Centrifugal fans and indoor units for air conditioners

Abstract

To reduce a recirculation flow and inhibit turbulence at the same time.SOLUTION: A centrifugal fan comprises: a main plate with a boss part having a center to which a rotary shaft of a motor is connected; a plurality of blades bonded to the main plate and arranged at equal intervals in the circumferential direction; a shroud bonded to the blades to face the main plate and being annular with an opening at a center; a bell mouth formed inside the shroud and gradually increased in the inner diameter toward the upstream side; and an annular member mounted on the outer periphery of the bell mouth with a gap formed downward from an inlet of the shroud. The annular member comprises: an annular flat plate part formed to be separate from and to face a lower end of the inlet of the shroud; and a protruding part which is formed on the outer periphery of a surface of the annular flat plate part facing the shroud side, and which has an outer surface that is a smooth curved surface.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a centrifugal fan and an indoor unit for an air conditioner. [Background technology]

[0002] Conventionally, centrifugal fans have been considered that reduce leakage flow (recirculation flow) caused by air blown out from the outlet of the centrifugal fan flowing in through gaps between the shroud and the bell mouth, as shown in Patent Document 1. Reducing the leakage flow (recirculation flow) improves the blowing performance of the centrifugal fan and reduces noise.

[0003] Specifically, in the centrifugal fan of Patent Document 1, a seal wall covering the air suction side end of the shroud is provided on the outer periphery of the air outlet part of the bell mouth so as to form a U-shaped cross section. By forming a pocket with a U-shaped cross section on the outer periphery of the air outlet part of the bell mouth in this way, the leakage flow path is lengthened, airflow resistance is increased, and the amount of leakage flow is reduced.

[0004] However, in the above configuration, the seal wall has a U-shaped structure that covers the air suction side end of the shroud, and there is a risk of contact due to vibrations during transportation or operation of the centrifugal fan, which could damage the shroud or bell mouth. Also, the opposing area between the seal wall and the shroud is large, which increases fluid friction loss due to viscosity near the wall surface, increasing windage loss and reducing the air blowing performance of the centrifugal fan. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-133297 Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, the present invention has been made to solve the above-mentioned problems, and its main object is to reduce the recirculation flow in a centrifugal fan, prevent damage to the shroud or bell mouth due to contact, and reduce windage loss. [Means for solving the problem]

[0007] That is, a centrifugal fan according to the present invention comprises: a main plate having a boss at the center to which a rotating shaft of a motor is connected; a plurality of blades joined to the main plate and arranged at equal intervals in the circumferential direction; a circular shroud facing the main plate and joined to the blades, the shroud having a central opening; a bell mouth provided inside the shroud and having an inner diameter gradually increasing toward the upstream side; and an annular member provided on the outer periphery of the bell mouth, with a gap provided upstream in the direction of the rotation axis from an inlet of the shroud, the annular member having an annular flat plate provided opposite and spaced from the upstream end of the inlet of the shroud, and a protrusion with a smoothly curved outer surface formed on the outer periphery of the surface of the annular flat plate facing the shroud.

[0008] In a centrifugal fan configured in this manner, an annular member is provided on the outer periphery of the bell mouth, with a gap provided upstream in the direction of the rotation shaft from the inlet of the shroud. This reduces the recirculation flow, prevents damage to the shroud or bell mouth due to contact, and reduces windage loss. Specifically, in the present invention, the annular member includes an annular flat plate portion spaced apart from and facing the upstream end of the shroud inlet portion, and a smoothly curved ridge portion formed on the outer periphery of the annular flat plate portion facing the shroud. Therefore, the recirculation flow flows along the ridge portion and then along the annular flat plate portion, i.e., in a generally S-shaped flow pattern. This increases the flow path length of the recirculation flow and increases flow resistance. As a result, the recirculation flow can be reduced. Furthermore, because the annular member is composed of the annular flat plate portion and the ridge portion, damage to the shroud or bellmouth due to contact can be prevented. Furthermore, fluid friction loss between the annular member and the shroud can be reduced, thereby reducing windage loss. Furthermore, because the outer surface of the ridge portion is a smoothly curved surface, turbulence caused by the edges of the ridge portion can be suppressed, thereby reducing noise generation. Furthermore, according to the present invention, rather than covering the inlet of the shroud so as to physically block it, the flow of the recirculation flow is taken into consideration and the gap between the shroud and the annular member and the outer end of the annular member are shaped to protrude, thereby making the flow of the recirculation flow roughly S-shaped and achieving both a reduction in the flow rate of the recirculation flow and the suppression of the generation of turbulence.

[0009] As a specific embodiment for making the outer surface of the protrusion a smoothly curved surface, it is desirable that the outer surface of the protrusion have a partially circular cross section.

[0010] As a specific embodiment for making the recirculation flow flowing into the inlet portion of the shroud approximately S-shaped, it is desirable that the protrusion portion be provided radially outward of the inlet portion of the shroud.

[0011] In order to suppress fluid friction loss while making the recirculation flow flowing into the inlet portion of the shroud approximately S-shaped, it is desirable that, in the annular member, the annular flat portion have a closest portion that is closest to the upstream end of the inlet portion of the shroud, and that the protrusion portion be farther from the upstream end of the inlet portion of the shroud than the closest portion.

[0012] It is desirable that a communication flow path be formed between the annular member and the bell mouth, the communication flow path being in communication with the rotation axis direction. This communication flow path makes it possible to form an airflow that flows along the outer circumferential surface of the bell mouth, and this airflow can cause the recirculation airflow to flow along the inner circumferential surface of the shroud. As a result, turbulence caused by flow separation can be suppressed, and air blowing performance can be improved while blowing noise can be reduced.

[0013] Furthermore, a centrifugal fan according to the present invention includes a main plate having a boss at the center to which a rotating shaft of a motor is connected, a plurality of blades joined to the main plate and arranged at equal intervals in the circumferential direction, a circular shroud facing the main plate and joined to the blades and having an opening in the center, a bell mouth provided inside the shroud and whose inner diameter gradually increases toward the upstream side, and a circular member provided on the outer periphery of the bell mouth, with a gap provided upstream in the direction of the rotation axis from the inlet of the shroud, and a communication flow passage connecting the circular member and the bell mouth along the direction of the rotation axis.

[0014] In a centrifugal fan configured in this manner, an annular member is provided on the outer periphery of the bell mouth, with a gap provided upstream in the direction of the rotation shaft from the inlet of the shroud. This reduces the recirculation flow, prevents damage to the shroud or bell mouth due to contact, and reduces windage loss. In particular, in the present invention, a communicating flow passage is formed between the annular member and the bell mouth along the rotational axis direction, so that an airflow that flows along the outer circumferential surface of the bell mouth can be formed, and this airflow can cause the recirculation air to flow along the inner circumferential surface of the shroud. As a result, turbulence caused by flow separation can be suppressed, and air blowing performance can be improved while air blowing noise can be reduced.

[0015] As a specific embodiment of the communicating flow passage, it is desirable that the communicating flow passage has an expanding portion in which the cross-sectional area of ​​the flow passage gradually expands from the inlet side to the outlet side. It is also desirable that the communicating flow passage has a contracting portion in which the cross-sectional area of ​​the flow passage gradually decreases on the inlet side of the expanding portion. With these configurations, the communicating flow passage functions as an orifice, and the airflow can be directed to the inlet portion of the shroud while increasing the flow velocity of the airflow flowing through the communicating flow passage. Furthermore, by increasing the flow velocity of the airflow flowing through the communicating flow passage, it is possible to prevent the recirculation airflow from flowing inward when it enters the centrifugal fan.

[0016] As a specific configuration of the communicating flow passage, it is desirable that the communicating flow passage be configured using the outer circumferential surface of the bell mouth. Here, in order to simply configure the communicating flow passage, it is desirable that the communicating flow passage be configured from the inner circumferential surface of an annular member and the outer circumferential surface of the bell mouth.

[0017] In order to efficiently direct the recirculation flow along the inner circumferential surface of the shroud, it is desirable to make the width of the communicating flow passage narrower than the gap between the shroud and the bell mouth, thereby making it easier to form an airflow flowing out of the communicating flow passage on the inner circumferential side of the recirculation flow near the flow passage outlet of the recirculation flow, without increasing the amount of leakage flow.

[0018] An indoor unit for an air conditioner using the centrifugal fan described above is also one aspect of the present invention. [Effects of the Invention]

[0019] According to the present invention configured in this manner, it is possible to reduce the recirculation flow, prevent damage to the shroud or bell mouth due to contact, and reduce windage loss. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a cross-sectional view schematically showing the configuration of an indoor unit for an air conditioner in one embodiment of the present invention. [Figure 2]FIG. 2 is a partially enlarged cross-sectional view schematically showing the configuration of the annular member of the embodiment. [Figure 3] 1A is a schematic diagram showing the distance of each part from the upstream end of the shroud, FIG. 1B is a graph showing the distance of each part from the upstream end of the shroud, and FIG. 1C is a graph showing fluid friction loss at each part in the same embodiment. [Figure 4] FIG. 10 is a partially enlarged cross-sectional view schematically illustrating the configuration of an annular member according to a modified embodiment. [Figure 5] 10 is a simulation result showing the flow of air currents when the annular member of the modified embodiment is provided and when it is not provided. [Figure 6] FIG. 10 is a partially enlarged cross-sectional view schematically illustrating the configuration of an annular member according to a modified embodiment. [Figure 7] FIG. 10 is a partially enlarged cross-sectional view schematically illustrating the configuration of an annular member according to a modified embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an indoor unit for an air conditioner using a centrifugal fan according to the present invention will be described below with reference to the drawings.

[0022] <1. Indoor unit for air conditioner> The air conditioner indoor unit 100 according to this embodiment is a ceiling-embedded type, and has an air inlet H1 and air outlets H2 formed on its underside. Here, the air inlet H1 is formed in the center of the underside, and four air outlets H2 are formed surrounding the air inlet H1. Note that these four air outlets H2 are formed to correspond to the four sides of a rectangle in plan view.

[0023] The air conditioner indoor unit 100 also houses a centrifugal fan 2 that draws in air through an air inlet H1 and blows out the air through an air outlet H2, and a heat exchanger 3 that is hit by the airflow generated by the centrifugal fan 2. The heat exchanger 3 is disposed so as to surround the periphery of the centrifugal fan 2. The air drawn in through the air inlet H1 by the centrifugal fan 2 undergoes heat exchange in the heat exchanger 3, and is then blown out into the room through the air outlet H2.

[0024] <2. Centrifugal fan 2> As shown in FIG. 1, the centrifugal fan 2 of this embodiment includes a main plate 21, a plurality of blades 22, a shroud 23, and a bell mouth 24.

[0025] The main plate 21 has a circular shape in a plan view and has a boss portion 21a at its center to which the rotating shaft 41 of the motor 4 is connected. The main plate 21 is connected perpendicularly to the rotating shaft 41 of the motor 4. A protrusion 21b is formed in the center of the main plate 21, giving the main plate 21 a mountain-like shape.

[0026] The blades 22 are joined to one surface of the main plate 21 where the protruding portion 21b is formed, and are arranged at equal intervals in the circumferential direction. The blades 22 are formed from the outer peripheral surface of the protruding portion 21b formed in the center of the main plate 21 to the outer periphery of the main plate 21. The specific configuration of the blades 22 will be described later.

[0027] The shroud 23 is disposed opposite the main plate 21 and has an annular shape with an opening in the center, joined to the other ends of the blades 22. Air is drawn in through the opening in the center of the shroud 23. Air is also blown out from openings formed between the shroud 23 and the main plate 21.

[0028] The bell mouth 24 is provided upstream of the shroud 23 in the direction of the rotation axis, with its downstream end 24a located inside the shroud 23 and its inner diameter gradually increasing toward the upstream side.

[0029] <3. Features of the centrifugal fan 2: Annular member 25> And a part of the air blown out from the outlet of the centrifugal fan 2 becomes a recirculation flow and flows in from the gap between the shroud 23 and the volute 24 (see FIG. 1). Therefore, in order to reduce the recirculation flow, the centrifugal fan 2 of the present embodiment is provided with an annular member 25 which is provided with a gap upstream in the rotation axis direction (here, downward) from the upstream end 23a (here, the lower end) of the inlet portion of the shroud 23 on the outer peripheral portion of the volute 24 as shown in FIGS. 1 and 2.

[0030] This annular member 25 is attached to the volute 24 and has an annular flat plate portion 251 provided to face away from the upstream end 23a of the inlet portion of the shroud 23, and a ridge portion 252 formed on the outer peripheral portion of the surface of the annular flat plate portion 251 facing the shroud 23 side. The ridge portion 252 is provided radially outside the inlet portion of the shroud 23. Further, the outer surface of the ridge portion 252 is a smooth curved surface, for example, having a partial circular cross-sectional shape or a cross-sectional shape of a ball edge. Furthermore, the upper end portion of the ridge portion 252 is located upstream in the rotation axis direction (here, the lower side) from the upstream end 23a of the inlet portion of the shroud 23. Also, as shown in FIG. 1, in the annular member 25, the annular flat plate portion 251 has a closest portion 25x closest to the upstream end 23a of the inlet portion of the shroud 23, and the ridge portion 252 is farther from the upstream end 23a of the inlet portion of the shroud 23 than the closest portion 25x (L1 < L2 in FIG. 1). The closest portion 25x of the present embodiment is a portion facing the upstream end portion 23a of the shroud 23 in the rotation axis direction.

[0031] By providing the annular member 25 in this manner, it becomes difficult for the recirculation flow to flow into the gap between the shroud 23 and the bell mouth 24. Furthermore, because the outer surfaces of the protrusions 252 are smoothly curved, the flow path through which the recirculation flow forms a roughly S-shape, and the recirculation flow flows in a roughly S-shape. As a result, as shown in Fig. 2, the recirculation flow decreases and flows into the centrifugal fan 2 along the outer circumferential surface of the bell mouth 24 just before the downstream end 24a of the bell mouth 24. Near the downstream end 24a of the bell mouth 24, the recirculation flow and the flow flowing into the centrifugal fan 2 along the inner circumferential surface of the bell mouth 24 merge without intersecting each other, resulting in a smooth flow into the centrifugal fan 2. This prevents the flow from becoming turbulent in the flow path through which the recirculation flow flows and inside the centrifugal fan 2, thereby reducing noise. Furthermore, because the annular flat portion 251 has a closest portion 25x and the protruding portion 252 is farther from the upstream end 23a of the shroud 23 than the closest portion 25x, the recirculation flow flowing into the inlet of the shroud 23 can be made to have a generally S-shaped shape while suppressing fluid friction loss. Note that the distance of each portion from the upstream end 23a of the shroud 23 and the fluid friction loss at each portion in this embodiment are shown in FIG. 3. As can be seen from FIG. 3, in this embodiment, fluid friction loss is suppressed in portions of the annular member 25 other than the closest portion 25x, and it can be seen that unnecessary torque increases can be suppressed.

[0032] <4. Effects of this embodiment> In the air conditioner indoor unit 100 configured in this manner, the annular member 25 is provided on the outer periphery of the bell mouth 24, with a gap provided upstream in the direction of the rotation axis from the inlet of the shroud 23. This reduces the recirculation flow, prevents damage to the shroud 23 or bell mouth 24 due to contact, and reduces windage loss.

[0033] Specifically, in this embodiment, the annular member 25 includes an annular flat plate portion 251 disposed opposite the upstream end 23a of the inlet portion of the shroud 23 at a distance from the inlet portion, and a smoothly curved ridge portion 252 formed on the outer periphery of the annular flat plate portion 251 facing the shroud 23. Therefore, the recirculation flow flows along the ridge portion 252 and then along the annular flat plate portion 251, i.e., in a generally S-shaped flow pattern. This increases the flow path length of the recirculation flow and increases flow resistance. As a result, the recirculation flow can be reduced. Furthermore, because the annular member 25 includes the annular flat plate portion 251 and the ridge portion 252, damage to the shroud 23 or the bellmouth 24 due to contact can be prevented. Furthermore, the opposing surface area between the annular member 25 and the shroud 23 can be reduced, thereby reducing fluid friction loss and windage loss. Furthermore, since the outer surfaces of the protrusions 252 are smoothly curved, turbulence caused by the edges of the protrusions 252 is suppressed, thereby reducing noise.

[0034] <5. Other Modified Embodiments> The present invention is not limited to the above-described embodiment.

[0035] For example, in addition to the configuration of the above embodiment, as shown in FIG. 4, a communication flow path 26 may be formed between the annular member 25 and the bell mouth 24, communicating along the rotation axis direction (up and down in this case).

[0036] The communicating flow passage 26 has a contracting section 261 in which the cross-sectional area of ​​the flow passage gradually decreases from the inlet side, and an expanding section 262 in which the cross-sectional area of ​​the flow passage gradually increases on the outlet side of the contracting section 261. In other words, the communicating flow passage 26 functions as an orifice, and increases the flow velocity of the airflow flowing through the communicating flow passage 26 while directing the airflow to the inlet portion of the shroud 23. Increasing the flow velocity of the airflow flowing through the communicating flow passage 26 can prevent the recirculation airflow from flowing inward when it enters the centrifugal fan 2.

[0037] Furthermore, the communicating flow passage 26 is formed using the inner circumferential surface of the annular member 25 and the outer circumferential surface of the bell mouth 24. With this configuration, the airflow that flows through the communicating flow passage 26 flows along the outer circumferential surface of the bell mouth 24. Furthermore, the width of the communicating flow passage 26 is narrower than the gap between the shroud 23 and the bell mouth 24. This makes it easier to form an airflow that flows out of the communicating flow passage 26 on the inner circumferential side of the recirculation flow near the flow passage outlet of the recirculation flow, without increasing the amount of leakage flow.

[0038] FIG. 5 shows the results of a simulation of the airflow when the annular member 25 shown in FIG. 4 is provided and when the annular member 25 is not provided. FIG. 5(a) shows the airflow when the annular member 25 is provided, and FIG. 5(b) shows the airflow when the annular member 25 is not provided. Comparing these figures, it can be seen that when the annular member 25 is not provided, the recirculation flow (leakage flow) is fast and flows toward the inner periphery of the centrifugal fan 2, whereas when the annular member 25 is provided, the recirculation flow speed decreases and the main flow tends to flow toward the outer periphery. In other words, by providing the annular member 25, the main flow can be directed toward the outer periphery, where the workload of the blades 22 is greater.

[0039] Also, as shown in FIG. 6, the tip portion 231 including the upstream end portion 23a of the inlet portion of the shroud 23 may be configured to have a smoothly curved surface (for example, a partially circular cross section or a beaded cross section) to prevent the recirculation flow from becoming turbulent when it flows into the inlet portion of the shroud 23.

[0040] 7, the bell mouth 24 and the annular member 25 may be integrally molded. By integrally molding them, mechanical strength can be ensured by a connecting portion (not shown) that connects the bell mouth 24 and the annular member 25.

[0041] In this configuration, a communicating flow path 26 is formed between the annular member 25 and the bell mouth 24, communicating along the rotational axis direction. This communicating flow path 26 is formed using the inner circumferential surface of the annular member 25 and the outer circumferential surface of the bell mouth 24. Specifically, a flow path forming wall 253 is formed on the inner circumferential edge of the annular member 25, and by setting this flow path forming wall 253 to a predetermined length, the communicating flow path 26 can be set to a desired flow path length. Setting the flow path length of the communicating flow path 26 in this manner makes it easy to adjust the flow rate of the airflow flowing along the outer circumferential surface of the bell mouth 24. Furthermore, the communicating flow path 26 in FIG. 7 is configured so that the flow path cross-sectional area gradually increases from the inlet side to the outlet side, making it easy to mold using a mold for resin injection molding. Furthermore, the width of the communicating flow passage 26 is narrower than the gap between the shroud 23 and the bell mouth 24, making it easier to form an airflow flowing out of the communicating flow passage 26 on the inner side of the recirculation flow near the flow passage outlet of the recirculation flow without increasing the amount of leakage flow.

[0042] Furthermore, in the above embodiment, an air conditioner indoor unit using a centrifugal fan has been described, but the centrifugal fan of the present invention can also be used in other types of blowers.

[0043] Furthermore, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications are possible without departing from the spirit of the present invention. [Explanation of symbols]

[0044] 100...Indoor unit for air conditioner 2. Centrifugal fan 3...Heat exchanger 4 Motor 41 Rotation axis 21a Boss part 21...Main plate 22 Feather 23 Shroud 23a...Upstream end 24 Bellmouth 25 Circular member 251 Annular flat plate 252... Protrusion section 26...Communicating flow path 261...reduction part 262...Enlarged section

Claims

1. a main plate having a boss portion at the center to which a rotating shaft of a motor is connected; a plurality of blades joined to the main plate and arranged at equal intervals in the circumferential direction; a shroud that faces the main plate and is joined to the blades, has an annular shape, has an opening at its center, and has an inner diameter that gradually decreases toward the upstream side; a bell mouth provided inside the shroud, the inner diameter of which gradually increases toward the upstream side; an annular member provided at an outer circumferential portion of the bell mouth on an upstream side in the rotational axis direction from an inlet portion of the shroud with a gap therebetween, the bell mouth is disposed such that a downstream end thereof is located downstream of an upstream end of the shroud in the direction of the rotation axis, a communication flow path that communicates along the rotation axis direction between the annular member and the bell mouth;

2. The centrifugal fan according to claim 1 , wherein the communication flow passage has an expanding portion in which a cross-sectional area of ​​the flow passage gradually expands from the inlet side to the outlet side.

3. The centrifugal fan according to claim 2 , wherein the communication passage has a contracting portion on an inlet side of the expanding portion, the cross-sectional area of ​​the passage gradually decreasing.

4. The centrifugal fan according to claim 1 , wherein the communication passage is defined by an outer circumferential surface of the bell mouth.

5. The centrifugal fan according to claim 1 , wherein a width of the communication passage is narrower than a gap between the shroud and the bell mouth.

6. The annular member is an annular flat plate portion provided opposite to and spaced from an upstream end portion of the inlet portion of the shroud; 6. The centrifugal fan according to claim 1, further comprising a ridge formed on an outer periphery of the surface of said annular flat plate facing the shroud, said ridge having a smoothly curved outer surface.

7. A centrifugal fan as described in Claim 6, wherein the outer surface of the protrusion portion has a partially circular cross section.

8. A centrifugal fan as described in claim 6 or 7, wherein the protrusion portion is located radially outward from the inlet portion of the shroud.

9. A centrifugal fan as described in any one of claims 6 to 8, wherein in the annular member, the annular flat portion has a nearest portion that is closest to the upstream end of the inlet portion of the shroud, and the protrusion portion is farther from the upstream end of the inlet portion of the shroud than the nearest portion.

10. An indoor unit for an air conditioner, comprising the centrifugal fan according to any one of claims 1 to 9.

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