Centrifugal Fan

Abstract

To provide a centrifugal fan capable of suppressing noise suitably.SOLUTION: A centrifugal fan 11 comprises a blade 21 arranged between a first member 13 attached to a rotational shaft 12 and a second member 14 arranged at a position opposite the first member 13. The blade 21 is formed by a solid part 22 and a pressure fluctuation suppression part 31. The pressure fluctuation suppression part 31 is provided on a positive pressure surface or negative pressure surface of the blade 21. The blade 21 has a leading edge 21a located radially inward, and a trailing edge 21b located radially outward. The position of the surface center of gravity of the pressure fluctuation suppression part 31 is closer to the leading edge 21a than to the trailing edge 21b.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to centrifugal fans. [Background technology]

[0002] Known technology relating to axial flow fans is that 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 the entire surface or part of the blade, thereby suppressing noise. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3071287 Summary of the Invention [Problem to be solved by the invention]

[0004] There is room for improvement in noise suppression in centrifugal fans. An object of the present disclosure is to provide a centrifugal fan that can effectively suppress noise. [Means for solving the problem]

[0005] A centrifugal fan of a first aspect that solves the above-mentioned problems includes a blade disposed between a first member attached to a rotating shaft and a second member provided opposite the first member, the blade being formed by a solid portion and a pressure fluctuation suppression portion provided on a positive pressure side or a negative pressure side of the blade, the blade having 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. According to this configuration, by providing the pressure fluctuation suppression portion on the blade of the centrifugal fan, pressure fluctuations that cause noise near the blade surface are eliminated, and the development of vortices near the blade surface is suppressed. Therefore, noise caused by turbulence of vortices interfering with the blade can be reduced. Thus, the centrifugal fan can effectively suppress noise. Furthermore, the centrifugal fan can effectively reduce noise because the pressure fluctuation suppression portion is disposed on the leading edge side of the blade.

[0006] 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. According to this configuration, noise caused by turbulence of vortices interfering with the blade can be reduced more than when the surface center of gravity is located at a position that is more than 40% of the blade chord length from the leading edge.

[0007] A centrifugal fan according to a third aspect is the centrifugal fan according to the second aspect, wherein the surface center of gravity is located within 20% of the blade chord length from the leading edge. With this configuration, noise caused by turbulence of vortices interfering with the blade can be reduced more than when the surface center of gravity is located at a position that is more than 20% of the blade chord length from the leading edge.

[0008] 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 provided at the leading edge. According to this configuration, since a solid portion is provided at the leading edge, the strength and rigidity of the wing can be increased.

[0009] A centrifugal fan according to a fifth aspect is the centrifugal fan according to any one of the first to third aspects, wherein the pressure fluctuation suppressing portion is provided at the leading edge. According to this configuration, since the pressure fluctuation suppression portion is provided on the leading edge, noise caused by vortex turbulence interfering with the blade can be reduced more than in the case where a pressure fluctuation suppression portion is not provided on the leading edge.

[0010] A centrifugal fan according to a sixth aspect is the centrifugal fan according to any one of the first to fifth aspects, wherein the pressure fluctuation suppressing portion is provided so as to communicate between the positive pressure surface and the negative pressure surface. According to this configuration, since the positive pressure surface and the negative pressure surface are in communication with each other, pressure fluctuations due to turbulent airflow can be sufficiently suppressed, and noise caused by turbulent vortices interfering with the blades can be reduced.

[0011] A centrifugal fan according to a seventh aspect is the centrifugal fan according to any one of the first to fifth aspects, wherein the pressure fluctuation suppressing portion is provided only on the negative pressure surface. According to this configuration, by providing the pressure fluctuation suppressing 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.

[0012] A centrifugal fan according to an eighth aspect is the centrifugal fan according to any one of the first to seventh aspects, wherein the blade further has a hollow portion, the hollow portion being adjacent to the pressure fluctuation suppressing portion. According to this configuration, pressure fluctuations caused by turbulent airflow occurring near the blade surface can be transmitted toward the inside of the blade, away from the blade surface, thereby reducing noise caused by turbulent vortices interfering with the blade.

[0013] A centrifugal fan in a ninth aspect is the centrifugal fan in 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. According to this configuration, pressure fluctuations caused by turbulent airflow occurring near the blade surface can be transmitted toward the inside of the blade, away from the blade surface, thereby reducing noise caused by turbulent vortices interfering with the blade.

[0014] 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 suppressing portion is formed from a porous material. With this configuration, the pressure fluctuations that cause noise near the blade surface are eliminated by passing through the inside of the porous material, suppressing the development of vortices near the blade surface, thereby reducing noise caused by turbulence of vortices that interfere with the blade. [Brief description of the drawings]

[0015] [Figure 1] 1 is a perspective view of a centrifugal fan according to a first embodiment. FIG. [Diagram 2] FIG. 2 is a side view of the centrifugal fan of FIG. [Diagram 3] FIG. 2 is a schematic cross-sectional view of a blade of the centrifugal fan of FIG. 1. [Figure 4] 10 is a graph showing the magnitude of noise reduction effect versus the installation position of a pressure fluctuation suppressing portion on a blade. [Diagram 5] FIG. 11 is a schematic cross-sectional view of a blade of a centrifugal fan according to a second embodiment. [Figure 6] 10 is a graph showing the magnitude of the noise reduction effect according to the width dimension of the hollow portion. [Figure 7] FIG. 11 is a schematic cross-sectional view of a blade of a centrifugal fan according to a third embodiment. [Figure 8] 11 is a graph showing blowing noise versus air volume when a pressure fluctuation suppression portion is provided only on a pressure surface, only on a suction surface, or on both the pressure surface and the suction surface of a blade, and when no pressure fluctuation suppression portion is provided on the blade. [Figure 9] FIG. 11 is a schematic cross-sectional view of a blade of a centrifugal fan according to a first modified example. [Figure 10] FIG. 11 is a schematic cross-sectional view of a blade of a centrifugal fan according to a second modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] First Embodiment A centrifugal fan 11 according to a first embodiment will be described with reference to FIGS.

[0017] <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 to blow air sucked from the air inlet 14a radially outward. The rotation direction R is, for example, a counterclockwise direction. The rotation direction R may also be a clockwise direction.

[0018] The centrifugal fan 11 is rotated by, for example, a motor. A rotation shaft 12 of the centrifugal fan 11 and a rotation shaft of the motor coincide with each other. The rotation shaft 12 has a central rotation axis C1.

[0019] The centrifugal fan 11 includes a first member 13 attached to the rotating shaft 12. The first member 13 rotates integrally with the rotating shaft 12. The first member 13 is, for example, a circular plate. A hole in which the rotating shaft 12 is provided is formed in the center of the first member 13. The material of the first member 13 is, for example, metal or resin.

[0020] The centrifugal fan 11 includes a second member 14 disposed at a position facing the first member 13. The second member 14 is, for example, a fan shroud. The second member 14 is circular in shape. An inlet 14a for sucking in air is formed in the center of the second member 14. The second member 14 is made of, for example, metal or resin.

[0021] The centrifugal fan 11 includes blades 21 arranged between the first member 13 and the second member 14 in the axial direction of the centrifugal fan 11. Between the first member 13 and the second member 14, the multiple blades 21 are arranged at predetermined intervals so as to surround the periphery of the rotating shaft 12. The multiple blades 21 number 10 or less. Preferably, the multiple blades 21 number 6. The multiple blades 21 may be any number between 10 and 7, or any number between 5 and 2. Each of the multiple blades 21 has the same shape.

[0022] The blade 21 has a leading edge 21a and a trailing edge 21b. The leading edge 21a is located downstream in the rotation direction R. The leading edge 21a is located on the rotating shaft 12 side. The leading edge 21a is located radially inward of the centrifugal fan 11 relative to the trailing edge 21b. The leading edge 21a curves toward the downstream side in the rotation direction R. For example, a middle portion of the leading edge 21a in the axial direction is curved so as to protrude most toward the downstream side in the rotation direction R.

[0023] 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.

[0024] The blades 21 gradually become thicker from the trailing edge 21b toward the leading edge 21a. An outlet 21e is provided between the leading edge 21a of one blade 21 and the trailing edge 21b of the other blade 21 of two circumferentially adjacent blades 21. When rotating in the rotation direction R, the centrifugal fan 11 draws in air from 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 outward in the radial direction of the centrifugal fan 11 from the outlet 21e.

[0025] 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, a metal or a 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.

[0026] 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 21a and the trailing edge 21b is defined as an imaginary line X. The dimension of the imaginary line X is defined as a blade chord length L.

[0027] The wing 21 includes a leading edge portion 23 and a trailing edge portion 24. A center boundary line Y is defined that passes through a point located 50% of the chord length L from the leading edge 21a and is perpendicular to the chord length L. The leading edge portion 23 is the portion of the wing 21 closer to the leading edge 21a than the center boundary line Y. The trailing edge portion 24 is the portion of the wing 21 closer to the trailing edge 21b than the center boundary line Y. The leading edge portion 23 is thicker in width in the direction perpendicular to the chord length L than the trailing edge portion 24.

[0028] 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 rotated. 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 rotated.

[0029] <Pressure fluctuation suppression section> The pressure fluctuation suppressing portion 31 is configured to reduce pressure fluctuations occurring in the blade 21. The pressure fluctuation suppressing portion 31 is provided, for example, on the leading edge 21a. Furthermore, the pressure fluctuation suppressing portion 31 is also provided on a portion of the leading edge portion 23 other than the leading edge 21a. The pressure fluctuation suppressing 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 suppressing portion 31 is represented by dots.

[0030] 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.

[0031] The material of the pressure fluctuation suppression part 31 is not particularly limited. The material of the pressure fluctuation suppression part 31 is, for example, a resin, a ceramic, a metal, or the like. For example, the resin is a foamed resin. For example, the ceramic or the metal is a porous sintered body. The metal may be a net-like body also called a mesh.

[0032] The pressure fluctuation suppression unit 31 is formed of, for example, a porous material. The porous material communicates the positive pressure surface 25 and the negative pressure surface 26 of the blade 21. The porous material has pores that communicate the positive pressure surface 25 and the negative pressure surface 26 of the blade 21. When the pressure fluctuation suppression unit 31 communicates 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 communicates 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.

[0033] 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 a 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 21a than to the trailing edge 21b.

[0034] 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.

[0035] 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 blade 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 blade cross section.

[0036] 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.

[0037] When pressure fluctuation suppression section 31 is provided in region A, the noise reduction effect is greater than when pressure fluctuation suppression section 31 is provided in regions B to D. When pressure fluctuation suppression section 31 is provided in region B, the noise reduction effect is greater than when pressure fluctuation suppression section 31 is provided in regions C and D. When pressure fluctuation suppression section 31 is provided in region C, the noise reduction effect is greater than when pressure fluctuation suppression section 31 is provided in region D.

[0038] <Advantages of the First Embodiment> The effects of the first embodiment will be described.

[0039] (1-1) A centrifugal fan 11 includes a blade 21 disposed between a first member 13 attached to a rotating shaft 12 and a second member 14 provided opposite the first member 13, the blade 21 being formed by a solid portion 22 and a pressure fluctuation suppression portion 31, the pressure fluctuation suppression portion 31 being provided on a positive pressure surface 25 or a negative pressure surface 26 of the blade 21, the blade 21 having a leading edge 21a located radially inward and a trailing edge 21b located radially outward, and the position of the surface center of gravity G of the pressure fluctuation suppression portion 31 being closer to the leading edge 21a than to the trailing edge 21b. According to this configuration, by providing the pressure fluctuation suppression section 31 on the blades 21 of the centrifugal fan 11, pressure fluctuations that cause noise near the blade surfaces are eliminated, and the development of vortices near the blade surfaces is suppressed. This makes it possible to reduce noise caused by turbulence of vortices that interfere with the blades 21. Thus, the centrifugal fan 11 can effectively suppress noise. In addition, in the centrifugal fan 11, the trailing edge 21b side of the blade 21 is thinner than the leading edge 21a side, so the strength and rigidity of the trailing edge 21b side are lower than those of the leading edge 21a side. Therefore, the trailing edge 21b side of the blade 21 is more likely to deform than the leading edge 21a side. In particular, in the case of a turbofan, the ratio of the pressure rise to the air volume is large, and the load on the blade 21 is large. If the pressure fluctuation suppression section 31, which has lower strength and rigidity than the solid section 22, is provided at the trailing edge 21b, the adverse effect of the deformation of the blade 21 is greater, and it is difficult to achieve a low noise effect. In the centrifugal fan 11, the pressure fluctuation suppression section 31 is disposed at the leading edge 21a side of the blade 21, so that the noise can be suitably reduced.

[0040] (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. According to this configuration, noise caused by turbulence of vortexes interfering with the blade 21 can be reduced more than when the surface center of gravity G is located at a position that is greater than 40% of the blade chord length L from the leading edge 21a.

[0041] (1-3) The surface center of gravity G is located within 20% of the chord length L from the leading edge 21a. According to this configuration, noise caused by turbulence of vortexes interfering with the blade 21 can be reduced more than when the surface center of gravity G is located at a position that is greater than 20% of the blade chord length L from the leading edge 21a.

[0042] (1-3) The pressure fluctuation suppressing portion 31 is provided on the leading edge 21a. According to this configuration, since the pressure fluctuation suppression portion 31 is provided on the leading edge 21a, noise caused by vortex turbulence interfering with the blade 21 can be reduced more than in the case where the pressure fluctuation suppression portion 31 is not provided on the leading edge 21a.

[0043] (1-4) The pressure fluctuation suppressing portion 31 is provided to communicate between the positive pressure surface 25 and the negative pressure surface 26. According to this configuration, since the positive pressure surface 25 and the negative pressure surface 26 are in communication with each other, pressure fluctuations due to turbulent airflow can be sufficiently suppressed, and noise caused by turbulent vortices interfering with the blades 21 can be reduced.

[0044] (1-5) The pressure fluctuation suppressor 31 is made of a porous material. According to this configuration, the pressure fluctuations that cause noise near the blade surface are eliminated by passing through the inside of the porous material, and the development of vortices near the blade surface is suppressed, thereby reducing noise caused by turbulence of vortices that interfere with the blade 21.

[0045] <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. Members similar to those in the first embodiment will be given the same names and will not be described.

[0046] 5, the blade 21 further has a hollow portion 27. The hollow portion 27 is adjacent to the pressure fluctuation suppressing portion 31. The pressure fluctuation suppressing portion 31 is adjacent to the hollow portion 27 so as to surround the periphery thereof.

[0047] 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 communicate only with the pressure surface 25 via the pressure fluctuation suppression portion 31. The hollow portion 27 may communicate only with the suction surface 26 via the pressure fluctuation suppression portion 31.

[0048] 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 include a portion provided in the leading edge portion 23.

[0049] In the blade cross section, the surface center of gravity G is in hollow portion 27. In hollow portion 27, the width dimension S of the widest portion in the direction perpendicular to the blade chord length L is 12 mm or more.

[0050] FIG. 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.

[0051] <Effects of the second embodiment> The following describes the effects of the second embodiment: In the second embodiment, the following effects can be obtained in addition to the effects of the first embodiment.

[0052] (2-1) The blade 21 further has a hollow portion 27 , and the hollow portion 27 is adjacent to the pressure fluctuation suppressing portion 31 . According to this configuration, pressure fluctuations due to turbulent airflow occurring near the blade surface can be transmitted toward the inside of the blade, away from the blade surface, thereby reducing noise caused by turbulent vortices interfering with the blade 21.

[0053] (2-2) In hollow portion 27, if the dimension of the line connecting leading edge 21a and trailing edge 21b is the chord length L, the width dimension S of the widest part in the direction perpendicular to chord length L is 12 mm or more. This configuration allows pressure fluctuations of turbulent airflow occurring near the blade surface to be transmitted toward the inside of the blade, away from the blade surface, thereby reducing noise caused by turbulent vortices interfering with the blade 21. In addition, by making the width dimension S 12 mm or more, the noise reduction effect can be further increased.

[0054] <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. Members similar to those in the first and second embodiments will be given the same names and descriptions thereof will be omitted.

[0055] 7, the blade 21 has a hollow portion 27. The hollow portion 27 is adjacent to the pressure fluctuation suppressing portion 31. The hollow portion 27 is provided in the leading edge portion 23 of the blade 21.

[0056] The pressure fluctuation suppressing portion 31 is provided only on the negative pressure surface 26. The pressure fluctuation suppressing portion 31 causes the hollow portion 27 to communicate only with the negative pressure surface 26.

[0057] 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 portion 24. A portion of the second solid portion 22b is provided at the leading edge portion 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.

[0058] 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 recess 29 provided in the blade 21. The hollow portion 27 is formed by the lid portion 28 covering the recess 29.

[0059] 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. A pressure fluctuation suppressing portion 31 may be provided between the lid portion 28 and the second solid portion 22b. 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.

[0060] The lid portion 28 may be included in the pressure fluctuation suppressing portion 31. When the lid portion 28 is included in the pressure fluctuation suppressing portion 31, the lid portion 28 is made of a porous material.

[0061] In the blade cross section, the surface center of gravity G is in hollow portion 27. In hollow portion 27, the width dimension S of the widest portion in the direction perpendicular to the blade chord length L is 12 mm or more.

[0062] 8 shows a graph of the blowing noise versus air volume for the first, second, third, and fourth patterns. The first pattern is when the pressure fluctuation suppression section 31 is provided only on the negative pressure surface 26. The second pattern is when the pressure fluctuation suppression section 31 is provided only on the positive pressure surface 25. The third pattern is when the pressure fluctuation suppression section 31 is provided on both the positive pressure surface 25 and the negative pressure surface 26. The fourth pattern is when the pressure fluctuation suppression section 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 part 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 part 31 is not provided on the blade 21. Also, when the pressure fluctuation suppression part 31 is provided only on the suction surface 26, the noise reduction effect is greater than when the pressure fluctuation suppression part 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 addition to the effects of the first and second embodiments, the third embodiment can provide the following effects.

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

[0067] (3-2) The pressure fluctuation suppressing portion 31 is provided only on the negative pressure surface 26. According to this configuration, by providing the pressure fluctuation suppressing portion 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 cover portion 28 and the solid portion 22, and by assembling these, the hollow portion 27 can be suitably formed.

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

[0070] 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 lid portion 28 covering the recess 29.

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

[0072] While the embodiment of the centrifugal fan 11 has been described above, it will be understood that various changes in form and details may be made without departing from the spirit and scope of the centrifugal fan 11 described in the claims. [Explanation of symbols]

[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...pressure surface, 26...suction surface, 27...hollow portion, 31...pressure fluctuation suppression portion, G...center of gravity of surface, L...blade chord length, S...width dimension.

Claims

1. A centrifugal fan (11), The rotor blade (21) is provided between a first member (13) attached to a rotating shaft (12) and a second member (14) provided at a position opposite to the first member (13), The blade (21) is formed of a solid portion (22) and a pressure fluctuation suppression portion (31) formed of a porous material, The pressure fluctuation suppression portion (31) is provided on a pressure surface (25) or a suction surface (26) of the blade (21), The blade (21) has a leading edge (21a) located radially inward and a trailing edge (21b) located radially outward, The position of 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), In a blade cross section perpendicular to the rotation axis (12), when a dimension of a line connecting the leading edge (21 a) and the trailing edge (21 b) is a blade chord length (L), the surface center of gravity (G) is located within 20% of the blade chord length (L) from the leading edge (21 a). Centrifugal fan.

2. The solid portion (22) is provided on the leading edge (21a). The centrifugal fan according to claim 1 .

3. The pressure fluctuation suppression portion (31) is provided on the leading edge (21a).

2. The centrifugal fan according to claim 1.

4. The pressure fluctuation suppression portion (31) is provided so as to communicate the positive pressure surface (25) and the negative pressure surface (26). The centrifugal fan according to claim 1 .

5. The pressure fluctuation suppression portion (31) is provided only on the negative pressure surface (26). The centrifugal fan according to claim 1 .

6. The blade (21) further has a hollow portion (27), The hollow portion (27) is adjacent to the pressure fluctuation suppression portion (31).

2. The centrifugal fan according to claim 1.

7. In the hollow portion (27), when the dimension of a line connecting the leading edge (21 a) and the trailing edge (21 b) is defined as a chord length (L), a width dimension (S) of a part having a maximum width in a direction perpendicular to the chord length (L) is 12 mm or more. The centrifugal fan according to claim 6.

Images