JP2019050273A - Reactor manufacturing method - Google Patents

Abstract

To provide a technology which releases strength anisotropy of a resin cover at a secondary molding step in a reactor manufacturing method.SOLUTION: A manufacturing method includes a preparation step, a primary molding step, an assembly step, and a secondary molding step. In the preparation step, a pair of coils and a pair of U-shaped cores are prepared. In the primary molding step, a bobbin 10a which covers a U-shaped curved part of a core and is provided with a flange 11 is formed in the core. In the assembly step, the core provided with the bobbin 10a is assembled from both sides in an axial direction of the coils 4a, 4b. In the secondary molding step, injection molding of a resin cover covering at least a part of the flange 11 and at least a part of the coil is performed by filler containing resin. In the primary molding step, there are provided a plurality of ribs 13 at the boundary of an outer flange surface 12 and a core covering surface 14 of the bobbin 10a continuing the outer flange surface 12. In the secondary molding step, a resin injection gate 32 of a metal mold molding the resin cover is provided at a position facing the core covering surface 14.SELECTED DRAWING: Figure 6

Description

  The technology disclosed herein relates to a method of manufacturing a reactor.

  A reactor is known in which a pair of U-shaped cores are arranged in a ring, and a coil is mounted on a pair of parallel parts of the ring. Patent Literatures 1 and 2 disclose such a reactor. The bobbin is injection molded into the U-shaped core. Patent Document 1 also discloses a method of manufacturing a reactor. First, a bobbin is injection-molded on each core (primary molding). The bobbin is provided with a flange which covers the U-shaped curved portion of the core and which defines the axial relative position of the coil to the core. Next, the bobbin core is assembled from both sides of the coil. Finally, a resin cover integrally covering the coil and the core is injection molded (secondary molding).

JP, 2013-149841, A JP, 2017-045894, A

  Since the resin parts (the bobbin and the resin cover) are injection molded, the bobbin and the resin cover are in close contact with the core. In that case, due to the difference in coefficient of linear expansion between the resin part and the core (sintered body of metal or metal and resin), the resin part is repeatedly subjected to a load from the core and deteriorated in the thermal cycle during use. In order to increase the strength of the resin parts, glass filler and metal filler may be mixed with the resin.

  When injection molding a resin cover, the resin injection gate of the mold may be provided at a position facing the core coating surface of the bobbin. Here, the core coating surface of the bobbin refers to a resin portion covering the core on the side opposite to the coil facing side of the flange. When the resin injection gate is disposed at such a position, the filler-containing resin injected from the resin injection gate flows and solidifies along the corner of the boundary between the flange and the core covering surface. Then, the fillers are aligned in a fixed direction, and the strength of the resin cover is anisotropic. Anisotropy of strength causes a direction in which the strength is higher than the expected strength and a direction in which only strength less than the expected strength can be exhibited. As a result, deterioration of the resin cover proceeds with a load in the direction of relatively weak strength. The present specification provides a technique for eliminating the strength anisotropy of the resin cover in the secondary molding process.

  The present specification discloses a method of manufacturing a reactor in which at least a portion of the core and at least a portion of the coil are covered with a resin. The manufacturing method includes a preparation process, a primary molding process, an assembly process, and a secondary molding process. In the preparation step, a pair of coils and a pair of U-shaped cores are prepared. In the primary forming step, the core is formed with a bobbin provided with a flange that covers the U-shaped curved portion of the core and defines the axial relative position of the coil with respect to the core. In the assembly process, the core provided with the bobbin is assembled from both sides in the axial direction of the coil. In the secondary molding step, a resin cover that covers at least a part of the flange and at least a part of the coil is injection molded with a filler-containing resin. In the primary forming step, a plurality of ribs are provided at the boundary between the flange surface opposite to the side facing the coil of the flange and the core coating surface of the bobbin following the flange surface. In the secondary molding process, a resin injection gate of a mold for molding a resin cover is provided at a position facing the core coating surface.

  According to the above manufacturing method, the flow of the molten resin injected from the resin injection gate is disturbed by the rib on the flange surface. Therefore, when the resin solidifies, the direction of the filler becomes random, and the strength of the resin cover becomes isotropic. The details and further improvement of the technology disclosed in the present specification will be described in the following "Forms for Carrying Out the Invention".

It is a perspective view of a reactor. It is a figure explaining a preparatory process. It is a figure explaining a primary forming process. It is a figure explaining an assembly process. It is a figure explaining a secondary forming process. FIG. 5 is a cross-sectional view of the assembly in a mold for secondary forming, cut at a plane through the ribs. It is sectional drawing which shows the flow of molten resin in case there is no rib.

  The manufacturing method of the embodiment will be described with reference to the drawings. First, the overall structure of the reactor will be described. FIG. 1 shows a perspective view of the reactor 2. In FIG. 2, the resin cover 18 is drawn by an imaginary line so that the internal structure of the resin cover 2 can be understood. The X axis of the coordinate system in the figure is defined to coincide with the axial direction of the coils 4a and 4b of the reactor 2.

  The reactor 2 is a passive element in which a pair of coils 4 a and 4 b is wound around a ring-shaped core 3. The coils 4a and 4b are made of one winding, and electrically one coil. The coils 4a and 4b are formed by winding a flat wire in an edgewise manner. The flat wire is coated with insulation so that it does not short circuit with the windings of adjacent pitches.

  As described later, the ring-shaped core 3 is configured of a pair of U-shaped cores 3a and 3b. The bobbin 10 is formed by injection molding so as to cover the core 3, and the coils 4 a and 4 b are wound around the cylindrical portion of the bobbin 10. The bobbins 10 are made by injection molding for the respective cores 3a, 3b. On the core 3a, a bobbin 10a in which the bobbin 10 is halved in its axial direction is formed by injection molding, and on the core 3b, the remaining portion (bobbin 10b) of the bobbin 10 is formed by injection molding (primary molding step). Each of the bobbins 10a and 10b is provided with a flange 11 which determines the relative position of the coils 4a and 4b in the axial direction with respect to the core 3. The coils 4a and 4b are formed in advance by winding flat wire, and the core 3a (3b) on which the bobbins 10a (10b) are formed is attached from both sides in the axial direction of the coils 4a and 4b. A part of the flanges 11 on both sides of the bobbin 10 and a part of the coils 4 a and 4 b are covered with a resin cover 18. The resin cover 18 is also made by injection molding (secondary molding process).

  The method for manufacturing the reactor 2 will be described with reference to FIGS. The reactor 2 is completed through a preparation process, a primary forming process, an assembly process, and a secondary forming process.

  (Preparation Step) First, a pair of U-shaped cores 3a and 3b and a pair of coils 4a and 4b are prepared (FIG. 2). The cores 3a and 3b are obtained by sintering iron powder and resin powder. The coils 4a and 4b are formed by winding the coated flat wire in an edgewise manner as described above. The coils 4a and 4b are made of one flat wire, and are electrically one coil.

  (Primary Forming Step) Next, bobbins 10a and 10b are formed by injection molding for each of the cores 3a and 3b (FIG. 3). The bobbin 10a is made by insert molding on the core 3a. That is, the core 3a is put in a mold, and the molten resin is injected into the cavity of the mold. The bobbin 10a covers the core side surface excluding the end face of the U-shaped arm of the core 3a. In other words, the bobbin 10a covers the side of the U-shaped arm of the core 3a and the U-shaped curved portion. Windows 15 and 16 are provided in several places of the part which covers the core 3a of the bobbin 10a. In other words, the side surfaces of the core 3a are exposed from the windows 15, 16 of the bobbin 10a.

  The bobbin 10a is provided with a flange 11 which determines the axial position of the coils 4a and 4b relative to the core 3 when the cores 3a and 3b and the coils 4a and 4b are assembled. For convenience of description, the surface of the flange 11 opposite to the side facing the coils 4 a and 4 b is referred to as an outer flange surface 12. Further, in the portion covering the core 3a of the bobbin 10a, the flat surface following the outer flange surface 12 is referred to as a core covering surface 14.

  The bobbin 10 a is provided with a plurality of ribs 13 in contact with both the outer flange surface 12 and the core coating surface 14 at the boundary between the outer flange surface 12 and the core coating surface 14. In addition, in FIG. 3, the code | symbol 13 was attached | subjected only to the rib of the both ends of the row of several ribs, and the code | symbol was abbreviate | omitted to the other rib. The bobbin 10a is manufactured by injection molding, but the plurality of ribs 13 are also molded simultaneously with the injection molding of the entire bobbin 10a by injection molding.

  The bobbin 10b is also made by injection molding. The bobbin 10b also includes a flange 11 that determines the relative position of the coils 4a and 4b in the axial direction. The flange 11 of the bobbin 10b is provided with a slit 19 through which the lead wires of the coils 4a and 4b pass. The rib 13 with which the bobbin 10a is provided is not provided in the bobbin 10b.

  (Assembly Process) The core 3a (3b) in which the bobbins 10a (10b) are formed is assembled from both sides in the axial direction of the coils 4a and 4b (FIG. 4). In FIG. 4, a portion covered by the resin cover 18 is shown by a hidden line (broken line) to aid understanding. The reactor (FIG. 4) before molding the resin cover 18 (see FIG. 1) is referred to as an assembly 21.

  (Secondary Forming Process) The assembly 21 is put in a mold, and a resin cover 18 covering at least a part of the coils 4a and 4b and at least a part of the flanges 11 on both sides in the axial direction is formed by injection molding (FIG. 5) . The plurality of ribs 13 are also covered by the resin cover 18. The resin used in the secondary molding process contains a glass filler. Glass filler is incorporated to increase the strength of the resin cover 18.

  A resin injection gate of a mold for producing the resin cover 18 is provided at a position facing the core coating surface 14 of the bobbin 10a described above. FIG. 6 shows a cross-sectional view cut in a plane parallel to the XY plane of the coordinate system in the figure, which is transverse to the ribs 13 of the assembly 21 placed in the mold 30. FIG. 6 is a partial cross-sectional view showing up to the middle of the coils 4a and 4b in the axial direction (X direction) of the coil. In FIG. 6, the resin injection gate 32 provided at a position facing the core coating surface 14 of the mold 30 is drawn by a broken line.

  In FIG. 6, the flow in the cavity 31 of the molten resin injected from the resin injection gate 32 is drawn by a thick arrow line. The cavity 31 is a space for molding the resin cover 18 inside the mold 30. Further, also in FIG. 6, among the plurality of ribs 13, only the ribs at both ends in the arrangement direction are denoted by reference numeral 13, and the remaining ribs are omitted from reference numerals. As indicated by thick arrows in FIG. 6, the flow of the molten resin collides against the rib 13 and the direction changes.

  As described above, the resin for molding the resin cover 18 is mixed with a glass filler. The glass filler is needle-like. When the glass filler is oriented in the same direction when the molten resin is solidified, anisotropy occurs in the strength of the solidified resin. Specifically, a resin containing a glass filler exhibits high strength against stress in the longitudinal direction of the needle-like glass filler, and relatively low strength against stress in the direction orthogonal to the longitudinal direction. Indicates The flow of the molten resin when the ribs 13 are not provided is shown in FIG. Also in FIG. 7, thick arrows indicate the flow of the molten resin. The molten resin flows uniformly along the outer flange surface 12. Therefore, the direction of the glass filler also tends to be the same. If the resin solidifies while the glass filler faces in the same direction, anisotropy occurs in the strength of the portion covering the outer flange surface 12 and the core coating surface 14 of the resin cover 18. The core 3 and the resin parts (bobbins 10a and 10b, and the resin cover 18) have different coefficients of linear expansion. When the reactor 2 is subjected to a thermal cycle when it is used, the resin part receives a load from the core 3 due to the difference in linear expansion coefficient. When the strength of the resin parts (bobbins 10a and 10b and the resin cover 18) is anisotropic, only the direction in which the strength is higher than the expected strength and the strength which does not meet the expected strength is exhibited. A direction that can not be done will occur. When the resin cover 18 is subjected to a load in a direction in which it can exert only a strength that does not meet the expected strength, deterioration progresses faster than in the case where the strength is isotropic. In the manufacturing method of the embodiment, as shown in FIG. 6, the flow of the molten resin is disturbed by the plurality of ribs 13 provided at the boundary between the outer flange surface 12 and the core coating surface 14, and the orientation of the glass filler is random. It becomes. Therefore, the strength of the resin cover 18 is isotropic, and the progress of deterioration is delayed with respect to the heat cycle.

  Points to note regarding the technology described in the embodiment will be described. The plurality of ribs 13 are preferably provided on the opposite side of the core coating surface 14 of the bobbin 10a, but may be provided at least on the core coating surface 14 on the side where the resin injection gate 32 exists. The plurality of ribs 13 is preferably provided on each of the bobbins 10a and 10b, but it may be provided at least on the flange 11 closer to the resin injection gate 32 when inserted into the mold 30.

  As mentioned above, although the specific example of this invention was described in detail, these are only an illustration and do not limit a claim. The art set forth in the claims includes various variations and modifications of the specific examples illustrated above. The technical elements described in the present specification or the drawings exhibit technical usefulness singly or in various combinations, and are not limited to the combinations described in the claims at the time of application. In addition, the techniques exemplified in the present specification or the drawings can simultaneously achieve a plurality of purposes, and achieving one of the purposes itself has technical utility.

2: Reactor 3: core 3a, 3b: core 4a, 4b: coil 10, 10a, 10b: bobbin 11: flange 12: outer flange surface 13: rib 14: core coating surface 15, 16: window 19: slit 21: assembly 30: Mold 31: Cavity 32: Resin injection gate

Claims (1)

A method of manufacturing a reactor, wherein at least a portion of the core and at least a portion of the coil are covered with resin,
Preparing a pair of coils and a pair of U-shaped cores;
Forming a bobbin on the core including a flange covering a U-shaped curved portion of the core and defining an axial relative position of the coil with respect to the core;
Assembling the core including the bobbin from both sides in the axial direction of the coil;
A secondary molding step of injection molding a resin cover covering at least a part of the flange and at least a part of the coil with a filler-containing resin;
Equipped with
In the primary forming step, a plurality of ribs are formed at the boundary between the flange surface opposite to the side facing the coil of the flange and the core covering surface of the bobbin following the flange surface;
The method of manufacturing a reactor, wherein in the secondary molding step, a resin injection gate of a mold for molding the resin cover is provided at a position facing the core coating surface.

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