Axial flow fan blade gradient porosity lightweight hub structure

Abstract

The invention relates to the technical field of fan blade hubs, in particular to an axial flow fan blade gradient porosity lightweight hub structure. Comprising a hub body and axial flow fan blades, the hub body comprises an annular wall, and arc-shaped grooves are formed in the annular wall in the circumferential direction; the arc-shaped groove comprises a mounting groove for mounting the axial-flow fan blade and a noise reduction groove without the axial-flow fan blade; grid-shaped connecting ribs are arranged at openings of the noise reduction grooves. The elastic pieces are arranged in the back cavities of the noise reduction grooves, the wave-shaped elastic pieces are arranged in the back cavities of the noise reduction grooves, captured vibration mechanical energy is converted into heat energy to be dissipated through the structural damping effect of the elastic pieces, and noise is restrained from the source; meanwhile, the elastic sheet is excited through the side face of the micro jet flow generated by modulating the airflow through the connecting rib grid, and the elastic sheet and the Helmholtz resonator composed of the back cavity volume and the rectangular hole opening act synergistically, specific aerodynamic noise is actively absorbed and offset, and therefore on the premise that the structural strength is guaranteed, the purposes of broadband noise reduction and light weight are achieved synergistically.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fan wheel hub, in particular to a gradient porosity lightweight hub structure of axial fan blade. BACKGROUND

[0002] When the axial fan is used, the flow direction of the generated airflow is basically parallel to the axis of the axial fan. The axial fan mainly consists of a motor, a rotating shaft, a wheel and a casing. The wheel mainly consists of a hub and blades. The basic structure of the hub includes a ring body and a shaft sleeve, the ring body is located in the peripheral direction of the shaft sleeve, and the two are connected by an end plate. The shaft sleeve of the hub is used to be sleeved on the rotating shaft, and the ring body of the hub is used to install the blades. Since the structure of the axial fan is simple, it is widely used in floor fans, air purifiers and other household electrical products.

[0003] However, in the existing household electrical appliances, the hub of the axial fan blade has a difficult-to-reconcile contradiction between lightweight design (such as opening weight-reducing holes or grooves) and ensuring structural strength and suppressing operating noise when the axial fan is used. Specifically, if the traditional hub is provided with weight-reducing holes or grooves, the structural rigidity will be weakened, and vibration will be easily generated under the action of rotating centrifugal force and radiate noise; while simply increasing the material or connecting rib to strengthen the structure can improve the strength, but it will increase the weight and cannot effectively eliminate the generated vibration and aerodynamic noise, resulting in that the fan system is difficult to balance high efficiency, lightweight and low noise operation. SUMMARY

[0004] The present application provides a gradient porosity lightweight hub structure of axial fan blade, which sets a wave-shaped elastic sheet in the back cavity of the noise reduction groove, converts the captured vibration mechanical energy into heat energy dissipation by using the structural damping effect, and suppresses the noise from the source; at the same time, the elastic sheet is excited by the microjet side flow generated by the connecting rib lattice and cooperates with the Helmholtz resonator composed of the back cavity volume and the rectangular orifice, actively absorbs and cancels the specific aerodynamic noise, so as to realize the noise reduction and lightweight in a wide frequency band on the premise of ensuring the structural strength, thereby solving the problems raised in the background art, that is: In the prior art, the lightweight design, structural strength improvement and operating noise suppression of the hub of the axial fan are mutually restricted, and cannot be optimized at the same time, resulting in that the fan system is difficult to balance high efficiency, lightweight and low noise operation.

[0005] To achieve the above purpose, the gradient porosity lightweight hub structure of axial fan blade includes a hub body and an axial fan blade, the hub body includes a ring wall, and an arc-shaped groove is formed circumferentially on the ring wall; The arc-shaped groove includes a mounting groove for mounting the axial fan blade and a noise reduction groove without mounting the axial fan blade; a grid-shaped connecting rib is arranged at the opening of the noise reduction groove; The back cavity is formed behind the connecting rib in the depth direction; The elastic sheet is arranged in the back cavity, and two ends of the elastic sheet are connected with the inner wall of the noise reduction groove through a fixing structure.

[0006] In the above technical solution, a plurality of noise reduction grooves are arranged on the annular wall of the hub body in the circumferential direction, which realizes a substantial weight reduction of the base; the noise reduction grooves are provided with grid-shaped connecting ribs at the openings, which greatly enhances the overall structural rigidity and stability of the hub body while effectively reducing the aerodynamic opening area to reduce wind resistance and noise, preventing the annular wall from deforming at high speed rotation; further, the elastic sheet with fixed two ends is ingeniously arranged in the back cavity of each noise reduction groove, which has the core effect of generating Helmholtz resonance effect or forced vibration with airflow sound waves of a specific frequency, actively absorbing and consuming wide-band aerodynamic noise energy, thereby achieving efficient noise reduction at the sound source.

[0007] Further, the thickness of the connecting rib extending into the noise reduction groove accounts for 25%-35% of the overall depth of the noise reduction groove; the connecting rib extending to 25%-35% of the depth of the noise reduction groove constitutes a solid framework deep into the back cavity, which enhances the ability of the annular wall to resist centrifugal deformation and vibration at high speed rotation, ensuring the structural reliability; at the same time, the design of this depth not only ensures that the connecting rib has sufficient effective length to provide strong structural support, but also ingeniously avoids excessive intrusion into the back cavity space, thereby maximizing the integrity of the back cavity volume, which is a key parameter determining the core noise reduction frequency of the Helmholtz resonator. Therefore, the design not only obtains excellent mechanical strength, but also strictly guarantees the stability of the natural frequency of the back cavity where the elastic sheet is located and the predictability of the noise reduction performance, which is the key optimization for realizing the synergy of strong structure and high noise reduction.

[0008] Preferably, the elastic sheet is a wave-shaped sheet structure, and when the elastic sheet is installed in the noise reduction groove, the turning points of the wave-shaped sheet structure are in contact with the inner wall of the noise reduction groove; the wave-shaped sheet structure can greatly improve the efficiency of vibration absorption and noise reduction in a wide frequency band by introducing multi-point contact pre-tightening and structural nonlinearity; specifically, when the elastic sheet is installed in a wave shape, each turning point of the elastic sheet forms a reliable contact point with the inner wall of the noise reduction groove, which is equivalent to providing the elastic sheet with multiple additional distributed elastic boundary constraints instead of simple two-end fixation; the contact points can efficiently convert mechanical vibration energy into heat energy dissipation under the excitation of airflow; at the same time, the pre-tightening contact state changes the stiffness and vibration mode of the elastic sheet, so that the elastic sheet can excite more complex nonlinear vibration when subjected to wide-frequency airflow excitation, thereby widening the frequency range of effective vibration absorption and no longer being limited to a single resonance frequency; in addition, the multi-point contact support also optimizes the stress distribution on the elastic sheet, avoids excessive local stress concentration, greatly improves the noise reduction effect, and also ensures the fatigue strength and reliability of the elastic sheet under long-term high-frequency vibration.

[0009] In addition, the fixing structure comprises an embedded groove formed in the inner wall of the two short faces of the noise reduction groove and a through hole penetrating through the ring wall and communicating with the embedded groove.

[0010] Further, the two ends of the elastic sheet are provided with fixing blocks with through holes, the fixing blocks are matched with the embedded grooves, and the elastic sheet is fixed by fasteners penetrating through the through holes and the through holes.

[0011] It should be noted that the connecting ribs at the opening of the noise reduction groove are a plurality of connecting ribs, and the plurality of connecting ribs are arranged in a staggered manner to form a rectangular hole; the width of the connecting rib is 1-2 mm, and the rectangular hole formed between adjacent connecting ribs has a hole diameter of 3-5 mm.

[0012] In addition, the hub body is made of one of PBT-GF30 and PA66-GF30 engineering plastics and is integrally formed by an injection molding process, and the noise reduction groove and the connecting rib are part of the hub body.

[0013] Furthermore, the manufacturing material of the elastic sheet is one of 304 stainless steel, 316 stainless steel and titanium alloy; and the thickness of the elastic sheet is 0.1-0.3 mm.

[0014] Compared with the prior art, the present application has the following advantages: By setting the elastic sheet in the wave shape in the back cavity of the noise reduction groove, the captured vibration mechanical energy is converted into heat energy dissipation by using the structural damping effect, and the noise is inhibited from the source; at the same time, the elastic sheet is excited by the micro jet flow generated by the connecting rib lattice and cooperates with the Helmholtz resonator composed of the back cavity volume and the rectangular orifice, actively absorbs and cancels the specific aerodynamic noise, so that the wide-band noise reduction and light weight goals are realized simultaneously under the premise of ensuring the structural strength. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 It is a schematic diagram of the overall structure of the axial flow fan blade of the present application; Figure 2 It is a schematic diagram of the connecting rib structure after the ring wall is unfolded on the outside; Figure 3 It is a schematic diagram of the elastic sheet unfolded on the inside of the ring wall; Figure 4 It is a schematic diagram of the elastic sheet structure of the present application.

[0016] The meanings of various reference numerals in the drawings are as follows: 100, hub body; 101, ring wall; 102, arc-shaped groove; 103, connecting rib; 104, back cavity; 105, elastic sheet; 106, through hole; 107, via hole; 108, fixing block; 109, mounting groove; 110, noise reduction groove; 200, axial flow fan blade. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0018] At present, in the prior art, the lightweight design, structural strength improvement and operation noise suppression of the axial flow fan hub are mutually restricted, and cannot be optimized at the same time, resulting in the problem that the fan system is difficult to balance high efficiency, lightweight and low noise operation. The present application provides a gradient porosity lightweight hub structure of axial flow fan blade, as shown in Figures 1-4 ​The hub structure comprises a hub body 100 and an axial flow fan blade 200, wherein the hub body 100 comprises a ring wall 101, the thickness of the ring wall 101 is preferably 5mm in the scheme, three groups of axial flow fan blades 200 are circumferentially mounted on the ring wall 101, the roots of the axial flow fan blades 200 are arc-shaped and matched with the arc-shaped grooves 102 circumferentially opened on the ring wall 101, and in the scheme, the arc-shaped grooves 102 circumferentially opened on the ring wall 101 are not only three groups, between the roots of the three groups of axial flow fan blades 200, the arc-shaped grooves 102 penetrating through the ring wall 101 are separately arranged, the arc-shaped grooves 102 comprise mounting grooves 109 for mounting the axial flow fan blades 200 and noise reduction grooves 110 without mounting the axial flow fan blades 200; the noise reduction grooves 110 without mounting the axial flow fan blades 200 are provided with grid-shaped connecting ribs 103 at the openings thereof; In the noise reduction grooves 110 without mounting the axial flow fan blades 200, the connecting ribs 103 are staggered and arranged near the side of the axial flow fan blades 200, and the connecting ribs 103 do not completely block the noise reduction grooves 110, but form a grid shape, the connecting ribs 103 extend to the inside of the noise reduction grooves 110 by a thickness of 30% of the overall depth of the noise reduction grooves 110, so that the hub body 100 can withstand the vibration energy caused by rotation while the noise reduction grooves 110 are opened during rotation of the axial flow fan blades 200, avoiding structural damage to the ring wall 101 caused by centrifugal force formed during rotation, and the thickness of 30% reserves a larger back cavity 104 volume, which is beneficial to forming a stronger Helmholtz resonance effect when wind penetrates, when the specific frequency noise generated by the fan propagates to the connecting ribs 103, the sound pressure formed will drive air to reciprocate at high speed like a piston at the rectangular hole, if the noise frequency matches the inherent resonance frequency of the rectangular hole, strong resonance will be excited, air will rub against the connecting ribs 103 wall in the narrow hole and convert sound energy into heat energy, finally realizing targeted absorption and attenuation of specific tone aerodynamic noise and preparing for subsequent improvement of noise reduction performance.

[0019] The two short face inner walls of the noise reduction groove 110 are provided with embedded grooves, the embedded grooves are rectangular, and a through hole 106 is arranged between the embedded grooves and the inner side of the ring wall 101. The back cavity 104 reserved by the noise reduction groove 110 is provided with an elastic sheet 105, the overall shape of the elastic sheet 105 matches the noise reduction groove 110, and the elastic sheet 105 is preferably in a wave shape in this scheme. When the elastic sheet 105 is installed in the noise reduction groove 110, the fixing blocks 108 with through holes 107 at both ends are directly embedded and matched along the rectangular embedded grooves. At this time, the through holes 107 of the elastic sheet 105 are coaxially corresponding to the through holes 106 of the embedded grooves. The operator can fix the both ends of the elastic sheet 105 by small rivets or fastening screws. After the fixing is completed, each wave-shaped turning part of the elastic sheet 105 is in contact with the inner wall of the noise reduction groove 110. This contact mode can enable the axial flow fan blade 200 to sequentially transmit vibration energy from the axial flow fan blade 200 to the ring wall 101 when rotating. Because the ring wall 101 is fixedly installed with the elastic sheet 105, the rigid structure is in contact, so the vibration energy can be transmitted not only from the through holes 107 at both ends, but also from the wave-shaped turning parts of the elastic sheet 105 in contact with the inner wall of the noise reduction groove 110. When the vibration frequency transmitted from the outside approaches the natural frequency of the elastic sheet 105, the elastic sheet 105 will enter a resonance state. The resonance state is specifically a violent swing opposite to the vibration direction of the hub body 100 and with an amplitude greater than the vibration of the hub body 100 itself. The violent swing of the elastic sheet 105 itself will cause the elastic sheet 105 to capture the harmful vibration mechanical energy originally concentrated on the hub body 100 and the axial flow fan blade 200 through the molecular friction inside the material itself, which is equivalent to a damping effect. The harmful vibration mechanical energy is irreversibly converted into heat energy. Then, the heat energy is dissipated in the air convection process through the wind disturbance of the axial flow fan blade 200. With the continuous consumption of vibration energy, the vibration as the source of noise is suppressed, so that the operation noise of the axial flow fan blade 200 is reduced. Regarding the selection of the noise reduction groove 110 with the same shape as the installation root of the axial flow fan blade 200 as the installation part of the elastic sheet 105 and the connecting rib 103 in the scheme: Firstly, from the perspective of structural mechanics and reliability, the design of the noise reduction groove 110 is the key to realizing stress smooth transition and avoiding concentrated damage. The arc profile of the root of the axial flow fan blade 200 is the main stress path. If a rectangular groove is used, the sharp right angle of the rectangular groove will form a stress concentration focus here, greatly increasing the risk of fatigue cracks. The use of the noise reduction groove 110 with the same shape as the root of the axial flow fan blade 200 enables the smooth transmission of aerodynamic load and centrifugal force along the smooth curve, and the stress flow line does not have sharp turns when bypassing the slot, which fundamentally improves the structural integrity and fatigue life of the hub body 100 and lays a foundation for realizing safe and reliable lightweight design. Secondly, from the perspective of vibration control and acoustic performance, the noise reduction groove 110 ensures the matching of vibration modes and efficient energy transmission; the forced vibration of the elastic sheet 105 suppresses the vibration of the axial flow fan blade 200, and the discontinuous distribution of the stiffness of the rectangular groove will distort and hinder the transmission of the vibration wave, resulting in a decrease in damping effect. The isomorphic noise reduction groove 110 and the root of the axial flow fan blade 200 form a vibration cooperative whole, which can make the vibration wave of the axial flow fan blade 200 more smoothly conduct to the elastic sheet 105, greatly optimizing the efficiency of the reverse damping, and the smooth arc shape is also conducive to maintaining the smoothness of the aerodynamic shape and avoiding the generation of additional vortex noise.

[0020] It needs to be further explained that the connecting ribs 103 provided in the noise reduction groove 110 close to the outer side of the axial flow fan blade 200 are in a grid shape, which itself has an additional effect in addition to strengthening the structural strength of the ring wall 101 due to its thickness, specifically: The adjacent connecting ribs 103 are interlaced to form a rectangular hole that allows airflow to pass through. When the axial flow fan blade 200 is running, the airflow is disturbed by the sheet-shaped axial flow fan blade 200, and the close airflow is pushed to the front of the axial flow fan blade 200. At this time, the airflow field at the root of the axial flow fan blade 200 is also disturbed in the opposite direction. Some of these airflows flow along the back of the axial flow fan blade 200, and the other part rushes to the noise reduction groove 110 opened by the ring wall 101. After passing through the rectangular hole between the connecting ribs 103, the rectangular hole forms a guide for the airflow and blows to the side of the elastic sheet 105, efficiently exciting the elastic sheet 105 to produce controlled high-frequency micro-vibration; Here, the specific excitation principle is further explained. When the high-speed but turbulent airflow passes through the rectangular hole of the connecting rib 103, its large-scale vortex is cut and broken by the connecting rib 103, forming a series of periodic micro-jets with strong directionality and energy concentration. These micro-jets directly act on the side of the elastic sheet 105 at a precise angle and higher flow rate, not only avoiding the problem of excessive damping caused by head-on impact, but also forming high-frequency and high-energy effective pressure pulsation on the surface of the elastic sheet 105. This pulsation quickly overcomes the structural damping of the elastic sheet 105, efficiently exciting the elastic sheet 105 to produce strong bending mode vibration at its natural frequency. This forced vibration in turn acts on the flow field, and its vibration energy is dissipated through the internal friction of the material and acoustic radiation. At the same time, the reverse sound waves generated by the vibration of the elastic sheet 105 interfere with and cancel the original aerodynamic noise sound waves in the sound field, thereby realizing energy resolution and cancellation of specific frequency noise at the source.

[0021] In the present scheme, it needs to be further supplemented that the hub body 100 adopts engineering plastics, and the specific model can adopt PBT-GF30 or PA66-GF30 through injection molding process, wherein the injection molding process is a mature technology, and will not be repeated here, and the PBT-GF30 or PA66-GF30 materials can be purchased from BASF (China) Co., Ltd.; and the hub body 100 integrally formed includes the noise reduction groove 110 and the connecting rib 103, wherein the connecting rib 103 has a thickness of 30% of the depth of the noise reduction groove 110, and the width of the connecting rib 103 is preferably 1-2mm in the present scheme, and the rectangular hole aperture between adjacent connecting ribs 103 is 3-5mm, which can optimally disperse the air flow into effective micro-jets under the premise of ensuring the structural strength; In addition, the elastic sheet 105 is preferably made of one of 304 stainless steel, 316 stainless steel and titanium alloy in the present scheme, and the thickness of the elastic sheet 105 is preferably 0.1-0.3mm, which is mainly selected for household appliances, and the target noise reduction range is 100Hz-2000Hz, which covers the main aerodynamic noise generated by the rotation of the axial fan blade 200 and the low-frequency noise generated by structural resonance.

[0022] Regarding the aforementioned back cavity 104, it needs to be further explained that the volume of the noise reduction groove 110 back cavity 104 and the cross-sectional area of the rectangular hole aperture jointly determine the resonance frequency of the Helmholtz resonator, and specifically, the resonance frequency f can be estimated by the following formula: In the formula, C is the speed of sound, A is the area of the rectangular hole aperture, V is the volume of the back cavity 104, and L is the effective length of the rectangular hole aperture. The design purpose of the back cavity 104 is to match the main aerodynamic noise frequency generated by the rotation of the axial fan blade 200, such as the BPF and its harmonics of the axial fan blade 200, to enhance the absorption effect of the noise of the frequency.

[0023] Example 1: suitable for air purifier (characteristics are medium size, low speed, target noise reduction frequency 620Hz.) Application product: air purifier. This product category requires quiet operation, and noise directly affects user experience.

[0024] Back cavity 104 and rectangular hole aperture experimental parameters: The volume of the back cavity 104 of a single noise reduction groove 110 is V=1.5×10 -5 m 3 ; The total aperture area of the rectangular hole is A=8.0×10 -6 m 2 ; Effective length of rectangular hole opening: L=5mm; The speed of sound is taken as 340 m / s at room temperature.

[0025] Substituting into the previous formula, the resonant frequency can be calculated. f The result is 603Hz, which is close to the target noise reduction frequency of 620Hz, and can effectively target specific noise peaks of air purifiers.

[0026] Example 2: Applicable to floor fans (large, low speed, target noise reduction frequency of 275Hz). Experimental parameters for the 104-cavity back cavity and the rectangular aperture: Single noise reduction slot 110 back cavity 104 volume: V=1.2×10 -4 m 3 ; Total area of ​​the rectangular hole opening: A = 3.0 × 10 -5 m 2 ; Effective length of rectangular hole opening: L=4mm; The speed of sound is taken as 340 m / s at room temperature.

[0027] Substituting into the previous formula, the resonant frequency can be calculated. f The result is 296Hz, which is close to the target noise reduction frequency of 275, and can effectively target specific noise peaks of floor fans.

[0028] The working principle is the synergy of structural damping and aeroacoustic effects: First, through the damping effect of the elastic plate 105, the mechanical vibration energy of the hub body 100 and the axial flow fan blade 200 is directly consumed, suppressing structural radiation noise from the source; at the same time, the grid-modulated airflow actively excites the elastic plate 105, and through the Helmholtz resonance effect, they work together on the flow field to absorb and cancel specific aerodynamic noise components. The two mechanisms are physically coupled and functionally complementary, jointly achieving a wide-bandwidth and high-efficiency noise reduction effect. In the overall design, the connecting rib 103, the back cavity 104, and the elastic sheet 105 are coupled together, working synergistically to form a hub structure that is efficient, lightweight, and operates with low noise. The rectangular orifices of the lattice-shaped connecting ribs 103 first form a Helmholtz resonator together with the back cavity 104, which targets specific aerodynamic noise frequencies for the first stage of sound energy consumption. More importantly, these orifices actively modulate and accelerate the airflow into a series of periodic micro-jets with precise direction and concentrated energy when the airflow passes through. These micro-jets efficiently excite the wave-shaped elastic sheet 105 to produce forced vibration from the side rather than the front. The elastic sheet 105, as a damping element, dissipates the mechanical energy of structural vibration from the hub through internal friction and interface slip. As an actively driven acoustic element, the elastic sheet 105, excited by the micro-jets, in turn modulates the flow field and radiates sound waves, which interfere with and cancel the original noise of specific frequencies.

[0029] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions in the specification are only preferred examples of the present application and are not intended to limit the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A axial flow fan blade gradient porosity lightweight hub structure, comprising a hub body (100) and an axial flow fan blade (200), characterized in that: The hub body (100) comprises a ring wall (101), and an arc-shaped slot (102) is formed in the ring wall (101) in a circumferential direction; The arc-shaped slot (102) comprises a mounting slot (109) for mounting the axial fan blade (200) and a noise reduction slot (110) without mounting the axial fan blade (200); the noise reduction slot (110) is provided with a grid-shaped connecting rib (103) at an opening thereof, and the noise reduction slot (110) is isomorphic with the mounting slot (109); The noise reduction slot (110) is formed with a back cavity (104) behind the connecting rib (103) in a depth direction; The back cavity (104) is provided with an elastic sheet (105), and both ends of the elastic sheet (105) are connected to the inner wall of the noise reduction slot (110) through a fixing structure.

2. The axial flow impeller gradient porosity light-weight hub structure according to claim 1, characterized in that: The thickness of the connecting rib (103) extending into the noise reduction slot (110) accounts for 25%-35% of the overall depth of the noise reduction slot (110).

3. The axial fan blade gradient porosity lightweight hub structure of claim 1, wherein: The elastic sheet (105) is a wave-shaped sheet structure, and when the elastic sheet (105) is installed in the noise reduction slot (110), the turning portions of the wave-shaped elastic sheet (105) are in contact with the inner wall of the noise reduction slot (110).

4. The axial flow impeller gradient porosity light-weight hub structure of claim 1, wherein: The fixing structure comprises an embedded groove formed in the inner wall of two short faces of the noise reduction slot (110) and a through hole (106) penetrating through the ring wall (101) and communicating with the embedded groove.

5. The axial fan blade gradient porosity light-weight hub structure of claim 4, wherein: Both ends of the elastic sheet (105) are provided with a fixing block (108) with a through hole (107), the fixing block (108) is matched with the embedded groove, and the elastic sheet (105) is fixed by a fastener penetrating through the through hole (107) and the through hole (106).

6. The axial fan blade gradient porosity light-weight hub structure of claim 1, wherein: The connecting rib (103) at the opening of the noise reduction slot (110) is a plurality of connecting ribs (103), and the plurality of connecting ribs (103) are arranged in a staggered manner to form a rectangular hole.

7. The axial fan blade gradient porosity light-weight hub structure of claim 1, wherein: The hub body (100) is made of one of PBT-GF30 and PA66-GF30 engineering plastics and is integrally formed by an injection molding process, and the noise reduction slot (110) and the connecting rib (103) are part of the hub body (100). 8.The axial-flow impeller gradient porosity light-weight hub structure of claim 1, characterized in that: The manufacturing material of the elastic sheet (105) is one of 304 stainless steel, 316 stainless steel and titanium alloy. 9.The axial-flow impeller gradient porosity light-weight hub structure of claim 1, characterized in that: The thickness of the elastic sheet (105) is 0.1-0.3mm. 10.The axial-flow fan blade gradient porosity light-weight hub structure of claim 6, wherein: The width of the connecting rib (103) is 1-2mm, and the aperture of the rectangular hole formed between adjacent connecting ribs (103) is 3-5mm.

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