Compact low-noise centrifugal fan

Abstract

The invention relates to the technical field of fans, in particular to a compact low-noise centrifugal fan. Comprising a volute body, an impeller arranged in the volute body and a driving motor installed on the volute body, an output shaft of the driving motor is connected with the impeller, and an air inlet and an air outlet are formed in the volute body; a volute tongue is arranged in the volute body; the volute body comprises a volute framework, a volute panel and a volute pore plate; the volute hole plate is arranged in the volute framework, and the volute framework is covered with the volute panel. A sound absorption material is filled between the volute panel and the volute pore plate, and a plurality of silencing holes are evenly distributed in the volute pore plate. Therefore, noise can be well absorbed by the sound absorption material through the silencing holes, and the noise reduction effect is improved.

Description

Technical Field

[0001] The invention relates to the technical field of fans, and in particular to a compact low-noise centrifugal fan. Background Art

[0002] When using centrifugal fans for ventilation and heat dissipation, the operating noise of the fan is harmful to the human body. Reducing the operating noise of the fan itself is of great help to reduce the system noise. Centrifugal fans have the characteristics of large flow coefficient, high pressure coefficient, high efficiency and relatively low noise, and are often used in special application fields. In the field of manned space flight, due to the small space environment, the noise generated and transmitted by conventional centrifugal fans has a more obvious impact on astronauts. Therefore, when selecting low-noise centrifugal fans, passive noise reduction design is also required, and a variety of measures are used to reduce the operating noise of the fan.

[0003] In the prior art, for example, a patent with announcement number CN212508886U discloses a low-noise rectangular centrifugal fan, comprising a centrifugal fan body, a rectangular shell sleeved on the outside of the centrifugal fan body, and a power motor fixed to the rectangular shell, wherein a sound-absorbing filler is filled between the centrifugal fan body and the rectangular shell; the centrifugal fan body comprises a fan volute, an air inlet arranged on the fan volute, an air outlet channel, and an impeller arranged in the fan volute; and a sound-absorbing plate is fixed on the inner wall of the fan volute and the air outlet channel.

[0004] In the above prior art, since the panel of the fan volute often adopts a solid plate structure, the noise reduction effect is not obvious. Therefore, it is necessary to provide a centrifugal fan with a more significant noise reduction effect. Summary of the invention

[0005] The main purpose of the present invention is to provide a compact low-noise centrifugal fan to solve the above technical problems.

[0006] To achieve the above-mentioned objectives, the present invention proposes a compact low-noise centrifugal fan, comprising a volute body, an impeller arranged inside the volute body, and a drive motor installed on the volute body, the output shaft of the drive motor is connected to the impeller, and an air inlet and an air outlet are arranged on the volute body; a volute tongue is arranged inside the volute body; the volute body comprises a volute frame, a volute panel and a volute orifice plate; the volute orifice plate is arranged in the volute frame, and the volute panel covers the volute frame; sound-absorbing material is filled between the volute panel and the volute orifice plate, and a plurality of silencer holes are evenly distributed on the volute orifice plate.

[0007] Preferably, an inner ring body and a current collector are installed at the air inlet; the inner ring body includes a cylindrical body, a circular ring body integrally formed on the inner wall of one end of the cylindrical body, and a flange edge integrally formed on the outer wall of the other end of the cylindrical body; a plurality of silencer holes are evenly distributed on the cylindrical body and the circular ring body respectively; the current collector is in a trumpet shape, the inner ring body is sleeved on the current collector, and sound-absorbing material is filled between the inner wall of the inner ring body and the outer surface of the current collector.

[0008] Preferably, the sound absorbing material is melamine foam or polyurethane foam; the sound absorbing material is wrapped with silk cloth; and the perforation rate of the muffler holes is 15% to 25%.

[0009] Preferably, the silencer hole is a through hole with a diameter of φ2.5 mm, and three adjacent silencer holes are distributed in a regular triangle with a side length of 6 mm.

[0010] Preferably, the impeller includes a wheel disc, blades and an impeller inlet ring; a plurality of blades are evenly distributed in an annular shape on the wheel disc, and the impeller inlet ring is sleeved on the outside of all blades close to one end of the inner ring body; the small end of the collector passes through the center hole of the annular body and extends into the impeller inlet ring, and the nesting length between the small end of the collector and the impeller inlet ring is L, satisfying L=5mm~10mm.

[0011] Preferably, the inlet edge tangent of the impeller inlet collar is V1, the outlet edge tangent of the collector is V2, and the angle between the tangent V1 and the tangent V2 is δ, satisfying δ=5°~10°.

[0012] Preferably, a bell-shaped air deflector is installed on the output shaft of the driving motor; the large end face of the air deflector abuts against the surface of the wheel disc; the inner hole of the small end of the air deflector is sleeved on the output shaft of the driving motor, and a slotted conical nut is screwed on the end of the output shaft of the driving motor and tightens the air deflector; the outer cylindrical surface of the slotted conical nut smoothly transitions to the outer surface of the air deflector.

[0013] Preferably, a bearing cover and a bearing are installed on the housing of the driving motor, and the bearing is sleeved on the output shaft, and the bearing cover abuts against the right end face of the outer ring of the bearing; a wheel disc mounting tube is integrally formed at the center of the wheel disc, the wheel disc mounting tube is sleeved on the output shaft of the driving motor, and a flat key is arranged between the wheel disc mounting tube and the output shaft; a retaining ring is sleeved on the output shaft, and the retaining ring is located between the bearing and the wheel disc mounting tube; a locking nut is screwed on the output shaft; when the locking nut is tightened, the locking nut abuts against the right end face of the wheel disc mounting tube, axially pushing the wheel disc mounting tube to tighten the retaining ring, and making the retaining ring tighten against the right end face of the inner ring of the bearing.

[0014] Preferably, a first annular boss is integrally formed at the left end of the outer circumferential surface of the retaining ring, and a second annular boss is integrally formed at the right end; the outer diameter of the second annular boss is larger than the outer diameter of the first annular boss; an annular groove is formed between the second annular boss and the first annular boss; the center hole of the bearing cover includes a first hole section and a second hole section from left to right; the diameter of the second hole section is larger than the diameter of the first hole section; the retaining ring is arranged in the center hole of the bearing cover, and the first annular boss is located in the first hole section, and the second annular boss is located in the second hole section.

[0015] Preferably, the volute tongue is provided with a guide surface and a mounting plane; a threaded hole is provided on the mounting plane; the height from one end of the guide surface to the mounting plane is h1, and the height from the other end to the mounting plane is h2; the curvature radius of the end with a distance of h1 is R1, and the curvature radius of the end with a distance of h2 is R2, satisfying: R1>R2, and h1<h2; the guide surface is an inclined surface whose curvature radius gradually decreases from R1 to R2.

[0016] Due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows:

[0017] (1) In the present invention, since the volute body includes a volute orifice plate, a volute frame and a volute panel from the inside to the outside, a plurality of silencer holes are evenly distributed on the volute orifice plate, and sound-absorbing material is filled between the volute panel and the volute orifice plate, the noise can be well absorbed by the sound-absorbing material through the silencer holes, thereby improving the noise reduction effect.

[0018] (2) In the present invention, the collector and the impeller inlet collar adopt a sleeve-type design, which increases the sealing between the impeller inlet collar and the collector and reduces leakage losses.

[0019] (3) In the present invention, the inlet edge tangent of the impeller inlet ring is V1, the outlet edge tangent of the collector is V2, and the angle between the tangent V1 and the tangent V2 is δ, satisfying δ=5°~10°. Through the above structural design, the interference of the leakage airflow on the working airflow can be reduced, thereby reducing the inlet aerodynamic noise.

[0020] (4) In the present invention, the volute tongue used has a guide surface with an inclined curved shape, which can reduce the main frequency amplitude of the fan noise, thereby reducing the operating noise of the fan as a whole. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0022] Figure 1 A cross-sectional view of the centrifugal fan provided by the present invention;

[0023] Figure 2 for Figure 1 The enlarged view of point A in the middle;

[0024] Figure 3 Schematic diagram of the angle between the inlet edge of the impeller inlet collar and the tangent direction of the outlet edge of the collector in the present invention;

[0025] Figure 4 for Figure 1 The enlarged view of point B in the middle;

[0026] Figure 5 It is a structural schematic diagram of the driving motor in the present invention;

[0027] Figure 6 The three-dimensional shape of the volute body in the present invention Figure 1 ;

[0028] Figure 7 The three-dimensional shape of the volute body in the present invention Figure 2 ;

[0029] Figure 8 The 3D diagram of the volute body after removing the volute panel in the present invention Figure 1 ;

[0030] Fig. 9 The 3D diagram of the volute body after removing the volute panel in the present invention Figure 2 ;

[0031] Fig.10 It is a three-dimensional structural diagram of the inner ring body in the present invention;

[0032] Fig.11 It is a structural schematic diagram of the air guide cover in the present invention;

[0033] Fig.12 is a main cross-sectional view of the slotted conical nut of the present invention;

[0034] Fig.13 It is a right side view of the slotted tapered nut of the present invention;

[0035] Fig.14 The three-dimensional structure of the snail tongue in the present invention Figure 1 ;

[0036] Fig.15 The three-dimensional structure of the snail tongue in the present invention Figure 2 ;

[0037] Fig.16 It is a schematic diagram of the arrangement rule of the muffler holes in the present invention.

[0038] Description of the accompanying figures: 1. volute body; 1a. air inlet; 1b. air outlet; 1c. volute frame; 1d. volute orifice plate; 1e. volute panel; 1f. mounting foot plate; 1g. reinforcing rib plate; 1h. motor mounting sleeve; 1j. collector mounting ring; 2. impeller; 2a. impeller inlet sleeve; 2b. blades; 2c. wheel disc; 2d. wheel disc mounting pipe; 3. drive motor; 3a. output shaft; 4. sound absorbing material; 5. Inner ring body; 5a, cylinder body; 5b, annular ring body; 5c, flange edge; 6, collector; 7, deflector; 8, flat key; 9, retaining ring; 9a, first annular boss; 9b, second annular boss; 10, locking nut; 11, slotted conical nut; 12, bearing cover; 12a, first hole section; 12b, second hole section; 13, bearing; 14, volute tongue; 14a, guide surface; 14b, mounting plane; 14c, threaded hole. DETAILED DESCRIPTION

[0039] 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.

[0040] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0041] In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0042] As shown in the accompanying drawings, a compact low-noise centrifugal fan includes a volute body 1, an impeller 2 arranged inside the volute body 1, and a drive motor 3 installed on the volute body 1, the output shaft 3a of the drive motor 3 is connected to the impeller 2, and an air inlet 1a and an air outlet 1b are arranged on the volute body 1; a volute tongue 14 is arranged inside the volute body 1; the volute body 1 includes a volute skeleton 1c, a volute panel 1e and a volute orifice plate 1d; the volute orifice plate 1d is arranged in the volute skeleton 1c, and the volute panel 1e covers the volute skeleton 1c; sound-absorbing material 4 is filled between the volute panel 1e and the volute orifice plate 1d, and a plurality of silencer holes are evenly distributed on the volute orifice plate 1d.

[0043] Combination Figure 1 and Fig.10 As shown, an inner ring body 5 and a collector 6 are installed at the air inlet 1a; the inner ring body 5 includes a cylindrical portion 5a, a circular ring body 5b integrally formed on the inner wall of one end of the cylindrical portion 5a, and a flange edge 5c integrally formed on the outer wall of the other end of the cylindrical portion 5a; a plurality of silencer holes are evenly distributed on the cylindrical portion 5a and the circular ring body 5b respectively; the collector 6 is in a trumpet shape, the inner ring body 5 is sleeved on the collector 6, and the inner wall of the inner ring body 5 and the outer surface of the collector 6 are filled with sound-absorbing material 4.

[0044] In this embodiment, the sound absorbing material 4 is melamine foam or polyurethane foam; the sound absorbing material 4 is wrapped with silk cloth, and the silk cloth wrapping can prevent the debris generated by the sound absorbing material 4 from entering the interior of the fan.

[0045] In this embodiment, the perforation rate of the muffler holes is 15% to 25%. The specific perforation rate needs to be appropriately adjusted according to the main frequency of the fan noise. Fig.16 As shown, the muffler hole is a through hole with a diameter of φ2.5 mm, and three adjacent muffler holes are distributed in a regular triangle with a side length of 6 mm.

[0046] Combination Figure 1 , Figure 2 As shown, the impeller 2 includes a wheel disc 2c, blades 2c and an impeller inlet collar 2a; multiple blades 2c are evenly distributed on the wheel disc 2c in an annular shape, and the impeller inlet collar 2a is sleeved on the outside of all blades 2c near one end of the inner ring body 5; the small end of the collector 6 passes through the central hole of the annular body 5b and then extends into the impeller inlet collar 2a, and the nesting length between the small end of the collector 6 and the impeller inlet collar 2a is L, satisfying L = 5mm ~ 10mm. The collector 6 and the impeller inlet collar 2a adopt a sleeve design to increase the sealing between the impeller inlet collar 2a and the collector 6 and reduce leakage losses.

[0047] Combination Figure 3As shown, the inlet edge tangent of the impeller inlet collar 2a is V1, the outlet edge tangent of the collector 6 is V2, and the angle between the tangent V1 and the tangent V2 is δ, satisfying δ=5°~10°. Through the above structural design, the interference of the leakage airflow on the working airflow can be reduced, thereby reducing the inlet aerodynamic noise.

[0048] Combination Figure 1 , Fig.11 As shown, a bell-shaped air deflector 7 is installed on the output shaft 3a of the driving motor 3; the large end face of the air deflector 7 abuts against the surface of the wheel disc 2c; the inner hole of the small end of the air deflector 7 is sleeved on the output shaft 3a of the driving motor 3, and a slotted conical nut 11 is screwed on the end of the output shaft 3a of the driving motor 3 and tightens the air deflector 7; the outer cylindrical surface of the slotted conical nut 11 smoothly transitions with the outer surface of the air deflector 7.

[0049] Combination Figure 1 and Figure 4 As shown, a bearing cover 12 and a bearing 13 are installed on the housing of the driving motor 3, and the bearing 13 is sleeved on the output shaft 3a, and the bearing cover 12 abuts against the right end face of the outer ring of the bearing 13; a wheel disc mounting tube 2d is integrally formed at the center of the wheel disc 2c, and the wheel disc mounting tube 2d is sleeved on the output shaft 3a of the driving motor 3, and a flat key 8 is arranged between the wheel disc mounting tube 2d and the output shaft 3a; a retaining ring 9 is sleeved on the output shaft 3a, and the retaining ring 9 is located between the bearing 13 and the wheel disc mounting tube 2d; a locking nut 10 is screwed on the output shaft 3a; when the locking nut 10 is tightened, the locking nut 10 abuts against the right end face of the wheel disc mounting tube 2d, axially pushing the wheel disc mounting tube 2d to press against the retaining ring 9, and making the retaining ring 9 press against the right end face of the inner ring of the bearing 13.

[0050] Combination Figure 4 As shown, a first annular boss 9a is integrally formed at the left end of the outer circumferential surface of the retaining ring 9, and a second annular boss 9b is integrally formed at the right end; the outer diameter of the second annular boss 9b is larger than the outer diameter of the first annular boss 9a; an annular groove 9c is formed between the second annular boss 9b and the first annular boss 9a; the center hole of the bearing cover 12 includes a first hole section 12a and a second hole section 12b from left to right; the diameter of the second hole section 12b is larger than the diameter of the first hole section 12a; the retaining ring 9 is arranged in the center hole of the bearing cover 12, and the first annular boss 9a is located in the first hole section 12a, and the second annular boss 9b is located in the second hole section 12b.

[0051] Combination Fig.15 and Fig.16As shown, the volute tongue 14 is provided with a guide surface 14a and a mounting plane 14b; a threaded hole 14c is provided on the mounting plane 14b; the height from one end of the guide surface 14a to the mounting plane 14b is h1, and the height from the other end to the mounting plane 14b is h2; the curvature radius of the end with a distance of h1 is R1, and the curvature radius of the end with a distance of h2 is R2, satisfying: R1>R2, and h1<h2; the guide surface 14a is an inclined surface with a curvature radius gradually decreasing from R1 to R2. In addition, in order to reduce the weight of the volute tongue 14, the back side of the volute tongue 14 is hollowed out.

[0052] Compared with the conventional straight volute tongue, the volute tongue 14 in this embodiment has a guide surface 14a in the shape of an inclined curved surface, and thus has the following effects:

[0053] ① Changing the airflow impact mode: The volute tongue 14 with an inclined curved surface can make the airflow thrown out from the impeller 2 contact it at a relatively gentler angle, avoiding the airflow from suddenly hitting the volute tongue 14 to generate strong vortex and pressure pulsation, thereby reducing the noise caused by the impact.

[0054] ② Disruption of vortex generation: The volute tongue 14 with an inclined curved surface can disrupt the original regularity of the airflow and easily form a strong vortex, thereby reducing the intensity and size of the vortex and reducing the aerodynamic noise caused by vortex separation.

[0055] ③ Dispersing noise frequency: Changing the natural frequency characteristics of the airflow and the volute tongue 14, making the noise frequency components more dispersed, avoiding the concentration of energy in certain specific frequencies to produce obvious harsh, high-decibel noise, thereby reducing the overall noise intensity felt by the human ear.

[0056] In this embodiment, a threaded hole 14c is provided on the mounting plane 14b of the volute tongue 14, and the threaded hole 14c is connected to the volute body 1 by screws, so that a detachable connection structure is formed between the volute tongue 14 and the volute body 1, so that the volute tongue 14 is easy to replace.

[0057] In this embodiment, the volute frame 1c, the volute panel 1e, the volute orifice plate 1d, and the sound-absorbing material 4 filled between the volute panel 1e and the volute orifice plate 1d together constitute an integrated muffler volute structure. The volute tongue 14 inside the volute body 1 is a detachable inclined volute tongue structure; the nested structure design of the collector 6 and the impeller inlet collar 2a forms a small-angle sleeve collector structure; the guide cover 7 at the inlet of the impeller 2 and the slotted conical nut 11 together form a two-stage guide structure; the impeller 2 is composed of a wheel disc 2c, blades 2c and an impeller inlet collar 2a, and the installation method of the impeller 2 forms a single-end spiral arm impeller installation structure. Through the above structural design, the purpose of greatly reducing the operating noise of the centrifugal fan can be achieved. The centrifugal fan provided in this embodiment can significantly reduce the fan operation noise in the entire frequency band, especially the high-frequency noise suppression effect is obvious. Using the same fan model for noise comparison, the noise on the air inlet side is reduced by 4dB(A)~6dB(A), and the shell noise is reduced by 5dB(A)~8dB(A).

[0058] In this embodiment, the volute frame 1c and the volute orifice plate 1d inside it are integrally formed by 3D printing. Figure 8 As shown, a mounting foot plate 1f is integrally formed at the bottom of the volute frame 1c, and a bolt through hole is set on the mounting foot plate 1f, and the mounting foot plate 1f is used for the installation and fixation of the entire fan. A reinforcing rib plate 1g is set between the mounting foot plate 1f and the volute frame 1c, which plays a reinforcing role and is used to improve the structural strength of the volute body 1.

[0059] Combination Figure 8 and Fig. 9 As shown, a motor mounting sleeve 1h is integrally formed on the volute frame 1c, and the drive motor 3 is inserted into the motor mounting sleeve 1h, and the inner hole of the motor mounting sleeve 1h is sealed with the outer circle of the drive motor 3. Furthermore, a collector mounting ring 1j is also integrally formed on the volute frame 1c, and the collector mounting ring 1j is located at the air inlet 1a. Figure 1 As shown, the flange edge 5c of the inner ring body 5 and the large end of the collector 6 are mounted on the collector mounting ring 1j at the air inlet 1a by screws.

[0060] In summary, the compact low-noise centrifugal fan provided in this embodiment has the following assembly steps:

[0061] Step 1: Install the drive motor 3 on the volute body 1 with screws. Specifically, the drive motor 3 is inserted into the motor mounting sleeve 1h on the volute frame 1c. The drive motor 3 and the mounting sleeve 1h are sealed to ensure that the high-pressure gas in the inner cavity of the volute body 1 will not leak to the outside.

[0062] Step 2: Install the retaining ring 9 on the output shaft 3a of the driving motor 3. Figure 4 As shown, the left end of the retaining ring 9 is in close contact with the inner ring of the bearing 13 of the drive motor 3 to complete axial fixation. The retaining ring 9 is arranged in the stepped hole in the center of the bearing cover 12. The first annular boss 9a, the second annular boss 9b, and the annular groove 9c on the retaining ring 9 and the first hole section 12a and the second hole section 12b of the bearing cover 12 together form a maze structure. The maze structure is used to prevent excess matter in the working medium inside the fan from being transmitted to the inside of the bearing 13.

[0063] Step 3: Install the flat key 8 on the output shaft 3a of the driving motor 3.

[0064] Step 4: Install the impeller 2 on the output shaft 3a of the driving motor 3, and the keyway on the wheel disc mounting tube 2d of the impeller 2 and the flat key 8 adopt transition fit.

[0065] Step 5: Install the locking nut 10 on the output shaft 3a of the driving motor 3, and tighten the locking nut 10 so that the locking nut 10 abuts against the right end surface of the wheel disc mounting tube 2d, and pushes the wheel disc mounting tube 2d axially to press the retaining ring 9, so that the retaining ring 9 presses against the right end surface of the inner ring of the bearing 13. The impeller 2 can be stably installed on the output shaft 3a.

[0066] Step 6: Install the air deflector 7 on the output shaft 3a of the driving motor 3. Specifically, the large end face of the air deflector 7 abuts against the surface of the wheel disc 2c, which can prevent the wheel disc 2c from vibrating and improve the rigidity of the wheel disc 2c. The inner hole of the small end of the air deflector 7 is sleeved on the mounting stop of the output shaft 3a. A slotted conical nut 11 is screwed on the end of the output shaft 3a and tightens the air deflector 7; the outer cylindrical surface of the slotted conical nut 11 smoothly transitions with the outer surface of the air deflector 7. The air deflector 7 is made of lightweight materials, which can reduce the weight of the rotating shaft system.

[0067] Step 7: Install the inner ring body 5 at the air inlet 1a end of the volute body 1 and fill it with the sound absorbing material 4, and insert the collector 9 into the inner ring body 5. Specifically, the flange edge 5c of the inner ring body 5 and the large end of the collector 6 are screwed together on the collector mounting ring 1j at the air inlet 1a.

[0068] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A compact low-noise centrifugal fan, comprising a volute body (1), an impeller (2) arranged inside the volute body (1), and a drive motor (3) mounted on the volute body (1), wherein an output shaft (3a) of the drive motor (3) is connected to the impeller (2), an air inlet (1a) and an air outlet (1b) are arranged on the volute body (1); a volute tongue (14) is arranged inside the volute body (1); and the characteristics are: The volute body (1) comprises a volute frame (1c), a volute panel (1e) and a volute orifice plate (1d); the volute orifice plate (1d) is arranged inside the volute frame (1c), and the volute panel (1e) covers the volute frame (1c); a sound absorbing material (4) is filled between the volute panel (1e) and the volute orifice plate (1d), and a plurality of sound-absorbing holes are evenly distributed on the volute orifice plate (1d).

2. A compact low-noise centrifugal fan according to claim 1, characterized in that: An inner ring body (5) and a current collector (6) are installed at the air inlet (1a); The inner ring body (5) comprises a cylindrical body (5a), a circular ring body (5b) integrally formed on the inner wall of one end of the cylindrical body (5a), and a flange edge (5c) integrally formed on the outer wall of the other end of the cylindrical body (5a); a plurality of sound-absorbing holes are evenly distributed on the cylindrical body (5a) and the circular ring body (5b); The current collector (6) is in a trumpet shape, the inner ring body (5) is sleeved on the current collector (6), and a sound absorbing material (4) is filled between the inner wall of the inner ring body (5) and the outer surface of the current collector (6).

3. A compact low-noise centrifugal fan according to claim 1 or 2, characterized in that: The sound absorbing material (4) is melamine foam or polyurethane foam; the sound absorbing material (4) is wrapped with silk cloth; the perforation rate of the sound-absorbing holes is 15% to 25%.

4. A compact low-noise centrifugal fan according to claim 1 or 2, characterized in that: The muffler holes are through holes with a diameter of φ2.5 mm, and three adjacent muffler holes are distributed in a regular triangle with a side length of 6 mm.

5. A compact low-noise centrifugal fan as claimed in claim 2, characterized in that: The impeller (2) comprises a wheel disc (2c), blades (2c) and an impeller inlet collar (2a); a plurality of blades (2c) are evenly distributed in an annular shape on the wheel disc (2c); the impeller inlet collar (2a) is sleeved on the outside of all blades (2c) close to one end of the inner ring body (5); the small end of the collector (6) passes through the central hole of the annular body (5b) and then extends into the impeller inlet collar (2a); the nesting length between the small end of the collector (6) and the impeller inlet collar (2a) is L, satisfying L=5mm-10mm.

6. A compact low-noise centrifugal fan as claimed in claim 5, characterized in that: The inlet edge tangent of the impeller inlet collar (2a) is V1, the outlet edge tangent of the collector (6) is V2, and the included angle between the tangent V1 and the tangent V2 is δ, satisfying δ=5°-10°.

7. A compact low-noise centrifugal fan as claimed in claim 5, characterized in that: A bell-mouth-shaped air guide cover (7) is mounted on the output shaft (3a) of the drive motor (3); The large end surface of the deflector (7) abuts against the surface of the wheel disc (2c); The inner hole of the small end of the air guide cover (7) is sleeved on the output shaft (3a) of the driving motor (3), and a slotted conical nut (11) is screwed on the end of the output shaft (3a) of the driving motor (3) and tightens the air guide cover (7); The outer cylindrical surface of the slotted conical nut (11) smoothly transitions to the outer surface of the air guide cover (7).

8. A compact low-noise centrifugal fan as claimed in claim 5, characterized in that: A bearing cover (12) and a bearing (13) are installed on the housing of the drive motor (3), and the bearing (13) is sleeved on the output shaft (3a), and the bearing cover (12) abuts against the right end surface of the outer ring of the bearing (13); A wheel disc mounting tube (2d) is integrally formed at the center of the wheel disc (2c), the wheel disc mounting tube (2d) is sleeved on the output shaft (3a) of the driving motor (3), and a flat key (8) is provided between the wheel disc mounting tube (2d) and the output shaft (3a); A retaining ring (9) is sleeved on the output shaft (3a), and the retaining ring (9) is located between the bearing (13) and the wheel disc mounting tube (2d); a locking nut (10) is screwed on the output shaft (3a); when the locking nut (10) is tightened, the locking nut (10) abuts against the right end surface of the wheel disc mounting tube (2d), axially pushing the wheel disc mounting tube (2d) to press against the retaining ring (9), and making the retaining ring (9) press against the right end surface of the inner ring of the bearing (13).

9. A compact low-noise centrifugal fan according to claim 8, characterized in that: A first annular boss (9a) is integrally formed at the left end of the outer peripheral surface of the retaining ring (9), and a second annular boss (9b) is integrally formed at the right end; the outer diameter of the second annular boss (9b) is greater than the outer diameter of the first annular boss (9a); an annular groove (9c) is formed between the second annular boss (9b) and the first annular boss (9a); The central hole of the bearing cover (12) comprises, from left to right, a first hole section (12a) and a second hole section (12b); the diameter of the second hole section (12b) is greater than the diameter of the first hole section (12a); The retaining ring (9) is arranged in the central hole of the bearing cover (12), and the first annular boss (9a) is located in the first hole section (12a), and the second annular boss (9b) is located in the second hole section (12b).

10. A compact low-noise centrifugal fan according to claim 1, characterized in that: The volute tongue (14) is provided with a guide surface (14a) and a mounting plane (14b); a threaded hole (14c) is provided on the mounting plane (14b); the height from one end of the guide surface (14a) to the mounting plane (14b) is h1, and the height from the other end to the mounting plane (14b) is h2; the curvature radius of the end with a distance of h1 is R1, and the curvature radius of the end with a distance of h2 is R2, satisfying: R1>R2, and h1<h2; the guide surface (14a) is an inclined surface with a curvature radius gradually decreasing from R1 to R2.

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