Axial flow cooling fan
By forming a rough area on the inner wall of the frame of the axial heat dissipation fan, and using laminar flow to block the return flow, the noise and efficiency problems caused by the return flow in the prior art are solved, and an efficient and low-cost heat dissipation effect is achieved.
Patent Information
- Application Number
- CN202311194639.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-15
- Publication Date
- 2025-03-18
AI Technical Summary
Existing axial heat dissipation fans are prone to reflux at the gap between the end edge of the blade and the inner wall of the frame, resulting in increased noise and reduced efficiency. Solving this problem by reducing the gap will lead to a decrease in yield and an increase in cost.
At least one rough area is formed on the inner wall of the frame of the axial heat dissipation fan, and laminar flow is generated when the end edge of the blade passes through the rough area, thereby preventing the occurrence of backflow.
Through a simple rough structure, the generation of reflux is effectively prevented, the efficiency and yield of the fan is improved, and the manufacturing cost is reduced.
Smart Images
Figure CN119641672A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a heat dissipation fan, in particular to an axial flow heat dissipation fan. Background Art
[0002] Axial flow fans have a simple structure and have air supply characteristics of large air volume and low static pressure, so they are widely used in cooling fans or ventilation fans for personal computers and servers. In order to improve the air supply characteristics of axial flow fans to reduce noise and other optimization purposes, the number and structure of fan blades are often adjusted, or various designs and tests are performed on the structure of the airflow passage.
[0003] Among the structural adjustment items at the airflow passage, one is to reduce the gap between the fan blades and the frame to reduce the pressure difference between the two opposing surfaces of the blades and cause the return airflow. However, the above process of reducing the gap, for example, reducing the gap between the blade tip and the frame from 1mm to 0.5mm, is limited by the precision of the fan component manufacturing and the assembly process. Although it can achieve the purpose, it will cause a decrease in yield and an increase in cost, which is not conducive to mass production. Summary of the invention
[0004] The invention is directed to an axial flow heat dissipation fan, which avoids backflow between the blade end edge and the inner wall of the frame through the rough inner wall of the frame.
[0005] According to an embodiment of the present invention, an axial flow cooling fan is suitable for electronic devices, including a frame and an impeller. The frame has an inlet, an outlet and an inner wall, the inner wall is connected between the inlet and the outlet, and the inner wall surrounds the impeller and has at least one rough area. The impeller is rotatably arranged in the frame and is located between the inlet and the outlet, and the airflow generated by the rotation enters the frame from the inlet and leaves the frame from the outlet. The blade tip of the impeller maintains a gap with the inner wall. When the impeller rotates, the blade tip passes through the rough area and generates a laminar flow at the gap to avoid backflow at the gap. The direction of the backflow is opposite to the direction of the airflow.
[0006] Based on the above, since the axial flow cooling fan forms at least one rough area on the inner wall of the frame, when the impeller rotates and the blade tip of the impeller passes through the rough area, a laminar flow will be generated in the gap between the blade tip and the inner wall, and the gap will block the backflow due to the laminar flow (to avoid the generation of backflow). In this way, compared with the existing method of reducing the gap, which results in poor yield and increased manufacturing cost, the present invention can effectively achieve the effect of preventing backflow with a simple rough structure. BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Figure 1 is a schematic diagram of an axial flow cooling fan according to an embodiment of the present invention;
[0008] Figure 2 is a simplified side view showing an axial flow cooling fan;
[0009] Figure 3 It is a simple schematic diagram of the existing axial flow fan generating backflow;
[0010] Figure 4 It is a simple schematic diagram of the fluid boundary layer;
[0011] Figure 5 It is a schematic diagram of the structure of the rough area;
[0012] Figure 6 FIG. 4 is a simplified side view of an axial flow cooling fan according to another embodiment of the present invention. DETAILED DESCRIPTION
[0013] Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals are used in the drawings and the description to refer to the same or like parts.
[0014] Figure 1 FIG. 4 is a schematic diagram of an axial flow cooling fan according to an embodiment of the present invention. Figure 2 is a simplified side view showing an axial flow cooling fan. Please also refer to Figure 1 and Figure 2 In this embodiment, the axial flow cooling fan 100 is suitable for electronic devices, such as a system fan or a CPU cooling fan installed in a computer desktop, and includes a frame 110 and an impeller 120, wherein the impeller 120 includes a hub 121 and a plurality of blades 122 surrounding the hub 121. The frame 110 has an inlet 111, an outlet 112, and an inner wall 113, wherein the inner wall 113 is connected between the inlet 111 and the outlet 112, wherein the inner wall 113 surrounds the impeller 120 and has at least one rough area (the figure provides a plurality of rough areas 114 as an example, and the range of the rough area is marked with a dotted line). The impeller 120 is rotatably disposed in the frame 110 and is located between the inlet 111 and the outlet 112. It is connected to the motor (not shown) and drives the hub 121 to rotate with the axis AX as a reference. When the blades 122 rotate along the axis AX with the hub 121, an air flow F1 is generated to enter the frame 110 from the inlet 111 and leave the frame 110 from the outlet 112.
[0015] Figure 3 This is a simple schematic diagram of the existing axial flow fan generating backflow. Please refer to Figure 3It should be noted that there is a gap G2 between the blade tip 222a of the impeller 220 of the existing axial flow cooling fan and the inner wall 213 of the frame. Therefore, it is inevitable that there is a pressure difference between the air suction surface S11 and the air outlet surface S21 of the blade 222 of the impeller 220, which causes a backflow F2 to be formed at the gap G2 when the impeller 220 rotates, and the direction of the backflow F2 is opposite to the direction of the airflow F1.
[0016] Therefore, in view of the fact that the aforementioned method of reducing the gap G2 is likely to result in poor precision and increased cost, the present invention is as follows Figure 1 , Figure 2 The structure of the frame 110 is changed as shown, that is, at least one rough area 114 is formed on the inner wall 113 to generate a laminar flow at the gap G1 when the impeller 120 rotates.
[0017] Figure 4 is a simple diagram of a fluid boundary layer. Figure 4 , the following briefly describes the formation principle of laminar flow. Generally speaking, the boundary layer formed between the fluid and the surface of an object will be affected by the roughness of the surface of the object. Figure 4 As shown on the right, when the fluid pressure increases, the fluid at the inner edge of the boundary layer will gradually generate a reverse flow field E due to the viscous resistance of the object surface, causing the fluid to separate from the object surface. This fluid separation phenomenon is the main cause of laminar flow.
[0018]
[0019] When u=v=0 and y=∞, u=U(x), where u and v represent the velocity components of the fluid in the x and y directions, U(x) represents the flow velocity, μ represents the dynamic viscosity (dynamic viscosity coefficient), ρ represents the fluid density, the direction along the wall of the object is the x-axis, and the direction perpendicular to the wall is the y-axis.
[0020] Based on the principle of forming laminar flow by separation of the boundary layer, the present invention forms a rough area 114 on the inner wall 113 of the frame 110, so that laminar flow can be smoothly generated at the gap G1 when the blade end 122a passes through the rough area 114. In this way, the laminar flow is equivalent to blocking or reducing the backflow (such as the backflow F2 mentioned above) at the location. Here, the blade end 122a refers to the side surface adjacent to the air suction surface S1 and the air outlet surface S2 of the blade 122.
[0021] Figure 5 This is a schematic diagram of the structure of the rough area, and a gold image micrograph is used here to illustrate it. Please also refer to Figure 2 and Figure 5In this embodiment, the rough area 114 has an etching microstructure and a plurality of etching particles 114a, and the roughness of the rough area 114 is defined by an etching depth of 10 μm to 45 μm of the etching microstructure and 15 to 150 etching particles 114a per centimeter to ensure the generation of laminar flow. The above etching is for the mold forming the inner wall 113. By forming an etching pattern on the mold, a corresponding pattern can be smoothly formed on the inner wall 113.
[0022] Please refer to Figure 1 and Figure 2 In this embodiment, although the formation of the rough area 114 helps to generate laminar flow, it will also reduce the overall flow rate of the airflow F1 due to increased friction. Accordingly, the present invention further provides relevant conditions to optimize the characteristics of the rough area 114. In one embodiment, the inner wall 113 of the frame 110 has a plurality of rough areas 114, and the number of the rough areas 114 is greater than or equal to the number of the plurality of blades 122 of the impeller 120. Figure 1 For example, the impeller 120 has 9 blades, so the number of the rough areas 114 on the inner wall 113 is greater than or equal to 9.
[0023] Furthermore, if Figure 2 As shown, because the generation of laminar flow is caused by the change of airflow at the gap G1 (separated by the boundary layer), it is actually determined by the blade end edge 122a and the inner wall 113. Therefore, the contour of the rough area 114 is actually based on the blade end edge 122a. In detail, the rough area 114 is formed by orthogonally projecting the contour of the blade end edge 122a onto the inner wall 113. Therefore, the width W2 of the rough area 114 is actually adjusted based on the width W1 of the blade end edge 122a. Based on the above description of the number of rough areas 114, when the number of rough areas 114 is equal to the number of blades 122, the minimum width W2 of the rough area 114 is greater than or equal to the width W1 of the orthogonal projection contour 122b of the blade end edge 122a projected onto the inner wall 113. When the number of rough areas 114 is greater than the number of blades 122, the minimum width W2 of the rough area 114 is less than the width W1 of the contour of the blade end edge 122a projected onto the inner wall 111.
[0024] In other words. In this embodiment, the number of rough areas 114 is used as the basis for adjusting the width W2 of the rough areas 114. When the number of rough areas 114 is relatively small (such as the number of rough areas 114 equals the number of blades 122), the width W2 of the rough areas 114 can be made greater than or equal to the width W1 of the positive projection profile of the blade end edge 122a projected onto the inner wall 113. Conversely, when the number of rough areas 114 is relatively large (such as the number of rough areas 114 is greater than the number of blades 122), the width W2 of the rough areas 114 can be appropriately reduced so that the width W2 of the rough areas 114 is smaller than the width W1 of the positive projection profile of the blade end edge 122a projected onto the inner wall 113.
[0025] Furthermore, the number and width W2 of the rough areas 114 can be adjusted based on the ratio of the area of the rough areas 114 to the area of the inner wall 113, that is, after determining the total area of the rough areas 114 according to the needs, the width W2 of the rough areas 114 is adjusted according to the number of blades 122, so as to optimize the rough areas 114. It should be noted that the aforementioned area ratio is based on the area of the inner wall 113 swept by the blade end 122a when the blade 122 rotates as the parent number.
[0026] Please refer to Figure 1 and Figure 2 In this embodiment, the rough area 114 is parallel to or consistent with the contour of the blade end edge 122a projected onto the inner wall 113. This is equivalent to forming a state where the rough area 114 and the smooth area 115 are staggered and have the same inclination (also consistent with the blade end edge 122a) on the inner wall 113. This makes the blade end edge 122a generate laminar flow only when passing through the rough area 114, but a wider laminar flow can be generated because the overlapping area of the rough area 114 and the contour of the blade end edge 122a projected onto the inner wall 113 is large.
[0027] Figure 6 This is a simple side view of an axial flow cooling fan according to another embodiment of the present invention. Figure 6 ,and Figure 2 The difference is that the rough area 214 on the inner wall 213 is perpendicular to the orthographic projection profile of the blade end edge 122a onto the inner wall 213. This increases the probability that the blade end edge 122a sweeps over the rough area 214, so it is beneficial to cover the area that the blade end edge 122a will sweep over with the least rough area 214.
[0028] Simultaneous comparison Figure 2 and Figure 6The difference between the two lies in the sweep relationship between the rough areas 114 and 214 and the blade end edge 122a. The rough area 114 can form a larger sweep area (equivalent to covering a larger range of gaps), while the rough area 214 increases the sweep probability by reducing the sweep area (equivalent to generating more sweep times per unit time). Designers can adjust them according to actual needs or mix and match them on the inner wall of the same frame.
[0029] In summary, in the above embodiment of the present invention, since the axial flow cooling fan forms at least one rough area on the inner wall of the frame, when the impeller rotates and the blade tip of the impeller passes through the above rough area, a laminar flow will be generated in the gap between the blade tip and the inner wall, and the gap will block the backflow due to the existence of the laminar flow. In this way, compared with the existing method of reducing the gap, which results in poor yield and increased manufacturing cost, the present invention can effectively achieve the effect of preventing backflow with a simple rough structure.
[0030] Furthermore, the designer can adjust the number and width of the rough areas according to the needs, or adjust the sweep relationship between the rough areas and the blade end edge according to the configuration orientation. In one embodiment, the rough areas can be parallel or consistent with the contour of the blade end edge projected onto the inner wall, so as to generate a wider range of laminar flow through a larger sweep area. In another embodiment, the rough areas can be perpendicular to the contour of the blade end edge projected onto the inner wall, so as to increase the number of laminar flow generation per unit time. The designer can adjust and optimize the above-mentioned rough areas and their sweep relationship with the blade end edge according to the needs.
[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. An axial flow cooling fan, characterized in that: Suitable for electronic devices, including: a frame having an inlet, an outlet, and an inner wall connected between the inlet and the outlet, wherein the inner wall has at least one rough area; and An impeller is rotatably disposed in the frame and located between the inlet and the outlet. The inner wall surrounds the impeller. The impeller rotates to generate an airflow that enters the frame from the inlet and leaves the frame from the outlet. The tip of the impeller blade maintains a gap with the inner wall. When the impeller rotates, the tip of the blade passes through the at least one rough area to generate and maintain laminar flow at the gap to avoid backflow at the gap. The direction of the backflow is opposite to the direction of the airflow.
2. The axial flow cooling fan according to claim 1, characterized in that: The rough area is parallel to or consistent with a contour of the blade tip projected onto the inner wall.
3. The axial flow cooling fan according to claim 1, characterized in that: The rough area is perpendicular to a contour of the blade tip projected onto the inner wall.
4. The axial flow cooling fan according to claim 1, characterized in that: The inner wall has a plurality of rough areas, and the number of the plurality of rough areas is greater than or equal to the number of the plurality of blades of the impeller.
5. The axial flow cooling fan according to claim 1, characterized in that: The inner wall has a plurality of rough areas. When the number of the plurality of rough areas is equal to the number of the plurality of blades of the impeller, the minimum width of the rough areas is greater than or equal to the width of the contour of the blade tip projected onto the inner wall.
6. The axial flow cooling fan according to claim 1, characterized in that: The inner wall has a plurality of rough areas. When the number of the plurality of rough areas is greater than the number of the plurality of blades of the impeller, the minimum width of the rough areas is smaller than the width of the contour of the blade tip projected onto the inner wall.
7. The axial flow cooling fan according to claim 1, characterized in that: The rough area has an etched microstructure, and the roughness of the rough area is defined by an etching depth of the etched microstructure of 10 μm to 45 μm and an etching particle number of 15 to 150 per centimeter.