JP2000309801A - Dust core and coil - Google Patents

Abstract

(57) [Problem] To provide an inexpensive dust core having high radial compression strength and excellent DC superimposition characteristics. SOLUTION: 1.0 to 10.0% by weight Si, 0.1 to 5.0% by weight.
A dust core in which 5.0 to 5.0 wt% of atomized powder is mixed with a pulverized alloy obtained by mechanically pulverizing an alloy composition of 0 wt% Mn, 0.05 to 5.0 wt% V, and the balance Fe.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dust core used for a choke coil or the like.

[0002]

2. Description of the Related Art Soft magnetic ferrite cores and dust cores are used as choke coils used at high frequencies. Among them, the soft magnetic ferrite core has a disadvantage that the saturation magnetic flux density is small. On the contrary,
A dust core manufactured by molding a ferromagnetic metal powder has a higher saturation magnetic flux density than a soft magnetic ferrite core, and thus has an advantage of being excellent in DC superposition.

Further, in response to recent demands for downsizing of electronic components accompanying downsizing of electronic devices, operating currents have been increasingly increased. Along with this, there is a strong demand for powder magnetic cores to be used with improved magnetic permeability in high magnetic fields.

Generally, in order to improve the DC superposition characteristics of a coil, it is necessary to select a magnetic core having high saturation magnetization, that is, a magnetic core which does not become magnetically saturated at a high magnetic field.

Therefore, a material having a necessarily high saturation magnetization is indispensable. In addition, when the material is constant, in order to obtain high saturation magnetization, the powder magnetic core must be molded at a high molding pressure to increase the filling factor of the ferromagnetic metal powder.

[0006]

However, when molding a high-pressure powder core at a high molding pressure, there are problems such as an increase in manufacturing cost due to an expensive mold and a shortened life of the mold. There is.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a dust core having high strength and excellent DC superposition characteristics using a ferromagnetic metal powder having a high saturation magnetization and a low coercive force in view of the above problems. And to provide an inexpensive coil using the same.

[0008]

Means for Solving the Problems Accordingly, the present inventors have:
As a result of studying the above-mentioned problems, a powder magnetic core alloy composition capable of obtaining excellent direct current superimposition characteristics has been proposed (Japanese Patent Application No. Hei 11 (1999)).
-30288). Furthermore, as a result of continuing the investigation, it was found that by mixing the atomized powder with the pulverized alloy powder, a high filling rate was obtained even at a low molding pressure, and a dust core having high strength and excellent DC superimposition characteristics was obtained. I came to find it.

In the process of finding, the powder shape of the pulverized alloy powder has a shape close to a scale, and the powder filling property and the fluidity are poor. There was a problem that. Also,
Even when an attempt was made to obtain high strength, there was a problem that the amount of the binder had to be increased.

[0010] On the other hand, the atomized powder has a problem that it has a low magnetic permeability as compared with a dust core made of a relatively coarse alloy powder because the powder particles are fine. Also, when the particle size of the atomized powder is increased,
Generally, it is difficult to use a coarse atomized powder as a soft magnetic material because the cooling time becomes longer, the powder is oxidized, and the soft magnetic properties deteriorate.

Therefore, the present inventors have found that by mixing the pulverized alloy powder and the atomized powder, a powder core having a high filling rate even at a low molding pressure, a high strength, and excellent DC superimposition characteristics can be obtained. I found out.

That is, according to the present invention, in a dust core obtained by compression-molding a powder obtained by mixing a ferromagnetic metal powder and a binder, the ferromagnetic metal powder contains 1.0 to 10.0% by weight of S
i, 0.1 to 5.0% by weight Mn, 0.05 to 5.0% by weight
V, an alloy powder obtained by mechanically pulverizing the alloy composition of Fe, and an atomized powder of the same composition system obtained by atomizing the alloy pulverized powder to 5.0.
It is a dust core mixed with ５０50.0 wt%.

[0013] The present invention also provides the dust core, wherein the powder size of the pulverized alloy powder is 250 µm or less and the powder particle size of the atomized powder is 50 µm or less.

The present invention also provides the dust core, wherein the core loss (Pcv) of the dust core is 2000 (100 kHz-1000 G) or less.

The present invention also provides a coil formed by winding a conductive wire around the dust core.

[0016]

Embodiments of the present invention will be described below.

The composition of the starting material is 1.0 to 10.0% by weight.
Si, 0.1 to 5.0% by weight Mn, 0.05 to 5.0% by weight
V, the balance being Fe. Further, the alloy pulverized powder is obtained by mechanically pulverizing an ingot produced by high-frequency melting, and the atomized powder is produced by a water atomizing method, and the composition is preferably uniform.

The pulverized metal powder is subjected to a heat treatment if necessary. Next, after fine atomized powder is mixed with the pulverized alloy powder, a binder is mixed, and the mixture is pressed into a desired shape using a mold.

At this time, the atomized powder is arranged in the gaps between the alloy pulverized powder particles while forming a particle group, and the filling rate is improved. Next, the compact is subjected to a strain relief heat treatment as required, whereby a dust core according to the embodiment of the present invention is manufactured.

The reason for setting the mixing ratio of the atomized powder to the pulverized alloy powder to 5.0 to 50.0 wt% is as follows.
If the content is less than 5.0 wt%, no improvement in the filling rate is observed and the characteristics are equivalent to those of the alloy pulverized powder alone.
%, The superimposition characteristics deteriorate.

Similarly, when the particle size of the alloy pulverized powder is 2
The reason for setting the particle diameter to 50 μm or less is that if the particle diameter is 250 μm or more, eddy current loss increases and good characteristics cannot be obtained.

In the present invention, the particle size of the atomized powder mixed with the alloy ground powder is set to 50.0 μm or less because the atomized powder is formed in the gap between the alloy ground powder particles when the particle size is 50.0 μm or more. Is not arranged efficiently, and the filling rate of the ferromagnetic metal powder into the dust core is not improved.

The reason why the core loss of the dust core is specified is that if the loss is 2000 or more, good DC superposition characteristics cannot be obtained.

[0024]

The present invention will be described below with reference to examples.

Example 1 6.5% Si, 1.0% Mn,
An alloy ingot having a composition of 0.5% V and the balance of Fe was produced by high frequency melting. This ingot is a jaw crusher,
Pulverize using a roll mill, and pulverize this alloy powder with Ar
After holding at 1000 ° C. for 2 hours in an atmosphere, the furnace was cooled as it was.

Next, the alloy pulverized powder is taken out of the furnace,
1000 μm to 750 μm, 750 μm to 500 μm,
500 μm to 250 μm, 250 μm to 150 μm, 1
After sieving into five types of 50 μm or less, the alloy pulverized powder and the atomized powder of 50 μm or less were mixed using a V-type mixer so that the weight ratio was 80:20.

[0027] A silicone resin is added to the mixed powder in an amount of 2.0 w.
Then, the mixture was molded at 10 (ton / cm ² ) at room temperature using a mold having an outer diameter of 20 mm and an inner diameter of 10 mm to obtain a toroidal dust core.

Next, this dust core was heat-treated in air at 170 ° C. for 2 hours to cure the binder. next,
For this dust core, in order to remove distortion during powder molding,
Heat treatment was performed in hydrogen at 600 ° C. for 2 hours. Next, a winding was applied to the powder magnetic core, and AC magnetic characteristics were measured with SY-8232 manufactured by Iwasaki Tsushin Co., Ltd. under the conditions of 100 kHz to 1000 G.

Table 1 shows the core loss of the dust core among the measurement results.

Next, the DC superposition characteristics were measured with a 4284A precision meter made by HP.

Of the measurement results, the applied magnetic field 40 (O
The magnetic permeability μ40 in e) was obtained by calculation, and the results are also shown in Table 1.

[0032]

[Table 1]

As is clear from Table 1, in the dust core according to the first embodiment of the present invention, the core loss is large in the dust core using the alloy pulverized powder having a particle diameter of 250 μm or more, and It can be seen that the magnetic permeability μ40 has decreased.

That is, it was found that good direct current superposition characteristics were obtained when the particle size of the pulverized alloy powder was 250 μm or less.

(Example 2) The alloy pulverized powder produced in Example 1 was classified to obtain an alloy pulverized powder having a size of 150 µm or less.
Next, 6.5% Si, 1.0% M
n, 0.5% V, with the balance being Fe composition 150 μm or less, 100 μm or less, 75 μm or less, 50 μm or less, 2
An atomized powder having a particle diameter of 2 μm or less was produced. Next, the alloy pulverized powder and the atomized powder were mixed using a V-type mixer such that the weight ratio was 80:20.

From each of these mixed powders, a toroidal dust core was prepared in the same manner as in Example 1, and the volume filling ratio of the mixed powder with respect to this dust core was measured. Next, a winding was applied to the dust core, and a DC superposition characteristic was measured with a 4284A precision meter made by HP.

Table 2 shows the results obtained by calculating the volume filling ratio of the mixed powder and the magnetic permeability μ40 at an applied magnetic field of 40 (Oe).

[0038]

[Table 2]

From Table 2, it can be seen that mixing an atomized powder having a size of 50 μm or less improves the volume filling ratio of the mixed powder and obtains a high magnetic permeability.

That is, it was found that good direct current superposition characteristics can be obtained when the atomized powder to be mixed has a powder particle size of 50 μm or less.

(Embodiment 3) 150 μm fabricated in Embodiment 2
m and an atomized powder of 50 μm or less, and the ratio of the alloy crushed powder to the atomized powder is 100: 0, 97: 3, 95: 5, 9 by weight ratio, respectively.
0:10, 80:20, 70:30, 60:40, 5
0:50, 40:60, 30:70, 20:80, 1
The mixture was mixed so as to be 0:90 and 0: 100, and stirred and mixed for 30 minutes using a V-type mixer.

Next, a dust core was prepared from these mixed powders in the same manner as in Examples 1 and 2, and the volume filling ratio and DC superimposition characteristics of the mixed powders were measured in the same manner as in Example 2. .

FIG. 1 shows the calculation results of the volume filling ratio of the mixed powder and the magnetic permeability μ40 at an applied magnetic field of 40 (Oe).

As shown in FIG. 1, the atomized powder was 5.0 wt%.
By mixing as described above, the volume filling ratio and the magnetic permeability μ40 of the mixed powder are improved as compared with the dust core composed of the crushed alloy powder alone and the atomized powder alone. However, when the mixing ratio (weight ratio) of the atomized powder exceeds 50 wt%, the volume filling rate and the magnetic permeability μ40 of the mixed powder are lower than that of the crushed alloy powder alone.

That is, the mixing ratio (weight ratio) of the atomized powder
It was found that a good direct current superposition characteristic was obtained when the content was 5.0 wt% to 50.0 wt%.

Example 4 150 μm manufactured in Example 3
m and an atomized powder having a particle size of 50 μm or less were mixed so that the ratio of the powdered alloy and the atomized powder was 80:20 by weight, and the mixture was stirred for 30 minutes using a V-type mixer.

The mixed powder was charged with 3.0 w of silicone resin.
%, and using a mold having an outer diameter of 20 mm and an inner diameter of 10 mm, at room temperature, 2.0, 3.5, 5.0, 7.5, 10.0 (t
on / cm ² ) to obtain a toroidal dust core. The dust core was heat-treated at 170 ° C. for 2 hours in the air to cure the binder.

Next, this powder magnetic core was subjected to a heat treatment in hydrogen at 600 ° C. for 2 hours in order to remove distortion during powder compaction. Show.

As a comparative example, a dust core made of only the alloy pulverized powder was prepared in the same manner, and the same measurement as above was performed. The result is shown in FIG. In the comparative examples, 2.
The dust core pressed at 0 ton / cm ² had extremely low strength, and was broken when taken out of the mold, making measurement impossible.

From FIG. 2, it can be seen that the radial crushing strength of the dust core is higher in the present example than in the comparative example. In addition, it can be seen that the moldability is particularly good at low pressure.

As described above, based on the results of Examples 1 to 4, the atomized powder having a particle diameter of 50 μm or less was used in an amount of 5.0 to 50.0 watts while the particle diameter of the alloy pulverized powder was 250 μm or less.
By mixing t%, a dust core having a high powder filling rate and a high magnetic permeability can be obtained. Furthermore, it turns out that low pressure molding is attained.

[0052]

As described above, according to the present invention,
By mixing the pulverized alloy powder and the atomized powder, it is possible to provide a dust core in which the filling ratio of these ferromagnetic metal powders is increased. Therefore, a dust core having excellent radial crushing strength and excellent DC superimposition characteristics even at low pressure molding can be obtained, so that a dust core and a coil using the same can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a diagram showing a mixing ratio of an atomized powder and a volume filling ratio of a mixed powder with respect to an alloy pulverized powder of a dust core in Example 3 of the present invention, and a calculation result of a magnetic permeability μ40 at an applied magnetic field of 40 (Oe). FIG.

FIG. 2 is a view showing the relationship between the molding pressure and the radial crushing strength of the dust cores of Example and Comparative Example in Example 4 of the present invention.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H01F 1/20 H01F 1/24 17/06 1/32 F term (reference) 4K018 AA26 BA16 BB04 BC01 BC12 BD01 CA11 FA09 KA44 5E041 AA11 AA19 AC05 BB06 CA01 HB00 HB05 HB07 NN01 NN06 NN15 5E070 AA01 AA20 AB03 AB10 BA14 BB01

Claims (4)

[Claims] 1. A dust core obtained by compression molding a powder obtained by mixing a ferromagnetic metal powder and a binder, wherein the ferromagnetic metal powder comprises 1.0 to 10.0% by weight of Si, 0.1% by weight.
To 5.0% by weight Mn, 0.05 to 5.0% by weight V, balance F
(e) mechanically pulverizing the alloy composition of (e) and an atomized powder of the same composition obtained by atomizing the alloy pulverized powder by 5.0 to 50.0 w.
A dust core characterized by being mixed with t%. 2. The powder size of the pulverized alloy powder is 250 μm.
2. The dust core according to claim 1, wherein the particle diameter of the atomized powder is 50 μm or less. 3. The core loss (Pcv) of the dust core is 2
3. The dust core according to claim 1, wherein the dust core is less than 000 (100 kHz-1000 G). 4. A coil formed by winding a conductive wire around the dust core according to any one of claims 1 to 3.