Patent Publication Number: US-11024453-B2

Title: Coil device

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a low-profile coil device having a high withstand voltage. 
     In the prior art shown in Patent Document 1 below, for example, a coil where a troidal core is directly wound by a wire is put into a mold terminal box, and a leading part of the wire is connected. 
     In such conventional techniques, since a wire is wound around a troidal core, workability is poor, and coil characteristics vary. In addition, since a core is wound and thereafter put into a mold terminal box, the terminal box is hard to be thinner. Moreover, a troidal core is fixed unstably, and there is a problem with withstand voltage. 
     In the prior art shown in Patent Document 2 below, a bobbin covers the entire surface of a core as a main component, and a coil is formed by winding a wire around an outer circumference of the bobbin. In this coil device, the entire surface of the core is covered with the bobbin, and withstand voltage can be high. 
     In this prior art, however, the bobbin is entirely wound by the wire, and the coil device cannot thereby be low. 
     Patent Document 1: JPH06325943 (A) 
     Patent Document 2: JPH10149932 (A) 
     BRIEF SUMMARY OF INVENTION 
     The present invention has been achieved under such circumstances. It is an object of the invention to provide a low-profile coil device excelling in productivity and having less variation in characteristics and high withstand voltage. 
     To achieve the above object, a coil device according to the present invention comprises a bobbin, a core body, a wire, and a plurality of terminals, wherein 
     the bobbin comprises:
         a pair of connection side portions arranged near both sides of a winding core of the core body and wound by the wire along with the winding core; and   a pair of terminal tables arranged on both ends of the connection side portions and respectively including the terminal protruding outward in a winding axis of the winding core,       

     the core body includes a pair of flanges arranged on both ends of the core body in the winding axis, and 
     each of the terminal tables includes a flange storage recess configured to contain the flange. 
     In the coil device according to the present invention, a coil is not formed by directly winding the wire around a troidal core, but is formed by winding the wire around the winding core of the core body along with the connection side portions, which are a part of the bobbin, while the core body is being attached to the bobbin. Thus, the wire is easily wound, and the coil device according to the present invention is excellent in productivity and has less variation in characteristics. 
     In the coil device according to the present invention, the bobbin does not entirely cover the winding core of the core body, but covers only both sides of the winding core or both sides and the bottom surface of the winding core and does not cover at least the top surface (or either the top or bottom surface) of the winding core. Thus, this reduces the height of the bobbin and consequently reduces the height of the coil device. 
     Moreover, each of the terminals is attached to protrude outward in the winding axis of the terminal table and is thereby prevented from unnecessarily protruding in the height direction of the coil device. This also reduces the height of the coil device. 
     Moreover, the flanges of the core body are housed in the flange storage recesses of the terminal tables, and withstand voltage is thereby improved. 
     Preferably, the wire is a conductive wire (also referred to as an insulation wire) whose outer circumference is covered with an insulation film. Moreover, the insulation film has substantially no pinholes. Since the wire partially contacts with the surface of the core body, the wire and the core can be insulated by the insulation film, and a conductive core, such as a metal core, can be used as the core body. 
     Preferably, each of the terminals comprises: 
     a wire joint part protruding from the terminal table and configured to connect with a leading end of the wire; 
     an embedded part integrally formed with the wire joint part and embedded in the terminal table; and 
     a mount part integrally formed with the embedded part and protruding from the terminal table at a different position from the wire joint part. 
     In this structure, the wire joint part is easily joined with the wire, and the coil device is easily mounted. Moreover, the terminals are easily formed integrally with the bobbin. 
     Preferably, the wire joint part and the mount part protrude outward from each of the terminal tables to be displaced in a height direction of the coil device. In this structure, the wire joint part is easily joined with the wire, and the coil device is easily mounted. Moreover, the terminals are easily formed integrally with the bobbin. 
     Preferably, the pair of terminal tables is integrally formed with the pair of connection side portions, and the wire is continuously wound so as to contact with the pair of connection side portions and top and bottom surfaces of the winding core. 
     In this structure, the coil device can easily have a small height. 
     Instead, the pair of terminal tables is integrally formed with the pair of connection side portions, the bobbin further comprises a bottom wall integrating the pair of connection side portions and covering a bottom surface of the winding core, and the wire is continuously wound so as to contact with the pair of connection side portions, the bottom wall, and a top surface of the winding core. 
     In this structure, withstand voltage is improved. 
     A partition wall may be formed at an intermediate position of the connection side portions in the winding axis, and the wires differing from each other are wound in sections of the connection side portions divided by the partition wall in the winding axis. In this structure, the insulation between the primary coil and the secondary coil is improved. 
     Preferably, an opening of the flange storage recess of the terminal table includes adhesive recesses configured to store an adhesive on flange wings protruding outward from both sides of the flange while the flange is being contained in the flange storage recess. The core body and the bobbin are easily fixed only by flowing an adhesive into the adhesive recesses. The core body and the bobbin are easily positioned, and variations in characteristics can be prevented. 
     Preferably, the terminal tables respectively include a notch configured to be inserted by a boundary part between the winding core and the flange. In this structure, the core body is easily attached and positioned to the bobbin, and workability is improved. 
     Preferably, both ends of a plate differing from the core body are inserted from above into the notches. In this structure, the plate, the core body, and the bobbin are thereby easily positioned and attached. Incidentally, the plate may be the same as or a different magnetic material from a magnetic material of the core body. In this case, magnetic characteristics are improved. Instead, the plate is not necessarily formed by a magnetic material. In this case, the plate can function as, for example, a suction part of the coil device. 
     Preferably, the terminal tables respectively include a notch configured to be inserted by a boundary part between the winding core and the flange, both ends of a plate differing from the core body are inserted from above into the notches, and the flange wings are positioned on both sides of the ends of the plate in the flange storage recess. 
     Preferably, each of the adhesive recesses is positioned on the flange wings. The adhesive recesses are filled with an adhesive, and this adhesive simultaneously joins the plate, the core body, and the bobbin. Preferably, the plate has a width that is smaller than a width of the flange. The plate may have a width that is substantially equal to a width of the winding core. 
     Preferably, a conductor passage where a leading part of the wire passes and goes to the terminal is formed on a bottom surface of the terminal table located opposite to an opening of the flange storage recess. In this structure, the wire is easily joined, and the insulation between the core body and the leading part is improved. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  a perspective view of a coil device according to an embodiment of the present invention. 
         FIG. 2  is a front view (cross-sectional view for only wires) of the coil device shown in  FIG. 1 . 
         FIG. 3  is a plane view (cross-sectional view for only wires) of the coil device shown in  FIG. 1 . 
         FIG. 4  is a bottom view (cross-sectional view for only wires) of the coil device shown in  FIG. 1 . 
         FIG. 5  is an exploded perspective view of the coil device (no illustration for wires) show in  FIG. 1 . 
         FIG. 6  is a perspective view of a bottom of the bobbin shown in  FIG. 5 . 
         FIG. 7  is a cross-sectional perspective view of the coil device (no illustration for wires) shown in  FIG. 1 . 
         FIG. 8  is a perspective view of a cross section on the plane side of the coil device shown in  FIG. 1 . 
         FIG. 9  is a perspective view of a coil device according to another embodiment of the present invention. 
         FIG. 10  is a front view (cross-sectional view for only wires) of the coil device shown in  FIG. 9 . 
         FIG. 11  is a plane view (cross-sectional view for only wires) of the coil device shown in  FIG. 9 . 
         FIG. 12  is a bottom view (cross-sectional view for only wires) of the coil device shown in  FIG. 9 . 
         FIG. 13  is an exploded perspective view of the coil device (no illustration for wires) show in  FIG. 9 . 
         FIG. 14  is a perspective view of a bottom of the bobbin shown in  FIG. 13 . 
         FIG. 15  is a cross-sectional perspective view of the coil device (no illustration for wires) shown in  FIG. 9 . 
         FIG. 16  is a perspective view of a cross section on the plane side of the coil device shown in  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
     Hereinafter, the present invention is described based on embodiments shown in the figures. 
     First Embodiment 
     A transformer  10  as a coil device according to the present embodiment shown in  FIG. 1  is used as, for example, a transformer, and is used for voltage conversion of battery of vehicles, such as automobiles, voltage conversion of battery of electronic devices, and the like, but is used for any purposes. The transformer  10  has a bobbin  20 , a core body  40 , a plate  50 , and a coil  60 . 
     As shown in  FIG. 5 , the bobbin  20  has a pair of terminal tables  22  and  23  arranged separately in the X-axis direction. The terminal tables  22  and  23  are connected by a pair of bar connection side portions  26  and are integrated. The pair of connection side portions  26  is separated in the Y-axis direction and extends in the X-axis direction. The terminal table  22  ( 23 ) is provided with a flange storage recess  24  ( 25 ) having an opening on their upper part in the Z-axis direction. Preferably, a taper inclined surface is formed in the openings of the flange storage recesses  24  and  25  for easy entrance of flanges  44  of the core body  40  mentioned below. 
     In the figures, the X-axis, the Y-axis, and the Z-axis are mutually substantially perpendicular. In the present embodiment, the X-axis substantially corresponds to a direction where the connection side portions  26  extend (also corresponding to the winding axis direction of the coil  60 ), the Y-axis substantially corresponds to a direction where the pair of connection side portions  26  separates from each other, the Z-axis direction corresponds to a height direction of the transformer  10 , and the lower side of the Z-axis direction is a mounting surface side. 
     As shown in  FIG. 5 , the core body  40  has a winding core  42  with a plane shape and a pair of flanges  44  arranged on both ends of the winding core  42  in the X-axis direction. Each of the flanges  44  has a flange central part  45  having a width in the Y-axis direction that is substantially the same as that of the winding core  42 . A pair of flange wings  46  is integrally formed on both sides of each flange central part  45  in the Y-axis direction and is configured to protrude outward in the Y-axis direction from both ends of the winding core  42  in the Y-axis direction. Incidentally, “outward” means a go-away direction from a center (center of gravity) of the transformer  10 , and “inward” means a go-back direction to the center (center of gravity) of the transformer  10 . 
     In the present embodiment, the flange central part  45  is configured to have a height in the Z-axis direction (hereinafter may merely be referred to as “height”) that is higher than the flange wings  46 , a step is formed on the top surface of each flange  44  in the Z-axis direction (hereinafter may merely be referred to as “top surface”), and the bottom surface of each flange  44  in the Z-axis direction (hereinafter may merely be referred to as “bottom surface”) are substantially flush. The steps formed on the top surfaces of the flanges  44  have any height Z 1 , but preferably have a height Z 1  of about 0.6 to 1.1 mm. 
     The bottom surface of the winding core  42  is substantially flush with the bottom surfaces of the flange central parts  45 . The winding core  42  has a thickness in the Z-axis direction (hereinafter may merely be referred to as “thickness”) that is substantially equal to a thickness of each connection side portion  26 . The bottom surfaces of the connection side portions  26  are substantially flush with the bottom surfaces of the flange storage recesses  24  and  25 . 
     In the present embodiment, when the flanges  44  are contained in the flange storage recesses  24  and  25  of the terminal tables  22  and  23 , as shown in  FIG. 7 , the winding core  42  of the core body  40  is located between the pair of connection side portions  26 , the top surface of the winding core  42  and the top surfaces of the connection side portions  26  substantially correspond to each other, and the bottom surface of the winding core  42  and the bottom surfaces of the connection side portions  26  correspond to each other. Incidentally, “substantially correspond” means that a slight gap is permissible if no errors occur in the following winding operation of wires  62  and  64 . 
     The height Z 2  of the steps from the top surface of the winding core  42  to the top surfaces of the flange central parts  45  shown in  FIG. 5  is needed to form a predetermined gap (corresponding to the height Z 2 ) between the top surface of the winding core  42  and the bottom surface of the plate  50 . The height Z 2  of the steps shown in  FIG. 5  is determined depending on the winding layer number of wires  62  and  64  constituting the coil  60  shown in  FIG. 2  or so, and is preferably 0.6 to 1.1 mm. 
     The plate  50  is prepared separately from the core body  40 . The plate  50  has a length that is substantially equal to a length of the core body  40  in the X-axis direction (hereinafter may merely be referred to as “length”) and has a width that is substantially equal to a width of the winding core  42  of the core body  40  in the Y-axis direction (hereinafter may merely be referred to as “width”). Preferably, the plate  50  has a thickness that is 70 to 130% of a thickness of the winding core  42 . 
     The core body  40  is formed by any material, such as a metal or a magnetic material of ferrite etc. The plate  50  is preferably formed by a magnetic material similar to a material of the core body  40 , but is not necessarily formed by the identical magnetic material. The plate  50  may be formed by a non-magnetic material, such as a synthetic resin. 
     As shown in  FIG. 5 , a notch  27  is formed on the inner wall of each terminal table  22  ( 23 ) of the bobbin  20  in the X-axis direction. Each of the notches  27  has a width that is equal to or larger than a width of the winding core  42  and is smaller than a distance between the pair of connection side portions  26  in the Y-axis direction. Each of the notches  27  has a height that is substantially equal to a depth (height) of the flange storage recess  24  ( 25 ). 
     Boundary parts of the core body  40  between the winding core  42  and the flanges  44  are inserted into the notches  27 , the flanges  44  are contained in the flange storage recesses  24  and  25 , and the winding core  42  is disposed between the pair of connection side portions  26 . Both ends of the plate  50  differing from the core body  40  are respectively inserted into the notches  27  from above, and the top surface of the plate  50  is configured to protrude upward in the Z-axis direction from the top surfaces of the terminal tables  22  and  23  with a predetermined height Z 3  as shown in  FIG. 2 . The predetermined height Z 3  is preferably ½ or less, more preferably ¼ or less, of a thickness of the plate  50 . The top surface of the plate  50  may be flush with the top surfaces of the terminal tables  22  and  23  or may be lower than the top surfaces of the terminal tables  22  and  23  in the Z-axis direction. 
     Each of the terminal tables  22  and  23  of the bobbin  20  shown in  FIG. 5  is provided with a pair of terminals  70  and  80 . The terminals  70  and  80  have a line-symmetry shape and have a similar structure, but are not completely the same member. 
     The terminal  70  has a wire joint part  72 , an embedded part  74 , and a mount part  76 , and these are integrally formed by pressing a conductive plate material, such as a metal piece. The wire joint part  72  is integrally formed with a caulking piece  73 . The terminal  80  has a wire joint part  82 , an embedded part  84 , and a mount part  86 , and these are integrally formed by pressing a conductive plate material, such as a metal piece. The wire joint part  82  is integrally formed with a caulking part  83 . The terminals  70  and  80  are formed by any conductive material, such as a metal of phosphor bronze, tough pitch steel, oxygen-free steel, stainless steel, brass, copper nickel alloy, etc. 
     As shown in  FIG. 2 , the embedded part  74  ( 84 ) of the terminal  70  ( 80 ) is embedded in an insulation material constituting the bobbin  20  located outside the terminal table  22  ( 23 ) in the X-axis direction and located below the terminal table  22  ( 23 ) in the Z-axis direction. Preferably, the embedded part  74  ( 84 ) is not exposed on the inner wall surface of the flange storage recess  24  ( 25 ) of the terminal table  22  ( 23 ), but is embedded in the insulation material constituting the bobbin  20 . 
     The insulation material constituting the bobbin  20  is any insulation material, such as a synthetic resin of LCP, nylon, phenol, DAP, PBT, PET, etc. The terminal  70  ( 80 ) is subjected to an insertion molding in the formation of the bobbin  20  and is integrated therewith. 
     As shown in  FIG. 2 , the mount part  76  ( 86 ) of the terminal  70  ( 80 ) is attached to the bobbin  20  so as to protrude outward in the X-axis direction from the end surface of the terminal table  22  ( 23 ) on the lower surface (bottom surface) of the bobbin  20 . The wire joint part  72  ( 82 ) is attached to the bobbin  20  so as to protrude outward in the X-axis direction from the end surface of the terminal table  22  ( 23 ) at a position that is higher than the mount part  76  ( 86 ) in the Z-axis direction. 
     As shown in  FIG. 3  and  FIG. 4 , the wire joint part  72  ( 82 ) and the mount part  76  ( 86 ) of the terminal  70  ( 80 ) are displaced in the Y-axis direction when viewed in the Z-axis direction. In the present embodiment, the embedded part  74  ( 84 ) shown in  FIG. 5  is embedded in the insulation material constituting the bobbin  20  so that the wire joint parts  72  and  82  are positioned inside the mount parts  76  and  86  in the Y-axis direction. 
     Incidentally, the terminal  80  and the terminal  70  of the terminal table  22  are arranged side by side in this order in the Y-axis direction as shown in  FIG. 3 , but the terminal  70  and the terminal  80  of the terminal table  23  are arranged in this order. 
     As shown in  FIG. 2 , the lower surface of the mount part  76  ( 86 ) is configured to protrude downward from the bottom surface of the bobbin  20  with a predetermined height Z 4 . The predetermined height Z 4  is preferably large than zero, and is preferably 0.5 to 2 times as large as a thickness of a plate material constituting the mount part  76  ( 86 ). 
     In the present embodiment, four mount-side protrusions  28  are formed in total on the bottom of the bobbin  20 , and the bottom surfaces of the mount-side protrusions  28  are the bottom surface of the bobbin  20 . As shown in  FIG. 4 , a pair of mount-side protrusions  28  is separately formed on the bottom surface of the terminal table  22  ( 23 ) in the Y-axis direction, and a leading communication groove (conductor passage)  29  is formed between the pair of mount-side protrusions  28 . 
     The leading communication grooves  29  have a width Y 1  in the Y-axis direction that is preferably substantially equal to or slightly smaller (or may be larger) than a distance Y 2  in the Y-axis direction between the wire joint parts  72  and  82  arranged inside the terminal table  22  ( 23 ) in the Y-axis direction. 
     A displacement width Y 3  between the wire joint part  72  ( 82 ) and the mount part  76  ( 86 ) is preferably larger than zero and smaller than ⅓ of a full width Y 0  of the bobbin  20  in the Y-axis direction. Preferably, Y 3 /Y 0  is ½ to 2 times as large as a width Y 4  of the mount part  76  ( 86 ). 
     As shown in  FIG. 4 , the outer end surfaces of the mount-side protrusions  28  in the X-axis direction are preferably recessed from the outer end surface of the bobbin  20  in the X-axis direction with a predetermined distance X 1 . The predetermined distance X 1  is determined in relation to a length X 2  of the terminal table  22  ( 23 ) in the X-axis direction. X 1 /X 2  is preferably ½ or less, more preferably ⅓ or less. X 1 /X 2  may be zero, but is preferably ⅙ or more. The length X 2  of the terminal table  22  ( 23 ) is determined based on a full length X 0  of the bobbin  20  or so. Preferably, X 2 /X 0  is 0.2 to 0.3. 
     In the present embodiment, as shown in  FIG. 2 , the mount parts  76  and  86  extend outward from the outer end surfaces of the mount-side protrusions  28  in the X-axis direction so as to protrude outside the outer end surface of the bobbin  20 . In this structure, the outer end surfaces of the mount-side protrusions  28  reinforce the boundary parts between the mount parts  76  and  86  and the embedded parts  74  and  84 , and the mount parts  76  and  86  are easily mounted on a mount surface, such as a circuit board. 
     Preferably, a protrusion height Z 5  of the mount-side protrusions  28  is determined so as to sufficiently secure a depth of the flange storage recess  24  ( 25 ) shown in  FIG. 1  and secure the leading communication grooves  29  shown in  FIG. 6 . 
     In the present embodiment, as shown in  FIG. 8 , a slight gap may be formed in the Y-axis direction between the connection side portions  26  and the winding core  42  while the winding core  42  of the core body  40  is positioned between the pair of connection side portions  26 . In this state, the connection side portions  26  sandwiching the winding core  42  are wound by two wires  62  and  64  constituting the coil  60 . 
     The wires  62  and  64  are a conductive wire (also referred to as an insulation wire) whose outer circumference is covered with an insulation film. In the present embodiment, the insulation film has no pinholes. For example, the insulation film of the wires  62  and  64  may be polyurethane, ETFE, PFA, PET, polyamide, PPS, etc. 
     The wires  62  and  64  are wound from outside the connection side portions  26  sandwiching the winding core  42 , and the coil  60  is thereby formed. The winding operation is preferably carried out automatically, but may be carried out manually. Both ends of the wire  62  pass the leading communication groove  29  shown in  FIG. 4  and are respectively led to the wire joint parts  72  and  82  as leading parts  62   a  and  62   b . Similarly, both ends of the wire  64  pass the leading communication groove  29  shown in  FIG. 4  and are respectively led to the wire joint parts  72  and  82  as leading parts  64   a  and  64   b.    
     The leading parts  62   a ,  62   b ,  64   a , and  64   b  are wound around the wire joint parts  72  and  82  as necessary and are preliminary fixed by the caulking pieces  73  and  83 . Then, joint portions  100  are formed at tips of the leading parts  62   a ,  62   b ,  64   a , and  64   b  by laser radiation or so, and the leading parts  62   a ,  62   b ,  64   a , and  64   b  and the wire joint parts  72  and  82  are electrically connected and fixed. In addition to laser radiation, the joint portions  100  can be formed by solder joint, a joint using a conductive adhesive, thermal fusion, resistance welding, etc. 
     In the present embodiment, the plate  50  is preferably attached to the bobbin  20  after the joint portions  100  shown in  FIG. 1  are formed, but the plate  50  may be attached to the notches  27  of the bobbin  20  before the joint portions  100  are formed and after the wires  62  and  64  are wound to form the coil  60 . After the plate  50  is attached, an adhesive is applied into adhesive recesses  30  formed on both sides of the flange storage recess  24  ( 25 ) in the Y-axis direction. The plate  50 , the core body  40 , and the bobbin  20  are simultaneously adhered and fixed by the application of the adhesive. The adhesive is any adhesive, such as silicone resin, epoxy resin, UV resin, and anaerobic resin. 
     In the transformer  10  according to the present embodiment, the coil  60  is not formed by directly winding a wire around a troidal core, but is formed by winding the wires  62  and  64  around the winding core  42  of the core body  40  along with the connection side portions  26 , which are a part of the bobbin  20 , while the core body  40  is being attached to the bobbin  20 . Thus, the wires  62  and  64  are easily wound, and the transformer  10  according to the present embodiment is excellent in productivity and has less variation in characteristics. 
     In the transformer  10  according to the present embodiment, the bobbin  20  does not entirely cover the winding core  42  of the core body  40 , but covers only both sides of the winding core  42  in the Y-axis direction and does not cover at least either the top or bottom surface of the winding core  42 . Thus, this reduces the height of the bobbin  20  and consequently reduces the height of the transformer  10 . In the present embodiment, a full height Z 0  of the coil device  10  can preferably be 4 mm or less, more preferably 3.5 mm or less. 
     Moreover, the terminal  70  ( 80 ) is attached to protrude outward in the winding axis (X-axis) of the terminal table  22  ( 23 ), and the terminal  70  ( 80 ) is thereby prevented from unnecessarily protruding in the height direction (Z-axis direction) of the transformer  10 . This also reduces the height of the transformer  10 . 
     Moreover, the flanges  44  of the core body  42  are housed in the flange storage recesses  24  and  25  of the terminal tables  22  and  23 , and withstand voltage is thereby improved. In the present embodiment, as shown in  FIG. 4 , a shortest distance between the core body  40  and the terminal  70  or  80  (insulation distance or creepage distance) can sufficiently be large (e.g., 5 mm or more), and insulation resistance is thereby excellent. 
     Moreover, the wires  62  and  64  are formed by a conductive wire (insulation wire) whose outer circumference is covered with an insulation film. This insulation film has substantially no pinholes. Since the wires  62  and  64  partially contact with the surface of the core body  40 , the wires  62  and  64  and the core  40  can be insulated by the insulation film, and a conductive core, such as a metal core, can be used as the core body  40 . 
     In the present embodiment, the terminal  70  ( 80 ) has the wire joint part  72  ( 82 ), the embedded part  74  ( 84 ), and the mount part  76  ( 86 ) protruding from the terminal table  22  ( 23 ) at a different position from the wire joint part  72  ( 82 ). In this structure, the wire joint part  72  ( 82 ) is easily joined with the wire  62  ( 64 ), and the transformer  10  is easily mounted. Moreover, the terminals  70  and  80  are easily formed integrally with the bobbin  20 . 
     In the present embodiment, the wire joint part  72  ( 82 ) and the mount part  76  ( 86 ) are arranged to protrude outward in the X-axis direction from the terminal table  22  ( 23 ) while being displaced in the Z-axis direction. In this structure, the wire joint part  72  ( 82 ) is easily joined with the wire  62  ( 64 ), and the transformer  10  is easily mounted. Moreover, the terminals  70  and  80  are easily formed integrally with the bobbin  20 . 
     In the present embodiment, the adhesive recesses  30  are formed in the flange storage recesses  24  and  25  of the terminal tables  22  and  23 . The adhesive recesses  30  can store an adhesive on the flange wings  46  of the flanges  44  while the flanges  44  are being housed in the flange storage recesses  24  and  25 . The core body  40  and the bobbin  20  are easily fixed only by flowing an adhesive into the adhesive recesses  30 . The core body  40  and the bobbin  20  are easily positioned, and variations in characteristics can be prevented. Moreover, the core body  40  and the bobbin  20  can simultaneously be adhered and fixed with the plate  50 . 
     Moreover, the terminal table  22  ( 23 ) is provided with the notch  27 , where the boundary part between the winding core  42  and the flange  44  are inserted. Thus, the core body  40  is easily attached and positioned to the bobbin  20 , and workability is improved. In addition, both ends of the plate  50 , which is different from the core body  40 , are respectively inserted into the notches  27  from above, and the plate  50 , the core body  40 , and the bobbin  20  are thereby easily positioned and attached. Incidentally, the plate  50  is not necessarily formed by a magnetic material. In this case, for example, the plate  50  can function as a suction part of a nozzle for mounter for moving a transformer in mounting it. 
     Moreover, as shown in  FIG. 4 , the leading communication grooves  29  as a conductor passage, where the leading parts  62   a ,  62   b ,  64   a , and  64   b  of the wires  62  and  64  pass and go to the wire joint parts  72  and  82  of the terminals  70  and  80 , are formed on the bottom surfaces of the terminal tables  22  and  23  located opposite to the openings of the flange storage recesses  24  and  25  in the Z-axis direction. In this structure, the wires  62  and  64  are easily joined, and the insulation between the core body  40  and the leading parts  62   a ,  62   b ,  64   a , and  64   b  is improved. 
     Second Embodiment 
     A transformer  10   a  as a coil device according to the present embodiment shown in  FIG. 9  to  FIG. 16  has similar structure and similar effects to those of the transformer  10  shown in  FIG. 1  to  FIG. 8  except for the structure of the bobbin. In the following description, common parts are not described as much as possible, and different parts are selectively described. In the figures, common members are provided with common member references. 
     In a bobbin  20   a  of the present embodiment, as most clearly shown in  FIG. 13 , the pair of terminal tables  22  and  23  is integrally formed with a pair of connection side portions  26   a  having a plate wall shape, and a bottom wall  32  having a plate shape integrates the pair of connection side portions  26   a  and covers the entire bottom surface of the winding core  42  of the core body  40 . The bottom wall  32  is also integrated with the terminal tables  22  and  23 . Preferably, the top surface of the bottom wall  32  is substantially flush with the bottom surfaces of the flange storage recesses  24  and  25 . 
     A partition wall  34  is formed at an intermediate position of the connection side portions  26   a  in the X-axis direction, and wires differing from each other are wound in divided sections in the X-axis direction. For example, as shown in  FIG. 12 , a coil  60   a  is constituted so that wires  62  and  63  are continuously wound so as to contact with the pair of connection side portions  26   a , the bottom wall  32 , and the top surface of the winding core  42  (see  FIG. 1 ) in a region located closer to the terminal table  22 , and a coil  60   b  is constituted so that wires  64  and  65  are continuously wound so as to contact with the pair of connection side portions  26   a , the bottom wall  32 , and the top surface of the winding core  42  (see  FIG. 1 ) in a region located closer to the terminal table  23 . 
     The coil  60   a  and the coil  60   b  are separated by the partition wall  34  in the X-axis direction, and for example, the insulation between a primary coil (coil  60   a ) and a secondary coil (coil  60   b ) is improved. Incidentally, the primary coil may be the coil  60   b , and the secondary coil may be the coil  60   a.    
     Three terminals  70   a ,  90 , and  80   a  are attached to each of the terminal tables  22  and  23  of the bobbin  20   a  shown in  FIG. 13 . The terminal  70   a  and the terminal  80   a  have a mutually line-symmetry shape and have a similar structure, but are not completely the same member. Unlike the terminal  70   a  and the terminal  80   a , the terminal  90  disposed between the terminal  70   a  and the terminal  80   a  in the Y-axis direction has two wire joint parts  92   a  and  92   b.    
     The terminal  70   a  has a wire joint part  72   a , an embedded part  74   a , and a mount part  76   a , and these are integrally formed by pressing a conductive plate material, such as a metal piece. The wire joint part  72   a  is integrally formed with a caulking piece  73   a . The terminal  80   a  has a wire joint part  82   a , an embedded part  84   a , and a mount part  86   a , and these are integrally formed by pressing a conductive plate material, such as a metal piece. The wire joint part  82   a  is integrally formed with a caulking part  83   a . The terminals  70   a  and  80   a  are formed by a conductive material that is similar to the material of the terminals  70  and  80  according to First Embodiment. 
     The terminal  90  is a terminal used as, for example, a center tap, and has two wire joint parts  92   a  and  92   b , an embedded part  94  formed integrally with the wire joint parts  92   a  and  92   b  so as to connect them, and a single mount part  96  continuing to the lower end of the embedded part  94 . As is the case with the terminals  70   a  and  80   a , the terminal  90  is also integrally formed by pressing a conductive plate material, such as a metal piece. The wire joint parts  92   a  and  92   b  are integrally formed with the caulking pieces  93   a  and  93   b , respectively. 
     As shown in  FIG. 10 , the embedded parts  74   a ,  84   a , and  94  of the terminals  70   a ,  80   a , and  90  are embedded in an insulation material constituting the bobbin  20   a  located outside the terminal table  22  ( 23 ) in the X-axis direction and located below the terminal table  22  ( 23 ) in the Z-axis direction. Preferably, the embedded part  74   a ,  84   a , and  94  are not exposed on the inner wall surface of the flange storage recess  24  ( 25 ) of the terminal table  22  ( 23 ), but are embedded in the insulation material constituting the bobbin  20   a.    
     The insulation material constituting the bobbin  20   a  is similar to the insulation material constituting the bobbin  20  according to First Embodiment. The terminals  70   a ,  80   a , and  90  are subjected to an insertion molding in the formation of the bobbin  20   a  and are integrated therewith. 
     As shown in  FIG. 10 , the mount parts  76   a ,  86   a , and  96  of the terminals  70   a ,  80   a , and  90  are attached to the bobbin  20   a  so as to protrude outward in the X-axis direction from the end surface of the terminal table  22  ( 23 ) on the lower surface (bottom surface) of the bobbin  20   a . The wire joint parts  72   a ,  82   a , and  92  are attached to the bobbin  20   a  so as to protrude outward in the X-axis direction from the end surface of the terminal table  22  ( 23 ) at a position that is higher than the mount parts  76   a ,  86   a , and  96  in the Z-axis direction. 
     As shown in  FIG. 11  and  FIG. 12 , the mount parts  76   a ,  86   a , and  96  and the wire joint parts  72   a ,  82   a ,  92   a , and  92   b  of the terminals  70   a ,  80   a , and  90  are displaced at substantially equal intervals in the Y-axis direction. In the present embodiment, the wire joint parts  72   a ,  92   a ,  92   b , and  82   b  are arranged in this order at substantially equal intervals in the Y-axis direction, and the embedded parts  74   a ,  94 , and  84   a  shown in  FIG. 10  are embedded into the insulation material constituting the bobbin  20   a  so that the mount parts  76   a ,  96 , and  86   a  are respectively arranged between the wire joint parts  72   a ,  92   a ,  92   b , and  82   a  at substantially equal intervals. 
     Incidentally, as shown in  FIG. 11 , the terminals  70   a ,  90 ,  80   a  of the terminal table  22  are arranged side by side in this order in the Y-axis direction, but the terminals  80   a ,  90 , and  70   a  of the terminal table  23  are arranged in this order. 
     As shown in  FIG. 10 , the bottom surfaces of the mount parts  76   a ,  86   a , and  96  are configured to protrude downward from the bottom surface of the bobbin  20   a  with a predetermined height Z 4 . The predetermined height Z 4  is similar to the predetermined height Z 4  according to First Embodiment. 
     In the present embodiment, as shown in  FIG. 14 , six mount-side protrusions  28  are formed in total on the bottom of the bobbin  20   a , and the bottom surfaces of the mount-side protrusions  28  are the bottom surface of the bobbin  20   a . As shown in  FIG. 12 , three mount-side protrusions  28  are respectively separately formed on the bottom surfaces of the terminal tables  22  and  23  in the Y-axis direction, and leading communication grooves (conductor passages)  29  are formed among the three mount-side protrusions  28 . 
     The leading communication groove  29  has a width Y 1   a  in the Y-axis direction that is preferably substantially equal to a width of the wire joint part  72   a  ( 82   a ,  92 ), but may be larger than a width of the wire joint part  72   a  ( 82   a ,  92 ). A displacement width Y 3  between the wire joint part  72   a  ( 82   a ,  92 ) and the mount part  76   a  ( 86   a ,  96 ) is preferably larger than zero and substantially equal to or less than a width Y 4  of the mount part  76   a  ( 86   a ,  96 ) in the present embodiment. 
     As shown in  FIG. 12 , the outer side surfaces of the mount-side protrusions  28  in the X-axis direction are preferably recessed from the outer end surface of the bobbin  20   a  in the X-axis direction with a predetermined distance X 1 . The predetermined distance X 1  is determined similarly to First Embodiment. A length X 2  of the terminal  22  ( 23 ) in the X-axis direction is also determined similarly to First Embodiment, but can be shorter than a length X 2  according to First Embodiment as the bobbin  20   a  is provided with the bottom wall  32  in the present embodiment. 
     In the present embodiment, as shown in  FIG. 10 , the mount part  76   a  ( 86   a ,  96 ) extends outward from the outer end surface of the mount-side protrusion  28  in the X-axis direction so as to protrude outward from the outer end surface of the bobbin  20   a . A protrusion height Z 5  of the mount-side protrusions  28  is determined similarly to First Embodiment. 
     In the present embodiment, as shown in  FIG. 16 , a slight gap may be formed in the Y-axis direction between the connection side portions  26   a  and the winding core  42  while the winding core  42  of the core body  40  is positioned between the pair of connection side portions  26   a  having a side wall shape. In this state, the connection side portions  26  sandwiching the winding core  42  and the bottom wall  32  located on the bottom surface of the winding core  42  (see  FIG. 14 ) are wound by two wires  62  and  63  constituting the coil  60   a  and two wires  64  and  65  constituting the coil  60   b.    
     The wires  62  to  65  are similar to the wires  62  and  64  according to First Embodiment. The wires  62  to  65  are wound around the winding core  42 , the connection side portions  26 , and the bottom wall  32 , and the coils  60   a  and  60   b  are thereby formed. The winding operation is preferably carried out automatically, but may be carried out manually. 
     Both ends of the wire  62  constituting the coil  60   a  pass the leading communication groove  29  of the terminal table  22  shown in  FIG. 14  and are respectively led to the wire joint parts  82   a  and  92   b  as leading parts  62   a  and  62   b  shown in  FIG. 9 . Similarly, both ends of the wire  63  pass the leading communication groove  29  of the terminal table  22  shown in  FIG. 14  and are respectively led to the wire joint parts  92   a  and  72   a  as leading parts  63   a  and  63   b.    
     The leading parts  62   a ,  62   b ,  63   a , and  63   b  are wound around the wire joint parts  82   a ,  92   b ,  92   a , and  72   a  as necessary and are preliminary fixed by the caulking pieces  83   a ,  93   b ,  93   a , and  73   a . Then, joint portions  100  are formed at tips of the leading parts  62   a ,  62   b ,  63   a , and  63   b , and the leading parts  62   a ,  62   b ,  63   a , and  63   b  and the wire joint parts  82   a ,  92   b ,  92   a , and  72   a  are electrically connected and fixed. Each leading part (not illustrated) of the wires  64  and  65  constituting the coil  60   b  are connected to the wire joint parts  82   a ,  92   b ,  92   a , and  72   a  of the terminal table  23  shown in  FIG. 12  similarly to the leading parts  62   a ,  62   b ,  63   a , and  63   b  mentioned above, and the joint portions  100  are formed. 
     Except for the following effects, the transformer  10   a  according to the present embodiment demonstrates similar effects to those of the transformer  10  according to First Embodiment. In the present embodiment, the bobbin  20   a  does not entirely cover the winding core  42  of the core body  40 , but covers only both sides of the winding core  42  in the Y-axis direction and the bottom surface of the winding core  42  and does not cover the top surface of the winding core  42 . As shown in  FIG. 15 , the bottom wall  32  of the bobbin  20   a  may have a thickness (Z-axis direction) that is smaller than a thickness (Y-axis direction) of the connection side portions  26   a.    
     In the present embodiment, the bobbin  20   a  has a small height, and the transformer  10   a  can thereby have a small height. In the present embodiment, the coil device  10   a  (see  FIG. 10 ) can have a full height Z 0  of preferably 4 mm or less, more preferably 3.5 mm or less. 
     In the present embodiment, withstand voltage is improved, since the flanges  44  of the core body  42  are embedded into the flange storage recesses  24  and  25  of the terminal tables  22  and  23 , and the bottom surface of the winding core  42  in the Z-axis direction and both side surfaces of the winding core  42  in the Y-axis direction are integrally covered with the bottom wall  32  and the connection side portions  26   a . In the present embodiment, a shortest distance between the core body  40  and the terminal  70  or  80  (insulation distance or creepage distance) can sufficiently be large (e.g., 5 mm or more), and insulation resistance is thereby excellent. 
     In the present embodiment, the pair of terminal tables  22  and  23  is formed integrally with the pair of connection side portions  26   a , and the bobbin  20   a  further has the bottom wall  32  integrating the pair of connection side portions  26   a  and covering the bottom surface of the winding core  42 . In the present embodiment, the wires  62  to  65  are furthermore continuously wound so as to contact with the pair of connection side portions  26   a , the bottom wall  32 , and the top surface of the winding core  42 . In this structure, withstand voltage is improved. 
     In the present embodiment, the partition wall  34  is formed at an intermediate position of the connection side portions  26   a  in the X-axis direction, and the wires  62  and  63  (or  64  and  65 ) differing from each other are wound in a divided section in the X-axis direction. In this structure, the insulation between the primary coil  60   a  and the secondary coil  60   b  is improved. 
     Incidentally, the present invention is not limited to the above-mentioned embodiments, and may variously be changed within the scope of the present invention. 
     For example, the core  40  has any shape with a winding core and flanges, such as a so-called U-type core and a drum-type core. Moreover, the number of wires is not limited, and the number of terminals is not limited. The present invention may be an embodiment that combines the components of First and Second Embodiments mentioned above. For example, the connection side portions  26  of First Embodiment may be provided with the partition wall  34  of Second Embodiment. The coil device of the present invention may not have the plate  50 . 
     DESCRIPTION OF THE REFERENCE NUMERICAL 
     
         
           10 ,  10   a  . . . transformer (coil device) 
           20 ,  20   a  . . . bobbin 
           22 ,  23  . . . terminal table 
           24 ,  25  . . . flange storage recess 
           26 ,  26   a  . . . connection side portion 
           27  . . . notch 
           28  . . . mount-side protrusion 
           29  . . . leading communication groove 
           30  . . . adhesive recess 
           32  . . . bottom wall 
           34  . . . partition wall 
           40  . . . core body 
           42  . . . winding core 
           44  . . . flange 
           45  . . . flange central part 
           46  . . . flange wing 
           50  . . . plate 
           60  . . . coil 
           62  to  65  . . . wire 
           62   a ,  62   b ,  63   a ,  63   b  . . . leading part 
           70 ,  70   a ,  80 ,  80   a ,  90  . . . terminal 
           72 ,  72   a ,  82 ,  82   a ,  92   a ,  92   b  . . . wire joint part 
           73 ,  73   a ,  83 ,  83   a ,  93   a ,  93   b  . . . caulking piece 
           74 ,  74   a ,  84 ,  84   a ,  94  . . . embedded part 
           76 ,  76   a ,  86 ,  86   a ,  96  . . . mount part 
           100  . . . joint portion