JP2015064399A - Active silencer and a blower using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an active silencer and a blower using the same capable of solving conventional problems that an air passage requires sufficiently large aperture not to increase pressure loss, and to eliminate high frequency noises which mainly cause noises on a blower, the air passage has to be divided into many parts resulting in a complicated structure.SOLUTION: A blower 2 has an active silencer 1 disposed at an air inlet 3 of a blow part 8. The inside of the active silencer 1 is divided into plural small air passages 9. Each of the small air passages 9 includes a microphone for detecting acoustic waves and a loudspeaker for outputting acoustic waves. An aperture of at least one of the small air passages 9 is arranged to be smaller than an aperture of the other small air passages 9. Thus, the blower with fewer number of air passages of the active silencer 1 which is capable of preventing increase of the pressure loss and capable of eliminating high frequency noises.

Description

  The present invention relates to a blower mainly used for ventilation and air conditioning in a house, a building, etc., and provided with an active silencer for silencing noise generated during operation.

  In recent years, blowers installed for ventilation and air conditioning in homes and office buildings have been required to reduce noise generated during operation. One means for solving such a problem is a method of mounting an active silencer in a ventilation fan.

  Conventionally, as the active silencer unit for ducts, as shown in the cross-sectional view of FIG. 3, a reference microphone 102 for internal original sound, a silencer speaker 103, which are sequentially attached to the interior of the duct 101 at appropriate intervals from the upstream side, An error microphone 104 and an operation controller 105 connected to each of them are known (see, for example, Patent Document 1).

  In this type of device, the generated sound propagating in the duct 101 together with the air flow 106 is detected by the reference microphone 102, and the arithmetic controller 105 generates a signal having a phase opposite to that of the original sound. 103 cancels and silences the original sound emitted into the duct 101, the error microphone 104 monitors the internal sound, and the arithmetic controller 105 automatically adjusts the mute speaker 103 so that the output of the error microphone 104 becomes zero. doing.

  Such an active silencing unit silences the noise propagating in the one-dimensional sound field, and the noise propagating through the air passage can be controlled up to the frequency propagating through the plane wave.

  However, the frequency propagated by the plane wave varies depending on the duct diameter, and when the duct diameter is large, the upper limit frequency that becomes a plane wave becomes low. If the frequency to be silenced is higher than the upper limit frequency, the noise cannot be assumed to be a one-dimensional sound field and cannot be silenced.

  For this reason, as an active silencing unit for large-diameter ventilation paths, the silencing ventilation path is divided into a combination of small-diameter ducts (small-diameter ducts), and the upper limit frequency of noise propagated by plane waves in each small-diameter duct Is known to control the frequency by increasing the frequency (see, for example, Patent Document 2).

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

  As shown in FIG. 4, the large-diameter duct is divided into small-diameter ducts 201, 202, 203, and 204 having the same diameter, and the speaker 103 is installed at the same position of each of the diameter ducts. Further, the reference microphone 102 is installed upstream of the installation position of the speaker 103 and the error microphone 104 is installed downstream of the small-diameter duct 201. The noise signals detected by the reference microphone 102 and the error microphone 104 are input to the arithmetic controller 105, and the arithmetic controller 105 generates a drive signal to be output to the speaker 103 based on these noise signals, and each small aperture. This drive signal is output to the speaker 103 installed in the duct, and the noise transmitted through each small-diameter duct is silenced by the same canceling sound. At this time, since the large-diameter duct is divided into small-diameter ducts, the upper limit of the frequency propagating by the plane wave can be increased and the sound can be silenced up to a high frequency.

  In FIG. 4, the same or similar components as those shown in FIG. 3 are indicated by the same reference numerals.

Japanese Utility Model Publication No. 5-11198 JP-A-9-160567

  When considering application of the active silencer described in Patent Document 2 to a blower, it is necessary to sufficiently increase the diameter of the air passage so as not to increase the pressure loss of the active silencer. However, when the frequency that is the main component of the noise of the blower is high, it is necessary to increase the number of divisions of the air passage in order to mute the noise, and there is a problem that the structure becomes complicated.

  Therefore, the present invention solves the above-described problems, and an active silencer that uses a small number of air passage divisions, suppresses an increase in pressure loss in the air passage, and can mute high-frequency noise. The purpose is to provide a blower.

  In order to achieve the above-mentioned object, the present invention is a duct-shaped active silencer that is divided into a plurality of small air passages, each of which has a microphone that detects sound waves and a speaker that emits sound waves. The active silencer is characterized in that the diameter of at least one small air passage is smaller than that of the other small air passages, thereby achieving the intended purpose.

  ADVANTAGE OF THE INVENTION According to this invention, the number of division | segmentation of an air path is small, the rise of the pressure loss of an air path can be suppressed, and the active silencer which can mute the high frequency noise, and a blower using the same can be provided. .

Side sectional view of the active silencer of Embodiment 1 of the present invention The top view of the active silencer of Embodiment 1 of this invention Sectional view showing a conventional active silencer A perspective view showing a conventional active silencer

  The active silencer according to claim 1 of the present invention is a duct-shaped active silencer that is divided into a plurality of small air passages and includes a microphone that detects sound waves and a speaker that emits sound waves in each of the small air passages. The diameter of at least one small wind path is smaller than the diameter of other small wind paths.

  This makes it possible to mute a part of high-frequency noise by using a small air passage having a smaller diameter than the other small air passages (hereinafter referred to as a small air passage) without increasing the number of divided air passages. Since the diameter of the small air passage other than the air passage is large, an increase in pressure loss due to the duct-shaped active silencer can be suppressed.

  Moreover, the blower according to claim 2 of the present invention includes a scroll-like casing having a suction port for sucking air and a discharge port for exhausting air, a blower unit having a centrifugal impeller and a motor, and the suction port of the casing. It is a blower in which the active silencer according to claim 1 is arranged, and has a configuration in which the diameter of the small air passage facing the tongue portion of the casing of the active silencer is smaller than the diameter of the other air passage.

  As a result, high-frequency noise generated from the tongue of the casing among the noise generated in the blower section is easily propagated to a small-diameter air passage having a high-frequency silencing capability, thereby enhancing the silencing effect of the active silencing device. There is an effect that can be.

(Embodiment 1)
Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 and 2.

  As shown in FIGS. 1 and 2, the blower 2 using the active silencer 1 of the present embodiment includes a scroll-like casing 5 having a suction port 3 for sucking air and a discharge port 4 for exhausting air, and a centrifugal An impeller 6 (in this embodiment, a diameter of 200 mm, the number of blades is 50) and a blower unit 8 provided with a motor 7 for rotating the centrifugal impeller 6 are provided. It arrange | positions so that one end may oppose the suction inlet 3 of the casing 5 of 8. As shown in FIG.

  The square duct-shaped active silencer 1 is internally divided into four rectangular small air passages 9, and each of the small air passages 9 has a reference microphone 10 for detecting noise propagating in the small air passage 9, and a reference microphone 10. A speaker 11 that emits sound having a phase opposite to that detected by the noise, an error microphone 12 that detects noise attenuated by the sound emitted from the speaker 11, and an arithmetic controller (not shown) that connects and controls them. Prepared). Of the four small air passages 9, the cross section of three small air passages 9 is a rectangle with one side of 150 mm and the other side is 120 mm, and the cross section of one small air passage 9 is a square with one side of 80 mm. The aperture is smaller than that of the passage 9 (this small air passage is hereinafter referred to as a small air passage 13). The frequency f that can be silenced by each small air passage 9 of the active silencer 1 is determined by f <sonic speed / (2L) depending on the width L of the small air passage 9, so the upper limit of the frequency that the small air passage 13 can mute is It is higher than other small wind paths 9. The upper limit frequency of the small-diameter air passage 13 is 2156 Hz when the sound speed is 345 m / s, and the other small air passage 9 is 1150 Hz. The small-diameter air passage 13 is disposed so as to face the tongue portion 14 of the casing 5.

  With the above configuration, when the centrifugal impeller 6 is rotated by the motor 7 of the blower unit 8 (in this embodiment, the rotation speed is 1000 rpm), the centrifugal impeller 6 boosts the pressure from the inlet 15 of the active silencer 1. The air that has flowed into the small air passage 9 flows from the suction port 3 of the casing 5 into the blower 8 and is exhausted from the discharge port 4. At the same time, noise is released from the suction port 3 of the casing 5 of the blower 8. The noise includes noise having a frequency range such as wind noise, turbulent flow noise, excessive friction noise, and the tongue of the casing 5. There is an interference sound generated by the interference between the section 14 and the centrifugal impeller 6 and a peak sound due to its harmonics. The primary frequency of the interference sound generated by the interference between the tongue portion 14 of the casing 5 and the centrifugal impeller 6 is determined by the number of blades and the rotational speed, and is 833 Hz in the present embodiment, and the secondary frequency is doubled 1667 Hz. . Those noises propagate through the small air passages 9 of the duct-shaped active silencer 1 and are emitted from the inlet 15 of the active silencer 1. When the noise passes through each small air passage 9, the noise is reduced by the silencing effect of the active silencing device 1.

  At this time, part of the high-frequency noise that cannot be silenced by the other small air passages 9 can be silenced by the small-diameter air passage 13 having a high upper limit of the frequency that can be silenced. Moreover, since the diameter of the small air passages 9 other than the small air passage 13 is large, the total cross-sectional area of the small air passages 9 is sufficient with respect to the air volume blown by the air blowing unit 8 without increasing the number of divisions of the air passages. The area does not increase the pressure loss.

  Further, since the secondary frequency of the interference sound generated by the interference between the tongue portion 14 of the casing 5 and the centrifugal impeller 6 is 1667 Hz, the sound can be silenced only by the small-diameter air passage 13 of the active silencer 1. Since the small-diameter air passage 13 is disposed at a position facing the tongue portion 14 of the casing 5, the noise of the secondary frequency of the interference sound generated from the tongue portion 14 of the casing 5 easily propagates to the small-diameter air passage 13. Thus, the silencing effect of the active silencing device 1 can be enhanced.

  The active silencer and the blower using the active silencer according to the present invention are useful for home or store exhaust facilities where quietness is required.

DESCRIPTION OF SYMBOLS 1 Active silencer 2 Air blower 3 Suction port 4 Discharge port 5 Casing 6 Centrifugal impeller 7 Motor 8 Air blower 9 Small air path 10 Reference microphone 11 Speaker 12 Error microphone 13 Small-diameter air channel 14 Tongue 15 Inlet

Claims (2)

A duct-shaped active silencer that includes a microphone that detects sound waves and a speaker that emits sound waves in each of the small air paths, the inside of which is divided into a plurality of small air paths. An active silencer characterized by being smaller than the diameter of the small air passage. A scroll-like casing having a suction port for sucking air and a discharge port for exhausting air, a centrifugal impeller, and a blower unit having a motor are provided, and the active silencer according to claim 1 is arranged at the suction port of the casing. The blower according to claim 1, wherein a diameter of the small air passage facing the tongue portion of the casing of the active silencer is smaller than a diameter of another air passage.

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