JPH03191279A - Low noise refrigerator - Google Patents

Abstract

PURPOSE:To suppress compressor noise by means of control noise by a method wherein a vibration pickup to detect vibration in the direction of the tangential line of a compressor body is mounted to the compressor body, and a control circuit to process an output signal from the vibration pickup and a sounding device driven by means of an output signal from the control circuit and emitting control sound to the interior of a machine room are provided. CONSTITUTION:A plateform jig 26 extending in the direction of a bus, i.e., a Y-axis, is erected on the peripheral surface of the body of a rotary compressor 20. A vibration pickup 30 is mounted on the surface of the jig 26 the normal of which is pointed in the direction of an X-axis, and vibration in the tangential direction of the compressor body is detected by the pickup 30. An output signal from the vibration pickup 30 is processed by a control circuit 40 and inputted to a speaker 50 pointed toward an opening 17 of a front inclination plate 14. By inputting a transfer function G to the control circuit 40, control sound A responding to compressor noise S is emitted from the speaker 50 and the noise S can be suppressed at the opening 17 of a machine room.

Description

[Detailed Description of the Invention] [Purpose of the Invention] (Industrial Application Field) The market demand for lower noise levels in home appliances is increasing year by year as the sound insulation properties of homes are improved and users become more affluent in their lifestyles. There is a tendency to

The present invention relates to a low-noise refrigerator equipped with a silencing system that employs a so-called active control method.

(Prior Art) Conventionally, attempts have been made to reduce the noise of compressors and fan motors themselves, which are the sources of noise in refrigerators, and vibration-proof designs have been made for refrigerant piping in machine rooms that house compressors. Additionally, the use of sound-absorbing/sound-insulating materials and mufflers has reduced the high-frequency components of compressor noise to some extent.

However, these conventional techniques have a problem in that a sufficient noise reduction effect cannot be obtained particularly in a low frequency band.

Therefore, it is conceivable to apply a silencing system that employs a so-called active control method to refrigerators.

This system actively emits control sounds from a speaker to cancel out noise.

FIG. 9 is a schematic diagram of a system in which this active control silencing system is applied to a refrigerator to cancel compressor noise.

A rotary compressor 20, which is the main source of refrigerator noise, is disposed in the machine room 10 located at the bottom of the back of the refrigerator. This machine room IO is sealed except for the only opening 17 for heat dissipation, evaporation of defrosting water, etc., and has a one-dimensional duct structure. That is, the cross-sectional dimension of the duct is made sufficiently small compared to the wavelength of the compressor noise S to be reduced, so that the compressor noise in the machine room 10 is made into a one-dimensional plane traveling wave. The compressor noise S is detected by a microphone 35 placed at a position away from the opening 17 in the machine room IO. The compressor noise detected by the microphone 35, that is, the detection stand M, is processed using, for example, a finite impulse response filter (hereinafter referred to as F) that processes the signal as it is in the time domain.
It's called an IR filter. ) is applied to the speaker 50 after being processed by the control circuit 40 of the transfer function G. The control sound A emitted from the speaker 50 causes the machine room opening 17 to
The compressor noise that is trying to come out is canceled out.

The transfer function G of the control circuit 40 is determined as follows.

First, the detection stand M using the microphone 35 determines the acoustic transfer function GsM between the compressor and the microphone and the acoustic transfer between the speaker and the microphone based on the noise S emitted from the rotary compressor 20 and the control sound A emitted from the muffling speaker 50. Using the function CAM, the following formula (
It can be expressed as 1).

M-SXG +AXG -...-"'
(1) If the microphone 55 for evaluating the silencing effect is installed in the machine room opening 17 for the SM test, the measurement sound R of the evaluation microphone 55 will be determined by the acoustic transfer function GSR between the compressor opening and the sound between the speaker and the opening. It can be expressed as in the following equation (2) using the transfer function GAR.

R-S x G + A x G -----
----(2) SRAR Also, since G is a transfer function between the microphone and the speaker, the following equation (3) holds true.

-MxG ......, (3) In order to cancel the compressor noise that is about to come out from the opening 17, the following equation (4) must hold.

−0 (4) From the above equations (1) to (4), the transfer function G for noise reduction
is expressed as the following equation (5).

G-GSR/(GSR"AM-GSMxGAR)...
(5) When the denominator and numerator of this equation (5) are divided by GSM't', the following equation (6) is obtained. However, GMR is defined by equation (7).

c l-G / (G MRX G AM -G A
R) MR ・・・・・・・・・ (6) GMR= GSR”8M ・・・・・・・・・
(7) Using these equations (6) and (7), even if the compressor noise S is unknown, the transfer function can be used to set the measured sound R to 0 by measuring the transfer function ratio GMt between GSR and GsM. Function G can be found.

At this time, the detection table M may be operated manually while the rotary compressor 20 generates the noise S, and the measurement sound R may be used as a response.

If the transfer function G determined as described above is given to the control circuit 40, the control sound A corresponding to the compressor noise S can be emitted to cancel out the noise S at the machine room opening 17.

(Problems to be Solved by the Invention) As explained above, when the active control method is adopted and the compressor noise S is detected by the microphone 35, the following problem occurs.

First, not only the noise S of the rotary compressor 20 but also the control sound A from the muffling speaker 5o may be transmitted to the microphone 35, causing howling. Therefore, the output of the speaker 5o cannot be increased much, and a sufficient silencing effect cannot be obtained. However, it is a play to prevent howling! If an echo canceller is installed in the s circuit 4o, the cost will be high.

Furthermore, if a fan for cooling the rotary compressor 20 is installed in the machine room IO, the noise emitted from this fan will also be picked up by the microphone 35.
Control for silencing becomes complicated.

Furthermore, there was also the risk that the sound deadening system would react to external sounds, for example.

The present invention has been made in consideration of the above circumstances, and
To prevent the occurrence of howling when reducing compressor noise of a refrigerator by adopting an active control silencing system, and to provide a silencing system that is not affected by sounds other than compressor noise.

[Structure of the Invention] (Means for Solving the Problem) In order to achieve the above-mentioned object, the low-noise refrigerator according to the present invention has a one-dimensional duct whose cross-sectional dimension is sufficiently small compared to the wavelength of the noise to be reduced. A machine room having a structure of 11
A rotary compressor with a cylindrical main body, which is a noise source, is placed in a machine room with an opening at the I position.A vibration pickup is attached to the main body of the compressor to detect vibrations in the tangential direction, and the output signal of this vibration pickup is processed. The system is equipped with a control circuit for controlling the compressor, and a sound generator that is driven by the output signal of the control circuit to emit a control sound inside the machine room.

(Function) The main part of the noise emitted from a rotary compressor is the rotation sound of the built-in rotor. The rotation of the rotor causes vibrations in the tangential direction of the compressor body, and these vibrations are emitted outside the compressor body as rotation noise. The vibration pickup for a low-noise refrigerator according to the present invention efficiently detects vibrations in the tangential direction of the compressor body corresponding to the rotation noise of the rotary compressor. The control circuit processes the output signal of this vibration pickup to drive a sound generator such as a speaker. As a result, the sound generator emits a control sound corresponding to the comb 1 noise, and the compressor noise that is about to come out from the machine room opening is canceled out by this control sound.

(Example) FIG. 1 is an exploded perspective view of the lowermost part of the back of a low-noise refrigerator according to an example of the present invention.

A rotary compressor 20, which is the main source of noise, is disposed in the machine room 10 located at the bottom of the back of the refrigerator. This machine room 10 is closed by side plates 11, 12, ceiling plate 1B, front inclined plate 14, bottom plate 15, and rear cover IB, and is provided for heat radiation etc. at the left end of cover 16 when viewed from the back of the refrigerator. All but the only opening 17 are sealed. The X axis is in the front and back direction of the refrigerator, the Y axis is in the left and right direction,
If two axes are taken in the vertical direction, the machine room 10 has a one-dimensional duct structure in seven wheel directions.

That is, the cross-sectional dimension of the machine room 10 in the X-2 plane is made sufficiently small compared to the wavelength of the compressor noise to be reduced, and the compressor noise becomes a one-dimensional plane traveling wave in the Y-axis direction. Specifically, 3. The dimension of the machine room IO in the Y-axis direction (
For example, if the duct length) is 640 mm or 880 mm, and the dimensions in the X-wheel and Z-axis directions are approximately 250 mm, then 8
Since acoustic modes occur only in the Y-axis direction at frequencies below 00 Hz, the machine room IO can be considered as a one-dimensional duct in the Y-axis direction. Furthermore, a sound absorbing material made of soft tape is attached to the inner wall surface of the machine room 1G to prevent the emission of high frequency noise of 800 Hz or more. Therefore, the muffling target frequency of the active control muffling system according to this embodiment is 1
00Hz or more and less than 800Hz.

The rotary compressor 20 is fixed in the Y-axis direction on the bottom plate 15 at the right end position in the figure.

This rotary compressor 20 has a cylindrical main body, with a motor section 21 on the right side of the main body and a mechanical section 22 on the left side of the main body. A cluster portion 23 is provided on the end surface on the motor portion 21 side.
is provided, and a suction vibrator 24 is connected to the end face on the mechanical part 22 side. A plate-shaped jig 26 is erected on the circumferential surface of the main body of the rotary compressor 20 and extends in the generatrix direction, that is, the Y-axis direction. A vibration pickup 30 is mounted on the surface of the jig 26 with its normal line facing the X-axis direction, and this pickup 30 detects vibrations in the tangential direction of the compressor body.

The output signal of the vibration pickup 30 is passed through a low-pass filter 41 . A control circuit 40 consisting of a cascade circuit of an A/D converter 42, an FIR filter 43, and a D/A converter 44.
It is provided to the speaker 50 facing the opening 17 attached to the left end position of the front inclined plate 14 in the figure. The low-pass filter 41 cuts signals with a high frequency of one-half or more of the sampling frequency of the A/D converter 42 in order to prevent occurrence of aliasing errors. The A/D converter 42 is a low-pass filter 4
1 is converted into a digital signal so that it can be processed by an FIR filter 43. FIR filter 43 convolves the digital input signal and produces a predetermined output signal. The D/A converter 44 converts the digital signal output from the FIR filter 43 into an analog signal,
This is given to the speaker 50. The control sound emitted from the speaker 50 cancels the compressor noise coming out from the machine room opening 17. Note that when the upper limit of the frequency to be muted is set to 800 Hz as described above, the sampling frequency is preferably set as high as 1.4 kHz or higher. If the duct length is 640 mm, 6.4 kHz,
In the case of 880 mm, 12.8 kHz is appropriate.

FIG. 2 is a schematic diagram showing an active control silencing system for a low-noise refrigerator according to the embodiment of the present invention described above.

In this embodiment, a vibration pickup 30 is used in place of the microphone 35 shown in FIG. FIG. 3 is a diagram showing the results of measuring the coherence function between the tangential vibration of the rotary compressor main body detected by the vibration pickup 30 and the compressor noise detected by the microphone using a two-channel FFT analyzer. As shown in this figure, there is a good correlation between the tangential vibration of the compressor body and the compressor noise S.

That is, in constructing a silencing system, instead of detecting the compressor noise S, it is possible to employ vibration measurement in the tangential direction of the compressor main body. Moreover, if the vibration pickup 80 is adopted, the speaker
The acoustic transfer function G between the knob and the knob becomes 0 (the following equation (8)).

% Formula % (8) By substituting this formula (8) into the above formula (6), the following very simple formula (9) is obtained. However, G is
It is a transfer function ratio between SR and GSM, and is defined by the above equation (7).

G --G MR/G AR (9) Using these equations (9) and (7), even if the compressor noise S is unknown, the transfer function ratio aMR+A>I constant can be determined as in the case of Fig. 9. By doing so, the transfer function G of the control circuit 40 for setting the measurement sound R at the aperture 17 to O can be obtained. However, since the noise emitted from the rotary compressor 20 has a discrete spectrum consisting of rotational sound and electromagnetic sound, only the rotation speed of the rotary compressor 20 and its harmonics, and the power supply frequency and the transfer function of its harmonics are valid data. , it is better to perform linear interpolation between them.

The example of the silencing transfer function G obtained in the above manner is shown in the fourth example.
As shown in the figure. If this transfer function G is given to the control circuit 40, the control sound A corresponding to the compressor noise S can be transmitted to the speaker 5.
This noise S, emitted from zero, can be canceled out at the machine room opening 17. The noise reduction effect of this active control silencing system is shown in FIG. The solid line in the figure indicates the noise level before muting, and the broken line indicates the noise level after muting. As shown in the figure, according to this embodiment, a noise reduction effect of, for example, about 10 dB can be obtained. Furthermore, since the compressor noise S is indirectly measured by the vibration pickup 30, there is no need to worry about howling due to the control sound A even if the output of the silencer speaker 50 is increased, and compressor noise such as fan noise or external noise It is not affected by sounds other than S.

However, the compressor vibration is picked up by the pickup 30,
This is processed by the control circuit 40 into a signal for silencing, the processed signal is input to the speaker 50, and the series of operations until the control sound A from the speaker 50 reaches the opening 17 is as follows:
The sound radiated from the rotary compressor 20 is transmitted through the opening 17.
must be completed before reaching. Therefore, in order to extend the processing time of the control circuit 40 as long as possible, the rotary compressor 20 should be
It is preferable to place the muffling speaker 50 as far away from the opening 17 as possible and near the opening 17.

For comparison with this embodiment, the drawings corresponding to the above-mentioned Figs. 3 to 5 are shown in Figs. 6 to 8, respectively, for the case where vibration in the normal direction of the compressor body is detected by the vibration vibration knob. Shown below. In this case, vibration detection sensitivity decreases,
Only about 7 dB of noise reduction effect can be obtained.

Note that in this embodiment, the control circuit 40 includes an FIR filter 43.
Although real-time control is performed by employing the following, for example, control with a one-cycle delay may be performed. As a countermeasure against deviations in the noise reduction transfer function G due to changes over time or individual differences,
It is also possible to employ so-called adaptive control, which automatically changes as appropriate.

[Effects of the Invention] As explained above, the low noise refrigerator according to the present invention has the following advantages:
Since it uses an active control silencing system that indirectly measures compressor noise through a vibration pickup, there is no need to worry about howling due to control sound even if the output of the silencing generator is increased. It is not affected by sounds other than compressor noise such as fan noise or external noise. Moreover, the low-noise refrigerator vibration pickup according to the present invention does not detect the vibration in the normal direction of the compressor body, but the vibration in the tangential direction thereof, so it can detect the rotation sound of the rotary compressor with high sensitivity. be able to.

Therefore, according to the present invention, the silencing system can be simplified and stabilized, and a great silencing effect can be obtained.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view of the bottom of the back of a low-noise refrigerator according to an embodiment of the present invention. FIG. 2 is a schematic diagram of the active control silencing system shown in the previous figure. Figure 4 shows the coherence function between the tangential vibration of the compressor body measured at the vibration pickup mounting position and the compressor noise. Figure 5 is a noise level diagram showing the noise reduction effect of the low-noise refrigerator shown in Figure 1. Figure 6 is a diagram showing the coherence function between the vibration in the normal direction of the compressor body and the compressor noise. Fig. 7 is a diagram showing an example of the silencing transfer function G given to the control circuit in the case of the previous figure, and Fig. 8 is a diagram showing an example of the silencing transfer function G given to the control circuit in the case of the previous figure. Figure 9 is a schematic diagram showing a comparative example of an active control silencing system for a low-noise refrigerator. Explanation of symbols 10... Machine room, 17... Opening, 20... Rotary compressor, 2B... Jig, 30... Vibration pickup, 40... Control circuit, 50... Speaker.

Claims (1)

[Claims] 1. A machine room with a one-dimensional duct structure with a cross-sectional dimension sufficiently small compared to the wavelength of the noise to be reduced, and a rotary compressor with a cylindrical main body, which is the noise source, is placed in the machine room with an opening in one place. A vibration pickup that detects vibrations in the tangential direction is attached to the main body of the compressor, a control circuit processes the output signal of this vibration pickup, and a control circuit is driven by the output signal of this control circuit to emit control sound into the machine room. 1. A low-noise refrigerator characterized in that the refrigerator is provided with a sound generator that emits a sound, and uses the control sound to cancel out compressor noise that is about to come out from the opening.