JP2009264121A - Centrifugal blower, and method for reducing noise of centrifugal fan - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a centrifugal blower of reduced noise used for a ventilation blower, or the like, improving a noise reduction effect in a high-frequency area, and reducing noise over a wide frequency range, from low frequency to high frequency. <P>SOLUTION: This centrifugal blower 1 is provided with within an outer shell 3; an electric motor 6 to which an impeller 5 is connected; a casing 10 surrounding the periphery of the impeller 5 and having a bell-mouthed suction opening 17 formed in one surface of the openinfg 7; and a bell-mouthed orifice 18 which is concentric with the suction opening 7 and is provided with a suction opening, having a diameter equivalent to that of the suction opening 7. A plurality of projections 22 are provided, in a resonance space 19 surrounded by the orifice 18, the casing 10 and the outer shell 3, and cavities 23 sandwiched between the projections 22 are formed. The centrifugal blower thus has a noise reduction effect against noise over a wide frequency range. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a centrifugal blower used for a ventilation blower or the like, and a noise reduction method for a centrifugal blower that reduces noise generated by the operation of the centrifugal blower.

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

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

  As shown in FIG. 10, the centrifugal blower 100 includes an outer shell 101 that is open on one surface, an impeller 103 that is rotatably supported by the top surface 102 in the outer shell 101, and an impeller 103 that is fixed to the top surface 102. An electric motor 104 that rotates the motor, a scroll casing 105 that surrounds the impeller 103, and a suction casing 107 that has a suction port 106. Furthermore, the centrifugal blower 100 includes an orifice 109 having a suction hole 108 that is equal to or smaller than the suction port 106 with a predetermined gap h from the suction casing 107. The orifice 109 is provided with the lower end 110 of the suction casing 107 and the end 111 of the orifice 109 separated by a gap dimension i. Thereby, the resonance space 112 communicated with the suction port 106 through the inlet portion 115 between the lower end 110 of the suction casing 107 and the end portion 111 of the orifice 109 is defined by the outer shell 101, the scroll casing 105, and the orifice 109. Yes. The centrifugal blower 100 includes a grill 113 disposed on one surface of the orifice 109 and a discharge port 114 provided on one side surface of the outer shell 101.

  In such a configuration of the conventional centrifugal blower 100, 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 the impeller 103. And is discharged from the discharge port 113 through the inside of the scroll casing 105. At this time, rotation noise generated when the pressure is increased by the impeller 103, turbulent noise due to vortex generated when passing through the scroll casing 105, and sound waves of noise generated in the scroll casing 105 are radiated from the suction port 106. A part of the light enters the resonance space 112 from the inlet 115 having the gap size i. Among the incident noise sound waves, noise sound waves of a frequency specified by the volume and shape of the resonance space 112 undergo air column resonance in the resonance space 112, and the sound wave level is reduced and resonance is silenced.

Japanese Patent No. 3279834

  In such a conventional centrifugal blower, a relatively low frequency noise of approximately 1 kHz or less can be reduced by the resonance silence effect, but a relatively low frequency noise reduction effect of approximately 1 kHz or more such as noise caused by turbulent flow is low. . Therefore, there is a problem that the amount of noise reduction is small when high-frequency noise is dominant, such as when the amount of air blown by the centrifugal blower is large. Therefore, the centrifugal blower is required to enhance the noise reduction effect in the high frequency range and reduce noise in a wide frequency range from low frequency to high frequency.

  The present invention solves such a conventional problem, and in a centrifugal blower, the noise reduction effect in the high frequency range can be enhanced, noise can be reduced in a wide frequency range from low frequency to high frequency, and noise can be reduced. It aims at providing the centrifugal blower which reduces.

  In order to achieve the above object, the present invention is configured as follows.

  According to the first aspect of the present invention, the outer shell having the opening, the impeller supported rotatably in the outer shell, the electric motor that rotationally drives the impeller, the first suction port, and the blade It is arranged at the opening of the outer shell so as to have a gap between the casing disposed in the outer shell so as to surround the periphery of the vehicle and the first suction port of the casing, and the opening of the outer shell and the first of the casing A bell mouth-shaped orifice having a second suction port communicating with the suction port, and communicated with the first suction port through a gap between the first suction port and the second suction port. Provided is a centrifugal blower in which a resonance space that resonates and muffles noise emitted from one suction port is defined with an orifice, a casing, and an outer shell as delimiting walls, and a plurality of protrusions are provided on the delimiting wall of the resonance space. .

  According to the second aspect of the present invention, each of the plurality of protrusions has an inclined surface that is inclined with respect to the defining wall surface of the resonance space at each of the formation positions. The centrifugal blower according to the first aspect is provided, in which a slope of another projection adjacent to the projection is connected to each other, and a recess is formed between the projections by each slope.

  According to the 3rd aspect of this invention, the angle of the connection part of each inclined surface in a recessed part is an acute angle, The centrifugal blower as described in a 2nd aspect is provided.

  According to the 4th aspect of this invention, a projection part provides the centrifugal air blower as described in a 2nd aspect or a 3rd aspect which has a flat surface in the top part.

  According to the fifth aspect of the present invention, there is provided the centrifugal blower according to any one of the second aspect to the fourth aspect, wherein the protrusion has a shape whose depth is long with respect to its height and width. .

  According to the sixth aspect of the present invention, the plurality of protrusion groups in which the plurality of protrusions are arranged with the depth direction parallel to each other are arranged such that the depth directions of adjacent protrusion groups intersect each other. The centrifugal blower according to the fifth aspect is provided.

  According to a seventh aspect of the present invention, in the fifth aspect, a plurality of protrusion groups in which a plurality of protrusions are arranged in parallel in the depth direction are arranged so that each depth direction is different. Provide centrifugal blower.

  According to the eighth aspect of the present invention, the plurality of recesses formed between the plurality of protrusions are formed so as to extend along the defining wall surface, and are at least in the radial direction, the circumferential direction, and the axial direction of the impeller. The centrifugal blower according to the fifth aspect is provided in which the extending directions of the respective recesses are arranged differently with respect to one direction.

  According to the ninth aspect of the present invention, any of the first to eighth aspects has the same shape of the plurality of protrusions and the same shape of the plurality of recesses formed between the plurality of protrusions. A centrifugal blower according to claim 1 is provided.

  According to the tenth aspect of the present invention, in any one of the first to eighth aspects, there are a plurality of types of protrusions and a plurality of types of recesses formed between the plurality of protrusions. A centrifugal blower as described is provided.

  According to an eleventh aspect of the present invention, there is provided the centrifugal blower according to any one of the first aspect to the tenth aspect, wherein a plurality of protrusions are provided on the orifice in the resonance space.

  According to a twelfth aspect of the present invention, the plurality of protrusions are integrally formed with an orifice, a casing, or a demarcating wall of the outer shell, according to any one of the first aspect to the eleventh aspect. Provide a blower.

  According to the thirteenth aspect of the present invention, there is provided the centrifugal blower according to any one of the first aspect to the eleventh aspect, wherein the protrusion is detachably installed on the defining wall.

  According to a fourteenth aspect of the present invention, there is provided the centrifugal blower according to the thirteenth aspect, wherein the protrusion is formed of a sound absorbing material.

  According to the fifteenth aspect of the present invention, any one of the first to fourteenth aspects is provided, wherein the protrusion is formed with a cavity inside, and a hole communicating the cavity and the resonance space is formed in the protrusion. A centrifugal blower according to claim 1 is provided.

  According to the sixteenth aspect of the present invention, the outer shell having the opening, the impeller rotatably supported in the outer shell, the first suction port, and surrounding the periphery of the impeller Is disposed in the opening of the outer shell so as to have a gap between the casing disposed in the casing and the first suction port of the casing, and the second opening for communicating the opening of the outer shell and the first suction port of the casing. In a centrifugal blower including a bell mouth-shaped orifice having a suction port, the first suction port is communicated with the first suction port through a gap between the first suction port and the second suction port to define the orifice, the casing, and the outer shell. A sound wave of noise generated in the casing as the impeller is driven to rotate is incident through a gap between the first suction port and the second suction port into the resonance space defined as a wall, Incident at Together reduce the acoustic level of the air column resonance, characterized in that to reduce the level of acoustic noise by diffused reflection of the acoustic waves of noise at the resonant space, provides a noise reduction method of the centrifugal blower.

  According to the centrifugal blower of the present invention, the resonance space communicated with the first suction port of the casing is provided, and a configuration in which a plurality of protrusions are provided in the resonance space is adopted. The sound wave level can be reduced by the air column resonance, and the sound wave level can be reduced by causing irregular reflection by the plurality of protrusions. Therefore, the two effects of air column resonance and diffuse reflection can enhance the noise reduction effect in the high frequency range of noise generated with the operation of the centrifugal blower, and reduce the noise in a wide frequency range from low frequency to high frequency. it can.

  Further, according to the noise reduction method for a centrifugal blower of the present invention, noise generated by the operation of the centrifugal blower is incident on the resonance space communicated with the first suction port of the casing of the centrifugal blower to enter the resonance space. The sound wave level of the incident noise can be reduced by air column resonance, and the sound wave level can be reduced by irregularly reflecting the sound wave of the noise in the resonance space. Therefore, the two effects of air column resonance and irregular reflection can enhance the noise reduction effect in the high frequency range of noise associated with the operation of the centrifugal blower, and reduce the noise in a wide frequency range from low frequency to high frequency.

  Embodiments according to the present invention will be described below in detail with reference to the drawings.

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

  An orifice 18 that is concentric with the suction port 7 of the casing 10 and has a bell mouth-shaped suction port 17 (second suction port) is disposed so as to close the opening 2 of the outer shell 3. That is, the opening 2 of the outer shell 3 communicates with the suction port 7 of the casing 10 through the suction port 17 of the orifice 18. Further, as shown in FIGS. 1A and 1B, the end 20 of the orifice 18 is located at a gap dimension j from the lower surface of the suction port 7 of the casing 10. A gap (gap) 21 is formed between them.

  Further, on the outer periphery of the orifice 18, a resonance space 19 defined by being surrounded by the orifice 18, the casing 10, and the outer shell 3 is defined. The resonance space 19 communicates with the suction port 7 of the casing 10 through a gap 21 between the orifice 18 and the casing 10.

  In the resonance space 19, a plurality of protrusions (projections) 22 are formed on the defining wall, and a recess (recess) 23 is formed between adjacent protrusions 22. Here, a schematic perspective view of the orifice 18 is shown in FIG. 2A, and a cross-sectional view taken along line AA in the orifice 18 of FIG. 2A is shown in FIG. As shown in FIGS. 2A and 2B, a plurality of protrusions 22 and depressions 23 are formed continuously on the inside of the resonance space 19 of the orifice 18. Further, in the first embodiment, each protrusion 22 and orifice 18 are one component integrally molded. In addition, the protrusion 22 has a shape that is longer in the depth direction (one direction in the plane) than the width in plan view. In addition, the protrusions 22 having such a long shape in the depth direction are arranged on the orifice 18 as a plurality of protrusion groups (protrusion part groups) 30 arranged in a set of three with the depth direction being parallel. As shown in FIG. 2A, the adjacent protrusion groups 30 are arranged so that the depth directions thereof are substantially orthogonal to each other.

  Here, an enlarged view of the protrusion 22 is shown in FIG. As shown in FIG. 3, the protrusion 22 has a shape in which the protrusion depth L (the length in the Y direction in the drawing) is longer than the protrusion height ho (the height in the Z direction in the drawing). Further, the protrusion 22 has a trapezoidal cross-sectional shape (XZ cross-sectional shape) perpendicular to the depth direction (Y direction). The top of the projection 22 is a flat surface 31, and the top flat surface 31 having a width a is spread on both sides by a width c as it goes downward, on both side surfaces (both side surfaces in the X direction) of the projection 22. An inclined surface 32 inclined with respect to the Z direction is formed. In addition, a recess 23 having a substantially V-shaped cross section is formed by two inclined surfaces 32 between two protrusions 22 arranged in parallel in the depth direction. The opening width of the upper portion of the recess 23 is b, and gradually decreases toward the lower side in the Z direction, and the two inclined surfaces 32 intersect at the recess angle α. The depression angle α is an acute angle.

  Next, in the centrifugal blower 1 having such a configuration, an effect of reducing noise generated by the rotational drive of the impeller 5 by the resonance space 19 and the plurality of protrusions 22 provided in the resonance space 19 will be described. In the centrifugal blower 1, when the impeller 5 is rotated by the electric motor 6, the intake air passes from the main body opening 2 through the suction port 17 of the orifice 18, enters the impeller 5 through the suction port 7 of the casing 10, and is boosted by the impeller 5. , Passes through the inside of the casing 10 and is discharged from the discharge adapter 12 to the duct 16 and discharged to the outdoors.

  At this time, rotational noise generated when the pressure is increased by the impeller 5, turbulent noise due to vortex generated when passing through the inside of the casing 10, and sound waves of noise amplified by resonance in the casing 10 are sucked in. A part of the sound wave of noise emitted from the inlet 7 of the casing 10 is radiated downward from the mouth 7, and the resonance space 19 is formed from the gap 21 formed between the end 20 of the orifice 18 and the casing 10. Incident to A part of the incident sound wave becomes an anti-phase sound wave by reflection at the fixed end on the wall surface (defining wall surface) inside the resonance space 19 and returns to the gap portion 21, and due to air column resonance that cancels a part of the sound wave emitted from the suction port 7. Since resonance silencing occurs, the sound wave level of noise can be reduced. The frequency of the canceled sound wave is determined by the sound wave path distance from the gap 21 to the position where the reflection occurs. Further, since there are a large number of protrusions 22 in the resonance space 19, the sound waves incident in the resonance space 19 are likely to be reflected by the large number of protrusions 22, and the distance between the gap portion 21 and the protrusions 22 varies. It is possible to reduce noise at a high frequency.

  Further, depending on the incident angle, a part of the sound wave colliding with the protrusion 22 is reflected and then directed to the adjacent protrusion 22, and energy is gradually reduced in the recess 23 due to irregular reflection that continues to be reflected thereafter. Can be reduced.

  Further, adjacent protrusions 22 are continuously arranged so that each recess 23 has a substantially V-shaped cross section, and the width of the recess 23 is set to be narrower, so that the sound wave incident on the recess 23 is more It is reflected many times and can cause irregular reflection, so that the sound reduction effect is strong and noise can be reduced. For example, the relationship of ho ≧ b is preferable with respect to the protrusion height ho and the recess opening width b.

  Further, the protrusion 22 has a trapezoidal cross-sectional shape perpendicular to the depth direction of the protrusion 22, and the shape of the recess 23 formed by the protrusion 22 is gradually narrowed toward the lower side. The time interval at which reflection occurs is shortened as the sound waves are irregularly reflected and the sound waves travel downward in the depression 23. Thereby, since the frequency | count of reflection increases and the sound reduction effect acts strongly, noise can be reduced. For example, the trapezoidal shape of the cross section of the protrusion 22 preferably has a relationship of ho ≧ c with respect to the protrusion height ho and the width c of the inclined surface 32.

  The same effect can be expected even if the cross-sectional shape of the protrusion 22 is a triangle. However, the volume of the recess 23 is adjusted by adjusting the width a of the top flat surface 31 of the protrusion 22 while keeping the angle of the inclined surface 32 at an optimum angle by making the cross-sectional shape of the protrusion 22 trapezoidal. can do. In order to realize resonance silencing by air column resonance, it is necessary to set the resonance space 19 to an optimal volume, and to optimize the volume, it is necessary to adjust the volume of the recess 23. Therefore, by making the cross-sectional shape of the protrusion 22 trapezoidal, adjustment for optimizing the volume of the resonance space 19 can be easily performed. Note that the same effect can be expected when the inclined surface of the protrusion 22 forming the recess 23 is not only formed as a flat surface but also when the inclined surface is a curved surface.

  In addition, by setting the dent angle α of the dent 23 to be an acute angle, irregular reflection is likely to occur even for a sound wave having a shallow incident angle with respect to the dent 23, so that a sound reduction effect can be easily obtained and noise can be effectively obtained. Can be reduced.

  Further, since the protrusion 22 has a shape that is longer than the height and width of the protrusion 22, the recess 23 formed by the protrusion 22 has a slit shape. Therefore, irregular reflection can be generated even for a sound wave having a shallow incident angle with respect to the depth direction of the protrusion 23 and the slit direction (that is, the Y direction), and a sound reduction effect can be easily obtained, thereby reducing noise. For example, regarding the protrusion depth L, the protrusion height ho, and the protrusion tip width a, it is preferable that L> 1.5ho or L> 1.5a.

  In addition, when the shape of each protrusion 22 is the same and the shape of the recess 23 formed by each protrusion 22 is the same, the frequency of the sound wave reduced by the irregular reflection at the recess 23 is Since it depends on the shape, the sound reduction effect works strongly for a specific frequency, and noise can be reduced.

  The sound wave entering the resonance space 19 from the gap 21 tends to be diffracted toward the orifice 18 in the resonance space 19 by the end 20 of the orifice 18 (see FIGS. 1A and 1B). . Therefore, by forming the plurality of protrusions 22 and the depressions 23 in the orifice 18 that is highly likely to collide with sound waves, the sound waves can be effectively incident into the depressions 23, and noise can be reduced by the sound reduction effect of the depressions 23. .

  Further, as shown in FIG. 2A, since the protrusion 22 and the orifice 18 are formed as one part integrally molded, the plurality of protrusions 22 and the recesses 23 can be formed in the resonance space 19 without increasing the number of parts. Can be provided within. For example, as shown in FIG. 2 (b), by making the cross-sectional shape of the orifice 18 into a shape that can be manufactured with a die cut in one direction, manufacturing is easy and manufacturing cost can be reduced.

  Further, by adopting a configuration in which a plurality of projection groups 30 each having a set of three projections 22 are alternately arranged in the vertical and horizontal directions, the slit-like depressions 23 arranged in parallel by one projection group 30 are maximized. Four can be formed. The incidence of irregular reflection by the depressions 23 becomes higher as the sound waves are perpendicular to the longitudinal direction of the slit-like depressions 23, and the characteristics are further enhanced by forming a set of four. In addition, although the incidence of irregular reflection is relatively low for sound waves that are nearly parallel to the longitudinal direction of the slit-like depressions 23, the projection groups 30 that form a set of four depressions 23 in the orifice 18 are arranged alternately vertically and horizontally. By doing so, it is possible to compensate for the low occurrence rate between adjacent sets. Therefore, irregular reflection by the depression 23 can be effectively generated, and a sound reduction effect can be obtained.

  In the centrifugal blower 1 according to the first embodiment, for example, the inner dimension of the outer shell 3 is 264 mm square, the height is 195 mm, the diameter of the impeller 5 is 183.5 mm, the inner diameter Di of the suction port 7 is 152 mm, and the suction port 17 The centrifugal blower of the example in which the inner diameter Do is 152 mm, the gap dimension j is 5 mm, the projection height ho is 20 mm, the projection top flat surface width a is 14 mm, the projection depth L is 66 mm, and the depression angle α is 41 °. FIG. 4 shows a graph of noise characteristic values of the centrifugal blower of the comparative example in which 22 is not provided (the other conditions are the same as those of the example). The solid line is the noise characteristic value of the centrifugal fan of the example having the protrusions 22 and the depressions 23, and the dotted line is the noise characteristic value of the centrifugal fan of the comparative example having no protrusions and depressions. As is clear from FIG. 4, the noise characteristics of the embodiment are such that the sound pressure levels at various frequencies are reduced, especially in the relatively high frequency range of 1 kHz to 1.4 kHz and 2.6 kHz to 3.4 kHz. It can be seen that the sound is more prominent than the comparative example. Therefore, it has been confirmed that by adopting the configuration of the centrifugal blower of the first embodiment, a noise reduction effect of 1 dB can be obtained in overall.

  As shown in FIG. 5, the depth direction of the protrusion 22 of each protrusion group 30 is arranged in a direction parallel to the radial direction of the impeller 5 and in a direction inclined from the orthogonal direction. The protrusion group 30 can also be arranged. Even in such a configuration, the same effect as the above-described configuration can be expected. An arbitrary angle can be adopted as the inclination angle in the inclined direction.

  Further, in the configuration of the centrifugal blower 1 of FIG. 1, the case where a plurality of protrusions 22 are formed on the orifice 18 in the resonance space 19 has been described, but instead of such a case, as shown in FIG. 6. In addition to the orifice 18, a configuration in which the protrusions 22 are also formed on the outer shell 3 and the casing 10 can be adopted. By adopting such a configuration, sound reduction due to air column resonance and irregular reflection is more likely to occur, so that a further sound reduction effect can be obtained and noise can be effectively reduced.

  According to the first embodiment, the sound reduction effect by air column resonance and the sound reduction effect by diffuse reflection are used together to enhance the sound reduction effect in the high frequency range and reduce the noise in a wide frequency range from low frequency to high frequency. A centrifugal blower can be obtained.

(Second Embodiment)
Next, a centrifugal blower according to a second embodiment of the present invention will be described. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. FIG. 7A shows a schematic perspective view of the orifice 18 included in the centrifugal blower of the second embodiment, and FIG. 7B shows a cross-sectional view of the orifice 18 in FIG.

  In FIG. 7A, a plurality of projections 22 are provided discontinuously on the inner side of the resonance space 19 of the orifice 18, that is, the side surfaces of the projections 22 are not directly connected to the side surfaces of the adjacent projections 22, Between the projections 22, there are provided recesses 23 formed by the side surfaces and the bottom surfaces of the adjacent projections 22. Further, the protrusion 22 and the orifice 18 are formed as a single molded part. Further, the individual protrusions 22 have different shapes, and the protrusions 22 having a plurality of types of shapes are provided. For this reason, there are a plurality of types of shapes of the recesses 23 formed by the protrusions 22. For example, as shown in the cross-sectional view of FIG. 7B, the plurality of protrusions 22 are discontinuously provided at intervals without directly connecting the respective side surfaces. Further, the recesses 23 are arranged at arbitrary intervals in the radial direction of the impeller 5. In addition, the respective recesses 23 are arranged in various directions along the slit-like longitudinal direction.

  By adopting such an arrangement configuration of the protrusions 22 and the depressions 23 of the second embodiment, the sound wave of the noise that has entered from the gap portion 21 has various directions due to diffraction and reflection inside the resonance space 19. Even if it is a case, since each hollow 23 is arrange | positioned in the slit-shaped longitudinal direction in various directions, the sound reduction effect is acquired also with respect to the sound wave of various directions, and noise can be reduced. it can.

  Moreover, since the frequency of the sound wave reduced by the irregular reflection at the depression 23 depends on the shape of the depression 23, there are a plurality of types of the projections 22, and there are a plurality of types of the depressions 23 formed by the projections 22. By adopting the configuration, a sound reduction effect can be obtained at various frequencies as compared with the configuration of the first embodiment, and noise can be reduced. In addition, as long as each protrusion 22 and the hollow 23 are arranged so that the longitudinal direction is different from at least one of the radial direction, the circumferential direction, and the axial direction of the impeller 5, various directions can be provided. A sound reduction effect for sound waves can be obtained.

  According to the second embodiment, the sound reduction effect by air column resonance and the sound reduction effect by diffuse reflection are used together to enhance the sound reduction effect in the high frequency range and reduce noise in a wide frequency range from low frequency to high frequency. A centrifugal blower that can be obtained is obtained.

(Third embodiment)
Next, a centrifugal blower according to a third embodiment of the present invention will be described. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. FIG. 8 shows a schematic perspective view of the orifice 18 included in the centrifugal blower of the third embodiment.

  As shown in FIG. 8, on the inner side of the resonance space 19 of the orifice 18, a pair of projections 22 having the same shape is provided in the same manner as the arrangement of the projections 22 in the first embodiment shown in FIG. As the group 30, a plurality of protrusion groups 30 are alternately arranged in the vertical and horizontal directions. In the first embodiment, the configuration in which the plurality of projection groups 30 are formed integrally with the orifice 18 is employed. However, in the third embodiment, the unit 24 to which the projection group 30 can be attached and detached is provided. In the point comprised as follows, the structure different from the said 1st Embodiment is employ | adopted. Specifically, the unit 24 (corresponding to the protrusion group 30) includes three protrusions 22 arranged in parallel in the depth direction, and a slit-like depression 23 formed by these protrusions 22 is parallel to the depth direction. Two are provided. On the inner side of the resonance space 19 of the orifice 18, a plurality of units 24 are arbitrarily arranged vertically and horizontally so that the depth directions of the adjacent units 24 intersect each other. Each unit 24 is fixed to the orifice 18 by a fixing means such as a screw, so that it can be detached from the orifice 18.

  By adopting such a configuration, the arrangement configuration of each unit 24 can be changed into various forms, and various arrangements of the depressions 23 can be created with one type of unit 24. Further, since the unit 24 is detachable, the frequency at which the sound can be reduced can be adjusted by changing the arrangement of the recesses 23.

  In addition, by using the unit 24 as a sound absorbing material such as glass wool, the gradual reduction of energy due to irregular reflection at the recess 23 becomes stronger, so that the sound reduction effect works strongly and noise can be reduced.

  According to the third embodiment, the sound reduction effect by air column resonance and the sound reduction effect by diffuse reflection are used together to enhance the sound reduction effect in the high frequency range, and reduce the noise in a wide frequency range from low frequency to high frequency. And a centrifugal blower in which the frequency of the noise to be reduced can be adjusted.

(Fourth embodiment)
Next, a centrifugal blower according to a fourth embodiment of the present invention will be described. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. 9A and 9B are schematic cross-sectional views showing the structures of the protrusions 22 and the depressions 23 provided in the centrifugal blower of the fourth embodiment.

  As shown in FIG. 9A, the projection 22 of the fourth embodiment has a plate thickness of 1 mm, for example, and has a hollow 25 inside thereof. Further, a hole 27 of φ1.5 mm, for example, is formed on the projection tip surface 26. It has. Further, the protrusion 22 forms a Helmholtz resonance structure in which the cavity 25 is a volume part and the hole 27 is a throat part. For example, as shown in FIG. 9B, such a structure of the projection 22 is formed by forming the orifice 18 with a thin plate to form the upper surface of each projection 22, and the plate part 28 from the lower side of the orifice 18 in the figure. By attaching, the cavity 25 can be easily formed inside each projection 22.

  According to the configuration of the fourth embodiment as described above, in addition to the sound reduction by the recess 23, the inside thereof is the cavity 25 and the hole 27 is formed, so that the resonance muffler due to the Helmholtz resonance structure is added. Therefore, a further sound reduction effect can be obtained and noise can be reduced.

  Therefore, according to the fourth embodiment, it is possible to obtain a centrifugal blower capable of enhancing the noise reduction effect in the high frequency range and reducing noise in a wide frequency range from low frequency to high frequency.

  It is to be noted that, by appropriately combining arbitrary embodiments of the various embodiments described above, the effects possessed by them can be produced.

  The present invention provides a centrifugal blower that enhances a sound reduction effect in a high frequency range, can reduce noise in a wide frequency range from low frequency to high frequency, and reduces noise. Is available.

It is a figure which shows the centrifugal blower concerning 1st Embodiment of this invention, (a) is a schematic cross section of a centrifugal blower, (b) is an enlarged view of the X section of (a). It is a figure which shows the orifice of 1st Embodiment of this invention, (a) is a model perspective view, (b) is AA sectional drawing in (a). The model perspective view which shows the shape of the protrusion and hollow of 1st Embodiment of this invention The figure which shows the noise reduction effect of 1st Embodiment of this invention. The schematic perspective view of the orifice concerning the modification of 1st Embodiment of this invention. Schematic sectional view of a centrifugal blower according to a modification of the first embodiment of the present invention. It is a figure which shows the orifice of 2nd Embodiment of this invention, (a) is a model perspective view, (b) is the BB sectional drawing in (a). Schematic perspective view of an orifice according to a third embodiment of the present invention It is a figure which shows the processus | protrusion and hollow of 4th Embodiment of this invention, (a) is typical sectional drawing, (b) is a schematic diagram which shows the example which comprises a cavity in processus | protrusion. Schematic sectional view showing a conventional centrifugal blower

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Centrifugal blower 2 Opening 3 Outer shell 4 Rotating shaft 5 Impeller 6 Electric motor 7 Suction port 8 Side wall 9 Discharge port 10 Casing 11 Discharge opening 12 Discharge adapter 13 Flange part 14 Hole 15 Ceiling material 16 Duct 17 Suction port 18 Orifice 19 Resonance space 20 End portion 21 Gap portion 22 Protrusion 23 Dimple 24 Unit 25 Cavity 26 Protrusion tip surface 27 Hole 28 Plate part 30 Protrusion group 31 Top flat surface 32 Inclined surface Di Suction port inner diameter Do Suction port inner diameter j Gap size ho Projection height L Projection depth a Protrusion tip width b Opening width c Top flat surface width α Depression angle

Claims (16)

An outer shell with an opening,
An impeller supported rotatably in the outer shell;
An electric motor for rotationally driving the impeller;
A casing having a first suction port and disposed in the outer shell so as to surround the periphery of the impeller;
A bell mouth shape having a second suction port which is disposed in an opening of the outer shell so as to have a gap between the first suction port of the casing and communicates the opening of the outer shell and the first suction port of the casing. With an orifice,
A resonance space communicating with the first suction port through a gap between the first suction port and the second suction port to resonate and muffle noise emitted from the first suction port is provided in the orifice, the casing, and the outer shell. Is defined as a demarcating wall, and a plurality of protrusions are provided on the demarcating wall of the resonance space. The plurality of protrusions have inclined surfaces that are inclined with respect to the defining wall surface of the resonance space at each forming position,
An inclined surface of one protruding portion and an inclined surface of another protruding portion adjacent to the one protruding portion are connected to each other, and a concave portion is formed between the protruding portions by each inclined surface. The centrifugal blower according to claim 1.   The centrifugal blower according to claim 2, wherein an angle of a connection portion of each inclined surface in the concave portion is an acute angle.   The centrifugal blower according to claim 2 or 3, wherein the protrusion has a flat surface at the top.   The centrifugal blower according to any one of claims 2 to 4, wherein the protrusion has a shape having a long depth with respect to its height and width.   The centrifugal blower according to claim 5, wherein the plurality of protrusion groups in which the plurality of protrusions are arranged in parallel with each other in the depth direction are arranged so that the depth directions of adjacent protrusion groups intersect each other. .   The centrifugal blower according to claim 5, wherein a plurality of protrusion groups in which a plurality of protrusions are arranged in parallel in the depth direction are arranged so that each of the depth directions is different.   A plurality of recesses formed between the plurality of protrusions are formed so as to extend along the demarcating wall surface, and each recess is provided in at least one of the radial direction, the circumferential direction, and the axial direction of the impeller. The centrifugal blower according to claim 5, wherein the extending directions are different from each other.   The centrifugal blower according to any one of claims 1 to 8, wherein the plurality of protrusions have the same shape, and the plurality of recesses formed between the plurality of protrusions have the same shape.   The centrifugal blower according to any one of claims 1 to 8, wherein there are a plurality of types of protrusions, and a plurality of types of recesses formed between the plurality of protrusions.   The centrifugal blower according to any one of claims 1 to 10, wherein a plurality of protrusions are provided on the orifice in the resonance space.   The centrifugal blower according to any one of claims 1 to 11, wherein the plurality of protrusions are formed integrally with an orifice, a casing, or a demarcation wall of the outer shell.   The centrifugal blower according to any one of claims 1 to 11, wherein the protrusion is detachably installed on the defining wall.   The centrifugal blower according to claim 13, wherein the protrusion is formed of a sound absorbing material.   The centrifugal blower according to any one of claims 1 to 14, wherein the protrusion is formed with a hollow inside, and a hole communicating the cavity and the resonance space is formed in the protrusion. An outer shell having an opening, an impeller rotatably supported in the outer shell, a casing having a first suction port and being arranged in the outer shell so as to surround the periphery of the impeller, A bell mouth-shaped orifice having a second suction port which is disposed in an opening of the outer shell so as to have a gap between the first suction port and communicates the opening of the outer shell and the first suction port of the casing; In a resonance space defined by the orifice, the casing, and the outer shell as a demarcating wall, and communicated with the first suction port through a gap between the first suction port and the second suction port. The sound wave of the noise generated in the casing as the impeller rotates is incident through the gap between the first suction port and the second suction port,
A centrifugal wave characterized by reducing the level of sound waves of noise incident in the resonance space by air column resonance and reducing the level of sound waves of noise by irregularly reflecting the sound waves of noise in the resonance space. Blower noise reduction method.

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