Reversible fan

Abstract

A reversible fan is provided, comprising: blades configured to generate both forward and reverse airflow; an impeller rotatable about a rotation axis; a motor that rotates the impeller; and a cylindrical frame housing the impeller and the motor. The blades are shaped to generate greater noise when generating forward airflow than when generating reverse airflow, and protrude radially inward from the inner circumferential surface of the frame.

Description

[Technical Field]

[0001] This disclosure relates to reversible fans. [Cross-reference to related applications] This case asserts priority based on Japanese Patent Application No. 2021-081097 filed with the Japan Patent Office on May 12, 2021, and all contents thereof are incorporated herein by reference. [Previous Technology]

[0002] For example, as described in Japanese Patent No. 6802022, there is a known reversible fan that generates airflow in both the forward and reverse directions. [Summary of the Invention]

[0003] The reversible fan of the present embodiment comprises: blades configured to generate both forward and reverse airflow; an impeller capable of rotating about a rotation axis; a motor for rotating the impeller; and a cylindrical frame housing the impeller and the motor. The blades are shaped to generate greater noise when generating forward airflow than when generating reverse airflow, and protrude radially inward from the inner circumferential surface of the frame.

Implementation Method

[0005] Detailed Description of the Invention

[0006] To explain the present invention, various specific details are set forth in the following detailed description to provide a thorough understanding of the disclosed embodiments. However, it will be apparent that more than one embodiment may be practiced without these specific details. In other instances, well-known structures and apparatuses are illustrated schematically to simplify the drawings.

[0007] Furthermore, such a reversible fan is, for example, installed on the wall of a residence. This reversible fan is used to draw in outside air when it is warmer to raise the room temperature, or to expel indoor air to lower the temperature when the indoor temperature is high. In this case, if the noise when drawing in outside air differs from the noise when expelling indoor air, residents may suspect that the fan is malfunctioning.

[0008] In situations where it is desirable to have the same noise characteristics when air is supplied in the forward direction as when air is supplied in the reverse direction, the method is generally adopted to reduce the noise level when air is supplied in the reverse direction, in order to match the lower noise level when air is supplied in the forward direction.

[0009] However, this embodiment differs from such a method in that it is found that the noise level during forward airflow can be increased depending on the application, thereby making the noise levels of both forward and reverse airflow equal. For example, as mentioned above, the noise levels during forward and reverse airflow are not equal, which would raise suspicion of machine malfunction. Therefore, even if the noise levels during forward and reverse airflow remain high, as long as the noise levels are equal, machine malfunction will not be suspected.

[0010] Therefore, the present disclosure aims to provide a reversible fan that increases the noise level when the air is blown in the forward direction, thereby making the noise level when the air is blown in the forward direction equal to the noise level when the air is blown in the reverse direction.

[0011] One embodiment of the reversible fan includes: blades configured to generate both forward and reverse airflow; an impeller capable of rotating about a rotation axis; a motor that rotates the impeller; and a cylindrical frame housing the impeller and the motor. The blades are shaped to generate greater noise when generating forward airflow than when generating reverse airflow, and protrude radially inward from the inner circumferential surface of the frame.

[0012] According to this embodiment, a reversible fan can be provided, which increases the noise level when blowing air in the forward direction, thereby making the noise level when blowing air in the forward direction the same as the noise level when blowing air in the reverse direction.

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Furthermore, in the description of the embodiments, the description of components having the same reference numerals as those already described is omitted for convenience. Also, for ease of explanation, the dimensions of each component shown in the drawings may differ from the actual dimensions of each component.

[0014] Figure 1 is a perspective view of the reversible fan 1 according to this embodiment. As shown in Figure 1, the reversible fan 1 includes an impeller 2 capable of rotating about a rotation axis X, a motor 3 that rotates the impeller 2, a base 4 supporting the motor 3, and a cylindrical frame 5 housing these components. The impeller 2, motor 3, and base 4 are housed within the frame 5 in an overlapping manner along the rotation axis X.

[0015] Furthermore, in this embodiment, the direction in which the impeller 2 of the reversible fan 1 shown in FIG1 discharges air (airflow) when rotating in the direction of arrow n (forward rotation direction) is referred to as the positive direction of the reversible fan 1. And the direction in which the impeller 2 discharges air (airflow) when rotating in the direction of arrow r (reverse rotation direction) is referred to as the negative direction of the reversible fan 1.

[0016] Reversible fan 1 is a fan that can blow air in both the forward and reverse directions (to generate airflow).

[0017] The impeller 2 is generally cup-shaped. A plurality of blades 2a (five in the example shown) are radially mounted around the impeller 2. The blades 2a are mounted such that their surfaces are inclined relative to the axial direction (the same direction as the rotation axis X) of the rotating shaft of the reversible fan 1. The impeller 2 generates airflow in either the forward or reverse direction by rotating the blades 2a.

[0018] The motor 3 is located inside the impeller 2. The motor 3 is, for example, a brushless motor of the external rotor type. The motor 3 has a stator and a rotor disposed on the outer periphery of the stator. The motor 3 inside the impeller 2 has its rotor portion fixed to the impeller 2. The motor 3 is assembled inside the impeller 2 in a manner that positions it further forward (on the positive side) than the impeller 2.

[0019] The base 4 is, for example, formed in a circular cup shape. The base 4 is provided in such a way that it covers the front side of the motor 3. The base 4 supports the stator of the motor 3. The base 4 is assembled into the frame 5 in such a way that it is disposed on the front side of the motor 3.

[0020] The base 4 is supported by a plurality of spokes 6. Each spoke 6 extends radially from the periphery of the base 4 and connects to the inner circumferential surface of the frame 5. The base 4, supported by the spokes 6, is mounted on the front side of the cylindrical frame 5 extending along the axis of rotation X.

[0021] The frame 5 has a main body 51 forming a cylindrical shape, and flanges 52a and 52b provided on the outer periphery of both ends of the main body 51. The frame 5 is provided with a plurality of blades 10 protruding radially inward from the inner peripheral surface of the frame 5. In this example, where the number of blades 2a is generally 5, the number of blades 10 is preferably 7 to 9, or 11 to 14. However, a number of blades 10 that is n times the number of blades (10 in the example shown (n=2)) is likely to produce sound resonance and is therefore excluded.

[0022] Next, referring to Figures 2 and 3, the wing 10 provided on the frame 5 will be described. Figure 2 is a partially enlarged view showing the wing 10 provided in area A of Figure 1. Figure 3 is a cross-sectional view along line BB of Figure 2.

[0023] As shown in Figures 2 and 3, the wing 10 is located at the end of the main body 51 in the opposite direction (arrow R direction) of the rotation axis X of the frame 5. The wing 10 extends along the rotation axis X. On the inner circumferential surface of the frame 5, at the inner circumference of the end in the opposite direction of the main body 51, a pull-out surface 53 that expands in the opposite direction is provided. The wing 10 is provided in a manner that protrudes inward in the radial direction from the pull-out surface 53 of the main body 51. Alternatively, the wing 10 is provided in a manner that protrudes inward in the radial direction from a surface that spans the pull-out surface 53 of the main body 51 and the inner circumferential surface of the main body 51 that is continuous with the pull-out surface 53. Furthermore, in the example shown, the pull-out surface 53 of the main body 51 is formed into a curved surface shape that protrudes inward in the radial direction.

[0024] The blade 10 is formed, for example, such that its width in the circumferential direction is at an angle of 3° to 40° with respect to the inner circumferential surface of the frame 5. For example, when the diameter of the reversible fan 1 is 160 mm, the blade 10 is formed such that its width is at an angle of 3° to 7° with respect to the inner circumferential surface of the frame 5. When the diameter is 136 mm to 126 mm, the blade 10 is formed such that its width is at an angle of 4° to 10°. When the diameter is 80 mm, the blade 10 is formed such that its width is at an angle of 5° to 15°. When the diameter is 40 mm, the blade 10 is formed such that its width is at an angle of 10° to 30°. Furthermore, the blade 10 is formed such that it has a height that does not contact the blade 2a of the impeller 2 in the direction of protruding inward in the radial direction. Furthermore, the blade 10 is formed such that it has a length in the direction of the rotation axis X that does not obstruct the track of the impeller 2.

[0025] The winglet 10 has a first curved surface 11 forming a surface in the forward rotation direction (arrow n direction), a second curved surface 12 forming a surface in the reverse rotation direction (arrow r direction), and an edge portion 13 connecting the first curved surface 11 and the second curved surface 12. The first curved surface 11 is formed to protrude in the forward rotation direction. The second curved surface 12 is formed to be concave in the forward rotation direction. In the illustrated example, the winglet 10 is formed as a thin plate having a first curved surface 11 as the surface and a second curved surface 12 as the interior.

[0026] A stripping space 14 is formed between the second curved surface 12 of the wing 10 and the inner peripheral surface of the frame 5 facing the second curved surface 12, allowing a portion of the airflow in a predetermined direction to flow. In the illustrated example, the stripping space 14 is formed between the second curved surface 12 of the wing 10 and the push surface 53 of the body portion 51 of the frame 5.

[0027] Next, referring to Figures 4 and 5, the airflow of the reversible fan 1 will be explained. Figure 4 shows the airflow around the blade 10 when the reversible fan 1 generates airflow in the forward direction. Figure 5 shows the airflow around the blade 10 when the reversible fan 1 generates airflow in the reverse direction.

[0028] In the stripping space 14, for example, a portion of the airflow generated in the opposite direction when the impeller 2 is rotated in the reverse rotation direction is stripped and flows by the reverse rotation end 13p of the edge 13 of the blade 10. Furthermore, in the stripping space 14, for example, a portion of the airflow generated in the forward rotation direction when the impeller 2 is rotated in the forward rotation direction will flow in.

[0029] The vane 10 has an opening that is open in the forward rotation direction of the impeller and also in the direction of airflow. That is, the vane 10 is shaped to expand in the opposite direction of airflow. On the other hand, the vane 10 is shaped to be concave in the direction of airflow. In other words, the vane 10 is formed in such a way that the airflow in the opposite direction has less fluid resistance than the airflow in the forward direction. The vane 10 is configured to generate noise from the airflow colliding with it. The vane 10 is shaped to generate more noise from the airflow in the forward direction than from the airflow in the reverse direction.

[0030] As shown in Figure 4, regarding the reversible fan 1, when the impeller 2 rotates in the forward direction (arrow n direction) and generates airflow in the forward direction (arrow N direction), the airflow flows into the frame 5 from the opening in the opposite direction. Therefore, a portion of this airflow flows into the stripping space 14 of the blade 10 located at the end opposite to the main body 51. Therefore, as indicated by arrows C1 and C2, the airflow flowing into the stripping space 14 is disturbed by being sprayed onto the second curved surface 12 of the blade 10. As a result, the airflow cannot be smoothly drawn into the frame 5. At this time, the airflow is obstructed by the blade 10, thus generating noise.

[0031] On the other hand, as shown in FIG5, regarding the reversible fan 1, when the impeller 2 rotates in the reverse direction (arrow r direction) to generate airflow in the opposite direction (arrow R direction), the airflow flows in from the opening in the positive direction of the frame 5. At this time, a portion of the airflow flowing out from the opening in the positive direction collides with the first curved surface 11 of the blade 10 located at the end of the body 51 in the opposite direction. The airflow colliding with the first curved surface 11 flows along the first curved surface 11. Therefore, the airflow does not generate much noise and flows smoothly. Furthermore, the airflow flowing along the first curved surface 11 is stripped from the first curved surface 11 (arc portion) of the blade 10 to the stripping space 14 by the end 13p of the edge 13 of the blade 10. Thereby, for example, as shown by arrows D1 and D2, the stripped airflow generates a certain vortex (turbulence) 15 in the stripping space 14. Therefore, its flow is regular and stable. This reduces the noise caused by airflow in the opposite direction.

[0032] In order to deepen the understanding of the wing 10 of this embodiment, the first comparative example to the third comparative example, which have different shapes from this embodiment and have different noise levels when the air is supplied in the forward direction and when the air is supplied in the reverse direction, will be described using Figures 6 to 8.

[0033] Figure 6 is a perspective view of the blade 100 of the first comparative example. The blade 100 is formed as a straight protrusion that extends vertically inward in the radial direction from the inner peripheral surface 151 of the frame 150. However, the surfaces of the blade 100 configured in this way are planar in the forward rotation direction (arrow n direction). Therefore, when the impeller 2 rotates in the reverse rotation direction (arrow r direction) and generates airflow in the opposite direction (arrow R direction), as shown by arrows E1 and E2, the airflow is obstructed by the blade 100. As a result, the noise level increases when air is delivered in the opposite direction. Consequently, it is impossible to suppress the difference in noise level.

[0034] Figure 7 is a perspective view of the blade 200 of the second comparative example. The surface of the blade 200 in the forward rotation direction (arrow n direction) is curved, just like the blade 10 in the aforementioned embodiment. Furthermore, the surface of the blade 200 in the reverse rotation direction (arrow r direction) is planar, just like the blade 100 in the first comparative example. With the blade 200 configured in this way, since the surface of the blade 200 in the forward rotation direction is curved, the noise level is slightly reduced when the impeller 2 rotating in the reverse direction generates airflow in the opposite direction (arrow R direction). However, since the surface of the blade 200 in the reverse rotation direction is planar, the noise level hardly increases when the impeller 2 rotating in the forward direction generates airflow in the forward direction (arrow N direction), and therefore the difference between the noise level when airflow is delivered in the forward direction and the noise level when airflow is delivered in the reverse direction cannot be reduced.

[0035] Figure 8 is a perspective view of the blade 300 of the third comparative example. The surface of the blade 300 in the forward rotation direction (arrow n direction) is constructed as a curved surface, similar to the blade 10 in the aforementioned embodiment. Furthermore, the surface of the blade 300 in the reverse rotation direction (arrow r direction) is constructed as a curved surface protruding in the reverse rotation direction. However, unlike the blade 10 in the aforementioned embodiment, a stripping space 14 is not provided. With the blade 300 constructed in this way, when the impeller 2 rotating in the forward rotation direction generates airflow in the forward direction (arrow N direction), and when the impeller 2 rotating in the reverse rotation direction generates airflow in the opposite direction (arrow R direction), the turbulence of the airflow increases. Therefore, the noise level increases when air is supplied in both directions.

[0036] In contrast, as shown in FIG2, in the reversible fan 1 of this embodiment, the blade 10 is provided in a manner that protrudes radially inward from the inner peripheral surface of the frame 5. The blade 10 has a first curved surface 11, a second curved surface 12, and an edge 13. The first curved surface 11 forms the surface of the blade 10 in the forward rotation direction and protrudes in that direction. The second curved surface 12 forms the surface of the blade 10 in the reverse rotation direction and is recessed in the forward rotation direction. The edge 13 connects the first curved surface 11 and the second curved surface 12. Furthermore, a separation space 14 is formed between the second curved surface 12 and the inner peripheral surface of the frame 5. When the impeller 2 rotates in the reverse rotation direction, a portion of the airflow is separated by the reverse rotation direction end 13p of the edge 13. Therefore, the airflow generated in the forward rotation direction (positive direction) during forward rotation collides with the second curved surface 12. The airflow colliding with the second curved surface 12 is disturbed by it, generating significant noise. Conversely, the airflow generated during the reverse rotation of the impeller 2, flowing in the opposite direction, collides with the first curved surface 11. The airflow colliding with the first curved surface 11 flows along it. Therefore, the noise does not increase. Furthermore, a portion of the airflow generated during reverse rotation is separated by the stripping space 14, creating vortices. This stabilizes the airflow during reverse rotation, thus suppressing noise. In this way, noise during reverse airflow is suppressed, while noise during forward airflow is increased. Therefore, the noise level during forward airflow is made equal to the noise level during reverse airflow.

[0037] Furthermore, according to the reversible fan 1, the vane 10 is concave for the airflow in the forward direction and expands for the airflow in the reverse direction. That is, the vane 10 is configured to give the airflow in the reverse direction less fluid resistance than the airflow in the forward direction. Therefore, the vane 10 generates more noise for the airflow in the forward direction than for the airflow in the reverse direction. Therefore, it is possible to make the noise level when the airflow is delivered in the forward direction the same as the noise level when the airflow is delivered in the reverse direction. Moreover, at this time, without affecting the airflow characteristics, static pressure characteristics, and power consumption of the reversible fan 1, it is possible to make the noise level when the airflow is delivered in the forward direction the same as the noise level when the airflow is delivered in the reverse direction.

[0038] Furthermore, according to the reversible fan 1, a push-pull surface 53 with an increased diameter in the opposite direction is formed at the end of the frame 5 in the opposite direction of the rotation axis X. The blade 10 is arranged such that it extends from the push-pull surface 53 of the frame 5 in the direction of the rotation axis X. With this structure, even with the blade 10, the frame 5 can be easily demolded.

[0039] (Modified Example) Next, a modified example of the winglet will be described. Figure 9 is a cross-sectional view showing the winglet 10A in the first modified example. As shown in Figure 9, the winglet 10A differs from the winglet 10 in that the cross-sectional shape of the stripping space 14A is formed to be closer to a rectangle. The winglet 10A is formed such that the surface 53A on the side constituting the frame 5A of the stripping space 14A, that is, the surface 53A facing the second curved surface 12A of the winglet 10A, extends along the positive direction of the rotation axis X (arrow N direction).

[0040] Figure 10 is a cross-sectional view showing the wing 10B of the second modified example. As shown in Figure 10, the wing 10B is formed such that the surface 53B on the side of the frame 5B constituting the stripping space 14B, that is, the surface 53B facing the second curved surface 12B of the wing 10B, is a curved surface that is recessed outward in the radial direction. In this respect, the wing 10B is different from the wing 10 in the embodiment that is formed with a curved surface that protrudes inward in the radial direction. Furthermore, the shape of the curved surface that is recessed outward in the radial direction may only be provided on the surface 53B facing the second curved surface 12B, or the shape of the recess may be provided on the entire push surface 53 of the body portion 51 of the frame 5 described in the embodiment.

[0041] Figure 11 is a cross-sectional view of the wing 10C in the third variation. As shown in Figure 11, the wing 10C differs from the wing 10B in the second variation shown in Figure 10 in that the direction in which the wing 10C extends is inclined relative to the rotation axis X. The wing 10C is configured to incline further inward in the radial direction (away from the surface 53C on the side of the frame 5C constituting the stripping space 14C) as it moves in the opposite direction (arrow R direction). In this respect, the wing 10C differs from the wing 10B in the second variation, which is configured to extend in the direction of the rotation axis X.

[0042] Figure 12 is a cross-sectional view showing the wing 10D of the fourth modified example. As shown in Figure 12, the wing 10D is formed to tilt inward in the radial direction (away from the surface 53D of the frame 5D constituting the stripping space 14D) as it moves in the opposite direction (arrow R direction). In this respect, the wing 10D is consistent with the wing 10C of the third modified example shown in Figure 11. However, the wing 10D is formed to include a curved surface that protrudes inward in the radial direction. In this respect, the wing 10C of the third modified example, which does not have such a curved surface, is different from the wing 10D.

[0043] Figure 13 is a cross-sectional view showing the wing 10E of the fifth modification. As shown in Figure 13, compared with the wing 10D of the fourth modification shown in Figure 12, the wing 10E has its surface 53E, which forms the frame 5E side of the stripping space 14E, that is, the surface 53E facing the second curved surface 12E of the wing 10E, formed along the direction of the rotation axis X. In this respect, the wing 10E is different from the wing 10D of the fourth modification of Figure 12, which is formed as a curved surface including an outer concave surface in the radial direction.

[0044] Figure 14 is a diagram showing the wing 10F of the sixth modified example. As shown in Figure 14, the wing 10F is formed such that the surface 53F constituting the frame 5F side of the stripping space 14F, that is, the surface 53F facing the second curved surface 12F of the wing 10F, is formed along the direction of the rotation axis X. In this respect, the wing 10F is different from the wing 10 of the embodiment of Figure 2, which is formed with a curved surface that includes an inwardly projecting curved surface in the radial direction.

[0045] Figure 15 is a diagram showing the wing 10G of the seventh modified example. As shown in Figure 15, the wing 10G is formed by making an arc-shaped notch in the radially outward side of the peripheral wall of the frame 5G, which is the side facing the second curved surface 12G of the wing 10G, on the side of the frame 5G constituting the stripping space 14G. In this respect, the wing 10G is different from the wing 10 of the embodiment of Figure 2, which is formed to include a curved surface that protrudes inward in the radial direction.

[0046] Figure 16 is a diagram showing the wing 10H of the eighth modified example. As shown in Figure 16, compared with the wing 10 of the embodiment shown in Figure 2, the wing 10H is formed by making a rectangular notch in the radial direction outward of the peripheral wall of the frame 5H, which is the surface 53H facing the second curved surface 12H of the wing 10H, on the side constituting the stripping space 14H. In this respect, the wing 10H is different from the wing 10 of the embodiment of Figure 2, which is formed to include a curved surface that protrudes inward in the radial direction.

[0047] According to the aforementioned modified example, each of the blades 10A to 10H can ensure a large stripping space 14A to 14H. Therefore, the noise level during forward airflow can be improved. In this way, the noise level during forward airflow can be made equal to the noise level during reverse airflow.

[0048] The present embodiment has been described above. However, the technical scope of the present embodiment should not be limited by the foregoing description of the embodiment, and is self-evident. The present embodiment is merely an example, and those skilled in the art will understand that various modifications to the embodiment can be made within the scope of the disclosure described in the claims. The technical scope of this disclosure should be determined according to the scope disclosed in the claims and its equivalents. The purpose of the detailed description above is for illustration and description. Various modifications and changes can be made based on the above teachings. It is not intended to be exhaustive or to limit the invention to the precise form disclosed herein. Although the invention is described using specific language of structural features and / or methodological actions, it is understood that the invention as defined in the claims is not limited to the specific features or actions described above. Rather, the specific features or actions disclosed above are merely exemplary forms for implementing the claims. [Simplified Explanation of the Diagram]

[0004] [Fig. 1] is a perspective view of the reversible fan of the disclosed embodiment viewed from the opposite direction. [Fig. 2] is a partially enlarged view of the airfoil provided in region A of Fig. 1. [Fig. 3] is a cross-sectional view along line BB of Fig. 2. [Fig. 4] is a diagram showing the flow of wind around the airfoil when generating airflow in the forward direction. [Fig. 5] is a diagram showing the flow of wind around the airfoil when generating airflow in the reverse direction. [Fig. 6] is a perspective view of the airfoil of the first comparative example. [Fig. 7] is a perspective view of the airfoil of the second comparative example. [Fig. 8] is a perspective view of the airfoil of the third comparative example. [Fig. 9] is a cross-sectional view of the airfoil of the first modified example. [Fig. 10] is a cross-sectional view of the airfoil of the second modified example. [Fig. 11] is a cross-sectional view of the airfoil of the third modified example. [Fig. 12] is a cross-sectional view of the airfoil of the fourth modified example. [Fig. 13] is a cross-sectional view of the wing in the fifth modified example. [Fig. 14] is a view of the wing in the sixth modified example. [Fig. 15] is a view of the wing in the seventh modified example. [Fig. 16] is a view of the wing in the eighth modified example.

Claims

1. A reversible fan comprising: a vane configured to generate both forward and reverse airflow; an impeller rotatable about a rotation axis; a motor for rotating the impeller; and a cylindrical frame housing the impeller and the motor, the frame having an inner circumferential surface extending from the forward end to the reverse end, the inner circumferential surface having a third curved surface continuous with the inner circumferential surface, the third curved surface being disposed at the reverse end of the frame, the diameter of the third curved surface extending in the reverse direction; the vane having a shape that generates greater noise when generating forward airflow than when generating reverse airflow, and protruding radially inward from the inner circumferential surface of the frame; the vane being disposed on the inner circumferential surface along the third curved surface in the direction of the rotation axis.

2. The reversible fan as described in claim 1, wherein, The aforementioned blade has an opening that is open in the positive rotation direction of the aforementioned impeller and also open in the positive direction of airflow.

3. The reversible fan as described in claim 1, wherein, When the aforementioned positive airflow is generated, the rotation direction of the aforementioned impeller is referred to as the positive rotation direction, and when the aforementioned negative airflow is generated, the rotation direction of the aforementioned impeller is referred to as the negative rotation direction. The aforementioned blade has a first curved surface, a second curved surface, and an edge. The aforementioned first curved surface is located in the aforementioned positive direction relative to the aforementioned second curved surface. The aforementioned first curved surface protrudes in the aforementioned positive rotation direction. The aforementioned second curved surface is recessed in the aforementioned positive rotation direction. The aforementioned edge connects the aforementioned first curved surface and the aforementioned second curved surface. Furthermore, a separation space is formed between the aforementioned second curved surface and the inner peripheral surface of the aforementioned frame. The aforementioned separation space is configured such that when the aforementioned impeller rotates in the aforementioned negative rotation direction, a portion of the aforementioned negative airflow is separated by the aforementioned edge and flows into the aforementioned separation space.

4. The reversible fan as described in claim 3, wherein, The portion of the inner circumferential surface of the aforementioned frame that faces the aforementioned second curved surface of the aforementioned winglet is recessed outward in the aforementioned radial direction.

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