JP2009164470A - Magnetic powder and dust core - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide powder for dust cores for securing the insulating properties of piezomagnetic powder and suppressing a reduction in the magnetic flux density of molded dust cores. <P>SOLUTION: Magnetic powder contains powders for dust cores 10A and 10B with an insulating layer formed on the surface 11a of magnetic powder 11. As the powder for dust cores, there are at least contained: a first powder for dust cores 10A having at least a first insulating layer 12a and a second insulating layer 12b successively formed as an insulating layer from the surface 11a of the magnetic powder 11 in the layer thickness direction of the insulating layer 12A, with the hardness of the second insulating layer 12b higher than the hardness of the first insulating layer 12a; and a second powder for dust cores 10B, with a soft insulating layer 12b having the hardness lower than the hardness of the second insulating layer 12a of the first powder for dust cores 10A formed as an insulating layer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a magnetic powder made of a powder for a powder magnetic core in which at least an insulating layer is coated on the surface of the magnetic powder, and a powder magnetic core molded from the magnetic powder.

  Conventionally, a magnetic core used for an electric motor or the like has been manufactured by compacting magnetic powder containing magnetic powder. The powder for the powder magnetic core constituting the magnetic powder used for such a powder magnetic core has an insulating layer on the surface of the magnetic powder in order to ensure electrical insulation between the magnetic powders after pressure molding. It is covered.

For example, as the powder for a powder magnetic core, a powder for a powder magnetic core in which a polymer resin having excellent insulating properties such as a silicone resin is applied to the surface of the magnetic powder and the resin layer is coated as an insulating layer, or the surface of the magnetic powder Examples thereof include powders for powder magnetic cores in which an oxide such as silica (SiO ₂ ) is deposited by chemical vapor deposition (CVD) and the oxide layer is coated as the insulating layer. In addition to this, as a powder for a powder magnetic core, a magnetic powder made of a powder for a powder magnetic core in which an oxide insulating layer and a silicone resin layer are sequentially formed as an insulating layer from the surface of the magnetic powder in the thickness direction. It has been proposed (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2006-233295

  By the way, when manufacturing a dust core from the magnetic powder containing the powder for powder magnetic cores, the magnetic powder is filled in a mold and sometimes molded under a high pressure condition of 1000 MPa or more. And the molded object after shaping | molding is thrown in in a furnace, and it anneals in a non-oxidizing atmosphere furnace of several 100 degreeC, and distortion removal heat processing is performed.

  However, when a resin layer of silicone resin is formed as an insulating layer of the powder for the powder magnetic core, the resin in the resin layer flows from the surface of the magnetic powder with the pressure during molding or the softening of the resin during heat treatment. was there. As a result, although the resin layer is provided as the insulating layer, the magnetic powders are in direct contact with each other, and sufficient insulating properties may not be ensured. In addition, depending on the conditions of the heat treatment, a polymer resin such as a silicone resin may change in quality or cause a chemical change, and a desired insulating property may not be obtained.

  On the other hand, when an oxide layer such as silica is coated as the insulating layer, since the oxide is a brittle material, the oxide layer composed of the oxide is deformed together with the plastic deformation of the magnetic powder at the time of molding. Often (the oxide layer cannot follow the plastic deformation of the magnetic powder) and is often destroyed. In this case as well, the magnetic powders are in direct contact with each other, and the powder magnetic core formed thereby cannot obtain sufficient insulating properties.

  Furthermore, even when the powder of Patent Document 1 is used, similarly, the silicone resin constituting the outer layer of the powder is washed away at the initial molding of the pressure molding. As the silicone resin flows, the powdered oxide insulating layers in which a part of the silicone resin layer disappears are in contact with each other, and as described above, the oxide insulating layers are destroyed and the magnetic powders are in direct contact with each other. There is a case.

  In view of this, for example, it is conceivable to increase the thickness of the silicone resin layer or to select an insulating property that does not easily flow instead of the silicone resin. However, since the powder for powder magnetic cores described in Patent Document 1 has a two-layer structure of insulating layers, the thickness of the insulating layers inevitably increases. For this reason, when a powder magnetic core is molded using magnetic powder containing the powder for powder magnetic core, the material constituting the magnetic powder in the powder magnetic core (for example, iron when the magnetic powder is made of iron powder) The space factor of (system materials) will be low. As a result, when the molded dust core is used as a magnetic core due to a decrease in the density of the material, a desired magnetic flux density may not be obtained.

  The present invention has been made in view of the above-mentioned problems, and the object of the present invention is to ensure insulation between magnetic powders even during molding into a powder magnetic core and during heat treatment after molding. Another object of the present invention is to provide a magnetic powder and a powder magnetic core that can suppress a decrease in magnetic flux density of the molded powder magnetic core.

  In order to solve the above problems, the magnetic powder according to the present invention is a magnetic powder including a powder for a powder magnetic core in which an insulating layer is formed on the surface of the magnetic powder, and the insulating layer is formed from the surface of the magnetic powder. At least a first insulating layer and a second insulating layer are sequentially formed in the layer thickness direction of the insulating layer, and the first pressure is higher than the hardness of the first insulating layer. The powder for powder magnetic core, and the second powder for powder magnetic core in which a soft insulating layer lower than the hardness of the second insulating layer of the powder for first powder magnetic core is formed as the insulating layer, It is at least included as a powder for powder magnetic cores.

  According to the magnetic powder of the present invention, when the first and second powder magnetic core powders are in contact with each other at the time of pressure molding, the contact portion is a hard insulation of the first powder magnetic core powder. A first insulating layer to be a soft insulating layer of the first powder magnetic core powder and a soft insulating layer of the second powder magnetic core powder are formed so as to sandwich the second insulating layer which is a layer. Will be. As a result, the following advantages can be obtained.

  First, even when a large stress is applied to the hard second insulating layer at the time of pressure molding, the soft insulating layer (first pressure) between the second insulating layer and the magnetic powder is used. The first insulating layer of the powder for the magnetic core and the soft insulating layer of the second powder for the powder magnetic core) function as a buffer against the stress and suppress the deformation / destruction of the hard second insulating layer. Insulation between them can be secured.

  Secondly, the soft insulating layers (the first insulating layer of the first powder magnetic core powder and the soft insulating layer of the second powder magnetic core powder) were washed away from the surface of the magnetic powder during the compacting. Even so, the hard second insulating layer is disposed between the magnetic powders, and the insulating properties of the magnetic powder can be ensured.

  Third, even when a stress higher than the above-described stress is applied and the hard second insulating layer is broken, the broken pieces of the second insulating layer are dispersed between the magnetic powders. The components of the soft insulating layer (the first insulating layer of the first dust core powder and the soft insulating layer of the second dust core powder) flow so as to fill the space between the dispersed pieces. Further, since further flow is suppressed, direct contact between the magnetic powders can be avoided and insulation between the magnetic powders can be ensured.

  Further, even when either the first insulating layer of the first powder magnetic core powder or the soft insulating layer of the second powder magnetic core powder is altered during annealing after molding, If insulation of the insulating layer can be ensured without alteration, insulation between the magnetic powders can be ensured.

  As described above, the magnetic powder according to the present invention includes both the first powder magnetic core powder and the second powder magnetic core powder, thereby including only the second powder magnetic core powder. Compared to the above, it is possible to ensure higher insulation in the dust core.

  Furthermore, when only the powder for the first powder magnetic core is used, since the insulating layer has at least a two-layer structure, the space factor of the magnetic powder of the molded powder magnetic core decreases, and the magnetic core When used, there is concern about a decrease in magnetic flux density. However, as in the present invention, by including the second powder magnetic core powder in the magnetic powder, a decrease in the space factor of the magnetic powder is suppressed, and the magnetic flux density is reduced. Can be suppressed.

  In addition, the magnetic powder as used in the field of this invention means the aggregate | assembly of the powder containing the powder for powder magnetic cores. Moreover, the insulating layer as used in the field of this invention is a layer for ensuring the electrical insulation between the magnetic powder (particle | grains) after shaping | molding. In addition, the hardness of the second insulating layer referred to in the present invention is higher than the hardness of the first insulating layer. The material constituting the second insulating layer is relatively less than the material constituting the first insulating layer. By meaning that it is hard and having such a relationship, the first insulating layer is more easily deformed by an external force than the second insulating layer.

  Moreover, the magnetic powder as used in the field of this invention means the powder which has magnetic permeability, and a soft magnetic metal powder is preferable, for example, iron, cobalt, nickel etc. can be mentioned. More preferable materials are iron-based materials such as iron (pure iron), iron-silicon alloys, iron-nitrogen alloys, iron-nickel alloys, iron-carbon alloys, iron-boron alloys, iron. -Cobalt-type alloy, iron-phosphorus-type alloy, iron-nickel-cobalt-type alloy, or iron-aluminum-silicon-type alloy etc. are mentioned. In addition, the magnetic powder can include water atomized powder, gas atomized powder, pulverized powder, etc. When considering the suppression of the breakdown of the insulating layer during pressure molding, a powder with less irregularities on the surface of the powder is selected. More preferably.

  The weight ratio of the first powder magnetic core powder to the second powder magnetic core powder contained in the powder magnetic core powder according to the present invention is in the range of 3: 7 to 9: 1. More preferably. By setting the weight ratio in the above range, the molded dust core has a higher specific resistance and further suppresses a decrease in magnetic flux density than a dust core molded in another range. Both can be achieved.

  In the magnetic powder according to the present invention, both the hardness of the first insulating layer and the hardness of the soft insulating layer are lower than the hardness of the magnetic powder of the first and second powder magnetic core powders. More preferred. According to the present invention, the hardness of the first insulating layer is lower than the hardness of the magnetic powder of the first and second powder magnetic core powders, so that the first insulating layer follows the deformation of the magnetic powder during molding. One insulating layer and the soft insulating layer can be deformed, and the second insulating layer is not easily destroyed. As a result, insulation between the magnetic powders can be ensured. Note that the hardness of the first insulating layer and the soft insulating layer referred to in the present invention is lower than the hardness of the magnetic powder means that the material constituting the first insulating layer and the soft insulating layer is the magnetic powder. It means that it is relatively soft compared to the constituent material.

  Moreover, as for the magnetic powder which concerns on this invention, it is more preferable that the hardness of said 2nd insulating layer is higher than the hardness of the magnetic powder of said 1st and 2nd powder magnetic core powder. According to the present invention, since the second insulating layer of the first powder magnetic core is made harder than the magnetic powder, even if the second insulating layer is destroyed at the time of pressure molding, the fragments are on the surface of the magnetic powder. The flow of the first insulating layer of the first powder magnetic core powder and the soft insulating layer of the second powder magnetic core powder can be suppressed by the effect of throwing the debris. As a result, insulation between the magnetic powders can be ensured.

  In the magnetic powder according to the present invention, it is more preferable that the first insulating layer and the soft insulating layer are made of a polymer resin, and the second insulating layer is made of an oxide such as a metal oxide. According to the present invention, by forming the second insulating layer as an oxide, the oxide does not change even when the polymer resin is altered during annealing after pressure molding. Can be ensured stably.

  For example, examples of the polymer resin include a polymer resin such as a polyimide resin, a polyamide resin, an aramid resin, and a silicone resin, and examples of the oxide include a ceramic material such as silica, alumina, or zirconia. It is preferable that the oxide be heat resistant. In addition, the materials constituting the first powder magnetic core powder and the second powder magnetic core powder may be different materials, but when a stable characteristic or the like is required by the powder magnetic core, More preferably, the same material is used.

  Furthermore, the layer thickness of the first insulating layer and the soft insulating layer is preferably 10 nm to 10 μm, more preferably 10 nm to 2 μm. According to the present invention, by providing the first insulating layer and the soft insulating layer in the range of the layer thickness, it is possible to more suitably ensure the insulation between the magnetic powders. That is, when the thickness of the first insulating layer is thinner than 10 nm, the first insulating layer and the soft insulating layer are unlikely to function as a buffer material during pressure molding, and sufficient insulation between the magnetic powders is ensured. It is difficult. Furthermore, when it is thicker than 2 μm, the functions of the first insulating layer and the soft insulating layer cannot be expected any more, and when it is thicker than 10 μm, when the dust core after molding is annealed, The shrinkage amount of the first insulating layer increases, and it becomes difficult to ensure the dimensional accuracy of the dust core.

As a more preferred embodiment, in the magnetic powder according to the present invention, the first insulating layer and the soft insulating layer are made of silicone resin, and the second insulating layer is made of silica. According to the present invention, the first insulating layer is made of silicone resin, and the second insulating layer is made of silica (SiO ₂ ), so that the silica and the silicone resin contain the same Si element as a main component. Therefore, familiarity is good and the anti-aggregation effect of the silicone resin at high temperatures can be enhanced. In addition, the material cost is relatively low, and the manufacturing cost can be reduced as much as possible when mass-producing the dust core.

  The average particle size of the magnetic powder is preferably 5 μm to 500 μm, more preferably 20 μm to 450 μm. By using the magnetic powder in the above range, a dust core having excellent insulating properties can be obtained. That is, when the average particle size is smaller than 20 μm, it may be difficult to coat the first insulating layer and the second insulating layer with a uniform thickness on the surface of the powder, and the average particle size is smaller than 5 μm. If it is small, in addition to the above reasons, it is difficult to produce the magnetic powder itself, which may increase the production cost. On the other hand, when it is larger than 450 μm, the ratio of the insulating material constituting the insulating layer is reduced, and it is difficult to obtain desired magnetic characteristics and insulation (specific resistance). In addition to the above reasons, it becomes difficult to compact the powder.

  As a method for coating the insulating layer on the magnetic powder of the first and second powder magnetic core powders described above, a liquid phase method (sol-gel method), a chemical vapor deposition method (CVD), a physical vapor deposition method. The method (PVD), CCVD (combustion chemical vapor deposition), anodizing treatment, etc. can be mentioned, and the particular method is limited as long as the method can coat the insulating layer uniformly and uniformly. It is not something.

  In addition, when the surface of the magnetic powder is coated with a silicone resin as the first insulating layer and the soft insulating layer, the surface of the magnetic powder is coated with a silicone resin, and when the second insulating layer is coated with silica. Is a method in which the powder after application of the silicone resin is put into an atmosphere in which LPG gas and a silane-based gas containing a silane compound are burned, and silica is deposited on the surface of the powder (combustion chemical vapor deposition (CCVD)). It is more preferable to coat by the method)).

  Moreover, as another aspect, the magnetic powder according to the present invention is a magnetic powder containing a powder for a powder magnetic core in which an insulating layer is formed on the surface of the magnetic powder, and the surface of the magnetic powder is used as the insulating layer. At least a first insulating layer and a second insulating layer are sequentially formed in the thickness direction of the insulating layer, and the hardness of the second insulating layer is lower than the hardness of the first insulating layer. A powder for powder magnetic core, and a second powder for powder magnetic core in which a hard insulating layer higher than the hardness of the second insulating layer of the powder for first powder magnetic core is formed as the insulating layer. The powder for powder magnetic core is at least included.

  According to the magnetic powder of the present invention, when the first and second powder magnetic core powders are in contact with each other at the time of pressure molding, the contact portion is soft insulation of the first powder magnetic core powder. A first insulating layer, which is a hard insulating layer of the first powder magnetic core powder, and a hard insulating layer of the second powder magnetic core powder are arranged so as to sandwich the second insulating layer which is a layer. Will be.

  And at the time of pressure molding, the second insulating layer, which is a soft insulating layer, functions as a buffer material, suppressing deformation and destruction of the hard first insulating layer and the hard insulating layer, and ensuring the insulation between the magnetic powders can do. In addition, even when the second insulating layer of the first powder for powder magnetic core is altered during annealing after molding, either the first insulating layer or the hard insulating layer is insulated without alteration. If the property can be secured, the insulation between the magnetic powders can be secured. Furthermore, when only the powder for the first powder magnetic core is used, since the insulating layer has at least a two-layer structure, the space factor of the magnetic powder of the molded powder magnetic core decreases, and the magnetic core When used, there is concern about a decrease in magnetic flux density. However, as in the present invention, by including the second powder magnetic core powder in the magnetic powder, a decrease in the space factor of the magnetic powder is suppressed, and the magnetic flux density is reduced. Can be suppressed.

  In the magnetic powder according to the present invention, it is more preferable that the hardness of the first insulating layer and the hardness of the hard insulating layer are higher than the hardness of the magnetic powder of the first and second dust core powders. The hardness of the second insulating layer is more preferably lower than the hardness of the magnetic powder of the first and second powders for dust core. Further, the first insulating layer and the hard insulating layer are made of an oxide, the second insulating layer is made of a polymer resin, more preferably, the first insulating layer and the soft insulating layer are made of silica, More preferably, the two insulating layers are made of silicone.

  In addition, the magnetic powder containing the powder for the powder magnetic core described above is filled in a molding die, press-molded by a warm mold lubrication molding method, dried and cooled, and finally subjected to strain removal heat treatment by annealing. Thus, a dust core having a high magnetic flux density and ensuring insulation can be obtained. Further, by pressure molding the powder magnetic core by the warm mold lubrication molding method, the powder magnetic core can be molded at a higher pressure than conventional room temperature molding.

  The dust core excellent in insulation and magnetic properties is suitable for a stator or rotor constituting a driving motor for a hybrid vehicle or an electric vehicle, and a reactor core (reactor core) constituting a power converter.

  As can be understood from the above description, according to the present invention, the insulating layer formed on the surface of the powder for compacting can be prevented from being destroyed during pressure molding, and the insulating layer is aggregated during annealing. Therefore, a dust core having high insulation can be obtained. Furthermore, a decrease in the magnetic flux density of the molded dust core can be suppressed.

  Below, with reference to drawings, it explains based on a first embodiment of magnetic powder concerning the present invention.

  FIG. 1: has shown the schematic diagram which showed the magnetic powder which concerns on 1st embodiment, (a) is a schematic diagram of the powder 10A for the 1st powder magnetic core contained in magnetic powder, (b) These are the schematic diagrams of 2nd powder 10B for powder magnetic cores contained in the said magnetic powder.

  2 is a diagram for explaining the behavior of the insulating layer when the dust core is dust-molded with the magnetic powder 1 including the first and second dust core powders 10A and 10B shown in FIG. (A) is the schematic diagram which showed the magnetic powder 1 before compacting, (b) is the schematic diagram for demonstrating the state of the magnetic powder before compacting at the time of throwing into a shaping | molding die. (C), (d) is a schematic diagram for demonstrating the state (powder magnetic core 100) of the magnetic powder 1 after a shaping | molding.

  The magnetic powder according to the present embodiment includes at least the first and second powders 10A and 10B for the dust core shown in FIGS. 1 (a) and 1 (b). Specifically, as shown in FIG. 1A, the first powder magnetic core powder 10 </ b> A included in the magnetic powder according to the present embodiment has at least an insulating layer 12 </ b> A coated on the surface of the magnetic powder 11. It is a powder. More specifically, as the insulating layer 12A, at least a first insulating layer 12a and a second insulating layer 12b are sequentially formed from the surface 11a of the magnetic powder 11 in the layer thickness direction of the insulating layer 12A. The second insulating layer 12b is a layer having a higher hardness than the second insulating layer 12a.

  Further, as shown in FIG. 1B, the second powder 10B for powder magnetic core contained in the magnetic powder according to the present embodiment is a powder in which at least the soft insulating layer 12c is coated on the surface of the magnetic powder 11. is there. The soft insulating layer 12c is an insulating layer having a hardness lower than that of the second insulating layer 12b of the first powder 12A for dust core.

  The magnetic powder 11 of the first and second powder magnetic core powders 10A and 10B is a powder made of pure iron manufactured by gas atomization, and is a soft magnetic metal powder having an average particle diameter of 20 to 450 μm. More preferred. Further, the first insulating layer 12a and the soft insulating layer 12c are not particularly limited as long as they are made of a material having electrical insulating properties, but the silicone formed by applying a silicone resin to the surface of the magnetic powder 11 is used. More preferably, the insulating layer is made of resin. Furthermore, the second insulating layer 12b is more preferably an insulating layer made of silica coated on the surface of the first insulating layer 12a by LPG gas and silane gas by a combustion vapor chemical vapor deposition method.

  By producing the first and second powders 10A and 10B for the powder magnetic core with the material, the second insulating layer 12b has a higher hardness than the first insulating layer 12a and the soft insulating layer 12c. And the hardness of the first insulating layer 12 a satisfies the relationship lower than the hardness of the magnetic powder 11, and the hardness of the second insulating layer 12 b satisfies the relationship higher than the hardness of the magnetic powder 11. By satisfying such a relationship at the same time, the dust core formed by using the magnetic powder containing the first and second dust core powders 10A and 10B has a magnetic characteristic as compared with the conventional one. It can be improved further.

  Furthermore, in the magnetic powder according to this embodiment, the weight ratio of the first powder magnetic core powder 10A and the second powder magnetic core powder 10B satisfies the range of 3: 7 to 9: 1. Thus, it is more preferable that the first and second dust cores 10A and 10B are mixed. This has been clarified by experiments and the like described later by the inventors, and the dust core molded in this range has a higher ratio than the dust core molded in another range. It is possible to achieve both ensuring of resistance and further suppression of decrease in magnetic flux density.

  Below, the manufacturing method of the dust core using the powder 10 for dust cores is demonstrated easily. Specifically, first, as shown in FIG. 2A, a first insulating layer (silicone resin layer) 12a and a second insulating layer (silica layer) 12b are sequentially formed from the surface of the magnetic powder 11. One powder 10A for a powder magnetic core and a second powder 10B for a powder magnetic core on which a soft insulating layer (silicone resin layer) 12c is formed are prepared.

  Then, the first and second powder magnetic core powders 10A and 10B are mixed to obtain the magnetic powder 1. At this time, as described above, the first powder magnetic core powder 10A and the second powder magnetic core powder 10B have a weight ratio satisfying the range of 3: 7 to 9: 1. And the second dust core powders 10A and 10B are uniformly mixed.

  Next, the magnetic powder 1 including the mixed first and second powders 10A and 10B for the dust core is placed in the molding (not shown). At this time, as shown in FIG. 2B, the first and second powder powders 10A and 10B are in contact with each other, but are not joined. Thereafter, the magnetic powder 1 including the first and second powders 10A and 10B for the dust core in the molding is pressurized to mold the dust core, and after molding, annealed in a non-oxidizing atmosphere furnace to remove strain. Heat treatment is performed.

  At this time, as shown in FIG. 2C, even if stress due to molding acts on the second insulating layer 12b which is harder than the first insulating layer 12a and the soft insulating layer 12c, The soft first insulating layer 12a and the soft insulating layer 12c between the layer 12b and the magnetic powder 11 function as a buffer against the stress, and suppress deformation and destruction of the hard second insulating layer 12b.

  Moreover, as shown in FIG. 2D, the relatively soft first insulating layer 12a and soft insulating layer 12c are swept away from the surface of the magnetic powder 11, and the components of the first insulating layer 12a are predetermined between the powders. The hard second insulating layer 12b is disposed between the magnetic powders 11 even when the agglomerated at the locations.

  Further, even when a higher stress acts to follow the plastic deformation of the magnetic powder 11 and the hard second insulating layer 12b is broken, the broken pieces 13 of the broken second insulating layer 12b are magnetic. Dispersed between the powders, the dispersed pieces 13 pierce the surface of the magnetic powder 11 and act as anchors. Thereby, a part of soft 1st insulating layer 12a and the soft insulating layer 12c flows so that the space between fragments may be filled, and the flow beyond it is suppressed. As a result, direct contact between the magnetic powders 11 can be avoided, and insulation between the magnetic powders can be ensured.

  Further, the magnetic powder includes the first powder magnetic core powder 10A and the second powder magnetic core powder 10B, so that the ratio of the magnetic material and the insulating material of the powder magnetic core to be molded can be appropriately adjusted. it can. As a result, a dust core having a desired specific resistance and magnetic flux density can be easily manufactured.

  FIG. 3: has shown the schematic diagram which showed the magnetic powder which concerns on 2nd embodiment, (a) is a schematic diagram of the powder for 1st powder magnetic cores contained in magnetic powder, (b) is FIG. 5 is a schematic view of a second powder magnetic core powder contained in the magnetic powder.

  As shown in FIG. 3, the magnetic powder according to the present embodiment is different from the first embodiment (shown in FIGS. 2A and 2B) in the first and second dust core powders 10C and 10D. Is included at least. Specifically, as shown in FIG. 3A, the first powder magnetic core powder 10 </ b> C included in the magnetic powder according to the present embodiment has at least an insulating layer 12 </ b> B coated on the surface of the magnetic powder 11. It is a powder. More specifically, as the insulating layer 12B, at least a first insulating layer 12d and a second insulating layer 12e are sequentially formed from the surface 11a of the magnetic powder 11 in the layer thickness direction of the insulating layer 12B. Further, the hardness of the second insulating layer 12e is lower than the hardness of the first insulating layer 12d.

  Further, as shown in FIG. 3 (b), the second dust core powder 10D contained in the magnetic powder according to the present embodiment is a powder in which the surface of the magnetic powder 11 is coated with at least a hard insulating layer 12f. is there. The hard insulating layer 12f is an insulating layer that is higher in hardness than the second insulating layer 12e of the first dust core powder 10C.

  The magnetic powder 11 of the first and second powder magnetic cores 10C and 10D is preferably a powder produced by the same production method as the powder according to the first embodiment, and the average particle size is also the first implementation. More preferably, it is a soft magnetic metal powder equivalent to that according to the form. Further, the first insulating layer 12d and the hard insulating layer 12c are not particularly limited as long as they are made of a material having an electrical insulating property. However, the magnetic powder is formed by a combustion vapor chemical vapor deposition method using LPG gas and silane gas. 11 is more preferably an insulating layer made of silica coated on the surface. The second insulating layer 12e is more preferably an insulating layer made of a silicone resin formed by applying a silicone resin to the surface of the magnetic powder 11.

  By producing the first and second powders 10C and 10D for the powder magnetic core with the material, the hardness of the first insulating layer 12d and the hardness of the hard insulating layer 12f are higher than the hardness of the second insulating layer 12e. And the relationship where the hardness of the first insulating layer 12 d is higher than the hardness of the magnetic powder 11 and the hardness of the second insulating layer 12 e is lower than the hardness of the magnetic powder 11. By satisfying such a relationship at the same time, the dust core formed by using the magnetic powder containing the first and second dust core powders 10A and 10B has more magnetic properties than the conventional one. Can be improved.

  That is, by comprising in this way, when the 1st and 2nd powder magnetic core powder 10C and 10D mutually contact at the time of pressure molding, the contact part is the powder for the 1st powder magnetic core. The first insulating layer 12d, which is a hard insulating layer of the first dust core powder 10C, and the second dust core powder 10D so as to sandwich the second insulating layer 12e, which is a 10C soft insulating layer, The hard insulating layer 12f is disposed.

  In this case, the second insulating layer 12e, which is a soft insulating layer, functions as a cushioning material, and deformation and destruction of the hard first insulating layer 12d and the hard insulating layer 12f can be suppressed. Further, even when the second insulating layer 12e of the first powder for powder magnetic core 10C is altered during annealing after molding, either the first insulating layer 12d or the hard insulating layer 12f made of silica is used. One component can ensure insulation without deterioration. In this way, insulation between the magnetic powders 11 and 11 can be ensured. Furthermore, when only the first powder for powder magnetic core 10C is used, since the insulating layer 12B has at least a two-layer structure, the space factor of the magnetic powder of the molded powder magnetic core decreases, When used as a magnetic core, there is a concern about a decrease in magnetic flux density. However, as in this embodiment, the inclusion of the second powder for magnetic powder core 10D in the magnetic powder increases the space factor of the magnetic powders 11 and 11. The decrease is suppressed, and the decrease in magnetic flux density can be suppressed.

  As this example, the magnetic powder according to the first embodiment was manufactured. Pure iron powder having an average particle size of 200 μm was prepared as a magnetic powder. Next, the 1st powder for powder magnetic cores was manufactured. Specifically, a silicone resin was applied to the surface of pure iron powder, and a first insulating layer made of a silicone resin having a layer thickness of 1 μm was covered. Furthermore, the surface of the first insulating layer on the magnetic powder was coated with a second insulating layer made of silica having a layer thickness of 200 nm by a combustion chemical vapor deposition method using LPG gas and a silane compound as raw materials. Further, as the second powder for powder magnetic core, a silicone resin was applied to the surface of pure iron powder, and a soft insulating layer made of a silicone resin having a layer thickness of 1 μm was coated. The first powder magnetic core powder is 50% by weight with respect to the magnetic powder, and the second powder magnetic core powder is 50% by weight with respect to the magnetic powder (the first powder magnetic core powder and the second powder These powders were mixed so that the weight ratio with the powder for powder magnetic core was 1: 1) to produce magnetic powder.

  A predetermined amount of the magnetic powder produced in this way was prepared, the magnetic powder was filled into a mold, and a molded body was obtained by a warm mold lubrication molding method. Further, the molded body was annealed at a temperature of 600 ° C. for 45 minutes to produce a test body corresponding to a dust core. The magnetic flux density was measured on the test specimen under the conditions of density and 5 kA / m. The result is shown in FIG. The density and magnetic flux density shown in FIG. 4 are normalized by the density and magnetic flux density of Comparative Example 1 described later.

[Comparative Example 1]
In the same manner as in Example 1, magnetic powder was produced. The difference from Example 1 is that magnetic powder made of only the first powder magnetic core powder (not including the second powder magnetic core powder) was produced as the magnetic powder. Then, using this magnetic powder, in the same manner as in Example 1, compacting and annealing were sequentially performed to produce a test body, and the density and magnetic flux density of the test body were measured. The result is shown in FIG.

[Result 1]
As shown in FIG. 3, the density of Example 1 was 3% higher than that of Comparative Example 1, and the magnetic flux density of Example 1 was 35% higher than that of Comparative Example 1.

[Discussion 1]
The density of Example 1 was higher than that of Comparative Example 1 because the magnetic powder contained the second powder magnetic core powder having a single insulating layer, and therefore the density of iron as a component of the magnetic powder was increased. This is thought to be due to the higher volume factor. And it is thought that the magnetic flux density of the test piece (powder magnetic core) of Example 1 is also improved compared to that of Comparative Example 1 due to the fact that the space factor of iron is increased. .

  In the same manner as in Example 1, magnetic powder was manufactured and a test specimen was manufactured. The difference from Example 1 is that, as shown in FIG. 5, the weight ratio of the first powder magnetic core powder to the second powder magnetic core powder is in the range of 3: 7 to 9: 1 ( Specifically, the ratios of the first powder magnetic core powder and the second powder magnetic core powder were 90% by weight: 10% by weight, 50% by weight: 50% by weight with respect to the magnetic powder (Example 1). And 30% by weight: 70% by weight) and mixed magnetic powder. Then, in the same manner as in Example 1, the magnetic flux density was measured, and the specific resistance of the test specimen was also measured. The result is shown in FIG. Note that the magnetic flux density and specific resistance shown in FIG. 5 are normalized by the magnetic flux density and specific resistance value of Comparative Example 2 described later.

[Comparative Example 2]
Magnetic powder was manufactured in the same manner as in Example 2. The difference from Example 2 is that magnetic powder made of only the first powder magnetic core powder (not including the second powder magnetic core powder) was manufactured as magnetic powder (corresponding to Comparative Example 1). It is. Then, using this magnetic powder, in the same manner as in Example 2, compacting and annealing were sequentially performed to produce a test body, and in the same manner as in Example 2, the magnetic flux density and specific resistance were measured. The result is shown in FIG.

[Comparative Example 3]
Magnetic powder was manufactured in the same manner as in Example 2. The difference from Example 2 is that magnetic powder made of only the second powder magnetic core powder (not including the first powder magnetic core powder) was produced as the magnetic powder. Then, using this magnetic powder, in the same manner as in Example 2, compacting and annealing were sequentially performed to produce a test body, and in the same manner as in Example 2, the magnetic flux density and specific resistance were measured. The result is shown in FIG.

[Result 2]
The magnetic flux density (◇) of Example 2 was higher than that of Comparative Example 2 (●), and the specific resistance (◇) of Example 2 was (◆) higher than that of Comparative Example 3.

[Discussion 2]
From the result 2, the magnetic flux density (◇) of Example 2 was higher than that of Comparative Example 2 (●). The magnetic powder contained the second powder magnetic core powder consisting of a single insulating layer. Therefore, it is considered that the space factor of iron which is a component of the magnetic powder is increased.

  In addition, the specific resistance (◇) of Example 2 was higher than that of Comparative Example 3 (◆) because the magnetic powder of Comparative Example 3 does not contain the first powder magnetic core powder. This is probably because the silica insulating layer could not follow the plastic deformation of the magnetic powder and was destroyed.

  As mentioned above, although embodiment of this invention has been explained in full detail using drawing, a concrete structure is not limited to this embodiment, Even if there is a design change in the range which does not deviate from the gist of the present invention. These are included in the present invention.

  For example, in this embodiment, the first insulating layer and the second insulating layer are sequentially coated on the surface of the magnetic powder, but the functions of the first insulating layer and the second insulating layer described above are ensured during molding and annealing. If necessary, a new layer may be provided between the surface of the magnetic powder and the first insulating layer, and between the first insulating layer and the second insulating layer, and the wettability between the first insulating layer and the magnetic core powder. An insulating layer for improving the above may be further provided.

The schematic diagram which showed the magnetic powder which concerns on 1st embodiment is shown, (a) is a schematic diagram of the powder for 1st powder magnetic cores contained in magnetic powder, (b) is the said magnetic powder The schematic diagram of the powder for 2nd powder magnetic cores contained in. It is a figure for demonstrating the behavior of an insulating layer when a powder magnetic core is dust-molded with the magnetic powder containing the powder for 1st and 2nd powder magnetic cores shown in FIG. 1, (a) is dust. It is the schematic diagram which showed the magnetic powder before shaping | molding, (b) is a schematic diagram for demonstrating the state of the magnetic powder before compaction shaping | molding at the time of throwing into a shaping | molding die, (c), (d) is The schematic diagram for demonstrating the state of the magnetic powder after shaping | molding. The schematic diagram which showed the magnetic powder which concerns on 2nd embodiment is shown, (a) is a schematic diagram of the powder for 1st powder magnetic cores contained in magnetic powder, (b) is the said magnetic powder. The schematic diagram of the powder for 2nd powder magnetic cores contained in. The figure which showed the density and specific resistance of the test body of Example 1 and Comparative Example 1. FIG. The figure which showed the magnetic flux density and specific resistance of the test body of Example 2, the comparative example 2, and the comparative example 3. FIG.

Explanation of symbols

  1: magnetic powder, 10A, 10C: first powder for powder magnetic core, 10B, 10D: second magnetic powder, 11: magnetic powder, 12A, 12B: insulating layer, 12a, 12c: first insulating layer, 12b , 12d: second insulating layer, 12c: soft insulating layer, 12f: hard insulating layer, 100: dust core

Claims (8)

A magnetic powder comprising a powder for a powder magnetic core having an insulating layer formed on the surface of the magnetic powder,
As the insulating layer, at least a first insulating layer and a second insulating layer are sequentially formed in the thickness direction of the insulating layer from the surface of the magnetic powder, and the hardness of the second insulating layer is the first insulating layer. A first powder for powder magnetic core higher than the hardness of the insulating layer;
As the insulating layer, a second powder magnetic core powder in which a soft insulating layer lower than the hardness of the second insulating layer of the first powder magnetic core powder is formed,
At least as the powder for powder magnetic core.   2. The magnetic powder according to claim 1, wherein a weight ratio of the first powder magnetic core powder to the second powder magnetic core powder is in the range of 3: 7 to 9: 1.   The magnetism according to claim 1 or 2, wherein the hardness of the first insulating layer and the hardness of the soft insulating layer are lower than the hardness of the magnetic powder of the first and second powder magnetic core powders. powder.   The magnetic powder according to any one of claims 1 to 3, wherein the hardness of the second insulating layer is higher than the hardness of the magnetic powder of the first and second powder magnetic core powders.   The magnetic powder according to claim 1, wherein the first insulating layer and the soft insulating layer are made of a polymer resin, and the second insulating layer is made of an oxide.   The magnetic powder according to claim 1, wherein the first insulating layer and the soft insulating layer are made of a silicone resin, and the second insulating layer is made of silica.   The powder magnetic core shape | molded with the magnetic powder in any one of the said Claims 1-6. A magnetic powder comprising a powder for a powder magnetic core having an insulating layer formed on the surface of the magnetic powder,
As the insulating layer, at least a first insulating layer and a second insulating layer are sequentially formed in the thickness direction of the insulating layer from the surface of the magnetic powder, and the hardness of the second insulating layer is the first insulating layer. A first dust core powder lower than the hardness of the insulating layer;
As the insulating layer, a second powder magnetic core powder in which a hard insulating layer higher than the hardness of the second insulating layer of the first powder magnetic core powder is formed,
At least as the powder for powder magnetic core.

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