JPS61204908A - Magnetic core - Google Patents

Abstract

PURPOSE:To obtain a magnetic core for non-linear choke having a simple structure and excellent performance by providing a gap in a portion of an annular magnetic core consisting of a soft magnetic material, and inserting into the whole or a part of the gap a gap spacer made of a soft magnetic material, the resistivity of which has a value sufficiently large as compared with the resistivity of the magnetic core. CONSTITUTION:A gap is provided in a portion of a magnetic core 1, 1' or 2 consisting of a soft magnetic material, and in the whole or a part of the gap, a member made of a soft magnetic material the resistivity of which has a value sufficiently large as compared with the resistivity of the magnetic core 1, 1' or 2 is inserted and arranged as a gap spacers 3, 3'. A thin amorphous alloy band is made by the one-side roll method, the obtained thin band is wound to make a magnetic core 2 having an outer diameter of 35mm, inner diameter of 20mm and thickness of 10mm, and the predetermined heat treatment is performed. After this is impregnated with epoxy resin and is hardened, a part of the magnetic path is cut by means of a grindstone so as to form a 0.8mm gap. A soft magnetic plate 3' made of a pressed powder of ferrite or permalloy having a shape of 15X15X0.8<t>mm is inserted into this gap portion and is fixed by means of an adhesive.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application 1 The present invention mainly relates to magnetic cores of coils used with superimposed direct current, and particularly to choke coils used in low-pass filters such as output smoothing circuits of switching power supplies. This invention relates to a magnetic core suitable as a commercial magnetic core. That is, the present invention aims to provide a magnetic core that has a high smoothing effect and generates little heat even when used at high frequencies.

Conventional technology 1 Conventionally, in coils that are used with superimposed direct current, such as choke coils, output filters of switching power supplies, or power transformers of flyback converters, in order to prevent magnetic saturation of the magnetic core due to direct current, ,
As illustrated in FIG. 5, a gap G1 or G2 is provided in a part of the magnetic core 1, 1' or 2.

By providing such a gap, as shown in FIG.

1" Change in the current flowing through the coil (7Q)
] Ile's inductance [-?, rj. In this case, as Gi~tsubu G becomes less crowded, the DC 1 tatami characteristic curve becomes 11-
+ l)→CO).

By the way, conventional magnetic cores of the type 1 shown in FIG. The 511-type steel alloy is used. (7 out of 4 types) These magnetic cores are used for the output of switching power supplies.
When using I-C, there is a problem that (if the current is small, that is, in the fl region where the choke current is discontinuous, the output voltage will increase significantly and the output stability will deteriorate). Therefore, in order to solve the above problem, we need to connect a dummy load in parallel with the load and design the circuit so that the current flowing through the choke coil does not become discontinuous, or when the load is lightly loaded, the inductance is large and the load current is The inductance becomes smaller when the inductance becomes smaller. "Use a quukil) / J law is urged (1, but the H -Law C (, dummy advice, dummy -′ '4 4)
, [If unnecessary current flows 1(], then lJ', (
7go i scarcity) ::j<t unfavorable. On the other hand, the front and rear Jl-linear 1-*-'7ko・~(ha, JP-A-Sho J 4
-50817 Publication, rotation or i, ') 8! T3
No. 1113, JP-A-Sho, No. 58-9070□1,
907+0ri: Publication.

Japanese Patent Publication No. 1983. -17410 September Publication, Unexamined Patent Publication No. 1lii,
"+ ri 17111 Q-in-law Kohokichi (Go2 soft one is known. However, it is 1111tlG 5081
Invention cs-1 described in the 7th Publication and 1t'A Y=”f
Create a nonlinear choke by crystallizing it.
”) - However, there remains a problem with the gap vi degree.
In a magnetic core with a gap in part of 1F, its VV
It is possible to obtain a nonlinear choke with this method by placing one magnetic wire of two or more types with different magnetic properties near the knob, but it is possible to obtain a nonlinear choke, but there is a new problem in that the structure becomes complicated. There are some problems.

Furthermore, in the inventions described in JP-A-58-90704 to Sho 58-90710, ``a magnetic core having a gap in a part is provided with a substantially amorphous magnetic book lI in the vicinity of the gap. However, even with these inventions, it is true that nonlinear chokes (q) have been developed, but because amorphous alloy ribbons have a small resistivity, their structure In this case, heat generation near the gap due to eddy current loss becomes a problem.

In addition, the invention described in JP-A-59-171409 is “
This is a magnetic core in which an air gap is provided in a part of the magnetic core (and an insertion member made of a magnetic material having a higher permeability V11! than the magnetic material forming the magnetic core is placed in this air gap), and the above invention also uses a nonlinear choke. (51) However, when the insertion member is made of metal, heat generation near the gap still becomes a problem.

In addition, the method described in Japanese Unexamined Patent Publication No. 171110 is that ``a constant-velocity magnetic core and a high-permeability magnetic core are arranged so as to magnetically form a parallel circuit, and a common winding is connected to these cores. It is possible to use a nonlinear choke with this invention.However, there is a problem in that the structure is somewhat complicated.

[Problem 1 to be solved by optics] In other words, there are various types of nonlinear choke coils that are used for the above-mentioned engraftment. A magnetic core for nonlinear chokes that is simple and has excellent performance was desired.

An object of the present invention is to solve the drawbacks of conventionally known nonlinear choke coils and to provide a magnetic core for a nonlinear choke that has a simpler structure and superior performance.

[Means for solving the problem]: The name of the present invention (3t(Φ'
? j') A magnetic core for a nonlinear choke was designed, and the 1ift hole was made of small 1-51. As a result, 1llt, 11VJ) A gap was provided in a part, and all of the gap was It is useful to use a magnetic core in which a member made of a soft magnetic material whose specific resistance is the same as that of the magnetic core is inserted and arranged as a Gisseps baser. He discovered that this is the case and completed the book 5N Ming.

In the present invention, the gap-based solid zero resistance is appropriately selected depending on the magnetic core material used, but generally when a magnetic core made of a metal-based soft magnetic material is used, a sufficient effect is obtained if it is 1 Ω・am or more. 1q can be obtained.

However, if a high magnetic permeability material is used for the magnetic cores 1, 1' and the soft magnetic material 1 for the gap spacer 3 in a magnetic core configured as shown in Fig. 1, it will exhibit a large inductance at light loads, and the load will be reduced. As the current increases, the magnetic material used as the gap spacer 3 becomes magnetically saturated, and that part essentially becomes an air gap, resulting in a sudden decrease in inductance, resulting in L as shown in Figure 2.
-N1M property is obtained. Here, the balance between the inductance size and the magnetomotive force Nlo that causes the soft magnetic material for the gap spacer to magnetically saturate is determined by appropriately selecting the magnetic permeability of the magnetic core and the soft magnetic material for the gap spacer, and the cross-sectional area ratio of each. Various types of nonlinear choke coils can be obtained.

The nonlinear choke coil according to the present invention having such a configuration has the following advantages over conventional ones.

That is, in an annular magnetic core like the one shown in FIG. 1(b), a non-magnetic gap spacer is usually inserted and fixed with an adhesive to fix the gap width, but the one of the present invention uses a non-magnetic gap spacer. By arranging a soft magnetic material 3' with a high specific resistance in place of the gap spacer, it is possible to obtain both the effect of fixing the gap and the effect of obtaining excellent magnetic properties. It is also economically preferable. Furthermore, since the specific resistance of the soft magnetic material used as the gap spacer is high, the problem of heat generation near the gap due to eddy current loss can be solved.

Permalloy is also used as the magnetic core material.

Although magnetic materials of various compositions such as silicon steel and amorphous alloy can be used, more favorable results can be obtained when using an amorphous alloy with a large saturation magnetic flux density, excellent soft magnetic properties, and low iron loss. get.

The most suitable amorphous alloy composition for the purpose of the present invention is as follows.

(Fe, clM, ),,,x, SiXByM
: Ni, C.

0≦×≦15 7≦y≦15 0α≦0.5 Here, M is a material that does not significantly impair saturation magnetic flux density, which is the most important property for a choke coil magnetic core, and has soft magnetic properties and corrosion resistance. It is an element that can improve

Here α is preferably 0.1 to 0.4, but O〈α
It may be ≦0.5.

If σ exceeds 0.5, it is unfavorable from both saturation magnetic flux density and soft magnetic properties. Also, α-〇 has a problem in terms of corrosion resistance.

As the soft magnetic material for the gap spacer, metal dust cores, ferrite, etc. can be considered, but it is more preferable to use ferrite, which has soft magnetic properties and is excellent in workability.

In the present invention, the annular magnetic core does not necessarily have to be a chaste circle, and even if it has an elliptical or rectangular shape, the same effect of 1% can be obtained. Furthermore, it goes without saying that various shapes can be selected for the thickness, shape, etc. of the magnetic core material for the gap spacer in order to satisfy the necessary electrical specifications.

[Real 711! example〕 The present invention will be explained below based on Examples.

Example 1 A micrometer-thick amorphous alloy ribbon was produced by a single roll method. )
The rolled thin strip has an outer diameter of 351 m and an inner diameter of 20 mm.

A magnetic core with a thickness of 10 mff1 was prepared and subjected to prescribed heat treatment.

After this was impregnated with epoxy resin and cured, a part of the magnetic path was cut using a grindstone to form a gap of 0.8 mm.

Various soft magnetic plates shown in Table 1 having a shape of 15x15x O, 8tll1m were inserted into this gap and fixed with an adhesive.

Table 1: Apply 1-ding to this magnetic core, and add 1, O to 1- of A.
A 7 mmφ Ormar wire is wound 35 times to form a non-linear f-
It was a yoke coil.

Figure 3 shows the DC superimposition characteristics of these chokes.

In the figure, the vertical axis is the inductance value per unit number of turns, that is, the inductance value per turn (Am-VAL
UE). The horizontal axis is the magnetizing force, which is expressed as the product of the number of turns N and the current .

Also, rated output 12V-5A, switching frequency +0
Using a 0kl-1 SWITCH power supply,
V: That's the guy who implemented the magnetic core! Measure r7 above the nearby temperature. Table 1 shows the values after standing for about 20 minutes.

As can be seen from Fig. 3, all of these (31) exhibit straight-line jog characteristics, but as can be seen from Table 1, the magnetic core of the present invention has a particularly small temperature rise near the girt, and has a low power supply efficiency. It can be seen that the drain and reliability aspects are extremely difficult.

Example 2 Next, the case where magnetic core materials (amorphous alloy is used for I),
Characteristics were compared with cases where permalloy, silicon steel 1-noji, and noelai 1- were used as comparative materials.

The magnetic core shape and measurement conditions are the same as in Example 1. (
The results are shown in Table 2 J3 and FIG. 4. The gap spacer is the same as in Example 1.

As is clear from the figures and tables in Table 2, when the magnetic core material is permalloy or silicon steel, the DC superposition characteristic is
Jf, the temperature at the gap part is larger than that of the magnetic core of the present invention. In addition, when using Fuchorai [・,
Above temperature? Although the performance is good, the direct current superimposition characteristics are inferior compared to other magnetic cores, so when it comes to magnetic core materials, those using 7t Rufus have a poor balance. .

Example 3 Next, the composition of 7t roots used as the magnetic core material, the saturation magnetic flux density Bs, f, the temperature [-- and the corrosion resistance were evaluated by 1°i.

As a material for dipping, 3s is less than 1n, the better the corrosion resistance, the easier it is to use, the evaluation of corrosion resistance ↑ 4 [, 1, high temperature and high humidity test (60"C, 80% Rl-, - 4, 4B+-
Evaluation was made on a five-point scale, with 1> being rated as (), 5 being no rust at all, and 1 being being completely rusted/j (). The results are shown in Table 3.

As is clear from Table 3, the alloy of the present invention has a high saturation magnetic flux density, a low temperature rise in the gap when used as a nonlinear choke, and excellent corrosion resistance, making it preferable as a magnetic core material for chokes. .

[Effects of the Invention] As explained in detail above, the nonlinear choke coil using the magnetic core according to the present invention has excellent nonlinear DC superposition characteristics, and is particularly suitable for use in output smoothing chokes of high-frequency driven switching power supplies. is small and has high practical value.

Further, the present invention can also be applied to a power transformer of a flyback converter, etc. with a similar design.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the shape of a magnetic core for a choke coil according to the present invention, FIG. 2 is a diagram showing an example of DC superposition characteristics of a nonlinear choke coil according to the present invention, and FIGS. 3 and 4 are diagrams showing an embodiment of the present invention. Figure 5 shows the shape of the conventional choke coil magnetic core. Figure 6 shows the DC bias characteristic of the conventional choke coil. Pano I NI (791 nails/1 (Me9γ)

Claims (1)

[Scope of Claims] 1. A gap is provided in a part of the annular magnetic core made of a soft magnetic material, and all or part of the gap is made of a soft magnetic material whose specific resistance is sufficiently larger than that of the magnetic core. A magnetic core characterized in that a gap spacer made of a magnetic material is inserted. 2. The magnetic core according to claim 1, wherein the magnetic material constituting the magnetic core is made of an amorphous alloy. 3. The composition of the amorphous alloy is (Fe_1_−_αM_α)_1_0_0_−_x_−
_ySi_xB_y However, M = 1 of Ni, Co
3. The magnetic core according to claim 2, characterized in that species or two species 0≦x≦15 7≦y≦15 0≦α≦0.5. 4. Claims 1 to 3, characterized in that a soft magnetic ferrite material is used as the gap spacer.
The magnetic core described in any of paragraphs.