WO2015045561A1

WO2015045561A1 - Dust core, method for producing dust core and coil component

Info

Publication number: WO2015045561A1
Application number: PCT/JP2014/068384
Authority: WO
Inventors: 友之上野; 麻子渡▲辺▼; 真人魚住
Original assignee: 住友電気工業株式会社; 住友電工焼結合金株式会社
Priority date: 2013-09-27
Filing date: 2014-07-10
Publication date: 2015-04-02
Also published as: JP2015070077A

Abstract

A dust core that contains a coated iron powder, each particle of which has an insulating coating, and an aliphatic lubricant. The coated iron powder has an average particle diameter of from 200 μm to 450 μm (inclusive), and the ratio of powder particles having a particle diameter of 75 μm or less is 10% by mass or less. The content of the aliphatic lubricant is from 0.0045% by mass to 0.02% by mass (inclusive). A method for producing a dust core, wherein a mixed powder containing a coated iron powder, which has an average particle diameter of from 200 μm to 450 μm (inclusive) and contains powder particles having a particle diameter of 75 μm or less at a ratio of 10% by mass or less, and from 0.2% by mass to 0.5% by mass (inclusive) of an aliphatic lubricant is filled into a mold and is pressurized and compressed so as to produce a compressed product that contains from 0.135% by mass to 0.485% by mass (inclusive) of the aliphatic lubricant, and then the compressed product is subjected to a heat treatment, thereby producing a dust core that contains from 0.0045% by mass to 0.02% by mass (inclusive) of the aliphatic lubricant.

Description

Powder magnetic core, method for manufacturing powder magnetic core, and coil component

発明 The present invention relates to a dust core used for a coil component and the like, a method for manufacturing a dust core, and a coil component including a dust core. In particular, the present invention relates to a dust core having a low core loss.

2. Description of the Related Art As magnetic cores for coil parts and the like, there are powder magnetic cores manufactured by molding raw material powder (Patent Documents 1 and 2). The dust core is typically manufactured as follows using a die having an annular die having a through hole, and a columnar upper punch and a lower punch. After filling the forming space formed by the through hole of the die and the lower punch with the raw material powder, the raw material powder is pressurized and compressed with the lower punch and the upper punch, and the formed compressed product is extracted from the die. A powder magnetic core is manufactured by subjecting this compressed product to a heat treatment for the purpose of removing strain.

As a raw material powder for a dust core, a coating powder having an insulating coating on the surface of metal particles is used (Patent Documents 1 and 2). By using the coating powder, the electrical resistance of the dust core can be increased by the insulating coating, and the core loss such as eddy current loss can be reduced. However, when compressing the raw material powder or extracting the compressed product, the powder particles or the inner peripheral surface of the through hole of the die and the raw material powder rub against each other, or the inner peripheral surface of the die and the compressed product rub against each other. As a result, the insulation coating may be damaged.
Therefore, it has been practiced to improve the lubricity by mixing a lubricant with the raw material powder. Patent Document 1 discloses an ester wax having a low melting point. As another method for improving lubricity, there is a method of applying a lubricant to the inner peripheral surface of the die (hereinafter, this method is referred to as external lubrication).

JP 2006-1000081 A JP 2011-089190 A

It is desired to reduce the core loss with respect to the dust core.

In order to reduce the core loss, for example, it is possible to reduce eddy current loss. In order to reduce eddy current loss, it is preferable to prevent damage to the insulation coating. In order to prevent damage to the insulating coating, for example, it is conceivable to increase the blending amount of the lubricant mixed with the raw material powder. However, if this lubricant is too much, too much lubricant can remain in the compressed product, resulting in a decrease in density, a decrease in strength, and a decrease in magnetic properties due to a decrease in density (permeability and saturation magnetic flux density). Decrease). In order to remove the lubricant remaining in the compressed product, for example, the heat treatment temperature may be increased or the heat treatment time may be increased. In this case, although the thermal decomposition of the lubricant can be sufficiently performed and the lubricant can be removed satisfactorily, the insulation coating can be thermally damaged.

In order to suppress lubricant residues (for example, soot-like or tar-like carbon components) after heat treatment, it is considered to use a low-melting-point lubricant having a melting point of 50 ° C. or less like the above-mentioned ester wax. It is done. However, when such a low-melting-point lubricant is used, the difference between the room temperature and the melting point is small, so that the lubricant can be liquefied and the viscosity of the raw material powder can be increased particularly in an atmosphere having a high room temperature (air temperature). . As a result, the fluidity of the raw material powder is remarkably reduced, workability is deteriorated, and particularly in continuous production, the dispersion of the filling state of the raw material powder into the mold is increased. obtain. In addition, when the compressed product is extracted from the mold, the lubricant may stay in the mold if the liquefied lubricant flows down from the compressed product. Depending on the retained lubricant, there may be problems such as variations in the filling state of the raw material powder, or a compressed product entrained with the retained lubricant, resulting in a significant decrease in the density of the compressed product.

On the other hand, if the above-mentioned external lubrication is performed without mixing the lubricant in the raw material powder, the decrease in density and the decrease in magnetic properties due to the remaining lubricant can be suppressed, and problems caused by the heat treatment hardly occur. However, in external lubrication, since it is necessary to apply a lubricant to a mold with a uniform thickness, there is a limit to the shape and size that can be molded. Specifically, in the case of a powder magnetic core having a shape that is long in the depth direction of the die with respect to the opening diameter of the through hole of the die, or in short, an elongated powder magnetic core, it is uniform on the inner peripheral surface of the die through hole. It is difficult to form a lubricant layer having an appropriate thickness. For example, in a dust core having a columnar shape, when the end face size is D and the side face size is L, a dust core having a ratio L / D of L to D exceeding 2.5 is not suitable for external lubrication. It can be said that the shape and size. The size D of the end face is the length perpendicular to the compression direction in the cross section of the columnar dust core, and is equal to the opening diameter of the through hole of the die. For example, when the dust core is a cylinder, the size D of the end face corresponds to the diameter. The size L of the side surface is the length in the compression direction in the cross section of the columnar dust core, and is equal to the size in the depth direction of the through hole of the die. For example, when the dust core is a cylinder, the size L of the side surface corresponds to the height.

Therefore, one of the objects of the present invention is to provide a dust core having a low core loss. Another object of the present invention is to provide a method of manufacturing a dust core that can manufacture a dust core having a low core loss. Furthermore, the other object of this invention is to provide a coil component provided with the powder magnetic core with a low core loss.

The dust core of the present invention includes a coated iron powder having an insulating coating and an aliphatic lubricant, and the coated iron powder has a mean particle size of 200 μm to 450 μm and a particle size of 75 μm or less. The ratio of the particles is 10% by mass or less, and the content of the aliphatic lubricant is 0.0045% by mass or more and 0.02% by mass or less.

The manufacturing method of the powder magnetic core of the present invention includes the following preparation process, molding process, and heat treatment process.
Preparation Step Coated iron powder having an average particle diameter of 200 μm or more and 450 μm or less and a ratio of powder particles having a particle diameter of 75 μm or less and 10% by mass or less, and an aliphatic of 0.2% by mass or more and 0.5% by mass or less A step of preparing a mixed powder containing a lubricant.
Molding step A step of producing a compressed product containing 0.135% by mass or more and 0.485% by mass or less of the aliphatic lubricant by filling the mixed powder in a mold and compressing the mixture under pressure.
A heat treatment step for producing a dust core containing 0.0045% by mass or more and 0.02% by mass or less of the aliphatic lubricant by subjecting the compressed product to a heat treatment.

コア The dust core of the present invention has a low core loss. The dust core manufacturing method of the present invention can manufacture a dust core having a low core loss.

It is a schematic block diagram which shows the coil components of Embodiment 1 provided with the powder magnetic core of embodiment. It is a schematic block diagram which shows the coil components of Embodiment 2 provided with the powder magnetic core of embodiment. It is a schematic block diagram which shows the coil components of Embodiment 3 provided with the powder magnetic core of embodiment. It is a schematic block diagram which shows the coil components of Embodiment 4 provided with the powder magnetic core of embodiment. It is a schematic block diagram which shows the coil components of Embodiment 5 provided with the powder magnetic core of embodiment. It is a schematic block diagram which shows the coil components of Embodiment 6 provided with the powder magnetic core of embodiment. It is a graph which shows an example of the particle size distribution of the covering iron powder used for a raw material.

[Description of Embodiment of the Present Invention]
If the lubricant remains in the powder magnetic core after the heat treatment, it causes a decrease in magnetic properties such as a decrease in density and magnetic permeability as described above. However, as a result of the study by the present inventors, a powder core having a specific size is used as a raw material and a mixed powder containing a specific lubricant in a specific range is molded into a raw material after heat treatment. Furthermore, it was found that a powder magnetic core with low core loss can be obtained by leaving a part of the lubricant used as a raw material. The present invention is based on the above findings. First, the contents of the embodiment of the present invention will be listed and described.

(1) The powder magnetic core which concerns on embodiment contains the covering iron powder provided with insulation coating, and an aliphatic lubricant. The coated iron powder has an average particle size of 200 μm or more and 450 μm or less, and a ratio of powder particles having a particle size of 75 μm or less is 10% by mass or less. The content of the aliphatic lubricant (hereinafter, sometimes referred to as a lubricant amount _{W C} of the powder magnetic core) is 0.02 mass% or less than 0.0045 wt%.

In the dust core according to the embodiment, the damage of the insulating coating is suppressed for the following reason, and the insulating coating exists in a healthy state, so that the eddy current loss can be reduced and the core loss is low.

The dust core of the embodiment is mainly composed of relatively coarse coated iron powder. From this, it can be said that the powder magnetic core of the embodiment is manufactured using relatively coarse coated iron powder as a raw material. Moreover, the powder magnetic core of the embodiment contains an aliphatic lubricant. From this, it can be said that the powder magnetic core of the embodiment is manufactured using an aliphatic lubricant having excellent demoldability as a raw material. By using as a raw material a coating powder that is relatively coarse and excellent in compression moldability, and is a material with high deformability (pure iron) and excellent in compression moldability, and an aliphatic lubricant, In order to increase the density in order to improve the characteristics, it is not necessary to set the molding pressure to a high pressure of 1000 MPa or more, further 1200 MPa or more. For example, the density can be increased even at a relatively low pressure of less than 1000 MPa. Therefore, the dust core according to the embodiment is manufactured using the above-mentioned specific raw materials, so that the insulation coating is damaged by rubbing between the powder particles during molding and rubbing with the mold during demolding. Can be said to be suppressed.

Further, in the dust core of the embodiment, even if there is a portion where the insulating coating is locally damaged, the above-mentioned extremely small amount of the aliphatic lubricant is interposed between the powder particles, and between the powder particles. Prevent contact. That is, it is considered that the aliphatic lubricant functions as an insulating material. In particular, the dust core of the embodiment contains an amount of an aliphatic lubricant sufficient to function as an insulating material. Also from this point, the dust core of the embodiment can suppress eddy current loss and has low core loss.

渦 It is known that eddy current loss is inversely proportional to electrical resistance. Although the powder particles constituting the powder magnetic core of the embodiment are relatively coarse, as described above, the electrical resistance is increased by the suppression of damage to the insulating coating and the intervention of the lubricant (insulating material), and the eddy current is increased. The loss can be reduced.

Furthermore, the powder magnetic core of the embodiment is excellent in magnetic properties (such as permeability and saturation magnetic flux density) because the contained nonmagnetic component (aliphatic lubricant) is extremely small and the ratio of the magnetic component is high. There are also special effects such as.

(2) As an example of the dust core according to the embodiment, the ratio L / D between the length L in the compression direction and the length D in the direction orthogonal to the compression direction is a cross section in the compression direction of the dust core. A form that is greater than 2.5.

形状 The shape in which the ratio L / D is more than 2.5 is simply an elongated shape. The said form is manufactured using the above-mentioned specific raw material, Even if it is such a shape which is comparatively difficult to shape | mold, damage to insulation coating is suppressed and a core loss is low.

(3) As an example of the dust core according to the embodiment, the aliphatic lubricant has a melting point of 70 ° C. or higher and 150 ° C. or lower and a boiling point of 220 ° C. or higher and 280 ° C. or lower.

Since this aliphatic lubricant is not too low in melting point, it is difficult to liquefy even when the temperature is high (for example, in summer) or when the mold is slightly heated by frictional heat during continuous molding in mass production. Since the fluidity of the powder is good and the melting point is not too high, the lubricant can be removed to some extent by rubbing with the mold during demolding. Further, this aliphatic lubricant has a relatively low boiling point and can be easily removed even if the heat treatment temperature is lowered. Furthermore, since the boiling point of this aliphatic lubricant is not too low, it is possible to prevent the lubricant from being excessively removed due to frictional heat with the mold during demolding. Since it is manufactured using such an aliphatic lubricant as a raw material, in the above-described embodiment, damage to the insulating coating in the molding process and heat treatment process is suppressed well, and the core loss is low.

(4) As an example of the dust core according to the embodiment, there is a form in which the aliphatic lubricant contains stearamide.

Stearic amide is a lubricant that satisfies the above-mentioned definition of the embodiment (3) and is excellent in demolding property. Since the said form is manufactured using such an aliphatic lubricant as a raw material, damage to insulation coating is suppressed well and core loss is low.

(5) as an example of a dust core according to the embodiment, the density can be cited embodiment is less 7.3 g / cm ³ or more 7.7 g / cm ^3.

Since the density is 7.3 g / cm ³ or more in the above form, the magnetic permeability and saturation magnetic flux density are high, and the magnetic characteristics are excellent. Moreover, although the density is 7.7 g / cm ³ or less, although a relatively coarse powder having excellent moldability is used as a raw material, it is not molded at an excessive pressure for further densification. It can be said. From this, the said form suppresses damage of the insulation coating especially in a shaping | molding process, and a core loss is low.

(6) A coil component according to the embodiment includes a coil and a magnetic core, and the dust core according to any one of the embodiments (1) to (5) is provided on at least a part of the magnetic core. Is provided.

The coil component according to the embodiment has a low loss because it includes the powder magnetic core according to the embodiment having a low core loss. In particular, a coil component that uses all of the magnetic components of the magnetic core as a dust core according to the embodiment has low loss and high magnetic permeability and saturation magnetic flux density, and is excellent in magnetic characteristics.

(7) The manufacturing method of the powder magnetic core which concerns on embodiment is equipped with the following preparatory processes, a formation process, and a heat treatment process.
Preparation Step A step of preparing a mixed powder containing coated iron powder and an aliphatic lubricant of 0.2% by mass or more and 0.5% by mass or less. The coated iron powder has an average particle size of 200 μm or more and 450 μm or less, and a ratio of powder particles having a particle size of 75 μm or less is 10% by mass or less. Hereinafter sometimes referred to as the content of the aliphatic lubricant in the powder mixture with a lubricant amount W _P of the mixed powder.
Molding step A step of producing a compressed product by filling the above-mentioned mixed powder into a mold and pressurizing and compressing the mixture. The compressed product contains 0.135% by mass or more and 0.485% by mass or less of the aliphatic lubricant. Hereinafter sometimes referred to as a lubricant amount W _G of compacts the content of the aliphatic lubricant in the compressed foam.
Heat treatment step A step of producing a dust core by subjecting the compressed product to a heat treatment. The dust core contains 0.0045% by mass or more and 0.02% by mass or less of the aliphatic lubricant.

The manufacturing method of the powder magnetic core of the embodiment uses (A) pure iron which is a material excellent in compression moldability as a raw material, and (B) a relatively coarse powder having a size excellent in compression moldability. The damage of the insulation coating can be satisfactorily suppressed from the point of using (C) an aliphatic lubricant having excellent demoldability. Moreover, the manufacturing method of the powder magnetic core of the embodiment uses a relatively coarse powder as a raw material, so that the total length of the powder grain boundaries in the unit cross-sectional area of the molded product (compressed material, powder magnetic core) (hereinafter, Therefore, even if the heat treatment temperature is relatively low, the aliphatic lubricant can be removed satisfactorily. When the total length of the powder grain boundary is short, the aliphatic lubricant tends to ooze out from the inside of the compressed product toward the surface. The exuding aliphatic lubricant can be removed to some extent by rubbing with the mold during demolding. By performing heat treatment on the lubricant whose amount has been reduced to some extent in the molding step, the amount of removal of the aliphatic lubricant required for the heat treatment step can be reduced. Even in the heat treatment step, the aliphatic lubricant is easily removed because the total length of the powder grain boundaries is short. From these points, the heat treatment temperature can be made relatively low. When the heat treatment temperature is relatively low, thermal damage to the insulating coating can be satisfactorily suppressed. Moreover, it is expected that a very small amount of an aliphatic lubricant is interposed between the powder particles by making the heat treatment temperature relatively low, and this inclusion can function as an insulating material. Furthermore, since the heat treatment time can be made relatively short, thermal damage of the insulating coating can be satisfactorily suppressed. From these points, the dust core manufacturing method of the embodiment can suppress damage to the insulation coating and reduce eddy current loss by the remaining aliphatic lubricant, so that the core with a low core loss (typically Can manufacture the dust core of the embodiment.

In particular, method for producing a dust core of the embodiment, by the raw material powder itself has excellent compression moldability, the amount of lubricant W _P of the mixed powder relatively small as 0.5 wt% or less than 0.2 wt% Even if it shape | molds well, even if it shape | molds by low pressure as mentioned above, a high-density powder magnetic core can be manufactured. Therefore, the method for manufacturing a dust core according to the embodiment can manufacture a dust core that is excellent in magnetic properties such as excellent strength and high permeability because of its high density. Further, the lubricant amount W _P of the mixed powder that it is relatively small, the proportion of the magnetic component according to the lubricant amount W _C of the dust core is kept to a trace amount, aliphatic lubricant remains excessively Can be suppressed. Also from this point, the dust core manufacturing method of the embodiment can manufacture a dust core having excellent magnetic properties.

代表 Here, as a typical application of the relatively coarse powder, a raw material for a high-density molded body utilizing the above-described excellent compression moldability can be cited. In order to increase the density, the above-mentioned external lubrication is used, or even when the lubricant is mixed with the raw material powder, the heat treatment temperature is increased, or the lubricant is completely removed. As a result, when coating powder is used as the raw material, damage to the insulating coating must be allowed. Alternatively, in this application, no coating powder is used as a raw material.

On the other hand, for example, as a typical application of a very fine coating powder having an average particle size of 100 μm or less, and further about 75 μm or less, molding having excellent high frequency characteristics utilizing the fact that the eddy current loss is small due to the small particle size. Examples include body materials. Since the fine powder has a large surface area and a large contact resistance between the powder particles, it is necessary to contain a large amount of lubricant in the raw material in order to reduce friction between the powder particles. Further, since fine powder is inferior to powder having a large deformability by compression, it is molded at a high pressure of 1000 MPa or more, further 1200 MPa or more in order to achieve high density. By molding at such a high pressure, even if there are many lubricants, the powder particles may rub against each other and the insulation coating may be damaged. Moreover, when it shape | molds at high pressure, there exists a possibility that an insulation coating may be damaged because the frictional force at the time of demolding becomes large by the spring back of a compressed material. Furthermore, when fine powder is used, the total length of the powder grain boundaries is long, so it is difficult to reduce the lubricant unless the heat treatment temperature after molding is increased or the heat treatment time is lengthened. However, when the heat treatment temperature is increased, the insulation coating may be thermally damaged as described above. As a result, in order to reduce damage to the insulation coating when a fine powder is used as the raw material, for example, heat treatment conditions must be adjusted to allow a large amount of lubricant to remain in the compressed product. Absent.

On the other hand, the manufacturing method of the powder magnetic core of the embodiment uses the relatively coarse powder as a raw material, but manufactures the above-described conventional high-density molded body in that a lubricant is included to some extent after heat treatment. It can be said that it is completely different from the case. In addition, in the method for manufacturing a powder magnetic core according to the embodiment, the above-described conventional high-frequency characteristics are excellent in that the amount of lubricant contained after heat treatment is extremely small, while damage to the insulating coating can be suppressed. It can be said that it is completely different from the case of manufacturing.

(8) As an example of the method for manufacturing a powder magnetic core according to the embodiment, a form in which the conditions for the heat treatment are as follows can be given.
Boiling point of the heat treatment temperature above aliphatic lubricants (hereinafter sometimes referred to as T _V) + 100 ℃ or higher and the boiling point of + 200 ° C. selected from the range of temperature.
The holding time of the heat treatment temperature is a time selected from 5 minutes to 60 minutes.
Atmosphere A mixed gas flow atmosphere of oxygen and inert gas is used.

In the above embodiment, the heat treatment temperature is sufficiently higher than T _V (° C.) and has a sufficient holding time, so that most of the aliphatic lubricant can be efficiently removed. In addition, the above-described form allows the above-mentioned amount of the aliphatic lubricant to remain after the heat treatment while suppressing the heat damage of the insulating coating by not having the heat treatment temperature too high and holding time being too long. Can do. Furthermore, the above-mentioned form is easy to thermally decompose the carbon component of the aliphatic lubricant into carbon monoxide, carbon dioxide, etc. by setting it as an oxygen-containing atmosphere. Since the flow atmosphere allows new oxygen (unbound oxygen) to be supplied in sequence, the above form is easy to thermally decompose the aliphatic lubricant. And by setting it as inert gas mixed atmosphere, reaction with iron components and gas other than oxygen can be prevented.

(9) As an example of the manufacturing method of the powder magnetic core which concerns on embodiment, the said coated iron powder has the form whose ratio of the powder particle whose particle size is 500 micrometers or more is 1 mass% or less.

The above form has very few powder particles that are too coarse, can prevent an increase in eddy current loss due to the presence of coarse particles, and can produce a low-loss dust core. In addition, it can be said that this coated iron powder is composed of powder particles having a uniform size with very few powder particles that are too fine and powder particles that are too coarse. Therefore, in the above-mentioned form, the coated iron powder is uniformly compressed (plastically deformed) to be easily molded, and the insulating coating of the coated particles (powder particles constituting the coated iron powder) compressed locally at high pressure is damaged. It is possible to prevent problems such as

(10) as an example of a method for producing a dust core according to the embodiment, the density of the density and the dust core of the compacts may include forms or less 7.3 g / cm ³ or more 7.7 g / cm ³ It is done.

By adjusting the molding pressure according to the particle size of the coated iron powder, a compressed product having a density in the above range can be obtained. Since the manufacturing method of the powder magnetic core of the embodiment uses the above-described specific raw material, the density of 7.7 g / cm ³ or less can be said to be a size that can be easily reached even at a relatively low pressure. Since the said form can be shape | molded by a comparatively low pressure, it can suppress the damage of the insulation coating at the time of shaping | molding. By setting the density of the compressed material to 7.7 g / cm ³ or less, it is not too dense, so that a sufficient discharge route for the lubricant during heat treatment can be secured, and lubrication can be achieved even if the heat treatment temperature is relatively low. It is easy to discharge the agent. Since the heat treatment temperature can be made relatively low, the above embodiment can suppress thermal damage to the insulating coating during the heat treatment. Further, by setting the density of the compressed product to 7.3 g / cm ³ or more and 7.7 g / cm ³ or less, the density of the high density dust core after heat treatment, specifically, the density of the dust core is 7.3 g / cm ^3. It may be cm ³ or more 7.7 g / cm ³ or less. Therefore, the said form can manufacture the powder magnetic core which is excellent in intensity | strength and a magnetic characteristic because it is high density. Note that, depending on the heat treatment conditions, the density before and after the heat treatment is substantially equal, the density is lowered after the heat treatment, and the density is increased after the heat treatment. The higher the density of the powder magnetic core as the final product, the better the strength and magnetic properties.

(11) as an example of a method for producing a dust core according to the embodiment, in the molding process, the melting point of the aliphatic lubricant the mold (hereinafter sometimes referred to as T _M) 1/2 or more The form which shape | molds in the state heated to the temperature below the said melting | fusing point is mentioned.

In the above form, the moldability of the raw material powder can be improved by performing molding in a state where the mold is heated to a specific temperature, that is, a temperature of (T _M / 2) ° C. or higher and T _M ° C. or lower. It is possible to manufacture compacts and powder magnetic cores with excellent accuracy. Further, when continuous molding is performed using a single mold, variation in molding state can be reduced by keeping the temperature of the mold constant from the initial molding stage to the final molding stage. Therefore, the said form is easy to manufacture a uniform product continuously, and can perform industrial mass production favorably.

(12) As an example of a method for manufacturing a powder magnetic core according to the embodiment, a die in which the mold has a through-hole, and a pair of punches that press-compress the mixed powder by forming a molding space together with the die. And the ratio L / D of the depth L to the opening diameter D in the molding space is more than 2.5.

In the above-described embodiment, a long and narrow powder magnetic core having the above-mentioned ratio L / D exceeding 2.5 can be manufactured.
Since the manufacturing method of the dust core according to the embodiment uses the above-described specific raw material, it is possible to manufacture a low-loss dust core by suppressing damage to the insulating coating even in such an elongated shape.

(13) Examples of the powder magnetic core according to the embodiment include those manufactured by the method for manufacturing a powder magnetic core described in any one of the above embodiments (7) to (12).

ため Since the dust core of this embodiment is manufactured by the method of manufacturing a dust core of the embodiment that can suppress damage to the insulation coating, the insulation coating exists in a healthy state and the core loss is low. Further, this dust core is expected to function as an insulating material with an aliphatic lubricant contained in a very small amount (0.0045 mass% or more and 0.02 mass% or less) interposed between powder particles. However, the eddy current loss can be reduced and the core loss is small. Furthermore, since this powder magnetic core has a small amount of aliphatic lubricant interposed between the powder particles, it is possible to suppress a decrease in the ratio of magnetic components due to this lubricant, and magnetic properties (such as permeability and saturation magnetic flux density). Excellent.

[Details of the embodiment of the present invention]
Hereinafter, a dust core according to an embodiment of the present invention, a method for manufacturing a dust core, and a coil component including a dust core and a coil will be described. In addition, this invention is not limited to these illustrations, is shown by the claim, and is intended that all the changes within the meaning and range equivalent to the claim are included. For example, in the test examples described later, the average particle size of the coated iron powder, the particle size distribution, the material of the insulation coating, the material and content of the aliphatic lubricant, the molding conditions (temperature, molding pressure, atmosphere, etc.), the heat treatment conditions ( Temperature, holding time, heating rate, atmosphere, etc.) can be changed as appropriate.

[Dust core]
The powder magnetic core of the embodiment is mainly composed of coated iron powder having an insulating coating, and the coated iron powder is compressed and compressed, and each powder particle (particularly iron particles) constituting the coated iron powder is plastically deformed. In other words, the molded body is held in shape by meshing with each other. The dust core according to the embodiment includes powder particles of a specific size and contains a specific lubricant in a specific range. Hereinafter, each configuration will be described in detail.

-Coated iron powder Coated iron powder is a coating comprising iron particles composed of so-called pure iron (99% by mass or more of Fe, the balance being inevitable impurities) and an insulating coating that exists so as to cover the surface of the iron particles. It is a coating powder containing particles as a constituent element.

..Iron particles (iron powder)
One feature of the dust core of the embodiment is that the magnetic component is pure iron, which is a soft magnetic material. The powder magnetic core of the embodiment has high permeability and saturation magnetic flux density by pure iron as a main component. Pure iron is excellent in plastic deformability, deforms well even at a relatively low pressure, and can firmly bond particles. Therefore, the powder magnetic core of the embodiment mainly composed of pure iron is excellent in formability and easy to manufacture, and also excellent in mechanical strength and magnetic characteristics. In addition, the composition of the iron particles in the dust core substantially maintains the composition of the iron particles constituting the coated iron powder used as the raw material.

.. Insulation coating The insulation coating functions as an insulating material interposed between the iron particles constituting the dust core to prevent direct contact between the iron particles and increase the electrical resistance of the dust core. If it can insulate between iron particles, it will accept | permit that the area | region where a part of surface of an iron particle is not covered with insulation coating among the covering iron powder which comprises a powder magnetic core exists. For example, insulating materials that are scattered so as to surround the periphery of the iron particles can be regarded as insulating coatings. The powder magnetic core of the embodiment contains a specific lubricant, and since this lubricant is an insulator, it can function as an insulating material by interposing between iron particles. Even if it exists discontinuously, insulation between iron particles can be secured. Of course, when the entire surface of the iron particles is covered with the insulating coating, it is easier to reduce the eddy current loss.

Various insulating materials can be used as the constituent material of the insulating coating. For example, the insulating material includes a compound containing a metal element. Specifically, one or more metal elements selected from Fe, Al, Ca, Mn, Zn, Mg, V, Cr, Y, Ba, Sr, and rare earth elements (excluding Y), oxygen, One or more compounds selected from nitrogen and carbon (for example, metal oxides, metal nitrides, metal carbides), zirconium compounds, aluminum compounds, and the like can be given.
Examples of the compound containing a nonmetallic element include a phosphorus compound and a silicon compound. As an insulating material containing a metal element or a non-metal element, a metal salt compound, for example, a metal phosphate compound (typically, iron phosphate, manganese phosphate, zinc phosphate, calcium phosphate, etc.), a borate metal salt compound, a silicate metal salt Compounds, metal titanate salts and the like. Since the phosphate metal salt compound is excellent in deformability, when the coated iron powder comprising the phosphate metal salt compound is used as the raw material, the insulation coating easily deforms following the deformation of the iron particles during molding. And hard to damage. In addition, the metal phosphate compound has high adhesion to iron and is difficult to drop off from the surface of the iron particles during molding. From these points, the dust core produced by using the coated iron powder comprising a metal phosphate compound as an insulating coating as a raw material tends to exist in a healthy state of the insulating coating, reducing eddy current loss, Core loss is low.

Examples of other insulating materials include resins such as thermoplastic resins and non-thermoplastic resins, and higher fatty acid salts. In particular, a silicone-based organic compound such as a silicone resin is excellent in heat resistance, and thus hardly decomposes when subjected to heat treatment. From this point, the powder magnetic core produced using the coated iron powder comprising a silicone-based organic compound as an insulating coating as a raw material, thermal damage of the insulating coating is suppressed, and the insulating coating tends to exist in a healthy state. Reduces eddy current loss and low core loss.

厚 The thickness of the insulating coating is, for example, 10 nm or more and 1 μm or less. When the thickness is 10 nm or more, good insulation between the iron particles can be secured. When the thickness is 1 μm or less, there is little insulation coating, and a decrease in the proportion of the magnetic component in the dust core can be suppressed. A more preferable thickness is 20 nm or more and 100 nm or less, and about 50 nm is ideal. The thickness of the insulating coating constituting the dust core is determined by the composition of the film obtained by composition analysis (analyzer using transmission electron microscope and energy dispersive X-ray spectroscopy (TEM-EDX)), and inductively coupled plasma mass. Considering the amount of element obtained by the analyzer (ICP-MS), the equivalent thickness is derived, and further, the insulation coating is directly observed by the TEM photograph, and the order of the equivalent thickness derived earlier is appropriate. The average thickness is determined by confirming the value.

Typically, the composition of the insulating coating in the compacted powder magnetic core substantially maintains the composition of the insulating coating provided for the coated iron powder used as the raw material. However, depending on the material of the insulating coating at the raw material stage and the heat treatment conditions (temperature, etc.), the composition of the insulating coating at the raw material stage and the composition of the insulating coating in the dust core after the heat treatment may be different. Even in this case, if the material present after the heat treatment can insulate between the iron particles, it is regarded as an insulation coating.

..Size One of the characteristics is that the coated iron powder in the dust core is relatively coarse. Specifically, the average particle diameter of the coated iron powder is preferably 200 μm or more and 450 μm or less. Such a powder magnetic core can be typically manufactured by using, as a raw material, coated iron powder whose average particle diameter satisfies the above range. Since the coated iron powder having an average particle size of 200 μm or more is excellent in compression moldability, it can be molded at a relatively low pressure. Therefore, the powder magnetic core manufactured using such coated iron powder as a raw material can suppress the damage of the insulation coating, the insulation coating tends to exist in a healthy state, reduce the eddy current loss, and reduce the core loss. Low. The larger the average particle size of the coated iron powder used as a raw material, the better the moldability, the higher the density easily even at a relatively low pressure, and the better the fluidity and the easier it is to fill the mold. Therefore, the powder magnetic core manufactured using such coated iron powder as a raw material is excellent in strength and magnetic characteristics. Furthermore, the larger the average particle diameter of the coated iron powder, the shorter the total length of the powder grain boundaries, so that it is difficult for the lubricant to be excessively contained in the dust core. That is, in this dust core, an extremely small amount of an aliphatic lubricant can be appropriately present, and a decrease in density and a decrease in strength due to the presence of an excessive lubricant can be reduced or prevented. From these points, the average particle diameter of the coated iron powder in the dust core can be 220 μm or more, further 240 μm or more, and further 300 μm or more.

On the other hand, if the coated iron powder in the dust core is too large, an increase in eddy current loss due to an increase in the diameter of the iron particles can be caused. Therefore, the average particle diameter of the coated iron powder in the dust core is preferably 450 μm or less. When the average particle size is 425 μm or less, and further 400 μm or less, an increase in eddy current loss generated in the iron particles can be easily suppressed.

Moreover, it is preferable that the ratio of the powder particle | grains whose particle size is 75 micrometers or less is 10 mass% or less in the covering iron powder in a powder magnetic core. That is, it is preferable that 90 mass% or more of the coated iron powder is a powder particle exceeding 75 μm. A powder magnetic core with few or very small fine powder particles of 75 μm or less has an advantage of high magnetic permeability, in other words, high magnetic flux density when a predetermined magnetic field is applied. It can be said that such a powder magnetic core was manufactured by using a raw material powder having few fine powder particles as described above. When the raw material powder has few fine powder particles, it is excellent in compression moldability as described above, and in addition to the average particle size of the raw material powder, the powder particles have a uniform size (particle size distribution). ), The powder particles can be uniformly compressed and deformed. Therefore, the dust core produced using such coated iron powder as a raw material is more resistant to damage to the insulation coating, and the insulation coating is likely to exist in a healthy state, reducing eddy current loss, Core loss is low. The smaller the number of such fine powder particles, the larger the number of coarse powder particles having excellent compressibility, and the more easily the damage to the insulating coating is suppressed as described above. The proportion of powder particles having a diameter of 75 μm or less is preferably 8% by mass or less, more preferably 5% by mass or less, 3% by mass or less, and further preferably 1.5% by mass or less.

Furthermore, the coated iron powder in the dust core preferably has a ratio of powder particles having a particle size of 500 μm or more of 1% by mass or less. Such a dust core having very few or substantially no powder particles that are too large can prevent an increase in eddy current loss due to the presence of coarse particles and has a low core loss. It can be said that the above-mentioned powder magnetic core in which the very coarse powder particles are very few or substantially absent is produced by using a raw material powder having very few such coarse powder particles. If there are few powder particles that are too coarse in the raw material powder, the powder particles will have a uniform size in combination with the average particle size of the raw material powder (because the width of the particle size distribution becomes narrow). Can be uniformly deformed. Therefore, the dust core produced using such coated iron powder as a raw material is more resistant to damage to the insulation coating, and the insulation coating is likely to exist in a healthy state, reducing eddy current loss, Core loss is low. The smaller the powder particles that are too coarse, the easier it is to reduce eddy current loss. Therefore, the proportion of powder particles having a particle size of 500 μm or more in the dust core is 0.5 mass% or less, and further 0.1 mass. % Or less, particularly not substantially present.

The size of the coated iron powder in the compacted powder magnetic core depends on the size of the raw material powder. However, although the raw material powder is deformed by pressure compression at the time of molding, the particle size changes to some extent, but it is considered that the amount of change in particle size due to this shape change is not so large. Therefore, the size of the coated iron powder in the dust core can be treated as being approximately equivalent to the size of the raw material powder. A method for measuring the average particle diameter of the coated iron powder in the dust core and the content of powder particles having a specific particle diameter will be described later.

.. Lubricant One of the features of the powder magnetic core of the embodiment is that it contains a slight amount of an aliphatic lubricant.
The dust core of such an embodiment can be manufactured by using an aliphatic lubricant as a raw material. In the dust core according to the embodiment, the aliphatic lubricant used as a raw material does not become soot-like or tar-like even after heat treatment, and remains in the material before heat treatment.

... Characteristics Aliphatic lubricants have a relatively high melting point compared to ester waxes. Therefore, the difference between the room temperature and the melting point is sufficiently large, for example, since liquefaction can be suppressed even when the room temperature (air temperature) is high, (1) the raw material powder is excellent in fluidity and easy to uniformly fill the mold. (2) The liquefied lubricant stays in the mold, and the density of the compressed material can be suppressed from being reduced by entraining the retained material, (3) excellent in demolding property, (4) raw material powder or compressed material It is easy to handle and has excellent workability. Further, aliphatic lubricants, since the boiling point T _V is relatively low, even if the heat treatment temperature is relatively low can be easily removed. From these points, in the dust core manufactured using an aliphatic lubricant as a raw material, damage to the insulating coating during demolding and heat treatment is well suppressed.

Specifically, the melting point T _M of the aliphatic lubricant include 70 ° C. or higher 0.99 ° C. or less. Due to the relatively high melting point _TM of 70 ° C. or higher, the liquefaction is suppressed as described above, and defects caused by the increase in the viscosity of the raw material powder due to the liquefaction (decrease in fluidity, decrease in fillability, low Density, workability reduction, etc.) can be suppressed. When the melting point _TM is 150 ° C. or lower, the aliphatic lubricant can be easily removed even if the heat treatment temperature is lowered. A powder magnetic core manufactured using such an aliphatic lubricant as a raw material does not contain an aliphatic lubricant excessively and has a high ratio of magnetic components. Melting point _{T M} of the aliphatic lubricant, 90 ° C. or higher 120 ° C. or less, further include 95 ° C. or higher 115 ° C. or less.

Boiling point _{T V} of aliphatic lubricant include 220 ° C. or higher 280 ° C. or less. When the boiling point T _V is 220 ° C. or higher, by at least 220 ° C. The heat treatment temperature in order to remove the aliphatic lubricant may satisfactorily remove distortion introduced in the coated particles during molding. Therefore, a dust core produced using such an aliphatic lubricant as a raw material can reduce hysteresis loss and has low core loss. When the boiling point is 280 ° C. or lower, the aliphatic lubricant can be satisfactorily removed even when the heat treatment temperature is relatively low. For example, even when the heat treatment temperature is 500 ° C. or less, the aliphatic lubricant can be volatilized well and most of it can be removed. Therefore, a dust core manufactured using such an aliphatic lubricant as a raw material can contain a very small amount of an aliphatic lubricant while suppressing thermal damage of the insulating coating. . Furthermore, the boiling point of the aliphatic lubricant is 240 ° C. or higher and 260 ° C. or lower.

... Specific material A stearamide is mentioned as a more specific aliphatic lubricant. Stearamide is an aliphatic lubricant that has a melting point of around 100 ° C. and a boiling point of around 250 ° C., has excellent demolding properties, and can easily reduce damage to the insulation coating. Note that commercially available stearic acid amide may partially contain palmitic acid amide. Since the physical properties such as melting point and boiling point of palmitic acid amide are substantially the same as stearic acid amide, it is necessary to include palmitic acid amide in a part of stearic acid amide (for example, about 55% or less by mass). Allow. The melting point and boiling point differ slightly depending on the amount of palmitic acid amide.

... Content The powder magnetic core of the embodiment includes an aliphatic lubricant in an amount of 0.0045% by mass or more and 0.02% by mass or less. Lubricant amount W _C of the dust core is that it is such a very small amount, the dust core of the embodiment, even the insulation coating by compression or heat treatment during molding is damaged, fat between iron particles It is thought that it functions as an insulating material with a group-based lubricant interposed. Therefore, the powder magnetic core of the embodiment has an increased electrical resistance, can reduce eddy current loss, and has a small core loss. The more the lubricant amount W _C of the dust core, insulation between the iron particles by intervention of the lubricant, and Hakare sufficiently reduce the damage to the insulating coating due to the lubricant is present at the time of manufacture, low-loss pressure It can be a powder magnetic core. Therefore, the lubricant amount _{W C} of the dust core is 0.005 mass% or more, further 0.006 mass% or more, further can be 0.01 mass% or more. On the other hand, can lead to such as a decrease in reduction and strength of the density by excessive lubricant, the lubricant amount _{W C} of the dust core is 0.018 mass% or less, further 0.015 mass% or less, even zero. It can be 013 mass% or less. The lubricant amount W _C of the dust core can be adjusted by the lubricant amount W _P of the mixed powder, molding conditions, heat treatment conditions, and the like. Method of measuring the amount of lubricant W _C of the powder magnetic core will be described later.

The reason why the content of the aliphatic lubricant in the powder magnetic core of the embodiment is within the above range is as follows. The specific gravity of the coated iron powder is assumed to be equivalent to the specific gravity of the pure iron powder, 7.84, the specific gravity of the aliphatic lubricant is 1.0, and the shape of the powder particles constituting the coated iron powder is a sphere. It is assumed that the aliphatic lubricant remains so as to cover the surface of the powder particles with a uniform thickness. Under this assumption, if the content of the aliphatic lubricant in the dust core is 0.0045% by mass, the thickness of the aliphatic lubricant is about 15 nm. When the content is 0.02% by mass, the thickness of the aliphatic lubricant is about 60 nm. Here, the thickness of the insulating coating is ideally about 50 nm as described above. If the content of the aliphatic lubricant is 0.02% by mass, the powder particles are sufficiently covered with the aliphatic lubricant even if the powder particles are not spherical and have a wider surface area. It is considered possible. In addition, even if there are powder particles whose insulation coating is damaged in some of the coated iron powder that constitutes the powder magnetic core, the coating damage portion of the powder particles is repaired by covering with an aliphatic lubricant. It is considered that a sufficient insulation thickness can be secured. Furthermore, even if the insulation coating of all the coated iron powders constituting the dust core is damaged, it is considered that the insulation coating can be formed if the aliphatic lubricant is 0.02% by mass. On the other hand, if the amount of the aliphatic lubricant is 0.0045% by mass, the damaged part of the insulating coating can be selectively repaired. Specifically, it is possible to repair more than about 1/4 of the surface area of the iron particles. It is thought that. Therefore, the lower limit of the content of the aliphatic lubricant is 0.0045% by mass, and the upper limit is 0.02% by mass.

-Shape The powder magnetic core of the embodiment can take various shapes by using various shapes of molds. Typically, a columnar body having two opposing surfaces as end faces and a cylindrical body having through holes penetrating both end faces are exemplified. More specifically, a cylinder, a cylinder, a ring (thickness), a rectangular column such as a rectangular parallelepiped, a square cylinder whose end face is a rectangular frame, and the like can be given. In addition, the outer shape such as a shape having one or a plurality of steps or a shape including one or a plurality of flange portions at the end portion may be an irregular columnar body or cylindrical body having an uneven shape.

In particular, as the dust core of the embodiment, a cross section in the compression direction is taken, the length L in the compression direction (hereinafter sometimes referred to as height L), and the length D in the direction orthogonal to the compression direction (hereinafter referred to as height L). , Which may be referred to as diameter D), and the ratio L / D is more than 2.5. In this form, the shape is such that the height L is larger than the diameter D, that is, the side surface (height L) is longer than the end surface (diameter D). Examples thereof include a prismatic cylinder and a square cylinder (see, for example, an I-shaped core piece 10i in FIGS. 1, 3, and 6 described later). In the case of a cylinder or cylinder, the outer diameter corresponds to the diameter D, and in the case of a prism or square cylinder, the diameter of the envelope circle on the end surface corresponds to the diameter D. As a specific size, for example, the height L may be 5 mm to 100 mm, 5 mm to 50 mm, 10 mm to 30 mm, 10 mm to 25 mm. More specific shapes include a cylinder or a cylinder having a diameter D of 10 mm and a height L of more than 25 mm, and a prism having a polygon envelope circle having a diameter D of 10 mm and a height L of more than 25 mm.

細長い It can be said that the elongated powder magnetic core as described above is generally difficult to manufacture. However, the powder magnetic core of the embodiment is manufactured using a specific raw material including the coated iron powder having a size and material excellent in compression moldability and an aliphatic lubricant excellent in demoldability as described above. Therefore, even if it is such a shape, it can manufacture favorably and is excellent in manufacturability. In addition, even in such an elongated shape, the dust core produced using a specific raw material excellent in moldability as described above is uniformly compressed, so there is little variation in the compressed state, The variation in density is small, and the mechanical characteristics, magnetic characteristics, shape accuracy and dimensional accuracy are also excellent.

In addition, as one of the indexes for discriminating the compression direction of the powder magnetic core, there is a cross section of the powder magnetic core, and the elongation direction of the powder particles existing in the cross section. Since the powder magnetic core compresses and compresses the raw material powder, each powder particle constituting the raw material powder is crushed (plastically deformed) in the compression direction, and typically extends in a direction orthogonal to the compression direction. Shape. Therefore, it can be expected that the direction perpendicular to the elongation direction of the powder particles present in the cross section is the compression direction. Another example of the index to be discriminated is an outer shape. Since the dust core is typically a molded body using a uniaxial mold, its outer shape is limited to a shape that can be extracted from the mold. For example, the U-shaped core piece 10p provided in the magnetic core 10A shown in FIG. 1 or the magnetic core 10B shown in FIG. 2, the E-shaped core piece provided in the magnetic core 10D shown in FIG. 4 or the magnetic core 10E shown in FIG. 10e, in the rectangular frame-shaped core piece 10f provided in the magnetic core 10F shown in FIG. 6, it can be expected that the direction orthogonal to the paper surface is the compression direction. The rectangular frame-shaped core piece 10f has a through hole 10h, and the axial direction of the through hole 10h (here, the direction orthogonal to the paper surface) can be expected to be the compression direction.
Another example of the index to be discriminated is the presence or absence of a sliding contact mark. When a die core is formed on the contact surface with the die that forms the outer peripheral surface of the dust core, or when a through hole is provided, the contact surface with the rod that forms the inner periphery surface of the dust core is removed from the die or when the rod is removed. The compressed material and the die or rod may be in sliding contact, and a sliding contact mark may remain. That is, it can be expected that the surface with the slidable contact mark is a surface (side surface or inner peripheral surface) formed by a die or a rod, and the surface without the slidable contact mark is an end surface formed by a punch. Then, it can be expected that the direction orthogonal to the pair of end faces opposed to each other is the compression direction.

-Density The powder magnetic core of the embodiment has, for example, a density of 7.3 g / cm ³ or more and 7.7 g / cm ³ or less. When the density is 7.3 g / cm ³ or more, the relative density ((apparent density / true density) × 100. True density = the density of pure iron powder) is as high as 92% or more. Excellent.
The higher the density is, the better the strength and magnetic properties are. Therefore, the density of the dust core can be 7.35 g / cm ³ or more, and further 7.4 g / cm ³ or more. The density of the dust core can be increased by compressing and densifying the raw material powder, and can finally approach the true density. However, if the molding pressure is increased too much for further densification, the insulation coating may be damaged and the core loss of the dust core may increase. Also, there may not satisfy a predetermined amount of lubricant W _C. Therefore, the density of the dust core of the embodiment is preferably 7.7 g / cm ³ or less. The density of the dust core, 7.65 g / cm ³ or less, it is possible to further 7.6 g / cm ³ or less.

-Property The dust core of the embodiment has excellent magnetic properties by satisfying the above-mentioned density, for example. Specifically, the powder magnetic core of the embodiment includes a form in which the maximum magnetic permeability satisfies 350 or more, further 360 or more, preferably 380 or more, more preferably 400 or more. Regarding the core loss, the absolute value of the core loss varies depending on the average particle size due to the influence of the average particle size of the powder particles constituting the dust core of the embodiment. For example, when the average particle size is about 200 μm or more and 250 μm or less, the core loss is 52 W / kg or less, further 50 W / kg or less, preferably 45 W / kg or less, more preferably 42 W / kg, under the measurement conditions of 0.1 T and 10 kHz. A form satisfying kg or less is mentioned.

[Use example of dust core]
The dust core of the embodiment can be used as a constituent member of a magnetic path. Specifically, the powder magnetic core of the embodiment includes a coil formed by winding a winding in a spiral shape, and a component member of a coil component including a magnetic core that forms a magnetic path of a magnetic flux generated by a current flowing through the coil. Available to: A magnetic core is provided with the coil arrangement | positioning part by which a coil is arrange | positioned at least in part. More specifically, the dust core of the embodiment can constitute at least a part of the magnetic core. 1 to 6 show an example of a coil component. In the figure, the same reference numerals indicate the same names.

A coil component 1A according to Embodiment 1 shown in FIG. 1 includes, as a magnetic core 10A, an I-shaped core piece 10i that is a coil placement portion 12 and a saddle-shaped core piece 10p (right diagram in FIG. 1). . This magnetic core 10A is an O-shaped magnetic core that constitutes a rectangular frame-shaped closed magnetic path by combining both

core pieces

10i and 10p (the left diagram in FIG. 1). Here, an example in which a gap G is provided between both

core pieces

10i and 10p is shown.

A coil component 1B according to Embodiment 2 shown in FIG. 2 includes a pair of hook-shaped

core pieces

10p and 10p as a magnetic core 10B (the right diagram in FIG. 2). The magnetic core 10B is an O-shaped magnetic core that constitutes a rectangular frame-shaped closed magnetic path by combining both

core pieces

10p and 10p (the left diagram in FIG. 2).
Here, an example is shown in which a gap G is provided between both

core pieces

10p, 10p. In the magnetic core 10B, two connecting leg portions configured to be joined via the gap G out of the

core pieces

10p and 10p are respectively referred to as

coil placement portions

12 and 12, and the

coils

20 and 20 are respectively disposed. . As in the first embodiment, only one of the connecting leg portions can be used as the coil placement portion 12.

The coil component 1C of the third embodiment shown in FIG. 3 includes four I-shaped core pieces 10i to 10i as the magnetic core 10C (the right diagram in FIG. 3). The magnetic core 10C is an O-shaped magnetic core that combines these four core pieces 10i to 10i to form a rectangular frame-shaped closed magnetic path (the left diagram in FIG. 3). Here, an example is shown in which a gap G is provided between two

core pieces

10i, 10i that are arranged in parallel and another core piece 10i that connects these two

core pieces

10i, 10i.
In the magnetic core 10 </ b> C, the two

core pieces

10 i and 10 i arranged in parallel are used as the

coil arrangement portions

12 and 12, respectively, and the

coils

20 and 20 are arranged, respectively. As in the first embodiment, only one core piece 10 i can be used as the coil placement portion 12.

The coil component 1D of the fourth embodiment shown in FIG. 4 includes an E-shaped core piece 10e and an I-shaped core piece 10i as the magnetic core 10D (the right diagram in FIG. 4). The magnetic core 10D is an EI type magnetic core that forms a closed magnetic circuit as shown by a two-dot chain line in FIG. 4 by combining both the

core pieces

10e and 10i (the left diagram in FIG. 4). Here, an example is shown in which the central leg portion of the E-shaped core piece 10e is the coil placement portion 12, and a gap G is provided between the leg portion and the core piece 10i.

The coil component 1E of Embodiment 5 shown in FIG. 5 includes a pair of

E-shaped core pieces

10e, 10e as the magnetic core 10E (the right diagram in FIG. 5). The magnetic core 10E is an EE type magnetic core or an ER type magnetic core that forms a closed magnetic circuit as shown by a two-dot chain line in FIG. 5 by combining both

core pieces

10e and 10e (FIG. 5). Left figure). Here, an example is shown in which a gap G is provided between the central leg portions of both

core pieces

10e, 10e. In the magnetic core 10 </ b> E, the connecting leg portion formed by joining the central leg portions of the

core pieces

10 e and 10 e via the gap G is referred to as a coil placement portion 12. The outer connection leg portions arranged on both sides of the central connection leg portion can also be used as the coil arrangement portion.

A coil component 1F of Embodiment 6 shown in FIG. 6 includes a rectangular frame-shaped core piece 10f having a through hole 10h as a magnetic core 10F, and an I-shaped core piece 10i disposed inside the core piece 10f. Is provided. The magnetic core 10F is combined so that each end face of the I-shaped core piece 10i faces two opposing inner faces of the rectangular frame-shaped core piece 10f, and a closed magnetic circuit as shown by a two-dot chain line in FIG. Configure. In the magnetic core 10 </ b> F, the I-shaped core piece 10 i is used as the coil placement portion 12. Here, an example is shown in which a gap G is provided between the end surface of the I-shaped core piece 10i and the inner peripheral surface of the rectangular frame-shaped core piece 10f. The outer leg portion parallel to the I-shaped core piece 10 i in the rectangular frame-shaped core piece 10 f can also be used as the coil placement portion 12.

For example, all the magnetic components (here, the

core pieces

10i, 10p, 10e, and 10f) in the magnetic cores 10A to 10F can be used as the dust core of the embodiment. Part of the magnetic component in the magnetic cores 10A to 10F, for example, a core piece including the coil placement portion 12 can be used as the dust core of the embodiment.

The shapes of the magnetic cores 10A to 10F and the

core pieces

10i, 10p, 10e, and 10f shown in FIGS. 1 to 6 are examples, and can be appropriately changed to known shapes. For example, it can be set as the shape which has the curved surface which rounded the corner | angular part. In addition, for example, the shape is not a simple shape as shown in FIGS. 1 to 6, but a shape having one or a plurality of steps, a shape having one or a plurality of flange portions at the end, and an irregular shape having an uneven shape. It can be made into three-dimensional. The magnetic core provided in the coil component can be configured to be constructed by combining three core pieces or five or more core pieces. The dust core of the embodiment can constitute at least a part of the magnetic cores having such various shapes and forms.

The winding which comprises the saddle coil 20 includes a covered wire having an insulating layer on the outer periphery of the conductor. Examples of the conductor include a wire made of a conductive material such as copper, copper alloy, aluminum, and aluminum alloy. Examples of the wire include a round wire having a circular cross section and a rectangular wire having a rectangular cross section. Examples of the constituent material of the insulating layer include enamel, tetrafluoroethylene-hexafluoropropylene copolymer (FEP) resin, polytetrafluoroethylene (PTFE) resin, and silicone rubber. Known windings can be used. The number of the coils 20 included in the coil component can be a form including one, such as the coil component 1A of the first embodiment, or a form including a plurality, such as the coil component 1B of the second embodiment. When the pair of

coils

20 and 20 are provided, a form in which the coil axes are arranged side by side so as to be parallel as shown in FIGS. 2 and 3 is representative.

The heel gap G can be appropriately provided so as to obtain desired magnetic characteristics. It can be set as the form which is not equipped with the gap G. The gap G can be an air gap in addition to a form using a gap material made of a nonmagnetic material.

[Production method of dust core]
The manufacturing method of the powder magnetic core of the embodiment prepares a mixed powder containing a coating powder mainly composed of a soft magnetic material and a specific lubricant as a raw material (preparation step), and mixes using a mold. The powder magnetic core is manufactured by compression-molding the powder (molding step) and then performing a heat treatment (heat treatment step). Hereinafter, each process will be described in detail.

-Preparation process In this process, first, the mixed powder used for a raw material is prepared. The coated iron powder, which is the main component of the mixed powder, is a coated powder containing coated particles including iron particles and an insulating coating as components, similar to the coated iron powder described in the above-mentioned powder magnetic core. Detailed descriptions of the iron particles, the material of the insulating coating, and the thickness are omitted because they overlap with the above-mentioned dust core.

As the iron powder constituting the coated iron powder used as the raw material for soot, for example, those manufactured by a known method such as an atomizing method such as a gas atomizing method or a water atomizing method can be used. Since the size of the coated iron powder depends on the size of the raw iron powder, the size of the raw iron powder is adjusted so that the coated iron powder has a desired size. For example, the size of the coated iron powder can be adjusted to a desired size by classification using a sieving method or the like.

For forming the insulation coating on the pig iron powder, for example, chemical conversion treatment such as phosphate chemical conversion treatment, spraying of a solvent, sol-gel treatment using a precursor, and the like can be used. When forming a coating of a silicone organic compound, wet coating using an organic solvent, direct coating using a mixer, or the like can be used. Commercially available coated iron powder can be used as the raw material coated iron powder.

One of the characteristics is that the coated iron powder used for the koji raw material is relatively coarse. Specifically, the average particle size of the coated iron powder is preferably 200 μm or more and 450 μm or less. By setting the average particle diameter of the coated iron powder as the raw material in the above range, the method for manufacturing a dust core according to the embodiment has the following effects (A) to (E). The average particle diameter of the coated iron powder used for the raw material can be 220 μm or more, further 240 μm or more, and further 300 μm or more. Moreover, the average particle diameter of the coated iron powder used for the raw material can be 425 μm or less, and further 400 μm or less. When using commercially available coated iron powder, it can be appropriately classified so as to obtain a desired particle size.

(A) Since it is excellent in compression moldability, it is easy to increase the density even if the molding pressure is relatively low. By suppressing the molding pressure to a low level, the method for manufacturing a dust core according to the embodiment can satisfactorily suppress damage to the insulation coating and manufacture a dust core having a low core loss.
(B) Since it is excellent in compression moldability, it can be satisfactorily molded even if the amount of aliphatic lubricant used is relatively small, and it is easy to increase the density. A dust core having a high ratio can be manufactured.
(C) Since the total length of the powder grain boundary can be shortened, in combination with the small amount of the above-mentioned aliphatic lubricant, a dust core containing an excessive amount of the aliphatic lubricant is manufactured. Can be prevented.
(D) It is possible to reduce iron particles that are too coarse, suppress an increase in eddy current loss due to the presence of coarse particles, and manufacture a dust core with low core loss.
(E) Excellent fluidity and easy to fill in the mold. Also from this point, the manufacturing method of the powder magnetic core of the embodiment can suppress the damage of the insulating coating, can manufacture the powder magnetic core with low core loss, and is excellent in workability.

It is preferable that the ratio of the powder particle whose particle size is 75 micrometers or less is 10 mass% or less for the covering iron powder used for a cocoon raw material. As explained in the above-mentioned section of the dust core, the powder having a small or very small particle size of 75 μm or less is mostly composed of relatively coarse powder particles having excellent compression moldability. It can be said that. The manufacturing method of the powder magnetic core of the embodiment uses the coated iron powder mainly composed of such relatively coarse coated particles (90% by mass or more) as a raw material, so that even if the molding pressure is relatively small, the method is high. Densification is possible. Therefore, the method for manufacturing a powder magnetic core according to the embodiment can manufacture a high-density powder magnetic core while suppressing the molding pressure low and satisfactorily suppressing damage to the insulating coating during molding. That is, the dust core manufacturing method of the embodiment can manufacture a dust core having low core loss and excellent strength and magnetic properties. In addition, this raw material powder, in combination with the above-mentioned average particle diameter, has a uniform powder particle size, and uniformly applies a molding pressure to the raw material powder to make the compressed state uniform. Easy to do. That is, it is difficult for powder particles to be locally compressed with a large pressure. Also from this point, the method for manufacturing a dust core according to the embodiment can favorably suppress damage to the insulating coating during molding. Furthermore, by using such a raw material powder, an increase in eddy current loss due to the presence of coarse grains can be suppressed as described above, and a low-loss dust core can be manufactured. Considering the reduction of eddy current loss, the proportion of powder particles having a particle size of 75 μm or less in the raw material powder is 8% by mass or less, further 5% by mass or less, 3% by mass or less, and further 1.5% by mass or less. preferable.

It is preferable that the ratio of the powder particle | grains whose particle size is 500 micrometers or more is 1 mass% or less, as for the covering iron powder used for a cocoon raw material. As explained in the above-mentioned section of the powder magnetic core, the raw material powder having very few or substantially no powder particles that are too coarse, such as 500 μm or more, is combined with the above average particle diameter, The size is uniform, uniform compression can be performed, and it is easy to prevent compression with excessive local pressure. Also from this point, the method for manufacturing a dust core according to the embodiment can favorably suppress damage to the insulating coating during molding. Furthermore, by using such raw material powder, an increase in eddy current loss due to the presence of coarse particles can be effectively suppressed as described above, and a low-loss powder magnetic core can be manufactured. Considering the reduction of eddy current loss, the ratio of the powder particles having a particle diameter of 500 μm or more in the raw material powder is preferably 0.5% by mass or less, more preferably 0.1% by mass or less, and particularly not substantially present.

It is preferable that the raw material powder satisfy | fills both the ratio of the powder particle whose particle size is 75 micrometers or less and 10 mass% or less and the ratio of the powder particle whose particle diameter is 500 micrometers or more are 1 mass% or less. Such a raw material powder, combined with the above-mentioned average particle size, has a more uniform size of the powder particles (the particle size distribution is very narrow) and, as described above, damage to the insulation coating, And it is easier to suppress an increase in eddy current loss. By pulverizing the iron powder or appropriately classifying the iron powder or the coating powder, a raw material powder having such a particle size distribution can be obtained. The magnitude | size of the covering iron powder in raw material powder, and the mass ratio of a specific particle size can be measured by using a commercially available particle size measuring apparatus. More simply, while classifying using a sieve, the mass ratio can also be measured by measuring the mass of the selected powder particles having a specific particle diameter.

One of the characteristics of the raw material powder is that it contains a relatively small amount of a specific lubricant (aliphatic lubricant) in addition to the coated iron powder. Specifically, the lubricant amount _{W P} of the mixed powder is 0.5 mass% or less than 0.2 wt%. A detailed description of the material and characteristics of the aliphatic lubricant is omitted because it overlaps with the term of the powder magnetic core described above.

As described above, the raw material powder containing 0.2% by mass or more of an aliphatic lubricant (for example, stearamide) that is excellent in demoldability and can be removed even at a relatively low temperature is obtained at the time of molding. It is possible to suppress damage to the insulating coating due to rubbing between the powder particles, and to suppress damage to the insulating coating due to rubbing between the compressed material and the mold during demolding. More lubricant amount W _P of the mixed powder is large, is enhanced lubricity, easy to suppress damage to the insulating coating. Further, as the lubricant amount W _P of the mixed powder is large, the insulation coated iron particles are exposed damaged portion even exists, brought sufficiently interposed aliphatic lubricant between the iron particles. Therefore, the lubricant amount _{W P} of the mixed powder can be 0.23 mass% or more, further 0.26% or more. When the lubricant amount W _P of the mixed powder is too large, or inhibit the dense compacts, decreases the proportion of the magnetic component is too large, the residual amount after heat treatment, a decrease in the degradation or magnetic properties of strength I invite you. Further, since the coated iron powder is excellent in compression deformability as described above, it can be densified and densified without using an aliphatic lubricant excessively. Therefore, the lubricant amount _{W P} of the mixed powder is 0.5 mass% or less. Lubricant amount _{W P} of the mixed powder can be 0.48 mass% or less, further 0.45% by weight or less.

It is preferable that the aliphatic lubricant is powdered so as to be easily mixed with the coated iron powder. The average particle size of the lubricant powder is preferably smaller than the average particle size of the coated iron powder so as to easily adhere to the coated particles. For example, the average particle diameter of the lubricant powder is 1 μm or more and 100 μm or less, and further 30 μm or more and 50 μm or less.

For mixing the cocoon-coated iron powder and the aliphatic lubricant, an appropriate mixer such as a V-type mixer or a double cone mixer can be used. In addition, the mixed powder can be obtained by spraying an aliphatic lubricant dissolved in a solvent so as to cover the surface of the coated iron powder. It is preferable to mix so as not to damage the insulating coating of the coated iron powder.

The content of the coated iron powder in the soot mixed powder is preferably 99.0% by mass or more and can be the remainder excluding the aliphatic lubricant. However, in order to improve the shape retention of the compressed product, the mixed powder can contain additives such as a resin that can be removed during heat treatment in addition to the coated iron powder and the aliphatic lubricant. If the additive content is too high, the ratio of magnetic components will decrease, the removal of lubricant will be hindered, the strength and magnetic properties will decrease due to the residue of the additive, and if the residue is a conductive substance such as carbon, eddy current Since there is a risk of increasing the loss, etc., 0.5% by mass or less is preferable. Specific additives include polyacetal (POM), polyamide (PA), polycarbonate (PC), polybutylene terephthalate (PBT), modified polyphenylene ether (m-PPE), polyphenylene sulfide (PPS), polyether ether ketone ( Engineering plastics such as PEEK) and polyetherimide (PEI).

-Molding process In this process, the above-mentioned mixed powder prepared as a raw material is filled in a mold and pressed and compressed to form a compressed product. The mold typically uses a die having a die having a through hole and a pair of punches that form a molding space together with the die and pressurize and compress the mixed powder. Specifically, a part of the inner peripheral surface of the die and one surface of one punch (the surface facing the other punch) form a bottomed cylindrical forming space, and this forming space is filled with mixed raw material powder Then, the mixed powder of the filled raw material is pressed and compressed by both punches and formed into a desired shape. And a compression thing is obtained by extracting from a die | dye. In the case of manufacturing a cylindrical or annular dust core having a through hole, it is preferable to use a die provided with a rod that is inserted into the through hole of the die and forms a through hole of the compressed product. When molding a compressed product having a step, a pair of punches each divided into a plurality of punches can be used. A known configuration can be used as the configuration of the mold.

Then, in the molding step, so that the lubricant amount W _G of compressed foam is 0.485 mass% or less than 0.135 wt%, and one feature that performs molding of compacts. Lubricant amount W _G of compacts adjusts the molding conditions for the lubricant amount W _P of the mixed powder to the extent that is reduced by the above-mentioned range.

Here, the lubricant in the mixed powder of the raw material is extruded and pressed out from between the powder particles to the surface of the compressed material by pressure compression, and prevents the surface of the compressed material (molded body) from being scratched during demolding. At the same time, the compressed product and the mold are rubbed together and scraped off. As a result, the lubricant amount W _G of compacts is smaller than the lubricant amount W _P of the mixed powder. The above-mentioned seepage and shaving off tend to increase due to, for example, an increase in molding pressure and an increase in friction force at the time of demolding due to an increase in springback due to an increase in molding pressure. It is in.
Further, the above-mentioned oozing and scraping off tends to increase when, for example, the mold temperature is high and the aliphatic lubricant easily flows. That is, when the lubricant amount W _G of compressed foam is too small, or have added a large molding pressure in the compression material, which may aliphatic lubricant may not be sufficiently remain in compacts. As a result, the insulating coating is easily damaged. Conversely, if the lubricant amount W _G of compressed foam is exists sufficient, it can be said that can reduce the damage to the insulating coating. Therefore, in the method for producing a dust core of the embodiment, a molding as a guide lubricant amount W _G of compacts. The amount of scraping off at the time of demolding in the aliphatic lubricant can be controlled, for example, by adjusting the pressure (holddown pressure) sandwiched between the upper and lower molds (a pair of punches) when extracting the compressed product. . For example, when the hold down pressure is reduced, the amount of scraping off tends to be reduced.

By lubricant amount W _G of compressed foam is 0.135 mass% or more, can reduce the damage to the insulating coating as described above. In addition, since the compressed product before heat treatment contains an aliphatic lubricant to this extent, most of it can be removed well during heat treatment, and a dust core containing a very small amount of aliphatic lubricant after heat treatment can be removed. Can be manufactured. Lubricant amount W _G of compacts, since it is considered easy to reduce damage often more insulating coating can be 0.14 mass% or more, further 0.145 mass% or more. When the lubricant amount W _G of compressed foam is too high, not completely removing the aliphatic lubricant in the heat treatment step, it becomes dust core aliphatic lubricant is too large, lowering the reduction and magnetic characteristics of strength.
Therefore, the lubricant amount _{W G} of compacts shall be 0.485 mass% or less. Lubricant amount _{W G} of compacts can be 0.48 mass% or less, further 0.475 mass% or less. Method of measuring the amount of lubricant W _G of compacts will be described later. In this step, the lubricant amount W _G 65% 97% or more degrees below the lubricant amount W _P of the mixed powder compacts, further set to be about 75% or more 90%.

In the molding step, for example, it is preferable to mold so that the density of the compressed product is 7.3 g / cm ³ or more and 7.7 g / cm ³ or less. Here, the density of the compressed product is typically increased by increasing the molding pressure. Conversely, if the molding pressure is relatively low and the density of the compressed product is reduced, the friction between the powder particles can be reduced, or the frictional force at the time of demolding can be reduced to reduce the friction between the mold and the compressed product. The insulation coating can be made difficult to be damaged by reducing the fit. That is, if the density of the compressed material is not too high, it can be said that damage to the insulating coating can be reduced. The density of 7.7 g / cm ³ or less is a molding pressure that takes into account the use of raw material powders excellent in compression moldability and the use of aliphatic lubricants excellent in demoldability. Even if it is relatively low, it can be reached relatively easily. If the molding pressure is relatively low, damage to the insulating coating can be reduced. Therefore, it is proposed that the density of the compressed material be in the above-mentioned range as a guide for reducing damage to the insulating coating in the molding process.

By setting the density of the compressed material to 7.3 g / cm ³ or more, the density of the dust core after the heat treatment can be easily set to 7.3 g / cm ³ or more, and a high-density dust core can be manufactured. The higher the density of the compressed material, the easier it is to produce a dust core having a higher density, that is, a powder core having a high strength and excellent magnetic properties. Therefore, it is 7.35 g / cm ³ or more, and further 7.4 g / cm ³ or more. It can be. On the other hand, the lower the density of the compressed product, the easier it is to reduce the molding pressure and the damage to the insulation coating can be reduced. Moreover, since it does not compress too much, it is easy to shorten the total length of the powder grain boundary of a compressed material, and can make it easy to discharge | emit an aliphatic lubricant at the time of heat processing. Thus, the density of the compacts is, 7.65 g / cm ³ or less, it is possible to further 7.6 g / cm ³ or less.

In the manufacturing method of the powder magnetic core of the embodiment, by using the above-described specific raw material that is excellent in moldability, high density can be achieved even if the molding pressure is relatively small. For example, the molding pressure can be less than 1000 MPa, further 900 MPa or less, and further 800 MPa or less. By molding at such a low pressure, it is possible to prevent damage to the insulating coating well and to prevent the aliphatic lubricant from flowing out excessively. Also, the mold is not easily damaged. On the other hand, a molding pressure 500MPa or more, further 550MPa or more, more With more than 600 MPa, while suppressing the damage to the insulating coating, can lubricant amount _{W G} of compacts than 0.135 wt%, more The density can be 7.3 g / cm ³ or more.

In the cocoon molding process, molding can be performed with the mold heated. Here, if the mold is in a heated state to some extent, the raw material powder is also warmed by heat conduction to improve the moldability of the coated iron powder, or the aliphatic lubricant is softened to some extent and becomes easy to flow. Thus, the compression moldability can be improved. For example, even when the molding pressure is lowered, a compressed product having excellent shape accuracy and dimensional accuracy can be produced. Therefore, the mold can be heated using an appropriate heating means. On the other hand, when continuous molding is performed using the same mold, the mold is heated to a temperature higher than room temperature (for example, about 20 ° C. to 25 ° C.) over time due to frictional heat between the mold and the compressed product. The state can be automatic (for example, about 40 ° C. to 50 ° C.). Therefore, in the middle stage and the final stage of molding, the moldability can be improved as described above without separately heating. On the other hand, when such continuous molding is performed, if the mold is not heated separately, the mold is at a low temperature at the initial stage of molding, so that the molded product is molded at the initial stage of molding and at the middle and final stages of molding. The state may be different. Therefore, in consideration of industrial mass production, when performing continuous molding as described above, it is preferable to keep the mold at a constant temperature from the initial stage of molding.

When the mold is heated, the mold temperature is, for example, (T _M / 2) ° C. or higher and T _M ° C. or lower. 1/2 or more temperatures the melting point _{T M} of the mold temperature aliphatic lubricants (e.g., if the melting point _{T M} is 90 ℃ ~ 120 ℃, 45 ℃ ~ 60 ℃ about) With the mold Can be sufficiently heated, and the above-described moldability can be improved. By controlling the mold temperature to a relatively low temperature of the melting point _TM or less (for example, if the melting point is 90 ° C. to 120 ° C., the melting point or less), excessive softening of the aliphatic lubricant is suppressed, the lubricant amount W _G of compressed foam becomes too small, i.e., it is possible to suppress the aliphatic lubricant remaining in the compressed material is too small. By setting the mold temperature within the above range, the aliphatic lubricant can be sufficiently softened by being heated close to its melting point T _M , and the aliphatic system that has exuded from the compressed material during demolding or the like. It becomes easy to remove the lubricant to some extent by rubbing with the mold. Accordingly, the form of adjusting the mold temperature to the above-mentioned range, the lubricant amount W _G of compressed foam is easily obtained compressed product is a particular range described above. Further, in this embodiment, since the aliphatic lubricant only reaches below its melting point T _M, not including aliphatic-based lubricant from the compressed product after demolding runs down, the lubricant amount W _G of compacts are A dust core satisfying a specific range can be manufactured. Mold temperature, be a _{(T M} × 0.5) ℃ above _{(T M} × 0.95) ℃ or less, further _{(T M} × 0.55) ℃ above _{(T M} × 0.9) ℃ or less Can do. Incidentally, the time required for die molding, is because, even if the mold temperature to the same temperature as the melting point T _M, never aliphatic lubricant is completely liquefied and extremely short time.

The mold can be held at a lower temperature (for example, room temperature or lower) using a water cooling device or the like. This form makes it easy to obtain a compressed product with excellent dimensional accuracy. In this embodiment, when performing the above-described continuous molding, the mold may be constantly cooled.

The atmosphere at the time of molding can be an air atmosphere, for example. Oxidation of an iron component can be prevented even if it is set as the atmosphere containing oxygen because the covering iron powder of a raw material is equipped with insulation coating. Moreover, since the air atmosphere is an inert atmosphere such as about 80% of nitrogen, even when the insulating coating is peeled off and a part of the iron particles is exposed, the iron component reacts with a gas other than oxygen. Can be prevented. Furthermore, since the atmospheric atmosphere is easy to control, it is excellent in workability.

The metal mold | die used for a cocoon molding process can be suitably selected so that the compression product (powder magnetic core) of a desired shape may be obtained. In particular, in the case of molding the above-described elongated magnetic core, the die has an opening diameter D (the diameter in the case of a circular hole, the shape in the case of a non-circular hole including a polygon). It is preferable to use a through hole having a sufficiently long axial length with respect to the diameter of the envelope circle. Specifically, it is preferable to use a material in which the ratio L / D of the depth L to the opening diameter D in the molding space formed by the die and the punch can be more than 2.5. A die having such a long through-hole is, for example, an assembly formed by combining a plurality of divided pieces, and these divided pieces are stacked in the axial direction of the through-hole to form a single through-hole communicating with the die. What you form can be used. The manufacturing method of the powder magnetic core of the embodiment is based on the use of a specific raw material containing an aliphatic lubricant that is mainly composed of coated iron powder having a material and size excellent in compression moldability and excellent in demoldability. Even a compressed product having such a shape that is inferior in mold release can be manufactured with high accuracy. In particular, even when a long and narrow compact is manufactured, the coated powder can move well in the mold, so that variations in the compressed state can be reduced, and a dust core with small variations in density can be manufactured.

In the mold, a release coating can be applied to a region in contact with the mixed powder or the compressed material. The release coating is selected from, for example, DLC, TiN, TiC, CrN, and Ti—XN (where X is at least one element selected from C, Al, Cr, Mo, and W). There is at least one kind. For forming the release coating, a known physical vapor deposition method, chemical vapor deposition method, arc method or the like can be used, and in particular, a sputtering method can be suitably used.
By performing release coating, it is possible to improve the demoldability.

Heat treatment step In this step, a heat treatment is performed on a compressed product containing a specific amount of an aliphatic lubricant. One purpose of this heat treatment is to remove the aliphatic lubricant. However, one feature of the method for manufacturing a dust core according to the embodiment is that the aliphatic lubricant is not completely removed, but heat treatment is performed so as to remain slightly. Specifically, the heat treatment conditions are adjusted so that the lubricant amount W _C of the dust core obtained after the heat treatment is 0.0045 mass% or more and 0.02 mass% or less. In this step, 1% 5% or more degrees below the lubricant amount W _G of the lubricant amount W _C compression of the powder magnetic core, and further set to be the extent of 4% or less than 2%.

Here, the lubricant in the compressed product disappears from the compressed product by liquefaction by heating or by thermal decomposition and vaporization. As a result, the lubricant amount W _C of the powder magnetic core is less than the lubricant amount W _G of compacts. The amount of the aliphatic lubricant removed from the compressed product depends on the heat treatment temperature and the holding time. The higher the heat treatment temperature and the longer the holding time, the greater the removal amount. That is, the lubricant in the powder magnetic core is not substantially remain, or has a residue such as soot and tar, when the lubricant amount W _C of the dust core is very small, the heat treatment temperature There is a risk that it is too high or the holding time is too long. As a result, the insulating coating is easily damaged by heat. Conversely, if the amount of lubricant W _C of compacts satisfies the specific range, it is possible to reduce the thermal damage to the insulating coating can be produced dust core sound insulating coating is present. Therefore, in the method of manufacturing a dust core according to the embodiment, heat treatment is performed using the lubricant amount W _C of the dust core as a guide. The method of manufacturing a dust core according to the embodiment is characterized in that the amount of lubricant is controlled in the three stages of the raw material stage (W _P ), the molding stage (W _G ), and the heat treatment stage (W _C ). One of them. The amount of lubricant W _C of the dust core is as described in the section above the dust core.

· Heat treatment conditions dust core lubricant amount W _C as a heat treatment condition for adjusting the range described above, for example, the following conditions (T _V: boiling aliphatic lubricant).
Heat treatment temperature: a temperature selected from the range of (T _V +100) ° C. to (T _V +200) ° C.
Heat treatment temperature holding time: a time selected from 5 minutes to 60 minutes.
Atmosphere: Flow atmosphere of mixed gas of oxygen and inert gas.

... Heat treatment temperature If the lower limit of the heat treatment temperature is (T _V +100) ° C. or higher, the heat treatment temperature is sufficiently higher than the boiling point T _V, so that the aliphatic lubricant is sufficiently volatilized, and the aliphatic lubricant Can be removed well. The higher the heat treatment temperature, the easier the aliphatic lubricant is volatilized. One of the purposes of the heat treatment is to reduce hysteresis loss by removing strain introduced into the compressed product during molding. The higher the heat treatment temperature, the better the strain can be removed. Therefore, by increasing the heat treatment temperature to (T _V +115) ° C. or higher and further to (T _V +125) ° C. or higher, it is easy to remove the aliphatic lubricant and strain. If the heat treatment temperature is too high, since the insulating coating is easily thermal _damage, preferably (T V +200) ℃ less, considering the suppression of damage to the insulating _coating, (T V +185) ℃ or less, further _{(T V} +175) ° C. or lower is preferable.

Specific heat treatment temperature includes, for example, 350 ° C. or higher and 450 ° C. or lower. In particular, when it exceeds 450 ° C., it is considered that an aliphatic lubricant such as stearamide completely disappears after heat treatment. Accordingly, the heat treatment temperature is preferably 450 ° C. or lower, more preferably 435 ° C. or lower, and further preferably 425 ° C. or lower.

... Holding time By making the holding time of the said heat processing temperature into 5 minutes or more, an aliphatic lubricant can be volatilized and most aliphatic lubricants can be removed favorably. The longer the holding time, the easier the aliphatic lubricant can be removed, and it can be 10 minutes or longer, and further 15 minutes or longer. On the other hand, by shortening the holding time, the time during which the dust core is exposed to a high temperature (heat treatment temperature) can be shortened, and thermal damage to the insulating coating can be easily suppressed. Therefore, the holding time can be 50 minutes or less, and further 45 minutes or less.

... Atmosphere Conventionally, when the raw material powder contains iron powder, the atmosphere of the heat treatment is often an inert atmosphere such as a nitrogen atmosphere in order to prevent oxidation. Also in the manufacturing method of the dust core of the embodiment, the atmosphere of the heat treatment can be an inert atmosphere using an inert gas such as nitrogen or argon. However, in order to thermally decompose and actively discharge components containing carbon (C) such as aliphatic lubricants, an atmosphere containing oxygen is preferable. In order to prevent excessive oxidation of the iron component, an atmosphere containing an inert gas is preferable. Therefore, the atmosphere during the heat treatment is preferably a mixed gas atmosphere containing oxygen and an inert gas.

The higher the oxygen content in the atmosphere, the easier the thermal decomposition of the aliphatic lubricant, the easier it is to chemically change the carbon component to carbon monoxide, carbon dioxide, etc., and the better the aliphatic lubricant can be removed. it is conceivable that. However, if there is too much oxygen, an insulating coating is provided, but the iron component may be oxidized. Therefore, the oxygen content in the atmosphere is 40 volume% or less, further 30 volume% or less, and further 25 volume. % Or less is preferable. The oxygen content in the atmosphere is preferably 5% by volume or more, more preferably 10% by volume or more, and further preferably about 15% by volume or more. In the method for manufacturing a dust core according to the embodiment, since damage to the insulating coating can be suppressed as described above, a portion where the insulating coating is damaged and the iron component is exposed hardly occurs. Therefore, it is easy to prevent oxidation of the iron component even in an oxygen-containing atmosphere. Since the heat treatment temperature can be made relatively low, it is easy to prevent oxidation. The manufacturing method of the powder magnetic core of the embodiment is highly industrially significant in that an oxygen-containing atmosphere that can efficiently decompose and remove the aliphatic lubricant can be used.

In particular, the mixed gas atmosphere can be an air atmosphere (the oxygen content is about 20% by volume). Use of air is preferable because it is easy to control and has excellent workability.

In particular, the atmosphere during the heat treatment is preferably a flow atmosphere. By setting it as a flow atmosphere, the new oxygen (unreacted oxygen) which is not couple | bonded with carbon etc. can be sequentially supplied to a compressed material. Therefore, it is considered that the carbon component of the aliphatic lubricant can be easily chemically changed to carbon monoxide, carbon dioxide, etc., and the aliphatic lubricant can be removed well.

.. Density The density of the dust core obtained after the heat treatment is as high as 7.3 g / cm ³ or more and 7.7 g / cm ³ or less as described in the section of the dust core of the above embodiment. Thus, a dust core having excellent strength and magnetic properties can be obtained, which is preferable. The density of the dust core after the heat treatment is higher than the density of the compressed product by removing the aliphatic lubricant by the heat treatment and densifying it. Depending on the heat treatment conditions, pores may be formed after the aliphatic lubricant is removed, and the density of the dust core may be lower than the density of the compact. Even in this case, the density of the compressed material is set to 7.3 g / cm ³ or more and 7.7 g / cm ³ or less, and the heat treatment conditions are adjusted so that the density is 7.3 g / cm ³ or more and 7.7 g / cm ³ or less. A powder magnetic core satisfying the above can be manufactured.

The density of the compacted powder magnetic core can typically be changed by adjusting the removal amount of the aliphatic lubricant. When the removal amount of the aliphatic lubricant is increased, that is, when the heat treatment temperature is increased or the holding time is lengthened, the density after the heat treatment tends to be increased. However, the insulating coating is likely to be thermally damaged. Conversely, if the heat treatment temperature is lowered or the retention time is shortened to reduce the amount of lubricant removed, thermal damage to the insulating coating is easily suppressed. Thus, it is considered that the density of the dust core can be used to some extent as a guideline for reducing damage to the insulating coating in the heat treatment process.

As described in the section of the dust core of the above-described embodiment, the dust core manufactured by the method of manufacturing the dust core of the above-described embodiment (one form of the dust core of the embodiment) Damage is suppressed and core loss is low. Detailed description is omitted.

[Test Example 1]
Powder magnetic cores were manufactured under various conditions, and the magnetic properties and core loss were investigated.

Here, a mixed powder containing coated iron powder as a raw material powder and stearamide as an aliphatic lubricant was prepared. The coated iron powder is mainly composed of coated particles having an insulating coating (thickness of about 50 nm) made of iron phosphate around iron particles made of pure iron (Fe is 99 mass% or more, the remainder is inevitable impurities). And The prepared coated iron powder was classified. Table 2 shows the average particle diameter, the ratio of powder particles having a particle diameter of 75 μm or less, and the ratio of powder particles having a particle diameter of 500 μm or more. The ratio of the powder particles having a specific particle size indicates the ratio of each particle size when the total weight of the raw material powder before classification is 100% by mass. Sample No. 1-1, no. 1-100, No. 1 The particle size distribution of the coated iron powder used for 1-200 is shown in FIG. The horizontal axis of the particle size distribution shown in FIG. 7 is the particle size (μm), the left vertical axis is frequency (%), and the right vertical axis is cumulative (%). Both frequency and accumulation are mass percentages.
The particle size distribution was measured using a commercially available laser diffraction / scattering particle size / particle size distribution measuring apparatus. The average particle size of the coated iron powder as a raw material is measured with the above particle size distribution measuring apparatus, and the particle size at which the integrated weight is 50%, that is, 50% particle size (mass). As shown in FIG. 7, this coated iron powder is a relatively coarse particle having a narrow particle size distribution and about 70% by mass or more being 200 μm or more. Sample No. 1-2 ~ No. Similarly, the coated iron powder used in 1-6 has many relatively coarse particles, and about 50% by mass or more is particles of 200 μm or more.

Table 2 shows the content of the aliphatic lubricant in the mixed powder (mass%, the ratio in which the mixed powder is 100 mass%), and the melting point T _M (° C.) and boiling point T _V (° C.) of the aliphatic lubricant. . Any of the aliphatic lubricants used for each sample is commercially available as stearamide. Sample No. When the composition of the mixed powder used in 1-1 was analyzed, the aliphatic lubricant used in this sample contained about half of stearamide and palmitic acid amide as shown in Table 1. When the composition of the mixed powder was analyzed for other samples, the aliphatic lubricant contained palmitic acid amide in addition to stearic acid amide. Some were slightly different from 1-1. The average particle diameter of the aliphatic lubricant used for each sample can be appropriately selected from the range of 1 μm or more and 100 μm or less.

The mold was filled with the mixed powder and pressed and compressed to form a cylindrical compact. For example, sample no. In 1-1, a compressed product having a diameter D of 10 mm (1 cm) and a height L of 30 mm (3.0 cm) was molded. About other samples, height L was changed suitably and ratio L / D was varied appropriately. Table 2 shows the ratio L / D of each sample. In any of the samples, the molding conditions were as follows: the atmosphere was an air atmosphere, the molding pressure was a value selected from 686 MPa to 882 MPa (7 ton / cm ² to 9 ton / cm ² ), and the mold temperature (° C.) was a value shown in Table 2. It was. The density (g / cm ³ ) of the obtained compressed product (molded product / intermediate product) and the lubricant amount W _G (% by mass) of the compressed product were measured. The results are shown in Tables 1 and 2.

The density of the compressed product was determined by measuring the mass (g) of the compressed product using the Archimedes method and dividing the measured mass by the volume of the compressed product (density = mass / volume).

Lubricant amount W _G of compacts was measured as follows. The compressed product is pulverized by a pulverizer (atmosphere), and 1 g of a powder having a size approximately equal to the coating powder used as a raw material is weighed. A mixed liquid is obtained by adding 1 ml of acetone to 1 g of the weighed powder. From this mixed solution, an aliphatic lubricant (here, stearamide and palmitic amide) is dissolved and recovered by ultrasonic extraction (60 minutes). The recovered aliphatic lubricant was qualitatively and quantitatively analyzed by gas chromatography. Lubricant amount W _G of compacts is the proportion of the compressed product is 100 mass%.

As shown in Table 1, Sample No. 1-1, because a relatively coarse powder was used as a raw material, a high-density compression of 7.48 g / cm ³ even at a relatively low pressure, such as a molding pressure of less than 1000 MPa (here, 900 MPa or less). It can be seen that a product is obtained (relative density: about 95%). Sample No. 1-2 ~ No. Similarly for 1-6, even with relatively low pressure molding as described above, as shown in Table 2, the density is very high at 7.32 g / cm ³ or more, and further 7.69 g / cm ^3. It can be seen that a compressed product is obtained.

In addition, as shown in Table 1, the obtained sample No. It can be seen that the compressed product of 1-1 has a reduced amount of the aliphatic lubricant as compared with the raw material mixed powder. Specifically, Sample No. 1-1 lubricant amount _{W P} of the mixed powder of a 0.409 wt%, but the lubricant amount _{W G} of compacts is 0.351 mass%. That is, sample no. Lubricant amount W _G of the compression of the 1-1 aliphatic lubricant is reduced about 15% in the mass ratio, the said. Thus the reason that can be reduced to some extent the aliphatic lubricant (10% to about 25% of the amount of lubricant W _P at a mass ratio), is considered below. Although the total length of the powder grain boundary is short due to the use of a relatively coarse powder, the amount of aliphatic lubricant used as a raw material is relatively small, and the density is not increased too much at a relatively low pressure. It is conceivable that the lubricant can be prevented from being excessively scraped off during demolding. Sample No. 1-2 ~ No. 1-6 Similarly, the lubricant amount W _G of compacts, it is seen that every time is reduced that is compared to the amount of lubricant W _P of the mixed powder. The obtained sample No. 1-1-No. As a result of visual confirmation of the compressed product 1-6, the contact surface of the compressed product with the die (side surface of the cylinder) had few scratch marks, and damage to the insulating coating of the coated iron powder constituting this surface was suppressed. It was confirmed that

The obtained compact is subjected to heat treatment under the following conditions to produce a dust core, and the density (g / cm ³ ) of the obtained dust core and the amount of lubricant W _C (% by mass) of the dust core. Was measured. The results are shown in Tables 1 and 3. Measurements of density and amount of lubricant W _C was conducted in the same manner as compacts. Lubricant amount W _C of the dust core is the proportion of the powder magnetic core is 100 wt%.

In all samples, the heat treatment conditions were such that the atmosphere was an air flow atmosphere, the heat treatment temperature (° C.) and the heat treatment temperature holding time (minutes) were as shown in Table 2, and the temperature elevation rate was 5 ° C./min.

As shown in Table 1, Sample No. 1-1 shows that the compact before heat treatment has a relatively high density, and the dust core (heat treated body) after heat treatment also has a high density of 7.48 g / cm ³ (relative density: About 95%). Sample No. 1-2 ~ No. 1-6 Similarly for a ^{7.3g / cm 3 ~ 7.7g / cm} 3 as shown in Table 2, it can be seen a high density. When these dust cores (heat treated bodies) were examined, the aliphatic lubricant was removed and pores existed inside. Due to the presence of the pores, it is likely that it is difficult to measure the density of the compressed product (molded body) before heat treatment with high accuracy compared to the dust core after heat treatment. For this reason, the density of the powder magnetic core may be slightly different from the density of the compressed product, but is approximately the same here.

In addition, as shown in Table 1, the obtained sample No. It can be seen that the powder magnetic core of 1-1 remained very slightly although the amount of the aliphatic lubricant was greatly reduced as compared with the compressed product before the heat treatment. Specifically, Sample No. 1-1 the lubricant amount _{W G} of the compression of a 0.351 wt%, but the lubricant amount _{W C} of the dust core is 0.013 mass%. The following is considered as the reason why such a trace amount of the aliphatic lubricant is left in the dust core. Since the total length of the powder grain boundary is short due to the use of a relatively coarse powder, the heat treatment temperature is relatively low (however, here the boiling point T _V + 100 ° C. or more) and the holding time is relatively Although it is a short time, it is considered that the aliphatic lubricant was sufficiently discharged from the grain boundary. Moreover, it is considered that the aliphatic lubricant was easily decomposed into carbon monoxide, carbon dioxide, etc. by setting it to an air flow atmosphere. Furthermore, because the density is not increased too much, it is considered that a sufficient discharge route for the volatilized aliphatic lubricant could be secured and the aliphatic lubricant could be discharged sufficiently. Sample No. 1-2 ~ No. Similarly, as shown in Tables 2 and 3, 1-6 also shows that although the amount of the aliphatic lubricant is greatly reduced as compared with the compressed product before the heat treatment, it remains very slightly. (0.005 mass% to 0.016 mass%). The obtained sample No. 1-1-No. When the 1-6 dust core was observed with a scanning electron microscope (SEM), thermal damage to the insulation coating could not be substantially confirmed. Therefore, it is considered that the above-described conditions used for the production of these dust cores can satisfactorily suppress damage to the insulation coating. In addition, in this test, it can be seen that when the heat treatment temperature is increased (here, close to 450 ° C.), the aliphatic lubricant can be sufficiently removed even in a shorter time (here, less than 15 minutes).

Here, the heat treatment temperature (typically, the temperature of the workpiece put into the furnace. For example, a hole is provided in the workpiece for temperature measurement, and a sensor such as a thermocouple is inserted in the center of the workpiece. can be measured by such.) was set to the boiling point T _V of aliphatic lubricant, by holding this temperature for a predetermined time, in theory, be removed by volatilizing the aliphatic lubricant Can do. However, depending on the size, shape, heating rate, etc. of the compressed product, for example, when the compressed product is long or large, when the heating rate is fast, an aliphatic lubricant present in the compressed product. The temperature that can be removed by volatilizing may be higher than the boiling point. Table 2 shows the temperature at which the aliphatic lubricant present in the compressed product can be volatilized and removed in this test as the volatilization completion temperature. The volatilization completion temperature is associated with the volatilization of the lubricant contained in the raw material powder when the raw material powder is heated at a predetermined temperature increase rate with a thermal analyzer (for example, a TG / DTA simultaneous measurement device manufactured by Shimadzu Corporation). This is the temperature at which weight loss is zero. The volatilization completion temperature is generally higher than the boiling point, and the higher the temperature increase rate during measurement, the higher the temperature. Sample No. 1-1-No. In No. 1-6, the aliphatic lubricant could be satisfactorily removed by setting the heat treatment temperature to the boiling point T _V + 100 ° C. or higher, the boiling point T _V , and a temperature sufficiently higher than the volatilization completion temperature. Conceivable. Incidentally, the heat treatment temperature even when the same temperature as the boiling point T _V of aliphatic lubricant, if longer holding time can be removed aliphatic lubricant. However, by setting the heat treatment temperature to the boiling point T _V or higher, preferably the boiling point T _V + 100 ° C. or higher, the holding time can be shortened, and the productivity can be improved by shortening the heat treatment time.

The average particle size of the coated iron powder constituting the obtained powder magnetic core was measured as follows. Take a cross-section parallel to two opposing flat surfaces (here, circular end faces) of the outer surface of the dust core, and observe this cross-section with a microscope. Extract. The area of the extracted coated particles is measured, and the diameter of a circle (equivalent area circle) equal to this area is taken as the diameter of the coated particles. The diameter of 100 or more coated particles existing in the visual field is measured, and the average is defined as the average particle diameter of the coated iron powder in the dust core. The extraction of the coated particles and the calculation of the diameter can be easily performed by image processing the observed image and binarizing it. The image processing can be easily performed by using a commercially available image processing apparatus. Further, in the coated iron powder constituting the obtained dust core, the mass ratio of powder particles having a particle size of 75 μm or less and the mass ratio of powder particles having a particle size of 500 μm or more were measured as follows. The area ratio of the coated particles in the cross section is converted into a volume ratio (for example, volume ratio = 1.5 to the area ratio), and the volume ratio and the density of the coated particles are used for calculation. The density of the coated particles can be calculated based on the composition by analyzing the composition by X-ray diffraction, EDX, or the like. As a result of the measurement, the average particle diameter of the coated iron powder in the dust core of each sample, the mass ratio of the powder particles having a particle diameter of 75 μm or less, and the mass ratio of the powder particles having a particle diameter of 500 μm or more are the values of the raw material powder. It was maintained substantially. In addition, the obtained powder magnetic core maintained the ratio L / D of the compressed product.

For comparison, Sample No. For Sample 1-1, the heat treatment conditions were changed. 1-100 was prepared. Sample No. The powder magnetic core of 1-100 had a heat treatment temperature of 530 ° C. (boiling point T _V + 280 ° C.) and a point other than the retention time of 30 minutes. It was produced in the same manner as in 1-1. The prepared sample No. For the dust core of 1-100, sample no. 1-1 In the same manner as, the measured amount of lubricant W _C, could not be substantially detected aliphatic lubricant.
Therefore, Table 3 shows the amount of lubricant _{W C} and 0 mass%. This is because, since the heat treatment temperature is much higher temperature than the boiling point T _V of aliphatic lubricants, aliphatic lubricant completely disappeared, believed.

For comparison, Sample No. In contrast to Sample 1-1, Sample No. 1 was obtained by changing the lubricant amount W _P of the mixed powder used as the raw material, the molding pressure, and the heat treatment conditions. 1-200 was prepared. Sample No. Dust core 1-200 are that the lubricant amount _{W P} of the mixed powder was 0.6 mass%, the point where the molding pressure was 1000 MPa, that was 325 ° C. The heat treatment temperature (the boiling point _T V + 75 ℃) The points other than the sample No. It was produced in the same manner as in 1-1. The prepared sample No. For the dust core of 1-200, Sample No. 1-1 In the same manner as, the measured amount of lubricant W _C, remained many aliphatic lubricant. Specifically, as shown in Table 3, the lubricant amount _{W C} is 0.050 mass%. This is because the relatively although coarse powder is used, on the amount of lubricant W _P is large, the molding pressure is too high longer total length of the grain boundaries, aliphatic lubrication during demolding This is probably because the aliphatic lubricant could not be discharged sufficiently because the agent was not removed much, the heat treatment temperature was low, and the holding time was relatively short.

The maximum magnetic permeability and core loss (W / kg) of the obtained dust core were measured. The results are shown in Table 3.

Maximum magnetic permeability and core loss were measured as follows by preparing a toroidal magnetic measurement test piece. The test piece is manufactured so as to have the same density and the same heat treatment condition as the density and heat treatment condition of each sample. The test piece has a toroidal shape, and the size is an outer diameter of 34 mm, an inner diameter of 20 mm, and a thickness of 7 mm. A copper wire is wound around the test piece of each sample to produce a measurement member (coil component) having a primary winding coil: 300 turns and a secondary winding coil: 20 turns. For the maximum magnetic permeability, the maximum magnetic permeability of the initial magnetization curve when the applied magnetic field was excited to 250 Oe (≈20 kA / m) was obtained using the produced measurement member and DC-BH curve tracer. The core loss is the iron loss (eddy current loss + hysteresis loss) of the sample when the excitation magnetic flux density Bm is 1 kG (= 0.1 T) and the measurement frequency is 10 kHz using the produced measurement member and AC-BH curve tracer. ) This iron loss is defined as core loss. Table 3 shows the maximum permeability and core loss.

As shown in Table 3, Sample No. containing an aliphatic lubricant in a very small amount (0.0045 mass% to 0.02 mass%). 1-1-No. It can be seen that all cores 1-6 have a low core loss. Here, Sample No. 1-1-No. All of 1-6 are 70 W / kg or less, and most are 60 W / kg or less. The reason for this is that, as described above, the sample No. 1-1-No. The 1-6 dust core was considered to have been able to satisfactorily suppress damage to the insulation coating as described above and to have high electrical resistance and low eddy current loss during the manufacturing process (particularly the molding process and heat treatment process). It is done. In addition, it is considered that the aliphatic lubricant contained in a very small amount was interposed between the powder particles and functioned as an insulating material between the powder particles, because the electrical resistance was increased. Thus, it can be seen that even a dust core made of relatively coarse coated iron powder can reduce the core loss.

試料 Also, sample no. 1-1-No. It can be seen that each of the 1-6 dust cores has a high magnetic permeability with a maximum magnetic permeability of 350 or more, further 400 or more. The reason for this is that, as described above, the sample No. 1-1-No. Although the 1-6 dust core contains an aliphatic lubricant, it is considered that the amount of the magnetic component is high and the density is high because the amount is extremely small.

On the other hand, Sample No. containing substantially no aliphatic lubricant. It can be seen that the 1-100 dust core has high core permeability but high core loss. The reason for this is that, as described above, the sample No. In 1-100, although the heat treatment temperature is too high, the insulating coating is thermally damaged, and the iron particles are connected to each other and the magnetic permeability is increased. However, the electrical resistance is reduced and the eddy current loss is increased. It is thought that.

On the other hand, sample no. No. 1-200 has a low maximum magnetic permeability, and the core loss is no. It is larger than 1-1. Sample No. The reason why the maximum magnetic permeability of 1-200 is low is thought to be that a large amount of the aliphatic lubricant, which is a non-magnetic material, remains and the distance between the iron particles spreads on the nanometer order and the gap is increased. Sample No. The reason why the core loss of 1-200 is large is that although the distortion introduced into the coated iron powder has increased due to the increased molding pressure, the distortion loss due to heat treatment is insufficient, and the hysteresis loss has increased. Conceivable.

From this test, the amount of lubricant in the molding process and heat treatment process is specified using a mixed powder mainly composed of coated iron powder of a specific material and size and containing an aliphatic lubricant in a specific range. It was confirmed that a powder magnetic core containing an extremely small amount of an aliphatic lubricant could be produced by producing so as to be in the above range. Moreover, it was confirmed that the obtained powder magnetic core had a low core loss.

The dust core of the present invention can be used for magnetic cores of various coil components (for example, reactors, transformers, motors, choke coils, antennas, fuel injectors, ignition coils, etc.). The method for manufacturing a dust core of the present invention can be used for manufacturing the dust core.
The coil component of the present invention can be used for a reactor, a transformer, a motor, a choke coil, an antenna, a fuel injector, an ignition coil, and the like.

1A, 1B, 1C, 1D, 1E,

1F Coil parts

10A, 10B, 10C, 10D, 10E, 10F Magnetic core 10i I-shaped core piece 10p U-shaped core piece 10e E-shaped core piece 10f Rectangular frame -Shaped core piece 10h Through-hole 12 Coil arrangement part G Gap 20 Coil

Claims

Coated iron powder with an insulating coating;
An aliphatic lubricant,
The coated iron powder is
The average particle size is 200 μm or more and 450 μm or less, and the proportion of powder particles having a particle size of 75 μm or less is 10% by mass or less,
A dust core in which the content of the aliphatic lubricant is 0.0045% by mass or more and 0.02% by mass or less.
2. The dust according to claim 1, wherein the ratio L / D between the length L in the compression direction and the length D in the direction orthogonal to the compression direction is greater than 2.5 for a cross section in the compression direction of the dust core. core.
The powder magnetic core according to claim 1 or 2, wherein the aliphatic lubricant has a melting point of 70 ° C or higher and 150 ° C or lower and a boiling point of 220 ° C or higher and 280 ° C or lower.
The powder magnetic core according to any one of claims 1 to 3, wherein the aliphatic lubricant contains stearamide.
The dust core according to any one of claims 1 to 4, wherein the density is 7.3 g / cm 3 or more and 7.7 g / cm 3 or less.
A coil component comprising a coil and a magnetic core,
A coil component comprising the dust core according to claim 1 in at least a part of the magnetic core.
Coated iron powder having an average particle diameter of 200 μm or more and 450 μm or less and a ratio of powder particles having a particle diameter of 75 μm or less and 10% by mass or less, and aliphatic lubrication of 0.2% by mass or more and 0.5% by mass or less A preparation step of preparing a mixed powder containing an agent;
A molding step of filling the mixed powder into a mold and pressurizing and compressing, and producing a compressed product containing 0.135% by mass or more and 0.485% by mass or less of the aliphatic lubricant,
A method for producing a dust core, comprising: subjecting the compressed product to a heat treatment to produce a dust core containing 0.0045% by mass or more and 0.02% by mass or less of the aliphatic lubricant.
The heat treatment conditions are as follows:
The heat treatment temperature is a temperature selected from the range of the boiling point of the aliphatic lubricant + 100 ° C. or more and the boiling point + 200 ° C. or less,
The holding time of the heat treatment temperature is a time selected from 5 minutes to 60 minutes,
The method for producing a dust core according to claim 7, wherein the atmosphere is a mixed gas flow atmosphere of oxygen and inert gas.
The method of manufacturing a dust core according to claim 7 or 8, wherein the coated iron powder has a ratio of powder particles having a particle size of 500 µm or more of 1 mass% or less.
The density of the compressed product and the density of the powder magnetic core are 7.3 g / cm 3 or more and 7.7 g / cm 3 or less. Production of the powder magnetic core according to any one of claims 7 to 9. Method.
The molding according to any one of claims 7 to 10, wherein in the molding step, molding is performed in a state where the mold is heated to a temperature equal to or higher than ½ of the melting point of the aliphatic lubricant and equal to or lower than the melting point. The manufacturing method of the powder magnetic core as described.
The mold includes a die having a through-hole, and a pair of punches that press-compress the mixed powder by forming a molding space together with the die.
The method for manufacturing a dust core according to any one of claims 7 to 11, wherein a ratio L / D of the depth L to the opening diameter D in the molding space is more than 2.5.
A dust core produced by the method for producing a dust core according to claim 7.