JPH02225981A - Noise suppressor for cooling device - Google Patents

Abstract

PURPOSE:To make possible the simplification of active control and the improvement of precision of control by arranging a compressor on one side in the longitudinal direction of a machine house while a radiation opening part is provided on the other side to form a noise suppressing speaker of a flat shape so as to arrange its longitudinal direction in the neighborhood of the radiation opening part at right angles to the longitudinal direction of the machine house. CONSTITUTION:Each dimension of depth, width and height of three dimensional direction in a machine house is made D, W and H respectively, for instance, a width directional dimension W is set larger than the other dimensions D and H to constitute so as to form the stationary wave of a sound in a machine house 17 of a primary mode alone. In addition, a compressor 18 is arranged at one side of the longitudinal direction of the machine house 17 while a radiation opening part 21a is provided at the other side to lengthen a distance between a noise source (compressor 18) and the radiation opening part 21a to form a noise suppressing speaker 23 of a flat shape so as to arrange its longitudinal direction in the neighborhood of the radiation opening part 21a in a state at right angles to the longitudinal direction (width direction) of the machine house 17.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a silencer used in a cooling device such as a refrigerator;
In particular, the present invention relates to a silencer for a cooling device that actively cancels out noise from a machine room housing a compressor.

(Prior Art) Cooling devices that use compressors, such as refrigerators, are often installed in the living space of ordinary households.
Moreover, since they are operated continuously regardless of the season, reducing noise has become an issue. in this case,
The most problematic noise source for refrigerators is the noise from the machine room in which the compressor and the piping system connected thereto are housed. That is, in the machine room, the compressor itself generates relatively large noises (compressor motor operating noise, fluid noise due to compressed gas, mechanical noise from movable mechanical elements of the compression mechanism, etc.), and the The piping system also generates noise due to its vibrations, and such machine room noise accounts for most of the refrigerator noise. Therefore, suppressing the noise from the machine room greatly contributes to reducing the noise of the refrigerator as a whole.

Therefore, conventional measures to reduce noise from the machine room include reducing the noise of the compressor itself (for example, using a rotary compressor), improving the vibration-proof support structure of the compressor, and improving the shape of the piping system. By doing this, vibration damping in the vibration propagation path can be achieved, or
By arranging sound absorbing members and sound insulating members around the compressor and the piping system, attempts are being made to increase the amount of absorption in the machine room and to increase the noise transmission loss.

(Problem to be Solved by the Invention) Generally, in the machine room of a refrigerated city, there are multiple openings for heat dissipation because it is necessary to release the heat generated by the drive of the compressor to the outside. Noise will leak outside through the opening.

For this reason, the conventional noise reduction measures mentioned above naturally have their limits, and the noise level reduction effect is at most 2 dB (A
) can only be expected.

On the other hand, in recent years, with the development of electronics application technology, especially acoustic data processing circuits and acoustic control technology, the application of active noise control technology, which reduces noise using sound wave interference, has attracted attention. has been done. That is, this active control basically converts the sound from the noise source into an electrical signal using a sound receiver installed at a specific position, and
By operating a silencing speaker based on a signal processed by a computing unit from this electric signal, the sound generator emits the original sound (sound from the noise source) at the opposite phase at the control target point and at the same wavelength and distance. The idea is to attenuate the original sound by generating an artificial sound with a certain amplitude and causing the artificial sound to interfere with the original sound.

However, when such active noise control is used to reduce machine room noise in a refrigerator, the machine room is not sealed and the noise generated within the machine room is freely diffused in three dimensions. As a result, there is a problem that the active control mode is extremely complicated, and the reality is that the practical application of active noise control in refrigerators is uncertain.

The present invention has been made in view of the above circumstances, and its purpose is to perform active control to cancel noise generated in a machine room in response to the drive of a compressor by interference with artificial sound. An object of the present invention is to provide a silencing device for a cooling device that can simplify the process and improve control accuracy.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention actively reduces the sound generated by the drive of a compressor housed in a machine room by interfering with artificial sound. In the noise damping device for a cooling device, the machine room is configured such that the standing wave of the sound only exists in a first-order mode below the frequency band to be canceled, and The compressor is disposed on one side, while a heat radiation opening is formed on the other side, and the noise-reducing speaker is formed in a flat shape so that its longitudinal direction is perpendicular to the longitudinal direction of the machine room. The heat dissipation opening is arranged in the vicinity of the heat dissipation opening.

(Function) For example, in the case of a refrigerator, which is a typical example of a cooling device, in the case of a refrigerator having an internal membrane structure, the acoustic level of the noise generated in response to the drive of the compressor is 700% as shown in FIG.
It develops the property that it becomes larger in the band below about Hz and in the band of 1°5 to 5 KHz. Among the noises corresponding to each of these bands, those on the high frequency side can be easily muffled by conventional noise reduction techniques using sound absorbing members or the like. Therefore, when actually performing active noise control, it is sufficient to set the noise on the low frequency side to the target frequency (in this case, approximately 700 Hz or less). In this way, when the target frequency is about 700 Hz or less, two of the height, depth, and width directions in the machine room are shorter than the principle sound wavelength (about 50 cm when the sound speed is 340 m/s).
If the remaining dimension in one direction is set to be longer than the above wavelength, only the first mode of the standing wave of noise generated in the machine room will be established. With this configuration, the sound generated inside the machine room can be regarded as a one-dimensional plane traveling wave, and the sound from the compressor can be muffled at the heat radiation opening, which is the outlet to the outside. Active control that attempts to muffle the artificial sound from the public speaker by interfering with the artificial sound can now be performed with good precision and accuracy both theoretically and technically.

Moreover, in this case, by arranging the compressor on the longitudinal direction of the machine room - the blade side, and forming the heat radiation opening on the other side, the noise source (compressor) and the heat radiation opening (the target point for silencing) can be arranged. ), the propagation time for the compressor noise to reach the heat dissipation opening is 1+
(see Fig. 2), and then form a noise-reducing speaker into a flat shape so that its longitudinal direction is perpendicular to the longitudinal direction of the machine room in the vicinity of the heat dissipation opening. For example, compared to the case where a circular sound-muffling speaker is used, the center of the sound-muffling speaker can be moved away from the noise source and closer to the heat dissipation opening, which reduces the output from the sound-muffling speaker. The propagation time t for the artificial sound to reach the heat radiation opening can be shortened. Therefore, it is possible to lengthen the time Δt MAX that the arithmetic unit can spend on arithmetic processing, which allows for a margin in arithmetic processing time and facilitates active control.

Here, ΔtMAX ""tl -tl-t),
tl is the propagation time for the compressor noise to reach the receiver.

Moreover, in this case, instead of reducing the diameter of the silencer speaker, its shape is flattened, so the effective area of the diaphragm of the silencer speaker can be secured, and this silencer speaker reduces out-of-phase sound. It can faithfully reproduce up to the frequency range and evenly mute the low frequency range.

(Example) An example in which the present invention is applied to a refrigerator will be described below. Prior to this, the principle of silencing by active control used in this example will be briefly described.

In the fourth factor, 1 is a noise source such as a compressor, 2
indicates the control target point for which noise is desired to be muted, and noise source 1
A sound receiver 3 such as a microphone converts the sound from the source into an electrical signal, and this electrical signal is processed through a computing unit 4 including a filter, etc., and the processed signal drives a silencing speaker 5. It has become.

That is, the sound generated by the noise source 1 is transmitted to Sl, the noise-reducing speaker 5
The sound generated by S2. The sound received by the sound receiver 3 is R1, the sound at the control target point 2 is R2, and the acoustic transfer functions between the above sound output and human power points are Tll and T21.
．． TI2. When T22 is assumed, the following equation holds true as a two-man power two-output system.

Therefore, the sound s2 that the silencer speaker 5 should generate is, from the above equation, S2 - (-TI2・RI+T1.1R2)
/(Tll-T22-T12T21); however, in this case, since the goal is to make the sound level at the control target point 2 zero, it can be set as R2-0. As a result, S2 ball R1φT12/(T12chiT
21-Tll@T22). As can be understood from this equation, in order to make the sound R2 at control target point 2 zero,
The sound R1 received by microphone 3 is F-T12/(T12・T21-T11T22
) The sound level at the control target point 2 can be theoretically reduced to zero by generating the processed sound S2 through the filter.

1 to 3 show a first embodiment of the present invention, which will be described below.

That is, in FIG. 3 showing the overall configuration of the refrigerator, 11 is a refrigerator main body, and inside this, from the top, there are freezer compartments 12. A refrigerator compartment 13 and a vegetable compartment 14 are provided. 1
5 is a cooler disposed at the back of the freezer compartment 12, and 16 is a fan that directly supplies cold air generated by the cooler 15 to the freezer compartment 12 and the refrigerator compartment 13. 17 is a machine room formed at the lower part of the back side of the refrigerator main body 11, and inside this is a rotary type compressor 18. A condenser vibrator 19 and a defrosting water evaporation device 20 using so-called ceramic fins are housed. In this case, as shown in FIG. 1, the compressor 18 is arranged on one longitudinal side of the machine room 17 (on the right side when viewed from the back side). On the other hand, the machine room cover 21 that closes off the back side of the machine room 17 has a
An elongated rectangular heat dissipation opening 21a extending in the vertical direction is formed. Thereby, the machine room 17 is in a closed state leaving the heat radiation opening 21a.

The machine room cover 21 is made of a material (M is a metal such as iron) that has excellent thermal conductivity and high sound transmission loss.

Reference numeral 22 denotes a sound receiver, such as a microphone, placed in the machine room 17. This is attached to the side surface 11a located near the compressor 18 and farthest from the heat radiation opening 21a. It is provided to convert the sound from the compressor 18, which is a noise source, into an electrical signal. Reference numeral 23 denotes a noise-reducing speaker placed in the machine room 17, which is used, for example, on the back wall of the machine room 17 (the
(equivalent to the bottom wall portion of the heat dissipation opening 21H). In this case, the silencer speaker 2
3 is formed into a flat shape, such as an ellipse or an ellipse,
It is attached so that its longitudinal direction is perpendicular to the longitudinal direction of the machine room 17. As a result, the center of the silencing speaker 23 is brought as close as possible to the side surface 11b side (heat radiation opening 21a side) of the machine room 17, and the center of the silencing speaker 23 is separated from the noise source (compressor 18) and the microphone 22. I'm keeping it as far away as possible. The muffling speaker 23 is operated by a signal obtained by processing an electrical signal from the microphone 22 by a computing unit 24 (see FIG. 2). This is done based on the above-mentioned active control silencing principle.

Therefore, in the case of the refrigerator configured as described above, the noise level generated in the machine room 17 in response to the drive of the compressor 18 is in the band of about 700 Hz or less and in the range of 1.5 to 5 KH2, as shown in FIG. This state has the property of increasing in each band. Among the noise corresponding to each of these bands, the noise on the high frequency side can be attenuated by transmission loss in the machine room cover 21, etc.
The microphone 22 as described above can be muted by installing an appropriate sound absorbing member inside the package.
．． Active control of noise by the silencing speaker 23 and the computing unit 24 may be performed with a target frequency of 700 Hz or less.

In addition, when performing active noise control as described above, it is important to configure the noise in the machine room 17 so that it becomes a one-dimensional plane traveling wave, both theoretically and technically. This is important for easy and accurate execution. Therefore, in this embodiment, among the three-dimensional dimensions of the machine room 17, such as depth, width, and height, of W and H, for example, the dimension W in the width direction is determined from the other dimensions, H. Large setting (specifically, W = 600 ass D
-H-2001111) so that the standing wave of sound within the machine room 17 is established only in the primary mode. That is, for example, when the machine room 17 is assumed to be a rectangular cavity, the following equation holds true.

f-C conflict NXX +yY +zz /2 However, f
are the resonance frequencies (Hz), NX, Ny.

Nz is the th mode in each direction of x, y, z, Lx, Ly, L
z is the dimension in each of the x, y, and z directions (that is, W, H) in the machine room 17, and C is the speed of sound. Therefore, from the above formula, x
, the frequency fx of the first standing wave in each of the y and z directions,
fy and fz can be found.

That is, as described above, when the depth dimension D-2001, the width dimension W-600wms, and the height dimension H=200I1m, the frequency fX of the first standing wave in the X direction is Ny - Nz =0, sound speed C=340m/
In seconds, fx -340 (1, 2), /2 850H2, and similarly, the frequencies fy, fz of the first standing wave in the Y and Z directions are fl -3401, /2 -283Hz fz -3401, /2 = 850Hz. As a result, the target frequency (-700H
7,) Below, the standing wave of noise in the machine room 17 is established only for the mode in the Y direction (width direction),
The noise within the machine room 17 can be considered as a one-dimensional plane traveling wave. Therefore, when silencing by active control of noise using the silencing speaker 23 or the like, theoretical handling of the wavefront becomes easy, and silencing control can be performed easily and accurately. 3.

Moreover, in this case, by arranging the compressor 18 on one side in the longitudinal direction of the machine room 17 and forming the heat dissipation opening 21a on the other side, the noise source (compressor 18
8) and the heat dissipation opening 21a (point to be controlled by the extinguisher 17) to increase the propagation time [1] for the noise of the compressor 18 to reach the heat dissipation opening 21a (see Fig. 2).
In addition, the silencer speaker 23 is formed into a flat shape so that its longitudinal direction is perpendicular to the longitudinal direction (width direction) of the machine room 17 in the vicinity of the heat dissipation opening 21a. Since the center of the silencer speaker 23 can be moved away from the noise source and closer to the heat dissipation opening 21a, compared to the case where a circular silencer speaker is used, for example, the center of the silencer speaker 23 can be moved closer to the heat radiation opening 21a. The propagation time t3 for the artificial sound outputted from the heat radiation opening 21a to reach the heat radiation opening 21a can be shortened. Therefore, the time Δt MAK that can be spent on the arithmetic processing by the arithmetic unit 24 can be increased, the arithmetic processing time can be increased, active control can be easily performed, and an improvement in the noise reduction effect can be expected.

Here, Δt MAX ” i H−t 2− t g
, and t2 is the propagation time until the noise from the compressor 18 reaches the microphone 22.

Moreover, in this case, the diameter of the silencer speaker 23 is not made small, but its shape is made flat, so that the effective area of the diaphragm of the silencer speaker 23 can be secured, and the silencer speaker 23 can faithfully reproduce out-of-phase sound down to the low frequency range, and can evenly muffle sound down to the low frequency range, improving noise reduction ability.

Of course, in this case, the machine room 17 is connected to the heat radiation opening 2.
Since it communicates with the outside through 1a, compressor 1
The temperature in the machine room 17 will not rise abnormally due to heat generated when the motor 8 is driven. In addition, machine room cover 2
1 is made of a material with excellent thermal conductivity,
The radiation efficiency of heat generated within the machine room 17 is improved, and from this point of view as well, the temperature rise within the machine room 17 can be suppressed to a low level.

Incidentally, in the above embodiment, the muffling speaker 23 is formed in an oval or elliptical shape, but it may be formed in a rectangular shape, for example, to have an eccentric shape.

In addition, the present invention is not limited to the embodiments described above and shown in the drawings. For example, the outdoor unit of an air conditioner or a refrigerated showcase may be applied as a cooling device to be silenced. Various modifications can be made without departing from the scope.

[Effects of the Invention] According to the present invention, as is clear from the above description, the machine room is configured so that only the first mode is established below the frequency band where the standing waves of noise are to be canceled, and the machine room is A compressor is placed on one side in the longitudinal direction, while a heat dissipation opening is formed on the other side, and a silencer speaker is placed on the other side.
Since it is formed into a flat shape and placed near the heat dissipation opening with its longitudinal direction perpendicular to the longitudinal direction of the machine room, noise generated in the machine room when the compressor is driven can be reduced. When carrying out active control in which the sound is canceled out by a signal sound from a silencing speaker, it is possible to simplify the active control and improve control accuracy.

Moreover, in this case, by arranging the compressor on one side in the longitudinal direction of the machine room and forming the heat dissipation opening on the other side, the noise source (compressor) and the heat dissipation opening (point to be controlled for noise reduction) are connected. By increasing the distance between them, the propagation time for compressor noise to reach the heat dissipation opening is increased, and on top of that, the silencer is formed into a flat shape so that its longitudinal direction is the longitudinal direction of the machine room. By arranging the center of the silencing speaker near the heat radiation opening at right angles to the noise source, the center of the silencing speaker can be moved away from the noise source and closer to the heat radiating opening. The propagation time for artificial sound to reach the heat dissipation opening can be shortened. Therefore, the time that the arithmetic unit can spend on arithmetic processing can be increased, and there is a margin in arithmetic processing time, and active control can be easily performed.

Moreover, instead of reducing the diameter of the silencer speaker,
Since the shape is flat, the effective area of the diaphragm of the noise-reducing speaker can be secured, and this noise-reducing speaker can faithfully reproduce out-of-phase sound down to the low frequency range, achieving an even muffling effect down to the low frequency range. be able to.

[Brief explanation of the drawing]

Figures 1 to 3 show an embodiment of the present invention, with Figure 1 being an exploded perspective view of the main parts, and Figure 2 showing the compressor, microphone, silencing speaker, and heat dissipation opening. A schematic plan view for explaining the arrangement relationship, and FIG. 3 is a longitudinal sectional side view of the refrigerator. Further, FIG. 4 is a schematic configuration diagram showing the principle of silencing by active control, and FIG. 5 is a noise level characteristic diagram. In the figure, 11 is the refrigerator body, 17 is the machine room, 18 is the compressor, 20 is the defrosting water evaporation device, and 21 is the machine room cover.
21g is an opening for heat radiation, 22 is a microphone (sound receiver)
, 23 is a silencing speaker, and 24 is a computing unit. Applicant: Toshiba Corporation

Claims (1)

[Claims] 1. The compressor is housed in the machine room, and the sound generated by the drive of the compressor is converted into an electrical signal by a sound receiver, and the noise-reducing speaker is operated based on the signal processed by this electrical signal by an arithmetic unit. In the noise damping device for a cooling device, which actively cancels the sound radiated from the machine room to the outside, the standing wave of the sound makes the machine room primary in a frequency band below the frequency band to be canceled. The compressor is disposed on one side in the longitudinal direction of the machine room, while a heat radiation opening is formed on the other side, and the noise-reducing speaker is formed in a flat shape. A silencer for a cooling device, characterized in that the silencer is disposed in the vicinity of the heat radiation opening in such a manner that its longitudinal direction is perpendicular to the longitudinal direction of the machine room.