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

Abstract

The invention provides a magnetic core, a manufacturing method thereof, a magnetic core with a coil, and a rotary electric machine. The magnetic core includes: a core back portion having a front surface facing a first direction when the magnetic core is assembled in a rotating electrical machine, the first direction facing a rotation axis of the rotating electrical machine; and a tooth portion. The tooth portion includes: a tooth body portion extending in a first direction from a front surface; and a tooth tip section provided at the tip of the tooth body section. The tooth tip portion has a back surface facing in a direction opposite to the first direction. The tooth main body has an end surface, and the end surface faces in a second direction along the end surface rotation axis when the magnetic core is assembled in the rotating electrical machine. The end surface 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 portion, and the curved surface is formed by a first curved surface forming portion that is a part of the tooth body portion.

Description

Technical Field

[0001] The present invention relates to a technology for alleviating the occurrence of magnetic saturation in a rotating electrical machine. Background Art

[0002] As an existing rotating electrical machine, for example, a motor described in Patent Document 1 is known. The motor described in Patent Document 1 includes: a stator; and a rotor, which is arranged inside the stator and makes the rotation center coincide with the axis of the stator. The stator includes: a stator core; and a stator coil wound around a plurality of teeth. The stator core is a powder core composed of a powder body containing magnetic material particles. The stator core is formed in one piece by compacting the powder body with a predetermined pressure using a forming die.

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

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

[0005] The tooth portion includes: a tooth main body portion extending from the inner peripheral surface of the yoke portion toward the inner side of the yoke portion and formed in a quadrangular prism shape; and a tooth terminal portion located at the terminal end of the tooth main body portion. When viewed from the axial direction of the stator, the tooth portion is formed in a substantially T-shaped shape. The tooth portion faces the rotor. A stator coil is wound on the tooth main body portion.

[0006] Patent Document 1: Japanese Patent Application Publication No. 2017-060395

[0007] In recent years, in order to increase the output of a device driven by a motor, there is a demand to increase the output torque of the motor. In order to increase the output torque of a motor having a stator core having the above-mentioned structure, it is necessary to increase the magnetic flux generated by the energization of the stator coil. The magnetic flux flows in the stator core.

[0008] On the other hand, especially in small motors, magnetic saturation is easily generated in the stator core as the stator core is miniaturized. If magnetic saturation occurs in the stator core, the magnetic flux flowing in the stator core cannot be increased, and there is a limit to increasing the output torque of the motor. Summary of the invention

[0009] Therefore, an object of the present invention is to provide a magnetic core capable of alleviating the occurrence of magnetic saturation, a method for manufacturing the same, a magnetic core with a coil, and a rotating electric machine.

[0010] A magnetic core according to one embodiment of the present invention is used for a rotating electrical machine. The magnetic core comprises: a core back having a front surface, which faces a first direction when the core is assembled in the rotating electrical machine, and the first direction faces the axis of rotation of the rotating electrical machine; and a tooth portion. The tooth portion comprises: a tooth body portion extending from the front surface in the first direction; and a tooth tip portion provided at the tip of the tooth body portion. The tooth tip portion has a back surface facing in the opposite direction to the first direction. The tooth body portion has an end surface, which faces a second direction along the axis of rotation when the core is assembled in the rotating electrical machine. The end surface 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 portion, and the curved surface is formed by a first curved surface forming portion that is a part of the tooth body portion.

[0011] In the past, the end face of the tooth body and the front surface of the core back or the end face of the tooth body and the back of the tooth end portion were connected to each other through a plane. In this case, a corner is formed at the portion where the end face of the tooth body is connected to the front surface of the core back or the back of the tooth end portion. When a magnetic core is assembled in a rotating electrical machine, if the coil wound on the tooth body is energized, a magnetic flux is generated inside the magnetic core through the tooth body. The direction of the magnetic flux is from the tooth body toward the front surface of the core back or the back of the tooth end portion. At this time, the flow of the magnetic flux is intended to form the shortest path inside the magnetic core. In the past, a corner was formed at the portion where the end face of the tooth body and the front surface of the core back or the end face of the tooth body and the back of the tooth end portion were connected. Therefore, the flow of the magnetic flux that is intended to flow in the shortest path is hindered by the corner, and the magnetic resistance of the magnetic circuit increases near the corner, and the magnetic flux is not easy to flow near the corner. Therefore, magnetic saturation occurs locally in the corner portion.

[0012] On the other hand, according to the above-mentioned magnetic core, 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 end portion, and the curved surface is formed by a first curved surface forming portion that is a part of the tooth body. Therefore, according to the above-mentioned magnetic core, no corner is formed in the first direction as in the prior art, and the magnetic flux can pass through the first curved surface forming portion and flow in a short path. As a result, the magnetic resistance of the magnetic circuit can be reduced. As a result, the occurrence of local magnetic saturation can be alleviated. In addition, with respect to the core back or the tooth end portion, the area where the magnetic flux flows can be expanded in a direction orthogonal to the first direction. As a result, the core back can be effectively utilized as a magnetic circuit. As a result, the output torque of a rotating electrical machinery equipped with the above-mentioned magnetic core can be further improved.

[0013] In the magnetic core, the end surface of the tooth body may include a first flat surface parallel to the first direction, and the first curved surface forming portion may protrude from the first flat surface toward the second direction and be located only on the second direction side relative to the first flat surface.

[0014] According to the above structure, the first curved surface forming portion is formed without reducing the cross-sectional area of ​​the tooth body portion in the second direction. 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 portion does not decrease. Therefore, it is possible to suppress the reduction in the output torque of the rotary electric machine.

[0015] Alternatively, in the magnetic core, the tooth body has a side surface, and when the magnetic core is assembled in a rotating electrical machine, the side surface faces the circumferential direction centered on the rotation axis of the rotating electrical machine. In this structure, the side surface has a concave curved surface that smoothly connects itself to the front surface of the core back or the back surface of the tooth terminal, and the curved surface is formed by the second curved surface forming portion that is a part of the tooth body.

[0016] According to the above structure, no corner is formed in the circumferential direction as in the prior art, and the magnetic flux can pass through the first curved surface forming portion and flow in a short path. As a result, the magnetic resistance of the magnetic circuit can be reduced. As a result, the occurrence of local magnetic saturation can be further alleviated.

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

[0018] According to the above structure, the second curved surface forming portion is formed without reducing the cross-sectional area of ​​the tooth body portion in the circumferential direction. Therefore, even if the second curved surface forming portion is formed, the saturation magnetic flux density of the magnetic flux flowing inside the tooth body portion does not decrease. Therefore, it is possible to suppress the reduction of the output torque of the rotating electrical machine.

[0019] Alternatively, in the magnetic core, the tooth body portion may include: a side surface facing a third direction which is a circumferential direction centered on the axis of rotation when the magnetic core is assembled in a rotary electrical machine; and an inclined surface connecting the end surface and the side surface. In this configuration, the inclined surface includes a curved surface which tapers to a terminal end so as to smoothly connect to an edge of the curved surface in the third direction, and the curved surface which tapers to a terminal end is formed by a third curved surface forming portion which is a part of the tooth body portion.

[0020] According to the above configuration, no corner is formed at the portion where the end surface and the side surface of the tooth body are connected on the core back side of the tooth body, and magnetic flux flows easily. This can further alleviate the occurrence of local magnetic saturation.

[0021] The magnetic core may be a molded body formed of soft magnetic powder.

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

[0023] A method for manufacturing a magnetic core according to one aspect of the present invention includes a finishing step of finishing the magnetic core by grinding using a spherical medium, wherein, in a stage prior to the finishing step, the magnetic core is manufactured so that the radius of curvature of the curved surface of the end face is larger than the diameter of the medium used in the finishing step.

[0024] According to the manufacturing method, the radius of curvature of the first curved surface is greater than the radius of the medium, so that in the finishing process, the medium can contact each corner of the curved surface of the end face of the tooth body, and the burrs formed on the curved surface of the end face of the tooth body in the previous stage of the finishing process can be removed by the finishing process. As a result, it is possible to suppress the damage to the coil when the coil is wound on the tooth body after the magnetic core is completed. In addition, after the finishing process, when an insulating film is applied to the surface of the magnetic core, the insulating film can be made thinner, the slot space factor of the coil can be increased, and the output efficiency of the rotating electrical machinery can be improved.

[0025] A method for manufacturing a magnetic core according to one aspect of the present invention includes a finishing step of finishing the magnetic core by grinding using a spherical medium, wherein, in a stage prior to the finishing step, the magnetic core is manufactured so that the radius of curvature of the curved surface on the side surface is larger than the diameter of the medium used in the finishing step.

[0026] According to the manufacturing method, the minimum value of the radius of curvature of the second curved surface is greater than the radius of the medium, so that in the finishing process, the medium can contact each corner of the curved surface of the side surface of the tooth body, and the burrs formed on the curved surface of the side surface of the tooth body in the previous stage of the finishing process can be removed by the finishing process. As a result, it is possible to suppress damage to the coil when the coil is wound around the tooth body after the magnetic core is completed. In addition, after the finishing process, when an insulating film is applied to the surface of the magnetic core, the insulating film can be made thinner, the coil slot space factor can be increased, and the output efficiency of the rotating electrical machinery can be improved.

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

[0028] Figure 1 1 is a perspective view of the appearance of a brushless motor 100 using the magnetic core 1 .

[0029] Figure 2 This is a schematic perspective view showing a part of the brushless motor 100 in section.

[0030] Figure 3 It is a three-dimensional diagram of the magnetic core 1.

[0031] Figure 4 It is a cross-sectional view of the magnetic core 1 and an enlarged cross-sectional view of the first curved surface forming portion R11 and its vicinity.

[0032] Figure 5 It is a cross-sectional view showing a state of magnetic flux flowing in the magnetic core 50 according to the comparative example in a motor including the magnetic core 50 according to the comparative example.

[0033] Figure 6 1 is a cross-sectional view showing the state of magnetic flux flowing through the core 1 in the brushless motor 100 .

[0034] Figure 7 1 is a cross-sectional view showing the state of magnetic flux flowing through two adjacent cores 1 in the brushless motor 100 .

[0035] Figure 8 It is a cross-sectional view showing an example of the manufacturing process of the magnetic core 1.

[0036] Fig. 9 3 is a diagram showing the relationship between the curvature radius CR1 of the first curved surface CS1 and the radius RA of the medium M.

[0037] Fig.10 It is a cross-sectional view showing the inside of the drum B during the finishing process.

[0038] Fig.11 It is a perspective view of the magnetic core 1a.

[0039] Fig.12 It is a perspective view of the magnetic core 1b.

[0040] Fig.13 It is a cross-sectional view of the magnetic core 1 b and an enlarged cross-sectional view of the vicinity of the second curved surface forming portion R21 .

[0041] Fig.14 3 is a diagram showing the relationship between the curvature radius CR2 of the second curved surface CS2 and the radius RA of the medium M. DETAILED DESCRIPTION

[0042] [First embodiment]

[0043] (Structure of Brushless Motor 100)

[0044] First, the structure of a brushless motor 100 according to a first embodiment of the present invention will be described below with reference to the drawings. Figure 1 1 is a perspective view of the appearance of the brushless motor 100 . Figure 2 This is a schematic perspective view showing a part of the brushless motor 100 in section.

[0045] In this specification, as an example, directions are defined as follows. A direction from the tooth tip portion 32 toward the rotation axis AR of the brushless motor 100 in a radial direction centered on the rotation axis AR of the brushless motor 100 is defined as a first direction DIR1. The first direction DIR1 is a direction toward the rotation axis AR of the brushless motor 100 when the magnetic core 1 is assembled in the brushless motor 100. A direction in which the axial center axis 21 protrudes from the opening OP toward the outside of the housing 15 along the axial direction of the rotation axis AR of the brushless motor 100 is defined as a second direction DIR2. A direction in a circumferential direction centered on the rotation axis AR of the brushless motor 100, which is a clockwise direction relative to the rotation axis AR of the brushless motor 100 when viewed in the second direction DIR2, is defined as a third direction DIR3. The opposite direction of the second direction DIR2 is defined as a fourth direction DIR4.

[0046] like Figure 2 As shown, the brushless motor 100 includes a rotor 20, a stator 10, a bearing 14, and a housing 15. In the present embodiment, the brushless motor 100 is an inner rotor type. That is, the stator 10 is arranged around the rotor 20. In addition, the brushless motor 100 is an example of a rotating electrical machine of the present invention. In addition, the brushless motor 100 may also be an outer rotor type. That is, the rotor 20 may also be arranged around the stator 10.

[0047] In addition, the rotating electrical machine may also be a structure that rotates the rotor by electricity. Alternatively, the rotating electrical machine may also be a structure that generates electricity by rotating the rotor. The rotating electrical machine includes a brushless motor, a permanent magnet synchronous motor, a permanent magnet synchronous generator, and the like.

[0048] The rotor 20 includes a shaft body 21 and a rotor member 22. The shaft body 21 is cylindrical. The rotor member 22 is cylindrical. The central axes of the shaft body 21 and the rotor member 22 coincide with each other, and the central axes form a rotation axis AR.

[0049] The rotor component 22 has a soft magnetic body 23 and a hard magnetic body 24. The rotor component 22 is mounted on the outer peripheral surface of the shaft body 21 in the radial direction with the rotation axis AR as the center. More specifically, the soft magnetic body 23 is mounted on the outer peripheral surface of the shaft body 21 in the radial direction with the rotation axis AR as the center. The hard magnetic body 24 is mounted on the outer peripheral surface of the soft magnetic body 23 in the radial direction with the rotation axis AR as the center.

[0050] The soft magnetic body 23 is a soft magnetic body. The hard magnetic body 24 is a magnetized hard magnetic body. The hard magnetic body is magnetized when a magnetic field is applied from the outside. Thereafter, even if the application of the magnetic field is stopped, the hard magnetic body does not lose its magnetization.

[0051] The bearing 14 supports the shaft body 21 so as to be rotatable in the circumferential direction around the rotation axis AR. In more detail, the bearing 14 has a first bearing 14a and a second bearing 14b. In the present embodiment, the first bearing 14a and the second bearing 14b are each a ball bearing. The first bearing 14a and the second bearing 14b are each cylindrical and extend along the rotation axis AR. The center axis of each of the first bearing 14a and the second bearing 14b is the rotation axis AR. That is, the center axis of each of the first bearing 14a and the second bearing 14b is consistent with the center axis of the shaft body 21. In addition, the first bearing 14a and the second bearing 14b are not limited to ball bearings.

[0052] The second bearing 14b is located closer to the fourth direction DIR4 than the first bearing 14a. In addition, the first bearing 14a is located closer to the second direction DIR2 than the rotor member 22. The second bearing 14b is located closer to the fourth direction DIR4 than the rotor member 22. The second bearing 14b supports the end of the shaft 21 in the fourth direction DIR4.

[0053] The stator 10 includes a coil 13 and a magnetic core 1. That is, in the present embodiment, the magnetic core 1 is used for the stator 10. In addition, the magnetic core according to the present invention may be used as a part of a rotor.

[0054] like Figure 1 As shown in FIG. 1 , the housing 15 includes a first housing 15a and a second housing 15b. Figure 1 and Figure 2 As shown, 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 closer to the second direction DIR2 than the second housing 15b. In addition, the first housing 15a has an opening OP. Thus, the shaft 21 protrudes from the opening OP to the second direction DIR2. That is, in this embodiment, the brushless motor 100 is a single-axis type. In addition, the brushless motor 100 is not limited to a single-axis type, and can also be a two-axis type.

[0055] The first housing 15a supports the first bearing 14a, the plurality of magnetic cores 1, and the plurality of coils 13. The second housing 15b supports the second bearing 14b. In the present embodiment, the first housing 15a and the second housing 15b are each made of SUS (Stainless Used Steel). In addition, the first housing 15a and the second housing 15b are each made of not limited to SUS (Stainless Used Steel), but may be made of a material with high rigidity.

[0056] In this embodiment, the number of coils 13 and the number of magnetic cores 1 are each 9. Figure 2In the figure, only representative ones of the nine magnetic cores 1 and the nine coils 13 are marked with reference numerals. The nine coils 13 and the nine magnetic cores 1 are arranged in a circumferential direction around the rotation axis AR. The nine magnetic cores 1 are arranged around the hard magnetic body 24 with a gap between them. In addition, the number of coils 13 and the number of magnetic cores 1 are not limited to nine.

[0057] The coil 13 is made of a conductive material such as copper. In addition, the coil 13 has a structure in which the surface of the copper wire is covered with an insulating film. By having a structure in which the surface of the copper wire is covered with an insulating film, the coil 13 is electrically insulated from the magnetic core 1. However, at both end portions of the coil 13, the surface of the copper wire is not covered with an insulating film, and the copper wire is exposed.

[0058] The coil 13 is supplied with current from a power source (not shown). The coil 13 generates a magnetic field by flowing current through the coil 13. The magnetic core 1 is magnetized by the magnetic field generated by the hard magnetic body 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).

[0059] (Structure of magnetic core 1)

[0060] Hereinafter, the structure of the magnetic core 1 according to the first embodiment of the present invention will be described with reference to the drawings. Figure 3 It is a three-dimensional diagram of the magnetic core 1. Figure 4 2 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. Figure 3 In the figure, only the representative slope SL among the four slopes SL is denoted by a reference numeral. Figure 4 The cross section of the core 1 in φ is a plane that passes through the first flat surface FS1 of the first end surface ES1 of the tooth body portion 31 and is orthogonal to the first flat surface FS1 of the first end surface ES1 of the tooth body portion 31 .

[0061] like Figure 3 As shown, the magnetic core 1 includes a core back 2 and a tooth portion 3. The core back 2 and the tooth portion 3 are included in the magnetic core 1 as a single member. Here, a single member refers to a member having a structure that is not damaged and cannot be separated.

[0062] The magnetic core 1 is a soft magnetic body. In the present embodiment, the magnetic core 1 is a molded body formed of soft magnetic powder. That is, the core back 2 and the tooth portion 3 are each a molded body formed of 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 a material obtained by mixing, for example, iron powder and epoxy resin powder, which is an example of a binder powder. Such a magnetic core 1 is made, for example, by compression molding. In addition, an insulating film (not shown) is applied to the surface of the magnetic core 1 that contacts other components. In addition, the magnetic core 1 may not be a molded body formed of soft magnetic powder.

[0063] The core back 2 has a front surface IS2 facing the first direction DIR1, a back surface OS2 facing the opposite direction of the first direction DIR1, two side surfaces connecting the front surface IS2 and the back surface OS2 and arranged in the third direction DIR3, and two end surfaces connecting the front surface IS2 and the back surface OS2 and arranged in the second direction DIR2. In the present embodiment, the front surface IS2, the two side surfaces arranged in the third direction DIR3, and the two end surfaces arranged in the second direction DIR2 are each a plane. The front surface IS32 is a curved surface that is concavely curved in the opposite direction of the first direction DIR1. The back surface OS2 is a curved surface that is convexly curved in the opposite direction of the first direction DIR1. The back surface OS2 forms a part of the outer peripheral surface of the stator 10. When the magnetic core 1 is assembled in the brushless motor 100, the side surface connecting the front surface IS2 and the back surface OS2 and the side surface connecting the front surface IS2 and the back surface OS2 of the adjacent magnetic core 1 are magnetically connected. In addition, the front surface IS2, the two side surfaces arranged in the third direction DIR3, and the two end surfaces arranged in the second direction DIR2 may each include a curved surface at least partially. In addition, the back surface OS2 may include a flat surface at least partially.

[0064] The tooth portion 3 has a shape extending from the core back 2 in the first direction DIR1. More specifically, the tooth portion 3 has a tooth body portion 31 extending from the front surface IS2 in the first direction DIR1 and a tooth terminal portion 32 provided at the terminal end of the tooth body portion 31. Figure 2As shown, the coil 13 is wound on the tooth body 31. When the magnetic core 1 is assembled in the brushless motor 100, the tooth end portion 32 faces the hard magnetic body 24 of the rotor 20 via a gap (air gap). In the present embodiment, the position of the end of the rotor component 22 in the second direction DIR2 in the second direction DIR2 is equal to the position of the end of the tooth body 31 in the second direction DIR2 in the second direction DIR2. In addition, the position of the end of the rotor component 22 in the fourth direction DIR4 in the fourth direction DIR4 is equal to the position of the end of the tooth body 31 in the fourth direction DIR4 in the fourth direction DIR4. In addition, the position of the end of the rotor component 22 in the second direction DIR2 in the second direction DIR2 may not be equal to the position of the end of the tooth body 31 in the second direction DIR2 in the second direction DIR2. Furthermore, the position of the end portion of the rotor member 22 in the fourth direction DIR4 and the position of the end portion of the tooth body portion 31 in the fourth direction DIR4 may not be equal to each other.

[0065] like Figure 3 As shown, the tooth end 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 and arranged in the third direction DIR3, and two end surfaces connecting the front surface IS32 and the back surface OS32 and arranged in the second direction DIR2. In the present embodiment, the back surface OS32, the two side surfaces arranged in the third direction DIR3, and the two end surfaces arranged in the second direction DIR2 are each a plane. The front surface IS32 is a curved surface that is concavely curved in the first direction DIR1. The front surface IS32 is along the outer peripheral surface of the rotor 20. The back surface OS32, the two side surfaces arranged in the third direction DIR3, and the two end surfaces arranged in the second direction DIR2 may each include a curved surface. In addition, the front surface IS32 may also include a flat surface.

[0066] In the present embodiment, the tooth body 31 has a shape obtained by chamfering each corner of a quadrangular prism extending in the first direction DIR1. Figure 4As shown, the tooth body portion 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 with the first side surface SS1 or the second side surface SS2. In the present embodiment, the first end face ES1 and the second end face ES2 each include a surface parallel to the first direction DIR1, that is, a first flat surface FS1. The first side surface SS1 and the second side surface SS2 each include a surface parallel to the first direction DIR1, that is, a second flat surface FS2. In addition, it is also possible that the first end face ES1 and the second end face ES2 each do not include a surface parallel to the first direction DIR1, that is, the first flat surface FS1. In addition, the first side surface SS1 and the second side surface SS2 may not include a second flat surface FS2 that is parallel to the first direction DIR1. In addition, the first end surface ES1 or the second end surface ES2 corresponds to the "end surface" of the present invention. The first side surface SS1 or the second side surface SS2 corresponds to the "side surface" of the present invention.

[0067] 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 2. Furthermore, 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. In addition, the tooth body portion 31 may not have a shape obtained by chamfering each corner of a quadrangular prism extending in the first direction DIR1.

[0068] In this embodiment, if Figure 3 and Figure 4As shown, four first curved surface forming portions R1 are formed in the tooth body portion 31. The four first curved surface forming portions R1 are parts 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 the present embodiment, the four first curved surface forming portions R1 have mutually symmetrical structures. Therefore, the description of the two first curved surface forming portions R1 formed at the end of the tooth body portion 31 in the fourth direction DIR4 is omitted. In addition, the number of the first curved surface forming portions R1 may not be four. In addition, the first curved surface forming portions R1 may not have mutually symmetrical structures.

[0069] First, the first curved surface forming portion R1 formed at the end of the tooth body portion 31 in the first direction DIR1 and the end of the tooth body portion 31 in the second direction DIR2 will be described. Hereinafter, the first curved surface forming portion R1 is referred to as a first curved surface forming portion R11.

[0070] The first curved surface forming portion R11 protrudes from the first flat surface FS1 of the first end surface ES1 toward the second direction DIR2. In addition, the first curved surface forming portion R11 is only located at a position closer to the second direction DIR2 side than the first flat surface FS1 of the first end surface ES1. In more detail, 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 curved in a concave shape. In the present embodiment, the first curved surface CS1 of the first curved surface forming portion R11 is curved in an arc shape in a cross section orthogonal to the third direction DIR3. In addition, the first curved surface CS1 of the first curved surface forming portion R11 has a radius of curvature CR1. In addition, it may be that the first curved surface CS1 of the first curved surface forming portion R11 is not curved in an arc shape in a cross section orthogonal to the third direction DIR3. In addition, the first curved surface CS1 of the first curved surface forming portion R11 may also have a plurality of radii of curvature CR1.

[0071] The first curved surface CS1 of the first curved surface forming portion R11 is a part of the first end surface ES1. The first curved surface CS1 of the first curved surface forming portion R11 is smoothly connected to the back surface OS32 of the tooth end portion 32. Therefore, the tooth body portion 31 is smoothly connected to the back surface OS32 of the tooth end portion 32 via the first curved surface CS1 of the first curved surface forming portion R11. In this embodiment, as shown in FIG. Figure 3 As shown, an edge E is formed at an end portion of the first curved surface CS1 of the first curved surface forming portion R11 in the third direction DIR3 and an end portion of the first curved surface CS1 of the first curved surface forming portion R11 in the direction opposite to the third direction DIR3.

[0072] Next, the first curved surface forming portion R1 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 will be described. Hereinafter, the first curved surface forming portion R1 is referred to as a first curved surface forming portion R12.

[0073] like Figure 4 As shown, the first curved surface forming portion R12 protrudes from the first flat surface FS1 of the first end surface ES1 toward the second direction DIR2 in the second direction DIR2. In addition, the first curved surface forming portion R12 is only located at a position closer to the second direction DIR2 side than the first flat surface FS1 of the first end surface ES1. In more detail, 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 concavely curved. In the present embodiment, the first curved surface CS1 of the first curved surface forming portion R12 is curved in an arc shape in a cross section orthogonal to the third direction DIR3. In addition, the first curved surface CS1 of the first curved surface forming portion R12 has a curvature radius CR1. In addition, it is also possible that the first curved surface CS1 of the first curved surface forming portion R12 is not curved in an arc shape in a cross section orthogonal to the third direction DIR3. Furthermore, the first curved surface CS1 of the first curved surface forming portion R12 may have a plurality of curvature radii CR1.

[0074] The first curved surface CS1 of the first curved surface forming portion R12 is a part of the first end surface ES1. 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 2. Therefore, the tooth body portion 31 is smoothly connected to the front surface IS2 of the core back 2 via the first curved surface CS1 of the first curved surface forming portion R12. In the present embodiment, an edge E is formed at the end of the first curved surface CS1 of the first curved surface forming portion R12 in the third direction DIR3 and at the end of the first curved surface CS1 of the first curved surface forming portion R12 in the opposite direction to the third direction DIR3.

[0075] According to the magnetic core 1, the occurrence of magnetic saturation can be alleviated. As a comparative example, a magnetic core 50 in which the first curved surface forming portion R1 is not formed in the tooth body portion 31 will be described with reference to the drawings. Figure 5 : is a cross-sectional view showing the state of magnetic flux flowing in the magnetic core 50 according to the comparative example in a motor provided with the magnetic core 50 according to the comparative example. Figure 5 In the figure, only representative magnetic field lines MFL among the plurality of magnetic field lines MFL are denoted by reference numerals. Figure 5 In the figure, for the sake of explanation, the boundary line between the tooth body portion 31 and the core back 2 and the boundary line between the tooth body portion 31 and the tooth tip portion 32 are omitted.

[0076] In the brushless motor 100, when the coil 13 wound around the tooth body 31 is energized, a magnetic flux is generated in the tooth body 31. The magnetic flux flows from the tooth body 31 toward the front surface IS2 of the core back 2 or the back surface OS32 of the tooth end 32. By changing the direction of the current flowing in the coil 13, the direction of the magnetic flux flow can be changed. At this time, the magnetic flux tends to flow in the shortest path inside the magnetic core 50 involved in the comparative example. In the magnetic core 50 involved in the comparative example, a corner A is formed in the portion connecting the first end surface ES1 of the tooth body 31 and the front surface IS2 of the core back 2 and the first end surface ES1 of the tooth body 31 and the back surface OS2 of the tooth end 32.

[0077] In the magnetic core 50 according to the comparative example, the flow of magnetic flux is blocked by the corner A, and the magnetic flux has to take a detour near the corner A and is not easy to flow. Therefore, residual stress is generated near the corner A, and the magnetic resistance of the magnetic circuit increases, so that magnetic saturation occurs locally at the corner A. Therefore, when the magnetic core 50 according to the comparative example is used in a motor, the output torque of the motor cannot be improved.

[0078] Next, the magnetic core 1 will be described with reference to the drawings. Figure 6 2 is a cross-sectional view showing the state of magnetic flux flowing in the core 1 in the brushless motor 100. Figure 6 In the figure, for the sake of explanation, the boundary between the tooth body portion 31 and the core back 2 and the boundary between the tooth body portion 31 and the tooth tip portion 32 are omitted. Figure 6 In the figure, only representative magnetic force lines MFL among the plurality of magnetic force lines MFL are denoted by reference numerals.

[0079] In the magnetic core 1, a first curved surface forming portion R11 having a concavely curved first curved surface CS1 is formed on the tooth body portion 31. The first curved surface CS1 of the first curved surface forming portion R11 is smoothly connected to the back surface OS32 of the tooth end portion 32. Figure 6As shown, by forming the first curved surface forming portion R11 in the tooth body portion 31, the magnetic flux can flow in the shortest path near the first curved surface forming portion R11 without taking a detour. Therefore, in the magnetic core 1, the magnetic flux flows more easily near the first curved surface forming portion R11 than in the magnetic core 50 involved in the comparative example. As a result, the generation of magnetic saturation can be alleviated near the first curved surface forming portion R11.

[0080] Furthermore, by forming the first curved surface forming portion R11 on the tooth body portion 31, the magnetic core 1 can better receive the magnetic flux generated by the hard magnetic body 24 and including the component in the second direction DIR2 or the fourth direction DIR4. This effect is more significant when the end of the rotor component 22 in the second direction DIR2 is located closer to the end of the tooth body portion 31 in the second direction DIR2 and the distance in the second direction DIR2 between the end of the rotor component 22 in the second direction DIR2 and the end of the tooth body portion 31 in the second direction DIR2 is longer, or when the end of the rotor component 22 in the fourth direction DIR4 is located closer to the end of the tooth body portion 31 in the fourth direction DIR4 and the distance in the fourth direction DIR4 between the end of the rotor component 22 in the fourth direction DIR4 and the end of the tooth body portion 31 in the fourth direction DIR4 is longer.

[0081] Compared with the case where the first curved surface CS1 of the first curved surface forming portion R11 is curved in a convex shape, the first curved surface CS1 of the first curved surface forming portion R11 is curved in a concave shape, so that the coil 13 can be wound more around the tooth body portion 31. As a result, the wire slot occupancy factor of the coil 13 can be increased, and the output torque of the brushless motor 100 can be improved.

[0082] Furthermore, in the magnetic core 1, the first curved surface forming portion R11 protrudes from the first flat surface FS1 of the first end surface ES1 toward the second direction DIR2 in the second direction DIR2, and is only located at a position closer to the second direction DIR2 side than the first flat surface FS1 of the first end surface ES1. In other words, in the second direction DIR2, the first curved surface forming portion R11 is formed 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. Therefore, it is possible to suppress a reduction in the output torque of the brushless motor 100.

[0083] In the magnetic core 1, a first curved surface forming portion R12 having a first curved surface CS1 curved in a concave shape is formed on the tooth body portion 31. 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 2. Since the first curved surface forming portion R12 is formed on the tooth body portion 31, the magnetic flux can flow in the shortest path without detouring near the first curved surface forming portion R12. Therefore, in the magnetic core 1, the magnetic flux flows more easily near the first curved surface forming portion R12 than in the magnetic core 50 involved in the comparative example. As a result, the generation of magnetic saturation can be alleviated near the first curved surface forming portion R12.

[0084] Compared with the case where the first curved surface CS1 of the first curved surface forming portion R12 is curved convexly, the first curved surface CS1 of the first curved surface forming portion R12 is curved concavely, so that the coil 13 can be wound more around the tooth body portion 31. As a result, the wire slot occupancy factor of the coil 13 can be increased, and the output torque of the brushless motor 100 can be improved.

[0085] By forming the first curved surface forming portion R12 on the tooth body portion 31, the area where the magnetic flux flows can be expanded in the direction orthogonal to the first direction DIR1 with respect to the core back 2. More specifically, when the magnetic core 1 is assembled in the brushless motor 100, the adjacent magnetic cores 1 are connected through their respective core backs 2. Hereinafter, one of the adjacent magnetic cores 1 is referred to as a magnetic core 11, and the other of the adjacent magnetic cores 1 is referred to as a magnetic core 12.

[0086] When the magnetic flux generated at the tooth body portion 31 of the magnetic core 11 by energizing the coil 13 wound at 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 2 of the magnetic core 11, a magnetic flux is formed in the direction from the core back 2 of the magnetic core 11 toward the core back 2 of the magnetic core 12 (the third direction DIR3).

[0087] The magnetic flux has the following property: although it wants to flow in the shortest path, a repulsive force acts between a plurality of magnetic fluxes, and the magnetic flux expands in the directions (the second direction DIR2 and the fourth direction DIR4) orthogonal to the first direction DIR1 and the third direction DIR3. In the magnetic core 50 involved in the comparative example, since the first curved surface forming portion R1 is not formed on the core back 2 side of the tooth body portion 31, a corner A is formed at the portion where the first end surface ES1 of the tooth body portion 31 and the front surface IS2 of the core back 2 are connected. Due to the corner A, the flow of the magnetic flux that wants to expand in the second direction DIR2 and the fourth direction DIR4 is hindered, and the area where the magnetic flux flows in the second direction DIR2 and the fourth direction DIR4 cannot be expanded for the core back 2, and the core back 2 cannot be effectively used as a magnetic circuit. If the area where the magnetic flux flows cannot be expanded, the magnetic resistance in the magnetic circuit increases, and when the magnetic core 50 involved in the comparative example is used in a motor, this becomes a cause of reducing the output efficiency of the motor.

[0088] Next, the magnetic core 1 will be described with reference to the drawings. Figure 7 2 is a cross-sectional view showing the state of magnetic flux flowing through two adjacent magnetic cores 1 in the brushless motor 100. Figure 7 In the figure, only representative magnetic force lines MFL among the plurality of magnetic force lines MFL are denoted by reference numerals.

[0089] In the magnetic core 11, a first curved surface forming portion R12 is formed on the tooth body portion 31, whereby, near the first curved surface forming portion R12, the flow of magnetic flux is not hindered by the corner, and the magnetic flux is easily expanded in the second direction DIR2. In addition, in the magnetic core 12, a first curved surface forming portion R12 is formed on the tooth body portion 31, whereby, near the first curved surface forming portion R12, the flow of magnetic flux is not hindered by the corner, and the magnetic flux is easily expanded in the second direction DIR2. In other words, in the magnetic core 11, the magnetic flux easily flows out toward the magnetic core 12, and in the magnetic core 12, the magnetic flux easily flows in from the magnetic core 11. As a result, the increase in the magnetic resistance of the magnetic circuit can be suppressed. Therefore, the reduction in the output efficiency of the brushless motor 100 can be suppressed.

[0090] Furthermore, in the magnetic core 1, in the second direction DIR2, the first curved surface forming portion R12 protrudes from the first flat surface FS1 of the first end surface ES1 toward the second direction DIR2, and is only located at a position closer to the second direction DIR2 side than the first flat surface FS1 of the first end surface ES1. In other words, in the second direction DIR2, the first curved surface forming portion R12 is formed 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. Therefore, it is possible to suppress a reduction in the output torque of the brushless motor 100.

[0091] (Method for Manufacturing Magnetic Core 1)

[0092] Hereinafter, a method for manufacturing the magnetic core 1 according to the first embodiment of the present invention will be described with reference to the drawings. Figure 8 It is a cross-sectional view showing an example of the manufacturing process of the magnetic core 1. Fig. 9 : is a diagram showing the relationship between the curvature radius CR1 of the first curved surface CS1 and the radius RA of the medium M. In addition, Fig. 9 In the figure, only a representative first curved surface CS1 among the four first curved surfaces CS1 is denoted by a reference numeral. Fig.10 It is a cross-sectional view showing the inside of the drum B during the finishing process.

[0093] like Figure 8 As shown, first, the soft magnetic powder SMP obtained by mixing iron powder and epoxy resin powder is filled into the mold DI. Next, the soft magnetic powder SMP filled into the mold DI is pressurized by the punch P, and the soft magnetic powder SMP is compression-molded. In addition, the punch P has a convex surface CON that is curved in a convex shape. In the present embodiment, the number of convex surfaces CON is 4. Therefore, when the soft magnetic powder SMP is compression-molded, four first curved surface forming portions R1 are formed on the tooth main body portion 31. At this moment, due to the presence of a tiny gap between the mold DI and the punch P, the rough surface of the punch P, and other reasons, burrs are formed on the surface of the soft magnetic powder SMP after compression molding. As shown Fig. 9 As shown, the curvature radius CR1 of the first curved surface CS1 of the compression-molded soft magnetic powder SMP is larger than the radius RA of the medium M. In addition, when the first curved surface CS1 of the compression-molded soft magnetic powder SMP has a plurality of curvature radii CR1, the minimum value of the plurality of curvature radii CR1 only needs to be larger than the radius RA of the medium M.

[0094] In the present manufacturing method, after the soft magnetic powder SMP is compression-molded, a finishing step of finishing the magnetic core 1 by grinding is performed. Fig.10 As shown, in the finishing process, first, the soft magnetic powder SMP after compression molding, the medium M, the grinding aid (not shown), and the water W are placed in the inside of the roller B which is hollow. The medium M has a spherical shape with a radius RA. In addition, in the present embodiment, the number of the soft magnetic powder SMP after compression molding and the medium M is one, but the number of the soft magnetic powder SMP after compression molding and the medium M can also be multiple. In the case where the number of the medium M is multiple, the magnetic core 1 can be finished efficiently. In the case where the number of the soft magnetic powder SMP after compression molding is multiple, multiple magnetic cores 1 can be finished at the same time.

[0095] In the finishing process, the roller B is rotated to make the medium M contact the soft magnetic powder SMP after compression molding, and the soft magnetic powder SMP after compression molding is ground. In the finishing process, the soft magnetic powder SMP after compression molding is ground by the medium M, thereby removing the burrs formed on the surface of the soft magnetic powder SMP after compression molding in the previous stage of the finishing process, and finishing the magnetic core 1. In addition, in the finishing process, the method of grinding the soft magnetic powder SMP after compression molding by the medium M is not limited to rotating the roller B, and it can also be performed by vibrating the roller B. In addition, in the finishing process, the roller B is not necessary, as long as the soft magnetic powder SMP after compression molding is ground by the medium M. Similarly, in the finishing process, the grinding aid and water W are not necessary.

[0096] The magnetic core 1 is a molded body formed of soft magnetic powder. Therefore, compared with a 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 above-mentioned method for manufacturing the magnetic core 1. As a result, the magnetic core 1 can be easily manufactured.

[0097] According to the manufacturing method of the magnetic core 1, the burrs formed on the first curved surface CS1 before the finishing process can be removed by the finishing process. More specifically, the radius of curvature CR1 of the first curved surface CS1 of the soft magnetic powder SMP after compression molding is greater than the radius RA of the medium M. Thus, in the finishing process, the medium M can contact each corner of the first curved surface CS1, and the burrs formed on the first curved surface CS1 in the previous stage of the finishing process can be removed by the finishing process. Thus, it is possible to suppress the damage of the coil 13 when the coil 13 is wound on the tooth body portion 31 after the magnetic core 1 is completed.

[0098] Furthermore, as shown in the above-mentioned core 1, when an insulating film is applied to the surface of the core 1 after the finishing process, the insulating film can be made thinner corresponding to the absence of burrs. This can increase the slot space factor of the coil 13 and improve the output efficiency of the brushless motor 100.

[0099] [First Modification]

[0100] (Structure of the magnetic core 1a)

[0101] Hereinafter, the structure of the magnetic core 1a according to the first modified example of the present invention will be described with reference to the drawings. Fig.11 is a three-dimensional diagram of the magnetic core 1a. Fig.11In the figure, only the representative first curved surface forming portion R1 and the first curved surface CS1 among the four first curved surface forming portions R1 and the four first curved surfaces CS1 are respectively marked with reference numerals. In addition, for the magnetic core 1a involved in the first variant, only the parts different from the magnetic core 1 involved in the first embodiment are described, and the rest will be omitted.

[0102] like Fig.11 As shown in FIG. 1 , the core 1 a is different from the core 1 in that four third curved surface forming portions R3 are formed in the tooth body portion 31 .

[0103] The four third curved surface forming portions R3 are parts 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 modification, the four third curved surface forming parts R3 have mutually symmetrical structures. In addition, the number of the third curved surface forming parts R3 may not be 4. In addition, the third curved surface forming parts R3 may not have mutually symmetrical structures.

[0104] Each of the four third curved surface forming portions R3 has a third curved surface CS3. Each of the four third curved surface forming portions R3 has a local portion of each of the four inclined surfaces SL. The third curved surface CS3 of each of the four third curved surface forming portions R3 gradually narrows at its distal end. In more detail, on the core back 2 side of the tooth body portion 31, the closer the third curved surface CS3 of each of the four third curved surface forming portions R3 is to the core back 2, the narrower the distal end is. In addition, on the tooth distal end portion 32 side of the tooth body portion 31, the closer the third curved surface CS3 of each of the four third curved surface forming portions R3 is to the tooth distal end portion 32, the narrower the distal end is. The third curved surface CS3 is smoothly connected to the edge E of the first curved surface CS1 in the third direction DIR3.

[0105] In the magnetic core 1a as described above, the same effect as that of the magnetic core 1 is achieved. In addition, in the magnetic core 1a, the third curved surface forming portion R3 is formed in the tooth body portion 31, so that the flow of magnetic flux is not hindered by the corner and flows easily at the portion where the first end surface ES1 or the second end surface ES2 of the tooth body portion 31 is connected to the first side surface SS1 or the second side surface SS2 on the core back 2 side or the tooth end portion 32 side of the tooth body portion 31. As a result, the occurrence of local magnetic saturation can be further alleviated.

[0106] [Second Modification]

[0107] (Structure of core 1b)

[0108] Hereinafter, the structure of the magnetic core 1b according to the second modified example of the present invention will be described with reference to the drawings. Fig.12 It is a perspective view of the magnetic core 1b. Fig.13 2 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. Fig.13 The cross section of the magnetic core 1 b 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 orthogonal to the second flat surface FS2 of the second side surface SS2 of the tooth body portion 31 . Fig.14 : is a diagram showing the relationship between the curvature radius CR2 of the second curved surface CS2 and the radius RA of the medium M. In addition, Fig.14 In the figure, only the representative second curved surface CS2 among the four second curved surfaces CS2 is denoted by a reference numeral. In addition, only the parts of the magnetic core 1b according to the second modification example that are different from the magnetic core 1a according to the first modification example will be described, and the rest will be omitted.

[0109] like Fig.12 and Fig.13 As shown in FIG. 1 , the core 1 b is different from the core 1 a in that the tooth body portion 31 has four second curved surface forming portions R 2 formed therein.

[0110] The four second curved surface forming portions R2 are parts 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 modification, the four second curved surface forming portions R2 have a mutually symmetrical structure. Therefore, the description of the two second curved surface forming portions R2 formed at the end of the tooth body portion 31 in the third direction DIR3 is omitted. In addition, the number of the second curved surface forming portions R2 may not be four. In addition, the second curved surface forming portions R2 may not have a mutually symmetrical structure.

[0111] First, the second curved surface forming portion R2 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 will be described. Hereinafter, the second curved surface forming portion R2 is referred to as a second curved surface forming portion R21.

[0112] In the opposite direction of the third direction DIR3, the second curved surface forming portion R21 protrudes from the second flat surface FS2 of the second side surface SS2 toward the opposite direction of the third direction DIR3. In addition, the second curved surface forming portion R21 is only located at a position closer to the opposite direction side of the third direction DIR3 than the second flat surface FS2 of the second side surface SS2. In more detail, 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 concavely curved. 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 orthogonal to the second direction DIR2. In addition, the second curved surface CS2 of the second curved surface forming portion R21 has a curvature radius CR2. In addition, it is also possible that the second curved surface CS2 of the second curved surface forming portion R21 is not curved in an arc shape in a cross section orthogonal to the second direction DIR2. Furthermore, the second curved surface CS2 of the second curved surface forming portion R21 may have a plurality of curvature radii CR2.

[0113] The second curved surface CS2 of the second curved surface forming portion R21 is a part of the second side surface SS2. The second curved surface CS2 of the second curved surface forming portion R21 is smoothly connected to the back surface OS32 of the tooth terminal portion 32. Therefore, the tooth body portion 31 is connected to the back surface OS32 of the tooth terminal portion 32 via the second curved surface CS2 of the second curved surface forming portion R21.

[0114] Next, the second curved surface forming portion R2 formed at the end of the tooth body portion 31 in the direction opposite to the first direction DIR1 and the end of the tooth body portion 31 in the direction opposite to the third direction DIR3 will be described. Hereinafter, the second curved surface forming portion R2 is referred to as a second curved surface forming portion R22.

[0115] In the opposite direction of the third direction DIR3, the second curved surface forming portion R22 protrudes from the second flat surface FS2 of the second side surface SS2 toward the opposite direction of the third direction DIR3. In addition, the second curved surface forming portion R22 is only located at a position closer to the opposite direction side of the third direction DIR3 than the second flat surface FS2 of the second side surface SS2. In more detail, 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 concavely curved. 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 orthogonal to the second direction DIR2. In addition, the second curved surface CS2 of the second curved surface forming portion R21 has a curvature radius CR2. In addition, it is also possible that the second curved surface CS2 of the second curved surface forming portion R22 is not curved in an arc shape in a cross section orthogonal to the second direction DIR2. Furthermore, the second curved surface CS2 of the second curved surface forming portion R22 may have a plurality of curvature radii CR2.

[0116] The second curved surface CS2 of the second curved surface forming portion R22 is a portion of the second side surface SS2. 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 2. Therefore, the tooth body portion 31 is smoothly connected to the front surface IS2 of the core back 2 via the second curved surface CS2 of the second curved surface forming portion R22.

[0117] The method for manufacturing the magnetic core 1b according to this modification is the same as the method for manufacturing the magnetic core 1 according to the first embodiment. Fig.14 As shown, the curvature radius CR2 of the second curved surface CS2 of the compression-molded soft magnetic powder SMP is larger than the radius RA of the medium M. In addition, when the second curved surface CS2 of the compression-molded soft magnetic powder SMP has a plurality of curvature radii CR2, the minimum value of the plurality of curvature radii CR2 may be larger than the radius RA of the medium M.

[0118] In the magnetic core 1b as described above, the same effect as that of the magnetic core 1a is achieved. In addition, in the magnetic core 1b, a second curved surface forming portion R21 having a second curved surface CS2 curved in a concave shape is formed in 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 end portion 32. By forming the second curved surface forming portion R21 in the tooth body portion 31, the magnetic flux can flow in the shortest path near the second curved surface forming portion R21 without detouring. Therefore, in the magnetic core 1b, the magnetic flux is easier to flow near the second curved surface forming portion R21 compared to the magnetic core 50 involved in the comparative example. As a result, the generation of magnetic saturation can be alleviated near the second curved surface forming portion R21.

[0119] By curving the second curved surface CS2 of the second curved surface forming portion R21 in a concave shape, the coil 13 can be wound more around the tooth body portion 31, compared with the case where the second curved surface CS2 of the second curved surface forming portion R21 is curved in a convex shape. As a result, the slot occupancy factor of the coil 13 can be increased, and the output torque of the brushless motor 100 can be improved.

[0120] Furthermore, in the magnetic core 1b, in the direction opposite to the third direction DIR3, the second curved surface forming portion R21 protrudes from the second flat surface FS2 of the second side surface SS2 and is only located at a position closer to the opposite direction side of the third direction DIR3 than the second flat surface FS2 of the second side surface SS2. In other words, in the direction opposite to the third direction DIR3, the second curved surface forming portion R21 is formed without reducing the cross-sectional area of ​​the tooth body portion 31. 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. Therefore, it is possible to suppress a reduction in the output torque of the brushless motor 100.

[0121] In the magnetic core 1b, a second curved surface forming portion R22 having a second curved surface CS2 curved in a concave shape is formed on the tooth body portion 31. 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 2. By forming the second curved surface forming portion R22 on the tooth body portion 31, the magnetic flux can flow in the shortest path near the second curved surface forming portion R22 without taking a detour. Therefore, in the magnetic core 1b, the magnetic flux flows more easily near the second curved surface forming portion R22 than in the magnetic core 50 involved in the comparative example. As a result, the generation of magnetic saturation can be alleviated near the second curved surface forming portion R22.

[0122] By bending the second curved surface CS2 of the second curved surface forming portion R22 in a concave shape, the coil 13 can be wound more around the tooth body portion 31 compared to the case where the second curved surface CS2 of the second curved surface forming portion R22 is bent in a convex shape. As a result, the wire slot occupancy factor of the coil 13 can be increased, and the output torque of the brushless motor 100 can be improved.

[0123] According to the manufacturing method of the magnetic core 1b, the burrs formed on the second curved surface CS2 before the finishing process can be removed by the finishing process. More specifically, the radius of curvature CR2 of the second curved surface CS2 of the soft magnetic powder SMP after compression molding is greater than the radius RA of the medium M. Thus, in the finishing process, the medium M can contact every corner of the second curved surface CS2, and the burrs formed on the second curved surface CS2 in the previous stage of the finishing process can be removed by the finishing process. Thus, it is possible to suppress the damage of the coil 13 when the coil 13 is wound on the tooth body 31 after the magnetic core 1b is completed.

[0124] [Other embodiments]

[0125] The magnetic core according to the present invention is not limited to the magnetic core 1, the magnetic core 1a, or the magnetic core 1b, and can be modified within the scope of the gist thereof. In addition, the structures of the magnetic core 1, the magnetic core 1a, or the magnetic core 1b can be arbitrarily combined.

[0126] In addition, the rotating electrical machine only needs to include the magnetic core 1, the magnetic core 1a, or the magnetic core 1b, and may have a brush.

[0127] The present invention has the following structure.

[0128] (1) A magnetic core is a magnetic core for a rotating electrical machine, comprising: a core back having a front surface, wherein when the magnetic core is assembled in the rotating electrical machine, the front surface faces a first direction, wherein the first direction faces an axis of rotation of the rotating electrical machine; and a tooth portion, wherein the tooth portion includes: a tooth body portion extending from the front surface in the first direction; and a tooth tip portion provided at a tip of the tooth body portion, wherein the tooth tip portion has a back surface facing in a direction opposite to the first direction, wherein the tooth body portion has an end surface, wherein when the magnetic core is assembled in the rotating electrical machine, the end surface faces a second direction along the axis of rotation, wherein the end surface has a concave curved surface which smoothly connects to the front surface of the core back or the back surface of the tooth tip portion, wherein the curved surface is formed by a first curved surface forming portion which is a part of the tooth body portion.

[0129] (2) In the magnetic core described in (1), the end surface 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 is located only at a position closer to the second direction side than the first flat surface.

[0130] (3) In the magnetic core described in (1) or (2), the tooth body portion has a side surface, and when the magnetic core is assembled in the rotating electrical machinery, the side surface is oriented in the circumferential direction centered on the axis of rotation, and the side surface 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 portion, and the curved surface is formed by a second curved surface forming portion which is a part of the tooth body portion.

[0131] (4) In the magnetic core described in (3), 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 toward the circumferential direction and is located only at a position closer to the circumferential direction than the second flat surface.

[0132] (5) In the magnetic core described in any one of (1) to (4), the tooth body portion has: a side surface facing in a third direction which is circumferential with the rotation axis as the center when the magnetic core is assembled in the rotating electrical machinery; and an inclined surface connecting the end face to the side surface, the inclined surface having a curved surface with a terminal end which is gradually narrowed so as to smoothly connect itself to an edge of the curved surface in the third direction, the curved surface with a terminal end being gradually narrowed by a third curved surface forming portion which is a part of the tooth body portion.

[0133] (6) In the magnetic core described in any one of (1) to (5), the core is a molded body formed of soft magnetic powder.

[0134] (7) A magnetic core with a coil, comprising: the magnetic core described in any one of (1) to (6); and a coil wound around the tooth body portion.

[0135] (8) A rotating electrical machine comprising the magnetic core described in any one of (1) to (6).

[0136] (9) A method for manufacturing a magnetic core, comprising: a finishing step of finishing the magnetic core described in any one of (1) to (6) by grinding using a spherical medium, and in a stage before the above-mentioned finishing step, the above-mentioned magnetic core is manufactured to a state where the radius of curvature of the above-mentioned curved surface becoming the above-mentioned end face is larger than the diameter of the above-mentioned medium used in the finishing step.

[0137] (10) A method for manufacturing a magnetic core, comprising: a finishing step of finishing the magnetic core described in (3) or (4) by grinding using a spherical medium, and in a stage before the above-mentioned finishing step, the above-mentioned magnetic core is manufactured to a state where the radius of curvature of the above-mentioned curved surface of the above-mentioned side surface is larger than the diameter of the above-mentioned medium used in the finishing step.

[0138] Description of Reference Numerals

[0139] 1, 11, 12, 1a, 1b... magnetic core; 2... back of the core; 3... tooth; 10... stator; 13... coil; 14... bearing; 14a... first bearing; 14b... second bearing; 15... housing; 15a... first housing; 15b... second housing; 20... rotor; 21... shaft; 22... rotor member; 23... soft magnetic body; 24... hard magnetic body; 31... main body of tooth; 32... end of tooth; 100... brushless motor; A... corner; B... roller; CON... convex surface; CR1, CR2... radius of curvature; CS1... first curved surface; CS2... second curved surface; CS3... third curved surface; DI... mold; DIR1...the first direction; DIR2...the second direction; DIR3...the third direction; DIR4...the fourth direction; ES1...the first end surface; ES2...the second end surface; FS1...the first flat surface; FS2...the second flat surface; IS2, IS32...the front surface; M...the medium; MFL...the magnetic lines of force; OP...the opening; OS2, OS32...the back surface; P...the punch; R1, R11, R12...the first curved surface forming portion; R2, R21, R22...the second curved surface forming portion; R3...the third curved surface forming portion; RA...the radius; SMP...the soft magnetic powder; SS1...the first side surface; SS2...the second side surface; SL...the inclined surface; W...water.

Claims

1. A magnetic core used for a rotating electrical machine, characterized in that: have: a core back having a front surface, wherein when the magnetic core is assembled in the rotating electrical machine, the front surface faces a first direction, the first direction faces a rotation axis of the rotating electrical machine; as well as Tooth, The tooth portion comprises: a tooth body portion extending from the front surface toward the first direction; as well as a tooth terminal portion, which is disposed at the terminal end of the tooth main body portion, The tooth tip portion has a back surface facing in the opposite direction to the first direction, The tooth body has an end face, and when the magnetic core is assembled in the rotary electrical machine, the end face faces the second direction along the rotation axis. The end surface has a concave curved surface that smoothly connects to the front surface of the core back or the back surface of the tooth tip portion, and the curved surface is formed by a first curved surface forming portion that is a part of the tooth body portion.

2. The magnetic core according to claim 1, characterized in that The end surface includes a first flat surface which is 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 second direction side relative to the first flat surface.

3. The magnetic core according to claim 1 or 2, characterized in that: The tooth body portion has a side surface that faces in a circumferential direction centered on the rotation axis when the magnetic core is assembled in the rotary electrical machine. The side surface has a concave curved surface that smoothly connects to the front surface of the core back or the back surface of the tooth tip portion, and the curved surface is formed by a second curved surface forming portion that is a part of the tooth body portion.

4. The magnetic core according to claim 3, characterized in that: The side surface includes a second flat surface which is parallel to the first direction. The second curved surface forming portion protrudes from the second flat surface toward the circumferential direction and is located only on the circumferential side of the second flat surface.

5. The magnetic core according to any one of claims 1 to 4, characterized in that: The tooth body portion has: a side surface facing a third direction which is a circumferential direction centered on the rotation axis when the magnetic core is assembled in the rotary electrical machine; and an inclined surface connecting the end surface and the side surface. The inclined surface has a curved surface that tapers to a terminal end so as to smoothly connect to an edge of the curved surface in the third direction, and the curved surface that tapers to a terminal end is formed by a third curved surface forming portion that is a part of the tooth body portion.

6. The magnetic core according to any one of claims 1 to 5, characterized in that: It is a molded body formed from soft magnetic powder.

7. A magnetic core with a coil, characterized in that: have: The magnetic core according to any one of claims 1 to 6; and The coil is wound around the tooth body.

8. A rotating electrical machine, characterized in that: A magnetic core according to any one of claims 1 to 6 is provided.

9. A method for manufacturing a magnetic core, characterized in that: The method comprises: a finishing step of finishing the magnetic core according to any one of claims 1 to 6 by grinding using a spherical medium; In a stage before the finishing step, the magnetic core is manufactured in a state where the radius of curvature of the curved surface to be the end surface is larger than the diameter of the medium used in the finishing step.

10. A method for manufacturing a magnetic core, characterized in that: The method comprises: a finishing step of finishing the magnetic core according to claim 3 or 4 by grinding using a spherical medium; In a stage before the finishing step, the magnetic core is manufactured in a state where the curvature radius of the curved surface of the side surface is larger than the diameter of the medium used in the finishing step.

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