Abstract:
A resonator for a vehicle, which reduces intake noise by using a resonance chamber for frequency tuning, includes an outer pipe having a first outer pipe with an inlet for introducing external air and a second outer pipe with an outlet for discharging the air introduced into the inlet to outside, an inner pipe disposed inside the outer pipe and having a plurality of slits for giving a passage of air, and an expansion pipe inserted between the outer pipe and the inner pipe to partition a space between the outer pipe and the inner pipe into a plurality of spaces and thus partition the resonance chamber into a plurality of regions.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to Korean Patent Application No. 10-2014-0016722 filed on Feb. 13, 2014, No. 10-2014-0016724 filed on Feb. 13, 2014 and No. 10-2014-0100471 filed on Aug. 5, 2014, and all the benefits accruing, therefrom under 35 U.S.C. §119, the contents of which in its entirety are herein incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    1. Field 
         [0003]    The present disclosure relates to a resonator for a vehicle, and more particularly, to a resonator for a vehicle, in which a plurality of resonance chambers are formed between an outer pipe configuring an outward appearance and an inner pipe disposed inside the outer pipe to improve noise reduction performance of the resonator. 
         [0004]    2. Description of the Related Art 
         [0005]    Generally, an intake system of a vehicle includes an air cleaner, a turbo-charger, an inter-cooler, an air duct and an engine manifold, and an external air introduced into an internal combustion engine by the intake system is repeatedly expanded and shrunken to cause intake pulsation. The intake pulsation causes noise due to the change of air pressure, and particularly, greater noise is caused due to air resonance of a vehicle body or an indoor space of the vehicle. 
         [0006]    In order to restrain the intake noise, a resonator for tuning the intake system into a specific frequency is installed at an intake hose which connects the air cleaner to the intake manifold. 
         [0007]    As an example of existing resonators, Korean Patent Publication No 2006-0116275 discloses a resonator, which includes an outer pipe configuring an outward appearance and an inner pipe installed in the outer pipe to give an air passage. A resonance chamber for tuning air frequency to reduce noise is formed in a space between the outer pipe and the inner pipe, and a slit for guiding air to the resonance chamber is formed at the inner pipe. In other words, the air flowing into the inner pipe moves to the resonance chamber through the slit, and the air moving to the resonance chamber may experience frequency tuning, thereby performing noise reduction of the air. 
         [0008]    However, this resonator has a limit in the number of resonance chambers, and thus the frequency tuning work for external air cannot be performed over a broad band. In other words, since the resonator has a limited number of resonance chambers, the degree of frequency tuning freedom is low, and thus the noise reduction for external air is not performed agreeably. 
         [0009]    Korean Patent Publication No. 2009-0047083 discloses a resonator in which a first duct and a second duct with different sectional areas are disposed therein, and a length of a region where two ducts overlap with each other is adjusted to reduce noise of a specific frequency. However, in spite of this technique, the number of resonance chambers for noise reduction is still limited, and thus it is not easy to reduce noise of a broad band. In particular, a turning work at a high frequency band is not easy, and thus noise reduction efficiency for external air is low. 
       SUMMARY 
       [0010]    The present disclosure is directed to providing a resonator for a vehicle, which may enhance the degree of frequency tuning freedom for air introduced into a resonance chamber by forming a plurality of resonance chambers between an outer pipe and an inner pipe of the resonator. 
         [0011]    In one aspect, there is provided a resonator for a vehicle, which reduces intake noise by using a resonance chamber for frequency tuning, the resonator including: an outer pipe having a first outer pipe with an inlet for introducing external air and a second outer pipe with an outlet for discharging the air introduced into the inlet to outside; an inner pipe disposed inside the outer pipe and having a plurality of slits for giving a passage of air; and an expansion pipe inserted between the outer pipe and the inner pipe to partition a space between the outer pipe and the inner pipe into a plurality of spaces and thus partition the resonance chamber into a plurality of regions. 
         [0012]    According to the present disclosure, since an expansion pipe is inserted between an outer pipe and an inner pipe, the number of resonance chambers formed between the outer pipe and the inner pipe may increase, and thus the degree of frequency tuning freedom may also be enhanced. 
         [0013]    In addition, since it is possible to increase the number of resonance chambers by inserting a plurality of expansion pipes between the outer pipe and the inner pipe as necessary, noise of various frequencies may be reduced. 
         [0014]    Moreover, since the resonator is coupled in an assembling way, the number of resonance chambers may be easily increased or decreased. 
         [0015]    In addition, since the outer pipe, the inner pipe and the expansion pipe are hermetically coupled by means of welding, leakage of external air may be prevented, and thus intake noise reduction efficiency may be maximized. 
         [0016]    Moreover, since it is possible to increase the number of resonance chambers by inserting an intermediate pipe and a barrier between the outer pipe and the inner pipe as necessary, noise of various frequencies may be reduced. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a perspective view showing a resonator according to the first embodiment of the present disclosure. 
           [0018]      FIGS. 2A and 2B  are exploded views showing an inner configuration of the resonator according to the first embodiment of the present disclosure. 
           [0019]      FIG. 3  is a cross-sectional view, taken along the line I-I′ of  FIG. 1 . 
           [0020]      FIG. 4  is a cross-sectional view, taken along the line II-II′ of  FIG. 1 . 
           [0021]      FIG. 5  is a diagram showing a flow of air passing through the resonator according to the first embodiment of the present disclosure. 
           [0022]      FIG. 6  is a diagram for illustrating a size of a plurality of pipes of a first resonance chamber and a size of an interval for guiding air to the first resonance chamber. 
           [0023]      FIG. 7  is a graph showing a noise reduction amount according to a frequency of air moving to the first resonance chamber. 
           [0024]      FIG. 8  is a cross-sectional view showing an inner configuration of a resonator according to the second embodiment of the present disclosure, observed from one side. 
           [0025]      FIG. 9  is a cross-sectional view showing an inner configuration of the resonator according to the second embodiment of the present disclosure, observed from another side. 
           [0026]      FIG. 10  is an enlarged view showing the portion E of  FIG. 9 , in which a flow of air passing through the resonator according to the second embodiment of the present disclosure is depicted. 
           [0027]      FIG. 11  is a cross-sectional view showing an inner configuration of a resonator according to the third embodiment of the present disclosure, observed from one side. 
           [0028]      FIG. 12  is a cross-sectional view showing an inner configuration of the resonator according to the third embodiment of the present disclosure, observed from another side. 
           [0029]      FIG. 13  is an enlarged view showing the portion F of  FIG. 12 , in which a flow of air passing through the resonator according to the third embodiment of the present disclosure is depicted. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    Hereinafter embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Even though the present disclosure is described based on the embodiments depicted in, the drawings, the technical spirit, essential features or operations of the present disclosure are not limited thereto. 
         [0031]      FIG. 1  is a perspective view showing a resonator according to the first embodiment of the present disclosure,  FIG. 2   a  is an exploded view showing a detailed configuration of the resonator,  FIG. 2   b  is a perspective view showing an expansion pipe which is a component of the resonator,  FIG. 3  is a cross-sectional view, taken along the line I-I′ of  FIG. 1 , and  FIG. 4  is a cross-sectional view, taken along the linen-II′ of  FIG. 1 . 
         [0032]    A resonator  1  according to the present disclosure includes a first outer pipe  10  configuring a part of an outward appearance and a second outer pipe  20  configuring another part of the outward appearance. An end diameter A of the first outer pipe  10  and an end diameter B of the second outer pipe  20  may be different from each other. For example, the end diameter A of the first outer pipe may be greater than the end diameter B of the second outer pipe. In addition, an end of the first outer pipe  10  may be an inlet  15  serving as an inflow passage of air, and an end of the second outer pipe  20  may be an outlet  45  serving as a discharge passage of air. 
         [0033]    An inner pipe  40  may be inserted into an inner space of the first outer pipe  10  and the second outer pipe  20 . At this time, if the end diameter A of the first outer pipe is 1.4 to 1.5 times of the end diameter B of the second outer pipe, the one end of the inner pipe  40  may not be easily coupled to any one of the outer pipes  10 ,  20 . 
         [0034]    Therefore, in this embodiment, an expansion pipe  30  may be inserted between the outer pipes  10 ,  20  and the inner pipe  40 . In detail, the expansion pipe  30  may be inserted into the inner space of the outer pipes  10 ,  20 , and the inner pipe  40  may be inserted into the inner space of the expansion pipe  30 . 
         [0035]    The expansion pipe  30  includes a first bent portion  31  having a hollow  31   a  for allowing air to pass, an internal coupling unit  32  coupled to the inner pipe  40 , and a chamber forming unit  33  coupled to the outer pipes  10 ,  20 . One end of the first bent portion  31  may be connected to the internal coupling unit  32 , and the other end of the first bent portion  31  may be bent. 
         [0036]    The first bent portion  31 , the internal coupling unit  32  and the chamber forming unit  33  may be fabricated in an integrally coupled state. In other words, the expansion pipe  30  may be prepared by expanding through a mold during a part production stage. 
         [0037]    The other end of the first bent portion  31  may be bent to a direction parallel to an extension direction of the first outer pipe  10 . Therefore, the first bent portion  31  may be spaced apart from the first outer pipe  10  by a predetermined distance. In other words, the first bent portion  31  is disposed to be spaced apart from the first outer pipe  10  with an interval L serving as an air passage. In other words, the interval L giving an air passage is formed between the first bent portion  31  and the first outer pipe  10 , and the air flowing into a resonance chamber  100  through the interval L may have reduced noise by means of frequency tuning. 
         [0038]    The chamber forming unit  33  includes a second bent portion  331  bent to a direction perpendicular to the internal coupling unit  32  based on, the moving direction of air, an external coupling unit  333  connected to the second bent portion  331  in a perpendicular direction and coupled to the outer pipes  10 ,  20 , and a third bent portion  332  bent to a direction perpendicular to the external coupling unit  333 . A terminal of the third bent portion  332  may be bent for convenient fabrication so as to be easily coupled to the inner pipe  40 . 
         [0039]    Heights M of the second bent portion  331  and the third bent portion  332  may be relatively greater than a height N of the first bent portion  31 . Therefore, the interval L serving as an air passage may be formed between the first bent portion  31  and the first outer pipe  10 . 
         [0040]    In an existing technique, if the inlet and the outlet have different diameters, an inclined portion should be formed to allow the inner pipe to be directly coupled to the outer pipe. However, in this embodiment, since the inner pipe  40  may be coupled to the outer pipes  10 ,  20  even though the expansion pipe  30  has no inclined portion, the resonator  1  may be easily fabricated. In addition, in an existing technique, a slit serving as an air passage should be formed in the inclined portion of the inner pipe, but this is a difficult work since the space for forming the slit is not sufficient. 
         [0041]    However, in this embodiment, the interval L may be formed between the outer pipes  10 ,  20  and the expansion pipe  30  instead of the slit to give an air passage, and thus the resonator  1  may use its internal space more efficiently. 
         [0042]    A plurality of slits  41  giving the same function as the interval L may be formed at the inner pipe  40 . In detail, the plurality of slits  41  includes a first slit  411  disposed adjacent to the inlet based on the moving direction of air, and a second slit  412  disposed spaced apart from the first slit  411  by a predetermined distance. 
         [0043]    In addition, the resonance chamber  100  for adjusting a frequency of external air is provided between the outer pipes  10 ,  20  and the inner pipe  40 . The resonance chamber  100  is divided into a plurality of regions by the expansion pipe  30  inserted between the outer pipes  10 ,  20  and the inner pipe  40 . In detail, the resonance chamber  100  includes a first resonance chamber  110  formed between the first bent portion  31  and the second bent portion  331 , a second resonance chamber  120  formed between the second bent portion  331  and the third bent portion  332 , and a third resonance chamber  130  formed among the third bent portion  332 , the second outer pipe  20  and the inner pipe  40 , based on the moving direction of air. 
         [0044]    The first resonance chamber  110  communicates with the interval L, and the second resonance chamber  120  communicates with the first slit  411 . In addition, the third resonance chamber  130  communicates with the second slit  412  for frequency tuning of air. 
         [0045]    Hereinafter, a moving passage of external air passing through the resonator  1  and a method for coupling a plurality of pipes of the resonator  1  will be described. 
         [0046]      FIG. 5  is a diagram showing a flow of air passing through the resonator according to the first embodiment of the present disclosure. 
         [0047]    As shown in  FIG. 5 , the resonator  1  of this embodiment includes a plurality of pipes which are coupled to each other by welding. In detail, coupling (a) among the expansion pipe  30 , the first outer pipe  10  and the second outer pipe  20 , coupling (b) between the expansion pipe  30  and the inner pipe  40  and coupling (c) between the second outer pipe  20  and the inner pipe  40  are all performed by welding along a circumferential direction. Since the plurality of pipes are hermetically sealed by welding, it is possible to prevent a leakage of external air and thus maximize the efficiency of intake noise reduction. 
         [0048]    Even though it has been illustrated in this embodiment that the plurality of pipes are coupled by welding, the present disclosure is not limited thereto, and another coupling method than welding may also be used as long as the plurality of pipes are hermetically coupled. If the plurality of pipes are hermetically coupled as described above, the resonator I for noise reduction is completely made as an assembly. 
         [0049]    Meanwhile, an existing resonator has a limit in the number of resonance chambers. However, the resonator of this embodiment may easily tune a frequency, different from the existing structure. 
         [0050]    However, in order to allow air having a high frequency to flow into the first resonance chamber  110 , the size the plurality of pipes  10 ,  20 ,  30 ,  40  may be limited to a predetermined ratio. 
         [0051]    Referring to  FIG. 6 , the first resonance chamber  110  is formed as a space surrounded by a part of the first outer pipe  10 , the first bent portion  31  spaced apart from the first outer pipe  10  by a predetermined distance, a second bent portion  331  extending in a direction parallel to the extending direction of the first bent portion  31 , and the internal coupling unit  32  having one end connected to the first bent portion  31  and the other end connected to the second bent portion  331 . 
         [0052]    Design conditions for the first resonance chamber  110  capable of absorbing air with a high frequency are as follows. 
         [0053]    First, a diameter D 1  of the first outer pipe  10  is 1.4 to 1.6 times of a diameter D 2  of the internal coupling unit  32 . In addition, a height W of the internal coupling unit  32  is 0.3 times of a diameter D 2  of the internal coupling unit  32 . In addition, a width L of the interval is 0.04 to 0.12 times of the diameter D 2  of the internal coupling unit  32 . 
         [0054]    Table 1 below shows the resonator  1  prepared using an exemplary ratio suitable for the above design conditions, and a maximum frequency of air absorbed into the first resonance chamber  110  is shown as an experimental example. 
         [0000]    
       
         
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                 maximum frequency of air absorbed to the first 
               
               
                 W/D2 
                 D1/D2 
                 L/D2 
                 resonance chamber (Hz) 
               
               
                   
               
             
             
               
                 0.3 
                 1.4 
                 0.08 
                 3600 
               
               
                   
                 1.5 
                 0.08 
                 4000 
               
               
                   
                 1.6 
                 0.08 
                 4300 
               
               
                   
               
             
          
         
       
     
         [0055]    As shown in Table 1 above, the resonator  1  of this embodiment fabricated according to the above design conditions may absorb air with a high frequency of 3600 Hz to 4300 Hz. If the above design conditions for the first resonance chamber  110  are changed, it is impossible to absorb air with a high frequency. For example, if a ratio of W/D 2  is changed to 0.2 as in Table 2 below, the maximum frequency of air absorbed to the first resonance chamber  110  decreases as follows. 
         [0000]    
       
         
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                   
                   
                   
                 maximum frequency of air absorbed to the first 
               
               
                 W/D2 
                 D1/D2 
                 L/D2 
                 resonance chamber (Hz) 
               
               
                   
               
             
             
               
                 0.2 
                 1.4 
                 0.08 
                 2800 
               
               
                   
                 1.5 
                 0.08 
                 3000 
               
               
                   
                 1.6 
                 0.08 
                 3200 
               
               
                   
               
             
          
         
       
     
         [0056]    If values of D 1 /D 2  and L/D 2  increase as in Table 2 above with W/D 2  being 0.2, this accompanies overall structural changes or manufacturing problems of the resonator  1 , and thus the maximum frequency of air absorbed to the first resonance chamber  110  may not have a value of 3600 Hz to 4300 Hz. In other words, the values of W/D 2 , D 1 /D 2  and L/D 2  shown in Table 1 may be regarded as optimal design conditions for absorbing air with a high frequency to the first resonance chamber  110 . 
         [0057]    In  FIG. 7 , a noise reduction amount according to a frequency of air absorbed to the first resonance chamber  110  under design conditions with W/D 2  of 0.3, D 1 /D 2  of 1.5, and L/D 2  of 0.08, which accord with the above conditions, is depicted with a graph. As shown in  FIG. 7 , since the resonance chamber for absorbing air with a maximum frequency of 3600 Hz to 4300 Hz is formed at the resonator  1  of the present disclosure, noise caused by air with the high frequency may be reduced. In addition, by changing the L/D 2  value, frequency tuning for a low frequency region is also available. 
         [0058]    Hereinafter, a moving pass of external air passing through the resonator  1  and a method for reducing intake noise will be described. 
         [0059]    First, a part of air flowing into the inlet  15  passes through the interval L and moves to the first resonance chamber  110 , and another part of the air flowing into the inlet  15  moves to the inner space of the resonator  1  formed by the inner pipe  40 . The air flowing into the first resonance chamber  110  may be air with a high frequency as described above as an example. In other words, the first resonance chamber  110  may be a resonance chamber for tuning air with a high frequency and thus reducing noise. 
         [0060]    Similarly, a part of air moving along the inner pipe  40  may pass the first slit  411  and another part of the air moving along the inner pipe  40  may pass the second slit  412 , and both of them move to the second resonance chamber  120  and the third resonance chamber  130 , respectively. The air flowing into the second resonance chamber  120  may be air with a relatively lower frequency in comparison to the air flowing into the first resonance chamber  110 . In the same principle, the air flowing into the third resonance chamber  130  may be air with a relatively lower frequency in comparison to the air flowing into the second resonance chamber  120 . Therefore, the air flowing into the inlet  15  moves to the first to third resonance chambers  110 ,  120 ,  130  depending on its frequency, and since the first to third resonance chambers  110 ,  120 ,  130  perform frequency tuning, the absorbed air discharges out through the outlet  45  with reduced noise. In this embodiment, since the air flowing in through the inlet  15  discharges out through the outlet  45 , it is possible to reduce noise by performing frequency tuning in a direction where an air frequency region decreases, namely from a high frequency region to a low frequency region. As another example, it is also possible to reduce noise by performing frequency tuning in a direction where an air frequency region increases, namely from a low frequency region to a high frequency region, by changing dimensions of the resonator  1 . 
         [0061]    In this embodiment, in order to form a plurality of resonance chambers  100 , a single expansion pipe  30  is inserted between the outer pipes  10 ,  20  and the inner pipe  40 . Hereinafter, another example for forming the plurality of resonance chambers  100  will be described. 
         [0062]      FIG. 8  is a cross-sectional view showing an inner configuration of a resonator according to the second embodiment of the present disclosure, observed from one side and  FIG. 9  is a cross-sectional view showing an inner configuration of the resonator according to the second embodiment of the present disclosure, observed from another side. 
         [0063]    Referring to  FIGS. 8 and 9 , in this embodiment, a plurality of expansion pipes  400 ,  600  are inserted between the outer pipes  10 ,  20  and the inner pipe  40 , different from the former embodiment. In detail, the expansion pipes of this embodiment include an inflow expansion pipe  400  disposed adjacent to the inlet  15  and a discharge expansion pipe  600  disposed adjacent to the outlet  45 . 
         [0064]    One surface of the inflow expansion pipe  400  is coupled in contact with the inner pipe  40 , and the other surface of the inflow expansion pipe  400  is coupled in contact with the first outer pipe  10 . Therefore, an inflow bent portion  410  extending from the inner pipe  40  to the first outer pipe  10  is formed at the inflow expansion pipe  400 . The resonance chamber  100  may be partitioned into a plurality of regions by the inflow bent portion  410 . 
         [0065]    A first discharge bent portion  610  extending from the inner pipe  40  to the second outer pipe  20  based on the moving direction of air and a second discharge bent portion  620  extending from the second outer pipe  20  to inner pipe  40  are formed at the discharge expansion pipe  600 . Therefore, the resonance chamber  100  may be partitioned into a plurality of regions by the first discharge bent portion  610  and the second discharge bent portion  620 . 
         [0066]    As a result, the resonance chamber  100  is partitioned into a plurality of regions by the inflow expansion pipe  400  and the discharge expansion pipe  600 . In detail, the resonance chamber  100  may be divided into a first resonance chamber  110 , a second resonance chamber  120 , a third resonance chamber  130  and a fourth resonance chamber  140 , respectively, based on the moving direction of air. The first resonance chamber  110  is a space formed between the inflow expansion pipe  400  and the first outer pipe  10 , and the second resonance chamber  120  is a space formed by the first outer pipe  10 , the first discharge bent portion  610 , the inner pipe  40  and the inflow bent portion  410 . In addition, the third resonance chamber  130  is a space formed between the discharge expansion pipe  600  and the inner pipe  40 , and the fourth resonance chamber  140  is a space formed by the second outer pipe  20 , the inner pipe  40  and the second discharge bent portion  620 . 
         [0067]    The second to fourth resonance chambers  120 ,  130 ,  140  communicate with the first to third slits  411 ,  412 ,  413  formed at the inner pipe  40 . Therefore, the air flowing into the inner pipe  40  through the inlet  15  moves to the second to fourth resonance chambers  120 ,  130 ,  140  through the first to third slits  411 ,  412 ,  413  and experiences frequency tuning. 
         [0068]    The first outer pipe  10  is formed by integrally coupling an inflow guide unit  210  for guiding a moving path of air flowing into the inlet  15  and a chamber partitioning unit  230  having a relatively greater diameter than the inflow guide unit  210 . The inflow guide unit  210  and the chamber partitioning unit  230  are integrally fabricate by an extension  220  which extends in a radial direction to connect the inflow guide unit  210  and the chamber partitioning unit  230 . In other words, one side of the extension  220  is connected to the inflow guide unit  210 , and the other side of the extension  220  is connected to the chamber partitioning unit  230 . 
         [0069]    A gap  250  for giving a moving path of air is formed between the inflow expansion pipe  400  and the extension  220  of the first outer pipe  10 . In other words, a predetermined space allowing movement of external air is formed between one side of the inflow expansion pipe  400  and the first outer pipe  10 . The air flowing into the inlet  15  passes through the gap  250  and moves to the first resonance chamber  110 . Therefore, the gap  250  plays the same role as the plurality of slits  411 ,  412 ,  413  formed at, the inner pipe  40 . 
         [0070]    Hereinafter, a moving path of external air passing through the resonator  2  of this embodiment and welding locations of the plurality of pipes of the resonator  2  will be described. 
         [0071]      FIG. 10  is an enlarged view showing the portion E of  FIG. 9 , in which a flow of air passing through the resonator according to the second embodiment of the present disclosure is depicted. 
         [0072]    As shown in  FIG. 10 , in the resonator  2  of this embodiment, the plurality of pipes are coupled to each other by welding. In detail, coupling (a) between the first outer pipe  10  and the second outer pipe  20 , coupling (b) between the inflow expansion pipe  400  and the inner pipe  40 , coupling (c, d) between the discharge expansion pipe  600  and the inner pipe  40  and coupling (e) between the second outer pipe  20  and the inner pipe  40  are all performed by welding. Since the plurality of pipes are hermetically sealed by welding, it is possible to prevent a leakage of external air and thus maximize the efficiency of intake noise reduction. 
         [0073]    Even though it has been illustrated in this embodiment that the plurality of pipes are coupled by welding, the present disclosure is not limited thereto, and another coupling method than welding may also be used as long as the plurality of pipes are hermetically coupled. 
         [0074]    If the plurality of pipes are hermetically coupled as described above, the resonator  2  for noise reduction is completely made as an assembly. Hereinafter, a moving path of external air passing through the resonator  2  and a method for reducing intake noise will be described. 
         [0075]    First, a part of air flowing into the inlet  15  passes through the gap  250  and moves to the first resonance chamber  110 , and another part of the air flowing into the inlet  15  moves to the inner pipe  40 . The air flowing into the first resonance chamber  110  may be air with a high frequency as an example. In other words, the first resonance chamber  110  may be a resonance chamber for tuning air with a high frequency and thus reducing noise. 
         [0076]    Similarly, a part of air moving along the inner pipe  40  may pass the first slit  411 , another part of the air moving along the inner pipe  40  may pass the second slit  412 , and still another part of the air moving along the inner pipe  40  may pass the third slit  413 . All of them move to the second resonance chamber  120 , the third resonance chamber  130 , and the fourth resonance chamber  140 , respectively. The air flowing into the second resonance chamber  120  may be air with a relatively lower frequency in comparison to the air flowing into the first resonance chamber  110 . In the same principle, the air flowing into the third resonance chamber  130  may be air with a relatively lower frequency in comparison to the air flowing into the second resonance chamber  120 , and the air flowing into the fourth resonance chamber  140  may be air with a relatively lower frequency in comparison to the air flowing into the third resonance chamber  130 . 
         [0077]    Therefore, the air flowing into the inlet  15  moves to the first to fourth resonance chambers  110 ,  120 ,  130 ,  140  depending on its frequency, and since the first to fourth resonance chambers  110 ,  120 ,  130 ,  140  perform frequency tuning, the absorbed air discharges out through the outlet  45  with reduced noise. 
         [0078]    Even though it has been illustrated in this embodiment that the frequency of air flowing into the resonance chamber  100  gradually decreases from the first resonance chamber  110  to the fourth resonance chamber  140 , the present disclosure is not limited thereto. For example, the third resonance chamber  130  and the fourth resonance chamber  140  may be resonance chambers for tuning air with a high frequency, and the first resonance chamber  110  and the second resonance chamber  120  may be resonance chambers for tuning air with a low frequency. 
         [0079]    In addition, the air flowing into the resonance chamber  100  may have different frequencies depending on various factors such as a thickness of the expansion pipe  400 ,  600 , a horizontal length of the expansion pipes  400 ,  600 , a volume of each resonance chamber  100 , a width of the gap  250  or the slits  411 ,  412 ,  413  serving as an air passage, or the like. However, if the number of the resonance chambers  100  increases, air with various frequencies may flow into each resonance chamber, and thus noise of a broad frequency band may be reduced. 
         [0080]      FIG. 11  is a cross-sectional view showing an inner configuration of a resonator according to the third embodiment of the present disclosure, observed from one side, and  FIG. 12  is a cross-sectional view showing an inner configuration of the resonator according to the third embodiment of the present disclosure, observed from another side. 
         [0081]    Referring to  FIGS. 11 and 12 , in this embodiment, in order to increase the number of the resonance chambers  100 , barriers  510 ,  520  and an intermediate pipe  530  are inserted between the outer pipes  10 ,  20  and the inner pipe  40 , different from the former embodiments (the first and second embodiments of the present disclosure). In detail, a resonator  3  of this embodiment includes a first outer pipe  10  having the inlet  15  serving as an inflow passage of external air and a second outer pipe  20  having the outlet  45  serving as a discharge passage of external air. The intermediate pipe  530  extending in a length direction is disposed between the first outer pipe  10  and the second outer pipe  20 . Therefore, the first outer pipe  10 , the second outer pipe  20  and the intermediate pipe  530  form an outward appearance of the resonator  3  of this embodiment. 
         [0082]    The first outer pipe  10  may be classified into an inflow guide unit  210 , an extension  220  and a chamber partitioning unit  230 , which may be integrally fabricated, similar to the second embodiment of the present disclosure. 
         [0083]    The inner pipe  40  having a plurality of slits  41  is inserted into the inner space of the outer pipes  10 ,  20 . As shown in  FIG. 11 , the slits formed at the inner pipe  40  may be a first slit  411 , a second slit  412  and a third slit  413 , respectively, based on the moving direction of air. 
         [0084]    The first barrier  510  is disposed between the first outer pipe  10  and the intermediate pipe  530 , and the second barrier  520  is disposed between the intermediate pipe  530  and the second outer pipe  20 . In other words, the first barrier  510  is disposed at one side of the intermediate pipe  530 , and the second barrier  520  is disposed at the other side of the intermediate pipe  530 . In this embodiment, the barrier has been illustrated as being classified into the first barrier  510  and the second barrier  520 , but the number of the barriers  510 ,  520  is not limited thereto. 
         [0085]    The first barrier  510  and the second barrier  520  are arranged side by side in a direction parallel to the extension  220  of the first outer pipe  10 . In other words, the first barrier  510  and the second barrier  520  may extend in a direction perpendicular to the intermediate pipe  530 . 
         [0086]    In addition, an outer circumference of the barriers  510 ,  520  may be exposed outwards. In detail, an outer surface of the resonator  3  may be configured with the first outer pipe  10 , the first barrier  510 , the intermediate pipe  530 , the second barrier  520  and the second outer pipe  20 , based on the moving direction of air. However, the first outer pipe  10 , the intermediate pipe  530  and the second outer pipe  20  may be integrally fabricated, and the barriers  510 ,  520  may be attached to an inner side of the outer surface of the resonator  3  integrally fabricated. 
         [0087]    The resonance chamber  100  for adjusting a frequency of external air is formed in the space between the outer pipes  10 ,  20  and the inner pipe  40  and the space between the intermediate pipe  530  and the inner pipe  40 . The resonance chamber  100  is divided into a plurality of regions by the barriers  510 ,  520 . 
         [0088]    In detail, the resonance chamber  100  is divided into a first resonance chamber  110 , a second resonance chamber  120  and a third resonance chamber  130 , respectively, based on the moving direction of air. The first resonance chamber  110  is a space formed among the first outer pipe  10 , the first barrier  510  and the inner pipe  40 , and the second resonance chamber  120  is a space formed by the first barrier  510 , the intermediate pipe  530 , the second barrier  520  and the inner pipe  40 . In addition, the third resonance chamber  130  is a space formed among the second barrier  520 , the second outer pipe  20  and the inner pipe  40 . 
         [0089]    In this embodiment, the resonance chamber  100  is divided into three chambers by two barriers  510 ,  520 , but the present disclosure is not limited thereto. For example, if three barriers are disposed in the resonance chamber  100 , the resonance chamber  100  may be divided into four chambers. 
         [0090]    The first to third resonance chambers  110 ,  120 ,  130  communicate with the first to third slits  411 ,  412 ,  413  formed at the inner pipe  40 . Therefore, the air flowing into the inner pipe  40  through the inlet  15  moves to the first to third resonance chambers  110 ,  120 ,  130  through the first to third slits  411 ,  412 ,  413 , thereby performing frequency tuning for the absorbed air. 
         [0091]    Hereinafter, a moving path of external air passing through the resonator  3  and welding locations of the plurality of  10 ,  20 ,  40 ,  530  and barriers  510 ,  520  of the resonator  3  will be described. 
         [0092]      FIG. 13  is an enlarged view showing the portion F of  FIG. 12 , in which a flow of air passing through the resonator according to the third embodiment of the present disclosure is depicted. 
         [0093]    As shown in  FIG. 13 , in the resonator  3  of this embodiment, the plurality of pipes  10 ,  20 ,  40 ,  530  and the barriers  510 ,  520  are coupled to each other by welding. In detail, coupling (a) between the first outer pipe  10  and the first barrier  510 , coupling (b) between the inner pipe  40  and the first barrier  510 , coupling (c) between the intermediate pipe  530  and the second barrier  520  and coupling (d) between the second barrier  520  and the inner pipe  40  are all performed by welding. Since the plurality of pipes are hermetically sealed by welding, it is possible to prevent a leakage of external air and thus maximize the efficiency of intake noise reduction. 
         [0094]    Even though it has been illustrated in this embodiment that the plurality of pipes are coupled by welding, the present disclosure is not limited thereto, and another coupling method than welding may also be used as long as the plurality of pipes are hermetically coupled. 
         [0095]    If the plurality of pipes are hermetically coupled as described above, the resonator  3  for noise reduction is completely made as an assembly. Hereinafter, a moving path of external air passing through the resonator  3  and a method for reducing intake noise will be described. 
         [0096]    First, a part of air flowing into the inlet  15  passes through the first slit  411  and moves to the first resonance chamber  110 , and another part of the air flowing into the inlet  15  moves to the inner pipe  40 . The air flowing into the first resonance chamber  110  may be air with a high frequency as an example. In other words, the first resonance chamber  110  may be a resonance chamber for tuning air with a high frequency and thus reducing noise. 
         [0097]    Similarly, a part of air moving along the inner pipe  40  passes the second slit  412  and moves to the second resonance chamber  120 , and another part of the air moving along the inner pipe  40  passes the third slit  413  and moves to the third resonance chamber  130 . The air flowing into the second resonance chamber  120  may be air with a relatively lower frequency in comparison to the air flowing into the first resonance chamber  110 . In the same principle, the air flowing into the third resonance chamber  130  may be air with a relatively lower frequency in comparison to the air flowing into the second resonance chamber  120 . Therefore, the air flowing into the inlet  15  moves to the first to third resonance chambers  110 ,  120 ,  130  depending on its frequency, and since the first to third resonance chambers  110 ,  120 ,  130  perform frequency tuning, the absorbed air discharges out through the outlet  45  with reduced noise. 
         [0098]    Even though it has been illustrated in this embodiment that the frequency of air flowing into the resonance chamber  100  gradually decreases from the first resonance chamber  110  to the third resonance chamber  130 , the present disclosure is not limited thereto. For example, the second resonance chamber  120  and the third resonance chamber  130  may be resonance chambers for tuning air with a high frequency, and the first resonance chamber  110  may be resonance chambers for tuning air with a low frequency. 
         [0099]    In addition, the air flowing into the resonance chamber  100  may have different frequencies depending on various factors such as a thickness of the barriers  510 ,  520 , locations of the barriers  510 ,  520 , a volume of each resonance chamber  100 , a width of the slits  411 ,  412 ,  413 , or the like. However, if the number of the resonance chambers  100  increases, air with various frequencies may flow into each resonance chamber, and thus noise of a broad frequency band may be reduced. 
         [0100]    While the exemplary embodiments have been shown and described, 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 present disclosure as defined by the appended claims. In addition, many modifications can be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular exemplary embodiments disclosed as the best mode contemplated for carrying out the present disclosure, but that the present disclosure will include all embodiments falling within the scope of the appended claims.