Fan blade, axial flow fan and air conditioner outdoor unit

Abstract

The application discloses a fan blade, an axial flow fan and an outdoor unit of an air conditioner, and relates to the technical field of fans. The fan blade comprises a hub and a plurality of blades which are arranged at intervals around the hub in the circumferential direction. The blade has a critical radial position, which is a position on the blade with a distance of a critical distance R1 from the axis of the hub. The relationship between the critical distance R1 and the radius R0 of the fan blade is R1 / R0=0.4-0.6. The radial position thickness of the blade gradually increases from the critical radial position in the radial direction. The radial position thickness of the blade at each radial position outside the critical radial position is not greater than the radial position thickness of the blade at the critical position. In the application, the thickness of the root of the blade itself is increased, so that the reinforcing ribs are not needed, and the connection strength is better. In addition, the problem of increased turbulence intensity and noise caused by the reinforcing ribs is avoided.

Description

Technical Field

[0001] This application relates to the field of fan technology, and more specifically, to a fan blade, an axial flow fan, and an outdoor unit for an air conditioner. Background Technology

[0002] Existing air conditioner outdoor units use axial flow fans to exhaust air for heat dissipation. The blades of existing axial flow fans consist of a hub and blades located on the outer periphery of the hub, with the blades having a relatively uniform thickness. However, during fan operation, the leading edge (the windward edge) at the root of the blades (the end connected to the hub) bears significant stress, making it prone to cracking. To strengthen the blades, related technologies employ reinforcing ribs at the leading edge of the blade root to reduce the risk of root cracking. However, the addition of these reinforcing ribs alters the aerodynamic shape of the blades, significantly increasing airflow noise and impacting the user experience. Utility Model Content

[0003] The problem addressed in this application is how to improve the structural strength of fan blades while simultaneously reducing noise.

[0004] To address the aforementioned issues, this application provides a fan blade, an axial flow fan, and an outdoor unit for an air conditioner.

[0005] In a first aspect, this application provides a fan blade for use in an axial flow fan. The fan blade includes a hub and a plurality of blades spaced circumferentially around the hub. The blades have a critical radial position, which is a position on the blade where the distance between the blade and the axis of the hub is a critical distance R1. The relationship between the critical distance R1 and the radius R0 of the fan blade is R1 / R0 = 0.4~0.6. Starting from the critical radial position, the radial thickness of the blade gradually increases radially inward. The radial thickness of the blade at a radial position refers to the maximum thickness of the blade at that radial position. The radial thickness of the blade at each radial position outside the critical radial position is not greater than the radial thickness of the blade at the critical radial position.

[0006] In this application, the blade thickness gradually increases radially from the critical radial position towards the hub, with the end of the blade connected to the hub having the greatest radial thickness, thus ensuring the connection strength between the blade and the hub. Because the thickness at the blade root is increased in this application, there is no need for reinforcing ribs, avoiding the increased turbulence intensity and noise caused by reinforcing ribs. Since the blade gradually thickens inward from the critical radial position, forming a relatively smooth thickness change, it has a smoother radial surface, giving the blade a better aerodynamic shape and helping to suppress noise. Furthermore, the increase in blade thickness is limited to the inner side of the critical radial position; the blade thickness on the outer side of the critical radial position does not increase, thus preventing an excessive increase in the overall blade weight and improving the reliability of the fan blade.

[0007] In an optional implementation, the radial thickness of the blade at each radial position outside the critical radial position is equal to the radial thickness at the critical radial position. By setting the radial thickness at each radial position outside the critical radial position to be equal, the radial component of the airflow can flow more smoothly, thereby reducing turbulence and helping to suppress noise.

[0008] In an optional implementation, the radial position thickness of the blade at the critical radial position is defined as the critical position thickness t1, where the critical position thickness t1 = (0.004~0.01) * R1.

[0009] In this embodiment, the critical position thickness t1 is a relatively small value, and the radial position thickness of the outer blades at the critical radial position is not greater than the critical position thickness t1. Therefore, the overall weight of the blades can be kept at a low level, which is beneficial to reducing the load on the blade roots during blade rotation.

[0010] In an optional implementation, the radial thickness of the blade near the hub is defined as the inner end thickness t2, where the inner end thickness t2 = (0.03~0.06) * R1.

[0011] In this embodiment, the thickness t2 at the inner end is a large value, which ensures a large connection surface between the blade root and the hub (i.e., the end face of the blade root), thereby ensuring the connection strength between the blade and the hub. Therefore, the fan blade does not need to be reinforced with stiffeners to meet the strength requirements.

[0012] In an optional implementation, the blade is divided into an inner section near the hub and an outer section away from the hub, with the critical radial position as the boundary. In the inner section of the blade, the distance between the maximum thickness at any radial position and the leading edge of the blade is less than the distance between the blade and the trailing edge.

[0013] In this embodiment, since the circumferential component of the airflow around the blade extends from the leading edge to the trailing edge, the stress near the leading edge is greater than the stress near the trailing edge. Therefore, setting the maximum thickness at each radial position of the inner section of the blade relatively close to the leading edge and relatively far from the trailing edge increases the reliability of the connection between the blade and the hub. Furthermore, setting the blade thicker near the leading edge and thinner near the trailing edge is a more reasonable aerodynamic shape, which helps reduce the turbulence intensity at the trailing edge, thereby reducing noise.

[0014] In an optional embodiment, the distance between the maximum thickness portion at any radial position in the inner section of the blade and the leading edge of the blade is less than 20% of the width of the blade at the corresponding radial position. By setting it in this way, the distance between the maximum thickness portion and the leading edge of the blade can be made sufficiently close, thereby ensuring the strength of the inner section near the leading edge.

[0015] In an optional embodiment, the blade has opposing positive and negative pressure surfaces, and in the inner section of the blade, the maximum thickness at any radial position forms a smooth protrusion on the positive and / or negative pressure surface. In this embodiment, forming a protrusion on either the positive or negative pressure surface effectively creates the maximum thickness, thereby improving strength. The smooth protrusion also allows for smoother airflow over the blade surface, thus suppressing noise.

[0016] In an optional embodiment, at any radial position of the blade, the maximum thickness portion of the blade is located between the leading and trailing edges, and the leading edge and the maximum thickness portion are connected by a smooth curved surface. By connecting the leading edge and the maximum thickness portion of the blade with a smooth curved surface, the airflow can smoothly transition to the maximum thickness portion as it flows from the leading edge to the trailing edge, reducing turbulence near the leading edge and thus suppressing noise.

[0017] Secondly, this application provides an axial flow fan, including a motor and fan blades of any of the foregoing embodiments, wherein the drive shaft of the motor is connected to the hub of the fan blades via a transmission connection.

[0018] Thirdly, this application provides an outdoor air conditioning unit, including a casing, an outdoor heat exchanger, a compressor, and the axial fan provided in the second aspect above. The outdoor heat exchanger and the compressor are disposed inside the casing, and the axial fan is disposed inside the casing and is used to exhaust air to the outside of the casing. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the guide ring and fan blades in related technologies; Figure 2 for Figure 1 Schematic diagram of section 1-1; Figure 3 for Figure 1 Schematic diagram of section 2-2; Figure 4 for Figure 1 Schematic diagram of section 3-3; Figure 5 This is a schematic diagram of the fan blades being positioned within the air guide ring in one embodiment of this application; Figure 6 for Figure 5 Schematic diagram of section 1-1; Figure 7 for Figure 5Schematic diagram of section 2-2; Figure 8 for Figure 5 Schematic diagram of section 3-3; Figure 9 This is a cross-sectional schematic diagram of the inner section of the blade in another embodiment of this application; Figure 10 This is a cross-sectional schematic diagram of the inner section of the blade in another embodiment of this application; Figures 11 to 13 This is a cross-sectional view of the inner section of the blade in three other embodiments of this application; Figure 14 This is a schematic diagram of an outdoor unit of an air conditioner in one embodiment of this application.

[0020] Explanation of reference numerals in the attached drawings: 10-Chassis; 100-Fan blade; 110-Hub; 120-Blade; 121-Critical radial position; 122-Leading edge; 123-Leading edge; 130-Reinforcing rib; 20-Motor bracket; 200-Motor; 30-Outdoor heat exchanger; 40-Compressor; 50-Guide ring. Detailed Implementation

[0021] Figure 1 This is a schematic diagram of the guide ring 50 and the fan blade 100 in the related technology; Figure 2 for Figure 1 Schematic diagram of section 1-1; Figure 3 for Figure 1 Schematic diagram of section 2-2; Figure 4 for Figure 1 A schematic diagram of section 3-3. (See diagram below.) Figures 1 to 4 As shown, the blade 120 has a relatively uniform thickness. To increase the connection strength between the root of the blade 120 and the hub 110, a reinforcing rib 130 is provided at the leading edge 122 of the blade 120 root. However, after the reinforcing rib 130 is provided, due to its function, both the positive pressure side 12hp and the negative pressure side 12hs obstruct the airflow near the leading edge 122, thereby causing the airflow X1 to separate at the leading edge 122 and forming strong turbulence R1 in the downstream region of the leading edge 122. Furthermore, as... Figure 4 As shown, on the outer periphery of blade 120, due to the influence of the separated airflow X1 at the leading edge 122 of blade 120 root, the airflow (inter-wing airflow) passing through blade 120 is deflected radially outward, resulting in a significant increase in airflow velocity on the outer periphery of blade 120. This not only exacerbates the turbulence R2 generated by the separated airflow X2 at 12ts on the negative pressure side of blade 120, but also makes the vortex Y1 released from the trailing edge 123 more pronounced.

[0022] Therefore, in the related technology, the turbulence intensity of the fan blade 100 is significantly enhanced from the hub side to the outer periphery side, as well as in the inter-blade and wake regions, resulting in a significant increase in air supply noise.

[0023] To address this, embodiments of this application provide a fan blade that, by altering the thickness at the blade root, eliminates the need for reinforcing ribs, thereby optimizing the aerodynamic shape of the fan blade and achieving a balance between blade connection strength and noise reduction. Additionally, embodiments of this application also provide an axial flow fan and an outdoor unit for an air conditioner.

[0024] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, specific embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0025] Figure 5 This is a schematic diagram of the fan blade 100 being positioned within the guide ring 50 in one embodiment of this application; Figure 6 for Figure 5 Schematic diagram of section 1-1; Figure 7 for Figure 5 Schematic diagram of section 2-2; Figure 8 for Figure 5 A schematic diagram of section 3-3. (See diagram below.) Figures 5 to 8 As shown, the fan blade 100 provided in this embodiment includes a plurality of blades 120 circumferentially spaced around the hub 110; the blades 120 have a critical radial position 121, which is the position on the blade 120 where the axial distance between the blade and the hub 110 is a critical distance R1. The relationship between the critical distance R1 and the radius R0 of the fan blade 100 is R1 / R0 = 0.4~0.6. Starting from the critical radial position 121 and moving radially inward, the radial thickness of the blade 120 gradually increases. The radial thickness t of the blade 120 at a radial position refers to the maximum thickness of the blade 120 at that radial position; the radial thickness t of the blade 120 at each radial position outside the critical radial position 121 is not greater than the radial thickness t of the blade 120 at the critical radial position 121. It should be understood that the same radial position has different thicknesses at different circumferential positions (e.g., Figure 7 and Figure 8 As shown in the figure, the radial position thickness t is the largest of these thicknesses.

[0026] For ease of description, the blade 120 is divided at a critical radial position 121, with the portion closer to the hub 110 defined as the inner section and the portion farther from the hub 110 defined as the outer section. In this embodiment, the end of the inner section farther from the outer section is the end connected to the hub 110, which is the root of the blade 120. The inner section of the blade 120 gradually thickens radially from the outside to the inside, giving the end of the blade 120 near the hub 110 a greater thickness, thereby ensuring the connection strength between the blade 120 and the hub 110.

[0027] In this embodiment, the radius R0 of the fan blade 100 is the sum of the radius of the hub 110 and the radial dimension of the blade 120. Optionally, the radius of the hub 110 is 10% to 30% of the radius R0 of the fan blade 100. Therefore, the inner section of the blade 120 has a smaller radial dimension than the outer section, so even if the inner section is thickened, the weight of the blade 120 itself will not increase excessively, avoiding excessive load on the connection at the root of the blade 120 due to excessive weight.

[0028] Because the thickness of the root of the blade 120 is increased in this application, there is no need to provide the reinforcing rib 130, thus avoiding the problem of increased turbulence intensity and noise caused by the reinforcing rib 130. Since the blade 120 gradually thickens inward from the critical radial position 121, forming a relatively smooth thickness change, it has a smoother surface in the radial direction, giving the blade 120 a better aerodynamic shape, which is beneficial for noise suppression. Furthermore, the increase in blade thickness is limited to the inner side of the critical radial position 121; the thickness of the blade 120 outside the critical radial position 121 does not increase, therefore it does not lead to an excessive increase in the overall weight of the blade 120, improving the reliability of the fan blade 100.

[0029] Furthermore, the radial position thickness of the blade 120 at each radial position outside the critical radial position 121 (i.e., the outer section) is equal to the radial position thickness at the critical radial position 121. By setting the radial position thickness at each radial position of the outer section of the blade 120 to be equal, the radial component of the airflow can flow in a smoother manner, thereby reducing turbulence and helping to suppress noise.

[0030] The radial thickness of the blade 120 at the critical radial position 121 is defined as the critical position thickness t1. Optionally, the critical position thickness t1 = (0.004~0.01) * R1. In this embodiment, the critical position thickness t1 is a relatively small value, and the radial thickness of the outer blades 120 at the critical radial position 121 is not greater than the critical position thickness t1. Therefore, the overall weight of the blade 120 can be kept at a low level, which is beneficial to reducing the load on the root of the blade 120 during the rotation of the fan blade 100.

[0031] The radial thickness of the end of the blade 120 near the hub 110 is defined as the inner end thickness t2. Optionally, the inner end thickness t2 = (0.03~0.06) * R1. In this embodiment, the inner end thickness t2 is a relatively large value, which ensures a large connection surface (i.e., the end face of the blade 120 root) between the root of the blade 120 and the hub 110, thereby ensuring the connection strength between the blade 120 and the hub 110. Therefore, the fan blade 100 does not need to be equipped with reinforcing ribs 130 to meet the strength requirements.

[0032] Figure 7 This is a cross-section of the inner section of the blade 120 in one embodiment of this application; Figure 8 This is a cross-section of the outer section of the blade 120 in one embodiment of this application. (Continue to refer to...) Figure 7 and Figure 8 In this embodiment, in the inner section of the blade 120, the distance between the maximum thickness at any radial position and the leading edge 122 of the blade 120 is less than the distance between the maximum thickness and the trailing edge 123 of the blade 120. This means that the maximum thickness is closer to the leading edge 122 in the circumferential direction of the blade 120. Since the circumferential component of the airflow around the blade 120 is from the leading edge 122 to the trailing edge 123, the stress near the leading edge 122 of the blade 120 is greater than the stress near the trailing edge 123. Therefore, setting the maximum thickness at each radial position of the inner section of the blade 120 to be relatively closer to the leading edge 122 and relatively farther from the trailing edge 123 can increase the connection reliability between the blade 120 and the hub 110. Furthermore, setting the blade 120 thicker near the leading edge 122 and thinner near the trailing edge 123 is a more reasonable aerodynamic shape, which can help reduce the turbulence intensity at the trailing edge 123, thereby reducing noise.

[0033] Furthermore, in the inner section of the blade 120, the distance between the maximum thickness at any radial position and the leading edge 122 of the blade 120 is less than 20% of the width of the blade 120 at the corresponding radial position. By setting it in this way, the distance between the maximum thickness and the leading edge 122 of the blade 120 can be made sufficiently close, thereby ensuring the strength of the inner section near the leading edge 122.

[0034] In this embodiment, the blade 120 has opposing positive and negative pressure surfaces. When the blade 100 rotates, the positive pressure surface is the windward side, while the negative pressure surface is the leeward side. In the inner section of the blade 120, the thickest portion at any radial position forms a smooth protrusion on the positive and / or negative pressure surface. In this embodiment, forming a protrusion on either the positive or negative pressure surface effectively creates the thickest portion, thereby improving strength. The smooth protrusion allows for smoother airflow over the blade 120 surface, thus suppressing noise. Figure 7 In the embodiment shown, the thickest part forms a smooth protrusion on both the positive and negative pressure surfaces.

[0035] Optionally, at any radial position of the blade 120, the maximum thickness portion of the blade 120 is located between the leading edge 122 and the trailing edge 123 of the blade 120, and the leading edge 122 and the maximum thickness portion of the blade 120 are connected by a smooth curved surface. By connecting the leading edge 122 and the maximum thickness portion of the blade 120 with a smooth curved surface, the airflow can smoothly transition to the maximum thickness portion when flowing from the leading edge 122 to the trailing edge 123, reducing turbulence near the leading edge 122 and thus suppressing noise.

[0036] exist Figure 7 and Figure 8 In the embodiment shown, the inner section of the blade 120 has an airfoil shape, while the outer section, which is farther from the hub 110, has a relatively uniform and thin cross-sectional shape. The radial thickness of the outer section is equal to the critical thickness t1.

[0037] With this blade 100 structure, in the inner section of the blade 120, the airflow flows along the gentle shape change of the leading edge 122 on the positive pressure side 15hp1 and the negative pressure side 15hs1 of the blade 120, thereby avoiding airflow separation at the leading edge 122. In addition, it can effectively suppress the separated airflow X3 caused by the bending of the blade 120 downstream of the negative pressure side 15hs1, thereby minimizing the turbulence R3 on the negative pressure side 15hs1 caused by the separated airflow X3.

[0038] Meanwhile, in the blade 120, the fan blade 100 structure of this embodiment can suppress the increase in inter-wing airflow velocity in the outer section caused by the airflow deflecting towards the outer section of the blade 120. Therefore, even if the outer section of the blade 120 adopts a near-uniform thin-walled cross-section design, it can significantly reduce the turbulence R4 caused by the separated airflow X4 at the negative pressure surface 15ts of the blade 120, and effectively reduce the intensity of the vortex Y3 released from the trailing edge 123.

[0039] In this embodiment, the thickness of the leading edge 122 of the inner section of the blade 120 gradually increases as it approaches the hub 110, while the outer section maintains a thin-walled cross-section design. This design not only helps to reduce the weight of the outer periphery of the blade 120, ensuring that even if stress is concentrated at the leading edge 122 when the fan blade 100 rotates, damage caused by deformation can be avoided; at the same time, in the inner section of the blade 120, the airfoil cross-section shape helps to prevent airflow separation at the leading edge 122, and further suppresses the turbulence R3 on the negative pressure side 15hs1 and the intensity of the vortex Y3 released from the trailing edge 123.

[0040] Figure 9 This is a cross-sectional schematic diagram of the inner section of the blade 120 in another embodiment of this application. Figure 9 The illustrated embodiments are relative to Figure 7In the illustrated embodiment, the cross-sectional shape of the outer segment has been adjusted. Figure 9 In this embodiment, the inner section of the blade 120 has a pointed leading edge 122 with a rounded transition; the outer section adopts a thin-walled cross-section design with uniform thickness. The negative pressure side 16hs1 of the trailing edge 123 gradually thins in a gentle rounded shape until it reaches its thinnest state near the tip.

[0041] Figure 9 The design shown allows the airflow to smoothly adapt to the gradually changing cross-sectional shape formed by the arc at the tip of the pointed leading edge 122 along the vicinity of the positive pressure side 16hp1 and the negative pressure side 16hs1 of the blade 120, thereby effectively avoiding airflow separation at the leading edge 122.

[0042] Furthermore, the blade 120 gradually transitions from a thin-walled section with a slightly uniform thickness to a gentle arc on the negative pressure side 16hs1 of the trailing edge 123, and finally connects well with the positive pressure side 16hp1 at the end of the trailing edge 123, which significantly reduces the shear force caused by the velocity difference between the pressure side 16hp1 and the negative pressure side 16hs1, thereby greatly suppressing the eddy Y4 released from the trailing edge 123.

[0043] Therefore, in the inner section of blade 120, as blade 120 gradually approaches hub 110, the thickness of its pointed leading edge 122 gradually increases accordingly. This increases the root strength of blade 120 without excessively increasing weight. The pointed cross-section design of the inner section successfully prevents airflow separation at the leading edge 122 and further reduces the vortex Y4 released from trailing edge 123 to a lower level.

[0044] Figure 10 This is a cross-sectional schematic diagram of the inner section of the blade 120 in another embodiment of this application. Figure 10 The illustrated embodiments are relative to Figure 7 and Figure 9 In the embodiment shown, the cross-sectional shape of the outer section of the blade 120 was adjusted. Figure 10 In one embodiment, the inner segment has a circular leading edge 122; the negative pressure side 17hs1 of the trailing edge 123 is a gentle arc shape, and the wall thickness of the trailing edge 123 is thinner the closer to the tip.

[0045] Therefore, in the inner section of the blade 120, the airflow flows in a smooth cross-sectional shape with a gradually changing circular shape along the positive pressure side 17hp1 and negative pressure side 17hs1 of the blade 120, thereby avoiding airflow separation at the leading edge 122.

[0046] Furthermore, the negative pressure side 17hs1 portion of the trailing edge 123 has a gentle arc transition and finally connects well with the positive pressure side 17hp1 at the end of the trailing edge 123, effectively reducing the shear force caused by the velocity difference between the positive pressure side 17hp1 and the negative pressure side 17hs1, thereby significantly suppressing the wake vortex Y5 released from the trailing edge 123.

[0047] Figures 11 to 13 This is a cross-sectional view of the inner section of blade 120 in three other embodiments of this application. (See also...) Figures 11 to 13 As shown, in Figure 7 , Figure 9 and Figure 10 Based on the embodiment, the cross-sectional shape of the inner section of blade 120 can be further improved. For example, Figure 11 Implementation examples relative to Figure 7 In this embodiment, the positive and negative pressure surfaces are designed asymmetrically, which also achieves the effect of reducing eddies and noise.

[0048] Figure 12 Implementation examples relative to Figure 9 In this embodiment, the positive and negative pressure surfaces are also configured as asymmetrical structures, that is... Figure 9 In this embodiment, the bulge of the thickest part on the positive pressure surface is eliminated, and only the bulge of the thickest part on the negative pressure surface is retained, forming... Figure 12 The structure shown in the embodiment can also achieve the effect of reducing eddy currents and noise.

[0049] Figure 13 Implementation examples relative to Figure 10 In this embodiment, the positive and negative pressure surfaces are also configured as asymmetrical structures, that is... Figure 10 In this embodiment, the bulge of the thickest part on the positive pressure surface is eliminated, and only the bulge of the thickest part on the negative pressure surface is retained, forming... Figure 13 The structure shown in the embodiment can also achieve the effect of reducing eddy currents and noise.

[0050] Figure 14 This is a schematic diagram of an outdoor unit of an air conditioner in one embodiment of this application. Figure 14 As shown in the illustration, this application also provides an axial flow fan and an outdoor air conditioning unit. The outdoor air conditioning unit includes a casing 10, an outdoor heat exchanger 30, a compressor 40, and an axial flow fan. The outdoor heat exchanger 30 and the compressor 40 are disposed inside the casing 10, and the axial flow fan is disposed in the casing 10 and is used to exhaust air to the outside of the casing 10.

[0051] The axial flow fan includes a motor 200 and fan blades 100 as described in the above embodiment. The drive shaft of the motor 200 is connected to the hub 110 of the fan blades 100. A motor bracket 20 is provided on the inner wall of the casing 10, and the motor 200 of the axial flow fan is mounted on the motor bracket 20. In addition, the outdoor unit of the air conditioner also includes a guide ring 50, which is arranged around the fan blades 100 and fixed to the casing 10. The guide ring 50 serves to guide airflow.

[0052] In this embodiment, the outdoor unit of the air conditioner has a top-discharge structure, that is, an axial fan is installed on the top of the casing 10 for vertically upward exhaust. In other optional embodiments, the outdoor unit of the air conditioner can also have a side-discharge structure.

[0053] While this application discloses the above information, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of this application; therefore, the scope of protection of this application shall be determined by the scope defined in the claims.

Claims

1. A fan blade used in an axial flow fan, characterized in that, The fan blade (100) includes a hub (110) and a plurality of blades (120) circumferentially spaced around the hub (110); the blades (120) have a critical radial position (121), which is the position on the blade (120) where the axial distance between the blade (120) and the hub (110) is a critical distance R1, and the relationship between the critical distance R1 and the radius R0 of the fan blade (100) is R1 / R0=0.4~0.6; from the critical radial position (121) inward along the radial direction, the radial position thickness of the blade (120) gradually increases, and the radial position thickness of the blade (120) at a radial position refers to the maximum thickness of the blade (120) at that radial position; the radial position thickness of the blade (120) at each radial position outside the critical radial position (121) is not greater than the radial position thickness of the blade (120) at the critical radial position.

2. The fan blade according to claim 1, characterized in that, The radial position thickness of the blade (120) at each radial position outside the critical radial position (121) is equal to the radial position thickness at the critical radial position.

3. The fan blade according to claim 1, characterized in that, The radial position thickness of the blade (120) at the critical radial position (121) is defined as the critical position thickness t1, and the critical position thickness t1 = (0.004~0.01) * R1.

4. The fan blade according to claim 1, characterized in that, The radial position thickness of the blade (120) near the hub (110) is defined as the inner end position thickness t2, and the inner end position thickness t2 = (0.03~0.06) * R1.

5. The fan blade according to claim 1, characterized in that, The blade (120) is divided into an inner section near the hub (110) and an outer section away from the hub (110) at the critical radial position (121). In the inner section of the blade (120), the distance between the maximum thickness at any radial position and the leading edge (122) of the blade (120) is less than the distance between the maximum thickness at any radial position and the leading edge (123) of the blade (120).

6. The fan blade according to claim 5, characterized in that, In the inner section of the blade (120), the distance between the maximum thickness at any radial position and the leading edge (122) of the blade (120) is less than 20% of the width of the blade (120) at the corresponding radial position.

7. The fan blade according to claim 5, characterized in that, The blade (120) has opposing positive and negative pressure surfaces, and in the inner section of the blade (120), the portion with the maximum thickness at any radial position forms a smooth protrusion on the positive and / or negative pressure surfaces.

8. The fan blade according to claim 1, characterized in that, At any radial position of the blade (120), the maximum thickness portion of the blade (120) is located between the leading edge (122) and the trailing edge (123) of the blade (120), and the leading edge (122) and the maximum thickness portion of the blade (120) are connected by a smooth curved surface.

9. An axial flow fan, characterized in that, It includes a motor (200) and a fan blade (100) according to any one of claims 1-8, wherein the drive shaft of the motor (200) is connected to the hub (110) of the fan blade (100).

10. An outdoor unit for an air conditioner, characterized in that, Includes a casing (10), an outdoor heat exchanger (30), a compressor (40), and an axial flow fan as described in claim 9, wherein the outdoor heat exchanger (30) and the compressor (40) are disposed inside the casing (10), and the axial flow fan is disposed in the casing (10) and is used to exhaust air to the outside of the casing (10).

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