JPH0950931A - Ferrite core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a ferrite core with less leakage flux by forming a through hole in the portion of an I-shaped ferrite core, opposed to the middle leg of an F-shaped ferrite core. SOLUTION: A through hole 34 is formed in the portion 33 of an I-shaped ferrite core 32, opposed to middle leg 31, so that leakage flux 35, which is produced when magnetic flux penetrates the I-shaped ferrite core 32 from the middle leg 31, will not be produced. The through hole 34 increases the magnetic resistance in that area, and thus reduces the tendency of leakage flux 35 to flow. For the reason, leakage flux flows to the I-shaped ferrite core 32. Even if part of magnetic flux goes beyond the through hole 34, it flows to a connection 34 through a magnetic substance ahead of the through hole 34. Therefore, leakage flux 35 is significantly reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EI type ferrite core used for a transformer / choke coil, etc., and more particularly to a transformer used for a power factor correction circuit, a power supply transformer for a CRT color monitor, etc. It is about the improvement of.

[0002]

2. Description of the Related Art A perspective view of a conventional EI type ferrite core is shown in FIG. This conventional example is an I-type ferrite core 51.
And an E-type ferrite core are butted against each other. This E-type ferrite core has a middle leg 52 and outer legs 53 on both sides thereof.
And a connecting portion that connects the legs. Then, the I-type ferrite core 51 is arranged so as to abut against each leg of the E-type ferrite core. FIG. 6 shows how the EI type ferrite core is wound. A magnetic flux 55 is generated when the winding 54 is applied to the EI type ferrite core to operate it. This magnetic flux 55
Occurs so as to go around the middle leg 52 and the outer leg 53.

[0003]

When the conventional EI type ferrite core is used for operation, the original circulating magnetic flux 5
In addition to 5, leakage magnetic flux 56 is generated. This leakage magnetic flux 56
Was generated from the central portion of the middle leg 52 in the extending direction. When this leakage magnetic flux is generated, it becomes noise to other circuits, and therefore, a core having a small leakage magnetic flux has been desired. An object of the present invention is to provide an EI type ferrite core, which has a small leakage flux.

[0004]

According to the present invention, in an EI type ferrite core, a through hole is formed in a portion of the I type ferrite core facing the middle leg of the E type ferrite core. Further, the present invention is the EI ferrite core, wherein the width of at least a part of the through hole is at least half the width of the middle leg. Further, according to the present invention, the through hole is an EI type ferrite core formed on an outer side of the middle leg. Further, according to the present invention, in the EI type ferrite core, the midpoint of the side of the I type ferrite core facing the E type ferrite core and the midpoint of the side on the side of the middle leg are connected and extended. A through hole is formed in the triangular region. Further, according to the present invention, in the EI type ferrite core, a through hole having a shape symmetrical to the center line of the middle leg is formed in a portion of the I type ferrite core facing the middle leg of the E type ferrite core.

[0005]

In the present invention, as shown in FIG. 8, the portion 33 of the I-type ferrite core 32 facing the middle leg 31 of the E-type ferrite core is a shaded portion in the figure. Then, as shown in FIG. 9, a through hole 34 is formed in a portion 33 facing the middle leg 31 of the I-type ferrite core 32 so that a leakage magnetic flux 35 generated by penetrating the I-type ferrite core 32 from the middle leg 31 is not generated. To form. With this through hole 34, the magnetic resistance of that portion can be increased and the leakage magnetic flux 35 can be made difficult to flow. Therefore, what used to be a leakage magnetic flux,
It flows into the I-type ferrite core 32. Further, even if a magnetic flux slightly passing through the through hole 34 is generated, the through hole 3
The magnetic flux that has passed through 4 flows through the magnetic body at the tip of the through hole 34 to the connecting portion 34, and the leakage magnetic flux 35 is significantly reduced. Further, the through hole of the present invention, as shown in FIG. 10, is a side of the portion 33 facing the middle leg of the I-type ferrite core on the side of the middle leg so as not to interfere with the magnetic path that goes around the middle leg and the outer leg. The midpoint 40 of the midpoint 40 and the midpoint 4 of the left and right sides 43 of the facing portion 33
4 is preferably formed in a triangular region 45 formed by connecting and extending the four. Further, it is desirable that the through hole of the present invention has a shape symmetrical with respect to the center line 42 of the middle leg as shown in FIG. In addition, the through hole of the present invention is shown in FIG.
Like the triangular region 41 shown in FIG. 3, which is formed by the outer side 38 of the portion 33 facing the middle leg of the I-type ferrite core and the middle point 39 of the side 40 on the middle leg side, is formed closer to the middle leg. It is preferable that the width is narrower when forming, and the width is wider when forming outside. Further, it is desirable that the through hole has a width of about this region 41 at the position where the through hole is formed. In addition, the through hole of the present invention has the above-mentioned region 41.
It is desirable that the width be between the area 45 and the area 45. On the other hand, as shown in FIG. 7, it is conceivable to form the recess 57 on the outer side of the I-type ferrite core.
In the case where such a recess 57 is provided, the effect of reducing the leakage magnetic flux is small, which is far below the effect of the present invention.
The shape of the through hole of the present invention can be selected variously, but it may be formed so as not to obstruct the flow of the magnetic flux (the magnetic flux 36 of FIG. 9 and the magnetic flux 55 of FIG. 6) around the middle leg and the outer leg. desirable.

[0006]

FIG. 1 is a front view of an embodiment according to the present invention. In this embodiment, an I-type ferrite core 1 and an E-type ferrite core 2 are butted. The E-type ferrite core 2 of this embodiment is composed of a middle leg 3, two outer legs 4 and a connecting portion for connecting them, and the I-type ferrite core 1 faces the middle leg 3 of the E-type ferrite core 2. The through hole 5 is formed in the portion to be formed. The width e of the through hole 5 is the same as the width of the middle leg. The position of this through hole is formed on the outer side of the middle leg 3,
It is formed on the outer side of more than half the thickness d of the I-type ferrite core 1. Although the through hole 5 has a rectangular shape, it may have a rounded corner or an oval shape. This example simulated leakage flux. In this embodiment, a = 49 mm, b = 49 mm, c = 16 mm, d
= 8 mm, thickness 17 mm, ferrite core, width e = 1
A through hole having a height of 7 mm and a height of f = 1.5 mm is formed in the extension of the middle leg of the connecting portion. The position of this through hole is the position of g dimension = 4.5 mm. FIG. 3 shows a graph of the leakage magnetic flux in the H portion when the magnetic flux density is 200 mT in this example. The horizontal axis of this FIG. 3 is the distance (mm) from the core, and the vertical axis is the leakage magnetic flux. For comparison,
A conventional example without a through hole is also shown. Looking at this Figure 3,
It is apparent that the present invention can reduce the leakage flux.

FIG. 2 shows a front view of another embodiment according to the present invention. In this embodiment, the I-type ferrite core 6 and E
The I-type ferrite core 6 and the I-type ferrite core 7 are abutted with each other. In this embodiment, the through hole 10 is also formed in a portion on the extension of the middle leg 9 of the E-type ferrite core 7. The through hole 10 has the same function as the through hole 8 formed in the I-type ferrite core 6, and may be formed in the same structure. As in this embodiment, through holes may be formed in the extension of the middle leg in both the I-type ferrite core and the E-type ferrite core. Thereby, the leakage magnetic flux can be reduced in both directions of the middle leg.

FIG. 4 shows a front view of another embodiment according to the present invention. In this embodiment, the shape of the through hole is triangular and its two sides are slightly curved. As described above, in the present invention, the shape of the through hole is not particularly limited. However, in order to effectively obtain the effect of reducing the leakage flux, the width of the through hole is preferably 1/2 or more of the width of the middle leg at the maximum portion, and the position of the maximum width of the through hole is desirable. Is preferably outside the connection. This means that, in FIG. 1, e ≧ c / 2 and g ≧ d /
It has shown that 2 is desirable.

FIG. 12 shows a perspective view of another embodiment according to the present invention. In this embodiment, the E-type ferrite core 11 is used.
A plate-shaped I-type ferrite core 12 is joined to the above, and a grooved I-type ferrite core 13 is stacked and joined on the I-type ferrite core 12 to form a through hole 14. According to this method, the present invention can be used even in a shape in which integral molding is difficult.

Further, in the embodiment of the present invention, the E-type ferrite core has been described by assuming that each leg has a rectangular shape. However, the leg may have a columnar shape and is not particularly influenced by the shape. is there. Further, although the EI type ferrite core has been described in the vertical structure, the effect of the present invention can be similarly obtained even in the horizontal structure. Further, in the above-mentioned embodiment, the leg portion is described as an E-type ferrite core having three pieces, but it is obvious that the leg portion is not limited to the E-type ferrite core in order to obtain the effect of the present invention. Even if there are two or four or more, it can be understood as the E-type ferrite core in the present invention. In this case, the leg to which the winding is applied is the middle leg.

[0011]

According to the present invention, it is possible to obtain a ferrite core having a small leakage flux. If the leakage magnetic flux is reduced, the efficiency of the transformer is naturally improved, which is beneficial. Also,
It is particularly effective for a transformer used for a power factor correction circuit, especially for a 50-60 Hz leakage flux countermeasure of a CRT color monitor power transformer.

[Brief description of drawings]

FIG. 1 is a front view of an embodiment according to the present invention.

FIG. 2 is a front view of another embodiment according to the present invention.

FIG. 3 is a graph of leakage magnetic flux of an example according to the present invention and a conventional example.

FIG. 4 is a front view of another embodiment according to the present invention.

FIG. 5 is a perspective view of a conventional example.

FIG. 6 is a diagram showing a magnetic flux of a conventional example.

FIG. 7 is a front view of a comparative example.

FIG. 8 is an explanatory diagram according to the present invention.

FIG. 9 is an enlarged explanatory view of a main part according to the present invention.

FIG. 10 is an enlarged explanatory view of a main part according to the present invention.

FIG. 11 is an enlarged explanatory view of a main part according to the present invention.

FIG. 12 is a perspective view of another embodiment according to the present invention.

[Explanation of symbols]

1, 6 I-type ferrite core 2, 7 E-type ferrite core 3, 9 Middle leg 4 Outer leg 5, 8, 10 Through hole 33 Part of I-type ferrite core facing the middle leg of E-type ferrite core 39 I-type ferrite Middle point of the side of the middle leg on the side of the E-type ferrite core facing the middle leg of the core 40 Side of the side of the middle leg of the I-type ferrite core facing the middle leg of the E-type ferrite core 43 I-type ferrite core Side of the side of the E-type ferrite core facing the middle leg 44 44 Midpoint of the side of the part of the I-type ferrite core facing the center leg of the E-type ferrite core

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshihiko Tanaka 33-12 Minamieicho, Tottori City, Tottori Prefecture Hitachi Ferrite Co., Ltd.

Claims (5)

[Claims] 1. An EI-type ferrite core, wherein a through-hole is formed in a portion of the EI-type ferrite core that faces the middle leg of the E-type ferrite core. 2. The EI type ferrite core according to claim 1, wherein the width of at least a part of the through hole is at least half the width of the middle leg of the E type ferrite core. 3. The EI type ferrite core according to claim 2, wherein the through hole is formed on an outer side of the middle leg. 4. An EI type ferrite core, which is formed by connecting and extending a midpoint of a side on the side of a middle leg and a midpoint of left and right sides in a portion of the I type ferrite core facing the middle leg of the E type ferrite core. An EI type ferrite core characterized in that a through hole is formed in a triangular region. 5. In the EI type ferrite core, a through hole having a shape symmetrical to the center line of the middle leg is formed in a portion of the I type ferrite core facing the middle leg of the E type ferrite core. EI type ferrite core.