Abstract:
An exhaust manifold and method of manufacturing the same is provided that includes at least one tube within shells of an exhaust manifold. The tube limits fluid communication from the tube into the shells of the exhaust manifold. An inlet flange is connectable to the exhaust manifold and is attachable to a cylinder head of a combustion engine. Exhaust gases expelled from the cylinder head are transmitted into the exhaust manifold. At least a portion of the exhaust gases pass through the tube. The exhaust manifold reduces NVH and cures emission control issues.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit from U.S. Provisional Patent Application No. 60/934,376, entitled “Exhaust Manifold Having Improved NVH Characteristics,” filed on Jun. 13, 2007, which is hereby incorporated in its entirety by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention generally relates to an exhaust manifold that may be incorporated into an internal combustion engine, and more particularly to an exhaust manifold having exhaust tubes within an exhaust manifold housing that may improve noise, vibration and harness characteristics of the manifold housing. 
       BACKGROUND 
       [0003]    In an internal combustion engine, a cylinder head is positioned atop an engine block having cylinders (or combustion chambers) extending therethrough. Upper portions of each combustion chamber extend through the cylinder head, where the upper portion of each combustion chamber corresponds with each cylinder of the engine block. The cylinder head may also house intake valves, exhaust valves, camshaft(s), rocker arms and pushrods, and numerous other mechanisms as is known in the art. 
         [0004]    In addition, an intake manifold and an exhaust manifold are typically coupled to the cylinder head. The intake manifold is typically located between the carburetor and the cylinder head to supply an air-fuel mixture to each combustion chamber through internal intake ports in the cylinder head. In multi-port injected engines, for example, the intake manifold contains fuel injectors that supply an air-fuel mixture to each combustion chamber. 
         [0005]    The exhaust manifold is typically coupled to the side of the cylinder head opposite the intake manifold (i.e. the “exhaust side”). The exhaust manifold collects exhaust gases exiting from each combustion chamber through internal exhaust ports in the cylinder head. The exhaust manifold then transfers the exhaust gases to an exhaust pipe of an exhaust system. Accordingly, the exhaust manifold is coupled to the cylinder head at the exhaust ports of the cylinder head such that the exhaust manifold collects exhaust gases exiting each combustion chamber within the manifold housing and transfers the exhaust gases to the exhaust pipe. 
         [0006]    Traditionally, exhaust manifolds have been made from conventional cast iron for strength and durability. However, these manifolds are heavy, cumbersome, and therefore detract from the fuel efficiency of the vehicle. In addition, the cast iron manifolds are difficult to manufacture into compact shapes and other distinct shapes as may be required by the underhood packaging constraints of modern vehicles. 
         [0007]    One solution to the problems presented by the traditional cast iron manifolds is to fabricate the exhaust manifolds from thin sheet metal, which is lightweight and more easily complies with underhood packaging constraints. However, these sheet metal manifolds present several disadvantages. In particular, since the sheet metal manifolds are thin and lighter in weight, the sheet metal manifolds provide noise, vibration, and harshness (“NVH”) problems. For example, the NVH problems present objectionable noise and vibration from the exhaust pulses. Specifically, the NVH passes from the manifold housing into the engine compartment, and ultimately onto the passenger compartment. Furthermore, the sharing of exhaust pulses among cylinders via the exhaust manifold (i.e. “cross-talk”) may compound the NVH problems and may result in further objectionable noise and vibration. The NVH transmitted and experienced by the passengers is bothersome and undesirable. 
         [0008]    Consequently, there exists a significant need for an exhaust manifold that is durable, lightweight and capable of reducing NVH. In addition, a need exists for an exhaust manifold capable of being tuned to reduce and/or to dampen noise and vibrations of an exhaust system, such as noise and vibrations due to exhaust pulses from the internal combustion process. 
       SUMMARY OF THE INVENTION 
       [0009]    An exhaust manifold assembly is provided. The exhaust manifold assembly may consist of an upper half shell secured to a lower half shell to form a housing. The upper half shell and/or the lower half shell may have one or more tubes extending within the interior of the housing. An inlet flange and an outlet flange may be attached to one of the shells. The inlet flange may be attached to a cylinder head to receive exhaust gases from the cylinder head. The exhaust gases may be received by the one or more tubes. Advantageously, the improved exhaust manifold assembly may reduce NVH. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0010]    Objects and advantages together with the operation of the invention may be better understood by reference to the following detailed description taken in connection with the following illustration, wherein: 
           [0011]      FIG. 1  is a cross-sectional view of an embodiment of an exhaust manifold in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    Referring now to  FIG. 1 , an exhaust manifold  10  is illustrated. The manifold  10  may include a lower half shell  20  and an upper half shell (not shown). The lower half shell  20  and the upper half shell may be integrally formed, attached, such as by welding or fastening, or otherwise joined together. The upper half shell and the lower half shell  20  may be joined to define a housing  25 . 
         [0013]    The housing  25  may be defined between the upper half shell and the lower half shell  20 . The housing  25  may have an outlet flange  40  providing fluid communication between an interior  15  of the housing  25  and an exterior  16  of the housing  25 . The outlet flange  40  may have an opening  55  permitting fluid communication between the remainder of the exhaust system and the housing  25 . The outlet flange  40  may be sized and shaped for attachment to a remaining portion of the exhaust system (e.g. exhaust piping, turbocharger, etc.). The outlet flange  40  may be connected to the housing  25 , such as to the upper half shell and/or the lower half shell  20 . For example, the outlet flange  40  may be coupled to a first side  36  of the housing  25 . The outlet flange  40  may be integrally formed with the lower half shell  20  and/or the upper half shell. Alternatively, the outlet flange  40  may be a separate piece which is secured to one of or both of the half shells via, for example fasteners, a press-fit, welding, brazing, an adhesive or the like. In an embodiment, the upper half shell may have a portion of the outlet flange  40 , and the lower half shell  20  may have a corresponding portion of the outlet flange  40  such that joining the upper half shell and the lower half shell  20  results in formation of the outlet flange  40 . 
         [0014]    An inlet flange  30  may be connected to the housing  25 . For example, the inlet flange  30  may be secured to one of or both of the upper half shell and the lower half shell  20  by way of fasteners, a press-fit, welding, brazing, an adhesive or in another manner that will be appreciated by a person of ordinary skill in the art. In an embodiment, the inlet flange  30  may be integrally formed with the upper half shell or the lower half shell  20  or may be separately connected to the housing  25 . The inlet flange  30  may be formed by the joining of the upper shell and the lower half shell  20 . For example the upper half shell may have a portion of the inlet flange  30  and the lower half shell  20  may have a corresponding portion of the inlet flange  30  such that joining the upper half shell and the lower half shell  20  results in formation of the inlet flange  30 . 
         [0015]    The inlet flange  30  may be positioned adjacent to or at a second side  35  of the housing  25 , which may be adjacent to the manifold  10 . The second side  35  of the housing  25  may be opposite to the first side  36  of the housing  25  where the outlet flange  40  may be attached. In use, the inlet flange  20  may be secured to the exhaust side of a cylinder head, for example. The inlet flange  30  may comprise one or more openings  50  (or apertures). Each of the openings  50  may provide fluid communication between the interior  15  of the housing  25  and the exterior  16  of the housing  25 . The openings  50  may transmit exhaust gases from the cylinder head into the housing  25 . In an embodiment, the number of the openings  50  may correspond to the number of the exhaust ports in the cylinder head. 
         [0016]    Alternatively, the number of the openings  50  may be greater than or less than the number of the exhaust ports in the cylinder head. In an embodiment, the inlet flange  30  may have at least one of the openings  50  receiving exhaust gases from two or more of the exhaust ports of the cylinder head. In another embodiment, the inlet flange  30  may have at least two of the openings  50  receiving exhaust gases from one of the exhaust ports of the cylinder head. A person of ordinary skill in the art should not be deemed as limited to any number of the openings  50 . The inlet flange  30  may have any number of the openings  50  and may attach to the cylinder head in any manner capable of transmitting exhaust gases from a cylinder head to the interior of the housing  25 . 
         [0017]    One or more tubes (or pipes)  60  may be positioned within the housing  25 . The one or more tubes  60  are hereinafter referred to as “the tubes  60 ” for simplicity and clarity purposes and not to limit the present invention to requiring two or more of the tubes  60 . It is clearly contemplated that “the tubes  60 ” may consist of a single tube. The tubes  60  may be any shape capable of transmitting fluids, such as exhaust gases therethrough. For example, the tubes  60  may be cylindrical pipes for transmitting fluids through the housing  25 . The tubes  60  may be separated from one another such that NVH, such as noise and vibrations from one of the tubes  60  is not transmitted to another one of the tubes  60 . In addition, the tubes  60  may absorb the NVH and dampen the NVH felt or otherwise received by the upper half shell and the lower half shell  20 . 
         [0018]    Each of the tubes  60  may be attached to the inlet flange  30 , the outlet flange  40 , and/or the housing  25 . The tubes  60  may be secured within the housing  25  via fasteners, a press-fit, welding, brazing, an adhesive or the like. The tubes  60  may be attached to or connected to the housing  25  to support the tubes, for example. Alternatively, the tubes  60  may simply rest on any suitable surface within the housing  25  or rest on mesh rings or pads  70  positioned between each tube  60  and any suitable surface within the housing  25 . The pads  70  may be attached to the upper half shell or the lower half shell  20  to support the tubes  60 . 
         [0019]    In an embodiment, the tubes  60  may be attached at the openings  50  of the inlet flange  30 . For example, the tubes  60  may extend from the inlet flange  30  to the outlet flange  40 . In such an embodiment, the tubes  60  may be attached to the inlet flange  30  and the outlet flange  40 . 
         [0020]    The tubes  60  may be die cast or formed by other methods and processes known to those skilled in the art. The upper half shell and the lower half shell  20  may be die cast or overmolded around the tubes  60 . In such an embodiment, the tubes  60  may be positioned within a mold at predetermined angles and lengths. The upper half shell and/or the lower half shell  20  may be cast with the tubes  60 . In such an embodiment, the tubes  60  may be integrally formed with the upper half shell and/or the lower half shell  20 . 
         [0021]    In another embodiment, each of the tubes  60  is secured to the inlet flange  30  and terminates within the housing  25 , without attachment to the outlet flange  40 . For example, the tubes  60  may terminate a distance from the outlet flange  40 . In such an example, the distance may be sufficient for the exhaust gases to mix within the interior  15  of the housing  25  prior to exiting at the outlet flange  40 . Termination of the tubes  60  short of the opening  55  of the outlet flange  40  may permit the exhaust gases exiting the tubes  60  to mix within the housing  25  prior to passing through the opening  55  and onto other components of the exhaust assembly, such as a HEGO sensor and/or catalytic converter. Properly mixing the exhaust gases within the housing  25  prior to exiting at the outlet flange  40  may reduce inaccurate emission readings and limit problems with emissions controls. 
         [0022]    In yet another embodiment, the tubes  60  may be attached to the outlet flange  40  without attachment to the inlet flange  30 . For example, the tubes  60  may extend from the outlet flange  40  towards the inlet flange  30  and terminate a distance from the inlet flange  30 . The tubes  60  may extend within the housing  25  without attachment to the inlet flange  30  and the outlet flange  40  in another embodiment of the present invention. In such an embodiment, the tubes  60  may terminate a first distance from the inlet flange  30  and a second distance from the outlet flange  40 . The first distance may be substantially similar to or different from the second distance. 
         [0023]    The tubes  60  may combine embodiments herein described. For example, one of the tubes  60  may be attached to the inlet flange  30 , and another one of the tubes  60  may not be attached to the inlet flange  30  and the outlet flange  40 . To this end, the tubes  60  may have different lengths and dimensions. 
         [0024]    The tubes  60  may have a wall structure  62  for preventing or at least limiting fluid communication from an interior  64  of the tubes  60  to the interior  15  of the housing  25 . To this end, the wall structure  62  of the tubes  60  may be metallic, plastic, or other material, preferably capable of transmitting relatively high temperature fluids therethrough. The wall structure  62  may have one or more layers separating an interior  64  of the tubes  60  from the interior  15  of the housing  25 . 
         [0025]    In an embodiment, the wall structure  62  may have one or more apertures or perforations (not shown) for permitting fluid communication from the interior  64  of the tubes  60  into the interior  15  of the housing  25 . The perforations (or apertures) may provide limited fluid communication to the interior  15  of the housing  25  such that a portion of the exhaust gases exit the tubes  60  into the interior  15  of the housing  25 . 
         [0026]    The tubes  60  may be arranged such that exhaust gases flow through each of the tubes  60  towards the opening  55  of the outlet flange  40 . Advantageously, the tubes  60  may capture exhaust pulses exiting the cylinders thereby insulating the outer shell of manifold  10  from sound waves associated with these exhaust pulses leading to NVH improvement of the manifold  10  and vehicle as a whole. Furthermore, the tubes  60  may allow more flow separation of exhaust gases exiting each cylinder thereby significantly reducing, or even eliminating, NVH problems from cross-talk among cylinders. Additionally, the tubes  60  may also absorb thermal energy from the exhaust gases thereby reducing thermal energy transferred to and absorbed by other components of the manifold  10  thus improving overall durability of the manifold  10 . 
         [0027]    In addition, the tubes  60  may be configured to provide additional NVH benefits, such as damping noise and vibration within the manifold  10  and/or tuning the manifold  10  to enhance the sound quality of the exhaust system and the entire vehicle. For example, some degree of tuning and/or damping may be possible by the appropriate selection of various physical characteristics of each tube  60 , such as length, cross-sectional shape, endform, wall structure, tube wall thickness, perforations or apertures in the wall structure of the tubes  60 , material composition, or the like. 
         [0028]    Although the preferred embodiment of the present invention has been illustrated in the accompanying drawing and described in the foregoing detailed description, it is to be understood that the present invention is not to be limited to just the preferred embodiment disclosed, but that the invention described herein is capable of numerous rearrangements, modifications and substitutions without departing from the scope of the claims hereafter.