Motor and method for manufacturing motor

Abstract

This motor comprises a rotor, a stator disposed with a gap of a design length in the rotating shaft direction of the rotor, a shaft that is the rotating shaft of the rotor, and a bearing for rotatably supporting the shaft, wherein the rotor and the shaft, or the shaft and the bearing are connected to each other by a press-fit structure.

Description

Motor and method for manufacturing motor

[0001] The present disclosure relates to a motor and a method for manufacturing a motor. This application claims priority based on Japanese Patent Application No. 2021-085672 filed on May 20, 2021, and incorporates by reference all of the contents of that application.

[0002] As shown in FIG. 10 of Patent Document 1, the axial gap type rotating electric machine of Patent Document 1 includes a case, a stator, a rotor, a shaft, and bearings. The case includes a cylindrical peripheral wall portion and a pair of disk-shaped plates. The pair of plates are attached to both ends of the peripheral wall portion. A through hole is formed in the center of the pair of plates. A shaft is provided in the through hole. The stator and rotor are arranged facing each other in the axial direction of the shaft inside the case. The stator is arranged on the plates. The rotor is provided with a gap between them. The shaft is the rotating axis of the rotor. The bearings support the shaft so that it can rotate freely.

[0003] Japanese Patent Application Laid-Open No. 2020-108323

[0004] The motor of the present disclosure comprises a rotor, a stator arranged in the direction of the rotor's rotational axis with a gap of a design length therebetween, a shaft which is the rotational axis of the rotor, and a bearing which rotatably supports the shaft, and the rotor and the shaft, or the shaft and the bearing, are joined by a press-fit structure.

[0005] The motor manufacturing method of the present disclosure includes a step of preparing parts for an axial gap type motor, and a step of assembling the parts, wherein the parts include a rotor, a stator, a shaft which is the rotation axis of the rotor, and a bearing which rotatably supports the shaft, and the step of assembling the parts includes a step of determining a first mounting position or a second mounting position, and a step of press-fitting the shaft into the rotor to obtain the first mounting position, or press-fitting the shaft into the bearing to obtain the second mounting position, wherein the first mounting position is a position of the rotor in the axial direction of the shaft where the length of the gap between the rotor and the stator is the designed length, and the second mounting position is a position of the bearing in the axial direction of the shaft where the length of the gap is the designed length.

[0006] FIG. 1 is a cross-sectional view schematically illustrating a motor according to a first embodiment. FIG. 2 is a cross-sectional view schematically illustrating an enlarged view of region A in FIG. 1 . FIG. 3 is a cross-sectional view schematically illustrating another example of region A in FIG. 1 . FIG. 4 is a cross-sectional view schematically illustrating an enlarged view of region B in FIG. 1 . FIG. 5 is a graph showing the relationship between the load on the inner race of the first bearing and the amount of misalignment of the inner race with respect to the outer race of the first bearing. FIG. 6 is a diagram illustrating a method for manufacturing the motor according to the first embodiment. FIG. 7 is a diagram illustrating a method for manufacturing the motor according to the first embodiment. FIG. 8 is a graph showing the transition of induced voltage values. FIG. 9A is a cross-sectional view schematically illustrating a method for manufacturing the motor according to the first embodiment. FIG. 9B is a cross-sectional view schematically illustrating a method for manufacturing the motor according to the first embodiment. FIG. 9C is a cross-sectional view schematically illustrating a method for manufacturing the motor according to the first embodiment. FIG. 9D is a cross-sectional view schematically illustrating a method for manufacturing the motor according to the first embodiment. FIG. 10 is a cross-sectional view schematically illustrating a method for manufacturing a motor according to a modified example. FIG. 11 is a cross-sectional view schematically illustrating an enlarged view of region A of the motor according to the second embodiment. Fig. 12 is an enlarged schematic cross-sectional view showing another example of region A of the motor according to embodiment 2. Fig. 13 is a diagram illustrating a method for manufacturing the motor according to embodiment 2.

[0007] [Problem to be Solved by the Present Disclosure] It is desired to improve the manufacturability of axial gap motors that have excellent assembly precision.

[0008] [Advantages of the Present Disclosure] One object of the present disclosure is to provide a motor that is excellent in assembly precision. Another object of the present disclosure is to provide a method for manufacturing the motor that is excellent in manufacturability.

[0009] The motor of the present disclosure has excellent assembly precision.

[0010] The method for manufacturing a motor according to the present disclosure is excellent in terms of manufacturability of the motor according to the present disclosure.

[0011] Description of an embodiment of the present disclosure An axial gap motor is manufactured, for example, through two assembly processes: a temporary assembly of motor parts and a final assembly. The reason for temporary assembly of parts is that it is difficult to assemble the parts once to achieve the designed gap length between the stator and rotor. The designed gap length is a target value for the designed gap length determined based on the motor specifications. Therefore, the gap length of the motor manufactured through temporary assembly is measured. The difference between the measured gap length and the designed gap length is calculated. After the measured gap length is calculated, the motor is disassembled.

[0012] The parts are assembled using a shim with a thickness equal to the difference. The shim is placed between the bearing and the plate. By placing the shim, the bearing is moved away from the plate by the thickness of the shim. By moving the bearing away, the shaft supported by the bearing is shifted in the axial direction of the shaft. By shifting the shaft, the rotor is moved away from the stator. By moving the rotor away, the length of the gap becomes longer than the measured length. In other words, the length of the gap becomes longer than the measured length by the thickness of the shim. By making the thickness of the shim the same as the difference, the length of the gap can be made the designed length.

[0013] The manufacturing method described above requires assembling parts twice, which makes the manufacturing process complicated. Furthermore, the number of parts increases by the number of shims used. Furthermore, the use of shims increases the preload on the bearings, which can lead to increased mechanical loss.

[0014] The present inventors have conducted extensive research into a method for manufacturing a motor without using shims. As a result, the present inventors have developed a manufacturing method that allows the length of the gap between the stator and rotor to be substantially the same as the designed length by assembling parts only once. First, embodiments of the present disclosure will be listed and described.

[0015] (1) A motor according to one aspect of the present disclosure includes a rotor; a stator arranged in the direction of the rotor's rotational axis with a gap of a design length therebetween; a shaft that is the rotor's rotational axis; and a bearing that rotatably supports the shaft, wherein the rotor and the shaft, or the shaft and the bearing, are joined by a press-fit structure.

[0016] The motor has excellent assembly precision. Because the rotor and shaft are connected only by a press-fit structure, the rotor can be moved in the axial direction of the shaft by applying a predetermined pressing force to the rotor along the axial direction of the shaft during the manufacturing process. Alternatively, because the shaft and bearing are connected only by a press-fit structure, the shaft can be moved in the axial direction of the bearing by applying a predetermined pressing force to the shaft along the axial direction of the bearing during the manufacturing process. Therefore, the rotor can be easily moved to a position where the gap length is the designed length. Because the rotor and shaft are connected by a press-fit structure, the rotor will not move in the axial direction of the shaft unless a predetermined pressing force is applied to the rotor along the axial direction of the shaft. Alternatively, because the shaft and bearing are connected by a press-fit structure, the shaft will not move in the axial direction of the bearing unless a predetermined pressing force is applied to the shaft along the axial direction of the bearing. Therefore, the rotor is positioned at a position where the gap length is the designed length.

[0017] The motor does not include a shim, which reduces the number of parts, and also reduces the increase in preload on the bearings, which reduces mechanical loss.

[0018] (2) In the motor of (1) above, the number of the stators and the number of the rotors may be one each.

[0019] The motor is a single stator / single rotor type, and is highly accurate in assembly.

[0020] (3) In the motor of (1) or (2), the stator may include a stator core made of a powder compact.

[0021] The motor described above has excellent assembly precision even when it includes a stator core made of a powder compact, which has lower dimensional precision than a stator core made of electromagnetic steel sheets.

[0022] (4) A motor manufacturing method according to one aspect of the present disclosure includes a step of preparing parts for an axial gap motor, and a step of assembling the parts, the parts including a rotor, a stator, a shaft that is the rotation axis of the rotor, and a bearing that rotatably supports the shaft, the step of assembling the parts includes a step of determining a first mounting position or a second mounting position, and a step of press-fitting the shaft into the rotor to obtain the first mounting position or press-fitting the shaft into the bearing to obtain the second mounting position, the first mounting position being a position of the rotor in the axial direction of the shaft where the length of the gap between the rotor and the stator is the designed length, and the second mounting position being a position of the bearing in the axial direction of the shaft where the length of the gap is the designed length.

[0023] The motor manufacturing method includes a step of determining a first mounting position and a step of press-fitting the shaft into the rotor so that the rotor is at the determined first mounting position, thereby enabling the rotor to be positioned at the first mounting position relative to the shaft. Alternatively, the motor manufacturing method includes a step of determining a second mounting position and a step of press-fitting the shaft into the bearing so that the rotor is at the determined second mounting position, thereby enabling the bearing to be positioned at the second mounting position relative to the shaft. Therefore, the motor manufacturing method can achieve the designed gap length by assembling the parts only once. Therefore, the motor manufacturing method is excellent in manufacturability, resulting in a motor with excellent assembly accuracy without using shims.

[0024] (5) In the motor manufacturing method of (4) above, the step of determining the first mounting position or the second mounting position may determine the first mounting position or the second mounting position taking into account actual dimensions of the stator.

[0025] The above-described method for manufacturing a motor makes it possible to determine the first mounting position or the second mounting position accurately, and therefore makes it possible to manufacture a motor with excellent assembly precision.

[0026] (6) In the method for manufacturing the motor of (4) above, the stator comprises a stator core having a yoke and a plurality of teeth, and a coil arranged on each of the plurality of teeth, and the step of determining the first mounting position or the second mounting position may determine the first mounting position or the second mounting position based on an induced voltage value generated in the coil.

[0027] The above-described motor manufacturing method can determine the first mounting position or the second mounting position so that the motor torque always has constant performance, making it possible to manufacture a motor with small torque variations.

[0028] (7) In the motor manufacturing method of (4) above, the step of determining the first mounting position or the second mounting position may determine the first mounting position or the second mounting position by sandwiching a plate portion having the same thickness as the design length between the stator and the rotor.

[0029] The above-described method for manufacturing a motor makes it possible to determine the first mounting position or the second mounting position accurately, and therefore makes it possible to manufacture a motor with excellent assembly precision.

[0030] Details of the embodiments of the present disclosure Details of the embodiments of the present disclosure are described below. The same reference numerals in the drawings indicate the same items.

[0031] <<Embodiment 1>> [Motor] A motor 1 of embodiment 1 will be described with reference to Figures 1 to 4. Figure 1 is a cross-sectional view of the motor 1 cut along a plane parallel to the axial direction of the shaft 4. The motor 1 illustrated in Figure 1 is a single stator / single rotor type axial gap motor. A single stator / single rotor type is a motor that has one stator 2 and one rotor 3. An axial gap motor is a motor in which the stator 2 and rotor 3 face each other with a gap in the axial direction of the shaft 4.

[0032] The motor 1 of this embodiment includes a stator 2, a rotor 3, a shaft 4, and a first bearing 51. The motor 1 has the stator 2, rotor 3, and shaft 4 housed in a case 7. The stator 2 and rotor 3 inside the case 7 face each other with a gap in the axial direction of the shaft 4. The length of this gap along the axial direction satisfies the design length G1. The design length G1 is a target value for the design gap length determined based on the specifications of the motor 1. The design length G1 has a certain tolerance. One of the features of the motor 1 of this embodiment is the fixing structure between the rotor 3 and the shaft 4.

[0033] 1, the stator 2 is disposed on the first plane 71f of the case 7. The stator 2 includes a stator core 21 and a plurality of coils 25. As shown in FIG.

[0034] (Stator Core) The stator core 21 includes a circular disk-shaped yoke 22 and a plurality of columnar teeth 23 .

[0035] <Yoke> The yoke 22 magnetically couples adjacent teeth 23 among the teeth 23 arranged in the circumferential direction of the yoke 22. As shown in FIG. 2 , the yoke 22 has a planar first surface 22f, a planar second surface 22s, an outer peripheral surface, and an inner peripheral surface. The first surface 22f and the second surface 22s connect the outer peripheral surface and the inner peripheral surface. The first surface 22f is in contact with the first plane 71f. The second surface 22s is a surface connected to the side surface of the tooth 23.

[0036] <Teeth> As shown in FIG. 1, the teeth 23 are provided with coils 25. There are a plurality of teeth 23. The teeth 23 are arranged at predetermined intervals in the circumferential direction of the yoke 22. The teeth 23 protrude perpendicular to the second surface 22s of the yoke 22 shown in FIG. 2. In this embodiment, the teeth 23 and the yoke 22 are formed as an integrated powder compact. The teeth 23 have the same shape and size. The teeth 23 are shaped like a rectangular pillar or a cylinder. Each tooth 23 has a side surface and an end surface 23a. The side surface is a surface that is connected to the second surface 22s of the yoke 22. The end surface 23a is a surface that is connected to the side surface. The end surface 23a faces a magnet 35 of the rotor 3, which will be described later.

[0037] <Hole> As shown in FIG. 1 , the stator core 21 has hole portions. Fastening members 91 are provided in the hole portions. The fastening members 91 fix the stator core 21 to the first plane 71f. The fastening members 91 suppress misalignment between the stator 2 and the first plane 71f. An example of the fastening members 91 is a screw or a bolt. The hole portions are formed from the first plane 22f to the middle of the teeth 23. The number of hole portions may be less than the number of the teeth 23 or may be the same as the number of the teeth 23.

[0038] <Constituent Materials> The powder compact that constitutes the stator core 21 is composed of an aggregate of a plurality of coated particles 24 shown in Fig. 4. Each coated particle 24 has metal particles 241 and an insulating coating 242.

[0039] Metal Particles The metal particles 241 are made of a soft magnetic material, such as pure iron or an iron-based alloy.

[0040] Pure iron has a purity of 99% or more. That is, pure iron has an iron (Fe) content of 99% by mass or more. The saturation magnetic flux density of pure iron is higher than that of iron-based alloys. Therefore, if the metal particles 241 of the powder compact are made of pure iron, the saturation magnetic flux density of the powder compact is likely to be improved. Furthermore, the formability of pure iron is superior to that of iron-based alloys. Therefore, if the metal particles 241 of the powder compact are made of pure iron, the relative density of the powder compact is likely to be high.

[0041] An iron-based alloy contains additive elements, with the remainder consisting of Fe and unavoidable impurities. The iron-based alloy contains the largest amount of Fe. The iron-based alloy is, for example, at least one selected from the group consisting of an Fe—Si (silicon)-based alloy, an Fe—Al (aluminum)-based alloy, an Fe—Si—Al-based alloy, and an Fe—Ni (nickel)-based alloy. An example of an Fe—Si-based alloy is silicon steel. An example of an Fe—Si—Al-based alloy is sendust. An example of an Fe—Ni-based alloy is permalloy. The electrical resistance of an iron-based alloy is higher than that of pure iron. Therefore, iron-based alloys are likely to reduce iron loss, such as eddy current loss. Therefore, if the metal particles 241 of the powder compact are made of an iron-based alloy, the loss of the powder compact is likely to be reduced. The powder compact may contain both metal particles 241 made of pure iron and metal particles 241 made of an iron-based alloy.

[0042] Insulating Coating The insulating coating 242 covers the metal particles 241. The insulating coating 242 can reduce iron loss such as eddy current loss. A powder compact including the insulating coating 242 is more likely to reduce loss. The material of the insulating coating 242 is, for example, an oxide. Examples of oxides are phosphate, silica, magnesium oxide, or aluminum oxide. Phosphate has excellent adhesion to the metal particles 241 and also excellent deformability. Therefore, if the insulating coating 242 is made of phosphate, the insulating coating 242 is more likely to deform in response to the deformation of the metal particles 241 during the process of producing the powder compact. Therefore, the insulating coating 242 is less likely to be damaged. Because the insulating coating 242 is less likely to be damaged, the loss of the powder compact is more likely to be reduced.

[0043] <Relative Density> The relative density of the powder compact may be 90% or more. A powder compact with a relative density of 90% or more is likely to have improved saturation magnetic flux density. A powder compact with a relative density of 90% or more is likely to have improved mechanical properties such as strength. The relative density may be 93% or more, or even 95% or more. The relative density may be 99% or less. A powder compact with a relative density of 99% is likely to have a stable induced voltage value measured in the second method described below.

[0044] The "relative density of a powder compact" refers to the ratio (%) of the density of an actual powder compact to the true density of the powder compact. That is, the relative density of a powder compact can be calculated by [(density of actual powder compact / true density of powder compact) × 100]. The density of an actual powder compact can be calculated by immersing the powder compact in oil to impregnate it with oil and calculating [oil-impregnated density × (mass of powder compact before oil impregnation / mass of powder compact after oil impregnation)]. The oil-impregnated density is (mass of powder compact after oil impregnation / volume of powder compact after oil impregnation). That is, the density of an actual powder compact can be calculated by (mass of powder compact before oil impregnation / volume of powder compact after oil impregnation). The volume of a powder compact after oil impregnation can typically be measured by the liquid displacement method. The true density of a powder compact is the theoretical density assuming no voids are present inside.

[0045] (Coil) Each coil 25 has a cylindrical portion. The cylindrical portion is formed by winding a wire in a spiral shape. The coil 25 in this embodiment is an edgewise wound coil. A coated rectangular wire is used for the winding of the coil 25. Each coil 25 is arranged on the outer periphery of the side surface of the tooth 23. The cross-sectional shape of the cylindrical portion of each coil 25 corresponds to the cross-sectional shape of the tooth 23, for example. The axial length of the cylindrical portion is slightly shorter than the length of the tooth 23. Note that FIG. 1 shows only the cylindrical portion, and both ends of the winding are not shown.

[0046] [Rotor] The rotor 3 is provided with a gap between it and the stator 2. The rotor 3 includes a rotor body 31 and at least one magnet 35.

[0047] (Rotor body) The rotor body 31 is rotatably supported relative to the case 7 by the shaft 4. The rotor body 31 is an annular member. A through hole is provided in the center of the rotor body 31. A second shaft portion 42, which will be described later, is press-fitted into this through hole. In this embodiment, the rotor body 31 and the second shaft portion 42 form a press-fit structure. The press-fit structure here refers to a structure in which the rotor body 31 and the second shaft portion 42 are joined by press-fitting. Stress acts on the inner circumferential surface of the rotor body 31, into which the second shaft portion 42 is press-fitted, in a radially outward direction of the rotor body 31.

[0048] The press-fit structure positions the rotor body 31 at a position where the gap length is the design length G1. Unless a predetermined pressing force is applied to the second surface 31s of the rotor body 31 (described later), the rotor body 31 does not move in the axial direction of the second shaft portion 42. Therefore, the position of the rotor body 31 along the axial direction of the second shaft portion 42 does not shift during use of the motor 1. Because the rotor body 31 and the second shaft portion 42 are only joined by the press-fit structure, the rotor body 31 can be moved along the axial direction of the second shaft portion 42 by applying a predetermined pressing force to the second surface 31s during the manufacturing process. In other words, the position of the rotor body 31 along the axial direction of the second shaft portion 42 is adjustable. Therefore, the gap length can be easily adjusted to the design length G1 during the manufacturing process. Furthermore, the press-fit structure tends to reduce runout of the rotor 3. With the press-fit structure, the rotor body 31 can be pulled out of the second shaft portion 42 by applying a predetermined pressing force to the rotor body 31 in the axial direction of the second shaft portion 42. In the pulled-out state, the diameter of the through hole of the rotor body 31 at the mating portion is smaller than the outer diameter of the second shaft portion 42 .

[0049] As shown in FIG. 2 , the rotor body 31 has a first surface 31f, a second surface 31s, an inner circumferential surface, and an outer circumferential surface. The first surface 31f and the second surface 31s connect the inner circumferential surface and the outer circumferential surface. The first surface 31f faces the stator 2. The second surface 31s faces the second bearing 55 shown in FIG. 1 . The second bearing 55 will be described later. In this embodiment, a recess 32 is provided in the first surface 31f. The recess 32 opens toward the stator 2. A magnet 35 is fixed to the bottom surface 32a of the recess 32. The inner circumferential surface of the rotor body 31 contacts the second shaft portion 42 of the shaft 4. As shown in FIG. 1 , the outer circumferential surface of the rotor body 31 does not contact the inner circumferential surface of the peripheral wall portion 73 of the case 7. A gap is provided between the outer circumferential surface of the rotor body 31 and the inner circumferential surface of the peripheral wall portion 73 of the case 7.

[0050] (Magnet) The magnet 35 is fixed to the rotor body 31. As shown in FIG. 2, adhesive 38 is used to fix the magnet 35. The number of magnets 35 may be one or more. If there is one magnet 35, the number of parts is fewer and the rotor 3 is easier to manufacture than when there are multiple magnets 35. This makes it easier to improve the manufacturability of the motor 1. Furthermore, it is easier to manufacture a motor 1 with excellent assembly precision.

[0051] When there is one magnet 35, the magnet 35 has an annular shape. The south and north poles of each magnet 35 are arranged alternately in the circumferential direction. When there are multiple magnets 35, the specific number of magnets 35 is the same as the number of teeth 23. The multiple magnets 35 are arranged at equal intervals in the circumferential direction of the rotor body 31. Each magnet 35 has, for example, a flat plate shape. The planar shape of each magnet 35 is, for example, the same as the planar shape of the end surface 23 a of the tooth 23. Each magnet 35 is magnetized in the axial direction of the rotation shaft of the rotor 3. The magnets 35 adjacent to each other in the circumferential direction of the rotor body 31 have opposite magnetization directions. The rotating magnetic field generated by the stator 2 repeatedly attracts and repels the magnet 35 to and from each tooth 23, causing the rotor 3 to rotate.

[0052] The magnet 35 is a permanent magnet. Specific examples of the permanent magnet include a ferrite magnet, a neodymium magnet, a samarium-cobalt magnet, and a bonded magnet. Neodymium magnets and samarium-cobalt magnets have particularly strong magnetic forces.

[0053] [Shaft] The shaft 4 is the rotation axis of the rotor 3. The shaft 4 is formed of a solid round bar. As shown in FIG. 1 , the shaft 4 has multiple shaft portions with different outer diameters. The multiple shaft portions are integrally formed. The shaft 4 of this embodiment has, in order from the first plate portion 71 toward the second plate portion 72 of the case 7, a first shaft portion 41, a second shaft portion 42, a third shaft portion 43, and a fourth shaft portion 44.

[0054] As shown in Fig. 1, the first shaft portion 41 is provided inside the first bearing 51. The outer peripheral surface of the first shaft portion 41 contacts the inner peripheral surface of the inner race 52 of the first bearing 51 as shown in Fig. 2.

[0055] The second shaft portion 42 is press-fit into the through hole of the rotor body 31. The outer peripheral surface of the second shaft portion 42 contacts the inner peripheral surface of the rotor body 31. Stress acts on the outer peripheral surface of the second shaft portion 42 in a direction toward the center of the second shaft portion 42. The second shaft portion 42 of this embodiment has a uniform outer diameter in the axial direction of the shaft 4. Unlike this embodiment, the outer peripheral surface of the second shaft portion 42 may be tapered toward the third shaft portion 43. The surface of the second shaft portion 42 that fits into the rotor body 31 may be knurled. As shown in FIG. 1, the second shaft portion 42 has an outer diameter larger than the outer diameter of the first shaft portion 41. As shown in FIG. 2, the second shaft portion 42 has a first end face 42f and a second end face 42s. The first end face 42f contacts the first end face 52f of the inner race 52. The first end face 42f does not contact the outer race 53 of the first bearing 51. The second end surface 42 s is in contact with a first end surface of an inner race 56 of the second bearing 55. The second end surface 42 s is not in contact with an outer race 57 of the second bearing 55.

[0056] The third shaft portion 43 is provided in the second bearing 55. The outer peripheral surface of the third shaft portion 43 contacts the inner peripheral surface of the inner race 56. The third shaft portion 43 has an outer diameter smaller than the outer diameter of the second shaft portion 42.

[0057] 1, the fourth shaft portion 44 is provided in a through hole 72h. The through hole 72h is provided in a second plate portion 72, which will be described later. The fourth shaft portion 44 has an outer diameter smaller than the outer diameter of the third shaft portion 43.

[0058] [First Bearing and Second Bearing] As shown in Fig. 1 , the first bearing 51 and the second bearing 55 rotatably support the shaft 4. The first bearing 51 is attached to the first shaft portion 41. The second bearing 55 is attached to the third shaft portion 43. The first bearing 51 and the second bearing 55 may have the same configuration as each other, or may have different configurations.

[0059] 2 and 3, the first bearing 51 is a radial bearing having an inner race 52 and an outer race 53. The radial bearing of this embodiment is a ball bearing in which balls 54 are arranged between the inner race 52 and the outer race 53.

[0060] The inner peripheral surface of the inner race 52 contacts the outer peripheral surface of the first shaft portion 41. The outer peripheral surface of the outer race 53 contacts a protrusion 71a (described later). The inner race 52 has a first end face 52f and a second end face 52s. The outer race 53 has a first end face 53f and a second end face 53s. The first end face 52f contacts the first end face 42f. The first end face 53f does not contact the shaft 4. The second end face 52s does not contact the case 7. In this embodiment, the second end face 52s contacts a fixing member (not shown). This fixing member mechanically fixes the first bearing 51 and the first shaft portion 41. Examples of this fixing member are a retaining ring or a shaft nut. When a shaft nut is used as the fixing member, it is preferable to form a threaded portion on the outer peripheral surface of the first shaft portion 41. This fixing member is not necessarily required. In this case, the inner race 52 and the first shaft portion 41 are fixed by being fitted together. The second end face 53s is in contact with the first flat surface 71f. Fig. 2 shows an example in which the first end face 52f and the first end face 53f are not misaligned along the axial direction of the first bearing 51. Fig. 3 shows an example in which the first end face 52f and the first end face 53f are misaligned along the axial direction of the first bearing 51. As will be described in detail later, the first end face 52f and the first end face 53f may also be misaligned along the axial direction of the first bearing 51.

[0061] The second bearing 55 has the same configuration as the first bearing 51. That is, as shown in FIGS. 2 and 3 , the second bearing 55 is a radial bearing having an inner race 56 and an outer race 57. The inner peripheral surface of the inner race 56 contacts the outer peripheral surface of the third shaft portion 43. The outer peripheral surface of the outer race 57 contacts the inner peripheral surface of the recess 72a. The recess 72a is provided in the second plate portion 72. The inner race 56 and the outer race 57 each have a first end face and a second end face. The first end face of the inner race 56 contacts the second end face 42s. The second end face of the inner race 56 does not contact the elastic member 8 or the case 7, which will be described later. The second end face of the inner race 56 may or may not contact a fixed member similar to the first bearing 51. This is because the elastic member 8 presses the outer race 57 toward the rotor 3. The first end face of the outer race 57 does not contact the rotor 3 or the shaft 4. The second end surface of the outer race 57 is in contact with the elastic member 8 shown in FIG.

[0062] Unlike this embodiment, at least one of the first bearing 51 and the second bearing 55 may be an angular ball bearing.

[0063] [Elastic Member] The elastic member 8 presses the second bearing 55 in a direction toward the rotor 3. The elastic member 8 is disposed between the outer race 57 and the bottom of the recess 72a. An example of the elastic member 8 is a spring washer, a disc spring washer, a wave washer, or a rubber O-ring.

[0064] [Case] ​​The case 7 accommodates the stator 2, the rotor 3, a portion of the shaft 4, the first bearing 51, and the second bearing 55. The case 7 includes a first plate portion 71, a second plate portion 72, and a peripheral wall portion 73.

[0065] In this embodiment, the peripheral wall portion 73 and the second plate portion 72 are integrally configured. In this embodiment, the peripheral wall portion 73 and the first plate portion 71 are separate bodies. Unlike this embodiment, the peripheral wall portion 73 and the first plate portion 71 may be integrally configured, and the peripheral wall portion 73 and the second plate portion 72 may be separate bodies. Also, unlike this embodiment, the peripheral wall portion 73, the first plate portion 71, and the second plate portion 72 may be separate bodies. In this embodiment, the peripheral wall portion 73 and the first plate portion 71 are fixed to each other by fastening members 92. Similar to the fastening members 91, an example of the fastening members 92 is a screw or a bolt.

[0066] The peripheral wall portion 73 surrounds the outer peripheries of the stator 2 and the rotor 3. A hole is provided in the end surface of the peripheral wall portion 73. A fastening member 92 is provided in this hole.

[0067] The first plate portion 71 has a first flat surface 71f, a protruding portion 71a, a first through hole, a second through hole, and a third through hole.

[0068] The first plane 71f is provided on the inside of the case 7. The stator 2 is disposed on the first plane 71f.

[0069] The protrusion 71a is provided between the stator 2 and the first bearing 51. The shape of the protrusion 71a is, for example, cylindrical. The protrusion 71a is connected to the first flat surface 71f. The inner circumferential surface of the protrusion 71a contacts the outer circumferential surface of the outer race 53. The protrusion 71a can be used to position the first bearing 51. The outer circumferential surface of the protrusion 71a may or may not contact the inner circumferential surface of the yoke 22.

[0070] A part of the first shaft portion 41 is provided in the first through hole. A fastening member 91 is provided in the second through hole. The second through hole is provided in a position corresponding to the hole portion of the stator core 21. A fastening member 92 is provided in the third through hole. The third through hole is provided in a position corresponding to the hole portion of the peripheral wall portion 73.

[0071] The second plate portion 72 has a recess 72a in its center. A through hole 72h is provided at the bottom of the recess 72a. The fourth shaft portion 44 is provided within the through hole 72h. The inner diameter of the through hole 72h is larger than the outer diameter of the fourth shaft portion 44. Therefore, the shaft 4 rotates without contact between the inner circumferential surface of the through hole 72h and the fourth shaft portion 44.

[0072] The motor 1 of this embodiment has excellent assembly precision. Because the second shaft portion 42 is simply press-fitted into the rotor 3, the rotor 3 can be moved in the axial direction of the second shaft portion 42 by applying a predetermined pressing force to the rotor 3 along the axial direction of the second shaft portion 42 during the manufacturing process. Therefore, the position of the rotor 3 can be easily moved to a position where the gap length is the designed length G1. Because the second shaft portion 42 is press-fitted into the rotor 3, the rotor 3 will not move in the axial direction of the second shaft portion 42 unless a predetermined pressing force is applied to the rotor 3 along the axial direction of the second shaft portion 42. Therefore, the rotor 3 is positioned at a position where the gap length is the designed length G1.

[0073] [Method of Manufacturing Motor] A method of manufacturing the motor of embodiment 1 will be described with reference to Figures 2, 3, and 5 to 9D. The method of manufacturing the motor of this embodiment includes process A and process B. Process A prepares motor parts. Process B assembles the parts.

[0074] [Step A] The parts prepared in step A are the parts of the motor 1 described above with reference to FIG. 1 . In this embodiment, the parts include the stator 2, the rotor 3, the shaft 4, the first bearing 51, the second bearing 55, the case 7, the elastic member 8, the fastening member 91, and the fastening member 92. As shown in FIG. 6 , the rotor 3 before assembly includes a rotor body 31 having an inner diameter smaller than the outer diameter of the second shaft portion 42 of the shaft 4. That is, the second shaft portion 42 before assembly has an outer diameter larger than the inner diameter of the rotor body 31. The corners between the outer peripheral surface of the second shaft portion 42 and the second end face 42s are chamfered. This chamfering facilitates press-fitting the second shaft portion 42 into the rotor body 31. In this application, the term "press-fit" is used in the usual sense to refer to a method of fitting a hole and a shaft. Press-fitting refers to a method in which the outer diameter of the hole before press-fitting is several tens of micrometers smaller than the outer diameter of the shaft, and the two shafts are fitted together by applying pressure. The dimensional difference between the hole and the shaft can comply with the usual fit tolerance. The pressure of the press-fitting is not limited as long as it is a force normally used depending on the material and the fit tolerance. The corners between the inner circumferential surface of the rotor body 31 and the first surface 31f may also be chamfered.

[0075] [Process B] In process B, in which the parts are assembled, each member is fixed in a predetermined position. By performing process B, the motor 1 shown in Fig. 1 is manufactured. As an example of the order in which the parts are assembled, the following processes B1 to B6 are performed in this order.

[0076] In step B1, an assembly combining the first plate portion 71, the stator 2, the first bearing 51, and the fastening member 91 is placed on the base 700. The fastening member 91 secures the stator 2, which is placed on the first flat surface 71f, to the first plate portion 71. The fastening member 91 is provided in the second through-hole of the first plate portion 71 and the hole in the stator 2. The first bearing 51 is placed on the first flat surface 71f. In step B2, the first shaft portion 41 is placed in the first bearing 51. In step B3, the second shaft portion 42 is press-fitted into the rotor 3. The second shaft portion 42 is press-fitted into the rotor 3 by pressing the second surface 31s of the rotor body 31 with a punch 500 of a press-fitting machine, which will be described later. The hollow arrow in FIG. 6 indicates the pressing direction of the punch 500. Details of step B3 will be described later. In step B4, the second bearing 55 is placed on the third shaft portion 43. In step B5, the elastic member 8 is placed on the second bearing 55. In step B6, the fourth shaft portion 44 is fitted into the through hole 72h of the second plate portion 72, and the end face of the peripheral wall portion 73 is butted against the first plate portion 71. Then, the first plate portion 71 and the peripheral wall portion 73 are fixed together with fastening members 92. The fastening members 92 are provided in the third through hole of the first plate portion 71 and the hole portion of the peripheral wall portion 73.

[0077] The punch 500 has a cylindrical shape. The inner diameter of the punch 500 is larger than the outer diameter of the second shaft portion 42. A recess 511 may be provided on the annular end surface 510 of the punch 500. The number of recesses 511 may be singular or plural. The single recess 511 may have, for example, an annular shape. The plural recesses 511 are provided at predetermined intervals in the circumferential direction of the end surface 510. When the punch 500 has a recess 511, it is preferable that the second surface 31s of the rotor body 31 has a protrusion 311. The protrusion 311 fits into the recess 511. When the punch 500 presses against the second surface 31s, the engagement of the protrusion 311 with the recess 511 suppresses rotation of the rotor body 31 and facilitates maintaining the horizontality of the rotor body 31. Note that a protrusion may be provided on the end surface 510 and a recess may be provided on the second surface 31s.

[0078] In step B3, the following steps B31 and B32 are performed. In step B31, a first mounting position is determined. The first mounting position is a position of the rotor 3 in the axial direction of the second shaft portion 42 where the gap length is the designed length G1. In step B32, the second shaft portion 42 is press-fitted into the rotor 3 so that the rotor 3 is at the determined first mounting position.

[0079] The first attachment position can be determined by the following three methods, namely, the first method to the third method.

[0080] (First Method) The first method is a method of determining the first mounting position taking into consideration the actual dimensions of the stator 2. The actual dimensions of the stator 2 are the dimensions obtained by actually measuring the stator 2 before assembly. Taking the actual dimensions into consideration includes taking into consideration the actual dimensions themselves and taking into consideration a calculated value obtained from the actual dimensions. The calculated value obtained from the actual dimensions is, for example, an average value of the actual dimensions of each stator 2 obtained from a plurality of stators 2.

[0081] The number of measurements for calculating the average value may be less than the number of motors 1 manufactured. For example, assume that 1,000 motors 1 are manufactured. If one stator 2 is used in one motor 1, the number of measurements for calculating the average value of the actual dimensions of that part may be less than 1,000. Even if two stators 2 are used, the number of measurements for calculating the average value of the actual dimensions of that part may be less than 1,000. More specifically, the average value is calculated from the actual dimensions of 50 or fewer stators 2. The average value may be calculated for each lot of stators 2.

[0082] The actual dimension of the stator 2 is the actual dimension of the length L1 of the stator core 21 shown in Fig. 2. The actual dimension of the length L1 is determined from the actual dimension of the length between the first surface 22f of the yoke 22 and the end surfaces 23a of the teeth 23. The actual dimension of the length between the first surface 22f and the end surfaces 23a can be measured using a height gauge equipped with a class 0 surface plate.

[0083] The stator core 21 is placed on a surface plate with the end face 23a facing upward. A plurality of measurement points are selected on the end face 23a. For example, the measurement points are set on a line drawn in a plan view of the stator core 21, passing through the center of gravity of the end face 23a and the center of the yoke 22. Three or more measurement points may be selected on the line. In particular, the measurement points on the line may include the center of gravity of the end face 23a, an edge of the end face 23a close to the center of the yoke 22, and an edge of the end face 23a far from the center of the yoke 22. The length between the first surface 22f and the end face 23a is the average length of the straight lines perpendicular to the surface plate that connect the surface plate and each measurement point.

[0084] When the stator 2 is placed on the first flat surface 71f as in this embodiment, the actual dimension of the stator 2 may be the actual dimension of the length between the first flat surface 71f and the end face 23a. The actual dimension of the length between the first flat surface 71f and the end face 23a is determined in the same manner as the actual dimension of the length between the first surface 22f and the end face 23a. That is, the first plate portion 71 is placed on a surface plate, and the stator core 21 is placed on the first plate portion 71. The measurement points are the same as the measurement points used when measuring the actual dimension of the length between the first surface 22f and the end face 23a.

[0085] As shown in FIG. 2, the first mounting position is a position where the length from the first surface 22f to the first end surface 35f is the "actual dimension of the stator 2 + design length G1." The length that the rotor 3 moves from the second end surface 42s to the first mounting position along the axial direction of the second shaft portion 42 toward the first shaft portion 41 is defined as a first movement length L01. The movement of the rotor 3 can be achieved by pressing the second surface 31s of the rotor body 31 with a punch 500. The first movement length L01 is the length from the second end surface 42s to the first surface 31f when the length from the first surface 22f or the first flat surface 71f to the first end surface 35f is the "actual dimension of the stator 2 + design length G1." The first movement length L01 is calculated by (length L2 + length L3) - (actual dimension of length L1 + design length G1 + length L5 - length L4).

[0086] Length L2 is the height of the first bearing 51. Length L3 is the length of the second shaft portion 42. That is, length L3 is the length between the first end face 42f and the second end face 42s. Length L4 is the depth of the recess 32. That is, length L4 is the length between the first face 31f and the bottom face 32a. Length L5 is the thickness Tm of the magnet 35. When the magnet 35 and the rotor body 31 are fixed with adhesive 38, length L5 is the sum of the thickness Tm of the magnet 35 and the thickness Ta of the adhesive 38.

[0087] All of these lengths are lengths along the axial direction of the shaft 4. Lengths L2 to L5 are all design dimensions and are known. The difference between the actual dimensions of lengths L2 to L5 and the design dimensions tends to be smaller than the difference between the actual dimension of length L1 and the design dimension. The difference between the actual dimension of length L1 and the design dimension tends to be larger, particularly when the stator core 21 is composed of a powder compact. Therefore, the first mounting position, i.e., the first movement length L01, must take into account the actual dimension of length L1. Of course, the first mounting position, i.e., the first movement length L01, may take into account at least one actual dimension of lengths L2 to L5. The concept of each actual dimension of lengths L2 to L5 is the same as the concept of the actual dimension of the stator 2. The concept of each calculated value obtained from each actual dimension of lengths L2 to L5 is the same as the concept of the actual dimension of the stator 2.

[0088] The actual dimension of length L2 may be either the actual dimension of the height of the inner race 52 or the actual dimension of the height of the outer race 53. The actual dimension of the height of the outer race 53 is easier to measure than the actual dimension of the height of the inner race 52. The actual dimension of the height of the inner race 52 or the actual dimension of the height of the outer race 53 is the average value of the heights at multiple measurement points. The measurement points are taken at equal intervals around the circumference of the inner race 52 or the outer race 53. The number of measurement points should be three or more.

[0089] The actual dimension of the length L3 is the average value of the lengths at a plurality of measurement points. The measurement points are set at equal intervals in the circumferential direction of the second shaft portion 42. The number of measurement points is three or more.

[0090] The actual dimension of length L4 is the average value of the depths at multiple measurement points. The measurement points are taken at equal intervals on the circumference of three concentric circles. The three circumferences refer to the circumference of the inner peripheral edge of recess 32, the circumference of the outer peripheral edge of recess 32, and the circumference of a midpoint between the inner peripheral edge and the outer peripheral edge of recess 32, when viewed from above. The number of measurement points on each circumference is three or more. A measurement point on the circumference of the inner peripheral edge, a measurement point on the circumference of the outer peripheral edge, and a measurement point on the circumference of the midpoint are located on a straight line along the radial direction of rotor 3. The depth of each measurement point is the length along the axial direction of rotor 3 between each measurement point and first surface 31f of rotor body 31.

[0091] When there are multiple magnets 35, the actual dimension of the length L5 is the average value of the thicknesses Tm of the multiple magnets 35. Each thickness Tm may be the thickness at one measurement point or the average value of the thicknesses Tm at multiple measurement points. One measurement point is the center of gravity of the first end face 35f when viewed from above. The multiple measurement points are set on a line drawn from the center of gravity of the first end face 35f to the center of the rotor 3 when viewed from above. Three or more measurement points may be set on the line. In particular, the multiple measurement points may include the center of gravity of the first end face 35f, an edge of the first end face 35f close to the center of the rotor 3, and an edge of the first end face 35f far from the center of the rotor 3. The thickness Tm of each magnet 35 is the average value of the length along the axial direction of the rotor 3 at each measurement point.

[0092] When there is one magnet 35 and the magnet 35 is annular, the actual dimension of the length L5 is the average value of the thicknesses Tm at multiple measurement points. The measurement points are taken at equal intervals on the circumference of three concentric circles. The three circumferences refer to the circumference of the inner periphery of the first end face 35f, the circumference of the outer periphery of the first end face 35f, and the circumference at the midpoint between the inner and outer peripheries of the first end face 35f, when viewed from above. The number of measurement points on each circumference is three or more. The measurement point on the circumference of the inner periphery, the measurement point on the circumference of the outer periphery, and the measurement point on the midpoint are located on a straight line along the radial direction of the rotor 3. The thickness at each measurement point is the length along the axial direction of the rotor 3 at that measurement point.

[0093] The actual dimension of length L5 is the actual dimension when the rotor body 31 and magnet 35 are fixed together when adhesive 38 is provided. That is, the actual dimension of length L5 is the average length along the axial direction of the rotor 3 between the measurement point of the thickness Tm of the magnet 35 and the bottom surface 32a of the recess 32.

[0094] The first mounting position may be determined by further considering the amount of deviation g of the first bearing 51 shown in Fig. 3. The amount of deviation g is the length along the axial direction of the first bearing 51 between the first end surface 53f and the first end surface 52f.

[0095] The amount of deviation g is determined by taking into consideration the load acting on the inner race 52 due to the weight of the shaft 4 and the rotor 3, and the load acting on the inner race 52 due to the attractive force of the magnet 35 toward the stator 2. The amount of deviation g is also determined by taking into consideration at least one of the load acting on the inner race 52 due to the weight of the second bearing 55, and the load acting on the inner race 52 due to the pressing force of the elastic member 8 pressing the second bearing 55 toward the first bearing 51.

[0096] The inner race 52 is primarily subjected to loads due to the weight of the shaft 4 and rotor 3 and the attractive force of the magnet 35 toward the stator 2. The inner race 52 is also subjected to at least one of the following loads: the weight of the second bearing 55 and the pressing force of the elastic member 8 pressing the second bearing 55 toward the first bearing 51. Depending on the magnitude of the load, the first end face 52f may be misaligned with respect to the first end face 53f. The misalignment of the first end face 52f is particularly influenced by the attractive force of the magnet 35. That is, the stronger the magnetic force of the magnet 35, the greater the misalignment of the first end face 52f. The length of the gap becomes shorter than the design length G1 by the amount of misalignment g. In this case, the misalignment g must be taken into consideration.

[0097] The amount of deviation g can be obtained from a graph such as that shown in Figure 5. The load (N) on the vertical axis of Figure 5 represents the load on the inner race 52 of the first bearing 51. The amount of deviation (mm) on the horizontal axis of Figure 5 represents the amount of deviation g of the first end face 52f of the inner race 52 relative to the first end face 53f of the outer race 53 of the first bearing 51. The graph of Figure 5 can be prepared in advance. Specifically, the graph of Figure 5 can be obtained by applying a load to the inner race 52 in the axial direction of the first bearing 51 while displacing the load.

[0098] The first mounting position is a position where the length from the first surface 22f to the first end surface 35f is "the actual dimension of the stator 2 + the design length G1 + the deviation g." The first movement length L01 is calculated by "(length L2 + length L3) - (the actual dimension of length L1 + the design length G1 + length L5 - length L4) - the deviation g."

[0099] (Second Method) The second method is a method of determining the first mounting position based on the induced voltage value generated in the coil 25, as shown in FIG. 7. FIG. 7 shows the state before the second shaft portion 42 is press-fitted into the rotor body 31. The induced voltage value can be measured by a voltmeter 110. The induced voltage value decreases as the gap length increases and increases as the gap length decreases. The target value of the designed induced voltage value determined based on the specifications of the motor 1 is set as the design voltage value. The design voltage value has a certain tolerance. The gap length based on this design voltage value is the design length G1.

[0100] In the second method, after the second shaft portion 42 is press-fitted into the rotor body 31, steps 1 and 2 are performed in this order. In step 1, the rotor 3 is moved toward the first shaft portion 41 along the axial direction of the second shaft portion 42. The movement distance of the rotor 3 in step 1 can be selected as appropriate. In step 2, the induced voltage value is measured. The induced voltage value may be measured without moving the rotor 3 along the axial direction of the second shaft portion 42, or may be measured while moving the rotor 3 along the axial direction of the second shaft portion 42. When the induced voltage value is measured without moving the rotor 3 along the axial direction of the second shaft portion 42, in step 1, the application of the pressing force to the rotor body 31 is stopped after the rotor 3 has moved a predetermined distance. Then, step 2 is performed. Steps 1 and 2 are repeated until the measured induced voltage value satisfies the design voltage value.

[0101] The graph in FIG. 8 shows an example in which procedure 1 and procedure 2 were performed four times. The induced voltage value (V) on the left vertical axis of FIG. 8 is the induced voltage value when the rotor 3 is moved to a predetermined position by procedure 1. The gap length on the right vertical axis of FIG. 8 is the gap length when the rotor 3 is moved to a predetermined position by procedure 1. The number of times on the horizontal axis of FIG. 8 is the number of times procedures 1 and 2 were performed. The moving length of the rotor body 31 increases with each execution of procedure 1. As the number of executions increases, the measured induced voltage value increases, as shown in FIG. 8. This is because the gap length decreases with each execution of procedure 1. When procedures 1 and 2 are performed one to three times, the induced voltage value does not fall within the design voltage range. By performing procedures 1 and 2 a fourth time, the induced voltage value falls within the design voltage range. That is, in the example shown in FIG. 8, by performing procedures 1 and 2 four times, the gap length becomes the design length G1. When measurements are taken while the rotor 3 is moved along the axial direction of the second shaft portion 42, the induced voltage value does not increase stepwise as in FIG. 8, but increases continuously.

[0102] If the measured induced voltage value exceeds the upper limit of the design voltage value, i.e., if the gap length is shorter than the design length G1, the following procedure should be taken: Remove the shaft 4 from the first bearing 51. Move the rotor body 31 toward the third shaft portion 43. Then, perform the above-described steps B2 and onward again.

[0103] The design voltage value may be a value that takes into account the amount of misalignment g of the first bearing 51 shown in Fig. 3. The design voltage value is the induced voltage value when the gap length is the sum of the design length G1 in the case where the first bearing 51 does not misalign and the amount of misalignment g.

[0104] (Third Method) In the third method, as shown in FIGS. 9A to 9D, the first mounting position is determined by sandwiching the plate portion 120 between the stator 2 and the rotor 3.

[0105] The plate portion 120 is a flat plate. The plate portion 120 is composed of multiple segments 121. The number of segments 121 can be selected as appropriate. The multiple segments 121 may be divided only in the circumferential direction, or may be divided in both the circumferential direction and the thickness direction. The plate portion 120 has a thickness equal to the design length G1. When the multiple segments 121 are divided only in the circumferential direction, the thickness of the plate portion 120 is the thickness of each segment 121. When the multiple segments 121 are divided in both the circumferential direction and the thickness direction, the thickness of the plate portion 120 is the total thickness of the multiple stacked segments 121.

[0106] In this embodiment, the multiple segments 121 are divided only in the circumferential direction. The number of segments 121 in this embodiment is two. In this embodiment, each segment 121 has a semi-annular shape. When the segments 121 are combined to form an annular shape, a through hole is provided in the center of the plate portion 120 through which the shaft 4 is placed. The inner diameter of the plate portion 120 is larger than the largest outer diameter of the shaft 4. The outer diameter of the plate portion 120 is larger than the outer diameter of the rotor 3. This plate portion 120 is used as follows.

[0107] As shown in Fig. 9A , the plate portion 120 is placed on the end face 23a of the tooth 23. The timing for placing the plate portion 120 on the end face 23a may be before or after the second shaft portion 42 is press-fitted into the rotor body 31. If the timing is after press-fitting, the plate portion 120 is placed on the end face 23a with the gap length longer than the design length G1. Fig. 9A shows an example in which each segment 121 is placed on the end face 23a by moving it from the outside to the inside in the radial direction of the stator 2, as indicated by the hollow arrows.

[0108] As shown in FIG. 9B , the second shaft portion 42 is press-fitted into the rotor body 31 .

[0109] As shown in FIG. 9C , the rotor body 31 is moved until the first end surface 35f of the magnet 35 comes into contact with the plate portion 120. Once the first end surface 35f comes into contact with the plate portion 120, the application of the pressing force to the rotor body 31 is stopped. The timing for stopping the application of the pressing force may be, for example, when the load of the punch 500 exceeds a predetermined value. Alternatively, the timing for stopping the application of the pressing force may be when a piezoelectric plate is placed between the multiple segments 121 stacked in the thickness direction and the piezoelectric plate detects a predetermined load and transmits a signal. When a piezoelectric plate is used, the thickness of the piezoelectric plate and the plate portion 120 is adjusted so that the total thickness of the piezoelectric plate and the plate portion 120 is the same as the design length G1.

[0110] As shown in FIG. 9D , the plate portion 120 is removed from between the first end face 35f and the end face 23a. As indicated by the hollow arrows, each segment 121 is moved radially outward. The plate portion 120 can be easily removed by lifting the shaft 4 together with the rotor 3. Because the rotor body 31 is positioned on the second shaft portion 42 by press-fitting, the rotor body 31 does not shift axially along the second shaft portion 42 even when the shaft 4 is lifted. When multiple segments 121 are stacked in the thickness direction, the plate portion 120 can be easily removed from between the magnet 35 and the tooth 23. In particular, when three or more segments 121 are stacked in the thickness direction, it is preferable to first remove the segment 121 sandwiched between the segments 121 at both ends in the thickness direction. This is because damage to the first end face 35f and the end face 23a due to sliding contact between the segments 121 and the first end face 35f and the end face 23a is more likely to be suppressed.

[0111] The thickness of the plate portion 120 should be determined taking into consideration the amount of misalignment g of the first bearing 51 shown in Fig. 3. The thickness of the plate portion 120 is the sum of the designed length G1 when the first bearing 51 does not misalign and the amount of misalignment g.

[0112] The first end surface and the second end surface of the plate portion 120 may be mirror-finished. Alternatively, the first end surface and the second end surface of the plate portion 120 may be provided with a coating layer (not shown). The first end surface of the plate portion 120 is the surface that contacts the first end surface 35f of the magnet 35. The second end surface of the plate portion 120 is the surface that contacts the end surface 23a of the tooth 23. When multiple segment pieces 121 are stacked in the thickness direction, the surface of the segment pieces 121 at both ends in the thickness direction that contacts the first end surface 35f of the magnet 35 is the first end surface, and the surface that contacts the end surface 23a of the tooth 23 is the second end surface. An example of the coating layer is a fluororesin. A specific example of a fluororesin is Teflon (registered trademark). When removing the plate portion 120, damage to the first end face 35f due to sliding contact between the first end face and the first end face 35f can be easily suppressed, and damage to the end face 23a due to sliding contact between the second end face and the end face 23a can be easily suppressed. When a coating layer is provided on the first end face and the second end face, the thickness of the coating layer and the plate portion 120 is adjusted so that the total thickness of the coating layer and the plate portion 120 is the same as the designed length G1.

[0113] The motor manufacturing method of this embodiment can determine the first attachment position of the rotor 3 that corresponds to the design length G1 before assembling the parts. Alternatively, the motor manufacturing method of this embodiment can determine the first attachment position of the rotor 3 that corresponds to the design length G1 while assembling the parts. Therefore, the motor manufacturing method of this embodiment can achieve the gap length as the design length G1 by assembling the parts only once. Therefore, the motor manufacturing method of this embodiment is excellent in manufacturability of the motor 1, which has excellent assembly accuracy, even without using shims.

[0114] As described above, the inner race 52 may be misaligned with respect to the outer race 53 of the first bearing 51. Even in this case, the motor manufacturing method of this embodiment can determine the first mounting position of the rotor 3 while taking into account the amount of misalignment g. Therefore, the motor manufacturing method of this embodiment is excellent in the manufacturability of the motor 1, which has excellent assembly precision, even if the inner race 52 is misaligned.

[0115] The motor manufacturing method of this embodiment is excellent in the manufacturability of multiple motors 1 with excellent assembly precision, even when the process of assembling parts is repeated. Therefore, the motor manufacturing method of this embodiment can manufacture multiple motors 1 with little variation in performance. In particular, by determining the first attachment position of the rotor 3 taking into account the average value of the actual dimensions of the stators 2, which is fewer than the number of motors to be manufactured, the manufacturability of the motor 1 is more easily improved than when the first attachment position of the rotor 3 is determined taking into account the actual dimensions of the same number of stators 2 as the number of motors to be manufactured.

[0116] <<Modification>> A manufacturing method of a motor according to a modification will be described with reference to FIG. 10 . For ease of explanation, FIG. 10 illustrates a state in which the base 700 and the first plate portion 71 are separated. As shown in FIG. 10 , the base 700 has a cylindrical recess 710. At least one protrusion 711 is provided on the inner circumferential surface of the recess 710. The protrusion 711 protrudes toward the center of the recess 710. When there are multiple protrusions 711, the multiple protrusions 711 are provided at equal intervals around the circumferential direction of the recess 710. The first shaft portion 41 of the shaft 4 has a length that fits into the recess 710. A slit portion 411 is provided on the outer circumferential surface of the first shaft portion 41. The protrusion 711 fits into the slit portion 411. The fit of the protrusion 711 into the slit portion 411 restricts rotation of the shaft 4. With the rotation of the shaft 4 restricted, the punch 500 can press the second surface 31s. This facilitates the pressing operation of the rotor body 31. Note that a slit may be provided on the inner peripheral surface of the recess 710, and a protrusion may be provided on the outer peripheral surface of the first shaft portion 41.

[0117] Another possible approach is to install a capacitor with a thickness equal to or less than the designed gap length G1 between the end face 23a of the tooth 23 and the first end face 35f of the magnet 35, and estimate the gap length by measuring the potential. In this case, the capacitor can be non-contact, so there is no deterioration of the capacitor due to wear, making it easier to maintain the quality of the measuring device.

[0118] Second Embodiment [Motor] A motor according to a second embodiment will be described mainly with reference to Figures 11 and 12. The motor according to this embodiment differs from the motor 1 according to the first embodiment in that the shaft 4 and the first bearing 51 are connected by a press-fit structure. The following description will focus on the differences from the motor 1 according to the first embodiment. Descriptions of the same configuration as the motor 1 according to the first embodiment may be omitted.

[0119] (Rotor body) In this embodiment, as in the first embodiment, the rotor body 31 and the shaft 4 are combined by press-fitting the shaft 4 into the through-hole of the rotor body 31. Unlike the first embodiment, in this embodiment, the position of the rotor body 31 along the axial direction of the shaft 4 is determined by the rotor body 31 abutting against a second end surface 42 s of a second shaft portion 42 of the shaft 4, which will be described later.

[0120] [Shaft] The shaft 4 has, in order from the first plate portion 71 toward the second plate portion 72 of the case 7, a first shaft portion 41, a second shaft portion 42, a third shaft portion 43, a fourth shaft portion 44, and a fifth shaft portion 45 shown in FIG. 13.

[0121] 11 , the first shaft portion 41 is provided inside the first bearing 51. The outer peripheral surface of the first shaft portion 41 contacts the inner peripheral surface of the inner race 52 of the first bearing 51.

[0122] The second shaft portion 42 has a diameter larger than the diameter of the first shaft portion 41. The diameter of the second shaft portion 42 is larger than the inner diameter of the rotor body 31. A first end surface 42f of the second shaft portion 42 does not contact the first bearing 51. A second end surface 42s of the second shaft portion 42 contacts the first surface 31f of the rotor body 31.

[0123] The third shaft portion 43 is provided in a through hole of the rotor body 31. The outer peripheral surface of the third shaft portion 43 contacts the inner peripheral surface of the rotor body 31. The third shaft portion 43 has a diameter smaller than the diameter of the second shaft portion 42. An end face 43 a of the third shaft portion 43 contacts a first end face of an inner race 56 of the second bearing 55.

[0124] The fourth shaft portion 44 is provided in the second bearing 55. The outer peripheral surface of the fourth shaft portion 44 contacts the inner peripheral surface of the inner race 56. The fourth shaft portion 44 has a diameter smaller than the diameter of the third shaft portion 43.

[0125] The fifth shaft portion 45 shown in Fig. 13 is provided in the through hole of the second plate portion 72 shown in Fig. 11. The through hole of the second plate portion 72 is the same as the through hole 72h described with reference to Fig. 1. The outer peripheral surface of the fifth shaft portion 45 does not contact the inner peripheral surface of the second plate portion 72. The fifth shaft portion 45 has a diameter smaller than the diameter of the fourth shaft portion 44. The end surface 45a of the fifth shaft portion 45 is flat.

[0126] [First Bearing / Second Bearing] The first shaft portion 41 is press-fitted into the inner race 52 of the first bearing 51. The inner race 52 and the first shaft portion 41 form a press-fit structure. The press-fit structure here refers to a structure in which the inner race 52 and the first shaft portion 41 are coupled by press-fitting. The press-fit structure positions the rotor body 31 at a position where the gap length is the design length G1. With the press-fit structure, the first shaft portion 41 can be pulled out of the first bearing 51 by applying a predetermined pressing force to the shaft 4 in the axial direction of the shaft 4. In the pulled-out state, the outer diameter of the first shaft portion 41 at the mating portion is larger than the inner diameter of the inner race 52. In this embodiment, the above-mentioned fixing member for fixing the inner race 52 and the first shaft portion 41 is not used. The second bearing 55 is attached to the fourth shaft portion 44.

[0127] The motor of this embodiment, like the first embodiment, has excellent assembly precision. Because the first shaft portion 41 of the shaft 4 is simply press-fitted into the inner race 52, applying a predetermined pressing force to the end face 45a shown in FIG. 13 during the manufacturing process allows the first shaft portion 41 to be moved along the axial direction of the first bearing 51. In other words, the position of the first shaft portion 41 along the axial direction of the first bearing 51 is adjustable. Therefore, during the manufacturing process, the position of the rotor 3 can be easily moved to a position where the gap length is the designed length G1. Because the first shaft portion 41 is press-fitted into the inner race 52, the first shaft portion 41 will not move in the axial direction of the first bearing 51 unless a predetermined pressing force is applied to the end face 45a during the manufacturing process. Therefore, the position of the first shaft portion 41 along the axial direction of the first bearing 51 will not shift when the motor 1 is in use. Therefore, the rotor 3 is positioned at a position where the gap length is the designed length G1.

[0128] [Motor Manufacturing Method] A method for manufacturing a motor according to the second embodiment will be described with reference to Figures 11 to 13. The method for manufacturing a motor according to the second embodiment also includes steps A and B similar to the method for manufacturing a motor according to the first embodiment. The method for manufacturing a motor according to the present embodiment differs from the method for manufacturing a motor according to the first embodiment mainly in the configuration of the shaft 4 prepared in step A and the order in which the parts are assembled in step B. The following description will focus on the differences from the method for manufacturing a motor according to the first embodiment. Description of the same configurations as those in the method for manufacturing a motor according to the first embodiment may be omitted.

[0129] [Step A] As described above, the shaft 4 prepared in step A includes the first shaft portion 41 to the fifth shaft portion 45. The first bearing 51 includes an inner race 52 having an inner diameter smaller than the outer diameter of the first shaft portion 41. That is, the first shaft portion 41 before assembly has an outer diameter larger than the inner diameter of the inner race 52. The corner between the outer peripheral surface and the end face 41 a of the first shaft portion 41 is chamfered. This chamfering makes it easier to press-fit the first shaft portion 41 into the first bearing 51. The corner between the inner peripheral surface and the first end face 52 f of the inner race 52 may also be chamfered.

[0130] [Step B] In the step B of assembling the parts, the following steps B1 to B5 are performed in this order, as an example of the order in which the parts are assembled. Step B1 is as described above.

[0131] In step B2, the first shaft portion 41 is press-fitted into the first bearing 51. Prior to step B2, a rotor assembly in which the rotor 3 and the shaft 4 are combined is prepared in advance. In this step B2, the first shaft portion 41 of the rotor assembly is press-fitted into the first bearing 51. The first shaft portion 41 is press-fitted into the first bearing 51 by pressing the end face 45a with a punch 500 of a press-fitting machine. The hollow arrow in Figure 13 indicates the pressing direction of the punch 500. The shape of the punch 500 is cylindrical. The diameter of the punch 500 is larger than the diameter of the end face 45a. The end face 510 of the punch 500 is flat. Details of step B2 will be described later.

[0132] In step B3, the second bearing 55 is placed on the fourth shaft portion 44 of the shaft 4. In step B4, the elastic member 8 is placed on the second bearing 55. In step B5, the through-hole of the second plate portion 72 is fitted onto the fifth shaft portion 45 of the shaft 4, and the end face of the peripheral wall portion of the case 7 is butted against the first plate portion 71. Then, the first plate portion 71 and the peripheral wall portion are fixed together with a fastening member.

[0133] In step B2, the following steps B21 and B22 are performed. In step B21, a second mounting position is determined. The second mounting position is a position of the first bearing 51 in the axial direction of the first shaft portion 41 where the gap length is the designed length G1. In step B22, the first shaft portion 41 is press-fitted into the first bearing 51 so that the first shaft portion 41 is at the determined second mounting position.

[0134] As in the first embodiment, the method for determining the second mounting position includes three methods, the first method to the third method. Only the first method will be described in detail below. The second and third methods are substantially the same as the second and third methods of the first embodiment except that the first shaft portion 41 is press-fitted into the first bearing 51, and therefore description thereof will be omitted. Note that when the first shaft portion 41 is press-fitted into the first bearing 51 as in this embodiment, in the second method described above, the induced voltage value may be measured while moving the first shaft portion 41 along the axial direction of the first bearing 51.

[0135] (First Method) The first method is a method in which the second mounting position is determined in consideration of the actual dimensions of the stator 2, as described above.

[0136] As shown in FIG. 11 , the second mounting position is a position where the length from the first surface 22 f to the first end surface 35 f is the "actual dimension of the stator 2 + the design length G1," similar to the first mounting position. The length of movement of the first shaft portion 41 from the first end surface 52 f to the second mounting position along the axial direction of the first bearing 51 toward the second end surface 52 s is defined as a second movement length L02. As shown in FIG. 13 , the shaft 4 can be moved by pressing the end surface 45 a with a punch 500. The second movement length L02 is the length from the end surface 41 a of the first shaft portion 41 to the first end surface 52 f when the length from the first surface 22 f or the first flat surface 71 f to the first end surface 35 f is the "actual dimension of the stator 2 + the design length G1."

[0137] The second movement length L02 is calculated by "length L2 + length L6." Length L6 is the protruding length of the first shaft portion 41 from the second end surface 52s. Length L6 is calculated by "length L7 + length L8 + length L4 - (actual dimension of length L1 + design length G1 + length L5)." That is, the second movement length L02 is calculated by "length L2 + length L7 + length L8 + length L4 - (actual dimension of length L1 + design length G1 + length L5)." Lengths L2, L4, the actual dimension of length L1, and length L5 are as described above.

[0138] Length L7 is the length of the first shaft portion 41. That is, length L7 is the length between the end face 41a and the first end face 42f. Length L8 is the length of the second shaft portion 42. That is, length L8 is the length between the first end face 42f and the second end face 42s. Both of these lengths are lengths along the axial direction of the shaft 4. Lengths L7 and L8 are both design dimensions and are known.

[0139] The second mounting position, i.e., the second movement length L02, may take into account at least one actual dimension of the lengths L2, L4, L5, L7, and L8. The concept of each actual dimension is the same as the concept of the actual dimensions of the stator 2. The concept of each calculated value obtained from each actual dimension is the same as the concept of the actual dimensions of the stator 2. The actual dimensions of the lengths L2, L4, and L5 are as described above.

[0140] The actual dimension of length L7 is the average value of the lengths at multiple measurement points. The measurement points are taken on the first end face 42f at equal intervals in the circumferential direction of the first end face 42f. The number of measurement points is three or more. The length along the axial direction of the first shaft portion 41 is calculated between each measurement point and the end face 41a. The average of all the calculated lengths is calculated.

[0141] The actual dimension of length L8 is the average value of the lengths at multiple measurement points. The measurement points are taken at equal intervals in the circumferential direction on both the first end face 42f and the second end face 42s. The number of measurement points on the first end face 42f and the second end face 42s is three or more. Furthermore, the number of measurement points on the first end face 42f and the number of measurement points on the second end face 42s are the same. The measurement points on the first end face 42f and the second end face 42s are taken at the same locations in the circumferential direction. The length along the axial direction of the second shaft portion 42 is calculated between each measurement point on the first end face 42f and each measurement point on the second end face 42s. The average of all the calculated lengths is calculated.

[0142] The second mounting position may be determined by further considering the amount of deviation g of the first bearing 51 shown in FIG. 12. The amount of deviation g is as described above. The second mounting position is a position where the length from the first surface 22f to the first end surface 35f is "the actual dimension of the stator 2 + the designed length G1 + the amount of deviation g." The second movement length L02 is determined by "length L2 + length L7 + length L8 + length L4 - (the actual dimension of length L1 + the designed length G1 + length L5) - the amount of deviation g."

[0143] The motor manufacturing method of this embodiment has the same effects as the motor manufacturing method of embodiment 1. That is, the motor manufacturing method of this embodiment is excellent in terms of manufacturability of motors with excellent assembly precision, even without using shims and even if the inner race 52 is misaligned. Furthermore, the motor manufacturing method of this embodiment is excellent in terms of manufacturability of multiple motors with excellent assembly precision, even when the part assembly process is repeated. Therefore, the motor manufacturing method of this embodiment can manufacture multiple motors with little variation in performance. In particular, the motor manufacturing method of this embodiment determines the second mounting position by taking into account the average value of the actual dimensions of stators 2, which is fewer than the number of stators to be manufactured. This makes it easier to improve motor manufacturability compared to a case where the second mounting position is determined by taking into account the actual dimensions of the same number of stators 2 as the number of stators to be manufactured.

[0144] The present invention is not limited to these examples, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0145] For example, the yoke may be made up of a plurality of fan-shaped yoke pieces, and the number of teeth connected to each yoke piece may be one or more.

[0146] The motor may also be a double stator / single rotor axial gap motor. A double stator / single rotor motor has two stators and one rotor. In a double stator / single rotor motor, two stators are assembled to sandwich one rotor.

[0147] DESCRIPTION OF SYMBOLS 1 Motor 2 Stator 21 Stator core 22 Yoke, 22f First surface, 22s Second surface 23 Teeth, 23a End surface 24 Coating particles, 241 Metal particles, 242 Insulating coating 25 Coil 3 Rotor 31 Rotor body 31f First surface, 31s Second surface, 311 Convex portion 32 Concave portion, 32a Bottom surface 35 Magnet, 35f First end surface 38 Adhesive 4 Shaft 41 First shaft portion, 411 Slit portion, 41a End surface 42 Second shaft portion, 42f First end surface, 42s Second end surface 43 Third shaft portion, 43a End surface 44 Fourth shaft portion 45 Fifth shaft portion, 45a End surface 51 First bearing 52 Inner race, 52f First end surface, 52s Second end surface 53 Outer race, 53f First end surface, 53s Second end surface 54 Ball 55 Second bearing 56 Inner race, 57 Outer race 7 Case 71 First plate portion, 71f First flat surface, 71a Protrusion 72 Second plate portion, 72a Recess, 72h Through hole 73 Peripheral wall portion 8 Elastic member 91, 92 Fastening member 110 Voltmeter 120 Plate portion, 121 Divided piece 500 Punch, 510 End surface, 511 Recess 700 Base, 710 Recess, 711 Protrusion A, B Region L01 First movement length, L02 Second movement length L1, L2, L3, L4, L5, L6, L7, L8 Length G1 Design length, g Misalignment amount Tm, Ta Thickness

Claims

1. A rotor; a stator disposed in a direction of a rotation axis of the rotor with a gap of a design length therebetween; A shaft that is a rotation axis of the rotor; A bearing that rotatably supports the shaft, the rotor and the shaft, or the shaft and the bearing, are joined by a press-fit structure; The shaft has a plurality of shaft portions having different outer diameters. Motor.

2. The shaft has a first shank into which the bearing is press-fitted and a second shank into which the rotor is press-fitted, The motor according to claim 1 , wherein the bearing is press-fitted so as to come into contact with a step portion between the first shaft portion and the second shaft portion.

3. 3. The motor according to claim 1, wherein the number of the stators and the number of the rotors are one each.

4. 3. The motor according to claim 1, wherein the stator comprises a stator core made of a powder compact.

5. preparing parts for an axial gap type motor; Assembling the parts; The parts are: A rotor; A stator; A shaft that is a rotation axis of the rotor; a bearing that rotatably supports the shaft; In the step of assembling the parts, determining a first attachment position or a second attachment position; and pressing the shaft into the rotor to be in the first mounting position or the shaft into the bearing to be in the second mounting position, the first mounting position is a position of the rotor in the axial direction of the shaft at which a length of a gap between the rotor and the stator is a designed length, The second mounting position is a position of the bearing in the axial direction of the shaft where the length of the gap is the designed length. A method for manufacturing a motor.

6. The method for manufacturing a motor according to claim 5 , wherein in the step of determining the first mounting position or the second mounting position, the first mounting position or the second mounting position is determined taking into account an actual size of the stator.

7. The stator includes: a stator core having a yoke and a plurality of teeth; a coil disposed on each of the plurality of teeth, 6. The motor manufacturing method of claim 5, wherein the step of determining the first mounting position or the second mounting position includes the steps of moving the rotor along the axial direction while the rotor is pressed onto the shaft, and measuring an induced voltage value generated in the coil at the moved position, and the first mounting position or the second mounting position is determined based on the induced voltage value.

8. the step of determining the first mounting position or the second mounting position is a step of determining the first mounting position or the second mounting position by sandwiching a plate portion having the same thickness as the design length between the stator and the rotor, The method for manufacturing a motor according to claim 5 , wherein the plate portion is composed of a plurality of divided pieces.