JPH02225968A - Noise suppressor for cooling device - Google Patents

Abstract

PURPOSE:To reduce the generation of noise by changing the rotary speed of a compressor with a control means by way of an inverter device under the assumption that a silencing capacity by a monitor of an auxiliary sound receiver fails to exceed a specified level and increasing the silencing capacity under control. CONSTITUTION:When an attempt is made to use a sound receiver 12 which converts generated sound accompanied by the drive of a compressor 8 housed in a machine room 7 into an electric signal, and a control sound generator 13 is operated based on the electric signal processed by a computing element 15 so as to cancel actively sound irradiated outside, an auxiliary sound receiver 16 is installed so as to monitor a silencing capacity of the control sound generator while an inverter device 18 is installed to control the rotary speed of the compressor 8. When the silencing capacity thus monitored fails to exceed a specified setting level, a control means 17 is installed to change the rotary speed of the compressor 8 by the inverter device 18 in such a direction that the silencing capacity may be increased.

Description

[Detailed Description of the Invention] [Statement 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 Piping systems also generate noise due to their vibrations.
This 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.

However, in the machine room of a refrigerator inside the shell, there are multiple openings for heat dissipation in order to release the heat generated by the compressor to the outside, and noise leaks to the outside from these openings. I'm going to go out. For this reason, the conventional noise reduction measures as described above naturally have a limit, and the effect of reducing the noise level can only be expected to be about 2 dB (A) at most.

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 by using sound wave interference, has attracted attention. 1-1. In other words, this active control basically converts the sound from the noise source into an electrical signal using a sound receiver (for example, a microphone) installed at a specific location, and then converts this electrical signal into a signal processed by a computing device. By operating a control sound generator (for example, a speaker) based on the control target point, 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. The idea is to attenuate the original sound by causing this artificial sound to interfere with the original sound.

(Problem to be Solved by the Invention) By the way, when performing active control as described above, depending on the shape of the machine room, the arrangement of the control sound generator, etc., the sound from the compressor is interfered with and muffled. There are sounds with difficult frequencies.

On the other hand, the noise generated by a compressor includes many sounds with frequencies that are integral multiples of the power supply frequency and rotation speed.
For example, if the rotation speed of the compressor fluctuates in response to changes in the load, and the noise generated at that time contains many sound components with frequencies that are difficult to muffle, as described above, the active control method described above may be used to muffle the noise. There is a problem that it becomes impossible to increase the amount.

The present invention has been made in view of the above circumstances, and its purpose is to eliminate noise generated from a compressor by using an active compressor. To provide a silencing device for a cooling device, which increases the amount of silencing even when there are many sound components at frequencies that are difficult to silence through control, thereby effectively suppressing leakage of noise to the outside through active control. be.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention converts the sound generated by the driving of a compressor housed in a machine room into an electrical signal using a sound receiver. At the same time, a sound muffling device for a cooling device is configured to actively cancel the sound radiated from the machine room to the outside by operating a control sound generator based on a signal processed by a computing unit from this electrical signal. In,
An auxiliary sound receiver is arranged so as to be able to monitor the amount of muting by the FF1LJ regular sound generator, and an inverter device is provided to control the number of revolutions of the compressor, and the amount of muting monitored by the auxiliary sound receiver reaches a predetermined level. When the rotation speed of the compressor is below the set level, the inverter device monitors the rotation speed of the compressor /l'! The configuration includes a control means for changing the volume in the direction of increasing the volume.

(Function) The sound from the compressor is converted into an electric signal by the sound receiver, and the arithmetic unit operates the control sound generator based on a signal obtained by processing the electric signal. As a result, active control is performed in which the sound from the compressor is canceled by interference between this and the artificial sound output from the control sound generator. In addition, the amount of silence caused by such active control is now monitored by an auxiliary sound receiver.
When the monitor silencing volume falls below a predetermined set level, that is, when the silencing volume through active control is insufficient and the noise leaking outside increases, the control means changes the rotation speed of the compressor via the inverter device. By changing the control light g5, the ln volume is increased.
73rrJ. As a result, even if the compressor rotation speed fluctuates due to load fluctuations and the resulting noise contains many sound components with frequencies that are difficult to actively control, the compressor rotation speed is changed to avoid this. Muffling by active control is effectively carried out.

(Example) Hereinafter, an example in which the present invention is applied to a refrigerator will be described.

First, in FIG. 3 showing the overall configuration of a refrigerator, 1 is a refrigerator main body which is a cooling device main body, and inside this, from the top, there are freezer compartments 2. A refrigerator compartment 3 and a vegetable compartment 4 are provided. 5 is a cooler disposed at the back of the freezer compartment 2; 6 is a fan that directly supplies cold air generated by the cooler 5 to the freezer compartment 2 and the refrigerator compartment 3. 7 is a machine room formed at the lower part of the back side of the refrigerator main body 1, and inside this is a rotary type compressor 8. A condenser vibrator 9 and a defrosting water evaporator 10 using so-called ceramic fins are housed.

Now, as shown in FIG. 4 (here, the illustration of the condenser vibrator 9 and the defrosting water evaporator 10 is omitted), the machine room 7 has a rectangular opening only on its back side. This opening portion is closed by a machine room cover 11. At this time, the machine room cover 11
The peripheral edge thereof is airtightly attached to the opening edge of the machine room 7, and an elongated rectangular heat dissipation opening 11a extending in the vertical direction is formed at the left edge in the figure. . That is, when the machine room cover 11 is attached, the machine room 7 is in a closed state leaving the heat radiation opening 11a. The machine room cover 11 is made of a material (for example, metal such as iron) that has excellent thermal conductivity and high sound transmission loss.

Further, in FIG. 4, 12 is a sound receiver such as a microphone placed in the machine room 7, and this is located on the opposite side of the compressor 8 from the heat radiation opening 11a (on the right side in the figure). The compressor 8 is arranged so as to face the compressor 8, and is provided so as to convert the sound from the compressor 8, which is a noise source, into an electrical signal. , 13 is a speaker as a control sound device arranged in the machine room 7, and this is, for example, a heat dissipation opening 11. It is installed and supported in a buried manner in a part near a.

As shown in FIG. 1, the speaker 13 is operated by a signal processed by the arithmetic unit 15 in the anti-phase sound generation circuit 14 from the electrical signal from the microphone 12. Processing of such electrical signals is performed based on the principle of silencing through active control as described below.

That is, to roughly explain the principle of silencing by active control with reference to FIG.
2. The sound received by the microphone 12 is R1, the sound at the heat radiation opening 11g which is the control target point is R2, and the acoustic transfer function between the above sound output and human power points is Tll, T21. , T1.2. When it is T22,
The following equation holds true for a two-man power two-output system.

Therefore, g S 2 to be generated by the speaker 13 is calculated from the above equation as S2 − (−Tl2・R1+TIlψR2)/(T
However, in this case, since the goal is to reduce the sound level at the heat radiation opening 11a to zero, it can be set as R2-0. As a result, S2-R1-Tl2/ (T12・T21-Tll-T
22). As can be understood from this equation, in order to reduce the sound R2 at the heat dissipation opening 11a to zero, the sound R1 received by the microphone 12 must be expressed as F-T12/(Tl2・721-T Il, -T
22) If the filtered and processed sound s2 is generated from the speaker 13, =e at the heat dissipation opening 11a
The level can be reduced to zero in theory, and the computing unit 15 performs such sound processing (performance '!i).
The output of the speaker 13 is controlled while performing this at high speed.

Here, in the case of the refrigerator configured as described above, the noise level generated in the machine room 7 according to the drive of the compressor 8 is in the band of about 700H2 or less and 1.5 to 5KHz as shown in FIG. It becomes a state in which it has the characteristic of becoming audible in each band. Among the noise corresponding to each of these bands,
The noise on the high frequency side is #! Since the sound can be attenuated by transmission loss at the machine left chamber cover 11, etc., and can be easily muffled by installing an appropriate sound absorbing member in the machine room 7, the microphone 12 as described in ii7,
Active control of noise by the speaker 13 and computing unit 15 is as follows:
The target frequency may be 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 7 so that it becomes a one-dimensional plane traveling wave, both theoretically and technically. It is important to do it efficiently and accurately.

Therefore, in this embodiment, among the three-dimensional depth, width, and height dimensions W and H in the machine room 7 shown in FIG. Dimensions.

Set larger than H (specifically, W-600mm.

By setting D=H-200 mm), the standing wave of sound in the machine room 7 is configured to be established only in the single layer mode. That is, for example, when the machine room 7 is assumed to be a rectangular cavity, the following equation holds true.

f−C・(NX/I,X)′ +(Ny/Ly)2”(
NZ/LZ)'/2, where f is the resonant frequency (Hz
) N NX , Ny -NZ is the number in each direction of x, y, and z! 1 mode, LX, Ly, Ly, is x in the machine room 7,
Dimensions in the y and z directions (that is, W and H), and C is the speed of sound. Therefore, from the above equation, the frequencies fl, fy, and fz of the first standing wave in each of the x, y, and z directions can be determined.

That is, as described above, when the depth dimension D-2001, the width dimension W-600 mm, and the height dimension H-20C1v are set, the frequency ex of the first standing wave in the X direction is Ny − Assuming Nz-0 and sound speed C = 340 m/s, fx-340(110,2) 2/2 -850 Hz, and similarly, the frequencies fy and fz of the first standing wave in the Y and Z directions are fy =34'o (110,6)'/2=283Hz fz-340(110,2)'/2-850 Hz. As a result, the target frequency (-700H
2) In the following, the standing wave of noise in the machine room 7 is expressed in the Y direction (
This is true only for the mode in the width direction), and the noise within the machine room 7 can be regarded as a one-dimensional plane traveling wave. Therefore, when silencing noise by active noise control using the speaker 13 or the like, theoretical handling of the wavefront becomes easy, and silencing control can be performed elegantly and accurately.

Now, in FIG. 1, reference numeral 16 denotes an auxiliary microphone serving as an auxiliary sound receiver, which is configured to convert the sound at the heat radiation opening 11a into an electric signal Se.
It is provided so that the amount of silencing caused by the noise can be monitored. Note that this monitoring is performed with artificial sound being output from the speaker 13, and in this state 18'A r
When the level of No. y Se is low, the amount of silence by the loudspeaker 13 is large. Then, the electric signal Se is transmitted to a control circuit 17 which is a control means in the negative phase sound generation circuit 14.
It is now entered into 18 is compressor 8
This is an inverter device that controls the rotation speed of the compressor 8, and this always controls the rotation speed of the compressor 8 according to negative 6q, and when a control signal is given from the control circuit 17, the rotation speed of the compressor will be described later based on this. The foundation is being revised as follows.

Therefore, in the following, the function of the out-of-phase sound generation circuit 14 including the front te@W7A 15 and the control circuit 17 will be explained with reference to the flowchart shown in FIG.

That is, operation S! 1i15 executes the active control routine 8 to drive the speaker 13 based on the calculation result based on the active control principle described above.
The artificial sound from the compressor 3 and the noise from the compressor 8 are made to interfere with each other to cancel the noise continuously. When executing such active control, the control circuit 17 controls, for example, every timing when the level of the artificial sound from the speaker 13 reaches approximately the peak value, in other words, the noise level from the compressor 8 (this is based on the power frequency of the compressor 8). At each timing when the signal (which changes periodically in response to the noise) is near the peak value, the amount of muting by the speaker 13 is monitored using the electrical signal Se from the auxiliary microphone 16 (steps B and C). As a result of the manual input of the electric signal Se in synchronization with the power supply frequency in this manner, the amount of silencing indicated by the human input electric signal Se becomes highly reliable as the influence of external noise is suppressed. Then, the control circuit 17 determines whether or not the muffling volume monitored as described above is below the set level (Step D). If it exceeds the set level, that is, if the muffling volume by the speaker 13 is sufficient, Without outputting control number 171 to the inverter device 18, the process directly returns to the previous self-active control routine A. Furthermore, if the monitor muting volume is below the set level, that is, if the volume of muting by the speaker 13 is insufficient and the noise has increased, the inverter device 18 sends M! The ll signal is outputted to change the rotation speed of the compressor 8 in a direction that increases the amount of silencing. Thereafter, when the monitor mute volume exceeds the set level, the process returns to active control routine A.

Note that the output frequency of the inverter device 18 is set taking into consideration the operating efficiency of the compressor 8, and in order to suppress an inadvertent decrease in the operating efficiency of the compressor 8, the upper and lower limits of the output frequency are set. It is desirable to set this in advance.

In summary, the out-of-phase sound generation circuit 14
When executing No@ control, the amount of noise attenuated by the artificial sound from the speaker 13 is monitored through the auxiliary microphone 16, and if the monitoring result is below the set level, the noise generated from the compressor has a frequency that is difficult to actively control. When a large amount of sound components are included, the control circuit 17 changes the rotation speed of the compressor 8 via the inverter device 18 in a direction that increases the amount of noise reduction until the amount of noise reduction reaches or exceeds the set level (step D). de rNOJ
(until it is determined that this is the case), thereby effectively executing the silencing operation during active control.

Of course, in the above embodiment, the machine room 7 has the heat radiation opening 1
Compressor 8 communicates with the outside through 1a.
The temperature in the machine room 7 will not rise abnormally due to heat generated during driving.

Furthermore, since the machine room cover 11 is made of abrasive material with excellent thermal conductivity, the heat dissipation efficiency of the heat generated within the machine room 7 is improved. Increases can be kept low.

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 sound generated when the compressor housed in the machine room is driven is transmitted from a control sound generator operated by a signal processed by a computing unit. In a silencing device for a cooling system, which actively cancels the artificial sound by interfering with the artificial sound, the above-mentioned sound at frequencies that are difficult to actively control can be suppressed from the compressor due to the shape of the machine room and the arrangement of the control sound generator. Even if there is a large amount of noise contained in the noise, the control means changes the rotation speed of the compressor via the inverter device to increase the amount of silencing, provided that the silencing amount as monitored by the auxiliary sound receiver is below a set level. The active control can be carried out even more effectively, and the generation of noise can be sufficiently reduced, which is an excellent effect.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is a schematic electrical configuration diagram, FIG. 2 is a flowchart showing the control contents of the arithmetic unit and the control channel (control means), and FIG. FIG. 4 is a longitudinal cross-sectional view of the refrigerator, FIG. 4 is a perspective view showing the main parts in an exploded state, FIG. 5 is a schematic configuration diagram showing the principle of noise reduction by active control, and FIG.
The figure is a schematic perspective view for explaining the q-modal relationship of the main parts.
The figure is a frequency characteristic diagram of the noise generated by the compressor. In the drawing, 1 is the refrigerator body, 7 is the machine room, 8 is the compressor, 10 is the defrosting water evaporator, 11 is the machine room cover 11
a is a heat radiation opening, 12 is a microphone (sound receiver), 1
3 is a speaker (control sound generator), 14 is an anti-phase sound generation circuit, 15 is an arithmetic unit, 16 is an auxiliary microphone (auxiliary sound receiver), 17 is a control circuit (control means), and 18 is an inverter device. . Applicant Toshiba Corporation Agent Patent Attorney Tsuyoshi Sato

Claims (1)

[Claims] 1. Converting the sound generated by the drive of the compressor housed in the machine room into an electrical signal using a sound receiver, and operating the control sound generator based on the signal processed by this electrical signal using an arithmetic unit. A silencer for a cooling device configured to actively cancel out sound radiated from the machine room to the outside, the auxiliary sound receiver being arranged to monitor the amount of silence by the control sound generator. an inverter device that controls the rotational speed of the compressor; and an inverter device that increases the rotational speed of the compressor by the inverter device when the muffling amount monitored by the auxiliary sound receiver is below a predetermined setting level. 1. A silencer for a cooling device, comprising: a control means for changing the direction.