JPH02223782A - Muffler for cooling device - Google Patents

Abstract

PURPOSE:To contrive the simplification of active control as well as the improvement of a control accuracy and to prevent the increase of unnecessary noise by a method wherein the stationary wave of sound in a machine room is constituted so that only the primary mode of the same is established in a frequency band area, which is the object of cancelling, while sound attenuating operation, effected by a sound generator for controlling, is effected during the operation of a compressor only. CONSTITUTION:A machine room 17 is constituted under a condition that the room is closed while leaving an opening 21a for heat dissipation and the size of one direction is designed so as to be larger than the sizes of other directions among three-dimensional directions so that only the primary mode of the stationary wave of sound in the machine room 17 is established in an area lower than a frequency band area which becomes the object of sound attenuation while sound attenuating operation, effected by a sound generator 23 for controlling, is effected during the operation of a compressor 18 only. As a result, the simplification of an active control as well as the improvement of a control accuracy may be realized upon effecting the active control, in which noise generated in accordance with the driving of the compressor 18 in the machine room 17 of non-sealed condition is cancelled by signal sounds from the sound generator 23 for controlling. On the other hand, the generation of unnecessary sound, which becomes the source of noise, when there is no noise of the compressor 18, may be prevented.

Description

[Detailed Description of the Invention] [Purpose 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 device N1 using a compressor For example, a refrigerator is often installed in the living room of a general household and is operated continuously regardless of the season. Noise reduction is one of the challenges. In this case, the most problematic noise source for the refrigerator is 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 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 increasing the amount of absorption in the machine room and increasing the noise transmission loss, by attenuating vibrations in the vibration propagation path, or by placing sound absorbing and sound insulating members around the compressor and piping system. Efforts are being made to achieve this.

(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 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 that uses sound wave interference to reduce noise has begun. Attention has been paid. In other words, 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 then uses a computer to process this electrical signal and generate a control signal based on the signal. By operating the sound generator, the sound generator generates an artificial sound that has the opposite phase, the same wavelength, and the same amplitude as the original sound (sound from the noise source) at the control target point, and the artificial sound and the original sound The idea is to attenuate the original sound by causing it to interfere.

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, and its purpose is to perform active control in which the noise generated in response to the drive of a compressor in an unsealed machine room is canceled by interference with artificial sound. To provide a silencing device for a cooling device, which can simplify the active control and improve the control accuracy, and can prevent an unnecessary increase in noise due to the above-mentioned active control being performed unnecessarily when the compressor is stopped. It is in.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above object, the present invention actively activates the sound generated by the drive of a compressor stored in a machine room by interference 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 radiation, and the dimension in one of the three-dimensional dimensions in the machine room is By setting the dimensions to be larger than the other dimensions, 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, and furthermore, the silencing operation by the control sound generator is The present invention is characterized in that it is provided with a control means that allows the operation to be performed only when the compressor is in operation.

(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.
It has the property that it increases in the band below about Hz and in the band from 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 control of noise, it is sufficient to set the noise on the low frequency side to the target frequency (in this case, about 700 Hz or less). In this way, if the target frequency is about 700 Hz or less, two of the height, depth, and width directions in the machine room should be shorter than the wavelength of the original noise (about 50 cm when the sound speed is 340 m/s), and the remaining one should be If the dimension in the 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 ( So that only the first-order mode is established below the target frequency) band? +l! With this configuration, the sound generated in the machine room can be regarded as a one-dimensional plane traveling wave, and the heat radiation opening that is the exit of the sound from the compressor to the outside. In theory and technology, it becomes possible to easily and accurately perform active control in which the sound is interfered with the artificial sound from the control sound generator in order to muffle the sound.

Further, when the operation of the compressor is stopped, the above-mentioned active control is also stopped by the control means, so that unnecessary artificial sounds are no longer emitted from the control sound generator. In other words, even if the sound receiver receives a sound from the outside, by emitting an artificial sound that cannot interfere with the sound as described above, this artificial sound is prevented from becoming a noise source.

Of course, since the machine room is provided with a heat dissipation opening, there is no risk of an abnormal rise in temperature in the machine room 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 St, the sound generated by the speaker 5 is 82, the sound received by the receiver 3 is R11, the sound at the control target point 2 is R2, and the output of the above sound and Let the acoustic transfer function between each of the input points be Tll, T21. T
12. 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 S2- (-TI2・R1+T11・R2)/(T11
-722-TI2Φ T21), but 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-R1・T12/(TI2・T 21-
T11・T22). As can be understood from this equation, in order to make gR2 at the control target point 2 zero, the sound R1 received by the microphone 3 is given by F-TI2/(T12・T21−T II・T22
) The sound level at the control target point 2 can be theoretically reduced to zero by generating the processed sound S2 from the speaker 5 through a filter.

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 the cooler 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. Inside this machine room, a rotary compressor 18°, a condenser vibe 19, and a defrosting water evaporator f20 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 on its back side, and this opening part is connected to the machine room cover 27. It is now closed due to 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. In other words, when the machine room cover 21 is attached,
The machine room 17 is in a closed state leaving a heat radiation opening 21a. Note that the machine room cover 21 is made of a material (for example, 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 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). Compressor 1, which is the source of noise,
It is provided to convert the sound from 8 into an electrical signal. Reference numeral 23 denotes a speaker serving as a control sound generator disposed in the machine room 17, and this is, for example, a heat dissipation opening 21a 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 nearby part.

FIG. 2 schematically shows an electrical configuration for driving and controlling the compressor 18. In this FIG. 2, 24 is a temperature detection circuit, which is composed of a thermistor 25 and a resistor 26 having a negative temperature coefficient, and a comparison circuit 27 detects a detected voltage according to the temperature inside the freezer compartment 12.
This is applied to the positive input terminal of . 28 is a setting circuit,
This generates a reference voltage corresponding to the set temperature and applies it to the negative input terminal of the comparison circuit 27. The comparison circuit 27 outputs an rHJ level compressor-on signal when the detected voltage exceeds the reference voltage, that is, when the temperature inside the freezer compartment 12 exceeds the reference temperature. Two drive circuits include a transistor 30, a relay 31, etc., which energize the relay 31 when a compressor-on signal is given from the comparator circuit 27. 32 is an AC power supply, and the glue L of the relay 31 is
/-Contact 31. Compressor 1-8 and F/16 are connected in parallel via a.

Reference numeral 33 denotes a negative phase sound generation circuit, which consists of an arithmetic unit 34 and a control circuit 35 serving as a control means. The eL calculator 34 is connected to the speaker 23 via the microphone 22 and amplifier 36, and is also connected to the comparison circuit 27 via a control circuit 35.

Therefore, the arithmetic unit 34 is operated by the control circuit 35 only when the comparator circuit 27 outputs the compressor-on signal, outputs a signal processed based on the electrical signal from the microphone 22, and outputs a signal to the speaker. 23. The processing of the electrical signals as described above is performed based on the above-mentioned silencing principle using active control.

In addition, the previous 5 self compressors 18. The positional relationship between the microphone 22 and the speaker 23 is determined by the propagation time of sound between the compressor 18 and the heat radiation opening 218, which is the point to be controlled for silencing. is the total time (tz+Δt+tq )
It is set so that a longer relationship will be established. .

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 5.5 Hz, as shown in FIG. The state is such that it increases in the KH2 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., and can be attenuated by installing an appropriate sound absorbing member in the machine room 17. Since the microphone 22. Active control of the noise caused by the speaker 23 and the 'a calculator 34 may be performed using 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 within the machine room 17 to be a one-dimensional plane traveling wave in order to control it easily and accurately both theoretically and technically. Therefore, in this embodiment, among the three-dimensional dimensions of the machine room 7 shown in FIG. The dimensions are set larger than H (specifically, W-600
1, D=H-200 mm), the standing wave of sound in the machine room 17 is established only in the first mode. That is, for example, when the machine room 17 is assumed to be a rectangular cavity, the following equation holds true.

f −C・(Nx/Lx)2”(Ny/I, y)2+(
Nz/Lz)2/2 However, [ is the resonance frequency (H2)
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 direction of y and z,
fy and fz can be found.

That is, as mentioned above, the depth dimension D-200ffif
fi% Width dimension W -6001111% Height dimension H-20
If it is set to 0 mm, the frequency fx of the first standing wave in the X direction is Ny - Nz - 0, the sound speed C
=340m/sec, fx -'340 (110,2) 2/2-850
Hz becomes 1, and similarly, the frequencies fy and fz of the first standing wave in the Y and Z directions are: fy -340 (110,6) 2/2283Hz f -340 (110,2) 2/2 = 850Hz becomes. 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, the wavefront can be theoretically handled easily, and silencing control can be performed easily and accurately. At this time, the time t2 for the sound from the compressor 18 to reach the microphone 22,
After converting the sound into an electrical signal, the time Δt for calculating a processed signal in the calculator 34 based on the electrical signal and the artificial sound output from the speaker 23 based on the processed signal are determined by the heat dissipation opening. 21a is shorter than the time t1 for the sound from the compressor 18 to reach the heat radiation opening 21a, so the sound from the compressor 18 and the artificial sound from the speaker 23 interfere with each other. There is no longer a risk that the artificial sound will be delayed, and active control of the glaring sound as described above can be performed in real time.

In addition, the control circuit 35 performs the above-described active control on the compressor 18 based on the compressor ON signal.
Since this is performed only when the compressor 18 is in operation, when there is no noise from the compressor 18, unnecessary artificial sounds are emitted from the speaker 23 in response to sounds reaching the machine room 17 from the outside, and conversely the noise source This will no longer be the case.

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.

Note that 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 in which the compressor is housed is configured in a closed state leaving an opening for heat dissipation, and the three-dimensional direction inside the machine room is By setting one direction of each dimension larger than the other dimensions, the standing wave of sound in the machine room is below the frequency band to be silenced (so that only the primary mode is established). This structure simplifies the active control in which the noise generated in the non-sealed machine room due to the drive of the Brezza is canceled out by the signal sound from the control sound generator. Furthermore, in the present invention, the control means is configured to perform the silencing operation by the control sound generator only when the compressor is operating, so that it can be performed when there is no noise from the compressor. In addition, the noise that reaches the machine room from the outside will not emit unnecessary noise and become a noise source.

[Brief explanation of the drawing]

Figures 1 to 4 show one embodiment of the present invention, with Figure 1 being an exploded perspective view of the main parts, and Figure 2 being a schematic diagram of the electrical configuration that outputs the compressor-on signal. , FIG. 3 is a schematic perspective view for explaining the dimensional relationship of main parts, and FIG. 4 is a longitudinal sectional view C of the refrigerator. Further, FIG. 5 is a schematic configuration diagram showing the principle of silencing by active control, and FIG. 6 is a frequency characteristic diagram of one noise level. In the drawing, 11 is the refrigerator body, 17 is a machine room, 18 is a compressor, 20 is a defrosting water evaporator, 21 is a machine room cover, 21a is a heat radiation opening, 22 is a microphone (sound receiver), and 23 is a speaker ( 27 is a comparison circuit, 33 is an anti-phase sound generation circuit, 34 is an arithmetic unit, and 35 is a control circuit (control means).

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. A silencing device for a cooling device, characterized in that the silencing device is configured so that only the first mode is established below the frequency band, and further includes a control means for causing the silencing operation by the control sound generator to be performed only when the compressor is operating.