JP4844678B2 - Centrifugal blower - Google Patents

Description

  The present invention relates to a centrifugal blower used for an indoor unit of an air conditioner, for example.

  Conventionally, for example, a centrifugal blower has been used as a blower for an indoor unit of an air conditioner. In this centrifugal blower, when the fan motor is driven and the impeller rotates, air is sucked into the indoor unit from the suction port of the indoor unit. The sucked air is guided to the air intake port of the shroud by the bell mouth (hereinafter, the air flow guided to the air intake port by the bell mouth is referred to as the mainstream).

  This mainstream air is sent to the outside in the radial direction by a plurality of blades arranged in the circumferential direction between the hub and the shroud, and most of the air is blown into the room through the blowout port of the indoor unit. The part circulates in the indoor unit through the space on the outer peripheral surface side of the shroud toward the bell mouth, and then merges with the main stream again through the gap between the bell mouth and the shroud (hereinafter referred to as the above, and the main stream through the gap). The flow of air that joins is called leakage flow.) When a leakage flow in which a part of the main flow branches is generated in this way, the amount of air blown into the room is reduced by that amount, so that the fan efficiency is lowered.

  For example, Patent Literature 1 discloses a centrifugal blower in which a large number of grooves are provided on the outer surface of a bell mouth (fan guide) in order to suppress a decrease in fan efficiency. In this centrifugal blower, the leakage flow that circulates through the space on the outer peripheral surface side of the shroud toward the bell mouth is introduced into the gap between the bell mouth and the shroud through the groove (paragraph number 0024 of Patent Document 1). , 0052, FIG. 5 and FIG. 6). Patent Document 1 describes that since the leakage flow is guided by the groove as described above and becomes a stable flow, it is possible to suppress a decrease in the blowing performance due to the fluctuation of the leakage flow.

JP 2001-3899 A

  By the way, in the centrifugal blower described in Patent Document 1, it is considered that a part of the air in the leakage flow needs to enter the inside of the groove in order for the leakage flow to be guided by the groove to become a stable flow.

  However, since the air flowing around the groove at a high speed easily passes through the vicinity of the groove rather than entering the groove, the effect of guiding the air through the groove is not necessarily sufficient. Therefore, further improvement in fan efficiency is desired in the centrifugal fan.

  Then, this invention is made | formed in view of this point, The place made into the objective is providing the centrifugal air blower which can suppress the fall of the fan efficiency resulting from a leak flow.

The centrifugal blower of the present invention includes an impeller (23) and a bell mouth (25). The impeller (23) has a hub (15) fixed to the rotating shaft (13) of the fan motor (11), and an air suction port (19a) opening in a circle around the rotating shaft (13). A shroud (19) disposed opposite to the hub (15) on the front (F) side in the axial direction (A) of the rotating shaft (13), the hub (15), and the shroud (19). And a plurality of blades (21) arranged along the circumferential direction of the air suction port (19a). The bell mouth (25) is opposed to the front (F) side in the axial direction (A) with respect to the shroud (19), and a part on the rear (R) side is the air inlet (19a). The air inlet (19a) is inserted into the shroud (19) with a predetermined gap between the peripheral edge (19e). The bell mouth (25) guides the air sucked from the front (F) side toward the rear (R) side in the axial direction (A) to the air suction port (19a) of the shroud (19). The bell mouth (25) has a plurality of wall portions (27) arranged on the outer peripheral surface (25s) at predetermined intervals along the circumferential direction and standing from the outer peripheral surface (25s). . Each wall (27) extends from the front (F) side to the rear (R) side of the axial direction (A) so as to be substantially parallel to the axial direction (A) and the radial direction of the bell mouth (25). The outer peripheral surface (25s) of the bell mouth (25) has a curved surface whose outer diameter decreases from the front (F) side to the rear (R) side. Each wall portion (27) is erected from the curved surface, and each wall portion (27) has a rear (R) side end portion (27r) at the air intake of the shroud (19). The curved surface is moved to a position substantially opposite to the peripheral edge portion (19e) of the mouth (19a) in the radial direction and to a position facing the gap between the bell mouth (25) and the shroud (19) in the front-rear direction. Extending along .

  In this configuration, since the bell mouth (25) has the plurality of wall portions (27), the wall portion (27) becomes a resistance to leakage flow, and the amount of leakage flow can be reduced. Moreover, since the direction of the leakage flow can be made closer to the direction of the main flow, it is possible to suppress the main flow from being disturbed when the leakage flow joins the main flow. Thereby, the fall of fan efficiency can be suppressed. Specifically, it is as follows.

  That is, the mainstream air guided to the air inlet (19a) of the shroud (19) by the bell mouth (25) is mainly in the axial direction of the rotating shaft (13) in the vicinity of the air inlet (19a) ( It flows in the direction along A). On the other hand, the leakage flow in the conventional centrifugal blower is affected by the air flow in the rotation direction caused by the rotation of the shroud (19), and is inclined in the rotation direction from the axial direction (A) of the rotation shaft (13). It is flowing in the direction. Thus, in the vicinity of the air inlet (19a) where the main flow and the leakage flow merge, the directions of the main flow and the leakage flow are greatly different. Therefore, when the leakage flow merges with the main flow, the main flow is disturbed by the leakage flow. As a result, fan efficiency is reduced.

  On the other hand, in the configuration of the present invention, from the front (F) side to the rear (R) side in the axial direction (A), the wall portion (27) is substantially parallel to the axial direction (A) and the radial direction. It extends along the outer peripheral surface (25s) of the bell mouth (25). That is, the air flow path (253) sandwiched between adjacent wall portions (27) is oriented in the direction along the axial direction (A). The air flow path (253) is a space in which both sides and the bottom are surrounded by the adjacent wall portion (27) and the outer peripheral surface (25s) of the bell mouth (25). The air flow path (253) The inlet and outlet of the leakage flow to the open are open and unobstructed. Therefore, since the leakage flow can be reliably guided and circulated in the air flow path (253) between the wall portions (27), an excellent effect of guiding the leakage flow can be obtained.

  When the leakage flow flowing in the inclined direction reaches the wall portion (27) and passes through the air flow path (253) between the wall portions (27), the leakage flow is caused by the air flow path (253). The direction is corrected in the axial direction (A). Therefore, compared with the case where there is no wall part (27), the resistance which air receives at the time of distribution | circulation increases. Thereby, the quantity of the leakage flow branched from the main flow can be reduced. Moreover, in the vicinity of the air suction port (19a), the flow direction of the leakage flow rectified by the air flow path (253) is close to the axial direction (A) which is the main flow direction. Accordingly, when the leakage flow merges with the main flow in the vicinity of the air suction port (19a), the degree of interference of the leakage flow with the main flow is reduced. Therefore, it is possible to suppress a decrease in fan efficiency due to the leakage flow.

Moreover, it is preferable that the edge part (27r) by the side of the back (R) of each wall part (27) is located inside radial direction rather than the inner surface of the air suction inlet (19a) of a shroud (19) .

  Further, the height of each wall portion (27) from the outer peripheral surface (25s) is higher than the end portion (27f) on the front (F) side than the end portion (27r) on the rear (R) side. The larger is preferable.

  In this configuration, the wall (27) can catch a large amount of leakage flow at the rear (R) side end (27r) where the standing height is large and guide it to the air flow path (253). Thus, the contact with the peripheral portion (19e) of the air suction port (19a) of the shroud (19) can be suppressed at the end (27f) on the front (F) side where the standing height is small.

  Further, the height of each wall portion (27) from the outer peripheral surface (25s) is directed from the rear (R) side end portion (27r) to the front (F) side end portion (27f). It may increase gradually.

  In this configuration, since the standing height of each wall portion (27) changes smoothly, the air flow in the air flow path (253) becomes smooth.

  Further, the rear (R) side end (27r) of each wall (27) has a standing height from the outer peripheral surface (25s) from the front (F) side to the rear (R) side. The peripheral surface portion (19e) of the air suction port (19a) may be an inclined surface facing the inclined surface of the wall portion (27).

  In this configuration, the rear (R) end (27r) of each wall (27) and the peripheral edge (19e) of the air suction port (19a) are the inclined surfaces facing each other. Further, the wall (27) can be extended to the vicinity of the shroud (19), and further, it is possible to suppress contact with each other during rotation.

  As described above, according to the present invention, it is possible to suppress a decrease in fan efficiency due to leakage flow.

It is sectional drawing which shows the indoor unit provided with the centrifugal blower which concerns on one Embodiment of this invention. It is a bottom view which shows the positional relationship of the impeller in the said indoor unit, a heat exchanger, and a blower outlet. It is a perspective view which shows the impeller of the said centrifugal blower. It is a side view which shows the bell mouth of the said centrifugal blower. It is a top view which shows the bell mouth of the said centrifugal blower. It is the side view to which a part of FIG. 4 was expanded. It is sectional drawing to which some centrifugal fans were expanded. It is sectional drawing which showed the positional relationship of the shroud of the said impeller, and the said bellmouth. It is sectional drawing which shows the modification of the said bellmouth. It is a graph which shows the relationship between an air volume and blowing sound. It is a graph which shows the relationship between an air volume and a motor input.

  Hereinafter, a centrifugal blower 51 and an indoor unit 31 including the centrifugal blower 51 according to an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the indoor unit 31 is a ceiling-embedded cassette indoor unit. The indoor unit 31 includes a substantially rectangular parallelepiped housing 33 embedded in an opening provided in the ceiling, and a decorative panel 47 attached to the lower portion of the housing 33. The decorative panel 47 is slightly larger in plan view than the housing 33 and is exposed to the room in a state of covering the opening of the ceiling. The decorative panel 47 has a rectangular suction grill 39 provided in the center thereof, and four elongated rectangular outlets 37 provided along each side of the suction grill 39.

  The indoor unit 31 includes a centrifugal blower (turbo fan) 51, a fan motor 11, a heat exchanger 43, a drain pan 45, an air filter 41, and the like in a housing 33. Centrifugal blower 51 includes an impeller 23 and a bell mouth 25. The fan motor 11 is fixed to the approximate center of the top plate of the housing 33. The rotation shaft 13 of the fan motor 11 extends downward.

  As shown in FIGS. 1 and 2, the heat exchanger 43 has a flat shape with a small thickness. The heat exchanger 43 is disposed so as to surround the periphery of the impeller 23 in a state where it rises upward from a dish-shaped drain pan 45 extending along the lower end portion thereof. The drain pan 45 stores water droplets generated in the heat exchanger 43. The stored water is discharged through a drainage path (not shown).

  The air filter 41 has a size that covers the inlet of the bell mouth 25, and is provided along the suction grill 39 between the bell mouth 25 and the suction grill 39. The air filter 41 captures dust in the air when the air sucked into the housing 33 from the suction grill 39 passes through the air filter 41.

  As shown in FIGS. 1 to 3, the impeller 23 includes a hub 15, a shroud 19, and a plurality of blades 21. The hub 15 is fixed to the lower end portion of the rotating shaft 13 of the fan motor 11. The hub 15 has a circular shape centered on the rotation shaft 13 in plan view.

  The shroud 19 is disposed opposite to the hub 15 on the front F side in the axial direction A of the rotary shaft 13. The shroud 19 has an air suction port 19 a that opens in a circle around the rotation shaft 13. The outer diameter of the shroud 19 increases from the front F side toward the rear R side.

  The plurality of blades 21 are arranged between the hub 15 and the shroud 19 at a predetermined interval along the circumferential direction of the air suction port 19a. The front F-side end of each blade 21 is joined to the inner surface of the shroud 19. The rear R-side end of each blade 21 is joined to the hub 15. Each blade 21 is a backward blade that is inclined in the direction opposite to the rotation direction (backward) with respect to the radial direction of the hub 15.

  The bell mouth 25 is disposed opposite to the shroud 19 on the front F side in the axial direction A. The bell mouth 25 includes a bell mouth main body 251 and a flange portion 252 projecting from the periphery on the front F side of the bell mouth main body 251 around the bell mouth main body 251. The bell mouth main body 251 has a through hole 25a penetrating in the front-rear direction. The outer peripheral surface 25s of the bell mouth main body 251 has a curved shape whose outer diameter decreases from the front F side toward the rear R side.

  As shown in FIG. 1, a part on the rear R side of the bell mouth main body 251 is inserted into the shroud 19 from the air suction port 19a with a predetermined gap between the peripheral portion 19e of the air suction port 19a. Has been. Thereby, the bell mouth 25 can guide the air sucked from the front F side toward the rear R side through the through hole 25 a to the air suction port 19 a of the shroud 19.

  As shown in FIGS. 4 and 5, the bell mouth 25 has a plurality of wall portions 27 arranged on the outer peripheral surface 25 s of the bell mouth main body 251 at predetermined intervals along the circumferential direction. Each wall 27 is erected from the outer peripheral surface 25 s of the bell mouth 25. Each wall portion 27 extends along the outer peripheral surface 25 s from the front F side toward the rear R side so as to be substantially parallel to the axial direction A and substantially parallel to the radial direction of the bell mouth 25.

  As shown in FIG. 6, the bell mouth 25 has a plurality of air flow paths 253 surrounded on three sides by the adjacent wall portions 27, 27 and the outer peripheral surface 25 s. The air flow path 253 faces in the direction along the axial direction A. The air flow path 253 is surrounded on both sides and bottom by the adjacent wall portion 27 and the outer peripheral surface 25s of the bell mouth 25, but the inlet and outlet of the leakage flow to the air flow path 253 are open. There is nothing to block. Therefore, the leakage flow is reliably guided to the inlet of the air flow path 253 between the wall portions 27 and guided in the air flow path 253 from the front F side toward the rear R side.

  As shown in FIGS. 7 and 8, the height of each wall portion 27 from the outer peripheral surface 25s gradually increases from the rear R-side end portion 27r toward the front F-side end portion 27f. Each wall 27 has a standing height Hf at the end portion 27f on the front F side that is larger than a standing height Hr at the end portion 27r on the rear R side. The standing height Hr and the standing height Hf are not particularly limited. For example, the standing height Hr is about 1 mm to 10 mm, and the standing height Hf is about 3 mm to 20 mm. it can.

  As shown in FIGS. 6 and 8, the rear end 27r of each wall 27 is an inclined surface that is inclined with respect to the axial direction A. In this inclined surface, the standing height from the outer peripheral surface 25s gradually decreases from the front F side toward the rear R side.

  On the other hand, as shown in FIG. 8, the peripheral edge portion 19 e of the air suction port 19 a is an inclined surface inclined with respect to the axial direction A. The inclined surface of the peripheral edge portion 19e is provided to face the inclined surface of the end portion 27r on the rear R side of the wall portion 27. In other words, the tip of the end portion 27r on the rear R side of each wall portion 27 is at a position (substantially the same height) that is substantially opposite to the tip of the peripheral edge portion 19e that is the end portion on the front F side of the shroud 19. Is provided. Both the inclined surface of the peripheral edge portion 19e and the inclined surface of the end portion 27s of the wall portion 27 are inclined such that the rear R side is located on the inner side in the radial direction than the front F side. As described above, since the end portions are formed of the inclined surfaces, the end portion 27r on the rear R side of the wall portion 27 can be extended to a position facing the peripheral edge portion 19e of the shroud 19 or the vicinity thereof.

  In the bell mouth 25, each wall portion 27 may be formed integrally with the bell mouth main body 251 by sheet metal processing, resin molding, or the like, and each wall portion 27 formed separately from the bell mouth main body 251 is formed as the bell mouth main body. It may be manufactured by bonding to H.251.

  FIG. 9 is a cross-sectional view showing a modified example of the bell mouth 25. Similar to the bell mouth 25 shown in FIG. 5, the bell mouth 25 has a plurality of wall portions 27 arranged on the outer peripheral surface thereof at predetermined intervals along the circumferential direction. Each wall portion 27 is erected from the outer peripheral surface of the bell mouth 25. Each wall portion 27 extends along the outer peripheral surface from the front F side toward the rear R side so as to be substantially parallel to the axial direction A and substantially parallel to the radial direction of the bell mouth 25.

  In the bell mouth 25, each wall 27 is formed integrally with the bell mouth main body by sheet metal processing, resin molding, or the like. On the inner surface of the bell mouth 25, a plurality of groove portions 254 are formed at positions corresponding to the plurality of wall portions 27, respectively. The grooves 254 are arranged on the inner surface at predetermined intervals along the circumferential direction. Each groove portion 254 extends along the inner surface from the front F side toward the rear R side so as to be substantially parallel to the axial direction A and substantially parallel to the radial direction of the bell mouth 25. Since the bell mouth 25 can have a substantially constant thickness as a whole, for example, when molding is performed by resin molding, it is possible to suppress the occurrence of molding defects such as sink marks. Further, these groove portions 254 serve to guide the main flow flowing through the through-hole 25a of the bell mouth 25.

  Next, the flow of air in the centrifugal blower 51 will be described. As shown in FIG. 8, the air of the mainstream S guided to the air suction port 19a of the shroud 19 by the bell mouth body 251 of the bell mouth 25 is mainly in the vicinity of the air suction port 19a. In the direction along the axial direction A.

  In the conventional centrifugal blower that does not have the wall 27, the leakage flow M1 is caused by the shroud 19 rotating in the rotation direction K in the vicinity of the air suction port 19a as indicated by the broken arrow M1. The air flows in the direction inclined from the axial direction A to the rotational direction K by being influenced by the air flow to K. Therefore, when this leakage flow M1 merges with the main flow S, the flow of the main flow S is disturbed by the leakage flow M1, resulting in an increase in blowing sound and a decrease in fan efficiency.

  On the other hand, in the centrifugal blower 51 of the present embodiment, as indicated by the dashed-dotted arrow M, the leakage flow M is along the air flow path 253 surrounded by the adjacent wall portion 27 and the outer peripheral surface 25S of the bell mouth main body 251. Then, it is guided from the front F side to the rear R side, and passes through the gap between the rear R side end of the bell mouth body 251 and the front F side end of the shroud 19. The leakage flow M that has passed through the gap is corrected so that the flow direction approaches the axial direction A in the vicinity of the air suction port 19a as compared with the conventional case. Accordingly, interference when the leakage flow M joins the main flow S is suppressed.

  FIG. 10 is a graph showing the relationship between the air volume and the blowing sound, and FIG. 11 is a graph showing the relationship between the air volume and the motor input. The solid lines in FIGS. 10 and 11 show the characteristics (examples) of the indoor unit 31 including the centrifugal fan 51 according to the present embodiment shown in FIGS. 1 to 8, and the broken lines in FIGS. The characteristic (comparative example) of the indoor unit 31 provided with the conventional bellmouth which 27 is not provided is shown.

  The data shown in FIG. 10 shows that the standing height Hr on the rear R side is 3 mm, the standing height Hf on the front F side is 5 mm, and the standing height is gradually increased from the rear R side toward the front F side. The measured wall 27 was measured using the bell mouth 25 provided on the bell mouth main body 251. The data shown in FIG. 11 shows that the standing height Hr on the rear R side is 6 mm, the standing height Hf on the front F side is 8 mm, and the standing height is gradually increased from the rear R side toward the front F side. The measured wall 27 was measured using the bell mouth 25 provided on the bell mouth main body 251.

  As shown in FIG. 10, it can be seen that the blowing sound is reduced in the example as compared with the comparative example. Moreover, the effect of reducing the blowing noise is increasing as the air volume increases. Note that one scale on the vertical axis of the graph of FIG. 10 is 1 dBA.

  As shown in FIG. 11, it can be seen that the motor input is reduced in the embodiment as compared with the comparative example. Thus, in the embodiment, the motor input required to obtain the same air volume as that in the comparative example is smaller than that in the comparative example. In other words, the example shows that the amount of leakage flow is smaller than that of the comparative example. In addition, 1 scale of the vertical axis | shaft of the graph of FIG. 11 is 10W.

  As described above, in the present embodiment, since the bell mouth 25 has the plurality of wall portions 27, the wall portion 27 provides resistance to leakage flow, and the amount of leakage flow can be reduced. . Moreover, since the direction of the leakage flow can be made closer to the direction of the main flow, it is possible to suppress the main flow from being disturbed when the leakage flow joins the main flow. Thereby, the fall of fan efficiency can be suppressed.

  In the present embodiment, the wall portion 27 can catch a large amount of leakage flow at the end portion 27r on the rear R side where the standing height is large and guide it to the air flow path 253. The contact with the peripheral edge portion 19e of the air suction port 19a of the shroud 19 can be suppressed at the end portion 27f on the front F side having a small height.

  In the present embodiment, the height of each wall portion 27 from the outer peripheral surface 25s gradually increases from the rear R-side end portion 27r toward the front F-side end portion 27f. That is, since the standing height of each wall 27 changes smoothly, the air flow in the air flow path 253 becomes smooth.

  Further, in the present embodiment, the end portion 27r on the rear R side of each wall portion 27 and the peripheral edge portion 19e of the air suction port 19a are the inclined surfaces facing each other. Further, it can be extended to the vicinity of each other, and it is possible to suppress contact with each other during rotation.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to each said embodiment, A various change, improvement, etc. are possible in the range which does not deviate from the meaning. For example, in the embodiment described above, an example in which the standing height of each wall portion is gradually increased from the rear side toward the front side has been described as an example, but the standing height is increased from the rear side to the front side. You may increase in steps toward. Moreover, the said standing height of each wall part may be constant from the back side to the front side, and may decrease toward the front side from the back side.

  Moreover, in the said embodiment, the said edge part of the said back side in each wall part is an inclined surface from which the said standing height reduces gradually toward the back side from the said front side, The said peripheral part of the said air inlet port Has been described by taking as an example the case of an inclined surface facing the inclined surface of the wall portion, but is not limited thereto. The rear end of each wall may be a surface perpendicular to the axial direction, not an inclined surface. Similarly, the peripheral edge portion of the air suction port may be a surface perpendicular to the axial direction.

  Moreover, in the said embodiment, the front-end | tip of the edge part of the rear side of each wall part is provided in the position (substantially the same height) which substantially opposes the front-end | tip of the peripheral part which is an edge part of the front side of a shroud. However, the present invention is not limited to this. The rear end of each wall may be provided on the front side or the rear side of the front end of the shroud.

  Moreover, although the said embodiment gave and demonstrated the case where the centrifugal air blower was used for the indoor unit of an air conditioning apparatus, it can also be used for another use.

DESCRIPTION OF SYMBOLS 11 Fan motor 13 Rotating shaft 15 Hub 17 Air inlet 19e Perimeter of air inlet 19 Shroud 21 Blade 23 Impeller 25 Bellmouth 251 Bellmouth body 252 Flange 253 Air flow path 25a Through-hole 25s Outer surface of Bellmouth body 27 Wall part 27f End part on the front side of the wall part 27r End part on the rear side of the wall part 31 Indoor unit A Axial direction of the rotating shaft of the fan motor F Front R Rear

Claims (5)

The hub (15) has a hub (15) fixed to the rotating shaft (13) of the fan motor (11), and an air suction port (19a) that opens circularly around the rotating shaft (13). On the other hand, the air intake port (19a) is disposed between the shroud (19) disposed opposite to the front (F) side in the axial direction of the rotating shaft (13), and between the hub (15) and the shroud (19). An impeller (23) including a plurality of blades (21) arranged along the circumferential direction of
The shroud (19) is disposed to face the front (F) side in the axial direction, and a part on the rear (R) side is a predetermined distance between the peripheral edge (19e) of the air suction port (19a). Air that is inserted into the shroud (19) from the air suction port (19a) in a state where a gap is provided, and that is sucked from the front (F) side toward the rear (R) side in the axial direction. A bell mouth (25) for guiding to the air inlet (19a) of (19),
The bell mouth (25) has a plurality of wall portions (27) arranged on the outer circumferential surface (25s) at predetermined intervals along the circumferential direction and standing from the outer circumferential surface (25s),
Each wall portion (27) has the outer peripheral surface (from the front (F) side to the rear (R) side in the axial direction so as to be substantially parallel to the axial direction and the radial direction of the bell mouth (25). 25s) ,
The outer peripheral surface (25s) of the bell mouth (25) has a curved surface whose outer diameter decreases from the front (F) side toward the rear (R) side,
Each wall (27) is erected from the curved surface,
Each wall portion (27) has a rear (R) side end portion (27r) at a position substantially opposite to the peripheral edge portion (19e) of the air inlet (19a) of the shroud (19) in the radial direction, and A centrifugal blower extending along the curved surface to a position facing in the front-rear direction with respect to a gap between the bell mouth (25) and the shroud (19) . The rear (R) end (27r) of each wall (27) is located radially inward from the inner surface of the air inlet (19a) of the shroud (19). Centrifugal blower. The hub (15) has a hub (15) fixed to the rotating shaft (13) of the fan motor (11), and an air suction port (19a) that opens circularly around the rotating shaft (13). On the other hand, the air intake port (19a) is disposed between the shroud (19) disposed opposite to the front (F) side in the axial direction of the rotating shaft (13), and between the hub (15) and the shroud (19). An impeller (23) including a plurality of blades (21) arranged along the circumferential direction of
The shroud (19) is disposed to face the front (F) side in the axial direction, and a part on the rear (R) side is a predetermined distance between the peripheral edge (19e) of the air suction port (19a). Air that is inserted into the shroud (19) from the air suction port (19a) in a state where a gap is provided, and that is sucked from the front (F) side toward the rear (R) side in the axial direction. A bell mouth (25) for guiding to the air inlet (19a) of (19),
The bell mouth (25) has a plurality of wall portions (27) arranged on the outer circumferential surface (25s) at predetermined intervals along the circumferential direction and standing from the outer circumferential surface (25s),
Each wall portion (27) has the outer peripheral surface (from the front (F) side to the rear (R) side in the axial direction so as to be substantially parallel to the axial direction and the radial direction of the bell mouth (25). 25s),
The height of each wall portion (27) from the outer peripheral surface (25s) is higher at the front end portion (27f) than at the rear end portion (27r). large, centrifugal blower. The standing height of each wall portion (27) from the outer peripheral surface (25s) gradually increases from the rear (R) side end portion (27r) toward the front (F) side end portion (27f). The centrifugal blower according to claim 3 , wherein the centrifugal blower is increasing. The hub (15) has a hub (15) fixed to the rotating shaft (13) of the fan motor (11), and an air suction port (19a) that opens circularly around the rotating shaft (13). On the other hand, the air intake port (19a) is disposed between the shroud (19) disposed opposite to the front (F) side in the axial direction of the rotating shaft (13), and between the hub (15) and the shroud (19). An impeller (23) including a plurality of blades (21) arranged along the circumferential direction of
The shroud (19) is disposed to face the front (F) side in the axial direction, and a part on the rear (R) side is a predetermined distance between the peripheral edge (19e) of the air suction port (19a). Air that is inserted into the shroud (19) from the air suction port (19a) in a state where a gap is provided, and that is sucked from the front (F) side toward the rear (R) side in the axial direction. A bell mouth (25) for guiding to the air inlet (19a) of (19),
The bell mouth (25) has a plurality of wall portions (27) arranged on the outer circumferential surface (25s) at predetermined intervals along the circumferential direction and standing from the outer circumferential surface (25s),
Each wall portion (27) has the outer peripheral surface (from the front (F) side to the rear (R) side in the axial direction so as to be substantially parallel to the axial direction and the radial direction of the bell mouth (25). 25s),
The end (27r) on the rear (R) side of each wall (27) has a standing height from the outer peripheral surface (25s) that gradually increases from the front (F) side toward the rear (R) side. a sloped surface decreasing, the said periphery of the air inlet (19a) (19e) is an inclined surface facing said inclined surface of said wall portion (27), centrifugal blowers.

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