JPH02225959A - Noise suppressor for cooling device - Google Patents

Abstract

PURPOSE:To perform active control in real time by setting propagation time of a sound between a compressor and a heat dissipation opening par to be longer than a total of the propagation time of the sound between the compressor and a sound receiver, time required for evaluation in an evaluation unit, and the propagation time of the sound between a sound generator and the opening part. CONSTITUTION:A machine room 17 is constructed in a closed state leaving a heat dissipation opening part 21a as it is, and a size in one direction among three-dimensional sizes in the machine room 17 is set larger than the other sizes. Thereby, the title device is constructed so that only a primary mode is formed in a frequency band or less where a standing wave of a sound in the machine room 17 is to be cancelled out. Further, a positional relationship between a compressor sound receiver 22 and a controlling sound producer 23 is set so that propagation time of the sound between the compressor 18 and the heat dissipation opening part 21a is longer than the total time of propagation time of the sound between the compressor 18 and the sound receiver 22, time required for evaluation of a processed signal by the evaluation unit 22, and propagation time of the sound between the controlling sound producer 23 and the heat dissipation opening part 21a. Thereby, simplification of the active control and improvement of control accuracy are assured, and any noise is reduced by performing the active control in real time.

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 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 refrigeration (h) is the noise from the machine room where the compressor and the piping system connected to it are housed. In addition to generating noise (compressor motor operating noise, fluid noise due to compressed gas, mechanical noise from movable mechanical elements in the compression mechanism, etc.), the piping system connected to the compressor also generates noise due to its vibration. Such machine room noise accounts for most of the refrigerator noise. Therefore, suppressing the noise from the machine room will greatly contribute to reducing the noise of the entire refrigerator.

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
BACKGROUND ART By arranging sound absorbing members and sound insulating members around the compressor and piping system, it is attempted to increase the amount of absorption in the machine room and increase the noise transmission loss.

(Problem to be Solved by the Invention) Generally, the machine room of a refrigerator is provided with multiple openings for heat dissipation due to the need to release heat generated by the compressor to the outside. Noise will leak outside.

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 the control sound generator based on the signal processed by the electric signal by the sound generator, the original sound (sound from the noise source) is emitted from the sound generator in an opposite phase at the control target point, and with the same wavelength and same wavelength. 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 leaks freely in three-dimensional directions. 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.
] The aim is to simplify active control and improve control accuracy when performing active control that cancels the noise generated by compressor drive in an unsealed machine room by interference with artificial sound. It is an object of the present invention to provide a silencing device for a cooling device that can perform active control in real time and fully exhibit a noise reduction effect.

[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 reduction device for a cooling device, the machine room is configured in a closed state leaving an opening for heat dissipation, and the dimensions in one of the three-dimensional dimensions in the machine room are set in the other direction. By setting the dimensions to be larger than the dimensions of the compressor sound receiver and the control sound generator, the standing wave of the sound in the machine room is configured so that only the primary mode is established below the frequency band to be canceled. The positional relationship is determined by the sound propagation time between the compressor and the heat radiation opening, the sound propagation time between the compressor and the sound receiver, the time required for processing the processing signal by the arithmetic unit, and the control sound generator and h'l. This is set so that the relationship with the propagation time between the heat openings is longer than the total time.

(Function) For example, in the case of a refrigerator, which is a typical example of a cooling device, the sound level of the noise generated in response to the drive of the compressor is 700,000 yen as shown in Fig. 6.
The property that H increases in the band below about Hz and in the band from 1.5 to 5 KHz is defined as H. 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 higher, two directions of the height, depth, and width inside the machine room should be shorter than the wavelength of the original noise (about 50 ern if the sound speed is 340 m/s), and the remaining If the dimension in one direction is set to be longer than the above wavelength, only the primary mode of the standing wave of noise generated in the machine room will be established. In other words, by setting one dimension of the three-dimensional directions (height, depth, and width) in the machine room larger than the other dimensions, the frequency at which the standing waves of sound in the machine room are canceled ( target frequency)
It can be configured so that only the first-order mode is established below the band, and when configured in this way, the sound generated in the machine room can be regarded as a one-dimensional plane traveling wave, and the sound from the compressor can be considered as a one-dimensional plane traveling wave. Theoretically and technically, active control, which aims to muffle the sound by interfering with the artificial sound from the control sound generator at the heat dissipation opening that is the exit to the outside, has been achieved with good quality and precision. become able to do it.

At this time, the time it takes for the sound from the compressor to reach the receiver, and the electric i
The sum of the time for calculating processing number 1g based on number t and the time 1141 until the artificial sound output from the control sound generator based on the processing signal reaches hk hot opening is the above-mentioned Since the time for the sound from the compressor to reach the heat dissipation opening is shorter than the time it takes for the sound from the compressor to reach the heat dissipation opening, when the sound from the compressor and the sound from the control sound generator interfere with each other, the artificial sound is delayed and the connection is eliminated. The active noise as mentioned above 1. IJ control can be performed in real time. Of course,
Since the machine room is provided with a heat dissipation opening, there is no risk of the temperature in the machine room increasing by 5'ζ due to heat generated when the compressor is driven.

(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 Figure 5, 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 via a computing unit 4 including a filter etc., and the processed signal drives a sound generator 5 such as a speaker. It is supposed to be done. .

That is, the sound generated by the noise source 1 is S1, the sound generated by the speaker 5 is 82, the sound received by the receiver 3 is R1, the sound at the control target point 2 is R2, and the output of the above sound is and the acoustic transfer function between each of the input points as TH, T21 . T1
2. When T22 is assumed, the following equation holds true as a two-man power two-output system.

Therefore, the sound S2 that the speaker 5 should generate is, from the above equation, S2 − (−TI2・RI+TIl・R2)
/(T1.1 T22-T!21 T21); however, in this case, since the goal is to make the sound level at control target point 2 zero, it can be set as R2-0. As a result, S2-R1・TI2/(T
12・T21−Tll−T22). As can be understood from this equation, in order to make the force R2 at the control target point 2 zero, the sound R1 received by the microphone 3 is filtered by F-T12/(TI2 pupil T21-Tli T22). If the processed sound S2 is generated from the speaker 5, the sound level at the control target point 2 can be theoretically reduced to zero.

1 to 4 show a first embodiment of the present invention, which will be described below.

That is, in FIG. 4 showing the overall structure of the refrigerator, 11 is a refrigerator main body which is a main body of a cooling device, and inside this, from above, there are freezing compartments 12. A refrigerator compartment 13 and a vegetable compartment 14 are provided. 15 is a cooler disposed at the back of the freezer compartment 12, and 16 is a fan that directly supplies cold air generated by cooling 2=15 to the freezer compartment 12 and the refrigerator compartment 13. Reference numeral 17 denotes a machine room formed at the lower part of the back side of the refrigerator main body 11, and a rotary type compressor 18 is installed inside this machine room.
A condenser vibrator 19 and a defrosting water evaporator 20 using so-called ceramic fins are housed.

Now, as shown in FIG. 1 (here, the illustration of the condenser vibe 19 and the defrosting water evaporator 20 is omitted),
The machine room 17 has a rectangular opening only at its back, and this opening is closed by a machine room cover 21. At this time, the peripheral edge of the machine room cover 21 is airtightly attached to the opening edge of the machine room 17, and the left edge in FIG. An opening 21a is formed therein. That is, when the machine room cover 21 is attached, 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 with excellent thermal conductivity and high sound transmission loss (for example, metal such as iron).
It is formed in

Reference numeral 22 denotes a sound receiver such as a microphone arranged in the machine room 17, and this is arranged so as to face the compressor 18 from the side opposite to the heat radiation opening 21a (the right side in FIG. 1). It is provided to convert the sound from the compressor 18, which is noise λ, into an electrical signal. Reference numeral 23 denotes a speaker serving as a control sound device disposed in the machine room 17, which is, for example, a heat dissipation opening 2t in the back wall of the machine room 17 (corresponding to the bottom wall of the refrigerator body 11).
It is installed and supported in a buried manner in a part near a.

Then, the speaker 23 transmits the electrical signal from the microphone 22 to an arithmetic unit (reference numeral 24 in FIG.
The processing of the electrical signals described above is based on the above-mentioned silencing principle using active control. There is.

In this case, the compressor 18. The positional relationship between the microphone 22 and the speaker 23 is as shown in FIG. Propagation time t2 and the arithmetic unit 2
frL calculation time Δt of processed signal by 4 and speaker 2
3 and the sound propagation time t3 between the heat dissipation openings 21a, which is set to be longer than the total time (t2+Δ[+t3).

Therefore, in the case of the refrigerator configured as described above, the level of noise generated in the machine room 17 in response to the drive of the compressor 18 is within the band of approximately 700 Hz or less and 1.5 Hz as shown in FIG. It becomes a state in which it has the property of becoming larger in the band of ~5 KHz. 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., and can be easily attenuated by installing an appropriate sound absorbing member in the machine room 17. Since the sound can be muted, the above-mentioned microphone 22. Active noise control using the speaker 23 and the W W 24 targets 1.700 Hz or less. It can be done as a Tsu wave number.

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, the machine room 1 shown in FIG.
Each dimension in the three-dimensional direction (depth, width, and height) within 7.

Of W and H, for example, the width direction dimension W is other dimensions,
Set larger than H (specifically, W-60OLleSD
-H=200msl; : setting), the standing wave of sound in the machine room 17 is configured to be 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−X, X + Ny I, y
+(Nz/l,z)2/2 However, f is the resonance frequency (
Hz), Nx, Ny.

N7. is the rotation mode in each direction of x, y, z, LX, Ly
, Lz are the dimensions 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 equation, the frequency f of the first standing wave in each direction of X, ¥, and 2
++, fy, and fz can be found.

That is, as mentioned above, the depth dimension D-20011 width.
J゛ method W600sa+, height dimension H=20. If it is set to Osv, the constant /
1: Wave frequency fx is Ny-, NZ-0, sound speed C-
Assuming 340 m/sec, fχ-340,2)''/2 850Hz, and similarly, the frequencies fy and fz of the first standing wave in the Y and Z directions are fy=340 1 0.6)/2=283 H
z fz −34010,2) /2 850Hz. As a result, the target frequency (-700H
z) In the following, the standing wave of noise in the machine room 17 is valid only for the mode in the Y direction (width direction), and the noise in the machine room 17 can be regarded as a one-dimensional plane traveling wave. can. Therefore, when silencing noise by active noise control using the speaker 23 or the like, it becomes easy to theoretically handle the wavefront, and the silencing control can be performed with high precision. At this time, the time t required for B from the compressor 18 to reach the microphone 22
2, time Δt for converting the sound into an electrical signal and calculating a processed signal in the calculator 24 based on the electrical signal, and heat dissipation of the artificial sweat output from the speaker 23 based on the processed signal. The total time t3 for the sound from the compressor 18 to reach the heat radiation opening 21a is shorter than the time t1 for the sound to reach the heat radiation opening 21a.
When the sound from the compressor 18 and the two sounds from the speaker 23 are made to interfere, there is no risk of a delay with the two sounds, making it possible to perform active noise control in real time as described above. .

Of course, in this case, the machine room 17 communicates with the outside through the heat dissipation opening 21a, so the temperature inside the machine room 17 will not rise abnormally due to heat generated when the compressor 18 is driven. In addition, since the machine room cover 21 is made of a material with excellent thermal conductivity, the heat dissipation efficiency of the heat generated within the machine room 17 is improved, and this also leads to an increase in the temperature inside the machine room 17. can be kept low.

Note that the present invention is not limited to the embodiments shown in the drawings described above, and for example, an outdoor unit of an air conditioner or a refrigerated showcase may be applied as a cooling device serving as a noise-reducing pair. Various modifications can be made without departing from the spirit of the invention.

[5i! According to the present invention, as is clear from the above description, the machine room in which the compressor is housed is configured in a closed state leaving an opening for heat dissipation, and the three-dimensional direction in the machine room is By setting one dimension of each dimension larger than the other dimensions, the structure was configured such that only the first mode of the standing wave of sound in the machine room is established in the frequency band targeted for silencing. Simplification of active control and improvement of control accuracy when performing active control in which the noise generated in response to the drive of the compressor in a non-sealed machine room is canceled by the ta sound from the control sound generator. It is possible to realize this. Further, in the present invention, the positional relationship between the compressor, the sound receiver, and the control sound generator is determined by calculating the sound propagation time between the compressor and the heat radiation opening and the sound propagation time between the compressor and the sound receiver. Since the relationship was set to be longer than the total time between the calculation time required for processing r= by the machine and the sound propagation time between the control sound generator and the heat radiation opening, the above-mentioned noise active 1
．． It is possible to control in real time,
This makes it possible to fully exhibit the noise reduction effect.

[Brief explanation of the drawing]

Figures 1 to 4 show an embodiment of the present invention. Figure 1 is an exploded perspective view of the main parts, and Figure 2 is the arrangement of the compressor, sound receiver, and control sound generator. FIG. 3 is a schematic perspective view for explaining the -Nj relationship of the main parts, and FIG. 4 is a longitudinal cross-sectional view of the refrigerator. Further, FIG. 5 is a schematic configuration diagram showing the principle of silencing by active control, and FIG. 6 is a noise level characteristic diagram. In the figure, 11 is the refrigerator body, 17 is the machine, machine room, 18 is the compressor, 20 is the defrosting water evaporator, 21 is the machine room cover, 21a is the heat radiation opening, 22 is the microphone (sound receiver), 23 is the A speaker (control sound generator), and 24 indicate a computing unit.

Claims (1)

[Claims] 1. A compressor is housed in a machine room, and a sound receiver converts the sound generated when the compressor is driven into an electrical signal, and a processor converts the electrical signal into a signal based on the signal. In the noise reduction device for a cooling device, the sound emitted from the machine room to the outside is actively canceled by operating a control sounder when the machine room is closed leaving an opening for heat radiation. By setting one dimension of the three-dimensional dimensions in the machine room larger than the other dimensions, the standing waves of the sound in the machine room can be set at the frequency at which the noise is to be canceled. The configuration is such that only the first-order mode is established below the frequency band, and the positional relationship of the compressor, sound receiver, and control sound generator is such that the propagation timing of sound between the compressor and the heat radiation opening is adjusted to match the compressor and the sound receiver. The setting is such that a relationship is established that is longer than the total time of the sound propagation time between the instruments, the time required for processing the processed signal by the arithmetic unit, and the sound propagation time between the control sound generator and the heat radiation opening. A silencer for a cooling device characterized by: