JPH0784974B2 - Silencer for cooling system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention relates to a silencer used for 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 that houses a compressor.

(Prior Art) A cooling device using a compressor, such as a refrigerator, is often installed in a living room of a general household.
Moreover, since it is operated continuously regardless of the season, reducing the noise is an issue. In this case, the most problematic noise source of the refrigerator is noise from the machine room in which the compressor and the piping system connected to the compressor are stored. That is, in the above machine room, the compressor itself generates relatively large noise (operation noise of the compressor motor, fluid noise due to compressed gas, mechanical noise in movable mechanical elements of the compression mechanism portion, etc.) and is connected to the compressor. The piping system also generates noise due to its vibration, and such machine room noise accounts for the majority of refrigerator noise. Therefore, suppressing the noise from the machine room greatly contributes to the noise reduction of the entire refrigerator.

Therefore, in the past, in order to reduce noise from the machine room, in addition to noise reduction of the compressor itself (for example, adoption of a rotary type compressor), improvement of the vibration isolation support structure of the compressor and improvement of the shape of the piping system etc. By doing so, the vibration can be damped in the vibration propagation path, or
By arranging a sound absorbing member and a sound insulating member around the compressor and the piping system, it is attempted to increase the sound absorption volume and increase the noise transmission loss in the machine room.

(Problems to be Solved by the Invention) In general, a mechanical room of a refrigerator is provided with a plurality of openings for heat radiation in order to release heat generated by driving a compressor to the outside. Noise will leak from the outside. Therefore, the conventional noise reduction measures as described above are naturally limited, and the noise level reduction effect can be expected to be only about 2 dB (A).

On the other hand, in recent years, along with the development of electronics application technology, especially the influence data processing circuit and acoustic control technology, the application of active noise control technology that 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 electric signal with a sound receiver provided at a specific position, and
By operating the control sounder based on a signal obtained by processing this electric signal by the arithmetic unit, the sounder has a phase opposite to that of the original sound (sound from the noise source), the same wavelength and the same amplitude. The artificial sound is generated, and the original sound is attenuated by 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 in a non-sealed state and the noise generated in the machine room leaks freely in three dimensions. Since it is below, there is a problem that the active control mode becomes extremely complicated, and it is the actual situation that there is no idea about the practical use of the active noise control in the refrigerator.

The present invention has been made in view of the above circumstances, and an object thereof is to perform active control of canceling noise generated by driving a compressor in an unsealed machine room by interference with an artificial sound. It is an object of the present invention to provide a silencer for a cooling device, which can simplify the active control and improve the control accuracy, can perform the active control in real time, and can sufficiently exert the noise reduction effect.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above-mentioned object, the present invention actively generates a sound generated by driving a compressor housed in a machine room by interference with an artificial sound. In the muffler of the cooling device that is designed to cancel, the machine room is configured to be closed except for the heat dissipation opening, and one dimension among the three-dimensional dimensions in the machine room is Is set to be larger than the above dimension, the standing wave of the sound in the machine room is constituted so that only the first-order mode is established below the frequency band to be canceled, and further, the compressor, the sound receiver and the control sounder. The positional relationship between the sound propagation time between the compressor and the heat dissipation opening, the sound propagation time between the compressor and the sound receiver, the time required for the processing signal to be calculated by the arithmetic unit, and the control sound generator, In which the total time from a long relationship between the propagation time of the sound between the heat opening is set to satisfy.

(Function) For example, in a refrigerator, which is a typical example of a cooling device, in the case of a refrigerator having a general structure, the sound level of noise generated by driving the compressor is 700 Hz as shown in FIG.
It has the property that it becomes large in the band below the range and in the band of 1.5 to 5 KHz. Of the noises corresponding to each of these bands, those on the high frequency side can be easily silenced by the conventional noise reduction technology using a sound absorbing member or the like. Therefore, when the active control of noise is actually performed, the noise on the low frequency side should be the target frequency (about 700 Hz or less in this case). Thus the target frequency is
When the frequency is about 700Hz or less, it is shorter than the wavelength of the original noise in the two directions of height, depth and width in the machine room (about 50cm at a sound velocity of 340m / sec), and the remaining dimension in one direction is more than the above wavelength. If it is set long, the standing wave of noise generated in the machine room can be established only in the primary mode. That is, by setting the dimension in one of the three-dimensional directions of the height, depth and width in the machine room to be larger than the other dimensions, the frequency of the standing wave of the sound in the machine room to be canceled ( It can be configured so that only the first-order mode can be established below the (target frequency) band. In such a configuration, the sound generated in the machine room can be regarded as a one-dimensional plane traveling wave, and The active control, in which the sound and the artificial sound from the control sound generator interfere with each other at the heat dissipation opening, which is the outlet of the sound from the outside, to suppress the sound, theoretically and technically, easily and accurately. You will be able to do well.

At this time, the time it takes for the sound from the compressor to reach the sound receiver, the time for converting the sound into an electric signal and then calculating the processing signal based on the electric signal, and the processing signal The total time taken for the artificial sound output from the control sound generator to reach the heat dissipation opening is shorter than the time for the sound from the compressor to reach the heat dissipation opening. When interfering with the artificial sound from the sound generator, there is no fear that the artificial sound will be delayed, so that the active control of noise as described above can be performed in real time. Of course, since the heat dissipation opening is provided in the machine room, there is no fear that the temperature inside the machine room will rise abnormally due to heat generated when the compressor is driven.

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

In FIG. 5, 1 is a noise source such as a compressor, 2
Indicates a control target point where noise suppression is desired. Sound from a noise source is converted into an electric signal by a sound receiver 3 such as a microphone, and this electric signal is processed through a calculator 4 including a filter or the like. However, the sounder 5 such as a speaker is driven by the processed signal.

That is, the sound generated by the noise source 1 is S1, the sound generated by the speaker 5 is S2, the sound received by the sound receiver 3 is R1, the sound at the controlled point 2 is R2, and the above-mentioned sound output And 2 when the acoustic transfer function between each of the input points is T11, T12, T22
2. The following equation holds as the output system.

Therefore, the sound S2 that should be generated by the speaker 5 is obtained from the above equation as S2 = (-T12 ・ R1 + T11 ・ R2) / (T11 ・ R22−T12 ・ T21). Since the target is to make the sound level of 0 to 0, it is possible to set R2 = 0. As a result, S2 = R1 · T12 / (T12 · T21-T11 · T22). As can be understood from this equation, in order to reduce the sound R2 at the controlled point 2 to zero, the sound received by the microphone 3
If the sound S2 processed by applying the filter F = T12 / (T12 ・ T21−T11 ・ T22) to R1 is generated from the speaker 5, the sound level at the controlled point 2 should be theoretically zero. You can

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

That is, in FIG. 4 showing the entire configuration of the refrigerator, 11 is a refrigerator main body which is a cooling device main body, and inside thereof, a freezing compartment 12, a refrigerating compartment 13 and a vegetable compartment 14 are provided in this order from above. Reference numeral 15 is a cooler arranged at the back of the freezer compartment 12, and 16 is a fan for directly supplying the cool air generated by the cooler 15 to the freezer compartment 12 and the refrigerating compartment 13. Reference numeral 17 denotes a machine room formed in the lower part of the rear side of the refrigerator main body 11, in which a rotary type compressor 18, a condenser pipe 19, and a defrosting water evaporation device 20 using a so-called ceramic fin are housed. .

By the way, as shown in FIG. 1 (the condenser pipe 19 and the defrosting water evaporator 20 are not shown here), the machine room 17 has a shape in which only the back surface thereof is opened in a rectangular shape. The opening is closed by the machine room cover 21. At this time, the machine chamber cover 21 is hermetically attached to the peripheral edge of the opening edge of the machine chamber 17, and has a vertically elongated elongated rectangular heat radiation at the left edge in FIG. An opening 21a for use is formed. That is, when the machine room cover 21 is attached, the machine room 17 is in a closed state except for the heat dissipation opening 21a. The machine chamber cover 21 is made of a material (for example, metal such as iron) that has excellent thermal conductivity and large sound transmission loss.

Reference numeral 22 denotes a sound receiver, for example, a microphone arranged in the machine room 17, which is arranged so as to face the compressor 18 from the side opposite to the heat dissipation opening 21a (right side in FIG. 1). Thus, the sound from the compressor 18, which is a noise source, is provided so as to be converted into an electric signal. Reference numeral 23 denotes a speaker, which is a speaker for control disposed in the machine room 17, and is located, for example, in a portion of the back wall of the machine room 17 (corresponding to the lower wall of the refrigerator body 11) near the heat dissipation opening 21a. It is mounted and supported in a buried form. Then, the speaker 23 is operated by a signal obtained by processing an electric signal from the microphone 22 by a calculator (indicated by reference numeral 24 in FIG. 2) in the anti-phase sound generation circuit. The processing of the electric signal as described above is performed based on the silencing principle by the active control described above.

In this case, the positional relationship between the compressor 18, the microphone 22 and the speaker 23 is such that the sound propagation time t ₁ between the compressor 18 and the heat dissipation opening 21a, which is the target point of the muffling control, is as shown in FIG. 18 and microphone 22
Longer than the total time (t ₂ + Δt + t ₃ ) of the sound propagation time t ₂ between them, the processing signal calculation time Δt by the calculator 24, and the sound propagation time t ₃ between the speaker 23 and the heat dissipation opening 21a. Are set so that

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 driving of the compressor 18 is in the band of about 700 Hz or less and 1.5 to 5 KHz as shown in FIG. It becomes a state that it has the property of becoming larger in each band. Of the noises corresponding to each of these bands, the noise on the high frequency side can be attenuated by the transmission loss in the machine room cover 21 and the like, and can be easily installed by installing an appropriate sound absorbing member in the machine room 17. Since the sound can be muted, the active control of noise by the microphone 22, the speaker 23, and the calculator 24 as described above may be performed with a target frequency of 700 Hz or less.

Further, when performing active control of noise as described above, it is possible to configure the noise in the machine room 17 to be a one-dimensional plane traveling wave, both theoretically and technically. It becomes important for easy and accurate operation.
Therefore, in the present embodiment, each dimension D in the depth, width and height directions, which are the three-dimensional directions in the machine room 17 shown in FIG. 3,
Of W and H, for example, the dimension W in the width direction is set larger than the other dimensions D and H (specifically, W = 600 mm, D = H = 200 mm
By setting), the standing wave of the sound in the machine room 17 is configured to be established only in the first-order mode. That is, for example, assuming that the machine room 17 is a rectangular cavity, the following equation holds.

However, f is the resonance frequency (Hz), Nx, Ny, Nz are the modes in the X, Y, Z directions, and Lx, Ly, Lz are the dimensions in the X, Y, Z directions in the machine room 17 (that is, D , W, H) and C are sound speeds. Therefore, from the above equation, the frequency fx, of the first standing wave in each of the X, Y, and Z directions,
fy and fz can be calculated.

That is, as described above, when the depth dimension D = 200 mm, the width dimension W = 600 mm, and the height dimension H = 200 mm are set, the frequency fx of the first standing wave in the X direction is Ny =
Nz = 0, sound velocity C = 340 m / sec, Similarly, the frequencies fy and fz of the first standing wave in the Y and Z directions are Becomes As a result, the target frequency (= 700Hz)
In the following, the standing wave of noise in the machine room 17 is established only in the Y direction (width direction) mode.
The noise inside can be regarded as a one-dimensional plane traveling wave. Therefore, at the time of silencing by active control of noise using the speaker 23 or the like, theoretical treatment of the wavefront becomes easy, and silencing control can be performed easily and accurately. At this time, the time t ₂ during which the sound from the compressor 18 reaches the microphone 22 and the time Δt for converting the sound into an electric signal and then calculating a processing signal in the calculator 24 based on the electric signal. And the artificial sound output from the speaker 23 based on the processed signal is emitted from the heat dissipation opening.
Since the sum of the time t ₃ until reaching 21a is shorter than the time t _{1 when} the sound from the compressor 18 reaches the heat dissipation opening 21a, the sound from the compressor 18 and the artificial sound from the speaker 23 are generated. When interfering, the artificial sound is less likely to be delayed, and thus the active control of noise as described above can be performed in real time.

Of course, in this case, the machine room 17 has the heat dissipation opening 21a.
Therefore, the temperature inside the machine room 17 does not rise abnormally due to heat generated when the compressor 18 is driven. Further, since the machine room cover 21 is made of a material having excellent thermal conductivity, the heat radiation efficiency of the heat generated in the machine room 17 is improved, and from this aspect, the temperature rise in the machine room 17 also increases. Will be kept low.

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

EFFECTS OF THE INVENTION According to the present invention, as is apparent from the above description, the machine room in which the compressor is housed is configured to be closed while leaving the heat radiation opening, and the three-dimensional direction in the machine room is set. Since the standing wave of the sound in the machine room is configured to be established only in the first-order mode below the frequency band to be silenced by setting the dimension in one direction larger than the other dimensions in each of the above, When performing active control of canceling the noise generated by the drive of the compressor in the unsealed machine room by the signal sound from the control sounder, simplification of the active control and improvement of control accuracy can be realized. It is a thing. Further, in the present invention, the positional relationship between the compressor, the sound receiver and the control sound generator is defined by the sound transmission time between the compressor and the heat dissipation opening and the sound transmission time between the compressor and the sound reception device. Since it is set so that the time required for calculation of the processing signal by the calculator and the propagation time of the sound between the control sounder and the heat dissipation opening is longer than the total time, the active control of the noise described above is performed. It can be performed in real time, and thus the noise reduction effect can be sufficiently exerted.

[Brief description of drawings]

1 to 4 show an embodiment of the present invention. FIG. 1 is a perspective view showing an essential part in an exploded state, and FIG. 2 is a positional relationship between a compressor, a sound receiver and a control sounder. FIG. 3 is a schematic plan view for explaining the above, FIG. 3 is a schematic perspective view for explaining the dimensional relationship of the main parts, and FIG. 4 is a vertical sectional view of the refrigerator. Further, FIG. 5 is a schematic configuration diagram showing a silencing principle by active control, and FIG. 6 is a noise level characteristic diagram. In the figure, 11 is a refrigerator body, 17 is a machine room, 18 is a compressor, 20 is a defrosting water evaporation device, 21 is a machine room cover, 21a is a heat dissipation opening, 22 is a microphone (sound receiver), and 23 is a speaker. (Speaker for control), 24 is a calculator.

Claims (1)

[Claims] 1. A machine room in which a compressor is housed, the sound generated when the compressor is driven is converted into an electric signal by a sound receiver, and the electric signal is processed by an arithmetic unit. In a silencer for a cooling device in which a sound emitted to the outside from the machine room is actively canceled by operating a control sounder based on a signal, the machine room is left with a heat dissipation opening. And a closed state, and by setting the dimension in one direction out of the dimensions in the three-dimensional direction of the machine room to be larger than the other dimension, the standing wave of sound in the machine room is canceled. It is configured such that only the first-order mode is established in a frequency band equal to or lower than that, and further, the positional relationship between the compressor, the sound receiver and the control sounder is set so that the sound propagation between the compressor and the heat dissipation opening is Is longer than the total time of the sound propagation time between the compressor and the sound receiver, the time required for the processing signal to be calculated by the calculator, and the sound propagation time between the control sounder and the heat dissipation opening. A silencer for a cooling device, which is set to hold.