Split core, annular core and method for manufacturing same, and rotating electrical machine

Abstract

This split core comprises a core back part and a tooth part. The core back part has: a first lateral surface facing a first direction, which is one way in a circumferential direction centered on a rotation axis of a rotating electrical machine when the split core is incorporated into said rotating electrical machine; an inner main surface facing a second direction toward the rotation axis; a first end surface facing a third direction along the rotation axis; and a second end surface facing a direction that is the opposite of the third direction. The tooth part extends from the inner main surface in the second direction. A first groove extending along the first direction is formed in the first lateral surface. The first groove is exposed from either the first end surface or the second end surface.

Description

Split Core, Annular Core, Method for Manufacturing the Same, and Rotating Electrical Machine

[0001] The present invention relates to a technique for more firmly adhering split cores to each other in a rotating electrical machine.

[0002] Conventionally, split cores have been used in rotating electrical machines in order to improve the productivity of rotating electrical machines. As a conventional rotating electrical machine provided with split cores, for example, the rotating electrical machine described in Patent Document 1 is known. The rotating electrical machine described in Patent Document 1 includes a rotor and a stator. The stator is configured by combining a plurality of stator cores in an annular shape. Each of the plurality of stator cores is a split core. Each of the plurality of stator cores includes a yoke portion, a tooth portion, and a chip portion. The yoke portion is formed in an arc shape in which the outer periphery of the yoke portion extends in the circumferential direction centered on the rotation axis of the rotor, and has a yoke portion side surface facing the circumferential direction in the rotating electrical machine and a yoke portion outer peripheral surface facing the direction from the rotation axis toward the yoke portion among the radial directions centered on the rotation axis in the rotating electrical machine. The tooth portion protrudes from the yoke portion in the direction from the yoke portion toward the rotation axis among the radial directions centered on the rotation axis. The chip portion is provided at the tip portion on the rotation axis side of the tooth portion and faces the rotor.

[0003] Also, in some cases, as in the electric motor described in Patent Document 2, the stator may be housed in a case.

[0004] Japanese Unexamined Patent Application Publication No. 2021-27601, Japanese Unexamined Patent Application Publication No. 2005-304106

[0005] When constructing the stator, after arranging a plurality of stator cores in an annular shape, an adhesive is infiltrated between the opposing yoke portion side surfaces (adhesive surfaces) of adjacent stator cores to fix the yoke portion side surfaces to each other. Thereby, a plurality of stator cores are fixed to constitute the stator. However, in the case of the rotating electrical machine described in Patent Document 1, there is a risk that the adhesive may not enter between the yoke portion side surfaces and may flow out to the outside. In this case, the adhesive strength between adjacent stator cores becomes low. Also, when the stator is housed in a case, the adhesive may solidify in a state where it has flowed out onto the outer peripheral surface of the yoke portion, and the adhesive that has flowed out onto the outer peripheral surface of the yoke portion may hinder the housing of the stator in the case.

[0006] Therefore, the object of the present invention is to provide a segmented core that can more reliably bond adhesive surfaces together, an annular core comprising a plurality of such segmented cores, a method for manufacturing the same, and a rotating electric machine equipped with such segmented cores.

[0007] A divided core according to one embodiment of the present invention is used in a rotating electric machine. The divided core comprises a core back portion and a teeth portion. The core back portion has a first side surface facing a first direction which is one of the circumferential directions around the rotation axis of the rotating electric machine when the divided core is incorporated into the rotating electric machine, an inner main surface facing a second direction toward the rotation axis, a first end surface facing a third direction along the rotation axis, and a second end surface facing the opposite direction to the third direction. The teeth portion extends from the inner main surface in the second direction. A first groove extending along the third direction is formed on the first side surface. The first groove is exposed from either the first end surface or the second end surface.

[0008] If the first groove is exposed from the first end face, liquid adhesive is applied to the first groove from the first end face side. If the first groove is exposed from the second end face, liquid adhesive is applied to the first groove from the second end face side. The adhesive applied to the first groove penetrates into the gap between the first side surface of the divided core and the second side surface of the divided core adjacent to it in the circumferential direction, and penetrates widely between the first and second side surfaces. Because the first and second side surfaces are in surface contact, a predetermined amount of time is required for the adhesive to penetrate.

[0009] If the first groove is not formed on the first side surface, the adhesive requires a predetermined amount of time to penetrate, and there is a risk that the adhesive may flow out before it can enter the gap between the first and second side surfaces. On the other hand, in a divided core according to one embodiment of the present invention, the adhesive can be temporarily retained in the space between the first groove and the second side surface. Thereafter, the adhesive can enter the gap between the first and second side surfaces over time. Therefore, the adhesive can enter the space between the first and second side surfaces without flowing out. As a result, the adhesive can penetrate more easily between the bonding surfaces.

[0010] Furthermore, since the bonding surfaces can be bonded more securely, no materials other than adhesive are required for bonding. Also, even when the annular core is housed in a case, the adhesive can prevent it from hindering the storage of the annular core in the case. In addition, the first groove can be used for positioning when arranging multiple segmented cores along the circumferential direction centered on the rotation axis of a rotating electric machine.

[0011] Furthermore, the first groove is exposed from either the first or second end face. In other words, the first groove does not penetrate the segmented core in a third direction. Therefore, the contact area between the first and second side surfaces is increased, allowing for more secure bonding between the adhesive surfaces.

[0012] In the above-described segmented core, the core back portion may have a second side surface that faces the other direction in the circumferential direction when the segmented core is assembled into a rotating electric machine. In this configuration, a second groove is formed on the second side surface. The second groove is exposed from either the first end face or the second end face, from which the first groove is exposed.

[0013] According to the above configuration, the temporary retention amount of adhesive can be increased in the divided core without increasing the width, depth, and height of the first groove. Therefore, the magnetic flux flowing through the core back portion is not significantly obstructed, and the impact on the motor characteristics of the rotating electric machine can be kept to a minimum.

[0014] In the above-described segmented core, when multiple segmented cores are incorporated into a rotating electric machine, the multiple segmented cores are arranged along the circumferential direction, and the first surface of each of the multiple segmented cores is in surface contact with the second surface of the adjacent segmented core in the circumferential direction, and the first groove and the second groove of the adjacent segmented core in the circumferential direction may form a single groove.

[0015] According to the above configuration, the adhesive only needs to be applied to the grooves. Therefore, compared to the case where the first groove of the divided core and the second groove of the divided core arranged adjacent to it in the circumferential direction form two or more grooves, the number of grooves to which the adhesive is applied can be reduced, contributing to improved productivity of the annular core.

[0016] In the above-described segmented core, a protrusion connected to the first groove may be formed on the first side surface. In this configuration, the protrusion has a shape that fits with a part of the second groove. When a plurality of segmented cores are incorporated into a rotating electric machine, the plurality of segmented cores are arranged along the circumferential direction, and the first side surface of each of the plurality of segmented cores is in surface contact with the second side surface of the adjacent segmented core in the circumferential direction, and the protrusion fits with a part of the second groove, and the first groove, the protrusion, and the second groove of the adjacent segmented core in the circumferential direction may form a single groove.

[0017] According to the above configuration, the protrusion can prevent adhesive from leaking from the second end face side. In addition, it facilitates positioning when arranging multiple segmented cores along the circumferential direction centered on the rotation axis of a rotating electric machine.

[0018] A divided core according to one embodiment of the present invention is used in a rotating electric machine. The divided core comprises a core back portion and a teeth portion. The core back portion has a first side surface facing a first direction which is one of the circumferential directions around the rotation axis of the rotating electric machine when the divided core is incorporated into the rotating electric machine, an inner main surface facing a second direction toward the rotation axis, a first end surface facing a third direction along the rotation axis, and a second end surface facing the opposite direction to the third direction. The teeth portion extends from the inner main surface in the second direction. A first recess extending along the first direction is formed on the first side surface. The first recess is exposed from either the first end surface or the second end surface.

[0019] The above-described segmented core allows for more reliable bonding between bonding surfaces. Furthermore, it does not require any materials other than adhesive for bonding. In addition, when housing the annular core in a case, the adhesive can prevent it from hindering the storage of the annular core in the case. Moreover, the first groove can be used for positioning when arranging multiple segmented cores along the circumferential direction centered on the rotation axis of a rotating electric machine.

[0020] Furthermore, the first groove is exposed from either the first or second end face. In other words, the first groove does not penetrate the segmented core in a third direction. Therefore, the contact area between the first and second side surfaces is increased, allowing for more secure bonding between the adhesive surfaces.

[0021] In the above-described segmented core, the first recess may have a curved surface that is curved to form a part of the surface of the ellipsoid.

[0022] The above configuration prevents adhesive from remaining in the space between the first recess and the second side surface. The adhesive applied to the first recess easily penetrates the gap between the first and second side surfaces. Therefore, the adhesive can penetrate more widely between the first and second side surfaces. As a result, the bonding surfaces can be bonded together more securely.

[0023] In the above-described segmented core, the core back portion may have a second side surface that faces the other direction in the circumferential direction when the segmented core is assembled into a rotating electric machine. In this configuration, a second recess is formed on the second side surface. The second recess is exposed from either the first end surface or the second end surface, from which the first recess is exposed.

[0024] According to the above configuration, the temporary retention amount of adhesive can be increased without increasing the size of the first recess. Therefore, the magnetic flux flowing through the core back section is not significantly obstructed, and the impact on the motor characteristics of the rotating electrical machine can be kept to a minimum.

[0025] In the above-described segmented core, when multiple segmented cores are incorporated into a rotating electric machine, the multiple segmented cores are arranged along the circumferential direction, and the first side surface of each of the multiple segmented cores is in surface contact with the second side surface of the adjacent segmented core in the circumferential direction, and the first recess and the second recess of the adjacent segmented core in the circumferential direction may form a single recess.

[0026] According to the above configuration, the adhesive only needs to be applied to the recesses. Therefore, compared to the case where the first recess of the divided core and the second recess of the divided core, which is positioned adjacent to it in the circumferential direction, form two or more recesses, the number of recesses to which the adhesive needs to be applied can be reduced, contributing to improved productivity of the annular core.

[0027] In the above-described segmented core, the first groove or first recess may be exposed only from either the first end face or the second end face, and from the first side surface.

[0028] With the above configuration, the adhesive is less likely to flow out onto the inner or outer main surface.

[0029] In the above-described segmented core, the core back portion may have an outer main surface that faces the opposite direction to the second direction when the segmented core is assembled into a rotating electric machine. In this configuration, the first groove or first recess is exposed from either the inner main surface or the outer main surface.

[0030] According to the above configuration, if the first groove or first recess is exposed from the outer main surface, the liquid adhesive can be applied to the first groove or first recess not only from the first end surface side but also from the outer main surface side. If the first groove or first recess is exposed from the inner main surface, the liquid adhesive can be applied to the first groove or first recess from the inner main surface side as well. Therefore, the adhesive is easy to apply to the first groove or first recess.

[0031] In the above-described segmented core, the teeth portion may include a teeth body portion around which a coil is wound when the segmented core is incorporated into a rotating electric machine. In this configuration, the first groove or first recess is exposed from the first end face and is located only on the third direction side from the teeth body portion.

[0032] According to the above configuration, the first groove or first recess does not obstruct the magnetic flux flowing through the core back portion, and the impact on the motor characteristics of the rotating electric machine can be kept to a minimum.

[0033] In the above-described segmented core, the core back portion may have an outer main surface that faces the opposite direction to the second direction when the segmented core is assembled into a rotating electric machine. In this configuration, the first groove or first recess is located only on the outer main surface side of the center plane between the inner main surface and the outer main surface.

[0034] According to the above configuration, the first groove or first recess does not obstruct the magnetic flux flowing through the core back portion, and the impact on the motor characteristics of the rotating electric machine can be kept to a minimum.

[0035] In the above-described segmented core, the teeth portion may include a teeth body portion around which a coil is wound when the segmented core is incorporated into a rotating electric machine. In this configuration, the first groove or first recess is located only on the first direction side from the teeth body portion.

[0036] According to the above configuration, the first groove or the first recess hardly inhibits the magnetic flux flowing through the core back portion, and the influence on the motor characteristics of the rotating electrical machine can be minimized.

[0037] In the above split core, the first groove or the first recess may be exposed from the first end face. In this configuration, the maximum distance along the first direction between the first groove or the first recess and the first side face becomes shorter as it moves away from the first end face.

[0038] According to the above configuration, the adhesive applied to the first groove or the first recess easily enters the gap between the first side face and the second side face. Therefore, the adhesive easily penetrates widely between the first side face and the second side face. As a result, the adhesive surfaces can be more reliably adhered to each other.

[0039] In the above split core, the first groove or the first recess may be exposed from the first end face. In this configuration, the first groove or the first recess may be smoothly connected to the first end face.

[0040] According to the above configuration, it is easy to apply the adhesive to the first groove or the first recess, and the adhesive hardly remains on the first end face.

[0041] In the above split core, the first groove or the first recess may be smoothly connected to the first side face.

[0042] According to the above configuration, the adhesive applied to the first groove or the first recess easily enters the gap between the first side face and the second side face.

[0043] In the above split core, the first groove or the first recess may be exposed from the first end face. In this configuration, the first groove or the first recess has a bottom surface portion connected to the first end face, a side surface portion connected to the first side face, and a concave curved surface portion. The curved surface portion smoothly connects the bottom surface portion and the side surface portion.

[0044] According to the above configuration, it is possible to suppress the adhesive temporarily staying in the space between the first groove or the first recess and the second side face from continuing to stay.

[0045] The above split core may be a molded body formed from soft magnetic powder.

[0046] According to the above configuration, the above split core can be easily manufactured.

[0047] An annular core according to an aspect of the present invention includes a plurality of the above split cores and an adhesive. The core back portions of the plurality of split cores each have a second side surface that faces the other in the circumferential direction when the split core is incorporated into a rotating electrical machine. The plurality of split cores are arranged along the circumferential direction. The first side surface of each of the plurality of split cores and the second side surface of the split core arranged adjacent in the circumferential direction are adhered by an adhesive.

[0048] According to the above configuration, the annular core becomes robust by more reliably adhering the first side surface of the split core and the second side surface of the split core arranged adjacent in the circumferential direction.

[0049] A method for manufacturing a split core according to an aspect of the present invention includes an arranging step of arranging a plurality of the above split cores along the circumferential direction, and an adhesive applying step of applying a liquid adhesive to each of the first grooves or the first recesses of the plurality of split cores after the arranging step. The core back portions of the plurality of split cores each have a second side surface that faces the other in the circumferential direction when the split core is incorporated into a rotating electrical machine. In the arranging step, the first side surface of each of the plurality of split cores is brought into surface contact with the second side surface of the split core arranged adjacent in the circumferential direction.

[0050] According to the above manufacturing method, the first side surface of the split core and the second side surface of the split core arranged adjacent in the circumferential direction can be more reliably adhered.

[0051] According to the present invention, it becomes easier for the adhesive to enter between the bonding surfaces.

[0052] Figure 1 is an external perspective view of a brushless motor 100 using a divided core 1. Figure 2 is a schematic perspective view showing a part of the brushless motor 100 cut off. Figure 3 is a plan view of the stator 10 viewed in the fourth direction DIR 4. Figure 4 is a perspective view of the divided core 1. Figure 5 is a plan view of the divided core 1 viewed in the fourth direction DIR 4. Figure 6 is a side view of the divided core 1 viewed in the sixth direction DIR 6. Figure 7 is a plan view showing an example of a method for manufacturing an annular core 11. Figure 8 is a diagram showing an example of the simulation results of the magnetic flux density distribution when current is passed through the coil 13. Figure 9 is a diagram showing an example of the simulation results of the magnetic flux density distribution when current is passed through the coil 13. Figure 10 is a perspective view of the divided core 1a. Figure 11 is a perspective view of the divided core 1a. Figure 12 is a plan view showing a part of the annular core 11a viewed in the fourth direction DIR 4. Figure 13 is a perspective view of the divided core 1b. Figure 14 is a perspective view of the divided core 1c. Figure 15 is a side view of the first recess R1 and the vicinity of the first recess R1 viewed in the sixth direction DIR6. Figure 16 is a side view of the first groove G1 and the vicinity of the first groove G1 viewed in the sixth direction DIR6. Figure 17 is a plan view showing a part of the annular core 11c viewed in the fourth direction DIR4. Figure 18 is a perspective view of the divided core 1d. Figure 19 is a cross-sectional view showing a cross section passing through the first groove G1 and perpendicular to the first side surface SS1. Figure 20 is a perspective view of the divided core 1f.

[0053] [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 in which a divided core 1 is used. Figure 2 is a schematic perspective view showing a part of the brushless motor 100 cut off. In Figure 2, reference numerals are given only to representative divided cores 1 and coils 13 from among the multiple divided cores 1 and coils 13.

[0054] In this specification, as an example, directions are defined as follows: Among the axial directions along the rotation axis AR of the brushless motor 100, the direction in which the shaft 21 protrudes from the opening OP to the outside of the housing 15 is defined as the third direction DIR3. The opposite direction of the third direction DIR3 is defined as the fourth direction DIR4. Among the circumferential directions centered on the rotation axis AR of the brushless motor 100, the direction clockwise with respect to the rotation axis AR of the brushless motor 100, as seen from the fourth direction DIR4, is defined as the first direction DIR1. Among the circumferential directions centered on the rotation axis AR of the brushless motor 100, the direction counterclockwise with respect to the rotation axis AR of the brushless motor 100, as seen from the third direction DIR3, is defined as the sixth direction DIR6. Of the radial directions centered on the rotation axis AR of the brushless motor 100, the direction from the tooth tip 32 toward the rotation axis AR of the brushless motor 100 is defined as the second direction DIR2. The opposite direction of the second direction DIR2 is defined as the fifth direction DIR5.

[0055] As shown in Figure 2, the brushless motor 100 comprises a stator 10, bearings 14, a housing 15, and a rotor 20. In this embodiment, the brushless motor 100 is an inner rotor type. That is, the stator 10 is arranged around the rotor 20. The stator 10 includes an annular core 11 and a plurality of coils 13. The brushless motor 100 is an example of a rotating electric machine according to 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.

[0056] 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, or permanent magnet synchronous generators, etc.

[0057] 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.

[0058] 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 centered on 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 centered on 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 centered on the rotation axis AR. The hard magnetic material 24 is magnetized. The hard magnetic material becomes magnetized when an external magnetic field is applied to it. After that, even if the application of the magnetic field is stopped, the hard magnetic material does not lose its magnetization.

[0059] 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.

[0060] The first bearing 14a is located in the third direction DIR3 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.

[0061] 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 third direction DIR3 from the second housing 15b. Also, as shown in Figure 1, the first housing 15a has an opening OP. As a result, the shaft 21 protrudes from the opening OP in the third direction DIR3. In other words, in this embodiment, the brushless motor 100 is a single-shaft type. Note that the brushless motor 100 is not limited to a single-shaft type, but may also be a double-shaft type.

[0062] The first housing 15a supports the first bearing 14a, the annular core 11, and the multiple 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.

[0063] Figure 3 is a plan view of the stator 10 as seen in the fourth direction DIR 4. As shown in Figure 3, the annular core 11 has a plurality of segmented cores 1 and a plurality of adhesives 12. The adhesive 12 is liquid before curing. In this embodiment, the plurality of segmented cores 1 have the same shape as each other. Also in this embodiment, the annular core 11 has nine segmented cores 1. A coil 13 is wound around each of the nine segmented cores 1. The nine segmented cores 1 are arranged along the circumferential direction centered on the rotation axis AR of the brushless motor 100, and the annular core 11 is formed by bonding each segmented core 1 to an adjacent segmented core 1 in that circumferential direction. Details of the manufacturing method of the annular core 11 will be described later. The annular core 11 is arranged around the hard magnetic material 24 with a gap between them. In this embodiment, the segmented cores 1 are used in the stator 10, but the segmented core according to the present invention may also be used as part of the rotor. Also, the plurality of segmented cores 1 do not have to have the same shape as each other. Furthermore, the number of partitioned cores is not limited to nine.

[0064] 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 divided 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.

[0065] The coil 13 is supplied with current from the power source. The coil 13 generates a magnetic field when current flows through it. The divided 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.

[0066] (Configuration of the divided core 1) Next, the configuration of the divided core 1 according to the first embodiment of the present invention will be described below with reference to the drawings. Figure 4 is a perspective view of the divided core 1. As shown in Figure 4, the divided 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 divided core 1, which is a single member. Here, a single member means a member that has a structure that cannot be separated without damage.

[0067] The segmented core 1 is made of a soft magnetic material. In this embodiment, the segmented 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 soft magnetic powder material 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 segmented core 1 is manufactured, for example, by compression molding. In addition, an insulating film (not shown) is applied to the surface of the segmented core 1 that comes into contact with another member. Note that the segmented core 1 does not have to be a molded body formed from soft magnetic powder.

[0068] The core back portion 2 has a first side surface SS1 facing the first direction DIR1, a second side surface SS2 facing the sixth direction DIR6, an inner main surface IS2 facing the second direction DIR2, an outer main surface OS2 facing the fifth direction DIR5, a first end surface ES1 facing the third direction DIR3, and a second end surface ES2 facing the fourth direction DIR4. In this embodiment, the first side surface SS1, the second side surface SS2, the inner main surface IS2, the first end surface ES1, and the second end surface ES2 are all flat surfaces. The outer main surface OS2 is a curved surface that curves convexly toward the fifth direction DIR5. Note that the shapes of the first side surface SS1, the second side surface SS2, the inner main surface IS2, the outer main surface OS2, the first end surface ES1, and the second end surface ES2 are not limited to the shapes shown in this embodiment.

[0069] A first groove G1 is formed on the first side surface SS1. The first groove G1 extends along the third direction DIR3. The first groove G1 reaches the first end face ES1 but does not reach the second end face ES2. Also, the first groove G1 does not reach the second side surface SS2. In this embodiment, the first groove G1 does not reach either the inner main surface IS2 or the outer main surface OS2. Therefore, the first groove G1 is exposed from the first side surface SS1 and the first end face ES1, but not from the second side surface SS2, the inner main surface IS2, the outer main surface OS2, and the second end face ES2. That is, the first groove G1 is exposed only from the first side surface SS1 and the first end face ES1.

[0070] Furthermore, the first groove G1 may not be exposed from the first end face ES1, but may be exposed from the second end face ES2. In other words, the first groove G1 only needs to be exposed from either the first end face ES1 or the second end face ES2. In this case, the first groove G1 may be exposed only from the first side surface SS1 and the second end face ES2.

[0071] A second groove G2 is formed on the second side surface SS2. The second groove G2 extends along the third direction DIR3. Similar to the first groove G1, the second groove G2 reaches the first end face ES1 but not the second end face ES2. Also, the second groove G2 does not reach the second side surface SS2. In this embodiment, the second groove G2 does not reach either the inner main surface IS2 or the outer main surface OS2. Therefore, the second groove G2 is exposed from the second side surface SS2 and the first end face ES1, but not from the first side surface SS1, the inner main surface IS2, the outer main surface OS2, and the second end face ES2. That is, the second groove G2 is exposed only from the second side surface SS2 and the first end face ES1. Note that in this embodiment, the second groove G2 does not necessarily have to be formed on the second side surface SS2.

[0072] Furthermore, the second groove G2 is formed to be exposed from the first end face ES1 when the first groove G1 is exposed from the first end face ES1, and to be exposed from the second end face ES2 when the first groove G1 is exposed from the second end face ES2. In other words, the second groove G2 is formed to be exposed from either the first end face ES1 or the second end face ES2, whichever of the first groove G1 is exposed.

[0073] The teeth portion 3 extends from the inner main surface IS2 of the core back portion 2 in the second direction DIR2. The teeth portion 3 extends from the center of the inner main surface IS2 in the second direction DIR2. The teeth portion 3 includes a teeth body portion 31 that extends from the inner main surface IS2 of the core back portion 2 in the second direction DIR2, and a teeth tip portion 32 provided at the tip of the teeth body portion 31. The coil 13 is wound around the teeth body portion 31. When the split core 1 is assembled into the brushless motor 100, the teeth tip portion 32 faces the hard magnetic material 24 of the rotor 20, with an air gap between them.

[0074] Figure 5 is a plan view of the divided core 1 as seen in the fourth direction DIR 4. In Figure 5, for explanatory purposes, a virtual extension line VEL extending the tooth body portion 31 toward the fifth direction DIR 5 is shown as a dotted line, and the center plane MS between the inner main surface IS2 and the outer main surface OS2 is shown as a dashed line.

[0075] As shown in Figure 5, the first groove G1 is located only on the DIR1 side in the first direction from the virtual extension line VEL. Therefore, the first groove G1 is located only on the DIR1 side in the first direction from the tooth body 31. Furthermore, the first groove G1 is located only on the OS2 side of the outer main surface from the center plane MS between the inner main surface IS2 and the outer main surface OS2.

[0076] The second groove G2 is located only on the DIR6 side in the sixth direction from the virtual extension line VEL. Therefore, the second groove G2 is located only on the DIR6 side in the sixth direction from the tooth body 31. Furthermore, the second groove G2 is located only on the OS2 side of the outer main surface from the center plane MS between the inner main surface IS2 and the outer main surface OS2.

[0077] Figure 6 is a side view of the divided core 1 as seen in the sixth direction DIR 6. In Figure 6, for explanatory purposes, a virtual extension line VEL is shown as a dotted line, representing the extension of the tooth body 31 toward the fifth direction DIR 5.

[0078] As shown in Figure 6, the first groove G1 is located only on the third direction DIR3 side of the virtual extension line VEL. Therefore, the first groove G1 is located only on the third direction DIR3 side of the tooth body 31. Similarly, the second groove G2 is also located only on the third direction DIR3 side of the tooth body 31.

[0079] (Method for Manufacturing the Annular Core 11) Next, a method for manufacturing the annular core 11 according to the first embodiment of the present invention will be described below with reference to the drawings. Figure 7 is a plan view showing an example of a method for manufacturing the annular core 11. In Figure 7, reference numerals are given only to representative first side surface SS1, second side surface SS2, first groove G1, second groove G2, and groove G from among the multiple first side surface SS1, second side surface SS2, first groove G1, second groove G2, and groove G.

[0080] As shown in Figure 7, multiple segmented cores 1 are arranged along the circumferential direction centered on the rotation axis AR of the brushless motor 100 (arrangement step). In the arrangement step, the first side surface SS1 of each of the multiple segmented cores 1 is brought into surface contact with the second side surface SS2 of the segmented core 1 that is arranged adjacent to it in the circumferential direction. In this embodiment, the first groove G1 of each of the multiple segmented cores 1 and the second groove G2 of the segmented core 1 that is arranged adjacent to it in the circumferential direction form a single groove G.

[0081] After the placement step, adhesive 12 is applied to the grooves G (the first groove G1 of the divided core 1 and the second groove G2 of the divided core 1 adjacent to it in the circumferential direction) (adhesive application step). Since the adhesive 12 is liquid before curing, it enters the gap between the first side surface SS1 of the divided core 1 and the second side surface SS2 of the divided core 1 adjacent to it in the circumferential direction, and penetrates widely between the first side surface SS1 and the second side surface SS2. Later, as the adhesive 12 that has entered and penetrated widely between the first side surface SS1 and the second side surface SS2 hardens, the first side surface SS1 of the divided core 1 and the second side surface SS2 of the divided core 1 adjacent to it in the circumferential direction are bonded together. As a result, the first side surface SS1 and the second side surface SS2 become the bonded surface.

[0082] The split core 1 allows for more reliable bonding between the bonding surfaces. More specifically, a first groove G1 extending along the third direction DIR 3 is formed on the first side surface SS1 of the core back portion 2. The first groove G1 is exposed from either the first end surface ES1 or the second end surface ES2. When the first groove G1 is exposed from the first end surface ES1, the liquid adhesive 12 is applied to the first groove G1 from the first end surface ES1 side. When the first groove G1 is exposed from the second end surface ES2, the liquid adhesive 12 is applied to the first groove G1 from the second end surface ES2 side. The adhesive 12 applied to the first groove G1 penetrates into the gap between the first side surface SS1 of the split core 1 and the second side surface SS2 of the split core 1, which is positioned adjacent to it in the circumferential direction, and penetrates widely between the first side surface SS1 and the second side surface SS2. Since the first side surface SS1 and the second side surface SS2 are in surface contact, a predetermined amount of time is required for the adhesive 12 to penetrate.

[0083] If the first groove G1 is not formed on the first side surface SS1, the adhesive 12 requires a predetermined amount of time to penetrate, and there is a risk that the adhesive 12 may flow out before it can enter the gap between the first side surface SS1 and the second side surface SS2. On the other hand, in the divided core 1, the adhesive 12 can be temporarily retained in the space between the first groove G1 and the second side surface SS2. Then, over time, the adhesive 12 can enter the gap between the first side surface SS1 and the second side surface SS2. Therefore, the adhesive 12 can enter the space between the first side surface SS1 and the second side surface SS2 without flowing out. As a result, the adhesive 12 can enter the space between the bonding surfaces more easily.

[0084] Furthermore, since the bonding surfaces can be bonded together more securely, no materials other than the adhesive 12 are required for bonding. Also, even when the annular core 11 is housed in a case, the adhesive 12 can prevent it from hindering the storage of the annular core 11 in the case. In addition, the first groove G1 can be used for positioning when arranging multiple divided cores 1 along the circumferential direction centered on the rotation axis AR of the brushless motor 100.

[0085] Furthermore, the first groove G1 is exposed from either the first end face ES1 or the second end face ES2. In other words, the first groove G1 does not penetrate the divided core 1 in the third direction DIR3. Therefore, the contact area between the first side surface SS1 and the second side surface SS2 is increased, and the bonding surfaces can be bonded together more reliably.

[0086] Furthermore, a second groove G2 extending along the third direction DIR3 is formed on the second side surface SS2 of the core back portion 2. The second groove G2 is exposed from either the first end face ES1 or the second end face ES2, where the first groove G1 is exposed. This allows for a large temporary retention amount of the adhesive 12 in the divided core 1 without increasing the width, depth, and height of the first groove G1. Consequently, the magnetic flux flowing through the core back portion 2 is not significantly obstructed, and the impact on the motor characteristics of the brushless motor 100 can be minimized.

[0087] Furthermore, considering the influence on the motor characteristics of the brushless motor 100, it is preferable that the width of the first groove G1 (length along the short side of the first side surface SS1) is half or less of the contact surface width between the first side surface SS1 and the second side surface SS2 (in this embodiment, the length of the short side of the first side surface SS1).

[0088] Furthermore, the first groove G1 of the divided core 1 and the second groove G2 of the divided core 1, which are adjacent in the circumferential direction, form one groove G. The adhesive 12 only needs to be applied to the groove G. Therefore, compared to the case where the first groove G1 of the divided core 1 and the second groove G2 of the divided core 1, which are adjacent in the circumferential direction, form two or more grooves G, the number of grooves G to which the adhesive 12 is applied can be reduced, contributing to improved productivity of the annular core 11.

[0089] Furthermore, the first groove G1 is exposed only from either the first end face ES1 or the second end face ES2, and from the first side surface SS1. Therefore, the adhesive 12 is less likely to flow out onto the inner main surface IS2 or the outer main surface OS2.

[0090] The following will explain, with reference to the drawings, why the first groove G1 does not significantly obstruct the magnetic flux flowing through the core back portion 2. Figures 8 and 9 are diagrams showing examples of simulation results of the magnetic flux density distribution when current is passed through the coil 13, respectively. The shades in Figures 8 and 9 indicate the amount of magnetic flux flowing through the divided core 1. Lighter shades indicate a larger amount of magnetic flux flowing through the target area. Darker shades indicate a smaller amount of magnetic flux flowing through the target area. Note that the coil 13 is omitted in Figures 8 and 9. The magnetic core in this simulation has the same shape as the divided core 1, except that the first groove G1 and the second groove G2 are not formed.

[0091] When current is passed through the coil 13 wound around the tooth body 31, magnetic flux flows through the divided core 1. As shown in Figures 8 and 9, the amount of magnetic flux flowing through the tooth body 31 is the largest of the total amount of magnetic flux flowing through the divided core 1. Furthermore, the amount of magnetic flux increases as you get closer to the tooth body 31. On the other hand, the amount of magnetic flux increases as you move away from the tooth body 31. As shown in Figure 8, the amount of magnetic flux flowing is small in the portion on the third direction DIR3 side of the tooth body 31. Here, the first groove G1 is exposed from the first end face ES1 and is located only on the third direction DIR3 side of the tooth body 31. Therefore, the first groove G1 does not obstruct the magnetic flux flowing through the core back portion 2, and its influence on the motor characteristics of the brushless motor 100 can be kept to a minimum.

[0092] The amount of magnetic flux flowing decreases as the core back portion 2 approaches the outer main surface OS2. Here, the first groove G1 is located only on the side of the outer main surface OS2 relative to the central plane MS between the inner main surface IS2 and the outer main surface OS2. Therefore, the first groove G1 does not obstruct the magnetic flux flowing through the core back portion 2, and its influence on the motor characteristics of the brushless motor 100 can be kept to a minimum.

[0093] The amount of magnetic flux flowing decreases as it approaches the first side surface SS1 of the core back portion 2. Here, the first groove G1 is located only on the first direction DIR1 side of the tooth body portion 31. Therefore, the first groove G1 does not obstruct the magnetic flux flowing through the core back portion 2, and its influence on the motor characteristics of the brushless motor 100 can be kept to a minimum.

[0094] Furthermore, the segmented core 1 is a molded body formed from soft magnetic powder. Therefore, the segmented core 1 can be easily manufactured.

[0095] Furthermore, the annular core 11 becomes more robust when the first side surface SS1 of the divided core 1 and the second side surface SS2 of the divided core 1, which is positioned adjacent to it in the circumferential direction, are more securely bonded together.

[0096] According to the method for manufacturing the annular core 11, the first side surface SS1 of the divided core 1 and the second side surface SS2 of the divided core 1, which is positioned adjacent to it in the circumferential direction, can be bonded more reliably.

[0097] [First Modification] The configurations of the divided core 1a and annular core 11a according to the first modification of the present invention will be described below with reference to the drawings. Figures 10 and 11 are perspective views of the divided core 1a viewed in the fifth direction DIR 5, respectively. Note that for the divided core 1a and annular core 11a according to the first modification, only the parts that differ from the divided core 1 and annular core 11 according to the first embodiment will be described, and the rest will be omitted.

[0098] As shown in Figures 10 and 11, in this modified example, a protrusion CP is further formed on the first side surface SS1. In addition, the second groove G2 reaches not only the first end surface ES1 but also the second end surface ES2.

[0099] The protrusion CP is located in the fourth direction DIR4 from the first groove G1. The protrusion CP is also connected to the first groove G1. The protrusion CP extends along the fourth direction DIR4. In this modified example, the protrusion CP reaches the second end face ES2. The protrusion CP also has a shape that fits with a part of the second groove G2. Note that the second groove G2 and the protrusion CP do not necessarily have to reach the second end face ES2. In this modified example, the second groove G2 reaches not only the first end face ES1 but also the second end face ES2, but the portion of the second groove G2 that does not fit with the protrusion CP does not necessarily have to reach the first end face ES1.

[0100] Figure 12 is a plan view showing a portion of the annular core 11a as viewed in the fourth direction DIR4. In Figure 12, reference numerals are assigned only to representative first side surface SS1, second side surface SS2, first groove G1, second groove G2, and groove G from among the multiple first side surface SS1, second side surface SS2, first groove G1, second groove G2, and groove G.

[0101] As shown in Figure 12, in the annular core 11a, the protrusion CP engages with a part of the second groove G2. At this time, the first groove G1 and protrusion CP of each of the multiple segmented cores 1a, as well as the second groove G2 of segmented cores 1a that are adjacent to each other in the circumferential direction, form a single groove G.

[0102] The segmented core 1a described above also provides the same effect as the segmented core 1. In addition, a protrusion CP is formed on the first side surface SS1 of the segmented core 1a. The protrusion CP has a shape that fits into a part of the second groove G2. When multiple segmented cores 1a are incorporated into the brushless motor 100, the first side surface SS1 of each of the multiple segmented cores 1a makes surface contact with the second side surface SS2 of the adjacent segmented core 1a in the circumferential direction. At this time, the protrusion CP fits into a part of the second groove G2. As a result, the protrusion CP prevents the adhesive 12 from leaking from the second end surface ES2 side. Furthermore, positioning becomes easier when arranging multiple segmented cores 1a along the circumferential direction centered on the rotation axis AR of the brushless motor 100.

[0103] [Second Modification] The configuration of the divided core 1b according to the first modification of the present invention will be described below with reference to the drawings. Figure 13 is a perspective view of the divided core 1b. Note that for the divided core 1b according to the second modification, only the parts that differ from the divided core 1 according to the first embodiment will be described, and the rest will be omitted.

[0104] As shown in Figure 13, in this modified example, the first groove G1 reaches the outer main surface OS2. Therefore, the first groove G1 is exposed from the outer main surface OS2. On the other hand, the first groove G1 does not reach the inner main surface IS2 and is not exposed from the inner main surface IS2. Similarly, the second groove G2 reaches the outer main surface OS2. Therefore, the second groove G2 is exposed from the outer main surface OS2. On the other hand, the second groove G2 does not reach the inner main surface IS2 and is not exposed from the inner main surface IS2.

[0105] Furthermore, the first groove G1 may not be exposed from the outer main surface OS2, but rather from the inner main surface IS2. In other words, in this modified example, the first groove G1 only needs to be exposed from either the inner main surface IS2 or the outer main surface OS2. The second groove G2 only needs to be exposed from either the inner main surface IS2 or the outer main surface OS2, from which the first groove G1 is exposed.

[0106] The segmented core 1b described above also produces the same effect as the segmented core 1. Furthermore, in the segmented core 1b, the first groove G1 is exposed from either the inner main surface IS2 or the outer main surface OS2. When the first groove G1 is exposed from the outer main surface OS2, the liquid adhesive 12 can be applied to the first groove G1 not only from the first end surface ES1 side but also from the outer main surface OS2 side. When the first groove G1 is exposed from the inner main surface IS2, the liquid adhesive 12 can be applied to the first groove G1 from the inner main surface IS2 side as well. Therefore, it is easy to apply the adhesive 12 to the first groove G1.

[0107] [Third Modification] The configurations of the divided core 1c and annular core 11c according to the third modification of the present invention will be described below with reference to the drawings. Figure 14 is a perspective view of the divided core 1c. Figure 15 is a side view of the first recess R1 and the vicinity of the first recess R1 viewed in the sixth direction DIR6. Note that for the divided core 1c and annular core 11c according to the third modification, only the parts that differ from the divided core 1 and annular core 11 according to the first embodiment will be described, and the rest will be omitted.

[0108] As shown in Figure 14, in this modified example, the first side surface SS1 has a first recess R1 instead of a first groove G1. Also, the second side surface SS2 has a second recess R2 instead of a second groove G2.

[0109] In this modified example, as shown in Figures 14 and 15, the first recess R1 has a curved surface that curves to form a part of the surface of a sphere. The first recess R1 is exposed from the first side surface SS1 and the first end surface ES1, but not from the second side surface SS2, the inner main surface IS2, the outer main surface OS2, and the second end surface ES2. That is, the first recess R1 is exposed only from the first side surface SS1 and the first end surface ES1. Note that the first recess R1 is not limited to a curved surface that curves to form a part of the surface of a sphere, but may also have a curved surface that curves to form a part of the surface of an ellipsoid. Furthermore, the shape of the first recess R1 is not limited to the shape shown in this modified example.

[0110] Furthermore, the first recess R1 may not be exposed from the first end face ES1, but may be exposed from the second end face ES2. In other words, the first recess R1 only needs to be exposed from either the first end face ES1 or the second end face ES2. In this case, the first recess R1 may be exposed only from the first side surface SS1 and the second end face ES2.

[0111] The second recess R2 is exposed from the second side surface SS2 and the first end surface ES1, but not from the first side surface SS1, the inner main surface IS2, the outer main surface OS2, and the second end surface ES2. In other words, the second recess R2 is exposed only from the second side surface SS2 and the first end surface ES1. Note that the second recess R2 is not limited to a curved surface that curves in the shape of a part of the surface of a sphere, but may also have a curved surface that curves in the shape of a part of the surface of an ellipsoid. Furthermore, the shape of the first recess R1 is not limited to the shape shown in this modified example.

[0112] Furthermore, the second recess R2 is formed to be exposed from the first end face ES1 when the first recess R1 is exposed from the first end face ES1, and to be exposed from the second end face ES2 when the first recess R1 is exposed from the second end face ES2. In other words, the second recess R2 is formed to be exposed from either the first end face ES1 or the second end face ES2, whichever of the first recess R1 is exposed.

[0113] Similar to the first groove G1, in this modified example, the first recess R1 is located only on the DIR1 side in the first direction from the tooth body 31. Furthermore, the first recess R1 is located only on the OS2 side of the outer main surface from the center plane MS between the inner main surface IS2 and the outer main surface OS2. Moreover, the first recess R1 is located only on the DIR3 side in the third direction from the tooth body 31.

[0114] Similar to the second groove G2, in this modified example, the second recess R2 is located only on the sixth direction DIR6 side from the tooth body 31. Furthermore, the second recess R2 is located only on the outer main surface OS2 side from the center plane MS between the inner main surface IS2 and the outer main surface OS2. Moreover, the second recess R2 is located only on the third direction DIR3 side from the tooth body 31. Note that the second recess R2 does not necessarily have to be formed on the second side surface SS2.

[0115] Figure 16 is a cross-sectional view showing a cross-section passing through the first recess R1 and perpendicular to the first side surface SS1. As shown in Figure 16, the maximum distance L along the first direction DIR1 between the first recess R1 and the first side surface SS1 decreases as you move away from the first end face ES1. In other words, the maximum distance L along the first direction DIR1 between the first recess R1 and the first side surface SS1 decreases as you move towards the fourth direction DIR4.

[0116] Figure 17 is a plan view showing a portion of the annular core 11c as viewed in the fourth direction DIR4. In Figure 17, reference numerals are assigned only to representative first side surface SS1, second side surface SS2, first recess R1, second recess R2, and recess R from among the multiple first side surface SS1, second side surface SS2, first recess R1, second recess R2, and recess R.

[0117] As shown in Figure 17, in the annular core 11c, the first recess R1 of each of the multiple divided cores 1c, and the second recess R2 of the divided cores 1c that are adjacent to each other in the circumferential direction, form a single recess R.

[0118] The split core 1c described above also produces the same effect as the split core 1. Furthermore, in the split core 1c, a first recess R1 is formed on the first side surface SS1 instead of the first groove G1. Therefore, compared to the case with the first groove G1, it is easier to increase the opening area on the first end face ES1 side or the second end face ES2 side. This makes it easier to apply the adhesive 12 to the first recess R1.

[0119] Furthermore, in the divided core 1c, the first recess R1 has a curved surface that is curved to resemble a part of the surface of the ellipsoid. This prevents the adhesive 12 that temporarily remains in the space between the first recess R1 and the second side surface SS2 from remaining there. The adhesive 12 applied to the first recess R1 can easily penetrate into the gap between the first side surface SS1 and the second side surface SS2. Therefore, the adhesive 12 can easily penetrate widely between the first side surface SS1 and the second side surface SS2. As a result, the bonding surfaces can be bonded together more reliably.

[0120] Furthermore, a second recess R2 is formed on the second side surface SS2 of the core back portion 2. The second recess R2 is exposed from either the first end face ES1 or the second end face ES2, where the first recess R1 is exposed. This allows for a larger temporary retention amount of adhesive 12 in the divided core 1c without increasing the size of the first recess R1. Consequently, the magnetic flux flowing through the core back portion 2 is not significantly obstructed, minimizing the impact on the motor characteristics of the brushless motor 100.

[0121] Furthermore, the first recess R1 of the divided core 1c and the second recess R2 of the divided core 1c, which is located adjacent to it in the circumferential direction, form a single recess R. The adhesive 12 only needs to be applied to the recess R. Therefore, compared to the case where the first recess R1 of the divided core 1c and the second recess R2 of the divided core 1c, which is located adjacent to it in the circumferential direction, form two or more recesses R, the number of recesses R to which the adhesive 12 is applied can be reduced, contributing to improved productivity of the annular core 11c.

[0122] Furthermore, in the divided core 1c, the maximum distance L along the first direction DIR1 between the first recess R1 and the first side surface SS1 becomes shorter as it moves away from the first end surface ES1. This makes it easier for the adhesive 12 applied to the first recess R1 to penetrate into the gap between the first side surface SS1 and the second side surface SS2. Consequently, the adhesive 12 can penetrate more widely between the first side surface SS1 and the second side surface SS2. As a result, the bonding surfaces can be bonded together more reliably.

[0123] Furthermore, not limited to the case of the first recess R1, the maximum distance L along the first direction DIR1 between the first groove G1 and the first side surface SS1 may become shorter as it moves away from the first end surface ES1. In this case as well, the adhesive 12 applied to the first groove G1 will be more likely to penetrate the gap between the first side surface SS1 and the second side surface SS2.

[0124] [Fourth Modification] The configuration of the divided core 1d according to the fourth modification of the present invention will be described below with reference to the drawings. Figure 18 is a perspective view of the divided core 1d. Note that for the divided core 1d according to the fourth modification, only the parts that differ from the divided core 1c according to the third modification will be described, and the rest will be omitted.

[0125] As shown in Figure 18, in this modified example, the first recess R1 and the second recess R2 may each be part of a funnel. In this case, when multiple segmented cores 1d are incorporated into the brushless motor 100, the first recess R1 of each of the multiple segmented cores 1d, and the second recess R2 of segmented cores 1d that are adjacent in the circumferential direction, form a single recess R, and the recess R becomes funnel-shaped.

[0126] The segmented core 1d described above also produces the same effect as the segmented core 1c. Furthermore, in the segmented core 1d, the first recess R1 and the second recess R2 are each part of a funnel. When multiple segmented cores 1d are incorporated into the brushless motor 100, the first recess R1 of each of the multiple segmented cores 1d, and the second recess R2 of segmented cores 1d that are adjacent in the circumferential direction, form a single recess R, and the recess R becomes funnel-shaped. As a result, the adhesive 12 applied to the first recess R1 penetrates more easily into the gap between the first side surface SS1 and the second side surface SS2 than in the case of the segmented core 1c.

[0127] [Fifth Modification] The configuration of the divided core 1e according to the fifth modification of the present invention will be described below with reference to the drawings. Figure 19 is a cross-sectional view showing a cross section passing through the first groove G1 and perpendicular to the first side surface SS1. Note that only the parts of the divided core 1e according to the fifth modification that differ from the divided core 1 according to the first embodiment will be described, and the rest will be omitted.

[0128] As shown in Figure 20, in this modified example, the first groove G1 is smoothly connected to the first end face ES1. Also, the first groove G1 is smoothly connected to the first side surface SS1.

[0129] Furthermore, the first groove G1 has a bottom surface BP, a side surface SP, and a curved surface CS. The bottom surface BP is connected to the first end surface ES1. The side surface SP is connected to the first side surface SS1. The curved surface CS is concave. The curved surface CS smoothly connects the bottom surface BP and the side surface SP.

[0130] The segmented core 1e, as described above, produces the same effect as the segmented core 1. Furthermore, in the segmented core 1e, the first groove G1 is smoothly connected to the first end face ES1. This makes it easier to apply the adhesive 12 to the first groove G1, and less adhesive 12 remains on the first end face ES1.

[0131] Furthermore, the first recess R1 may be smoothly connected to the first end face ES1, not just in the case of the first groove G1. In this case as well, the adhesive 12 is easy to apply to the first recess R1, and the adhesive 12 is less likely to remain on the first end face ES1.

[0132] Furthermore, in the divided core 1e, the first groove G1 is smoothly connected to the first side surface SS1. This makes it easier for the adhesive 12 applied to the first groove G1 to penetrate the gap between the first side surface SS1 and the second side surface SS2.

[0133] Furthermore, the first recess R1 may be smoothly connected to the first side surface SS1, not just in the case of the first groove G1. In this case as well, the adhesive 12 applied to the first recess R1 will easily penetrate into the gap between the first side surface SS1 and the second side surface SS2.

[0134] Furthermore, in the divided core 1e, the bottom portion BP and the side portion SP are smoothly connected by the curved portion CS. This prevents the adhesive 12 that temporarily remains in the space between the first groove G1 and the second side portion SS2 from remaining there.

[0135] Furthermore, not limited to the case of the first groove G1, the first recess R1 may also have a bottom portion BP connected to the first end face ES1, a side portion SP connected to the first side surface SS1, and a concave curved portion CS smoothly connecting the bottom portion BP and the side portion SP. In this case as well, the adhesive 12 that temporarily remains in the space between the first recess R1 and the second side surface SS2 is prevented from remaining there.

[0136] [Sixth Modification] The configuration of the divided core 1f according to the sixth modification of the present invention will be described below with reference to the drawings. Figure 20 is a perspective view of the divided core 1f. Note that for the divided core 1f according to the sixth modification, only the parts that differ from the divided core 1 according to the first embodiment will be described, and the rest will be omitted.

[0137] As shown in Figure 20, in this modified example, the first groove G1 extends along the second direction DIR2. In this modified example, the first groove G1 reaches the outer main surface OS2, but does not reach the inner main surface IS2. The first groove G1 does not reach either the first end surface ES1 or the second end surface ES2. Therefore, the first groove G1 is exposed from the first side surface SS1 and the outer main surface OS2, but not from the second side surface SS2, the inner main surface IS2, the first end surface ES1, or the second end surface ES2. In other words, the first groove G1 is exposed only from the first side surface SS1 and the outer main surface OS2.

[0138] Furthermore, the first groove G1 may not be exposed from the outer main surface OS2, but may be exposed from the inner main surface IS2. In other words, the first groove G1 only needs to be exposed from either the inner main surface IS2 or the outer main surface OS2. In this case, the first groove G1 may be exposed only from the first side surface SS1 and the inner main surface IS2.

[0139] Similar to the first groove G1, the second groove G2 reaches the outer main surface OS2 but not the inner main surface IS2. The second groove G2 does not reach either the first end surface ES1 or the second end surface ES2. Therefore, the second groove G2 is exposed from the second side surface SS2 and the outer main surface OS2, but not from the first side surface SS1, the inner main surface IS2, the first end surface ES1, or the second end surface ES2. In other words, the second groove G2 is exposed only from the second side surface SS2 and the outer main surface OS2. In this modified example, the second groove G2 does not need to be formed on the second side surface SS2.

[0140] Furthermore, the first groove G1 may not be exposed from the outer main surface OS2, but may be exposed from the inner main surface IS2. In other words, the first groove G1 only needs to be exposed from either the inner main surface IS2 or the outer main surface OS2. In this case, the first groove G1 may be exposed only from the first side surface SS1 and the inner main surface IS2.

[0141] Furthermore, the second groove G2 is formed to be exposed from the outer main surface OS2 when the first groove G1 is exposed from the outer main surface OS2, and to be exposed from the inner main surface IS2 when the first groove G1 is exposed from the inner main surface IS2. In other words, the second groove G2 is formed to be exposed from either the inner main surface IS2 or the outer main surface OS2, whichever of the first groove G1 is exposed.

[0142] Even with the split core 1f described above, the same effect as with split core 1 is achieved.

[0143] [Other Embodiments] The divided core according to the present invention is not limited to divided cores 1, 1a to 1f, but can be modified within the scope of its gist. Furthermore, the structures of divided cores 1, 1a to 1f may be combined arbitrarily.

[0144] The annular core according to the present invention is not limited to annular cores 11, 11a, and 11c, but can be modified within the scope of its essence. Furthermore, the structures of the annular cores 11, 11a, and 11c may be arbitrarily combined.

[0145] The method for manufacturing an annular core according to the present invention is not limited to the method for manufacturing an annular core according to the first embodiment, but can be modified within the scope of its gist.

[0146] The rotating electric machine according to the present invention may be provided with at least one of the divided cores 1, 1a to 1f.

[0147] 1, 1a-1f: Split core 2: Core back section 3: Teeth section 10: Stator 11, 11a, 11c: Annular core 12: Adhesive 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 material 24: Hard magnetic material 31: Teeth body section 32: Teeth tip section 100: Brushless motor AR: Rotating shaft BP: Bottom section CP: Convex section CS: Curved section DIR1: First direction DIR2: Second direction DIR3: Third direction DIR4: Fourth direction DIR5: Fifth direction DIR6: Sixth direction ES1: First end face ES2: Second end face G: Groove G1: First groove G2: Second groove IS2: Inner main surface L: Maximum distance MS: Center surface OP: Opening OS2: Outer main surface R: Recess R1: First recess R2: Second recess SP: Side surface SS1: First side surface SS2: Second side surface VEL: Virtual extension line

Claims

1. A segmented core for use in a rotating electric machine, comprising: a core back portion and a teeth portion, wherein the core back portion has a first side surface facing a first direction which is one of the circumferential directions centered on the rotation axis of the rotating electric machine when the segmented core is incorporated into the rotating electric machine, an inner main surface facing a second direction toward the rotation axis, a first end surface facing a third direction along the rotation axis, and a second end surface facing the opposite direction to the third direction, the teeth portion extending from the inner main surface in the second direction, a first groove extending along the third direction formed on the first side surface, and the first groove being exposed from either the first end surface or the second end surface, the segmented core.

2. The core back portion has a second side surface that faces the other of the circumferential directions when the divided core is assembled into the rotating electric machine, and a second groove is formed on the second side surface, and the second groove is exposed from either the first end surface or the second end surface on which the first groove is exposed, the divided core according to claim 1.

3. When a plurality of the divided cores are incorporated into the rotating electric machine, the plurality of divided cores are arranged along the circumferential direction, and the first side surface of each of the plurality of divided cores is in surface contact with the second side surface of the adjacent divided core in the circumferential direction, and the first groove and the second groove of the adjacent divided core in the circumferential direction form a single groove, the divided core according to claim 2.

4. The first side surface has a protrusion that is connected to the first groove, the protrusion has a shape that fits into a part of the second groove, and when a plurality of the divided cores are incorporated into the rotating electric machine, the plurality of divided cores are arranged along the circumferential direction, the first side surface of each of the plurality of divided cores is in surface contact with the second side surface of the adjacent divided core in the circumferential direction, and the protrusion fits into a part of the second groove, and the first groove, the protrusion, and the second groove of the adjacent divided core in the circumferential direction form a single groove, the divided core according to claim 2.

5. A segmented core for use in a rotating electric machine, comprising: a core back portion and a teeth portion, wherein the core back portion has a first side surface facing a first direction which is one of the circumferential directions centered on the rotation axis of the rotating electric machine when the segmented core is incorporated into the rotating electric machine, an inner main surface facing a second direction toward the rotation axis, a first end surface facing a third direction along the rotation axis, and a second end surface facing the opposite direction to the third direction, the teeth portion extending from the inner main surface in the second direction, a first recess formed on the first side surface, and the first recess exposed from either the first end surface or the second end surface, the segmented core.

6. The segmented core according to claim 5, wherein the first recess has a curved surface that is curved in the shape of a part of the surface of the ellipsoid.

7. The core back portion has a second side surface that faces the other of the circumferential directions when the divided core is assembled into the rotating electric machine, and a second recess is formed on the second side surface, and the second recess is exposed from either the first end surface or the second end surface from which the first recess is exposed, the divided core according to claim 5 or claim 6.

8. The segmented core according to claim 7, wherein when a plurality of the segmented cores are incorporated into the rotating electric machine, the plurality of segmented cores are arranged along the circumferential direction, and the first side surface of each of the plurality of segmented cores is in surface contact with the second side surface of the adjacent segmented core in the circumferential direction, and the first recess and the second recess of the adjacent segmented core in the circumferential direction form a single recess.

9. The segmented core according to any one of claims 1 to 8, wherein the first groove or first recess is exposed only from either the first end face or the second end face and the first side surface.

10. The core back portion has an outer main surface facing the opposite direction to the second direction when the divided core is assembled into the rotating electric machine, and the first groove or first recess is exposed from either the inner main surface or the outer main surface, the divided core according to any one of claims 1 to 8.

11. The divided core according to any one of claims 1 to 10, wherein the teeth portion includes a teeth body portion around which a coil is wound when the divided core is incorporated into the rotating electric machine, and the first groove or first recess is exposed from the first end face and is located only on the third direction side from the teeth body portion.

12. The core back portion has an outer main surface facing the opposite direction to the second direction when the divided core is assembled into the rotating electric machine, and the first groove or first recess is located only on the outer main surface side of the central plane between the inner main surface and the outer main surface, according to any one of claims 1 to 11.

13. The divided core according to any one of claims 1 to 12, wherein the teeth portion includes a teeth body portion around which a coil is wound when the divided core is incorporated into the rotating electric machine, and the first groove or first recess is located only on the first direction side of the teeth body portion.

14. The segmented core according to any one of claims 1 to 13, wherein the first groove or first recess is exposed from the first end face, and the maximum distance along the first direction between the first groove or first recess and the first side surface decreases as it moves away from the first end face.

15. The segmented core according to any one of claims 1 to 14, wherein the first groove or first recess is exposed from the first end face and smoothly connected to the first end face.

16. The segmented core according to any one of claims 1 to 15, wherein the first groove or first recess is smoothly connected to the first side surface.

17. The divided core according to any one of claims 1 to 16, wherein the first groove or first recess is exposed from the first end face, the first groove or first recess has a bottom portion connected to the first end face, a side portion connected to the first side, and a concave curved portion, the curved portion smoothly connecting the bottom portion and the side portion.

18. A divided core according to any one of claims 1 to 17, which is a molded body formed from soft magnetic powder.

19. An annular core comprising a plurality of segmented cores according to any one of claims 1 to 18, and an adhesive, wherein the core back portion of each of the plurality of segmented cores has a second side surface that faces the other of the circumferential directions when the segmented core is assembled into the rotating electric machine, the plurality of segmented cores are arranged along the circumferential direction, and the first side surface of each of the plurality of segmented cores and the second side surface of a segmented core that is adjacent to it in the circumferential direction are bonded together by the adhesive.

20. A rotating electric machine comprising a divided core according to any one of claims 1 to 18.

21. A method for manufacturing an annular core, comprising: an arrangement step of arranging a plurality of divided cores according to any one of claims 1 to 18 along the circumferential direction; and an adhesive application step of applying a liquid adhesive to each of the first grooves or first recesses of the plurality of divided cores after the arrangement step, wherein the core back portion of each of the plurality of divided cores has a second side surface that faces the other of the circumferential direction when the divided core is assembled into the rotating electric machine, and in the arrangement step, the first side surface of each of the plurality of divided cores is brought into surface contact with the second side surface of a divided core that is arranged adjacent to it in the circumferential direction.

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