Abstract:
An air induction housing as for example for a motor vehicle having an auxiliary tuning volume which provides an enhancement of the attenuation and a broadening of the bandwidth of attenuation of any primary attenuator of the air induction housing, yet with a minimal expense, complexity and packaging volume, and without adversely affecting the air flow path. The auxiliary tuning volume is characterized by an intermediate wall having a tuning slot, wherein the wall separates a tuning chamber of the auxiliary tuning volume from the main airflow passage of the housing.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to air induction housings as for example used in the automotive arts for air intake and air filtration for supplying intake air to a normally aspirated or charged internal combustion engines, hydrogen fuel cells, etc. More particularly, the present invention relates to an air induction housing having an auxiliary tuning volume which provides attenuation enhancement and bandwidth broadening for a primary attenuator connected to the air induction housing. 
       BACKGROUND OF THE INVENTION 
       [0002]    Internal combustion engines and hydrogen fuel cells rely upon an ample source of clean air for proper combustion therewithin of the oxygen in the air mixed with a supplied fuel (internal combustion) or the oxygen required for the hydrogen fuel cell chemical reaction. In this regard, an air induction housing is provided which is connected with the intake manifold/air supply of the engine/fuel cell, wherein the air induction housing has at least one air induction opening for the drawing-in of air, and further has a filter disposed thereinside such that the drawn-in air must pass therethrough and thereby be cleaned prior to exiting the air induction housing on its way to the intake manifold/fuel cell turbine inlet. 
         [0003]    Problematically, a consequence of the combustion of the fuel-air mixture within the internal combustion engine or the high rpm turbine inlet of the hydrogen fuel cell is the generation of noise (i.e., unwanted sound). A component of this noise is intake noise which travels through the intake manifold or from the fuel cell turnbine inlet, into the air induction housing, and then radiates out from the at least one air induction opening. The intake noise varies in amplitude across a wide frequency spectrum dependent upon the operational characteristics of the internal combustion engine or the design/rpm range of the fuel cell turbine inlet, and to the extent that it is audible to passengers of the motor vehicle and persons exposed to the sound during a passby event, it is undesirable. 
         [0004]    As shown at  FIG. 1 , a solution to minimize the audibility of intake noise is to equip an air induction housing  10  with an externally disposed Helmholtz attenuator  11  which is composed of a Helmholtz chamber (also referred to as a resonator)  12  and a snorkel  14  externally connected to the air induction housing. The air induction housing  10  has upper and lower housing components  16 ,  18  which are sealed with respect to each other, and are also selectively separable for servicing a filter media (not shown) which is disposed thereinside. An induction duct  20  is connected to the induction housing and defines an air induction opening  22  for providing a source of intake air to the air induction housing at one side of the filtration media, as for example by being interfaced with the lower housing component  18 . An intake manifold duct  24  is adapted for connecting with the intake manifold of the internal combustion engine or the turbine inlet of the hydrogen fuel cell and is disposed so as to direct the intake air at the other side of the filtration media out of the air induction housing  10 , as for example via the upper housing component  16 . 
         [0005]    One end of the snorkel  14  is connected to the induction duct  20  adjacent the air intake opening  22 . The other end of the snorkel  14  is connected to the Helmholtz chamber  12 . Each end of the snorkel  14  is open so that intake noise may travel between the induction duct  20  and the Halmholtz chamber  12 . The Helmholtz chamber  12  is shaped and the snorkel  14  configured (as for example as two snorkel tubes  14   a ,  14   b ) such that the intake noise passing through the induction duct toward the air intake opening in part passes into the resonator and then back into the induction duct so as to attenuate the intake noise by frequency interference such that the audibility of the intake noise exiting the air intake opening is minimized. 
         [0006]    While the prior art solution to provide attenuation of intake noise does work, it does so by requiring the inclusion of an externally disposed snorkel and resonator combination which adds expense, installation complexity and packaging volume accommodation. 
         [0007]    Accordingly, what is needed in the art is to somehow provide an enhancement of the attenuation and broadening of the bandwidth of attenuation of any primary attenuator of the air induction housing, yet with a minimized expense, complexity and packaging volume, and without adversely affecting the air flow path. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention is an air induction housing as used for example, but not limitation, supplying intake air to normally aspirated or charged internal combustion engines, hydrogen fuel cells, etc., wherein the air intake housing has an auxiliary tuning volume with a specific sized tuning slot opening for a tuning chamber which operates in conjunction with a primary attenuator of the air intake housing, and wherein the auxiliary tuning volume enhances the attenuation and broadens the bandwidth of attenuation of any primary attenuator of the air induction housing, yet with a minimal expense, complexity and packaging volume, and without adversely affecting the air flow path. 
         [0009]    The air induction housing according to the present invention includes a main airflow passage and further includes an auxiliary tuning volume composed of a tuning chamber, preferably disposed at an upper portion of the air intake housing, which communicates with the main airflow passage. The tuning chamber is, in part, defined by an intermediate wall, wherein the tuning chamber has a predetermined volume and shape. A tuning slot is provided in the intermediate wall which communicates between the tuning chamber and the main airflow passage, wherein the tuning slot has a length (which exceeds its width), wherein the length is oriented in transverse relation to the direction of airflow (the airflow path) through the main airflow passage. 
         [0010]    The auxiliary tuning volume according to the present invention provides enhancement of the attenuation of any primary sound attenuator, while additionally broadening the bandwidth (frequency spectrum) of the sound attenuation of the primary sound attenuator. 
         [0011]    A significant aspect of the present invention is that the intake noise attenuation enahncement and bandwidth broadening are accomplished inherently at the air induction housing, with a minimization of packaging volume of the housing and of the primary sound attenuator, and minimal weight, yet is configurationally simplistic and does not adversely affect the airflow path of the intake air through the main airflow passage. 
         [0012]    Accordingly, it is an object of the present invention to provide an air induction housing having an integrated auxiliary tuning volume which provides both enhancement of sound attenuation and broadening of the bandwidth of the sound attenuation for any primary sound attenuator of the air intake housing, wherein the tuning chamber thereof has a tuning slot opening into the main airflow passage and oriented transverse to the airflow through the main airflow passage of the housing. 
         [0013]    This and additional objects, features and advantages of the present invention will become clearer from the following specification of a preferred embodiment. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a perspective view of a prior art air induction housing including a Helmholtz attenuator in the form of an external snorkel and resonator combination for attenuating intake noise. 
           [0015]      FIG. 2  is a perspective plan view of an air intake housing having a primary sound attenuator and an auxiliary tuning volume according to the present invention. 
           [0016]      FIG. 3  is a perspective sectional view, seen along line  3 - 3  of  FIG. 2 . 
           [0017]      FIG. 3A  is a perspective view as in  FIG. 3 , wherein, in contrast with  FIG. 3 , the tuning chamber sidewalls are now integrated with the air induction housing. 
           [0018]      FIG. 4  is a perspective, detail, partly sectional view of the air induction housing of  FIG. 2 , wherein the tuning chamber sidewalls of the auxiliary tuning volume are sectioned. 
           [0019]      FIG. 5  is a perspective sectional view, seen along line  5 - 5  of  FIG. 2 . 
           [0020]      FIG. 6  is a graph of frequency of sound versus sound level, wherein a first plot is for an air intake housing as in  FIG. 2 , having a primary sound attenuator and the auxiliary tuning volume, and a second plot is for the air intake housing as generally in  FIG. 2  but with primary sound attenuator alone. 
           [0021]      FIG. 7  is a graph of frequency of sound versus sound level, wherein a first plot is for an air intake housing as in  FIG. 2 , having a primary sound attenuator and the auxiliary tuning volume, and a second plot is an exemplar baseline for the air induction housing. 
           [0022]      FIG. 8  is a perspective view of an air induction housing generally similar to that of  FIG. 1 , but now including an auxiliary tuning volume according to the present invention. 
           [0023]      FIG. 9  is a bottom perspective view of the upper housing component of an air induction housing of  FIG. 8 , showing the auxiliary tuning volume of the present invention. 
           [0024]      FIG. 10  is a sectional view seen along line  10 - 10  of  FIG. 9 . 
           [0025]      FIG. 11  is a graph of engine RPM versus sound level, wherein a first plot is for an air induction housing as in  FIG. 1  having a snorkel and Helmholtz chamber alone, a second plot is for the air intake housing as in  FIG. 8  having the auxiliary tuning volume, and a third plot is for a predetermined acceptable quietness level. 
           [0026]      FIG. 12  is a flow chart exemplifying an optimization algorithm for tuning the auxiliary tuning volume according to the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0027]    Referring now to the Drawing,  FIGS. 2 through 12  depict various aspects of an air induction housing having an auxiliary tuning volume according to the present invention. 
         [0028]    With regard to intake noise attenuation provided by a (sound) attenuation chamber, the attenuation may operate on the basis of a Helmholtz attenuator (resonator), as for example discussed in U.S. Pat. No. 5,979,598, wherein the resonant frequency thereof is given by (see for example http://en.wikipedia.org/wiki/Helmholtz_resonator): 
         [0000]    
       
         
           
             
               
                 
                   
                     ω 
                     H 
                   
                   = 
                   
                     
                       γ 
                        
                       
                         
                           
                               
                           
                            
                           
                             A 
                             2 
                           
                         
                         m 
                       
                        
                       
                         
                           P 
                           0 
                         
                         
                           V 
                           0 
                         
                       
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
         [0000]    where γ is the adiabatic index, A is the cross-sectional area of an aperture (or neck in a classic Helmholtz resonator), m is the mass of the gas in the cavity, P 0  is the static pressure in the cavity, V 0  is the static volume of the cavity. 
         [0029]    Referring firstly to  FIGS. 2 through 5 , a first exemplary configuration of an air induction housing  100  with an auxiliary tuning volume  102  according to the present invention is depicted. It is to be understood that the detailed description and accompanying drawing are merely exemplary, and that the present invention has wide application to air induction housings generally as used for example, but not limitation, supplying intake air to normally aspirated or charged internal combustion engines, hydrogen fuel cells, etc. 
         [0030]    The air induction housing  100  has a generally unified construction defined by a housing sidewall  104 , composed of, for example, a plastic material. At an upstream housing end  100   a  of the air induction housing  100  is an intake opening  106  whereat is situated an air filter  108 . At a downstream housing end  100   b  of the air induction housing  100  is a neck  110  which connects to a ducting  112  and eventually interconnects to intake components of the motor vehicle engine. The shape of the housing sidewall  104  is determined to provide an adequate supply of airflow A to the engine, wherein in this respect the shape and size of main airflow passage  114  takes into account the rate of airflow and airflow turbulence. The shape of the housing sidewall  104  also must fit into whatever packaging constraint may subtend in the engine compartment, which often favors smaller, compact shapes. As used herein, the terms “upstream” and “downstream” are defined by the direction of airflow A through the main airflow passage  114 . 
         [0031]    The auxiliary tuning volume  102  according to the present invention is mounted, by preferred example, at a top portion  100   t  of the air induction housing  100 . The auxiliary tuning volume  102  is in the form of a tuning chamber  116 , defined by a chamber sidewall  118  and an intermediate wall  120  which separates the tuning chamber from the main airflow passage  114 . A tuning slot  122  is formed in the intermediate wall  120  which permits air borne sound communication between the tuning chamber  116  and the main airflow passage  114 . The tuning slot  122  has a longest axis along its length L (the width being shorter), wherein the length is oriented transversely in relation to the direction of the airflow A through the main airflow passage  114  (see  FIG. 4 ). In this regard, it is preferred for the tuning slot to be located at a downstream end  116   a  of the tuning chamber  116 , whereby sound entering thereinto through the tuning slot  112  is caused to travel toward the upstream end  116   b  of the tuning chamber (the end closest to the air intake opening  106 ). 
         [0032]    Comparing  FIG. 3  with  FIG. 3A , different modalities for attachment of the auxiliary tuning chamber  116  are depicted. At  FIG. 3 , the intermediate wall  120  is integral with the housing sidewall  104 , wherein the chamber sidewall  118  is attached, as for example by vibration welding, to the housing sidewall. Whereas, at  FIG. 3A , the chamber sidewall  118 ′ is integral with the housing sidewall  104 ′, wherein the intermediate wall  120 ′ is attached, as for example by vibration welding, to the housing sidewall. 
         [0033]    The auxiliary tuning volume  102  according to the present invention operates in conjunction with any primary sound attenuator  130  of the air intake housing  100  so as to enhance the sound attenuation and broaden the sound attenuation bandwidth thereof (the term “primary sound attenuator” refers to any number of sound attenuators that are being used). As shown at  FIGS. 2 ,  3  and  5 , the primary sound attenuator  130  is in the form of a primary Helmholtz attenuator  132 , which is, for example, in the form of a generally box-shaped primary Helmholtz chamber  134  which has a primary opening  136  near the downsteam housing end  100   b . Attenuators similar to the primary Helmholtz attenuator  132  are generally known in the prior art, as for example the Helmholtz attenuator  11  of  FIG. 1 . 
         [0034]    As discussed further hereinbelow with respect to  FIG. 12 , the auxiliary tuning volume  102  is optimized empirically and/or analytically in relation to the air intake housing  100 , airflow demand and intake noise generation of the associated engine, as well as the primary sound attenuator  130  of the air intake housing  100  in order to amplify the sound attenuation and broaden the bandwidth of the sound attenuation of the primary sound attenuator. 
         [0035]    As a general rule of thumb, the tuning chamber may have a volume in the neighborhood of about 0.5 L, but his depends on the environment of operation of the auxiliary tuning volume  102 . By way of example, and not limitation, with respect to  FIGS. 2 through 5 , the tuning chamber  116  has a volume of about 616069.8 mm 3 , the tuning slot  112  has an area of about 6552 mm 2 , defined by a length L of about 157.14 mm and a width W of about 41.67 mm, wherein the air flow passage  114  has a volume of about 4127799.7 mm 3 , and the primary Helmholtz attenuator  132  has a primary Helmholtz chamber  134  having a volume of about 411691.3 mm 3  and an opening having an area of about 2392.23 mm 2 . 
         [0036]    The auxiliary tuning  102  according to the present invention provides enhancement of the attenuation of the primary sound attenuator  130  (i.e., the primary Helmholtz attenuator  132 ), while additionally broadening the bandwidth (frequency spectrum) of the sound attenuation thereof. This result is exemplified in the graphical representations of  FIGS. 6 and 7 . 
         [0037]      FIG. 6  is a graph  140  of frequency of sound versus sound level, wherein a first plot  142  is for an air induction housing  100  having a primary 600 Hz Helmholtz attenuator  132  and the auxiliary tuning volume  102 , as depicted at  FIG. 2 , and a second plot  144  is for an air induction housing similar to that of  FIG. 2 , having the primary 600 Hz Helmholtz attenuator, but not including the auxiliary tuning volume of the present invention. It will be seen that plot  142  has a much broader bandwidth (frequency range) than that of plot  144 , which broadening can be tuned based upon selection of tuning chamber  116  volume and tuning slot  112  dimension selection. 
         [0038]      FIG. 7  is a graph  150  of frequency of sound versus sound level, wherein a first plot  152  is for an air induction housing  100  having a primary 600 Hz Helmholtz attenuator  132  and the auxiliary tuning volume  102 , as depicted at  FIG. 2 , and a second plot  154  is a baseline for an air induction housing similar to that of  FIG. 2 , having the primary 600 Hz Helmholtz attenuator, but not including the auxiliary tuning volume of the present invention. It will be seen that plot  152  has better sound (i.e., supercharger noise) attenuation than that of plot  154  over a broad bandwidth. 
         [0039]    Turning attention now to  FIGS. 8 ,  9  and  10 , the air intake housing  100 ′ is modified from the air intake housing  10  of  FIG. 1  to now include an auxiliary tuning volume  102 ′ according to the present invention. 
         [0040]    The description of the air intake housing  100 ′ is the same for all aspects of the lower housing component  18 , as depicted at  FIG. 1  (all numbers associated therewith carrying over to  FIG. 8 ) wherein the Helmholtz attenuator  11  is now the primary sound attenuator as used in the present invention. However, the upper housing component  16  of  FIG. 1  is modified as per the upper housing component  160  of  FIGS. 8 ,  9  and  10 . 
         [0041]    The upper housing component  160  is defined by an upper sidewall  162  having an upper wall  162   a . The auxiliary tuning volume  102 ′ according to the present invention is mounted (as for example by any suitable plastic welding technique) to the upper wall  162   a  internally to the upper housing component  160 . The auxiliary tuning volume  102 ′ is in the form of a tuning chamber  116 ′, defined by a chamber sidewall  118 ′ which includes an intermediate wall  120 ′ whereby the tuning chamber is separated from the main airflow passage  114 ′. A tuning slot  122 ′ is formed in the intermediate wall  120 ′ which permits air borne sound communication between the tuning chamber  116 ′ and the main airflow passage  114 ′. The tuning slot  118 ′ has a longest elongation length L′ which is oriented transversely in relation to the direction of the airflow A′ though the main airflow passage  114 ′. In this regard, it is preferred for the tuning slot to be located at a downstream end  116   a ′ of the tuning chamber  116 ′, whereby sound entering thereinto through the tuning slot  112 ′ is caused to travel toward the upstream end  116   b ′ of the tuning chamber (the end closest to the air intake opening  22  of  FIG. 8 ). 
         [0042]    It is to be understood that the auxiliary tuning volume  102 ′ of the upper housing component  160  may be utilized with other configured lower housing components having different types of primary sound attenuators, as for example those disclosed in U.S. patent application Ser. No. 11/681,286, filed on Mar. 2, 2007, Ser. No. 12/057,401, filed on Mar. 28, 2008, both to Julie Ann Koss, the disclosures of which are hereby herein incorporated by reference. The volume of the tuning chamber  116 ′ and the area of the tuning slot  112 ′ are optimized per the associated intake housing, airflow rate, engine (per its airflow requirements and intake noise generation), and type of primary sound attenuator, as per the discussion hereinbelow with respect to  FIG. 12 . 
         [0043]      FIG. 11  is a graph  170  of engine RPM versus sound level, wherein a first plot  172  is for an air induction housing  10  as in  FIG. 1  having a snorkel and Helmholtz chamber (having an inlet extension, ¼ wave, primary Helmholtz attenuator), a second plot  174  is for an air induction housing  100 ′ as in  FIG. 8  (having an inlet extension, ¼ wave, primary Helmholtz attenuator), which includes an auxiliary tuning volume  102 ′ (of 1.5 L total volume), and a third plot  176  is for a predetermined acceptable quietness level. It is seen that plot  174  clearly provides sound attenuation much better than plot  172 , indeed well below the baseline of plot  176  over the indicated range of engine RPM. 
         [0044]    Turning attention now to  FIG. 12 , depicted is an example of an algorithm for tuning the auxiliary tuning volume according to the present invention whereby, for any primary sound attenuator of the air induction housing, the auxiliary tuning volume is tuned to optimize the attenuation enhancement and the bandwidth broadening for the primary sound attenuator. While the description below, by way of example, is based upon  FIGS. 2 through 5 , it is to be understood that the description is generally applicable to an air induction housing as used for example, but not limitation, supplying intake air to normally aspirated or charged internal combustion engines, hydrogen fuel cells, etc. 
         [0045]    At Block  202 , the algorithm is initialized. At Block  204 , the engine airflow rate requirement of a selected internal combustion engine is determined. At Block  206 , the necessary airflow passage is determined such that back pressure is not an issue for the operation of the internal combustion engine, which determination includes any packaging constraints of the engine compartment. At Block  208 , a primary sound attenuator is determined, and the sound (acoustic) attenuation performance is selected, for example, with respect to the engine and the air intake housing, taking into further account engine intake noise over a selected range of engine RPM. 
         [0046]    Next, at Blocks  210  and  212 , an auxiliary tuning volume configuration is selected, based mainly upon the tuning chamber volume selection and tuning slot area selection, taking into account any engine compartment packaging constraints. At Block  214 , determined are the enhancement of attenuation of the primary sound attenuator provided by the auxiliary Helmholtz attenuator, as well as the broadening of the bandwidth of the sound attenuation of the primary sound attenuator as provided by the auxiliary tuning volume. 
         [0047]    At Decision Block  216 , inquiry is made whether the attenuation and bandwidth performance of the auxiliary tuning volume at Block  214  meets predetermined quietness specifications, wherein, if the answer to the inquiry is yes, the optimization is complete and fabrication of the air induction housing with the auxiliary tuning volume may proceed; otherwise, if the answer to the inquiry is no, then the algorithm loops back to Block  210  for further optimization processing as described above. 
         [0048]    To those skilled in the art to which this invention appertains, the above described preferred embodiment may be subject to change or modification. Such change or modification can be carried out without departing from the scope of the invention, which is intended to be limited only by the scope of the appended claims.