JPH083396B2 - Silencer for cooling system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Industrial field of application) The present invention actively suppresses noise from a silencer used in a cooling device such as a refrigerator, and particularly from a machine room accommodating a compressor. The present invention relates to a sound deadening device for a cooling device.

(Prior Art) A cooling device using a compressor, for example, a refrigerator is often installed in a living room of a general household and is continuously operated regardless of the season. Noise reduction 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 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, as measures 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, vibration can be damped in the vibration propagation path, or sound-absorbing members and sound-insulating members are placed around the compressor and piping system to increase sound absorption volume and increase noise transmission loss. Is being carried out.

(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, with the development of electronics application technologies, especially acoustic data processing circuits and acoustic control technologies, the application of active noise control technology that reduces noise by using sound wave interference has attracted attention. Has been done.
That is, this active control basically converts a sound from a noise source into an electric signal by a sound receiver provided at a specific position, and controls the electric signal based on a signal processed by an arithmetic unit. By operating the sound generator, an artificial sound having a phase opposite to that of the original sound (sound from the noise source) at the control target point and having the same wavelength and the same amplitude is generated from the sounder, and the artificial sound and the original sound are generated. It is intended to attenuate the original sound by causing interference. 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 due to 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, improve control accuracy, and expand the frequency range in which the noise can be eliminated, and can be applied to a small cooling device.

[Configuration 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 a muffler for a cooling device that cancels out, a duct portion that opens the machine chamber to the outside is arranged in the machine chamber in the up-down direction, and one of the three-dimensional dimensions of the duct unit is used. Is set larger than other dimensions, so that the standing wave of the sound radiated from the machine room into the duct section is established only in the first-order mode below the frequency band to be canceled. Is configured.

(Operation) 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 in response to driving of the compressor is almost as shown in FIG.
Noise that increases in the band of about 1 KHz or less and that is higher than this 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 may be canceled.

Thus, when the sound radiated from the machine room is guided to the muffler to be silenced as in the present invention, if the target frequency is, for example, about 700 Hz or less, the effective length of the duct part is the wavelength of the original noise (700 Hz) If it is set longer than about 50 cm (in case of 340 m / sec), the standing wave of the noise radiated from the machine room into the duct will be established only in the primary mode below the target frequency band (target frequency) to be canceled. Become. With such a configuration, the sound generated in the machine room can be regarded as a one-dimensional plane traveling wave, and the sound from the compressor is output to the outside at the outlet side of the duct section. The active control of interfering with the artificial sound from the control sounding device to suppress the sound can be performed easily and accurately both theoretically and technically.

In this case, the machine room itself is not used as a muffling duct, but because the machine room is provided with a duct part, it is not limited to a storage space such as a compressor or a defrosting water evaporation tray, and the duct part The thickness dimension can be set freely, and the target frequency range can be easily expanded by reducing the dimension. Moreover, since the ducts are arranged vertically, for example, in a refrigerator,
The length of the duct part can be made longer than in the case where the duct part is arranged in the horizontal direction (width direction or depth direction of the refrigerator), and the distance from the noise source to the outlet of the duct part can be made longer.
The calculation processing time of the active control can be afforded, the active control can be easily performed, and the duct portion required for the active control can be sufficiently secured even in a small cooling device. This is because a cooling device such as a refrigerator is generally vertically long.

(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. 4, 1 is a noise source such as a compressor,
Reference numeral 2 denotes a control target point for which it is desired to muffle noise. The sound from the noise source 1 is converted into an electric signal by a sound receiver 3 such as a microphone, and the electric signal is passed through an arithmetic unit 4 including a filter or the like. The sound generator 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 the acoustic transfer function between each of the input points is T11, T21, T12, T22,
The following equation holds as a two-input two-output system.

Therefore, the sound S2 to be generated by the speaker 5 is obtained from the above equation as S2 = (-T12 / R1 + T11 / R2) / (T11 / T22-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 3 show one embodiment of the present invention, which will be described below.

Reference numeral 11 denotes a refrigerator main body, inside of which a freezer compartment (not shown) and a refrigerating compartment 12 (see FIG. 2) are vertically provided. A machine room 13 is formed in a horizontally long shape at the lower part of the rear side of the refrigerator body 11, and a rotary compressor 14, a defrosting water evaporator (not shown), etc. are arranged in the machine room 13. ing. The machine room cover 15 that closes the back surface of the machine room 13 is made of a material (for example, metal such as iron) that has excellent thermal conductivity and large sound transmission loss.

Reference numeral 16 denotes a sound receiver, for example, a microphone disposed in the machine room 13, which is disposed near the central portion of the compressor 14 and receives sound from the compressor 14 which is a noise source and converts it into an electric signal. Reference numeral 17 denotes a rectangular tubular duct portion arranged vertically on the back side of the refrigerator main body 11. The duct portion 17 is integrally formed of, for example, styrofoam. In this duct portion 17, a lower end opening 17a is connected to an opening in the center of the upper surface of the machine room 13, and an upper end opening 17b (outlet) is substantially flush with the upper surface of the refrigerator body 11 and is open upward. And
In the vicinity of the upper end opening 17b of the duct portion 17, a speaker 18, which is a control sound generator, is attached so as to be exposed toward the inside of the duct portion 17. The speaker 18 is adapted to be operated by a signal obtained by processing an electric signal from the microphone 16 by a reverse phase sound calculation circuit (not shown) of a calculator, and The processing is performed based on the silencing principle by the active control described above.

In this embodiment, a fitting recess 11a is vertically formed on the back surface of the refrigerator main body 11 so that the duct 17 can be easily positioned in the assembly process at the time of manufacturing, and the duct 17 is formed in the fitting recess 11a. Are fitted and installed. The duct portion 17 is pressed and fixed from the back side by the back cover 19, and the vacant spaces on the left and right sides of the duct portion 17 are filled with a heat insulating material 20 such as glass wool.

However, in the case of the refrigerator configured as described above, the noise level generated in the machine room 13 in response to the driving of the compressor 14 has a property that it increases in a band of about 1 KHz or less as shown in FIG. Have. Noise on the higher frequency side than this can be attenuated by the transmission loss in the machine room cover 15 and the like, and can be easily silenced by installing an appropriate sound absorbing member in the description chamber 13. The active control of noise by the microphone 16, the speaker 18, and the anti-phase sound calculation circuit as described above may be performed with a target frequency of approximately 1 Kz or less.

Further, when performing active control of noise as described above,
The sound radiated from the machine room 13 into the duct 17 is
In order to control it easily and accurately both theoretically and technically, it is important to configure it so as to have a one-dimensional plane traveling wave. Therefore,
In this embodiment, the size of the duct portion 17 is set to, for example, the width W.
= 150 mm, depth D = 50 mm, height H = 600 mm or more, so that the standing wave of sound in the duct part 17 is established only in the first-order mode. That is, the duct part
The resonance frequency f within 17 is However, Nx, Ny, Nz are the second modes in each direction of X, Y, Z, Lx, Ly, Lz
Is the dimension in each direction of X, Y, Z in the duct part 17 (that is, D, W, H),
C is the speed of sound. Therefore, the frequencies fx, fy, fz of the first standing wave in the X, Y, Z directions can be obtained from the above equation.

That is, as described above, the depth dimension D = 50 mm, the width dimension W
= 150mm and height H = 600mm or more,
The frequency fx of the first standing wave in the X direction is Ny = Nz =
0, sound speed 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 (approximately 1KHz)
In the following, the standing wave of the noise in the duct portion 17 is established only in the Z direction (height direction) mode, and the noise in the duct portion 17 can be regarded as a one-dimensional plane traveling wave. . Therefore, at the time of silencing by active control of noise using the speaker 18 or the like, theoretical treatment of the wavefront becomes easy, and silencing control can be performed easily and accurately.

In this case, the machine room 13 itself is not used as a duct for muffling, but the machine room 13 is provided with the duct portion 17, so that the storage space for the compressor 14, the defrosting water evaporator, etc. is not limited. , Width W of duct part 17
The × D can be set freely, and the target frequency range can be expanded to 1 KHz or more by reducing its size.
Therefore, the silencing effect can be obtained in a wider frequency band, and the noise reduction performance can be improved.

Moreover, since the duct portion 17 is arranged in the vertical direction, the length of the duct portion 17 can be made longer than in the case where the duct portion 17 is arranged in the horizontal direction (width direction or depth direction of the refrigerator body 11). The distance from the noise source to the outlet 17b of the duct unit 17 can be increased, and the calculation processing time of the active control can be spared by that amount, which facilitates the active control and contributes to the improvement of the control accuracy. That is, if the length of the duct part 17 is short, the time until the sound of the noise source reaches the outlet 17a of the duct part 17 becomes extremely short, and the calculation process in the anti-phase sound calculation circuit is not speeded up by that much. This is because the sound emitted from the speaker 18 is delayed and cannot be silenced. Since there is a certain limit to the speedup of this arithmetic processing time, the length of the duct part 17 is, for example, 60
It is preferably 0 mm or more. Therefore, for example, a small refrigerator of 70 class (for example, width 440mm, height 800m
In m), if the duct part is arranged in the lateral width direction, the length of the duct part required for active control cannot be secured. However, in the present embodiment, since the duct portion 17 is arranged in the vertical direction, it is possible to secure a sufficient length of the duct portion 17 necessary for active control even in a small refrigerator, and it is possible to use it even in a small refrigerator. Noise can be reduced by control.

Further, in this embodiment, the position of the speaker 18 is the refrigerator main body.
Since it is located at the upper part of 11 and is away from the compressor 14, there is an advantage that deterioration of the speaker 18 due to heat radiation of the compressor 14 can be suppressed as much as possible and the life of the speaker 18 can be extended.

On the other hand, since the machine room 13 can be ventilated to the outside through the duct portion 17, it is possible to prevent the temperature inside the machine room 13 from rising abnormally due to heat generated when the compressor 14 is driven.
Further, since the machine room cover 15 is made of a material having excellent thermal conductivity, the heat dissipation efficiency of the heat generated in the machine room 13 is improved, and from this aspect as well, the temperature rise in the machine room 13 is increased. Can be kept low.

If the height dimension H of the duct portion 17 becomes large, air convection for heat dissipation is less likely to occur. In this case, therefore, a small vent hole () that does not cause sound leakage at a frequency below the target frequency ( For example, several openings having a size of about 5 mm × 10 mm) may be formed at the bottom of the machine room 13.

Further, the present embodiment is an application example of a refrigerator in which the machine room 13 is provided at the bottom of the refrigerator main body 11, but a duct section is also provided from the machine room to the refrigerator in which the machine room is provided above the refrigerator main body. The present invention can be applied by arranging downward.

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

[Effects of the Invention] As is apparent from the above description, according to the present invention, a duct portion that opens the inside of the machine chamber to the outside is disposed in the vertical direction, and the duct portion is arranged in a three-dimensional direction. By setting the dimension in one direction larger than the other dimension among the dimensions, only the first-order mode is established below the frequency band in which the standing wave of the sound radiated from the machine room into the duct section is canceled. Since the duct part is configured as described above, when performing active control in which noise generated in response to the drive of the compressor in the machine room is canceled by the signal sound from the control sounder, simplification of the active control and control accuracy Can be realized.

Moreover, since the machine room itself is not used as a duct for noise reduction, the duct part is provided in the machine room, so the duct space is not limited to the storage space for the compressor, defrost water evaporation tray, etc. The size of the target frequency can be freely set, and the range of the target frequency can be easily expanded by reducing the size, so that the silencing effect can be obtained in a wider frequency band and the noise reduction performance can be improved. Moreover, since the duct is arranged vertically, the distance from the noise source to the outlet of the duct can be increased,
As a result, the processing time for active control can be spared, which facilitates active control, and even with a small cooling device, the length of the duct part required for active control can be sufficiently secured, and a small cooling device can be obtained. Also, in the case of active control, noise reduction is possible.

[Brief description of drawings]

1 to 3 show an embodiment of the present invention. FIG. 1 is a perspective view of a refrigerator viewed from the rear side, FIG. 2 is a vertical side view of a lower portion of the refrigerator, and FIG. 3 is a duct part. FIG.
Further, FIG. 4 is a schematic configuration diagram showing a silencing principle by active control, and FIG. 5 is a noise level characteristic diagram. In the figure, 11 is a refrigerator main body, 13 is a machine room, 14 is a compressor, 15 is a machine room cover, 16 is a microphone (sound receiver),
Reference numeral 17 is a duct part, and 18 is a speaker (control sound generator).

Claims (1)

[Claims] 1. A sound receiver converts a sound generated by driving a compressor housed in a machine room into an electric signal, and a control sounder is operated based on a signal obtained by processing the electric signal by an arithmetic unit. A silencer for a cooling device that actively cancels the sound radiated from the machine room to the outside by operating the machine room in the vertical direction with a duct part that opens the machine room to the outside. By arranging and setting the dimension in one direction out of the respective dimensions in the three-dimensional direction of the duct section to be larger than the other dimension, the standing wave of the sound radiated from the machine room into the duct section is canceled. A silencer for a cooling device, characterized in that the duct section is configured so that only a primary mode is established in a frequency band below a target frequency band.