JPH05243054A - Magnetic core - Google Patents

Abstract

PURPOSE:To ensure excellent magnetic properties with high reliability and increase space factor by forming on the surface of a thin plate an insulating modified layer which takes as a chief component a component with which the thin plate is formed. CONSTITUTION:An oxide layer is formed on the surface of a thin plate comprising a Co amorphous magnetic alloy by dipping said thin plate in water at ordinary temperature, and thereafter taking it out heating and drying the same. Successively, the thin plate is wound into a wound structure to which a heat treatment is in turn applied in the atmosphere of nitrogen gas and which is then coated with epoxy resin to fabricate a magnetic core. Hereby, fixation strength of a modified layer with respect to the thin plate is increased to result in high reliability of the same. Thus, there is ensured excellent magnetic properties possessed by a magnetic alloy thin plate, and an occupation rate is more increased compared with the case where interlayer insulation is attained with a film comprising inorganic powder formed on the thin plate surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic core formed by winding or laminating magnetic alloy thin plates.

[0002]

2. Description of the Related Art A magnetic core made of an amorphous magnetic alloy thin plate is used for a switching power supply and a choke coil of a high frequency circuit.

This magnetic core is formed by winding or laminating amorphous magnetic alloy thin plates, and specifically, is formed by winding a band-shaped amorphous magnetic alloy thin plate, or a circular ring. It is formed by laminating amorphous magnetic alloy thin plates punched in a circular shape, and is used as it is, or housed in an insulating resin case or molded with an insulating resin.

The amorphous magnetic alloy thin plate has various excellent magnetic characteristics such as high magnetic permeability and small loss characteristics such as hysteresis loss and eddy current loss. The formed magnetic core is small in size but has excellent magnetic characteristics due to the above-mentioned material characteristics. In this magnetic core, in order to ensure the low loss characteristic of the material, interlayer insulation is generally provided between the adjacent amorphous magnetic alloy thin plates.

Conventionally, in order to provide interlayer insulation between adjacent amorphous magnetic alloy thin plates in a magnetic core made of amorphous magnetic alloy thin plates, an inorganic powder is applied to the surface of the thin plates to form an insulating film. ing. That is, an inorganic material that is hard to deteriorate, for example, finely crushed magnesia or alumina is mixed with water, the thin plate is immersed in this water to apply the inorganic powder to the surface of the thin plate, and then the applied inorganic substance Is dried to form a film on the surface of the thin plate.

When manufacturing the magnetic core, an insulating film is formed on the surface of the amorphous magnetic alloy thin plate by the above-mentioned method, and then the amorphous magnetic alloy thin plate is wound or laminated to obtain the magnetic core. ing.

[0007]

However, the interlayer insulation in the magnetic core made of such an amorphous magnetic alloy thin plate has the following problems.

The insulating film formed by applying the inorganic powder is liable to be peeled off when it comes into sliding contact with another article and is poor in reliability. Therefore, when manufacturing an iron core, a thin insulating film slides on, for example, an adjacent thin plate, and the inorganic powder is separated from the surface of the thin plate to make the thickness of the insulating film uneven, or the insulating film exceeds the limit. May become thin.

If the thickness of the insulating film becomes non-uniform, or if the thickness exceeds the limit, the degree of interlayer insulation becomes non-uniform,
The required interlayer insulation characteristics cannot be ensured and the improvement of low loss characteristics is hindered. Further, the peeled powder is a cause of soiling the manufacturing apparatus or impairing the operation of the manufacturing apparatus.

It is difficult to apply the inorganic powder evenly to the surface of the thin plate, and the unevenness of the application may make the thickness of the insulating film uneven. When the thickness of the insulating film becomes nonuniform, the degree of insulation between layers becomes nonuniform, which hinders the improvement of low loss characteristics.

An insulating film made of an inorganic powder applied on the surface of a thin plate has a limit in securing interlayer insulation in order to reduce the film thickness. Therefore, there is a limit to increase the proportion of the amorphous magnetic alloy thin plate in the overall size of the magnetic core, that is, the space factor.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a magnetic core having interlayer insulation, which is highly reliable, can secure excellent magnetic characteristics, and can increase the space factor. And

[0013]

The inventor of the present invention has conducted various studies on interlayer insulation in a magnetic core made of a magnetic alloy thin plate. The inventor first tried to form an insulating film on the surface of a magnetic alloy thin plate by changing the material and the forming method. However, in each case, the above-mentioned problems occur in the case of the insulating film made of the inorganic powder.

Therefore, the inventor considers that the problem of interlayer insulation cannot be solved by the method of forming an insulating film which is a separate object on the surface of the magnetic alloy thin plate, and thus the surface of the magnetic alloy thin plate has an electric insulation property integrated with the thin plate. We focused on forming a layer and using it as interlayer insulation. Then, as a result of various experiments based on this idea, it was found that it is possible to avoid the problems that occur in the method of forming an insulating film which is a separate substance on the surface of the magnetic alloy thin plate. The present invention has been made based on such findings.

That is, the magnetic core of the present invention is a magnetic core formed by winding or laminating a magnetic alloy thin plate, and the surface of the thin plate has an insulating property containing a component forming the thin plate as a main component. It is characterized in that a metamorphic layer is generated.

The magnetic core of the present invention is intended for one formed by winding a strip-shaped magnetic alloy thin plate, or one formed by laminating magnetic alloy thin plates formed in a circular ring shape. The magnetic alloy thin plate forming the magnetic core is not limited in any way, but especially Fe as an amorphous magnetic alloy thin strip is used.
Various amorphous magnetic alloys such as Co type and Co type.

For example, a metamorphic layer having an electrically insulating property is formed on the surface of the amorphous magnetic alloy thin plate. This insulating film is formed on the surface of the amorphous magnetic alloy thin plate with a property of having an electrical insulating property with a component forming the thin plate as a main component.

The form of the electrically insulating metamorphic layer is not limited in any way, and one example thereof is an oxide layer. That is, the oxide layer is formed on the surface of the thin plate by oxidizing the components forming the amorphous magnetic alloy thin plate.

As a method for forming an oxide layer on the surface of the amorphous magnetic alloy thin plate, the amorphous magnetic alloy thin plate is immersed in water before being wound or laminated, and then the amorphous magnetic alloy thin plate is taken out. And a method of drying.

An example of a specific manufacturing method will be described. First, the time for immersing the thin plate in water is not particularly limited, but is preferably 30 minutes to 20 hours, and the temperature of water is 0 to 0.
The temperature is 100 ° C, preferably 10 to 50 ° C. The subsequent drying time is equal to or lower than the crystallization temperature of the amorphous magnetic alloy thin plate, preferably 100 to 250 ° C, more preferably 180 to 250 ° C.
It is 220 ° C.

Drying is performed at a temperature lower than the crystallization temperature of the amorphous magnetic alloy thin plate, but if the temperature is close to the crystallization temperature, the thin plate becomes brittle and molding (rolling) becomes difficult, In addition, there is a risk that the oxide layer will peel off from the thin plate. When drying at a temperature close to the crystallization temperature, the amorphous magnetic alloy thin plates are immersed in water in a wound or laminated state and dried. In other words, the heat treatment for strain removal of the magnetic core is also performed, so that the metamorphic layer is liable to peel off. Therefore, it is desirable that the drying is performed in the temperature range of 100 to 250 ° C. The water for immersing the amorphous magnetic alloy thin plate is not limited in any way, and various kinds of water such as pure water and tap water can be used.

Other methods for forming an oxide layer on the surface of the amorphous magnetic alloy thin plate include a method using an oxidizing gas and a chemical agent. Also in this method, it is necessary to perform the drying at a temperature lower than the crystallization temperature.

Here, when the oxidizing gas is used, it is possible to achieve the object, but there is a tendency that the magnetic core has a large variation due to the tension at the time of molding and the surface property of the thin plate surface. However, caution is required to obtain stable magnetic properties.

Therefore, in manufacturing the magnetic core in the present invention, the step of forming a metamorphic layer on the surface of the amorphous magnetic alloy thin plate-the step of winding or laminating the amorphous magnetic alloy thin plate-amorphous magnetic Manufacturing is performed in the order of steps for subjecting a wound body or a laminated body of alloy thin plates to a strain relief heat treatment. Then, if necessary, resin coating or putting in a case. The magnetic core of the present invention configured as described above can obtain the following effects.

A metamorphic layer having electrical insulation is formed on the surface of the amorphous magnetic alloy thin plate in the magnetic core. Therefore, in a magnetic core formed by winding a band-shaped amorphous magnetic alloy thin plate, a thin film metamorphic layer acts as interlayer insulation on each winding layer of the amorphous magnetic alloy thin plate.

Further, in a magnetic core formed by laminating amorphous magnetic alloy thin plates formed in a circular ring shape, a metamorphic layer of the thin plates acts as interlayer insulation between the laminated layers of the amorphous magnetic alloy thin plates. Therefore, the magnetic core of the present invention can secure the excellent magnetic characteristics of the amorphous magnetic alloy thin plate.

In the magnetic core of the present invention, the metamorphic layer formed on the surface of the amorphous magnetic alloy thin plate in order to provide the interlayer insulation, the components forming the thin plate are metamorphosed and integrated with the thin plate as a part of the thin plate. Since it is generated on the surface of the amorphous magnetic alloy thin plate, the adhesion strength to the thin plate is higher than that of the insulating film formed as a separate object by applying powder to the surface of the amorphous magnetic alloy thin plate. High reliability without peeling.

Therefore, it is possible to prevent the thickness of the knitting layer from becoming non-uniform and the insulating film from being thinned beyond the limit due to peeling. Therefore, the degree of interlayer insulation between the amorphous magnetic alloy thin plates is uniform, the required interlayer insulation characteristics are secured, and the low loss characteristics of the magnetic core can be improved. Moreover, the peeled powder does not pollute the manufacturing apparatus or impair the operation of the manufacturing apparatus. Further, since the metamorphic layer is formed integrally with the amorphous magnetic alloy thin plate, it can be formed with a uniform thickness as compared with the insulating film,
A uniform degree of interlayer insulation can be ensured.

Further, since the metamorphic layer is formed integrally with the amorphous magnetic alloy thin plate, it can be thinner than the insulating film in order to obtain the same interlayer insulating property. Therefore, in the case of a wound type magnetic core, the interlayer insulating portion between each wound layer is thinned,
The outer diameter of the magnetic core can be made smaller than that when an insulating film is formed.

That is, in the magnetic core of the present invention, if the outer diameter is the same as that of the conventional magnetic core, the ratio of the amorphous magnetic alloy thin plate is large and the space factor is large. In the case of a laminated type magnetic core, the thickness of the magnetic core can be reduced as compared with the case where an insulating film is formed by thinning the interlayer insulating portion between each laminated layer.
That is, if the thickness of the magnetic core of the present invention is the same as that of the conventional magnetic core, the ratio of the amorphous magnetic alloy thin plate is large and the space factor is large.

[0031]

【Example】

Invention Example a Fe 4.45 at%, Nb 0.7 at%, Si 9.2a
Co consisting of t%, B2.2 at% and the balance substantially Co
A thin strip having a width of 5 mm and made of a system amorphous magnetic alloy was prepared. This ribbon is immersed in water at room temperature for 1 hour, then taken out and the temperature is 2
It was heated and dried in a constant temperature bath of 00 ° C. to form an oxide layer on the surface of the ribbon. Next, the ribbon is wound and the outer diameter is 5 mm and the inner diameter is 3
A wound body having a size of 3 mm and a height of 3 mm was prepared, and the wound body was subjected to strain relief heat treatment in a nitrogen gas atmosphere at a temperature of 400 ° C. and then coated with an epoxy resin to manufacture a magnetic core.

Inventive Example b The same amorphous magnetic alloy ribbon as in Inventive Example a was prepared. The ribbon was passed through this solution using a 2% nitric acid solution and then passed through a drying oven at 200 ° C. for drying. In this case, the moving speed of the ribbon in the drying furnace was 1 m / min. This ribbon is wound and the outer diameter is 5 mm, the inner diameter is 3 mm, and the height is 5 mm.
The wound body was manufactured, and the wound body was subjected to strain relief heat treatment in a nitrogen gas atmosphere at a temperature of 400 ° C. for a time of 30 minutes, and was coated with an epoxy resin to manufacture a magnetic core.

Comparative Example a The same amorphous magnetic alloy thin plate as the example of the present invention was prepared as an example in which no insulation treatment was performed, and this thin plate was wound to produce a wound body having an outer diameter of 5 mm, an inner diameter of 3 mm and a height of 5 mm. Then, the wound body was subjected to strain relief heat treatment at a temperature of 400 ° C. for 30 minutes in a nitrogen gas atmosphere, and was coated with an epoxy resin to manufacture a magnetic core.

Comparative Example b The same amorphous magnetic alloy thin plate as in the example of the present invention was prepared, and the thin plate was immersed in water mixed with pulverized powder of MgO, taken out and heated to form a powder film on the surface of the thin plate. Formed. Then, this thin plate is wound and the outer diameter is 5 mm, the inner diameter is 3 mm, and the height is 5 mm.
The wound body was manufactured, and the wound body was subjected to strain relief heat treatment in a nitrogen gas atmosphere at a temperature of 400 ° C. for a time of 30 minutes, and was coated with an epoxy resin to manufacture a magnetic core.

The magnetic core of the present invention manufactured as described above,
In the magnetic core of Comparative Example a and the magnetic core of Comparative Example b, the inductance (L value) which is the magnetic characteristic, the coercive force and the squareness ratio at 10 KHz and the iron loss at 2 KG as the AC magnetic characteristic were measured.

As a result, the inductance (L value) was 22 μH in the invention sample a, 21 μH in the invention sample b, and the comparative example a10.
5 μH and Comparative Example b 20 μH. Also, the coercive force is
Inventive Example aO. 19 Oe, the present invention example b0.20 Oe, the comparative example a0.30 Oe, the comparative example bO. It was 21 Oe.

The squareness ratios were as follows: Inventive Example a 98%, Inventive Example b 98%, Comparative Example a 94.5%, Comparative Example b 95%. Further, the iron loss is 350 nW / cc of the present invention example a,
Inventive Example b380 nW / cc, Comparative Example a800 nW / c
c, Comparative Example b 450 nW / cc. As described above, the magnetic core of the present invention has excellent magnetic characteristics as compared with other magnetic cores. It was also found that the space factor of the magnetic core of the present invention example was higher than that of the magnetic core of the comparative example.

[0038]

As described above, according to the magnetic core of the present invention, an insulating metamorphic layer containing a component forming a thin plate as a main component is formed on the surface of a magnetic alloy thin plate to perform interlayer insulation. Compared to the case where the metamorphic layer has high adhesion strength to the thin plate and the reliability of the metamorphic layer is high, the excellent magnetic properties of the magnetic alloy thin plate can be secured, and interlayer insulation is obtained by the film made of inorganic powder formed on the thin plate surface. And the space factor can be increased.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location 8935-5E H01F 27/24 Q

Claims (2)

[Claims] 1. A magnetic core formed by winding or laminating a magnetic alloy thin plate, wherein an insulating metamorphic layer containing a component forming the thin plate as a main component is formed on the surface of the thin plate. Magnetic core. 2. The magnetic core according to claim 1, wherein the magnetic alloy thin plate is an amorphous magnetic alloy ribbon.