JPS61152004A - Iron core - Google Patents

Abstract

PURPOSE:To improve the frequency characteristics of permeability, to enhance the density of magnetic flux, and to reduce the iron loss on a high frequency band by a method wherein an iron core is formed using metal magnetic powder, electrically insulative bonding resin and phosphate as essential ingredients. CONSTITUTION:An iron core is formed by the molded body having metal magnetic powder, electrically insulative bonding resin and phosphate as essential ingredients. Pure iron powder, Fe-Si alloy powder, Fe-Al alloy powder, Fe-Si-Al alloy powder, Fe-Ni alloy powder, Fe-Co alloy powder, amorphous alloy magnetic powder containing iron and the like are used, for example, as the metal magnetic powder. The surface of the magnetic powder is covered by electrically insulative bonding resin through the intermediary of phosphate, an electrically insulative state is formed between each magnetic powder, an effective electric resistance value enough to perform an AC magnetization on the entire iron core is given, and at the same time, said powder is brought in the state wherein it functions as a binder with which the powder is bonded. Also, the wetting property and the adhesive property of the magnetic powder and the bonding resin are enhanced by the phosphate, and the phosphate also has the function to lower the releasing force of the metal mold after a compression molding is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention 1] The present invention relates to an iron core, and more particularly to an iron core that has good electrical insulation between magnetic powders and reduces iron loss in a high frequency band. It is something.

[Technical background of the invention and its problems] In general, there are devices that convert alternating current into direct current, devices that convert direct current to alternating current, devices that convert alternating current of a certain frequency to alternating current of a different frequency, and devices that convert direct current such as so-called choppers. Power conversion devices such as devices that convert to DC, or electrical equipment such as non-contact circuit breakers, have the following as components of their electrical circuits:
Semiconductor switching elements such as thyristors or transistors, as well as turn-on stress relieving reactors, commutation reactors, energy storage reactors, matching transformers, and the like connected thereto are used.

In addition to the current at the same frequency as the switching frequency, in addition to the current at the same frequency as the switching frequency, in addition to the current at the same frequency as the switching frequency, in addition to the current at the same frequency as the switching frequency, in addition to the current at the same frequency as the switching frequency, in addition to the current at the same frequency as the switching frequency, in addition to the current at the same frequency as the switching frequency, the accelerator and transformer have a frequency of several tens of kHz, which is much higher than the switching frequency, and in some cases exceeds 500 kHz. Currents with high frequency components reaching up to

Conventionally, primary cores have been used for the iron cores that constitute such axles and transformers.

(a) A laminated iron core made of thin electromagnetic steel sheets with interlayer insulation or laminated with barmilo, etc., (b) A so-called dust core made of carbonyl iron fine powder, permalloy fine powder, etc. bound together using a resin such as phenol resin. Iron core.

(c) A so-called ferrite core made by sintering an oxide-based magnetic material, etc.

Among these, although the laminated core exhibits excellent electrical characteristics at commercial frequencies, the iron loss of the core becomes significantly large in high frequency bands.

In particular, eddy current loss increases in proportion to the square of the frequency, and the magnetizing force becomes difficult to change as it enters the interior from the surface of the plate material forming the iron core due to the skin effect of the iron core material. .

Therefore, in the high frequency band, the laminated iron core
It can only be used at a magnetic flux density that is much lower than the saturation magnetic flux density that the iron core material itself originally has.
There is also the problem that eddy current loss becomes extremely large.

Furthermore, the laminated core has a problem in that the effective magnetic permeability for high frequencies is significantly lower than the effective magnetic permeability for commercial frequencies.

When using a laminated iron core with these gaps and illumination points in a reactor or transformer that is connected to a semiconductor switching element and through which current with high frequency components flows, it is necessary to In order to compensate for this, the iron core itself had to be made larger, which led to an increase in iron loss and a disadvantage in that the length of the coil wound around the core became longer, resulting in an increase in copper loss.

In addition, it has been conventionally practiced to use the powder magnetic material called the dust core as the iron core.
This is explained in detail in Publication No. 235.

However, such dust cores generally have fairly low values of magnetic flux density and magnetic permeability. Among these, even the dust core using carbonyl iron powder, which has a relatively high magnetic flux density, has a magnetic flux density of 100OO
The magnetic flux density at a magnetizing force of A/m is slightly over 0.1 T, and the magnetic permeability is approximately 1.25×10 4 H/layer.

Therefore, when dust cores are used as core materials or in accelerators and transformers, in order to compensate for the low magnetic flux density and magnetic permeability, it is unavoidable to increase the size of the core, just as in the case of laminated cores. The disadvantage was that the length of the coil wound around the iron core became longer, increasing copper loss in reactors, transformers, etc.

Furthermore, ferrite cores, which are often used in small electrical devices, have a high specific resistance value and relatively excellent high frequency characteristics.

However, the magnetic flux density of the ferrite core at a magnetizing force of 10 GOOA/s is as low as about 0.4 T, and the value of magnetic permeability and magnetic flux density at the same magnetizing force is low in the operating temperature range of the iron core, 0°C to 120°C. There is a problem in that each changes by several tens of percent.

For this reason, when a ferrite core is connected to a semiconductor switching element or used as an iron core material for an axle, a transformer, etc., it is necessary to make the iron core large because the magnetic flux density is low. However, since ferrite is a sintered body, it is difficult to manufacture large cores, and it is difficult to apply it to large power cores.

Furthermore, since the ferrite core has a low magnetic flux density, the length of the coil wound around the iron core becomes long, resulting in large copper loss. Furthermore, since the magnetic permeability and magnetic flux density are greatly affected by the operating temperature, the magnetic properties change greatly when used in reactors and transformers. Furthermore, since the magnetostriction is greater than that of electromagnetic steel sheets, etc., there have been various problems such as increased noise emitted from the iron core.

[Purpose of the invention]

The present invention has solved the above-mentioned problems and is suitable for use as an iron core that is connected to semiconductor devices or used in accelerators, transformers, etc., has excellent frequency characteristics of magnetic permeability, has high magnetic flux density, and has a high frequency band. The purpose of the present invention is to provide an iron core for a compression molded body that has low iron loss during manufacturing and has excellent workability such as low demolding pressure during manufacturing.

[Summary of the Invention] The iron core of the present invention is characterized in that it is a molded article containing a metal magnetic powder, an electrically insulating binder resin, and a phosphate ester as essential components.

First, the metal magnetic powder used in the present invention includes, for example, pure iron powder, Fe-9i alloy powder represented by Fe-3XSi, Fe-A9. alloy powder, Fe-9i-141
alloy powder.

Examples include Fe-old yarn alloy powder, Fe-Go alloy powder, and amorphous alloy magnetic powder containing iron. The magnetic powders described above may be used alone or in appropriate combinations.

In addition, the above-mentioned magnetic powder has a specific electrical resistivity of 10%.
The resistance ranges from Ω・C■ to several tens of Ω・C1 at most.

Therefore, in order to obtain sufficient core material properties even in alternating currents that include high frequencies where the skin effect occurs, these magnetic powders must be made into fine particles to ensure sufficient magnetization from the particle surface to the inside of the particle. No.

For the reasons mentioned above, for iron cores that are excited by currents with frequency components up to several tens of kHz and require magnetic permeability characteristics up to that frequency range, the average particle size of the magnetic powder must be approximately 3001 L■ or less. is desirable.

Similarly, in an iron core where the frequency band exceeds 100 kHz, it is desirable that the average particle size of the magnetic powder is about 100 gm or less.

However, when the average particle size is extremely small, less than 101 L, manufacturing becomes difficult.

Also, the 100O
If the molding pressure is less than NPa, the density of the obtained iron core will not increase, resulting in the disadvantage of a decrease in magnetic flux density, so it is desirable that the molding pressure be about 1101 L or more.

The blending ratio of the magnetic powder in the molded body can be appropriately set depending on the required magnetic properties 1, such as magnetic flux density. However, if the magnetic powder exceeds 88% by volume, the resin component described below will decrease and binding between the magnetic powders will be insufficient, so it is preferably 38% or less, and the magnetic powder is less than 60% by volume. Then, the magnetic flux density of the iron core at an excitation force of 10,000^/mass is about the same as that of a ferrite core (0,47)
Therefore, if a higher magnetic flux density is required, it is desirable that the magnetic flux density is 60% or more.

The electrically insulating binder resin in the present invention coats the surface of the magnetic powder via a phosphate ester, which will be described later, to electrically insulate the magnetic powders from each other and to provide sufficient effective electrical resistance to alternating current magnetization of the entire core. At the same time as giving a value,
It functions as a binder that binds these powders together.

Examples of such electrically insulating binder resin include tf,
Examples include epoxy resin, polyamide resin, polyimide resin, polyester resin, and polycarbonate resin. The resins described above may be used alone or in appropriate combinations.

The blending ratio of the binder resin in the molded body is preferably 0.7% or more by volume.

If the amount is less than this, the binding strength to magnetic powder will be weakened.

The phosphoric acid ester in the present invention has the function of increasing the wettability and adhesion between the magnetic powder and the binder resin and lowering the ejection pressure from the mold after compression molding for reasons described later. Therefore, the phosphoric acid ester improves the dispersibility of the binder resin and the magnetic powder coating, thereby increasing the electrical insulation between the magnetic powders and reducing the iron loss of the core.

Although the phosphoric acid ester in the present invention is not particularly limited, compounds represented by the linear formula are particularly preferable, that is, the following formula: [)101,1-P-[OR1]n,
-(1) (in the formula, 1.Ill represents the number 1 or 2, respectively, and satisfies the relationship 11+n1m3, and R1 represents an alkyl group having 8 or more carbon atoms), and the following: Formula: [HOlml-P-[(QC)12CH2)
nOR21nl = (2) (In the formula, sl and nl each represent the number 1 or 2, and
(R2 represents an alkyl group or alkylphenyl group having 8 or more carbon atoms, and n represents a natural number.)
It is a phosphoric acid ester represented by

When the phosphoric ester is mixed with the magnetic powder and the binder resin, the hydroxyl group in the phosphoric ester shown by the above formula easily reacts with the moisture adsorbed on the surface of the magnetic powder at room temperature, and the phosphorus atom becomes oxygen. Strongly bonds to magnetic surfaces through atoms. On the other hand, other groups that remained unreacted (for example, OR', +0
CH211:H2+n0R2, etc.) has excellent wettability and adhesiveness with a binder resin, which is an organic substance. Therefore, the phosphoric acid ester exhibits excellent bonding and adhesive properties to both the magnetic powder and the binder resin.

Examples of the phosphoric acid ester represented by the above formula (1) include GgH17 dioctyl phosphate.

OO O Monoisodecyl phosphate etc.

Examples of the phosphoric acid ester represented by the above formula (2) include (OCH2C)12)20CBJ7 di(octoxyethoxyethyl)phosphate.

Examples include O mono(methylphenoxyethyl)phosphate. One type of these compounds may be used, or a mixture of two or more types may be used.

Note that in the present invention, the above-mentioned wettability and adhesive effects can be achieved by adding a small amount of phosphoric acid ester.
1+ k 4 YuN & J ll
J-4,, l-44mm &-11414411
11 does not go around sufficiently and the insulation becomes low, so the effect of reducing iron loss is small, so in practical terms it is 0.1% by volume.
It is preferable that it is above.

In the present invention, a sufficient effect of reducing iron loss can be obtained using only the above-mentioned three components, but an electrically insulating inorganic compound powder may be further added.

The electrically insulating inorganic compound powder reduces the frictional resistance between the magnetic powders during the molding of the core, increasing the compaction density of the core, and at the same time increases the AC magnetization of the entire core by intervening between the magnetic powders, which are conductors. It has the function of increasing the effective electrical resistance value and reducing iron loss.

Examples of such electrically insulating inorganic compound powders include powders of calcium carbonate, silica, magnesium, alumina, and various glasses. These inorganic compounds are the magnetic powders mentioned above.

The above-mentioned inorganic compounds, which must not cause chemical reactions with the binder resin, may be used alone or in appropriate combinations.

The average particle size of the above-mentioned inorganic compound powder is determined by its dispersibility,
In view of the relationship with the properties of the iron core material, it is preferable that the average particle size is smaller than the above-mentioned average particle size of the magnetic powder, preferably 20 or less.

The inorganic compound powder exhibits its effect in small amounts, but its blending ratio is preferably in the range of 0.3 to 30% in terms of volume ratio.If it is less than 0.3%, it may improve the molding density and reduce iron loss. This is because the effect of reduction is small, and if it exceeds 30%, the mechanical strength of the iron core will decrease.

Next, a method for manufacturing an iron core according to the present invention will be explained.

First, magnetic powder and phosphoric acid ester are mixed directly or in a state in which the phosphoric acid ester is dissolved in a solvent. In this step, the surface of the magnetic powder is covered with phosphoric acid ester, and then a binder resin is added thereto to form a mixture.

In this case, the three components of the magnetic powder, the binder resin, and the phosphate ester may be mixed at the same time, or the magnetic powder may be mixed into a pre-mixed mixture of the phosphate ester and the binder resin.

When an inorganic compound is also blended in addition to the above three components, (1) A method of mixing magnetic powder and inorganic compound powder, and then sequentially mixing phosphate ester and binder resin.

(2) A method of simultaneously mixing magnetic powder, inorganic compound powder, binder resin, and phosphate ester.

(3) Any method may be used, such as mixing magnetic powder or phosphate ester with an inorganic compound powder dispersed in a binder resin in advance, but it is preferable to adding the inorganic compound powder alone. An effective method is to disperse it in advance in a binder resin.

Next, the above mixture is filled into a mold and compression molded. The molding pressure applied at this time may be 1000 MPa or less. The obtained molded body having a predetermined shape can be used as an iron core as it is, but may be subjected to heat treatment to harden the binder resin, if necessary.

[Embodiments of the invention] The present invention will be explained in detail below.

Magnetic powder, binder resin, phosphate ester, and inorganic compound were blended in predetermined proportions and thoroughly mixed. At this time, the inorganic compound powder was dispersed and mixed in the binder resin in advance.

After the obtained mixture was filled into a mold and compression molded at a pressure of 800 MPa, the molded body was extracted from the mold, and the obtained molded body was heat-treated to produce an iron core.

As for this heat treatment, when an epoxy resin was used as the binder resin, heating was performed at 160 to 200°C for 0.5 to 2 hours, and when a polyamide resin was used, heating was performed at 180°C for 15 minutes.

Table 1 shows the composition types and blending ratios of the magnetic powder, binder resin, phosphate ester, and inorganic compound powder, as well as the average particle size of the powder. In addition, 9 = 0.0
The iron loss at 50kHz and 100kHz at 5T is also shown.

Examples 1 to 8 In Examples 1 to 8, the blending ratio of magnetic powder was fixed and the blending ratio of phosphate ester and inorganic compound was changed. Moreover, Comparative Examples 1 to 3 do not contain phosphoric acid ester.

There was no obvious difference in iron loss values between the samples at the commercial frequency of 50Hz, but at 50k, the high frequency band.
Hz and 100kHz, as is clear from Table 1, Example 1 in which 0.1% or more of phosphoric acid ester was added
-8 had significantly smaller iron loss than Comparative Examples 1-3. Furthermore, at 200kHz, the difference is large.
It has increased more than five times. Also, by reducing part of the binder resin, C
It can be seen that the iron loss is further reduced in the case where aCO3 is added.

The reason why the iron core of the present invention achieves a reduction in iron loss in the high frequency range is because the insulation between the magnetic powders is good and the eddy current loss is small.

Further, FIG. 1 shows the frequency characteristics of the effective magnetic permeability of Example 3 (curve a), and Comparative Example 2 is also shown as a curve in FIG. As is clear from the figure, the example of the present invention has excellent frequency characteristics with almost no change in effective permeability over a wide frequency range of 40 kHz to 1000 kHz, whereas the comparative example shows a significant increase in effective permeability in the high frequency range. It can be seen that the magnetic property is decreasing.

As described above, the present invention, which has small eddy current loss, has little decrease in effective magnetic permeability in the high frequency band, and even in Example 5 containing CaCO3, almost no decrease in effective magnetic permeability in the high frequency band was observed. In Example 6, in which the magnetic powder particle size was large, there was a tendency for a slight decrease.

Further, for the core samples of Example 3 and Comparative Example 2, the ejection pressures were compared for molded bodies of the same shape and size (cylindrical shape of 20 cm in diameter and 20 cm in height) after molding.

As a result, in Example 3, the weight was 1000 kg or less, but
Comparative Example 2 had a high weight of 1,500 to 2,000 kg, and the phosphoric acid ester reduces the punching pressure after molding, making the molding process easier, and also has the effect of reducing core breakage during punching and improving yield. There was found.

The core samples of Examples 1 to 8 had an excitation force of 10,000 A/■
In all cases, a high magnetic flux density of 0.8 T or more was exhibited.

Examples 9 to 15 In Examples 9 to 15, the blending ratio of magnetic powder was changed,
Comparative Examples 4 to 9 do not contain phosphate ester.

As is clear from Table 1, when comparing samples with approximately the same blending ratio of magnetic powder, the iron core of the present invention has less iron loss.
Especially at 100kHz, the difference becomes even larger.

Further, even larger differences were observed between Example 11 and Comparative Example 6, in which C; acO3 was added as the inorganic compound powder, and Example 13 and Comparative Example 8, in which SiO2 was added.

Note that the iron core of this example exhibits a magnetic flux density of 0.5 T or more at an excitation force of 10,000 A/■, but the blending ratio of magnetic powder is 80%.
In Example 15, the iron loss is small, but the excitation force is less than 10.
The magnetic flux density at 000 A/m was 0.4 T or less.

Examples 18-18 In Examples 18-19, only the magnetic powder was changed, and in Comparative Examples 10-13, no phosphate ester was contained.

As is clear from Table 1, the examples of the present invention have lower iron loss, and in particular, the iron loss at a high frequency of 100 kHz is much smaller than that of the comparative example.

Further, FIG. 2 shows the frequency characteristics of the effective magnetic permeability of Example 17 (curve C).

Further, Comparative Example 11 is also shown as a curve d in FIG. 2.

It can be seen that the iron core according to the present invention shows almost no decrease in effective magnetic permeability even in a high frequency band, but the iron core of the comparative example shows a significant decrease in effective permeability above 100 kHz.

This tendency was observed in Example 18 and Comparative Example 10, and in Example 18 and Comparative Example 12. The same applies to Example 19 and Comparative Example 13.

In addition, the excitation force of the iron core samples of Examples 18 to 18 was 10
000A/magnetic flux density in the intestines was 1 at 0.8T or higher in all cases.

Example 20 An iron core was produced in the same manner as in Example 18, except that 85% of Fe-9i-B amorphous magnetic powder with an average particle size of 1105 IL was blended. Further, as Comparative Example 14, an iron core was produced in the same manner as in Example 20, except that no phosphoric acid ester was blended.

When the iron loss was measured when B = 0.057, it was found that the iron loss of Example 20 was reduced by 55% at 50 kHz and 70% at 100 kL (z) compared to the comparison piece. .

[Effects of the Invention] As explained above, in the iron core of the present invention, the surface of the magnetic powder is coated with a phosphoric acid ester, and due to the action of the lipophilic group of the phosphoric acid ester, the wettability of the magnetic powder and the binder resin is improved. It also has very good binding and dispersibility.

Therefore, the iron core of the present invention has excellent electrical insulation due to the binder resin between the magnetic powders, and therefore has low eddy current loss.

Therefore, the iron core of the present invention has excellent magnetic properties such as low iron loss, especially in a high frequency band, and the ability to maintain high magnetic flux density without generating heat or decreasing effective magnetic permeability.

Furthermore, the pressure for ejecting from the mold after compression molding is small and the workability is good.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are diagrams showing the frequency characteristics of effective magnetic permeability in the iron core, respectively.

Claims (1)

[Scope of Claims] 1. An iron core characterized in that it is a molded body containing a metal magnetic powder, an electrically insulating binder resin, and a phosphate ester as essential components. 2. The content of the phosphoric acid ester is 0.1% by volume
The iron core according to claim 1, which is the above. 3. The phosphoric acid ester has the following formula: ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (In the formula, m_1 and n_1 each represent the number 1 or 2, and satisfy the relationship m_1 + n_1 = 3, R^
1 represents an alkyl group having 8 or more carbon atoms. ) The iron core according to claim 1 or 2, which is a compound represented by: 4. The phosphoric acid ester has the following formula: ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (In the formula, M_1 and n_1 each represent the number 1 or 2, and satisfy the relationship m_1 + n_1 = 3, R^
2 represents an alkyl group or alkylphenyl group having 8 or more carbon atoms, and n represents a natural number. ) The iron core according to claim 1 or 2, which is a compound represented by: 5. The iron core according to claim 1, 2, 3, or 4, wherein the molded body further contains powder of an electrically insulating inorganic compound.