JP5135967B2 - 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. 15, 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 casing 105 surrounding the periphery of the impeller 103, and a suction port having a suction port 106. The centrifugal blower including the casing 107 has an orifice 109 having a suction hole 108 that is equal to or smaller than the suction port 106 with a predetermined gap h between the suction casing 107 and a lower end 110 of the suction casing 107 and an end 111 of the orifice 109. A resonance space 112 is formed with a dimension i apart. 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. And discharged from the discharge port 114. At this time, rotational noise generated when the pressure is increased by the impeller 103, turbulent noise due to vortex generated when passing through the casing 105, and sound waves of noise generated in the casing 105 are radiated from the suction port 106, and A part of the light enters the resonance space 112 from the entrance 115 having the gap size i. 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

  The frequency of noise that is resonated and muffled in the resonance space 112 is specified by the volume and shape of the resonance space 112. However, in such a conventional centrifugal blower, the range in which the volume and shape of the resonance space 112 can be adjusted is narrow, so There is a problem that the range of the frequency of the noise that can be silenced is narrow, and it is required to widen the range of the frequency of the noise that can be silenced.

  In addition, in order to mute low frequency noise, it is necessary to increase the volume of the resonance space 112, and there is a problem that the size of the outer shell 101 becomes large. Without changing the size of the outer shell 101, There is a demand to be able to mute lower frequency noise.

  In addition, since the volume of the resonance space 112 cannot be easily changed, noise reduction by resonance muffing can be performed when the main noise frequency changes depending on the installation state of the centrifugal blower or when there are multiple protruding frequency noises. There is a problem that the effect is reduced, and it is required to be able to adjust the frequency that can be silenced.

  The present invention solves such a conventional problem, can expand the range of noise frequency that can be silenced, can mute low frequency noise without changing the size of the outline, and can mute noise It aims at providing the centrifugal blower which can adjust the frequency of.

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 member for closing the gap between the end of the orifice and the casing is used as a sound-absorbing structural material, and a space formed by the orifice Resonance-type sound absorbing structure is formed as a back air layer, a wall is provided in the space, the thickness of the back air layer is increased, and the wall provided in the space is a cylinder concentric with the suction port and one end in contact with the casing The centrifugal blower is characterized by being tubular .

  By this means, a resonance type sound absorbing structure can be formed by the member that closes the gap and the space formed by the orifice, so that a centrifugal blower that can expand the range of noise frequency that can be silenced is obtained. In addition, the length of the path through which the sound wave of the noise propagates around the wall in the space can be regarded as the thickness of the back air layer in the resonance type sound absorbing structure, so that the thickness of the back air layer can be increased. A centrifugal blower that can muffle low-frequency noise without changing the size of the outer shell is obtained. In addition, since the sound wave of the noise goes around the wall in the space is only a single U-bend and the sound wave of the noise can be smoothly propagated, the thickness of the back air layer can be increased more stably. Thus, a centrifugal blower that can muffle low-frequency noise without changing the size of the outer shell by a wall having a simple structure can be obtained.

  Another means is a centrifugal blower in which the inner diameter D of the cylindrical tubular wall concentric with the suction port provided in the space is not uniform in the circumferential direction.

  By this means, since the inner diameter D of the cylindrical tubular wall portion is partially different, a portion having a different thickness of the back air layer can be formed, so that noise of a plurality of frequencies can be silenced and the range of noise frequencies that can be silenced is expanded. A centrifugal blower that can be obtained is obtained.

  Another means is a centrifugal blower in which the height of a cylindrical tubular wall concentric with the suction port provided in the space is not uniform in the circumferential direction.

  By this means, the height of the cylindrical tubular wall part is partially different, so that the part of the thickness of the back air layer is different, so that noise of a plurality of frequencies can be silenced and the range of noise frequencies that can be silenced is expanded. A centrifugal blower that can be obtained is obtained.

  Another means is a centrifugal blower capable of adjusting the inner diameter of a cylindrical tubular wall concentric with a suction port provided in the space.

  By this means, the thickness of the back air layer can be adjusted by adjusting the inner diameter of the cylindrical tubular wall, so that a centrifugal blower capable of adjusting the frequency of noise that can be silenced can be obtained.

  Another means is a centrifugal blower in which the height of a cylindrical tubular wall concentric with a suction port provided in the space can be adjusted.

  By this means, since the thickness of the back air layer can be adjusted by adjusting the height of the cylindrical tubular wall body, a centrifugal blower capable of adjusting the frequency of noise that can be silenced is obtained.

  Further, the other means includes at least one cylindrical tubular wall body concentric with the suction port of the casing and one end in contact with the casing, and at least one cylindrical tubular wall body concentric with the suction port of the casing and in contact with the orifice at one end. The centrifugal blowers are alternately arranged in the radial direction.

  By this means, a labyrinth structure in which sound waves of noise alternately propagate around the wall in the space can be made, the thickness of the back air layer can be made thicker, and the size of the outer shell can be changed. Thus, a centrifugal blower that can mute low-frequency noise is obtained.

  Another means is a centrifugal blower provided with a partition that divides the space formed by the orifice into a plurality of parts.

  By this means, a plurality of resonance type sound absorbing structures having different space shapes and volumes can be formed, so that a centrifugal blower that can mute noises at a plurality of frequencies and expand the range of noise frequencies that can be muffled is obtained. It is done.

  Another means is a centrifugal blower in which a plurality of spaces divided by the partition walls are provided with members that close the gaps, and at least two types of members are applied.

  By this means, a plurality of types of resonance type sound absorbing structures can be formed, so that a centrifugal blower that can mute noises at a plurality of frequencies and expand the range of noise frequencies that can be muffled can be obtained.

  Another means is a centrifugal blower in which walls having different shapes are provided in each of a plurality of spaces divided by the partition walls, and the thickness of the back air layer is increased in each space.

  By this means, each of the divided spaces can form a resonance type sound absorbing structure having a different thickness of the back air layer. Therefore, it is possible to mute noises of a plurality of frequencies, and it is possible to widen the range of noise frequencies that can be muffled. A centrifugal blower is obtained.

  Another means is a centrifugal blower in which the outer peripheral space surrounded by the side wall and the outer shell of the casing is used as a back air layer.

  By this means, the outer peripheral space can be used as the back air layer of the resonance type sound absorbing structure, so that the thickness of the back air layer can be increased, and low frequency noise can be reduced without changing the size of the outer shell. A centrifugal blower that can be silenced is obtained.

  Another means is a centrifugal blower in which the back side space between the motor side outer wall and the outer shell of the casing is used as a back air layer.

  By this means, the back side space can be used as the back air layer of the resonance type sound absorbing structure, so that the thickness of the back air layer can be increased and low frequency noise can be reduced without changing the size of the outer shell. A centrifugal blower that can be silenced is obtained.

  ADVANTAGE OF THE INVENTION According to this invention, the range of the frequency of the noise which can be silenced can be expanded, the low frequency noise can be silenced without changing the magnitude | size of an outline, and the centrifugal blower which can adjust the frequency of the noise which can be silenced 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. And a bell mouth-like orifice having an opening communicating with the opening of the first member, and a member for closing the gap between the end of the orifice and the casing is used as a sound-absorbing structural material, and a space formed by the orifice is a back air layer As a centrifugal blower characterized by forming a resonance type sound absorbing structure as described above, the resonance type sound absorbing structure can be formed by a space that is formed by an orifice and a member that closes the gap portion, so that noise that can be silenced This has the effect of extending the frequency range of. In addition, it is a centrifugal blower characterized in that a wall is provided in the space and the thickness of the back air layer is increased, and the length of the path through which the sound wave of the noise propagates around the wall in the space Can be regarded as the thickness of the back air layer in the resonance type sound absorbing structure, the thickness of the back air layer can be increased, and low frequency noise can be silenced without changing the size of the outer shell. Has an effect. In addition, the wall body provided in the space is a centrifugal blower that is concentric with the suction port and has a cylindrical tubular shape with one end in contact with the casing, and the path of the sound wave of the noise around the wall body in the space is only one U-bend. Since the sound wave of noise can be propagated smoothly, the thickness of the back air layer can be increased more stably, and the low-frequency can be reduced without changing the size of the outer shell by a simple wall structure. The noise can be silenced.

  Moreover, it is a centrifugal blower that uses a membrane-like material as a member that closes the gap, and forms a vibration system in which the membrane-like material is a mass and the space as a back air layer is a spring. The film-like sound absorbing structure can be formed, so that the range of the noise frequency that can be silenced can be expanded.

  In addition, it is a centrifugal blower that uses a perforated plate as a member that closes the gap, and forms a vibration system in which the air in the hole portion of the perforated plate is a mass and the back air layer is a spring, thereby forming a Helmholtz resonance. Since it is possible to form a perforated plate sound absorbing structure of a resonance type sound absorbing structure that absorbs sound according to the same principle as that of a container, it has the effect that the range of the frequency of noise that can be silenced can be expanded.

  Moreover, it is a centrifugal blower that uses a porous material as a member that closes the gap, and can absorb relatively high-frequency noise by the porous material itself, and the porous material is a mass and the back air layer is a spring. By forming a vibration system, it is possible to form a porous sound absorbing structure of a resonance type sound absorbing structure, so that relatively low frequency noise can be silenced, and the range of noise frequencies that can be silenced can be expanded. It has the action.

  In addition, the inner diameter D of the cylindrical tubular wall that is concentric with the suction port provided in the space is a centrifugal blower that is not uniform in the circumferential direction, and the inner diameter D of the cylindrical tubular wall is partially different, Since portions having different thicknesses of the back air layer are formed, noises having a plurality of frequencies can be silenced, and the range of noise frequencies that can be silenced can be expanded.

  In addition, the height of the cylindrical tubular wall that is concentric with the suction port provided in the space is a centrifugal blower that is not uniform in the circumferential direction, and the height of the cylindrical tubular wall is partially different, Since portions having different thicknesses of the back air layer are formed, noises having a plurality of frequencies can be silenced, and the range of noise frequencies that can be silenced can be expanded.

  Further, the centrifugal blower is capable of adjusting the inner diameter of the cylindrical tubular wall concentric with the suction port provided in the space, and the thickness of the back air layer can be adjusted by adjusting the inner diameter of the cylindrical tubular wall. Therefore, it has the effect that the frequency of noise that can be silenced can be adjusted.

  In addition, the centrifugal blower can adjust the height of the cylindrical tubular wall concentric with the suction port provided in the space, and the thickness of the back air layer can be adjusted by adjusting the height of the cylindrical tubular wall. Since it can be adjusted, the frequency of the noise that can be silenced can be adjusted.

  Also, at least one cylindrical tubular wall body concentric with the casing suction port and one end contacting the casing, and at least one cylindrical tubular wall body concentric with the casing suction opening and one end contacting the orifice are alternately arranged in the radial direction. It can be a labyrinth structure in which sound waves of noise alternately travel around the wall and propagate in the space, and the thickness of the back air layer can be made thicker. It has the effect that low frequency noise can be silenced without changing the size of the outer shell.

  In addition, the centrifugal blower is provided with a partition that divides the space formed by the orifice into a plurality of parts, and a plurality of resonance type sound absorbing structures having different shapes and volumes of the spaces can be formed. The noise can be silenced, and the frequency range of the noise that can be silenced can be expanded.

  In addition, a centrifugal blower is provided with a member that closes the gap in each of the plurality of spaces divided by the partition walls, and at least two types of members are applied, and can form a plurality of types of resonance type sound absorbing structures. Therefore, it is possible to mute noises having a plurality of frequencies and to expand the range of noise frequencies that can be muffled.

  In addition, a centrifugal blower is provided in which a wall having a different shape is provided in each of a plurality of spaces divided by the partition walls, and the thickness of the back air layer is increased in each space. Therefore, it is possible to mute noises at a plurality of frequencies and to widen the range of noise frequencies that can be muffled.

  In addition, it is a centrifugal blower in which the outer peripheral space surrounded by the side wall and outer shell of the casing is used as a back air layer, and since the outer peripheral space can be used as a back air layer of the resonance type sound absorbing structure, The thickness of the air layer can be increased, and the low frequency noise can be silenced without changing the size of the outer shell.

  Further, the centrifugal blower is configured to use the back side space between the motor side outer wall and the outer casing of the casing as a back air layer, and the back side space can be used as the back air layer of the resonance type sound absorbing structure. Therefore, the thickness of the back air layer can be increased, and the low-frequency noise can be silenced without changing the size of the outer shell.

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

(Embodiment 1)
As shown in FIG. 1, a centrifugal blower 1 used as a ceiling-embedded ventilation fan is rotated around a rotating shaft 4 in an outer shell 3 having an inner dimension of 265 mm square and a height of 195 mm and having an opening 2 on the lower surface. An electric motor 6 connected to a multi-blade type impeller 5 having a diameter of 180 mm and a surrounding area of the impeller 5, a bell mouth shape on the lower surface and a suction port 7 having an inner diameter Di of 150 mm, and a discharge port on the side wall 8 A casing 10 having 9 is provided. The side wall 8 of the casing 10 has a scroll shape in which the air passage gradually expands toward the discharge port 9, and the discharge port 9 of the casing 10 passes through the discharge opening 11 provided on one side surface of the outer shell 3 and discharge adapter 12. Communicated with. In a part between the casing 10 and the outer shell 3, an electrical component 13 that houses electrical components such as connection connectors and terminals for electrically connecting the motor 6 and an external power source is disposed. There is a flange portion 14 on the outer periphery of the lower surface of the outer shell 3. The outer shell 3 is fixed to the ceiling material 15 with screws or the like through a hole 16 provided in the flange portion 14, and a duct 17 arranged on the ceiling and communicating with the outside is discharged. It is joined to the discharge port 9 via the adapter 12.

  Further, an orifice 19 having a bell mouth-shaped opening 18 having a 148 mm inner diameter which is concentric with the suction port 7 of the casing 10 and has an inner diameter equal to or smaller than that of the suction port 7 is spaced 60 mm from the suction port 7 of the casing 10. 2, and a space 20 surrounded by the casing 10, the orifice 19, and the outer shell 3 is formed. The end portion 21 of the orifice 19 is located 20 mm away from the lower surface of the casing 10 to form a gap portion 22, and a vinyl sheet that is a film-like material 23 as a member for closing the gap portion 22 so as to close the gap portion 22. The vinyl sheet, which is a film-like material 23 as a sound-absorbing structure material that is a member that closes the gap portion 22, becomes a mass, and the space 20 becomes a back air layer 24 of the film-like material 23 and becomes a spring. By forming the vibration system, a kind of film-like sound absorbing structure of the resonance type sound absorbing structure is formed.

  A gap 22 is provided between the suction port 7 of the casing 10 and the space 20, and the suction port 7 and the space 20 of the casing 10 communicate with each other. The gap 22 is blocked by the communicating gap 22. Thus, the vinyl sheet which is the film-like material 23 is provided, the suction port 7 and the space 20 are blocked, and the space 20 becomes the air layer 24 behind the film-like material 23.

  In the above configuration, when the impeller 5 is rotated by the electric motor 6, the intake air passes through the opening 18 of the orifice 19 from the opening 2 of the main body, enters the smooth impeller 5 through the bell mouth-shaped suction port 7 of the casing 10, and the blade The pressure is increased by the vehicle 5, passes through the inside of the scroll-shaped casing 10, the dynamic pressure is efficiently converted to static pressure, discharged from the discharge adapter 12 to the duct 17, and discharged outside. The diameter of the opening 18 of the orifice 19 is equal to or smaller than the inner diameter Di of the suction port of the casing 10, but has a sufficiently wide area and has a bell mouth shape for smoothly introducing the suction air. The aerodynamic performance of the centrifugal fan 1 is not reduced due to pressure loss.

  At the same time, rotational sound generated when the pressure is increased by the impeller 5, turbulent noise due to vortices generated when passing through the inside of the casing 10, and sound waves of noise amplified by resonance in the casing 10 are sucked in. Although radiated downward from the mouth 7, a part of the sound wave of the noise radiated from the suction port 7 of the casing 10 was installed in the gap portion 22 formed between the end portion 21 of the orifice 19 and the casing 10. The light enters the vinyl sheet that is the film-like material 23. At this time, the opening 18 of the orifice 19 is concentric with the suction port 7 of the casing 10, and the diameter of the opening 18 of the orifice 19 is equal to or smaller than the inner diameter Di of the suction port of the casing 10. A part of the sound wave of the noise radiated from is easily incident on the film-like material 23 installed in the gap portion 22 formed between the end portion 21 of the orifice 19 and the casing 10. At this time, a resonance type sound absorbing structure is formed by a space 20 surrounded by the orifice 19, the casing 10, and the outer shell 3, and a vinyl sheet that is a film-like material 23 that closes the gap 22 between the end 21 of the orifice 19 and the lower surface of the casing 10. Therefore, among the sound waves of noise incident on the vinyl sheet that is the film material 23, the frequency of the sound wave coincides with the resonance frequency of the vibration system of the film sound absorption structure. The vinyl sheet which is the film-like material 23 vibrates and a sound wave is absorbed by internal friction, and a part of the noise can be silenced, and the frequency at which the sound can be silenced by the action of the film-like sound absorbing structure is the thickness of the film-like material 23 Since it can be changed depending on the surface density and mass, the tension at which the film-like material 23 is installed, the thickness of the back air layer 24, etc., the range of the noise frequency that can be silenced can be expanded.

  In addition, the film-like material 23 can obtain the same effect even if it uses a cellophane, an aluminum film, a polyethylene film, etc. other than a vinyl sheet.

  It should be noted that the space 20 serving as the back air layer 24 only needs to be surrounded by a structure so as to form a resonance type sound absorption structure, and even if there is a gap communicating with the outside to some extent, the degree of effect is inferior, The effect of can be obtained.

  In this configuration, the space 20 formed by the orifice 19 is formed by being surrounded by the orifice 19, the casing 10, and the outer shell 3, but other structures of the product on which the orifice 19 and the centrifugal blower 1 are mounted, for example, It may be a space 20 surrounded by a filter, a heater, an electrical component, a case of the electrical component, or the like. The space 20 becomes a back air layer 24 of the film-like material 23 to form a vibration system that serves as a spring. The same effect can be obtained if a kind of film-like sound absorbing structure of the sound absorbing structure is formed.

  The centrifugal blower 1 can obtain the same effect even if it is mounted sideways on the wall instead of the ceiling.

(Embodiment 2)
As shown in FIG. 2, a hard fiber board having a hole ratio of 10% in which a large number of small holes 25 having a diameter of 5 mm are opened is installed as a perforated plate 26 so as to close the gap 22.

  With this configuration, a vibration system in which the air in the small hole 25 portion of the perforated plate 26 is a mass and the space 20 surrounded by the orifice 19, the casing 10, and the outer shell 3 serves as a spring is formed as a back air layer 24, and the resonance type sound absorption A perforated plate sound absorbing structure that absorbs sound according to the same principle as a Helmholtz resonator is formed, and a part of the sound wave of noise radiated from the suction port 7 of the casing 10 is incident on the perforated plate 26. When the sound wave of the incident noise has a frequency that matches the resonance frequency of the vibration system of the perforated plate sound absorbing structure, the energy of the sound wave is absorbed by the friction loss caused by the vigorous vibration of the air in the small hole 25 part. Therefore, a part of the noise can be silenced. At this time, the frequency that can be silenced by the function of the perforated plate sound absorbing structure can be changed depending on the plate thickness and aperture ratio of the perforated plate 26, the diameter and pitch of the small holes 25, the thickness of the back air layer 24, and the like. The frequency range can be expanded.

  Note that the same effect can be obtained by using a gypsum board or an aluminum plate as the perforated plate 26 in addition to the hard fiber board.

  The same effect can be obtained by using a plate having a large number of slit-like long holes instead of the holed plate 26 having a large number of small circular holes 25.

(Embodiment 3)
As shown in FIG. 3, a flexible urethane foam is used as a porous material 27 so as to close the gap 22.

  With this configuration, when a part of the noise sound wave radiated from the suction port 7 of the casing 10 enters the porous material 27, the sound wave absorption of the noise sound wave having a frequency depending on the sound absorption characteristic of the porous material 27 itself is obtained. In addition, the sound wave of noise transmitted through the porous material 27 and reflected by the orifice 19, the casing 10, and the outer shell 3 is incident on the porous material 27 again, so that the sound wave of noise can be absorbed. A space 20 surrounded by the orifice 19, the casing 10 and the outer shell 3 as a mass and a back air layer 24 forms a vibration system that acts as a spring, and forms a kind of porous sound absorbing structure of a resonance type sound absorbing structure. Among the sound waves, the energy of the sound waves whose frequency matches the resonance frequency of the vibration system of the porous sound absorbing structure is generated by the porous material 27 itself or the air inside the porous material 27. Is absorbed by the friction loss caused by the movement, it is possible to mute a portion of the noise. At this time, the frequency that can be silenced by the function of the porous sound absorbing structure is such that the material, thickness, and sound absorbing characteristics of the porous material 27, the thickness of the back air layer 24, and the porous material 27 having different sound absorbing characteristics are overlapped. Since it can be changed, the range of noise frequencies that can be silenced can be expanded.

  In general, the frequency of noise that can be absorbed by the porous material 27 is relatively high, and the frequency of noise that can be silenced by the porous sound absorbing structure is relatively low, so that the range of the frequency of noise that can be silenced at the same time can be expanded.

  In addition, the porous material 27 can obtain the same effect by using glass wool or rock wool in addition to the flexible urethane foam.

  The same effect can be obtained even if the porous material 27 is covered with a material that transmits sound waves such as cloth in order to prevent the porous material 27 from scattering.

  In addition, the same effect can be obtained by applying a material having sound absorption characteristics other than the porous material 27, for example, a porous molded plate material such as a rock wool plate, or a flexible material such as a sponge.

(Embodiment 4)
As shown in FIG. 4, a vinyl sheet that is a film-like material 23 is provided so as to close the gap 22, the vinyl sheet that is the film-like material 23 becomes a mass, and the space 20 is connected to the air layer 24 behind the film-like material 23. In the centrifugal blower 1 in which a kind of film-like sound absorbing structure of a resonance type sound absorbing structure is formed by forming a vibration system that becomes a spring, the cylindrical tubular wall body 28 concentric with the suction port 7 of the casing 10 has the casing 10. The cylindrical tubular wall body 28 has a thickness of 2 mm and a height of 28 mm, and the wall body has an inner diameter D of 216 mm.

  It is generally known that the frequency that can be silenced by the film-like sound absorbing structure is inversely proportional to the square root of the thickness of the back air layer 24. With this configuration, sound waves of noise propagate around the wall body 28 in the space 20 and propagate. Since the length of the path to be performed can be regarded as the thickness of the back air layer 24, the thickness of the back air layer 24 can be increased, and the frequency of noise that can be silenced can be reduced. Low frequency noise can be silenced without changing the frequency.

  Further, since the cylindrical tubular wall body 28 is a cylindrical tubular tube having one end concentric with the suction port 7 integrated with the casing 10, the path of the sound wave of the noise around the wall body 28 in the space 20 is only one U-bend. Therefore, sound waves of noise can be smoothly propagated, the thickness of the back air layer 24 can be increased more stably, and the wall 28 having a simple structure can be reduced without changing the size of the outer shell 3. Frequency noise can be silenced.

  In this configuration, the gap portion 22 is closed with the film-like material 23. However, even when the gap portion 22 is closed with the perforated plate 26, the frequency of the noise that is silenced by the perforated plate sound absorbing structure is behind. Since it is inversely proportional to the square root of the thickness of the air layer 24, it is possible to reduce the frequency that can be similarly silenced. Further, when the gap portion 22 is closed with the porous material 27, the frequency of the noise that is silenced by the porous sound absorbing structure is inversely proportional to the thickness of the back air layer 24. it can.

  In addition, the cylindrical tubular wall body 28 has only to have a shape that can elongate the path of the sound wave in the space 20 and bend the path in a U shape on the cross section passing through the rotation shaft 4. A tube shape or an elliptical tube shape may be used, and the same effect can be obtained even when the center of the casing 10 is shifted from the center.

(Embodiment 5)
As shown in FIG. 5, a vinyl sheet that is a film-like material 23 is provided so as to close the gap 22, the vinyl sheet that is the film-like material 23 becomes a mass, and the space 20 is connected to the air layer 24 behind the film-like material 23. In the centrifugal blower 1 in which a kind of film-like sound absorbing structure of a resonance type sound absorbing structure is formed by forming a vibration system that becomes a spring, the cylindrical tubular wall body 28 concentric with the suction port 7 of the casing 10 has the casing 10. The cylindrical tubular wall body 28 has a thickness of 2 mm and a height of 28 mm. The inner diameter D of the wall body is partly 216 mm and partly 160 mm, and is uniform in the circumferential direction. It is not a configuration.

  With this configuration, since the inner diameter D of the cylindrical tubular wall portion is partially different, a portion having a different thickness of the back air layer 24 can be formed. Therefore, noises of a plurality of frequencies can be silenced, and the range of noise frequencies that can be silenced is reduced. Can be spread.

(Embodiment 6)
As shown in FIG. 6, a vinyl sheet that is a film-like material 23 is provided so as to close the gap 22, the vinyl sheet that is the film-like material 23 becomes a mass, and the space 20 is connected to the air layer 24 behind the film-like material 23. In the centrifugal blower 1 in which a kind of film-like sound absorbing structure of a resonance type sound absorbing structure is formed by forming a vibration system that becomes a spring, the cylindrical tubular wall body 28 concentric with the suction port 7 of the casing 10 has the casing 10. The cylindrical tubular wall body 28 has a thickness of 2 mm, an inner diameter D of the wall body of 216 mm, a height of 28 mm and a part of 40 mm, and is uniform in the circumferential direction. It has a different configuration.

  With this configuration, since the height of the cylindrical tubular wall 28 is partially different, a portion having a different thickness of the back air layer 24 can be formed. Therefore, it is possible to mute a plurality of frequencies, and a noise frequency range that can be muffled. Can be spread.

(Embodiment 7)
As shown in FIG. 7, a vinyl sheet that is a film-like material 23 is provided so as to close the gap 22, the vinyl sheet that is the film-like material 23 becomes a mass, and the space 20 is connected to the air layer 24 behind the film-like material 23. The centrifugal blower 1 in which a film-like sound absorbing structure of a resonance type sound absorbing structure is formed by forming a vibration system that becomes a spring is provided with a screw receiver 29 on the lower surface of the casing 10 and a cylinder provided with a screw allowance 30. The tubular wall body 28 is fixed with a screw 31 so that it can be attached and detached, and a cylindrical tubular wall body 28 having an inner diameter D of a different wall body can be attached.

  With this configuration, the thickness of the back air layer 24 can be adjusted by changing the inner diameter D of the cylindrical tubular wall body even if the frequency of the noise radiated from the suction port 7 changes due to the installation state of the centrifugal blower 1 or the like. The frequency of noise that can be silenced can be adjusted.

(Embodiment 8)
As shown in FIG. 8, a vinyl sheet that is a film-like material 23 is provided so as to close the gap 22, the vinyl sheet that is the film-like material 23 becomes a mass, and the space 20 is connected to the air layer 24 behind the film-like material 23. The cylindrical tubular wall body 28 concentric with the suction port 7 provided in the space 20 of the centrifugal blower 1 in which a kind of film-like sound absorbing structure of the resonance type sound absorbing structure is formed by forming a vibration system that becomes a spring, The double pipe 34 is constituted by an inner wall 32 and an outer wall 33, and the height of the wall body 28 can be adjusted by sliding the outer wall 33.

  With this configuration, the thickness of the back air layer 24 can be adjusted by adjusting the height of the cylindrical tubular wall 28, so that the frequency of noise that can be silenced can be adjusted.

(Embodiment 9)
As shown in FIG. 9, a vinyl sheet that is a film-like material 23 is provided so as to close the gap 22, the vinyl sheet that is the film-like material 23 becomes a mass, and the space 20 is connected to the air layer 24 behind the film-like material 23. In the space 20 of the centrifugal fan 1 in which a kind of film-like sound absorbing structure of the resonance type sound absorbing structure is formed by forming a vibration system that becomes a spring, one end of the centrifugal fan 1 concentrically contacts with the casing 10 at the inlet 10 of the casing 10. The cylindrical tubular wall body 28 has two wall bodies 28 having an inner diameter D of 180 mm and 240 mm, and a cylindrical tubular body having an inner diameter D of 216 mm concentric with the suction port 7 of the casing 10 and having one end in contact with the orifice 19. The wall body 28 is arranged.

  With this configuration, a labyrinth structure in which sound waves of noise alternately propagate around the wall body 28 in the space 20 can be obtained, the thickness of the back air layer 24 can be increased, and the size of the outer shell 3 can be increased. Low frequency noise can be silenced without changing the frequency.

(Embodiment 10)
As shown in FIG. 10, a vinyl sheet that is a film-like material 23 is provided so as to close the gap 22, the vinyl sheet that is the film-like material 23 becomes a mass, and the space 20 is connected to the air layer 24 behind the film-like material 23. In the centrifugal blower 1 in which a kind of film-type sound absorbing structure of the resonance type sound absorbing structure is formed by forming a vibration system that becomes a spring, the partition wall 35 that divides the space 20 into two parts with different volumes is provided with the rotating shaft 4. It is the structure provided on the plane which passes.

  With this configuration, a plurality of resonance type sound absorbing structures having different shapes and volumes of the space 20 serving as the back air layer 24 can be formed. Therefore, noises with a plurality of frequencies can be silenced, and the range of noise frequencies that can be silenced is expanded. be able to.

(Embodiment 11)
As shown in FIG. 11, one gap portion 22 of the space 20 divided into two by the partition wall 35 is closed with a vinyl sheet that is a film-like material 23, and the gap portion 22 of the other space 20. Is formed by a hard fiber board having a hole ratio of 10% in which a plurality of small holes 25 having a diameter of 5 mm, which are perforated plates 26, are opened.

  With this configuration, since two types of resonance type sound absorbing structures can be formed, noise of a plurality of frequencies can be silenced, and the range of noise frequencies that can be silenced can be expanded.

  Note that one of the gaps 22 in the divided space 20 may not be closed, and may be configured to be resonantly silenced by air column resonance in the space 20.

(Embodiment 12)
As shown in FIG. 12, each of the spaces 20 divided into two by the partition walls 35 is provided with a cylindrical tubular wall 28 concentric with the suction port 7 whose one end is in contact with the casing 10 at different heights. In the space 20, the thickness of the back air layer 24 is increased.

  With this configuration, each of the spaces 20 divided into two by the partition wall 35 is provided with a wall 28 having a different shape, and each of the divided spaces 20 forms a resonance type sound absorbing structure having a different thickness of the back air layer 24. Therefore, it is possible to mute noise having a plurality of frequencies, and it is possible to widen the range of noise frequencies that can be muffled.

  Note that the cylindrical tubular wall body 28 concentric with the suction port 7 whose one end is in contact with the casing 10 is installed in each of the spaces 20 divided into two by the partition wall 35, not only the height but also the inner diameter and thickness, Even if the combinations are different, the same effect can be obtained.

(Embodiment 13)
As shown in FIG. 13, a vinyl sheet that is a film-like material 23 is provided so as to close the gap 22, the vinyl sheet that is the film-like material 23 becomes a mass, and the space 20 is connected to the air layer 24 behind the film-like material 23. In the centrifugal blower 1 in which a film-like sound absorbing structure of a resonance type sound absorbing structure is formed by forming a vibration system that becomes a spring, the outer peripheral space 36 surrounded by the side wall 8 and the outer shell 3 of the casing 10 And a space 20 configured to be surrounded by the casing 10 and the outer shell 3.

  With this configuration, since the outer peripheral space 36 can be used as the back air layer 24 of the resonance type sound absorbing structure, the thickness of the back air layer 24 can be increased, and the size of the outer shell 3 can be reduced without changing. Frequency noise can be silenced.

(Embodiment 14)
As shown in FIG. 14, a vinyl sheet that is a film-like material 23 is provided so as to close the gap 22, and the vinyl sheet that is the film-like material 23 becomes a mass, and the space 20 is connected to the air layer 24 behind the film-like material 23. In the centrifugal blower 1 in which a kind of film-like sound absorbing structure of the resonance type sound absorbing structure is formed by forming a vibration system that becomes a spring, a part of the electric motor 6 protrudes from the casing 10 in the outer shell 3, and the casing 10 is connected to the outer peripheral space 36 surrounded by the side wall 8 and the outer shell 3 of the casing 10, and the outer peripheral space 36 is connected to the orifice 19, the casing 10, and the outer shell 3. It is configured to communicate with the enclosed space 20.

  With this configuration, the back space 38 can be used together with the outer peripheral space 36 as the back air layer 24 of the resonance type sound absorbing structure, so that the thickness of the back air layer 24 can be increased and the size of the outer shell can be changed. It is possible to mute low frequency noise.

  The present invention provides a centrifugal blower that can expand the range of noise frequencies that can be silenced, can mute low-frequency noise without changing the size of the outer shell, and can adjust the noise frequency that can be silenced. .

The figure which shows the centrifugal blower of Embodiment 1 of this invention ((a) sectional side view, (b) lower surface fragmentary sectional view) Side sectional view which shows the centrifugal blower of Embodiment 2 of this invention. Side sectional view which shows the centrifugal blower of Embodiment 3 of this invention. The figure which shows the centrifugal blower of Embodiment 4 of this invention ((a) sectional side view, (b) lower surface partial sectional drawing) Side sectional view which shows the centrifugal blower of Embodiment 5 of this invention. 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 which shows the centrifugal blower of Embodiment 8 of this invention. Sectional side view which shows the centrifugal blower of Embodiment 9 of this invention. The figure which shows the centrifugal blower of Embodiment 10 of this invention ((a) sectional side view, (b) lower surface partial sectional drawing) Sectional side view which shows the centrifugal blower of Embodiment 11 of this invention. Sectional side view which shows the centrifugal blower of Embodiment 12 of this invention. Sectional side view which shows the centrifugal blower of Embodiment 13 of this invention. Sectional side view which shows the centrifugal blower of Embodiment 14 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 Di Suction port inner diameter 7 Suction port 8 Side wall 9 Discharge port 10 Casing 11 Discharge opening 12 Discharge adapter 13 Electrical component 14 Flange portion 15 Ceiling material 16 Hole 17 Duct 18 Opening 19 Orifice 20 Space 21 End 22 Gap 23 Membrane material 24 Back air layer 25 Small hole 26 Perforated plate 27 Porous material 28 Wall body D Wall body inner diameter 29 Screw receiver 30 Screw margin 31 Screw 32 Inner side wall 33 Outer wall 34 Double pipe 35 Bulkhead 36 Outer space 37 Motor side outer wall 38 Back side space

Claims (11)

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 resonance type sound absorbing structure including a bell mouth-shaped orifice having a member for closing a gap between the end of the orifice and the casing as a material for sound absorbing structure, and a space formed by the orifice as a back air layer The wall body is provided in the space, the thickness of the back air layer is increased, and the wall body provided in the space is a cylindrical tube that is concentric with the suction port and has one end in contact with the casing. Centrifugal blower. The centrifugal blower according to claim 1, wherein an inner diameter D of a cylindrical tubular wall concentric with a suction port provided in the space is not uniform in the circumferential direction. The centrifugal blower according to claim 1 or 2, wherein the height of the cylindrical tubular wall concentric with the suction port provided in the space is not uniform in the circumferential direction. The centrifugal blower according to any one of claims 1 to 3, wherein an inner diameter of a cylindrical tubular wall concentric with a suction port provided in the space is adjustable. The centrifugal blower according to any one of claims 1 to 4, wherein the height of a cylindrical tubular wall concentric with a suction port provided in the space is adjustable. 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 resonance type sound absorbing structure including a bell mouth-shaped orifice having a member for closing a gap between the end of the orifice and the casing as a material for sound absorbing structure, and a space formed by the orifice as a back air layer At least one cylindrical tubular wall that is concentric with the suction port of the casing and has one end in contact with the casing, the wall body being provided in the space, the thickness of the back air layer being increased, A centrifugal blower in which at least one cylindrical tubular wall body concentric with the suction port and having one end in contact with the orifice is alternately arranged in the radial direction. The centrifugal blower according to any one of claims 1 to 6, further comprising a partition wall that divides a space formed by the orifice into a plurality. The centrifugal blower according to claim 7, wherein a member that closes the gap is provided in each of the plurality of spaces divided by the partition walls, and at least two types of members are applied. The centrifugal blower according to claim 7 or 8, wherein a wall having a different shape is provided in each of the plurality of spaces divided by the partition walls, and the thickness of the back air layer is increased in each of the spaces. The centrifugal blower according to any one of claims 1 to 9, wherein an outer peripheral space surrounded by a side wall and an outer shell of the casing is used as a back air layer. The centrifugal blower according to claim 10, wherein a back side space between the motor side outer wall and the outer shell of the casing is used as a back air layer.

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