motor

Abstract

To provide a motor which inhibits temperature rise of a bearing and can be driven stably for a long time.SOLUTION: A motor includes: a cylindrical holding part; a rotor disposed inside the holding part and having a shaft rotatable about a central axis; a bearing part rotatably supporting the shaft; and a stator disposed at the radially outer side of the holding part. The bearing part has a first bearing and a second bearing. The holding part includes a first holding part and a second holding part extending upward from an upper end of the first holding part. The stator is fixed to an outer peripheral surface of the first holding part, and an outer ring of the first bearing is fixed to a lower end of an inner peripheral surface. At least a portion of an outer ring of the second bearing is fixed to an inner peripheral surface of the second holding part. The second holding part is radially spaced from a stator core. A radial thickness of the second holding part is smaller than a distance between an outer peripheral surface of the second holding part and an inner peripheral surface of the stator core.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a motor.

Background Art

[0002] In a conventional motor, a shaft is rotatably supported via a bearing fixed to a bearing housing press-fitted into a base plate. And a stator core is fixed to an outer peripheral surface of the bearing housing. (For example, refer to Japanese Patent Application Laid-Open No. 2022-95017).

Prior Art Documents

Patent Documents

[0003] [[ID=2​​​​​​​​​​​​​​​​​​​​​​An exemplary motor of the present invention includes a rotor having a shaft and rotor magnets that rotate around a central axis extending vertically, a stator having a stator core and facing radially inward and radially opposite to the rotor magnets, a bearing portion that rotatably supports the shaft, and a cylindrical retaining portion that holds the bearing portion, centered on the central axis. The bearing portion includes a first bearing and a second bearing disposed above the first bearing. The retaining portion includes a cylindrical first retaining portion extending along the central axis and a cylindrical second retaining portion extending upward along the central axis from the upper end of the first retaining portion. The stator core is fixed to the outer circumferential surface of the first retaining portion, the outer ring of the first bearing is fixed to the lower end of the inner circumferential surface, and at least a portion of the outer ring of the second bearing is fixed to the inner circumferential surface of the second retaining portion. The second retaining portion is arranged with a radial gap between it and the stator core, and the radial thickness of the second retaining portion is smaller than the radial distance between the outer circumferential surface of the second retaining portion and the inner circumferential surface of the stator core. [Effects of the Invention]

[0007] The objective of this exemplary motor of the present invention is to suppress the temperature rise of the bearings and to provide a motor that can operate stably over a long period of time. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a perspective view of the motor. [Figure 2] Figure 2 is an exploded perspective view of the motor. [Figure 3] Figure 3 is a longitudinal cross-sectional view of the motor. [Figure 4] Figure 4 is an enlarged cross-sectional view of the motor's holding section and bearing section. [Figure 5] Figure 5 is an enlarged cross-sectional view of the motor holder of a modified example. [Modes for carrying out the invention]

[0009] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. In this specification, the direction parallel to the central axis Cx of the motor 100 will be referred to as the "axial direction," the direction perpendicular to the central axis Cx will be referred to as the "radial direction," and the direction along the arc centered on the central axis Cx will be referred to as the "circumferential direction."

[0010] Furthermore, in this specification, the axial direction of the motor 100 is defined as the vertical direction, but the vertical direction is merely a descriptive term and does not limit the positional relationship and direction in the actual operating state of the motor 100. Moreover, in this specification, "parallel" includes not only precisely parallel but also cases where they are arranged side by side without intersecting within a practical range.

[0011] <Motor 100> Figure 1 is a perspective view of the motor 100. Figure 2 is an exploded perspective view of the motor 100. Figure 3 is a longitudinal cross-sectional view of the motor 100. Figure 4 is an enlarged cross-sectional view of the holding portion 30 and bearing portion 50 of the motor 100. As shown in Figure 1, the motor 100 has a rotor 10, a stator 20, a holding portion 30, and a bearing portion 50. The motor 100 is a so-called outer rotor type brushless DC motor, and the rotor magnet 13 of the rotor 10, which will be described later, is arranged radially outward from the stator 20. The rotor magnet 13 of the rotor 10 faces radially toward the radial outer surface of the stator 20.

[0012] <Rotor 10> The rotor 10 rotates around its central axis Cx. As shown in Figures 1 and 2, the rotor 10 includes a shaft 11, a rotor case 12, and a rotor magnet 13.

[0013] The shaft 11 is cylindrical with a central axis Cx. A portion of the shaft 11 is positioned inside the holding portion 30. The shaft 11 rotates around the central axis Cx. The upper part of the shaft 11 is positioned above the upper end of the holding portion 30. Details of the holding portion 30 will be described later.

[0014] The rotor case 12 is a covered cylindrical shape formed of a magnetic material, and has a rotor hub 121 and a cylindrical portion 122. The rotor hub 121 is fixed to the shaft 11. That is, the rotor 10 has a rotor hub 121 fixed to the shaft 11. The rotor hub 121 is an annular shape having a through hole 123 penetrating axially in the center. That is, the rotor hub 121 has a through hole 123 disposed at the center as viewed axially and in which the shaft 11 is disposed.

[0015] The rotor hub 121 has a cylindrical rotor boss 124 extending axially downward from the edge of the through hole 123. The shaft 11 is fixed to the rotor boss 124. In other words, the shaft 11 and the rotor case 12 are fixed by the rotor boss 124. The rotor boss 124 and the shaft 11 are fixed here by press-fitting, but are not limited thereto. Fixing methods can widely adopt methods such as adhesion, welding, screwing, etc. that can firmly fix the rotor boss 124 to the shaft 11.

[0016] The cylindrical portion 122 is cylindrical and extends axially from the radially outer edge of the rotor hub 121. The rotor magnet 13 is fixed to the inner peripheral surface of the cylindrical portion 122.

[0017] The rotor magnet 13 is cylindrical. At least the inner peripheral surface of the rotor magnet 13 has N poles and S poles arranged alternately in the circumferential direction. In the present embodiment, the rotor magnet 13 is cylindrical, but is not limited thereto. For example, a plurality of flat magnets may be arranged and fixed in the circumferential direction on a cylindrical rotor core.

[0018] That is, the rotor 10 has a shaft 11 and a rotor magnet 13 that rotate about a central axis Cx extending vertically.

[0019] <Stator 20> The stator 20 is disposed radially inside the rotor magnet 13 and faces the rotor magnet 13 in the radial direction. The stator 20 has a stator core 21, an insulator (not shown), and a coil 22. That is, the stator 20 has the stator core 21 and faces the inner side in the radial direction of the rotor magnet 13 in the radial direction. The stator core 21 is a laminate formed by laminating electromagnetic steel sheets in the axial direction. Note that the stator core 21 is not limited to a laminate formed by laminating electromagnetic steel sheets, and may be a single member such as powder sintering or casting, for example.

[0020] The stator core 21 has an annular core back 211 and a plurality of teeth 212. The inner peripheral surface 213 of the annular core back 211 is fixed to the holding portion 30 of the base plate 40. Thereby, the center of the stator core 21 overlaps with the central axis Cx of the motor 100. Note that a fixing member may be interposed between the core back 211 and the holding portion 30.

[0021] The plurality of teeth 212 extend radially outward from the outer peripheral surface of the core back 211. The plurality of teeth 212 are arranged at equal intervals in the circumferential direction. The insulator (not shown) is formed of an insulating material such as resin, for example, and covers at least the teeth 212.

[0022] The insulator (not shown) electrically insulates the stator core 21 and the coil 22. Note that the insulator (not shown) is not limited to resin, and a material that can insulate the stator core 21 and the coil 22 can be widely adopted. When the conductor and the teeth 212 are insulated, the insulator (not shown) may be omitted.

[0023] Coil 22 is formed by winding a wire around teeth 212 via an insulator (not shown) that covers teeth 212. The wires constituting coil 22 are connected to a circuit board (not shown). Three currents with different phases are supplied to coil 22 from the circuit board. When current is supplied to coil 22, coil 22 is excited, and an attractive or repulsive force is generated between coil 22 and rotor magnet 13. By adjusting the timing of the current supply to coil 22, the rotor 10 rotates due to the attractive or repulsive force.

[0024] <Holding part 30> The retaining portion 30 protrudes upward along the central axis Cx from the upper surface of the base plate 40, which is positioned axially below the rotor 10 and stator 20. The retaining portion 30 and the base plate 40 are integrally formed. Alternatively, the retaining portion 30 may be formed separately from the base plate 40, and the retaining portion 30 may be fixed to the base plate 40.

[0025] As shown in Figures 2 and 3, the holding portion 30 has a first holding portion 31 and a second holding portion 32, and holds the bearing portion 50. That is, the holding portion 30 is cylindrical with a central axis Cx as its center, and holds the bearing portion 50. The holding portion 30 has a through hole 300 that penetrates vertically along the central axis Cx. The bearing portion 50 is arranged inside the through hole 300, and the bearing portion 50 rotatably supports the shaft 11. That is, the bearing portion 50 rotatably supports the shaft 11. The first holding portion 31 is cylindrical with a central axis Cx as its center. That is, the holding portion 30 is cylindrical extending along the central axis Cx. The first holding portion 31 is connected to the base plate 40 at its lower end.

[0026] The outer circumferential surface 311 of the first retaining portion 31 is provided with a core fixing portion 312, a small diameter portion 313, and an outer retaining surface 314. The stator core 21 is fixed to the first retaining portion 31 with its inner circumferential surface in contact with the core fixing portion 312. In this case, the method of fixing the first retaining portion 31 to the core fixing portion 312 is press-fitting. However, the method of fixing the stator core 21 to the first retaining portion 31 is not limited to press-fitting, and a wide range of fixing methods that can firmly fix the stator core 21 to the first retaining portion 31 can be employed, such as adhesive bonding, welding, brazing, or screw fastening. As shown in Figure 3, the upper end portion 210 of the stator core 21 fixed to the first retaining portion 31 is located above the upper end portion 320 of the second retaining portion 32.

[0027] The small-diameter portion 313 is connected to the core fixing portion 312 in the axial direction and above. The small-diameter portion 313 has a tapered portion that becomes smaller in diameter as it extends upward from the core fixing portion 312. The outer diameter of the small-diameter portion 313 is smaller than the outer diameter of the core fixing portion 312. That is, the first retaining portion 31 has a small-diameter portion 313 on the upper part of the outer peripheral surface 311 that is smaller in diameter than the portion that contacts the lower stator core 21.

[0028] When attaching the stator core 21 to the retaining part 30, the upper part of the retaining part 30, i.e., the second retaining part 32, is inserted into the interior of the stator core 21. Then, the small-diameter portion 313 of the first retaining part 31 is inserted into the stator core 21. The inner circumferential surface 213 of the stator core 21 is fixed in contact with the core fixing part 312. Therefore, the inner diameter of the inner circumferential surface 213 of the stator core 21 and the outer diameter of the core fixing part 312 are approximately equal. The outer diameter of the small-diameter portion 313 and the outer diameter of the second retaining part 32 are smaller than the outer diameter of the core fixing part 312. Therefore, the second retaining part 32 and the small-diameter portion 313 can be inserted into the interior of the stator core 21 without contacting the inner circumferential surface 213 of the stator core 21. Therefore, it is easier to insert the retaining part 30 into the stator core 21, improving workability when manufacturing the motor.

[0029] The outer retaining surface 314 is annular in shape, extending radially outward from the first retaining portion 31 in a direction perpendicular to the central axis Cx. When the stator core 21 is attached to the retaining portion 30 from the upper part, the lower end of the core back 211 comes into contact with the outer retaining surface 314. This positions the stator core 21 axially relative to the retaining portion 30.

[0030] The second retaining portion 32 is cylindrical with respect to the central axis Cx. In the retaining portion 30, the second retaining portion 32 protrudes upward from the upper end portion 310 of the first retaining portion 31. That is, the second retaining portion 32 is cylindrical and extends upward along the central axis Cx from the upper end portion 310 of the first retaining portion 31.

[0031] The second retaining portion 32 is formed integrally with the first retaining portion 31. However, the invention is not limited to the case in which the first retaining portion 31 and the second retaining portion 32 are formed integrally. The second retaining portion 32 may be formed separately from the first retaining portion 31, and then fixed to the first retaining portion 31 by fixing methods such as adhesive bonding, welding, or press-fitting. Furthermore, the method of fixing the second retaining portion 32 to the first retaining portion 31 is not limited to the above, and a wide range of fixing methods that can firmly fix the second retaining portion 32 to the first retaining portion 31 can be employed.

[0032] The upper end portion 310 of the first retaining portion 31 is an annular plane that extends in a direction perpendicular to the central axis Cx. As a result, a stepped portion perpendicular to the central axis Cx is formed at the boundary between the first retaining portion 31 and the second retaining portion 32, and the small diameter portion 313 is positioned below the stepped portion. The radial thickness W1 of the second retaining portion 32 is thinner than the radial thickness of the first retaining portion 31. The outer diameter of the second retaining portion 32 is smaller than the outer diameter of the upper end portion 310 of the first retaining portion 31, that is, the upper end of the small diameter portion 313. Therefore, when positioning the stator core 21 from the upper end portion of the retaining portion 30, the second retaining portion 32 is less likely to get in the way.

[0033] The through hole 300 of the holding portion 30 has holes of different inner diameters connected in the axial direction. The axial middle portion is the intermediate hole portion 303, the portion below the intermediate hole portion 303 is the lower hole portion 304, and the portion above is the upper hole portion 305. The through hole 300 has a first inner holding surface 301 that expands radially inward at the joint between the intermediate hole portion 303 and the lower hole portion 304. The through hole 300 also has a second inner holding surface 302 that expands radially inward at the joint between the intermediate hole portion 303 and the upper hole portion 305. In the holding portion 30, the second inner holding surface 302 is positioned below the upper end of the first holding portion 31. That is, the holding portion 30 has an inner holding surface 302 that expands radially inward from the inner circumferential surface axially below the upper end portion 310 of the first holding portion 31.

[0034] <Bearing part 50> The bearing section 50 includes a first bearing 51 and a second bearing 52. The first bearing 51 and the second bearing 52 are fixed to the inner circumferential surface of the through hole 300 of the holding section 30, and rotatably support the shaft 11 relative to the holding section 30. The first bearing 51 supports the lower axial portion of the shaft 11, and the second bearing 52 supports the portion of the shaft 11 above the first bearing 51. In other words, the bearing section 50 includes a first bearing 51 and a second bearing 52 positioned above the first bearing 51. Because the first bearing 51 and the second bearing 52 rotatably support the shaft 11 at positions separated in the axial direction, wobble during rotation of the shaft 11 is suppressed.

[0035] Here, the detailed configurations of the first bearing 51 and the second bearing 52 will be described. In the bearing section 50, the first bearing 51 and the second bearing 52 have the same configuration. Here, the first bearing 51 will be described as a representative of the first bearing 51 and the second bearing 52, and the configuration of the second bearing 52 will be described in relation to the configuration of the first bearing 51.

[0036] The first bearing 51 has an inner ring 511, an outer ring 512, and balls 513. The inner ring 511 and the outer ring 512 are cylindrical. In the first bearing 51, the inner ring 511 and the outer ring 512 are arranged radially opposite each other with respect to the central axis Cx. A plurality of balls 513 are arranged circumferentially between the inner ring 511 and the outer ring 512. In other words, the first bearing 51 is a ball bearing.

[0037] The inner ring 511 of the first bearing 51 is fixed to the outer circumferential surface of the shaft 11. The outer ring 512 of the first bearing 51 is fixed to the inner circumferential surface of the lower hole 304 of the through hole 300 of the retaining portion 30. In other words, the outer ring 512 of the first bearing 51 is fixed to the lower end of the inner circumferential surface of the first retaining portion 31.

[0038] As a result, the outer ring 512 is positioned in the axial direction. The first bearing 51 is held in a position that overlaps radially with the first retaining portion 31.

[0039] The inner ring 511 and outer ring 512 of the first bearing 51 are fixed to the lower hole 304 and the shaft 11, for example, by press-fitting. However, the fixing of the inner ring 511 and outer ring 512 of the first bearing 51 to the lower hole 304 and the shaft 11 is not limited to press-fitting; welding, bonding, etc., can also be used. In addition, a wide range of fixing methods that restrict the circumferential movement of the inner ring 511 and outer ring 512 can be employed.

[0040] The second bearing 52 has an inner ring 521 corresponding to the inner ring 511 of the first bearing 51, an outer ring 522 corresponding to the outer ring 512, and balls 523 corresponding to the balls 513. The second bearing 52 is also attached to the retaining portion 30 and rotatably supports the shaft 11.

[0041] The inner ring 521 of the second bearing 52 is fixed to the outer circumferential surface of the shaft 11. The outer ring 522 of the second bearing 52 is fixed to the inner circumferential surface of the upper hole 305 of the through hole 300 of the retaining portion 30. In other words, at least a portion of the outer ring 522 of the second bearing 52 is fixed to the inner circumferential surface of the second retaining portion 32.

[0042] At this time, the lower end of the outer ring 522 of the second bearing 52 comes into contact with the second inner retaining surface 302. This positions the outer ring 522 in the axial direction. In the motor 100 of this embodiment, the outer ring 522 of the second bearing 52 is in direct contact with the second inner retaining surface 302, but this is not limited to this, and contact may be made indirectly, for example, through a member such as a washer. In other words, the lower end of the outer ring 522 of the second bearing 52 comes into direct or indirect contact with the inner retaining surface 302. In this way, it is possible to adjust the axial position of the second bearing 52 by interposing a member.

[0043] The inner ring 521 and outer ring 522 of the second bearing 52 are fixed to the upper hole 305 and the shaft 11, for example, by press-fitting. However, the fixing of the inner ring 521 and outer ring 522 of the second bearing 52 to the shaft 11 and the upper hole 305 is not limited to press-fitting; welding, bonding, etc., can also be used. In addition, a wide range of fixing methods that restrict the circumferential movement of the inner ring 521 and outer ring 522 can be employed.

[0044] In the through hole 300, the second inner retaining surface 302 is positioned below the upper end of the first retaining portion 31. Therefore, the lower end of the second bearing 52 is held by the first retaining portion 31, and the remaining portion is held by the second retaining portion 32.

[0045] The first retaining portion 31 has a greater radial thickness than the second retaining portion 32. Therefore, the first retaining portion 31 has higher rigidity than the second retaining portion 32. Furthermore, since the lower end of the second bearing 52 is held by the first retaining portion 31, the rigidity of the mounting of the second bearing 52 can be increased. As a result, rattling and loosening of the second bearing 52 are suppressed, and stable operation of the second bearing 52 is possible over a long period of time.

[0046] As shown in Figures 3 and 4, the first bearing 51 holds the lower part of the shaft 11. The second bearing 52 is positioned above the first bearing 51 on the shaft 11. More specifically, the second bearing 52 holds the portion of the shaft 11 above the portion held by the first bearing 51. By being held by the first bearing 51 and the second bearing 52, the shaft 11's center coincides with the central axis Cx, and the shaft 11 is rotatable about the central axis Cx.

[0047] Furthermore, as shown in Figures 3 and 4, the lower end 125 of the rotor boss 124 contacts the inner ring 521 of the second bearing 52 below the upper end 210 of the stator core 21. By positioning a portion of the rotor boss 124 below the upper end 210 of the stator core 21, the axial height of the motor 100 can be reduced. In addition, the lower end 125 of the rotor boss 124 presses against the inner ring 521 of the second bearing 52, thereby suppressing the axial movement of the second bearing 52.

[0048] The motor 100 according to this embodiment has the configuration described above.

[0049] Next, the relative positions of the various parts of the motor 100 will be described. As shown in Figure 4, in the motor 100, the stator core 21 is fixed to the core fixing portion 312 of the first holding portion 31 of the holding portion 30. That is, the stator core 21 is fixed to the outer peripheral surface 311 of the first holding portion 31.

[0050] As shown in Figure 4, the upper end 310 of the first retaining portion 31 is located above the axial center line 21C of the stator core 21. The upper end 320 of the second retaining portion 32 is located below the upper end 210 of the stator core 21.

[0051] This configuration allows at least a portion of the rotor boss 124 and other components of the rotor case 12 to be positioned below the upper end portion 210 of the stator core 21. This reduces the axial height of the motor 100.

[0052] Furthermore, as shown in Figure 4, the axial length L1 from the outer holding surface 314 to the upper end 310 of the first holding portion 31 is greater than the axial length L2 of the second holding portion 32.

[0053] This configuration allows the stator core 21 to be firmly held by the first holding portion 31. Furthermore, shortening the second holding portion 32 reduces the weight of the motor 100.

[0054] Furthermore, the radial thickness W1 of the second retaining portion 32 is thinner than the radial thickness of the first retaining portion 31. Therefore, when the stator core 21 is fixed to the core fixing portion 312 of the first retaining portion 31, a gap Th is formed between the second retaining portion 32 and the inner circumferential surface 213 of the core back 211 of the stator core 21. In other words, the second retaining portion 32 is positioned radially with a gap Th between it and the stator core 21.

[0055] The radial thickness W1 of the second retaining portion 32 is smaller than the radial distance W2 of the gap Th. That is, the second retaining portion 32 is positioned radially with respect to the stator core 21 via a gap Th, and the radial thickness W1 of the second retaining portion 32 is smaller than the radial distance W2 between the outer circumferential surface 321 of the second retaining portion 32 and the inner circumferential surface 213 of the stator core 21.

[0056] <Motor 100 drive> As described above, the motor 100 rotates the rotor 10 around the central axis Cx by supplying current to the coil 22. Current is supplied to the coil 22. When current is supplied to the coil 22, the coil 22 generates heat. The heat generated in the coil 22 is conducted throughout the motor 100 via the stator 20 and the holding part 30 in contact with the stator 20.

[0057] In the motor 100, the stator core 21 is made of a magnetic material, for example, a metal such as iron. Therefore, the heat generated in the coil 22 is conducted to the stator core 21. A gap Th is formed between the second holding part 32 and the stator core 21.

[0058] Since the second retaining portion 32 and the stator core 21 do not come into direct contact, and the radial distance W2 between the second retaining portion 32 and the stator core 21 is greater than the radial thickness W1 of the second retaining portion 32, heat is not easily transferred directly from the stator core 21 to the second retaining portion 32. In addition, because there is a gap Th between the outer circumference of the second retaining portion 32 and the stator core 21, even if heat is transferred from the first retaining portion 31 to the second retaining portion 32, the transferred heat is released to the outside from the outer circumference of the second retaining portion 32. As a result, heat conduction to the second bearing 52 is suppressed, and deterioration of the second bearing 52 due to temperature rise (especially deterioration of the lubricant) can be suppressed, enabling stable operation of the second bearing 52 over a long period of time. Furthermore, since the lower part of the first bearing 51 faces the opening at the bottom of the through hole 300, it is not easily heated. As a result, deterioration due to temperature rise is also suppressed for the first bearing 51, and it operates stably over a long period of time.

[0059] <Variation> Figure 5 is an enlarged cross-sectional view of the holding portion 30A of the modified motor 100A. As shown in Figure 5, the holding portion 30A of the motor 100A differs from the holding portion 30 of the motor 100 in that it has a groove 33. In all other respects, the motor 100A has the same configuration as the motor 100. Therefore, parts of the motor 100A that are substantially the same as those of the motor 100 are given the same reference numerals, and detailed descriptions of these same parts are omitted.

[0060] As shown in Figure 5, in the retaining portion 30A, the first inner retaining surface 301 is positioned axially lower than the outer retaining surface 314. As a result, the first bearing 51 is positioned axially offset from the stator core 21. Therefore, heat from the stator core 21 is less likely to be directly transferred to the first bearing 51.

[0061] As shown in Figure 5, in the motor 100A, the first retaining portion 31A of the retaining portion 30A has a groove 33 that is recessed radially inward from the outer circumferential surface 311. The groove 33 is located in a position that overlaps radially with the first bearing 51. Furthermore, the groove 33 is continuous in the circumferential direction. That is, the first retaining portion 31A has a groove 33 that is recessed radially inward on the outer circumferential surface 311 that overlaps radially with the first bearing 51. The groove 33 is continuous in the circumferential direction.

[0062] By forming the groove 33, a gap Tm is formed radially outward of the portion of the first retaining part 31 that holds the first bearing 51. As a result, heat from the first retaining part 31 is released to the outside through the gap Tm, making it difficult for heat to be transferred to the first bearing 51, and thus preventing the first bearing 51 from overheating. Therefore, deterioration of the first bearing 51 due to overheating (especially deterioration of the lubricant) is suppressed, and stable operation of the first bearing 51 is possible over a long period of time.

[0063] Furthermore, the grooves 33 may consist of multiple grooves spaced apart in the circumferential direction, each having a constant central angle centered on the central axis Cx. Even with such a configuration, heat conduction to the first bearing 51 can be suppressed, and deterioration of the first bearing 51 due to temperature rise can be prevented.

[0064] Although embodiments of the present invention have been described above, various modifications to the embodiments are possible within the scope of the spirit of the present invention.

[0065] <Summary> The present invention has the following configuration.

[0066] (1) The rotor has a shaft and rotor magnets that rotate around a central axis extending vertically, a stator having a stator core and facing radially inward of the rotor magnets, a bearing portion that rotatably supports the shaft, and a retaining portion that is formed in a cylindrical shape around the central axis and holds the bearing portion. The bearing portion has a first bearing and a second bearing disposed above the first bearing. The retaining portion has a cylindrical first retaining portion that extends along the central axis and a cylindrical second retaining portion that extends upward along the central axis from the upper end of the first retaining portion. The stator core is fixed to the outer circumferential surface of the first retaining portion, and the outer ring of the first bearing is fixed to the lower end of the inner circumferential surface. At least a part of the outer ring of the second bearing is fixed to the inner circumferential surface of the second retaining portion. A motor in which the second retaining portion is arranged with a radial gap between it and the stator core, and the radial thickness of the second retaining portion is smaller than the radial distance between the outer circumferential surface of the second retaining portion and the inner circumferential surface of the stator core.

[0067] (2) The retaining portion has an inner retaining surface that extends radially inward from the inner circumferential surface below the upper end of the first retaining portion. The lower end of the outer ring of the second bearing is in direct or indirect contact with the inner retaining surface, as described in (1).

[0068] (3) The motor according to (1) or (2), wherein the upper end of the first retaining portion is located above the axial center of the stator core, and the upper end of the second retaining portion is located below the upper end of the stator core.

[0069] (4) The first retaining portion has an outer retaining surface that extends radially outward below the upper end of the first retaining portion and contacts the lower end of the stator core. The motor according to any one of (1) to (3), wherein the axial length from the outer retaining surface to the upper end of the first retaining portion is greater than the axial length of the second retaining portion.

[0070] (5) The motor according to (4), wherein the first retaining portion has a small-diameter portion on the upper part of its outer circumferential surface that is smaller in diameter than the portion that contacts the lower stator core.

[0071] (6) The rotor has a rotor hub fixed to the shaft. The rotor hub has a through hole centered in the axial direction in which the shaft is positioned, and a cylindrical rotor boss extending downward in the axial direction from the edge of the through hole to which the shaft is fixed. The motor according to any one of (1) to (5), wherein the lower end of the rotor boss contacts the inner ring of the second bearing below the upper end of the stator core.

[0072] (7) The first retaining portion has a recessed groove that is recessed radially inward in the portion of its outer circumferential surface that overlaps radially with the first bearing. The recessed groove is continuous in the circumferential direction. The motor according to any one of (1) to (6). [Industrial applicability]

[0073] The motor of the present invention can be used, for example, as a drive device for rotating an impeller. [Explanation of Symbols]

[0074] 100, 100A motor 10 rotors 11 shafts 12 Rotor Case 121 Rotor Hub 122 Cylinder part 123 Through hole 124 Rotor Boss 125 Lower end 13 Rotor Magnet 20 staters 21 Stator Core 210 Upper end 211 Coreback 212 Teeth 213 Inner surface 21C Chuo Line 22 coils 30, 30A holding part 300 through holes 301 1st inner holding surface 302 Inner holding surface 302 2nd inner holding surface 303 Intermediate hole 304 Lower hole 305 Upper hole 31, 31A 1st holding part 310 Upper end 311 Outer surface 312 Core fixing part 313 Small diameter section 314 Outer holding surface 32 Second holding part 320 Upper end 33 grooves 40 base plate 50 Bearing section 51 First bearing 511 Inner circle 512 Outer ring 513 Ball 52 First bearing 521 Inner circle 522 Outer ring 523 Ball

Claims

1. A rotor having a shaft that rotates around a central axis extending vertically and a rotor magnet, A stator having a stator core and facing radially inward and radially opposite the rotor magnet, A bearing portion that rotatably supports the aforementioned shaft, It is cylindrical with the aforementioned central axis as its center, and has a holding portion that holds the bearing portion, The bearing portion comprises a first bearing and a second bearing positioned above the first bearing. The aforementioned retaining part is A cylindrical first holding portion extending along the central axis, It has a cylindrical second holding portion that extends upward along the central axis from the upper end of the first holding portion, The stator core is fixed to the outer circumferential surface of the first retaining portion, and the outer ring of the first bearing is fixed to the lower end of the inner circumferential surface. At least a portion of the outer ring of the second bearing is fixed to the inner circumferential surface of the second retaining portion. The second retaining portion is arranged with a radial gap between it and the stator core, The outer diameter of the second retaining portion is smaller than the outer diameter of the first retaining portion. A motor in which the radial thickness of the second retaining portion is smaller than the radial distance between the outer circumferential surface of the second retaining portion and the inner circumferential surface of the stator core.

2. A rotor having a shaft that rotates around a central axis extending vertically and a rotor magnet, A stator having a stator core and facing radially inward and radially opposite the rotor magnet, A bearing portion that rotatably supports the aforementioned shaft, It is cylindrical with the aforementioned central axis as its center, and has a holding portion that holds the bearing portion, The bearing portion comprises a first bearing and a second bearing positioned above the first bearing. The aforementioned retaining part is A cylindrical first holding portion extending along the central axis, It has a cylindrical second holding portion that extends upward along the central axis from the upper end of the first holding portion, The stator core is fixed to the outer circumferential surface of the first retaining portion, and the outer ring of the first bearing is fixed to the lower end of the inner circumferential surface. At least a portion of the outer ring of the second bearing is fixed to the inner circumferential surface of the second retaining portion. The second retaining portion is arranged with a radial gap between it and the stator core, and the radial thickness of the second retaining portion is smaller than the radial distance between the outer circumferential surface of the second retaining portion and the inner circumferential surface of the stator core. The first retaining portion has an outer retaining surface that extends radially outward below the upper end of the first retaining portion and contacts the lower end of the stator core. The axial length from the outer retaining surface to the upper end of the first retaining portion is greater than the axial length of the second retaining portion. The first holding portion is a motor having a smaller diameter portion on the upper part of its outer circumferential surface, which is smaller in diameter than the portion that contacts the lower stator core.

3. A rotor having a shaft that rotates around a central axis extending vertically and a rotor magnet, A stator having a stator core and facing radially inward and radially opposite the rotor magnet, A bearing portion that rotatably supports the aforementioned shaft, It is cylindrical with the aforementioned central axis as its center, and has a holding portion that holds the bearing portion, The bearing portion comprises a first bearing and a second bearing positioned above the first bearing. The aforementioned retaining part is A cylindrical first holding portion extending along the central axis, It has a cylindrical second holding portion that extends upward along the central axis from the upper end of the first holding portion, The stator core is fixed to the outer circumferential surface of the first retaining portion, and the outer ring of the first bearing is fixed to the lower end of the inner circumferential surface. At least a portion of the outer ring of the second bearing is fixed to the inner circumferential surface of the second retaining portion. The second retaining portion is arranged with a radial gap between it and the stator core, and the radial thickness of the second retaining portion is smaller than the radial distance between the outer circumferential surface of the second retaining portion and the inner circumferential surface of the stator core. The first retaining portion has a groove on its outer circumferential surface that overlaps radially with the first bearing, which is recessed radially inward. The aforementioned groove is continuous in the circumferential direction of the motor.

4. The retaining portion has an inner retaining surface that extends radially inward from the inner circumferential surface below the upper end of the first retaining portion, The motor according to any one of claims 1 to 3, wherein the lower end of the outer ring of the second bearing is in direct or indirect contact with the inner retaining surface.

5. The upper end of the first retaining portion is located above the axial center of the stator core, The motor according to any one of claims 1 to 3, wherein the upper end of the second holding portion is located below the upper end of the stator core.

6. The first retaining portion has an outer retaining surface that extends radially outward below the upper end of the first retaining portion and contacts the lower end of the stator core. The motor according to claim 1 or claim 3, wherein the axial length from the outer holding surface to the upper end of the first holding portion is greater than the axial length of the second holding portion.

7. The motor according to claim 6, wherein the first holding portion has a small-diameter portion on the upper part of its outer circumferential surface that has a smaller diameter than the portion that contacts the lower stator core.

8. The rotor has a rotor hub fixed to the shaft, The rotor hub is, A through hole in which the shaft is positioned, located at the center when viewed from the axial direction, It has a cylindrical rotor boss that extends axially downward from the edge of the through hole, to which the shaft is fixed, The motor according to any one of claims 1 to 3, wherein the lower end of the rotor boss contacts the inner ring of the second bearing below the upper end of the stator core.

9. The first retaining portion has a groove on its outer circumferential surface that overlaps radially with the first bearing, which is recessed radially inward. The motor according to claim 1 or claim 2, wherein the groove is continuous in the circumferential direction.

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