JPH04260775A - Noise suppressor for cooler - Google Patents

Abstract

PURPOSE:To solve the problem of the cost increase arising from the provision of a mounting tool by mounting a vibration sensor for active control of noise suppression directly to the leg part of a compressor. CONSTITUTION:A vibration sensor 35 is mounted to the leg part 33 of a rotary compressor 28. When the rotary compressor 28 is driven, since the vibration sensor 35 is excited in the vibrating direction of the rotary compressor 28, the vibration sensor 35 can efficiently detect the vibration of the rotary compressor 28. In this way a control circuit 36 executes the computation for active control based on an electric signal from the vibration sensor 35 and also outputs a control noise from a speaker 41 and, therefore, the noise from the rotary compressor 28 is suppressed at an opening part 32.

Description

[Detailed description of the invention]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silencing device for a cooling device such as a refrigerator, which actively cancels the noise of a compressor in the cooling device.

0003

[Prior Art] Cooling devices using compressors, such as refrigerators, are often installed in the living spaces of ordinary households and are operated continuously regardless of the season. Reducing that noise has become an important technical issue in recent years. In this case, the most problematic noise source for the refrigerator is noise from the machine room in which the compressor and the piping system connected thereto are housed.

[0004] In recent years, in order to effectively reduce noise in machine rooms, attention has been paid to the application of active noise control technology that uses sound wave interference to reduce noise. This active control basically detects the sound from the noise source using a detection means (for example, a microphone) installed at a specific location and converts it into an electrical signal, and then uses the control circuit to control the sound based on this electrical signal. By operating a sound generator (for example, a speaker), the sound generator produces 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 opening of the machine room). The idea is to attenuate the original sound by causing this artificial sound to interfere with the original sound.

By the way, as a detection means for detecting the sound from the compressor, it has been considered to attach a vibration sensor to the compressor to directly detect the vibration sound of the compressor. In this case, the vibration sensor detects only the vibration sound of the compressor, which eliminates the risk of detecting noise other than the compressor and outputting the wrong control sound from the speaker, which is the case with microphones, which improves the muffling effect of active control. can be done.

FIGS. 10 to 12 show an example of a configuration in which a vibration sensor is directly attached to a compressor. Machine room cover 1
In FIG. 10 shown in an open state, a rotary compressor 4 for supplying refrigerant is disposed in a machine room 3 provided at the bottom of the refrigerator body 2, and this rotary compressor 4 is connected to the machine room 3 through legs 5. Fixed to the bottom.

As shown in FIG. 11 showing a part of the front of the rotary compressor 4 and FIG. 12 showing a part of the side,
A vibration sensor 6 is attached to the outer peripheral surface of the rotary compressor 4. This vibration sensor 6 is positioned by a fixture 7 so that its detection direction is along the tangential direction of the outer peripheral surface of the rotary compressor 4, that is, along the vibration direction of the rotary compressor 4.

In FIG. 10, a speaker 8 is disposed on the back wall of the machine room 3, and faces an opening 9 of the machine room cover 1. Then, the electrical signal from the vibration sensor 6 is passed through a low-pass filter 10 and converted into a digital signal by an A/D converter 11. The converted digital signal is subjected to arithmetic processing for active control by the FIR filter 12, is D/A converted by the D/A converter 13, and is output from the speaker 8. Here, the FIR filter 12 is configured to convert a digital signal corresponding to an electric signal from the vibration sensor 6 into a digital signal at high speed. As a result, the speaker 8 outputs a control sound corresponding to the vibration of the rotary compressor 4, so that the noise from the rotary compressor 4 is muffled at the opening 9 of the machine room cover 1.

[0009]

[Problems to be Solved by the Invention] In the case of the above-mentioned conventional structure, the vibration sensor 6 is fixed to the outer circumferential surface of the rotary compressor 4 using the fixture 7. 4.The overall manufacturing cost increases. Further, since the fitting 7 is provided in a form that protrudes from the rotary compressor 4, measures must be taken to prevent the fitting 7 from being damaged during transportation of the rotary compressor 4, and also measures must be taken to prevent the fitting 7 from being damaged during transportation of the rotary compressor 4. There is also the problem that loading efficiency is reduced.

The present invention has been made in view of the above circumstances, and its purpose is to actively cancel the noise accompanying the drive of the compressor based on an electrical signal from a vibration sensor attached to the compressor. , the mounting bracket for attaching the vibration sensor to the compressor was abolished,
It is an object of the present invention to provide a silencing device for a cooling device that is effective in reducing manufacturing costs.

[Configuration of the invention]

0012

[Means for Solving the Problems] A silencer for a cooling device according to the present invention detects vibrations accompanying the drive of a compressor disposed in a machine room using a vibration sensor, converts the vibrations into an electrical signal, and converts the detected vibrations into an electrical signal. In the silencing device for a cooling device, the sound emitted from the machine room to the outside is actively canceled by operating a control sounder based on the vibration sensor, the detection direction of which is the direction of the compressor. It is attached to the leg of the compressor in a state that matches the vibration direction.

[0013]

[Operation] Since the compressor is disposed through the legs, the legs vibrate in response to the vibrations of the compressor. At this time, since the detection direction of the vibration sensor attached to the leg of the compressor matches the vibration direction of the compressor, the vibration sensor can efficiently detect the vibration of the compressor.

Since the control circuit operates the control sound generator based on the electric signal from the vibration sensor, the sound emitted from the machine room to the outside is muffled by the control sound from the control sound generator.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a refrigerator will be described below with reference to FIGS. 1 to 9. First, in FIG. 2 showing the overall configuration of a refrigerator, a refrigerator main body 21, which is a cooling device main body, is provided with a freezing compartment 22, a refrigerating compartment 23, and a vegetable compartment 24 in this order from the top. A cooling system is provided inside the refrigerator main body 21, and these components will be explained below.

That is, a cooler 25 is disposed at the back of the freezer compartment 22. A fan 26 is provided above the cooler 25.
The cool air generated by the cooler 25 by the fan 26 is sent to the freezer compartment 22 and the refrigerator compartment 23.
is supplied to

A machine compartment 2 is located at the bottom of the back side of the refrigerator body 21.
7 is formed. Inside this machine room 27,
A tally compressor 28, a condenser pipe 29, and a defrosting water evaporation device 30 using so-called ceramic fins are housed. When the rotary compressor 28 is in the driving state, the refrigerant from the rotary compressor 28 is supplied to the cooler 25 through a refrigerant passage (not shown) and is cooled, and the fan 26 is driven to
Heat exchange takes place between the inside of the refrigerator and the inside of the refrigerator.

Now, FIG. 1 (here, condenser pipe 2
9 and the defrosting water evaporation device 30 are omitted), the machine room 27 has a rectangular opening only at the back side, and this opening part is a part of the machine room cover.
It is now closed due to 31. At this time, the peripheral edge of the machine room cover 31 is airtightly attached to the opening edge of the machine room 27, and the left edge in the figure has an elongated rectangular heat dissipation device extending in the vertical direction. An opening 32 is formed. That is, when the machine room cover 31 is attached, the machine room 27 is in a closed state with the heat radiation opening 32 remaining.

In FIG. 3 showing the plane of the rotary compressor 28, the legs 33 of the rotary compressor 28 are fixed to the bottom plate of the machine room 27 via rubber (not shown), so that the rotary compressor 28 is fixed to the bottom plate of the machine room 27.
It is fixed in a vibration-proof state. Further, a hole 34 is formed in the leg portion 33 of the rotary compressor 28, and a vibration sensor 35 is mounted in the hole 34.

On the other hand, in FIG. 1, the refrigerator main body 21 is equipped with a control circuit 36 for executing noise reduction. This control circuit 36 includes a low-pass filter 37 that processes the electrical signal Sm from the vibration sensor 35, and an A/D converter 3.
8. Consisting of an FIR filter 39 and a D/A converter 40, the processed control signal Pa drives a speaker 41, which is a control sound device provided in the machine room 27, and actively cancels noise in the machine room 27. (Figure 4)
reference).

The principle of silencing by active control will be schematically explained below with reference to FIG. Here, the sound generated by the rotary compressor 28 which is the noise source is S1,
The sound generated by the speaker 41 is S2, the vibration sound detected by the vibration sensor 35 is R1, the sound at the heat radiation opening 32 which is the control target point is R2, and the sound output and input points as described above are The acoustic transfer function between each is T11 (acoustic transfer function from the compressor 28 to the vibration sensor 35)
, T21 (acoustic transfer function from the speaker 41 to the vibration sensor 35), T12 (acoustic transfer function from the compressor 28 to the opening 32)
) and T22 (acoustic transfer function from the speaker 41 to the opening 32), the following equation holds true as a two-input, two-output system.

[0022]

[Math 1]

Therefore, the sound S2 to be generated by the speaker 41
From the above formula, S2 = (-T12・R1 +T11・
R2 )/(T11・T22−T12・T21), but in this case, the goal is to make the sound level at the heat radiation opening 32 zero, so R2 = 0.
You can leave it as 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 heat dissipation opening 32 to zero, the sound R1 received by the vibration sensor 35 must be calculated by F = T12/(T12・T21−T11・T22).
...(1) If the filtered and processed sound S2 is generated from the speaker 41, the sound level at the heat dissipation opening 32 can be reduced to zero in theory, and the control circuit 36 , is configured to apply the control signal Pa to the speaker 41 while performing such sound processing (calculation) at high speed.

Now, in the above equation (1), F=G,T
12=Gso, T21=Gam, T11=Gsm, T2
When replacing 2=Gao, G=Gso/(Gso・Gam−Gsm・Gao)
...(2). Here, Gso,
Gam, Gsm, and Gao mean that the first subscript corresponds to the input side and the second subscript corresponds to the output side (response side). For example, Gam indicates that the input signal to the speaker 41 is the input side, and the aperture 32 shows an acoustic transfer function when the noise at No. 32 is measured using the output signal from the monitor microphone as the output side. In this case, since the vibration sensor 35 does not receive sound from the speaker 41, Gam can be considered to be zero. Therefore, the above equation (2) is expressed as G=-Gso/(
Gsm・Gao) ...(3). Here, since Gso/Gsm=Gmo, the above (3
) formula is G=-Gmo/Gao
...(4). In other words, the sound level at the heat dissipation opening 32 can be theoretically determined by generating a sound from the speaker 41 that is processed by filtering the electrical signal from the vibration sensor 35 according to G shown in equation (4) above. It can be set to zero at the top.

On the other hand, in the case of the refrigerator configured as described above, the machine room 2
The noise level generated within 7 is 700 as shown in Figure 7.
It becomes a state in which it has the property of increasing in the band below about Hz and in the band from 1.5 to 5 KHz. Among the noise corresponding to each of these bands, noise on the high frequency side can be attenuated by transmission loss in the machine room cover 31, etc., and can be easily attenuated by installing an appropriate sound absorbing member in the machine room 27. Therefore, active control of noise using the vibration sensor 35, speaker 41, and control circuit 36 as described above can be performed with a target frequency of 700 Hz or less.

In addition, in the case of active noise control as described above, configuring the noise in the machine room 27 to be a one-dimensional plane traveling wave is theoretically possible. It is also important to perform the above operations easily and accurately. Therefore, in this embodiment, among the dimensions D, W, and H in the three-dimensional directions of the machine room 27 shown in FIG. Set larger than D and H (specifically, W=
600 mm and D=H=200 mm), so that the standing wave of sound in the machine room 27 is established only in the first mode. In other words, for example, the machine room 27
When it is assumed that is a rectangular cavity, the following equation holds true.

[0027]

[Math 2]

[0028] However, f is the resonance frequency (Hz), Nx
, Ny, Nz are the th modes in each of the X, Y, and Z directions,
Lx, Ly, and Lz are the dimensions in each of the X, Y, and Z directions (that is, D, W, and H) in the machine room 7, and C is the speed of sound. Therefore, from the above equation, the frequencies fx, fy, fz of the first standing wave in each of the X, Y, and Z directions can be determined.

That is, as mentioned above, the depth dimension D=2
00mm, width dimension W=600mm, height dimension H=200
If it is set to mm, the frequency fx of the first standing wave in the X direction is Ny = Nz = 0, sound speed C = 340 m/s,

[0030]

[Math 3]

Similarly, the frequencies fy and fz of the first standing wave in the Y and Z directions are as follows:

[0032]

[Math 4]

[0033] As a result, below the target frequency (=700Hz), the standing wave of noise in the machine room 27 only exists in the mode in the Y direction (width direction), and the noise in the machine room 27 is Noise can be considered as a one-dimensional plane traveling wave. Therefore, the speaker 41
When silencing noise through active noise control using
The theoretical handling of the wavefront becomes easier, and silencing control can be performed easily and accurately.

[0034] Here, the inventor of the present application has investigated the silencing effect of active control when the vibration sensor 35 is attached to the leg portion 33 of the rotary compressor 28 and when it is attached to the outer peripheral surface of the rotary compressor 28 (conventional configuration). compared.

FIG. 8 shows the machine room 27 when the vibration sensor 35 is attached to the leg 33 of the rotary compressor 28.
FIG. 9 shows the noise level characteristics of the opening 32 when the vibration sensor 35 is attached to the outer peripheral surface of the rotary compressor 28.

As is clear from comparing FIGS. 8 and 9,
The vibration sensor 35 is connected to the leg 33 of the rotary compressor 28.
It has been found that the silencing ability when the vibration sensor 35 is attached to the rotary compressor 28 is comparable to the silencing ability when the vibration sensor 35 is attached to the outer peripheral surface of the rotary compressor 28.

In short, according to the above configuration, the detection direction of the vibration sensor 35 is aligned with the rotary compressor 4.
Since the rotary compressor 28 is mounted on the legs 33 of the rotary compressor 28 so as to match the vibration direction of the rotary compressor 41 (the tangential direction of the outer circumferential surface), the vibration of the rotary compressor 41 can be efficiently detected by the vibration sensor 35. Therefore, compared to the conventional configuration in which the vibration sensor is attached to the outer circumferential surface of the compressor using a fitting, the manufacturing cost of the compressor 28 can be reduced by omitting the fitting. Furthermore, since there are no protrusions on the outer circumferential surface of the rotary compressor 28 by omitting the attachment, there is no need to take special measures to protect the attachment when transporting the rotary compressor 28, and the loading of the rotary compressor 28 is also possible. It is possible to avoid a decrease in efficiency.

[0038]

Effects of the Invention As is clear from the above description, according to the silencer for a cooling device of the present invention, the vibration sensor for detecting the vibration of the compressor is connected to the compressor with its detection direction matching the vibration direction of the compressor. Since the vibration sensor is attached to the leg of the compressor, the noise caused by the drive of the compressor is actively canceled based on the electric signal from the vibration sensor attached to the compressor. This provides excellent effects such as eliminating the need for fixtures and reducing manufacturing costs.

[Brief explanation of the drawing]

[Fig. 1] A perspective view of a machine room showing an embodiment of the present invention.

[Figure 2
] Longitudinal cross-sectional view of a refrigerator

[Figure 3] Plan view of rotary compressor

[Figure 4] Schematic configuration diagram of the silencer

[Figure 5] Schematic configuration diagram showing the principle of silencing by active control

[Fig. 6] Schematic perspective view for explaining the dimensional relationship of the machine room

[Figure 7] Noise level characteristic diagram

[Figure 8] Noise level characteristic diagram by active control

[Figure 9] A diagram equivalent to Figure 8 when the vibration sensor is attached to the outer peripheral surface of the rotary compressor

[Figure 10] A diagram equivalent to Figure 1 showing a conventional example

[Fig. 11] Front view showing a part of the rotary compressor

[
Figure 12: Side view showing part of the rotary compressor

[Explanation of symbols]

21 is the refrigerator body (cooling device), 27 is a machine room, 28 is a rotary compressor, 31 is a machine room cover, 33 is a leg, 35 is a vibration sensor, 36 is a control circuit, and 41 is a speaker (control sound generator). be.

Claims (1)

[Claims] 1. A vibration sensor detects vibrations caused by driving a compressor disposed in a machine room, converts the detected vibrations into an electric signal, and operates a control sound generator based on this electric signal. In a silencer for a cooling device that actively cancels sound radiated from a room to the outside, the vibration sensor is attached to a leg of the compressor with its detection direction matching the vibration direction of the compressor. A silencer for a cooling device characterized by: