JPH06224060A - Manufacture of magnetic core for high frequency - Google Patents

Abstract

PURPOSE:To lessen remarkedly the iron loss of a magnetic core at a high-frequency region by a method wherein an amorphous magnetic alloy thin strip, which has specified conditions about its thickness, is manufactured by a molten metal quenching method and the magnetic core is obtained using this thin strip. CONSTITUTION:An amorphous magnetic alloy thin strip of a composition, which is shown by the formula [(The t) and the (t) respectively show the maximum value of the thickness of the thin strip and the mean value of the thickness of the thin strip and the (t) corresponds to the mean values of W, (d), (l) and (p) (The W, the (d), the (l) and the (p) respectively show the weight, width, length and density of the thin strip.)]. is manufactured by a molten metal quenching method. That is, a molten alloy of this composition is made to jet on a single roll, which is rotated at high speed, by an argon gas pressure through a quartz tube nozzle, is quenched and a thin strip sample is manufactured. This sample is cut off, is wound on a bobbin made of aluminium, is subjected to heat treatment and thereafter, a magnetic core is obtained. Thereby, the iron loss of the magnetic core at a high-frequency region can be remarkedly lessened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-loss amorphous magnetic alloy magnetic core effective for use in an electromagnetic device.
The present invention relates to a method for manufacturing a high frequency magnetic core, which has a significantly small iron loss in a high frequency region (10 kHz to 200 kHz) and is suitable for a switching regulator or the like.

[0002]

2. Description of the Related Art Conventionally, crystalline materials such as permalloy and ferrite have been used as magnetic cores used in high frequencies such as switching regulators.

However, since permalloy has a small specific resistance, iron loss at high frequencies becomes large. Also, although ferrite has a high frequency and a small loss, the magnetic flux density is at most 500.
It is as small as 0 G, so that when it is used with a large operating magnetic flux density, it approaches saturation, resulting in an increase in iron loss. Recently, in the transformer used at high frequency such as the power transformer used for the switching regulator,
Although it is desired to reduce the size of the shape, in this case, the operating magnetic flux density must be increased, so that the increase in iron loss of the ferrite becomes a serious problem in practical use.

On the other hand, amorphous magnetic alloys having no crystal structure have recently attracted attention because they exhibit excellent soft magnetic characteristics such as high magnetic permeability and low coercive force. These amorphous magnetic alloys are based on Fe, Co, Ni, etc., on which P, C, B, Si, Al, and
It includes Ge and the like.

However, not all of these amorphous magnetic alloys have small iron loss in the high frequency region. For example, an Fe-based amorphous alloy shows a very small iron loss of about 1/4 that of silicon steel in the low frequency region of 50 to 60 Hz, but exhibits a significantly large iron loss in the high frequency region of 1 kHz or more, which is very low. It is not suitable for use in high frequency areas such as switching regulators. This is a phenomenon based on eddy current loss that is proportional to the square of the operating frequency. Therefore, the amorphous magnetic alloy ribbon is used as a magnetic core for 1K.
When used in a high frequency region of Hz or higher, it is generally necessary to adjust the thickness of the ribbon to 30 μm or less.

On the other hand, a ribbon of an amorphous magnetic alloy is usually produced by applying a molten alloy of a predetermined composition which is melted in a heat-resistant container such as quartz to the alloy at high speed from a nozzle at the tip of the container. It is prepared by a molten metal quenching method in which it is jetted onto a rotating surface of a rotating metal single roll or twin rolls and rapidly cooled. However, the surface of the ribbon thus produced has fine irregularities, and the state of the irregularities increases iron loss in a high frequency region, and the space factor is significantly reduced. There was a case where the inconvenience was caused.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object thereof is to provide a method of manufacturing a high frequency magnetic core which uses an amorphous alloy and realizes low iron loss in a high frequency region. And

[0008]

Means and Actions for Solving the Problems The present inventors have
As a result of intensive studies on the relationship between the surface roughness of the ribbon of amorphous magnetic alloy and the iron loss in the high frequency region, particularly in the high frequency region of 10 to 200 kHz, the maximum thickness and the thickness of the thin ribbon The present invention has been completed by finding the fact that the iron loss becomes small when the surface roughness calculated and displayed from the average value is in a predetermined value range, and when the maximum thickness value is in a predetermined range. Came to.

An object of the present invention is to provide a high frequency magnetic core having a remarkably small iron loss in the high frequency region.

The present invention has a surface roughness

[0011]

[Equation 2] It is characterized in that an amorphous magnetic alloy ribbon satisfying the above conditions is manufactured by a molten metal quenching method and is used as a magnetic core.

In the magnetic core of the present invention, the amorphous magnetic alloy constituting the magnetic core is generally represented by a composition formula of M _100-2 Nz. Here, M is at least one of Fe, Co, and Ni.
It is a seed element, some of which are Ti, V, Cr, MnC.
1 to 10 atom% may be substituted with at least one element selected from the group consisting of o, Zr, Nb, Mo, Ta and W. N is at least one element of metalloid such as P, C, B, Si, Al and Ge, and Z is a number satisfying 15 <Z <30. Particularly, the effect is large when a Co-based amorphous magnetic alloy having a magnetic flux density of 7 KG or less is used.

Such an amorphous magnetic alloy is prepared by mixing the above-mentioned respective components of M and N in a predetermined ratio and then melting them.
This is made into an amorphous magnetic alloy by a method such as a melt quenching method, and then in a non-magnetic field at a predetermined temperature (for example, 400 to 4).
It can be easily prepared by heat treatment at 50 ° C.
In the above equation, t is obtained as an actual measurement value regarding the ribbon, and t is the weight, width, length, and density of the ribbon, respectively,
It is a calculated value calculated from the equation of t = W / d · l · ρ, where d, l and ρ.

When the value of the surface roughness exceeds 0.30, the surface irregularity of the ribbon becomes remarkable (the surface becomes rough), and the iron loss in the high frequency region becomes extremely large, which makes it unsuitable for use. . Further, if it exceeds 0.30, the squareness ratio also decreases.

Further, in the ribbon, the maximum thickness value (t)
If it is less than 5 μm, a large amount of interlayer insulator is required during winding of the obtained magnetic core, so that the space factor thereof is remarkably reduced, which is not practical. Further, when t exceeds 30 μm, iron loss in the high frequency region remarkably increases regardless of the surface roughness. Therefore, in the magnetic core of the present invention, it is preferable to set the maximum thickness of the ribbon in the range of 5 μm ≦ t ≦ 30 μm.

The magnetic core of the present invention has an operating frequency of 10 to 200 kHz and is particularly effective in reducing iron loss.

In the melt quenching method, the maximum thickness of the ribbon forming the magnetic core of the present invention depends on the number of rotations of the roll, the gas pressure applied to the molten alloy when it is ejected from the nozzle, and the like. The surface roughness can be adjusted to an appropriate value by further adjusting the distance between the nozzle and the roll within the range of 0.1 to 0.5 mm.

However, in the present invention, it is important that the above conditions are satisfied after the molten metal is rapidly cooled, and even if this condition is satisfied by polishing or the like, the effect of improving the magnetic properties of the present invention cannot be achieved. This is because the fine irregularities present on the surface of the amorphous magnetic alloy ribbon produced by the melt quenching are lost by the polishing treatment, and the above conditions are satisfied after the melt quenching as in the present invention. Then, it is considered that the state of the amorphous magnetic alloy ribbon surface is slightly different. Further, the polishing treatment introduces strain into the amorphous magnetic alloy ribbon, which is also not preferable in terms of magnetic characteristics.

[0019]

EXAMPLES The present invention will be described below based on examples. Example 1 Thin ribbons of amorphous magnetic alloys having various compositions shown in the table were prepared by a melt quenching method. That is, molten alloys of various compositions were jetted from a quartz tube nozzle onto a high-speed rotating single roll at an argon gas pressure and rapidly cooled to prepare a ribbon sample having a width of 5 mm and a length of 100 m. At this time, the roll rotation speed, gas pressure, and the distance between the nozzle and the roll were variously changed to change the maximum thickness value and the surface roughness.

A length of 14 m was cut from a thin strip sample, which was wound around an alumina pobin having a diameter of 20 mm, and the whole was 4
After heat treatment at 00 ℃ for 15 minutes, inner diameter 20mm, outer diameter 30
Put in a plastic case of mm and wind 70 times both as a primary coil and a secondary coil. Use a wattmeter to measure magnetic flux density (Bm) 3kG, frequency 20kHz, 100kHz.
Was measured for iron loss. The saturation magnetic flux density of the ribbon sample was measured using a sample vibrating magnetometer. The results are shown collectively in the table. The maximum value was obtained by measuring every 10 cm with a micrometer.

[0021]

[Table 1] As is clear from the table, the ribbon samples (sample numbers 1 to 6) according to the present invention have a magnetic flux density of 3 kG, a frequency of 20 kHz, and 100 kHz as compared with the comparative ribbon samples (sample numbers 7 and 8).
It was found that the iron loss at z was extremely small. Example 2 A magnetic core composed of a ribbon of an amorphous magnetic alloy of composition (Fe _0.6 Ni _0.2 ) ₇₈ Si ₈ B ₁₄ and having various surface roughnesses, magnetic flux density of 3 kG, frequency of 20 kHz, 100 k.
The iron loss at Hz was measured. The results are shown in the figure as a relation of surface roughness. As is clear from the figure, when the surface roughness exceeds 0.30, the iron loss suddenly increases.

Composition (Co _0.94 Fe _0.06 ) ₇₁ (Si _0.6 B
_0.4 ) ₂₉ amorphous magnetic alloy (magnetic flux density 6.1 kG) was prepared by the single roll method. The surface property was changed based on a plate thickness of 18 μm and a width of 10 mm.

The amorphous magnetic alloy ribbon was wound to form a toroidal core having an outer diameter of 18 mm and an inner diameter of 12 mm. Next, heat treatment was performed at an optimum temperature not lower than the Curie temperature and not higher than the crystallization temperature, and then cooled at 4 ° C./min.

The obtained core is provided with primary and secondary windings,
A hysteresis curve at a frequency of 100 kHz was measured by applying an external magnetic field of 1 Oe using an AC magnetization measuring device, and the squareness ratio B _r / B ₁ (B _r : residual magnetic flux density, B ₁ : 1) was measured.
The magnetic flux density in Oe) was determined. The result is shown in FIG.

[0025]

As described above, the core made of the ribbon of the amorphous magnetic alloy of the present invention has a remarkably small iron loss in the high frequency region, and therefore, the high frequency transformer and the like can be miniaturized. Therefore, its industrial value is great.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing iron loss of the present invention.

FIG. 2 is a characteristic diagram showing the squareness of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichiro Inomata 1 Komukai Toshiba-cho, Kouki-ku, Kawasaki-shi, Kanagawa Toshiba Research Institute, Ltd.

Claims (1)

[Claims] 1. The equation 1 A method for producing a high frequency magnetic core, characterized in that an amorphous magnetic ribbon satisfying the above conditions is prepared by a molten metal quenching method, and the amorphous magnetic alloy ribbon is used to form a magnetic core.