Patent Publication Number: US-2019170043-A1

Title: Muffler for single-cylinder diesel engine

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation under 35 U.S.C. § 120 of International Application PCT/EP2017/068077, filed Jul. 18, 2017, which claims priority to German Application No. 10 2016 113 756.1, filed Jul. 26, 2016, the contents of each of which are incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a muffler for a single-cylinder diesel engine having an oxidation catalyst. 
     BACKGROUND 
     Such drives are known. Reference is made to DE 101 39 700 A1 and JP 2015-143 510 A. They are preferably used to operate construction machinery or as low-power stationary drives. 
     In this connection, the requirements applicable to the cleaning/detoxification of the exhaust gas are different. Frequently, the treatment of the exhaust gas by means of an oxidation catalyst is sufficient, i.e. the oxidation of the CO components in the exhaust gas to CO 2  as well as of hydrocarbons to CO 2  and water. 
     In the case of retrofitting of an oxidation catalyst in an existing single-cylinder diesel engine, allowance is to be made from the viewpoint of structural mechanics that an oxidation catalyst is to be associated with the existing muffler without altering the natural frequency of the overall unit in the process, in order to avoid unfavorable vibrational loads. In this way, it is possible to prevent damage to the working machine connected to the drive unit. 
     The present invention therefore has as an underlying object of combining an oxidation catalyst appropriately with a muffler while avoiding the said disadvantages, especially of lowering the natural frequency and the resonance-induced damage associated therewith. 
     SUMMARY 
     To achieve this object, it is provided according to the invention that the muffler housing is attached by means of a flanged joint directly to the cylinder head and that the intermediate wall ( 3 ) has openings for gas-tight installation of mounting pipes ( 14 ), which traverse the muffler housing and at their engine-side ends are fastened to the inside of a muffler-side attachment flange ( 9 ) in association with its joint bores ( 15 ), for the purpose of applying a screw coupling of the attachment flange ( 9 ) to a corresponding flange part of the cylinder head. 
     In this way, the extra weight introduced by the oxidation catalyst into the muffler can be absorbed by the intermediate wall and distributed over the entire muffler housing. Thus the said natural frequency of the muffler can be kept within a noncritical range, so that resonance-induced damage to the muffler housing or the overall apparatus can be avoided, for example by vibratory plates used in the construction industry. 
     During the use of diesel oxidation catalysts, carbon monoxide (CO) is oxidized to carbon dioxide (CO 2 ) and hydrocarbons (C n H m ) in the exhaust gas to carbon dioxide (CO 2 ) and water. Within the scope of the present invention, the high exhaust-gas temperatures that are advantageous for oxidation are maintained by the fact that the muffler has a flanged joint by means of which it can be attached directly to the cylinder head. 
     In this connection, a particularly advantageous configuration consists in the fact that the intermediate wall has openings for the gas-tight penetration of mounting pipes, which traverse the muffler housing and at their engine-side ends are fastened to a muffler-side attachment flange in association with its joint bores. 
     According to an embodiment of the invention, a robust embodiment that is stable to vibrations consists in the fact that the muffler-side attachment flange is welded at its lateral periphery in gas-tight manner to an embossment of the muffler housing encircling it. 
     According to an embodiment of the invention, the intermediate wall itself is fastened in gas-tight manner between two separate housing parts of the muffler housing, namely a housing rear wall turned toward the engine and a housing cover. Both housing parts are welded along their periphery to the intermediate wall. 
     The intermediate wall is advantageously designed to be dish-shaped with convex bulge toward the exhaust gas flowing into the inlet chamber of the muffler. Thereby the intermediate wall is stiffened and thus an improved stiffness of the entire muffler housing is achieved. 
     The catalyst body itself punches through the intermediate wall in which it is received in gas-tight manner in an opening. The untreated exhaust gas therefore flows out of the inlet chamber formed by the housing rear wall through the catalyst body into the outlet chamber separated by the housing cover and from there as post-treated exhaust gas into the outlet pipe of the engine. 
     A particularly stable seat of the closed inner end of the outlet pipe is achieved according to an embodiment of the invention by the fact that the intermediate wall has an opening for receiving the inner end of the outlet pipe in gas-tight manner. 
     For this purpose, it is provided in a further advantageous configuration of the holder of the outlet pipe in the interior of the muffler housing that its inner end projects into the inlet chamber of the muffler housing and is braced displaceably there in an associated indentation of the housing rear wall of the muffler housing. 
     With the objective of suppressing vibrations of the muffler housing as well as possible, the housing itself is equipped with beads provided on all sides and similar embossed shapes of the housing parts, which not only impart stiffness but also favor the prevention of resonance vibrations. This objective is also served by the structure—which according to an embodiment of the invention is perforated—of the exhaust pipe in its portion inside the outlet chamber of the muffler housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       An embodiment of the invention will be described hereinafter on the basis of the drawing, wherein 
         FIG. 1  shows a sectional diagram of the muffler according to I-I of  FIG. 2 , 
         FIG. 2  shows a view toward the housing rear wall of the muffler with attachment flange, 
         FIG. 3  shows a perspective view of the housing cover with outgoing exhaust-gas pipe, 
         FIG. 4  shows a sectional diagram of the muffler according to IV-IV of  FIG. 3 , 
         FIG. 5  shows a variant of the sectional diagram according to  FIG. 4 , and 
         FIG. 6  shows a perspective view of the housing rear wall of the variant according to  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The figures of the drawings show the muffler housing with housing rear wall  1  and housing cover  2 , between which an intermediate wall  3  is fastened. Intermediate wall  3  extends in gas-tight manner transversely through the entire muffler housing; it is designed in dish-shaped manner and possesses a convex bulge in an inlet chamber  4  formed by housing rear wall  1 ; with its convex side, it therefore bounds an outlet chamber  5  formed by housing cover  2 . Intermediate wall  3  possesses an encircling bulged connecting rim  6 , into which the open end  7 , facing it, of housing cover  2  penetrates, so that a gas-tight joint between the two housing parts, namely the housing rear wall  1  and the housing cover  2 , is assured, for example by welding. 
     Catalyst body  28  of an oxidation catalyst extends from inlet chamber  4  through intermediate wall  3 , to which it is joined in gas-tight manner, into outlet chamber  5 . The exhaust gas from the cylinder head flows via a flanged joint through an attachment flange  9  fastened to housing rear wall  1  in the direction of arrow P 1  in the interior of inlet chamber  4  and from there flows through catalyst body  28  according to arrow P 2 . The exhaust gas treated in catalyst body  28  passes from catalyst body  28  into outlet chamber  5  and from there into an outlet pipe  10 ,  10 ′ for the treated exhaust gas (see  FIG. 4-6 ). After exiting catalyst body  28 , the treated exhaust gas flows through perforations  11  into the interior of exhaust pipe  10 ,  10 ′ and further, according to arrow P 3 , P 3 ′, through an exhaust-gas line (not illustrated) into the environment. 
     Concerning the geometry of the muffler housing, its housing rear wall  1  and its housing cover  2 , is stiffened multiple times as indicated with contour lines, for example by beads  12  in the region of housing rear wall  1  ( FIG. 4 ) or by indentations/embossments  13 ,  22  of the housing dishes, preferably in regions of connection to other components. Due to such stamped shapes, the housing parts of the muffler housing acquire greater stiffness, whereby the tendency toward housing vibrations is reduced. 
     It is self-evident that built-in parts of the muffler housing that punch through the housing wall and the intermediate wall in the regions of the respective openings are joined in gas-tight manner to the intermediate wall or to the housing walls, for which purpose welded joints are normally provided. This is the case for the passage of catalyst body  28  through intermediate wall  3 , for the passage of outlet pipe  10  through housing cover  2  as well as for outlet pipe  10 ′ through housing rear wall  1  ( FIG. 5 ) and also for the passage of the three mounting pipes  14  shown in the exemplary embodiment through housing rear wall  1 , intermediate wall  3  and housing cover  2 . The three mounting pipes  14  are joined firmly at their engine-side ends to attachment flange  9 , so that attachment bores  15  ( FIG. 2 ) of attachment flange  9  can be reached by the mounting tool, which is inserted on the side of housing cover  2 , through mounting pipes  14 . The fastening of attachment flange  9  to a corresponding flange part (not illustrated) of the cylinder head takes place by applying a screw coupling for establishment of a strong and tight flanged joint between the muffler housing on the one hand and the cylinder block on the other. A flanged seal (not illustrated) ensures that the untreated exhaust gas passes from the combustion chamber of the engine directly and along the shortest path through flange bore  16  into inlet chamber  4  inside housing rear wall  1 . Fastening points  17  on the outside of housing cover  2  and on the outside of housing rear wall  1  are used to fasten a heat shield  18 , which is shown schematically as a broken line in  FIGS. 1 and 2 . It functions as protection against burns due to contact and extends along the outside of housing cover  2  and, with an angled part, over a narrow side of the muffler housing. 
     In  FIG. 4 , the closed inside end of outlet pipe  10  is illustrated. A cover  19  closes the inside end of outlet pipe  10 . The end of outlet pipe  10  is braced relative to the adjacent housing rear wall  1  in longitudinally displaceable manner in a guide (not illustrated). 
     The sectional diagrams according to  FIGS. 4 and 5  show similar cross sections in plane IV-IV of  FIG. 3  through the muffler housing. 
     In  FIG. 4 , outlet pipe  10  passes through housing cover  2  toward the outside with outflow of the cleaned exhaust gas according to arrow P 3 . 
       FIG. 5  shows an alternative approach to this. Here, outlet pipe  10 ′ passes through housing rear wall  1  toward the outside with outflow of the cleaned exhaust gas according to arrow P 3 ′. Through a perforated pipe length  21  in the interior of outlet chamber  5 , the cleaned exhaust gas passes according to arrow P 2 ′ via outlet pipe  10 ′, which traverses inlet chamber  4  in gas-tight manner, then according to arrow P 3 ′ to the outside. 
       FIG. 6  shows a perspective view of the muffler housing toward its housing cover  2 . According to the variant shown in  FIG. 5 , outlet pipe  10 ′ discharges outward through housing rear wall  1 . In other respects, the muffler housing corresponds to the view shown in  FIG. 3 , as described there.