Abstract:
An exhaust gas manifold for mounting on a cylinder head of an internal combustion engine, composed of at least one cylinder support having bores for evacuating the exhaust gas. The exhaust gas manifold comprises an exhaust gas manifold collector housing ( 9 ) for collecting exhaust gas from the cylinder head, and a sealing device ( 10 ) placed between the exhaust gas collector housing ( 9 ) and the cylinder head ( 2 ). The exhaust gas manifold collector housing ( 9 ) is provided with recesses ( 12 ) so that it can be directly connected to the cylinder head ( 2 ) via a fixation mechanism ( 18 ), whereby the effect of heat enables movements between the exhaust gas manifold collector housing ( 9 ) and the cylinder head ( 2 ).

Description:
FIELD OF THE INVENTION 
     The invention relates to an exhaust manifold for mounting on a cylinder head of an internal combustion engine. 
     BACKGROUND OF THE INVENTION 
     In EP 0 709 557 A1, an exhaust-tube manifold is described in a design as used in very many internal combustion engines. Each exhaust tube is welded to a flange which is then screwed onto the cylinder head of the internal combustion engine. The exhaust tubes open in a known manner into a collector tube, which continues into an exhaust pipe. 
     Known exhaust manifolds of this type are disadvantageously very heavy and expensive and have the further disadvantage that because of their large mass they take away very large amounts of heat from the exhaust gas passed into them. This reduces the temperature of the exhaust gas, which has the effect that the catalytic converter arranged in the exhaust pipe has very poor efficiency, particularly during starting of the internal combustion engine. 
     In order to improve the efficiency and the light-off performance of the catalytic converter, according to one prior art which is known from practice, exhaust manifolds having “air gap insulation” have been developed, in which a housing and a gas-conducting pipe arranged in the housing are provided. 
     Even here, however, the relatively high mass and, in particular, the high outlay on welding work for assembling the housing surrounding the inner gas-conducting pipe and for mounting this housing on a cylinder head flange remain disadvantageous, since both contribute to increasing the costs of exhaust manifolds of this type. The required tightness of the exhaust manifold means that in the case of the known constructions, welding work of this type may not, however, be omitted. 
     It is, therefore, the object of the present invention to provide an exhaust manifold for mounting on a cylinder head of an internal combustion engine, said exhaust manifold being simple and cost-effective to produce, having a low mass and being able to be mounted on the cylinder head of the internal combustion engine in a simple manner. 
     According to the invention, this object is achieved by the features mentioned in claim  1 . 
     DETAILED DESCRIPTION OF THE INVENTION 
     The exhaust manifold according to the invention can be connected directly to the cylinder head by suitable fastening means, for example screws. In order to achieve a seal between the exhaust-gas collector housing and the cylinder head, just one sealing device is necessary between the exhaust-gas collector housing and the cylinder head, and costly welding work can be omitted. 
     The exhaust-gas collector housing can advantageously expand with respect to the cylinder head and can execute a corresponding movement, with the result that costly constructions having sliding flanges or the like can be avoided. 
     One particular advantage of the exhaust manifold according to the invention is the low degree of deformation required, as a result of which very thin metal plates having a correspondingly low mass can be used. This leads to very low material and production costs and to an extremely small amount of heat being removed from the exhaust gas. Furthermore, the exhaust manifold according to the invention has the advantage of requiring a relatively small amount of space in the engine compartment of a motor vehicle. 
     If, in one advantageous development of the invention, a flange is arranged between the exhaust-gas collector housing and the cylinder head, then an even better sliding movement of the exhaust-gas collector housing with respect to the cylinder head is possible on account of said housing possibly undergoing thermal expansion. In addition, this advantageously enables the cylinder head to be uncoupled from the exhaust-gas collector housing. 
     In a further advantageous refinement of the invention, a gas-conducting channel can be arranged in the exhaust-gas collector housing. This produces an exhaust manifold having air gap insulation, which exhaust manifold removes relatively little heat from the exhaust gas owing to the thin walls of the gas-conducting channel and the air gap between the exhaust-gas collector housing and the gas-conducting channel. This prevents the exhaust-gas temperature from dropping and results in better light-off performance and efficiency of a catalytic converter arranged in the exhaust pipe adjoining the exhaust manifold. 
     Furthermore, when a gas-conducting channel is used, an exhaust-gas collector housing consisting of cost-effective structural steel which can easily be deformed is advantageously used, since said housing is thermally less severely stressed. 
     Also in this embodiment, a flange can be arranged between the exhaust-gas collector housing and the cylinder head, which flange permits the better sliding movement of the exhaust-gas collector housing with respect to the cylinder head. 
     In the case of all of the embodiments, a low degree of deformation arises, which leads advantageously to thin metal plates and therefore to the individual components having very small masses. 
     In a further advantageously embodiment of the invention, provision can be made for the gas-conducting channel to be provided, on its side facing the cylinder head, with a circumferential collar which, in the assembled state, is at least indirectly wedged between the exhaust-gas collector housing and the sealing device, movements caused by the effect of heat being possible between the gas-conducting channel and the sealing device. 
     This results in a very simple fastening of the gas-conducting channel, but displacement thereof in the plane of the cylinder head remaining possible, however, and, at the same time, movement thereof perpendicularly with respect to this plane and clattering possibly caused thereby being prevented. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described, by way of example, with reference to the accompanying drawings in which: 
     Further advantageously refinements and developments of the invention emerge from the remaining subclaims and from the exemplary embodiment illustrated in principle below with reference to the drawing. In the drawing: 
     FIG. 1 shows a highly schematized internal combustion engine with an exhaust manifold mounted thereon; 
     FIG. 2 shows an exploded illustration of the exhaust manifold from FIG. 1 in a first embodiment; 
     FIG. 3 shows a section according to the line III—III from FIG. 2; 
     FIG. 4 shows an exploded illustration of the exhaust manifold from FIG. 1 in a second embodiment; 
     FIG. 5 shows a section according to the line V—V from FIG. 4; 
     FIG. 6 shows an exploded illustration of the exhaust manifold from FIG. 1 in a third embodiment; 
     FIG. 7 shows a section according to the line VII—VII from FIG. 6; 
     FIG. 8 shows an exploded illustration of the exhaust manifold from FIG. 1 in a fourth embodiment; 
     FIG. 9 shows a section according to the line IX—IX from FIG. 8; 
     FIG. 10 shows an exploded illustration of the exhaust manifold from FIG. 1 in a fifth embodiment; 
     FIG. 11 shows a section according to the line XI—XI from FIG. 10; 
     FIG. 12 shows a sectional illustration of the exhaust manifold from FIG. 1 in a sixth embodiment; and 
     FIG. 13 shows a sectional illustration of the exhaust manifold from FIG. 1 in a seventh embodiment. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows an exhaust manifold  1  which is mounted on a cylinder head  2  of an internal combustion engine  3 . The present embodiment concerns an internal combustion engine  3  of series construction, in which the cylinder head  2  has just one cylinder bank  4  with four cylinders  5  in this case. In the case of internal combustion engines  3  of V-type construction, a plurality of cylinder banks  4  could, of course, be provided and the exhaust manifold  1  would then be mounted in each case on them. Situated in the cylinder head  2  are a plurality of exhaust-gas bores  6  which lead away from the cylinders  5  and open into the exhaust manifold  1 , as a result of which the exhaust gas passes into the exhaust manifold  1 . The exhaust manifold  1  is provided, on its side facing away from the internal combustion engine  3 , with an opening  7 , which can be situated at any desired location and into which an exhaust pipe  8  is inserted in a known manner. A catalytic converter (not illustrated) used for cleaning the exhaust gases can be situated in the exhaust pipe  8 . 
     In FIGS. 2 to  6 , the exhaust manifold  1  is illustrated by means of exploded drawings, in each case in different embodiments. 
     The exhaust manifold  1  according to FIG. 2 comprises an exhaust-gas collector housing  9 , which receives the exhaust gases from all of the exhaust-gas bores  6  of a cylinder bank  4 , and a sealing device  10 . The exhaust gases can leave the exhaust-gas collector housing  9  again through the opening  7 , which is situated on that side of the housing which faces away from the cylinder head  2 , and can, therefore, enter into the exhaust pipe  8 . The exhaust-gas collector housing  9  is surrounded on its entire circumference by a collar  11  in which are situated recesses  12  for the passage of fastening means (not illustrated in FIG.  2 ), such as screws, for example. The fastening means are used to mount the exhaust-gas collector housing  9  on the cylinder head  2 . 
     The sealing device  10  corresponds in its shape to that side of the exhaust-gas collector housing  9  which faces the cylinder head  2 , runs over the entire region between the exhaust-gas collector housing  9  and the cylinder head  2  and accordingly likewise has a collar  13  having recesses  14 , the positions of which at least approximately correspond with the positions of the recesses  12  in the collar  11  of the exhaust-gas collector housing  9 . 
     Furthermore, the sealing device  10  has a plurality of bores  15 , the number of which and positions of which at least approximately correspond with the positions of the exhaust-gas bores  6  in the cylinder head  2 , in order to ensure that the exhaust gas flows out of the exhaust-gas bores  6  into the exhaust-gas collector housing  9 . On its side facing the exhaust-gas collector housing  9 , the sealing device  10  is provided with beads or impressions  16  which produce a gap between the cylinder head  2  and the sealing device  10 . The sealing device  10  may, for example, be constructed from a metallic material. 
     Furthermore, it can be gathered from FIG. 2 that the exhaust-gas collector housing  9  has a beading  17  on its outside. This beading  17  bounds the collar  11  of the exhaust-gas collector housing  9  to the outside and increases the strength of the exhaust-gas collector housing  9 . In the present embodiment, the exhaust-gas collector housing  9  consists of a material with high temperature stability, and is able to execute small movements with respect to the sealing device  10  and therefore with respect to the cylinder head  2 , which movements are caused by the introduction of heat by the exhaust gas and the associated expansion of the exhaust-gas collector housing  9 . 
     It would also be possible to produce the exhaust-gas collector housing  9  from multi-layered metal plates in a sandwich-type construction, as a result of which the radiation of sound could be reduced. In the case of a sandwich-type construction of this type, one layer could, for example, consist of steel and the other layer of aluminum, in which case the production of exhaust-gas collector housings  9  which withstand high temperatures would also be possible. 
     In order to be able to clean the exhaust gas in a simple manner, a plurality of individual catalytic converter elements  39  are arranged in the exhaust-gas collector housing  9 . In this arrangement, each catalytic converter element  39  is assigned to an exhaust-gas bore  6  or to a cylinder  5 , with the result that in all of the exemplary embodiments four catalytic converter elements  39  are provided. The catalytic converter elements  39 , which comprise, for example, a wrap-around plate which is known per se, are of cylindrical design and can be arranged standing or lying. In the exhaust-gas collector housing  9 , the catalytic converter elements  39  are held by knitted wire fabric elements, which are not illustrated. As an alternative to this, the use of a conventional catalytic converter in the exhaust pipe  8  is of course also possible, as already mentioned above. 
     In FIG. 3, the abovementioned fastening means which are designed as screws  18  and are intended for mounting the exhaust-gas collector housing  9  on the cylinder head  2  are illustrated. Said fastening means are passed through the recesses  12  in the exhaust-gas collector housing  9  and the recesses  14  in the sealing device  10 . Appropriate tightening of the screws  18  enables the displacability specified above of the exhaust-gas collector housing  9  with respect to the cylinder head  2  to be set. However, in this case tightness of the exhaust manifold  1  is ensured at all times. Furthermore, it can be seen that the bores  15  of the sealing device  10  are provided with beadings  19  which reach into the exhaust-gas bores  6  of the cylinder head  2 . 
     FIG. 4 shows a further embodiment of the exhaust manifold  1 , in which again the exhaust-gas collector housing  9  and the sealing device  10  are provided, but in addition a flange  20  and a further sealing device  10   a  are provided, in order to form the exhaust manifold  1 . In the illustration according to FIG. 4, only the sealing device  10   a  can be seen. The flange  20  is provided with bores  21 , the number and positions of which at least approximately correspond with the positions of the exhaust-gas bores  6  in the cylinder head  2 . In this case, the bores  21  are of round design. Furthermore, the flange  20  has a circumferential collar  22  and a beading  23 , recesses  24  being placed in the collar  22 , the positions of which recesses correspond with the positions of the recesses  12  in the exhaust-gas collector housing  9 . 
     In this case, the sealing device  10   a  does not have any bores  15  corresponding to the exhaust-gas bores  6 ; rather, it has a recess  25  which runs over approximately the entire length and over approximately the entire width of the sealing device  10   a . However, in the manner according to FIG. 2, the sealing device  10   a  is again provided with a collar  13   a  and recesses  14   a . On account of the large recess  25 , the sealing is undertaken merely by the collar  13   a  of the sealing device  10   a.    
     In FIG. 5, the mounting of the exhaust manifold  1  on the cylinder head  2  is illustrated in section. It can be seen here that the sealing device  10   a  is arranged between the flange  20  and the exhaust-gas collector housing  9 . The further sealing device  10  is situated between the cylinder head  2  and the exhaust-gas collector housing  9 , but in contrast with FIG.  2  and FIG. 3 it is designed without impressions  16  and without beadings  17 . It is also revealed in this Figure that the inner contour of the beading  23  of the flange  20  corresponds with the outer contour of the collar  11  surrounding the exhaust-gas collector housing  9 , with the result that the exhaust-gas collector housing  9  finds space within the beading  23  of the flange  20 . In this case, however, the exhaust-gas collector housing  9  does not have any beading  17 . The exhaust-gas collector housing  9  can be preassembled by means of embossings or spot welds. 
     Here too, again, movements caused by the effect of heat are possible between the exhaust-gas collector housing  9  and the flange  20 , specifically on account of the sealing device  10   a  mounted between them. As previously, the fastening devices  18  are passed through the recesses  12  in the exhaust-gas collector housing  9 , the recesses  24  in the flange  20  and the recesses  14  and  14   a  in the sealing devices  10  and  10   a  for the purpose of mounting the exhaust manifold  1  on the cylinder head  2 . 
     FIG. 6 shows a further embodiment of the exhaust manifold  1  which again has the exhaust-gas collector housing  9  and the sealing device  10 . However, a gas-conducting channel  26  is arranged in the exhaust-gas collector housing  9 , said gas-conducting channel being of two-part design with a bottom part  27  and a cover part  28 . As previously, the exhaust-gas collector housing  9  is provided with the collar  11  and the recesses  12  situated therein, and also with the beading  17  which surrounds the collar  11 . Likewise as described above, the sealing device  10  has the collar  13 , the recesses  14  and the bores  15 . 
     The bottom part  27  of the gas-conducting channel  26 , which is produced from a material with high temperature stability, is provided with bores  29 , the positions of which at least approximately correspond with the positions of the exhaust-gas bores  6  of the cylinder head  2 . This enables the exhaust gas to pass into the gas-conducting channel  26 . Baffle plates  30  are arranged within the gas-conducting channel  26 , said baffle plates conducting the gas flow from the bores  29  to an opening  31  which leads to the exhaust pipe  8  and is situated in the cover part  28  of the gas-conducting channel  26 . The baffle plates  30  can be welded either to the exhaust-gas collector housing  9  or the gas-conducting channel  26 , or can be stamped out of the material of the bottom part  27  and/or the cover part  28  of the gas-conducting channel  26 . During the installation of the exhaust manifold  1 , retaining brackets  33 , which are used for fastening the gas-conducting channel  26 , are placed onto indentations  32  made on the outside of the cover part  28 . In other words, the retaining brackets  33  are arranged in such a manner that when the exhaust-gas collector housing  9  is mounted on the cylinder head  2 , the retaining brackets  33  secure the gas-conducting channel  26  by means of the fastening means  18 . The tightness of the gas-conducting channel  26  is ensured by the bottom part  27  corresponding in a very precisely fitting manner with the cover part  28 , and these two parts are locked tightly together by the force supplied by means of the retaining brackets  33 . In addition, the bottom part  27  is also embossed with the cover part  28  or spot-welded thereto, with the result that complete pre-assembly is possible. 
     The retaining brackets  33 , which are designed as resilient or damping elements, can consist of a material with high temperature stability, for example even of a knitted wire fabric with high temperature stability. This type of installation enables costly welding work to be omitted. 
     The abovementioned catalytic converter elements  39  for cleaning the exhaust gas can likewise be arranged in the gas-conducting channel  26 , and can be held therein by knitted wire fabric elements (not illustrated). 
     As an alternative to the design which is illustrated, the gas-conducting channel  26  can also consist of a material which is permeable for fluids, in this case for exhaust gases. This can be achieved, for example, by a woven fabric or by a perforated plate. By this means, the mass of the gas-conducting channel  26  is reduced yet further, and the latter can thus remove less heat from the exhaust gas. Even in this embodiment, the exhaust gas nevertheless endeavors to flow in the direction of the opening  31 , and only a very small part will pass through-the gas-conducting channel  26  to the exhaust-gas collector housing  9 . 
     It can be seen in FIG. 7 that an air gap  34  is produced between the gas-conducting channel  26  and the exhaust-gas collector housing  9 , said air gap isolating from the exhaust-gas collector housing  9  the exhaust gas flowing into the gas-conducting channel  26 . By this means, the exhaust-gas collector housing  9  is heated only insignificantly and therefore removes comparatively little heat from the exhaust gas, which has the effect that the catalytic converter, which is situated in the exhaust pipe  8 , has a better light-off performance and better efficiency on account of the relatively high exhaust-gas temperatures. Furthermore, this enables the exhaust-gas collector housing  9  to be produced from an inexpensive structural steel, if appropriate also from aluminized steel, since, as a rule, it does not come into contact with the exhaust gas. The sealing device  10  is mounted between the exhaust-gas collector housing  9  and the cylinder head  2 . 
     In all of the designs in which it occurs, the air gap  34  may also be filled with sound-insulating materials, such as rock wool, ceramic wool, knitted wire fabric or individual wire pieces which are pressed together, in order to obtain appropriate sound insulation. 
     FIG. 8 shows an embodiment of the exhaust manifold  1 , which approximately corresponds with the embodiment according to FIG.  6 . In contrast thereto, in FIG. 8 the flange  20 , which is of very similar design to the flange  20  according to FIG. 4, is provided below the bottom part  27  of the gas-conducting channel  26 . However, the bores  21  in said flange are of oval design, i.e. the diameter of the bores  21  is larger in the longitudinal direction of the flange  20  than the diameter of the bores  21  in the transverse direction of the flange  20 . This makes possible a displacement or expansion movement of the gas-conducting channel  26  within the bores  21  on account of thermal expansion caused by the exhaust-gas temperatures. On account of the exhaust-gas collector housing  9  being accommodated in the flange  20  in a similar manner to FIG. 4, the exhaust-gas collector housing  9  is not provided with the beading  17 , but merely has the collar  11 . 
     It can be seen in FIG. 9 that the sealing device  10   a  is again used between the flange  20  and the exhaust-gas collector housing  9  and the sealing device  10  is used between the exhaust-gas collector housing  9  and the cylinder head  2 . Here too, the retaining brackets  33  and the baffle plates  30  are provided as in FIG.  6  and FIG.  7 . 
     FIG. 10 illustrates a further exhaust manifold  1  which is of very similar design to the exhaust manifold  1  illustrated in FIG.  8 . The gas-conducting channel  26  is also provided here, but comprises a plurality of individual channels  35  which are designed in each case with connections  36  to the bores  21  in the flange  20 , which is also provided here. The bores  21  have a round cross section and the connections  36  are inserted into these bores  21  and optionally welded into place. As an alternative, other forms of the bores  21 , for example oval or rectangular, would also be possible in which case the connections  36  would then be adapted to these forms of the bores  21  and appropriate sealing would additionally be undertaken. 
     At their connecting points, the individual channels  35  are connected to one another by portions, which are provided at in each case one of the ends of the individual channels  35  and in which the next individual channel  35  is inserted and optionally welded. Situated in the exhaust-gas collector housing  9  are retaining rings  37  which bear against the latter and surround the gas-conducting channel  26 . The gas-conducting channel  26  is prevented from vibrating by the retaining rings  37 , which consist, for example, of a wire knitted fabric. 
     An outlet  38 , having an opening  31 , leads away from one of the individual channels  35  through the opening  7  in the exhaust-gas collector housing  9  to the exhaust pipe  8 , which is also fitted here to the exhaust-gas collector housing  9 . 
     In the section according to FIG. 11, it can be seen that, here too, the sealing device  10   a  is used between the exhaust-gas collector housing  9  and the flange  20  and the sealing device  10  is used between the flange  20  and the cylinder head  2 . Furthermore, as in the case of the embodiment according to FIGS. 6,  7 ,  8  and  9 , the air gap  34  is situated between the gas-conducting channel  26  and the exhaust-gas collector housing  9 . This gas-conducting channel  26  can also consist of a material which has high temperature stability and is permeable for exhaust gases. 
     FIG. 12 shows a further exhaust manifold  1  which likewise has a gas-conducting channel  26  in its interior. The gas-conducting channel  26  is provided, on its side facing the cylinder head  2 , with a circumferential collar  40 , which is arranged between the sealing device  10  on its lower side and an additional clamping element  41  on its upper side. The clamping element  41  partially overlaps the collar  40  and covers the latter on its entire circumference. In order to achieve tightness of the exhaust manifold  1 , the clamping element  41  is provided, on its side facing the exhaust-gas collector housing  9 , with a circumferential sealing layer  42 . 
     The fastening means  18  are, of course, also provided here and, with the aid of the clamping element  41 , clamp the gas-conducting channel  26  between the exhaust-gas collector housing  9  and the sealing device  10  or cylinder head  2  with the desired force. The construction mentioned prevents movement of the gas-conducting channel  26  perpendicularly with respect to the plane of the cylinder head  2 , but with appropriate tightening of the screws  18  movement of the gas-conducting channel  26 , triggered by the effect of heat, in the plane of the cylinder head  2  is still possible. 
     The gas-conducting channel  26  is provided with a circumferential collar  40  in the case of the exhaust manifold according to FIG. 13 too. However, said collar is clamped directly between the exhaust-gas collector housing  9  and the flange  20 , which is likewise provided in this case, again by means of the fastening means or screws  18 . In addition, a circumferential sealing device  43  is provided on the circumference of the collar  40 , specifically likewise between the exhaust-gas collector housing  9  and the flange  20 . By means of raised portions  44  protruding in the direction of the cylinder head  2  on the sealing device  43  and/or by an appropriate selection of the thickness of the sealing device  43  and corresponding tightening of the screws  18 , movement of the gas-conducting channel  26  in the plane of the cylinder head  2  is also possible here, it being possible at the same time to prevent undesirable vibrations of said channel.