JP2010010544A - Method of manufacturing mold coil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a mold coil with high performance. <P>SOLUTION: In the method of manufacturing the mold coil which employs a plastic molding method, and seals the coil with a magnetic substance mold resin obtained by kneading a resin and magnetic powder, the magnetic substance mold resin is used which contains ≥65 vol.% of the magnetic powder in terms of a volume ratio. Then a molding die is used which partially has a gap for discharging part of the magnetic substance mold resin from a cavity. The magnetic substance mold resin is filled into the cavity, and part of the magnetic substance mold resin in a fused state which is filled into the cavity is discharged from the cavity through the gap. The discharged magnetic substance mold resin has a relatively low volume ratio of magnetic powder than that of the magnetic substance mold resin filled into the cavity. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a molded coil using a plastic molding method.

  Conventionally, a molded coil in which a winding is sealed with a magnetic powder and a resin has been widely used. As a method for manufacturing a mold coil, there are mainly a compacting method and a plastic molding method. The compacting method is a method of filling a mold with a powder material in which a magnetic powder and a resin are mixed, and pressurizing to form a desired shape. For example, Patent Document 1 discloses a molded coil using a conventional compacting method. On the other hand, the plastic molding method is a method in which a magnetic mold resin in which magnetic powder and resin are kneaded is filled in a mold and melted to be molded into a desired shape. A molded coil using a conventional plastic molding method is disclosed in Patent Document 2, for example. In general, the plastic molding method has higher moldability than the powder molding method, and a molded body with higher molding accuracy than the powder molding method can be obtained. For this reason, it is an effective means to use a plastic molding method when molding a small-sized or complicated shaped mold coil.

  However, in the conventional plastic molding method, in order to ensure high moldability, the volume ratio of the magnetic powder cannot be easily increased as in the compacting method. For this reason, a conventional molded coil using a plastic molding method uses a magnetic mold resin with a magnetic powder volume ratio of about 50 Vol%, and the magnetic current cannot be sufficiently obtained, and characteristics such as rated current and direct current resistance are not obtained. I was not able to get what I was satisfied with. Therefore, in the previously filed Japanese Patent Application No. 2008-108794, the applicant used a magnetic molding resin containing 65 to 80% by volume of iron-based magnetic powder and an outer and outer coil of a rectangular wire to reduce the size and It is proposed that a molded coil with high DC superposition characteristics and low DC resistance can be realized while being tall.

  By the way, there are two indexes that define the rated current of the molded coil used for power supply applications, namely, the DC superposition allowable current and the temperature rise allowable current. The DC superposition allowable current is a DC current value at which the inductance value (hereinafter referred to as L value) is reduced by 30% from the initial value, and is determined by the magnetic flux density in the coil and the saturation magnetic flux density of the magnetic material. On the other hand, the temperature rise allowable current is a direct current value when the coil temperature rises by 40 ° C. with an ambient temperature of 20 ° C. as a reference, and is inversely proportional to the direct current resistance value of the coil. The standard displays the smaller allowable current in consideration of safety.

  In general, it is said that the temperature rise allowable current is smaller than the DC superposition allowable current in a molded coil using iron-based magnetic powder. Here, when the coils having the same outer dimensions and inductance values using the ferrite-based magnetic powder and the iron-based magnetic powder are compared, as shown in Table 1, the difference between the magnetic powders can be seen. As is apparent from Table 1, when the ferrite-based magnetic powder is used, the DC superposition allowable current is smaller than the temperature rise allowable current. On the other hand, in the iron-based magnetic powder, it can be seen that the DC superposition allowable current is much larger than the temperature rise allowable current.

This allowable temperature rise current is inversely proportional to the DC resistance value of the coil as described above. That is, the temperature rise allowable current can be increased as the DC resistance value is decreased. In order to reduce the DC resistance value, it is necessary to reduce the number of turns of the coil and increase the coil wire diameter. Therefore, in order to obtain a predetermined L value with a small number of turns, it is desired to improve the relative magnetic permeability of the magnetic mold resin.
JP 2007-49073 A JP-A-4-338613

  Here, the relative magnetic permeability will be described. The relative magnetic permeability μ of the magnetic mold resin is expressed by the following empirical formula. In Equation 1, μ1 represents the relative permeability of the magnetic powder, μ2 represents the relative permeability of the mixture (resin, air, etc.), and ν represents the volume ratio of the magnetic powder.

  When the mixture is resin or air, it can be handled as μ2 = 1. Using this value, Equation 1 can be converted to Equation 2 below.

  As apparent from Equation 2, the volume ratio ν of the magnetic powder is exponentially related to the relative permeability μ of the magnetic mold resin. Here, an example of a magnetic mold resin using a magnetic powder of an iron-based material is specifically shown. For example, the magnetic permeability μ1 of the magnetic powder of the iron-based material is 100, and the volume ratio of the magnetic powder in the magnetic mold resin is changed from 50 Vol% (ν = 0.50) to 51% (ν = 0.51). When increased, the relative permeability μ increases from 10 to 10.5.

  When the volume ratio of the magnetic powder in the magnetic mold resin is increased from 70 Vol% (ν = 0.70) to 71% (ν = 0.71), the relative permeability μ is 25.1. Increase to 26.3. That is, when the volume ratio of the magnetic powder is low and high, even if the volume ratio ν is increased by the same amount, the higher the volume ratio, the greater the effect of improving the relative permeability μ. Therefore, if the volume ratio ν of the magnetic powder is high, the effect of improving the relative magnetic permeability μ becomes obvious even if it is a slight increase.

  However, as the volume ratio of the magnetic powder in the magnetic mold resin increases, the fluidity of the magnetic mold resin deteriorates. In particular, when the volume ratio of the magnetic powder becomes 65 Vol% or more, even a slight increase of about 1 Vol% or 2 Vol% has a great influence on the fluidity. Although higher magnetic permeability is desired, the magnetic mold resin must ensure a certain degree of fluidity in order to maintain high moldability. For this reason, the volume ratio of the magnetic powder in the magnetic mold resin cannot be easily increased.

  Accordingly, an object of the present invention is to provide a method for producing a high-performance molded coil by increasing the volume ratio of the magnetic material in the molded coil.

In order to solve the above-described problems, a method for manufacturing a molded coil according to the present invention is a method for manufacturing a molded coil in which a coil is sealed with a magnetic mold resin obtained by kneading a resin and a magnetic powder using a plastic molding method. , A magnetic mold resin containing 65 vol% or more of magnetic powder in volume ratio is used. A molding die having a gap for discharging a part of the magnetic mold resin from the cavity is used as a part thereof. The cavity is filled with the magnetic mold resin, and a part of the melted magnetic mold resin filled in the cavity is discharged from the cavity to the outside of the cavity. The discharged magnetic material mold resin is characterized in that the volume ratio of the magnetic material powder is relatively lower than the magnetic material resin filled in the cavity.
It is characterized by.

  The method for producing a mold coil according to the present invention gives priority to the resin over the magnetic powder in the magnetic mold resin by providing a gap having a maximum particle size of the magnetic powder in the magnetic mold resin in the molding die. Therefore, the volume ratio of the magnetic powder of the magnetic mold resin in the cavity can be increased. And even if it uses magnetic body resin whose magnetic body powder is 65 Vol% or more, the volume ratio of the magnetic body powder in a mold coil can be raised.

  If the manufacturing method of the mold coil of this invention is used, a very favorable relative magnetic permeability can be obtained. Therefore, when obtaining a predetermined L value, the number of turns of the coil can be reduced as compared with the conventional method. The coil wire diameter can be increased by the volume integral with the reduced number of turns, and the direct current resistance can be reduced to greatly improve the temperature rise allowable current.

  Hereinafter, embodiments of the method for molding a magnetic mold resin of the present invention will be described with reference to the drawings and tables. First, the magnetic mold resin used in the embodiment of the present invention will be described.

  In the embodiment of the present invention, amorphous alloy powder materials A to D are used as magnetic powder. Table 2 shows the characteristics of the magnetic powders (material A to material D) used in the examples of the present invention. As is clear from Table 2, the materials A and B are granulated using the gas atomizing method, and the materials C and D are granulated using the water atomizing method. The average particle sizes of the materials A to D are 30 μm, 25 μm, 10 μm, and 5 μm in order from the material A, and the maximum particle sizes are 100 μm, 60 μm, 45 μm, and 20 μm. The average particle diameter is measured using a laser diffraction scattering method, and the maximum particle diameter is a numerical value obtained by sieving classification.

  Table 3 shows the conditions and characteristics of the magnetic mold resins (samples 1 to 8) used in the examples of the present invention. The magnetic powders shown in materials A to D and the novolac-type epoxy resin were kneaded at the ratio shown in Table 3, and 0.5 wt% curing accelerator (triphenylphosphine) was added to the resin and kneaded. The kneaded material was cooled and pulverized to obtain Samples 1 to 8.

  In general, a magnetic powder having a higher sphericity is obtained when the gas atomization method is used than the water atomization method. The fluidity of the magnetic mold resin is better when the magnetic powder having high sphericity is used. Therefore, sample 2 and sample 4 are easier to secure the fluidity of the magnetic mold resin than sample 6, and the magnetic material volume ratio is high.

  Next, the air core coil used in the embodiment of the present invention will be described. FIG. 1 shows an outer-wound coil used in an embodiment of the present invention. In the embodiment of the present invention, a wire having a self-bonding insulating layer having a flat cross section, a width of 0.25 mm, and a thickness of 0.10 mm is used. Using this core material having a core diameter of 1.3 mm, the outer and outer windings were wound in two layers for 11 turns and further fused to obtain an air core coil 1 as shown in FIG.

(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS. In the first embodiment, a molded coil is formed by a transfer molding method. Reference numerals in the drawings are 2 for a mold, 3 for an upper mold, 4 for a lower mold, 5 for a plunger, 6 for a cavity, 7 for a gate, 8 for a sprue, and 9 for a chamber pot. Further, s represents a spacer, and a gap generated from the spacer s is defined as d.

  2 to 4 show a molding die for transfer molding used in the first embodiment of the present invention. 4 is a cross-sectional view taken along the line A-A 'of FIG.

  In the first embodiment, as is apparent from FIG. 2, a cavity 6 and a chamber pot 9 are formed by using a molding die having a mold 2, an upper die 3, a lower die 4 and a plunger 5 and combining them. . The upper die 3 is composed of a first upper die 3a and a second upper die 3b to form a sprue 8. Similarly, the lower die 4 is also composed of a first lower die 4a and a second lower die 4b. Form. Each of the first upper mold 3a and the first lower mold 4a has a gate 7 for connecting the cavity 6 and the sprue 8 at positions facing each other with the air-core coil 1 as the center. The magnetic mold resin is pushed out by the plunger 5, passes through the sprue 8 and the gate 7, and is filled into the cavity 6.

  As shown in FIG. 3, the mold 2 is composed of a first mold 2 a and a second mold 2 b, and by combining them, a columnar through hole having a cross section of 3 mm square is formed. Further, the mold 2 can be fixed while sandwiching the lead wire portion of the air-core coil 1 between the first mold 2a and the second mold 2b.

  Further, as shown in FIG. 4, a spacer s is inserted between the mold 2 and the first upper mold 3a, and a gap d is formed between the mold 2 and the first upper mold 3a. ing. Similarly, a spacer s is also inserted between the mold 2 and the first lower mold 4a, and a gap d is formed between the mold 2 and the first lower mold 4a. A part of the magnetic mold resin 10 filled in the cavity 6 is discharged out of the cavity 6 through these gaps d. For example, a metal plate such as stainless steel or brass may be used as the spacer, but any spacer may be used as long as the gap d can be formed at a desired interval.

  Next, a method for manufacturing the molded coil of the first embodiment will be described. 5 and 6 show the main part of the method of manufacturing the molded coil of the first embodiment. First, as shown in FIG. 5, the air-core coil 1, the mold 2, the upper mold 3, and the lower mold 4 are fixed, the chamber pot 9 is filled with the magnetic mold resin 10, and the plunger 5 is set. At this time, the air-core coil 1 sandwiches and fixes the lead wire portion of the air-core coil 1 between the first mold 2a and the second mold 2b.

  Next, as shown in FIG. 6, the magnetic mold resin 10 is heated to 180 ° C. in the chamber pot 9 to be in a molten state, and the magnetic mold resin 10 is injected into the cavity 6 using the plunger 5, and 200 kgf The magnetic mold resin 10 was cured by holding for 8 minutes under the above pressure. Next, the cured product of the magnetic mold resin 10 was released from the molding die to obtain a molded body.

  Next, as shown in FIG. 7, an external electrode 11 obtained by processing a phosphor bronze plate having a thickness of 0.08 mm into an L shape is pasted to a predetermined position of the molded body with an epoxy resin, and a lead wire portion of the air-core coil 1 The lead wire portion of the air-core coil 1 and the external electrode 6 are joined by soldering to obtain a molded coil. In this embodiment, the outer dimensions are L * W = 3.0 mm and H = 1.2 mm. The obtained molded coil was measured for L value at a measurement frequency of 100 kHz using an LCR meter 4284A manufactured by Agilent Technologies.

  Table 4 lists L values of molded coils obtained by molding Samples 1 to 8 with molding dies having different gaps d. In Table 3, no spacer is formed using a conventional molding die. The thicknesses of the various spacers s are 30 μm for spacer 1, 60 μm for spacer 2, and 100 μm for spacer 3. Here, the thickness of the spacer s is treated as the width of the gap d.

  Each sample is compared with reference to Table 4. First, when Sample 1 to Sample 6 using one type of each of Material A to Material C were compared, as apparent from Table 4, the L value was higher as the magnetic material volume ratio was higher.

  Next, when the samples 1 to 6 were compared with or without the spacer s, the L value was highest when the spacer 1 was used for any of the samples 1 to 6. Further, when the spacer s having the maximum particle diameter of the magnetic powder used in each sample was used, the L value was higher than that without the conventional spacer.

  As a result, the molten magnetic mold resin 10 filled in the cavity 6 enters the gap d provided by the spacers s from the cavity 6. At this time, if the gap d is equal to or smaller than the maximum particle size of the magnetic powder, the magnetic powder hardly enters the gap d and tends to stay in the cavity 6. On the other hand, since the resin has a higher degree of freedom in the magnetic molding resin than the magnetic powder, it can easily enter the gap d as compared with the magnetic powder. Therefore, it is considered that the resin is preferentially discharged out of the cavity 6 through the gap d over the magnetic powder.

  As a result, it is considered that the magnetic mold resin 10 in the cavity 6 has a higher magnetic material volume ratio than that of the kneaded material, and the L value of the mold coil is also improved. However, if a gap d larger than the maximum particle size of the magnetic powder is provided, it is considered that the L value is not improved because the magnetic powder is discharged out of the cavity 6 together with the resin.

  Next, Sample 7 and Sample 8 using two types of magnetic powders having different particle sizes of Material B and Material D will be compared. The method of using several kinds of magnetic powders having different particle diameters such as Sample 7 and Sample 8 is an effective means for improving the magnetic material volume ratio. Therefore, it is used to obtain a molded coil with high electrical characteristics. As is clear from Table 3, Sample 7 and Sample 8 were improved in L value when a moderate gap was provided, as in Samples 1 to 6, than when no spacer was provided. Therefore, even when two types of magnetic powders having different particle diameters such as Sample 7 and Sample 8 are used, the method of the present invention is effective. In particular, the magnetic mold resin having a magnetic material volume ratio of 70 Vol% or more as in Sample 8 has a large increase in the L value compared with the conventional Sample 7 of about 50 Vol%, and the method of the present invention is very effective. I understand that.

  As described above, in the molded coil in which the coil is sealed with the magnetic mold resin, the magnetic volume ratio of the magnetic mold resin in the mold coil can be improved by providing an appropriate gap. And even if it is magnetic body resin which contains 65 volume% or more of magnetic body powders, the improvement of the magnetic body volume ratio can be aimed at further.

  Further, since the method of the present invention can obtain a higher magnetic permeability than the conventional method in which no gap is provided, the number of turns of the coil can be reduced as compared with the conventional method when obtaining the same L value. The coil diameter can be increased by the volume integral with the reduced number of turns, and the DC resistance can be reduced and the temperature rise allowable current can be greatly improved without increasing the size of the molded coil.

(Second embodiment)
A second embodiment of the present invention will be described with reference to FIGS. A molded coil having the same external dimensions was formed using the same material as in the first example. Description of the parts common to the first embodiment is omitted. FIG. 8 shows a molding die for compression molding used in the second embodiment. FIG. 8 (a) is a top view, and FIG. 8 (b) is a BB 'cross section of FIG. 8 (a). FIG. In the drawings, reference numeral 1 denotes an air-core coil, 10 denotes a magnetic molding resin, 12 denotes a die, 13 denotes an upper punch, 14 denotes a lower punch, and 15 denotes a cavity. Further, c in the figure indicates a clearance between the die 12 and the upper punch 13 and a one-side clearance between the die 12 and the lower punch 14 (hereinafter, clearance). The clearance c corresponds to the gap of the present invention.

  As shown in FIG. 8, in the second embodiment, a die having a die 12 and an upper punch 13 and a lower punch 14 that can be moved up and down is used. The die 12 includes a first die 12a and a second die 12b, and by combining them, a columnar through hole having a cross section of 3 mm square is formed. This through-hole can be fitted with the upper punch 13 and the lower punch 14, and the cavity 15 is formed by combining them. Further, similarly to the mold of the first embodiment, the lead wire portion of the air-core coil 1 can be fixed between the first die 12a and the second die 12b.

  As shown in FIG. 8A, the diameter Dp of the upper punch 13 is smaller than the diameter Dc of the cavity, and a clearance c is formed. The width of the clearance c is set to be equal to or less than the maximum particle size of the magnetic powder in the magnetic mold resin. The width of the clearance c is calculated using c = 1/2 × (Dc−Dp). In this embodiment, the lower punch 14 has the same shape as the upper punch 13 and the clearance c is formed in the same manner as the upper punch 13 side.

  Next, the manufacturing method of the molded coil of this invention is demonstrated. 9 to 11 show the main part of the mold coil manufacturing process according to the second embodiment of the present invention. 9 to 11 show cross sections at each stage at the position B-B ′ shown in FIG.

  As shown in FIG. 9, the lead wire portion of the air-core coil 1 is sandwiched between the first die 12 a and the second die 12 b which are the dies 12, and the air-core coil 1 is fixed at a desired position in the cavity 15. The upper punch 13 and the lower punch 14 were fitted from both the upper and lower sides of the through hole of the die 12, and the die 12, the upper punch 13 and the lower punch 14 were heated to preheat the inside of the cavity 15 to 180 ° C. Next, the upper punch 13 and the lower punch 14 are once removed, and a predetermined amount of a bulk-shaped magnetic material mold resin 10 is introduced from both the upper and lower sides of the cavity 15, and the upper punch 13 and the lower punch 14 are again attached to the die 12. It was made to fit in the through-hole.

  Next, as shown in FIG. 10, the magnetic mold resin 10 in the cavity 15 is melted by preheating in the cavity 15, and a molding pressure of 10 kgf is applied using the upper punch 13 and the upper punch 14, and 8 ° C. at 8 ° C. The magnetic mold resin 10 was cured by holding for a minute. Next, as shown in FIG. 11, the second die 12b and the upper punch 13 were removed, and the molded body was released. An external electrode was attached to the molded body to obtain a molded coil. The obtained molded coil was measured for L value by the same method as in the first example.

  Table 5 shows L values of molded coils obtained by molding Sample 3, Sample 4, Sample 7, and Sample 8 using punches having different diameters. The molded coil shown in Table 5 is formed using a punch having a diameter Dp of 2.94 mm, 2.88 mm, and 2.80 mm. At this time, the diameter Dc of the cavity 15 is 3.00 mm, and the clearance c between the die and each punch is 30 μm for the clearance 1, 60 μm for the clearance 2, and about 100 μm for the clearance 3 respectively.

  The first and second embodiments will be compared with reference to Tables 4 and 5. As is clear from Tables 4 and 5, it can be seen that when the gap distance of the first embodiment and the clearance c of the second embodiment are approximately the same, the L value is also approximately the same. Therefore, the volume ratio of the magnetic material in the mold coil can be increased also by adjusting the clearance between the die and the punch, and the method of the present invention can be implemented by the compression molding method.

  As described above, in the method for producing a molded coil of the present invention, a gap is provided in the molding die, and after filling the cavity with the magnetic molding resin, the resin in the magnetic molding resin is discharged out of the cavity from the gap. The gap is preferably set to 3 μm or more and not more than the maximum particle size of the magnetic powder. If it is smaller than 3 μm, it is not desirable because it is technically difficult and the molding die becomes very expensive.

  Since the volume ratio of the magnetic material of the magnetic mold resin in the cavity is increased, it is possible to improve the relative permeability and the L value. And since the method of the present invention can be expected to further improve the volume ratio of the magnetic material in the mold coil from the state of using 65 vol% or more of the magnetic material mold resin, which makes it difficult to increase the volume ratio of the magnetic material, it is not possible in the past. A high-quality molded coil can be obtained.

  When the method for manufacturing a molded coil according to the present invention is used, a very good relative magnetic permeability can be obtained. Therefore, when a predetermined L value is obtained, the number of turns of the coil can be reduced as compared with the conventional method. The coil wire diameter can be increased by the volume integral with the reduced number of turns, and the direct current resistance can be reduced to greatly improve the temperature rise allowable current.

  In the above embodiment, iron-based amorphous alloy powder is used as the magnetic powder, but it is also effective to use other metal-based magnetic powder or ferrite-based magnetic powder. Moreover, in the above-mentioned examples, examples of magnetic powders granulated by the gas atomization method and the water atomization method have been shown, but other granulation methods such as atomization methods such as a high-speed rotating water atomization method, pulverization, plasma rotating electrode method, etc. It can also be implemented using magnetic powder. It can also be carried out by subjecting the magnetic powder to surface modification such as surface oxidation or insulation film coating. In the above embodiment, the novolac type epoxy resin is used as the resin. However, the present invention is not limited to this, and the present invention can be carried out by using other thermosetting resins or thermoplastic resins.

  In the above-described embodiment, the method using the transfer molding method and the compression molding method is shown. However, other plastic molding methods such as an injection molding method can be used. Further, the present invention is not limited to the molding die shown in the above embodiment, and any molding die may be used as long as it has a gap not larger than the maximum particle size of the magnetic powder and can properly mold the mold coil.

It is a perspective view which shows the air-core coil used in the Example of this invention. It is a figure which shows the structure of the shaping die used in the 1st Example of this invention. It is a figure which shows the structure of the shaping die used in the 1st Example of this invention. It is a figure which shows the structure of the shaping die used in the 1st Example of this invention. It is sectional drawing explaining the principal part of the manufacturing method of the mold coil of the 1st Example of this invention. It is sectional drawing explaining the principal part of the manufacturing method of the mold coil of the 1st Example of this invention. It is a perspective view which shows the mold coil of the Example of this invention. It is a figure which shows the structure of the shaping die used in the 2nd Example of this invention, (a) is a top view, (b) is B-B 'sectional drawing of (a). It is sectional drawing explaining the principal part of the manufacturing method of the mold coil of the 2nd Example of this invention. It is sectional drawing explaining the principal part of the manufacturing method of the mold coil of the 2nd Example of this invention. It is sectional drawing explaining the principal part of the manufacturing method of the mold coil of the 2nd Example of this invention.

Explanation of symbols

1: air core coil, 2: mold (2a: first mold, 2b: second mold), 3: upper mold (3a: first upper mold, 3b: second upper mold), 4: lower mold (4a: first lower mold, 4b: second lower mold), 5: plunger, 6: cavity, 7: gate, 8: sprue, 9: chamber pod, 10: magnetic mold resin 11: external electrode 12, die (12a: first die, 12b: second die), 13: upper punch, 14: lower punch, 15: cavity

Claims (5)

In a method for producing a molded coil in which a coil is sealed with a magnetic molding resin in which a resin and a magnetic powder are kneaded using a plastic molding method,
Using the magnetic material mold resin containing 65% by volume or more of the magnetic material powder,
Using a molding die having a gap for discharging a part of the magnetic mold resin from the cavity in a part thereof,
Filling the cavity with the magnetic molding resin,
A part of the molten magnetic mold resin filled in the cavity is discharged from the cavity to the outside of the cavity through the gap,
A method for producing a mold coil, characterized in that the volume ratio of the magnetic powder is relatively lower in the discharged magnetic mold resin than in the magnetic mold resin filled in the cavity.   The method for producing a molded coil according to claim 1, wherein the gap is equal to or smaller than a maximum particle size of the magnetic powder.   The method for manufacturing a molded coil according to claim 1, wherein the magnetic powder is a powder of an iron-based magnetic material.   The method of manufacturing a molded coil according to claim 1, wherein the gap is formed by interposing a spacer in the molding die.   The method for manufacturing a molded coil according to claim 1, wherein the coil is a winding.

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