JP2019186299A - Reactor - Google Patents

Abstract

To provide a reactor with good core loss and excellent in DC superposition characteristics.SOLUTION: In a reactor 1 including a core 2 consisting of powder magnetic core, and coils 3A, 3B wound to cover a part of the core 2, each soft magnetic particle composing the powder magnetic core includes a base metal composed of an Fe-Si-Al alloy, and an aluminum nitride layer or an aluminum oxide layer covering the base metal, and the particle size of each soft magnetic particle composing the first parts 21, 21 covered by the coils 3A, 3B, out of the core 2, is smaller than the particle size of each soft magnetic particle composing the second parts 22, 22 exposed from the coils 3A, 3B.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a reactor including a core made of a dust core and a coil wound so as to cover a part of the core.

  2. Description of the Related Art Conventionally, a reactor is used in a hybrid vehicle, an electric vehicle, a solar power generation device, and the like, and this reactor has a structure in which a coil is wound around a ring-shaped core that is a dust core.

  As an example of such a reactor, for example, Patent Document 1 discloses a reactor including a core formed of a dust core and a coil wound so as to cover a part of the core. In this reactor, each soft magnetic particle constituting the dust core includes a base material made of an Fe—Si—Al alloy and an aluminum nitride layer covering the base material. Such a reactor can stably secure the inductance of the reactor even in an environment where a high magnetic field is applied while reducing iron loss.

JP 2017-76689 A

  However, as a result of experiments, the inventors have found that the magnetic resistance and the like differ depending on the size of each soft magnetic particle constituting the dust core. Therefore, it is considered that the reactor described in Patent Document 1 has room for improving iron loss and inductance in consideration of the size of the soft magnetic particles.

  This invention is made | formed in view of the said point, and this invention provides the reactor which is excellent in direct current | flow superimposition characteristic and has favorable core loss.

  In order to solve the above problems, the present invention is a reactor comprising a core made of a dust core and a coil wound so as to cover a part of the core, and the dust core is Each of the soft magnetic particles included includes a base material made of an Fe-Si-Al alloy and an aluminum nitride layer or an aluminum oxide layer that covers the base material, and is covered with the coil of the core. The particle diameter of each soft magnetic particle constituting the first portion is smaller than the particle diameter of each soft magnetic particle constituting the second portion exposed from the coil.

  According to the present invention, as will be described in Examples below, when the particle size of the soft magnetic particles is small, the magnetic resistance is increased by increasing the content of aluminum nitride or aluminum oxide. By using such soft magnetic particles in the first portion, saturation of magnetic flux density can be prevented as compared with the case of using a powder containing soft magnetic particles having a larger particle diameter. As a result, the direct current superimposition characteristics of the reactor can be improved.

  Further, as will be described in the examples described later, when the particle diameter is small, the eddy current loss during application of an alternating magnetic field is low. By using such soft magnetic particles in the first portion, the core loss can be improved as compared with the case of using a powder containing soft magnetic particles having a larger particle diameter.

(A) is a schematic top view of the reactor which concerns on this embodiment, (b) is typical sectional drawing of the reactor which concerns on this embodiment. It is a graph which shows the relationship between the particle size of powder for powder magnetic cores, and N amount. It is a graph which shows the relationship between the particle size of the powder for powder magnetic cores, and initial inductance. It is a graph which shows the relationship between the particle size of the powder for dust cores, and an iron loss. (a) is a graph which shows the relationship between an inductance and a direct current | flow superimposed current about Example 1 and the comparative example 1, FIG.5 (b) is direct current superimposed current 150-250A shown with a black frame in FIG. 5 (a). It is the graph which expanded the area | region of. 6 is a graph showing losses of reactor models according to Example 1 and Comparative Example 1. (A) is a schematic top view of the reactor which concerns on the comparative example 1, (b) is typical sectional drawing of the reactor which concerns on the comparative example 1. FIG.

  Hereinafter, an embodiment of a reactor 1 according to the present invention will be described with reference to FIG. FIG. 1A is a schematic plan view of the reactor 1 according to this embodiment, and FIG. 1B is a schematic cross-sectional view of the reactor 1 according to this embodiment.

  In this specification, “median diameter D30”, “median diameter D50”, and “median diameter D90” are the mass cumulative distribution curve of the particle size distribution by analysis using a test sieve defined in JIS-Z8801. From the small diameter side, it means the particle diameter corresponding to 30%, 50% and 90% respectively.

  The reactor 1 of the present embodiment is mounted on a vehicle such as a hybrid electric vehicle (HEV) or an electric vehicle (EV), and can be used, for example, in a converter that steps up or down a voltage. As shown in FIG. 1, the reactor 1 according to the present embodiment includes a core 2 composed of a dust core and coils 3 </ b> A and 3 </ b> B wound so as to cover a part of the core 2. Yes.

  In the present embodiment, as an example, the ring-shaped core 2 is provided so that the pair of coils 3A and 3B face each other. The coils 3A and 3B are electrically connected in series and function as one coil.

  The core 2 is made of a powder magnetic core, and the powder magnetic core is obtained by press-molding a powder for a powder magnetic core having soft magnetic particles, which will be described later, and annealing the molded body. The particle diameter of the dust core particles thus obtained is approximately equal to the particle diameter of the soft magnetic particles.

  Each soft magnetic particle constituting the dust core includes a base material made of an Fe—Si—Al alloy and an aluminum nitride layer or an aluminum oxide layer covering the base material.

  The base material is made of an Fe-Si-Al alloy (iron alloy), and the Fe-Si-Al alloy is inevitable that Si is 0.5 to 9% by mass, Al is 0.5 to 5% by mass, and the balance is iron. It is preferable to consist of impurities.

  When the content of Al or Si is less than the above range, the iron loss of the dust core increases due to the deterioration of the magnetocrystalline anisotropy. On the other hand, if the content of Al or Si is more than the above range, it is not preferable because the magnetic properties and moldability of the powder magnetic core are lowered and the cost is increased.

  Examples of the alloy powder in which the base material Fe—Si—Al alloy (particles) is aggregated include water atomized powder, gas atomized powder, gas water atomized powder, and pulverized powder. In consideration of the suppression of the destruction of the aluminum nitride layer or the aluminum oxide layer at the time of compacting, it is more preferable to select a surface with less unevenness on the surface of the base material.

  The aluminum nitride layer or the aluminum oxide layer is formed as an insulating layer on the surface of the base material. In the present embodiment, as the particle diameter (particle size) of the soft magnetic particles decreases, the content of aluminum nitride or aluminum oxide derived from the aluminum nitride layer or aluminum oxide layer increases. Thereby, the magnetic resistance of the dust core can be increased.

  For example, when an aluminum nitride layer is formed, the nitrogen content can be determined by examining the nitrogen (N) content of the soft magnetic particles (soft magnetic powder). Specifically, as in Examples described later, when soft magnetic powder, which is an aggregate of soft magnetic particles, is classified into powder having fine particle size, intermediate particle size, and coarse particle size, powder nitrogen having fine particle size is obtained. The content is preferably 0.8 to 1.5 mass%, more preferably 1.0 to 1.3 mass%. The nitrogen content of the powder having an intermediate particle size is preferably 0.3 to 0.7 mass%, more preferably 0.4 to 0.6 mass%. 0.1-0.5 mass% is preferable and, as for the nitrogen content of the powder which has a coarse powder particle size, 0.2-0.4 mass% is more preferable. In addition, 0.1-1.0 mass% is preferable and, as for the nitrogen content of the powder which has all the particle sizes including a fine particle size, an intermediate particle size, and a coarse particle size, 0.3-0.7 mass% is more preferable.

  In this embodiment, the particle diameter of each soft magnetic particle which comprises the 1st part 21 and 21 covered with each coil 3A, 3B among the core 2 is the 2nd part exposed from each coil 3A, 3B. 22 and 22 are smaller than the particle diameter of each soft magnetic particle. Thereby, as will be described later, the DC superposition characteristics and the core loss can be improved.

  Here, the particle diameter is not limited as long as the particle size can be compared. For example, the particle diameter corresponds to a predetermined cumulative value (%) in the volume or mass cumulative distribution curve related to the particle size distribution, or An average particle diameter etc. can be mentioned.

  When the particle diameter corresponding to the above-described cumulative value is used as the particle diameter, the particle diameter of each soft magnetic particle constituting the first portion 21 or 21 is a fine particle size (median diameter D30: particle diameter 10 to 100 μm). preferable. On the other hand, the particle diameter of each soft magnetic particle constituting the second portions 22 and 22 is preferably a coarse particle size (median diameter D90: particle diameter 100 to 250 μm).

  The soft magnetic particles having such fine and coarse particle sizes are further provided with a low-melting glass film made of low-melting glass so as to cover the surface of the aluminum oxide layer or aluminum nitride layer formed on the soft magnetic particles. It may be formed.

  Examples of the low melting point glass include silicate glass, borate glass, bismuth silicate glass, borosilicate glass, vanadium oxide glass, and phosphate glass. These low-melting-point glasses have a softening point temperature lower than the annealing temperature of the powder compacted powder when the powder magnetic core is annealed.

The silicate-based glass, for _example, a main component _{SiO 2 -ZnO, SiO 2 -Li 2} O, SiO 2 -Na 2 O, SiO 2 -CaO, SiO 2 -MgO, a SiO 2 _-Al 2 _{O 3,} etc. There is something to do. Examples of the bismuth silicate glass include SiO ₂ —Bi ₂ O ₃ —ZnO, SiO ₂ —Bi ₂ O ₃ —Li ₂ O, SiO ₂ —Bi ₂ O ₃ —Na ₂ O, and SiO ₂ —Bi ₂ O. _{Some have 3-} CaO or the like as a main component. The borate-based glass, for _{example, B 2 O 3 -ZnO, B} 2 O 3 -Li 2 O, B 2 O 3 -Na 2 O, B 2 O 3 -CaO, B 2 O 3 -MgO, B 2 Some have O ₃ —Al ₂ O ₃ or the like as a main component. The borosilicate based glass, for _{example, SiO 2 -B 2 O 3 -ZnO} , SiO 2 -B 2 O 3 -Li 2 O, SiO 2 -B 2 O 3 -Na 2 O, SiO 2 -B 2 O _{Some have 3-} CaO or the like as a main component. The vanadium oxide-based glass, for _{example, V 2 O 5 -B 2 O} 3, V 2 O 5 -B 2 O 3 -SiO 2, V 2 O 5 -P 2 O 5, V 2 O 5 -B 2 O _{Some have 3-} P ₂ O ₅ or the like as a main component. The phosphoric acid-based glass, for _{example, P 2 O 5 -Li 2 O} , P 2 O 5 -Na 2 O, P 2 O 5 -CaO, P 2 O 5 -MgO, P 2 O 5 -Al 2 O 3 Etc. as a main component. These low-melting-point glasses can appropriately contain one or more of SiO ₂ , ZnO, Na ₂ O, B ₂ O ₃ , Li ₂ O, SnO, BaO, CaO, Al ₂ O _{3 and the} like in addition to the components described above. .

  The content of the low-melting-point glass is preferably 0.05 to 5.0% by mass when the entire powder magnetic powder or the entire powder magnetic core is 100% by mass. When the content of the low melting point glass is 0.05% by mass or more, it becomes easy to form a sufficient low melting point glass film, and it becomes easy to obtain a dust core having a high specific resistance and high strength. When content of low melting glass is 5.0 mass% or less, the fall of the magnetic characteristic of a powder magnetic core can be suppressed effectively.

  The low melting point glass film may be a layer adhered to the surface of the soft magnetic particle as fine particles having a particle diameter smaller than that of the soft magnetic particle, or may be a layer continuously adhered to the surface of the soft magnetic particle.

  The structure of the core 2 shown in FIG. 1 employs a structure in which two U-shaped cores are combined, but the shape of the core 2 is particularly suitable if the coil turns a part of the magnetic path of the core 2. It is not limited. Specific examples include EI type, EE type, EER type, PQ type, and EB type.

  In the reactor 1 having the above-described configuration, current is passed through the coils 3A and 3B to alternately store and release energy and convert the voltage.

  According to this embodiment, each soft magnetic particle constituting the dust core includes a base material made of an Fe—Si—Al alloy and an aluminum nitride layer or an aluminum oxide layer that covers the base material. Of the core 2, the particle diameter of each soft magnetic particle constituting the first portion 21, 21 is smaller than the particle diameter of each soft magnetic particle constituting the second portion 22, 22.

  As will be described in Examples below, when the particle diameter of the soft magnetic particles is small as described above, the magnetic resistance is increased by increasing the content of the aluminum nitride layer or the aluminum oxide layer. By using such soft magnetic particles for the first portions 21, 21, saturation of magnetic flux density can be prevented as compared with the case where powder containing soft magnetic particles having a larger particle diameter is used. As a result, the direct current superimposition characteristic of the reactor 1 can be improved.

  In addition, as will be described in Examples below, when the particle size is small, eddy current loss during application of an alternating magnetic field is low. By using such soft magnetic particles for the first portions 21 and 21, the core loss can be improved as compared with the case of using a powder containing soft magnetic particles having a larger particle diameter.

  The manufacturing method of the reactor of this embodiment is demonstrated below.

<Preparation of powder for powder magnetic core>
First, an alloy powder in which an Fe—Si—Al alloy (particles) as a base material is assembled is prepared. Next, an aluminum nitride layer or an aluminum oxide layer is formed on the surface of the base material. When an aluminum nitride layer is formed, nitriding is performed. Specifically, the alloy powder is heated in a nitriding atmosphere. More specifically, in a nitrogen gas atmosphere, the heating temperature is preferably 800 ° C. to 1250 ° C., more preferably 900 ° C. to 1150 ° C. On the other hand, when an aluminum oxide layer is formed, an oxidation process is performed in an atmosphere equivalent to air. Specifically, the alloy powder is heated in an oxidizing atmosphere. More specifically, in the air, the heating temperature is preferably 800 ° C to 1100 ° C, more preferably 900 ° C to 1050 ° C. In this way, a soft magnetic powder in which soft magnetic particles having an aluminum nitride layer or an aluminum oxide layer are gathered is obtained.

  In the present embodiment, the acquired soft magnetic powder is classified using a sieve or the like, and a fine powder and a coarse powder are acquired from the soft magnetic powder as a powder for a dust core. As an example, the fine powder is composed of soft magnetic particles having a fine particle size corresponding to the median diameter D30, and the coarse powder is composed of soft magnetic particles having a coarse particle size corresponding to the median diameter D90.

  If necessary, a low melting point glass is added to the fine and coarse powders to form a low melting point glass made of a low melting point glass so as to cover the surface of the aluminum oxide layer or aluminum nitride layer formed on the soft magnetic particles. A glass film may be further formed.

  For example, when forming a low-melting glass film, fine powder made of low-melting glass and soft magnetic powder that is an aggregate of soft magnetic particles may be mixed in a dispersion medium and dried. Low melting glass softened by heating may be attached to the soft magnetic powder. Moreover, you may couple | bond the fine particle powder and soft-magnetic powder which consist of low melting glass with binders (binders), such as PVA or PVB. When the low melting point glass film is composed of a layer adhered to the surface of the soft magnetic powder as fine particles having a particle diameter smaller than that of the soft magnetic powder, it can be a continuous film through subsequent compaction molding and annealing.

<Preparation of dust core (core 2)>
First, the obtained fine powder and coarse powder are compacted to form a compact. The compacting is performed by, for example, a generally known warm mold lubrication molding method (see, for example, Japanese Patent No. 3309970) or a warm compression molding method including an internal lubricant (for example, Japanese Patent Laid-Open No. 2016-148100). For example). At this time, in the present embodiment, fine powder and coarse powder are used for each first portion 21 and each second portion 22.

  In the case of the warm mold lubrication molding method, the molding temperature may be a temperature within a range where the warm mold lubrication molding method can be performed. For example, the molding temperature is preferably 70 to 200 ° C, more preferably 100 to 180 ° C.

  In the warm mold lubrication molding method or the warm compression molding method including an internal lubricant, a decrease in mold life can be suppressed even if the molding pressure is increased. Such a molding pressure is preferably 400 to 1800 MPa, and more preferably 600 to 1600 MPa.

  In the core 2, each first portion 21 and each second portion 22 may be formed by integral molding. Alternatively, after forming each first portion 21 and each second portion 22 separately, the second portions 22 and 22 sandwich the first portions 21 and 21 (see FIG. 1). You may combine with an adhesive agent etc.

  Next, the molded powder compact is annealed by heat treatment to obtain a powder magnetic core, which is used as the core 2. The particle diameter of the powder magnetic core (core 2) obtained in this way is approximately equal to the particle diameter of the soft magnetic particles. For example, the compacting body is preferably annealed at an annealing temperature of 600 ° C. to 1000 ° C., more preferably 700 ° C. to 900 ° C. Thereby, the residual strain and residual stress introduced into the soft magnetic particles in the dust core can be removed, and the coercive force or hysteresis loss of the dust core can be reduced.

<Preparation of reactor 1>
A coil 3A is formed so as to cover the first portion 21 by winding a wire around one of the two first portions 21 and 21 using the fine powder to the acquired core 2. Form. Similarly, a wire is wound around the other first portion 21 to form the coil 3 </ b> B so as to cover the first portion 21. Thereby, the 2nd parts 22 and 22 using coarse-grained powder will be in the state where it is not covered with coil 3A and coil 3B.

  Thus, the manufactured reactor 1 can improve the superimposed current characteristics and the core loss as described above. Further, according to the manufacturing method of the present embodiment, the soft magnetic powder is classified, and two kinds of powders having different soft magnetic particle diameters are obtained as powders for the dust core from the soft magnetic powder. As a result, each of the two types of classified powders can be selectively used as the first portion 21 and the second portion 22 of the core 2 as the powder for the dust core. Therefore, the nitrogen content or the oxygen content of the powder for the powder magnetic core used for the core 2 can be adjusted by a single nitriding treatment or oxidizing treatment. As a result, it is possible to improve the DC superposition characteristics and core loss of the reactor 1 without reducing the yield.

  The present invention will be described based on examples.

  First, using the test samples according to Reference Examples 1 to 3 and Comparative Reference Example 1 described below, soft magnetic particles (powder for powder magnetic core) having different particle diameters (particle sizes), nitrogen content, and initial inductance Or a test to confirm the relationship with iron loss.

(Reference Example 1)
<Preparation of powder for powder magnetic core>
As an alloy powder in which Fe-Si-Al alloy (particles) as a base material is gathered, an iron-silicon-aluminum alloy (Fe-2. A gas water atomized powder composed of 0Si-3.0Al) (a ratio of 45 μm or less was 30% by mass (measured using a test sieve specified in JIS-Z8801)) was prepared.

  Next, the prepared alloy powder was nitrided by heating at 1100 ° C. for 5 hours in a nitrogen gas atmosphere (nitrogen gas 100% by volume) at a nitrogen gas pressure of 110 KPa. As a result, a soft magnetic powder, which is an aggregate of soft magnetic particles having an aluminum nitride layer formed on the surface of the base material, was obtained.

  Next, the obtained soft magnetic powder is classified using a test sieve specified in JIS-Z8801, and soft magnetic particles having a fine particle size (median diameter D30: particle diameter of 10 to 50 μm) are collected from the soft magnetic powder. A fine powder was obtained. The obtained powder was used as the powder for dust core of Reference Example 1.

<Preparation of ring specimen (dust core)>
The obtained powder for powder magnetic core is put into a mold, and the outer diameter is 39 mm, the inner diameter is 30 mm, and the thickness is 5 mm by the mold lubrication warm molding method under the conditions of a mold temperature of 130 ° C. and a molding pressure of 10 t / cm ² . A compact formed body having a toroidal core shape (ring shape) was produced. The formed green compact was annealed (sintered) for 30 minutes at 750 ° C. in a nitrogen atmosphere. In this manner, a ring test piece (a dust core) according to Reference Example 1 was produced.

(Reference Example 2)
A ring test piece (dust core) of Reference Example 2 was produced in the same manner as Reference Example 1. The difference from Reference Example 1 is that a medium-sized powder in which soft magnetic particles having an intermediate particle size (median diameter D50: particle diameter 50 to 150 μm) are gathered is separated from the soft magnetic powder, and this powder is used as a powder for a dust core. It is used.

(Reference Example 3)
A ring test piece (a dust core) of Reference Example 3 was produced in the same manner as Reference Example 1. The difference from the reference example 1 is that a coarse powder in which soft magnetic particles having a coarse powder particle size (median diameter D90: particle diameter 150 to 250 μm) are aggregated is separated from the soft magnetic powder, and this is used as a powder for a powder magnetic core. It is used as.

(Comparative Reference Example 1)
In the same manner as in Reference Example 1, a ring test piece (dust core) of Comparative Reference Example 1 was produced. The difference from Reference Example 1 was that the soft magnetic powder was used as it was as a powder for a dust core without being classified using a sieve. In addition, the soft magnetic powder is composed of soft magnetic particles having a fine particle size according to Reference Example 1, soft magnetic particles having an intermediate particle size according to Reference Example 2, and soft magnetic particles having a coarse particle size according to Reference Example 3. Powder. This powder was made into the whole grain powder which has all the particle sizes.

<N amount of powder for dust core>
The nitrogen (N) content of the powder for powder magnetic cores used for the production of the ring test pieces according to Reference Examples 1 to 3 and Comparative Reference Example 1 was measured using an inert gas transport melting thermal conductivity method: ON analyzer ( Measured using HORIBA. The results are shown in FIG. FIG. 2 is a graph showing the relationship between the particle size (particle diameter) of the powder for powder magnetic core and the N amount (mass%).

[Result 1]
As can be seen from Reference Examples 1 to 3 in FIG. 2, the nitrogen content increased as the particle size decreased from the coarse particle size to the fine particle size. This is presumably because the specific surface area of the particles increased as the particle diameter decreased, and the proportion of aluminum nitride derived from the aluminum nitride layer increased. As a result, in Reference Example 1 having a fine particle size, the content of nitrogen increased as compared to the case of all particle sizes including not only the fine particle size but also a particle size larger than the fine particle size, as in Comparative Reference Example 1.

<Measurement of initial inductance>
A primary (excitation) coil and a secondary (detection) coil were formed on each of the ring test pieces according to Reference Examples 1 to 3 and Comparative Reference Example 1 using an insulation-coated copper wire as a winding. About each of the ring test piece which gave the winding, inductance was measured on condition of 10 mA and 20 kHz using the alternating current magnetism measuring device (product made from IWASU). The result is shown in FIG.

[Result 2]
FIG. 3 is a graph showing the relationship between the particle size of the powder for powder magnetic core and the initial inductance. The initial inductance means an inductance when the DC superimposed current is 0 A. In FIG. 3, the initial inductance of the reference comparative example 1 is 1, and the inductances according to the reference examples 1 to 3 are shown.

  As can be seen from Reference Examples 1 to 3 in FIG. 3, the initial inductance decreases as the particle diameter of the powder for the powder magnetic core decreases. This is because the smaller the soft magnetic particles, the larger the amount of aluminum nitride (AlN) contained in the dust core (see result 1 above) and the greater the magnetic resistance of the dust core. It is done.

  For this reason, the reference example 1 having a fine particle size has a lower initial inductance and a higher magnetic resistance than the case of the total particle size including not only the fine particle size but also a larger particle size as in the comparative reference example 1. became. Specifically, when it had the fine particle size of Reference Example 1, it was reduced by 21% with respect to the inductance of all the particle sizes of Comparative Reference Example 1.

<Measurement of iron loss>
Further, for Reference Examples 1 to 3 and Comparative Reference Example 1, the iron loss was measured using a test piece wound with a wire used for the inductance measurement. In this measurement, AC iron loss was measured under the conditions of 0.1 T and 20 kHz using an AC magnetometer (manufactured by IWASU). The result is shown in FIG.

[Result 3]
FIG. 4 is a graph showing the relationship between the particle size of the powder for powder magnetic cores and the iron loss. FIG. 4 shows the iron loss according to Reference Examples 1 to 3, where the iron loss in Reference Comparative Example 1 is 1. ing. As can be seen from FIG. 4, the iron loss was higher in the case of the powder for the powder magnetic core having the coarse particle size as in Reference Example 3 as compared with Reference Example 1 and Reference Example 2. This can be considered that the larger the particle diameter of the soft magnetic particles, the higher the eddy current loss when an AC magnetic field is applied. For this reason, the reference example 1 having a fine particle size reduces the iron loss as compared with the case of the total particle size including not only the fine particle size but also a larger particle size as in the comparative reference example 1, specifically, The iron loss was reduced by 20% compared to the case of all the particle sizes.

<Confirmation test (analysis)>
Next, based on the results 1 to 3 described above, assuming the reactor model shown in FIGS. 1 and 7 as Example 1 and Comparative Example 1, the DC superimposition characteristics and the loss of the reactor were simulated. Confirmed.

  FIG. 7A is a schematic plan view of the reactor according to Comparative Example 1, and FIG. 7B is a schematic cross-sectional view of the reactor according to Comparative Example 1. In FIG. 7, the same members and portions as those of the above-described embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

Example 1
In the reactor model according to the first embodiment, the first part covered by the two coils and the second part exposed from these coils are each soft magnetic having the fine particle size used in Reference Example 1. Particles and soft magnetic particles having a coarse particle size used in Reference Example 3.

(Comparative Example 1)
The difference between the model of Comparative Example 1 and Example 1 is that, as shown in FIG. 7, the entire core has the entire particle size according to Comparative Reference Example 1 regardless of the first part and the second part. It is composed of soft magnetic particles.

<Evaluation of DC superposition characteristics>
The DC superposition characteristics of Example 1 and Comparative Example 1 were analyzed using electromagnetic field analysis software J-MAG manufactured by J-SOL Co., Ltd. The results are shown in FIG.

[Result 4]
FIG. 5A is a graph showing the relationship between the inductance and the DC superimposed current for Example 1 and Comparative Example 1, and FIG. 5B is the DC superimposed current indicated by a black frame in FIG. 5A. It is the graph which expanded the area | region of 150-250A.

  As can be seen from FIGS. 5A and 5B, compared to Comparative Example 1, as in Example 1, the first portion of the core is composed of soft magnetic particles having a fine particle size. The inductance in the high current region was improved by 20%.

  In general, in the case of a reactor, electrical energy supplied to a coil is stored as magnetic energy in an excitation region of a core (a dust core). Here, as in Comparative Example 1, in the case of the total particle size including not only the fine particle size but also a larger particle size, the magnetic resistance is smaller than that of the fine particle size (see Result 2 and FIG. 3), and the magnetism is transmitted. Cheap.

  For this reason, as in Comparative Example 1, in the case of a core composed of soft magnetic particles having a small magnetic resistance (that is, a high magnetic permeability), when the magnetic field applied to the dust core is increased, the inductance is lowered early. Therefore, since the magnetic flux density is saturated early, it is difficult to store magnetic energy in the dust core.

  On the other hand, when soft magnetic particles having a fine particle size are used in the first portion serving as the excitation region as in Example 1, although the initial inductance is small, AlN derived from the aluminum nitride layer is formed on the surface of the soft magnetic particles. Since there are more, the magnetic resistance of the dust core is increased (see results 1 and 2 and FIGS. 2 and 3). In such a case, when the magnetic field applied to the dust core is increased, the inductance is improved and the magnetic flux density is prevented from being saturated. Compared with Comparative Example 1, the magnetic energy is increased in the excitation region of the core (dust core). It becomes easy to store. Therefore, in order to efficiently store magnetic energy, it can be said that it is preferable to use soft magnetic particles having a fine particle size for the first portion serving as the excitation region.

<Measurement of iron loss>
Furthermore, about Example 1 and the comparative example 1, the iron loss was analyzed using the electromagnetic field analysis software J-MAG by J-SOL Corporation. The result is shown in FIG.

[Result 5]
FIG. 6 is a graph showing the loss of the reactor model according to Example 1 and Comparative Example 1. In the figure, bar graphs indicate coil loss and core loss. Compared to Comparative Example 1, when the soft magnetic particles used in the first part had a fine particle size as in Example 1, the core loss was reduced by 5%. This is because, as in Comparative Example 1, the soft magnetic particles used in the first part have a higher iron loss than the fine particle size when the total particle size includes not only the fine particle size but also the larger particle size. (See Result 3 and FIG. 4).

  In view of the above-described results, it is considered that the core is preferably composed only of soft magnetic particles having a fine particle size. However, the core is composed of such particles up to the second portion which is a non-excitation region. As a result, the magnetic resistance of the second portion also increases. As a result, when a high magnetic field is applied, the magnetic flux density in the core is reduced as compared with the case where soft magnetic particles having a coarse powder particle size are used, and the desired magnetic properties may not be obtained. . In this way, the second portion is made up of particles having a larger particle diameter than the particles in the first portion, so that a decrease in magnetic flux density in this portion can be suppressed.

  In the test described above, soft magnetic particles having an aluminum nitride layer were used. However, the inventors have similar to the aluminum nitride layer even when the soft magnetic particles have an aluminum oxide layer instead of the aluminum nitride layer. It is known that there is an effect of.

  Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention described in the claims. Design changes can be made.

  1: Reactor, 2: Core, 3A: Coil, 3B: Coil, 21: First part, 22: Second part

Claims (1)

A reactor comprising a core composed of a dust core and a coil wound so as to cover a part of the core,
Each soft magnetic particle constituting the dust core includes a base material made of an Fe-Si-Al alloy, and an aluminum nitride layer or an aluminum oxide layer covering the base material,
Of the core, the particle diameter of each soft magnetic particle constituting the first part covered by the coil is larger than the particle diameter of each soft magnetic particle constituting the second part exposed from the coil. A reactor characterized by being small.