Heat exchangers and manufacturing processes for heat exchangers

Abstract

Heat exchanger, in particular for motor vehicles, consisting of a brazed flat tube finned block (10) in which the flat tubes are formed from a single metallic strip, and with collecting boxes (50) arranged at the ends of the flat tubes, characterized in that the wall thickness of the flat tubes is 0.050 mm - 0.25 mm and the wall thickness of the ribs is 0.030 mm - 0.090 mm and that the soldered flat tube-rib block (10) has free flat tube ends (11) which can be inserted into receiving openings (12) of the collecting box (50) and fastened and that the free flat tube ends (11) are glued into the receiving openings (12) of the collection box (50), the adhesive being placed in a gap (13) between the individual flat tube ends (11) and the wall of the receiving openings (12).

Description

TECHNICAL AREA

[0001] The invention relates to heat exchangers, in particular for motor vehicles, which have flat tubes, and to a manufacturing method for heat exchangers. STATE OF THE ART

[0002] The flat tube with the characteristics described above is known from EP 0 907 062 A1. The flat tube described therein is advantageously suited for use in various types of heat exchangers, particularly for applications in the automotive sector. In that patent, the flat tubes are brazed from sheet metal strip during their manufacture (see the relevant section therein). Fig. 10c).

[0003] A similar flat tube is known from WO 00 / 52 409 A1.

[0004] Since one of the narrow sides of this state of the art has folds, care must be taken when assembling the flat tubes to the heat exchanger to ensure that the flat tubes are correctly oriented, as the stable narrow side – viewed in the direction of travel of the vehicle – should always be at the front. This can be considered a disadvantage of this state of the art.

[0005] Furthermore, there is an almost unmanageable number of other publications concerning flat tubes for heat exchangers.

[0006] Modern heat exchangers for motor vehicles currently on the market, for example in coolant coolers, feature flat tubes with a wall thickness of approximately 0.20 mm. These flat tubes are manufactured from sheet metal strip and welded with a longitudinal seam.

[0007] Further reduction of the wall thickness reaches its limits in terms of manufacturing feasibility. For example, it is known, and has also been confirmed in tests carried out by the applicant, that the soldering of the flat tube ends to the significantly thicker tube sheets (due to strength considerations) becomes increasingly difficult as the wall thickness of the flat tubes decreases. Similar difficulties arise with regard to the reliable production of high-quality longitudinal welds in the flat tubes manufactured from sheet metal strip when the wall thickness falls significantly below the specified value.

[0008] EP 1 158 260 A1 describes a heat exchanger with a core consisting of tubes provided with media passages and fins attached to the tubes, wherein a tube is shaped to have a flat cross-sectional form by joining the ends of one or two plates, the ends of the plates having a contact section formed by repeatedly bending at least one of the plate ends and overlapping one end over the other. GB 683 161 A describes a thin-walled, narrow heat exchanger tube with a quasi-rectangular cross-section, manufactured from a pair of rectangular sheets, wherein the noses of the tube are formed by compact zigzag folds. PRESENTATION OF THE INVENTION

[0009] The object of the invention is to provide a suitable flat tube with a significantly thinner wall thickness, to specify a manufacturing process for it, and to present a heat exchanger which, despite the small wall thickness of its flat tubes, can be manufactured particularly cost-effectively, as well as to describe a cost-effective manufacturing process for the heat exchanger.

[0010] The heat exchanger according to the invention has the features of claim 1. The manufacturing process for heat exchangers according to the invention is carried out with the process steps of claim 7. The dependent claims contain further developments and variants. The inventors proceed from the understanding that established paths must be abandoned and new ones taken in order to achieve a significant competitive advantage. Flat tubes are provided which can be manufactured from a single piece, a single continuous sheet metal strip, or an undivided continuous strip, which, after forming, is joined at the longitudinal edges of the strip by brazing or welding, preferably at one of the narrow sides. The flat tubes according to the invention are characterized in that, despite the extremely small sheet metal strip thickness, they have not just one but two very stable narrow sides and that, due to the small wall thickness, they exhibit good thermal properties.The assembly of the flat tubes into the heat exchanger was therefore also simplified.

[0011] The first folds forming the narrow sides are arranged perpendicular or parallel to the broad sides. These folds are multiple folds and can have varying lengths, thus preventing cracks caused by excessive temperature fluctuations. Since the second narrow side also has multiple folds, it is possible, despite the thin sheet thickness of 0.05 mm to 0.20 mm, to join the longitudinal edges of the sheet metal strip on this narrow side of the flat tube by welding. This has the advantage, among others, that the flat tubes, cut to length, cannot subsequently unfold or open up.

[0012] The broad sides of the flat tube exhibit further folds or other deformations within the tube. These other deformations can be inwardly directed beads or similar features, which, however, do not extend to the other broad side. These further folds form flow channels within the flat tube. The further folds can also be multiple folds, with individual folds arranged close together.

[0013] The spacing of the further folds can increase from the narrow sides towards the center, which also improves resistance to high temperature cycling.

[0014] The inventors propose a heat exchanger intended primarily for use as a vehicle radiator. The flat tubes used have a wall thickness of 0.050 mm to 0.25 mm, preferably with an upper limit of 0.15 mm to 0.20 mm. This significant reduction in the wall thickness of the flat tubes initially leads to a considerably improved heat transfer. Furthermore, this measure naturally results in a significantly reduced weight of the heat exchanger.

[0015] Because the inventors anticipate inadequate solder joints between the flat tube ends and the tube sheets in such flat tubes, they depart from the well-established and currently practiced method of heat exchanger manufacturing and propose soldering the network of flat tubes and corrugated fins—in which the corrugated fins also have wall thicknesses in the range of 0.030 mm to 0.090 mm—without tube sheets or manifolds. The flat tube ends protruding from the network remain free during soldering. Free flat tube ends, therefore, are those that have no fins between them and no tube sheets into whose openings the flat tube ends are inserted in the prior art. The flat tube ends protrude from the flat tube-fin block preferably by a few millimeters and are thus described as "free."

[0016] Furthermore, the inventors propose using collection boxes that have at least one series of receiving openings into which the free flat tube ends of the at least one series of flat tubes of the already soldered network can be inserted. Preferably, the collection boxes are made of plastic. They are considering manufacturing the collection boxes as one-piece injection-molded parts, i.e., the at least one series of receiving openings is integrated into the collection boxes. Should the production of two or more collection boxes prove more advantageous, then collection boxes should be used that have the at least one series of receiving openings in one piece and the remaining wall of the collection box in at least one other piece. The at least two pieces of the collection boxes would then be tightly joined together later.The proposed collection boxes have no, or if any, negligible overhang of the cooling network in the direction of its depth. Therefore, no waste of the already limited installation space in the vehicle occurs.

[0017] The inventors may prefer not to deform the flat tube ends. However, they also state that there are applications where deformed flat tube ends can be advantageous, for example, given the aforementioned minimal overhang of the collection boxes. This deformation is intended to be carried out without significant stress on the wall, considering the exceptionally thin wall thickness of the flat tubes. Specifically, the circumference of the undeformed flat tube end remains the same as the circumference of the deformed flat tube end, thus ensuring that the wall is not subjected to any significant elongation. In practice, this means that during the deformation process, the larger diameter of the flat tube end is reduced by a certain amount, and the smaller diameter of the flat tube end is increased by the corresponding amount.It should be noted that the length of the free flat tube ends is somewhat greater when their forming is planned than in cases without forming.

[0018] The inventors focused primarily on CAB soldering technology for the production of the aforementioned cooling core and identified the appropriate soldering parameters. The proposed cooling cores are manufactured with significantly less energy consumption because the belt or conveyor chain speed, at which the cooling cores are transported through the different temperature zones of the CAB soldering oven, is considerably higher than current standard speeds. This is due to the extremely thin sheet metal of the flat tubes and corrugated fins, which allows the soldering temperature to be reached much faster than with thicker sheets. The transport speeds were optimized with corresponding temperature settings. Furthermore, they were improved through the use of suitable suspensions and / or...Auxiliary devices were used to ensure that the proposed cooling cores did not lose their shape after the soldering process was completed; that is to say, that the expansion and contraction of the cooling cores during heating and cooling did not lead to distortion that fell outside the permissible tolerance range. However, the tolerance range is relatively narrow.

[0019] After the radiator cores have left this manufacturing stage, their free flat tube ends are inserted into the aforementioned receiving openings of the manifolds in a further step. If the aforementioned forming of the flat tube ends is required, this should be carried out now, preferably before the flat tube ends are inserted into the corresponding receiving openings. The receiving openings have corresponding ramps to facilitate the insertion of the flat tube ends. Preferably, the flat tube ends should not protrude into the interior of the manifold so that the otherwise unavoidable pressure loss in the medium flowing through the flat tubes remains at the desired low level.

[0020] The inventors opted for a type of adhesive bond between the flat tube ends and the mounting openings. For this purpose, injection ports for the adhesive are provided in the wall of each mounting opening. Using these injection ports, the adhesive is introduced into the gap between the individual flat tube ends and the wall of their mounting openings, where it hardens and ensures a permanent and tight bond between the flat tube ends and the mounting openings. As an alternative, the adhesive can also be applied without injection ports, as access to the gap is possible from below.

[0021] It was found that the width of the aforementioned gap should be in the range of 1.0 mm. The adhesive should, however, ideally cover the entire circumference of the flat tube end. The adhesive in question is a suitable plasticized sealant. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The invention is described below using exemplary embodiments, with reference to the accompanying drawings. Further features and effects, which may be essential, will become apparent from this description.

[0023] The figures show the following: The Fig. Figure 1 shows manufacturing stages and a narrow side of a flat tube. Fig. Figure 2 shows a section of another flat tube. Fig. Figure 3 shows a section of another flat tube. The Fig. Figures 4-9 show further flat tubes in cross-section. The Fig. Figures 10-12 show a collection box of a first embodiment of a heat exchanger without inserted flat tubes. The Fig. 13 and Fig. Figure 14 shows sections of the first embodiment with inserted flat tubes. The Fig. Figures 15-17 show a heat exchanger from different perspectives. The Fig. 18 and Fig. Figure 19 shows sections of another embodiment with inserted flat tubes. The Fig. Figures 20-23 show a collection box of another embodiment of a heat exchanger without inserted flat tubes. The Fig. 24 and Fig. Figure 25 shows sections of another embodiment with inserted flat tubes. The Fig. Figures 26-28 show a collection box of yet another embodiment of a heat exchanger without inserted flat tubes. The Fig. Figure 29 schematically shows the manufacturing process of a heat exchanger. DESCRIPTION OF EXAMPLES OF EXECUTION

[0024] The following description focuses primarily on a new coolant radiator for motor vehicles, without, however, excluding other uses, particularly in motor vehicles. For example, the flat tubes and heat exchangers according to the invention are also intended for use in charge air coolers and oil coolers, where they essentially differ only in their dimensions. One difference worth mentioning between coolant radiators and charge air coolers is that the flat tubes according to the invention, when used as charge air coolers, can have larger cross-sections and usually separate internal inserts. The flat tubes for coolant radiators shown in the exemplary embodiments do not have separate internal inserts.

[0025] The strip thickness, or the subsequent wall thickness of the flat tubes, is 0.10 mm in this case. The strip material, made of an aluminum alloy, has a solder coating on both sides. The thickness of the solder coating is 10–20% of the thickness of the strip. The small diameter d of these flat tubes should be in the range of 0.8 mm to 1.5 mm or 2.0 mm. The large diameter D is (also) freely selectable within certain limits. In the example shown, it is 50 mm. However, flat tubes with virtually any dimensions can be produced using the proposed method, for which, of course, a strip material of a specific width Bb must be provided, and the production line equipment must be adjusted accordingly.

[0026] In the area of ​​the narrow sides 1 of the flat tubes, a multiple fold 31 is present, which, despite the extremely thin wall thickness of the flat tubes, results in relatively stable narrow sides 1 that provide sufficient protection of the flat tubes against damage. This is of great importance when using the heat exchangers in motor vehicles.

[0027] According to the Fig. 1. First, single folds 30 or multiple folds 31 are formed in the endless, one-piece, metallic strip. These single folds 30 or multiple folds 31 later lead to flow channels SK, which are formed in the flat tube. Then, another multiple fold 31 is produced, forming one of the narrow sides 1.1, by folding the strip over immediately at the multiple fold 31 according to the arrow shown, in order to obtain the first and second broad sides 2.1 and 2.2 of the flat tube. The second narrow side 1.2 and the multiple fold 31 also present there were in the Fig. 1 not shown.

[0028] The Fig. 2 and Fig. Figure 3 shows different formations of single folds 30 and multiple folds 31, which form flow channels SK.

[0029] The Fig. 4 - 7 now show, in contrast to the Fig. 1, the entire flat tube in cross-section and in three different versions. In the Fig. 6 and Fig. In section 7, it was shown that the single folds 30 and multiple folds 31 forming the flow channels SK can have increasing distances a and increasing flow channels SK, respectively, starting from the narrow sides 1.1 and 1.2 towards the center of the flat tube. The number of individual folds forming a multiple fold 31 is expediently defined. In the Fig. 4 The multiple folds 31, for example, have a fourfold wall thickness, or two individual, closely spaced single folds 30, and in the Fig. 5 provides for a wall thickness six times greater (three individual folds) than the multiple folds 31. In the Fig. 6 only single folds 30 were used to form the flow channels SK.

[0030] Furthermore, the Fig. 4 a flat tube in which the multiple folds 31 forming the two narrow sides 1.1 and 1.2 are arranged perpendicular to the broad sides 2.1 and 2.2. The multiple folds 31 themselves are also formed differently. While the right narrow side 1.1 is a multiple fold 31 formed from the strip, the left narrow side 1.2 is provided with a multiple fold 31 formed from the two longitudinal edges of the single strip. Finally, it is also possible to generate the multiple fold 31 from a single longitudinal edge and simply attach the other longitudinal edge to the multiple fold 31 thus generated (not shown). In contrast, the Fig. 5, that it is furthermore possible to design one narrow side 1.1 with multiple folds 31 arranged vertically to the broad sides 2.1, 2.2 and to form the other narrow side 1.2 with a multiple fold 31 arranged horizontally to the broad sides 2.1 and 2.2.

[0031] The Fig. 6, Fig. 7 and Fig. Figure 8 shows flat tubes with multiple folds 31 arranged horizontally on both narrow sides 1.1 and 1.2. Such multiple folds 31 can also have different lengths L, as shown in the Fig. Figure 7 illustrates this. This measure is particularly effective with regard to temperature fluctuations. It avoids abrupt transitions from the narrow sides 1.1, 1.2 to the wide sides 2.1, 2.2. In the Fig. 7. The central fold 3 was designed as a multiple fold 31, while all other folds 3 are single folds 30. Another measure aimed at improving thermal cycling resistance is the one already described above, whereby the distances a of the folds 3 or the flow channels SK from the narrow sides 1.1, 1.2 become larger, see Fig. 2, Fig. 6 and Fig. 7.

[0032] The Fig. Figure 9 again shows only one of the narrow sides 1.1 of the flat tube with a further embodiment of the multiple fold 31 forming the narrow side 1.1. The other narrow side 1.2 could, for example, be as in Fig. Figures 4-8 are shown. It should be noted that the distances a are usually very small. They can start at 0.5 mm and not exceed a few millimeters. Furthermore, it should be pointed out that the illustrations depicting the flat tubes are multiple magnifications. Thus, a flat tube with a width of 42 mm will have significantly more single folds 30 and multiple folds 31 or flow channels SK than, for example, in the Fig. Figure 1 is shown. A flat tube currently considered quite promising is in the Fig. Figure 8 illustrates this. Only half of the flat tube is shown there. The distances a are equal and very small in magnitude. However, the preceding remarks do not preclude distances a in the centimeter range.

[0033] The Fig. Figures 10-14 now show a first embodiment of a heat exchanger, which has flat tubes as described in a previously described embodiment. The same applies to the following embodiments of a heat exchanger – they also have such flat tubes.

[0034] For example, flat tubes, which are in the Fig. The embodiments shown in Figure 8 are cut to the length required for the respective application. Subsequently, the flat tube-rib block 10 is formed from flat tubes and corrugated ribs 9 by alternating stacking of flat tubes and corrugated ribs 9, as is the case, for example, in the Fig. Figure 15 shows a front view of an already assembled heat exchanger. The flat tube fin block 10 initially has free flat tube ends 11 at both ends. In the Fig. The free flat tube ends 11 are already inserted into the receiving openings 12 of the collection boxes 50. The flat tube-rib block 10, which contains the free flat tube ends 11, is placed in a soldering furnace to metallically join the flat tubes with the corrugated ribs 9. The flat tube-rib block 10 then passes through a cooling zone and is available as a united flat tube-rib block 10 for further assembly. A collection box 50 is then slid onto each of the free flat tube ends 11, which, for example, is placed in the Fig. 10, Fig. 11 and Fig. Figure 12 shows that the collection boxes 50 are made of plastic using injection molding, a method that has been successful for decades. However, the details of this embodiment are taken from the... Fig. 13 and Fig. 14 better to

[0035] The flat tube ends 11 remain undeformed in this embodiment. The collection box 50 has a series of receiving openings 12. Each receiving opening 12 is enclosed by a wall and receives a flat tube end 11. The flat tube ends 11 located in the receiving openings 12 terminate below the inner surface 51 of the collection box 50 to minimize pressure loss. The end of the receiving openings 12 is designed or dimensioned so narrowly that the flat tube end 11 can be inserted with slight pressure. A stop for the flat tube ends 11 may also be provided to limit their insertion depth. Fig. Figure 29 schematically illustrates the manufacturing process of the heat exchanger described here, in four grouped stations. It also shows a soldered flat tube finned block 10, onto whose free flat tube ends 11 the collector boxes 50 are placed. The term "station" is merely a descriptive aid. It does not necessarily imply a physical separation between the "stations." For example, where the collector boxes 50 are slid onto the free flat tube ends 11 (Station III), the adhesive 20 can be applied immediately afterward and at the same location (Station IV).

[0036] The liquid coolant of the vehicle engine should ideally not come into contact with the adhesive 20 used. In the Fig. 13 and Fig. Figure 24 indicates that the adhesive 20 was applied to one of the flat tube ends 11. This measure is intended to help prevent mutual interference. Therefore, it was decided not to apply the adhesive 20 to the very end of the flat tubes. This is achieved through different designs. In the case mentioned, as stated, the flat tube ends 11 are seated in narrow receiving openings 12 at their very end. Furthermore, the insertion of the flat tube ends 11 of the entire flat tube-rib block 10 into their respective receiving openings 12 is carried out in one continuous operation. When the manifold 50 with its receiving openings 12 is properly seated on the flat tube ends 11, the adhesive 20 – a suitable plastic sealant – is injected – preferably also in one continuous operation – through the injection openings 15 into the gap 13 between the flat tube ends 11 and the wall of the receiving openings 12. As the Fig. As best illustrated in Figure 14, it is advantageous—though not essential—to form a series of injection openings 15 on each of the long sides of the collection box 50 so that the adhesive 20 reliably wets the entire circumference and / or fills as much of the gap 13 as possible. In this case, the adhesive 20 is also applied simultaneously from both sides. The width of the gap 13 in this embodiment need not be greater than approximately 1.0 mm. It can even be considerably smaller, perhaps 0.3 mm. The injection openings 15 can also be omitted if the adhesive 20 is applied from the underside 80 ( Fig. 14) is entered into column 13.

[0037] As is known, the collection boxes 50 have connection openings 61, 62 for the coolant to operate the heat exchanger. It is understood that one of the collection boxes 50 could also be designed as a diverter box, in which case both connection openings 61, 62 would be arranged on a single collection box 50. Cooling air flows through the fins 9 of the flat tube-fin block 10. The exemplary embodiments, beginning with the Fig. 18, have flat tube ends 11 which have been formed and which should of course have correspondingly adapted designs of the receiving openings 12. The forming of the flat tube ends 11 (not shown) preferably takes place after completion of the brazing process, ( Fig. 29, after station II) i.e. before the insertion of the flat tube ends 11 into the receiving openings 12 - also in a forming process step. In the Fig. 18 and Fig. 19 The reshaped very last ends of the flat tube ends 11 sit in tightly formed ends of the receiving openings 12, similar to the first embodiment.

[0038] The above regarding the timing of the forming process does not preclude the possibility that, after the flat tube ends 11 have been inserted, they may be additionally pressed into the receiving openings 12 using a tool or otherwise machined to improve their fit. (not shown)

[0039] In the Fig. 24 and Fig. In contrast, in embodiment 25 a slot or groove 55 is provided circumferentially in the receiving openings 12, into which the very last ends of the flat tube ends 11 are initially inserted without the use of an adhesive 20. These grooves 55 also have a stop to limit the insertion depth. The adhesive 20 is also preferably applied after insertion. The inventors propose, mainly for the embodiments with formed flat tube ends 11, to install external filler pieces between the flat tube ends 11, which are intended to help prevent deformation of the flat tube ends 11 under internal pressure. In the Fig. Figure 24 shows such filler pieces with reference numeral 70. In the illustrated embodiment, they have a trapezoidal cross-section. This measure (filler pieces 70) may be necessary because the forming of the flat tube ends 11 inevitably involves the removal of the folds 3 present inside the flat tubes in the forming area. The filler pieces 70 can be inserted before or after the application of the adhesive 20 ( Fig. 29 after station III or before or after station IV). They can be made of plastic or metal, and they can be formed in one piece, for example, comb-like, with the individual filler pieces 70 arranged at appropriate intervals on a straight rail by means of which all filler pieces 70 can be inserted in one go. The rail can be removed after insertion or remain on the collection box 50, as it takes up hardly any space. (not shown) To attach and secure the filler pieces 70, corresponding openings 72 can be arranged in the two opposite walls of the collection box 50, through which the filler pieces 70 are inserted and finally held in their position. The series of openings 72 extends from the Fig. 26. The term "filler pieces" does not necessarily mean that their entire space must be filled. These pieces only need to be suitable for acting as supports for the flat tube ends 11. This can mean that a hardening compound (adhesive 20) is also a filler piece 70. Furthermore, it can mean that a correspondingly shaped hollow body is also a filler piece 70. In addition, stiffeners 71 can be formed in the collection box 50 between the wall of the receiving openings 12, extending transversely to the collection box 50, and are particularly effective when the depth of the flat tube rib block 10 or the collection box 50 requires stiffening measures. The stiffeners 71 are formed during the aforementioned injection molding process of the collection box 50 and are thus part of the collection box 50 or part of a collection box component. In the diagram showing a cross-section through the collection box 50 Fig. In section 25, it was suggested what it might look like if the collection box 50 consisted of two parts 50a and 50b. The parts 50a and 50b are connected along a line in the Fig. The Z-shaped line shown in bold is preferably tightly connected by welding or gluing. Whether two parts 50a, 50b, or more parts are provided depends on the manufacturability of the collection box as an injection-molded product, i.e., on the intended shape of the collection box 50. The manufacturing costs must be taken into account here. In a two-part design, the stiffeners 71 are located in the lower part 50a.

[0040] It may also be provided that at least one longitudinal stiffener 75 is arranged between the receiving openings 12. Fig. Figure 11 shows another cross-section through the collection box 50, in which a portion of the longitudinal stiffening 75 lying on the center line is visible, extending over the entire length of the collection box 50.

[0041] How a comparison of Fig. 14 with the Fig. 19 or the Fig. Figure 25 shows that the reshaped flat tube ends 11 allow for a minimized or even no overhang Ü of the manifold 50 over the flat tube fin block 10, which meets the need for minimal space consumption of the heat exchanger. As the Fig. As shown in section 14, the overhang Ü is also relatively small compared to the state of the art, only a few millimeters, even when there are undeformed flat tube ends 11.

Claims

[1] Heat exchanger, especially for motor vehicles, consisting of a brazed flat tube finned block (10) in which the flat tubes are formed from a single metallic strip, and with collector boxes (50) arranged at the ends of the flat tubes, characterized by , that the wall thickness of the flat tubes is 0.050 mm - 0.25 mm and the wall thickness of the ribs is 0.030 mm - 0.090 mm and that the soldered flat tube-rib block (10) has free flat tube ends (11) which can be inserted into receiving openings (12) of the collecting box (50) and fastened and that the free flat tube ends (11) are glued into the receiving openings (12) of the collection box (50), the adhesive being placed in a gap (13) between the individual flat tube ends (11) and the wall of the receiving openings (12). [2] Heat exchanger according to claim 1, characterized by, that the receiving openings (12) are surrounded by a wall, and a gap (13) is formed between the wall and the flat tube end (11). [3] Heat exchanger according to claim 2, characterized by that there is either at least one injection opening (15) in the wall, or that there is access to the gap (13) from the underside (80). [4] Heat exchanger according to any of the preceding claims, characterized by , that the receiving openings (12) are designed in such a way that the adhesive (20) can as little as possible come into contact with the medium flowing through the heat exchanger. [5] Heat exchanger according to any of the preceding claims, characterized by , that the connection (4) of each flat tube can be made during the soldering of the flat tube rib block (10). [6] Heat exchanger according to any of the preceding claims, characterized by that the flat tubes are welded flat tubes. [7] Method for manufacturing a heat exchanger, in particular for motor vehicles, comprising a brazed flat tube finned block (10) the flat tubes of which are manufactured from a single part, characterized by , that the flat tube rib block (10) is formed such that initially free flat tube ends (11) are present, that the flat tube rib block (10) having the free flat tube ends (11) is soldered in the soldering furnace, that a collecting box (50) having receiving openings (12) for the flat tube ends (11) or a first collecting box part (50a) with receiving openings (12) is placed on the free flat tube ends (11) of the soldered flat tube rib block (10), and that an adhesive (20) is applied to a gap (13) between the flat tube ends (11) and the wall of the receiving openings (12). [8] Method according to claim 7, characterized by, that if necessary a second collection box part (50b) is connected to the first collection box part (50a), this step being carried out before or after the application of the adhesive (20). [9] Method according to claims 7 or 8, characterized by that the adhesive (20) is introduced into the gap (13) through at least one injection opening (15) or from the underside (80). [10] Method according to any one of claims 7-9, characterized by that the flat tube ends (11) are preferably formed before being inserted into the receiving openings (12). [11] Method according to any one of claims 7-10, characterized by , that filler pieces (70) are inserted between the flat tube ends (11) to support the flat tubes against internal pressure. [12] Method according to any one of claims 7-11, characterized by , that the flat tube ends (11) are inserted into the receiving openings (12) without being reshaped.

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