JP2013036444A - Centrifugal blower - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a centrifugal blower capable of suppressing decrease in fan efficiency caused by a leak flow.SOLUTION: The centrifugal blower 51 includes an impeller 23 and a bell mouth 25. The bell mouth 25 has a plurality of walls 27 on the outer peripheral surface 25s thereof, and the walls are arranged at predetermined intervals in the circumferential direction and raised from the outer peripheral surface 25s. Each wall 27 is parallel to the axial direction A and the radial direction of the bell mouth 25. A portion 271 at a radial outer side of each wall 27 is positioned closer to a rear side R in the axial direction A than a facing portion 273.

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.

  (1) The centrifugal blower of the present invention includes an impeller (23) and a bell mouth (25). The impeller (23) includes a shroud (19) having an air suction port (19a) that opens in a circle around the rotation shaft (13) of the fan motor (11), and a circumferential direction of the air suction port (19a). And a plurality of blades (21) arranged along. The bell mouth (25) is disposed on the front side (F) in the axial direction (A) of the rotating shaft (13) with respect to the shroud (19). A predetermined gap (G) is provided in the radial direction between the bell mouth (25) and the peripheral edge portion (19e) of the air suction port (19a).

  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 portion (27) is parallel to the axial direction (A) and the radial direction of the bell mouth (25). The rear end portion (27r) of each wall portion (27) includes a radially outer portion (271) located radially outward from the peripheral edge portion (19e) and a radially inner side than the peripheral edge portion (19e). A radially inner portion (272) located at a position opposite to the peripheral portion (19e) in the front-rear direction. The radially outer portion (271) is located on the rear side (R) of the axial direction (A) with respect to the facing portion (273).

  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, the plurality of wall portions (27) are erected from the outer peripheral surface (25s) of the bell mouth (25) in a posture parallel to the axial direction (A) and the radial direction. 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.

  Further, in this configuration, the radially outer portion (271) at the rear end portion (27r) is located on the rear side (R) in the axial direction (A) with respect to the opposing portion (273). The distance (clearance) between each wall part (27) and the shroud (19) can be reduced while avoiding contact between the (27) and the shroud (19). By reducing the clearance, the resistance when the leakage flow flows into the gap (G) between the bell mouth (25) and the shroud (19) is increased, and the amount of leakage flow is further reduced. Specifically, it is as follows.

  That is, if the opposing part (273) which opposes the peripheral part (19e) of a shroud (19) in the front-back direction is extended to the peripheral part (19e) side (the rear side (R) of the rotating shaft (A)). Since the possibility of a contact with a wall part (27) and a peripheral part (19e) increases, it is unpreferable. Therefore, in this configuration, the radially outer portion (271) is positioned on the rear side (R) of the rotation axis (A) with respect to the facing portion (273). Thereby, the distance (clearance) between each wall part (27) and a shroud (19) can be made small, avoiding a contact with a wall part (27) and a shroud (19).

  (2) In the centrifugal blower, the radially outer portion (271) is preferably opposed to the peripheral edge portion (19e) in the radial direction.

  In this configuration, the distance (clearance) between the wall portion (27) and the shroud (19) in the front-rear direction can be further reduced. Thereby, the resistance when the leakage flow flows into the gap (G) between the bell mouth (25) and the shroud (19) is further increased, and the amount of the leakage flow is further reduced.

  (3) Moreover, the said centrifugal blower WHEREIN: The said radial direction outer side part (271) may be located in the back side (R) of the said axial direction (A) rather than the said peripheral part (19e).

  In this configuration, since the radially outer portion (271) of each wall portion (27) is arranged to cover the peripheral edge portion (19e) from the radially outer side, the bell mouth (25) and the shroud (19) The resistance when the leakage flow flows into the gap (G) is further increased, and the amount of leakage flow is further reduced.

  (4) In the centrifugal blower, the radially inner portion (272) is preferably located on the rear side (R) in the axial direction (A) with respect to the facing portion (273).

  In this configuration, the gap (G) between the bell mouth (25) and the peripheral edge portion (19e) of the air suction port (19a) is avoided while avoiding contact between the wall portion (27) and the shroud (19). The rectifying effect of the inflowing leakage flow can be enhanced. That is, the radially inner portion (272) is located radially inward of the facing portion (273) and faces the gap (G) in the front-rear direction. Therefore, the wall portion (27) can be brought closer to the gap (G) by positioning the radially inner portion (272) on the rear side (R) in the axial direction (A) than the facing portion (273). it can. Thereby, the rectification effect of the leakage flow which flows into the said clearance gap (G) can be heightened.

  (5) In the centrifugal fan, the radially inner portion (272) is preferably opposed to the peripheral edge portion (19e) in the radial direction.

  In this configuration, since the radially inner portion (272) is positioned in the vicinity of the gap (G), the leakage flow is guided by the wall (27) until just before flowing into the gap (G). Then, it flows into the gap (G). Thereby, the rectification effect of the leakage flow can be further enhanced.

  (6) In the centrifugal blower, the rear end portion (27r) connects the radially inner portion (272), the opposed portion (273), and the radially outer portion (271) to the axial direction (A ) Has a concave curved surface (275) that is recessed on the front side (F), the distance from the peripheral edge portion (19e) can be easily secured over the entire concave curved surface (275) as compared to the case of a flat surface.

  (7) When the concave curved surface (275) has an arc shape, the distance between the peripheral edge (19e) and the concave curved surface (275) can be ensured uniformly over the entire concave curved surface (275). Accordingly, the radially outer portion (271) and / or the radially inner portion (272) is positioned on the rear side (R) while securing the distance between the concave curved surface (275) and the peripheral edge portion (19e). Can do.

  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 1st 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 top view which shows the bell mouth of the said centrifugal blower. It is sectional drawing to which some centrifugal fans were expanded. It is a figure for demonstrating the flow of air, and is sectional drawing to which some centrifugal fans were expanded. It is a graph which shows the relationship between an air volume and a motor input. It is sectional drawing to which a part of centrifugal fan which concerns on 2nd Embodiment of this invention was expanded. It is sectional drawing to which a part of centrifugal blower concerning a 3rd embodiment of the present invention was expanded. It is sectional drawing to which a part of centrifugal fan which concerns on 4th Embodiment of this invention was expanded. It is sectional drawing to which some centrifugal blowers concerning a 5th embodiment of the present invention were expanded.

  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.

<First Embodiment>
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 to face the front side F in the axial direction A of the rotary shaft 13 with respect to the hub 15. 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 becomes larger toward the rear side R.

  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 end of each blade 21 is joined to the inner surface of the shroud 19. The end of the rear side R 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 to face the front side F in the axial direction A with respect to the shroud 19. The bell mouth 25 includes a bell mouth main body 251 and a flange portion 252 protruding from the peripheral edge of the front side F of the bell mouth main body 251 to the periphery of 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 that decreases as the outer diameter increases toward the rear side R.

  As shown in FIGS. 1 and 6, a part of the rear side R of the bell mouth body 251 is shroud from the air suction port 19a with a predetermined gap G between the peripheral portion 19e of the air suction port 19a. 19 is inserted. Thereby, the bell mouth 25 can guide the air sucked toward the rear side R 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 27 extends along the outer peripheral surface 25s from the front side F toward the rear side R so as to be parallel to the axial direction A and parallel to the radial direction of the bell mouth 25. Each wall portion 27 is provided at a position separated from the shroud 19.

  As shown in FIG. 4, the bell mouth 25 has a plurality of air flow paths 253 surrounded on three sides by adjacent wall portions 27 and 27 and an 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. The air flow path 253 has an inlet for leakage flow (swirl flow) to the air flow path 253. The exit is open and unobstructed. 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 side F toward the rear side R.

  As shown in FIG. 6, the outer portion 274 of each wall 27 is parallel to the axial direction A, but is not limited thereto. For example, the outer portion 274 may be curved along the curved shape of the outer peripheral surface 25 s of the bell mouth 25.

  As shown in FIG. 6, the rear end portion 27r of each wall portion 27 has a radially outer portion 271 located radially outside the peripheral edge portion 19e of the air suction port 19a of the shroud 19 and the peripheral edge portion 19e. It includes a radially inner portion 272 located on the radially inner side and a facing portion 273 that faces the peripheral edge portion 19e in the front-rear direction.

  The radially outer portion 271 is located on the rear side R in the axial direction A with respect to the facing portion 273. The radially inner portion 272 is located on the rear side R in the axial direction A with respect to the facing portion 273. The radially outer portion 271 mainly plays a role of increasing resistance when a leakage flow flows into the gap G. The radially inner portion 272 mainly plays a role of guiding the leakage flow to the gap G while rectifying the leakage flow.

  Each wall portion 27 is directed toward the rear side R to a position where the radially inner portion 272 at the rear end portion 27r faces the front-rear direction with respect to the gap G provided between the bell mouth 25 and the peripheral edge portion 19e. It extends.

  The rear end 27r has a concave curved surface 275 that connects the radially inner portion 272, the opposing portion 273, and the radially outer portion 271 and is recessed in the front side F in the axial direction A. The concave curved surface 275 has an arc shape. Specifically, the shape of the cross section of the concave curved surface 275 (the cross section including the center of the rotation shaft 13) is a semicircular arc.

  The position of the concave curved surface 275 can be determined based on, for example, an arc centered on the peripheral edge 19e (a point on the peripheral edge 19e). The radius of the arc is determined in consideration of, for example, a range of mounting errors in manufacturing the bell mouth 25, a range of rotational runout of the impeller 23, and a safety allowance. As a result, the distance between the peripheral edge portion 19e and the concave curved surface 275 can be made uniform to some extent over substantially the entire concave curved surface 275, and contact between the shroud 19 and the wall portion 27 due to attachment error, rotational runout, or the like can be suppressed. The concave curved surface 275 may be a concave curved surface that is recessed in a direction away from the peripheral edge portion 19e, and does not necessarily have to be an arcuate curve such as an accurate arc or elliptical arc.

  The radially outer portion 271 is opposed to the peripheral edge portion 19e in the radial direction. The radially inner portion 272 faces the peripheral edge portion 19e in the radial direction. That is, in the radial direction, the peripheral edge portion 19e is sandwiched between the radially outer portion 271 and the radially inner portion 272.

  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.

  Next, the flow of air in the centrifugal blower 51 will be described. As shown in FIG. 6, the mainstream S air guided to the air suction port 19a of the shroud 19 by the bell mouth main 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 first embodiment, as indicated by the dashed-dotted arrow M, the leakage flow M flows into 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. Along the rear side R, and passes through the gap G between the rear R end of the bell mouth body 251 and the front F end of the shroud 19. The leakage flow M that has passed through the gap G is corrected in the vicinity of the air suction port 19a so that the flow direction approaches the axial direction A as compared with the conventional case. Accordingly, interference when the leakage flow M joins the main flow S is suppressed.

  Further, in the centrifugal blower 51 of the first embodiment, as shown by the one-dot chain line arrow M2, even when the leakage flow M2 flowing in the region near the peripheral edge portion 19e is generated, the radially outer portion 271 is the opposite portion 273. Therefore, the resistance when the leakage flow M2 flows into the gap G is further increased, and the amount of the leakage flow M2 is reduced.

  FIG. 7 is a graph showing the relationship between air volume and motor input. This graph shows the characteristics of the indoor unit 31 including the centrifugal blower 51 according to the first embodiment and the characteristics of the indoor unit including the bell mouth of the reference example in which the wall portion 27 is not provided.

  As shown in FIG. 7, it can be seen that the motor input is reduced in the first embodiment compared to the reference example. In particular, the effect of reducing motor input in a region with a large air volume is high. Thus, in 1st Embodiment, the motor input required in order to obtain the same air volume as a reference example is small compared with a reference example, and fan efficiency is high. Therefore, in the first embodiment, it is considered that the amount of leakage flow is reduced compared to the reference example, and the loss is reduced.

Second Embodiment
FIG. 8 is an enlarged cross-sectional view of a part of the centrifugal blower 51 according to the second embodiment. The centrifugal blower 51 according to the second embodiment is different from the first embodiment in the configuration of the wall portion 27 provided in the bell mouth 25, and the configuration other than the wall portion 27 is the same as in the first embodiment. is there. Therefore, hereinafter, the wall portion 27 of the bell mouth 25 will be described, and the other components will be denoted by the same reference numerals as those of the first embodiment and description thereof will be omitted.

  The radially outer portion 271 of the rear end 27r of the wall 27 in the second embodiment is located on the rear R of the axial direction A with respect to the peripheral edge 19e. The rear end portion 27r includes a semicircular arc-shaped concave curved surface 275 and an inner flat surface 276 extending from the radially outer portion 271 to the front side F. In the second embodiment, since the radially outer portion 271 of each wall portion 27 is arranged so as to cover the peripheral edge portion 19e from the radially outer side, the leakage flow into the gap G between the bell mouth 25 and the shroud 19 The resistance at the time of inflow increases further, and the amount of leakage flow is further reduced. Except for these points, the second embodiment is the same as the first embodiment.

<Third Embodiment>
FIG. 9 is an enlarged cross-sectional view of a part of the centrifugal blower 51 according to the third embodiment. The centrifugal blower 51 according to the third embodiment is different from the first embodiment in the configuration of the wall portion 27 provided in the bell mouth 25, and the configuration other than the wall portion 27 is the same as in the first embodiment. is there.

  As shown in FIG. 9, the radially outer portion 271 is located on the front side F in the axial direction A with respect to the peripheral edge portion 19e. Therefore, the amount of the leakage flow M2 is smaller than that in the first embodiment and the second embodiment. The effect of reducing is reduced. However, since the radially outer portion 271 is located on the rear side R of the axial direction A with respect to the facing portion 273, the position in the front-rear direction of the radially outer portion 271 is comparable to that of the facing portion 273. If so, the amount of leakage flow M2 can be reduced.

<Fourth embodiment>
FIG. 10 is an enlarged cross-sectional view of a part of the centrifugal blower 51 according to the fourth embodiment. The centrifugal blower 51 according to the fourth embodiment is different from the first embodiment in the configuration of the wall portion 27 provided in the bell mouth 25, and the configuration other than the wall portion 27 is the same as in the first embodiment. is there.

  In the fourth embodiment, the radially outer portion 271 is located on the rear side R in the axial direction A with respect to the facing portion 273 and faces the peripheral edge portion 19e in the radial direction. On the other hand, the radially inner portion 272 is positioned in the front-rear direction at the same level as the facing portion 273 or on the front side F of the facing portion 273.

  The rear end 27r has a concave curved surface 275 that connects the radially inner portion 272, the opposing portion 273, and the radially outer portion 271 and is recessed in the front side F in the axial direction A. The concave curved surface 275 is an arc-shaped curved surface such as an arc or an elliptical arc whose cross-sectional shape is smoothly curved.

<Fifth Embodiment>
FIG. 11 is an enlarged cross-sectional view of a part of the centrifugal blower 51 according to the fifth embodiment. The centrifugal blower 51 according to the fifth embodiment is different from the first embodiment in the configuration of the wall portion 27 provided in the bell mouth 25, and the configuration other than the wall portion 27 is the same as in the first embodiment. is there.

  In the fifth embodiment, the radially outer portion 271 is located on the rear side R in the axial direction A with respect to the facing portion 273 and faces the peripheral edge portion 19e in the radial direction. On the other hand, the radially inner portion 272 is positioned in the front-rear direction at the same level as the facing portion 273 or on the front side F of the facing portion 273.

  The rear end 27r has an inclined surface 277 that connects the radially inner portion 272, the opposing portion 273, and the radially outer portion 271. The inclined surface 277 is a plane that is inclined with respect to the axial direction A. The inclined surface 277 is inclined so as to be located radially outward as it goes to the rear side R.

  As described above, in each embodiment, since the bell mouth 25 has the plurality of wall portions 27, the wall portion 27 serves as 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.

  Moreover, in each embodiment, since the radial direction outer side part 271 in the rear side edge part 27r is located in the rear side R of the axial direction A rather than the opposing part 273, contact with the wall part 27 and the shroud 19 is avoided. However, the distance (clearance) between the wall portions 27 and the shroud 19 in the front-rear direction can be reduced. By reducing the clearance, the resistance when the leakage flow flows into the gap G between the bell mouth 25 and the shroud 19 is further increased, and the amount of the leakage flow is further reduced.

  In the first embodiment, the fourth embodiment, and the fifth embodiment, since the radially outer portion 271 is opposed to the peripheral edge portion 19e in the radial direction, the distance between the wall portion 27 and the shroud 19 in the front-rear direction. (Clearance) can be further reduced. Thereby, the resistance when the leakage flow flows into the gap G between the bell mouth 25 and the shroud 19 is further increased, and the amount of the leakage flow is further reduced.

  In the second embodiment, the radially outer portion 271 is located on the rear side R in the axial direction A with respect to the peripheral portion 19e, and thus the radially outer portion 271 of each wall portion 27 has a radius with respect to the peripheral portion 19e. It arrange | positions so that it may cover from the direction outer side. Thereby, the resistance when the leakage flow flows into the gap G between the bell mouth 25 and the shroud 19 is further increased, and the amount of the leakage flow is further reduced.

  In the first embodiment, the second embodiment, and the third embodiment, the radially inner portion 272 is located on the rear side R of the axial direction A with respect to the facing portion 273, so that the wall portion 27 and the shroud 19 The rectification effect of the leakage flow flowing into the gap G between the peripheral edge portion 19e can be enhanced while avoiding the contact. That is, the radially inner portion 272 is located radially inward of the facing portion 273 and faces the gap G in the front-rear direction. Therefore, the wall portion 27 can be brought closer to the gap G by positioning the radially inner portion 272 closer to the rear side R in the axial direction A than the facing portion 273. Thereby, the rectification effect of the leak flow flowing into the gap G can be enhanced.

  In the first embodiment, the second embodiment, and the third embodiment, since the radially inner portion 272 is opposed to the peripheral edge portion 19e in the radial direction, the radially inner portion 272 is positioned in the vicinity of the gap G. Will do. Thus, the leakage flow is guided to the gap G by the wall portion 27 and then flows into the gap G. Thereby, the rectification effect of the leakage flow can be further enhanced.

  In the first embodiment, the second embodiment, the third embodiment, and the fourth embodiment, the rear end 27r connects the radially inner portion 272, the opposing portion 273, and the radially outer portion 271 in the axial direction A. Since it has the concave curved surface 275 recessed in the front side F, it is easy to ensure the distance with the peripheral part 19e over the whole concave curved surface 275 compared with the inclined surface 277 comprised by the plane like 5th Embodiment.

  In the first embodiment, the second embodiment, the third embodiment, and the fourth embodiment, since the concave curved surface 275 has an arc shape, the distance between the peripheral edge portion 19e and the concave curved surface 275 can be secured evenly over the entire concave curved surface 275. . Thereby, the radial direction outer side part 271 and / or the radial direction inner side part 272 can be located in the back side R, ensuring the distance of this concave curved surface 275 and the peripheral part 19e.

  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 each embodiment, although the case where the centrifugal blower was used for the indoor unit of the air conditioning apparatus was described as an example, it can be used for other purposes.

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 portion 27f Front end portion of wall portion 27r Rear end portion of wall portion 271 Radial outer portion 272 Radial inner portion 273 Opposed portion 275 Concave surface 277 Inclined surface 31 Indoor unit A Axial direction of rotation axis of fan motor F Axial front side R Axial rear side

Claims (7)

A shroud (19) having an air suction port (19a) that opens circularly around the rotation shaft (13) of the fan motor (11), and a plurality of the shroud (19a) arranged along the circumferential direction of the air suction port (19a) An impeller (23) including a blade (21);
It is arranged on the front side (F) in the axial direction (A) of the rotating shaft (13) with respect to the shroud (19), and is predetermined in the radial direction between the peripheral portion (19e) of the air suction port (19a). A bell mouth (25) provided with a gap (G) of
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 (27) is parallel to the axial direction (A) and the radial direction of the bell mouth (25),
The rear end portion (27r) of each wall portion (27) includes a radially outer portion (271) located radially outward from the peripheral edge portion (19e) and a radially inner side than the peripheral edge portion (19e). A radially inner portion (272) located at the front and a facing portion (273) facing the peripheral portion (19e) in the front-rear direction,
The centrifugal blower, wherein the radially outer portion (271) is located on the rear side (R) of the axial direction (A) with respect to the facing portion (273).   The centrifugal blower according to claim 1, wherein the radially outer portion (271) is opposed to the peripheral edge (19e) in the radial direction.   The centrifugal blower according to claim 1, wherein the radially outer portion (271) is located on the rear side (R) of the axial direction (A) with respect to the peripheral edge portion (19e).   The centrifuge according to any one of claims 1 to 3, wherein the radially inner portion (272) is located on the rear side (R) of the axial direction (A) with respect to the facing portion (273). Blower.   The centrifugal blower according to claim 4, wherein the radially inner portion (272) is opposed to the peripheral edge portion (19e) in the radial direction.   The rear end portion (27r) connects the radially inner portion (272), the opposed portion (273), and the radially outer portion (271), and is recessed in the front side (F) in the axial direction (A). The centrifugal blower according to any one of claims 1 to 5, having a concave curved surface (275).   The centrifugal blower according to claim 6, wherein the concave curved surface (275) has an arc shape.

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