JP5195983B2 - 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.

  (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). In the rear end portion (27r) of each wall portion (27), the radially outer portion (271) is located on the front side (F) of the radially inner portion (272).

  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.

  In this configuration, the rear end portion (27r) of each wall portion (27) has the radially outer portion (271) positioned on the front side (F) of the radially inner portion (272). Therefore, contact with each wall part (27) and shroud (19) can be suppressed. Specifically, it is as follows. That is, there is a concern that the wall portion (27) may come into contact with the shroud (19) when the mounting error in manufacturing the bell mouth (25) or the rotational runout of the impeller (23) increases. Therefore, in this configuration, in the rear end portion (27r) of each wall portion (27), the radially outer portion (271), that is, the shroud (19) side portion (271) is changed to the radially inner portion ( 272) is positioned on the front side (F), so that the contact between each wall portion (27) and the shroud (19) is suppressed.

  (2) In the centrifugal blower, since the radially outer portion (271) is positioned in front (F) of the radially inner portion (272), the rear end (27r) is the bell mouth Each wall (27) extends toward the rear side (R) to a position facing the gap (G) provided between (25) and the peripheral edge (19e) in the front-rear direction. Can do. Therefore, in this structure, the distance (clearance) of each wall part (27) and shroud (19) in the front-back direction can be made small, avoiding contact with each wall part (27) and shroud (19). it can. 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. And since each wall part (27) is extended to the position where a rear side edge part (27r) opposes the said clearance gap (G) in the front-back direction, the rectification effect of the leak flow which flows in into the said clearance gap (G) Can be increased.

  (3) Further, in the centrifugal blower, each wall portion (27) is directed toward the rear side (R) until the rear end portion (27r) is opposed to the peripheral edge portion (19e) in the radial direction. In the case where it extends, the distance (clearance) between the wall portions (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. And since each wall part (27) is extended to the position where a rear side edge part (27r) opposes a radial direction with respect to a peripheral part (19e), each wall part (27) has a leak flow in the said clearance gap. The leakage flow can be rectified until just before entering (G). Thereby, the rectification effect of the leakage flow can be further enhanced.

  (4) In the centrifugal blower, it is preferable that the rear end portion (27r) is provided with a concave curved surface (273) that is recessed in a direction away from the peripheral edge portion (19e).

  In this configuration, the rear end portion (27r) is provided with a concave curved surface (273) that is recessed in a direction away from the peripheral edge portion (19e). For example, the rear end portion (27r) is, for example, a flat surface. Compared to the case, it is easier to secure the distance from the peripheral edge (19e).

  (5) In the centrifugal blower, it is preferable that the peripheral edge portion (19e) is provided with a convex curved surface (191) facing the concave curved surface (273) of the rear side end portion (27r).

  In this configuration, since the convex curved surface (191) of the peripheral edge portion (19e) is provided at a position facing the concave curved surface (273) of the rear side end portion (27r), the rear side end portion (27r ) And the peripheral edge portion (19e), while making the rear end portion (27r) closer to the peripheral edge portion (19e) and reducing the distance between the rear end portion (27r) and the peripheral edge portion (19e). can do.

(6) The centrifugal blower according to the third embodiment 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 of the rotating shaft (13) with respect to the shroud (19). A predetermined gap (G) is provided in the radial direction between the rear side (R) portion of the bell mouth (25) in the axial direction and the peripheral portion (19e) of the air suction port (19a). Yes.

  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 and the radial direction of the bell mouth (25). Each wall portion (27) has a rear end portion (27r) facing the gap (G) provided between the bell mouth (25) and the peripheral edge portion (19e) in the front-rear direction. Extends toward the rear side (R). The end surface of the rear end portion (27) is perpendicular to the axial direction.

  In this configuration, similarly to the centrifugal blower described in (1), the bell mouth (25) has the plurality of wall portions (27), so that the wall portion (27) is resistant to leakage flow. Thus, 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.

  Further, in this configuration, the rear end portion (27r) reaches a position facing the gap (G) provided between the bell mouth (25) and the peripheral edge portion (19e) in the front-rear direction. Each wall (27) extends toward the rear side (R). Thereby, the distance (clearance) of each wall part (27) and the shroud (19) in the front-back direction can be made small. By reducing the clearance, the resistance when the leakage flow flows into the gap (G) between the bell mouth (25) and the shroud (19) increases, and the amount of leakage flow is reduced. And since each wall part (27) is extended to the position where a rear side edge part (27r) opposes the said clearance gap (G) in the front-back direction, the rectification effect of the leak flow which flows in into the said clearance gap (G) Can be increased.

  In addition, as described above, the rear end of each wall (27) is extended by extending each wall (27) to a position where the rear end (27r) opposes the gap (G) in the front-rear direction. Although the possibility of contact between the portion (27r) and the peripheral portion (19e) of the shroud (19) is increased, in this configuration, in order to avoid such contact, the rear end (27) Are arranged so that the end faces thereof are perpendicular to the axial direction. That is, in this configuration, when the impeller (13) rotates, the end surface of the rear end portion (27) is parallel to the plane including the locus drawn by the peripheral edge portion (19e) of the shroud (19). Contact between the end face of the end (27) and the peripheral edge (19e) is suppressed.

  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 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 a figure for demonstrating the flow of air, and is sectional drawing to which some centrifugal fans were expanded. It is the side view to which the bell mouth in the centrifugal blower which concerns on 2nd Embodiment of this invention was expanded. It is sectional drawing which expanded a part of centrifugal blower which concerns on 2nd Embodiment. It is sectional drawing which expanded a part of centrifugal blower which concerns on 2nd Embodiment. 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. It is an enlarged sectional view of a portion of the centrifugal blower according to a third form state. 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.

<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 8, a part of the rear side R of the bell mouth main 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. 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. 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 FIGS. 7 and 8, the standing height from the outer peripheral surface 25s of each wall portion 27 gradually increases from the rear end portion 27r toward the front end portion 27f. Each wall 27 has a standing height Hf at the front end 27f that is higher than a standing height Hr at the rear end 27r. 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, in the rear end 27r of each wall 27, the radially outer portion 271 is located on the front side F with respect to the radially inner portion 272. An end surface of the rear end portion 27r in each wall portion 27 is an inclined surface inclined with respect to the axial direction A. This inclined surface gradually decreases as the standing height from the outer peripheral surface 25s goes to the rear side R.

  Each wall portion 27 extends toward the rear side R to a position where 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. A radially inner portion 272 in the rear end portion 27r of each wall portion 27 faces the peripheral edge portion 19e in the radial direction. A portion 271 on the outer side in the radial direction of the rear end portion 27r is located on the inner side in the radial direction with respect to the peripheral edge portion 19e of the shroud 19.

  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 rear side end portion 27r of the wall portion 27. In other words, the front end of the rear end portion 27r of each wall portion 27 is provided at a position (substantially the same height) that is substantially opposite to the front end of the peripheral portion 19e that is the end portion of the front side F of the shroud 19 in the radial direction. Yes. 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 so that the rear side R is positioned more radially inward than the front side F. As described above, since the end portions are formed of the inclined surfaces, the rear end portion 27r 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.

  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 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 a gap 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 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.

Second Embodiment
FIG. 9 is an enlarged side view of the bell mouth 25 in the centrifugal blower 51 according to the second embodiment of the present invention. FIG. 10 is an enlarged cross-sectional view of a part of the centrifugal blower 51 according to the second embodiment. FIG. 11 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.

  As shown in FIGS. 9 to 11, the bell mouth 25 has a plurality of wall portions 27 which are arranged on the outer peripheral surface 25 s at predetermined intervals along the circumferential direction and are erected from the outer peripheral surface 25 s. . Each wall portion 27 is parallel to the axial direction A and the radial direction of the bell mouth 25. In the rear end 27r of each wall 27, the radially outer portion 271 is located on the front side F with respect to the radially inner portion 272. Each wall portion 27 is provided at a position separated from the shroud 19.

  Each wall portion 27 extends toward the rear side R to a position where 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. The rear end portion 27r of each wall portion 27 faces the peripheral edge portion 19e in the radial direction. Specifically, the radially inner portion 272 in the rear end portion 27r of each wall portion 27 is opposed to the radially outer portion of the peripheral edge portion 19e in the radial direction. A portion 271 on the outer side in the radial direction of the rear end portion 27r is located on the inner side in the radial direction with respect to the peripheral edge portion 19e of the shroud 19.

  The rear end 27r of each wall 27 in the second embodiment is provided with a concave curved surface 273 that is recessed in a direction away from the peripheral edge 19e. The concave curved surface 273 is smoothly curved from the radially inner portion 272 to the radially outer portion 271. The concave curved surface 273 is curved in an arc shape in a cross section (a cross section including the center of the rotating shaft 13) shown in FIG.

  The entire end surface of the rear end portion 27r is preferably a concave curved surface 273. However, as shown in FIG. 11, the end surface of the rear end portion 27r is a combination of a concave curved surface 273 and, for example, an inclined surface. It may be configured. In the second embodiment, as for the end surface of the rear end portion 27r, only a part of the radially inner portion 272 is an inclined surface and the remaining most part is a concave curved surface 273. A convex curved surface 191 facing the concave curved surface 273 of the rear end portion 27r is provided on the peripheral edge portion 19e of the air suction port 19a of the shroud 19.

  In the second embodiment, the position and shape of the concave curved surface 273 can be determined as follows, for example. The position and shape of the concave curved surface 273 provided on the end surface of the rear end 27r are, for example, points on the peripheral edge 19e (for example, points on the convex curved surface 191) in the cross section shown in FIG. 11 (cross section including the center of the rotating shaft 13). ) Based on an arcuate curve such as an arc or an elliptical arc. The distance from the point on the peripheral edge portion 19e to the concave curved surface 273 is determined in consideration of, for example, the range of mounting errors in manufacturing the bell mouth 25, the range of rotational runout of the impeller 23, and the safety allowance. The concave curved surface 273 may be a concave curved surface that is recessed in the 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.

  FIG. 12 is a graph showing the relationship between the air volume and the blowing sound, and FIG. 13 is a graph showing the relationship between the air volume and the motor input. These graphs are provided with the characteristics of the indoor unit 31 including the centrifugal blower 51 according to the first embodiment, the characteristics of the indoor unit 31 including the centrifugal blower 51 according to the second embodiment, and the wall portion 27. It shows the characteristics of an indoor unit with a bell mouth of a reference example that is not.

  As shown in FIG. 12, it can be seen that the blowing sound is reduced in the first embodiment and the second embodiment as compared to the reference example. Moreover, as shown in FIG. 13, it turns out that motor input is reduced in 1st Embodiment and 2nd Embodiment compared with the reference example. Thus, in 1st Embodiment and 2nd 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 and the second embodiment, it is considered that the amount of leakage flow is reduced and the loss is reduced as compared with the reference example.

<Third form Thailand>
Figure 14 is an enlarged cross-sectional view of a portion of the centrifugal blower according to a third form state. Centrifugal blower 51 according to a third form state, the configuration of the wall portion 27 provided in the bell mouth 25 is different from the first embodiment, 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.

  As shown in FIG. 14, the bell mouth 25 has a plurality of wall portions 27 that are arranged on the outer peripheral surface 25 s at predetermined intervals along the circumferential direction and are erected from the outer peripheral surface 25 s. Each wall portion 27 is parallel to the axial direction A and the radial direction of the bell mouth 25. Each wall portion 27 is provided at a position separated from the shroud 19.

  Each wall portion 27 extends toward the rear side R up to a position where the rear end portion 27r faces the gap G provided between the bell mouth 25 and the peripheral edge portion 19e in the front-rear direction. Specifically, the end surface 274 of the rear end portion 27 r extends to the vicinity of the peripheral edge portion 19 e of the shroud 19. Here, the vicinity of the peripheral edge portion 19e refers to the rear end of the rotation of the impeller 23 in consideration of the manufacturing error range of the bell mouth 25, the rotational runout range of the impeller 23, and the safety allowance. This is the shortest distance that can avoid contact between the side end portion 27r and the peripheral edge portion 19e of the shroud 19.

  The end surface of the rear end portion 27r is perpendicular to the axial direction A. Further, the peripheral edge portion 19 e of the shroud 19 extends in an annular shape in a direction perpendicular to the axial direction A. A portion 271 on the outer side in the radial direction of the rear end portion 27r is located on the inner side in the radial direction with respect to the peripheral edge portion 19e of the shroud 19.

FIG. 15 is a graph showing the relationship between air volume and motor input. This graph shows the characteristics of the indoor unit 31 provided with a centrifugal fan 51 according to a third form state, and a characteristic of the indoor unit having a bellmouth of reference example wall 27 is not provided.

As shown in FIG. 15, it can be seen that the motor input is reduced in the third form states in comparison with the reference example. Thus, in the third form state, the motor input required is smaller than that in Reference Example to obtain the same air volume as in Reference Example. Therefore, in the third form state is considered the amount of leakage flow is low in comparison with the reference example.

  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.

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

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

  In the first embodiment and the second embodiment, the rear end 27r of each wall 27 has a radially outer portion 271 located on the front side F of the radially inner portion 272. Contact between the wall portion 27 and the shroud 19 can be suppressed.

  Moreover, in 1st Embodiment and 2nd Embodiment, each wall part 27 is until the position where the rear side edge part 27r opposes the clearance gap G provided between the bellmouth 25 and the peripheral part 19e in the front-back direction. Extends toward the rear side R. Therefore, in the first embodiment and the second embodiment, the distance (clearance) between the wall portions 27 and the shroud 19 in the front-rear direction can be reduced while avoiding contact between the wall portions 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 further increased, and the amount of the leakage flow is further reduced. And since each wall part 27 is extended to the position where the rear side edge part 27r opposes the clearance gap G in the front-back direction, the rectification effect of the leakage flow which flows into the clearance gap G can be heightened.

  Further, in the first embodiment and the second embodiment, each wall 27 extends toward the rear side R up to a position where the rear end 27r is opposed to the peripheral edge 19e in the radial direction. 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. In addition, since each wall 27 extends to a position where the rear end 27r is opposed to the peripheral edge 19e in the radial direction, each wall 27 does not leak until just before the leakage flows into the gap G. Can be rectified. Thereby, the rectification effect of the leakage flow can be further enhanced.

  In the second embodiment, since the rear end 27r is provided with a concave curved surface 273 that is recessed in a direction away from the peripheral edge 19e, for example, the peripheral edge 19e compared to the case where the rear end 27r is flat, for example. It is easy to secure the distance.

  In the second embodiment, since the convex curved surface 191 of the peripheral edge portion 19e is provided at a position facing the concave curved surface 273 of the rear side end portion 27r, contact between the rear side end portion 27r and the peripheral edge portion 19e is avoided. However, the distance between the rear end portion 27r and the peripheral edge portion 19e can be reduced by bringing the rear end portion 27r closer to the peripheral edge portion 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 of the embodiments, an example in which the standing height of each wall portion is gradually increased from the rear side to the front side has been described as an example, but the standing height is changed from the rear side to the front side. May be increased step by step. Moreover, the said standing height of each wall part may be constant from the rear side to the front side, and may decrease toward the front side from the rear side.

  Moreover, in 1st Embodiment and 2nd Embodiment, although the case where the rear side edge part of each wall part was provided in the position facing the peripheral part of a shroud in a radial direction was mentioned as an example, It is not limited. The rear end portion of each wall portion may be provided in front of the peripheral portion of the shroud.

  Moreover, in 2nd Embodiment, although the case where the peripheral part 19e was the convex curve 191 was illustrated, the peripheral part 19e does not necessarily need to be the convex curve 191, For example, even if it is a plane perpendicular | vertical to the axial direction A, It may be an inclined surface inclined with respect to the axial direction A.

  Moreover, 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 side portion 272 Radial inner side portion 273 Curved surface 31 Indoor unit A Axial direction of rotation axis of fan motor F Axial front side R-axis rear side

Claims (5)

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) is a centrifugal blower in which the radially outer portion (271) is located on the front side (F) of the radially inner portion (272).   Each wall portion (27) has the rear end portion (27r) opposed in the front-rear direction to the gap (G) provided between the bell mouth (25) and the peripheral edge portion (19e). The centrifugal blower according to claim 1, wherein the centrifugal blower extends toward the rear side (R) to a position.   Each wall portion (27) extends toward the rear side (R) to a position where the rear end portion (27r) radially opposes the peripheral edge portion (19e). Centrifugal blower.   The centrifugal blower according to any one of claims 1 to 3, wherein the rear end (27r) is provided with a concave curved surface (273) that is recessed in a direction away from the peripheral edge (19e). The centrifugal blower according to claim 4, wherein the peripheral edge portion (19e) is provided with a convex curved surface (191) facing the concave curved surface (273) of the rear end portion (27r).

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