TW202003152A - Belt type grinding tool - Google Patents

Abstract

To provide a belt type grinding tool configured so that an endless grinding belt can be more efficiently cooled. This belt type grinding tool 10 is provided with a fan 36 disposed on the inside of the outer peripheral section 28 of a drive pulley 22. The belt type grinding tool 10 has formed therein an air flow path 68 which extends on the inside of the outer peripheral section 28 from an inner opening 62 in a cover 52, passes through a through-hole 46 in the drive pulley 22, bends around a side edge 28b of the outer peripheral section 28, extends on the outside of the outer peripheral section 28, and reaches an outer opening 64 in the cover 52. When the fan 36 is rotated together with the drive pulley 22, outside air is sucked into a containing space 58 from the inner opening 62, flows along the air flow path 68 and is discharged to the outside of the containing space 58 from the outer opening 64. The drive pulley 22 and the endless belt 24 are efficiently cooled by the air.

Description

Belt grinding tool

The present invention relates to a belt-type grinding tool, and more specifically, to a belt-type grinding tool having a "function for cooling an endless grinding belt".

A belt grinding tool is provided with an idler wheel configured to rotate freely, a driving pulley driven by a motor, and a continuous grinding belt hung on the idler wheel and the driving pulley. A continuous polishing belt that rotates and rotates is pressed against the object to be polished, and a tool that performs polishing of the object to be polished (Patent Document 1). In such a belt-type polishing tool, during the polishing operation, the continuous polishing belt is heated due to friction with the object to be polished.

As the continuous polishing belt is heated, the drive pulley, the motor shaft, and the like also become hot. In particular, the bearing that rotatably supports the aforementioned member may be deteriorated due to heat. For such a problem, for example, in the belt sander shown in Patent Document 2, a fan is provided on the driving roller, and by rotating the fan together with the driving roller, the external Gas is drawn into the tool. The attracted air is guided into the dust bag by other dust collecting fans through the inside of the driving roller. By this, air is formed to flow around the "shaft of the driving roller and the bearing forming the rotational support for the former", and these components are cooled by the flow of air. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2014-166668 [Patent Document 2] Japanese Shikai Fair No. 6-13827

[Problems to be solved by invention]

There is another problem when the continuous grinding belt is heated, and the continuous grinding belt may break. Continuous grinding tape is usually formed by bonding both ends of the tape material with an adhesive to form an endless tape. Once the adhesive part becomes excessively hot, the adhesive will be dissolved, and sometimes the tape may be caused. fracture. Even in the above-mentioned belt sand mill, although the continuous grinding belt is indirectly cooled to some extent by cooling the driving roller, in this belt sand mill, the cooling "driving roller" is mainly formed The "shaft and bearing" structure is not sufficient for the cooling effect of the continuous grinding belt.

In view of this, an object of the present invention is to provide a belt-type grinding tool that can efficiently cool a continuous grinding belt hanging on an idler and a driving pulley. [Means to solve the problem]

That is, the present invention provides a belt-type grinding tool, including: Tool body with motor; and Idler wheel, mounted relative to the tool body so that it can rotate freely; and The driving pulley, driven by the motor, has a cylindrical outer peripheral portion for supporting the "continuous grinding belt stretched between the idler pulley"; and The fan, at least a part of which is arranged radially inward of the outer peripheral portion, rotates together with the drive pulley, and generates: an air flow passing through the inner side of the outer peripheral portion in the direction of the rotation axis of the drive pulley; and The cover has a cover plate portion disposed on a side end edge adjacent to one side of the outer peripheral portion in the direction of the rotation axis, and a housing space for housing the driving pulley is defined between the tool body and the cover The plate portion is formed with "an inner opening portion that forms an opening toward the housing space at a position radially inward relative to the inner peripheral surface of the outer peripheral portion" and "a position radially outward relative to the inner peripheral surface of the outer peripheral portion" , An outer opening forming an opening toward the receiving space"; and The ventilation path passes through the inside of the outer peripheral portion from the inner opening to bypass the side edge of the other side of the outer peripheral portion in the housing space, and reaches the outer opening through the outer side of the outer peripheral portion, When the fan rotates, external air is drawn into the housing space from one of the inner opening and the outer opening, flows along the ventilation path, and from the other of the inner opening and the outer opening One is discharged outside the containment space.

In this belt-type grinding tool, the air sucked into the storage space by the fan is formed not only by the inside of the outer periphery of the driving pulley, but also by the outside. Therefore, it is formed that not only the driving pulley, but also the continuous grinding belt supported on the outer peripheral surface is directly cooled. Thereby, the continuous grinding belt can be cooled more efficiently, and the breakage of the continuous grinding belt due to heat can be prevented.

Specifically, the cover plate portion has a notch "extending from a radially inner position of the inner peripheral surface of the outer peripheral portion to a radially outer position", the inner opening portion and the outer opening portion may be It is formed as part of this notch.

It is preferable that the notch can be bent to extend in the radial direction of the rotation axis. Compared with a linear hole, the opening area can be increased, and air can be sucked into the storage space more efficiently.

Preferably, the notch forms a size (dimension) that cannot be accessed by human fingers. With this, it is possible to prevent fingers from accidentally contacting the rotating driving pulley and the continuous grinding belt and being injured. The so-called "size (size) that human fingers cannot enter" means that the test finger selected according to the use environment cannot reach the size (size) in the storage space.

Specifically, the driving pulley further includes: a central fixing portion connected to the "rotation shaft driven by the motor" and a connecting portion "extending from the outer peripheral portion to the central fixing portion". The part is formed with a through hole "direction penetrating the rotation axis", and the ventilation path can pass through the through hole.

More specifically, when the fan rotates, external air can be drawn into the receiving space from the inner opening along the ventilation path, pass through the inner side of the outer periphery, and bypass the outer periphery after passing through the through hole The side edge of the other side of the part is discharged from the outer opening through the outer side of the outer peripheral part to the outside of the storage space.

Preferably, it can be formed that the fan has a plurality of blades arranged at a first interval in the circumferential direction of the outer peripheral portion, and the through-hole is arranged at a second interval different from the first interval in the circumferential direction Pcs.

Preferably, it may be formed that a gap in the rotation axis direction is formed between the fan and the coupling portion of the drive pulley. With this, it can be formed that the through hole is not blocked by the fan.

In addition, the present invention provides a belt-type grinding tool, comprising: Tool body with motor; and Idler wheel, mounted relative to the tool body so that it can rotate freely; and The driving pulley, driven by the motor, has a cylindrical outer peripheral portion for supporting the "continuous grinding belt stretched between the idler pulley"; and The fan, at least a part of which is arranged radially inward of the outer peripheral portion, rotates together with the drive pulley, and generates: an air flow passing through the inner side of the outer peripheral portion in the direction of the rotation axis of the drive pulley; and The cover has a cover plate portion disposed on a side end edge adjacent to one side of the outer peripheral portion in the direction of the rotation axis, and a housing space for housing the driving pulley is defined between the tool body and the cover The plate portion is formed with a notch that extends from "an inner opening that forms an opening toward the receiving space at a position radially inward relative to the inner peripheral surface of the outer peripheral portion" to "inwardly relative to the outer peripheral portion" A position on the radially outer side of the circumferential surface, an outer opening that forms an opening toward the storage space"; and When the fan rotates, external air is drawn into the storage space from the notch, and is discharged to the outside of the storage space through the inside of the outer peripheral portion.

According to this belt-type grinding tool, since the notch provided in the cover extends from the inside to the outside of the outer peripheral portion of the driving pulley, when the outside air is drawn into the storage space by the fan, air is formed on the side edge Blow attached to the outer periphery. In addition, the opening area of the slot becomes larger, which can attract more air. With this, the drive pulley can be efficiently cooled.

Hereinafter, embodiments of the belt-type grinding tool of the present invention will be described based on the drawings.

As shown in FIGS. 1 to 3, a belt grinding tool 10 according to one embodiment of the present invention includes: a tool body 12 extending in the direction of the longitudinal axis L; and a front end portion 14 of the tool body 12 that can be mounted A freely rotating idler 16; and a driving pulley 22 fixed to a "rotating shaft 20 driven and connected by an electric motor 18 included in the tool body 12". Between the idler 16 and the drive pulley 22, a continuous grinding belt 24 is stretched. The driving pulley 22 is rotationally driven by the electric motor 18 in the counterclockwise direction seen in FIG. 2, and along with this, the continuous polishing belt 24 also rotates in the same direction. A slide rail 25 is attached to the tool body 12 along the inner circumferential surface 24a of the continuous polishing belt 24, and the rotating continuous polishing belt 24 is pressed against the object to be polished by the position of "supported by the slide rail 25 from the inside" To execute the polishing operation on the object to be polished.

As shown in FIG. 3, the driving pulley 22 has: a cylindrical center fixing portion 26 fixed to the rotating shaft 20; and a cylindrical outer peripheral portion 28 supporting the continuous grinding belt 24; and a rotation axis relative to the driving pulley 22 R extends in the radial direction and connects the connecting portion 30 of the center fixing portion 26 and the outer peripheral portion 28. The driving pulley 22 is fixed to the rotating shaft 20 by a hex nut 32 that is locked to the rotating shaft 20. In the rotation axis R direction, the side end edges 28 a and 28 b on both sides of the outer peripheral portion 28 are provided with flange portions 34 that prevent the continuous polishing belt 24 from falling off.

A fan 36 is provided radially inside the outer periphery 28 of the drive pulley 22. The fan 36 has a center fixing portion 38 and blades 40 extending from the center fixing portion 38 to the radially outer side. As is clear from FIG. 2, five blades 40 are arranged at equal intervals in the circumferential direction. The fan 36 is fixed to the hexagonal nut 32 by the fixing screw 42 in a state where the hexagonal nut 32 is partially received in the center fixing portion 38. The inner circumferential surface 38a of the central fixing portion 38 of the hexagon nut 32 is received, and a hexagonal shape matching the outer diameter of the hexagon nut 32 is formed to securely fix the fan 36 to the hexagon nut 32 in the rotation direction. The fixing screw 42 is fixed in a state where its end surface 42a abuts on the end surface 20a of the rotating shaft 20. As a result, the hexagonal nut 32 and the fixing screw 42 are not easily loosened (loose). An O-ring 44 is arranged between the fan 36 and the hexagon nut 32. The O-ring 44 is a member that presses the fan 36 against the head of the fixing screw 42 and prevents the fan 32 from wobbling. Although the entire fan 36 is located inside the outer peripheral portion 28, it may have a shape that partially protrudes outside the outer peripheral portion 28.

The connecting portion 30 of the drive pulley 22 is formed with a through hole 46 penetrating through the rotation axis R direction. Although the through holes 46 are partially hidden by the blades 40 of the fan 36 in FIG. 2 and are not visible, eight are provided at the same interval in the circumferential direction. By arranging the blades 40 and the through holes 46 of the fan 36 at different intervals in the circumferential direction, even in the case where "the fan 36 is mounted on the drive pulley 22 regardless of the direction of rotation", it will not Formation: The front surface of all the through holes 46 is covered by the blade 40. In addition, a gap 48 in the rotation axis R direction is formed between the blade 40 of the fan 36 and the coupling portion 30 of the drive pulley 22 so that the through hole 46 of the coupling portion 30 is not blocked by the blade 40 of the fan 36, Will not hinder the flow of air.

The tool body 12 is further provided with a cover 52 by fixing screws 50. The cover 52 has: a fixing portion 54 fixed to the tool body 12 by a fixing screw 50; and a cover plate portion 56 disposed adjacent to a side edge 28a of one side of the outer peripheral portion 28 in the direction of the rotation axis R, and Between the tool bodies 12, a housing space 58 for housing the drive pulley 22 is defined. As shown in FIG. 1, the cover plate portion 56 is provided with a plurality of notches 60 that are curved and extended with respect to the radial direction of the rotation axis R. The notch 60 extends from a position radially inward of the inner peripheral surface 28c of the outer peripheral portion 28 of the drive pulley 22 to a position radially outward, and has a position relative to the inner peripheral surface 28c of the outer peripheral portion 28 In the radial inner position, an inner opening 62 that opens toward the storage space 58; and in the radial outer position, an outer opening 64 that opens toward the storage space 58. The notch 60 forms a size (size) in which the human finger cannot enter the storage space 58. Specifically, it is designed to be a size (dimension) that cannot be entered into the storage space 58 by a test finger appropriately selected according to the usage environment. The test finger used in the design of this embodiment is based on the international standard IEC60529. In the vicinity of the center of the cover plate portion 56, an arrow-shaped hole 66 indicating the rotation direction of the drive pulley 22 is formed.

In this belt-type grinding tool 10, the ventilation path 68 shown by the arrow in FIG. 3 is formed by the above-mentioned structure. The ventilation path 68 passes from the inner opening 62 of the cover 52 through the inner side of the outer peripheral portion 28 of the drive pulley 22, and after passing through the through hole 46 of the coupling portion 30, bypasses the other side edge of the outer peripheral portion 28 28b passes through the outer side of the outer peripheral portion 28 and reaches the outer opening 64. As described above, since the fan 36 disposed inside the driving pulley 22 is fixed to the rotating shaft 20, once the driving pulley 22 is rotationally driven, it rotates together with the driving pulley 22. Once the fan 36 rotates, it will be generated by the fan 36: in the direction of the rotation axis R, the flow of air passing through the inside of the outer peripheral portion 28 of the driving pulley 22. Once so, the air flows along the ventilation path 68. Specifically, outside air is drawn into the storage space 58 from the inner opening 62, passes through the inside of the outer peripheral portion 28 of the driving pulley 22 where the fan 36 is disposed, and passes through the through hole 46 toward the driving pulley 22 Outflow. The air that has passed through the through hole 46 contacts the inner peripheral surface 58a of the housing space 58 and changes direction radially outward, bypassing the other side edge 28b of the outer peripheral portion 28. The air further passes through the outer side of the outer peripheral portion 28 and is discharged from the outer opening 64 to the outside of the storage space 58. A part of the air discharged from the outer opening 64 flows out of the outer side of the cover 52 along the notch 60 or temporarily, and then is sucked into the storage space 58 from the inner opening 62 again. In addition, since the front portion 58b (the upper portion seen in FIGS. 1 and 2) and the lower portion 58c (the left portion seen in FIGS. 1 and 2) of the storage space 58 are formed, they are opened A part of the air sucked into the storage space 58 is discharged out of the storage space 58 from the aforementioned front portion 58b and lower portion 58c after passing through the through hole 46. Since the front portion 58b and the lower portion 58c pass through the continuous polishing belt 24, a part of the air discharged from the front portion 58b and the lower portion 58c is blown onto the continuous polishing belt 24.

In this way, in this belt-type grinding tool 10, the outside air drawn into the storage space 58 by the fan 36 passes through both the inside and the outside of the outer peripheral portion 28 of the driving pulley 22, so the drive can be cooled more efficiently Pulley 22. According to this, the continuous grinding belt 24 can be cooled more efficiently through the drive pulley 22. In addition, the air flowing through the ventilation path 68 also directly contacts the continuous polishing belt 24 when passing through the outside of the outer peripheral portion 28, so the continuous polishing belt 24 can also be directly cooled. Thereby, compared with the conventional belt grinding tool 10, the cooling of the continuous grinding belt 24 can be performed more efficiently, and the breakage of the continuous grinding belt 24 due to heat can be prevented.

In addition, in the above embodiment, since the notch 60 extends from the inner side to the outer side of the outer peripheral portion 28 of the drive pulley 22, and is also located on the side edge portion 28a of one side of the outer peripheral portion 28, it is formed as follows: When sucking air, the air is blown onto the outer peripheral portion 28 at the side edge 28a. According to this, the cooling of the drive pulley 22 can also be performed more efficiently, and the breakage of the continuous grinding belt 24 due to heat can be more reliably prevented. In addition, since a part of the air discharged from the front portion 58b and the lower portion 58c of the storage space 58 is blown onto the continuous polishing belt 24, the continuous polishing belt 24 can also be cooled.

The shape and arrangement of the inner opening 62 and the outer opening 64 provided in the cover 52 can be arbitrarily changed. For example, in the cover 152 shown in FIG. 4, the inner opening 162 and the outer opening 164 are formed as independent holes. However, in such a case, air cannot be blown onto the outer peripheral portion 28 of the drive pulley 22. In the cover 252 shown in FIG. 5, the notch 260 has a zigzag shape, and the opening area of the outer opening 264 becomes larger. In the cover 352 shown in FIG. 6, the bending direction of the notch 360 is opposite to the cover 52 in FIG. 1. In the cover 452 shown in FIG. 7, the linear long notches 460-1 and the short notches 460-2 are alternately arranged in the circumferential direction. The shapes and arrangements of these notches, inner openings, and outer openings are merely examples, and other shapes than those described above may be used.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments. For example, although in the above embodiment, the outside air is sucked by the inner opening and discharged from the outer opening, the direction of rotation of the drive pulley may be reversed, or the direction of the blades of the fan may be reversed. Instead, the air flows in the opposite direction. That is, it can also be formed that outside air is drawn into the storage space from the outer opening, passes through the outer side of the outer peripheral portion of the driving pulley, bypasses the side edge of the other side of the outer peripheral portion, and passes through the through hole of the connecting portion, The inside of the outer peripheral portion is discharged from the inside opening to the outside of the storage space. In addition, although it is expected to have both "a structure that is sucked into the storage space and directly attached to the outer periphery of the drive pulley" and a "structure that flows along the ventilation path passing through the inside and outside of the outer periphery", However, it is not necessary to have the aforementioned two structures. Even if any one of the aforementioned structures, compared with the conventional technology, it can obtain a very superior cooling effect. In addition, the number of blades of the fan and the number of through-holes in the connecting portion may be changed. Although the above-mentioned embodiment is an electric belt polishing tool provided with an electric motor, it may be a pneumatic belt polishing tool that uses a pneumatic motor instead of the electric motor.

10‧‧‧band grinding tool 12‧‧‧Tool body 14‧‧‧Front end 16‧‧‧idle pulley 18‧‧‧Electric motor 20‧‧‧Rotation axis 20a‧‧‧End 22‧‧‧Drive pulley 24‧‧‧Continuous grinding belt 24a‧‧‧Inner peripheral surface 25‧‧‧shoe 26‧‧‧ Center Fixed Department 28‧‧‧Outer periphery 28a‧‧‧Side end edge 28b‧‧‧Side end edge 28c‧‧‧Inner peripheral surface 30‧‧‧Link 32‧‧‧Hexagon nut 34‧‧‧Flange 36‧‧‧Fan 38‧‧‧ Center Fixed Department 38a‧‧‧Inner peripheral surface 40‧‧‧blade 42‧‧‧Screw 42a‧‧‧End 44‧‧‧O-ring 46‧‧‧Through hole 48‧‧‧ gap 50‧‧‧fixing screw 52‧‧‧ Cover 54‧‧‧Fixed Department 56‧‧‧Cover Department 58‧‧‧ containment space 58a‧‧‧Inner peripheral surface 58b‧‧‧Front part 58c‧‧‧lower part 60‧‧‧slot opening 62‧‧‧Inside opening 64‧‧‧Outside opening 66‧‧‧arrow shaped hole 68‧‧‧Ventilation path 152‧‧‧ cover 162‧‧‧Inside opening 164‧‧‧Outside opening 252‧‧‧ cover 260‧‧‧Notch 264‧‧‧Outside opening 352‧‧‧ cover 360‧‧‧Notch 452‧‧‧ cover 460-1‧‧‧Long slot 460-2‧‧‧Short notch L‧‧‧longitudinal axis R‧‧‧Rotation axis

Fig. 1 is a side view of a belt grinding tool according to one embodiment of the present invention. Fig. 2 is a side view of the state where the cover of the belt-type grinding tool of Fig. 1 has been removed. Figure 3: It is a partial cross-sectional view along line A-A of Figure 1. Fig. 4: A diagram showing a second embodiment of the cover. Fig. 5 is a diagram showing a third embodiment of the cover. Fig. 6 is a diagram showing a fourth embodiment of the cover. Fig. 7 is a diagram showing a fifth embodiment of the cover.

12‧‧‧Tool body

18‧‧‧Electric motor

20‧‧‧Rotation axis

20a‧‧‧End

22‧‧‧Drive pulley

24‧‧‧Continuous grinding belt

26‧‧‧ Center Fixed Department

28‧‧‧Outer periphery

28a‧‧‧Side end edge

28b‧‧‧Side end edge

28c‧‧‧Inner peripheral surface

30‧‧‧Link

32‧‧‧Hexagon nut

34‧‧‧Flange

36‧‧‧Fan

38‧‧‧ Center Fixed Department

38a‧‧‧Inner peripheral surface

40‧‧‧blade

42‧‧‧Screw

42a‧‧‧End

44‧‧‧O-ring

46‧‧‧Through hole

48‧‧‧ gap

50‧‧‧fixing screw

52‧‧‧ Cover

56‧‧‧Cover Department

58‧‧‧ containment space

58a‧‧‧Inner peripheral surface

60‧‧‧Notch

62‧‧‧Inside opening

64‧‧‧Outside opening

66‧‧‧arrow shaped hole

68‧‧‧Ventilation path

R‧‧‧Rotation axis

Claims (9)

A belt grinding tool with: Tool body with motor; and Idler wheel, mounted relative to the tool body so that it can rotate freely; and The driving pulley, driven by the motor, has a cylindrical outer peripheral portion for supporting a continuous grinding belt, the continuous grinding belt being stretched between the idler pulley; and The fan, at least a part of which is arranged radially inward of the outer peripheral portion, rotates together with the drive pulley, and generates: an air flow passing through the inner side of the outer peripheral portion in the direction of the rotation axis of the drive pulley; and The cover has a cover plate portion disposed on a side end edge adjacent to one side of the outer peripheral portion in the direction of the rotation axis, and a housing space for housing the driving pulley is defined between the tool body and the cover The plate portion is formed with an inner opening portion and an outer opening portion, the inner opening portion is formed toward the accommodating space at a position radially inward relative to the inner peripheral surface of the outer peripheral portion, and the outer opening portion is opposed to the outer peripheral portion The radially outer position of the inner peripheral surface forms an opening toward the receiving space; and The ventilation path passes through the inside of the outer peripheral portion from the inner opening to bypass the side edge of the other side of the outer peripheral portion in the housing space, and reaches the outer opening through the outer side of the outer peripheral portion, When the fan rotates, external air is drawn into the housing space from one of the inner opening and the outer opening, flows along the ventilation path, and from the other of the inner opening and the outer opening One is discharged outside the containment space. The belt-type abrasive tool according to claim 1, wherein the cover plate portion has a notch extending from a position radially inward of the inner peripheral surface of the outer circumference portion to a position radially outward, the inner opening portion The outer opening is formed as a part of the notch. The belt-type grinding tool according to claim 2, wherein the notch extends to bend the radial direction of the rotation axis. The belt grinding tool as described in claim 2 or claim 3, wherein the notch has a size that cannot be entered by a human finger. The belt-type grinding tool according to any one of claim 1 to claim 3, wherein the driving pulley further includes: a central fixing portion connected to a rotating shaft driven by the motor, and the outer periphery The portion extends to the connecting portion of the center fixing portion, and a through hole penetrating the direction of the rotation axis is formed in the connecting portion, and the ventilation path passes through the through hole. The belt grinding tool according to claim 5, wherein when the fan rotates, outside air is drawn into the receiving space from the inner opening along the ventilation path, through the inner side of the outer peripheral portion, and through the After passing through the hole, the side edge of the other side of the outer peripheral portion is bypassed, and is discharged from the outer opening portion to the outside of the storage space through the outer side of the outer peripheral portion. The belt polishing tool according to claim 5, wherein the fan has a plurality of blades arranged at a first interval in the circumferential direction of the outer peripheral portion, and the through-hole is different from the first interval in the circumferential direction A plurality of second intervals are arranged. The belt-type grinding tool according to claim 5, wherein a gap in the direction of the rotation axis is formed between the fan and the coupling portion of the drive pulley. A belt grinding tool with: Tool body with motor; and Idler wheel, mounted relative to the tool body so that it can rotate freely; and The driving pulley, driven by the motor, has a cylindrical outer peripheral portion for supporting a continuous grinding belt, the continuous grinding belt being stretched between the idler pulley; and The fan, at least a part of which is arranged radially inward of the outer peripheral portion, rotates together with the drive pulley, and generates: an air flow passing through the inner portion of the outer peripheral portion in the direction of the rotation axis of the drive pulley; and The cover has a cover plate portion disposed on a side end edge adjacent to one side of the outer peripheral portion in the direction of the rotation axis, and a housing space for housing the driving pulley is defined between the tool body and the cover The plate portion is formed with a notch that extends from the inner opening to the outer opening, and the inner opening forms an opening toward the receiving space at a position radially inward relative to the inner circumferential surface of the outer peripheral portion, the outer side The opening is formed toward the storage space at a position radially outward of the inner peripheral surface of the outer peripheral portion, When the fan rotates, external air is drawn into the storage space from the notch, and is discharged to the outside of the storage space through the inside of the outer peripheral portion.

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