JPS5890706A - Magnetic core - Google Patents

Abstract

PURPOSE:To stabilize coil output and to reduce loss when a DC current is superimposed in a magnetic core having a gap at its part by a construction wherein an amorphous magnetic thin belt of small magnetic distorsion having the specified composition represented by (FejNikColMm)xBy (where M represents transition metal elements other than Fe, Ni and Co) is attached near the gap. CONSTITUTION:E-shaped cores 3, 4 are combined to form an air gap Ga between their center portions 3a and 4a, and a thin magnetic substance 5 is attached round the gap Ga. An amorphous magnetic thin belt of small magnetic distorsion having composition of (FejNikColMm)xBy is used as the magnetic substance 5. In the above formula, M represents transition metal elements other than Fe, Ni and Co. And there exist the following two relations; x+y=100at%, where y=10-35at%, and j+k+l+m=100%, where j=3-20%, k=0.1-50% and m=0.1-10%. A part of B may be replaced by Si to enhance corrosion resistance and improve a degree of change with aging. A part of B and Si may be also replaced by other vitrifiable elements to further improve a degree of change with aging.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic core suitable for constructing coils that are used with superimposed direct current.

For example, in coils that are used with DC current superimposed, such as cheek coils, output filters of switching power supplies, or power transformers of flyback converters, the example shown in Figure 1 is used to improve the DC superimposition characteristics. As such, it is common to use a ferrite magnetic core in which an air gap Ga is provided in a part of the closed magnetic path of the core center portion. If such an air gap Ga is provided, the second
This is because, as shown in the figure, a flat direct current superposition characteristic in which the inductance L of the coil remains constant with respect to changes in ampere turns IN over a certain width can be obtained. Note that the DC superimposition characteristic shifts as shown by curve A, →Am→A, as the air gap Ga increases.

However, a switching gray using a cheek coil that uses a magnetic core. Rake has the disadvantage that the output voltage is not high when the load current is small, and the output stability is poor. Figure 3 is a circuit diagram of a conventionally known general one-stone forward converter, in which the transfer transformer T
The primary winding N, of
N is supplied, and one end of the secondary winding is connected to a diode DI.
is connected to one end of the capacitor C via a cheek coil L using the magnetic core, and the other end of the secondary winding II Nm is connected to a connection point between the diode D1 and the cheek coil L via a diode D. It is connected to the other end of the capacitor C, and is configured to output another DC voltage vo to both ends of the capacitor C.

In such a circuit, load current I0 and output voltage V・
As shown in Figure 4, the load current is 1. When is small, that is, in a region where the current flowing through the coil LK is discontinuous, the output voltage V0 becomes high. The region of discontinuous current is shown by T: switch 81k ON 10FF period ■, ≦・comb = 3 D: switch S ON period L L: inductance of cheek coil L, thus improving output stability. This can be achieved by increasing the inductance L to narrow the discontinuous region of the cheek current, or by adding a dummy load to the output terminal, but in the former case, the increase in the number of turns of the cheek coil reduces the This results in increased losses, decreased efficiency, and larger parts, and in the latter case,
It has drawbacks such as increased power consumption and heat generation, and improvements to these problems have been strongly desired.

In addition, when a magnetic core with an air gap Ga is used for a power transformer of a frequency-modulated flyback converter, the DC superposition characteristic of the magnetic core becomes flat as shown in Fig. 2, and the load fluctuation is also reduced. Since the inductance remains constant, there are drawbacks such as very high frequencies during light loads, which can cause intermittent oscillation, a drastic increase in the load on the switching element transistor, leading to increased loss, and strict heat dissipation measures. was there.

The present invention eliminates the above-mentioned conventional drawbacks, suppresses abnormal increases in output voltage or frequency during light loads, and improves output stability when used in cheek coils, output filters of switching power supplies, power transformers, etc. The purpose of the present invention is to provide a magnetic core that can improve the magnetic field and reduce loss.

In order to achieve the above object, composite magnetic cores having special configurations have been devised and previously proposed. (Actual 11vi!
J56-74915) This book was obtained as a result of intensive research efforts into the magnetic materials that compose the skeleton composite magnetic core, and it is essentially amorphous! The present invention was developed based on the finding that a bonded magnetic core with suitable characteristics can be obtained by using a magnetic ribbon having a specific composition among the 7 types of magnetic ribbons.

That is, the present invention is characterized in that, in a magnetic core having a gap in part, a substantially amorphous magnetic ribbon having a composition represented by the following formula is added near the gap.

Formula (FekNikColMm) . Furthermore, j
+ + l + m = 100%, of which j is 5 to 20
%, k is Ql~501. m is α1 to 10chi.

If y is smaller than 1091 or larger than 3591, it is difficult to make it amorphous, and it is not suitable for production with a good yield.

One company selects a range of 3 to 20% to reduce magnetostriction.

If k is greater than 50, the saturation magnetization will be small and there will be problems in terms of magnetic properties.

As M, Mn, Cr, Mo, and W are particularly preferable, and Mn
improves magnetic properties and changes over time as a magnetic material, and C
r improves stability when used under poor conditions, and Mo and W improve stability as a magnetic material, facilitate heat treatment, and improve properties.

When using these elements as M, m is α1~1
0- is preferred. If it is smaller than α11s, it is difficult to obtain this effect, and even if it is larger than α10s, the effect will not increase in practical terms, and on the contrary, problems will arise in terms of magnetic properties and ease of amorphization. come. Furthermore, by substituting a part of B with St, it becomes easier to become amorphous, corrosion resistance is increased, and deterioration over time is also improved, resulting in better characteristics. The amount to be replaced is determined by changing the composition to (FejNikCol Mm)*(
81pBq) When written as y, p + q = 100
It is appropriate that α01≦p≦80%. When p<α01%, it is difficult to obtain this effect, and when p) is 80%, on the contrary, it is difficult to make it amorphous. Furthermore, by substituting a part of B and Sl with other metalloid elements, such as P and C, the change over time is further improved and good drag properties can be obtained.

The amount to be replaced is determined by changing the composition to (FejNikCol) x (81
When written as pBqXr)y (where x=p, c or at least one or more other metalloid elements),
p+q+r=100chi, αo1chi≦°r≦10%1, preferably αo1≦r≦5%. r((
It is difficult to obtain this effect at LO1%, r ) 5
On the other hand, if r>10-, problems arise in terms of magnetic properties. Further, as for magnetostriction, #1λ5ly(:1ox1o') gives preferable results.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The content of the present invention will be specifically described below with reference to the accompanying drawings, which are examples. FIG. 5(A) is a front sectional view of the magnetic core according to the present invention, and FIG. 5(B) is a sectional view taken along line B and -B in FIG. 5(A). this! l! In the example, two E
The mold cores 3.4 are combined to form an air gap Ga between their center portions 5m-4&, and a thin magnetic material 5 is attached to the circumference of the air gap G&. As the magnetic material 5, a magnetic ribbon having a small magnetostriction, having the above composition, and being substantially amorphous is used. In addition, as a method for attaching the magnetic body 5 to the shank of the air gap Ga, the center portion 3 is attached inside the inner diameter part of the magnetic body 5 which is previously formed into a cylindrical shape.
m, 4m from both sides, or as shown in FIG. , a method of winding an appropriate number of layers around a 4 m long windshield is considered.

Furthermore, in the embodiments shown in FIGS. 5(A), (B) and 6, the magnetic body 5 is formed in an endless shape, but as shown in FIG. It is also effective to form the When the magnetic body 5 is formed in an endless shape, the magnetic body 5 forms a short circuit for the electromotive force generated in the magnetic body 5 due to the magnetic flux flowing between the center portions 5m and 4a.
Although the loss and heat generation in the magnetic body 5 increase, if the magnetic body 5 is provided with the gap g as described above and has an end shape, the electromotive force generated in the magnetic body 5 is affected by the gap g. This is because an open circuit is formed, reducing loss and heat generation. Note that the gap g is not limited to an empty gap, but may also be formed of an insulating material such as an insulating resin.

As mentioned above, if the structure is such that the gap Ga has the above-mentioned composition and a substantially amorphous magnetic ribbon with low magnetostriction is added, the mosquito magnetic core can be used to form a Q-coil. In this case, the effect is that the inductance rapidly increases when the load is light, but this effect is greater than when the magnetic material disclosed in Japanese Utility Model Application No. 56-74915 is used as the magnetic body 5.

(Experiment A) Figure 8 is a current-inductance characteristic diagram of each cheek coil with a different magnetic core structure.The horizontal axis shows the coil current I (A), and the vertical axis shows the inductance L.
(m) Take I). Curve A is the characteristic of a cheek coil using a conventional magnetic core, Curve IIB is the characteristic when using a magnetic core with magnetic material 5 made of composite resin ferrite wrapped around the circumference of gap G1, and curve C is the characteristic when gap G1 is used. Around (Fel)JCoaANiu)so(Siu, B1
These are the characteristics when using a magnetic core wrapped with a magnetic material 5 made of an amorphous alloy having a composition of 1Lt)to, and all are comparative examples.

The curve is according to the present invention, and (F'eQJ)5 Nl
111 coQjMOaos ) yy (Sl (
The characteristics are shown respectively when a magnetic core having a composition of L4 BH3) 2s and wound with a magnetic material 5 made of an amorphous material having a magnetostriction of λS~0 is used. The amorphous ribbon in this song MD was manufactured by a high-speed quenching method, and was wound around the gap with the same thickness, shape, and weight as the amorphous ribbon in song 1ic. .

(Experiment B) A cheek coil having the same direct current resistance characteristics as in Experiment A was created by changing the structure of the amorphous magnetic ribbon 0 to form the magnetic material 5. Table 1 shows the inductance values when the DC current is α03A.

Among these samples, (1), (2), and (3) are comparative examples, and (IL(2) is magnetostrictive lλml') 1o
There was xto4te.

(Experiment C) (4), (5), used in Experiment B
(7), (8), G1゜01. (2), G3.
G4. A life test was conducted at 120° C. for 1000 hours using amorphous materials having the compositions (g), (b), target, and (to).

The deterioration of magnetic permeability is (7), (8) is 5- or more, (4
), (5), (g).

01, (a), (to) to 5ch, and all others were s% or less.

As is clear from these experiments, when a substantially amorphous magnetic ribbon having the composition of the present invention is used as the magnetic material, a magnetic core with very good characteristics can be obtained, and the coil current It is observed that as the load decreases and the load becomes lighter, the inductance L tends to increase rapidly.

As described above, by using the magnetic ribbon of the present invention, it is possible to most effectively increase the light load, especially the inductance L. Therefore, by using the magnetic core of the present invention, the output filter or the When a power transformer or the like is configured, as shown in Figure 9, the output voltage V, which conventionally had a tendency to rise abnormally as shown in (b) at light loads, is reduced due to an increase in inductance L. The rise is←
), the output stability is very good. In addition, since the rise in output voltage during light loads is small, power consumption and heat generation are reduced even when a dummy load is added, and a small capacity dummy load is sufficient.
Benefits such as improved heat dissipation measures can also be obtained. Similar effects can be obtained when used in a Bushepr converter other than a forward converter, for example.

Furthermore, when the magnetic core is used in a power transformer of a frequency modulation type flyback converter, the inductance L increases during light loads, suppressing the increase in frequency, reducing the load on the switching transistor, and reducing loss. .

Furthermore, since leakage magnetic flux is reduced, there is also the advantage that leakage inductance is reduced.

As described above, the present invention is characterized in that a magnetic core having a gap in part is provided with a substantially amorphous magnetic ribbon having a specific composition near the gap. When used as a coil where direct current is superimposed, such as in the power transformer of a 1-17 light pack converter, output filter for switching power supplies, etc., suppresses increases in output voltage and frequency at light loads. Therefore, it is possible to provide a magnetic core that can improve output stability and reduce loss.

[Brief explanation of drawings]

Figure 1 is a front view of a conventional magnetic core, Figure 2 is its DC superimposition characteristic diagram, Figure 5 is a circuit diagram of a general single-stone forward converter, and Figure 4 is a front view of a conventional magnetic core. Fig. 5(A) is a front sectional view of the magnetic core according to the present invention, Fig. 5(B) is an output current-output voltage characteristic diagram when a converter is configured.
is a cross-sectional view on the line B, -B of FIG. 5(A), No. 6
7 and 7 are cross-sectional views of other embodiments of the magnetic core according to the present invention, and FIG. 8 is a diagram showing the current-inductance characteristics of a coil using the magnetic core according to the present invention in comparison with a conventional one. FIG. 9 is an output current-output voltage characteristic diagram when using the magnetic core according to the present invention. G1... Gap 5... Magnetic material

Claims (5)

[Claims] (1) In a magnetic core having a gap in a part thereof, a substantially amorphous magnetic ribbon having a composition represented by the following formula and having a low magnetostriction is attached near the gap. core. Formula (FejNikColMm)xBy However, in the above formula, M represents one or more transition metal elements other than F, Nl and Co, and x+y=100at-, of which y is 10 to gsats. be. Furthermore, j +1 + m = 100%. ], of which j is 5~2O-1k is α1~50-1
m is (L1~10'lA). (2) A magnetic core having a gap in a part thereof, characterized in that a substantially amorphous-like magnetic ribbon having a composition represented by the following formula and having a small magnetostriction is attached near the gap. Formula (F@jNikCo1Mm)x(81pBQ)y
However, in the above formula, M represents one or more types of transition metal elements other than F., Nl and Co, and! +3'=100a
tl, of which y is 10 to s at-. Furthermore, +1+m=100 arrogant to J+, p+q=100-
Of these, j is from 5 to 20, and k is from (11 to 501).
, m is CL1-101G, and p is 101-80. (3) A magnetic core having a gap in a part thereof, characterized in that a substantially amorphous magnetic ribbon having a composition represented by the following formula and having a small magnetostriction is attached near the gap. Formula (FejNikColM,m)x(SipBqX
r)y However, in the above formula, M represents one or more transition metal elements other than F., N1 and Co, and
represents one or more other vitrifying elements other than Also, x
+y-100at-ash, of which yalo ~5s
It is at-. Furthermore, +l+m=100S, p+ for j+
q+r-1oo-ash, of which j Id 5-2
o*%k Fi (L1~5 am, m is 11~10-
1 In addition, p is α01-8O-1r is α0110-. (4) The magnetic core according to any one of claims 1 to 5, wherein the substantially amorphous magnetic ribbon has at least one cut in the circumferential direction of the gap. (5) The magnetic core according to any one of claims 1 to 4, wherein the substantially amorphous magnetic ribbon has an electrically insulating layer on its surface.