Abstract:
A base plate where at least part of an antenna member is disposed, an inner cover attached to the base plate so as to cover at least part of the antenna member, and an outer cover covering the inner cover on the base plate, a locking claw for fixing the outer cover is provided on the inner cover side. A fixing piece engaged with the locking claw is provided on the outer cover side, an engaging portion of the fixing piece is formed as a concave surface instead of the through opening. The configuration eliminates the need for providing the fixing piece with a claw-shaped protrusion, damage of the fixing piece can be prevented. In addition, the fixing piece is not readily subject to a defect such as a weld, so that increased mechanical strength can be improved.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2014-131020, filed on Jun. 26, 2014 and PCT Application No. PCT/JP2015/068345, filed on Jun. 25, 2015, the entire contents of which are incorporated herein by reference. 
     
    
     FIELD 
       [0002]    The present invention relates to antenna unit and, for example, to an assembly structure of an antenna unit to be mounted on a mobile body such as an automobile. 
       BACKGROUND 
       [0003]    An antenna unit installed on a roof of a vehicle or the like has a structure in which a base plate is fixed to an exterior plate and an outer cover appearing externally is mounted on the base plate so that an antenna member is contained inside. In this antenna unit, the outer cover is uniquely shaped and colored to improve not only functionality but also design quality. 
         [0004]    As an antenna unit of this type, one in a double case structure configured of a base plate, an inner cover, and an outer cover has been known. In this case, the base plate is fixed to a vehicle main body, and the outer cover is mounted so as to cover the base plate and the inner cover. For example, in the case of the double case structure, to allow the outer cover to be mountable after the inner plate is attached to the base plate, an engaging part is provided which fixes the outer cover and the base plate, or the outer cover and the inner cover. 
         [0005]    In the engaging part to mount the outer cover on the base plate or the inner cover, in many cases, a structure is adopted in which a fixing piece having a locking claw is provided to the outer cover and an engaging part which engages with the locking claw is provided on a base plate or inner cover side (refer to Japanese Patent Application Laid-Open No. 2006-345083, U.S. Pat. No. 7,429,958, and Japanese Patent Application Laid-Open No. 2012-085044). 
       SUMMARY 
       [0006]    An antenna unit according to one embodiment of the present invention includes a base plate where at least part of an antenna member is disposed and an outer cover provided on the base plate, the base plate has a locking claw which fixes the outer cover, and the outer cover has a fixing piece which engages with the locking claw. 
         [0007]    According to this antenna unit, with the locking claw provided on a base plate side and the fixing piece which engages with the locking claw provided on an outer cover side, a claw-shaped protrusion does not have to be provided to the fixing piece. With this, damage of the fixing piece can be prevented. 
         [0008]    An antenna unit according to one embodiment of the present invention includes a base plate where at least part of an antenna member is disposed, an inner cover attached to the base plate so as to cover at least part of the antenna member, and an outer cover covering the inner cover on the base plate, the inner cover has a locking claw which fixes the outer cover, and the outer cover has a fixing piece which engages with the locking claw. 
         [0009]    According to this antenna unit, with the locking claw provided to the inner cover to be mounted on the base plate and the fixing piece which engages with the locking claw provided on an outer cover side, a claw-shaped protrusion does not have to be provided to the fixing piece. With this, damage of the fixing piece and operator&#39;s injury due to damage of the fixing piece can be prevented. 
         [0010]    As another mode of the antenna unit according to one embodiment of the present invention, in the structure having the inner cover, the inner cover may have an opening at a position where the locking claw is provided, and the locking claw may be provided on an inner wall surface of the opening. Also, the fixing piece provided to the outer cover may be provided so as to fit in the opening of the inner cover. 
         [0011]    With the opening provided in the inner cover and the locking claw provided on the inner wall surface of the opening, the locking claw can be prevented from being exposed outside. With the fixing piece of the outer cover provided so as to fit in the opening of the inner cover, even if an external force is applied to the outer cover, one end of the opening supports the fixing piece, and therefore the fixing piece can be prevented from being ruptured. Also, when the fixing piece engages with the locking claw, the opening supports the fixing piece. Therefore, even if swing or vibration acts on the antenna unit, the fixing piece can be prevented from being bent to be detached from the locking claw. 
         [0012]    As another mode of the antenna unit according to one embodiment of the present invention, in the structure having the inner cover, a through hole may be provided in the base plate so as to match the opening of the inner cover. With this, an increase in pressure occurring in a space surrounded by the outer cover and the inner cover is prevented. Also, if water or the like infiltrated, water can be drained through the through hole. 
         [0013]    As another mode of the antenna unit according to one embodiment of the present invention, the fixing piece provided to the outer cover preferably has the engaging part which engages with the locking claw formed as a recessed surface part. That is, this engaging part is formed as a recessed surface part with a depression provided at a position of engaging with the locking claw of the fixing piece and is not formed as a through hole, thereby capable of increasing mechanical strength. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0014]      FIG. 1  is a perspective view describing the structure of an antenna unit according to one embodiment of the present invention; 
           [0015]      FIG. 2  is a sectional view describing the structure of the antenna unit according to one embodiment of the present invention; 
           [0016]      FIG. 3  is a sectional view describing the structure of the antenna unit according to one embodiment of the present invention; 
           [0017]      FIG. 4A  is a plan view describing the structure of a base plate of the antenna unit according to one embodiment of the present invention; 
           [0018]      FIG. 4B  is a plan view describing the structure of an inner cover of the antenna unit according to one embodiment of the present invention; 
           [0019]      FIG. 4C  is a plan view describing the structure of an outer cover of the antenna unit according to one embodiment of the present invention; 
           [0020]      FIG. 5A  is a diagram describing a relation between a fixing piece and a locking claw in which depicts a structure according to one embodiment of the present invention; 
           [0021]      FIG. 5B  is a diagram describing a relation between a fixing piece and a locking claw in which depicts a structure according to a conventional locking claw; 
           [0022]      FIG. 6A  is a perspective view depicting a mode of the fixing piece according to one embodiment of the present invention; 
           [0023]      FIG. 6B  is a perspective view depicting a mode of the fixing piece according to one embodiment of the present invention; 
           [0024]      FIG. 7  is a perspective view describing the structure of an antenna unit according to one embodiment of the present invention. 
           [0025]      FIG. 8  is a sectional view describing the structure of the antenna unit according to one embodiment of the present invention. 
           [0026]      FIG. 9  is a sectional view describing the structure of the antenna unit according to one embodiment of the present invention. 
           [0027]      FIG. 10A  is a plan view describing the structure of a base plate of the antenna unit according to one embodiment of the present invention; and 
           [0028]      FIG. 10B  is a plan view describing the structure of an outer cover of the antenna unit according to one embodiment of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0029]    In the following, embodiments of the present invention are described with reference to the drawings and others. However, the present invention can be implemented in many different modes, and should not be interpreted as being limited to details of the description of the embodiments exemplarily described below. 
         [0030]    Note that in the details of the invention described in the following, a same reference character is commonly used among different drawings for same portions and portions having a similar function and, in that case, repetitive description is omitted unless there are special circumstances. 
         [0031]    The antenna unit described in Japanese Patent Application Laid-Open No. 2006-345083 has a structure in which the outer cover fits in the inner cover, the locking claw is provided at the tip of the fixing piece provided to stand inside the outer cover. Therefore, a finger or glove may be caught when handling the outer cover, damaging the fixing piece and/or the locking claw to cause operator&#39;s injury. 
         [0032]    In the antenna units described in U.S. Pat. No. 7,429,958 and Japanese Patent Application Laid-Open No. 2012-085044, as with Japanese Patent Application Laid-Open No. 2006-345083, the locking claw is provided to the fixing piece on an outer cover side. In a portion where this locking claw is formed, a penetrating opening (hole) is provided, and this is a factor in decreasing the strength of the fixing piece. That is, when the outer cover is injection-molded by using a resin material, the resin material is branched and then again merged at an opening portion of the fixing piece, a weld is formed at a merging point. When a weld is formed at the tip portion of the fixing piece, the strength of this portion decreases, and therefore rupture takes place in the fixing piece and/or the locking claw from the weld part, thereby problematically impairing attachment stability of the outer cover. 
       First Embodiment 
       [0033]    An antenna unit according to one embodiment of the present invention is described with reference to the drawings.  FIG. 1  is a perspective view of a base plate  102 , an inner cover  104 , and an outer cover  106  configuring an antenna unit  100  according to the present embodiment. Note that, for description,  FIG. 1  depicts a state in which the base plate  102 , the inner cover  104 , and the outer cover  106  are each separated. Also, a sectional view along an A 1 -A 2  cutting line depicted in  FIG. 1  is depicted in  FIG. 2 , and a sectional view along a B 1 -B 2  cutting line is depicted in  FIG. 3 . Note that, for convenience, as for the outer cover  106 ,  FIG. 1  depicts a sectional part when cut out in an A 1 -A 2  direction depicted in the drawing so that the sectional part is displayed forward in the drawing. 
         [0034]    The antenna unit  100  is attached typically to a vehicle such as an automobile. However, other than that, the antenna unit according to the present embodiment can be attached to other various exterior surfaces. 
         [0035]    The antenna unit  100  is configured to include the base plate  102 , the inner cover  104 , and the outer cover  106 . Of these, the base plate  102  is mounted on an exterior plate of a vehicle or the like. Thus, the base plate  102  may have added thereto a fastening tool for fixing to the exterior plate or a fixing tool substituted therefor. 
         [0036]    On an upper surface of the base plate  102 , the inner cover  104  is mounted. The inner cover  104  is fixed to the base plate  102  at fastening parts  118  with fastening tools  116 . While  FIG. 1  depicts an example in which countersunk screws are used as the fastening tools  116 , other fastening tools such as bolts and locking pins can also be used. 
         [0037]    The outer cover  106  is attached onto the base plate  102  so as to cover the inner cover  104 . Covered with the outer cover  106 , the inner cover  104  is not exposed outside in a normal use state of the antenna unit  100 . The outer cover  106  may not simply cover the inner cover  104  but also have contrived coloring and shape in consideration of aesthetic outer appearance, aerodynamic characteristics when the vehicle is running, and so forth. For example, as a form, the outer cover  106  may have a streamline shape such as one called “shark fin”, and may have coloring suitable for the vehicle for installation. 
         [0038]    The inner cover  104  and the outer cover  106  are fixed by a locking claw  112  and a fixing piece  108  provided with an engaging part  110  which engages with the locking claw  112 . Note that the locking claw  112  is provided to the inner cover  104 , and the fixing piece  108  is provided to the outer cover  106 . 
         [0039]    Preferably, the locking claws  112  are provided at a plurality of locations on the inner cover  104  and, for example, as depicted in  FIG. 1  and  FIG. 3 , are preferably provided on both left and right sides of the inner cover  104  in a longitudinal direction. In this manner, with the locking claws  112  and the fixing pieces  108  engaged together at the plurality of locations, the outer cover  106  can be stably attached to the antenna unit  100 . In addition to this, as depicted in  FIG. 1  and  FIG. 2 , with the locking claw  112  provided also in a direction crossing the longitudinal direction, the outer cover  106  can be more stably fixed. 
         [0040]    Note that as depicted in the sectional views of  FIG. 2  and  FIG. 3 , the locking claw  112  is formed as a protruding member on a wall surface of an opening  114  of the inner cover  104 . That is, the locking claw  112  is fixed to the wall surface of the inner cover  104 , thereby making the structure strong. 
         [0041]    By contrast, the fixing piece  108  is a plate-shaped member provided to stand from the inner wall surface of the outer cover  106  toward the inner cover  104 . This fixing piece  108  is provided with the engaging part  110  which engages with the locking claw  112  provided to the opening  114  of the inner cover  104 . This engaging part  110  is formed by making the fixing piece  108  depressed at a position engaging with the locking claw  112 . With this, when the outer cover  106  is overlaid on the inner cover  104  to engage the fixing piece  108  and the locking claw  112  with each other, since the locking claw  112  is fixed to the wall surface of the inner cover  104 , the fixing piece  108  is temporarily bent, thereby allowing a claw portion of the locking claw  112  to be engaged in the depression of the engaging part  110  of the fixing piece  108 . 
         [0042]    In  FIG. 2 , a mode in which the locking claw  112  and the fixing piece  108  are engaged with each other is depicted as an enlarged view of a region M 1  surrounded by a one-dot chain line in the drawing. With reference to the enlarged view of the M 1  part, a tip region of the fixing piece  108 , that is, the engaging part  110  which engages with the locking claw  112 , is molded in a recessed shape. In this manner, with the depression in the engaging part formed as a recessed surface part in a recessed shape, a force of engaging with the locking claw  112  can be made strong. And, with the claw portion of the locking claw  112  engaging with the recessed surface part in the engaging part  110  of the fixing piece  108 , the inner cover  104  and the outer cover  106  are fixed. The shape of the locking claw  112  preferably has a so-called wedge-type shape in which the thickness of the protruding part gradually increases along a direction in which the fixing piece  108  is inserted so that the fixing piece  108  is easily bent. 
         [0043]    In this manner, with the locking claw  112  provided to the inner cover  104  and the fixing piece  108  which engages with this locking claw  112  provided to the outer cover  106 , a claw-shaped protrusion is not required to be provided to the fixing piece  108 . With this, a finger or glove can be prevented from being caught when handling the outer cover to damage the fixing piece and cause operator&#39;s injury due to the damage of the fixing piece. 
         [0044]    The locking claw  112  can be provided at any position of the inner cover  104  as long as the locking claw engages with the fixing piece  108  of the outer cover  106  at that position. As a preferable mode, as depicted in  FIG. 1 , the opening  114  may be provided to the inner cover  104 , and the locking claw  112  may be provided to the inner wall surface of the opening  114 . In this case, the fixing piece  108  provided to stand on the inner wall surface of the outer cover  106  is inserted in this opening  114 , thereby being engaged with the locking claw  112 . 
         [0045]    With reference to the enlarged view of the M 1  part depicted in  FIG. 2 , a state is depicted in which the fixing piece  108  is inserted into the opening  114  of the inner cover  104  to engage with the locking claw  112 . In this engaged state, the structure is preferably such that at least one end of the opening  114  is in contact with or extremely in the vicinity of the fixing piece  108 . With one end of the opening  114  provided in the inner cover  104  in contact with or extremely in the vicinity of the fixing piece  108 , even if an external force is applied to the outer cover  106 , one end of the opening  114  can support the fixing piece  108 , and therefore the fixing piece  108  can be prevented from being damaged. Also, when the fixing piece  108  engages with the locking claw  112 , at least one end part of the opening  114  supports the fixing piece  108 . Therefore, even if swing or vibration acts on the antenna unit  100 , the fixing piece  108  can be prevented from being detached from the locking claw  112  or bent. 
         [0046]    In the above, an example in which the locking claw is provided on the inner wall surface of the opening of the inner cover is described, but this is not meant to be restrictive. For example, the locking claw can be provided to the surface of the inner cover. In this case, an opening is not required to be provided. Also, the locking claw can be provided at the tip of a plate-shaped elastic body extending from part of the inner cover. 
         [0047]      FIG. 4A ,  FIG. 4B , and  FIG. 4C  depicts details of each part configuring the antenna unit  100 .  FIG. 4A  depicts a plan view of the base plate  102 ,  FIG. 4B  depicts a plan view of the inner cover  104 , and  FIG. 4C  depicts a plan view of the outer cover  106 . 
         [0048]    In  FIG. 4A , the base plate  102  is provided with the fastening part  118  for fixing the inner cover  104 . A seal member  120  is arranged in an inner region of these fastening parts  118 . With the base plate  102  and the inner cover  104  fastened by the fastening tools at the fastening parts  118  across the seal member  120 , an inner region surrounded by the seal member  120  is configured to prevent infiltration of water or the like from outside. 
         [0049]    In  FIG. 4B , the inner cover  104  is provided with the locking claws  112  at a position corresponding to the fixing pieces  108 . The inner cover  104  depicted in  FIG. 4B  is further provided with the openings  114 . When the openings  114  are provided in the inner cover  104 , the locking claw  112  is preferably provided to the inner wall surface of the opening  114 . Also, the inner cover  104  may be provided with the fastening parts  118  for fixation with the base plate  102 . The fastening part  118  is provided with a through hole for insertion of the fastening tool, and so forth. 
         [0050]    In  FIG. 4C , when the outer cover  106  is viewed from the upper surface, the fixing pieces  108  do not appear on the outer surface of the outer cover  106 , and are provided inside the outer cover  106 . While the shape of the outer cover  106  is any, for example, as depicted in the drawing, at least paired left and right fixing pieces  108  are preferably provided along a longitudinal direction of the outer cover  106 . In addition to this, by providing the fixing piece  108  also in a direction crossing the longitudinal direction, the outer cover  106  can be stably fixed as described above. 
         [0051]    Also, an opening  114   b  is provided also in the base plate  102  at a position overlaying the opening  114  of the inner cover  104 . This opening  114   b  is an opening penetrating through the base plate  102 . With the presence of this opening  114   b , the structure is such that an inner space surrounded by the inner cover  104  and the outer cover  106  and an outer space surrounding the antenna unit communicate with each other. With this structure, internal pressure of the inner space surrounded by the inner cover  104  and the outer cover  106  is prevented from increasing. Also, even if water or the like infiltrates, water can be drained to the outside through the openings  114  and  114   b.    
         [0052]    In consideration of a more specific example, when the antenna unit according to the present embodiment is installed in a vehicle such as an automobile, even if high-pressure water is applied at car wash and water infiltrates into the inside of the outer cover, that water can be drained from the openings. Also, the fixing pieces can be moved by using a jig or the like, and therefore the outer cover can be easily replaced. 
         [0053]    In the antenna unit according to the present embodiment, the locking claw is not provided to the fixing piece  108  of the outer cover  106 , but the locking claw  112  is provided to the inner cover  104 , thereby reliably fixing the outer cover  106  and preventing damage of the fixing piece  108 . Details about this are described with reference to  FIG. 5A  and  FIG. 5B . 
         [0054]      FIG. 5A  depicts a structure according to the present embodiment, in which the locking claw  112  is provided to an inner cover  104  side, and the fixing piece  108  is provided to an outer cover  106  side. On the other hand,  FIG. 5B  depicts a conventional structure, in which a protruding locking claw  112   b  is provided at the tip of a fixing piece  108   b  on an outer cover  106  side and an engaging part  110   b  which engages with this locking claw  112   b  is provided to a wall surface of an inner cover  104  side so as to be in a protruding shape. 
         [0055]      FIG. 5A  and  FIG. 5B  both depict a state in which the fixing piece  108  (or the fixing piece  108   b ) engages with the engaging part. For detachment of the locking claw at the engaging part, the fixing piece is required to be bent. In  FIG. 5A , a deformation amount of the fixing piece  108  engaging with the locking claw  112  is indicated by an angle θ 1  from a center position of the depression of the fixing piece. On the other hand, in  FIG. 5B , a deformation amount of the fixing piece  108   b  is indicated by an angle θ 2  from a center position of a swelling part of the locking claw  112   b  provided to the fixing piece  108   b.    
         [0056]    In the above case, the deformation amount of the fixing piece increases as the angle θ increases and, as a result, a load on the fixing piece also increases. It is depicted that the angle θ 2  indicated in  FIG. 5B  becomes larger than the angle θ 1  indicated in  FIG. 5A , and it can be found that the load on the fixing piece in the conventional structure is larger. It can be found that the fixing piece  108   b  in the conventional structure more tends to be damaged than the fixing piece  108  of the present embodiment when the outer cover is pulled to be detached from the inner cover. 
         [0057]      FIG. 6A  depicts an enlarged view of the fixing piece  108  according to the present embodiment. The fixing piece  108  has a recessed surface part which engages with the locking claw, that is, the engaging part  110 . This engaging part  110  is formed in a recessed surface part so as to engage with the protruding part (claw part) of the locking claw  112 , and a through hole is not provided in the fixing piece  108 . With this, even if the outer cover  106  is manufactured by injection molding or the like with a resin material, the entire fixing piece  108  is in a plate surface shape, and a weld can be prevented from being formed. With this, the present embodiment has an advantage in which the strength of the fixing piece  108  can be enhanced. Also, variation in quality for each product can be reduced. 
         [0058]    As depicted in  FIG. 6B , as another mode of the fixing piece  108 , one end of the engaging part  110  may be an open end. When the locking claw  112  engages with the engaging part  110 , even if both are strongly engaged and firmly fit together, with this open end provided, play which allows even a little sliding of one of the locking claw and the fixing piece is provided, and the occurrence of unwanted stress to the fixing piece  108  can be prevented. 
         [0059]    In any case, the structure of the fixing piece  108  depicted in  FIG. 6A  and  FIG. 6B  does not have a protruding part as a locking claw with a pointed claw tip. Therefore, a finger or glove can be prevented from being caught when handling the outer cover to damage the fixing piece and cause operator&#39;s injury due to the damage of the fixing piece. 
         [0060]    Note that, although not depicted in  FIG. 1 , an antenna member implemented on the antenna unit  100  is provided inside the inner cover  104 . Alternatively, part of the antenna member may be arranged not only inside the inner cover  104  but also between the inner cover  104  and the outer cover. 
         [0061]    To protect the antenna member and its accompanying components, the seal member  120  may be provided between the inner cover  104  and the base plate  102 . With the seal member  120  provided so as to abut on the base plate  102  and an outer edge surface of the inner cover  104 , the inner region of the inner cover  104  can be made waterproof. 
         [0062]    In this manner, according to the present embodiment, with the fixing piece which engages with the locking claw provided to the outer cover and the locking claw provided to the inner cover, damage of the fixing piece is prevented, and the outer cover can be reliably fixed. Also, with the locking claw of the inner cover provided inside the opening provided in the inner cover, the fixing piece can be engaged with the locking claw as being supported by an end part of the opening or the inner wall part. Therefore, also with this, damage of the fixing piece can be prevented. With an opening provided also in the base plate so as to match the opening of the inner cover, water infiltrating into the space surrounded by the outer cover and the inner cover can be discharged. 
       Second Embodiment 
       [0063]    In the present embodiment, an antenna unit with a configuration different from that of the first embodiment and not provided with an inner cover is exemplarily described. 
         [0064]      FIG. 7  depicts an antenna unit  100   b  according to the present embodiment, depicting the base plate  102  and the outer cover  106 . For description,  FIG. 7  depicts a state in which these components are each separated. Also, a sectional view along a C 1 -C 2  cutting line depicted in  FIG. 7  is depicted in  FIG. 8 , and a sectional view along a D 1 -D 2  cutting line is depicted in  FIG. 9 . Note that, for convenience, as for the outer cover  106 ,  FIG. 7  depicts a sectional part when cut out in a C 1 -C 2  direction depicted in the drawing so that the sectional part is displayed forward in the drawing. 
         [0065]    In the antenna unit  100   b  according to the present embodiment, as depicted in  FIG. 7 , the locking claw  112  is provided on the outer edge part of the base plate  102 . With the locking claw  112  and the fixing piece  108  of the outer cover  106  engaging with each other, the outer cover  106  is fixed to the base plate  102 . As a mode of the locking claw  112  provided to the base plate  102  and the fixing piece  108  provided to the outer cover  106 , one similar to that of the first embodiment is applied. An antenna member is provided in an inner region surrounded by the base plate  102  and the outer cover  106 . 
         [0066]    As depicted in the sectional views of  FIG. 8  and  FIG. 9 , the locking claw  112  is provided between the outer edge part of the base plate  102  and a wall surface part  122  provided to stand from the base plate. By contrast, in the fixing piece  108 , a plate-shaped member is provided in a state of standing from the inner wall surface of the outer cover  106 , and a recessed part is provided so that a claw is engaged with a surface which engages with the locking claw. While the present embodiment has a structure with an inner cover omitted, with the locking claw  112  provided to the base plate  102 , the outer cover  106  can be fixed to the base plate  102 . In this case, the fixing piece  108  of the outer cover  106  directly engages with the locking claw  112  of the base plate  102 , and therefore positional misalignment between the outer cover  106  and the base plate  102  can be reduced. 
         [0067]    Preferably, the locking claws  112  are provided at a plurality of locations on the base plate  102  and, for example, are preferably provided on both left and right sides of the base plate  102  in a longitudinal direction. In addition to this, if the locking claw  112  is provided also in a direction crossing the longitudinal direction, the outer cover  106  can be more stably fixed. 
         [0068]    In this manner, with the locking claw  112  provided to the base plate  102  and the fixing piece  108  which engages with this locking claw  112  provided on an outer cover  106  side, a claw-shaped protrusion is not required to be provided to the fixing piece  108 . With this, a finger or glove can be prevented from being caught when handling the outer cover to damage the fixing piece and cause operator&#39;s injury due to the damage of the fixing piece. 
         [0069]    Note that one mode in which the fixing piece  108  engages with the locking claw  112  is depicted in  FIG. 8  as an enlarged view of a region M 2  surrounded by a one-dot chain line in the drawing. With reference to the enlarged view of the M 2  part, the wall surface part  122  is provided on a side opposed to the locking claw  112  provided to the base plate  102 . In this one mode, the fixing piece  108  is inserted so as to be interposed between the locking claw  112  and the wall surface part  122 . In this one mode, the structure is preferably such that at least part of the wall surface part  122  is in contact with or extremely in the vicinity of the fixing piece  108 . With at least part of the wall surface part  122  in contact with or extremely in the vicinity of the fixing piece  108 , even if an external force is applied to the outer cover  106 , the fixing piece  108  is supported by the wall surface part  122 , and therefore the fixing piece  108  can be prevented from being damaged. 
         [0070]      FIG. 10A  and  FIG. 10B  depicts details of each part configuring the antenna unit  100   b .  FIG. 10A  depicts a plan view of the base plate  102  and  FIG. 10B  depicts a plan view of the outer cover  106 . 
         [0071]    In  FIG. 10A , between the outer edge part of the base plate  102  and the wall surface part  122 , the locking claws  112  are provided so as to correspond to the fixing pieces  108 . The locking claws  112  are preferably formed integrally with the base plate  102 , thereby allowing the outer cover  106  to be stably fixed even if the outer cover  106  is attached. With the locking claws  112  integrally formed with the base plate  102 , the number of components of the antenna unit can be decreased. Also, as described with reference to the enlarged view of the M 2  part depicted in  FIG. 8 , the wall surface parts  122  may be provided so as to be opposed to the locking claws  112 . 
         [0072]    In  FIG. 10B , when the outer cover  106  is viewed from the upper surface, the fixing pieces  108  do not appear on the outer surface, and are provided inside the outer cover  106 . While the shape of the outer cover  106  is any, for example, as depicted in the drawing, at least paired left and right fixing pieces  108  are preferably provided along a longitudinal direction of the outer cover  106 . Also, in addition to this, by providing the fixing piece  108  also in a direction crossing the longitudinal direction, the outer cover  106  can be more stably fixed to the outer cover  106 . 
         [0073]    Note that, although not depicted in  FIG. 7 , the antenna member implemented on the antenna unit  100   b  is provided in a region surrounded by the base plate  102  and the outer cover  106 . To protect the antenna member and its accompanying components, the seal member  120  may be provided between the inner cover  104  and the base plate  102 . With a through hole ( 114   b  of  FIG. 4A ) provided in the base plate  102 , water can be drained. Furthermore, with a through hole ( 114   b  of  FIG. 4A ) provided in the base plate  102 , the fixing pieces can be moved by using a jig or the like, and therefore the outer cover can be easily replaced. 
         [0074]    In this manner, according to the present embodiment, with the fixing piece having the engaging part provided to the outer cover and the locking claw provided to the base plate, the fixing piece is prevented from being damaged, and the outer cover can be reliably fixed. Also, by fixing the outer cover with the locking claw provided to the base plate, attachment to the base plate can be made without misalignment of the position of the outer cover.