KR20080037722A - Centrifugal fan and air conditioner using the same - Google Patents

Abstract

Provided are a centrifugal fan where airflow speed distribution at a fan blowout opening, in the direction of the height of a blade, is uniformized to reduce operation noise, and an air conditioner in which the centrifugal fan is used to reduce operation noise. The centrifugal fan has a hub for fixing the rotating shaft of a motor, a main plate formed at the outer circumference of the hub, a shroud placed facing the main plate to form an airflow path, blades placed between the main plate and the shroud, and a bell mouth placed on the suction side of the shroud. Ridges or recesses are formed in that surface of the shroud which faces the bell mouth, and the ridges or recesses form, in fan operation, an airflow along the surface from the center of the shroud toward its outer circumference. The air conditioner has the centrifugal fan constructed as above.

Description

Centrifugal fan and air conditioner using it {CENTRIFUGAL FAN AND AIR CONDITIONER USING THE SAME}

The present invention relates to a centrifugal fan and an air conditioner using the same, and more particularly, to a low noise level in a centrifugal fan and an air conditioner using the same.

In general, centrifugal fans are highly efficient and low noise, and they are often used in air conditioners. In recent years, a ceiling-mounted air conditioner has been widely used in the field of work, and a wall-mounted air conditioner has been used in the field of home use. In any of these air conditioners, in order to downsize, the structure in which the heat exchanger is arrange | positioned at the extraction side of a centrifugal fan is increasing.

As described above, in the structure in which the heat exchanger is arranged on the ejection side of the centrifugal fan, in order to uniformize the distribution of the wind speed in the heat exchanger, the axial length of the impeller, that is, the height of the blade is often increased to match the size of the heat exchanger. .

By the way, in a centrifugal fan generally, peeling flow arises in the vicinity of the fan outlet on the surface with respect to the shroud main plate. In addition, noise is generated by this peeling flow, and there is a problem that the wind speed distribution of the air flow at the fan outlet is inclined to the main plate. Moreover, in the air conditioner in which the heat exchanger is arrange | positioned at the ejection side of a centrifugal fan, the wind speed distribution of the air flow in a fan outlet becomes inclined to the abacus, and the wind speed distribution of a heat exchanger becomes uneven and heat exchange of a heat exchanger is carried out. Along with the decrease in efficiency, the ventilation resistance of the heat exchanger is increased. As a result, the power required for the rotation of the fan increases and the energy efficiency is lowered.

This peeling flow is demonstrated using FIG. 10 and FIG. 10 is a perspective view showing the appearance of an impeller of a turbofan as a conventional centrifugal fan, and FIG. 11 is a longitudinal sectional view showing a part of the same turbofan. As shown in these figures, the turbo fan is disposed so as to face the hub 101 fixing the rotational axis of the motor, the main plate 102 formed integrally with the outer circumference of the hub 101, and the main plate 102, and the gas flow path 103. Shroud 104 forming a), a plurality of wings 105 disposed between the abacus 102 and the shroud 104, and a bell mouth disposed on the suction side of the shroud 104 Has 106. The hub 101, the main plate 102, the shroud 104, and the blade 105 constitute an impeller of a turbo fan. This impeller rotates in the direction of arrow R shown in FIG. The bell mouse 106 is attached to a member constituting an air conditioner in which a turbo fan is used, for example, a casing. The fan suction port 107 is formed in the center part of the bell mouth 106, and the part corresponding to the outer periphery of the shroud 104 in the air flow path 103 comprises the fan blower outlet 108. As shown in FIG.

In the turbo fan having such a configuration, some of the air flow blown from the fan outlet 108 enters the inlet 104a of the shroud 104 along the surface of the bell mouth 106. Then, a part of the air flow is sucked into the impeller of the turbo fan from the gap 109 of the bell mouth 106 and the shroud 104, and forms a circulating air flow which is blown again from the fan outlet 108. Doing. Since the change of the shape of the surface 104b with respect to the main plate 102 of the shroud 104 from the inlet 104a to the fan outlet 108 is abrupt, the peeling flow E is generated near the fan outlet 108. Is formed. And this peeling flow (E) generate | occur | produced the noise as mentioned above, and there existed a problem which the wind speed distribution in the fan outlet 108 biases the main plate 102.

As a solution to such a problem, a turbo fan described in Patent Document 1 is proposed. The basic structure of this turbofan is the same as that of the turbofan shown in FIGS. 10 and 11, but the shape of the blade is studied as follows. That is, in the blade | wing of the turbofan of patent document 1, the position of the engaging part with the shroud in the trailing edge part is offset by the predetermined amount to the side opposite to a rotation direction rather than the position of the engaging part with a main plate. In addition, the positive pressure surface of the shroud side wing portion is formed in a projection shape, and the maximum bending position of the camber wire of the shroud side wing portion is located at the leading edge than the middle position of the blade length. Further, the wing entrance angle of the shroud side is formed at the same angle as the case where the camber wire of the shroud side wing portion is a single arc camber wire, and the camber wire of the main plate side wing portion has a single arc shape. For this reason, the wing exit angle of the shroud side becomes large, and this wing exit angle of the shroud side approaches the wing exit angle of the main plate side.

The turbo fan described in Patent Literature 1 intends to suppress the peeling flow by applying a force in the shroud direction to the air flow flowing from the leading edge of the blade and flowing toward the trailing edge of the blade, as the blade is configured as described above. Doing. In addition, the turbo fan achieves a uniform air velocity distribution in the height direction of the blade at the fan outlet by making the blade exit angle on the shroud side close to the blade exit angle on the main plate side.

[Patent Document 1: Japanese Patent Application Laid-Open No. H5-312189]

However, in the turbofan of patent document 1, the peeling flow which generate | occur | produces in the vicinity of the fan outlet in the surface with respect to the main plate of shroud was not fully restrained. For this reason, the noise by peeling flows could not be fully suppressed. Moreover, the wind speed distribution of the height direction of the blade | wing in the fan outlet was biased to the abacus. Moreover, the air conditioner equipped with the turbo fan of patent document 1 has a problem that operation sound is large. While the turbo fan described in Patent Document 1 is used, in the air conditioner in which the heat exchanger is arranged on the fan ejecting side, the wind speed distribution in the heat exchanger becomes uneven. Therefore, the ventilation resistance of the heat exchanger became large, the power required for rotation of a fan became large, and the heat exchange efficiency of the heat exchanger fell. As a result, there is a problem that the energy efficiency of the air conditioner is lowered. For this reason, even in the turbofan described in Patent Document 1, further improvement of the wind speed distribution in the height direction of the blade at the fan outlet is required. Moreover, since the blade of the turbofan of patent document 1 has a special shape, it cannot be applied to the centrifugal fan of a general air conditioner. Therefore, the improvement applicable to the centrifugal fan of a general air conditioner was desired.

An object of the present invention is a novel constitution that can be applied to a centrifugal fan of a general air conditioner, and in the fan outlet of a centrifugal fan by suppressing the peeling flow occurring near the fan outlet on the surface of the shroud to the main plate. It is to provide a centrifugal fan which can uniformize the wind speed distribution in the height direction of the blade and reduce the operation sound of the centrifugal fan. Another object of the present invention is to provide an air conditioner in which an operation sound can be reduced by using a centrifugal fan configured as described above in an air conditioner on which a centrifugal fan is mounted.

In one embodiment of the present invention, there is provided a hub for fixing a rotating shaft of a motor, an abacus formed on an outer periphery of the hub, a shroud disposed opposite the abacus to form a gas flow path, a plurality of wings disposed between the abacus and the shroud, and a shroud. A centrifugal fan is provided having a bell mouse disposed on the suction side of the wood. On the surface of the shroud of the bell mouse, a plurality of protrusions or recesses are formed to form air flows outward from the center of the shroud along the surface upon operation of the fan.

According to this structure, the airflow toward the outer periphery from the center of the shroud along the surface is generated by the protrusion or the recess formed on the surface of the shroud of the bell mouse. This air flow is circulated from the center of the shroud back to its periphery in the space formed between the surface of the bell mouse of the shroud and the bell mouse via the surface of the outer wall of the bell mouse from the perimeter of the shroud. Develop into airflow For this reason, a part of the air flow discharged from the fan outlet port is attracted to this circulation air stream and circulates. Part of the air circulating in this way flows from the gap between the hub and shroud along the surface of the shroud's main plate toward the fan outlet, thereby increasing the airflow along the surface of the shroud's main plate. As a result, the peeling flow which arises in the vicinity of the fan outlet in the surface with respect to the main plate of a shroud is suppressed, the operation sound of a centrifugal fan falls, and the wind speed distribution of the height direction of the vane in a fan outlet is equalized. do.

It is preferable that the surface of the shroud of the bell mouth is provided with a plurality of rib-shaped protrusions which form an air flow from the center of the shroud to the outer circumference along the surface during operation of the fan. According to this structure, it becomes easy to act as a wing | blade-like protrusion part, and compared with the case where the recessed part which has a groove shape is formed in the surface with respect to the bell mouth of a shroud, the circulation airflow toward the outer periphery from the center of a shroud is made. It becomes easy to produce it.

The rib-shaped protrusion on the surface of the shroud bell mouth has approximately the same inclination as the camber line of the shroud side wing of the wing, and is formed at equal intervals over the entire circumference of the shroud bell mouth. It is preferable. According to this structure, the airflow direction in the outer peripheral part of the shroud of the circulation airflow formed in the surface with respect to the bell mouth of the shroud can match the airflow direction of the airflow discharged from a fan outlet. Therefore, the amount attracted to the circulation airflow of the surface with respect to the bell mouth of the shroud increases from the airflow discharged from the fan outlet. As a result, the airflow from the inlet of the shroud to the fan outlet along the surface of the shroud's main plate increases, and further, the peeling flow occurring near the fan outlet on the surface of the shroud's main plate can be further suppressed. Can be.

It is preferable that the pitch of the rib-shaped protrusion of the surface with respect to the bell mouth of a shroud is smaller than the pitch of a wing | blade. According to this configuration, the circulation airflow can be efficiently generated in the space between the surface of the bell mouse of the shroud and the bell mouse.

It is preferable that the height of the rib-shaped protrusion of the surface with respect to the bell mouth of a shroud is about the same as the plate | board thickness which forms a shroud. According to this configuration, when the shroud is integrally molded with a resin, the amount of change in the thickness of the shroud as a whole can be reduced, and the shroud is easily formed. In addition, the rib-shaped protrusion of the shroud has an appropriate height for a small space formed between the shroud and the bell mouth. As a result, the circulation airflow can be generated efficiently, and noise can be efficiently reduced.

The rib-shaped protrusion of the surface to the bell mouse of the shroud extends perpendicularly from the surface to the bell mouse of the shroud, and is located in front of the impeller in the rotational direction and the surface to the bell mouse of the shroud. It is preferable to have a rear side surface which extends vertically from the rear surface and located rearward with respect to the rotation direction of the impeller, and a front end surface which connects both side surfaces. In this case, the front end surface and the front side surface are connected to be substantially orthogonal to each other, and the rear side surface is curved toward the front side surface toward the front end.

According to this structure, since the front side surface which becomes a positive pressure side is extended vertically to a front end surface, the generation | occurrence | production ability of the airflow toward the outer periphery from the center in the surface with respect to the bell mouth of a shroud can be maintained high. Moreover, since the rear side surface serving as the negative pressure side is curved toward the front side as it faces the tip, the air easily enters the negative pressure surface side, and generation of vortex on the negative pressure surface side can be suppressed. As a result, it becomes possible to generate | occur | produce the airflow toward the outer periphery more efficiently from the center at the surface with respect to the bell mouse of the shroud, and can suppress the noise by the vortex on the negative pressure surface side.

In another aspect of the present invention, an air conditioner equipped with the centrifugal fan is provided. According to this structure, the operation sound of a centrifugal fan is reduced, and the noise of an air conditioner can be reduced.

It is preferable that an air intake port for sucking indoor air is formed on the front surface of the fan intake port of the centrifugal fan. In this case, the heat exchanger is arrange | positioned at the extraction side of a centrifugal fan. Downstream of the heat exchanger is an air outlet for blowing air into the room. According to this configuration, a structure suitable for compacting the air conditioner is provided. Moreover, the wind speed distribution in the height direction of the blade | wing in the fan outlet of a centrifugal fan becomes uniform, and the wind speed distribution of a heat exchanger is improved. As a result, the heat exchange efficiency of the heat exchanger is improved, the resistance in the air conditioner is reduced, and the energy efficiency of the air conditioner is improved.

The centrifugal fan is preferably a turbo fan. According to this configuration, the fan efficiency can be improved and the driving sound can be further suppressed.

1 is a perspective view showing an appearance of an air conditioner according to an embodiment of the present invention.

2 is a plan sectional view showing an air conditioner.

3 is a perspective view showing a state in which the front of the air conditioner is open.

4 is a perspective view showing an impeller constituting a turbo fan of the air conditioner.

5 is an enlarged perspective view of a part of an impeller;

6 is an enlarged longitudinal sectional view of a portion of a turbo fan.

7 is an enlarged cross-sectional view of a rib-shaped protrusion in the impeller.

8 is a sectional view showing a modification of the rib-shaped protrusion;

9 is a perspective view illustrating a heat exchanger in an air conditioner.

The perspective view which shows the impeller in the turbofan which concerns on a conventional example.

11 is a longitudinal sectional view showing a part of a turbo fan.

EMBODIMENT OF THE INVENTION Hereinafter, the centrifugal fan which concerns on embodiment of this invention, and the air conditioner which mounts this centrifugal fan is demonstrated based on drawing.

The air conditioner which concerns on this embodiment is an indoor unit of a wall-mounted air conditioner, and has a horizontally long box shape as shown to the perspective view of FIG. This indoor unit is formed so that the dimension of the thickness direction (up-down direction of FIG. 2) may become small, as shown to the flat sectional drawing of FIG. The main body casing 1 houses a turbo fan 2 as an indoor fan and a heat exchanger 4 for cooling or heating indoor air.

The main body casing 1 is provided with the front plate 11 in the front surface of the said main body casing 1, as shown to the perspective view of FIG. The front plate 11 has an air inlet 12 for sucking indoor air at the center portion, and an air outlet 13 for blowing air heat exchanged by the heat exchanger 4 at both sides. . Inside the main body casing 1, as shown in the sectional view of FIG. 2 and the perspective view of FIG. 3, the turbo fan 2 is arrange | positioned at the center part, and the heat exchanger 4 is arrange | positioned at both sides. The turbo fan 2 is arrange | positioned so that the air sucked in from the air suction port 12 may be blown in to the side of the turbo fan 2. The heat exchanger 4 is located on the take-out side of the turbo fan 2. In the main body casing 1, the air passage 14 is formed so that the air sucked into the turbo fan 2 is blown into the room from the air outlet 13 after the heat exchanger 4 exchanges heat.

As shown in FIG. 2, the turbo fan 2 has an impeller 21, a bell mouth 22 for guiding air to the impeller 21, and a motor 23 for driving the impeller 21. have. The rotating shaft of the impeller 21, that is, the rotating shaft 23a of the motor 23, is disposed in the center portion of the main body casing 1 so as to extend in the thickness direction of the main body casing 1. The bell mouth 22 is arrange | positioned in the position corresponding to the air intake port 12. As shown in FIG. As the motor 23, a thin-shaped motor, for example, a print motor, is used, and is fixed at a position corresponding to the impeller 21 on the back wall of the main body casing 1.

As shown in FIGS. 2-6, the impeller 21 has the hub 24 which fixes the rotating shaft 23a of the motor 23, the main plate 25 integrally formed in the outer periphery of the hub 24, and the main plate ( It is comprised by the shroud 27 which is arrange | positioned facing 25 and forms the gas flow path 26, and the 6 blade | wing 28 arrange | positioned between the main plate 25 and the shroud 27. As shown in FIG. Fig. 4 is a perspective view showing the appearance of the impeller, Fig. 5 is a perspective view showing an enlarged appearance of a part of the impeller, and Fig. 6 is a longitudinal sectional view showing a part of the turbo fan. 3-5, and the arrow R in each figure of FIG. 7 and FIG. 8 mentioned later have shown the rotation direction of the impeller 21. As shown in FIG. The fan suction port 29 is formed in the center portion of the bell mouse 22. As shown in FIG. 2, the bell mouse 22 also functions as a partition wall for partitioning the suction side of the heat exchanger 4 in cooperation with the front plate 11. In the gas flow path 26, a portion corresponding to the outer circumference of the shroud 27, that is, the trailing edge of the blade 28 constitutes the fan outlet 30.

The structure of the blade | wing 28 is the same as that of the blade | wing of patent document 1 mentioned above. That is, the wing | blade 28 is offset by the predetermined amount in the position opposite to the rotation direction rather than the position of the engagement part with the shroud 27 in the trailing edge with respect to the position of the engagement part with the main plate 25. In addition, the positive pressure surface of the shroud side wing portion is formed in a projection shape, and the maximum bending position of the camber wire of the shroud side wing portion is located at the leading edge than the middle position of the blade length. In addition, the wing entrance angle of the shroud side is formed at the same angle as the case where the camber wire of the shroud side wing portion is a unitary camber line, and the camber wire of the main plate side wing portion is a single arc. It has a shape.

3 to 6, the surface 27a of the bell mouth 22 of the shroud 27 is circumferentially from the center of the shroud 27 along the surface 27a at the time of operation of the fan. A plurality of rib-shaped protrusions 31 are formed to form an air stream directed toward the. These rib-shaped protrusions 31 are formed to have approximately the same inclination as the camber line of the shroud side wing portion of the blade 28 and are formed at equal intervals over the entire circumference of the surface 27a of the shroud 27. have. The pitch of each rib-shaped protrusion 31 is formed to be about 1/10 of the pitch of each blade 28. The height of the rib-shaped protrusions 31 is about the same as the plate thickness forming the shroud 27, and is formed about 1 mm. As shown in FIG. 7, the rib-shaped protrusion part 31 has the front side 32 located in the front, the rear side 33 located in the rear, and these both sides (in the rotation direction of the impeller 21). It has a front end surface 34 which connects 32 and 33. Each side surface 32 and 33 extends perpendicularly from the surface 27a of the shroud 27. The front face 32 and the tip face 34 are connected to be substantially perpendicular to each other. The rear side surface 33 is curved toward the front side surface 32 toward the front end.

Each heat exchanger 4 is arrange | positioned substantially symmetrically through the turbo fan 2, as shown in FIG. As shown in the perspective view of FIG. 9, the dispersedly arranged heat exchangers 4 are connected to each other by a refrigerant pipe 41 arranged using a space at the bottom of the main body casing 1 and are configured to work integrally. It is. In each heat exchanger 4, as shown in FIG. 9, between the front plate 42 and the rear plate 43, six rows of flat tubes 44 extend in the thickness direction of the main body casing 1 and further. It is arranged parallel to each other. Colgate fins 45 are interposed between the flat tubes 44 and between the flat tubes 44 and the front plate 42 or the rear plate 43. The flat tube 44 and the corrugated fin 45 are joined by soldering, for example.

The air conditioner comprised as mentioned above, and the turbo fan mounted in the air conditioner act as follows. When the operation of the air conditioner is started and the turbo fan 2 is operated, indoor air is sucked in from the air intake 12. This indoor air is taken in by the gas flow path 26 of the turbofan 2 from the fan intake port 29, is boosted by the vanes 28, and discharged from the fan outlet 30. The air blown in from the fan blower outlet 30 is heat-exchanged by each heat exchanger 4, and blown into the room from the air blower outlet 13. As shown in FIG.

5 and 6, in the turbo fan 2, a plurality of rib-shaped protrusions 31 formed on the surface 27a of the shroud 27 act like a wing to the surface 27a. Therefore, the air flow S1 toward the outer periphery is generated from the center of the shroud 27. This air flow S1 is formed in the space formed between the surface 27a of the shroud 27 and the bell mouth 22, from the outer periphery of the bell mouth 22 to the outer periphery of the shroud 27. It develops into the circulation airflow S2 which goes to the outer periphery from the center of the shroud 27 via the surface. For this reason, the air flow S4 which is a part of the air flow S3 discharged | emitted from the fan outlet 30 is attracted to this circulation airflow S2, and it circulates. Air flow S4 which is a part of the air circulating in this way is a fan along the surface 27b with respect to the main plate 25 of the shroud 27 from the gap 35 of the hub 24 and the shroud 27. It flows toward the outlet 30. Therefore, the air flow S5 along the surface 27b of the shroud 27 increases. As a result, the peeling flow E which arises in the vicinity of the fan outlet port 30 in the surface 27b of the shroud 27 is suppressed, the operation sound of the turbo fan 2 falls, and a fan outlet port is reduced. The wind speed distribution in the height direction of the blade | wing in 30 is equalized.

The rib-shaped protrusion 31 is formed to have approximately the same inclination as the camber line of the shroud side blade portion of the blade 28. Therefore, the airflow direction in the outer periphery of the shroud 27 of the airflow S1 flowing along the surface 27a of the shroud 27, and the airflow S3 discharged from the fan outlet 30 The airflow direction can be matched. As described above, the air flow directions of the air flow S1 and the air flow S3 substantially coincide with each other, thereby circulating air flow S2 on the surface 27a of the shroud 27 from the air flow S3 discharged from the fan outlet 30. The amount of air flow (S4) attracted to) increases. As a result, the air flow S5 from the inlet of the shroud 27 toward the fan outlet 30 increases along the surface 27b of the shroud 27, and the surface 27b of the shroud 27 increases. The peeling flow E which generate | occur | produces in the vicinity of the fan outlet 30 in this can be suppressed further.

The rib-shaped protrusion part 31 is formed so that the pitch may become considerably smaller than the pitch of the blade | wing 28. As shown in FIG. Therefore, in the small space between the surface 27a of the shroud 27 and the bell mouth 22, the circulation airflow S2 can be efficiently generated.

The height of the rib-shaped protrusion part 31 is about the same as the plate | board thickness which forms the shroud 27. As shown in FIG. Therefore, when the whole shroud 27 is integrally molded with resin, the amount of change of the thickness in the whole shroud 27 can be made small, and shaping of the shroud 27 becomes easy. Moreover, the rib-shaped protrusion part 31 has a suitable height with respect to the small space formed between the shroud 27 and the bell mouth 22, and efficiently produces the said circulation airflow S2, and efficiently makes noise. Can be reduced.

As for the rib-shaped protrusion part 31, as shown in FIG. 7, since the front surface 32 located in the positive pressure side is extended vertically to the front end surface 34, in the surface 27a of the shroud 27, It is possible to maintain a high generation capacity of the air flow (S1) from the center to the outer periphery. Moreover, the front-end | tip part of the rear side surface 33 located in the negative pressure side is formed in circular arc shape. Therefore, air tends to enter the negative pressure side, and generation | occurrence | production of the vortex F in the negative pressure side can be suppressed. As a result, it becomes possible to generate | occur | produce the airflow toward the outer periphery from the center in the surface 27a of the shroud 27 more efficiently, and can suppress the noise by the vortex which arises on the negative pressure side.

In the turbo fan 2 according to the present embodiment, like the turbo fan described in Patent Document 1, the position of the engaging portion with the shroud 27 in the trailing edge of the blade 28 is the main plate 25. The predetermined amount is offset to the side opposite to the rotation direction from the position of the engaging portion with the. Therefore, the force in the direction of the shroud 27 is given to the airflow which flows in from the leading edge of the blade 28 and flows toward the trailing edge of the blade 28. Therefore, peeling flow E is suppressed also from this point. In addition, the positive pressure surface of the shroud side wing portion is formed into a projection shape, and the maximum bending position of the camber wire of the shroud side wing portion is located at the leading edge than the middle position of the blade length. Further, the wing entrance angle of the shroud side is formed at the same angle as the case where the camber wire of the shroud side wing portion is a single arc camber wire, and the camber wire of the main plate side wing portion has a single arc shape. For this reason, the wing exit angle of the shroud side is enlarged and the wing exit angle of the shroud side is made closer to the wing exit angle of the main plate side. By having such a structure, the wind speed distribution of the height direction of the blade | wing 28 in the fan outlet 30 is equalized.

The air conditioner which concerns on this embodiment can reduce the operation sound as an air conditioner by reducing the operation sound of the turbofan 2.

This air conditioner has an air inlet 12 for sucking indoor air in front of the fan inlet 29 of the turbofan 2. The heat exchanger 4 is arrange | positioned at the blow-out side of the turbo fan 2, and the air blower outlet 13 which blows air into the room downstream of this heat exchanger 4 is arrange | positioned. Therefore, by making the dimension of the heat exchanger 4 in the thickness direction of the main body casing 1 small, it becomes possible to make the external dimension of the thickness direction of an air conditioner small. The wind speed distribution in the height direction of the blade | wing in the fan outlet 30 of the turbo fan 2 becomes uniform, and the wind speed distribution of the heat exchanger 4 is improved. As a result, the heat exchange efficiency of the heat exchanger 4 is improved, the resistance in the air conditioner is reduced, and the energy efficiency of the air conditioner is improved.

In this air conditioner, the turbo fan 2 is used as an indoor fan. Therefore, the fan efficiency can be improved and the driving sound can be further suppressed as compared with the case where other centrifugal fans are used.

This embodiment may be changed as follows.

(1) In this embodiment, the blade | wing 28 has the same structure as the blade | wing of patent document 1 mentioned above. It is not limited to this, For example, the two-dimensional shape by which the leading edge part and trailing edge part of the blade | wing 28 introduce | transduced as a prior art in patent document 1 orthogonal to the main plate 25 and the shroud 27, respectively, is a blade | wing. (28) may have. Also in this case, the present invention can be applied.

(2) Although the noise reduction with respect to the turbo fan 2 is demonstrated in this embodiment, there exists a similar problem also about other centrifugal fans, such as a sirocco fan and a radial fan. And also in the other centrifugal fan, the rib-shaped protrusion part 31 may be provided in the surface 27a of the shroud 27 like the case of this embodiment. Also in this case, the effect similar to this embodiment can be acquired.

(3) Including the present embodiment and the case of the modifications (1) and (2), and instead of the rib-shaped protrusion 31, a protrusion having a wing shape or an concave groove forming the air stream S1; The same concave portion may be formed on the surface 27a of the shroud 27. However, although the concave groove can be simply formed by cutting, a deep concave groove cannot be obtained in relation to the plate thickness of the shroud 27. In addition, the air flow changes more than in the case of the rib-shaped protrusion 31, and the air flow S1 directed from the center of the shroud 27 to the outer circumference along the surface 27a of the shroud 27 is efficiently It is thought that it is difficult to generate.

(4) In the rib-shaped protrusion part 31, as shown in FIG. 8, the front end surface 34 and the front side surface (static pressure surface) 32 are connected so as to be substantially orthogonal to each other, and the front end surface 34 and the rear side are shown. The side surfaces (negative pressure surface) 33 may be connected to be substantially perpendicular to each other. However, in this case, since air is less likely to enter the rear side (negative pressure surface) 33, the generation of the vortex F becomes large, and the noise reduction effect and the rib-shaped convex portion 31 in the present embodiment and The uniforming effect of the wind speed distribution at the fan outlet is deteriorated.

(5) The height of the rib-shaped protrusions 31 is approximately 1 mm in this embodiment. The height of the rib-shaped protrusions 31 is not limited to this, and, for example, depending on the diameter of the impeller of the turbofan 2 or the size of the space formed between the shroud 27 and the bell mouth 22. It may change suitably. However, if the rib-shaped protrusions 31 are excessively high with respect to the size of the space formed between the shroud 27 and the bell mouth 22, the vortices generated around the rib-shaped protrusions 31 become large and make noise. The reduction effect is impaired.

(6) This embodiment has described the wall-mounted air conditioner. The present invention is not limited to this, and the present invention may be applied to an air conditioner having a type other than the type of the present embodiment. The present invention is suitable for, for example, a compact ceiling embedded type. As the heat exchanger 4 provided on the take-out side of the turbo fan 2 as the centrifugal fan, a heat exchanger having a type other than the type of the present embodiment, for example, a cross fin coil type heat exchanger, may be used. The air conditioner is not limited to the structure in which the heat exchanger is arranged on the take-out side of the turbo fan 2 as the centrifugal fan, but is not the case in the air conditioner in which the heat exchanger 4 is arranged on the suction side of the turbo fan 2. The centrifugal fan which concerns on this invention may be applied.

The centrifugal fan which concerns on this invention can be applied to general centrifugal fans, such as a turbo fan, a sirocco fan, and a radial fan. Moreover, the air conditioner equipped with this centrifugal fan can be applied to the various types of air conditioners for home use and business use.

Claims (9)

A hub for fixing the rotation axis of the motor, a main plate formed on the outer periphery of the hub, a shroud disposed opposite the main plate to form a gas flow path, a plurality of wings disposed between the main plate and the shroud, and a shroud A bell mouth disposed on the suction side of the plurality of surfaces, the surface of the shroud of the bell mouth having a plurality of air flows toward the periphery from the center of the shroud along the surface during operation of the fan; A centrifugal fan, wherein a protrusion or a recess is formed. The method according to claim 1, The surface of the shroud of the bell mouse, the centrifugal fan, characterized in that a plurality of rib-shaped protrusions are formed to form an air flow from the center of the shroud to the outer circumference along the surface during operation of the fan. The method according to claim 2, The rib-shaped protrusion of the surface of the shroud relative to the bell mouth has an approximately same inclination as the camber line of the shroud side wing of the wing, and is formed at equal intervals over the entire circumference of the surface of the shroud bell mouth. Centrifugal fan characterized in that. The method according to claim 3, The pitch of the rib-shaped protrusion of the surface with respect to the bell mouth of the shroud is smaller than the pitch of the blade. The method according to claim 4, The height of the rib-shaped protrusion of the surface with respect to the bell mouse of the shroud is about the same as the plate thickness forming the shroud. The method according to any one of claims 2 to 5, The rib-shaped protrusion on the surface of the shroud with respect to the bell mouse has an anterior side extending in the rotational direction of the impeller while extending vertically from the surface with respect to the bell mouse of the shroud, and with respect to the bell mouse of the shroud. It extends vertically from the surface and has a rear surface located rearward in the direction of rotation of the impeller, and a front end surface connecting both sides, the front end surface and the front side are connected to be substantially orthogonal to each other, the rear surface, A centrifugal fan, which is curved toward the front side as it faces the tip. An air conditioner, comprising the centrifugal fan according to any one of claims 1 to 6. The method according to claim 7, An air inlet for sucking indoor air is formed on a front surface of the fan inlet of the centrifugal fan, a heat exchanger is disposed at the outlet side of the centrifugal fan, and an air outlet for blowing air into the room is disposed downstream of the heat exchanger. Air conditioner, characterized in that. The method according to claim 7 or 8, And the centrifugal fan is a turbo fan.

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