JP5952800B2 - Centrifugal fan - Google Patents

Description

  The present invention relates to a centrifugal fan that sends wind to a combustion device or the like.

  A centrifugal fan is known as a blower used for a combustion device or the like (for example, Patent Document 1). The centrifugal fan includes a cylindrical impeller in which a plurality of blade pieces are arranged radially with respect to the rotation shaft, and a scroll casing that houses the impeller. This scroll casing is formed in a cylindrical shape whose radius with respect to the rotation axis of the impeller increases in the rotation direction of the impeller, and air is applied to the inner side of the impeller on the cover plate that covers one end side in the axial direction of the rotation shaft. A bellmouth to guide is formed. Moreover, the air flow path is extended in the tangential direction from the surrounding surface by the side with the larger radius of a scroll casing. When the impeller is rotated, air blows out from the inner side to the outer side of the impeller, so that the air sucked from the bell mouth can be sent to a combustion device connected to the air passage.

  When such a centrifugal fan is used, generation of a large noise may be a problem. This noise includes noise generated by the centrifugal fan itself (single noise) and noise caused by resonance in the entire apparatus including the centrifugal fan (resonant sound). Of these, it has been found from experience that resonance sound can be suppressed by reducing the diameter (opening area) of the bell mouth through which air flows.

JP 2005-180179 A

  However, if the diameter of the bell mouth of the centrifugal fan is reduced, the single noise of the centrifugal fan tends to increase, and there is a problem that it is difficult to suppress the single noise while suppressing the resonance sound.

  The present invention has been made in response to the above-described problems of conventional techniques, and an object of the present invention is to provide a centrifugal fan that can achieve both suppression of resonance noise and suppression of unit noise.

In order to solve the above-described problems, the centrifugal fan of the present invention employs the following configuration. That is,
A cylindrical impeller in which a plurality of blade pieces erected from the outer edge portion of the rotating disk are arranged radially with respect to the rotating shaft, the impeller is accommodated, and a radius with respect to the rotating shaft is A scroll casing formed in a cylindrical shape that increases in the rotational direction, a bottom plate that closes one axial end surface of the rotary shaft of the scroll casing, and an end surface opposite to the bottom plate of the scroll casing; The impeller includes a cover plate having a first bell mouth that guides air to the inside of the impeller, and an air passage that extends in a tangential direction from a peripheral surface of the scroll casing having a larger radius with respect to the rotation shaft. In the centrifugal fan that sends air to the air passage by rotating the
The tip of the first bell mouth with the reduced opening area is located on the inner side of the impeller and on the bottom plate side than the end on the lid plate side of the wing piece,
On the impeller side surface of the lid plate, a second bell mouth having a diameter larger than that of the first bell mouth surrounds the first bell mouth, and the blade pieces of the first bell mouth and the impeller Between
Tip opening area is narrowed in the second bell mouth is characterized by being located before the bottom plate side of the end portion of the cover plate side of Kitsubasahen.

As described above, in the centrifugal fan, it is known that when the diameter (opening area) of the bell mouth into which air flows is reduced, the resonance noise can be suppressed, but the single noise increases. Here, the reason why single noise is generated is considered as follows. First, the air sucked into the inside of the impeller vigorously from the bell mouth by rotating the impeller flows toward the back side (bottom plate side) of the impeller, and mainly on the bottom plate side from the center of the blade piece. Blow out from the part to the outside of the impeller. Since the pressure increases when the blown air flow collides with the tongue (the connection portion between the peripheral surface of the fan casing having a smaller radius and the air passage), the end of the blade plate on the lid plate side and the lid plate In the gap, a reverse flow is generated from the outside to the inside of the impeller. And such a back flow collides with the air which flows in from bellmouth, and disturbs a flow, and single-piece noise is generated. Therefore, in the centrifugal fan of the present invention, the second bell mouth is provided between the first bell mouth into which the tip is inserted inside the impeller and air is introduced, and the blade piece of the impeller, and the second The tip of the bell mouth is inserted closer to the bottom plate than the end of the wing piece on the lid plate side. By so doing, the direction of the air flowing backward through the gap between the end of the blade plate on the lid plate side and the lid plate is bent toward the back side (bottom plate side) of the impeller by the peripheral wall of the second bell mouth. As a result, the flow of air flowing in from the first bell mouth is less likely to be disturbed by the backflow, so that single noise can be suppressed.

  Even if the second bell mouth is provided on the surface of the cover plate on the impeller side, the opening area through which air flows is not increased, and therefore the resonance noise is not adversely affected. And even if the opening area of the first bell mouth is reduced so that no resonance sound is generated, if the second bell mouth is installed between the first bell mouth and the blade of the impeller, the unit noise can be suppressed. . Thus, according to the centrifugal fan of the present invention, it is possible to achieve both the suppression of the unit noise and the suppression of the resonance sound.

  In the centrifugal fan of the present invention described above, the position of the tip of the second bell mouth is positioned closer to the cover plate than the surface inclined toward the bottom plate at an angle of 45 degrees from the tip of the first bell mouth toward the outside in the radial direction. It may be set.

  Extending the tip of the second bell mouth toward the bottom plate increases the effect of directing the back flow of air toward the back side of the impeller by guiding the peripheral wall of the second bell mouth, thereby reducing the influence of the back flow and suppressing single noise It is effective. However, if the tip of the second bell mouth is extended too much, the flow of air flowing in from the first bell mouth toward the wing piece may hit the tip of the second bell mouth and generate wind noise. Therefore, if the position of the tip of the second bell mouth is set as described above, it is difficult for the tip of the second bell mouth to block the air flow from the first bell mouth, so that the generation of wind noise can be suppressed. .

  In the centrifugal fan of the present invention, the gap between the tip of the first bell mouth and the tip of the second bell mouth may be closed with a closing plate.

  By providing such a blocking plate, the air flowing from the first bell mouth does not flow between the first bell mouth and the second bell mouth, and the air flow toward the wing piece becomes smooth. Therefore, it is possible to suppress noise generated by the disturbance of the air flow and to reduce the noise of the centrifugal fan.

  In the centrifugal fan of the present invention described above, the first bell mouth, the second bell mouth, and the closing plate may be integrally formed.

  By integrally forming in this way, unevenness due to bonding or the like can be reduced (surface resistance is reduced) on the tip side of the first bell mouth and the second bell mouth as compared with the case where each is separate. In addition, since it is difficult for the air flow flowing from the first bell mouth to flow toward the wing piece, the noise can be further reduced.

It is the perspective view which showed the state which decomposed | disassembled the centrifugal fan 10 of a present Example. It is explanatory drawing which showed a mode that the centrifugal fan 10 rotated the impeller 20 and sent out a wind. It is explanatory drawing which showed a mode that the backflow of air produced in the vicinity of the tongue part 50c. It is explanatory drawing which showed the reason the single-piece | unit noise is suppressed by providing the 2nd bellmouth 58 in the upper board 56. FIG. 5 is a graph showing the relationship between the minimum inner diameter of the second bell mouth 58 formed on the upper plate 56 and the noise value measured for the centrifugal fan 10. 5 is a graph showing the relationship between the height of the second bell mouth 58 formed on the upper plate 56 and the noise value measured for the centrifugal fan 10. It is explanatory drawing which showed the position of the front-end | tip of the 2nd bell mouth 58 which suppresses generation | occurrence | production of a wind noise. It is explanatory drawing which showed the structure of the centrifugal fan 10 of a 1st modification. It is explanatory drawing which showed the structure of the centrifugal fan 10 of a 2nd modification.

  FIG. 1 is a perspective view showing a state in which the centrifugal fan 10 of this embodiment is disassembled. The centrifugal fan 10 is connected to a combustion device (not shown) incorporating a burner, for example, and is used to send combustion air to the burner. As illustrated, the centrifugal fan 10 includes an impeller 20 that generates wind by rotating, a drive motor 30 that rotates the impeller 20, a fan case 50 that houses the impeller 20, and the like.

  The impeller 20 of the present embodiment is a so-called sirocco fan, and a plurality of blade pieces 24 that are elongated in the axial direction of the rotary shaft 32 of the drive motor 30 are arranged radially at predetermined intervals with respect to the rotary shaft 32. It has a cylindrical shape. One end (the lower end in the figure) of these wing pieces 24 is attached to the outer edge portion of the substantially circular rotating disk 22, and the other end (the upper end in the figure) of the wing piece 24 is attached to the annular support plate 26. It is attached. The rotary disc 22 is fixed to the rotary shaft 32 of the drive motor 30 at the center, and the impeller 20 rotates around the rotary shaft 32 by the drive of the drive motor 30.

  The fan case 50 includes a bottom plate 52 that is fixed to the main body of the drive motor 30, a peripheral wall plate 54 that is curved so as to surround the outer periphery of the impeller 20, and an upper plate that faces the bottom plate 52 via the peripheral wall plate 54. 56 is joined. Further, a guide plate 70 on which a first bell mouth 72 that guides air to the inside of the impeller 20 is formed is attached to the outside (upper side in the drawing) of the upper plate 56. The opening center of the first bell mouth 72 is collinear with the rotation shaft 32. Further, the guide plate 70 of this embodiment is fixed in close contact with the upper plate 56. The bottom plate 52, the peripheral wall plate 54, the upper plate 56, and the guide plate 70 can be formed from a metal flat plate by pressing or the like. Further, the upper plate 56 and the guide plate 70 of this embodiment correspond to the “lid plate” of the present invention.

  The upper plate 56 is formed with a second bell mouth 58 whose opening area decreases toward the inside of the fan case 50. The center of the opening of the second bell mouth 58 is collinear with the rotation axis 32. Further, the second bell mouth 58 has a minimum inner diameter (inner diameter on the tip side with a reduced opening area) that is larger than the minimum inner diameter of the first bell mouth 72 and smaller than the inner diameter of the impeller 20, so that the second bell mouth 58 is located between the first bell mouth 72 and the blade 24 of the impeller 20.

  FIG. 2 is an explanatory view showing a state in which the centrifugal fan 10 rotates the impeller 20 to send out wind. FIG. 2 shows a cross-sectional view of the centrifugal fan 10 cut along a plane perpendicular to the rotation shaft 32 of the drive motor 30. First, as shown in the figure, the fan case 50 (peripheral wall plate 54) includes a scroll casing 50a surrounding the impeller 20 and a blower passage 50b connected to a combustion device or the like through which the centrifugal fan 10 sends air. . The scroll casing 50 a is formed in a cylindrical shape whose radius is larger in the rotation direction of the impeller 20 (counterclockwise in the illustrated example) with respect to the rotation shaft 32 of the drive motor 30. An air passage 50b having a rectangular cross section extends from the peripheral surface of the scroll casing 50a on the larger radius side in a tangential direction, and a discharge port 60 is provided at the end of the air passage 50b.

  The plurality of blade pieces 24 of the impeller 20 are provided with the outer peripheral side curved in the rotation direction of the impeller 20. When the impeller 20 is rotated by driving the drive motor 30, a flow of air from the inside to the outside of the impeller 20 is generated by centrifugal force, and the air sucked from the first bell mouth 72 is between the plurality of blade pieces 24. Blow out from. In FIG. 2, the air flow in the centrifugal fan 10 is indicated by a one-dot chain line arrow. The blown air advances while rotating along the inner surface of the scroll casing 50a of the fan case 50 (peripheral wall plate 54), and is discharged from the discharge port 60 through the air passage 50b.

  However, in the vicinity of the connection portion (tongue portion) 50c between the peripheral surface of the scroll casing 50a on the smaller radius side and the air passage 50b, as shown by the arrow with A in FIG. Backflow of air toward

  FIG. 3 is an explanatory diagram showing a state in which a backflow of air occurs in the vicinity of the tongue 50c. FIG. 3 shows a cross-sectional view of the centrifugal fan 10 taken along a plane that includes the rotating shaft 32 of the drive motor 30 and faces the tongue 50c. The arrow of the dashed-dotted line in the figure has shown the flow of the air in the centrifugal fan 10. FIG. First, the basic flow of air generated by the rotation of the impeller 20 will be described. By rotating the impeller 20, the air sucked into the inside of the impeller 20 from the first bell mouth 72 vigorously flows toward the back side (the bottom plate 52 side) in the axial direction of the rotary shaft 32. Therefore, the air is blown out of the impeller 20 through the plurality of blade pieces 24 mainly from the portion on the rotating disk 22 side (lower side in the drawing) from the center of the blade pieces 24. .

  Thus, when the air flow blown out of the impeller 20 collides with the tongue 50c without being discharged from the discharge port 60, the pressure from the outside of the impeller 20 to the inside is increased by increasing the pressure in the vicinity of the tongue 50c. Backflow occurs. In particular, in the gap between the upper plate 56 and the support plate 26 of the impeller 20, it is not pushed back by the blade piece 24 of the rotating impeller 20, so that a strong backflow occurs. The backflow collides with the air flowing in from the first bell mouth 72 and disturbs the flow, thereby generating noise (unit noise) of the centrifugal fan 10. In addition, when the minimum inner diameter (opening area) of the first bell mouth 72 is reduced, the basic noise of the air flowing in from the first bell mouth 72 is easily affected by the back flow, and the single noise becomes a noise level. Tend to be larger. Therefore, in the centrifugal fan 10 of the present embodiment, the second bell mouth 58 is provided on the upper plate 56 in order to suppress single noise.

  FIG. 4 is an explanatory diagram showing the reason why the unit noise is suppressed by providing the second bell mouth 58 on the upper plate 56. 4 is an enlarged view of the tongue 50c side of the second bell mouth 58 in the cross-sectional view of the centrifugal fan 10 shown in FIG. As shown in the drawing, the second bell mouth 58 has a tip (an end with a narrowed opening area) entering the back side (bottom plate 52 side) of the impeller 20 rather than the support plate 26 of the impeller 20. It is disposed between the first bell mouth 72 and the blade 24 of the impeller 20.

  Such a peripheral wall of the second bell mouth 58 of this embodiment is configured so that the flow of air that flows backward from the outside to the inside of the impeller 20 through the gap between the upper plate 56 and the support plate 26 (see FIG. Guide it toward the lower side. Thus, if the reverse flow of air is changed downward, the basic flow of air flowing in from the first bell mouth 72 can be approached by the rotation of the impeller 20. Thereby, since the influence by the backflow in the tongue part 50c is reduced (the basic flow becomes difficult to be disturbed by the backflow collision), the single unit noise generated by the centrifugal fan 10 can be suppressed.

  Further, by forming a resonator with a casing such as a combustion device to which the centrifugal fan 10 is connected, a resonance sound may be emitted from the entire device including the centrifugal fan 10 to generate noise. Such resonance sound is likely to be generated when the opening area of the opening (first bell mouth 72 in this embodiment) through which air flows into the inside of the impeller 20 of the centrifugal fan 10 is increased. In the centrifugal fan 10 of the present embodiment, the guide plate 70 is attached in close contact with the upper plate 56 without providing a gap, so that air flows between the upper plate 56 and the guide plate 70. Even if the second bell mouth 58 is provided on the upper plate 56, the opening area through which air flows into the inside of the impeller 20 is not increased, so that the resonance sound is not adversely affected. Even if the opening area of the first bell mouth 72 is reduced so as not to generate a resonance sound, the second bell mouth 58 is installed between the first bell mouth 72 and the blade of the impeller 20. Thereby, the single unit noise of the centrifugal fan 10 can be suppressed. As described above, according to the centrifugal fan 10 of this embodiment, it is possible to achieve both suppression of single noise and suppression of resonance noise.

  FIG. 5 is a graph showing the relationship between the minimum inner diameter of the second bell mouth 58 formed on the upper plate 56 and the noise value measured for the centrifugal fan 10. In the example shown in FIG. 5, the inner diameter of the impeller 20 is fixed to 75 mm, and the minimum inner diameter of the first bell mouth 72 is fixed to 46 mm. In addition, at the left end of the graph of FIG. 5, a noise value when a simple opening is provided in the upper plate 56 (when the second bell mouth 58 is not provided) is shown as a comparison. In contrast, when the second bell mouth 58 having a minimum inner diameter of 68 mm is provided on the upper plate 56, the back flow of air is directed downward (by the bottom plate 52 side) by guiding the peripheral wall of the second bell mouth 58 as described above. ), The influence of backflow is reduced, and the noise level is reduced.

  When the minimum inner diameter of the second bell mouth 58 is 63 mm, the noise value is further reduced. This is because when the distance between the first bell mouth 72 and the second bell mouth 58 is set appropriately, the air flow changed downward on the peripheral wall of the second bell mouth 58 is changed to the air flowing in from the first bell mouth 72. It is thought that the disturbance at the time of merging was reduced by approaching the basic flow.

  FIG. 6 is a graph showing the relationship between the height of the second bell mouth 58 formed on the upper plate 56 and the noise value measured for the centrifugal fan 10. The height of the second bell mouth 58 refers to the distance from the opening surface on the side with the large opening area (the flat surface side of the upper plate 56) to the opening surface on the side with the small opening area (tip side). . In the example shown in FIG. 6, the inner diameter of the impeller 20 is fixed to 75 mm, the minimum inner diameter of the second bell mouth 58 is fixed to 63 mm, and the minimum inner diameter of the first bell mouth 72 is fixed to 46 mm. As shown in the figure, the noise value decreases when the height of the second bell mouth 58 is 14 mm rather than 10 mm. This is because the tip of the second bell mouth 58 enters deeper into the back side (bottom plate 52 side) of the impeller 20, so that the peripheral wall of the second bell mouth 58 causes a backflow of air as described above. This is thought to be due to the fact that the action to guide the camera toward the camera has increased.

  However, if the second bell mouth 58 is extended too much, the flow of air flowing in from the first bell mouth 72 toward the wing piece 24 may hit the tip of the second bell mouth 58 and generate wind noise. Therefore, as shown in FIG. 7, a surface inclined toward the bottom plate 52 (downward in the drawing) at an angle of 45 degrees from the tip of the first bell mouth 72 toward the outside in the radial direction (in the cross-sectional view of FIG. If the height of the second bell mouth 58 is set so that the tip of the second bell mouth 58 is located on the upper plate 56 side (upward in the figure) from the upper plate 56 (shown by a broken line), This makes it difficult for the air flow to hit the tip of the second bell mouth 58 (the tip of the second bell mouth 58 is difficult to block the air flow), so that it is possible to suppress the generation of wind noise.

  The centrifugal fan 10 of the present embodiment described above includes the following modifications. In the following, modifications will be described focusing on differences from the above-described embodiment.

  FIG. 8 is an explanatory view showing the structure of the centrifugal fan 10 of the first modification. FIG. 8A is a cross-sectional view in which the distal ends of the first bell mouth 72 and the second bell mouth 58 are enlarged by cutting the centrifugal fan 10 of the first modified example on a plane including the rotation shaft 32 of the drive motor 30. It is shown. As shown in the drawing, in the centrifugal fan 10 of the first modified example, there is a gap between the tip of the first bell mouth 72 formed on the guide plate 70 and the tip of the second bell mouth 58 formed on the upper plate 56. It is blocked by the closing plate 80. As shown in the perspective view of FIG. 8B, the closing plate 80 is formed in an annular shape.

  By providing such a blocking plate 80, the air flowing from the first bell mouth 72 does not flow between the first bell mouth 72 and the second bell mouth 58, and the air flow toward the wing piece 24 is prevented. Become smooth. Therefore, it is possible to reduce the noise of the centrifugal fan 10 by suppressing the noise generated by the disturbance of the air flow.

  FIG. 9 is an explanatory view showing the structure of the centrifugal fan 10 of the second modified example. FIG. 9 is a cross-sectional view of the upper plate 56 of the second modified example cut along a plane including the rotation shaft 32 of the drive motor 30. The upper plate 56 of the second modified example is formed integrally with the guide plate 70 by die casting. In such an upper plate 56 of the second modified example, the inner peripheral side of the thick bell mouth corresponds to the first bell mouth 72 of the embodiment, the outer peripheral side corresponds to the second bell mouth 58 of the embodiment, and the lower end surface. Corresponds to the closing plate 80 of the first modification. In addition, the material which forms the upper board 56 of a 2nd modification is not restricted to a metal, Resin may be sufficient.

  Thus, by forming the 1st bellmouth 72, the 2nd bellmouth 58, and the obstruction board 80 integrally, the front-end | tip of the 1st bellmouth 72 and the 2nd bellmouth 58 compared with the case where each is separate. It is possible to reduce unevenness due to bonding or the like on the side (low surface resistance), and it is difficult for the air flow from the first bell mouth 72 to flow toward the wing piece 24 so that noise is further reduced. It becomes possible to plan.

  The centrifugal fan 10 of this embodiment and the modification has been described above, but the present invention is not limited to the above-described embodiment and modification, and can be implemented in various modes without departing from the scope of the invention. Is possible.

10 ... Centrifugal fan, 20 ... Impeller, 22 ... Rotating disc,
24 ... Wings, 26 ... Support plate, 30 ... Drive motor,
32 ... Rotating shaft, 50 ... Fan case, 50a ... Scroll casing,
50b ... Air passage, 50c ... Tongue, 52 ... Bottom plate,
54 ... peripheral wall plate, 56 ... upper plate, 58 ... second bellmouth,
60 ... discharge port, 70 ... guide plate, 72 ... first bell mouth,
80: A closing plate.

Claims (4)

A cylindrical impeller in which a plurality of blade pieces erected from the outer edge portion of the rotating disk are arranged radially with respect to the rotating shaft, the impeller is accommodated, and a radius with respect to the rotating shaft is A scroll casing formed in a cylindrical shape that increases in the rotational direction, a bottom plate that closes one axial end surface of the rotary shaft of the scroll casing, and an end surface opposite to the bottom plate of the scroll casing; The impeller includes a cover plate having a first bell mouth that guides air to the inside of the impeller, and an air passage that extends in a tangential direction from a peripheral surface of the scroll casing having a larger radius with respect to the rotation shaft. In the centrifugal fan that sends air to the air passage by rotating the
The tip of the first bell mouth with the reduced opening area is located on the inner side of the impeller and on the bottom plate side than the end on the lid plate side of the wing piece,
On the impeller side surface of the lid plate, a second bell mouth having a diameter larger than that of the first bell mouth surrounds the first bell mouth, and the blade pieces of the first bell mouth and the impeller Between
The tip opening area is narrowed in the second bell mouth is a centrifugal fan, characterized by being located on the bottom plate side of the end portion of the cover plate side of the front Kitsubasahen. The centrifugal fan according to claim 1, wherein
The tip of the second bell mouth is located closer to the cover plate than the surface inclined to the bottom plate at an angle of 45 degrees from the tip of the first bell mouth radially outward. Centrifugal fan to play. The centrifugal fan according to claim 1 or 2,
A centrifugal fan, wherein a gap between the tip of the first bell mouth and the tip of the second bell mouth is closed by a closing plate. The centrifugal fan according to claim 3,
The centrifugal fan, wherein the first bell mouth, the second bell mouth, and the closing plate are integrally formed.

Images