Magnetic core and method for manufacturing the same, magnetic core with coil, and rotating electrical machine

Abstract

This magnetic core comprises a core back part and a tooth part, said core back part having a front surface facing a first direction toward the rotation axis of a rotary electric machine when the magnetic core is incorporated in the rotary electric machine. The tooth part includes a tooth body part extending from the front surface in the first direction and a tooth tip part provided at the tip of the tooth body part. The tooth tip part has a back surface facing the reverse direction of the first direction. The tooth body part has an end surface that faces a second direction along the rotation axis when the magnetic core is incorporated in the rotary electric machine. The end surface has a recessed curved surface that smoothly connects the end surface to the front surface of the core back part or the back surface of the tooth tip part, and the curved surface is formed by a first curved surface formation part that is a part of the tooth body part.

Description

Technical Field

[0001] The present invention relates to a technique for reducing the occurrence of magnetic saturation in a rotary electric machine. Background Art

[0002] As a conventional rotary electric machine, for example, the motor described in Patent Document 1 is known. The motor described in Patent Document 1 includes a stator and a rotor arranged inside the stator such that the axis of the stator coincides with the rotation center of the rotor. The stator includes a stator core and stator coils wound around a plurality of teeth. The stator core is a compressed powder core formed of a powder and granular material containing particles of a magnetic material. The stator core is integrally formed by compacting the powder and granular material at a predetermined pressure using a molding die.

[0003] The stator core includes a yoke and a plurality of teeth. The yoke is formed in a cylindrical shape. Each tooth extends inward of the yoke from the inner circumferential surface of the yoke. The plurality of teeth are formed on the inner circumferential surface of the yoke and arranged at equal intervals in the circumferential direction. A stator coil is wound around each of the plurality of teeth.

[0004] The cylindrical yoke of the stator core is divided into a plurality of parts in the circumferential direction. The stator core has a plurality of yoke pieces formed by the division. Each yoke piece includes one tooth.

[0005] The tooth includes a tooth main body formed in a quadrangular prism shape extending inward of the yoke from the inner circumferential surface of the yoke, and a tooth tip located at a tip end of the tooth main body. The tooth is formed in a substantially T-shape when viewed from the axial direction of the stator. The tooth faces the rotor. A stator coil is wound around the tooth main body. Prior Art Documents Patent Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2017-060395 [Overview of the project] [Problems that the invention aims to solve]

[0007] In recent years, there has been a demand to increase the output torque of motors in order to increase the output of equipment driven by motors. To increase the output torque of a motor equipped with a stator core with the above configuration, it is necessary to increase the magnetic flux generated by energizing the stator coil. This magnetic flux flows within the stator core.

[0008] On the other hand, especially in small motors, as the stator core is miniaturized, magnetic saturation is more likely to occur in the stator core. When magnetic saturation occurs in the stator core, the magnetic flux flowing through the stator core cannot be increased, limiting the improvement of the motor's output torque.

[0009] Therefore, the object of the present invention is to provide a magnetic core that can mitigate the occurrence of magnetic saturation, a method for manufacturing the same, a magnetic core with a coil, and a rotating electric machine. [Means for solving the problem]

[0010] A magnetic core according to one embodiment of the present invention is used in a rotating electric machine. The magnetic core comprises a core back portion having a front surface that faces a first direction toward the axis of rotation of the rotating electric machine when the magnetic core is incorporated into the rotating electric machine, and a teeth portion. The teeth portion includes a teeth body portion extending from the front surface in the first direction and a teeth tip portion provided at the tip of the teeth body portion. The teeth tip portion has a back surface facing the opposite direction to the first direction. The teeth body portion has an end surface that faces a second direction along the axis of rotation when the magnetic core is incorporated into the rotating electric machine. The end surface has a concave curved surface that smoothly connects itself to the front surface of the core back portion or the back surface of the teeth tip portion, and this curved surface is formed by a first curved surface forming portion which is part of the teeth body portion.

[0011] Conventionally, the end face of the tooth body and the front surface of the core back or the back surface of the tooth tip were connected by a plane. In this case, a corner is formed at the point where the end face of the tooth body and the front surface of the core back or the back surface of the tooth tip connect. When a magnetic core is incorporated into a rotating electric machine and current is passed through the coil wound on the tooth body, a magnetic flux is generated inside the magnetic core through the tooth body. The direction of this magnetic flux is from the tooth body towards the front surface of the core back or the back surface of the tooth tip. At this time, the flow of magnetic flux tries to take the shortest path inside the magnetic core. Conventionally, because a corner was formed at the point where the end face of the tooth body and the front surface of the core back or the back surface of the tooth tip connected, the flow of magnetic flux that tries to flow along the shortest path was obstructed by this corner, increasing the magnetic resistance in the magnetic circuit near the corner, and making it difficult for the magnetic flux to flow near the corner. As a result, localized magnetic saturation occurred at the corner.

[0012] On the other hand, with the magnetic core described above, the end face of the tooth body has a concave curved surface that smoothly connects itself to the front surface of the core back or the back surface of the tooth tip, and this curved surface is formed by a first curved surface forming portion which is part of the tooth body. Therefore, with the magnetic core described above, in the first direction, the magnetic flux can pass through the first curved surface forming portion without forming a corner as in the conventional design, and can flow along a short path. This makes it possible to lower the magnetic resistance in the magnetic circuit. As a result, the occurrence of localized magnetic saturation can be mitigated. In addition, with respect to the core back or tooth tip, the region over which the magnetic flux flows can be expanded in a direction perpendicular to the first direction. This makes it possible to effectively utilize the core back as a magnetic circuit. As a result, the output torque of a rotating electric machine equipped with the magnetic core described above can be further improved.

[0013] In the magnetic core described above, the end face of the tooth body portion includes a first flat surface which is parallel to the first direction, and the first curved surface forming portion protrudes from the first flat surface toward the second direction and may be located only on the side of the first flat surface toward the second direction.

[0014] According to the above configuration, the first curved surface forming portion is formed in the second direction without reducing the cross-sectional area of ​​the tooth body. Therefore, even if the first curved surface forming portion is formed, the saturation magnetic flux density of the magnetic flux flowing inside the tooth body does not decrease. Consequently, a decrease in the output torque of the rotating electric machine can be suppressed.

[0015] In the magnetic core described above, the tooth body portion may have a side surface that faces in the circumferential direction with respect to the rotation axis of the rotating electric machine when the magnetic core is incorporated into the rotating electric machine. In this configuration, the side surface has a concave curved surface that smoothly connects itself to the front surface of the core back portion or the back surface of the tooth tip portion, and this curved surface is formed by a second curved surface forming portion which is part of the tooth body portion.

[0016] According to the above configuration, in the circumferential direction, no angle is formed as in the conventional method, and the magnetic flux is, 2It can pass through the curved surface formation section and flow along a short path. This allows for a reduction in magnetoresistance in the magnetic circuit. As a result, the occurrence of localized magnetic saturation can be further mitigated.

[0017] In the magnetic core described above, the side surface includes a second flat surface which is parallel to the first direction, and the second curved surface forming portion protrudes from the second flat surface in the circumferential direction and may be located only on the circumferential side of the second flat surface.

[0018] According to the above configuration, a second curved surface forming portion is formed in the circumferential direction without reducing the cross-sectional area of ​​the tooth body. Therefore, even with the formation of the second curved surface forming portion, the saturation magnetic flux density of the magnetic flux flowing inside the tooth body does not decrease. Consequently, a decrease in the output torque of the rotating electrical machine can be suppressed.

[0019] In the magnetic core described above, the tooth body may have a side surface facing a third direction which becomes the circumferential direction around the axis of rotation when the magnetic core is incorporated into a rotating electric machine, and a bevel connecting the end face and the side surface. In this configuration, the bevel has a tapered curved surface that smoothly connects itself to the edge in the third direction of the curved surface, and this tapered curved surface is formed by a third curved surface forming portion which is part of the tooth body.

[0020] According to the above configuration, no corner is formed at the point where the end face and side surface of the tooth body connect on the core back side of the tooth body, allowing magnetic flux to flow more easily. This further reduces the occurrence of localized magnetic saturation.

[0021] The magnetic core described above may be a molded body formed from soft magnetic powder.

[0022] According to the above configuration, the magnetic core can be easily manufactured.

[0023] A method for manufacturing a magnetic core according to an aspect of the present invention includes a finishing step of finishing the magnetic core by polishing using spherical media, and in a step preceding the finishing step, the magnetic core is manufactured such that the radius of curvature of the curved surface of the end face is already larger than the diameter of the medium used in the finishing step.

[0024] According to the above manufacturing method, since the radius of curvature of the first curved surface is larger than the radius of the medium, the medium can contact every corner of the curved surface of the end face of the tooth body in the finishing step, and burrs formed on the curved surface of the end face of the tooth body in the step preceding the finishing step can be removed in the finishing step. This can suppress damage to the coil when the coil is wound around the tooth body after the magnetic core is completed. In addition, when an insulating film is applied to the surface of the magnetic core after the finishing step, the insulating film can be made thinner, which increases the slot space factor of the coil and improves the output efficiency of a rotary electric machine.

[0025] A method for manufacturing a magnetic core according to an aspect of the present invention includes a finishing step of finishing the magnetic core by polishing using spherical media, and in a step preceding the finishing step, the magnetic core is manufactured such that the radius of curvature of the curved surface of the side face is already larger than the diameter of the medium used in the finishing step.

[0026] According to the above manufacturing method, since the minimum value of the radius of curvature of the second curved surface is larger than the radius of the medium, the medium can contact every corner of the curved surface of the side face of the tooth body in the finishing step, and burrs formed on the curved surface of the side face of the tooth body in the step preceding the finishing step can be removed in the finishing step. This can suppress damage to the coil when the coil is wound around the tooth body after the magnetic core is completed. In addition, when an insulating film is applied to the surface of the magnetic core after the finishing step, the insulating film can be made thinner, which increases the slot space factor of the coil and improves the output efficiency of a rotary electric machine.

Effect of the Invention

[0027] According to the present invention, the occurrence of magnetic saturation can be mitigated. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] [Figure 1] FIG. 1 is an external perspective view of a brushless motor 100 in which a magnetic core 1 is used. [Figure 2] FIG. 2 is a schematic perspective view showing a partially cutaway brushless motor 100. [Figure 3] FIG. 3 is a perspective view of the magnetic core 1. [Figure 4] FIG. 4 is a cross-sectional view of the magnetic core 1 and an enlarged cross-sectional view of the vicinity of a first curved surface forming portion R11. [Figure 5] FIG. 5 is a cross-sectional view showing the state of magnetic flux flowing through a magnetic core 50 according to a comparative example, in a motor including the magnetic core 50 according to the comparative example. [Figure 6] FIG. 6 is a cross-sectional view showing the state of magnetic flux flowing through the magnetic core 1 in the brushless motor 100. [Figure 7] FIG. 7 is a cross-sectional view showing the state of magnetic flux flowing through two adjacent magnetic cores 1 in the brushless motor 100. [Figure 8] FIG. 8 is a cross-sectional view showing an example of a manufacturing process of the magnetic core 1. [Figure 9] FIG. 9 is a diagram showing the relationship between the radius of curvature CR1 of a first curved surface CS1 and the radius RA of a medium M. [Figure 10] FIG. 10 is a cross-sectional view showing the inside of a barrel B in a finishing step. [Figure 11] FIG. 11 is a perspective view of a magnetic core 1a. [Figure 12] FIG. 12 is a perspective view of a magnetic core 1b. [Figure 13] FIG. 13 is a cross-sectional view of the magnetic core 1b and an enlarged cross-sectional view of the vicinity of a second curved surface forming portion R21. [Figure 14]Figure 14 shows the relationship between the radius of curvature CR2 of the second surface CS2 and the radius RA of the media M. [Modes for carrying out the invention]

[0029] [First Embodiment] (Configuration of brushless motor 100) First, the configuration of the brushless motor 100 according to the first embodiment of the present invention will be described below with reference to the drawings. Figure 1 is an external perspective view of the brushless motor 100. Figure 2 is a schematic perspective view showing a part of the brushless motor 100 cut off.

[0030] In this specification, as an example, directions are defined as follows: The first direction DIR1 is defined as the radial direction centered on the rotation axis AR of the brushless motor 100, from the tooth tip 32 toward the rotation axis AR of the brushless motor 100. The first direction DIR1 is the direction toward the rotation axis AR of the brushless motor 100 when the magnetic core 1 is incorporated into the brushless motor 100. The second direction DIR2 is defined as the axial direction along the rotation axis AR of the brushless motor 100, in which the shaft 21 protrudes from the opening OP to the outside of the housing 15. The third direction DIR3 is defined as the circumferential direction centered on the rotation axis AR of the brushless motor 100, in relation to the second direction DIR2, which is clockwise with respect to the rotation axis AR of the brushless motor 100. The fourth direction DIR4 is defined as the opposite direction of the second direction DIR2.

[0031] As shown in Figure 2, the brushless motor 100 comprises a rotor 20, a stator 10, bearings 14, and a housing 15. In this embodiment, the brushless motor 100 is an inner rotor type. That is, the stator 10 is arranged around the rotor 20. Note that the brushless motor 100 is an example of a rotating electric machine of the present invention. Alternatively, the brushless motor 100 may be an outer rotor type. That is, the rotor 20 may be arranged around the stator 10.

[0032] Furthermore, a rotating electric machine may have a structure in which the rotor rotates using electricity. Alternatively, a rotating electric machine may have a structure in which electricity is generated by the rotation of the rotor. Rotating electric machines include brushless motors, permanent magnet synchronous motors, permanent magnet synchronous generators, and the like.

[0033] The rotor 20 includes a shaft 21 and a rotor member 22. The shaft 21 is cylindrical. The rotor member 22 is cylindrical. The central axes of the shaft 21 and the rotor member 22 coincide, and these central axes form the axis of rotation AR.

[0034] The rotor member 22 has a soft magnetic material 23 and a hard magnetic material 24. The rotor member 22 is attached to the outer circumferential surface of the shaft 21 in the radial direction around the rotation axis AR. More specifically, the soft magnetic material 23 is attached to the outer circumferential surface of the shaft 21 in the radial direction around the rotation axis AR. The hard magnetic material 24 is attached to the outer circumferential surface of the soft magnetic material 23 in the radial direction around the rotation axis AR.

[0035] Hard Magnetic material 24 is a magnetized hard magnetic material. A hard magnetic material becomes magnetized when an external magnetic field is applied to it. Even after the application of the magnetic field is stopped, the hard magnetic material does not lose its magnetization.

[0036] The bearing 14 supports the shaft 21 so that it can rotate in the circumferential direction about the rotation axis AR. More specifically, the bearing 14 has a first bearing 14a and a second bearing 14b. In this embodiment, each of the first bearing 14a and the second bearing 14b is a ball bearing. Each of the first bearing 14a and the second bearing 14b is cylindrical and extends along the rotation axis AR. The central axis of each of the first bearing 14a and the second bearing 14b is the rotation axis AR. That is, the central axes of each of the first bearing 14a and the second bearing 14b coincide with the central axis of the shaft 21. Note that each of the first bearing 14a and the second bearing 14b is not limited to a ball bearing.

[0037] The second bearing 14b is located in the fourth direction DIR4 from the first bearing 14a. The first bearing 14a is located in the second direction DIR2 from the rotor member 22. The second bearing 14b is located in the fourth direction DIR4 from the rotor member 22. The second bearing 14b supports the end of the shaft 21 with respect to the fourth direction DIR4.

[0038] The stator 10 includes a coil 13 and a magnetic core 1. In other words, in this embodiment, the magnetic core 1 is used in the stator 10. The magnetic core according to the present invention may also be used as part of the rotor.

[0039] As shown in Figure 1, the housing 15 has a first housing 15a and a second housing 15b. As shown in Figures 1 and 2, the first housing 15a is cylindrical. The central axis of the first housing 15a is the rotation axis AR. The first housing 15a is located in a second direction DIR2 relative to the second housing 15b. The first housing 15a also has an opening OP. As a result, the shaft 21 protrudes from the opening OP in the second direction DIR2. In other words, in this embodiment, the brushless motor 100 is a single-shaft type. However, the brushless motor 100 is not limited to a single-shaft type and may be a double-shaft type.

[0040] The first housing 15a supports the first bearing 14a, a plurality of magnetic cores 1, and a plurality of coils 13. The second housing 15b supports the second bearing 14b. In this embodiment, the material of the first housing 15a and the second housing 15b is SUS (Stainless Used Steel). However, the material of the first housing 15a and the second housing 15b is not limited to SUS (Stainless Used Steel), and any material with high rigidity may be used.

[0041] In this embodiment, the number of coils 13 and the number of magnetic cores 1 are both nine. In Figure 2, only representative magnetic cores 1 and coils 13 from the nine magnetic cores 1 and nine coils 13 are given reference numerals. The nine coils 13 and nine magnetic cores 1 are arranged in the circumferential direction around the rotation axis AR. The nine magnetic cores 1 are arranged around the hard magnetic material 24 with a gap between them. Note that the number of coils 13 and magnetic cores 1 are not limited to nine.

[0042] The coil 13 is made of a conductive material such as copper. The coil 13 has a structure in which the surface of the copper wire is covered with an insulating coating. Because the surface of the copper wire is covered with an insulating coating, the coil 13 and the magnetic core 1 are electrically insulated. However, at the two ends of the coil 13, the surface of the copper wire is not covered with an insulating coating, and the copper wire is exposed.

[0043] The coil 13 is supplied with current from a power source (not shown). The coil 13 generates a magnetic field when current flows through it. The magnetic core 1 is magnetized by the magnetic field generated by the hard magnetic material 24 and the magnetic field generated by the coil 13. The rotation of the rotor 20 is controlled by controlling the current supplied from the power source (not shown).

[0044] (Configuration of magnetic core 1) The configuration of the magnetic core 1 according to the first embodiment of the present invention will be described below with reference to the drawings. Figure 3 is a perspective view of the magnetic core 1. Figure 4 is a cross-sectional view of the magnetic core 1 and an enlarged cross-sectional view of the vicinity of the first curved surface forming portion R11. In Figure 3, only a representative inclined surface SL of the four inclined surfaces SL is given a reference numeral. In Figure 4, the cross-section of the magnetic core 1 is a plane that passes through the first flat surface FS1 of the first end face ES1 of the tooth body portion 31 and is perpendicular to the first flat surface FS1 of the first end face ES1 of the tooth body portion 31.

[0045] As shown in Figure 3, the magnetic core 1 comprises a core back portion 2 and a teeth portion 3. The core back portion 2 and the teeth portion 3 are included in the magnetic core 1, which is a single component. Here, a single component means a component that has a structure that cannot be separated without damage.

[0046] The magnetic core 1 is a soft magnetic material. In this embodiment, the magnetic core 1 is a molded body formed from soft magnetic powder. That is, the core back portion 2 and the teeth portion 3 are each molded bodies formed from soft magnetic powder. The material of the soft magnetic powder includes, for example, iron and a binder. The binder is, for example, a resin. The soft magnetic powder is, for example, a mixture of iron powder and epoxy resin powder, which is an example of a binder powder. Such a magnetic core 1 is manufactured, for example, by compression molding. In addition, an insulating film (not shown) is applied to the surface of the magnetic core 1 that comes into contact with another member. Note that the magnetic core 1 does not have to be a molded body formed from soft magnetic powder.

[0047] The core back portion 2 has a front surface IS2 facing the first direction DIR1, a rear surface OS2 facing the opposite direction of the first direction DIR1, two side surfaces connecting the front surface IS2 and the rear surface OS2, which are aligned in the third direction DIR3, and two end surfaces connecting the front surface IS2 and the rear surface OS2, which are aligned in the second direction DIR2. In this embodiment, each of the front surface IS2, the two side surfaces aligned in the third direction DIR3, and the two end surfaces aligned in the second direction DIR2 are planar. . back Surface OS2 is a curved surface that is convex in the direction opposite to the first direction DIR1. The back surface OS2 forms part of the outer circumferential surface of the stator 10. When the magnetic core 1 is incorporated into the brushless motor 100, the side surface connecting the front surface IS2 and the back surface OS2 is magnetically connected to the side surface connecting the front surface IS2 and the back surface OS2 of the adjacent magnetic core 1. Note that the front surface IS2, the two side surfaces aligned in the third direction DIR3, and the two end surfaces aligned in the second direction DIR2 may each include a curved surface in at least a part. In addition, the back surface OS2 may include a flat surface in at least a part.

[0048] The tooth portion 3 has a shape that extends from the core back portion 2 in the first direction DIR1. More specifically, the tooth portion 3 has a tooth body portion 31 that extends from the front surface IS2 in the first direction DIR1, and a tooth tip portion 32 provided at the tip of the tooth body portion 31. As shown in Figure 2, a coil 13 is wound around the tooth body portion 31. When the magnetic core 1 is incorporated into the brushless motor 100, the tooth tip portion 32 faces the hard magnetic material 24 of the rotor 20, with an air gap between them. In this embodiment, the position of the end of the rotor member 22 with respect to the second direction DIR2 is the tooth Tip 32 The position of the end in the second direction DIR2 is equal to the position of the end in the second direction DIR2 for the second direction DIR2. Also, the position of the end in the fourth direction DIR4 for the rotor member 22 is equal to the position of the teeth Tip 32 The position of the end in the fourth direction DIR4 is equal to the position of the end in the fourth direction DIR4. Note that the position of the end in the second direction DIR2 of the rotor member 22 is equal to the position of the teeth Tip 32 The position of the end in the second direction DIR2 does not have to be equal to the position of the end in the second direction DIR2. Also, the position of the end in the fourth direction DIR4 of the rotor member 22 is the position of the teeth Tip 32 The position of the end in the fourth direction DIR4 does not have to be equal to the position of the fourth direction DIR4 of the end.

[0049] As shown in Figure 3, the tooth tip portion 32 has a front surface IS32 facing the first direction DIR1, a back surface OS32 facing the opposite direction of the first direction DIR1, two side surfaces connecting the front surface IS32 and the back surface OS32, which are aligned in the third direction DIR3, and two end surfaces connecting the front surface IS32 and the back surface OS32, which are aligned in the second direction DIR2. In this embodiment, the back surface OS32, the two side surfaces aligned in the third direction DIR3, and the two end surfaces aligned in the second direction DIR2 are all flat. The front surface IS32 faces the first direction DIR1 The opposite directionIn this case, it is a concave curved surface. The front surface IS32 follows the outer circumferential surface of the rotor 20. The rear surface OS32, the two side surfaces aligned in the third direction DIR3, and the two end faces aligned in the second direction DIR2 may each include a curved surface. The front surface IS32 may also include a flat surface.

[0050] In this embodiment, the tooth body 31 has a shape in which each corner of a rectangular prism extending in the first direction DIR1 is chamfered. More specifically, as shown in Figure 4, the tooth body 31 has a first end face ES1 facing the second direction DIR2, a second end face ES2 facing the fourth direction DIR4, a first side surface SS1 facing the third direction DIR3, a second side surface SS2 facing the opposite direction of the third direction DIR3, and four inclined surfaces SL connecting the first end face ES1 or the second end face ES2 to the first side surface SS1 or the second side surface SS2. In this embodiment, each of the first end face ES1 and the second end face ES2 includes a first flat surface FS1 which is parallel to the first direction DIR1. Each of the first side surface SS1 and the second side surface SS2 includes a second flat surface FS2 which is parallel to the first direction DIR1. Note that the first end face ES1 and the second end face ES2 do not necessarily include a first flat surface FS1 which is parallel to the first direction DIR1. Also, the first side surface SS1 and the second side surface SS2 do not necessarily include a second flat surface FS2 which is parallel to the first direction DIR1. Furthermore, the first end face ES1 or the second end face ES2 corresponds to the "end face" of the present invention. The first side surface SS1 or the second side surface SS2 corresponds to the "side surface" of the present invention.

[0051] When the magnetic core 1 is viewed in the first direction DIR1, the outer edge of the tooth body portion 31 is surrounded by the outer edge of the core back portion 2. Also, when the magnetic core 1 is viewed in the first direction DIR1, the outer edge of the tooth body portion 31 is surrounded by the outer edge of the tooth tip portion 32. Note that the tooth body portion 31 does not necessarily have to have a shape in which each corner of a rectangular prism extending in the first direction DIR1 is chamfered.

[0052] In this embodiment, as shown in Figures 3 and 4, four first curved surface forming portions R1 are formed on the tooth body portion 31. The four first curved surface forming portions R1 are part of the tooth body portion 31. One of the four first curved surface forming portions R1 is formed at the end of the tooth body portion 31 in the first direction DIR1 and at the end of the tooth body portion 31 in the second direction DIR2. One of the four first curved surface forming portions R1 is formed at the end of the tooth body portion 31 in the opposite direction to the first direction DIR1 and at the end of the tooth body portion 31 in the second direction DIR2. One of the four first curved surface forming portions R1 is formed at the end of the tooth body portion 31 in the first direction DIR1 and at the end of the tooth body portion 31 in the fourth direction DIR4. One of the four first curved surface forming portions R1 is formed at the end of the tooth body portion 31 in the opposite direction to the first direction DIR1, and at the end of the tooth body portion 31 in the fourth direction DIR4. In this embodiment, the four first curved surface forming portions R1 have a symmetrical structure. Therefore, the description of the two first curved surface forming portions R1 formed at the ends of the tooth body portion 31 in the fourth direction DIR4 is omitted. Note that the number of first curved surface forming portions R1 does not have to be four. Also, the first curved surface forming portions R1 do not have to have a symmetrical structure.

[0053] First, we will explain the first curved surface forming portion R1, which is formed at the end of the tooth body portion 31 in the first direction DIR1 and at the end of the tooth body portion 31 in the second direction DIR2. Hereinafter, this first curved surface forming portion R1 will be referred to as the first curved surface forming portion R11.

[0054] The first curved surface forming portion R11 protrudes from the first flat surface FS1 of the first end face ES1 toward the second direction DIR2. Furthermore, the first curved surface forming portion R11 is located only on the side of the first flat surface FS1 of the first end face ES1 toward the second direction DIR2. More specifically, the first curved surface forming portion R11 has a first curved surface CS1. The first curved surface CS1 of the first curved surface forming portion R11 is concave. In this embodiment, the first curved surface CS1 of the first curved surface forming portion R11 is curved in an arc shape in a cross section perpendicular to the third direction DIR3. Furthermore, the first curved surface CS1 of the first curved surface forming portion R11 has one radius of curvature CR1. Note that the first curved surface CS1 of the first curved surface forming portion R11 does not have to be curved in an arc shape in a cross section perpendicular to the third direction DIR3. Furthermore, the first curved surface CS1 of the first curved surface forming portion R11 may have multiple radii of curvature CR1.

[0055] The first curved surface CS1 of the first curved surface forming section R11 is part of the first end surface ES1. The first curved surface CS1 of the first curved surface forming section R11 is smoothly connected to the back surface OS32 of the tooth tip 32. Therefore, the tooth body 31 is smoothly connected to the back surface OS32 of the tooth tip 32 via the first curved surface CS1 of the first curved surface forming section R11. In this embodiment, as shown in Figure 3, edges E are formed at the end of the first curved surface CS1 of the first curved surface forming section R11 in the third direction DIR3, and at the end of the first curved surface CS1 of the first curved surface forming section R11 in the opposite direction of the third direction DIR3.

[0056] Next, we will explain the first curved surface forming portion R1, which is formed at the end of the tooth body portion 31 in the direction opposite to the first direction DIR1 and at the end of the tooth body portion 31 in the second direction DIR2. Hereinafter, this first curved surface forming portion R1 will be referred to as the first curved surface forming portion R12.

[0057] As shown in Figure 4, the first curved surface forming portion R12 protrudes toward the second direction DIR2 from the first flat surface FS1 of the first end face ES1 toward the second direction DIR2. Furthermore, the first curved surface forming portion R12 is located only on the side of the second direction DIR2 from the first flat surface FS1 of the first end face ES1. More specifically, the first curved surface forming portion R12 has a first curved surface CS1. The first curved surface CS1 of the first curved surface forming portion R12 is concave. In this embodiment, the first curved surface CS1 of the first curved surface forming portion R12 is curved in an arc shape in a cross section perpendicular to the third direction DIR3. Furthermore, the first curved surface CS1 of the first curved surface forming portion R12 has one radius of curvature CR1. Note that the first curved surface CS1 of the first curved surface forming portion R12 does not have to be curved in an arc shape in a cross section perpendicular to the third direction DIR3. Furthermore, the first curved surface CS1 of the first curved surface forming portion R12 may have multiple radii of curvature CR1.

[0058] The first curved surface CS1 of the first curved surface forming section R12 is part of the first end surface ES1. The first curved surface CS1 of the first curved surface forming section R12 is smoothly connected to the front surface IS2 of the core back section 2. Therefore, the teeth body section 31 is smoothly connected to the front surface IS2 of the core back section 2 via the first curved surface CS1 of the first curved surface forming section R12. In this embodiment, edges E are formed at the end of the first curved surface CS1 of the first curved surface forming section R12 in the third direction DIR3, and at the end of the first curved surface CS1 of the first curved surface forming section R12 in the opposite direction of the third direction DIR3.

[0059] The magnetic core 1 can mitigate the occurrence of magnetic saturation. As a comparative example, a magnetic core 50 in which the first curved surface forming portion R1 is not formed on the tooth body portion 31 will be described with reference to the drawings. Figure 5 is a cross-sectional view showing the magnetic flux flowing through the magnetic core 50 in a motor equipped with the magnetic core 50 according to the comparative example. In Figure 5, only representative magnetic field lines MFLs among the multiple magnetic field lines MFLs are given reference numerals. Also, in Figure 5, for explanatory purposes, the boundary line between the tooth body portion 31 and the core back portion 2, and the boundary line between the tooth body portion 31 and the tooth tip portion 32 have been omitted.

[0060] In the brushless motor 100, when current is applied to the coil 13 wound around the tooth body 31, a magnetic flux is generated in the tooth body 31. This magnetic flux flows from the tooth body 31 toward the front surface IS2 of the core back portion 2 or the back surface OS32 of the tooth tip portion 32. By changing the direction of the current flowing through the coil 13, the direction of the magnetic flux can be changed. At this time, the magnetic flux attempts to flow along the shortest path inside the magnetic core 50 according to the comparative example. In the magnetic core 50 according to the comparative example, the first end surface ES1 of the tooth body 31, the front surface IS2 of the core back portion 2, and the back surface OS32 of the tooth tip portion 32 32 An angle A was formed at the point where each of them connected to the other.

[0061] In the comparative example's magnetic core 50, the flow of magnetic flux was obstructed by angle A, forcing the flux to detour near angle A, making it difficult to flow. As a result, residual stress was generated near angle A, increasing the magnetic resistance in the magnetic circuit, and causing localized magnetic saturation at angle A. Consequently, when the comparative example's magnetic core 50 was used in a motor, the motor's output torque could not be improved.

[0062] Next, the magnetic core 1 will be described with reference to the drawings. Figure 6 is a cross-sectional view showing the magnetic flux flowing through the magnetic core 1 in the brushless motor 100. In Figure 6, for illustrative purposes, the boundary lines between the tooth body 31 and the core back 2, and the boundary lines between the tooth body 31 and the tooth tip 32 have been omitted. Also, in Figure 6, only representative magnetic field lines MFLs among the multiple magnetic field lines MFLs are given reference numerals.

[0063] In the magnetic core 1, the tooth body portion 31 has a first curved surface forming portion R11 having a concave curved first curved surface CS1. The first curved surface CS1 of the first curved surface forming portion R11 is smoothly connected to the back surface OS32 of the tooth tip portion 32. As shown in Figure 6, because the first curved surface forming portion R11 is formed on the tooth body portion 31, the magnetic flux can flow in the vicinity of the first curved surface forming portion R11 without detouring, taking the shortest path. Therefore, in the magnetic core 1, the magnetic flux flows more easily in the vicinity of the first curved surface forming portion R11 compared to the magnetic core 50 of the comparative example. This makes it possible to mitigate the occurrence of magnetic saturation in the vicinity of the first curved surface forming portion R11.

[0064] Furthermore, because the first curved surface forming portion R11 is formed on the tooth body portion 31, the magnetic core 1 can better receive magnetic flux generated by the hard magnetic material 24 that includes components in the second direction DIR2 or the fourth direction DIR4. This effect becomes more pronounced the longer the distance in the second direction DIR2 between the end of the rotor member 22 with respect to the second direction DIR2 and the end of the tooth body portion 31 with respect to the second direction DIR2, or the longer the distance in the fourth direction DIR4 between the end of the rotor member 22 with respect to the second direction DIR4 and the end of the tooth body portion 31 with respect to the second direction DIR4, or the longer the distance in the fourth direction DIR4 between the end of the rotor member 22 with respect to the fourth direction DIR4 and the end of the tooth body portion 31 with respect to the fourth direction DIR4.

[0065] Because the first curved surface CS1 of the first curved surface forming section R11 is concave, more coils 13 can be wound around the tooth body section 31 compared to when the first curved surface CS1 of the first curved surface forming section R11 is convex. This increases the slot occupancy ratio of the coils 13 and improves the output torque of the brushless motor 100.

[0066] Furthermore, in the magnetic core 1, the first curved surface forming portion R11 protrudes from the first flat surface FS1 of the first end face ES1 toward the second direction DIR2 in the second direction DIR2, and is located only on the side of the first flat surface FS1 of the first end face ES1 toward the second direction DIR2. In other words, the first curved surface forming portion R11 is formed in the second direction DIR2 without reducing the cross-sectional area of ​​the tooth body portion 31. Therefore, even if the first curved surface forming portion R11 is formed, the saturation magnetic flux density of the magnetic flux flowing inside the tooth body portion 31 does not decrease. Consequently, a decrease in the output torque of the brushless motor 100 can be suppressed.

[0067] In the magnetic core 1, the tooth body portion 31 has a first curved surface forming portion R12 having a concave curved first curved surface CS1. The first curved surface CS1 of the first curved surface forming portion R12 is smoothly connected to the front surface IS2 of the core back portion 2. Because the first curved surface forming portion R12 is formed on the tooth body portion 31, magnetic flux can flow in the vicinity of the first curved surface forming portion R12 without having to detour. Therefore, in the magnetic core 1, magnetic flux flows more easily in the vicinity of the first curved surface forming portion R12 compared to the magnetic core 50 according to the comparative example. As a result, the occurrence of magnetic saturation in the vicinity of the first curved surface forming portion R12 can be mitigated.

[0068] Because the first curved surface CS1 of the first curved surface forming section R12 is concave, more coils 13 can be wound around the tooth body section 31 compared to when the first curved surface CS1 of the first curved surface forming section R12 is convex. This increases the slot occupancy ratio of the coils 13 and improves the output torque of the brushless motor 100.

[0069] Because the first curved surface forming portion R12 is formed on the tooth body portion 31, the region over which magnetic flux flows in the core back portion 2 in a direction perpendicular to the first direction DIR1 can be expanded. More specifically, when the magnetic core 1 is incorporated into the brushless motor 100, adjacent magnetic cores 1 are connected by their respective core back portions 2. Hereinafter, one of these adjacent magnetic cores 1 will be referred to as magnetic core 11, and the other as magnetic core 12.

[0070] When the magnetic flux generated in the tooth body portion 31 of the magnetic core 11 by energizing the coil 13 wound around the tooth body portion 31 of the magnetic core 11 flows from the tooth body portion 31 of the magnetic core 11 toward the front surface IS2 of the core back portion 2 of the magnetic core 11, a magnetic flux is formed in the direction toward the core back portion 2 of the magnetic core 11 toward the core back portion 2 of the magnetic core 12 (third direction DIR3).

[0071] While magnetic flux tends to flow along the shortest path, a repulsive force acts between multiple magnetic fluxes, causing it to spread in directions perpendicular to the first direction DIR1 and the third direction DIR3 (the second direction DIR2 and the fourth direction DIR4). In the comparative example magnetic core 50, because the first curved surface forming portion R1 was not formed on the core back portion 2 side of the tooth body portion 31, an angle A was formed where the first end face ES1 of the tooth body portion 31 and the front surface IS2 of the core back portion 2 connected. This angle A hindered the flow of magnetic flux that tended to spread in the second direction DIR2 and the fourth direction DIR4, preventing the core back portion 2 from expanding the region through which magnetic flux flows in the second direction DIR2 and the fourth direction DIR4, and thus preventing the core back portion 2 from being effectively utilized as a magnetic circuit. The inability to expand the region through which magnetic flux flows leads to an increase in magnetic resistance in the magnetic circuit, which was a factor in reducing the output efficiency of the motor when the comparative example magnetic core 50 was used in a motor.

[0072] Next, the magnetic core 1 will be explained with reference to the drawings. Figure 7 is a cross-sectional view showing the magnetic flux flowing through two adjacent magnetic cores 1 in the brushless motor 100. In Figure 7, only representative magnetic field lines MFLs among the multiple magnetic field lines MFLs are given reference numerals.

[0073] In the magnetic core 11, the formation of a first curved surface portion R12 on the tooth body portion 31 allows the magnetic flux to spread more easily in the second direction DIR2 without being obstructed by corners near the first curved surface portion R12. Similarly, in the magnetic core 12, the formation of a first curved surface portion R12 on the tooth body portion 31 allows the magnetic flux to spread more easily in the second direction DIR2 without being obstructed by corners near the first curved surface portion R12. In other words, in the magnetic core 11, magnetic flux can more easily flow out toward the magnetic core 12, and in the magnetic core 12, magnetic flux can more easily enter from the magnetic core 11. This makes it possible to suppress an increase in magnetic resistance in the magnetic circuit. Therefore, it is possible to suppress a decrease in the output efficiency of the brushless motor 100.

[0074] Furthermore, in the magnetic core 1, the first curved surface forming portion R12 protrudes from the first flat surface FS1 of the first end face ES1 toward the second direction DIR2 in the second direction DIR2, and is located only on the side of the first flat surface FS1 of the first end face ES1 toward the second direction DIR2. In other words, the first curved surface forming portion R12 is formed in the second direction DIR2 without reducing the cross-sectional area of ​​the tooth body portion 31. Therefore, even if the first curved surface forming portion R12 is formed, the saturation magnetic flux density of the magnetic flux flowing inside the tooth body portion 31 does not decrease. Consequently, a decrease in the output torque of the brushless motor 100 can be suppressed.

[0075] (Manufacturing method for magnetic core 1) The following describes a method for manufacturing a magnetic core 1 according to a first embodiment of the present invention, with reference to the drawings. Figure 8 is a cross-sectional view showing an example of the manufacturing process of the magnetic core 1. Figure 9 is a diagram showing the relationship between the radius of curvature CR1 of the first curved surface CS1 and the radius RA of the media M. In Figure 9, only a representative first curved surface CS1 out of the four first curved surfaces CS1 is given a reference numeral. Figure 10 is a cross-sectional view showing the inside of the barrel B during the finishing process.

[0076] As shown in Figure 8, first, soft magnetic powder SMP, a mixture of iron powder and epoxy resin powder, is filled into the mold DI. Next, the soft magnetic powder SMP filled into the mold DI is pressed by a punch P to compress and mold the soft magnetic powder SMP. The punch P has a convex surface CON that curves in a convex shape. In this embodiment, there are four convex surfaces CON. As a result, when the soft magnetic powder SMP is compressed and molded, four first curved surface forming portions R1 are formed on the tooth body portion 31. At this point, burrs are formed on the surface of the compressed and molded soft magnetic powder SMP due to the existence of a minute gap between the mold DI and the punch P, and the rough surface of the punch P. As shown in Figure 9, the radius of curvature CR1 of the first curved surface CS1 of the compressed and molded soft magnetic powder SMP is greater than the radius RA of the media M. If the first curved surface CS1 of the compressed and molded soft magnetic powder SMP has multiple radii of curvature CR1, it is sufficient that the minimum value of the multiple radii of curvature CR1 is greater than the radius RA of the media M.

[0077] In this manufacturing method, after compression molding of soft magnetic powder SMP, a finishing process is performed in which the magnetic core 1 is finished by polishing. As shown in Figure 10, in the finishing process, first, the compressed soft magnetic powder SMP, media M, polishing aid (not shown), and water W are placed inside a hollow barrel B. The media M has a spherical shape with radius RA. In this embodiment, there is one of each compressed soft magnetic powder SMP and media M, but the number of each compressed soft magnetic powder SMP and media M may be multiple. When there are multiple media M, the magnetic core 1 can be finished efficiently. When there are multiple compressed soft magnetic powder SMP, multiple magnetic cores 1 can be finished simultaneously.

[0078] In the finishing process, the media M is applied to the compression-molded soft magnetic powder SMP by rotating the barrel B, thereby polishing the compression-molded soft magnetic powder SMP. In the finishing process, the burrs formed on the surface of the compression-molded soft magnetic powder SMP in the preceding stage are removed by polishing the compression-molded soft magnetic powder SMP with the media M, thereby finishing the magnetic core 1. Note that in the finishing process, the method of polishing the compression-molded soft magnetic powder SMP with the media M is not limited to rotating the barrel B; it may also be done by vibrating the barrel B. Furthermore, the barrel B is not essential in the finishing process; it is sufficient to polish the compression-molded soft magnetic powder SMP with the media M. Similarly, the polishing aid and water W are not essential in the finishing process.

[0079] The magnetic core 1 is a molded body formed from soft magnetic powder. Therefore, compared to the case where the magnetic core is formed by laminating electromagnetic steel sheets, the first curved surface forming portion R1 can be easily formed as shown in the manufacturing method of the magnetic core 1 described above. As a result, the magnetic core 1 can be easily manufactured.

[0080] According to the manufacturing method of the magnetic core 1, burrs formed on the first curved surface CS1 before the finishing process can be removed in the finishing process. More specifically, the radius of curvature CR1 of the first curved surface CS1 of the compression-molded soft magnetic powder SMP is larger than the radius RA of the media M. As a result, in the finishing process, the media M can make contact with every corner of the first curved surface CS1, and burrs formed on the first curved surface CS1 in the preceding stage of the finishing process can be removed in the finishing process. This makes it possible to suppress damage to the coil 13 when the coil 13 is wound around the tooth body 31 after the completion of the magnetic core 1.

[0081] Furthermore, as shown in the magnetic core 1 above, when an insulating film is applied to the surface of the magnetic core 1 after the finishing process, the absence of burrs allows the insulating film to be made thinner. This increases the slot occupancy rate of the coil 13 and improves the output efficiency of the brushless motor 100.

[0082] [First variation] (Configuration of magnetic core 1a) The configuration of the magnetic core 1a according to the first modified example of the present invention will be described below with reference to the drawings. Figure 11 is a perspective view of the magnetic core 1a. In Figure 11, reference numerals are given only to representative first curved surface forming portions R1 and first curved surfaces CS1 from among the four first curved surface forming portions R1 and four first curved surfaces CS1, respectively. Furthermore, only the parts of the magnetic core 1a according to the first modified example that differ from the magnetic core 1 according to the first embodiment will be described, and the rest will be omitted.

[0083] As shown in Figure 11, the magnetic core 1a differs from the magnetic core 1 in that four third curved surface forming portions R3 are formed on the tooth body portion 31.

[0084] The four third curved surface forming portions R3 are part of the tooth body portion 31. One of the four third curved surface forming portions R3 is formed at the end of the tooth body portion 31 in the opposite direction to the third direction DIR3 and at the end of the tooth body portion 31 in the second direction DIR2. One of the four third curved surface forming portions R3 is formed at the end of the tooth body portion 31 in the opposite direction to the third direction DIR3 and at the end of the tooth body portion 31 in the fourth direction DIR4. One of the four third curved surface forming portions R3 is formed at the end of the tooth body portion 31 in the third direction DIR3 and at the end of the tooth body portion 31 in the second direction DIR2. One of the four third curved surface forming portions R3 is formed at the end of the tooth body portion 31 in the third direction DIR3 and at the end of the tooth body portion 31 in the fourth direction DIR4. In this modified example, the four third curved surface forming portions R3 have a symmetrical structure. Furthermore, the number of third curved surface forming sections R3 does not have to be four. Also, the third curved surface forming sections R3 do not have to have a symmetrical structure.

[0085] Each of the four third surface forming sections R3 has a third surface CS3. Each of the four third surface forming sections R3's third surface CS3 is a part of each of the four slopes SL. Each of the four third surface forming sections R3's third surface CS3 tapers. More specifically, each of the four third surface forming sections R3's third surface CS3 tapers towards the core back section 2 on the tooth body section 31 side as it approaches the core back section 2. Also, each of the four third surface forming sections R3's third surface CS3 tapers towards the tooth tip section 32 on the tooth body section 31 side as it approaches the tooth tip section 32. The third surface CS3 smoothly connects to the edge E in the third direction DIR3 of the first surface CS1.

[0086] The magnetic core 1a described above also produces the same effect as the magnetic core 1. Furthermore, in the magnetic core 1a, the third curved surface forming portion R3 is formed on the tooth body portion 31, which affects the core back of the tooth body portion 31. Part 2On the side or the tooth tip portion 32 side, at the point where the first end face ES1 or the second end face ES2 of the tooth body portion 31 connects with the first side portion SS1 or the second side portion SS2, the flow of magnetic flux is not obstructed by the corner and flows more easily. This further reduces the occurrence of localized magnetic saturation.

[0087] [Second variation] (Configuration of magnetic core 1b) The configuration of the magnetic core 1b according to the second modified example of the present invention will be described below with reference to the drawings. Figure 12 is a perspective view of the magnetic core 1b. Figure 13 is a cross-sectional view of the magnetic core 1b and an enlarged cross-sectional view of the vicinity of the second curved surface forming portion R21. The cross-section of the magnetic core 1b in Figure 13 is a plane that passes through the second flat surface FS2 of the second side surface SS2 of the tooth body portion 31 and is perpendicular to the second flat surface FS2 of the second side surface SS2 of the tooth body portion 31. Figure 14 is a diagram showing the relationship between the radius of curvature CR2 of the second curved surface CS2 and the radius RA of the media M. In Figure 14, only the representative second curved surface CS2 of the four second curved surfaces CS2 are given reference numerals. Furthermore, only the parts of the magnetic core 1b according to the second modified example that differ from the magnetic core 1a according to the first modified example will be described, and the rest will be omitted.

[0088] As shown in Figures 12 and 13, the magnetic core 1b differs from the magnetic core 1a in that four second curved surface forming portions R2 are formed on the tooth body portion 31.

[0089] The four second curved surface forming portions R2 are part of the tooth body portion 31. One of the four second curved surface forming portions R2 is formed at the end of the tooth body portion 31 in the first direction DIR1 and at the end of the tooth body portion 31 in the opposite direction to the third direction DIR3. One of the four second curved surface forming portions R2 is formed at the end of the tooth body portion 31 in the opposite direction to the first direction DIR1 and at the end of the tooth body portion 31 in the opposite direction to the third direction DIR3. One of the four second curved surface forming portions R2 is formed at the end of the tooth body portion 31 in the first direction DIR1 and at the end of the tooth body portion 31 in the third direction DIR3. One of the four second curved surface forming portions R2 is formed at the end of the tooth body portion 31 in the opposite direction to the first direction DIR1 and at the end of the tooth body portion 31 in the third direction DIR3. In this modified example, the four second curved surface forming portions R2 have a symmetrical structure. Therefore, the description of the two second curved surface forming portions R2 formed at the ends of the tooth body portion 31 in the third direction DIR3 is omitted. Note that the number of second curved surface forming portions R2 does not have to be four. Also, the second curved surface forming portions R2 do not have to have a symmetrical structure.

[0090] First, we will explain the second curved surface forming portion R2, which is formed at the end of the tooth body portion 31 in the first direction DIR1 and at the end of the tooth body portion 31 in the opposite direction to the third direction DIR3. Hereinafter, this second curved surface forming portion R2 will be referred to as the second curved surface forming portion R21.

[0091] The second curved surface forming portion R21 protrudes from the second flat surface FS2 of the second side surface SS2 in the direction opposite to the third direction DIR3, in the direction opposite to the third direction DIR3. Furthermore, the second curved surface forming portion R21 is located only on the side of the second flat surface FS2 of the second side surface SS2 that is opposite to the third direction DIR3. More specifically, the second curved surface forming portion R21 has a second curved surface CS2. The second curved surface CS2 of the second curved surface forming portion R21 is curved in a concave shape. In this modified example, the second curved surface CS2 of the second curved surface forming portion R21 is curved in an arc shape in a cross section perpendicular to the second direction DIR2. Furthermore, the second curved surface CS2 of the second curved surface forming portion R21 has one radius of curvature CR2. Note that the second curved surface CS2 of the second curved surface forming portion R21 does not have to be curved in an arc shape in a cross section perpendicular to the second direction DIR2. Furthermore, the second curved surface CS2 of the second curved surface forming portion R21 may have multiple radii of curvature CR2.

[0092] The second curved surface CS2 of the second curved surface forming section R21 is part of the second side surface SS2. The second curved surface CS2 of the second curved surface forming section R21 smoothly connects to the back surface OS32 of the tooth tip 32. Therefore, the tooth body 31 connects to the back surface OS32 of the tooth tip 32 via the second curved surface CS2 of the second curved surface forming section R21. Smoothly They are connected.

[0093] Next, we will explain the second curved surface forming portion R2, which is formed at the end of the tooth body portion 31 in the opposite direction to the first direction DIR1 and at the end of the tooth body portion 31 in the opposite direction to the third direction DIR3. Hereinafter, this second curved surface forming portion R2 will be referred to as the second curved surface forming portion R22.

[0094] The second curved surface forming portion R22 protrudes in the opposite direction of the third direction DIR3 from the second flat surface FS2 of the second side surface SS2. Furthermore, the second curved surface forming portion R22 is located only on the side of the second flat surface FS2 of the second side surface SS2 that is opposite to the third direction DIR3. More specifically, the second curved surface forming portion R22 has a second curved surface CS2. The second curved surface CS2 of the second curved surface forming portion R22 is curved in a concave shape. In this modified example, the second curved surface CS2 of the second curved surface forming portion R22 is curved in an arc shape in a cross section perpendicular to the second direction DIR2. R22 The second curved surface CS2 of the second curved surface forming section R22 has one radius of curvature CR2. The second curved surface CS2 of the second curved surface forming section R22 does not necessarily have to be curved in an arc shape in a cross section perpendicular to the second direction DIR2. Furthermore, the second curved surface CS2 of the second curved surface forming section R22 may have multiple radii of curvature CR2.

[0095] The second curved surface CS2 of the second curved surface forming section R22 is part of the second side surface SS2. The second curved surface CS2 of the second curved surface forming section R22 is smoothly connected to the front surface IS2 of the core back section 2. Therefore, the tooth body section 31 is smoothly connected to the front surface IS2 of the core back section 2 via the second curved surface CS2 of the second curved surface forming section R22.

[0096] The method for manufacturing the magnetic core 1b according to this modified example is the same as the method for manufacturing the magnetic core 1 according to the first embodiment. However, as shown in Figure 14, the radius of curvature CR2 of the second curved surface CS2 of the compression-molded soft magnetic powder SMP is greater than the radius RA of the media M. If the second curved surface CS2 of the compression-molded soft magnetic powder SMP has multiple radii of curvature CR2, it is sufficient that the minimum value of the multiple radii of curvature CR2 is greater than the radius RA of the media M.

[0097] The magnetic core 1b described above also produces the same effect as the magnetic core 1a. Furthermore, in the magnetic core 1b, a second curved surface forming portion R21 having a concave curved second curved surface CS2 is formed on the tooth body portion 31. The second curved surface CS2 of the second curved surface forming portion R21 is smoothly connected to the back surface OS32 of the tooth tip portion 32. Because the second curved surface forming portion R21 is formed on the tooth body portion 31, the magnetic flux can flow in the vicinity of the second curved surface forming portion R21 without detouring, taking the shortest path. Therefore, in the magnetic core 1b, the magnetic flux flows more easily in the vicinity of the second curved surface forming portion R21 compared to the magnetic core 50 of the comparative example. As a result, the occurrence of magnetic saturation in the vicinity of the second curved surface forming portion R21 can be mitigated.

[0098] Because the second curved surface CS2 of the second curved surface forming section R21 is concave, more coils 13 can be wound around the tooth body section 31 compared to when the second curved surface CS2 of the second curved surface forming section R21 is convex. This increases the slot occupancy ratio of the coils 13 and improves the output torque of the brushless motor 100.

[0099] Furthermore, in the magnetic core 1b, the second curved surface forming portion R21 protrudes from the second flat surface FS2 of the second side surface SS2 in the opposite direction of the third direction DIR3, and is located only on the side of the second flat surface FS2 of the second side surface SS2 in the opposite direction of the third direction DIR3. In other words, the second curved surface forming portion R21 is formed without reducing the cross-sectional area of ​​the tooth body portion 31 in the opposite direction of the third direction DIR3. Therefore, even if the second curved surface forming portion R21 is formed, the saturation magnetic flux density of the magnetic flux flowing inside the tooth body portion 31 does not decrease. Consequently, a decrease in the output torque of the brushless motor 100 can be suppressed.

[0100] In the magnetic core 1b, a second curved surface forming portion R22 is formed on the tooth body portion 31, which has a concave curved second curved surface CS2. The second curved surface CS2 of the second curved surface forming portion R22 is smoothly connected to the front surface IS2 of the core back portion 2. Because the second curved surface forming portion R22 is formed on the tooth body portion 31, magnetic flux can flow in the vicinity of the second curved surface forming portion R22 without having to detour. Therefore, in the magnetic core 1b, magnetic flux flows more easily in the vicinity of the second curved surface forming portion R22 compared to the magnetic core 50 according to the comparative example. As a result, the occurrence of magnetic saturation in the vicinity of the second curved surface forming portion R22 can be mitigated.

[0101] Because the second curved surface CS2 of the second curved surface forming section R22 is concave, more coils 13 can be wound around the tooth body section 31 compared to when the second curved surface CS2 of the second curved surface forming section R22 is convex. This increases the slot occupancy ratio of the coils 13 and improves the output torque of the brushless motor 100.

[0102] According to the manufacturing method of the magnetic core 1b, burrs formed on the second curved surface CS2 before the finishing process can be removed in the finishing process. More specifically, the radius of curvature CR2 of the second curved surface CS2 of the compression-molded soft magnetic powder SMP is larger than the radius RA of the media M. This allows the media M to make contact with every corner of the second curved surface CS2 during the finishing process, and burrs formed on the second curved surface CS2 in the preceding stage of the finishing process can be removed in the finishing process. This makes it possible to suppress damage to the coil 13 when the coil 13 is wound around the tooth body 31 after the completion of the magnetic core 1b.

[0103] [Other embodiments] The magnetic core according to the present invention is not limited to magnetic core 1, magnetic core 1a, or magnetic core 1b, but can be modified within the scope of its gist. Furthermore, the structures of magnetic core 1, magnetic core 1a, or magnetic core 1b may be arbitrarily combined.

[0104] The rotating electric machine only needs to be equipped with a magnetic core 1, a magnetic core 1a, or a magnetic core 1b, and may also be equipped with brushes.

[0105] The present invention has the following configuration.

[0106] (1) A magnetic core used in rotating electrical machinery, A core back portion having a front surface that faces a first direction toward the rotation axis of the rotating electric machine when the magnetic core is incorporated into the rotating electric machine, Teeth section, Equipped with, The aforementioned teeth portion is, The tooth body portion extends from the front surface in the first direction, The tooth tip portion provided at the tip of the tooth body portion, Includes, The tip of the tooth has a back surface facing the opposite direction to the first direction, The tooth body portion has an end face that faces a second direction along the rotation axis when the magnetic core is incorporated into the rotating electric machine, The end face has a concave curved surface that smoothly connects itself to the front surface of the core back portion or the back surface of the tooth tip portion, and this curved surface is formed by a first curved surface forming portion which is part of the tooth body portion. Magnetic core.

[0107] (2) The end face includes a first flat surface which is a surface parallel to the first direction, The first curved surface forming portion protrudes from the first flat surface toward the second direction and is located only on the side of the first flat surface toward the second direction. (1) The magnetic core described above.

[0108] (3) The tooth body portion has a side surface that faces in the circumferential direction with respect to the rotation axis when the magnetic core is incorporated into the rotating electric machine, The aforementioned side surface has a concave curved surface that smoothly connects itself to the front surface of the core back portion or the back surface of the tooth tip portion, and this curved surface is formed by a second curved surface forming portion which is part of the tooth body portion. A magnetic core as described in (1) or (2).

[0109] (4) The aforementioned side surface includes a second flat surface which is a surface parallel to the first direction, The second curved surface forming portion protrudes from the second flat surface in the circumferential direction and is located only on the circumferential side of the second flat surface. (3) The magnetic core described above.

[0110] (5) The tooth body portion has a side surface facing a third direction which becomes the circumferential direction around the rotation axis when the magnetic core is incorporated into the rotating electric machine, and a slope connecting the end face and the side surface. The inclined surface has a tapered curved surface that smoothly connects itself to the edge of the curved surface in the third direction, and the tapered curved surface is formed by a third curved surface forming portion which is part of the tooth body portion. A magnetic core as described in any of (1) to (4).

[0111] (6) It is a molded body formed from soft magnetic powder. A magnetic core as described in any of (1) to (5).

[0112] (7) A magnetic core as described in any of (1) to (6), The coil wound around the main body of the teeth, Equipped with, Magnetic core with coil.

[0113] (8) (1) to (6) comprising a magnetic core as described in any of the above, Rotating electrical machinery.

[0114] (9) (1) to (6) The magnetic core is finished by polishing using a spherical medium, including a finishing step In the step prior to the finishing process, the magnetic core is manufactured such that the radius of curvature of the curved surface of the end face is already larger than the diameter of the media used in the finishing process. A method for manufacturing a magnetic core.

[0115] (10) (3) or (4) includes a finishing step of finishing the magnetic core by polishing with a spherical media, In a step prior to the finishing process, the magnetic core is manufactured such that the radius of curvature of the curved surface on its side is already larger than the diameter of the medium used in the finishing process. A method for manufacturing a magnetic core. [Explanation of symbols]

[0116] 1,11,12,1a,1b: Magnetic core 2: Core back section 3: Teeth section 10: Status 13: Coil 14: Bearings 14a: First bearing 14b: Second bearing 15: Cabinet 15a: First enclosure 15b: Second cabinet 20: Rotor 21: Shaft 22: Rotor component 23: Soft magnetic material 24:Hard magnetic material 31: Teeth main body 32: Tip of the tooth 100: Brushless motor A: Corner B: Barrel CON: Convex CR1,CR2: radius of curvature CS1: 1st surface CS2: 2nd surface CS3: 3rd surface DI: Type DIR1: 1st direction DIR2:Second direction DIR3: Third direction DIR4: Fourth direction ES1: 1st end surface ES2: 2nd end face FS1: 1st flat surface FS2: 2nd flat surface IS2, IS32: Front M: Media MFL: Magnetic field lines OP: Opening OS2, OS32: Back P: Punch R1, R11, R12: First curved surface forming part R2, R21, R22: Second curved surface forming part R3: Third curved surface forming part RA: radius SMP: Soft magnetic powder SS1: First side SS2: Second side SL: Slope W:Water

Claims

1. A magnetic core used in rotating electrical machinery, which is a compressed molded body of soft magnetic powder, A core back portion having a front surface that faces a first direction toward the rotation axis of the rotating electric machine when the magnetic core is incorporated into the rotating electric machine, Teeth section, Equipped with, The aforementioned teeth portion is, The tooth body portion extends from the front surface in the first direction, The tooth tip portion provided at the tip of the tooth body portion, Includes, The tip of the tooth has a back surface facing the opposite direction to the first direction, The aforementioned tooth body is, The end face that faces a second direction along the axis of rotation when the magnetic core is incorporated into the rotating electric machine, When the magnetic core is incorporated into the rotating electric machine, the side that faces the circumferential direction with respect to the rotation axis, A slope connecting the end face and the side surface, It has, The end face has a concave curved surface that smoothly connects itself to the front surface of the core back portion and the back surface of the tooth tip portion, and this curved surface is formed by a first curved surface forming portion which is part of the tooth body portion, and is smoothly connected to the slope. Magnetic core.

2. A magnetic core according to claim 1, The coil wound around the main body of the teeth, Equipped with, Magnetic core with coil.

3. A magnetic core as described in claim 1, Rotating electrical machinery.

4. A method for manufacturing a magnetic core used in a rotating electric machine, The magnetic core is A core back portion having a front surface that faces a first direction toward the rotation axis of the rotating electric machine when the magnetic core is incorporated into the rotating electric machine, Teeth section, Equipped with, The aforementioned teeth portion is, The tooth body portion extends from the front surface in the first direction, The tooth tip portion provided at the tip of the tooth body portion, Includes, The tip of the tooth has a back surface facing the opposite direction to the first direction, The tooth body portion has an end face that faces a second direction along the rotation axis when the magnetic core is incorporated into the rotating electric machine, The end face has a concave curved surface that smoothly connects itself to the front surface of the core back portion and the back surface of the tooth tip portion, and this curved surface is formed by a first curved surface forming portion which is part of the tooth body portion. The process includes finishing the magnetic core by polishing using a spherical media, In the step prior to the finishing process, the magnetic core is manufactured such that the radius of curvature of the curved surface of the end face is already larger than the diameter of the media used in the finishing process. A method for manufacturing a magnetic core.

5. The end face includes a first flat surface which is a surface parallel to the first direction, The first curved surface forming portion protrudes from the first flat surface toward the second direction and is located only on the side of the first flat surface toward the second direction. A method for manufacturing a magnetic core according to claim 4.

6. A method for manufacturing a magnetic core used in a rotating electric machine, The magnetic core is A core back portion having a front surface that faces a first direction toward the rotation axis of the rotating electric machine when the magnetic core is incorporated into the rotating electric machine, Teeth section, Equipped with, The aforementioned teeth portion is, The tooth body portion extends from the front surface in the first direction, The tooth tip portion provided at the tip of the tooth body portion, Includes, The tip of the tooth has a back surface facing the opposite direction to the first direction, The tooth body portion has an end face that faces a second direction along the rotation axis when the magnetic core is incorporated into the rotating electric machine, The end face has a concave curved surface that smoothly connects itself to the front surface of the core back portion and the back surface of the tooth tip portion, and this curved surface is formed by a first curved surface forming portion which is part of the tooth body portion. The tooth body portion has a side surface that faces in the circumferential direction with respect to the rotation axis when the magnetic core is incorporated into the rotating electric machine, The aforementioned side surface has a concave curved surface that smoothly connects itself to the front surface of the core back portion or the back surface of the tooth tip portion, and this curved surface is formed by a second curved surface forming portion which is part of the tooth body portion. The process includes finishing the magnetic core by polishing using a spherical media, In a step prior to the finishing process, the magnetic core is manufactured such that the radius of curvature of the curved surface on its side is already larger than the diameter of the medium used in the finishing process. A method for manufacturing a magnetic core.

7. The end face includes a first flat surface which is a surface parallel to the first direction, The first curved surface forming portion protrudes from the first flat surface toward the second direction and is located only on the side of the first flat surface toward the second direction. A method for manufacturing a magnetic core according to claim 6.

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