EP1411248A1

EP1411248A1 - IMPELLER OF CENTRIFUGAL BLOWER, AND CENTRIFUGAL BLOWER HAVING THE IMPELLER

Info

Publication number: EP1411248A1
Application number: EP02738677A
Authority: EP
Inventors: Masahito c/o DAIKIN INDUSTRIES LTD. HIGASHIDA
Original assignee: Daikin Industries Ltd
Current assignee: Daikin Industries Ltd
Priority date: 2001-06-28
Filing date: 2002-06-12
Publication date: 2004-04-21
Anticipated expiration: 2022-06-12
Also published as: CN1395045A; EP1411248B8; ES2387063T3; CN1212479C; WO2003002873A1; EP1411248B1; ATE556226T1; EP1411248A4; CN2575343Y

Abstract

The present invention provides an impeller that is capable of reducing noise and provides a low noise centrifugal fan.

A multi-blade fan (40) is primarily composed of an impeller (63), a casing (11) that covers the impeller (63), and a motor (14) that rotates the impeller (43). The impeller (43) includes a disk-shaped main plate (61) to which a plurality of blades (33) are fixed to the outer peripheral edge thereof, and an annular side plate (62) to which the other ends of the plurality of blades (33) are connected. The plurality of blades (33) (described below) are formed around the outer peripheral edge of the main plate (61) and are equidistant with respect to each other in the rotational direction. Jagged shaped wave form members (64) are formed around a circumference of the inner peripheral edge near the inner peripheral edges of the plurality of blades (33). Jagged shaped wave form members (66) are formed on the main plate (61) side of the side plate (62).

Description

TECHNICAL FIELD

The present invention relates to an impeller for a centrifugal fan and a centrifugal fan equipped with the same. More particularly, the present invention relates to an impeller for a centrifugal fan in which the ends of a plurality of blades that extend from a main plate are connected by means of an annular side plate, and to a centrifugal fan equipped with the same.

BACKGROUND ART

A centrifugal fan is employed in devices such as air purifiers, air conditioners, and the like (hereinafter referred to as "air conditioners") in order to blow air. An conventional centrifugal fan known as a multi-blade fan is shown in Figs. 1-3. Fig. 1 shows lateral cross-sectional views of a conventional multi-blade fan, Fig. 2 shows a perspective view of an impeller for the conventional multi-blade fan, and Fig. 3 shows a plan view of the impeller for the conventional multi-blade fan.
The multi-blade fan 10 includes an impeller 13, a casing 11 that covers the impeller 13, and a motor 14 that rotates the impeller 13. The impeller 13 includes a disk-shaped main plate 31 to which one end of each of a plurality of blades 33 are fixed to the outer peripheral edge thereof, and an annular side plate 32 to which the other ends of the blades 33 are connected. An air discharge port 11a, and an air intake port 11b that is surrounded by a bell mouth 12, are formed in a casing 11. The intake port 11b faces the side plate 32 of the impeller 13. In addition, the discharge port 11a is formed in a direction that is perpendicular to the intake port 11b so that air is blown out in a direction approximately perpendicular to a rotational axis O-O of the impeller 13.
When the motor 14 rotates to operate the multi-blade fan 10, the impeller 13 rotates in a rotational direction R (shown in Fig. 3) with respect to the casing 11. This allows each blade 33 of the impeller to scoop out air from the inner peripheral side of the impeller 13 to a space on the outer peripheral side thereof, draw in air from the intake port 11b into the inner peripheral space of the impeller 13, and blow the air that was pushed out to the outer peripheral side of the impeller 13 through the discharge port 11a. In other words, the multi-blade fan 10 draws in air from the intake port 11b and blows air out from the discharge port 11a.
This type of multi-blade fan 10 produces turbulent vortices that causes noise to be produced near the main plate 31. More specifically, these turbulent vortices are generated by the mechanism described below.
As shown in Fig. 1(a), air drawn into the interior of the impeller 13 from the intake port 11b mainly flows toward the main plate 31 and then gradually toward the outer periphery (see air flow W). However, as shown in Fig. 1(b), a portion of the air drawn in from the intake port 11b collides with the main plate 31, and then flows toward the outer peripheral side near the main plate 31 (see air flow X). Turbulent vortices are generated in this air flow X due to the collision with the main plate 31. The turbulent vortices flow in the air flow X toward the outer periphery and further merge with the air flow that collides with the main plate 31. The turbulent vortices in the air flow X then gradually grow, and the biggest turbulent vortices are formed on the inner peripheral edges of the blades 33. These enlarged turbulent vortices are scooped out toward the outer periphery by the blades 33, and this generates noise.
In addition, swirling vortices are produced in this type of multi-blade fan 10 in which the centers thereof are near the outer peripheral edge of the side plate 32. The swirling vortices do not assist the impeller 13 to blow air, and thus as a result, the swirling vortices cause noise and reduce fan efficiency. More specifically, the swirling vortices are generated by the mechanism described below.
As shown in Fig. 1(a), air drawn into the interior of the impeller 13 from the intake port 11b first flows toward the main plate 31 and then gradually toward the outer periphery (see air flow W). As shown in Fig. 1(c), a portion of the air inside the casing 11 is scooped out to the outer periphery of the impeller 13, and then swirling vortices Y are produced near the side plate 32 such that air is again drawn in from near the bell mouth 12 of the impeller 13 to the inner peripheral side of the impeller 13. Because of this, a portion of the air cannot be effectively blown, and this portion corresponds to a ratio b/B (hereinafter referred to as blockage factor B_F) between a length b in the axial direction of the portion of the impeller 13 that produces the swirling vortices Y and a length B in the axial direction of the entire impeller 13. Because of this, there will be a reduction in fan efficiency and noise will be generated.
There is a need to further reduce the amount of noise generated by multi-blade fans employed in air conditioners. In addition, the noise caused by turbulent vortices generated near the main plate is not limited to multi-blade fans, but is also produced in centrifugal fans that include a turbo fan and the like.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide an impeller that is capable of reducing noise, and to provide a low noise centrifugal fan.
An impeller of a centrifugal fan disclosed in claim 1 includes a main plate that rotates about a rotational axis, a plurality of blades that are annularly disposed about the rotational axis with one end of each of the plurality of blades fixed to the main plate, and an annular side plate that connects with the other ends of the plurality of blades. Then, jagged shaped wave form members are at least formed on the side plate side of the main plate surface near the inner peripheral edges of the plurality of blades.
With this centrifugal fan impeller, turbulent vortices that grow due to the collision of the air flow with the main plate and the merger with the air flow will be reduced in size immediately before reaching the blades because the jagged shaped wave form members are formed on at least the side plate side of the main plate surface near the inner peripheral edges of the blades. This allows the noise generated when the air flow is scooped out by the blades to be reduced.
As noted above, reducing the turbulent vortices immediately before they are scooped out by the blades is most effective because the turbulent vortices grow from the inner peripheral side of the main plate toward the outer peripheral side thereof. In other words, the position in which the wave form members are formed must at least be on the side plate side of the main plate surface near the inner peripheral edges of the blades. Furthermore, the wave form members are preferably placed inside an area that is the length in the radial direction of the blades from the inner peripheral edges of the blades to the inner peripheral sides thereof so that the turbulent vortices that were reduced in size by the wave form members will not re-grow.
In addition, the wave form members may not only be placed near the inner peripheral edges of the blades but may also be placed near the rotational axis. In this way, the turbulent vortices produced when the air flow again collides with the main plate can be reduced.
The impeller of a centrifugal fan disclosed in claim 2 includes a main plate that rotates about a rotational axis, a plurality of blades that are annularly disposed about the rotational axis with one end of each of the plurality of blades fixed to the main plate, and an annular side plate that connects with the other ends of the plurality of blades. Then, jagged shaped wave form members are formed on the main plate side of the side plate surface.
With this centrifugal fan impeller, pressure fluctuations near the impeller exit of the side plate will be reduced because the jagged shaped wave form members are formed on the main plate side of the side plate surface. When this occurs, it will become difficult for the air flow scooped out by the impeller on the exit side to be again drawn into the inner peripheral side of the impeller from the side plate side in the rotational axis direction of the impeller, and thus swirling vortices produced near the side plate will be reduced. This allows fan efficiency to improve and noise to be reduced because the B_F value will be reduced and the portion of the impeller can effectively blow air will be enlarged.
The impeller for a centrifugal fan disclosed in claim 3 is the impeller disclosed in claim 1 or claim 2, in which the wave form members are triangular wave forms.
The impeller for a centrifugal fan disclosed in claim 4 is the impeller disclosed in claim 1 or claim 2, in which the wave form members are sine wave forms.
The impeller for a centrifugal fan disclosed in claim 5 is the impeller disclosed in claim 1 or claim 2, in which the wave form members are rectangular wave forms.
The impeller for a centrifugal fan disclosed in claim 6 is the impeller disclosed in any of claims 1 to 5, in which the wave form members have wave pitches in a range between 2 mm and 8 mm and wave heights in a range between 1 mm and 5 mm.
With the impeller for a centrifugal fan of claims 3 to 6, the shapes and dimensions of the wave form members are specified.
When these wave form members are provided on the side plate side of the main plate surface near the inner peripheral side of the blades, the wave form members will be better able to reduce noise causing turbulent vortices produced on the surface of the main plate on the side plate side near the inner peripheral side of the blades. In addition, when these wave form members are provided on the surface of the side plate on the main plate side, the wave form members will be better able to reduce swirling vortices near the side plate that cause an increase in the B_F value.
The centrifugal fan disclosed in claim 7 includes the impeller set forth in any of claims 1 to 6, a drive means that rotates the main plate, and a casing that covers the impeller and which includes an intake port that faces an opening in an inner peripheral side of the side plate and a discharge port that is provided on an outer peripheral side of the impeller and which blows air in a direction approximately perpendicular to the rotational axis.
With this centrifugal fan, the impeller rotates with respect to the casing when the main plate is rotated by the drive means. When this occurs, each blade of the impeller scoops out air from the inner peripheral side of the impeller to a space on the outer peripheral side thereof, draws in air from the intake port into the inner peripheral space of the impeller, and blows the air that was pushed out to the outer peripheral side of the impeller through the discharge port. In other words, the centrifugal fan draws in air from the intake port and blows out air from the discharge port.
When this occurs, because the impeller disclosed in any of claims 1 to 6 is employed, turbulent vortices produced by the collision of the air flow with the main plate and the merger with the air flow will be reduced in size by the wave form members formed on the main plate. This allows the noise generated when the air is scooped out by the blades to be reduced.
In addition, the swirling vortices produced near the side plate will be reduced by the wave form members formed on the side plate surface. This allows fan efficiency to improve and noise to be reduced because the B_F value will be reduced and the portion of the impeller can effectively blow air will be enlarged.

(BRIEF DESCRIPTION OF THE DRAWINGS)

Fig. 1(a) is a lateral view of a conventional multi-blade fan (casing portion is a cross-sectional view).
Fig. 1(b) is a lateral view of the conventional multi-blade fan, and describes a mechanism by which noise is generated near a main plate (a portion of an impeller shown in cross-section).
Fig. 1(c) is a lateral view of the conventional multi-blade fan, and describes a mechanism by which noise is generated near a side plate (a portion of the impeller shown in cross-section).
Fig. 2 is a perspective view of the impeller of the conventional multi-blade fan.
Fig. 3 is a plan view of the impeller of the conventional multi-blade fan.
Fig. 4 is a lateral view of a multi-blade fan of a first embodiment (casing portion is a cross-sectional view).
Fig. 5 is a lateral view of an impeller of the multi-blade fan of the first embodiment (one portion is a cross-sectional view).
Fig. 6 is a plan view of the impeller of the multi-blade fan of the first embodiment.
Fig. 7(a) is an enlarged view of wave form members (triangular wave forms).
Fig. 7(b) is an enlarged view of wave form members (sine wave forms).
Fig. 7(c) is an enlarged view of wave form members (rectangular wave forms).
Fig. 8(a) is a lateral view of the multi-blade fan of the first embodiment, and describes the noise reduction effect of the wave form members formed on the main plate (a portion of the impeller shown in cross-section).
Fig. 8(b) is a lateral view of the multi-blade fan of the first embodiment, and describes the noise reduction effect of the wave form members formed on the side plate.
Fig. 8(c) is a lateral view of the multi-blade fan of the first embodiment, and describes the noise reduction effect of inter-blade cut-out portions on the main plate (a portion of the impeller shown in cross-section).
Fig. 9 is a cross-sectional plan view of an impeller of a turbo fan of a second embodiment.

(BEST MODE FOR CARRYING OUT THE INVENTION)

First Embodiment

(1) Configuration of the multi-blade fan

A multi-blade fan (centrifugal fan) according to an embodiment of the present invention differs from the conventional multi-blade fan 10 shown in Figs. 1 to 3 in that the impeller 13 includes jagged shaped wave form members on the main plate 31 near the inner peripheral edges of the plurality of blades, jagged shaped wave form members on the main plate 31 side of the side plate 32, and a plurality of inter-blade cut-out portions 35 that have been cut out from the main plate 31 on the front side in the rotational direction of the blades 33.
Fig. 4 shows a lateral cross-sectional view of a multi-blade fan 40 of the present embodiment, and Figs. 5 and 6 show a lateral cross-sectional view and a plan view of an impeller 43 of the multi-blade fan 40.
The multi-blade fan 40 is primarily composed of an impeller 63, a casing 11 that covers the impeller 63, and a motor 14 that rotates the impeller 43.
The impeller 43 includes a disk-shaped main plate 61 to which a plurality of blades 33 are fixed to the outer peripheral edge thereof, and an annular side plate 62 to which the other ends of the plurality of blades 33 are connected. A detailed description of the impeller 43 will be provided below.
An air discharge port 11a, and an air intake port 11b that is surrounded by a bell mouth 12, are formed in the casing 11. The intake port 11b faces the side plate 62 of the impeller 43. Air that flows through the intake port 11b and into the space in the interior of the impeller 43 generally flows along the rotational axis O-O of the impeller 43 when it enters this space, and then flows in a direction away from the rotational axis O-O (toward the outer periphery of the impeller 43) due to the rotation of the impeller 43. In addition, the discharge port 11a is formed such that it is perpendicular to the intake port 11b, so that air is blown out in a direction approximately perpendicular to the rotational axis O-O of the impeller 43.
A rotation shaft of the motor 14 is mounted in a central hole 61a in the main plate 61 (see Fig. 6), and rotates the impeller 43 by rotating the main plate 61. The main portion of the motor 14 is fixed to the casing 11.
The impeller 43 will now be described.
As shown in Figs. 5 and 6, the impeller 43 includes the main plate 61, the plurality of blades 33, and the annular side plate 62. In the present embodiment, the impeller 43 is a product made of a synthetic resin in which a mold is used to unitarily form the main plate 61, the plurality of blades 33, and the side plate 62 together.
As shown in Fig. 6, the main plate 61 is a disk-shaped member in which the central hole 61 a is formed, and the rotation shaft of the motor 14 is fixed in the central hole 61 a.
The plurality of blades 33 (described below) are formed around the outer peripheral edge of the main plate 61 and are equidistant with respect to each other in the rotational direction. Jagged shaped wave form members 64 are formed around a circumference of the main plate 61 near the inner peripheral edges of the plurality of blades 33. Here, the wave form members 64 include triangular wave forms that have a wave pitch P of 3 mm and a wave height H of 2 mm (see Fig. 7(a)). Note that the wave form members are not limited to triangular wave forms, and as shown in Figs. 7(b) and 7(c), may have wave forms shaped like sine waves or rectangles. In addition, the dimensions of the wave form members are not limited to those of the present embodiment, and the wave pitch P may be in a range between 2 mm and 8 mm, and the wave height H may be in a range between 1 mm and 5 mm.
Furthermore, inter-blade portions 65 located between the plurality of blades 33 are cut out from the main plate 61 on the front sides in the rotational direction of the plurality of blades 33. The plurality of inter-blade portions 65 are larger in the circumferential direction than the thickness in the circumferential direction of the blades 33, and are cut out on the front side in the rotational direction of the blade 33 with a length that does not reach the rear side in the rotational direction of the adjacent other blades 33. In addition, the inter-blade portions 65 are cut out in the radial direction along the shape of the blades 33 at a length that extends from the outer peripheral edge of the blades 33 to the inner peripheral edge of the blades 33.
The blades 33 include a recessed surface on the front sides thereof in the rotational direction, and these members are annularly disposed with the rotational axis O-O at the center thereof. One end of the blades 33 are fixed to the outer peripheral edge of the main plate 61, and extend lengthwise from this point along the rotational axis O-O without twisting. Then, as shown in Figs. 5 and 6, the other end of the blades 33 are connected to the annular side plate 62.
The annular side plate 62 is disposed on the outer peripheral side of the other ends of the blades 33, and is connected to each blade 33. The side plate 62 is unitarily formed together with the main plate 61 and the plurality of blades 33. The jagged shaped wave form members 66 are formed on the main plate 61 side of the side plate 62. Here, like the wave form members 64 on the main plate 61, the wave form members 66 includes triangular wave forms that have a wave pitch P of 3 mm and a wave height H of 2 mm (see Fig. 7(a)). Note that the wave form members are not limited to triangular wave forms, and as shown in Figs. 7(b) and 7(c), may have wave forms shaped like sine waves or rectangles. In addition, the dimensions of the wave form members are not limited to those of the present embodiment, and the wave pitch P may be in a range between 2 mm and 8 mm, and the wave height H may be in a range between 1 mm and 5 mm.

(2) Operation of the multi-blade fan

When the motor 14 rotates to operate the multi-blade fan 40, the impeller 43 rotates in a rotational direction R (shown in Fig. 6) with respect to the casing 11. In other words, air will be scooped out primarily by the recessed surface on the front side in the rotational direction of the blades 33 of the multi-blade fan 40. This allows the blades 33 of the impeller 43 to scoop out air from the inner peripheral side of the impeller 43 to a space on the outer peripheral side thereof, draw in air from the intake port 11b into the inner peripheral space of the impeller 43, and accumulate and blow the air that was scooped out to the outer peripheral side of the impeller 43 and out the discharge port 11a (see air flow Z in Fig. 4). In other words, the multi-blade fan 40 draws in air from the intake port 11b along the rotational axis O-O, and the air is then blown out from the discharge port 11a in a direction that is perpendicular to the rotational axis O-O. Note that although only the air flow Z on the right side of the rotational shaft O-O is shown in Fig. 4, the air scooped out to the outer peripheral side of the impeller 13 on the left side of the rotational axis O-O will flow along the casing 11 to the discharge port 11a and then be blown out.

(3) Transporting the impeller

When the impeller 43 is to be transported, a plurality of impellers 43 are stacked along the rotational axis O-O.
Here, as noted above, the inter-blade portions 65 on the main plate 61 of the impeller 43 of the present embodiment are larger in the circumferential direction that the thickness in the circumferential direction of the blades 33, and the inter-blade portions 65 are cut out to a length that extend from the outer peripheral edge of the blades 33 to the inner peripheral edges of the blades 33 along the curved shape of the blades 33. The inter-blade portions 65 are used to stack two impellers 43 along the rotational axis O-O. The blades 33 on one impeller 43 can be fit into the corresponding plurality of inter-blade portions 65 on another impeller 43. Two impellers 43 fit together in this way can be stacked together to a predetermined height and then transported.

(4) Example

The results of an experiment in which sound measurements taken from a multi-blade fan in which the impeller of the present embodiment was used will now be described.
The present experiment is one in which sound measurements were taken from the conventional example shown in Figs. 2 and 3 and the present embodiment shown in Figs. 5 and 6. Note that in the present embodiment, the wave form members 64 formed on the main plate 61, the wave form members 66 formed on the side plate 62, and the inter-blade portions 65 on the main plate 61 are simultaneously formed in order to reduce noise. Accordingly, in order to confirm the sound reduction effects of these three elements, impellers having only one of each of these three elements were prepared and a sound reduction experiment was conducted on each impeller. The results of these sound reduction experiments are shown below.
1. An impeller in which only the wave form members 64 were formed on the main plate 61 There was a 0.8 dB reduction in noise compared to the conventional example.
2. An impeller in which only the wave form members 66 were formed on the side plate 62 There was a 0.5 dB reduction in noise compared to the conventional example.
3. An impeller having only the inter-blade portions 65 on the main plate 61 There was a 0.5 dB reduction in noise compared to the conventional example.The aforementioned results confirm that there is a reduction in noise in the present embodiment when any of the three elements are adopted with the goal of reducing noise.
(5) Special characteristics of the multi-blade fan The special characteristics of the multi-blade fan of the present embodiment are as follows.

1. Reduction in noise due to the wave form members formed on the main plate of the impeller

In the conventional multi-blade fan 10, noise is produced by turbulent vortices generated near the main plate 31. More specifically, the turbulent vortices are generated by the mechanism described below.
As shown in Fig. 1(b), a portion of the air drawn in from the intake port 11b collides with the main plate 31 in the interior of the impeller 13, and then flows near the main plate 31 toward the outer peripheral side (see air flow X). Turbulent vortices are generated in this air flow X due to the collision with the main plate 31. The turbulent vortices flow with the air flow X toward the outer periphery and further merge with the air flow that collides with the main plate 31. The turbulent vortices in the air flow X then gradually grow, and the biggest turbulent vortices are formed on the inner peripheral edges of the blades 33. These enlarged turbulent vortices are scooped out toward the outer periphery by the blades 33, and this generates noise.
On the other hand, as shown in Fig. 8, with the impeller 43 of the multi-blade fan 40 of the present embodiment, the turbulent vortices that grew due to the collision of the air flow Z1 with the main plate 61 and the merger with the air flow will be reduced in size immediately before reaching the blades 33 because the wave form members 64 are formed on at least the side plate 62 side of the main plate 61 near the inner peripheral edges of the blades 33. This allows the noise generated when the air flow Z1 is scooped out by the blades 33 to be reduced.

2. Reduction in noise due to the wave form members formed on the side plate of the impeller

In the conventional multi-blade fan 10, swirling vortices are produced in which the centers thereof are near the outer peripheral edge of the side plate 32. The swirling vortices do not assist the impeller 13 to blow air, and thus as a result, the swirling vortices cause noise and reduce fan efficiency. More specifically, the turbulent vortices are generated by the mechanism described below.
As shown in Fig. 1(c), a portion of the air inside the casing 11 is scooped out to the outer periphery of the impeller 13, and then swirling vortices Y are produced near the side plate 32 such that air is again drawn in from near the bell mouth 12 of the impeller 13 to the inner peripheral side of the impeller 13. Because of this, a portion of the air cannot be effectively blown, and this portion corresponds to a ratio b/B (hereinafter referred to as blockage factor B_F) between a length b in the axial direction of the portion of the impeller 13 that produces the swirling vortices Y and a length B in the axial direction of the entire impeller 13. Because of this, there will be a reduction in fan efficiency and noise will be generated.
On the other hand, with the impeller 43 of the multi-blade fan 40 of the present embodiment, the pressure fluctuations near the impeller 43 exit of the side plate 62 will be reduced because the wave form members 66 are formed on the main plate 61 side of the side plate 62 surface. When this is done, as shown in Fig. 8(b), it will become difficult for the air flow scooped out by the impeller 43 on the exit side to be again drawn into the inner peripheral side of the impeller 43 from the side plate 62 side in the rotational direction of the impeller 43, and thus the swirling vortices Z2 produced near the side plate 62 will be reduced. This allows fan efficiency to improve and noise to be reduced because the B_F value will be reduced to b1/B1 and the portion of the impeller 43 that can effectively blow air will be enlarged.

3. Noise reduction due to the inter-blade portions on the main plate of the impeller

With the impeller 43 of the multi-blade fan 40 of the present embodiment, as shown in Fig. 8(c), because inter-blade portions 65 disposed between the plurality of blades 33 on the main plate 61 are cut out from the front side in the rotational direction, a portion of the turbulent vortices that grew due to the collision of the air flow Z3 with the main plate 61 and the merger with the air flow are allowed to travel from the cut-out inter-blade portions 65 toward the outer side in the axial direction of the main plate 61 immediately before they are scooped out by the blades 33. Like the wave form members 64 formed on the main plate 61 shown in Fig. 8(a), this allows a reduction in the noise generated when the air flow is scooped out by the blades 33.
In addition, the inter-blade portions 65 of the impeller 43 of the present embodiment are partially cut out from the front side in the rotational direction of the main plate 61, and are not cut out up to the rear side in the rotational direction of the inter-blade portions 65. Thus, there will be no increase in air flow breakaway on the rear sides in the rotational direction of the inter-blade portions 65. In this way, there will be no damage to the noise reduction effect produced by the cut-outs on the front side in the rotational direction of the inter-blade portions 65.
Furthermore, the turbulent vortices of the air flow Z3 easily escape from the cut-out inter-blade portions 65 before they arrive at the outer peripheral edges of the blades 33 because the inter-blade portions 65 of the impeller 43 of the present embodiment are cut out from the outer peripheral edges of the blades 33 to the inner peripheral edges thereof. In this way, the turbulent vortices that arrive at the outer peripheral edges of the blades 33 can be further diminished, and noise can be further reduced.

4. Increase in load efficiency when transporting impellers

As noted above, the inter-blade portions 65 of the main plate 61 of the impeller 43 of the present embodiment are larger in the circumferential direction that the thickness in the circumferential direction of the blades 33, and the inter-blade portions 65 are cut out to a length that extends from the outer peripheral edges of the blades 33 to the inner peripheral edges of the blades 33 along the curved shape of the blades 33. This shape is used to stack two impellers 43 from the rotational axis O-O, and the blades 33 can be respectively fit into the cut-outs of the plurality of inter-blade portions 65. In this way, the load efficiency when loading the impellers 43 can be improved.

Second Embodiment

In the present embodiment, the present invention is applied to impellers for turbo fans. In other words, the wave form members 64 formed on the main plate 61 of the multi-blade fan 40 of the aforementioned embodiment is applied to an impeller 73 of a turbo fan.
Fig. 9 shows a cross-sectional plan view of the impeller 73 of the turbo fan of the present embodiment.
The impeller 73 includes a disk-shaped main plate 91 to which a plurality of blades 93 are fixed to the outer peripheral edge thereof, and an annular shroud (side plate) not shown in the figures to which the other ends of the plurality of blades 93 are connected.
The plurality of blades 93 are formed around the outer peripheral edge of the main plate 91 and are equidistant with respect to each other in the rotational direction. Jagged shaped wave form members 94 are formed around a circumference of the main plate 91 near the inner peripheral edges of the plurality of blades 93. Here, like in the aforementioned embodiment, the wave form members 94 include the triangular waves, sine waves or rectangles shown in Figs. 7(a) - 7(c) that have a wave pitch P between 2 mm and 8 mm and a wave height H between 1 mm and 5 mm.
In this embodiment, like in the aforementioned embodiment, because the wave form members 94 are formed at least on the shroud side of the main plate 91 near the inner peripheral edges of the blades 93, turbulent vortices that grew due to the collision of the air flow with the main plate 91 and the merger with the air flow will be reduced in size immediately before reaching the blades 93, and noise generated when the air flow is scooped out by the blades 93 can be reduced.

Other Embodiments

In the aforementioned embodiments, the present invention was applied to a centrifugal fan that employs an impeller made of a synthetic resin. However, the present invention can be applied to a centrifugal fan that employs an impeller made of sheet metal.

INDUSTRIAL APPLICABILITY

If the present invention is used, noise in an impeller of a centrifugal fan can be reduced.

Claims

An impeller (43, 73) of a centrifugal fan, comprising:

a main plate (61, 91 ) that rotates about a rotational axis (O-O);

a plurality of blades (33, 93) that are annularly disposed about the rotational axis (O-O), one end of each of the plurality of blades (33, 93) fixed to the main plate (61, 91); and

an annular side plate (62) that connects with the other ends of the plurality of blades (33, 93);

wherein jagged shaped wave form members (64, 94) are formed at least on a side plate (62) side of the main plate (61, 91) near inner peripheral edges of the plurality of blades (33, 93).
An impeller (43) of a centrifugal fan, comprising:

a main plate (61) that rotates about a rotational axis (O-O);

a plurality of blades (33) that are annularly disposed about the rotational axis (O-O), one end of each of the plurality of blades (33) fixed to the main plate (61, 91); and

an annular side plate (62) that connects with the other ends of the plurality of blades (33);

wherein jagged shaped wave form members (66) are formed on the main plate (61) side of the side plate (62).
The impeller (43, 73) for a centrifugal fan set forth in claim 1 or claim 2, wherein the wave form members (64, 66, 94) include triangular wave forms.
The impeller (43, 73) for a centrifugal fan set forth in claim 1 or claim 2, wherein the wave form members (64, 66, 94) include sine wave forms.
The impeller (43, 73) for a centrifugal fan set forth in claim 1 or claim 2, wherein the wave form members (64, 66, 94) include rectangular wave forms.
The impeller (43, 73) for a centrifugal fan set forth in any of claims 1 to 5, wherein the wave form members (64, 66, 94) have wave pitches in a range between 2 mm and 8 mm and wave heights in a range between 1 mm and 5 mm.
A centrifugal fan, comprising:

the impeller (43, 73) set forth in any of claims 1 to 6;

a drive means (14) that rotates the main plate (61, 91); and

a casing (11) that covers the impeller (43, 73), and includes an intake port (11b) that faces an opening in an inner peripheral side of the side plate 62 and a discharge port (11a) that is provided on an outer peripheral side of the impeller (43, 73) and which blows air in a direction approximately perpendicular to the rotational axis (O-O).