JP5309516B2 - 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 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 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 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

  In such a conventional centrifugal blower, when work inside the outer shell is necessary for construction or maintenance, it is necessary to remove the grill 113 and the orifice 109, and there is a problem that workability is poor at the time of construction and maintenance. There is a demand to improve workability with the addition of.

  In addition, since the orifice 109 is necessary, there is a problem that the number of parts increases and the manufacturing cost increases, and it is required to add a silencing function at a low cost.

  The present invention solves such a conventional problem, and is capable of improving workability while adding a silencing function, can be manufactured at low cost, and can reduce noise radiated from a suction port. The purpose is to provide a blower.

In order to achieve the above object, a centrifugal blower of the present invention has a casing provided with a circular bell mouth-shaped suction port, an impeller disposed inside the casing, an electric motor for rotating the impeller, and the casing. A projecting portion that is disposed so as to surround the suction port and projects to the outside of the casing in the direction of the rotation axis of the impeller, and the projecting portion includes a circular inner wall, a circular outer wall, and an end side wall. The inner wall and the suction port are concentric, the outer diameter of the circular portion located closest to the suction side around the suction port is the same as the outer diameter of the inner wall, and the circular portion and the protrusion The circular portion and the protruding portion are integrally molded so that the inner wall of the portion is connected, the circular portion is detachable from the casing, and the circular portion and the protruding portion form an integrated detachable portion. , The detachable part is front A suction port is integrally formed, and a cavity is provided inside the protrusion, and a slit-like hole communicating with the cavity is provided on the suction port side of the protrusion, and the slit-like hole is formed between the inner wall and the inner wall. The centrifugal blower is characterized by being in the joint portion of the end side wall.

By this means, the detachable part can be made as one part that can be manufactured with a die cut in one direction, the protrusion can be easily manufactured, the number of parts can be reduced, and it can be manufactured at low cost. Since the noise radiated from the suction port of the casing can be resonantly silenced by the hole and the cavity, a centrifugal blower capable of improving workability and reducing noise while adding the silencing function is obtained. Since the intake air can be smoothly guided to the casing, a centrifugal blower capable of reducing noise can be obtained. Since the protrusion can be easily manufactured, a centrifugal blower that can be manufactured at low cost and can reduce noise radiated from the suction port is obtained. Since the noise radiated from the suction port of the casing can be smoothly guided to the hole in the inner wall and the suction air can be smoothly guided to the casing, a centrifugal blower capable of reducing noise can be obtained. Since the impeller can be removed without removing the casing, a centrifugal blower that can improve maintenance workability is obtained. The other means is a hole has a centrifugal blower, characterized in that at the junction between the circular portion of the inner wall the detachable portion. By this means, the attaching / detaching portion and the projecting portion of the casing can be constituted by a single part that can be manufactured by a die having one direction, so that a centrifugal blower that can be manufactured at a low cost is obtained.

  Another means is a centrifugal blower characterized in that the inner diameter of the inner wall of the protrusion gradually decreases toward the suction port.

  By this means, noise radiated from the suction port of the casing can be smoothly guided to the hole in the inner wall, and since the suction air can be smoothly guided to the casing, a centrifugal blower that can reduce noise is provided. can get.

  Another means is a centrifugal blower characterized in that the hole is a slit hole that is long in a direction perpendicular to the protruding direction of the protruding portion.

  By this means, noise radiated from the suction port of the casing is likely to enter the cavity, so that a centrifugal blower capable of reducing noise is obtained.

According to another aspect of the invention, at least a part of the outer shape of the outer wall is the same dimension as the outer shape of the casing and the outer shape of the outer wall, or at least a part of the outer shape of the outer wall is the casing. It is a centrifugal blower characterized by being smaller than the outer shape of

  By this means, a centrifugal blower capable of improving workability is obtained by arranging the parts installed on the outer periphery of the casing in a portion where the outer shape of the protruding portion is equal to or less than the outer shape of the casing.

  Another means is a centrifugal blower characterized in that the outer shape of the detachable portion is larger than the outer shape of the impeller.

  By this means, since the impeller can be removed without removing the casing, a centrifugal blower capable of improving maintenance workability is obtained.

  Another means is a centrifugal blower characterized in that one of the inner wall and the outer wall does not contact the casing.

  By this means, when vibration is generated during operation of the centrifugal blower, a centrifugal blower that can suppress the occurrence of noise due to the inner wall or the outer wall colliding with the casing due to insufficient mounting strength of the detachable portion or the like is obtained. .

  Another means is a centrifugal blower characterized in that a protrusion is provided with a handle.

  By this means, a centrifugal blower that can be easily held when removing the detachable portion and can improve workability can be obtained.

  Another means is a centrifugal blower characterized in that a sound absorbing material is provided inside the cavity.

  By this means, in addition to the resonance noise reduction by the hole and the cavity, noise reduction by the sound absorbing material is also performed, so that a centrifugal blower capable of reducing noise can be obtained.

According to the present invention, a casing having a circular bell mouth-shaped suction port, an impeller disposed inside the casing, an electric motor that rotates the impeller, and the suction port of the casing are surrounded. A projecting portion that is disposed and projects to the outside of the casing in the direction of the rotation axis of the impeller, the projecting portion comprising a tubular inner wall, a tubular outer wall, and an end wall; The suction port is concentric, the outer diameter of the circular portion located closest to the suction side around the suction port and the outer diameter of the inner wall are the same, and the circular portion and the inner wall of the protruding portion are connected to each other The circular portion and the protruding portion are integrally molded, and the circular portion is detachable from the casing. The circular portion and the protruding portion form an integrated detachable portion, and the detachable portion is the suction port. Is integrally molded, A cavity is provided inside the projecting portion, a slit-shaped hole communicating with the cavity is provided on the suction port side of the projecting portion, and the slit-shaped hole is at a joint portion between the inner side wall and the end side wall. Thus, it is possible to provide a centrifugal blower that can be manufactured as a single part that can be manufactured with a mold that can be removed in one direction, that is easy to manufacture the protrusion, can reduce the number of parts, and can be manufactured at low cost. Since the impeller can be removed without removing the casing, it is possible to provide a centrifugal blower that can improve the workability of maintenance. A centrifugal blower that can reduce noise radiated from the suction port can be provided.

The invention according to claim 1 of the present invention includes a casing having a circular bell mouth-shaped suction port, an impeller disposed inside the casing, an electric motor for rotating the impeller, and the suction of the casing. A projecting portion that is disposed so as to surround the mouth and projects to the outside of the casing in the direction of the rotation axis of the impeller, and the projecting portion includes a tubular inner wall, a tubular outer wall, and an end wall; The inner wall and the suction port are concentric, the outer diameter of the circular portion located closest to the suction side around the suction port and the outer diameter of the inner wall are the same, and the circular portion and the protrusion The circular portion and the protruding portion are integrally molded so that the inner wall is connected, the circular portion is detachable from the casing, and the circular portion and the protruding portion form an integrated detachable portion, and the detachable The part includes the suction port The projection is provided with a cavity inside the protrusion, and a slit-like hole communicating with the cavity is provided on the suction port side of the protrusion. The slit-like hole is a joint between the inner wall and the end wall. It is a centrifugal blower characterized by being in the part, and the detachable part can be made as one part that can be manufactured with a mold with one direction removed, the protrusion can be easily manufactured, and the number of parts can be reduced The centrifugal blower that can be manufactured at a low cost can be provided. Since an impeller can be removed without removing a casing, it has the effect | action that the centrifugal blower which can improve the workability | operativity of a maintenance can be provided. Since the noise radiated from the suction port of the casing can be resonantly silenced by the hole and the cavity, the workability can be improved and the noise can be reduced while the silencing function is added. Since noise emitted from the suction port of the casing can be smoothly guided to the hole in the inner wall and the suction air can be smoothly guided to the casing, the noise can be reduced. In addition, the centrifugal blower is characterized in that the hole is in the joint portion between the inner wall and the circular portion of the attaching / detaching portion, and the attaching / detaching portion and the projecting portion of the casing can be manufactured by a mold with one direction removed. Since it can be comprised with one component, it has the effect | action that it can manufacture at low cost.

  In addition, the centrifugal blower is characterized in that the inner diameter of the inner wall of the protrusion gradually decreases toward the suction port, and smoothly guides noise radiated from the suction port of the casing to the hole in the inner wall. In addition, since the intake air can be smoothly guided to the casing, the noise can be reduced.

  In addition, it is a centrifugal blower characterized in that the hole is a slit hole that is long in the direction perpendicular to the protruding direction of the protruding portion, and noise radiated from the suction port of the casing is likely to enter the cavity, It has the effect | action that a noise can be reduced.

Also, make sure that at least part of the outer wall contour is at least as large as the casing contour and at least part of the outer wall contour, or at least part of the outer wall contour is smaller than the casing contour. The centrifugal blower is characterized by the fact that the parts installed on the outer periphery of the casing are placed in the part where the outer shape of the projecting part is equal to or less than the outer shape of the casing, thereby improving workability while adding a silencing function. It has the effect of being able to.

  In addition, the centrifugal blower is characterized in that the outer shape of the detachable part is larger than the outer shape of the impeller, and since the impeller can be removed without removing the casing, maintenance is performed with the sound deadening function added. The workability can be improved.

  Further, the centrifugal blower is characterized in that one of the inner wall and the outer wall is not in contact with the casing, and when vibration occurs during operation of the centrifugal fan, the inner wall or It has the effect | action that it can suppress that an outer wall collides with a casing and a noise generate | occur | produces.

  In addition, the centrifugal blower is characterized in that the outer wall has a circular tube shape, and has an effect that it is easy to hold when removing the detachable part and workability can be improved.

  In addition, the centrifugal blower is characterized in that the protrusion is provided with a handle, and has an effect that it can be easily held when the detachable part is removed and workability can be improved.

  In addition, it is a centrifugal blower characterized by having a sound absorbing material inside the cavity, and in addition to the resonance silence by the hole and the cavity, the sound absorbing material is also silenced, so that the noise can be reduced. Has an effect.

  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 an upper surface 2, a lower surface 3, and a part of a side surface 4 opened to 230 mm. An outer shell 5 having a corner and a height of 175 mm, a flat top plate 6 fixed to the upper surface 2 of the outer shell 5, an electric motor 7 fixed to the upper plate 6, and a blade fixed to the electric motor 7 so as to be rotatable. A centrifugal impeller 8 having a vehicle outer diameter D of 148 mm, a scroll-like casing 9 fixed so as to cover the centrifugal impeller 8, and an adapter communicating with the discharge port 10 of the casing 9 and the opening of the side surface 4 of the outer shell 5 11 is provided.

  The casing 9 includes a bell mouth-shaped suction port 13 having a suction port inner diameter Do of 113 mm around the rotation shaft 12 of the centrifugal impeller 8, and the rotation shaft of the centrifugal impeller 8 is disposed around the suction port 13 of the casing 9. A projecting portion 14 projecting outward of the casing 9 in the direction of 12, the projecting portion 14 having a tubular inner wall 15 having an inner wall inner diameter D1 of 149 mm and a tubular outer wall 16 having an outer wall outer diameter D2 of 178 mm; Each end wall 17 is formed with a thickness of 1.8 mm, and a cavity 18 is formed therein. The cavity 18 communicates with the cavity 18 at the joint between the inner wall 15 and the end side wall 17 of the projecting portion 14. And a slit-like hole 19 having a width of 5 mm. The slit-shaped hole 19 is divided into four parts and arranged on the entire circumference of the circular inner wall 15. The outer diameter of the outer wall 16 of the projecting portion 14 is 178 mm, so that it does not protrude from the outer shape of the casing 9.

  The casing 9 is concentric with the suction port 13, and a circular portion 20 having a diameter of 150.8 mm and having the same diameter as the inner wall 15 is detachable from the casing 9, and the inner wall 15 of the circular portion 20 and the projecting portion 14. The circular portion 20 and the protruding portion 14 are integrally molded so as to be connected to each other to form a one-part detachable portion 21.

  With the above configuration, when the centrifugal impeller 8 is rotated by applying a driving force from the electric motor 7, the intake air is guided to the centrifugal impeller 8 through the opening of the lower surface 3 of the outer shell 5 and the suction port 13 of the casing 9. The pressure is increased, and when passing through the casing 9, the dynamic pressure is gradually converted into a static pressure, and is discharged from the discharge port 10 to the outside through the adapter 11. At this time, since the projecting direction of the projecting portion 14 is the same direction as the rotary shaft 12 of the centrifugal impeller 8 and the inner wall 15 of the projecting portion 14 is a circular tube concentric with the suction port 13, the sucked air is smoothly casing. 9 can be led.

  At the same time, rotational noise of the centrifugal impeller 8, turbulent noise generated inside the casing 9, and sound waves of noise amplified by resonance in the casing 9 are radiated from the suction port 13 of the casing 9. A part of the light enters a cavity 18 inside the protrusion 14 from a slit-like hole 19 in the inner wall 15 of the protrusion 14 disposed around the suction port 13, and the cavity 18 inside the protrusion 14. And the slit-like hole 19 in the inner wall 15 form a resonance-type silencer structure, so that the frequency of the sound wave of noise incident on the cavity 18 inside the protrusion 14 is a cavity inside the protrusion 14. A part of the sound wave having a frequency that matches the resonance frequency of the resonance type silencing structure formed by the slit 18 and the slit-shaped hole 19 of the inner wall 15 is silenced, and noise emitted to the outside of the centrifugal blower 1 is reduced.

  Since the suction port 13 of the casing 9 and the tubular inner wall 15 of the projecting portion 14 are both centered on the rotating shaft 12 and the hole 19 is a slit hole that is long in the direction perpendicular to the projecting direction of the projecting portion 14, Sound waves of noise radiated from the suction port 13 of the casing 9 can be smoothly guided to the hole 19 in the inner wall 15 of the protrusion 14.

  Further, since the circular portion 20 and the projecting portion 14 of the casing 9 form an integral attachment / detachment portion 21 and the outer diameter of the circular portion is larger than the outer diameter of the centrifugal impeller 8, it is possible to remove the casing 9. The centrifugal impeller 8 can be removed, and workability during maintenance such as cleaning of the centrifugal impeller 8 can be improved.

  Further, since the outer wall 16 has a circular tube shape, and the outer shape of the outer wall 16 does not protrude from the casing 9, the protruding portion 14 serves as a handle when the detachable portion 21 is removed. It becomes easy to remove, can improve workability during maintenance, and when there is a component 22 such as an electrical component installed on the outer periphery of the casing 9, the protruding portion 14 does not interfere with the operation on the component 22, Workability can be improved.

  Further, the projecting portion 14 is composed of an inner wall 15, an outer wall 16 and an end side wall 17, and the circular portion 20 and the projecting portion 14 of the casing 9 form an integral detachable portion 21, and the outer diameter and the circular portion of the inner wall 15 are formed. Since the outer diameter of 20 is the same diameter and the slit-shaped hole 19 is at the joint between the inner side wall 15 and the end side wall 17, the detachable part 21 can be made as one part that can be manufactured with a one-way die. The projecting part can be easily manufactured, the number of parts can be reduced, and it can be manufactured at low cost.

  FIG. 5 shows a graph of the frequency characteristics of the noise of the centrifugal blower 1 when the protrusion 14 is present and when the protrusion 14 is not present. It can be seen that the sound pressure level of some frequencies is reduced. In the configuration of Embodiment 1 of the present invention, a reduction effect of 1.2 dB was confirmed. Therefore, workability can be improved with the mute function added.

  In the first embodiment of the present invention, the projecting portion 14 is on the entire circumference around the suction port 13 of the casing 9. However, even if there is a limitation due to the outer shape of the casing 9 and the like, the resonance silencer structure is not possible. If the cavity 18 and the hole 19 are formed to such an extent that can be formed, the same effect can be obtained although the degree is inferior.

(Embodiment 2)
The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. In the second embodiment of the present invention, as shown in FIG. 6, the inner wall inner diameter D1 of the inner wall 15 of the projecting portion 14 is 160 mm on the end wall 17 side and 136 mm on the suction port 13 side of the casing 9, The configuration gradually decreases toward the mouth 13.

  With the above configuration, a part of the sound wave of noise radiated from the suction port 13 of the casing 9 can be smoothly guided to the hole 19 of the inner wall 15 and the suction air can be smoothly guided to the suction port 13 of the casing 9. Therefore, noise can be reduced.

(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. 7, the casing body component 23 in which the casing 9 and the inner wall 15 of the protruding portion 14 are integrally molded, and the outer wall 16 and the end side wall 17 of the protruding portion 14 are integrated. The casing 9 and the protruding portion 14 are constituted by the molded protruding component 24.

  With the above configuration, each of the casing main body part 23 and the protruding part 24 can be manufactured with a die without one direction, so that it can be manufactured at low cost.

(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. In the fourth embodiment of the present invention, as shown in FIG. 8, a slit-like hole 19 is provided at the joint between the inner wall 15 and the circular portion 20, and the protruding portion 14 and the circular portion 20 form an attachment / detachment portion 21. It has become.

  With the above configuration, the detachable portion 21 can be made as one component that can be manufactured with a die cut in one direction, the protrusion 14 can be easily manufactured, the number of components can be reduced, and the manufacturing can be performed at low cost.

(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 Embodiment 4 of the present invention, as shown in FIG. 9, the detachable portion 21 is constituted by the protruding portion 14 and the circular portion 20, and a 2 mm gap 25 is provided between the outer wall 16 and the casing 9. It has a configuration.

  With the above configuration, when vibration is generated during operation of the centrifugal blower 1, it is possible to prevent the outer wall 16 from colliding with the casing 9 due to insufficient attachment strength of the detachable portion 21 to generate noise.

(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. In the fourth embodiment of the present invention, as shown in FIG. 10, the projecting portion 14 and the circular portion 20 constitute an attaching / detaching portion 21, and the projecting portion 14 includes a handle 26.

  By the said structure, it becomes easy to have when removing the attachment / detachment part 21, and workability | operativity can be improved.

(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. In the fourth embodiment of the present invention, as shown in FIG. 11, a sound absorbing material 27 is provided in the cavity 18.

  With the above configuration, in addition to the resonance muffling by the hole 19 and the cavity 18, the sound absorbing material 27 is also muffled, so that noise can be reduced.

  The present invention provides a centrifugal blower that has good workability, can be manufactured at low cost, and can reduce noise radiated from a suction port, and is particularly applicable to air conditioning equipment and ventilation blower equipment.

The perspective view which shows the centrifugal blower of Embodiment 1 of this 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 figure which shows the attachment or detachment part of the centrifugal blower of Embodiment 1 of this invention ((a) The front side perspective view, (b) The back side perspective view) 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. The figure which shows the attachment or detachment part of the centrifugal blower of Embodiment 4 of this invention ((a) same front side perspective view, (b) same back side perspective view) 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 Upper surface 3 Lower surface 4 Side surface 5 Outer surface 6 Top plate 7 Electric motor D Impeller outer diameter 8 Centrifugal impeller 9 Casing 10 Discharge port 11 Adapter Do Suction port inner diameter 12 Rotating shaft 13 Suction port 14 Projection part D1 Inner side wall inner diameter 15 Inner side Wall D2 Outer side wall outer diameter 16 Outer side wall 17 End side wall 18 Cavity 19 Hole 20 Circular part 21 Detachable part 22 Part 23 Casing body part 24 Projection part 25 Gap 26 Handle 27 Sound absorbing material

Claims (9)

A casing having a circular bell mouth-shaped suction port, an impeller disposed inside the casing, an electric motor that rotates the impeller, and a blade that is disposed so as to surround the suction port of the casing. Protruding portions projecting outward of the casing in the direction of the rotation axis, the projecting portions are formed by a circular inner wall, a circular outer wall, and an end wall, and the inner wall and the suction port are concentric. The outer diameter of the circular portion located closest to the suction side around the suction port and the outer diameter of the inner wall are the same, and the circular portion and the inner wall of the projecting portion are connected to each other. A protruding portion is integrally molded, the circular portion is detachable from the casing, the circular portion and the protruding portion form an integral detachable portion, and the detachable portion is integrally molded including the suction port, Inside the protrusion A centrifugal blower comprising a cavity, a slit-like hole communicating with the cavity on the suction port side of the protrusion, and the slit-like hole being at a joint portion between the inner side wall and the end side wall . A casing having a circular bell mouth-shaped suction port, an impeller disposed inside the casing, an electric motor that rotates the impeller, and a blade that is disposed so as to surround the suction port of the casing. Protruding portions projecting outward of the casing in the direction of the rotation axis, the projecting portions are formed by a circular inner wall, a circular outer wall, and an end wall, and the inner wall and the suction port are concentric. The outer diameter of the circular portion located closest to the suction side around the suction port and the outer diameter of the inner wall are the same, and the circular portion and the inner wall of the projecting portion are connected to each other. A protruding portion is integrally molded, the circular portion is detachable from the casing, the circular portion and the protruding portion form an integral detachable portion, and the detachable portion is integrally molded including the suction port, Inside the protrusion Comprising a cavity provided with a slit-like hole for the cavity and communicating with the inlet side of the projecting portion, the hole, characterized in that at the junction between the circular portion of the detachable part and the inner wall centrifugal Blower. The centrifugal blower according to claim 1 or 2, wherein the inner diameter of the inner wall of the projecting portion gradually decreases toward the suction port. The centrifugal blower according to claim 1, wherein the hole is a slit hole that is long in a direction perpendicular to the protruding direction of the protruding portion. The outer shape of the outer wall is at least partly the same size as the outer shape of the casing, or at least part of the outer shape of the outer wall is smaller than the outer shape of the casing. Centrifugal blower. The centrifugal blower according to any one of claims 1 to 5, wherein the outer shape of the detachable portion is larger than the outer shape of the impeller. The centrifugal blower according to any one of claims 1 to 6, wherein one of the inner wall and the outer wall does not contact the casing. The centrifugal blower according to any one of claims 1 to 7, wherein a handle is provided on the protruding portion. The centrifugal blower according to any one of claims 1 to 8, wherein a sound absorbing material is provided inside the cavity.

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