Centrifugal fan

Abstract

A centrifugal fan comprises an upper cover, a base and an impeller. The upper cover is provided with an air inlet, a first annular groove and a second annular groove, and the first annular groove and the second annular groove sequentially surround the air inlet and are arranged on the inner side face of the upper cover. The base and the upper cover are combined to form a fan frame, and an air outlet is formed between the upper cover and the radial outer end of the base. The impeller is rotatably arranged in the fan frame and comprises a plurality of fan blades and an upper ring, and the upper ring is connected with the fan blades and located between the fan blades and the upper cover. A first annular protruding structure and a second annular protruding structure are formed on the upper ring, the first annular protruding structure axially protrudes towards the first annular groove, and the second annular protruding structure protrudes towards the second annular groove and is bent in the direction away from the air inlet.

Description

Technical Field

[0001] The present disclosure relates to a centrifugal fan. Background Art

[0002] Fans are commonly used heat dissipation components. When a fan operates, it will generate some noise. Especially when the fan operates at high speed, it is more likely to generate significant noise. Therefore, how to reduce noise is an important issue in the design of fans. Summary of the Utility Model

[0003] In view of this, an object of the present disclosure is to provide a centrifugal fan with low noise.

[0004] To achieve the above object, according to some embodiments of the present disclosure, a centrifugal fan includes an upper cover, a base, and an impeller. The upper cover has an air inlet, a first annular groove, and a second annular groove, and the first annular groove and the second annular groove sequentially surround the air inlet and are disposed on the inner side surface of the upper cover. The base is combined with the upper cover to form a fan frame, and an air outlet is formed between the radially outer ends of the upper cover and the base. The impeller is rotatably disposed in the fan frame and includes a plurality of fan blades and an upper ring. The upper ring is connected to the aforementioned fan blades and is located between the fan blades and the upper cover. The upper ring is formed with a first annular protrusion structure and a second annular protrusion structure. The first annular protrusion structure axially protrudes toward the first annular groove, and the second annular protrusion structure protrudes toward the second annular groove and bends in a direction away from the air inlet.

[0005] In one or more embodiments of the present disclosure, in the radially outward direction, the gap between the upper cover and the upper ring has a plurality of vertical heights, and the aforementioned vertical heights are not all the same. The dimensions of the aforementioned vertical heights are large-small-large or small-large-small in sequence.

[0006] In one or more embodiments of the present disclosure, at least one fan blade has an outer edge, and the aforementioned outer edge faces the air outlet and includes a rectangular serrated structure. The impeller further includes a bottom plate. The fan blades are connected between the upper ring and the bottom plate. An air flow channel is formed between the upper ring, the bottom plate, and any two adjacent fan blades. The two ends of the air flow channel face the air inlet and the air outlet respectively.

[0007] In one or more embodiments of the present disclosure, the upper ring extends radially outward from the outer edge of the fan blade to have a bottom surface of the outer edge of the upper ring, and the bottom plate extends radially outward from the outer edge of the fan blade to have a top surface of the outer edge of the bottom plate, wherein the bottom surface of the outer edge of the upper ring is parallel to the top surface of the outer edge of the bottom plate.

[0008] In one or more embodiments of the present disclosure, the air flow path has a first position, a second position, a third position, and a fourth position, and the first position, the second position, the third position, and the fourth position are arranged in sequence from the air inlet to the air outlet. The first position has a first axial height, the second position has a second axial height, the third position has a third axial height, and the fourth position has a fourth axial height, where the first axial height is greater than the second axial height, the second axial height is less than the third axial height, and the third axial height is greater than the fourth axial height. In addition, the third axial height is less than the first axial height, and the fourth axial height is less than the second axial height.

[0009] In one or more embodiments of the present disclosure, the upper ring has a first wavy surface facing the bottom plate, and the bottom plate has a second wavy surface facing the upper ring. The axial height changes of the air flow path at the first position, the second position, the third position, and the fourth position are generated by the first wavy surface and the second wavy surface.

[0010] In one or more embodiments of the present disclosure, the inner edge of at least one fan blade is exposed outside the central opening and the air inlet of the upper ring. The upper edge surface of the aforementioned inner edge close to the air inlet is a flat surface, a curved surface, an inclined surface, or a concave surface. The number of fan blades is 18 or 36.

[0011] In one or more embodiments of the present disclosure, the upper cover has a bottom surface of the upper cover air outlet duct near the air outlet, and the base has a top surface of the base air outlet duct near the air outlet, and the bottom surface of the upper cover air outlet duct faces the top surface of the base air outlet duct, where in the direction radially away from the fan blade starting from the outer edge of the fan blade, the vertical distance dimension between the bottom surface of the upper cover air outlet duct and the top surface of the base air outlet duct is large-small-large or small-large-small in sequence.

[0012] In one or more embodiments of the present disclosure, the upper cover and the base are connected by a plurality of connecting columns, and the upper cover, the base, and the connecting columns jointly form the air outlet. The cross-section of the connecting column is circular, polygonal, teardrop-shaped, or other shapes with a convex curved surface.

[0013] In one or more embodiments of the present disclosure, the second annular protrusion structure includes an axially extending portion and a radially extending portion, and the axially extending portion is connected between the upper surface of the upper ring and the radially extending portion.

[0014] In one or more embodiments of the present disclosure, the second annular protrusion structure is disposed on the upper surface of the upper ring, and the upper surface has a first platform area and a second platform area. The first platform area is located between the first annular protrusion structure and the second annular protrusion structure, and the second platform area is located on the side of the second annular protrusion structure away from the first annular protrusion structure. In terms of the axial horizontal height, the air inlet, the first platform area, and the second platform area are arranged in sequence.

[0015] In one or more embodiments of the present disclosure, the upper surface of the upper ring further has an inclined surface or a vertical surface located between the first platform area and the second platform area.

[0016] In summary, the centrifugal fan of the present disclosure achieves noise reduction and improvement in operating efficiency through at least one of the following structural features: (1) The fan frame has two annular grooves, and the impeller has two annular protrusion structures respectively corresponding to the two annular grooves, wherein the annular protrusion structure on the outer side is bent away from the air inlet of the fan; (2) The impeller includes an upper ring, a bottom plate, and a plurality of fan blades connected between the upper ring and the bottom plate. The fan blades divide the space between the upper ring and the bottom plate into a plurality of air flow channels. From the air inlet to the air outlet, the air flow channels first narrow and then expand, and then narrow again after expansion (the air flow channels have at least three width changes); (3) The outer edge of the fan blade includes a rectangular serrated structure; (4) The inner edge of the fan blade is exposed at the air inlet; (5) The upper edge surface of the inner edge of the fan blade near the air inlet is a flat surface, a curved surface, an inclined surface, or a concave surface; (6) The number of fan blades is 18 or 36; (7) The size of the fan frame at the air outlet presents large-small-large or small-large-small; (8) The cross-section of the connecting column connecting the upper cover and the base is circular, polygonal, teardrop-shaped, or other shapes with a convex outer surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] To make the above and other objects, features, advantages, and embodiments of the present disclosure more obvious and understandable, the descriptions of the accompanying drawings are as follows:

[0018] Figure 1 A combined view of a centrifugal fan according to an embodiment of the present disclosure;

[0019] Figure 2 To illustrate Figure 1 An exploded view of the centrifugal fan shown;

[0020] Figure 3 To illustrate Figure 2 A top view of the impeller of the centrifugal fan shown;

[0021] Figure 4 To illustrate Figure 1 A cross-sectional view of the centrifugal fan shown at the marked position of line segment 4-4';

[0022] Figure 5 To illustrate Figure 4 An enlarged view of the centrifugal fan shown at the marked position of frame line 5;

[0023] Figure 6 A partially enlarged cross-sectional view of a centrifugal fan according to another embodiment of the present disclosure;

[0024] Figure 7 A partially enlarged cross-sectional view of a centrifugal fan according to another embodiment of the present disclosure.

[0025]

Symbol Explanation

[0026] 12: Centrifugal fan

[0027] 13: Fan frame

[0028] 14: Air inlet

[0029] 15: Air outlet

[0030] 16: Base

[0031] 17: Shaft tube

[0032] 20: Upper cover

[0033] 21: First annular groove

[0034] 22: Second annular groove

[0035] 23: Top surface

[0036] 30: Stator assembly

[0037] 31: Drive circuit board

[0038] 32: Coil assembly

[0039] 35: Bearing

[0040] 50, 50A, 50B: Impeller

[0041] 51: First annular protrusion structure

[0042] 52, 52B: Second annular protrusion structure

[0043] 53, 53A, 53B: Upper ring

[0044] 54: Central opening

[0045] 55, 55A: Upper surface

[0046] 56: Bottom plate

[0047] 57: Fan blade

[0048] 58: Inner edge

[0049] 59: Outer edge

[0050] 60: Shaft part

[0051] 61: First wavy surface

[0052] 62: Second wavy surface

[0053] 63: First end

[0054] 64: Second end

[0055] 65: Rectangular serrated structure

[0056] 66: Axial extension

[0057] 67: Radial extension

[0058] 68,69: Inclined plane

[0059] 68A: Upright surface

[0060] 71: First platform area

[0061] 72: Second platform area

[0062] 80: Connection port

[0063] 81: Bottom surface of the outer edge of the upper ring

[0064] 82: Top surface of the outer edge of the bottom plate

[0065] 83: Connection column

[0066] 84: Bottom surface of the air outlet duct of the upper cover

[0067] 85: Top surface of the air outlet duct of the base

[0068] A1: First position

[0069] A2: Second position

[0070] A3: Third position

[0071] A4: Fourth position

[0072] D1,D2: Direction

[0073] G: Gap

[0074] P: Air flow channel

[0075] R: Axis

[0076] W1: First axial height

[0077] W2: Second axial height

[0078] W3: Third axial height

[0079] W4: Fourth axial height Detailed implementation manners

[0080] To make the description of the present disclosure more detailed and complete, reference may be made to the accompanying drawings and the various embodiments described below. The elements in the drawings are not drawn to scale and are provided only for illustrating the present disclosure. Many practical details are described below to provide a comprehensive understanding of the present disclosure. However, those of ordinary skill in the relevant art should understand that the present disclosure may be implemented without one or more of these practical details. Therefore, these details should not be used to limit the present disclosure.

[0081] Please refer to Figure 1 。 Figure 1 FIG. is a combined view showing a centrifugal fan 12 according to an embodiment of the present disclosure. As shown, the centrifugal fan 12 includes a fan frame 13 and an impeller 50. The fan frame 13 has an air inlet 14 and at least one air outlet 15. The air inlet 14 is disposed at the central position of the fan frame 13, and the air outlet 15 is disposed on the side of the fan frame 13. The impeller 50 is rotatably disposed in the fan frame 13. The impeller 50 is configured to rotate about an axis R. When the impeller 50 rotates, air can be introduced into the fan frame 13 through the air inlet 14 and then blown out through the air outlet 15.

[0082] As Figure 1 shown, in some embodiments, the fan frame 13 includes a base 16 and an upper cover 20. The base 16 and the upper cover 20 are combined to form the fan frame 13. The upper cover 20 has a central opening as the air inlet 14 of the fan frame 13. At least one gap is maintained between the upper cover 20 and the base 16 as the air outlet 15. Specifically, the air outlet 15 is formed between the radially outer ends of the upper cover 20 and the base 16. The impeller 50 can be disposed in the space between the base 16 and the upper cover 20. The base 16 and the upper cover 20 can be combined by screwing or other suitable means. In some embodiments, the fan frame 13 further includes a connection port 80. The connection port 80 is, for example, an electrical connector for connecting to a system using the centrifugal fan 12 to allow the system to transmit signals to the centrifugal fan 12.

[0083] Please refer to Figure 2 。 Figure 2 To illustrate Figure 1Exploded view of the centrifugal fan 12 shown. As shown, the impeller 50 includes an upper ring 53, a bottom plate 56, and a plurality of fan blades 57. The upper ring 53 and the bottom plate 56 are disposed opposite to each other. The upper ring 53 is located on the side of the impeller 50 facing the upper cover 20, while the bottom plate 56 is located on the side of the impeller 50 facing the base 16 (in other words, the bottom plate 56 is located on the side of the impeller 50 away from the upper cover 20). The upper ring 53 has a central opening 54, and the central opening 54 faces the air inlet 14. The fan blades 57 are connected between the upper ring 53 and the bottom plate 56, and divide the space between the upper ring 53 and the bottom plate 56 into a plurality of air flow channels P. The upper cover 20 and the base 16 are connected by a plurality of connecting columns 83, and the upper cover 20, the base 16, and the connecting columns 83 together form the air outlet 15. The cross-section of the connecting column 83 is, for example, circular, polygonal, drop-shaped, or other shapes with a convex curved surface. When the cross-section of the connecting column 83 is drop-shaped or other shapes with a convex curved surface, the centrifugal fan 12 can obtain higher operating efficiency and lower operating noise.

[0084] As Figure 2 shown, each air flow channel P is defined by the upper ring 53, the bottom plate 56, and any two adjacent fan blades 57. The two ends of the air flow channel P face the air inlet 14 and the air outlet 15 of the fan frame 13 respectively. When the impeller 50 rotates, air can be introduced into the fan frame 13 through the air inlet 14 and enter the air flow channel P of the impeller 50, and finally the air is blown out through the air outlet 15.

[0085] As Figure 2 shown, in some embodiments, the centrifugal fan 12 further includes a stator assembly 30. The stator assembly 30 is disposed in the fan frame 13 and is configured to drive the rotation of the rotor assembly including the impeller 50. In some embodiments, the stator assembly 30 includes a drive circuit board 31 and a coil assembly 32. The coil assembly 32 is disposed on the drive circuit board 31 and is electrically connected to the drive circuit board 31. When the coil assembly 32 is energized, a magnetic field is generated to drive the rotation of the rotor assembly with magnets (the magnets are not shown in the figure; for example, the magnets can be disposed inside the impeller 50). In some embodiments, the coil assembly 32 may include a bobbin and a plurality of coils wound around the bobbin.

[0086] As Figure 2 shown, in some embodiments, the rotor assembly further includes a shaft member 60. The top end of the shaft member 60 is fixedly connected to the impeller 50. A bearing 35 is disposed on the base 16, and the bearing 35 is coupled to the shaft member 60 to support the rotational movement of the rotor assembly. In some embodiments, the base 16 includes a shaft tube 17 that protrudes toward the upper cover 20. The bearing 35 is disposed in the shaft tube 17, and the shaft member 60 extends into the shaft tube 17 and passes through the central hole of the bearing 35. In some embodiments, the drive circuit board 31 and the coil assembly 32 of the stator assembly 30 are disposed on the base 16 and are disposed around the shaft tube 17.

[0087] Please refer to Figure 3 . Figure 3 To illustrate Figure 2 a top view of the impeller 50 of the centrifugal fan 12 shown. As shown in the figure, each blade 57 has opposite inner edges 58 and outer edges 59. The inner edge 58 is adjacent to the center of the upper ring 53 and the bottom plate 56, while the outer edge 59 is adjacent to the outer peripheral edge of the upper ring 53 and the bottom plate 56 and faces the air outlet 15 of the fan frame 13. The inner edge 58 of the blade 57 can be exposed at the central opening 54 of the upper ring 53 and at the air inlet 14 of the fan frame 13 (for reference, see Figure 1 ). Through the foregoing technology, the centrifugal fan 12 can achieve higher operating efficiency and lower operating noise. In addition, the upper edge surface of the inner edge 58 close to the air inlet 14 is a flat surface, a curved surface, an inclined surface or a concave surface. When the upper edge surface is a curved surface, an inclined surface or a concave surface, the operating efficiency of the centrifugal fan 12 can be further improved and the operating noise of the centrifugal fan 12 can be reduced.

[0088] In some embodiments, the blade 57 has a curved shape. The number of blades 57 is preferably 18 or 36. When the number of blades 57 is this number, the operating efficiency of the centrifugal fan 12 can be further improved and the operating noise of the centrifugal fan 12 can be reduced.

[0089] Please refer to Figure 4 . Figure 4 To illustrate Figure 1 a cross-sectional view of the centrifugal fan 12 shown at the position marked by the line segment 4-4'. As shown in the figure, in some embodiments, the outer edge 59 of each blade 57 includes a rectangular serrated structure 65 (for reference, see also Figure 2 ). The rectangular serrated structure 65 includes one or more protruding rectangular teeth, and there may be recesses between two adjacent rectangular teeth. When the impeller 50 rotates, the rectangular serrated structure 65 has the effect of dispersing the eddy current near the air outlet 15, which helps to reduce the noise generated by the centrifugal fan 12. In some embodiments, the rectangular serrated structure 65 includes at least two rectangular teeth to effectively reduce noise.

[0090] In addition, the upper ring 53 radially extends outward from the outer edge 59 to have an upper ring outer edge bottom surface 81, and the bottom plate 56 radially extends outward from the outer edge 59 to have a bottom plate outer edge top surface 82. When the upper ring outer edge bottom surface 81 and the bottom plate outer edge top surface 82 are parallel, the centrifugal fan 12 can achieve higher operating efficiency and lower operating noise.

[0091] The upper cover 20 has a bottom surface 84 of the upper cover air duct near the air outlet 15, and the base 16 has a top surface 85 of the base air duct near the air outlet 15, and the bottom surface 84 of the upper cover air duct faces the top surface 85 of the base air duct. When the vertical distance dimension between the bottom surface 84 of the upper cover air duct and the top surface 85 of the base air duct sequentially presents a large-small-large or small-large-small dimension change in the direction radially away from the fan blade 57 starting from the outer edge 59, the centrifugal fan 12 can obtain higher operating efficiency and lower operating noise.

[0092] Please refer to Figure 5 as well. Figure 5 For showing Figure 4 the enlarged view of the centrifugal fan 12 shown at the position marked by the frame line 5. As Figure 4 shown in Figure 5 and

[0093] It should be noted that the term "axial direction" used herein refers to the direction in which the axis R of the impeller 50 extends (i.e., the direction D1 marked in the figure), and the term "radial direction" refers to the direction pointing laterally outward from the axis R (i.e., the direction D2 marked in the figure).

[0094] As Figure 4 shown in Figure 5As shown, in some embodiments, the upper ring 53 has a first wavy surface 61 facing the bottom plate 56 and connecting the fan blades 57, the bottom plate 56 has a second wavy surface 62 facing the upper ring 53 and connecting the fan blades 57, and the axial height changes of the air flow path P at the first position A1, the second position A2, the third position A3, and the fourth position A4 are generated by the first wavy surface 61 and the second wavy surface 62. The peak positions of the first wavy surface 61 and the second wavy surface 62 can be axially aligned with each other, and the valley positions of the first wavy surface 61 and the second wavy surface 62 can be axially aligned with each other.

[0095] As Figure 4 shown Figure 5 As shown, in some embodiments, the third axial height W3 of the air flow path P is less than the first axial height W1, and the fourth axial height W4 is less than the second axial height W2. In other words, between the second position A2 and the third position A3, the air flow path P expands without exceeding the first axial height W1 that is not wider than the first position A1.

[0096] As Figure 4 shown Figure 5 As shown, in some embodiments, the air flow path P can have more than three width changes. For example, the air flow path P can have a fifth axial height at the fifth position, the fifth position is located between the fourth position A4 and the air outlet 15, and the fifth axial height is greater than the fourth axial height W4 (that is, between the fourth position A4 and the fifth position, the air flow path P expands). For example, the air flow path P can have a sixth axial height at the sixth position, the sixth position is located between the fifth position and the air outlet 15, and the sixth axial height is less than the fifth axial height (that is, between the fifth position and the sixth position, the air flow path P contracts). And so on. In some embodiments, the fifth axial height of the air flow path P is less than the third axial height W3. In some embodiments, the sixth axial height of the air flow path P is less than the fourth axial height W4.

[0097] As Figure 4 shown Figure 5 As shown, the upper ring 53 of the impeller 50 extends from the air inlet 14 to the air outlet 15. In order to allow the impeller 50 to rotate freely, the upper ring 53 does not contact the upper cover 20 of the fan frame 13, and there is a gap G between the upper ring 53 and the upper cover 20. When the centrifugal fan 12 operates, due to the existence of the gap G, part of the air will enter the gap G from one end of the gap G adjacent to the air outlet 15 to generate a reverse flow of air. In some embodiments, in the radially outward direction, the gap G has a plurality of vertical heights, and the aforementioned vertical heights are not all the same. In the radially outward direction, the dimensions of the aforementioned vertical heights are in the order of large-small-large or small-large-small, and at this time, the operating volume of the centrifugal fan 12 can be further reduced and the operating efficiency of the centrifugal fan 12 can be improved.

[0098] As shown Figure 4 in Figure 5 FIGS. 2 and 3, in some embodiments, a first annular groove 21 and a second annular groove 22 are provided on an inner side surface of the upper cover 20 of the fan frame 13 (i.e., the side surface facing the gap G). The first annular groove 21 and the second annular groove 22 are sequentially arranged around the air inlet 14, and the first annular groove 21 is located between the air inlet 14 and the second annular groove 22.

[0099] As shown Figure 4 in Figure 5 FIGS. 2 and 3, in some embodiments, the upper ring 53 includes a first annular protrusion structure 51 and a second annular protrusion structure 52 (see also Figure 2 ). The first annular protrusion structure 51 and the second annular protrusion structure 52 are disposed on an upper surface 55 of the upper ring 53 facing the upper cover 20, and respectively correspond to the first annular groove 21 and the second annular groove 22. The first annular protrusion structure 51 and the second annular protrusion structure 52 are arranged around a central opening 54 of the upper ring 53, and the first annular protrusion structure 51 is located between the central opening 54 and the second annular protrusion structure 52. The first annular protrusion structure 51 axially protrudes toward the first annular groove 21, and the second annular protrusion structure 52 protrudes toward the second annular groove 22 and bends away from the air inlet 14 (or bends away from the central opening 54 of the upper ring 53), so that a groove facing away from the air inlet 14 and the central opening 54 is formed between the second annular protrusion structure 52 and the upper surface 55 of the upper cover 20.

[0100] As shown Figure 4 in Figure 5 FIGS. 2 and 3, the arrangements of the first annular groove 21, the second annular groove 22, the first annular protrusion structure 51, and the second annular protrusion structure 52 cause changes in the flow path of the reverse flow air in the radial and axial directions, which helps to reduce the reverse flow air, reduce the noise generated by the centrifugal fan 12, and improve the efficiency of the centrifugal fan 12.

[0101] As shown Figure 4 in Figure 5 FIGS. 2 and 3, in some embodiments, the second annular protrusion structure 52 has opposite first end 63 and second end 64. The first end 63 is connected to the upper surface 55 of the upper ring 53, and the second end 64 is farther from the upper surface 55 of the upper ring 53 and farther from the rotation axis R of the impeller 50 (or, farther from the central opening 54 of the upper ring 53) relative to the first end 63. Therefore, the second annular protrusion structure 52 extending from the first end 63 to the second end 64 has an axial component and a radial component.

[0102] As shown Figure 4 in Figure 5As shown, in some embodiments, the second annular protrusion structure 52 includes an axially extending portion 66 and a radially extending portion 67. The axially extending portion 66 is connected between the upper surface 55 of the upper ring 53 and the radially extending portion 67. The radially extending portion 67 is substantially perpendicular to the axially extending portion 66 and together with the axially extending portion 66 forms an L-shaped structure.

[0103] As Figure 4 with Figure 5 As shown, in some embodiments, the first annular protrusion structure 51 and the second annular protrusion structure 52 are disposed at one end of the upper ring 53 adjacent to the air inlet 14. Correspondingly, the first annular groove 21 and the second annular groove 22 are disposed adjacent to the air inlet 14. In other embodiments, the first annular protrusion structure 51 and the second annular protrusion structure 52 may also be disposed at one end of the upper ring 53 adjacent to the air outlet 15. Correspondingly, the first annular groove 21 and the second annular groove 22 are disposed adjacent to the air outlet 15.

[0104] As Figure 4 with Figure 5 As shown, in some embodiments, the first annular protrusion structure 51 is higher than the second annular protrusion structure 52. That is, in the axial direction, the distance between the first annular protrusion structure 51 and the top surface 23 of the upper cover 20 (i.e., the surface of the upper cover 20 away from the impeller 50 and the base 16) is less than the distance between the second annular protrusion structure 52 and the top surface 23 of the upper cover 20. Correspondingly, the bottom surface of the first annular groove 21 may be higher than the bottom surface of the second annular groove 22. That is, in the axial direction, the distance between the bottom surface of the first annular groove 21 and the top surface 23 of the upper cover 20 is less than the distance between the bottom surface of the second annular groove 22 and the top surface 23 of the upper cover 20.

[0105] As Figure 4 with Figure 5 As shown, in some embodiments, the upper surface 55 of the upper ring 53 has a first platform area 71 and a second platform area 72. The first platform area 71 is located between the first annular protrusion structure 51 and the second annular protrusion structure 52, and the second platform area 72 is located on the side of the second annular protrusion structure 52 away from the first annular protrusion structure 51. The second platform area 72 is lower than the first platform area 71. That is, in the axial direction, the distance between the second platform area 72 and the top surface 23 of the upper cover 20 is greater than the distance between the first platform area 71 and the top surface 23 of the upper cover 20. Specifically, in the axial horizontal height, the air inlet 14, the first platform area 71, and the second platform area 72 are arranged in sequence. The design of the first platform area 71 and the second platform area 72 having a height difference helps to further reduce the reverse flow of air and achieve a better effect of reducing fan noise. The first platform area 71 and the second platform area 72 may be arranged substantially along the radial direction D2 as shown in the figure, or may be inclined to the direction D2.

[0106] As Figure 4 shown in Figure 5 FIG. 1, in some embodiments, the upper surface 55 of the upper ring 53 further has an inclined surface 68 located between the first platform area 71 and the second platform area 72. In this embodiment, the inclined surface 68 is located outside the second annular protrusion structure 52 and together with the second annular protrusion structure 52 forms a groove facing away from the air inlet 14 and the central opening 54. In some embodiments, the upper surface 55 of the upper ring 53 further has an inclined surface 69 located between the second platform area 72 and the outer peripheral edge of the upper ring 53.

[0107] Please refer to Figure 6 . Figure 6 FIG. 2 is a partially enlarged cross-sectional view of a centrifugal fan according to another embodiment of the present disclosure. The difference between this embodiment and the foregoing embodiment is that the upper surface 55A of the upper ring 53A of the impeller 50A has a vertical surface 68A instead of the foregoing inclined surface 68, and the vertical surface 68A connects the first platform area 71 and the second platform area 72 with a height difference.

[0108] Please refer to Figure 7 . Figure 7 FIG. 3 is a partially enlarged cross-sectional view of a centrifugal fan according to another embodiment of the present disclosure. Different from the foregoing embodiment, the second annular protrusion structure 52B of the upper ring 53B of the impeller 50B in this embodiment is an arc-shaped structure. The second annular protrusion structure 52B has opposite first end 63 and second end 64. The first end 63 is connected to the upper surface 55 of the upper ring 53B, and the second end 64 is farther from the upper surface 55 of the upper ring 53B and farther from the rotation axis of the impeller 50B (or, farther from the central opening 54 of the upper ring 53) relative to the first end 63. Therefore, the second annular protrusion structure 52B extending from the first end 63 to the second end 64 has an axial component and a radial component, and can also achieve the effect of reducing the reverse flow of air.

[0109] In summary, the centrifugal fan of the present disclosure achieves noise reduction and improvement in operating efficiency through at least one of the following structural features: (1) The fan frame has two annular grooves, and the impeller has two annular protrusion structures respectively corresponding to the two annular grooves, wherein the annular protrusion structure on the outer side is bent away from the air inlet of the fan; (2) The impeller includes an upper ring, a bottom plate, and a plurality of fan blades connected between the upper ring and the bottom plate. The fan blades divide the space between the upper ring and the bottom plate into a plurality of air flow channels. From the air inlet to the air outlet direction, the air flow channels first narrow and then expand, and then narrow again after expansion (the air flow channels have at least three width changes); (3) The outer edge of the fan blade includes a rectangular serrated structure; (4) The inner edge of the fan blade is exposed at the air inlet; (5) The upper edge surface of the inner edge of the fan blade near the air inlet is a flat surface, a curved surface, an inclined surface or a concave surface; (6) The number of fan blades is 18 or 36; (7) The size of the fan frame at the air outlet presents large-small-large or small-large-small; (8) The cross section of the connecting column connecting the upper cover and the base is circular, polygonal, teardrop-shaped or other shapes with a convex curved surface.

[0110] Although the present disclosure has been disclosed as above in embodiments, it is not intended to limit the present disclosure. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be subject to the scope defined by the appended claims.

Claims

1. A centrifugal fan, characterized in that: Include: An upper cover having an air inlet, a first annular groove and a second annular groove, wherein the first annular groove and the second annular groove sequentially surround the air inlet and are disposed on the inner side surface of the upper cover; A base, combined with the upper cover to form a fan frame, and an air outlet is formed between the upper cover and the radial outer end of the base; and An impeller is rotatably disposed in the fan frame and includes a plurality of fan blades and an upper ring, the upper ring is connected to the plurality of fan blades and is located between the plurality of fan blades and the upper cover, the upper ring is formed with a first annular protrusion structure and a second annular protrusion structure, the first annular protrusion structure protrudes axially toward the first annular groove, the second annular protrusion structure protrudes toward the second annular groove and bends in a direction away from the air inlet.

2. The centrifugal fan according to claim 1, wherein: In the radially outward direction, the gap between the upper cover and the upper ring has a plurality of vertical heights, and the plurality of vertical heights are not all the same.

3. The centrifugal fan according to claim 2, wherein: In the radially outward direction, the sizes of the plurality of vertical heights are in the order of large-small-large or small-large-small.

4. The centrifugal fan according to claim 1, wherein: At least one of the plurality of fan blades has an outer edge, which faces the air outlet and includes a rectangular sawtooth structure.

5. The centrifugal fan according to claim 4, characterized in that: The impeller also includes a base plate, and the plurality of blades are connected between the upper ring and the base plate. An air flow channel is formed between the upper ring, the base plate and any two adjacent ones of the plurality of blades, and the two ends of the air flow channel face the air inlet and the air outlet respectively.

6. The centrifugal fan according to claim 5, characterized in that: in The upper ring extends radially outward from the outer edge to form an upper ring outer edge bottom surface; and The bottom plate extends radially outward from the outer edge to form a bottom plate outer edge top surface, wherein the upper ring outer edge bottom surface is parallel to the bottom plate outer edge top surface.

7. The centrifugal fan according to claim 5, characterized in that: The air flow channel has a first position, a second position, a third position and a fourth position, and the first position, the second position, the third position and the fourth position are arranged in sequence from the air inlet to the air outlet, wherein the first position has a first axial height, the second position has a second axial height, the third position has a third axial height and the fourth position has a fourth axial height, wherein the first axial height is greater than the second axial height, the second axial height is less than the third axial height, and the third axial height is greater than the fourth axial height.

8. The centrifugal fan according to claim 7, characterized in that: The third axial height is smaller than the first axial height, and the fourth axial height is smaller than the second axial height.

9. The centrifugal fan according to claim 7, wherein: The upper ring has a first wavy surface facing the base plate, and the base plate has a second wavy surface facing the upper ring, wherein the axial height variation of the air flow channel at the first position, the second position, the third position and the fourth position is generated by the first wavy surface and the second wavy surface.

10. The centrifugal fan according to claim 1, wherein: An inner edge of at least one of the plurality of blades is exposed from a central opening of the upper ring and the air inlet.

11. The centrifugal fan according to claim 10, wherein: The upper edge surface of the inner edge close to the air inlet is a flat surface, a curved surface, an inclined surface or a concave surface.

12. The centrifugal fan according to claim 1, wherein: The number of the plurality of blades is 18 or 36.

13. The centrifugal fan according to claim 1, wherein: in The upper cover has an upper cover air outlet bottom surface adjacent to the air outlet; and The base has a base air outlet top surface adjacent to the air outlet, and the bottom surface of the upper cover air outlet faces the top surface of the base air outlet, wherein in a direction radially away from the multiple fan blades from the outer edges of the multiple fan blades, the vertical distance between the bottom surface of the upper cover air outlet and the top surface of the base air outlet is large-small-large or small-large-small in sequence.

14. The centrifugal fan according to claim 1, wherein: The upper cover and the base are connected via a plurality of connecting columns, and the upper cover, the base and the plurality of connecting columns together form the air outlet.

15. The centrifugal fan according to claim 14, wherein: A cross section of the plurality of connection pillars is circular, polygonal, teardrop-shaped or other shapes with convex curved surfaces.

16. The centrifugal fan according to claim 1, wherein: The second annular protrusion structure includes an axial extension portion and a radial extension portion. The axial extension portion is connected between an upper surface of the upper ring and the radial extension portion.

17. The centrifugal fan according to claim 1, wherein: The second annular protrusion structure is arranged on an upper surface of the upper ring, and the upper surface has a first platform area and a second platform area, the first platform area is located between the first annular protrusion structure and the second annular protrusion structure, and the second platform area is located on a side of the second annular protrusion structure away from the first annular protrusion structure, wherein in the axial horizontal height, the air inlet, the first platform area and the second platform area are arranged in sequence.

18. The centrifugal fan according to claim 17, wherein: The upper surface of the upper ring further has an inclined surface or a vertical surface located between the first platform area and the second platform area.

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