JP5309737B2 - Centrifugal blower - Google Patents

Description

  The present invention relates to a centrifugal blower used mainly for a ventilation blower installed on a ceiling.

  Conventionally, this type of centrifugal blower is used for a ceiling-embedded ventilation fan or the like, and is known in which an opening different from a suction casing having a bell mouth-shaped suction port is provided in an opening on one surface of an outer shell ( For example, see Patent Document 1).

  Hereinafter, the centrifugal blower will be described with reference to FIG. As shown in FIG. 12, an outer shell 101 having an open 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 fan provided with the casing 107 is provided with an orifice 109 having a suction hole 108 which is equal to or smaller than the suction port 106, and a lower end 110 of the suction casing 107 and an end portion 111 of the orifice 109 with a gap 115 having a gap dimension i therebetween. A resonance space 112 having a height h is formed. 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 gap 115. Among the sound waves of the incident noise, the sound waves of the noise specified by the volume and shape of the gap 115 and the resonance space 112 undergo air column resonance in the resonance space 112 and are resonated.
Japanese Patent No. 3279834

  In such a conventional centrifugal blower, the frequency band that can be silenced is specified by the volume and shape of the gap 115 and the resonance space 112, but the noise frequency characteristics also change depending on the load of the fan, which varies depending on external factors, and therefore can be silenced. When the frequency band deviates from the frequency of the generated noise, there is a problem that the noise reduction effect is reduced, and when a sound insulating plate and a sound absorbing material are used frequently in order to increase the noise reduction effect by expanding the frequency band that can be silenced, There are problems such as increased manufacturing costs, obstructing the air flow path, increasing the load on the fan, and obstructing the maintenance, making it easy to install and maintain without burdening the fan There is a need to expand the frequency band that can be silenced with the.

  The present invention solves such a conventional problem, and expands the frequency band that can be silenced with a structure that is easy to install and maintain without giving a load to the fan at low cost, even if the state of the fan load changes. It aims at providing the centrifugal blower which can reduce a noise.

Centrifugal fan of the present invention in order to achieve the above object, a casing which encloses the outer Guo, a power unit, a centrifugal impeller for blowing air rotated by the power unit inside the outer Guo, a centrifugal impeller having an opening And an adapter for guiding the air from the casing to the duct, and the casing is a centrifugal blower having a suction port facing the opening of the outer shell and a side wall, and a plurality of air gaps at predetermined intervals between the suction port of the casing and the opening of the outer shell. A plurality of orifice plates that form spaces having different volumes are provided, each of the plurality of orifice plates is provided with a communication hole that communicates the suction port of the casing with the opening of the outer shell, and the opening side of the outermost shell among the plurality of orifice plates The orifice hole of the orifice plate is provided with a bell mouth-like suction cylinder, and the suction port of the casing and the communication holes of the plurality of orifice plates are concentric circles, The communication holes of the plurality of orifice plates are provided with bellmouth-shaped or cylindrical suction cylinders, and at least one of the plurality of gaps formed by the end portions of the suction cylinders and the orifice plates is different. This is a centrifugal blower.

By this means, noise radiated from the suction port of the casing can be resonantly silenced in a plurality of spaces having different volumes to reduce noise in a plurality of frequency bands, so that a centrifugal blower capable of expanding the frequency band that can be silenced is obtained. It is done. Further, by this means, air can smoothly flow into the outer shell, so that a centrifugal blower that can form a silencing mechanism without applying a load to the fan is obtained. Further, by this means, since the air flowing into the outer casing can be linearly guided to the suction port of the casing, a centrifugal blower that can form a silencing mechanism without applying a load to the fan is obtained. In addition, by this means, the frequency at which resonance can be silenced varies depending on the gap of the suction cylinder, but since at least one gap is different, noise in a plurality of frequency bands can be reduced, and the centrifugal blower that can expand the frequency band that can be silenced Is obtained. In addition, by this means, the frequency at which resonance can be silenced varies depending on the volume of the space formed by the orifice plate, but since at least one volume is different, noise in a plurality of frequency bands can be reduced and the frequency band where noise can be silenced is expanded. A centrifugal blower that can be obtained is obtained.

  Another means is a centrifugal blower characterized in that the height Hc of the casing is smaller than the inner diameter Dd of the duct.

  By this means, a space that can be used for resonance silencing in the outer shell can be increased, so that a centrifugal blower that can expand the frequency band that can be silenced is obtained.

  Another means is that, among the plurality of orifice plates, the inner diameter of the communication hole of the orifice plate on the most casing side is equal to or larger than the inner diameter of the suction port of the casing, and the inner diameters of the communication holes of the adjacent orifice plates are the same or outline. The centrifugal blower is characterized in that the side located on the opening side is larger.

  This means that the air that has flowed into the outer casing can be smoothly guided to the inlet of the casing without sudden expansion or contraction of the flow path, so that a centrifugal blower that can form a silencing mechanism without applying a load to the fan Is obtained.

  By this means, the frequency at which the resonance can be silenced varies depending on the volume of the space formed by the orifice plate. However, since all the volumes are the same, it is possible to concentrate and reduce the noise in the frequency band with a particularly large noise level. A centrifugal blower that can be obtained is obtained.

  Another means is a centrifugal blower characterized in that the casing is a scroll casing having a substantially spiral side wall.

  By this means, the side wall is spiral, so that the air blowing efficiency is good and the load of the fan can be reduced. Also, a substantially triangular corner space can be formed between the outer shell and the casing, so the volume of the space for resonance silence is increased. Therefore, a centrifugal blower that can expand the frequency band that can be silenced is obtained.

  Another means is a centrifugal blower characterized in that a sound absorbing material is provided in at least one of a plurality of spaces formed by a plurality of orifice plates.

  By this means, in addition to resonance silence, sound absorption by the sound absorbing material can be performed, so that a centrifugal blower that can expand the frequency band that can be silenced is obtained.

  Another means is a centrifugal blower characterized in that it includes two orifice plates, a first orifice plate adjacent to the casing and a second orifice plate adjacent to the outer opening. .

  By this means, noise reduction of both low frequency and high frequency can be efficiently performed with two orifice plates, so that a centrifugal blower capable of expanding the frequency band that can be silenced at low cost is obtained.

  According to another aspect of the present invention, there is provided an extended side wall in which a side wall of the casing extends to an opening side of the outer shell, and the first space is formed by the extended side wall and a first orifice plate having the same outer shape as the extended side wall. This is a centrifugal blower.

  By this means, high-frequency noise can be reduced in the first space having a relatively small volume, and low-frequency noise can be reduced in the second space having a relatively large volume. Both low and high frequencies can be efficiently performed. Since the noise can be reduced, a centrifugal blower that can expand the frequency band that can be silenced is obtained.

  Another means is a centrifugal blower characterized in that an interval H1 between the suction port of the casing and the first orifice plate is smaller than an interval H2 between the first orifice plate and the second orifice plate. .

  By this means, the volume of the second space formed by the second orifice plate can be increased, so that low frequency noise can be further reduced in the second space, and the frequency band that can be silenced is expanded. A centrifugal blower can be obtained.

  According to another aspect, at least one of the first space formed by the first orifice plate and the second space formed by the second orifice plate is divided into a plurality in the circumferential direction. And a centrifugal blower.

  By this means, the number of spaces having different volumes can be increased, so that a centrifugal blower capable of expanding the frequency band that can be silenced is obtained.

  Another means is a centrifugal blower characterized in that the second orifice plate is movable.

  By this means, since the volume and gap of the second space can be changed, a centrifugal blower that can adjust the frequency band that can be silenced is obtained.

  Another means is a centrifugal blower characterized in that the suction cylinder of the second orifice plate can be expanded and contracted.

  By this means, since the gap between the end of the suction cylinder of the second orifice plate and the first orifice plate can be changed, a centrifugal blower capable of adjusting the frequency band that can be silenced is obtained.

  Another means is a centrifugal blower characterized in that an opening / closing part is provided in the second orifice plate.

  By this means, work can be performed from the opening side of the outer shell with respect to the connection portion and the electrical component installed in the outer shell, so that a centrifugal blower capable of facilitating construction and maintenance is obtained.

  The other means includes an extended side wall in which the side wall of the casing extends to the opening side of the outer shell, and the first space is formed by the extended side wall and the first orifice plate having the same outer shape as the extended side wall. The centrifugal blower is characterized in that a second space is formed by a second orifice plate having an outer shape.

  By this means, work can be performed from the opening side of the outer shell with respect to the connection portion and the electrical component installed in the outer shell, so that a centrifugal blower capable of facilitating construction and maintenance is obtained.

  Another means is a centrifugal blower characterized in that a drain hole is provided only in the first orifice plate.

  By this means, the condensed water overflowing from the first orifice plate can be prevented from dripping from the outer shell, and the drain water can be stored in the second space having a relatively large volume. In addition, since the drain water can be treated simply by removing the second orifice plate, a centrifugal blower that facilitates maintenance can be obtained.

  Another means is a centrifugal blower characterized in that a grill is provided so as to cover the opening of the outer shell, and the grill and the second orifice plate are integrated.

  By this means, since the grill and the second orifice plate can be made into one component, a centrifugal blower that can expand the frequency band that can be silenced at low cost is obtained.

  According to the present invention, there is provided a centrifugal blower capable of reducing the noise even when the fan load is changed by expanding the frequency band that can be silenced with a structure that is easy to install and maintain without giving a load to the fan at low cost. it can.

The invention of claim 1, wherein the present invention includes an outer Guo having an aperture, a power unit, a centrifugal impeller for blowing rotating air by the power unit inside the outer Guo, a casing and a casing which encloses the centrifugal impeller The casing is a centrifugal blower having a suction opening facing the opening of the outer shell and a side wall, and the casing has a plurality of different volumes at predetermined intervals between the suction opening of the casing and the opening of the outer shell. A plurality of orifice plates that form a space, each of the plurality of orifice plates being provided with a communication hole that communicates the suction port of the casing with the opening of the outer shell, and the suction of the casing Since noise radiated from the mouth can be resonated and muffled in multiple spaces to reduce noise in multiple frequency bands, the frequency band that can be muffled can be expanded. To. In addition, a centrifugal blower is characterized in that a bell mouth-shaped suction cylinder is provided in the communication hole of the orifice plate at the most opening side of the plurality of orifice plates, and air smoothly flows into the outer shell. Therefore, the noise reduction mechanism can be formed without applying a load to the fan. In addition, the centrifugal blower is characterized in that the suction port of the casing and the communication holes of the plurality of orifice plates are concentric circles, and air that has flowed into the outer shell can be linearly guided to the suction port of the casing. Therefore, there is an effect that a silencing mechanism can be formed without applying a load to the fan. Also, the communication holes of all the plurality of orifice plates are provided with bellmouth-shaped or cylindrical suction cylinders, and at least one of the plurality of gaps formed by the end portions of the respective suction cylinders and the orifice plates is different. The frequency at which resonance can be silenced fluctuates depending on the gap of the suction cylinder, but since at least one gap is different, noise in multiple frequency bands can be reduced, and the frequency band that can be silenced can be expanded. Has the effect of being able to. In addition, the centrifugal blower is characterized in that at least one of the volumes of the space formed by the plurality of orifice plates is different, and the frequency at which resonance can be silenced varies depending on the volume of the space formed by the orifice plates. However, since at least one volume is different, noise in a plurality of frequency bands can be reduced, and the frequency band that can be silenced can be expanded.

  Further, the centrifugal blower is characterized in that the height Hc of the casing is smaller than the inner diameter Dd of the duct, and since the space that can be used for resonance silencing can be increased in the outer shell, the frequency band that can be silenced is expanded. It has the effect of being able to.

  In addition, the inner diameter of the communication hole of the orifice plate on the most casing side of the plurality of orifice plates is equal to or greater than the inner diameter of the suction port of the casing, and the inner diameter of the communication holes of the adjacent orifice plates is the same or on the opening side of the outer shell. It is a centrifugal blower characterized in that the position side is larger, and it can smoothly guide the air flowing into the outer casing without sudden expansion or contraction of the flow path to the suction port of the casing, There is an effect that a silencing mechanism can be formed without applying a load to the fan.

  Further, the casing is a centrifugal blower characterized in that the side wall is a spiral casing, and the side wall is spiral, so the blowing efficiency is good and the load on the fan can be reduced. Since a substantially triangular corner space can be formed between the casings, it is possible to increase the volume of the space where resonance is silenced and to expand the frequency band where noise can be silenced.

  Further, the centrifugal blower is characterized in that a sound absorbing material is provided in at least one of a plurality of spaces formed by a plurality of orifice plates, and the sound absorbing material can absorb the sound in addition to the resonance silence. It has the effect that the frequency band that can be expanded.

  Further, the centrifugal blower is characterized in that it includes two orifice plates, a first orifice plate adjacent to the casing and a second orifice plate adjacent to the opening of the outer shell. Since the low-frequency and high-frequency noise can be efficiently reduced by the orifice plate, the frequency band that can be silenced at low cost can be expanded.

  According to another aspect of the present invention, there is provided an extended side wall in which a side wall of the casing extends to an opening side of the outer shell, and the first space is formed by the extended side wall and a first orifice plate having the same outer shape as the extended side wall. The high frequency noise can be reduced in the first space having a relatively small volume, and the low frequency noise can be reduced in the second space having a relatively large volume. Since both can be efficiently reduced in noise, the frequency band that can be silenced can be expanded.

  Further, the centrifugal blower is characterized in that the interval H1 between the suction port of the casing and the first orifice plate is smaller than the interval H2 between the first orifice plate and the second orifice plate. Since the volume of the second space formed by the orifice plate can be increased, low frequency noise can be further reduced in the second space, and the frequency band that can be silenced can be expanded. Have.

  A centrifugal blower characterized in that at least one of the first space formed by the first orifice plate and the second space formed by the second orifice plate is divided into a plurality in the circumferential direction. Since the number of spaces having different volumes can be increased, the frequency band that can be silenced can be expanded.

  Further, the centrifugal blower is characterized in that the second orifice plate is movable, and since the volume and gap of the second space can be changed, the frequency band that can be silenced can be adjusted. It has the action.

  In addition, the centrifugal blower is characterized in that the suction cylinder of the second orifice plate can be expanded and contracted, and the gap between the end of the suction cylinder of the second orifice plate and the first orifice plate is changed. Therefore, the frequency band that can be silenced can be adjusted.

  Moreover, it is a centrifugal blower characterized by having an opening / closing part on the second orifice plate, so that work can be performed from the opening side of the outer part to the connection part and electrical part installed in the outer part. Therefore, it has the effect that construction and maintenance can be facilitated.

  In addition, an extended side wall is provided by extending the side wall of the casing toward the opening side of the outer shell, and a first space is formed by the extended side wall and a first orifice plate having the same outer shape as the extended side wall, and a second space having the same outer shape as the extended side wall. This is a centrifugal blower characterized in that the second space is formed by the orifice plate, and it becomes possible to work from the opening side of the outer shell with respect to the connection part and the electrical part installed in the outer shell. Therefore, it has the effect that construction and maintenance can be facilitated.

  Further, the centrifugal blower is characterized in that a drain hole is provided only in the first orifice plate, and it is possible to prevent the condensed water overflowing from the first orifice plate from dripping from the outer shell. In addition, since the drain water can be stored in the second space having a relatively large volume, it can be naturally evaporated, and the drain water can be treated simply by removing the second orifice plate. It has the effect | action that can be made easy.

  Also, the present invention is a centrifugal blower characterized in that a grill is provided so as to cover the opening of the outer shell, and the grill and the second orifice plate are integrated, and the grill and the second orifice plate are one component. Therefore, the frequency band that can be silenced at low cost can be expanded.

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

(Embodiment 1)
A first embodiment of the present invention will be described with reference to FIGS. As shown in the figure, a centrifugal blower 1 used as a ceiling-embedded ventilation fan attached to a ceiling for ventilating a space such as a bathroom or a toilet has a 260 mm square with an opening 3 on a lower surface 2 and a height of 200 mm. The outer shell 4, the flat top plate 5 fixed horizontally in the outer shell 4, the electric motor 6 fixed to the upper plate 5, and the outer diameter fixed to the electric motor 6 so as to be rotatable is 183 mm. The centrifugal impeller 7 with Hc of 60 mm, the side wall 24 fixed so as to cover the centrifugal impeller 7, the scroll-shaped casing 8, the discharge port 9 of the casing 8, and the discharge port 11 of the side surface 10 of the outer shell 4. An adapter 13 that communicates with the φ12 mm duct 12 is provided.

  The duct inner diameter Dd is 107 mm, the casing height Hc is 75 mm, and the casing 8 is provided with a bell mouth-shaped suction port 15 having a suction port inner diameter D0 of 150 mm around the rotation shaft 14 of the centrifugal impeller 7.

  A first orifice plate 16 is provided between the casing 8 and the opening 3 of the outer shell 4 at a distance H1 (30 mm) from the suction port 15 of the casing 8, and is located at a distance H2 (60 mm) from the first orifice plate 16. The first orifice plate 16 and the second orifice plate 17 are respectively provided with a first communication hole 19 having a bell mouth-shaped first suction cylinder 18 and a second suction plate. A second communication hole 21 having a body 20 is provided, and both the first communication hole 19 and the second communication hole 21 are concentric with the same diameter as the suction port 15 of the casing 8.

  The first gap t1 between the first end 22 of the first suction cylinder 18 of the first orifice plate 16 and the suction port 15 of the casing 8 is 10 mm, and the second suction cylinder 20 of the second orifice plate 17 is. The second gap t2 between the second end portion 23 and the first orifice plate 16 is 25 mm.

  The outer shape of the first orifice plate 16 is the same as that of the casing 8, and a first space 26 is formed by the extended side wall 25 in which the side wall 24 of the casing 8 extends to the opening 3 side of the outer shell 4 and the first orifice plate 16. A part of the first orifice plate 16 is provided with a drain hole 27 for discharging condensed water.

  Further, the outer shape of the second orifice plate 17 extends so as to fill the inside of the outer shell 4, thereby forming a second space 28.

  The substantially triangular space surrounded by the outer shell 4 and the tongue portion 29 of the casing 8 is provided with an electrical component 30 for accommodating components for drawing in and connecting power lines from the outside and electrical components for driving the motor. The second orifice plate 17 has a structure in which an opening / closing part 31 is provided in a part corresponding to the electrical part.

  With the above configuration, when the centrifugal impeller 7 is rotated by applying a driving force from the electric motor 6, the suction air is supplied to the opening 3 on the lower surface 2 of the outer shell 4, the second communication hole 21 of the second orifice plate 17, the first The orifice plate 16, the first communication hole 19, and the suction port 15 of the casing 8 are sequentially led to the centrifugal impeller 7 to be pressurized, and the dynamic pressure gradually becomes static pressure when passing through the scroll-shaped casing 8. It is converted and discharged from the duct 12 to the outside through the discharge port 9 and the discharge port 11 of the outer shell 4 and the adapter 13.

  At this time, rotational noise of the centrifugal impeller 7, turbulent noise generated inside the casing 8, and sound waves of noise amplified by resonance in the casing 8 are radiated from the suction port 15 of the casing 8, A part of the light enters the first space 26 and the second space 28 from the first gap t1 and the second gap t2, respectively, and the first gap t1, the first space 26, and the second gap t2. And the second space 28 respectively form a resonance-type silencing structure, so that a part of the sound wave having a frequency matching the resonance frequency of each resonance-type silencing structure is muted among the sound waves of the incident noise. The noise emitted to the outside of the centrifugal fan 1 is reduced. Since the first gap t1 and the second gap t2, and the volume of the first space 26 and the volume of the second space 28 are different from each other, the resonance frequency of each resonance type silencing structure is different, and noise in different frequency bands. Can be silenced, and the frequency band that can be silenced can be expanded. The first space 26 is surrounded by the extended side wall 25 of the casing 8, and the interval H1 between the casing 8 and the first orifice plate 16 is larger than the interval H2 between the first orifice plate 16 and the second orifice plate 17. Since it is small, the first space 26 can reduce relatively high-frequency noise. Further, the interval H2 between the second spaces 28 is larger than the interval H1 between the first spaces 26, the casing 8 has a scroll shape, and the first orifice plate 16 has the same outer shape as the casing 8 as the casing 8. Therefore, the space around the casing 8 can also be included in the second space 28, and the height Hc of the casing 8 is smaller than the duct inner diameter Dd, so that the volume of the second space 28 is increased. Therefore, it is possible to increase the frequency band, to reduce the low-frequency noise, and to expand the frequency band that can be silenced.

  At this time, since the second suction cylinder 20 of the second communication hole 21 of the second orifice plate 17 closest to the opening 3 of the outer shell 4 has a bell mouth shape, air can flow smoothly. In addition, since the first communication hole 19 and the second communication hole 21 of the suction port 15 of the casing 8, the first orifice plate 16, and the second orifice plate 17 are concentric, respectively, air is sucked into the suction port 15 of the casing 8. The suction port 15 of the casing 8, the first communication hole 19, and the second communication hole 21 have the same diameter, and the flow path is rapidly expanded to the suction port 15 of the casing 8. It can be guided smoothly without sudden reduction, and a silencer mechanism can be formed without applying a load to the fan.

  Moreover, since the opening / closing part 31 is provided in the 2nd orifice board 17, since it becomes possible to work from the opening 3 side of the outer shell 4 with respect to 30 electrical equipment parts, construction and maintenance can be facilitated.

  Further, since the drain hole 27 is provided only in the first orifice plate 16, it is possible to prevent the condensed water overflowing from the first orifice plate 16 from dripping from the outer shell 4, and to have a relatively large volume. Since the drain water can be stored in the large second space 28, it can be naturally evaporated, and the drain water can be treated simply by removing the second orifice plate 17, thus facilitating maintenance. be able to.

  FIGS. 5 and 6 show the centrifugal blower 1 according to the first embodiment, the centrifugal blower 1 when neither the first orifice plate nor the second orifice plate is provided, and the centrifugal blower 1 when only the first orifice is installed. The graph of the frequency characteristic of noise is shown. It can be seen that the sound pressure level of some frequencies is reduced. In the configuration of the first embodiment of the present invention, a noise reduction effect of 2.4 dB is achieved as compared with the case where there is neither the first orifice plate nor the second orifice plate, and compared with the case where only the first orifice is used. The noise reduction effect of 1.1 dB was confirmed.

  In the first embodiment of the present invention, the first communication hole 19 and the second communication hole 21 are both concentric and have the same diameter as the suction port 15 of the casing 8, but the inner diameter of the second communication hole 21 is the first. The first communication hole 19 may be larger than the inner diameter of the first communication hole 19, and the first communication hole 19 is not concentric with the second communication hole 21 but is viewed from the opening 3 side of the outer shell 4. If it is located inside, the same effect can be obtained.

  In the first embodiment of the present invention, the first gap t1 and the second gap t2, and the volume of the first space 26 and the volume of the second space 28 are different from each other. The frequency can be concentrated and silenced.

(Embodiment 2)
The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. The second embodiment of the present invention has a configuration in which a sound absorbing material 32 is provided in the second space 28 as shown in FIG.

  With the above configuration, since sound absorption by the sound absorbing material 32 can be performed in addition to resonance silencing, the frequency band that can be silenced can be expanded.

(Embodiment 3)
The same parts as those in the first or second embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. In the third embodiment of the present invention, as shown in FIG. 8, the first space formed by the first orifice plate 16 is divided into two in the circumferential direction by the dividing wall 36. Yes.

  With the above configuration, the number of spaces having different volumes can be increased, so that a plurality of resonance silencers having different resonance frequencies can be formed, and the frequency band that can be silenced can be expanded.

(Embodiment 4)
The same parts as those in the first to third embodiments are denoted by the same reference numerals, and detailed description thereof is omitted. As shown in FIG. 9, the fourth embodiment of the present invention includes a fixing component 34 that can adjust the fixing position in the vertical direction by the slit hole 33 in the side surface 10 of the outer shell 4, and is fixed to the fixing component 34. The position of the orifice plate 17 can be changed.

  With the above configuration, the resonance frequency can be changed by changing the volume of the second space 28 and the second gap t2, and the frequency band that can be silenced can be adjusted.

(Embodiment 5)
The same parts as those in the first to fourth embodiments are denoted by the same reference numerals, and detailed description thereof is omitted. In the fourth embodiment of the present invention, as shown in FIG. 10, the second suction cylinder 20 of the second orifice plate 17 has a double structure and can be expanded and contracted.

  With the above configuration, since the second gap t2 between the second end 23 of the second suction cylinder 20 of the second orifice plate 17 and the first orifice plate 16 can be changed, the resonance frequency is changed. The frequency band that can be muted can be adjusted.

(Embodiment 6)
The same parts as those in the first to fifth embodiments are denoted by the same reference numerals, and detailed description thereof is omitted. As shown in FIG. 11, the fourth embodiment of the present invention includes an extended side wall 25 in which the side wall 24 of the casing 8 extends to the opening 3 side of the outer shell 4. A first space 26 is formed by one orifice plate 16, and a second space 28 is formed by a second orifice plate 17 having the same outer shape as the extended side wall 25.

  With the above configuration, the electrical component 30 installed in the outer shell 4 can be directly operated from the opening 3 side of the outer shell 4, so that construction and maintenance can be facilitated.

(Embodiment 7)
The same parts as those in the first to sixth embodiments are denoted by the same reference numerals, and detailed description thereof is omitted. As shown in FIG. 12, the fourth embodiment of the present invention includes a grill 35 that is attached so as to cover the opening 3 of the outer shell 4 in order to improve the appearance, and the grill 35 includes the second suction cylinder 20. The second communication hole 21 is provided.

  With the above configuration, since the second space 28 can be formed by the grill 35, it is possible to improve the appearance and reduce noise due to resonance mute at a low cost.

  The present invention provides a centrifugal blower capable of reducing the noise even when the fan load changes, by expanding the frequency band that can be silenced with a structure that is easy to install and maintain without giving a load to the fan at a low cost. In particular, it can be used for air-conditioning equipment and ventilation blower equipment.

The perspective view which shows the centrifugal blower of Embodiment 1 of this invention. The perspective sectional view showing the centrifugal blower of Embodiment 1 of the present invention. Side sectional view which shows the centrifugal blower of Embodiment 1 of this invention. The lower surface fragmentary sectional view which shows the centrifugal blower of Embodiment 1 of this invention. The graph of the frequency characteristic showing the noise reduction effect of the centrifugal blower of Embodiment 1 of this invention The graph of the frequency characteristic showing the noise reduction effect of the centrifugal blower of Embodiment 1 of this invention 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. Side sectional view which shows the centrifugal blower of Embodiment 4 of this invention. 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 showing a conventional centrifugal blower

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Centrifugal blower 2 Lower surface 3 Opening 4 Outer shell 5 Top plate 6 Electric motor Hc Casing height 7 Centrifugal impeller 8 Casing 9 Discharge port 10 Side surface 11 Discharge port 12 Duct 13 Adapter Dd Duct inner diameter 14 Rotating shaft D0 Suction port inner diameter 15 Suction port H1 Interval 16 First orifice plate H2 Interval 17 Second orifice plate 18 First suction cylinder 19 First communication hole 20 Second suction cylinder 21 Second communication hole 22 First end t1 First gap 23 second end t2 second gap 24 side wall 25 extended side wall 26 first space 27 drain hole 28 second space 29 tongue 30 electrical component 31 opening / closing part 32 sound absorbing material 33 slit hole 34 fixing part 35 grill 36 dividing wall

Claims (15)

An outer Guo having an opening, and a power unit, guides the centrifugal impeller for blowing rotating air by the outer Guo inside the power section, the air from the casing and the casing which encloses the centrifugal impeller into the duct adapter The casing is a centrifugal blower provided with a suction port facing the opening of the outer shell and a side wall, and a plurality of volumes differ at a predetermined interval between the suction port of the casing and the opening of the outer shell. A plurality of orifice plates that form a space, each of the plurality of orifice plates having a communication hole that communicates the suction port of the casing with the opening of the outer shell, and the outermost plate of the plurality of orifice plates. The communication hole of the orifice plate on the opening side is provided with a bell mouth-shaped suction drum, and the communication port of the suction port of the casing and the plurality of orifice plates is provided. Each of the plurality of orifice plates is provided with a bell mouth-shaped or cylindrical suction cylinder, and at least a plurality of gaps formed by the end portions of the suction cylinders and the orifice plate. Centrifugal blower characterized in that one is different.
The centrifugal blower according to claim 1, wherein a height Hc of the casing is smaller than an inner diameter Dd of the duct. Among the plurality of orifice plates, the inner diameter of the communication hole of the orifice plate closest to the casing is equal to or larger than the inner diameter of the suction port of the casing, and the inner diameter of the communication hole of the orifice plates adjacent to each other is the same or an outer opening. The centrifugal blower according to claim 1 or 2 , wherein the side located on the side is larger. The centrifugal blower according to any one of claims 1 to 3 , wherein the casing is a scroll casing having a substantially spiral side wall. The centrifugal blower according to any one of claims 1 to 4 , wherein a sound absorbing material is provided in at least one of the plurality of spaces formed by the plurality of orifice plates. The centrifugal blower according to any one of claims 1 to 5 , comprising two orifice plates, a first orifice plate adjacent to the casing and a second orifice plate adjacent to the outer opening. Claim comprises an extension sidewalls extending side walls of the casing to the contour of the opening side, wherein said extension side walls, said extended side walls and first the first space by the orifice plate of the outer shape is formed 6 The centrifugal blower described in The centrifugal blower according to claim 6 or 7 , wherein an interval H1 between the suction port of the casing and the first orifice plate is smaller than an interval H2 between the first orifice plate and the second orifice plate. At least one of the first space and the second space formed by the second orifice plate formed by the first orifice plate according to claim 6, characterized in that it is divided into a plurality of circumferentially- 8. Centrifugal blower in any one of 8 . The centrifugal blower according to any one of claims 6 to 9, wherein the second orifice plate is movable. The centrifugal blower according to any one of claims 6 to 10 , wherein the suction cylinder of the second orifice plate is extendable and contractible. Centrifugal blower according to claim 6-1 1, further comprising a switching unit to the second orifice plate. An extended side wall is formed by extending a side wall of the casing to the opening side of the outer shell, and a first space is formed by the extended side wall and a first orifice plate having the same outer shape as the extended side wall, and a first space having the same outer shape as the extended side wall is formed. The centrifugal blower according to any one of claims 6 to 12, wherein a second space is formed by two orifice plates. Centrifugal blower according to claim 6-1 3, characterized in that it comprises a drain hole only in the first orifice plate. The centrifugal blower according to any one of claims 6 to 14 , further comprising a grill attached so as to cover an opening of the outer shell, wherein the grill and the second orifice plate are integrated.

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