JPH02225969A - Noise suppressor for cooling device - Google Patents

Abstract

PURPOSE:To inhibit the generation of careless noise due to adaptive control by allowing a control means to function only when background sound monitored by an auxiliary sound receiver a specified level. CONSTITUTION:A silencer for a cooling device which is designed to cancel actively sound irradiated from a machine room 7 outside by allowing a sound receiver 12 to convert generated sound accompanied by the drive of a compressor housed in the machine room 7 into an electrical signal and driving a control sound generator 13 based on the electrical signal processed by a computing element 15, is provided with an auxiliary sound receiver 16 which is capable of monitoring the silencing effect by the control sound generator 13 and background sound as well, and a control means 17 which controls so that the aforesaid silencing effect may stay within a specified range by changing an operation factor of the computing element 15 when the silencing effect by the control sound generator 13 monitored by the auxiliary sound receiver 16 deviates from the specified range. Moreover, the silencer is designed to allow the control means 17 to perform the changing motion of the operation factor when the background sound monitored by the auxiliary sound receiver 16 exceeds the specified level.

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. Also, in the machine room, if the compressor itself generates relatively large noise (compressor motor operating noise, fluid noise due to compressed gas, mechanical noise from moving mechanical elements of the compression mechanism, etc.), the compressor may The connected piping system also generates noise due to its vibrations, and noise from the machine room accounts for most of the refrigerator noise. Therefore, suppressing noise from the machine room is the best way to reduce noise from the entire refrigerator. Therefore, in the past, as measures to reduce noise from the machine room, in addition to reducing the noise of the compressor itself (for example, adopting a rotary type compressor), improvements to the vibration-proof support structure of the compressor, In addition, by improving the shape of the piping system, we aim to dampen vibrations in the vibration propagation path, or
By arranging sound absorbing members and sound insulating members around the compressor nozzle and the piping system, it is attempted to increase the amount of absorption in the machine room and increase the noise transmission loss. However, in the mechanical room of a refrigerator, 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 'F8g control technology, active noise control technology that uses sound waves to reduce noise has been applied. is attracting attention. In other words, this active control basically converts the sound from the noise source into an electrical signal using a 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 original sound (sound from the noise source) is inversely #11 at the control target point.
The idea is to attenuate the original sound by generating an artificial sound with the same wavelength and amplitude and causing the artificial sound to interfere with the original sound. (Problem to be Solved by the Invention) In realizing the above-mentioned active control, it is desirable to correct characteristic fluctuations due to aging of the components constituting the signal system for noise reduction and characteristic fluctuations due to ambient temperature. For this correction, it is most appropriate to correct the calculation coefficient (transfer function) of the arithmetic unit by following the change in the silencing ability due to the change in the characteristics. Therefore, conventionally, for the above-mentioned correction, for example, the silencing effect of the control issuer is monitored at every fixed time set in a timer or every time the degree of rise in the ambient temperature exceeds a set amount. An auxiliary sound receiver (for example, a microphone) is provided, and if the monitor result is outside a predetermined tolerance range, the calculation coefficient of the calculator is moxibusted so that the monitor result falls within the tolerance range. It has been considered to provide a tIJatt means to perform so-called adaptive control in which the silencing ability is always kept optimal during active control. However, during the period in which the calculation coefficients of the arithmetic unit are changed during execution of the above-mentioned adaptive control, the silencing effect of the control sound is insufficient, and there is a risk that the noise will increase during this period. remained an unresolved issue. The present invention has been made in view of the above-mentioned circumstances, and its purpose is to perform adaptive control that maintains the silencing effect of the control sound generator at an optimum level while compensating for variations in the characteristics of the components that constitute the silencing control system. The object of the present invention is to provide a silencing device for a cooling device that can suppress an inadvertent increase in noise caused by adaptive control. C Configuration of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention converts the sound generated by driving 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. , an auxiliary sound receiver is arranged so as to monitor the silencing effect of the control sound generator and background noise, and the silencing effect of the control sound generator monitored by the auxiliary sound receiver is outside a predetermined tolerance range. If the above-mentioned side! 'II f, the operation of changing the arithmetic coefficient by stage is performed when the background noise monitored by the auxiliary sound receiver is at a predetermined level or higher. In this case, the operation of changing the arithmetic coefficient may be forcibly executed when the monitored background noise remains below a predetermined level for a predetermined period of 11.17 hours or more. (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 the signal added with the electric signal. As a result, active control is performed in which the sound from the compressor is canceled by the interference between this and the artificial sound output from the control sound generator. In addition, the silencing effect of such active control is now monitored by an auxiliary sound receiver, and if the monitoring result falls outside a predetermined tolerance range, that is, the silencing effect of active control is insufficient and the noise is increasing. If the noise has increased, the control means changes the calculation coefficient (transfer function) of the calculation unit when the background noise monitored by the auxiliary sound receiver exceeds a predetermined level, thereby reducing the silencing effect of the control sound generator. Control to within acceptable range. As a result, the increase in noise is suppressed, and thus the sound receiver constitutes a control system for noise reduction. Even if the characteristics of components such as the auxiliary sound receiver and the control sound generator change, so-called adaptive control is performed in which the silencing ability during active control is maintained optimally. At this time, since the above-mentioned adaptive control is executed when the background noise is high, the silencing effect by the control oscillator is achieved during the time when the calculation coefficient of the computing unit is changed during the execution of the adaptive control. Even if this becomes insufficient, it will not lead to an increase in noise based on the human hearing characteristics. In addition, if the control means is configured to forcibly change the calculation coefficient when the monitor background noise remains below a predetermined level for a predetermined period of time or more, the background noise remains low for a long period of time. Adaptive control will always be performed at predetermined intervals even if (Example) An example in which the present invention is applied to a refrigerator will be described above. First, in FIG. 3 showing the overall configuration of the refrigerator, the symbol 2 is the refrigerator main body which is the main body of the cooling device. 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 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 nozzle 9 and the defrosting water evaporator 10 is omitted),
The machine room 7 has a rectangular opening only at its back, and this opening is closed by a machine room cover 11. At this time, machine room cover 1
1, whose peripheral edge 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. There is. 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 designed to convert the sound from the compressor 8, which is a noise source, into an electrical signal. Reference numeral 13 denotes a speaker serving as a control sound generator disposed in the machine room 7, and this is placed, for example, in a part of the back wall of the machine room 7 (corresponding to the bottom wall of the refrigerator body 1) near the heat radiation opening 11a. It is installed and supported in a buried manner. As shown in FIG. 1, the speaker 13 is operated by a signal processed by the arithmetic unit 15 in the out-of-phase sound generation circuit 14 from the electrical signal from the microphone 12. The processing of Denki No. 13 like Maki is carried out based on the principle of noise reduction 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 11a which is the control target point is R2, and the acoustic transfer function between the sound output and human power points as described above is T.
ll, T21, TI2. When T22 is assumed, the following equation holds true as a two-man power two-output system. Therefore, the sound S2 to be generated by the speaker 13 is calculated from the above equation as follows: S2- (-T12-R1+T11-R2)/(T1
It is obtained as 1Φ722-T1.2T21),
In this case, since the 11 target is to make the TS9 level at the heat dissipation opening 11a zero, it can be set as R2-0. As a result, S2-R1・TI2/(TI2・T21-Tll・T2
2). As can be understood from this equation, the heat dissipation opening 1.1. In order to make the B R2 at a zero, the sound R1 received by the microphone 12 is processed by applying a filter of F-TI2/(T12・T21−Tll・T22) and the processed sound S2 is generated from the speaker 13. If so, the sound level at the heat dissipation opening 11a can be theoretically reduced to zero, and the arithmetic unit 1
5 is configured to control the output of the speaker 13 while performing such sound processing (calculation) at high speed. Here, in the case of the refrigerator configured as described above, the noise level generated in the machine room 7 in response to the drive of the compressor 8 is in the band of about 700H2 or less and in the range of 1.5 to 5. It becomes a state in which H has the property of increasing in the KHz band. Among the noise corresponding to λ·1 in each of these bands, the noise on the high frequency side can be attenuated by transmission loss in the machine room cover 11, etc.
The microphone 12 as described above can be easily muffled by installing an appropriate sound absorbing member inside the microphone 12.
The active control of noise by the speaker 13 and the arithmetic unit 15 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 7 so that it becomes a one-dimensional one-plane traveling wave, both theoretically and technically. 1llf is required to perform the process 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. By setting it larger than H (specifically, W = 600 mm; setting D = H - 2UOsv), it is configured so that the standing wave of sound in the machine room 7 is established only in the 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−X,X+Ny1. y +0IZ1.
Z) /2 However, f is both 1 frequency (Hz),
NX,, Ny. NZ is the th mode in each direction of x, y, z, LX, Ll, L
t is the dimension in each of the x, y, and z directions in the machine room 7 (that is,
W, H), C is the speed of sound. Therefore, from the above formula, x,
Frequencies fx, f of standing waves for one round in each direction of y and z
y and fz can be found. That is, as mentioned above, the depth method D-200-1,
When the width dimension W-600ms and the height dimension H-200+s are set, the frequency fx of the standing wave at the first mouth in the X direction is Ny -Nz-0, and the sound speed C=340.
As rn/second, fx -3401,-/2 = 850Hz, and similarly, the frequencies fy and fz of the standing waves of 1] in the Y and Z directions are fy-340,6) /2 = 283Hz fz -340,2) 72 850Hz. As a result, the target frequency (-700H
z> Below, the standing wave of noise in the machine room 7 is Y7ff
This holds true only for the direction (width direction) mode,
The noise within the machine room 7 can be regarded as a one-dimensional traveling wave on the shell surface. Therefore, when silencing noise through active noise control using the speaker 13 or the like, theoretical handling of the wavefront becomes easy, and silencing control can be carried out easily 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, and is then transmitted to the speaker 13 as described later. The silencing effect (silencing amount) and background noise can be monitored. The electric signal Ss is then manually inputted to an adaptive control circuit 17 which is a control means within the out-of-phase sound generation circuit 14. Therefore, the functions of the adaptive control circuit 17 will be explained below with reference to the flowchart of FIG. That is, the adaptive control circuit 17 has a timer time of, for example, 100.
There is a main timer whose time is set to approximately 5 minutes, and a sub-timer (both not shown) whose timer time is set to approximately 5 minutes, and the main timer and sub-timer are sequentially initialized and started as shown in Figure 2. (Steps A, B
). Next, it is determined whether or not the sub-timer has timed up, that is, whether 5 minutes have elapsed (step C). If rNOJ is determined here, it is determined whether or not the main timer has timed up, that is, whether 10 minutes have passed or not. Step D), and if rNOJ is determined here as well, the process returns to Step C. Then, in step C, the adaptive control circuit 17
When it is determined that, for example, the level of the artificial sound from the speakers 1-3 is approximately at its lowest level, in other words, the noise level from the compressor 8 (this varies circumferentially depending on the power frequency of the compressor 8). The background noise is monitored by the electrical signal Se from the auxiliary microphone 16 at each timing when the signal (step E) is near the lowest value (steps E and F). In other words, since background noise is monitored in synchronization with the power supply frequency, the monitoring results are highly reliable. Next, the background noise Δ monitored as above
Step G) determines whether or not the monitor background noise is above a predetermined level, and if it is below a predetermined level, returns to step B and resets the sub-timer; however, if the monitor background noise is above the set level, the adaptive Execute control routine H. In this adaptive control routine H, when the silencing effect of the speaker 13 monitored by the auxiliary microphone 16 is out of a predetermined tolerance range, the speaker 13 is controlled so that the silencing effect is within an allowable range, and then the process returns to step A and the main timer is reset. Further, in the above adaptive control routine H, in the step D, r
It is also executed when the judgment is YESJ. In summary, the adaptive control circuit 17 monitors the background noise through the auxiliary microphone 16 every five minutes set in the sub-timer, and if the monitored background noise exceeds the set level, the adaptive control circuit 17 performs active control. The calculation coefficient (transfer function) of the arithmetic unit 15 is changed on the condition that the silencing effect is outside a predetermined tolerance range (that is, the silencing effect due to active control is suppressed and the noise is increasing). By doing so, adaptive control is executed such that the silencing effect of the speaker 13 is controlled to be within an allowable range. At this time, if the background noise after 5 minutes is below the set level as described above, the adaptation 1111 go
5 minutes without running! ! It is something to wait until you meet someone.
Furthermore, if the ten minutes set in the main timer elapse without the adaptation 111 being performed, the adaptive control is executed regardless of the monitor background noise. As a result of adaptive control as described above, even if the characteristics of the components (microphone 12, speaker 13, auxiliary microphone 16, etc.) that make up the signal system for noise reduction change, the ability to suppress sound during active control increases. will be maintained optimally. Furthermore, since the above-mentioned adaptive control is executed when the background noise is high, the silencing effect by the speaker 13 becomes insufficient during the period in which the calculation coefficient of the computing unit 15 is changed during the execution of the adaptive control. Even if this happens, it will not lead to an increase in noise based on the human hearing characteristics. In addition, if the background noise remains low for a long time, adaptive control will not be performed at each timing of 5 minutes. Since adaptive control will be forcibly performed regardless of the situation, the noise suppression effect of active control will not be affected. 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. In addition, since the machine room cover 11 is made of a material with excellent thermal conductivity, the heat dissipation efficiency of the heat generated in the machine room 7 is improved, and this also leads to an increase in the temperature inside the machine room 7. 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] As is clear from the above description, according to the silencer for a cooling device according to claim 1, the sound generated by the driving of the compressor housed in the machine room can be suppressed by using a computing unit.
In a device that actively cancels out interference with artificial sounds from a control sound generator operated by two signals, control is performed while compensating for the characteristic cystic motion of the parts that make up the control system for noise reduction. When performing adaptive control to maintain the silencing effect of the sound generator at an optimum level, the present invention has excellent effects such as being able to suppress the sudden increase in noise caused by the adaptive control. Moreover, according to the silencer of the cooling device according to claim 2,
This eliminates the possibility that adaptive control will not be performed for an unnecessarily long period of time due to continued low background noise, and thus the noise suppression effect can always be maintained in a good state.

[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 control means, FIG. 3 is a longitudinal cross-sectional view of the refrigerator l1If, and FIG. 4
The figure is a perspective view showing the main parts in an exploded state, Fig. 5 is a schematic configuration diagram showing the principle of silencing by active control, Fig. 6 is a schematic perspective view for explaining the dimensional relationship of the main parts, and Fig. 7 is a noise reduction diagram. It is a level characteristic diagram. In the figure, 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 11a
is a heat radiation opening, 12 is a microphone (receiver C1),
Reference numeral 13 indicates a speaker (control sound generator), 14 indicates an anti-phase sound generation circuit, 15 indicates an arithmetic unit, 16 indicates an auxiliary microphone (auxiliary sound receiver), and 17 indicates an adaptive control circuit (control means).

Claims (1)

[Claims] 1. The sound generated by the drive of the compressor housed in the machine room is converted into an electrical signal by a sound receiver, and the electrical signal is processed by a computing unit for control purposes based on the signal. A silencing device for a cooling device that actively cancels out sound radiated from the machine room to the outside by operating a sound generator, which allows monitoring of the silencing effect of the control sound generator as well as background noise. If the silencing effect of the auxiliary sound receiver arranged as shown in FIG. and a control means for controlling the effect so that it falls within the permissible range,
A silencer for a cooling device, characterized in that the control means is configured to change the operation coefficient when background noise monitored by the auxiliary sound receiver exceeds a predetermined level. 2. The control means is configured to forcibly execute the operation of changing the calculation coefficient when the background noise monitored by the auxiliary sound receiver remains below a predetermined level for a predetermined time or more. A silencer for a cooling device according to claim 1.