Patent Application
20120240562
Exemplary embodiments of the present invention relate to exhaust treatment devices for internal combustion engines and, more particularly, to an exhaust treatment device having a thermally efficient configuration.
A typical exhaust system for an internal combustion engine may involve the placement of an exhaust treatment system or assembly in close fluid communication with the exhaust manifold of the internal combustion engine. Such an exhaust treatment system is typically a catalytic device in which regulated exhaust constituents (ex. CO, HC, NOR, Particulates, etc.) are converted to non-regulated compounds (ex. CO2, H2O, etc.). An exhaust treatment system that is closely coupled to the engine exhaust manifold minimizes thermal loss in the exhaust gas, between the engine and the exhaust treatment system, resulting in higher temperatures and quicker catalytic activation since the catalyst compounds that are typically used for treating engine exhaust gas constituents often operate at optimal efficiency at temperatures in excess of 350° C.
In an exemplary embodiment of an exhaust treatment system, a plurality of catalytic devices may be disposed in a multiple piece housing or canister that is closed at each end by an inlet or an outlet cone. The inlet and outlet cones are in fluid communication with the exhaust system of the internal combustion engine. Each catalytic device is typically constructed as a catalyst coated, flow-though substrate constructed of ceramic or metal, that is supported within the canister by an insulating and cushioning mat material interposed between the outer surface of the flow-through substrate and the inner wall of the canister. An axially extending gap may be located between each catalytic device and can be useful as a location for various sensors that monitor the performance of the exhaust treatment system. The axially extending gap will typically not receive the insulative benefit of the insulating and cushioning mat material that is interposed between the outer surface of the flow-through substrate and the inner wall of the canister and, as such, a portion of the housing or canister may be directly subjected to the high temperatures of the exhaust gas resulting in a portion of the outer surface of the housing or canister reaching temperatures that necessitate the addition of a heat shield. Multiple piece housings have been proposed that have an insulating mat disposed in the region of the axially extending gap. Such solutions may utilize a tapered portion of one of the housing pieces to define a gap into which the insulating mat is disposed. Such designs have suffered during the assembly process which requires that the mat maintain dimensional stability as the multiple housing pieces are engaged with one another through a sliding, axial overlap. Such a sliding assembly method may result in the mat being dimensionally compromised.
In an exemplary embodiment of the invention an exhaust gas treatment system for the reduction of regulated exhaust gas constituents produced by an internal combustion engine comprises a multiple piece canister comprising a first canister portion and a second canister portion, a conical portion extending axially from an end of the first canister portion including a wall that is inclined inwardly, towards a central axis of the multiple piece canister, a funnel portion extending axially from an end of the second canister portion including a wall that is inclined outwardly, away from the central axis of the multiple piece canister, the wall of the conical portion and the wall of the funnel portion defining an insulation gap therebetween and an annular band of insulating and cushioning mat material, disposed under compression by the walls, within the insulation gap.
In another exemplary embodiment of the invention, a method is provided for assembling an exhaust gas treatment system for the reduction of regulated exhaust gas constituents produced by an internal combustion engine comprising a multiple piece canister having a first canister portion and a second canister portion, a conical portion extending axially from an end of the first canister portion including a wall that is inclined inwardly, towards a central axis of the multiple piece canister, a funnel portion extending axially from an end of the second canister portion including a wall that is inclined outwardly, away from the central axis of the multiple piece canister, the wall of the conical portion and the wall of the funnel portion defining an insulation gap therebetween and an annular band of insulating and cushioning mat material disposed under compression by the walls within the insulation gap. The method comprises disposing the annular band of insulating and cushioning mat material about the wall of the conical portion and moving the first and second canister portions axially together along the central axis until an end of the wall of the funnel portion is positioned circumferentially about, and adjacent to, an outer surface of the first canister portion to define an insulation gap between the wall of the conical portion and the wall of the funnel portion, wherein the annular band of insulating and cushioning mat material is in compression between the walls to thereby fix the material in place within the insulation gap.
In yet another exemplary embodiment of the invention, an internal combustion engine having an exhaust gas treatment system for the reduction of regulated exhaust gas constituents produced thereby comprises an exhaust manifold configured to conduct exhaust gas from the engine. A split volume, common can catalytic converter is configured to receive the exhaust gas and comprises a multiple piece canister comprising a first canister portion and a second canister portion, a conical portion extending axially from an end of the first canister portion including a wall that is inclined inwardly, towards a central axis of the multiple piece canister, a funnel portion extending axially from an end of the second canister portion including a wall that is inclined outwardly, away from the central axis of the multiple piece canister, the wall of the conical portion and the wall of the funnel portion defining an insulation gap therebetween and an annular band of insulating and cushioning mat material disposed under compression by the walls within the insulation gap.
The above features and advantages, and other features and advantages of the invention are readily apparent from the following detailed description of the invention when taken in connection with the accompanying drawings.
Other features, advantages and details appear, by way of example only, in the following detailed description of the embodiments, the detailed description referring to the drawings in which:
The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.
Referring now to
In an exemplary embodiment, the cylinder head 18 is associated with an exhaust manifold 26 that is configured to conduct combustion constituents or exhaust gas 27 therefrom. Referring to
In an exemplary embodiment, exhaust gas passages 46, which are essentially direct paths from the upstream fluid inlets 48 to the downstream fluid outlets 50 of each substrate 44, 45, may be defined by substantially longitudinally extending walls 52 on which various catalytic materials (not shown) are coated so that the exhaust gas 27 that passes through the catalyst substrates 44 and 45 contacts the catalytic material to thereby initiate a chemical conversion process. For example, in an exemplary embodiment, as the exhaust gas 27 traverses the length of the first catalyst substrate 44 a precious metal or Platinum group metal catalyst compound, including platinum group metals such as platinum (Pt), palladium (Pd), rhodium (Rh) or other suitable oxidizing catalysts, or combination thereof, catalyzes the oxidation of carbon monoxide (“CO”) to carbon dioxide (“CO2”) in the presence of oxygen (“O2”), as well as catalyzing the oxidation of various hydrocarbons, including gaseous HC and liquid HC particles including unburned fuel or oil as well as HC reductants, that may have been introduced into the exhaust gas 27, to form CO2 and H20. As the exhaust gas traverses the length of the second catalyst substrate 45 a precious metal or Platinum group metal catalyst compound, including platinum group metals such as platinum (Pt), palladium (Pd), rhodium (Rh) or other suitable oxidizing catalysts, or combination thereof, catalyzes the oxidation of remaining carbon monoxide (“CO”) to carbon dioxide (“CO2”) in the presence of oxygen (“O2”), as well as catalyzing the oxidation of various remaining hydrocarbons, including gaseous HC and liquid HC particles including unburned fuel or oil as well as HC reductants, that may have been introduced into the exhaust gas 27, to form CO2 and H20. Other combinations of catalyst compounds, such as a Selective Catalyst Reduction (“SCR”) catalyst, are of course contemplated and will be selected based on various parameters such as the type of engine (ex. diesel or gasoline) as well as the application of the internal combustion engine 12 and/or the vehicle type in which the engine is operated.
Closing a first inlet end 54 of the canister 41 is an inlet end cone 56 that is in fluid communication with the exhaust manifold 26 of the cylinder head 18 and is configured to receive exhaust gas therefrom for passage through the first and second catalyst substrates 44 and 45, respectively. Similarly, closing the second, outlet end 58 of the multiple piece canister 41 is an outlet end cone 60 that may be configured in a cone or semi-conical configuration to provide a smooth transition of the exhaust gas to an exhaust gas conduit 62 with which the collector outlet end cone 60 is in fluid communication.
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While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the present application.
