JPH02183508A - Low-loss core - Google Patents

Abstract

PURPOSE:To provide a core which is superb in DC superposition characteristics which enables operation magnetic flux density to be large at low loss by providing a gap on at least one position of a magnetic path formed by an ultrafine crystal soft magnetic alloy thin band and then placing a soft ferrite on that cut edge surface or an abutment surface. CONSTITUTION:It has a composition expressed by (Fe1-aMa)100-x-y- z-alphaCuxSiyBzM'alpha, (where M is Co or Ni or M' is Nb, W, Ta, Zr, Hf, Ti, or Mo). It is wound in toroidal shape after creating a thin band by the single roll method using an amorphous alloy. Then, it is heat-treated to produce an Fe based ultrafine crystal alloy whose 50% of composition consists of a fine crystal grain. Then, in the case of a winding core, it is dipped or coated and then gap is formed or cutting is made. Then, a soft ferrite is placed on the cut edge surface or abutment edge surface of the gap part for producing core.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gapped core or cut core made of an ultrafine crystalline soft magnetic alloy used in choke coils, high frequency transformers, etc.

[Prior Art] Conventionally, silicon steel cores, permalloy cores, ferrite cores, and the like have been used as magnetic cores for high-frequency transformers and choke coils.

Silicon steel magnetic cores are advantageous in terms of miniaturization in frequency ranges where the saturation magnetic flux density is high and the heat generation of the magnetic core is not much of a problem, but the large core loss makes it difficult to use them, especially in frequency bands of several tens of kilohertz or higher. . Although permalloy magnetic cores have better high frequency characteristics than silicon steel magnetic cores, they have the disadvantage that at frequencies above several tens of kilohertz, core loss is large and magnetic characteristics tend to deteriorate due to distortion and deformation. Ferrite magnetic cores have lower core loss than silicon steel at frequencies of several 10 KI (z or higher) and are used in main transformers of switching power supplies, etc., but their saturation magnetic flux density is low and their Curie temperature is also low, so they have the disadvantage that they cannot increase the operating magnetic flux density. For this reason, it is not often used in transformers such as inverters because the magnetic core becomes large.Furthermore, in recent years, switching regulators, etc. have become increasingly high-frequency, and some that drive at several hundred kilohertz have appeared.For this reason, high-frequency transformers are used. It is becoming important to reduce the loss of magnetic cores used in magnets and smooth choke coils.

However, the Ferrite 1 core has a low saturation magnetic flux density and cannot increase the operating magnetic flux density when used in a transformer. When used in smooth choke coils, there is a problem of poor DC superimposition characteristics.

[Problems to be Solved by the Invention] In order to solve the above-mentioned problems, there have recently been attempts to use amorphous magnetic cores in high-frequency transformers.

For example, such an attempt is made in IEICE Technical Report PE84-381.
It is described on page 2. However, in this report, since Fe-based amorphous magnetic core is used in the high frequency transformer,
It has been reported that magnetostriction is large and properties tend to deteriorate due to mechanical stress, and when impregnated cores or cut cores are used, crystal frequency magnetic properties deteriorate. Furthermore, the Fe-based amorphous magnetic core also has the disadvantage of producing beats due to magnetostriction. On the other hand, a CO-based amorphous magnetic core has a drawback that deterioration due to strain is small, but changes over time are large. Furthermore, in a frequency band where the core loss is small and the temperature rise of the magnetic core is not much of a problem, the saturation magnetic flux density is lower than that of silicon steel or Fe-based amorphous, which is disadvantageous in terms of miniaturizing the magnetic core.

Incidentally, in the case of high-frequency transformers, etc., a single-core core is preferred and used in order to facilitate winding.

However, in the case of amorphous alloys, as mentioned above, it has been reported that cutting or creating gaps increases core loss.

In order to solve this problem, an attempt to arrange soft ferrite on the end face of the cut portion has been reported in the 12th Japan Society of Applied Magnetics, Academic Conference Abstracts, page 89, etc.

However, what is mentioned here is that when Co-based amorphous with low magnetostriction is used, the operating magnetic flux density cannot be increased, when used in smooth choke coils, the DC superimposition characteristics are insufficient, and over time. The problem was that there was a lot of change. In addition, in the case of Fe-based amorphous alloys, although the saturation magnetic flux density is high, the magnetostriction is extremely large, so if impregnation is performed when forming a cup or gap, the core loss will increase significantly, and if rough ferrite is arranged, However, there is a problem that the magnetic core loss cannot be sufficiently reduced.6 An object of the present invention is to provide a magnetic core that can increase the operating magnetic flux density with low loss and has excellent DC superimposition characteristics.

[Means for solving the problems] The present invention uses Fe, Cu and M (where M is N b +
W + T a r Z r + Hf + T i
and Mo (at least one element selected from the group consisting of Mo) as an essential element, and at least 50% of the structure
is a magnetic core with a gap at at least one point in a magnetic path formed from an ultrafine crystal soft magnetic alloy ribbon consisting of fine crystal grains, or a cut magnetic core with a soft ferrite placed on the cut end face, and a combined magnetic core. In the present invention, which is a characteristically low-loss magnetic core, an Fe-based ultrafine crystal alloy, which the present inventors previously filed as Japanese Patent Application No. 62-367187, can be used. This alloy has a composition formula: % formula % (where M is Co and/or Ni, 1M' is Nb,
At least one element selected from the group consisting of W, Ta, Zt, HF, Ti, and Mo, a+X+ y+
Z and α are 0≦a≦0.5, 0.1≦X≦3, respectively.
0.0≦y≦30. O≦2≦25, 5≦y1z≦30 and 0.1≦α≦30 are satisfied. ), and at least 50% of the structure consists of fine grains, or (Fel-aMa) 100-x-y-z-a-β-y
CuxSiyBzM' a M"βX (where M is C
O and/or Ni, and 1M' is Nb, W, Ta, Zr
, HF, Ti, and Mo, Mu is V, Cr, Mn, Al, platinum element, X is C, Ge, P, Ga, Sb, In, Be, A
at least one element selected from the group consisting of s, a.

X+y*Z+ α, β and γ are each 0≦a≦0.5
,0.1≦X≦3.0. O≦y≦30, 0≦2≦25,
5≦y+z≦30 and 0.1≦α≦30, β≦10.
γ≦10 is satisfied. ), and is an Fe-based ultrafine-crystalline alloy in which at least 50% of the structure consists of fine crystal grains.

Here, Fe, Cu and M (where M is Nb).

At least one element selected from the group consisting of W, Ta, Zr, HF, Ti, and Mo) was made an essential element because Cu and Cu are considered to be elements that promote the formation of crystal nuclei and promote crystal growth. This is because an Fe-based ultrafine-crystalline alloy is obtained through the interaction of M, which is considered to be an element that suppresses crystal growth. This microcrystalline alloy becomes amorphous, and preferably contains elements that promote amorphization, such as Si and B, in addition to the above-mentioned essential elements.

In addition, if at least 50% of the structure is made up of fine crystal grains, if there are many amorphous parts, the change over time will become large.
This is because the magnetostriction increases, so it is more preferable to have an alloy structure consisting of substantially fine crystal grains.

The magnetic core of the present invention is manufactured in a conventional manner.

First, an amorphous alloy ribbon with the above composition is produced by a single roll method, then rolled into a toroidal shape, or processed into various shapes by punching and photo-etching, etc., and then heat treated to produce a material with a small structure, 50% of which is fine. An Fe-based ultrafine crystal alloy consisting of crystal grains is produced.

Next, in the case of a wound magnetic core, it is impregnated or coated, and then gaps are formed or cut.

In the case of laminated magnetic cores, the shaped cores are laminated and bonded,
Depending on the shape, it may be cut or used in combination.

Next, soft ferrite is placed on the cut end face of the gap portion and the end face of the mating portion to produce the magnetic core of the present invention. Examples of shapes according to the present invention are shown in FIGS. 1(a), (b), and (c).

The heat treatment of the magnetic core of the present invention may be performed in a magnetic field.

It may be done in multiple sessions. Further, when impregnating with a heat-resistant resin, heat treatment may be performed after impregnation. Further, the surface of the alloy ribbon may be interlayer insulated if necessary.

Soft ferrite is Mn-Zn ferrite.

Ni-Zn ferrite or the like can be used, and after being processed to an appropriate size, it is placed on the cut surface or the end surface of the mating portion. Ferrite is usually fixed by adhesive, but in some cases it may be just pressed.

Further, more favorable results can be obtained if the cut surface is flattened by hand polishing or the like.

[Example] The present invention will be described in detail below, but the present invention is not limited thereto.

Example 1 Cu1.1%, Nd2.5%, 5i13.5 in atomic %
%, 87.3% The remainder was quenched by a single roll method to form a molten alloy with a width of 25ffi.

An amorphous alloy ribbon with a thickness of 19 m was produced. Next, the four alloy strips were wound while applying MgO powder to the surface of the alloy ribbon by electrophoresis to produce a wound core having the shape shown in FIG. 2(a).

Next, this magnetic core was placed in a furnace maintained at 450"C and held for 1 hour, then raised to 550°C at a rate of 2.5°C/min, held for 1 hour, and then heated to 200°C at a rate of approximately 5°C/min. ℃ and then taken out of the furnace and cooled to room temperature.As a result of observation using a transmission electron microscope, this alloy had an ultrafine grain structure with a grain size of approximately 100 μm.Next, this magnetic core was impregnated with epoxy resin and hardened. After that, cut it with a peripheral slicer as shown in Figure 2 (
A cut core as shown in b) was produced. Next, the end faces of the cut portions were hand-polished, and Mn-Zn ferrite plates were attached to the mating portions, and the cut magnetic cores were assembled as shown in FIG. 2(C). The core loss of this core was measured at 100 KHz and 2 KG and was found to be -450 mV/cc. The saturation magnetic flux density was 13.5KG.

Next, a non-magnetic spacer with a thickness of 50 IU was inserted between the mating portions, and the core loss was measured in the same manner. Core loss is 450
mW/cc, and almost no change was observed.

The same thing happened when a 100 μs spacer was inserted, but when no ferrite was placed, it was reported that the core loss significantly increased when a gap was formed.

For comparison, F e,, CrlS i,, B with the same shape.

(at%) An amorphous alloy core was produced, but the core loss was 18
00 mW/cc, and the core loss was significantly larger than that of the magnetic core of the present invention. This is considered to be because the magnetostriction of the Fe-based amorphous alloy is extremely large, so that its properties deteriorate due to impregnation.

As described above, since the magnetic core of the present invention has a high saturation magnetic flux density and low loss, it is ideal for high frequency transformers, smooth choke coils, and the like.

Example 2 Cu1.2%, Nd3%, 5i17% in atomic%.

A molten alloy consisting essentially of 85% Fe was rapidly cooled by a single roll method to produce an amorphous alloy ribbon having a thickness of 17 ttm and a width of 19 mm. Next, this alloy ribbon was punched out to form a thin plate with a shape as shown in Fig. 3(a).
Heat treatment was performed at ℃ for 1 hour. The microstructure of the alloy was similar to Example 1.

Next, this alloy is laminated and bonded, and M
As shown in FIG. 3(b), a dowel winding was provided with n-Zn ferrite, and the core loss was measured. 10
0K) 12.2KG core loss was 390mW/CC. This value is equivalent to the case where CO-based amorphous is used. Moreover, the saturation magnetic flux density was about 12KG.

The saturation magnetic flux density is 5 to 9 when a Co-based amorphous alloy is used, which is larger than G, allowing the magnetic core to be miniaturized.

Example 3 A molten alloy having the composition shown in Table 1 was rapidly cooled by a single roll method to produce an amorphous alloy ribbon having a thickness of 18/ffi and a width of 5 mm.

Next, the surface of this alloy ribbon was subjected to electric field adhesion using Af1203 and then wound to produce a 5-turn magnetic core.

Next, this magnetic core was placed in a furnace maintained at 550° C. for 1 hour, and then cooled to room temperature at a rate of about 20° C./min. This magnetic core was impregnated and hardened with a silicone face, and then cut with an outer peripheral slicer to produce a cut core.

Next, the end face of the cut part was polished by hand, and a Mn-Zn ferrite plate was attached to the core loss Pc' at 100KHz and 2KG.
was measured. Next, this magnetic core was held at 120° C. while applying a magnetic field in the magnetic path direction 100e for 500 hours, and then the core loss was measured at room temperature. Cobal of the same shape for comparison
, F e4. Cr4. Si...

B1. Core loss Pc' of a magnetic core using an amorphous alloy
and P c5011 were measured.

Table 1 shows the ratio of core loss P c ' nn/ P c ″
shows.

As can be seen from the table, the magnetic core of the present invention has a smaller change in core loss over time than a cut core using a conventional Co-based amorphous magnetic core, and is a practical magnetic core.

[Effects of the Invention] According to the present invention, it is possible to provide a core with a gap or a cut core that can increase the operating magnetic flux density with low loss, so the effects are remarkable.

[Brief explanation of the drawing]

FIGS. 1(a), (b), and (C) are diagrams showing examples of the shapes of the low-loss magnetic cores of the present invention, and FIGS. 2(a), (b),
(c) is. Explanatory diagram showing the process of creating the magnetic core of the present invention, FIG. 3(a)
, (b') are explanatory diagrams of other embodiments of the present invention. Figure 2 (b) Written amendment to soft ferrite procedure (voluntary) Relationship to Patent Application No. 003031 of 1999 Address of patent applicant 2-1-2 Marunouchi, Chiyoda-ku, Tokyo Contents of the amendment (1) Page 4 After "Also," in the 5th line, "The rCo-based amorphous magnetic core is" is added. (2) Correct "small" in line 6 of page 4 to "because it is small." (3) On page 4, line 18, change “in the case,” to “in the case,
” he corrected. (4) Correct "main switch" in lines 17 to 18 of page 3 to "sub switch." (5) In page 5, line 5, "in forming" is corrected to "in order to form." (B) Drawings. 13. The "Detailed Description of the Invention" column and drawings of the above specification.

Claims (2)

[Claims] (1) Fe, Cu and M (where M is Nb, W, Ta
, Zr, HF, Ti, and Mo) as an essential element, and at least 50% of the structure is composed of crystal grains. A low-loss magnetic core, characterized in that a magnetic path of the magnetic core has a gap at at least one location, and a soft ferrite is disposed in the gap. (2) Fe, Cu and M (where M is Nb, W, Ta
, Zr, HF, Ti, and Mo) as an essential element, and at least 50% of the structure is composed of crystal grains. A low-loss magnetic core characterized in that the magnetic core is a cut magnetic core or a combination magnetic core in which soft ferrite is arranged in the abutting portion.