Abstract:
The invention relates to a device for treating exhaust gases of internal combustion engines, including a housing, at least one gas treating body, a first support material, an internal shield, and a second support material. The housing includes an inlet, an outlet and an interior chamber between the inlet and the outlet. The gas treating body or bodies are located within the chamber, and the first support material is located between the outer surface of the gas treating body or bodies and the inner surface of the chamber. The internal shield is coupled with the inner surface of the housing via the second support material, which is located between the outer surface of the internal shield and the inner surface of the housing. The cross sectional area of the housing is generally constant in the region proximal to the internal shield.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The invention relates to an emission controlling device suitably used in automobiles powered by an internal combustion engine. More particularly, the invention relates to a device for treating exhaust gases of internal combustion engines and still more particularly to the thermal shielding of a catalytic converter.  
           [0003]    2. Description of Related Art  
           [0004]    A conventional device for treating exhaust gases of internal combustion engines, such as a catalytic converter, includes a housing connected to an inlet conduit and an outlet conduit. The housing contains at least one exhaust gas treating body, commonly known as a substrate. The substrate is typically a monolith that possess hundreds or thousands of channels arranged in a honeycomb structure, which serve as exhaust channels through which exhaust gas from the engine flows from an inlet conduit and to an outlet conduit.  
           [0005]    The monolith is typically ceramic, but it can also be composed of metal. Substrates are also often coated with an active catalytic layer such as aluminum oxide, platinum, palladium, and/or rhodium. As the exhaust flows through the substrate(s), it interacts with the active catalysts and chemical reactions reduce the pollutants in the exhaust, such as carbon monoxide (CO), hydrocarbons (HCs), and nitrogen oxides (NO or NO 2 ).  
           [0006]    Catalytic converters also often include a system to monitor the oxygen level in the exhaust. A sensor located in the catalytic converter measures the oxygen level in the exhaust, and determines whether or not the exhaust system is operating properly and emissions are within acceptable limits.  
           [0007]    The exhaust flowing through the catalytic converter is extremely hot (exhaust temperatures may be as high as 1900 degrees Fahrenheit). Excessive housing temperatures potentially pose a danger to the automobile itself and the environment, potentially causing undesired thermal incidents. Therefore, catalytic converters often contain insulation and/or shielding to reduce the housing temperature or exposure of other components.  
           [0008]    Catalytic converters are known to possess internal shields welded to the housing inner surface for certain applications. However, it is difficult to successfully weld a shield to the housing, when the outer housing is one solid piece instead of two pieces connected together. Additionally, insulation material can interfere with the welding process.  
           [0009]    Also known are catalytic converters with internal shields installed in the housing by the process of forming the housing. During forming, the internal shield is positioned in its desired location, and part of the housing is deformed such that the cross-sectional contour of the housing is not uniform in the axial direction in the area proximal to the internal shield. This deformation prevents the internal shield from moving in the axial direction of the catalytic converter. One disadvantage to forming is that the sensor, sensor boss, housing opening, internal shield, or other components may be damaged during the process. This problem is especially prevalent where the sensor is located along the area proximal to the internal shield.  
           [0010]    The prior art further discloses a catalytic converter with one continuous piece of insulation surrounding the substrate(s) and the internal shield. Using one piece of insulation may cause problems during manufacturing because it may require the manufacturer to insert all of the elements (the insulation, the substrate(s), and the internal shield) into the housing all at once. Additionally, it is more difficult to achieve a tight interference fit for both the coupling between the shield and insulation and the coupling between the substrate(s) and insulation if the same insulation is used for both applications.  
           [0011]    In view of the above, it is clear that an emission control device housing with a uniform cross-sectional contour in the axial direction in the area proximal to the internal shield would be advantageous. Additionally, insulation that does not require the manufacturer to simultaneously install many elements into the housing would be advantageous.  
         BRIEF SUMMARY OF THE INVENTION  
         [0012]    In overcoming the above and other disadvantages and limitations of the prior art, the present invention provides a catalytic converter in which an insulation material supports the internal shield to the housing of the catalytic converter. This is done without requiring deformation of the housing itself to restrict axial movement of the shielding located therein. In achieving the above, the present invention provides an exhaust gas treatment device, for an internal combustion engine, having a housing defining an internal chamber located between an inlet on one end and outlet on the opposing end. Located within the chamber, between the inlet and the outlet, is an exhaust gas treating body. While two are utilized in the preferred embodiment, there need only be at least one exhaust gas treatment body. This body, the substrate, is chemically coated so as to react with the exhaust gases and thereby reducing the amount of undesirable material in the exhaust gas when it exits the treatment device. Also located within the chamber of the housing is an internal shield. The internal shield is retained and engaged with the housing by means of a support material that radially surrounds the internal shield. This support material is preferably an insulation material. In the present invention, the support material between the internal shield and the housing is in a frictional engagement with both the housing and the internal shield and as such, this interference or frictional engagement is what is utilized to retain the internal shielding to the housing.  
           [0013]    Accordingly, in one aspect, the present invention is an exhaust gas treatment device for an internal combustion engine comprising a housing having portions defining an inlet, an outlet and an interior chamber between said inlet and said outlet; at least one exhaust gas treating body located between said inlet within said chamber and said outlet; a first support material located radially between an inner surface of said housing and said at least one exhaust gas treating body; an internal shield located within said housing; a second support material radially surrounding said internal shield and located between said inner surface of said housing and said internal shield, said second support material retaining said internal shield in engagement within said housing wherein said housing exhibits a substantially constant cross sectional area along its length in a region proximal to said internal shield.  
           [0014]    The above and other objects, features, and advantages of the present invention will be made more apparent from the following description of the preferred embodiments, with reference to the accompanying drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 is a side view of an exhaust gas treatment device embodying the principles of the present invention for treating exhaust gases of internal combustion engines; and  
         [0016]    [0016]FIG. 2 is an enlarged view of a portion of the device seen in FIG. 1 and generally encircled within Line  2 , with portions in section and broken away. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]    Referring now to the drawings, a device for treating the exhaust gas of internal combustion engines, specifically a catalytic converter  10 , is shown in FIG. 1. The catalytic converter  10  includes a housing  12  connected at one end to an inlet conduit  16  and at another end to an outlet conduit  20 . An inlet zone  14  and an outlet zone  18  are contained within the housing  12 , each located at an axial end of the catalytic converter  10 . The housing  12  can be made of any type of commonly used metal or other rigid material, but it is preferably made of AK Steel 18CrCb steel (manufactured by AK Steel Corporation, Middletown, Ohio), 409SS, 441SS, or 439SS steel. The exhaust gas  46  flows from the inlet to the outlet through the catalytic converter  10 .  
         [0018]    As seen in the preferred embodiment of FIG. 2, the housing  12  contains at least one substrate  38 , which reacts with exhaust gas  46  to reduce pollutants in the exhaust gas  46 . The preferred embodiment of a substrate  38  is a monolith  39  with hundreds or thousands of channels  34  arranged in a honeycomb structure (although triangular, rectangular, ovalar and circular structures could be employed) and serving as conduits for the exhaust gas  46 . Other structural shapes, as long as they readily permit the flow of exhaust gas there through, may also be used instead of the honeycomb type monolith  39 . The preferred embodiment shown in FIG. 2 includes two substrates  38  (one toward the inlet and one toward the outlet), but the catalytic converter  10  may have more or less than two substrates  38 . The substrates  38  are preferably made of ceramic, but they can also be made of another material, such as metal.  
         [0019]    Exhaust gas  46  flows through the inlet conduit  16 , into the inlet zone  14 , and through the channels  34  of the substrates  38 . The channels  34  are coated with an active catalytic layer such as aluminum oxide, platinum, palladium, and/or rhodium. As the exhaust gas  46  flows through the channels  34 , it interacts with the active catalysts and a chemical reaction reduces the pollutants, such as carbon monoxide (CO), hydrocarbons (HCs), or nitrogen oxides (NO or NO 2 ), in the exhaust gas  46 .  
         [0020]    In the preferred embodiment, after the exhaust gas  46  flows through the first substrate  38 , it flows through a conduit formed by an internal shield  30  and passes a sensor  22 . Although the preferred method includes a sensor  22 , it is not always required. The sensor  22  is held in place by a sensor boss  24 , which is connected to the housing  12 . The exhaust gas  46  next preferably flows through a second substrate  38 , into the outlet zone  18  and through the outlet conduit  20 .  
         [0021]    As seen in FIG. 2, the sensor  22  located in the catalytic converter  10  measures the oxygen level in the exhaust gas  46 , and, in response to a signal therefrom, a controller  40  accordingly determines the effectiveness of the catalysts.  
         [0022]    The housing  12  contains support material and an internal shield  30 , located either before or after the substrate  38  or between the two substrates  38  (in the illustrated embodiment). Both the support material and the internal shield  30  together operate to reduce the temperature of the housing  12 , particularly the temperature of the housing outer surface  11 . Additionally, they operate to reduce the excessive gas pressure drop caused by the sudden flow expansion in the region between the substrates  38 .  
         [0023]    The preferred embodiment includes two support materials, a first support material  26  and a second support material  28 . The first support material  26  is located between the substrate  38  and the housing inner surface  13 , and it is preferably composed of an intumescent mat, which expands, once the initial thermal cycle reaches the appropriate temperature for the intumescent, and thereafter remains in the expanded state. Some preferred types of intumescent mat used as the first support material  26  are Interam™ 100 or Interam™ 550, manufactured by 3M™. However, the first support material  26  can be made from other types of materials, such as a non-intumescent mat or a wire mesh. The first support material  26  and the substrates  38  are fixedly held in place in an interference fit with the housing  12 , which becomes a tighter fit after the first support material  26  expands under heat.  
         [0024]    The second support material  28  is located between the housing inner surface  13  and the internal shield  30 , and it is preferably composed of an intumescent mat, which expands, once the initial thermal cycle reaches the appropriate temperature for the intumescent, and thereafter remains in the expanded state. Some preferred types of intumescent mat used as the second support material  28  are Interam™ 550 or Interam™ 900HT, manufactured by 3M™. However, the second support material  28  can be made from other types of materials, such as a non-intumescent mat or a wire mesh. The second support material  28  and the internal shield  30  are fixedly held in place relative to one another and the housing  12  via an interference fit between the second support material  28  and the housing  12  and between the second support material  28  and the internal shield  30 , which becomes a tighter fit after the second support material  28  expands during the initial thermal cycle and upon reaching the appropriate temperature for the intumescent. The second support material  28  is preferably only located in the area axially between the ends of the internal shield, designated as a first edge  42  and a second edge  44 .  
         [0025]    The internal shield  30  can be made of any type of metal or other rigid material, but it is preferably made of AK Steel 18CrCb steel, 409SS, 441SS or 439SS steel. The internal shield  30  preferably contains two flanges  32 , although if desired one or both flanges  32  may be eliminated. The flanges  32  are preferably located such that the internal shield first edge  42  and the internal shield second edge  44  are the outboard edges of the flanges  32 . The flanges  32  are also preferably angled, with respect to a constant diameter center section of the internal shield  30 , toward the housing  12  such that the distance between the flanges  32  and the housing inner surface  13  is shorter than the distance between the internal shield  30  and the housing inner surface  13 .  
         [0026]    The sensor boss  24  is attached to the housing  12  via a housing opening  52  and is preferably axially located in the housing  12  at a point located between the internal shield first edge  42  and the internal shield second edge  44 . The sensor  22  is mounted within the sensor boss  24  such that it can monitor the flow of the exhaust gas  46  and the internal shield  30  is provided with a shield aperture  48  having a diameter at least as large as the cross-sectional diameter of the sensor  22 . During installation, the internal shield  30  is aligned such that the sensor  22  extends through the shield aperture  48  into the exhaust gas flow.  
         [0027]    The catalytic converter  10  may be manufactured using a variety of known methods such as, but not limited to, shrinking, stuffing, clamshell, tourniquet, or shoebox method. In a shrinking method, the substrate(s)  38 , the first support material  26 , the internal shield  30 , and the second support material  28  are first inserted into the housing  12 . The housing  12  is then swaged such that the diameter becomes smaller, but the contour of the housing  12  remains substantially constant. The housing  12  is swaged by tightening a plurality of adjacent vise jaws, preferably nine or more. The jaws may be concave in shape such that the contact surface of each jaw is substantially flush with the surface of the housing  12 . Various known methods can be used to compress the housing  12 .  
         [0028]    When manufactured via a stuffing method, the substrate  38  is wrapped with the first support material  26  and inserted into a conical device that compresses the first support material  26  as it is pushed through. The wrapped substrate  38  is then ejected from the compression cone into the housing  12 . The substrate  38  and the first support material  26  create an interference fit with the housing inner surface  13 . The internal shield  30  is wrapped with the second support material  26  and inserted into the housing  12  in a similar fashion.  
         [0029]    In a clamshell method, the housing  12  is comprised of an upper section and a lower section. The two sections are welded together along the axis of the housing  12 . In a shoebox method, the housing  12  is similarly comprised of an upper section and a lower section. The two sections fit together in a method that can be likened to that of a shoebox—such that one section fits within the other section.  
         [0030]    In a tourniquet method, the first support material  26  is wrapped around the substrate  38 , the second support material  28  is wrapped around the internal shield  30 , and then the substrate  38  and the internal shield  30  are inserted into the housing  12 . Next, the housing  12  is compressively closed around the substrate  38  and the internal shield  30  with a tourniquet strap force. Specifically, the housing  12  is wrapped in a casing which surrounds the periphery of the housing  12  to compressively close the housing  12  around the substrate  38  and the internal shield  30  to a desired compression distance or pressure.  
         [0031]    Among the methods described above, the shrinking, stuffing, clamshell, and shoebox methods are the preferred methods because they do not alter the cross-sectional contour of the housing  12 . More specifically, the housing  12  of a catalytic converter  10  manufactured with these methods has a uniform cross-sectional contour in the axial direction in the area proximal to the internal shield  30 . The uniform cross-sectional contour minimizes potential damage to elements such as the sensor  22 , the sensor boss  24 , the housing opening  52 , the internal shield  30 , and other components.  
         [0032]    During the preferred methods of manufacturing the catalytic converter  10 , the second support material  28  is wrapped around the radial surface of the internal shield  30 . The second support material  28  may contain a material opening  50  at least as large as the cross-sectional diameter of the sensor  22 , positioned such that the material opening  50  and the shield aperture  48  are substantially aligned. In one preferred method, the material opening  50  is formed before the second support material  28  is wrapped around the internal shield  30 , and the material opening  50  is aligned with the shield aperture  48  during the wrapping process. In another preferred method, the second support material  28  is wrapped around the internal shield  30 , and the material opening  50  is formed after wrapping in a location substantially proximal to the shield aperture  48 . Although these are the preferred methods of connecting the second support material  28  and the internal shield  30 , other methods may be used.  
         [0033]    While this invention has been described in terms of certain embodiments thereof, it is not intended to be limited to the described embodiments, but only to the extent set forth in the claims that follow.