JPS59119710A - Iron core - Google Patents

Abstract

PURPOSE:To obtain a core which has excellent frequency characteristics of permeability and high flux density by a method wherein either one or both of iron powder and ferroalloy magnetic powder, which have specific average particle diameter, and the powder of electrical insulating binding resin and electrical insulating inorganic compound, which is to be mixed with former material or materials and whose content is specified, are introduced to form the core. CONSTITUTION:Either one or both of iron powder and ferroalloy magnetic powder, which have average particle diameter of 10-100mum, and the powder of electrical insulating binding resin and electrical insulating inorganic compound, which is mixed with the former material or materials of 1.5-4.0vol%, are introduced to form a core. If the average particle diameter of the iron powder or the ferroalloy magnetic powder is defined as Dmum and the specific resistivity as rhomuOMEGA-cm, the relation rho/D<2>>=4X10<-3> should be established. The average particle diameter of the inorganic compound powder should be specified to be less than 20mum. The iron powder may be such as pure iron powder, Fe-Si alloy powder and Fe-Al alloy powder and the resin may be such as epoxy, polyamide and polyester and the inorganic compound may be such as calcium carbonate and silica.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an iron core, and more particularly to an iron core having excellent frequency characteristics of magnetic permeability and high magnetic flux density.

[Technical background of the invention and its problems]

Conventionally, power conversion devices such as devices that convert alternating current to direct current, devices that convert direct current to alternating current, devices that convert alternating current of different frequencies to alternating current of different frequencies, devices that convert direct current to direct current such as so-called choppers, etc. , or an electrical device such as a non-contact circuit breaker, has a semiconductor switching element represented by a thyristor or transistor as its electrical circuit component, and a turn-on stress relieving reactor, commutation reactor, or energy storage reactor connected to this. Alternatively, a matching transformer or the like is used. As an example of such a power conversion device, FIG. 1 shows an electric circuit diagram of a device that converts direct current into alternating current.

The power converter shown in FIG. 1 includes a semiconductor switching element 1,
It is composed of a turn-on stress relieving reactor 2 and a matching transformer 3.

These electric currents and transformers have a frequency range of 100 KHz to 500 KHz in some cases due to semiconductor device switching.
Currents containing high frequency components, even reaching levels above Hz, may flow.

Conventionally, the following types of iron cores have been used to construct such axles and transformers: That is, (&) a laminated core made by laminating thin electromagnetic steel plates or permalloy plates with interlayer insulation; (b) a laminated iron core made by laminating carbonyl iron fine powder, permalloy fine powder, etc. using a resin such as phenol resin; (c) A so-called ferrite core made by sintering an oxide-based magnetic material, and the like.

Among these, laminated cores exhibit excellent electrical properties in the commercial frequency band, but in high frequency bands, the core loss is significant, and in particular, the eddy current loss is proportional to the square of the frequency. Furthermore, as the magnetizing force increases from the surface of the plate material forming the core to the inside, it has a property that the magnetizing force becomes difficult to change due to the skin effect of the core material. Therefore, in high frequency bands, laminated cores can only be used at magnetic flux densities that are much lower than the saturation magnetic flux density that the core material itself originally has, and the eddy current loss is also extremely large! It has the problem of

Furthermore, the effective magnetic permeability of the laminated core at high frequencies is
The problem is that the effective magnetic permeability at commercial frequencies is significantly lower than that at commercial frequencies. When a laminated core with these problems is connected to a semiconductor switching element or used in an accelerator or transformer where a current with high frequency components flows, effective magnetic permeability and magnetic flux@degree are compensated. In order to do this, the single core itself must be made large, which, together with the low effective magnetic permeability, also poses the problem of increased copper loss.

On the other hand, a powder magnetic material called a dust core is used as an iron core material, and is described in detail in, for example, Japanese Patent No. 112235. However, such dust cores generally have very low values for their magnetic flux density and magnetic permeability. Among these, Kerr has a relatively high magnetic flux density, even in the dust core using nil iron powder, which has a magnetic flux density of 100OOA/? The magnetic flux density at the magnetizing force of FI is a little over 0.1 T, and the magnetic permeability is about 1.25 x I F5H/m. Therefore, when guest cores are used as core materials, or in accudres, transformers, etc., in order to compensate for the low magnetic flux density and magnetic permeability, it is unavoidable that the core becomes large, and accordingly, reactors, transformers, etc. The problem is that copper loss increases.

Further, ferrite cores used in small electrical devices have high specific resistance values and relatively hard high frequency characteristics. However, the ferrite core is 10,000
A: The magnetic flux density at a magnetizing force of 7 m is as low as about 0.4 T, and the magnetic permeability and the magnetic flux density at the same magnetizing force change by several tens of degrees in the operating temperature range of the iron core, 140 to 120 degrees Celsius. There are problems. 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 the ferrite core is a sintered body, it is difficult to manufacture a large iron core, and it is not suitable as an iron core. In addition, ferrite cores have large copper loss due to their low magnetic flux density, and their magnetic permeability and magnetic flux density are greatly affected by temperature, so their characteristics change significantly when used in reactors and transformers. Furthermore, since the magnetostriction is large when compared with electromagnetic steel sheets, etc., there are problems such as increased noise emitted from the iron core.

[Object of the Invention] The object of the present invention is to solve the above-mentioned problems, and to provide an iron core that has excellent magnetic permeability, frequency characteristics, and high magnetic flux density, and can be used as an iron core connected to semiconductor devices or used in accelerators, transformers, etc. The goal is to provide the core.

[Summary of the invention]

The iron core of the present invention is a molded body made of magnetic powder, binder resin, and inorganic compound powder. That is, the iron core of the present invention is
Either or both of iron powder and iron alloy magnetic powder having an average particle size of 10 to 100 μm, and powder of an electrically insulating binder resin and an electrically insulating inorganic compound having a content of 1.5 to 40 cm by volume. It is characterized by being a molded article.

The iron powder or iron alloy magnetic powder used in the present invention has a specific electrical resistivity of 10 μΩ to at most several tens of μΩ, so it can be used as a sufficient iron core material even under alternating current including high frequencies that cause the skin effect. In order to obtain these characteristics, these powders must be made into fine particles that sufficiently contribute to magnetization from the particle surface to the inside of the particle, so it is necessary that the average particle size is 100 μm or less. . However, when the average particle size becomes extremely small, less than 10 μm, the 1
If the molding pressure is less than 0,000 MPa, the density of the obtained iron core will not increase, resulting in the disadvantage of a decrease in magnetic flux density. After all, in the present invention, the average particle size of the iron powder or iron alloy magnetic powder is set in the range of 10 to 100 μm.

Also, regarding the relationship between the average particle diameter (Dμm) of these powders and their specific electrical resistivity (ρμΩ−α), D and ρ
It is preferable to express only numerical values and satisfy the relationship ρ/D2≧4×10″−3.

The iron powder or iron alloy magnetic powder used in the present invention may be any powder as long as it satisfies the above specifications, but examples include pure iron powder and Fe-8t alloy powder represented by Fe-3Si. ,
Fe-At alloy powder, Fe-8t-At alloy powder, Fe
-Ni alloy powder and Fe-Co alloy powder can be used, and powders of each of these or an appropriate combination thereof can be used.

The electrically insulating binder resin used in the present invention coats the surface of the above-described iron powder or iron alloy magnetic powder to electrically insulate the powders from each other and has a sufficient effective electrical resistance value against alternating current magnetization of the entire iron core. At the same time, it also functions as a binder to bind these powders together. Examples of such a binder resin include various resins such as epoxy resins, polyamide resins, polyimide resins, and polyester resins, or resins formed by appropriately combining these resins.

In addition, the electrically insulating inorganic compound powder used in the present invention reduces the frictional resistance between iron powder or iron alloy magnetic powder during forming of the iron core, increases the compacted density of the iron core, and at the same time is a conductor. It also serves the function of increasing the effective electrical resistance value of the entire core against alternating current magnetization by being interposed between the iron powder or iron alloy magnetic powder. Examples of such inorganic compounds include calcium carbonate, silica, magnesia, alumina, various glasses, and appropriate combinations thereof. However, it goes without saying that these inorganic compounds must not react with the above-mentioned iron powder or iron alloy magnetic powder and the binder resin.

Note that the average particle size of the inorganic compound powder is preferably V5 or less (20 μm or less) of the average particle size of the iron powder or iron alloy magnetic powder, considering its dispersibility and the relationship with the iron core material properties.

In the iron core of the present invention, the content of the binder resin and the inorganic compound powder is set in a range of 1.5 to 40% compared to the total volume. When this volume ratio is less than 1.5%, the compacted density of the core does not increase and the effective electrical resistance value decreases, and when it exceeds 4.()%, the increasing tendency of the effective electrical resistance value reaches a saturated state. Furthermore, the molding density is reduced and the saturation magnetic flux density is also low.At a magnetizing force of 10,000 A/m, the magnetic flux density becomes about that of ferrite.

Regarding the mutual volume/volume ratio of the binder resin and the inorganic compound powder, the ratio of the former to the latter is 9.8 to 20 vot%.
:...2r: ~8. Ovat%, preferably 9
5-3 Q voL Chi: 5-7 Q Vat Chi.

The iron core of the present invention is manufactured, for example, in the following manner. That is, a predetermined amount of iron powder, iron alloy magnetic powder, or a mixture of both powders, a binder resin, and an inorganic compound powder are thoroughly mixed in a mixer, and the resulting mixed material is filled into a mold. This is compression molded. At this time, the molding pressure applied is usually
It may be 10,000 MPa or less. The obtained molded body can be used as an iron core as it is, but if necessary, it can be
The binder resin may be cured by heat treatment at a temperature of about 0 to 300°C.

[Embodiments of the invention]

Examples 1 to 7 Various magnetic powders having different average particle diameters, inorganic compound powders, and binder resins were blended in the proportions (volume %) shown in Table 1, and thoroughly kneaded. The obtained mixed wire material was filled into an iron core molding die, and was press-molded at various pressures to obtain a molded body of a predetermined shape. This molded body was heat-treated to harden the binder resin to form an iron core.

For these cores, the density and magnetic flux density at a magnetizing force of 10,000 A/m were measured, and the effective electrical resistivity was calculated from the eddy current loss of the cores with respect to AC magnetization.

The above results are collectively shown in Table 1.

Further, when the changes in magnetic permeability and magnetic flux density at temperatures of -40 to 120°C were measured for the iron cores of Examples 1 to 4, the rate of change was less than 10% in all cases.

Further, for the iron core of Example 3 and the iron core made of a conventional dust core, DC magnetization curves representing changes in magnetic flux density at each magnetization were determined and are shown in FIG. It was confirmed that the iron core of the present invention (curve A) has a higher magnetic flux density than the conventional iron core (curve B).

Examples 8 to 11 Iron powder or iron alloy magnetic powder with different specific electrical resistivities (ρ) and average particle diameters (D) 84 vot%, average particle diameter 1
Alumina powder below μm 1 vot%, epoxy resin 1
After kneading 5 vot% and molding the kneaded product at a pressure of 600 MPa, the obtained molded product was heat-treated at 200° C. for 1 hour to form an iron core.

For these cores, the effective magnetic permeability from 1 kHz to 500 kHz was measured, and the ratio was determined based on the effective magnetic permeability at 1 kHz. The results are shown in Example 1 as a relationship with ρ/D2.
2 Fe-3At powder 40voA with average particle size 63ttm
%, Fe-Ni powder with an average particle size of 53 μm or less 10
voA%, Fe powder with an average particle size of 44 μm or less, 0.8 vot% of glass powder with an average particle size of 8 μm, and 14.2 vot% of polyamide resin were kneaded, and the mixture was heated to 800 MPa.
After pressure molding at a pressure of 100° C., the molded product was heat-treated at 100° C. for 1 hour to obtain an iron core. The effective electrical resistivity of this iron core was 350 mΩ-α or more.

In the above examples, similar results were obtained when polyimide resins and polycarnate resins were used in place of the epoxy resins, and when other inorganic compounds such as ma and gnesia were used.

〔Effect of the invention〕

As is clear from the above description, the iron core of the present invention has a much higher magnetic flux density and a higher effective electrical resistivity than conventional ferrite core iron cores and dust core iron cores. Furthermore, compared to laminated iron cores, the
The change in effective magnetic permeability in the z frequency band is small, and its industrial value is great.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an example of an electric circuit diagram of a device that converts direct current to alternating current, and Fig. 2 is a diagram showing DC magnetization curves in the iron core of the present invention (Example 3) and a conventional dust core. ...Semiconductor switching element, 2...Reactor for reducing turn-on stress, 3...Matching transformer, 4...Load for alternating current, 5...DC power supply, A
. . . DC magnetization curve of the iron core of the present invention, B . . . Linear magnetization curve of the conventional Guess I core. Figure 1 Figure 2 Aoya Ibshi θ [A/m] Procedural amendment February 16, 1980 Kazuo Wakasugi, Commissioner of the Patent Office 1, Indication of the case 1982 Patent Application No. 226736 2. Name of the invention Iron core 3. Relationship with the case of the person making the amendment Patent applicant 5. Date of the amendment order Voluntary action

Claims (1)

[Claims] 1. Either or both of iron powder and iron alloy magnetic powder having an average particle size of 10 to 100 μm, and an electrically insulating binder resin having a content of 1.5 to 40% by volume. and an electrically insulating inorganic compound powder. 2. Iron powder or iron alloy magnetic powder has an average particle size of 0 μm1
Claim 1 which is an iron powder or iron alloy magnetic powder that satisfies the relationship ρ/D2≧4X10-5, where D and ρ are expressed only in numerical values, where the specific electrical resistivity is ρμΩ-m. iron core. 3. The iron core according to claim 1, wherein the average particle size of the inorganic compound powder is 20 μm or less.