WO2009139422A1

WO2009139422A1 - Centrifugal fan

Info

Publication number: WO2009139422A1
Application number: PCT/JP2009/058938
Authority: WO
Inventors: 真吾大山
Original assignee: ダイキン工業株式会社
Priority date: 2008-05-14
Filing date: 2009-05-13
Publication date: 2009-11-19
Also published as: CN101990604A; JPWO2009139422A1; EP2275689A1; AU2009247219A1; KR20100134011A; US20110023526A1

Abstract

A centrifugal fan (1) has three-dimension-shaped blades (44), a main plate (43) to which one end surface of each blade (44) with respect to the span direction thereof is fixed with predetermined circumferential intervals between each blade (44), a ring-shaped side plate (45) mounted to the other end surface of each blade (44) with respect to the span direction thereof, and a motor (41) for rotating the blades (44) through the main plate (43). The radial length of that portion of the rear edge (44b) of each blade (44) which is on the main plate (43) side is set greater than the radial length of that portion of the rear edge (44b) which is on the side plate (45) side.

Description

Centrifugal blower

The present invention relates to a centrifugal blower, and more particularly, to a structure of an impeller blade of a centrifugal blower.

Generally, centrifugal fans such as turbofans have a problem of large noise, so it is a problem to reduce noise. Therefore, various technologies have been developed so far in the centrifugal blower in order to reduce the blowing sound. As a general design method for reducing the blowing noise, an increase in the outer diameter of the fan impeller can be mentioned.

Suppose that a constant air volume is obtained, the rotation speed of the fan impeller can be reduced by increasing the outer diameter of the fan impeller. Thereby, the flow velocity of the airflow blown from the fan impeller is reduced. The blowing sound is proportional to the sixth power of the flow velocity.

However, simply increasing the outer diameter of the fan impeller will increase the overall size of the blower including the in-machine passage. In addition, the manufacturing cost of the blower is increased, and other parameters of the blade shape (inlet angle / outlet angle) and in-machine layout need to be reviewed.

For this reason, for example, a thick blade (blade), that is, an airfoil blade, is used to reduce the separation of the airflow around the blade and to reduce noise at the lowest possible cost (for example, Patent Documents). 1).

However, simply adopting an airfoil blade as a blade does not eliminate the air flow separation on the entire surface of the blade. Noise caused by wake vortices occurring at the trailing edge of the blade is not effectively reduced. Further, the flow velocity of the blown airflow is different in the blade span direction. That is, a non-uniform velocity distribution of airflow appears between the main plate and the side plate.

Therefore, a noise reduction technique in which dimples and serrations are further provided on the surface of the entire blade has been proposed (see, for example, Patent Document 2). According to such a configuration, it is possible to further suppress the separation of the air flow, to subdivide the disturbance due to the separation, and to further suppress the development of the wake vortex. As a result, noise caused by the wake vortex is reduced.

However, even with such a configuration, it is possible to suppress the occurrence of non-uniform velocity distribution of the blown airflow in the blade main plate side portion and the blade side plate side portion in the blade span direction, and the generation of wake vortices. Can not do it. Therefore, it is impossible to effectively prevent noise caused by the influence of the wake vortex. Further, in the case of the same configuration, there is a disadvantage that the manufacturing process such as processing and die cutting on the blade surface becomes complicated.

On the other hand, there are various techniques for improving the velocity distribution of the airflow at the outlet of the impeller as described above. Some blades are cut off to shorten the blades on the side plate side of the blade, thereby preventing airflow separation on the blade side plate side, thereby making the velocity distribution at the impeller outlet uniform. (See Patent Document 3).

However, in this technique, since the notch is formed in the side plate side portion of the blade, the length of the blade is relatively shorter than the blade without the notch. Therefore, the amount of work that the blades give to the airflow is reduced.

Moreover, the above technique is effective in a centrifugal fan whose blade width is sufficiently small with respect to the outer shape, as described in Patent Document 3. That is, by cutting out the blade, it is possible to prevent the suction airflow from separating near the side plate side of the blade, and to flow the airflow along the vicinity of the side plate side of the blade. However, when the blade width is sufficiently wide as in an ordinary centrifugal blower, that is, when the influence of peeling on the side plate side is not dominant, the above technique is not necessarily effective.

Also, if the vicinity of the side plate side of the blade is cut off, the airflow passing through the side plate side portion of the blade interferes with the corner portion of the main plate side of the blade. As a result, there is a possibility that new noise having discretely protruding frequencies may be generated.

Also, when the blades are arranged so as to be orthogonal to the main plate and the side plate, there is a technique for changing the thickness of the blade from the end surface on the main plate side of the blade to the end surface on the side plate side of the blade. Thereby, the fluctuation | variation of the wind speed distribution in the blower outlet of a blade | wing is suppressed. Furthermore, in that case, the outer diameter on the main plate side of the impeller and the outer diameter on the side plate side of the impeller are not the same at the blower outlet (end surface on the outer peripheral side of the impeller), and the shape of the blade approaches the main plate. There is also a similar enlargement (see, for example, Patent Document 4). As a result, flow speed fluctuations in the blade wake are suppressed.

However, in this configuration, the ratio of the outer diameter on the main plate side of the impeller / the outer diameter on the side plate side of the impeller is set to 1.2 to 1.6 at the outlet of the impeller. Therefore, when the extension amount due to the expansion of the blades is small, the noise reduction effect cannot be obtained, and conversely, when the extension amount is too large, the flow rate characteristic is deteriorated.

As a result, at least the outer diameter on the main plate side of the impeller is expanded by 20% relative to the outer diameter on the side plate side. This does not provide an advantage over a technology that simply enlarges the fan diameter and simply enlarges the fan. In the first place, the increase in size by more than 20% cannot solve the problem of the reduction in size and noise that is the conventional problem at all.

On the other hand, an impeller employing a three-dimensional blade extending in the direction of the rotation axis of the fan while twisting from the main plate to the side plate has also been proposed (see, for example, Patent Document 2).
According to the impeller that employs such a three-dimensional blade, the load distribution on the surface of the blade and the pressure of the airflow passing between the blades are compared to those employing the two-dimensional blade as described above. Variability is improved.

Now, the configuration of a centrifugal blower employing three-dimensional blades and an air conditioner employing the centrifugal blower will be described with reference to FIGS. 25 to 32. FIG.
First, FIG. 25 shows an air conditioner 1 that employs a centrifugal blower having an impeller. The air conditioner 1 is a ceiling-embedded air conditioner, and includes a casing 2 that houses various components therein, and a decorative panel 3 that is disposed below the casing 2. More specifically, the casing 2 of the air conditioner 1 is inserted into an opening formed in the ceiling U of the air conditioning room, and the decorative panel 3 is disposed along the ceiling U.

The casing 2 is a box-like body having an opening below, and has a substantially octagonal shape in which long sides and short sides are alternately arranged in a plan view. The casing 2 has a substantially octagonal top plate 21 in which long sides and short sides are alternately formed, and a side wall plate 22 extending downward from the periphery of the top plate 21.

The decorative panel 3 is a substantially quadrangular plate in plan view. The decorative panel 3 is positioned substantially in the center and is formed to correspond to each of the four sides of the air inlet 31 for sucking air in the air-conditioned room, and a plurality of air outlets for blowing air from the casing 2 into the air-conditioned room. 32. Each side of the decorative panel 3 is disposed so as to correspond to each long side of the top plate 21 of the casing 2.

Each air inlet 31 is a substantially square opening. On the other hand, each air outlet 32 is a rectangular opening extending along the direction along each side of the decorative panel 3. The air inlet 31 is provided with an air inlet grill 33 and a filter 34 for removing dust in the air sucked from the air inlet 31.

Furthermore, each air outlet 32 is provided with a horizontal flap 35 that can swing around an axis extending along the longitudinal direction of the air outlet 32. The horizontal flap 35 is a rectangular blade member extending in the longitudinal direction of each air outlet 32. In addition, each horizontal flap 35 rotates the shaft support pins provided at both ends in the longitudinal direction thereof by a motor (not shown), so that the air blown out from the air outlet 32 toward the air-conditioned room. Change the wind direction.

Inside the casing 2, a blower 4 that mainly sucks air in the air-conditioned room into the casing 2 through the air inlet 31 of the decorative panel 3 and blows it out in the outer peripheral direction, and is arranged so as to surround the outer periphery of the blower 4. A heat exchanger 6 is arranged.

The blower 4 is a turbo fan as an example of a centrifugal blower targeted by the present invention. The blower 4 is connected to a fan motor (impeller driving means) 41 provided downward in the center of the top plate 21 of the casing 2 and a shaft (rotary shaft) 41 a of the fan motor 41 and is rotated. An impeller 42.

The heat exchanger 6 is a cross fin tube type heat exchanger that is formed by being bent in a substantially square shape so as to surround the outer periphery of the blower 4. A refrigerant pipe is connected to an outdoor unit (not shown) installed outdoors. Connected through. The heat exchanger 6 functions as an evaporator during cooling operation and as a condenser during heating operation. As a result, the heat exchanger 6 exchanges heat with the air sucked into the casing 2 through the air suction port 31 by the blower 4, and cools the air during the cooling operation, while cooling the air during the heating operation. Heat.

A drain pan 7 for receiving drain water generated by condensation of moisture in the air on the surface of the heat exchanger 6 is disposed below the heat exchanger 6. The drain pan 7 is attached to the lower part of the casing 2. The drain pan 7 further includes an air suction hole portion 71 formed so as to communicate with the air suction port 31 of the decorative panel 3, and an air outlet hole portion formed so as to correspond to the air outlet 32 of the decorative panel 3. 72 and a drain water receiving groove 73 for receiving drain water formed so as to cover the lower portion of the heat exchanger 6.

Also, a bell mouth 5 for guiding the air sucked from the air suction port 31 of the decorative panel 3 to the impeller 42 of the blower 4 is disposed in the air suction hole portion 71 of the drain pan 7.

Next, the structure of the impeller 42 of the centrifugal blower 4 will be specifically described with reference to FIGS. Here, FIG. 26 is an external perspective view of the impeller 42. FIG. 27 is a side view of the impeller 42 of FIG.

The impeller 42 mainly includes a disk-shaped main plate 43, an annular side plate 45 disposed at a distance from the main plate 43, and a plurality of blades 44 disposed between the main plate 43 and the side plate 45. . The main plate 43 is connected to the shaft 41a of the fan motor 41 described above. The plurality of blades 44 are disposed along the main plate 43 at a predetermined angle with the shaft 41a of the fan motor 41 as the central axis.

The main plate 43 is a resin member. A substantially frustoconical convex portion 43 a is formed at the central portion of the main plate 43 so as to protrude toward the air suction port 31. A main plate cover 46 is fixed to the lower surface of the main plate 43 so as to be disposed at a predetermined interval from the main plate 43 and cover the cooling air holes. A plurality of guide blades 46 a extending radially are provided on the surface of the main plate cover 46 that faces the main plate 43. As a result, a part of the air blown out of the impeller 42 is subjected to static pressure in the space between the main plate 43 and the casing 2 and static pressure in the space between the main plate 43 and the side plate 45. Flows around the main plate 43 due to the pressure difference between them. Specifically, a part of the blown air passes through the vicinity of the fan motor 41 to cool the fan motor 41. Thereafter, the air is blown out again into the space inside the impeller 42 through the cooling air holes of the main plate 43 and the guide vanes 46 a of the main plate cover 46.

The side plate 45 has a diameter that gradually decreases from the outer periphery toward the central opening. The side plate 45 is a bell-shaped resin member that protrudes toward the air inlet 31.

Next, the structure of each blade 44 of the impeller 42 will be described in detail with reference to FIGS. Here, FIG. 28 is a perspective view of the blade 44 as viewed from the left rear. FIG. 29 is a projection view of the blade 44 of FIG. 28 as viewed from above. 30 is a side view in which a plurality of cutting lines 31A-31A to 31E-31E are inserted into the blade 44 of FIG. 31 (a) to 31 (e) are cross-sectional views taken along lines 31A-31A to 31E-31E in FIG. 30, respectively. FIG. 32 is an explanatory view showing the operation of the blade 44.

Each of the blades 44 is a resin member formed separately from the main plate 43 and the side plate 45 described above. One end surface of each blade 44 is fixed to the main plate 43, and the other end surface of each blade 44 is fixed to the side plate 45. In the side view of the impeller 42, each blade 44 is inclined with the end on the side plate 45 side inclined behind the end on the main plate 43 side as shown in FIG. 28. Further, as shown in FIG. 29, each blade 44 is formed so that these end portions intersect with each other in a substantially X shape. That is, the blade 44 has a three-dimensional shape extending in parallel with the rotation axis while being twisted between the main plate 43 and the side plate 45.

The front end in the rotational direction of the blade 44, which is the three-dimensional blade, that is, the front edge 44a extends from the end on the main plate 43 side to a predetermined position on the side plate 45 side so as to have substantially the same radius. On the other hand, the blade 44 has an inclined edge that recedes outward so that the radius gradually decreases from a predetermined position on the side plate 45 side to the side plate 45. On the other hand, the end of the blade 44 in the direction opposite to the rotation direction R, that is, the rear edge 44b has a shape in which the position on the main plate 43 side and the position on the side plate 45 side are connected by a straight line extending parallel to the rotation.

According to the above configuration, the load distribution on the surface of the blade 44 and the distance between the blades 44 are compared with the blade shape made on the basis of the blade element drawn in a plane like

Patent Documents

1, 3, and 4 described above. The pressure fluctuation of the airflow passing through the air is greatly improved. Therefore, at least noise caused by air pressure fluctuation is effectively reduced.

However, since the rear edge 44b of the blade 44 has a shape in which both ends are linearly connected between the main plate 43 and the side plate 45, there is still a problem that noise due to the influence of the wake vortex is generated. As shown in FIG. 32, the air flow F ₂ flowing along the rounded surface of the side plate 45 out of the air flow sucked from the vicinity of the side plate 45 of the blade 44 is small. On the other hand, the original main flow F ₁ having a large flow rate sucked from the center of the side plate 45 flows in the vicinity of the main plate 43 due to the relationship between the flow velocity vectors. Therefore, the wind speed distribution of the blown airflow at the exit portion of the blade 44 is not uniform in the span direction of the blade 44. Further, the wake vortex generated downstream of the trailing edge 44b of the blade 44 cannot be suppressed. As a result, there is still a problem that noise is generated due to the influence of the wake vortex.
JP 2002-339897 A JP 2005-155510 A JP-A-5-60096 JP 2001-132687 A

An object of the present invention is to provide a centrifugal fan that can further reduce noise with respect to a three-dimensional blade used in the centrifugal fan.
In order to solve the above problems, according to one aspect of the present invention, a plurality of three-dimensional blades and a span end direction of each blade are fixed at predetermined intervals in the circumferential direction. A centrifugal blower comprising a main plate, a ring-shaped side plate provided on the other end surface of each blade in the span direction, and blade driving means for rotating the blade via the main plate, A centrifugal blower is provided in which the radial length of the outer peripheral end portion on the main plate side is set longer than the radial length of the outer peripheral end portion on the side plate side of each blade.

According to such a configuration, the velocity distribution of the mainstream portion of the airflow that flows biased toward the main plate side portion of the blade is greatly improved. Therefore, the static pressure-flow rate characteristic of the blower is improved in the entire flow rate range, and the blown amount is increased. Moreover, the specific noise characteristic of the blower is also greatly improved, and the influence of the wake vortex generated at the blade trailing edge on the three-dimensional blade main plate side can be relatively reduced. As a result, noise caused by the wake vortex is effectively reduced.

By setting the radial length of the outer peripheral end on the main plate side of each blade longer than the radial length of the outer peripheral end on the side plate side of each blade, the airflow passing through each blade is It is preferable that work on the main plate side of the blade is effectively received from the blade, and the velocity of the airflow in the span direction of each blade is effectively developed in the main plate side portion of each blade.

The radial length of the outer peripheral end of the blade on the main plate side is extended in the radial direction of the outer peripheral end of the blade on the side plate side by extending the trailing edge of the blade toward the rear of the air flow. It is preferably formed longer than the length.

In this way, by extending the trailing edge of the blade toward the rear of the air flow, the velocity distribution of the main flow portion of the airflow that is biased toward the main plate side of the blade is greatly improved. Therefore, the static pressure-flow rate characteristic of the blower is improved in the entire flow rate range, and the blown amount is increased. Moreover, the specific noise characteristic of the blower is also greatly improved, and the influence of the wake vortex generated at the blade trailing edge on the three-dimensional blade main plate side can be relatively reduced. As a result, noise caused by the wake vortex is effectively reduced.

The trailing edge is preferably extended so as to gradually become longer from the side plate toward the main plate.
According to such a configuration, the shape of the trailing edge of the blade becomes a substantially tapered shape that is enlarged from the side plate to the main plate. Therefore, the shape of the trailing edge of the blade can be made appropriate according to the change in the velocity distribution of the main flow that is biased toward the portion of the blade on the main plate side. The substantially tapered shape that gradually expands from the side plate to the main plate may be either a linear change or a curved change.

The trailing edge may be extended in a curved shape, and a bulging portion may be formed at a portion on the main plate side of the trailing edge so that one or more inflection points exist in the curved portion. preferable.
The centrifugal blower forms a laminar shear layer under the influence of the airflow in the vicinity of the main plate due to the viscosity of the wall surface of the main plate. As a result, the main flow path is narrowed, and the fan performance may be reduced. However, according to said structure, development of the said shear layer can be suppressed and fan performance can be improved.

It is preferable that the trailing edge is extended long backward corresponding to the velocity distribution of the main stream of the airflow at the trailing edge.
According to such a configuration, the shape of the extended trailing edge can be made more appropriate according to the change in the mainstream speed distribution, and the fan performance can be further improved.

It is preferable that a step portion extended by a predetermined length in front of the blade is provided in a portion of the front edge of each blade on the main plate side.
With such a configuration, when the airflow sucked into the impeller through the air suction port is blown outward from the trailing edge of the blade, the airflow that peels from the suction surface side of the blade is effectively suppressed. Can do. Thereby, the noise of the blower can be further effectively reduced.

It is preferable that the diameter of the main plate is enlarged in accordance with the extension of the blades.
Corresponding to the extension of the length of the trailing edge of the blades, the structural strength of the centrifugal fan can be improved at the same time by extending the diameter of the main plate.

It is preferable that the centrifugal blower is configured as a blower of an indoor unit for an air conditioner.
An air blower of an indoor unit for an air conditioner is essentially required to have a large air volume and quietness due to its characteristics. Therefore, the centrifugal blower of the present invention that is small in size, high in blowing performance, and low in noise is optimal as a blower for an indoor unit for an air conditioner.

As described above, according to the present invention, it is possible to provide a centrifugal blower suitable for a blower of an indoor unit for an air conditioner that has a large air volume and is excellent in quietness and can be downsized.

The perspective view which shows the external appearance of the air conditioning apparatus which employ | adopted the centrifugal blower concerning one Embodiment of this invention. The longitudinal cross-sectional view which shows the air conditioning apparatus of FIG. The perspective view which shows the impeller of the centrifugal blower of FIG. The side view which shows the impeller of FIG. The bottom view which shows the impeller of FIG. The side view which shows the braid | blade (blade | wing) of the impeller of FIG. The projection which looked at the braid | blade of FIG. 6 from the direction of the side plate side. The perspective view which looked at the braid | blade of FIG. 6 from the left back upper part. FIG. 10 is a side view showing the blade of FIG. 6 together with a plurality of cutting lines 10A-10A to 10E-10E. (A)-(e) is sectional drawing of the braid | blade corresponding to each cutting position of FIG. Sectional drawing which shows the shape of the trailing edge of the braid | blade of this Embodiment of FIG. 6 in contrast with the shape of the trailing edge of the conventional blade. Explanatory drawing which shows the effect | action (characteristic) of the braid | blade of FIG. In order to confirm the effect of the blade according to the present embodiment, FIG. 35 is a graph showing changes in the static pressure coefficient as parameters for the flow rate coefficient for four examples, (a) is the conventional fan of FIGS. (b) is an enlargement of the outer diameter of the conventional fan by 5% overall, (c) is an enlargement of only the lower part (main plate side) of the blade of this embodiment by 5%, and (d) is This corresponds to an enlargement of only 10% of the lower side (main plate side) of the blades of this embodiment. In order to confirm the effect of the blade of this Embodiment, the graph which showed the change of the blowing sound about the four examples of FIG. 13 as the parameter of ventilation volume. In order to confirm the effect of the blade of this embodiment, graphs showing changes in specific noise for the four examples in FIG. Explanatory drawing which shows the effect | action of the braid | blade of the modification 1 which changed the shape of the trailing edge of the braid | blade which concerns on this Embodiment into the curve shape. Explanatory drawing which shows the effect | action of the braid | blade of the modification 2 which changed the shape of the trailing edge of the braid | blade which concerns on this Embodiment into what can suppress a shearing force. The longitudinal cross-sectional view of the air conditioning apparatus which employ | adopted the centrifugal blower of the modification 3 which provided the step part in the front edge by the side of the main board of the blade of this embodiment. The side view which shows the blade of the impeller of the air conditioning apparatus. The perspective view which looked at the braid | blade of FIG. 19 from the left back upper part. 19 is an explanatory diagram showing the action of the blade. FIG. 19 is a graph showing the change in specific noise with the flow coefficient as a parameter for the four examples in order to confirm the effect of the blade. FIG. 19 (a) is a conventional blade of FIGS. (B) is a conventional blade of FIG. 25 to FIG. 32 provided with a step, (c) is the present embodiment of FIG. 1 to FIG. 12, and (d) is shown in FIG. 18 to FIG. This corresponds to the third modification of the present embodiment. FIG. 19 is a graph showing changes in the static pressure coefficient with the flow coefficient as a parameter for the four examples of FIG. 22 in order to confirm the effect of the blade. Explanatory drawing which shows the effect | action of the braid | blade of the modification 4 of this Embodiment. The longitudinal cross-sectional view which shows the air conditioning apparatus which employ | adopts the conventional centrifugal blower. The perspective view which shows the impeller of the centrifugal blower of FIG. The side view which shows the braid | blade (blade | wing) of the impeller of FIG. The perspective view which looked at the impeller of FIG. 26 from diagonally backward. FIG. 29 is a projection view showing the blade of FIG. 28. The side view which shows the braid | blade of FIG. 28 with a cutting line. FIGS. 30A to 31E are cross-sectional views taken along lines 31A-31A to 31E-31E in FIG. Explanatory drawing which shows the effect | action of the braid | blade of FIG.

Hereinafter, a configuration of a centrifugal blower according to an embodiment of the present invention and an air conditioner employing the centrifugal blower will be described in detail with reference to the accompanying drawings.
(1) Whole structure of air conditioning apparatus FIG. 1: shows the external appearance perspective view (ceiling part is abbreviate | omitted) which shows the air conditioning apparatus 1 which employ | adopts the centrifugal blower concerning one embodiment of this invention. The air conditioner 1 is a ceiling-embedded air conditioner, and includes a casing 2 that houses various components therein, and a decorative panel 3 that is disposed below the casing 2. More specifically, the casing 2 of the air conditioner 1 is inserted into an opening formed in the ceiling U of the air conditioning room, for example, as shown in FIG. 2 (vertical sectional view of the air conditioner 1). The decorative panel 3 is arranged along the ceiling U.

The blower 4 is a turbo fan as an example of a centrifugal blower targeted by the present invention. The blower 4 is connected to a fan motor (impeller driving means) 41 provided downward in the center of the top plate 21 of the casing 2 and a shaft (rotary shaft) 41 a of the fan motor 41 and is rotated. An impeller 42. The detailed structure of the impeller 42 will be described later.

As described above, the air-conditioning apparatus 1 according to the present embodiment has the above-described configuration through the filter 34, the bell mouth 5, the drain pan 7, the blower 4, and the heat exchanger 6 from the air suction port 31 of the decorative panel 3. The air flow paths leading to the four air outlets 32 are formed. The air conditioner 1 can inhale the air in the air-conditioned room and exchange heat with the refrigerant in the heat exchanger 6 and then blow out the temperature-controlled air in all directions of the air-conditioned room through the air flow path. .

(2) Structure of Impeller of Centrifugal Blower Next, the structure of the impeller 42 of the centrifugal blower 4 will be described in detail with reference to FIGS. Here, FIG. 3 is a perspective view showing an appearance of the impeller 42. FIG. 4 is a side view showing the impeller 42 of FIG. Further, FIG. 5 is a view of the impeller 42 installed as shown in FIG. 4 as viewed from above.

The impeller 42 mainly includes a disk-shaped main plate 43, an annular side plate 45 disposed at a distance from the main plate 43, and a plurality of blades 44 disposed between the main plate 43 and the side plate 45. . The main plate 43 is connected to the shaft 41a of the fan motor 41 described above. The plurality of blades 44 are disposed along the main plate 43 at a predetermined angle with the shaft 41a of the fan motor 41 as the central axis. The rotation direction of the impeller 42 is indicated by an arrow R in FIG.

The main plate 43 has an outer diameter Db ′. The main plate 43 is a resin member. A substantially frustoconical convex portion 43 a is formed at the central portion of the main plate 43 so as to protrude toward the air suction port 31. A main plate cover 46 is fixed to the lower surface of the main plate 43 so as to be disposed at a predetermined interval from the main plate 43 and cover the cooling air holes. A plurality of guide blades 46 a extending radially are provided on the surface of the main plate cover 46 that faces the main plate 43. As a result, a part of the air blown out of the impeller 42 is subjected to static pressure in the space between the main plate 43 and the casing 2 and static pressure in the space between the main plate 43 and the side plate 45. Flows around the main plate 43 due to the pressure difference between them. Specifically, a part of the blown air passes through the vicinity of the fan motor 41 to cool the fan motor 41. Thereafter, the air is blown out again into the space inside the impeller 42 through the cooling air holes of the main plate 43 and the guide vanes 46 a of the main plate cover 46.

The side plate 45 has an outer diameter Da. The side plate 45 has a shape that gradually decreases from the outer periphery toward the central opening. The side plate 45 is a bell-shaped resin member that protrudes toward the air inlet 31.

(3) Structure of Blade (Blade) of Impeller Next, the structure of each blade 44 of the impeller 42 will be described in detail with reference to FIGS. Here, FIG. 6 is a side view of the blade 44 as seen from the direction of the suction surface, for example. FIG. 7 is a projection view of the blade 44 of FIG. 6 as viewed from above. FIG. 8 is a perspective view of the blade 44 of FIG. FIG. 9 is a side view in which a plurality of cutting lines 10A-10A to 10E-10E are entered from the lower part to the upper part (the end part on the main plate 43 side to the end part on the side plate 45 side) of the blade 44 in FIG. 10A to 10E are cross-sectional views taken along lines 10A-10A to 10E-10 in FIG. 9, respectively. FIG. 11 is a cross-sectional view of the main part showing the characteristics of the blade 44 (difference from the conventional shape of FIGS. 25 to 32) (contrast with the cross-sectional view taken along the line 31B-31B in FIGS. 10 and 31). .

An end on the front side in the rotational direction of the blade 44, which is the three-dimensional blade, that is, the front edge 44a extends from the end on the main plate 43 side to a predetermined position on the side plate 45 side so as to have substantially the same radius. On the other hand, the blade 44 has an inclined edge that recedes outward so that the radius gradually decreases from a predetermined position on the side plate 45 side to the side plate 45. On the other hand, an end portion (hereinafter referred to as a trailing edge) 44b in the direction opposite to the rotation direction R side of the blade 44 has a shape different from that of the conventional blade. Unlike the conventional example shown in FIGS. 25 to 32, the trailing edge 44b is a straight line (perpendicular to the main plate 43) that extends in parallel with the rotation axis between the end on the main plate 43 side and the end on the side plate 45 side of the blade 44. Does not have a tied shape. For example, as shown in FIGS. 6 to 11, the rear edge 44b extends from the end on the side plate 45 side to the end on the main plate 43 side so that the degree of extension increases as the side plate 45 approaches the main plate 43. It is extended to the rear of the air flow. Thus, the diameter of the centrifugal fan of the main flow F ₁ is the radial length of the edge 44b after the main plate 43 side of the blade 44 to pass (Rb 'in FIG. 5), the edge 44b after the side plate 45 side of the blade 44 It is set longer than the length in the direction (Ra in FIG. 5). Thereby, the velocity distribution of the air flow in the span direction of the blade 44 is effectively developed in the portion on the main plate 43 side where the flow rate is large.

The extension of the trailing edge 44b is performed without changing the basic blade surface shape of the three-dimensional blade, and is performed along the same shape. In this case, the extension amount of the rear edge 44b is based on the outer diameter Db ′ (FIG. 12) of the enlarged main plate 43 based on the outer diameter Db of the original main plate 43 (the outer diameter Da of the side plate 45). The outer diameter Db is preferably 10% or less of the outer diameter Db. In other words, the extension amount of the trailing edge 44b is preferably 10% or less of the outer diameter Da of the side plate 45.

6 to 12 described above, the outer diameter Db ′ of the main plate 43 is enlarged by, for example, about 5% with respect to the outer diameter Db of the conventional main plate 43 shown in FIGS.
Further, when the trailing edge 44b is extended, the inlet angle, the outlet angle, the mounting angle, and the skew angle of the blade element on the main plate 43 side of the blade 44 are maintained at the values of the original blade 44 shown in FIGS. Therefore, the blade 44 of the present embodiment has a shape in which the mounting position on the rear edge 44b side swells in the rotational direction, as shown in the perspective view of FIG.

Of course, the outer diameter of the main plate 43 is also increased in accordance with the increase in the radius of the end of the blade 44 on the main plate 43 side.
In this way, in correspondence with the extension of the length of the rear edge 44b of the blade 44, the outer diameter of the main plate 43 is also extended, so that the structural strength of the impeller 42 of the centrifugal fan can be improved at the same time. it can.

With the configuration as described above, for example, as shown in FIG. 12, the velocity distribution of the main flow F ₁ flowing in the vicinity of the main plate 43 is greatly improved as compared to the flow F ₂ in the vicinity of the side plate 45. Therefore, the static pressure-flow rate characteristic (PQ characteristic) of the blade 44 is improved in the entire flow rate range, and the air flow rate is increased. In addition, the specific noise characteristics are greatly improved, and the influence of the wake vortex generated at the trailing edge 44b of the three-dimensional blade 44 on the main plate 43 side can be relatively reduced. As a result, noise caused by the wake vortex is effectively reduced.

Further, in the present embodiment, the rear edge 44b extended rearward as it approaches the main plate 43 is extended so as to gradually become longer from the side plate 45 to the main plate 43 as shown in FIG. That is, the shape of the rear edge 44 b of the blade 44 has a taper shape that is expanded in a straight line from the side plate 45 to the main plate 43. Thereby, the velocity distribution at the outlet of the blade 44 is effectively developed in the main flow F ₁ . Therefore, the influence of the wake generated at the trailing edge 44b of the blade 44 on the main plate 43 side is relatively weakened.

Therefore, by the trailing edge 44b is enlarged with a tapered shape, to changes in the velocity distribution of the main flow F ₁ flow rate increases toward the main plate 43, the trailing edge 44b becomes a more suitable shape ing. That is, the shape of the blade 44 can be optimized with respect to the velocity distribution of the airflow, and the fan performance can be further improved.

Therefore, by using the centrifugal blower of the present embodiment, it is possible to realize a small-sized air conditioner with a large air volume and high silence at low cost.
In particular, in the impeller of the centrifugal blower of the present embodiment, the blade 44 is a three-dimensionally shaped blade as described above (see FIGS. 7 and 8). Therefore, the load distribution on the surface of the blade 44 and the pressure fluctuation of the airflow passing between the blades 44 are greatly improved as compared with the blade shape made on the basis of the conventional planarly drawn blade element.

Therefore, when the blade 44 of the present embodiment having the above-described action is combined with such a three-dimensional wing, the influence of the wake vortex can be more effectively eliminated.

Of course, as described above, there are various techniques for improving the velocity distribution of the blown air at the outlet of the blade 44 as described above. For example, Patent Document 3 discloses a blade that is shortened by cutting out a portion on the side plate side. Thereby, the separation of the airflow in the portion on the side plate side of the blade is suppressed, and the velocity distribution at the outlet of the blade is made uniform.

However, in this technique, since the notch is formed in the side plate side portion of the blade, the length of the blade is relatively shorter than the blade without the notch. Therefore, the amount of work that the blades give to the airflow is reduced. In the present embodiment, the blades 44 themselves are not shortened. On the contrary, since the area of the blade 44 is increased, there is no such drawback, and the work amount of the blade 44 is effectively increased.

Moreover, the above technique is effective in a centrifugal fan whose blade width is sufficiently small with respect to the outer shape, as described in Patent Document 3. That is, by cutting out the blade, it is possible to prevent the suction airflow from separating at the side plate side portion of the blade, and to flow the airflow along the side plate side portion of the blade. However, when the blade width is sufficiently wide as in an ordinary centrifugal blower, that is, when the influence of peeling on the side plate side is not dominant, the above technique is not necessarily effective.

Also, if the blade side plate side portion is cut off, the airflow passing through the blade side plate side portion interferes with the corner portion of the blade main plate side. As a result, there is a possibility that new noise having discretely protruding frequencies may be generated. In the present embodiment, since there is no change in the basic shape of the blade 44 itself, those problems do not occur.

Also, when the blades are arranged so as to be orthogonal to the main plate and the side plate, there is a technique for changing the thickness of the blade from the end surface on the main plate side of the blade to the end surface on the side plate side of the blade. Thereby, the fluctuation | variation of the wind speed distribution in the blower outlet of a blade | wing is suppressed. Further, in that case, the outer diameter of the blade on the main plate side and the outer diameter of the blade on the side plate side are not the same, and the blade shape is enlarged as it approaches the main plate (for example, see Patent Document 4). reference). As a result, flow speed fluctuations in the blade wake are suppressed.

However, in this configuration, the ratio of the diameter at the end face on the main plate side of the impeller / the diameter at the end face on the side plate side of the impeller is set to 1.2 to 1.6. Therefore, when the extension amount due to the expansion of the blades is small, the noise reduction effect cannot be obtained, and conversely, when the extension amount is too large, the flow rate characteristic is deteriorated.

As a result, at least the diameter of the end portion on the main plate side of the impeller is enlarged by 20% with respect to the diameter on the side plate side. This does not provide an advantage over a technology that simply enlarges the fan diameter and simply enlarges the fan. In the first place, the increase in size by more than 20% cannot solve the problem of the reduction in size and noise that is the conventional problem at all.

However, in this embodiment, such a problem is effectively solved.
In particular, in the present embodiment, the rear edge 44b extended backward as it approaches the main plate 43 is extended from the side plate 45 to the main plate 43 little by little as shown in FIG.

According to such a configuration, the shape of the rear edge 44 b of the blade 44 becomes a substantially tapered shape that is enlarged from the side plate 45 to the main plate 43. As shown in FIG. 12, the trailing edge 44 b has a more suitable shape with respect to the change in the velocity distribution of the main flow F ₁ that flows in the vicinity of the main plate 43. In this case, of course, the outer diameter of the main plate 43 is also increased in accordance with the increase in the radial length of the rear edge 44b of the blade 44 on the main plate 43 side.

In this way, the length of the rear edge 44b of the blade 44 is extended, and the outer diameter of the main plate 43 is also extended, so that the structural strength of the impeller 42 of the centrifugal blower is improved at the same time. be able to.

<Example>
Now, using two conventional examples a and b and two examples c and d according to the present invention, the air blowing characteristics of the examples are confirmed. In Example c, in the blade 44 according to the present embodiment, the expansion ratio of the outer diameter Db ′ of the main plate 43 (the extension ratio of the width of the rear edge portion 44b to the rear of the air flow) is 5%. An impeller with wings. Example d is an impeller provided with a three-dimensional blade in which the enlargement ratio of the outer diameter Db ′ of the main plate 43 is 10% in the blade 44 of the present embodiment. As a comparative example, Conventional Example a is an impeller using the conventional blades shown in FIGS. Conventional example b is obtained by enlarging the entire diameter of the fan of conventional example a by 5%.

In the examples c and d, the portion of the blade 44 on the main plate 43 side (lower side in the state of FIGS. 6 to 9) through which the main flow F ₁ that is dominant in the fan characteristics passes is 5% behind the air flow. 10% extended. Therefore, by increasing the amount of work that the blade 44 imparts to the airflow, the flow rate of air blown from the impeller can be effectively increased. Thus, compared with the conventional example a and the conventional example b in which the diameter of the fan is simply expanded by 5%, in the examples c and d, for example, as shown in FIG. 13, the static pressure flow characteristic (PQ characteristic) is shown. Improved in all flow ranges. Moreover, in Example c and d, as shown in FIG. 14, a ventilation sound also becomes small except a low air volume area | region.

Further, by improving these two characteristics, the specific noise characteristics are greatly improved in Examples c and d, for example, as shown in FIG. The characteristics of these Examples c and d are clearly improved as compared with the conventional example b in which the fan diameter is uniformly expanded as a whole.

In addition, when compared with the similarly enlarged blade shown in Patent Document 4 described above, the same result as above was obtained at an enlargement ratio of 10% or less (5%). Therefore, it can be seen that the impeller has a large increase in air volume and is quiet, and can be further downsized.

<Modification 1>
Note that the shape of the rear edge 44b of the blade 44 that expands (extends) the main plate 43 is not limited to the linearly expanded shape (linear taper shape) as described above. For example, it may be a quadratic curve shape that draws a parabola as shown in FIG.

The curved shape of the trailing edge 44b takes into account the deviation of the wind speed distribution of the airflow blown from the impeller, and the trailing edge 44b of the blade 44 is extended more in the radial direction as it approaches the main plate 43 than the side plate 45. Become.

According to such a configuration, the shape of the trailing edge 44 b of the blade 44 becomes a quadratic function taper shape that expands in an arc shape from the side plate 45 to the main plate 43. The trailing edge 44b of the blade 44 can be made more suitable for the velocity distribution of the main flow F ₁ that flows in the vicinity of the main plate 43 as shown in FIG.

That relative velocity distribution of the main flow F _1, it is possible to more effectively optimize the shape of the edge 44b of the blade 44, expected that further improvement in the fan performance.
<Modification 2>
In the centrifugal blower as described above, the airflow in the vicinity of the main plate 43 forms a laminar shear layer due to the influence of viscosity due to the wall surface of the main plate 43. As a result, the flow path of the mainstream F ₁ is narrowed, and the fan performance may be reduced.

Therefore, in order to deal with such a problem, for example, as shown in FIG. 17, the rear edge 44b is formed so that one or more inflection points exist in the curved portion. Thereby, the rear edge 44b has a bulging portion in the vicinity of the main plate 43. In consideration of the velocity distribution of the blown airflow, the enlargement of the rear edge 44b of the end surface of the main plate 43 is set slightly shorter than the maximum extension portion (however, at least the radius of the end portion of the rear edge 44b on the side plate 45 side). The

With such a configuration, the development of the shear layer can be suppressed and the fan performance can be further improved.
<Modification 3>
As shown in FIGS. 18 to 21, the front edge 44 a of the blade 44 further includes first and second protrusions that project in a stepped manner toward the inside of the impeller 42 (in this embodiment, two stepped portions).

Steps

44c and 44d may be provided. In the first and second sets of

step portions

44c and 44d, the airflow sucked into the impeller 42 through the air inlet 31 and the bell mouth 5 of FIG. In this case, the blade 44 has a function of suppressing separation from the suction surface side. Thereby, the 1st and

2nd step parts

44c and 44d are contributing to making the blowing noise of the air blower 4 still smaller.

Here, the negative pressure surface refers to the surface of the blade 44 facing the inner peripheral side of the impeller 42, and the surface opposite to the negative pressure surface, that is, the surface of the blade 44 facing the outer peripheral side of the impeller 42 is positive. It is a pressure side.

The lengths La · Lb, Lc · Ld of the first and

second step portions

44c, 44d are 0.09 to 0. 0 of the original chord lengths L ₁ , L ₂ , L ₃ in the span direction of the blade 44. It is set to 18 times. That is, the length of the lower first step portion 44c varies in the span direction in a range of 0.15 (La) to 0.2 (Lb) times, and the length of the upper second step portion 44d is It varies in the range of 0.08 (Lc) to 0.1 (Ld) times.

Now, the blade 44 of the third modification is represented as a trapezoid stepped embodiment d. Further, the embodiment shown in FIGS. 1 to 12 where the first and

second step portions

44c and 44d are not attached to the front edge 44a described above (this is shown as trapezoidal stepless) c. The comparative example b is provided with first and

second step portions

44c and 44d with respect to a conventional blade. When Example c is compared with Example d, for example, as shown in FIG. 22, the specific noise characteristic is reduced in the entire flow region. In Example c, a reduction effect of at least 1.1 [dBA] can be obtained particularly at the lowest specific noise point. This is because when the impeller is rotating, a vertical vortex is generated with respect to the airflow before flowing into the reference blade 44 due to the protruding shape of the first and

second step portions

44c and 44d of the front edge 44a. This is because peeling from the front edge 44a can be suppressed by the action of the vertical vortex.

In particular, the centrifugal blower of the present embodiment shown in FIGS. 1 to 12 described above is designed such that the airflow passing through the impeller flows below the blade 44 as compared with the conventional example a. Therefore, the peeling suppression effect by the vertical vortex generated by the first and

second step portions

44c and 44d of the front edge 44a is more effectively affected.

As shown in FIG. 23, in the aerodynamic characteristics, Example c is inferior in the low air volume region as compared with Comparative Example b. In Example d, the first and

second step portions

44c and 44d were added to improve the characteristics in the low air volume region as compared with Comparative Example b. Thereby, compared with the comparative example b, the aerodynamic characteristic of Example d is also improved in the entire air volume region. As a result, the centrifugal blower using the embodiment d according to the invention of the third modification can generate a larger amount of air at the same static pressure.

From the above results, the centrifugal blower of the present modification 3 has a lower specific noise than conventional centrifugal blowers and can increase the air volume even at the same static pressure. This makes it possible to develop a fan that is small and quiet.

As a result, when the centrifugal blower is used, it is possible to realize a more compact air conditioner that is superior in quietness while maintaining a large air volume.
<Modification 4>
Note that the first and

second step portions

44c and 44d of Modification 3 can be combined with Modification 2 described above, for example, as shown in FIG.

<Application object of centrifugal blower of the present invention>
In general, the deviation of the velocity distribution of the blown airflow in the main plate side portion of the blade as described above is a problem that always occurs in various centrifugal fans. Therefore, the present invention is applicable to the impellers of such various types of centrifugal blowers (for example, turbo type, sirocco type, radial type, etc.). In that case, the fan characteristics can be improved sufficiently effectively.

Claims

A plurality of three-dimensional blades, a main plate for fixing one end surface in the span direction of each blade at a predetermined interval in the circumferential direction, and provided on the other end surface in the span direction of each blade A centrifugal blower comprising a ring-shaped side plate and blade driving means for rotating the blade via the main plate, wherein the radial length of the outer peripheral end of the blade on the main plate side is the same as that of the blade. A centrifugal blower set longer than the length in the radial direction of the outer peripheral end on the side plate side.
By setting the radial length of the outer peripheral end on the main plate side of each blade longer than the radial length of the outer peripheral end on the side plate side of the blade, the airflow passing through each blade is 2. Centrifugation according to claim 1, wherein work is effectively received from a portion of the blade on the main plate side, and air velocity in the span direction of each blade is effectively developed in the portion of the blade on the main plate side. Blower.
The radial length of the outer peripheral end of the blade on the main plate side is extended in the radial direction of the outer peripheral end of the blade on the side plate side by extending the trailing edge of the blade toward the rear of the air flow. The centrifugal blower according to claim 1 or 2, wherein the centrifugal blower is formed longer than the length.
The centrifugal blower according to claim 3, wherein the rear edge is extended so as to gradually increase from the side plate toward the main plate.
The rear edge is extended in a curved shape, and a bulging portion is formed in a portion on the main plate side of the rear edge so that one or more inflection points exist in the curved portion. 4. The multiblade centrifugal blower according to 4.
The centrifugal blower according to claim 3, wherein the trailing edge is extended rearward long corresponding to the velocity distribution of the main stream of the airflow at the trailing edge.
The centrifugal blower according to claim 6, wherein the extension amount of the trailing edge is 10% or less of the outer diameter of the side plate.
The centrifugal blower according to any one of claims 1 to 7, wherein a step portion extending a predetermined length in front of the blade is provided at a portion of the front edge of each blade on the main plate side.
The centrifugal blower according to any one of claims 1 to 8, wherein an outer diameter of the main plate is enlarged in accordance with an extension of the blade.
The centrifugal blower according to any one of claims 1 to 9, wherein the centrifugal blower is configured as a blower of an indoor unit for an air conditioner.