Abstract:
An exhaust gas recirculation system is provided that includes an internal combustion engine, which is supplied with exhaust gas, diverted at a removal point and returned via a return point and/or charge air, having a heat exchanger arranged between the removal point and the return point, for the returned exhaust gas and/or the charge air, and having an exhaust gas recirculation valve, by means of which the amount of returned exhaust gas and/or charge air can be regulated. To provide an exhaust gas recirculation system, which has a simple structure and can be manufactured cost-effectively, the exhaust gas recirculation valve is connectable between the removal point and the heat exchanger.

Description:
This nonprovisional application claims priority under 35 U.S.C. §119(a) to European Patent Application No. EP 09290726.0, which was filed on Sep. 25, 2009, and which is herein incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an exhaust gas recirculation system having an internal combustion engine, which is supplied with exhaust gas, diverted at a removal point and returned via a return point, and/or charge air, having a heat exchanger, arranged between the removal point and the return point, for the returned exhaust gas and/or the charge air, and having an exhaust gas recirculation valve, by means of which the amount of returned exhaust gas and/or charge air can be regulated. 
     2. Description of the Background Art 
     An exhaust gas recirculation line with a heat exchanger is known from the DE 698 17 294 T2 of the European Pat. App. No. EP 0 913 561 B1, which corresponds to U.S. Pat. No. 6,155,042, which is arranged between an engine and a catalyst container in series with restriction component for generating back pressure, whereby the heat exchanger flow is upstream of the restriction component. In the exhaust gas recirculation line, an exhaust gas recirculation valve is connected downstream of the heat exchanger. A throttle plate is connected parallel to the heat exchanger. An exhaust gas line for an internal combustion engine with a circulation line is known from the German patent publication No. DE 103 92 766 T5, which is connected directly or indirectly to an exhaust gas channel, for recycling a fraction of the exhaust gases. To cool the recycled fraction of the exhaust gases, a heat exchanger is connected between an exhaust gas catalyst container and a catalytic element. An exhaust gas system for a heat engine with a waste heat recovery region for recovering heat from the exhaust gas and transferring the recovered heat to a heating medium, which is arranged in the exhaust gas line, is known from the unexamined German Pat. App. No. DE 102 59 702 A1. To burn fuel, a burner, which is also called a combustor, is provided in the exhaust gas line. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an exhaust gas recirculation system, which has a simple structure and can be manufactured cost-effectively. 
     The object in the case of an exhaust gas recirculation system having an internal combustion engine, which is supplied with exhaust gas, diverted at a removal point and returned via a return point, and/or charge air, having a heat exchanger, arranged between the removal point and the return point, for the returned exhaust gas and/or the charge air, and having an exhaust gas recirculation valve, by means of which the amount of returned exhaust gas and/or charge air can be regulated, is achieved in that the exhaust gas recirculation valve is connected between the removal point and the heat exchanger. All of the exhaust gas diverted at the removal point or all of the charge air diverted there is taken via the exhaust gas recirculation valve for heat exchange by the heat exchanger. 
     An exemplary embodiment of the exhaust gas recirculation system is characterized in that the heat exchanger is assigned a diverter valve through which the exhaust gas, diverted at the removal point and emerging from the heat exchanger, and/or the charge air are returned via the return point or removed via a branch line. The exhaust gas and/or the charge air diverted at the removal point, at least partially, together with the exhaust gas not diverted at the removal point can be discharged into the environment via the diverter valve by means of an exhaust system, which optionally comprises a catalytic device. 
     Another exemplary embodiment of the exhaust gas recirculation system is characterized in that the exhaust gas, diverted at the removal point and emerging from heat exchanger, and/or charge air are returned by the diverter valve totally or partially via the return point or discharged via the branch line. The heat exchanger can be used in one regard in a warm-up phase of the internal combustion engine to cool the exhaust gas diverted at the removal point for heat recovery. Moreover, the heat exchanger can be used to cool the exhaust gas returned to the return point to recover heat. 
     Another exemplary embodiment of the exhaust gas recirculation system is characterized in that the diverter valve is integrated into the heat exchanger. Alternatively or in addition, the exhaust gas recirculation valve can be integrated into the heat exchanger. 
     Another exemplary embodiment of the exhaust gas recirculation system is characterized in that the diverter valve is provided at the outlet of the heat exchanger. It is achieved thereby in a simple manner that all of the exhaust gas diverted at the removal point is first subjected to a heat exchange. 
     Another exemplary embodiment of the exhaust gas recirculation system is characterized in that the exhaust gas diverted at the removal point and/or the charge air can flow or do flow through the heat exchanger only in one direction. A heat exchanger of this type is also called an I-flow heat exchanger. 
     Another exemplary embodiment of the exhaust gas recirculation system is characterized in that the branch line and a return line are connected to one end of the heat exchanger. The other end of the two ends of the heat exchanger is preferably linked to the removal point for the exhaust gas and/or the charge air. 
     Another exemplary embodiment of the exhaust gas recirculation system is characterized in that the exhaust gas diverted at the removal point and/or the charge air can flow or do flow through the heat exchanger in opposite directions. A heat exchanger of this type is also called a U-flow heat exchanger. 
     Another exemplary embodiment of the exhaust gas recirculation system is characterized in that the branch line is connected to one end of the heat exchanger, which is linked to the removal point for the exhaust gas and/or the charge air. It is achieved thereby that the exhaust gas, diverted at the removal point and not returned to the return point, flows through the heat exchanger multiple times. The heat recovery can be improved further thereby. 
     Another exemplary embodiment of the exhaust gas recirculation system is characterized in that a return line is connected to the other end of the two ends of the heat exchanger. A filter can be arranged in the return line. 
     Another exemplary embodiment of the exhaust gas recirculation system is characterized in that a back pressure valve is connected downstream of the removal point. The back pressure valve is used to build up back pressure at the removal point. As a result, the temperature of the exhaust gas can be increased and the heat recovery improved. 
     Another exemplary embodiment of the exhaust gas recirculation system is characterized in that an additional removal point, which can be connected via another exhaust gas recirculation valve to another return point, which is provided between the return point and the internal combustion engine, is provided between the internal combustion engine and the removal point. An uncooled recirculation of the exhaust gas is made possible thereby in a simple manner. 
     Another exemplary embodiment of the exhaust gas recirculation system is characterized in that between the return point and the internal combustion engine a compressor for the exhaust gas and/or the charge air is provided, which is driven by a turbine, which is provided between the internal combustion engine and the removal point. The additional removal point is preferably provided between the internal combustion engine and the turbine. The additional return point is preferably provided between the compressor and the internal combustion engine. 
     Another exemplary embodiment of the exhaust gas recirculation system is characterized in that a charge air cooler is connected between the compressor and the internal combustion engine. The additional return point is preferably provided between the charge air cooler and the internal combustion engine. 
     Another exemplary embodiment of the exhaust gas recirculation system is characterized in that a diesel particle filter is connected downstream of the turbine. The diesel particle filter is preferably connected between the turbine and the removal point. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein: 
         FIG. 1  shows a simplified illustration of an exhaust gas recirculation system of the invention with an internal combustion engine and a heat exchanger; 
         FIG. 2  shows the heat exchanger of  FIG. 1  in an I-flow design in an exhaust gas recirculation mode; 
         FIG. 3  shows the heat exchanger of  FIG. 2  in a heat recovery mode; 
         FIG. 4  shows the heat exchanger of  FIG. 1  in a U-flow design in the heat recovery mode; and 
         FIG. 5  shows the heat exchanger of  FIG. 4  in the exhaust gas recirculation mode. 
     
    
    
     DETAILED DESCRIPTION 
     An exhaust gas recirculation system  1  in the form of a simplified fluid circuit diagram is shown in  FIG. 1 . A fluid, particularly air or a fuel/air mixture, is supplied in exhaust gas recirculation system  1  in a known manner at a point  2 . The fluid is preferably supplied via a compressor  4  and optionally a charge air cooler  5  to an internal combustion engine  6 , which is also called a combustion engine. A turbine  7 , which is used, as indicated by a dashed double arrow  8 , to drive compressor  4 , is connected downstream of internal combustion engine  6 . A diesel particle filter  9 , for example, is connected downstream of turbine  7 . 
     The performance of internal combustion engine  1  depends on the cubic capacity, rotational speed, and the average fluid pressure, particularly gas pressure. The filling of the combustion chambers can be improved considerably by charging of the internal combustion engine  6  and the engine performance increased thereby. The fluid or fuel/air mixture or the air is precompressed totally or partially outside the cylinder of the internal combustion engine. In an engine with an exhaust turbocharger, the exhaust gases drive the turbine and the turbine drives the compressor. The compressor takes over the intake and supplies the engine with a precompressed fresh gas charge. Charge air cooler  5  in the charge line dissipates the compression heat into the ambient air. As a result, the cylinder filling is improved further. 
     The exhaust gas released by the internal combustion engine is diverted at a first removal point  11  and a second removal point  12 . The exhaust gas diverted at the first removal point  11  can be returned cooled via a first return line  13 , in which a first exhaust gas recirculation valve  14  is arranged. The exhaust gas diverted at the second removal point  12  can be returned uncooled via a second return line  16 , in which a second exhaust gas recirculation valve  17  is arranged. 
     For cooling the exhaust gas diverted at first removal point  11 , a heat exchanger  18  is connected downstream of the first exhaust gas recirculation valve  14 . The exhaust gas diverted at first removal point  11  and cooled in heat exchanger  18  can be supplied again to internal combustion engine  6  via a heat exchanger return line  20  and via a first return point  21 . The exhaust gas diverted at second removal point  12  can be returned again uncooled to internal combustion engine  6  via the second exhaust gas recirculation valve  17  via a second return point  22 . 
     First removal point  11  is connected between diesel particle filter  9  and a back pressure valve  24 , which serves to build up back pressure when needed at first removal point  11 . Second removal point  12  is arranged between internal combustion engine  6  and turbine  7 . First return point  21  is arranged between point  2  and compressor  4 . Second return point  22  is arranged between charge air cooler  5  and internal combustion engine  6 . A third return point  23  is connected downstream of back pressure valve  24 . An arrow  25  indicates that the exhaust gas of internal combustion engine  6  is supplied to a preferably sound-absorbing exhaust system, which can comprise a catalytic device. 
     The exhaust gas recirculation is used to cool the exhaust gas as much as possible. The returned exhaust gas no longer participates in the combustion in the internal combustion engine but heats up. Overall, the temperature in the internal combustion engine or the engine is reduced by the returned exhaust gas. The formation of nitrous oxides, which are highly dependent on the temperature in the engine, can be reduced by lower temperatures in the engine. A filter  26  can be arranged in the heat exchanger return line  20 . 
     Heat exchanger  18  according to an essential aspect of the invention comprises a diverter valve  28 , which is connected downstream of the first exhaust gas recirculation valve  14 . Diverter valve  28  makes sure that both the exhaust gas diverted at first removal point  11  and returned via heat exchanger return line  20  and the exhaust gas diverted at first removal point  11  and diverted via a heat exchanger branch line  19  for the purpose of heat exchange first flows through a heat exchanger block  29  of heat exchanger  18 , as indicated by an arrow  30 . 
     Heat exchanger  18  can be operated in two different modes. In an exhaust gas recirculation cooling mode, heat exchanger  18  operates preferably as an I-flow heat exchanger, to lower the temperature of the gas flow of the returned exhaust gas. In a heat recovery mode, the gas flow diverted from the returned exhaust gas is used to heat the coolant passed through the heat exchanger, particularly in a warm-up phase of the internal combustion engine. Diverter valve  28  of the invention enables in a simple manner the illustration of the two modes with only one heat exchanger. 
     It is shown in  FIGS. 2 and 3  that heat exchanger  18  of  FIG. 1  can be made as a one-way flow-through heat exchanger  40 , which is also called an I-flow heat exchanger. Heat exchanger  40  comprises a one-way flow-through heat exchanger block  42  with a header box  43  at one end. Header box  43  has an inlet connection  44 , through which, as indicated by an arrow  45 , exhaust gas diverted at removal point  11  enters header box  43 . At the other end of heat exchanger block  42 , a header box  46  is provided into which a diverter valve  48  with a valve flap  49  is integrated. Header box  46  has two outlet connections  51 ,  52 , through which the exhaust gas flow passed through heat exchanger block  42  emerges depending on the position of valve flap  49  of diverter valve  48 . 
     In  FIG. 2 , valve flap  49  of diverter valve  48  blocks outlet connection  52 , so that, as indicated by arrow  53  and  54 , the entire volume flow passed through heat exchanger block  42  emerges from outlet connection  51 , to which heat exchanger return line  20  is preferably connected. In the mode shown in  FIG. 2 , no gas emerges from outlet connection  52 , as indicated by a dashed arrow  55 . Heat exchanger branch line  19  is preferably connected to outlet connection  52 . The first return line  13  is preferably connected to inlet connection  44 . 
     In  FIG. 3 , valve flap  49  of diverter valve  48  is in its second extreme position in which, as indicated by arrows  56  and  57 , all of the exhaust gas flow passed through heat exchanger block  42  emerges through outlet connection  52 . A dashed arrow  58  indicates that in this position of valve flap  49 , no exhaust gas emerges from outlet connection  51 . 
     Shown in simplified form in  FIGS. 4 and 5  is a heat exchanger  60  with at least one partition wall, which is indicated by a dashed line  61  and divides a heat exchanger block  62  so that it can be flown through in a U-shaped manner in opposite directions. Heat exchanger  60  at one end of heat exchanger block  62  comprises a header box  63  with an inlet connection  64  and an outlet connection  65 , as indicated by arrows. At the other end of heat exchanger block  62 , a header box  66  is provided, into which a diverter valve  68  with a valve flap  69  is integrated. Header box  66  comprises another outlet connection  72  through which, depending on the position of valve flap  69  of diverter valve  68 , exhaust gas does or does not exit. 
     In  FIG. 4 , valve flap  69  of diverter valve  68  closes the additional outlet connection  72 , so that, as indicated by arrows  73 ,  74 , and  75 , the flow passes through heat exchanger block  62  in a U-shaped manner. No exhaust gas exits through outlet connection  72 , as indicated by a dashed arrow  76 . 
     The first return line  13  is preferably connected to inlet connection  64 . Heat exchanger branch line  19  is connected to outlet connection  65 . Heat exchanger return line  20  is connected to the additional outlet connection  72 . 
     In  FIG. 5 , valve flap  69  of diverter valve  68  is in a middle position in which the U-shaped flow, indicated in  FIG. 4  of heat exchanger block  62 , is interrupted. Arrows  77 ,  78 ,  79 , and  80  in  FIG. 5  indicate that the exhaust gas flow entering through inlet connection  64  flows one-way through heat exchanger block  62  in an I-shaped manner and again leaves completely through outlet connection  72 . A dashed arrow  81  in  FIG. 5  indicates that in this position of valve flap  69  of diverter valve  68 , no exhaust gas emerges from outlet connection  65 . 
     Of course, in addition to the extreme positions shown in  FIGS. 2 to 5  of valve flap  49 ;  69  of diverter valve  48 ;  68 , intermediate positions are possible in which in each case only a fraction of the exhaust gas flow supplied through the first return line  13  reaches the heat exchanger return line  20  or heat exchanger branch line  19 . 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.