Patent Publication Number: US-6213105-B1

Title: Device for exhaust recycling for an internal combustion engine and method of making same

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     This application claims the priority of German application 197 50 588.0, filed in Germany on Nov. 17, 1997, the disclosure of which is expressly incorporated by reference herein. 
     The invention relates to a device for exhaust recycling for an internal combustion engine with an exhaust cooler and with a valve that determines the quantity of recycled exhaust, controllable by an adjusting element. 
     Recycling of cooled exhaust to an internal combustion engine, especially for lowering diesel emissions, is known from ATZ Automobiltechnische Zeitschrift, Vol. 99 (1997), No. 9 (R. Lutz: “Lowering Diesel Emissions by Recycling Cooled Exhaust”). The exhaust recycling valve (AGR valve) and the exhaust cooler (exhaust heat-transfer device) are parts that are independent of one another, installed at different points in the vehicle, and connected with one another by an exhaust line. 
     A goal of the invention is to modify a device of the type recited at the outset so that a simplified method of manufacturing is obtained. 
     This goal is achieved by connecting the exhaust cooler and valve directly together so that they form a module. As a result, a simplified and hence less expensive method of manufacture can be performed since individual previously provided elements can be eliminated. In particular, the gas line between the valve and the exhaust cooler is eliminated, together with the connections required therefor. 
     In preferred embodiments of the invention, provision is made for the adjusting element to be mounted on a part that is in a heat-conducting relationship with the exhaust cooler. This has the advantage that a cooling effect is exerted on the adjusting element by the exhaust cooler, so that the adjusting element is subjected to less heat stress. 
     In another embodiment of the invention, provision is made such that the adjusting element is mounted on a part provided with one or more channels for a liquid coolant. This produces the advantage that the valve and especially its adjusting element are cooled actively. 
     Both embodiments allow the valve to be mounted on the exhaust supply side of the exhaust cooler. Mounting the valve on the supply side of the exhaust cooler, i.e. on the side at which the hot exhaust enters, has the advantage that there is a relatively small danger of residues from the exhaust adhering to the valve and its valve elements. This danger, which is even greater when the valve is located downstream from the exhaust cooler, means that adjusting elements with relatively high adjusting forces must be provided which can reliably overcome any jamming of the valve elements caused by deposits of exhaust residues. When it is mounted on the exhaust supply side, the danger of deposits composed of exhaust residues is much less. On the other hand, there is still the danger with this arrangement that the adjusting elements, especially electrical adjusting elements, will be subjected to excessive heat stress. This thermal overloading is offset by the fact that the adjusting element is mounted on a part whose temperature is significantly less than the temperature of the exhaust coming from the internal combustion engine. 
     In certain preferred embodiments of the invention, provision is made such that the channel or channels of the part that supports the positioning element is/are connected to a coolant supply to the exhaust cooler. Further simplification can be achieved in this manner, since no external connecting lines need be provided between the channels that serve for cooling of the part that supports the positioning element and the exhaust cooler. 
     In certain preferred embodiments of the invention, provision is made such that the exhaust cooler has an elongate form and that the adjusting element is arranged essentially parallel next to the exhaust cooler. This results in a compact design that can be accommodated relatively simply in a vehicle. 
     Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a module composed of an exhaust cooler and a valve that determines the volume of exhaust flowing through, constructed according to a preferred embodiment of the present invention; 
     FIG. 2 is a view taken in the direction of arrow II in FIG. 1; 
     FIG. 3 is a perspective view of a module composed of an exhaust cooler and a valve with active cooling of an adjusting element that belongs to the valve, constructed according to another embodiment of the present invention; and 
     FIG. 4 is a view taken in the direction of arrow IV in FIG.  3 . 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     The module shown in FIGS. 1 and 2 comprises an exhaust cooler  10  and a valve  11 , a so-called AGR valve. Valve  11  and exhaust cooler  10  are preferably arranged as shown in FIG. 2 of the reference cited at the outset, i.e. valve  11  is located on the exhaust supply side of exhaust cooler  10 . 
     Valve  11  is provided with a connecting flange  12  by which it can be connected to an exhaust line coming from an internal combustion engine. Inside the valve housing, in a manner not shown in greater detail, an adjustable valve element is provided that is associated with a valve seat. The valve determines the quantity of exhaust that flows into exhaust cooler  10 . The valve element is adjusted by means of an adjusting element  13 , especially an electromagnetic adjusting element. Depending on the engine data specified, valve  11  determines the quantity of exhaust to be mixed with fresh air supplied to the internal combustion engine. Adjusting element  13  can operate so that it performs two-point regulation or cross-section regulation. Valve  11  is provided with fastening means  14  enabling it to be fastened to a mount, for examine the engine block of the internal combustion engine. Valve  11  has a distribution chamber  15  that expands funnelwise, by means of which the exhaust is supplied to exhaust cooler  10 . 
     Exhaust cooler  10  is designed in principle in the same way as is known from the reference mentioned at the outset (ATZ Automobiltechnische Zeitschrift, Vol. 99 (1997), No. 9). At each of its ends, it has a bottom into which the ends of a plurality of rectangular tubes are inserted, said ends being located at a distance from one another. The tube bundle made of rectangular tubes is surrounded by a jacket  16  that forms reversing chambers  17 ,  18  at the two end areas. Chambers  17 ,  18  are provided with connections  19 ,  20  through which the coolant is supplied to the engine cooling circuit and removed therefrom. Preferably the coolant flows parallel to the exhaust in exhaust cooler  10  so that connection  19  is a supply connection and connection  20  is a recycling connection. 
     A collecting chamber  21  that tapers roughly in the shape of a funnel abuts the bottom that closes off chamber  18  and receives the ends of the tube bundle, said chamber making a transition to a flange  22  connected with an exhaust line that leads further. 
     The end of exhaust cooler  10  that faces valve  11  is provided with a flange  23  which preferably also forms the bottom for the tube bundle of the exhaust cooler. The housing of valve  11  is flanged to this flange  23 . Adjusting element  13  is fastened to flange  23  next to exhaust cooler  10 , said element being aligned essentially parallel to jacket  16  of the exhaust cooler. Flange  23  is made with relatively thick walls so that it forms a thermal barrier between the housing of valve  11  and adjusting element  13 . Flange  23 , which is also cooled by the coolant flowing through exhaust cooler  10 , has a much lower temperature than the valve housing of valve  11 , so that adjusting element  13  is isolated thermally from valve  11  and accordingly is subjected only to a relatively low heat stress. 
     The module of the embodiment in FIGS. 3 and 4, likewise composed of an exhaust cooler  10  and a valve  11 , corresponds in theoretical design and theoretical arrangement to the embodiment in FIGS. 1 and 2. Unless otherwise explained, the similarly numbered parts of the embodiment of FIGS. 3 and 4 operate as described for the FIGS. 1 and 2 embodiment. Exhaust cooler  10  however is provided with a thicker flange  24  (as compared to flange  23  of FIGS. 1 and 2) that is provided in a manner not shown in greater detail with channels that lead from a supply connection  25  to chamber  17  of jacket  16 , through which channels the coolant of the internal combustion engine is guided to chamber  17  of exhaust cooler  10 . Flange  24  is therefore cooled actively, so that even better thermal isolation is obtained between valve  11  and adjusting element  13 . 
     In the embodiments according to FIGS. 1,  2  and  3 ,  4 , an electromagnetic adjusting element  13  is provided in each case, said element being equipped with a connecting plug  26  for the power supply. In modified embodiments, other adjusting elements are provided, for example pneumatic adjusting elements that perform the same function. These adjusting elements are likewise then isolated thermally to a significant degree from the valve so that they are exposed to only a relatively low temperature stress. 
     The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.