Abstract:
A manifold for a multicylinder internal combustion engine which includes a plurality of outlets ( 1 ) comprises upper, lower and central shells ( 15, 5, 51 ) that are connected with one another and define inlet channels and outlet spaces ( 63, 65 ). A baffle plate ( 35 ) is attached to different shells ( 5, 15 ) by means of a fixed/movable bearing and can expand thermally without transferring thermal stresses to the shells ( 5, 15 ).

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National counterpart application of International Application Serial No. PCT/EP2005/005593 filed May 24, 2005, which claims priority to German Patent Application No. 10 2004 025 407.9 filed May 24, 2004. The entirety of both of these applications is hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a manifold composed of a plurality of shells, for a multicylinder internal combustion engine. 
     In particular, the invention relates to a so-called three-shell manifold, in which a lower, an upper and a central shell are connected with one another on the edges, so that a plurality of inlet channels and a plurality of associated outlet spaces are provided. Each outlet on the engine block side opens into a separate, associated inlet channel of the manifold, which in turn continues into an outlet space. Generally, several inlet channels continue into a shared outlet space, in which the hot exhaust gases spread, expand and are cooled to some degree. The manifolds are exposed to extreme thermal stresses. These stresses are extreme in particular in the areas of the connecting weld seams between the shells and the wall sections which are impinged by the exhaust gas stream directly from the engine. Also, especially in a cold start, different sections of the manifold expand with varying degrees of rapidity and intensity, so that high tensions develop here in the areas of the weld seams. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention is intended to reduce these stresses on the weld seams and the walls and to largely uncouple the walls of the outlet spaces from one another in terms of forces. 
     This is achieved by a manifold for a multicylinder internal combustion engine which includes a plurality of outlets, comprising a plurality of shells connected with one another on the edges to provide inlet channels and or at least one outlet space into which the inlet channels or at least some of the inlet channels open, and a baffle plate that is provided for the exhaust gas flowing in via at least one inlet channel and is associated with an outlet space, the baffle plate being firmly connected on the edge at one end with one of the shells and being displaceably connected with another one of the shells at an end remote therefrom. 
     The exhaust gas from the outlets of the engine which enters the manifold first impinges on the baffle plate which, as a consequence, is subjected to the highest thermal stresses. This baffle plate, however, does not connect shells directly with each other, but is displaceably attached to one shell, so that it can expand thermally without this resulting in tensions between the shells. Furthermore, the baffle plate distributes the flow in the outlet space, forming, as it were, a section of the wall thereof, and in this way provides for a more uniform and faster temperature distribution of the hot exhaust gas in the outlet space, so that the other wall sections of the outlet space are likewise subjected to more uniform and therefore lower stresses as a whole. 
     According to the preferred embodiment, the manifold according to the invention is provided with lower and upper shells connected with one another on the edges to provide outer inlet channels and an outlet space into which the outer inlet channels open, and a central shell connected on the edge with at least one of the lower and upper shells to provide at least one middle inlet channel located between the outer inlet channels and a second outlet space into which the middle inlet channel opens. The baffle plate is provided for the exhaust gas flowing in via the middle inlet channel and is associated with the second outlet space, and at one end it is firmly connected on the edge with one shell and at an opposite end it is displaceably connected with another shell. 
     According to the preferred embodiment, one end of the baffle plate is welded to a shell in order to arrange for a secure, rigid connection. 
     At the displaceable end, the attachment of the baffle plate is constituted e.g. by a U-shaped open end into which an edge projects, so that it is guided between the legs of the U-shaped end. 
     In this connection it is possible for the edge to be provided on the baffle plate or else, in preference, on a shell, so that in this preferred embodiment the U-shaped end is situated on the baffle plate. 
     One end of the baffle plate, for example, is attached to the lower shell and prevents the lower shell from being directly impinged by the flow. 
     The upper shell may have a cut-out in the region of the baffle plate and therefore have the shape of a U, so that the baffle plate is seated inside the “U” and possibly even fills it out completely. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Further features and advantages of the invention will be apparent from the description below and from the accompanying drawings, to which reference is made and in which: 
         FIG. 1  shows a diagrammatic sectional view of the manifold according to the invention in a plane parallel to the engine flange; 
         FIG. 2  shows a perspective top view onto the manifold according to the invention, with the central shell being illustrated partly cut open in the middle in order to expose a view onto the baffle plate; and 
         FIGS. 3 and 4  show perspective sectional views in the regions of the planes and IV-IV, but slightly turned in order to expose the view onto the cut-open manifold in the area of the second outlet space. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates a manifold for a four-cylinder internal combustion engine, the internal combustion engine having four outlets  1  which, in relation to the cutting plane of  FIG. 1 , would be located above the plane of projection and are indicated by broken lines only for the purpose of an enhanced understanding. 
     The manifold, which is bolted to the engine block, has a flat, plate-like flange  3  (see  FIG. 2 ) and three shells made of sheet metal and connected with each other, which define inlet channels for each outlet  1  and outlet spaces that combine a plurality of inlet channels. 
     A lower shell  5  made of sheet metal has a trough-shaped section  7  and four extensions which protrude to the flange  3  and have been reshaped to form a lower tube part  9 ,  11  and  13 . Because of the sections performed, the fourth lower tube part is not shown in the figures. Each lower tube part  9  through  13  has the shape of a half-shell. The lower tube parts  9  through  13  project through corresponding openings in the flange  3  and are attached thereto. 
     Placed on the lower shell  5  is an upper shell  15  having an outer edge  17  which is welded and/or crimped to the outer edge  19  of the lower shell  5 . The upper shell  15  has only two extensions pointing towards the flange  3 , which have been reshaped into upper tube parts  21 ,  23  in the shape of half-shells (see  FIG. 2 ). The upper tube parts  21 ,  23  are in contact with the two outer lower tube parts (lower tube part  9  and the lower tube part that is not shown) and are connected with the latter on the edges, so that two outer inlet channels  25 ,  27  are formed, which are associated with the outer outlets  1 . 
     In the region of the middle outlets  1 , the upper shell  15  has a depression (see  FIG. 1 ) which extends remote from the flange  3  to closer to the flange  3  increasingly downward towards the lower shell  5 . This depression is defined by a wall  29  facing the rear side of the flange and by side walls  31  which continue into the wall  29 . The wall  29  has a cut-out  33 , so that the upper shell  15 , as viewed from the top, is formed in the shape of a U. 
     The width of the cut-out  33 , as related to  FIG. 1 , is adapted to the width of the baffle plate  35 , which has a lower end  37  welded to the lower shell  5 , the weld seam being denoted by  39 . The width of the baffle plate  35  is selected such that in the view according to  FIG. 1 , it covers both projections of the middle outlets  1 . As shown in  FIGS. 3 and 4 , the baffle plate  35  extends from the lower shell  5  obliquely upward and away from the flange  3  towards the wall  29 , which likewise extends obliquely upward and away from the flange  3 . 
     The wall  29  and the baffle plate  35  partly run parallel to each other in the vicinity of the lateral edges of the baffle plate  35 . 
     A U-shaped metal plate  43  which extends across the entire width of the baffle plate  35  is welded onto the rear side of the baffle plate  35 , in the area of the upper end  41  thereof (see  FIGS. 3 and 4 ). The metal plate  43  also extends downward along the lateral edges of the baffle plate  35 . The baffle plate  35  and the metal plate  43  are somewhat bent away from each other behind the welding point, so that they constitute a receiving groove which is U-shaped in cross-section and open to the outside and which extends along the lateral edges and the upper end  41 . The edge  45  of the cut-out  33  is inserted so as to be displaced within this receiving groove, so that a displaceable bearing is produced between the baffle plate  35  and the upper shell  15 . 
     A central shell  51  is located above the area of the indentation of the upper shell  15  and the baffle plate  35 . The central shell  51  has two extensions pointing towards the flange  3 , which form upper tube parts  53 ,  55  and are connected with the middle lower tube parts  11 ,  13  of the lower shell  5  to define two middle inlet channels  57 ,  59 . 
     The displaceable connection between the upper shell  15  and the baffle plate  35  may be, but need not be, limited to the upper edge  41 . Rather, as described above, additionally or alternatively the lateral edges of the baffle plate  35  may also be correspondingly connected for displacement with the upper shell  15 . 
     The lower and upper shells  5 ,  15  constitute a common outlet space  63  which extends beneath the baffle plate  35  and into which the two outer inlet channels  25 , 27  open. 
     The two middle inlet channels  57 ,  59  open into a common, second outlet space  65  which is defined by the baffle plate  35 , the middle portion of the upper shell  15 , and the central shell  51 . 
     Both outlet spaces  63 ,  65  lead to a single exhaust pipe  67  ( FIG. 2 ), which is defined by the lower and central shells  5 ,  51 . 
     The exhaust pipe  67  is divided in two by a tongue  81  of the upper shell  15  running transversely through the exhaust pipe  67 , dividing it into an upper section for the middle inlet channels  57 ,  59  and a lower section for the outer inlet channels  25 ,  27 . 
     This division of the flow is advantageous if a turbocharger operating according to the twin scroll concept is connected to the manifold. 
     As an alternative, the outlet spaces  63 ,  65  could also be united within the manifold, or else a shared outlet space could be provided. 
     The exhaust gas flowing into the middle inlet channels  57 ,  59  strikes directly onto the baffle plate  35  and is distributed by the latter in the second outlet space  65  to finall y  reach the exhaust pipe  67 , from where it flows to the turbocharger and to exhaust gas purification systems.