JP4900804B2 - Dust core - Google Patents

Description

  The present invention relates to a powder magnetic core used for a power factor collection (PFC) for suppressing high frequency, a normal mode choke, a power choke, and a power circuit reactor for driving a high output electric motor of a hybrid vehicle. Is.

Three types of magnetic cores are mainly used as power circuit magnetic cores. In the region of several tens of kHz or less, silicon steel plates, amorphous soft magnetic strips, microcrystalline soft magnetic strips, etc. are mainly used as magnetic core materials. These magnetic core materials are mainly composed of iron, and have an advantage that the saturation magnetic flux density Bs and the relative permeability μr are large. However, silicon steel plates have the disadvantage that high frequency magnetic core loss is large, and amorphous soft magnetic strips and microcrystalline soft magnetic strips have a magnetic core shape that is constrained by a wound core shape or a laminated core shape, which will be described later. It has a drawback that it is difficult to form into various shapes like ferrite.
In the region of several tens of kHz or more, ferrite cores typified by Mn—Zn and Ni—Zn are widely used. Since this ferrite core has a small high-frequency core loss and is relatively easy to mold, it has the feature that various shapes can be mass-produced. However, the saturation magnetic flux density Bs is only about one-third to one-half that of the aforementioned silicon steel plate, amorphous soft magnetic strip, and microcrystalline soft magnetic strip. There is a disadvantage that the cross-sectional area becomes large.

  There is a dust core as a magnetic core for a reactor used in a region from several kHz to several hundred kHz. The dust core is formed by subjecting the surface of the magnetic powder to insulation treatment and then processing, and generation of eddy current loss is suppressed by the insulation treatment. For this reason, the high frequency magnetic core loss of the dust core is small compared to the silicon steel sheet.

  In particular, a hybrid vehicle that has begun to spread rapidly has a high-output electric motor, and a power source circuit that drives the motor needs a reactor that can withstand a high voltage and a large current. There is a strong demand for miniaturization, low noise, low loss, and durability for this reactor. The characteristics of the magnetic core material used for the reactor include a high saturation magnetic flux density Bs, an appropriate range of relative permeability μr, and a high machine. It is required that the volume deformation rate when magnetized is low in order to reduce the mechanical strength and noise.

  As a reactor core for large current, there is one using the above-mentioned dust core. Soft magnetic strips such as silicon steel plates, amorphous soft magnetic strips, and microcrystalline soft magnetic strips have a magnetic permeability of about 500 to 5000, but a dust core has a magnetic core of about 10 to 200. The gap can be reduced compared to the strip. In this case, since the fringing magnetic flux is smaller than that of the soft magnetic strip, the eddy current generated in the coil can be suppressed. The reactor loss can be reduced by using a dust core having a small magnetic core loss. In addition, since the dust core is not easily saturated, there is an advantage that a high magnetic permeability can be obtained at a large current.

Patent documents 1 and patent documents 2 are indicated as a dust core which shows low noise. In Patent Document 1, noise is suppressed by improving hardness and strength. Moreover, in patent document 2, the noise is suppressed by controlling the particle size of the powder which comprises a powder magnetic core. Patent Document 3 discloses that a powder magnetic core is obtained by mixing an amorphous alloy powder and a soft magnetic powder.
JP-A-6-176914 JP 2006-147959 A JP 2006-176817 A

However, in the mixed powder using the amorphous alloy powder and the soft magnetic powder, the magnetic characteristics greatly depend on what kind of soft magnetic powder is used. Furthermore, for example, when a dust core is used as the magnetic core of the high current reactor, it is difficult to obtain a high mechanical strength, low noise, and excellent magnetic characteristics. This is because the noise generated when the reactor is driven, the mechanical strength to obtain the durability that does not deteriorate the characteristics even if it is driven for a long time, the alloy composition of the powder, the particle size, the type and amount of the insulating material to be coated, and the pressure This is because it largely depends on the porosity of the powder and the like and often has a trade-off relationship.
An object of the present invention is to solve these problems of dust cores, and to provide a dust core having higher mechanical strength and lower noise than the conventional ones and having good magnetic properties.

The present invention relates to at least one granular amorphous alloy powder selected from the group consisting of Fe-Si-B, Fe-Si-B-Cu-Nb, Fe-Zr-B, and Co-Fe-Si-B. And a granular pure Fe powder of more than 99.5% by mass of Fe is mixed , the average particle diameter of the amorphous alloy powder and the pure Fe powder differ by 20 μm or more, and the weight ratio with respect to the whole amorphous alloy powder is 20 It is in a range of ˜40 %, has a resistivity of 1 × 10 ⁴ Ωm or more, and has a magnetic permeability at a magnetic field of 10,000 A / m higher than that of a compact powder of pure Fe powder .

  The present invention mixes amorphous alloy powder and pure Fe powder with more than 99.5% Fe to form a powder magnetic core, thereby providing a powder magnetic core with high mechanical strength, low noise, and excellent magnetic properties. Can be obtained. In addition, by setting the weight ratio of pure Fe powder, the aspect ratio of amorphous alloy powder and pure Fe powder, and the average particle size of both powders to predetermined values, mechanical strength, low noise, and magnetic properties are further improved. An excellent powder magnetic core can be obtained. These dust cores suppress noise when operated in an alternating magnetic field, and their characteristics are unlikely to deteriorate even if they are driven for a long time.

  In the present invention, an amorphous alloy powder having an excellent soft magnetic property and a sufficient space factor can be obtained by using a pure Fe powder having a mass fraction of 50% or more and a soft Fe powder of more than 99.5% Fe. By mixing 10% or more in mass fraction, the resistivity is greatly improved, and the coercive force is 5000 A / m to 15000 A / m, and the permeability is higher than the dust core of pure Fe powder alone. An excellent powder magnetic core was obtained. In addition to the amorphous alloy powder and the pure Fe powder, it is preferable to make an existing inorganic insulating binder layer so as to exist uniformly between the powders.

The amorphous alloy powder is selected from Fe-Si-B, Fe-Si-B-Cu-Nb, Fe-Zr-B, and Co-Fe-Si-B. Fe may be substituted with at least one element selected from Ni, Cr, Mo, Zr, Hf, or Mn. In particular, Mn has an effect of slightly improving B 2 _S when added in a small amount. These substitution elements are preferably 5 atomic% or less. C improves the squareness of the material and B _S and can reduce the size of the magnetic core, and also has the effect of reducing the noise. C is preferably added in the range of 5 atomic% or less.
In addition, as an inevitable impurity, at least one element selected from S, P, Sn, Cu, Al, and Ti may be contained in a range of 0.50% or less.

  In the soft magnetic powder constituting the dust core, either the amorphous alloy powder or the pure Fe powder may be spherical, and the other irregular flat shape. Pure Fe powder is more easily plastically deformed than amorphous alloy powder. When these mixed powders are compression molded, the amorphous alloy powder moves between pure Fe powders without greatly plastic deformation, and the space factor increases. Thereby, the mechanical strength converted into the crushing strength can be increased as the ratio of the pure Fe powder to the whole is increased.

  In the mixed powder, it is preferable to change the average particle diameter of the amorphous alloy powder and the pure Fe powder by 20 μm or more. Pure Fe powder enters between the amorphous alloy powders, increasing the space factor and improving the mechanical strength.

  As a method of reducing the volume deformation rate when the magnetization of the powder magnetic core is saturated, ceramic binders and insulating materials such as alumina, silica, magnesia, kaolin, etc. are used as a coating agent between soft magnetic powders. May be blended in. Further, in order to reduce the volume deformation rate when the magnetization of the powder magnetic core is saturated, an organic solution such as an epoxy resin, an acrylic resin, a phenol resin, a silicon resin, or a polyamide resin is added to the powder magnetic core of the present invention, Alternatively, it is also effective to impregnate an inorganic solution such as water glass, colloidal silica, colloidal alumina, and then cure.

  When the dust core of the present invention is used as a reactor magnetic core, the magnetic core vibration during operation is reduced, so that noise can be sufficiently suppressed, and an unprecedented high performance reactor can be obtained. In addition, since the dust core used here has high mechanical strength, the characteristics hardly deteriorate even if the reactor is driven for a long time. In order to prevent the fringing magnetic flux from affecting the external circuit, it is preferable to design a shape in which the periphery of the ceramic plate used as a nonmagnetic gap for adjusting the relative permeability μr is covered with a coil.

EXAMPLES The present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
Example 1
Using the water atomization method, 99.9% pure Fe powder was produced. This pure Fe powder is a granular powder having an average flow diameter of 90 μm. Further, an amorphous alloy powder (product name Kuwatet) manufactured by ATMIX manufactured by the Swap method was used as the amorphous alloy powder. This amorphous alloy powder is a granular powder having an alloy composition of atomic% and represented by (Fe _0.97 Cr _0.03 ) ₇₆ (Si _0.5 B _0.5 ) ₂₂ C 2 and an average flow diameter of 65 μm. These two types of soft magnetic powders were mixed at different mass ratios. Moreover, 0.5 mass% of kaolin, 1.5 mass% of amorphous silica, 1.5 mass% of acrylic emulsion, and 0.4 mass% of zinc stearate were added to each mixed powder.
Each of the mixed powders was molded at a molding pressure of 20 ton / cm ² , and then subjected to a heat treatment at a holding temperature of 470 ° C. for 1 hour in an atmosphere in nitrogen to produce a green compact for the dust core of the present invention. Depending on the mixing ratio of pure Fe powder and amorphous alloy powder, DC superposition characteristics measured by changing the DC current while changing the DC current under the conditions of compaction characteristics, 100 kHz, AC voltage 1 V, AC B under the conditions of 50 kHz, 50 mT The influence of the core loss when measured with a -H analyzer and the resistivity measured at a voltage of 50 V by the two-terminal method were investigated.
FIG. 1 shows the relationship between the mixing ratio of the amorphous alloy powder and the space factor. Even when the mixing ratio of the amorphous alloy powder is 50%, the space factor is almost equivalent to a dust core made of pure Fe powder alone. In the dust core, the space factor of the soft magnetic powder and the mechanical strength are almost proportional. When the mechanical strength is high, the amount of deformation of the dust core due to magnetostriction is reduced, leading to suppression of noise due to magnetostrictive vibration.
FIG. 2 shows the relationship between coercivity and initial permeability when the mixing ratio of amorphous alloy powder is changed. A powder magnetic core with a mixing ratio of pure Fe powder of 60% and 80% (a mixing ratio of amorphous alloy powder of 40% and 20%) has a coercive force H between 5000 and 15000 A / m. The initial permeability is higher than that of a powder magnetic core made of a simple substance. In particular, a reactor for HEV requires excellent direct current superposition characteristics, and the dust core of the present invention having a mixing ratio of amorphous alloy powder of 10 to 50% is useful.
FIG. 3 shows the relationship between the mixing ratio of the amorphous alloy powder and the core loss. As the mixing ratio of the amorphous alloy powder increases, the core loss decreases.
FIG. 4 shows the relationship between the mixing ratio of the amorphous alloy powder and the resistivity. When the mixing ratio of the amorphous alloy powder exceeds 10%, the resistivity is rapidly improved. In particular, when the mixing ratio of the amorphous alloy powder is 15% or more, the resistivity ρv is 1 × 10 ³ Ωm, and when it is 20% or more, the resistivity ρv is 1 × 10 ⁴ Ωm.
For this reason, it is useful for power factor correction (PFC) for suppressing high frequency, a normal mode choke, a power choke, and a reactor magnetic core used in a power supply circuit that drives a high output electric motor of a hybrid vehicle.

It is a figure which shows the relationship between the mixing ratio of the amorphous alloy powder of a powder magnetic core, and a space factor. It is a figure which shows the relationship between the mixing ratio of the amorphous alloy powder of a powder magnetic core, and direct current | flow superimposition characteristic. It is a figure which shows the relationship between the mixing ratio of the amorphous alloy powder of a powder magnetic core, and a core loss. It is a figure which shows the relationship between the mixing ratio of the amorphous alloy powder of a powder magnetic core, and resistivity.

Claims (1)

At least one granular amorphous alloy powder selected from the group consisting of Fe-Si-B, Fe-Si-B-Cu-Nb, Fe-Zr-B, and Co-Fe-Si-B, and 99.5 Particulate pure Fe powder with a mass% exceeding Fe is mixed , the average particle diameter of the amorphous alloy powder and the pure Fe powder is different by 20 μm or more, and the weight ratio of the amorphous alloy powder to the whole is 20 to 40%. A dust core having a range, a resistivity of 1 × 10 ⁴ Ωm or more, and a magnetic permeability at a magnetic field of 10000 A / m higher than that of a pure powder of pure Fe powder .

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