Patent Publication Number: US-10760537-B2

Title: Air cleaner

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an air cleaner for filtering air supplied to an internal combustion engine. 
     An air cleaner for an internal combustion engine has a first housing having an inlet and an opening, a second housing having an outlet and an opening, a filter element arranged between the opening of the first housing and the opening of the second housing. 
     In the air cleaner described in Japanese Laid-Open Patent Publication No. 2000-110682, the inner surface of the first housing is in contact with an entire opposed surface of a sound absorbing member made of a porous material such as foamed plastic. The sound absorbing member reduces the intake noise. 
     However, in the above-described air cleaner, the effect of reduction of the intake noise by the sound absorbing member is limited and there is room for improvement. 
     SUMMARY OF THE INVENTION 
     An objective of the present invention is to provide an air cleaner capable of effectively reducing intake noise. 
     To achieve the foregoing objectives and in accordance with one aspect of the present invention, an air cleaner is provided that includes a first housing including an inlet and an opening, a second housing including an outlet and an opening, and a filter element arranged between the opening of the first housing and the opening of the second housing. At least one of the first housing and the second housing includes a looped fixing rib, which protrudes from an inner surface thereof, and a sound absorbing member, which is made of an air permeable material and fixed to an upper end of the fixing rib. The inner surface of the at least one of the housings, an inner peripheral surface of the fixing rib, and the sound absorbing member define an air chamber. 
     Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: 
         FIG. 1  is a cross-sectional view showing an air cleaner according to one embodiment; 
         FIG. 2  is a perspective view showing the first housing of the embodiment; 
         FIG. 3  is a perspective view showing the sound absorbing member and the covering layer of the embodiment; 
         FIG. 4  is a perspective view of the first housing of the embodiment, illustrating a state in which the sound absorbing member and the covering layer are fixed; and 
         FIG. 5  is a cross-sectional view showing the air chamber and its surroundings of the embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An air cleaner according to one embodiment will now be described. 
     An air cleaner shown in  FIG. 1  is arranged in an intake passage of a vehicle-mounted internal combustion engine and includes a first housing  10  having a cylindrical inlet  11  and a second housing  20  having a cylindrical outlet  21 . 
     As shown in  FIGS. 1 and 2 , the first housing  10  includes an upper opening  12 , a peripheral wall  13 , which surrounds the upper opening  12 , and a bottom wall  14 . An outward extending flange  15  is provided around the entire periphery of the upper opening  12 . The inlet  11  protrudes from the outer surface of the peripheral wall  13 . The first housing  10  is made of a hard synthetic plastic. 
     As shown in  FIG. 1 , the second housing  20  includes a lower opening  22 , a peripheral wall  23 , which surrounds the lower opening  22 , and a top wall  24 . An outward extending flange  25  is provided around the entire periphery of the lower opening  22 . The outlet  21  protrudes from the outer surface of the peripheral wall  23 . The second housing  20  is made of a hard synthetic plastic. 
     A filter element  30  is arranged between the upper opening  12  of the first housing  10  and the lower opening  22  of the second housing  20 . The filter element  30  has a filtration portion  31  and a loop-shaped sealing portion  32 . The filtration portion  31  is formed by pleating a filtering medium sheet of filter paper or nonwoven fabric, and the sealing portion  32  is provided at the outer periphery of the filtration portion  31 . 
     In the air cleaner, the sealing portion  32  of the filter element  30  is held by the flange  15  of the first housing  10  and the flange  25  of the second housing  20 . The sealing portion  32  seals the gap between the first housing  10  and the second housing  20 . 
     A vibration reducing structure for reducing intake noise is arranged on the bottom wall  14  of the first housing  10 . The vibration reducing structure will now be described. 
     As shown in  FIGS. 1 and 2 , fixing ribs  16 A,  16 B protrude from the inner surface of the bottom wall  14  of the first housing  10 . The fixing ribs  16 A and  16 B are composed of two fixing ribs  16 A extending parallel with each other and two fixing ribs  16 B extending parallel with each other in a direction orthogonal to the fixing ribs  16 A. The fixing ribs  16 A and  16 B are arranged to form a lattice shape on the entire bottom wall  14  of the first housing  10 . As shown in  FIG. 2 , columnar fixing portions  18  are formed so as to protrude from the parts where the fixing ribs  16 A,  16 B intersect, that is, from the corners of the looped rectangle formed by the fixing ribs  16 A,  16 B (hereinafter referred to as a looped wall  17 ). 
     Also, as shown in  FIGS. 1 and 2 , a reinforcing rib  19  protrudes from the inner surface of the bottom wall  14  of the first housing  10 . The reinforcing rib  19  is located between the two fixing ribs  16 A and extends in parallel with the fixing ribs  16 A. The height of the reinforcing rib  19  (the amount of protrusion from the bottom wall  14 ) is set to be lower than the height of the fixing ribs  16 A,  16 B. 
     As shown in  FIGS. 1 and 3 , a sound absorbing member  41  made of nonwoven fabric is installed in the first housing  10 . The sound absorbing member  41  is arranged to block the upper opening  17 A, which is surrounded by the looped wall  17 . 
     The sound absorbing member  41  has a rectangular plate-shaped sound reducing portion  43  and a flange  44 , which is formed on the entire periphery of the upper end of the sound reducing portion  43  and has a rectangular looped shape in a plan view. The nonwoven fabric sheet constituting the sound absorbing member  41  is composed of known sheath-core type conjugate fiber including cores made of, for example, polyethylene terephthalate (PET) fiber and sheaths made of modified PET having a melting point lower than that of the PET fiber of the cores (neither is illustrated). The sound absorbing member  41  is formed integrally by hot pressing the nonwoven fabric sheet. In the forming of the sound absorbing member  41 , the degree of compression of the peripheral portion (the flange  44 ) of the sound absorbing member  41  is set to be greater than the degree of compression of the central portion (the sound reducing portion  43 ) of the sound absorbing member  41 . As a result, the air permeability of the flange  44  (substantially 0 in the present embodiment) is lower than the air permeability of the sound reducing portion  43 . The flange  44 , which has a rectangular looped shape in a plan view, has a through-hole (not shown) in each of the four corners. 
     A covering layer  45  is fixed to the upper surface of the sound absorbing member  41 . The covering layer  45  has a rectangular shape in a plan view and covers the entire upper surface of the sound absorbing member  41 . The nonwoven fabric sheet constituting the covering layer  45  is composed of main fibers made of PET and binder fibers that are made of polypropylene (PP) and bind the main fibers together. The air permeability of the covering layer  45  is set to be lower than that of the sound reducing portion  43  of the sound absorbing member  41 . Specifically, the air permeability of the covering layer  45  is preferably 3 cm 3 /cm 2 ·s to 50 cm 3 /cm 2 ·s and is set to 10 cm 3 /cm 2 ·s in the present embodiment. The air permeability of the covering layer  45  is measured by a measuring method in which a Frazier-type tester specified in JIS. L. 1096, A-method is used. The covering layer  45 , which has a rectangular shape in a plan view, has a through-hole  45 A in each of the sections that correspond to the through-holes of the sound absorbing member  41  at the corners. 
     The sound absorbing member  41  and the covering layer  45  are fixed to the first housing  10  in the following manner. 
     First, as shown in  FIGS. 2 to 4 , the fixing portions  18  on the upper surface of the looped wall  17  of the first housing  10  are inserted through the through-holes of the sound absorbing member  41  and the through-holes  45 A ( FIG. 3 ) of the covering layer  45 . Accordingly, the sound absorbing member  41  and the covering layer  45  are in a state of closing the upper opening  17 A of the looped wall  17  (the state shown in  FIG. 1 ). In this state, the ends of the fixing portions  18  (specifically, the portions protruding above the covering layer  45 ) are thermally swaged. In this way, the sound absorbing member  41  and the covering layer  45  are fixed to the upper end of the looped wall  17 . 
     By fixing the sound absorbing member  41  and the covering layer  45  in the above-described manner, the inner surface of the bottom wall  14 , the inner peripheral surface of the looped wall  17 , and the lower surface of the sound absorbing member  41  define an air chamber  46  ( FIG. 1 ) in the first housing  10 . In the air cleaner of the present embodiment, the sound absorbing member  41  does not contact the reinforcing rib  19 . 
     Operation of the present embodiment will now be described. 
     When the wave of intake noise traveling inside the air cleaner collides with the covering layer  45 , the covering layer  45  is pushed, and the sound absorbing member  41  and the air in the air chamber  46  act like a spring, so that the covering layer  45  vibrates. Then, the vibration of the covering layer  45  and the vibration of the sound absorbing member  41 , which is integral with the covering layer  45 , are converted into thermal energy, so that the intake noise is reduced. 
     The lower the air permeability of the covering layer  45 , the lower becomes the frequency at which the covering layer  45  resonates. It is thus possible to effectively reduce the sound pressure level of lower frequency components of the intake noise. In the air cleaner of the present embodiment, the covering layer  45 , which is made of a material having a lower air permeability than the sound absorbing member  41 , is provided to cover the entire surface of the sound absorbing member  41 . It is thus possible to effectively reduce the sound pressure level of low frequency components as compared with an air cleaner lacking the covering layer  45 . 
     In the air cleaner of the present embodiment, the air permeability of the portion sandwiched between the covering layer  45  and the peripheral portion (the flange  44 ) of the sound absorbing member  41 , that is, the upper end of the looped wall  17  of the sound absorbing member  41  is set low. Thus, when the covering layer  45  vibrates, air is prevented from leaking from or entering into the air chamber  46  through between the covering layer  45  and the looped wall  17 . As a result, the covering layer  45  easily vibrates, and the vibration is easily converted into thermal energy, so that the intake noise is effectively reduced. 
     Further, some of the wave of the intake noise passes through the covering layer  45  and the sound absorbing member  41  (more specifically, the sound reducing portion  43 ). When passing through the sound absorbing member  41 , the intake noise vibrates the sound absorbing member  41  and the air in the gaps in the sound absorbing member  41 . The resultant friction converts the vibration energy into thermal energy, which reduces the vibration and the intake noise. 
     Even if a covering layer is provided on the surface of the sound absorbing member  41  on the inner side of the air chamber  46  (the surface on the lower side in  FIG. 1 , hereinafter referred to as the inner surface of the sound absorbing member  41 ), the covering layer vibrates due to the intake noise passes through the sound absorbing member  41  and reaches the covering layer. The sound pressure level of low frequency components thus can be reduced. In this case, however, part of the intake noise that contains low frequency components is reflected by the surface of the sound absorbing member  41  and returns into the air cleaner before reaching the covering layer, so that the sound pressure level of low frequency components are less effectively reduced. In this respect, in the air cleaner of the present embodiment, the covering layer  45  is provided on the surface of the sound absorbing member  41  on the outer side of the air chamber  46  (the surface on the upper side in  FIG. 1 , hereinafter referred to as the outer surface of the sound absorbing member  41 ). Thus, all the sound of low frequency components first enter the covering layer  45 . Therefore, it is possible to restrain sound of low frequency components from being reflected without reducing the sound pressure level. This effectively reduces the sound pressure level of low frequency components reflected by the sound absorbing member  41  and the covering layer  45 . 
     Also, as shown in  FIG. 5 , the wave of intake noise that has entered the air chamber  46  after passing through the covering layer  45  and the sound absorbing member  41  is reflected by the inner surface of the first housing  10  and returns to the sound absorbing member  41 . In the air cleaner of the present embodiment, the intake noise that is reflected and returns to the sound absorbing member  41  in this way (the reflected wave indicated by arrow A in  FIG. 5 ) and the intake noise that enters the sound absorbing member  41  from the outside of the air chamber  46  (the incident wave indicated by arrow B in  FIG. 5 ) are caused to interfere with each other, so that the intake noise can be reduced. 
     In the air cleaner of the present embodiment, the air chamber  46  is defined between the inner surface of the first housing  10  and the sound absorbing member  41 . Thus, unlike an air cleaner lacking the air chamber  46 , it is possible to change the distance traveled by the intake noise until it returns to the sound absorbing member  41  after passing through the sound absorbing member  41  and being reflected. In the air cleaner of the present embodiment, based on the results of various experiments and simulations, the shape of the air chamber  46  is determined such that the above distance is a length that causes part of the incident wave of the intake noise and part of the reflected wave to be in opposite phases. Therefore, according to the air cleaner of the present embodiment, it is possible to effectively reduce the intake noise by canceling out the incident wave and the reflected wave of the intake noise. 
     Furthermore, the air cleaner of the present embodiment includes, in the air chamber  46 , the reinforcing rib  19 , which protrudes from the inner surface of the bottom wall  14  of the first housing  10  and has the upper end separated from the lower surface of the sound absorbing member  41 . As a result, the vibration reducing structure, which is constituted by the fixing ribs  16 A,  16 B, the sound absorbing member  41 , and the covering layer  45 , is provided on the inner surface of the first housing  10 . Also, a reinforcing rib is arranged on the portion of the vibration reducing structure so as not to interfere with the vibration of the sound absorbing member  41  and the covering layer  45 . Therefore, it is possible to prevent the stiffness of the first housing  10  from being reduced due to the disposition of the vibration reducing structure. 
     As described above, the present embodiment achieves the following advantages. 
     (1) When passing through the sound absorbing member  41 , the intake noise vibrates the air in the gaps in the sound absorbing member  41 . The resultant friction converts the vibration energy into thermal energy, which reduces the vibration and the intake noise. Moreover, the incident wave of the intake noise entering the sound absorbing member  41  from the outside of the air chamber  46  is caused to interfere with (cancel out) the reflected wave of the intake noise that enters the air chamber  46  after passing through the sound absorbing member  41 , is reflected by the inner surface of the first housing  10 , and returns to the sound absorbing member  41 . This also reduces the intake noise. As described above, the air cleaner of the present embodiment is capable of effectively reducing intake noise. 
     (2) The covering layer  45 , which is made of a material having a lower air permeability than the sound absorbing member  41 , is provided to cover the entire outer surface of the sound absorbing member  41 . It is thus possible to effectively reduce the sound pressure level of low frequency components as compared with an air cleaner lacking the covering layer  45 . 
     (3) The air permeability of the flange  44  of the sound absorbing member  41  is lower than the air permeability of the sound reducing portion  43 , and the flange  44  is fixed to the upper end of the looped wall  17 . As a result, the covering layer  45  easily vibrates, and the vibration is easily converted into thermal energy, so that the intake noise is effectively reduced. 
     (4) The reinforcing rib  19 , which is provided in the air chamber  46 , protrudes from the inner surface of the bottom wall  14  of the first housing  10  and has an upper end separated from the sound absorbing member  41 . Therefore, it is possible to prevent the stiffness of the first housing  10  from being reduced due to the disposition of the vibration reducing structure. 
     &lt;Modifications&gt; 
     The above illustrated embodiment may be modified as follows. 
     The sound absorbing member  41  does not necessarily need to be made of nonwoven fabric, but it may be made of a porous material such as a foamed plastic (for example, foamed polyurethane). 
     The reinforcing rib  19  may be omitted. In addition, portions other than the looped wall  17  may be omitted from the fixing ribs  16 A and  16 B. 
     The flange  44  of the sound absorbing member  41  may be adhered and fixed to the upper end of the looped wall  17  so as to seal the entire circumference between the flange  44  and the upper end of the looped wall  17 . Thus, when the covering layer  45  vibrates, air is reliably prevented from leaking from or entering into the air chamber  46  through between the covering layer  45  and the looped wall  17 . As a result, the covering layer  45  more easily vibrates, and the vibration is easily converted into thermal energy, so that the intake noise is effectively reduced. 
     The upper end of the looped wall  17  and the flange  44  of the sound absorbing member  41  may be fixed to each other by welding. 
     The shapes of the fixing ribs  16 A and  16 B, the reinforcing rib  19 , and the sound absorbing member  41  may be determined such that the upper end of the reinforcing rib  19  and the lower surface of the sound absorbing member  41  contact each other. With this configuration, the reinforcing rib  19  is caused to contact the sound absorbing member  41  when being installed. The reinforcing rib  19  thus functions as a member that determines the position of the sound absorbing member  41 . The reinforcing rib  19  also functions as a stopper member that determines the maximum deformation position of the sound absorbing member  41 . 
     In addition to providing the covering layer  45  on the outer surface of the sound absorbing member  41 , a covering layer made of an air permeable material may be provided also on the inner surface of the sound absorbing member  41 . In this case, the covering layer  45  on the outer surface of the sound absorbing member  41  and the covering layer on the inner surface of the sound absorbing member  41  may have different air permeabilities. When the air permeability of a covering layer is changed, the frequency at which the covering layer resonates changes. Thus, the frequency components the sound pressure level of which can be effectively reduced also change. Specifically, if the other conditions are the same, the lower the air permeability of the covering layer, the lower becomes the resonance frequency of the covering layer. Accordingly, frequency components the sound pressure level of which can be effectively reduced become lower frequency components. Therefore, by providing covering layers having different air permeabilities on the inner surface and the outer surface of the sound absorbing member  41  like the air cleaner described above, it is possible to effectively reduce the sound pressure levels of different frequency components, respectively, so that the intake noise is more effectively reduced. 
     The covering layer  45  may be omitted. 
     Two or more air chambers equivalent to the air chamber  46  may be provided in the air cleaner. In this case, the air chambers may have different volumes. When the volume of an air chamber is changed, the frequency at which the covering layer resonates changes. Thus, the frequency components the sound pressure level of which can be effectively reduced also change. Specifically, if the other conditions are the same, the larger the volume of the air chamber, the lower becomes the resonance frequency of the covering layer. Accordingly, the frequency components the sound pressure level of which can be effectively reduced become lower frequency components. Therefore, by providing air chambers having different volumes like the air cleaner described above, it is possible to effectively reduce the sound pressure levels of different frequency components, respectively, so that the intake noise is more effectively reduced. 
     The vibration reducing structure may be arranged on the peripheral wall  13  of the first housing  10  or on the peripheral wall  23  and the top wall  24  of the second housing  20 .