JP2018107410A - Manufacturing method of core with resin coating, and core with resin coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a core with resin coating capable of forming resin coating of uniform thickness on an inner peripheral surface, an outer peripheral surface and both side faces of a core, and the core with resin coating which improves magnetic characteristics.SOLUTION: Multiple cores are passed through a rotary roll which is adjusted into a temperature lower than a fusion temperature of a thermosetting resin, a torque is applied to the cores that are being supported by the rotary roll and suspended while being spaced apart from each other in an axial direction, by the rotary roll, such that the cores are brought into a rotational state. In a suspension direction of the cores, the cores are immersed from an outer diameter side to an inner diameter side in a powdery thermosetting resin flowing within a container, and the rotary roll is coated without being immersed therein as a whole. Further, the cores are heated and the applied thermosetting resin is cured, such that resin coating is provided.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing a magnetic core with a resin coating and a magnetic core with a resin coating, in which a thermosetting resin is coated on an annular magnetic core used in a transformer or a reactor.

  Conventionally, coil parts such as inductors, transformers, chokes, and motors have been used in various applications such as home appliances, industrial equipment, and vehicles. A general coil component is often composed of a magnetic core (magnetic core) and a coil wound around the magnetic core. In such magnetic cores, soft ferrites having excellent magnetic properties, flexibility in shape and price are widely used as magnetic materials.

  In recent years, as power supply devices such as electronic devices have been downsized, the demand for coil parts that are small and low in profile and can be used for large currents has become stronger, and the saturation magnetic flux density is higher than that of soft ferrite. Adoption of magnetic cores using high metal magnetic materials is advancing. Examples of metal-based magnetic materials include Fe-Si, Fe-B-Si, Fe-Ni, Fe-Si-Cr, Fe-Si-Al, and Fe-Al-Cr. Magnetic alloy powders, Fe- and Co-based amorphous alloy powders and ribbons, and nanocrystalline soft magnetic alloy powders and ribbons such as Finemet (registered trademark) are used.

In a magnetic core using ferrite or a metal-based magnetic material, a resin film is formed by coating the outer surface of the magnetic core with a resin so as to improve impact resistance, insulation, and weather resistance. In many cases, the fluid coating method is used for resin coating on the magnetic core. As an example, a conventional coating method using a fluid dipping method disclosed in Patent Document 1 will be described with reference to FIG.
The hollow portion of the annular magnetic core 100 is passed through the rod 120, and the magnetic core 100 is suspended from the rod 120 by its own weight. The inner peripheral surface 100b of the magnetic core 100 is in contact with the outer peripheral surface of the rod 120 on the upper side in the figure, and forms a space with the outer peripheral surface of the rod 120 on the lower side in the figure. The magnetic core 100 is rotated by the rotational force applied from the rod 120. Further, as illustrated by arrows in the drawing, the entire magnetic core 100 is swung in a state in which gas is ejected from the air hole 130 provided in the rod 120. Coating is performed by dipping in a resin powder in a powder flow tank (not shown) together with the rod 120.

JP-A-11-197585

  In Patent Document 1, powder coating is performed while gas is ejected from the air holes 130 formed in the rod 120, so that the resin powder is prevented from being deposited on the inner peripheral surface 100b of the magnetic core 100, and the resin powder is cured. An increase in the thickness of the resin coating on the peripheral surface 100b is prevented. However, in this method, there are some problems when a plurality of magnetic cores 100 are passed through the rod 120 and are applied side by side. One is that when a plurality of magnetic cores 100 are arranged through the rod 120 as shown in FIG. 5, a space S is formed between adjacent magnetic cores 100. The gas ejected outward from the space S prevents the resin powder from flowing into the space S, and the thickness of the resin coating on both sides 100c and 100d of the magnetic core is thinner than the thickness of the outer peripheral side 100a of the magnetic core. There is a problem that tends to become non-uniform. If the space S is widened, the inflow inhibition of the resin powder is improved, but the number of the magnetic cores 100 passing through the rod 120 must be reduced.

  Further, the contact resistance between the magnetic core 100 and the rod 120 is likely to be reduced by the gas passing between the inner peripheral surface 100b of the magnetic core 100 and the rod 120 as compared with the case where the gas is not ejected. Therefore, it is easily affected by the shape and weight balance of the magnetic cores 100. When the magnetic cores are rotated, they move in the axial direction of the rod 120, the adjacent magnetic cores 100 gradually approach each other, and the space S is narrowed. In some cases, the magnetic core side surfaces 100c and 100d are not sufficiently coated due to contact with each other, and the appearance quality may be impaired. In order to limit the movement of the magnetic core in the axial direction of the rod 120, it is effective to provide steps and protrusions for partitioning and positioning, but the flow of the resin powder to the inner peripheral side of the magnetic core is further hindered and the resin powder There is a concern that the body will be insufficiently supplied and the film thickness non-uniformity of the resin coating will increase.

  Further, if the thickness of the resin coating is not uniform, there is a problem that the magnetic characteristics of the magnetic core are deteriorated or the resin coating is cracked due to a locally generated stress difference. In addition, it was necessary to consider the deterioration of the magnetic properties due to the effect of stress due to the shrinkage of the resin film and the difference in thermal expansion coefficient from the magnetic core. In addition, there is a problem that the magnetic property deterioration is greatly affected when a material having a large magnetostriction such as an Fe-based amorphous alloy is used as the magnetic material of the magnetic core.

  Accordingly, an object of the present invention is a method of manufacturing a magnetic core with a resin coating provided with a resin coating process in which a thermosetting resin is applied to an annular magnetic core, the inner peripheral surface, the outer peripheral surface and both side surfaces of the magnetic core. It is an object of the present invention to provide a method for producing a magnetic core with a resin film capable of forming a resin film with a uniform film thickness and a magnetic core with a resin film excellent in magnetic properties.

  The present invention is a method for producing a magnetic core with a resin coating, comprising a resin coating step in which a powdered thermosetting resin is coated on an annular magnetic core by a flow dipping method, wherein the resin coating step A first step of heating above the temperature at which the thermosetting resin melts, a plurality of magnetic cores passed through a rotating roll adjusted to a temperature lower than the melting temperature of the thermosetting resin, and supported in the rotating roll in the axial direction The magnetic core in a suspended state with a gap is applied to the magnetic core in a rotating state by applying a rotational force by the rotating roll, and in a suspension direction of the magnetic core, a powdery thermosetting resin that flows in the container A second step in which the magnetic core is immersed from the outer diameter side to the inner diameter side and the entire rotating roll is not immersed, and the magnetic core that has passed through the second step is heated to cure the coated thermosetting resin. 3rd resin coating Has a degree, the thermosetting resin is an epoxy resin impregnated with an inorganic filler in epoxy resin, the average thickness of the resin film is a production method of the following resin film with a magnetic core 500μm or 200 [mu] m.

  In the method for producing a resin-coated magnetic core of the present invention, it is preferable to use a chamfered magnetic core.

  In the method for producing a magnetic core with a resin coating according to the present invention, in the third step, it is preferable to continuously heat at a temperature of 200 ° C. or more for 10 minutes or more.

  In the method for manufacturing a magnetic core with a resin coating according to the present invention, in the third step, the thermosetting resin may be cured in a state where the magnetic core is suspended from the rotating roll, or the magnetic core is removed from the rotating roll and thermoset. The functional resin may be cured. You may do both.

In the method for manufacturing a magnetic core with a resin coating according to the present invention, the magnetic material used for the magnetic core is preferably a metal magnetic material having an absolute value of magnetostriction constant λs of 30 × 10 ⁻⁶ or less. More preferably, the metallic magnetic material is an Fe-based amorphous alloy, and the magnetic core contains metallic Cu as a Cu powder, and when the total amount of the Fe-based amorphous alloy powder and the Cu powder is 100% by mass, the Cu powder is The content is preferably 7% by mass or less. By including Cu, the space factor of the magnetic core is improved, and the magnetic core loss can be reduced while maintaining the magnetic permeability. Moreover, when the powder of Cu which is a nonmagnetic substance exceeds 7 mass%, the magnetic permeability maintained by the improvement of the space factor will begin to decrease, and the resulting saturation magnetic flux density will also decrease. The difference in thermal expansion coefficient between the Fe-based amorphous powder and the resin coating is preferably within 70 ppm / ° C. As the difference in thermal expansion coefficient is smaller, the stress acting on the magnetic core can be made smaller and the increase in the core loss can be suppressed, and the occurrence of defects such as cracks in the resin film can be prevented.

In the method for producing a magnetic core with a resin coating of the present invention, the average thickness of the resin coating is preferably 200 μm or more and 500 μm or less. If the thickness of the resin coating is less than 150 μm, pits are likely to occur, and various properties (impact resistance, insulation, weather resistance) expected for the resin coating may not be obtained, and the average thickness is 150 μm or more. Is preferably 200 μm or more.
Further, even when the average thickness of the resin coating is more than 500 μm, the above-mentioned characteristics are slightly improved, the outer dimensions are increased, and the region on the inner peripheral side is narrowed, which may make winding difficult. In addition, as the thickness of the resin coating increases, the stress applied to the magnetic core also increases, leading to an increase in magnetic core loss, resulting in limitations such as the use of a magnetic material with a small magnetostriction, and the degree of freedom in material selection is narrowed. The average thickness is preferably 500 μm or less.

In the method for producing a magnetic core with a resin coating according to the present invention, the inorganic filler is not particularly limited as long as it imparts a low thermal expansion to the resin coating and is insulative or flame resistant, but in particular a CaCO ₃ or SiO ₂ powder. Is preferred. The average particle size of the powder of the inorganic filler can be appropriately set in consideration of the thickness and strength of the resin film to be formed, mixing / dispersibility in the thermosetting resin, etc., but the average thickness of the resin film to be obtained Is 500 μm or less, the average particle diameter is preferably 0.2 μm to 5 μm, and it is preferable to classify and remove coarse particles of 10% or more of the average thickness of the resin coating with a sieve. Moreover, it is preferable that content of an inorganic filler is 10 mass%-60 mass% with respect to the thermosetting resin from the intensity | strength of a resin film, or the fluidity | liquidity at the time of a fusion | melting.

The present invention also relates to a magnetic core with a resin coating in which the surface of a magnetic core is coated with a thermosetting resin, the magnetic core mainly comprising a metal magnetic material having a magnetostriction constant λs of 30 × 10 ⁻⁶ or less as an absolute value, The curable resin contains an inorganic filler, and the resin film directly coated on the surface of the magnetic core has an average thickness of 200 μm or more and 500 μm or less, a core loss Pcv of 190 kW / m ^{3 under} the conditions of a maximum magnetic flux density of 150 mT and a frequency of 20 kHz. It is a magnetic core with a resin film of less than.

The inorganic filler contained in the resin coating of the magnetic core with the resin coating is preferably CaCO ₃ or SiO ₂ powder.

  The magnetic core used for the resin-coated magnetic core includes Fe-based amorphous alloy powder and Cu powder, and when the total amount of Fe-based amorphous alloy powder and Cu powder is 100 mass%, Cu powder is 7 mass% or less. And the space factor of the magnetic core is preferably 75% or more.

  The present invention relates to a method of manufacturing a magnetic core with a resin coating provided with a resin coating step of coating a thermosetting resin on an annular magnetic core, the film being uniform on the inner peripheral surface, outer peripheral surface and both side surfaces of the magnetic core It is possible to provide a method of manufacturing a magnetic core with a resin film capable of forming a thick resin film and a magnetic core with a resin film excellent in magnetic properties.

It is a figure which shows the process of the manufacturing method of the magnetic core with a resin film which concerns on one Embodiment of this invention. (A)-(d) is a principal part expanded sectional view for demonstrating operation | movement of a coating device in the 2nd process of the manufacturing method of the magnetic core with a resin film which concerns on one Embodiment of this invention. FIG. 3 is a cross-sectional view taken along the line a-a ′ of FIG. (A) is a front view which shows the magnetic core with a resin film obtained with the manufacturing method of the magnetic core with a resin film which concerns on one Embodiment of this invention, (b) is a perspective view which shows the bb 'cross section in (a). It is. It is a principal part expanded sectional view for demonstrating operation | movement of the coating device by the fluid immersion method shown by the prior art example.

  Hereinafter, the manufacturing method of the magnetic core with a resin film which concerns on one Embodiment of this invention is demonstrated concretely. However, the present invention is not limited to this. Note that in some or all of the drawings, portions that are not necessary for the description are omitted, and there are portions that are illustrated in an enlarged or reduced manner for ease of description. Further, the dimensions and shapes shown in the description, the relative positional relationships of the constituent members, and the like are not limited to these unless otherwise specified. Further, in the description, the same name and reference numeral indicate the same or the same members, and the detailed description may be omitted even if illustrated.

  The method of manufacturing a magnetic core with a resin coating according to the present invention is a method for coating an annular magnetic core by a flow dipping method, and a rotating roll is passed through a hollow portion of a heated annular magnetic core, and the magnetic core is formed by the rotating roll. While rotating, it is immersed in a powdered thermosetting resin to a predetermined depth in the container for a predetermined time, and the heat of the heated magnetic core melts the thermosetting resin powder, and the surface of the magnetic core is molten resin. Coat with. Thereafter, the magnetic core is heated at a predetermined temperature for a predetermined time to cure the thermosetting resin to form a resin film.

  FIG. 1 is a diagram showing steps of a method for manufacturing a magnetic core with a resin coating according to an embodiment of the present invention. FIGS. 2A to 2D are enlarged cross-sectional views for explaining the operation of the coating apparatus in the second step of the method for manufacturing the magnetic core with a resin coating according to the embodiment of the present invention. FIG. 3 is a cross-sectional view taken along the line a-a ′ of FIG. 4A and 4B are a front view showing a magnetic core obtained by the method for manufacturing a magnetic core with a resin coating according to one embodiment of the present invention and a perspective view showing a partial cross section.

  In the method of manufacturing a magnetic core with a resin coating, a thermosetting resin is applied to an annular magnetic core by a fluid immersion method. The resin coating step is divided into a plurality of steps, and roughly divided into first to third steps shown in FIG. In the first step, the magnetic core is heated to a temperature at which the thermosetting resin melts. Next, in the second step, the surface of the magnetic core is coated by melting the thermosetting resin powder with the residual heat of the magnetic core. In the third step, the coated thermosetting resin is cured to complete a resin film.

The material of the magnetic core to be coated is not particularly limited, such as the above-mentioned soft ferrite or metal magnetic material. Further, the form thereof may be any of a sintered body, a wound core, a laminated core, a dust core, etc. depending on the material. Preferably, the magnetic core is a dust core excellent in saturation magnetic flux density and magnetic core loss. For example, an Fe-based amorphous alloy having a magnetostriction constant λs of 30 × 10 ⁻⁶ or less is preferably used. The Fe-based amorphous alloy is, for example, an Fe-B-Si alloy. Fe-based amorphous alloy is used as a powder, but further, Cu powder is added, Cu powder is dispersed between powders of Fe-based amorphous alloy, and bonded with a resin binder such as an epoxy system. Also good. If the Cu powder is 7% by mass or less with respect to 100% by mass of the total amount of the Fe-based amorphous alloy powder and the Cu powder, the Cu powder is non-magnetic, but the compressibility at the time of molding is increased and the space is increased. The core loss can be reduced while increasing the rate and suppressing the decrease in magnetic permeability. More preferably, it is 0.1 mass%-1.5 mass%. Further, atomized powder of Fe-based magnetic alloys such as Fe-Si, Fe-Ni, Fe-Si-Cr, Fe-Si-Al, and Fe-Al-Cr may be used. Moreover, in the magnetic core using a metallic magnetic material, it is preferable that the space factor represented by the ratio of the magnetic body to the volume is 75% or more.

  The shape of the magnetic core 2 may be a substantially annular shape having a hollow portion. Here, the substantial annular shape means that the inner peripheral side (hollow portion) of the magnetic core and the outer peripheral portion of the magnetic core 2 are circular or elliptical. Even if it is a polygonal shape, it can be approximated to a circle as long as it is rotatable with the rotation of the rotary roll 50, and deformation such as irregularities may be added. The dimensions can be appropriately set within the range where the effects of the present invention can be obtained. However, in consideration of the diameter dimension of the rotating roll 50 and the rotational force applied, the outer diameter is 20 to 75 mm, the inner diameter is 10 to 50 mm, and the height is 5 It is desirable to be about ˜25 mm.

  In the first step, the magnetic core 2 is heated to a high temperature that is equal to or higher than the temperature at which the thermosetting resin melts. The heating temperature can be appropriately set according to the type of the thermosetting resin, the magnetic core material, and the like, but can be selected from a range of about 130 to 350 ° C., for example. As the heating furnace, a known apparatus such as a thermostatic bath or a reflow furnace can be used.

  In the second step, the residual heat of the magnetic core is used to melt and coat the thermosetting resin powder. As shown in FIG. 2, the coating contains a rotating roll 50 through which a plurality of magnetic cores 2 can be inserted, a rotating mechanism (not shown) for rotating the rotating roll 50, and a thermosetting resin powder. A powder flow tank 150 which is a container, and an elevating means (not shown) for moving the rotary roll 50 or the powder flow tank 150 up and down to immerse the magnetic core 2 in the thermosetting resin powder; It is preferable to use a coating apparatus 200 provided with a cooling mechanism (not shown) for adjusting the temperature of the rotary roll 50. In the powder flow tank 150, as shown in FIG. 3, gas is fed from the gas flow path 135 below the porous plate 125, and the thermosetting resin powder is in a fluidized state. Yes.

Next, the second step will be described in detail in the order of work.
First, a plurality of magnetic cores 2 are passed through a skewer-shaped rotating roll 50 (FIGS. 2A to 2B). At that time, the rotating roll 50 may be in a rotating state, but it is easier and preferable to perform the operation while the rotation is stopped. The rotating roll 50 is kept at a temperature lower than the melting temperature of the thermosetting resin. By adjusting the temperature of the rotary roll 50, the thermosetting resin is prevented from being welded to the rotary roll 50 itself. In addition, the thermosetting resin powder wound between the rotating roll 50 and the inner peripheral surface of the magnetic core 2 is discharged into the container as a surplus with the rotation of the rotating roll 50 and the magnetic core 2, and the inner peripheral side of the magnetic core 2 is discharged. The resin film thickness is prevented from becoming unnecessarily thick. Therefore, it is preferable that the temperature of the rotary roll 50 is lower than the melting temperature Tm of the thermosetting resin and is adjusted at 10 to 80 ° C. In addition, when the distance from the inner peripheral surface 2b on the lower end side of the magnetic core 2 suspended from the rotary roll 50 to the outer peripheral surface 50a of the rotary roll 50 is narrow, the gap between the rotary roll 50 and the inner peripheral surface 2b of the magnetic core 2 is reduced. Since the surplus portion of the powder of the thermosetting resin that has entered becomes difficult to be discharged and the rotation of the magnetic core 2 may be hindered, the interval is preferably set to 2 mm or more.

  The plurality of magnetic cores 2 that are supported and suspended by the rotary roll 50 with an axial interval S are given a rotational force by the rotary roll 50. The magnetic core 2 is rotated by the rotational force from the rotary roll 50, but if the rotational speed of the magnetic core is slow, the thickness of the resin film tends to be uneven, and if it is fast, the thermosetting resin powder is contained in the rotary roll 50 and the magnetic core 2. It becomes easy to get caught between the peripheral surfaces. Therefore, the rotation of the rotary roll 50 is appropriately set according to the state of the resin coating. However, it is preferable to set the rotation speed of about 25 to 300 rpm to the magnetic core as long as the magnetic core has the dimensions described above.

  The root side of the rotating roll 50 extends into the interior of the coating apparatus 200, and rotation of a motor (not shown) in the coating apparatus 200 is given to the rotating roll 50 via a transmission means such as a gear. Moreover, it is preferable to provide a cooling mechanism in the coating apparatus 200 and adjust the temperature by rotating the rotary roll 50 with air or water from its root side. Moreover, it is good also as a rotary heat pipe structure which lets cooling water pass. The material of the rotating roll 50 depends on strength, thermal conductivity, etc., but is preferably stainless steel, for example. The thermal conductivity may be improved as an integral structure in which the rotating roll 50 is formed with a hollow sleeve having an opening and a highly heat conductive metal such as Cu having excellent thermal conductivity.

  The outer diameter of the rotating roll 50 needs to be a dimension that supports the magnetic core and can provide a driving force sufficient to rotate the magnetic core in the thermosetting resin powder. Further, in order to prevent the powder of the thermosetting resin from flowing into the inner diameter side of the magnetic core 2 and prevent the entrainment, it is only necessary to secure the interval between the outer periphery of the rotating roll and the inner periphery of the magnetic core. Furthermore, it is desirable that the outer diameter D1 of the rotating roll is sufficiently smaller than the inner diameter D2 of the magnetic core. The ratio D1 / D2 between the outer diameter D1 of the rotating roll and the inner diameter D2 of the magnetic core is preferably 0.2 or more and 0.96 or less.

  Next, the magnetic core 2 is immersed in a thermosetting resin powder 170 that flows in the powder flow tank 150 while being rotated, and then pulled up (FIGS. 2C to 2D). The rotary roll 50 or the powder flow tank 150 can be moved up and down by lifting means (not shown), and the magnetic core 2 can be immersed in the thermosetting resin powder 170 by moving either one of them. By controlling the elevating means, the thermosetting resin powder 170 flowing in the powder flow tank 150 can be immersed for a predetermined time at a predetermined immersion depth while rotating the magnetic core 2.

  As shown in FIG. 4, the immersion depth D in the thermosetting resin powder 170 of the magnetic core 2 is the thermosetting resin powder 170 appearing from the powder flow tank 150 from the lower end of the outer periphery of the magnetic core 2 in the hanging direction. Defined by the distance to the surface 175 of Usually, the thermosetting resin powder 170 is in a fluid state, and its surface is irregularly wavy. Therefore, in the present invention, the state of being immersed in the powdered thermosetting resin flowing in the container from the outer diameter side to the inner diameter side in the hanging direction of the magnetic core is referred to as “immersion beyond the inner diameter side of the magnetic core 2. ” If the lower end side 50a of the rotating roll 50 is not completely buried in the curable resin powder, "the rotating roll is not immersed". In any case, the state may be determined by visual confirmation.

  By defining the upper limit position of the immersion depth of the magnetic core 2 (a position where no more is immersed), the magnetic core 2 is prevented from being immersed in the thermosetting resin powder 170 so that the resistance caused by the immersion in the powder is reduced. Thus, the rotation of the magnetic core 2 can be stably maintained, and the part of the magnetic core to be immersed can be renewed without rotation evenly.

  Moreover, since only a part of the magnetic core 2 is immersed in the powder, the immersion depth can be reduced, so that the magnetic core 2 can be held at a predetermined immersion depth and the thickness of the resin film can be easily controlled by the holding time. Become. In this case, since the time during which the magnetic core is immersed in the powder becomes longer if the speed of immersing in or pulling out the powder is slow, it is desirable that the speed of immersing the magnetic core is 6 m / min or more. In terms of time, it is desirable that the time be less than 0.5 seconds. Moreover, it is good also as a desired resin film thickness by controlling coating time with the speed | rate until it reaches the depth to make it immerse, and the drawing | extracting speed, without hold | maintaining the magnetic core 2 by immersion depth.

  The immersion time can be adjusted depending on the thickness of the coating film to be obtained, but is preferably less than 5 seconds if the average thickness is 500 μm or less. Here, the immersion time is the total time that the outer peripheral side of the magnetic core 2 is in contact with the thermosetting resin powder 170. As the coating thickness increases as a whole, the resin on the surface tends to be in a semi-molten state, and the surface roughness of the coating becomes rougher. It is necessary to apply heat again to completely dissolve the resin on the surface. It may be difficult to obtain sex.

  The thermosetting resin powder used is preferably an epoxy resin in which an inorganic filler is contained in an epoxy resin. Although the particle size of the thermosetting resin powder depends on the outer dimensions of the magnetic core, it is preferably 10 μm to 300 μm in view of fluidity and uniformity of the coating thickness. An inorganic filler will not be specifically limited if it contributes to the improvement of the mechanical strength of the resin film of a thermosetting resin, and low thermal expansion. Further, it is more preferable to improve the insulation. Examples of the inorganic filler that can be used include oxides such as titanium oxide, alumina, and silica, and carbonates such as calcium carbonate and magnesium carbonate. The content of the inorganic filler is preferably 10% by mass to 60% by mass in the total solid content of the thermosetting resin. When there are many inorganic fillers, the fluidity | liquidity of the melted thermosetting resin may be bad, and the thickness of a film may vary. On the other hand, if the amount is small, the mechanical strength may not be sufficiently improved and the thermal expansion may not be sufficiently achieved. When using Fe-based amorphous alloy powder as the magnetic material used for the magnetic core, the difference in thermal expansion coefficient between the Fe-based amorphous alloy and the resin coating is preferably within 70 ppm / ° C.

  The epoxy resin is not particularly limited, but bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bisphenol novolac type epoxy resin, and the like may be used.

  The epoxy resin contains a curing agent and may further contain a curing accelerator. As the curing agent, for example, a phenolic curing agent such as a phenol novolak resin, an alkylphenol novolak resin, or a bisphenol A novolak resin may be used. The curing accelerator is not particularly limited, but is preferably an imidazole compound that is compatible with the resin component constituting the thermosetting resin.

  In the third step, the magnetic core subjected to the second step is heated to cure the thermosetting resin, thereby completing the resin coating 10. Since the thermosetting resin may be insufficiently cured only by the residual heat of the magnetic core, it is preferable to heat at a temperature higher than the temperature of the first step. In particular, an epoxy resin containing an inorganic filler in an epoxy resin tends to require a long time for curing, and therefore, it is desirable to continuously heat at a temperature of, for example, 200 ° C. for 10 minutes or more.

  The obtained resin coating 10 of the magnetic core preferably has an average thickness of 200 μm or more and 500 μm or less in the entire outer peripheral side 10a, inner peripheral side 10b, first side surface side 10c, and second side surface side 10d.

  Further, when a conductor is wound around the magnetic core 1 with a resin coating, if there is a corner portion that is not chamfered on the magnetic core, the coating thickness becomes thin, the conductor hits there, and stress is easily concentrated locally, and the resin coating 10 is cracked. May occur. Therefore, it is preferable to use a magnetic core whose corners on the inner and outer peripheral sides are chamfered. As shown in FIG. 4 (b), it is also preferable that burrs that prevent rotation of the magnetic core 2 are removed by chamfering the corners of the inner and outer circumferences of the magnetic core 2.

  Below, based on an Example, this invention is demonstrated in detail. In the description, the magnetic material used for the magnetic core is an Fe-based amorphous alloy, but the scope of the present invention is not intended to be limited thereto unless otherwise specified.

(Production of magnetic core)
As the Fe-based amorphous alloy, Metglas (registered trademark) 2605SA1 material manufactured by Hitachi Metals, Ltd. and Fe ₇₄ B ₁₁ Si ₁₁ C ₂ Cr ₂ material manufactured by Epson Atmix Co., Ltd. (atomized powder; average particle diameter D50 = 6 μm) are used. It was. The 2605SA1 material was supplied as a ribbon having a thickness of 25 μm, and this was pulverized. The obtained pulverized powder was passed through a sieve having an aperture of 106 μm (diagonal 150 μm), and then the pulverized powder passing through the sieve having an aperture of 35 μm (diagonal 49 μm) was removed. The ground powder classified by a sieve was treated with TEOS (tetraethoxysilane, Si (OC ₂ H ₅ ) ₄ ) to obtain a powder on which a silicon oxide film was formed. The Cu powder used was a HXR-Cu material manufactured by Nippon Atomizing Co., Ltd., and a spherical powder having an average particle size (D50) of 5 μm. The thermal expansion coefficient of the Fe-based amorphous alloy 2605SA1 which is the main constituent of the magnetic core is 7.6 × 10 ⁻⁶ / ° C., and the magnetostriction is 27 × 10 ⁻⁶ . As will be described later, since the magnetic core is mainly composed of a ground powder of an Fe-based amorphous alloy, according to the knowledge of the present inventor, the thermal expansion coefficient and magnetostriction of the magnetic core can be referred to the value of 2605SA1 material, If the proportion of the 2605SA1 material is 90% by mass or more, it can be regarded as the value of the magnetic core.

  The pulverized powder of the Fe-based amorphous alloy was 91.5% by mass, the atomized powder was 7% by mass, and the Cu powder was 1.5% by mass, and weighed so that the total amount would be 100% by mass. Furthermore, 1% by mass of phenylmethylsilicone (SILRES H44 manufactured by Asahi Kasei Wacker Silicone Co., Ltd.) as a binder for high temperature and acrylic resin (Polysol manufactured by Showa Polymer Co., Ltd.) as an organic binder with respect to 100% by mass of these powders. AP-604) was adjusted to 1.5% by mass and mixed with the pulverized powder and the like, and then dried at 120 ° C. for 10 hours to obtain a mixed powder.

  The obtained mixed powder is passed through a sieve having an opening of 425 μm to obtain a granulated powder. After mixing 40 g of zinc stearate with this granulated powder, the outer diameter is 33 mm, the inner diameter is 20 mm, and the height is 12 using a press machine. The powder was compacted with a pressure of 2 GPa and a holding time of 2 seconds so as to form an annular shape of 5 mm. C1.5 chamfering was performed on the inner peripheral side corner and the outer peripheral side corner of the obtained molded body. The molded product after chamfering was heat-treated in a constant temperature bath in an air atmosphere at a peak temperature of 400 ° C. and a holding time of 1 hour to obtain a magnetic core having a space factor of 79%.

(Resin coating process)
(First step)
The magnetic core was heated and heated at a peak temperature of 215 ° C. for 5 minutes using a mesh belt type continuous heat treatment furnace so that the sample temperature became 170 ° C. or higher.

(Second step)
The thermosetting resin was applied by a fluid immersion method using the coating apparatus shown in FIGS.
The following three types of thermosetting resins were prepared. One (Sample No. 1) is Sumitomo Bakelite Co., Ltd.'s epoxy resin powder coating, Sumilite Resin (registered trademark) ECP series, which has a melting temperature of 100 ° C using silica as an inorganic filler, and thermal expansion after curing. This is a thermosetting resin powder (hereinafter referred to as resin powder A) having a coefficient of 45 ppm / ° C.
The second (sample No. 2) is a thermosetting resin powder (hereinafter referred to as resin powder B) having a melting temperature of 155 ° C. and a thermal expansion coefficient after curing of 40 ppm / ° C. using calcium carbonate as an inorganic filler. It is.
The third (sample Nos. 4 and 5) is an epoxy resin powder paint Epiform F-235 manufactured by Somaru Co., Ltd., with a melting temperature of 80 ° C. and a thermal expansion coefficient of 65 ppm / ° C. after curing. Resin powder (hereinafter referred to as resin powder C). Epiform F-235 used as a comparative example does not contain an inorganic filler.

  Six of the rotating rolls 50 having an outer diameter of φ10 mm and adjusted to 20 ° C. were passed through the magnetic core 2 and arranged at intervals of 20 mm. The distance between the outer periphery of the rotary roll 50 and the inner periphery of the magnetic core 2 in the hanging direction (vertical direction) is 10 mm. The rotating roll 50 is rotated so that the rotation speed of the magnetic core 2 is 40 rpm, and the immersion depth D is * No. Except for No. 3, it is assumed to be approximately halfway between the inner peripheral surface of the magnetic core on the lower end side in the hanging direction and the outer peripheral surface of the rotary roll. For No. 3, the entire magnetic core is set to two conditions immersed in the thermosetting resin powder, and the immersion time for maintaining the immersion depth is No. 3. 1, * No. 4 is set to 3.5 seconds. 2 is 4 seconds, * No. 3 is 2 seconds, and * No. In No. 5, the coating was performed by fluid immersion for 5 seconds.

(Third step)
The magnetic core coated with the thermosetting resin was heat-treated, and heated using a mesh belt type continuous heat treatment furnace at a peak temperature of 220 ° C. for 10 minutes to obtain a magnetic core 1 with a resin coating.
Table 1 summarizes the conditions for the produced magnetic core with resin coating. In the table, the comparative sample is No. Are distinguished by adding *.

(Evaluation method and results)
The magnetic core loss and the film thickness were evaluated for each resin coated magnetic core produced by the above steps.

(Core loss Pcv)
Using the magnetic core as the object to be measured, the primary side winding and the secondary side winding were wound by 51 turns and 17 turns, respectively, and a maximum magnetic flux density of 150 mT and a frequency of 20 kHz were obtained by BH Analyzer SY-8232 made by Iwatatsu Measurement Co., Ltd. Under these conditions, the core loss Pcv (kW / m ³ ) was measured at room temperature.

(Film thickness)
As shown in FIG. 4, the resin coated magnetic core 10 is cut in the radial direction passing through the center with a cutting machine, and the outer peripheral resin coated film 10a observed in the cross section on one side of the divided arc-shaped magnetic core 10, The thicknesses of the resin film 10b on the inner peripheral side, the resin film 10c on the first side surface, and the resin film 10d on the second side surface were measured using a universal projector. The thickness of the coating was the distance to the thickest portion of the coating on the basis of the magnetic core surface.

  In Table 2, sample No. 1, 2, and * No. The relationship between the average film thickness of 4 and 5 and the core loss is shown. The average film thickness is an average value of the thicknesses of the two side surfaces and the inner and outer peripheral surfaces in one sample. The resin-coated magnetic core using the resin powder A (No. 1) and B (No. 2) containing the inorganic filler is the same as the resin-coated magnetic core (* No. 4) using the resin powder C not containing the inorganic filler. * No. 5).

  Sample No. with different immersion depths 1 and * No. Table 3 shows the average value of the coating thickness when the number of samples is n = 12 (average thickness of the resin coatings on the two side surfaces and the inner and outer peripheral surfaces in the entire sample), the standard deviation σ, and the inner peripheral side coating of the magnetic core. The difference (Tia-Toa) between the average value (Tia) of the thickness and the average value (Toa) of the outer peripheral side film thickness is shown. Sample No. No. 1 coating thickness variation is * No. Compared to 3, the difference in film thickness between the inner and outer circumferences was also small.

  Sample No. of Example 1, the sample * No. Compared to 3, the difference between the maximum value and the minimum value of the film thickness is small, and a resin film having a uniform thickness can be formed over the entire magnetic core. Even when the entire magnetic core was not immersed in the resin powder, the surface of the resin coating was smooth and no pits were observed. According to the present invention, a resin film having a uniform film thickness can be formed as a whole without pits in the magnetic core. The obtained resin-coated magnetic core is excellent in impact resistance, insulation and weather resistance, and also in magnetic core loss.

DESCRIPTION OF SYMBOLS 1 Magnetic core with resin film 2 Magnetic core 10 Resin film 50 Rotary roll 120 Rod 125 Porous board 130 Fumarole hole 135 Gas flow path 150 Powder flow tank 200 Coating device

Claims (12)

A method of manufacturing a magnetic core with a resin coating, comprising a resin coating step of coating an annular magnetic core with a powdered thermosetting resin by a fluid immersion method,
The resin coating step includes
A first step of heating the magnetic core above a temperature at which the thermosetting resin melts;
A plurality of magnetic cores are passed through a rotating roll adjusted to a temperature lower than the melting temperature of the thermosetting resin, and the magnetic core is supported by the rotating roll and suspended in an axial direction by the rotating roll. A rotational force is applied to bring the magnetic core into a rotating state, and in the direction in which the magnetic core is suspended, the magnetic core is immersed in a powdered thermosetting resin flowing in the container from the outer diameter side to the inner diameter side of the magnetic core. A second step of painting without immersing the whole;
Heating the magnetic core that has undergone the second step, and curing the coated thermosetting resin to form a resin film;
The thermosetting resin is an epoxy resin in which an inorganic filler is included in an epoxy resin,
The manufacturing method of the magnetic core with a resin film whose average thickness of the said resin film is 200 micrometers or more and 500 micrometers or less. A method for producing a magnetic core with a resin coating according to claim 1,
A method of manufacturing a magnetic core with a resin coating using a chamfered magnetic core. A method for producing a magnetic core with a resin coating according to claim 1 or 2,
The manufacturing method of the magnetic core with a resin film which heats continuously for 10 minutes or more at the temperature of 200 degreeC or more in the said 3rd process. A method for producing a magnetic core with a resin coating according to claim 3,
In the third step, a method for manufacturing a magnetic core with a resin coating, wherein the thermosetting resin is cured in a state where the magnetic core is suspended from a rotating roll. A method for producing a resin-coated magnetic core according to claim 3 or 4,
In the third step, a method of manufacturing a magnetic core with a resin coating, wherein the magnetic core is removed from the rotating roll and the thermosetting resin is cured. A method for producing a magnetic core with a resin coating according to claim 1,
A method of manufacturing a resin-coated magnetic core, wherein the magnetic material used for the magnetic core is a metal magnetic material having an absolute value of magnetostriction constant λs of 30 × 10 ⁻⁶ or less. It is a manufacturing method of the magnetic core with a resin film according to claim 6,
The magnetic core includes a Fe-based amorphous alloy powder and a Cu powder, and when the total amount of the Fe-based amorphous alloy powder and the Cu powder is 100% by mass, the resin coating includes 7% by mass or less of the Cu powder. A manufacturing method of a magnetic core. It is a manufacturing method of the magnetic core with a resin film according to claim 7,
A method for producing a magnetic core with a resin coating, wherein the difference in thermal expansion coefficient between the Fe-based amorphous alloy powder and the resin coating is within 70 ppm / ° C. A method for producing a resin-coated magnetic core according to any one of claims 1 to 8,
Method for producing a resin film with the magnetic core is the inorganic filler is CaCO ₃ or SiO ₂ powder. A magnetic core with a resin film in which the surface of the magnetic core is coated with a thermosetting resin,
The magnetic core is mainly composed of a metal magnetic material having a magnetostriction constant λs of 30 × 10 ⁻⁶ or less as an absolute value,
The thermosetting resin includes an inorganic filler,
The average thickness of the resin film directly coated on the surface of the magnetic core is 200 μm or more and 500 μm or less,
A resin coated magnetic core having a core loss Pcv of less than 190 kW / m ³ under conditions of a maximum magnetic flux density of 150 mT and a frequency of 20 kHz. A magnetic core with a resin coating according to claim 10,
A magnetic core with a resin coating, wherein the inorganic filler is CaCO ₃ or SiO ₂ powder. A magnetic core with a resin coating according to claim 10 or 11,
The magnetic core includes Fe-based amorphous alloy powder and Cu powder, and when the total amount of the Fe-based amorphous alloy powder and Cu powder is 100% by mass, the magnetic core contains 7% by mass or less of the Cu core, Magnetic core with resin coating whose rate is 75% or more.

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