Method for manufacturing motor core and method for manufacturing stator

Abstract

The present invention provides a method for manufacturing a motor core of a radial gap motor whereby a motor core of a radial gap motor having an annular back yoke and a plurality of teeth extending from the back yoke is manufactured, the method comprising: a preparing step of preparing a plurality of split cores having arc-shaped back yoke sections and teeth extending from the back yoke sections; an inserting step of inserting the back yoke sections of the plurality of split cores into a back yoke mold that forms the outer and inner circumferential surfaces of the back yoke; and a pressurizing step of pressurizing the back yoke sections of the plurality of split cores in the back yoke mold after the inserting step.

Description

Motor core manufacturing method and stator manufacturing method

[0001] The present invention relates to a method for manufacturing a motor core and a method for manufacturing a stator.

[0002] A radial gap motor uses a motor core (stator core) with multiple teeth extending from an annular back yoke, and in this motor core, a winding is wound around each tooth to generate a magnetic field.

[0003] JP 2018-168413 A

[0004] Because the motor core has multiple adjacent teeth, the windings are wound around each tooth using a method called nozzle winding. In nozzle winding, the winding is wound around each tooth by winding the nozzle around the teeth while unwinding the wire from the tip of the nozzle. However, with this type of nozzle winding, there is a limit to how high the winding density can be, making it difficult to increase the magnetic flux density.

[0005] Therefore, a method has been devised to increase magnetic flux density by manufacturing a motor core by joining multiple split cores (see, for example, Patent Document 1). The split core is composed of an arc-shaped back yoke portion and one tooth extending from the back yoke portion. With a split core, there are no obstacles around the teeth, so windings can be wound densely around the teeth. Therefore, by winding windings around the teeth of each split core and then joining the multiple split cores, the windings are wound densely, resulting in a high magnetic flux density.

[0006] When manufacturing a motor core in this manner, it is conceivable to wind a winding around the teeth of each split core, then arrange the split cores in a ring shape and join adjacent split cores by welding, adhesive, or the like. However, unless the split cores are aligned with extremely high precision, the roundness of the back yoke will be low. For this reason, after joining the split cores, it is necessary to cut the inner and outer peripheral surfaces of the back yoke to improve the roundness of the back yoke.

[0007] Furthermore, powder molded bodies are sometimes used as motor cores, but it is difficult to cut powder molded bodies with high precision. Therefore, if multiple split cores made of powder molded bodies are joined using the method described above, it is difficult to subsequently cut the inner and outer surfaces of the back yoke to increase the roundness of the back yoke.

[0008] Therefore, an object of the present disclosure is to provide a method for manufacturing a motor core and a method for manufacturing a stator that can obtain a high magnetic flux density and easily improve the roundness of the back yoke.

[0009] [1] A motor core manufacturing method according to the present disclosure is a method for manufacturing a motor core for a radial gap motor, which manufactures a motor core for a radial gap motor having an annular back yoke and a plurality of teeth extending from the back yoke, and includes a preparation step of preparing a plurality of split cores having an arc-shaped back yoke portion and teeth extending from the back yoke portion, an insertion step of inserting the back yoke portions of the plurality of split cores into a back yoke mold that forms the outer and inner surfaces of the back yoke, and a pressurization step of pressurizing the back yoke portions of the plurality of split cores within the back yoke mold after the insertion step.

[0010] This motor core manufacturing method uses multiple split cores each having a back yoke portion and teeth to manufacture the motor core. This allows windings to be wound around the teeth of each of the multiple split cores. This allows for high-density winding of the windings around the teeth, resulting in high magnetic flux density. The back yoke portions of the multiple split cores are then inserted into a back yoke mold, and pressure is applied to the back yoke portions of the multiple split cores within the back yoke mold. The back yoke portions of the multiple split cores inserted into the back yoke mold are stretched in a direction different from the direction of pressure application and pressed against the back yoke mold. This allows the back yoke portions of the multiple split cores to be molded using the back yoke mold, thereby easily improving the roundness of the back yoke consisting of the back yoke portions of the multiple split cores. After the pressure application step, a back yoke in which the back yoke portions of the multiple split cores are connected can be obtained by joining adjacent back yoke portions or binding the multiple back yoke portions with cable ties.

[0011] [2] In the motor core manufacturing method described in [1], the connecting end surface of the back yoke portion that connects to the adjacent split core may be formed into a flat surface. In this motor core manufacturing method, the connecting end surface of the back yoke portion is formed into a flat surface, making it easy to manufacture the split core.

[0012] [3] In the motor core manufacturing method described in [1], the connecting end faces of the back yoke parts that connect to adjacent split cores may be curved in an arc. In this motor core manufacturing method, since the connecting end faces of the back yoke parts are curved in an arc, it becomes easier to align the multiple split cores when the back yoke parts of the multiple split cores are inserted into the back yoke mold.

[0013] [4] In the motor core manufacturing method described in [3], one connecting end face of the back yoke portion may be convexly curved and the other connecting end face of the back yoke portion may be concavely curved. In this motor core manufacturing method, since one connecting end face of the back yoke portion is convexly curved and the other connecting end face of the back yoke portion is concavely curved, the multiple split cores can have the same shape while the connecting end faces of the back yoke portion are curved in an arcuate shape.

[0014] [5] The motor core manufacturing method according to any one of [1] to [4] may further include a connecting step of joining adjacent back yoke portions of the plurality of split cores after the pressing step. In this motor core manufacturing method, by joining adjacent back yoke portions of the plurality of split cores after the pressing step, a back yoke in which the back yoke portions of the plurality of split cores are connected can be obtained.

[0015] [6] The motor core manufacturing method according to any one of [1] to [5] may further include a connecting step of binding the multiple split cores with a cable tie after the pressurizing step. In this motor core manufacturing method, by binding the multiple split cores with a cable tie after the pressurizing step, a back yoke in which the back yoke portions of the multiple split cores are connected can be obtained.

[0016] [7] In the motor core manufacturing method according to any one of [1] to [6], each of the multiple split cores may be a powder compact. In this motor core manufacturing method, because each of the multiple split cores is a powder compact, it is difficult to cut them with high precision. However, by including the insertion step and the pressure step as described above, it is possible to easily improve the roundness of the back yoke formed by the back yoke portions of the multiple split cores.

[0017] [8] A method for manufacturing a stator according to the present disclosure is a method for manufacturing a stator for a radial gap motor, which manufactures a stator for a radial gap motor having an annular back yoke, a plurality of teeth extending from the back yoke, and windings wound around each of the plurality of teeth, and includes: a preparation step for preparing a plurality of split cores having an arc-shaped back yoke portion and teeth extending from the back yoke portion; a winding step for winding windings around each tooth of the plurality of split cores; an insertion step for inserting the back yoke portions of the plurality of split cores into a back yoke mold that forms the outer and inner surfaces of the back yoke; and a pressurizing step for pressurizing the back yoke portions of the plurality of split cores within the back yoke mold after the insertion step.

[0018] In this stator manufacturing method, a winding is wound around each tooth of a plurality of split cores. This allows the winding to be wound around the teeth at high density, resulting in a high magnetic flux density. The back yoke portions of the plurality of split cores are then inserted into a back yoke mold, and pressure is applied to the back yoke portions of the plurality of split cores within the back yoke mold. This causes the back yoke portions of the plurality of split cores inserted into the back yoke mold to expand in a direction different from the pressure direction and be pressed against the back yoke mold. This allows the back yoke portions of the plurality of split cores to be molded by the back yoke mold, thereby easily improving the roundness of the back yoke consisting of the back yoke portions of the plurality of split cores. After the pressure application step, a back yoke in which a plurality of split cores are connected can be obtained by joining adjacent back yoke portions or binding the plurality of back yoke portions with cable ties.

[0019] [9] The method for manufacturing a stator according to [8] may further include a connecting step of joining adjacent back yoke portions of the plurality of split cores after the pressing step. In this method for manufacturing a stator, by joining adjacent back yoke portions of the plurality of split cores after the pressing step, a back yoke in which the back yoke portions of the plurality of split cores are connected can be obtained.

[0020]

[10] In the stator manufacturing method according to [8] or [9], each of the multiple split cores may be a powder compact. In this stator manufacturing method, since each of the multiple split cores is a powder compact, it is difficult to cut them with high precision. However, by including the insertion step and the pressure step as described above, it is possible to easily improve the roundness of the back yoke formed by the back yoke portions of the multiple split cores.

[0021] A high magnetic flux density can be obtained and the roundness of the back yoke can be easily improved.

[0022] FIG. 1 is a schematic cross-section of a radial gap motor according to an embodiment. FIG. 2 is a perspective view of a motor core according to the present embodiment. FIG. 3 is a perspective view of a split core prepared in a preparation step. FIG. 4 is a cross-sectional view of the teeth shown in FIG. 3. FIG. 5 is a front view for explaining the winding step. FIG. 6 is a front view for explaining the insertion step. FIG. 7 is a cross-sectional view for explaining the pressurizing step. FIG. 8 is a cross-sectional view for explaining the pressurizing step. FIG. 9 is a cross-sectional view for explaining the pressurizing step. FIG. 10 is a cross-sectional view for explaining the connection step. FIG. 11 is a plan view of multiple split cores according to a modified example. FIG. 12 is a cross-sectional view of a tooth according to a modified example. FIG. 13 is a plan view of a motor core according to a modified example.

[0023] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. In the drawings, identical or corresponding parts are designated by the same reference numerals, and duplicate explanations will be omitted. Also, in the drawings, dimensional proportions and the like have been appropriately changed to make the explanation easier to understand.

[0024] [Radial Gap Motor] Fig. 1 is a schematic cross-sectional view of a radial gap motor according to an embodiment. As shown in Fig. 1, the radial gap motor 1 according to this embodiment includes a stator 2, a rotor 3 arranged rotatably relative to the stator 2, and a shaft 4 fixed to the rotor 3. The stator 2 and the rotor 3 are arranged to be spaced apart in the radial direction of the shaft 4. A shaft hole 5 through which the shaft 4 is inserted is formed in the center of the rotor 3.

[0025] [Stator] The stator 2 according to this embodiment is the stator of the radial gap motor 1. The stator 2 includes a motor core 6 and windings 7 wound around the motor core 6. The motor core 6 is the portion of the stator 2 excluding the windings 7, and is also called a stator core.

[0026] [Motor Core] Figure 2 is a perspective view of the motor core according to this embodiment. As shown in Figures 1 and 2, the motor core 6 according to this embodiment includes an annular back yoke 8 and a plurality of teeth 9 extending from the back yoke 8. Here, the axial direction of the back yoke 8 is referred to as the axial direction D1, the radial direction of the back yoke 8 is referred to as the radial direction D2, and the circumferential direction of the back yoke 8 is referred to as the circumferential direction D3. The axial direction D1 is also the thickness direction of the back yoke 8 (the rotational axis direction of the rotor 3 in the radial gap motor 1). The radial direction D2 is also the radial direction of the circle formed by the back yoke 8 (the radial direction of the rotor 3 in the radial gap motor 1). The circumferential direction D3 is also the circumferential direction of the circle formed by the back yoke 8 (the rotational direction of the rotor 3 in the radial gap motor 1).

[0027] The plurality of teeth 9 extend radially inward in the direction D2 from the back yoke 8. In this embodiment, the motor core 6 is described as having four teeth 9, but the number of teeth 9 is not particularly limited as long as it is two or more.

[0028] The outer peripheral surface 8a of the back yoke 8 is formed in a perfect circular shape. Note that a perfect circular shape includes not only a completely perfect circular shape but also an approximately perfect circular shape that has been deformed due to manufacturing errors, etc. The inner peripheral surface 8b of the back yoke 8 may be formed in an arc shape, a flat shape, or a polygonal shape.

[0029] [Method for Manufacturing Motor Core and Stator] Next, a method for manufacturing the motor core and stator according to this embodiment will be described. This method is a method for manufacturing the motor core 6 and stator 2 described above.

[0030] The manufacturing method of the motor core and the stator includes a preparing step, a winding step, an inserting step, a pressing step, and a connecting step.

[0031] FIG. 3 is a perspective view of a split core prepared in the preparation process. FIG. 4 is a cross-sectional view of the tooth shown in FIG. 3. As shown in FIGS. 3 and 4, in the preparation process, multiple split cores 10 are prepared. The multiple split cores 10 have, for example, the same shape. Each of the multiple split cores 10 has an arc-shaped back yoke portion 11 and teeth 9 extending from the back yoke portion 11. Here, the direction in which the back yoke portion 11 extends in an arc shape is referred to as the arc direction D4, the radial direction of the arc formed by the back yoke portion 11 is referred to as the radial direction D5, and the direction perpendicular to the arc direction D4 and the radial direction D5 is referred to as the thickness direction D6. The arc direction D4 is also the circumferential direction D3 of the motor core 6. The radial direction D5 is also the radial direction D2 of the motor core 6. The thickness direction D6 is also the axial direction D1 of the motor core 6.

[0032] The back yoke portion 11 is formed by dividing the back yoke 8 in the circumferential direction D3. The back yoke portions 11 of the multiple split cores 10 are connected in an annular arrangement to form the back yoke 8 of the motor core 6. Both end faces of the back yoke portion 11 in the arc direction D4 serve as connecting end faces that connect to the back yoke portions 11 of adjacent split cores 10. The connecting end face on one side of the back yoke portion 11 is referred to as a first connecting end face 13, and the connecting end face on the other side of the back yoke portion 11 is referred to as a second connecting end face 14. The first connecting end face 13 and the second connecting end face 14 are formed in a planar shape that extends along the radial direction D5 and the thickness direction D6.

[0033] The tooth 9 is one of the multiple teeth 9 of the motor core 6. In other words, one tooth 9 is provided for one split core 10. The tooth 9 has a winding surface 15 around which the winding 7 is wound. The winding surface 15 is the surface of the tooth 9 around the radial direction D5. The winding surface 15 has a first winding surface portion 15a and a second winding surface portion 15b that face each other in the thickness direction D6, and a third winding surface portion 15c and a fourth winding surface portion 15d that face each other in the arc direction D4. The first winding surface portion 15a and the second winding surface portion 15b are adjacent to the third winding surface portion 15c on one side in the arc direction D4, and the first winding surface portion 15a and the second winding surface portion 15b are adjacent to the fourth winding surface portion 15d on the other side in the arc direction D4. The third winding surface portion 15c and the fourth winding surface portion 15d are adjacent to the first winding surface portion 15a on one side in the thickness direction D6, and the third winding surface portion 15c and the fourth winding surface portion 15d are adjacent to the second winding surface portion 15b on the other side in the thickness direction D6. The winding surface 15 of the tooth 9 is formed into a rectangle by the first winding surface portion 15a, the second winding surface portion 15b, the third winding surface portion 15c, and the fourth winding surface portion 15d.

[0034] Each of the multiple split cores 10 is, for example, a powder compact formed by pressing soft magnetic powder coated with an insulating material. Each of the multiple split cores 10, which are powder compacts, can be molded, for example, using a commercially available powder compacting device. The soft magnetic powder material is, for example, pure iron, iron-silicon, or iron-cobalt. The average particle size of the soft magnetic powder is, for example, 3 μm to 300 μm, 30 μm to 200 μm, or 50 μm to 150 μm. The insulating material is, for example, an insulating coating containing phosphoric acid, silicone, or the like. The average particle size of the soft magnetic powder is measured using a robot shifter (model number: RPS-205) manufactured by Seishin Enterprise Co., Ltd. Each of the multiple split cores 10 may be a laminate formed by stacking multiple electromagnetic steel sheets.

[0035] The winding process can be performed at any timing before the insertion process. For example, the winding process may be performed before the preparation process, after the preparation process, or simultaneously with the preparation process. FIG. 5 is a front view illustrating the winding process. As shown in FIG. 5 , in the winding process, the winding 7 is wound around each tooth 9 of the multiple split cores 10. The winding 7 can be wound around the teeth 9 by, for example, spindle winding, nozzle winding, flyer winding, or the like, in which the split cores 10 are rotated to wind the winding 7 around the winding surfaces 15 of the teeth 9.

[0036] The insertion process is performed after the preparation process and the winding process. Fig. 6 is a front view illustrating the insertion process. As shown in Fig. 6, in the insertion process, the back yoke portions 11 of the multiple split cores 10 are inserted into a back yoke mold 20. The back yoke mold 20 is a molding mold that molds the outer peripheral surface 8a and inner peripheral surface 8b of the back yoke 8 (see Fig. 2) of the motor core 6. The back yoke mold 20 has an outer mold portion 21 that molds the outer peripheral surface 8a of the back yoke 8 and an inner mold portion 22 that molds the inner peripheral surface 8b of the back yoke 8.

[0037] The outer mold portion 21 has an outer mold forming surface 21a for forming the outer peripheral surface 8a of the back yoke 8. The outer mold forming surface 21a is formed in a perfect circular shape corresponding to the outer peripheral surface 8a of the back yoke 8.

[0038] The inner mold portion 22 has a plurality of inner mold forming surfaces 22a for forming the inner peripheral surface 8b of the back yoke 8. Each of the plurality of inner mold forming surfaces 22a is formed in a shape corresponding to the portion of the inner peripheral surface 8b of the back yoke 8 between adjacent teeth 9.

[0039] The outer mold part 21 and the inner mold part 22 may be one mold or different molds. When the outer mold part 21 and the inner mold part 22 are different molds, the outer mold part 21 may be formed, for example, in an annular shape with the outer mold molding surface 21a as the inner peripheral surface. When the outer mold part 21 and the inner mold part 22 are different molds, the inner mold part 22 may be, for example, one mold provided with a plurality of inner mold molding surfaces 22a, or may be a plurality of arc-shaped molds each having a plurality of inner mold molding surfaces 22a.

[0040] The multiple split cores 10 are then inserted into the back yoke mold 20 so that the teeth 9 of each of the multiple split cores 10 are positioned between the multiple inner mold molding surfaces 22a. As a result, the back yoke portions 11 of the multiple split cores 10 are arranged in an annular shape similar to the back yoke 8 of the motor core 6. Note that, because the windings 7 are wound around the teeth 9 in the winding process performed before the insertion process, the back yoke mold 20 (inner mold portion 22) is formed so as not to interfere with the windings 7 wound around the teeth 9 in the winding process.

[0041] The pressurizing process is performed after the insertion process. FIGS. 7 to 9 are cross-sectional views illustrating the pressurizing process. FIGS. 7 and 8 are cross-sectional views taken along line VII-VII in FIG. 6 , and FIG. 9 is a cross-sectional view taken along line IX-IX in FIG. 8 . As shown in FIGS. 7 to 9 , in the pressurizing process, the back yoke portions 11 of the multiple split cores 10 are pressed in the back yoke mold 20. That is, the back yoke portions 11 of the multiple split cores 10 are pressed in the thickness direction D6. The thickness direction D6 is also the central axis direction of the back yoke portions 11 of the multiple split cores 10 arranged in an annular shape, and is also the axial direction D1 of the motor core 6. As a result, the back yoke portions 11 of the multiple split cores 10 inserted into the back yoke mold 20 contract in the pressurizing direction and expand in a direction different from the pressurizing direction. Then, the back yoke portions 11 of the multiple split cores 10 are pressed in the thickness direction D6 until the back yoke portions 11 of the multiple split cores 10 expand and are pressed against the outer mold portion 21 (outer mold molding surface 21 a) and the inner mold portion 22 (inner mold molding surface 22 a) of the back yoke mold 20. As a result, the back yoke portions 11 of the multiple split cores 10 are molded by the outer mold portion 21 (outer mold molding surface 21 a) and the inner mold portion 22 (inner mold molding surface 22 a) of the back yoke mold 20. Therefore, even if the back yoke portions 11 of the multiple split cores 10 are not aligned with high precision, by pressurizing the back yoke portions 11 of the multiple split cores 10 within the back yoke mold 20 and pressing the back yoke portions 11 of the multiple split cores 10 against the back yoke mold 20, the back yoke portions 11 of the multiple split cores 10 will be aligned with high precision.

[0042] If each of the multiple split cores 10 is a powder compact, the pressurizing step involves re-compressing the powder compact. When each of the multiple split cores 10 is a powder compact, the back yoke portions 11 of the multiple split cores 10 tend to elongate by a larger amount in a direction different from the re-compressing direction than when each of the multiple split cores 10 is a laminate of multiple electromagnetic steel sheets.

[0043] The connecting process is performed after the pressing process. FIG. 10 is a cross-sectional view illustrating the connecting process. As shown in FIG. 10 , in the connecting process, the back yoke portions 11 of the multiple split cores 10 are connected. The connecting process is performed, for example, with the back yoke portions 11 of the multiple split cores 10 inserted into the back yoke mold 20. The back yoke portions 11 of the multiple split cores 10 are connected by joining adjacent back yoke portions 11 of the multiple split cores 10. In other words, the first connecting end surface 13 of one adjacent back yoke portion 11 is joined to the second connecting end surface 14 of the other adjacent back yoke portion 11. The joining of adjacent back yoke portions 11 of the multiple split cores 10 can be performed by welding, adhesive bonding, or the like. Then, the back yoke portions 11 of the multiple split cores 10 are removed from the back yoke mold 20.

[0044] This results in the motor core 6 and the stator 2. In other words, the back yoke portions 11 of the multiple split cores 10 are connected to each other to form the annular back yoke 8, and the teeth 9 of the multiple split cores 10 form multiple teeth 9 extending from the back yoke 8. Note that by not performing the above-mentioned winding process, it is possible to manufacture only the motor core 6 without the windings 7.

[0045] As described above, in the motor core manufacturing method according to this embodiment, the motor core 6 is manufactured using a plurality of split cores 10 each having a back yoke portion 11 and teeth 9, and therefore the windings 7 can be wound around the teeth 9 of each of the plurality of split cores 10. This allows the windings 7 to be wound around the teeth 9 at high density, thereby obtaining a high magnetic flux density. Then, by inserting the back yoke portions 11 of the plurality of split cores 10 into the back yoke mold 20 and applying pressure to the back yoke portions 11 of the plurality of split cores 10 within the back yoke mold 20, the back yoke portions 11 of the plurality of split cores 10 inserted into the back yoke mold 20 stretch in a direction different from the pressure direction and are pressed against the back yoke mold 20. As a result, the back yoke portions 11 of the plurality of split cores 10 are molded by the back yoke mold 20, and the roundness of the back yoke 8 consisting of the back yoke portions 11 of the plurality of split cores 10 can be easily improved.

[0046] In the stator manufacturing method according to this embodiment, the windings 7 are wound around each tooth 9 of the multiple split cores 10. This allows the windings 7 to be wound around the teeth 9 at high density, thereby achieving a high magnetic flux density. The back yoke portions 11 of the multiple split cores 10 are then inserted into the back yoke mold 20, and pressure is applied to the back yoke portions 11 of the multiple split cores 10 within the back yoke mold 20. As a result, the back yoke portions 11 of the multiple split cores 10 inserted into the back yoke mold 20 stretch in a direction different from the pressure direction and are pressed against the back yoke mold 20. As a result, the back yoke portions 11 of the multiple split cores 10 are molded by the back yoke mold 20, which makes it easy to improve the roundness of the back yoke 8 made up of the back yoke portions 11 of the multiple split cores 10.

[0047] Furthermore, in this motor core manufacturing method and stator manufacturing method, the first connecting end face 13 and the second connecting end face 14 of the back yoke portion 11 are formed flat, so that the split core 10 can be easily manufactured.

[0048] Furthermore, in this motor core manufacturing method and stator manufacturing method, adjacent back yoke portions 11 of multiple split cores 10 are joined after the pressing process, thereby obtaining a back yoke 8 in which the back yoke portions 11 of multiple split cores 10 are connected.

[0049] Furthermore, in this motor core manufacturing method and stator manufacturing method, it is difficult to cut the multiple split cores 10 with high precision because each of the multiple split cores 10 is a powder compact. However, by including the insertion process and pressure application process as described above, it is possible to easily improve the roundness of the back yoke 8 made up of the back yoke portions 11 of the multiple split cores 10.

[0050] The present disclosure is not limited to the above-described embodiments, and modifications can be made as appropriate without departing from the spirit of the present disclosure.

[0051] For example, in the above embodiment, the connection end surface of the back yoke portion that is connected to the adjacent split core is described as being formed in a flat shape, but as shown in Figure 11, the connection end surface of the back yoke portion that is connected to the adjacent split core may be curved in an arc shape.

[0052] Fig. 11 is a plan view of multiple split cores according to a modified example. As shown in Fig. 11, each of the multiple split cores 10A according to the modified example has a first connecting end face 13A and a second connecting end face 14A of the back yoke portion 11A that are curved in an arc shape. The first connecting end face 13A is a connecting end face on one side of the back yoke portion 11A and is curved, for example, in a convex shape. The second connecting end face 14A is a connecting end face on the other side of the back yoke portion 11A and is curved, for example, in a concave shape.

[0053] In this way, since the first connecting end face 13A and the second connecting end face 14A of the back yoke portion 11A are curved in an arc shape, it becomes easier to align the multiple split cores 10A when the back yoke portions 11A of the multiple split cores 10A are inserted into the back yoke mold 20.

[0054] Furthermore, by having the first connecting end face 13A on one side of the back yoke portion 11A curved convexly and the second connecting end face 14A on the other side of the back yoke portion 11A curved concavely, the multiple split cores 10A can be made to have the same shape, while the first connecting end face 13A and the second connecting end face 14A of the back yoke portion 11A can be made to be curved in an arc shape.

[0055] In addition, in the above embodiment, the winding surface of the tooth is described as being formed into a rectangle by a first winding surface portion, a second winding surface portion, a third winding surface portion, and a fourth winding surface portion, but as shown in Figure 12, at least one corner of the winding surface of the tooth may be formed into a curved shape.

[0056] Fig. 12 is a cross-sectional view of a tooth according to a modified example. The winding surface 15B of the tooth 9B according to the modified example shown in Fig. 12 has a first winding surface portion 15Ba and a second winding surface portion 15Bb that face each other in the thickness direction D6, and a third winding surface portion 15Bc and a fourth winding surface portion 15Bd that face each other in the arc direction D4. The first winding surface portion 15Ba and the second winding surface portion 15Bb are adjacent to the third winding surface portion 15Bc on one side in the arc direction D4, and the first winding surface portion 15Ba and the second winding surface portion 15Bb are adjacent to the fourth winding surface portion 15Bd on the other side in the arc direction D4. Furthermore, the third winding surface portion 15Bc and the fourth winding surface portion 15Bd are adjacent to the first winding surface portion 15Ba on one side in the thickness direction D6, and the third winding surface portion 15Bc and the fourth winding surface portion 15Bd are adjacent to the second winding surface portion 15Bb on the other side in the thickness direction D6.

[0057] At least one of the first winding surface portion 15Ba and the third winding surface portion 15Bc, the first winding surface portion 15Ba and the fourth winding surface portion 15Bd, the second winding surface portion 15Bb and the third winding surface portion 15Bc, and the second winding surface portion 15Bb and the fourth winding surface portion 15Bd is connected in a curved shape. In this modification, all of the first winding surface portion 15Ba and the third winding surface portion 15Bc, the first winding surface portion 15Ba and the fourth winding surface portion 15Bd, the second winding surface portion 15Bb and the third winding surface portion 15Bc, and the second winding surface portion 15Bb and the fourth winding surface portion 15Bd are connected in a curved shape.

[0058] In this way, on the winding surface 15B of each tooth of the multiple split cores, at least one of the first winding surface portion 15Ba and the third winding surface portion 15Bc, the first winding surface portion 15Ba and the fourth winding surface portion 15Bd, the second winding surface portion 15Bb and the third winding surface portion 15Bc, and the second winding surface portion 15Bb and the fourth winding surface portion 15Bd is connected in a curved shape, which makes it easier to align the winding 7 along the winding surface 15B when the winding 7 is wound around the winding surface 15B of the tooth. This makes it possible to suppress floating of the winding 7 from the winding surface 15B, thereby increasing the magnetic flux density.

[0059] Furthermore, in the above embodiment, the connection process has been described as joining adjacent back yoke portions of multiple split cores, but as shown in FIG. 13, adjacent back yoke portions of multiple split cores may be connected by restraining the multiple split cores with cable ties, or by both joining adjacent back yoke portions of the multiple split cores and restraining the multiple split cores with cable ties.

[0060] Fig. 13 is a plan view of a modified motor core. In the motor core 6C shown in Fig. 13, multiple split cores 10 are connected by being bound with cable ties 30. The cable ties 30 may be made of, for example, resin or metal. In a motor core manufacturing method for manufacturing this motor core 6C and a stator manufacturing method for manufacturing a stator including this motor core 6C, in the connecting step, the multiple split cores 10 are bound with the cable ties 30 to connect the back yoke portions 11 of the multiple split cores 10.

[0061] In this way, by binding the multiple split cores 10 with the binding bands 30 after the pressurizing step, it is possible to obtain a back yoke 8 in which the back yoke portions 11 of the multiple split cores 10 are connected.

[0062] The present disclosure can be used as a method for manufacturing a motor core and a method for manufacturing a stator.

[0063] 1...Radial gap motor, 2...Stator, 3...Rotor, 4...Shaft, 5...Shaft hole, 6...Motor core, 7...Winding, 8...Back yoke, 8a...Outer peripheral surface, 8b...Inner peripheral surface, 9, 9B...Teeth, 10, 10A...Split core, 11, 11A...Back yoke portion, 13, 13A...First connecting end surface, 14, 14A...Second connecting end surface, 15, 15B...Winding surface, 15a, 1 5Ba...first winding surface portion, 15b, 15Bb...second winding surface portion, 15c, 15Bc...third winding surface portion, 15d, 15Bd...fourth winding surface portion, 20...back yoke mold, 21...outer mold portion, 21a...outer mold forming surface, 22...inner mold portion, 22a...inner mold forming surface, 30...cable tie, D1...axial direction, D2...radial direction, D3...circumferential direction, D4...arc direction, D5...radial direction, D6...thickness direction.

Claims

1. A method for manufacturing a motor core for a radial gap motor, the method comprising the steps of: a preparation step of preparing a plurality of split cores having an arc-shaped back yoke portion and the teeth extending from the back yoke portion; an insertion step of inserting the back yoke portions of the plurality of split cores into a back yoke mold that forms the outer and inner surfaces of the back yoke; and a pressurizing step of pressurizing the back yoke portions of the plurality of split cores within the back yoke mold after the insertion step.

2. The method of manufacturing a motor core according to claim 1, wherein a connecting end face of the back yoke portion that is connected to an adjacent split core is formed into a flat surface.

3. A method for manufacturing a motor core as set forth in claim 1, wherein a connecting end face of the back yoke portion which is connected to an adjacent split core is curved in an arc shape.

4. A method for manufacturing a motor core as set forth in claim 3, wherein the connection end face on one side of the back yoke portion is curved convexly, and the connection end face on the other side of the back yoke portion is curved concavely.

5. A method for manufacturing a motor core according to any one of claims 1 to 4, further comprising a connecting step of joining adjacent back yoke portions of the plurality of split cores after the pressing step.

6. A method for manufacturing a motor core as set forth in any one of claims 1 to 5, further comprising a connecting step of binding the plurality of split cores with cable ties after the pressurizing step.

7. A method for manufacturing a motor core according to any one of claims 1 to 6, wherein each of the plurality of split cores is a powder compact.

8. A method for manufacturing a stator for a radial gap motor, the method comprising the steps of: preparing a plurality of split cores having an arc-shaped back yoke portion and the teeth extending from the back yoke portion; a winding process for winding a winding around the teeth of each of the plurality of split cores; after the winding process, inserting the back yoke portions of the plurality of split cores into a back yoke mold that forms the outer and inner surfaces of the back yoke; and after the insertion process, applying pressure to the back yoke portions of the plurality of split cores within the back yoke mold.

9. The method for manufacturing a stator according to claim 8, further comprising a connecting step of joining adjacent back yoke portions of the plurality of split cores after the pressing step.

10. The method for manufacturing a stator according to claim 8 or 9, wherein each of the plurality of split cores is a powder compact.

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