JP2008270438A - Inductor, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small closed magnetic path type inductor which has a good DC superposition characteristic at a large current and does not require high material dimensional accuracy and/or assembly accuracy. <P>SOLUTION: This inductor is formed of a coil 1 wound in a vertical shape, a magnetic core 2 consisting of a mixture of a magnetic substance powder and an adhesive, and a magnetic substance core material 3 such as ferrite, and the magnetic core 2 having an I-shaped cross-section and the magnetic substance core material 3 having a U-shaped cross-section are combined to form a closed magnetic path having a square-shaped cross-section. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an inductor used as a choke coil, a transformer or the like in a general circuit or a high frequency circuit.

With the downsizing, multi-functionality, and high performance of electronic equipment, there is a need for the commercialization of a closed magnetic circuit type inductor that can deal with large currents with a small amount of leakage magnetic flux that enables high-density mounting.
When a large current is passed through the inductor, the magnetic flux in the core increases and magnetic saturation occurs, and the inductance is lowered and good DC superposition characteristics cannot be maintained.
Therefore, in order to cope with a large current, in principle, it is necessary to make the core larger or to provide a gap in a part of the magnetic path so that magnetic saturation is difficult.
Therefore, if the inductor has a large current / closed magnetic circuit structure, the outer dimensions are inevitably increased.
In addition, in the combination of magnetic core materials such as EI type and EE type, the inductance varies greatly depending on the air gap amount. Therefore, the required material dimensional accuracy and assembly accuracy are high in terms of characteristic variation, and the product cost is reduced. It was raised.

  The problems to be solved are as described above, and the present invention provides a closed magnetic circuit type inductor that is small and has good DC superimposition characteristics at a large current and does not require high material dimensional accuracy and assembly accuracy. It was made for the purpose.

  Therefore, the present invention fills the inner periphery of the coil with a mixture of magnetic powder and adhesive to form a magnetic core portion, and combines the magnetic core portion and the magnetic core material disposed on the outer periphery of the coil to form a core without a gap. The main feature is to form a closed magnetic circuit type magnetic circuit that forms a loop.

In the present invention, a magnetic core portion having a high saturation magnetic flux density is arranged on the inner circumference of the coil where the magnetic flux is concentrated to make the magnetic saturation difficult, and a magnetic core material having a high permeability is arranged on the outer circumference of the coil where the magnetic flux is dispersed. A large inductance is obtained. Therefore, it is possible to prevent the deterioration of the DC superimposition characteristics at the time of a large current without increasing the core.
In addition, since there is no gap in the core, gap management requiring high material dimensional accuracy and assembly accuracy is not required, and the product cost can be reduced.

  Embodiments of the present invention will be described below.

FIG. 1 shows an exploded perspective view of an inductor embodying the present invention.
The inductor is composed of a vertically wound coil 1, a magnetic core 2 made of a mixture of magnetic powder and adhesive, and a magnetic core material 3 such as ferrite. As shown in FIG. A closed magnetic circuit having a square U-shaped cross section is formed by combining the magnetic core 2 and the magnetic core material 3 having a U-shaped cross section.
Thus, if a magnetic body is arrange | positioned to both the magnetic path formed in the inner peripheral side and outer peripheral side of the coil 1, a leakage magnetic flux can be reduced in both magnetic paths, and a big inductance can be obtained.

The coil 1 is a solenoid coil of a bobbin or a coreless winding wound with a copper wire coated with urethane enamel or the like, and the winding start is bent downward to form one lead terminal 11 for external connection. Then, the winding end is folded back to the outside of the coil to form the other lead terminal 11. Therefore, the lead terminal 11 at the winding end turn-up portion protrudes to the outside of the coil. The lead terminal 11 peels off the insulating film at the tip to make it a coil terminal 12.
The coil 1 may have a shape in which a rectangular wire is edgewise wound to minimize the thickness of the winding. As a result, it is possible to increase the line area ratio, further reduce the size and thickness of the coil, and improve the heat dissipation.

The magnetic core 2 is filled with a mixture of magnetic powder and adhesive in the coil 1 in a fluid state before curing, and is fitted between the upper and lower horizontal plates of the magnetic core material 3 having a U-shaped cross section. And both ends are fixed to the upper and lower horizontal plates of the magnetic core material 3.
The air core coil changes its inductance by vibration as it is, but unnecessary vibration can be suppressed by filling the magnetic core portion 2 with a mixture containing an adhesive and mechanically fixing it.
Further, since the heat generated in the coil 1 is efficiently transmitted to the magnetic core material 3 through the magnetic core 2, the heat accumulated in the coil 1 can be quickly released to prevent thermal destruction of the coil 1.

The magnetic powder is made of a metallic material such as Fe-Si, Fe-Si-Cr, Sendust (Fe-Al-Si), Permalloy, Carbonyl iron, etc., which has a higher saturation magnetic flux density than ferrite.
One of these magnetic powders is used, but a plurality may be used in combination.
As the adhesive, a thermosetting resin such as an epoxy resin, a phenol resin, or a polyamide resin is used. However, a chemically reactive curable resin or a photocurable resin such as an ultraviolet ray may be used.
The mixing ratio of the magnetic powder and the adhesive increases the magnetic permeability of the magnetic core 2 as the magnetic powder increases. However, if the amount of the adhesive is small, the fluidity decreases and the filling becomes difficult, and the strength after curing also decreases. Therefore, the mixing ratio of the magnetic powder to the adhesive is preferably 50 to 95% by weight.

The adhesive contained in the mixture is dispersed between the magnetic powders and apparently functions as a gap, so that the magnetic path can be a gapless closed magnetic path. This eliminates the need for gap adjustment that requires high dimensional accuracy, thereby reducing the manufacturing cost.
In addition, if there is a gap, the leakage magnetic flux density around the gap becomes high and may cause noise, but this also disappears.
The gap can be easily adjusted by changing the mixing ratio of the magnetic powder and the adhesive.
Further, the adjustment of the inductance characteristics can be easily performed by changing the length of the magnetic path occupied by the magnetic core material 3 having a high magnetic permeability and mainly responsible for the inductance characteristics in the closed magnetic path.

The magnetic core material 3 is formed of a ferrite material which is a polycrystalline sintered body in which oxides such as Mn, Ni and Zn are combined, and a plurality of magnetic materials are filled by filling a fine powder of the ferrite material into a mold. The core material 3 is integrally pressure-molded, and the pressure-molded body is then fired at a high temperature.
Since the magnetic core material 3 can be easily manufactured by such press working, the component cost can be reduced.
As the ferrite material, NiZn or MnZn having a high magnetic permeability is used.

About the combination of the magnetic core part 2 and the magnetic body core material 3, it is desirable that both saturation magnetic flux densities are high and become a substantially equal value. This is because if one saturation magnetic flux density is low, only that one is first magnetically saturated, and the overall DC superposition characteristics are deteriorated.
Therefore, in the inductor of the present invention, a core material having a low magnetic permeability is disposed on the inner periphery of the coil 1 where a large amount of magnetic flux is collected, and a core material having a high magnetic permeability is disposed on the outer periphery of the coil 1 having a small magnetic flux. The density is made uniform.

As shown in FIG. 3A, the shape of the magnetic core 2 and the magnetic core material 3 is such that the magnetic core 2 integrated with the coil 1 is curved into an arc having a central angle of 90 °, and both ends thereof are L-shaped in cross section. The plate-like magnetic core material 3 may be joined.
Alternatively, as shown in FIG. 3B, the magnetic core 2 integrated with the coil 1 may be curved in a semicircular shape, and both ends thereof may be joined to a plate-like magnetic core material 3 having an I-shaped cross section. .

FIG. 4 shows a schematic diagram of an inductor manufacturing process embodying the present invention.
In FIG. 4, first, as shown in (1), an air core coil 1 is produced by winding a work bobbin. In this manufacturing method, since the coil can be wound first, the assembly becomes easier as compared with the case where the coil is wound later.

Next, as shown in (2), a paste-like mixture obtained by quantitatively weighing and mixing and kneading the magnetic powder and adhesive is injected and injected into the coil 1, and an uncured magnetic core portion 2 is placed in the coil 1. Form.
The injection injection is performed in a large amount so that the surplus portion overflows from both ends of the coil 1.

Next, as shown in (3), the magnetic core 2 integrated with the coil 1 is fitted between the upper and lower horizontal plates of the magnetic core material 3. At this time, excess portions overflowing from both ends of the magnetic core portion 2 are sandwiched between the upper and lower horizontal plates and pushed out in the lateral direction.
As a result, the dimensional mismatch is automatically adjusted, so that the material dimensional accuracy and assembly accuracy are relaxed, and the manufacturing cost is reduced.
Moreover, since the adhesive agent is contained in the paste-like mixture, the labor of assembling with the adhesive agent can be saved.

Next, as shown in (4), after removing the excess portions overflowing from both ends of the magnetic core portion 2, the magnetic core portion 2 is heated and cured, so that the magnetic core portion 2 integrated with the coil 1 is formed into the magnetic core material 3. Stick.
This completes the inductor.

It is a disassembled perspective view of the inductor which implemented this invention. It is sectional drawing of the inductor which implemented this invention. It is a modification of the inductor which implemented this invention. It is the schematic of the manufacturing process of the inductor which implemented this invention.

Explanation of symbols

1 Coil 11 Lead Terminal 12 Coil Terminal 2 Magnetic Core 3 Magnetic Core Material

Claims (7)

Fill the inner circumference of the coil with a mixture of magnetic powder and adhesive to form the magnetic core,
An inductor characterized by forming a closed magnetic circuit type magnetic circuit in which a loop is formed by a core without a gap by combining the magnetic core portion and a magnetic core material disposed on the outer periphery of the coil.   The core is formed by filling a coil of a mixture of magnetic powder and adhesive into a coil in a fluid state before curing, and bonding both ends of the coil to a magnetic core material and curing. The inductor according to claim 1.   2. The inductor according to claim 1, wherein the magnetic powder is at least one of Fe-Si, Fe-Si-Cr, Sendust, Permalloy, Carbonyl iron, or a mixture thereof.   2. The inductor according to claim 1, wherein the adhesive is at least one of an epoxy resin, a phenol resin, and a polyamide resin.   2. The inductor according to claim 1, wherein a mixing ratio of the magnetic substance powder to the adhesive is 50 to 95% by weight.   The inductor according to claim 1, wherein the magnetic core material is ferrite. Creating an air core coil;
Filling the air core coil with a mixture of magnetic powder and adhesive to form an uncured magnetic core;
Joining both ends of the magnetic core to the magnetic core material in an uncured state;
Curing the magnetic core bonded to the magnetic core material;
An inductor manufacturing method characterized by passing through

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