Patent Publication Number: US-2021183563-A1

Title: Coil component

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims benefit of priority to Japanese Patent Application No. 2019-223502, filed Dec. 11, 2019, the entire contents of which is incorporated herein by reference. 
     BACKGROUND 
     Technical Field 
     The present disclosure relates to coil components and more specifically to a coil component, such as a common-mode choke coil, in which a holder holds a pair of coil conductors cylindrically wound and a frame-shaped magnetic core extending through the coil conductors. 
     Background Art 
     In recent years, small coil components, such as common-mode choke coils, in power supply circuits in electric vehicles or the like have been used to reduce noise arising from switching in the circuits. 
     For such coil components, a technique of housing a coil conductor and a magnetic core in a casing made of an insulating material has been known. 
     One example coil component proposed in Japanese Unexamined Patent Application Publication No. 2009-123825 (see, for example, pars. [0019] to [0028] and FIG. 4), which is illustrated in  FIG. 21 .  FIG. 22  is an enlarged cross-sectional view of an “a” section in  FIG. 21 . 
     In the coil component in Japanese Unexamined Patent Application Publication No. 2009-123825, a pair of coil conductors and a pair of magnetic cores (not illustrated) are housed in a coil casing  103  including a first casing member  101  and a second casing member  102 . The first casing member  101  includes a base plate section  104 , a first barrier plate section  105 , a partition barrier plate section  106 , and side plate sections  107   a  and  107   b,  and those elements are integrally formed of an insulating material. The first barrier plate section  105  has bobbin insertion holes  105   a  and  105   b  in predetermined positions. The second casing member  102  includes a second barrier plate section  108  and a pair of coil bobbin sections  109   a  and  109   b,  and those elements are integrally formed of an insulating material. The second barrier plate section  108  has a partition insertion hole  110  for fitting a leading end of the partition barrier plate section  106  therein, as illustrated in  FIG. 22 . 
     The coil component in Japanese Unexamined Patent Application Publication No. 2009-123825 is assembled in the following way. That is, after the pair of coil conductors are arranged in predetermined positions in space defined by the base plate section  104  and the side plate sections  107   a  and  107   b,  the second casing member  102  is mounted to the first casing member  101  while the coil bobbin sections  109   a  and  109   b  are inserted into the coil conductors and the bobbin insertion holes  105   a  and  105   b  and the leading end of the partition barrier plate section  106  is inserted into the partition insertion hole  110 . Of the pair of magnetic cores, one magnetic core is inserted into the coil bobbin sections  109   a  and  109   b  from the side on which the first barrier plate section  105  in the first casing member  101  is positioned, the other magnetic core is inserted into the coil bobbin sections  109   a  and  109   b  from the side on which the second barrier plate section  108  in the second casing member  102  is positioned, the pair of magnetic cores are coupled together and form a closed magnetic circuit, and the coil component is obtained. 
     In recent years, a driving voltage for a power supply circuit in an electric vehicle or the like has tended to increase, and there have been demands that a coil component used therein have satisfactory withstand voltage performance and be miniaturized. 
     In the coil component in Japanese Unexamined Patent Application Publication No. 2009-123825, however, as illustrated in  FIG. 22  described above, because the partition barrier plate section  106  for separating the coil conductors is inserted into the partition insertion hole  110 , a gap t is inevitably present between the partition insertion hole  110  and the partition barrier plate section  106 . That is, for the coil component in Japanese Unexamined Patent Application Publication No. 2009-123825, because of the gap t between the partition insertion hole  110  and the partition barrier plate section  106 , the insulation between the coil conductors may be inadequate, and its withstand voltage performance may be insufficient. 
     SUMMARY 
     Accordingly, the present disclosure provides a coil component, such as a common-mode choke coil, being small, capable of ensuring sufficient insulation, and having satisfactory withstand voltage performance. 
     According to preferred embodiments of the present disclosure, a coil component includes a frame-shaped magnetic core including wound sections facing each other, a pair of coil conductors in which a wire is cylindrically wound, and a holder made of an insulating material and surrounding and holding the pair of coil conductors and the magnetic core. The magnetic core extends through the coil conductors such that the coil conductors and the wound sections are associated with each other. The holder includes a first partition disposed between the magnetic core and a first winding wire end of each of the coil conductors, a second partition disposed between the magnetic core and a second winding wire end of each of the coil conductors, and a third partition disposed between the pair of coil conductors. The first partition, the second partition, and the third partition are integrally formed. 
     Because the first partition, the second partition, and the third partition are integrally formed, no gaps are present between the first to third partitions, and the coil component that can ensure sufficient insulation and that has satisfactory withstand voltage performance is obtainable. 
     According to preferred embodiments of the present disclosure, the magnetic core in the coil component may preferably is separable into a first magnetic core and a second magnetic core, the first partition may preferably be disposed between the first magnetic core and each of the first winding wire ends, and the second partition may preferably be disposed between the second magnetic core and each of the second winding wire ends. 
     After the pair of coils are set to the first to third integrally formed partitions, the first magnetic core and the second magnetic core are set, and therefore, sufficient electrical insulation is provided between the magnetic core and each of the first and second coil conductors and between the first coil conductor and the second coil conductor. Thus, the coil component that can ensure sufficient insulation and that has satisfactory withstand voltage performance and a closed magnetic circuit configuration is easily obtainable. 
     According to preferred embodiments of the present disclosure, the wire in the coil component may preferably be a rectangular wire. 
     Because the space factor in the case of the rectangular wire can be larger than that in the case of a round wire, the rated current can be increased, and the high-performance coil component is obtainable. 
     According to preferred embodiments of the present disclosure, the magnetic core in the coil component may preferably be fixed by a fastening unit made of a metallic material. 
     According to preferred embodiments of the present disclosure, the fastening unit in the coil component may preferably include a terminal section, and the terminal section may preferably be arranged in a position opposed to a mounting substrate. The terminal section may preferably be coated with plating. 
     The terminal section in the fastening unit can be bonded directly to the mounting substrate with soldering or the like interposed therebetween, the strength of adhesion between the mounting substrate and the coil component can be easily enhanced, and the coil component with satisfactory substrate mountability is obtainable. 
     According to preferred embodiments of the present disclosure, the coil conductors in the coil component may preferably be of a transversely wound type or a longitudinally wound type. 
     When the coil conductors of the transversely wound type or the longitudinally wound type is used, the coil component with satisfactory insulation and satisfactory withstand voltage performance is obtainable. 
     According to preferred embodiments of the present disclosure, the holder in the coil component may preferably be placed on a support. 
     Even when the coil component is of the longitudinally wound type, because the holder holding the magnetic core and the coil conductors is disposed on the support, like the transversely wound type, the coil component that can ensure sufficient insulation and that has satisfactory withstand voltage performance is obtainable. 
     According to preferred embodiments of the present disclosure, the magnetic core in the coil component may preferably be made of a ferrite-based material. 
     According to preferred embodiments of the present disclosure, the coil component may preferably be a common-mode choke coil. 
     Even when being used in a power supply line, the common-mode choke coil having satisfactory insulation, having satisfactory withstand voltage performance, and being useful as a noise reduction filter is obtainable. 
     According to the coil component in preferred embodiments of the present disclosure, no gaps are present between the first to third partitions, and the small coil component that can ensure sufficient insulation and that has satisfactory withstand voltage performance is obtainable. 
     Other features, elements, characteristics and advantages of the present disclosure will become more apparent from the following detailed description of preferred embodiments of the present disclosure with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an overall perspective view that schematically illustrates one embodiment (first embodiment) of a common-mode choke coil as a coil component according to the present disclosure; 
         FIG. 2  is a front view of the first embodiment; 
         FIG. 3  is a cross-sectional view in the direction of the arrows A in  FIG. 2 ; 
         FIG. 4  is a side view of  FIG. 2 ; 
         FIG. 5  is a bottom view of  FIG. 2 ; 
         FIG. 6  is a front view of a holder according to the first embodiment; 
         FIG. 7  is a perspective view of the holder; 
         FIG. 8  is a perspective view in the direction of the arrows B in  FIG. 7 ; 
         FIG. 9  is a perspective view in the direction of the arrows C in  FIG. 7 ; 
         FIG. 10  is a perspective view for describing an assembly process in the first embodiment; 
         FIG. 11  is an overall perspective view that schematically illustrates a second embodiment of the common-mode choke coil as the coil component according to the present disclosure; 
         FIG. 12  is a plan view of the second embodiment; 
         FIG. 13  is a cross-sectional view in the direction of the arrows D in  FIG. 12 ; 
         FIG. 14  is a side view of  FIG. 12 ; 
         FIG. 15  is a perspective view of a support; 
         FIG. 16  is a bottom view of  FIG. 12 ; 
         FIG. 17  is an overall perspective view of a holder according to the second embodiment; 
         FIG. 18  is a perspective view in the direction of the arrows E in  FIG. 16 ; 
         FIG. 19  is a perspective view in the direction of the arrows F in  FIG. 16 ; 
         FIG. 20  is a perspective view for describing an assembly process in the second embodiment; 
         FIG. 21  is a cutaway front view of a coil casing described in Japanese Unexamined Patent Application Publication No. 2009-123825; and 
         FIG. 22  is an enlarged cross-sectional view of  FIG. 21 . 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure are described below. 
     First Embodiment 
       FIG. 1  is an overall perspective view that schematically illustrates one embodiment (first embodiment) of a common-mode choke coil as a coil component according to the present disclosure, and  FIG. 2  is a front view thereof. 
     The common-mode choke coil includes a frame-shaped magnetic core  1  made of a ferrite material, a pair of coil conductors (first coil conductor  3   a  and second coil conductor  3   b ) in which a wire  2  is cylindrically wound, and a holder  4  made of an insulating material and surrounding and holding the first and second coil conductors  3   a  and  3   b  and the magnetic core  1 . 
     In the first embodiment, the first and second coil conductors  3   a  and  3   b  are of the transversely wound type in which their winding axes are substantially in parallel with a horizontal plane. 
       FIG. 3  is a cross-sectional view in the direction of the arrows A in  FIG. 2 . 
     That is, the magnetic core  1  is separated into a first magnetic core  1   a  and a second magnetic core  1   b.  The first magnetic core  1   a  and the second magnetic core  1   b  are coupled together and form the frame-shaped magnetic core  1 . 
     Specifically, the magnetic core  1  includes a pair of wound sections (first wound section  5   a  and second wound section  5   b ) facing each other. The first and second wound sections  5   a  and  5   b  in the magnetic core  1  extend through the first and second coil conductors  3   a  and  3   b,  respectively, such that the first coil conductor  3   a  and the first wound section  5   a  are associated with each other and the second coil conductor  3   b  and the second wound section  5   b  are associated with each other. 
     The ferrite material of the magnetic core  1  is not limited, and various ferrite materials can be used. Examples thereof may include Ni-based, Cu—Zn-based, Ni—Zn-based, Mn—Zn-based, and Ni—Cu—Zn-based ferrite materials. 
     The holder  4  includes first to third partitions  24  to  26 . Those first to third partitions  24  to  26  are integrally formed, and thus sufficient electrical insulation is provided between the magnetic core  1  and the first and second coil conductors  3   a  and  3   b  and desired withstand voltage performance is ensured. Specifically, the first to third partitions  24  to  26  are integrally formed by shape processing, such as injection molding, so as to have a substantially I-shaped cross section at the time of producing the holder  4 . That is, the first partition  24  is disposed between the first magnetic core  1   a  and each of the first and second coil conductors  3   a  and  3   b,  the second partition  25  is disposed between the second magnetic core  1   b  and each of the first and second coil conductors  3   a  and  3   b,  and the third partition  26  is disposed between the first coil conductor  3   a  and the second coil conductor  3   b.    
       FIG. 4  is a side view of the common-mode choke coil and illustrates the details of the coil conductors. 
     In the first embodiment, the wire  2  is a coated rectangular wire. The coated rectangular wire is the one in which the core is made of a metal material, such as copper, aluminum, or an alloy of them, and is coated with an enamel material, such as polyamide-imide. When the coated rectangular wire is used as the wire  2 , the space factor can be increased, and the rated current can be raised, in comparison with the case where a coated round wire is used. Thus, the high-performance small common-mode choke coil is obtainable. 
     The first coil conductor  3   a  and the second coil conductor  3   b  have the same shape, and in the first embodiment, they are edgewise wound coils in which a flat coated rectangular wire is bent in the width direction and wound. 
     The first and second coil conductors  3   a  and  3   b  include winding sections  6   a  and  6   b  in which the wire  2  is cylindrically wound, as illustrated in  FIG. 4 . The winding sections  6   a  and  6   b  have first winding wire ends  7   a  and  7   b  bent into an approximately U shape and forming inclined sections  8   a  and  8   b.  The distal ends of the inclined sections  8   a  and  8   b  are bent into an approximately L shape toward the winding sections  6   a  and  6   b  so as to be able to engage with the holder  4  and thus form first extended sections  9   a  and  9   b.  The winding sections  6   a  and  6   b  has second winding wire ends  10   a  and  10   b  extending downward and having distal ends curved into an approximately V shape and forming inclined sections  11   a  and  11   b.  The distal ends of the inclined sections  11   a  and  11   b  are bent into an approximately L shape toward the winding sections  6   a  and  6   b,  that is, in positions facing the first extended sections  9   a  and  9   b  so as to be able to engage with the holder  4  and thus form second extended sections  12   a  and  12   b.    
     The magnetic core  1  is fixed by a fastening unit  13  made of a metallic material and laid across the holder  4 , as illustrated in  FIGS. 1 and 2 . Specifically, the fastening unit  13  has an approximately U-shaped cross section, and both of its distal ends are bent into an approximately L shape, face each other so as to be able to engage with the holder  4 , and form terminal sections  14   a  and  14   b.  The terminal sections  14   a  and  14   b  are arranged in positions opposed to a mounting substrate (not illustrated) and can be bonded to the mounting substrate by soldering or the like. Therefore, it is not necessary to provide a dummy electrode or the like on the back side of the holder  4 , the bonding strength between the common-mode choke coil and the mounting substrate can be enhanced, and the common-mode choke coil with satisfactory mounting strength is obtainable. 
     In that case, the fastening unit  13  can be made of any metallic material and may preferably be made of a known material having satisfactory wettability, such as nickel silver, which is a copper-zinc-nickel alloy. If other general metallic material is used, at least the terminal sections  14   a  and  14   b  may preferably be coated with plating using tin, a tin alloy, or the like. That plating leads to satisfactory solderability even when reflow heating is performed, and desired satisfactory mounting strength is obtainable. 
     The fastening unit  13  may preferably be subjected to processing for springiness. When the fastening unit  13  has the springiness, the distance between the terminal sections  14   a  and  14   b  in the fastening unit  13  can be slightly narrowed, and upon attaching the fastening unit  13  from above the holder  4 , the fastening unit  13  can firmly fix the magnetic core  1  by its elastic urging force. 
       FIG. 5  is a bottom view of the common-mode choke coil and illustrates a relation of the extended sections in the coil conductors, the terminal sections in the fastening unit, and the holder. 
     In the first embodiment, the holder  4  is arranged in a position opposed to the mounting substrate (not illustrated), the terminal sections  14   a  and  14   b  in the fastening unit  13  are secured in a substantially central area of the holder  4 , and the extended sections  9   a,    9   b,    12   a,  and  12   b  in the first and second coil conductors  3   a  and  3   b  are secured in the vicinities of both ends of the holder  4 . 
     Next, the holder  4  is described in detail with reference to  FIGS. 6 to 9 . 
       FIG. 6  is a front view of the holder  4 .  FIG. 7  is an overall perspective view of the holder  4 .  FIG. 8  is a perspective view in the direction of the arrows B in  FIG. 7 .  FIG. 9  is a perspective view in the direction of the arrows C in  FIG. 7 . 
     The holder  4  includes an upper surface section  15  and a lower surface section  16 , both of which have a flat shape, and an intermediate section  17  disposed between the upper surface section  15  and the lower surface section  16  and on which the first and second coil conductors  3   a  and  3   b  and the magnetic core  1  are arranged. The upper surface section  15 , the lower surface section  16 , and the intermediate section  17  are made of an insulating material, such as insulating resin, and are integrally formed by shape processing, such as injection molding or transfer molding. 
     The upper surface section  15  has a slot section  18  for use in fitting and attaching the fastening unit  13  thereto in a substantially central area in the surface. The slot section  18  is substantially parallel with the winding axes of the first and second coil conductors  3   a  and  3   b.    
     The lower surface section  16  has a pair of first depressions  19   a  and  19   b  for engaging with the terminal sections  14   a  and  14   b  in the fastening unit  13  in side positions opposed to the slot section  18 . The lower surface section  16  also has a pair of second depressions  20   a  and  20   b  and a pair of third depressions  21   a  and  21   b  for engaging with the extended sections  12   a  and  9   a  in the first coil conductor  3   a  and the extended sections  12   b  and  9   b  in the second coil conductor  3   b,  respectively, in side positions in the vicinities of both end portions. 
     As illustrated in  FIGS. 8 and 9 , the intermediate section  17  has a pair of cavities  22   a  and  22   b  having a substantially U-shaped cross section, allowing insertion of the first and second coil conductors  3   a  and  3   b  from directions with arrows X and X′ and insertion of the first and second magnetic cores  1   a  and  1   b  from directions with arrows Y and Y′, and enabling electrical insulation between the first and second coil conductors  3   a  and  3   b.    
     Therefore, the first partition  24  is disposed between the magnetic core  1  (first magnetic core  1   a ) and the first winding wire ends  7   a  and  7   b  of the first and second coil conductors  3   a  and  3   b,  the second partition  25  is disposed between the magnetic core  1  (second magnetic core  1   b ) and the second winding wire ends  10   a  and  10   b  of the first and second coil conductors  3   a  and  3   b,  and moreover, the third partition  26  is disposed between the first coil conductor  3   a  and the second coil conductor  3   b.  That is, the first to third partitions  24  to  26  are integrally formed so as to have a substantially I-shaped cross section. 
       FIG. 10  is a perspective view that illustrates a process for assembling the common-mode choke coil. 
     First, the first and second coil conductors  3   a  and  3   b  are inserted into the cavities  22   a  and  22   b  in the holder  4 , the end portions of the first and second coil conductors  3   a  and  3   b  are bent into an approximately L shape and form the extended sections  12   a,    9   a,    12   b,  and  9   b,  and the extended sections  12   a,    9   a,    12   b,  and  9   b  are secured to the second and third depressions  20   a,    20   b,    21   a,  and  21   b  in the holder  4  (lower surface section  16 ). Then, the first magnetic core  1   a  and the second magnetic core  1   b  are inserted into the cylindrical spaces of the first and second coil conductors  3   a  and  3   b,  the first magnetic core  1   a  and the second magnetic core  1   b  are coupled together, and the frame-shaped magnetic core  1  is produced. After that, the fastening unit  13  is fit and attached to the slot section  18  in the holder  4  (upper surface section  15 ), and the terminal sections  14   a  and  14   b  are secured to the first depressions  19   a  and  19   b  in the holder  4  (lower surface section  16 ). In that way, the common-mode choke coil is assembled. 
     In the common-mode choke coil having the above-described configuration, the magnetic core  1 , in which the first magnetic core  1   a  and the second magnetic core  1   b  are coupled, forms a closed magnetic circuit. When a normal-mode current flows through the first and second coil conductors  3   a  and  3   b,  magnetic fluxes occur in the first and second coil conductors  3   a  and  3   b  in mutually opposite directions, the magnetic fluxes are canceled out, and they do not serve the function as an inductor. In contrast, when a common-mode current flows through the first and second coil conductors  3   a  and  3   b,  magnetic fluxes occur in the first and second coil conductors  3   a  and  3   b  in the same direction, and they function as the inductor. That is, they does not function as the inductor and a signal component is transmitted in the normal mode, whereas they function as the inductor and a noise component is transmitted in the common mode. Therefore, signals and noises can be separated by the use of the above-described difference in the transmission modes, and the noises can be reduced. 
     In the first embodiment, the holder  4  includes the first partition  24  disposed between the first magnetic core  1   a  included in the magnetic core  1  and the first winding wire ends  7   a  and  7   b  of the first and second coil conductors  3   a  and  3   b,  the second partition  25  disposed between the second magnetic core  1   b  included in the magnetic core  1  and the second winding wire ends  10   a  and  10   b  of the first and second coil conductors  3   a  and  3   b,  and the third partition  26  disposed between the first coil conductor  3   a  and the second coil conductor  3   b,  and the first partition  24 , the second partition  25 , and the third partition  26  are integrally formed by shape processing, such as injection molding. Therefore, there are no gaps between the first to third partitions  24  to  26 , and accordingly, sufficient electrical insulation is provided between the magnetic core  1  and each of the first and second coil conductors  3   a  and  3   b  and between the first coil conductor  3   a  and the second coil conductor  3   b,  the insulation can be stabilized, and the coil component with satisfactory withstand voltage performance is obtainable. 
     In addition, because the fastening unit  13  includes the terminal sections  14   a  and  14   b  and may preferably be made of a known material having satisfactory wettability, such as nickel silver, or the terminal sections  14   a  and  14   b  may preferably be coated with plating, the terminal sections  14   a  and  14   b  are fixed directly to a mounting substrate with soldering or the like interposed therebetween, the adhesion strength between the mounting substrate and the common-mode choke coil can be easily enhanced, and the common-mode choke coil with satisfactory substrate mountability is obtainable. 
     Moreover, because the wire  2  is a coated rectangular wire, the space factor can be increased, and the rated current can be raised, in comparison with the case where a coated round wire is used. Thus, the high-performance coil component is obtainable. 
     Second Embodiment 
       FIG. 11  is an overall perspective view that illustrates a second embodiment of the common-mode choke coil as the coil component according to the present disclosure, and  FIG. 12  is a plan view thereof. 
     In the first embodiment, the common-mode choke coil of the transversely wound type is illustrated. In the second embodiment, the common-mode choke coil of the longitudinally wound type is illustrated. 
     That is, the common-mode choke coil according to the second embodiment includes a frame-shaped magnetic core  31  made of a ferrite material, a first coil conductor  33   a  and a second coil conductor  33   b  in which a wire  32  is cylindrically wound, and a holder  34  made of an insulating material and surrounding and holding the first and second coil conductors  33   a  and  33   b  and the magnetic core  31 , approximately like the first embodiment. In the second embodiment, the magnetic core  31  is arranged in a direction substantially perpendicular to a horizontal plane, the magnetic core  31  extends through the first and second coil conductors  33   a  and  33   b,  the winding axes of the first and second coil conductors  33   a  and  33   b  are substantially perpendicular to the horizontal plane, and the holder  34  is placed on a support  35 . 
       FIG. 13  is a cross-sectional view in the direction of the arrows D in  FIG. 12 . 
     The magnetic core  31  is separated into a first magnetic core  31   a  and a second magnetic core  31   b,  approximately like the first embodiment. The first magnetic core  31   a  and the second magnetic core  31   b  are coupled together and form the frame-shaped magnetic core  31 . 
     Specifically, the magnetic core  31  includes a first wound section  36   a  and a second wound section  36   b  facing each other and extends through the first and second coil conductors  33   a  and  33   b  such that the first coil conductor  33   a  and the first wound section  36   a  are associated with each other and the second coil conductor  33   b  and the second wound section  36   b  are associated with each other. 
     The holder  34  includes first to third partitions  37  to  39 , and the first to third partitions  37  to  39  are integrally formed. Therefore, sufficient electrical insulation is provided between the magnetic core  31  and the first and second coil conductors  33   a  and  33   b,  and desired withstand voltage performance is ensured. Specifically, approximately like in the first embodiment, the first to third partitions  37  to  39  are integrally formed by shape processing, such as injection molding, so as to have a substantially I-shaped cross section at the time of producing the holder  34 . That is, the first partition  37  is disposed between the first magnetic core  31   a  and the first and second coil conductors  33   a  and  33   b,  the second partition  38  is disposed between the second magnetic core  31   b  and the first and second coil conductors  33   a  and  33   b,  and the third partition  39  is disposed between the first coil conductor  33   a  and the second coil conductor  33   b.    
       FIG. 14  is a side view of the common-mode choke coil and illustrates the details of the coil conductors. 
     The first coil conductor  33   a  and the second coil conductor  33   b  have the same shape, like in the first embodiment, and include winding sections  40   a  and  40   b  in which the wire  32  being a coated rectangular wire is cylindrically wound. In the first and second coil conductors  33   a  and  33   b,  the winding sections  40   a  and  40   b  include first winding wire ends  41   a  and  41   b,  their distal ends are curved and form inclined sections  42   a  and  42   b,  and distal ends of the inclined sections  42   a  and  42   b  are bent toward the winding sections  40   a  and  40   b  into an approximately L shape so as to be able to engage with the support  35  and form first extended sections  43   a  and  43   b.  The winding sections  40   a  and  40   b  include second winding wire ends  44   a  and  44   b  extending downward, their distal ends are curved into an approximately V shape and form inclined sections  45   a  and  45   b,  and distal ends of the inclined sections  45   a  and  45   b  are bent into an approximately L shape toward the winding sections  40   a  and  40   b,  that is, in positions facing the first extended sections  43   a  and  43   b  so as to be able to engage with the support  35  and form second extended sections  46   a  and  46   b.    
     The magnetic core  31  and the holder  34  are fixed by a fastening unit  47  made of a metallic material. Specifically, as illustrated in  FIGS. 11 and 12 , the fastening unit  47  has an approximately square U-shaped cross section and includes a cross-shaped flat section  48  in contact with the magnetic core  31 , and both of its distal ends are bent into an approximately L shape and face each other so as to be able to engage with the support  35  grasped by the holder  34 . Thus, the distal ends of the fastening unit  47  form terminal sections  49   a  and  49   b  and, like in the first embodiment, the common-mode choke coil can be easily mounted on the mounting substrate (not illustrated) with soldering or the like interposed therebetween. 
       FIG. 15  is a perspective view that illustrates an example of the above-described support. 
     That is, the support  35  is made from a flat plate and has a substantially oval hole  50  for allowing the magnetic core  31  to extend therethrough. The support  35  includes a pair of first support depressions  51   a  and  51   b  grasped by the holder  34  and engaging with the terminal sections  49   a  and  49   b  in the fastening unit  47  in substantially central areas of its sides. The support  35  also includes a pair of second support depressions  52   a  and  52   b  and a pair of third support depressions  53   a  and  53   b  for engaging with the extended sections  46   a  and  43   a  in the first coil conductor  33   a  and the extended sections  46   b  and  43   b  in the second coil conductor  33   b,  respectively, in the vicinities of both end portions. 
       FIG. 16  is a bottom view of the common-mode choke coil and illustrates a relation of the support, the magnetic core, the extended sections in the coil conductors, and the terminal sections in the fastening unit. 
     The support  35  opposed to the mounting substrate (not illustrated) has the substantially oval hole  50  for allowing the magnetic core  31  to be exposed, as previously described, the terminal sections  49   a  and  49   b  in the fastening unit  47  are secured in the substantially central areas, and the extended sections  43   a  and  46   a  in the first coil conductor  33   a  and the extended sections  43   b  and  46   b  in the second coil conductor  33   b  are secured in the vicinities of both ends. 
     Next, the holder  34  is described in detail with reference to  FIGS. 17 to 19 . 
       FIG. 17  is an overall perspective view of the holder  34 .  FIG. 18  is a perspective view in the direction of the arrows E in  FIG. 17 .  FIG. 19  is a perspective view in the direction of the arrows F in  FIG. 17 . 
     The holder  34  includes an upper surface section  54  and a lower surface section  55 , both of which have a flat shape, and an intermediate section  56  connecting the upper surface section  54  and the lower surface section  55 . Like in the first embodiment, the upper surface section  54 , the lower surface section  55 , and the intermediate section  56  are integrally formed by shape processing, such as injection molding or transfer molding. 
     The upper surface section  54  has a pair of upper U-shaped depressions  57   a  and  57   b  having a substantially U shape in both end portions so as to allow the magnetic core  31  to extend therethrough. 
     The lower surface section  55  has a flat shape, like the upper surface section  54 , and includes lower U-shaped depressions  58   a  and  58   b  having a substantially U shape and facing the upper U-shaped depressions  57   a  and  57   b.  The lower surface section  55  includes projections  59   a  and  59   b  having a substantially L-shaped cross section and used for grasping the support  35  in substantially central areas thereof. 
     As illustrated in  FIGS. 18 and 19 , the intermediate section  56  has a pair of U-shaped cavities  60   a  and  60   b  having a substantially U shape, allowing insertion of the first and second coil conductors  33   a  and  33   b  from directions with arrows V and V′ and insertion of the first and second magnetic cores  31   a  and  31   b  from directions with arrows W and W′, and continuous with the upper U-shaped depressions  57   a  and  57   b  and the lower U-shaped depressions  58   a  and  58   b  so as to enable electrical insulation between the first and second coil conductors  33   a  and  33   b.    
     Therefore, the first partition  37  is disposed between the magnetic core  31  (first magnetic core  31   a ) and the first winding wire ends  41   a  and  41   b  of the first and second coil conductors  33   a  and  33   b,  the second partition  38  is disposed between the magnetic core  31  (second magnetic core  31   b ) and the second winding wire ends  44   a  and  44   b  of the first and second coil conductors  33   a  and  33   b,  and, moreover, the third partition  39  is disposed between the first coil conductor  33   a  and the second coil conductor  33   b.    
       FIG. 20  is a perspective view that illustrates a process for assembling the common-mode choke coil. 
     That is, the projections  59   a  and  59   b  in the holder  34  are secured to the first support depressions Ma and  51   b  in the support  35 , thus the support  35  is grasped by the holder  34 , and the holder  34  is placed on the support  35 . Then, the first and second coil conductors  33   a  and  33   b  are inserted into the U-shaped cavities  60   a  and  60   b  in the holder  34 , and the extended sections  43   a  and  46   a  in the first coil conductor  33   a  and the extended sections  43   b  and  46   b  in the second coil conductor  33   b  are secured to the second support depressions  52   b  and  52   a  and the third support depressions  53   b  and  53   a  in the support  35 . Then, the first magnetic core  31   a  and the second magnetic core  31   b  are inserted into the cylindrical spaces of the first and second coil conductors  33   a  and  33   b,  and both are coupled together. After that, the fastening unit  47  is attached such that the cross-shaped flat section  48  is positioned on the surface of the magnetic core  31 , and the terminal sections  49   a  and  49   b  in the fastening unit  47  are secured to the first support depressions  51   a  and  51   b  in the support  35 . In that way, the common-mode choke coil can be assembled. 
     In the common-mode choke coil having the above-described configuration, like in the first embodiment, the holder  34  includes the first partition  37  disposed between the first magnetic core  31   a  and the first winding wire ends  41   a  and  41   b  of the first and second coil conductors  33   a  and  33   b,  the second partition  38  disposed between the second magnetic core  31   b  and the second winding wire ends  44   a  and  44   b  of the first and second coil conductors  33   a  and  33   b,  and the third partition  39  disposed between the first coil conductor  33   a  and the second coil conductor  33   b.  Because the first partition  37 , the second partition  38 , and the third partition  39  are integrally formed by shape processing, such as injection molding, there are no gaps between the first to third first partitions  37  to  39 , like in the first embodiment. Accordingly, sufficient electrical insulation is provided between the magnetic core  31  and the first and second coil conductors  33   a  and  33   b  and between the first coil conductor  33   a  and the second coil conductor  33   b,  the insulation is stabilized, and the coil component with satisfactory withstand voltage performance is obtainable. 
     The present disclosure is not limited to the above-described embodiments, and they can be changed within a range that does not depart from the scope. That is, in the present disclosure, the above-described first to third partitions  24  to  26  and  37  to  39  are integrally formed, and the other shapes in the above-described embodiments are illustrated as examples. The processing performed as appropriate in the above-described embodiments exerts no effect on the present disclosure. 
     As for the plating on the fastening units  13  and  47 , only the terminal sections  14   a,    14   b,    49   a,  and  49   b  are coated with the plating in the above-described embodiments. The fastening units  13  and  47  may be entirely coated with the plating. 
     Example application to the common-mode choke coil is described in the above-described embodiments. The present disclosure is also applicable to various types of coil components, other than the common-mode choke coil. 
     The small coil component that can ensure sufficient insulation and that has satisfactory withstand voltage performance is obtainable. 
     While preferred embodiments of the disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the disclosure. The scope of the disclosure, therefore, is to be determined solely by the following claims.