TWI585787B - Powder core - Google Patents

Description

Powder core

The present invention relates to a powder magnetic core comprising a soft magnetic powder and an insulating bonding material for a choke coil and the like and a method of manufacturing the same.

For a powder magnetic core used in a booster circuit for a hybrid vehicle or a reactor for power generation, substation, a transformer, a choke coil, etc., it is assumed that it is in a high temperature environment for a long time, and is required It has thermal stability of magnetic properties.

The powder magnetic core can be obtained by subjecting a mixture comprising a soft magnetic powder and a binding material (adhesive resin) to powder compaction and further applying heat treatment. Since this heat treatment is a process necessary for improving the magnetic properties of the soft magnetic powder, the industry has designed a resin which is excellent in thermal stability as a binder resin or the like.

However, according to the experiment, it is known that under the previous structure of the powder magnetic core, the heat resistance test causes a problem that the magnetic permeability deterioration is increased and the thermal stability of the inductance is lowered.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2010-251600

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2010-232223

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2009-212385

[Patent Document 4] Japanese Patent Laid-Open Publication No. 2004-143554

[Patent Document 5] Japanese Patent Laid-Open Publication No. 2010-27854

The invention of the patent document 1 relates to a powder for a powder magnetic core which is obtained by dispersing a glass powder in an alkoxide layer coated with a soft magnetic metal powder, and further comprising an insulating layer covering the alkoxide layer. Further, the object of the invention described in Patent Document 1 is to obtain a high-strength powder magnetic core.

The invention of Patent Document 2 relates to an insulating coated soft magnetic powder comprising a core portion of a soft magnetic material and a coating layer obtained by fixing particles of an insulating material covering the core portion. Further, an object of the invention described in Patent Document 2 is to provide a powder magnetic core having a small eddy current loss.

The invention of Patent Document 3 relates to a composite soft magnetic material comprising a soft magnetic powder and an insulating bonding material, and Patent Document 3 discloses that the insulating bonding material is lead-free glass, and a polyfluorene can be added to the composite soft magnetic material. Any one of an oxygen resin or a stearate. Further, the object of the invention described in Patent Document 3 is to maintain the performance of the powder magnetic core for a long period of time. Here, performance is listed as iron loss and strength.

The invention of Patent Document 4 relates to a coated iron-based powder obtained by coating a surface of an iron-based powder with a coating material, and Patent Document 4 discloses that the coating material includes glass, a binder, and a glass and a binder. Insulating, thermally stable substance. Further, the object of the invention described in Patent Document 4 is to obtain a powder magnetic core which can ensure insulation and improve strength.

Patent Document 5 discloses a powder magnetic core in which an amorphous soft magnetic alloy powder and a glass powder are mixed with a binder resin, and the mixture is press-formed to form a molded body, which is relatively amorphous and soft. The magnetic alloy powder is formed by heat treatment at a temperature at which the crystallization temperature is low. Further, the object of the invention described in Patent Document 5 is to obtain a powder magnetic core having a low loss.

As described above, in each of the patent documents, there is no literature that seeks thermal stability of magnetic permeability. In addition, there is no improved bonding material for achieving thermal stability of magnetic permeability. A patent document on the material composition and the relationship with heat treatment. The invention described in Patent Document 5 describes an experiment on iron loss and magnetic permeability. However, Patent Document 5 aims to reduce the eddy current loss for the first purpose, and does not improve the relationship between the bonding material and the heat treatment from the viewpoint of magnetic permeability. Further, the inventors of the present invention considered that under the experimental conditions of Patent Document 5, the amount of the bonding material (adhesive resin) added is too small, and the strength of the powder magnetic core cannot be sufficiently ensured.

Accordingly, the present invention has been made to solve the above-mentioned problems, and an object thereof is particularly to provide a powder magnetic core capable of improving the thermal stability of magnetic permeability and a method of manufacturing the same.

The powder magnetic core of the present invention is characterized in that it is obtained by compression-molding a mixture comprising a soft magnetic powder and an insulating bonding material, which comprises a binder resin and glass, and the glass is The glass transition temperature (Tg) is lower than the temperature of the above heat treatment.

Further, the method for producing a powder magnetic core according to the present invention includes the steps of: mixing a soft magnetic powder with an adhesive resin as an insulating bonding material and a glass powder to form a mixture; and compressing and forming the mixture, and The heat treatment temperature higher than the glass transition temperature (Tg) of the above glass powder is followed by heat treatment.

It is considered that according to the present invention, the glass contained in the insulating bonding material is deformed by heat treatment in the manufacturing process of the powder magnetic core or the glass is bonded to each other, whereby the expansion or contraction due to thermal deterioration of the adhesive resin can be alleviated ( It is considered that the mechanical strength of the insulating bonding material can be improved). In other words, it is considered that the glass is not dispersed in the insulating bonding material as a simple filler, but also functions as a wedge for preventing expansion or contraction of the adhesive resin layer in the insulating bonding material.

Here, the magnetic permeability of the powder magnetic core can be expressed by the Olenddrof type indicating the DC magnetic permeability of the aggregate of the ferromagnetic powder.

The filling rate η of the soft magnetic powder, the effective demagnetization coefficient N of the soft magnetic powder, and the inherent magnetic permeability μ _t of the soft magnetic powder are as follows: Among them, μ ₀ is the magnetic permeability of vacuum 4π×10 ^-7 Hm ^-1 .

It is conceivable that, for the effective demagnetization coefficient N, the effective demagnetization coefficient N becomes smaller than the soft magnetic powder alone by the shape of the soft magnetic powder or the magnetic interaction between the soft magnetic powders in the state of filling the soft magnetic powder. N in the state.

As described above, in the present invention, the glass is mixed in the insulating bonding material, and at this time, by selecting a glass having a glass transition temperature (Tg) having a lower heat treatment temperature in the manufacturing step of the powder magnetic core (by The glass is heated at a temperature higher than the temperature at which the glass is transferred. The glass serves as a wedge member for preventing the expansion or contraction of the adhesive resin layer, and it is considered that the powder magnetic core is used between soft magnetic powders even in a long-term exposure to high temperature. The interval is also not easily changed, and the change in the effective demagnetization coefficient N is small. Therefore, the variation of the initial magnetic permeability can be reduced.

By the above manner, the thermal stability of the initial magnetic permeability of the powder magnetic core can be improved as compared with the prior art.

In the present invention, the content of the glass is preferably in the range of 0.1% by mass or more and 0.60% by mass or less based on the mass of the soft magnetic powder. Thereby, the initial magnetic permeability (initial) which is equivalent to the previous (excluding glass) can be obtained, and the thermal stability of the initial magnetic permeability can also be improved.

Further, in the invention, the glass preferably contains at least P ₂ O ₅ , B ₂ O ₃ and BaO, and the composition ratio a of P ₂ O ₅ is 40 to 60 mol%, and the composition ratio of B ₂ O ₃ is b. 2~20mol%, BaO composition ratio c is 5~45mol%, SnO composition ratio d is 0~45mol%, Al ₂ O ₃ composition ratio e is 0~15mol%, and satisfies a+b+c+ d+e 100 mol% relationship. When the glass 2 and the glass 3 were obtained in the experiment described later, the initial magnetic permeability (initial) which is substantially equivalent to the previous example in which no glass was added was obtained, and the thermal stability of the initial magnetic permeability was improved.

Further, in the present invention, the composition ratio e of Al ₂ O ₃ is preferably from 2 to 15 mol%.

Further, in the present invention, it is preferable that the composition ratio f of Li ₂ O is 0 to 1 mol%, the composition ratio g of CeO ₂ is 0 to 10 mol%, and the composition ratio i of TiO ₂ is 0 to 1 mol%, and satisfies a. +b+c+d+e+f+g+h+i=100mol% relationship.

Further, in the present invention, the glass transition temperature (Tg) of the glass is preferably in the range of 280 ° C to 470 ° C. Further, the glass transition temperature (Tg) of the above glass is more preferably 360 ° C or more and less than 470 ° C.

Further, in the present invention, the thermal expansion coefficient of the glass is preferably 60 to 110 (×10 ^-7 /°C). The thermal expansion coefficient of the above glass is preferably 60 to 90 (×10 ^-7 /°C).

By adjusting the glass composition as described above, controlling the glass transition temperature (Tg), and further controlling the coefficient of thermal expansion, the thermal stability of the initial magnetic permeability can be more effectively improved.

Further, in the invention, it is preferable that the insulating bonding material contains the glass and magnetic fine particles having a particle diameter smaller than that of the soft magnetic powder. As a result, in the present invention, it is considered that the effective demagnetization coefficient N can be reduced by causing the magnetic fine particles to exist between the soft magnetic powders, so that the initial magnetic permeability (initial) can be improved.

Further, by adding magnetic fine particles, the thermal stability of the iron loss can be improved. Here, the iron loss (core loss) of the powder magnetic core can be generally classified into a hysteresis loss proportional to the measurement frequency and an eddy current loss proportional to the square of the measurement frequency. It is considered that the iron loss is increased by an increase in the above-described effective demagnetization coefficient N or an increase in hysteresis loss caused by the residual stress of the insulating magnetic material on the soft magnetic powder. Therefore, it is considered that magnetic fine particles are added to the insulating bonding material as in the present invention, and by adding to the insulating bonding material. In combination with magnetic particles and glass, the high mechanical strength of the insulating bonding material can be obtained even in a use environment exposed to high temperature for a long period of time, and the variation of residual stress can be effectively suppressed, and the initial The magnetic permeability together increases the thermal stability of the iron loss.

In the present invention, the content of the magnetic fine particles is preferably in a range of more than 0% by mass and not more than 0.60% by mass based on the mass of the soft magnetic powder. In this case, the magnetic fine particles are oxide magnetic materials, and specifically, at least one of NiZn ferrite or MnZn ferrite is preferable. Thereby, the initial magnetic permeability (initial) can be improved, and the initial magnetic permeability and the thermal stability of the iron loss can also be effectively improved.

According to the powder magnetic core of the present invention and the method of manufacturing the same, the thermal stability of the initial magnetic permeability can be improved.

In addition, by adding not only glass to the insulating bonding material but also magnetic fine particles having a particle diameter smaller than that of the soft magnetic powder, the initial magnetic permeability (initial) can be improved, and not only the thermal stability of the initial magnetic permeability can be improved. It can also improve the thermal stability of iron loss.

1, 3‧‧‧ powder core

2‧‧‧The coil is sealed into the powder core

4‧‧‧ coil

5‧‧‧Soft magnetic powder

6‧‧‧Insulating bonding materials

7‧‧‧ pores

Figure 1 is a perspective view of a powder magnetic core (iron core).

Figure 2 is a plan view of the coil enclosed in the powder magnetic core.

Fig. 3 is a partially enlarged sectional view (schematic diagram) of a powder magnetic core according to an embodiment of the present invention.

Fig. 4 is a graph showing the correlation between the initial magnetic permeability (initial) and the iron loss (initial) of the powder magnetic core to which the glass 1 having a glass transition temperature (Tg) of 280 ° C is added, and the amount of glass added.

5 is a heat resistance test in which a powder magnetic core to which a glass 1 having a glass transition temperature (Tg) of 280 ° C is added is heated at a temperature of 180 ° C and 250 ° C and a heating time is set to 1000 hours, after the heat resistance test. A graph showing the correlation between the rate of change (%) of the initial magnetic permeability and the amount of change in iron loss (%) and the amount of glass added.

Figure 6 shows the initial magnetic permeability of the powder magnetic core to which the glass 2 and the glass 3 are respectively added (initial Period) and the correlation between the iron loss (initial) and the amount of glass added.

Fig. 7 is a view showing the initial magnetic permeability after the heat resistance test in the heat resistance test in which the powder magnetic core to which the glass 2 and the glass 3 are respectively added is set to a heating temperature of 200 ° C and 250 ° C and the heating time is set to 1000 hours. A graph of the correlation between the rate of change (%) and the amount of glass added.

Fig. 8 is a graph showing the rate of change in iron loss after the heat resistance test in a heat resistance test in which the powder magnetic core to which the glass 2 and the glass 3 are respectively added is heated at 200 ° C and 250 ° C and the heating time is set to 1000 hours ( %) A graph of the correlation with the amount of glass added.

Fig. 9 is a graph showing the correlation between the initial magnetic permeability (initial) and the iron loss (initial) and the amount of NiZn ferrite added to the powder magnetic core to which the NiZn ferrite is added (but without adding glass).

Fig. 10 is a view showing the heat-resistant test after the heat-resistance test is performed on a powder magnetic core to which a NiZn ferrite is added (but without adding glass) at a heating temperature of 200 ° C and 250 ° C and a heating time of 1000 hours. A graph showing the correlation between the rate of change (%) of magnetic permeability and the rate of change (%) of iron loss and the amount of addition of NiZn ferrite.

Fig. 11 is a graph showing the correlation between the initial magnetic permeability (initial) and the iron loss (initial) and the amount of glass added in each of the glass 2 and the glass 3, and the powder magnetic core of NiZn ferrite.

Fig. 12 is a view showing the heat resistance test after the heat resistance test is performed on a powder magnetic core to which the glass 2, the glass 3 and the NiZn ferrite are added and the heating temperature is 200 ° C and 250 ° C and the heating time is 1000 hours. A graph showing the correlation between the rate of change (%) of the initial magnetic permeability and the amount of glass added.

Fig. 13 is a view showing the heat resistance test after the heat resistance test is performed on a powder magnetic core to which the glass 2, the glass 3 and the NiZn ferrite are added and the heating temperature is 200 ° C and 250 ° C and the heating time is 1000 hours. A graph showing the correlation between the rate of change of iron loss (%) and the amount of glass added.

Fig. 14 is a graph showing the relationship between the glass transition temperature of glass, the thermal expansion coefficient of glass, and the initial magnetic permeability (initial) of a plurality of powder magnetic cores containing glass.

Fig. 15 is a graph showing the relationship between the glass transition temperature of glass, the thermal expansion coefficient of glass, and the iron loss (initial) among a plurality of powder magnetic cores containing glass.

16 is a heat resistance test in which the glass transition temperature of the glass is the horizontal axis and the thermal expansion coefficient of the glass is the vertical axis, and the heating temperature of the plurality of powder magnetic cores containing the glass is set to 200 ° C and the heating time is set to 1000 hours. At the time, the rate of change (%) of the initial magnetic permeability after the heat resistance test described above.

17 is a heat resistance test in which the glass transition temperature of the glass is the horizontal axis and the thermal expansion coefficient of the glass is the vertical axis, and the heating temperature of the plurality of powder magnetic cores containing the glass is set to 200 ° C and the heating time is set to 1000 hours. The graph of the rate of change (%) of iron loss after the above heat resistance test.

Fig. 1 is a perspective view of a powder magnetic core (iron core), and Fig. 2 is a plan view of a coil sealed with a powder magnetic core. Figure 3 is a partially enlarged cross-sectional view (schematic diagram) of a powder magnetic core.

The powder magnetic core 1 shown in Fig. 1 can be obtained by compression-molding and heat-treating a mixture containing a soft magnetic powder and an insulating bonding material.

The symbol 5 shown in Fig. 3 is a soft magnetic powder, and the symbol 6 is an insulating bonding material. As shown in FIG. 3, the insulating bonding material 6 surrounds the surface of the soft magnetic powder 5, and exists between the soft magnetic powders 5 to hold (support) the plurality of soft magnetic powders 5.

Further, as shown in FIG. 3, the voids 7 are formed everywhere in the insulating bonding material 6. It should be noted that in FIG. 3, all of the soft magnetic powder 5 and the voids 7 are not labeled.

The coil-sealed powder magnetic core 2 shown in FIG. 2 is composed of a powder magnetic core 3 and a coil 4 covered by the powder magnetic core 3. The internal structure of the powder magnetic core 3 is the same as that of Fig. 3.

The soft magnetic powder 5 is, for example, an amorphous soft magnetic powder produced by a water atomization method. The above amorphous soft magnetic powder (Fe-based metallic glass alloy powder) has, for example, a composition formula represented by Fe _100-abcxyzt Ni _a Sn _b Cr _c P _x C _y B _z Si _t , and 0 at% a 10at%, 0at% b 3at%, 0at% c 6at%, 6.8at% x 10.8at%, 2.0at% y 9.8at%, 0at% z 8.0at%, 0at% t 5.0at%.

The soft magnetic powder 5 has an average crystal grain size (D50) of about 10 μm to 70 μm. Here, in the present embodiment, the soft magnetic powder 5 is not limited to amorphous, but the powder magnetic core formed by powder compaction using an amorphous soft magnetic powder and an insulating bonding material and soft magnetic iron are used. Compared with the case of oxygen or the like, it has a large saturation magnetic flux density, and thus is advantageous for miniaturization.

The insulating bonding material 6 shown in Fig. 3 is composed of an adhesive resin and glass.

The binder resin is a polyoxymethylene resin, an epoxy resin, a phenol resin, a urea resin, a melamine resin or the like.

It is particularly preferable to use a polyoxyl resin as a heat-stable resin for the adhesive resin.

The binder resin is added in an amount of 0.5 to 5.0% by mass based on the mass of the soft magnetic powder 5 contained in the powder magnetic core.

In the present embodiment, as described above, the insulating adhesive material 6 contains glass. Here, it is considered that the glass is dispersed in the adhesive resin layer.

The glass is first mixed with the soft magnetic powder 5 or the binder resin in a powder form, and the heat treatment after compression molding into the shape of the powder magnetic cores 1 and 3 shown in Fig. 1 or Fig. 2 is high in the present embodiment. It is carried out at the temperature of the glass transition temperature (Tg) of the glass.

Therefore, in the present embodiment, it is considered that the glass is deformed from the initial powder form, or the glass is bonded to each other, a part is diffused into the resin, and the resin is fused.

In the present embodiment, it is possible to form a plurality of soft magnetic powders 5 by an adhesive resin layer having a small Young's modulus, and further heat treatment by a glass transition temperature (Tg) in a manufacturing step of the powder magnetic core. The glass having a low temperature is introduced into the insulating bonding material 6 to alleviate the structure of expansion and contraction due to thermal deterioration of the adhesive resin layer. It is considered that the glass (powder) is deformed after being exposed to a heat treatment higher than the glass transition temperature (Tg), or the glass is bonded to each other, and the like, thereby serving as a wedge member for preventing expansion and contraction of the adhesive resin layer. use.

One of the factors determining the magnetic permeability of the powder magnetic cores 1, 3 is the effective demagnetization coefficient N. With respect to the effective demagnetization coefficient N, it is considered that, as shown in FIG. 3, in the state in which a plurality of soft magnetic powders 5 are filled, the effective demagnetization coefficient N becomes smaller than the magnetic interaction between the soft magnetic powders 5 close to each other. The value of the effective demagnetization coefficient N of the soft magnetic powder 5 in a single state.

In the use environment where the temperature is exposed to high temperature for a long period of time, if the change in the interval between the soft magnetic powders 5 is small, the change in the effective demagnetization coefficient N is small.

As described above, in the present embodiment, it is considered that the glass having a glass transition temperature (Tg) lower than the temperature of the heat treatment performed in the production step of the powder magnetic core can alleviate the expansion due to thermal deterioration of the adhesive resin layer. Or shrinkage, even in a use environment exposed to high temperature for a long period of time, the variation between the intervals of the soft magnetic powders 5, 5 in the powder magnetic cores 1, 3 can be made smaller than the previous one, thereby reducing effective demagnetization The change in the coefficient N.

Based on the above, it can be seen that according to the present embodiment, the thermal stability of the initial magnetic permeability of the powder magnetic cores 1, 3 can be improved as compared with the prior art. Therefore, the thermal stability of the inductance can be improved.

In the present embodiment, the content of the glass is preferably in the range of 0.1% by mass or more and 0.60% by mass or less based on the mass of the soft magnetic powder 5. When the amount of glass added is too large, the interval between the soft magnetic powders 5 and 5 (initial) becomes large when the powder magnetic core is formed, and the value of the effective demagnetization coefficient N itself becomes large, so that the initial magnetic permeability is liable to lower.

In the present embodiment, by limiting the amount of addition of the glass as described above, the initial magnetic permeability (initial) equivalent to the previous (excluding glass) can be obtained, and the thermal stability of the initial magnetic permeability can be improved. Here, the initial magnetic permeability (initial) refers to the initial magnetic permeability before the formation of the powder magnetic core (initial) and before exposure to a high-temperature use environment.

Further, the glass is preferably composed of at least P ₂ O ₅ , B ₂ O ₃ and BaO, the composition ratio a of P ₂ O ₅ is 40 to 60 mol%, and the composition ratio b of B ₂ O ₃ is 2 to 20 mol%. The composition ratio b of BaO is 5 to 45 mol%, the composition ratio d of SnO is 0 to 45 mol%, and the composition ratio e of Al ₂ O ₃ is 0 to 15 mol%, and satisfies a+b+c+d+e. 100 mol% relationship.

In the composition range of the glass, the initial magnetic permeability (initial) and the previous glass are not added by containing the glasses 2 and 3 in the experiment described later and appropriately controlling the glass transition temperature (Tg) according to the glass. The examples are approximately equal and the thermal stability of the initial permeability can be improved.

In addition, by setting the content of the glass of the above composition to the mass of the soft magnetic powder 5 in the range of 0.1% by mass or more (% by weight) or more and 0.60% by mass or less (% by weight) or less, it is understood from the experiment described later that the initial value can be improved. The thermal stability of the magnetic permeability can further reduce the iron loss (initial) to the previous (without glass).

Further, in the present embodiment, the composition ratio e of Al ₂ O ₃ is preferably 2 to 15 mol%. Further, the composition ratio a of P ₂ O ₅ is preferably from 41 to 55 mol%. Further, the composition ratio b of B ₂ O ₃ is preferably from 2 to 15 mol%. Further, the composition ratio c of BaO is preferably from 5 to 30 mol%. The composition ratio d of SnO is preferably from 0 to 30 mol%, more preferably from 25 to 30 mol%. Further, the composition ratio of Al ₂ O ₃ is more preferably 2 to 10 mol%.

Further, in the present embodiment, at least one of Li ₂ O, CeO ₂ and TiO ₂ may be contained in addition to the above. In this case, it is preferable that the composition ratio f of Li ₂ O is 0 to 1 mol%, the composition ratio g of CeO ₂ is 0 to 10 mol%, and the composition ratio i of TiO ₂ is 0 to 1 mol%, and satisfies a+b. +c+d+e+f+g+h+i=100mol% relationship.

The heat treatment performed after compression-molding the mixture containing the soft magnetic powder 5 and the insulating bonding material 6 is an important step in eliminating the strain of the soft magnetic powder 5 and obtaining good magnetic properties. Therefore, the most suitable temperature for the heat treatment depends on the soft magnetic powder 5, and in the present embodiment, the glass transition temperature (Tg) having a lower temperature than the (most suitable) heat treatment performed in the manufacturing step of the powder magnetic core is selected. Glass.

The glass transition temperature (Tg) of the glass in the present embodiment is preferably about 280 ° C to 470 ° C. Further, the glass transition temperature (Tg) is preferably 360 ° C or more and less than 470 ° C. Further, the glass transition temperature (Tg) is more preferably 440 ° C or more and less than 470 ° C.

By using the glass having the above composition, the glass transition temperature (Tg) can be controlled to the above-mentioned range Inside.

Further, it is considered that both (the heat treatment temperature - glass transition temperature (Tg)) are not sufficiently large, and both the initial magnetic permeability and the thermal stability of the initial magnetic permeability can be effectively improved. In addition, the initial iron loss (core loss) may be set to be equal to or less than the previous example in which glass is not added. Here, the "early iron loss" refers to the iron loss before the powder magnetic core is formed (initial) and exposed to a high-temperature use environment.

Specifically, (heat treatment temperature - glass transition temperature (Tg)) is about 2 to 100 ° C, preferably 2 to 28 ° C.

Further, it is considered that it is preferable to control the thermal expansion coefficient α of the glass together with the glass transition temperature (Tg) to improve the thermal stability of the initial magnetic permeability. The coefficient of thermal expansion α is preferably 60 to 110 (×10 ^-7 /°C), more preferably 60 to 90 (×10 ^-7 /°C).

Further, in the present embodiment, it is preferable that the insulating binder 6 has magnetic fine particles having a particle diameter smaller than that of the soft magnetic powder 5. The particle diameter of the magnetic fine particles is a small particle diameter which can enter the interval between the soft magnetic powders 5 and 5 shown in FIG. 3 and which hardly enlarges the interval. Specifically, the magnetic fine particles are nano particles. A particle size sufficiently smaller than that of the soft magnetic powder 5. The magnetic fine particles may be selected from materials different from the soft magnetic powder 5.

For example, the magnetic fine particles are oxidized magnetic powder, and specifically, at least one of NiZn ferrite or MnZn ferrite is preferable.

When the insulating adhesive material 6 contains not only glass but also magnetic fine particles, the magnetic fine particles are present between the soft magnetic powders 5 and 5, and the value of the effective demagnetization coefficient N can be reduced. Thereby, the initial magnetic permeability of the powder magnetic cores 1, 3 can be improved.

Further, by adding magnetic fine particles, the thermal stability of the iron loss can be improved. One of the factors for reducing the iron loss is to reduce the stress (residual stress) which the soft magnetic powder 5 receives. In this case, it is considered that by adding magnetic fine particles to the insulating adhesive material 6 and bonding the magnetic fine particles to the glass, it is possible to improve not only the long-term exposure to high temperature. The mechanical strength of the insulating bonding material 6 in the environment is used, and the variation of the residual stress of the soft magnetic powder 5 can be effectively suppressed, whereby the thermal stability of the iron loss can be improved together with the initial magnetic permeability.

In the present embodiment, the content of the magnetic fine particles is preferably in a range of more than 0% by mass and 0.60% by mass or less based on the mass of the soft magnetic powder 5.

By adjusting the amount of the glass and the magnetic fine particles added to the insulating adhesive material 6 in the present embodiment as described above, it is understood from the experiments described later that the initial magnetic permeability and the thermal stability of the iron loss can be effectively improved. Further, the initial magnetic permeability (initial) can be set to be equal to or higher than the previous example (excluding glass and magnetic fine particles). Although the initial iron loss is slightly higher than the previous example (excluding glass and no magnetic particles), it is also within the usable range.

Hereinafter, a method of manufacturing the powder magnetic core of the present embodiment will be described.

First, a soft magnetic powder, a binder resin, a glass powder, a lubricant, and a coupling agent produced by a water atomization method or the like are stirred and mixed with a solvent to prepare a slurry. Further, magnetic fine particles such as NiZn ferrite or MnZn ferrite may be further mixed.

Here, as the lubricant, zinc stearate, aluminum stearate or the like can be used. Further, as the coupling agent, a decane coupling agent or the like can be used.

The slurry is placed in a conventional granulation apparatus, and the solvent of the slurry is instantaneously dried to form a granular mixture containing the soft magnetic powder and the insulating bonding material.

Then, the above mixture was filled into a forming mold, and compression-molded into the shape of a powder magnetic core. Then, the powder magnetic core is subjected to heat treatment. The heat treatment at this time is carried out at a temperature higher than the glass transition temperature (Tg) of the glass. At this time, since the heat treatment temperature most suitable for eliminating the strain of the soft magnetic powder is previously determined, it is necessary to set the heat treatment temperature to a temperature higher than the glass transition temperature (Tg), and it is necessary to select a glass transition temperature lower than the heat treatment temperature ( Tg) glass.

It is considered that by this heat treatment, most of the lubricant is vaporized and disappears, and the resin is bonded. Be one. A part of the adhesive resin also disappeared. In the present embodiment, the glass and the binder resin are present as a part of the insulating bonding material 6 between the soft magnetic powders. The glass is also mixed in a powder form at the stage of slurry formation as described above. However, after compression molding and heat treatment, the glass is deformed from powder or formed into a state in which the glass is bonded to each other. Therefore, it is considered that the glass is not a simple filler. It also functions as a wedge member for preventing the expansion or contraction of the adhesive resin layer in the insulating bonding material.

The powder magnetic core of the present embodiment is excellent in initial magnetic permeability and thermal stability of iron loss. Therefore, it is particularly suitable for use in a booster circuit such as a hybrid vehicle or a reactor, a transformer, a choke coil, or the like used in power generation and substation equipment, and is required to have thermal stability in a long-time high-temperature environment.

[Examples] (Experiment to determine the relationship between the amount of glass 1 and the characteristics and thermal stability of the powder core)

Fe _74.43at% Cr _1.96at% P _9.04at% C _2.16at% B _7.54at% Si _4.87at% is an amorphous soft magnetic powder, a _{polyoxyxylene} resin, and zinc stearate. Phosphoric acid glass powder (glass 1) was mixed to prepare a mixture. The phosphoric acid glass was KF9079 powder manufactured by AGC TECHNO GLASS. The glass transition temperature (Tg) of the glass 1 was 280 °C. In addition, the blending amount of the polyoxyl resin in the above mixture is 1.4 wt% with respect to the mass of the soft magnetic powder, and the blending amount of zinc stearate is 0.3 wt% with respect to the mass of the soft magnetic powder, and the blending amount of the glass powder is relatively The mass of the soft magnetic powder was 0 wt%, 0.3 wt%, 0.6 wt%, 1.2 wt%, 2.4 wt%, 4.2 wt%, and 6.1 wt%.

Then, the mixture was filled in a mold, and pressure-molded at a bearing pressure of 1470 MPa to prepare a ring-shaped sample having an outer diameter of 20 mm, an inner diameter of 12 mm, and a thickness of 6.8 mm. The obtained ring-shaped sample was heat-treated at 470 ° C for 1 hour in a nitrogen gas atmosphere to thereby prepare a powder magnetic core.

Using a super megohmmeter (SM-8213 manufactured by DKK-TOA), the intrinsic resistance of the obtained annular powder magnetic core was measured, and the copper wire was wound around the annular powder magnetic core. The initial magnetic permeability was measured using an impedance analyzer (HP 4192A), and the iron loss (initial) was measured using a BH Analyzer (manufactured by Iwasaki Communications) at a frequency of 100 kHz and Bm = 100 mT. In the heat resistance test, the annular powder magnetic core was placed in a drying oven at 180 ° C and 250 ° C in the atmosphere for 1,000 hours, and then the initial magnetic permeability and iron loss were measured. The results of each measurement are shown in Table 1.

Fig. 4 is a graph showing the relationship between the amount of glass 1 added to each of the powder magnetic cores shown in Table 1 and the initial magnetic permeability (initial) and iron loss (initial). As can be seen from Table 1 and FIG. 4, as the amount of addition of the glass 1 increases, the initial magnetic permeability decreases, but on the other hand, the iron loss increases. When the amount of glass added exceeds 0.6% by weight, the initial magnetic permeability is decreased by 10% or more as compared with No. 1 (previous example) in which no glass is added, but on the other hand, the iron loss is increased by 40% or more. From this, it is understood that in order to prevent the magnetic properties of the powder magnetic core from being lowered, the amount of glass added is required to be 0.6 wt% or less.

The inherent resistance of the powder magnetic core shown in Table 1 showed a tendency to increase as the amount of glass 1 added increased, and any sample showed 10 ⁶ Ω. Above cm, it is understood that the inherent resistance of the powder magnetic core is a sufficiently high value as a powder magnetic core.

Fig. 5 is a view showing the addition amount of the glass 1 and the initial magnetic permeability after the heat resistance test in the heat resistance test in which the heating temperature of each of the powder magnetic cores of Table 1 is set to 180 ° C and 250 ° C and the heating time is set to 1000 hours. A graph showing the relationship between the rate of change (%) and the amount of change in iron loss (%). Here, the "rate of change in initial magnetic permeability" is represented by [(initial permeability after heat resistance test - initial magnetic permeability in initial stage) / initial initial magnetic permeability] × 100 (%). "Initial initial permeability" refers to the initial permeability before the powder core is formed (initial) and exposed to high temperature use. rate.

In addition, the "iron loss change rate" is represented by [(iron loss after heat resistance test - initial iron loss) / initial iron loss] × 100 (%). "Initial iron loss" refers to the iron loss before the powder core is formed (initial) and exposed to high temperature use.

As a target of thermal stability, the rate of change of the initial magnetic permeability is set to be within ±15% after 180 to 200 ° C × 1000 hours, preferably within ± 10%, and ± 25 after 250 ° C × 1000 hours. Within %, preferably within ±20%, and the rate of change in iron loss is set to be within ±40% after 180~200°C×1000 hours, preferably within ±30%, after 250°C×1000 hours It is within ±70%, preferably ±50%.

As shown in Table 1 and FIG. 5, as the amount of addition of the glass 1 increases, the rate of change (%) of the initial magnetic permeability after the heat resistance test is a negative value, but the absolute value tends to decrease. In addition, the rate of change in iron loss (%) also tends to decrease. When the amount of addition of the glass 1 is 1.2% by weight or more, the above-mentioned heat stability stability can be more effectively satisfied. However, as shown in Table 1 and FIG. 4, the amount of glass added is 1.2 wt% or more. The problem that the initial magnetic permeability (initial) is low and the iron loss (initial) becomes large.

On the other hand, when the addition amount of the glass 1 is 0.6 wt% or less, although the rate of change of the initial magnetic permeability after 250 ° C × 1000 hours slightly exceeds -20%, the initial magnetic after 180 ° C × 1000 hours The rate of change of the conductivity is maintained at a low value of -2% to -3%. In addition, when the amount of addition of the glass 1 is 0.6 wt% or less, the iron loss change rate after 180 ° C × 1000 hours can be maintained within 30%.

(Manufacture of glass 2, 3)

The glasses 2 and 3 are produced by the following production methods.

Commercially available orthophosphoric acid, boron oxide powder, cerium carbonate powder, tin oxide powder, and alumina powder are used as the glass raw material. The raw materials are metered in such a manner as to achieve a specific blending amount, charged into a platinum crucible for premixing, and then melted in an atmosphere using an electric furnace. The set temperature of the electric furnace is 1000~1300 °C.

Then, the platinum crucible was taken out from the electric furnace, and the glass melt was cast in an iron mold to obtain glass. The glass was coarsely pulverized in a mortar, and then pulverized using a ball mill to obtain a glass powder.

In addition, a glass block of 3 mm × 3 mm × 20 mm was cut out from one part of the cast glass, and after annealing treatment for strain relief, the glass transition temperature, yield temperature, and thermal expansion coefficient were measured using a thermomechanical analysis device (TMA8310 manufactured by Rigaku Motor Co., Ltd.). . The blending amounts of the glass 2, 3 produced, the glass transition temperature, the yield temperature, and the thermal expansion coefficient are shown in Table 2.

(Experiment to determine the relationship between the amount of glass 2 and 3 and the characteristics and thermal stability of the powder core)

Fe _77at% Cr _1at% P _9.23at% C _2.2at% B _7.7at% Si _2.87at% amorphous soft magnetic alloy powder, _polyxanthene resin, zinc stearate and powder The glass 2 or the powdery glass 3 is mixed to form a mixture.

Here, as shown in Table 2, the glass transition temperature (Tg) of the glass 2 (phosphoric acid glass) was 468 ° C, which was 2 ° C lower than the temperature (470 ° C) of the heat treatment performed in the manufacturing step of the powder magnetic core. Further, the glass transition temperature of the glass 3 (phosphoric acid glass) was 442 ° C, which was 28 ° C lower than the temperature (470 ° C) of the heat treatment performed in the manufacturing step of the powder magnetic core.

In addition, the blending amount of the polyoxyl resin in the mixture is 2.0 wt% with respect to the mass of the soft magnetic powder, and the blending amount of zinc stearate is 0.3 wt% with respect to the mass of the soft magnetic powder, and the blending of each of the glasses 2 and 3 The amount is 0 wt%, 0.1 wt%, 0.3 wt%, 0.6 wt% with respect to the mass of the soft magnetic powder.

Then, the above mixture was filled into a mold to carry a pressure of 1470 MPa. Press-formed to form a ring-shaped sample having an outer diameter of 20 mm, an inner diameter of 12 mm, and a thickness of 6.8 mm. The obtained ring-shaped sample was heat-treated at 470 ° C for 1 hour in a nitrogen gas atmosphere to prepare a powder magnetic core.

The density of the magnetic core is calculated based on the mass and outer dimensions of the obtained annular powder magnetic core, and the occupancy of the soft magnetic powder is calculated using the value of the formulated amount. The calculation formula of the occupancy rate of the soft magnetic powder is as follows.

Then, the intrinsic resistance of the ring-shaped powder core was measured using a superinsulator (SM-8213 manufactured by DKK-TOA), the copper wire was wound around the ring-shaped powder core, and the initial permeability was measured using an impedance analyzer (HP 4192A). The iron loss was measured at a frequency of 100 kHz and Bm = 100 mT using a BH Analyzer (manufactured by Iwasaki Communications). In the heat resistance test, the annular magnetic powder core was placed in a drying oven at 200 ° C and 250 ° C in the atmosphere for 1,000 hours, and then the initial magnetic permeability and iron loss were measured. The results of each measurement are shown in Table 3.

In addition, the powder magnetic core No. 9-11 shown in Table 3 uses the glass 2, and the powder magnetic core No. 12-14 uses the glass 3. The powder magnetic core No. 8 is a prior example in which no glass is added.

Fig. 6 is a view showing the initial magnetic permeability of each of the powder magnetic cores to which the glass 2 having a glass transition temperature (Tg) of 468 ° C and the glass 3 having a glass transition temperature (Tg) of 442 ° C are added, respectively. A graph showing the relationship between the rate (initial) and the iron loss (initial) and the amount of addition of the glasses 2 and 3. It can be seen that in the case of using any kind of glass, the initial magnetic permeability tends to decrease slightly as the amount of glass added increases, and the initial magnetic permeability when the glass addition amount is 0.6 wt% and No. 8 without glass addition. (Previous example) The decrease is about 2~4%.

Further, as shown in Table 3 and FIG. 6, it is understood that when the glass 2 is used, the iron loss (initial) tends to decrease as the amount of the glass 2 increases, and on the other hand, when the glass 3 is used. At the time, it shows a substantially fixed value with respect to the addition amount of the glass 3.

By using glass 2, 3 having a glass transition temperature (Tg) lower than the heat treatment temperature in the manufacturing process of the powder magnetic core, when adding 0.1 wt% to 0.6 wt% of the glass 2, 3, the pressure is applied. The initial magnetic permeability of the powder magnetic core is equal or slightly lower than that in the case where no glass is added, and the iron loss is equal or slightly increased (may be reduced) as compared with the case where no glass is added.

The increase in the intrinsic resistance shown in Table 3 relative to the addition of the glass 2, 3 is small, and any sample shows 10 ⁶ Ω. Above cm, it is understood that the inherent resistance of the powder magnetic core is a sufficiently high value as a powder magnetic core. In addition, the occupancy rate of the amorphous soft magnetic powder occupying the powder magnetic core is 78 to 80%.

Figure 7 shows the powder cores of the glass 2 having a glass transition temperature (Tg) of 468 ° C and the glass 3 having a glass transition temperature (Tg) of 442 ° C added at 200 ° C × 1000 hours, respectively. A graph showing the relationship between the amount of addition of the glasses 2 and 3 and the rate of change (%) of the initial magnetic permeability after 250 ° C × 1000 hours. The initial magnetic permeability after 200 ° C × 1000 hours of the powder magnetic core to which the glass 2 is added is reduced to about -11% when the amount of the glass 2 added is 0.3 wt%, but the addition amount of the glass 2 is set to At 0.6 wt%, the rate of change of the initial magnetic permeability was -4%. The rate of change of the initial magnetic permeability after 250 ° C × 1000 hours of the powder magnetic core to which the glass 2 was added showed a substantially fixed value of about -13% regardless of the amount of the glass 2 added.

On the other hand, the rate of change of the initial magnetic permeability of the powder magnetic core to which the glass 3 is added decreases as the amount of glass added increases, and the initial magnetic permeability changes when 0.6 wt% of the glass 3 is added. The conversion rate was -2% after 200 ° C × 1000 hours, and -8% after 250 ° C × 1000 hours.

Figure 8 shows the powder cores of the glass 2 having a glass transition temperature (Tg) of 468 ° C and the glass 3 having a glass transition temperature (Tg) of 442 ° C added at 200 ° C × 1000 hours, respectively. A graph showing the relationship between the amount of addition of the glasses 2 and 3 and the rate of change in iron loss (%) after 250 ° C × 1000 hours.

As shown in Table 3 and FIG. 8, the iron loss change rate after 200 ° C × 1000 hours and 250 ° C × 1000 hours of the powder magnetic core to which the glass 2 is added uniformly increases as the amount of the glass 2 increases. When 0.6 wt% of glass 2 was added, the iron loss change rates were +80% and +138%, respectively. On the other hand, the change of the iron loss after 200 ° C × 1000 hours and after 250 ° C × 1000 hours of the powder magnetic core to which the glass 3 is added has a small change with respect to the increase of the addition amount of the glass 3, respectively, +44 %, +58%.

From this, it can be seen that the initial magnetic permeability (initial) can be set to the same extent as in the case where no glass is added (No. 8) by increasing the amount of the glass 2 and the addition amount of 0.1 to 0.6 wt%, and it can be improved. Thermal stability of initial permeability (heat resistance). Further, the iron loss (initial) is substantially equal to the previous example (No. 8) or can be reduced to the previous example (No. 8) or less.

Comparing the glass 1 with the glasses 2 and 3, the glass transition temperature (Tg) of the glass 1 is 280 ° C, which is about 200 ° C lower than the temperature (470 ° C) of the heat treatment performed in the manufacturing process of the powder magnetic core, but the glass The glass transition temperature (Tg) of 2, 3 is only 2 to 28 ° C lower than the temperature (470 ° C) of the heat treatment performed in the manufacturing steps of the powder magnetic core.

In addition, when the glass 1 is used for a powder magnetic core, the rate of change of the initial magnetic permeability after 180 ° C × 1000 hours can be suppressed to be low, but the initial magnetic permeability is likely to be greatly lowered. tendency. On the other hand, in the case where the glasses 2 and 3 are used for the powder magnetic core, the initial magnetic permeability (initial) can be equivalent to the case where no glass is added, and not only 180 ° C × 1000 hours, but also 250 ° C The rate of change of the initial magnetic permeability after 1000 hours may also be suppressed to be low.

It can be seen that as the glass for the powder magnetic core, glass 2, 3 is used as compared with the glass 1. It is preferred in terms of thermal stability of high initial magnetic permeability.

(Experiment of adding glass and magnetic particles together)

Fe _77at% Cr _1at% P _9.23at% C _2.2at% B _7.7at% Si _2.87at% amorphous soft magnetic alloy powder, polyfluorene oxide resin, zinc stearate and NiZn The ferrite powder (magnetic microparticles) is mixed to form a mixture. This NiZn ferrite powder was KN1-106GMS manufactured by Kawasaki Steel, and was pulverized in a ball mill for 30 hours, and then dried and used.

Further, Fe _77at% Cr _1at% P _9.23at% C _2.2at% B _7.7at% Si _2.87at% , which is produced by the water atomization method, is an amorphous soft magnetic alloy powder, a _polyoxyn resin, or a zinc stearate. NiZn ferrite powder and glass 2 or glass 3 are separately mixed to form a mixture. Further, the blending amount of the polyoxyl resin in the mixture is 2.0% by weight based on the mass of the soft magnetic powder, and the blending amount of zinc stearate is 0.3% by weight based on the mass of the soft magnetic powder, and NiZn ferrite powder is used. The blending amount was 0.3%, 0.6%, and 1.2% by weight based on the mass of the soft magnetic powder, and the blending amounts of the glasses 2 and 3 were 0%, 0.1%, 0.3%, and 0.6% by weight, respectively, based on the mass of the soft magnetic powder.

Then, the mixture was filled in a mold, and subjected to pressure molding at a bearing pressure of 1470 MPa to prepare a ring-shaped sample having an outer diameter of 20 mm, an inner diameter of 12 mm, and a thickness of 6.8 mm. The obtained ring-shaped sample was heat-treated at 470 ° C for 1 hour in a nitrogen gas atmosphere to prepare a powder magnetic core.

The density of the magnetic core was calculated from the mass and outer dimensions of the obtained annular powder magnetic core, and the occupancy of the amorphous soft magnetic alloy powder was calculated using the value of the blending amount (see Equation 2). In addition, the intrinsic resistance of the annular powder core was measured using a superinsulator (SM-8213 manufactured by DKK-TOA), the copper wire was wound around the ring-shaped powder core, and the initial permeability was measured using an impedance analyzer (HP 4192A). The iron loss was measured at a frequency of 100 kHz and Bm = 100 mT using a BH Analyzer (manufactured by Iwasaki Communications). In the heat resistance test, the annular powder magnetic core is placed in a drying oven at 200 ° C and 250 ° C in the atmosphere, and the measurement is maintained for 1000 hours. Initial permeability and iron loss. The results of each measurement are shown in Table 4.

Fig. 9 is a graph showing the relationship between the amount of NiZn ferrite added to the powder magnetic core No. 15 to 18 (with NiZn ferrite added and no glass added) and the initial magnetic permeability (initial) and iron loss (initial). Figure. The powder magnetic core No. 15 is a prior art which does not contain both glass and NiZn ferrite.

It is understood that as the amount of addition of NiZn ferrite increases, the initial magnetic permeability (initial) and iron loss (initial) of the powder magnetic core increase.

Fig. 10 is a view showing the addition amount of NiZn ferrite when the powder magnetic core No. 15 to 18 (with NiZn ferrite added and no glass added) is exposed to a heat resistance test at 200 ° C and 250 ° C for 1000 hours. A graph showing the relationship between the rate of change of initial permeability and the rate of change of iron loss. As the amount of NiZn ferrite added increases, the rate of change of the initial magnetic permeability decreases and the absolute value gradually increases. When the amount of NiZn ferrite added is 1.2 wt%, after 200 ° C × 1000 hours, After 250 ° C × 1000 hours, it was -12%, -18%. The rate of change of iron loss monotonously decreases in the heat resistance test at 200 ° C. In the heat resistance test at 250 ° C, the rate of change in iron loss begins to decrease after the maximum amount of NiZn ferrite added at 0.3 wt%, when NiZn ferrite When the amount added was 1.2 wt%, it was +6% and +34%, respectively.

Fig. 11 is a view showing the addition amount of the glass 2, 3 of the powder magnetic core No. 19 to 24 (with NiZn ferrite, glass 2, 3) and the initial magnetic permeability (initial) and iron loss of the powder magnetic core. Diagram of the relationship between (initial). Glass 2 is added to the powder magnetic core No. 19 to 21, and the powder magnetic core No. Glass 3 is added to 21~24. Further, as shown in Table 4, in the powder magnetic core Nos. 19 to 24, the addition amount of the NiZn ferrite system was 0.6 wt%.

In addition, the initial magnetic permeability (initial) and the iron loss (initial) when the addition amount of the glass 2 and 3 in FIG. 11 is 0 wt% is a powder magnetic core No. 17 in which NiZn ferrite is set to 0.6 wt%. value.

As can be seen from FIG. 11 and Table 4, the initial magnetic permeability tends to decrease slightly as the amount of the glass 2, 3 is increased. However, if the addition amount of the glass 2, 3 is 0.1 wt%, the glass is not added. The initial magnetic permeability can be improved as compared with the powder magnetic core No. 15 (previous example) of both NiZn ferrite.

On the other hand, the iron loss (initial) does not depend on the amount of addition of the glasses 2 and 3, and shows a substantially fixed value. However, by adding the glass 2, with respect to the powder magnetic core No. 17 (the amount of glass added is 0 wt%), There is a tendency that the iron loss (initial) is slightly decreased by adding the glass 3 to the powder magnetic core No. 17 (the glass addition amount is 0 wt%).

Fig. 12 is a view showing the amount of glass added and the initial magnetic force when the powder magnetic core No. 19 to 24 (with NiZn ferrite and glass 2, 3 added) were subjected to a heat resistance test at 200 ° C for 1000 hours and 250 ° C for 1000 hours. A graph of the relationship between the rate of change of conductivity.

In addition, the rate of change of the initial magnetic permeability when the addition amount of the glass 2 and 3 of FIG. 12 is 0 wt% is the value of the powder magnetic core No. 17 which made NiZn ferrite into 0.6 weight%.

As can be seen from Fig. 12 and Table 4, the rate of change of the initial magnetic permeability after 200 ° C × 1000 hours was a negative value, but the absolute value gradually decreased as the amount of glass 2 added. In the case where the glass 3 is added, when the amount of addition is 0.3 to 0.6% by weight, the rate of change of the initial magnetic permeability remains almost unchanged at -3%.

Then, as shown in FIG. 12 and Table 4, the rate of change of the initial magnetic permeability after 250 ° C × 1000 hours is a negative value, but in the case where the glass 2 is added, the initial magnetic permeability increases as the amount of glass added increases. The rate of change (absolute value) of the rate gradually decreases. On the other hand, although the rate of change of the initial magnetic permeability when the glass 3 was added was also shown to be a negative value, the rate of change of the initial magnetic permeability (absolute value) and the case where no glass was added (the powder magnetic core No. 17) ) is reduced compared to. its In the case where the glass 3 was added, the rate of change of the initial magnetic permeability did not change even if the amount of glass added changed.

Fig. 13 is a graph showing the amount of glass added and the rate of change in iron loss when the powder magnetic core No. 19 to 24 (with NiZn ferrite, glass 2, 3 added) was subjected to a heat resistance test at 200 ° C and 250 ° C for 1000 hours. Diagram of the relationship.

In addition, the iron loss change rate when the addition amount of the glass 2 and 3 of FIG. 13 is 0 wt% is the value of the powder magnetic core No. 17 which made NiZn ferrite into 0.6 weight%.

The iron loss change rate showed a tendency to be substantially the same when the heat test temperature was 200 ° C and 250 ° C. In the case where the glass 2 was added, the iron loss change rate was substantially the same even when the addition amount was increased to 0.3 wt%, and the iron loss change rate was increased when the addition amount was increased to 0.6 wt%.

On the other hand, when the glass 3 was added, the iron loss change rate was minimized when the addition amount was 0.1 wt%, and the iron loss change rate was increased when the addition amount was further increased.

As can be seen from Table 4 and FIG. 11 to FIG. 13 , by adding the glass and the NiZn ferrite in combination, a relatively high initial magnetic permeability (initial) can be ensured, and the thermal stability of the initial magnetic permeability can be improved. Further, the rate of change in iron loss can be reduced, and the thermal stability of iron loss can be improved. In particular, in the powder magnetic core (especially the powder magnetic core No. 22) to which the glass 3 having a glass transition temperature (Tg) of 442 ° C is added, the rate of change in iron loss can be effectively reduced, thereby making it more effective Improve the thermal stability of iron loss.

As described above, in the present embodiment, the amount of the glass added is set to be 0.1% by mass or more and 0.6% by mass or less based on the mass of the soft magnetic powder, and when magnetic fine particles are further added, the magnetic fine particles are added. The amount of addition is set to be more than 0% by mass and 0.6% by mass or less based on the mass of the soft magnetic powder.

(Experimental experiment on the characteristics of each powder core with different compositions of glass)

A variety of glasses having the following glass compositions are produced.

With respect to each of the glasses 4 to 18 of Table 5, the raw materials were metered in such a manner as to achieve the specific blending amount shown in Table 5, which was placed in a platinum crucible for premixing, and then melted in an atmosphere using an electric furnace. The set temperature of the electric furnace is 1000~1300 °C.

Then, the platinum crucible was taken out from the electric furnace, and the glass melt was cast in an iron mold to obtain glass. The glass was coarsely pulverized in a mortar, and then pulverized using a ball mill to obtain a glass powder.

In addition, a glass block of 3 mm × 3 mm × 20 mm was cut out from one part of the cast glass, and after annealing treatment for strain relief, the glass transition temperature and the glass softening temperature (yield) were measured using a thermomechanical analysis device (TMA8310 manufactured by Rigaku Motor Co., Ltd.). Temperature) and coefficient of thermal expansion. The blending amounts of the respective glass 4 to 18 produced, the glass transition temperature, the glass softening temperature (yield temperature), and the thermal expansion coefficient are shown in Table 5.

In addition, the specific gravity and the glass transition temperature are also included in Table 5.

Then, each glass, amorphous soft magnetic alloy powder, polyoxynoxy resin, zinc stearate, and the like shown in Table 5 were mixed to prepare a mixture. The amorphous soft magnetic alloy powder used was Fe _{77 at%} Cr _{1 at%} P _{9.23 at%} C _{2.2 at%} B _{7.7 at%} Si _{2.87 at%} amorphous soft magnetic alloy powder produced by a water atomization method.

In addition, the blending amount of the polyoxyl resin in the mixture is 2.0 wt% with respect to the mass of the soft magnetic powder, and the blending amount of zinc stearate is 0.3 wt% with respect to the mass of the soft magnetic powder, and the blending amount of each glass is relatively The mass of the soft magnetic powder was 0.6% by weight.

Then, the mixture was filled in a mold, and subjected to pressure molding at a bearing pressure of 1470 MPa to prepare a ring-shaped sample having an outer diameter of 20 mm, an inner diameter of 12 mm, and a thickness of 6.8 mm. The obtained ring-shaped sample was heat-treated at 470 ° C for 1 hour in a nitrogen gas atmosphere to prepare a powder magnetic core.

In the experiment, the copper wire was wound around the annular powder magnetic core, and the initial magnetic permeability was measured using an impedance analyzer (HP 4192A), and the iron loss was measured using a BH Analyzer (manufactured by Iwasaki Communication) at a frequency of 100 kHz and Bm = 100 mT. . In the heat resistance test, the annular powder magnetic core was placed in a drying oven at 200 ° C or 250 ° C in the atmosphere, and the initial magnetic permeability and iron loss after 1000 hours were measured. In addition, a compressive force is applied to the powder magnetic core, and the compressive force when the powder magnetic core is damaged is taken as the maximum strength of the iron core. The results of each measurement are shown in Table 6.

The column of glass shown in Table 6 corresponds to the glass No. of Table 5. In addition, in Table 6, the values of "μ' (100 kHz)" and "iron loss (100 kHz, 100 mT)" in the columns of 200 ° C and 250 ° C are initial values. In Table 6, the values of the initial values of the same powder magnetic core No. are slightly different, and they are measured by using other powder magnetic cores produced under the same conditions, and each of the powder magnetic cores is used and measured separately. The rate of change of each value after maintaining at 200 ° C and 250 ° C for 1000 hours.

Fig. 14 is a graph showing the initial magnetic permeability (initial) of each of the powder magnetic cores shown in the column of 200 °C of Table 6. In Fig. 14, the glass transition temperature Tg of the glass added to each of the powder magnetic cores is As the horizontal axis, the thermal expansion coefficient α of the glass is taken as the vertical axis. Therefore, the experimental results of the powder magnetic core of the prior example in which no glass was added were not included in FIG.

In addition, Fig. 15 is a graph showing the iron loss (initial) of each of the powder magnetic cores shown in the column of 200 °C of Table 6. In Fig. 15, the glass transition temperature Tg of the glass added to each of the powder magnetic cores is taken as the horizontal axis, and the thermal expansion coefficient α of the glass is taken as the vertical axis. Therefore, the experimental results of the powder magnetic core of the prior example in which no glass was added were excluded from FIG.

In addition, FIG. 16 is a rate of change of initial magnetic permeability (200 ° C, 1000 hours) of each of the powder magnetic cores shown in Table 6, and FIG. 17 is a graph showing the rate of change in iron loss with each of the powder magnetic cores (200 ° C, Figure of the relationship of 1000 hours). In Fig. 16 and Fig. 17, the glass transition temperature Tg of the glass added to each of the powder magnetic cores is defined as the horizontal axis, and the thermal expansion coefficient α of the glass is taken as the vertical axis. Therefore, the experimental results of the powder magnetic core of the prior art in which no glass was added were not included in FIGS. 16 and 17.

First, since the heat treatment temperature at the time of compression molding each of the powder magnetic cores was set to 470 ° C, all of the powder magnetic cores to which glass having a glass transition temperature (Tg) higher than 470 ° C were added were comparative examples.

In Figs. 14 to 17, a line of glass transition temperature (Tg) of 470 ° C is drawn. The portion on the right side of the line is a comparative example.

Observing the experimental results of Table 6, FIG. 14 and FIG. 16, it can be seen that by making the glass transition temperature (Tg) of the glass lower than 470 ° C, a relatively high initial magnetic permeability (initial) can be obtained, and the previous example (not The rate of change (absolute value) of the initial magnetic permeability can be effectively reduced as compared with the addition of glass. As can be seen, the thermal stability of the initial magnetic permeability can be effectively improved according to the present embodiment. Further, the glass transition temperature (Tg) of the glass is preferably 360 ° C or higher.

Further, the thermal expansion coefficient α (×10 ^-7 /°C) of the glass is preferably from 60 to 110, or from 60 to 90. Thereby, the absolute value of the rate of change of the initial magnetic permeability can be more effectively reduced, and the thermal stability can be improved.

It can be seen that in the present embodiment, the initial magnetic permeability can be changed after 200 ° C and 1000 hours. The inhibition rate (absolute value) is suppressed to 4% or less, preferably 3% or less, more preferably 2% or less, and still more preferably 1.5% or less.

Further, with respect to iron loss, thermal stability can be improved by setting the glass transition temperature (Tg) of the glass to a value of 360 ° C or higher and lower than 470 ° C.

5‧‧‧Soft magnetic powder

6‧‧‧Insulating bonding materials

7‧‧‧ pores

Claims (14)

A powder magnetic core obtained by compression-molding a mixture comprising a soft magnetic powder and an insulating bonding material, wherein the insulating bonding material comprises a binder resin and glass, and the glass of the glass The transition temperature (Tg) is lower than the temperature of the heat treatment, and a part of the glass is diffused and fused into the resin, and the difference between the heat treatment temperature and the glass transition temperature is 2 to 100 °C. The powder magnetic core according to claim 1, wherein the content of the glass is in a range of 0.1% by mass or more and 0.60% by mass or less based on the mass of the soft magnetic powder. The powder magnetic core of claim 1, wherein the insulating adhesive material surrounds a surface of the soft magnetic powder and is present between the soft magnetic powders. The powder magnetic core of claim 2, wherein the glass system comprises at least P ₂ O ₅ , B ₂ O ₃ and BaO, and the composition ratio of P ₂ O ₅ is 40 to 60 mol%, and the composition of B ₂ O ₃ The ratio b is 2 to 20 mol%, the composition ratio of BaO is 5 to 45 mol%, the composition ratio d of SnO is 0 to 45 mol%, and the composition ratio e of Al ₂ O ₃ is 0 to 15 mol%, and satisfies a+b+ c+d+e 100 mol% relationship. The powder magnetic core of claim 4, wherein the composition ratio e of Al ₂ O ₃ is 2 to 15 mol%. The powder magnetic core of claim 4 or 5, wherein the composition ratio f of Li ₂ O is 0 to 1 mol%, the composition ratio g of CeO ₂ is 0 to 10 mol%, and the composition ratio i of TiO ₂ is 0 to 1 mol%. And it satisfies the relationship of a+b+c+d+e+f+g+h+i=100mol%. A powder magnetic core obtained by compression-molding a mixture comprising a soft magnetic powder and an insulating bonding material, wherein the insulating bonding material comprises a binder resin and glass, The glass transition temperature (Tg) of the glass is lower than the temperature of the heat treatment, and a part of the glass is diffused and fused into the resin, and the glass transition temperature (Tg) of the glass is in the range of 280 ° C to 470 ° C. The powder magnetic core of claim 4, wherein the glass transition temperature (Tg) of the glass is in the range of 360 ° C or more and less than 470 ° C. The powder magnetic core of claim 4, wherein the glass has a thermal expansion coefficient of 60 to 110 (×10 ^-7 /°C). The powder magnetic core of claim 4, wherein the glass has a thermal expansion coefficient of 60 to 90 (×10 ^-7 /°C). A powder magnetic core according to claim 1, wherein said insulating adhesive material contains said glass and magnetic fine particles having a particle diameter smaller than said soft magnetic powder. The powder magnetic core according to claim 11, wherein the content of the magnetic fine particles is in a range of more than 0% by mass and 0.60% by mass or less with respect to the mass of the soft magnetic powder. The powder magnetic core of claim 11, wherein the magnetic fine particles are oxide magnetic materials. The powder magnetic core of claim 11, wherein the oxide magnetic material is at least one of NiZn ferrite or MnZn ferrite.