JPH0441482B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a gapped magnetic core used in a choke coil, a transformer, etc.

[Background technology]

Recently, magnetic ribbons produced using an ultra-quenching method have been attracting attention as magnetic materials with low iron loss in the high frequency range, and examples of this type of magnetic ribbons include the following.

Amorphous alloy ribbon Iron-based F _e79 B ₁₆ S _i5 F _e78 B ₁₃ S _i9 Iron/Nickel-based F _e40 N _i38 M _p4 B ₁₈ Cobalt-based C ₀₇₅ B ₁₅ S _i10 C ₀₇₄ F _e6 B ₂₀ Crystalline alloy thin Strip 3.5% S _i −F _e 6.5% S _i −F _eBy the way, when forming a magnetic core using these magnetic ribbons, conventionally, the magnetic ribbons are wound and laminated and then cut and divided appropriately. After the coil is installed, a magnetic core is formed by making both cut surfaces face each other closely or with an appropriate gap, but iron loss increases due to a sudden increase in magnetic flux density at the cut part and iron loss due to abnormal eddy current loss. The problem was that there was a large increase in In other words, the magnetic ribbon is formed by ultra-quenching using high-speed rotating rolls, and air is trapped between the molten metal and the roll surface, making one surface of the magnetic ribbon rough (sharply uneven surface due to air bubbles). Therefore, even when laminated in a cylindrical shape, the space factor (space factor) is 70 to 80%, which is lower than that of silicon steel sheets (more than 95%), and the magnetic flux density near the cut portion is low. rapidly increasing. By the way, the iron loss W _i /cc is W _i /cc=K ₁ fB ^n/m + K ₂ f ² B ^2/m t ² f: frequency, B _n maximum magnetic flux density t: thickness of magnetic ribbon, K ₁ , K ₂ is a constant n≈2 and is approximately proportional to the square of the maximum magnetic flux density B _n , so that in a small-capacity magnetic core, the increase in iron loss due to cutting becomes quite large. On the other hand, on the cut surface, iron loss due to abnormal eddy current loss (generated by the concentration of alternating magnetic flux near the domain wall) due to disturbance of the magnetic domain structure is added, and the increase in iron loss due to the cut becomes considerably large.

By the way, when a desired inductance is obtained by winding a coil around a gapped magnetic core and adjusting the gap length, the gap length is set to t,
If the number of turns of the coil winding is N and the average magnetic path cross-sectional area of the gap portion is S _g , then the inductance L is L=μ ₀ S _g /t·N ² where μ ₀ is expressed as the magnetic permeability of air. Therefore, it is sufficient to set the gap length t appropriately based on the above formula, but
In a cut core made of a magnetic ribbon, there is a problem in that when the gap length t is increased, abnormal eddy current loss at the cut surface increases, resulting in a significant increase in iron loss.

[Purpose of the invention]

The present invention has been made in view of the above points,
To provide a gapped magnetic core capable of reducing abnormal eddy current loss on a cut surface of a cut core, and in which iron loss does not change even if the gap length is changed.

[Disclosure of the invention]

(Example) Fig. 1 is a partially cutaway perspective view of an example of the present invention, in which 1 shows a structure in which magnetic ribbons (width 10 mm) made of an amorphous alloy (C ₀₇₅ B ₁₅ S _i10 ) are wound and laminated. This is a cut core formed into a U-shape by cutting appropriately, and the average magnetic path cross-sectional area of cut core 1 is 70 mm ² and the average magnetic path length is 60 mm.
mm. 2 is a magnetic piece made of ferrite (TDK H7CI) (a = 10 mm, b = 14 mm, c = 2
mm), one side of each magnetic piece 2 is joined to the cut surface of the cut core 1, and the length t of the air gap 3 formed between the opposing surfaces of both magnetic pieces 2 is set to a predetermined value. . Reference numeral 4 denotes a coil wound around the cut core 1, and in the embodiment, a wire (strand diameter: 0.13 mm, number of strands: 17) is wound with 100 turns.

Now, the material iron loss (iron loss in an uncut toroidal state) measured at a frequency of 20 KHz and an operating magnetic flux density of 3 KG is 80 mW/cc for a magnetic ribbon made of an amorphous alloy and 80 mW/cc for a ferrite.
250mW/cc, and as in the example, the magnetic material piece 2 is bonded to the cut surface of the cut core 1.
The iron loss was 150 mW/cc when an air gap 3 was formed between the opposing surfaces. However, the iron loss was measured based on the shape of the magnetic ribbon of the cut core 1 on the assumption that the magnetic flux passed only through the main magnetic path. For comparison, the iron loss was measured when the magnetic piece 2 was removed and an air gap 3 was formed between the cut surfaces, and an iron loss of 240 mW/cc was found. It was found that the effect of reducing iron loss was remarkable. This iron loss reduction effect is achieved by bringing a magnetic material with high resistance and high permeability, such as ferrite, into contact with the cut surface, which bends the magnetic flux generated at the cut portion (increases the component perpendicular to the main magnetic flux). This is thought to be achieved by reducing abnormal eddy current loss due to disturbances in the magnetic domain structure.

Figure 2 shows the results of measuring changes in inductance L by varying the gap length t.
As the gap length t increases, the inductance L decreases, and at this time, even if the gap length t changes, the iron loss does not change. Furthermore, the inductance L can also be changed by changing the shapes a, b, and c of the magnetic piece 2.

(Example 2) Figure 3 shows another example, in which a pair of magnetic ribbons made of an amorphous alloy (F _e40 N _i40 P ₁₄ B ₆ ) is used as in Example 1. It is composed of cut cores 1a and 1b, and a magnetic piece 2 made of ferrite (SB7C manufactured by Nippon Ferrite Co., Ltd.) inserted between the cut surfaces of both cut cores 1a and 1b, and has the same effect as Example 1. Moreover, since the air gap 3 is formed in the internal magnetic path, magnetic flux is unlikely to leak to the outside of the coil, and stable operating characteristics can be obtained when incorporated into an electric circuit.

(Embodiment 3) Fig. 4 shows still another embodiment, in which a pair of cut cores 1a, 1 are integrated in an I-shape.
b is formed using a magnetic ribbon made of an amorphous alloy (F _e80 B ₂₀ ), and the magnetic pieces 2 a and 2 b are formed using ferrite (Q ₂ M manufactured by TDK). The same effect was confirmed.

Note that a dust core having characteristics similar to ferrite (high electrical resistance and high magnetic permeability) may be used as the magnetic piece 2.

〔Effect of the invention〕

The present invention consists of a U-shaped cut core made by winding and laminating magnetic thin strips and cutting them as appropriate, and magnetic pieces made of ferrite bonded to both cut surfaces of the cut core, one surface of which is connected to the cut surface of the cut core. Since an air gap is formed between the opposing surfaces perpendicular to the one surface of the two magnetic pieces to be joined to the above, a magnetic piece made of ferrite with high electrical resistance and high magnetic permeability is brought into contact with the cut surface of the cut core. This reduces abnormal eddy current loss on the cut surface, and since an air gap is formed between the facing surfaces of both magnetic material pieces in a direction perpendicular to the above-mentioned one surface, even when the length of the air gap is changed, This has the effect that iron loss does not increase as in the case where an air gap is formed on the cut surface as in the conventional example.

[Brief explanation of drawings]

Fig. 1 is a partially cutaway perspective view of one embodiment of the present invention, Fig. 2 is an explanatory diagram of the same operation as above, Fig. 3 is a perspective view of another embodiment, and Fig. 4 is a perspective view of still another embodiment. It is. 1 is a cut core, 2 is a magnetic piece, and 3 is an air gap.

Claims (1)

[Claims] 1 Consists of a U-shaped cut core made by winding and laminating magnetic thin strips and cutting them as appropriate, and magnetic pieces made of ferrite that are bonded to both cut surfaces of the cut core, one side of which is bonded to the cut surface of the cut core. A gapped magnetic core characterized in that an air gap is formed between opposing surfaces of both magnetic material pieces in a direction perpendicular to the one surface.