Patent Description:
Conventionally, when winding a conductive wire, for example, a conductive wire covered with an insulating material such as polyurethane or polyester, around a winding portion of a core component such as a ferrite core, as shown in <FIG>, a conductive wire <NUM> is mounted in a state of being aligned with a winding portion <NUM> by fixing the end of the conductive wire <NUM> to any one of a flange portion <NUM> provided at both ends of the winding portion <NUM> of a core component <NUM>, and feeding the conductive wire <NUM> from one end to the other end of the winding portion <NUM> while bringing adjacent conductive wires <NUM> and <NUM> into contact with each other (<CIT>). In <FIG>, reference numeral <NUM> is a lead-out electrode connecting both ends of the conductive wire <NUM>. <CIT> discloses a core component according to the preamble of Laid-Open No. <CIT>, the miniaturization of electronic devices such as portable terminals is progressing, and the demand for miniaturization of ferrite cores mounted on such electronic devices is also increasing. Further, <CIT> discloses that the conductive wire which is wound around the winding portion is also thinned, and the diameter thereof is as thin as about <NUM>.

<CIT> proposes an inductance core having a columnar coil winding portion having a substantially elliptical cross section, and a pair of flanges each composed of substantially elliptical flat plate at both ends thereof.

<CIT> discloses a ceramic core including an axial core part extended in the longitudinal direction, and a pair of flanges located at both ends in the longitudinal direction of the axial core part and projecting around the periphery of the axial core part in the height and width directions.

The present invention provides a core component according to claim <NUM>, a method according to claim <NUM>, and an inductor according to claim <NUM>. Further embodiments of the present invention are disclosed in the dependent claims.

Hereinafter, core components according to an embodiment of the present disclosure will be described. As shown in <FIG>, a core component <NUM> includes a columnar winding portion <NUM> having a first axial end and a second axial end and a flange portion <NUM> integrally formed with the winding portion <NUM> at both axial ends of the winding portion <NUM>. The core component <NUM> is made of a sintered body of an inorganic powder such as alumina in addition to ferrite. A conductive wire (not shown) is wound around the winding portion <NUM>. Both ends of the conductive wire are connected to the lead-out electrodes formed on the flange portion <NUM>. For example, the length in the axial direction of the winding portion <NUM> is <NUM> to <NUM>, and the diameter is <NUM> to <NUM>. Further, the length (width) of each flange portion <NUM> in the axial direction is <NUM> to <NUM>, and the diameter is <NUM> to <NUM>.

As shown in <FIG> and <FIG> described later, in the cross section orthogonal to the axial center, the winding portion <NUM> has a first region <NUM> having a curved outer peripheral surface having a first radius of curvature, and a second region <NUM> having a curved surface having a second radius of curvature. The second radius of curvature is smaller than the first radius of curvature. The first region <NUM> and the second region <NUM> are connected to each other via the projection <NUM>. Therefore, disconnection of the conductive wire can be suppressed.

The projection <NUM> preferably has a curved outer peripheral surface. Further, the height of the projection <NUM> is preferably equal to or smaller than the diameter of the conductive wire in order to suppress the disconnection of the conductive wire. Here, the height of the projection <NUM> can be obtained by subtracting (the length from the axial center to the surface of the second region <NUM> including a second radius of curvature) from (the length from the axial center to the surface of the projection <NUM>). In addition, in the case of the conductive wire provided with the coating, let the diameter of conductive wire be a diameter including a coating. Furthermore, the outer peripheral surface of the projection <NUM> preferably has a radius of curvature smaller than that of the second radius of curvature of the winding portion <NUM>. As a result, the residual stress in the projection <NUM> is reduced, so that the projection <NUM> is less likely to be brittlely fractured, and the occurrence of particle shedding due to the brittle fracture is reduced.

Alternatively, a stepped portion <NUM> may be largely removed by polishing or the like, and the portion may be processed into a planar shape. In this case, as shown in <FIG>, in the cross section orthogonal to the axial center, a winding portion <NUM>' has a first region <NUM>' having a curved outer peripheral surface having a first radius of curvature, and a second region <NUM>'having a curved outer peripheral surface having the second radius of curvature and a flat portion <NUM> continuous with the curved outer peripheral surface. A second region <NUM>' is connected to the first region <NUM>' via a projection <NUM>'.

As shown in <FIG>, in the cross section orthogonal to the axial center, the flange portion <NUM> has a first region <NUM> having a curved outer peripheral surface having a first radius of curvature, and a second region <NUM> including a curved surface portion having a curved surface having a second radius of curvature smaller than the first radius of curvature, and the first region <NUM> and the second region <NUM> are connected via a projection <NUM>. As a result, it is possible to suppress the occurrence of particle shedding from the projection <NUM>.

The projection <NUM> preferably has a curved outer peripheral surface. Furthermore, the outer peripheral surface of the projection <NUM> preferably has a radius of curvature smaller than that of the second radius of curvature of the flange portion. As a result, the residual stress in the projection <NUM> is reduced, so that the projection <NUM> is less likely to be brittlely fractured, and the occurrence of particle shedding due to the brittle fracture is reduced.

As in the winding portion <NUM> shown in <FIG>, the second region <NUM> may include the flat portion <NUM> which is continuous with a curved peripheral surface having the second radius of curvature and is connected to the first region <NUM> via the projection at the flat portion <NUM>.

In the core component <NUM> of the present embodiment, as shown in <FIG>, when the winding portion <NUM> is observed in a cross section perpendicular to the axial direction, a surface layer portion <NUM> of the winding portion <NUM> has an area occupancy of voids smaller than that of an inside <NUM> of the winding portion <NUM>. For example, the area occupancy of voids in the surface layer portion <NUM> of the winding portion <NUM> is <NUM> to <NUM>%.

Therefore, since the surface layer portion <NUM> of the winding portion <NUM> is dense, the conductive wire can be wound around the winding portion <NUM> with high accuracy, the strength of the winding portion <NUM> is improved, the resistance to deformation is improved, and particle shedding is also suppressed.

Here, the surface layer portion <NUM> refers to a region having a depth of <NUM> or less from the surface of the winding portion <NUM> toward the axial center. The inside <NUM> refers to a region excluding the surface layer portion <NUM>. Further, in order to obtain the area occupancy of voids, for example, the portion where the size and distribution of the voids are observed on average is selected among the mirror surface of each of the surface layer portion <NUM> and the inside <NUM> obtained by polishing them using diamond abrasive grains having an average particle diameter of <NUM> (this mirror surface is the cross section perpendicular to the axial direction of the winding portion <NUM>). For example, the range in which the area is <NUM> × <NUM>-<NUM> mm<NUM> (lateral length is <NUM>, longitudinal length is <NUM>) is photographed with a scanning electron microscope at a magnification of <NUM> to obtain an observation image. Then, for this observation image, the area occupancy of voids can be determined by a method called the particle analysis using the image analysis software "A-Zou Kun (ver <NUM>)" (registered trademark, manufactured by Asahi Kasei Engineering Corporation, in the following description, the description of the image analysis software "A-Zou Kun" refers to the image analysis software manufactured by Asahi Kasei Engineering Corporation).

The area occupancy of voids of the flange portion <NUM> may have the same relationship as that of the winding portion <NUM>. That is, as shown in <FIG>, when the flange portion <NUM> is observed in a cross section perpendicular to the axial direction, the surface layer portion of the flange portion <NUM> has an area occupancy of voids smaller than an area occupancy of voids of an inside <NUM> of the flange portion <NUM>. For example, the area occupancy of voids in a surface layer portion <NUM> of the flange portion <NUM> is <NUM> to <NUM>%.

In addition, it is preferable that a gap C between adjacent voids represented by the following Formula at least in the surface layer portion <NUM> of the winding portion <NUM> be <NUM> to <NUM>. <MAT> where, L is the average value of the distance between the centers of gravity between adjacent voids in the surface layer portion <NUM> or the inside <NUM>, and R is the average value of the equivalent circle diameters of the voids in the surface layer portion <NUM> or the inside <NUM>.

At this time, it is more preferable that the voids present in the surface layer portion <NUM> have a larger gap C between adjacent voids than the voids present in the inside <NUM>. Specifically, it is preferable that the difference between the gap Csi between the voids in the surface layer portion <NUM> and the gap CS2 between the voids in the inside <NUM> obtained from the above formula be <NUM> or more.

As described above, since the void distribution at least in the surface layer portion <NUM> of the winding portion <NUM> is sparse, so that the particle shedding generated from the inside and the outline of the voids is reduced, and when the conductive wire is wound around the winding portion <NUM>, it is not likely to cause damage to the conductive wire such as disconnection.

As in the winding portion <NUM>, the voids present in the surface layer portion <NUM> of the flange portion <NUM> may have a larger gap C between adjacent voids shown by the above formula than the voids present in the inside <NUM>. Specifically, the difference between the gap CF1 between the voids in the surface layer portion <NUM> and the gap CF2 between the voids in the inside <NUM> is <NUM> or more. Here, the surface layer portion <NUM> refers to a region having a depth of <NUM> or less from the surface of the flange portion <NUM> toward the axial center. The inside <NUM> refers to a region excluding the surface layer portion <NUM>.

The average value of the distance between the centers of gravity between the voids and the average value of the equivalent circle diameters of the voids can be determined by the following method.

First, the portion where the size and distribution of the voids are observed on average is selected among the mirror surface of each of the surface layer portion and the inside obtained by polishing them using diamond abrasive grains (this mirror surface is the cross section perpendicular to the axial direction of the winding portion <NUM>). For example, the range in which the area is <NUM> × <NUM>-<NUM> mm<NUM> (lateral length is <NUM>, longitudinal length is <NUM>) is photographed with a scanning electron microscope at a magnification of <NUM> to obtain an observation image. Next, using the above-mentioned image analysis software "A-Zou Kun", the average value of the distances between the centers of gravity of the voids can be determined by the distance-between-centroid method of dispersion measurement.

In addition, the average value of the equivalent circle diameters of the voids can be determined by performing analysis using the same observation image as the above-described observation image by means of the particle analysis using the image analysis software "A-Zou Kun".

As the setting conditions of the distance-between-centroid method and the particle analysis, for example, a threshold value which is an index indicating light and dark of an image may be <NUM>, lightness may be dark, a small figure removing area may be <NUM><NUM> and a noise removing filter may be present. In the above measurement, the threshold value is <NUM>, but the threshold value may be adjusted according to the brightness of the observation image. The lightness is dark, the method of binarization is manual, and the small figure removing area is <NUM><NUM> and a noise removing filter is present. The threshold value may be adjusted so that a marker whose size changes according to the threshold value in the observation image matches the shape of the voids.

The winding portion <NUM> preferably has a cutting level difference (Rδc) of the surface roughness curve of <NUM> or more and <NUM> or less. The cutting level difference (Rδc) represents the difference between the cutting level at a <NUM>% loading length rate in the surface roughness curve and the cutting level at a <NUM>% loading length rate in the roughness curve. The cutting level difference (Rδc) is a parameter that represents both the axial direction and the radial direction.

Similarly, the cutting level difference Rδc of the roughness curve on the surface of the flange portion <NUM> is preferably <NUM> or more and <NUM> or less.

When the cutting level difference (Rδc) is <NUM> or more, an appropriate anchor effect can be given to the conductive wire. Therefore, the slip of the conductive wire is appropriately suppressed, the winding installation becomes easy, and the winding of the conductive wire to the winding portion <NUM> can be performed with high accuracy, so that the occurrence of winding deviation or the like can be prevented. On the other hand, the cutting level difference (R5c) is <NUM> or less, so that it is possible to suppress the variation in the intervals between the wound conductive wires and the height difference between the adjacent conductive wires.

Moreover, it is preferable that the root mean square height (Rq) in a roughness curve be <NUM> or more and <NUM> or less.

When the root mean square height (Rq) is <NUM> or more, an appropriate anchor effect can be given to the conductive wire, which facilitates the mounting. On the other hand, when the conductive wire is wound with a root mean square height (Rq) of <NUM> or less, the risk of disconnection can be reduced.

The winding portion <NUM> is pressure-molded at a high pressure by a lower punch <NUM> and an upper punch <NUM> as described later, so that the surface layer portion <NUM> of the winding portion <NUM> is denser than a surface layer portion <NUM>' of an inner portion of the flange portion <NUM> shown in <FIG>. Therefore, when the conductive wire is wound, it is possible to reduce the risk of particle shedding caused by the winding.

The cutting level difference R5c and the root mean square height (Rq) of the roughness curve are in accordance with JIS B <NUM>: <NUM>, and can be measured by a ultra-depth color 3D shape measuring microscopes (for example, VK-<NUM> manufactured by Keyence Corporation). The measurement conditions are as follows; measurement mode: color ultra depth, gain: <NUM>, measurement resolution in the height direction (pitch): <NUM>, magnification: <NUM> times, cutoff value λs: <NUM>, cutoff value λc: <NUM>.

Here, it is sufficient that the measurement range per one location is <NUM> to <NUM> × <NUM> to <NUM> when the winding portion <NUM> is to be measured, and <NUM> to <NUM> × <NUM> to <NUM> when the flange portion <NUM> is to be measured.

As shown in <FIG>, the radius of curvature of a corner portion <NUM> where the winding portion <NUM> and the flange portion <NUM> intersect is preferably equal to or smaller than the diameter of the conductive wire. Specifically, the radius of curvature of the corner portion <NUM> is <NUM> or less, preferably <NUM> to <NUM>.

As a result, the occurrence of offset at the corner portion can be suppressed, and the conductive wire can be accurately wound in a state of being aligned with the winding portion.

Next, a method of manufacturing the core component <NUM> by press molding will be described based on <FIG> and <FIG>. <FIG> are a cross-sectional view and a longitudinal-sectional view, respectively, showing the molding state of the core component <NUM>. The press molding apparatus used includes a die <NUM>, the lower punch <NUM> and the upper punch <NUM>. The lower punch <NUM> includes a first lower punch <NUM> and a second lower punch <NUM>. The upper punch <NUM> includes a first upper punch <NUM> and a second upper punch <NUM>.

As shown in <FIG>, the lower punch <NUM> and the upper punch <NUM> have arc-shaped pressing surfaces 50a, 50b, 60a, and 60b for forming the winding portion <NUM> and the flange portion <NUM>, respectively. The radiuses of curvature of the pressing surfaces 50a and 50b of the lower punch <NUM> and the pressing surfaces 60a and 60b of the upper punch <NUM> at the portion forming the winding portion <NUM> and the flange portion <NUM> are different. In this embodiment, the radius of curvature of the pressing surfaces 60a and 60b of the upper punch <NUM> is formed larger than the radius of curvature of the pressing surfaces 50a and 50b of the lower punch <NUM>. Conversely, the radius of curvature of the pressing surfaces 50a and 50b of the lower punch <NUM> may be larger than the radius of curvature of the pressing surfaces 60a and 60b of the upper punch <NUM>.

Therefore, stepped portions <NUM> and <NUM>' are formed on both sides in a state where the pressing surfaces 50a and 50b of the lower punch <NUM> and the pressing surfaces 60a and 60b of the upper punch <NUM> overlap with each other.

In the present embodiment, at least the radius of curvature of the pressing surface 50a of the lower punch <NUM> and the radius of curvature of the pressing surface 60a of the upper punch <NUM> may be different from each other at a portion where the flange portion <NUM> is to be formed.

In molding, first, the lower punch <NUM> is fixed in the die <NUM> as shown in <FIG>, and an inorganic powder <NUM> as the raw material is supplied to the pressing surfaces 50a and 50b of the upper surface of the lower punch <NUM>. Then, the upper punch <NUM> is lowered to press the inorganic powder between the lower punch <NUM> and the upper punch <NUM>.

The molding pressure at the time of pressure molding is <NUM> MPa or more, preferably <NUM> to <NUM> MPa. Since such a high pressure can be used for pressure molding, the resulting compact has a high density and is closely packed especially on the surface portion, and faithfully reflects the surface shape of the molding die (lower punch <NUM> and upper punch <NUM> described later), so that the radius of curvature of the corner portion <NUM> where the winding portion <NUM> and the flange portion <NUM> intersect can be equal to or smaller than the diameter of the conductive wire.

Further, as described above, the area occupancy of voids of the surface layer portion <NUM> of the winding portion <NUM> can be made smaller than that of the inside <NUM> of the winding portion.

For the same reason, the void distribution at least in the surface layer portion <NUM> of the winding portion <NUM> can be made sparse, and the gap C between adjacent voids can be made <NUM> to <NUM>.

In addition, the compact has a dense and closely packed surface, in particular, on the surface portion, so that the cutting level difference R5c of the roughness curve of the surface of the winding portion <NUM> can be <NUM> to <NUM>.

Such high pressure can be applied because, as described above, the pressing surfaces 50a and 50b of the lower punch <NUM> and the pressing surfaces 60a and 60b of the upper punch <NUM> have different radiuses of curvature. On the other hand, when the pressing surfaces 50a and 50b of the lower punch <NUM> and the pressing surfaces 60a and 60b of the upper punch <NUM> have the same radius of curvature, the compact cannot be taken out of the molding die when pressurized with high pressure. Therefore, since it cannot be pressurized at high pressure but must be pressurized at low pressure, the core component <NUM> formed by pressure molding has a lot of voids, the strength is inferior, and further, it is easy to generate the particle shedding.

After molding, as shown in <FIG>, the die <NUM> is lowered relative to the lower punch <NUM> and the upper punch <NUM> so that the stepped portions <NUM> and <NUM>' and the upper end face of the die <NUM> on the overlapping surface of the lower punch <NUM> and the upper punch <NUM> have approximately the same height. Next, the upper punch <NUM> is moved upward relative to the lower punch <NUM>. At this time, first, the first upper punch <NUM> on both sides is raised, and then the second upper punch <NUM> is raised. This facilitates separation of the upper punch <NUM> from the compact <NUM>.

The second lower punch <NUM> is relatively raised with respect to the die <NUM> simultaneously with or after the rise of the upper punch <NUM>. As a result, the compact <NUM> can be pushed up, and the compact <NUM> can be easily taken out.

After removing the raw material powder adhering to the obtained compact <NUM> by air blow or the like if necessary, for example, the compact <NUM> is held at the maximum temperature of <NUM> to <NUM> for <NUM> to <NUM> hours in an air atmosphere to obtain the sintered body. Further, the sintered body is subjected to polishing such as barrel polishing, if necessary, to obtain the core component <NUM>.

Stepped portions <NUM> and <NUM>' corresponding to the stepped portions <NUM> and <NUM>' due to the difference in the radiuses of curvature of the pressing surfaces 50a and 50b of the lower punch <NUM> and the pressing surfaces 60a and 60b of the upper punch <NUM> is formed on the surface of the compact <NUM> corresponding to the winding portion <NUM> and the flange portion <NUM>. If the stepped portions <NUM> and <NUM>' have a problem in winding the conductive wire around the surface of the winding portion <NUM>, it is preferable to remove as much as possible by polishing.

As shown in <FIG>, for the core component <NUM> obtained by polishing, the winding portion <NUM> has a first region <NUM> having a curved outer peripheral surface with a large radius of curvature and a second region <NUM> having a curved outer peripheral surface with a small radius of curvature in a cross section orthogonal to the axial center, and the first region <NUM> and the second region <NUM> are connected via a projection <NUM>. At this time, the height of the projection <NUM> is preferably equal to or smaller than the diameter of the conductive wire wound around the outer peripheral surface of the winding portion <NUM>. As a result, the occurrence of disconnection and offset of the conductive wire can be suppressed.

In addition, the stepped portions <NUM> and <NUM>' may be largely removed by polishing, and the portion may be processed into a planar shape. In this case, as shown in <FIG>, in the cross section orthogonal to the axial center, a winding portion <NUM>' has a first region <NUM>' having a curved outer peripheral surface with a large radius of curvature, and a second region <NUM>' consisting of a flat portion <NUM> whose outer peripheral surface is connected to the first region <NUM>' and a curved surface portion continuous with the flat portion <NUM> with a small radius of curvature, and the first region <NUM>' and the second region <NUM>' are connected via a projection <NUM>'.

The above polishing process may be applied not only to the winding portions <NUM> and <NUM>' but also to the flange portion <NUM> in the same manner.

Claim 1:
A core component (<NUM>) made of a sintered body of an inorganic powder (<NUM>), the core component (<NUM>) comprising:
a columnar winding portion (<NUM>) for winding a conductive wire around the columnar winding portion (<NUM>), the columnar winding portion (<NUM>) having a first axial end and a second axial end;
a flange portion (<NUM>) integrally formed with the columnar winding portion (<NUM>) at both axial ends of the columnar winding portion (<NUM>),
wherein the flange portion (<NUM>) includes, in a cross section orthogonal to an axial center, a first region (<NUM>) including a curved outer peripheral surface having a first radius of curvature and a second region (<NUM>) including a curved surface having a second radius of curvature, wherein the second radius of curvature is smaller than the first radius of curvature, and
the first region (<NUM>) and the second region (<NUM>) are connected with each other via a projection (<NUM>).