JP2002075721A - Dust core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dust core having high magnetic flux density. SOLUTION: A dust core is formed of Fe-Co soft magnetic powder that contains 3 to 35(%) Co, so that the dust core can be more improved in density by pressure molding, and it has higher magnetic flux density than an iron powder core.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an improvement of a dust core.

[0002]

2. Description of the Related Art For example, a powder magnetic core obtained by press-molding a metal powder includes a magnetic core of an operating coil of an electromagnetic valve, a motor core,
Yoke, DC output side smoothing choke coil of switching power supply, AC input side normal mode noise filter core, power factor improvement active filter core,
Alternatively, it is used in various fields such as a magnetic core of a step-up and step-down coil of a DC-DC converter. Among these applications, the magnetic core of the operating coil of the solenoid valve, the motor yoke, and the like are particularly designed so as to obtain a high magnetic force (attraction force) capable of realizing miniaturization, improvement of operation speed, and increase of torque. High magnetic flux density is required. Conventionally, iron powder has been used as a dust core material requiring such a high magnetic flux density.However, in order to further improve the operating speed, a dust powder having a magnetic flux density superior to the iron powder core is used. A magnetic core is desired.

[0003]

By the way, generally, permendur (Fe-5) is used as a magnetic core material having a high magnetic flux density.
0Co or Fe-49Co-2V) is known. However, since permendur is a high-hardness material and has poor workability, even if the powder is molded under pressure, the compressibility at the time of molding is poor and a high-density dust core cannot be obtained. Therefore, a dust core having a high magnetic flux density inherent to the material cannot be manufactured, and characteristics higher than those of the iron powder core cannot be realized. Among the above two types of permendur, those containing 2% of vanadium (V) improved the workability and enabled rolling.However, even with such a composition, powder pressing was performed. Thus, a magnetic core having a high magnetic flux density cannot be obtained as a sufficient density.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a dust core having a high magnetic flux density.

[0005]

Means for Solving the Problems To achieve the above object, the gist of the dust core of the present invention is that Co is 3 (%)
The soft magnetic powder composed of Fe-Co-based particles having a mass ratio in the range of more than 35% and less than 35% is formed by pressure molding.

[0006]

According to the present invention, since the dust core is composed of the Fe-Co-based soft magnetic powder having a Co content of 3 to 35 (%), it is compacted at a high pressure. Therefore, a higher magnetic flux density can be obtained as compared with an iron powder core. The magnetic flux density of the Fe-Co soft magnetic material tends to increase as the amount of Co increases, and when the Co content is 3% or less, the magnetic flux density of the dust core becomes higher than that of the iron powder core. Cannot be density. On the other hand, if it is 35 (%) or more, the particles become hard and the molding density becomes low, so that a dust core having a high magnetic flux density cannot be obtained even if the original magnetic flux density of the material becomes high. In the present application, “(%)” such as content and amount added is a mass percentage unless otherwise specified.

[0007]

In another embodiment of the present invention, preferably, the soft magnetic powder has an average particle size of more than 30 (μm) and less than 110 (μm). In this case, since the average particle size of the magnetic powder is in an appropriate range, the density of the molded body can be further increased, so that a dust core having a higher magnetic flux density can be obtained.
When the average particle size is 30 (μm) or less, the average particle size is 110 (μm) due to pressure loss during pressurization for molding.
Above all, it is difficult to sufficiently increase the density of the molded article in any case due to the existence of large voids between the particles mainly during filling for molding. Further, in the present application, "average particle size" is, for example, 50 of the cumulative mass measured by a sieve
(%) Is the particle size.

Preferably, the soft magnetic powder comprises M
It contains at least one of n, Cu, Ni, Ti, Nb, Cr, Mo, Al, Si, and V in a mass ratio of 5 (%) or less in total. By doing so, the alloy to which these elements are added alone or in combination increases the electrical resistivity,
The electric resistivity of the magnetic core is increased. Therefore, a dust core with small energy loss (iron loss) due to eddy current loss can be obtained. Although Co is an exception, generally, when an alloying element is added to Fe, the magnetic flux density tends to decrease as the amount of addition increases. Therefore, the above elements in total
If it exceeds 5 (%), a magnetic flux density higher than that of the iron powder magnetic core cannot be obtained, so it is necessary to add the iron in a range of 5 (%) or less.

[0009] Preferably, the magnetic powder has an insulating film provided on the surface of each particle. In this case, since the electrical contact between the magnetic powder particles is inhibited, there is an advantage that the electric resistivity of the magnetic core is further increased and the energy loss can be further suppressed. The insulating film is desirably provided so as to cover each particle of the magnetic powder. However, the insulating film does not necessarily have to completely cover the particles, and may be partially broken during pressure molding. Therefore, there may be a portion where the magnetic powder particles are in direct contact with each other. Further, "individually" means having an insulating film for each particle, but it is not necessary that all particles constituting the magnetic core be in such an ideal state. For example, there may be a portion in which about 2 to 3 particles are collected and an insulating film is present around the particle.

Preferably, the insulating film is made of a heat-resistant material such as a silicate glass derived from water glass, a silicone resin, a phenol resin, or an epoxy resin. In this way, even when the compact is heated in the annealing step for removing the strain generated in the particles during the pressure molding of the magnetic powder in manufacturing the dust core, the insulating film remains between the particles. Will do. Therefore, even after annealing, the insulating property of the insulating film is maintained at a desired value and the bonding action between particles is maintained to some extent, so that a dust core having high electric resistivity can be obtained.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a magnetic core 10 according to an application example of the present invention.
FIG. The magnetic core 10 has an outer shape of 28 (m
m), an inner diameter of 20 (mm) and a thickness of about 5 (mm). As shown in FIG. 2, for example, as shown in FIG.
4 and so on. In FIG. 2, the conductive wire 12 is extremely coarsely wound, but the winding density is appropriately changed according to the required coil characteristics.

The magnetic core 10 is, for example, a dust core obtained by press-molding an Fe—Co-based soft magnetic powder containing Co at a ratio of more than 3% and less than 35%. This magnetic powder has an average particle diameter of 30 (μm) as measured by a sieve, for example.
And a size of less than 110 (μm). Therefore, since the magnetic core 10 is a molded body having a high relative density, the magnetic flux density suitable for applications such as an operation coil of an electromagnetic valve, when the magnetic field strength is 10,000 (A / m) 1.4
It has high characteristics exceeding (T). In addition, the surface of the magnetic powder particles is individually or collectively about two or three,
For example, the magnetic core 10 is substantially covered with a thin insulating film made of, for example, a silicone resin, and the particles constituting the magnetic core 10 are substantially insulated from each other, or conduction is hindered.
Therefore, since the magnetic core 10 has a high electrical resistivity, it has a characteristic of relatively low energy loss. Since the electrical resistivity of the magnetic core 10 tends to decrease as the average particle size of the constituent particles increases, as described above,
By using a powder less than m), the electric resistivity is further increased, and the energy loss is further suppressed.

Such a magnetic core 10 is manufactured, for example, as follows. Hereinafter, a method for manufacturing the magnetic core 10 will be described with reference to the process chart shown in FIG. First, in the powder manufacturing process 20, for example, a molten metal obtained by adding cobalt (Co) to iron (Fe) at a ratio within a range of 3 to 35 (%) is caused to flow out of pores.
A Fe-Co based magnetic powder is produced by a spraying method or the like in which the powder is scattered and powdered by the action of a compressed gas or a water jet. At this time, the powder having the above-mentioned average particle size can be obtained by appropriately setting the production conditions such as the temperature of the molten metal, the amount of outflow from the pores, the blowing pressure of compressed gas, and the like. . The temperature of the molten metal is, for example, 1500-1650 (° C).
The pore diameter is set to, for example, about 3 to 10 (mm).

Next, in the coating step 22, an insulating film is formed on the particles of the magnetic powder with a silicone resin so as to cover about 1 (%) of the magnetic powder with respect to 100 (%) of the magnetic powder. In the coating step 22, for example, the silicone resin is added to the magnetic powder, and the mixture is stirred and mixed (or kneaded) with a stirrer or the like, or the silicone resin is sprayed and then dried at an appropriate temperature of about 50 to 200 (° C.). Can be performed. Therefore, when forming the insulating film, since a part of the magnetic powder is agglomerated particles, as described above, not all the particles necessarily have the insulating film in an independent state. In some cases, agglomerated particles obtained by agglomerated particles are covered with one insulating film. The insulating coating not only insulates the particles after molding but also functions as a binder (binder) for securing the shape retention of the molded body by binding the particles to each other. For this reason, the constituent material of the insulating film is preferably a material having heat resistance enough to maintain the insulating property without burning out even during the heat treatment described later, and such a material is selected in the present embodiment.

In the subsequent molding step 24, the magnetic powder is reduced to an outer shape of about 28 (mm), an inner diameter of about 20 (mm), and a thickness of 5 mm using a cold dry press forming apparatus equipped with a mold having a predetermined shape.
(mm). At this time, the molding pressure is, for example, about 1666 (MPa) [= 17 (tonf / cm ² )], but in the present embodiment, the hardness is relatively low because the amount of Co is suppressed to less than 35 (%). 30-11 with being lowered
Since a powder having an average particle diameter suitable for filling of about 0 (μm) is used, a high-density compact having a relative density of about 90 (%) or more can be obtained. The relative density refers to the ratio of the actual density to the theoretical density when no voids are present in the compact.

In the annealing step 26, for example,
Heat treatment is performed at a temperature of about 700 (° C.) for about one hour in a non-oxidizing atmosphere such as a vacuum of about 13 (Pa) [= 10 ⁻⁴ (Torr)]. Thereby, the distortion generated in the molded body in the molding step 24, more specifically, the distortion generated in the magnetic particles constituting the molded body is removed, and the magnetic core 10 is obtained.
Residual stress is inherent in the magnetic particles when pressed in the molding process, and it is known that the strain caused by such residual stress increases the coercive force of the magnetic core. Therefore, by heating, the residual stress is released, the distortion is removed, and the coercive force is reduced. In addition, since the crystal grains of the magnetic particles are slightly increased by the heating, the domain wall is easily moved when a magnetizing force is applied from the outside, and the hysteresis loss is reduced.
The heat treatment also reduces the energy loss of the magnetic core. The annealing is performed in a vacuum to suppress an increase in coercive force due to entrapment of oxygen in the magnetic core, oxidation of the magnetic powder, and the like.

Here, Table 1 below shows the magnetic core 1 of this embodiment.
The characteristics of No. 0 were measured by variously changing the composition and the average particle diameter of the magnetic material powder, and the values were shown in comparison with Comparative Examples in which the values were out of the range of the present invention. In Table 1, "Material"
The column shows the composition of the magnetic material powder, and the numbers and element symbols shown in this column are the ratio (mass percentage) and type of the element added to Fe, respectively. The “magnetic flux density” column is 10,000 (A / A) measured using a DC BH tracer.
m) the magnetic flux density in the magnetic field of the strength, the `` Relative density '' column is the ratio to the theoretical density of the magnetic core, Each represents a particle size. The “Formability” column shows the molding process 24
Were evaluated in three steps to determine whether or not a good molded body (magnetic core) was obtained, and “○” indicates that a good molded body was obtained, and “△” indicates that the molded body (magnetic core) was obtained. And "x" represent those in which cracks occurred in the molded body.

[0019] [Table 1] EXAMPLES flux density relative density average particle size material (T) (%) (μm ) formability 1 10Co 1.55 94.0 70 ○ 2 20Co 1.70 93.5 70 ○ 3 20Co 1.60 93.0 50 ○ 4 20Co 1.55 92.0 35 ○ 5 20Co 1.65 92.0 90 ○ 6 30Co 1.55 91.0 70 ○ 7 20Co-2Cr-1Mo 1.65 94.0 70 ○ 8 15Co-3Cr-1Si 1.55 93.0 70 ○ 9 20Co-1Si-1Al 1.60 94.0 70 ○ 10 20Co-1V 1.65 94.0 70 ○ [Comparative example] flux density relative density average particle size material (T) (%) (μm ) moldability 11 ○ 12 pure iron 1.40 95.0 70 3Co 1.40 94.0 70 ○ 13 40Co 1.20 86.0 70 × 14 50Co 1.05 82.0 70 × 15 49Co-2V 1.30 87.0 70 × 16 20Co 1.40 88.0 110 ○ 17 20Co 1.15 86.0 20 △ 18 20Co-4Cr-3Mo 1.30 90.0 70 △ 193 3Si 1.20 90.0 70 △

In Table 1 above, when the Co content is in the range of 10 to 30 (%), a high magnetic flux density of 1.55 (T) or more can be obtained at various average particle sizes. Further, as shown in Examples 7 to 10, the Fe-Co material containing 15 (%) or 20 (%) Co was added in a range of about 1 to 3 (%) and a total of 4 (%) or less, respectively. Even if a small amount of Cr, Mo, Si, Al, V, etc. (hereinafter, referred to as trace addition elements) is added in a small amount, a powder magnetic core with a high magnetic flux density comparable to that obtained when only Co is added can be obtained. it can. However, as shown in Comparative Examples 18 and 19, when the ratio of the trace added element exceeds 5 (%) in total or when no Co is contained, the iron powder core is inferior to 1.20 to 1.30 (T). Only an insufficient magnetic flux density is obtained.

FIGS. 4 to 6 are graphs respectively showing the relationship between the composition and average particle size of the magnetic powder shown in Table 1 and the characteristic values (magnetic flux density and relative density) of the magnetic core. First, FIGS. 4 and 5 show that the Co particles having an average particle diameter of 70 (μm)
It shows the relationship between the quantity, the magnetic flux density and the relative density, respectively. In FIG. 4, the magnetic flux density is the same as that of pure iron when the amount of Co is 3 (%) or less, but when the amount of Co exceeds 3 (%), the magnetic flux density increases sharply as the amount of addition increases, and 20 (%). )), A high value of about 1.7 (T) can be obtained. That is, within the range of 3 to 20 (%), the addition of Co does not deteriorate or substantially does not deteriorate the formability (compressibility), and the effect of improving the magnetic flux density according to the added amount can be obtained. The relative density shown in FIG. 5 is an index of the formability, and the amount of Co is 20 (%).
Up to this point, the relative density has hardly decreased compared to pure iron. However, if the Co content exceeds 20 (%), the formability deteriorates due to an increase in the material hardness and the relative density decreases, and the magnetic flux density decreases rapidly.If the Co content exceeds 35 (%), the iron powder magnetism increases. Insufficient value of less than 1.4 (T) which is inferior to the core. From the above, it can be said that the Co addition amount is preferably in the range of 3 to 35 (%).

In short, according to this embodiment, since it is composed of the Fe-Co-based soft magnetic powder having a Co content of 3 to 35 (%), it can be compacted at high density under pressure. Higher magnetic flux density can be obtained as compared with iron powder cores. By the way, in the case of Fe-Co steels manufactured by casting, etc., the magnetic flux density tends to increase up to the higher Co content range.
The maximum magnetic flux density is obtained with the addition amount of about 50 (%). That is, in FIG. 4, the decrease in the magnetic flux density in the range of the Co content of 20 (%) or more is due to the deterioration of the formability of the inherent properties of the material. As is clear from FIG. 4, when a higher magnetic flux density is desired,
What is necessary is just to set Co amount. For example, if a magnetic flux density of 1.45 (T) or more is desired, the Co amount may be set within the range of 5 to 33 (%). If a magnetic flux density of 1.5 (T) or more is desired, the Co amount may be set. To
It may be set within the range of 7.5 to 31 (%). Also, 1.55 (T)
If a higher magnetic flux density is desired, the amount of Co must be
It should be within the range of 10 to 30 (%).

FIG. 6 shows the relationship between the average particle size and the magnetic flux density when the amount of Co is 20 (%). In the figure, up to about 70 (μm), the magnetic flux density increases as the average particle size increases, and at 30 (μm) or more, the magnetic flux density exceeds 1.4 (T), which is the same as that of iron powder cores, but the average particle size increases. When it exceeds 70 (μm), the magnetic flux density tends to decrease, and when it exceeds 110 (μm), the magnetic flux density becomes a value less than 1.4 (T) which is inferior to the iron powder core. This is because, as shown in Table 1, the relative density of the magnetic core depends on the average particle diameter, and the maximum value is about 70 (μm). Is reduced. Therefore, the average particle size is 30
It can be seen that the thickness is preferably 110 to 110 (μm). When a higher magnetic flux density is desired, for example, when a magnetic flux density of 1.5 (T) or more is desired, a magnetic powder having an average particle diameter in the range of about 35 to 100 (μm) may be used.

Examples 7 to 10 shown in Table 1 were used.
The trace added element added in the above increases the electric resistivity of the material, thereby increasing the electric resistivity of the magnetic core 10 in combination with the insulating action between the particles of the insulating film made of the silicone resin, Although the energy loss is reduced, the amount of addition is limited to a range of 5 (%) or less without lowering the magnetic flux density as described above. Therefore, with these compositions, a magnetic core having higher characteristics with less energy loss while maintaining high magnetic flux density can be obtained.

As described above, one embodiment of the present invention has been described in detail with reference to the drawings. However, the present invention can be implemented in still another embodiment.

For example, in the embodiments, the case where the present invention is applied to the magnetic core of the operating coil of the solenoid valve has been described. However, even if the magnetic core is used for other purposes, a high magnetic flux density is desired. If so, motor yoke, choke coil,
The present invention is similarly applied to magnetic cores for various uses such as a noise filter. The size and shape of the magnetic core are appropriately changed according to the application.

In the embodiment, the case where the magnetic core 10 is manufactured using the magnetic material powder manufactured by the spraying method has been described, but various known methods can be applied to the method of manufacturing the powder. For example, a method of generating from a solid phase such as mechanical pulverization or reduction of a metal salt, a method of generating from a liquid phase such as precipitation, precipitation, and electrolysis, and a method of generating from a gas phase such as thermal decomposition are to be generated. It can be appropriately used depending on the composition to be formed, the size and shape of the particles, and the like.

In the embodiment, the magnetic core 10 is manufactured by press-molding the powder at a pressure of about 1666 (MPa). However, the compacting pressure depends on the properties of the powder and the desired relative density. It is appropriately changed according to the characteristics. It is also possible to use other molding methods such as hot isostatic pressing (HIP) and cold isostatic pressing (CIP).

Further, in the embodiment, the silicone resin is coated on the magnetic powder particles by kneading or spraying, but other methods such as immersion in a material to be an insulating film can be used. In addition, as the insulating film, besides the silicone resin, a glass film derived from water glass, a phenol resin, an epoxy resin, or any other material that does not lose its insulating properties when heated in the annealing step 26 is preferably used. The addition amount is not limited to 1 (%) shown in the examples, and is appropriately determined according to the required insulation properties, moldability, and the like.

Further, in the embodiment, an annealing step 26 of performing a heat treatment at a temperature of about 700 (° C.) in a vacuum of about 0.013 (Pa) is performed following the forming step 24.
The processing conditions are appropriately determined according to the type of the insulating film, the type, shape, and size of the magnetic material powder, the required characteristics of the magnetic core 10, and the like. The non-oxidizing atmosphere for suppressing the oxidation of the magnetic powder can be realized in an inert gas atmosphere such as argon instead of the vacuum atmosphere. Further, the degree of vacuum in the case of processing in a vacuum is appropriately determined according to the allowable degree of oxidation of the powder and the like. The annealing temperature and time are determined by the type of magnetic powder material,
It is determined according to the furnace atmosphere, the type of insulating film, etc., for example, an appropriate temperature is selected within a range of about 500 to 1000 (° C.), and the heating time is longer or shorter than 1 hour. Is set as appropriate. When distortion due to molding is not a problem, it is not necessary to perform annealing.

In the embodiment, the magnetic material powder is
Fe-Co-based material containing Co in the range of 3 to 35 (%),
As long as the characteristics of the magnetic core 10 are not affected or are less affected, in addition to the trace addition elements such as Cr, Mo, Si, Al and V shown in the examples, Mn, Cu, Ni, Ti, Nb, etc. Further, other elements may be added in a range up to about 5 (%). That is, the "Fe-Co-based particles" referred to in the claims include those to which these other components are added in addition to Co, and contain unavoidable impurities in a range of about 0.1 (%) or less. It is acceptable.

Although not specifically exemplified, the present invention
The present invention can be implemented in a mode in which various changes are made without departing from the spirit thereof.

[Brief description of the drawings]

FIG. 1 is a diagram showing a magnetic core manufactured by a manufacturing method according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a use form of the magnetic core of FIG. 1 as a coil.

FIG. 3 is a process diagram illustrating a main part of a manufacturing process of the magnetic core of FIG. 1;

FIG. 4 is a graph showing the relationship between the amount of Co and the magnetic flux density of a magnetic core.

FIG. 5 is a graph showing the relationship between the amount of Co and the relative density of the magnetic core.

FIG. 6 is a graph showing a relationship between an average particle diameter of a magnetic powder and a magnetic flux density.

[Explanation of symbols]

 10: Magnetic core

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C22C 33/02 C22C 33/02 L

Claims (3)

[Claims] A powder compact formed by press-molding a soft magnetic powder comprising Fe-Co-based particles containing Co in a mass ratio of more than 3 (%) and less than 35 (%). Magnetic core. 2. The soft magnetic powder has an average particle size of 30 (μm).
2. The dust core according to claim 1, which is in the range of more than m) and less than 110 (μm). 3. The soft magnetic powder comprises Mn, Cu, Ni, Ti,
5% of at least one of Nb, Cr, Mo, Al, Si, and V
3. The dust core according to claim 1, wherein the dust core is contained in the following mass ratio.