JP6506788B2 - Magnetic core using soft magnetic composite material and reactor using magnetic core - Google Patents

Description

  The present invention relates to a soft magnetic composite material suitable for a reactor called a metal composite type, a magnetic core using the soft magnetic composite material, and a reactor using the soft magnetic composite material.

  A reactor called a metal composite type is a reactor manufactured by integrally molding a magnetic core using a material in which soft magnetic powder and resin are mixed and a coil. This reactor is characterized in that magnetic saturation is less likely to occur in a high temperature range as compared with a laminated type reactor using ferrite for the magnetic core.

  The magnetic core used for the reactor of the metal composite type is called a metal composite core. This is manufactured by mixing soft magnetic powder and resin to make a soft magnetic composite material and solidifying it. Patent Document 1 discloses a method of obtaining a soft magnetic composite material having a relatively low relative magnetic permeability and a high saturation magnetic flux density by using a soft magnetic powder having a predetermined density ratio.

JP, 2014-160828, A

  In the MC core, a resin is present between the magnetic powders to prevent contact between the magnetic powders. In other words, the resin ensures insulation between the magnetic powders. When such an MC core is used at high temperature for a long time, the resin is decomposed, and the deterioration of the magnetic properties due to the contact between the magnetic powders is regarded as a problem.

  SUMMARY OF THE INVENTION The object of the present invention is to solve the problems of the prior art as described above, and it is a composite soft magnetic composite material which suppresses deterioration of magnetic properties when used for a long time under high temperature, metal A method of manufacturing a composite core and a metal composite core is provided.

In order to achieve the above object, the magnetic core of the present invention is a magnetic core composed of a soft magnetic composite material formed by mixing magnetic powder and a resin, and the resin is exposed to an atmosphere of 220 ° C. for 40 hours. Decrease rate of less than 0.1%.

  The reduction rate may be 0.08% or less.

  The reduction rate may be a reduction rate of the weight of the resin.

  The magnetic powder may include a first magnetic powder having a predetermined average particle size, and a second magnetic powder having an average particle size smaller than the first magnetic powder.

  The average particle diameter of the first magnetic powder may be 100 to 200 μm, and the average particle diameter of the second magnetic powder may be 5 to 10 μm.

  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 may be 20 to 40 wt%.

  The resin may be a thermosetting resin.

  The resin may be an epoxy resin.

The magnetic core is the rate of change of core loss upon exposure over 500 hours to an atmosphere of 155 ° C. may be 10% or less.

Furthermore, a reactor including the magnetic core and a coil is an aspect of the present invention.

  According to the present invention, in the soft magnetic composite material, the reduction ratio of the resin mixed with the magnetic powder when exposed at 220 ° C. for 40 hours is set to 0.1% or less. Thus, even when the magnetic core and the reactor composed of this soft magnetic composite material are exposed to high temperatures for a long time, the disappearance of the resin present between the magnetic powders can be suppressed, and as a result, With the magnetic core and the reactor, it is possible to suppress the deterioration of the magnetic characteristics when used under high temperature for a long time.

It is a flowchart for demonstrating the manufacturing method of the metal composite core which concerns on embodiment. It is a figure for demonstrating a formation process and a pressurization process. It is a graph which shows the relationship between the leaving time in the high temperature leaving test, and the iron loss Pcv.

[1. Embodiment]
[1-1. Constitution]
The soft magnetic composite material of the present embodiment includes magnetic powder and a resin. As a resin contained in the soft magnetic composite material, a resin having a reduction rate (hereinafter, loss on heating) of 0.1% or less when exposed to an atmosphere at 220 ° C. for 40 hours is used. The resin changes in volume and weight by being exposed to a high temperature atmosphere for a long time. The heat loss is a value indicating the rate of change in weight or volume of the resin before and after exposure to high temperature, and the heat loss is calculated based on the weight or volume of the resin before and after exposure to high temperature. In the following, the heating loss is calculated based on the change in weight of the resin, but may be calculated based on the change in volume. Even when heat loss is calculated based on weight change and volume change, in the present embodiment, a resin with a heat loss of 0.1% or less when exposed to an atmosphere at 220 ° C. for 40 hours is used.

  In the present embodiment, a clay-like soft magnetic composite material is obtained by mixing the magnetic powder and the resin. Further, in the present embodiment, the clay core soft magnetic composite material is filled in a predetermined container and pressurized to form the magnetic core into a predetermined shape. The shape of the magnetic core can be, for example, various shapes such as a toroidal core, an I-shaped core, a U-shaped core, a θ-shaped core, an E-shaped core, and an EER-shaped core.

(Magnetic powder)
As the magnetic powder, plural magnetic powders having different average particle sizes may be used. For example, it may be composed of two types of magnetic powders having different average particle sizes. Below, the mixed powder which mixed the soft magnetic powder of a kind is demonstrated to an example. However, it is not necessary to necessarily mix two types of powder. For example, one type of soft magnetic powder may be used, or three or more types of soft magnetic powder may be mixed.

  When mixing two types of magnetic powder, the magnetic powder is composed of a first magnetic powder and a second magnetic powder having a smaller average particle size than the first magnetic powder. It is preferable that the weight ratio of the first magnetic powder to the second magnetic powder is set to first magnetic powder: second magnetic powder = 80: 20 to 60:40. With this range, the density is improved, the permeability is also improved, and the core loss can be reduced.

  The average particle diameter of the first magnetic powder is preferably 100 μm to 200 μm, and the second magnetic powder is preferably 5 μm to 10 μm. By mixing two types of magnetic powders having different average particle sizes, the second magnetic powder having a smaller average particle size enters the gaps between the first magnetic powders. As a result, the density and permeability can be improved and iron loss can be reduced.

  Soft magnetic powders can be used as the first magnetic powder and the second magnetic powder, and in particular, Fe powder, Fe-Si alloy powder, Fe-Al alloy powder, Fe-Si-Al alloy powder (sendust), and these A mixed powder of two or more powders, or an amorphous soft magnetic alloy powder can be used. As Fe-Si alloy powder, Fe-6.5% Si alloy powder and Fe-3.5% Si alloy powder can be used, for example. The average particle size (D50) of the soft magnetic powder is preferably 20 μm to 150 μm. In the present specification, “average particle diameter” refers to D50, that is, median diameter, unless otherwise noted.

  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 0.94 or more. This is because the gaps between the first magnetic powders are reduced, and a large number of second magnetic powders can easily enter into the gaps, and the density and the permeability can be improved.

  The types of the first magnetic powder and the second magnetic powder may be the same or different. When three or more types of soft magnetic powders are mixed, three or more types of different magnetic powders may be mixed.

  As the first magnetic powder and the second magnetic powder, those manufactured by a gas atomization method, a water atomization method or a water gas atomization method can be used. The average circularity of the particles formed by these methods is desirably 0.90 or more, and when the powder having an average circularity of 0.90 or more can not be formed only by various atomization methods, the average circularity of the particles is further increased. It may be processed to increase the degree. For example, soft magnetic powder by gas atomization is approximately spherical particles. Therefore, it is possible to use the powder formed by the gas atomization method as it is without processing. On the other hand, the soft magnetic powder produced by the water atomization method is non-spherical particles having irregularities formed on the surface thereof. In this case, the average circularity of the particles can be increased by leveling the surface asperities using a ball mill, mechanical alloying, jet mill, attritor or surface modification device.

(resin)
The resin is mixed with the mixed powder, and has a function of holding the first powder and the second powder in a homogeneously mixed state. The resin is mixed with the magnetic powder and holds the mixed magnetic powder. When the magnetic powder is composed of powders having different average particle sizes, each powder is kept in a homogeneously mixed state. As the resin, a resin having a heating loss of 0.1% or less, preferably 0.08% or less when heated at 220 ° C. for 40 hours is used. As the resin, a curable resin can be used. If the heating loss is 0.1% or less, a thermosetting resin, an ultraviolet curable resin, or a thermoplastic resin can be used as the resin. As the thermosetting resin, phenol resin, epoxy resin, unsaturated polyester resin, polyurethane, diallyl phthalate resin, silicone resin and the like can be used. As an ultraviolet curable resin, urethane acrylate resin, epoxy acrylate resin, acrylate resin and epoxy resin can be used. As the thermoplastic resin, it is preferable to use a resin excellent in heat resistance such as polyimide or fluorine resin. The epoxy resin cured by the addition of the curing agent is suitable for the present invention because its viscosity can be adjusted by the addition amount of the curing agent and the like. Thermoplastic acrylic resins and silicone resins can also be used.

  The resin is preferably contained in an amount of 3 to 5% by weight based on the magnetic powder. When the content of the resin is less than 3 wt%, the bonding strength of the magnetic powder is insufficient, and the mechanical strength of the core is reduced. If the content of the resin is more than 5 wt%, the resin formed between the first magnetic powder enters and the second magnetic powder can not fill the gap, so that the density of the core decreases. The initial permeability μ0 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 in the magnetic powder at the time of mixing, the magnetic powder and the resin are easily separated in the container, and the density or the strength of the core varies. When the viscosity exceeds 5000 mPa · s, the viscosity becomes too high, for example, the resin formed between the first magnetic powder enters and the second magnetic powder can not fill the gap, and the density of the core Decreases and the initial permeability μ 0 decreases.

For 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 size of the filler as the viscosity adjusting material is preferably equal to or less than the average particle size of the second magnetic powder, and preferably 1/3 or less of the average particle size of the second magnetic powder. When the average particle size of the filler is large, the density of the obtained core is reduced. Moreover, high thermal conductivity materials such as Al ₂ O ₃ , BN, and 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 more than 76.47%, and more preferably 77.5% or more. When the proportion is more than 76.47%, the permeability can be increased. Conversely, if the ratio is 76.47% or less, the low density results in low permeability.

(coil)
The coil is a conducting wire provided with an insulation coating, and a copper wire or an aluminum wire can be used as a wire material. The coil is formed or mounted by winding a wire around at least a portion of the core, and is disposed around at least a portion of the core. The winding method of the coil, the material of the wire, and the shape are not particularly limited.

[1-2. Method of manufacturing metal composite core]
A method of manufacturing a metal composite core according to the present embodiment will be described with reference to the drawings. As shown in FIG. 1, the method for producing the metal composite core comprises (1) mixing step, (2) molding step, (3) pressing step, and (4) curing step.

(1) Mixing Step The mixing step is a step of mixing the magnetic powder and the resin. In the mixing step, a first magnetic powder and a second magnetic powder having a smaller average particle diameter than the first magnetic powder are mixed to form a magnetic powder, and a magnetic powder mixing step of 3 to 3 with respect to the magnetic powder. A resin mixing step of adding 5 wt% of resin and mixing the magnetic powder and the resin.

  The mixing of each mixing step can be performed automatically or manually using a predetermined mixer. Although the mixing time of each mixing process can be set suitably, It does not specifically limit, For example, it is 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 and mixed in a container for molding the composite magnetic material in the molding step. As a result, it is not necessary 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 of placing the composite magnetic powder in a container of a predetermined shape and molding it into a predetermined shape. In the molding step, the coil may be put together with the composite magnetic powder and molded.

  As a container, the thing of various shapes is used according to the shape of the core to manufacture. In the case of inserting the coil, the container uses a top open type box or dish container so that the coil can be inserted from above. The container used in the molding step can also be used as an outer case of a metal composite core that accommodates the core and the coil as it is. If the container is used as an outer case, there is an advantage that it is not necessary to take out the container after curing of the composite magnetic powder. When the container is not used as an exterior case, a plurality of metal composite cores may be manufactured in one container. That is, a plurality of metal composite cores 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, the manufacturing efficiency can be improved because only one molding step is required for a plurality of metal composite cores.

  As a container used for a shaping | molding process, the whole or one part can be comprised with a resin molding. By making the container made of resin, the manufacturing cost can be reduced, and the advantage that the MC core can have an arbitrary shape can be utilized. 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.

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

(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 contained in the container with a pressing member, the composite magnetic material is spread in the shape of the container, and the voids contained in the composite magnetic material are reduced, and the apparent density and Improve initial permeability.

  When the coil is not put in the container, the composite magnetic material becomes the shape of the inside of the container by the process. That is, the molded object of the predetermined shape comprised from composite magnetic material can be obtained.

  When the coil is placed in the container, as shown in FIG. 2, the composite magnetic material is placed in the container, and the composite magnetic material is spread by the pressing member into the shape of the container. Thereafter, a coil is inserted into a space created by pressing the composite magnetic material, and the composite magnetic material is further filled, and the composite magnetic material is pressed from above by the pressing member together with the coil. Alternatively, the composite magnetic material may be placed in a container, and then the coil may be embedded in the composite magnetic material, and the composite magnetic material may be pressed from above with the coil. Thus, by pressing the composite magnetic material together with the coil, it is possible to reduce the voids contained in the composite magnetic material and to improve the apparent density and the magnetic permeability. Note that only the composite magnetic material may be pressed by avoiding the portion where the coil exists. Thus, according to the process, it is possible to obtain a molded body of composite magnetic material of a predetermined shape including a coil.

  As described above, in the pressing process, the composite magnetic material may be pressed by the pressing member and the material may be in the shape of the container. In this case, the pressing process can be regarded as the pressing process and the forming process. .

The pressure for pressing the composite magnetic material is preferably 2.0 kg / cm ² or more. If it is less than this value, the pressure to press 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 10.0 kg / cm < ² > or less. Even if pressing is performed beyond this value, the effect of improving the apparent density is small.

  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 by setting the temperature of the container or the pressing member for pressing the composite magnetic material to a temperature higher than normal temperature (for example, 25 ° C.). 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 formability can be improved, and the material can easily flow into the void in the composite magnetic material, and the apparent density can be improved. The temperature of the pressing member for pressing the container or the composite magnetic material may be 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 pressing the composite magnetic material.

  In the pressing step, the temperature of the container or the pressing member may be raised, or the composite magnetic material may be pressed while the composite magnetic material itself is warmed. The temperature of the pressing member for pressing 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. In the curing step, the resin is cured by a drying profile that controls the drying temperature and time based on the dry state of the resin. Although drying time can be suitably changed according to the kind of resin, content, drying temperature, etc., although it can be set as 1 hour-4 hours, for example, it is not limited to this. Although drying temperature can be suitably changed according to the kind of resin, content, drying time, etc., it can be 85 degreeC-150 degreeC, for example, It is not limited to this. The drying temperature is the temperature of the drying atmosphere.

  Moreover, hardening of resin is not restricted to drying, and the hardening method changes with kinds of resin. For example, if the resin is a thermosetting resin, the resin is made to cross by applying heat, and if the resin is an ultraviolet curable resin, the resin is cured by irradiating the molded body with ultraviolet light.

  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. Also, for example, in the case of curing by drying of the resin, the drying temperature or the drying time may be changed every time it is repeated a plurality of times.

[1-3. Action / Effect]
(1) As a resin used for the magnetic core of the present embodiment, the reduction rate when the resin is exposed to an atmosphere of 220 ° C. for 40 hours is 0.1% or less, preferably 0.08% or less . The rate of decrease is the rate of decrease in weight when the resin is exposed to an atmosphere at high temperature. In the magnetic core produced from the soft magnetic composite material of the present embodiment, even when used at high temperature for a long time, the contact between the magnetic powders inside the magnetic core can be suppressed. In the magnetic core, an eddy current is generated according to the size of the soft magnetic powder contained inside. When the magnetic core is exposed to high temperatures for a long time, if the reduction rate of the resin contained in the magnetic core is more than 0.1%, the resin is decomposed and eliminated by the influence of heat. When the magnetic powders separated by the resin contact with each other due to the disappearance of the resin, a larger eddy current is generated.

(2) As the magnetic powder of the present embodiment, a plurality of magnetic powders having different average particle sizes were used. For example, the average particle size of the first magnetic powder is 100 to 200 μm, and the average particle size of the second magnetic powder is 5 to 10 μm. Further, the ratio of the magnetic powder is such that the amount of the first magnetic powder added is 60 to 80 wt%, and the amount of the second magnetic powder is 20 to 40 wt%. As a result, the second magnetic powder enters the gap between the first magnetic powders, and the density and the permeability can be improved and the core loss can be reduced.

(3) As the resin, although a thermosetting resin, an ultraviolet curable resin, or a thermoplastic resin can be used, a thermosetting resin can be used. Among them, it is preferable to use an epoxy resin. The epoxy resin not only has a high glass transition point and is excellent in heat resistance, but also does not by-produce volatile substances at the time of curing, so the dimensional change of the molded product is small. In addition, since it is rich in fluidity and can be molded even at a relatively low pressure, the process can be simplified.

(4) The magnetic core produced using the soft magnetic composite material of the present embodiment can suppress the change rate of the iron loss small even when exposed to an atmosphere of 155 ° C. for a long time. More preferably, a soft magnetic composite material is used which can produce a magnetic core having a core loss change rate of 10% or less when exposed to an atmosphere of 155 ° C. for 500 hours or more. Even if the core of such a magnetic powder is exposed to an atmosphere of 155 ° C. for 1000 hours or more, the resin does not decompose or disappear under the influence of heat. In other words, it is possible to shorten the time of the high-temperature leaving test by saying that it is possible to predict the rate of change of iron loss after 1000 hours by the rate of change of iron loss after 500 hours. Is also possible.

[1-4. Example]
Examples of the present invention are described below with reference to Tables 1 to 3 and FIG.

<Resin (heat loss)
Four kinds of resins A to D different in heating loss were prepared, test pieces to be samples were prepared using the resins A to D, and the heating loss of each resin was measured. The heating loss of the resin was measured by the following method. Since the loss on heating of the resin differs depending on the dimensions of the sample, the dimensions of the samples of the resin to be compared need to be uniform. In the present example, the loss on heating of resins A to D was measured using a cylindrical sample of “diameter 40 × height 10 (mm)”.

(1) Measurement Method of Heat Loss (a) Preparation of Test Piece First, a mold or a container having an inner diameter of a predetermined size was prepared. In this example, the predetermined dimension is a mold having an inner diameter of “diameter 40 × height 10 (mm)”. The molding material used as resin A-D material was thrown into the inside of a metal mold | die, and the metal mold was heated at 150 degreeC. The heat applied causes the molding material to melt and then a chemical reaction takes place to solidify in the form of the mold. The heating time of resin AD at the time of sample preparation is 4 hours.

(B) Mass Measurement Before Heating The solidified resins A to D were taken out from the mold and used as test pieces A to D. The mass of each of the test pieces A to D was measured to 1 mg. This value is M0.

(C) High-Temperature Storage Test The test pieces A to D are heated to 220 ° C. The heating time is 20 hours or 40 hours.

(D) Mass Measurement after Heating The test pieces A to D after a predetermined time had passed were taken out, and after heat release, the mass was measured to 1 mg. This value is M1.

(E) Calculation of heating loss The heating loss was calculated by the following equation.
(M0-M1) ÷ M0 × 100 = heat loss (%)

Table 1 is a graph showing the loss on heating when resins A to D were subjected to a high-temperature standing test in an atmosphere of 220 ° C. for 20 hours or 40 hours. As shown in Table 1, Resin A had a heating loss of 0.09% when exposed for 20 hours, a heating loss of 0.12% when exposed for 40 hours, and a heating when exposed for 20 hours. The weight loss is 0.07%, the weight loss upon heating for 40 hours is 0.08%, and the weight loss for resin C is 20% after heating for 0.05%, the weight loss for heating for 40 hours is 0. In the resin D, the heat loss upon exposure for 20 hours is 0.08%, and the heat loss upon exposure for 40 hours is 0.10%.

[The first characteristic comparison (comparison of the influence on the iron loss by the difference in the heating loss)]
In the first characteristic comparison, the characteristics of reactors created using resins A to D with different heating loss are compared.

(2) Measurement items The measurement items are iron loss. With respect to each of the manufactured samples of the cores, windings of 40 turns of the primary winding and 3 turns of the secondary winding were applied with a copper wire of φ 1.2 mm to produce a reactor. 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. Moreover, the iron loss of the produced reactor was computed on condition of the following.

<Iron loss>
The iron loss measurement conditions were a frequency of 20 kHz and a maximum magnetic flux density Bm = 30 mT. The iron loss was calculated using a BH analyzer (Iwatari Measurement Co., Ltd .: SY-8232) which is a magnetic measurement device. This calculation was performed by calculating the hysteresis loss coefficient and the eddy current loss coefficient by the least squares method with the following (1)-(3) frequency curves of iron loss.

Pcv = Kh × f + Ke × f ² (1)
Phv = Kh x 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 the present example, the average particle diameter and the degree of circularity of each powder were obtained by averaging 3000 particles using the following apparatus, and the powder was dispersed on a glass substrate and the powder photograph was obtained by a microscope. Each shot was automatically measured from the image.
Company name: Malvern
Device name: morphologi G3S
The specific surface area was measured by the BET method.

(3) Preparation Method of Sample The sample of the core uses Fe6.5Si having an average particle diameter of 123 μm as a first magnetic powder. Next, Fe6.5Si having an average particle size of 5.1 μm is prepared as a second magnetic powder. Then, the first magnetic powder and the second magnetic powder are mixed at a weight ratio of 70:30 to obtain a mixture of two magnetic powders having different average particle sizes.

  And the said magnetic powder was put into the aluminum cup, resin AD was added with respect to the said magnetic powder, and it mixed manually using a spatula for 2 minutes. Thereby, 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 at a pressure of 600 N (a surface pressure of 9.4 kg using a hydraulic press) It pressed for 10 seconds by / cm < ² >, and produced the toroidal-shaped molded object. During this press, the temperature of the container was kept at 25 ° C.

  Then, the molded body is dried in the air at 85 ° C. for 2 hours, then dried at 120 ° C. for 1 hour, and further dried at 150 ° C. for 4 hours to cure the resin, thereby producing a toroidal core as a sample. A sample using resin A (comparative example 1), a sample using resin B (example 1), a sample using resin C (example 2), a sample using resin D (comparative example 2) The Thereafter, 40 turns of the primary winding and 3 turns of the secondary winding were applied to the obtained toroidal core with the above-mentioned copper wire to produce an original reactor.

(4) Heat resistance test Next, a high temperature storage test was performed using samples of Examples 1 and 2 and Comparative Examples 1 and 2. In the high-temperature storage test, the samples of Examples 1 and 2 and Comparative Examples 1 and 2 were exposed to an atmosphere of 155 ° C. for 24 hours to 1000 hours, and the iron loss Pcv after that was measured.

Table 2 is a table showing the rate of change of iron loss (Pcv) when the high temperature storage test is performed on the samples of Examples 1 to 3 and Comparative Example 1. The change rate of iron loss (Pcv) was calculated as the iron loss at the start of the test (Pcv0) and the iron loss after a predetermined time (Pcv1), and calculated according to the following equation.
(Pcv1-Pcv0) ÷ Pcv0 × 100 = rate of change of Pcv (%)

  FIG. 3 is a graph created based on Table 2. The vertical axis in FIG. 3 indicates the rate of change in iron loss (Pcv), and the horizontal axis indicates the elapsed time in the high-temperature storage test.

  As shown in FIG. 3, when the samples of Examples 1 to 3 and Comparative Example 1 are exposed to 155 ° C., the change rate of iron loss (Pcv) in all the samples from the start of the test to 24 hours after the start of the test. Will rise significantly. In the samples of Examples 1 to 3 and Comparative Example 1, the change rate of iron loss (Pcv) at 24 hours after the start of the test is 6.3 to 9.3%. This is a phenomenon that occurs regardless of the weight loss of the resin, and heating the resin solidifies the resin again, and the stress generated at that time affects (Pcv).

  From the start of the test to 400 hours after the start of the test, the change rate of iron loss (Pcv) does not change significantly in all samples. However, when 400 hours have passed since the start of the test, the rate of change in iron loss (Pcv) of the sample (resin A) of Comparative Example 1 becomes large. On the other hand, when 400 hours have passed after the start of the test, there is no significant change in the rate of change in iron loss (Pcv) of the samples (Resins B to D) of Examples 1 to 3. This is because the resin contained in the sample of Comparative Example 1 is included in the samples of Examples 1 to 3 while heat is decomposed or dissipated, the magnetic powders contact with each other, and the eddy current loss Pev rises. This is because resin does not cause decomposition or disappearance.

  Furthermore, when 500 hours have passed after the start of the test, the change (%) in iron loss (Pcv) of the sample (resin D) of Example 3 becomes large. This is decomposition of the resin due to heat in the resin D in which the heating loss in 40 hours is slightly higher than that of the resin B with a heating loss of 0.08% in 40 hours and the resin with a heating loss of 0.05% in 40 hours Or it is thought that it originates in disappearance being started.

  On the other hand, in the samples of Examples 1 and 2 using resins B and C having a heating loss of 0.08% or less when heated at 155 ° C. for 40 hours, iron loss (Pcv) was observed even after 1000 hours from the start of the test. There is no significant change in the rate of change in%). This is because the resin contained in the samples of Example 1 and Example 2 does not decompose or disappear due to heat and secures insulation between the magnetic powders, so that the eddy current loss Pev suppresses an increase. .

  From the above, even if the magnetic core is exposed to an atmosphere of 155 ° C. for 400 hours or more by using a resin having a heating loss of 0.1% or less when exposed to an atmosphere of 220 ° C. for 40 hours, iron loss (Pcv) Change can be suppressed. Furthermore, by using a resin with a weight loss on heating of 0.08% or less when exposed to an atmosphere of 220 ° C. for 40 hours, even if the magnetic core is exposed to an atmosphere of 155 ° C. for more than 1000 hours, iron loss (Pcv) Change can be suppressed.

(Details about change of iron loss Pcv)
The iron loss Pcv is a value of the sum of the hysteresis loss Phv and the eddy current loss Pev. In the high-temperature standing test in Table 1 and FIG. 3, the eddy current loss Pev was cited as a cause of the increase in the iron loss Pcv. In the following, taking the samples of Comparative Example 1 and Example 2 in which the resin A is used as an example, the rise of the change rate (%) of Pcv and the change amounts of the hysteresis loss Phv and the eddy current loss Pev are verified.

Table 2 shows iron loss Pcv, hysteresis loss Phv, and eddy current loss Pev from the start of the test on the sample of Comparative Example 1 using Resin A and the sample of Example 2 on the basis of Resin C from the start of the test to 1000 hours after the start of the test. Is a table showing the values of.
As shown in Table 2, in the sample of Comparative Example 1, the eddy current loss Pev after 400 hours from the start of the test is 6.2, while after 1000 hours from the start of the test, the eddy current loss Pev is 6.2. The eddy current loss Pev is 9.0. The rate of change of the eddy current loss Pev at this time is 45% from (9.0−6.2) /6.2×100. On the other hand, the hysteresis loss Phv after 400 hours from the start of the test is 21.3, while the hysteresis loss Phv after 1000 hours from the start of the test is 23.1. It can be seen that the hysteresis loss Phv change rate at this time is approximately 8.5% from (23.1-21.3) /21.3×100. That is, in Table 1 and FIG. 3, when the change rate of Pcv is changing a lot, it turns out that the eddy current loss Pev is changing a lot.

  On the other hand, in the sample of Example 2, the eddy current loss Pev after 400 hours from the start of the test is 6.0, while the eddy current loss Pev after 1000 hours after the start of the test is 6.0. Is 6.1. The rate of change of the eddy current loss Pev is 1.7% from (6.1−6.0) /6.0×100. On the other hand, while the hysteresis loss Phv after 400 hours from the start of the test is 20.1, the hysteresis loss Phv after 1000 hours from the start of the test is 20.2. The rate of change of the hysteresis loss Phv is about 0.5% from (20.2-20.1) /20.1×100. In Table 2, in the sample of Example 2, neither the eddy current loss Pev nor the hysteresis loss Phv changes significantly. Therefore, it is understood that the change rate (%) of the iron loss Pcv is also small in Table 2 and FIG.

(Conclusion)
From the above, the magnetic core prepared from a soft magnetic composite material containing a resin having a heating loss of 0.1% or less when heated at 220 ° C. for 40 hours, even when used for a long time at 155 ° C. It can be seen that the rate of change (%) can be kept small. This is because a resin having a small loss on heating when heated at 220 ° C. for 40 hours can prevent contact between magnetic powders because the resin does not decompose or disappear even when exposed to a high temperature atmosphere for a long time. This makes it possible to realize low eddy current losses.

[2. Other embodiments]
The present invention is not limited to the above embodiment as it is, and at the implementation stage, the constituent elements can be modified and embodied without departing from the scope of the invention. In addition, various inventions can be formed by appropriate combinations of a plurality of constituent elements disclosed in the above embodiment.

  For example, in the embodiment, as a method of providing a coil in a reactor, a method of placing a coil in a container and embedding in a composite magnetic material in a molding step has been described, but a molded body of a predetermined shape made of composite magnetic material is molded in advance Alternatively, a method may be employed which includes a winding step of winding a conductive wire constituting a coil around the molded body.

  Moreover, although the magnetic core was created by pouring in the container the soft-magnetic composite material which mixed the soft-magnetic powder and resin beforehand in this embodiment, you may create it with the following method. After the mixed powder of the first powder and the second powder is filled in the container, the density of the mixed powder in the container is increased by vibrating the entire container. Then, the resin is made to permeate into the mixed powder whose density is increased by vibration, and is hardened by the curing method according to the type of resin. As a method of vibration, the whole container may be vibrated up and down or / and back and forth / left / right using a motor or a cam, etc., or the container may be finely hit with a hammer-like member. The entire container may be vibrated by an ultrasonic pendulum.

Furthermore, in the present embodiment, the pressing step of pressing the easily input composite magnetic material with the pressing member is included between the molding step and the curing step, but the pressing step may be omitted. Depending on the type of magnetic powder or resin used and the method of the forming process, it is possible to form a magnetic core having excellent magnetic properties even if the pressing process is omitted. In this case, it is possible to omit the pressurization process for the purpose of reducing the number of processes and the cost.

Claims (10)

A magnetic core comprising a soft magnetic composite material comprising a mixture of magnetic powder and resin,
A magnetic core characterized in that the reduction rate when the resin is exposed to an atmosphere at 220 ° C. for 40 hours is 0.1% or less. The magnetic core according to claim 1, wherein the reduction rate is 0.08% or less. The magnetic core according to claim 1 or 2, wherein the reduction rate is a reduction rate of the weight of the resin. The magnetic powder is
A first magnetic powder of a predetermined average particle size,
A second magnetic powder having an average particle size smaller than the first magnetic powder;
The magnetic core according to any one of claims 1 to 3, further comprising: The average particle diameter of the first magnetic powder is 100 to 200 μm,
The magnetic core according to claim 4, wherein an average particle diameter of the second magnetic powder is 5 to 10 m. The magnetic core according to claim 4 or 5, wherein the addition amount of the first magnetic powder in the magnetic powder is 60 to 80 wt%, and the second magnetic powder is 20 to 40 wt%. The magnetic core according to any one of claims 1 to 6, wherein the resin is a thermosetting resin. The magnetic core according to any one of claims 1 to 7, wherein the resin is an epoxy resin. The magnetic core according to any one of claims 1 to 8 wherein the magnetic property core, the rate of change of core loss upon exposure over 500 hours to an atmosphere of 155 ° C. is equal to or less than 10% . The reactor provided with the magnetic core of any one of the said Claims 1 thru | or 9, and a coil.