JP5151631B2 - Centrifugal blower - Google Patents

Description

  The present invention relates to a centrifugal blower used for a ventilation blower or the like.

  Conventionally, this type of centrifugal blower is used for a centrifugal blower or the like, and is known to have an orifice on one surface of an outer shell that is different from a suction casing having a bell mouth-like suction port (for example, a patent) Reference 1).

  Hereinafter, the centrifugal blower will be described with reference to FIG.

  As shown in FIG. 10, an outer shell 101 having an opening on one surface, an electric motor 104 having an impeller 103 fixed to a top surface 102 in the outer shell 101, a scroll casing 105 surrounding the periphery of the impeller 103, and a suction port 106 are provided. The centrifugal blower including the suction casing 107 includes an orifice 109 having a suction hole 108 that is equal to or smaller than the suction port 106 with a predetermined gap h from the suction casing 107. The resonance space 112 is configured by providing the end portion 111 with a gap dimension j therebetween. Further, a grill 113 and a discharge port 114 provided on one side of the outer shell 101 are provided on one surface of the orifice 109.

In the above configuration, when the impeller 103 rotates, the intake air passes from the grill 113 through the suction hole 108 of the orifice 109, enters the impeller 103 through the suction port 106 of the suction casing 107, and is pressurized by the impeller 103. It is discharged from the discharge port 113 through the inside. At this time, sound waves of rotation noise generated when the pressure is increased by the impeller 103, turbulent flow noise caused by the vortex generated when passing through the scroll casing 105, and noise generated in the scroll casing 105 are radiated from the suction port 106. A part of the light enters the resonance space 112 from the entrance 115 having the gap dimension j. Among incident noise sound waves, noise sound waves having a frequency specified by the volume and shape of the resonance space 112 undergo air column resonance in the resonance space 112 and are resonated.
Japanese Patent No. 3279834

  Such a conventional centrifugal blower can mute relatively low frequency noise of approximately 1 kHz or less due to the resonance mute effect, but has a low muffle effect of relatively high frequency noise of approximately 1 kHz or more such as noise caused by turbulence, and the air volume. There is a problem that the amount of noise reduction is small when the noise in the high frequency range is dominant, such as when there is a large amount of noise, and there is a demand for enhancing the noise reduction effect in the high frequency range and reducing the noise.

  The present invention solves such a conventional problem, and an object of the present invention is to provide a centrifugal blower that enhances a high-frequency silencing effect and reduces noise.

In order to achieve the above object, the centrifugal blower of the present invention has an outer casing provided with an opening, an electric motor in which an impeller is connected to be rotatable around a rotating shaft, and a casing that surrounds the impeller and has a suction port. And a bell mouth-shaped orifice having an opening communicating with the opening of the outer shell, and a centrifugal blower that resonates and muffles noise emitted from the suction port by a resonance space formed by the orifice. reflective walls for reflecting sound waves of the noise which is incident on the resonant space from the gap between the end portion and the casing of the orifice therein provided, in which the reflecting wall and wherein Rukoto provided to said orifice.

The frequency of the sound wave that is silenced by this means depends on the reflection distance, which is the distance between the incident position of the sound wave and the reflection position. Here, the incident position is a gap and the reflection position is mainly the outline. At this time, by providing a reflection wall in the resonance space, the reflection position of the sound wave is close to the incident position by the reflection wall, and the reflection distance is shortened, so that a silencing effect is exerted on the high-frequency sound wave and noise can be reduced. A centrifugal blower is obtained. In addition, by this means, the reflection distance can be shortened by the reflection wall while ensuring the path of the sound wave to be reflected at the back and maintaining the sound reduction effect at low frequency, and the sound deadening effect works on the high frequency sound wave. A centrifugal blower that can reduce noise is obtained.

  Another means is a centrifugal blower characterized in that the casing has a scroll shape.

  By this means, the dynamic pressure of the air flowing out from the impeller can be efficiently converted into a static pressure and discharged from the discharge port, so that a centrifugal blower capable of improving the blowing efficiency and reducing noise can be obtained.

  Another means is a centrifugal blower characterized in that the suction port of the casing has a bell mouth shape.

  By this means, it is possible to obtain a centrifugal blower that can smooth the inflow of air into the casing, improve the blowing efficiency, and reduce noise.

  Another means is a centrifugal blower characterized in that the opening of the orifice is concentric with the suction port of the casing.

  By this means, the sound wave of the noise emitted from the suction port can be smoothly guided to the entire resonance space, so that the resonance silencing by the resonance space is easy to work, and the air can be smoothly guided to the casing by the orifice. A centrifugal blower that can reduce the pressure is obtained.

  Another means is a centrifugal blower characterized in that a reflection wall is provided perpendicular to the sound wave diffracted by the end of the orifice.

  By this means, by providing the reflecting wall perpendicular to the traveling direction of the sound wave, the sound deadening effect by the reflection is surely generated, so that a centrifugal blower capable of reducing noise can be obtained.

  Another means is a centrifugal blower characterized in that the reflection wall is a cylindrical wall surface concentric with the opening of the orifice.

  By this means, since the reflection distance is constant over the entire circumference, a strong silencing effect acts on a specific frequency, and a centrifugal blower capable of reducing noise can be obtained.

  Another means is a centrifugal blower characterized in that a plurality of cylindrical wall surfaces having different diameters are provided.

  By this means, reflection of sound waves is generated by cylindrical wall surfaces having different diameters, and a frequency to be reduced is newly added, so that a centrifugal blower capable of reducing noise can be obtained.

  In addition, another means is a far grand blower characterized in that a cylindrical wall surface having a larger diameter has a larger wall surface height.

  By this means, the sound wave is reflected by the cylindrical wall surface having a large diameter without being blocked by the cylindrical wall surface having a small diameter, so that a centrifugal blower capable of reducing noise can be obtained.

  Another means is a centrifugal blower characterized in that a wall surface is provided in the radial direction between the cylindrical wall surfaces.

  By this means, since a plurality of branch pipes are formed between the cylindrical wall surfaces, a resonance silencer due to air column resonance by the branch pipes is added, and a centrifugal blower capable of reducing noise is obtained.

  Another means is a centrifugal blower characterized in that the reflection wall is an arc wall surface.

  By this means, the high frequency range is reduced for the sound wave of noise incident on the area where the arc wall is installed, and the low frequency range is reduced for the sound wave of noise incident on the area where it is not installed. Can be left strong, and a centrifugal blower that can reduce noise is obtained.

  Another means is a centrifugal blower characterized in that the reflection wall is an elliptical wall surface.

  By this means, since the reflection distance varies, a centrifugal blower capable of obtaining a sound reduction effect in a wide range of high frequencies and reducing noise can be obtained.

  Another means is a centrifugal blower characterized in that the height of the reflecting wall is higher than the height of the orifice.

  By this means, the sound wave entering from the gap can be reliably reflected with a short reflection distance, and a centrifugal blower capable of obtaining a sound reduction effect in a high frequency range and reducing noise can be obtained.

  Another means is a centrifugal blower characterized in that the reflection wall is a cylindrical wall surface and the end of the cylindrical wall surface is in contact with the casing.

  By this means, it is possible to reflect all sound waves of noise entering from the gap with a short reflection distance, and to obtain a centrifugal blower capable of obtaining a strong sound reduction effect in a high frequency range and reducing noise.

  Another means is a centrifugal blower characterized in that the reflecting wall is an arc wall surface and the end of the arc wall surface is in contact with the casing.

  By this means, most of the sound wave of noise incident on the area where the arc wall is installed can be reflected with a short reflection distance, and a strong sound reduction effect can be obtained in the high frequency range, and noise incident on the area where it is not installed A centrifugal blower capable of reducing the noise in the low frequency region can be strongly left against the sound wave of the above, and noise can be obtained.

  Another means is a centrifugal blower characterized in that the height of the reflecting wall is equal to or less than the height of the orifice.

  By this means, the path to the innermost reflection position is prevented from being blocked as much as possible, the sound reduction effect in the low frequency range is maintained, the reflection distance is shortened by the reflection wall, and the sound reduction effect is obtained in the high frequency range. A centrifugal blower that can reduce the pressure is obtained.

  Another means is a centrifugal blower characterized in that the distance between the axial position of the position where the sound wave is reflected and the gap is shortened.

  By this means, by shortening the distance between the sound wave axial reflection position and the gap portion, the reflection distance is shortened, the sound reduction effect is moved to a higher frequency range, and a centrifugal blower capable of reducing noise can be obtained.

  Another means is a centrifugal blower characterized in that the orifice is provided with a reflecting wall, the reflecting wall is a cylindrical wall surface concentric with the orifice, and a horizontal wall surface extending in the direction perpendicular to the rotation axis is provided inside the cylindrical wall surface. Is.

  By this means, the sound wave is reflected by the horizontal wall surface, so the axial position of the position where the sound wave is reflected and the gap can be shortened, and the reflection distance is shortened, so the sound reduction effect moves to a higher frequency range. Thus, a centrifugal blower that can reduce noise is obtained.

  Another means is a centrifugal blower characterized by comprising a ring extending from the end of the orifice toward the reflecting wall.

  By this means, the cavity formed by the reflecting wall, the orifice and the ring, and the gap between the ring and the reflecting wall form a Helmholtz resonator. can get.

  ADVANTAGE OF THE INVENTION According to this invention, the centrifugal blower which improves the noise reduction effect of a high frequency region and reduces noise can be provided.

According to a first aspect of the present invention, there is provided an electric motor having an impeller connected to an impeller so as to be rotatable about a rotating shaft, a casing having a suction port surrounding the impeller, and an outer shell. A centrifugal mouth blower that resonates and muffles noise emitted from the suction port by a resonance space formed by the orifice. A centrifugal blower characterized in that a reflection wall is provided for reflecting sound waves of noise that has entered the resonance space from the gap between the end of the housing and the casing, and the distance between the sound wave incident position and the reflection position By shortening the reflection distance, a silencing effect is exerted on high-frequency sound waves, and noise can be reduced. In addition, the centrifugal blower is characterized by having a reflection wall in the orifice, and the reflection distance is shortened by the reflection wall while ensuring the sound wave path to be reflected at the back and maintaining the sound reduction effect at low frequencies. It has a function that a silencing effect acts on high-frequency sound waves and noise can be reduced.

  In addition, the centrifugal blower is characterized in that the casing has a scroll shape, and the dynamic pressure of the air flowing out from the impeller can be efficiently converted into static pressure and discharged from the discharge port. It has the effect | action which can improve ventilation efficiency and can reduce noise.

  Moreover, it is a centrifugal blower characterized in that the suction port of the casing has a bell mouth shape, and has an effect of facilitating the inflow of air into the casing, improving the blowing efficiency, and reducing noise. .

  In addition, the centrifugal fan is characterized in that the orifice opening is concentric with the suction port of the casing, and the sound wave of noise radiated from the suction port can be smoothly guided to the entire resonance space. Resonance silencing due to space is easy to work, and since air can be smoothly guided to the casing by the orifice, there is an effect that noise can be reduced.

  In addition, the centrifugal blower is characterized in that a reflection wall is provided perpendicular to the sound wave diffracted by the end of the orifice. By providing the reflection wall perpendicular to the traveling direction of the sound wave, it is reliably reflected. Since the silencing effect is generated, the noise can be reduced.

  In addition, it is a centrifugal blower characterized in that the reflection wall is a cylindrical wall surface concentric with the opening of the orifice, and since the reflection distance is constant over the entire circumference, a strong silencing effect acts on a specific frequency, It has the effect of reducing noise.

  In addition, it is a centrifugal blower characterized by providing a plurality of cylindrical wall surfaces with different diameters, and the reflection of sound waves is generated by the cylindrical wall surfaces with different diameters, and the frequency to be reduced is newly added. It has the effect of reducing noise.

  In addition, it is a far grand blower characterized in that the larger the cylindrical wall surface is, the larger the wall height is. The sound wave is reflected by the larger cylindrical wall surface without being blocked by the smaller cylindrical wall surface. Therefore, the noise can be reduced.

  In addition, the centrifugal blower is characterized by having a wall surface in the radial direction between the cylindrical wall surfaces. Since a plurality of branch pipes are formed between the cylindrical wall surfaces, resonance silence due to air column resonance by the branch pipes is added. And has the effect of reducing noise.

  In addition, the centrifugal blower is characterized in that the reflecting wall is an arc wall surface, and the high frequency region is reduced with respect to the sound wave of the noise incident on the area where the arc wall surface is installed, and is not installed. For sound waves of noise incident on the range, the sound reduction effect in the low frequency region can be strongly left, and the noise can be reduced.

  In addition, the centrifugal blower is characterized in that the reflection wall is an elliptical wall surface, and since the reflection distance varies, it has the effect of reducing the noise in a wide range of high frequencies and reducing noise. .

  In addition, the centrifugal blower is characterized in that the height of the reflecting wall is higher than the orifice height, and the sound wave entering from the gap can be reliably reflected with a short reflection distance, and the sound reduction effect is achieved in the high frequency range. Obtained, and has the effect of reducing noise.

  In addition, it is a centrifugal blower characterized in that the reflection wall is a cylindrical wall surface, and the end of the cylindrical wall surface is in contact with the casing, and all sound waves of noise entering from the gap can be reflected with a short reflection distance, A strong sound reduction effect is obtained in a high frequency range, and noise can be reduced.

  In addition, the centrifugal wall blower is characterized in that the reflecting wall is an arc wall surface and the end of the arc wall surface is in contact with the casing, and most of sound waves of noise incident on the area where the arc wall surface is installed have a short reflection distance. The sound can be reflected at high frequencies, and a strong sound reduction effect can be obtained in the high frequency range. Has the effect of being able to.

  In addition, the centrifugal blower is characterized in that the height of the reflecting wall is equal to or less than the height of the orifice, and the noise reduction effect in the low frequency range is suppressed as much as possible to prevent the path to the deepest reflection position from being blocked. The reflection distance is shortened by the reflection wall, the sound reduction effect is obtained in the high frequency region, and the noise can be reduced.

  In addition, the centrifugal blower is characterized in that the distance between the axial position where the sound wave is reflected and the gap portion is shortened, and the distance between the axial reflection position of the sound wave and the gap portion is reduced. The distance is shortened, the sound reduction effect moves to a higher frequency region, and noise can be reduced.

  Further, the orifice is provided with a reflecting wall, the reflecting wall is a cylindrical wall surface concentric with the orifice, and a centrifugal blower characterized by providing a horizontal wall surface extending in the vertical direction of the rotation axis inside the cylindrical wall surface, Since the sound wave is reflected by the horizontal wall surface, the axial position of the position where the sound wave is reflected and the gap portion can be shortened, and the reflection distance is shortened. It has the effect that it can be reduced.

  In addition, the centrifugal blower is characterized by including a ring extending from the end of the orifice toward the reflecting wall, and a gap formed between the reflecting wall, the orifice and the ring, and the ring and the reflecting wall is provided. Since the Helmholtz resonator is formed, resonance silence is added by the Helmholtz resonator, and noise can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
As shown in FIGS. 1 (a) and 1 (b), a centrifugal blower 1 used as a ceiling-embedded ventilation fan has a multi-blade that is rotatable around a rotating shaft 4 in an outer shell 3 having an opening 2 on a lower surface. An electric motor 6 to which a type impeller 5 is connected, and a scroll-shaped casing 10 that surrounds the periphery of the impeller 5 and has a bell mouth-like suction port 7 in an opening and a discharge port 9 in a side wall 8 are provided. The discharge port 9 of the casing 10 communicates with the discharge adapter 12 through a discharge opening 11 provided on one side surface of the outer shell 3. A flange portion 13 is provided on the outer periphery of the lower surface of the outer shell 3, and the outer shell 3 is fixed to the ceiling material 15 with screws or the like through a hole 14 provided in the flange portion 13, and a duct 16 disposed on the ceiling and communicating with the outside is discharged. It is joined to the discharge port 9 via the adapter 12.

  In addition, an orifice 18 that is concentric with the suction port 7 of the casing 10 and has a bell mouth-shaped opening 17 is disposed so as to close the opening 2 of the outer shell 3, and is surrounded by the casing 10, the orifice 18, and the outer shell 3. A space 19 is formed. Further, the end 20 of the orifice 18 is located at a gap dimension j from the lower surface of the casing 10 to form a gap 21.

  The orifice 18 includes a cylindrical wall surface 22 concentric with the opening 17.

  In the above configuration, when the impeller 5 is rotated by the electric motor 6, the intake air passes through the opening 17 of the orifice 18 from the opening 2, enters the impeller 5 through the suction port 7 of the casing 10, and is pressurized by the impeller 5. 10 is discharged from the discharge adapter 12 to the duct 16 and discharged to the outside.

  At this time, the rotation noise generated when the pressure is increased by the impeller 5, the turbulent noise caused by the vortex generated when passing through the inside of the casing 10, and the sound wave of the noise amplified by the resonance in the casing 10 are sucked in. A part of the sound wave of noise emitted from the inlet 7 of the casing 10 is radiated downward from the mouth 7, and the resonance space 19 is formed from the gap 21 formed between the end 20 of the orifice 18 and the casing 10. Incident to A part of the incident sound wave becomes an anti-phase sound wave due to reflection at the fixed end on the wall surface inside the resonance space 19 and returns to the gap 21, and resonance silencing due to air column resonance that cancels part of the sound wave emitted from the suction port 7 occurs. Therefore, noise can be reduced. Here, the main elements that reflect sound waves in the resonance space 19 are the outer shell 3 and the cylindrical wall surface 22, and the reflection distance that is the distance between the gap portion 21 that is the incident position of the sound wave and the reflection position is short. Is a reflection position. Since the frequency of the sound wave canceled out by the resonance muffler becomes higher as the reflection distance is shorter, by providing the cylindrical wall surface 22, the noise reduction effect in the high frequency region works and noise is reduced.

  Moreover, since the dynamic pressure of the air which flowed out from the impeller 5 can be efficiently converted into a static pressure and discharged from the discharge port 9 by the scroll-shaped casing 10, the blowing efficiency can be improved and noise can be reduced.

  Moreover, since the suction inlet 7 is bell mouth shape, the inflow of the air to the casing 10 can be made smooth, ventilation efficiency can be improved, and noise can be reduced.

  In addition, since the opening 17 of the orifice 18 and the suction port 7 are concentric circles, the sound wave of the noise radiated from the suction port 7 can be smoothly guided to the entire resonance space 19, so that the resonance silencing by the resonance space 19 is easy to work. Further, since the air can be smoothly guided to the casing 10 by the orifice 18, the blowing efficiency is improved and noise can be reduced.

  Further, since the orifice 18 is provided with a cylindrical wall surface 22 and a sound wave path to a reflection position on the back side such as the outer shell 3 is secured, a high frequency region by the cylindrical wall surface 22 is maintained while maintaining a sound reduction effect in a low frequency region. Therefore, noise can be reduced.

  In addition, since the cylindrical wall surface 22 is concentric with the opening 17 of the orifice 18, the reflection distance is constant over the entire circumference of the opening 17 and the cylindrical wall surface 22, so that a strong noise reduction effect acts on a specific frequency, and noise. Can be reduced.

  For example, the centrifugal blower 1 has an inner dimension of 264 mm square, a height of 195 mm, an impeller 5 diameter of 183.5 mm, a suction port inner diameter Di of 152 mm, an opening inner diameter Do of 152 mm, and a gap dimension j of 5 mm. In Embodiment 1 of this invention when the internal diameter De is 172 mm, the graph of the noise characteristic value of the centrifugal blower 1 with and without the cylindrical wall surface 22 is shown in FIG. A solid line is a case where the cylindrical wall surface 22 is provided, and a broken line is a noise value characteristic when the cylindrical wall surface 22 is not provided. By providing the cylindrical wall surface 22, the sound pressure level is reduced in the high frequency range, and the sound reduction is particularly remarkable in the peak value of 1.1 kHz and in the range of 2.1 kHz to 3 kHz. In the configuration of Embodiment 1 of the present invention, a noise reduction effect of 0.5 dB was confirmed with the overall.

  As shown in FIG. 3A, the height of the cylindrical wall surface 22 is made lower than the height of the orifice 18, so that the sound wave path to the far side position becomes wider. A sound reduction effect in a high frequency range can be obtained while keeping it strong.

  In addition, as shown in FIG.3 (b), the sound reduction effect in a high frequency region can be heightened by making the height of the cylindrical wall surface 22 into the height of the orifice 18 or more. Furthermore, by extending the end of the cylindrical wall surface 22 and bringing it into contact with the casing 10, the reflection distance of most of the sound waves incident from the gap 21 is shortened, so that a strong sound reduction effect is obtained in the high frequency range and noise is reduced. can do.

(Embodiment 2)
A second embodiment of the present invention will be described with reference to FIGS. The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. 4 (a) and 4 (b), the orifice 18 includes an orthogonal wall surface 23 that intersects perpendicularly with the sound wave entering from the gap 21.

  At this time, the sound wave of the noise incident from the gap 21 is more likely to be diffracted as the sound wave is closer to the end 20 of the orifice 18. Therefore, an orthogonal wall surface 23 having a shape that intersects the orifice 18 perpendicular to the direction of the sound wave is provided. The sound wave reflected by the orthogonal wall surface 23 surely travels in the opposite direction in the incident path, so that the silencing due to the reflection works strongly, a sound reduction effect is obtained in a high frequency range, and noise can be reduced. Since the direction distribution 24 of the sound waves tends to spread radially from the gap portion 21, the side cross-sectional shape of the orthogonal wall surface is an arc shape centered on the gap portion 21, so that the sound deadening due to reflection works more reliably. , Noise can be reduced.

(Embodiment 3)
A third embodiment of the present invention will be described with reference to FIGS. The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. In FIG. 5A, the orifice 18 includes a cylindrical wall surface 22 and a second cylindrical wall surface 25 having a larger diameter than the cylindrical wall surface 22. The cylindrical wall surface 22 and the second cylindrical wall surface 25 are concentric with the orifice 18, and the height of the second cylindrical wall surface 25 is larger than the height of the cylindrical wall surface 22.

  At this time, in addition to the noise reduction effect in the high frequency range by the cylindrical wall surface 22, a noise reduction effect in the high frequency range is newly added by the second cylindrical wall surface 25, so that noise can be reduced. Further, since the height of the second cylindrical wall surface 25 is larger than the cylindrical wall surface 22, the sound waves are reflected by the second cylindrical wall surface 25 without being blocked by the cylindrical wall surface 22, and the sound reduction effect by the second cylindrical wall surface 25 is obtained. Since it works strongly, a further sound reduction effect can be obtained.

  Furthermore, as shown in FIG. 5B, a partition wall surface 26 is provided between the cylindrical wall surface 22 and the second cylindrical wall surface 25 in the radial direction. At this time, the cylindrical wall surface 22, the second cylindrical wall surface 25, and the partition wall surface 26 form a plurality of branch pipes 27. Resonance silencing occurs due to air column resonance of the branch pipes 27, and noise can be reduced.

(Embodiment 4)
A fourth embodiment of the present invention will be described with reference to FIGS. The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. 6 (a) and 6 (b), the orifice 18 includes an arc wall surface 28.

  At this time, since the circular arc wall surface 28 is partially provided with respect to the gap portion 21 instead of the entire circumference, a sound reduction effect is exerted in a high frequency range for a sound wave incident on the range where the circular arc wall surface 28 is provided. Since the sound wave path to the reflection position on the back side of the outer shell 3 or the like is secured for the sound wave that has entered the range where it does not work, the sound reduction effect works in the low frequency range, and the noise can be reduced.

  Further, by extending the end of the arc wall surface 28 and bringing it into contact with the casing, the reflection distance of most sound waves incident on the area where the arc wall surface 28 is provided is shortened, so that a strong sound reduction effect is obtained in the high frequency region. For the sound wave incident on the range where the arc wall surface 28 is not provided, the sound wave path to the reflection position on the back side such as the outer shell 3 is secured, so the sound reduction effect is applied to the sound wave of the low frequency range noise. Works and can reduce noise.

(Embodiment 5)
A fourth embodiment of the present invention will be described with reference to FIGS. The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. 7A and 7B, the orifice 18 has an elliptical wall surface 29.

  At this time, since the reflection wall, which is the reflection position of the sound wave of noise, has an elliptical shape, the reflection distance, which is the distance between the gap portion 21, which is the incident position of the sound wave of noise, and the reflection position has various lengths. A sound reduction effect works on sound waves of noise in a wide frequency range, and noise can be reduced.

  A similar effect can be expected by providing the orifice 18 with the cylindrical wall surface 22 eccentric with respect to the opening 17 of the orifice 18.

  A similar effect can be expected by providing the orifice 18 with a polygonal reflecting wall.

(Embodiment 6)
A fourth embodiment of the present invention will be described with reference to FIG. The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. In FIG. 8, the orifice 18 includes a cylindrical wall surface 22 and a horizontal ring plate 30 that is perpendicular to the rotary shaft 4 inside the cylindrical wall surface 22.

  At this time, the reflection of the sound wave by the horizontal ring plate 30 is a reflection at a position where the reflection position in the direction of the rotation axis 4 is close to the gap portion 21, so that the reflection distance is shortened, so that the sound wave is reduced to a high-frequency noise sound wave. The effect works and can reduce noise.

(Embodiment 7)
A fourth embodiment of the present invention will be described with reference to FIG. The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. In FIG. 9, the orifice 18 includes a cylindrical wall surface 22 and a ring 31 extending from the end 20 of the orifice 18 toward the cylindrical wall surface 22. Here, the ring 31 extends to a position 1 mm away from the cylindrical wall surface 22, and a gap 32 is formed.

  A cavity 33 is constituted by the orifice 18, the cylindrical wall surface 22, and the ring 31, and a Helmholtz resonance structure is formed with the cavity 33 as a volume part and the gap 32 as a throat part.

  At this time, resonance silencing due to the Helmholtz resonance structure occurs, and noise can be reduced.

  The present invention provides a centrifugal blower that enhances the noise reduction effect in the high frequency range and reduces noise, and can be used for air conditioning equipment and ventilation blower equipment.

The figure ((a) sectional side view (b) bottom view) which shows the centrifugal blower of Embodiment 1 of this invention The graph which shows the noise reduction effect of Embodiment 1 of this invention Side sectional view which shows the other example of the centrifugal blower of Embodiment 1 of this invention. The figure which shows the centrifugal blower of Embodiment 2 of this invention ((a) sectional side view (b) partial sectional side view) The figure which shows Embodiment 3 of this invention ((a) Centrifugal blower sectional side view (b) The bottom view of the orifice which shows another example) The figure which shows the centrifugal blower of Embodiment 4 of this invention ((a) sectional side view (b) bottom view) The figure which shows the centrifugal blower of Embodiment 5 of this invention ((a) sectional side view (b) bottom view) Side sectional view which shows the centrifugal blower of Embodiment 6 of this invention. Side sectional view which shows the centrifugal blower of Embodiment 7 of this invention. Side sectional view showing a conventional centrifugal blower

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Centrifugal blower 2 Opening 3 Outer shell 4 Rotating shaft 5 Impeller 6 Electric motor 7 Suction port 8 Side wall 9 Discharge port 10 Casing 11 Discharge opening 12 Discharge adapter 13 Flange part 14 Hole 15 Ceiling material 16 Duct 17 Opening part 18 Orifice 19 Resonance space 20 End portion 21 Gap portion 22 Cylindrical wall surface 23 Orthogonal wall surface 24 Direction distribution 25 Second cylindrical wall surface 26 Partition wall surface 27 Branch pipe 28 Arc wall surface 29 Elliptical wall surface 30 Horizontal ring plate 31 Ring 32 Clearance 33 Cavity Di Suction port inner diameter Doo Opening inner diameter De Cylindrical wall inner diameter j Gap size

Claims (18)

An electric motor in which an impeller is connected to be rotatable about a rotation shaft, a casing having a suction port surrounding the impeller, and an opening communicating with the opening of the outer shell. A centrifugal mouth blower that resonates and muffles noise emitted from the suction port by a resonance space formed by the orifice, and has an end portion of the orifice and the inside of the resonance space. reflective walls for reflecting sound waves of the noise which is incident on the resonant space from the gap portion between the casing provided, centrifugal blower you characterized by comprising the reflecting wall to said orifice. The centrifugal blower according to claim 1, wherein the casing has a scroll shape. The centrifugal blower according to claim 1 or 2, wherein the suction port of the casing has a bell mouth shape. The centrifugal blower according to any one of claims 1 to 3, wherein the opening of the orifice is concentric with the suction port of the casing. The centrifugal blower according to any one of claims 1 to 4 , wherein a reflecting wall is provided perpendicular to the traveling direction of the sound wave diffracted by the end of the orifice. The centrifugal blower according to any one of claims 1 to 4, wherein the reflecting wall is a cylindrical wall surface concentric with the opening of the orifice. The centrifugal blower according to claim 6 , wherein a plurality of cylindrical wall surfaces having different diameters are provided. The centrifugal blower according to claim 7 , wherein a cylindrical wall surface having a larger diameter has a higher wall surface height. The centrifugal blower according to claim 7 or 8 , further comprising a wall surface in a radial direction between the cylindrical wall surfaces. The centrifugal blower according to any one of claims 1 to 4 , wherein the reflecting wall is an arc wall surface. The centrifugal blower according to any one of claims 1 to 4 , wherein the reflecting wall is an elliptical wall surface. Centrifugal blower according to claim 1 to 1 1, the height of the reflection wall may be higher than the orifice height. Reflection wall a cylindrical wall, a centrifugal blower according to claim 1 2 in which the end of said cylindrical wall, characterized in that the contact with the casing. Reflecting walls as an arc wall surface, the centrifugal blower of claim 1 2 in which an end of the arcuate wall is equal to or in contact with the casing. Centrifugal blower according to claim 1 to 1 1, the height of the reflection wall is equal to or less than the orifice height. The centrifugal blower according to any one of claims 1 to 15 , wherein the distance between the axial position of the position where the sound wave is reflected and the gap is shortened. The centrifugal wall according to claim 16 , wherein the orifice includes a reflecting wall, and the reflecting wall is a cylindrical wall surface concentric with the orifice, and a horizontal wall surface extending in a direction perpendicular to the rotation axis is provided inside the cylindrical wall surface. Blower. The centrifugal blower according to any one of claims 1 to 17 , further comprising a ring extending from an end of the orifice toward the reflecting wall, wherein a gap is formed by the end of the reflecting wall and the outer peripheral end of the ring.

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