JP2013036402A - Multiblade blower - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multiblade blower that can control a decrease in blowing efficiency and an increase in blowing noise attributable to a swirl flow.SOLUTION: The multiblade blower 1 includes an impeller 3 in which a plurality of front-facing vanes 31 are arranged along a circumferential direction centered on a rotary shaft A, and a case 2 provided with a bellmouth 27 having an inner circumferential surface 27a centered on the rotary shaft A and its rear face 27b that accommodates the impeller 3. The bellmouth 27 includes a plurality of guide walls 51 arranged at predetermined intervals over the whole circumference of the rear face 27b. Each of the guide walls 51 is parallel to the direction of the rotary shaft A and the radial direction of the bellmouth 27.

Description

  The present invention relates to a multiblade fan having a plurality of forward-facing blades.

  Conventionally, for example, a multi-blade fan (so-called sirocco fan) has been used as a blower for an indoor unit of an air conditioner (for example, Patent Document 1). In this multiblade fan, when the fan motor is driven and the impeller rotates, air is sucked into the case along the inner peripheral surface of the bell mouth and guided to the impeller (hereinafter, the inner periphery of the bell mouth). The flow of air guided to the impeller along the surface is called the mainstream.)

Japanese Patent No. 3698150

  By the way, this mainstream air is sent to the outside in the radial direction by a plurality of forward-facing blades arranged along the circumferential direction, most of which is blown out through the blowout port of the multiblade blower, but a part is blower Circulates toward the bell mouth through the space outside the impeller in the radial direction, flows again into the impeller along the outer peripheral surface (back surface) of the bell mouth, and merges with the mainstream (hereinafter referred to as the circulatory flow as described above). The flow that re-enters the impeller along the back of the bell mouth is called the swirl flow.) Since the swirl flow in which a part of the main flow branches in this way has a component in the rotation direction of the impeller, a difference is generated with respect to the main flow vector flowing in a direction close to the direction of the rotation axis. . Such a vector difference causes a decrease in the blowing efficiency of the multiblade fan and an increase in blowing sound.

  Then, this invention is made | formed in view of this point, The place made into the objective is to provide the multiblade fan which can suppress the fall of the ventilation efficiency resulting from a turning flow, and the increase in blowing sound. .

  The multiblade fan of the present invention has an impeller (3) in which a plurality of forward-facing blades (31) are arranged along a circumferential direction around the rotation axis (A), and the rotation axis (A) as a center. A bell mouth (27) having an inner peripheral surface (27a) and a rear surface (27b) thereof is provided, and includes a case (2) for housing the impeller (3). The bell mouth (27) has a plurality of guide walls (51) arranged at a predetermined interval over the entire circumference of the back surface (27b), and each guide wall (51) is connected to the rotating shaft (A). Direction and parallel to the radial direction of the bellmouth (27).

  In this configuration, the bell mouth (27) has a plurality of guide walls (51) arranged at predetermined intervals over the entire circumference of the back surface (27b), and each guide wall (51) has a rotation axis (A). And the radial direction of the bell mouth (27). Therefore, when the swirl flow is guided to the impeller (3) by the plurality of guide walls (51), the direction of the swirl flow is corrected so as to approach the direction of the rotation axis (A). Thereby, the vector of the swirl flow has a smaller difference between the vectors of the main flow. Therefore, the fall of the ventilation efficiency resulting from a turning flow, and the increase in blowing sound can be suppressed.

  In the multiblade fan, the back surface (27b) of the bell mouth (27) has a curved surface recessed in a groove shape on the opposite side to the impeller (3) in the direction of the rotation axis (A). It is preferable.

  In this configuration, the swirl flow F2 flows into the space surrounded by the curved surface recessed in the groove shape, is rectified by the guide wall 51 provided in the space, and then flows out of the space. In this configuration, in addition to the rectifying effect by the guide wall 51, the rectifying effect of the groove-like curved surface itself can be obtained, so that a higher effect of rectifying the swirling flow F2 can be obtained.

  In the multiblade fan, the bell mouth (27) has a plurality of inner guide walls (61) arranged at predetermined intervals over the entire circumference of the inner peripheral surface (27a), and each inner guide wall (61 ) Is preferably parallel to the direction of the rotation axis (A) and the radial direction of the bell mouth (27).

  In this configuration, the bell mouth (27) has a plurality of inner guide walls (61) arranged at predetermined intervals over the entire circumference of the inner peripheral surface (27a), and each inner guide wall (61) is rotated. Parallel to the direction of the axis (A) and the radial direction of the bell mouth (27). Therefore, the direction of the mainstream guided to the impeller (3) along the inner peripheral surface (27a) can be made closer to the direction of the rotation axis (A). Therefore, the vector difference between the main flow and the swirl flow can be further reduced.

  In the multiblade fan, it is preferable that a radially inner surface of each inner guide wall (61) has a curved surface along the inner peripheral surface (27a).

  In this structure, it can suppress that the air resistance at the time of inflow of a bell mouth (27) resulting from providing a some inner side guide wall (61) increases.

  In the multiblade fan, it is preferable that the radially outer end of each guide wall (51) is located radially outward from the rear edge of the forward blade (31).

  In this configuration, each guide wall (51) can effectively catch the swirl flow (F2) flowing radially outward from the rear edge (31B) of the forward blade (31). The rectifying effect can be further enhanced.

  As described above, according to the present invention, in the multiblade fan, it is possible to suppress a decrease in blowing efficiency and an increase in blowing sound due to the swirling flow.

It is a top view which shows the multiblade fan which concerns on 1st Embodiment of this invention. It is the II-II sectional view taken on the line of FIG. (A), (B) has shown the annular plate of the case of the said multiblade fan, (A) is the IIIA-IIIA sectional view taken on the line of (B), (B) is a rear view. . (A), (B) is sectional drawing to which a part of said annular plate was expanded. (A) is the schematic which shows the flow of the air in the multiblade fan which concerns on 1st Embodiment, (B) is the schematic which shows the flow of the air in the multiblade fan of a reference example. (A), (B) has shown the annular plate of the case of the multiblade fan which concerns on 2nd Embodiment of this invention, (A) is the VIA-VIA sectional view taken on the line of (B), (B) is a rear view. (A) is a side view which shows the inner side guide wall provided in the said annular ring plate in 2nd Embodiment, (B) is the back view. It is the schematic which shows the flow of the air in the multiblade fan which concerns on 2nd Embodiment. It is the graph which compared the noise characteristic of the multiblade fan which concerns on 1st Embodiment, the noise characteristic of the multiblade fan which concerns on 2nd Embodiment, and the noise characteristic of the multiblade fan of a reference example. (A) is sectional drawing which shows the modification of the multiblade fan which concerns on 1st Embodiment, (B) is sectional drawing which shows the modification of the multiblade fan which concerns on 2nd Embodiment.

  Hereinafter, the multiblade fan 1 which concerns on embodiment of this invention is demonstrated with reference to drawings.

<First Embodiment>
The multiblade blower 1 according to the present embodiment is used as a blower for a refrigeration apparatus including a refrigerant circuit such as an air conditioner, a refrigerator, a refrigerator, a heat pump water heater, and the like. As shown in FIGS. 1 and 2, the multiblade fan 1 includes a case 2, an impeller 3 accommodated in the case 2, and a motor 41. The impeller 3 is rotated in the rotation direction D around the rotation axis A by the motor 41.

  Case 2 has a scroll shape. The case 2 has an air inlet 25 provided on the front side in the direction of the rotation axis A, and an air outlet 26 that opens radially outward with respect to the rotation axis A. Case 2 includes a case body 20 and an annular plate 24 fixed to case body 20. The case main body 20 includes a front plate 21, a back plate 22, and a side plate (body plate) 23 connecting them. The front plate 21 has a circular opening to which the annular plate 24 is attached.

  The impeller 3 includes a main plate 30, a plurality of forward-facing blades 31, and a ring portion (side plate) 32. The main plate 30 has a circular shape centered on the rotation axis A in front view. A radially outer portion 30 a of the main plate 30 is close to the back plate 22. The radially inner portion 30b of the main plate 30 has a concave shape that is recessed from the radially outer portion 30a to the front side. A motor attachment portion 33 to which the shaft 42 of the motor 41 is attached is provided at the center of the radially inner portion 30b. The motor 41 is fixed to the inner surface of the back plate 22 of the case 2. A plurality of through holes 34 arranged in the circumferential direction are provided in the radially inner portion 30b.

  Each forward blade 31 has a blade outlet inclined in the rotational direction. Each forward blade 31 has a rear end fixed to a radially outer portion 30 a of the main plate 30. The several forward blade | wing 31 is arranged along the circumferential direction at predetermined intervals mutually. The ring portion 32 is fixed to front end portions of the plurality of forward-facing blades 31. The ring portion 32 is disposed so as to surround the periphery of the plurality of forward-facing blades 31.

  As shown in FIGS. 3A and 3B, the annular plate 24 of the case 2 includes a bell mouth 27 and an outer edge portion 28 fixed to the opening of the front plate 21 of the case 2. The outer edge portion 28 has a step surface 28a in which a part of the inner surface is recessed in an annular shape on the front side. The step surface 28a faces the step surface 21a provided at the inner edge of the opening of the front plate 21 (see FIG. 2). The step surface 28a and the step surface 21a are joined together by means such as fusion.

  The bell mouth 27 has an inner peripheral surface 27 a that forms the suction port 25. The inner peripheral surface 27a has a curved shape whose inner diameter becomes smaller toward the back side. The inner peripheral surface 27 a plays a role of guiding air to the impeller 3.

  4A and 4B are cross-sectional views in which a part of the annular plate 24 is enlarged. In FIG. 4A, the guide wall 51 shown in FIG. 4B is not shown. As shown in FIG. 4A, the bell mouth 27 has a back surface 27b on the back side of the inner peripheral surface 27a. The back surface 27b is provided in an annular shape around the rotation axis A. The back surface 27b is a curved surface that is recessed in a groove shape on the front side in the direction of the rotation axis A (the side opposite to the impeller 3). In the back surface 27b, the radius of curvature R1 of the radially inner region is smaller than the radius of curvature R2 of the radially outer region.

  In the groove-like back surface 27b, in the cross section shown in FIG. 4A, the tangent line at the edge 27e1 on the radially outer side, which is the region where the swirling flow F2 flows, and the radially inner side, which is the region where the swirling flow F1 flows. When compared with the tangent at the edge portion 27e2, there are the following characteristics. In other words, the tangent at the radially inner edge 27e2 has a smaller angle with the rotation axis A than the tangent at the radially outer edge 27e1.

  That is, the tangent line at the edge 27e1 on the radially outer side is greatly inclined with respect to the rotation axis A so that the swirl flow F2 can easily flow into the space surrounded by the groove-shaped back surface 27b. On the other hand, when the swirl flow F2 flows out of the space surrounded by the groove-shaped back surface 27b, the tangent at the edge 27e2 on the radially inner side is in the direction of the rotation axis A so that the outflow direction approaches the rotation axis A. It is approached.

  The outer surface on the front side of the bell mouth 27 is a curved surface that follows the curved shape of the back surface 27 b, and slightly protrudes to the front side from the outer surface on the front side of the outer edge portion 28.

  As shown in FIGS. 3A, 3B, and 4B, the bell mouth 27 has a large number of guide walls 51 arranged at predetermined intervals over the entire circumference of the back surface 27b. Each guide wall 51 is parallel to the direction of the rotation axis A and the radial direction of the bell mouth 27.

  Each guide wall 51 has an end surface 51c on the back side and a pair of side surfaces 51g and 51h located on one side and the other side in the circumferential direction. The pair of side surfaces 51g and 51h are substantially parallel to each other. The side surface 51g of the guide wall 51, the side surface 51h of the guide wall 51 facing the circumferential direction in the circumferential direction, and the back surface 27b form a swirl flow path 27F2 that rectifies the swirl flow F2. Therefore, the bell mouth 27 is formed with a plurality of swirl passages 27F2 arranged in the circumferential direction.

  The outer end portion 51 a on the outer side in the radial direction of each guide wall 51 is located on the outer side in the radial direction with respect to the rear edge 31 </ b> B of the forward blade 31. The inner end 51a on the radially inner side of each guide wall 51 is located between the front edge 31F and the rear edge 31B of the forward blade 31 in the radial direction. The end face 27c of the bell mouth 27 is located between the front edge 31F and the rear edge 31B of the forward blade 31 in the radial direction.

  The end face (back side surface) 51c of each guide wall 51 is in the same position as the end face (back side surface at the inner edge) 27c of the bell mouth 27 in the direction of the rotation axis A. The end surface 51 c of each guide wall 51 is in the same position as the inner surface 24 a of the annular plate 24 adjacent to the guide wall 51 on the radially outer side in the direction of the rotation axis A. That is, the end surface 51c, the end surface 27c, and the inner surface 24a are located on the same plane.

  The front edge of each guide wall 51 has a curved shape along the back surface 27 b of the bell mouth 27. Therefore, in the front edge 51d of each guide wall 51, the radius of curvature of the radially inner region is smaller than the radius of curvature of the radially outer region. As shown in FIG. 4B, the top 51 e located on the most front side of the edge 51 d is located radially inward of the radial center of the guide wall 51.

  As shown in FIG. 3B, the size of the gap between the guide walls 51 is larger than the thickness of the guide walls 51. The thickness of the guide wall 51 refers to the dimension of the guide wall 51 in the direction perpendicular to the radial direction and the direction of the rotation axis A. The size of the gap between the guide walls 51 is smaller than the length from the inner end portion 51 a to the outer end portion 51 a of the guide wall 51. The length from the inner end portion 51 a to the outer end portion 51 a of the guide wall 51 is larger than the length in the radial direction of the end surface 27 c of the bell mouth 27.

  Each guide wall 51 extends in the radial direction. That is, the plurality of guide walls 51 are arranged radially about the rotation axis A. The angle θ formed by the adjacent guide walls 51, 51 is preferably set to about 1 to 10 degrees, for example. In the present embodiment, the case where the angle θ is set to about 2.5 degrees is illustrated.

  FIG. 5A is a schematic diagram showing the air flow in the multiblade fan 1 according to the first embodiment, and FIG. 5B is a schematic diagram showing the air flow in the multiblade fan of the reference example. is there. The multi-blade fan of the reference example shown in FIG. 5B is different from the multi-blade fan 1 according to the first embodiment only in that the guide wall 51 is not provided.

  As shown in FIG. 5B, in the multi-blade fan of the reference example, a part of the main flow F1 circulates through the space radially outside the impeller 3 toward the bell mouth 27 in the case, and the bell mouth A swirling flow F <b> 2 that flows into the impeller 3 again along the back surface 27 b of 27 is generated. The swirl flow F2 merges with the main flow F1 introduced into the case along the inner peripheral surface 27a of the bell mouth 27. However, since the swirl flow F2 includes a lot of velocity components in the rotation direction D of the impeller 3, there is a large difference with respect to the vector of the main flow F1 that flows in a direction close to the direction of the rotation axis A. . Such a vector difference causes a decrease in the blowing efficiency of the multiblade fan and an increase in blowing sound.

  On the other hand, in the multiblade fan 1 according to the first embodiment, a plurality of guide walls 51 are provided on the back surface 27 b of the bell mouth 27. As described above, each guide wall 51 is parallel to the direction of the rotation axis A and the radial direction of the bell mouth 27. Accordingly, as shown in FIG. 5A, the swirl flow F2 is corrected so that the direction of the swirl flow F2 approaches the direction of the rotation axis A when being guided to the impeller 3 by the plurality of guide walls 51. The As a result, the vector of the swirl flow F2 has a smaller difference from the vector of the main flow F1. Therefore, the fall of the ventilation efficiency resulting from the turning flow F2 and the increase in blowing sound can be suppressed.

Second Embodiment
As shown in FIGS. 6A, 6B, 7A, 7B, and 8, the multiblade blower 1 according to the second embodiment has a plurality of inner guide walls 61 on the bell mouth 27. Furthermore, the point provided is different from the multiblade fan 1 according to the first embodiment. Hereinafter, differences from the first embodiment 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 bell mouth 27 has a plurality of inner guide walls 61 arranged at predetermined intervals over the entire circumference of the inner peripheral surface 27a. Each inner guide wall 61 is parallel to the direction of the rotation axis A and the radial direction of the bell mouth 27. Each inner guide wall 61 extends in the direction of the rotation axis A from the inner peripheral surface 27 a of the bell mouth 27. The inner guide wall 61 is located on the radially inner side with respect to the guide wall 51, and is arranged linearly with respect to the guide wall 51 in the radial direction.

  Each inner guide wall 61 includes a radially inner inner surface 61d, a rear end surface 61c, a front side end surface 61f on the opposite side (front side) of the end surface 61c, and a pair of circumferentially positioned one and the other. It has side surfaces 61g and 61h. A radially outer portion 61 e of each inner guide wall 61 is connected to the inner peripheral surface 27 a of the bell mouth 27.

  The inner surface 61 d of each inner guide wall 61 is curved along the inner peripheral surface 27 a of the bell mouth 27. Each inner surface 61d has a curved shape with an inner diameter that decreases toward the back side. Each end surface 61 c is located at the same position as the end surface 27 c of the bell mouth 27 in the direction of the rotation axis A. In the direction of the rotation axis A, the end surface 61c of the inner guide wall 61, the end surface 51c, the end surface 27c, and the inner surface 24a of the guide wall 51 are located on the same plane.

  A front-side end surface 61f of each inner guide wall 61 is parallel to the end surface 61c. The pair of side surfaces 61g and 61h are substantially parallel to each other. The side surface 61g of the inner guide wall 61, the side surface 61h of the inner guide wall 61 opposed to the inner guide wall 61 in the circumferential direction, and the inner peripheral surface 27a form a main flow path 27F1 that rectifies the flow of the main flow F1. Therefore, the bell mouth 27 has a plurality of main flow paths 27F1 arranged in the circumferential direction.

  The radially inner end 61a of each inner guide wall 61 is located at the same position as the rear edge 31B of the forward blade 31 or radially inward of the rear edge 31B. The outer end 51a on the radially outer side of each guide wall 51 is located between the front edge 31F and the rear edge 31B of the forward blade 31 in the radial direction.

  As shown in FIG. 6B, the size of the gap between the inner guide walls 61 is larger than the thickness of the inner guide wall 61. The thickness of the inner guide wall 61 refers to the dimension of the inner guide wall 61 in the direction orthogonal to the radial direction and the direction of the rotation axis A. The size of the gap between the inner guide walls 61 is smaller than the length from the end 61 a to the end 61 b of the inner guide wall 61. The angle formed between the adjacent inner guide walls 61, 61 is set similarly to the angle formed between the guide walls 51, 51 described above. The length from the end portion 61 a to the end portion 61 b of the inner guide wall 61 is larger than the length in the radial direction of the end surface 27 c of the bell mouth 27.

  FIG. 8 is a schematic view showing the flow of air in the multiblade blower 1 according to the second embodiment. In the multiblade blower 1 according to the second embodiment, the bell mouth 27 has a plurality of guide walls 51, so that the effect as in the first embodiment shown in FIG. Furthermore, since the bell mouth 27 has a plurality of inner guide walls 61, the following effects can be obtained.

  That is, each inner guide wall 51 is parallel to the direction of the rotation axis A and the radial direction of the bell mouth 27. Therefore, as shown in FIG. 8, the main flow F <b> 1 is corrected so as to be closer to the direction of the rotation axis A when being introduced into the impeller 3 by the plurality of inner guide walls 61. As a result, the difference between the vector of the main flow F1 and the vector of the swirl flow F2 is further smaller than that of the first embodiment. Therefore, the fall of the ventilation efficiency resulting from the turning flow F2 and the increase in blowing sound can be further suppressed.

  FIG. 9 is a graph comparing the noise characteristics of the multiblade fan 1 according to the first embodiment, the noise characteristics of the multiblade fan 1 according to the second embodiment, and the noise characteristics of the multiblade fan of the reference example. . As shown in FIG. 9, in the multiblade fan 1 of 1st Embodiment and 2nd Embodiment, it turns out that the specific noise is reduced compared with the multiblade fan of a reference example. In particular, the multiblade fan 1 according to the second embodiment has a higher noise reduction effect than the multiblade fan 1 according to the first embodiment.

  As described above, in the present embodiment, the bell mouth 27 has the plurality of guide walls 51 arranged at predetermined intervals over the entire circumference of the back surface 27b, and each guide wall 51 has the direction of the rotation axis A and the bell. It is parallel to the radial direction of the mouse 27. Therefore, when the swirl flow F2 is guided to the impeller 3 by the plurality of guide walls 51, the direction of the swirl flow F2 is corrected so as to approach the direction of the rotation axis A. Thereby, the vector of the swirl | flow flow F2 becomes small [the difference of the vector of the mainstream F1]. Therefore, the fall of the ventilation efficiency resulting from the turning flow F2 and the increase in blowing sound can be suppressed.

  In the second embodiment, the bell mouth 27 has a plurality of inner guide walls 61 arranged at predetermined intervals over the entire circumference of the inner peripheral surface 27a, and each inner guide wall 61 has a direction of the rotation axis A. And parallel to the radial direction of the bell mouth 27. Therefore, the direction of the main flow F1 guided to the impeller 3 along the inner peripheral surface 27a can be made closer to the direction of the rotation axis A. Therefore, the vector difference between the main flow F1 and the swirl flow F2 can be further reduced.

  In the second embodiment, since the radially inner surface 61 d of each inner guide wall 61 has a curved surface along the inner peripheral surface 27 a, the bell is caused by providing a plurality of inner guide walls 61. It is possible to suppress an increase in air resistance when the mouse 27 flows in.

  In the first embodiment and the second embodiment, the outer end portion 51a on the outer side in the radial direction of each guide wall 51 is located on the outer side in the radial direction with respect to the rear edge 31B of the forward blade 31. Can effectively catch the swirl flow F2 flowing radially outward from the rear edge 31B of the forward blade 31. Thereby, the rectification effect of the swirl | vortex flow F2 can be improved more.

  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 above embodiment, the case where the back surface 27b of the bell mouth 27 is a curved surface recessed in a groove shape on the front side is illustrated, but the present invention is not limited to this. As shown in FIG. 10A, for example, the rear surface 27b of the bell mouth 27 is substantially parallel to the curved surface portion 27b1 along the curvature of the inner peripheral surface 27a and the radially outer end of the curved surface portion 27b1 in the radial direction. The shape which has the plane part 27b2 extended may be sufficient. And each guide wall 51 may be provided, for example in the curved surface part 27b1, and may be provided so that the curved surface part 27b1 and the plane part 27b2 may be straddled. In this case, it is preferable that the outer end portion on the radially outer side of each guide wall 51 is located on the radially outer side with respect to the rear edge of the forward blade 31 as shown in FIG. Thereby, since each guide wall 51 can catch a swirl flow more upstream, the rectifying effect of the swirl flow can be further enhanced. Further, as shown in FIG. 10B, an inner guide wall 61 may be provided on the inner peripheral surface 27 a of the bell mouth 27.

  In the said embodiment, although the annular plate 24 and the front board 21 were separate bodies and illustrated the case where these were joined together, these may be integrally molded.

  In the embodiment, the end surface 51c of the guide wall 51, the end surface 61c, the end surface 27c, and the inner surface 24a of the inner guide wall 61 are illustrated on the same plane. However, the present invention is not limited to this. For example, the end surface 51c of the guide wall 51 may protrude to the back side from the end surface 27c and the inner surface 24a. Thereby, the rectification effect of the swirl | vortex flow F2 can be improved more. Moreover, the end surface 61c of the inner side guide wall 61 may protrude in the back side rather than the end surface 27c. Thereby, the rectification effect of mainstream F1 can be improved more.

  In the said embodiment, although the case where the inner surface 61d of radial inner side in each inner side guide wall 61 has a curved surface along the inner peripheral surface 27a was illustrated, it is not limited to this. The inner surface 61d may be a plane parallel to the rotation axis A, for example. Further, the inner surface 61d may have an angular shape.

  In the above-described embodiment, the outer end 51a on the outer side in the radial direction of each guide wall 51 is illustrated as being located on the outer side in the radial direction with respect to the rear edge 31B of the forward blade 31. The same position may be sufficient, and it may be located inside radial direction rather than the trailing edge 31B.

  In the embodiment, the case where the pair of side surfaces 51g and 51h of the guide wall 51 are parallel to each other is illustrated, but one of the side surfaces 51g and 51h may be slightly inclined with respect to the other. Although the case where the pair of side surfaces 61g and 61h in the inner guide wall 61 are parallel to each other is illustrated, one of the side surfaces 61g and 61h may be slightly inclined with respect to the other.

DESCRIPTION OF SYMBOLS 1 Multiblade fan 2 Case 20 Case main body 21 Front plate 22 Back plate 23 Side plate (body plate)
24 circular plate 25 suction port 26 outlet 27 bell mouth 28 outer edge portion 3 impeller 30 main plate 31 forward blade 32 ring portion 33 motor mounting portion 34 opening portion 41 motor 42 shaft 51 guide wall 61 inner guide wall A rotation axis D rotation direction

Claims (5)

An impeller (3) in which a plurality of forward-facing blades (31) are arranged along a circumferential direction around the rotation axis (A);
A bell mouth (27) having an inner peripheral surface (27a) centered on the rotating shaft (A) and a back surface (27b) thereof, and a case (2) for accommodating the impeller (3). ,
The bell mouth (27) has a plurality of guide walls (51) arranged at a predetermined interval over the entire circumference of the back surface (27b), and each guide wall (51) is connected to the rotating shaft (A). A multi-blade fan which is parallel to the direction and the radial direction of the bellmouth (27).   The back surface (27b) of the bell mouth (27) has a curved surface recessed in a groove shape on the opposite side to the impeller (3) in the direction of the rotation axis (A). The multiblade blower described.   The bell mouth (27) has a plurality of inner guide walls (61) arranged at predetermined intervals over the entire circumference of the inner peripheral surface (27a), and each inner guide wall (61) has the rotating shaft. The multiblade fan according to claim 1 or 2, which is parallel to the direction (A) and the radial direction of the bell mouth (27).   The multiblade fan according to claim 3, wherein a radially inner surface of each inner guide wall (61) has a curved surface along the inner peripheral surface (27a).   The multiblade according to any one of claims 1 to 4, wherein a radially outer end of each guide wall (51) is located radially outward from a rear edge of the forward blade (31). Blower.

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