Abstract:
An antenna is adapted to be mounted on a vehicle body. An antenna base is formed with a first through hole. A first fixing screw is provided with a thread portion adapted to be inserted into a second through hole formed in the vehicle body via the first through hole, and a head portion continued from the thread portion and having a size larger than the second through hole. A receptacle is provided on the antenna base and receiving the head portion such that an axis of the first fixing screw is swingable relative to the vehicle body A nut is adapted to be fitted with the thread portion so as to clamp the vehicle body together with the head portion.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a structure suitable for mounting an antenna base to a vehicle body having a curved surface.  
         [0002]     As shown in Japanese Patent Publication Nos. 8-335824A and 8-237014A, in a conventional attaching structure for mounting an antenna to a vehicle body, a single fixing screw is arranged so as to protrude downward from an antenna base. Then, the fixing screw is inserted into a hole drilled in a vehicle body, while a nut is engaged from the back side. Thus, the vehicle body is clamped between the antenna base and the nut, so that the antenna base is fixed to the vehicle body.  
         [0003]     The above-mentioned conventional structure does not have a specific problem as long as the size of the antenna base is not very large and a single fixing screw suffices for fixing the antenna base reliably. However, popularization of car-installed communication equipments with composite construction in recent years leads to, in turn, necessity of the suitable antenna with composite construction, and hence increase of the size of the antenna base for mounting the antenna to the vehicle body is unavoidable. In this case, fixing the antenna base with a single fixing screw may be unstable in view of mechanical intensity. Thus, plural fixing screws are necessary for reliably fixing the antenna base to the vehicle body.  
         [0004]      FIG. 13  shows such a structure in which two fixing screws  16  are integrally arranged so as to protrude downward in an antenna base  12  having a relatively large size. In this structure, the two fixing screws  16  integrally provided with the antenna base  12  are inserted into holes  22  drilled in a vehicle body  20 , while nuts  32  are engaged with the fixing screws  16  respectively from the back side. Further, a pad  26  having elasticity is inserted between the antenna base  12  and the vehicle body  20 . Thus, when the nuts  32  are tightened, the antenna base  12  is reliably fixed to the vehicle body  20 , while the pad  26  prevents rain water from entering into the vehicle body through the holes  22 . Here, in  FIG. 13 , numeral  10  indicates an antenna case in a bottom face part of which the antenna base  12  is arranged appropriately. Numeral  14  indicates a rod-shaped antenna element a pedestal end of which is fixed to the antenna case  10 . Numeral  28  indicates a washer inserted between the vehicle body  20  and the nut  32 .  
         [0005]     In recent years, the vehicle body  20  is formed with a combination of complicated curved surfaces for the purpose of good appearance. Thus, there will be no problem, if the bottom surface of the antenna base  12  had a shape corresponding to the curved surface of the attached portion of the vehicle body  20 . However, when the bottom surface of the antenna base  12  would not agree with the shape of the vehicle body  20 , the tightening of the nuts  32  could generate deformation in the vehicle body  20  so as to follow the shape of the bottom surface of the antenna base  12 .  
         [0006]     Here, it should be noted that even in the conventional structure where a single fixing screw is arranged and protruded and where the bottom surface of the antenna base is a curved surface in agreement with the curved surface of the vehicle body, the tightening of the nut could similarly generate deformation in the vehicle body if the antenna base would deviate from an appropriate attached portion, so that the bottom surface of the antenna base would not agree with the curved surface of the vehicle body.  
       SUMMARY OF THE INVENTION  
       [0007]     It is therefore object of the invention to provide a structure that allows an antenna base to be mounted on a vehicle body without generating the above-mentioned deformation in the vehicle body.  
         [0008]     In order to achieve the above object, according to the invention, there is provided an antenna adapted to be mounted on a vehicle body, comprising:  
         [0009]     an antenna base, formed with a first through hole;  
         [0010]     a first fixing screw, comprising a first thread portion adapted to be inserted into a second through hole formed in the vehicle body via the first through hole, and a first head portion continued from the first thread portion and having a size larger than the second through hole;  
         [0011]     a receptacle, provided on the antenna base and receiving the first head portion such that an axis of the first fixing screw is swingable relative to the vehicle body; and  
         [0012]     a first nut, adapted to be fitted with the first thread portion so as to clamp the vehicle body together with the first head portion.  
         [0013]     With this configuration, the first fixing screw swings in accordance with the curved surface of the vehicle body, and thereby reduces deformation in the vehicle body in comparison with a conventional example where a fixed fixing screw is solely used.  
         [0014]     The antenna may further comprise:  
         [0015]     a second fixing screw integrally provided on the antenna base, the second fixing screw comprising a second thread portion adapted to be inserted into a third through hole formed in the vehicle body, and a second head portion continued from the second thread portion and having a size larger than the third through hole; and  
         [0016]     a second nut, adapted to be fitted with the second thread portion so as to clamp the vehicle body together with the second head portion.  
         [0017]     In this case, the first fixing screw is swingable under a condition that the antenna base is provisionally fixed on the vehicle body by the second fixing screw and the second nut.  
         [0018]     The antenna may further comprise an elastic pad disposed between the antenna base and the vehicle body.  
         [0019]     In this case, the pad can absorb variation in the gap dimension between the antenna base and the vehicle body.  
         [0020]     A size of the first through hole may be smaller than the size of the first head portion so that the receptacle has a receiving face brought into contact with a lower face of the first head portion.  
         [0021]     In this case, the fixing screw can be prevented from escaping toward the vehicle body with a simple structure.  
         [0022]     Here, at least one of the receiving face and the lower face of the first head portion may be rounded.  
         [0023]     In this case, the swing movement of the first fixing screw can be smoothened.  
         [0024]     The antenna may further comprise an elastic spacer disposed between the receptacle and the first head portion.  
         [0025]     In this case, the gap between the first head portion and the receptacle can be reduced. This allows the antenna base to be fixed stably to a vehicle body.  
         [0026]     A direction that the first fixing screw is swingable may be so restricted as to be a longitudinal direction of the antenna base.  
         [0027]     Here, the first head portion may be provided with a shaft member extending in a direction perpendicular to the longitudinal direction of the antenna base, and the receptacle may be formed with a groove receiving the shaft member.  
         [0028]     Alternatively, a protrusion may be formed on the antenna base so as to extend in a direction perpendicular to the longitudinal direction of the antenna base, and the first head portion may be formed with a groove receiving the protrusion.  
         [0029]     In this case, the deformation in the vehicle body which tends to be large in the longitudinal direction of the antenna base can be effectively reduced.  
         [0030]     The antenna may further comprise a retainer provided on the antenna base so as to hang over the first head portion to prevent the first fixing screw from escaping in a direction being away from the vehicle body. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0031]     The above objects and advantages of the present invention will become more apparent by describing in detail preferred exemplary embodiments thereof with reference to the accompanying drawings, wherein:  
         [0032]      FIG. 1  is a side section view of a structure for mounting an antenna base on a vehicle body, according to a first embodiment of the invention;  
         [0033]      FIG. 2A  is a top view of the antenna base of  FIG. 1 ;  
         [0034]      FIG. 2B  is a side view of the antenna base of  FIG. 2A ;  
         [0035]      FIG. 2C  is a section view taken along a line IIC-IIC in  FIG. 2A ;  
         [0036]      FIG. 3A  is a top view of a swingable fixing screw in the mounting structure of  FIG. 1 ;  
         [0037]      FIG. 3B  is a side view of the swingable fixing screw of  FIG. 3A ;  
         [0038]      FIG. 3C  is a bottom view of the swingable fixing screw of  FIG. 3A ;  
         [0039]      FIG. 4  is a side view for explaining how to retain the swingable fixing screw in the antenna base;  
         [0040]      FIG. 5A  is a side section view of a pad in the mounting structure of  FIG. 1 ;  
         [0041]      FIG. 5B  is a bottom view of the pad of  FIG. 5A ;  
         [0042]      FIG. 6  is an enlarged side section view of a swingable fixing screw in a mounting structure according to a second embodiment of the invention;  
         [0043]      FIG. 7  is a side section view of a mounting structure according to a third embodiment of the invention;  
         [0044]      FIG. 8  is a side section view of a mounting structure according to a fourth embodiment of the invention;  
         [0045]      FIG. 9A  is a top view of a swingable fixing screw in a mounting structure according to a fifth embodiment of the invention;  
         [0046]      FIG. 9B  is a partially sectional side view of the mounting structure of  FIG. 9A ;  
         [0047]      FIG. 9C  is a section view taken along a line IXC-IXC in  FIG. 9B ;  
         [0048]      FIG. 10A  is a top view of a swingable fixing screw in a mounting structure according to a sixth embodiment of the invention;  
         [0049]      FIG. 10B  is a partially sectional side view of the mounting structure of  FIG. 10A ;  
         [0050]      FIG. 10C  is a section view taken along a line XC-XC in  FIG. 10B ;  
         [0051]      FIG. 11A  is a top view of a mounting structure according to a seventh embodiment of the invention;  
         [0052]      FIG. 11B  is a partially sectional side view of the mounting structure of  FIG. 11A ;  
         [0053]      FIG. 12A  is a top view of a mounting structure according to an eighth embodiment of the invention;  
         [0054]      FIG. 12B  is a partially sectional side view of the mounting structure of  FIG. 12A ; and  
         [0055]      FIG. 13  is a side section view of a conventional mounting structure. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0056]     A first embodiment of the invention will be described below in detail with reference to  FIGS. 1 through 5 B.  
         [0057]     In  FIG. 1 , a metallic antenna base  12  is arranged appropriately in a bottom face part of an antenna case  10 . A pedestal end of a rod-shaped antenna element  14  is fixed to the antenna case  10 . The antenna case  10  accommodates a GPS antenna and other planar antennas as well as appropriate electrical circuits, which are not shown. Two fixing screws  16  and  18  are arranged so as to protrude downwardly at front and rear positions, respectively, on a straight line in the longitudinal direction of the antenna base  12  (corresponding to the front-rear direction of the vehicle). Then, one fixing screw  16  arranged on the front side is fixed to the antenna base  12 , while the other fixing screw  18  arranged on the rear side is arranged in a manner freely swingable by a small angle relative to the antenna base  12  by a structure described later.  
         [0058]     In a vehicle body  20  to which the antenna base  12  is attached, two holes  22  and  24  are drilled in correspondence to the two fixing screws  16  and  18 . Then, in such a manner that a pad  26  having elasticity is arranged on the bottom surface of the antenna base  12 , the two fixing screws  16  and  18  are inserted into the holes  22  and  24 , respectively. Nuts  32  and  34  are then engaged via washers  28  and  30  from the inner side of the vehicle body, so that the antenna base  12  is fixed to the vehicle body  20 .  
         [0059]     As shown in  FIGS. 2A  to  2 C, the bottom surface of the antenna base  12  is formed in a curved surface having an appropriate curvature radius R 1  in accordance with the curved surface of the installation part of the vehicle body  20 . Further, a step portion  16   a  is formed in the fixing screw  16  to be fixed to the antenna base  12 . Further, in the antenna base  12 , a hole  12   a  is drilled into which the fixing screw  18  arranged swingably is inserted. An upper face edge  12   b  of this hole  12   a  is tapered so as to have an appropriate curvature radius R 2 . Then, a pair of caulking protrusions  12   c  are provided in upper face periphery of the hole  12   a . Further, a pair of protrusions  12   d  are so provided as to prevent the fixing screw  18  from rotating about the screw axis.  
         [0060]     As shown in  FIGS. 3A  to  3 C, in the fixing screw  18  to be arranged swingably, a bulge  18   a  is provided at an end. Further, a step portion  18   b  is formed, while a male screw  18   c  is engraved at the other end which is to be inserted into the hole  12   a . Then, a bottom surface of the bulge  18   a  is so curved as to have a curvature radius R 2 . Further, in the bulge  18   a , cutouts  18   d  are provided to restrict the rotation of the screw  18 . The shape in top view of the bulge  18   a  is slightly smaller than but in approximate similarity to the shape in top view of the upper face edge  12   b  of the hole  12   a  of the antenna base  12 .  
         [0061]     Further, as shown in  FIG. 4 , the male screw  18   c  of the fixing screw  18  is inserted into the hole  12   a  of the antenna base  12  from the above. Then, downward escape of the screw  18  is restricted by the bulge  18   a . In this arrangement, the shape of the upper face edge  12   b  of the hole  12   a  of the antenna base  12  agrees with the shape of the bulge  18   a  of the fixing screw  18 , so that the fixing screw  18  does not rotate relative to the hole  12   a  about the screw axis. Here, the shape of the upper face edge  12   b  of the hole  12   a  and the shape of the bulge  18   a  have dimensions so as to restrict solely the relative rotation of the fixing screw  18  about the screw axis and not to restrict the swing of the screw axis of the fixing screw  18  relative to the hole  12   a  in an appropriate range. Further, the protrusions  12   c  of the antenna base  12  are bent (as indicated by arrows) so as to hang over the bulge  18   a  of the fixing screw  18  as shown in  FIG. 1 , so that the fixing screw  18  should not escape upward from the hole  12   a . The bending of the protrusions  12   c  is set up to such an extent that it restricts solely the upward escape of the fixing screw  18 , and does not restrict the swing of the fixing screw  18  in the screw axis direction.  
         [0062]     In this embodiment, both of the bottom surface of the bulge  18   a  of the fixing screw  18  and the upper face edge  12   b  of the hole  12   a  of the antenna base  12  are rounded. However, as far as at least one of these surfaces is rounded, smooth swing is achieved in the fixing screw  18 .  
         [0063]     Further, in the pad  26  inserted between the antenna base  12  and the vehicle body  20 , ridges  26   a  are provided in the bottom surface so as to surround the two fixing screws  16  and  18  as shown in  FIGS. 5A and 5B . Further, a rim  26   b  is provided in the periphery edge of the pad  26 . The pad  26  is composed of elastic material such as rubber. When attached to the antenna base  12  as shown in  FIG. 1 , the pad  26  is compressed between the antenna base  12  and the vehicle body  20 , so that the ridges  26   a  and the rim  26   b  respectively deform elastically and thereby contact closely to the vehicle body  20 .  
         [0064]     In this configuration, the fixing screws  16  and  18  are inserted respectively into the holes  22  and  24  of the vehicle body  20 , so that the antenna case  10  is installed in the vehicle body  20 . Then, first, the nut  32  is engaged and tightened on the one fixing screw  16  to be fixed to the antenna base  12 , so that the vehicle body  20  is clamped between the step portion  16   a  and the washer  28 . After that, the nut  34  is engaged and tightened on the other fixing screw  18  to be arranged swingably relative to the antenna base  12 , so that the vehicle body  20  is clamped between the step portion  18   b  and the washer  30 . Then, the compressed pad  26  elastically biases the antenna base  12  upward, and thereby causes the upper face edge  12   b  of the hole  12   a  of the antenna base  12  to contact with the bottom surface of the bulge  18   a  of the fixing screw  18 . As a result, the antenna base  12  is fixed stably to the fixing screw  18 . Here, in the engaging of the nut  34 , rotation of the fixing screw  18  about the screw axis is restricted by the structure formed by the bulge  18   a  of the fixing screw  18  and the upper face edge  12   b  of the hole  12   a . Thus, the antenna base  12  is fixed to the vehicle body  20 , and the antenna case  10  is fixed to the vehicle body  20 .  
         [0065]     In the fixing of the antenna case  10  to the vehicle body  20 , even when the curved surface of the vehicle body  20  deviates from the curved surface of the bottom face of the antenna base  12 , the swingable fixing screw  18  swings appropriately relative to the vehicle body  20  so that the screw axis direction is adjusted and fixed in a perpendicular orientation. Here, since the rounded bottom surface of the bulge  18   a  is brought into contact with the rounded upper face edge  12   b  of the hole  12   a  having the same curvature radius, the swing of the fixing screw  18  is achieved very smoothly. This remarkably reduces deformation in the vehicle body  20 . Further, the pad  26  absorbs variation in the gap between the vehicle body  20  and the antenna base  12 , and further prevents rain water from entering into the vehicle body  20  through the holes  22  and  24 .  
         [0066]     In this embodiment, the fixed fixing screw  16  is arranged on the front side of the antenna base  12 , while the swingable fixing screw  18  is arranged on the rear side, However, the freely swingable fixing screw  18  may be arranged on the front side of the antenna base  12 , and the fixed fixing screw  16  may be arranged on the rear side. Further, while a pair of protrusions  12   c  are provided on the upper face of the antenna base  12  in this embodiment, merely a single protrusion  12   c  may be arranged, or alternatively, two or more protrusions may be provided, as long as the upward escape of the fixing screw  18  is prevented.  
         [0067]     Next, a second embodiment of the invention will be described below with reference to  FIG. 6 . Similar components to those in the first embodiment will be designated by the same reference numerals, and repetitive explanations for those will be omitted.  
         [0068]     In this embodiment, a spacer  36  composed of elastic material such as rubber is inserted between the bottom surface of the bulge  18   a  of the fixing screw  18  and the upper face edge  12   b  of the hole  12   a  of the antenna base  12 . The spacer  36  is so compressed therebetween, so that the antenna base  12  downward is elastically urged downwardly. This eliminates a gap between the antenna base  12  and the bottom surface of the bulge  18   a  of the fixing screw  18 , and thereby allows the antenna base  12  to be fixed more reliably to the fixing screw  18 . Thus, the antenna base  12  is fixed stably to the vehicle body  20 .  
         [0069]     Here, the bottom surface of the bulge  18   a  of the fixing screw  18  and the upper face edge  12   b  of the hole  12   a  of the antenna base  12  need not necessarily be rounded. That is, variation in the gap between the bottom surface of the bulge  18   a  and the upper face edge  12   b  of the hole  12   a  is absorbed by the spacer  36 , and thereby does not hinder the smooth swing of the fixing screw  18 .  
         [0070]     Next, a third embodiment of the invention will be described below with reference to  FIG. 7 . Similar components to those in the first embodiment will be designated by the same reference numerals, and repetitive explanations for those will be omitted.  
         [0071]     In this embodiment, a single fixing screw  18  is solely arranged that can swing relative to the antenna base  12 . The fixing screw  18  is fixed in an orientation perpendicular to the vehicle body  20 . Thus, even when the curved surface of the bottom face of the antenna base  12  deviates slightly from the curved surface of the vehicle body  20 , deformation is not generated in the vehicle body  20 .  
         [0072]     Next, a fourth embodiment of the invention will be described below with reference to  FIG. 8 . Similar components to those in the first embodiment will be designated by the same reference numerals, and repetitive explanations for those will be omitted.  
         [0073]     In this embodiment, two fixing screws  18  which are swingable relative to the antenna base  12  are arranged at front and rear positions on a straight line in the longitudinal direction of the antenna base  12 . Accordingly, each of the two fixing screws  18  is fixed in an orientation perpendicular to the vehicle body  20 . This further reduces deformation in the vehicle body  20 .  
         [0074]     Next, a fifth embodiment of the invention will be described below with reference to  FIGS. 9A  to  9 C. Similar components to those in the first embodiment will be designated by the same reference numerals, and repetitive explanations for those will be omitted.  
         [0075]     In the first through the fourth embodiments described above, the direction of the swing of the swingable fixing screw  18  relative to the antenna base  12  is not restricted at all. In this embodiment, the swingable direction is restricted. Specifically, at an upper end of an fixing screw  38 , a pair of swing shafts  38   a  are provided so that they protrude toward both sides of a direction perpendicular to the screw axis. Corresponding to these shafts  38   a , in the periphery of the hole  12   a  on the upper face of the antenna base  12 , bearings  12   f  formed with U-shaped grooves  12   e  into which the swing shafts  38   a  are inserted from above are protruded on both sides in a direction parallel to the screw axis. The fixing screw  38  is inserted into the hole  12   a  of the antenna base  12 , while the swing shafts  38   a  are inserted into the U-shaped grooves  12   e  of the bearings  12   f . This prevents the fixing screw  38  from escaping downwardly, and still allows the screw to swing about the swing shafts  38   a  serving as a pivot center. Here, the fixing screw  38  is arranged in a manner swingable within a plane that is approximately perpendicular to the antenna base  12  and that includes a straight line connecting the positions of the fixing screw  16  fixed to the antenna base  12  and the swingable fixing screw  18 . In this embodiment, a bulge is formed at the upper end of the fixing screw  38 . However, the bulge need not necessarily be formed.  
         [0076]     This configuration simplifies the arrangement that allows the fixing screw  38  to swing relative to the antenna base  12 . Further, the two fixing screws  16  and  38  are arranged in the longitudinal direction of the antenna base  12 , and the fixing screw  38  can swing in the direction approximately perpendicular to a plane including the longitudinal direction. While the shape of the curved surface of the vehicle body  20  of the longitudinal direction can easily deviate from the curved surface of the bottom face of the antenna base  12 , the deformation of the vehicle body  20  due to the deviation of the curved surface can be effectively prevented by the configuration of this embodiment.  
         [0077]     Next, a sixth embodiment of the invention will be described below with reference to  FIGS. 10A  to  10 C. Similar components to those in the first embodiment will be designated by the same reference numerals, and repetitive explanations for those will be omitted.  
         [0078]     In this embodiment, at an upper end of an fixing screw  40 , a pair of bearings  40   a  are provided so that they protrude on both sides in a direction perpendicular to the screw axis. In the bearings  40   a , U-shaped grooves  40   b  are formed respectively from below. Then, on the upper face of the antenna base  12 , there is provided a pair of protrusions  12   g , each upper end of which is formed in a semicircular shape in vertical cross section. Then, the fixing screw  40  is inserted into the hole  12   a  of the antenna base  12 , and the protrusions  12   g  are respectively inserted into the U-shaped grooves  40   b  of the bearings  40   a . This prevents the fixing screw  40  from escaping downwardly, and still allows the screw to swing about the upper ends of the protrusions  12   g  serving as a pivot center. Obviously, the configuration is such that the upper ends of the protrusions  12   g  should contact the bottoms of the U-shaped grooves  40   b . Advantage similar to that in the fifth embodiment can be obtained.  
         [0079]     Here, in the fifth and the sixth embodiments, the fixed fixing screw  16  and the swingable fixing screw  38  or  40  are arranged in the antenna base  12 . However, in place of the fixed fixing screw  16 , the swingable fixing screw  18  of the first embodiment may be arranged. Alternatively, the swingable fixing screw  38  or  40  of the fifth or the sixth embodiment may be arranged. Further, a swing shaft may be arranged through a pair of arms protruding from the upper face of the antenna base  12 , and the swing shaft may penetrate through the upper end portion of the fixing screw so that the fixing screw is swingable about the swing shaft.  
         [0080]     Next, a seventh embodiment of the invention will be described below with reference to  FIGS. 11A and 11B . Similar components to those in the first embodiment will be designated by the same reference numerals, and repetitive explanations for those will be omitted.  
         [0081]     In the first embodiment, the protrusions  12   c  are provided on the upper face of the antenna base  12  and adapted to be bent so as to prevent the fixing screw  18  from escaping upward. In the present embodiment, a pair of bosses  12   h  are provided on the upper face of the antenna base  12 , while a retainer  42  composed of resin or metal is fixed to the bosses  12   h  by caulking or the like (as indicated by arrows). The retainer  42  fixed to the bosses  12   h  is obviously arranged so as to hang over the bulge  18   a  of the fixing screw  18 .  
         [0082]     With the above configuration, the structure for preventing the fixing screw  18  from escaping upward can be simplified in comparison with the work of bending the protrusions  12   c  in the first embodiment.  
         [0083]     Next, an eighth embodiment of the invention will be described below with reference to  FIGS. 12A and 12B . Similar components to those in the first embodiment will be designated by the same reference numerals, and repetitive explanations for those will be omitted.  
         [0084]     In this embodiment, a retainer  44  composed of resin is arranged over the bulge  18   a  of the fixing screw  18 , and the both ends thereof are fixed to the antenna base  12  by screws  46 .  
         [0085]     With the above configuration, the structure for preventing the fixing screw  18  from escaping upward can be remarkably simplified.  
         [0086]     In the above embodiments, one or two swingable fixing screws  18  are provided in the antenna base  12 . However, three or more fixing screws may be provided in an antenna base  12  having a relatively large base area, while at least one or more of them may be configured to be swingable.  
         [0087]     Although the present invention has been shown and described with reference to specific preferred embodiments, various changes and modifications will be apparent to those skilled in the art from the teachings herein. Such changes and modifications as are obvious are deemed to come within the spirit, scope and contemplation of the invention as defined in the appended claims.