Abstract:
An air gap-insulated exhaust manifold ( 10 ) for a supercharged internal combustion engine ( 1 ), preferably of a motor vehicle has an engine flange ( 11 ) fastening the exhaust manifold to an engine block ( 2 ) and a turbine flange ( 12 ) fastening the exhaust manifold to a turbine ( 8 ) of an exhaust gas turbocharger ( 7 ). Two inner pipes ( 13, 14 ) lead from an inlet opening, for exhaust gas, adjacent to the engine flange to an outlet opening ( 18 ), for exhaust gas, adjacent to the turbine flange. An outer pipe ( 15 ) envelopes the two inner pipes, forming an air gap insulation ( 21 ), and extends from the engine flange to the turbine flange. A separation partition ( 16 ) separates, in the interior space ( 22 ) of the outer pipe, two interior spaces ( 23, 24 ), in which one each of the two inner pipes is arranged. Reduced wear is achieved with the partition arranged loosely at the turbine flange.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority under 35 U.S.C. §119 of German Patent Application DE 10 2013 211 390.0 filed Jun. 18, 2013, the entire contents of which are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention pertains to an air gap-insulated exhaust manifold for a supercharged internal combustion engine, preferably of a motor vehicle. The present invention pertains, in addition, to an exhaust system equipped with such an exhaust manifold for an internal combustion engine, preferably of a motor vehicle. 
     BACKGROUND OF THE INVENTION 
     An exhaust manifold is used as the inlet area of an exhaust system and merges the separate exhaust gas streams usually coming from a plurality of combustion chambers of the internal combustion engine. An exhaust manifold usually comprises for this an engine flange, with which the exhaust manifold can be fastened to an engine block of the internal combustion engine. Separate inlet openings, which are associated with the individual combustion chambers of the internal combustion engine, are, in turn, provided in the area of the engine flange. The exhaust manifold is usually connected permanently with a turbine flange on the discharge side in a supercharged internal combustion engine in order to feed the exhaust gases arriving from the internal combustion engine to the turbine as close to the engine as possible. Double-flow turbines, so-called twin-scroll turbines, may be used in internal combustion engines that have two cylinder banks or two groups of cylinders. To prevent the two cylinder groups from mutually interacting with one another, the exhaust gas is likewise routed in two flows up to the double-flow turbine, so that the exhaust manifold has separate manifolds for the two cylinder groups, which said manifolds lead each from a plurality of inlet openings to an outlet opening, and the two outlet openings of the separate manifolds feed the separate exhaust gas streams to separate inlet openings of the turbine in the turbine flange. 
     It is known that such an exhaust manifold can be equipped with an air gap insulation for improved heat insulation. This is achieved by an exhaust gas-carrying inner pipe being enveloped by an outer pipe, forming a gap, and this gap between the inner pipe and the outer pipe forms the desired air gap insulation. The outer pipe and inner pipe may also be called outer shell and inner shell, respectively. 
     For a supercharged internal combustion engine with twin-scroll turbine, an air gap-insulated exhaust manifold thus comprises an engine flange for fastening the exhaust manifold to the engine block of the internal combustion engine, a turbine flange for fastening the exhaust manifold to the turbine of the exhaust gas turbocharger, two separate inner pipes, which lead each from at least one inlet opening for exhaust gas arranged in the area of the engine flange to an outlet opening for exhaust gas arranged in the area of the turbine flange, as well as an outer pipe, which envelops the two inner pipes, forming an air gap insulation and extends essentially from the engine flange to the turbine flange. 
     The inner pipes may have a multipart design in order to make it possible to merge a plurality of inlet openings into a common outlet opening in a simpler manner. The individual members of the respective inner pipe may be inserted one into another to make relative motions caused by thermal effects possible. Leaks may develop due to these plug-type connections, as a result of which exhaust gas can escape from the respective inner pipe and enter the interior space of the outer pipe, which said interior space is enveloped by the outer pipe. Such tolerable leaks occur in a pulsed manner, corresponding to the working rhythm of the internal combustion engine. To prevent these pressure pulsations of the two cylinder groups within the exhaust manifold from mutually affecting each other, a partition, which divides the interior space of the outer pipe into two interior spaces, in which one of the two inner pipes each is arranged, may be arranged in the outer pipe. This partition advantageously extends from the turbine flange to the engine flange. 
     It was found that such a partition is subject to very high thermal loads because of it being positioned between the two inner pipes. In particular, the partition is subject to strong thermal expansion effects. Undesired wear may develop as a result. 
     SUMMARY OF THE INVENTION 
     The present invention pertains to the object of providing an improved embodiment, which is characterized especially by reduced wear, for an exhaust manifold of the type described in the introduction or for an exhaust system equipped therewith. 
     According to the invention, an air gap-insulated exhaust manifold is provided for a supercharged internal combustion engine. The exhaust manifold comprises an engine flange for fastening the exhaust manifold to an engine block of the internal combustion engine and a turbine flange for fastening the exhaust manifold to a turbine of an exhaust gas turbocharger. Two separate inner pipes lead each from at least one inlet opening for exhaust gas arranged in the area of the engine flange to an outlet opening for exhaust gas arranged in the area of the turbine flange. An outer pipe envelopes the two inner pipes, forming an air gap insulation. The outer pipe extends between the engine flange and the turbine flange. A separate partition separates two interior spaces, in which one each of the two inner pipes is arranged, from each other in the interior space of the outer pipe. The partition is arranged loosely at the turbine flange. 
     The present invention is based on the general idea of designing the partition as a separate component and arranging it movably, i.e., loosely, at least in relation to the turbine flange. The partition can move relative to the turbine flange, at least in the area of a front side facing the turbine flange, due to this design. As a consequence, the partition can expand based on thermal stress and move relative to the turbine flange in the process without a risk of excessive wear occurring. Furthermore, the risk of mechanical damage to the turbine flange due to the partition possibly supported thereon can be reduced due to the loose arrangement of the partition in relation to the turbine flange. 
     Corresponding to another advantageous embodiment, the partition may be guided at the turbine flange by guide contours in a positive-locking manner. A guiding is defined hereby for the motions of the partition relative to the turbine flange, which simplifies these relative motions and reduces the risk of wear. A positive-locking guiding can be achieved in an especially simple manner without additional components, because the partition is guided directly at the turbine flange if the guide contours are formed integrally on the turbine flange. 
     According to a preferred variant, the respective guide contour may be formed by a guide support, which is formed in the turbine flange and with which a lateral edge area of the partition meshes (engages) in a positive-locking manner. Such a guide support can be formed as an integral component at the turbine flange in an especially simple manner. In the area of a front side facing the turbine flange, the partition can simply mesh with lateral edge areas facing away from one another with the diametrically opposite guide supports, as a result of which a secure guiding is achieved for the partition. 
     The partition may also be arranged loosely at the outer pipe in another embodiment. This means that the partition is also arranged movably in relation to the outer pipe, i.e., it can, in particular, expand thermally without blocking with the outer pipe. 
     According to a preferred variant, the partition may be positioned at the outer pipe in positioning contours in a positive-locking manner. Such positioning contours can be integrated in the outer pipe in an especially simple manner. For example, the outer pipe may be manufactured as a shell construction, wherein the individual shells can be manufactured by means of the deep-drawing technique or blow-molding technique. Such positioning contours can thus be formed integrally with the outer pipe in an especially simple manner, without additional effort. 
     According to a preferred variant, the positioning contour may be formed by a positioning support, which is formed in the outer pipe and with which support a lateral edge area of the partition meshes. Permanent positioning is achieved by means of the respective positive-locking connection in this case as well, without additional fastening measures being necessary. 
     The respective positioning contour may extend, in principle, from the engine flange to the turbine flange on the outer pipe. However, an embodiment in which the respective positioning contour is located at a spaced location from the engine block and at a spaced location from the turbine flange is preferred. As a consequence, the positioning contour extends only over part of the respective lateral edge of the partition. For example, the respective positioning contour extends only over a maximum of 50% of the respective lateral edge of the partition. The respective positioning contour preferably extends over about 25% of the respective lateral edge. If the positioning contour does not extend over the entire respective lateral edge of the partition, the edge area of the partition, which cooperates with the positioning contour and consequently meshes with same, is preferably formed by a projection, which projects from the rest of the lateral edge and meshes with the respective positioning support. 
     The partition may also be arranged loosely at the engine flange in another embodiment. In other words, the partition can also move relative to the engine flange, as a result of which motions caused by thermal effects are possible here as well and stresses caused by thermal effects can be reduced. 
     According to an advantageous variant, the partition may be held at the engine flange in at least one holding contour in a positive-locking manner. The need for separate holding means are eliminated due to the use of a positive-locking connection in this case as well, as a result of which the holding contour can be embodied in an especially simple manner. 
     According to an advantageous variant, the respective holding contour may be formed by a holding support, which is formed in the engine flange and with which a front-side edge area of the partition meshes. Such a holding support can be manufactured integrally with the engine flange in an especially simple manner, for example, by taking it into account in an injection mold, which is used to manufacture the engine flange. 
     The turbine flange may have an open design in another advantageous embodiment. This means that an open connection is present within the turbine flange to the air gap insulation, i.e., to the intermediate space between the inner pipes and the outer pipe. As a result, the turbine flange will have a considerably simplified design, and, in particular, it is possible to eliminate a middle web, which extends between the two inner parts, in the area of the respective outlet opening. In addition, the risk of collision of the partition with the middle web can be efficiently avoided in the absence of a middle web. 
     The turbine flange may preferably have a single flange opening, which surrounds the two inner pipes in the area of the respective outlet opening and in which the partition ends in a detached manner on the front side. Due to the partition ending in a detached manner, the partition can move quasi as desired within the flange opening in the direction of the turbine, without colliding with an obstacle. The wear on the partition and turbine flange can be reduced in this manner. 
     The turbine flange may have a closed design in another embodiment. This means that the air gap insulation is also closed in the turbine flange. Leaks, which could lead to an undesired interaction between the two interior spaces separated from each other by the partition, can be avoided as a result in the area of the turbine flange as well. 
     The turbine flange may advantageously have two separate flange openings, which enclose each one of the inner pipes in the area of the respective outlet opening. Each inner pipe is thus enclosed in itself, preferably extensively tightly, for example, in the manner of a plug-type connection with sliding fit. The partition may be supported now on the front side at a support area of the turbine flange. Due to the front-side support of the partition at the turbine flange, efficient sealing can be achieved between the two interior spaces in this area as well. The support area is formed in this case at a middle web of the turbine flange, which separates the two flange openings from one another and which thus passes through between the two inner pipes. 
     Corresponding to an advantageous variant, the support area may have at least one elastic support element, via which the partition is supported on the turbine flange on the front side. Such an elastic support element thus makes relative motions possible between the partition and the aforementioned middle web of the turbine flange, without excessive mechanical stress developing in the process. Such an elastic support element may be formed, for example, by a wire mesh element. Such wire mesh elements are characterized by high thermal loadability as well as high elasticity. 
     The partition may be arranged in a detached or contactless manner, i.e., without contact, in relation to the two inner pipes. This measure also reduces the risk of wear. 
     Further, the partition may preferably be flat, so that it extends in a partition plane. As a result, the partition can be manufactured at an especially low cost. For example, the partition may be formed by a sheet metal body, which can be manufactured in an especially simple manner, for example, by means of a punching operation. In case of a flat partition, the partition may mesh with the respective guide support preferably in parallel to the plane of the partition. Further, the partition may mesh with the respective positioning support in parallel to the plane of the partition. Finally, the partition may mesh with the respective holding support in parallel to the plane of the partition. Furthermore, provisions may be made for the partition to be arranged movably in the respective guide support in parallel to the plane of the partition, in which case the direction of motion is oriented in parallel to the direction of a gap between the engine flange and the turbine flange. Furthermore, the partition may be arranged movably in the respective positioning support in parallel to the plane of the partition, in which case the direction of motion is oriented at right angles to the direction of the gap between the engine flange and the turbine flange. Finally, the partition may be arranged movably in the respective holding support in parallel to the plane of the partition. The direction of motion is again oriented in parallel to the direction of the gap between the engine flange and the turbine flange in this case. 
     It is also possible, as an alternative, to make the partition uneven and to provide it, for example, with a curvature or crown. Such a curvature can help avoid unintended deformations during heating up and cooling. Such an uneven partition may also be flat or straight in the area of the respective guide contour in order to bring about linear guiding. This also applies analogously to the area of the respective positioning contour and/or of the holding contour. 
     It is also possible, according to another alternative, to provide the partition with a bent rim in the area of the respective positioning contour. The respective positioning contour is designed in this case to receive the rim. Further, it is possible, in principle, to provide the respective positioning contour with a mounting contour, which makes possible a positive-locking connection with the respective rim. 
     Two positioning contours, which are located diametrically opposite at the outer pipe, may be provided in another embodiment. Furthermore, the two positioning contours may be advantageously arranged approximately centrally between the engine flange and the turbine flange. A variant in which the positioning contours are used as fixed mounts for expansion motions of the partition oriented in parallel to the direction of the gap between the engine flange and the turbine flange, while the guide contours and at least one holding contour are used each as movable mounts, in which the relative motions between the partition and turbine flange, on the one hand, as well as between the partition and engine flange, on the other hand, take place. 
     Furthermore, provisions may be made for the partition, which is preferably flat, to extend essentially at right angles to a plane of the turbine flange. Simple kinematics is achieved hereby for the thermal expansion effects, as a result of which it is possible, in particular, to avoid warping and the like. 
     An exhaust system according to the present invention, which is intended for a supercharged internal combustion engine, especially in a motor vehicle, comprises a turbine of an exhaust gas turbocharger as well as an exhaust manifold of the above-described type, via which the exhaust system can be fastened to the internal combustion engine. The engine flange is fixed for this to the engine block of the internal combustion engine, while the turbine flange is fixed to the turbine of the exhaust gas turbocharger. 
     Further important features and advantages of the present invention appear from the subclaims, from the drawings, and from the corresponding description of the figures on the basis of the drawings. 
     It is obvious that the above-mentioned features, which will also be explained below, can be used not only in the particular combination indicated, but also in other combinations or alone, without going beyond the scope of the present invention. 
     Preferred exemplary embodiments of the present invention are shown in the drawings and will be explained in more detail in the following description, in which identical reference numbers designate identical or similar or functionally identical components. 
     The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a highly simplified, diagram-like general view of an internal combustion engine with an exhaust system, which has an exhaust manifold shown in section; 
         FIG. 2  is an axial view of the exhaust manifold in the area of a turbine flange; 
         FIG. 3  is an axial sectional view of the exhaust manifold through the turbine flange; 
         FIG. 4  is an axial view of the exhaust manifold in the area of the turbine flange in another embodiment; 
         FIG. 5  is an axial view of the exhaust manifold through the turbine flange in the embodiment shown in  FIG. 4 ; and 
         FIG. 6  is a longitudinal sectional view of the exhaust manifold in the area of the turbine flange. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings in particular, corresponding to  FIG. 1 , an internal combustion engine  1  comprises an engine block  2  with a plurality of combustion chambers  3 , which are formed by a cylinder  4  each in the usual manner, in which a piston each, not shown here, is arranged in such a manner that its stroke is adjustable. The internal combustion engine  1  has a fresh air feed unit  5  for supplying the combustion chambers  3  with fresh air. Further, an exhaust system  6  is provided, which removes exhaust gas from the combustion chambers  3  during the operation of the internal combustion engine  1 . The internal combustion engine  1  is designed as a supercharged internal combustion engine  1 . It is correspondingly equipped here with an exhaust gas turbocharger  7 , which has a turbine  8  and a compressor  9  in the usual manner. The compressor  9  is integrated into the fresh air feed unit  5  and is drive-connected with the turbine  8 , which is integrated into the exhaust system  6 . The exhaust system  6  has an exhaust manifold  10 , which connects the block  2  with the turbine  8 . 
     Corresponding to  FIGS. 1 through 6 , the exhaust manifold  10  has an engine flange  11 , which is used to fasten the exhaust manifold  10  to the engine block  12 . The exhaust manifold  10  has, in addition, a turbine flange  12 , which is used to fasten the exhaust manifold  10  to the turbine  8 . Further, the exhaust manifold  10  comprises two separate inner pipes  13 ,  14 , an outer pipe  15  as well as a partition  16 . The respective inner pipe  13 ,  14  extends from at least one inlet opening  17  arranged in the area of the engine flange  11  to an outlet opening  18  arranged in the area of the turbine flange  12 . In the example shown in  FIG. 1 , the engine block  2  has six cylinders  4 , which are combined in two cylinder groups  19 ,  20 , so that each cylinder group  19 ,  20  has exactly three cylinders  4 . The two inner pipes  13 ,  14  are separately associated with these two cylinder groups  19 ,  20 . Each inner pipe  13  correspondingly has three inlet openings  17  and one outlet opening  18 . Consequently, two such outlet openings  18  are merged at the turbine flange  12 . The turbine  8  is preferably designed as a twin-scroll turbine, i.e., as a double-flow turbine  8 , so that the two outlet openings  18  of the exhaust manifold  10  are led in separate exhaust gas paths in the turbine  8 . The two inner pipes  13 ,  14  may also be called inner shells  13 ,  14 . 
     The outer pipe  15 , which may also be called outer shell  15 , envelops the two inner pipes  13 ,  14 , such that an air gap insulation  21  is formed now. The outer pipe  15  extends here essentially from the engine flange  11  to the turbine flange  12 . The outer pipe  15  is connected permanently directly with the engine flange  11  and with the turbine flange  12  in the examples being shown. It is likewise conceivable to fasten the outer pipe  15  indirectly to the engine flange  11  and/or to the turbine flange  12 , namely, via the respective inner pipe  13 ,  14 , which is permanently connected at least in this case with the engine flange  11  and with the turbine flange  12 , respectively. 
     The partition  16  forms a separate component in relation to the inner pipe  13 ,  14 , outer pipe  15 , engine flange  11  and turbine flange  12 . The partition  16  is arranged in an interior space  22  of the outer pipe  15 , such that it separates two interior spaces  23 ,  24  from one another in the interior space  22 . One of the two inner pipes  13 ,  14  each is arranged in each interior space  23 ,  24 . 
     Corresponding to  FIGS. 2 through 6 , the partition  16  is arranged loosely at the turbine flange  12 , i.e., it is not fixed to it directly, so that the partition  16  is movable relative to the turbine flange  12 . According to  FIGS. 2, 3 and 5 , guide contours  25 , which guide the partition  16  in a positive-locking manner, are formed on the turbine flange  12 . The respective guide contour  25  is formed here by a guide support  26 , which is formed directly in the turbine flange  12  and with which meshes a lateral edge area  27  of the partition  16  in a positive-locking manner. 
     The partition  16  may be arranged, in addition, loosely at the outer pipe  15 . According to  FIGS. 3 and 5 , the outer pipe  15  may have two positioning contours  28  for this, which bring about a positive-locking positioning of the partition  16 . The respective contour  28  is formed here by a positioning support  29 , which is formed in the outer pipe  15  and with which a lateral edge area  30  of the partition  16  meshes. The positioning contours  28  are arranged diametrically opposite each other in the example. Further, the two positioning contours  28  are arranged each approximately centrally between the engine flange  11  and the turbine flange  12 . The positioning contours  28  are designed such that the partition  16  is fixed relative to the outer pipe  15  in relation to a direction  31  of the gap between the engine flange  11  and the turbine flange  12 , whereas the partition  16  is arranged movably in the positioning contours  28  at right angles to the direction  31  of the gap. The positioning contours  28  form fixed mounts here, so that the partition  16  can expand thermally starting from the positioning contours  28 . 
     According to  FIGS. 3, 5 and 6 , the partition  16  is advantageously also arranged loosely at the engine flange  11 , i.e., it is not fixed to it directly. The engine flange  11  may have for this at least one holding contour  32  according to  FIG. 6 , which brings about positive-locking holding of the partition  16 . The respective holding contour  32  is formed in the example by a holding support  33 , which is formed directly on the engine flange  11  and with which a front-side edge area  34  of the partition  16  meshes in a positive-locking manner. 
     As can be seen especially in  FIG. 6 , the inner pipes  13 ,  14  are of a multipart design, so that they are consequently composed of a plurality of individual pipes. 
     The turbine flange  12  is designed as an open flange in the embodiment shown in  FIGS. 2 and 3 , as a result of which the air gap insulation  21  is visible especially in the axial view according to  FIG. 2 . The turbine flange  12  has a single flange opening  35  in this case, through which both inner pipes  13 ,  14  are led. This common flange opening  35  thus encloses both inner pipes  13 ,  14  each in the area of the respective outlet opening  18 . An inner edge of the flange opening  35 , not designated specifically, is flatly and sealingly in contact with the respective inner pipe  13 ,  14  in a circumferential section facing away from the partition  16 . Contrary to this, the partition  16  ends in a detached manner in the flange opening  35 . As can be recognized, the partition  16  is located now at a spaced location from both inner pipes  13 ,  14 . It can be recognized especially from  FIG. 3  that the partition  16  has no axial obstacle at the flange  12  and is consequently movable within the guide contours  25 . 
     Contrary to  FIGS. 2 and 3 ,  FIGS. 4 and 5  show an embodiment in which the turbine flange  12  has a closed design. The air gap insulation  21  is not consequently visible here. The turbine flange  12  has two separate flange openings  36 ,  37  in this case, through which one each of the inner pipes  13 ,  14  is passed. Thus, each flange opening  36 ,  37  encloses one of the two inner pipes  13 ,  14  in the area of the corresponding outlet opening  18 . An inner wall of the respective flange opening  36 ,  37 , not designated more specifically, is flatly in contact with the respective inner pipe  13 ,  14 , extending circularly in a closed pattern in the circumferential direction. The turbine flange  12  has in this embodiment a middle web  38 , which passes through between the two inner pipes  13 ,  14  and which separates the two flange openings  36 ,  37  from each other. 
     According to  FIG. 5 , the partition  16  is supported in this embodiment at a support area  39  of the turbine flange  12 , namely, via a front side  40  facing the turbine flange  12 . This support area  39  may have at least one elastic support element  41 , which may be especially a wire mesh element, which will likewise be designated by  41  hereafter. 
     As can be determined especially from  FIGS. 2 and 6 , the partition  16  is arranged in a detached manner in relation to the inner pipes  13 ,  14 . Further, the partition  16  is preferably of a flat design, so that it extends in the partition plane  42  suggested in  FIG. 6 . The partition  16  advantageously meshes with the guide supports  25 , positioning supports  28  and holding support  32  in parallel to the partition plane  42 . Further, the partition  16  is arranged movably in the guide contours  25 , in the positioning contours  28  and in the holding contour  32  in parallel to the partition plane  42 . This mobility is oriented in parallel to the direction  31  of the gap in the guide contours  25  and in the holding contour  32  and at right angles to the direction  31  of the gap in the positioning contours  28 . Further, the partition plane  42  extends essentially at right angles to a flange plane  43  of the turbine flange  12  shown in  FIGS. 3 and 5 , in which plane the turbine flange  12  extends. 
     Finally, a ring groove  44  can be recognized in  FIGS. 2 through 6 , wherein said groove  44  is milled into the turbine flange  12  and a seal can be inserted into it in order to seal the connection between the turbine flange  12  and a flange of the turbine  8 , which latter flange is complementary thereto. 
     As can be seen especially in  FIGS. 3 and 5 , the positioning contour  28  is positioned in the embodiments shown here at a spaced location from the engine flange  11  and at a spaced location from the turbine flange  12 , so that it does not extend over the respective entire side wall  45  of the partition  16 . A projection  46 , which projects from the respective side wall  45  outwardly and forms the edge area  30  of the partition  16  meshing with the positioning support  29 , is correspondingly formed at the respective side wall  45 . 
     While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.