includes a horizontal portion 11a parallel to a circuit board (described later), a vertical portion 11b bent upward from one side of the horizontal portion 11a, a folded portion 11c bent 90 degrees backward from the vertical portion 11b, and a leg portion 11d bent downward from the folded portion 11c. The horizontal portion 11a is attached to the inner surface of the wall body 22 at a predetermined interval so as to be in contact with the wall body 22.

[0015] As shown in Fig. 1(B), the plurality of (e.g., six) pressing pieces 23a to 23f for fixing the antenna element 11B to the inner surface of the wall body 22 have a cross-sectional shape consisting of horizontal portions and leg portions so as to have a predetermined distance from the inner surface of the wall body 22 to form a gap into which the antenna element 11B is inserted. As shown in Fig. 1(A), the pressing pieces 23a to 23f are all formed to face the same direction (diagonally downward and left in the figure). The same number (six) of pressing pieces 23g, 23h, etc. for fixing the antenna element 11A to the inner surface of the wall body 22 are also provided with the same shape as the pressing pieces 23a to 23f, and are formed in positions symmetrical to the pressing pieces 23a to 23f across the center line of the case 20, so as to face the opposite direction (diagonally upward and right).

[0016] As described above, by forming the pressing pieces 23a to 23f to face in the same direction, during assembly, antenna element 11B is first joined to the inner surface of wall 22, and then slid along the surface, so that it can be press-fitted into the gaps between pressing pieces 23a to 23f and the inner surface of wall 22 and attached to a predetermined position on the inner surface of case 20. The original gaps between pressing pieces 23a to 23f and the inner surface of wall 22 are set to be slightly narrower than the plate thickness of antenna element 11B, and in the inserted state, the elastic restoring force of pressing pieces 23a to 23f presses and fixes antenna element 11B.

[0017] In the antenna device of this embodiment, an opening 11w is formed on the base side of the horizontal portion 11a of the antenna element 11B corresponding to one (23d) of the pressing pieces 23a to 23f, and pressing piece 23e is inserted into this opening 11w so that pressing piece 23e presses and fixes the edge of opening 11w. By providing opening 11w and pressing piece 23e in this way, it is possible to prevent the base of antenna element 11B from locally lifting up from the inner surface of wall 22 of case 20, and to prevent a gap from occurring.

[0018] Furthermore, in the antenna device of this embodiment, in order to suppress abnormal noise caused by contact between the antenna elements and the case due to bending of the antenna elements 11A and 11B fixed to the case 20, the thickness, width, length and spacing of the pressing pieces 23a to 23f are set taking into account the elastic modulus of the material of the case 20 so that the difference in the amount of bending between the wall 22 of the case 20 and the antenna elements 11A and 11B when the case vibrates is 0.01 mm or less.

[0019] Here, the reason why the difference in the amount of deflection between wall 22 of case 20 and antenna elements 11A and 11B when the case vibrates is set to 0.01 mm or less will be explained. In an antenna device configured as shown in Figure 1, when the case vibrates, the case and antenna element bend, but because the amount of bending differs, abnormal noise occurs when the case and antenna element come into contact. To prevent abnormal noise, the case and antenna element must either A. always be separated even when acceleration is applied, or B. always be in contact with each other, and the amount of bending continues to match even when acceleration is applied.

[0020] However, from the perspective of antenna performance, it is difficult to create a situation where the antennas are always free from contact under condition A. Under condition B, although different amounts of deflection occur due to the differences in the materials and thicknesses of the antennas, preliminary studies by the inventors revealed that, even if a gap occurs and the antennas collide with each other, no abnormal noise will be generated, or even if a noise is generated, it will be so quiet that it is inaudible.

[0021] In preliminary studies, the gap size (threshold value) at which it was determined that no abnormal noise would occur was 0.01 mm. The inventors then conducted a simulation to verify the relationship between the spacing between pressing pieces 23a, 23b, and 23c and the difference (gap size) between the case and the amount of deflection of the antenna element when the case 20 was made of polycarbonate ABS resin and the pressing pieces 23a to 23c were 1 mm thick, 6 mm wide, and 5 mm long for an antenna element with a thickness of 0.6 mm and a length of 49.4 mm.

[0022] As a result, the results shown in FIG. 2 were obtained. From FIG. 2, it was confirmed that the gap could be suppressed to the threshold value of 0.01 mm or less by setting the spacing between the pressure pieces 23a, 23b, and 23c to 20 mm or less. Therefore, with the antenna device of this embodiment described above, it is possible to suppress the abnormal noise caused by the antenna element hitting the case wall to an inaudible level. Note that the size of the pressure pieces 23 in this embodiment is not limited to the above dimensions, and the size and spacing of the pressure pieces 23 are set so as to suppress the gap between the antenna element and the case to 0.01 mm or less. Furthermore, the material of the case 20 is not limited to polycarbonate ABS resin.

[0023] 1 does not show all the components of the antenna device, and antenna elements 11A and 11B in Fig. 1 are mounted on a circuit board and housed in case 20, and a bracket is further attached to cover the opening of case 20 to form a finished product. The overall configuration of the antenna device will be described below with reference to Figs. 3 and 4. 3, antenna device 10 of this embodiment includes two antenna elements 11A and 11B, circuit board 12 on which antenna elements 11A and 11B are mounted, and flat bracket 13 made of conductive metal that is disposed below circuit board 12 and connected to the underside of circuit board 12 with bolts, and a ground potential is applied to bracket 13, so that bracket 13 functions as a ground board. Note that bracket 13 is rectangular and slightly larger than circuit board 12, and also functions as a housing that protects the underside of circuit board 12.

[0024] Although not particularly limited, in the antenna device 10 of this embodiment, the two antenna elements 11A and 11B have symmetrical shapes and are formed to receive signals (radio waves) in the same frequency band. Each of the antenna elements 11A and 11B is formed into a hook shape with a horizontal portion 11a parallel to the circuit board 12, a vertical portion 11b hanging down from one side of the horizontal portion 11a toward the circuit board 12, a folded portion 11c bent 90 degrees backward from the vertical portion 11b, and a leg portion 11d bent downward from the folded portion 11c, and are arranged at a predetermined interval.

[0025] Furthermore, a plurality of (for example, two) engaging protrusions 11e are provided at the lower ends of the leg portions 11d of the antenna elements 11A and 11B, and these engaging protrusions 11e engage with slit-shaped engaging holes formed in predetermined portions of the circuit board 12, thereby connecting the antenna elements 11A and 11B to the circuit board 12. The two engaging protrusions 11e are connected to the circuit board 12 by soldering, and of the two engaging protrusions 11e, the engaging protrusion 11e located on the lateral side of the board is adhered to the circuit board 12 by soldering, and is electrically connected to a slit top line for power supply formed to electrically connect that portion with a terminal of the connector, and is configured to serve as a power supply point for the antenna elements 11A and 11B.

[0026] The circuit board 12 is a printed circuit board having a wiring pattern made of conductive layers, and although not shown, electronic components constituting a distributor, amplifier, filter, attenuator, etc. are mounted on the circuit board 12. A spring contact 14 made of a conductive leaf spring that protrudes downward and is Z-shaped when viewed from behind is fixed to the underside of the circuit board 12 near the vertical portions 11b of the antenna elements 11A and 11B. Specifically, the spring contact 14 has an upper horizontal piece, an inclined piece that protrudes diagonally downward from the end of the upper horizontal piece, and a lower horizontal piece that folds back horizontally from the inclined piece, and the upper horizontal piece is connected to the underside of the circuit board 12. The shape of the spring contact 14 is not limited to the Z-shape.

[0027] A connector 15 is provided on the edge of the underside of circuit board 12 on the antenna element coupling side, into which an end of a coaxial cable (hereinafter simply referred to as cable) connected to a device called a head unit having a tuner or the like is inserted from below to connect. Connector 15 has a plurality of locking pieces 15a formed on both sides of its upper surface, each of which protrudes upward and has a claw at its tip, and these locking pieces 15a are inserted into engaging holes formed in predetermined parts of circuit board 12, thereby connecting to circuit board 12. Circuit board 12 is also formed with a linear wiring pattern (strip line) that connects terminals to which inner cable conductors of connector 15 are connected and the feeding points of antenna elements 11A and 11B.

[0028] Furthermore, a conductive layer is formed over most of the area of ​​the circuit board 12, including the installation position of the spring contact 14, excluding the wiring pattern (strip line) that electrically connects the electronic components together and between the electronic components and the connector. The spring contact 14 is connected to the circuit board 12 while being electrically connected to this conductive layer, and the height is set so that the lower horizontal piece at the lower end of the inclined piece of the spring contact 14 is joined to the bracket 13, as shown in FIG.

[0029] As described above, by connecting the spring contact 14 to the bracket 13 at the ground potential, the ground potential is applied to the conductive layer of the circuit board 12. In other words, the spring contact 14 serves as the ground point of the circuit board 12. On the other hand, openings 13a are formed in bracket 13 at locations corresponding to connector 15, and connector 15 is inserted into openings 13a. In addition, base portions 13b are formed at multiple locations (four locations in the figure) on bracket 13 by cutting out and bending a portion of bracket 13 into a "U" shape when viewed from the front.

[0030] The lower surface of the circuit board 12 is joined to the upper surfaces of the four pedestal portions 13b, and as shown in Fig. 5(A), screws 16 are inserted into screw insertion holes 12b formed in corresponding portions of the upper horizontal pieces of the pedestal portions 13b and the circuit board 12, and screwed into boss portions 24 (see Fig. 1) provided on the inside of the case 20, thereby integrating the case 20, the circuit board 12, and the bracket 13 into a completed product. Fig. 5(B) shows the antenna device in the completed state of Fig. 5(A).

[0031] In the antenna device configured as shown in Fig. 3, the distance between antenna elements 11A, 11B and circuit board 12 affects the receiving sensitivity of the antenna, so a larger distance is preferable. However, the distance between circuit board 12 and bracket 13 does not affect the receiving sensitivity of the antenna, so it is possible to eliminate base 13b and connect the bottom surface of circuit board 12 to the top surface of bracket 13. Nevertheless, base 13b is provided on bracket 13 as described above because it is difficult to sufficiently reduce the height of connector 15 used, and the amount of protrusion of connector 15 from the bottom surface of the case that houses the entire antenna device shown in Fig. 1 is regulated by user specifications. Therefore, depending on the conditions, it is possible not to provide base 13b on bracket 13.

[0032] Furthermore, the conductive layer in the circuit board 12 extends around the screw insertion holes 12b of the circuit board 12 that correspond to two of the four pedestal portions 13b located on the left and right of the connector 15. As a result, when the circuit board 12 and the bracket 13 are joined by inserting conductive screws into the screw insertion holes 12b of the circuit board 12 that correspond to the screw insertion holes of the pedestal portions, the circuit board 12 and the bracket 13 are electrically connected via the screws.

[0033] On the other hand, the conductive layer does not extend around the screw insertion holes 12b of the circuit board 12 that correspond to two of the four pedestal portions 13b that are located farther from the connector 15. In other words, the application of the ground potential to the conductive layer of the circuit board 12 is limited to the spring contact 14 and the two pedestal portions 13b located on the left and right of the connector 15. This is because in the antenna device of this embodiment, portions of the antenna elements 11A and 11B are located above the two base portions located farther from the connector 15, and if the conductive layer of the circuit board 12 is extended to this portion, the distance between the antenna elements 11A and 11B and the conductive layer becomes small, resulting in a decrease in receiving sensitivity.

[0034] In contrast, since there are no antenna elements 11A, 11B above the two base portions 13b located on the left and right of the connector 15, there is no decrease in reception sensitivity even when the conductive layer of the circuit board 12 is connected to the bracket 13. Therefore, it is possible to connect to the ground potential even at the two base portions located on the left and right of the connector 15. However, since the application of the ground potential is insufficient with this connection, in this embodiment, a separate spring contact 14 is provided to avoid the situation where the application of the ground potential is insufficient.

[0035] Note that, instead of the elastically deformable spring contacts 14, a non-elastically deformable member such as a screw may be used to connect the conductive layer of the circuit board 12 to the connector 15, and the spring contacts 14 and the screws are not limited to being made of metal, but may be made of a conductive material other than metal, such as resin. Furthermore, the antenna device 10 of this embodiment is provided with two antenna elements 11A and 11B that receive signals (radio waves) in the same frequency band, but the antenna elements 11A and 11B may be configured to receive signals (radio waves) in different frequency bands by changing their lengths.

[0036] In the antenna device of the embodiment shown in Fig. 1, the antenna elements 11A and 11B are mounted to the case 20 by sliding the antenna elements 11A and 11B from the center side to the side, respectively, and press-fitting the antenna elements 11A and 11B into the gaps between the retaining pieces 23a to 23f and the inner surface of the case 20. However, the present invention is not limited to this. For example, as shown in Fig. 6, the antenna element 11B may be mounted by sliding it from the center side to the side (Y direction) and then sliding it forward (X direction) to insert it into the gaps between the retaining pieces 23a to 23f and the inner surface of the case 20. In this configuration, the retaining pieces 23e of the retaining pieces 23a to 23f may be formed so that their orientation is changed by 90 degrees from the other retaining pieces and faces backward. The same applies to the other antenna element 11A.

[0037] Although the invention made by the present inventor has been specifically described above based on the embodiments, the present invention is not limited to the above embodiments. For example, in the above embodiments, the connection between the ground point of circuit board 12 and bracket 13 is made by means of physical contact such as a spring contact, but the ground point does not need to be in physical contact as long as it is connected at high frequency by, for example, a structure in which opposing electrodes or metal layers face each other and behave like a capacitor.

[0038] In addition, in the above embodiment, two antenna elements 11A and 11B are mounted on circuit board 12, but the number of antenna elements is not limited to two and may be one or three or more. The shape of the antenna element is also not limited to that shown in Fig. 1, and the present invention can be applied to an antenna device in which antenna elements having other shapes are mounted on a circuit board. [Explanation of symbols]

[0039] 10...antenna device, 11A, 11B...antenna element, 12...circuit board (printed circuit board), 12b...screw insertion hole, 13...bracket (ground board), 13b...base portion, 14...spring contact (ground point), 15...cable connector, 16...fastening screw, 20...case (housing), 21...frame body, 22...wall body, 23...pressing piece, 24...boss portion

Claims

1. An antenna device comprising: one or more antenna elements; a housing having a wall body to which the antenna elements are attached with the wall body being joined to the inner surface; and a printed circuit board on one surface of which the antenna elements are mounted by connecting legs of the antenna elements, the printed circuit board being housed inside the housing; a plurality of pressing pieces are formed on the inner surface of the wall of the housing at predetermined intervals to sandwich the antenna element between the wall and the housing; An antenna device characterized in that the size and spacing of the multiple pressure pieces are set so that the difference between the amount of deflection of the wall body and the amount of deflection of the antenna element when the housing vibrates is less than a predetermined value.

2. The antenna device according to claim 1, characterized in that an opening through which the pressing piece can be inserted is formed in the antenna element, and one of the plurality of pressing pieces is configured to clamp the edge of the opening between the wall body.

3. 3. The antenna device according to claim 1, wherein the plurality of pressing pieces provided corresponding to one of the antenna elements are formed so as to face in the same direction.

4. a ground substrate that is disposed on a surface of the printed circuit board opposite to the one surface thereof and is spaced apart from the printed circuit board at a predetermined distance and to which a ground potential is applied; 2. The antenna device according to claim 1, wherein the ground substrate is connected to the opening side of the housing with a plurality of screws, thereby storing the printed circuit board inside the housing.

5. 5. The antenna device according to claim 4, wherein one end of a spring contact made of a conductive leaf spring is connected to a grounding point on a surface of the printed circuit board facing the ground board, and the other end of the spring contact is connected to a portion of the ground board facing the printed circuit board.

6. 2. The antenna device according to claim 1, wherein the predetermined value is 0.01 mm.

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