Abstract:
A device for exhaust gas recirculation for a combustion engine is provided that includes an exhaust gas pipe configured to conduct exhaust gas and a channel configured to conduct air to the combustion engine. The exhaust gas pipe terminates in the channel, wherein the exhaust gas pipe, in an area of insertion in the channel exhaust, is in thermal exchange with a coolant from a coolant circuit.

Description:
This nonprovisional application claims priority under 35 U.S.C. §119(a) to European Patent Application No. EP 09290103.2 which was filed on Feb. 12, 2009, and which is herein incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a device for exhaust gas recirculation for a combustion engine. 
     2. Description of the Background Art 
     The recirculation of exhaust gas of a combustion engine, for example in order to reduce pollutants, is known for commercial vehicles as well as passenger cars. As demands for low amounts of pollutants are rising, increasing recirculation rates become necessary, e.g. up to more than 30%. Even though measures like exhaust gas coolers are provided, the recirculated exhaust gas can have very high temperatures depending on the recirculation rate and the operating condition. It is known to provide the insertion of the recirculated exhaust gas into a plenum area (intake manifold) formed of metal. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to provide a device for exhaust gas recirculation for a combustion engine, by which a large stream of hot exhaust gas can be inserted into the combustion air in a simple manner. 
     By means of a thermal exchange with a coolant, an overheating of the insertion area of the exhaust gas into the air-ducting channel is avoided. Thereby, surrounding parts can be laid out less critical and a higher safety for cases of extreme operating conditions and in cases of malfunction, e.g. of exhaust gas coolers or an exhaust gas control, is achieved. A coolant in the sense of the invention can be understood as any suitable fluid circuit of the combustion engine or even of a vehicle in general, like for instance the engine-coolant circuit, a separate low-temperature circuit or even the refrigeration circuit of an air conditioning system. The coolant can be a liquid, but can also be gaseous or be present in multiple phases. 
     In an embodiment of the invention, the exhaust gas pipe can be connectable to an assembly member, which can be formed of metal, wherein the coolant flows through a coolant channel provided at the assembly member. Thereby the assembly member can be cooled, thus making it possible to provide the assembly member at structures which are not heat-resistant. Examples for such structures are, for example, an air-conducting channel made from plastics or even a charge air cooler made from aluminum. Examples of an assembly member can be a plate, a formed sheet metal part, a part formed by milling or any other suitable part, in particular made from Aluminum or from steel, which is laid out, on the one hand, to receive the exhaust gas pipe and, on the other hand, to be fixed to the air-ducting channel. The respective way of fixing is at will according to the respective demands, e.g. by bonding (soldering, welding, gluing etc.), using fixation means like screws, nails, bolts, clips etc. or in any other way. 
     For the purpose of simple fixing, in an embodiment, the exhaust gas pipe has a flange which can be connected to the assembly member. Thereby, a particularly detachable connection, e.g. by means of screwing down of the flange, is possible. In this respect, it may be provided in a further embodiment that the coolant channel also flows around the screws or a fixation component, as these constitute heat bridges. Further, a seal can be arranged between the flange and the assembly member. Thereby, not only providing a sealing between the exhaust gas pipe and outside area, but also as an additional insulation against a heat transfer from the hot exhaust gas pipe to the assembly member. The coolant channel can be arranged on a side of the assembly member which is opposite to flange, but may even be arranged on the same side according to respective demands. 
     In another embodiment of the invention, the coolant channel is provided as a tube which is connectable to the assembly member, for example, by bonding. Such tube may have a cornered or round cross section. The connection of the coolant channel with a cooling circuit may then, for instance, take place by simple plugging of hoses onto free ends of the tube. 
     In an another embodiment, the coolant channel may also be provided as a sheet metal part, either one-piece or multipart, which is connectable with the assembly member, for example, by bonding. 
     In an embodiment of the invention, the insertion area of the exhaust gas pipe can be provided at a charge air cooler which is passed through by the coolant. Thereby the exhaust gas can enter the charged air in the region of the cooler, hence a good swirling and, simultaneously, a further cooling of the exhaust gas, or rather a better use of the charge air cooler, being achieved. In an embodiment, in order to simplify the construction, the insertion area can be provided at a coolant-sided header member of the charge air cooler. With a suitable design of the header member, a sufficient cooling of the insertion area can already be achieved in this way by means of the coolant streams in the header. According to the respective demands, an additional coolant pipe may also be provided for the cooling of the exhaust gas pipe. 
     In another embodiment, the exhaust gas pipe enters into the channel upstream of a charge air cooler. Particularly in this region, conventional air-ducting channels are made from plastics in order to save costs and weight, which has been opposing to an insertion of hot exhaust gas up to now. Generally it is further advantageous, that with an insertion upstream of the charge air cooler, an optimum mixing and further cooling of the mixture of exhaust gas and charged air within the charge air cooler results. 
     Generally, in order to save costs and weight, it is provided and made possible by the invention that the channel can be made of plastics at least in a region of insertion of the exhaust gas pipe. 
     By way of designing the exhaust gas pipe in a region of its insertion into the channel as at least one tube section, the tube section having a plurality of outlet openings for the exhaust gas along the tube section, a distribution of the exhaust gas stream into multiple partial streams over a large area of space is achieved. Thereby, an excessive local heating, e.g. of a wall of the channel, is avoided and furthermore the mixing of exhaust gas and air is improved. 
     In an embodiment, the exhaust gas pipe branches into a number of tube sections in the region of its insertion, a particularly homogenous distribution of the exhaust gas is thereby achieved. On the other hand, only a single tube section for the injection of the exhaust gas into the air can be provided on behalf of a simple construction. 
     In another embodiment of the invention, the outlet openings can be, with respect to number and/or size, distributed alongside the tube section in a way that a hydraulic outflow width per length of the tube section increases in the flow direction of the exhaust gas. Thereby a pressure decrease over the length of the tube section is taken into account, the emerging mass flow of the exhaust gas being distributable according to the demands, and in particular homogenously, over the length of the tube section. 
     As a supplementary or alternative measure, flow obstacles are arranged at at least some of the outlet openings, a swirl being achievable and/or a preferred outflow direction being provided. Thereby, a harmful heat transfer, e.g. into the walls of the channel, can be further avoided. 
     For optimizing the distribution of the exhaust gas in the air stream which is flowing through the channel, and hence for the purpose of homogenizing the temperature or avoiding of temperature peaks, it may be provided that the outlet openings are, at least predominantly, aligned at an outlet angle of between 45° and 135°, in particular between 90° and 135°, with respect to a main flow direction of the air in the channel. 
     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 cross section through a first exemplary embodiment of the invention; 
         FIG. 2  shows a plain view of an assembly member of the example of  FIG. 1 ; 
         FIG. 3  shows a lateral and surfacing plain view of an exhaust gas pipe of the example of  FIG. 1 ; 
         FIG. 4  shows a sectional view of a second embodiment of the invention; 
         FIG. 5  shows a sectional view of a third embodiment of the invention; 
         FIG. 6  shows a plain view of the example of  FIG. 5 ; 
         FIG. 7  shows a sectional view of a fourth embodiment of the invention; 
         FIG. 7   a  shows a variation of the fourth embodiment; 
         FIG. 8  shows a plain view of a fifth embodiment of the invention; 
         FIG. 9  shows a plain view of a sixth embodiment of the invention; 
         FIG. 10  shows the embodiment of  FIG. 9  with inserted exhaust gas pipe; 
         FIG. 11  shows a sectional view through a seventh embodiment of the invention; 
         FIG. 12  shows a sectional view through an eighth embodiment of the invention; 
         FIG. 13  shows a sectional view through a ninth embodiment of the invention; 
         FIG. 14  shows a sectional view through a tenth embodiment of the invention; 
         FIG. 15  shows four sectional views and partial plain views in several plains of the embodiment of  FIG. 14 ; and 
         FIG. 16  shows different outlet angles of an eleventh embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     A device for recirculation of exhaust gas according to a first embodiment of the invention ( FIG. 1 ) comprises an assembly member  2  that is formed as an open-worked aluminum plate, the assembly member is fixed above a lateral opening of a channel  1  which is conducting compressed combustion air. The fixation at the channel may be established at will, e.g. by means of gluing, positive fitting and/or screwing. 
     The assembly member has a central opening  2   a , an exhaust gas pipe  3  made from a temperature-resistant material, such as stainless steel, being inserted in the opening such that the exhaust gas (dashed arrow) flows into the channel in order to mix with the combustion air (solid arrows). The position of the injection into the channel  1  is located upstream of a charge air cooler. 
     A flange  4  is provided on the exhaust gas pipe  3 , the assembly member  2  and the exhaust gas pipe  3  being connected to each other in a sealed manner by means of the flange. For this purpose, a seal  5  is located between flange  4  and assembly member  2 . The flange  4  can be detachably fixed by, for example, screws (not shown) which protrude through corresponding screw apertures  4   a ,  2   b  of the flange and the assembly member. 
     A coolant channel  6 , which substantially or partially surrounds the central opening  2   a , is provided at the assembly member in order to cool it. The coolant channel  6  is located at an opposite side of the flange  4  and is configured as a round tube. The coolant channel  6 , can be, for example, made from aluminum and can be soldered to the plate  2  in aerial contact. Its connection (not shown) to a cooling circuit may be provided by simple plugging of hoses onto its ends  6   a . The cooling circuit may, for instance, be the cooling circuit of the combustion engine or even a separate or connected low-temperature-circuit. 
     It is obvious from the drawings that the coolant channel  6  can be entirely arranged at the assembly member  2 . This is true for all of the embodiments with a coolant channel  6  described hereinafter. In this respect, no gasket is provided between the coolant channel on one side and channels for air and/or exhaust gas on the other side, which makes a hazardous break-in of coolant into the combustion gas of the engine impossible because the coolant channel  6  is completely separated from the channel and the exhaust pipe. 
     The invention works as follows: 
     During operation of the combustion engine, an adjustable portion of the exhaust gas is branched off and, if applicable after cooling in an exhaust gas cooler (not shown), is fed into the compressed combustion air in the channel  1  through the exhaust gas pipe  3 . In doing so, the exhaust gas pipe can heat up to a high temperature of several hundred ° C. A damaging of the material of the channel  1  is avoided by the fact that the exhaust gas pipe, in the region of its insertion, transfers heat to the coolant in the coolant channel  6 , the assembly member  2  at any time having an uncritical temperature at least in the region of its contact with the channel  1 . By means of the seal  5 , an additional insulation between assembly member  2  and exhaust gas pipe  3  is provided. 
     Second Embodiment ( FIG. 4 ) 
     As distinguished from the embodiment of  FIG. 1 , the tube of the coolant channel  6  can have a rectangular cross section, a particularly large contact area between coolant channel  6  and assembly member  2  being thereby available. 
     Third Embodiment ( FIG. 5 ) 
     As distinguished from the first two embodiments, the coolant channel  6  now is built from a formed sheet metal part  6   b  which is open towards the assembly member, the assembly member  2  forming a part of the wall of the coolant channel  6 . 
     The formed part  6   b  is connected to the assembly member  6  in aerial contact, whereby for instance at least one of the parts may be formed from a sheet cladded with brazing material.  FIG. 6  shows, in an exemplary way, the course which the formed sheet metal part  6   b  may provide for the coolant channel  6 . Furthermore, ports  6   a  for the coolant circuit are arranged at the formed sheet metal part  6   b.    
     Fourth Embodiment ( FIG. 7 ,  FIG. 7   a ) 
     As distinguished from the third embodiment, coolant channel  6  and flange  4  are located on the same side of the assembly member  2 . In this case, the flange  4  sits, with its seal  5 , directly on the formed metal sheet part  6   b , a particularly good and actively cooled insulation between flange  4  and assembly member  2  being provided. In  FIG. 7   a  the possibility is shown that the formed metal sheet part may well be constructed from several segments  6   b ,  6   c.    
     Fifth Embodiment ( FIG. 8 ) 
     As distinguished from the third embodiment (see  FIG. 6 , for instance), here the coolant channel is formed such that it also envelopes the fixation screws  2   b . Thereby, also these heat bridges are actively cooled. 
     Sixth Embodiment ( FIG. 9 ,  FIG. 10 ) 
     In the sixth embodiment, the device according to the invention is provided as a structural unit with an indirect and/or coolant-operated charge air cooler  7 , which has flat tubes  9 , the tubes being circulated around by air and passed through by coolant, the charge air cooler being in close proximity to the exhaust gas pipe. In this case, a bottom  8  of the charge air cooler  7  is enlarged or designed in such way that it comprises an opening  8   a  for the exhaust gas pipe  3 . Additionally, a header cap  10  or water tank of the charge air cooler is formed correspondingly. It may be provided to combine the header cap  10  or water tank of the charge air cooler and a coolant channel  6  in a formed sheet metal part, which for instance may be deep drawn. According to the respective form, a coolant channel  6  is not necessarily provided in the case of this embodiment, as an active cooling of the exhaust gas pipe  3  is already provided because of the feeding through the header. Anyway, a coolant channel  6  with a port  6   a  is noticeably formed in the present drawings  FIG. 9 ,  FIG. 10 , the port  6   a  simultaneously being a connection of the charge air cooler with the coolant circuit. 
     Seventh Embodiment ( FIG. 11 ) 
       FIG. 11  shows an embodiment similar to the example from  FIG. 9 ,  FIG. 10 , with the exhaust gas pipe ending directly into a charge air cooler. A flange  4  of the exhaust gas pipe  3  sits on a header tank  10  in a sealing manner, the header tank  10  surrounding a recess  11  which is passed through by the exhaust gas pipe and which is not passed by the coolant. In this embodiment, the header tank as a whole is defined as a coolant channel for the exhaust gas pipe. 
     Furthermore, the exhaust gas pipe  3 , which protrudes into the charge air cooler  7 , is formed as a tube section  12  with a plurality of radially oriented outlet openings  13  for the exhaust gas. Thereby, the exhaust gas is distributed on several small partial streams, hence avoiding a local overheating of parts of the charge air cooler  7 . Basically, such tube section  12  may, even under retaining the mentioned advantages, end into a simple channel  1 ; see for example the first embodiment. 
     In the present case, the tube section  12  is closed at its end, the tube section being accommodated with its closed end in a sealing  14  in an aperture of a bottom  8 ′, which is positioned opposite to the bottom  8  of the insertion side. According to the respective construction, the tube section may, of course, alternatively protrude freely into the charge air cooler  7 . 
     Eighth Embodiment ( FIG. 12 ) 
     As distinguished from the seventh embodiment, in the case of the eighth embodiment a branching of the exhaust gas tube into several, presently three, tube sections  12  is given, a still further distribution of the effusion of the exhaust gas being achieved. The branching is placed inside the charge air cooler behind the recess  11  and/or the bottom  8  of the insertion side. 
     Ninth Embodiment ( FIG. 13 ) 
     This embodiment refers to a development of an exhaust gas pipe  3  with a tube section  12  like in the example of  FIG. 11 . Presently, the outlet openings  13  are provided over the extension of the tube section  12  with increasing spatial density (see top cutting edge of the tube section  12 ) and/or with increasing sectional area in the case of a constant distance (see bottom cutting edge of the tube section  12 ). In each case it is achieved that a hydraulic outflow width per length unit of the tube section  12  is increasing in the flow direction, hence the pressure loss caused by the outflow being compensated. Altogether, a more homogenous mass flow of the effusing exhaust gas over the length of the tube section  12  is achieved. 
     Tenth Embodiment ( FIG. 14 ,  FIG. 15 ) 
     As a further possibility to influence the exhaust gas effusion, in the example of  FIG. 14  flow obstacles  15  are arranged over at least some of the outlet openings  13 . The flow obstacles  15  are presently formed as slide-on sheet metal rings, which, at the positions of the overlay with the outlet openings  13 , comprise flaps which are of defined dimension and set up. Depending on the position at the tube section  12 , the flaps or flow obstacles are differently shaped and/or set up. For reasons of clarity,  FIG. 15  displays four sectional views through the four sheet metal rings shown in  FIG. 14 , as well as a respective partial plain view on the flaps. 
     Eleventh Embodiment of the Invention ( FIG. 16 ) 
     In  FIG. 16 , streams of charged air (solid lines) as well as exhaust gas (dashed lines) which effuses from a tube section  12  are displayed, the outlet openings being aligned, in each case, in different angles with respect to the symmetry plane or main flow direction of the charged air. 
     It becomes obvious that in the case of too small angles (e.g. 0°) as well as too big angles (e.g. 180°), a relatively compact exhaust gas plume is formed. This means a relatively poor mixing and the danger of a local overheating of parts of the air channel and/or charge air cooler. 
     Hence, an angle of the outlet openings  13  with respect to the geometrical flow direction of the charged air (i.e. horizontally from right to left in the drawings) is selected between 45° and 135°, preferredly between 90° and 135°. 
     It is to be understood that any individual features of the embodiments described above can be combined in a reasonable manner according to the respective demands. In particular the provision of a tube section  12  with a number of outlet openings  13  and its respective detailed embodiments can be combined with any of the other embodiments. In a possible embodiment of the invention it is not necessarily provided that the exhaust gas pipe  3  with the tube section  12  is cooled by means of a coolant. A more homogenous distribution of the hot exhaust gas over a larger space area can be achieved by means of the tube section  12  itself, a critical heat exposure of e.g. a channel wall being avoided. 
     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. For example, one skilled in the art can combine any of the features illustrated with one another that are described in the specification and/or in the drawings.