JP2015135920A - Low-noise reactor, dust core, and method for producing the dust core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a low noise reactor capable of reducing manufacturing cost and effectively suppressing noise generation by increasing hardness of an insulation layer of a dust core; a dust core; and a method for producing the dust core.SOLUTION: A dust core is obtained by molding a mixture to a predetermined shape and subjecting the molded body to heat treatment, the mixture comprising: pure iron powder and Fe-Si-Al alloy powder constituting a composite soft magnetic material; a condensed phosphoric acid metal salt; and a binding insulating resin. In the dust core, the ratio of the Fe-Si-Al alloy powder in the composite soft magnetic material is 10-30 wt.%, and the additive amount of the condensed phosphoric acid metal salt is 0.15-1.5 wt.% with respect to the composite soft magnetic material.

Description

  The present invention relates to a low-noise reactor, a dust core suitable for the low-noise reactor, and a manufacturing method thereof.

  Choke coils are used for control power supplies such as office automation equipment, solar power generation systems, automobiles, and uninterruptible power supplies, and ferrite cores and dust cores are used as the cores. Among these, the ferrite core has a defect that the saturation magnetic flux density is small. On the other hand, a dust core produced by molding metal powder has a higher saturation magnetic flux density than soft magnetic ferrite, and thus has excellent DC superposition characteristics. The high density molded dust core has a high magnetic flux density and exhibits excellent magnetic properties.

  The powder magnetic core is required to have a magnetic characteristic that can obtain a large magnetic flux density with a small applied magnetic field and a magnetic characteristic that an energy loss due to a change in the magnetic flux density is small because of demands for improving energy exchange efficiency and low heat generation.

  When the dust core is used in an alternating magnetic field, an energy loss called iron loss (Pc) occurs. This iron loss is represented by the sum of hysteresis loss (Ph) and eddy current loss (Pe) as shown in Equation 1.

  Hysteresis loss is proportional to the operating frequency, and eddy current loss is proportional to the square of the operating frequency. Therefore, the hysteresis loss is dominant in the low frequency region, and the eddy current loss is dominant in the high frequency region. The dust core is required to have magnetic characteristics that reduce the occurrence of this iron loss.

Pc = Ph + Pe, Ph = Kh × f, Pe = Ke × f ² Formula 1
Kh: Hysteresis loss coefficient, Ke: Eddy current loss coefficient, f: Frequency

  In order to reduce the hysteresis loss of the dust core, the domain wall can be easily moved. To that end, the coercive force of the soft magnetic powder particles can be reduced. By reducing the coercive force, the initial permeability can be improved and the hysteresis loss can be reduced.

On the other hand, eddy current loss is inversely proportional to the specific resistance of the core, as shown in Equation 2.
^{Ke = k1 (Bm 2 · t} 2) / ρ ... Equation 2
k1: coefficient, Bm: magnetic flux density, t: particle diameter (thickness in the case of plate material), ρ: specific resistance

JP 2008-192897 A

  A photovoltaic power generation system or the like often has units such as indoor units and has a problem such as noise. As a material for a powder magnetic core of a reactor used for these, Fe-6.5Si alloy powder, Fe- A low magnetostrictive material such as Si-Al alloy (Sendust) is suitable.

  However, these Fe-6.5Si alloy powders and Fe-Si-Al alloys (Sendust) are very expensive compared to pure iron powders, which has led to an increase in manufacturing costs. For this reason, there has been a strong demand for using pure iron powder that is as inexpensive as possible for the material of the dust core.

  On the other hand, Patent Document 1 describes a dust core using a composite soft magnetic material in which pure iron powder and Fe—Si alloy powder are mixed as a material of the dust core. That is, a powder magnetic core is described in which the blending ratio of the flat pure iron powder in the composite soft magnetic material is 10 wt% to 55 wt%, and the rest is Fe—Si alloy powder. The purpose of mixing these powders is not to reduce the manufacturing cost but to suppress the noise increase by improving the core strength.

  However, by simply mixing Fe-Si alloy powder, which is a low magnetostrictive material, with pure iron powder, noise is generated by collision of powders or vibration of powders due to the magnetic attraction force between the powders generated by applying an excitation magnetic field. Therefore, the noise suppression effect is small.

  Patent Document 1 introduces a technique for increasing the occupancy rate by mixing Fe—Si alloy and pure iron as a noise reduction technique. However, even if the occupancy was increased and the number of empty walls was reduced, the effect of suppressing powder vibration consisting of an excitation magnetic field was small.

  The present invention has been proposed to solve the above-described problems of the prior art. An object of the present invention is to provide a low-noise reactor, a dust core for a reactor, and a method for manufacturing the same, which can increase the hardness of an insulating layer of the dust core and effectively suppress noise generation while reducing the manufacturing cost. It is in.

In order to achieve the above object, the powder magnetic core of the present invention is characterized by adopting the following configuration.
(1) A compact formed by molding a mixture containing pure iron powder and Fe-Si-Al alloy powder constituting the composite soft magnetic material and a condensed phosphate metal salt into a predetermined shape, and heat-treating the molded body. Make a magnetic core.
(2) The ratio of the Fe—Si—Al alloy powder in the composite soft magnetic material is 10 wt% to 30 wt%.
(3) The addition amount of the condensed phosphate metal salt is 0.15 wt% to 1.5 wt% with respect to the composite soft magnetic material.

Moreover, you may make it have the following structure.
(4) The addition amount of the condensed phosphate metal salt is preferably 0.25 wt% to 1.0 wt% with respect to the composite soft magnetic material.
(5) The condensed phosphate metal salt is preferably condensed aluminum phosphate.
(6) The condensed aluminum phosphate is preferably a simple substance of aluminum tripolyphosphate or aluminum metaphosphate, or a mixture of both.
(7) The insulating layer formed around the pure iron powder or the Fe—Si—Al alloy powder may contain insulating fine powder and / or a hardening accelerator.
(8) The condensed phosphoric acid metal salt has basic substances such as Al ₂ O ₃ , SiO ₂ , MgO, Mg (OH) ₂ , CaO, Ca (OH) ₂ , asbestos, talc and fly ash as curing accelerators. At least one kind is preferably added.

  The low-noise reactor according to the present invention is characterized in that a coil is wound around a dust core having the above-described configuration.

  The method for producing a dust core according to the present invention includes a first mixing step in which pure iron powder and Fe-Si-Al alloy powder constituting a composite soft magnetic material are mixed with a condensed phosphate metal salt, and a first mixing step. The second mixing step of mixing the binding insulating resin with the mixture obtained in step 1, the pressure forming step of pressure-molding the mixture obtained in the second mixing step, and the molding obtained in the pressure molding step A heat treatment step of heat treating the body at a temperature of 500 ° C. or higher, and in the first mixing step, the ratio of the Fe—Si—Al alloy powder in the composite soft magnetic material is 10 wt% to 30 wt%, and condensed phosphoric acid The addition amount of the metal salt is 0.15 wt% to 1.5 wt% with respect to the composite soft magnetic material.

Moreover, you may make it have the following structures.
(1) It is preferable that the addition amount of the condensed phosphate metal salt is 0.25 wt% to 1.0 wt% with respect to the composite soft magnetic material.
(2) The condensed metal phosphate is preferably condensed aluminum phosphate.
(3) It is preferable that the condensed aluminum phosphate is a simple substance of aluminum tripolyphosphate or aluminum metaphosphate, or a mixture of both.
(4) Al ₂ O ₃ , SiO ₂ , MgO, Mg (OH) ₂ , CaO, Ca (OH) ₂ , asbestos, talc, fly ash basic substance as a curing accelerator for condensed phosphate metal salt It is preferable that at least one kind of is added.
(5) Before the first mixing step, it is preferable to have a powder heat treatment step of adding and mixing insulating fine powder to the pure iron powder and heat-treating the mixed powder in a hydrogen atmosphere.

  According to the present invention, a low-noise reactor, a dust core, and a method for producing the same that can reduce the manufacturing cost, increase the hardness of the insulating layer of the dust core, suppress vibration of the core powder, and effectively suppress noise generation. Can be provided.

It is a graph which shows the relationship between the addition amount of Fe-Si-Al alloy powder, and noise. It is a graph which shows the relationship between the addition amount of Fe-Si-Al alloy powder, and a magnetic characteristic (L value). It is a graph which shows the relationship between the addition amount of condensed metal phosphate (aluminum tripolyphosphate) and noise.

(1) Composite Soft Magnetic Material The composite soft magnetic material is a mixture having pure iron powder and a low magnetostrictive material as constituent elements. As the pure iron powder, those conventionally used can be used. For example, pure iron powder exceeding 99.5% by mass can be used.

Moreover, as pure iron powder, before mixing with a low magnetostrictive material, insulating fine powder was added to pure iron powder and mixed, and the mixed powder was heat-treated at around 1000 ° C. in a hydrogen atmosphere. May be used. By performing this heat treatment, a noise suppression effect can be obtained. This is presumably because impurities can be removed by reducing the oxygen concentration and the particle diameter in the crystal can be grown, so that the domain wall movement becomes smooth, the follow-up performance of the excitation magnetic field increases, and noise can be reduced. As the insulating fine powder, alumina powder (Al ₂ O ₃ ), SiO ₂ , MgO, talc, or the like can be used. By adding the insulating fine powder, it is possible to prevent the pure iron powders from sticking to each other, harden the insulating layer around the pure iron powder, suppress vibrations of the pure iron powder, and obtain a noise suppressing effect. From the viewpoint of noise suppression effect, the average particle size of the insulating fine powder is preferably 7 nm to 1 μm. More preferably, the thickness is 7 nm to 500 nm. The addition of the insulating fine powder may be performed on the Fe—Si—Al alloy powder, and the insulating layer formed around it can be hardened.

  As the low magnetostrictive material, sendust (Fe-Si-Al alloy) powder, Fe-Si alloy powder and the like can be used, but sendust (Fe-Si-Al alloy) powder is preferable. The average particle diameter of the pure iron powder, Sendust (Fe—Si—Al alloy) powder, and Fe—Si alloy powder is preferably 20 μm to 100 μm.

  As the low magnetostrictive material, those produced by a water atomizing method, a gas atomizing method, or a water / gas atomizing method can be used, and those by a water atomizing method are particularly preferable. The reason is that the water atomization method is rapidly cooled at the time of atomization, so that it is difficult to crystallize. Since pure iron powder and low magnetostrictive material (powder) are both soft magnetic, these powders are sometimes referred to as soft magnetic powders in the following.

  The ratio (addition amount) of the low magnetostrictive material in the composite soft magnetic material is preferably 10 wt% to 30 wt%. By setting it within this range, it is possible to reduce collision between powders and powder vibration when applying an exciting magnetic field, so that a noise suppression effect can be obtained. If the amount (content) of the low magnetostrictive material is less than this range, the noise suppression effect cannot be obtained. When the amount (content) of the low magnetostrictive material is larger than this range, the magnetic characteristics such as the DC superimposition characteristics are deteriorated and a practical reactor cannot be obtained, which is not preferable.

(2) Condensed phosphate metal salt As the condensed phosphate metal salt, condensed aluminum phosphate is suitable. Among them, aluminum tripolyphosphate, aluminum metaphosphate, or a mixture thereof obtained by heating and dehydrating primary aluminum phosphate is suitable. In particular, aluminum dihydrogen tripolyphosphate is suitable. The average particle diameter of the condensed aluminum phosphate is more preferably 1.5 μm to 6.0 μm. In addition, condensed calcium phosphate and condensed magnesium phosphate have the same effect.

  The condensed metal phosphate is added to and mixed with the composite soft magnetic powder. Further, the condensed phosphate metal salt may be added to and mixed with either the pure iron powder or the low magnetostrictive material. In any case, by adding and mixing the condensed phosphate metal salt, a film of the condensed phosphate metal salt is formed around the soft magnetic powder of the pure iron powder or the low magnetostrictive material.

  The addition amount of the condensed phosphate metal salt is preferably 0.15 wt% to 1.5 wt% with respect to the composite soft magnetic material. By setting it within this range, the insulating layer around the soft magnetic powder can be hardened and the adhesion strength between the soft magnetic powder and the insulating layer can be improved. Therefore, the impact and vibration of the powder can be suppressed, and a low noise effect can be obtained. When the amount of the condensed phosphate metal salt added to the composite soft magnetic material is 0.25 wt% to 1.0 wt%, the low noise effect is particularly great. If the addition amount is less than 0.15 wt%, the noise suppression effect cannot be obtained. If the addition amount exceeds 1.5 wt%, the dip current increases due to a decrease in magnetic permeability, and noise increases due to increased vibration and collision. To increase.

(3) Curing accelerator A basic substance can be added to the condensed phosphate metal salt as the curing accelerator. The curing accelerator hardens the insulating layer around pure iron powder or Fe—Si—Al alloy powder, and acts as a curing agent. Note that an effect of curing the insulating layer in a short time may be included. The curing accelerator is preferably added when the insulating fine powder is not added to the composite soft magnetic material. Further, even when insulating fine powder is added, a curing accelerator can be added. Examples of the basic substance include at least one of Al ₂ O ₃ , SiO ₂ , MgO, Mg (OH) ₂ , CaO, Ca (OH) ₂ , asbestos, talc, and fly ash. It is particularly preferable to add Al ₂ O ₃ from the viewpoint of obtaining a low noise effect, and it is even better when the particle size is 7 nm to 500 nm. In the case of adding MgO, a low noise effect can be obtained in the same manner, and the particle size is more preferably 0.2 μm to 1.0 μm. The addition amount of the curing accelerator is preferably 10 wt% to 30 wt% with respect to the condensed phosphate metal salt. This is because if it is less than 10 wt%, the effect as a curing agent is small, and if it exceeds 30 wt%, formation of a film of the condensed phosphate metal salt on the soft magnetic powder surface is hindered.

(4) Binder Insulating Resin The binder insulating resin is added to and mixed with a mixture of the composite soft magnetic material and the condensed metal phosphate. As a binder insulating resin, when a mixture of a composite soft magnetic material and a condensed metal phosphate is pressurized at room temperature, a molded body in a state of being densified to a certain degree is obtained, and the molded body is excessively large. Unless a force is applied, a resin having a viscosity that can maintain a predetermined shape is used.

  Examples include silicone resins and waxes. As the silicone resin, methylphenyl silicone resin is preferable. An appropriate amount of methylphenyl silicone resin is 0.75 wt% to 2.0 wt% with respect to the composite soft magnetic material. If it is less than this, the strength of the molded product will be insufficient and cracks will occur. If it is more than this, there arises a problem that the maximum magnetic flux density is decreased due to the decrease in density and the magnetic characteristics are decreased due to an increase in hysteresis loss.

  As other binder resin, an acrylic acid copolymer resin (EAA) emulsion can be used. The addition amount of the acrylic acid copolymer resin (EAA) emulsion to be mixed is 0.5 wt% to 2.0 wt% with respect to the composite soft magnetic material, and the drying temperature and drying time in that case are 80 ° C. to 150 ° C. 2 hours. Instead of the acrylic acid copolymer resin (EAA) emulsion, an aqueous PVA (polyvinyl alcohol) solution (12% aqueous solution) may be used. The addition amount of the PVA (polyvinyl alcohol) aqueous solution (12% aqueous solution) is appropriately 0.5 wt% to 3.0 wt% with respect to the composite soft magnetic material.

  Moreover, a solution (12% solution) of PVB (polyvinyl butyral) may be used, or it may be used after being dissolved in a solvent such as xylene or butanol. The amount added to the composite soft magnetic material in that case is the same as that of PVA.

(5) Lubricating resin As the lubricating resin, stearic acid and metal salts thereof and waxes such as ethylene bisstearamide can be used. By mixing the lubricating resin, it is possible to improve the sliding between the powders, so that the density at the time of mixing can be improved and the molding density can be increased. Furthermore, it is possible to reduce the punching pressure of the upper punch during molding and to prevent the vertical stripes on the core wall surface from being generated due to the contact between the mold and the powder. The addition amount of the lubricious resin is preferably about 0.1 wt% to 1.0 wt%, and generally about 0.5 wt% with respect to the composite soft magnetic material.

(6) Manufacturing method The manufacturing method of the powder magnetic core of this embodiment has the following processes.
(A) A first mixing step of mixing pure iron powder, a low magnetostrictive material, and a condensed metal phosphate.
(B) A second mixing step in which the binding insulating resin is mixed with the mixture obtained in the first mixing step.
(C) A pressure molding step of pressure molding the mixture obtained in the second mixing step.
(D) A heat treatment step of heat-treating the molded body obtained in the pressure molding step.

(A) First mixing step In the first mixing step, for example, a mixture of pure iron powder having an average particle diameter of 20 μm to 100 μm and Fe—Si—Al alloy powder (10 wt% to 30 wt%) as a low magnetostrictive material, respectively. The 0.15 wt% to 1.5 wt% condensed phosphate metal salt is added to and mixed with the composite soft magnetic material. For example, the above mixture is mixed for about 2 hours using a V-type mixer.

  The timing of adding the condensed phosphate metal salt may be after the pure iron powder and the Fe-Si-Al alloy powder are mixed as described above, or the Fe-Si-Al alloy powder is added to the pure iron powder. The same timing as the addition may be in the middle of mixing the pure iron powder and the Fe—Si—Al alloy powder. Further, the timing of adding the condensed phosphoric acid metal salt is not necessarily this step, and in the second mixing step of mixing the binding insulating resin of the following (b), it can be added and mixed together with the lubricant. is there. However, the film formation on the surface of the soft magnetic powder is more effectively performed by mixing the condensed phosphate metal salt in the previous step than the mixing of the binding insulating resin.

Before the first mixing step, insulating fine powders such as alumina powder (Al ₂ O ₃ ), SiO ₂ , MgO, and talc are added to and mixed with pure iron powder, and the mixed powder is placed in a hydrogen atmosphere. A powder heat treatment step in which heat treatment is performed at around 1000 ° C.

(B) Second mixing step With respect to the mixture of the composite soft magnetic material and the condensed phosphate metal salt, a binding insulating resin of 0.75 wt% to 2.0 wt% with respect to the composite soft magnetic material, and 0.1 wt% % To 1.0 wt% of a lubricating resin is added and further mixed. It is also possible to simultaneously perform the mixing of the condensed phosphate metal salt (a) and the binding resin and the lubricating resin (b).

  In the step of mixing the binding insulating resin, a silane coupling agent can be added. The silane coupling agent may be added to the mixture in the first mixing step after being mixed with the silicone resin or the like, or may be added to the composite soft magnetic material separately or simultaneously with the silicone resin or the like. When a silane coupling agent is used, the amount of the binding insulating resin can be reduced. As the type of silane coupling agent having good compatibility, aminosilane-based, epoxysilane-based, and isocyanurate-based silane coupling agents can be used. The amount of the silane coupling agent added to the binding insulating resin is preferably 0.25 wt% to 1.0 wt%. By adding a silane coupling agent in this range to the binding insulating resin, the standard deviation, magnetic characteristics, and strength characteristics of the density of the molded dust core can be improved.

(C) Pressure molding process In a pressure molding process, the mixture which passed through the 2nd mixing process is filled in a metal mold, and is pressure-molded. In that case, the mold temperature is preferably room temperature, but may be in the range up to 80 ° C. That is, the normal temperature here means a range from 5 ° C. to 35 ° C., but may be a range from 5 ° C. to 80 ° C. The molding pressure is, for example, 900 MPa to 1700 MPa.

(D) Heat treatment process The heat treatment with respect to the molded body has a heating temperature of 500 ° C. or higher, and a heat holding time is about 2 to 4 hours. The heat treatment atmosphere is preferably a nitrogen atmosphere, a reducing atmosphere such as 10% to 30% hydrogen gas. Further, if the heat treatment temperature is raised too much, dielectric breakdown will occur and eddy current loss will increase. Therefore, from the viewpoint of suppressing an increase in iron loss, 500 ° C to 650 ° C, particularly 600 ° C to 650 ° C is preferable. The noise of the reactor produced by setting it as these temperature ranges becomes low.

  An insulating layer (having a thickness of about 20 nm to 50 nm) is formed around pure iron powder or Fe—Si—Al alloy powder in the molded body obtained through the heat treatment step. This insulating layer may contain insulating fine powder and / or curing accelerator by addition of insulating fine powder and / or curing accelerator. In addition, when a binding insulating resin containing silicone is added in the second mixing step, the binding insulating resin is changed to a silica layer by the heat treatment step. That is, pure iron powder and Fe—Si—Al alloy powder constituting the composite soft magnetic material are covered with a silica layer containing a condensed phosphate metal salt by a heat treatment process. For example, when a methylphenyl silicone resin or a silane coupling agent is also added as the binding insulating resin, these are oxidized to form a silica layer. By using the silica layer, the hardness of the surrounding layer of the soft magnetic powder is improved, and the hardness of the silica layer is further improved by including the condensed metal phosphate, so that a low noise effect is obtained. When a curing accelerator is contained in the silica layer in addition to the condensed metal phosphate, a further low noise effect can be obtained.

When aluminum tripolyphosphate, aluminum metaphosphate or a mixture thereof is added as a condensed phosphate metal salt, the molded product after heat treatment molding contains Al and P, but the added condensed phosphate metal salt has It may be changed by heat treatment and may remain as metaphosphoric acid type A (Al (PO ₃ ) ₃ ) or metaphosphoric acid type B (Al (PO ₃ ) ₃ ). When condensed calcium phosphate or condensed magnesium phosphate is added as the condensed phosphate metal salt, the composition after heat treatment molding contains Ca and P or Mg and P in its composition.

  Examples of the present invention will be described below with reference to Tables 1 to 3 and FIGS.

(1) Measurement items Measurement items are magnetic permeability, iron loss, noise, and inductance (L value). For measurement of magnetic permeability and calculation of iron loss, a primary winding (42 turns) was applied to each of the produced dust cores to produce a reactor. For measurement of noise and inductance (L value), a reactor was manufactured by winding 42 turns of copper powder of φ2.6 mm on each of the prepared dust core samples. Each dust core had an outer diameter of 77.8 mm, an inner diameter of 49.2 mm, and a height of 30 mm. Moreover, the magnetic permeability and iron loss of the produced reactor were computed on the following conditions, and the noise and inductance (L value) which generate | occur | produce from a reactor on the following conditions were measured.

<Permeability and iron loss>
The measurement conditions for the magnetic permeability and iron loss were a secondary winding (2 turns), a frequency of 20 kHz, and a maximum magnetic flux density Bm = 20 mT. The magnetic permeability was the amplitude magnetic permeability when the maximum magnetic flux density Bm was set when measuring the iron loss Pcv. The iron loss was calculated using a BH analyzer (Iwatori 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 of the iron loss frequency curve by the following method (1) to (3) by the least square method.

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

<Noise measurement>
Regarding noise measurement, its measurement equipment, measurement environment, measurement method, etc. are shown below.
[Noise evaluation equipment and software]
(1) Measuring device SOUND LEBEL METER NL-31 ...
(2) Measurement environment Anechoic box (background noise is 25 dB) KM-1 ... Made by Accor Corporation
(3) Power amplifier (sound source) HIGH SPEED POWER AMPLIFIER / BIPOLAR POWER SUPPLY 4025 ... NF ELECTRONIC INSTRUMENTS
(4) Oscillator 80MHz Function / Arbitrary Waveform Generator 33250A ... made by Agilent Technologies
(5) Analysis processing software SA-01 CATSYSSA Ver3.5… Rion Co., Ltd.

[Measuring method]
(1) The produced reactor was connected to a photovoltaic power conditioner.
(2) Microphone distance: 10 mm from the measurement sample.
(3) The measurement sample was placed in an anechoic box, and the distance of the noise measurement microphone was 10 mm from the sample.

<Measurement of inductance (L value)>
Magnetic characteristics (inductance L value) were measured on the manufactured reactor under conditions of an applied magnetic field of 6.5 kA / m and 10 kA / m, respectively.

(2) Sample preparation method The sample of the powder magnetic core is as follows: (a) the ratio of the low magnetostrictive material (Fe-Si-Al alloy powder) to the composite soft magnetic material; (b) the condensed metal phosphate It was produced from the viewpoint of the amount of addition. These production methods and the results are shown below in order.

(a) Ratio of low magnetostrictive material (Fe—Si—Al alloy powder) to composite soft magnetic material Alumina powder (average particle size) of 100 m ² / g as an insulating fine powder with respect to pure iron powder having an average particle size of 30 μm 1.0 wt% of the particle diameter of about 7 nm) was mixed, and the mixed powder was heat-treated at 1020 ° C. for 2 hours in a hydrogen atmosphere. The obtained powder was mixed with Fe-Si-Al alloy powder (crushed powder, average particle size 43 μm), which is a low magnetostrictive material, and 0.25 wt% aluminum tripolyphosphate with the composition shown in Table 1 below. To this mixture, 0.5 wt% silane coupling agent and 1.0 wt% methylphenyl silicone resin are mixed, dried by heating at 150 ° C. for 2 hours, passed through a sieve having an opening of 300 μm, A lubricant was mixed at 0.5 wt%.

  This was pressure-molded at a pressure of 1000 MPa at room temperature to produce a ring-shaped molded body having an outer diameter of 77.8 mm, an inner diameter of 49.2 mm, and a height of 30.0 mm, and a holding time at 550 ° C. in a nitrogen atmosphere. Heat treatment was performed for 2 hours to produce a dust core.

  With respect to these samples, as shown in the above “(1) Measurement item”, a reactor was manufactured, and permeability, iron loss calculation, and noise measurement were performed. The results are shown in Table 1 and FIG.

In Table 1, the sample of the dust core produced in the above (a) is item B. Items A and C in Table 1 show comparative examples for item B. Item A is the same as the sample preparation method (a) except that aluminum tripolyphosphate is not added. Item C is the same as the sample preparation method of (a) above except that Fe-6.5% Si alloy powder is used alone as the soft magnetic powder and that aluminum tripolyphosphate is not added. . Similarly to the item B, the magnetic permeability, iron loss, and noise were measured for the dust core produced under the conditions of the items A and C. The results are shown in Table 1 and FIG. In Tables 1 to 3, μa represents magnetic permeability, and Pcv represents iron loss. The noise Max value is a peak value at the carrier frequency (20 kHz).

  FIG. 1 is a graph showing the relationship between the addition amount of Fe—Si—Al alloy powder and noise, and shows a noise comparison between item A and item B. When item A and item B are compared, it can be confirmed that noise is reduced overall in item B to which aluminum tripolyphosphate is added, compared to item A to which aluminum triphosphate is not added. That is, it can be seen that the addition of aluminum tripolyphosphate greatly contributes to the noise suppression effect. In other words, since item A has the same or less noise suppression effect than item C using Fe6.5% Si alloy powder, pure iron powder and Fe-Si-Al alloy are simply used. A large noise suppression effect cannot be obtained only by using a composite soft magnetic material mixed with powder.

In addition, for the sample of the powder magnetic core of item B, a 42-turn winding was made with a copper wire of φ2.6 mm to produce a reactor, and the applied magnetic field was 6.5 kA / m and 10 kA / m, respectively. Magnetic characteristics (inductance L value) were measured. The results are shown in Table 2 and FIG.

  FIG. 2 is a graph showing the relationship between the added amount of Fe—Si—Al alloy powder and the magnetic characteristics (L value). When the applied magnetic field is 6.5 kA / m, the L value as a whole is high and good magnetic properties can be obtained. On the other hand, when the applied magnetic field is 10 kA / m, relatively good magnetic properties can be obtained when the addition amount of the Fe—Si—Al alloy powder is 30 wt% or less with respect to the composite soft magnetic material, but the L value is linear. Since it tends to decrease, if it exceeds 30 wt%, the DC superimposition characteristics deteriorate, and the magnetic characteristics required for the reactor cannot be obtained.

  From the results of Table 1, Table 2, FIG. 1 and FIG. 2, the total amount of Fe-Si-Al alloy powder is 10 wt% with respect to the composite soft magnetic material, considering the low noise effect and magnetic characteristics comprehensively. It is preferable that it is -30 wt%. That is, if it is less than 10 wt%, a low noise effect cannot be obtained, but if it is 10 wt% or more, a low noise effect can be obtained. However, as shown in Table 1 and FIG. 1, it can be seen that a low noise effect can be obtained up to 10 wt% to 50 wt%. However, as shown in Table 2 and FIG. 2, the amount of Fe—Si—Al alloy powder added As the (ratio) increases, the inductance (L value) tends to decrease. For this reason, if the amount of Fe—Si—Al alloy powder added exceeds 30 wt%, the DC superposition characteristics deteriorate, and the magnetic characteristics required for the reactor cannot be obtained. Therefore, the addition amount of the Fe—Si—Al alloy powder is in the range of 10 wt% to 30 wt% with respect to the composite soft magnetic material.

  It should be noted that the level required by the environment in which the reactor is used depends on how much noise level the low noise indicates. Generally, the level of noise that does not feel uncomfortable when the reactor is used is set to 42 dB or less, but is not limited thereto. On the other hand, when a unit such as a solar power generation system is arranged indoors, a lower noise level may be required. Even in such a case, in this example, the Fe—Si—Al alloy powder is added in an amount of 15 wt% or more (15 wt% to 30 wt%), whereby Fe—Si shown in item C of Table 1 is obtained. Demonstrates a low noise effect at the same level or higher than the low noise effect when using a single alloy powder.

  As described above, by adding a condensed phosphate metal salt without using a large amount of Fe-Si-Al alloy powder or Fe-Si alloy powder that is more expensive and exhibits a low noise effect than pure iron powder, Fe-Si-Al alloy powder is reduced as much as possible, and even if a lot of cheap pure iron powder is used, the insulating layer formed around pure iron powder or Fe-Si-Al alloy powder can be hardened. The low noise effect can be obtained, and the manufacturing cost can be reduced. That is, an inexpensive pure iron powder is used as the main ratio, and an Fe-Si-Al alloy powder, which is an expensive low magnetostrictive material, is used as a secondary ratio. Compared to the case where only Si—Al alloy powder or Fe—Si alloy powder is used, the same or higher noise suppression effect can be obtained.

(b) Addition amount of condensed metal phosphate Phosphorus iron powder with an average particle size of 30 μm is mixed with 1.0 wt% of alumina powder (average particle size of about 7 nm) having a specific surface area of 100 m ² / g as an insulating fine powder. The mixed powder was heat-treated at 1020 ° C. for 2 hours in a hydrogen atmosphere. The resulting powder was mixed with Fe-Si-Al alloy powder (crushed powder, average particle size 43 μm), which is a low magnetostrictive material, and aluminum tripolyphosphate in the amount shown in Table 3 below with the formulation shown in Table 3 below. . To this mixture, 0.5 wt% silane coupling agent and 1.0 wt% methylphenyl silicone resin are mixed, dried by heating at 150 ° C. for 2 hours, passed through a sieve having an opening of 300 μm, A lubricant was mixed at 0.5 wt%.

  This was pressure-molded at a pressure of 1000 MPa at room temperature to produce a ring-shaped molded body having an outer diameter of 77.8 mm, an inner diameter of 49.2 mm, and a height of 30.0 mm, and a holding time at 550 ° C. in a nitrogen atmosphere. Heat treatment was performed for 2 hours to produce a dust core.

With respect to these samples, as shown in the above “(1) Measurement item”, a reactor was manufactured, and permeability, iron loss calculation, and noise measurement were performed. The results are shown in Table 3 and FIG.

  FIG. 3 is a graph showing the relationship between the amount of aluminum tripolyphosphate added and noise. As apparent from the results of Table 3 and FIG. 3, the low noise effect is good when the amount of aluminum tripolyphosphate added to the composite soft magnetic material is 0.15 wt% to 1.5 wt%. In particular, when the content is 0.25 wt% to 1.0 wt%, a further low noise effect can be obtained. If the amount of aluminum tripolyphosphate added to the composite soft magnetic material is less than 0.15 wt%, a low noise effect cannot be obtained, and if it exceeds 1.5 wt%, the magnetic permeability decreases and the dipple current increases, Noise increases. Moreover, since an iron loss increases, it is not preferable. Note that even when the addition amount is 2.0 wt%, the noise Max value is 41.0 and a noise suppression effect can be obtained, but from the viewpoint of magnetic permeability and iron loss, it is set to 1.5 wt% or less.

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

(1) In the above embodiment, the composite soft magnetic material is composed of pure iron powder and a low magnetostrictive Fe—Si—Al alloy powder. ) Of 10 wt% to 30 wt%, Fe-Si alloy powder or mixed powder of Fe-Si-Al alloy powder and Fe-Si alloy powder may be used as the low magnetostrictive material.

Claims (13)

In a powder magnetic core formed by molding a mixture containing pure iron powder and Fe-Si-Al alloy powder constituting a composite soft magnetic material and a condensed phosphate metal salt into a predetermined shape, and heat-treating the molded body,
The ratio of the Fe—Si—Al alloy powder in the composite soft magnetic material is 10 wt% to 30 wt%,
The dust core according to claim 1, wherein the amount of the condensed metal phosphate is 0.15 wt% to 1.5 wt% with respect to the composite soft magnetic material.   2. The dust core according to claim 1, wherein an amount of the condensed metal phosphate added is 0.25 wt% to 1.0 wt% with respect to the composite soft magnetic material.   The dust core according to claim 1 or 2, wherein the condensed metal phosphate is condensed aluminum phosphate.   The dust core according to claim 3, wherein the condensed aluminum phosphate is a simple substance of aluminum tripolyphosphate or aluminum metaphosphate, or a mixture of both.   The insulating layer formed around the pure iron powder or the Fe-Si-Al alloy powder contains an insulating fine powder, a hardening accelerator, or both. The dust core according to any one of the above. The condensed phosphate metal salt has at least a basic substance such as Al ₂ O ₃ , SiO ₂ , MgO, Mg (OH) ₂ , CaO, Ca (OH) ₂ , asbestos, talc, and fly ash as the curing accelerator. 6. A dust core according to claim 5, wherein one kind is added.   A low noise reactor comprising a coil wound around the dust core according to any one of claims 1 to 6. A first mixing step of mixing pure iron powder and Fe-Si-Al alloy powder constituting the composite soft magnetic material, and a condensed phosphate metal salt;
A second mixing step of mixing a binding insulating resin with the mixture obtained in the first mixing step;
A pressure molding step of pressure molding the mixture obtained in the second mixing step;
A heat treatment step of heat-treating the molded body obtained in the pressure molding step at a temperature of 500 ° C. or higher,
In the first mixing step, a ratio of the Fe—Si—Al alloy powder in the composite soft magnetic material is 10 wt% to 30 wt%,
The method for producing a dust core, wherein an amount of the condensed metal phosphate added is 0.15 wt% to 1.5 wt% with respect to the composite soft magnetic material.   The method for producing a dust core according to claim 8, wherein an amount of the condensed metal phosphate added is 0.25 wt% to 1.0 wt% with respect to the composite soft magnetic material.   The method for producing a dust core according to claim 8 or 9, wherein the condensed metal phosphate is condensed aluminum phosphate.   The method for producing a dust core according to claim 10, wherein the condensed aluminum phosphate is a simple substance of aluminum tripolyphosphate or aluminum metaphosphate, or a mixture of both. As the hardening accelerator, the condensed phosphate metal salt has at least a basic substance of Al ₂ O ₃ , SiO ₂ , MgO, Mg (OH) ₂ , CaO, Ca (OH) ₂ , asbestos, talc, fly ash. The method for producing a dust core according to any one of claims 8 to 11, wherein one kind is added.   9. A powder heat treatment step of adding an insulating fine powder to the pure iron powder and mixing the pure iron powder and heat-treating the mixed powder in a hydrogen atmosphere before the first mixing step. The manufacturing method of the powder magnetic core of any one of Claim 12.