JP6858158B2 - Core, reactor, core manufacturing method and reactor manufacturing method - Google Patents

Description

The present invention relates to a core having a metal composite core composed of a magnetic powder and a resin, a reactor, a method for producing a core, and a method for producing a reactor.

Reactors are used in various applications such as office automation equipment, photovoltaic power generation systems, automobiles, and uninterruptible power supplies. The reactor is used, for example, in a filter for preventing the outflow of harmonic current to an output system, a voltage elevating converter for raising or lowering a voltage, or the like.

The reactor is required to have magnetic characteristics such as magnetic permeability, inductance value, and iron loss according to the application. For example, a reactor used in a converter for voltage raising and lowering is required to improve energy conversion efficiency, and thus is required to have a small iron loss, which is an energy loss.

There is also a demand for molding the core used for the reactor into an arbitrary shape in order to support various applications. As a reactor that meets such demands, there is one equipped with a type of core called a metal composite core. The metal composite core (hereinafter, also simply referred to as MC core) is a core formed by molding a material in which a metal magnetic powder and a resin are mixed into a predetermined shape and solidifying the material.

Japanese Unexamined Patent Publication No. 2012-33727

Since the material of the conventional MC core is in the form of a slurry and the material is molded by pouring the material into a container, the desired shape can be easily molded, and there is an advantage in moldability that there are few restrictions on the shape. However, the conventional MC core material has a high resin content in order to improve the fluidity in the container. For this reason, the proportion of the magnetic powder in the material is reduced, which leads to a decrease in the core density, and as a result, the magnetic characteristics are deteriorated.

On the other hand, there is also a type of core called a dust core (hereinafter, also referred to as a dust core) in which excellent magnetic characteristics can be obtained by obtaining a high magnetic permeability even when used in a high magnetic field. However, the dust core is 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.} For this reason, the manufacturing equipment including the mold becomes large and costly. Further, in order to mold the dust core, it is necessary to use a mold that can withstand high pressure. Therefore, the shape of the mold is limited, and the shape that can be molded is also limited. Further, since die cutting is required to mold the dust core, there are cases where a surface orthogonal to the die cutting direction cannot be formed, and the degree of freedom in shape is low.

In order to deal with this, it is conceivable to form a dust core having a desired shape by combining partial cores having a shape that is easy to mold depending on the mold. However, in the case of such a divided configuration, it is necessary to prepare various molds, mold each partial core with each mold, and further combine them, which causes a problem in cost and productivity. There is.

An object of the present invention is to provide a core, a reactor, a method for producing a core, and a method for producing a reactor, which can achieve both excellent moldability and magnetic properties.

In order to achieve the above object, the present invention presents a magnetic powder and a resin composed of Fe powder, Fe-Si alloy powder, Fe-Al alloy powder, Fe-Si-Al alloy powder, or a mixed powder of two or more of these powders. The magnetic powder comprises a first magnetic powder having an average particle diameter of 100 μm or more and 200 μm or less and a second magnetic powder having an average particle diameter of 3 μm or more and 10 μm or less. The amount of the first magnetic powder added to the powder is 60 to 80 wt%, the ratio of the apparent density of the core to the true density of the magnetic powder is 76.6% or more and less than 82%, and the initial magnetic permeability. Is 30 or more, the magnetic permeability of 12 kA / m is 24 or more, and the amount of resin is 3 to 5 wt% with respect to the magnetic powder.

Ratio of the apparent density of the core relative to the true density before Symbol magnetic powder, it may be 77% or more.

The circularity of the first magnetic powder may be 0.93 or more. The entire surface of the core may be a non-sliding surface. A reactor provided with the core and a coil is also an aspect of the present invention.

Further, the method for producing the core of the present invention is a magnetic powder and a resin composed of Fe powder, Fe-Si alloy powder, Fe-Al alloy powder, Fe-Si-Al alloy powder, or a mixed powder of two or more of these powders. The magnetic powder contains a first magnetic powder having an average particle diameter of 100 μm or more and 200 μm or less and a second magnetic powder having an average particle diameter of 3 μm or more and 10 μm or less. Obtained in the mixing step and the mixing step of mixing so that the addition amount of the first magnetic powder to the magnetic powder is 60 to 80 wt% and the content of the resin to the magnetic powder is 3 to 5 wt%. Clay so that the ratio of the apparent density of the core to the true density of the magnetic powder during the molding step of placing the mixture in a predetermined container and molding is 76.6% or more and less than 82%. The pressurizing step includes a pressurizing step of pressing the mixed powder with a pressing member and a curing step of curing the resin in the molded body obtained in the molding step. is 1.6 kg / cm ² or more 15.7 kg / cm ² or less.

Na us, a core manufactured by the method of the core, the manufacturing method of the reactor and a coil mounted on the core is also an aspect of the present invention.

According to the present invention, it is possible to provide a core, a reactor, a method for producing a core, and a method for producing a reactor, which are easy to mold and can obtain excellent magnetic properties.

It is a flowchart for demonstrating the manufacturing method of the reactor which concerns on embodiment. It is a figure for demonstrating the molding process and the pressurizing process. It is a graph of the theoretical density with respect to the surface pressure of Examples 1 to 4 and Comparative Example 1. It is an SEM photograph (100 times) of the core cross section of Example 3. It is an SEM photograph (100 times) of the core cross section of Comparative Example 1. It is a graph of the magnetic permeability with respect to the surface pressure of Examples 1 to 4 and Comparative Example 1. It is a graph of the iron loss with respect to the surface pressure of Examples 1 to 4 and Comparative Example 1. It is a graph of the magnetic permeability with respect to the resin amount of Examples 5-9 and Comparative Examples 2-4. It is a graph of the iron loss with respect to the resin amount of Examples 5-9 and Comparative Examples 2-4. It is a graph of the magnetic permeability with respect to the surface pressure of Examples 10 to 13. It is a graph of iron loss with respect to the surface pressure of Examples 10-13. It is a graph of the magnetic permeability with respect to the addition amount of the 2nd magnetic powder of Examples 2, 14, 15 and Comparative Examples 5 to 7. It is a graph of the density with respect to the addition amount of the 2nd magnetic powder of Examples 2, 14, 15 and Comparative Examples 5 to 7. It is an SEM photograph (100 times) of the core cross section corresponding to this embodiment. It is an SEM photograph (1000 times) of the cross section of a dust core. It is a graph of the inductance with respect to the DC exciting current of the reactor of Examples 16 and 17 and Comparative Example 8.

[1. Embodiment]
[1-1. Constitution]
The reactor of this embodiment includes a core and a coil. The core is a metal composite core (hereinafter, also referred to as MC core) composed of a magnetic powder and a resin. A clay-like mixture of magnetic powder and resin is filled in a predetermined container and pressed to form a core into a predetermined shape. The shape of the core can be various, for example, a toroidal core, an I-type core, a U-type core, a θ-type core, an E-type core, an EER-type core, and the like.

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 20 μm to 150 μm. In the present specification, the "average particle size" refers to D50, that is, the median diameter, unless otherwise specified.

The magnetic powder is composed of magnetic powders having different average particle sizes. That is, the magnetic powder includes a first magnetic powder and a second magnetic powder having an average particle size smaller than that of the first magnetic powder. 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, the weight ratio thereof may be the first magnetic powder: the second magnetic powder = 80:20 to 60:40. preferable. Within this range, the density can be improved, the magnetic permeability can be improved, and the iron loss can be reduced.

The average particle size of the first magnetic powder is preferably 100 μm to 200 μm. The second magnetic powder is preferably 3 μm to 10 μm. This is because the second magnetic powder having a small average particle size enters the gap between the first magnetic powders, and the density and magnetic permeability can be improved and the iron loss can be reduced. The core of the present embodiment has an initial magnetic permeability of 30 or more and a magnetic permeability of 12 kA / m of 24 or more.

The first magnetic powder and the second magnetic powder are preferably spherical. The circularity of the first magnetic powder is preferably 0.93 or more, and the circularity of the second magnetic powder is preferably 0.95 or more. This is because the gap between the first magnetic powders is reduced, and a large amount of the second magnetic powder can easily enter the gap, so that the density and the magnetic permeability can be improved. In the case of the MC core, the pressure applied in the pressurizing step is several kg / cm ² to several tens of kg / cm ² , and the dust core (hereinafter referred to as “dust magnetic core”) requiring several t / cm ² to several tens of t / cm ^2. Since it is very small, about 1/1000, as compared with (also called a dust core), 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, the circularity of such a magnetic powder cannot be obtained.

Since it is sufficient that the first magnetic powder having the largest average particle size contains the second magnetic powder having a smaller average particle size than the first magnetic powder, the second magnetic powder has an average particle size. It may contain different magnetic powders. That is, the second magnetic powder may be a magnetic powder whose average particle size can be defined as one, or may be a magnetic powder whose average particle size is specified by two or more. Further, the materials of the first magnetic powder and the second magnetic powder, that is, the types may be the same or different. If they are different, there may be three or more. When the magnetic powder is composed of three or more kinds of powders, the average particle size may be different for each kind.

As the first magnetic powder, it is preferable to use a pulverized portion. As the second magnetic powder, those produced by a water atomizing method, a gas atomizing method, or a water / gas atomizing method can be used, but those produced by the water atomizing method are particularly preferable. The reason is that the water atomization method rapidly cools the powder during atomization, so that the powder is difficult to crystallize.

The resin is mixed with the magnetic powder and retains the magnetic powder. When the magnetic powder is composed of powders having different average particle diameters, each powder is held in a homogeneously mixed state. As the resin, a thermosetting resin, an ultraviolet curable resin, or a thermoplastic resin can be used. As the thermosetting resin, phenol resin, epoxy resin, unsaturated polyester resin, polyurethane, diallyl phthalate resin, silicone resin and the like can be used. As the ultraviolet curable resin, urethane acrylate-based, epoxy acrylate-based, acrylate-based, and epoxy-based resins can be used. As the thermoplastic resin, it is preferable to use a resin having excellent heat resistance such as polyimide or fluororesin. The 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 or the like. Thermoplastic acrylic resin and silicone resin can also be used.

The resin is preferably contained in an amount of 3 to 5 wt% with respect to the magnetic powder. If the resin content is less than 3 wt%, the bonding force of the magnetic powder is insufficient and the mechanical strength of the core is lowered. Further, if the content of the resin is more than 5 wt%, the resin formed between the first magnetic powders enters, and the second magnetic powder cannot fill the gaps, so that the density of the core decreases. 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 get 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 5000 mPa · s, the viscosity becomes too high, for example, the resin formed between the first magnetic powders enters and the gaps cannot be filled by the second magnetic powders. Decreases, and the magnetic permeability decreases.

As the resin, SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , BN, AlN, ZnO, TiO _{2 and the} like can be used as the viscosity adjusting material. The average particle size of the filler as the viscosity adjusting material is preferably 1/3 or less of the average particle size of the second magnetic powder, preferably 1/3 or less of the average particle size of the second magnetic powder. This is because if the average particle size 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, and Al N 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%. It is more preferably 77% or more. When the ratio is 76.6% or more, the magnetic permeability can be maintained high even in a high magnetic field. On the contrary, when the ratio is less than 76.6%, the magnetic permeability in a high magnetic field tends to decrease due to the low density. Further, when trying to create the same magnetic permeability characteristics with 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 of the dust core is formed when the powder itself is coated with a resin and compacted with a very high pressure as described above. In the MC core, the magnetic powder is dispersed and mixed in the resin, and as described above, the MC core is only pressurized to the extent that the air inside is evacuated, so that the resin hardens without compaction. There is. 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, the dust core is produced by putting a soft magnetic powder coated with an insulating resin into a mold and performing a heat treatment such as annealing on a molded body pressure-molded at a very high pressure as described above. Therefore, the surface of the dust core is relatively smooth. On the other hand, the MC core is molded into a predetermined shape by putting a composite magnetic powder mixed with an insulating resin as described above into a container having a predetermined shape and applying a relatively low pressure. Therefore, the surface of the MC core is rougher than that of the dust core. For example, the MC core has minute holes and irregularities that the dust core does not have, and the surface roughness is rougher than that of the dust core.

For the dust core, soft magnetic powder coated with an insulating resin is put into the region formed by the inner peripheral surface of the molding hole of the outer mold and the upper surface of the lower mold, compressed by the upper mold, and then removed from the upper mold. Molded by. 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, on the surface of the dust core, sliding marks are formed on the portion that slides with respect to the inner peripheral surface of the mold at the time of taking out. The sliding marks are a plurality of linear marks formed by moving while rubbing the surface of the mold. Since the MC core of the present 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. In the MC core of this embodiment, all surfaces are non-sliding surfaces.

The coil is a conducting wire 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 wire around at least a part of the core, and is arranged around at least a part of the core. The winding method of the coil and the shape of the wire are not particularly limited.

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

(1) Mixing step The mixing step is a step of mixing the magnetic powder and the resin. When the magnetic powder is composed of two kinds of magnetic powders having different average particle diameters, the mixing step involves the first magnetic powder and the second magnetic powder having an average particle diameter smaller than that of the first magnetic powder. It has a magnetic powder mixing step of mixing the two to form a magnetic powder, and a resin mixing step of adding 3 to 5 wt% of the resin to the magnetic powder and mixing the magnetic powder and the resin.

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

By such a mixing step, a mixture of the magnetic powder and the 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. As a result, it is not necessary to transfer the composite magnetic material to the container, and the manufacturing man-hours can be reduced.

(2) Molding step The molding step is a step of putting the composite magnetic powder into a container having a predetermined shape and molding the composite magnetic powder into a predetermined shape. In the molding step, a coil may be inserted together with the composite magnetic powder for molding.

As the container, various shapes are used according to the shape of the core to be manufactured. When inserting the coil, use a box-shaped or dish-shaped container with an open top so that the coil can be inserted from above. The container used in the molding process can also be used as it is as an outer case of the reactor that houses 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 an 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 at the bottom of the container and inserting a composite magnetic material and a coil into the recesses. By doing so, it is possible to improve the manufacturing efficiency because only one molding step is required for a plurality of reactors.

The container used in the molding process may be entirely or partially made of a resin molded product. By making the container made of resin, it is possible to reduce the manufacturing cost and take advantage of the fact that the MC core can have an arbitrary shape. That is, since the resin is a relatively inexpensive material, the cost of manufacturing the container can be suppressed, 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 and magnesium. This is because, as will be described later, it becomes easier to heat the composite magnetic material in the pressurizing step.

(3) Pressurization step The pressurization step is a step of pressing the composite magnetic material with a pressing member during the molding process. By pressing the clay-like composite magnetic material placed in the container with a pressing member, the composite magnetic material is expanded into the shape of the container, and the voids contained in the composite magnetic material are reduced, resulting in apparent density and permeability. Improve magnetic coefficient.

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

When the coil is put in the container, as shown in FIG. 2, the composite magnetic material is put in the container, and the composite magnetic material is spread in the shape of the container by the pressing member. After that, 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 the pressing member. Alternatively, the composite magnetic material may be placed in a container, and then the coil may be embedded in the composite magnetic material including the inner and outer circumferences thereof, and the composite magnetic material may be pressed together with the coil from above. By pressing the composite magnetic material together with the coil in this way, the voids contained in the composite magnetic material can be reduced, and the apparent density and the magnetic permeability can be improved. It should be noted that the portion where the coil exists may be avoided and only the composite magnetic material may be pressed. In this way, a molded body of a composite magnetic material having a predetermined shape including a coil can be obtained by the step.

As described above, in the pressurizing step, the composite magnetic material may be pressed by the pressing member to form the shape of the container. In this case, the pressurizing step can be regarded as a pressurizing 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 initial magnetic permeability can be 30 or more, and the magnetic permeability of 12 kA / m can be 24 or more. However, it is more preferably 6.3 kg / cm ^{2 or more.} This is because 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. Moreover, even if it is more than the said value, it is preferable that it is ^{15.7 kg / cm 2 or less.} This is because even if the pressure exceeds this value, the effect of improving the apparent density is small. Further, if the pressure exceeds this value, only the resin is pressed and the insulating property between the magnetic powders deteriorates.

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 10 seconds.

The pressurizing step may be performed at a temperature higher than room temperature (for example, 25 ° C.) of the pressing member that presses the container or the composite magnetic material. By raising the temperature of the container or pressing member, the resin is warmed and softened. Therefore, the composite magnetic material can easily flow into the gaps in the container to improve the moldability, and the material can easily flow into the voids in the composite magnetic material to improve the density. The temperature of the pressing member that presses the container or 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 pressurizing step may be performed while maintaining the temperature of the pressing member that presses the container or the composite magnetic material.

Further, in the pressurizing step, the temperature of the container or the pressing member may be raised, or the composite magnetic material itself may be warmed to press the composite magnetic material. The temperature of the pressing member that presses the container or the composite magnetic material may be maintained, and the composite magnetic material itself may be warmed 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 can be an air atmosphere. The drying time can be appropriately changed according to the type, content, drying temperature, etc. 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, etc. of the resin, and can be, for example, 85 ° C. to 150 ° C., but is not limited thereto. The drying temperature is the temperature of the drying atmosphere.

Further, the curing of the resin is not limited to drying, and the curing method differs depending on the type of 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 molded body is irradiated with ultraviolet rays to cure the resin.

As the curing step, the step of curing the molded product 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 different each time the resin is repeated a plurality of times.

[1-3. Action / effect]
(1) The core of the present embodiment is a core composed of a magnetic powder and a resin, and the magnetic powder is a first magnetic powder and a second magnetic powder having an average particle diameter smaller than that of the first magnetic powder. The amount of the first magnetic powder added to the magnetic powder is 60 to 80 wt%, and the ratio of the apparent density of the core to the true density of the magnetic powder is 76.6% or more and less than 82%. The magnetic permeability is 30 or more, and the magnetic permeability of 12 kA / m is 24 or more.

Therefore, both excellent moldability and magnetic properties can be achieved at the same time. That is, since the core of the present embodiment is an MC core, the degree of freedom in shape is higher than that of the dust core, and a core having a desired shape can be easily created without a divided configuration. Since the gap can be eliminated by not using the divided configuration, when the core of the present embodiment is configured as a reactor, the leakage flux to the coil can be reduced and the copper loss is reduced, thereby suppressing the heat generation of the coil. be able to. In addition, it is possible to obtain a magnetic permeability comparable to that of a dust core in a high magnetic field. That is, since the existence of the gap contributes to maintaining the magnetic permeability in a high magnetic field, the dust core may intentionally generate a gap as a divided configuration. The distance between the magnetic powders also plays a role of a gap, but the dust core has a gap as a divided structure because the distance between the magnetic powders is close and the function as a gap is weak. On the other hand, since the distance between the magnetic powders in the MC core is sparser than that in the dust core, this distance acts as a gap, so that high magnetic permeability can be obtained even in a high magnetic field without forming a divided structure. .. Further, since the core of the present embodiment can be molded at low pressure, the manufacturing equipment can be miniaturized and the cost can be reduced.

(2) The core of the present embodiment contains 3 to 5 wt% of resin with respect to the magnetic powder. As a result, it is possible to obtain a core with improved productivity and density while obtaining the advantage of moldability. That is, since the amount of resin is set to 3 to 5 wt%, the composite magnetic material becomes clay-like and easy to handle, and productivity can be improved.

(3) In the core of the present embodiment, the ratio of the apparent density of the core to the true density of the magnetic powder is 77% or more. Therefore, even more excellent magnetic permeability can be obtained.

(4) The entire surface of the core of the present embodiment is a non-sliding surface. Therefore, although it is not a dust core, the above-mentioned excellent magnetic characteristics can be obtained. That is, since the insulating film covering the magnetic powder of the dust core is peeled off due to the sliding marks, the eddy current loss is exacerbated. On the other hand, the core of the present embodiment has a lower loss than the dust core because no sliding marks are generated.

(5) In the core of the present embodiment, the circularity of the first magnetic powder is 0.93 or more. Therefore, although it is not a dust core, the above-mentioned excellent magnetic characteristics can be obtained. That is, the dust core is deformed by the magnetic powder due to pressurization, so that the hysteresis loss becomes large. On the other hand, in the core of the present embodiment, the magnetic powder is not deformed by pressurization, so that hysteresis loss can be suppressed. The dust core needs to be annealed after pressure molding in order to reduce the deterioration of hysteresis loss. On the other hand, the core of the present embodiment does not require annealing because there is no deterioration in hysteresis loss.

(6) The method for producing a core of the present embodiment is a method for producing a core containing a magnetic powder and a resin, and the magnetic powder is a first magnetic powder and a first magnetic powder having an average particle diameter smaller than that of the first magnetic powder. The amount of the first magnetic powder added to the magnetic powder is 60 to 80 wt%, and the mixing step of mixing the resin with the magnetic powder and the mixture obtained in the mixing step are placed in a predetermined container. A molding step of molding by putting in the powder, and a pressurizing step of pressing the mixture so that the ratio of the apparent density of the core to the true density of the magnetic powder is 76.6% or more and less than 82% during the molding step. It has a curing step of curing the resin in the molded body obtained in the molding step.

As a result, it is possible to obtain a core with improved productivity and density while obtaining the advantage of moldability. By having the pressurizing step, it is possible to secure the advantage of moldability, which is the advantage of the MC core that the shape of the composite magnetic material can be molded into a predetermined shape, and by pressing the composite magnetic material. , The material can easily enter the voids contained in the composite magnetic material, and the apparent density and magnetic properties of the core can be improved.

(7) In the pressurizing step, the pressure for pressing the mixture was set to 1.6 kg / cm ² or more. This makes it possible to improve the magnetic characteristics of the core even though it is an MC core.

[1-4. Example]
Examples of the present invention will be described below with reference to Tables 1 to 3 and FIGS. 3 to 9.
(1) Measurement items The measurement items are density, magnetic permeability and iron loss. A reactor was prepared by winding 40 turns of a copper wire having a diameter of 2.6 mm for each core sample produced. The shape of the sample of each core was a toroidal shape having an outer diameter of 35 mm, an inner diameter of 20 mm, and a height of 11 mm. In addition, the magnetic permeability and iron loss of the prepared reactor were calculated under the following conditions.

<Density>
The core density 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 measured mass was divided by the calculated volume to calculate the core density.

<Permeability and iron loss>
The measurement conditions for magnetic permeability and iron loss were a frequency of 20 kHz and a maximum magnetic flux density of Bm = 30 mT. The magnetic permeability was taken as the amplitude magnetic permeability when the maximum magnetic flux density Bm was set at the time of iron loss Pcv measurement. The iron loss was calculated using a BH analyzer (Iwatsu Measurement Co., Ltd .: SY-8232), which is a magnetic measuring instrument. This calculation was performed by calculating the hysteresis loss coefficient and the eddy current loss coefficient by the least squares method using the following equations (1) to (3) for the frequency curve of iron loss.

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 embodiment, the average particle size and circularity of each powder are obtained by taking the average value of 3000 pieces using the following apparatus, the powder is dispersed on a glass substrate, and one powder photograph is taken with a microscope. It was automatically measured from the image every time.
Company name: Malvern
Device name: morphology G3S
The specific surface area was measured by the BET method.

(2) Sample preparation method The core sample was prepared from the viewpoints of (a) the press surface pressure in the pressurizing step, (b) the amount of resin, and (c) the temperature of the container. These production methods and their results are shown below in order.

(a) Press surface pressure in the pressurizing step First, as a mixing step, Fe-6.5% Si alloy powder (circularity 0.943) having an average particle size of 123 μm and Fe-6 having an average particle size of 5.1 μm. A 5% Si alloy powder (circularity 0.908) was mixed at a weight ratio of 70:30 in a V-type mixer for 30 minutes to form a magnetic powder. Then, the magnetic powder was placed in an aluminum cup, 3.5 wt% epoxy resin was added to the magnetic powder, and the mixture was manually mixed with a spatula for 2 minutes. As a result, a composite magnetic material which is a mixture of magnetic powder and resin was obtained.

Next, the composite magnetic material obtained in the mixing step is filled in a resin container having a toroidal-shaped space, and the composite magnetic material in the container is pressed with the press pressure shown in Table 1 for 10 seconds using a hydraulic press. , A toroidal shaped molded body was produced. During this pressing, the temperature of the container was kept at 25 ° C.

The molded product thus obtained in the pressurization step and the molding step was 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 to prepare a sample. Toroidal core was produced.

Tables 1 and 3 to 7 show the results of core density, magnetic permeability, and iron loss in Examples 1 to 4 and Comparative Example 1 obtained at each press pressure. In Examples 1 to 4, the press pressure was 100N, 400N, 600N, 1000N, and in Comparative Example 1, there was no press. The pressed surfaces are the same.

The "theoretical density" in Table 1 is a ratio calculated by the apparent density of the core / the true density of the magnetic powder. Here, both the first magnetic powder and the second magnetic powder use Fe-6.5% Si alloy powder, and the theoretical density is calculated ^{assuming that the true density is 7.63 g / cm 3.} ..

FIG. 3 is a graph of the theoretical density with respect to the surface pressure of Examples 1 to 4 and Comparative Example 1. As shown in Table 1 and FIG. 3, the theoretical density with respect to the surface pressure of Examples 1 to 4 is higher in Examples 1 to 4 in which the pressurizing step is performed than in Comparative Example 1 in which the pressurizing step is not performed. It can be seen that the surface pressure tends to increase as the surface pressure increases. In Example 1 where the surface pressure is 1.6 kg / cm ² , the theoretical density is 76.62%, which is small from the theoretical density of 76.47% in Comparative Example 1 without pressurization. However, in Example 1, as will be described later, the magnetic permeability can be increased. In Examples 2 to 4 having a surface pressure of 6.3 kg / cm ² or more, the theoretical density is 77.5% or more, which is higher than that of Comparative Example 1 and Example 1. That is, it can be seen that when the surface pressure is 6.3 kg / cm ² or more, the density is improved by spreading the material to the voids contained in the composite magnetic material and every corner of the container. Further, it can be seen that the theoretical density is almost constant when the surface pressure is 6.3 kg / cm ^{2 or more.}

FIG. 4 is an SEM photograph (100 times) of the core cross section of Example 3. FIG. 5 is an SEM photograph (100 times) of the core cross section of Comparative Example 1. In FIGS. 4 and 5, reference numeral 1 indicates a first magnetic powder, and reference numeral 2 indicates a second magnetic powder. Reference numeral 3 indicates a resin, and reference numeral 4 indicates a void. The void 4 is a portion represented by dark black in the SEM photograph, whereas the portion represented by relatively light black is the resin 3. As is clear from FIGS. 4 and 5, in Example 3 shown in FIG. 4, the number of voids 4 in the composite magnetic material is smaller than that in Comparative Example 1 shown in FIG. 5, and the size of the voids 4 itself is also large. You can see that it can be made smaller.

The magnetic permeability is an amplitude magnetic permeability, which was calculated from the inductance of the strength of each magnetic field at 20 kHz and 1.0 V by using the impedance analyzer described above. “Μ0” in Table 1 indicates the initial magnetic permeability in a state where direct current is not superimposed, that is, when the strength of the magnetic field is 0H (A / m). “Μ12000” in Table 1 indicates the magnetic permeability when the strength of the magnetic field is 12 kHz (kA / m).

FIG. 6 is a graph of magnetic permeability with respect to the surface pressure of Examples 1 to 4 and Comparative Example 1. As shown in Table 1 and FIG. 6, it can be seen that the magnetic permeability of Examples 1 to 4 under pressure is higher than that of Comparative Example 1 without pressurization. For example, it can be seen that the initial magnetic permeability μ0 of Example 2 is increased by about 8.7% as compared with Comparative Example 1. Even in Example 1 in which pressurization is applied, the magnetic permeability is higher than that in Comparative Example 1 in which no pressurization is performed. However, the contribution to the increase in core density is relatively small. That is, as described above, the theoretical density of Example 1 is 76.62%, which is small from the theoretical density of 76.47% of Comparative Example 1 without pressurization. Therefore, from the common general knowledge that the density is related to the magnetic permeability, it is assumed that the magnetic permeability cannot be dramatically improved by the difference in the theoretical density between Comparative Example 1 and Example 1. However, in Example 1, the present inventors have an initial magnetic permeability of 33.0 and μ12000 of 24.4. Therefore, in Comparative Example 1, the initial magnetic permeability of μ0 is 31.1 and μ12000 is 23.5. We have found that the magnetic permeability can be dramatically improved compared to some cases. That is, when paying attention to the magnetic permeability, setting the theoretical density to 76.6% or more has a critical significance.

FIG. 7 is a graph of iron loss with respect to the surface pressure of Examples 1 to 4 and Comparative Example 1. As shown in Table 1 and FIG. 7, it can be seen that the iron loss is lower in the pressurized Examples 1 to 4 than in the non-pressurized Comparative Example 1. In particular, it can be seen that the hysteresis loss (Phv) tends to decrease by increasing the surface pressure. It can be seen that even in Example 1 in which pressurization is applied, the iron loss is reduced as compared with Comparative Example 1 in which no pressurization is performed, but in Examples 2 to 4, the iron loss is further reduced.

When the surface pressure is 6.3 kg / cm ² or more, both the magnetic permeability and the iron loss become almost constant, and it can be seen that the effect of pressurization on the magnetic characteristics tends to be saturated. In other words, it can be seen that the effect of improving the magnetic permeability and reducing the iron loss can be obtained by having the pressurizing step in the range of the surface pressure in the range of 1.6 to 15.7 kg / cm ^2. Further, it can be seen that when the value is 6.3 kg / cm ² or more, it greatly contributes to the increase in density and the iron loss reduction effect is high.

(b) Amount of resin A core sample (Examples 5 to 9 and Comparative Examples 2 to 4) was prepared in the same procedure as in Example 3 under the conditions shown in Table 2 for the amount of resin in Example 3. Table 2, FIGS. 8 and 9 show the results of the density, magnetic permeability, and iron loss of Examples 5 to 9 and Comparative Examples 2 to 4. Note that μ0 and μ12000 in Table 2 have the same meanings as those in Table 1.

FIG. 8 is a graph of magnetic permeability with respect to the amount of resin of Examples 5 to 9 and Comparative Examples 2 to 4. FIG. 9 is a graph of iron loss with respect to the amount of resin of Examples 5 to 9 and Comparative Examples 2 to 4. As shown in Table 2 and FIGS. 8 and 9, when the amount of resin is less than 3 wt% with respect to the composite magnetic material, the number of voids contained in the core increases and the density decreases. As a result, it causes a decrease in magnetic permeability and an increase in hysteresis loss. Further, when the amount of resin is less than 3 wt%, the magnetic powders are likely to come into point contact with each other, which causes an increase in eddy current loss. On the other hand, when the amount of resin is more than 5 wt% with respect to the composite magnetic material, the decrease in density becomes remarkable. As a result, the hysteresis loss increases.

(c) Container temperature Core samples were prepared at different container temperatures. As described in (a) above, in Examples 1 to 4 and Comparative Example 1, the temperature of the container was set to 25 ° C. Further, the samples obtained by setting the temperature of the container to 70 ° C. and performing the same steps as in the above step (a) except for the temperature of the container were designated as Examples 10 to 13. Table 3, FIG. 10, and FIG. 11 show the results of the density, magnetic permeability, and iron loss of Examples 1 to 4, 10 to 13 and Comparative Example 1. The theoretical densities, μ0 and μ12000 in Table 3 have the same meanings as those in Table 1.

FIG. 10 is a graph of magnetic permeability with respect to the surface pressure of Examples 10 to 13. FIG. 11 is a graph of iron loss with respect to the surface pressure of Examples 10 to 13. As shown in Table 3 and FIGS. 6, 7, 10 and 11, the densities of Examples 10 to 13 in which the temperature of the container was 70 ° C. were higher than those of Examples 1 to 4 in which the temperature of the container was 25 ° C. It can be seen that the theoretical density tends to increase and the iron loss tends to decrease. It was found that the magnetic permeability increased or decreased depending on the surface pressure.

Further, even when the temperature of the container was set to 70 ° C. and the temperature was raised, the theoretical density of Examples 11 to 13 was 77.9% or more, which was higher than that of Example 10 by increasing the surface pressure. I understand. By warming the container above room temperature (25 ° C.) in this way, the resin in the composite magnetic material becomes soft, and the material easily flows into the voids in the material, thereby improving the apparent density and the theoretical density. Is expected to improve. As a result, it was found that the effect of reducing iron loss can be obtained.

(d) Measurement of resin viscosity The viscosity of the resin used in this example will be described. The viscosity of the resin used in this example was determined by measuring the depth of subduction of the weight placed on the composite magnetic material as follows.

That is, first, the amount of the resin added was set to the conditions shown in Table 4, and a composite magnetic material was produced in the same manner as in the mixing step of (a) above. Next, the obtained composite magnetic material was put into an aluminum container having a diameter of 5 mm so as to have a thickness of 3 mm, and a JIS standard 10 g weight was placed in the center on the composite magnetic material. Then, 10 seconds after the weight was placed, the weight was removed, and the depth of the dent of the composite magnetic material formed by the weight of the weight was measured. The results are shown in Table 4.

As shown in Table 4, it can be seen that the greater the amount of the resin added, the deeper the depth of the dent, the lower the viscosity of the composite magnetic material, and the easier it is for the weight to sink.

(e) Resin blending ratio The core sample (Examples 14 and 15) was prepared in the same procedure as in Example 2 under the conditions shown in Table 5 for the blending ratio of the first magnetic powder and the second magnetic powder in Example 2. And Comparative Examples 5 to 7) were prepared. Table 5, FIG. 12, and FIG. 13 show the results of the density, magnetic permeability, and iron loss of Examples 14 and 15 and Comparative Examples 5 to 7. The densities in Table 5 have the same meaning as the theoretical densities in Table 1, and μ0 and μ12000 have the same meanings as those in Table 1.

FIG. 12 is a graph of the magnetic permeability with respect to the addition amount of the second magnetic powder of Examples 2, 14, 15 and Comparative Examples 5 to 7. FIG. 13 is a graph of the theoretical density with respect to the addition amount of the second magnetic powder of Examples 2, 14, 15 and Comparative Examples 5 to 7. As shown in Table 5 and FIGS. 12 and 13, when the amount of the second magnetic powder added is less than 20 wt%, the voids contained in the core increase and the density decreases. As a result, it causes a decrease in magnetic permeability and an increase in iron loss. On the other hand, when the amount of the second magnetic powder added exceeds 40 wt%, the density is significantly reduced. As a result, iron loss increases.

[Difference between MC core and dust core]
(cross section)
FIG. 14 is an SEM photograph (100 times) of a cross section of the core of the present embodiment. The material of the molded core is as follows.
First magnetic powder ... Average particle size 80 μm
Second magnetic powder ... Average particle size 10 μm
First magnetic powder: Second magnetic powder = 70:30 (weight ratio)
Resin: 5 wt%
FIG. 15 is an SEM photograph (1000 times) of a cross section of the dust core. In FIGS. 14 and 15, reference numeral 1 indicates a first magnetic powder, and reference numeral 2 indicates a second magnetic powder. Reference numeral 3 indicates a resin. As is clear from FIGS. 14 and 15, the MC core shown in FIG. 14 has a higher circularity of the first magnetic powder 1 than the dust core shown in FIG. That is, since the dust core is ^{pressurized at a high pressure of several t / cm 2} to several tens t / cm ² , the powders come into contact with each other and the particle size of the magnetic powder is deformed. On the other hand, the MC core is only pressurized to the extent that the air inside the resin containing the magnetic powder is evacuated at a low pressure of ^{several kg / cm 2} to several tens of kg / cm ^{2, and the core is formed by thermosetting the resin.} Because of this, the magnetic powder does not deform. This difference is visually recognizable, as can be seen from the SEM photographs of FIGS. 14 and 15.

(Comparison of characteristics with reactor)
The characteristics of Examples 16 and 17, which are reactors to which the MC core corresponding to the present embodiment is applied, and Comparative Example 8 which is a reactor to which a dust core is applied are compared.

実施例１６、１７のコアの磁性粉末は実施例２と同様であり、比較例８のコアの磁性粉末はセンダストである。実施例１６、１７、比較例８のコアは、一対のヨーク部によって一対のリム部（脚部）を繋ぐことにより磁路が形成された構成である。コアの断面積は、６．１５ｍｍ^２である。実施例１６、実施例１７のコアは、全体が継ぎ目なく形成されているため、ギャップが存在しない。比較例８のコアは、ヨーク部とリム部が別々に成型された分割構成であり、４箇所の接続部分において、それぞれ０．２５ｍｍ間隔のギャップが存在する。比較例８のコアは、ヨーク部の初透磁率が１４７、リム部の初透磁率が７５である。 The specifications of Examples 16 and 17 and Comparative Example 8 are shown in Table 6 below.

The magnetic powder of the cores of Examples 16 and 17 is the same as that of Example 2, and the magnetic powder of the core of Comparative Example 8 is sendust. The cores of Examples 16 and 17 and Comparative Example 8 have a configuration in which a magnetic path is formed by connecting a pair of rim portions (leg portions) with a pair of yoke portions. The cross-sectional area of the core is 6.15 mm ² . Since the cores of Examples 16 and 17 are formed seamlessly as a whole, there are no gaps. The core of Comparative Example 8 has a divided structure in which the yoke portion and the rim portion are separately molded, and each of the four connecting portions has a gap of 0.25 mm. In the core of Comparative Example 8, the initial magnetic permeability of the yoke portion is 147, and the initial magnetic permeability of the rim portion is 75.

Regarding the number of coil turns, in Comparative Example 8 and Example 16, 41 [T (Turns)] was wound around each of the pair of rims, and in Example 17, 39 [T] was wound around each of the pair of rims. Has been done. Regarding the size of the reactor, the lengths and volumes of the three orthogonal sides L, W, and H are the same in Comparative Example 8 and Example 16, but the volume is smaller in Example 17.

That is, in Example 16, the dust core of Comparative Example 1 is replaced with an MC core, and in Example 17, the coil has an inductance value (L value) equivalent to that of Comparative Example 1 at 30A. The number of turns is reduced. Therefore, when cores and coils of the same size are used, the MC core can raise the L value of the reactor at 30 A more than the dust core. It is also possible to reduce the size of the reactor.

Further, since the dust core is inferior in moldability, it is necessary to use a split core, which has a gap. However, the MC core has no gap because the whole can be formed seamlessly. Therefore, since the leakage flux to the coil can be reduced, the copper loss can be reduced and the heat generation of the coil can be suppressed.

ＭＣコアを用いた実施例１６のリアクトルでは、ダストコアを用いた比較例８に比べて、３０Ａ以上において高いＬ値を得ることができるので、直流重畳特性が良好となる。従って、実施例１７のようにコイルの巻数を落として比較例１と同等以上のＬ値を得るとともに、小型化を図ることができる。 Table 7 and FIG. 16 show in detail the L value corresponding to each value (A) in which the DC exciting current (Idc) is changed in the reactors of Comparative Example 8, Examples 16 and 17.

In the reactor of Example 16 using the MC core, a higher L value can be obtained at 30 A or more as compared with Comparative Example 8 using the dust core, so that the DC superimposition characteristic is good. Therefore, as in Example 17, the number of turns of the coil can be reduced to obtain an L value equal to or higher than that of Comparative Example 1, and the size can be reduced.

[3. Other embodiments]
The present invention is not limited to the above-described embodiment as it is, and at the implementation stage, the components can be modified and embodied within a range that does not deviate from the gist thereof. In addition, various inventions can be formed by an appropriate combination of the plurality of components disclosed in the above-described embodiment. For example, some components may be removed from all the components shown in the embodiments. In addition, components across different embodiments may be combined as appropriate.

1 1st magnetic powder 2 2nd magnetic powder 3 Resin 4 Voids

Claims (7)

A core composed of a magnetic powder and a resin composed of Fe powder, Fe-Si alloy powder, Fe-Al alloy powder, Fe-Si-Al alloy powder, or a mixed powder of two or more of these powders.
The magnetic powder contains a first magnetic powder having an average particle size of 100 μm or more and 200 μm or less, and a second magnetic powder having an average particle size of 3 μm or more and 10 μm or less.
The amount of the first magnetic powder added to the magnetic powder is 60 to 80 wt%, and the amount is 60 to 80 wt%.
The ratio of the apparent density of the core to the true density of the magnetic powder is 76.6% or more and less than 82%.
The initial magnetic permeability is 30 or more, and the magnetic permeability of 12 kA / m is 24 or more.
The resin content is 3 to 5 wt% with respect to the magnetic powder.
The core that features. The core according to claim 1, wherein the ratio of the apparent density of the core to the true density of the magnetic powder is 77% or more. The core according to claim 1 or 2, wherein the circularity of the first magnetic powder is 0.93 or more. The core according to any one of claims 1 to 3, wherein the entire surface of the core is a non-sliding surface. A reactor comprising the core according to any one of claims 1 to 4 and a coil. A method for producing a core containing a magnetic powder and a resin composed of Fe powder, Fe-Si alloy powder, Fe-Al alloy powder, Fe-Si-Al alloy powder, or a mixed powder of two or more of these powders.
The magnetic powder contains a first magnetic powder having an average particle size of 100 μm or more and 200 μm or less, and a second magnetic powder having an average particle size of 3 μm or more and 10 μm or less.
The amount of the first magnetic powder added to the magnetic powder is 60 to 80 wt%, and the amount is 60 to 80 wt%.
A mixing step of mixing so that the content of the resin with respect to the magnetic powder is 3 to 5 wt%,
A molding step of putting the mixture obtained in the mixing step into a predetermined container and molding the mixture,
During the molding process, the ratio of the apparent density of the core to the true density of the magnetic powder was 7
A pressurizing step of pressing the clay-like mixture with a pressing member so as to be 6.6% or more and less than 82%.
A curing step of curing the resin in the molded body obtained in the molding step, and
Have,
Said pressurizing step, the pressure for pressing the mixture, 1.6 kg / cm ² or more 15.7 kg / cm ² or less,
A method of manufacturing a core characterized by. A core containing a magnetic powder and a resin composed of Fe powder, Fe-Si alloy powder, Fe-Al alloy powder, Fe-Si-Al alloy powder, or a mixed powder of two or more of these powders, and a core attached to the core. It is a method of manufacturing a reactor equipped with a coil.
The magnetic powder contains a first magnetic powder having an average particle size of 100 μm or more and 200 μm or less, and a second magnetic powder having an average particle size of 3 μm or more and 10 μm or less.
The amount of the first magnetic powder added to the magnetic powder is 60 to 80 wt%, and the amount is 60 to 80 wt%.
A mixing step of mixing so that the content of the resin with respect to the magnetic powder is 3 to 5 wt%,
A molding step of putting the mixture obtained in the mixing step into a predetermined container and molding the mixture,
During the molding process, the ratio of the apparent density of the core to the true density of the magnetic powder was 7
A pressurizing step of pressing the clay-like mixture with a pressing member so as to be 6.6% or more and less than 82%.
A curing step of curing the resin in the molded body obtained in the molding step, and
Including
Said pressurizing step, the pressure for pressing the mixture, 1.6 kg / cm ² or more 15.7 kg / cm ² or less,
A method for manufacturing a reactor characterized by.

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