A low noise cooling fan

Abstract

The invention relates to the technical field of heat dissipation devices, and discloses a low-noise heat dissipation fan, comprising a base and double-layer blades, wherein a bearing is arranged at the center of the base, and a stator is arranged in a circumferential array on the side surface of the bearing, the stator is an iron core, and is wrapped by a painted coil to form an electromagnet, the energization state of the coil is controlled by a control circuit, and a Hall sensor is arranged for detection, the double-layer blades are composed of a rotor, a connecting ring and blades, the rotor is located at the axis center of the double-layer blades, and is cylindrical, a crankshaft connected to the stator is arranged at the axis center of the bottom of the double-layer blades, blades are arranged in a circumferential array on the side surface of the rotor and are connected to the connecting ring, and blades are also arranged in a circumferential array on the outer side surface of the connecting ring to form a double-layer blade structure, the inner wall surfaces of the rotor and the connecting ring are evenly arrayed with permanent magnets, and the permanent magnets located in the connecting ring and the permanent magnets in the rotor are arranged at different angles.

Description

Technical Field

[0001] The invention relates to the technical field of heat dissipation devices, and in particular to a low-noise heat dissipation fan. Background Art

[0002] In today's rapidly developing science and technology and industrial fields, with the continuous improvement of the integration of electronic equipment and the significant increase in power density, heat dissipation issues are increasingly becoming a key factor restricting equipment performance and stability. Especially in high-performance computers, data centers, industrial automation equipment and various consumer electronic products, the demand for efficient heat dissipation solutions is becoming more and more urgent. Traditional heat dissipation methods such as natural convection heat dissipation and heat pipe heat dissipation are incapable of meeting the design requirements of high power density and compact space. Therefore, as an active heat dissipation method, the cooling fan has gradually become the mainstream choice in heat dissipation solutions due to its advantages of high efficiency, flexibility and strong controllability. The cooling fan drives the blades to rotate through the motor, generates a strong airflow, accelerates the air flow, quickly takes away the heat from the heat source, and effectively reduces the temperature of the equipment. The working principle of the cooling fan is based on electromagnetic Based on the induction principle, the Hall sensor component is used as a synchronous detection device to control the circuit to switch the winding power-on sequence, thereby generating a rotating magnetic field to drive the fan blades to rotate. The DC motor is its core component, consisting of a stator and a rotor. After power is turned on, the magnetic poles on the stator interact with the magnetic poles on the rotor to form a rotational torque to drive the fan to rotate. With the continuous progress in the fields of material science, motor technology, aerodynamics, etc., the performance of cooling fans is also continuously improving, including higher air volume, lower noise, longer service life and more intelligent temperature control systems. In addition, with the enhancement of environmental awareness and the improvement of energy efficiency requirements, the design of cooling fans also pays more attention to energy conservation and emission reduction and the improvement of energy efficiency ratio. For example, measures such as using low-power motors, optimizing the shape of fan blades, and introducing intelligent speed regulation technology are aimed at achieving greener and more efficient cooling solutions.

[0003] During the use of cooling fans, especially in places with high demand, noise will be generated during the operation of the fan, which will make people feel uncomfortable. The noise mainly comes from the vibration of the motor and the vibration generated by the fan itself during rotation. Especially at high speeds, these noises may be more obvious, and because of the high-speed movement of the airflow, eddy currents and collisions will occur, causing air vibration to produce noise. Although brushless motors have significantly improved in noise control compared to brushed motors, there is still room for further optimization to meet application scenarios with higher requirements for quietness. The stator in the brushless motor forms an electromagnet by energizing it, which will generate a certain amount of heat during operation. In addition, the stator is located on the inside of the rotor, and the overall ventilation and heat dissipation effect is not good. It is easy to accumulate heat and cause damage, or the magnetic field changes due to overheating, which affects the attraction of the permanent magnet in the rotor, causing jitter during rotation. Summary of the invention

[0004] (I) Technical problems to be solved: In view of the deficiencies in the prior art, the present invention provides a low-noise heat dissipation fan, which has the advantages of stable operation and low noise, and solves the problem of noise generated during the operation of the heat dissipation fan.

[0005] (ii) Technical solution: In order to achieve the above-mentioned purpose of stable operation and low noise, the present invention provides the following technical solution: a low-noise heat dissipation fan, comprising a base and a double-layer fan blade, a bearing is arranged at the center of the base, and a stator is arranged in a circular array on the side of the bearing, the stator is an iron core, and is wrapped by a painted coil to form an electromagnet, the power-on state of the coil is controlled by a control circuit, and a Hall sensor is arranged for detection, the double-layer fan blade is composed of a rotor, a connecting ring and fan blades, the rotor is located at the axis of the double-layer fan blade and is cylindrical, a crankshaft connected to the stator is arranged at the axis of the bottom of the double-layer fan blade, the side of the rotor is arranged in a circular array with fan blades and connected to the connecting ring, the outer side of the side of the connecting ring is also arranged in a circular array with fan blades to form a double-layer fan blade structure, the inner wall of the rotor and the connecting ring is evenly arrayed with permanent magnets, and the permanent magnets located in the connecting ring and the permanent magnets in the rotor are arranged at different angles.

[0006] Preferably, the permanent magnet is in an arc shape, and the permanent magnet fits the rotor and the wall surface of the connecting ring.

[0007] Preferably, the base has outer ring ventilation openings in an array along the axial circumference, the outer ring ventilation openings are arranged on the base outside the stator, and the area of ​​each outer ring ventilation opening is greater than 4% of the total area of ​​the base.

[0008] Preferably, rotor vents are provided on the side of the rotor, and the number and angle of the rotor vents are consistent with the permanent magnets located on the inner side of the connecting ring.

[0009] Preferably, the base has inner ring vents in an array along the axial circumference, air enters from the inner ring vents and contacts the stator, and is affected by the airflow at the outer ring vents, and then flows out from the rotor vents.

[0010] Preferably, the connecting column formed by the spacing between the outer ring ventilation openings and the ventilation openings in the inner ring ventilation openings is provided with rounded corners.

[0011] Preferably, a fixing ring is provided on the base, and when the double-layer fan blades are installed on the base, the fixing ring limits the connecting ring.

[0012] Preferably, the permanent magnet is made of neodymium iron boron, and the stator is made of silicon steel sheets.

[0013] Preferably, the total number of permanent magnets is the same as the number of stators.

[0014] (III) Beneficial effects: Compared with the prior art, the present invention provides a low-noise cooling fan having the following beneficial effects: 1. The low-noise cooling fan, through a double-layer fan blade structure, especially the inner fan blade adopts a blade design with a larger chord length, so that when the air passes through the inner fan blade, the throat of the flow channel can be closer to the fan blade, and when the outer circle flow channel continues to converge, the inner circle flow channel has already diverged and expanded. Therefore, the two circles of nested airflows are gathered and decelerated due to the collision, and the aerodynamic noise can be reduced by reducing airflow disturbance and vortex generation. This design is particularly important for equipment that requires a low-noise environment, such as server rooms, libraries, offices, etc. A brushless motor is used to replace the traditional brushed motor, which eliminates the mechanical friction between the carbon brush and the commutator, thereby significantly reducing mechanical noise and electromagnetic noise. The electromagnetic interference of the brushless motor is also small, further improving the overall quiet performance. The inner and outer layers of the double-layer fan blade structure The permanent magnets each generate a magnetic field and superimpose on each other to form a stronger total magnetic field, which not only improves the magnetic coupling efficiency between the motor and the fan, but also enables the motor to more efficiently convert electrical energy into mechanical energy when driving the fan, thereby helping to improve the heat dissipation effect. By optimizing the layout and pole configuration of the two layers of permanent magnets, a more uniform magnetic field distribution and more effective torque transmission can be achieved, thereby increasing the speed. By controlling the mass and distribution of the two layers of permanent magnets, the unbalanced force during rotation can be reduced, thereby reducing vibration and noise, improving the stability of the fan, and helping to reduce vibration, thereby reducing mechanical noise caused by vibration. The double-layer double-magnet design and double-layer blade design enable the fan to be adjusted according to different usage scenarios or different usage requirements during design, and can produce a variety of products, solving the noise generated by the cooling fan's own vibration, motor vibration, and airflow vibration during operation.

[0015] 2. The low-noise cooling fan has an outer ring vent array along the axis of the base. Its large area design effectively avoids the noise and turbulence caused by the airflow passing through the vent at too fast a speed. This design not only ensures the smooth flow of air, but also significantly reduces the noise caused by the acceleration of airflow. The inner ring vent allows air to enter and contact the stator, while the outer ring vent forms a negative pressure effect, guiding the air to flow out from the stator through the rotor vent. This design forms an effective air circulation path, which promptly takes away the heat generated by the stator during operation, effectively avoiding heat. The number and angle of the rotor vents are consistent with the permanent magnets on the inner side of the connecting ring. This design ensures that when the stator attracts or repels the permanent magnets, the airflow can accurately flow through the working stator and take away the heat generated by it. This targeted heat dissipation design further improves the heat dissipation efficiency of the fan. Through the optimized vent design, the heat generated by the stator during operation can be quickly taken away, thereby reducing heat accumulation. This not only helps to reduce the operating temperature of the motor and extend the service life of the motor, but also improves the operating efficiency and stability of the motor.

[0016] 3. The low-noise cooling fan has a connecting column formed by the spacing between the vents in the outer ring vents and the inner ring vents, and is provided with a rounded corner. The rounded corner design can significantly reduce the resistance generated when the airflow passes through the connecting column between the vents. Sharp corners are likely to cause turbulence and eddy currents in the airflow, increase noise and energy loss, while the rounded corners can make the airflow transition more smoothly, reduce noise and improve ventilation efficiency. The rounded corner design can also enhance the structural strength of the connecting column to a certain extent, and reduce the risk of fracture caused by stress concentration, which is of great significance for ensuring the long-term stable operation of the fan. The permanent magnet is in an arc shape, and the rotor and the wall of the connecting ring fit together. The arc-shaped permanent magnet design can better match the shape of the magnetic field generated by the stator, so that the magnetic field is more evenly distributed on the surface of the permanent magnet. This uniform magnetic field distribution helps to improve the magnetic coupling efficiency, so that the motor can more efficiently convert electrical energy into mechanical energy when driving the fan. Efficient magnetic coupling can also reduce magnetic flux Leakage and energy loss, further improving the performance of the fan, the close fit between the permanent magnet and the rotor and the connecting ring wall helps to reduce the flow resistance of air between them, this design allows air to flow more smoothly when passing through the fan, reducing the noise and vibration caused by air flow disturbance, at the same time, the close-fitting structure can also reduce the energy loss caused by air leakage, and improve the overall aerodynamic performance of the fan, a fixing ring is provided on the base, when the double-layer fan blades are installed on the base, the fixing ring limits the connecting ring, the setting of the fixing ring can ensure that the double-layer fan blades have the correct position and angle when installed on the base, this limiting effect helps to reduce the performance degradation and noise increase caused by installation errors, the fixing ring not only plays a limiting role, but also provides additional support and fixing force during the operation of the fan, which helps to prevent the double-layer fan blades from loosening or shifting when rotating at high speed, and improves the stability and reliability of the entire fan structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The structure of the present invention is shown in FIG. Figure 1 .

[0018] Figure 2 The structure of the present invention is shown in FIG. Figure 2 .

[0019] Figure 3 The double-layer fan blades in the present invention are shown in FIG. Figure 1 .

[0020] Figure 4 The double-layer fan blades in the present invention are shown in FIG. Figure 2 .

[0021] Figure 5 The base of the present invention is shown in FIG. Figure 1 .

[0022] Figure 6 The base of the present invention is shown in FIG. Figure 2 .

[0023] Figure 7 Schematic diagram of gas flow in the present invention.

[0024] Figure 8 It is a schematic diagram of gas gathering and diffusion in the present invention.

[0025] In the figure: 1. base; 2. double-layer fan blades; 11. stator; 12. outer ring vents; 13. fixing ring; 21. rotor; 22. connecting ring; 111. bearing; 121. inner ring vents; 211. permanent magnet; 212. crankshaft; 213. rotor vents. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] See also Figure 1-Figure 6 A low-noise cooling fan comprises a base 1 and a double-layer blade 2. A bearing 111 is arranged at the center of the base 1, and a stator 11 is arranged in a circular array on the side of the bearing 111. The stator 11 is an iron core and is wrapped by a painted coil to form an electromagnet. The energization state of the coil is controlled by a control circuit, and a Hall sensor is arranged for detection. The double-layer blade 2 is composed of a rotor 21, a connecting ring 22 and a blade. The rotor 21 is located at the axis of the double-layer blade 2 and is cylindrical. A crankshaft 212 connected to the stator 11 is arranged at the axis of the bottom of the double-layer blade 2. Blades are arranged in a circular array on the side of the rotor 21 and are connected to the connecting ring 22. Blades are also arranged in a circular array on the outer side of the side of the connecting ring 22 to form a double-layer blade structure. The inner wall surfaces of the rotor 21 and the connecting ring 22 are uniformly arrayed with permanent magnets 211, and the permanent magnets 211 located in the connecting ring 22 are arranged at different angles from the permanent magnets 211 in the rotor 21.

[0028] The fan of the present invention adopts double-layer blades 2, and the inner blades adopt blades with a larger chord length, so that when the air passes through the inner blades, the throat of the flow channel can be closer to the blades. When the outer circle flow channel continues to converge, the inner circle flow channel has already diverged and expanded. Therefore, the two circles of nested airflows are gathered and decelerated due to collision, so that the cross-sectional area of ​​the flow channel expands rapidly. Figure 8, becoming an airflow with a faster decaying forward speed but a larger cross-sectional size, which can reduce the turbulent noise and mechanical vibration noise generated by the air flow, which is particularly important for equipment that requires a low-noise operating environment, and the cooling fan used for the equipment generally sucks the hot air flow inside the equipment from the back of the fan and blows it out, so even if the air flow speed slows down due to collision, it has little effect on the heat dissipation of the equipment. The double-layer fan blade 2 of the present invention is installed on the bearing 111 in the middle of the base 1 through the crankshaft 212, and a stator 11 is arranged on the side of the bearing 111 of the base 1. The stator 11 is an energized coil, and permanent magnets 211 are installed inside the rotor 21 of the double-layer fan 2 and on the inner side of the connecting ring 22 to form a brushless motor. The double-layer fan blade 2 is driven to rotate by adjusting the magnetic attraction and repulsion of the permanent magnet of the stator 11. Compared with a brushless motor, the brushless motor has less noise. The machine does not use carbon brushes, and the electromagnetic interference generated by the rotation of the motor is small, which helps to reduce the electromagnetic noise when the motor is running, making the brushless motor more advantageous in noise control. At the same time, permanent magnets 211 are arranged inside the rotor 21 of the double-layer fan blades 2 and on the inner side of the connecting ring 22, forming a double-layer structure. When rotating, the inner and outer layers of permanent magnets 211 will each generate a magnetic field, and these two magnetic fields can be superimposed on each other to a certain extent, thereby forming a stronger total magnetic field in the fan working area. The enhanced magnetic field can improve the magnetic coupling efficiency between the motor and the fan, so that the motor can more efficiently convert electrical energy into mechanical energy when driving the fan. The strong permanent magnet 211 magnetic field helps to stabilize the operation of the motor and reduce the high-order harmonic content in the armature magnetic field. This can not only reduce the electromagnetic noise of the motor, but also reduce the eddy current loss caused by high-order harmonics, thereby improving the overall efficiency of the motor.

[0029] See also Figure 4 and Figure 6-Figure 7The base 1 is provided with an outer ring vent 12 in an array along the axis circumference. The outer ring vent 12 is arranged on the base 1 outside the stator 11, and the area of ​​each outer ring vent 12 is greater than 4% of the total area of ​​the base 1. The larger vent area can effectively prevent the airflow from passing through the vent too fast, causing noise and turbulence. The side of the rotor 21 is provided with a rotor vent 213. The number and angle of the rotor vent 213 are consistent with the permanent magnet 211 located on the inner side of the connecting ring 22. The base 1 is provided with an inner ring vent 121 in an array along the axis circumference. The air enters from the inner ring vent 121 and contacts with the stator 11, and is affected by the airflow at the outer ring vent 12 to form Negative pressure, the air at the stator 11 flows outward from the rotor vents 213, effectively avoiding heat accumulation at the stator 11. The total number of permanent magnets 211 is the same as the number of stators 11, and the number and angle of the rotor vents 213 are consistent with the permanent magnets 211 located on the inner side of the connecting ring 22. The essence of the working principle of the brushless motor is the attraction and repulsion of the permanent magnets 211 by the magnetic field generated by the stator 11. When the working stator 11 attracts the permanent magnets 211 located on the outer ring connecting ring 22, the stator 11, the rotor vents 213 and the permanent magnets 211 are located in a straight line, so that the airflow can pass through the working stator 11 and take away the heat generated when the stator 11 is powered on.

[0030] The connecting column formed by the spacing between the vents in the outer ring vents 12 and the inner ring vents 121 is provided with rounded corners. The rounded corner design can significantly reduce the resistance generated when the airflow passes through the connecting column between the vents. Sharp corners can easily cause turbulence and eddy currents in the airflow, increase noise and energy loss, while the rounded corners can make the airflow transition more smoothly, reduce noise and improve ventilation efficiency. The rounded corner design can also enhance the structural strength of the connecting column to a certain extent and reduce the risk of fracture due to stress concentration, which is of great significance for ensuring the long-term stable operation of the fan.

[0031] See also Figure 3-Figure 4 The permanent magnet 211 is in an arc shape, and the walls of the rotor 21 and the connecting ring 22 fit closely together. The arc-shaped permanent magnet 211 design can better match the shape of the magnetic field generated by the stator, so that the magnetic field is more evenly distributed on the surface of the permanent magnet 211. This uniform magnetic field distribution helps to improve the magnetic coupling efficiency, so that the motor can more efficiently convert electrical energy into mechanical energy when driving the fan. Efficient magnetic coupling can also reduce magnetic flux leakage and energy loss, further improving the performance of the fan. The close fit between the permanent magnet 211 and the walls of the rotor 21 and the connecting ring 22 helps to reduce the flow resistance of air between them. This design allows air to flow more smoothly when passing through the fan, reducing noise and vibration caused by airflow disturbances. At the same time, the tightly fitting structure can also reduce energy losses caused by air leakage, thereby improving the overall aerodynamic performance of the fan.

[0032] A fixing ring 13 is provided on the base 1. When the double-layer fan blades 2 are installed on the base 1, the fixing ring 13 limits the connecting ring 22. The setting of the fixing ring 13 can ensure that the double-layer fan blades 2 have the correct position and angle when installed on the base 1. This limiting effect helps to reduce the performance degradation and noise increase caused by installation errors. The fixing ring 13 not only plays a limiting role, but also provides additional support and fixing force during the operation of the fan, which helps to prevent the double-layer fan blades 2 from loosening or deflecting when rotating at high speed, thereby improving the stability and reliability of the entire fan structure.

[0033] The permanent magnet 211 is made of neodymium iron boron. Neodymium iron boron material has a high magnetic energy product, which means that it can store more magnetic energy per unit volume. This feature enables the brushless motor to achieve a higher magnetic flux density, thereby improving the torque and power density of the motor and enhancing the overall performance of the motor. The magnetic properties of neodymium iron boron material are stable and have high coercive force, that is, its magnetism is not easily disturbed by external factors, which helps the motor to maintain a stable magnetic field distribution and a high magnetic flux density during operation, further improving the efficiency and reliability of the motor. The stator 11 is made of silicon steel sheets. Silicon steel sheets have the characteristics of low magnetic permeability, low iron loss and low eddy current loss. The low magnetic permeability and low iron loss are mainly due to the irregular grain orientation of the silicon steel sheets, which makes it difficult for the magnetic field to pass smoothly, thereby producing the effect of low magnetic permeability and low iron loss. The low eddy current loss is due to the high resistivity and low magnetic permeability of the silicon steel sheets, which makes the eddy current generate resistance when passing through the silicon steel sheets, thereby reducing the eddy current.

[0034] Working principle: The working principle of an ordinary fan is to drive the blades to rotate through a motor, and the blades push the air to move. At the same time, the air is not only pushed by the blades, but also has a speed in the tangential direction of the blades, turning into a spiral slipstream (specifically refers to an airflow disturbed by the propeller behind the impeller disk. This airflow not only has a larger axial flow velocity than the incoming flow velocity from a distance, but also is accompanied by a certain rotational motion). The closer the slipstream speed is to the root of the blade, the smaller the flow velocity is. The slipstream at the tip of the blade has the fastest flow velocity, forming a high-and-low-speed nested situation between the inner and outer circles of the impeller. When the air flows through the blades, it will converge and expand. Because the air moves in the low-pressure area of ​​the fan, it will be continuously pushed and accelerated by the pressure difference. Since the air flow is mass continuous, the cross-sectional area of ​​the accelerated air flow channel is reduced, and it reaches When the air is in the high-pressure area of ​​the fan, the air obtains a pressure difference in the forward direction and continues to accelerate, so that the flow channel maintains a convergent shape. When the air moves to a distance of about 1 / 4 of the diameter behind the blade, the slipstream is blocked due to the collision with the surrounding air and reaches the maximum speed, and then turns into turbulence and continues to decelerate, so that the flow channel becomes expansionary again. Therefore, when the air passes through the electric fan blades, the throat of the flow channel will appear at a certain distance behind the blowing surface. The fan of the present invention adopts double-layer blades 2, and the inner blades adopt blades with a larger chord length, so that when the air passes through the inner blades, the throat of the flow channel can be closer to the blades. When the outer circle flow channel continues to converge, the inner circle flow channel has already diverged and expanded. Therefore, the two circles of nested airflows are gathered and decelerated due to collision, so that the cross-sectional area of ​​the flow channel expands rapidly. See Figure 8, becoming an airflow with a faster decay of forward speed but a larger cross-sectional size, which can reduce the turbulent noise and mechanical vibration noise generated by air flow, which is particularly important for equipment that requires a low-noise operating environment. The double-layer fan blade 2 of the present invention is installed on the bearing 111 in the middle of the base 1 through the crankshaft 212, and a stator 11 is arranged on the side of the bearing 111 of the base 1. The stator 11 is an energized coil, and a permanent magnet 211 is installed inside the rotor 21 of the double-layer fan 2 and on the inner side of the connecting ring 22 to form a brushless motor. The double-layer fan blade 2 is driven to rotate by adjusting the magnetic attraction and repulsion of the permanent magnet of the stator 11. Compared with a brushless motor, the brushless motor has less noise. Since the brushless motor does not use carbon brushes, the electromagnetic interference generated by the rotation of the motor is small, which helps to reduce the motor running. The electromagnetic noise of the brushless motor makes it more advantageous in noise control. At the same time, permanent magnets 211 are arranged inside the rotor 21 of the double-layer fan blades 2 and on the inner side of the connecting ring 22 to form a double-layer structure. When rotating, the inner and outer layers of permanent magnets 211 will each generate a magnetic field. These two magnetic fields can be superimposed on each other to a certain extent, thereby forming a stronger total magnetic field in the fan working area. The enhanced magnetic field can improve the magnetic coupling efficiency between the motor and the fan, so that the motor can more efficiently convert electrical energy into mechanical energy when driving the fan. The strong magnetic field of the permanent magnet 211 helps to stabilize the operation of the motor and reduce the high-order harmonic content in the armature magnetic field, which can not only reduce the electromagnetic noise of the motor, but also reduce the eddy current loss caused by high-order harmonics, thereby improving the overall efficiency of the motor.

[0035] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0036] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A low-noise heat dissipation fan, comprising a base (1) and double-layered fan blades (2), wherein a bearing (111) is arranged at the center of the base (1), and a stator (11) is arranged in a circular array on the side of the bearing (111), wherein the stator (11) is an iron core and is wrapped with a painted coil to form an electromagnet, wherein the energization state of the coil is controlled by a control circuit and a Hall sensor is arranged for detection, and wherein the stator (11) is characterized in that: The double-layered fan blade (2) is composed of a rotor (21), a connecting ring (22), and a fan blade. The rotor (21) is located at the axis of the double-layered fan blade (2) and is cylindrical. A crankshaft (212) connected to the stator (11) is provided at the axis of the bottom of the double-layered fan blade (2). The side of the rotor (21) is provided with fan blades in a circular array and is connected to the connecting ring (22). The side of the connecting ring (22) is provided with fan blades in a circular array outside, forming a double-layered fan blade structure. The inner wall surfaces of the rotor (21) and the connecting ring (22) are evenly arrayed with permanent magnets (211), and the permanent magnets (211) located in the connecting ring (22) and the permanent magnets (211) in the rotor (21) are arranged at different angles.

2. A low-noise cooling fan according to claim 1, characterized in that: The permanent magnet (211) is in an arc shape, and the permanent magnet (211) fits the wall surfaces of the rotor (21) and the connecting ring (22).

3. A low-noise cooling fan according to claim 1, characterized in that: The base (1) has outer ring ventilation openings (12) arranged in an array along the circumference of the axis, the outer ring ventilation openings (12) being arranged on the base (1) outside the stator (11), and the area of ​​each outer ring ventilation opening (12) being greater than 4% of the total area of ​​the base (1).

4. A low-noise cooling fan according to claim 3, characterized in that: The side surface of the rotor (21) is provided with a rotor vent (213), and the number and angle of the rotor vent (213) are consistent with those of the permanent magnet (211) located inside the connecting ring (22).

5. A low-noise heat dissipation fan according to claim 4, characterized in that: The base (1) has inner ring vents (121) arranged in an array along the circumference of the axis. Air enters from the inner ring vents (121) and contacts the stator (11). Air is affected by airflow at the outer ring vents (12) and flows out from the rotor vents (213).

6. A low-noise heat dissipation fan according to claim 5, characterized in that: The connecting column formed by the spacing between the ventilation holes in the outer ring ventilation holes (12) and the inner ring ventilation holes (121) is provided with rounded corners.

7. The low-noise heat dissipation fan according to claim 1, characterized in that: A fixing ring (13) is provided on the base (1); when the double-layered fan blades (2) are mounted on the base (1), the fixing ring (13) limits the position of the connecting ring (22).

8. The low-noise heat dissipation fan according to claim 1, characterized in that: The permanent magnet (211) is made of neodymium iron boron, and the stator (11) is made of silicon steel sheets.

9. The low-noise heat dissipation fan according to claim 6, characterized in that: The total number of the permanent magnets (211) is the same as the number of the stators (11).

Images