EP3505769B1

EP3505769B1 - Multiblade centrifugal fan

Info

Publication number: EP3505769B1
Application number: EP18188101.2A
Authority: EP
Inventors: Akihiro Shigeta
Original assignee: Panasonic Intellectual Property Management Co Ltd
Current assignee: Panasonic Intellectual Property Management Co Ltd
Priority date: 2017-12-26
Filing date: 2018-08-08
Publication date: 2021-04-07
Anticipated expiration: 2038-08-08
Also published as: CN109958633B; CN109958633A; EP3505769A1; ES2871900T3; JP6844526B2; JP2019113037A

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a sirocco fan which is a multiblade centrifugal fan used in an air conditioner or the like for example.

Description of the Related Art

Conventionally, a multiblade centrifugal fan of this kind includes a scroll casing 101 and an impeller 102, as illustrated in FIG. 8, FIG. 9, FIG. 10 and FIG. 11 (for example, see Japanese Patent Laid-Open No. 2013-50031 ).
FIG. 8 illustrates a perspective view of a conventional multiblade centrifugal fan described in the gazette.
In addition, FIG. 9 illustrates a cross-sectional view (X-X' sectional view in FIG. 8) on a plane passing through a center axis of an impeller of the conventional multiblade centrifugal fan and a substantially center in a height direction of an air outlet.
FIG. 10 illustrates a perspective view of the impeller of the conventional multiblade centrifugal fan.
FIG. 11 illustrates a partial sectional view of a Y-Y' cross section in FIG. 10 of the impeller of the conventional multiblade centrifugal fan.
As illustrated in FIG. 8 and FIG. 9, the multiblade centrifugal fan includes a scroll casing 101 including an air outlet 103, a bellmouth 104 serving as an air inlet, a helical air flow path 105 and a tongue part 106 in a roughly circular arc shape connecting a lower part of the air outlet 103 with the air flow path 105, and a multiblade centrifugal impeller 102 inside the scroll casing 101, including many blades 109 annularly arranged from a main plate 108 integrated with a bearing 107, and blowing off air sucked from an inlet 110 formed at an end in a rotation axis direction facing the bellmouth 104 into a centrifugal direction from between the blades 109. A holding ring 111 for holding the blades 109 is provided on an axial end part on an outer periphery of the impeller 102, and near the tongue part 106 on an inner surface of the scroll casing 101 facing the holding ring 111, a recessed part 112 having a width wider than the holding ring 111 is provided. Thus, a gap dimension of the scroll casing 101 and the impeller 102 can be made closer than before, and noise and power consumption at the same air volume as before can be reduced.
As illustrated in FIG. 9, in the multiblade centrifugal fan including the scroll casing generally, a circulating flow W' in which part of air W blown off from the impeller passes through an inner side of the bellmouth and flows from an inlet into the impeller again is generated.
However, in the conventional configuration, there are problems that, in the partial sectional view of the holding ring 111 as illustrated in FIG. 11, when the circulating flow W' flowing near the holding ring 111 returns between the blades 109, separation of an air flow occurs at a connection part 111c where a holding ring first end face 111a which is substantially perpendicular to a center axis Z of the impeller 102 and is an endmost part of the impeller 102 and a holding ring inner surface 111b which is substantially parallel to the center axis Z of the impeller 102 and connected with the blades 109 are connected substantially at right angles, and noise increases.
JP 2012-140881 , forming the closest prior art, discloses a multiblade blower capable of reducing noise attributable to a cycle flow. The multiblade blower includes an impeller rotating around a rotary shaft and having a plurality of blades in a circumferential direction, and a casing accommodating the impeller and having a bellmouth in one of the axial directions of the rotary shaft for the impeller. At least part of communication sections located at a bellmouth side of the clearances between the blades is located outside the end of the bellmouth in a radial direction. The impeller has an air flow resistance part plugging a part of the communication sections and extending annularly along the circumferential direction.

SUMMARY OF THE INVENTION

In order to solve the conventional problem, a multiblade centrifugal fan according to the present invention, which is defined in appended claim 1, is provided, such a fan includes an impeller and a scroll casing disposed to surround the impeller, a holding ring of the impeller includes a holding ring first end face which is substantially perpendicular to a center axis of the impeller and is an endmost part of the impeller, a holding ring inner surface which is substantially parallel to the center axis of the impeller and connected with the blades, and a connection surface configured between the holding ring first end face and the holding ring inner surface.
Thus, even when an air flow separates at a connection part of the holding ring first end face and the connection surface and a connection part of the connection surface and the holding ring inner surface, the air flow sticks again to the connection surface or the holding ring inner surface and forms the flow along a wall surface.
Therefore, since the connection part of the holding ring first end face and the connection surface and the connection part of the connection surface and the holding ring inner surface are connected at an obtuse angle, the separation of the air flow is reduced compared to the connection part connected substantially at right angles.
The multiblade centrifugal fan of the present invention suppresses the separation of the air flow at the connection part of the connection surface and the holding ring inner surface when the circulating flow in which part of the air flow blown off in the centrifugal direction from the impeller passes through a gap between the bellmouth and the holding ring and is sucked again to the impeller flows in again from between the blades along the holding ring, and noise due to the separation of the air flow can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a multiblade centrifugal fan in a first embodiment of the present invention;
FIG. 2 is an A-A' sectional view of the multiblade centrifugal fan in the first embodiment of the present invention;
FIG. 3 is a B-B' sectional view of the multiblade centrifugal fan in the first embodiment of the present invention;
FIG. 4 is a perspective view of an impeller of the multiblade centrifugal fan in the first embodiment of the present invention;
FIG. 5 is a partial sectional view of a C-C' cross section of the impeller in the first embodiment of the present invention;
FIG. 6 is a partial sectional view of the C-C' cross section of a holding ring of a connection surface in an arc shape in the first embodiment of the present invention;
FIG. 7 is a perspective enlarged view of the impeller in the first embodiment of the present invention;
FIG. 8 is a perspective view of a conventional multiblade centrifugal fan;
FIG. 9 is an X-X' sectional view of the conventional multiblade centrifugal fan;
FIG. 10 is a perspective view of the impeller of the conventional multiblade centrifugal fan; and
FIG. 11 is a partial sectional view of a Y-Y' cross section of the impeller of the conventional multiblade centrifugal fan.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention relates to a multiblade centrifugal fan as defined in appended claim 1.
Thus, even when an air flow separates at a connection part of the holding ring first end face and the connection surface and a connection part of the connection surface and the holding ring inner surface, the air flow sticks again to the connection surface or the holding ring inner surface and forms the flow along a wall surface.
Therefore, since the connection part of the holding ring first end face and the connection surface and the connection part of the connection surface and the holding ring inner surface are connected at an obtuse angle, the separation of the air flow is reduced compared to the connection part connected substantially at right angles.
Thus, the separation of the air flow at the connection part of the connection surface and the holding ring inner surface when a circulating flow in which part of the air flow blown off in a centrifugal direction from the impeller passes through a gap between the bellmouth and the holding ring and is sucked again to the impeller flows in again from between the blades along the holding ring is suppressed, and noise due to the separation of the air flow can be reduced.
A first embodiment is that the connection surface is in an arc shape in a cross-sectional view in which the holding ring is cut in a center axis direction of the impeller at an arbitrary position. Thus, the separation of the air flow at the connection part of the holding ring first end face and the holding ring inner surface is reduced compared to a polygonal connection part.
In addition, generally, when a speed of the air flow is low, the separation of the air flow increases. Thus, even in a case where a difference from a pressure of a space between the bellmouth and the holding ring is relatively small and the speed of the circulating flow is low, the separation of the air flow at the connection surface is suppressed.
Therefore, even during a low-load operation in which a speed is low and the circulating flow becomes relatively slow, the separation of the air flow at the connection part of the connection surface and the holding ring inner surface when the air flow flows in again from between the blades is suppressed, and the noise due to the separation of the air flow can be reduced.
A second embodiment is that each of the blades is stretched to a position in contact with the connection surface. Thus, part of the flow along the holding ring is guided to the blade.
Therefore, even in the case where a rotation number of the impeller is high and the flow along the holding ring flows in at an angle facing an end part of the blade, a disturbance of the air flow due to a collision with the blade is suppressed.
Thus, even in the case of a high-load operation in which the rotation number of the impeller is highest, the separation of the air flow due to the collision with the blade when the air flow flowing along the holding ring flows in at the angle facing the end part of the blade is suppressed, and the noise due to the separation of the air flow can be reduced.
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the present invention is not limited by the embodiment.

(Embodiment 1)

FIG. 1 illustrates a perspective view of the multiblade centrifugal fan in the first embodiment of the present invention. In addition, FIG. 2 illustrates a cross-sectional view (A-A' sectional view in FIG. 1) viewing a longitudinal section at an arbitrary position between the bellmouth serving as an air inlet and the main plate of the impeller of the multiblade centrifugal fan in the first embodiment of the present invention from a bellmouth side to a center side of the impeller.
FIG. 3 illustrates a cross-sectional view (B-B' sectional view in FIG. 2) on a plane passing through a center axis of the impeller and a substantially center in a height direction of the air outlet of the multiblade centrifugal fan in the first embodiment of the present invention.
FIG. 4 illustrates a perspective view of the impeller of the multiblade centrifugal fan in the first embodiment of the present invention.
In FIG. 1 to FIG. 4, the multiblade centrifugal fan includes an impeller 1 and a scroll casing 2.
The impeller 1 includes a main plate 3, a bearing 4 disposed at a substantially center of the main plate 3 and integrated with the main plate 3, a plurality of blades 5 disposed radially with respect to the center axis of the main plate 3 so as to be tilted forward to a rotation direction M on the outer periphery of the main plate 3, and a holding ring 6 which fixes the outer periphery of the plurality of blades 5 on a side opposite to a part where the blades 5 and the main plate 3 are joined. To the bearing 4, a rotating shaft of a fan motor (not illustrated) is pivoted.
The scroll casing 2 includes an air outlet 7, a bellmouth 8 serving as an air inlet, and a tongue part 9 in a circular arc shape disposed at a position at which a gap between the outer periphery of the impeller 1 and the inner periphery of the scroll casing 2 is minimum.
FIG. 5 illustrates a partial sectional view of a C-C' cross section of the impeller in the first embodiment of the present invention.
In FIG. 5, the holding ring 6 includes a holding ring first end face 6a which is substantially perpendicular to the center axis of the impeller 1 and is the endmost part of the impeller 1, a holding ring second end face 6b which is substantially perpendicular to the center axis of the impeller 1 and is positioned facing the holding ring first end face 6a, a holding ring inner surface 6c which is substantially parallel to the center axis of the impeller 1 and connected with the blades 5, a holding ring outer surface 6d which is substantially parallel to the center axis of the impeller 1 and is an outermost periphery of the impeller 1, and a connection surface 6e configured between the holding ring first end face 6a and the holding ring inner surface 6c, and includes a first connection part 6f which is a connection part of the holding ring first end face 6a and the connection surface 6e and a second connection part 6g which is a connection part of the connection surface 6e and the holding ring inner surface 6c.
Note that, for the connection surface 6e, it is preferable that an angle D which is an angle formed by a line connecting the first connection part 6f with the second connection part 6g and the center axis Z of the impeller 1 on a side close to the holding ring 6 is 20° to 70°.
For the multiblade centrifugal fan configured as described above, the operation and the function will be described hereinafter. First, as illustrated in FIG. 2, by rotation of the impeller 1 in the rotating direction M, air W between the plurality of blades 5 is jetted to the outer periphery of the impeller 1 by the blades 5, collides with the inner periphery of the scroll casing 2, then flows along the inner periphery of the scroll casing 2 in the same direction as the rotating direction M, and is blown off from the air outlet 7. Then, the pressure of the air at the inner periphery of the impeller 1 declines, and the air is made to flow from the bellmouth 8 into the impeller 1 by a pressure difference from an atmospheric pressure.
The air is blown by the series of flow, and in the multiblade centrifugal fan like the one of the present embodiment in particular, the air jetted to the outer periphery of the impeller 1 at a high speed is converted to the pressure when the speed is lowered as the gap between the impeller 1 and the scroll casing 2 is enlarged from the tongue part 9, and compatibility of a high air volume and a static pressure is realized.
After the air flow W which is a main flow collides with the inner periphery of the scroll casing 2, a part is attracted to the part where the pressure of the air is low between the blades 5 and a circulating flow W' is generated. At the time, as illustrated in FIG. 3, the flow bypasses the holding ring 6 from a flow path formed at a gap between the inner surface of the bellmouth 8 and the impeller 1, and then flows again from between the blades 5 to the impeller 1.
In the present embodiment, since the connection surface 6e is configured between the holding ring first end face 6a and the holding ring inner surface 6c, the connection part 6f of the holding ring first end face 6a and the connection surface 6e and the connection part 6g of the connection surface 6e and the holding ring inner surface 6c are connected at the obtuse angle so that the separation of the air flow flowing in again to the impeller 1 is reduced compared to the impeller having the connection part connected substantially at right angles.
Thus, the circulating flow W' flowing along the holding ring 6 sticks again to the connection surface 6e and the holding ring inner surface 6c and can smoothly join the main flow W.
As described above, in the present embodiment, since the connection surface 6e is configured between the holding ring first end face 6a and the holding ring inner surface 6c, the connection part 6f of the holding ring first end face 6a and the connection surface 6e and the connection part 6g of the connection surface 6e and the holding ring inner surface 6c are connected at the obtuse angle so that the separation of the air is reduced compared to the connection part connected substantially at right angles, and the noise due to the separation of the air flow can be reduced.
In addition, FIG. 6 illustrates a partial sectional view of the C-C' cross section of the holding ring of the connection surface in the arc shape in the first embodiment of the present invention.
By turning the connection surface of the present embodiment to a connection surface 6h in the arc shape as illustrated in FIG. 6, the separation of the air flow is reduced compared to the connection surface 6e in a polygonal shape.
In addition, generally, when the speed of the air flow is low, the separation of the air flow increases. Thus, even in the case where the difference from the pressure of the space between the bellmouth 8 and the holding ring 6 is relatively small and the speed of the circulating flow W' is low, the separation of the air flow at the connection surface 6h in the arc shape is suppressed.
Therefore, even during the low-load operation in which the speed is low and the circulating flow W' becomes relatively slow, the separation of the air flow at the connection part of the connection surface 6h in the arc shape and the holding ring inner surface 6c when the air flow flows in again from between the blades 5 is suppressed, and the noise due to the separation of the air flow can be reduced.
In addition, FIG. 7 illustrates a perspective enlarged view of the impeller in the first embodiment of the present invention.
As illustrated in FIG. 7, in the present embodiment, a blade stretch part 5a for which a part joined with the holding ring 6 of the blade 5 is stretched to a position in contact with the connection surface 6h in the arc shape so that part of the flow along the connection surface 6h in the arc shape from the holding ring first end face 6a is guided to the blade 5.
Therefore, even in the case where the rotation number of the impeller 1 is high and the flow along the holding ring 6 flows in at the angle facing the end part of the blade 5, the disturbance of the air flow due to the collision with the blade 5 is suppressed.
Thus, even in the case of the high-load operation in which the rotation number of the impeller 1 is the highest, the separation of the air flow due to the collision with the blade 5 when the air flow flowing along the holding ring 6 flows in at the angle facing the end part of the blade 5 is suppressed, and the noise due to the separation of the air flow can be reduced.
As described above, the multiblade centrifugal fan according to the present invention suppresses the separation at the holding ring of the circulating flow in which part of the air flow jetted from the impeller outer periphery flows in from between the blades, and is applicable for purposes of an air conditioner, an air cleaner, a drier and a car air conditioner or the like.

1: impeller
2: scroll casing
3: main plate
5: blade
5a: blade stretch part
6: holding ring
6a: holding ring first end face
6b: holding ring second end face
6c: holding ring inner surface
6d: holding ring outer surface
6e: connection surface
6h: connection surface in the arc shape
7: air outlet
8: bellmouth (air inlet)

Claims

A multiblade centrifugal fan comprising: an impeller (1) including a main plate (3), a plurality of blades (5) disposed on an outer periphery of the main plate (3) radially with respect to a center axis of the main plate (3), and a holding ring (6) to fix an outer periphery of the plurality of blades (5) on a side opposite to a part where the blades (5) and the main plate (3) are joined; and a scroll casing (2) disposed to surround the impeller (1), the scroll casing (2) including an air outlet (7), and a bellmouth (8) serving as an air inlet,
wherein the holding ring (6) at least includes a holding ring first end face (6a) which is substantially perpendicular to a center axis (Z) of the impeller (1) and is an endmost part of the impeller (1), a holding ring second end face (6b) which is substantially perpendicular to the center axis (Z) of the impeller (1) and is positioned facing the holding ring first end face (6a), a holding ring inner surface (6c) which is substantially parallel to the center axis (Z) of the impeller (1) and connected with the blades (5), a holding ring outer surface (6d) which is substantially parallel to the center axis (Z) of the impeller (1) and is an outermost periphery of the impeller (1), and a connection surface (6e, 6h) configured between the holding ring first end face (6a) and the holding ring inner surface (6c),
characterized in that at the side opposite to a part where the blades and the main plate are joined, the holding ring (6) is an only member that fixes the plurality of blades (5) to each other.
The multiblade centrifugal fan according to claim 1, wherein the connection surface (6h) is in an arc shape in a cross-sectional view in which the holding ring (6) is cut in a center axis direction of the impeller (1) at an arbitrary position.
The multiblade centrifugal fan according to claim 1 or 2, wherein each of the blades (5) is stretched to a position in contact with the connection surface (6e, 6h).