Motor and motor production method

Abstract

A motor comprising: a shaft; a bearing that rotatably supports the shaft; a rotor that is integrally fixed to the shaft; and a stator that is disposed such that a gap of a designed length is provided between the stator and the rotor in the axial direction of the shaft, wherein the stator is provided with a stator core composed of a molded powder compact, the stator core has a first surface that faces the gap and a second surface that is provided to the opposite side from the first surface in the axial direction, and grinding marks are provided to at least one among the first surface and the second surface.

Description

Motor and method for manufacturing the motor

[0001] The present disclosure relates to a motor and a method for manufacturing the motor. This application claims priority to Japanese Patent Application No. 2021-102188 filed on June 21, 2021, and incorporates by reference all of the contents of said Japanese 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 disclosed herein comprises a shaft, a bearing supporting the shaft for rotation, a rotor fixed integrally with the shaft, and a stator arranged relative to the rotor in the axial direction of the shaft with a gap of a design length therebetween, the stator having a stator core made of a pressed powder compact, the stator core having a first surface facing the gap and a second surface provided on the opposite side of the first surface in the axial direction, and having grinding marks on at least one of the first surface and the second surface.

[0005] The motor manufacturing method of the present disclosure includes a step of adjusting the height of a stator in an axial gap motor, and a step of assembling parts of the motor, the parts including a rotor, the stator, a shaft that is the rotation axis of the rotor, and a bearing that rotatably supports the shaft, the stator having a stator core made of a pressed powder compact, the step of adjusting the height of the stator includes a step of determining a design height of the stator core in consideration of the actual dimensions of the shaft and the bearing, and a step of grinding at least one of a first surface and a second surface of the stator core to achieve the determined design height, the design height being a height at which the length of the gap between the rotor and the stator is the design length, the first surface being a surface facing the gap, and the second surface being a surface provided on the opposite side of the first surface in the axial direction of the shaft.

[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 schematic perspective view of a stator core provided in the motor according to the first embodiment. FIG. 5 is a cross-sectional view taken along the line V-V in FIG. 4. FIG. 6 is a cross-sectional view schematically illustrating an enlarged view of region B in FIG. 5. FIG. 7 is a graph showing the relationship between the load on the inner race of the first bearing and the amount of deviation of the inner race from the outer race of the first bearing. FIG. 8 is a view illustrating an example of a grinding process in a manufacturing method for the motor according to the first embodiment. FIG. 9 is a view illustrating another example of a grinding process in a manufacturing method for the motor according to the first embodiment. FIG. 10 is a cross-sectional view schematically illustrating a motor according to a second embodiment.

[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] An object of the present disclosure is to provide a motor that can be assembled with excellent precision. Another object of the present disclosure is to provide a method for manufacturing such a motor that can be easily manufactured.

[0009] [Advantages of the Present Disclosure] 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 shaft, a bearing supporting the shaft for rotation, a rotor fixed integrally with the shaft, and a stator arranged relative to the rotor in the axial direction of the shaft with a gap of a design length therebetween, the stator having a stator core made of a pressed powder compact, the stator core having a first surface facing the gap and a second surface provided on the opposite side of the first surface in the axial direction, and having grinding marks on at least one of the first surface and the second surface.

[0016] The motor has excellent assembly precision. The grinding marks are formed by the grinding process during the manufacturing process. Although the stator core is made of a powder compact, which has lower dimensional precision than electromagnetic steel sheets, the grinding process allows the stator core to have a height that matches the designed gap 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 stator core has a circular plate-shaped yoke and a plurality of columnar teeth spaced apart circumferentially around the yoke, the yoke has an outer peripheral surface, an inner peripheral surface, and a planar upper surface and a planar lower surface connecting the outer peripheral surface and the inner peripheral surface, each of the plurality of teeth has a side surface connected to the upper surface of the yoke and an end surface connected to the end of the side surface opposite to the side connected to the upper surface, the lower surface being the second surface and the end surface being the first surface, and the difference between the maximum and minimum heights between the lower surface of the yoke and the end surfaces of each of the plurality of teeth may be 0.02 mm or less.

[0019] The motor is likely to reduce noise and vibration because the difference is 0.02 mm or less, which makes it easy to reduce torque ripple.

[0020] (3) In the motor of (1) or (2), the powder compact may have a relative density of 90% or more.

[0021] A powder compact having a relative density of 90% or more is likely to have improved magnetic properties such as saturation magnetic flux density, and is also likely to have improved mechanical properties such as strength.

[0022] (4) In any of the motors (1) to (3) above, the powder compact includes a plurality of coated particles, each of which has a metal particle made of a soft magnetic material and an insulating coating covering the metal particle, and the metal particle is made of pure iron or an iron-based alloy, and the iron-based alloy may be an Fe-Si alloy, an Fe-Al alloy, or an Fe-Si-Al alloy.

[0023] The saturation magnetic flux density of pure iron is higher than that of iron-based alloys. Therefore, if the metal particles of a powder compact are made of pure iron, the saturation magnetic flux density of the powder compact is likely to be high. Furthermore, the formability of pure iron is superior to that of iron-based alloys. Therefore, if the metal particles of a powder compact are made of pure iron, the relative density of the powder compact is likely to be high.

[0024] Iron loss, such as eddy current loss, of an iron-based alloy is easier to reduce than that of pure iron, so if the metal particles of the powder compact are made of an iron-based alloy, the loss of the powder compact can be easily reduced.

[0025] (5) In any of the motors described in (1) to (4) above, the motor may further include a case having a first plane on which the stator is placed, and a fastening member that fixes the first plane and the stator.

[0026] The motor described above has excellent assembly precision because the fastening member can suppress misalignment between the stator and the first plane.

[0027] (6) In the motor according to any one of (1) to (5) above, the number of the stators and the number of the rotors may be one each.

[0028] The motor is a single stator / single rotor type, and is highly accurate in assembly.

[0029] (7) In the motor according to any one of (1) to (5) above, the number of the stators may be two, and the number of the rotors may be one.

[0030] The motor is a double stator / single rotor type, and is highly accurate in assembly.

[0031] (8) A motor manufacturing method according to one aspect of the present disclosure includes a step of adjusting the height of a stator in an axial gap motor and a step of assembling parts of the motor, the parts including a rotor, the stator, a shaft that is the rotation axis of the rotor, and a bearing that rotatably supports the shaft, the stator having a stator core made of a powder molded body, the step of adjusting the height of the stator includes a step of determining a design height of the stator core taking into account the actual dimensions of the shaft and the bearing, and a step of grinding at least one of a first surface and a second surface of the stator core to achieve the determined design height, the design height being a height at which the length of a gap between the rotor and the stator is the design length, the first surface being a surface facing the gap, and the second surface being a surface provided on the opposite side of the first surface in the axial direction of the shaft.

[0032] The motor manufacturing method includes a step of determining a design height and a step of grinding a predetermined surface of the stator core to the determined design height, thereby enabling the manufacture of a stator core with the design height. The design height is the height of the stator core at which the gap length is the design length. The motor manufacturing method also allows the assembly of a motor using parts including a stator core with the design height. Therefore, the motor manufacturing method allows the gap length to be the design length by assembling the parts only once. Therefore, the motor manufacturing method provides excellent manufacturability for a motor with excellent assembly accuracy, even without using shims.

[0033] (9) In the motor manufacturing method of (8) above, the rotor has a circular plate-shaped rotor body and at least one magnet fixed to the rotor body, the rotor body has a first surface facing the magnet, and the magnet has a first end surface facing the stator, and the step of determining the design height may determine the design height by taking into account the actual dimension of the length between the first surface of the rotor body and the first end surface of the magnet in the rotor to which the rotor body and the magnet are fixed.

[0034] The above-described motor manufacturing method makes it possible to obtain an accurate design height, and therefore to manufacture a motor with excellent assembly precision.

[0035] (10) In the motor manufacturing method of (8) or (9) above, the process of assembling the parts is repeated, and the process of determining the design height may involve determining the design height by taking into account the average values ​​of the actual dimensions of the shafts and bearings in a number that is less than the number of motors to be manufactured.

[0036] The above-described motor manufacturing method makes it possible to obtain an accurate design height, and therefore to manufacture a motor with excellent assembly precision.

[0037] (11) In the motor manufacturing method according to any one of (8) to (10) above, the grinding process may be surface grinding.

[0038] The above-described motor manufacturing method makes it easy to manufacture a stator core with the designed height.

[0039] (12) In the motor manufacturing method of any one of (8) to (11) above, the part may include a case having a first plane on which the stator is placed, and the grinding process may include grinding the second surface while the stator and the case are combined.

[0040] The above-described motor manufacturing method can manufacture a motor with excellent assembly precision.

[0041] (13) In the motor manufacturing method of any one of (8) to (11) above, the parts may include a case having a first plane on which the stator is placed, and the grinding process may include grinding at least one of the first surface and the second surface of the stator core when the stator and the case are not combined.

[0042] The motor manufacturing method described above allows for easy grinding of the stator core, making it possible to manufacture a motor with excellent assembly precision. Also, grinding debris from the stator core can be easily removed.

[0043] 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.

[0044] First Embodiment [Motor] A motor 1 of the first embodiment will be described with reference to Figures 1 to 6. Figure 1 is a cross-sectional view of the motor 1 cut along a plane parallel to the axial direction of the shaft 4. Figure 1 illustrates an axial gap motor of a single stator / single rotor type as the motor 1. A single stator / single rotor type is a motor having 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 across a gap in the axial direction of the shaft 4. For ease of explanation, Figure 4 is a perspective view showing only the stator core 21 of the motor 1.

[0045] The motor 1 of this embodiment includes a stator 2, a rotor 3, a shaft 4, and a first bearing 51. The stator 2, rotor 3, and shaft 4 of the motor 1 are housed in a case 7, which will be described later. 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 that the stator 2 has a specific stator core 21.

[0046] 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.

[0047] (Stator Core) The stator core 21 includes a circular disk-shaped yoke 22 and a plurality of columnar teeth 23 .

[0048] <Yoke> The yoke 22 magnetically couples adjacent teeth 23 among the teeth 23 arranged circumferentially of the yoke 22. As shown in FIG. 2 , the yoke 22 has a planar upper surface 22a, a planar lower surface 22b, an outer peripheral surface, and an inner peripheral surface. The upper surface 22a and the lower surface 22b connect the outer peripheral surface and the inner peripheral surface. The upper surface 22a connects to the side surface 23b of the tooth 23. The lower surface 22b is a surface that contacts the first plane 71f. The lower surface 22b is the second surface 21s of the stator core 21. The second surface 21s is a surface of the stator core 21 that is located on the opposite side of the first surface 21f in the axial direction of the shaft 4. The first surface 21f of the stator core 21 is a surface that faces the gap. The top and bottom referred to here do not necessarily coincide with the top and bottom of the motor 1.

[0049] <Teeth> As shown in FIG. 1, the teeth 23 are provided with coils 25. There are multiple teeth 23. The teeth 23 are arranged at predetermined intervals around the yoke 22. Each tooth 23 protrudes perpendicular to the upper surface 22a of the yoke 22 shown in FIG. 2. In this embodiment, the teeth 23 and the yoke 22 are integrally formed as a powder compact. The powder compact will be described later. Each tooth 23 has the same shape and size. Each tooth 23 is shaped like a rectangular pillar or a cylinder. Each tooth 23 has a side surface 23b and an end surface 23a. The side surface 23b is a surface connected to the upper surface 22a of the yoke 22. The end surface 23a is a surface connected to the side surface 23b. The end surface 23a is a first surface 21f. The end surface 23a faces a magnet 35 of the rotor 3, which will be described later.

[0050] <Grinding Marks> At least one of the lower surface 22b, which is the second surface 21s, and the end surface 23a, which is the first surface 21f, has grinding marks. The grinding marks are formed by grinding during the manufacturing process. In FIG. 4, for convenience of explanation, the grinding marks 231 on one end surface 23a are exaggerated. Grinding marks on the other end surface 23a are omitted from FIG. 4. The grinding marks 231 are streak-like irregularities that occur during grinding. The grinding marks 231 are formed along the relative movement direction between the end surface 23a and a grinding machine 1000, which will be described later with reference to FIGS. 8 and 9, during grinding. The grinding marks refer to streak-like irregularities having an arithmetic mean roughness Ra of 0.1 μm or more and 50 μm or less. The arithmetic mean roughness Ra is a value measured in accordance with JIS B 0601 (2013). The arithmetic mean roughness Ra may further satisfy a range of 0.1 μm to 10 μm, particularly 0.1 μm to 5 μm. Unlike the end faces 23 a, the side faces 23 b are not ground. If the second surface 21 s is ground during the manufacturing process, grinding marks similar to the grinding marks 231 shown in FIG. 4 will also be formed on the second surface 21 s, although not shown in the figure.

[0051] <Hole> As shown in FIG. 1 , the stator core 21 has a hole. A fastening member 91 is provided in the hole. The fastening member 91 fixes the stator core 21 to the first plane 71f. The fastening member 91 prevents misalignment between the stator 2 and the first plane 71f. An example of the fastening member 91 is a screw or a bolt. The hole is formed from the second plane 21s to the middle of the tooth 23. The number of holes may be less than the number of the teeth 23 or may be the same as the number of the teeth 23.

[0052] 2, 3, and 5, the height of the stator core 21 satisfies the design height H1. The design height H1 is the height of the stator core 21 at which the length of the gap is the design length G1. The design height H1 has a certain tolerance.

[0053] At least one of the lower surface 22b, which is the second surface 21s, and the end surface 23a, which is the first surface 21f, is ground, so that the difference between the maximum and minimum values ​​of the height of the stator core 21 is small, as shown in Fig. 5. The difference is the difference between the maximum and minimum values ​​of the length between each end surface 23a and the lower surface 22b.

[0054] A micrometer is used to measure the length between each end face 23a and the lower surface 22b. Multiple measurement points are selected on each end face 23a. The measurement points are set, for example, 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 are selected on the line. In particular, the measurement points on the line 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 each end face 23a and the lower surface 22b is the average length of the lines perpendicular to the lower surface 22b that connect the lower surface 22b to each measurement point.

[0055] The difference may be 0.02 mm or less. If the difference is 0.02 mm or less, the torque ripple of the motor 1 is small. Therefore, the noise and vibration of the motor 1 are small. The smaller the difference, the easier it is to reduce the torque ripple. The difference may be 0.01 mm or less, further 0.008 mm or less, and particularly 0.005 mm or less.

[0056] [Parallelism] The parallelism between the lower surface 22b and each end surface 23a may be 0.02 mm or less. If the parallelism is 0.02 mm or less, the torque ripple of the motor 1 is small. Therefore, the noise and vibration of the motor 1 are small. The smaller the parallelism, the easier it is to reduce the torque ripple. The parallelism may be 0.01 mm or less, further 0.008 mm or less, and particularly 0.005 mm or less.

[0057] The parallelism is determined as follows: A height gauge equipped with a class 0 surface plate is used. The stator core 21 is placed on the surface plate with the end face 23a facing upward. Multiple measurement points are selected on each end face 23a. The measurement points are set on a line drawn through the center of gravity of the end face 23a and the center of the yoke 22 when the stator core 21 is viewed in plan. Three or more measurement points are selected on the line. The measurement points on the line 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 parallelism between the lower surface 22b and each end face 23a is the average length of the straight lines perpendicular to the surface plate that connect the surface plate to each measurement point.

[0058] <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. 6. Each coated particle 24 has metal particles 241 and an insulating coating 242.

[0059] Metal Particles The metal particles 241 are made of a soft magnetic material, such as pure iron or an iron-based alloy.

[0060] Pure iron is iron with a purity of 99% or more. That is, pure iron is iron with 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.

[0061] 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 tend 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 made of pure iron and metal particles made of an iron-based alloy.

[0062] 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, and 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.

[0063] <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.

[0064] 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.

[0065] (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 23b 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.

[0066] [Rotor] The rotor 3 is provided with a gap between it and the stator 2. The rotor 3 is fixed integrally to the shaft 4. This fixation allows the rotor 3 to rotate integrally with the shaft 4 around the rotation axis of the shaft 4. The rotor 3 includes a rotor body 31 and at least one magnet 35.

[0067] (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 third shaft portion 43 of the shaft 4, which will be described later, is provided in this through hole. In this embodiment, the rotor body 31 and the shaft 4 are combined by press-fitting the shaft 4 into the through hole. This press-fitting tends to reduce runout of the rotor 3. 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 face 42s of a second shaft portion 42, which will be described later.

[0068] 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 third shaft portion 43 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.

[0069] (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.

[0070] 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.

[0071] 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.

[0072] [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, a fourth shaft portion 44, and a fifth shaft portion 45.

[0073] 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.

[0074] As shown in Fig. 1, the second shaft portion 42 has a diameter larger than the 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 is in contact with a first end face 52f of the inner race 52. The first end face 42f is not in contact with the outer race 53 of the first bearing 51. The second end face 42s is in contact with a first surface 31f of the rotor body 31.

[0075] As shown in Fig. 1, the third shaft portion 43 is provided in a through hole of the rotor body 31. As shown in Fig. 2, the outer peripheral surface of the third shaft portion 43 contacts the inner peripheral surface of the rotor body 31. As shown in Fig. 1, the third shaft portion 43 has a diameter smaller than the diameter of the second shaft portion 42. As shown in Fig. 2, the third shaft portion 43 has an end face 43a. The end face 43a contacts a first end face of the inner race 56 of the second bearing 55.

[0076] 1, the fourth shaft portion 44 is provided inside the second bearing 55. The outer peripheral surface of the fourth shaft portion 44 contacts the inner peripheral surface of the inner race 56 of the second bearing 55. The fourth shaft portion 44 has a diameter smaller than the diameter of the third shaft portion 43.

[0077] The fifth shaft portion 45 is provided in the through hole 72h of the second plate portion 72 of the case 7. 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.

[0078] [First Bearing and Second Bearing] The first bearing 51 and the second bearing 55 support the shaft 4 so that it can rotate freely around the rotation axis. The first bearing 51 is attached to the first shaft portion 41 of the shaft 4. The second bearing 55 is attached to the fourth shaft portion 44 of the shaft 4. The first bearing 51 and the second bearing 55 may have the same configuration as each other, or may have different configurations.

[0079] The first bearing 51 is a radial bearing or an angular bearing. As shown in Figures 2 and 3, the first bearing 51 has an inner race 52 and an outer race 53. In this embodiment, the first bearing 51 is a ball bearing in which balls 54 are disposed between the inner race 52 and the outer race 53. The inner peripheral surface of the inner race 52 contacts the outer peripheral surface of the first shaft portion 41 of the shaft 4. The outer peripheral surface of the outer race 53 contacts a protrusion 71a, which will be described later.

[0080] 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. An example of this fixing member is 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 does not have to be used. In that case, the inner race 52 and the first shaft portion 41 are fixed by fitting together. The second end face 53s contacts the first flat surface 71f. Fig. 2 shows an example in which the first end surface 52f and the first end surface 53f are not misaligned along the axial direction of the first bearing 51. Fig. 3 shows an example in which the first end surface 52f and the first end surface 53f are misaligned along the axial direction of the first bearing 51. As will be described in detail later, the first end surface 52f and the first end surface 53f may also be misaligned along the axial direction of the first bearing 51.

[0081] The second bearing 55 is a radial bearing or an angular bearing. 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 has an inner race 56 and an outer race 57. As shown in FIG. 1 , the second bearing 55 is a ball bearing in which balls 58 are disposed between the inner race 56 and the outer race 57. The inner circumferential surface of the inner race 56 contacts the outer circumferential surface of the third shaft portion 43. The outer circumferential surface of the outer race 57 contacts the inner circumferential surface of the recess 72 a. The recess 72 a is provided in the second plate portion 72 of the case 7. 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 end face 43 a. 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 be in contact with a fixed member similar to the first bearing 51. This is because the outer race 57 is pressed in the direction toward the rotor 3 by the elastic member 8. The first end face of the outer race 57 is not in contact with the rotor 3 or the shaft 4. The second end face of the outer race 57 is in contact with the elastic member 8 shown in FIG. 1 .

[0082] [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.

[0083] [Case] ​​The case 7 accommodates the stator 2, the rotor 3, a portion of the shaft 4, the first bearing 51, the second bearing 55, etc. The case 7 includes a first plate portion 71, a second plate portion 72, and a peripheral wall portion 73.

[0084] 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.

[0085] 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.

[0086] 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. The stator 2 is disposed on the first flat surface 71f. The protruding portion 71a is provided between the stator 2 and the first bearing 51. The protruding portion 71a is connected to the first flat surface 71f. The shape of the protruding portion 71a is, for example, cylindrical. The inner circumferential surface of the protruding portion 71a contacts the outer circumferential surface of the outer race 53. The protruding portion 71a can be used to position the first bearing 51. The outer circumferential surface of the protruding portion 71a may or may not contact the inner circumferential surface of the yoke 22. A portion 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.

[0087] 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 fifth shaft portion 45 is provided within the through hole 72h. The inner diameter of the through hole 72h is larger than the outer diameter of the fifth shaft portion 45. Therefore, the shaft 4 rotates without contact between the inner circumferential surface of the through hole 72h and the fourth shaft portion 44.

[0088] The motor 1 of this embodiment has excellent assembly precision. This is because, although the stator core 21 is made of a powder compact, which has lower dimensional precision than electromagnetic steel sheets, grinding during the manufacturing process allows the stator core 21 to have a height that ensures the gap length is the designed length H1. Because the motor 1 does not include shims, an increase in the number of parts can be suppressed. Furthermore, the motor 1 can suppress an increase in bearing preload, thereby suppressing an increase in mechanical loss.

[0089] [Method of Manufacturing Motor] A method of manufacturing the motor of embodiment 1 will be described with reference to Figures 2, 3, and 7 to 9. The method of manufacturing the motor of this embodiment includes process A and process B. Process A adjusts the height of the stator. Process B assembles the motor parts.

[0090] Step A includes steps A1 and A2. Step A1 determines the design height H1 of the stator core 21. Step A2 grinds at least one of the lower surface 22b, which is the second surface 21s of the stator core 21, and the end surface 23a, which is the first end surface 21f. This grinding process sets the height of the stator core 21 to the design height H1. The parts assembled in step B are the parts of the motor 1 described above with reference to FIGS. 1 to 3. 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.

[0091] The stator core 21 is produced by pressure molding a raw material powder. The raw material powder includes a plurality of coated particles. The coated particles have metal particles and an insulating coating. The materials of the metal particles and the insulating coating are as described above. In addition to the coated particles, the raw material powder may also include a binder and a lubricant. A lubricant may be applied to the inner peripheral surface of the die, which will be described later.

[0092] A press molding machine or the like can be used to pressure-mold the raw material powder. The press molding machine is equipped with a die, a core rod, an upper punch, and a lower punch. The die and core rod form a cavity into which the raw material powder is filled. The upper punch and lower punch pressure-mold the raw material powder filled in the cavity.

[0093] The pressure during compaction is, for example, 500 MPa or more and 2000 MPa or less. If the pressure during compaction is 500 MPa or more, a powder compact with a high relative density can be produced. If the pressure during compaction is 2000 MPa or less, the insulating coating of the coated particles is less likely to be damaged. The pressure during compaction may further be 700 MPa or more and 1800 MPa or less, or particularly 800 MPa or more and 1500 MPa or less.

[0094] [Step A] (Step A1) In step A1, the design height H1 of the stator core 21 manufactured as described above is determined. The design height H1 is determined by taking into consideration the actual dimensions of the shaft 4 and the first bearing 51. For example, the actual dimension of the shaft 4 is the dimension obtained by actually measuring the shaft 4 before assembly. The same concept applies to the actual dimension of the first bearing 51. Taking the actual dimension into consideration includes cases where the actual dimension itself is taken into consideration and cases where a calculated value obtained from the actual dimension is taken into consideration. For example, the calculated value obtained from the actual dimension of the shaft 4 is the average value of the actual dimensions of each shaft 4 obtained from multiple shafts 4. The same concept applies to the calculated value of the first bearing 51.

[0095] 1 to 3, when the first end surface 35f is closer to the stator 2 than the first surface 31f, the design height H1 further takes into account the actual dimensions of the rotor 3. Unlike the motor 1 described above, when the first surface 31f and the first end surface 35f are flush with each other, the design height H1 can be determined by taking into account the actual dimensions of the shaft 4 and the first bearing 51, as described above.

[0096] The number of measurements to calculate 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 motor 1 uses one particular part, the number of measurements to calculate the average value of the actual dimensions of that part may be less than 1,000. Even if two parts are used, the number of measurements to calculate 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 parts of that part. The average value may also be calculated for each lot of that part.

[0097] 2, when the first end face 35f is closer to the stator 2 than the first face 31f and the first end face 52f and the first end face 53f are not misaligned along the axial direction of the first bearing 51, the design height H1 is calculated by "length L1 + length L2 + length L3 - (length L4 + design length G1)." Although not shown, when the first face 31f and the first end face 35f are flush with each other and the first end face 52f and the first end face 53f are not misaligned along the axial direction of the first bearing 51, the design height H1 is calculated by "length L1 + length L2 - design length G1."

[0098] Length L1 is the height of the first bearing 51. Length L2 is the length of the second shaft portion 42. That is, length L2 is the length between the first end face 42f and the second end face 42s. Length L3 is the depth of the recess 32. That is, length L3 is the length between the first face 31f and the bottom face 32a. Length L4 is the thickness Tm of the magnet 35. When the magnet 35 and the rotor body 31 are fixed with adhesive 38, length L4 is the sum of the thickness Tm of the magnet 35 and the thickness Ta of the adhesive 38. All of these lengths are lengths along the axial direction of the shaft 4.

[0099] The actual dimension of length L1 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.

[0100] The actual dimension of the length L2 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.

[0101] The actual dimension of length L3 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 at a midpoint between the inner and outer peripheral edges of recess 32, when viewed from above. The number of measurement points on each circumference is three or more. A certain measurement point on the circumference of the inner peripheral edge, a certain measurement point on the circumference of the outer peripheral edge, and a certain measurement point on the circumference at the midpoint are located on a straight line along the radial direction of rotor 3.

[0102] When there are multiple magnets 35, the actual dimension of the length L4 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 the magnet 35 is viewed from above. The multiple measurement points are set on a line drawn through the center of gravity of the first end face 35f and the center of the rotor 3 when the magnet 35 is viewed from above. Three or more measurement points are set on the line. In particular, the multiple measurement points 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 on the line.

[0103] When there is one magnet 35 and the magnet 35 is annular, the actual dimension of the length L4 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.

[0104] The actual dimension of length L4 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 L4 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.

[0105] 3, when the first end face 52 f and the first end face 53 f are misaligned along the axial direction of the first bearing 51, the design height H1 is determined taking into consideration the amount of misalignment g of the first bearing 51. The amount of misalignment g is the length along the axial direction of the first bearing 51 between the first end face 53 f and the first end face 52 f.

[0106] 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 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.

[0107] 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 loads, 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 gap length becomes shorter than the design length G1 by the amount of misalignment g. Therefore, the misalignment g must be taken into consideration.

[0108] The amount of deviation g can be obtained from a graph such as that shown in FIG. 7. The load (N) on the vertical axis of FIG. 7 represents the load on the inner race 52 of the first bearing 51. The amount of deviation (mm) on the horizontal axis of FIG. 7 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 FIG. 7 can be prepared in advance. Specifically, the graph of FIG. 7 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.

[0109] 3, when the first end face 35f is closer to the stator 2 than the first face 31f, and the first end face 52f and the first end face 53f are misaligned in the axial direction of the first bearing 51, the design height H1 can be calculated by "(length L1 - misalignment g) + length L2 + length L3 - (length L4 + design length G1)." Although not shown, when the first face 31f and the first end face 35f are flush with each other, and the first end face 52f and the first end face 53f are misaligned in the axial direction of the first bearing 51, the design height H1 can be calculated by "(length L1 - misalignment g) + length L2 - design length G1."

[0110] (Step A2) In step A2, grinding is performed by the amount corresponding to the difference between the design height H1 obtained in step A1 and the actual height of the stator core 21. When grinding both the lower surface 22b, which is the second surface 21s, and the end surface 23a, which is the first surface 21f, the total grinding length is set to the difference between the design height H1 obtained in step A1 and the actual height of the stator core 21.

[0111] The actual height of the stator core 21 is determined from the actual length between the lower surface 22 b and the end surface 23 a. The actual length between the lower surface 22 b and the end surface 23 a is determined by the same measurement method as the above-mentioned method for measuring the length between each end surface 23 a and the lower surface 22 b.

[0112] The timing for performing step A2 is before step B, which will be described later, or between steps B2 and B3. FIG. 8 shows an example in which grinding is performed before step B. FIG. 9 shows an example in which grinding is performed between steps B2 and B3. As shown in FIG. 8, the stator core 21 is ground before the stator core 21 and the first plate portion 71 are assembled together. In this case, at least one of the lower surface 22b and the end surface 23a of the stator core 21 can be ground. Alternatively, as shown in FIG. 9, the stator core 21 is ground after the stator core 21 and the first plate portion 71 are assembled together. In this case, only the end surface 23a can be ground.

[0113] 8 and 9, a grinding machine 1000 can be used for the grinding process. The grinding process may be surface grinding. Surface grinding makes it easy to align the positions of the end faces 23a of the stator core 21 in the height direction.

[0114] When grinding the end faces 23 a, the end faces 23 a may be ground while fixing the end of the side face 23 b of each tooth 23 as shown in Fig. 8 or 9. The end may be fixed using, for example, a plate-like member 1100 as shown in Fig. 8.

[0115] The plate-like member 1100 has a plurality of through holes 1110. The through holes 1110 are holes into which the ends of the teeth 23 can be inserted. The number of through holes 1110 corresponds to the number of teeth 23. The inner peripheral shape of the through holes 1110 is similar to the outer peripheral shape of the teeth 23. The size of the through holes 1110 is such that the ends can be inserted, and when the ends are inserted, there is a very small gap between the side surface 23b and the inner peripheral surface of the through holes 1110. The inner peripheral shape and size of each through hole 1110 are the same.

[0116] As shown in Figures 8 and 9, each tooth 23 is inserted into each through hole 1110. The side surface 23b is held by the inner peripheral surface of the through hole 1110. While held, the end surface 23a is ground. For ease of explanation, Figures 8 and 9 exaggerate the exposed area of ​​each tooth 23 from the plate-shaped member 1100. By fixing the vicinity of the end surface 23a of each tooth 23 with the plate-shaped member 1100, it is possible to prevent chipping near the ridge between the end surface 23a and the side surface 23b during the grinding process. The plate-shaped member 1100 may also be ground during the grinding process.

[0117] The ground end surface 23a has the grinding marks 231, which have been described with reference to Fig. 4. When the lower surface 22b is ground, grinding marks similar to the grinding marks 231 are also formed on the lower surface 22b, although this is not shown in the drawing.

[0118] [Process B] In process B, in which the parts are assembled, each member is fixed in a predetermined position. By going through process B, the motor 1 as 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 carried out in order.

[0119] In step B1, the stator 2 and the first bearing 51 are disposed on the first flat surface 71 f of the first plate portion 71 .

[0120] In step B2, the first plate portion 71 and the stator 2 are fixed together by the fastening member 91. The fastening member 91 is provided in the second through-hole of the first plate portion 71 and the hole of the stator 2.

[0121] In step B3, the first shaft portion 41 of the shaft 4 is placed in the first bearing 51. A rotor assembly in which the rotor 3 and shaft 4 are combined is prepared in advance. In step B3, the first shaft portion 41 of the rotor assembly is placed in the first bearing 51. In this case, step B4 is performed without going through step B31. If the rotor 3 and shaft 4 are prepared without being combined without preparing a rotor assembly, step B31 is performed before step B4. In step B31, the rotor 3 is fitted onto the shaft 4 in a state in which the first shaft portion 41 is placed in the first bearing 51.

[0122] In step B4, the second bearing 55 is fitted onto the fourth shaft portion 44 of the shaft 4.

[0123] In step B5, the elastic member 8 is placed on the second bearing 55.

[0124] In step B6, the through hole 72h 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 73 is butted against the first plate portion 71. Then, the first plate portion 71 and the peripheral wall portion 73 are fixed together by 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.

[0125] [Step C] The method for manufacturing a motor according to the present embodiment may further include step C of heat treating the stator core 21. Step C is performed before step A or between step A and step B.

[0126] The heat treatment temperature is, for example, 350°C or higher and 800°C or lower. The heat treatment temperature may further be 400°C or higher and 750°C or lower, particularly 450°C or higher and 700°C or lower. The heat treatment holding time is, for example, 5 minutes or higher and 60 minutes or lower. The heat treatment holding time may further be 10 minutes or higher and 45 minutes or lower, particularly 15 minutes or higher and 30 minutes or lower. The heat treatment atmosphere is, for example, an oxidizing atmosphere. The oxygen concentration in the oxidizing atmosphere is, for example, 500 ppm or higher and 20,000 ppm or lower. The oxygen concentration here is a volume fraction. The oxygen concentration in the oxygen atmosphere may further be 700 ppm or higher and 10,000 ppm or lower, 1,000 ppm or higher and 7,500 ppm or lower, particularly 2,000 ppm or higher and 5,000 ppm or lower.

[0127] When process C is performed before process A, oxides are formed between the coating particles near the surface of the stator core 21. The formed oxides suppress the plastic flow of the metal particles 241 that occurs during grinding. Therefore, even if the insulating coating 242 is damaged by grinding, adjacent metal particles 241 can be prevented from connecting to each other. On the other hand, when process C is performed between process A and process B, the ground surface is oxidized. That is, even if the insulating coating 242 is damaged by grinding and adjacent metal particles 241 connect to each other, the connected portions are oxidized. Therefore, adjacent metal particles 241 are insulated from each other by an oxide film. Therefore, by performing process C, eddy current loss is reduced, and ultimately loss is reduced.

[0128] The motor manufacturing method of this embodiment can determine the design height H1 of the stator core 21, which corresponds to the design length G1, before assembling the parts. The motor manufacturing method of this embodiment can then adjust the height of the stator core 21 to the design height H1 by grinding before or during the assembly of the parts. Therefore, the motor manufacturing method of this embodiment can adjust the gap length to the design length G1 by assembling the parts only once. Therefore, the motor manufacturing method of this embodiment provides excellent manufacturability for the motor 1, which has excellent assembly accuracy, even without using shims.

[0129] As described above, the inner race 52 may be misaligned with respect to the outer race 53 of the first bearing 51. Even in such cases, the motor manufacturing method of this embodiment can calculate the design height H1 while taking into account the amount of misalignment g. Therefore, the motor manufacturing method of this embodiment provides excellent manufacturability for the motor 1, which has excellent assembly accuracy, even if the inner race 52 is misaligned.

[0130] 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 design height H1 based on the average value of the actual dimensions of certain parts that are fewer than the number of parts to be manufactured, the manufacturability of the motor 1 is more easily improved than when the design height H1 is determined based on the actual dimensions of certain parts in the same number as the number of parts to be manufactured.

[0131] <<Embodiment 2>> [Motor] A motor 1 of embodiment 2 will be described with reference to FIG. 10 . The motor 1 of embodiment 2 differs from the motor 1 of embodiment 1 mainly in that it is a double stator / single rotor type axial gap motor. A double stator / single rotor type motor 1 has two stators 2 and one rotor 3. In a double stator / single rotor type, one rotor 3 is assembled between two stators 2 and is sandwiched between the two stators 2 in the axial direction of the shaft 4. At least one of the two stators 2 is the stator 2 described in embodiment 1. Both of the two stators 2 may be the stator 2 described in embodiment 1. The following description will focus on the differences from embodiment 1. Descriptions of configurations similar to embodiment 1 may be omitted.

[0132] [Rotor] The rotor body 31 is an annular flat plate member. The rotor body 31 has a first through hole and at least one second through hole. The first through hole is provided in the center. The third shaft portion 43 of the shaft 4 is provided in the first through hole. The second through hole is provided on the outer periphery of the first through hole. A magnet 35 is provided in the second through hole. The number of second through holes is the same as the number of magnets 35.

[0133] As shown in FIG. 10 , in this embodiment, the thickness of the rotor body 31 and the thickness of the magnet 35 are the same. That is, the first surface of the rotor body 31 and the first end surface of the magnet 35 are flush with each other. Furthermore, the second surface of the rotor body 31 and the second end surface of the magnet 35 are flush with each other. The first surface of the rotor body 31 and the first end surface of the magnet 35 are surfaces closer to the first stator 2. The second surface of the rotor body 31 and the second end surface of the magnet 35 are surfaces closer to the second stator 2. Here, the stator 2 shown in the lower part of FIG. 10 is the first stator 2. Furthermore, the stator 2 shown in the upper part of FIG. 10 is the second stator 2. Although not shown, the thickness of the rotor body 31 and the magnet 35 do not have to be the same.

[0134] [Case] ​​The case 7 of this embodiment includes a pair of first plate portions 71 and a peripheral wall portion 73. The pair of first plate portions 71 and the peripheral wall portion 73 are configured as separate bodies. The first first plate portion 71 and the peripheral wall portion 73 are fixed together by fastening members 92. The second first plate portion 71 and the peripheral wall portion 73 are fixed together by fastening members 92.

[0135] [Motor Manufacturing Method] In the motor manufacturing method, the design height of the first stator core 21 is determined by taking into consideration the actual dimensions of the shaft 4 and the first bearing 51 shown on the lower side of Fig. 10. The design height of the first stator core 21 is determined by "actual dimension of the height of the first bearing 51 + actual dimension of the length of the second shaft portion 42 - design length G1".

[0136] The design height of the second stator core 21 is determined by taking into consideration the actual dimensions of the rotor 3, the shaft 4, and the first bearing 51 shown in the upper part of Fig. 10. The design height of the second stator core 21 is determined by "actual dimension of the height of the first bearing 51 + actual dimension of the length of the third shaft portion 43 - (thickness of the magnet 35 + design length G1)."

[0137] The actual length of the third shank 43 is the actual length between the end face 43a and the second end face 42s. The actual length of the third shank 43 is the average value of the lengths at multiple measurement points. The measurement points are taken at equal intervals around the circumference of the third shank 43. The number of measurement points is three or more. The length at each measurement point is the length along the axial direction of the third shank 43 at that measurement point.

[0138] The motor 1 of this embodiment has excellent assembly precision, similar to that of embodiment 1. The method for manufacturing the motor of this embodiment is excellent in manufacturability of the motor 1, which has excellent assembly precision, even without using shims.

[0139] 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 equivalent to the claims.

[0140] 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.

[0141] REFERENCE SIGNS LIST 1 Motor 2 Stator 21 Stator core, 21f First surface, 21s Second surface 22 Yoke, 22a Upper surface, 22b Lower surface 23 Teeth, 23a End surface, 23b Side surface, 231 Grinding marks 24 Coated particles, 241 Metal particles, 242 Insulating coating 25 Coil 3 Rotor 31 Rotor body, 31f First surface, 31s Second surface 32 Recess, 32a Bottom surface 35 Magnet, 35f First end surface 38 Adhesive 4 Shaft 41 First shaft portion 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 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 58 Ball 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 1000 Grinding machine 1100 Plate-shaped member, 1110 Through hole A, B Region G1 Design length, g Misalignment amount H1 Design height L1, L2, L3, L4 Length Tm, Ta Thickness

Claims

1. A shaft, a bearing that rotatably supports the shaft; a rotor fixed integrally to the shaft; a stator disposed relative to the rotor in the axial direction of the shaft with a gap of a design length therebetween; The stator has a stator core made of a powder compact, the stator core has a first surface facing the gap and a second surface provided on an opposite side to the first surface in the axial direction, At least one of the first surface and the second surface has a grinding mark. Motor.

2. The stator core is A circular plate-shaped yoke; a plurality of columnar teeth arranged at intervals in a circumferential direction of the yoke; The yoke is The outer periphery and An inner circumferential surface; A planar upper surface and a planar lower surface connecting the outer peripheral surface and the inner peripheral surface, Each of the plurality of teeth includes a side surface connected to the top surface of the yoke; an end surface connected to an end portion of the side surface opposite to a side connected to the upper surface, the lower surface is the second surface, the end surface is the first surface, 2. The motor according to claim 1, wherein a difference between a maximum value and a minimum value of a height between the lower surface of the yoke and the end surface of each of the plurality of teeth is 0.02 mm or less.

3. A motor as described in claim 1 or claim 2, having grinding marks on both the first surface and the second surface.

4. A motor as described in claim 2, wherein the parallelism between the lower surface and the end face of each of the plurality of teeth is 0.02 mm or less.

5. 3. The motor according to claim 1, wherein the powder compact has a relative density of 90% or more.

6. The powder compact comprises a plurality of coated particles, Each of the plurality of coated particles comprises Metal particles made of a soft magnetic material; an insulating coating covering the metal particles; The metal particles are composed of pure iron or an iron-based alloy, 3. The motor according to claim 1, wherein the iron-based alloy is an Fe-Si alloy, an Fe-Al alloy, or an Fe-Si-Al alloy.

7. a case having a first plane on which the stator is mounted; The motor according to claim 1 or 2, further comprising: a fastening member that fixes the first plane and the stator.

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

9. The number of the stators is two, 3. The motor according to claim 1, wherein the number of the rotors is one.

10. adjusting the height of a stator in an axial gap type motor; and assembling the parts of the motor. The parts are: A rotor, The stator; A shaft that is a rotation axis of the rotor; a bearing that rotatably supports the shaft; The stator has a stator core made of a powder compact, The step of adjusting the height of the stator includes: determining a design height of the stator core in consideration of the actual dimensions of the shaft and the bearing; and grinding at least one of the first surface and the second surface of the stator core to obtain the desired design height. the design height is a height at which a length of a gap between the rotor and the stator is a design length, the first surface is a surface facing the gap, The second surface is a surface provided on the opposite side of the first surface in the axial direction of the shaft. A method for manufacturing a motor.

11. A method for manufacturing a motor as described in claim 10, wherein the grinding process grinds both the first surface and the second surface.

12. The rotor is A rotor body having a circular ring shape; At least one magnet fixed to the rotor body, the rotor body has a first surface facing the magnet; The magnet has a first end surface facing the stator, 12. The method for manufacturing a motor according to claim 10 or 11, wherein the step of determining the design height determines the design height by taking into account an actual dimension of the length between the first surface of the rotor body and the first end surface of the magnet in the rotor in which the rotor body and the magnet are fixed.

13. Repeating the process of assembling the parts; 12. The method for manufacturing a motor according to claim 10, wherein the step of determining the design height determines the design height by taking into consideration average values ​​of actual dimensions of the shafts and the bearings, the number of which is smaller than the number of motors to be manufactured.

14. The method for manufacturing a motor according to claim 10 or 11, wherein the grinding process is surface grinding.

15. The part includes a case having a first plane on which the stator is mounted; The method for manufacturing a motor according to claim 10 , wherein the grinding step includes grinding the second surface in a state where the stator and the case are combined together.

16. The part includes a case having a first plane on which the stator is mounted; The method for manufacturing a motor according to claim 10 , wherein the grinding step includes grinding at least one of the first surface and the second surface of the stator core in a state in which the stator and the case are not assembled together.