Motor and fan device

Abstract

To provide a technique for improving the yield at low cost in a motor for adjusting rotation balance by using a balance adjustment pin.SOLUTION: A motor (2) includes a rotor yoke (232) having a cylindrical outer peripheral wall (232A) that is disposed radially outward than a stator (24) and supports a plurality of permanent magnets (231) on an inner peripheral surface, a cylindrical inner peripheral wall (232B) that is disposed radially inward of the stator and being rotatably supported by the shaft (21), and a disk-shaped connecting wall (232C) that connects one end of the outer peripheral wall and one end of the inner peripheral wall in a shaft direction to each other. On the connecting wall, a plurality of through holes (233) each penetrating in a thickness direction are formed at positions spaced apart in a circumferential direction. The rotor yoke further includes a balance adjusting pin (25) having a cylindrical shape in which a slit extending in the shaft direction is formed in part in the circumferential direction, and being press-fitted into at least one of the plurality of through holes.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a motor, a fan unit equipped with the motor, Place Regarding. [Background technology]

[0002] In recent years, efforts have been made to promote the Sustainable Development Goals (2030 Agenda for Sustainable Development, adopted at the United Nations Summit on September 25, 2015, hereafter referred to as "SDGs"). Accordingly, technologies that aim to reduce waste and defective products in order to ensure sustainable production and consumption patterns have become well known.

[0003] An outer rotor brushless motor that rotates a rotor yoke located outside the stator is used, for example, as a motor that drives a cooling fan. In order to adjust the rotational balance of the rotor yoke in such a motor, putty may be applied to the rotor yoke (see, for example, Patent Document 1), or a solid balance adjustment pin may be press-fitted into a through-hole provided in the rotor yoke. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-095405 Summary of the Invention [Problem to be solved by the invention]

[0005] However, with the method of Patent Document 1, if the putty is not firmly attached to the rotor yoke, there is a possibility that it will peel off during rotation of the rotor yoke. Furthermore, with the method of press-fitting solid balance adjustment pins into the through holes of the rotor yoke, there is a possibility that the rotor yoke will deform when the balance adjustment pins are press-fitted unless the press-fit allowance is set with high precision. This results in issues such as increased motor manufacturing costs and reduced yields.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a technique for improving yield at low cost in motors in which the rotational balance is adjusted using balance adjustment pins. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a motor including a motor bracket, a shaft fixed to the motor bracket, a rotor yoke rotatably supported on the shaft, a plurality of permanent magnets fixed to the rotor yoke at intervals in the circumferential direction, and a stator fixed to the motor bracket inside the plurality of permanent magnets and wound with a coil that generates a magnetic field for rotating the rotor yoke, wherein the rotor yoke has a cylindrical outer peripheral wall that is arranged radially outward from the stator and supports the plurality of permanent magnets on its inner peripheral surface, a cylindrical inner peripheral wall that is arranged radially inward from the stator and rotatably supported on the shaft, and a disk-shaped connecting wall that connects one axial end of the outer peripheral wall and the inner peripheral wall, and the connecting wall has a plurality of through holes formed in it at circumferentially spaced positions, each passing through in a thickness direction, Complex a balance adjustment pin press-fitted into at least one of the through holes, The balance adjustment pin has a cylindrical shape with a slit extending in the axial direction formed in a part of the circumferential direction, and the outer dimension of the tip is smaller than the opening width in the radial direction of the through hole, and the outer dimension of the center is larger than the opening width in the radial direction of the through hole. It is characterized by: [Effects of the Invention]

[0008] According to the present invention, in a motor in which the rotational balance is adjusted using balance adjustment pins, it is possible to improve the yield at low cost. Problems, configurations, and effects other than those described above will become clear from the description of the following embodiments. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is an external perspective view showing an example of the configuration of a fan device according to an embodiment; [Figure 2] FIG. 2 is an exploded perspective view of the motor and the fan. [Figure 3] FIG. 2 is a perspective view of the motor as viewed from the front side. [Figure 4] FIG. 2 is a perspective view showing the configuration of the motor with the rotor yoke removed. [Figure 5] FIG. 4 is a cross-sectional view taken along line VV in FIG. [Figure 6] FIG. 4 is a diagram showing the configuration of a balance adjustment pin. [Figure 7] FIG. 10 is a plan view of the rotor yoke with balance adjustment pins attached thereto. [Figure 8] 8 is a cross-sectional view of a main part showing the position of the waterline when the rotor yoke shown in FIG. 7 is tilted. FIG. [Figure 9] 10 is a flowchart showing the steps of a rotational balance adjustment method. [Figure 10] FIG. 10 is a perspective view of the rotor yoke in the process of adjusting the rotational balance. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A fan device mounted on a vehicle such as an automobile to cool engine coolant flowing through a radiator will be described below as one aspect of a fan device according to an embodiment of the present invention.

[0011] (Overall configuration of fan device 1) First, the overall configuration of a fan device 1 will be described with reference to Figures 1 and 2. Figure 1 is an external perspective view showing an example of the configuration of a fan device 1 according to an embodiment. Figure 2 is an exploded perspective view of a motor 2 and a fan 3 disassembled.

[0012] 1 and 2, the fan device 1 includes a motor 2 as a drive source and a fan 3 that is rotated and driven by the motor 2 to generate cooling air. The fan device 1 is disposed, for example, in an engine room so as to face a radiator. For example, when the vehicle body is positioned on a horizontal plane, the fan device 1 is disposed in the engine room so that the shaft 21 of the motor 2 extends horizontally. However, if the vehicle body tilts, the extension direction of the shaft 21 also tilts from the horizontal direction.

[0013] The fan 3 is fastened to the motor 2 by a plurality of screws 10. The plurality of screws 10 are fastened from the front side of the fan 3 (the side opposite to the side facing the motor 2) through screw holes formed in a boss portion 31 which is the center of the fan 3 to the rotor yoke 232 of the motor 2.

[0014] In this embodiment, taking into consideration the rotational balance of the fan 3, three screws 10 are attached at equal intervals on a circle centered on the rotation center of the fan 3. It is not necessary to use three screws 10 as fastening members for fastening the fan 3 to the motor 2, and there are no particular limitations on the number of screws 10 or the type of fastening member as long as the fan 3 can be fastened to the motor 2.

[0015] The fan 3 has a boss portion 31 that rotates integrally with the rotor 23 with the axis of the shaft 21 as its center of rotation, a plurality of blades 32 (seven in this embodiment) that extend radially from the outer periphery of the boss portion 31, and a plurality of connecting members 33 (seven in this embodiment) that connect adjacent blades 32 at their tip ends.

[0016] The boss portion 31 includes a disk-shaped disk portion 311 arranged opposite the connecting wall 232C of the rotor yoke 232, and a peripheral wall portion 312 extending from the outer edge of the disk portion 311 to the outside of the outer peripheral wall 232A of the rotor 23 and having a plurality of blades 32 attached thereto.

[0017] (Motor 2 configuration) Next, the configuration of the motor 2 will be described with reference to Figures 3 to 5. Figure 3 is an external perspective view of the motor 2 as seen from the front side. Figure 4 is a perspective view showing the configuration of the motor 2 with the rotor yoke 232 removed. Figure 5 is a cross-sectional view taken along line VV in Figure 3.

[0018] As shown in FIGS. 3 to 5, motor 2 is an electric motor including outer rotor type brushless motor 201 and driver circuit 202 that controls brushless motor 201 (generation of a magnetic field by coil 243).

[0019] 3, brushless motor 201 is supported by motor bracket 203. Brushless motor 201 is disposed on one side (front surface side) of motor bracket 203 in the thickness direction.

[0020] 5, a driver bracket 204 is fastened to the other side (rear side) in the thickness direction of the motor bracket 203 by a plurality of screws 205. As a result, an accommodation space 206 is formed between the motor bracket 203 and the driver bracket 204. The driver circuit 202 is accommodated in this accommodation space 206.

[0021] In addition, a connector unit 207, which combines two connectors to which an external harness is connected, is attached to an end of the motor bracket 203. The brushless motor 201, the driver circuit 202, and the connector unit 207 are electrically connected to one another via the motor bracket 203.

[0022] As shown in Figures 4 and 5, brushless motor 201 has shaft 21, bearings 22A and 22B provided on the outer periphery of shaft 21, rotor 23 rotatably supported around the axis of shaft 21 via bearings 22A and 22B, and annular stator 24 wound with coil 243 that generates a magnetic field for rotating rotor 23.

[0023] The shaft 21 is a fixed shaft fixed to the motor bracket 203. In the following description of the components of the motor 2, the axial direction of the shaft 21 will be simply referred to as the "axial direction," the radial direction around the axial center of the shaft 21 will be simply referred to as the "radial direction," and the circumferential direction around the axial center of the shaft 21 will be simply referred to as the "circumferential direction."

[0024] The rotor 23 has a plurality of permanent magnets 231 arranged at equal intervals in the circumferential direction so as to surround the outer periphery of the stator 24, and a rotor yoke 232 covering the stator 24 and the plurality of permanent magnets 231.

[0025] 5, rotor yoke 232 is disposed on the surface side of motor bracket 203 so as to be concentric with the axis of shaft 21. Rotor yoke 232 is rotatably supported on shaft 21 via bearings 22A and 22B. Rotor yoke 232 includes outer peripheral wall 232A, inner peripheral wall 232B, connecting wall 232C, and yoke flange 232D.

[0026] The outer peripheral wall 232A has a cylindrical outer shape. The outer peripheral wall 232A is disposed radially outward of the stator 24. The inner peripheral surface of the outer peripheral wall 232A supports a plurality of permanent magnets 231. In other words, the plurality of permanent magnets 231 are fixed to the inner peripheral surface of the outer peripheral wall 232A at predetermined intervals in the circumferential direction.

[0027] The inner circumferential wall 232B has a cylindrical outer shape and is disposed radially inward of the stator 24. The inner circumferential wall 232B is rotatably supported by the shaft 21 via bearings 22A and 22B.

[0028] The connecting wall 232C has a disk-like outer shape. The connecting wall 232C connects one axial end of the outer peripheral wall 232A and one axial end of the inner peripheral wall 232B. Furthermore, as shown in Figures 3 and 5, the connecting wall 232C has a plurality of through holes 233 formed therein.

[0029] The plurality of through holes 233 are formed at predetermined intervals in the circumferential direction on an imaginary circle centered on shaft 21. The plurality of through holes 233 also penetrate connecting wall 232C in the thickness direction. The plurality of through holes 233 are elongated holes extending in the circumferential direction and having an arc-shaped outer shape. A balance adjustment pin 25 may be press-fitted into at least one of the plurality of through holes 233 to adjust the rotational balance of rotor yoke 232. The plurality of through holes 233 also function as drainage ports for draining water that has entered the rotor yoke 232.

[0030] 5, the plurality of through holes 233 are formed at positions where at least a portion of them overlap with the permanent magnets 231 when the rotor yoke 232 is viewed in a plan view from the axial direction. In this embodiment, there are ten (even number) permanent magnets 231 and nine (odd number) through holes 233. However, the specific numbers are not limited to the above example, as long as the permanent magnets 231 are either odd or even and the through holes 233 are the other of odd and even.

[0031] Yoke flange 232D is provided at the other axial end of outer peripheral wall 232A (i.e., the opposite end from connecting wall 232C). Yoke flange 232D also protrudes radially outward from outer peripheral wall 232A. Yoke flange 232D also extends in the circumferential direction. However, yoke flange 232D does not need to be provided around the entire circumference of outer peripheral wall 232A, and may be partially cut out to adjust the rotational balance of rotor yoke 232.

[0032] The stator 24 is housed in a space surrounded by the outer peripheral wall 232A, the inner peripheral wall 232B, the connecting wall 232C, and the motor bracket 203. The stator 24 is fixed to the surface side of the motor bracket 203, radially inward from the plurality of permanent magnets 231. The stator 24 faces the plurality of permanent magnets 231 across a predetermined radial gap.

[0033] As shown in Figures 4 and 5, the stator 24 has a cylindrical stator core 241, insulating insulators 242 attached to both axial sides of a plurality of teeth protruding radially outward from the stator core 241, and a conductive coil 243 wound around the insulator 242.

[0034] The stator 24 generates a magnetic field when a current flows through the coil 243. Then, the rotor yoke 232 rotates around the axis of the shaft 21 due to attractive and repulsive forces generated between the magnetic field generated by the coil 243 and the plurality of permanent magnets 231.

[0035] (Balance adjustment pin 25 configuration) FIG. 6 is a diagram showing the configuration of the balance adjustment pin 25. As shown in FIG. 6, the balance adjustment pin 25 has a generally cylindrical outer shape. The balance adjustment pin 25 is hollow and has open both axial end faces. The balance adjustment pin 25 is made up of a main body portion 251 and an inclined portion 252. Furthermore, the balance adjustment pin 25 has a slit 253 formed therein.

[0036] The main body 251 has a cylindrical outer shape. The inclined portions 252 are provided at both ends of the main body 251. The inclined portions 252 are inclined so that the outer dimensions decrease as they approach the axial ends of the balance adjustment pin 25. In other words, the balance adjustment pin 25 has a tapered shape. The inclined portions 252 function as guide surfaces when the balance adjustment pin 25 is press-fitted into the through-hole 233.

[0037] The slits 253 are formed in a portion of the circumferential direction of the balance adjustment pin 25. The slits 253 are also formed over the entire axial area of ​​the balance adjustment pin 25. Furthermore, the slits 253 penetrate the balance adjustment pin 25 in the thickness direction. In other words, the balance adjustment pin 25 is configured to be elastically contractible.

[0038] 6(B), when the balance adjustment pin 25 is viewed from above in the axial direction, the balance adjustment pin 25 has a C-shaped outer shape. The slits 253 communicate with openings on both axial end faces of the balance adjustment pin 25. The internal space of the balance adjustment pin 25 is opened to the outside by both axial end faces and the slits 253. The outer dimensions of the tip (inclined portion 252) of the balance adjustment pin 25 are set smaller than the radial opening width of the through hole 233. On the other hand, the outer dimensions of the center (main body portion 251) of the balance adjustment pin 25 are set slightly larger than the radial opening width of the through hole 233.

[0039] Therefore, the tip of the balance adjustment pin 25 can be inserted into the through hole 233. Then, as the balance adjustment pin 25 continues to be inserted into the through hole 233, the outer surface of the balance adjustment pin 25 comes into contact with the circumferential surface that defines the through hole 233, and the balance adjustment pin 25 elastically contracts in diameter. Then, as shown in FIG. 5 , when the balance adjustment pin 25 is inserted to a position where it does not contact the permanent magnet 231, the balance adjustment pin 25 is fixed in the through hole 233 by the force of the balance adjustment pin 25 elastically trying to expand in diameter.

[0040] (Drainage of rotor yoke 232) Next, the drainage performance of rotor yoke 232 according to this embodiment will be described with reference to Figures 7 and 8. Figure 7 is a plan view of rotor yokes 232, 232' with balance adjustment pins 25, 25' attached. Figure 8 is a cross-sectional view of a main part showing the position of the waterline when rotor yokes 232, 232' shown in Figure 7 are tilted.

[0041] First, as in this embodiment shown in Fig. 7(A), the arc-shaped through-hole 233 into which the C-shaped balance adjustment pin 25 is press-fitted is open at a position adjacent to the balance adjustment pin 25. Therefore, even when the balance adjustment pin 25 is press-fitted, the through-hole 233 can continue to function as a drainage port. Furthermore, because the balance adjustment pin 25 itself penetrates in the axial direction, drainage through the internal space of the balance adjustment pin 25 can also be expected.

[0042] In contrast, as shown in FIG. 7(B), circular through-holes 233' are formed in a connecting wall 232C' of a conventional rotor yoke 232' at predetermined intervals in the circumferential direction. A solid balance adjustment pin 25' is press-fitted into at least one of the through-holes 233'. The outer dimensions of the balance adjustment pin 25' are set to be slightly larger than the diameter of the through-hole 233'. Therefore, when the balance adjustment pin 25' is inserted into the through-hole 233', the through-hole 233' loses its function as a drainage port.

[0043] Next, as shown in FIG. 8, suppose that the motors 2, 2' to which the rotor yokes 232, 232' shown in FIG. 7 are attached are tilted so that the connecting walls 232C, 232C' face downward, and the through holes 233, 233' into which the balance adjustment pins 25, 25' are press-fitted are positioned at the lowest position. In this case, in the rotor yoke 232 according to this embodiment, water is drained through the through hole 233 into which the balance adjustment pin 25 is press-fitted. On the other hand, in the conventional rotor yoke 232', water is drained through the other through hole 233' adjacent to the through hole 233' into which the balance adjustment pin 25' is press-fitted. As a result, the rotor yoke 232 according to this embodiment can lower the waterline position compared to the conventional rotor yoke 232'.

[0044] (Rotational balance adjustment method) Next, a method for adjusting the rotational balance of rotor yoke 232 according to this embodiment will be described with reference to Figures 9 and 10. Figure 9 is a flowchart showing the steps of the rotational balance adjustment method. Figure 10 is a perspective view of rotor yoke 232 in the process of adjusting the rotational balance.

[0045] First, rotor yoke 232 is attached to a balance measurement device and rotated to measure the rotational balance (S11). The rotational balance measured here includes static balance and dynamic balance. Static balance refers to balance in the radial direction (vertical direction) perpendicular to shaft 21. Dynamic balance refers to balance in the axial direction (horizontal direction) of shaft 21.

[0046] The rotational balance is measured on both the first correcting plane side (connecting wall 232C side) and the second correcting plane side (yoke flange 232D side). The rotational balance (e.g., eccentricity) measured by the balance measurement device is a physical quantity that increases as the degree of imbalance increases. Then, it is determined whether the measured rotational balance is within a preset numerical range for each of the first correcting plane side and the second correcting plane side (S12, S13).

[0047] If the rotational balance on both sides of the first and second correction planes is within a preset numerical range (S12: No & S13: No), balance adjustment is terminated. That is, if it is determined in the first steps S12 and S13 that the rotational balance is within the preset numerical range, rotor yoke 232 is obtained in which balance adjustment pin 25 is not press-fitted into through-hole 233 and yoke flange 232D is not cut out.

[0048] If the rotational balance on the first correction plane side is outside the preset numerical range (S12: Yes), one or more balance adjustment pins 25 are press-fitted into at least one of the plurality of through holes 233 (S14), as shown in Fig. 10(A), and the processing from step S11 onwards is executed again. Note that the number and positions of the balance adjustment pins 25 to be press-fitted in step S14 are the same as in the conventional balance adjustment method, so explanation will be omitted.

[0049] Furthermore, if the rotational balance on the first adjustment plane side is within a preset numerical range and the rotational balance on the second adjustment plane side is outside the preset numerical range (S12: No & S13: Yes), a portion of the yoke flange 232D is cut out (S15), and the processes from step S11 onward are executed again. For example, as shown by the dashed-dotted line in FIG. 10(B), a portion of the yoke flange 232D may be cut out along a linear cutting line. However, the method of cutting out the yoke flange 232D is not limited to the above-described example. Note that the position and extent of the cutout in step S15 is the same as in the conventional balance adjustment method in which the outer surface of the outer peripheral wall 232A is cut, and therefore a description thereof will be omitted.

[0050] Then, by repeating the processes of steps S11 to S15, it is possible to obtain rotor yoke 232 whose rotation balance has been adjusted to fall within a preset numerical range.

[0051] According to the above embodiment, for example, the following advantageous effects are achieved.

[0052] According to the above embodiment, C-shaped balance adjustment pins 25 each having a slit 253 formed therein are press-fitted into through holes 233 of rotor yoke 232. Since balance adjustment pins 25 elastically contract in diameter to match the size of through holes 233, the rotational balance of rotor yoke 232 can be appropriately adjusted without requiring a high degree of press-fit accuracy. As a result, a motor 2 can be obtained at low cost and with a high yield. The aforementioned effects are further enhanced by providing inclined portions 252 at the tips of balance adjustment pins 25. To achieve the aforementioned effects, through holes 233 do not necessarily need to be arc-shaped extending in the circumferential direction, and may be perfectly circular as shown in FIG. 7(B).

[0053] Furthermore, according to the above embodiment, by making the through-hole 233 an elongated hole with an arc shape extending in the circumferential direction, it is possible to maintain its function as a drainage port even after the balance adjustment pin 25 is press-fitted. This allows the waterline inside the rotor yoke 232 to be lowered. As a result, when the motor 2 is used in an environment where water may enter the rotor yoke 232 (for example, outdoors), the drainage performance inside the motor 2 is improved. Note that in order to obtain the above-mentioned effects, the balance adjustment pin 25 does not necessarily need to have the slit 253 formed therein, and may be solid as shown in FIG. 7(B).

[0054] Furthermore, according to the above embodiment, by forming the through holes 233 at positions overlapping the permanent magnets 231 when the rotor yoke 232 is viewed in a plan view from the axial direction, it is possible to adjust the rotational balance using lightweight balance adjustment pins 25. This contributes to reducing the weight of the motor 2. It also allows the waterline to be further lowered.

[0055] Furthermore, in the above embodiment, by making the axial gap between the balance adjustment pin 25 and the permanent magnet 231 shorter than the length of the balance adjustment pin 25 protruding from the connecting wall 232C to the outside of the rotor yoke 232 (the side opposite the permanent magnet 231), it is possible to prevent the balance adjustment pin 25 from falling off into the interior of the rotor yoke 232.

[0056] Furthermore, according to the above embodiment, the rotational balance is adjusted not only by press-fitting the balance adjustment pins 25 into the through holes 233 but also by cutting out a portion of the yoke flange 232D, thereby obtaining a motor 2 with excellent rotational balance. Note that the method of cutting out the yoke flange 232D does not reduce the magnetic path, and therefore can prevent a decrease in the performance of the motor 2 compared to a method of grinding the outer surface of the outer peripheral wall 232A.

[0057] Furthermore, according to the above embodiment, the rotational balance of rotor yoke 232 is adjusted according to the procedure shown in FIG. 9, so that the rotational balance of rotor yoke 232 can be optimized with low labor costs.

[0058] In the above embodiment, an example in which the fan device 1 is used to supply cooling air to a radiator has been described, but the use of the fan device 1 is not limited to this. Also, in the above embodiment, an example in which the motor 2 is used as a fan motor that rotates and drives the fan 3 has been described, but the use of the motor 2 is not limited to this.

[0059] The above describes an embodiment of the present invention. However, the present invention is not limited to the above embodiment and includes various modifications. For example, the above embodiment has been described in detail to clearly explain the present invention, and is not necessarily limited to an embodiment including all of the described configurations. Furthermore, it is possible to replace part of the configuration of this embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of this embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of this embodiment with other configurations. [Explanation of symbols]

[0060] 1: Fan device 2,2': Motor 3: Fan 10,205:Screw 21: Shaft 22A, 22B: Bearings 23: Rotor 24: Stator 25,25': Balance adjustment pin 31: Boss Department 32: Feather 33: Connecting member 201: Brushless motor 202: Driver circuit 203: Motor bracket 204: Driver bracket 206: Containment space 207: Connector unit 231: Permanent magnet 232,232': Rotor yoke 232A,232A' :Outer wall 232B,232B' :Inner peripheral wall 232C,232C' :Connecting wall 232D, 232D': Yoke flange 233, 233': Through hole 241: Stator core 242: Insulator 243: Coil 251: Main body 252: Inclined part 253: Slit 311: Disc section 312: Peripheral wall part

Claims

1. A motor bracket; a shaft fixed to the motor bracket; a rotor yoke rotatably supported on the shaft; a plurality of permanent magnets fixed to the rotor yoke at intervals in the circumferential direction; a stator fixed to the motor bracket inside the plurality of permanent magnets and wound with a coil that generates a magnetic field for rotating the rotor yoke, The rotor yoke is a cylindrical outer circumferential wall disposed radially outward of the stator and supporting the plurality of permanent magnets on an inner circumferential surface thereof; a cylindrical inner peripheral wall disposed radially inward of the stator and rotatably supported by the shaft; a disk-shaped connecting wall that connects one axial end of the outer peripheral wall and one axial end of the inner peripheral wall, The connecting wall has a plurality of through holes formed at circumferentially spaced positions, each of the through holes penetrating the connecting wall in a thickness direction, a balance adjustment pin press-fitted into at least one of the plurality of through holes; The balance adjustment pin has a cylindrical shape with a slit extending in the axial direction formed in part of its circumferential direction, and the outer dimension of the tip is smaller than the radial opening width of the through hole, and the outer dimension of the center is larger than the radial opening width of the through hole.

2. 2. The motor according to claim 1, The motor is characterized in that each of the plurality of through holes is an arc-shaped elongated hole extending in the circumferential direction.

3. 3. The motor according to claim 1, The motor is characterized in that the plurality of through holes are formed at positions where at least a portion of the through holes overlaps with the permanent magnets when the rotor yoke is viewed in a plan view from the axial direction.

4. The motor according to any one of claims 1 to 3, the number of the permanent magnets is one of odd and even; The motor is characterized in that the number of the plurality of through holes is the other of an odd number and an even number.

5. The motor according to any one of claims 1 to 4, the rotor yoke has a yoke flange that protrudes radially from the other axial end of the outer peripheral wall and extends circumferentially, A motor characterized in that a portion of the yoke flange is cut out.

6. The motor according to any one of claims 1 to 5, The motor is characterized in that the through hole extends in a circumferential direction of the connecting wall.

7. A motor according to any one of claims 1 to 6; a fan that is rotationally driven by the motor to generate cooling air.

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