JP6423629B2 - Powder core and coil parts - Google Patents

Description

  The present invention relates to a dust core used for a coil component and the like, and a coil component including a dust core. In particular, the present invention relates to a dust core having a high magnetic permeability, a low core loss, and excellent manufacturability.

  As a magnetic core for a coil component or the like, there is a powder magnetic core manufactured by molding raw material powder. In Patent Document 1, a coated iron alloy powder having an insulating film and a coated iron powder having a particle size larger than that of the iron alloy powder and mixed with an insulating film are molded and molded, and the demolded compressed material is 500 ° C. or higher. Discloses a dust core produced by heat treatment at a high temperature.

Japanese Patent Laying-Open No. 2005-303006

  Development of a powder magnetic core having high magnetic permeability, low core loss and excellent manufacturability is desired.

  The permeability of the powder magnetic core is increased as the soft magnetic powder constituting the powder becomes larger. Therefore, the dust core of Patent Document 1 containing iron powder larger than the iron alloy powder can easily increase the magnetic permeability. Further, a dust core in which an insulating material such as an insulating film is interposed between metal particles such as iron particles can increase electrical resistance and reduce core loss such as eddy current loss. In the powder magnetic core of Patent Document 1, even if the insulating coating of the iron particles is thermally deteriorated by high-temperature heat treatment, the coated iron alloy powder that is difficult to proceed with the thermal deterioration of the insulating coating and easily holds the insulating coating is interposed between the large iron particles. Thus, the insulation between the iron particles is easily maintained. However, when high-temperature heat treatment is performed, the number of steps is large and the productivity of the dust core is poor. In addition, damage to the insulating film due to high-temperature heat treatment cannot be prevented.

  Damage to the insulating coating can occur not only during heat treatment, but also due to friction between powder particles, friction between the compact and the mold, during molding before heat treatment. In patent document 1, when resin, such as a silicone resin, is added to raw material powder, moldability can be improved and damage to the insulation film at the time of shaping | molding can be suppressed. However, the resin alone does not provide sufficient lubricity at the time of molding, and it is desired that damage to the insulating coating at the time of molding can be further reduced.

  Accordingly, one of the objects of the present invention is to provide a dust core having a high magnetic permeability, a low core loss, and an excellent manufacturability. Another object of the present invention is to provide a coil component including a dust core having a high magnetic permeability, a low core loss, and an excellent manufacturability.

  The powder magnetic core which concerns on 1 aspect of this invention contains the covering iron powder provided with an insulating film, and a 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 lubricant has a content of 0.3% by mass to 0.8% by mass and includes a fatty acid amide.

  The coil component which concerns on 1 aspect of this invention is a coil component provided with a coil and a magnetic core, Comprising: Said powder magnetic core is provided in at least one part of the said magnetic core.

  The dust core and the coil component have a high magnetic permeability, a low core loss, and an excellent manufacturability.

It is explanatory drawing which shows typically the structure | tissue of the powder magnetic core of embodiment. FIG. 2 is a schematic configuration diagram illustrating a coil component according to the first embodiment. FIG. 6 is a schematic configuration diagram showing a coil component according to a second embodiment. FIG. 6 is a schematic configuration diagram illustrating a coil component according to a third embodiment. FIG. 6 is a schematic configuration diagram illustrating a coil component according to a fourth embodiment. FIG. 10 is a schematic configuration diagram illustrating a coil component according to a fifth embodiment. FIG. 10 is a schematic configuration diagram illustrating a coil component according to a sixth embodiment.

[Description of Embodiment of the Present Invention]
As a result of various studies using the coating powder in producing a dust core having high magnetic permeability and low core loss, the present inventors have obtained the following knowledge.
In order to increase the magnetic permeability, it is preferable that the soft magnetic powder constituting the powder magnetic core has a large number of powder particles so that the magnetic flux can easily pass therethrough.
In order to reduce the core loss, it is effective to reduce the damage to the insulating film during the manufacturing process in order to increase the insulation of the dust core (in order to increase the electrical resistance). In order to reduce the damage to the insulating coating, it is necessary to use iron powder having a high deformability and a relatively large particle size, omitting heat treatment, and sufficiently adding a lubricant having excellent lubricity to the raw material powder. preferable.
-Measures for reducing the damage of the insulating coating described above can improve the manufacturability of the dust core.
-By omitting the heat treatment, the lubricant added to the raw material powder is substantially not thermally denatured, unlike the case where the heat treatment is performed, and substantially maintains the same components and addition amount as the raw material.

  Based on the above findings, the powder core has a high magnetic permeability, low core loss, and excellent manufacturability, including relatively large coated iron powder, including lubricant in a specific range and specified as a lubricant It is proposed to contain First, the contents of the embodiment of the present invention will be listed and described.

  (1) The powder magnetic core which concerns on 1 aspect of this invention contains the covering iron powder provided with an insulating film, and a 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 lubricant has a content of 0.3% by mass to 0.8% by mass and includes a fatty acid amide.

  The dust core has a high magnetic permeability because it includes a relatively large iron powder. In addition, the above-described dust core has a small amount of small coated iron powder, so that the reduction in the ratio of the magnetic component due to the insulating coating provided on these powder particles can be reduced, so that the magnetic permeability can be increased. And since said powder magnetic core has high electrical resistance because an insulating film and a lubricant intervene between iron particles for the following reasons, core loss can be lowered.

  The above-mentioned dust core contains relatively large iron powder, contains a relatively large amount of lubricant, and contains a specific component lubricant, thus effectively reducing and preventing damage to the insulation film during the manufacturing process. Thus, it can be said that the insulating coating of the coated iron powder used for the raw material powder exists in a healthy state. In addition, even if there is a damaged portion, it can be said that the lubricant, which is an insulating material, is sufficiently contained, so that the lubricant can be interposed between many iron particles, and these iron particles can be insulated. Therefore, it can be said that the above-mentioned powder magnetic core is excellent in insulating properties due to interposition of an insulating film or a lubricant between iron particles, and has high electric resistance. Since the eddy current loss is inversely proportional to the electric resistance, the above-described dust core having a high electric resistance has a low eddy current loss and consequently a low core loss.

  Furthermore, since the above-mentioned dust core sufficiently contains the lubricant and contains the lubricant of the specific component, it can be said that the lubricant used in the manufacturing process remains, that is, the heat treatment is omitted. From this point, it is excellent in manufacturability.

  In addition, since the above-mentioned dust core contains a relatively large coated iron powder, a relatively large coated iron powder is used as a raw material powder, and the powder particles are sufficiently meshed and densified (during molding) during the manufacturing process. However, it has excellent strength and high density. In addition, the above-described dust core is likely to have high magnetic permeability even by densification.

  (2) As an example of the above-mentioned powder magnetic core, it includes bare iron powder not provided with an insulating coating, and the bare iron powder has an average particle diameter of 40 μm or more and 150 μm or less, and is a powder particle having a particle diameter of 200 μm or more. The form whose ratio is 10 mass% or less is mentioned.

  The said form is excellent in intensity | strength compared with the case where only coating | coated iron powder is used. The above-mentioned form containing bare iron powder is a component that is easily deformed because the bare iron powder of the raw material powder is easily deformed, and since there is no insulating film, the deformed bare iron particles are interposed between the coated iron particles. This is because the coated iron particles can be firmly bonded to each other. Since the surface of the bare iron powder without the insulating coating is not very smooth, it is considered that it can be firmly joined because it is easy to mesh with the coated iron particles. In addition, bare iron powder that is sufficiently smaller than the coated iron powder is interposed in a gap (such as a triple point) formed by the large coated iron particles, so that it is easy to densify and to increase the density. It is easy to deform in the gaps and the like, and is excellent in manufacturability. Furthermore, from the viewpoints of strengthening the bonding state between the large coated iron particles, densification, and suppressing the decrease in the ratio of the magnetic component due to the insulating coating, the above configuration can increase the magnetic permeability of the material containing relatively small bare iron powder. Because it is possible to suppress the increase in eddy current loss due to the bare iron particles that are too large, and because the insulation of the coated iron powder and lubricant are present around the bare iron particles, the bare iron particles are difficult to contact with each other, so the insulation is excellent. In the above-described embodiment, the core loss of the bare iron powder having no insulating coating is low. In addition, the amount of coated iron powder can be reduced by containing bare iron powder, and cost reduction can be expected.

  (3) As an example of said powder magnetic core, the form whose content of the said covered iron powder in the magnetic component of the said powder magnetic core is 50 to 100 mass% is mentioned.

  In the above form, since the large coated iron powder occupies more than half of the magnetic component, the magnetic permeability is high, the insulation is excellent, and the core loss is low. When the above-mentioned bare iron powder is included (when the content of the coated iron powder is less than 100% by mass), it is possible to achieve high strength and low cost as described above. If only the coated iron powder (content of the coated iron powder is 100% by mass), the magnetic permeability is high, the insulation is superior due to the intervening insulating coating and lubricant, and the core loss is lower.

  (4) As an example of the dust core including the bare iron powder, a form in which the content of the bare iron powder in the magnetic component of the dust core is 10% by mass or more and 45% by mass or less can be given.

  In the above-mentioned form, since the large coated iron powder occupies the majority (55% by mass or more) of the magnetic component, the magnetic permeability is high, the core loss is low, and the bare iron powder is included in a specific range. In addition, high strength and low cost can be achieved. In particular, since the above form does not have too many bare iron powders, the contact between the bare iron particles can be reduced or suppressed, and the insulation properties of those containing bare iron powders are excellent. Within the above range, there is no insulating coating, and even if there are many relatively small bare iron powders, the magnetic permeability can be high and the core loss can be low.

  (5) As an example of said powder magnetic core, the form in which the said fatty acid amide contains stearic acid amide is mentioned.

  Stearamide is superior in lubricity compared to resin and can satisfactorily prevent damage to the insulating coating during the production process (particularly during demolding). Therefore, in the above-described embodiment, damage to the insulating film during the manufacturing process is effectively reduced and prevented, and the insulating property is excellent and the core loss is low.

  (6) As an example of the powder magnetic core which concerns on 1 aspect of this invention, the form in which the said lubricant contains a fatty acid metal salt is mentioned.

  The fatty acid metal salt is excellent in lubricity and can satisfactorily prevent damage to the insulating coating. In the above-mentioned form, the lubricant contains both a fatty acid amide and a fatty acid metal salt that are excellent in lubricity, so that damage to the insulating coating in the production process is effectively reduced and prevented, and the insulation is excellent, and as a result, the core loss is reduced. Low.

  (7) As an example of the dust core according to one embodiment of the present invention, a form containing a polyamide-based resin in an amount of more than 0 to 0.5% by mass or less can be given.

  The polyamide-based resin functions as a binder for the powder particles constituting the powder magnetic core, and can increase the strength. Therefore, the said form is excellent in intensity | strength.

  (8) A coil component according to an aspect of the present invention includes a coil and a magnetic core, and the dust core according to any one of (1) to (7) above is provided on at least a part of the magnetic core. Is provided.

  The coil component has a high magnetic permeability because the powder core has the high magnetic permeability, the core loss is low, and the above-described dust core having excellent manufacturability is provided in at least a part (preferably all) of the magnetic core. Low core loss and excellent manufacturability.

[Details of the embodiment of the present invention]
Hereinafter, a dust core, a manufacturing method thereof, and a coil component according to an embodiment of the present invention will be described in detail with reference to the drawings as appropriate. FIG. 1 schematically shows the size and shape of powder particles, the blending ratio of powder, and the like for convenience of explanation, and the actual size, shape, and blending ratio may differ.

[Dust core]
The dust core 1 of the embodiment is a molded body mainly composed of soft magnetic powder, and is coated iron powder composed of coated iron particles in which the outer periphery of iron particles 12 is covered with an insulating coating 14 as shown in FIG. 10 is included. The powder core 1 typically retains its shape, for example, when the raw material powder P is compressed and compressed, and the powder particles constituting the coated iron powder 100 are plastically deformed and meshed with each other. The dust core 1 further includes a lubricant 30. Further, the dust core 1 can include bare iron powder 20 in addition to the coated iron powder 10. Hereinafter, each configuration will be described in detail.

・ Coated iron powder ・ ・ Iron powder (iron particles)
One feature of the dust core 1 of the embodiment is that the magnetic component is pure iron. By using pure iron as the main component, the dust core 1 has high permeability and saturation magnetic flux density. Moreover, since the main component of the raw material powder P is also pure iron because the main component is pure iron, the powder core 1 is excellent in plastic deformability, easy to mold, and excellent in manufacturability. The effect (especially magnetic permeability) is easily improved, and the powder particles are sufficiently meshed with each other to provide excellent mechanical strength. Therefore, in the powder magnetic core 1, both the iron particles 12 of the coated iron powder 10 that are essential components and the bare iron powder 20 that is an optional component are pure iron.

  As for the pure iron which comprises the iron particle 12 and the bare iron powder 20, 99 mass% or more is Fe, and the remainder makes an inevitable impurity. It is expected that the hysteresis loss can be reduced as the inevitable impurities in the pure iron are reduced, and that the electrical resistance is increased and the eddy current loss can be reduced to some extent as it is higher. The total impurity amount of the coated iron powder 10 in the dust core 1 (when the bare iron powder 20 is included, the total amount of the coated iron powder 10 and the bare iron powder 20) is, for example, 2000 mass ppm or more and 8000 mass ppm. The following are mentioned. If it is this range, the fall of the magnetic permeability resulting from inclusion of an impurity can be suppressed, and if the total amount of impurities is smaller (for example, 3000 mass ppm or less), the hysteresis loss can be easily reduced as described above. (For example, more than 3000 ppm by mass and more than 4000 ppm by mass) is expected to contribute to the reduction of eddy current loss. The total amount of impurities is typically extracted by pulverizing the powder magnetic core 1 and removing the lubricant 30 and other additives described later from the mixture of the pulverized powder and an organic solvent such as acetone. It can be measured by analyzing the remainder (see the method for measuring the amount of lubricant in Test Example 1 described later). In the case where a component that does not dissolve in the organic solvent can be contained, for example, a comprehensive analysis can be performed by performing thermal analysis or infrared spectroscopic analysis. It is difficult to separate the iron particles 12 and the insulating coating 14 and analyze the components precisely. Therefore, component analysis is performed in a state including the coated iron powder 10. When the coated iron powder 10 and the bare iron powder 20 are included, the pulverized powder is separated into the respective powders 10 and 20, and the components of the coated iron powder 10 and the bare iron powder 20 are analyzed, and impurities of both are analyzed. Add up. Examples of the inevitable impurities of the bare iron powder 20 include Mn, Cu, Ni, Cr, Mo, Zn, S, P, Si, carbon, oxygen, and the like. The element of inevitable impurities of the bare iron powder 20 substantially matches the component of the bare iron powder 200 of the raw material powder P. The impurities of the coated iron powder 10 typically include the elements listed above, but are considered to be constituents of the insulating coating 14 (for example, P for oxygen phosphate, oxygen, and Si for silicone resin). , Oxygen) is not an impurity. Impurities in the dust core 1 may include impurities in the lubricant 30 and other additives described later, in addition to those contained in the coated iron powder 10 and the bare iron powder 20. The lower the amount of these impurities, the lower the permeability can be reduced.

  The composition of the coated iron powder 10, the composition of the bare iron powder 20, and the composition of the lubricant 30 in the powder magnetic core 1 are not subjected to heat treatment after compression in the manufacturing process, so that the raw material powder P (coated iron powder 100, bare iron powder) 200, substantially the composition of the lubricant 300).

Insulating film The insulating film 14 mainly functions as an insulating material that prevents direct contact between the iron particles 12 and increases the electrical resistance of the dust core 1. The powder magnetic core 1 of the embodiment is typically obtained by a specific manufacturing method in which the raw material powder P includes a specific amount of the lubricant 300 and includes a specific component and does not perform heat treatment after compression, as will be described later. . Therefore, damage to the insulating coating 140 during the manufacturing process is effectively prevented, and the iron particles 12 can be maintained sufficiently covered with the remaining insulating coating 14. If the entire surface of the iron particles 12 is covered with the insulating coating 14, it is preferable to easily reduce eddy current loss. As long as it can insulate between the iron particles 12 or between the iron particles 12 and the bare iron particles, the insulating coating 14 may not cover the entire surface of the iron particles 12, and a part of the iron particles 12 may be exposed. Allow presence state.

  The constituent material of the insulating coating 14 can take various insulating materials. For example, a compound containing a metal element or a compound containing a nonmetallic element can be given. The former includes 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, nitrogen, And one or more compounds selected from carbon (for example, metal oxides, metal nitrides, metal carbides), zirconium compounds, aluminum compounds, and the like. Examples of the latter include phosphorus compounds and silicon compounds. Other examples include metal phosphate compounds (typically iron phosphate, manganese phosphate, zinc phosphate, calcium phosphate, etc.), metal salt compounds such as borate metal salt compounds, silicate metal salt compounds, and titanate metal salt compounds. The dust core 1 including the metal phosphate compound as the insulating coating 14 has the insulating coating 14 in an excellent manner and has excellent insulation, low eddy current loss, and thus low core loss. Since the metal phosphate compound is excellent in deformability, when the coated iron powder 100 including the insulating coating 140 of the metal phosphate compound is used as the raw material powder P, the metal phosphate compound follows the deformation of the iron particles 120 during molding. This is because it easily deforms and is not easily damaged, and has high adhesion to iron, so that it is difficult to drop off from the surface of the iron particles 120 during molding or the like. On the other hand, phosphorus contained in the metal phosphate compound diffuses into the iron particles 12, which may increase core loss. Therefore, it is considered that the content of phosphorus contained in the entire powder magnetic core 1 is preferably 1000 mass ppm or less, and more preferably 600 mass ppm or less. The components of the iron particles 120, the components of the insulating coating 140, and the thickness may be adjusted so that the phosphorus amount becomes a desired value.

  Examples of other constituent materials of the insulating coating 14 include various resins and higher fatty acid salts. Specific examples of the resin include polyamide resins and silicone resins. Examples of polyamide resins include nylon 6 and nylon 66.

  Examples of the thickness of the insulating coating 14 include 10 nm or more and 1 μm or less. If the thickness is 10 nm or more, good insulation between the iron particles 12 can be secured. If the said thickness is 1 micrometer or less, there are few insulation films 14, the fall of the ratio of the magnetic component in the dust core 1 can be suppressed, and it is easy to raise a magnetic permeability. A more preferable thickness is 20 nm or more and 100 nm or less. The thickness of the insulating coating 14 in the dust core 1 depends on 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. Considering the amount of element obtained by the mass spectrometer (ICP-MS), the equivalent thickness is derived, and further, the insulating film 14 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 that the value is correct. The thickness of the insulating coating 14 generally maintains the thickness of the insulating coating 140 of the raw material powder P.

-Size The coated iron powder 10 in the powder magnetic core 1 is characterized by containing relatively large powder particles. Since the coated iron powder 10 is large, the dust core 1 can sufficiently secure a magnetic flux path and have high magnetic permeability. Specifically, the average particle diameter of the coated iron powder 10 is preferably 200 μm or more and 450 μm or less. If the average particle size of the coated iron powder 10 is 200 μm or more, in addition to high permeability, 1. It is easy to reduce the core loss by providing the insulating coating 14 well. 2. It is easily densified and has excellent manufacturability. 3. Powder particles are sufficiently meshed with each other and have excellent mechanical strength. There is an effect that the magnetic permeability can be easily increased by increasing the density. Above 1. ~ 3. The reason for the effect is as follows. The powder magnetic core 1 in which the average particle diameter of the coated iron powder 10 is in the above range can be typically manufactured by using the coated iron powder 100 whose average particle diameter satisfies the above range as the raw material powder P. If the average particle diameter of the coated iron powder 100 of the raw material powder P is 200 μm or more, it is excellent in compression moldability, and is therefore easily densified even at a relatively low pressure. If the molding pressure is reduced, damage to the insulating coating 140 during molding can be suppressed, and the insulating coating 14 tends to exist in a healthy state. As the average particle size of the coated iron powder 100 of the raw material powder P is larger, the powder particles are more likely to mesh with each other and more excellent in compression moldability, excellent in fluidity and easy to fill into a mold, and can be densified even when the molding pressure is reduced. From this point, it is excellent in manufacturability. Since all of the above effects are more easily obtained as the average particle size is larger, the average particle size of the coated iron powder 10 in the dust core 1 can be 220 μm or more, further 235 μm or more, and further 300 μm or more.

  If the average particle diameter of the coated iron powder 10 in the dust core 1 is 450 μm or less, it is difficult to increase the eddy current loss generated in the iron particles 12 due to the increase in the diameter of the iron particles 12, and the core loss can be reduced. From this point, the average particle diameter of the coated iron powder 10 in the dust core 1 can be 425 μm or less, and further 400 μm or less.

  The coated iron powder 10 in the dust core 1 preferably has few fine powder particles. Specifically, it is preferable that the ratio of powder particles (coated iron particles) having a particle diameter of 75 μm or less is 10% by mass or less, with the coated iron powder 10 being 100% by mass. Furthermore, in the coated iron powder 10, the ratio of the powder particles having a particle size of 100 μm or less is more preferably 10% by mass or less, and the ratio of the powder particles having a particle size of 120 μm or less is more preferably 10% by mass or less. . That is, 90% by mass or more of the coated iron powder 10 is preferably powder particles exceeding 75 μm, further powder particles exceeding 100 μm, and further powder particles exceeding 120 μm. The dust core 1 having a small number of fine powder particles has a high magnetic permeability because of a large number of powder particles having a large particle diameter, and has a high magnetic flux density when a predetermined magnetic field is applied. Moreover, the powder magnetic core 1 with few said fine powder particles is easy to make a core loss low for the following reasons. The powder magnetic core 1 having a small number of fine powder particles can be typically produced by using the coated iron powder 100 having a small particle size of 75 μm or less as the raw material powder P. The raw material powder P with a small number of fine powder particles and a large number of large powder particles is easily compressed and deformed, and in addition to the average particle size, the powder particles tend to have a uniform size (the width of the particle size distribution is wide). Therefore, the material powder P can be uniformly compressed and deformed, and damage to the insulating coating during molding due to non-uniform compression can be suppressed. The smaller the fine powder particles, the more easily the damage of the insulating coating 140 of the larger powder particles is suppressed, and the dust core 1 having the insulating coating 14 and having excellent insulating properties is obtained. Further, the insulating coating 14 of fine powder particles causes a decrease in the magnetic component, which in turn causes a decrease in the magnetic permeability. Therefore, in the coated iron powder 10 in the powder magnetic core 1, the proportion of powder particles having a particle size of 75 μm or less (preferably 100 μm or less, more preferably 120 μm or less) is 9% by mass or less, and further 7% by mass or less, 5 It can be set to not more than mass%, not more than 3 mass%, and further not more than 1.5 mass%.

  The coated iron powder 10 in the dust core 1 preferably has few powder particles that are too large. Specifically, the ratio of powder particles (coated iron particles) having a particle diameter of 500 μm or more is preferably 1% by mass or less, with the coated iron powder 10 being 100% by mass. The dust core 1 having a small number of 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. On the other hand, too large powder particles have large gaps formed by powder particles such as triple points, and as a result, vacancies are easily generated. As a result, the magnetic component is lowered, and the permeability is lowered. From this point, the ratio of the powder particles having a particle diameter of 500 μm or more in the coated iron powder 10 in the powder magnetic core 1 is 0.5% by mass or less, further 0.1% by mass or less, particularly not substantially present. It is preferable. Note that the above-described powder magnetic core 1 with few powder particles that are too large can be typically produced by using the coated iron powder 100 with few powder particles having a particle size of 500 μm or more as the raw material powder P. Since the raw material powder P also has a narrow particle size distribution as described above, it can be uniformly compressed and deformed, and damage to the insulating coating 140 during molding can be suppressed. Also from this point, the above-described powder magnetic core 1 having few powder particles that are too large has excellent insulating properties, lowers eddy current loss, and has low core loss.

  Furthermore, it is preferable that the coated iron powder 10 in the powder magnetic core 1 satisfies both the above-described small amount of fine powder particles and the above-described small amount of powder particles that are too large.

  The size of the coated iron powder 10 in the dust core 1 and the size of the bare iron powder 20 described later depend on the size of the raw material powder P as described above. Although the raw material powder P changes its shape such as flattening due to plastic deformation at the time of molding, 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 10 and the size of the bare iron powder 20 in the dust core 1 can be treated as being substantially equivalent to the size of the coated iron powder 100 of the raw material powder P and the size of the bare iron powder 200. A method for measuring the average particle diameter of the coated iron powder 10, the average particle diameter of the bare iron powder 20, and the ratio of powder particles having a specific particle diameter in the dust core 1 will be described later.

-Content As the content of the coated iron powder 10 in the magnetic component of the powder magnetic core 1 is higher, it is easier to obtain effects such as high magnetic permeability and low core loss. Therefore, the content of the coated iron powder 10 is 50% by mass or more, more than 50% by mass, further 55% by mass or more, and further 60% by mass or more, with the magnetic component of the dust core 1 being 100% by mass. it can. When the content of the coated iron powder 10 is less than 100% by mass, the remainder of the magnetic component is preferably a bare iron powder 20 described later. When the content of the coated iron powder 10 is 100% by mass, the magnetic permeability and the low core loss are easily obtained. The mass of the magnetic component of the dust core 1 is a value obtained by dividing the mass of the dust core by the mass of the lubricant (the total mass of the lubricant and the additive when an additive described later is included).

Lubricant The powder magnetic core 1 of the embodiment includes a specific amount of the lubricant 30 and the lubricant 30 includes a specific component. The lubricant 30 in the dust core 1 mainly has a function of reducing friction between the powder particles of the raw material powder P in the manufacturing process, friction between the compressed product and the mold during demolding, and the like. Furthermore, since the lubricant 30 is an insulator, when there is a portion where the iron particles 12 are exposed as described above, the lubricant 30 is interposed between the iron particles 12 and 12 or between the iron particles 12 and the bare iron particles for insulation. Also functions as a material.

-Content The powder magnetic core 1 of embodiment contains the lubricant 30 by 0.3 mass% or more and 0.8 mass% or less by making the powder magnetic core 1 into 100 mass%. By containing 0.3% by mass or more of the lubricant 30, it is possible to effectively reduce the rubbing in the manufacturing process described above and reduce the damage to the insulating coating 140, and between the iron particles 12 and 12, or between the iron particles. 12 can be sufficiently interposed between the bare iron particles. Therefore, the powder magnetic core 1 containing 0.3% by mass or more of the lubricant 30 is provided with the insulating coating 14 and has excellent insulating properties and low core loss. The content of the lubricant 30 in the dust core 1 can be 0.36% by mass or more, and further 0.40% by mass or more.

  If the content of the lubricant 30 in the dust core 1 is 0.8% by mass or less, it is possible to suppress a decrease in the proportion of the magnetic component due to an excess of the lubricant 30 and an inhibition of the meshing of the powder particles during the manufacturing process. . That is, a decrease in magnetic characteristics and a decrease in strength can be suppressed. Further, since the coated iron powder 100 of the raw material powder P is relatively large, even if the lubricant 300 is not excessively contained, the densification and the high density can be achieved. Therefore, the dust core 1 containing the lubricant 30 in an amount of 0.8% by mass or less tends to have a high density and strength. Moreover, since the powder magnetic core 1 contains relatively large powder particles, the lubricant 30 may be present in a gap formed by the above-described large powder particles. That is, the lubricant 30 may be present locally rather than uniformly around the powder particles. Therefore, it is easy to prevent a decrease in magnetic permeability due to the inclusion of the lubricant 30, and the dust core 1 is considered to have a high magnetic permeability. The content of the lubricant 30 in the dust core 1 can be 0.75% by mass or less, and further 0.70% by mass or less.

  The addition amount of the lubricant 300 in the raw material powder P may be adjusted so that the content of the lubricant 30 in the dust core 1 satisfies the above range.

.. Ingredient The powder magnetic core 1 of the embodiment is characterized in that the lubricant 30 contains a fatty acid amide. The fatty acid amide typically has a melting point of about 70 ° C. or higher and 150 ° C. or lower, more preferably about 90 ° C. or higher and 120 ° C. or lower, and has a relatively high melting point. For this reason, in the manufacturing process, (1) if the usage environment is lower than the melting point (for example, room temperature of about 20 ° C. to 25 ° C.), the raw material powder P is excellent in fluidity and easily filled into the mold. 2) The liquefied lubricant is retained in the mold, and the density of the compressed material can be suppressed due to the raw material powder P being entrained in the retained material. (3) Excellent in demoldability and damage to the insulating coating 140. It is easy to reduce, and (4) it is easy to handle the raw material powder P and has excellent workability. Moreover, if the operating temperature of the powder magnetic core 1 is about room temperature (air temperature) to the melting point or less, liquefaction can be suppressed and excessive outflow of the lubricant 30 accompanying liquefaction can be prevented, so that the lubricant 30 is insulated. Can function as.

  Specific fatty acid amides include stearic acid amide (melting point around 100 ° C.), palmitic acid amide and the like. Commercial stearic acid amide may contain palmitic acid amide in part. Since palmitic acid amide and stearic acid amide have substantially the same physical properties, both stearic acid amide and palmitic acid amide may be included. Although the mass ratio of palmitic acid amide in the fatty acid amide can be appropriately selected, for example, it is about 55% or less.

  The lubricant 30 can further contain a fatty acid metal salt. Since the fatty acid metal salt typically has a melting point of 100 ° C. or higher, the fatty acid metal salt functions as an insulating material in addition to the effects (1) to (4) as in the case of the fatty acid amide. Specific fatty acid metal salts include zinc stearate, lithium stearate, and the like, and may include one or more.

  The lubricant 30 preferably has a higher fatty acid amide content (when the fatty acid metal salt is included, the total content of the fatty acid amide and the fatty acid metal salt) is preferably superior in lubricity, and substantially contains only the fatty acid amide. Or it is preferable to use only fatty acid amides and fatty acid metal salts. When both the fatty acid amide and the fatty acid metal salt are included, the blending ratio of both is 100% by mass in total, and the content of the fatty acid metal salt is more than 0 and 70% by mass or less.

  The components of the lubricant 300 in the raw material powder P may be adjusted so that the lubricant 30 in the dust core 1 becomes a specific component.

-Shape The powder 30 is an example of the presence shape of the lubricant 30. If a powdery material is used as the lubricant 300 of the raw material powder P, it may exist in a powdery state even after compression molding. In addition, the lubricant 30 is deformed at the time of molding, and the lubricant 30 exists in an arbitrary shape along the coated iron particles or bare iron particles, or exists in a smaller powder form or a larger powder form.

Bare iron powder The powder magnetic core 1 of the embodiment includes a coated iron powder 10 having an insulating coating 14 and a bare iron powder 20 not having an insulating coating, in addition to a form in which the magnetic component is only the coated iron powder 10. It can be set as the form (FIG. 1) including both. The components of the bare iron powder 20 are the same as those of the iron particles 12 described above. The form including the bare iron powder 20 can be expected to be particularly excellent in strength. Since the bare iron powder 20 is superior in plastic deformability due to its component and structure (no insulating coating), the coated iron particles 20 can be firmly bonded to each other when deformed and interposed between the coated iron particles. It is. In addition, the bare iron powder 20 does not have an insulating coating, and the surface tends to be relatively uneven, and therefore, it is considered that the bare iron powder 20 is easily meshed with the coated iron particles.

.. Size When the bare iron powder 20 is included, the bare iron powder 20 is preferably smaller than the coated iron powder 10. If the bare iron particles are small, they can be densified and densified by interposing in the gaps formed by the large coated iron particles. As a result, the powder magnetic core 1 containing the small bare iron powder 20 is expected to increase the magnetic permeability by increasing the density while suppressing the decrease in the ratio of the magnetic component due to the insulating coating. Further, if the bare iron particles are small, it is easy to ensure insulation between the bare iron particles by the lubricant 30 interposed between the bare iron particles. As a result, although the powder magnetic core 1 contains the bare iron powder 20, it is considered that it is excellent in insulation. Furthermore, if the bare iron particles are small, it is easy to reduce eddy currents generated in the particles. From this point, it can be set as the powder core 1 of the low core loss, including the bare iron powder 20.

  Specifically, the average particle diameter of the bare iron powder 20 in the dust core 1 is preferably 40 μm or more and 150 μm or less. If the average particle diameter of the bare iron powder 20 is 40 μm or more, the bare iron powder 200 is easy to handle in the manufacturing process and excellent in fluidity and excellent in deformability. Therefore, it is easy to increase the strength by deformation, and it is excellent in manufacturability. Since this effect is more easily obtained as the average particle size is larger, the average particle size of the bare iron powder 20 in the dust core 1 can be 50 μm or more, further 60 μm or more, and further 70 μm or more.

  If the average particle diameter of the bare iron powder 20 in the powder magnetic core 1 is 150 μm or less, the bare iron particles are easily interposed between the gaps formed by the coated iron particles and are easily densified. Further, it is difficult to increase the eddy current generated in the bare iron particles due to the increase in the diameter of the bare iron particles, and the core loss can be reduced. Furthermore, since the insulating property can be easily improved by the lubricant 30 interposed between the bare iron particles, the core loss can be reduced. In addition, if the bare iron particles are small, it is possible to reduce the problem that the bare iron particles are bonded to each other by plastic deformation and a large conductive portion is formed due to plastic deformation, so that the core loss can be reduced. From these points, the average particle diameter of the bare iron powder 20 in the powder magnetic core 1 can be 120 μm or less, further 100 μm or less, and further 95 μm or less.

  The bare iron powder 20 in the dust core 1 preferably has few powder particles that are too large. Specifically, it is preferable that the ratio of powder particles (bare iron particles) having a particle diameter of 200 μm or more is 10% by mass or less, with the bare iron powder 20 being 100% by mass. The dust core 1 having a small number of 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. From this point, the ratio of the powder particles having a particle diameter of 200 μm or more in the bare iron powder 20 in the dust core 1 is 5% by mass or less, further 3% by mass or less, 2% by mass or less, 1% by mass or less, In particular, it is preferably substantially absent. The powder magnetic core 1 having a small number of powder particles that are too large can be manufactured by using, as the raw material powder P, the bare iron powder 200 having a small number of powder particles having a particle size of 200 μm or more. Since such a bare iron powder 200 has a narrow particle size distribution, it is possible to uniformly move the bare iron powder 200 in the mold and compress the raw material powder P during the manufacturing process, resulting in non-uniform compression. It is expected that damage to the insulating coating 140 can be suppressed.

.. Content If the content of the bare iron powder 20 in the magnetic component of the dust core 1 is 10% by mass or more when the magnetic component of the dust core 1 is 100% by mass, the effect of including the bare iron powder 20 ( Densification, high strength, excellent deformability, etc.) can be obtained. Moreover, the usage-amount of the covering iron powder 100 can be reduced and it can contribute to cost reduction. If the content of the bare iron powder 20 is 15% by mass or more, further 20% by mass or more, and further 30% by mass or more, it is easy to obtain the above effect, and the magnetic permeability is higher or the core loss is lower. Sometimes it becomes. On the other hand, if the content of the bare iron powder 20 is 45% by mass or less, the dust core 1 sufficiently includes the large coated iron powder 10, and thus it is easy to improve the insulation. The content of the bare iron powder 20 can be 35% by mass or less, and further 30% by mass or less.

-Other inclusions The powder magnetic core 1 can contain resin etc. as another additive. Specifically, polyacetal (POM), polyamide (PA), polycarbonate (PC), polybutylene terephthalate (PBT), modified polyphenylene ether (m-PPE), polyphenylene sulfide (PPS), polyether ether ketone (PEEK) Engineering plastics such as polyetherimide (PEI). The content of the additive is preferably more than 0 and 0.5% by mass or less, with the dust core 1 being 100% by mass. By including a resin or the like within this range, the moldability and shape retention can be improved, and a decrease in the proportion of the magnetic component due to the resin content can be prevented. In particular, a polyamide-based resin is preferable because the molding strength is increased. Examples of the polyamide-based resin include a form that exists as the insulating coating 14 and a form that exists as a powder as described above. In the case of powder, resin powder may be mixed with the raw material powder P.

-Shape The powder magnetic core 1 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.

  As a specific shape, a cross section in the compression direction of the dust core 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). That is, the columnar body has a height L greater than the diameter D. To put it simply, it is an elongated solid whose side surface (height L) is larger than the end surface (diameter D) (for example, the I-shaped core of FIGS. 2, 4, and 7 described later). See fragment 10i). In the cylinder, the outer diameter corresponds to the diameter D, and in the prism, 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 having a diameter D of 10 mm and a height L of more than 25 mm, and a prismatic cylinder having a polygon envelope circle having a diameter D of 10 mm and a height L of more than 25 mm. Alternatively, a thin cylindrical body such as a cylinder or a square cylinder having a thickness of the length D may be used. Specific thickness D is 2 mm or more and 5 mm or less.

  It can be said that the elongated powder magnetic core and the thin-walled powder magnetic core as described above are generally difficult to manufacture. However, the dust core 1 according to the embodiment includes the coated iron powder 100 and the bare iron powder 200 as appropriate, which are excellent in size and material as described above, and the lubricant 300 including a component excellent in demoldability. Even if it is such a shape, it can manufacture favorably and is excellent in manufacturability. In addition, even with such an elongated shape, by using the raw material powder P that is excellent in moldability as described above, it is uniformly compressed and small in variation in compressed state and variation in density, The dust core 1 is excellent in magnetic characteristics, mechanical strength, shape accuracy, and dimensional accuracy.

  In addition, as one of the indexes for determining the compression direction of the powder magnetic core 1, there is a cross section of the powder magnetic core 1 and the elongation direction of the powder particles existing in the cross section. Since the powder magnetic core 1 compresses and compresses the raw material powder P, each powder particle constituting the raw material powder P is crushed (plastically deformed) in the compression direction, and is typically orthogonal to the compression direction. It becomes the shape extended in the direction. 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 1 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, in the case of a dust core having a through hole (such as the core piece 10f in FIG. 7), the axial direction of the through hole 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. At the time of extracting the compressed material from the die on the contact surface with the die that forms the outer peripheral surface of the dust core 1 or the contact surface with the rod that forms the inner peripheral surface of the dust core when there is a through hole, When the rod is withdrawn, the compressed product and the die or the rod are in sliding contact, and a sliding contact mark may remain. That is, it can be expected that the surface having the sliding contact mark is a surface formed by a die or a rod, and the surface having no sliding 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.

- An example of a dust core 1 density embodiment include those having a density satisfies the 7.3 g / cm ³ or more 7.7 g / cm ³ or less. If the density is 7.3 g / cm ³ or more, the relative density ((apparent density / true density) × 100. The true density = the density of the pure iron powder) is 92% or more, the magnetic permeability is high, and the strength is high. Excellent. Since the magnetic permeability and strength increase as the density increases, the density of the dust core 1 preferably satisfies 7.35 g / cm ³ or more, and more preferably 7.4 g / cm ³ or more. On the other hand, if the density of the powder magnetic core 1 is 7.7 g / cm ³ or less, it can be said that the core loss can be reduced because it is manufactured at a relatively low molding pressure and damage to the insulating coating during molding is reduced. Thus, the density of the dust core 1, 7.65 g / cm ³ or less, it is possible to further 7.6 g / cm ³ or less.

-Property The dust core 1 of the embodiment has a high magnetic permeability. For example, the AC magnetic permeability of the dust core 1 is 150 or more, further 160 or more, and further 170 or more when the measurement condition is 0.1 T / 10 kHz.

[Coil parts (use example of dust core)]
The dust core 1 of the embodiment can be used as a constituent member of a magnetic path. For example, in a coil component including a coil formed by winding a winding in a spiral shape and a magnetic core in which the coil is arranged to form a magnetic path, the dust core 1 can be used for at least a part of the magnetic core. 2-7 shows 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. 2 includes an I-shaped core piece 10i and a bowl-shaped core piece 10p as a magnetic core 10A (the right diagram in FIG. 2). 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. 2). Here, an example is shown in which a gap G is provided between both core pieces 10i and 10p, and a coil C is arranged on the I-shaped core piece 10i.

  The coil component 1B of Embodiment 2 shown in FIG. 3 includes a pair of hook-shaped core pieces 10p, 10p as the magnetic core 10B (the right view of FIG. 3). The magnetic core 10B is an O-shaped magnetic core that constitutes a rectangular frame-shaped closed magnetic path by combining both the core pieces 10p and 10p (the left diagram in FIG. 3). Here, a gap G is provided between both core pieces 10p and 10p, and coils C and C are respectively arranged on two connecting legs formed by joining via the gap G between the core pieces 10p and 10p. An example is shown. Like the coil component 1 </ b> A of the first embodiment, the coil C can be provided only on one of the connection legs.

  The coil component 1C of the third embodiment shown in FIG. 4 includes four I-shaped core pieces 10i to 10i as the magnetic core 10C (the right diagram in FIG. 4). 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 circuit (the left diagram in FIG. 4). Here, a gap G is provided between two parallel core pieces 10i, 10i and another core piece 10i connecting the two core pieces 10i, 10i, and the two parallel pieces described above are provided. An example in which coils C and C are respectively disposed on the core pieces 10i and 10i is shown. As in the coil component 1A of the first embodiment, the coil C can be provided only in any one of the core pieces 10i.

  Coil component 1D of Embodiment 4 shown in FIG. 5 is provided with E-shaped core piece 10e and I-shaped core piece 10i as magnetic core 10D (the right figure of FIG. 5). The magnetic core 10D is an EI type magnetic core that forms a closed magnetic path as shown by a two-dot chain line in the left diagram of FIG. 5 by combining both core pieces 10e and 10i. Here, an example is shown in which the coil C is disposed at the center leg of the E-shaped core piece 10e and a gap G is provided between the leg and the core piece 10i. Coils C can be provided on at least one of the outer legs disposed on both sides of the central leg.

  The coil component 1E of Embodiment 5 shown in FIG. 6 includes a pair of E-shaped core pieces 10e and 10e as the magnetic core 10E (the right diagram in FIG. 6). 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 the left diagram of FIG. 6 by combining both the core pieces 10e and 10e. . Here, a gap G is provided between the central leg portions of both core pieces 10e, 10e, and a coil is connected to the connecting leg portion formed by joining the central leg portions of both core pieces 10e, 10e via the gap G. An example in which C is arranged is shown. Coils C can be provided on at least one of the outer connecting legs arranged on both sides of the central connecting leg.

  The coil component 1F of the sixth embodiment shown in FIG. 7 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, as shown by a two-dot chain line in the left diagram of FIG. A closed magnetic circuit. Here, the 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, and the coil C is disposed on the I-shaped core piece 10i. Indicates. The coil C can be provided on at least one of the outer legs parallel to the I-shaped core piece 10i in the rectangular frame-shaped core piece 10f.

  For example, all the magnetic components (here, the core pieces 10i, 10p, 10e, and 10f) in the magnetic cores 10A to 10F can be the dust core 1 of the embodiment. Alternatively, a core piece including a part of the magnetic component in the magnetic cores 10 </ b> A to 10 </ b> F, for example, a part where the coil C is disposed can be used as the dust core 1 of the embodiment.

  The shapes of the magnetic cores 10A to 10F and the core pieces 10i, 10p, 10e, and 10f shown in FIGS. 2 to 7 are examples, and can be appropriately changed to known shapes. For example, the shape etc. which have the curved surface which rounded the corner | angular part are mentioned. Also, it is not a simple shape as shown in FIG. 2 to FIG. 7, but an outer shape with irregularities such as a shape having one or a plurality of steps, a shape having one or a plurality of flanges at the end, etc. It can be an irregular solid having The number of core pieces provided in the coil component can be appropriately changed, and FIGS. 2 to 7 are examples.

  As for the coil | winding which comprises the coil 20, the covered wire | wire which equips the outer periphery of a conductor with an insulating layer is mentioned. 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 coils C included in the coil component can be changed as appropriate, and FIGS. 2 to 7 are examples.

  The gap G can be appropriately provided so as to obtain desired magnetic characteristics. For example, it can be set as the form which is not provided 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 powder magnetic core 1 of the embodiment can be manufactured by a manufacturing method that includes, for example, the following preparation process and a molding process and does not perform heat treatment after the molding process.
(Preparation step) The 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 is 10% by mass or less, and 0.3% by mass or more and 0.0. A step of preparing a raw material powder containing 8% by mass or less of a lubricant (molding step) A step of filling the raw material powder into a mold and pressurizing and compressing it to produce a dust core. A dust containing bare iron powder 20 When the magnetic core 1 is manufactured, in the preparation step, the ratio of the coated iron powder, the lubricant, and the powder particles having an average particle size of 40 μm to 150 μm and a particle size of 200 μm or more is 10% by mass. A raw material powder containing the following bare iron powder is prepared.

  According to said manufacturing method, the heat damage of an insulating film can be effectively prevented by not heat-processing with respect to the shape | molded compressed object. In addition to containing fatty acid amides with excellent mold release properties, the inclusion of a specific amount of lubricant reduces the friction between the powder particles and the friction between the compressed material and the mold, and the insulating coating at the time of molding Damage can be effectively prevented. Furthermore, since the raw material powder is extremely excellent in compression moldability by containing pure iron having excellent deformability as a main component and containing a relatively large coated iron powder, it is easily densified even if the molding pressure is lowered. If the molding pressure is lowered, it is easy to reduce the above-mentioned friction, and from this point, it is possible to effectively prevent damage to the insulating coating. Therefore, according to the above manufacturing method, it is possible to manufacture a dust core in which the insulating coating exists in a healthy state and has excellent insulation, high electrical resistance, and low core loss. By using the raw material powder of a specific size, the coated iron powder constituting the dust core is not too large, and the increase in eddy current loss due to the presence of coarse powder particles can also be suppressed. Can produce a dust core with low core loss. In addition, the above manufacturing method can reduce the production of dust cores by omitting heat treatment, ease of mold filling due to excellent flowability of raw material powder, use of raw material powder with excellent moldability, reduction of molding pressure, etc. Can be manufactured well.

  In the above manufacturing method, since heat treatment is not performed after molding, the constituents of the obtained compressed product (dust core 1) substantially maintain the constituents of the raw material powder P as described above. In addition, although the raw material powder P is slightly deformed by molding, the size and the mixing ratio of the powder particles constituting the powder magnetic core 1 depend on the size and the mixing ratio of the powder particles included in the raw material powder P and are generally maintained. Tend to. Therefore, detailed description of the component, size, blending ratio, etc. of the raw material powder P is omitted. The matters described regarding the coated iron powder 10, the lubricant 30, and the bare iron powder 20 included in the dust core 1 can be applied to the coated iron powder 100, the lubricant 300, and the bare iron powder 200 included in the raw material powder P, respectively. Other matters are described below.

-Preparation process The covering iron powder 100 used for the raw material powder P can be manufactured by forming the insulating coating 140 in a pure iron powder. The pure iron powder used for the coated iron powder 100 and the bare iron powder 200 can be manufactured by a known method such as an atomizing method such as a gas atomizing method or a water atomizing method. For the formation of the insulating coating 140, for example, chemical conversion treatment such as phosphate chemical conversion treatment, spraying of a solvent, sol-gel treatment using a precursor, or 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. As the coated iron powder 100, commercially available coated iron powder can be used. The size of the coated iron powder 100 and the size of the bare iron powder 200 can be adjusted by pulverizing pure iron powder, or the coated iron powder 100 or the bare iron powder 200 can be classified by a sieving method or the like. You can adjust it.

  About the covering iron powder 100 and the bare iron powder 200 in the raw material powder P, a mass ratio of a magnitude | size and a specific particle size can be measured by using a commercially available particle size measuring apparatus. As a simple measurement, the mass ratio of the specific particle size is classified using a sieve and the mass of the selected powder particles having the specific particle size is measured.

  The lubricant 300 in the raw material powder P is preferably in a powder form because it is easy to mix with the coated iron powder 100 and the bare iron powder 200. The average particle size of the lubricant powder is preferably smaller than the average particle size of the coated iron powder 100 so as to be easily attached to the coated iron particles in order to suppress damage to the insulating coating 140. For example, the average particle diameter of the lubricant powder is 1 μm or more and 100 μm or less, and further 3 μm or more and 50 μm or less. In addition, the lubricant that oozes from the surface of the compressed product at the time of demolding may be removed by rubbing against the mold. As a result, the content of the lubricant 30 in the dust core 1 can be smaller than the content of the lubricant 300 in the raw material powder P. For example, the amount of decrease may be about 3% to 25% by mass ratio. The content of the lubricant 300 in the raw material powder P may be adjusted so that the content of the lubricant 30 in the dust core 1 satisfies the above range.

  For mixing the raw material powder P, an appropriate mixer such as a V-type mixer or a double cone mixer can be used. This mixing is preferably performed to such an extent that the insulating coating 140 of the coated iron powder 100 is not damaged. In addition, the mixed powder can be obtained by spraying the lubricant 300 dissolved in the solvent so as to cover the surface of the coated iron powder 100 or the bare iron powder 200.

-Molding step Typically, the mold for compressing and compressing the prepared raw material powder P (mixed powder) typically includes a die having a through hole and a pair of punches for compressing and compressing the raw material powder P. It is done. Specifically, a bottomed cylindrical molding space is formed by a part of the inner peripheral surface of the die and one surface of one punch (the surface facing the other punch), and the raw powder P is filled in this molding space. Then press and compress with both punches to form the desired shape. The compressed product extracted from the die is the dust core 1. In the case of manufacturing a cylindrical or annular dust core having a through hole (such as the core piece 10f in FIG. 7), the through hole of the compressed material is formed by being inserted into the through hole of the die as a mold. A thing provided with a rod should be used. 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.

  The molding pressure can be, for example, less than 1200 MPa, further 1000 MPa or less, and further 800 MPa or less. By molding at such a low pressure, damage to the insulating coating can be satisfactorily prevented. Since the raw material powder P is excellent in compressive deformability as described above, the molding pressure is set to 500 MPa or more, further 550 MPa or more, and further 600 MPa or more, so that the insulating film is prevented from being damaged and densified and densified. I can plan.

Molding can be performed in a state in which the mold is heated to some extent (the processing heat resulting from continuous molding may be sufficient). In this case, the moldability of the coated iron powder 100 or the bare iron powder 200 can be improved, or the lubricant 300 can be softened to some extent to facilitate flow, thereby improving the compression moldability. Therefore, the molding pressure can be further reduced. In the case of heating the mold, the mold temperature is, for example, (T _M / 2) ° C. or higher and T _M ° C or lower when the melting point of the lubricant is T _M. For example, the melting point _{T M} is if 90 ° C. to 120 ° C., include about 45 ° C. to 60 ° C.. If it is this range, it is excellent in a moldability, and also suppresses excessive softening of the lubricant 300 (suppresses seepage due to liquefaction), and the lubricant 30 of the dust core 1 becomes too small. Can be suppressed.

  The mold can be held at a lower temperature (for example, room temperature or lower) using a water cooling device or the like. In this case, it is easy to obtain a compressed product with excellent dimensional accuracy.

  The atmosphere at the time of molding includes, for example, an air atmosphere. The coated iron powder 100 is provided with an insulating coating, and the bare iron powder 200 is in contact with the lubricant 300, so that oxidation of the iron component can be prevented even in an atmosphere containing oxygen. The atmosphere is excellent in workability because it is easy to control.

  In the mold, a release coating can be applied to a region in contact with the raw material powder P 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 the release coating, it is possible to further improve the demolding property and easily prevent the insulating coating 140 from being damaged.

  In the case of molding the above-described elongated magnetic core, the die has an opening diameter D (diameter in the case of a circular hole, an envelope circle of the shape in the case of a non-circular hole including a polygon). The diameter of the through hole may be sufficiently long with respect to the diameter of the through hole. 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 annular divided pieces, and these divided pieces are stacked in the axial direction of the through-hole to communicate with each other. Those that form holes can be used. The above-described thin cylindrical powder magnetic core can be formed in the same manner.

[Test Example 1]
The dust core was manufactured under various conditions, and the permeability and core loss were examined.

Here, a mixed powder containing coated iron powder, a lubricant, and bare iron powder (pure iron powder without an insulating coating) as appropriate was prepared as a raw material powder.
・ Sample No. 1-1 and 1-110 are samples using a mixed powder containing coated iron powder (coated iron powder 2 to be described later) and a lubricant and not containing bare iron powder.
・ Sample No. 1-2, 1-120, 1-3, 1-130 are samples using mixed powder containing coated iron powder (coated iron powder 1 described later), a lubricant, and bare iron powder. The blending ratio of the coated iron powder and the bare iron powder is such that the total amount of both powders (total amount of magnetic components) is 100% by mass. 1-2 and 1-120 are 90% by mass of coated iron powder and 10% by mass of bare iron powder. In 1-3 and 1-130, the coated iron powder was 60% by mass, and the bare iron powder was 40% by mass.
・ Sample No. 1-200 is a comparative sample using fine coated iron powder. This fine coated iron powder is a commercial product (average particle size: 55 μm, insulating coating: iron phosphate).

  Two types of coated iron powders (coated iron powders 1 and 2) having different particle size distributions were prepared. Each of the coated iron powders 1 and 2 is an insulating film (average thickness of about 20 nm to 100 nm) made of iron phosphate around iron particles made of pure iron (Fe is 99% by mass or more, the remainder is inevitable impurities). ). The prepared coated iron powders 1 and 2 were classified. For coated iron powders 1 and 2, the average particle size (μm), the proportion of powder particles with a particle size of 75 μm or less (mass%), the proportion of powder particles with a particle size of 100 μm or less (mass%), the particle size of 500 μm or more Table 1 shows the ratio (% by mass) of the powder particles. The ratio of the powder particles having a specific particle size indicates the ratio of each particle size when the total weight of the coated iron powder before classification is 100% by mass. The particle size distribution was measured using a commercially available laser diffraction / scattering particle size / particle size distribution measuring apparatus. The average particle diameters of the prepared coated iron powders 1 and 2 are both measured by the particle size distribution measuring apparatus, and are set to a particle diameter at which the integrated weight (mass) is 50%, that is, 50% particle diameter (mass).

  Bare iron powder is a collection of iron particles composed of pure iron (Fe 99% by mass or more and the balance inevitable impurities (total 1500 ppm to 3500 ppm by mass)). The prepared bare iron powder was classified in the same manner as the above coated iron powder, and the average particle size and particle size distribution were measured. Regarding the bare iron powder, Table 1 shows the average particle diameter (μm) and the ratio (mass%) of powder particles having a particle diameter of 200 μm or more when the total weight of the bare iron powder before classification is 100 mass%.

  In any sample, when the mixed powder used in each sample was 100% by mass, the content of the lubricant was 0.4% by mass. The lubricant of each sample was a powder containing stearamide (melting point: about 100 ° C.). Sample No. using the coated iron powder 2 The lubricants 1-1 and 1-110 were stearamide and zinc stearate. The blending ratio of stearic acid amide and zinc stearate was such that the content of zinc stearate was about 45% by mass when the total amount was 100% by mass. The other lubricants were stearamide. The stearamide (commercial product) used was analyzed and found to contain stearamide and palmitic acid amide. The average particle size of the lubricant powder was selected from the range of 1 μm to 100 μm.

The mold was filled with the mixed powder and pressed and compressed to form a cylindrical compact. In each sample, a compact having a diameter D of 10 mm (1 cm) and a height L of 30 mm (3.0 cm) was molded.
For all samples, the molding conditions were an atmospheric atmosphere, the molding pressure was selected from 686 MPa to 882 MPa ( ⁷ ton / cm ² to 9 ton / cm ² ), and the mold temperature (° C.) was selected from 50 ° C. to 60 ° C. . In particular, sample no. For 1-1 to 1-3 and 1-110 to 1-130, the molding pressure was selected from the above range so that the densities were approximately equal.

  Sample No. 1-110 to 1-130, no. The 1-200 compact was heat treated. As heat treatment conditions, the atmosphere was an air flow atmosphere, the heating temperature was the temperature (° C.) shown in Table 2, and the holding time was 30 minutes. Sample No. The compressed product of 1-1 to 1-3 is not subjected to heat treatment.

  The prepared sample No. 1-1 to 1-3 compressed product (dust core) and sample No. With respect to the heat-treated products 1-110 to 1-130, the amount of lubricant was measured as follows. Each of the compressed product and the heat-treated product is pulverized by a pulverizer (atmosphere), and 1 g of the powder having the same size as that of the raw material is weighed. A liquid mixture obtained by adding acetone to 1 g of the weighed powder is obtained. The lubricant (here, stearamide, palmitic amide) is dissolved and recovered from this mixture by ultrasonic extraction. The recovered lubricant was qualitatively and quantitatively analyzed by gas chromatography. That is, the amount x (g) of lubricant per 1 g of the pulverized powder is obtained, and the mass ratio of the lubricant to the mass of the compressed product ((xx) / y) × using the mass y (g) of the compressed product. 100 was determined. The amount of the lubricant is a ratio in which the compressed product or the heat-treated product is 100% by mass. The measurement results are shown in Table 2. Sample No. containing zinc stearate 1-1 was comprehensively judged by performing thermal analysis and the like together. The recovered magnetic component was analyzed for impurities. 1-1 to 1-3 each had a total impurity amount of 5000 ppm to 8000 ppm by mass (the total impurity amount of Sample No. 1-1 was a component of zinc stearate by thermal analysis or the like. Removed amount).

  Sample No. 1-1 to 1-3, no. A toroidal test piece (outer diameter 34 mmφ, inner diameter 20 mmφ, thickness 7 mm) was produced under the same conditions using the raw material powders 1-110 to 1-130, and the following test pieces were used. Thus, AC magnetic permeability and core loss (W / kg) (both measurement conditions: 0.1 T / 10 kHz) were measured. The measurement results are shown in Table 2.

  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. Using the produced measurement member and AC-BH curve tracer, the AC magnetic permeability of the sample is determined from the slope of the AC-BH curve when the excitation magnetic flux density Bm is 1 kG (= 0.1 T) and the measurement frequency is 10 kHz. At the same time, eddy current loss (eddy loss) and hysteresis loss (his loss) of the sample were obtained. The core loss, which is the sum of eddy loss and hiss loss, is defined as core loss.

  As shown in Table 2, the sample No. which was not heat-treated. Although the amount of lubricant in the compressed materials (dust cores) 1-1 to 1-3 was slightly reduced (by mass ratio of about 15% or less), the amount of lubricant in the raw material powder was substantially maintained. You can see that On the other hand, the heat-treated sample No. 1-110 to 1-130 show that the lubricant added to the raw material powder is substantially absent. This is considered to be because the lubricant was volatilized and removed by the heat treatment, or was thermally denatured to become another substance (soot, etc.).

  As shown in Table 2, sample no. The compacts 1-1 to 1-3 (dust cores) are sample Nos. 1 and 2 using fine powder. It can be seen that it has a higher magnetic permeability than 1-200. The reason for this is that, as the raw material powder, a coated iron powder (where the average particle size is 220 μm or more and the particle size of 100 μm or less is 8% by mass or less) is relatively large and contains few fine powder particles. This is probably because the powder magnetic core itself is mainly composed of coated iron powder with many relatively large powder particles and few fine powder particles. In addition, although it contains a lubricant, it is considered that the presence of the lubricant relatively non-uniformly allows a magnetic flux to pass through by contact between large powder particles.

  Sample No. using only large coated iron powder. It can be seen that the compressed product (dust core) of 1-1 has a higher magnetic permeability. On the other hand, Sample No. using bare iron powder finer than the coated iron powder as the raw material powder. 1-2 and 1-3 are also sample Nos. It is lower than 1-1 and has a high magnetic permeability. The reason for this is that it can be densified with fine bare iron powder, the proportion of the insulating coating can be reduced to prevent a reduction in the proportion of the magnetic component due to the insulating coating, and large coated iron particles of 300 μm or more are included. It is thought that there is.

  As shown in Table 2, the sample No. which was not heat-treated. 1-1 to 1-3 compacts (dust cores) were subjected to heat treatment on sample Nos. Compared to 1-110 to 1-130, it can be seen that when samples having the same magnetic component are compared, eddy current loss is low and core loss is low. This is because sample no. In 1-110 to 1-130, the insulating film is damaged by the heat treatment, and the lubricant as the insulating material is removed, so that a conductive portion in which the iron particles are in direct contact with each other is generated and the electric resistance is low. It is thought that it became. Sample No. containing bare iron powder 1-120 and 1-130 have particularly large eddy current loss, and it is considered that there are many conductive portions.

  Sample No. using only large coated iron powder. It can be seen that the compressed product (powder magnetic core) 1-1 is superior in insulation properties and has a lower core loss because the entire constituent powder has an insulating coating. This is because sample no. 1-1 is considered to be because an increase in eddy current loss due to coarse iron particles could be suppressed because large iron particles of 500 μm or more were not included. On the other hand, Sample No. using bare iron powder finer than the coated iron powder as the raw material powder. 1-2 and 1-3 are also sample Nos. Although higher than 1-1, the core loss is lower than when heat treatment is performed. The reason for this is that heat treatment is not performed, so that a lubricant can be interposed between fine bare iron particles, or an insulating coating of coated iron powder can be interposed, thereby improving the insulation between the bare iron particles. It is thought that it was because In addition, it is considered that the increase in eddy current loss due to the size of the bare iron particles could be suppressed because the bare iron powder was small.

In addition, Sample No. Compression of 11 to 13 for (dust core) was measured density was in 7.4 g / cm ³ or more as shown in Table 1 (relative density: 94% or more). The density 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). Sample No. 1-1 to 1-3 use a relatively large powder as the raw material powder and mainly consist of pure iron having a high deformability, so that the molding pressure is relatively low, such as less than 1200 MPa (here, 1000 MPa or less). It is thought that the density was also increased. In addition, it is considered that the magnetic properties can be enhanced by increasing the density and the strength is also excellent.

  Sample No. As for the compressed product (powder magnetic core) of 1-1 to 1-3, when visually confirmed, the contact surface (side surface of the cylinder) with the die in the compressed product has few scratch marks, and the coated iron constituting this surface It was confirmed that damage to the insulating coating of the powder was suppressed.

  The obtained sample No. 1-1, the average particle diameter of the coated iron powder constituting the compressed product (dust core), Sample No. The average particle diameter of the coated iron powder and the average particle diameter of the bare iron powder constituting the compressed product (powder magnetic core) of 1-2 and 1-3 were measured as follows.

  Take a cross-section parallel to two opposing flat surfaces (here, circular end faces) of the outer surface of the compact (dust core), and observe this cross-section with a microscope to take a field of view in the observed image and exist in the field of view The coated iron particles to be extracted (coated iron particles and bare iron particles in sample Nos. 1-2 and 1-3) are extracted. In the observed image, particles having an insulating coating are extracted as coated iron particles, and particles having no insulating coating are extracted as bare iron particles. The areas of the extracted coated iron particles and bare iron particles are measured, and the diameter of a circle (equivalent area circle) equal to the area is defined as the diameter of the coated iron particles and the diameter of the bare iron particles. The diameter of 100 or more coated iron particles and the diameter of 100 or more bare iron particles present in the field of view are measured, and the average of each is the average particle diameter of the coated iron powder in the dust core and the average of the bare iron powder. The particle size. Extraction of the coated iron particles and bare iron particles and calculation of the diameter can be easily performed by performing image processing on the observed image and binarization. The image processing can be easily performed by using a commercially available image processing apparatus.

  The obtained sample No. 1-1, the coated iron powder constituting the compressed product (dust core), Sample No. In the coated iron powder constituting the compressed product (powder magnetic core) of 1-2, 1-3, the mass ratio of powder particles having a particle diameter of 75 μm or less, the mass ratio of powder particles having a particle diameter of 100 μm or less, and the particle diameter are The mass ratio of powder particles of 500 μm or more was measured as follows. Sample No. In the bare iron powder constituting the compressed product (powder magnetic core) of 1-2 and 1-3, the mass ratio of powder particles having a particle size of 200 μm or more was measured as follows.

  The area ratio of the coated iron particles in the above-mentioned cross section is converted into a volume ratio (for example, volume ratio = area ratio to the power of 1.5), and each mass ratio is calculated using the volume ratio and the density of the coated iron particles. To do. Similarly, for the bare iron powder, the mass ratio of the powder particles of 200 μm or more is calculated using the volume ratio converted from the area ratio and the density of the bare iron particles. The density of the coated iron particles and the density of the bare iron particles can be calculated based on the composition by performing the composition analysis described above.

  As a result of the measurement, sample No. The average particle diameter of the coated iron powder in the 1-1 dust core, the mass ratio of powder particles having a particle diameter of 75 μm or less, the mass ratio of powder particles having a particle diameter of 100 μm or less, and the mass of powder particles having a particle diameter of 500 μm or more The ratio substantially maintained each value of the raw material powder. Sample No. The average particle diameter of the coated iron powder in the powder core of 1-2, 1-3, the mass ratio of powder particles having a particle diameter of 75 μm or less, the mass ratio of powder particles having a particle diameter of 100 μm or less, and the particle diameter of 500 μm or more The mass ratio of the powder particles, the average particle diameter of the bare iron powder, and the mass ratio of the powder particles having a particle diameter of 200 μm or more substantially maintained the respective values of the raw material powder.

  The obtained sample No. In the compressed product (powder magnetic core) of 1-2 and 1-3, the blending ratio of the coated iron powder and the pure iron powder was calculated using the volume ratio and the density described above. Maintained.

  From this test, a mixed powder containing a specific size of coated iron powder, a specific amount of a lubricant containing a specific component, and a specific size of bare iron powder is compressed as a raw material powder. It was confirmed that by molding, a dust core having high magnetic permeability and low core loss can be produced. Moreover, it has confirmed that the said powder magnetic core was manufacturable, without performing heat processing.

[Test Example 2]
As the raw material powder, the sample No. described in Test Example 1 was used. 1-2 mixed powder (coated iron powder 1 (310 μm) + bare iron powder (mixing ratio 10 mass%) + lubricant) and mixed powder not containing bare iron powder (coated iron powder 1 (310 μm) + lubricant) ) And a powder magnetic core not subjected to heat treatment (sample No. 2-1: no bare iron powder, sample No. 2-2: Manufactured with bare iron powder) and examined its strength.

  The prepared sample No. Using the compressed materials of 2-1 and 2-2 (powder magnetic core, 55 mmL long, 10 mmW wide, 5 mm thick bending test piece), a three-point bending test was performed to determine the bending strength. Specifically, in a state where both sides of the test piece are supported on the back surface (anti-bending span 40 mmL), a load is applied from above to the center of the surface of the test piece, and the maximum load when the test piece is broken is obtained. The maximum load (average of n = 5) was taken as the bending strength (MPa), and the strength was evaluated.

  As a result, Sample No. using a mixed powder containing no bare iron powder. The bending strength of 2-1 is 13.9 MPa, and sample No. using a mixed powder containing coated iron powder and bare iron powder. The bending strength of 2-2 was 15.6 MPa, both of which were high strength. The reason for this is considered that the coated iron particles are sufficiently meshed with each other and the lubricant is relatively non-uniform so that it is difficult to inhibit the direct bonding between the powder particles. In particular, Sample No. using bare iron powder. 2-2 is Sample No. It is stronger than 2-1. The reason for this is considered that the bare iron powder that was plastically deformed could firmly bond the coated iron particles. From this test, it was confirmed that a compact and high-strength powder magnetic core was obtained even though it was not heat-treated after molding and contained a lubricant. Moreover, it has confirmed that the powder magnetic core which is excellent in intensity | strength is obtained even if it is the same density by containing fine bare iron powder.

  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 example, the average particle size / particle size distribution of the coated iron powder, the component / thickness of the insulating coating, the component / content of the lubricant, the average particle size / particle size distribution of the bare iron powder, the coated iron powder and the bare iron The blending ratio with the powder and the molding conditions (mold temperature, molding pressure, atmosphere, etc.) can be changed as appropriate. Further, as a magnetic component, a form in which at least a part of pure iron is replaced with an iron-based alloy such as Fe—Si or Fe—Si—Al can be considered.

  The dust core of the present invention can be used for a magnetic core of various coil components (for example, a reactor, a transformer, a motor, a choke coil, an antenna, a fuel injector, an ignition coil, etc.). 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.

DESCRIPTION OF SYMBOLS 1 Powder magnetic core 10 Coated iron powder 12 Iron particle 14 Insulating coating 20 Bare iron powder 30 Lubricant P Raw material powder 100 Coated iron powder 120 Iron particle 140 Insulating coating 200 Bare iron powder 300 Lubricant 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 G Gap C coil

Claims (7)

Including coated iron powder with an insulating coating, bare iron powder without an insulating coating, and a 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 bare iron powder has an average particle size of 40 μm or more and 150 μm or less, and the proportion of powder particles having a particle size of 200 μm or more is 10% by mass or less,
The lubricant is a dust core having a content of 0.36% by mass to 0.8% by mass and containing a fatty acid amide. The dust core according to claim 1 , wherein the content of the coated iron powder in the magnetic component of the dust core is 50% by mass or more and less than 100% by mass. The dust core according to claim 1 or 2, wherein a content of the bare iron powder in a magnetic component of the dust core is 10 mass% or more and 45 mass% or less. The dust core according to any one of claims 1 to 3 , wherein the fatty acid amide includes stearic acid amide. The lubricant is a dust core according to any one of claims 1 to 4, which comprises a fatty acid metal salt. The powder magnetic core according to any one of claims 1 to 5 , comprising a polyamide-based resin in an amount of more than 0 and 0.5% by mass or less. A coil component comprising a coil and a magnetic core,
A coil component comprising the dust core according to any one of claims 1 to 6 in at least a part of the magnetic core.

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