Patent Publication Number: US-2019172625-A1

Title: Reactor and reactor manufacturing method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2017-234589, filed on Dec. 6, 2017, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The disclosure herewith relates to a reactor and a reactor manufacturing method. 
     BACKGROUND 
     A reactor is a passive element in which a coil is wound on a bobbin through which a core is inserted. A reactor is known in which a core is divided into a plurality of core blocks and a gap plate is interposed between each pair of adjacent core blocks inside a bobbin. For example, JP 2016-122764 describes such a reactor. In the reactor of JP 2016-122764, a bobbin is provided with grooves at its inner periphery, and gap plates are arranged in the grooves. Positions of the gap plates are accurately set by the grooves. 
     SUMMARY 
     A bobbin may be formed around core blocks by insert molding. In the insert molding, so-called flash (or burrs) may be generated around solidified resin. The flash is generated at a boundary between objects to be inserted in a mold and a cavity of the mold, that is, at a boundary between the bobbin and the core blocks. A bobbin part may be insert molded for each of adjacent core blocks and the two bobbin parts provided with the core blocks may be joined with a gap plate interposed therebetween to manufacture a reactor. In the case where the two bobbin parts with the core blocks are joined with the gap plate interposed therebetween, a position of the gap plate would be displaced if flash is caught between the core blocks and the gap plate. The disclosure herein provides a reactor having a shape suitable for insert molding a bobbin, and a reactor manufacturing method. 
     A reactor disclosed herein may comprise a pair of core blocks, a gap plate, and a bobbin. An end surface of one of the core blocks may be opposed to an end surface of the other of the core blocks. The gap plate may be interposed between the end surfaces of the core blocks. The reactor disclosed herein may comprise three or more core blocks. In the technique disclosed herein, a focus will be placed on the pair of core blocks adjacent to each other with the gap plate interposed therebetween. The bobbin may be a cylindrical insulation member into which a core is inserted, and it may surround side surfaces of the pair of core blocks and a side surface of the gap plate. The bobbin may be constituted of resin. The bobbin at least needs to surround boundaries between the core blocks and the gap plate. The gap plate may include a plurality of protrusions contacting the end surfaces of the core blocks. An inner surface of the bobbin may include a positioning portion that contacts an edge of the gap plate at a position separated from the protrusions. In this reactor, since the protrusions of the gap plate contacting the core blocks are separated from the positioning portion contacting the edge of the gap plate, when flash is generated around the positioning portion, the flash would not be caught between any of the protrusions of the gap plate and one or both of the core blocks. 
     In the reactor disclosed herein, a gap may be provided between the inner surface of the bobbin and the edge of the gap plate except at the positioning portion. The flash may be generated at the boundaries between the bobbin and the core blocks. Due to this, so long as the gap is secured between the inner surface of the bobbin and the gap plate, the flash enters this gap and does not affect positioning of the gap plate. The gap may be filled by another resin after the bobbin, the gap plate, and the core blocks are assembled. 
     The positioning portion may be configured as follows, for example. The gap plate may include a notch at the edge at the position separated from the protrusions. The positioning portion may include a projection that projects from the inner surface of the bobbin and fits the notch. Alternatively, the positioning portion may be configured as follows. The gap plate may include a positioning projection that projects from the edge of the gap plate at the position separated from the protrusions as seen along a normal direction of the gap plate. The positioning portion may include a recess that is provided in the inner surface of the bobbin and fits the positioning projection. 
     The aforementioned reactor may be manufactured by a method described below. The method may comprise preparing the pair of core blocks and the gap plate that includes the plurality of protrusions on surfaces of the gap plate that are to face the end surfaces of the core blocks; insert-molding bobbin parts for the core blocks respectively, each of the bobbin parts surrounding the side surface of corresponding one of the core blocks; and arranging the core blocks to be opposed to each other such that the gap plate is interposed between the end surfaces of the core blocks with the protrusions being in contact with the end surfaces, and joining the bobbin parts to complete the bobbin. The insert-molding of the bobbin parts may include forming the positioning portion that contacts the edge of the gap plate on at least one of the bobbin parts, the positioning portion being formed at a position separated from the protrusions of the gap plate in a state where the gap plate is attached to the at least one of the bobbin parts. Even when the flash is generated around the positioning portion upon the insert molding, the flash is prevented from being caught between the protrusions of the gap plate and the core blocks since the protrusions of the gap plate are separated from the positioning portion. 
     Details and further improvements of the technique disclosed herein will be described in Detailed Description below. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a reactor. 
         FIG. 2  is a cross-sectional view of the reactor along an XY plane in  FIG. 1 . 
         FIG. 3  is a disassembled perspective view of the reactor before bobbin parts (a bobbin) are formed. 
         FIG. 4  is a disassembled perspective view of the reactor after the bobbin parts have been formed (before gap plates are attached). 
         FIG. 5  is a disassembled perspective view of the reactor after the bobbin parts have been formed (after the gap plates have been attached). 
         FIG. 6  is a front view of the gap plate attached to the bobbin part. 
         FIG. 7  is a cross-sectional view along a line VII-VII in  FIG. 6 . 
         FIG. 8  is a front view of a gap plate of a first variant. 
         FIG. 9  is a front view of a gap plate of a second variant. 
         FIG. 10  is a front view of a gap plate of a third variant. 
         FIG. 11  is a front view of a gap plate of a fourth variant. 
     
    
    
     DETAILED DESCRIPTION 
     Representative, non-limiting examples of the present invention will now be described in further detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Furthermore, each of the additional features and teachings disclosed below may be utilized separately or in conjunction with other features and teachings to provide improved reactor and reactor manufacturing method, as well as methods for using the same. 
     Moreover, combinations of features and steps disclosed in the following detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Furthermore, various features of the above-described and below-described representative examples, as well as the various independent and dependent claims, may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings. 
     All features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, independent of the compositions of the features in the embodiments and/or the claims. In addition, all value ranges or indications of groups of entities are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter. 
     A reactor  2  of an embodiment will be described with reference to the drawings.  FIG. 1  shows a perspective view of the reactor  2 .  FIG. 2  shows a cross sectional view of the reactor  2  along an XY plane according to a coordinate system shown in  FIG. 1 . The reactor  2  includes a ring-shaped core  3 , a bobbin  10 , coils  4   a,    4   b,  and a resin cover  18 . In  FIGS. 1 and 2 , the resin cover  18  is depicted with a virtual line to allow a structure inside the resin cover  18  to be seen. A lower portion of  FIG. 2  shows an enlarged view of a rectangular range with a broken line shown in an upper portion of  FIG. 2 . 
     The ring-shaped core  3  is constituted of a pair of U-shaped core blocks  3   a,    3   b  and gap plates  20 . The pair of core blocks  3   a,    3   b  is arranged such that their end surfaces  31   a,    31   b  at ends of the U-shapes are opposed to each other, and each of the gap plates  20  is interposed between its corresponding pair of the end surfaces  31   a,    31   b  (see the lower portion of  FIG. 2 ). 
     The ring-shaped core  3  is covered by the bobbin  10 . More specifically, the core block  3   a  is covered by a bobbin part  10   a,  and the core block  3   b  is covered by a bobbin part  10   b.  The bobbin part  10   a  covering the core block  3   a  and the bobbin part  10   b  covering the core block  3   b  are joined with the gap plates  20  interposed therebetween, by which the ring-shaped core  3  and the bobbin  10  are completed. When the bobbin parts  10   a,    10   b  are joined, portions of the U-shaped core blocks  3   a ,  3   b  corresponding to arms of the U-shapes are inserted to the coils  4   a,    4   b,  and then the bobbin parts  10   a,    10   b  are joined. The coils  4   a,    4   b  are constituted of a single flat wire, and are electrically a single coil. The bobbin  10  is a cylindrical member, on an outside thereof the coils  4   a,    4   b  are wound, and inside thereof the core  3  is inserted. The bobbin  10  of the embodiment also covers curved portions of the core  3 , however, the bobbin  10  simply needs to cover portions of the core  3  where the coils  4   a,    4   b  are wound, that is, side surfaces of the core  3  on both sides of each gap plate  20 . The bobbin  10  includes flanges  11  that restrict movement of the coils  4   a,    4   b  in an axial direction (an X direction in the drawings). The bobbin  10  simply needs to cover the side surfaces of the core  3  and side surfaces of the gap plates  20  at least between a pair of the flanges  11 . 
     The coils  4   a,    4   b  have a square columnar shape. The coils  4   a,    4   b,  the core  3 , and the bobbin  10  are covered by the resin cover  18  except for one side surface (bottom surface) of each of the square columnar coils  4   a,    4   b  and a surface of the core  3  (bottom surface of the core  3 ) facing in the same side as each of the side surfaces. 
     A structure of one of the gap plates  20  and its surrounding structure will be described with reference to the lower portion of  FIG. 2 . The gap plates  20  have an identical structure. The gap plate  20  includes protrusions  21  at four corners on each surface thereof that faces the end surface  31   a  ( 31   b ) of the core block  3   a  ( 3   b ). A vertex surface of each protrusion  21  contacts its corresponding end surface  31   a  ( 31   b ), and other portion of this gap plate  20  does not contact the end surface  31   a  ( 31   b ). Thus, a space SP 2  is secured between the gap plate  20  and each end surface  31   a  ( 31   b ). Further, a space SP 1  is also secured between each of the side surfaces of the gap plate  20  and an inner surface of the bobbin  10 . Each of the protrusions  21  is provided with a space therearound except at its portion contacting the corresponding core block  3   a  ( 3   b ). A distance to each end surface  31   a  ( 31   b ) is accurately set for the gap plate  20  by the protrusions  21  at the four corners contacting the end surface  31   a  ( 31   b ) of the core block  3   a  ( 3   b ). 
     Each bobbin part  10   a  ( 10   b ) is constituted of resin and is insert-molded to its corresponding core block  3   a  ( 3   b ). In the insert molding, each core block  3   a  ( 3   b ) is arranged in a cavity of a mold and molten resin is poured around the core block  3   a  ( 3   b ) to form each of the bobbin parts  10   a,    10   b.  Due to this, flash (or burrs) may be generated at boundaries between the bobbin part  10   a  ( 10   b ) and the core block  3   a  ( 3   b ). When the flash is caught between the protrusions  21  and the end surface  31   a  ( 31   b ), the distance between the gap plate  20  and the end surface  31   a  ( 31   b ) may not be set accurately. Further, when the flash is caught between inner surface of the bobbin part  10   a  ( 10   b ) and the gap plate  20 , a position of the gap plate  20  in directions parallel to the end surface  31   a  ( 31   b ) may not be set accurately. The reactor  2  has the gaps secured around the gap plates  20  except at the vertex surfaces of the protrusions  21 , so the flash does not affect the positions of the gap plates  20  including the protrusions  21 . Next, a manufacturing method of the reactor  2  will be described and the aforementioned advantage will be supplemented. The gaps around the gap plates  20  simply need to exist when the gap plates  20 , the core blocks  3   a,    3   b,  and the bobbin parts  10   a,    10   b  are assembled. After the gap plates  20 , the core blocks  3   a,    3   b,  and the bobbin parts  10   a,    10   b  have been assembled, the gaps may be filled with another resin. 
     (Preparation Step) In a manufacturing process of the reactor  2 , firstly, the pair of core blocks  3   a,    3   b,  the coils  4   a,    4   b,  and the gap plates  20  are prepared ( FIG. 3 ). The protrusions  21  are provided at the four corners of each surface of the gap plates  20  that is to face the corresponding core block  3   a  ( 3   b ). For details of the protrusions  21 ,  FIG. 4  should be referred to. 
     (Bobbin Forming Step) The bobbin part  10   a  ( 10   b ) is insert-molded for each of the pair of core blocks  3   a,    3   b  such that the bobbin part  10   a  ( 10   b ) surround at least the side surfaces of the core block  3   a  ( 3   b ).  FIG. 4  shows each bobbin part  10   a  ( 10   b ) formed to surround peripheries of the U shaped-arm of the core block  3   a  ( 3   b ). Each bobbin part  10   a  ( 10   b ) is provided with the flange  11  restricting the movement of the coils  4   a,    4   b  in the axial direction. Further, each bobbin part  10   a  ( 10   b ) is provided with windows  15 ,  16  through which the core block  3   a  ( 3   b ) is exposed. The bobbin parts  10   a  and  10   b  have an identical shape. Hereinbelow, the core block  3   b,  the bobbin part  10   b  surrounding the core block  3   b,  and the gap plates  20  will mainly be described. Reference signs of the corresponding portions of the bobbin part  10   a  and the core block  3   a  will be described in parentheses. 
     An enlarged view of the end surface of the bobbin part  10   b  (the end surface  31   b  of the core block  3   b ) and one of the gap plates  20  is shown at a left lower portion of  FIG. 4 . As aforementioned, the protrusions  21  that protrude toward the end surface  31   b  ( 31   a ) are provided at the four corners of the gap plate  20 . Further, the gap plate  20  includes notches  22  at its edge at positions separated from the protrusions  21 . The notches  22  are provided respectively at two opposite sides of the rectangular gap plate  20 . The bobbin part  10   b  ( 10   a ) has a cylindrical shape surrounding the core block  3   b  ( 3   a ) and the gap plate  20 , and projections  42  are provided at an inner surface  41  of this cylinder. The projections  42  correspond to the notches  22  of the gap plate  20 , and when the gap plate  20  is attached to the bobbin part  10   b  ( 10   a ), the projections  42  fit the notches  22 . The fitting of the projections  42  and the notches  22  sets the position of the gap plate  20  in the directions parallel to the end surface  31   b  ( 31   a ) of the core block  3   b  ( 3   a ). The projections  42  provided on the inner surface  41  of the bobbin part  10   b  ( 10   a ) are portions that define the position of the gap plate  20 . 
       FIG. 5  shows a diagram in which the gap plates  20  are arranged inside the bobbin part  10   b.  The ends of the bobbin part  10   b  protrude outward than the end surface  31   b  of the core block  3   b,  and the gap plates  20  are arranged inside the ends of the cylinder of the bobbin part  10   b.    
     As aforementioned, the projections  42  of the bobbin part  10   b  fit the notches  22  provided respectively on the two parallel sides of each gap plate  20 , by which positions of the gap plates  20  in an in-plane direction are determined. The “in-plane direction” herein means the directions parallel to the end surface  31   b  of the core block  3   b,  as aforementioned. 
       FIG. 6  shows a front view of one of the gap plates  20  attached to the bobbin part  10   b,    FIG. 7  shows a cross-sectional view along a line VII-VII in  FIG. 6 . A reference sign  20   a  in  FIG. 6  shows the edge of the gap plate  20  (side surfaces of the gap plate  20 ). In  FIG. 6 , blacked-out ranges in the protrusions  21  mean regions to be in contact with the core block  3   a  ( 3   b ). Further, in  FIGS. 6 and 7 , a light-gray range Ba indicates a region where the flash might be generated upon the insert molding. 
     As aforementioned, the region where the flash might be generated is the boundary between the bobbin part  10   b  ( 10   a ) and the core block  3   b  ( 3   a ). As shown in  FIGS. 6 and 7 , the gap plate  20  secures the spaces SP 1 , SP 2  therearound except at the vertex surfaces of the protrusions  21  (the blacked-out ranges in  FIG. 6 ) and at the notches  22 . Especially, except for the contact portions between the notches  22  and the projections  42 , the space SP 1  is secured around the edge  20   a  of the gap plate  20 . As shown in  FIG. 7 , the space SP 2  is also secured between the gap plate  20  (except at the protrusions  21 ) and the core block  3   b,  so the edge  20   a  of the gap plate  20  and the range Ba (the range where the flash might be generated) do not contact each other. The generated flash stays in the spaces SP 1 , SP 2 , and is not caught between the protrusions  21  and the end surface  31   b  ( 31   a ). The contact portions between the notches  22  and the projections  42  are also separated from the core block  3   b,  so the flash does not affect the contact portions between the notches  22  and the projections  42 . 
     (Assembling Step) As shown in  FIG. 5 , the core blocks  3   a,    3   b  are arranged to be opposed to each other with the gap plates  20  interposed therebetween such that the protrusions  21  contact the end surface  31   b  ( 31   a ) of the core block  3   b  ( 3   a ), and the bobbin parts  10   a,    10   b  are joined to complete the bobbin  10 . Adhesive is used for joining the bobbin parts  10   a,    10   b.  The bobbin parts  10   a,    10   b  may be joined by another method, such as ultrasonic joining. As aforementioned, even when the flash is generated at the boundaries between the core block  3   b  ( 3   a ) and the bobbin part  10   b  ( 10   a ), the flash does not contact the gap plates  20 , so the positions of the gap plates  20  are not affected by the flash. 
     Finally, the resin cover  18  shown by the virtual line in  FIGS. 1 and 2  is formed. The resin cover  18  is formed by insert molding as well. In forming the resin cover  18 , the spaces SP 1 , SP 2  that were secured around the gap plates  20  may be filled by resin of the resin cover  18 . 
     As aforementioned, in the reactor  2  for which the bobbin parts  10   a,    10   b  are formed by the insert molding, portion where the flash is expected to be generated (the range Ba in  FIG. 6 ) is separated from both the vertex surfaces of the protrusions  21  and the notches  22 . Further, the gap plates  20  are also separated from the end surface  31   b  ( 31   a ) of the core block  3   b  ( 3   a ) except at the vertex surfaces of the protrusions  21 . Due to this, the flash that might be generated at the boundaries between the inner surface  41  of the bobbin part  10   b  ( 10   a ) and the core block  3   b  does not affect the positions of the gap plates  20 . 
       FIG. 8  shows a front view of a gap plate  120  of a variant. In  FIGS. 8 and 9 to 11 , a bobbin part  110  ( 210   b,    310   b ) is depicted with hatching for easier understanding. 
     The gap plate  120  includes one notch  22  at its edge  120   a.  The bobbin part  110   b  includes a first projection  42  and a second projection  142  projecting from a cylindrical inner surface  141 . The first projection  42  and the second projection  142  are provided at positions opposed to each other on the cylindrical inner surface of the bobbin part  110   b.  The first projection  42  fits in the notch  22 . The second projection  142  is in contact with the edge  120   a  of the gap plate  120  at an opposite side from the notch  22 . The fitting between the notch  22  and the first projection  42  accurately sets a position of the gap plate  120  in a Y direction. Further, the gap plate  120  is interposed between the first projection  42  and the second projection  142 , so its position in a Z direction is thereby set accurately. 
       FIG. 9  shows a front view of a gap plate  220  of a second variant. The gap plate  220  is not provided with a notch at its edge  220   a.  Meanwhile, the bobbin part  210   b  includes four projections  242  projecting from a cylindrical inner surface  241 . The four projections  242  are in contact with the edge  220   a  of the rectangular gap plate  220  at its four sides. When seen along a normal direction (X direction), the gap plate  220  is held by the projections  242  projecting from four sides of the inner surface  241 , by which its position in a YZ plane is accurately set. 
       FIG. 10  shows a front view of a gap plate  320  of a third variant. The gap plate  320  includes two projections  321  projecting from its edge  320   a  when seen along the normal direction (the X direction in the drawing). The projections  321  project to opposite directions from each other. An inner surface  341  of the bobbin part  310  surrounding the gap plate  320  is provided with recesses  343  corresponding to the projections  321  of the gap plate  320 . Each of the projections  321  fits its corresponding one of the recesses  343 . The fitting between the projections  321  and the recesses  343  accurately sets a position of the gap plate  320  in the in-plane direction. 
     Each of the gap plates  120 ,  220 ,  320  shown in  FIGS. 8 to 10  includes the protrusions  21  at its four corners when seen along the normal direction of the gap plate.  FIG. 11  shows a front view of a gap plate  420  of a fourth variant. A shape of a contour of the gap plate  420  is the same as that of the gap plate  320  of the third variant. On the gap plate  420 , protrusions  421  at its four corners are arranged slightly inward than the protrusions  21  of the other variants. The protrusions are desirably provided at the four corners to contact the edge of the gap plate when seen along the normal direction of the gap plate, however, they may be provided slightly inward than the edge. 
     Some features regarding the technique described in the embodiment will be described. The reactor  2  of the embodiment includes the core  3  that configures a ring by the pair of U-shaped core blocks  3   a,    3   b.  The technique disclosed herein may be applied to a reactor including three or more core blocks. In a case with the reactor including three or more core blocks, a gap plate may be interposed between a particular pair of the core blocks adjacent to each other, and this gap plate and its surround simply need to have the features described in the embodiment or in any of the variants. 
     Each of the projections  42 ,  142 ,  242 , and the recesses  343  provided on the cylindrical inner surfaces of the bobbin parts corresponds to a portion that sets the position of the gap plate (positioning portion). Each of the projections  321  provided in the gap plate  320  of the third variant corresponds to a positioning projection projecting from the edge  320   a  of the gap plate  320  when seen along the normal direction of the gap plate  320 . 
     In the reactor of the embodiment, a positioning portion for setting an in-plane position of each gap plate is provided in each of the pair of bobbin parts  10   a,    10   b.  However, the positioning portion simply needs to be provided in at least one of the pair of bobbin parts  10   a,    10   b.    
     Specific examples of the present invention has been described in detail, however, these are mere exemplary indications and thus do not limit the scope of the claims. The art described in the claims include modifications and variations of the specific examples presented above. Technical features described in the description and the drawings may technically be useful alone or in various combinations, and are not limited to the combinations as originally claimed. Further, the art described in the description and the drawings may concurrently achieve a plurality of aims, and technical significance thereof resides in achieving any one of such aims.