Abstract:
A heat exchanger, particularly for charge air or exhaust gas, performs heat exchange between a first fluid and a second fluid, and includes heat exchanging guides for the first and second fluids, the guides being separated from each other in a core, the core having a plurality of flow channels through which the first fluid flows, and a housing that receives the flow channels and through which the second fluid flows. The heat exchanger also includes at least one compartment lid, which is flow-connected to the flow channels, and a base that is attached to the compartment lid and that is equipped with one or more passage openings for flow channels. The compartment lid is attached to the base via one or more connections which connections are bolted connections and/or a slotted crimping.

Description:
This nonprovisional application is a continuation of International Application No. PCT/EP2008/002904, which was filed on Apr. 11, 2008, and which claims priority to German Patent Application Nos. DE 102007017330, DE 102007029300, and DE 102008014163, which were filed in Germany on Apr. 11, 2007, Jun. 22, 2007, and Mar. 14, 2008, respectively, and which are all herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a heat exchanger for heat exchange between a first fluid and a second fluid, the heat exchanger includes a core for guidance of the first and second fluid separately from one another and in a heat-exchanging manner, which core has a number of flow channels that can be flowed through by the first fluid and a housing accommodating the flow channels, which housing can be flowed through by the second fluid; at least one case cover that is flow-connected to the flow channels; and a base, which is fixed to the cover and is provided with one or more through openings for flow channels. The invention further relates to a use of the heat exchanger. 
     2. Description of the Background Art 
     With a known heat exchanger, a case cover can be formed from deep-drawn sheet metal, which is soldered to the core during the production process. Although this has advantages in the high-temperature range, attachment elements such as, e.g., holders or flanges for sensors must be produced as additional parts from sheet metal and connected to the case cover before the soldering, which makes the production process more complicated. Furthermore, a more complex case shape can generally no longer be produced as a deep-drawn part, so that in this case a casting production must be carried out and the case cover must generally be welded to the core. This type of case has proven to be comparatively expensive and complex to produce, particularly with more complex designs. 
     A more cost-effective alternative to heat exchangers of this type is a heat exchanger of the type mentioned at the outset, in which the case has a case cover of plastic. Here comparatively complex designs can be realized, wherein higher temperature ranges can definitely be realized with corresponding plastic materials and a corresponding design of the case. Examples of case covers of plastic are given in DE 10 2004 051 207 A1 and DE 10 2004 047 901 A1, which corresponds to U.S. Publication No. 20070175612, and which are all herein incorporated by reference. 
     There are fundamentally different ways of attaching a plastic case cover to the heat exchanger, thus, for example, attachments such as are shown in WO 2004/09457, FIG. 2 or DE 199 53 785 A1, FIG. 4, which is also herein incorporated by reference. 
     DE 10 2005 012 761 A1 discloses a heat exchanger mentioned at the outset with a housing of two side parts and two housing covers, wherein the side parts are soldered to the core and the housing covers are welded to the side parts. Furthermore, collecting boxes of plastic are mechanically connected to tube sheets with the interposition of a seal. The mechanical connection is carried out by bending tabs of the tube sheets over the edge of the collecting box. This type of heat exchanger is in need of improvement. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an improved connection of a case cover, in particular a case cover of a non-metal material to a metal part, on a heat exchanger, preferably taking into account an improved sealing effect. An improvement of the housing is also desirable. 
     In an exemplary embodiment, a heat exchanger is provided, in which the case cover of a case is connectable to a base, in which the case cover of a non-metal material is attached to the metal base, preferably while improving a sealing effect. In particular, a further object of the invention is to provide a heat exchanger with an improved housing. 
     The object is attained with a heat exchanger of the type mentioned at the outset in which it is provided according to the invention that the case cover is fixed, preferably connected to the base via one or more connections, such as, via a threaded connection and/or slot flange. This concept according to the invention has proven to be advantageous, for example, in the event that the case cover and the base are composed of different materials. 
     A heat exchanger of the type mentioned at the outset can be formed in particular as a charge-air heat exchanger, in which the first fluid is a charge air, or as an exhaust gas heat exchanger, in which the first fluid is an exhaust gas. The first fluid can also be an exhaust gas/charge air mixture or the like fluid for charging an internal combustion engine. The second fluid, in particular a coolant, is, for example, a water-based or other expedient coolant. 
     The invention is based on the concept that a connection of a case cover, in particular made of non-metal, for example, a plastic, fibrous composite or a ceramic, should be comparatively secure and, on the other hand, sufficiently flexible with respect to thermal relative movements of the base, which is preferably composed of metal, e.g., aluminum and a base cover. The invention has recognized that to this end a threaded connection or a slot flange or a combination of a threaded connection and a slot flange is suitable in a superior manner compared to known types of connection. A connection type according to the concept of the invention thus renders possible a particularly cost-effective connection of a base cover, e.g., of metal, but in particular of non-metal, to an otherwise metallic construction of a heat exchanger, so that in particular even more complex case forms are rendered possible while avoiding more expensive production methods. 
     A heat exchanger in the form of a charge-air heat exchanger, in particular a charge-air cooler, which has the features according to the concept of the invention, has proven to be particularly preferred as a further development of the invention. The problems set forth above have resulted in particular with plenum chambers, wherein due to installation space restrictions in the front of the vehicle, indirect charge-air cooling is becoming increasingly popular in this area. In this context, a further development leads in a particularly preferred manner to the use of the heat exchanger according to the concept of the invention as a charge-air cooler for indirect cooling of charge air in a charge-air system for an internal combustion engine of a motor vehicle. 
     Furthermore, the inventive concept can also be realized in a heat exchanger as is described in the applicant&#39;s German patent application DE 10 2008 018 594, which is incorporated herein by reference. A heat exchanger of the type mentioned at the outset is disclosed there, in which the base has at least one first groove, in which the case cover or a wall section of the case cover of the case extends. A case here means in particular the case cover, a seal and optionally the base. The documents of the cited application are hereby incorporated by this reference into the disclosure of this application. It has been shown that the connection concept of a threaded connection and/or a slot flange between the case cover and the base can be realized in a particularly advantageous manner in the heat exchanger described in the cited application. 
     The base can comprises a metal, in particular aluminum. An adequate thermal stability as well as an advantageous attachment of the flow channels in the through openings of the base is thereby rendered possible. 
     In order to ensure a further improved tight connection of the case cover, an embodiment provides that a seal is fixed between the base and the case cover. 
     It is provided in an embodiment that the base and/or the case cover has a bead, which can be designed to accommodate the seal. In particular the bead can be arranged in a base edge region and/or a case cover edge region. 
     It has been proven to be particularly effective in a sealing of the case for a front face of the case cover or of a wall section of the case cover and/or of the base to extend along the bead. 
     The previously mentioned embodiments are particularly suitable, preferably to improve a sealing effect, for fixing the base and the case cover relative to one another—in a bead. Optionally, one or more beads can be arranged on the case cover. A front face of the base can extend along the bead. Preferably, one or more beads can be arranged on the base and advantageously a front face of the case cover extends along the bead. In other words, one or more beads can be used in order to achieve an improved and tighter fixing of base and case cover relative to one another, in particular in comparison with the conventional art. 
     According to a first variant of the invention, it is provided that the case cover or a wall section of the case cover and/or of the base can meet the base bluntly by means of a front face, in particular such that the front face overlaps the bead. In other words, the width of the front face is greater than the width of the bead. 
     The aforementioned first variant of the invention has proven to be particularly effective, in particular with reference to a threaded connection, in particular with respect to its sealing effect, but is not restricted thereto. 
     In principle, a realization of the threaded connection can be carried out in various ways. A further development of the invention provides to embody the threaded connection in a particularly secure manner. Within the scope of the concept of the invention, in particular a further development has proven to be advantageous in which the base has a number of eyes for accommodating respectively one threaded connection. An eye can be arranged in particular on a corner and/or on a side of the base. The attachment of eight eyes has proven to be particularly effective—one each on a corner and a side of the base. In general, two adjacent eyes can have a spacing that lies in the range of between 40 and 90 mm, preferably between 50 and 70 mm. In principle, the number of the eyes depends on the dimensions of the base. The cited spacing ranges have proven to be particularly advantageous for preferred base dimensions and form an expedient comprise between stability and material expenditure. 
     The production process can be simplified if a lock nut is provided on the base or on the case to form the threaded connection. 
     According to a second variant of the invention, it is provided that a front face of the cover or of a wall section of the cover and/or of the base engages in a bead. The second variant has proven to be particularly effective within the context of a slot flange, preferably for a corrugated slot flange, but is not restricted thereto. In this way, it is possible to realize a particularly advantageous sealing action, and the slot flange can be used in a particularly space-saving manner. The slot flange is advantageously designed as a corrugated slot flange, since this has proven to be reliable and falls within the scope of previous production concepts. 
     In an embodiment of the invention, the possibility for savings in terms of material has been produced in that a base thickness is advantageously reduced radially outwards across a bead. The base thickness at least at the bead base is preferably smaller than at a point of the base which is situated further inwards along the radius. The abrasion forces for the slot flange or corrugated slot flange are correspondingly smaller than in other designs due to the reduced material thickness. One particularly advantageous compromise between the material expenditure and stability results if the ratio of a greatest base thickness to a smallest base thickness is in the range between 1.5:1 and 4:1, in particular between 2:1 and 4:1. 
     The base can be fixed to the housing, for example, by means of an adhesive or mechanical connection, or by means of some other connection that is suitable for the fastening of the base, of the base to the housing. In particular, the base holds the flow channels in the one or more through openings. This ensures sufficient retention of the flow channels on the base, and the core is arranged in the housing in a particularly advantageous manner. 
     The housing can have side walls that extend along a flow direction, and can be formed in a multiple-part manner. This renders possible a particularly simple assembly of the core in the housing and of the heat exchanger overall. It has been found to be particularly advantageous according to the further development that at least one housing part forms a housing edge, i.e., is formed in a one-piece manner. In this way, it is possible to avoid leaks as a result of joints of housing parts at a housing edge, and the assembly of the housing is made considerably simpler. At least one housing part, at least in some regions, preferably forms a first and a second side wall which are aligned at an angle with respect to one another, in a one-piece manner. This has the advantage that, in contrast to the prior art, housing side walls no longer need to be provided separately, but rather are provided in a one-piece manner in a single housing part. In particular, this reduces the number of housing parts. 
     Preferably, according to a first modification, at least one housing part can be designed in a U-shaped manner, for example, to provide a cover wall and at least a part of a first side wall and at least a part of a second side wall of the housing. The housing is preferably formed from two U-shaped housing parts. The two housing parts are particularly preferably formed as mating parts, such that an entire housing casing can be formed therefrom in a simple manner. It can be advantageous in particular for the two U-shaped housing parts to be formed symmetrically or virtually identically, which considerably simplifies the production process. To form a housing casing, and in particular in the case of housing parts formed in a U-shaped manner, a parting edge of housing parts is preferably arranged in the region of a side wall. 
     In a second modification, it has proven to be advantageous for at least one housing part to be designed in an L-shaped manner, for example, as a cover wall and side wall of the housing formed with the one-piece housing part. The housing can be formed overall from two L-shaped housing parts. In particular, the two L-shaped housing parts are formed as mating parts or largely symmetrical or identical, which considerably reduces the production expenditure. Preferably within the context of the second modification, it has proven to be advantageous to arrange a parting edge of housing parts in the region of a housing edge. 
     Within the context of a further embodiment of the invention, the core has a first arrangement and a second arrangement of flow channels, wherein the first arrangement and the second arrangement are arranged on opposite sides of an intermediate base. The integrity and stability of the heat exchanger are thus considerably improved, and it is nevertheless possible to provide a comparatively large flow cross section for the first fluid, for example, an exhaust gas or a charge air. 
     An intermediate base can be arranged parallel to and/or essentially in a plane spanned by the parting edges of housing parts. This has proven to be advantageous in particular in the case of U-shaped housing parts, in which a parting edge is arranged in the region of a side wall. This advantageously renders possible the arrangement of an intermediate base virtually centrally and parallel to the side walls and in the plane spanned by the parting edges of the U-shaped housing parts. 
     It is fundamentally advantageous within the scope of the above-mentioned further development that opposite parting edges of the housing parts form a gap, in particular with a gap width of 1 mm to 2 mm. The selection of the gap width is important in particular in the soldering of the components to one another, in particular to form the solder meniscus, since adequate soldering is not ensured if a gap is too large or too small. 
     According to a first modification of this further development, an intermediate base can engage in a gap formed by opposite parting edges of the housing parts. This stabilizes the multiple-part housing in connection with the core. Furthermore, the intermediate base lying in the gap can be used to seal the housing parts with respect to one another. In an embodiment, a web can cover parting edges of the housing parts, and can be arranged in particular on the outside on the housing. The measure provided additionally or alternatively to the first modification can likewise be used to stabilize the multiple-part housing. A web can preferably have a bead, in particular a bead that is designed additionally for reinforcement. It is particularly preferable in a further development of this second modification for a bead of the web to be designed such that it engages in a gap formed by opposite parting edges of the housing parts. 
     In an advantageous further development of the invention, at least two components of the heat exchanger are soldered to one another. 
     In an advantageous further development of the invention, all of the components of the heat exchanger, with the exception of the at least one case cover, in particular the two case covers, are soldered to one another. 
     Overall, according to the above-mentioned further developments relating to the housing, a particularly stable housing is provided which can be assembled using comparatively few parts. The measures explained above for the design or arrangement of the parting edges of the housing parts furthermore lead to a particularly preferable further stabilization or reinforcement of the multiple-part housing. 
     While the invention has proven to be particularly useful in the scope of a use of the heat exchanger in the form of a charge-air heat exchanger, in particular a charge-air cooler, for example, for the indirect or direct cooling of charge air in a charge-air supply system for an internal combustion engine of a motor vehicle, and is to be understood in this sense, and while the invention is described in detail below on the basis of examples from this field, it should nevertheless be clear that the concept described here, as claimed, is likewise useful in the scope of other applications that lie outside the examples explicitly stated and relate to other applications which are not explicitly specified. For example, the concept of the invention presented could likewise be applied to the use of a heat exchanger as an exhaust-gas heat exchanger, in particular an exhaust-gas cooler, for example, for exhaust-gas cooling in an exhaust-gas recirculation system of an internal combustion engine of a motor vehicle or as an auxiliary heater for heating the interior space of a motor vehicle. Furthermore, a use as an oil cooler is possible, in particular for cooling engine oil and/or transmission oil, or a use as a refrigerant cooler or refrigerant condenser in a refrigerant circuit of an air-conditioning system of a motor vehicle. In this context, the invention also encompasses an exhaust-gas recirculation system for an internal combustion engine, having an exhaust-gas recirculation line, a compressor and a heat exchanger in the form of an exhaust-gas heat exchanger, in particular a cooler, according to the concept of the invention. The invention also encompasses a charge-air supply system for an internal combustion engine, having a charge-air induction, an air filter, a compressor and a heat exchanger according to the concept of the invention in the form of a charge-air heat exchanger, in particular a cooler. 
     Exemplary embodiments of the invention are now explained below on the basis of the drawing. This drawing is not intended to illustrate the exemplary embodiments to scale; in fact, where useful for explanation the drawing is shown in schematized and/or slightly distorted form. With regard to enhancements of the teaching which can be directly gathered from the drawing, reference is made to the relevant prior art. 
     It should be taken into consideration thereby that various modifications and amendments relating to the shape and details of an embodiment can be carried out without departing from the general concept of the invention. The features of the invention disclosed in the above description, in the drawing and in the claims can be essential both individually and in combination for the further development of the invention. The general concept of the invention is not restricted to the precise shape or the detail of the embodiments shown and described below, or restricted to a subject matter which would be restricted in relation to the subject matter claimed in the claims. Where dimensional ranges are specified, values which fall within the specified limits are also intended to be disclosed as limit values and usable and claimable in any desired manner. The drawing shows in detail different embodiments according to the concept of the invention, wherein a realization of the core of the heat exchanger in detail as described in the applicant&#39;s German patent application cited above has proven to be advantageous. 
    
    
     
       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 an embodiment of a heat exchanger according to the first variant of the invention; 
         FIG. 2  shows an enlarged perspective partial sectional representation of the base area of the embodiment from  FIG. 1 ; 
         FIG. 3  is an exploded view of  FIG. 2 ; 
         FIG. 4  is a sectional representation of the detail of a threaded connection in the embodiment according to  FIG. 1  through  FIG. 3 ; 
         FIG. 5  shows an embodiment according to the second variant of the invention; 
         FIG. 6  is an enlarged perspective partial sectional representation of the embodiment from  FIG. 5 ; 
         FIG. 7  is an exploded view of  FIG. 6 ; 
         FIG. 8  is a perspective partial sectional representation of the detail of a corrugated slot flange in  FIG. 6 ; 
         FIGS. 9 and 10  are a sectional representation of the detail of the corrugated slot flange of the embodiment in  FIG. 5  through  FIG. 8 ; 
         FIG. 11  is a perspective representation of an embodiment of a heat exchanger according to the first or second variant of the invention, in which the housing is formed in a first modification of two U-shaped housing parts and is reinforced with a web with a reinforcement bead shown in exploded view; 
         FIG. 12  is a perspective representation of the heat exchanger of  FIG. 11 ; 
         FIG. 13  is a perspective representation of another embodiment of the heat exchanger similar to that according to  FIG. 11  and  FIG. 12 , wherein in contrast an intermediate base engages in a gap formed by opposite parting edges of U-shaped housing parts; 
         FIG. 14  is an exploded view of the heat exchanger shown in  FIG. 13 ; 
         FIG. 15  is a perspective representation of a still further embodiment of a heat exchanger according to the first or second variant of the invention, in which the housing in a second modification is formed with L-shaped housing parts and an angled parting edge; 
         FIG. 16  is an exploded view of the housing of the heat exchanger shown in  FIG. 15 ; 
         FIG. 17   a  is a first perspective representation of a further embodiment of the heat exchanger; 
         FIG. 17   b  is a second perspective representation of the heat exchanger; 
         FIG. 18  is a perspective representation of the heat exchanger core of the further embodiment; and 
         FIG. 19  is a sectional representation of a tube sheet section. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a heat exchanger  10  in the form of a charge-air cooler for an indirect charge-air cooling, which can be used in a charge-air system for an internal combustion engine. A charge-air system, not shown further, moreover has a charge-air induction, an air filter and a compressor. The heat exchanger  10  represents an exemplary embodiment of the first variant of the invention, according to which a case cover  11  is fixed to a base  15  via several connections, for example, threaded connections  19 . 
     As is discernible when considering together  FIG. 1  and  FIG. 2 , the heat exchanger  10  has a core  1 , which is provided for the guidance separately from one another and in a heat exchanging manner of a first fluid in the form of a charge air  3  as well as a coolant, not shown in further detail. To this end, the core  1  has a number of flow channels  5 , which can be flowed through by the charge air  3 , as well as a housing  7  that accommodates the flow channels  5  and can be flowed through by the coolant. In this example, the charge-air cooler  10  has two cases  9 ,  9 ′, of which the front case  9  is shown in more detail in  FIG. 2  through  FIG. 4 . Both cases  9 ,  9 ′ are flow-connected to the flow channels  5  and have a case cover  11 ,  11 ′, embodied differently in detail corresponding to the connections for the charge air  3 . In this embodiment, both of the case covers  11 ,  11 ′ are made of plastic, wherein the front cover  11  with a single diffuser arrangement  13  that is formed in one piece for the charge-air connection is shown in more detail. A base  15  is fixed to the cover  11 , which base has through openings  17 , shown clearly in  FIG. 3 , and flow channels  5  assigned to these through openings  17 . 
     In a modified embodiment the heat exchanger can also be embodied as an exhaust-gas heat exchanger, which accordingly can be flowed through by exhaust gas, instead of by charge air  3 . 
     In the embodiment shown in  FIG. 1  through  FIG. 4  according to the first variant of the invention, the case cover  11 ,  11 ′ is fixed to the base  15  with several threaded connections  19  shown in more detail in  FIG. 4 . The base  15  thereby has a bead  21 , in this case running completely along the base  15 , in which a seal  23 , here in the form of a ring seal, is accommodated. 
     As can be seen in  FIG. 4  considered together with  FIG. 1  through  FIG. 3 , the front face  25  of the case cover  11 ,  11 ′ extends along the bead  21  and thereby meets the base  15  bluntly, wherein the front face  25  overlaps the bead  21 . The seal  23  is thereby pressed by the front face  25  into the bead  21 , so that a very effective seal is achieved between the base  15  and the case cover  11 . The threaded connections  19  are formed in this case respectively by a screw  19 A and a lock nut  19 B held in a screw eye  19 C. As is clearly shown in  FIG. 1  through  FIG. 3 , respectively one screw eye  19 C is arranged at respectively one corner or a side center of the base  15 . The threaded connection is furthermore secured through an annular flange  19 D between the lock nut  19 B and the screw  19 A. Through the threaded connection  19  a pressing pressure is exerted between the case cover  11  and the base  15  on the seal  23 , which seal due to the pressing pressure expands in the bead  21  and effectively seals mounting surfaces between the case cover  11  and the base  15 . 
     The screw eyes  19 C are spaced apart from one another evenly—in this case the spacing should be approx. 50 to 80 mm. Lock nuts  19 B are arranged for securing either on the base side facing towards the core  1  or on the case  9 ,  9 ′. In this case, the screw  19 A is inserted through a box pedestal in the form of a metal sleeve on the base  1  and screwed to the nut  19 B behind the base  1 . 
     In the threaded connection  19 , the groove width in the base  1  is approx. 3 mm. The seal  23 , which is 2 mm wide, is pressed into the bead  21 . The bead  21 ,  21 ′ is thickened to the bead measurement at some places locally, in this case every 30 mm, so that the seal  23  is positioned. 
       FIG. 5  shows a different charge-air cooler  20 , likewise for an indirect charge-air cooling as described in more detail above with reference to the charge-air cooler  10 , in which, in the present case, according to an embodiment of the second variant of the invention, the case cover  11  is fixed to the base  15  via a slot flange  26  as a corrugated slot flange. Identical reference symbols have been used for corresponding parts of the charge-air coolers  10  and  20 . 
     In contrast to the embodiment described with reference to  FIG. 1  through  FIG. 4 , in the embodiment of a charge-air cooler  20  shown here, the case cover  11 ′ is fixed to the base  15 ′ via a corrugated slot flange  26 . For this purpose, a seal  23 ′ is placed into the bead  21 ′ which is formed in the present corrugated slot flange  26 , which seal  23 ′, after the case cover  11 ′ has been placed, is pressed into the bead  21 ′ in a sealing manner by the front face  25 ′ of the case cover  11 ′, which front face engages in the bead  21 ′. A particularly advantageous sealing of the case  9 ,  9 ′ is thus achieved. The wall section  28  of the case cover  11 ′, which wall section forms the front face  25 ′ of the case cover  11 ′, merges at one end into the previously described air connection, which is embodied as a diffuser  13 , and at the other end, the wall section  28 , along a height H of the bead  21 ′, has ribs  27  which are semi-cylindrical in shape and which are arranged with a spacing  29 . Respectively on elongated hole  31  of a flank  33  lying opposite the wall section  28  is arranged opposite the ribs  27 . The material  35  of the flank  33 , which material lies between the elongated holes  31  and in the present case is aluminum, is arranged opposite the spacing  29 . During the closing of the slot flange  26 , this material  35  can be pressed into the spacing  29  between the ribs  27  to form the corrugated slot flange. At least some of the components of the heat exchanger  10  are soldered, in particular Nocolok-soldered, to one another. In another exemplary embodiment, all the components of the heat exchanger  10 , with the exception of the at least one case cover, in particular the case covers, are soldered, for example Nocolok-soldered, to one another. 
     The representation shown in  FIG. 10 , which is equally applicable to a heat exchanger  10  and a heat exchanger  20 , also shows that a base thickness is reduced radially outwards across the bead  21 ′, in the present case, from the greatest value D in the region of the openings  17  for the flow channels  5 , in the present case tubes, via a value D′ in the region of the bead  21 ′, to a smallest value d in the region of the outer flank  33  of the bead  21 ′, the material  35  of which flank is flanged to form the corrugated slot flange  26 . In the present case, the thickness of the base  15 ′ varies from D=4 mm to d=1.5 mm, in particular from D=3 mm to d=2 mm, i.e., overall it is possible in embodiments of this type to reduce the base material by 30 to 70%, in particular by 50 to 70%. Furthermore, it has been found that it is also possible for this purpose to form the thickness at the lowest point T of the bead  21 ′ to be even in the range of the smallest value d. It is otherwise possible regardless of the embodiment described here for the transition from the large thickness D to the thin thickness d to be of any desired design. 
     The described design of the bead  21 ′ has the advantage that the base  15 ′ permits a good tube soldering and flow channel soldering with a good bundling process in the region of the openings  17  with the large thickness D. In contrast, due to the smallest value d of the small material thickness in the region of the corrugated slot flange  26 , a concept is achieved which particularly saves installation space and keeps abrasive forces low. For example, the material  35  to be flanged can be pressed away in the scope of a punching process. As a result of the material reduction in the region of the flank  33 , the fastening of the case  9 ,  9 ′ can be implemented with a considerably reduced installation space requirement. At least some of the components of the heat exchanger  10  are soldered, in particular Nocolok-soldered, to one another. In another exemplary embodiment, all the components of the heat exchanger  10 , with the exception of the at least one case cover, in particular the case covers, are soldered, for example Nocolok-soldered, to one another. 
     The embodiments of a heat exchanger in the form of a charge-air cooler  30 ,  40 ,  50 , which embodiments are explained on the basis of  FIG. 11  through  FIG. 16 , show advantageous examples of a design of a housing  7  as is generally shown in the previously described  FIG. 1  through  FIG. 10 . The modifications of a housing  37 ,  47 ,  57  shown in  FIG. 11  through  FIG. 16  can be used, as required, for a housing  7  of  FIG. 1  through  FIG. 10 . The embodiments of a heat exchanger  30 ,  40 ,  50  described in  FIG. 11  through  FIG. 16  are illustrated merely by way of example as embodiments according to the second variant of the invention, in which a case cover of the heat exchanger  30 ,  40 ,  50  is fixed to the base as a support flange. The statements made with regard to  FIG. 11  through  FIG. 16  can be applied equally to an embodiment (not shown) of a heat exchanger in which the case cover is fixed to the base by means of a threaded connection. Overall, the features disclosed in  FIG. 1  through  FIG. 10 , in particular relating to the fixing of the case cover to the base, can be combined in any manner both individually and in combination with the features disclosed in  FIG. 11  through  FIG. 16 , in particular regarding the embodiment of a housing  37 ,  47 ,  57 , individually or in combination and used depending on the intended use. In this respect, in the exemplary embodiments, the same reference symbols have been used for identical parts or parts with the same function. At least some of the components of the heat exchanger are soldered, in particular Nocolok-soldered, to one another. In another embodiment, all the components of the heat exchanger, with the exception of the at least one case cover, in particular the case covers, are soldered, for example Nocolok-soldered, to one another. 
       FIG. 11  shows a heat exchanger  30  in the form of a charge-air cooler as an embodiment according to the second variant of the invention, similar to the heat exchanger  20  described in  FIG. 5 . This heat exchanger again has a core  1  with a number of flow channels  5  which can be flowed through by charge air  3  and which are accommodated in a housing  37  which can be flowed through by the coolant. As is explained on the basis of  FIG. 5  through  FIG. 10 , cases  9 ,  9 ′ are flow-connected to the flow channels  5  and have a case cover  11 ,  11 ′ which is designed differently in detail corresponding to the connections for the charge air  3 . These case covers are in each case fixed to the base  15 ,  15 ′ corresponding to the manner explained with regard to  FIG. 5  through  FIG. 10 . The base  15 ,  15 ′ is fixed to the housing, wherein the flow channels  5  penetrate the through openings  17  shown in more detail in  FIG. 7 . 
     The housing  37 , which is shown in a perspective view in  FIG. 12  and as an exploded representation in  FIG. 11 , has two cover walls  36  and two side walls  38 , with a cover wall  36  being aligned essentially at right angles to the side wall  38 . An upper housing part  37 . 1 , which is U-shaped in the present case, forms a first and a second upper housing edge  39 . 1 ,  39 . 2 , while a second lower housing part  37 . 2  forms a first lower housing edge  39 . 3  and a second lower housing edge  39 . 4  (not shown). The upper housing part  37 . 1  is formed as a mating part to be essentially identical to the lower housing part  37 . 2 , with the exception of coolant connections  41 ,  42 ,  43 . Coolant  4  is supplied to and discharged from the interior of the housing  37 , in a manner not shown in further detail, via the coolant connections  41 ,  42 ,  43  in order to purge the flow channels  5 . In the present case, the entire housing casing of the housing  37  is formed by means of the upper housing part  37 . 1  and the lower housing part  37 . 2  The parting edges  44 . 1  and  44 . 2  of the upper housing part  37 . 1  and of the lower housing part  37 . 2  in the present case are arranged in the region of a side wall  38  of the housing  37  and are located opposite one another so as to form a gap  45 . For the sealing closure of the housing  37 , the gap  45  is covered by a web  46 , with a stiffening bead  46 . 1  of the web engaging in the gap  45 . In addition to sealing closure of the housing  37 , the attachment of the web  46  means that the stability of the housing  37 , which is already comparatively high as a result of the one-piece design of the upper housing part  37 . 1  and of the lower housing part  37 . 2 , is improved still further. At least some of the components of the heat exchanger are soldered, in particular Nocolok soldered, to one another. In another exemplary embodiment, all the components of the heat exchanger, with the exception of the at least one case cover, in particular the case covers, are soldered, for example Nocolok soldered, to one another. 
       FIG. 13  shows in perspective representation and  FIG. 14  shows an exploded representation a further embodiment of a heat exchanger  40  in the form of a charge-air cooler, the housing  47  of which is again formed from an upper housing part  47 . 1  and a lower housing part  47 . 2 , wherein the housing parts  47 . 1  and  47 . 2  are formed in a U-shaped manner virtually identical to the housing parts  37 . 1  and  37 . 2  of  FIG. 11 . The opposite parting edges  44 . 1 ,  44 . 2  of the housing parts  47 . 1 ,  47 . 1  again form a gap  45 , in which an intermediate base  48 , shown in more detail in  FIG. 14 , engages. In this case the core  1  has a first arrangement  1 . 1  and a second arrangement  1 . 2  of flow channels  5 , with the first arrangement  1 . 1  and the second arrangement  1 . 2  being arranged on opposite sides of the intermediate base  48 . At least some of the components of the heat exchanger are soldered, in particular Nocolok soldered, to one another. In another exemplary embodiment, all the components of the heat exchanger, with the exception of the at least one case cover, in particular the case covers, are soldered, for example Nocolok soldered, to one another. 
     It can be seen from the representations in  FIG. 11  through  FIG. 14  that a heat exchanger  30 ,  40  having the U-shaped housing parts  37 . 1 ,  37 . 2 ,  47 . 1 ,  47 . 2  can be bundled in a particularly simple manner, wherein in the embodiment shown in  FIG. 11  and  FIG. 12 , a web  46  is used to seal the gap  45  between the parting edges  44 . 1  and  44 . 2 , while in the embodiment shown in  FIG. 13  and  FIG. 14 , an intermediate base  48  is used to seal the gap  45 . The housing parts  37 . 1 ,  37 . 2  and  47 . 1 ,  47 . 2  in the present case are soldered to one another—alternatively or additionally the housing parts can also be welded to one another. In a way which is not shown, the housing parts can also additionally or alternatively be joined to one another mechanically. 
       FIG. 15  shows a further embodiment of a heat exchanger  50 , in which a housing  57  is formed in the manner shown in  FIG. 16  with an upper L-shaped housing part  57 . 1  and a lower L-shaped housing part  57 . 2 . Again, each L-shaped housing part  57 . 1 ,  57 . 2  forms a housing edge  59 . 1  and  59 . 2 , and in each case one cover wall  56  and side wall  58  of the housing  57 . In the embodiment shown in  FIG. 15  and  FIG. 16 , a cover wall  56  is provided in each case with stiffening areas and/or openings  51 , while in the embodiments shown in  FIG. 11  through  FIG. 14 , stiffening areas  52  and/or openings are formed on a side wall  38 . At least some of the components of the heat exchanger are soldered, in particular Nocolok soldered, to one another. In another exemplary embodiment, all the components of the heat exchanger, with the exception of the at least one case cover, in particular the case covers, are soldered, for example Nocolok soldered, to one another. 
     As can be seen from  FIG. 16 , the first housing part  57 . 1  and the second housing part  57 . 2  are again formed as mating parts, such that through the assembly of the same at a parting edge  54 . 1 ,  54 . 2  the entire housing casing of the housing  57  is completed. In the present case, parting edges  54 . 2  lying respectively diagonally opposite are provided with a bent over tab  55  which—as well as stiffening the L-shaped housing part  57 . 1 ,  57 . 2 —also serves the improved positive attachment of the housing parts  57 . 1 ,  57 . 2 . In this regard, advantageously in each case one parting edge  54 . 1  is pushed under the tab  55  of the opposite parting edge  54 . 2  in order to provide the housing casing of the housing  57 . The housing parts  57 . 1 ,  57 . 2  are soldered to one another in the present case. At least some of the components of the heat exchanger are soldered, in particular Nocolok soldered, to one another. In another exemplary embodiment, all the components of the heat exchanger, with the exception of the at least one case cover, in particular the case covers, are soldered, for example Nocolok soldered, to one another. 
     Overall, the embodiments of a housing  37 ,  47 ,  57  shown in  FIG. 11  through  FIG. 16  render possible a realization of a multiple-part and nevertheless particularly stable housing. 
     In summary, a heat exchanger  10 ,  20 ,  30 ,  40 ,  50  is disclosed, in particular a charge-air heat exchanger or exhaust-gas heat exchanger, for an exchange of heat between a first fluid, in particular a charge air  3  or an exhaust gas, and a second fluid, in particular a coolant, which heat exchanger has: separate and heat-exchanging guidance, in the core  1 , of the first and second fluids, which core  1  has a number of flow channels  5  which can be flowed through by the first fluid and a housing  7 ,  37 ,  47 ,  57  which accommodates the flow channels  5  and which can be flowed through by the second fluid; at least one case cover  11 , it which is flow-connected to the flow channels  5 , a base  15 ,  15 ′ which is fixed to the case cover  11 ,  11 ′ and which is provided with one or with a plurality of through openings  17  for flow channels  5 . In order to obtain an advantageous connection of the case cover  11 ,  11 ′ to the base  15 ,  15 ′, in particular in the event that the case cover  11 ,  11 ′ and base  15 ,  15 ′ are composed of different materials, the invention provides that the case cover  11 ,  11 ′ is fixed to the base  15 ,  15 ′ via one or more connections as a screw connection  19  and/or slot flange  26 . 
       FIG. 17   a  shows a first perspective representation of a further embodiment of the heat exchanger and  FIG. 17   b  shows a second perspective representation of the heat exchanger, wherein in  FIG. 17   b  the web  76  is shown in an exploded view. Compared to the previous embodiments, the web  76  is embodied to be wider and has openings  73 , in particular tongue-like openings. 
     The housing  37  with the cover walls  36  is embodied such that the at least one cover wall  36  has openings  72 . The openings  72  correspond to the openings  73 . The openings  72  are embodied essentially in a tongue-like manner. The web  76  likewise has a stiffening bead  76 . 1 . Furthermore, the web  76  does not have openings  79 . 
       FIG. 18  shows a perspective representation of the heat exchanger core of the further embodiment. The features shown in  FIG. 18  have the same reference symbols as in the previous figures. 
       FIG. 19  shows a sectional representation of a tube sheet section. The tube sheet has an essentially peripheral groove. At least a radius r is provided in the area of the groove bottom. The radius r assumes in particular values of 1 to 5 mm, in particular values of 2 mm to 3 mm. The base has a thickness d 1  in the groove bottom. This thickness d 1  merges into the thickness d 2 . The thickness d 2  is essentially arranged according to the radius r. The thickness d 1  has a value of, for example, the value 3 mm. The thickness d 2  has the value, for example, of 2 mm. 
     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.