JP2006019706A - Coil-encapsulated dust core manufacturing method and coil encapsulated dust core - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of efficiently manufacturing a coil encapsulated dust core, having little variations in the inductance value, or the like. <P>SOLUTION: A method of manufacturing by a pressure forming of one time the coil encapsulated dust core constituted by enclosing in a dust body a coil 1 having a winding portion and an edge extracted from this winding portion, comprises a primary filling step of filling soft magnetic metal powder, containing an insulating agent in a cavity; a coil arranging step of arranging the coil 1 on the soft magnetic metal powder, filled in the primary filling step; a secondary filling step of filling the soft magnetic metal powder in the cavity so as to cover the coil 1; and a compacting step of compacting the soft magnetic metal powder covering the coil 1, wherein in the primary filling step, an amount of the soft magnetic metal powder filled in a portion which corresponds to the winding portion is set to be smaller than that in a portion which does not correspond to the winding portion, based on a top face and a bottom face of the winding portion, and this state is set maintained in the compacting step. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an inductor integrated with a magnetic core, a coil-embedded dust core used for other electronic components, and a method for manufacturing a coil-embedded dust core. More specifically, the present invention relates to a method for manufacturing a coil-embedded dust core in which an air-core coil is sealed in a green compact.

In recent years, the miniaturization of electric and electronic devices has progressed, and there is a demand for a compact magnetic core that is small (low profile) and can handle a large current.
Ferrite powder and ferromagnetic metal powder are used as the material for the dust core, but ferromagnetic metal powder has a higher saturation magnetic flux density than ferrite powder, and DC superposition characteristics are maintained up to a high magnetic field. . Therefore, when producing a dust core corresponding to a large current, it has become mainstream to use a ferromagnetic metal powder as the material of the dust core.
Further, in order to further promote the miniaturization (low profile) of the core, a coil in which the coil and the magnetic powder are integrated has been proposed. In this specification, the inductor having this structure is referred to as a “coil-enclosed dust core”.

  Conventionally, a method for manufacturing a surface-mount type inductor having a structure of a coil-embedded dust core has been proposed. For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 5-291046) discloses that external electrodes are connected to an insulation-coated conductor and molded together with magnetic powder so as to wrap them. Patent Document 2 (Japanese Patent Laid-Open No. 11-273980) discloses a soft magnetic composite material obtained by mixing a flat soft magnetic metal powder and a binder, and a coil in a mold including a die and a lower punch. Are simultaneously inserted and compression molded. Further, in Patent Document 3 (Japanese Patent No. 2958807), in order to obtain a large inductance value, molding is performed while orienting the easy magnetization axis direction of the magnetic powder particles along the direction of the magnetic field formed by energizing the coil. An inductor manufacturing method is disclosed. Furthermore, in Patent Document 4 (Japanese Patent No. 3108931), first and second green compacts that are preliminarily pressed are prepared, and a coil is sandwiched from above and below by these green compacts. A method for manufacturing an inductor by press-molding until the interface between the first green compact and the second green compact is removed is disclosed. According to the method described in Patent Document 4 (Japanese Patent No. 3108931), since the filling amount of the magnetic powder constituting the green compact can be increased, the above-mentioned Patent Document 1 (Japanese Patent Laid-Open No. 5-291406) is disclosed. ), Patent Document 2 (Japanese Patent Laid-Open No. 11-273980), Patent Document 3 (Japanese Patent No. 2958807), and a larger inductance value can be obtained.

Japanese Patent Application Laid-Open No. 5-291406 JP-A-11-273980 Japanese Patent No. 2958807 Japanese Patent No. 3108931

  However, according to the method described in Patent Document 4 (Japanese Patent No. 3108931), the first green compact preform, the second green compact preform, and the coil as the first green compact Three times of molding operations are required to perform the main molding performed between the second green compact and one inductor. When these molding operations are performed by one molding machine, the molding die must be exchanged for each molding operation, which is very inefficient. Furthermore, since the molding is performed so that the interface of the preformed core does not remain, the molding pressure must be increased, which causes problems such as coil deformation and insulation failure.

In addition, as described above, the coil-embedded dust core is small and can provide a large inductance value. However, there is a strong demand for improving the quality of the coil-embedded dust core as electric and electronic devices are rapidly downsized. . Specifically, as the frequency at which the coil-embedded dust core is used shifts to the high frequency side, there is an increasing demand for the accuracy of the inductance value. Since the impedance increases in proportion to the frequency, the inductance value must be designed to decrease as the frequency at which the coil-embedded dust core is used shifts to the high frequency side. On the other hand, it is necessary to avoid a situation in which a part of the magnetic material is magnetically saturated and a predetermined inductance value (design value) cannot be obtained. That is, it is required to stably obtain a predetermined inductance value based on the operating frequency.
Therefore, in view of the above points, the present invention has an object to provide a method for efficiently producing a coil-embedded dust core that achieves a predetermined inductance value (design value) and has a small variation in inductance value. To do.

  In order to solve the above-mentioned problems, the present inventor has made various studies. As a result, the position of the coil in the coil-filled dust core, particularly the position in the consolidation direction, has a great influence on the inductance, and the density of the green compact. It has been found that the variation of the inductance value is reduced by making the entire area uniform. And in order to make the density of the green compact in the coil-embedded dust core as a whole uniform, the amount of the soft magnetic metal powder filled in the part corresponding to the winding part of the air-core coil is changed to the winding part. It was also confirmed that it is simple and effective to reduce the amount of the soft magnetic metal powder filled in other parts not corresponding to the above. That is, the present invention manufactures a coil-embedded dust core formed by enclosing an air-core coil having a winding portion and an end portion drawn from the winding portion in a green compact by a single press molding. A primary filling step in which a cavity is filled with a soft magnetic metal powder containing an insulating material constituting a green compact, and an air-core coil is disposed on the soft magnetic metal powder filled in the primary filling step. A coil placement step, a secondary filling step in which the soft magnetic metal powder is filled in the cavity so as to cover the air core coil, and a soft magnetic metal powder covering the air core coil is consolidated in the axial direction of the air core coil. And in the primary filling step, the amount of the soft magnetic metal powder filled in the portion corresponding to the winding portion is determined based on the upper surface or the lower surface of the winding portion as other reference that does not correspond to the winding portion. Less than the amount of soft magnetic metal powder filled in the part And have state, in consolidation process, a method of manufacturing a coil-embedded dust core, characterized in that the compacted while the state is maintained.

  Here, as another part, the part corresponding to the hollow part of an air-core coil is mentioned. That is, consolidation is performed in a state where more soft magnetic metal powder is filled in a portion corresponding to the hollow portion of the air-core coil than a portion corresponding to the winding portion. Also, it is preferable that the portion corresponding to the corner of the green compact and the periphery of the end drawn from the winding portion are filled with a larger amount of soft magnetic metal powder than the portion corresponding to the winding portion. The soft magnetic metal powder filled in the portion corresponding to the winding portion of the air-core coil (hereinafter referred to as “coil portion” as appropriate) is the other portion not corresponding to the winding portion (hereinafter referred to as “non-coil portion” as appropriate). ), The coil part inevitably tends to be denser than the non-coil part, but the non-coil part has a higher density than the coil part in advance. By performing consolidation in the state filled with the soft magnetic metal powder, it is possible to obtain a coil-embedded dust core having a uniform density as a whole. Then, according to the coil-embedded dust core having a uniform density as a whole, variation in inductance value is reduced, and a predetermined inductance value can be stably obtained. In addition, since the coil is a metal, it is harder to compress than the soft magnetic metal powder, and the coil may be damaged if it is forcibly pressed. However, according to the method proposed by the present invention, the overall density without damaging the coil. Can obtain a uniform coil-embedded dust core.

In the consolidation step described above, the compression ratio of the soft magnetic metal powder in the portion corresponding to the maximum number of windings in the winding portion and the compression ratio of the soft magnetic metal powder in the other portion can be made equal. In order to form terminals on both sides of the component, for example, when an air-core coil is produced by winding a conductor for 2.5 turns, there are a 3-turn portion and a 2-turn portion. In this case, the 3-turn portion is the portion corresponding to the maximum number of turns in the winding portion, and usually the compression ratio of this portion is the highest, but according to the method of the present invention, It is possible to equalize the compression ratio of the soft magnetic metal powder between the portion corresponding to the maximum number of turns and the other portion, for example, the portion corresponding to the hollow portion of the coil. Here, the compression ratio in this specification is the ratio of the thickness of the soft magnetic metal powder before and after compression.
Further, according to the method of manufacturing a coil-embedded dust core according to the present invention, the density of the green compact in the vicinity of the upper surface or the lower surface of the portion corresponding to the maximum number of windings in the winding portion and the pressure in the other portion. The density of the powder can be made uniform.

Furthermore, the present invention provides a cuboid green compact having front and back surfaces facing each other with a predetermined interval and side surfaces formed around the front and back surfaces, and a winding portion and an end drawn from the winding portion. A coil-embedded dust core made of a single pressure molding, wherein at least a wound portion is disposed in the green compact, and the density of the green compact Are equal in the portion corresponding to the maximum number of windings in the winding portion and the hollow portion of the air-core coil, and the air-core coil is arranged in the green compact along the direction of pressure molding. A coil-embedded dust core is provided. According to the coil-embedded dust core of the present invention, the difference in density between the portion corresponding to the maximum number of turns in the winding portion and the hollow portion of the air-core coil is set to 0.3 g / cm ³ or less. As a result, a coil-embedded dust core having a small variation in inductance value can be finally obtained.
In addition, the above-described air-core coil is preferably composed of a rectangular wire. Furthermore, it is effective to use a so-called terminal-integrated air core coil in which a part of the air core coil functions as a terminal portion. Furthermore, the end of the air-core coil can be exposed from the center of the side surface of the green compact to the outside of the green compact with reference to the thickness direction of the green compact. If the connecting part is located inside the green compact, defects are likely to occur at the time of molding, but the end of the air-core coil functions as a terminal part and this end is exposed to the outside of the green compact. As a result, the connection outside the green compact becomes possible. As a result, it is possible to obtain a coil-embedded dust core in which poor bonding and poor insulation are unlikely to occur. In the present specification, the connecting portion refers to a portion in which components are electrically connected to each other, and a portion to be soldered to an external electrode such as a land pattern on a surface mounting board is referred to as a terminal portion. I will do it. Also, in order to expose the end of the air-core coil from the center of the side surface of the green compact to the outside of the green compact with reference to the thickness direction of the green compact, a coil with a flat conductive wire wound is used. And what is necessary is just to implement the manufacturing method of the coil enclosure dust core which this invention proposes using the coil in which the both ends were formed on the same plane.

  As described above, according to the present invention, it is possible to efficiently manufacture a coil-embedded dust core that achieves a predetermined inductance value (design value) and has little variation in inductance value. In addition, according to the present invention, it is not necessary to increase the molding pressure, so that coil deformation, insulation failure, and the like are unlikely to occur.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
FIG. 1 is a plan sectional view of a coil-embedded dust core according to the present embodiment. 2 (a) and 2 (b) are side sectional views of the coil-embedded dust core, and FIG. 2 (b) is a simplified illustration of FIG. 2 (a). FIG. 3 is a plan view of a coil (air core coil) 1 used in the present embodiment, and FIG. 4 is a side view of the coil 1. As shown in FIGS. 1 to 4, the coil 1 includes a winding portion 3 in which a flat conductor 2 is wound and laminated, and lead-out end portions 4 a and 4 b respectively drawn from the winding portion 3. It is an air core coil. The green compact 10 covers the periphery of the coil 1 except for the drawing end portions 4 a and 4 b of the coil 1. Although detailed description will be given later, in the present embodiment, since the extraction end portions 4a and 4b of the coil 1 function as the terminal portion 100, the coil 1 has a so-called terminal-integrated structure.

As described above, the coil-embedded dust core in the present embodiment includes a portion (coil portion) corresponding to the winding portion 3 of the coil 1 and a non-coil portion (portion corresponding to the hollow portion of the coil 1, dust). The density of the portion corresponding to the corner of the body 10 and the periphery of the end portion drawn out from the winding portion 3 is uniform. Here, as shown in FIG. 2A, the portion corresponding to the winding portion 3 of the coil 1 is the winding portion in the green compact 10 with the axial direction (thickness direction) of the coil 1 as a reference. 3 is a portion corresponding to the upper and lower surfaces. Moreover, the part corresponding to the hollow part of the coil 1 means the part which extended the hollow part of the coil 1 and the hollow part of the coil 1 to the upper surface and lower surface of the compact 10 in the axial direction.
One feature of the coil-embedded dust core in the present embodiment is that the coil 1 is accurately positioned in the center of the powder compact 10 in the axial direction. That is, as shown in FIG. 2 (b), the coil-embedded dust core in the present embodiment has a distance H1 from the extraction end 4a (4b) to the upper surface of the green compact 10, and the extraction end 4a ( The distance H2 from 4b) to the lower surface of the green compact 10 is uniform. Further, the distance H3 from the upper surface of the winding part 3 of the coil 1 to the upper surface of the green compact 10 and the distance H4 from the lower surface of the winding part 3 of the coil 1 to the lower surface of the green compact 10 are equal. . Furthermore, as will be described in detail in the examples below, the coil-embedded dust core in the present embodiment has a density corresponding to the winding portion 3 of the coil 1 indicated by 2 and 3 in FIG. And in FIG.2 (b), the density of the part corresponding to the hollow part of the coil 1 shown by 1 is equal.

First, the green compact 10 will be described.
The green compact 10 is produced by adding and mixing an insulating material to magnetic metal powder, and then pressurizing under predetermined conditions. Further, after drying the ferromagnetic metal powder to which the insulating material has been added, it is preferable to add and mix a lubricant to the dried magnetic powder.

  Examples of the ferromagnetic metal powder used for the green compact 10 include a single metal powder, two or more metal powders having different compositions, or an alloy powder. The metal powder can be composed of any transition metal element exhibiting soft magnetism, or an alloy composed of a transition metal element and another metal element. Specific examples of the soft magnetic metal include an alloy mainly composed of one or more of Fe, Co, and Ni. For example, permalloy (Fe—Ni alloy, Fe—Ni—Mo alloy), sendust (Fe—Si). -Al alloy), Fe-Si alloy, Fe-Co alloy, Fe-P alloy and the like are preferable. Among these, permalloy is preferable because of its high magnetic permeability and good workability.

When an Fe—Ni alloy (permalloy) is selected as the ferromagnetic metal powder used for the green compact 10, the composition is Fe: 15-60 wt% and Ni: 40-85 wt%. When a Fe—Ni—Mo alloy (permalloy) is selected as the ferromagnetic metal powder used for the green compact 10, the composition is Fe: 15-30 wt%, Ni: 70-85 wt%, Mo: 1— 5 wt%.
The shape of the particles of the ferromagnetic metal powder used for the green compact 10 is not particularly limited, but it is preferable to use a spherical powder or an elliptical powder.

  The ferromagnetic metal powder can be obtained by a gas atomizing method, a water atomizing method, a rotating disk method or the like.

Further, by adding an insulating material, the ferromagnetic metal powder is insulated. The insulating material is appropriately selected according to the required characteristics of the magnetic core. For example, various organic polymer resins, silicone resins, phenol resins, epoxy resins, water glass, etc. may be used as the insulating material. In addition, these resins and inorganic substances may be used in combination.
Although the addition amount of the insulating material varies depending on the required characteristics of the magnetic core, about 1 to 10 wt% can be added. When the added amount of the insulating material exceeds 10 wt%, the magnetic permeability decreases and the loss tends to increase. On the other hand, when the added amount of the insulating material is less than 1 wt%, there is a possibility of insulation failure. A preferable addition amount of the insulating material is 1.5 to 5 wt%.

The addition amount of the lubricant can be about 0.1 to 1.0 wt%, the desired addition amount of the lubricant is 0.2 to 0.8 wt%, and the more desirable addition amount of the lubricant is 0.3 to 0 0.8 wt%.
When the addition amount of the lubricant is less than 0.1 wt%, it is difficult to remove the mold after molding, and molding cracks are likely to occur. On the other hand, when the addition amount of the lubricant exceeds 1.0 wt%, the density is lowered and the magnetic permeability is reduced.
The lubricant may be appropriately selected from, for example, aluminum stearate, barium stearate, magnesium stearate, calcium stearate, zinc stearate, strontium stearate, and the like. From the viewpoint that so-called spring back is small, it is preferable to use aluminum stearate as a lubricant.

  A predetermined amount of a crosslinking agent can be added to the ferromagnetic metal powder. By adding a crosslinking agent, the strength can be increased without deteriorating the magnetic properties of the green compact 10. A preferable addition amount of the crosslinking agent is 10 to 40 wt% with respect to an insulating material such as silicone resin. As the crosslinking agent, an organic titanium-based one can be used.

Next, the structure of the coil 1 is demonstrated using FIG. 3 and FIG.
As shown in FIGS. 3 and 4, the coil 1 is obtained by winding the conductor 2 by edgewise winding for 2.5 turns, and the lead-out end portions 4 a and 4 b of the conductor 2 are formed by reverse forming from the main body portion of the coil 1. Each has a drawn structure. That is, the coil 1 is integrally formed without a seam.

The cross section of the conductor 2 forming the coil 1 is flat. Here, examples of the flat cross section include a rectangular, trapezoidal, and elliptical cross section. As the conductor 2 having a rectangular cross section, there is a flat wire that is an insulation-coated copper wire. When using a flat wire as the conductor 2, the cross-sectional dimension can be about 0.1-1.0 mm in length x 0.5-5.0 mm in width.
The insulation coating of the conductor 2 can usually be enamel coating, but the thickness of the enamel coating is approximately 3 μm.

  When the coil 1 is formed by winding the flat conductor 2, the layers of the windings constituting the coil 1 can be brought into close contact with each other as shown in FIG. Therefore, the current capacity per volume can be improved as well as being advantageous for lowering the height than the case of using a conductor having a circular cross section. In addition, the wire occupation ratio can be greatly improved as compared with the case where the coil 1 is formed by winding a conductor having the same number of turns and a circular cross section. Therefore, the coil 1 produced by winding the flat conductor 2 is suitable for producing a coil encapsulating dust core for large current.

Next, FIG. 5 shows a cross-sectional shape before winding the flat conductor 2 and a cross-sectional shape after winding the flat conductor 2.
When a flat wire is used as the flat conductor 2, the thickness of the cross section before winding the conductor 2 is uniform as shown in FIG. When the conductor 2 is wound from this state, as shown in FIG. 5B, the thickness on the outer peripheral side (outside of the winding) of the coil 1 becomes thinner than the thickness on the inner peripheral side (inside of the winding). Here, as described above, the coil 1 is formed by winding the conductor 2 several times. When the conductor 2 is wound, the windings come into contact with each other. As shown in FIG. 5B, when the conductor 2 is wound, the thickness on the outer peripheral side of the coil 1 becomes the thickness on the inner peripheral side. Thus, the air core coil can be manufactured by winding the conductor 2 while preventing the coating of the conductor 2 from peeling off and damaging it.
If the coil 1 in which the coating of the conductor 2 is peeled off or damaged is encapsulated in the green compact 10, the inductance value of the coil-embedded dust core will be significantly reduced.

  In addition, as shown in FIG. 5C, when the flat conductor 2 is wound and the pressing is performed in a state where the outer peripheral side thickness of the coil 1 is thinner than the inner peripheral side thickness. There is an effect that the insulating coating on the outer peripheral side of the coil 1 is hardly damaged. As shown in FIG. 5D, if the press working is performed in a state where the outer peripheral side thickness and the inner peripheral side thickness of the coil 1 are substantially uniform, the insulating coating on the outer peripheral side of the coil 1 is damaged. Cheap.

  In addition, based on the cross-sectional shape of the coil 1 formed after winding the conductor 2, you may select suitably the cross-sectional shape of the conductor 2 in trapezoid shape.

Next, the manufacturing method of the coil 1 which concerns on this Embodiment is demonstrated using FIGS.
FIG. 6 is a flowchart showing manufacturing steps of the coil 1 according to the present embodiment. As shown in FIG. 6, in manufacturing the coil 1 according to the present embodiment, the winding process of the conductor 2 (step S101), the forming process (step S102), and the pressing process (crushing process) (step S103). , A sizing process (step S104), and a bending process (step S105).

<Conductor 2 winding process>
First, in step S101, as shown in FIGS. 7A and 7B, the flat conductor 2 is wound to form the winding portion 3 and the leading end portions 4a and 4b of the coil 1. The number of windings of the conductor 2 is appropriately set according to the required inductance value, and can be about 1 to 6 turns, preferably 2 to 4 turns. Here, FIG. 7B shows a side view of the coil 1 after the conductor 2 has been wound 2.5 turns by edgewise winding. As shown in FIG. 7 (b), it is possible to reduce the number of work steps and to occupy the electric wire by keeping the layers of the windings constituting the coil 1 in very close contact with each other already in the winding step in step S101. It is preferable from the viewpoint of improvement of the above.

<Forming process>
In subsequent step S102, the coil 1 is formed. FIG. 8 is a plan view showing a state in which the lead-out end portions 4a and 4b of the conductor 2 are drawn out from the winding portion 3 of the coil 1 by reverse forming. Here, the direction in which the drawer end 4a is pulled out is preferably different from the direction in which the drawer end 4b is pulled out. This is because it is difficult to form the terminal portions 100 on both sides of the coil-embedded dust core when the pull-out end portions 4a and 4b are pulled out in the same direction. This is based on the reasons that it is inconvenient when performing the press processing, and that it is difficult to place the coil 1 at the center of the green compact 10 when producing the coil-embedded dust core. . Further, as shown in FIG. 8, it is more preferable to perform the forming so that the leading end portions 4a and 4b are arranged symmetrically. Accordingly, when the coil-embedded dust core using the coil 1 is a surface-mounted component, the extraction positions of the extraction end portions 4a and 4b that function as the terminal portion 100 can be made symmetrical. Therefore, when handling the coil 1, for example, when the coil 1 is arranged in a molding die, it is not necessary to distinguish the direction of the coil 1.

<Pressing (crushing) process>
After forming the coil 1 in step S102, the process proceeds to step S103. In step S103, the drawing ends 4a and 4b are pressed (crushing). This step is performed in order for the lead-out end portions 4a and 4b of the coil 1 to function as the terminal portion 100. Through this step, the plane of the lead-out end portions 4a and 4b is wider than the plane of the conductor 2 and Formed thin.
The press working in step S103 is desirably performed until the thickness of the conductor 2 becomes about 0.1 to 0.3 mm. As described above, the pressing process is performed so that the flat surfaces of the extraction end portions 4a and 4b are wider and thinner than the flat surface of the conductor 2, but the extraction end portion that functions as the terminal portion 100 by the pressing process. The effect that the intensity | strength of 4a, 4b increases can also be anticipated.

Here, FIG. 9 shows a state after the drawing ends 4a and 4b are pressed. FIG. 9A is a plan view of the coil 1, and FIG. 9B is a side view of the coil 1.
As shown in FIG. 9A, when the drawing ends 4a and 4b are subjected to press working, the conductor 2 at that portion is extended isotropically. That is, the shape of the lead-out ends 4a and 4b cannot be made rectangular simply by crushing the conductor 2. On the other hand, the shape of the lead-out ends 4a and 4b is preferably rectangular to match the land pattern of the substrate on which the coil-embedded dust core using the coil 1 is mounted. This is because the land pattern tends to become smaller as the surface mounting density increases, and it is necessary to improve the accuracy of the dimensions and shapes of the terminals.

<Sizing process>
In step S103, after the drawing ends 4a and 4b are pressed, the process proceeds to step S104. In step S104, sizing processing is performed on the drawn end portions 4a and 4b that have been subjected to press working. This sizing process can be performed using, for example, a punching die. As described above, since the land pattern of the substrate on which the coil-embedded dust core is mounted is generally rectangular, it is preferable that the extraction ends 4a and 4b be rectangular in order to match this. For example, when the coil-embedded dust core is used for a notebook computer, the shape of the extraction end portions 4a and 4b can be rectangular and the dimensions can be about 20 × 30 mm to 50 × 60 mm.
It is to be noted that the rectangular shape of the extraction end portions 4a and 4b is not an essential requirement for causing the extraction end portions 4a and 4b to function as the terminal portion 100, and the dimensions of the extraction end portions 4a and 4b after press working are determined by the substrate. If it falls within the land pattern, the sizing process in step S104 can be omitted as appropriate. However, since the land pattern is becoming narrower with the improvement of the surface mounting density, there is a strong demand for the shape and dimensional accuracy of the terminal portion 100, so that the sizing process is performed on the drawn end portions 4a and 4b subjected to press working It is preferable to apply. Here, a plan view of the coil 1 that has been subjected to the sizing process is in a state shown in FIG. 3, for example.

<Bending process>
After performing the sizing process in step S104, the process proceeds to step S105. In step S105, the drawing ends 4a and 4b subjected to the sizing process are subjected to bending processing. This bending process is a characteristic part of the present invention, and this process is performed in order to arrange the drawing end portions 4a and 4b functioning as the terminal portion 100 on the same plane.

Hereinafter, the content of the bending process will be described in more detail with reference to FIG. 10A to 10C are side views of the coil 1, respectively.
FIG. 10A is a diagram showing a state in which the extraction end portions 4a and 4b are arranged on the same plane with the intermediate layer of the winding portion 3 as a reference plane. As shown in FIG. 10 (a), when the intermediate layer of the winding part 3 is used as a reference plane, the drawing end parts 4a and 4b are bent at substantially the same amount by a certain angle, and the drawing end part 4a and the winding end part are wound. Bending portions 4c are formed between the turning portions 3 and between the drawing end portion 4b and the winding portion 3, respectively. Thus, when arrange | positioning extraction | drawer edge part 4a, 4b on the same plane by making the intermediate | middle layer of the winding part 3 into a reference plane, in the sizing process process (step S104) mentioned above, The lengths are substantially equal, that is, as shown in FIGS. 9A and 9B, the length La from the center line of the winding portion 3 of the coil 1 to the tip of the lead-out end portion 4a, and the coil 1 If the length Lb from the center line of the winding part 3 to the tip of the drawing end part 4b is made to coincide, the distance between the drawing end part 4a and the winding part 3 and between the drawing end part 4b and the winding part 3 When the bent portions 4c are respectively formed therebetween, the length L1 of the extraction end portion 4a and the length L2 of the extraction end portion 4b can be substantially matched.

  FIG. 10B shows that the uppermost layer of the winding part 3 is the reference plane, and the leading ends 4a and 4b are on the same plane, that is, one of the front and back surfaces of the leading end 4a is the leading end. It is a figure which shows the state formed in the same plane as any one surface of the surface and the back surface in the part 4b. As shown in FIG. 10 (b), when the uppermost layer of the winding part 3 is used as a reference plane, only one of the leading end parts 4b is bent at a certain angle, and between the leading end part 4b and the winding part 3 The bent portion 4c is formed. Further, when the drawing end portions 4a and 4b are arranged on the same plane with the lowermost layer of the winding portion 3 as a reference plane, only one drawing end portion 4a is at an angle as shown in FIG. 10 (c). The bent portion 4c may be formed between the drawing end 4a and the winding portion 3.

  As shown in FIG. 10B, in the case where the leading end portions 4a and 4b are arranged on the same plane with the uppermost layer of the winding portion 3 as a reference plane, in the above-described sizing process step (step S104), The length of the drawing end 4b is made longer than the length of the drawing end 4a. That is, the length Lb from the center line of the winding part 3 of the coil 1 to the tip of the lead end 4b is longer than the length La from the center line of the coil 3 of the coil 1 to the tip of the lead end 4a. Steps S101 to S104 described above are performed so as to be longer. The same applies to the case where the drawing end portions 4a and 4b are arranged on the same plane with the lowermost layer of the winding portion 3 as a reference plane.

  In addition, when forming the bending part 4c by bending the extraction | drawer edge parts 4a and 4b, you may bend the part to which the crushing process is given, and you may bend the part to which the crushing process is not given. As described above, since the thickness of the drawing end portions 4a and 4b is 0.1 to 1.0 mm before the press processing and 0.1 to 0.3 mm after the press processing, the drawing end portions 4a and 4b are Can be folded easily.

As described above, the bending process (step S105), which is a characteristic process of the present invention, has been described with reference to FIG. 10, but this process is an indispensable process for arranging the extraction end portions 4a and 4b on the same plane. is there. That is, as shown in FIG. 7B and FIG. 9B, the bent portion 4 c is provided between the drawing end portion 4 a and the winding portion 3 and between the drawing end portion 4 b and the winding portion 3. In the state where it is not formed, the drawer end portions 4a and 4b cannot be arranged on the same plane.
In the above description, the example in which the bending process (step S105) is performed after the pressing process (step S103) and the sizing process (step S104) has been described. However, after the bending process (step S105) is performed. You may perform a press work process (step S103) and a sizing process process (step S104). Further, the bending process (step S105) may be performed between the press process (step S103) and the sizing process (step S104).

  As will be described later in detail, as shown in FIGS. 10A to 10C, when the coil 1 in which the extraction end portions 4a and 4b are arranged on the same plane is used, a desired inductance value is used. As well as the effect of reducing variation in inductance value. Of course, it is possible to adopt not only the reference plane indicated by the solid line in FIGS. 10A to 10C but also the reference plane indicated by the phantom line in FIG. 10C. . In this case, the distance Ha from the predetermined reference surface to the extraction end 4a (one of the front and back surfaces) and the predetermined reference surface to the extraction end 4b (one of the front and back surfaces) The bent portion 4c may be formed so that the distance Hb is substantially uniform.

  The method for manufacturing the coil 1 has been described above through the steps S101 to S105. However, the pressing process (step S103) and the sizing process (step S104) can be performed substantially simultaneously. Here, “substantially simultaneous” means immediately after a predetermined press pressure is applied to the drawer end portions 4a and 4b when a predetermined press pressure is applied to the drawer end portions 4a and 4b that function as the terminal portion 100. Both of the cases where the sizing process is applied to the above are included. In order to perform the pressing process (step S103) and the sizing process (step S104) substantially simultaneously, for example, a punching die is provided around the punching punch, and a predetermined pressing pressure is applied to the drawing end portions 4a and 4b. It is only necessary that the punching die is lowered immediately after applying a predetermined pressure or a predetermined pressing pressure so as to cut the extraction ends 4a and 4b into a predetermined shape.

  Furthermore, the pressing process (step S103), the sizing process (step S104), and the bending process (step S105) can be performed substantially simultaneously. That is, the coil 1 in the state shown in FIG. 4 can be obtained in one step from the state of the coil 1 shown in FIG. In this case, a part of the drawing end portions 4a and 4b is bent while applying a predetermined pressing pressure to the drawing end portions 4a and 4b, and between the drawing end portion 4a and the winding portion 3 and between the drawing end portion 4b and the winding end. The bent portion 4c may be formed in at least one of the portions 3. Then, immediately after the bent portion 4c is formed, for example, the punching die is lowered to cut the drawing end portions 4a and 4b into a predetermined shape.

  As described above, since the coil 1 includes the lead end portions 4a and 4b of the conductor 2 as the terminal portion 100, it is not necessary to provide an independent terminal portion. That is, according to the coil-embedded dust core in the present embodiment, there is no connecting portion between the coil and the terminal portion. By eliminating the connecting portion, the conventional problems such as poor connection between the coil and the terminal portion or poor insulation between the coil and the terminal portion and the magnetic powder do not occur. In addition, since the coil 1 according to the present embodiment is an air-core coil manufactured by winding a flat conductor 2, a large inductance value can be obtained with a small number of turns, and the core can be reduced in size (low Can be further promoted. Furthermore, when the pressing process and the sizing process are performed substantially simultaneously, the number of steps for producing the coil 1 can be reduced, so that the working efficiency is improved. Moreover, since the coil 1 is not moved when the pressing process and the sizing process are performed substantially simultaneously, the positioning accuracy at the time of the sizing process is improved as compared with the conventional one, and thereby the extraction end part 4a functioning as the terminal part 100, It can be expected that the processing accuracy for 4b is improved. The coil 1 in which the extraction end portions 4a and 4b are arranged on the same plane has a small variation in inductance value and high performance.

Next, a method for manufacturing the coil-embedded dust core according to the present embodiment will be described with reference to FIGS.
FIG. 11 is a flowchart showing the manufacturing process of the coil-embedded dust core of the present invention. Note that the coil 1 around which the flat conductor 2 is wound is prepared in advance.
First, a ferromagnetic metal powder and an insulating material are selected according to necessary magnetic characteristics, and these are weighed (step S201). In addition, when adding a crosslinking agent, in step S201, the crosslinking agent is also weighed.
After the weighing, the ferromagnetic metal powder and the insulating material are mixed (step S202). In addition, when adding a crosslinking agent, the ferromagnetic metal powder, the insulating material, and the crosslinking agent are mixed in step S202. Mixing is performed using a pressure kneader or the like, preferably at room temperature for 20 to 60 minutes. The obtained mixture is preferably dried at about 100 to 300 ° C. for 20 to 60 minutes (step S203). Next, the dried mixture is crushed to obtain a ferromagnetic powder for a dust core (step S204).
In subsequent step S205, a lubricant is added to the ferromagnetic powder for dust core. It is desirable to mix for 10 to 40 minutes after adding the lubricant.

After the lubricant is added, the process proceeds to the molding process (step S206). Hereinafter, the molding process in step S206 will be described with reference to FIGS. FIG. 12 is a flowchart showing each step of the molding process. Moreover, FIGS. 13-15 has shown a mode that the ferromagnetic powder for dust cores which added and mixed the lubricant is shape | molded using a metal mold | die.
First, the metal mold | die suitably used for the formation process in this Embodiment is demonstrated using Fig.13 (a).
As shown in FIG. 13A, the mold is composed of an upper die 5A and a lower die 5B, an upper punch 6, a lower punch 7, and a die 8. The upper die 5A and the lower die 5B, and the upper punch 6 and the lower punch 7 are provided at opposing positions, and the upper die is constituted by the upper die 5A and the upper punch 6 that moves up and down in the upper die 5A. The lower die is constituted by the lower die 5B and the lower punch 7 that moves up and down in the lower die 5B. Further, the lower punch 7 is divided into a lower punch main body 7a and a cylindrical divided body (tubular member) 7b having a top portion substantially the same shape as the planar shape of the coil 1, and the cylindrical divided body 7b is a lower die. Moves up and down in 5B. Thus, the reason why the lower punch 7 is provided with the cylindrical divided body 7b is that the density of the molded body of the part corresponding to the winding part 3 of the coil 1 and the other part not corresponding to the winding part 3 of the coil 1 This is because of equalization. That is, it is a device for filling the portion corresponding to the winding portion 3 of the coil 1 with a smaller amount of the ferromagnetic powder for dust core than the other portion not corresponding to the winding portion 3 of the coil 1. .
On the other hand, the upper punch 6 is not provided with a cylindrical divided body corresponding to the cylindrical divided body 7b for the following reason. That is, in this embodiment, when filling the powder for the dust core into the mold cavity, the freight filling using the feeder box is performed. Correspondingly, the upward pressing is most preferably performed using a punch having a flat surface. Further, since the lower punch 7 is divided to devise a technique for making the compact density uniform, it is not necessary to divide the upper punch 6. In addition, the division of the upper punch 6 is not preferable from the viewpoint of cost, and even if the upper punch 6 is divided, it cannot be molded in the manner described later.

  Before starting the molding process (step S206), the mold is in the state shown in FIG. As will be described below, the upper die 5A, the lower die 5B, the upper punch 6, the cylindrical divided body 7b, and the die 8 are positioned from the state shown in FIG. 13A in each step of the molding step (step S206). However, the lower punch body 7a does not move from the predetermined reference plane in any step. Hereinafter, with the upper surface of the lower punch body 7a as a reference surface (hereinafter referred to as “reference surface”), the upper die 5A, the lower die 5B, the upper punch 6, the cylindrical divided body 7b, and the die 8 in the molding step (step S206). Explain the relative movement.

(Step S301 primary filling)
The state shown in FIG. 13A, that is, the lower die 5B, the cylindrical divided body 7b, and the die 8 are simultaneously raised from the reference surface to predetermined positions to form a cavity in the lower die 5B (FIG. 13B). . Here, as shown in FIG. 13B, the upper surfaces of the lower mill 5B and the die 8 are located on the same plane. Further, since the lower punch body 7a does not move and only the cylindrical divided body 7b rises, the lower punch main body 7a and the cylindrical divided body 7b are positioned at different levels.

When the positioning of the cylindrical divided body 7b and the lower mill 5B is completed, the feeder box F containing the mixed powder 20 (mixed lubricant in the above-mentioned insulated ferromagnetic powder for dust core) has the lower mill 5B. Move upward and fill the cavity of the lower die 5B with a predetermined amount of the mixed powder 20. In addition, since the feeder box F performs wear-off filling, the primary filling amount and the volume of the cavity of the lower die 5B substantially coincide. Therefore, it is necessary to accurately control in advance the positions of the cylindrical divided body 7b and the lower mortar 5B based on the thickness of the coil-embedded dust core to be finally obtained and the number of turns of the coil 1.
When the mixed powder 20 is scraped and filled into the cavity of the lower die 5B by the feeder box F, the feeder box F temporarily retracts.

(Step S302 Die 8 rise)
Subsequently, the die 8 is accurately raised to a predetermined position as shown in FIG. Specifically, the die 8 is raised so that the upper surface of the notch 8a of the die 8 is located on the same plane as the upper surface of the lower mill 5B. In step S302, the die 8 is raised, but the lower mill 5B and the cylindrical divided body 7b remain at the same positions as those shown in FIG. 13 (b).

(Step S303 Coil 1 insertion)
Next, as shown in FIG. 14A, the coil 1 around which the flat conductor 2 is wound is inserted into the lower die 5B. Note that the coil 1 is an air-core coil prepared in advance by the procedure described above. On the upper surface of the lower mill 5B, engravings (grooves) are formed in accordance with the shapes of the extraction end portions 4a and 4b. In step S303, the coil 1 is placed in the lower mortar 5B so that the lead-out ends 4a and 4b of the coil 1 are inserted into the engraving. As shown in FIG. 10, since the drawing end portions 4a and 4b of the coil 1 are formed on the same plane, when the drawing end portions 4a and 4b are inserted by fitting into the engraving of the lower mill 5B, for example, the coil 1 Is positioned horizontally in the lower mill 5B without being inclined. That is, with reference to the horizontal direction, the coil 1 can finally be positioned in the center and horizontally of the green compact 10.

(Step S304 Fixing of coil 1 and cavity formation)
In step S303, after the coil 1 is inserted into the lower die 5B, the upper die 5A is lowered to the lower die 5B as shown in FIG. 14 (b). Due to the lowering of the upper die 5A, the extraction end portions 4a and 4b of the coil 1 are sandwiched and fixed between the upper die 5A and the lower die 5B. Thereby, the horizontal movement of the coil 1 is controlled. Further, as shown in FIG. 14B, as the upper die 5A is lowered, a new cavity is formed on the upper surface of the coil 1 by the upper die 5A.

(Step S305 secondary filling)
When the lowering of the upper die 5A is detected by a sensor (not shown), the feeder box F once retracted approaches the mold again. Then, as shown in FIG. 14C, a predetermined amount of the mixed powder 20 is filled in the newly formed cavity so as to cover the upper surface of the coil 1 in step S <b> 304. As for the secondary filling, similarly to the primary filling, scraping filling is performed up to the upper surface of the bottom of the upper die 5A. In addition, finally, the consolidation direction of the lower mortar 5B, the cylindrical divided body 7b, and the lower punch body 7a in FIG. 13B described above so that the coil 1 is accurately positioned in the center of the green compact 10 in the axial direction. The relative position control is performed in advance.

(Step S306 Upper punch 6 descent)
When filling is completed in FIG. 14C, the feeder box F is retracted again, and at the same time, as shown in FIG. 15A, the upper punch 6 descends to the upper surface of the bottom of the upper die 5A. That is, in this state, the tip of the upper punch 6 and the upper surface of the bottom of the upper die 5A are located on the same plane.

(Step S307 material transfer synchronization, step S308 pressurization)
In step S306, the upper punch 6 is lowered, and the tip of the upper punch 6 and the bottom upper surface of the upper die 5A are located on the same plane (FIG. 15A). The die 5B, the die 8 and the cylindrical divided body 7b are lowered in synchronization with the upper punch 6 (FIG. 15 (b)). As a result, the mixed powder 20 sandwiched between the upper punch 6 and the lower punch 7 is pressurized from above and below and consolidated in the axial direction of the coil 1 (FIG. 15C). Here, as described above, the extraction end portions 4a and 4b of the coil 1 are sandwiched and fixed between the upper die 5A and the lower die 5B. Therefore, the upper die 5A and the lower die 5B gradually descend according to the amount of compression in the axial direction while holding the extraction end portions 4a and 4b of the coil 1 so that the extraction end portions 4a and 4b are not damaged. (FIG. 15 (b), FIG. 15 (c)). Further, as shown in FIG. 15B, the cylindrical divided body 7b also gradually descends based on the lowering amount of the upper punch 6, that is, the axial compression amount. Then, the cylindrical divided body 7b finally descends to the reference plane and stops (FIG. 15 (c)). In addition, as for the conditions of the pressurization in FIG.15 (b) and FIG.15 (c), it is desirable to set it as 100-600 MPa.

  Since the mixed powder 20 filled in the part corresponding to the winding part 3 of the coil 1 is more easily consolidated than the mixed powder 20 filled in the part not corresponding to the winding part 3, the winding part 3 of the coil 1. If the same amount of the mixed powder 20 is filled in the portion corresponding to 1 and the portion not corresponding to the winding portion 3, the density of the green compact 10 cannot be made uniform overall. In consideration of this, in the present embodiment, the cylindrical divided body 7b has substantially the same shape as the planar shape of the coil 1, and the portion corresponding to the winding portion 3 is mixed more than the portion not corresponding to the winding portion 3. Filling is performed so that the amount of the powder 20 is reduced. Thereby, finally, the part corresponding to the winding part 3 of the coil 1 and the part not corresponding to the winding part 3, specifically, the hollow part of the coil 1 and the periphery of the lead-out ends 4a and 4b of the coil 1 The density and the compression ratio of the portion corresponding to the corner of the green compact 10 can be made uniform.

  Steps S306 to S308 are continuously performed. In steps S307 and S308, the components of the mold other than the lower punch body 7a, that is, the upper die 5A, the upper punch 6, the lower die 5B, the die 8 and the cylinder. Each of the divided parts 7b is lowered to a predetermined position.

(Extract Step S309)
After press molding in FIG. 15C, the upper die 5A and the upper punch 6 are raised as shown in FIG. 15D, and the lower die 5B and the die 8 are lowered to the reference plane. And a molded object (coil enclosure dust core) is extracted from a metal mold | die, and, thereby, one cycle of a shaping | molding process is complete | finished. At the time of extraction in step S309, the lower die 5B, the die 8, the lower punch body 7a, and the cylindrical divided body 7b are all located on the reference plane. Further, since the upper die 5A and the upper punch 6 are also raised to their original positions, in FIG. 15 (d), the mold is returned to the state shown in FIG. 13 (a). In addition, the ring-shaped trace corresponding to the top shape of the cylindrical division body 7b remained in the molded object obtained through the shaping | molding process (step S206) mentioned above.

  By passing through the processes shown in steps S301 to S309, a compact molded body (coil-enclosed dust core) of about 5 to 15 mm in length, 5 to 15 mm in width, and 2 to 7 mm in thickness can be obtained. . According to the method for producing a coil-embedded dust core of the present invention, pre-forming is not required and pressure forming is only required once. Therefore, it is excellent in work efficiency and productivity. In addition, the structure of the mold is devised so that the cylindrical divided body 7 b has substantially the same shape as the planar shape of the coil 1, and the mixed powder 20 in the portion corresponding to the winding portion 3 is greater than the portion not corresponding to the winding portion 3. Pressurize after filling to reduce the amount of. Thereby, the density of a molded object can be equalized.

  Further, by accurately controlling the position in the consolidation direction using the method for producing a coil-embedded dust core of the present invention, the position in the axial direction of the coil 1 is compressed as shown in FIG. It can be accurately positioned in the center of the powder 10. As described above, the position of the coil 1 in the consolidation direction has a great influence on the inductance of the coil-embedded dust core, but the axial position of the coil 1 is accurately positioned at the center of the green compact 10. A large inductance value can be obtained, and variations in the inductance value are greatly reduced. In this way, the variation in inductance value is reduced by accurately controlling the axial position of the coil 1 so that the magnetic path length and cross-sectional area of the coil-embedded dust core can be controlled to a predetermined value. This is probably because of this. Further, if the position of the coil 1 in the axial direction is biased, local magnetic saturation is likely to occur, and the inductance value tends to decrease. However, according to the method for manufacturing a coil-embedded dust core of the present invention, such a problem is caused. Therefore, a desired inductance value can be obtained with certainty. The operation of the mold has been described above using the upper surface of the lower punch body 7a as the reference surface. However, the reference surface is not limited to the above-described one as long as the mold moves relatively in the same manner.

Now, after the molding process in step S206 shown in FIGS. 11 and 12, the process proceeds to a curing process (thermosetting process) (step S207). In the curing process, the molded body obtained in the molding process (step S206) is held at 150 to 300 ° C. for 15 to 45 minutes. Thereby, the resin in the molded body is cured.
After the curing process, the process proceeds to the rust prevention treatment process (step S208). The rust prevention treatment is performed, for example, by spray-coating an epoxy resin or the like on a molded body composed of the coil 1 and the green compact 10. The film thickness by spray coating is about 15 μm. It is desirable to perform heat treatment at 120 to 200 ° C. for 15 to 45 minutes after the rust prevention treatment.

  As described above, in the coil-embedded dust core according to the present embodiment, a part of the coil 1 is used as the terminal portion 100. However, a conductor 2 having an insulating film such as enamel formed on the surface is used. According to the observation by the present inventors, a copper oxide film is formed immediately below the insulating film in the curing step of step S207. Furthermore, a coating film is formed on the insulating film by a rust prevention treatment process (step S208). It is a sandblasting step (step S209) to remove the film formed on the terminal portion 100.

  As a method of removing the three-layered film formed on the surface of the coil 1, there is a method of corroding with a chemical. However, since the chemicals required to remove the respective films are different, a plurality of treatments must be performed when removing the three-layered film. Further, according to the chemical corrosion method, it is necessary to heat the chemical, and there is a possibility that alkali fine particles or acid fine particles may adhere to the coating film or insulating film of the terminal portion 100 during the heating. If such adhesion is present, corrosion over time on the coating film or insulating film proceeds over a long period of time, which tends to cause deterioration in rust prevention performance, short circuit between the coils 1, and the like. In order to avoid such a risk, there is a mechanical removal method using a tool, but the thickness of the terminal portion 100 of the coil-embedded dust core according to the present embodiment is about 5 mm or less (0.1-0. Therefore, a tool that may cause damage to the copper portion of the conductor 2 cannot be used. Therefore, in this embodiment, a method of removing the three-layered film using sand blasting is adopted.

  When the terminal part 100 is a surface-mounting terminal part, the terminal part 100 is soldered (step S210). Then, if the terminal part 100 which has been crushed and bent is bent as necessary, it is convenient when the coil-embedded dust core is mounted on the substrate.

According to the coil-embedded dust core in the present embodiment, the following effects can be obtained.
(1) Since the position of the coil 1 in the axial direction is accurately located in the center of the green compact 10 and the density of the magnetic material is uniform as a whole, the variation in inductance value is greatly reduced, and a predetermined value is obtained. An inductance value can be obtained stably.
(2) Since the coil 1 wound with the flat conductor 2 is used, a large inductance value can be obtained with a small number of turns. Moreover, a small (low profile) coil-embedded dust core having a length of 5 to 15 mm, a width of 5 to 15 mm, and a thickness of about 2 to 7 mm can be obtained.
(3) Since the extraction end portions 4a and 4b, which are part of the coil 1, are configured as the terminal portion 100, it is not necessary to connect the coil 1 to the terminal portion. Therefore, it is possible to solve the problem of bonding failure and insulation failure caused by the connection.
(4) Since the lead-out end portions 4a and 4b are formed on the same plane, positioning when the coil 1 is disposed in the mold can be easily and accurately performed. As a result, the mixed powder 20 can be uniformly filled, and the variation in inductance value is small.
(5) Since the lead-out end portions 4a and 4b, which are part of the coil 1, are configured as the terminal portion 100, it is not necessary to prepare a terminal portion separately. Therefore, the number of parts can be reduced.

The coil-embedded dust core of the present invention will be described in detail in Examples.
Example 1
Thirty coil-embedded dust core samples with a core size of 12.5 mm long × 12.5 mm wide × 3.5 mm thick were prepared according to the following procedure.
Magnetic powder: Permalloy powder (45% Ni-Fe) produced by atomization method (average particle size 25 μm)
Insulation material: Silicone resin (SR2414LV manufactured by Toray Dow Corning Silicone Co., Ltd.)
Lubricant: Aluminum stearate (SA-1000, Sakai Chemical)
Prepared.

  Next, 2.4 wt% (weight%) of an insulating material was added to the magnetic powder, and these were mixed with a pressure kneader at room temperature for 30 minutes. Then, it was dried in air at 150 ° C. for 30 minutes. 0.4 wt% lubricant was added to the dried magnetic powder and mixed for 15 minutes by a V mixer.

  Then, it shape | molded by the procedure of Fig.13 (a)-FIG.15 (d), and produced 30 molded objects. The coil 1 is obtained by winding a conductor 2 having a rectangular cross section (0.45 mm × 2.5 mm) for 2.5 turns. Moreover, the pressurization in FIG.15 (d) was 490 Mpa. The pressed body was heat-treated at 200 ° C. for 15 minutes to cure the silicone resin as an insulating material, and further bent the terminal portion 100 to prepare 30 coil-embedded dust core samples. FIG. 16A shows the inductance values of 30 samples. Note that “0A” and “20A” in FIG. 16A indicate values of DC current superimposed on the inductance measurement AC signal (0.05 V, 100 kHz).

  As shown in FIG. 16 (a), it can be seen that the sample according to the present embodiment formed by the procedure of FIGS. 13 (a) to 15 (d) has a small variation in inductance value. Specifically, in the case of only alternating current (when the superimposed direct current is 0 A), the inductance values are all in the range of 0.60 to 0.64 μH, and the difference between the minimum value and the maximum value is slightly 0. 0. 04 μH. Further, it can be seen from FIG. 16A that even when 20 A direct current is superimposed, the same tendency as in the case of only alternating current is shown. That is, all the inductance values were in the range of 0.53 to 0.57 μH, and the difference between the minimum value and the maximum value was only 0.04 μH. Therefore, according to the present embodiment formed by the procedure of FIGS. 13A to 15D, the variation of the inductance value is small and the direct current superimposition characteristic is also good.

Subsequently, the density of the center part of the sample was measured with a glove denso mat (a density measuring machine using γ rays) manufactured by Crab Seege. As a result, the density of the hollow portion 1 of the coil 1 shown in FIG. 2B, the density of the portion 2 corresponding to the lower surface of the winding portion 3 of the coil 1, and the portion corresponding to the upper surface of the winding portion 3 of the coil 1 All the densities of 3 were 6.4 to 6.5 g / cm ³ . The density of the portion 2 corresponding to the lower surface of the winding portion 3 of the coil 1 and the density of the portion 3 corresponding to the upper surface of the winding portion 3 of the coil 1 is measured at the portion where the number of windings is the maximum, that is, on the 3 turn side. did.
Moreover, when the position of the consolidation direction (thickness direction) of the coil 1 was measured from an X-ray projection photograph (manufactured by Shimadzu Corporation), it was confirmed that the coil 1 was located at the center in the axial direction of the green compact 10. It was.

(Comparative Example 1)
Before inserting the coil 1 in FIG. 14A, the lower core was preformed. Further, before the main pressurization in FIG. 15D, the main punch was performed after exchanging the upper punch 6 with one having a flat surface. Except for this, 30 coil-embedded dust core samples were prepared in the same procedure as in Example 1. In producing this sample, the pressure for the preforming was 150 MPa, and the main pressure in FIG. 15D was 490 MPa. The inductance value of the sample in Comparative Example 1 is shown in FIG. The measurement condition of the inductance value is the same as that in the first embodiment.

  Comparing FIG. 16A and FIG. 16B, it can be seen that the sample whose inductance value is shown in FIG. 16B, that is, the sample in which the lower core is preformed, has a large variation in inductance value. Specifically, in the case of only alternating current (when the superimposed direct current is 0 A), the sample inductance values are all in the range of 0.53 to 0.61 μH, and the difference between the minimum value and the maximum value is 0. 0. It was 08 μH. When 20 A DC was superimposed, the sample inductance values were all in the range of 0.46 to 0.54 μH, and the difference between the minimum value and the maximum value was 0.08 μH.

Next, as in Example 1, the density of the central portion of the sample of Comparative Example 1 was measured, and as a result, it was 6.6 to 6.8 g / cm ³ .
Further, when the position of the coil 1 was measured from an X-ray projection photograph (manufactured by Shimadzu Corporation), the position in the consolidation direction (thickness direction) of the coil 1 is shifted upward from the axial center of the green compact 10. It was confirmed.
From the above results, the density of the central part of the sample in which the lower core is preformed is slightly higher than that of the sample according to the present embodiment that has been molded according to the procedure of FIGS. 13 (a) to 15 (d). However, it was found that the inductance value variation was larger and the inductance value was smaller than that of the sample of Example 1. This is presumably because the position of the coil 1 is deviated from the axial center of the green compact 10, so that magnetic saturation locally occurs and the inductance value decreases.

(Comparative Example 2)
Except for the following points, 30 coil-embedded dust core samples were produced in the same procedure as in Example 1.
In the steps shown in FIGS. 13A to 15D, molding was performed while the cylindrical divided body 7b was fixed to the reference surface. That is, the filling amount of the mixed powder 20 was not adjusted between the portion corresponding to the winding portion 3 of the coil 1 and the portion not corresponding to the winding portion 3 of the coil 1. Further, in FIG. 13B and FIG. 13C, the position control of the lower die 5B and the die 8 was not strictly performed. FIG. 16C shows the inductance values of the 30 samples thus manufactured.

As shown in FIG. 16C, it can be seen that the sample produced in Comparative Example 2 has a large variation in inductance value as in the sample produced in Comparative Example 1 (see FIG. 16B). Specifically, in the case of only alternating current (when the superimposed direct current is 0 A), the inductance value is in the range of 0.55 to 0.63 μH, and the difference between the minimum value and the maximum value is 0.08 μH. It was. When 20 A DC was superimposed, the inductance values were all in the range of 0.47 to 0.56 μH, and the difference between the minimum value and the maximum value was 0.09 μH.
Next, as in Example 1, the density of the center portion of the sample was measured with a glove denso mat (a density measuring machine using γ rays) manufactured by Kleve Sege. As a result, the density of the portion 2 corresponding to the lower surface of the winding portion 3 of the coil 1 and the density of the portion 3 corresponding to the upper surface of the winding portion 3 of the coil 1 shown in FIG. while there was a .5g / cm ^3, the density of the hollow portion 1 of the coil 1 was 5.0~5.4g / cm ^3. That is, in the sample produced in Example 1, the difference in density corresponding to the upper and lower surfaces of the winding portion 3 of the coil 1 and the density corresponding to the hollow portion 1 of the coil 1 is only 0.1 g / cm ^3. On the other hand, in the sample produced in Comparative Example 2, the difference in density corresponding to the upper and lower surfaces of the winding part 3 of the coil 1 and the density corresponding to the hollow part 1 of the coil 1 is 1.4 g / It was found to be as large as cm ³ or more. Further, when the position of the coil 1 was measured from an X-ray projection photograph (manufactured by Shimadzu Corporation), the position of the coil 1 in the consolidation direction (thickness direction) was from the axial center of the green compact 10 to the upper side or the lower side. It was confirmed that it was shifted.

(Example 2)
Of the 30 samples produced in Example 1, 20 samples were destroyed and the part corresponding to the winding part 3 of the coil 1 shown in FIG. 2 (a) was obtained by the Archimedes method using silicone oil. The density and the density of the part corresponding to the hollow part of the coil 1 were measured. The results are shown in Table 1. In addition, since the weight of each part was small, each part was taken out from 20 samples, and it measured collectively. The specific gravity of silicone oil is 0.817.

As shown in Table 1, the density of the portion corresponding to the winding portion 3 of the coil 1 shown in FIG. 2A is 6.50 g / cm ³ , and the density of the portion corresponding to the hollow portion of the coil 1 is 6. It was 42 g / cm ³ . That is, the difference between the density of the portion corresponding to the winding portion 3 of the coil 1 and the density corresponding to the hollow portion of the coil 1 was only 0.08 g / cm ³ . From this result, it was confirmed that according to the method recommended by the present invention, a coil-embedded dust core having a uniform density as a whole can be obtained.

  Although the embodiments and examples of the present invention have been described above, it is obvious to those skilled in the art that the present invention is not limited thereto and various modifications and changes can be made within the scope of the claims. I will.

It is a plane sectional view of the coil enclosure dust core in this embodiment. It is a sectional side view of the coil enclosure powder magnetic core in this Embodiment. It is a top view of the coil used by this Embodiment. It is a side view of the coil used by this Embodiment. It is a figure which shows the cross-sectional shape before winding a flat conductor, and the cross-sectional shape after winding. It is a flowchart which shows the manufacturing process of the coil in this Embodiment. It is a figure for demonstrating a winding process. It is a figure for demonstrating a forming process. It is a figure for demonstrating a press work process. It is a figure for demonstrating a bending process. It is a flowchart which shows the manufacturing process of the coil enclosure dust core in this Embodiment. It is a flowchart which shows each step of the shaping | molding process in step S206 of FIG. It is a figure explaining the shaping | molding process in step S206 of FIG. It is a figure explaining the shaping | molding process in step S206 of FIG. It is a figure explaining the shaping | molding process in step S206 of FIG. It is a figure which shows the inductance value measured in Example 1, the comparative example 1, and the comparative example 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Coil, 2 ... Conductor, 3 ... Winding part, 4a, 4b ... Extraction end part (terminal part 100), 4c ... Bending part, 5A ... Upper die, 5B ... Lower die, 6 ... Upper punch, 7 ... Lower Punch, 7a ... lower punch body, 7b ... cylindrical divided body (tubular member), 8 ... die, 10 ... green compact, 20 ... mixed powder

Claims (9)

A method for producing a coil-embedded dust core formed by enclosing an air-core coil having a winding portion and an end portion drawn out from the winding portion in a green compact by one press molding,
A primary filling step of filling the cavity with a soft magnetic metal powder containing an insulating material constituting the green compact;
A coil placement step of placing the air-core coil on the soft magnetic metal powder filled in the primary filling step;
A secondary filling step of filling the cavity with the soft magnetic metal powder so as to cover the air-core coil;
A consolidation step of consolidating the soft magnetic metal powder covering the air core coil in an axial direction of the air core coil;
With
In the primary filling step, the amount of the soft magnetic metal powder filled in the portion corresponding to the winding portion is set to the other portion not corresponding to the winding portion with reference to the upper surface or the lower surface of the winding portion. The state is smaller than the amount of the soft magnetic metal powder to be filled,
The method for producing a coil-embedded dust core, wherein in the consolidation step, consolidation is performed while the state is maintained.   The method for producing a coil-embedded dust core according to claim 1, wherein the other portion is a portion corresponding to a hollow portion of the air-core coil.   In the consolidation step, the compression ratio of the soft magnetic metal powder in a portion corresponding to the maximum number of windings in the winding portion and the compression ratio of the soft magnetic metal powder in the other portion are equal. The method for producing a coil-embedded dust core according to claim 1, wherein   The density of the green compact in the upper surface or the vicinity of the lower surface of the portion corresponding to the maximum number of windings in the winding portion and the density of the green compact in the other portion are equal. 2. A method for producing a coil-embedded dust core according to 1. A rectangular parallelepiped green compact having front and back surfaces facing each other with a predetermined interval and side surfaces formed around the front and back surfaces;
A coil having a winding portion and an end portion drawn out from the winding portion, and at least the winding portion is an air-core coil disposed in the green compact, and is manufactured by a single pressure molding An encapsulated dust core,
The density of the green compact is equal in the portion corresponding to the maximum number of turns in the winding portion and the hollow portion of the air-core coil,
A coil-embedded dust core, wherein the air-core coil has an axis arranged in the powder compact along the direction of pressure molding. 6. The coil encapsulation according to claim 5, wherein a difference in density between a portion corresponding to the maximum number of turns in the winding portion and a hollow portion of the air-core coil is 0.3 g / cm ³ or less. Powder magnetic core.   The coil-embedded dust core according to claim 5, wherein the air-core coil is composed of a flat wire.   The coil-embedded dust core according to claim 5, wherein a part of the air-core coil functions as a terminal portion. The coil sealing pressure according to claim 5, wherein the end portion is exposed to the outside of the green compact from a center of a side surface of the green compact with reference to a thickness direction of the green compact. Powder magnetic core.

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