JP2015004329A - Cooling fan, motor, and method of adjusting rotation balance of motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor capable of correcting balance with high accuracy in a short time without demounting a resin cooling fan from the motor in correcting the balance of the entire rotary component, thus balance correction can be easily executed on a motor finished product.SOLUTION: A mounting hole for mounting a rivet as a weight for correcting balance, is formed on a resin cooling fan, thus the resin cooling fan having lead-time and cost advantages can be used even in correcting the balance of the motor with high accuracy. Further the balance correction can be executed without demounting the cooling fan even when the balance correction is executed on a motor finished product, by forming a clearance gap to make a rivet mounting work easy, around the rivet mounting hole so that the rivet can be mounted by a hand gun.

Description

  The present invention relates to a cooling fan, an electric motor, and an electric motor rotation balance adjusting method for adjusting the rotation balance of the entire rotating component.

  In general, an electric motor is often provided with a cooling fan for cooling, and a material made of a resin superior in lead time and cost is widely used.

  The cooling fan rotates together with the rotor and generates cooling air to cool the electric motor. However, the rotation always generates large and small vibrations. In order to reduce the vibration of the motor, it is necessary to correct the rotation balance of the entire rotating component. In the case of a standard motor, the mounting seat for mounting the balance correction weight provided on the rotor In general, a balance correcting weight is attached, the balance is corrected, and the vibration of the motor is adjusted to a control value or less.

  A general electric motor shown in FIGS. 10 to 14 will be described. 1 is a stator, 2 is a rotor, 3 is an external cooling fan made of resin, 4 is a housing, 5 is a housing cooling fin, 6 is a bracket, 7 is a rotating shaft, 8 is a bearing, 9 is a fan cover, and 11 is a rotation The center of the axis. The outer cooling fan 3 has a fan boss 12, a fan base 13, and a plurality of blades 14. A plurality of balance correction weight mounting seats 10 arranged in the circumferential direction are provided on both end faces of the rotor 2, and the balance adjusting weight 15 is fitted in a predetermined position to be balanced, and the mounting seat 10 is crimped to rotate parts. The balance is corrected.

  From the standpoint of environmental protection, etc., it is desirable that the vibration generated by the motor be as small as possible. Depending on the installation location of the motor, the vibration value generated by the motor may be limited. In this case, the entire rotating parts of the motor It is necessary to adjust the vibration generated by the motor to a specified value or less by correcting the balance of the motor with high accuracy. However, when the balance of the electric motor is corrected with high accuracy, the vibration generated by the electric motor may not be adjusted to a specified value or less only with the balance correcting weight attached to the rotor.

  In such a case, as shown in Patent Document 1, the entire rotating parts of the electric motor can be obtained by screwing and attaching a balance correction weight to the inner cooling fan disposed on both sides of the rotor, or by processing the cooling fan. It is known to correct the balance.

  In addition, assuming that a balance correction weight is to be attached to the external cooling fan, a resin cooling fan can generally be equipped with a balance correction weight to correct the balance, or the balance can be corrected by processing. Less is. For this reason, when correcting the balance of the electric motor with high accuracy, it is conceivable to change the outer cooling fan to a casting cooling fan or a steel plate cooling fan. Then, in the casting cooling fan as shown in FIG. 14 (a), the hole 15 is processed in the outer peripheral portion to adjust the weight, and in the steel plate cooling fan as shown in FIG. 14 (b), the outer peripheral portion is adjusted. It is conceivable to adjust the weight by attaching the balance adjusting weight 16 by welding or the like, and to correct the balance of the entire rotating parts of the electric motor.

  Further, Patent Document 2 describes a metal blower that squeezes eyelets and rivets to correct the rotational balance, and Patent Document 3 describes a screw that balance screws into a metal centrifugal fan. Yes.

JP 2007-33061 A JP 2012-137071 A Japanese Utility Model Publication No. 54-17905

  However, the above-described work for correcting the rotation balance of the entire rotating component by metal processing, welding, and screwing of the weight of the cooling fan increases lead time and cost. In addition, work such as attaching a weight for adjusting the balance to the external cooling fan or internal cooling fan can only be performed when the cooling fan is in a single state, so it is necessary to remove the cooling fan from the assembled electric motor and install weights. Reassembly work and balance inspection work are required, and enormous work man-hours are required for balance adjustment. In addition, cooling fan processing, welding and weight screwing can cause pressure on the cooling fan and cause deformation, which can adversely affect fan performance. Further, in the caulking work of eyelets and rivets, a caulking tool is required on the side opposite to the insertion side, and the work cannot be performed in a narrow place where the tool does not enter.

  In view of the above-mentioned problems of the prior art, the present invention can correct the balance of the entire rotating part without removing the resin cooling fan from the electric motor, and can correct the balance with high accuracy in a short time. The present invention also provides an electric motor that can be easily implemented.

  In order to solve the above-mentioned problems, the present invention provides a resin cooling fan fixed to a rotating shaft of an electric motor, wherein a plurality of mounting holes for adjusting a rotation balance weight arranged in a circumferential direction around the rotating shaft are provided. And a weight attached to the attachment hole at a predetermined position from one side.

  In the cooling fan described above, the rotation balance correction weight is attached in a state of being fixed to the rotation shaft.

  The cooling fan described above is characterized in that a flat mounting seat is formed around the mounting hole to maintain a weight posture during mounting.

  In the cooling fan described above, the mounting hole is provided in the direction of the rotation axis.

  The cooling fan described above includes a fan base and a plurality of blades provided on one surface of the fan base, and the mounting holes are provided in the fan base at equal intervals in the circumferential direction. It is characterized by being.

  In the cooling fan described above, the mounting holes are provided at equal intervals in the circumferential direction on the outer peripheral side and the inner peripheral side of the fan base.

  In the cooling fan described above, a blind rivet is used as the weight for correcting the rotation balance, and the blind rivet is attached to the attachment hole from one side of the resin cooling fan by caulking.

In order to solve the above-described problems, the present invention provides a stator that generates a rotating magnetic field by receiving power supply, a rotor that rotates by the rotating magnetic field from the stator, and a resin that is fixed to the rotating shaft of the rotor. In an electric motor having a cooling fan and a fan cover that covers the resin cooling fan,
The fan cover is detachably attached to the electric motor body, and the resin cooling fan has a plurality of rotation balance correcting weight mounting holes arranged in the circumferential direction, and is attached to the mounting hole at a predetermined position from one side. It is characterized by having a weight.

  In the electric motor described above, the resin cooling fan is fixed to a rotating shaft of a rotor, and the weight for correcting the rotation balance is attached.

  Further, the electric motor described above is characterized in that a flat mounting seat is formed around the mounting hole so as to maintain a weight posture during mounting.

  In the electric motor described above, the attachment hole is provided in the direction of the rotation axis.

  Further, in the electric motor described above, the resin cooling fan includes a fan base and a plurality of blades provided on one surface of the fan base, and the mounting hole surrounds the fan base. It is provided at equal intervals in the direction.

  In the electric motor described above, the mounting holes are provided at equal intervals in the circumferential direction on the outer peripheral side and the inner peripheral side of the fan base.

  In the electric motor described above, a blind rivet is used as the weight for correcting the rotation balance, and the blind rivet is attached to the attachment hole from one side of the resin cooling fan by caulking.

In order to solve the above-described problems, the present invention provides a stator that generates a rotating magnetic field by receiving power supply, a rotor that rotates by the rotating magnetic field from the stator, and a resin that is fixed to the rotating shaft of the rotor. In a method for adjusting the rotational balance of an electric motor having a cooling fan made of a resin and a fan cover covering the cooling fan made of resin,
The resin cooling fan is provided with a weight mounting hole for correcting rotation balance arranged at equal intervals in the circumferential direction, and a weight is inserted from one side of the resin cooling fan to be mounted in the mounting hole. To do.

  In the motor rotation balance adjustment method described above, the fan cover is removed, and the weight for correcting the rotation balance is attached to the resin cooling fan fixed to the rotating shaft of the rotor. And

  Further, in the motor rotation balance adjustment method described above, a blind rivet is used as the weight for correcting the rotation balance, and the blind rivet is inserted into a mounting hole at a predetermined position from one side of the resin cooling fan and attached by caulking. It is characterized by that.

  Further, in the above-described method for adjusting the rotational balance of the electric motor, the blind rivet includes a tube portion having a rivet head and a core portion penetrating the tube portion, and the tube portion is used as an attachment hole of the resin cooling fan. The tube portion is crimped by pulling the core portion to one side in the inserted state.

  In the above-described method for adjusting the rotational balance of the electric motor, the blind rivet is characterized in that the pipe portion is crimped by pulling the core portion to one side while holding the rivet head with a tool. .

  According to the present invention, it is possible to use a resin cooling fan superior in lead time and cost when correcting the balance of the entire rotating parts of the electric motor with high accuracy. Further, when the balance correction is performed on the finished motor product, the balance correction can be performed without removing the cooling fan, and the lead time and cost can be significantly reduced.

BRIEF DESCRIPTION OF THE DRAWINGS Structure explanatory drawing which notches and shows a part of electric motor which is an Example of this invention. Explanatory drawing which similarly shows the detailed structure of an external cooling fan. Similarly explanatory drawing of the balance correction work of a rotary body and a cooling fan. Explanatory drawing which balance correction was similarly given to the resin-made cooling fans. The perspective view of the rivet similarly fixed to an outside cooling fan. Explanatory drawing of the fixing operation | work of a rivet similarly. Similarly explanatory drawing of the fixed state of a rivet. Similarly explanatory drawing of the position which should avoid a rivet attachment hole. Similarly explanatory drawing of a rivet attachment hole. Structure explanatory drawing which cuts and shows a part of general electric motor. Explanatory drawing which similarly shows the detailed structure of an external cooling fan. Similarly explanatory drawing of the balance correction work of a rotary body and a cooling fan. Similarly, a balance weight installation explanatory view. Explanatory drawing of processing of an outside cooling fan similarly.

Embodiments of the present invention will be described below with reference to the drawings.
(Example)
FIG. 1 is a structural explanatory view showing a part of an electric motor according to an embodiment of the present invention. 21 is a stator, 22 is a rotor, 23 is an external cooling fan made of resin, 24 is a housing, 25 is a housing cooling fin, 26 is a bracket, 27 is a rotating shaft, 28 is a bearing, 29 is a fan cover, 31 is a rotation This is the rotation center of the shaft 27. As shown in FIG. 3, a plurality of rotational balance correction weight mounting seats 30 are provided in the circumferential direction on both end faces of the rotor 22, and the balance adjusting weights are fitted at predetermined positions for balancing. The balance of the rotating parts is corrected by crimping to 30. This balance correction is performed in the same manner as in FIG.

  The outer cooling fan 23 is attached to the rear end of the rotating shaft 27 and rotates together with the rotating shaft to blow cooling air into the housing 24. The outer cooling fan 23 is covered with a fan cover 29 at the rear, and cooling air is sucked from an opening (not shown) provided in the cover. The fan cover 29 is screwed to the housing 24 or the bracket 26 so as to be detachable from the motor body alone.

  As shown in FIG. 2, the outer cooling fan 23 is formed by integrally molding a fan boss 32, a fan base 33, and a plurality of blades 34. 2A is a front view of a quarter of the cooling fan, and FIG. 2B is a cross-sectional view taken along lines C to F in FIG. The fan boss 32 is fixed to the rotating shaft 27, and the outer cooling fan 23 is rotated by the rotation of the rotating shaft 27. The fan base 33 has a disk-like shape centered on the rotary shaft 27, and a plurality of blades 34 arranged uniformly in the circumferential direction on one side (left side in the figure) are integrally molded with resin. Thus, it is formed upright in the rotation axis direction. The fan base 33 is provided with a plurality of mounting holes (through holes) 35 and 36 at the outer peripheral position and the inner peripheral position, respectively, at equal intervals in the circumferential direction. The attachment holes (through holes) 35 and 36 are provided at the time of molding a cooling fan made of resin. A rivet is attached to the predetermined hole of the attachment hole as a weight for correcting the rotational balance of the fan.

  Rivet mounting seats 35a and 36a that form a flat surface portion in the radial direction of the rotating shaft 27 are provided on the front and back of the mounting holes (through holes) 35 and 36. It is held in the direction of the rotation axis. When attaching the rivet, the vibration direction and amount of rotation are measured in advance, and the attachment hole at a predetermined position where the rivet is to be attached is specified based on the result. If the mounting seats 35a and 36a are not provided, the rivet may be tilted and mounted, and if it is tilted, the center of gravity position of the rivet in the mounting hole is different from the plan, making it difficult to adjust the rotation balance.

  The outer rivet mounting hole 35 is lighter than the inner rivet mounting hole 36 and can adjust the balance with high accuracy. FIG. 4 shows a state in which a rivet 37 is inserted and fixed in the specified mounting holes 35 and 36.

  Adjustment of the rotation balance of the entire rotating parts of the electric motor is performed by first attaching a weight to the mounting seat 30 of the rotor 22 to correct the balance of the rotor 22 alone, and incorporating the rotor with the corrected balance into the electric motor. To complete. As described above, the rotation balance of the entire rotating component is corrected by correcting the balance of the rotor 22 alone. However, there is a case where the vibration generated by the electric motor cannot be adjusted to a specified value or less simply by correcting the balance of the rotor 22 alone. In the embodiment of the present invention, the balance of the motor completed product is further balanced with the outer cooling fan 23. By attaching a weight for correction, the rotational balance of the entire rotating component is corrected with high accuracy.

  FIG. 5 is a perspective view of a rivet as a weight for correcting the rotation balance. Reference numeral 40 denotes the entire blind rivet, 41 is a hollow tube portion, and 43 is a rivet head formed integrally with the rear end of the tube portion 41. Reference numeral 44 denotes a core portion having a distal end head portion 42 having an outer diameter larger than the inner diameter of the tube portion 41 at the distal end, and is inserted into the tube portion 41 from the side opposite to the rivet head portion 43. Configured to protrude from. The distal end head portion 42 and the core portion 44 are connected by a constricted portion 46 (see FIG. 5). The tube portion 41 has a dimension longer than the thickness of the mounting seats 35a and 36a of the outer cooling fan 23 so as to protrude to the opposite side when inserted into the rivet mounting holes (through holes) 35 and 36. The blind rivet 40 is made of metal such as aluminum or stainless steel.

  6 to 7 show a rivet fixing operation. Reference numeral 50 denotes a hand gun (tool) that holds the rivet 40 and inserts and fixes the rivet 40 into the mounting hole. The hand gun 50 has a hole that penetrates the core part 44 of the rivet, and incorporates a chuck 51 that grips the core part 44 that penetrates the hole. The chuck 51 includes a tooth portion 52 on a surface for gripping the core portion 44 and is configured to move in the direction of the arrow in the tool 50 in a state where the core portion 44 is securely gripped.

  When attaching the blind rivet 40, first, the fan cover 29 is removed from the electric motor main body, and the hand gun (tool) 50 is moved closer to the outer cooling fan 23 from the left side (one side) in the rotation axis direction. As shown in FIG. 6, the hand gun 50 holds the rivet 40 and inserts it from the tip head portion 42 into the mounting holes (through holes) 35 and 36 of the outer cooling fan 23 in the direction of the rotation axis. Since the mounting holes 35 and 36 are provided in the fan base in the rotation axis direction, the rivet 40 can be easily inserted. At this time, the front end surface of the hand gun 50 is in contact with the rivet head 41. Next, in a state where the rivet head 41 is pressed by the distal end surface of the handgun 50, the chuck 51 is pulled to the left side (one side) with the rotation axis as indicated by an arrow, and the core portion 44 is pulled out from the tube portion 41.

  As shown in FIG. 7, by the movement of the chuck 51 and the core 44 in the direction of the arrow, a compressive stress acts on the rivet tube 41 between the rivet head 41 and the tip head 42, and the rivet tube 41 is compressed in the axial direction. By this compression, the pipe portion 41 is plastically deformed so that the portion protruding from the attachment hole is compressed by the distal end head portion 42 to form an enlarged portion 45 larger than the inner diameter of the attachment hole. Since the constricted portion 46 has a lower tensile strength than others, the constricted portion 46 is torn after the enlarged portion 45 is formed by the movement of the core portion 44 in the arrow direction.

  In this manner, the blind rivet 40 is caulked so that the mounting seat is clamped from both sides by the distal end head portion 42 and the enlarged portion 45, and is securely attached to the attachment holes (through holes) 35 and 36. In this attachment, since no deformation pressure is applied in the radial direction of the fan base, the cooling fan is not deformed even if it is made of resin.

  A general rivet is a solid metal and has a head on one side. When inserting into a fixed object and caulking, the opposite side of the head is crushed by applying a tool to both ends and compressing. It is caulking. Therefore, it is necessary to arrange a caulking tool on the side opposite to the rivet insertion side of the fixed object, and the caulking work cannot be performed in a narrow place where the tool does not enter. Incidentally, the space | interval of the external cooling fan 23 of FIG. 1 and the bracket 26 is narrow, and a crimping tool cannot be put in.

  In the embodiment of the present invention, by using the blind rivet as described above, the rivet can be attached from one side. Therefore, the rivet can be easily attached from one side of the outside cooling fan opened by removing the fan cover. be able to.

  In the mounting operation of the embodiment of the present invention, the hand gun (tool) 50 approaches the outer cooling fan 23 from the left side of the figure with the fan cover 29 removed, and pulls the core part 44 from the pipe part 41 to the left side of the figure. Therefore, a series of mounting operations can be performed on one side (one direction) of the outer cooling fan 23, and the working efficiency is greatly improved. Accordingly, the rotational balance can be corrected accurately in a very short time without removing the external cooling fan from the electric motor.

  In this mounting operation, the rivet head 41 is pressed by the tip surface of the hand gun 50, so that the rivet head 41 does not apply pressure such as bending to the fan base 33 when the chuck 51 is moved, and the external cooling fan 23 is not deformed. Therefore, since no distortion remains in the entire fan, no new noise is caused when the fan rotates.

  The mounting operation is performed by removing the fan cover 29 in FIG. 1 and mounting a blind rivet from one side (the side opposite to the motor) to the outer cooling fan 23 that is fixed to the rotating shaft 27 of the motor. Accordingly, since it is not necessary to arrange a tool or the like on the opposite side of the outer cooling fan 23, the installation work can be easily performed in a short time, and the work efficiency is greatly improved. This mounting operation is performed only by removing the fan cover 29, and the outer cooling fan 23 is fixed to the rotating shaft 27 of the motor, and does not disassemble the finished motor. Can be reduced.

  Next, the arrangement of the mounting holes will be described with reference to FIGS. The number of the mounting holes is not particularly limited. As shown in FIG. 8, the interval between the outer peripheral side mounting holes 35 is set as G-1 to G-3, and the interval between the inner peripheral side mounting holes 36 is set. When the intervals between the mounting holes are not equal as in H-1 to H-3, the weight balance of the resin cooling fan itself is deteriorated.

  Accordingly, the interval between the outer rivet mounting holes 35 is as indicated by L-1 to L-3 in FIG. 9, and the interval between the inner rivet mounting holes 36 is indicated as M-1 to M- in FIG. As shown in FIG. 3, it is preferable to provide a plurality of mounting hole intervals at equal intervals over the entire 360 ° circumference.

  Also, as shown in FIG. 8, if the gap between the attachment hole 35 and the blade 34 is as narrow as J, the handgun is difficult to enter and the rivet attachment operation becomes difficult. For this reason, it is preferable to provide a gap between the attachment hole 35 and the blade 34 so that the hand gun can easily enter and the rivet attachment operation is easy, as indicated by N in FIG.

  Further, as shown in FIG. 8, if the gap between the rivet mounting hole 36 and the fan boss 32 is as narrow as K, the handgun is difficult to enter and the rivet mounting operation becomes difficult. For this reason, it is preferable to provide a clearance between the rivet mounting hole 36 and the fan boss 32 so that the hand gun can easily enter and the rivet mounting operation is easy, as indicated by P in FIG.

  Further, in order to keep the rivet from being tilted, the rivet mounting surfaces on both sides of the mounting seats 35a and 36a shown in FIG. 2B are preferably parallel to each other.

  According to the present embodiment, even when the balance of the motor is corrected with high accuracy, it is possible to use a resin cooling fan that is superior in terms of lead time and cost. In addition, even when the balance of the finished motor is corrected, the balance of the entire rotating parts of the motor can be corrected without removing the cooling fan and without disassembling the motor body.

  Furthermore, in the present embodiment, the attachment holes 35 and 36 are through holes, but they may be replaced by bag holes. In this case, when the blind rivet is attached, the pipe portion 41 is fixed with the enlarged portion 45 formed in the bag hole.

  In addition, the structure demonstrated above is an Example for description, In actual design and commercialization, you may add a change suitably.

21: Stator 22: Rotor 23: Cooling fan (resin cooling fan)
24: Housing 25: Housing cooling fin 26: Bracket 27: Rotating shaft 28: Bearing 29: Fan cover 30: Balance adjusting weight mounting seat 32: Fan boss 33: Fan base 34: Blades 35, 36: Mounting holes (rivet mounting) Hole)
35: Outer mounting hole 36: Inner mounting hole 35a, 36a: Mounting seat 37: Weight (rivet)
40: rivets, blind rivets 41: pipe portion 42: tip head portion 43: rivet head portion 39: rotor 44: core portion 45: enlarged portion 46: constricted portion G1 to G3: inner mounting holes H1 to H3: inside Peripheral side mounting hole J: Gap K: Gap L1 to L3: Outer rivet mounting hole interval M1 to M3: Inner peripheral rivet mounting hole interval N: Gap P: Gap

Claims (19)

In the resin cooling fan fixed to the rotating shaft of the motor,
A cooling fan comprising a plurality of rotation balance correcting weight mounting holes arranged in a circumferential direction around a rotation axis, and a weight mounted from one side to the mounting hole at a predetermined position. .   The cooling fan according to claim 1, wherein the weight for correcting the rotation balance is attached while being fixed to the rotating shaft.   The cooling fan according to claim 1 or 2, wherein a flat mounting seat is formed around the mounting hole so as to maintain a posture of a weight during mounting.   The cooling fan as described in any one of Claims 1-3 WHEREIN: The said attachment hole was provided in the said rotating shaft direction, The cooling fan characterized by the above-mentioned.   The cooling fan according to any one of claims 1 to 4, comprising a fan base and a plurality of blades provided on one surface of the fan base, wherein the mounting hole is formed in the fan base. A cooling fan provided at equal intervals in the circumferential direction.   6. The cooling fan according to claim 1, wherein the mounting holes are provided at equal intervals in the circumferential direction on the outer peripheral side and the inner peripheral side of the fan base.   The cooling fan according to any one of claims 1 to 6, wherein a blind rivet is used as the weight for correcting the rotation balance, and the blind rivet is attached to a mounting hole from one side of the resin cooling fan by caulking. A cooling fan characterized by that. A stator that generates a rotating magnetic field by receiving power supply, a rotor that is rotated by a rotating magnetic field from the stator, a resin cooling fan that is fixed to a rotating shaft of the rotor, and a resin cooling fan In an electric motor with a fan cover to cover,
The fan cover is detachably attached to the electric motor body, and the resin cooling fan has a plurality of rotation balance correcting weight mounting holes arranged in the circumferential direction, and is attached to the mounting hole at a predetermined position from one side. An electric motor characterized by a weight.   9. The electric motor according to claim 8, wherein the resin cooling fan is fixed to a rotating shaft of a rotor and attached with a weight for correcting the rotational balance.   10. The electric motor according to claim 8, wherein a flat mounting seat is formed around the mounting hole so as to maintain a weight posture during mounting.   The electric motor according to any one of claims 8 to 10, wherein the attachment hole is provided in the direction of the rotation axis.   12. The electric motor according to claim 8, wherein the resin cooling fan includes a fan base and a plurality of blades provided on one surface of the fan base. The motor is characterized in that the holes are provided in the fan base at equal intervals in the circumferential direction.   13. The electric motor according to claim 8, wherein the mounting holes are provided at equal intervals in the circumferential direction on the outer peripheral side and the inner peripheral side of the fan base.   The electric motor according to any one of claims 8 to 13, wherein a blind rivet is used as the weight for correcting the rotation balance, and the blind rivet is attached to an attachment hole from one side of the resin cooling fan by caulking. An electric motor characterized by A stator that generates a rotating magnetic field by receiving power supply, a rotor that is rotated by a rotating magnetic field from the stator, a resin cooling fan that is fixed to a rotating shaft of the rotor, and a resin cooling fan In the method of adjusting the rotational balance of the electric motor with the fan cover to cover,
The resin cooling fan is provided with a weight mounting hole for correcting rotation balance arranged at equal intervals in the circumferential direction, and a weight is inserted from one side of the resin cooling fan to be mounted in the mounting hole. To adjust the rotation balance of the motor.   16. The method of adjusting a rotation balance of an electric motor according to claim 15, wherein the fan cover is removed and the weight for correcting the rotation balance is attached to the resin cooling fan fixed to the rotating shaft of the rotor. A method for adjusting the rotational balance of the motor.   The rotation balance adjustment method for an electric motor according to claim 15 or 16, wherein a blind rivet is used as the weight for correcting the rotation balance, and the blind rivet is inserted into a mounting hole at a predetermined position from one side of the resin cooling fan. A method for adjusting the rotational balance of an electric motor, wherein the motor is attached by caulking.   The rotation balance adjustment method for an electric motor according to claim 17, wherein the blind rivet includes a tube portion having a rivet head and a core portion penetrating the tube portion, and the tube portion is used as an attachment hole of the resin cooling fan. A method of adjusting the rotational balance of an electric motor, wherein the tube portion is crimped by pulling the core portion to one side in an inserted state.   The rotation balance adjustment method for an electric motor according to claim 18, wherein the blind rivet is caulked by pulling the core part to one side while holding a rivet head with a tool. A method for adjusting the rotation balance of an electric motor.

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