JP2009094245A - Drum-type core - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drum-type core which satisfies a request of miniaturization and thinning of an inductor, maintains a superior superimposition characteristic and can make much currents flow. <P>SOLUTION: The drum-type core 2 has brim parts 7a and 7b provided at both ends of a core part 6. The core part 6 and the brim parts 7a and 7b are formed of three layer structures formed of materials different in magnetic characteristics. Layer bonding parts 8a and 8b formed in the brim parts 7a and 7b are integrally coupled by sintering. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a drum core used for an inductor for a power supply circuit.

  In general, as a wound inductor, a coil is wound around a magnetic core of a drum core having a flange at both ends, a terminal of the winding is connected to a terminal electrode, and a ferromagnetic such as a permanent magnet is connected to the flange. A combined type is known (see Patent Document 1).

  By the way, as represented by mobile phones, recent portable electronic devices have a strong demand for thinning, and therefore, inductors to be mounted also tend to be thinned. On the other hand, recent mobile phones have become more multifunctional, and there is a demand for flowing more current through the power supply circuit.

Conventionally, a drum-type core used for an inductor has been mainly made of a manganese zinc alloy or a nickel zinc alloy. However, although manganese zinc alloy has high magnetic permeability and excellent superposition characteristics, it must have an insulating coating on the magnetic core around which the coil is wound in order to have conductivity. Not suitable. On the other hand, since nickel-zinc alloys are non-conductive, it is not necessary to apply an insulation coating like manganese-zinc alloys. However, the superposition characteristics are reduced as inductors become smaller and thinner, resulting in a large amount of current. There is a problem that it cannot be washed away.
Japanese Patent Publication No. 7-38351

  Therefore, the problem to be solved by the present invention is to provide a drum-type core that can satisfy a demand for a smaller and thinner inductor, maintain excellent superposition characteristics, and allow a large amount of current to flow.

  The drum-type core of the present invention is characterized in that the magnetic core portion and the collar portion have at least a two-layer structure formed of materials having different magnetic characteristics.

  The two-layer structure is characterized in that the layer joints are integrally bonded by sintering.

  In one embodiment, one layer of the two-layer structure is formed from a manganese zinc alloy material, and the other layer is formed from a nickel zinc alloy material.

  According to the drum core of the present invention, the magnetic core portion and the collar portion are composed of at least a two-layer structure formed of materials having different magnetic characteristics, so that excellent superposition characteristics can be maintained by appropriately selecting the materials, Thin and thin drum cores were achieved.

  Hereinafter, the best embodiment of the drum core according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a perspective view of an inductor using a drum core according to the present invention, and FIG. 2 is a cross-sectional view taken along line AA in FIG. 1 showing an embodiment of the drum core according to the present invention.

  In FIG. 1, an inductor 1 has a structure in which the periphery of a drum-type core 2 of the present invention is shielded by a mold resin 3, and a terminal electrode 4 for surface mounting is provided at a corner of a bottom surface of the square mold resin 3. ing.

  As shown in FIG. 2, the drum-type core 2 in this embodiment has a basic structure that is similar to the conventional structure, a cylindrical magnetic core portion 6 around which the coil 5 is wound, and upper and lower ends of the magnetic core portion 6. It consists of a pair of provided flange portions 7a and 7b, but differs from the conventional one in that the magnetic core portion 6 and the flange portions 7a and 7b are formed of materials having different magnetic properties.

  The drum-type core 2 shown in FIG. 2 has a three-layer structure of the magnetic core portion 6 and the collar portions 7a and 7b by using two kinds of materials having different magnetic characteristics. The upper and lower collar portions 7a and 7b are respectively formed with layer joint portions 8a and 8b in the horizontal direction, and each collar portion 7a and 7b has two layers. By the layer joint portions 8a and 8b, a layer including the magnetic core portion 6 and the inner portions 9a and 9b of the flange portions 7a and 7b close to the magnetic core portion 6 and an outer portion of the flange portions 7a and 7b not including the magnetic core portion 6. The magnetic characteristics of the layers 10a and 10b are different.

  As the magnetic characteristics, initial permeability and saturation magnetic flux density that affect the superposition characteristics are important. As materials having high initial magnetic permeability and saturation magnetic flux density, for example, manganese zinc alloy and amorphous are known. However, since the manganese zinc alloy and amorphous have conductivity, when the groove width w of the magnetic core portion 6 is reduced, it is difficult to uniformly coat the surface of the magnetic core portion 6 with an insulating layer. It cannot be used.

  Therefore, in this embodiment, as two types of molding materials having different magnetic characteristics, a material for forming the layers of the outer portions 10a and 10b of the collar portions 7a and 7b not including the magnetic core portion 6 is a manganese zinc alloy having excellent magnetic characteristics. On the other hand, the material forming the layer including the magnetic core portion 6 and the inner portions 9a, 9b of the flange portions 7a, 7b close to the magnetic core portion 6 is made of a nickel zinc alloy having a non-conductive property although the magnetic properties are somewhat inferior Used.

  In this embodiment, a three-layer structure is formed by pressure-molding and sintering a manganese zinc alloy and a nickel-zinc alloy having different magnetic properties. Therefore, the layer joint portions 8a and 8b between the layers have a structure integrally bonded by sintering. That is, in the vicinity of the layer joints 8a and 8b, as shown in FIG. 3, the manganese zinc alloy particles 11 and the nickel zinc alloy particles 12 are bonded in a mixed state, and the binder is evaporated. After that, while maintaining this state, the two are joined together. As a result, a magnetic gap does not occur at the joint between the layer formed of the manganese zinc alloy and the layer formed of the nickel zinc alloy. That is, for example, when a manganese zinc alloy layer and a nickel zinc alloy layer are separately formed and joined together with an adhesive after forming, the adhesive layer causes a magnetic gap. Since there is no adhesive layer between the two layers, no magnetic gap is created.

  Next, one method for forming the drum core having the above configuration will be described with reference to FIG. First, an appropriate raw material is mixed from manganese oxide, nickel oxide, zinc oxide, etc., and pre-fired to make an alloy. Next, a binder is added to the alloy and pulverized, and further granulated to a predetermined size to produce a manganese zinc alloy and a nickel zinc alloy granular molding material.

  Next, the core before grooving is pressure-molded using a mold. As one means of pressure molding, for example, a granular manganese zinc alloy is supplied into a mold, a part to be one collar portion 7b is pressure molded, and a granular nickel zinc alloy is placed on the mold inside the mold. The portion to be the magnetic core portion 6 is pressure-molded, and further the granular manganese zinc alloy is again fed into the mold and the other portion to be the collar portion 7a is pressure-molded. A cylindrical core before groove processing having a three-layer structure is formed.

  Next, the magnetic core portion 6 is formed by grooving the middle portion of the cylindrical core. At this time, the groove processing is performed so that the upper and lower layer joint portions 8a and 8b remain in the flange portions 7a and 7b.

  The core after the groove processing is put in a firing furnace and fired in a predetermined temperature and atmosphere, thereby forming a drum core in which the layer bonding portions 8a and 8b are integrally coupled.

  An inductor was manufactured using the drum core obtained as described above, and the superposition characteristics were measured. Using the manganese zinc alloy and the nickel zinc alloy, the intermediate magnetic characteristics when the inductor was manufactured independently were obtained. I knew I would get it.

  In the above embodiment, the drum type core 2 having a three-layer structure has been described. However, as in the drum type core 20 shown in FIG. Can be made of a manganese zinc alloy, the magnetic core portion 6 and the other collar portion 7b can be formed of a nickel zinc alloy, and a two-layer structure in which the layer joint portion 8a is provided only on one collar portion 7a can be formed.

  In addition to the manganese zinc alloy, amorphous or silicon steel can be used as a material having excellent magnetic properties.

  The drum-type core of the present invention is highly useful as an inductor core mounted on a thin portable electronic device such as a recent mobile phone.

It is sectional drawing which shows the inductor incorporating the drum type core of this invention. It is the sectional view on the AA line in FIG. It is an enlarged view of the B section in FIG. It is process drawing which shows the manufacturing process of the drum type core of this invention. It is sectional drawing which shows the other example of the drum type core of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inductor 2 Drum type core 3 Mold resin 4 Terminal electrode 5 Coil 6a, 6b Magnetic core part 7a, 7b Collar part 8a, 8b Layer junction part 9a, 9b Inner part of collar part
10a, 10b Outer portion of the collar portion 11 Manganese zinc alloy particles 12 Nickel zinc alloy particles

Claims (7)

In a drum-type core having flange portions at both ends of the magnetic core portion,
A drum core having at least a two-layer structure in which the magnetic core portion and the collar portion are formed of materials having different magnetic characteristics. The drum core according to claim 1, wherein the layer including the magnetic core portion and the layer including no magnetic core portion have different magnetic properties, and the layer including the magnetic core portion has lower magnetic properties than the layer not including the magnetic core portion. The drum-type core according to claim 1, wherein the two-layer structure has layer joints integrally bonded by sintering. The drum core according to claim 3, wherein the layer bonding portion is formed on at least one of the flange portions. The drum core according to claim 1 or 2, wherein the materials having different magnetic characteristics are materials having different initial magnetic permeability and saturation magnetic flux density. The drum core according to claim 2, wherein the layer including the magnetic core is formed of a nickel zinc alloy. The drum core according to claim 2, wherein the layer not including the magnetic core is formed of a manganese zinc alloy or an amorphous material.

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