Centrifugal fan

Abstract

A centrifugal fan (11) is provided with: a first member (13) attached to a rotating shaft (12); a second member (14) provided at a position facing the first member (13); and a blade (21) disposed between the first member (13) and the second member (14). The blade (21) includes a solid part (22) and a pressure fluctuation suppression part (31). The pressure fluctuation suppression part (31) is provided on the pressure surface or the suction surface of the blade (21). The blade (21) has a front edge (21a) positioned on the radially inner side and a rear edge (21b) positioned on the radially outer side. The position of the center of gravity of the surface of the pressure fluctuation suppression part (31) is closer to the front edge (21a) than to the rear edge (21b).

Description

centrifugal fan

[0001] The present disclosure relates to centrifugal fans.

[0002] A known technology related to an axial flow fan is described in Patent Document 1. In Patent Document 1, a hollow layer is provided inside the blade of a blower impeller, and a porous material that connects the hollow layer to the outside is used on all or part of the blade, thereby reducing noise.

[0003] Patent No. 3071287

[0004] There is room for improvement in noise suppression in centrifugal fans. One of the objects of the present disclosure is to provide a centrifugal fan that can suitably suppress noise.

[0005] A centrifugal fan of a first aspect that solves the above problem comprises a first member attached to a rotating shaft, a second member provided at a position opposite the first member, and a blade arranged between the first member (13) and the second member (14), wherein the blade includes a solid portion and a pressure fluctuation suppression portion, the pressure fluctuation suppression portion is provided on a positive pressure surface or a negative pressure surface of the blade, the blade has a leading edge located radially inward and a trailing edge located radially outward, and the position of the surface center of gravity of the pressure fluctuation suppression portion is closer to the leading edge than to the trailing edge.

[0006] According to this configuration, by providing a pressure fluctuation suppression unit on the blade of the centrifugal fan, pressure fluctuations that cause noise near the blade surface are eliminated, thereby suppressing the development of vortices near the blade surface. This reduces noise caused by turbulence from vortices that interfere with the blade. As a result, the centrifugal fan can effectively suppress noise. Furthermore, since the pressure fluctuation suppression unit is located on the leading edge side of the blade, the centrifugal fan can effectively reduce noise.

[0007] A centrifugal fan of a second aspect is the centrifugal fan of the first aspect, wherein, in a blade cross section perpendicular to the rotation axis, when the dimension of a line connecting the leading edge and the trailing edge is defined as a blade chord length, the surface center of gravity is located within 40% of the blade chord length from the leading edge.

[0008] According to this configuration, noise caused by turbulence of vortices interfering with the blades can be reduced compared to when the center of gravity of the surface is located at a position more than 40% of the chord length from the leading edge. A centrifugal fan according to a third aspect is the centrifugal fan according to the second aspect, wherein the center of gravity of the surface is located within 20% of the chord length from the leading edge.

[0009] According to this configuration, noise caused by turbulence of vortices interfering with the blade can be reduced more than when the center of gravity of the surface is located at a position more than 20% of the chord length from the leading edge. A centrifugal fan according to a fourth aspect is the centrifugal fan according to any one of the first to third aspects, wherein the solid portion is located at the leading edge.

[0010] According to this configuration, since the solid portion is provided at the leading edge, the strength and rigidity of the blade can be increased. A centrifugal fan according to a fifth aspect is the centrifugal fan of any one of the first to third aspects, wherein the pressure fluctuation suppression portion is provided at the leading edge.

[0011] According to this configuration, since the pressure fluctuation suppression portion is provided on the leading edge, noise caused by turbulence of vortices interfering with the blades can be reduced compared to when the pressure fluctuation suppression portion is not provided on the leading edge. A centrifugal fan according to a sixth aspect is the centrifugal fan of any one of the first to fifth aspects, wherein the pressure fluctuation suppression portion is provided so as to communicate the pressure surface and the negative pressure surface.

[0012] According to this configuration, since the positive pressure surface and the negative pressure surface are in communication with each other, pressure fluctuations due to turbulence in the airflow can be sufficiently suppressed, thereby reducing noise caused by turbulence of vortices interfering with the blades. A centrifugal fan according to a seventh aspect is the centrifugal fan of any one of the first to fifth aspects, wherein the pressure fluctuation suppression unit is provided only on the negative pressure surface.

[0013] According to this configuration, by providing the pressure fluctuation suppression portion only on the negative pressure surface, costs can be reduced and noise caused by turbulence of vortices interfering with the blades can be reduced. A centrifugal fan according to an eighth aspect is the centrifugal fan according to any one of the first to seventh aspects, wherein the blades further have a hollow portion, and the hollow portion is adjacent to the pressure fluctuation suppression portion.

[0014] This configuration allows the airflow near the blade surface to pass inward, away from the blade surface, thereby suppressing pressure fluctuations caused by turbulence in the airflow near the blade surface and thereby reducing noise caused by turbulence in vortices interfering with the blade.

[0015] A centrifugal fan of a ninth aspect is the centrifugal fan of the eighth aspect, wherein, when the dimension of a line connecting the leading edge and the trailing edge in the hollow portion is defined as a blade chord length, the width dimension of the widest part in a direction perpendicular to the blade chord length is 12 mm or more.

[0016] This configuration allows the airflow near the blade surface to pass inward, away from the blade surface, thereby suppressing pressure fluctuations caused by turbulence in the airflow near the blade surface and thereby reducing noise caused by turbulence in vortices interfering with the blade.

[0017] A centrifugal fan according to a tenth aspect is the centrifugal fan according to any one of the first to ninth aspects, wherein the pressure fluctuation suppression portion is formed of a porous material. With this configuration, pressure fluctuations that cause noise near the blade surface are eliminated by the airflow near the blade surface passing through the interior of the porous material, thereby suppressing the development of vortices near the blade surface. This makes it possible to reduce noise caused by turbulence from vortices that interfere with the blade.

[0018] FIG. 1 is a perspective view of a centrifugal fan of a first embodiment. FIG. 2 is a side view of the centrifugal fan of FIG. 1. FIG. 3 is a schematic cross-sectional view of a blade of the centrifugal fan of FIG. 1. FIG. 4 is a graph showing the magnitude of noise reduction effect versus the installation position of a pressure fluctuation suppression unit on the blade. FIG. 5 is a schematic cross-sectional view of a blade of a centrifugal fan of a second embodiment. FIG. 6 is a graph showing the magnitude of noise reduction effect versus the width dimension of a hollow section. FIG. 7 is a schematic cross-sectional view of a blade of a centrifugal fan of a third embodiment. FIG. 8 is a graph showing blowing noise versus air volume when a pressure fluctuation suppression unit is provided only on the pressure surface, only on the negative pressure surface, or on both the pressure surface and the negative pressure surface of the blade, and when no pressure fluctuation suppression unit is provided on the blade. FIG. 9 is a schematic cross-sectional view of a blade of a centrifugal fan of a first modified example. FIG. 10 is a schematic cross-sectional view of a blade of a centrifugal fan of a second modified example.

[0019] <First Embodiment> A centrifugal fan 11 according to a first embodiment will be described with reference to Figures 1 to 4. <Centrifugal Fan> The centrifugal fan 11 is a device for circulating air in a room. The centrifugal fan 11 includes, for example, a turbo fan or a sirocco fan. In this embodiment, the centrifugal fan 11 will be described as a turbo fan. The centrifugal fan 11 is configured to rotate in a rotation direction R of the centrifugal fan 11, thereby blowing air drawn in through the air inlet 14a radially outward. The rotation direction R is, for example, counterclockwise. The rotation direction R may also be clockwise.

[0020] The centrifugal fan 11 is rotated by, for example, a motor. The rotation shaft 12 of the centrifugal fan 11 coincides with the rotation shaft of the motor. The rotation shaft 12 has a central rotation axis C1. The centrifugal fan 11 includes a first member 13 attached to the rotation shaft 12. The first member 13 rotates integrally with the rotation shaft 12. The first member 13 is, for example, a circular plate. A hole is formed in the center of the first member 13, through which the rotation shaft 12 is disposed. The first member 13 is made of, for example, metal or resin.

[0021] The centrifugal fan 11 includes a second member 14 disposed opposite the first member 13. The second member 14 is, for example, a fan shroud. The second member 14 has a circular shape. An air inlet 14a is formed in the center of the second member 14. The second member 14 is made of, for example, metal or resin.

[0022] The centrifugal fan 11 includes blades 21 arranged between a first member 13 and a second member 14 in the axial direction of the centrifugal fan 11. A plurality of blades 21 are arranged at predetermined intervals between the first member 13 and the second member 14 so as to surround the periphery of the rotary shaft 12. The number of blades 21 is 10 or less. Preferably, the number of blades 21 is 6. The number of blades 21 may be anywhere between 10 and 7, or between 5 and 2. Each of the plurality of blades 21 has the same shape.

[0023] Each blade 21 has a leading edge 21 a and a trailing edge 21 b. The leading edge 21 a is located downstream in the direction of rotation R. The leading edge 21 a is located closer to the rotary shaft 12. The leading edge 21 a is located radially inward of the centrifugal fan 11 relative to the trailing edge 21 b. The leading edge 21 a curves toward the downstream side in the direction of rotation R. For example, the leading edge 21 a curves so that a middle portion in the axial direction of the leading edge 21 a protrudes most toward the downstream side in the direction of rotation R.

[0024] The trailing edge 21b is located upstream in the rotation direction R. The trailing edge 21b is located radially outward of the centrifugal fan 11 relative to the leading edge 21a. The trailing edge 21b includes, for example, an uneven portion 21c and a notch 21d. The uneven portion 21c has, for example, a sawtooth shape. The uneven portion 21c is provided on the second member 14 side of the trailing edge 21b. The notch 21d is provided on the first member 13 side of the trailing edge 21b. The uneven portion 21c and the notch 21d may be omitted.

[0025] The blades 21 gradually become thicker from the trailing edge 21b toward the leading edge 21a. Of two circumferentially adjacent blades 21, an air outlet 21e is provided between the leading edge 21a of one blade 21 and the trailing edge 21b of the other blade 21. When rotating in the rotation direction R, the centrifugal fan 11 draws air through the suction port 14a of the second member 14. The centrifugal fan 11 guides the drawn air from the leading edge 21a to the trailing edge 21b of the blade 21 and blows the air radially outward from the centrifugal fan 11 through the air outlet 21e.

[0026] The blade 21 is formed by a solid portion 22 and a pressure fluctuation suppressing portion 31. The solid portion 22 is dense. The material of the solid portion 22 is not particularly limited. The material of the solid portion 22 is, for example, metal or resin. The solid portion 22 has a higher density than the pressure fluctuation suppressing portion 31. Details of the pressure fluctuation suppressing portion 31 will be described later.

[0027] 3 shows a blade cross section perpendicular to the rotation axis 12. The blade cross section is, for example, a cross section of the blade 21 in a direction perpendicular to the rotation axis 12. The blade cross section is, for example, a cross section of the blade 21 at an equal distance from the first member 13. In the blade cross section, a line connecting the leading edge 21 a and the trailing edge 21 b is defined as an imaginary line X. The dimension of the imaginary line X is defined as the blade chord length L.

[0028] The blade 21 includes a leading edge 23 and a trailing edge 24. A center boundary line Y is defined that passes through a point 50% of the blade chord length L from the leading edge 21 a and is perpendicular to the blade chord length L. The leading edge 23 is the portion of the blade 21 that is closer to the leading edge 21 a than the center boundary line Y. The trailing edge 24 is the portion of the blade 21 that is closer to the trailing edge 21 b than the center boundary line Y. The leading edge 23 is wider in the direction perpendicular to the blade chord length L than the trailing edge 24.

[0029] The blade 21 has a positive pressure surface 25 and a negative pressure surface 26. The positive pressure surface 25 is a blade surface where the airflow creates positive pressure in the adjacent space when the centrifugal fan 11 is rotating. The negative pressure surface 26 is a blade surface where the airflow creates negative pressure in the adjacent space when the centrifugal fan 11 is rotating.

[0030] <Pressure Fluctuation Suppression Portion> The pressure fluctuation suppression portion 31 is configured to reduce pressure fluctuations occurring in the blade 21. The pressure fluctuation suppression portion 31 is provided, for example, on the leading edge 21 a. Furthermore, the pressure fluctuation suppression portion 31 may also be provided on a portion of the leading edge portion 23 that is different from the leading edge 21 a. The pressure fluctuation suppression portion 31 is formed integrally with the solid portion 22 by insert molding, bonding, or fitting. In Figures 1 to 3, 5, 7, 9, and 10, the pressure fluctuation suppression portion 31 is represented by dots.

[0031] The pressure fluctuation suppression section 31 is provided on the pressure surface 25 or the suction surface 26 of the blade 21. The pressure fluctuation suppression section 31 is provided on both the pressure surface 25 and the suction surface 26 of the blade 21. The pressure fluctuation suppression section 31 is provided so as to communicate between the pressure surface 25 and the suction surface 26 of the blade 21. The pressure fluctuation suppression section 31 may be provided only on the pressure surface 25 of the blade 21, or may be provided only on the suction surface 26.

[0032] The material of the pressure fluctuation suppression unit 31 is not particularly limited. The material of the pressure fluctuation suppression unit 31 may be, for example, a resin, a ceramic, a metal, or the like. For example, the resin may be a foamed resin. For example, the ceramic or metal may be a porous sintered body. The metal may be a mesh-like body.

[0033] The pressure fluctuation suppression unit 31 is formed of, for example, a porous material. The porous material provides communication between the positive pressure surface 25 and the negative pressure surface 26 of the blade 21. The porous material has pores that provide communication between the positive pressure surface 25 and the negative pressure surface 26 of the blade 21. When the pressure fluctuation suppression unit 31 provides communication between the positive pressure surface 25 and the negative pressure surface 26 of the blade 21, the positive pressure surface 25 is the surface from which air flows out of the pressure fluctuation suppression unit 31 when the centrifugal fan 11 is rotated. When the pressure fluctuation suppression unit 31 provides communication between the positive pressure surface 25 and the negative pressure surface 26 of the blade 21, the negative pressure surface 26 is the surface from which air flows in from the pressure fluctuation suppression unit 31 when the centrifugal fan 11 is rotated.

[0034] The pressure fluctuation suppressing portion 31 has a surface center of gravity G. The surface center of gravity G is the center of gravity of the cross section of the pressure fluctuation suppressing portion 31 when the specific gravity of the pressure fluctuation suppressing portion 31 is uniform. The position of the surface center of gravity G of the pressure fluctuation suppressing portion 31 is closer to the leading edge 21 a than to the trailing edge 21 b.

[0035] A first boundary line Y1 is defined on the imaginary line X, passing through a point located 10% of the chord length L from the leading edge 21a and perpendicular to the imaginary line X. A second boundary line Y2 is defined on the imaginary line X, passing through a point located 20% of the chord length L from the leading edge 21a and perpendicular to the imaginary line X. A third boundary line Y3 is defined on the imaginary line X, passing through a point located 40% of the chord length L from the leading edge 21a and perpendicular to the imaginary line X. A fourth boundary line Y4 is defined on the imaginary line X, passing through a point located 60% of the chord length L from the leading edge 21a and perpendicular to the imaginary line X. A fifth boundary line Y5 is defined on the imaginary line X, passing through a point located 100% of the chord length L from the leading edge 21a and perpendicular to the imaginary line X.

[0036] The surface center of gravity G is located within 40% of the chord length L from the leading edge 21a. Specifically, the surface center of gravity G is located in a region closer to the leading edge 21a than the third boundary line Y3 in the aerofoil cross section. Preferably, the surface center of gravity G is located within 20% of the chord length L from the leading edge 21a. Specifically, the surface center of gravity G is located in a region closer to the leading edge 21a than the second boundary line Y2 in the aerofoil cross section.

[0037] Fig. 4 shows an example of the noise reduction effect obtained depending on the region where the pressure fluctuation suppression portion 31 is provided in the chord direction along the imaginary line X. As shown in Fig. 3, a region A from the leading edge 21a to the first boundary line Y1, a region B from the first boundary line Y1 to the third boundary line Y3, a region C from the third boundary line Y3 to the fourth boundary line Y4, and a region D from the fourth boundary line Y4 to the fifth boundary line Y5 are defined.

[0038] When the pressure fluctuation suppression unit 31 is provided in region A, the noise reduction effect is greater than when the pressure fluctuation suppression unit 31 is provided in regions B to D. When the pressure fluctuation suppression unit 31 is provided in region B, the noise reduction effect is greater than when the pressure fluctuation suppression unit 31 is provided in regions C and D. When the pressure fluctuation suppression unit 31 is provided in region C, the noise reduction effect is greater than when the pressure fluctuation suppression unit 31 is provided in region D.

[0039] Advantages of the First Embodiment The following describes advantages of the first embodiment. (1-1) A centrifugal fan 11 includes a first member 13 attached to a rotating shaft 12, a second member 14 disposed opposite the first member 13, and a blade 21 disposed between the first member (13) and the second member (14), the blade 21 including a solid portion 22 and a pressure fluctuation suppression portion 31, the pressure fluctuation suppression portion 31 being disposed on a pressure surface 25 or a suction surface 26 of the blade 21, the blade 21 having a leading edge 21 a located radially inward and a trailing edge 21 b located radially outward, and the surface center of gravity G of the pressure fluctuation suppression portion 31 being closer to the leading edge 21 a than to the trailing edge 21 b.

[0040] According to this configuration, by providing the pressure fluctuation suppressor 31 on the blades 21 of the centrifugal fan 11, pressure fluctuations that cause noise near the blade surfaces are eliminated, thereby suppressing the development of vortices near the blade surfaces. This reduces noise caused by turbulence from vortices that interfere with the blades 21. As a result, the centrifugal fan 11 can effectively suppress noise.

[0041] Furthermore, in the centrifugal fan 11, the portion of the blade 21 on the trailing edge 21b side is thinner than the portion on the leading edge 21a side, and therefore the portion on the trailing edge 21b side has lower strength and rigidity than the portion on the leading edge 21a side. Therefore, the portion on the trailing edge 21b side of the blade 21 is more susceptible to deformation than the portion on the leading edge 21a side. In particular, in the case of a turbofan, the ratio of the pressure rise to the airflow rate is large, and the load on the blade 21 is heavy. If the pressure fluctuation suppression portion 31, which has lower strength and rigidity than the solid portion 22, is provided on the trailing edge 21b, the adverse effects of deformation of the blade 21 are greater, and it is difficult to achieve a low-noise effect. In the centrifugal fan 11, the pressure fluctuation suppression portion 31 is disposed on the portion on the leading edge 21a side of the blade 21, thereby enabling favorable noise reduction.

[0042] (1-2) In a blade cross section perpendicular to the rotation axis 12, if the dimension of the line connecting the leading edge 21a and the trailing edge 21b is the blade chord length L, the surface center of gravity G is located within 40% of the blade chord length L from the leading edge 21a.

[0043] This configuration can reduce noise caused by vortex turbulence interfering with the blade 21 more than when the surface center of gravity G is located at a position more than 40% of the chord length L from the leading edge 21a. (1-3) The surface center of gravity G is located within 20% of the chord length L from the leading edge 21a.

[0044] This configuration can reduce noise caused by turbulence of vortices interfering with the blade 21 more than when the surface center of gravity G is located at a position from the leading edge 21a that is more than 20% of the blade chord length L. (1-3) The pressure fluctuation suppression portion 31 is provided at the leading edge 21a.

[0045] According to this configuration, since the pressure fluctuation suppression section 31 is provided on the leading edge 21a, noise caused by vortex disturbances interfering with the blade 21 can be reduced more than when the pressure fluctuation suppression section 31 is not provided on the leading edge 21a.

[0046] (1-4) The pressure fluctuation suppression unit 31 is provided to communicate between the pressure surface 25 and the suction surface 26. With this configuration, communication between the pressure surface 25 and the suction surface 26 allows pressure fluctuations caused by turbulence in the airflow to be sufficiently suppressed, thereby reducing noise caused by turbulence of vortices interfering with the blades 21.

[0047] (1-5) The pressure fluctuation suppression section 31 is made of a porous material. With this configuration, pressure fluctuations that cause noise near the blade surface are eliminated by the airflow passing through the porous material, thereby suppressing the development of vortices near the blade surface. Therefore, noise caused by turbulence from vortices interfering with the blade 21 can be reduced.

[0048] Second Embodiment A centrifugal fan according to a second embodiment will be described with reference to Figures 1, 2, 5, and 6. In the second embodiment, differences from the first embodiment will be described. Components similar to those in the first embodiment will be given the same names and will not be described again.

[0049] As shown in Figure 5, the blade 21 further has a hollow portion 27. The hollow portion 27 is adjacent to the pressure fluctuation suppression portion 31. The pressure fluctuation suppression portion 31 is adjacent to and surrounds the periphery of the hollow portion 27. The hollow portion 27 is provided in the leading edge portion 23 of the blade 21. The hollow portion 27 communicates with the pressure surface 25 and the suction surface 26 via the pressure fluctuation suppression portion 31. The hollow portion 27 may also communicate with only the pressure surface 25 via the pressure fluctuation suppression portion 31. The hollow portion 27 may also communicate with only the suction surface 26 via the pressure fluctuation suppression portion 31.

[0050] The hollow portion 27 is adjacent to the solid portion 22 in the chord direction along the imaginary line X. The solid portion 22 includes a portion provided in the trailing edge portion 24. The solid portion 22 may also include a portion provided in the leading edge portion 23.

[0051] The surface center of gravity G is located at the hollow portion 27 in the blade cross section. In the hollow portion 27, the width dimension S of the portion where the width in the direction perpendicular to the blade chord length L is greatest is 12 mm or more. Figure 6 shows an example of the noise reduction effect obtained depending on the width dimension S. When the width dimension S is 12 mm or more, the noise reduction effect is greater than when the width dimension S is less than 12 mm. When the width dimension S is 12 mm or more, the noise reduction effect increases as the width dimension S increases. In one example, when the width dimension S is 12 mm, the noise reduction effect is greater than when the width dimension S is 6 mm.

[0052] <Effects of Second Embodiment> The effects of the second embodiment will be described. In the second embodiment, the following effects can be obtained in addition to the effects of the first embodiment.

[0053] (2-1) The blade 21 further has a hollow portion 27, which is adjacent to the pressure fluctuation suppression portion 31. With this configuration, the airflow near the blade surface can pass through in a direction away from the blade surface toward the interior of the blade, thereby suppressing pressure fluctuations caused by turbulence in the airflow near the blade surface, and thus reducing noise caused by turbulence in vortices that interfere with the blade 21.

[0054] (2-2) In the hollow portion 27, if the dimension of the line connecting the leading edge 21a and the trailing edge 21b is the chord length L, the width dimension S of the widest part in the direction perpendicular to the chord length L is 12 mm or more.

[0055] This configuration allows the airflow near the blade surface to pass inward, away from the blade surface, thereby suppressing pressure fluctuations caused by turbulence in the airflow at the blade surface and thereby reducing noise caused by turbulence of vortices interfering with the blade 21. Furthermore, by making the width dimension S 12 mm or more, the noise reduction effect can be further enhanced.

[0056] Third Embodiment A centrifugal fan according to a third embodiment will be described with reference to Figures 1, 2, 7, and 8. In the third embodiment, differences from the first and second embodiments will be described. Components similar to those in the first and second embodiments will be given the same names and will not be described again.

[0057] As shown in Figure 7, the blade 21 has a hollow portion 27. The hollow portion 27 is adjacent to the pressure fluctuation suppression portion 31. The hollow portion 27 is provided in the leading edge portion 23 of the blade 21. The pressure fluctuation suppression portion 31 is provided only on the suction surface 26. The hollow portion 27 communicates only with the suction surface 26 via the pressure fluctuation suppression portion 31.

[0058] The solid portion 22 includes a first solid portion 22a and a second solid portion 22b. The first solid portion 22a is provided at the leading edge 21a. The second solid portion 22b is provided at the trailing edge 24. A portion of the second solid portion 22b is provided at the leading edge 23. The hollow portion 27 is adjacent to the first solid portion 22a and the second solid portion 22b. In the chord direction along the imaginary line X, the hollow portion 27 is provided between the first solid portion 22a and the second solid portion 22b.

[0059] The blade 21 further has a lid portion 28. The solid portion 22 includes the lid portion 28. The lid portion 28 is provided between the first solid portion 22a and the second solid portion 22b in the blade chord direction along the imaginary line X. The lid portion 28 is provided on the pressure surface 25. The lid portion 28 is configured to cover a recessed portion 29 provided in the blade 21. The hollow portion 27 is formed by the lid portion 28 covering the recessed portion 29.

[0060] A pressure fluctuation suppressing portion 31 may be provided between the lid portion 28 and the first solid portion 22a. When the pressure fluctuation suppressing portion 31 is provided between the lid portion 28 and the first solid portion 22a, the pressure fluctuation suppressing portion 31 is, for example, a gap between the lid portion 28 and the first solid portion 22a. When the pressure fluctuation suppressing portion 31 is provided between the lid portion 28 and the second solid portion 22b, the pressure fluctuation suppressing portion 31 is, for example, a gap between the lid portion 28 and the second solid portion 22b.

[0061] The lid portion 28 may be included in the pressure fluctuation suppression portion 31. When the lid portion 28 is included in the pressure fluctuation suppression portion 31, the lid portion 28 is made of a porous material. The surface center of gravity G is located in the hollow portion 27 in the blade cross section. In the hollow portion 27, the width dimension S of the widest part in the direction perpendicular to the blade chord length L is 12 mm or more.

[0062] 8 shows graphs of blowing noise versus air volume for the first, second, third, and fourth patterns. The first pattern is a case where the pressure fluctuation suppression unit 31 is provided only on the negative pressure surface 26. The second pattern is a case where the pressure fluctuation suppression unit 31 is provided only on the positive pressure surface 25. The third pattern is a case where the pressure fluctuation suppression unit 31 is provided on both the positive pressure surface 25 and the negative pressure surface 26. The fourth pattern is a case where the pressure fluctuation suppression unit 31 is not provided on the blade 21.

[0063] In the case of the third pattern, the blowing noise relative to the air volume is smaller than in the first, second, and fourth patterns. In the case of the first pattern, the blowing noise relative to the air volume is smaller than in the second and fourth patterns. In the case of the second pattern, the blowing noise relative to the air volume is smaller than in the fourth pattern.

[0064] 8, when the pressure fluctuation suppression unit 31 is provided on the pressure surface 25 or the suction surface 26, a noise reduction effect is achieved compared to when the pressure fluctuation suppression unit 31 is not provided on the blade 21. Furthermore, when the pressure fluctuation suppression unit 31 is provided only on the suction surface 26, a greater noise reduction effect is achieved than when the pressure fluctuation suppression unit 31 is provided only on the pressure surface 25.

[0065] <Effects of the Third Embodiment> The following describes the effects of the third embodiment. In the third embodiment, the following effects can be obtained in addition to the effects of the first and second embodiments.

[0066] (3-1) The solid portion 22 is provided on the leading edge 21a. According to this configuration, the solid portion 22 is provided on the leading edge 21a, so that the strength and rigidity of the blade 21 can be increased.

[0067] (3-2) The pressure fluctuation suppression section 31 is provided only on the suction surface 26. According to this configuration, by providing the pressure fluctuation suppression section 31 only on the suction surface 26, costs can be reduced and noise caused by turbulence of vortices interfering with the blades 21 can be reduced.

[0068] (3-3) The blade 21 further has a lid portion 28 and a recessed portion 29, and the hollow portion 27 is formed by the lid portion 28 and the recessed portion 29. According to this configuration, the blade 21 is divided into the lid portion 28 and the solid portion 22, and the hollow portion 27 can be suitably formed by assembling them.

[0069] <Modifications> In addition to the above-described embodiments, the centrifugal fan 11 of the present disclosure may be configured in the following modifications or a combination of at least two modifications that are not mutually contradictory.

[0070] As shown in Fig. 9, the blade 21 may be formed hollow, and the pressure fluctuation suppression portion 31 may be provided only on the negative pressure surface 26. In this case, the solid portion 22 and the pressure fluctuation suppression portion 31 are configured to surround the hollow portion 27. When the blade 21 is formed hollow, the pressure fluctuation suppression portion 31 may be provided only on the positive pressure surface 25. When the blade 21 is formed hollow, the hollow portion 27 is formed by the cover portion 28 covering the recess 29.

[0071] 10 , the pressure fluctuation suppression section 31 may be provided only on the positive pressure surface 25. When the pressure fluctuation suppression section 31 is provided only on the positive pressure surface 25, the hollow section 27 communicates only with the positive pressure surface 25 via the pressure fluctuation suppression section 31.

[0072] Although the embodiment of the centrifugal fan 11 has been described above, it will be understood that various modifications of the form and details are possible without departing from the spirit and scope of the centrifugal fan 11 described in the claims.

[0073] 11...centrifugal fan, 12...rotating shaft, 13...first member, 14...second member, 21...blade, 21a...leading edge, 21b...trailing edge, 22...solid portion, 25...positive pressure surface, 26...negative pressure surface, 27...hollow portion, 31...pressure fluctuation suppression portion, G...surface center of gravity, L...blade chord length, S...width dimension.

Claims

1. A centrifugal fan (11), comprising: a first member (13) attached to a rotating shaft (12); a second member (14) provided at a position opposite the first member (13); and a blade (21) arranged between the first member (13) and the second member (14), wherein the blade (21) includes a solid portion (22) and a pressure fluctuation suppression portion (31), wherein the pressure fluctuation suppression portion (31) is provided on a positive pressure surface (25) or a negative pressure surface (26) of the blade (21), wherein the blade (21) has a leading edge (21a) located radially inward and a trailing edge (21b) located radially outward, and wherein the surface center of gravity (G) of the pressure fluctuation suppression portion (31) is closer to the leading edge (21a) than to the trailing edge (21b).

2. The centrifugal fan according to claim 1, wherein, in a blade cross section perpendicular to the rotation axis (12), when the dimension of a line connecting the leading edge (21a) and the trailing edge (21b) is defined as a blade chord length (L), the surface center of gravity (G) is located within 40% of the blade chord length (L) from the leading edge (21a).

3. A centrifugal fan according to claim 2, wherein the surface center of gravity (G) is located within 20% of the blade chord length (L) from the leading edge (21a).

4. The centrifugal fan according to any one of claims 1 to 3, wherein the solid portion (22) is provided at the leading edge (21a).

5. The centrifugal fan according to any one of claims 1 to 3, wherein the pressure fluctuation suppressing portion (31) is provided on the leading edge (21a).

6. The centrifugal fan according to any one of claims 1 to 5, wherein the pressure fluctuation suppressing portion (31) is provided so as to communicate between the positive pressure surface (25) and the negative pressure surface (26).

7. The centrifugal fan according to any one of claims 1 to 5, wherein the pressure fluctuation suppressing portion (31) is provided only on the negative pressure surface (26).

8. The centrifugal fan according to any one of claims 1 to 7, wherein the blade (21) further has a hollow portion (27), and the hollow portion (27) is adjacent to the pressure fluctuation suppression portion (31).

9. The centrifugal fan according to claim 8, wherein, when the dimension of a line connecting the leading edge (21a) and the trailing edge (21b) in the hollow portion (27) is taken as a chord length (L), a width dimension (S) of a part having the greatest width in a direction perpendicular to the chord length (L) is 12 mm or more.

10. The centrifugal fan according to any one of claims 1 to 9, wherein the pressure fluctuation suppressing portion (31) is formed of a porous material.

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