JP3922781B2 - Silencer and blower - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a blower, and more particularly, to a blower with improved noise reduction characteristics.
[0002]
[Prior art]
For example, as shown in FIGS. 3 and 4, the centrifugal blower B accelerates the gas sucked from the suction port 12 of the casing 10 in the circumferential direction by the rotation of the impeller 14, and converts the velocity energy into pressure by the scroll 16 or the diffuser. It is configured to convert and discharge from the discharge port. The inlet 18 in the center of the impeller 14 and the suction port 12 of the casing 10 are connected to each other by a suction pipe 20 having a substantially hyperbolic cross section.
[0003]
In such a blower B, noise of a frequency that is the product of the number of blades and the rotation frequency is generated from the main body, and this leaks to the outside from the suction port 12, which is a big problem in environmental measures. Therefore, as shown in FIG. 3 and FIG. 4, a silencer (silencer) S is provided in the front part of the suction port 12.
[0004]
In FIG. 3, a cylindrical inner case 26 is arranged inside the outer case 24, and a meandering flow path 28 is formed therebetween, and a sound absorbing material such as glass wool covering these flow path surfaces in these cases. 30 is attached with a metal mesh (punching metal). FIG. 4 shows a structure in which a sound absorbing material 34 is fixed to the inner surface of a box-shaped cover 32 and silencer inlets 36 are provided in two directions, left and right or up and down.
[0005]
[Problems to be solved by the invention]
However, in the conventional techniques as described above, the shape and material of the silencer flow path are not appropriate, and thus good results could not be obtained. For example, in the case shown in FIG. 3, a large loss is caused due to the distortion of the flow, and the performance of the blower B is deteriorated, and noise due to a rapid change in the flow path is generated. On the other hand, in the case shown in FIG. 4, a sufficient silencing function could not be obtained.
[0006]
In addition, sound absorbing materials such as glass wool have environmental hygiene problems themselves, and since they do not have a self-shape maintaining function, they must be fixed using a wire mesh, and man-hours for manufacturing and maintenance are also required. There were many.
[0007]
The present invention provides a silencer that can absorb the sound of the blower without emitting it to the outside without greatly deteriorating the performance of the blower, and can suppress noise generation by itself and obtain a sufficient silencing function. For the purpose.
[0008]
[Means for Solving the Problems]
The invention according to claim 1 has an air outlet attached to the air inlet of the blower and an air inlet arranged on a peripheral surface surrounding the axis of the air outlet, and smoothly connects the air outlet and the air inlet. The internal flow path is formed of a sound absorbing material capable of maintaining its shape, and the sound absorbing material includes a main shielding portion having a convex portion facing the air outlet, and a sub shielding portion surrounding the air outlet. The internal flow path has a total flow path cross-sectional area that linearly decreases as the total flow path cross-sectional area becomes maximum at the air inlet and from the air inlet toward the air outlet. It is the silencer characterized by being formed in this way.
[0009]
Thereby, the area of the inlet can be made larger than that of the outlet, and the wind speed can be reduced. Therefore, the noise can be reduced at the inlet where the noise most affects the surroundings. The inlet and the outlet are arranged so as to be substantially orthogonal, so that most of the noise on the blower side is absorbed by the sound absorbing material, and the sound coming out from the inlet is greatly reduced. In addition, since the internal flow path is slanted and outwardly extended from the center outlet toward the inlet on the peripheral surface, there is no sudden flow path change and energy loss and noise generation due to air Is prevented.
[0010]
In addition, since the flow path itself is formed of a sound absorbing material, the silencing effect is great and the manufacturing process is simplified. By using a self-maintaining material as the sound absorbing material, it is no longer necessary to use a metal mesh such as punching metal, which is indispensable when attaching a conventional sound absorbing material (for example, glass wool). The flow path is formed to be axially symmetric with respect to the axis unless otherwise specified, but may be asymmetric depending on the case. The inlet usually opens to the entire peripheral surface, but may be an opening separated at an appropriate interval.
[0012]
The main shielding part prevents the noise from the blower from directly coming out. By forming these separately and attaching them to the casing, it is possible to adjust the cross-sectional area of the internal flow path by changing the gap between them, and it is possible to cope with various blowers in one shape .
[0013]
Further , by forming the internal flow path so that the total flow path cross-sectional area at the entrance is maximized, the wind speed at the entrance can be reduced, and the noise at the entrance where the noise has the greatest influence on the surroundings can be reduced. .
[0014]
Also, more and this total flow path cross-sectional area as it goes from the inlet to the outlet is adapted to decrease approximately linearly, by suppressing the variation of the flow it is possible to suppress the occurrence of noise.
[0015]
The sound absorbing material is preferably urethane foam. This can hold the self shape and has sufficient durability. In addition, foamed ceramics or the like can be used.
[0016]
The invention according to claim 2 is a blower characterized in that the silencer according to claim 1 is attached to a suction port.
[0017]
The invention described in claim 3 is a centrifugal blower in which the blower includes a suction pipe having a constricted portion , and the internal flow path of the silencer is an air flow path formed by an impeller of the centrifugal blower The blower according to claim 2 , wherein the blower is substantially plane-symmetric with respect to a cross section of the constricted portion of the suction pipe .
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the silencer of the present invention is used in a centrifugal blower B will be described with reference to the drawings. The right part of FIG. 1 is a centrifugal blower B to which the silencer S is attached. The gas sucked from the suction port 12 of the blower casing 10 is accelerated in the circumferential direction by the rotation of the impeller 14, and the speed energy is obtained by the scroll 16. The pressure is converted into pressure and discharged from the discharge port. The impeller is bolted to a rotating shaft 22 that is rotationally driven by a driving means (not shown).
[0019]
A suction pipe 20 having a substantially hyperbolic cross section is attached to the inside of the suction port 12 of the blower casing 10 by bolting the flange, and the suction pipe 20 has a minimum cross-sectional area at the central constricted portion 20a. It expands and communicates with the inlet 18 of the downstream impeller 14.
[0020]
In this example, the silencer S is formed in a disk shape having a thickness approximately the same as that of the blower casing 10 and is coaxially attached to the outside of the suction port side casing 10a of the blower B. The silencer is composed of two disk-like mounting plates 50 and 52 and sound absorbing materials 54a and 54b attached to the inside of each mounting plate, and the inside that introduces air into the suction port 12 by these sound absorbing materials. A flow path P is formed. As the sound absorbing material, a self-holding material such as urethane foam is used, and this is processed into a predetermined shape and fixed to the mounting plate.
[0021]
The internal flow path P is opened at a position outlet P _o correspond with suction port 12, inlet P _i is open over the entire surface of the peripheral surface. Therefore, the flow path from the inlet P _i to the outlet P _o extends obliquely to the axis and toward the center. The internal flow path P has a smooth curve as shown in FIG. 1 in the cross section including the axis, and the flow path shape including the suction pipe 20 and the impeller 14 is a cross section of the constricted portion 20 a of the suction pipe 20. The shape is almost plane-symmetric.
[0022]
Outside the attached sound absorbing material to the mounting plate 50 (main shielding section) 54a, a smooth convex portion 56 in the central portion is formed, the sound absorbing material surrounding the outlet P _o (sub shielding portion) 54b is a blower B Is formed with a bulge 58 so that the noise from the air does not come out directly from the outlet. The main shielding portion 54a and the sub shielding portion 54b are formed separately, and the mounting plates 50 and 52 are individually fixed to the casing 10a of the blower B by bolts or the like. In this example, the main shielding portion 54 a is fixed using a long bolt 60 and a spacer tube 62, and the cross-sectional area of the flow path P can be adjusted by changing the length of the spacer tube 62. Therefore, it is possible to correspond to the blower B having various blowing capabilities in one shape.
[0023]
As shown in FIG. 1, when the passage P to the entrance P _i Karakubire portion 20a of the inlet 0, a length dimensionless the constricted portion as 1 to _{L / L T, L / L} T increases Accordingly, the width W of the flow path also increases. However, the dimensionless total channel cross-sectional area (A / A _o = 2πWR / A _o ) at each dimensionless length is the largest at the inlet, and is almost as it goes from the inlet P _i to the outlet as shown in FIG. It is designed to decrease linearly.
[0024]
When the blower B configured as described above is operated, air is introduced from the inlet P _i that opens to the peripheral surface of the silencer S, flows through the internal flow path P toward the outlet, and further passes through the constricted portion of the suction pipe. Then head to the impeller 14. In this process, since the flow path P is smoothly bent, turbulent flow is difficult to be generated, and energy loss and generation of noise due to vortex flow are small. Further, since the flow path P itself is formed of a sound absorbing material such as urethane foam, vibration and noise associated with the air flow are less likely to occur.
[0025]
In addition, since the inlet P _i is open to the peripheral surface, the total flow passage cross-sectional area at the inlet P _i is large, and noise can be reduced at the inlet P _{i where} the noise most affects the surroundings. . Further, by uniformly reducing the cross-sectional area, it is possible to suppress the change in flow and suppress the generation of noise.
[0026]
【The invention's effect】
As described above, according to the present invention, noise on the blower side is efficiently absorbed by the sound absorbing material, and there is no sudden flow path change in the internal flow path. Is prevented. Since the flow path itself is made of a sound absorbing material, the silencing effect is great and the manufacturing process is simplified. Therefore, it is possible to provide a silencer that can absorb the noise of the blower without emitting it to the outside without greatly deteriorating the performance of the blower, and can suppress noise generation by itself and obtain a sufficient silencing function. it can.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a centrifugal blower with a silencer according to an embodiment of the present invention.
FIG. 2 is a graph showing a change in flow path cross-sectional area of the embodiment of FIG.
FIG. 3 is a cross-sectional view showing an example of a silencer of a conventional blower.
FIG. 4 is a cross-sectional view showing another example of a silencer of a conventional blower.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Casing 12 Inlet 14 Impeller 16 Scroll 18 Inlet 20 Intake pipe B Blower P Flow path S Silencer

Claims (3)

An air outlet attached to the air inlet of the blower and an air inlet arranged on the peripheral surface surrounding the axis of the air outlet, and the internal flow path smoothly connecting the air outlet and the air inlet maintains its own shape Made of possible sound absorbing material ,
The sound-absorbing material has a main shielding portion having a convex portion facing the air outlet, and a sub-shielding portion surrounding the air outlet,
The internal flow path is formed such that the total flow path cross-sectional area is maximized at the air inlet, and the total flow path cross-sectional area decreases linearly from the air inlet toward the air outlet. silencer, characterized in that is. A blower, wherein the silencer according to claim 1 is attached to a suction port. The blower is a centrifugal blower provided with a suction pipe having a constricted portion , and the internal flow path of the silencer includes an air flow path formed by an impeller of the centrifugal blower and a constricted portion of the suction pipe. The blower according to claim 2 , wherein the blower is substantially plane-symmetric with respect to the cross section .

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