KR100305328B1 - Manufacturing method of mold release dust core - Google Patents

Abstract

The present invention relates to a method for manufacturing an E-shaped soft magnetic metal powder core used in an inductor coil of a secondary DC circuit of a switching mode power supply (SMPS) to suppress electronic noise. Sender alloy powder consisting of ˜13% Si and 3-9% Al, and residual amount of Fe, alloy powder consisting of 45-55% Ni and residual amount of Fe (Permalloy) powder, Mo 2%, Ni 80%, balance Fe It is configured to prepare any one of the metal powder from the Molley Permalloy powder (MPP), and to insulate the prepared metal powder, to form a high pressure, and then to heat treatment in a reducing atmosphere.

According to the present invention, a soft magnetic E-type core without an air gap in which an air gap (air gap) is uniformly distributed can be manufactured. According to such an E-type core, a large current DC overlapping characteristic is remarkably improved. In addition, it is possible to reduce the winding cost by taking advantage of the winding automation using bobbins, and in the case of ferrite cores, surface machining of air gaps after molding and sintering could not be avoided, thus eliminating the cost and cost. We can save.

Description

Manufacturing method of this type sendust powder core

The present invention relates to an E-shaped core for suppressing electronic noise or used in an inductor coil of a secondary DC circuit of a switching mode power supply (SMPS), and more particularly, to disperse fine pores between powders. The present invention relates to a method of manufacturing an E-type core made of a soft magnetic metal powder which can be automated by winding and the surface processing process can be omitted.

Conventional soft magnetic core materials used in the field include ferrite cores (Ni-Zn ferrite, Mn-Zn ferrite), metal powder cores such as pure iron, and the like.

In addition, when classified into a core shape, various shapes of cores such as a toroidal core, an EI core, an EE core, an EC core, a UU core, and a drum core are used.

Among them, the toroidal core has the advantage that the magnetic path is composed of a closed circuit, which has a low leakage magnetic flux and a large inductance (L) can be obtained compared to the number of coil windings. Do.

On the other hand, the E-shaped core uses a separate bobbin for winding, which has the advantage of automating the winding, which significantly lowers the winding cost, but the relatively complicated shape requires precise control of the molding and sintering process during core manufacturing. do.

Cores used in smooth choke coils for switching power supplies (SMPS) usually overlap large DC currents when overlapping. These superimposition of DC currents reduces the magnetic permeability of soft magnetic cores and sometimes causes magnetic saturation, thus losing their function as a magnetic body. It is possible to select materials with the lowest possible permeability reductions when employing soft magnetic cores, and design specifications to operate at conditions below the magnetic saturation region.

Ferrite cores, which are oxides, are inexpensive, have a low core loss at high frequencies because they are easy to manufacture complex shapes of cores and have high self-resistance.

However, in order to be used as a smooth chalk, the high current characteristics should be good, but when the E-type ferrite core is manufactured in the form of no air gap, there is a problem in that the permeability is sharply reduced at the high current, so that the smooth chalk flowing the high current cannot be used.

In order to solve this problem, as shown in FIG. 1, in the case of an E-shaped ferrite core 10, an air gap 1 is forcibly formed to be designed to satisfy a large current characteristic.

When the air gap 1 is formed in the core, the magnetic resistance increases in the magnetic circuit, so that the magnetic permeability is lowered. However, under a large current condition, a leakage magnetic flux may occur to prevent the core from saturation and allow a large current to flow.

However, when forming an air gap in an E-type ferrite core and using it as a choke core, the winding bobbin can be used to automate the winding to reduce the winding cost, but the size of the air gap is as small as 100 to 200 μ. Since it is difficult to manufacture a mold for molding, there is a problem of separately surface processing to maintain final precision, and core loss is also increased due to leakage flux near the air gap.

Moreover, under the recent situation where the use condition of smooth choke coil requires a large current DC current, it is limited to control the air gap of ferrite core, and ferrite is harmful to the temperature stability of choke coil due to the large permeability change with temperature. In addition, when the critical current value is exceeded, the ferrite core has a problem that the rigidity according to the use condition is required because the permeability is rapidly lowered to almost zero.

Accordingly, the present invention has been made to solve the problem of a ferrite core with a forced air gap as described above, it is possible to remove the air gap is easy to manufacture the mold for molding, the core loss is small and the permeability decrease is moderate It is an object of the present invention to provide a method for producing an E-type soft magnetic metal powder core.

1 is a view showing the shape of an air gap E-I core used in the prior art,

2 is a view showing an E-type core made of a metal powder according to the present invention;

Figure 3 is a view showing the large current DC overlapping characteristics of the E-type core made of a soft magnetic metal powder of the present invention compared with the conventional example.

<Explanation of symbols for main parts of drawing>

1: Ferrite core 10: Air gap 20: Metal powder core

Method for producing an E-type soft magnetic metal powder core of the present invention for achieving the above object, by weight%, to prepare a sender alloy powder consisting of 7 to 13% Si, 3 to 9% Al, and the remaining amount of Fe Steps; Insulating coating the prepared sendust alloy powder with a mixed ceramic; High pressure molding the E-type core at a molding pressure of 13-18 ton / cm ³ by adding a lubricant to the insulation coated sendust alloy powder; Formed core is characterized in that it comprises a step of heat-treating in nitrogen, hydrogen or a mixed atmosphere of nitrogen and hydrogen for 0.5-2 hours at a temperature of 600-800 ℃.

Hereinafter, the present invention will be described in detail with reference to the preferred embodiments.

According to the present invention, when the core is manufactured from a metal powder such as a center dust, the permeability decreases as the DC value is increased, and the permeability change according to the temperature is very low, and the Curie temperature (ferromagnetic → paramagnetic transformation temperature) Curie Point) is also very high compared to ferrite, and is made with the focus on producing a relatively stable soft magnetic core.

In the present invention, first, the weight percent of the composition having a high permeability characteristics, the sender alloy powder composed of 7 to 13% Si, 3 to 9% Al, and the remaining amount of Fe, and 45 to 55% of ductility and high permeability An alloy (Permalloy) powder consisting of Ni and a residual amount of Fe, and a sender alloy powder consisting of 2% Mo, 80% Ni and the balance Fe are prepared.

The alloy powder is prepared by powder preparation by water spraying or gas spraying.

Subsequently, the prepared sender alloy powder was subjected to an insulation coating with an insulating material such as magnesium hydroxide (Mg (OH) ₂ ), kaolin, talc, and mixed glass of water glass, and 13 to 18 ton / E-type cores are high-pressure molded at a molding pressure of cm 2.

Molding is carried out using a Power Press in a die, where a lubricant is used to reduce the friction between the molding die and the compacted compacts and the friction between the powder particles.

Subsequently, in order to remove residual stress and strain, the molded E-core core was heat-treated in a water-reducing reducing atmosphere at a temperature of 600 to 800 ° C. for 0.5 to 2.0 hours in a continuous furnace to produce a soft magnetic E-type core. The heat treatment conditions are controlled in this respect.

E type cores prepared by heat treatment are impregnated with an epoxy resin to improve strength.

As shown in FIG. 2, the manufactured E-shaped core 20 does not have an air gap unlike a conventional ferrite core.

In this way, in the case of E type core made of a metal powder in which a fine air gap is dispersed between powders, an inductor having excellent high current DC overlapping characteristics can be made.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1

In this embodiment, after producing a sand dust powder consisting of Si: 9.7%, Al: 5.7%, the balance Fe by a method of water injection, magnesium hydroxide (Mg (OH) 2), kaolin, talc and water glass 2.0% mixed ceramics were added, followed by insulation coating, followed by the addition of 0.9% lubricant and a molding density of 5.8 g / cm 2 to form E cores, followed by heat treatment at 780 ° C. for 1 hour in a water-reducing atmosphere. Subsequently, it was impregnated with an epoxy resin to increase the strength to prepare a Permalloy E type core (Invention material 1). After winding 20 times of enameled copper wire using a manufactured E type core bobbin, 1V AC voltage of 100 Hz frequency was obtained. DC superposition characteristics were evaluated using a precision LCR meter. The results are shown in FIG.

Comparative example

In Comparative Example, E-type cores without air gaps were prepared using ferrite powder (Comparative Material 1), and E-type cores with air gaps were prepared (Comparative Material 2) as ferrite powder for comparison. After winding the enameled copper wire 20 times using bobbin for the manufactured E-type core, 1V AC voltage of 100 kHz was applied and DC overlapping characteristics were evaluated using a precision LCR meter, and the result is shown in FIG. 3. .

As can be seen from FIG. 3, the core (invention material 1) DC overlapping characteristics of the dust powder were good, and the ferrite core without air gap of the comparative material 1 had a low magnetization strength (H) of about 1 Oe. The degradation of the properties was observed, and the ferrite core with air gap of Comparative Material 2 was maintained to about 8 Oe to some extent, but at the higher magnetization strength (large current), the characteristics rapidly decreased. On the other hand, in Inventive Material 1, the characteristics are maintained up to about 70 Oe or more, and thus it is applicable to a large current.

Therefore, according to the present invention as described above, according to the soft magnetic E-type core made of a metal powder without air gap in which the air gap is uniformly distributed, the large current DC overlapping characteristics are notably improved, and windings using bobbins are used. By taking advantage of the automation, it is possible to reduce the winding cost, and in the case of ferrite core, the surface processing of the air gap could not be avoided after molding sintering, and thus, the surface processing process can be omitted, thereby saving labor and cost. .

Claims (1)

Preparing, in weight percent, a sendust alloy powder consisting of 7-13% Si and 3-9% Al and a residual amount of Fe, an alloy powder consisting of 45-55% Ni and a residual amount of Fe; Insulating coating the prepared sendust alloy powder with a mixed ceramic; High pressure molding the E-type core at a molding pressure of 13-18 ton / cm ³ by adding a lubricant to the insulating coated sendust alloy powder; A method for producing a mold sender powder core, characterized in that the prepared core comprising the step of heat-treating at a temperature of 600-800 ℃ for 0.5-2 hours in nitrogen, hydrogen or a mixed atmosphere of nitrogen and hydrogen.