Balance weight, blower, and method for manufacturing balance weight

Abstract

To provide a balance weight capable of enhancing adhesive strength between the balance weight and a rotor, a blower, a method for manufacturing a balance weight.SOLUTION: A balance weight 65 for adjusting a balance of a rotor 12 rotatable with a center axis as a center and having a first surface 61d facing one side of a first direction and a second surface 61e facing a second direction intersecting the first direction includes a first contact part 65e coming into contact with the first surface and a second contact part 65f coming into contact with the second surface. The surface facing the one side of the first direction has a curved part to be convex on the one side of the first direction when viewed from a direction perpendicular to the first direction. An area projected to a virtual surface perpendicular to the first direction is larger than an area of the first contact part.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a balancing weight, a blower, and a method for manufacturing the balancing weight. [Background technology]

[0002] 2. Description of the Related Art A motor is known in which unbalanced rotation of a rotor yoke is corrected by applying a balance weight to the rotor yoke (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2001-298929 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned motor, if the contact area between the balance weight and the rotor yoke is small, there is a risk that the adhesive strength between the balance weight and the rotor yoke cannot be sufficiently increased, and therefore there is a risk that the balance weight will peel off from the rotor yoke due to the centrifugal force acting on the balance weight when the rotor yoke rotates.

[0005] In view of the above circumstances, one aspect of the present invention has an object to provide a balance weight, a blower, and a method for manufacturing a balance weight that can increase the adhesive strength between the balance weight and a rotating body. [Means for solving the problem]

[0006] One embodiment of the balance weight of the present invention is a balance weight for adjusting the balance of a rotor that is rotatable about a central axis and has a first surface facing one side of a first direction and a second surface facing a second direction intersecting the first direction, the balance weight having a first contact portion in contact with the first surface and a second contact portion in contact with the second surface. When viewed from a direction perpendicular to the first direction, the surface facing one side of the first direction has a curved portion that is convex toward one side of the first direction. The area projected onto a virtual plane perpendicular to the first direction is larger than the area of ​​the first contact portion.

[0007] One aspect of the blower of the present invention includes the balance weight described above, a rotor rotatable about a central axis, and an impeller portion connected to the rotor and rotatable about the central axis. The rotor and the impeller portion form a rotating body.

[0008] One embodiment of the method for manufacturing a balance weight of the present invention is a method for adjusting the balance of a rotating body having a first surface facing one side of a first direction and a second surface facing a second direction intersecting the first direction, and molding a balance weight onto the rotating body, the balance weight having a first contact portion in contact with the first surface and a second contact portion in contact with the second surface, the method including an application step of applying molten balance weight onto the first surface, a spraying step of blowing air onto the balance weight applied to the first surface to spread the balance weight over the rotating body, and a hardening step of hardening the balance weight. In the blowing process, air is blown onto the balance weight to change the shape of the balance weight so that, when viewed from a direction perpendicular to the first direction, the surface facing one side of the first direction has a curved portion that is convex toward one side of the first direction, and the area projected onto an imaginary plane perpendicular to the first direction is larger than the area of ​​the first contact portion, and the balance weight is brought into contact with the second surface. Effect of the Invention

[0009] According to one aspect of the present invention, in a manufacturing method of a balancing weight, a balancing weight, and a blower, it is possible to increase the adhesive strength between the balancing weight and the rotating body. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a top view showing the blower of the first embodiment. [Diagram 2] FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1, showing the blower of the first embodiment. [Diagram 3] FIG. 3 is a perspective view showing the impeller portion of the first embodiment. [Figure 4] FIG. 4 is a cross-sectional view showing the balance weight of the first embodiment. [Diagram 5] FIG. 5 is a diagram showing the balance weight of the first embodiment projected onto a virtual plane. [Figure 6] FIG. 6 is a flowchart showing a manufacturing method of the balance weight of the first embodiment. [Figure 7] FIG. 7 is a first cross-sectional view showing the manufacturing method of the balance weight according to the first embodiment. [Figure 8] FIG. 8 is a second cross-sectional view showing the manufacturing method of the balance weight of the first embodiment. [Figure 9] FIG. 9 is a cross-sectional view showing a balance weight according to the second embodiment. [Figure 10] FIG. 10 is a cross-sectional view showing a balance weight according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, a blower according to an embodiment of the present invention will be described with reference to the drawings. Note that the scope of the present invention is not limited to the following embodiment, and can be modified as desired within the scope of the technical concept of the present invention. In addition, in the following drawings, the scale and number of each structure may differ from the actual structure in order to make each structure easier to understand.

[0012] The Z-axis direction shown in each drawing is the direction in which the central axis J of the rotor extends. The central axis J is a virtual axis. In the following description, the direction parallel to the Z-axis direction is called the "axial direction". The radial direction centered on the central axis J is simply called the "radial direction". The circumferential direction centered on the central axis J is simply called the "circumferential direction". In each drawing, the circumferential direction is indicated by an arrow θ. The side of the axial direction toward which the Z-axis arrow points (+Z side) is called the "upper side". The side of the axial direction opposite to the side toward which the Z-axis arrow points (-Z side) is called the "lower side". Note that the upper side and the lower side are names simply used to describe the relative positional relationship of each part, and the actual positional relationship, etc. may be a positional relationship, etc. other than the positional relationship, etc. indicated by these names.

[0013] The circumferential direction is indicated by the arrow θ in each drawing. The side of the circumferential direction toward which the arrow θ points is called "one circumferential side." The side of the circumferential direction opposite to the side toward which the arrow θ points is called "the other circumferential side." The one circumferential side (+θ side) is the side that advances counterclockwise around the central axis J when viewed from above. The other circumferential side (-θ side) is the side that advances clockwise around the central axis J when viewed from above.

[0014] The first direction D1 shown in each figure is the direction in which the first surface of the rotor faces. In this embodiment, the first surface is the surface on which the balance weight is molded. In this embodiment, the first direction D1 is a direction parallel to the axial direction. The first direction D1 may be a direction intersecting with the axial direction. In the following description, the side to which the arrow of the first direction D1 faces (+D1 side) is called "one side of the first direction D1", and the opposite side to the side to which the arrow of the first direction D1 faces (-D1 side) is called "the other side of the first direction D1". The one side of the first direction D1 (+D1 side) faces in the same direction as the upper side. The other side of the first direction D1 (-D1 side) faces in the same direction as the lower side. The second direction D2 shown in each figure is a direction intersecting with the first direction D1. In this embodiment, the second direction D2 is a direction perpendicular to the first direction D1. In this embodiment, the second direction D2 is parallel to the radial direction.

[0015] First Embodiment The blower 10 of this embodiment shown in Fig. 1 is, for example, an electric cooling fan for cooling electronic devices. The blower 10 of this embodiment is an axial fan that blows air in the axial direction. As shown in Fig. 2, the blower 10 includes a motor 15, a housing 50, an impeller portion 60, and a balance weight 65. The blower 10 also includes a rotor 12.

[0016] The impeller portion 60 is rotatable about a central axis J. The impeller portion 60 has an impeller cup 61 and a plurality of blade portions 62. The impeller cup 61 is substantially cylindrical and extends in the axial direction about the central axis J. The impeller cup 61 opens downward. The motor 15 is housed inside the impeller cup 61. As shown in FIG. 3, the impeller cup 61 has a first outer surface 61a, a groove portion 61c, a first surface 61d, a second surface 61e, and a third surface 61f.

[0017] The first outer surface 61a is a surface of the outer surface of the impeller portion 60 facing one side (+D1 side) in the first direction D1. When viewed in the axial direction, the first outer surface 61a has a substantially circular shape centered on the central axis J. The groove portion 61c is a groove recessed downward from the first outer surface 61a, i.e., toward the other side (-D1 side) in the first direction D1. When viewed in the axial direction, the groove portion 61c has an annular shape centered on the central axis J. The groove portion 61c extends around the circumference in the circumferential direction.

[0018] In this embodiment, the first surface 61d is a surface facing the upper side of the inner surface of the groove portion 61c, that is, one side (+D1 side) of the first direction D1. When viewed from the axial direction, the first surface 61d is annular. The first surface 61d extends around the circumference along the circumferential direction. In this embodiment, the second surface 61e is a surface facing the radially inward side of the inner surface of the groove portion 61c. The second surface 61e faces the second direction D2. The second surface 61e faces a direction intersecting the first direction D1. In this embodiment, the second surface 61e faces a direction perpendicular to the first direction D1. When viewed from the axial direction, the second surface 61e is circumferential. The second surface 61e extends around the circumference along the circumferential direction. In this embodiment, the third surface 61f is a surface facing the radially outward side of the inner surface of the groove portion 61c. The third surface 61f faces the second direction D2. The third surface 61f faces a direction intersecting the first direction D1. In this embodiment, the third surface 61f faces a direction perpendicular to the first direction D1. The third surface 61f faces the second surface 61e in the radial direction.

[0019] Each of the multiple blade portions 62 protrudes radially outward from the outer circumferential surface of the impeller cup 61. The impeller portion 60 has five blade portions 62. The blade portions 62 are arranged side by side in the circumferential direction along the outer circumferential surface of the impeller cup 61. When the impeller portion 60 rotates around the central axis J, each blade portion 62 blows air in the axial direction.

[0020] As shown in FIG. 2, the housing 50 accommodates the motor 15 and the impeller portion 60 therein. The housing 50 holds the motor 15 and the impeller portion 60. The housing 50 has a peripheral wall portion 51 and a motor holding portion 55. As shown in FIGS. 1 and 2, the peripheral wall portion 51 is in the shape of a square tube extending in the axial direction. As shown in FIG. 2, the peripheral wall portion 51 surrounds the impeller portion 60 and the motor 15 from the radially outer side. The motor holding portion 55 is in the shape of a cylinder extending in the axial direction with the central axis J as the center. The motor holding portion 55 is disposed inside the impeller cup 61.

[0021] The motor 15 is accommodated inside the peripheral wall portion 51. The motor 15 includes a rotor 20, a shaft 23, a first bearing 24a, a second bearing 24b, a rotor bearing 25, a stator 30, and a circuit board 70. The motor 15 of this embodiment is an outer rotor motor in which the rotor 20 is disposed radially outside the stator 30. The rotor 20 is rotatable about the central axis J. The rotor 20 is held on the inner peripheral surface of the impeller cup 61. This allows the impeller portion 60 to be connected to the rotor 20. When the rotor 20 rotates about the central axis J, the impeller portion 60 rotates about the central axis J. The rotor 20 has a magnet 22.

[0022] The shaft 23 is cylindrical and extends in the axial direction around the central axis J. The shaft 23 is disposed inside the motor holding portion 55. An upper portion of the shaft 23 is rotatably held by the first bearing 24a. A lower portion of the shaft 23 is rotatably held by the second bearing 24b. The first bearing 24a and the second bearing 24b are each held on the inner circumferential surface of the motor holding portion 55. This allows the shaft 23 to rotate around the central axis J. The rotor bearing 25 is substantially cylindrical and centered on the central axis J. The shaft 23 is inserted in the axial direction into the rotor bearing 25. A portion of the shaft 23 including the upper end is fitted into the rotor bearing 25. The rotor bearing 25 supports the rotor 20 to rotate around the central axis J.

[0023] The stator 30 is annular and surrounds the central axis J. The stator 30 is disposed inside the rotor 20. The stator 30 faces the magnet 22 in the radial direction with a gap therebetween. The stator 30 includes a stator core 31, a coil portion 35, an insulator 40, and a connection pin 80.

[0024] The stator core 31 is annular around the central axis J. The stator core 31 has a core back portion 32 and a plurality of teeth portions 33. The core back portion 32 is annular about the central axis J. The core back portion 32 is fixed to the outer peripheral surface of the motor holding portion 55. Each tooth portion 33 protrudes radially outward from the outer peripheral surface of the core back portion 32. Although not shown, each tooth portion 33 is disposed at intervals along the outer peripheral surface of the core back portion 32. The insulator 40 insulates the stator core 31 from the coil portion 35. The insulator 40 is attached to the stator core 31.

[0025] The connection pins 80 are columnar and extend in the axial direction. The connection pins 80 are conductive. Although not shown in the figure, the stator 30 has two connection pins 80. Each connection pin 80 is held by the insulator 40. Although not shown in the figure, the lower end of each connection pin 80 is connected to the circuit board 70.

[0026] The coil portion 35 is electrically connected to the circuit board 70 via the connection pin 80. When a current is supplied to the coil portion 35 from the circuit board 70, a rotational torque is generated in the rotor 20 by a magnetic force between the magnetic poles of the electromagnets formed by the stator 30 and the magnets 22. The coil portion 35 has a plurality of coil main body portions 36 and coil lead wires 38.

[0027] Each coil body 36 is attached to a different tooth portion 33 of the stator core 31 via an insulator 40. The coil lead wires 38 are drawn out from the coil body 36. Although not shown, in this embodiment, the stator 30 has two coil lead wires 38. Each coil lead wire 38 is connected to a different connection pin 80. As a result, the coil portion 35 is electrically connected to the circuit board 70 via the connection pins 80.

[0028] The circuit board 70 is disposed below the stator core 31. The circuit board 70 is in the form of a plate extending in a direction perpendicular to the axial direction. As described above, the circuit board 70 is connected to the connection pins 80. The circuit board 70 supplies a current to the coil portion 35 via the connection pins 80.

[0029] In this embodiment, the rotating body 12 is a member that can rotate around the central axis J among the various members included in the blower 10. In this embodiment, the rotating body 12 is composed of an impeller portion 60 and a rotor 20. In this embodiment, a balance weight 65 is molded in the rotating body 12. In this embodiment, the balance weight 65 is molded in the impeller portion 60. The balance weight 65 may be molded in the rotor 20, or may be molded in each of the impeller portion 60 and the rotor 20.

[0030] As shown in FIG. 3, the balance weight 65 is disposed inside the groove 61c of the impeller portion 60. The balance weight 65 is molded on the first surface 61d. In this embodiment, the balance weight 65 is a weight that adjusts the balance of the rotor 12. Since the balance weight 65 of this embodiment is composed of one part, the number of parts Na of the balance weight 65 is 1. By molding the balance weight 65 of a predetermined weight at a predetermined position in the circumferential direction of the first surface 61d, the deviation of the center of gravity of the rotor 12 with respect to the central axis J can be reduced. This allows the rotor 12 to rotate stably around the central axis J. Note that the impeller portion 60 does not need to have the groove 61c, and in this case, the balance weight 65 may be molded on the first outer surface 61a. The balance weight 65 may also be molded on the outer surface of the rotor 20. For example, when the balance weight 65 is formed on a surface facing the radial direction of the rotor 20, the first direction D1 is a direction perpendicular to the axial direction, and the second direction D2 is a direction intersecting the radial direction.

[0031] As shown in Fig. 4, in this embodiment, the balance weight 65 includes a metal powder 65b and a resin portion 65a containing the powder 65b. The powder 65b may be made of a metal such as tungsten or stainless steel. The resin portion 65a is made of a resin having thermoplastic properties. The resin portion 65a may be made of a thermoplastic resin such as polyethylene, polypropylene, or polyvinyl chloride.

[0032] As shown in FIG. 3, the balance weight 65 of this embodiment has a substantially spherical shape flattened in the axial direction. As shown in FIG. 4, when viewed from a direction perpendicular to the first direction D1, the balance weight 65 has a substantially elliptical shape with a minor axis extending in the axial direction. The upper end of the balance weight 65 is located below the first outer surface 61a. The upper end of the balance weight 65 may be located above the first outer surface 61a. When viewed from a direction perpendicular to the first direction D1, the dimension of the balance weight 65 in the second direction D2 increases from the lower end to the upper side, and after the dimension in the second direction D2 becomes the largest, the dimension in the second direction D2 decreases toward the upper side. That is, the dimension of the balance weight 65 in the direction perpendicular to the first direction D1 is maximum between the upper end and the lower end. In the following description, the maximum dimension of the balance weight 65 in the second direction D2 is simply referred to as the dimension L2 of the balance weight 65. A dimension L3 of the balance weight 65 in the first direction D1 is smaller than a dimension L2 in the second direction D2 that is perpendicular to the first direction D1.

[0033] When viewed from a direction perpendicular to the first direction D1, the upper side of the balance weight 65, i.e., the upper surface 65h which is the surface facing one side (+D1 side) of the first direction D1, is curved and convex upward. That is, when viewed from a direction perpendicular to the first direction D1, the upper surface 65h has a curved portion that is convex upward. In this embodiment, when viewed from a direction perpendicular to the first direction D1, the upper surface 65h is substantially elliptical and convex upward. The balance weight 65 has a first contact portion 65e and a second contact portion 65f.

[0034] The first contact portion 65e is a surface of the outer surface of the balance weight 65 that contacts the first surface 61d of the rotating body 12. The first contact portion 65e is bonded to the first surface 61d. This fixes the balance weight 65 to the rotating body 12. The first contact portion 65e extends in a direction perpendicular to the first direction D1. In the second direction D2 perpendicular to the first direction D1, the dimension L1 of the first contact portion 65e is smaller than the dimension L2 of the balance weight 65. The imaginary plane Sv shown in FIG. 5 is an imaginary plane that extends in a direction perpendicular to the first direction D1. The outer edge of the balance weight 65 projected onto the imaginary plane Sv surrounds the outer edge of the first contact portion 65e. The area Sb of the balance weight 65 projected onto the imaginary plane Sv is larger than the area S1 of the first contact portion 65e.

[0035] As shown in FIG. 4, the second contact portion 65f is a surface of the outer surface of the balance weight 65 that contacts the second surface 61e of the rotor 12. The second contact portion 65f is bonded to the second surface 61e. This fixes the balance weight 65 to the rotor 12. The second contact portion 65f extends in the axial and circumferential directions. Although not shown, the outer edge of the balance weight 65 projected onto the second surface 61e surrounds the outer edge of the second contact portion 65f. In this embodiment, the balance weight 65 is disposed with a gap between it and the third surface 61f in the radial direction.

[0036] Next, a manufacturing method Mb of the balance weight 65 of this embodiment will be described. In the manufacturing method Mb of the balance weight 65, the balance weight 65 is molded on the rotating body 12. As shown in FIG. 6, the manufacturing method Mb of the balance weight 65 of this embodiment includes a first inspection step S02 for inspecting the balance of the rotating body 12, a coating step S03 for coating the first surface 61d of the rotating body 12 with the molten balance weight 65, a spraying step S04 for blowing air A onto the balance weight 65 coated on the first surface 61d to spread the balance weight 65 on the rotating body 12, a hardening step S05 for hardening the balance weight 65, and a second inspection step S08 for inspecting the balance of the rotating body 12 on which the balance weight 65 is molded. In the following description, "workers, etc." includes workers who perform each task and assembly equipment, etc. Each task may be performed only by a worker, only by an assembly equipment, or by a worker and an assembly equipment.

[0037] When starting the molding of the balance weight 65, the number of portions Nm of the balance weight 65 molded on the rotating body 12 is 0 (S01). As described above, the number of portions Na of the balance weight 65 in this embodiment is 1. In the first inspection step S02, the balance of the rotating body 12 is inspected. Although not shown, an operator or the like measures the amount of deviation of the center of gravity of the rotating body 12 from the central axis J using a known balance measuring device. The balance measuring device may measure the amount of deviation of the center of gravity by rotating the rotating body 12, or may measure the amount of deviation of the center of gravity while the rotating body 12 is stationary. The operator or the like calculates the molding position Pm, which is the position where the balance weight 65 is molded, and the molded weight Wb, which is the weight of the balance weight 65 to be molded, from the amount of deviation of the center of gravity. When the molding position Pm and the molded weight Wb are calculated, the first inspection step S02 is completed. The molding position Pm and the molded weight Wb may be calculated by the balance measuring device. In this embodiment, the molding position Pm is a part of the first surface 61d. The molding position Pm may be a part of the impeller portion 60 other than the first surface 61d, or may be a part of the rotor 20.

[0038] In the coating step S03, the molten balance weight 65 is applied to the rotor 12. As shown in FIG. 7, in the coating step S03, an operator applies the heated and melted balance weight 65 to the first surface 61d by the coating device 91 arranged above the impeller unit 60. In this embodiment, the balance weight 65 contains powder 65b, so the melted balance weight 65 is in a paste form. In this embodiment, the coating device 91 is a dispenser capable of discharging a predetermined weight of the melted balance weight 65. Therefore, the difference between the weight of the melted balance weight 65 applied to the rotor 12 and the molding weight Wb can be reduced. In addition, the coating device 91 is connected to the inside of a container having a heating means such as a heater (not shown). The balance weight 65 heated and melted by the heating means is accommodated inside the container. The melted balance weight 65 inside the container is supplied to the coating device 91. When the molten balance weight 65 with the molding weight Wb is applied to the molding position Pm of the first surface 61d by the application device 91, the application step S03 is completed.

[0039] Since the molten balance weight 65 has a certain degree of viscosity, the shape of the balance weight 65 applied to the first surface 61d is substantially spherical, as shown in Fig. 8. Also, a protrusion 65c that protrudes to one side (+D1 side) in the first direction D1 is formed on the surface of the balance weight 65. Although not shown in the figures, in this embodiment, the dimension in the second direction D2 of the balance weight 65 applied to the first surface 61d is smaller than the dimension L2 in the second direction D2 of the balance weight 65 molded on the first surface 61d shown in Fig. 4.

[0040] In the spraying step S04, air A is sprayed onto the balance weight 65 applied to the rotor 12, and the balance weight 65 is spread over the rotor 12. In the spraying step S04, an operator or the like uses a spray device 92 disposed above the impeller portion 60 to spray air A onto the molten balance weight 65 from above. The air A is compressed air compressed by a compressor (not shown). In this embodiment, the temperature of the air A is higher than the melting point of the resin portion 65a of the balance weight 65. The temperature of the air A may be lower than the melting point of the resin portion 65a of the balance weight 65.

[0041] The melted balance weight 65 spreads along the first surface 61d due to the wind pressure of the air A. The protruding portion 65c is taken into the melted balance weight 65 by the wind pressure of the air A. As a result, the balance weight 65 becomes a substantially elliptical shape with a minor axis extending in the axial direction when viewed from a direction perpendicular to the first direction D1, as shown in FIG. 4. More specifically, the dimension L3 of the balance weight 65 in the first direction D1 is smaller than the dimension L2 of the balance weight 65 in the direction perpendicular to the first direction D1. When viewed from a direction perpendicular to the first direction D1, the upper surface 65h has a curved portion that is convex upward. When viewed from a direction perpendicular to the first direction D1, the upper surface 65h becomes a substantially elliptical arc shape that is convex upward. The first contact portion 65e contacts the first surface 61d. The second contact portion 65f contacts the second surface 61e. When the balance weight 65 is spread over the rotor 12, the spraying step S04 ends.

[0042] In the hardening step S05, the balance weight 65 is hardened. In the hardening step S05, the worker or the like hardens the balance weight 65 by cooling the molten balance weight 65. The cooling of the balance weight 65 may be performed in a room temperature atmosphere, or may be performed in a low temperature atmosphere by storing the rotor 12 in a cooling furnace (not shown). When the balance weight 65 is hardened, the hardening step S05 ends. In this embodiment, the worker or the like ends the hardening step S05 before the balance weight 65 is completely hardened. More specifically, the worker or the like ends the hardening step S05 when the balance weight 65 is hardened to a degree of hardness that allows the shape shown in FIG. 4 to be maintained even if the rotor 12 is subjected to vibration. In addition, the worker or the like may end the hardening step S05 after the balance weight 65 is completely hardened.

[0043] 6, when the hardening step S05 is completed, the number of portions Nm of the balance weight 65 molded on the rotating body 12 becomes 1 (S06). As described above, the number of portions Na of the balance weight 65 molded in this embodiment is 1, so that a predetermined number of portions of the balance weight 65 are molded on the rotating body 12. Therefore, an operator or the like performs the second inspection step S08 (S07).

[0044] In the second inspection step S08, the balance of the rotating body 12 on which the balance weight 65 is molded is inspected. The worker or the like measures the amount of deviation of the center of gravity of the rotating body 12 on which the balance weight 65 is molded using a balance measuring device (not shown) or the like described above. If the amount of deviation of the center of gravity of the rotating body 12 is equal to or less than a predetermined amount, that is, if the balance of the rotating body 12 is within a predetermined standard (S09), the worker or the like ends the molding of the balance weight 65. At this time, the balance of the rotating body 12 is adjusted by the balance weight 65. On the other hand, if the balance of the rotating body 12 is not within the predetermined standard (S09), the worker or the like molds the balance weight 65 with the molding weight Wb at the newly calculated molding position Pm (S03 to S06), and then performs the second inspection step S08. The workers etc. repeat the second inspection step S08 and the molding of the balance weight 65 until the balance of the rotor 12 falls within a predetermined standard, and when the balance of the rotor 12 falls within the predetermined standard, the workers etc. end the molding of the balance weight 65 (S09). At this time, the balance of the rotor 12 has been adjusted by the balance weight 65.

[0045] According to this embodiment, the balance weight 65 has a first contact portion 65e that contacts the first surface 61d and a second contact portion 65f that contacts the second surface 61e. Therefore, the balance weight 65 contacts the second surface 61e in addition to the first surface 61d of the rotor 12, so that the contact area between the balance weight 65 and the rotor 12 can be increased. Therefore, the adhesive strength between the balance weight 65 and the rotor 12 can be increased. As a result, the balance weight 65 can be prevented from peeling off from the rotor 12 due to the centrifugal force applied to the balance weight 65 when the rotor 12 rotates around the central axis J during operation of the blower 10. Therefore, the rotation balance of the rotor 12 can be suitably stabilized, so that the rotor 12 can be stably rotated around the central axis J. As a result, vibration and noise during operation of the blower 10 can be suppressed.

[0046] When the balance weight 65 contacts only the first surface 61d of the rotating body 12, in order to increase the contact area between the balance weight 65 and the rotating body 12, it is necessary to spread the molten balance weight 65 over a wide range in the direction perpendicular to the first direction D1 in the blowing step S04. Therefore, it is necessary to lengthen the time for blowing the air A to the molten balance weight 65 in the blowing step S04, or to increase the speed and pressure of the air A blown to the balance weight 65. Therefore, there is a risk that the number of steps in the blowing step S04 will increase and the manufacturing cost of the blowing device 92 will increase. In contrast, in this embodiment, as described above, the balance weight 65 contacts the second surface 61e in addition to the first surface 61d, so that the contact area between the balance weight 65 and the rotating body 12 can be increased without increasing the range over which the molten balance weight 65 is spread in the direction perpendicular to the first direction D1. This makes it possible to suppress an increase in the time for which the air A is blown onto the molten balance weight 65 in the blowing step S04, or an increase in the speed and pressure of the air A blown onto the balance weight 65. Therefore, it is possible to increase the adhesive strength between the balance weight 65 and the rotating body 12 while suppressing an increase in the work hours in the blowing step S04 and the manufacturing cost of the blowing device 92.

[0047] Further, according to this embodiment, the upper surface 65h facing the upper side, i.e., one side (+D1 side) of the first direction D1, has a curved portion that is convex upward when viewed from a direction perpendicular to the first direction D1. The area Sb projected onto the imaginary surface Sv perpendicular to the first direction D1 is larger than the area S1 of the first contact portion 65e. When the balance weight 65 has such a shape, the balance weight 65 can be molded without significantly changing the shape of the balance weight 65 immediately after application by the application device 91. Therefore, the time for blowing the air A onto the molten balance weight 65, or the speed and pressure of the air A blown onto the balance weight 65 can be reduced. Therefore, in this embodiment, the balance weight 65 can be brought into contact with two surfaces while the balance weight 65 is shaped as described above by blowing the air A onto the molten balance weight 65. Therefore, the adhesive strength between the balance weight 65 and the rotating body 12 can be increased while suppressing an increase in the time for which air A is blown onto the molten balance weight 65 or the speed and pressure of the air A blown onto the balance weight 65.

[0048] In this embodiment, since the air A is blown in the blowing step S04 to the protrusion 65c formed on the surface of the balance weight 65 in the application step S03, the protrusion 65c can be taken into the balance weight 65 as described above. This makes it possible to prevent the protrusion 65c from coming off the balance weight 65 when the blower 10 is operating. This makes it possible to prevent the protrusion 65c from being caught between the rotor 20 and the stator 30, for example, and therefore makes it possible to improve the stability of the operation of the blower 10.

[0049] Furthermore, in this embodiment, the air resistance acting on the balance weight 65 when the rotor 12 rotates about the central axis J can be reduced compared to when the balance weight 65 has the protruding portion 65c that protrudes upward. Therefore, the rotor 12 can be rotated about the central axis J more stably, and the drive efficiency of the blower 10 can be improved.

[0050] According to this embodiment, the dimension L3 of the balance weight 65 in the first direction D1 is smaller than the dimension L2 in the direction perpendicular to the first direction D1. Therefore, the dimension L3 of the balance weight 65 in the first direction D1, i.e., the height of the balance weight 65, can be easily reduced, and therefore the air resistance applied to the balance weight 65 when the rotor 12 rotates about the central axis J can be easily reduced. Therefore, the rotor 12 can be rotated about the central axis J more stably, and the drive efficiency of the blower 10 can be more suitably improved.

[0051] According to this embodiment, the rotor 12 has a first outer side 61a facing upward, i.e., one side (+D1) of the first direction D1, and a groove 61c recessed downward from the first outer side 61a, i.e., the other side (-D1 side) of the first direction D1, and the first surface 61d is a surface facing upward among the inner surfaces of the groove 61c, and the second surface 61e is a surface facing a direction perpendicular to the first direction D1 among the inner surfaces of the groove 61c. The balance weight 65 is disposed inside the groove 61c. Therefore, since the balance weight 65 is disposed inside the groove 61c, the air resistance applied to the balance weight 65 when the rotor 12 rotates around the central axis J can be more suitably reduced. Therefore, the rotor 12 can be more stably rotated around the central axis J, and the driving efficiency of the blower 10 can be more suitably increased.

[0052] According to this embodiment, the groove portion 61c extends around the circumference, and the second surface 61e faces radially inward. Therefore, when the rotor 12 rotates around the central axis J, centrifugal force facing radially outward is applied to the balance weight 65, and the balance weight 65 is pressed against the second surface 61e with which the second contact portion 65f is in contact. This can prevent the balance weight 65 from moving radially outward. Therefore, during operation of the blower 10, the balance weight 65 can be more suitably prevented from peeling off from the rotor 12. This can more suitably stabilize the rotational balance of the rotor 12, and the rotor 12 can be more stably rotated around the central axis J.

[0053] When applying the balance weight 65 to the inside of the groove 61c with a member such as a spatula, a rib may be provided inside the groove 61c to scrape off the balance weight 65 from the member such as the spatula. In contrast, in this embodiment, the balance weight 65 is applied to the first surface 61d by the application device 91 in the application step S03 as described above. Therefore, even if the groove 61c extends around the entire circumference, that is, the groove 61c is not provided with a rib, the balance weight 65 can be easily applied inside the groove 61c. Therefore, in this embodiment, the shape of the groove 61c can be simplified, and therefore the structure of the mold used to mold the impeller portion 60 can be simplified. Therefore, the manufacturing cost of the mold can be prevented from increasing.

[0054] According to this embodiment, the blower 10 includes a balance weight 65, a rotor 20 rotatable about a central axis J, and an impeller unit 60 connected to the rotor 20 and rotatable about the central axis J. The rotor 20 and the impeller unit 60 constitute the rotor 12. As described above, the balance of the rotor 12 can be adjusted by the balance weight 65 formed on the rotor 12, so that the rotor 20 can be rotated stably about the central axis J. This can suppress fluctuations in the radial position of the rotor 20 relative to the stator 30 when the rotor 20 rotates about the central axis J. Therefore, it is possible to suppress fluctuations in the magnetic force between the magnetic poles of the electromagnets constituted by the stator 30 and the magnets 22 of the rotor 20, so that the rotation speed and rotation torque of the rotor 20 and the impeller unit 60 can be stabilized. This can stabilize the operation of the blower 10.

[0055] According to this embodiment, the manufacturing method Mb of the balance weight 65 is a manufacturing method of the balance weight that molds the balance weight 65 having a first contact portion 65e that contacts the first surface 61d and a second contact portion 65f that contacts the second surface 61e on the rotating body 12, and includes an application step S03 of applying the molten balance weight 65 to the first surface 61d, a spraying step S04 of blowing air A onto the balance weight 65 applied to the first surface 61d to spread the balance weight 65 on the rotating body 12, and a hardening step S05 of hardening the balance weight 65. Therefore, in the spraying step S04, the balance weight 65 can be spread on the rotating body 12, and therefore the contact area between the first contact portion 65e and the first surface 61d can be increased. In addition, by spreading the balance weight 65 over the rotating body 12, the balance weight 65 can be brought into contact with the second surface 61e, and the second contact portion 65f that comes into contact with the second surface 61e can be stably formed. As a result, the contact area between the balance weight 65 and the rotating body 12 can be increased, and the adhesive strength between the balance weight 65 and the rotating body 12 can be increased.

[0056] In this embodiment, the balance weight 65 includes the metal powder 65b and the resin portion 65a containing the powder 65b. Therefore, the specific gravity of the balance weight 65 can be increased compared to when the balance weight 65 does not include the metal powder 65b. This reduces the volume of the balance weight 65 molded on the rotor 12, thereby suppressing increases in the work time for applying the molten balance weight 65 to the rotor 12 in the application step S03 and the time for hardening the balance weight 65 in the hardening step S05. Therefore, the number of steps required to manufacture the balance weight 65 can be suppressed from increasing, and therefore the number of steps required to manufacture the blower 10 can be suppressed from increasing.

[0057] Furthermore, in this embodiment, since the balance weight 65 is spread over the rotor 12 in the spraying step S04, the surface area of ​​the balance weight 65 can be increased. This increases the cooling efficiency of the balance weight 65 in the hardening step S05, thereby shortening the time it takes for the balance weight 65 to harden. Therefore, an increase in the number of steps required to manufacture the balance weight 65 can be suppressed, and an increase in the number of steps required to manufacture the blower 10 can be suppressed.

[0058] <Second embodiment> 9, a balance weight 265 included in the blower 210 of this embodiment contacts the first surface 61d, the second surface 61e, and the third surface 61f of the rotor 12. In the following description, the same components as those in the first embodiment described above are denoted by the same reference numerals, and the description thereof will be omitted.

[0059] When viewed from a direction perpendicular to the first direction D1, the balance weight 265 is substantially elliptical with a minor axis extending in the axial direction. The balance weight 265 has a maximum dimension in a direction perpendicular to the first direction D1 between the upper end and the lower end. The dimension L23 of the balance weight 265 in the first direction D1 is smaller than the dimension L22 in the second direction D2, which is a direction perpendicular to the first direction D1. When viewed from a direction perpendicular to the first direction D1, the upper surface 265h of the balance weight 265 is curved and convex upward. That is, when viewed from a direction perpendicular to the first direction D1, the upper surface 265h has a curved portion that convex upward. The balance weight 265 has a first contact portion 265e, a second contact portion 65f, and a third contact portion 265g.

[0060] The first contact portion 265e is a surface of the outer surface of the balance weight 265 that contacts the first surface 61d of the rotating body 12. The first contact portion 265e is bonded to the first surface 61d. In the second direction D2 that is a direction perpendicular to the first direction D1, the dimension L21 of the first contact portion 265e is smaller than the dimension L22 of the balance weight 265. Although not shown, the area Sb of the balance weight 265 projected onto the imaginary surface Sv is larger than the area S1 of the first contact portion 265e. Other configurations of the first contact portion 265e of this embodiment are similar to other configurations of the first contact portion 65e of the first embodiment described above.

[0061] The third contact portion 265g is a surface of the outer surface of the balance weight 265 that contacts the third surface 61f of the rotor 12. In this embodiment, the balance weight 265 contacts the third surface 61f. As described above, the third surface 61f faces radially outward. The third contact portion 265g is bonded to the third surface 61f. This allows the balance weight 265 to be fixed to the rotor 12. The third contact portion 265g extends in the axial and circumferential directions. Other configurations of the blower 210 of this embodiment are similar to those of the blower 10 of the first embodiment described above.

[0062] According to this embodiment, the balance weight 265 contacts the third surface 61f of the inner surface of the groove portion 61c facing radially outward. Therefore, the balance weight 265 contacts the third surface 61f in addition to the first surface 61d and the second surface 61e of the rotor 12, so that the contact area between the balance weight 265 and the rotor 12 can be further increased. Therefore, the adhesive strength between the balance weight 265 and the rotor 12 can be further increased. This makes it possible to more suitably prevent the balance weight 265 from peeling off from the rotor 12 during operation of the blower 210. Therefore, the rotation balance of the rotor 12 can be more suitably stabilized, so that the rotor 12 can be more stably rotated around the central axis J.

[0063] <Third embodiment> 10, the balance weight 365 of the blower 310 of this embodiment is composed of multiple parts molded on the rotor 12. In the following description, the same components as those in the first embodiment described above are denoted by the same reference numerals, and the description thereof will be omitted.

[0064] The balance weight 365 has a shape flattened in the axial direction. Between the upper end and the lower end, the balance weight 365 has a maximum dimension in a direction perpendicular to the first direction D1. The dimension L33 of the balance weight 365 in the first direction D1 is smaller than the dimension L32 in the circumferential direction perpendicular to the first direction D1. The balance weight 365 of this embodiment has a first portion 366 and a second portion 367. The balance weight 365 of this embodiment is composed of two portions, the first portion 366 and the second portion 367. The number of portions Na of the balance weight 365 of this embodiment is 2. The balance weight 365 may be composed of three or more portions. The balance weight 365 also has a first contact portion 365e and a second contact portion (not shown). The second contact portion is in contact with a second surface (not shown).

[0065] When viewed from a direction perpendicular to the first direction D1, the first portion 366 is substantially elliptical with a minor axis extending in the axial direction. The first portion 366 has a maximum dimension in a direction perpendicular to the first direction D1 between the upper end and the lower end. When viewed from a direction perpendicular to the first direction D1, the upper side of the first portion 366, that is, the first upper surface 366h which is a surface facing one side (+D1 side) of the first direction D1, is curved and convex upward. That is, when viewed from a direction perpendicular to the first direction D1, the first upper surface 366h has a curved portion which is convex upward. The first portion 366 contacts the first surface 61d. Although not shown, the first portion 366 contacts the second surface. That is, the first portion 366 contacts both the first surface 61d and the second surface. The first portion 366 may contact the third surface 61f.

[0066] The second portion 367 has a shape that is flattened in the axial direction. In this embodiment, the second portion 367 is disposed on the other circumferential side (-θ side) of the first portion 366. The second portion 367 may be disposed on one circumferential side (+θ side) of the first portion 366 and radially inward of the first portion 366. The second portion 367 is connected to the first portion 366 in the circumferential direction. The second portion 367 does not have to be connected to the first portion 366.

[0067] When viewed from a direction perpendicular to the first direction D1, the upper side of the second portion 367, that is, the second upper surface 367h which is a surface facing one side (+D1 side) of the first direction D1, is curved and convex upward. That is, when viewed from a direction perpendicular to the first direction D1, the second upper surface 367h has a curved portion which is convex upward. In this embodiment, the upper surface 365h which is a surface facing the upper side of the balance weight 365 is composed of the first upper surface 366h and the second upper surface 367h. Therefore, when viewed from a direction perpendicular to the first direction D1, the upper surface 365h has a curved portion which is convex upward. The second portion 367 contacts the first surface 61d. The second portion 367 may or may not contact the second surface 61e and the third surface 61f. The second portion 367 contacts at least the first surface 61d.

[0068] The first contact portion 365e is a surface of the outer surface of the balance weight 365 that contacts the first surface 61d of the rotating body 12. The first contact portion 365e is bonded to the first surface 61d. In this embodiment, the first contact portion 365e is formed by a portion of the outer surface of each of the first portion 366 and the second portion 367 that contacts the first surface 61d. In the circumferential direction that is a direction perpendicular to the first direction D1, the dimension L31 of the first contact portion 365e is smaller than the dimension L32 of the balance weight 365. Although not shown, the area Sb of the balance weight 365 projected on the virtual surface Sv is larger than the area S1 of the first contact portion 365e.

[0069] Next, a manufacturing method Mb of the balance weight 365 of this embodiment will be described. In this embodiment, the above-mentioned coating step S03, spraying step S04, and hardening step S05 are performed for each of the first portion 366 and the second portion 367. This forms the second portion 367 connected to the hardened first portion 366. In the following description, the same operations as those in the first embodiment may be omitted. As shown in FIG. 6, when starting to form the balance weight 365, the number of portions Nm formed on the rotor 12 is 0 (S01). Also, as described above, the number of portions Na of the balance weight 365 formed in this embodiment is 2.

[0070] In the first inspection step S02, the worker calculates a molding position Pm, which is a position on the rotating body 12 where the balance weight 365 is molded, and a molding weight Wb, which is the weight of the molded balance weight 365. Next, the worker molds the first portion 366 at the molding position Pm. First, in the application step S03, the worker applies the heated and melted balance weight to the first surface 61d by the application device 91. At this time, a first weight Wb1, which is the weight of the balance weight applied to the first surface 61d, is smaller than the molding weight Wb. The first weight Wb1 is the weight of the first portion 366. Next, in the blowing step S04, the worker blows air A onto the melted balance weight by the blowing device 92, and spreads the melted balance weight in the second direction D2 along the first surface 61d. Next, in a hardening step S05, the worker or the like hardens the first portion 366 by cooling it, and the first portion 366 is molded into the rotor 12.

[0071] When the hardening step S05 is completed, the number of portions Nm formed on the rotating body 12 becomes 1 (S06). As described above, the number of portions Na of the balance weight 365 to be formed is 2, so next, the worker or the like forms the second portion 367 connected to the first portion 366 (S07).

[0072] First, in the application step S03, the worker applies the heated and melted balance weight to a portion of the first surface 61d on the other circumferential side (-θ side) of the first portion 366. At this time, a second weight Wb2, which is the weight of the balance weight applied to the first surface 61d, is the difference between the molding weight Wb and the first weight Wb1. The second weight Wb2 is the weight of the second portion 367. Next, in the blowing step S04, the worker blows air A onto the melted balance weight using the blowing device 92, spreading the melted balance weight in the second direction D2 along the first surface 61d. As a result, the second portion 367 is connected to the first portion 366. Next, in the hardening step S05, the worker hardens the second portion 367 by cooling it. As a result, the second portion 367 connected to the first portion 366 is formed, and the balance weight 365 is formed on the rotating body 12. When the hardening step S05 is completed, the number of portions Nm formed on the rotating body 12 becomes 2 (S06). As described above, the number of portions Na of the balance weight 365 to be formed is 2, and therefore a predetermined number of portions of the balance weight 365 are formed on the rotating body 12. Therefore, the worker or the like performs the second inspection step S08 (S07).

[0073] In the second inspection step S08, the worker inspects the balance of the rotating body 12 on which the balance weight 365 is molded. The work in the steps after the second inspection step S08 in this embodiment is similar to the work in the steps after the second inspection step S08 in the above-described first embodiment. When the balance of the rotating body 12 falls within a predetermined standard, the worker finishes molding the balance weight 365.

[0074] According to this embodiment, the balance weight 365 has a first portion 366 and a second portion 367 connected to the first portion 366, the first portion 366 contacts both the first surface 61d and the second surface 61e, and the second portion 367 contacts at least the first surface 61d. When viewed from a direction perpendicular to the first direction D1, the upper side of the first portion 366, that is, the first upper surface 366h which is a surface facing one side (+D1 side) of the first direction D1, and the second upper surface 367h which is a surface facing the upper side of the second portion 367 each have a curved portion that is convex upward. When a heavy balance weight 365 is molded on the rotating body 12 by applying the air A once, the time required to spread the balance weight 365 on the rotating body 12 by blowing the molten balance weight 365 with the air A and the time required to harden the balance weight 365 tend to increase. Therefore, the number of steps in the spraying step S04 and the number of steps in the hardening step S05 are likely to increase. In contrast, in this embodiment, the second portion 367 is molded after the first portion 366 is molded, so that it is possible to suppress an increase in each of the first weight Wb1 of the first portion 366 and the second weight Wb2 of the second portion 367. This makes it possible to suppress an increase in the number of steps in the spraying step S04 and the number of steps in the hardening step S05 when molding each of the first portion 366 and the second portion 367. Therefore, even when molding a heavy balance weight 365, it is possible to suppress an increase in the number of steps in manufacturing the balance weight 365.

[0075] In this embodiment, the balance weight 365 has a first contact portion 365e that contacts the first surface 61d of the rotor 12, and a second contact portion (not shown) that contacts the second surface. This increases the contact area between the balance weight 365 and the rotor 12, thereby increasing the adhesive strength between the balance weight 365 and the rotor 12. This makes it possible to suitably prevent the balance weight 365 from peeling off from the rotor 12 during operation of the blower 10. This makes it possible to suitably stabilize the rotational balance of the rotor 12, thereby allowing the rotor 12 to rotate stably around the central axis J.

[0076] Although one embodiment of the present invention has been described above, each configuration and their combination in the embodiment is merely an example, and addition, omission, substitution, and other modifications of the configuration are possible without departing from the spirit of the present invention. Furthermore, the present invention is not limited to the embodiment. For example, the uses of the balance weight and the blower shown in the above embodiment are not particularly limited.

[0077] The blower may be, for example, a centrifugal fan that blows air radially outward. In this case, too, the balance of the rotor can be adjusted by forming a balance weight on the rotor, so that the rotor can rotate stably around the central axis J.

[0078] The manufacturing method of the balance weight is not limited to this embodiment, and for example, the spraying process and the hardening process may be performed simultaneously. In this case, the balance weight can be cooled and hardened while spreading on the first surface by setting the temperature of the air lower than the melting point of the resin part. Therefore, it is possible to suppress an increase in the number of steps in manufacturing the balance weight.

[0079] The shape of the balance weight is not limited to this embodiment, and for example, the dimension in the first direction may be greater than the dimension in the direction perpendicular to the first direction. Also, when viewed from the direction perpendicular to the first direction, the balance weight may have another shape, such as a substantially circular shape.

[0080] The present technology can be configured as follows. (1) A balance weight for adjusting the balance of a rotating body that is rotatable about a central axis and has a first surface facing one side of a first direction and a second surface facing a second direction intersecting the first direction, the balance weight having a first contact portion in contact with the first surface and a second contact portion in contact with the second surface, the surface facing one side of the first direction having a curved portion that is convex toward one side of the first direction when viewed from a direction perpendicular to the first direction, and an area projected onto a virtual plane perpendicular to the first direction is greater than an area of ​​the first contact portion. (2) The balance weight according to (1), wherein the dimension in the first direction is smaller than the dimension in a direction perpendicular to the first direction. (3) A balance weight as described in (1) or (2), which has a first portion and a second portion connected to the first portion, the first portion being in contact with both the first surface and the second surface, the second portion being in contact with at least the first surface, and when viewed from a direction perpendicular to the first direction, a surface of the first portion facing one side in the first direction and a surface of the second portion facing one side in the first direction each have a curved portion that is convex toward one side in the first direction. (4) The balance weight described in any one of (1) to (3), wherein the rotating body has a first outer surface facing one side of the first direction and a groove portion recessed from the first outer surface to the other side of the first direction, the first surface being a surface of the inner surface of the groove portion facing one side of the first direction, the second surface being a surface of the inner surface of the groove portion facing a direction perpendicular to the first direction, and the balance weight is positioned inside the groove portion. (5) The balance weight according to (4), wherein the groove portion extends around the entire circumference in a circumferential direction, and the second surface is a surface facing radially inward. (6) The balance weight according to (5), which contacts a third surface of the inner surface of the groove portion that faces radially outward. (7) A blower comprising: a balance weight according to any one of (1) to (6); a rotor rotatable about a central axis; and an impeller portion connected to the rotor and rotatable about the central axis, wherein the rotating body is constituted by the rotor and the impeller portion. (8) A method for manufacturing a balance weight, which adjusts the balance of a rotating body having a first surface facing one side of a first direction and a second surface facing a second direction intersecting the first direction, and molds a balance weight onto the rotating body, the balance weight having a first contact portion in contact with the first surface and a second contact portion in contact with the second surface, the method including: an application process for applying molten balance weight onto the first surface; a spraying process for blowing air onto the balance weight applied to the first surface to spread the balance weight over the rotating body; and a hardening process for hardening the balance weight. [Explanation of symbols]

[0081] 10,210,310...blower, 12...rotating body, 20...rotor, 60...impeller portion, 61a...first outer surface, 61c...groove portion, 61d...first surface, 61e...second surface, 61f...third surface, 65,265,365...balance weight, 65e,265e,365e...first contact portion, 65f...second contact portion, 366...first portion, 367...second portion, A...air, D1...first direction, D2...second direction, J...central axis, S03...coating process, S04...spraying process, S05...curing process, Sv...virtual surface

Claims

1. A balance weight for adjusting the balance of a rotor, the rotor being rotatable about a central axis and having a first surface facing one side of a first direction and a second surface facing a second direction intersecting the first direction, a first contact portion in contact with the first surface and a second contact portion in contact with the second surface; When viewed from a direction perpendicular to the first direction, a surface facing one side in the first direction has a curved portion that is convex toward the one side in the first direction, A balance weight, the area of ​​which projected onto a virtual plane perpendicular to the first direction is larger than the area of ​​the first contact portion.

2. The balance weight according to claim 1 , wherein a dimension in the first direction is smaller than a dimension in a direction perpendicular to the first direction.

3. A first portion and a second portion connected to the first portion, the first portion contacts both the first surface and the second surface; the second portion contacts at least the first surface; 2. The balance weight according to claim 1, wherein, when viewed from a direction perpendicular to the first direction, a surface of the first portion facing one side in the first direction and a surface of the second portion facing one side in the first direction each have a curved portion that is convex toward one side in the first direction.

4. the rotating body has a first outer surface facing one side in the first direction and a groove portion recessed from the first outer surface toward the other side in the first direction, the first surface is a surface of an inner surface of the groove portion facing one side in the first direction, and the second surface is a surface of an inner surface of the groove portion facing a direction perpendicular to the first direction, The balance weight according to claim 1 , wherein the balance weight is disposed inside the groove.

5. The groove portion extends around the circumference in a circumferential direction, The balance weight according to claim 4 , wherein the second surface is a surface facing radially inward.

6. The balance weight according to claim 5 , wherein the balance weight contacts a third surface of the inner surface of the groove portion that faces radially outward.

7. A balance weight according to any one of claims 1 to 3; A rotor rotatable about a central axis; an impeller portion connected to the rotor and rotatable about a central axis; Equipped with The rotating body is constituted by the rotor and the impeller portion.

8. A method for manufacturing a balance weight, comprising: adjusting the balance of a rotating body having a first surface facing one side of a first direction and a second surface facing a second direction intersecting the first direction; and forming a balance weight on the rotating body, the balance weight having a first contact portion in contact with the first surface and a second contact portion in contact with the second surface, the method comprising: a coating step of coating the molten balance weight on the first surface; a blowing step of blowing air onto the balance weight applied to the first surface to spread the balance weight over the rotating body; a hardening step of hardening the balance weight; Including, In the blowing process, air is blown onto the balance weight to change the shape of the balance weight so that, when viewed from a direction perpendicular to the first direction, a surface facing one side of the first direction has a curved portion that is convex toward one side of the first direction, and the area projected onto a virtual plane perpendicular to the first direction is larger than the area of ​​the first contact portion, and the balance weight is brought into contact with the second surface.

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