JP4650588B2 - Centrifugal blower - Google Patents

Description

  The present invention relates to the structure of a centrifugal blower.

  FIG. 18 shows the structure of a ceiling-embedded air conditioner 1 including a conventional turbo fan as an example of a centrifugal blower. As shown in FIG. 18, the air conditioner 1 has a cassette-type main body casing 2. The main body casing 2 is embedded in the ceiling 3 so that a lower surface panel (a panel provided with an air inlet and an air outlet) 4 is continuous with the ceiling 3 in substantially the same plane.

  A square air suction grille 5 is provided at the center of the lower panel 4. Inside the air suction grill 5, a pre-filter F, a bell mouth 6, an impeller 17, and a fan motor 13 that rotates the impeller 17 provided along the air suction grill 5 are provided from the front F side. They are arranged in this order toward the rear R side. A plurality of air outlets 9 extending along the outer periphery of the air suction grill 5 are provided around the air suction grill 5 of the lower panel 4.

  In the main casing 2, air flow paths 10 are formed from the air suction grille 5 through the bell mouth 6 and the impeller 11 to each air outlet 9. The air flowing through the air flow path 10 flows in from the air suction grill 5, passes through the bell mouth 6, and then flows outward in the radial direction so as to spread over the entire circumference of the impeller 17. An air heat exchanger 12 is disposed in the air flow path 10 so as to surround the impeller 17.

  The impeller 17 forms a circular hub (main plate) 14 fixed to the rotating shaft 13a of the fan motor 13 and an air suction port in the centrifugal direction inside the impeller 17, and has a diameter on one end side and the other end side. And a plurality of blades (blades) 16 arranged in parallel in the circumferential direction with a predetermined blade angle and a predetermined blade interval between the hub 14 and the shroud 15.

  In the air suction side end portion 15a of the shroud 15, an air outlet portion 6c on the downstream side of the bell mouth 6 is inserted with a predetermined gap G with a predetermined gap G.

  As shown in FIG. 18, the bell mouth 6 has an airflow guide surface including an air inflow port portion 6b and an air outflow port portion 6c. The air inflow port portion 6b is formed of an arc surface having a predetermined curvature radius that extends inwardly from the mounting edge portion 6a to the lower panel 4 and gradually decreases in opening diameter from the upstream side to the downstream side of the air flow. The air outlet part 6 c extends from the air inlet part 6 b toward the air suction side end part 15 a of the shroud 15. Thereby, the bell mouth 6 can smoothly flow the air sucked from the air suction grille 5 into the air suction side end portion 15a of the shroud 15 forming the air suction port of the impeller 17.

  The shroud 15 of the impeller 17 reduces aerodynamic noise generated during blowing as much as possible by smoothly guiding the air on the suction side of the impeller 17 in the centrifugal direction that is the blowing direction.

  In this way, in centrifugal fans such as turbofans, the airflow guide surfaces of the bell mouth and shroud are brought close to the ideal shape, thereby reducing the disturbance of the airflow at the outer periphery of the impeller and the suction portion as much as possible. We are trying to reduce it.

  However, the following aerodynamic noise is also generated in the centrifugal fan. For example, as shown in FIG. 19, when the impeller 17 rotates, the high-speed leakage flow B leaking from the gap G between the shroud 15 and the bell mouth 6 and the main flow A ′ near the shroud 15 of the original main flow A. The airflow separation on the surface of the shroud 15 and the airflow separation on the suction surface side of the blade 16 increase due to the interference with the airflow. Thereby, noise is generated.

  By the way, the gap G between the bell mouth 6 and the shroud 15 is provided so that the shroud 15 does not contact the bell mouth 6 when the impeller 17 rotates.

  The width of the gap G is generally set in consideration of the following three factors.

(1) Rotary shake caused by fan manufacturing accuracy (2) Indoor unit assembly error (3) Impeller misalignment that may occur during installation of the indoor unit However, due to the presence of the gap G, for example, as shown in FIG. A part of the air flow blown out from the blade 16 portion of the impeller 17 through the gap G between the shroud 15 and the bell mouth 6 is leaked to the suction side of the impeller blade 16 at high speed. Arise. This leakage flow B generates aerodynamic noise as described above and causes a decrease in fan efficiency.

  Until now, attempts have been made to improve the manufacturing accuracy of the impeller 17 and reduce rotational shake as much as possible. In addition, efforts have been made to reduce the assembly error of indoor units. Furthermore, an attempt has been made to reduce the misalignment of the impeller 17 due to minute deformation of the indoor unit while maintaining the level as much as possible when installing the indoor unit.

  However, in practice, a certain amount of misalignment is unavoidable. For example, the gap G is set larger than a predetermined dimension. Therefore, as described above, the occurrence of the leakage flow B reduces the fan efficiency and increases the input of the fan motor. Therefore, the leakage flow B is a factor that impairs the energy saving performance of the air conditioner.

  In response to the above-described problems, for example, the outer periphery of the insertion portion in which the air outlet portion 6c on the downstream side of the bell mouth 6 is inserted into the air suction side end portion 15a of the shroud 15 with a predetermined gap G interposed therebetween. An air conditioner has been proposed in which a cylindrical wall is provided between the outer peripheral surface of the shroud and the outer peripheral surface of the bell mouth so as to cover (for example, Patent Document 1).

JP 2004-156886 A (FIGS. 2 and 3)

  In the air conditioner of Patent Document 1, the leakage flow flowing through the gap between the bell mouth air outlet and the bell mouth side air suction side end of the shroud is reduced by reducing the passage area. It is described that the flow velocity of the flow is made uniform.

  However, in the air conditioner of Patent Document 1, since the leakage flow is still disturbed, there remains a problem that the disturbed airflow collides with the blades and causes an increase in aerodynamic noise.

  Then, this invention is made | formed in view of this point, The place made into the objective is to provide the centrifugal air blower which can reduce the noise resulting from a leak flow.

(1) The centrifugal blower of the present invention is attached to the fan motor (13). This centrifugal blower includes an impeller (17), a bell mouth (6), and an airflow resistance member (20, 21, 22). The impeller (17) includes a circular hub (14) fixed to the front side in the axial direction of the rotation shaft of the fan motor (13), and a plurality of blades (16) arranged in the circumferential direction of the hub (14). And a shroud (15) having an air suction side end (15a) that opens around the rotation axis and fixed to the front side of the plurality of blades (16). The bell mouth (6) has an air outlet (6c) that opens around the rotation axis. The bell mouth (6) is partially inserted on the air outlet (6c) side with a predetermined gap in the opening of the air suction side end (15a) . Before SL airflow resistance member (20, 21, 22) reduces the airflow amount of the leakage flow. In the leakage flow, a part of the airflow from the impeller (17) passes between the shroud (15) and the bell mouth (6), and the air suction side end (15a) and the airflow. It is the flow of the air which flows in into the said impeller (17) from the said clearance gap with an exit part (6c). The airflow resistance member (20, 21, 22) has a net structure knitted with a synthetic resin striate or a lattice structure formed with a synthetic resin. Rectified into a smooth flow.

  In this configuration, the airflow resistance member (20, 21, 22) through which the airflow can pass substantially evenly is provided in a portion through which the leakage flow passes. The amount of the leakage flow is reduced by uniformly suppressing the passage of the leakage flow through the gap between the air suction side end portion (15a) of the shroud (15) and the air outlet portion (6c) of the bell mouth (6). While reducing, the flow is rectified by uniformly trickling the leakage flow.

  Therefore, the amount of leakage flow is effectively reduced by the air flow resistance when the leakage flow passes through the air flow resistance member (20, 21, 22), and the leakage flow is rectified into a flow having a uniform flow velocity. , Leakage flow disturbance is reduced. In the case of this configuration, the leakage flow can pass through the airflow resistance member (20, 21, 22) substantially evenly, and therefore the change in the flow direction of the leakage flow is small. As a result, noise due to the provision of the airflow resistance member (20, 21, 22) hardly occurs. In addition, since the leakage flow flows smoothly, fan efficiency is improved, and air flow separation on the suction surface side of the blade (16) due to interference with the main flow is also effectively suppressed. Therefore, as compared with the conventional centrifugal blower, the blowing performance is improved and the blowing sound is effectively reduced. Further, the input of the fan motor (13) is reduced, and the energy saving performance is improved.

Further, in the configuration in which the airflow resistance member (20, 21, 22) has a net structure knitted with a synthetic resin linear body, the airflow resistance member (20, 21, 22) has the net structure knitted with a synthetic resin linear body. The amount of the leakage flow is reduced by the airflow resistance when the leakage flow passes through the airflow resistance member (20, 21, 22), and the leakage flow is rectified to reduce the disturbance of the leakage flow.

In particular, when the filament is made of a thin thread, the disturbance of the leakage flow when the leakage flow passes through the airflow resistance member (20, 21, 22) becomes smaller. Moreover, when the said linear body consists of a thin thread | yarn, when the said leakage flow passes the said airflow resistance member (20, 21, 22), the change of the flow direction of the said leakage flow can be made smaller. As a result, noise due to the provision of the airflow resistance member (20, 21, 22) hardly occurs. Thereby, the noise (wind noise) at the time of passage of the leakage flow can be further suppressed. In addition, since the leakage flow flows more smoothly, fan efficiency is improved and separation of the blade (16) on the suction surface side due to interference with the main flow is effectively suppressed. Therefore, as compared with the conventional centrifugal blower, the blowing performance is improved and the blowing sound is effectively reduced. Further, the input of the fan motor (13) is reduced, and the energy saving performance is improved.

In addition, in the configuration in which the airflow resistance member (20, 21, 22) has a lattice structure formed from a synthetic resin, the airflow resistance member (20, 21, 22) having a lattice structure formed from a synthetic resin. The amount of the leakage flow is reduced by the airflow resistance when the leakage flow passes through, and the leakage flow is rectified to reduce the disturbance of the leakage flow. Thereby, since the said leak flow flows smoothly, fan efficiency improves and peeling on the suction surface side of the blade | wing (16) by interference with a mainstream is also suppressed effectively. Therefore, as compared with the conventional centrifugal blower, the blowing performance is improved and the blowing sound is effectively reduced. Further, the input of the fan motor (13) is reduced, and the energy saving performance is improved. Moreover, since the airflow resistance member (20, 21, 22) having the lattice structure can be easily molded, it can be manufactured at low cost.

Moreover, in this structure, when the grating | lattice is comprised by the flat plate piece, the noise (wind noise) at the time of the said leakage flow passing through the said airflow resistance member (20, 21, 22) can be suppressed lower. it can.

  (2) It is preferable that the airflow resistance member (20, 21) is provided at an outer peripheral portion of the air suction side end portion (15a) of the shroud (15).

  In this configuration, the amount of leakage flow is effectively reduced by the airflow resistance when the leakage flow passes through the airflow resistance member (20, 21) surrounding the outer periphery of the air suction side end (15a). The leakage flow is rectified into a flow having a uniform flow velocity, and the disturbance of the leakage flow is reduced. In the case of this configuration, the leakage flow can pass through the airflow resistance member (20, 21, 22) substantially evenly, and therefore the change in the flow direction of the leakage flow is small. As a result, noise due to the provision of the airflow resistance member (20, 21) is unlikely to occur. In addition, since the leakage flow flows smoothly, fan efficiency is improved and separation of the blade (16) on the suction surface side due to interference with the main flow is effectively suppressed. Therefore, as compared with the conventional centrifugal blower, the blowing performance is improved and the blowing sound is effectively reduced. Further, the input of the fan motor (13) is reduced, and the energy saving performance is improved.

  (3) The airflow resistance member (22) surrounds the air suction side end portion (15a) of the shroud (15) between the airflow outlet portion (6c) of the bell mouth (6). It may be provided.

  In this configuration, the airflow resistance member (so as to surround the air suction side end (15a) of the shroud (15) between the bell mouth (6) and the air outlet (6c). 22) The amount of the leakage flow is reduced by the airflow resistance when the leakage flow passes through 22), and the leakage flow is rectified to reduce the disturbance of the leakage flow.

  In particular, in this configuration, the airflow resistance member (22) is close to the gap between the air suction side end (15a) of the shroud (15) and the air outlet (6c) of the bell mouth (6). Therefore, mixing of the airflow is promoted in the gap due to a small disturbance of the scale caused by finely disturbing the leakage flow when the leakage flow passes through the airflow resistance member (22). The reason is estimated as follows. That is, since the gap (overlap portion) between the air suction side end portion (15a) and the air outlet port portion (6c) is small, the leakage flow has a high flow velocity in and around the gap. Therefore, when this leak flow with a high flow velocity passes through the airflow resistance member (22), several small scale disturbances (vortices) are generated on the downstream side by the airflow resistance member (22). These small vortices promote turbulent mixing of the airflow, thus improving the drift in the gap. Thereby, since the effect which eliminates the drift which arises, for example due to the rotational shake of an impeller (17), etc. becomes high, the ventilation sound resulting from a drift is reduced effectively.

  Moreover, in this structure, it is preferable that the said airflow resistance member (22) is provided separately from the said bellmouth (6). For example, as compared with the case where the bell mouth (6) and the airflow resistance member (22) are integrally formed, the forming is easy and the cost can be reduced.

  Moreover, in this structure, the front-end | tip of the said airflow resistance member (22) is provided apart from the said shroud (15) by the predetermined dimension, and interference with the said shroud (15) rotating is avoided.

  (4) The airflow resistance member (20, 21, 22) may be provided so as to extend in a cylindrical shape from the bell mouth (6) side to the shroud (15) side.

  In this configuration, the amount of the leakage flow is reduced by the airflow resistance when the leakage flow passes through the tubular airflow resistance member (20, 21, 22), and the leakage flow is rectified, Leakage flow disturbance is reduced. Thereby, since the said leak flow flows smoothly, fan efficiency improves and peeling on the suction surface side of the blade | wing (16) by interference with a mainstream is also suppressed effectively. Therefore, as compared with the conventional centrifugal blower, the blowing performance is improved and the blowing sound is effectively reduced. Further, the input of the fan motor (13) is reduced, and the energy saving performance is improved.

  In this configuration, the airflow resistance member (20, 21, 22) is preferably provided separately from the bell mouth (6). For example, as compared with the case where the bell mouth (6) and the airflow resistance member (20, 21, 22) are integrally molded, the molding is easy and the cost can be reduced.

  Moreover, in this structure, the front-end | tip of the said airflow resistance member (20, 21, 22) is provided apart from the said shroud (15) by the predetermined dimension, and interference with the said shroud (15) rotating is avoided.

(5) The centrifugal blower is used as a blower for an air conditioner, for example.

  With this configuration, an air conditioner indoor unit with high performance, low noise, and high energy saving performance can be realized at low cost.

(6) The centrifugal blower of the present invention may have the following configuration. That is, the centrifugal blower of the present invention is attached to the fan motor (13). This centrifugal blower includes an impeller (17), a bell mouth (6), and an airflow resistance member (20). The impeller (17) includes a circular hub (14) fixed to the front side in the axial direction of the rotation shaft of the fan motor (13), and a plurality of blades (16) arranged in the circumferential direction of the hub (14). And a shroud (15) having an air suction side end (15a) that opens around the rotation axis and fixed to the front side of the plurality of blades (16). The bell mouth (6) has an air outlet (6c) that opens around the rotation axis. The bell mouth (6) is a state in which a part of the air outlet part (6c) side is provided with a predetermined gap between an edge of the opening of the air suction side end part (15a). It is inserted in the opening of the air suction side end (15a). The airflow resistance member (20) has a cylindrical shape. The airflow resistance member (20) is provided with a plurality of substantially uniform holes over substantially the whole. The said airflow resistance member (20) is arrange | positioned so that the said air suction side edge part (15a) and the said air outflow port part (6c) may be located in the inner side.

  In this configuration, the airflow resistance member (20) having a cylindrical shape and provided with a plurality of substantially uniform holes over substantially the whole is provided with the air suction side end portion (15a) and the airflow outlet portion. (6c) is positioned so that the leakage flow is introduced into the impeller (17) from the gap between the air suction side end (15a) and the air outlet (6c). Before flowing in, it passes through the airflow resistance member (20).

  Therefore, in this structure, since the said airflow resistance member (20) becomes resistance of a leak flow, compared with the case where the said airflow resistance member (20) is not provided, the amount of the said leak flow can be reduced. Moreover, since the airflow resistance member (20) is provided with a plurality of substantially uniform holes over substantially the whole, it is possible to trickle the leakage flow and suppress the turbulence of the airflow. Thus, the amount of the leakage flow is reduced, and the disturbance of the leakage flow is suppressed, so that the blowing sound can be reduced.

(7) It is preferable that the outer diameter of the rear end portion in the axial direction of the airflow resistance member (20) is larger than the outer diameter of the shroud (15).

  In this configuration, since the outer diameter of the rear end portion of the airflow resistance member (20) is larger than the outer diameter of the shroud (15), the outer diameter of the impeller (17) is slightly increased. Even when positional deviation (center misalignment), rotational shake during rotation of the impeller (17), or the like occurs, the airflow resistance member (20) can be prevented from contacting the shroud (15).

(8) The airflow resistance member (20) may have a substantially truncated cone shape whose outer diameter increases from the front side toward the rear side.

  In this configuration, the airflow resistance member (20) having a substantially frustoconical shape has the effect of suppressing contact with the shroud (15), and further, the airflow resistance member (20) having a substantially constant outer diameter. In comparison, the effect of reducing the amount of the leakage flow and the effect of suppressing the turbulence of the air flow by trickling the leakage flow can be further enhanced. That is, the airflow resistance member (20) having a substantially frustoconical shape compared to the airflow resistance member (20) having a substantially constant outer diameter increases the area of the side surface even when the axial length is the same. Can do. Accordingly, since the area through which the leakage flow passes can be increased as compared with the airflow resistance member (20) having a substantially constant outer diameter, the leakage flow resistance is increased and the amount of the leakage flow is reduced. The effect can be enhanced, and the effect of suppressing the turbulence of the air flow by trickling the leakage flow can be enhanced.

  Therefore, in this structure, even if it is a centrifugal blower of a type with a small axial interval between the outer peripheral surface of the shroud (15) and the outer peripheral surface of the bell mouth (6), the airflow resistance member (20) Since it can suppress that the area of a side surface becomes small, it can suppress that the effect which reduces the quantity of the said leakage flow, and the effect which makes the said leakage flow trickle and suppresses turbulence of an airflow reduce.

(9) The airflow resistance member (20) may have a corrugated cross section.

  In this configuration, the airflow resistance member (20) having a corrugated cross section has a side area even when the axial length is the same as that of the airflow resistance member (20) having a substantially constant outer diameter. Can be bigger. Thereby, the said effect similar to the case of the said airflow resistance member (20) of substantially frustoconical shape can be acquired.

(10) The airflow resistance member (20) may have a curved cross section.

  In this configuration, the airflow resistance member (20) having a curved cross-section has a side area even when the axial length is the same as that of the airflow resistance member (20) having a substantially constant outer diameter. Can be bigger. Thereby, the said effect similar to the case of the said airflow resistance member (20) of substantially frustoconical shape can be acquired.

(11) The airflow resistance member (20) preferably has a net structure having a mesh of 30 mesh to 70 mesh.

  In this configuration, as shown in Examples 1 to 5 to be described later, a significant effect of reducing the blowing sound can be obtained.

  As described above, according to the present invention, it is possible to provide a centrifugal blower that can reduce noise caused by the leakage flow.

It is sectional drawing which shows the ceiling embedded type air conditioner provided with the centrifugal blower which concerns on 1st Embodiment of this invention. It is a perspective view which shows the airflow resistance member of the said centrifugal blower of 1st Embodiment. It is an expansion perspective view which shows the said airflow resistance member in 1st Embodiment. It is an expanded sectional view showing the composition of the shroud, bell mouth, and airflow resistance member of the centrifugal blower of the first embodiment, and the flow of the airflow. It is an expanded sectional view which shows the structure of the shroud, bellmouth, and airflow resistance member of the centrifugal blower which concerns on 2nd Embodiment of this invention, and the flow of an airflow. It is a perspective view which shows the said airflow resistance member in 2nd Embodiment. It is an expansion perspective view which shows the said airflow resistance member in 2nd Embodiment. It is sectional drawing which shows the ceiling embedded type air conditioner provided with the centrifugal blower which concerns on 3rd Embodiment of this invention. It is an expanded sectional view showing the composition of the shroud, bell mouth, and airflow resistance member of the centrifugal blower of a 3rd embodiment, and the flow of airflow. It is a perspective view which shows the impeller of the centrifugal blower which concerns on 4th Embodiment of this invention. (A) is a top view which shows the bell mouth of the centrifugal blower which concerns on 4th Embodiment, (b) is a perspective view which shows the state which attached the airflow resistance member to the bell mouth of (a). It is a bottom view for demonstrating arrangement | positioning of each component accommodated in the main body casing of the air conditioner provided with the centrifugal blower of 4th Embodiment. (A) is sectional drawing which shows the centrifugal blower provided with the said airflow resistance member in 4th Embodiment, (b) is sectional drawing which shows the centrifugal blower provided with the modification 1 of the airflow resistance member, (C) is sectional drawing which shows the centrifugal air blower provided with the modification 2 of the airflow resistance member. It is sectional drawing which shows the air conditioner provided with the airflow resistance member of the modification 2. (A) is sectional drawing which shows the centrifugal blower provided with the modification 3 of the airflow resistance member in the said 4th Embodiment, (b) is equipped with the modification 4 of the airflow resistance member in the said 4th Embodiment. It is sectional drawing which shows the centrifugal blower. It is a graph which shows the result of having measured the ventilation sound when changing the air volume of an air conditioner. It is a graph which shows the result of having measured the ventilation sound when changing the air volume of an air conditioner. It is sectional drawing which shows the ceiling embedding type air conditioner provided with the conventional centrifugal blower. It is an expanded sectional view which shows the flow of the airflow in the conventional centrifugal blower.

(First embodiment)
1 to 4 show a ceiling-embedded air conditioner 1 including a turbo fan 11 as a centrifugal blower according to a first embodiment of the present invention, and an airflow resistance member 20 of the turbo fan 11.

  As shown in FIG. 1, the air conditioner 1 has a cassette-type (box-type) main body casing 2. The main body casing 2 is embedded in the ceiling 3 such that a lower surface panel (a panel provided with an air inlet and an outlet) 4 is continuous with the ceiling 3 in substantially the same plane.

  The lower panel 4 is provided with a square air suction grille 5 at the center. Inside the air suction grill 5, a pre-filter F, a bell mouth 6, an impeller 17, and a fan motor 13 that rotates the impeller 17 provided along the air suction grill 5 are provided from the front F side. They are arranged in this order toward the rear R side. A plurality of air outlets 9 extending along the outer periphery of the air suction grill 5 with a predetermined width are provided around the air suction grill 5 of the lower panel 4.

  In the main casing 2, air flow paths 10 are formed from the air suction grille 5 through the bell mouth 6 and the impeller 11 to each air outlet 9. The air flowing through the air flow path 10 flows in from the air suction grill 5, passes through the bell mouth 6, and then flows outward in the radial direction so as to spread over the entire circumference of the impeller 17. An air heat exchanger 12 is disposed in the air flow path 10 so as to surround the impeller 17.

  The impeller 17 forms a circular hub (main plate) 14 fixed to the rotating shaft 13a of the fan motor 13 and an air suction port in the centrifugal direction inside the impeller 17, and has a diameter on one end side and the other end side. And a plurality of blades (blades) 16 of a backward-facing type arranged in the circumferential direction with a predetermined blade angle and a predetermined blade interval between the hub 14 and the shroud 15. ing.

  An air outlet 6c on the downstream side of the bell mouth 6 is inserted into the air suction side end 15a of the shroud 15 with a predetermined gap G so that the shroud 15 can rotate.

  As shown in FIG. 1, the bell mouth 6 has an airflow guide surface composed of an air inflow port portion 6b and an air outflow port portion 6c. The air inflow port portion 6b is formed of an arc surface having a predetermined curvature radius extending inwardly from the mounting edge portion 6a to the lower panel 4 and gradually decreasing in opening diameter from the upstream side to the downstream side of the air flow. The air outlet part 6 c extends from the air inlet part 6 b toward the air suction side end part 15 a of the shroud 15. Thereby, the bell mouth 6 can smoothly flow the air sucked from the air suction grille 5 into the air suction side end portion 15a of the shroud 15 forming the air suction port of the impeller 17.

  The shroud 15 of the impeller 17 reduces aerodynamic noise generated during blowing as much as possible by smoothly guiding the air on the suction side of the impeller 17 in the centrifugal direction that is the blowing direction.

  As shown in FIG. 2, the centrifugal blower 11 of the first embodiment includes a cylindrical airflow resistance member 20. The airflow resistance member 20 has a plurality of gaps through which airflow can pass substantially uniformly over the entire circumference of the wall surface. The airflow resistance member 20 is disposed so as to surround the outer periphery of the air suction side end 15 a of the shroud 15. Specifically, the airflow resistance member 20 has an outer peripheral surface of the shroud 15 so as to cover the outer periphery of the insertion portion in which the air outlet portion 6c of the bell mouth 6 is inserted into the air suction side end portion 15a of the shroud 15. And the outer peripheral surface of the bell mouth 6.

  As shown in FIG. 3, the airflow resistance member 20 has a lattice structure obtained by molding a synthetic resin, for example. The airflow resistance member 20 includes a plurality of vertical lattices 20a and a plurality of horizontal lattices 20b, and the plurality of gaps are formed by the lattices 20a and 20b.

  As shown in FIGS. 1 and 4, the airflow resistance member 20 extends in a cylindrical shape from the outer peripheral surface of the bell mouth 6 toward the outer peripheral surface of the shroud 15. The peripheral edge on the rear R side of the airflow resistance member 20 is arranged with a predetermined gap so as not to contact (interfere) with the rotating shroud 15.

  As described above, in this embodiment, as shown in FIG. 4, a cylindrical airflow resistance member is provided between the outer peripheral surface of the bell mouth 6 and the outer peripheral surface of the shroud 15 so as to surround the outer periphery of the insertion portion. A fence made of 20 is formed. The presence of this fence not only increases the airflow resistance against the leakage flow B and reduces the amount of the leakage flow B, but the leakage flow B itself is finely and evenly trickled and rectified, and is not disturbed at a uniform flow rate. As it starts to flow, the flow becomes stable.

  As a result, the fan efficiency is improved, and the leakage flow B that has passed through the peripheral portion on the rear R side of the bell mouth 6 flows smoothly along the inner surface of the shroud 15. Thereby, the separation of the airflow on the suction surface side of the blade 16 due to the interference between the leakage flow B and the main flow A ′ near the shroud 15 as in the prior art is also effectively suppressed. Therefore, as compared with the conventional centrifugal blower, the blowing performance is improved and the blowing sound is effectively reduced.

  Further, even if rotational shake or misalignment occurs in the impeller 17 and the size of the gap of the insertion portion increases on one side in the radial direction, the drift is effectively reduced (uniformized). be able to.

  Furthermore, since the airflow resistance member 20 has a lattice structure obtained by molding a synthetic resin as shown in FIG. 3, for example, it can be easily and inexpensively formed by, for example, injection molding.

  Further, the airflow resistance member 20 is provided separately from the bell mouth 6. For example, as compared with the case where the bell mouth and the airflow resistance member are integrally formed, the forming is easy and the cost can be reduced.

  In addition, since the airflow resistance member 20 is configured by a flat plate piece, a noise (wind noise) when the leakage flow passes through the airflow resistance member 20 can be further suppressed.

  Therefore, according to the first embodiment, a centrifugal fan having low aerodynamic noise and high blowing performance, and an air conditioner having high blowing performance, low noise, and excellent energy saving performance can be provided at low cost.

(Second Embodiment)
5 to 7 show a ceiling-embedded air conditioner 1 including a turbo fan 11 as a centrifugal blower according to a second embodiment of the present invention, and an airflow resistance member 21 of the turbo fan 11.

  The centrifugal blower 11 of the second embodiment includes an airflow resistance member 21 shown in FIGS. 6 and 7. The airflow resistance member 21 includes a cylindrical mesh member 21a having a net structure in which a plurality of thin linear bodies X and a plurality of thin linear bodies Y made of synthetic resin or metal are knitted in a mesh shape. . The cylindrical mesh member 21a is reinforced by a plurality of vertical ribs 21c and a plurality of horizontal ribs 21b arranged at predetermined intervals on the inside thereof.

  In the second embodiment, as shown in FIG. 5, a fence made of a cylindrical net structure is provided between the outer peripheral surface of the bell mouth 6 and the outer peripheral surface of the shroud 15 so as to surround the outer periphery of the insertion portion. Is formed. Due to the presence of this fence, the airflow resistance against the leakage flow B is increased and the amount of the leakage flow B flowing through the gap G of the insertion portion is effectively reduced. The flow is rectified into a uniform flow rate.

  Therefore, even if rotational shake or misalignment occurs in the impeller 17, the amount of leakage flow is reduced uniformly over the entire circumference, and the flow becomes smooth. As a result, fan efficiency is improved, and air flow separation on the suction surface of the blade 16 due to interference with the mainstream is also effectively suppressed.

  In particular, in the case of the second embodiment, when the filaments X and Y are made of thin threads, the disturbance of the leakage flow B when the leakage flow B passes through the airflow resistance member 21 becomes smaller. Thereby, the noise (wind noise) at the time of passage of the leakage flow B can be suppressed lower.

  As a result, the blowing performance is improved and the blowing sound is effectively reduced as compared with the conventional centrifugal blower.

  Therefore, according to the second embodiment, a centrifugal fan having low aerodynamic noise and high blowing performance, and an air conditioner having high blowing performance, low noise, and excellent energy saving performance can be provided at low cost.

(Third embodiment)
8 and 9 show a ceiling-embedded air conditioner 1 including a turbo fan 11 as a centrifugal blower according to a third embodiment of the present invention.

  As shown in FIGS. 8 and 9, the turbofan 11 includes an airflow resistance member 22 instead of the airflow resistance members 20 and 21 in the first embodiment or the second embodiment. The airflow resistance member 22 has a cylindrical side wall portion 22a and a flange portion 22b bent inward in the radial direction from the bottom portion of the side wall portion 22a, and has a bowl-shaped cross section. This airflow resistance member 22 has the same net structure made of synthetic resin or metal as in the second embodiment.

  The airflow resistance member 22 is disposed between the side wall portion 22a and the flange portion 22b and the outer peripheral surface of the air outlet portion 6c of the bell mouth 6 so as to surround the air suction side end portion 15a of the shroud 15. .

  In the third embodiment, as shown in FIG. 8, the net-structure fence is formed so as to surround the vicinity of the insertion portion. Due to the presence of this fence, the airflow resistance against the leakage flow is increased, the amount of the leakage flow flowing through the gap G of the insertion portion is reduced, the flow is trickled, and the flow is rectified into a uniform flow velocity, Leakage flow disturbance is reduced.

  Therefore, even if rotational shake or misalignment occurs in the impeller 17, the amount of leakage flow is reduced and fan efficiency is improved, and the flow itself is smooth and the suction surface of the blade 16 due to interference with the main flow. The separation of the airflow in the is also effectively suppressed.

  Moreover, in the case of the third embodiment, as is clear from FIG. 9, since the airflow resistance member 22 is provided in the state of being close to the gap G of the insertion portion, the leakage flow B passes through the airflow resistance member 22. In doing so, the leakage flow is finely disturbed, and mixing of the airflow is promoted in the gap G. Thereby, for example, since the effect of eliminating the drift caused by the rotational shake of the impeller 17 or the like becomes high, the blowing sound caused by the drift is effectively reduced. Therefore, compared with the conventional centrifugal blower, the air blowing performance is improved, and the noise caused by the drift is effectively reduced.

  In the third embodiment, the airflow resistance member 22 is provided separately from the bell mouth 6. For example, as compared with the case where the bell mouth 6 and the airflow resistance member 22 are integrally molded, the molding is easy and the cost can be reduced.

  Moreover, in this 3rd Embodiment, the front-end | tip of the airflow resistance member 22 is provided apart from the shroud 15 by the predetermined dimension, and interference with the rotating shroud 15 is avoided.

  Therefore, according to the third embodiment, it is possible to provide a centrifugal fan with low aerodynamic noise and high blowing performance, and an air conditioner with high blowing performance, low noise, and excellent energy saving performance at low cost.

(Fourth embodiment)
FIG. 10 is a perspective view showing an impeller 17 used in a turbofan 11 as a centrifugal blower according to the fourth embodiment. Fig.11 (a) is a top view which shows the bellmouth 6 used for the turbo fan 11 of 4th Embodiment. FIG.11 (b) is a perspective view which shows the state which attached the airflow resistance member 20 to the bellmouth 6 of Fig.11 (a). FIG. 12 is a bottom view for explaining the arrangement of the components housed in the main casing 2 in the ceiling-embedded air conditioner 1 including the turbo fan 11 according to the fourth embodiment. In addition, about the structure similar to 1st Embodiment, the same code | symbol as 1st Embodiment is attached | subjected and description is abbreviate | omitted.

  The turbo fan 11 of this 4th Embodiment is equipped with the impeller 17, the bell mouth 6, and the airflow resistance member 20 similarly to 1st Embodiment (refer FIG. 1). As shown in FIG. 10, the impeller 17 includes a hub 14, a shroud 15, and a plurality of blades 16.

  The hub 14 is fixed to the lower end portion of the rotation shaft 13 a of the fan motor 13. The hub 14 has a circular shape centered on the rotation shaft 13a in plan view.

  The shroud 15 is disposed opposite to the hub 14 on the front F side in the axial direction of the rotation shaft 13a. The shroud 15 has an air suction side end portion 15a that opens around a rotation shaft 13a (a straight line passing through the rotation shaft 13a). The outer diameter of the shroud 15 increases from the front F side toward the rear R side.

  The plurality of blades 16 are arranged at a predetermined interval along the circumferential direction of the impeller 17 between the hub 14 and the shroud 15. Each blade 16 is a backward-facing blade that is inclined in the direction opposite to the rotational direction (backward) with respect to the radial direction of the hub 14.

  The end on the rear R side of each blade 16 is joined to the hub 14. The front F-side end of each blade 16 is joined to the shroud 15. Specifically, a part (protrusion part) 16 a on the front F side of each blade 16 is joined to the shroud 15 in a state of being inserted into a through hole (not shown) provided in the shroud 15. Therefore, the protrusion 16a protrudes from the surface of the shroud 15 toward the front F side. As a method for joining the protruding portion 16a to the shroud 15, for example, welding by a laser or the like can be cited.

  As shown in FIG. 1, the bell mouth 6 is disposed to face the shroud 15 on the front F side in the axial direction. As shown in FIGS. 11A and 11B, the bell mouth 6 has a through-hole through which air passes. The bell mouth 6 includes an air inlet 6b serving as an air inlet on the front F side of the through hole, an air outlet 6c serving as an air outlet on the rear R side of the through hole, and an air inlet. A mounting edge portion 6a projecting in a flange shape from the portion 6b and a step portion 6d recessed toward the rear R side from the mounting edge portion 6a are included.

  The attachment edge 6 a is attached to the lower panel 4. The air inlet 6b has a curved shape in which the inner diameter and the outer diameter become smaller from the front F side toward the rear R side. An elongated rectangular electrical component box 31 shown in FIG. 12 is arranged in a space formed below the step portion 6d (front F side).

  As shown in FIG. 1, the bell mouth 6 has an air suction side end portion 15 a in a state where a part of the air outlet portion 6 c side is provided with a predetermined gap with the air suction side end portion 15 a of the shroud 15. Is inserted into the opening.

  As shown in FIGS. 1 and 11B, the airflow resistance member 20 has a cylindrical shape, and an air suction side end portion 15a of the shroud 15 and an airflow outlet portion of the bell mouth 6 are provided inside (inside the hollow). 6c is located. As shown in FIG. 11B, a part of the airflow resistance member 20 is cut out along the shape of the step portion 6 d of the bell mouth 6.

  The airflow resistance member 20 has a front F-side end (peripheral edge) in contact with the surface of the mounting edge 6 a of the bell mouth 6, and a cylindrical shape toward the rear R-side end (peripheral edge) 15 b of the shroud 15. It extends to. The front F-side end of the airflow resistance member 20 is fixed to the surface of the attachment edge 6a by welding, brazing, or the like. Therefore, the airflow resistance member 20 covers almost the entire opening portion that is formed by the surface of the mounting edge portion 6a of the bell mouth 6 and the peripheral edge portion 15b on the rear R side of the shroud 15 and opens in the entire circumferential direction. Is provided. Thereby, since most of the leakage flow that passes through the opening that opens in the circumferential direction passes through the airflow resistance member 20, the amount of leakage flow can be effectively reduced and the leakage flow can be effectively rectified. it can.

  The airflow resistance member 20 includes a net portion 20a, a plurality of horizontal frames 20b that support the net portion 20a, and a plurality of vertical frames 20c. Each horizontal frame 20b has a circular shape, and is arranged at a predetermined interval in the front-rear direction with respect to adjacent horizontal frames 20b. Each vertical frame 20c has a bar shape extending in the front-rear direction, and is arranged at a predetermined interval in the circumferential direction with respect to the adjacent vertical frame 20c. Each vertical frame 20c connects a plurality of horizontal frames 20b. A plurality of openings are formed by combining a plurality of horizontal frames 20b and a plurality of vertical frames 20c in a lattice shape.

  The net part 20a is fixed to the horizontal frame 20b and the vertical frame 20c so as to cover the plurality of openings. The net part 20a has a net structure in which a plurality of substantially uniform holes are formed over substantially the whole. The method for producing the net part 20a is not particularly limited, and examples thereof include a method of combining a plurality of fine wires made of a metal such as stainless steel, a synthetic resin, etc. by knitting in a net shape.

  The fineness of the net part 20a is preferably 10 mesh or more, more preferably 30 mesh or more, and still more preferably about 30 mesh to 70 mesh. As shown in the examples described later, when the fineness of the net 20a is 30 mesh or more, a particularly remarkable effect of reducing the blowing sound is obtained. The mesh represents the number of eyes per inch.

  Moreover, it is preferable to make the thickness of the net part 20a small in order to enhance the effect of reducing the blowing sound. The thickness of the net part 20a is preferably 1 mm or less, more preferably 0.5 mm or less, and even more preferably 0.25 mm or less. Therefore, it is preferable to select a thin wire having a small diameter so that the thickness of the net portion 20a falls within the above range as the thin wire constituting the net portion 20a.

  The airflow resistance member 20 shown in FIG. 13A has a cylindrical shape with a substantially constant outer diameter over the front-rear direction. The outer diameter of the airflow resistance member 20 is substantially the same as the outer diameter of the peripheral edge portion 15b on the rear R side of the shroud 15. The airflow resistance member 20 is disposed at a predetermined interval so that the airflow resistance member 20 does not come into contact with the shroud 15 and the protruding portion 16a when the impeller 17 rotates. In the airflow resistance member 20 shown in FIG. 13A, the peripheral portion on the rear R side is close to the shroud 15 and the protruding portion 16a.

  FIG. 13B is a cross-sectional view showing the turbofan 11 including the modification 1 of the airflow resistance member 20. As with the airflow resistance member 20 of FIG. 13A, the airflow resistance member 20 has a substantially constant outer diameter in the front-rear direction, but the airflow resistance member 20 has an outer diameter on the rear R side of the shroud 15. It is larger than the outer diameter of the peripheral edge portion 15b. Therefore, the rear edge side of the airflow resistance member 20 has a larger distance between the rear edge part 15b and the protrusion 16a on the rear R side of the shroud 15 than the airflow resistance member 20 of FIG. Thereby, since the airflow resistance member 20 becomes more difficult to contact the shroud 15 and the protrusion 16a, the impeller 17 can be rotated more smoothly.

  FIG. 13C is a cross-sectional view showing the turbofan 11 including the second modification of the airflow resistance member 20. The airflow resistance member 20 has a cylindrical shape, and its outer diameter increases from the front F side toward the rear R side. That is, the airflow resistance member 20 has a substantially truncated cone shape in a side view. The outer diameter of the peripheral portion on the rear R side of the airflow resistance member 20 is larger than the outer diameter of the peripheral portion 15b on the rear R side of the shroud 15. On the other hand, the outer diameter of the peripheral portion on the front F side of the airflow resistance member 20 is equal to or smaller than the outer diameter of the peripheral portion 15b on the rear R side of the shroud 15.

  The airflow resistance member 20 of this modification 2 is effective when the air conditioner 1 has a structure as shown in FIG. 14, for example. In the air conditioner 1 shown in FIG. 14, a drain pan 18 provided below the heat exchanger 12 projects to the rotation center side of the impeller 17 compared to the air conditioner 1 shown in FIG. 1. Even in such a configuration, the airflow resistance member 20 of Modification 2 has a substantially truncated cone shape, so that it is separated radially outward from the peripheral edge 15b on the rear R side of the shroud 15. Thus, a sufficient interval can be maintained, and the drain pan 18 can be maintained at a sufficient distance by being spaced radially inward. After maintaining these intervals, the airflow resistance member 20 of Modification 2 is formed by the circumferential opening formed by the surface of the mounting edge 6 a of the bell mouth 6 and the peripheral edge 15 b on the rear R side of the shroud 15. Almost all of the part can be covered.

  Further, in the airflow resistance member 20 shown in FIG. 11B, a part of the airflow resistance member 20 is notched in order to conform to the shape of the stepped portion 6d for arranging the electrical component box 31. By using the substantially frustoconical airflow resistance member 20 as in Example 2, the stepped portion 6d can be avoided even if the area where the airflow resistance member 20 is cut out is small (or even if the airflow resistance member 20 is not cut out). The airflow resistance member 20 can be arranged.

  Moreover, since the airflow resistance member 20 of the modification 2 is substantially frustoconical, the side surface is inclined with respect to the axial direction of the rotating shaft 13a. Therefore, compared with the airflow resistance member 20 having a substantially constant outer diameter as shown in FIG. 13 (a) or FIG. 13 (b), the airflow resistance member 20 of Modification 2 has the same length in the axial direction. Even if it exists, the area (area of a side surface) of the net part 20a can be enlarged. Thereby, in the modification 2, the effect of reducing the amount of leakage flow and the effect of rectifying the leakage flow can be further improved.

  FIG. 15A is a cross-sectional view showing the turbofan 11 including the third modification of the airflow resistance member 20. As shown to Fig.15 (a), the airflow resistance member 20 of this modification 3 has a cylinder shape, and the cross section of the net part 20a is curving in circular arc shape. In the third modification, the arc shape protrudes outward in the radial direction, but the protruding direction may be the inner side in the radial direction.

  FIG. 15B is a cross-sectional view showing the turbofan 11 including the modification 4 of the airflow resistance member 20. As shown in FIG. 15B, the airflow resistance member 20 of the modification 4 has a cylindrical shape, and the cross section of the net portion 20a is refracted into a waveform.

  Since the airflow resistance member 20 of Modification 3 has a curved cross section, and the airflow resistance member 20 of Modification 4 has a corrugated cross section, the outer diameter as shown in FIG. 13A or FIG. Compared with the substantially constant airflow resistance member 20, the airflow resistance members 20 of the modification examples 3 and 4 can increase the area (side area) of the net portion 20a even if the axial length is the same. it can. Thereby, in the modified examples 3 and 4, the effect of reducing the amount of leakage flow and the effect of rectifying the leakage flow can be further improved.

  FIG. 16 is a graph showing the results of measuring the blowing sound when the air volume is changed using the air conditioner 1 as shown in FIG. In Examples 1 to 3, a test was performed using an airflow resistance member 20 having an outer diameter substantially constant in the front-rear direction as shown in FIG. In the comparative example, the test was performed without attaching the airflow resistance member 20.

  In the net part 20a of Example 1, a single net having a mesh size of 30 mesh in the vertical direction and a mesh size of 30 mesh in the horizontal direction was used. In the net part 20a of Example 2, one net having a mesh size of 60 mesh in the vertical direction and a mesh size of 40 mesh in the horizontal direction was used. In the net portion 20a of Example 3, one net having 70 mesh in the vertical direction and 70 mesh in the horizontal direction was used.

  Moreover, the thickness of the net part 20a of Example 1 is about 0.103 mm, the thickness of the net part 20a of Example 2 is about 0.098 mm, and the thickness of the net part 20a of Example 3 is about 0.085 mm. Met.

  As shown in FIG. 16, in Examples 1-3, it turns out that the ventilation sound is reduced about 1 dBA compared with the comparative example. Moreover, it turns out that the reduction effect of blowing sound is improved, so that the fineness of the net | network part 20a is made finer.

  FIG. 17 is a graph showing the results of measuring the blowing sound when the air volume is changed using the air conditioner 1 as shown in FIG. In Examples 2, 4 and 5, the test was performed using the airflow resistance member 20 whose outer diameter was substantially constant in the front-rear direction as shown in FIG. In the comparative example, the test was performed without attaching the airflow resistance member 20.

  As in FIG. 16, the net portion 20a of Example 2 was a single net having a mesh size of 60 mesh in the vertical direction and a mesh size of 40 mesh in the horizontal direction. In the net part 20a of the fourth example, two identical nets as in the second example were used. In the net part 20a of Example 5, three same nets as in Example 2 were used.

  Moreover, the thickness of the net part 20a of Example 2 is about 0.098 mm, the thickness of the net part 20a of Example 4 is about 0.171 mm, and the thickness of the net part 20a of Example 5 is about 0.228 mm. Met.

  As shown in FIG. 17, in Examples 2, 4, and 5, it can be seen that the blowing sound is reduced by about 1 dBA compared to the comparative example. Further, the effect of reducing the blowing sound is improved in Example 4 in which two nets are overlapped and in Example 5 in which three nets are overlapped, compared to Example 2 in which one net is used. Recognize. There was no significant difference between Example 4 and Example 5 in the effect of reducing the blowing sound.

  As described above, in the fourth embodiment, the airflow resistance member having a cylindrical shape and provided with a plurality of substantially uniform holes over substantially the entire air suction side end portion and the air Since the outlet portion is arranged so that the leak flow flows into the impeller from the gap between the air suction side end portion and the air outlet portion, the airflow resistance member is pass.

  Therefore, in this 4th Embodiment, since the said airflow resistance member becomes resistance of a leak flow, compared with the case where the said airflow resistance member is not provided, the quantity of the said leak flow can be reduced. In addition, since the airflow resistance member has a plurality of substantially uniform holes extending over substantially the entire airflow resistance member, it is possible to trickle the leakage flow and suppress the turbulence of the airflow. Thus, the amount of the leakage flow is reduced, and the disturbance of the leakage flow is suppressed, so that the blowing sound can be reduced.

  Moreover, in 4th Embodiment, when the outer diameter of the said edge part of the said back side of the said airflow resistance member is made larger than the outer diameter of the said shroud, the slight position shift at the time of the assembly of the said impeller ( Even if a misalignment, a rotational shake at the time of rotation of the impeller, and the like occur, the airflow resistance member can be prevented from contacting the shroud.

  In addition, in the fourth embodiment, when the airflow resistance member has a substantially truncated cone shape, when the cross section is a wave shape, or when the cross section is a curved shape, in addition to the effect of suppressing contact with the shroud. In addition, the effect of reducing the amount of the leakage flow and the effect of suppressing the turbulence of the air flow by making the leakage flow trickle can be further enhanced as compared with the airflow resistance member having a substantially constant outer diameter. That is, in these cases, the area of the side surface of the airflow resistance member can be increased even when the airflow resistance member has the same axial length as compared with the airflow resistance member having a substantially constant outer diameter. Therefore, the area through which the leakage flow passes can be increased. Thereby, the effect of increasing the resistance of the leak flow and reducing the amount of the leak flow can be enhanced, and the effect of suppressing turbulence of the air flow by trickling the leak flow can be enhanced.

  Therefore, in these cases, even if the axial blower has a small distance between the outer peripheral surface of the shroud and the outer peripheral surface of the bell mouth, the area of the side surface of the airflow resistance member is reduced. Therefore, it is possible to suppress the effect of reducing the amount of the leakage flow and the effect of suppressing the turbulence of the air flow by trickling the leakage flow.

  In these cases, since the area of the side surface of the airflow resistance member is large, even if the mesh is somewhat rough, the effect of reducing the amount of leakage flow, and the effect of suppressing the turbulence of the airflow by trickling the leakage flow Can be reduced.

  Moreover, in 4th Embodiment, when the said airflow resistance member has the net | network structure which has a mesh of 30 mesh-70 mesh, it can acquire the especially remarkable reduction effect of blowing sound.

  As mentioned above, although each embodiment of this invention was described, this invention is not limited to each said embodiment, A various change, improvement, etc. are possible in the range which does not deviate from the meaning. For example, in the fourth embodiment, the case where the airflow resistance member 20 includes the net portion 20a, a plurality of horizontal frames 20b that support the net portion 20a, and a plurality of vertical frames 20c has been described as an example. However, it is not limited to this. For example, when the net portion 20a of the airflow resistance member 20 has a certain degree of rigidity, one or both of the horizontal frame 20b and the vertical frame 20c can be omitted.

DESCRIPTION OF SYMBOLS 1 Air conditioner 2 Main body casing 3 Ceiling 4 Lower surface panel 5 Air suction grille 6 Bell mouth 6c Air outlet part 9 Air outlet 10 Air flow path 11 Turbo fan 13 Fan motor 14 Hub 15 Shroud 15a Air suction side edge part 16 Blades 17 Impeller 18 Drain pan 20, 21, 22 Airflow resistance member

Claims (11)

A centrifugal blower attached to a fan motor,
A circular hub (14) fixed to the front side in the axial direction of the rotating shaft of the fan motor (13), a plurality of blades (16) arranged in the circumferential direction of the hub (14), and the shaft of the rotating shaft An impeller (17) having an air suction side end (15a) that opens about the direction and including a shroud (15) fixed to the front side of the plurality of blades (16);
It has an air outlet part (6c) that opens around the rotation axis, and maintains a predetermined gap in the opening of the air suction side end part (15a). The bell mouth (6) with the part inserted,
Part of the air flow from the impeller (17) passes between the shroud (15) and the bell mouth (6), and the air suction side end (15a) and the air outlet (6c). comprising a, a gas flow resistance member to reduce the passage of the leakage flow (20, 21, 22) flowing into the impeller (17) in through the gap between,
The airflow resistance member (20, 21, 22) has a net structure knitted with a synthetic resin striate or a lattice structure formed with a synthetic resin. Centrifugal blower that rectifies the air flow .   The centrifugal blower according to claim 1, wherein the airflow resistance member (20, 21) is provided at an outer peripheral portion of the air suction side end (15a) of the shroud (15).   The airflow resistance member (22) is provided so as to surround the air suction side end (15a) of the shroud (15) between the airflow outlet (6c) of the bell mouth (6). The centrifugal blower according to claim 1 or 2.   The centrifugal blower according to claim 1 or 2, wherein the airflow resistance member (20, 21, 22) is provided so as to extend in a cylindrical shape from the bell mouth (6) side to the shroud (15) side. The centrifugal blower according to any one of claims 1 to 4, wherein the centrifugal blower is configured as a blower for an air conditioner . A centrifugal blower attached to a fan motor (13),
A circular hub (14) fixed to the front side in the axial direction of the rotating shaft of the fan motor (13), a plurality of blades (16) arranged in the circumferential direction of the hub (14), and the rotating shaft as a center An impeller (17) having an air suction side end (15a) that opens as a shroud (15) fixed to the front side of the plurality of blades (16);
It has an air outlet part (6c) that opens around the rotation axis, and a part of the air outlet part (6c) side is connected to an edge of the opening of the air suction side end part (15a). A bell mouth (6) inserted into the opening of the air suction side end (15a) with a predetermined gap therebetween,
An airflow resistance member (20) having a cylindrical shape and provided with a plurality of substantially uniform holes over substantially the whole,
The airflow resistance member (20) is a centrifugal blower in which the air suction side end portion (15a) and the air outflow port portion (6c) are positioned inside thereof . The centrifugal blower according to claim 1 or 6, wherein an outer diameter of an end portion on the rear side in the axial direction of the airflow resistance member (20) is larger than an outer diameter of the shroud (15) . The centrifugal air blower according to claim 7 , wherein the airflow resistance member (20) has a substantially truncated cone shape whose outer diameter increases from the front side toward the rear side . The centrifugal air blower according to any one of claims 1 and 6 to 8, wherein the airflow resistance member (20) has a corrugated cross section . The centrifugal air blower according to any one of claims 1 and 6 to 8, wherein the airflow resistance member (20) has a curved cross section . The centrifugal air blower according to any one of claims 1 and 6, wherein the airflow resistance member (20) has a net structure having a mesh of 30 mesh to 70 mesh .

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