Patent ID: 12228141

DETAILED DESCRIPTION

Hereinafter, a multi-blade centrifugal air-sending device100according to an embodiment will be described with reference to the drawings. In the following drawings includingFIG.1, relative dimensional relationships, shapes, and others of constituent members may differ from actual ones. Members having identical signs in the following drawings are identical or correspond to each other, which is common to the entire content of the description. For ease of understanding, terms indicating directions (for example, “upper”, “lower”, “forward”, “rearward”, and the other similar terms) are used, as appropriate. These terms are, however, merely thus used for convenience of description and are not intended to limit the arrangements and orientations of a device or components.

Embodiment 1

FIG.1is a schematic external view of a configuration of the multi-blade centrifugal air-sending device100according to Embodiment 1 as viewed in a direction parallel to a rotational axis RS.FIG.2is a sectional view in which a section of the multi-blade centrifugal air-sending device100inFIG.1along line A-A is schematically illustrated. With reference toFIG.1andFIG.2, a basic structure of the multi-blade centrifugal air-sending device100will be described.

As illustrated inFIG.1, the multi-blade centrifugal air-sending device100is an air-sending device of a multi-blade centrifugal type and includes a fan10that generates an airflow, and a scroll casing20that houses the fan10. The fan10includes a back plate11having a disk shape, a rim13(FIG.2) having an annular shape and facing the back plate11, and a plurality of blades12arranged at a peripheral portion of the back plate11in the circumferential direction of the back plate11. The back plate11is provided with a shaft portion11bto which a motor (not illustrated) is connected.

The scroll casing20includes a scroll portion21and a discharge portion22having a discharge port22bfor air, and rectifies the airflow blown out from the fan10in a centrifugal direction. The scroll casing20has a spiral shape, and an air passage20aexpanding gradually toward the discharge port22bis formed in the inside of the scroll casing20.

The scroll portion21forms the air passage20athat converts a dynamic pressure of the airflow generated by the rotation of the fan10into a static pressure. The scroll portion21includes a side wall23covering the fan10in the axial direction of the rotational axis RS of the fan10and each having an air inlet23bthrough which air is sucked; and a peripheral wall24surrounding the fan10from the outer side in the radial direction of the rotational axis RS. The scroll portion21also includes a tongue portion25positioned between the discharge portion22and a winding start portion24aof the peripheral wall24and constituting a curved surface. The tongue portion25is configured to guide the airflow blown out from the fan10in the centrifugal direction in the vicinity of the winding start portion24a,to be in a rotational direction R of the fan10to move toward the discharge port22bvia the scroll portion21.

The radial direction of the rotational axis RS is a direction perpendicular to the axial direction of the rotational axis RS. An internal space of the scroll portion21constituted by the peripheral wall24and the side wall23serves as the above-described air passage20a.In the air passage20a,the airflow blown out from the fan10flows along the peripheral wall24.

In the example illustrated inFIG.2, the multi-blade centrifugal air-sending device100is a double-suction-type centrifugal air-sending device configured to suck air from both end sides in the axial direction of the imaginary rotational axis RS of the fan10. The side wall23is disposed on both sides of the fan10in the axial direction of the rotational axis RS of the fan10. Each side wall23of the scroll casing20has the air inlet23bto enable air to circulate between the fan10and the outside of the scroll casing20. As illustrated inFIG.1, the air inlet23bhas a circular shape, and the fan10is disposed in the scroll casing20such that the center of the air inlet23band the center of the shaft portion11bof the fan10substantially coincide with each other.

As illustrated inFIG.2, the scroll casing20is a casing of a double suction type having, on both sides of the back plate11in the axial direction of the rotational axis RS of the fan10, the side wall23having the air inlet23b.The two side walls23are provided to face each other with the peripheral wall24interposed therebetween in the scroll casing20.

As illustrated inFIG.1, the air inlet23bprovided at each side wall23is formed by a bell mouth26. That is, the bell mouth26forms the air inlet23bin communication with a space formed by the back plate11and the plurality of blades12in the fan10. In the following description, the space formed by the back plate11and the plurality of blades12may be referred to as a flow passage11aof the fan10.

As illustrated inFIG.2, the bell mouth26rectifies the air sucked through the air inlet23bof each side wall23and causes the air to flow into a central portion of the fan10through a fan air inlet10a.The bell mouth26is provided to project from the side wall23toward the inside. More specifically, the bell mouth26is formed such that the opening diameter thereof decreases gradually from the side wall23of the scroll casing20toward the inside. With such a configuration, when the fan10rotates, the air in the vicinity of the air inlet23bof each side wall23flows smoothly along the bell mouth26and flows into the fan10efficiently through the fan air inlet10a.

As illustrated inFIG.1, the peripheral wall24is constituted by a wall surface curved in the rotational direction R of the fan10. The peripheral wall24is present, as illustrated inFIG.2, between the two side walls23facing each other in the scroll casing20and is provided, as illustrated inFIG.1, to connect portions of the outer peripheral edges of the two side walls23to each other. The peripheral wall24has a curved inner peripheral surface24cand guides the airflow blown out to the air passage20ain the scroll portion21from the fan10, so as to flow along the inner peripheral surface24cto the discharge port22b.

The peripheral wall24has a configuration in which the wall surface curved as illustrated inFIG.1extends parallel to the axial direction of the rotational axis RS of the fan10as illustrated inFIG.2. The peripheral wall24may have a form inclined with respect to the axial direction of the rotational axis RS of the fan10, and is not limited to having the form disposed parallel to the axial direction of the rotational axis RS.

As illustrated inFIG.1, the peripheral wall24covers the fan10from the outer side in the radial direction of the shaft portion11bof the fan10, and the inner peripheral surface24cof the peripheral wall24faces end portions of the plurality of later-described blades12on the outer peripheral side. That is, the inner peripheral surface24cof the peripheral wall24faces the air blowing-out side of the blades12of the fan10. The peripheral wall24is provided to extend in the rotational direction R of the fan10from the winding start portion24apositioned at the boundary between the peripheral wall24and the tongue portion25to a winding end portion24bpositioned at the boundary between the discharge portion22and the scroll portion21on the side away from the tongue portion25. The winding start portion24ais, of the peripheral wall24constituted by the curved wall surface, an end portion on the upstream side of the airflow generated by the rotation of the fan10, and the winding end portion24bis an end portion of the peripheral wall24on the downstream side of the airflow generated by the rotation of the fan10. More specifically, the peripheral wall24has a spiral shape. The spiral shape is, for example, a logarithmic spiral, an Archimedes' spiral, or a spiral shape based on an involute curve or any other curve. With such a configuration, the airflow blown out from the fan10into the air passage20aof the scroll casing20flows in the gap between the fan10and the peripheral wall24smoothly to the direction of the discharge portion22. Therefore, the static pressure of air increases in the rotational direction R of the fan10from the tongue portion25toward the discharge portion22in the scroll casing20.

The discharge portion22forms the discharge port22bthrough which the airflow that has been generated by the rotation of the fan10and passed through the air passage20aof the scroll portion21is discharged. The discharge portion22is constituted by a hollow pipe whose section orthogonal to the flow direction of discharged air has a rectangular shape. The discharge portion22is constituted by, for example, plate-shaped four side surfaces. Specifically, the discharge portion22includes an extended plate221smoothly connected to the winding end portion24bof the peripheral wall24, and a diffuser plate222extending from the tongue portion25to face the extended plate221. The discharge portion22also includes a first side wall portion and a second side wall portion (not illustrated) each extended from a corresponding one of the two side walls23to connect both ends of the extended plate221and the diffuser plate222in the axial direction of the rotational axis RS to each other. The sectional shape of the discharge portion22is not limited to a rectangular shape. The discharge portion22forms a discharge-side air passage22athat guides the airflow discharged from the fan10and flowing through the gap between the peripheral wall24and the fan10, to be discharged to the outside of the scroll casing20.

The tongue portion25is formed between the diffuser plate222of the discharge portion22and the winding start portion24aof the peripheral wall24in the scroll casing20. The tongue portion25is formed to have a predetermined radius of curvature, and the peripheral wall24is smoothly connected to the diffuser plate222with the tongue portion25interposed therebetween. The tongue portion25suppresses the inflow of air from the winding end portion to the winding start portion of the spiral air passage20aformed in the inside of the scroll casing20. In other words, the tongue portion25has a role of separating the airflow flowing from an upstream portion of the air passage20ain the rotational direction R of the fan10and the airflow flowing from a downstream portion of the air passage20atoward the discharge port22bin a discharge direction from each other. The static pressure of the airflow flowing into the discharge-side air passage22aof the discharge portion22increases while the airflow passes through the scroll casing20, to be higher than in the scroll casing20. The tongue portion25is thus configured to have a function of partitioning such different pressures.

FIG.3is a schematic view of a configuration of the fan10of the multi-blade centrifugal air-sending device100inFIG.1as viewed in a direction parallel to the rotational axis RS.FIG.4is a sectional view in which a section of the fan10inFIG.3along line B-B is schematically illustrated. As illustrated inFIG.3, the fan10is a centrifugal fan. The fan10is constituted by, for example, a resin material, and, for example, the back plate11, the plurality of blades12, and the rim13can be integrally molded by injection molding. The fan10is configured to be driven to rotate by, for example, a motor (not illustrated) and to forcibly send air in the centrifugal direction, that is, radially outward by a centrifugal force generated by rotating and suck air through the fan air inlet10a(refer toFIG.4) provided on the side of the rim13. The fan10is rotated by, for example, a motor in the rotational direction R.

As illustrated inFIG.4, the back plate11may be formed such that the wall thickness thereof increases toward the center in the radial direction with the rotational axis RS as the center, or may be formed to have a thickness that is constant in the radial direction with the rotational axis RS as the center. The back plate11may have a shape other than a disk shape as long as the back plate11has a plate shape and may have, for example, a polygonal shape or any other shape. A motor (not illustrated) is connected to the shaft portion11bprovided at a center portion of the back plate11, and the back plate11is driven to rotate by the motor via the shaft portion11b.

As illustrated inFIG.3, the plurality of blades12are disposed in the circumferential direction of a plate surface111of the back plate11with the rotational axis RS as the center such that a predetermined interval is formed between mutually adjacent blades12. The plurality of blades12disposed at the back plate11form the cylindrical shape of the fan10. A gap G formed between mutually adjacent blades12constitutes the flow passage11aof the fan10.

Each of the plurality of radially provided blades12includes a sirocco blade portion30constituted by a forward blade, and a turbo blade portion40constituted by a rearward blade. The turbo blade portion40is connected to the sirocco blade portion30in the radial direction, and each blade12has a shape curved in the radial direction. The turbo blade portion40is provided on the inner peripheral side with respect to the sirocco blade portion30to be continuous with the sirocco blade portion30. The sirocco blade portion30and the turbo blade portion40are smoothly connected to each other at a blade boundary12bbetween the sirocco blade portion30and the turbo blade portion40.

As illustrated inFIG.3andFIG.4, in the rotation of the back plate11about the rotational axis RS, an end surface of each blade12on the inner peripheral side is a blade leading edge12f,and an end surface of each blade12on the outer peripheral side is a blade trailing edge12r.In the example illustrated inFIG.3, the turbo blade portion40is linearly formed from the blade boundary12bto the blade leading edge12f. As illustrated inFIG.4, the blade leading edge12fis inclined with respect to the axial direction of the rotational axis RS such that the blade leading edge12fgradually approaches the rotational axis RS from the side of the rim13toward the side of the back plate11in the axial direction of the rotational axis RS. The blade trailing edge12rand the blade boundary12bare each substantially parallel to the rotational axis RS. The detailed configuration of each of the blades12will be described later.

As illustrated inFIG.4, each of the plurality of blades12is provided between the back plate11and the rim13in the axial direction of the rotational axis RS. In the axial direction of the rotational axis RS, one end of each of the blades12is connected to the back plate11, and the other end of each of the blades12extends to the position of the rim13.

In the following description, the one end of each blade12connected to the back plate11and the other end of the blade12on the side of the rim13in the axial direction of the rotational axis RS may be referred to as an end portion12don the side of the back plate11and an end portion12uon the side of the rim13, respectively. In addition, in the following description, a portion of the blade leading edge12fof each of the blades12connected to the end portion12don the side of the back plate11is referred to as a main-plate-side inner peripheral end12fd, and a portion of the blade leading edge12fof each of the blades12connected to the end portion12uon the side of the rim13is referred to as a side-plate-side inner peripheral end12fu.

InFIG.3, a first imaginary circle C1passing through the main-plate-side inner peripheral ends12fdof the blade leading edges12fof the plurality of blades12is indicated by a dash-dotted line, and a third imaginary circle C3passing through the blade boundaries12bof the plurality of blades12is indicated by a dashed line. In addition, a second imaginary circle C2formed by projecting the inner peripheral ends, that is, the air inlets23bof the side wall23of the scroll casing20illustrated inFIG.1in the axial direction is indicated by a dashed double-dotted line inFIG.3. The first imaginary circle C1, the second imaginary circle C2, and the third imaginary circle C3are each a circle centered at the imaginary rotational axis RS of the back plate11.

In a state in which the fan10is housed in the scroll casing20as illustrated inFIG.2, the end portion12uof each blade12on the side of the rim13extends along the side wall23to be substantially parallel to the side wall23, and a portion of each blade12extends toward the inner side further than the inner peripheral ends of the side wall23. In the example illustrated inFIG.2, the end portion12uof each blade12on the side of the rim13and the end portion12dthereof on the side of the back plate11are substantially parallel to each other and extend linearly in a direction perpendicular to the axial direction of the rotational axis RS.

The rim13maintains the positional relationship of the tips of the blades12and reinforces the plurality of blades12. The fan air inlet10afor causing a gas to flow into the flow passage11aof the fan10is provided on the side of the rim13in the fan10.

In the example illustrated inFIG.4, the rim13is provided on the side of the blade trailing edges12rat the end portions12uof the plurality of blades12. In addition, in the example illustrated inFIG.4, the rim13and the plurality of blades12are provided on both sides of the back plate11in the axial direction of the rotational axis RS. The rim13provided on the side of the plate surface111of the back plate11on one side couples the plurality of blades12disposed on the side of the plate surface111of the back plate11on the one side to each other. The rim13provided on the side of the plate surface112of the back plate11on the other side couples the plurality of blades12disposed on the side of the plate surface112of the back plate11on the other side to each other.

As illustrated inFIG.2, the fan10is housed in the scroll casing20such that the side wall23of the scroll casing20faces the end portions12uof the plurality of blades12of the fan10. Specifically, the fan10is set in the scroll casing20such that the center of the fan air inlet10aprovided on the side of the rim13in the fan10and the center of the air inlet23bprovided at each side wall23of the scroll casing20coincide with each other. The fan10is supported about an axis by the scroll casing20to be rotatable.

Since a portion of each blade12extends on the inner peripheral side further than the inner peripheral ends of the side wall23as described above, the air sucked through the fan air inlet10ais easily taken into the flow passage11aof the fan10due to the extended blade portion. Since the blade leading edge12fis inclined as described with reference toFIG.4, it is possible to reduce resistance on the side of the rim13at the blade portion extending further on the inner peripheral side than the inner peripheral ends of the side wall23, and possible to suppress, for example, obstruction of air suction into the back plate11and an increase of noise.

Since the turbo blade portion40is provided on the inner peripheral side with respect to the sirocco blade portion30as illustrated inFIG.3, the gap G between mutually adjacent blades12is inclined from the side of the blade leading edge12ftoward the blade boundary12bin a direction opposite to the rotational direction R. Therefore, the air caused by the rotation of the fan10to flow into a central portion through the fan air inlet10acan be highly efficiently taken into and sent to the flow passage11aof the fan10. It is thus possible to obtain an effect of increasing the air volume.

FIG.5is a partial perspective view in which a portion of an outer peripheral portion of the fan10inFIG.3is enlarged. InFIG.5, a portion of the fan10on the side of the plate surface111of the back plate11on one side is illustrated. Hereinafter, with the side of the rim13and the side of the back plate11in the axial direction of the rotational axis RS being defined as the upper side and the lower side, respectively, a detailed configuration of the blades12will be described with reference toFIG.3andFIG.5.

As illustrated inFIG.5, in the blades12, the blade boundaries12bindicated by the third imaginary circle C3are positioned on the outer peripheral side with respect to the side-plate-side inner peripheral ends12fuof the blade leading edges12f.The end portion12uof each blade12on the upper side includes an upper end portion constituting the upper surface of the sirocco blade portion30and an upper end portion constituting the upper surface of the turbo blade portion40. The end portion12dof each blade12on the lower side includes a lower end portion constituting the lower surface of the sirocco blade portion30and a lower end portion constituting the lower surface of the turbo blade portion40. The turbo blade portion40includes a first turbo blade portion41connected to the sirocco blade portion30, and a second turbo blade portion42on the inner peripheral side with respect to the first turbo blade portion41. The first turbo blade portion41includes the entirety of the upper end portion of the turbo blade portion40and has a quadrangular shape when the blade12is viewed from the rear side in the rotational direction R. The second turbo blade portion42includes the entirety of the blade leading edge12fof the blade12and has a triangular shape when the blade12is viewed from the rear side in the rotational direction R.

In a state in which the fan10is housed in the scroll casing20as illustrated inFIG.1, the blade boundaries12bof the blades12indicated by the third imaginary circle C3inFIG.5are positioned on the outer peripheral side with respect to the inner peripheral ends of the side wall23indicated by the second imaginary circle C2.

In the example illustrated inFIG.5, the side-plate-side inner peripheral ends12fuof the blade leading edges12fare positioned at the inner peripheral ends of the side wall23(refer toFIG.1) indicated by the second imaginary circle C2in the radial direction. That is, in the example illustrated inFIG.5, the entirety of the upper surface of the first turbo blade portion41is covered by the side wall23, and the entirety of the second turbo blade portion42is exposed on the inner side from the side wall23. In the radial direction, the positions of the side-plate-side inner peripheral ends12fuof the blade leading edges12fdo not need to coincide with the positions of the inner peripheral ends of the side wall23. As long as at least a portion of the turbo blade portion40is positioned on the inner peripheral side with respect to the inner peripheral ends of the side wall23in the radial direction, air can be taken into the flow passage11aof the fan10by an extended portion of each blade12. Preferably, in order to increase the suction air volume also on the side of the rim13of the blades12, the side-plate-side inner peripheral ends12fuof the blade leading edges12fare positioned on the inner peripheral side with respect to the inner peripheral ends of the side wall23(FIG.1) indicated by the second imaginary circle C2in the radial direction.

FIG.6is a view of a configuration of a portion of the outer peripheral portion of the fan10illustrated inFIG.5as viewed in a direction parallel to the rotational axis RS. As illustrated inFIG.6, in each blade12set on the back plate11, the main-plate-side inner peripheral end12fdand the side-plate-side inner peripheral end12fuof the blade leading edge12fare substantially parallel to each other.

In the example illustrated inFIG.6, each of the blades12has a wall thickness that is substantially uniform in the radial direction. As illustrated inFIG.6, a wall thickness W2of each blade12at the end portion12uon the side of the rim13is thinner than a wall thickness W1of the blade12at the end portion12d(FIG.5) on the side of the back plate11, and the wall thickness of the blade12is configured to become thinner gradually from the end portion12dtoward the end portion12u.Therefore, the gap G formed between mutually adjacent blades12expands gradually from the blade leading edge12ftoward the blade trailing edge12rin the radial direction and expands gradually from the side of the back plate11toward the side of the rim13in the axial direction.

With reference toFIG.1toFIG.6, operation of the multi-blade centrifugal air-sending device100will be described. As illustrated inFIG.1, when the fan10is driven to rotate about the rotational axis RS by a motor (not illustrated), air outside the multi-blade centrifugal air-sending device100flows into a central portion of the fan10in the axial direction through the air inlets23bof the scroll casing20and the fan air inlet10a. The air that has flowed into the central portion of the fan10is taken into the flow passage11aof the fan10from the blade leading edges12fdue to the rotation of the fan10and flows radially outward in the flow passage11a.

As described with reference toFIG.5andFIG.6, the gap G formed between mutually adjacent blades12expands gradually from the blade leading edge12ftoward the blade trailing edge12rand expands gradually from the side of the back plate11toward the side of the rim13. Therefore, it is possible to increase the suction air volume on the side of the rim13at the second turbo blade portion42, send the air that has been taken into the flow passage11afrom the side of the back plate11at the blade leading edge12f,to the side of the rim13, that is, to the upper side, and increase the air volume on the side of the rim13even in a configuration in which the blade leading edge12fis inclined. The airflow that flows toward the blade boundary12bon the upper side of the flow passage11ain which the air volume is increased is highly efficiently pressurized by the first turbo blade portion41extending from the back plate11to the rim13and covered by the side wall23(FIG.1).

The pressurized airflow that has flowed along the first turbo blade portion41in the flow passage11areaches the blade boundary12band then flows toward the blade trailing edge12rwhile changing the traveling direction thereof along the sirocco blade portion30. Thereafter, the airflow that has reached the blade trailing edge12ris sent from the flow passage11aof the fan10to the air passage20aof the scroll casing20. The airflow that has been sent from the fan10to the air passage20ais further pressurized when passing through the spiral air passage20aexpanding toward the discharge port22b,and is blown out to the outer peripheral side through the discharge port22b.

In Embodiment 1, the multi-blade centrifugal air-sending device100that is a double-suction-type centrifugal air-sending device has been described. The multi-blade centrifugal air-sending device100, however, may be a single-suction-type centrifugal air-sending device. The number of the blades12is not limited to that in the drawings.

As described above, in Embodiment 1, the multi-blade centrifugal air-sending device100includes the fan10and the scroll casing20having a spiral shape. The fan10includes the back plate11having a disk shape, the plurality of blades12arranged in the circumferential direction at the peripheral portion of the back plate11, and the rim13having an annular shape and coupling the plurality of blades12to each other. Respective first end portions (end portions12d) of the plurality of blades12on one side are connected to the back plate11, and the rim13is provided at respective second end portions (end portions12u) of the plurality of blades12on a side opposite to the one side where the respective first end portions are present. The scroll casing20includes the side wall23which faces the fan10where the air inlet23bis provided and the peripheral wall24. The scroll casing20houses the fan10such that the side wall23faces the second end portions (end portions12u) of the plurality of blades12, and is configured such that air is introduced through the air inlets23band blown out to the outer peripheral side. Each blade12includes the sirocco blade portion30constituted by the forward blade, and the turbo blade portion40constituted by the rearward blade and provided on the inner peripheral side with respect to the sirocco blade portion30. The second end portion (end portion12u) of each blade12extends along the side wall23and includes an end surface of the sirocco blade portion30and an end surface of the turbo blade portion40. Each blade12extends from the inner peripheral ends of the side wall23toward the inner peripheral side such that a portion of the end surface of the turbo blade portion40is positioned on the inner peripheral side with respect to the inner peripheral ends of the side wall23while a remaining portion of the end surface of the turbo blade portion40is covered by the side wall23.

Consequently, the flow passage11acovered by the side wall23and in which the gap G between the blades12is widened gradually toward the outer peripheral side by the turbo blade portion40is formed on the side of the rim13in the axial direction of the fan10. It is thus possible to provide the multi-blade centrifugal air-sending device100capable of pressurizing air on the side of the rim13in the flow passage11aof the fan10.

The wall thicknesses W1and W2of each blade12are configured to decrease gradually from the first end portion (end portion12d) on the side of the back plate11toward the second end portion (end portion12u) on the side of the rim13. Consequently, the gap G formed between the mutually adjacent blades12expands gradually from the end portion12don the side of the back plate11toward the end portion12uon the side of the rim13in the axial direction, and it is thus possible to increase the suction air volume on the side of the rim13.

The turbo blade portion40of each blade12is formed to extend linearly from the side of the sirocco blade portion30toward the inner peripheral side. Consequently, it is possible to simplify the shape of each blade12and possible to facilitate manufacture of the fan10and reduce costs thereof, compared with a configuration in which the turbo blade portion40is curved in each blade12.

Embodiment 2

FIG.7is a schematic view of a configuration of the turbo blade portion40of each blade12of the multi-blade centrifugal air-sending device100according to Embodiment 2 as viewed in a direction parallel to the rotational axis RS. In Embodiment 2, the positional relationship between the main-plate-side inner peripheral end12fdand the side-plate-side inner peripheral end12fuof the blade leading edge12fdiffers from that in Embodiment 1.

InFIG.7, the arrow F21indicates the direction of an airflow that passes the vicinity of the main-plate-side inner peripheral end12fdof the blade leading edge12fduring rotation of the fan10, and the arrow F22indicates the direction of an airflow that passes the vicinity of the side-plate-side inner peripheral end12fuof the blade leading edge12fduring rotation of the fan10. While the fan10rotates, as illustrated inFIG.7, an airflow in which the percentage of a circumferential-direction component increases toward the outer peripheral side of the blade leading edge12fis generated in the vicinity of the blade leading edge12f.In other words, at the blade leading edge12f,the percentage of the circumferential-direction component in the airflow that passes the side-plate-side inner peripheral end12fuis larger than the percentage of the circumferential-direction component in the airflow that passes the main-plate-side inner peripheral end12fd.

Thus, in Embodiment 2, the blade leading edge12fis configured such that an angle θ2formed by the side-plate-side inner peripheral end12fuof the blade leading edge12fand a pressure surface121is larger than an angle θ1formed by the main-plate-side inner peripheral end12fdof the blade leading edge12fand the pressure surface121. A corner where the blade leading edge12fand the pressure surface121meet each other may be chamfered into an arc shape. In Embodiment 2, the angle θ1and the angle θ2satisfy the following relationship.
[Math. 1]
0°<θ1 <θ2<90°  (Formula 1)

As described above, in Embodiment 2, the blade leading edge12fof each blade12is formed such that the angle θ2formed by the side-plate-side inner peripheral end12fuof the blade leading edge12fand the pressure surface121is larger than the angle θ1formed by the main-plate-side inner peripheral end12fdof the blade leading edge12fand the pressure surface121.

Consequently, it is possible to suppress generation of a separation vortex W at a suction surface122on the side of the side-plate-side inner peripheral end12fuof the blade leading edge12f,and possible to suppress a decrease of the air volume due to separation of the airflow from the suction surface122and suppress an increase of noise due to generation of the separation vortex W.

Embodiment 3

FIG.8is a schematic view of a configuration of the turbo blade portion40of each blade12of the multi-blade centrifugal air-sending device100according to Embodiment 3 as viewed in a direction parallel to the rotational axis RS. As with Embodiment 2, the configuration in Embodiment 3 also satisfies the relationship in Formula 1. In Embodiment 3, the shape of the turbo blade portion40in the radial direction differs from those in Embodiment 1 and Embodiment 2. InFIG.8, the arrow F31indicates the direction of an airflow that passes the vicinity of the main-plate-side inner peripheral end12fdof the blade leading edge12fduring rotation of the fan10.

As illustrated inFIG.8, the turbo blade portion40is constituted by a linear portion extending linearly from the blade boundary12b(FIG.3) with respect to the sirocco blade portion30toward the inner peripheral side, and an inner peripheral end portion42bcurved and connected to the linear portion in the radial direction. The inner peripheral end portion42bof the turbo blade portion40includes at least a portion of the blade portion extending toward the inner side further than the inner peripheral end of the side wall23inFIG.1. In the example illustrated inFIG.8, the linear portion of the turbo blade portion40is constituted by the first turbo blade portion41and a portion42aof the second turbo blade portion42on the side of the first turbo blade portion41. The inner peripheral end portion42bof the turbo blade portion40is constituted by a remaining portion of the second turbo blade portion42excluding the portion42a.

The inner peripheral end portion42bof the turbo blade portion40is curved with respect to the linear portion in a direction opposite to the rotational direction R of the fan10, and has a shape protruding in the rotational direction R of the fan10.

Generally, the direction of the airflow flowing into the fan10of the multi-blade centrifugal air-sending device100varies depending on an environment (including atmospheric pressure conditions, and other conditions) in which the multi-blade centrifugal air-sending device100is used and on the capacity range to which the multi-blade centrifugal air-sending device100belongs. For example, under a high-pressure environment, the airflow does not easily flows in the radial direction compared with under a low-pressure environment, and the percentage of the circumferential-direction component in the airflow increases compared with under a low-pressure environment. Meanwhile, under a low-pressure environment, the airflow easily flows in the radial direction compared with under a high-pressure environment, and the percentage of a radial-direction component in the airflow increases compared with under a high-pressure environment.

Thus, in Embodiment 3, the inner peripheral end portion42bof the turbo blade portion40has a curved shape to thereby configure such that an inclination of the blade leading edge12fin accordance with a usage environment can be easily formed while maintaining the relationship in Formula 1 by adjusting the degree of the curve.

As described above, in the multi-blade centrifugal air-sending device100according to Embodiment 3, the turbo blade portion40of each blade12is constituted by the linear portion extending linearly from the side of the sirocco blade portion30toward the inner peripheral side, and the inner peripheral end portion42bcurved and connected to the linear portion in the radial direction.

Consequently, it becomes easy to provide the multi-blade centrifugal air-sending device100in which the inclination of the main-plate-side inner peripheral end12fdvaries while the relationship in Formula 1 is satisfied. Therefore, it is possible to provide the multi-blade centrifugal air-sending device100capable of, in response to an airflow whose direction changes at the main-plate-side inner peripheral end12fdof the blade leading edge12fdepending on an environment in which the multi-blade centrifugal air-sending device100is used, pressurizing the airflow highly efficiently while suppressing separation of the airflow from the suction surface122.

Note that the embodiments can be combined together, and modifications and omissions can be performed, as appropriate, in each embodiment. For example, the rim13of the fan10may be configured to extend from the blade trailing edges12rto the positions of the inner peripheral ends of the side wall23indicated by the second imaginary circle C2to cover the entirety of the end portion12uof each blade12.