Patent Publication Number: US-7714690-B2

Title: Coil component

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a coil component in which first and second coil parts are coupled together. 
   2. Related Background Art 
   Japanese Patent Application Laid-open No. 2006-332263 describes a coil component comprised of two coil parts and a middle core. Each of the two coil parts has a drum core with a winding wound thereon. The middle core couples the two coil parts to each other to form closed magnetic paths with their drum cores. 
   SUMMARY OF THE INVENTION 
   In the coil component described in the foregoing Application Laid-open No. 2006-332263, the middle core functions as a common magnetic path to the two coil parts. In this case, a problem of occurrence of crosstalk arises when a signal is allowed to flow simultaneously through the two coil parts. 
   The present invention has been accomplished in order to solve the above problem and an object of the invention is to provide a coil component with a first coil part and a second coil part being coupled together, which is capable of achieving reduction in crosstalk between the first and second coil parts. 
   A coil component of the present invention comprises: a first coil part and a second coil part each of which includes a core having a winding drum and a flange located at least at one end of the winding drum, and a winding arranged in the winding drum; a middle member located between the first coil part and the second coil part arranged in a state in which axes of the winding drums in the respective first and second coil parts are parallel to each other; and a resinous shield member formed at least in part of peripheral surfaces of the respective first and second coil parts and containing a magnetic material powder; wherein a magnetic permeability of the middle member is lower than that of the core and the shield member. 
   In the coil component of the present invention, the middle member with the magnetic permeability lower than that of the core and the shield member is located between the first coil part and the second coil part. This configuration reduces the crosstalk between the first coil part and the second coil part. Since the shield member is formed at least in part of the peripheral surfaces of the respective first and second coil parts, mutually different magnetic paths are formed for the first and second coil parts. Consequently, this configuration enhances the shield effect and improves the inductance characteristics. Since the shield member is resinous, it can be readily formed at any position on the first and second coil parts even in the coil component of a compact size. 
   Preferably, the middle member is bonded to the flange with an adhesive. When the coil component is constructed in this configuration, the middle member can define a distance between the first coil part and the second coil part in a production process. This can reduce variation in the distance between the first and second coil parts. Therefore, a minimum distance can be defined taking the crosstalk between the first and second coil parts into account whereby the coil component can be constructed in a more compact size. 
   Preferably, the middle member is a resinous member and is in close contact with the first and second coil parts. In this case, the middle member is filled and hardened between the first and second coil parts and in gaps to enhance the strength of the component. 
   Preferably, the magnetic permeability of the shield member is lower than that of the core. This allows the shield member to exercise a function equivalent to a gap, in a magnetic path composed of the core and the shield member. Therefore, it becomes feasible to achieve excellent DC bias characteristic. 
   The present invention reduces the crosstalk between the first and second coil parts in the coil component in which the first coil part and the second coil part are coupled together. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a coil component according to the first embodiment. 
       FIG. 2  is a schematic view showing a II-II cross section of the coil component shown in  FIG. 1 . 
       FIG. 3  is a schematic view showing a III-III cross section of the coil component shown in  FIG. 1 . 
       FIG. 4  is a perspective view of a middle member in the coil component shown in  FIG. 1 . 
       FIG. 5  is a schematic view of a coil component according to a first modification example of the first embodiment. 
       FIG. 6  is a schematic view of a coil component according to a second modification example of the first embodiment. 
       FIG. 7  is a perspective view of a coil component according to the second embodiment. 
       FIG. 8  is a schematic view showing an VIII-VIII cross section of the coil component shown in  FIG. 7 . 
       FIG. 9  is a schematic view showing a IX-IX cross section of the coil component shown in  FIG. 7 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. The same elements or elements with the same functionality will be denoted by the same reference symbols throughout the description, without redundant description. 
   First Embodiment 
   A configuration of a coil component  1  according to the first embodiment will be described with reference to  FIGS. 1 to 4 .  FIG. 1  is a perspective view of the coil component according to the first embodiment.  FIG. 2  is a schematic view showing a II-II cross section of the coil component shown in  FIG. 1 .  FIG. 3  is a schematic view showing a III-III cross section of the coil component shown in  FIG. 1 .  FIG. 4  is a perspective view of a middle member in the coil component shown in  FIG. 1 . 
   The coil component  1  of the present embodiment is composed of a first coil part  10  and a second coil part  20 , a middle member  30 , and shield members  41 ,  42 . The middle member  30  is located between the first coil part  10  and the second coil part  20 . The shield members  41 ,  42  are formed in the first and second coil parts  10 ,  20 , respectively. 
   The first coil part  10  is composed of a core  11  and a winding  12 . The core  11  is a drum core and has a winding drum  11   a  of a circular cylinder shape, and flanges  11   b ,  11   c  provided at the two ends of the winding drum  11   a . Each of the flanges  11   b ,  11   c  radially spreads in directions normal to the axis I, from the axis I of the winding drum  11   a  and the periphery thereof is formed in a circular shape. Any cross section including the axis I of the winding drum  11   a  in the core  11  is an H-shape and is symmetrical with respect to the axis I. The core  11  is made of a magnetic material such as ferrite. The relative magnetic permeability μ of the core  11  is approximately 300. The winding  12  is a conducting wire coated with an insulating material. The winding  12  is wound around the winding drum  11   a  of the core  11 .  FIG. 2  shows the cross section II-II perpendicular to the axis I through the winding  12 . 
   The second coil part  20  is composed of a core  21  and a winding  22  similar to those of the first coil part  10 , and thus has the shape and configuration similar to the first coil part  10 . The core  21  includes a winding drum  21   a , and flanges  21   b ,  21   c  provided at the two ends of the winding drum  21   a . The first coil part  10  and the second coil part  20  are arranged so that the axes I of the respective winding drums  11   a ,  21   a  are parallel to each other.  FIG. 3  shows the cross section III-III in a plane including the axis I of the winding drum  11   a  and the axis I of the winding drum  21   a.    
   The middle member  30 , as shown in  FIG. 4 , includes a plane  30   a  and a plane  30   b  opposed in parallel to each other, a plane  30   c  and a plane  30   d  perpendicular to the planes  30   a ,  30   b  and opposed in parallel to each other, and a curved surface  30   e  and a curved surface  30   f  opposed to each other. 
   The planes  30   a  and  30   b  are planes perpendicular to the direction of the axes I of the winding drums  11   a ,  21   a . The plane  30   a  is flush with the outside surface normal to the axis I in the flange  11   b . The plane  30   b  is flush with the outside surface normal to the axis I in the flange  11   c . Namely, the size in the direction of the axes I in the middle member  30  is approximately equal to the size in the direction of the axes I of the first and second coil parts  10 ,  20 . 
   The planes  30   c  and  30   d  are planes parallel to the direction of the axes I and the row direction of the first and second coil parts  10 ,  20 . The distance between the plane  30   c  and the plane  30   d  is approximately equal to the diameter of the peripheral circles in the flanges  11   b ,  11   c ,  21   b ,  21   c . The plane  30   c  and the plane  30   d  are flush with two respective tangent planes to the peripheral circles of the flanges  11   b ,  11   c ,  21   b ,  21   c , which are opposed to each other. 
   The curved surface  30   f  is located on the first coil part  10  side. The curved surface  30   f  is depressed on the curved surface  30   e  side so as to extend along the flanges  11   b ,  11   c  and a cross section thereof normal to the axis I is a nearly half circle having the curvature approximately equal to that of the flanges  11   b ,  11   c . The curved surface  30   e  is located on the second coil part  20  side. The curved surface  30   e  is depressed on the curved surface  30   f  side so as to extend along the flanges  21   b ,  21   c  and a cross section thereof normal to the axis I is a nearly half circle having the curvature approximately equal to that of the flanges  21   b ,  21   c.    
   The middle member  30  has a bulge  31  continuously extending from the plane  30   a  to the plane  30   b  on the plane  30   c  side of the curved surface  30   f . The middle member  30  has a bulge  32  continuously extending from the plane  30   a  to the plane  30   b  on the plane  30   d  side of the curved surface  30   f . The middle member  30  has a bulge  33  continuously extending from the plane  30   a  to the plane  30   b  on the plane  30   c  side of the curved surface  30   e . The middle member  30  has a bulge  34  continuously extending from the plane  30   a  to the plane  30   b  on the plane  30   d  side of the curved surface  30   e . The bulges  31 - 34  are semicircular in a cross section normal to the axes I. 
   The bulges  31  and  32  are in contact with the peripheral surfaces of the flanges  11   b ,  11   c  of the first coil part  10  near their top. A space surrounded by the curved surface  30   f , the bulge  31 , the bulge  32 , and the peripheral surface of the flange  11   b  of the first coil part  10  is filled with an adhesive  35 , and the adhesive  35  bonds between the first coil part  10  and the middle member  30 . A space surrounded by the curved surface  30   f , the bulge  31 , the bulge  32 , and the peripheral surface of the flange  11   c  of the first coil part  10  is filled with the adhesive  35  and the adhesive  35  bonds between the first coil part  10  and the middle member  30 . A gap  36  is present between the curved surface  30   f  and the winding  12  of the first coil part  10 . This gap  36  may also be filled with the adhesive. 
   The bulges  33  and  34  are in contact with the peripheral surfaces of the flanges  21   b ,  21   c  of the second coil part  20  near their top. A space surrounded by the curved surface  30   e , the bulge  33 , the bulge  34 , and the peripheral surface of the flange  21   b  of the second coil part  20  is filled with the adhesive  35  and the adhesive  35  bonds between the second coil part  20  and the middle member  30 . A space surrounded by the curved surface  30   e , the bulge  33 , the bulge  34 , and the peripheral surface of the flange  21   c  of the second coil part  20  is filled with the adhesive  35  and the adhesive  35  bonds between the second coil part  20  and the middle member  30 . A gap  36  is present between the curved surface  30   e  and the winding  22  of the second coil part  20 . This gap  36  may also be filled with the adhesive. 
   As described above, the bulges  31 - 34  form the spaces filled with the adhesive. While the bulges  31 - 34  are in contact with the first and second coil parts  10 ,  20 , they exercise a function to determine the relative positions of the first and second coil parts  10 ,  20 . The middle member  30  is made of a material with the magnetic permeability lower than that of the core  11 . The middle member  30  is made of alumina (Al 2 O 3 ) or sintered ferrite and the relative magnetic permeability μ thereof is approximately 1. 
   The shield member  41  is formed on the outside surface of the winding  12  in the first coil part  10 . The shield member  41  is formed between the flange  11   b  and the flange  11   c  on the outside surface of the winding  12  in a wound state. This shield member  41  is in contact with each of the surfaces on the winding  12  side perpendicular to the axis I in the flange  11   b  and the flange  11   c . The shield member  41  is formed on the side opposite to the middle member  30 . The shield member  42  is formed on the outside surface of the winding  22  in the second coil part  20 . The shield member  42  is formed between the flange  21   b  and the flange  21   c  on the outside surface of the winding  22  in a wound state. The shield member  42  is in contact with each of the surfaces on the winding  22  side perpendicular to the axis I in the flange  21   b  and the flange  21   c . The shield member  42  is formed on the side opposite to the middle member  30 . 
   The shield members  41 ,  42  are made of a resin containing a magnetic material powder. The magnetic permeability of the shield members  41 ,  42  is lower than that of the cores  11 ,  21  but higher than that of the middle member  30 . The relative magnetic permeability μ of the shield members  41 ,  42  is approximately 5. 
   A closed magnetic path is made by the winding drum  11   a , the part of the flange  11   b  opposite to the middle member  30 , the shield member  41 , and the part of the flange  11   c  opposite to the middle member  30 . A closed magnetic path is also made by the winding drum  21   a , the part of the flange  21   b  opposite to the middle member  30 , the shield member  42 , and the part of the flange  21   c  opposite to the middle member  30 . Namely, the shield members  41 ,  42  form their respective different closed magnetic paths for the first coil part  10  and for the second coil part  20 . 
   The size of the shield members  41 ,  42  in a direction perpendicular to the direction of the axes I and the row direction of the first and second coil parts  10 ,  20  is preferably as large as over the diameter of the winding drums  11   a ,  21   a . This allows the coil component to establish the closed magnetic paths more efficient in terms of the magnetic flux density. 
   The coil component  1  is constructed in symmetry with respect to a plane including the axis I of the winding drum  11   a  and the axis I of the winding drum  21   a . When the direction of the axes I is defined as a vertical direction, the coil component  1  is made in symmetry with respect to a vertical center line and a horizontal center line. 
   The coil component  1  described above can be produced as described below. First, the windings  12 ,  22  are wound around the respective winding drums  11   a ,  21   a  of the drum cores  11 ,  21  to form the first coil part  10  and the second coil part  20 . Then the middle member  30  is molded. Next, the flanges  11   b ,  11   c  of the first coil part  10  are placed in contact with the bulges  31 ,  32  of the middle member  30  and the flanges  21   b ,  21   c  of the second coil part  20  are placed in contact with the bulges  33 ,  34  of the middle member  30 . 
   Subsequently, the spaces surrounded by the curved surface  30   f , the bulge  31 , the bulge  32 , and the peripheral surfaces of the flanges  11   b ,  11   c  are filled with the adhesive  35  to bond the first coil part  10  to the middle member  30 . The spaces surrounded by the curved surface  30   e , the bulge  33 , the bulge  34 , and the peripheral surfaces of the flanges  21   b ,  21   c  are filled with the adhesive  35  to bond the second coil part  20  to the middle member  30 . Thereafter, the resin containing the magnetic material powder is applied to form the shield members  41 ,  42 . 
   In this manner, the coil component  1  is produced in the size of about 1 mm in the direction of the axes I, in the size of about 6 mm in the row direction of the first and second coil parts  10 ,  20 , and in the size of about 2.5 mm in the direction perpendicular to the direction of the axes I and the row direction. It is also possible to adopt a method of first forming the shield members  41 ,  42  on the first coil part  10  and on the second coil part  20 , respectively, and then bonding the first coil part  10  and the second coil part  20  to the middle member  30  with the adhesive  35 . 
   Since in the coil component  1  of the present embodiment described above, the middle member  30  having the magnetic permeability lower than those of the cores  11 ,  21  and the shield members  41 ,  42  is located between the first coil part  10  and the second coil part  20 , the crosstalk is reduced between the first coil part  10  and the second coil part  20 . 
   Since in the coil component  1  the shield members  41 ,  42  are formed on the outside surfaces in the wound state of the windings  12 ,  22  in the respective first and second coil parts  10 ,  20 , the separate magnetic paths are formed in the first and second coil parts  10 ,  20 , so as to enhance the magnetic flux density. Consequently, this configuration enhances the shield effect and improves the inductance characteristics. 
   In the coil component  1 , the cores  11 ,  21  have the flanges  11   b ,  11   c ,  21   b ,  21   c  located at the ends of the winding drums  11   a ,  21   a , and the shield members  41 ,  42  are formed between the flange  11   b  and the flange  11   c  and between the flange  21   b  and the flange  21   c , respectively. This permits the closed magnetic path to be made by the winding drum  11   a ,  21   a , the flanges  11   b ,  11   c ;  21   b ,  21   c , and the shield member  41 ,  42  in each of the first and second coil parts  10 ,  20 . 
   The shield member  41  is located at the position opposite to and apart from the second coil part  20 , in the first coil part  10  and the shield member  42  is located at the position opposite to and apart from the first coil part  10 , in the second coil part  20 ; therefore, the crosstalk is further reduced between the first coil part  10  and the second coil part  20 . 
   In the coil component  1 , the shield members  41 ,  42  are resinous, and therefore they can be readily formed at any positions on the first and second coil parts  10 ,  20  even in the coil component  1  of a compact size. 
   In the coil component  1  the middle member  30  is bonded to the portions on the middle member  30  side of the flanges  11   b ,  11   c ,  21   b ,  21   c  with the adhesive  35 . Furthermore, the first coil part  10  is in contact with the bulges  31 ,  32  of the middle member  30  and the second coil part  20  in contact with the bulges  33 ,  34  of the middle member  30 . This allows the distance between the first and second coil parts  10 ,  20  to be defined by the middle member  30  in the production process, which reduces variation in the distance between the first and second coil parts  10 ,  20 . Accordingly, it becomes feasible to define a minimum distance taking the crosstalk between the first and second coil parts  10 ,  20  into account and to construct the coil component in a more compact size. 
   In the coil component  1  the magnetic permeability of the shield members  41 ,  42  is lower than that of the cores  11 ,  21 . This configuration allows the shield members  41 ,  42  to exercise a function equivalent to a gap in the magnetic paths made by the cores  11 ,  21  and the shield members  41 ,  42 , so as to enable achievement of excellent DC bias characteristic. Namely, it becomes feasible to achieve the DC bias characteristic as excellent as that of a structure in which the cores  11 ,  21  are provided with a gap. 
   The necessary condition for the shield members is that they are formed at least in part of the peripheral surfaces of the respective first and second coil parts  10 ,  20 , and a variety of modifications can be contemplated as to the forming positions of the shield members. The shield members may be located between the flange  11   b  and the flange  11   c  and between the flange  21   b  and the flange  21   c , and may be formed on the peripheral portions of the flanges  11   b ,  11   c ,  21   b ,  21   c . Besides them, first and second modification examples will be described below as examples of the first embodiment. 
   First Modification Example of First Embodiment 
     FIG. 5  is a sectional view of a coil component according to the first modification example of the first embodiment. The coil component  2  according to the first modification example of the first embodiment is composed of a first coil part  10 , a second coil part  20 , and a middle member  30  similar to those in the aforementioned coil component  1 . The middle member  30  is bonded to the first coil part  10  and to the second coil part  20  with the adhesive  35  as in the coil component  1 . 
   The shield members  43 - 46  in the coil component  2  will be described below. The shield members  43 ,  44  are formed on the outside surface of the winding  12  in the wound state on the winding drum  11   a  in the first coil part  10 . The shield members  43 ,  44  are filled between the flange  11   b  and the flange  11   c . The shield members  43 ,  44  are in contact with the flanges  11   b ,  11   c . The shield member  43  is located on the plane  30   c  side of the middle member  30  with respect to the winding drum  11   a  and the shield member  44  on the plane  30   d  side of the middle member  30  with respect to the winding drum  11   a . The shield member  43  and the shield member  44  are not in contact with each other and are separated with a gap in between. 
   The shield members  45 ,  46  are formed on the outside surface of the winding  22  in the wound state on the winding drum  21   a  in the second coil part  20 . The shield members  45 ,  46  are filled between the flange  21   b  and the flange  21   c . The shield members  45 ,  46  are in contact with the flanges  21   b ,  21   c . The shield member  45  is located on the plane  30   c  side of the middle member  30  with respect to the winding drum  21   a  and the shield member  46  on the plane  30   d  side of the middle member  30  with respect to the winding drum  21   a . The shield member  45  and the shield member  46  are not in contact with each other and are separated with a gap in between. 
   In the coil component  2 , a closed magnetic path is made by the winding drum  11   a , the flange  11   b  on the plane  30   c  side, the shield member  43 , and the flange  11   c  on the plane  30   c  side. Another closed magnetic path is made by the winding drum  11   a , the flange  11   b  on the plane  30   d  side, the shield member  44 , and the flange  11   c  on the plane  30   d  side. A closed magnetic path is made by the winding drum  21   a , the flange  21   b  on the plane  30   c  side, the shield member  45 , and the flange  21   c  on the plane  30   c  side. Another closed magnetic path is made by the winding drum  21   a , the flange  21   b  on the plane  30   d  side, the shield member  46 , and the flange  21   c  on the plane  30   d  side. 
   The shield member  43  and the shield member  44  are made each by pouring a resin of a material from the mutually opposed portions on the plane  30   c  side and on the plane  30   d  side in the winding drum  11   a , on the outside surface of the winding  12  in the wound state. The shield member  45  and the shield member  46  are made each by pouring the resin of the material from the mutually opposed portions on the plane  30   c  side and on the plane  30   d  side in the winding drum  21   a , on the outside surface of the winding  22  in the wound state. It should be noted that the shield member  43  and the shield member  44  may be arranged in contact with each other and that the shield member  45  and the shield member  46  may be arranged in contact with each other. 
   Second Modification Example of Second Embodiment 
     FIG. 6  is a sectional view of a coil component according to the second modification example of the first embodiment. The coil component  3  according to the second modification example of the first embodiment is composed of a first coil part  10 , a second coil part  20 , and a middle member  30  similar to those in the aforementioned coil component  1 . The middle member  30  is bonded to the first coil part  10  and to the second coil part  20  with the adhesive  35  as in the coil component  1 . 
   The shield members  47 ,  48  in the coil component will be described below. The shield member  47  is formed on the outside surface of the winding  12  in the wound state on the winding drum  11   a  in the first coil part  10  and is filled between the flange  11   b  and the flange  11   c . The shield member  47  is formed throughout the entire circumference of the outside surface of the winding  12  in the wound state and is in contact with the flanges  11   b ,  11   c  throughout the entire circumference. The shield member  48  is formed on the outside surface of the winding  22  in the wound state on the winding drum  21   a  in the second coil part  20  and is filled between the flange  21   b  and the flange  21   c . The shield member  48  is formed throughout the entire circumference of the outside surface of the winding  22  in the wound state and is in contact with the flanges  21   b ,  21   c  throughout the entire circumference. 
   The shield members  47 ,  48  cover the entire region of the outside surface of the respective windings  12 ,  22  in the wound state in the first and second coil parts  10 ,  20 , so as to enhance the inductance characteristics. In addition, the shield effect is improved in each of the first coil part  10  and the second coil part  20 , whereby the crosstalk between the first and second coil parts  10 ,  20  can be reduced more definitely. 
   Second Embodiment 
   A configuration of a coil component  4  according to the second embodiment will be described below with reference to  FIGS. 7 to 9 .  FIG. 7  is a perspective view of the coil component according to the first embodiment.  FIG. 8  is a schematic view showing an VIII-VIII cross section of the coil component shown in  FIG. 7 .  FIG. 9  is a schematic view showing a IX-IX cross section of the coil component shown in  FIG. 7 . 
   The coil component  4  of the present embodiment has a middle member  50  instead of the middle member  30  of the aforementioned coil component  1  and is made without the adhesive  35 . The coil component  4  is composed of a first coil part  10  and a second coil part  20 , and shield members  47 ,  48  formed in the respective first and second coil parts  10 ,  20 , similar to those in the aforementioned coil component  3 .  FIG. 8  shows the cross section VIII-VIII normal to the axis I through the winding  12 .  FIG. 9  shows the cross section IX-IX in a plane including the axis I of the winding drum  11   a  and the axis I of the winding drum  21   a.    
   The middle member  50  is located between the first coil part  10  and the second coil part  20  and couples the first coil part  10  and the second coil part  20  to each other. The middle member  50  includes a plane  50   a  and a plane  50   b  opposed in parallel to each other, a plane  50   c  and a plane  50   d  perpendicular to the planes  50   a ,  50   b  and opposed in parallel to each other, and a curved surface  50   e  and a curved surface  50   f  opposed to each other. 
   The planes  50   a  and  50   b  are planes perpendicular to the direction of the axes I of the winding drums  11   a ,  21   a . The plane  50   a  is flush with the outside surface perpendicular to the axis I in the flange  11   b . The plane  50   b  is flush with the outside surface perpendicular to the axis I in the flange  11   c . Namely, the size in the direction parallel to the axes I in the middle member  50  is approximately equal to the size in the direction of the axes I of the first and second coil parts  10 ,  20 . 
   The planes  50   c  and  50   d  are planes parallel to the direction of the axes I and the row direction of the first and second coil parts  10 ,  20 . The distance between the plane  50   c  and the plane  50   d  is approximately equal to the diameter of the peripheral circles in the flanges  11   b ,  11   c ,  21   b ,  21   c . The planes  50   c  and  50   d  are flush with two respective tangent planes to the peripheral circles of the flanges  11   b ,  11   c ,  21   b ,  21   c , which are opposed to each other. 
   The curved surface  50   f  is located on the first coil part  10  side. The curved surface  50   f  is depressed on the curved surface  50   e  side and is closely bonded to the portion on the middle member  50  side of the first coil part  10 . Namely, the curved surface  50   f  is closely bonded to portions on the middle member  50  side of the flanges  11   b ,  11   c  and the shield member  47 . The curved surface  50   e  is located on the second coil part  20  side. The curved surface  50   e  is depressed on the curved surface  50   f  side and is closely bonded to the portion on the middle member  50  side of the second coil part  20 . Namely, the curved surface  50   e  is closely bonded to the portions on the middle member  50  side of the flanges  21   b ,  21   c  and the shield member  48 . 
   The middle member  50  is made of a material having the magnetic permeability lower than that of the core  11 . The middle member  50  is made of a thermosetting resin or a thermoplastic resin, and the relative magnetic permeability μ thereof is approximately 1. When the middle member  50  is made of the thermosetting resin, the resin can be selected on an as-needed basis from epoxy resin, phenol resin, polyurethane, polyimide, and so on. When the middle member  50  is made of the thermoplastic resin, the resin can be selected on an as-need basis from polyethylene, polypropylene, polyvinyl chloride, acrylic resin, and so on. 
   The coil component  4  described above can be produced as described below. First, the first coil part  10  and the second coil part  20  are prepared. Then a resin containing a magnetic material powder is applied onto each of the first coil part  10  and the second coil part  20  to form the shield members  47 ,  48 . Subsequently, the first coil part  10  and the second coil part  20  with the shield members  47 ,  48  thereon are placed at a predetermined distance in a forming frame for mainly forming the planes  50   a ,  50   b ,  50   c ,  50   d  of the middle member  50 , and the resin as a material for the middle member  50  is poured into the forming frame. 
   When the material of the middle member  50  is the thermosetting resin, the resin is heated to cure, whereby the middle member  50  is molded integrally with the first coil part  10  and the second coil part  20  with the shield members  47 ,  48  thereon. When the material of the middle member  50  is the thermoplastic resin, the resin is poured into the forming frame and is left to harden, whereby the middle member  50  is molded integrally with the first coil part  10  and the second coil part  20  with the shield members  47 ,  48  thereon. It is also possible to adopt a method of first integrally molding the middle member  50  with the first coil part  10  and the second coil part  20  and thereafter forming the shield members  47 ,  48  thereon. 
   In the coil component  4  of the present embodiment described above, the middle member  50  having the magnetic permeability lower than those of the cores  11 ,  21  and the shield members  47 ,  48  is located between the first coil part  10  and the second coil part  20  and therefore the crosstalk between the first coil part  10  and the second coil part  20  is reduced thereby. 
   Since in the coil component  4  the shield members  47 ,  48  are formed so as to connect between the upper and lower flanges on the outside surfaces of the windings  12 ,  22  in the wound state in the respective first and second coil parts  10 ,  20 , the separate magnetic paths are formed in the first and second coil parts  10 ,  20 . 
   In the coil component  4  the cores  11 ,  21  have the flanges  11   b ,  11   c ,  21   b ,  21   c  located at the ends of the winding drums  11   a ,  21   a  and the shield members  47 ,  48  are formed between the flange  11   b  and the flange  11   c  and between the flange  21   b  and the flange  21   c , respectively. This permits a closed magnetic path to be made by the winding drum  11   a ,  21   a , the flanges  11   b ,  11   c ,  21   b ,  21   c , and the shield member  47 ,  48  in each of the first and second coil parts  10 ,  20 . 
   Since in the coil component  4  the shield members  47 ,  48  are resinous, they can be readily formed at any positions on the first and second coil parts  10 ,  20  even in the coil component  4  of a compact size. 
   In the coil component  4  the magnetic permeability of the shield members  47 ,  48  is lower than that of the cores  11 ,  21 . This allows the shield members  47 ,  48  to exercise a function equivalent to a gap, in the magnetic paths made by the cores  11 ,  21  and the shield members  47 ,  48 , so as to enable achievement of excellent DC bias characteristic. Namely, it becomes feasible to achieve the DC bias characteristic as excellent as that in the structure in which the cores  11 ,  21  are provided with a gap. 
   Since in the coil component  4  the middle member  50  is the resinous member integrally molded with the first and second coil parts  10 ,  20 , the middle member  50  is filled and hardened between the first and second coil parts  10 ,  20  and in gaps, so as to enhance the coupling strength between the first coil part  10  and the second coil part  20 . 
   The necessary condition for the aforementioned shield members is that they are formed at least in part of the peripheral surfaces of the respective first and second coil parts  10 ,  20 , and a variety of modifications can be contemplated as to the forming positions of the shield members. The shield members may be located between the flange  11   b  and the flange  11   c  and between the flange  21   b  and the flange  21   c , or may be formed on the peripheral portions of the flanges  11   b ,  11   c ,  21   b ,  21   c . For example, the aforementioned shield members  41 ,  42  may be formed in the respective first and second coil parts  10 ,  20 , and the shield members  43 - 46  may be formed in the respective first and second coil parts  10 ,  20 . 
   It is noted that the present invention is by no means limited to the above embodiments but can be modified in various ways. For example, the above embodiments showed the configurations in which the first coil part  10  and the second coil part  20  were similar to each other, but they may be formed so as to have mutually different inductance characteristics of the first coil part and the second coil part. In that case, the numbers of turns of the windings in the first coil part and in the second coil part may be made different from each other, or the magnetic permeability of the cores or the shield members may be made different from each other, in order to achieve the different inductance characteristics of the first coil part and the second coil part. As long as the shield effect is exhibited, the first coil part and the second coil part may be made different in the position where the shield member is located, the area covering the winding, or the like. 
   The above embodiments showed the examples in which the contours of the flanges  11   b ,  11   c ,  21   b ,  21   c  of the first coil part  10  and the second coil part  20  were circular, but they may be formed in a polygon such as a quadrilateral or an octagon. 
   The middle member  50  was formed in the second embodiment, but it is also possible to adopt a method of, while forming the middle member  50 , molding the material of the middle member  50  in a state in which terminal electrodes are electrically connected with the first coil part  10  and the second coil part  20  and exposed in part. This enables insert molding of the terminal electrodes simultaneous with the molding of the middle member  50 . 
   The above embodiments used the cores  11 ,  21  with the relative magnetic permeability μ of about 300, but it is also possible to use those with the relative magnetic permeability of about 200 to 800.