JP6236628B2 - Active silencer - Google Patents

Description

  The present invention relates to an active silencer that is arranged in an internal air passage to silence noise generated during fan operation.

  In recent years, in air blowers such as air conditioners and ventilation fans, it has been required to reduce noise generated during operation. As one of means for solving such a problem, there is a method in which an active silencer having a duct structure is mounted on the internal air passage.

  Conventionally, as this type of active silencer, there has been known one in which a microphone is installed with a space provided in a low-speed airflow range in order to reduce the influence of the airflow in the air passage (see, for example, Patent Document 1).

  Hereinafter, the active silencer will be described with reference to FIGS.

  Conventionally, as an active silencer having a duct structure, an internal original sound reference microphone 111, a silencer speaker 112, and an error microphone, which are sequentially attached at appropriate intervals from the upstream side inside a rectangular duct 101 made of a thin steel plate, respectively. 113 and an arithmetic controller 102 respectively connected to them are known.

  In this type of apparatus, the generated sound propagating in the rectangular duct 101 together with the airflow 103 is detected by the reference microphone 111, and the arithmetic controller 102 generates a signal having a phase opposite to that of the original sound. The original sound emitted from the speaker 112 into the rectangular duct 101 is canceled and muffled, the error microphone 113 monitors the internal sound, and the mute speaker 112 is set so that the output of the error microphone 113 becomes zero by the arithmetic controller 102. The reference microphone 111 and the error microphone 113 are automatically adjusted, and as shown in FIG. 7, a microphone section 104 is provided in the corner low velocity air flow range of the square duct 101.

  As a result, the reference microphone 111 and the error microphone 113 are respectively disposed in the microphone section 104 in the low-speed airflow range at the corner of the duct via the communication port 105, so that local turbulence in which the airflow in the duct is generated. In addition to not picking up the noise based on the noise, it is possible to sufficiently pick up the noise original sound that propagates the air flow, and the feedback function of the silencer is improved.

Japanese Utility Model Publication No. 5-11198

  However, in the device described in the above-mentioned conventional patent document 1, a duct with a finite length is included in the blower housing due to the setting in the blower, etc., and a rapidly expanding air passage that spreads from the downstream end of the duct to the entire housing. In this case, since a vortex is generated from the downstream end of the duct, a reference microphone or an error microphone serving as a downstream microphone and a downstream microphone (because the noise source may be upstream or downstream with respect to the airflow) As a result, noise based on local disturbance generated by the noise is picked up, and the noise becomes noise when detecting the original noise, and there is a problem that a sufficient silencing effect cannot be obtained.

  Therefore, the present invention solves the above-described problems, and an object of the present invention is to provide an active silencer that suppresses a reduction in the silencing effect due to airflow.

  In order to achieve the above object, the present invention is an active silencer in which a rectangular duct disposed inside the blower and an upstream microphone, a speaker, and a downstream microphone are installed in the duct from the upstream side in the airflow direction. The downstream microphone is installed in the vicinity of the downstream end of the duct, and is throttled so that the air path gradually narrows from a position downstream of the downstream microphone on the downstream microphone installation surface toward the downstream end. It has a shape, thereby achieving its intended purpose.

  According to the present invention, in an active silencer having a duct configuration in an airflow field, even if the active silencer has a finite length such that a suddenly expanding air path is formed at the downstream end of the duct, a reduction in the silencing effect due to the airflow is suppressed. be able to.

Side sectional view of Embodiment 1 of the present invention Outline sectional view of the active silencer Outline sectional view of conventional active silencer The graph of the effect of Embodiment 1 of the present invention Outline sectional view of the active silencer Outline sectional view of conventional active silencer Side sectional view of an application example of Embodiment 1 of the present invention Side sectional view of Embodiment 2 of the present invention Outline perspective view showing a conventional active silencer Outline perspective view showing a conventional active silencer

  The active silencer according to claim 1 of the present invention is an active silencer that is installed in the order of a rectangular duct arranged in the internal air passage and an upstream microphone, a speaker, and a downstream microphone from the upstream side in the airflow direction in the duct. The downstream microphone is installed in the vicinity of the downstream end of the duct, and the air path on the downstream microphone installation surface is gradually narrowed from the position downstream of the downstream microphone toward the downstream end. It has a diaphragm shape.

  As a result, since the vortex from the downstream end of the duct on the downstream microphone installation surface closest to the downstream microphone flows on the same plane as the downstream microphone setting surface when there is no aperture, the direct vortex is caused directly. If the wave is easy to be transmitted to the downstream microphone and has a diaphragm shape, the vortex is emitted inward of the duct on the same plane as the microphone installation surface, but is swept into the mainstream and becomes a vortex along the duct. For the downstream microphone, the vortex is located on the other side of the squeezed microphone installation surface, and the diaphragm shape blocks the direct wave caused by the vortex. Furthermore, when the throttle shape deflects the flow, the local flow velocity near the throttle shape decreases. Noise noise is detected when there is a flow with a large flow velocity in the vicinity of the microphone, but noise can be suppressed by arranging a downstream microphone in the flow velocity reduction region due to the aperture shape. Therefore, it is possible to suppress a decrease in the silencing effect of the active silencing device by reducing noise caused by these airflows.

  The active silencer according to claim 2 is an active silencer in which a plurality of rectangular ducts are arranged side by side in parallel with the airflow direction, and the diaphragm shape is unified on the inner surface or the outer surface that is symmetrical. It is a thing.

  As a result, when an axial fan is provided in the air blower, for example, in the vicinity of the downstream of the active silencer, the airflow is centered by providing the throttle shape of each duct on the outer peripheral side of the active silencer combined with the duct. For example, when the air path is divided outside by providing an obstacle in the vicinity of the downstream of the active silencer extension line, the throttle shape of each duct on the inner peripheral side of the active silencer combined with the duct It is possible to rectify the airflow to the outside by providing, and to suppress the reduction of the noise reduction effect of the active silencer by suppressing the noise caused by external disturbance and the generation of a new noise source it can.

(Embodiment 1)
Embodiment 1 of the present invention will be described below with reference to FIG.

  As shown in the immediate sectional view of a part of the substantially cubic blower in FIG. 1, the active silencer 1 of the first embodiment is installed upstream of the axial fan 3 in the internal air passage 2 of the blower. The sound that is transmitted from the right side to the left side using the axial fan 3 as a sound source and silenced in the suction space 4 in the state where there is an airflow directed from the left to the right in the figure is silenced.

Here, the active silencer 1 includes a rectangular duct 5, an error microphone 6 as an internal upstream microphone, a speaker 7, and a reference microphone 8 as a downstream microphone. A storage unit 9 is provided for routing the wiring of the speaker 7 and the reference microphone 8. Since the target frequency <0.5 × sound speed / duct width, the duct width is set to 85 mm and the frequency to be silenced is set to about 2 kHz. In this case, the required air volume (in this case, for example, 150 m ³ / h) It is a large axial fan 3 for securing. Therefore, the active silencer 1 is configured to be slightly smaller than the outline of the blower, and is a wind path that rapidly expands between the active silencer 1 and the axial fan 3.

  Further, the reference microphone 8 is installed in the vicinity of the downstream end portion 10 of the duct 5, and the diaphragm shape portion 11 is provided so that the air path gradually narrows from the position of the reference microphone 8 toward the downstream end portion 10. Yes.

  Further, the downstream end portion 10 has a configuration in which a bent portion 12 is formed by bending the edge outward so as to be substantially perpendicular to the airflow direction.

  With the above configuration, when the axial flow fan 3 is operated in the active silencer 1, an air flow is generated, and at the same time, the noise of the axial flow fan 3 is radiated to the suction space 4 through the internal air passage 2. In the middle of this, the active silencer 1 is arranged, a noise signal detected by the reference microphone 8 is input to an arithmetic controller (not shown), and the arithmetic control unit is a speaker that serves as a sound and a silence point received by the reference microphone 8. Based on the signal from the reference microphone 8 under the condition that the correlation between the nearby sound and the sound from the error microphone 6 is high, a silence signal that predicts the silence signal output to the speaker 7 from the correlation is generated. The noise is silenced by the canceling sound that has the opposite phase to the noise of the blower. Further, the error microphone 6 monitors the internal sound and the speaker 7 is automatically adjusted by the arithmetic controller so that the output of the error microphone 6 becomes zero.

  At this time, with respect to the air flow and sound waves at the downstream end 10 in the internal air passage 2, FIG. 2 shows a schematic cross-sectional view of a conventional configuration without the throttle-shaped portion 11, and FIG. 3 shows a schematic cross-sectional view of the configuration of the present invention. .

  FIG. 2 shows a state in which the airflow attached and moving on the duct inner wall 13 is separated from the duct inner wall 13 at the point of the downstream end 10 and the end vortex 14 is generated by the separation. Here, the sound wave generated in the space using the pressure fluctuation of the end vortex 14 as a sound source affects only the vicinity as noise, but as shown by the propagation 15 of the sound wave, between the end vortex 14 and the reference microphone 8. Since there is nothing to block the noise, only the noise of the reference microphone 8 has a great influence, so that the correlation between the reference microphone 8 and the silencing point is lowered, and the silencing effect is lowered.

  However, in FIG. 3, the airflow attached and moving on the duct inner wall 13 is rolled up along the throttle shape portion 11 at the downstream end portion 10, but is flowed to the mainstream and is away from the throttle shape portion 11 for the reference microphone 8. An end vortex 14 is located. For this reason, the sound from the end vortex 14 is hindered by the diaphragm-shaped portion 11 as shown in the sound wave propagation 15, and the influence on the reference microphone 8 is reduced, and the correlation between the reference microphone 8 and the silence point is not lowered. It is possible to suppress a decrease in the silencing effect.

  Here, FIG. 4 shows an example of a graph of the effect of the present invention. The higher the correlation coefficient, the greater the silencing effect of the active silencer, but the correlation coefficient can be increased by the active silencer of the present invention.

  In addition, the active silencer 1 of Embodiment 1 is installed in the downstream of the axial fan 3 of the internal air path 2 of a ventilation apparatus, as shown in the sectional side view of the application example of FIG. In the state where there is an airflow directed from the left to the left, the sound that is transmitted from the right to the left using the axial fan 3 as a sound source and muffled in the blowing space 18 may be silenced. By providing the end portion 19, the influence on the error microphone 6 is reduced, the correlation between the error microphone 6 and the reference microphone 8 is not lowered, and it is possible to suppress a decrease in the silencing effect.

  Moreover, about the airflow of the bending part 12 of the downstream end part 10, the schematic sectional drawing in the conventional structure without a bending part is shown in FIG. 5, and the schematic sectional drawing in the structure of this invention is shown in FIG.

  FIG. 5 shows a state in which the airflow attached and moving on the duct inner wall 13 is separated from the duct inner wall 13 at the downstream end 10 and the end vortex 16 is generated by the separation. Here, since the space 17 is provided outside the duct 5, the air in this portion is attracted by the main flow blown out of the duct 5, thereby generating a flow at the center of the duct downstream of the downstream end portion 10. The part vortex 16 is also drawn toward the center of the duct. As a result, the end vortex 16 approaches the reference microphone 8 provided inside the duct 5, so that the reference microphone 8 is affected as noise, and the correlation between the reference microphone 8 and the silence point is reduced. The silencing effect is reduced.

  However, in FIG. 6, the airflow attached and moving to the duct inner wall 13 does not generate an induced airflow toward the center because the space outside the duct 5 is blocked by the bent portion 12, and the downstream end 10 The downstream is almost along the duct, and the end vortex 16 also goes straight downstream. As a result, the end vortex 16 does not approach the reference microphone 8 provided inside the duct 5, so that the influence on the reference microphone 8 is reduced, and a reduction in the silencing effect can be suppressed.

  The bent portion 12 may be attached to the end of the aperture-shaped portion 11 and is blocked from the flow of the outer space, thereby preventing the end vortex 16 from approaching the reference microphone and suppressing the reduction in the silencing effect. It becomes possible.

(Embodiment 2)
In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, detailed description thereof will be omitted, and description will be made with reference to FIG.

  As shown in the immediate sectional view of a part of the air blower in FIG. 8, the active silencer 20 is installed on the upstream side of the centrifugal fan 21 and the fan casing 22 in the internal air passage 2 of the air blower. In the state where there is an airflow directed from right to left in the figure, the sound emitted from the right to the left and discharged into the suction space 4 is silenced using the centrifugal fan 21 having suction ports on both sides of the upper and lower axes in the figure as a sound source. Is.

  Here, in order to reduce the resistance of the air passage, the active silencer 20 has a plurality of rectangular ducts 5 combined to increase the cross-sectional area of the air passage. The ducts of the respective ducts 5 are in contact with each other to form a partition surface. An error microphone 6 as a downstream microphone, a speaker 7 and a reference microphone 8 as an upstream microphone are provided at the center of the air path 2.

  Further, in each duct 5, the reference microphone 8 is installed in the vicinity of the downstream end portion 10 of the duct 5, and the air path gradually narrows from the position of the reference microphone 8 toward the downstream end portion 10. A diaphragm shape portion 11 is provided on the same surface as the reference microphone 8.

  With the above configuration, the centrifugal fan 21 has a structure that divides the airflow in the internal air passage 2 to both outer sides.

  Here, since the throttle-shaped portion 11 is provided in the central portion of the internal air passage 2, the airflow is bent outward so as to be guided to the throttle-shaped portion 11, thereby producing a rectifying effect. Therefore, as compared with the case where the throttle-shaped portion 11 is provided on another surface, the airflow is less disturbed, so that the pressure loss in the machine can be reduced and the air volume of the blower can be increased, and the sound generated from the airflow disturbance can be reduced. Thus, the influence of noise on the reference microphone 8 is reduced, and the correlation between the reference microphone 8 and the silencing point is not lowered, and it is possible to suppress a decrease in the silencing effect.

  In the second embodiment, in the case of the centrifugal fan 21 having the suction ports on both sides of the shaft, the throttle-shaped portion 11 is provided in the central portion of the internal air passage 2 that is in contact with the duct and serves as a partition. When an axial fan or an obstacle structure is provided outside the internal air passage 2, an error microphone 6, a speaker 7, and a reference microphone 8 are used to guide the airflow to the center of the internal air passage 2. The diaphragm shape portion 11 is provided on the outer surface where the duct is not in contact, and the air flow is guided to the center portion by the diaphragm shape portion 11, so that the influence of noise on the reference microphone 8 is reduced, and the correlation between the reference microphone 8 and the silence point is reduced. Therefore, it is possible to suppress a decrease in the silencing effect.

  Even if it installs in an airflow field, the active silencer concerning this invention can suppress the fall of a silencing effect, and is useful as an active silencer with which the inside of a ventilation apparatus or the middle of a ventilation wind path is equipped.

DESCRIPTION OF SYMBOLS 1 Active silencer 2 Internal air path 3 Axial fan 4 Suction space 5 Duct 6 Error microphone 7 Speaker 8 Reference microphone 9 Storage part 10 Downstream end part 11 Diaphragm-shaped part 12 Bending part 13 Duct inner wall 14 End part vortex 15 Propagation of sound wave 16 End Vortex 17 Space 18 Blowout Space 19 Downstream End 20 Active Silencer 21 Centrifugal Fan 22 Fan Casing

Claims (2)

A rectangular duct arranged in an internal air passage, and an active silencer installed in the duct in order of an upstream microphone, a speaker, and a downstream microphone from the upstream side in the airflow direction, wherein the downstream microphone is connected to the downstream end of the duct Active silencer characterized in that it has a throttle shape so that the air path gradually narrows from a position downstream of the downstream microphone on the downstream microphone installation surface toward the downstream end portion. . 2. An active silencer in which a plurality of rectangular ducts are arranged in parallel in the airflow direction, and the diaphragm shape is unified on an inner surface or an outer surface that is symmetrical, and is provided on the outer surface. Active silencer.

Images