JP5292759B2 - Centrifugal blower - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a centrifugal blower which has a small number of parts used for adding a sound absorbing function, which can be manufactured at low costs, and which can reduce noise radiated from a suction opening. <P>SOLUTION: The centrifugal blower is provided with an outer frame 6 having an opening, a centrifugal impeller 8, a casing 9, and an inner frame 27. The casing 9 incorporates the centrifugal impeller 8, and the inner frame 27 incorporates the casing 9. The casing 9 is constituted by a casing side wall 12 and a casing ceiling panel 13. The casing side wall 12 surrounds the circumference side of the centrifugal impeller 8, and the casing ceiling panel 13 is arranged on the upstream side of air. The centrifugal blower is also provided with a communicating pipe 21 which communicates a suction port 19 of an orifice 20 and the suction port 15 of the lid 14 of the casing ceiling panel 13. A plurality of slit holes 22 which are circumferentially long are provided to the communicating pipe 21, and the lid 14 can be attached to and detached from the casing ceiling panel 13. Then an integral-type part 23 is formed by integrally molding the orifice 20, the lid 14, and the communicating pipe 21. Thus, the centrifugal blower can be constituted so as to have excellent workability at the time of maintenance, and to reduce noise radiated from the suction opening. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

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 112 having a gap dimension i therebetween. A resonance space 113 is formed. Further, a grill 114 and a discharge port 115 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 114 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 115. 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 113 from the gap 112. Among the incident sound waves, the sound waves having a frequency specified by the volume and shape of the resonance space 113 undergo air column resonance in the resonance space 113 and are resonated.
Japanese Patent No. 3279834

  In such a conventional centrifugal blower, when the impeller 103 is cleaned, it is necessary to remove the grill 114, the orifice 109, and the suction 107, and there is a problem that the number of parts to be removed when cleaning the impeller 103 is large and workability is poor. There is a need to reduce the number of parts for adding a silencing function and improve workability.

  In addition, when work inside the outer shell is necessary for construction or maintenance, it is necessary to remove the grille 114 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.

  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, has a small number of parts for adding a silencing function, has good workability, can be manufactured at low cost, and reduces noise radiated from a suction port. It aims to provide a centrifugal blower that can.

  In order to achieve the above object, the centrifugal blower of the present invention has an outer frame having an opening, a power unit, a centrifugal impeller that rotates by the power unit inside the outer frame and blows air, and a casing that contains the centrifugal impeller. A flat plate in the opening, the flat plate is provided with an orifice having a bell mouth-shaped suction hole, the flat plate and the orifice are integrated, and the casing spirally surrounds the circumferential side of the centrifugal impeller. It is composed of a casing top plate located on the upstream side. The casing top plate has a lid larger than the outer shape of the centrifugal impeller, the lid is detachable from the casing top plate, and the lid is a suction port for sucking air by the centrifugal impeller A centrifugal blower characterized by comprising a communication pipe connecting the suction hole of the orifice and the suction port, the communication pipe having a hole, and integrally forming the orifice, the lid and the communication pipe. That.

  By this means, noise radiated from the suction port enters the cavity surrounded by the outer frame, the casing, and the orifice from the hole of the communication pipe. At this time, since the holes and cavities have a silencer structure equivalent to that of the resonance silencer, a part of the sound wave of the noise that has entered is equal to the resonance frequency of the resonance silencer, and the suction hole A centrifugal blower that reduces noise emitted from the fan can be obtained. In addition, the orifice, the lid, and the communication pipe can be formed with one component, and the number of components can be reduced, so that a centrifugal blower that can reduce the manufacturing cost can be obtained. Moreover, since it becomes a state which can remove an impeller only by removing the integral part which integrally molded the orifice, the lid | cover, and the communicating pipe, the centrifugal air blower which becomes easy to work can be obtained.

  Another means is that the suction port is circular, the suction hole of the orifice is concentric with the suction port, the suction hole has a diameter larger than that of the suction port, the communication pipe is cylindrical, and the connection between the lid and the communication pipe A plurality of slit holes that are long in the circumferential direction of the cylinder are formed at locations, and the centrifugal blower is characterized in that an orifice, a lid, and a communication pipe are integrally formed.

  By this means, the cavity and the slit hole have a silencing mechanism, and since air can be smoothly guided to the casing, a centrifugal blower capable of reducing noise can be obtained.

  Another means is a centrifugal blower characterized in that the lid has a circular shape and the outer diameter of the suction hole is equal to the outer diameter of the lid.

  By this means, since the shape change from the suction port to the suction hole of the integrally molded component is only enlarged, a centrifugal blower that can be easily manufactured is obtained.

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

  By this means, since air can be smoothly guided to the casing, a centrifugal blower capable of reducing noise can be obtained.

  Another means is a centrifugal blower characterized in that the suction port includes a suction cylinder extending in the air blowing direction, and the inner diameter of the communication pipe is equal to the inner diameter of the suction port.

  By this means, since the noise radiated from the suction port surely enters from the slit hole, the silencer works strongly, and a centrifugal blower capable of reducing noise is obtained.

  Another means is a centrifugal blower having three or more slit holes.

  By this means, there are three or more connection points between the communication pipe and the suction port, and the center of gravity of the communication pipe and the suction port is securely fixed to each other, so that the communication pipe and the suction port can be stably connected, and the rigidity A strong centrifugal blower is obtained.

  Another means is a centrifugal blower characterized in that the total value of the circumferential lengths of the slit holes is 2.2 to 2.7 times the inner diameter of the suction port.

  By this means, if the total length of the slit holes in the circumferential direction is 2.2 times or more of the suction port inner diameter, noise will surely enter the slit holes and the silencing mechanism will work strongly. If the total length in the circumferential direction is not more than 2.7 times the inner diameter of the suction port, the communication pipe and the suction port can be stably connected, so that the centrifugal blower has high rigidity and can reduce noise. Is obtained.

  Another means is a centrifugal blower characterized in that the length of the slit hole in the direction of the communicating tube axis is 0.04 to 0.2 times the inner diameter of the suction port.

  By this means, it is possible to mute sound waves having a frequency corresponding to the length of the slit hole in the communication pipe axis direction, and if the length of the slit hole in the communication pipe axis direction is 0.04 times or more than the suction port inner diameter. If noise reliably enters through the slit hole and the silencing mechanism works strongly, and the length of the slit hole in the communication tube axial direction is 0.2 times or less of the suction port inner diameter, the flow of air sucked by the centrifugal impeller is large. Since it does not become resistance, a centrifugal blower that can reduce noise is obtained.

  Another means is a centrifugal blower characterized in that the shape of the lid is a concentric circle with the suction port, and the suction port is located at the center of the outer frame.

  By this means, the degree of freedom in the mounting direction of the integral part increases, so that the assembly of the integral part is facilitated, and a centrifugal blower with good workability can be obtained.

  Another means is a centrifugal blower characterized in that the communication pipe is proportionally enlarged from the suction port side toward the orifice side.

  By this means, since air can be smoothly guided to the casing, a centrifugal blower capable of reducing noise can be obtained.

  Another means is a centrifugal blower characterized in that a sound absorbing material is attached in a space formed outside the casing.

  By this means, in addition to the silencing effect by the silencing mechanism, the sound absorbing material is also silenced, so that a centrifugal blower capable of reducing noise is obtained.

  ADVANTAGE OF THE INVENTION According to this invention, the centrifugal blower which can reduce the noise radiated | emitted from a suction hole can be reduced, the number of parts for adding a silencing function is few, workability | operativity is good, it is compact, suppresses manufacturing cost.

  According to the first aspect of the present invention, in order to achieve the above object, the centrifugal blower of the present invention is a centrifugal that rotates with an outer frame having an opening, a power unit, and a power unit inside the outer frame to blow air. An impeller, a casing containing the centrifugal impeller, a flat plate in the opening, a flat plate provided with an orifice having a bell mouth-shaped suction hole, and the flat plate and the orifice are integrated, and the casing is the circumferential side of the centrifugal impeller The casing side wall and the casing top plate located on the upstream side of the air, the casing top plate has a lid larger than the outer shape of the centrifugal impeller, the lid is detachable from the casing top plate, The lid has a suction port for sucking air by a centrifugal impeller, a communication pipe that connects the suction hole of the orifice and the suction port, the communication pipe has a hole, and the orifice, the lid, and the communication pipe are integrally molded. The orifice, lid and communication pipe are integrally molded, the cavity surrounded by the outer frame, casing and integral parts, and the hole of the communication pipe have a silencing mechanism. Since the impeller can be removed simply by removing the integral part integrally formed with the communication pipe, the manufacturing cost can be reduced, noise can be reduced, and workability can be improved.

  In addition, the suction port is circular, the suction hole of the orifice is concentric with the suction port, the suction hole has a diameter larger than that of the suction port, the communication pipe is a cylinder, and the connection place between the lid and the communication pipe is circumferential. This is a centrifugal blower characterized in that a plurality of long slit holes are formed, and an orifice, a lid, and a communication pipe are integrally molded. The cavity and slit holes have a silencing mechanism, and air is smoothly casing. Therefore, the noise can be reduced.

  Further, the shape of the lid is circular, and the centrifugal blower is characterized in that the outer diameter of the suction hole is equal to the outer diameter of the lid, and the shape change from the suction port to the suction hole of the integrally molded component Since it is only enlarged, it has the effect | action that it can manufacture easily.

  In addition, the centrifugal blower is characterized in that the suction port has a bell mouth shape, and since air can be smoothly guided to the casing, there is an effect that noise can be reduced.

  In addition, the suction port includes a suction cylinder extending in the air blowing direction, and is a centrifugal blower characterized in that the inner diameter of the communication pipe and the inner diameter of the suction port are equal, and noise radiated from the suction port However, since it surely enters from the slit hole, the silencing mechanism works strongly, and the noise can be reduced.

  In addition, the centrifugal blower is characterized in that there are three or more slit holes. Since there are three connection points between the cylinder and the suction port, the center of gravity of the communication pipe and the suction port is securely fixed to each other. The communication pipe and the suction port can be stably connected, and the rigidity is strong.

  Moreover, it is set as the centrifugal blower characterized by the total value of the circumferential direction length of a slit hole being 2.2 to 2.7 times the suction port inner diameter, and the length of the circumferential direction of a slit hole If the total value is 2.2 times the suction port inner diameter or more, noise will surely enter from the slit hole and the silencing mechanism will work strongly, and the total length of the slit hole in the circumferential direction will be the suction port inner diameter. If it is 2.7 times or less, the communication pipe and the lid can be stably connected, so that the rigidity is strong and the noise can be reduced.

  In addition, the length of the slit hole in the direction of the communication pipe axis is 0.04 to 0.2 times the inner diameter of the suction port. The sound wave of the corresponding frequency can be silenced, and if the length of the slit hole in the direction of the connecting pipe axis is 0.04 times or more than the inner diameter of the suction port, noise will surely enter from the slit hole and the silencer mechanism will work strongly If the length of the slit hole in the communication tube axial direction is 0.2 times or less the inner diameter of the suction port, the flow of air sucked by the centrifugal impeller does not become a great resistance, so that noise can be reduced. Have

  Moreover, the shape of the lid is a concentric circle with the suction port, and the suction port is located in the center of the outer frame. This increases the degree of freedom in the mounting direction of the integrated part. As a result, it is easy to assemble the integrated part, and the workability is good.

  Further, the communication pipe is a centrifugal blower characterized in that it is proportionally enlarged from the suction port side toward the orifice side, and since air can be smoothly guided to the casing, noise can be reduced. It has the action.

  In addition, it is a centrifugal blower characterized by mounting a sound absorbing material in the space formed on the outside of the casing. In addition to the silencing effect by the silencing mechanism, the sound absorbing material is also silenced, reducing noise It has the effect of being able to.

  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, the centrifugal blower 1 includes an outer frame 6 composed of a 230 mm square upper plate 3 located on the upper surface 2 and a side plate 5 having a height of 175 mm located on the side surface 4. A power unit 7 fixed to the plate 3, a centrifugal impeller 8 having an outer diameter D of 148 mm fixed rotatably to the power unit 7, and a casing 9 fixed to cover the centrifugal impeller 8, An adapter 11 communicating with the discharge port 10 of the casing 9 and the opening of the side plate 5 of the outer frame 6 is provided.

  The casing 9 is composed of a casing side wall 12 that covers the circumferential side of the centrifugal impeller 8 in a spiral shape, and a casing top plate 13 that is located on the opposite side of the power unit across the centrifugal impeller. Is provided with a lid 14 that is concentric with the centrifugal impeller and has an outer diameter Dc of 160 mm. The lid 14 is provided with a bell mouth-shaped suction opening 15 that is concentric with the centrifugal impeller 8 and has a suction inlet inner diameter Do of 113 mm. A flat plate 18 is provided at the position of the opening 17 on the lower surface 16, and the flat plate 18 is integrated with an orifice 20 having a bell mouth shape suction hole 19 concentric with the suction port 15 and having a suction hole inner diameter D1 of 131 mm. A cylindrical communication pipe 21 that communicates with the suction hole 19 is provided. The communication pipe 21 includes three slit holes 22 that are long in the circumferential direction at the connection portion between the cylindrical end and the lid 14, and the orifice 20 and the communication pipe 21. The lid 14 is integral part 23 are integrally molded, the outer frame 6 and the casing 9 and the unitary component 23 form a cavity 24. Here, the shape of the slit hole 22 is the same at all three locations, the total length L of the circumferential length of the slit hole 22 is 264 mm, and the relationship between the suction port inner diameter Do and 2.2Do <L <2.7Do is established. Fulfill. The axial height h of the slit hole 22 is 5 mm, which satisfies the relationship of the suction port inner diameter Do and 0.04Do <h <0.2Do.

  With the above configuration, when the centrifugal impeller 8 is rotated by applying a driving force from the power unit 7, air is guided into the casing 9 through the suction hole 19 of the orifice 20, the communication pipe 21, and the suction port 15 of the lid 14. The pressure is increased by the centrifugal impeller 8, and the dynamic pressure is gradually converted into a static pressure when passing through the casing 9, and is discharged to the outside from the discharge port 10 through the adapter 11.

  At this time, the 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 15 of the casing 9, A part thereof enters the cavity 24 from the slit hole 22 at the connection portion between the communication pipe 21 and the lid 14, and the cavity 24 and the slit hole 22 have a silencing mechanism having the same structure as that of the resonance silencer. A part of the sound wave having a frequency equal to the resonance frequency of the resonance silencer among the sound waves entering the inside is silenced, and noise radiated from the suction hole 19 is reduced.

  In addition, since the orifice 20, the communication tube 21, and the lid 14 are an integral part 23 formed integrally, the number of parts for forming the silencing mechanism is small, the manufacturing cost can be suppressed, and the lid outer diameter Dc is centrifugal. Since it is larger than the outer diameter D of the impeller 8, it becomes possible to remove the centrifugal impeller 8 by removing the integral part 23, so that workability during maintenance such as cleaning of the centrifugal impeller 8 is improved.

  Moreover, since the suction hole inner diameter D1 of the orifice 20 is larger than the suction hole inner diameter Do, and the suction port 15 and the suction hole 19 are bell-mouth shaped, a large amount of air can be sucked smoothly, and the blowing performance is improved.

  Moreover, since the air sent out to the outer peripheral side of the centrifugal impeller 8 by rotation of the centrifugal impeller 8 can be efficiently guided to the discharge port 10 by the spiral casing side wall 12, the air blowing performance is improved.

  Further, since there are three slit holes 22 and there are also three connection pieces 25 connecting the communication pipe 21 and the lid 14, the centers of gravity of the lid 14, the communication pipe 21 and the orifice 20 are securely fixed to each other. Therefore, the communication pipe 21 and the suction port 15 can be stably connected, and the rigidity of the integrated component 23 is increased.

  In addition, the slit hole 22 is long in the circumferential direction of the communication pipe 21, and the total value L of the lengths of the three locations is 264 mm, and satisfies the relationship of the suction port inner diameter Do and 2.2Do <L <2.7Do, If the total value L of the circumferential lengths of the slit holes is 2.2 times or more of the suction port inner diameter Do, noise will surely enter from the slit holes 22 and the silencing mechanism will work strongly. If the total length L in the circumferential direction is not more than 2.7 times the suction port inner diameter Do, the communication pipe 21 and the lid 14 can be stably connected. Increases rigidity.

  Further, the length h of the slit hole 22 in the axial direction of the communicating tube 21 is 5 mm and satisfies 0.04 Do <h <0.2 Do, and the resonance frequency of the silencing mechanism is determined according to the length of the communicating tube in the axial direction. A part of the sound wave of the resonance frequency can be silenced, and noise is reduced.

(Embodiment 2)
The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. A second embodiment of the present invention will be described with reference to FIG. In the drawing, the lid outer diameter Dc is equal to the suction hole outer diameter D1o of the orifice 20.

  At this time, in the integrated part 23, since the shape change from the suction port 15 to the suction hole 19 is only the expansion in the radial direction, the integrated part 23 can be manufactured with a die without a single direction. 23 can be easily manufactured, the number of parts can be reduced, and the manufacturing cost can be reduced.

(Embodiment 3)
The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. A third embodiment of the present invention will be described with reference to FIG. In the figure, the suction port 15 includes a suction cylinder 26 extending in the air blowing direction, and the suction hole inner diameter D1 is equal to the suction port inner diameter Do.

  At this time, in the integrated component 23, the slit hole 22 is located on the circumference having the same diameter as the suction port 15, so that a part of the noise radiated from the suction port 15 spreads in the circumferential direction of the suction port 15. Therefore, a lot of noise enters the cavity 24 from the slit hole 22 and the sound deadening mechanism works strongly.

( Reference form 1 )
The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. A fourth embodiment of the present invention will be described with reference to FIGS.

  As shown in the drawing, an inner frame 27 that encloses a casing 9 is provided inside the outer frame 6, and the inner frame 27 covers an inner frame side surface 28 that covers the casing side wall 12 side of the casing 9 and an upstream side of the air flow in the casing 9. The inner frame flat plate 29 can be separated from the inner frame side surface 28. The inner frame flat plate 29 is concentric with the suction port 15 and has a bell mouth shape having a suction hole inner diameter D1 of 131 mm. It is integral with the orifice 20 having the suction hole 19, and includes a cylindrical communication pipe 21 that communicates the suction hole 15 and the suction hole 19, and the communication pipe 21 is provided in a circumferential direction at a connection portion between the cylindrical end portion and the lid 14. The orifice 20, the communication pipe 21, and the lid 14 are an integral part 23 that is integrally molded, and the inner frame 27, the casing 9, and the integral part 23 form a cavity 24, and Inner frame 27 inside frame 6 Forms a space 30 surrounded by the inner frame 27 and outer frame 6 to the side, it comprises a component 31, such as electrical equipment section in the interior space 30.

  At this time, since the cavity 24 and the slit hole 22 have a silencing mechanism having a structure equivalent to that of a resonance silencer, noise radiated from the suction hole is reduced.

  In addition, by providing the component 31 in the space 30 surrounded by the outer frame 6 and the inner frame 27, the component 31 can be touched without removing other components during maintenance of the electrical equipment section and the workability is good.

Further, another example 1 of reference of the first embodiment of the present invention, as shown in FIG. 8 (a), the inner frame sides 28 of the inner frame 27 is provided on the opening 17 side extension of the casing side wall 12 of the casing 9 The extended wall surface 32 may be used. With such a configuration, the space 30 surrounded by the outer frame 6 and the inner frame 27 can be expanded, the installation space for the component 31 is increased, and the extended wall surface 32 is compared with the inner frame side surface 28. Since there are few materials, manufacturing cost can be held down.

Further, another example 2 reference to Embodiment 1 of the present invention, as shown in FIG. 8 (b), the inner frame 27 inside the cavity 24, to contain the internal space of the outer frame 6 which part 31 is not installed May be. With such a configuration, it is possible to widen the cavity 24 of the silencing mechanism while securing the installation space for the component 31, and the silencing effect by the silencing mechanism is increased, so that the noise radiated from the suction hole 19 is reduced. To do.

  Further, the flat plate 18 may be disposed inside the outer frame 6. With this configuration, the resonance frequency of the silencing mechanism is determined corresponding to the position of the flat plate 18 inside the outer frame 6, and a part of the sound wave having the resonance frequency can be silenced, thereby reducing noise. .

  The present invention provides a centrifugal blower that has a small number of parts for adding a silencing function, has good workability, is compact, can reduce manufacturing costs, and can reduce noise radiated from a suction hole. Especially, 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. Side sectional view which shows the centrifugal blower of Embodiment 1 of this invention. The perspective view which shows the integrated component of Embodiment 1 of this invention The figure which shows the integrated component of Embodiment 2 of this invention ((a) same perspective view, (b) same side sectional drawing) The figure which shows the integrated component of Embodiment 3 of this invention ((a) same perspective view, (b) same side sectional drawing) The perspective sectional view showing the centrifugal blower of Reference form 1 of the present invention The bottom view which shows the centrifugal blower of the reference form 1 of this invention The perspective view which shows the other examples of the centrifugal blower of the reference form 1 of this invention ((a) The perspective view of the other example 1, (b) The perspective view of the other example 2) Side sectional view showing a conventional centrifugal blower

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Centrifugal blower 2 Upper surface 3 Upper plate 4 Side surface 5 Side plate 6 Outer frame 7 Power part 8 Centrifugal impeller 9 Casing 10 Discharge port 11 Adapter 12 Casing side wall 13 Casing top plate 14 Lid 15 Suction port 16 Lower surface 17 Open 18 Flat plate 19 Suction hole 20 Orifice 21 Communicating pipe 22 Slit hole 23 Integrated part 24 Cavity 25 Connection piece 26 Suction cylinder 27 Inner frame 28 Inner frame side surface 29 Inner frame flat plate 30 Space 31 Parts 32 Extension wall surface Dc Lid outside diameter Do Suction hole inner diameter D1 Suction hole inner diameter D1o suction hole outer diameter

Claims (11)

An outer frame having an opening; a power unit; a centrifugal impeller that is rotated by the power unit to blow air inside the outer frame; a casing that encloses the centrifugal impeller; and a flat plate in the opening; Includes an orifice having a bell mouth-shaped suction hole, the flat plate and the orifice are integrated, and the casing is located on the upstream side of the air, and a casing side wall that spirally surrounds the circumferential side of the centrifugal impeller The casing top plate has a lid larger than the outer shape of the centrifugal impeller, the lid is detachable from the casing top plate, and the lid sucks air by the centrifugal impeller. Provided with a suction port, provided with a suction pipe of the orifice and a communication pipe communicating the suction port, the communication pipe provided with a hole, and integrally forming the orifice, the lid and the communication pipe Centrifugal blower, characterized in that the. The suction port is circular, the suction hole of the orifice is concentric with the suction port, the suction hole has a diameter larger than that of the suction port, the communication pipe is a cylinder, and the connection point between the lid and the communication pipe is The centrifugal blower according to claim 1, wherein a plurality of slit holes that are long in a circumferential direction of the cylinder are formed, and the orifice, the lid, and the communication pipe are integrally formed. The centrifugal blower according to claim 1 or 2, wherein the lid has a circular shape, and the outer diameter of the suction hole is equal to the outer diameter of the lid. The centrifugal blower according to any one of claims 1 to 3, wherein the suction port has a bell mouth shape. The centrifugal blower according to claim 2, wherein the suction port includes a suction cylinder extending in the air blowing direction, and the inner diameter of the communication pipe is equal to the inner diameter of the suction port. The centrifugal blower according to any one of claims 2 to 5, wherein there are three or more slit holes. The centrifugal blower according to any one of claims 2 to 6, wherein a total value of circumferential lengths of the slit holes is 2.2 to 2.7 times an inner diameter of the suction port. The centrifugal blower according to any one of claims 2 to 7, wherein the length of the slit hole in the communication tube axial direction is 0.04 to 0.2 times the inner diameter of the suction port. The centrifugal blower according to claim 1, wherein the shape of the lid is a concentric circle with the suction port, and the suction port is located at the center of the outer frame. The centrifugal blower according to any one of claims 1 to 9, wherein the communication pipe is proportionally enlarged from the suction port side toward the orifice side. The centrifugal blower according to any one of claims 1 to 10 , wherein a sound absorbing material is attached in a space formed outside the casing.

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