Abstract:
An air duct assembly supplies air from an air cleaner housing to an engine throttle and includes a first duct connected to the air cleaner housing and a second duct connected to the engine air intake. Open ends of the first and second ducts are spaced from one another and the second duct has a flared bell mouth at its open end. The second duct includes a sleeve that defines an attenuation chamber. A flexible bellows overlies the first and second ducts and the sleeve, and extends across the space between the first and second ducts to provide an airtight connection therebetween and flex during relative motion between the air cleaner housing and the engine air intake. A hydrocarbon adsorbing material can be housed within the attenuation chamber.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to an air induction system for an engine and more particularly provides a new and improved duct assembly for accommodating relative movement between the engine and the air filter and for attenuating engine noise. 
       BACKGROUND OF THE INVENTION 
       [0002]    Motor vehicle internal combustion engines use a throttle body to govern the engine power settings. Some engines have additional charging equipment including turbo and supercharger mechanisms that compress intake air upstream of the throttle body to enhance engine performance. All internal combustion engines must receive a constant supply of clean air in order to enable the combustion of the fuel. The engine induction system is located upstream of the engine air intake and its primary functions are air filtration and noise attenuation. 
         [0003]    The induction system begins with an inlet duct which draws cool dry air into the system. The inlet duct will deliver the air into an air filter housing that has an internal filter to capture incoming particulates to protect the engine. The air filter housing will also typically have a mass air flow meter port and a sensor downstream of the filter, to meter the air for combustion. The outlet duct will be connected between the air filter housing and the engine air intake. The air filter housing can be mounted to the engine or on the vehicle body structure. If mounted on the body structure, the duct will need a compliant feature such as a flexible bellows to decouple normal engine motion from the body mounted air filter housing. The induction system provides a pathway to deliver filtered dry cool air to the engine. 
         [0004]    Air induction systems must also attenuate acoustic noise that is produced from the engine. Vehicles must comply with Federal regulations limiting vehicle pass-by noise. The engine will release noise from the throttle body that has harmonic components that are orders of engine speed. It may also contain higher frequency content that is produced from high RPM components like turbos and superchargers. Inductions systems will use the air filter housing size, geometry, and high and low frequency tuners to meet defined sub-system performance noise targets. 
         [0005]    Vehicle emission standards have been mandated by the Federal government. Some engines use a strategically placed hydrocarbon adsorber in the induction system to catch hydrocarbons that are leaking from parked engines. The hydrocarbon adsorber uses carbon or other materials to capture the hydrocarbons before they escape the induction system and enter the environment. The adsorber is typically packaged on the clean filtered side of the induction system and has some exposed surface area adjacent to incoming air flow streams. This exposure allows the hydrocarbons to be captured upon engine shutdown and then be stripped from the adsorber material when the engine is running. 
         [0006]    Induction system pressure loss is very important to develop peak engine power. Internal air flow within a duct will add incremental restriction if the area is constricted or if the boundary condition is irregular or coarse. Studies have shown that internal air flow within the bellows region of the duct assembly develops a higher restriction than flow through a smooth tube. 
         [0007]    The clean air duct must fit within the distance between the air filter housing and the engine air inlet. Some applications can present a very short duct length due to the close proximity of the engine inlet and air filter housing. Incorporation of a high frequency tuner will reduce the available length for the bellows. The shorter length will eliminate convolutes increasing the stress per convolute reducing the durability life of the duct. Applications with short longitudinal lengths where length is consumed by bellows and tuner limit hydrocarbon filter space. It would be desirable to provide a new and improved air duct assembly for efficiently communicating air from the air filter housing to the engine air intake in a limited packaging space. 
       SUMMARY OF THE INVENTION 
       [0008]    An air duct assembly supplies air from an air cleaner housing to an engine throttle and includes a first duct connected to the air cleaner housing and a second duct connected to the engine air intake. Open ends of the first and second ducts are spaced from one another and the second duct has a flared bell mouth at its open end. The second duct includes a sleeve that defines an attenuation chamber. A flexible bellows overlies the first and second ducts and the sleeve, and extends across the space between the first and second ducts to provide an airtight connection therebetween and flex during relative motion between the air cleaner housing and the engine air intake. A hydrocarbon adsorbing material can be housed within the attenuation chamber. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0010]      FIG. 1  is a perspective view of an air induction system of the prior art and having a bellows and a sound attenuating tuner. 
           [0011]      FIG. 2  is a cross section view taken through the air duct assembly of the present invention. 
           [0012]      FIG. 3  is a cross section view taken through the air duct assembly of a second embodiment of the invention. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0013]    The following description of certain exemplary embodiments is exemplary in nature and is not intended to limit the invention, its application, or uses. 
         [0014]    Referring to  FIG. 1 , a prior art air induction system provides clean air to an engine air intake. The air induction system includes an air filter housing  14  that contains an air filter, not shown. Ambient air enters the air filter housing  14  through an air inlet duct  16 . After passing through the filter that is housed within the housing  14 , the air exits through an outlet duct assembly, generally indicated at  20 . The air flow will continue into the engine air inlet which could be a throttle body, turbo or supercharger inlet. As seen in  FIG. 1 , the duct assembly  20  includes an air filter housing  24 , a flexible bellows  26 , a sound attenuating tuner  28 , and a flexible bellows  30 . The bellows  26  is attached to the air filter housing  24  with a hose clamp  34 . The bellows  26  is attached to the tuner  28  by a hose clamp  36 . The bellows  30  is attached to the tuner  28  by a hose clamp  38 . The bellows  30  is attached to the engine air intake by a hose clamp  40 . The tuner  28  is a plastic or metal tuner housing  44  that encloses a perforated duct portion  46 . The perforated duct portion  46  is perforated by a plurality of openings  50 . The tuner  28  is designed to attenuate noise emanating from the engine. 
         [0015]      FIG. 2  shows a new and improved air duct assembly, generally indicated at  56 . The first duct  58  has a duct wall  60  defining an air flow passage  61  and is connected to an air filter housing, not shown. The first duct  58  and air flow passage  61  have an open end  62 . A second duct  66  is connected, either directly, or by a flexible connector, to the engine air intake, which can be either a throttle body, turbocharger, or supercharger. The second duct  66  has a duct wall  68  defining an air flow passage  69  with an open end  70 . The duct wall  68  is flared outwardly at the open end  70  to create a bell mouth  72 . 
         [0016]    As seen in  FIG. 2 , the open end  62  of the first duct  58  is spaced from the bell mouth  72  of the open end  70  of the second duct  66 . Also as seen in  FIG. 2 , a portion of the length of the second duct  66 , generally adjacent the open end  70 , is perforated to provide a plurality of openings  76  in the duct wall  68  of the second duct  66 .  FIG. 2  shows the openings  76  as being round holes, however, the openings  76  can be holes, slots, or any shape. The first duct  58  and the second duct  66  are preferably of molded plastic, but alternatively can be of metal construction. 
         [0017]    The second duct  66  includes a sleeve  78  that creates an annular sound attenuation chamber  80 . The sleeve  78  includes a concentric wall  82 , and end walls  84  and  86 . The end walls  84  and  86  extend radially inward from the concentric wall  82  and are suitably attached to the duct wall  68 . As seen in  FIG. 2 , the sound attenuation chamber  80  is radially outboard of the air flow passage  69 . The size of the attenuation chamber  80  will be determined by the diameter of the concentric wall  82  of the sleeve  78  and also the distance between the end walls  84  and  86 . In particular, the distance between the end walls  84  and  86  determines the length of the attenuation chamber  80 , and the radial extent of the end walls  84  and  86  will define the radial depth of the attenuation chamber  80 . The sound that is emanating through the air duct assembly  56  in the form of high frequency perturbations of airflow is attenuated by passing through the perforated openings  76  and into the attenuation chamber  80 . The sound attenuating characteristics of the attenuation chamber  80  can be tuned by properly sizing the volume of the attenuation chamber  80  and also the size, shape and number of the perforated openings  76 . 
         [0018]    The first duct  58  and the second duct  66  are connected together by a flexible bellows  90 . The flexible bellows  90  is radially outboard of the second duct  66  and its sleeve  78  and the attenuation chamber  80 . As seen in  FIG. 2 , a left-hand end  92  of the bellows  90  is attached to the first duct  58  by a clamp  94  and a right-hand end  96  of the bellows  90  is connected to the sleeve  78  at its end wall  86  and attached by a clamp  98 . The sleeve  78  has a support rib  100  that underlies the clamp  98  so that the installation of the clamp  98  will not deform the sleeve  78 . 
         [0019]    In operation, the engine air intake will draw air through the duct assembly  56  and through the air filter housing  14 . The air flows through the air flow passage  61  of the first duct  58  and then across the space between the first duct  58 , and into the second duct  66 . The space between the ends of the ducts  58  and  66  will permit the two ducts  58  and  66  to move relative to one another during movement of the engine. The bell mouth  72  will smooth the air flow across the space between the ends of the ducts  58  and  66  and smooth the intake of the air flow into the open end  70  of the duct  66 . The bellows  90  is flexible and can yield as needed to accommodate the relative movement between the first duct  58  and the second duct  66 . Engine noise that is emanating through the duct  66  in the form of high frequency air vibrations can be attenuated by escaping through the openings  76  into the attenuation chamber  80 . 
         [0020]    Thus, as shown in  FIG. 2 , the attenuation chamber  80  and the bellows  90  are provided concentric with one another and are concentric with the air flow passage  69 . By arranging the attenuation chamber  80  and the bellows  90  in this fashion, the flexibility function provided by the bellows  90  and attenuation function provided by the attenuation chamber  80  can be performed within an overall length designated  104 . In contrast, referring again to  FIG. 1 , we see that the prior art air duct assembly had arranged the bellows  26  and  30 , and the tuner  28  in series, and required a greater length  106  in order to perform the functions of flexibility and sound attenuation. In addition, comparing the prior art of  FIG. 1  with the invention of FIG.  2 , it is seen that, in the prior art air duct assembly of  FIG. 1 , the air passing through the duct assembly  20  was exposed directly to the convolutions on the inside of the bellows  26  and  30 , which in turn creates incremental restriction. In contrast, in the new and improved air duct of  FIG. 2 , the airflow can pass directly from the open end  62  of the first duct  58  and into the second duct  66  without exposure to the convoluted wall of the bellows  90 . In addition, the bell mouth  72  aids in maintaining an aligned flow of air through the duct assembly  56  even during relative movement between the ducts  58  and  66  caused by engine movement. 
         [0021]    Referring to  FIG. 3 , another embodiment of the invention is shown. In  FIG. 3 , first duct  158  has a duct wall  160  defining an air flow passage  161 . A second duct  166  has a duct wall  168  defining an air flow passage  169 . The duct wall  168  of the second duct  166  is flanged outwardly at flange end wall  186  to form a duct wall  182  that is integral with the cylindrical wall  168 . A bellows  190  surrounds the duct wall  182  and includes a left-hand end  192  connected to the first duct  158  and attached with a clamp  194 . Bellows  190  has a right-hand end  196  that is attached to the duct wall  182  by a clamp  198 . 
         [0022]    As seen in  FIG. 3 , an annular sleeve  200  is installed inside the duct wall  182 . The sleeve  200  has an interior passage  202  that aligns with the second duct  166  and has the same diameter as the duct wall  168  of the second duct  166  so that the sleeve  200  becomes an integral extension of the second duct  166 . The right-hand end of sleeve  200  has a flange  206  suitably attached to the flange  186 . The left-hand end of sleeve  200  has an outwardly flared wall  208  that is connected to the end of the duct wall  182 . Internal radial extending dividing walls  210  and  212  are provided between the duct  182  and the sleeve  200  to thereby define separate chambers  216 ,  218  and  220 . The chamber  218  is an attenuation chamber and a plurality of openings  176  are provided in the sleeve  200  to provide airflow communication between the duct  166  and the attenuation chamber  218 .  FIG. 3  shows that a hydrocarbon adsorbing material  214  is housed within the chambers  216  and  220 . The hydrocarbon adsorbing material can be activated charcoal or other material capable of adsorbing hydrocarbons. Slots  224  are provided in the sleeve  200  to communicate airflow from the duct  166  to the hydrocarbon adsorbing material  214  housed in the chamber  216 . Similar slots  226  are provided in the sleeve  200  to communicate airflow to the hydrocarbon adsorbing material  214  housed in the chamber  220 . The presence of the hydrocarbon adsorbing material within a chamber may influence the sound attenuating characteristics, and accordingly, the hydrocarbon adsorbing material can be located in only some of the chambers or all of the chambers as appropriate to accomplish the needed level of sound attenuation and hydrocarbon adsorption. 
         [0023]    During normal operation of the engine, sound will be attenuated by the communication of airflow perturbations into the attenuating chamber  218 . Upon shutdown of the engine, it is known that some of the hydrocarbon combustion products will leak back through the throttle body or turbocharger and into the duct  166 . These hydrocarbons will be exposed to the hydrocarbon adsorbing material  214  residing in the chambers  216  and  220  and will be adsorbed. Later, upon restarting of the engine, the hydrocarbons will be released from the hydrocarbon adsorbing material and flow back into the engine where these polluting products can be re-combusted and then processed through the engines pollution control system. 
         [0024]    The foregoing drawings and description disclose typical embodiments of the invention. A person of ordinary skill in the art may make modifications within the scope of the invention. For example, in  FIG. 2 , the drawings show that the right-hand end  96  of the bellows  90  is attached onto the outer surface of the sleeve  78 . As an alternative, the right-hand end  96  of the bellows  90  can be attached onto the outer surface of the second duct  66 . Although the drawings herein show hose clamps for attaching the bellows, it will be understood that other mechanical fasteners, adhesives, friction or snap attachments can be employed. In addition, it will be understood that the relative sizes of the sound attenuation chamber and the hydrocarbon adsorbing chambers can be modified as desired to optimize the performance of the duct assembly of this invention, and that any number of chambers can be employed. The ducts and the sleeves are shown herein as being circular cylinders, however, the ducts and sleeve can be other tubular shapes such as octagonal, hexagonal, oval, or square cross section. 
         [0025]    Thus, the invention offers a method to longitudinally consolidate an induction clean air duct bellows and a high frequency tuner. Today, these components are packaged in series along the duct. This arrangement will axially consolidate these parts and provide a flow liner within the bellows. This feature will reduce internal flow restriction by improving the boundary shape. Alternatively, all or part of the high frequency tuner cavity can also be used to package a hydrocarbon adsorbing material. The cavity for the hydrocarbon adsorbing material is well positioned to capture the hydrocarbons and also have an interior surface adjacent to the flow field to regenerate the adsorbing material.