Patent Publication Number: US-8122732-B2

Title: Refrigerator with noise reduction structure using inverse phase sound wave

Description:
RELATED APPLICATIONS 
     This application is the U.S. National Phase under 35 U.S.C. §371 of International Application No. PCT/KR2007/004334, filed on Sept. 7, 2007, which in turn claims the benefit of Korean Patent Application No. 10-2006-0086086, filed on Sept 7, 2006, the disclosures of which Applications are incorporated by reference herein. 
     TECHNICAL FIELD 
     The invention relates to a refrigerator having a noise reduction structure, and more particularly, to a refrigerator having a noise reduction structure of a new type wherein a branch pipe is provided to an outer periphery of a discharge pipe so as to reduce the intensive noise occurring from an impeller part, and a traveling sound wave, which travels toward the discharge pipe, and a reverse wave, which travels toward the branch pipe, are thus cancelled at a point at which the two waves meet, thereby reducing the noise. 
     BACKGROUND ART 
     As shown in  FIG. 1 , a refrigerator, which is typically used, comprises an evaporator  10 , an impeller part  12  and a condenser  14  and has such a structure that the evaporator  10 , the impeller part  12  and the condenser  14  are organically connected to each other to circulate the refrigerant. To be more specific, the refrigerant is transferred from the evaporator  10  to the condenser  14  through a discharge pipe  16  via the impeller part  12  compressing the refrigerant. At this time, a traveling sound wave  22 , which is generated while the impeller part  12  compresses and discharges the refrigerant to the discharge pipe  16 , is spread along the discharge pipe  16 . However, since the discharge pipe  16  has a hollow structure having a constant inner diameter, it is impossible to reduce the traveling sound wave  22  that travels along the discharge pipe  16 , which causes the serious noise pollution. 
     In order to solve the above problem, it has been used a method wherein a separate silencer or resonator is installed in the discharge pipe  16  to cause an acoustic resonance, thereby reducing the noise. According to the conventional method, the silencer or resonator is inserted into the discharge pipe  16  and is then fixed to the discharge pipe  16  using a welding and the like. Therefore, it is not easy to install the noise reduction apparatus. In addition, the acoustic absorption/sound isolation means may be provided to a periphery of the discharge pipe  16  or refrigerator. However, such method increases the related costs. 
     DISCLOSURE OF INVENTION 
     Technical Problem 
     The invention has been made to solve the above problems occurring in the prior art. An object of the invention is to provide a refrigerator having a noise reduction structure, in which a traveling sound wave is branched along a branch pipe to produce a reverse sound wave having an inverse phase and the reverse sound wave is enabled to join with the traveling sound wave, thereby canceling the traveling sound wave. 
     Another object of the invention is to provide a refrigerator having a noise reduction structure, in which a branch pipe is provided to prevent back pressure from being applied to an inside of a discharge pipe and can be easily installed. 
     Still another object of the invention is to provide a refrigerator having a noise reduction structure, in which a branch pipe is installed to an outer periphery of a discharge pipe to cancel a traveling sound wave on a surface of the discharge pipe, thereby remarkably reducing the noise to be emitted to an outside. 
     Technical Solution 
     In order to achieve the above objects, there is provided a refrigerator having a noise reduction structure comprising an impeller part compressing refrigerant, a condenser condensing the compressed refrigerant and a refrigerant discharge pipe connecting the impeller part and the condenser, wherein the refrigerator further comprises a branch pipe that is provided to an outer periphery of the discharge pipe to bypass the refrigerant flowing in the discharge pipe to an outside in a predetermined section, the traveling sound wave of the refrigerant branched through an end of the branch pipe from the discharge pipe is converted into a reverse sound wave having an inverse phase to the traveling sound wave flowing in the discharge pipe while traveling in the branch pipe, and the reverse sound wave re-joins into the discharge pipe at the other end of the branch pipe and is thus cancelled with the traveling sound wave. 
     In particular, a diameter of the branch pipe is between 25% and 100% of a wavelength of the traveling sound wave. 
     In addition, the branch pipe is plurally provided along a longitudinal direction of the discharge pipe. 
     Further, the branch pipe is plurally provided along a circumferential direction of the outer periphery of the discharge pipe. 
     ADVANTAGEOUS EFFECTS 
     According to the invention, the branch pipe for reducing the intensive noise occurring from the impeller part is provided to the discharge pipe connected so that the refrigerant is discharged in a direction of the condenser from the impeller part. Therefore, the traveling sound wave of the noise traveling along the discharge pipe and the reverse sound wave traveling toward the branch pipe meet each other, so that the both sound waves are cancelled to reduce the noise. 
     In addition, according to the invention, since the branch pipe is provided to the outer periphery of the discharge pipe, the back pressure in the discharge pipe is insignificant. Further, since it is not necessary to fix the branch pipe in the discharge pipe, it is possible to easily equip the branch pipe and to reduce the costs. 
     In particular, according to the invention, the traveling sound wave on the surface of the discharge pipe is cancelled to considerably reduce the noise to be emitted to the outside through the surface of the discharge pipe. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic sectional view showing a part of the general refrigerator; 
         FIG. 2  is a schematic longitudinal view showing a noise reduction structure of a refrigerator according to an embodiment of the invention; 
         FIG. 3  is a sectional view taken along an A-A line of  FIGS. 2 ; and 
         FIG. 4  is a waveform diagram showing a phenomenon that a traveling sound wave traveling toward a discharge pipe and a reverse sound wave traveling toward a branch pipe meet and are thus cancelled. 
     
    
    
     MODE FOR THE INVENTION 
     Hereinafter, a preferred embodiment of the present invention will be described with reference to the accompanying drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. 
       FIG. 2  is a schematic longitudinal view showing a noise reduction structure of a refrigerator according to an embodiment of the invention,  FIG. 3  is a sectional view taken along a A-A line of  FIG. 2  and  FIG. 4  is a waveform diagram showing a phenomenon that a traveling sound wave  22  traveling toward a discharge pipe  16  and a reverse sound wave  24  traveling toward a branch pipe  20  meet and are thus cancelled. 
     As shown in  FIG. 2 , a refrigerator according to an embodiment of the invention comprises a branch pipe  20  that is formed at an outer periphery of a discharge pipe  16  connecting an impeller part  12  and a condenser  14 . The branch pipe  20  is protruded to an outside of the discharge pipe  16  from the outer periphery of the discharge pipe  16 . As shown in  FIGS. 2 and 3 , the discharge pipe  16  and the branch pipe  20  communicate with each other. Therefore, a part of the traveling sound wave  22  traveling along the discharge pipe  16  is branched along the branch pipe  20  and thus bypasses. 
     To be more specific, while the partial traveling sound wave  22  branched into the branch pipe  20  travels along the branch pipe  20 , it becomes a reverse sound wave  24  having an inverse phase to the traveling sound wave  22  flowing along the discharge pipe  16 , meets the traveling wave  22  at a cancellation point  26  in the discharge pipe  16  and is thus cancelled. 
       FIG. 4  is a graph showing a principle of the noise reduction structure of the invention. The reverse sound wave  24  having an inverse phase to the traveling sound wave  22  traveling along the discharge pipe  16  should have a phase difference of π (half period) with the traveling sound wave  22 . As shown, when it is assumed that a waveform P(t) of the traveling sound wave  22  toward the discharge pipe  16  is P(t)=A sin (ωt), a waveform P′(t) of the reverse sound wave  24  having an inverse phase should be P′(t)=A sin (ωt+π) so that the both sound waves  22 ,  24  can be cancelled. Here, ω is an angular velocity and t is time. 
     Considering the wavelength and phase of the traveling sound wave  22 , a length of the branch pipe  20  should be determined so that the sound wave branched from the traveling sound wave  22  has a phase difference of π with the traveling sound wave  22 . Regarding this, a total length of the branch pipe  20  for forming the reverse sound wave  24  canceling the traveling sound wave  22  is calculated by multiplying the phase velocity and the time. 
     In general, R-134a of the hydro fluoro carbon (HFC) series, which is the refrigerant used for a refrigerator, has a phase velocity of about 145 m/sec in the discharge pipe  16 . If it is assumed that the rotating speed of the impeller part  12  is 14,500 rpm and the number of the outlet blades of the impeller part  12  is  22 , the frequency of the traveling sound wave  22  is as follows: f(Hz)=145,000/60×22=5,316 Hz. 
     Since the inverse phase wave capable of canceling the traveling sound wave  22 , i.e., reverse sound wave  24  should have a phase difference of π with the traveling sound wave  22 , ωt should be equal to π (ωt=π) in  FIG. 4  and the total length of the branch pipe  20  is C (phase velocity)×t (time). Since ω=2πf, t=9.41×10 −5 . In addition, C=5,316 Hz. Therefore, a part of the traveling sound wave  22  branched into the branch pipe  20  can be the reverse sound wave  24  having an inverse phase when a total length of the branch pipe  20  is 0.0136 m (=13.6 cm). 
     Like this, the traveling sound wave  22 , which travels along the discharge pipe  16 , and the reverse sound wave  24 , which is branched into the branch pipe  20 , join at the cancellation point  26  at which the branch pipe  20  and the discharge pipe  16  meet. 
     The exemplary length (i.e., 13.6 cm) of the branch pipe  20  is the minimum length of the branch pipe  20  according to the above assumption. When the branch pipe is designed to have a length equal to or larger than the exemplary length, the same noise reduction is effected even when the total length is extended by odd multiples of the exemplary length so as to maintain the inverse phase of the reverse sound wave  24 . 
     In addition, when the sound wave traveling in the branch pipe  20  is not a plane wave, the noise may be increased. Therefore, a diameter of the branch pipe  20  is determined in consideration of the wavelength of the sound wave traveling therein. 
     In the mean time, when the diameter of the branch pipe  20  is larger than the wavelength (λ) of the sound wave, a plane wave is not formed in the branch pipe  20 . As a result, a phase of the sound wave is different in the diametrical direction of the branch pip  20 , so that the noise may be increased. Therefore, a diameter of the branch pipe  20  is preferably designed so that it is smaller than the wavelength (λ) of the sound wave. 
     In addition, the velocity of the sound wave is maximized at λ/4 and 3λ/4 points due to the characteristic of a wave. Accordingly, a diameter of the branch pipe  20  is preferably designed so that it is larger than 25% of the wavelength (λ) of the sound wave. 
     As shown in  FIG. 2 , the branch pipe  20  has a “ ” shape in which both ends are connected to the outer periphery of the discharge pipe  16 . However, the invention is not limited thereto. For example, the branch pipe  20  may be manufactured to have a length capable of forming the reverse sound wave  24 . Further, the branch pipe  20  may be provided in a form of several strands having a smaller diameter, rather than a single thick pipe shape, and may be plurally provided along the longitudinal direction of the discharge pipe  16 . In addition, as shown in  FIG. 3 , the branch pipe  20  may be provided along a circumferential direction of the outer periphery of the discharge pipe  16 , thereby canceling the traveling sound wave  22  traveling along the surface of the discharge pipe  16 . The noise, i.e., traveling sound wave  22  travels along the surface of the discharge pipe  16  and is a high frequency having a short wavelength. Therefore, the traveling sound wave is difficult to spread to a center of the discharge pipe  16 . Thus, since the noise is spread from the surface of the discharge pipe  16 , it is possible to efficiently block the noise to be spread from the surface of the discharge pipe  16  when the branch pipe  20  is provided to the outer periphery of the discharge pipe  16 . 
     Moreover, since the branch pipe  20  is protruded to the outside from the outer periphery of the discharge pipe  16 , there is no concern that it reduces the internal space of the discharge pipe  16  to apply the back pressure. In addition, the branch pipe  20  can be welded to the outer periphery of the discharge pipe  16 , it is easy to equip the branch pipe  20 . 
     INDUSTRIAL APPLICABILITY 
     The refrigerator of the invention has a noise reduction structure, so that the noise traveling along the discharge pipe can be remarkably reduced. 
     In addition, in the refrigerator having a noise reduction structure according to the invention, the branch pipe is provided to the outer periphery of the discharge pipe. Therefore, the back pressure is applied in the discharge pipe and the branch pipe can be easily equipped and fixed. 
     While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made thereto without departing from the spirit and scope of the invention as defined by the appended claims.