JP2012104725A - Dust core and coil component using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the strength of a dust core while avoiding degradation in permeability of the whole dust core.SOLUTION: The dust core 12 is configured of a pair of outer magnetic legs 7 facing each other formed by pressure molding magnetic powder, a middle magnetic leg 8 located between the outer magnetic legs 7, and a back magnetic leg 9 coupling the middle magnetic leg 8 and the outer magnetic legs 7. An impregnated magnetic material layer 10 formed by impregnating with resin is provided on the entire surface of the dust core 12, and a non-impregnated magnetic material layer 11 is provided on the inner surface of the impregnated magnetic material layer 10.

Description

  The present invention relates to a dust core used for a magnetic component in various electronic devices and a coil component using the same.

  Hereinafter, a conventional dust core will be described with reference to the drawings. FIG. 8 is a cross-sectional view of a coil component 2 using a conventional powder magnetic core 1, and the powder magnetic core 1 has an outer magnetic leg 3, a middle magnetic leg 4, and a back magnetic leg 5 connecting them. The dust cores 1 are opposed to each other, and the winding part 6 is disposed around the middle magnetic leg 4 to constitute the coil component 2.

  And this powder magnetic core 1 forms the insulating film of an inorganic substance on the surface of a magnetic body by performing high temperature processing after pressure-molding the mixture of a powdery magnetic body and organic substance, and there is mechanical strength after high temperature processing there The strength of the molded body made of a magnetic material is raised to a sufficient level by performing a resin impregnation treatment on the molded body in a low state.

  For example, Patent Document 1 is known as prior art document information relating to the invention of this application.

JP 2009-218268 A

  However, as shown in FIG. 8, the conventional powder magnetic core 1 impregnates all parts of the middle magnetic leg 4, the outer magnetic leg 3 and the back magnetic leg 5 with a non-impregnated region (not shown). Was not allowed to exist. As a result, although the mechanical strength of the dust core 1 is expected to be improved, the magnetic permeability is lowered and the choke coil (not shown) or transformer (not shown) to which the dust core 1 is applied is also introduced. There existed a subject that it might become a factor which reduces a characteristic.

  This is because, in general, a non-impregnated powder magnetic core changes the distance between individual magnetic powders by applying resin impregnation, and magnetic properties of individual magnetic powders by applying stress to each magnetic powder. It is said that the change will occur.

  Then, an object of this invention is to provide the powder magnetic core which suppressed deterioration of the magnetic permeability, and a coil component using the same.

  And in order to achieve this object, it consists of a magnetic body formed by pressure-molding magnetic powder, a pair of outer magnetic legs, a middle magnetic leg located between the outer magnetic legs, the middle magnetic leg, A back magnetic leg for connecting the external magnetic leg, the outer magnetic leg, the middle magnetic leg, and the back magnetic leg, and an impregnated magnetic layer formed on each surface; The formed non-impregnated magnetic layer is provided.

  According to the present invention, the strength of the dust core is increased and the reliability of the dust core is improved by forming a non-impregnated layer for avoiding the deterioration of the magnetic permeability of the whole dust core. It is possible to maintain a good magnetic characteristic.

The perspective view of the powder magnetic core in the 1st Embodiment of this invention 1st sectional drawing of the powder magnetic core in the 1st Embodiment of this invention Manufacturing process diagram of dust core in the first embodiment of the present invention 2nd sectional drawing of the powder magnetic core in the 1st Embodiment of this invention 3rd sectional drawing of the powder magnetic core in the 1st Embodiment of this invention Sectional drawing of the coil components in the 1st Embodiment of this invention 4th sectional view of a dust core in a 1st embodiment of the present invention. Sectional view of conventional coil components

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a perspective view of a dust core according to the first embodiment of the present invention, and FIG. 2 is a sectional view thereof. As shown in the perspective view of FIG. 1, a pair of outer magnetic legs 7, a middle magnetic leg 8 positioned between the outer magnetic legs 7, and the middle magnetic leg 8 and both outer magnetic legs 7 are connected. It is set as the structure of the external appearance provided with the back magnetic leg 9 to do. Here, as shown in the sectional view of FIG. 2, the outer magnetic leg 7, the middle magnetic leg 8, and the back magnetic leg 9 have a surface layer of less than half the thickness of the outer magnetic leg 7 and the back magnetic leg 8. An impregnated magnetic layer 10 formed as a thin layer impregnated with an epoxy resin, and a non-impregnated magnetic layer 11 formed on the inner surface side of the impregnated magnetic layer 10 as a surface layer and not impregnated with an epoxy resin. Provided.

  According to this configuration, the impregnated magnetic layer 10 having a relatively low magnetic permeability is formed as a high-strength region in a very thin region of the surface of the dust core 12, while the non-impregnated magnetic material having a relatively high magnetic permeability is formed. By forming the layer 11 in most regions other than the surface of the dust core 12, high strength can be obtained while suppressing deterioration of the magnetic permeability of the dust core 12 as a whole, and high reliability against impact and the like. It is possible to obtain sex.

  Here, although the permeability of the impregnated magnetic layer 10 is relatively low and the permeability of the non-impregnated magnetic layer 11 is relatively high is included, In this manufacturing process to be described, before and after curing of the impregnating resin in the step of allowing a resin such as an epoxy resin to enter as an impregnating resin between individual metal magnetic powders (not shown here) and further curing the impregnating resin In general, it is caused by a change in stress or accumulation of small changes in the positional relationship between individual metal magnetic powders (not shown here).

  And this powder magnetic core 12 is manufactured as shown, for example in the manufacturing-process figure of the powder magnetic core of FIG.

  First, there is a kneading and dispersing step 13 as a first step, in which a metal magnetic powder 14 composed of grains of various sizes and a resin 15 containing a solvent are mixed to produce a clay-like mixture 16.

  Next, there is a granulation step 17 as a second step. The mixture 16 produced in the kneading and dispersing step 13 is dried after being made into a predetermined lump such as a columnar solid 18, and is initially included in the mixture 16. The solvent which has been removed is removed, and then the columnar solid 18 is pulverized. As a result, a solid piece 19 after pulverization is obtained. This solid piece 19 is formed as an aggregate of a plurality of powders of various sizes, each having a resin film 20 having a substantially constant thickness around the surface of the metal magnetic powder 14. ing. And the granulated powder 21 which consists of the particle size limited in the range of arbitrary magnitude | sizes by classifying the solid piece 19 is obtained.

  In addition, although the method of obtaining the granulated powder 21 from the mixture 16 produced | generated at the 1st process is shown as an example here as a 2nd process, this invention is not limited to this, Metal magnetic powder As a form in which the resin 15 containing a solvent is sprayed on 14 and then applied, the kneading and dispersing step 13 as the first step and the granulating step 17 as the second step are performed simultaneously. I do not care.

  Next, there is a pressing step 22 as a third step, and the granulated powder 21 generated in the granulating step 17 is pressure-formed by a molding die (not shown) to form a molded body having a desired shape. In the pressing step 22, pressure is applied in the directions of arrows Y0 and Y1 when, for example, the split magnetic core 23 is formed as a compact. Then, the thick portion 24 and the connecting portion 26, which are large portions when viewed from the directions of the arrows Y0 and Y1, are pressed with a high pressure, and the thin portion 25, which is also a small area, is pressed with a low pressure. . Thus, the thick portion 24 and the connecting portion 26 are the granulated powder 21, the metal magnetic powder 14 or the high density portion of the magnetic material, and the thin portion 25 is the granulated powder 21, the metal magnetic powder 14 or the low density portion of the magnetic material. The thin portion 25 has a lower density than the thick portion 24 and the connecting portion 26.

  Here, the pressure molding of the thick portion 24 and the connecting portion 26 under a high pressure and the thin portion 25 under a low pressure is for considering the life of the molding die, By controlling the density of the magnetic material, the permeability is controlled and the degree of penetration of the impregnating resin is adjusted. At this time, the granulated powder 21 is pressed and densely packed in the thick portion 24 and the connecting portion 26 of the divided magnetic core 23 in a high density state, and the resin film 20a is greatly compressed and the metal magnetic powder is compressed. 14a is densely arranged and close to each other. On the other hand, in the thin portion 25 of the split magnetic core 23 that is molded under the condition that the pressure is lower than that of the thick portion 24 and the connecting portion 26 of the split magnetic core 23, the resin film 20b is applied. The degree of compression is smaller than that of the thick portion 24 and the connecting portion 26, and the metal magnetic powders 14b are discretely arranged in a sparse state.

  Here, although the shape of the split magnetic core 23 is described as an E type, the present invention is not limited to this, and the application of this process is not limited to this shape.

  Next, there is an annealing heat treatment step 27 as a fourth step, in which the formed body formed in the pressing step 22 is heat treated at a high temperature. By this heat treatment, the resin films 20a and 20b in the thick portion 24, the thin portion 25 and the connecting portion 26 of the divided magnetic core 23 are removed, and the metal magnetic powders 14a and 14b are separated from the individual metal magnetic powders 14a and 14b. Eddy currents generated on the surfaces of the metal magnetic powders 14a and 14b when they are mechanically coupled at a non-contact position by an inorganic substance (not shown) generated by annealing heat treatment that is positioned between the metal magnetic powders 14a and 14b. The positional relationship to reduce eddy current loss due to is maintained. At this time, the shape of the thick portion 24, the thin portion 25, and the connecting portion 26 of the split magnetic core 23, which is a molded body, is maintained, but the mechanical strength is low. Further, in this annealing heat treatment step 27, the hysteresis loss is simultaneously reduced by removing the stress of the metal magnetic powders 14a and 14b that have been stressed by the pressure forming in the pressing step 22.

  Next, there is an impregnation step 28 which is a fifth step. In the molded body after the annealing heat treatment in the annealing heat treatment step 27, the impregnation resin is injected into the split magnetic core 23 having the portions where the resin films 20a and 20b are removed. I do. In the pressing step 22, which is the third step described above, the thick portion 24 and the connecting portion 26 are formed at a high pressure, and the thin portion 25 is formed at a low pressure. There is a difference between the degree of mechanical coupling between the metal magnetic powders 14a of the thick part 24 and the connecting part 26 and the degree of mechanical coupling between the metal magnetic powders 14b of the thin part 25 under molding conditions lower in pressure. At the same time, there is a difference in each density. Therefore, even in the divided magnetic core 23 which is the same molded body, the mechanical strength and the density of the magnetic body are different depending on the portion there. On the other hand, in the impregnation step 28, the individual metal magnetic powders 14a of the split magnetic core 23, which is a molded body in which the resin films 20a and 20b are removed by temporarily performing the heat treatment in the annealing heat treatment step 27 to reduce the bonding force, Impregnation resin is impregnated and injected into the spaces around each of 14b, and then the impregnation resin is cured, and the mechanical strength of the molded body is improved by the bonding strength of the impregnation resin after curing.

  Here, since the bond strength after curing of the impregnated resin is very large compared to the bond strength obtained by pressing at the time of molding in the pressing step 22 which is the third step, the impregnated resin after curing is The bonding strength of the material becomes dominant also in the mechanical strength of the molded body. The thickness of the impregnated resin after hardening is compared with the thin portion 25 or the connecting portion 26 where the density of the metal magnetic powder 14a is high, and the thin portion 25 where the density of the metal magnetic powder 14b is low. 25 impregnates more impregnated resin than the thick portion 24 and the connecting portion 26, and the thin portion 25 is made higher than the thick portion 24 and the connecting portion 26 with respect to the strength per unit volume after curing. It will be. In addition, when the impregnating resin is injected into the divided magnetic core 23 after the annealing heat treatment, the amount and the intrusion region of the impregnating resin can be controlled by adjusting the pressure and time during the impregnation. Thus, even in the thick portion 24, the impregnating resin is increased to increase the strength, but the relatively low permeability region is reduced, and the impregnating resin is decreased to reduce the strength of the relative permeability. It is also possible to form the high area within the same site.

  After that, there will be a polishing step 29 for refining the dimensions of the split magnetic core 23 and an assembly step 30 for assembling them.

  As described above, by changing the molding density of each part in the pressing step 22, it is possible to give a difference in magnetic permeability between the individual parts of the split magnetic core 23. Also, in the impregnation step 28, the permeability of the impregnated resin can be adjusted in accordance with the magnetic body density, so that the magnetic permeability in each part of the divided magnetic core 23 can be adjusted. That is, regardless of the outer magnetic leg 7, the middle magnetic leg 8 or the back magnetic leg 9 shown in FIG. 2, the density of the magnetic material is reduced to increase the thickness of the impregnating resin, and the magnetic permeability of the part is reduced. On the contrary, it is possible to increase the magnetic material density and reduce the thickness of the impregnated resin, thereby increasing the magnetic permeability of the portion.

  In the above example, as shown in the sectional view of FIG. 2, the outer magnetic leg 7, the middle magnetic leg 8, and the back magnetic leg 9 are impregnated with layers impregnated with epoxy resin as the respective surface layers. It is assumed that a magnetic layer 10 and a non-impregnated magnetic layer 11 formed on the inner surface side from the impregnated magnetic layer 10 which is a surface layer are provided. On the other hand, as shown in the cross-sectional view of FIG. 4, the outer magnetic leg 7, the middle magnetic leg 8, and the back magnetic leg 9 have a high impregnation degree formed by layers impregnated with epoxy resin as the respective surface layers. A magnetic layer 31 and a first low impregnation degree magnetism formed at a first impregnation resin density smaller than the impregnation resin density in the high impregnation degree magnetic substance layer 31 on the inner surface side from the high impregnation degree magnetic substance layer 31 as a surface layer. The body layer 32 and the second low-impregnation degree magnetic substance layer 33 formed at the inner surface side of the first low-impregnation degree magnetic substance layer 32 with the second impregnation resin density smaller than the first impregnation resin density are provided. It is said.

  As a result, although the resin impregnation density is the boundary between layers, and the boundary between the layers with different mechanical strength tends to concentrate stress due to some external impact, etc., the resin impregnation step by step Since the stress is dispersed by using a plurality of layers whose density is changed, the mechanical strength can be stabilized.

  In the drawing, the high impregnation degree magnetic substance layer 31, the first low impregnation degree magnetic substance layer 32, and the second low impregnation degree magnetic substance layer 33 are shown only in the middle magnetic leg 8, but of course, they are described above. As described above, the present invention may be applied to the outer magnetic leg 7 and the back magnetic leg 9 as well.

  According to this configuration, the high-impregnation magnetic layer 31 having a relatively low magnetic permeability is formed as a high-strength region in a very thin region on the surface of the dust core 12, while the first having a relatively high magnetic permeability. By forming the second low-impregnation magnetic layers 32 and 33 in most of the regions other than the surface of the dust core 12, the deterioration of the magnetic permeability of the dust core 12 as a whole is suppressed and high strength is obtained. It is possible to obtain high reliability against impact and the like. This is because by reducing the density of the impregnating resin, the generation of stress and the like is suppressed as compared with the portion of the high impregnating resin density, so the magnetic permeability is increased, and the overall density of the impregnating resin is substantially uniform. Compared to the case, since a region having a low magnetic resistance can be formed, deterioration of the magnetic permeability of the entire dust core 12 can be suppressed.

  Further, here, as the high impregnation degree magnetic body layer 31, the first low impregnation degree magnetic substance layer 32, and the second low impregnation degree magnetic substance layer 33, those in which the respective impregnation degrees change discontinuously are shown as examples. However, it is more desirable that the change depending on the position of the impregnation degree is continuous. For example, the first low impregnation degree magnetic layer 32 is in a state in which the impregnation degree is gradually decreased, and the second low impregnation degree magnetic substance layer 33 is. May be in a state very close to the non-impregnated state.In this case, a discontinuous point of mechanical strength, which is also a discontinuity point of the impregnation degree, is provided by providing a layer in which the impregnation degree gradually decreases to make the change continuous. It can be removed and mechanically stable characteristics can be obtained.

  Here, the high impregnation degree magnetic substance layer 31 means that the impregnated resin covers the periphery of individual magnetic substance powder (not shown) constituting the dust core 12, and then the individual magnetic substance powder (FIG. The high-impregnation magnetic layer 31 may have a high mechanical strength while the magnetic properties of the individual magnetic body (not shown) are high. It will deteriorate compared to the case where it is not in the surroundings. Further, the first low impregnation degree magnetic substance layer 32 is made up of individual magnetic substance powder (not shown), although the impregnated resin covers the periphery of individual magnetic substance powder (not shown) constituting the dust core 12. The first low-impregnation magnetic layer 32 is lower than the high-impregnation magnetic layer 31 but has a relatively high mechanical strength. However, although the degree of deterioration of the magnetic characteristics is smaller than that of the high impregnation degree magnetic layer 31, it is deteriorated as compared with the case where the resin is not present around the individual magnetic bodies (not shown). The second low impregnation degree magnetic layer 33 is in a state in which the amount of resin impregnated further from the first low impregnation degree magnetic substance layer 32 is reduced, and the impregnated resin constitutes the dust core 12. The magnetic material powder (not shown) may be hardened in a state of partially covering the periphery, and although the mechanical strength is low, the magnetic properties are inferior to those in the case where there is no resin around. It will not be. As described above, the adjustment of these states may be performed according to the density at the time of molding the magnetic material, the pressure at the time of impregnating the resin, and the time.

  Up to now, as shown in FIG. 2, the outer magnetic leg 7, the middle magnetic leg 8 and the back magnetic leg 9 all have different magnetic permeability between the surface layer and the deep layer. As shown in the cross-sectional view, the outer magnetic leg 7 and the back magnetic leg 9 are all formed by the impregnated magnetic layer 10, and only the middle magnetic leg 8 is formed as a very thin surface layer impregnated with epoxy resin. You may comprise as the dust core 12 which provided the layer 10 and the non-impregnated magnetic body layer 11 formed as a deep layer in the deep part side from the impregnated magnetic body layer 10 which is a surface layer.

  For example, as shown in the cross-sectional view of FIG. 6, when forming a coil component by abutting the powder magnetic core 12 and winding and arranging a winding portion 34 around the middle magnetic leg 8, the winding portion Most of the magnetic flux generated by the current flowing through 34 flows through the middle magnetic leg 8, and the total magnetic permeability of the two dust cores 12 in a state where the permeability of the middle magnetic leg 8 is abutted. It will have a very large contribution. On the other hand, with respect to the outer magnetic leg 7 and the back magnetic leg 9, the magnetic flux generated in the winding portion 34 is distributed approximately in half and accompanied by a leakage magnetic flux, and therefore flows to the outer magnetic leg 7 and the back magnetic leg 9. The amount of magnetic flux is small, and as a result, the magnetic permeability of the outer magnetic leg 7 and the back magnetic leg 9 contributes less to the overall magnetic permeability of the dust core 12 than the magnetic permeability of the middle magnetic leg 8. .

  Therefore, in order to improve the magnetic permeability of the middle magnetic leg 8, the impregnated magnetic layer 10 that lowers the magnetic permeability of only the middle magnetic leg 8 is only formed very thin on the surface, and the other non-impregnated magnetic layer 11 is otherwise formed. And Thereby, it is possible to improve the magnetic permeability of the whole of the dust core 12.

  In particular, the outer magnetic leg 7 has a thin dimensional shape compared to other parts from the viewpoint of the amount of magnetic flux flowing, and the magnetic material density is accordingly reduced compared to other parts. Are more easily penetrated than others, and the degree of difficulty in adjusting the degree of penetration of the impregnating resin is higher than in other parts. It is also possible to suppress variation in characteristics due to the individual dust cores 12.

  Furthermore, when the dust core 12 is applied as a choke coil or a transformer as a coil component, it is not uncommon to apply a large current or high voltage to the winding portion 34. Sometimes insulation is required around the winding 34. Here, by providing the impregnated magnetic layer 10 on the surface of the dust core 12, the surface of the dust core 12 can be provided with a moisture-proof effect, and deterioration of insulation due to moisture absorption of the dust core 12 can be suppressed. It is also a thing.

  Although not shown here, as a means for abutting and fixing the dust core 12, the periphery of the dust core 12 and the region where the winding portion 34 is disposed are exterior resin (not shown). One of them is to seal with. Of course, at this time, the butting state of the dust core 12 is required to be stable at all times. However, if the distance between the dust cores 12 facing each other changes, the coil component is changed accordingly. It will affect the characteristics as. For example, when the middle magnetic leg 8 is formed only by the impregnated magnetic layer 10 and the non-impregnated magnetic layer 11 is not provided, the impregnated magnetic layer is generated due to the stress including the surrounding environment and the generation of stress accompanying it. 10 is decomposed and deposited on the surface of the dust core 12 as the pressure of the impregnated magnetic layer 10 increases, and the surface state of the dust core 12 changes, whereby the dust core 12 There is a possibility that the characteristics such as the inductance value of the coil component may be deteriorated by changing the abutting surface and the abutting state. On the other hand, by providing the impregnated magnetic layer 10 formed on the surface of the middle magnetic leg 8 in the middle magnetic leg 8 and the non-impregnated magnetic layer 11 on the inner surface side of the impregnated magnetic layer 10, the middle magnetic leg 8 is provided. The volume of the impregnated magnetic layer 10 that is easily affected by stress is reduced, and the non-impregnated magnetic layer 11 buffers even if the epoxy resin in the impregnated magnetic layer 10 increases in pressure. In this case, the modified epoxy resin or the like is prevented from being deposited on the surface of the dust core 12.

  As a result, by providing the impregnated magnetic layer 10 and the non-impregnated magnetic layer 11 on the inner surface side of the impregnated magnetic layer 10, not only the decrease in the magnetic permeability of each individual part is suppressed, but also the dust core 12 is abutted. By stabilizing the shape greatly related to the surface and the butted state, it is possible to suppress the deterioration of the characteristics of the entire coil component including the winding portion 34.

  Further, in a state similar to that shown in FIG. 4, the high impregnation degree magnetic layer 31 formed as a surface layer only on the middle magnetic leg 8 and the inner surface side of the high impregnation degree magnetic layer 31 as the surface layer. The first low impregnation degree magnetic body layer 32 formed with a first impregnation resin density smaller than the impregnation resin density in the high impregnation degree magnetic substance layer 31, and further the first low impregnation degree magnetic substance layer 32 on the deep layer side. The second low impregnation degree magnetic material layer 33 formed with the second impregnation resin density smaller than the impregnation resin density is provided, and the outer magnetic leg 7 and the back magnetic leg 9 are all formed of the impregnation magnetic material layer 10. It doesn't matter.

  Also by this, it is possible to improve the whole magnetic permeability of the dust core 12 by improving the magnetic permeability of the middle magnetic leg 8.

  In the examples shown so far, the effects relating to the magnetic characteristics due to the provision of the impregnated magnetic layer 10 and the non-impregnated magnetic layer 11 shown in FIG. 2 are mainly described. In this case, as shown in the cross-sectional view of FIG.

  Here, the thickness dimension of the corner-impregnated magnetic body layer 10 a at the tip-side corner 8 a of the middle magnetic leg 8 corresponds to the tip surface portion 8 b corresponding to the top surface of the middle magnetic leg 8 and the peripheral surface of the middle magnetic leg 8. The shape is made larger than the thickness dimension of the surface portion-impregnated magnetic body layer 10b in the side surface portion 8c.

  In general, since the coil component is formed by abutting the powder magnetic core 12 as shown in FIG. 6, the tip side corner 8a of the middle magnetic leg 8 shown in FIG. 7 is a portion where stress is easily generated. It is desirable to have a corresponding strength. Therefore, the thickness dimension of the corner portion impregnated magnetic layer 10a is preferably larger than the thickness dimension of the surface portion impregnated magnetic layer 10b. Here, the thickness dimension of the surface portion-impregnated magnetic layer 10b may be approximately near the center of the front end surface portion 8b or near the center of the side surface portion 8c. Thereby, it is possible to suppress deterioration of characteristics due to damage such as chipping of the middle magnetic leg 8.

  Further, from the viewpoint of stress concentration, it is desirable to continuously change the thickness dimension of the surface-impregnated magnetic layer 10b with a curve as shown in the figure. As a result, a discontinuous point with a clear thickness does not occur at the boundary between the corner-impregnated magnetic layer 10a and the surface-impregnated magnetic layer 10b, and stress concentration at the discontinuous point can be avoided. It is.

  Here, the impregnated magnetic layer 10 and the non-impregnated magnetic layer 11 shown in FIG. 2 have been described as examples. However, as shown in the cross-sectional view of FIG. The above dimensional relationship may be applied to the middle magnetic leg 8 constituted by the body layer 32 and the second low impregnation degree magnetic body layer 33. In this case, since the structure is such that discontinuities are less likely to occur, it is possible to obtain a great effect for improving reliability.

  The dust core of the present invention has the effect of improving the characteristics of coil components by improving the magnetic permeability of the entire dust core, and is useful in various electronic devices.

7 outer magnetic leg 8 middle magnetic leg 8a tip end corner 8b tip end 8c side 9 back magnet 10 impregnated magnetic layer 10a corner impregnated magnetic layer 10b surface impregnated magnetic layer 11 non-impregnated magnetic layer 12 compact Magnetic core 13 Kneading and dispersing process 14 Metal magnetic powder 14a Metal magnetic powder 14b Metal magnetic powder 15 Resin 16 Mixture 17 Granulation process 18 Columnar solid 19 Solid piece 20 Resin film 20a Resin film 20b Resin film 21 Granulated powder 22 Pressing process 23 Divided magnetic core 24 Thick part 25 Thin part 26 Connecting part 27 Annealing heat treatment process 28 Impregnation process 29 Polishing process 30 Assembly process 31 High impregnation degree magnetic substance layer 32 First low impregnation degree magnetic substance layer 33 Second low impregnation degree magnetic substance layer 34 Winding part

Claims (8)

A magnetic powder is pressure-molded and consists of a pair of opposing outer magnetic legs, a middle magnetic leg sandwiched between the outer magnetic legs, and a back magnetic leg that connects the middle magnetic leg and the outer magnetic leg. In the formed dust core, an impregnated magnetic layer formed by impregnating a resin is provided on the entire surface of the dust core, and the inner surface of the impregnated magnetic layer is not impregnated with the resin. A dust core provided with a magnetic layer. A magnetic powder is pressure-molded and consists of a pair of opposing outer magnetic legs, a middle magnetic leg sandwiched between the outer magnetic legs, and a back magnetic leg that connects the middle magnetic leg and the outer magnetic leg. In the formed dust core, an impregnated magnetic layer formed by impregnating a resin is provided on the entire surface of the dust core, and at least one low-impregnated magnetic body is provided on the inner surface side of the impregnated magnetic layer. A dust core in which a layer is provided and the low-impregnated magnetic layer has a lower density than the resin impregnated in the impregnated magnetic layer located on the surface side. A magnetic powder is pressure-molded and consists of a pair of opposing outer magnetic legs, a middle magnetic leg sandwiched between the outer magnetic legs, and a back magnetic leg that connects the middle magnetic leg and the outer magnetic leg. In the dust core thus formed, an impregnated magnetic layer formed by impregnating a resin is provided on the entire surface of the outer magnetic leg and the back magnetic leg of the dust core and on the surface of the middle magnetic leg, and the middle magnet A dust core in which a non-impregnated magnetic layer not impregnated with the resin is provided on an inner surface side of an impregnated magnetic layer formed on a surface of a leg. A magnetic powder is pressure-molded and consists of a pair of opposing outer magnetic legs, a middle magnetic leg sandwiched between the outer magnetic legs, and a back magnetic leg that connects the middle magnetic leg and the outer magnetic leg. In the dust core thus formed, an impregnated magnetic layer formed by impregnating a resin is provided on the entire surface of the outer magnetic leg and the back magnetic leg of the dust core and on the surface of the middle magnetic leg, and the middle magnet At least one low-impregnated magnetic layer is provided on the inner surface side of the impregnated magnetic layer formed on the surface of the leg, and this low-impregnated magnetic layer is made of resin impregnated in the impregnated magnetic layer located on the surface side. A dust core with a density lower than the density. The dust core according to any one of claims 1 to 4, wherein a thickness dimension of a corner portion of the impregnated magnetic layer formed on the middle magnetic leg is thicker than a thickness dimension other than the corner portion. The dust core according to any one of claims 1 to 5, wherein the density of the resin impregnated in the impregnated magnetic layer gradually decreases toward the non-impregnated magnetic layer or the low-impregnated magnetic layer. The dust core according to any one of claims 1 to 6, wherein the density of the magnetic powder constituting the outer magnetic leg is lower than the density of the magnetic powder constituting the middle magnetic leg and the back magnetic leg. The coil component provided with the powder magnetic core as described in any one of Claims 1-7.

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