JP2009185312A - Composite soft magnetic material, dust core using the same, and their production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soft magnetic powder material which achieves both the suppression in the reduction of a core loss and the deterioration of magnetic flux density, to provide a dust core. <P>SOLUTION: In the composite soft magnetic material (3) comprising: a metal magnetic particle (1); and an insulating film (2) formed on the surface of the metal magnetic particle (1), the material further comprises an insulating film protective part (5) comprising metal oxide magnetic particles (4) formed at least at a part of the surface of the insulating film (2) and whose particle diameter is smaller than that of the metal magnetic particle. Also disclosed are a dust core using the same, and their production methods. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention provides a magnetic core having a composite soft magnetic material having metal magnetic particles and an insulating film formed on the surface of the metal magnetic particles, in which a decrease in magnetic flux density is suppressed and iron loss is reduced. The present invention relates to a powder magnetic core and a composite soft magnetic material that can be advantageously used in the production of the powder magnetic core. Furthermore, the present invention relates to such a composite soft magnetic material and a method for producing a dust core.

  In recent years, with the miniaturization and high density of electrical and electronic equipment, the demand for small, high magnetic flux density, high magnetic permeability and low iron loss is increasing for the magnetic core materials used for them. It is coming. Examples of the magnetic core material include a laminated magnetic core in which silicon steel plates are laminated, and a powder magnetic core in which a composite soft magnetic material in which soft magnetic powder is coated with an insulating resin is compression-molded. The powder magnetic core has a low iron loss in the high frequency region and is excellent in formability as compared with the laminated magnetic core, but further higher magnetic flux density and lower iron loss are desired.

  Up to now, the powder magnetic core has been made to be low in iron loss by being electrically insulated by, for example, a phosphate film provided on the surface of the iron powder and a resin mixed at the time of molding (see Patent Document 1). However, recently, the need for further reduction of iron loss has increased, and at a high temperature (for example, 600 ° C. or higher, that is, the heat resistance temperature of the resin or higher) that can sufficiently recover the distortion of iron powder generated during molding under high pressure. Annealing is an issue. As an insulating structure that does not rely on the insulating properties of the resin, for example, a film made of an inorganic compound as in Patent Document 2 or a phosphate film with improved heat resistance as in Patent Document 3 Therefore, securing insulation is being studied.

  However, in general, inorganic compounds and phosphate films are more fragile than resins, and breakage occurs at a high pressure during molding, which makes it difficult to ensure insulation. Therefore, in Patent Document 4, in order to protect the insulating film, the surface of the insulating film is covered with metal soap, or metal soap and oxide particles are disposed inside and on the surface of the insulating film, thereby improving the lubricity of the metal soap. It is said that the insulating film can be protected by rolling of the oxide particles. However, the metal soap has a lubricating effect and is soft, so it has a buffering effect to protect the insulating film and reduce iron loss. However, since it does not have magnetism, there is a problem that the magnetic flux density decreases depending on the amount of addition. It was. In addition to having the above-mentioned problems when using non-magnetic particles, oxide particles cannot be expected to have a buffering effect due to their hardness, and the protection of the insulating film is insufficient only by the rolling effect. .

  As described above, the important magnetic characteristics of the dust core that can be used as a core of a motor or a solenoid are magnetic flux density and iron loss. The higher the magnetic flux density is, the lower the iron loss is. In a dust core, an insulating film that electrically insulates individual iron powders is a key point for reducing iron loss, which is an important characteristic. Among them, it is one of important issues to protect the insulating film from a high molding pressure of around 1000 MPa in the step of molding iron powder. Conventionally, this has been dealt with by mixing a lubricant such as metal soap or coating the surface of the insulating film. However, since the lubricant does not have magnetism, the magnetic flux density generally decreases according to the amount of addition.

JP 2002-246219 A Japanese Patent Laying-Open No. 2005-206880 JP 2005-93350 A JP 2005-129716 A

  The present invention has been made in view of such conventional problems. In particular, the magnetic flux density is reduced because the particles have magnetism and the film is protected by the rolling action of the particles and the buffering action of the organic matter. An object of the present invention is to obtain a soft magnetic powder material and a powder magnetic core that have the feature of suppressing the above.

  Invention of Claim 1 of this application (henceforth "the 1st invention of this application") has a metal magnetic particle (1) and the insulating film (2) formed in the surface of a metal magnetic particle (1) In the composite soft magnetic material (3), the insulating film protection comprising metal oxide magnetic particles (4) having an average particle size smaller than that of the metal magnetic particles (1) formed on at least a part of the surface of the insulating film (2). The present invention provides a composite soft magnetic material, further comprising a portion (5). FIG. 1 schematically shows the composite soft magnetic material according to the first invention of the present application. The composite soft magnetic material according to the first invention of the present application is represented by a single particle as shown in FIG. 1 for the sake of clarity, but is usually handled by a large number of particle groups.

  In the first invention of the present application, a composite soft magnetic material obtained by using metal oxide magnetic particles having an average particle size smaller than that of metal magnetic particles, for example, iron oxide nanoparticles having magnetism as a main component of a lubricant. However, it can be advantageously used in the manufacture of a dust core that enables both iron loss reduction and suppression of magnetic flux density reduction.

  The invention according to claim 19 of the present application (hereinafter referred to as “the second invention of the present application”) includes a metal magnetic particle (1), an insulating film (2) formed on the surface of the metal magnetic particle (1), An insulating film protecting part (5) including metal oxide magnetic particles (4) having an average particle size smaller than that of the metal magnetic particles (1), which is formed on at least a part of the surface of the insulating film (2). The present invention provides a dust core manufactured using a group of composite soft magnetic materials (3). FIG. 2 schematically shows a part of the cross section of the dust core (7) according to the second invention of the present application.

In FIG. 2, 1 is a metal magnetic particle, and a typical example is pure iron powder. Reference numeral 2 denotes an insulating film formed on the surface of the metal magnetic particles, and phosphates, metal oxides, and metal nitrides are preferable. 4 is a metal oxide magnetic particle having magnetism for protecting the insulating film, and Fe ₃ O ₄ , MnFe ₂ O ₄ , CoFe ₂ O ₄ , NiFe ₂ O _{4 and the} like are preferable. A group consisting of a plurality of composite soft magnetic materials (3) composed of the metal magnetic particles (1), the insulating film (2), and the metal oxide magnetic particles (4) is molded at a pressure of about 500 to 1500 MPa and compacted. Get the body. At this time, the metal oxide magnetic particles (4) exhibit a function of preventing breakage of the insulating film by a rolling effect and a buffering effect. Thereafter, annealing is performed at a high temperature of 400 ° C. or higher, preferably 550 ° C. or higher and 800 ° C. or lower, more preferably 600 ° C. or higher and 800 ° C. or lower, to obtain a dust core (7) having excellent magnetic properties.

  In the second invention of the present application, a composite soft magnetism having a metal oxide magnetic particle (4) having an average particle size smaller than that of the metal magnetic particle (1), for example, iron oxide nanoparticles having magnetism as a main component of a lubricant. By using the group of materials (3), it is possible to provide a dust core (7) that achieves both iron loss reduction and magnetic flux density reduction suppression.

The invention according to claim 22 of the present application (hereinafter referred to as “the third invention of the present application”) is a method for producing a composite soft magnetic material having metal magnetic particles and an insulating film formed on the surface of the metal magnetic particles.
Forming an insulating film (2) on the surface of the metal magnetic particles (1);
Forming metal oxide magnetic particles (4) having an average particle size smaller than that of the metal magnetic particles (1);
Characterized in that it has a step of forming the insulating film protective part (5) by attaching the formed metal oxide magnetic particles (4) to at least a part of the surface of the formed insulating film (2). A method for producing the composite soft magnetic material (3) is provided.

  In the third invention of the present application, similarly to the first invention, metal oxide magnetic particles having an average particle size smaller than that of the metal magnetic particles, for example, iron oxide nanoparticles having magnetism are used as the main component of the lubricant. According to the manufacturing method, a composite soft magnetic material that can be used for manufacturing a dust core that enables both reduction of iron loss and suppression of decrease in magnetic flux density can be advantageously obtained.

The invention according to claim 23 of the present application (hereinafter referred to as “the fourth invention of the present application”) is a pressure composed of a group of composite soft magnetic materials having metal magnetic particles and an insulating film formed on the surface of the metal magnetic particles. In the manufacturing method of the powder magnetic core,
Metal oxide having a smaller average particle diameter than metal magnetic particles (1) formed on at least a part of the surface of metal magnetic particles (1) and insulating film (2) formed on the surface of metal magnetic particles (1) Filling a molding die with a group of composite soft magnetic materials (3) further having an insulating film protective part (5) containing magnetic particles (4);
Pressure-molding the group of composite soft magnetic materials (3) in the molding die;
The present invention provides a method for producing a powder magnetic core (7), comprising a step of heat-treating the obtained molded body at 400 ° C or higher and 1000 ° C or lower.

  In the fourth invention of the present application, similarly to the second invention, metal oxide magnetic particles (4) having an average particle size smaller than that of the metal magnetic particles (1), for example, iron oxide nanoparticles having magnetism, are used as a lubricant. By using the group of the composite soft magnetic material (3) having the main component, a dust core (7) that achieves both reduction of iron loss and suppression of reduction of magnetic flux density can be advantageously manufactured.

  In the invention according to claim 2 as a preferred embodiment of the composite soft magnetic material in the first invention of the present application, a composite soft magnetic material in which the metal oxide magnetic particles (4) are ferromagnetic is provided. Various ferromagnetic materials can be used. For example, a material having a Curie temperature of 250 ° C. or higher and 700 ° C. or lower, which is a transition temperature at which it exhibits paramagnetism, can be preferably used.

  In the present invention, the magnetic flux in the case where a layer for protecting the insulating film is provided in the dust core using the composite soft magnetic material by using the ferromagnetic material as the metal oxide magnetic particles (4) as described above. This makes it possible to suppress density reduction.

  In the invention according to claim 3 as another preferred embodiment of the composite soft magnetic material in the first invention of the present application, the metal oxide magnetic particles (4) are substantially spherical.

Examples of the substantially spherical metal oxide magnetic particles (4) include metal oxide magnetic particles such as iron oxide nanoparticles. Here, the substantially spherical shape means a substantially spherical shape. More specifically, for example, when the shape is defined by a major axis r ₁ , a minor axis r ₂ , and a thickness r ₃ (provided that r ₁ ≧ r ₂ ≧ r ₃ ), the ratio of the major axis r ₁ to the minor axis r ₂ (r ₂ / r ₁ ) is in the range of 0.5 to 1.0, the thickness r ₃ and the minor axis r the ratio of _{2 (r} 3 / r ₂₎ is meant in the range of 0.7 to 1.0.

  In this aspect of the present invention, since the shape is substantially spherical, friction reduction of the insulating film can be expected due to the rolling effect of the metal oxide magnetic particles on the surface of the insulating film in the compression molding process at the time of manufacturing the dust core.

In the invention according to claim 4 as another preferred embodiment of the composite soft magnetic material in the first invention of the present application, the metal oxide magnetic particles (4) have an average particle diameter of 0.5 μm or less. The average particle size of the metal oxide magnetic particles (4) is more preferably 0.001 μm to 0.1 μm, and particularly preferably 0.005 μm to 0.05 μm. Further, the average particle size ratio _r 2 / _{r 1} to the average particle diameter _{r 1} of _{r 2} of the metal magnetic particles (1) of the metal oxide magnetic particles (4) is preferably either 0.00001 or 0.01 of 0.00005 to 0.0005 is particularly preferable.

  In such an aspect of the present invention, the composite soft magnetic material obtained by using metal oxide magnetic particles having a significantly smaller average particle diameter than the metal magnetic particles, such as iron oxide nanoparticles, as the main component of the lubricant, It can be advantageously used by manufacturing a dust core that enables both iron loss reduction and suppression of magnetic flux density reduction.

  In the invention according to claim 5 as another preferred embodiment of the composite soft magnetic material in the first invention of the present application, the metal oxide magnetic particles (4) contain Fe, and the metal oxide magnetic particles include Of the metal elements contained, the Fe content is preferably 30% by mass or more, and particularly preferably 50% by mass or more and 100% by mass or less.

  This aspect of the present invention makes it possible to improve the saturation magnetic flux density of the metal oxide magnetic particles.

In another preferred embodiment of the composite soft magnetic material, the metal oxide magnetic particles (4) are magnetite (Fe ₃ O ₄ ).

  This aspect of the present invention enables further improvement in the saturation magnetic flux density of the metal oxide magnetic particles.

  In the invention according to claim 7 as another preferred embodiment of the composite soft magnetic material, the metal oxide magnetic particles (4) are selected from the group consisting of Co, Mn and Ni in addition to Fe. It further contains at least one element. In such an embodiment, the content of Co in the metal element contained in the metal oxide magnetic particles is preferably 5% by mass or more, and particularly preferably 20% by mass or more and 50% by mass or less. Of the metal elements contained in the magnetic particles, the Mn content is preferably 5% by mass or more, particularly preferably 20% by mass or more and 50% by mass or less, and the Ni content is preferably 5% by mass. It is at least 20% by mass, particularly preferably at least 20% by mass and not more than 50% by mass.

  Such an aspect of the present invention is intended to improve the specific volume resistance of the metal oxide magnetic particles and to improve the specific resistance as a dust core.

In the invention according to claim 8 as another preferred embodiment of the composite soft magnetic material, the metal oxide magnetic particles (4) are cobalt ferrite (CoFe ₂ O ₄ ), manganese ferrite (MnFe ₂ O ₄ ). And at least one selected from the group consisting of nickel ferrite (NiFe ₂ O). As the metal oxide magnetic particles (4), cobalt ferrite and manganese ferrite are more preferable, and those using manganese ferrite alone are particularly preferable.

  Such an aspect of the present invention is intended to improve the specific volume resistance of the metal oxide magnetic particles and to improve the specific resistance as a dust core.

  In the invention according to claim 9 as another preferred embodiment of the composite soft magnetic material in the first invention of the present application, the metal oxide magnetic particles (4) have a saturation magnetic flux density of 0.1 T or more.

  In another preferred embodiment of the composite soft magnetic material, the saturation magnetic flux density is 0.5 T or more.

  In the present invention, the saturation magnetic flux density can usually be measured by a standard sample vibration type magnetometer (VSM) apparatus using a measurement sample dried after preparation.

  This aspect of the present invention makes it possible to suppress the decrease in the magnetic flux density of the dust core due to the provision of the coating protective layer due to the high magnetic flux density of the metal oxide magnetic particles.

  In the invention according to claim 11 as another preferred embodiment of the composite soft magnetic material in the first invention of the present application, the metal oxide magnetic particles (4) have a volume resistivity of 10 μΩ · m or more. The volume resistivity is more preferably 100 μΩ · m or more.

In another preferred embodiment of the composite soft magnetic material, the volume specific resistance is 1000 μΩ · m or more. The volume resistivity is more preferably 1 × 10 ⁵ μΩ · m or more, and more preferably 1 × 10 ⁸ μΩ · m or more.

  In the present invention, the volume resistivity can usually be measured by a standard electrometer apparatus using a measurement sample of a sintered body of metal oxide magnetic particles.

  This aspect of the present invention makes it possible to improve the specific resistance of the dust core by increasing the volume resistivity of the metal oxide magnetic particles.

  In the invention according to claim 13 as another preferred embodiment of the composite soft magnetic material in the first invention of the present application, the surfactant (6) is present on the surface of the metal oxide magnetic particles (4). It is. FIG. 1 schematically shows a composite soft magnetic material in which such a surfactant (6) is present on the surface of metal oxide magnetic particles (4).

  In such an embodiment, a surfactant which is an aliphatic amine is appropriately selected and used as the surfactant. Specific examples thereof include monoalkyl primary amines, among which oleylamine and laurylamine are preferable.

Such a surfactant (6) is present on the surface of the metal oxide magnetic particle (4) as at least a part of the surface of the metal oxide magnetic particle (4). Preferably, the surfactant (6) is present in a layered manner on most of the surface of the metal oxide magnetic particle (4), particularly preferably on the entire surface of the metal oxide magnetic particle (4), The amount of the surfactant (6) present on the surface of the metal oxide magnetic particle (4) is usually preferably 0.5 to 5 molecules / nm ² per unit surface area of the metal oxide magnetic particle (4). 1-3 molecules / nm ² are preferred. Moreover, as a binding state of the surfactant (6) and the metal oxide magnetic particles (4), it is usually preferable that the amino group in the amine is adsorbed on the surface of the metal oxide magnetic particles.

  In such an embodiment of the present invention, since a surfactant part, preferably a surfactant layer, is formed on the surface of the metal oxide magnetic particle (4), a buffering effect against pressure can be expected.

  In the invention according to claim 14 as another preferred embodiment of the composite soft magnetic material in the first invention of the present application, the insulating film protecting portion (5) is formed in a layered manner on the entire surface of the insulating film (2). It is what. In the composite soft magnetic material according to the first invention of the present application, the insulating film protecting portion (5) is formed on at least a part of the surface of the insulating film (2), and more preferably the insulating film (2 ), Particularly preferably over the entire surface of the insulating film (2). FIG. 1 schematically shows a composite soft magnetic material in which the insulating film protecting portion (5) is formed in a layered manner on the surface of the insulating film (2).

  In the invention according to claim 15 as another preferred embodiment of the composite soft magnetic material, the layered insulating film protective part (5) has a thickness of 0.005 μm or more and 1 μm or less. Is more preferably 0.01 μm or more and 0.1 μm or less.

  This aspect of the present invention enhances the protective effect of the insulating film and enables the specific resistance of the dust core to be improved.

  In another preferred embodiment of the composite soft magnetic material according to the first invention of the present application, the metal oxide magnetic particles (4) are added in an amount of 0. 0 relative to the mass of the composite soft magnetic material (3). It is contained in a ratio of 01% by mass or more and 1% by mass or less, and the ratio is more preferably 0.05% by mass or more and 0.5% by mass or less, and the vicinity of 0.2% by weight is the best. .

  In this aspect of the present invention, only a necessary amount of the coating protective part is formed, and the magnetic flux density lowering of the dust core can be suppressed.

  In the invention according to claim 17 as another preferred embodiment of the composite soft magnetic material in the first invention of the present application, the insulating film (2) is selected from the group consisting of phosphate, metal oxide and metal nitride. It contains at least one kind.

In such an embodiment, the phosphate is preferably iron phosphate, zinc phosphate, manganese phosphate or calcium phosphate. As the metal oxide, SiO ₂ , MgO, ZrO ₂ , Al ₂ O ₃ , CaO, TiO ₂ , Y ₂ O ₃ , Nb ₂ O _{5 and the} like are preferable, and SiO ₂ , Al ₂ O ₃ and a composite thereof are particularly preferable. . As the metal nitride, AlN, Si ₃ N ₄ or the like is preferable. Among these, SiO ₂ , Al ₂ O ₃ and combinations thereof are preferable.

  The thickness of the insulating film (2) formed on the surface of the metal magnetic particles (1) is usually preferably 0.001 μm to 1 μm, particularly preferably 0.01 μm to 0.5 μm.

  Such an aspect of the present invention makes it possible to improve the specific resistance of the dust core.

  In the invention according to claim 18 as another preferred embodiment of the composite soft magnetic material in the first invention of the present application, the metal magnetic particles (1) are mainly composed of Fe, and specifically, Examples of materials that are usually used include pure iron powder, alloy powder to which 0.1 to 5% of Si, Al and the like are added. Further, the average particle diameter of the metal magnetic particles (1) is usually used, and specifically, preferably 30 μm or more and 300 μm or less. The shape of the metal magnetic particles (1) is not particularly limited as long as it is normally used.

  The invention according to claim 20 as another preferred embodiment of the dust core according to the second invention of the present application is the magnetic flux density when a magnetic field of 10,000 (A / m) is applied to the dust core (7). Is a dust core of 1.5T or more.

  In such an embodiment, the magnetic flux density is more preferably 1.6 T or more, and particularly preferably 1.7 T or more. In addition, the measuring method of magnetic flux density is normally performed according to said measuring method of saturation magnetic flux density.

  Such an aspect of the present invention enables application to a motor, a solenoid valve, or the like.

  The invention according to claim 21 as another preferred embodiment of the dust core in the second invention of the present application is a dust core in which metal oxide magnetic particles are sintered by annealing. This is because by applying nano-sized particles of fine particle size as the metal oxide particles, the metal oxide particles are sintered in the heating process such as the annealing process of the dust core to form a layered metal oxide layer can do. In such an embodiment, by using metal oxide magnetic particles sintered by annealing, a metal oxide film is further formed, which has an insulating function and magnetic properties, thereby enabling further improvement of magnetic properties. Is.

  In addition, also in the manufacturing method of the powder magnetic core in the second invention of the present application, the aspect of the composite soft magnetic material (3) in the first invention of the present application can be applied.

  In the method for producing the composite soft magnetic material (3) according to the third invention of the present application, for example, the metal magnetic particles are obtained by dissolving a silicone resin “KR220L” manufactured by Shin-Etsu Chemical in alcohol and mixing and drying with the metal magnetic particles (1). An insulating film (2) is formed on the surface of (1), and metal oxide magnetic particles (4) are formed. If necessary, the metal oxide magnetic particles (4) are further treated with a surfactant to form a surfactant part on the surface thereof. Then, the metal oxide magnetic particles are dispersed in an appropriate solvent, mixed and dried with the metal magnetic particles on which the insulating film is formed, and the formed metal oxide is formed on the surface of the formed insulating film (2). The composite soft magnetic material (3) is manufactured by attaching the magnetic material particles (4) to form the insulating film protecting part (5).

  Note that the aspect of the composite soft magnetic material (3) in the first invention of the present application can also be applied to the method of manufacturing the composite soft magnetic material (3) in the third invention of the present application.

  In the method of manufacturing a dust core (7) according to the fourth invention of the present application, for example, a group of particles made of the composite soft magnetic material (3) manufactured as described above is formed into a predetermined molding die. The group of the composite soft magnetic materials (3) in the molding die is filled into a green compact of a predetermined shape under a condition that the pressure is about 500-1500 MPa and the temperature is about room temperature to 200 ° C. The molded body obtained by pressure molding and subjected to a heat treatment such as annealing at a temperature of 400 ° C. or higher and 1000 ° C. or lower, preferably 550 ° C. or higher and 800 ° C. or lower, in a reducing gas such as vacuum or inert gas or hydrogen. In addition, if necessary, an annealing treatment is performed at a high temperature of 600 ° C. or higher to produce a dust core (7).

  In the method of manufacturing the dust core (7) according to the fourth invention of the present application, the aspect of the composite soft magnetic material (3) according to the first invention of the present application and the composite soft magnetic material according to the third invention of the present application are also described. The aspect about the manufacturing method of magnetic material (3) may be applied.

  Examples of the present invention will be described below more specifically with reference to examples of the present invention. However, the present invention is not limited to these examples.

Example 1
A solution in which a silicone resin “KR220L” manufactured by Shin-Etsu Chemical Co., Ltd. is dissolved in alcohol on the surface of 1000 g of metal magnetic particles (1) (product name ABC100.30 manufactured by Höganäs Co., Ltd.) whose main component is Fe and whose average particle size is about 80 μm. Were mixed and dried, and coated with 2 g in terms of solid weight, thereby forming an insulating film (2) having a component that changed to SiO ₂ in the subsequent annealing step. The thickness of the insulating film (2) was measured with a transmission electron microscope and found to be 0.1 μm. Separately, _(purity 70～80Mol% alkylamine mixture of _C 14 ~C ₂₀₎ Fe iron acetylacetonate complex and oleylamine as the molar concentration of the ion is 0.5 mol / L and mixed 270 ° C. and After heating for 120 minutes, unreacted substances and excess oleylamine are removed to form metal oxide magnetic particles (4) composed of Fe ₃ O ₄ and having an average particle size of 0.015 μm, and a surfactant part on the surface. did. The ratio of the surfactant to the metal oxide magnetic particles was 10% by mass. Next, 1 g of the metal oxide magnetic particles (4) is dispersed in hexane, mixed and dried with the metal magnetic particles (1) coated with the insulating film (2), and then on the surface of the insulating film (2). By coating, the metal oxide magnetic particles (4) were adhered to form the insulating film protection part (5), and particles of the composite soft magnetic material (3) were obtained. In addition, it was 0.02 micrometer when the thickness of the layer of the insulating-film protection part (5) was measured with the transmission electron microscope.

Next, about 9 g of the particle group composed of the composite soft magnetic material (3) is filled in a predetermined molding die, and the composite in the molding die is subjected to a pressure of 1000 MPa and a temperature of 130 ° C. by a hydraulic press. The group of soft magnetic materials (3) was pressure-molded into a green compact in a ring shape (outer diameter: about 24 mm, inner diameter: about 16 mm). Then, the green compact obtained in a vacuum atmosphere is annealed under the conditions of a pressure of 1 × 10 ⁻² Pa and a temperature of 600 ° C., and a dust core (7) (outer diameter: about 24 mm, inner diameter: about 16 mm) is obtained. Obtained.

  With respect to the obtained dust core (7), a magnetic field of 10000 (A / m) was applied by a BH analyzer, and the magnetic flux density was measured to be 1.61 T. Further, with respect to the obtained dust core (7), the eddy current loss was measured at a magnetic flux density of 1.5 T and a frequency of 400 Hz with an AC magnetization characteristic measurement device, and it was 11 W / kg.

Example 2
As a starting material for metal oxide magnetic particles, an iron acetylacetonate complex and a manganese acetylacetate were prepared so that the total molar concentration of Fe ions and Mn ions was 0.5 mol / L and the ratio of Fe ions to Mn ions was 2: 1. A dust core was obtained in the same manner as in Example 1 except that the narate complex and oleylamine were mixed. With respect to the obtained dust core (7), a magnetic field of 10000 (A / m) was applied by a BH analyzer and the magnetic flux density was measured, and it was 1.61 T. Further, with respect to the obtained powder magnetic core (7), the eddy current loss was measured at a magnetic flux density of 1.5 T and a frequency of 400 Hz using an AC magnetization characteristic measurement device, and found to be 9 W / kg.

  In Examples 1 and 2, the protective effect of the metal oxide magnetic particles and the surfactant on the surface of the metal oxide magnetic particles, and further, the metal oxide magnetic particles sinter in the annealing process to act as an insulating film. It seems that the eddy current loss is reduced as described above.

  In addition to the above examples, the metal oxide magnetic particles are directly coated on the surface of the metal magnetic particles without providing an insulating film, and after compression molding, annealing is performed to sinter the metal oxide magnetic particles. Alternative applications are also possible.

Comparative Example 1
A solution in which a silicone resin “KR220L” manufactured by Shin-Etsu Chemical Co., Ltd. is dissolved in alcohol on the surface of 1000 g of metal magnetic particles (1) (product name ABC100.30 manufactured by Höganäs) whose main component is Fe and the average particle diameter is about 80 μm. Were mixed and dried, and coated with 2 g in terms of solid weight, thereby forming an insulating film (2) having a component that changed to SiO ₂ in the subsequent annealing step. The thickness of the insulating film (2) was measured with a transmission electron microscope and found to be 0.1 μm. A powder magnetic core was obtained in the same manner as in Example 1 by using the group consisting of metal magnetic particles having an insulating film formed on the surface thus obtained. With respect to the obtained dust core (7), a magnetic field of 10000 (A / m) was applied by a BH analyzer, and the magnetic flux density was measured to be 1.62T. Further, with respect to the obtained dust core (7), the eddy current loss was measured at a magnetic flux density of 1.5 T and a frequency of 400 Hz with an AC magnetization characteristic measurement device, and found to be 35 W / kg.

Comparative Example 2
A solution in which a silicone resin “KR220L” manufactured by Shin-Etsu Chemical Co., Ltd. is dissolved in alcohol on the surface of 1000 g of metal magnetic particles (1) (product name ABC100.30 manufactured by Höganäs) whose main component is Fe and the average particle diameter is about 80 μm. Were mixed and dried, and coated with 2 g in terms of solid weight, thereby forming an insulating film (2) having a component that changed to SiO ₂ in the subsequent annealing step. The thickness of the insulating film (2) was measured with a transmission electron microscope and found to be 0.1 μm. The surface of the insulating film was obtained by mixing and drying 2.5 g of metal soap (product name, Himicron F930, manufactured by Chukyo Yushi Co., Ltd.) to 1000 g of the metal magnetic particles having an insulating film formed on the surface. By coating on the top, a metal soap was adhered to form an insulating film protection part, and particles of a composite soft magnetic material were obtained. A dust core was obtained in the same manner as in Example 1 by using the group of particles of the composite soft magnetic material thus obtained. With respect to the obtained dust core (7), a magnetic field of 10000 (A / m) was applied by a BH analyzer, and the magnetic flux density was measured to be 1.56 T. Further, with respect to the obtained dust core (7), the eddy current loss was measured at a magnetic flux density of 1.5 T and a frequency of 400 Hz with an AC magnetization characteristic measurement device, and found to be 12 W / kg.

Comparative Example 3
A solution in which a silicone resin “KR220L” manufactured by Shin-Etsu Chemical Co., Ltd. is dissolved in alcohol on the surface of 1000 g of metal magnetic particles (1) (product name ABC100.30 manufactured by Höganäs) whose main component is Fe and whose average particle diameter is about 80 μm. Were mixed and dried, and coated with 2 g in terms of solid weight, thereby forming an insulating film (2) having a component that changed to SiO ₂ in the subsequent annealing step. The thickness of the insulating film (2) was measured with a transmission electron microscope and found to be 0.1 μm. After 1 g of manganese ferrite (MnFe ₂ O ₄ ) powder (average particle size of about 5 μm) was mixed with 1000 g of metal magnetic particles having an insulating film formed on the surface thus obtained, the same as in Example 1 was performed. To obtain a dust core. With respect to the obtained dust core (7), a magnetic field of 10,000 (A / m) was applied by a BH analyzer and the magnetic flux density was measured, and it was 1.60 T. Further, with respect to the obtained powder magnetic core (7), the eddy current loss was measured at a magnetic flux density of 1.5 T and a frequency of 400 Hz by using an AC magnetization characteristic measurement device, and found to be 32 W / kg.

  For the above Examples 1 and 2 and Comparative Examples 1 to 3, the magnetic flux density and eddy current loss of each obtained dust core are shown in FIG. As shown in FIG. 3, the dust cores in Examples 1 and 2 according to the invention of the present application do not perform film protection in Comparative Examples 1 and 3, and use metal soap in Comparative Example 2 for film protection It can be seen that both low eddy current loss, that is, low iron loss and high magnetic flux density can be achieved.

It is explanatory drawing which showed typically the composite soft-magnetic material of this invention. It is explanatory drawing which showed typically a part of cross section of the powder magnetic core of this invention. It is explanatory drawing which showed the magnetic flux density and eddy current loss of the powder magnetic core in the Example and comparative example of this invention.

Claims (23)

  In a composite soft magnetic material (3) having metal magnetic particles (1) and an insulating film (2) formed on the surface of the metal magnetic particles (1), at least a part of the surface of the insulating film (2) The composite soft magnetic material further comprising an insulating film protecting part (5) formed of a metal oxide magnetic particle (4) having an average particle size smaller than that of the metal magnetic particle (1).   The composite soft magnetic material according to claim 1, wherein the metal oxide magnetic particles (4) are ferromagnetic.   The composite soft magnetic material according to claim 1 or 2, wherein the metal oxide magnetic particles (4) are substantially spherical.   The composite soft magnetic material according to any one of claims 1 to 3, wherein the metal oxide magnetic particles (4) have an average particle size of 0.5 µm or less.   The composite soft magnetic material according to any one of claims 1 to 4, wherein the metal oxide magnetic particles (4) contain Fe. The composite soft magnetic material according to claim 5, wherein the metal oxide magnetic particles (4) are Fe ₃ O ₄ .   The composite soft magnetic material according to claim 5, wherein the metal oxide magnetic particles (4) further contain at least one element selected from the group consisting of Co, Mn and Ni. The composite soft particle according to claim 7, wherein the metal oxide magnetic particles (4) are composed of at least one selected from the group consisting of CoFe ₂ O ₄ , MnFe ₂ O ₄ and NiFe ₂ O. Magnetic material.   The composite soft magnetic material according to any one of claims 1 to 8, wherein the metal oxide magnetic particles (4) have a saturation magnetic flux density of 0.1 T or more.   The composite soft magnetic material according to claim 9, wherein the saturation magnetic flux density is 0.5 T or more.   11. The composite soft magnetic material according to claim 1, wherein the metal oxide magnetic particles (4) have a volume resistivity of 10 μΩ · m or more.   The composite soft magnetic material according to claim 11, wherein the volume resistivity is 1000 μΩ · m or more.   The composite soft magnetic material according to any one of claims 1 to 12, wherein a surfactant (6) is present on the surface of the metal oxide magnetic particles (4).   The composite soft magnetic material according to any one of claims 1 to 13, wherein the insulating film protecting portion (5) is formed in a layered manner on the entire surface of the insulating film (2).   The composite soft magnetic material according to claim 14, wherein the layered insulating film protective part (5) has a thickness of 0.001 μm or more and 1 μm or less.   The said metal oxide magnetic particle (4) is contained in the ratio of 0.01 mass% or more and 1 mass% or less with respect to the mass of a composite soft magnetic material (3). The composite soft magnetic material described in 1.   The composite according to any one of claims 1 to 16, wherein the insulating film (2) contains at least one selected from the group consisting of phosphates, metal oxides and metal nitrides, and silicone resins. Soft magnetic material.   The composite soft magnetic material according to any one of claims 1 to 17, wherein the metal magnetic particles (1) are mainly composed of Fe.   Metal magnetic particles (1), an insulating film (2) formed on the surface of the metal magnetic particles (1), and the metal magnetic particles (at least partially formed on the surface of the insulating film (2)) 1) A dust core produced by using a group of composite soft magnetic materials (3) having a metal oxide magnetic particle (4) having a smaller average particle diameter and an insulating film protective part (5).   The dust core according to claim 19, wherein a magnetic flux density is 1.5 T or more when a magnetic field of 10,000 (A / m) is applied to the dust core (7).   The dust core according to claim 19 or 20, wherein the metal oxide magnetic particles are sintered by annealing. In the method for producing a composite soft magnetic material having metal magnetic particles and an insulating film formed on the surface of the metal magnetic particles, a step of forming an insulating film (2) on at least the surface of the metal magnetic particles (1);
It has the process of attaching the formed metal oxide magnetic particles (4) to at least a part of the surface of the formed insulating film (2) to form an insulating film protecting part (5). A method for producing a composite soft magnetic material (3). In the method for producing a powder magnetic core comprising a group of composite soft magnetic materials having metal magnetic particles and an insulating film formed on the surface of the metal magnetic particles,
The average particle diameter of the metal magnetic particles (1) and the metal magnetic particles (1) formed on at least a part of the surface of the insulating film (2) formed on the surfaces of the metal magnetic particles (1) is smaller. Filling a molding die with a group of composite soft magnetic materials (3) further comprising an insulating film protective part (5) containing metal oxide magnetic particles (4);
Pressure-molding the group of composite soft magnetic materials (3) in the molding die;
A method for producing a powder magnetic core (7), comprising a step of heat-treating the obtained molded body at 400 ° C or higher and 1000 ° C or lower.

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