Abstract:
A method for manufacturing a wound coil which has a stable appearance configuration with improved shape accuracy of a coating resin formed on the wound coil. A wound coil element is pressed into a holding jig including an elastic holding hole, and held therein such that an upper end of a coil is level with or lower than an upper end of the holding hole, and a gap G is present between an inner surface of the holding hole and the coil. Next, a flowable coating resin is supplied into the holding hole holding the wound coil element such that the coating resin is held without flowing away downwardly from the gap G, and the upper end  16   a  of the coil is buried in the coating resin. Next, the supplied coating resin is subjected to curing, thereby forming a wound coil.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit of priority to Japanese Patent Application 2015-112306 filed Jun. 2, 2015, the entire content of which is incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    The present disclosure relates to a method for manufacturing a wound coil, and more particularly, to a method for manufacturing a wound coil provided with a coating resin so as to cover a coil wound around a winding core. 
       BACKGROUND 
       [0003]    Typical wound coil elements include an element where a wire is wound around a winding core of a core including the winding core and a pair of flanges provided at both ends of the winding core, and a beginning and an end of the wire are connected to terminal electrodes provided on the flanges. In addition, such wound coils include a wound coil provided with a coating resin so as to cover a wire wound around a winding core. 
         [0004]    Further, Japanese Patent Application Laid-Open No. 2000-286140 discloses, as shown in  FIG. 13 , a wound coil  101  including a core  113  that has a winding core  111  and a pair of flanges  112  provided at both ends of the winding core  111 ; and a wire  115  wound around the winding core  111 , where a coating resin  117  is provided so as to cover the entire perimeter of the wire  115  wound around the winding core  111 . 
         [0005]    Further, in accordance with a method for manufacturing a wound coil according to Japanese Patent Application Laid-Open No. 2000-286140, as shown in  FIG. 14 , the coating resin  117  is applied around the wire  115 , and with the resin dried in contact with a finger (dried such that no paint adheres to a fingertip when a center of the coated surface is touched with a finger), a wound coil element  110  is then pressed into a component housing part  124  composed of an elastic body of heat-resistant rubber, and heated to form the coating resin  117  into a shape corresponding to the shape of the component housing part  124 . 
         [0006]    It is to be noted that the flanges  112  are provided with four relief parts  118  such that the coating resin  117  protruded around the winding core  111  can be relieved when the coating resin  117  is shaped, and the shaping is adaptively carried out with the coating resin  117  retained in the relief parts  118 . 
         [0007]    However, in accordance with the method in Japanese Patent Application Laid-Open No. 2000-286140, the wound coil element  110  is pressed into the component housing part  124  with the coating resin  17  dried in contact with a finger, and there is thus a problem that the shape of the coating resin  117  is lost by the elastic force of the component housing part  124 , thereby failing to form the resin into a desired shape. 
         [0008]    In addition, the shape of the coating resin  117  retained in the relief parts  118  of the flanges  112  may vary depending on the multiple relief parts  118 , and there is a problem that the appearance configuration is not stable. 
       SUMMARY 
       [0009]    The present disclosure is intended to solve the problems mentioned above, and an object of the disclosure is to provide a method for manufacturing a wound coil, which is capable of efficiently manufacturing a wound coil which has a stable appearance configuration with improved shape accuracy of a coating resin formed on the wound coil. 
         [0010]    In order to solve the problems mentioned above, a method for manufacturing a wound coil according to the present disclosure is a method for manufacturing a wound coil including: a wound coil element including a core having a winding core and a pair of flanges provided at both ends of the winding core, terminal electrodes provided on the pair of flanges, and a wire wound around the winding core to constitute a coil, with a beginning and an end of the wire connected to the terminal electrodes; and a coating resin provided to bury the coil from an upper portion to both side portions of the winding core,
       the method is characterized in that it includes the steps of:   pressing the wound coil element in a holding hole of a holding jig, the holding hole having an inner surface made of an elastic material, and holding the wound coil element such that an upper end of the coil is level with or lower than an upper end of the holding hole, and a gap is present between the inner surface of the holding hole and the coil;   supplying the coating resin with fluidity into the holding hole holding the wound coil element such that the coating resin is held in the gap between the inner surface of the holding hole and the coil without causing the coating resin to flow away downwardly from the gap, and the coil is buried from the upper portion to both side portions of the winding core; and   curing the supplied coating resin, with the wound coil element held in the holding jig.       
 
         [0015]    It is to be noted that in the present disclosure, the attitude of the holding jig in supplying the coating resin is not limited to attitude cases where the principal surface of the jig is horizontal, whereas the axial direction of the holding hole is a vertical direction, but the disclosure is intended to encompass cases of supplying the coating resin, for example, in an attitude where the principal surface of the holding jig is sloped with respect to the horizontal direction (an attitude where the axial direction of the holding hole makes an angle with respect to the vertical direction). 
         [0016]    It is to be noted that the same applies to the attitude of the holding jig in supplying the coating resin, also in the case of the configurations according to the present disclosure. 
         [0017]    In addition, the step of supplying the coating resin includes supplying the coating resin up to a level above the upper end of the holding hole, and the step of curing the supplied coating resin is carried out after removing the coating resin present above the level of the holding hole. 
         [0018]    In the case of supplying the coating resin up to a level above the upper end of the holding hole, removing the coating resin present above the level of the holding hole, and then curing the coating resin, it is possible to efficiently manufacture a wound coil provided with the coating resin on the upper surfaces and side surfaces of the coil. 
         [0019]    In addition, it is possible to form the shape of the coating resin by curing so as to correspond to the shape of the holding hole provided in the holding jig, thereby making it possible to provide a wound coil which is less likely to vary in size. 
         [0020]    In addition, the method preferably further includes a step of removing, after the step of curing the coating resin, the cured coating resin present above the upper end of the holding hole, when the cured coating resin is present above the upper end of the holding hole. 
         [0021]    When the above-mentioned configuration is adopted, it is possible to further reliably achieve an electronic component with high dimensional accuracy, and it is possible to remove foreign substances such as unnecessary cured resin from the upper surface (including the region without any holding hole formed) of the holding jig and to prepare the holding jig for the next use, thereby making it possible to improve the productivity. 
         [0022]    In addition, the step of supplying the coating resin includes disposing a mask having an opening corresponding to the holding hole so as to cover the holding jig, and supplying the coating resin through the opening of the mask. 
         [0023]    The configuration mentioned above can suppress the adhesion of the coating resin to the upper surface of the holding jig, thereby reducing the burden required for cleaning the holding jig. 
         [0024]    In addition, the holding hole is preferably rectangular in shape as viewed from an axial direction of the holding hole. 
         [0025]    When the holding hole is rectangular in shape as viewed from the axial direction, it is possible to reliably hold the flanges of the wound coil element in the holding hole, thereby making it possible to improve the productivity. 
         [0026]    In addition, the wound coil element may be held such that a gap is provided between the inner surface of the holding hole and a side surface of each of the flanges, by using a holding jig with the holding hole for elastically holding outer end surfaces of the flanges of the core, the outer end surfaces being opposed to each other. 
         [0027]    The adoption of the configuration as described above makes it possible to increase the thickness of the coating resin covering the coil. 
         [0028]    In addition, it is also possible for the method to be configured in such way that the wound coil element is held such that a gap is provided between the inner surface of the holding hole and a part of a side surface of each of the flanges, by using a holding jig with the holding hole for elastically holding outer end surfaces of the flanges of the core, the outer end surfaces of the flanges of the core being opposed to each other, and elastically holding regions that are the part of the side surface of each of the flanges located near the outer end surfaces of the flanges of the core. 
         [0029]    Even when the configuration is adopted as described above, it is possible to increase the thickness of the coating resin covering the coil. 
         [0030]    In addition, the wound coil element is held in the holding hole such that upper ends of the flanges are lower in level than the upper end of the holding hole, and the coating resin is supplied up to a level above the upper ends of the flanges in the step of supplying the coating resin. 
         [0031]    When the configuration is adopted as described above, it is possible to increase the thickness of the coating resin covering the upper end of the coil. 
         [0032]    The method for manufacturing a wound coil according to the present disclosure is configured to supply the flowable coating resin into the holding hole holding the wound coil element such that the coating resin is held in the gap between the inner surface of the holding hole and the coil without causing the coating resin to flow away downwardly from the gap, and the upper end of the coil is buried in the coating resin, and cure the resin, thus providing a wound coil including the coating resin corresponding to the shape of the holding hole, and making it possible to efficiently manufacture a wound coil which has excellent shape accuracy as a whole including the coating resin, and having a favorable appearance. 
         [0033]    In addition, when, for example, a resin material containing a magnetic powder is used as a material for the coating resin, it is possible to manufacture a wound coil which is excellent in terms of electrical characteristics such as magnetic flux shielding performance and inductance acquisition efficiency, and less likely to vary in electrical characteristics. 
         [0034]    In addition, the need to adopt the structure where flanges are provided with relief parts as in the prior art is eliminated, thereby making it possible to simplify the core shape. 
         [0035]    It is to be noted that, in the present disclosure, the aspect of the coating resin held in the gap between the inner surface of the holding hole and the coil without causing the coating resin to flow away downwardly from the gap can be achieved by appropriately selecting the viscosity and surface tension of the coating resin before being subjected to curing, the size of the gap between the inner surface of the holding hole and the coil, the relationship between the geometry of the coil formed by the wire wound around the winding core and the geometry of the inner surface, the property (the degree of repelling the coating resin) of the inner surface, and the like. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0036]      FIGS. 1A and 1B  are perspective views for explaining a wound coil, which illustrate a wound coil (wound coil element) before being coated with a coating resin and a wound coil obtained by coating the wound coil element with a coating resin, respectively. 
           [0037]      FIGS. 2A, 2B, and 2C  are diagrams illustrating the wound coil shown in  FIG. 1B , which are a plan view, a schematic cross-sectional view along the line  2 - 2 , and a schematic cross-sectional view along the line  3 - 3 , respectively. 
           [0038]      FIG. 3  is a perspective view of a holding jig for holding a wound coil element. 
           [0039]      FIGS. 4A, 4B, and 4C  are diagrams illustrating a wound coil element held by a holding jig, which are a plan view of a part C in  FIG. 3 , a schematic cross-sectional view along the line  4 - 4 , and a schematic cross-sectional view along the line  5 - 5 , respectively. 
           [0040]      FIGS. 5A, 5B, and 5C  are diagrams illustrating a coating resin supplied to a wound coil element, which are diagrams illustrating just after supplying the coating resin above a winding core, filling, with the coating resin, the gap between the inner surface of a holding hole of the holding jig and a coil, and removing the coating resin present above the level of the upper end of the holding hole, respectively. 
           [0041]      FIG. 6  is a diagram illustrating the removal of a cured coating resin present above the level of a holding hole of a holding jig. 
           [0042]      FIGS. 7A to 7C  are diagrams illustrating another method in the case of supplying a coating resin to a wound coil element. 
           [0043]      FIG. 8  is a diagram illustrating yet another method in the case of supplying a coating resin to a wound coil element. 
           [0044]      FIG. 9  is a diagram (plan view) illustrating another method for manufacturing a wound coil. 
           [0045]      FIG. 10  is a diagram (plan view) illustrating yet another method for manufacturing a wound coil. 
           [0046]      FIG. 11  is a diagram (cross-sectional view along line A 2 -A 2 ) illustrating yet another method for manufacturing a wound coil. 
           [0047]      FIG. 12  is a diagram illustrating yet another method for manufacturing a wound coil, and a holding jig for use in the case of a cylindrical coil. 
           [0048]      FIG. 13  is a diagram illustrating a conventional wound coil. 
           [0049]      FIG. 14  is a diagram for explaining a method for manufacturing a conventional wound coil. 
       
    
    
     DETAILED DESCRIPTION 
       [0050]    Features of the present disclosure will be described in more detail below with reference to an embodiment of the present disclosure. 
         [0051]    First, a wound coil that is prepared by a method for manufacturing a wound coil according to the present disclosure will be described with reference to  FIGS. 1A and 1B  and  FIGS. 2A to 2C . It is to be noted that  FIGS. 1A and 1B  show a wound coil element  10  and a wound coil  1  where lower surfaces  12   b  of flanges  12  provided with terminal electrodes  14  are faced up. 
         [0052]    The wound coil element  10  includes, as shown in  FIG. 1A , a core  13  including: a winding core  11  that is rectangular in cross-sectional shape in a direction perpendicular to a winding axis  11   a;  and a pair of flanges  12  provided at both ends of the winding core  11 , which is rectangular in shape as viewed in the axial direction of the winding axis  11   a.  The terminal electrodes  14  are formed on the lower surfaces  12   b  of the flanges  12 , which serve as surfaces opposed to an object (e.g., a circuit board) on which the wound coil  1  is to be mounted. Further, a wire  15  is wound around the winding core  11  to constitute a coil  16 , and a beginning and an end of the wire  15  are respectively connected to the different terminal electrodes of the pair of terminal electrodes  14 . 
         [0053]    Further, the wound coil  1  includes, as shown in  FIG. 1B  and  FIG. 2 , a coating resin  17  that coats a main part of the coil (a region excluding the region opposed to an object on which the coil  16  is to be mounted). More specifically, the coating resin  17  is provided in such a way as to coat, of the coil  16  composed of the wire  15  wound around the winding core  11 , an upper portion (upper end)  16   a  that is a region corresponding to an upper surface of the winding core  11 , and a pair of side portions (side ends)  16   c  that are regions corresponding to both side portions (both side surfaces) of the winding core  11 , but not to coat a lower part (lower end)  16   b  that is a region corresponding to a lower surface of the winding core  11 . 
         [0054]    Next, a method for manufacturing a wound coil according to an embodiment of the present disclosure will be described. 
         [0055]    (1) First, a holding jig  21  is prepared as shown in  FIGS. 3 and 4A to 4C . The holding jig  21  includes a jig body  22  of a rigid material, and a number of holding holes  24  for elastically holding wound coil elements  1 , with inner surfaces  24   c  of an elastic material, and an axial direction X perpendicular to a principal surface  21   a  of the holding jig  21 . 
         [0056]    The holding holes  24  are provided respectively so as to pass through a number of elastic members  23  recessed in a matrix form in the jig body  22 , and the planar shape (the shape of the holding hole  24  as viewed from the axial direction X) is made rectangular. 
         [0057]    It is to be noted that a silicone rubber that has heat resistance is used as the elastic material constituting the inner surfaces  24   c  of the holding holes  24 . 
         [0058]    (2) Next, wound coil elements  10  are pressed into the holding holes  24  of the holding jig  21 . The pressed wound coil element  10  is elastically held by the elastic force of the elastic material constituting the inner surface  24   c,  with outer end surfaces  12   d  and both side surfaces  12   c  of the flanges  12  in abutment with the inner surface  24   c  of the holding hole  24  (see  FIG. 4A ). 
         [0059]    In this regard, the holding jig  21  is provided on a stage (not shown) such that the axial direction X of the holding hole  24  is vertically oriented, and the pressed wound coil element  10  is held such that the surfaces of the flanges  12  with the terminal electrodes  14  formed are located as lower surfaces. 
         [0060]    Further, the wound coil element  10  is configured to be held with the upper end (upper portion)  16   a  of the coil  16  equivalent to or lower than an upper end  24   a  of the holding hole  24 , and held in such a way that gaps G are formed between both side ends (both side portions)  16   c  of the coil  16  and the inner surface  24   c  of the holding hole  24  (see  FIG. 4C ). 
         [0061]    It is to be noted that the gaps G are made, for example, 0.05 mm or more and 0.2 mm or less in this embodiment. 
         [0062]    In addition, in this embodiment, the wound coil element is held such that the lower end  16   b  of the coil  16  wound around the winding core  11  is level with a lower end  24   b  of the holding hole  24 . 
         [0063]    For example, when a design is created such that the distance from the upper end (the upper surface in this embodiment)  12   a  of the flange  12  to the lower end  16   b  of the coil  16  is equal to the distance from the upper end  24   a  of the holding hole  24  to the lower end  24   b  thereof, the upper end (upper surface)  12   a  of the flange  12  is located to be aligned with the upper end  24   a  of the holding hole  24 , thereby making it possible to hold the element such that the lower end  16   b  of the coil  16  is level with the lower end  24   b  of the holding hole  24 , and the level of the wound coil element  10  held can be easily adjusted, which is preferable. 
         [0064]    (3) Next, as shown in  FIG. 5A , the flowable coating resin  17  is supplied onto the holding hole  24  holding the wound coil element  10 . The coating resin  17  is supplied up to a higher level than the upper end  24   a  of the holding hole  24 , with the use of a resin supply device (for example, dispenser)  31 . 
         [0065]    It is to be noted that a magnetic powder-containing resin with Fe powder (60 to 80 weight %) dispersed in an epoxy resin as a thermosetting resin is used as the coating resin  17  in this embodiment. 
         [0066]    The viscosity of the magnetic powder-containing resin is, for example, 10 Pa·s or more and 90 Pa·s or less. 
         [0067]    The coating resin  17  supplied onto the holding hole  24  moves, as shown in  FIG. 5B , downwardly along the gaps G between the inner surface  24   c  of the holding hole  24  and the coil  16  by its own weight and capillary action. The moving coating resin  17  is held in the gaps G by surface tension, and never flows away downwardly from the gaps G. In this embodiment, the side portions (side surfaces) of the coil  16  wound around the winding core  11  that is rectangular in cross-sectional shape are parallel to the inner surface  24   c  of the holding hole  24 , and the coating resin  17  is thus held in a position that is roughly level with the lower ends of the side portions (side ends)  16   c  of the coil  16  or the lower end  24   b  of the holding hole  24 , as lower ends of the regions where the inner surface  24   c  of the holding hole  24  is opposed to the side surface of the coil  16 . 
         [0068]    (4) Then, as shown in  FIG. 5( c ) , the coating resin  17  present above the level of the upper end  24   a  of the holding hole  24  of the holding jig  21  is removed with an elastic squeegee  32 . 
         [0069]    (5) Next, the wound coil elements  10  are put along with the holding jig  21  in an oven (not shown) at 100° C. to 150° C., for thermally curing the coating resin  17 . 
         [0070]    Thereafter, the wound coil elements  10  are taken out from the holding jig  21 , thereby providing the wound coil  1  which has a structure where the upper portion (upper end)  16   a  and both side portions (both side ends)  16   c  of the coil  16  are coated with the coating resin  17 , whereas the lower part (lower end)  16   b  thereof is not coated with the coating resin  17 , as shown in  FIGS. 1B  and  FIGS. 2A to 2C . 
         [0071]    It is to be noted that when the coating resin (excess cured resin)  17  is left above the level of the surface of the holding jig  21  (the upper end  24   a  of the holding hole  24 ) after the thermal curing as shown in  FIG. 6 , it is also possible to remove the coating resin  17  by a cured resin removal device (e.g., a cleaning brush)  35 . 
         [0072]    In such a case, at the same time, the effect of being able to remove a burr of the cured resin, which is formed around the upper end of the holding hole  24 , is achieved. 
         [0073]    In addition, in the case of supplying the coating resin  17 , it is also possible to cause the coating resin  17  to be efficiently supplied into the holding hole  24  in such a way that an excessive amount of coating resin  17  is supplied to the upper surface of the holding jig  21 , and the excess is then scraped with the use of a scraper  36  provided above the holding jig  21  so that the required amount is left on the holding jig  21  as shown in  FIG. 7A . 
         [0074]    The gaps G between the inner surface  24   c  of the holding hole  24  and the coil  16  are filled with the supplied coating resin  17  by its own weight and capillary action as shown in  FIG. 7B . Then, as shown in  FIG. 7C , the coating resin  17  present above the level of the upper end  24   a  of the holding hole  24  is scraped with a squeegee  32 . 
         [0075]    In addition, in the case of supplying the coating resin according to the embodiment described above, it is also possible to, while a metal mask  37  with an opening  37   a  corresponding to the holding hole  24  is disposed so as to cover the holding jig  21 , supply the coating resin  17  from the opening  37   a  with the use of the squeegee  32  as shown in  FIG. 8 . 
         [0076]    In addition, according to the present disclosure, it is also possible to form a wound coil  1 A with a wound coil element  10  held, according to an embodiment as shown in  FIG. 9 . 
         [0077]    More specifically, while the wound coil element  10  is held, with the use of a holding jig  21  that has a holding hole  24  for elastically holding outer end surfaces  12   d  of a pair of flanges  12  of a core  13 , which are opposed to each other, in such a way that gaps are formed between an inner surface  24   c  of the holding hole  24  and side surfaces  12   c  of the flanges  12 , a coating resin  17  is supplied into the holding hole  24 , thereby making it possible to form the wound coil  1 A which has a structure where not only a coil  16  but also the side surfaces  12   c  of the flanges  12  are coated with the coating resin  17 . 
         [0078]    In addition, according to the present disclosure, it is also possible to form a wound coil  1 B with a wound coil element  10  held, according to an embodiment as shown in  FIG. 10 . 
         [0079]    More specifically, while the wound coil element  10  is held, with the use of, as the holding jig, a holding jig  21  that has a holding hole  24  for elastically holding outer end surfaces  12   d  of flanges  12  and elastically holding regions that are parts of side surfaces  12   c  of the flanges  12  near the outer end surfaces  12   d,  in such a way that gaps are formed between an inner surface  24   c  of the holding hole  24  and parts of the side surfaces  12   c  of the flanges  12 , a coating resin  17  is supplied into the holding hole  24 , thereby making it possible to form the wound coil  1 B which has a structure where not only a coil  16  but also the parts of the side surfaces  12   c  of the flanges  12  are coated with the coating resin  17 . 
         [0080]    In addition, according to the present disclosure, it is also possible to form a wound coil  1 C with a wound coil element  10  held, according to an embodiment, as shown in  FIG. 11 . 
         [0081]    More specifically, while the wound coil element  10  is held in a holding hole  24  in such a way that upper ends (upper surfaces)  12   a  of flanges  12  are lower in level than an upper end  24   a  of the holding hole  24 , a coating resin  17  is supplied up to a position above the upper ends  12   a  of the flanges  12  in a step of supplying the coating resin  17 , thereby making it possible to form the wound coil  1 C which has a structure where an upper portion (upper end)  16   a  of a coil  16  is coated thickly with the coating resin  17 . 
         [0082]    It is to be noted that in the present disclosure, the attitude of the holding jig in supplying the coating resin is not limited to attitude cases where the principal surface of the jig is horizontal, whereas the axial direction of the holding hole is vertical, and the disclosure is not intended to exclude cases of supplying the coating resin, for example, in an attitude where the principal surface of the holding jig is somewhat sloped with respect to the horizontal direction (an attitude where the axial direction of the holding hole makes a certain angle with respect to the vertical direction). 
         [0083]    In addition, the coating resin goes into gaps between the inner surface of the holding hole and the coil by capillary action, and thus, also in this respect, the attitude of the holding jig in supplying the coating resin is not limited to attitudes where the axial direction of the holding hole is vertical. 
         [0084]    It is to be noted that while a case where the core constituting the wound coil is a coil including a winding core that is rectangular in cross-sectional shape in a direction perpendicular to the winding axis has been explained in the embodiment described above, the method for manufacturing a wound coil according to the present disclosure can also be applied to a case where the core has a winding core that is polygonal or circular in cross-sectional shape in a direction perpendicular to the winding axis. 
         [0085]    In such a case, the shape of the inner surface of the holding hole is desirably a shape corresponding to the shape of a coil wound around the winding core that is polygonal or circular in cross-sectional shape in a direction perpendicular to the winding axis as described above. 
         [0086]    For example, when a cylindrical coil  16  is formed as shown in  FIG. 12  by winding a wire around a winding core that is circular in cross-sectional shape, an inner surface  24   c  of a holding hole  24  follows the outer circumference of the coil  16 , and has a predetermined gap formed between the inner surface and the outer circumference of the coil  16 , while the inner surface  24   c  of the holding hole  24  has a partially cylindrical shape that is substantially concentric with the coil  16  with a curvature radius larger by a predetermined amount than the curvature radius of the coil  16 , thereby making it possible to ensure that the outer circumference of the coil  16  is coated with a coating resin. 
         [0087]    It is to be noted that the present disclosure is not limited to the embodiment described above in other respects, but various applications and modifications can be made within the scope of the present disclosure.