JPH11260652A - Ferrite core and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize high inductance in ferrite core, when a plurality of leg parts are butted and used as a core in a transformer or an inductor, by manufacturing butting faces of middle and outer leg parts to a mirror surface finish with adequate satisfactorily planarity and a uniform manufactured shape. SOLUTION: A magnetic core has a core structure made up of a central leg part 1, an outer leg part 2, and a bottom part 3 that joins these leg parts 1 and 2. The outer leg part 2 is slightly longer than the middle leg part 1, and these leg parts 1 and 2 are subjected to mirror-surface finish manufacturing in a way that the difference between a maximum point of a top face of the outer leg part 2 and a minimum point of a top face of the middle leg part 1 is made 0.3 μm or below. As a result, an air gap at butted faces of these leg parts can be made adequately small when a plurality of leg parts are butted, to be used as a core in a transformer or an inductor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an electric signal carrier,
The present invention relates to a ferrite core used for a transformer for a power supply, an inductor, a filter, and the like, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, a ferrite core called an E core or a pot core is known as a typical example of a ferrite core having a center leg, an outer leg, and a bottom portion connecting these legs. Further, a ferrite core in which an opening is formed by cutting out a part of the outer leg and the bottom of the pot core is also used.

FIGS. 9 and 10 show examples of a conventional ferrite core called an E-core. FIG. 9 shows that the outer leg 2 is longer than the center leg 1 even after mirror polishing, and The figure shows a case where the height difference d between the highest point of the leg tip surface and the lowest point of the central leg tip surface is about 0.5 μm. Conversely, FIG. 10 shows that the center leg 1 is longer than the outer leg 2 even after mirror finishing, and the height between the highest point of the center leg tip surface and the lowest point of the outer leg tip surface is higher. The case where the difference d is about 0.5 μm is shown. In such an E-core, the flatness of the tip surfaces of the center leg 1 and the outer leg 2 after mirror finishing is set to 0.5.
Conventionally, it has been considered difficult to reduce the thickness to μm or less.

FIGS. 11 and 12 show a mirror finishing process of a conventional E core. As shown in these figures, a large number of E-cores 10 as workpieces are arranged on the upper surface of the magnet chuck 11 (which is a surface plate having good flatness) with the processing surface facing upward, and are in close contact with each other. Supported by the support block 12 as described above. The magnet chuck 11 has an electromagnet structure.
The core 10 and the support block 12 are sucked. Then, with the rotation of the magnet chuck 11 in the direction of the arrow P, the processing surface of each E core 10 comes into contact with the grindstone 13 rotating at high speed in the direction of the arrow Q, and mirror processing of the processing surface is executed.

In such a conventional mirror finishing process,
The following reasons can be considered as factors that deteriorate the flatness of the end surfaces of the center leg 1 and the outer leg 2 that are the processing surfaces.

[0006] The E-core 10 is
Is magnetically attracted, stress is applied to the E core 10 and mirror processing is performed in a state where distortion occurs in the E core 10. For this reason, when the E core 10 is removed from the magnet chuck 11, the stress disappears. As a result, the distortion of the E core 10 returns to its original state.
The flatness of the mirror-finished surface decreases.

As shown in FIG. 12, the thickness of the E core 10 after sintering is not constant due to the density distribution at the time of molding, and the tip direction of each of the central leg and the outer leg may become thin. In such a case, FIG.
As shown by the arrow R in FIG. 2, the E core 10 oscillates, and the flatness of the mirror-finished surface also decreases.

[0008]

As described above, in the conventional ferrite magnetic core, it is difficult to make the flatness of the central leg and the outer leg, which are the abutting surfaces, less than 0.5 μm, and the shape is also difficult. Even if the ferrite core is made of MnZn-based ferrite of high permeability material with initial permeability μi = 5000 or more because it is not uniform, the ferrite cores are mutually butted to form the core of a transformer or inductor. However, there is a problem that the air gap at the abutting surface becomes large, and the effect of using the high magnetic permeability material is diminished.

The present invention has been made in view of the above points, and has been developed in such a manner that the flatness of the central leg and the outer leg serving as the abutting surface is sufficiently satisfactorily mirror-finished so that the shape after the processing is uniform. It is an object of the present invention to provide a ferrite core capable of realizing a high inductance when used as a core of a transformer or an inductor by abutting pieces, and a method of manufacturing the same.

[0010] Other objects and novel features of the present invention will be clarified in embodiments described later.

[0011]

In order to achieve the above object, a ferrite magnetic core according to the present invention comprises a center leg, an outer leg, and a bottom connecting the two legs. The outer legs slightly longer than the part,
The height difference between the highest point of the outer leg tip surface and the lowest point of the center leg tip surface is mirror-finished to 0.3 μm or less. An abrasive trace is formed in a longitudinal direction along the central leg and the outer leg.

In the ferrite core, the surface roughness of the central leg and the outer leg may be 0.07 μm or less.

[0013] The ferrite core may be made of MnZn-based ferrite having an initial permeability of 5000 or more.

The method of manufacturing a ferrite magnetic core according to the present invention is directed to a method of manufacturing a ferrite magnetic core comprising a center leg, an outer leg, and a bottom connecting these legs, without using a magnet chuck. Holding the core and running a grindstone in the longitudinal direction along the central leg and the outer leg, mirror-finish the distal end surfaces of the central leg and the outer leg, and the highest point of the distal end surface of the outer leg. And the difference between the height of the tip of the center leg and the lowest point of the center leg is 0.3 μm or less, and the traces of polishing on the tip of the center leg and the outer leg are attached to the center leg and the outer leg. It is characterized by being formed in the longitudinal direction along.

[0015]

In the ferrite magnetic core of the present invention, the flatness of the center leg and the outer leg serving as the butting surfaces can be sufficiently improved by mirror finishing, and the shapes are uniform. It is possible to sufficiently reduce the air gap generated on the mating surface when the magnetic core of the transformer or the inductor is formed. For this reason, it is possible to prevent a decrease in inductance due to the air gap. Also,
Since the air gap is sufficiently small, when the ferrite core is made of a high permeability material of MnZn-based ferrite having an initial permeability μi of 5000 or more, the performance of the high permeability material can be sufficiently exhibited.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a ferrite magnetic core according to the present invention and a method for manufacturing the same will be described below with reference to the drawings.

1 and 2, an embodiment of a ferrite core according to the present invention and a method for manufacturing the same will be described. In these figures, the E core as a ferrite core is
It is composed of a central leg 1, an outer leg 2 and a bottom surface 3, and the outer leg 2 is longer than the central leg 1, and the highest point of the outer leg tip surface and the lowest point of the central leg tip surface. The height difference d is 0.3
μm or less, and mirror-finished so that the surface roughness is 0.07 μm or less. This high-precision mirror polishing does not use a magnet chuck at the time of mirror polishing, eliminates the lateral runout of the E core, and runs the grindstone in the longitudinal direction along the center leg and the outer leg of the E core. It is realized by doing. For this reason, as shown in FIG. 2, the grinding traces S on the tip surfaces of the central leg 1 and the outer leg 2 are substantially linear in the longitudinal direction along the central leg and the outer leg (actually, the grinding stones). (A circular arc determined by the radius of rotation). In addition,
The polishing traces S are difficult to discern with the naked eye, but can be recognized by observing the distal end surfaces of the central leg 1 and the outer leg 2 with a microscope or the like while enlarging them.

When a magnetic core of a transformer or an inductor is formed by joining two E cores shown in this embodiment, for example, the flatness of the mating surface is 0.3 μm or less and the shape is stable. The air gap between the surfaces can be made small, and a decrease in inductance due to the air gap can be prevented. Further, since the air gap is sufficiently small, MnZ of a high permeability material having an initial permeability of 5000 or more is used.
When made of n-type ferrite, the performance of the high magnetic permeability material can be sufficiently exhibited (the performance is rarely reduced by the air gap). In addition, since the central leg 1 is slightly shorter than the outer leg 2, the structure when two butts are joined together by fastening metal fittings or taping or the like is stabilized, so that as shown in the above embodiment, Electromagnetic performance of a transformer or the like using a ferrite core is not easily affected by external vibration and the like.

In the above embodiment, the E core is exemplified, but the ER core in FIG. 3, the PQ core in FIG. 4, and the RM core in FIG.
Core, EP core of FIG. 6, LP core of FIG. 7, EPC of FIG.
The present invention is also applicable to a ferrite magnetic core including a central leg, an outer leg, and a bottom connecting these legs, such as a core.

Although the embodiments of the present invention have been described above, it is obvious to those skilled in the art that the present invention is not limited to the embodiments and various modifications and changes can be made within the scope of the claims. There will be.

[0021]

As described above, according to the present invention,
In a magnetic core structure including a central leg, an outer leg, and a bottom connecting the two legs, the outer leg is slightly longer than the central leg, and the highest point of the outer leg tip surface. Difference between the height of the center leg and the lowest point of the tip of the center leg is 0.3 μm
m or less, a small air gap is generated when used as a magnetic core of a transformer or inductor by abutting a plurality of parts, so high inductance can be realized and even when a high permeability material is used. The performance of the high magnetic permeability material is not impaired.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of a ferrite magnetic core according to the present invention.

FIG. 2 is a perspective view of the embodiment showing polishing marks.

FIG. 3 is a perspective view showing an ER core to which the present invention can be applied.

FIG. 4 is a perspective view showing a PQ core to which the present invention can be applied.

FIG. 5 is a perspective view showing an RM core to which the present invention can be applied.

FIG. 6 is a perspective view showing an EP core to which the present invention can be applied.

FIG. 7 is a perspective view showing an LP core to which the present invention can be applied.

FIG. 8 is a perspective view showing an EPC core to which the present invention can be applied.

FIG. 9 is a front view showing an example of a conventional E core.

FIG. 10 is a front view showing another example of the conventional E core.

FIG. 11 is a perspective view showing a mirror polishing step of a conventional E core.

FIG. 12 is an enlarged view for explaining a problem in a conventional mirror polishing process of an E core.

[Explanation of symbols]

 1 center leg 2 outer leg 10 E core

Claims (4)

[Claims] 1. A ferrite core comprising a central leg, an outer leg, and a bottom connecting the two legs, wherein the outer leg is slightly longer than the central leg, and The difference in height between the highest point of the tip surface and the lowest point of the center leg tip surface is mirror-finished to 0.3 μm or less, and the grinding traces on the tip surfaces of the center leg and the outer leg are centered on the center. A ferrite magnetic core formed in a longitudinal direction along a leg and an outer leg. 2. The ferrite magnetic core according to claim 1, wherein the surface roughness of the central leg and the outer leg is 0.07 μm or less. 3. The ferrite core according to claim 1, wherein the ferrite core is composed of MnZn-based ferrite having an initial permeability of 5000 or more. 4. A method of manufacturing a ferrite core comprising a center leg, an outer leg, and a bottom connecting the two legs, wherein the ferrite core is held without using a magnet chuck, and By running a grindstone in the longitudinal direction along the outer leg portion, the tip surfaces of the central leg portion and the outer leg portion are mirror-finished, and the highest point of the tip surface of the outer leg portion and the lowest point of the tip surface of the central leg portion are processed. The height difference from the point is set to 0.3 μm or less, and polishing marks on the tip surfaces of the central leg and the outer leg are formed in the longitudinal direction along the central leg and the outer leg. A method for producing a ferrite magnetic core.