JPS59204216A - Magnetic core - Google Patents

Abstract

PURPOSE:To reduce eddy current loss of a magnetic core at a high-frequency region by a method wherein a fine wire consisting of a soft magnetic metal having 20 oersted or less of coercive force, and moreover having 0.01mm.<2> or less of the sectional area is wound round. CONSTITUTION:The fine wire 1 of a soft magnetic metal is wound round in a loop type to form a toroidal type magnetic core 2. An exciting winding 3 is wound around the magnetic core 2 by the desired number of turns, and moreover an output winding 4 is wound around by the desired number of turns as occasion demands. The fine wire 1 is made as to form a shape forming a magnetic path in bundled condition in relation to the exciting winding 3. As the manufacturing method of the fine wire of the soft magnetic metal, the desired soft magnetic metal is wrapt with a glass material, and after heated at the temperature of a melting point or more, wire drawing is performed to obtain the fine wire.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic core that exhibits excellent magnetic properties even in a high frequency range.

The magnetic core utilizes the characteristics of a soft magnetic material, such as saturable magnetic flux characteristics, nonlinearity, magnetic flux level retention characteristics, or high magnetic permeability characteristics.

Materials for this type of magnetic core are generally F a -8i alloy or p e -S i -A e alloy for transformers or actances, and Fe - S i -A e alloy for magnetic flux control elements in magnetic amplifiers. N1 alloy etc. are used, and in recent years, amorphous alloy ribbons manufactured by liquid phase quenching method etc. have begun to be used.

By the way, the above-mentioned materials have a common problem that the upper limit of the usable frequency is not very high because the eddy current loss increases rapidly as the usable frequency becomes higher.

Such eddy current losses include microscopic ones related to domain wall movement and macroscopic ones related to spin rotation.

In this case, to reduce the vortex flow loss related to the former,
It is effective to cause as many domain walls to move as possible during magnetization reversal, and to minimize the displacement path and movement distance of each domain wall, and to reduce the eddy current loss associated with the latter It is effective to form the material in the form of a deciduous film as much as possible. However, when considering a thin strip-shaped material, even if the film thickness of this material is made thinner, the number of domain walls that this material has does not change, but rather the total number of magnetic flux obtained is reduced. In order to avoid this, it is necessary to widen the width of this ribbon-shaped material, and therefore the moving distance of the domain wall becomes larger. Therefore, in magnetic cores whose magnetization reversal mainly depends on the movement of domain walls, for example, magnetic cores for magnetic flux control elements that require high squareness, reduction of eddy current loss, that is, high frequency It has been extremely difficult to improve magnetic properties in this region.

The present invention was made in view of the above circumstances, and its purpose is to provide a magnetic core having high-frequency magnetic properties that are improved by reducing eddy current loss in the high-frequency range. be.

The magnetic core according to the present invention will be explained below.

The basic principle of the magnetic core according to this invention is that the basic unit of the magnetic material is a 1iill line with a minute area.
The objective is to obtain an eddy current reduction effect equivalent to that achieved by thinning the film, and also to increase the number of domain walls and minimize the moving distance of the domain walls during magnetization reversal. That is, now,
Comparing a thin strip-shaped soft magnetic material with a predetermined film thickness and a thin wire-shaped magnetic material having a cross-sectional diameter equivalent to the film thickness arranged by the width of the thin strip, it is found that in the thin strip-shaped material, the domain wall In contrast, a structure made of thin wires has at least as many domain walls as there are thin wires. Furthermore, in this case, in the case of a structure made of thin wires, the movement distance of the domain wall is limited to the thin wire where the domain wall exists, so it becomes extremely small, and high-speed reversal of the magnetic flux becomes possible. For example, it is made of Fe-8i alloy or amorphous T'j alloy and has a thickness of 20 μm and a width of 5.
Considering the conventional thin Mf-like soft magnetic material of rnm,
It is known from numerous experimental results that the number of domain walls generated during magnetization reversal in such soft magnetic materials is 20 or less. On the other hand, in order to obtain a magnetic flux equal to that described above, if a soft magnetic material with an effective cross-sectional area of 20 μm x 5 is formed into a thin wire shape with a diameter of 20 μm and the required number of wires are bundled together, the obtained The number of domain walls is (20X5X103)÷(πX10')≠32
0, which means that the number of heart walls is 16 times larger.

In the above case, the cross-sectional area of the thin wire GtQ, Q 1 mTl!
In the following, in the case of a thin wire with a circular cross section that can be easily formed, it is desirable that the diameter is 112 μm or less, and if the cross-sectional area (or diameter) is larger than this, the movement distance of the domain wall during magnetization reversal will be becomes large, making it impossible to obtain a sufficient effect of reducing eddy current loss.

Next, regarding the soft magnetic metal applied to the present invention, it is preferable that the soft magnetic metal can be formed into a thin wire and has a coercive magnetic force Hc of 20 oersted or less. This is generally the case for soft magnetic materials.
It is desirable that the saturation magnetic flux density Bs is high, the magnetic permeability μ is high, the specific resistance ρ is high, and the coercive force Ha is low, but when considering loss in the high frequency range, it is especially important that the coercive force Ho is low. It is from. Therefore, examples of the above-mentioned soft magnetic metals include those shown in Table 1.

Table 1 Next, the form of the magnetic core formed using the soft magnetic metal thin wire as described above will be explained. As a magnetic core according to the present invention, for example, as shown in the first leap and FIG. . The magnetic core 2 may be configured by winding the excitation conducting wire 3 with a desired number of turns and, if necessary, by winding the output conducting wire 4 with a desired number of turns.

In addition, although the cross-sectional shape of the magnetic core 2 is circular in these figures, this is just an example, and other shapes such as a rectangular shape may be used. Furthermore, as another example of the form of the magnetic core according to the present invention, first, the excitation groove #3 (and, if necessary, the output conductor 4) are spring-drilled concentrically with approximately the same diameter, and these conductors 3 (and the conductor 4), it is also possible to form the magnetic core 2 by winding the thin wire 1 made of soft magnetic metal.In this case, the thin wire 1 is bundled around the excitation conductor 3 (and the output conductor 4). What is necessary is to form the magnetic core into a shape that forms a magnetic path.
By selecting the soft magnetic metal to be used and optimizing the heat treatment method for removing magnetostriction, it is possible to impart desired magnetic permeability, magnetic flux level retention characteristics, saturability characteristics, nonlinearity, etc.

Furthermore, as a method for producing a thin wire of soft magnetic metal in the present invention, a desired soft magnetic metal is wrapped in a glass body, heated to a temperature higher than the melting point, and then drawn to obtain a thin wire. A manufacturing method such as a method of blowing the soft magnetic metal into a cooling medium through a nozzle to obtain a thin wire can be applied.

Hereinafter, practical examples of this invention will be explained in detail.

] Bizus (Coo, Q4 -, Feo, o
6)75 (Sj-0-4%BO4)2 11
An alloy having the composition of is wrapped in quartz glass and heated to 1250'C.
After heating back and forth, it was drawn out into a thread to obtain a p-shaped thin wire covered with quartz glass. The diameter of this thin wire was 50±10 μm. Next, this thin wire was heat-treated in a magnetic field to remove magnetostriction, and then the quartz glass coating was removed, leaving only the thin wire. Next, as shown in FIG.
The magnetic core 2 was manufactured by winding the magnetic core 17 approximately 1,500 times around the V-circle.

Then, as shown in FIG. 6, an excitation conducting wire 3 and an output conducting wire 4 were wound around this magnetic core 2. In addition, in order to compare with the magnetic core 2, a bobbin 5' having the same shape as the bobbin 5 was prepared with a thickness of 20 μm and a width of 5 m, which had the same composition as the thin wire 1 and was manufactured by a twin-roll liquid phase quenching method.
Another magnetic core 7 is prepared by winding a thin strip-shaped core material 6 of 200 mm (see FIG. 7).
Similarly to the magnetic core 2, the excitation conductor and output conductor were wound +111iJ L.

Next, a rectangular current In is applied to each excitation conductor of each of the magnetic cores 2.7 to generate a magnetic field 1 (m) that reverses the magnetization of these magnetic cores and causes them to reach one magnetic saturation state. At this time, from the waveform of the H1z flow obtained in the output conductor, the time required for each magnetic flux of these magnetic cores 2.7 to reverse 90%, that is, the switching time Ts, was measured and plotted in Figure 9. . In FIG. 9, the characteristic curve plotted with white circles corresponds to the magnetic core 7, that is, the ribbon; 2 shows the switching characteristics of a conventional magnetic core using the magnetic core material 6, while the characteristic curve plotted with black circles shows the switching characteristics of the magnetic core 2, that is, the magnetic core according to the embodiment of the present invention. and,
As is clear from this figure, the magnetic core 2 according to the present invention
exhibited switching characteristics that were approximately 10 times faster than the conventional magnetic core 7 (that is, frequency characteristics that had an upper limit frequency that was approximately 10 times higher).

As is clear from the above description, the magnetic core according to the present invention has a coercive force Hc of 20 oersted or less.
Since it is made of magnetic metal and is wound with a deep bed of thin wire with a cross-sectional area of 0.01- or less, the number of domain walls increases significantly compared to conventional magnetic cores, and the number of domain walls increases when magnetization is reversed. The travel distance is shortened, which reduces eddy current loss in the high frequency range and significantly increases the usable upper limit frequency.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing an example of the form of the magnetic core according to the present invention, Fig. 2 is a sectional view taken along the line ■-■ in Fig. 1, and Fig. 3 is another example of the form of the magnetic core according to the invention. 4 is a sectional view taken along the line ■-■ in FIG. 3, FIG. 5 is a sectional view of a magnetic core according to a practical example of the present invention, and FIG. 6 is a perspective view of the same magnetic core. FIG. 7 is a cross-sectional view of another magnetic core manufactured for comparison with the magnetic core according to the above embodiment;
The figure is an explanatory diagram showing a method for measuring the switching characteristics of each of the magnetic cores, and FIG. 9 is a characteristic diagram showing the switching characteristics of the magnetic core according to the present invention and other magnetic cores. 1...Thin wire, 2...Magnetic core.

Claims (1)

[Claims] 1. A magnetic core comprising a thin wire wound with a soft magnetic metal having a coercive force HC of 20 Oersteds or less and a cross-sectional area of 0.01- or less.