JPH07160280A - Electronic silencer of air conditioning system - Google Patents

Abstract

PURPOSE:To provide a silencer capable of positively erasing low-frequency components of noises down to 500Hz generated from the rotating parts of an air conditioning apparatus by executing control of an open loop type. CONSTITUTION:This air conditioning system is constituted by installing a microphone 7 in the central part of feed air flow of an air conditioning system for feeding the conditioning air from the air conditioner 1 incorporating an air feed fan 2 through an air feed chamber 5 and an air feed duct 4 to an air conditioning zone and installing a speaker 8 on the downstream side of the feed air flow of this microphone 7. This electronic silencer for the air conditioning system executes the control of the opened loop so as to create the secondary sound shifting the phase of the primary sound detected by the microphone 7 by 180 deg. and to silence the low-frequency components down to 500Hz by emitting these sounds from the speaker 8, thereby superposing the primary sound and the secondary sound. The silencer is so constituted that the delay time since the detection of the primary sound by the microphone 7 until the emission of the secondary sound by the speaker 8 is the difference between the time before the sound is propagated up to the silencing center where the primary sound from the microphone 7 and the secondary sound are superposed and the time since the primary sound is detected by the microphone 7 until the secondary sound is transmitted to the silencing center.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner for supplying air into a room from an air outlet via an air supply duct installed in a ceiling of a building or the like, and propagates indoors via the air supply duct. The present invention relates to an electronic muffler for air conditioning equipment that prevents noise.

[0002]

2. Description of the Related Art In office buildings and the like, it is most common to produce conditioned air with an air conditioner installed in a machine room or the like and supply this to the room through an air supply duct installed in the ceiling or the like. ing. In this case, the noise generated in the movable part of the air conditioning equipment may propagate to the room through the air supply duct, and may cause noise in the room.

In order to prevent noise from passing through such an air supply duct, conventionally, the surroundings of an air conditioner, which is a noise source, are surrounded by a material having a large sound absorption coefficient (a material having a low transmittance) to insulate the sound. ， Are the sound absorbing material attached to the duct, especially on the elbow?
Or a muffler was installed.

[0004] Such sound insulation / silence technology is 1000H
It was intended for noise with a relatively high frequency component of z or higher, and was effective for noise with a high frequency component.
There was almost no effect on noise of low frequency components below Hz.

On the other hand, in the above-mentioned building air conditioning, noise generated from the rotating part of the air supply fan (often installed in the air conditioner) is the main. The part of the noise generated from the fan rotating part that has the largest energy is the main mode corresponding to the rotation cycle. For example, 2700 rp
The main mode of noise of a fan rotating at m appears at 45 Hz. The generated noise is mainly the overtone of this main mode. Further, the farther away from the noise source of the fan rotating section, that is, the further to the downstream side of the duct, the reflected sound and the non-linear component overlap, and further the plate vibration of the duct and other non-linear components also overlap.

As a technique for eliminating the duct noise, there has been proposed a method of hitting an antiphase sound having the same sound pressure level as that of the sound in the duct and having a completely antiphase relationship. This is called active noise control, which uses the well-known physical law of "sound synthesis", but the controllability has been improved by the recent development of electronic devices and acoustic technology, and its muffling effect is also improved. It started to improve.

The conventionally proposed active noise control for duct noise is shown in FIGS. As shown in FIG. 10, the speaker 5 is provided upstream of the microphone 51 installed in the air supply duct 50.
2 is installed, and the noise that minimizes the noise in the air supply duct 50 detected by the microphone 51 is generated by the electronic filter 53.
It is a silencer for performing so-called closed loop type feedback control, which is configured so as to cancel out sounds by irradiating the created sounds from the speaker 52.

In the structure shown in FIG. 11, microphones 56 and 57 are installed at two locations, upstream and downstream, in the air supply duct 55, and a speaker 58 is installed between them. The electronic filter 59 produces a sound that minimizes the detected noise in the air supply duct 55, and the produced sound is produced by the speaker 58.
The so-called closed-loop feed-forward control is configured so that the sounds are canceled by irradiating from each other, and the sound in the air supply duct 55 after being muted is detected by the microphone 57 on the downstream side and fed back. It is a muffling device that performs.

[0009]

The noise reduction target of the noise reduction device in the air conditioning equipment described above is noise having the fundamental harmonic vibration as the main component. Therefore, when trying to muffle higher-order harmonic vibrations having different vibration modes with the conventional noise reducer as shown in FIG. 10 and FIG. 11, since it is closed loop type feedback control or closed loop type feedforward control, On the contrary, control was often unstable.

In particular, the noise generated from the rotating part of an air conditioner equipment such as an air conditioner or a fan has its component determined by the rotation frequency of the equipment, so the frequency of the noise should be known by analyzing the rotation frequency of the equipment. In addition, since air conditioners generally operate at a constant number of revolutions, a closed-loop type that controls the capacity of an electronic filter for delaying signals by catching changes in frequency and sound pressure with a microphone every time as in the past. The circuit that performs feedback or feedforward control is complicated.

Therefore, according to the present invention, by performing the open loop type control, 500H generated from the rotating part of the air conditioning equipment
An object of the present invention is to provide a silencer capable of positively eliminating low frequency components of noise up to z.

[0012]

According to the present invention, in an air conditioner for supplying conditioned air from an air conditioner equipped with an air supply fan to an air conditioning zone through an air supply chamber and an air supply duct, A microphone is installed in the center, and a speaker is installed downstream of the microphone in the air supply, so that the primary sound detected by the microphone is
It creates a secondary sound whose phase is shifted by 0 degree and irradiates this from a speaker to superimpose the primary sound and the secondary sound to mitigate low frequency components up to 500 Hz. Therefore, the delay time from the detection of the primary sound by the microphone to the irradiation of the secondary sound by the speaker is defined as the time until the sound is propagated from the microphone to the silencing center where the primary and secondary sounds are superposed. Provide an electronic muffler for air conditioning equipment configured to have a difference from the time from the detection of the primary sound by the microphone to the transmission of the secondary sound to the muffling center.

[0013]

According to the electronic muffler of the present invention, an open loop feedforward control system is used for noise (primary sound) generated from a rotating part of an air conditioner operating at a constant rotation speed. The noise detected by the microphone and the secondary sound having the opposite phase with the phase shifted by 180 degrees are generated, and the primary sound and the secondary sound are superposed on each other to cancel each other, thereby performing stable silencing.

[0014]

FIG. 1 shows an embodiment of the present invention.
Is an air conditioner, 2 is an air supply fan in the air conditioner 1, and 3 is a heat exchanger. The conditioned air produced by the air conditioner 1 is sent to the air-conditioning zone (not shown) through the air supply duct 4, but the air conditioner 1 and the air supply duct 4 pass through the rectangular air supply chamber 5. Connected.

In the illustrated example, the air supply fan 2 includes the heat exchanger 3
It is installed on the downstream side of the air supply fan 2, and the air supply air from the air outlet 6 of the air supply fan 2 is directly discharged to the center of the air supply chamber 5, and the air supplied into the air supply chamber 5 is After flowing parallel to the chamber wall, it flows into the air supply duct 4.

A microphone 7 is provided upstream of the air supply duct 4.
Is installed. On the other hand, a speaker 8 is attached to the air supply duct 4 downstream of the microphone 7 at a position where sound can be directly emitted to the air supply.

Next, the open-loop feedforward control will be described with reference to FIG. Microphone 7
Noise (primary sound) in the air supply duct 4 at its installation position
Is detected, and the detected value is input to the electronic device 10. In the electronic device 10, the delay time (from the position of the primary sound to the position of the secondary sound) corresponding to the straight line distance from the position of the primary sound to the position (the position of the secondary sound, for example, point 11 in FIG. 1) for which predetermined silencing is aimed. In addition to adjusting the time at which the sound is transmitted to the position, a sound with a phase completely opposite to that of the primary sound is produced and output to the audio amplifier 12. The audio amplifier 12 adjusts this input signal to the same sound pressure level as the secondary sound and outputs it to the speaker 8, so that the secondary sound is emitted from the speaker 8 after a delay time has elapsed.

As shown in FIG. 3, the delay time given by the electronic device is the time A until the sound propagates in the distance from the installation position of the microphone 7 to the silencing center point 11 in the air supply duct 4 and the microphone 7. It is the difference in the processing time B from the detection of the primary sound to the transmission of the secondary sound produced by the electronic device 10 to the silencing center point 11, and is expressed by the following equation. Delay time = A-B (1)

According to the above, at the position 11 of the secondary sound, the noise (primary sound) propagated from the fan 2 side into the air supply duct 4 and the sound pressure level which is the same as the noise are 180 degrees phase. Will collide with the displaced secondary sound of the opposite phase. The noise propagated from the side of the fan 2 into the air supply duct 4 is dominated by the main mode corresponding to the rotation cycle of the fan 2 and its overtones. When the sound in this low frequency range collides with the sound in the opposite phase, it cancels out and is muted. Therefore, the amount of the low frequency noise transmitted to the air supply duct 4 is reduced.

Along with this, even at the downstream side (air outlet side) of the air supply duct 4, high-frequency sound generated by repeated reflection and attenuation of the sound of the main mode and vibration of the duct plate are generated. The vibration noise generated by this is also reduced, and noise is prevented from being brought to the air conditioning zone. Thus, the open-loop feedforward control method provides stable silencing that is insensitive to higher harmonic vibrations.

It should be noted that the propagation time A and the processing time B in the above equation (1) show different values due to different temperatures and different sound velocities in the summer and winter, and therefore the equation ( The delay times determined in 1) are different values.
Therefore, if this delay time is configured to be changeable in summer and winter, it is convenient because control can be performed according to each season. In addition, the temperature of the conditioned air produced by the air conditioner 1 is normally only switched between two stages, the summer temperature and the winter temperature, so the delay time can be changed to the two stages for summer and winter. It is enough if you configure it.

It should be noted that it is advisable to provide an anti-vibration mechanism in the air supply duct 4 for preventing howling that occurs as a result of self-excited oscillation between the microphone 7 and the speaker 8 to improve the sound deadening effect. FIG. 4 shows an example of an anti-vibration mechanism. A directional microphone 7 is installed so as to detect noise toward the upstream side of the air supply duct 4, and the microphone 7 is fixed by an anti-vibration material 15. As a result, the secondary sound emitted from the speaker 8 is prevented from being picked up by the microphone 7 as much as possible to prevent howling. Further, the duct wall around the supporting portion of the microphone 7 is formed of a steel plate having a plate thickness thicker than usual, and is firmly fixed to the inspection port for maintenance to prevent plate vibration, and the inner wall of the air supply duct 4 is made of glass wool. Vibration is prevented from being transmitted to the microphone 7 by mounting the vibration isolator 16 made of.

Further, since the air flow produced by the air conditioner 1 directly contacts the microphone 7, the microphone 7 may detect wind noise. Therefore, the muffler shown is equipped with a windshield that prevents the microphone 7 from detecting wind noise.

Further, a conduit 17 for directing the secondary sound emitted from the speaker 8 is provided, and at the mute position 11,
The primary sound and the secondary sound with the opposite phase are sure to collide with each other.

Although the microphone 7 is installed upstream of the air supply duct 4 in FIG. 1, the microphone 7 is installed inside the air supply chamber 5 as compared with the microphone 7 as shown in FIG. Downstream air supply duct 4
It is of course possible to attach the speaker 8 to the. In either case, it is advisable to install the microphone 7 at the center of the air supply created by the air conditioner 1. A microphone 7 is installed on the upstream side of the air supply, a speaker 8 is attached on the downstream side of the microphone 7, and a secondary sound obtained by shifting the phase of the primary sound detected by the microphone 7 by 180 degrees is emitted from the speaker 8. It is a feature of the present invention that open-loop control is performed to mute the sound.

Now, the silencing effect of the silencing device of the present invention will be described in comparison with the case where no silencing is performed. First, referring to FIG. 6, the speaker 8 is connected to the conduit 17 as described in FIG.
In the muffling device with the attached,
The comparison data with the case where the sound is not muted are shown. As shown in the figure, it can be seen that the low frequency of 500 Hz or less was effectively silenced.

FIG. 7 shows comparison data between the case where the noise is eliminated and the case where the noise is not eliminated in the muffler without the conduit 17. Although it can exhibit the sound deadening effect,
It was found that the effect was less than that of the muffler with the conduit 17 attached.

Next, referring to FIG. 8, in the silencer in which the microphone 7 is fixed by the vibration isolator 15 as described in FIG.
The following shows the comparison data between the case where the sound is muted and the case where the sound is not muted. As shown in the figure, it can be seen that the low frequency of 500 Hz or less could be effectively silenced.

FIG. 9 shows the comparison data between the case where the sound deadening device is not fitted with the vibration isolator 15 and the case where the sound deadening is not carried out. Although it can exhibit the sound deadening effect,
It can be seen that the effect is less than that of a muffler equipped with a vibration isolation mechanism.

[0030]

According to the present invention, when duct air-conditioning is performed, noise can be eliminated under the noise source, the device is simple, and even if the air supply duct is branched into a plurality of places, It is economical because a silencer is sufficient. In addition, stable and easy-to-manage silencing can be performed simply by changing the delay time between summer and winter.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of equipment arrangement showing an embodiment of the device of the present invention.

FIG. 2 is a block diagram of a silencer.

FIG. 3 is an explanatory diagram of a delay time.

FIG. 4 is a schematic cross-sectional view of the device layout of the silencer.

FIG. 5 is a schematic cross-sectional view of equipment arrangement showing another embodiment of the device of the present invention.

FIG. 6 is a graph showing a sound deadening effect when a conduit is attached.

FIG. 7 is a graph showing a sound deadening effect when a conduit is not attached.

FIG. 8 is a graph showing a sound deadening effect when image stabilization processing is performed.

FIG. 9 is a graph showing the sound deadening effect when no image stabilization processing is performed.

FIG. 10 is a block diagram of a conventional silencer.

FIG. 11 is a block diagram of a conventional silencer.

[Explanation of symbols]

 1 Air Conditioner 2 Air Supply Fan 4 Air Supply Duct 5 Air Supply Chamber 6 Air Supply Discharge Port 7 Primary Sound Detection Microphone 8 Speaker 10 Electronic Device 12 Audio Amplifier

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G10K 11/16

Claims (5)

[Claims] 1. An air conditioner for supplying conditioned air to an air conditioning zone from an air conditioner equipped with an air supply fan through an air supply chamber and an air supply duct, wherein a microphone is installed at a central portion of the air supply and A speaker is installed on the downstream side of the air supply than the microphone, and the primary sound detected by the microphone is 180 degrees phase-shifted to create a secondary sound, and the secondary sound is emitted from the speaker to overlap the primary sound and the secondary sound. In total, it controls the open loop so as to mute low frequency components up to 500 Hz. The delay time from the detection of the primary sound by the microphone to the irradiation of the secondary sound by the speaker The time until the sound is propagated to the center of the muffling where the primary sound and the secondary sound are superposed, and the secondary sound after the primary sound is detected by the microphone. An electronic muffler for air conditioning equipment that is configured to have a difference from the time until it is transmitted to the muffling center. 2. The electronic silencer for an air conditioner according to claim 1, wherein the delay time from the detection of the primary sound by the microphone to the irradiation of the secondary sound by the speaker is changed in the summer and winter. . 3. The electronic muffler for air conditioning equipment according to claim 1, wherein the microphone is equipped with a windshield for avoiding wind noise. 4. The electronic muffler for an air conditioner according to claim 1, further comprising a vibration isolation mechanism for preventing vibration of the air supply duct from being transmitted to the microphone. 5. An electronic device for air conditioning equipment according to claim 1, wherein a conduit for directing a secondary sound from a speaker is provided at a silencing center where the primary sound and the secondary sound are superimposed. Silencer.