JP2000164428A - Magnetic core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce noise of a magnetic core with a gap by a method wherein the magnetic gap is provided in a magnetic path and a spacer consisting of an aramid paper is inserted in the gap. SOLUTION: This structure of a magnetic core with a gap is constituted into a structure, wherein as the magnetic core 21, a wound magnetic core, which contains Fe as its main component and consists of a nanocrystal soft magnetic alloy thin strip, 50% or higher of the whole volume of whose organization is occupied by fine crystal grains of a crystal grain diameter of 50 nm or shorter, for example, is used. This wound magnetic core is formed by a method wherein after the alloy thin strip is wound, the wound alloy thin strip is impregnated with a synthetic resin such as an epoxy, and is made to cover with the synthetic resin to cure the alloy thin strip in a constant shape and the cured alloy thin strip is cut to separate into nanocrystal soft magnetic alloy thin strips. Here, the magnetic gap is provided in a magnetic path, a spacer 22 is arranged in this gap part and an aramid paper is used as this spacer 22. Moreover, if an acrylic bonding agent or an epoxy bonding agent is used as bonding agent in the case where this aramid paper 22 is made to bond to the magnetic core 21, this structure is preferable to a reduction in the noise of the magnetic core 21 and the structure is effective also to the noise of the magnetic core 21, which is constituted by winding or laminating a thin strip-shaped magnetic core material, such as a silicon steel sheet, as the other magnetic material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic core with a gap, and to a transformer and a choke coil using the same.

[0002]

2. Description of the Related Art Conventionally, a magnetic core with a gap has been used in which a gap is provided in a magnetic path of a magnetic core, a spacer is arranged in the gap, and the core is bonded to the magnetic core. This conventional example is shown in FIG. In this conventional example, a spacer 22 is arranged on the abutting surface of two U-shaped magnetic cores 21 and fixed with an adhesive.

As a material of the magnetic core, ferrite, an amorphous soft magnetic alloy, a nanocrystalline soft magnetic alloy, a silicon steel plate and the like are used.

[0004]

A transformer and a choke coil are formed by winding a coil around this magnetic core with a gap. For example, in applications where a load is periodically turned on and off, such as a choke coil of a switching power supply, the magnetic core may vibrate and generate noise. In particular, when this cycle is in the audible frequency band, this noise has been a serious problem.

[0005] It is an object of the present invention to provide a structure of a magnetic core with a gap capable of reducing this noise, and to provide a transformer and a choke coil with reduced noise.

[0006]

The present invention is characterized in that a magnetic gap is provided in a magnetic path, and a spacer is inserted into the gap portion, and a spacer is inserted into the gap, wherein aramid paper is used as the spacer. Things.

Further, the present invention is characterized in that the aramid paper is bonded to a magnetic core with an acrylic adhesive or an epoxy adhesive.

Further, the present invention is characterized in that the magnetic core is made of a thin ribbon of a nanocrystalline soft magnetic alloy.

Further, the present invention is a transformer or a choke coil, wherein the transformer is formed by applying a winding to the magnetic core according to any one of claims 1 to 3.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention focuses on the generation of noise and the structure of a joint portion of a magnetic core in a magnetic core with a gap, and makes various studies to find a spacer arranged in the gap portion of the magnetic core with a gap. It has been found that noise can be reduced by using aramid paper. Further, they have found that it is preferable to use an acrylic adhesive or an epoxy adhesive to reduce noise when the aramid paper and the magnetic core are bonded.

Further, it has been found that the structure of the present invention is highly effective when a nanocrystalline soft magnetic alloy is used as a magnetic core material, particularly when a nanocrystalline soft magnetic alloy of a low magnetostrictive material is used. In addition, the present invention is effective for a magnetic core formed by winding or laminating a thin magnetic core material such as a silicon steel plate or an amorphous material such as a silicon steel plate, or even a ferrite magnetic core.

Hereinafter, embodiments will be described in detail. still,
The appearance of the magnetic core of this embodiment is the same as that of FIG.

The magnetic core is composed mainly of Fe and has a crystal grain size of 5
Fine grains of 0 nm or less form 50% of the entire volume of the structure.
% Of a nanocrystalline soft magnetic alloy ribbon. After winding a nanocrystalline soft magnetic alloy ribbon, the wound core is impregnated and coated with a synthetic resin such as epoxy to cure it into a predetermined shape, cut and separated.

With respect to this magnetic core, the noise level was evaluated by changing the spacer and the adhesive. Table 1 shows the results.
In Table 1, DuPont Nomex was used for the aramid paper, and the thickness was 0.5 mm. The PET film was made to thickness 0.5 mm using a Toray Le mirror. The acrylic adhesive uses Loctite 352,
As the epoxy adhesive, EP-331 manufactured by Cemedine was used. The measurement conditions were 1 kHz, 2 kHz for the choke coil.
A signal of 0 Ap-p was input and measured at a position 100 mm away from the coil.

[0015]

[Table 1]

As shown in Table 1, by using aramid paper as the spacer, noise could be reduced. In particular, when an acrylic adhesive was used, variation between samples was small, and good results were obtained. Good results were also obtained with an epoxy adhesive. Further, even when the spacer was a conventional PET film, the effect of reducing noise was obtained by using an acrylic adhesive.
This indicates that noise can be reduced to some extent by using an acrylic adhesive even with a conventional spacer. In Table 1, Comparative Example 2 corresponds to the conventional structure.

The present invention is not limited to a magnetic core made of a nanocrystalline soft magnetic alloy material, and similar effects can be expected even with a magnetic core with a gap made of ferrite, an amorphous soft magnetic alloy, a silicon steel plate or the like. Further, the form of the magnetic core is not limited to the UU type, but may be an E type, a ring type, etc., and the gap is not limited to the two places as described above, and may be provided at one place or at three or more places.

[0018]

According to the present invention, it is possible to obtain a magnetic core with a gap for a transformer and a choke coil with little noise, thereby improving the quality of the transformer and the choke coil.

[Brief description of the drawings]

FIG. 1 is a perspective view of a magnetic core with a gap.

[Explanation of symbols]

 21 Magnetic core 22 Spacer

Claims (4)

[Claims] 1. A magnetic core with a gap formed by providing a magnetic gap in a magnetic path and inserting a spacer into the gap, wherein aramid paper is used as the spacer. 2. The magnetic core according to claim 1, wherein the aramid paper is bonded to the magnetic core with an acrylic adhesive or an epoxy adhesive. 3. The magnetic core according to claim 1, wherein the magnetic core comprises a thin ribbon of a nanocrystalline soft magnetic alloy. 4. A transformer or a choke coil, wherein a winding is applied to the magnetic core according to claim 1.