JP2020053439A - Composite magnetic material, metal composite core, reactor, and method of manufacturing metal composite core - Google Patents

Abstract

To provide a composite magnetic material which is a material of a metal composite core with excellent magnetic properties, a metal composite core, a reactor, and a method of manufacturing the metal composite core.SOLUTION: The composite magnetic material is obtained by mixing a magnetic powder and a resin. The magnetic powder includes: a first magnetic powder; and a second magnetic powder having a smaller average particle size than the first magnetic powder. The coercive force of the first magnetic powder is set to Hc=0.70A/cm or less, and the circularity is set to 0.9 or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a composite magnetic material comprising a magnetic powder and a resin, a metal composite core, a reactor, and a method for manufacturing a metal composite core.

  Reactors are used in various applications such as OA equipment, solar power generation systems, automobiles, and uninterruptible power supplies. The reactor is used for, for example, a filter for preventing a harmonic current from flowing out to an output system, a converter for raising and lowering a voltage, and the like.

  Reactors are required to have magnetic properties such as magnetic permeability, inductance value, and iron loss according to the application. For example, a reactor used in a converter for raising and lowering a voltage is required to have improved energy conversion efficiency, and therefore is required to have a small iron loss as an energy loss.

  There is also a demand for molding a core used in a reactor into an arbitrary shape in order to meet various uses. As a reactor that meets such a demand, there is a reactor provided with a type of core called a metal composite core. A metal composite core (hereinafter, also simply referred to as an MC core) is a core obtained by molding a material obtained by mixing a metal magnetic powder and a resin into a predetermined shape and solidifying the material.

JP 2012-33727 A

  The conventional MC core is in the form of a slurry, and is molded by pouring the material into a container. Therefore, a desired shape can be easily molded, and there is an advantage in moldability that the shape is less restricted. On the other hand, in order to improve the fluidity in the container, it is necessary to add a certain amount or more of the resin. Had declined. In addition, in the MC core, there are factors other than a decrease in the core density, which cause a decrease in the magnetic properties, and it is desired to suppress the influence thereof and improve the magnetic properties.

  An object of the present invention is to provide a composite magnetic material, a metal composite core, a reactor, and a method for manufacturing a metal composite core, which are materials of a metal composite core having excellent magnetic properties.

  The present inventors have conducted intensive studies and have found that, in a metal composite core using two types of magnetic powders, large and small, as the soft magnetic powder, the first magnetic powder having a large average particle diameter is increased in circularity to improve the core density. It has been found that low magnetic permeability is achieved, low coercive force of the first magnetic powder is suppressed, low iron loss is realized, and the magnetic properties of the metal composite core can be improved by a synergistic effect of these. Was.

  In order to achieve the above object, the present invention provides a composite magnetic material obtained by mixing a magnetic powder and a resin, wherein the magnetic powder has a first magnetic powder and an average particle diameter larger than that of the first magnetic powder. A small second magnetic powder is included, and the first magnetic powder has a coercive force Hc = 0.70 A / cm or less and a circularity of 0.9 or more.

  The first magnetic powder may have a powder hardness of 278 Mpa or more.

  The first magnetic powder may have a coercive force Hc = 0.48 A / cm or less and a circularity of 0.92 or more.

  The first magnetic powder may have a powder hardness of 403 Mpa or more.

  The second magnetic powder may have a coercive force Hc = 0.93 A / cm or less and a circularity of 0.98 or more.

  The second magnetic powder may have a powder hardness of 239 Mpa or more.

  The amount of the first magnetic powder added to the magnetic powder may be 60 to 80 wt%, and the amount of the second magnetic powder added to the magnetic powder may be 40 to 20 wt%.

  The mixing amount of the resin may be 3 to 5 wt% of the magnetic powder.

  A metal composite core formed from the composite magnetic material is also one embodiment of the present invention.

  In the metal composite core of the present invention, the entire surface of the core may be a non-sliding surface.

  A reactor including the metal composite core and the coil is also one embodiment of the present invention.

  The method of manufacturing a core according to the present invention is a method of manufacturing a core including a magnetic powder and a resin, wherein the magnetic powder has a coercive force Hc = 0.70 A / cm or less and a circularity of 0.9 or more. A mixing step of mixing a resin with the first magnetic powder, the second magnetic powder having a smaller average particle diameter than the first magnetic powder, and mixing the mixture obtained in the mixing step in a predetermined container; And a curing step of curing the resin in the molded body obtained in the molding step.

  According to the present invention, it is possible to provide a composite magnetic material, a metal composite core, a reactor, and a method of manufacturing a metal composite core, which are materials of a metal composite core having excellent magnetic properties.

It is a flow chart for explaining a manufacturing method of a reactor concerning an embodiment. It is a figure for explaining a molding process and a pressurization process. It is a graph of magnetic permeability (micro | micron | mu) _12k with respect to iron loss Pcv of Examples 1-5 and the comparative example 1. Is a graph of magnetic permeability mu _12k to iron loss Pcv indicating a ratio of the apparent density of the MC core relative apparent density of a dust core for powder hardness of the first magnetic powders of Examples 4, 5 and Comparative Example 1.

[1. Embodiment]
[1-1. Constitution]
The reactor of the present embodiment includes a core and a coil. The core is a metal composite core (hereinafter, also referred to as MC core) configured to include a magnetic powder and a resin. A core can be formed into a predetermined shape by filling a predetermined container with a clay-like mixture obtained by mixing a magnetic powder and a resin and applying pressure. The shape of the core can be various shapes such as, for example, a toroidal core, an I-type core, a U-type core, a θ-type core, an E-type core, and an EER-type core.

  As the magnetic powder, soft magnetic powder can be used, and in particular, Fe powder, Fe-Si alloy powder, Fe-Al alloy powder, Fe-Si-Al alloy powder (Sendust), or a mixed powder of two or more of these powders Etc. can be used. As the Fe-Si alloy powder, for example, Fe-6.5% Si alloy powder and Fe-3.5% Si alloy powder can be used. The average particle size (D50) of the soft magnetic powder is preferably from 20 μm to 150 μm. In this specification, the “average particle diameter” refers to D50, that is, the median diameter, unless otherwise specified.

  The magnetic powder is composed of magnetic powders having different average particle diameters. That is, the magnetic powder includes the first magnetic powder and the second magnetic powder having a smaller average particle diameter than the first magnetic powder. It is desirable that the first magnetic powder and the second magnetic powder have a low coercive force. The coercive force of the first magnetic powder is preferably 0.70 A / cm or less, more preferably 0.48 A / cm or less. In an MC core using a magnetic powder having a large coercive force, the hysteresis loop in the MC core also becomes large. Therefore, the hysteresis loss of the MC core increases. Therefore, by suppressing the coercive force of the first magnetic powder to be low, it is possible to realize an MC core with low iron loss. The coercive force of the second magnetic powder is desirably 0.93 A / cm or less. The coercive force of the second magnetic powder has less influence on the hysteresis loop of the MC core than the coercive force of the first magnetic powder. However, when the coercive force of the second magnetic powder exceeds 0.93 A / cm, the hysteresis loop in the MC core also increases, and the hysteresis loss of the MC core increases.

The first magnetic powder and the second magnetic powder are preferably spherical. The circularity of the first magnetic powder is preferably 0.90 or more, and the circularity of the second magnetic powder is preferably 0.98 or more. This is because gaps between the first magnetic powders are reduced, and more second magnetic powders are more likely to enter the gaps, so that the density and the magnetic permeability can be improved. When pressurizing the MC core, the pressure applied in the pressurizing step is several kg / cm ² to several tens kg / cm ² , and a dust core requiring several t / cm ² to several tens t / cm ² ( (Hereinafter, also referred to as a dust core), which is extremely small, about 1/1000, so that the circularity of the magnetic powder can be maintained. That is, in the case of a dust core that needs to be pressurized with a high pressure, such circularity of the magnetic powder cannot be obtained.

  Further, the amount of the first magnetic powder added to the magnetic powder is preferably 60 to 80 wt%. That is, when the magnetic powder is composed of the first magnetic powder and the second magnetic powder, it is preferable that the weight ratio of the first magnetic powder: the second magnetic powder = 80: 20 to 60:40. By setting the content in this range, the density of the core is improved, and the iron loss Pcv can be reduced.

  The first magnetic powder preferably has an average particle size of 50 μm to 200 μm. The second magnetic powder preferably has a thickness of 3 μm to 25 μm. This is because the second magnetic powder having a small average particle diameter enters the gaps between the first magnetic powders, so that the core density can be improved and the iron loss can be reduced.

  The powder hardness of the first magnetic powder is preferably 278 Mpa or more, more preferably 403 Mpa or more. The MC core is different from the dust core in that magnetic powders are adhered to each other by a resin. On the other hand, when the dust core is applied with a high pressure applied in the pressing step to deform the magnetic powder, the moldability is improved. In the dust core, the powder hardness is desirably equal to or less than a certain value, but in the MC core, there is no limitation. Further, in the case of the MC core, unlike the dust core, the magnetic powder is not deformed by pressurization, so that there is no adverse effect on the hysteresis loss. When the first magnetic powder is spherical, the powder hardness tends to increase. By making the first magnetic powder spherical, the magnetic permeability of the MC core can be kept low and the density can be improved. The powder hardness of the second magnetic powder is desirably 239 Mpa or more. As with the first magnetic powder, the density and the magnetic permeability of the MC core can be improved by the high powder hardness.

  Since the second magnetic powder having an average particle diameter smaller than the first magnetic powder having the maximum average particle diameter may be included, the second magnetic powder is a magnetic powder having a different average particle diameter. May be included. That is, the second magnetic powder may be a magnetic powder whose average particle diameter can be defined as one, or a magnetic powder whose average particle diameter is defined as two or more. Further, the material, that is, the type of the first magnetic powder and the second magnetic powder may be the same or different. If different, the material may be three or more. When the magnetic powder is composed of three or more types of powder, the average particle size may be different for each type.

  As the first magnetic powder, a pulverized Fe-based amorphous powder, a powder produced by a water atomization method, a gas atomization method, or a water / gas atomization method can be used. In particular, a water atomization method is preferable. The reason is that the water atomization method rapidly cools during the atomization, so that the powder is hardly crystallized. As the second magnetic powder, a powder produced by a water atomizing method, a gas atomizing method, or a water / gas atomizing method can be used.

  The resin is mixed with the magnetic powder and holds the magnetic powder. When the magnetic powder is composed of powders having different average particle diameters, the respective powders are maintained in a state of being homogeneously mixed. As the resin, a thermosetting resin, an ultraviolet curable resin, or a thermoplastic resin can be used. As the thermosetting resin, a phenol resin, an epoxy resin, an unsaturated polyester resin, a polyurethane, a diallyl phthalate resin, a silicone resin and the like can be used. Urethane acrylate, epoxy acrylate, acrylate, and epoxy resins can be used as the ultraviolet curable resin. As the thermoplastic resin, it is preferable to use a resin having excellent heat resistance, such as polyimide or fluororesin. An epoxy resin that is cured by adding a curing agent is suitable for the present invention because its viscosity can be adjusted by the amount of the curing agent added and the like. Thermoplastic acrylic resins and silicone resins can also be used.

  It is preferable that the resin is contained in an amount of 3 to 5% by weight based on the magnetic powder. If the content of the resin is less than 3 wt%, the bonding strength of the magnetic powder becomes insufficient, and the mechanical strength of the core decreases. On the other hand, if the content of the resin is more than 5% by weight, the resin formed between the first magnetic powders enters, and the gap between the first magnetic powders cannot be filled with the second magnetic powder. , The magnetic permeability decreases.

  The viscosity of the resin is preferably 50 to 5000 mPa · s when mixed with the magnetic powder. When the viscosity is less than 50 mPa · s, the resin does not become entangled with the magnetic powder during mixing, the magnetic powder and the resin are easily separated in the container, and the density or strength of the core varies. If the viscosity exceeds 5,000 mPa · s, the viscosity becomes too high, for example, the resin formed between the first magnetic powders enters, and the gaps cannot be filled with the second magnetic powder, and the density of the core decreases. As a result, the magnetic permeability decreases.

As the resin, SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , BN, AlN, ZnO, TiO ₂ or the like can be used as a viscosity adjusting material. The average particle diameter of the filler as a viscosity adjusting material is preferably equal to or less than the average particle diameter of the second magnetic powder, and preferably equal to or less than 1/3 of the average particle diameter of the second magnetic powder. If the average particle diameter of the filler is large, the density of the obtained core decreases. Further, a high thermal conductivity material such as Al ₂ O ₃ , BN, or AlN can be added to the resin.

  The ratio of the apparent density of the core to the true density of the magnetic powder is preferably 76.6% or more and less than 82%. More preferably, it is 77% or more. When the ratio is 76.6% or more, the magnetic permeability can be maintained high even in a high magnetic field. Conversely, if the ratio is less than 76.6%, the magnetic permeability in a high magnetic field tends to decrease due to the low density. Further, if the same magnetic permeability characteristics are to be manufactured using a dust core, the ratio of the apparent density of the core to the true density of the magnetic powder reaches about 82% to 88%. This is because the outer shape is formed when the dust core is coated with a resin with a single powder and compacted with a very high pressure as described above. In the MC core, the magnetic powder is dispersed and mixed with the resin, and since the pressure is only increased to the extent that the internal air is released at a low pressure as described above, the resin is hardened without being compacted. . Therefore, the ratio of the apparent density of the MC core of the present embodiment to the true density of the magnetic powder is less than 82%.

  The surface of the MC core and the surface of the dust core of the present embodiment have the following differences. First, as described above, the dust core is manufactured by placing a soft magnetic powder coated with an insulating resin in a mold and performing a heat treatment such as annealing on a molded body that is pressure-molded with a very high pressure. For this reason, the surface of the dust core is relatively smooth. On the other hand, the MC core is formed into a predetermined shape by placing the composite magnetic powder mixed with the insulating resin as described above in a container having a predetermined shape and applying a relatively low pressure. For this reason, the surface of the MC core is rougher than the dust core. For example, the MC core has differences such as minute holes and irregularities which are not present in the dust core, and the surface roughness is coarser than the dust core.

  For the dust core, put the soft magnetic powder coated with the insulating resin into the area formed by the inner peripheral surface of the molding hole of the outer die and the upper surface of the lower die, compress the upper die, and then remove the upper die. Molding. At this time, since the soft magnetic powder coated with the insulating resin is pressurized at a high pressure in the mold, a force is applied to the mold when the formed dust core is taken out. Therefore, a sliding mark is formed on the surface of the dust core at a portion that slides on the inner peripheral surface of the mold at the time of removal. The sliding marks are a plurality of linear marks formed by moving while rubbing the surface of the mold. Since the MC core of this embodiment becomes a core by curing the resin in the mold, the core is not pressed against the mold, and its surface has no sliding marks. The surface having no sliding marks is the non-sliding surface. All surfaces of the MC core of the present embodiment are non-sliding surfaces.

  The coil is a conductive wire coated with an insulating coating, and a copper wire or an aluminum wire can be used as the wire material. The coil is formed or mounted by winding a conductive wire around at least a part of the core, and is disposed around at least a part of the core. The method of winding the coil and the shape of the wire are not particularly limited.

[1-2. Reactor manufacturing method]
A method for manufacturing a reactor according to the present embodiment will be described with reference to the drawings. As shown in FIG. 1, the reactor manufacturing method includes (1) a mixing step, (2) a molding step, (3) a pressing step, and (4) a curing step.

(1) Mixing Step The mixing step is a step of mixing the magnetic powder and the resin. The mixing step includes mixing the first magnetic powder and the second magnetic powder having an average particle diameter smaller than that of the first magnetic powder to form a magnetic powder; and mixing the magnetic powder with 3 to 5 wt% of the magnetic powder. A resin mixing step of adding a resin and mixing the magnetic powder and the resin.

  The mixing in each mixing step can be performed automatically or manually using a predetermined mixer. The mixing time in each mixing step can be appropriately set and is not particularly limited, but is, for example, 2 minutes.

  By such a mixing step, a mixture of a magnetic powder and a resin (hereinafter, also referred to as a composite magnetic material) can be obtained. In the mixing step, the magnetic powder and the resin may be filled in a container for molding the composite magnetic material in the molding step and mixed. Thus, there is no need to transfer the composite magnetic material to the container, and the number of manufacturing steps can be reduced.

(2) Molding Step The molding step is a step in which the composite magnetic powder is put into a container having a predetermined shape and molded into a predetermined shape. In the molding step, a coil may be put together with the composite magnetic powder and molded.

  Containers of various shapes are used according to the shape of the core to be manufactured. When inserting a coil, a box-shaped or dish-shaped container with an open top is used so that the coil can be inserted from above. The container used in the molding step can be used as it is as an outer case of the reactor for accommodating the core and the coil. If the container is used as an outer case, there is an advantage that it is not necessary to take out the container after the composite magnetic powder is cured. When the container is not used as the outer case, a plurality of reactors may be manufactured in one container. That is, a plurality of reactors may be manufactured by forming a plurality of recesses in the bottom of the container and placing the composite magnetic material and the coil in the recesses. By doing so, a single molding step is required for a plurality of reactors, so that manufacturing efficiency can be improved.

  The container used in the molding step may be entirely or partially made of a resin molded product. By making the container made of resin, the manufacturing cost can be reduced, and the advantage that the MC core can have any shape can be utilized. That is, since the resin is a relatively inexpensive material, the cost of manufacturing the container can be reduced, and a core having an arbitrary shape can be formed by injection molding or the like. As the material of the resin molded product, for example, unsaturated polyester resin, urethane resin, epoxy resin, BMC (bulk molding compound), PPS (polyphenylene sulfide), PBT (polybutylene terephthalate) and the like can be used.

  Further, all or a part of the container may be made of a metal having high thermal conductivity such as aluminum or magnesium. This is because the composite magnetic material can be easily warmed in the pressing step, as described later.

(3) Pressing Step The pressing step is a step of pressing the composite magnetic material with a pressing member during the molding step. By pressing the clay-like composite magnetic material placed in the container with a pressing member, the composite magnetic material is pushed out into the shape of the container and the voids contained in the composite magnetic material are reduced, increasing the apparent density Let it.

  When the coil is not put in the container, the composite magnetic material takes a shape inside the container by this step. That is, it is possible to obtain a molded body having a predetermined shape made of the composite magnetic material.

  When a coil is put in a container, as shown in FIG. 2, a composite magnetic material is put in a container, and the composite magnetic material is pushed and expanded in a container shape by a pressing member. Thereafter, the coil is inserted into the space created by pressing the composite magnetic material, the composite magnetic material is further filled, and the composite magnetic material is pressed together with the coil from above by a pressing member. Alternatively, the composite magnetic material may be put in a container, and then the coil may be embedded in the composite magnetic material including its inner and outer circumferences, and the composite magnetic material may be pressed together with the coil from above. As described above, by pressing the composite magnetic material together with the coil, voids contained in the composite magnetic material can be reduced, and the apparent density and the magnetic permeability can be improved. Note that the composite magnetic material alone may be pressed while avoiding the portion where the coil exists. As described above, a molded body of a composite magnetic material having a predetermined shape including a coil can be obtained by this step.

  In the pressing step, the composite magnetic material may be pressed by a pressing member to make the material into a container shape. In this case, the pressing step can be regarded as a pressing step and a molding step.

The pressure for pressing the composite magnetic material is preferably 1.6 kg / cm ² or more. With this pressure, the apparent density can be improved. However, it is more preferable that it is 6.3 kg / cm ² or more. If it is less than 6.3 kg / cm ² , the pressing pressure is small and the effect of improving the apparent density is small. Further, even if the value is not less than the value, it is preferable that the value is not more than 15.7 kg / cm ² . This is because, even if the pressing force exceeds this value, the effect of improving the apparent density is small. Also, if the pressure exceeds this value, only the resin is pressed, and the insulation between the magnetic powders is deteriorated.

  The time for pressing the composite magnetic material can be appropriately changed depending on the content and viscosity of the resin. For example, it can be set to 10 seconds.

  The pressing step may be performed at a temperature higher than the normal temperature (for example, 25 ° C.) of the pressing member for pressing the container or the composite magnetic material. By raising the temperature of the container or the pressing member, the resin is warmed and softened. Therefore, the composite magnetic material can easily flow into the gap in the container, and the moldability can be improved. In addition, the material can easily flow into the voids in the composite magnetic material, and the density can be improved. The temperature of the container or the pressing member that presses the composite magnetic material is preferably higher than the softening point of the resin contained in the composite magnetic material. This is because the resin can be effectively softened. The pressing step may be performed while maintaining the temperature of the container or the pressing member that presses the composite magnetic material.

  In the pressing step, in addition to increasing the temperature of the container or the pressing member, the composite magnetic material itself may be heated to press the composite magnetic material. The temperature of the container or the pressing member that presses the composite magnetic material may be maintained, and the composite magnetic material itself may be heated and pressed.

(4) Curing Step The curing step is a step of curing the resin in the molded body obtained in the molding step. When the resin in the molded body is cured by drying, the drying atmosphere may be an air atmosphere. The drying time can be appropriately changed according to the type, content, drying temperature, and the like of the resin, and can be, for example, 1 hour to 4 hours, but is not limited thereto. The drying temperature can be appropriately changed according to the type, content, drying time, and the like of the resin, and can be, for example, 85 ° C. to 150 ° C., but is not limited thereto. Note that the drying temperature is the temperature of the drying atmosphere.

  The curing of the resin is not limited to drying, and the curing method differs depending on the type of the resin. For example, if the resin is a thermosetting resin, the resin is cured by applying heat, and if the resin is an ultraviolet curable resin, the resin is cured by irradiating the molded body with ultraviolet rays.

  In the curing step, the step of curing the molded body at a predetermined temperature for a predetermined time may be repeated a plurality of times. Further, for example, when the resin is cured by drying, the drying temperature or the drying time may be changed each time the resin is repeated a plurality of times.

[1-3. Action / Effect]
(1) The MC core of the present embodiment is a core made of a magnetic powder and a resin, and the magnetic powder includes a first magnetic powder and a second magnetic powder having an average particle diameter smaller than that of the first magnetic powder, The first magnetic powder has a coercive force Hc = 0.70 A / cm or less and a circularity of 0.9 or more.

  Therefore, by using a soft magnetic powder having a high circularity and a high coercive force for the MC core, it is possible to realize a high core density, and thus to improve the magnetic characteristics of the MC core. Can be. In addition, by setting the coercive force of the first magnetic powder to be equal to or less than Hc = 0.70 A / cm, the hysteresis loop in the MC core can be reduced, the increase in hysteresis loss is suppressed, and the magnetic characteristics are reduced. It is possible to suppress the decrease.

There is also a type of core called a dust core manufactured by putting a soft magnetic powder coated with an insulating resin into a mold and press-molding it at a high pressure of 10 to ²⁰ t / cm ² . Since the dust core is pressure-formed at a pressure 1000 times higher than that of the MC core, the apparent density is generally high. In a reactor having a core having a high apparent density, a gap may be provided between the cores in order to maintain the magnetic permeability in a high magnetic field. The gap between the magnetic powders also plays the role of a gap, but the dust core has a small gap between the magnetic powders and has a weak function as a gap. On the other hand, in the MC core, the interval between the magnetic powders is sparser than that in the dust core, so that this interval plays a role of a gap, so that a high magnetic permeability can be obtained even in a high magnetic field without a split configuration. .

  The first magnetic powder may have a circularity of 0.9 or more and a powder hardness of 278 Mpa or more. Examples of such first magnetic powder include pulverized powder of Fe—Si—Al alloy powder (Sendust). By producing the MC core using a soft magnetic powder having a circularity of 0.9 or more and a powder hardness of 278 Mpa or more, the apparent density can be 89.34 or more. Thereby, it becomes possible to manufacture an MC core having a density and a magnetic permeability based on the apparent density, which is comparable to that of the dust core.

(2) Further, the first magnetic powder may have a coercive force Hc = 0.48 A / cm or less and a circularity of 0.92 or more. By setting the degree of circularity to 0.92 or more, a higher core density can be realized, so that the density and the magnetic permeability of the MC core can be improved. Further, by setting the coercive force to Hc = 0.48 A / cm or less, it is possible to suppress an increase in hysteresis loss and to suppress a decrease in magnetic characteristics.

  The first magnetic powder may have a circularity of 0.92 or more and a powder hardness of 278 Mpa or more. Examples of such a first magnetic powder include a gas atomized powder of an Fe—Si—Al alloy powder (Sendust). By manufacturing the MC core using a soft magnetic powder having a circularity of 0.9 or more and a powder hardness of 403 Mpa or more, the apparent density can be 91.67 or more. Thereby, it becomes possible to manufacture an MC core having a density and a magnetic permeability based on the apparent density, which is comparable to that of the dust core.

  In addition, since the core of the present embodiment is an MC core, the degree of freedom in shape is higher than that of a dust core, and a core having a desired shape can be easily manufactured without using a divided configuration. Since the gap can be eliminated by not using the split configuration, when the core of the present embodiment is configured as a reactor, the magnetic flux leakage to the coil can be reduced, and the copper loss is reduced, thereby suppressing the heat generation of the coil. be able to.

(3) The magnetic powder includes a first magnetic powder and a second magnetic powder having an average particle diameter smaller than that of the first magnetic powder, wherein the amount of the first magnetic powder added to the soft magnetic powder is 60 to 80 wt%, The amount of the second magnetic powder added to the powder is 40 to 20 wt%. By including the first magnetic powder and the second magnetic powder in the above ratio, the second magnetic powder having a small average particle diameter enters the gap between the first magnetic powders, thereby improving the density of the core and reducing iron loss. be able to.

(4) In the core of the present embodiment, the resin is 3 to 5% by weight based on the magnetic powder. Thereby, it is possible to obtain a core with improved productivity and density while obtaining the advantage of moldability. That is, since the amount of the resin is set to 3 to 5 wt%, the composite magnetic material becomes clay-like and easy to handle, so that the productivity can be improved.

(5) The entire surface of the core of the present embodiment is a non-sliding surface. For this reason, excellent magnetic properties as described above can be obtained despite the fact that it is not a dust core. In other words, the dust core causes the insulating coating covering the magnetic powder to be peeled off due to the sliding marks, so that the eddy current loss worsens. On the other hand, in the core of the present embodiment, since no sliding trace is generated, the loss is lower than that of the dust core.

(6) The method of manufacturing a core according to the present embodiment is a method of manufacturing a core including a magnetic powder and a resin, wherein the magnetic powder has a coercive force Hc = 0.70 A / cm or less and a powder hardness of 278 Mpa or more. A mixing step of mixing a resin with the first magnetic powder, the second magnetic powder having a smaller average particle diameter than the first magnetic powder, and mixing the mixture obtained in the mixing step in a predetermined container; And a curing step of curing the resin in the molded body obtained in the molding step.

  Thereby, a core with improved density and magnetic permeability can be obtained. Furthermore, by having the pressing step, the advantage of the moldability, which is the advantage of the MC core, that the shape of the composite magnetic material can be molded into a predetermined shape, can be secured, and the composite magnetic material is pressed. This makes it easier for the material to enter the voids contained in the composite magnetic material, thereby improving the apparent density and magnetic properties of the core.

[1-4. Example]
Examples of the present invention will be described below with reference to Tables 1 to 4 and FIG.
(Measurement item)
The measurement items are density, magnetic permeability, and iron loss Pcv. A reactor was manufactured by applying 40 turns of a copper wire having a diameter of 2.6 mm to the manufactured sample of each core. The shape of each core sample was a toroidal shape having an outer diameter of 35 mm, an inner diameter of 20 mm, and a height of 11 mm. The magnetic permeability and iron loss Pcv of the produced reactor were calculated under the following conditions.

<Density>
The density of the core is the apparent density. That is, the outer diameter, inner diameter, and height of the sample of each core were measured, and the volume (cm ³ ) of the sample was calculated from these values based on π × (outer diameter ² −inner diameter ² ) × height. Then, the mass of the sample was measured, and the density of the core was calculated by dividing the measured mass by the calculated volume.

<Permeability and iron loss>
The measurement conditions of the magnetic permeability and the iron loss Pcv were a frequency of 20 kHz and a maximum magnetic flux density Bm = 30 mT. The magnetic permeability was defined as the amplitude magnetic permeability when the maximum magnetic flux density Bm was set at the time of measuring the iron loss Pcv. The iron loss Pcv was calculated by using a BH analyzer (Iwatsu Keisoku Co., Ltd .: SY-8219) which is a magnetic measurement device. This calculation was performed by calculating a hysteresis loss coefficient and an eddy current loss coefficient from the frequency curve of the iron loss Pcv by the least square method using the following equations (1) to (3).

Pcv = Kh × f + Ke × f ² (1)
Phv = Kh × f (2)
Pev = Ke × f ² (3)
Pcv: Iron loss Kh: Hysteresis loss coefficient Ke: Eddy current loss coefficient f: Frequency Phv: Hysteresis loss Pev: Eddy current loss

In this example, the average particle diameter and circularity of each powder were obtained by taking the average value of 3000 particles using the following apparatus. The powder was dispersed on a glass substrate, and a powder photograph was taken with a microscope. It was measured automatically from the image every time.
Company name: Malvern
Apparatus name: morphology G3S
The specific surface area was measured by the BET method.

[1. First characteristic comparison (comparison by type of soft magnetic powder)]
In the first characteristic comparison, the types of the first magnetic powder and the second magnetic powder included in the soft magnetic powder are changed to compare the characteristics.

(Sample preparation method)
In this characteristic comparison, the cores of Examples 1 to 5 and Comparative Example 1 were produced by changing the types of the first magnetic powder and the second magnetic powder. In the production of the core, the powder shown in Table 1 was used as the first magnetic powder, and the powder shown in Table 2 was used as the second magnetic powder.

[Table 1]

[Table 2]

  Hereinafter, a method for manufacturing a core sample will be described in order.

  Samples of the cores of Examples 1 to 5 and Comparative Example 1 were prepared by combining the first magnetic powder and the second magnetic powder shown in Table 3, the addition ratio of the magnetic powder, the amount of the epoxy resin added, and the pressing pressure.

[Table 3]

(Production procedure)
In the mixing step, the first magnetic powder and the second magnetic powder of the types corresponding to Examples 1 to 5 and Comparative Example 1 were mixed at a weight ratio of 70:30 by a V-type mixer for 30 minutes to obtain a magnetic powder. Configured. Then, the magnetic powder was put in an aluminum cup, 4.0 wt% of an epoxy resin was added to the magnetic powder, and the mixture was manually mixed with a spatula for 2 minutes. Thus, a composite magnetic material which was a mixture of a magnetic powder and a resin was obtained.

Next, the composite magnetic material obtained in the mixing step is filled in a resin container having a toroidal space, and the composite magnetic material in the container is pressed using a hydraulic press at a press pressure of 6.3 kg / cm ^3. Pressing for 10 seconds produced a toroidal shaped molded body. During this pressing, the temperature of the container was kept at 25 ° C.

  The molded body obtained in the pressing step and the molding step is dried in the air at 85 ° C. for 2 hours, then at 120 ° C. for 1 hour, and further dried at 150 ° C. for 4 hours. A toroidal core was prepared.

[Table 4]

Table 4 shows the apparent densities, initial magnetic permeability μ ₀ , magnetic permeability μ _12k , iron loss Pcv (iron loss Pcv, hysteresis loss Phv, and eddy current loss Pev) of the fabricated MC cores of Examples 1 to 5 and Comparative Example 1. FIG. The magnetic permeability in Table 4 is the amplitude magnetic permeability, and was calculated from the inductance of the strength of each magnetic field at 20 kHz and 1.0 V by using the above-described impedance analyzer. “Μ ₀ ” in Table 1 indicates the initial magnetic permeability when no DC is superimposed, that is, when the magnetic field strength is 0 H (A / m). “Μ _12k ” in Table 1 indicates the magnetic permeability when the strength of the magnetic field is ₁₂ kHz (kA / m).

The graph of FIG. 3 was prepared based on Table 1. Figure 3 is a graph showing the permeability _{mu 12k} for core loss Pcv.

(Correlation between the coercive force and powder hardness of the first magnetic powder and the magnetic properties of the MC core)
As shown in Table 4 and FIG. 4, the MC core of Comparative Example 1 using the first magnetic powder having a coercive force of 1.83 A / cm has an iron loss Pcv of 22.9. On the other hand, in the MC cores of Examples 1 to 5 using the first magnetic powder having the coercive force Hc = 0.70 A / cm or less, the iron loss Pcv is 16.7 or less. This is because when the coercive force of the first magnetic powder is 1.83 A / cm or more, the hysteresis loss Phv increases due to the influence of the coercive force. Also, from Table 4, in Comparative Example 1, not only the hysteresis loss Phv but also the eddy current loss Pev is increased, and the iron loss Pcv is increased by increasing both the hysteresis loss and the current loss Pev. Recognize.

As described above, the circularity of the first magnetic powder has a great influence on the magnetic permeability (μ _12k ) at the time of superposition. As shown in Table 4, also in Example 2 using the first magnetic powder having a circularity of 0.90, the magnetic permeability (μ _12k ) was 15.2. This value is a sufficiently high magnetic permeability. Further, in Examples 1 and 3 to 5 in which the circularity is 0.92 or more, the magnetic permeability (μ _12k ) is 20.3 or more. Due to the difference in circularity of 0.02, the magnetic permeability (μ _12k ) differs by 5 or more. On the other hand, the difference in magnetic permeability (μ _12k ) between Example 1 (circularity 0.92) and Example 3 (circularity 0.94) having different circularities of 0.02 is 0.02. That is, in order to improve the magnetic permeability (μ _12k ) at the time of superimposition, the circularity of the first magnetic powder is preferably set to 0.90 or more, and by setting the circularity to 0.92 or more, the superposition is further improved. It is possible to improve the magnetic permeability (μ _12k ) at the time.

As described above, as shown in Example 2, by using the first magnetic powder having a coercive force of 0.70 A / cm or less and a circularity of 0.90 or more, excellent magnetic permeability (μ _12k ) at the time of superposition is obtained. An MC core having both low iron loss can be realized. Further, as shown in Examples 1 and 3 to 5, by setting the first magnetic powder to a coercive force of 0.48 A / cm or less and a circularity of 0.92 or more, excellent magnetic permeability during superposition (μ _{12 k} ) And low iron loss, and an MC core that realizes a further superior magnetic permeability (μ _12k ) during superposition can be realized.

(Correlation between the coercive force and powder hardness of the second magnetic powder and the magnetic properties of the MC core)
As shown in Table 3, in the combination of Example 1 and Example 5 and the combination of Example 3 and Example 4, the type of the first magnetic powder was the same in each set, but the type of the second magnetic powder was Different types. The second magnetic powder used in Example 4 and Example 5 had a coercive force Hc = 0.61 A / cm or less, and the second magnetic powder used in Example 1 and Example 3 had a coercive force Hc = 0.93 A / cm or less. It can be seen that even when a magnetic powder having a coercive force Hc = 0.93 A / cm or less is used as the second magnetic powder, the iron loss Pcv can be reduced to 16.7 or less.

That is, as shown in Example 1 and Example 3, when the coercive force Hc is 0.93 A / cm or less and the circularity is 0.98 or more, the second magnetic powder used for the MC core has excellent superposition during superposition. MC core having both a low magnetic permeability (μ _12k ) and a low core loss can be realized. Further, as shown in Example 4 and Example 5, by setting the coercive force of the second magnetic powder to 0.61 A / cm or less, the hysteresis loss can be further reduced, and excellent magnetic permeability during superposition is obtained. While realizing (μ _12k ), an MC core with lower iron loss can be realized.

[2. Second characteristic comparison (density ratio between apparent density of MC core and apparent density of dust core)]
This characteristic comparison was performed by using a magnetic powder of the same type as the first magnetic powder used in Example 4, Example 5, and Comparative Example 1 to fabricate a dust core based on conditions that increase the apparent density. The apparent densities of the dust cores and the MC cores of Comparative Example 1, Example 4, and Example 5 were compared.

  When comparing the apparent density of the MC core and the apparent density of the dust core, the condition of the magnetic powder of the dust core to be compared with the MC core was one of the conditions of the first magnetic powder used in Example 4, Example 5, and Comparative Example 1. Changed department. That is, instead of simply using the first magnetic powder having the same average particle diameter as the first magnetic powder used in Example 4, Example 5, and Comparative Example 1, a dust core having an optimum apparent density can be obtained. The average particle diameter of one magnetic powder was taken as the average particle diameter. In addition, the presence or absence of the second magnetic powder is an important factor in the production conditions of the dust core having the optimum apparent density, and therefore, from the viewpoint of producing the dust core having the optimum apparent density, Was appropriately determined.

  Dust cores to be compared with Comparative Example 1, Example 4, and Example 5 were produced under the following conditions.

Manufacturing method of dust core to be compared with Comparative Example 1 (1) 0.5 wt% of alumina powder was mixed with Fe-6.5Si alloy powder having an average particle diameter (D50) of 35 μm prepared by gas atomization method.
(2) To the Fe-6.5Si alloy powder in which the alumina powder was mixed, 0.5 wt% of a silicone oligomer was added and mixed, followed by heating and drying at 200 ° C. for 2 hours.
(3) 1.5 wt% of silicone resin was mixed with the dried powder, and heated and dried at 150 ° C. for 2 hours.
(4) A sieve with a mesh size of 250 μm was used for the purpose of breaking up the lump formed after heating and drying. Thereafter, 0.5 wt% of ethylene bis stearamide was mixed as a lubricant.
(5) A compact was produced from the Fe-6.5Si alloy powder on which the insulating film was formed by the above-described process, at a compaction pressure of 15 ton / cm ² .
(6) Finally, heat treatment was performed at a heat treatment temperature of 850 ° C. for 2 hours in a nitrogen atmosphere to produce a dust core.

-Method for manufacturing dust core to be compared with Example 4 (1) First amorphous powder having an average particle diameter (D50) of 35 μm prepared by a water gas atomizing method and an average particle diameter (D50) formed by a water atomizing method ) Was mixed with a second amorphous powder having a thickness of 5.0 μm at a ratio of 70:30. 1.3 wt% of low melting point glass and 0.3 wt% of lithium stearate as a lubricant were mixed with the mixed powder. Mixing is performed using a V-type mixer for 1 hour.
(2) 0.1 wt% of a silane coupling agent and 1.5 wt% of a silicone resin were mixed with the mixed powder, and heated and dried at 150 ° C. for 2 hours.
(3) For the purpose of crushing the lump formed after the heating and drying, the mixture was sieved through an opening of 250 μm. Thereafter, 0.3 wt% of lithium stearate was mixed as a lubricant.
(4) A molded body was produced from the mixed powder on which the insulating film was formed by the above process, at a molding pressure of 15 ton / cm ² .
(5) Finally, heat treatment was performed in the air at a heat treatment temperature of 420 ° C. for 2 hours to produce a dust core.

Production method of dust core to be compared with Example 5 (1) 0.3 wt% of a silane coupling agent with respect to an Fe-Si-Al alloy powder having an average particle diameter (D50) of 35 μm prepared by a gas atomization method, 1.0 wt% of a silicone oligomer was added and mixed, followed by heating and drying at 200 ° C. for 2 hours.
(2) 1.5 wt% of silicone resin was mixed with the dried powder, and further heated and dried at 150 ° C. for 2 hours.
(3) For the purpose of crushing the lump formed after the heating and drying, the mixture was sieved through an opening of 250 μm. Thereafter, 0.5 wt% of ethylene bis stearamide was mixed as a lubricant.
(4) A compact was produced from the Fe-Si-Al alloy powder on which the insulating coating was formed by the above-described process at a compaction pressure of 15 ton / cm ² .
(5) Finally, heat treatment was performed in the air at a heat treatment temperature of 700 ° C. for 2 hours to produce a dust core.

[Table 5]

  Table 5 shows the apparent density and the density ratio (apparent density / theoretical density) of the MC cores of Comparative Example 1, Example 4, and Example 5, and the dust cores to be compared with Comparative Example 1, Example 4, and Example 5. The ratio of the apparent density of the MC core to the apparent density is shown. Further, the graph of FIG. 4 was prepared based on Table 5. FIG. 4 is a graph showing the ratio of the apparent density of the MC core to the apparent density of the dust core with respect to the first powder hardness.

As shown in Table 5, the apparent density of the MC core of Comparative Example 1 having a powder hardness of 255 MPa was 5.91 g / cm ³ . The apparent density of the dust core to be compared in Comparative Example 1 is 6.65 g / cm ³ . When the ratio of the apparent density of the MC core to the apparent density of the dust core in Comparative Example 1 is calculated from these values, it is 88.87% (5.91 ÷ 6.65 × 100). Similarly, in Example 4 in which the powder hardness is 700 MPa, the ratio of the apparent density of the MC core to the apparent density of the dust core is 91.67%, and in Example 5 in which the powder hardness is 403 Mpa, The percentage of apparent density of the core is 89.34%.

  As shown in FIG. 4, there is a correlation between the powder hardness of the first magnetic powder and the ratio of the apparent density of the MC core to the apparent density of the dust core. When the powder hardness of the first magnetic powder increases, the apparent density of the dust core increases. The ratio of the apparent density of the MC core to the ratio increases. That is, when the powder hardness is improved, the apparent density of the MC core approaches the apparent density of the dust core manufactured based on the conditions so that the apparent density is increased. In particular, it is remarkable when the powder hardness is 403 Mpa or more. As described above, by using the first magnetic powder having a powder hardness of 403 Mpa or more, the apparent density of the MC core can be made closer to the apparent density of the dust core.

[3. Other Embodiments]
The present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying constituent elements in an implementation stage without departing from the scope of the invention. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Further, components of different embodiments may be appropriately combined.

  In the present invention, the step of manufacturing the MC core includes the pressing step, but may be omitted. Depending on the density, magnetic permeability, and iron loss Pcv that the MC core aims at, the MC core may be manufactured by a mixing step, a molding step, and a curing step.

Claims (12)

A composite magnetic material obtained by mixing a magnetic powder and a resin,
The magnetic powder includes a first magnetic powder and a second magnetic powder having a smaller average particle size than the first magnetic powder,
The composite magnetic material, wherein the first magnetic powder has a coercive force Hc of 0.70 A / cm or less and a circularity of 0.9 or more.   The composite magnetic material according to claim 1, wherein the first magnetic powder has a powder hardness of 278 Mpa or more.   The composite magnetic material according to claim 1, wherein the first magnetic powder has a coercive force Hc of 0.48 A / cm or less and a circularity of 0.92 or more.   The composite magnetic material according to claim 3, wherein the first magnetic powder has a powder hardness of 403 Mpa or more.   The composite magnetic material according to any one of claims 1 to 4, wherein the second magnetic powder has a coercive force Hc of 0.93 A / cm or less and a circularity of 0.98 or more.   The composite magnetic material according to claim 5, wherein the second magnetic powder has a powder hardness of 239 Mpa or more. An amount of the first magnetic powder added to the magnetic powder is 60 to 80 wt%,
The amount of the second magnetic powder to be added to the magnetic powder is 40 to 20 wt%;
The composite magnetic material according to any one of claims 1 to 6, wherein:   The composite magnetic material according to any one of claims 1 to 7, wherein a mixed amount of the resin is 3 to 5 wt% of the magnetic powder.   A metal composite core formed by forming the composite magnetic material according to claim 1.   The metal composite core according to claim 9, wherein the entire surface of the core is a non-sliding surface.   A reactor comprising the metal composite core according to claim 9 or 10 and a coil. A method for producing a core containing a magnetic powder and a resin,
The magnetic powder includes a first magnetic powder having a coercive force Hc = 0.70 A / cm or less and a circularity of 0.9 or more, and a second magnetic powder having a smaller average particle diameter than the first magnetic powder,
A mixing step of mixing a resin with the magnetic powder,
A molding step of molding the mixture obtained in the mixing step into a predetermined container,
A curing step of curing the resin in the molded body obtained in the molding step,
Having
A method for producing a metal composite core.

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