JP2008305812A - Production apparatus of radial anisotropic ring magnet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a production apparatus of radial anisotropic ring magnet in which deflection of magnetic powder is reduced during orientation by reducing the slope of magnetic field in the axial direction of a cavity. <P>SOLUTION: The production apparatus of radial anisotropic ring magnet has a pair of coils 10A and 10B generating magnetic fields facing each other toward the axial direction, and a metal mold 20 arranged between the pair of coils 10A and 10B with a core 22 and a die 21 arranged around the core 22 and forming a cavity 28 to which magnetic powder is supplied between the core 22 and the die 21. The core 22 includes such a portion 22A as the magnetic reluctance from the center of core to a part corresponding to the central portion of the cavity 28 in the axial direction is lower than the magnetic reluctance at the parts corresponding to the opposite ends of the cavity 28 in the axial direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a manufacturing apparatus for a radial anisotropic ring magnet, for example, a manufacturing apparatus for manufacturing a radial anisotropic ring magnet having a good shape accuracy and a high orientation ratio used for a rotor of a brushless DC motor. .

  Conventionally, a radial anisotropic ring magnet has a magnetic circuit composed of a ferromagnetic and non-magnetic yoke between a pair of electromagnets with the same pole facing each other, and the radial anisotropic ring magnet is radially contained in a ring-shaped cavity filled with magnetic powder. By producing a magnetic field in the direction, the magnetic powder is oriented, compression-molded by upper and lower punches, and sintered. The magnetic field generated in the cavity includes a method using a stationary magnetic field and a method using a pulsed instantaneous magnetic field (pulse magnetic field).

  A small-diameter radial anisotropic ring magnet has a cross-sectional area of the ferromagnetic material of the yoke that is inserted into the inner periphery of the ring-shaped cavity in the manufacturing process, and the ferromagnetic member is magnetically saturated. The magnetic field for orienting decreases. Therefore, it becomes difficult to orient the magnetic powder in the magnetic field direction, the orientation rate of the radial anisotropic ring magnet after sintering is reduced, and the magnetic force generated in the radial direction is reduced. Therefore, in Patent Document 1, for example, a pulse current is applied using a pair of coils and an insulator mold, and magnetic powder in the mold is oriented by a large magnetic field, thereby realizing a radial anisotropic ring magnet with a high orientation ratio. ing.

Japanese Patent No. 2916879

  In the above-mentioned Patent Document 1, a cylindrical laminated body in which a plurality of ferromagnetic bodies are electrically insulated from each other is provided at the core of a mold core, thereby generating a large pulse magnetic field, and a ring magnet having a high orientation ratio. Manufacture. However, in such a configuration, the magnetic field generated in the cavity has a gradient in the axial direction, and is weak at the axial center and strong at the axial end. Due to the magnetic field having a gradient in the axial direction, the magnetic powder filled in the cavity is biased toward the end in the axial direction where the magnetic field is strong, resulting in a density difference in the axial direction after compression molding. When the density is different in the axial direction, the shrinkage rate after sintering is changed, so that the axial end portion having a high density does not shrink much in the radial direction, and the axial center portion having a low density shrinks well in the radial direction. Therefore, the ring magnet after sintering is distorted in the shape of its axis and becomes like an inverted drum. Ring magnets are generally machined for shape finishing after sintering, but if the shape accuracy is poor, the machining allowance increases, more magnets are discarded without becoming a product, and the processing time also increases. There was a problem of poor yield.

  The present invention has been made in order to solve the above-described problems, and reduces the magnetic field gradient in the axial direction of the cavity, thereby reducing the bias of the magnetic powder during orientation, and an apparatus for manufacturing a radial anisotropic ring magnet I will provide a.

  A manufacturing apparatus for a radial anisotropic ring magnet according to the present invention includes a pair of coils that generate magnetic fields facing each other in the axial direction, and a die disposed between the pair of coils and around the core. And a die in which a cavity to which magnetic powder is supplied is formed between the core and the die, and in the core, the magnetoresistance of the portion corresponding to the axial central portion of the cavity from the core portion, A portion that is smaller than the magnetic resistance of the portion corresponding to both ends in the axial direction of the cavity is provided.

  According to the radial anisotropic ring magnet manufacturing apparatus of the present invention, the magnetoresistance of the portion corresponding to the axial center portion of the cavity from the core portion of the core is changed to the magnetoresistance of the portion corresponding to both axial end portions of the cavity. Compared with the magnetic field generated in the cavity, the gradient of the magnetic field in the axial direction of the cavity can be reduced, the bias of the magnetic powder during orientation is reduced, and the ring molded body after molding The difference in density distribution in the axial direction is reduced. Therefore, the shape accuracy after sintering of the ring molded body is improved, and a radial anisotropic ring magnet having a good machining yield for shape finishing can be provided.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

Embodiment 1 FIG.
1 is a cross-sectional view showing an apparatus for manufacturing a radial anisotropic ring magnet according to Embodiment 1 of the present invention. The manufacturing apparatus according to the present embodiment includes a pair of air-core coils 10A and 10B, and a mold 20 disposed between the coils 10A and 10B. The pair of coils 10A and 10B are connected in series and connected to a 4000 μF, 3000 V pulse power supply. The magnetic lines of force generated by the pair of coils 10 </ b> A and 10 </ b> B extend in the axial direction from the center of each coil, as shown by the dotted lines in the figure, and repel each other in the mold 20 and face in the radial direction. Although not shown, one of the pair of coils 10A and 10B can be reciprocated in the vertical direction in the figure by hydraulic pressure or an air cylinder.

  The mold 20 according to the present embodiment includes a cylindrical core 22, a die 21 disposed around the core 22, and a lower punch 25 and an upper punch 26 disposed between the die 21 and the core 22. ing. A cavity 28 that is a ring-shaped space is formed between the die 21, the core 22, the lower punch 25, and the upper punch 26, and the cavity 28 is filled with magnetic powder. The die 21 is made of a nonmagnetic insulator such as ceramic having a high compressive strength. The core 22 is composed of a ferromagnetic member 22A such as permendur and a nonmagnetic insulator 22B such as ceramic. The lower punch 25 and the upper punch 26 are made of an insulator such as ceramic. Note that the ferromagnetic member 22A is not limited to permendur, but may be iron, Fe—Co—Si—B based amorphous alloy, or the like. When an amorphous alloy is used as the ferromagnetic member 22A, the magnetic field gradient in the axial direction in the cavity can be reduced as described later, and the eddy current generated by the pulsed magnetic field can be further reduced, so that the magnetic field in the cavity can be reduced. Disturbance can be reduced.

  FIG. 2 is a perspective view showing the core 22 of the present embodiment. The ferromagnetic member 22A used as the core of the core 22 has a shape in which the outer diameter changes in the axial direction, for example, the outer diameter is small at positions corresponding to both ends in the axial direction of the cavity as shown in FIG. The outer diameter is increased at a position corresponding to the central portion in the direction. The core 22 is formed by fitting ring-shaped insulators 22B made of ceramic or the like to both ends in the axial direction of the ferromagnetic member 22A and bonding them by brazing or the like. The shape of the ferromagnetic member 22A is such that its outer diameter changes smoothly as shown in FIGS. 3 (a) and 3 (b), and the outer shape thereof as shown in FIG. 3 (c). The shape may be such that the diameter changes stepwise.

  After the magnetic powder filled in the cavity 28 is oriented, the mold 20 is taken out from the coils 10A and 10B, and the magnetic powder in the cavity 28 can be compressed by pressurizing the upper punch 26 by a hydraulic press servo press or the like. It has become. At this time, if the magnetic powder is compressed only from the upper punch 26, the pressure is most transmitted to the magnetic powder on the upper punch 26 side, so that the density of the ring molded body decreases from the upper punch 26 side toward the lower punch 25 side. . Therefore, in order to further reduce the density difference and improve the shape accuracy after sintering, it is more desirable that the pressurizer can pressurize not only the upper punch 26 but also the lower punch 25.

  The magnetic field generated from the coils 10A and 10B becomes weaker as the distance from the coil increases. As shown in FIG. 4A, when the core 22 is composed only of an insulator, the magnetic field generated from the opposing coils 10A and 10B and guided to the cavity 28 is intermediate between the pair of coils 10A and 10B. The magnetic field is weak at the axial center of the cavity, and the magnetic field is strong at the cavity axial end located at a short distance from the pair of coils 10A and 10B. That is, as shown in the magnetic flux density distribution B (z) in FIG. 4A, the magnetic field gradient in the axial direction (Z direction) of the cavity 28 increases. When the magnetic field gradient in the axial direction of the cavity 28 is increased, the magnetic attractive force to the both ends in the axial direction of the magnetic powder generated due to the magnetic field gradient is attracted to the center of the core 22 and the mold 20. It becomes larger than the frictional force. As a result, the magnetic powder moves toward both ends of the cavity 28 in the axial direction, and the magnetic powder in the axial direction can be densified in the cavity 28 before compression molding.

  Therefore, in the present embodiment, the ferromagnetic member 22A having a shape in which the outer diameter changes in the axial direction, for example, a shape in which the outer diameter is small at both ends in the axial direction and the outer diameter is large at the central portion in the axial direction. By using the core 22 which has, the above-mentioned problem can be solved. As shown in FIG. 4B, since the distance from the cavity 28 to the ferromagnetic member 22A is longer at both axial ends of the cavity 28 than at the axial center of the cavity 28, both axial ends of the cavity 28 The magnetic field passing through the part passes through a space having a large magnetic resistance. Further, since the ferromagnetic member 22A has a low magnetic resistance, the magnetic flux passes through a path that flows to the ferromagnetic member 22A rather than a space having a high magnetic resistance. Therefore, the magnetic field passing through both ends of the cavity 28 in the axial direction is smaller than that in the case where the ferromagnetic member 22A is not provided at the core of the core 22 as shown in FIG. The magnetic field becomes larger than that in FIG. 4A, and the magnetic field gradient in the axial direction of the cavity 28 becomes smaller. When the magnetic field gradient in the axial direction of the cavity 28 is reduced, the magnetic attraction force toward both ends in the axial direction caused by the magnetic field gradient with respect to the magnetic powder filled in the cavity 28 is the center of the core 22 (ferromagnetic member 22A). Therefore, the magnetic powder does not move toward both ends in the axial direction. As a result, the density difference (dense / dense) of the magnetic powder in the axial direction of the cavity 28 is reduced, the density difference in the axial direction after compression molding is reduced, the shrinkage during sintering is made uniform, and the shape accuracy is improved.

  Here, when the density difference in the axial direction of the ring molded body is large, the ring molded body is significantly deformed due to the shrinkage difference during sintering, and the orientation is disturbed during sintering. However, according to the configuration of the present embodiment, the ring molded body that has been oriented and compression molded has a small density difference in the axial direction, and therefore has a small shrinkage difference during sintering. Therefore, the disorder of orientation during sintering shrinkage is reduced, the orientation rate is improved, and the magnetic powder oriented in the radial direction can be increased (the orientation direction is more aligned in the radial direction), and the radial direction component of the ring magnet The amount of magnetic flux can be increased.

Here, as shown in FIG. 5, the axial length of the cavity 28 is Lc, the axial length of the portion having the large outer diameter of the ferromagnetic member 22A is L _0, and L ₀ / Lc is used as a parameter, using the finite element method. Magnetic field analysis was performed on the magnetic flux density generated in the cavity. In FIG. 6, the horizontal axis represents (L ₀ / Lc), and the vertical axis represents the difference (Be−Bc) between the magnetic flux density (Be) at the cavity axial end and the magnetic flux density (Bc) at the central cavity axial direction. This shows the relationship between the two cases. From FIG. 6, when L ₀ / Lc is 1 or less, that is, when the axial length of the portion having a large outer diameter of the ferromagnetic member is equal to or less than the axial length of the cavity, the magnetic flux density difference (Be−Bc) becomes small, preferably (L ₀ / Lc) is between 0.3 and 0.6, the magnetic flux density difference (Be−Bc) is 1000 G or less, and the axial magnetic field gradient can be further reduced. When the magnetic circuit is designed so that the magnetic flux density (Bc) in the axial center is about 3T or more, if the magnetic flux density difference (Be−Bc) is 1000G or less, a magnetic field gradient of about 3% or less is obtained. Can be achieved. The stronger the magnetic flux density in the central portion in the axial direction, the greater the force that resists the force attracted by the magnetic field gradient (the force attracted to the ferromagnetic member 22A that is the core of the core 22). Further suppression can be achieved.

Further, assuming that the maximum outer diameter of the ferromagnetic member 22A is D ₀ , the minimum outer diameter is Dc, and D ₀ / Dc, the magnetic flux density (Be) at the end in the cavity axis direction and the center in the cavity axis direction using the finite element method. The relationship of the magnetic flux density difference (Be-Bc) of the magnetic flux density (Bc) is shown in FIG. From FIG. 7, if (D ₀ / Dc) is 0.8 or less, the magnetic flux density difference (Be−Bc) is 500 G or less, and the magnetic field gradient in the axial direction can be further reduced. Incidentally, in FIG. 5, (D ₀ /Dc)=0.6.

  Next, a method for manufacturing the radial anisotropic ring magnet according to the first embodiment will be described. The permanent magnet material is made of a rare earth element-Fe-B magnet material, and a material with a small amount of additives is used as a raw material. More specifically, an R-Fe-B-based (R is a La-based rare earth element) magnet material typified by an Nd-Fe-B-based magnet, a substance for improving magnet characteristics such as a small amount of Co, Ni, A material containing a substance for improving corrosion resistance, heat resistance, and workability such as Al is used as a raw material. Then, these raw materials are melted at about 1500 degrees in a vacuum, and the molten metal is poured into a copper mold or a copper rotating roll to be rapidly cooled to produce a magnet alloy. Then, the magnet alloy is subjected to hydrogen embrittlement treatment and then finely pulverized by a jet mill, a ball mill or the like to produce a magnetic powder. Next, the mold 20 is configured by filling the ring-shaped cavity 28 formed by the die 21, the core 22, and the lower punch 25 of this embodiment with magnetic powder, and inserting the upper punch 26. Then, the mold 20 is placed in an empty space by moving the upper coil 10A upward, and the upper coil 10A is moved downward to sandwich the mold 20 between the pair of upper and lower coils 10A and 10B. At this time, the upper punch 26 is stopped at a position in a lid state where the magnetic powder is not compressed. Next, a pulse current is applied to the coils 10A and 10B by a pulse power source, and an opposing pulse magnetic field is applied. Thereafter, the upper coil 10A is moved upward, the mold 20 is taken out from the coils 10A and 10B, the upper punch 26 is pressurized by a hydraulic press, and the magnetic powder is compression-molded in 2 t. The mold 20 of the present embodiment can generate more magnetic field by using the ferromagnetic member 22A for the core of the core 22, and the non-magnetic insulator such as ceramic other than the core of the core 22 can be generated. Since it is constituted by 22B, the magnetic field disturbance due to the eddy current can be reduced. The compression-molded ring molded body was sintered at 1080 degrees in a vacuum and then subjected to an aging treatment at 500 degrees.

About the radial anisotropic ring magnet manufactured by the above-mentioned manufacturing method, the orientation rate was measured with a pulse BH tracer and the outer diameter shape was measured with a three-dimensional measuring instrument. Table 1 shows the results of measuring the outer diameters of the axial end and axial center of the ring magnet using L ₀ / Lc as a parameter. Here, D ₀ /Dc=0.6 and constant. In addition, the orientation ratio here is the orientation ratio (%) = Br / Bs, where Bs is the saturation magnetic flux density in the radial direction when 5000 kA / m is applied to the test piece, and Br is the residual magnetic flux density in the radial direction. . As is evident from Table 1, the difference between the outer diameter of the axial center portion of both end portions in the axial _direction, 0.05 mm from _{0.52mm (L 0 /Lc=1.0) (L} 0 / Lc = 0.4). It can also be seen that the orientation ratio is also improved from 92.2% (L ₀ /Lc=1.0) to 95.6% (L ₀ /Lc=0.4).

  As described above, the present embodiment is arranged between the pair of coils 10A and 10B that generate magnetic fields facing each other in the axial direction and the pair of coils 10A and 10B. And a die having a cavity 28 to which magnetic powder is supplied between the core 22 and the die 21, and from the core of the core 22 toward the axial center of the cavity 28. Thus, a ferromagnetic body 22A that is a portion having a small magnetic resistance is provided, and an insulator 22B that is a portion having a large magnetic resistance is provided at locations corresponding to both axial ends of the cavity. As a result, the magnetic field gradient in the axial direction is reduced with respect to the magnetic field in the cavity generated by the pair of coils 10A and 10B, the magnetic powder is less biased during orientation, and the axial density difference after compression molding is reduced. Therefore, the shape accuracy in the axial direction of the ring magnet after sintering can be improved, the yield at the time of machining the shape finish can be improved, and productivity and cost reduction can be realized.

Embodiment 2. FIG.
As described in the first embodiment, the magnetic fields generated from the pair of coils 10A and 10B facing each other with the same polarity repel each other in the axial direction and then rebound near the center in the axial direction and travel in the radial direction. I take the. As shown in FIG. 8, in the case where a lump of ferromagnetic member 22A having a high magnetic permeability is arranged inside the core 22, the higher the frequency of the pulse magnetic field generated from the coils 10A and 10B, the higher the magnetic field directed in the axial direction. An eddy current Iec1 that rotates with respect to the central axis 22 is generated, and an eddy current Iec2 that rotates with respect to the central axis in the radial direction is generated by a magnetic field directed in the radial direction.

  The purpose of this embodiment is to reduce the eddy current of the core generated by the above-described pulse magnetic field. FIG. 9 is a perspective view showing a ferromagnetic member 220 built in a core according to Embodiment 2 of the present invention.

  As shown in FIG. 9, the ferromagnetic member 220 according to the second embodiment is formed by laminating a 0.5 mm-thick disk made of a ferromagnetic material having a very high permeability such as permendur in the axial direction. It is a laminate fixed in the direction by bonding, caulking, welding, or the like. Each disk constituting the ferromagnetic member 220 is covered with an insulating film, and the disks are electrically insulated from each other. Further, the material of the disk is not limited to permendur, but may be iron, Fe—Co—Si—B based amorphous alloy, or the like. The outer diameter of the ferromagnetic member 220 is different in the axial direction, the outer diameter of the laminated body 220b at the central portion in the axial direction is as large as 30 mm, and the outer diameter of the laminated body at both end portions in the axial direction is as small as 5 mm. And the ferromagnetic member 220 which is a laminated body is made of ceramics, and the inside is stepped so as to follow the outer diameter of the ferromagnetic member 220, and is divided into core outer shells (not shown). Fit. Then, after the divided core outer shell is bonded by brazing or the like, the core is formed by covering the outer periphery of the core outer shell with a nonmagnetic ring of about 1 mm.

  According to the ferromagnetic member 220 of the present embodiment, the eddy current inside the core generated by the pulse magnetic field, in particular, the eddy current Iec2 shown in FIG. 8 can be divided, and the disturbance of the magnetic field can be minimized. Therefore, the magnetic powder can be oriented in the radial direction while generating a large magnetic field during magnet orientation, and the magnetic field gradient in the axial direction can be reduced. Therefore, the shape accuracy of the ring magnet after sintering is improved, the yield in the shape finishing machining process is improved, and productivity and cost reduction can be realized.

  FIG. 10 is a perspective view showing a ferromagnetic member 221 built in the core according to another example of the second embodiment of the present invention. The ferromagnetic member 221 shown in FIG. 10 has a laminated cylindrical portion 221a made of a ferromagnetic material arranged at the core of a core, and a laminated ring portion 221b made of a ferromagnetic material is fitted to the axial center of the laminated cylindrical portion 221a. It is constituted by. The laminated cylindrical portion 221a is formed by laminating thin plates made of a ferromagnetic material having a very high permeability such as permendur, and the cylinder is cut in the axial direction. Each thin plate is covered with an insulating film, and the thin plates are Are electrically isolated from each other. The laminated ring part 221b is a laminate of ring-shaped thin plates made of a ferromagnetic material having a very high permeability such as permendur, and each thin plate is covered with an insulating film, and the thin plates are electrically connected to each other. Is electrically insulated.

  According to the ferromagnetic member 221 of FIG. 10, the eddy currents in both the axial direction and the radial direction inside the core generated by the pulsed magnetic field, that is, the eddy current Iec1 and the eddy current Iec2 shown in FIG. Disturbance can be minimized. Therefore, the magnetic powder can be oriented in the radial direction while generating a large magnetic field during magnet orientation, and the magnetic field gradient in the axial direction can be reduced. Therefore, the shape accuracy of the ring magnet after sintering is improved, the yield in the shape finishing machining process is improved, and productivity and cost reduction can be realized.

Embodiment 3 FIG.
11 (a) is a cross-sectional view showing a core according to Embodiment 3 of the present invention, FIG. 11 (b) is a cross-sectional view taken along the line AA ′ of FIG. 11 (a), and FIG. 11 (c) is FIG. It is a BB 'line sectional view of).

  The ferromagnetic member 222 of the present embodiment bundles a φ0.5 mm wire made of a ferromagnetic material having a very high permeability such as permendur, and the bundle of the wire is bundled in an insulator made of an insulator such as ceramic. It is arranged around the circumference. Each said wire is electrically insulated from each other by being covered with an insulating film. Further, the material of the wire is not limited to permendur, but may be iron, Fe—Co—Si—B based amorphous alloy, or the like. The outer diameter of the bundle of wires constituting the ferromagnetic member 222 is different in the axial direction, the outer diameter at the central portion in the axial direction is the largest, and the outer diameter at both ends in the axial direction is the smallest. Further, as shown in FIG. 12, the cross-sectional shape of the wire may be a circle, a polygon such as a quadrangle, or a hexagon. Furthermore, the outer diameter of the bundle of wires is made slightly larger than the desired outer diameter, and is pressed to the desired outer diameter by applying pressure from the outer periphery, and is placed on the inner periphery of the ring made of an insulator such as ceramic. It is desirable to increase the density of the magnetic material. In addition, as a method for increasing the density, wires having different cross-sectional shapes or wire diameters may be combined.

  According to the ferromagnetic member 222 of the present embodiment, the eddy currents in both the axial direction and the radial direction inside the core generated by the pulse magnetic field, that is, the eddy currents Iec1 and Iec2 shown in FIG. Magnetic field disturbance can be minimized. Therefore, the magnetic powder can be oriented in the radial direction while generating a large magnetic field during magnet orientation, and the magnetic field gradient in the axial direction can be reduced. Therefore, the shape accuracy of the ring magnet after sintering is improved, the yield in the shape finishing machining process is improved, and productivity and cost reduction can be realized.

It is sectional drawing which shows the manufacturing apparatus of the radial anisotropic ring magnet by Embodiment 1 of this invention. It is a perspective view which shows the core by Embodiment 1 of this invention. It is sectional drawing which shows the core by Embodiment 1 of this invention. It is a figure for demonstrating the magnetic field near the cavity of a manufacturing apparatus. It is sectional drawing which shows the dimensional relationship of the manufacturing apparatus of the radial anisotropic ring magnet by Embodiment 1 of this invention. It is a diagram showing a relationship between the dimensional ratio of the embodiment (L 0 _/ Lc) and the difference between the axial magnetic flux density of the cavities (Be-Bc). It is a diagram showing the relationship between the magnetic flux density difference between the axial direction of the cavity of the embodiment (Be-Bc) and the dimensional ratio (D 0 _/ Dc). It is sectional drawing which shows the eddy current which generate | occur | produces in the core of the manufacturing apparatus of a radial anisotropic ring magnet. It is a perspective view which shows the ferromagnetic member incorporated in the core by Embodiment 2 of this invention. It is a perspective view which shows the ferromagnetic member incorporated in the core by the other example of Embodiment 2 of this invention. It is sectional drawing which shows the core by Embodiment 3 of this invention. It is a figure which shows the cross-sectional shape of the wire of the core by Embodiment 3 of this invention.

Explanation of symbols

10A coil, 10B coil, 20 mold, 21 die, 22 core,
22A ferromagnetic member, 22B insulator, 25 lower punch, 26 upper punch,
28 cavities, 220 ferromagnetic members, 221 ferromagnetic members, 222 ferromagnetic members.

Claims (8)

A pair of coils generating magnetic fields facing each other in the axial direction;
A die that is disposed between the pair of coils and includes a core and a die disposed around the core, and a cavity in which a magnetic powder is supplied between the core and the die;
In the core, a radial difference is provided in which a portion of the core corresponding to the axial central portion of the cavity has a smaller magnetic resistance than that of the portion corresponding to both axial end portions of the cavity. Equipment for manufacturing anisotropic ring magnets. A ferromagnetic member is provided in the core portion of the core, and a cross-sectional shape perpendicular to the axis of the ferromagnetic member varies depending on the axial position, and the outer diameter of the axial center portion of the cavity is the both axial end portions of the cavity. The apparatus for manufacturing a radial anisotropic ring magnet according to claim 1, which is larger than an outer diameter of the radial anisotropic ring magnet. The manufacturing apparatus of a radial anisotropic ring magnet according to claim 2, wherein the outer diameter of the ferromagnetic member is largest at the axial center of the cavity and decreases toward both axial ends of the cavity. 3. The radial anisotropic ring magnet according to claim 2, wherein the outer diameter of the ferromagnetic member changes stepwise so that the outer diameter of the ferromagnetic member is largest at an axial center portion of the cavity and becomes small at both axial end portions of the cavity. Manufacturing equipment. The apparatus for manufacturing a radial anisotropic ring magnet according to any one of claims 2 to 4, wherein the ferromagnetic member is an amorphous alloy. The radial anisotropic ring magnet according to any one of claims 2 to 4, wherein the ferromagnetic member is a laminated body in which discs made of a ferromagnetic material and having an insulating coating formed thereon are laminated in an axial direction. Manufacturing equipment. Both end portions in the axial direction of the ferromagnetic member are made of a laminated body of thin ferromagnetic materials having an insulating film formed and cut in the axial direction, and an insulating film is formed in the axial center portion of the ferromagnetic member. The apparatus for manufacturing a radial anisotropic ring magnet according to any one of claims 2 to 4, comprising a laminate of thin sheets of ferromagnetic material having a shape cut perpendicular to an axis. The radial anisotropic ring magnet according to any one of claims 2 to 4, wherein the ferromagnetic member is a bundle of wires extending in an axial direction made of a ferromagnetic material and having an insulating coating formed thereon. Manufacturing equipment.

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