TWI742364B - Impeller and axial fan - Google Patents

Abstract

The impeller (11) system includes: a hub part (2) that can rotate around a rotating shaft (6); and blades (1) that extend radially from the hub part (2). The top-view shape of the blade (1) when the blade (1) is projected vertically to the rotating shaft (6) is the outer edge of the blade (1) facing the hub part (2) by the rotation of the blade (1) The leading edge portion (13) of the blade in the traveling direction has: a first curved portion (17) that is curved in the opposite direction of the traveling direction; a second curved portion (18) is set closer to the first curved portion (17) The side of the rotating shaft (6) is curved in the direction of travel; and the third bending part (19) is arranged closer to the opposite side of the rotating shaft (6) than the first bending part (17), and is curved in the direction of travel.

Description

Impeller and axial fan

The present invention relates to an impeller and an axial fan that generate air flow in the direction of the rotation axis.

In order to reduce the noise generated by the rotation of the impeller, various axial fan shapes have been proposed to form the impeller. In Patent Document 1, there is disclosed an impeller in which the top view shape of the blade when the blade is vertically projected onto the rotating shaft is regarded as the shape of the forward blade chord centerline toward the direction of travel of the blade by the rotation of the impeller. The blade chord center line is the line connecting the center of the blade chord line. The so-called advancing blade chord centerline toward the direction of travel means that as the spin axis leaves, the blade chord centerline is bent forward in the direction of travel. In the impeller of Patent Document 1, the outflow of the airflow entering from the leading edge of the blade in the traveling direction of the blade is promoted, so that the separation vortex generated at the leading edge of the blade becomes a stable vertical vortex. Seek to reduce the noise caused by the peeling vortex. [Advanced Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 2-2000

[The problem to be solved by the invention]

However, as the impeller system advances toward the centerline of the blade chord, the stress concentration in the vicinity of the leading edge of the blade becomes more pronounced. According to the prior art disclosed in Patent Document 1, it is difficult to both reduce noise and reduce stress concentration.

The present invention was developed in view of the above problems, and its purpose is to obtain an impeller that can reduce noise and reduce stress concentration. [Means to solve the problem]

In order to solve the above-mentioned problems and achieve the objective, the impeller system of the present invention includes: a hub portion that can rotate around a rotating shaft; and blades that extend radially from the hub portion. The top-view shape of the blade when the blade is projected perpendicularly to the axis of rotation is the outer edge of the blade, and the leading edge of the blade in the direction of travel of the blade made by the rotation, which faces the hub part, has: the first bend, which is in the direction of travel Bending in the opposite direction; the second bending part is set closer to the rotating shaft than the first bending part, and is bent in the direction of travel; and the third bending part is set closer to the rotating shaft than the first bending part Bend in the direction of travel. [Effects of the invention]

The impeller of the present invention can exert the effect of reducing noise and reducing stress concentration.

Hereinafter, the impeller and the axial fan according to the embodiment of the present invention will be described in detail based on the drawings. Furthermore, the present invention is not limited to this embodiment.

Implementation mode 1. Fig. 1 is a diagram showing a schematic structure of an axial fan 10 having an impeller 11 according to Embodiment 1 of the present invention. The axial fan 10 is used for cooling fans, ventilating fans, air conditioners, or equipment.

The axial flow fan 10 has: an impeller 11, which can generate air flow by rotation; and a motor 12, which drives the impeller 11 in rotation. In addition, the axial flow fan 10 has a frame that rotatably accommodates the impeller 11. The motor 12 is held by the frame. The frame has an opening through which the air flow generated by the rotation of the impeller 11 passes. At the edge of the opening, there is a bell mouth whose diameter expands toward the upstream side of the airflow. In Figure 1, the illustration of the frame and the bell mouth is omitted.

The impeller 11 system has: a supporting blade 5, which is taken from a sheet of material; and three curved plates 3, which are joined to the supporting blade 5. The supporting blade 5 has: a hub part 2 which is a main plate part at the center of the supporting blade 5; and three mounting parts 4 arranged around the hub part 2. The hub portion 2 is connected to the motor 12, and driven by the motor 12, the hub portion 2 is rotated in the rotation direction C with the rotating shaft 6 as the center.

Each curved plate 3 constitutes the blade 1. The bent plate 3 is formed by applying press processing to sheet metal. The curved plate 3 is mounted on each mounting portion 4 and is joined to the end of the mounting portion 4 on the opposite side of the rotating shaft 6. The mounting portion 4 corresponds to the root portion on the side of the hub portion 2 in the blade 1. The curved plate 3 is joined to the mounting part 4 by welding or riveting.

In this way, the impeller 11 has a hub portion 2 that is rotatable about the rotating shaft 6 and three blades 1 that extend radially from the hub portion 2. Each blade 1 is composed of a curved plate 3 and a mounting portion 4. The blade 1 is a part on the opposite side of the rotating shaft 6 and has a curved shape inclined toward the upstream side of the airflow. The axial fan 10 rotates in the rotation direction C by the impeller 11 to generate an air flow in the direction of the arrow A parallel to the direction of the rotation axis 6.

The impeller 11 is not limited to the one composed of the supporting blade 5 and the curved plate 3, and it may be one having a cylindrical hub portion 2 and a blade 1 attached to the hub portion 2. The number of blades 1 provided on the impeller 11 is not limited to three, and it may be any number. The blades 1 provided on the impeller 11 all have the same three-dimensional shape. For the description of the blade 1 described below, it is assumed that each blade 1 provided in the impeller 11 is common.

Fig. 2 is a diagram showing the top view shape of the impeller 11 shown in Fig. 1. Fig. 2 shows the top view shape of the impeller 11 when the impeller 11 is vertically projected onto the rotating shaft 6. Fig. 3 is a diagram showing the top-view shape of the blade 1 and the hub portion 2 of the impeller 11 shown in Fig. 2. In Figures 2 and 3, the X axis and the Y axis are perpendicular to each other. The origin O of the X axis and the Y axis is the position of the rotation axis 6.

The outer edge of the top view of the blade 1 has: the front edge 13 of the blade, which is the part facing the direction of travel of the blade 1 made by the rotation of the hub part 2; The portion on the opposite side of the direction; the outer peripheral portion 15 of the blade, which is the portion facing the opposite side of the rotating shaft 6, and the portion of the inner peripheral portion 16 of the blade, which faces the rotating shaft 6. In the plan view shape, the inner peripheral portion 16 of the blade is formed as an arc along the outer edge of the hub portion 2. The blade 1 has a tip portion 20 protruding in the traveling direction of the blade 1.

In the plan view shape, the outer peripheral portion 15 of the blade is formed as an arc with the rotating shaft 6 as the center. The outer peripheral portion 15 of the blade may be a curve other than an arc. In the three-dimensional shape of the blade 1, the outer peripheral portion 15 of the blade is curved toward the upstream side of the airflow. The impeller 11 is bent on the outer peripheral portion 15 of the blade to suppress the generation of blade end vortices caused by the air leakage from the pressure surface side of the blade 1 in the outer peripheral portion 15 of the blade to the negative pressure surface side of the blade 1. In this way, the impeller 11 can reduce the blade end vortex generated by the blade 1 and the noise caused by interference with the pressure surface, other blades 1 or the aforementioned bell mouth.

In a plan view, the leading edge portion 13 of the blade has: a first curved portion 17 that is curved in a direction opposite to the traveling direction of the blade 1, and a second curved portion 18 is provided closer to the rotating shaft 6 than the first curved portion 17 The side is curved in the direction of travel; and the third bending portion 19 is provided on the opposite side of the rotating shaft 6 than the first bending portion 17 and bends in the direction of travel. In this way, the blade front edge portion 13 forms a curve in which the direction of bending changes between the first bending portion 17 and the second bending portion 18 and between the first bending portion 17 and the third bending portion 19. The third curved portion 19 constitutes the outer peripheral portion 15 and the tip portion 20 of the blade. In the following description, sometimes the direction of travel of the blade 1 is referred to as the front, and the direction opposite to the direction of travel of the blade 1 is sometimes referred to as the rear. In addition, a combination of the first bending portion 17 and the second bending portion 18 and the third bending portion 19 may be referred to as unevenness. In other words, for example, in the second figure of the present application, the combined shape of the first bending portion 17 and the second bending portion 18 and the third bending portion 19 is a concave-convex shape with a turning point at least at the position 27.

The line segment 21 represents the first tangent as the tangent in the position 25 of the tip portion 20 in the outer peripheral portion 15 of the blade. The position 25 is a position behind the vertex 24 between the outer peripheral portion 15 of the blade and the front edge portion 13 of the blade. The line segment 22 represents the second tangent as the tangent included in the position 26 of the tip portion 20 in the third bending portion 19. The position 26 is a position closer to the side of the rotation shaft 6 than the apex 24. The line segment 23 represents the third tangent as the tangent at the position 27 of the end on the side of the second bending portion 18 in the first bending portion 17.

The blade chord centerline 30 of the blade 1 is further bent forward as it departs from the rotating shaft 6. The tip portion 20 is toward the front, the tip becomes thinner and protrudes toward the front. The angle θ1 as the first angle is regarded as the angle between the line segment 21 and the line segment 22, and includes the angle in the range of the tip portion 20. The angle θ2 as the second angle is regarded as the angle between the line segment 22 and the line segment 23, and includes the angle in the range of the first bending portion 17. The angle θ1 is smaller than the angle θ2.

Fig. 4 is a diagram illustrating the state of airflow around the blade 1 shown in Fig. 3. In Figure 4 In, it shows the cross-section along the IV-IV line shown in Fig. 3. As shown in FIG. 3, the blade end vortex 28 is generated in the vicinity of the outer peripheral portion 15 of the blade in the blade 1. The blade end vortex 28 is formed by the pressure difference between the pressure surface 31 and the negative pressure surface 32 of the blade 1 when the impeller 11 rotates. In the front edge portion 13 of the blade, a separation vortex 29 is formed in the vicinity of the front edge portion 13 of the blade because the airflow from the front flows in and the airflow is sucked in from the side of the bell mouth. The axial flow fan 10 is a blade end vortex 28 and a separation vortex 29 generated by the blade 1, and generates noise by colliding with other blades 1, a bell mouth or a frame adjacent to the blade 1.

On the negative pressure surface 32 side of the blade 1, an airflow 33 in the turbulent boundary layer is generated. The larger the separation vortex 29 generated near the front edge portion 13 of the blade, the more turbulent the airflow 33 flows toward the rear edge portion 14 of the blade, whereby the vortex 34 becomes larger after being generated behind the rear edge portion 14 of the blade. In the axial flow fan 10, the larger the separation vortex 29 and the rear flow vortex 34, or the larger the turbulence of the airflow 33, the worse the noise characteristics.

In the first embodiment, the tip portion 20 that becomes sharper toward the front is provided. By this, the longitudinal vortex system that revolves from the leading edge portion 13 of the blade to the side of the negative pressure surface 32 adheres to the negative pressure surface 32 and becomes The separation vortex 29 generated by the leading edge portion 13 of the blade is a relatively stable longitudinal vortex. With the separation vortex 29 being more stable, the turbulence of the airflow 33 can be suppressed, and the rear flow vortex 34 can be made smaller. Thereby, the axial flow fan 10 can suppress the deterioration of noise characteristics.

Next, the relationship between the shape of the tip portion 20 and the strength of the blade 1 will be described. FIG. 5 is a diagram illustrating the relationship between the shape of the blade 1 shown in FIG. 3 and the strength of the blade 1. In Fig. 5, the shape of the blade 1 is shown when the shape of the blade 1 is different so that the curvature of the center line 30 of the blade chord becomes larger. With the state from the left to the right in Figure 5, the curvature of the blade chord center line 30 becomes larger, and the protrusion toward the front of the tip portion 20 becomes larger. In addition, in Fig. 5, the shape of the blade 1 is simplified, and the illustration of the structure that is unnecessary for the description is omitted.

The line segment 35 is a straight line connecting a position 36 on an arbitrary radius R in the front edge portion 13 of the blade and a position 37 on the outer peripheral portion 15 of the blade. The line 35 is perpendicular to the tangent to the outer peripheral portion 15 of the blade at the position 37. As the protrusion of the tip portion 20 to the front becomes larger, the angle θ1 becomes smaller. The smaller the angle θ1, the shorter the line segment 35 becomes. The shorter the line 35 is, the stress concentration in the vicinity of the leading edge 13 of the blade becomes It becomes more pronounced, therefore, the blade 1 is more likely to deform.

Assuming that the front edge portion 13 of the blade is not provided with the above-mentioned concavities and convexities, when the angle θ1 is reduced by increasing the forward bending of the blade chord centerline 30, as shown above, the noise caused by the stability of the peeling vortex 29 can be achieved The characteristics are improved, and in addition, the blade 1 becomes more susceptible to deformation due to stress concentration. In the first embodiment, by providing concavities and convexities at the leading edge portion 13 of the blade, stress concentration in the blade 1 can be alleviated.

Fig. 6 is a plan view showing the negative pressure surface 32 side of the impeller 11 shown in Fig. 2. Fig. 7 is a plan view showing the pressure surface 31 side of the impeller 11 shown in Fig. 2. In the portion 40 surrounded by the broken line in each blade 1, the stress generated by the rotation of the impeller 11 is concentrated. The portion 40 is near the front edge portion 13 of the blade and is close to the position where the curved plate 3 is joined to the mounting portion 4. The position of the curved plate 3 joined to the mounting portion 4 becomes a fulcrum and the blade 1 is deformed. Therefore, the stress is concentrated by the portion 40 of each blade 1.

Here, the blade 1 with the tip portion 20 having the same angle θ1 will be described where the blade front edge 13 is not provided with concavities and convexities, and the blade front edge 13 is provided with concavities and convexities in the first embodiment, and the stress is measured.的例。 Examples. The stress example described here is when the rotation speed of the impeller 11 is 1800 min ^-1 , the thickness of the curved plate 3 is 1 mm, the thickness of the supporting blade 5 is 3 mm, and the material of the curved plate 3 and the supporting blade 5 is general steel stress. When there is no unevenness on the leading edge 13 of the blade, the maximum stress that the blade 1 bears is 57.2 MPa. In addition, in the case of Embodiment 1 in which the front edge portion 13 of the blade is provided with unevenness, the maximum stress that the blade 1 bears is 48.2 MPa. The maximum stress that the blade 1 bears is due to the unevenness on the leading edge 13 of the blade, which is about 15.7% less than the case where the unevenness is not provided. In this way, the impeller 11 is provided with the first bending portion 17, the second bending portion 18 and the third bending portion 19 at the leading edge portion 13 of the blade, so that the stress concentration in the blade 1 can be alleviated.

The impeller 11 can suppress the deformation of the blade 1 by alleviating the stress concentration in the blade 1. Compared with the case where the impeller 11 increases the thickness of the blade 1 in order to increase the strength of the blade 1, the weight can be reduced, and the amount of material used can be reduced, thereby reducing the manufacturing cost. In addition, the impeller 11 is compared with the case where a high-strength and expensive material is used as the material of the blade 1 in order to increase the strength of the blade 1. Down, the cost of materials can be suppressed.

Next, the relationship between the above-mentioned angle θ1 and angle θ2 and the characteristics of the impeller 11 will be described. Figure 8 is a diagram illustrating the noise characteristics of the impeller 11 of the first embodiment. Figure 9 is a diagram illustrating the air volume-static pressure characteristics of the impeller 11 of the first embodiment. Fig. 10 is a diagram showing an example of the angle θ1 and the angle θ2 shown in Fig. 2 for the impeller 11 of the first embodiment. The graph shown in Figure 8 is an example of the relationship between air volume and specific noise level. The graph shown in Figure 9 is an example of the relationship between air volume and static pressure.

The "impeller A1" is the impeller 11 of the first embodiment, in which the angle θ1 is 42.1 degrees, and the angle θ2 is 130.0 degrees. The "impeller A2" is the impeller 11 of the first embodiment, in which the angle θ1 is 29.4 degrees, and the angle θ2 is 111.6 degrees. The "impeller A3" is the impeller 11 of the first embodiment, in which the angle θ1 is 20.2 degrees, and the angle θ2 is 90.0 degrees. "Impeller B1" is the impeller of the comparative example, and among them, it is one that does not have the above-mentioned unevenness. In the "impeller B1", the angle θ1 is 67.6 degrees. "Impeller A1", "Impeller A2", "Impeller A3" and "Impeller B1" are those with a diameter of 260mm. In the impeller 11 of the first embodiment, the angle θ1 is included in the range of 20.2 degrees to 42.1 degrees.

The blade 1 has an angle θ2 greater than 90 degrees, and the first curved portion 17, the second curved portion 18, and the third curved portion 19 are smoothly connected. Thereby, the impeller 11 can reduce the influence of the airflow in the front edge portion 13 of the blade due to the unevenness on the front edge portion 13 of the blade.

In Figure 8, the vertical axis represents the total pressure reference ratio noise K _T (dB), and the horizontal axis represents the air volume Q (m ³ /min). In Figure 9, the vertical axis represents the static pressure P _s (Pa), and the horizontal axis represents the air volume Q (m ³ /min). The relationship between specific noise K _T and air volume Q is expressed by formula (1). In the formula (1), SPL _A represents the noise level applied with the correction caused by the A characteristic. The P _T series means total pressure.

K _T =SPL _A -10‧log(Q‧P _T ^2.5 )‧‧‧(1)

When referring to Figure 9, the air volume-static pressure characteristics of "impeller A1", "impeller A2" and "impeller A3" are regarded as the same as the air volume-static pressure characteristics of "impeller B1". When referring to Figure 8, the relationship between the noise characteristics of "Impeller A1" and "Impeller A2" and "Impeller A3" is the relationship of "Impeller B1" In comparison, it is improved to reduce the noise by up to about 2dB.

Fig. 11 is a diagram showing an example of the relationship between the angle θ1 of the impeller 11 and the air volume Q in the first embodiment. The graph shown in Fig. 11 is an example of the relationship between the angle θ1 in the open point where the static pressure is zero and the air volume ratio ΔQ. The air volume ratio ΔQ represents the ratio of the air volume Q of the "impeller B1" whose angle θ1 is 67.6 degrees to the air volume Q of each impeller 11. In Figure 11, the vertical axis represents the air volume ratio ΔQ (%), and the horizontal axis represents the angle θ1 (degrees). The curve in the graph in Figure 11 shows the relationship between the angle θ1 and the air volume ratio ΔQ for "impeller A1", "impeller A2", "impeller A3" and "impeller B1". The graph showing the relationship between the angle θ1 and the air volume ratio △Q is obtained by the relationship between the angle θ1 between the interpolation curves and the air volume ratio △Q.

According to Fig. 11, it can be confirmed that the smaller the angle θ1, the smaller the air volume ratio ΔQ tends to be. However, when the angle range of the angle θ1 is changed from 67.6 degrees to 20.2 degrees, the decrease in the air volume ratio ΔQ is suppressed by 0.6% at the maximum. Therefore, the impeller 11 of the first embodiment can be said to be limited in the reduction of the air volume caused by the reduction of the angle θ1.

Fig. 12 is a diagram showing an example of the relationship between the angle θ1 of the impeller 11 and the minimum specific noise K _{Tmin in the first embodiment.} In Figure 12, the vertical axis represents the minimum specific noise difference ΔK _Tmin (dB), and the horizontal axis represents the angle θ1 (degrees). The minimum specific sound level difference △ K _Tmin based θ1 represents an angle of 67.6 degrees "impeller B1" minimum noise ratio of the difference between the smallest noise ratio K _Tmin K _Tmin with the impeller 11. The curve in the graph in Figure 12 shows the relationship between the angle θ1 for "impeller A1", "impeller A2", "impeller A3" and "impeller B1" and the minimum specific noise difference △K _Tmin. The angle θ1 represents the minimum noise graph showing the relationship of the ratio of the difference between △ K _Tmin, the angle between lines by interpolation curve of the minimum order θ1 noise ratio relationship of a difference △ K _Tmin.

According to Fig. 12, when the angle θ1 is in the range of 15 degrees to 55 degrees, the noise characteristic of the impeller 11 is improved to a minimum specific noise difference ΔK _Tmin lowered by more than 0.5dB. Furthermore, when the angle θ1 is 29.4 degrees, the noise characteristic of the impeller 11 is improved to a minimum specific noise difference ΔK _Tmin lowered by 2 dB.

Fig. 13 is a diagram showing an example of the relationship between the angle θ1 of the impeller 11 and the maximum stress σ max in the first embodiment. In Figure 13, the vertical axis represents the maximum stress ratio △σ max (%), and the horizontal axis represents Angle θ1 (degrees). The maximum stress ratio Δσ max indicates the ratio of the maximum stress σ max of the "impeller B1" with an angle θ1 of 67.6 degrees to the maximum stress σ max of each impeller 11. The curve in the graph in Figure 13 shows the relationship between the angle θ1 and the maximum stress ratio Δσ max for "impeller A1", "impeller A2", "impeller A3" and "impeller B1". The graph showing the relationship between the angle θ1 and the maximum stress ratio Δσ max is obtained by interpolating the relationship between the angle θ1 between the curves and the maximum stress ratio Δσ max.

According to Figure 13, when the angle θ1 is included in the range of 20.2 degrees to 55 degrees, the maximum stress σ max is reduced by 4% to 9%. The impeller 11 is set within the range of 20.2°~42.1° by the angle θ1, which can reduce noise and ease stress concentration. Moreover, as described above, because the angle θ2 is greater than 90 degrees, the relationship θ2>θ1 holds. Therefore, when the angle θ1 of the impeller 11 is smaller than the angle θ2, noise and stress concentration can be reduced.

According to the first embodiment, the impeller 11 is attached to the blade leading edge portion 13 of each blade 1, and the first bending portion 17, the second bending portion 18, and the third bending portion 19 are provided. If the impeller 11 has an angle θ1 smaller than the angle θ2 in the top view shape of the blade 1, noise and stress concentration can be reduced. Thereby, the impeller 11 series can exert the effect of reducing noise and reducing stress concentration.

The structure shown in the above embodiment is an example of the content of the present invention, which can be combined with other well-known technologies, or a part of the structure can be omitted or changed without departing from the scope of the present invention.

1: blade

2: Wheel hub

3: curved board

4: Installation department

5: Support the blade

6: Rotation axis

10: Axial fan

11: Impeller

12: Motor

13: The leading edge of the blade

14: The trailing edge of the blade

15: The outer periphery of the blade

16: The inner circumference of the blade

17: The first bend

18: The second bend

19: The third bend

20: Tip

21, 22, 23, 35: line segment

24: vertex

25, 26, 27, 36, 37: position

28: Blade end vortex

29: Peeling Vortex

30: blade chord centerline

31: Pressure side

32: negative pressure surface

33: Airflow

34: Back flow vortex

40: part

C: Rotation direction

Figure 1 is a diagram showing a schematic structure of an axial fan having an impeller according to Embodiment 1 of the present invention. Fig. 2 is a diagram showing the top view shape of the impeller shown in Fig. 1. Fig. 3 is a diagram showing the top shape of the blades and the hub portion of the impeller shown in Fig. 2. Fig. 4 is a diagram illustrating the state of airflow around the blade shown in Fig. 3. Figure 5 is a diagram illustrating the relationship between the shape of the blade and the strength of the blade shown in Figure 3. Fig. 6 is a plan view showing the negative pressure surface side of the impeller shown in Fig. 2. Fig. 7 is a plan view showing the pressure surface side of the impeller shown in Fig. 2. Figure 8 is a diagram illustrating the noise characteristics of the impeller in the first embodiment. Figure 9 is a diagram illustrating the air volume-static pressure characteristics of the impeller in the first embodiment. Fig. 10 is a diagram showing an example of the angle θ1 and the angle θ2 shown in Fig. 2 for the impeller of the first embodiment. Fig. 11 is a diagram showing an example of the relationship between the angle θ1 of the impeller and the air volume Q in the first embodiment. Figure 12 is a diagram showing an example of the relationship between the angle θ1 of the impeller and the minimum specific noise K _{Tmin in the first embodiment.} Figure 13 is a diagram showing an example of the relationship between the angle θ1 of the impeller and the maximum stress σmax of the first embodiment.

1: blade

2: Wheel hub

3: curved board

4: Installation department

5: Support the blade

6: Rotation axis

11: Impeller

13: The leading edge of the blade

14: The trailing edge of the blade

15: The outer periphery of the blade

16: The inner circumference of the blade

17: The first bend

18: The second bend

19: The third bend

20: Tip

21: Line segment

22: line segment

23: line segment

24: vertex

25: location

26: Location

27: Location

Claims (2)

An impeller, comprising: a hub portion capable of rotating around a rotation axis; and blades extending radially from the hub portion, and the top view shape of the blade when the blade is projected perpendicularly to the rotation axis is the outer side of the blade Among the edges, the leading edge portion of the blade facing the direction of travel of the blade by rotation of the hub portion has: a first curved portion that is curved in a direction opposite to the direction of travel; a second curved portion is set to be larger than the first 1 The bending part is also closer to the side of the rotating shaft and bends in the direction of travel; and the third bending part is set to be closer to the opposite side of the rotating shaft than the first bending part, and bends in the direction of travel; The shape formed by the combination of the first curved portion, the second curved portion and the third curved portion is a concave-convex shape with a twist; the blade has a tip portion protruding in the direction of travel; it will be included in the top view shape of the blade The tangent at the position of the tip portion in the outer peripheral portion of the blade opposite to the rotating shaft is regarded as the first tangent, and the tangent at the position of the tip included in the third curved portion is regarded as the second For the tangent line, the tangent line located in the position of the end on the side of the second bending part in the first bending part is regarded as the third tangent line, and the angle between the first tangent line and the second tangent line, and including the tip part The angle in the range is regarded as the first angle, and the angle between the second tangent and the third tangent, and the angle in the range including the first curved portion is regarded as the second angle, and the first angle is smaller than the second angle. Angle; the first angle is included in the range of 20.2 degrees to 42.1 degrees; the second angle is greater than 90 degrees; the blade system has the outer peripheral part of the blade facing the opposite side of the rotating shaft, and the outer peripheral part of the blade is borrowed The upstream side of the airflow generated by the rotation of the impeller is curved. An axial flow fan, which includes the impeller described in item 1 of the scope of patent application, and a rotating The motor that drives the aforementioned impeller.

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