Abstract:
The invention relates to a fully-metal heat exchanger comprising flat tubes ( 1 ), which have two narrow sides and two wide sides ( 2, 3 ), and comprising fins ( 4 ) which form a block together with the flat tubes, and comprising either at least one tube plate ( 5 ) and one collecting tank ( 6 ), with edges ( 10 ) of the collecting tank ( 6 ) being connected, for example soldered, to edges ( 20 ) of the tube plate ( 5 ), or at least one collecting tank ( 6 ) which contains the tube plate, and having projections ( 11 ) which are arranged at intervals. The invention leads to a heat exchanger which has a small installation space requirement while having comparatively good thermal properties in that, according to the invention, the projections ( 11 ) engage in the ends of the flat tubes ( 1 ) in the region of the narrow sides ( 2 ). The production method according to the invention accordingly provides that the projections ( 11 ) are inserted into the ends of the flat tubes ( 1 ) approximately in the region of the narrow sides ( 2 ).

Description:
TECHNICAL FIELD 
       [0001]    The invention relates to a fully-metal heat exchanger, composed of flat tubes having two narrow and two wide sides and of fins which, together with the flat tubes, form a block, and which fully-metal heat exchanger has either at least one tube base and a collecting tank, with edges of the collecting tank being connected, for example soldered, to edges of the tube base, or at least one collecting tank which contains the tube base, and having projections which are arranged at intervals. The invention also relates to a production method for heat exchangers. 
       PRIOR ART 
       [0002]    The heat exchanger described above is known, for example, from DE 198 19 247 A1. The projections therein correspond to openings in the tube bases. In this way, it is provided that the individual parts are provisionally held together before the soldering process is carried out. The expenditure for auxiliary soldering aids can be considerably reduced. A certain disadvantage of the known heat exchanger is that the tube base still protrudes a considerable distance beyond the fin/flat-tube block, which could be considered to be an unnecessary spatial requirement. In addition, the ratio of the cross sections taken up by the flat tubes in relation to the overall cross section of the heat exchanger or of its tube bases is not optimal, so that improvements are possible with regard to an efficient heat exchanger. 
       ILLUSTRATION OF THE INVENTION 
       [0003]    The object of the invention is that of providing a heat exchanger which, while providing comparatively good thermotechnical values, has a low spatial requirement. 
         [0004]    It is possible as a side effect to expect a production-friendly, in particular also flexible design. 
         [0005]    The object is achieved according to the invention with regard to the fully-metal heat exchanger by using the features of claim  1 . The production method according to the invention is the subject matter of claim  22 . It is provided that the projections engage in the region of the narrow sides into the ends of the flat tubes. The projections are preferably situated at the opposite longitudinal edges of the collecting tank. 
         [0006]    Preferably means in this case that embodiments may be provided in which the projections are arranged at the longitudinal edges of the tube base, possibly associated with the disadvantage that the tube bases become more complex and some other advantages are not provided. Another possible design is to provide a metallic, frame-like additional part which has the projections. 
         [0007]    The production method leads to several advantages. The projections, which are inserted into the flat tube ends, at the two opposite edges of the collecting tank hold the flat tubes under tension during the subsequent soldering process, so that the risk of a so-called “falling in” of the flat tubes, with the result of inadequate soldered connections to the tube base, is significantly reduced. The invention therefore also permits the use of flat tubes whose wide sides can have relatively large dimensions, and accordingly avoids the use, which is complex in production terms, of a plurality of flat tube rows in the direction of the depth of the flat-tube/fin block. In other words, it is possible by means of the invention to provide heat exchangers over a significantly wider power spectrum with significantly less variation expenditure. 
         [0008]    In addition, the abovementioned advantages of the prior art are maintained, that is to say in particular the expenditure for auxiliary soldering aids is considerably reduced, since the inserted projections assist in holding together the assembled individual parts of the heat exchanger. 
         [0009]    Because the flat tubes extend over the entire depth of the tube base—and preferably even beyond this—there is practically no space which would not be available for the purpose of heat transfer. In other words, that cross-sectional area of the flat tubes through which flow passes is in a favorable ratio to the entire area covered by the tube base, which is in turn approximately the same as the area in this regard which is covered by the entire heat exchanger. 
         [0010]    In addition, the proposed heat exchanger has a higher degree of process reliability during production than heat exchangers which do not have tube bases but have, instead of the tube bases, widened flat tube ends, as are known for example from DE 195 43 986 A1 or from even much earlier documents. 
         [0011]    It is the case either that the flat tubes protrude with their narrow sides beyond the width of the tube base, and in the protruding region, the projections engage into the ends of the flat tubes, or that the tube base width protrudes beyond the narrow sides of the flat tubes, and in the protruding region, the projections engage into the ends of the flat tubes. 
         [0012]    The first of said alternatives is, as mentioned, preferable, because it better prevents the previously mentioned “falling in” of the flat tubes, since in this case the edge of the collecting tanks with the projections bear from the outside against the edge of the tube base, and because, as a result, the projections are particularly resistant to forces which act in the direction of the wide side, that is to say transversely with respect to the longitudinal direction of the flat tubes. In addition, said alternative also appears to be more favorable with regard to producing sealed connections. 
         [0013]    The projections in each case make contact with the narrow sides of the flat tubes from the inside, and are preferably soldered there. 
         [0014]    The tube base preferably has edges, which are bent in a way known per se, and openings for receiving in each case one flat tube end. According to the proposal, however, the openings extend into the bent edges. 
         [0015]    The tube bases have edges bent only at the two longitudinal sides, so that said tube bases can be produced from one sheet-metal strip of any desired length. The tooling costs for changing over to different heat exchanger sizes are considerably reduced as a result. 
         [0016]    The collecting tank has end-side openings. Each collecting tank is therefore constituted by only one metal sheet with two bends, which is likewise advantageous in production terms. 
         [0017]    The end-side openings of the collecting tank are closed off by means of side parts, which are known per se, which extend over the length of the flat tubes. 
         [0018]    The projections are expediently shaped in such a way as to assist their insertion into the ends of the flat tubes. One advantageous refinement provides forming the projections in the manner of incisors. Said design makes it possible to better compensate length tolerances in the flat tubes. Despite the unavoidable length tolerances, it is possible to produce sealed connections between the projections and the flat tube ends. 
         [0019]    The fully-metal heat exchanger can, in the widest sense, be used to advantage anywhere where there is a requirement for good heat transfer efficiency with a simultaneously low spatial requirement. The inventor envisages using heat exchangers of said type specifically as air-cooled charge-air coolers in motor vehicles, but without thereby excluding any other possible application, especially in the field of motor vehicles. 
         [0020]    A fully-metal heat exchanger should be a heat exchanger whose constituent parts, which are specified in the claims, are composed of metal, preferably of aluminum, regardless of whether or not other, non-metal parts which could belong to the system are subsequently fastened to said heat exchanger. For example, comparatively complex accessories are to be attached and securely fastened to fully-metal heat exchangers which are produced from shaped metal sheets. 
         [0021]    The projections, which are provided on a comb-like additional part such as a sheet metal strip or the like which is connected to the wall of the collecting tank, which sit in the flat tube ends hold the flat tubes under tension during the subsequent soldering process, so that the risk of the abovementioned “falling in” of the flat tubes, with the result of inadequate soldered connections in the receiving openings, is also significantly reduced by the provision of the additional part. In addition, the advantages of the prior art are maintained, that is to say in particular the expenditure for auxiliary soldering aids is considerably reduced, since the strips (additional parts) have hooks on the ends which assist in holding the assembled individual parts of the heat exchanger together by engaging over the side parts. 
         [0022]    The collecting tanks can be of single-part or multi-part design. A prominent feature is a part which has a U-shaped cross section, with the base section being provided with receiving openings for the tube ends, and the two limbs forming the two walls of the collecting tank. If the walls are shaped and joined together to form a space, then single-part collecting tanks are formed. If the walls remain substantially planar, a second part is required for forming the closed space, resulting then in two-part collecting tanks being formed. The receiving openings extend at least into the walls of the collecting tank. 
         [0023]    Said projections are also expediently shaped so as to assist their insertion into the ends of the flat tubes. 
         [0024]    The additional part is a chamber-like sheet-metal strip which in shaping terms is easy to process in order to form the additional part. Within the context of the present invention, the term “strip” encompasses all possible physical embodiments, so that an additional part can be generally referred to thereby. Said projections on the strip or additional parts can be first projections for the case that second projections are provided on the strip. The second projections are then arranged between the first projections. The second projections improve the assembly or the preparation of the heat exchanger for the following soldering process. 
         [0025]    The method according to the invention for producing a fully-metal heat exchanger, with flat tubes and fins being placed together to form a flat-tube/fin block, whereafter tube bases are placed on the ends of the flat tubes and finally collecting tanks are placed with their edges on the edges of the tube bases, is characterized in that projections which are arranged on a component are inserted, in the region of the narrow sides of the flat tubes, into the ends thereof. 
         [0026]    The longitudinal edges of the collecting tank preferably bear against the longitudinal edges of the tube base from the outside. The narrow sides of the flat tubes protrude beyond the longitudinal edges, so that projections situated at the longitudinal edges of the collecting tank can be inserted into the protruding flat tube regions. In this way, the projections hold the flat tubes in a tensioned state. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    The invention is described in the following in two exemplary embodiments with reference to the appended drawings. 
           [0028]      FIG. 1  shows an exploded illustration of the heat exchanger according to the invention; 
           [0029]      FIG. 2  shows a front view; 
           [0030]      FIG. 3  shows a plan view; 
           [0031]      FIGS. 4 and 5  show perspective views of a part of a heat exchanger; 
           [0032]      FIG. 6  shows a perspective overall view of the heat exchanger; 
           [0033]      FIG. 7  shows a detail of the flat tube; 
           [0034]      FIGS. 8 and 9  show an alternative embodiment; 
           [0035]      FIG. 10  shows an exploded illustration of the heat exchanger according to the invention. 
           [0036]      FIGS. 11 and 12  show perspective views of the fully-produced heat exchanger. 
           [0037]      FIGS. 13 and 14  show perspective views of a part of the heat exchanger in an assembly situation. 
           [0038]      FIG. 15  shows an advantageous design of the projections. 
       
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0039]    All of the illustrated individual parts of the heat exchanger are composed of metal, preferably of aluminum or aluminum alloys, which is expediently coated with a solder layer. The individual parts, such as flat tubes  1 , fins  4 , tube bases  5 , collecting tanks  6  and side parts  30 , are produced from metal sheets, though it is not excluded that for example the flat tubes  1  could also be produced as drawn tubes. The flat tubes  1  have an approximately rectangular cross section, it however being possible for the narrow sides  2  to also be arched outward slightly. In the embodiment shown, the inner inserts are situated in the flat tubes  1 . The flat tubes  1  are then stacked with fins  4  in order to form a flat-tube/fin block. Tube bases  5  are placed on the ends of the flat tubes  1 , with the ends of the flat tubes  1  being situated in openings  21  of the tube bases  5 , where a sealed soldered connection is later formed. The collecting tanks  6  are then placed on, specifically, as can be seen in particular from  FIG. 4 , with the projections  11  at the edges  10  of the collecting tanks  6  thereby being inserted into those edge regions of the flat tubes  1  which are formed by the narrow sides  2 , which protrude slightly beyond the edges  20  of the tube base  5 , of the flat tubes  1 . Preferably situated at the edge of the openings  21  in the tube bases  5  are rim holes (not illustrated) which preferably point away from the collecting tank  6 , so that the flat tube ends do not protrude inward in order to ensure a low loss of pressure of the medium flowing into the flat tubes  1 . Webs  22  are provided between the openings  21  in the tube bases  5 . The webs  22  can be of profiled design in order to increase their stiffness. Finally, the side parts  30  are placed on, which side parts  30  at the same time close off the end-side openings  60  of the collecting tanks  6 . For this purpose, the side parts  30  have, at their ends, in each case one cup-shaped closure piece which fits into the opening  60 . The side parts  30  are provisionally fixed, and hold the individual parts of the heat exchanger together, by means of deformable retaining elements  61  which engage into a slot  62  of the side parts. In said form, the heat exchanger is substantially prepared for carrying out the CAB hard soldering process. All the connections are produced in one working operation in the soldering furnace. 
         [0040]    The shape of the projections  11  is expediently matched to the contour of the flat tubes  1  which is provided in the region of the narrow sides  2 , so that both the insertion is facilitated and also sealed soldered connections are provided. Certain production tolerances are also absorbed in this way. The spacing of the projections  11  at the edge of the collecting tanks  6  corresponds to the spacing of the flat tubes  1  in the row or with the height of the fins  4  arranged between the flat tubes  1 . Here, certain tolerances must be permissible which can however be compensated by the expedient shape of the projections  11  (see the description of  FIGS. 15 and 16  further below). 
         [0041]    The collecting tanks  6  are of particularly production-friendly, simple configuration. Only two bends are necessary in order to form the two longitudinal walls and a transverse wall. Connecting pipes  70 , for example, can be easily produced by means of shaping processes. 
         [0042]    Particularly production-friendly tube bases  5  are also to be used, which are manufactured from endless band and need merely be cut to the appropriate length, because said tube bases do not have any bent edges at their end sides. Accordingly, no expensive drawing tools are required. It is expedient to make reference here to  FIGS. 4 and 5 . It can be seen in said figures that a lug  100 , which is comparable to the projections  11 , is provided at the edge  10  of the collecting tank  6 . Said lug  100  interacts with the corresponding cut-out  101  at the edge  20  of the tube base  5  and ensures sealed soldered connections there. It can also be seen from  FIG. 5  that the openings  21  in the tube base  5  extend into the edge  20 , as indicated by the reference symbol  22 . The tube bases  5  can therefore, during assembly, also be pushed transversely with respect to their longitudinal direction, or in the direction of the wide sides  3  of the flat tube ends, onto said flat tube ends. In the prior art, a movement in the longitudinal direction of the flat tubes is required for this purpose. This is referred to as “drawing on” the tube bases. 
         [0043]      FIGS. 3 and 6  in particular show, in a view of one of the side parts  30 , that there are no lateral protrusions of the tube bases  5  beyond the flat-tube/fin block. The width of the side parts  30  corresponds approximately to the dimension of the wide sides  3  of the flat tubes  1 . 
         [0044]    It is also to be pointed out that the heat exchanger according to the invention permits relatively easy access from the outside to connections which are critical in soldering terms. Critical connections of said type are the flat-tube/tube-base connections. Should leakages be present there after the soldering process is carried out, the corresponding points can, by virtue of being largely accessible, be easily aftertreated and eliminated in a second soldering process. In heat exchangers of the prior art, it is often not possible to do this, resulting in high rejection rates. 
         [0045]      FIG. 7  schematically shows one individual flat tube  1 , specifically in a view of the flat tube end. Flat tubes  1  of said type are provided in desired numbers in the heat exchanger. Two projections  11  extend into each flat tube  1 . The penetration depth need only be a few millimeters; 10-15 mm is more than enough. It would practically be even less. It is self-evident that the one projection  11  is situated on the one edge of the collecting tank  6  and the other projection  11  is situated on the opposite, other edge  10  of the collecting tank  6 . The projections  11  bear tightly from the inside against the narrow sides  2  of the flat tubes  1 . Situated in the flat tubes  1  is an inner insert  80 , as is typical in particular for charge air coolers which are impinged on by cooling air. In other applications, an inner insert is dispensed with entirely. It is practically often difficult to insert the inner inserts  80  into the flat tubes  1  in such a way that the least possible bypass is generated in the region of the narrow sides  2  for the charge air flowing through, which has an adverse effect on the heat transfer. As shown in  FIG. 7 , the projections  11  have a favorable effect on the reduction of the disadvantageous bypass, which is a further advantage of the invention. The small gaps in the corners of the flat tubes  1  are caused by the illustration. They are in practice not present or are securely closed off in the soldering process. Said gaps will also level out as the projections  11  are inserted, since the projections  11  hold the two wide sides  3  under a certain tension in the direction of the arrow. 
         [0046]      FIGS. 8 and 9  now show an alternative design in which the projections  11  are arranged on the tube bases  5 . In said case, the tube bases  5  must be drawn on in the tube longitudinal direction, with the projections  11  simultaneously being inserted into the flat tube ends  1 . Thereafter, the collecting tanks  6  and the side parts  30  are placed on and mounted. 
         [0047]    Single-part collecting tanks  6  have been provided at least in the exemplary embodiment which is shown in  FIGS. 10-14 . It is however provided in any case that the collecting tanks  6  also comprise the tube bases  5 , so that therefore no classic tube bases are provided as separate parts, as can be gathered from said figures. The collecting tank  6  has a base section  106  from which extend two bent walls  107  of the collecting tank  6 . The walls  107  are shaped and can be connected by means of a longitudinal weld seam (not shown) in order to form the collecting tank  6 . Provided in the base section  106  are receiving openings  21  for the flat tube ends, wherein the spacings of the flat tubes  1  should accordingly correspond to the spacings of the receiving openings  21 . A very prominent feature is that the receiving openings  21  extend into the walls  107 , that is to say they extend slightly beyond the bent edge of the walls  107  on the base section  106 , as can be seen sufficiently clearly from  FIG. 14  at reference symbol  22 . In the exemplary embodiments shown, in each case one strip (additional part)  110  is situated on all the walls  107  of the two collecting tanks  6 . At the walls  107  of the one collecting tank  6 , the strips  110  have been formed with additional functions such as for example with retaining functions  90  for accessories (not illustrated). It is not strictly necessary to provide strips  110  on all the walls  107 . It is advantageous to provide a trip  110  in particular whenever additional functions  70  are to be carried out. In the present exemplary embodiment, it would be fundamentally entirely possible to dispense with those narrow strips  110  at the walls  107  of the left-hand collecting tank  6  which do not provide any additional function, and for this purpose to provide there the solution described above, that is to say, there, the projections  11  would be arranged directly on the walls  107  of the collecting tank  6 , and tube bases would be provided as individual parts, as shown in the figures. 
         [0048]    A further advantage of the strip  110  can be gathered from  FIG. 12 . It can be seen in said figure that the strip  110 , which is formed with the stated additional functions, can also contribute to the strength of the collecting tank  6 . It can be seen in  FIG. 12  that the strip  110  extends over a considerable part of the wall  107  of the collecting tank and is soldered to said wall  107 . 
         [0049]    It is possible from  FIGS. 13 and 14  to more clearly see the design of the strip  110  with regard to the projections  11  which are arranged thereon at intervals. The projections  11  can be provided with a contour which serves to facilitate the sliding of said projections  11  into the flat tubes  1 . Between the projections  11 , which are first projections  11 , are situated in each case second projections  12 . As can be seen, in each case one second projection  12  has been arranged between two first projections  11 . The second projections  12  cause a counteracting moment of the strip  110  which could otherwise, when the first projections  11  are situated in the flat tube ends, seek to stick out away from the wall  107 , which is undesirable. Since the second projections  12  bear in each case against the fins  4  from the outside, this is prevented or at least counteracted. 
         [0050]    It can also be seen from  FIGS. 13 and 14  that it is advantageous to form a hook  13  at the ends of the strip  110 , which hook  13  is suitable to fixedly hold the side part  30  against the outer fin  4 . This assists in holding the entire heat exchanger together before soldering. In addition, this also suppresses the abovementioned “sticking out” of the strip  110  from the wall  107 . In addition, it is also possible in this way to dispense with the brackets, shown in  FIG. 1  at positions  61  and  62 , which are intended to retain the side parts  30  in the end-side openings  60  of the collecting tank  6 , which is also advantageous in production terms. 
         [0051]      FIG. 15  shows a detail with only one projection  11 . The projections  11  have been designed in the manner of incisors  111 . Length tolerances in the flat tubes which are in the range from +/−1.0 mm can be better absorbed in this way. Sharp edges  112  have been formed on said projections  11 , which sharp edges  112  also extend in the radii, that is to say in the region of the transition from the projection  11  into the wall of the collecting tank  6  or of the additional part or of the tube base. As the projections  11  are inserted into the flat tube ends, the sharp edges  112  cut said ends of those flat tubes which are in the upper length tolerance range open slightly and “crumple” said ends around slightly. This can be clearly seen in  FIG. 16  at k. The central tube there is slightly longer than the two other tubes. The sharp edge of the projection  11  is produced for example by means of cold shaping. The thickness difference between the projections  11  and the wall of the flat tubes assists said process. The wall of the collecting tank  6 , from which the projections  11  are for example formed, can be approximately 1.0-2.0 mm thick, while the thickness of the wall of the flat tubes can be in the range from 0.05-0.25 mm. 
         [0052]    Overall, the invention accordingly provides an innovative product which, compared to the prior art, leaves little to be desired.