EP1805469A1

EP1805469A1 - Flat tube for a heat exchanger

Info

Publication number: EP1805469A1
Application number: EP05800345A
Authority: EP
Inventors: Jürgen Hägele
Original assignee: Behr GmbH and Co KG
Current assignee: Mahle Behr GmbH and Co KG
Priority date: 2004-10-12
Filing date: 2005-10-11
Publication date: 2007-07-11
Anticipated expiration: 2025-10-11
Also published as: DE102004049809A1; TR201910994T4; US20070295490A1; EP1805469B1; JP2008516177A; WO2006040118A1

Abstract

The invention relates to a multi-channel flat tube (1) for a heat exchanger, especially for use in motor vehicles, which comprises a first lateral wall (14), a second lateral wall (15) substantially parallel to the first lateral wall (14), and at least one curved end section (17). A projection (9) from the material of the lateral wall (14, 15) is configured on at least one lateral wall (14, 15) on the inside facing a fluid flow in the interior of the flat tube (1). On the outside facing away from the fluid, the lateral wall (14, 15) is substantially planar in the area of the projection (9).

Description

Flat tube for heat exchanger

The present invention relates to a flat tube for a heat exchanger, in particular for a motor vehicle. Heat exchangers in motor vehicles, such as, for example, in motor vehicle air conditioning systems, have in the prior art, in addition to collecting devices for a refrigerant, flat tubes which are provided for the forwarding of the refrigerant or other fluids.

These flat tubes are connected to the collection devices via tube sheets or the like. In this connection, particular importance is attached to the tightness.

The flat tubes known from the state of the art have ridges or projections in their interior which cause the flat tube to be multi-channeled overall.

These known from the prior art webs consist of both sides molded beads or one-sided molded webs. However, the flat tubes do not have a closed or smooth profile on their outside in the region of the webs. This non-smooth outer profile of the flat tubes means that when inserting the flat tubes into the trays, a higher process outlay has to be carried out in order to produce a fluid flow. to achieve an id-free connection. Moreover, in the prior art, the webs on the outside are not sufficiently closed so that leaks occur in the connection between the pipe and the bottom at the remaining tube outer cavities. In addition, it comes in a remaining groove on the outside of the flat tube to alloys during soldering. Furthermore, in the prior art, the tube outer cavities formed in the areas of the webs must be recalibrated after tube production at the tube ends in order to achieve smooth tubes on the outside.

EP 0 854 343 shows such Fiachrohre, which have on its outer side considerable external cavities, which are reduced drive by a complex Ver¬.

The present invention is therefore based on the object to provide a flat tube, which has projections in its interior and at the same time largely avoids recesses or Aus¬ savings on its outer side in the region of the projections.

This is inventively achieved by a flat tube according to claim 1 and a method for its preparation according to claim 12. Preferred developments of the flat tube and the method are the subject of the dependent claims.

The multichannel flat tube according to the invention for a heat exchanger, in particular for a motor vehicle, has a first longitudinal wall, a second longitudinal wall, which lies substantially parallel to the first longitudinal wall, and at least one curved end section. In this case, at least one longitudinal wall on an inner side of the material of the longitudinal wall facing the fluid flow in the interior of the flat tube is provided with a projection. trained. According to the invention, the longitudinal wall is substantially flat on its outer side facing away from the fluid in the region of the projection.

A multi-channel tube is understood to mean that a plurality of essentially separate channels are formed in the interior of the tube. A flat tube is understood to mean a tube that is configured in cross-section such that it far exceeds a further expansion direction in an expansion direction.

A longitudinal wall of the flat tube is understood to mean that wall which runs along one of the longitudinal sides. Under a formed from the material of the longitudinal wall projection is understood such a projection which is not subsequently applied to the wall, but - in particular, but not exclusively - is formed by a molding process from the wall itself.

The region of the projection is understood to mean that geometric region of the corresponding longitudinal wall in which the projection is formed. In essence, it is understood that the outer profile in the region of the projections has no recesses or only recesses with a small cross-sectional area.

In a further preferred embodiment, the projection is in contact with the other longitudinal wall, that is, the projection is formed on a longitudinal wall and contacts the opposite longitudinal wall. In this way, substantially separate channels can be created within the flat tube from each other.

In a further preferred embodiment, the flat tube has two curved end sections. Preferably, at least one end portion is bent through substantially 180 degrees to cause the two - A -

Longitudinal walls are arranged substantially parallel with respect to each other. The second end section can also be bent in an anterior fashion for closing off the flat tube, because, for example, in the course of the production process, the respective end regions of the base material can be partially bent by a predetermined angle, in order then to be joined together at this point.

In a further preferred embodiment, a plurality of projections are formed on a longitudinal wall of the material of the longitudinal wall.

In a further preferred embodiment, projections are formed on both longitudinal walls of the material of the longitudinal walls. In this case, in a further preferred embodiment, all projections contact the respectively opposite longitudinal wall. In this way it can be achieved that, in the manufactured state, the flat tube is formed with a plurality of chambers which are substantially separated from each other.

In this case, the distances between the projections can be chosen such that the finished flat tube has channels with a substantially constant cross-sectional area.

In a further preferred embodiment, it is also possible to form the projections in such a way that they do not contact the opposite longitudinal wall, but rather a further projection arranged on the opposite longitudinal wall.

In a further preferred embodiment, at least one projection preferably has a plurality, particularly preferably all projections, a substantially symmetrical profile. This means that the protrusion has a symmetry which is essentially perpendicular to the plane of the longitudinal wall. with respect to which the projection is formed substantially axially symmetrical.

In a further preferred embodiment, the flat tubes have a depth of between 0.5 mm and 5 mm, preferably between 0.8 mm and 4 mm and particularly preferably between 1 mm and 3 mm. These respective depths depend on the actual applications in the heat exchangers to be manufactured.

In a further preferred embodiment, at least one wall has a wall thickness between 0.05 mm and 0.8 mm, preferably between 0.07 mm and 0.6 mm, and more preferably between 0.1 mm and 0.5 mm. Depending on this wall thickness, the corresponding protrusions are preferably adapted, wherein, in particular, procedural conditions must also be taken into account.

The present invention is further directed to a method of manufacturing a multi-channel flat tube for a heat exchanger. In this case, in one method step, a projection having a predetermined profile is produced from a material strip by means of a first shaping unit and a second shaping unit interacting with the first shaping unit.

In a further method step, the profile of the projection is changed by means of a third shaping unit and a fourth shaping unit interacting with the third shaping unit.

A change in the profile is understood to mean that predetermined geometric changes are made to the projection or its cross section. A shaping unit is understood to mean a device which acts on the material to be processed in such a way that its shape is changed at least locally.

The shaping units are preferably rollers that rotate relative to one another. Thus, preferably, the first and the second shaping unit are designed as mutually rotating upper and lower rollers, between which the material to be processed is arranged. Also in the third and fourth shaping unit are corresponding roles, between which the material to be processed is arranged.

The rollers are preferably designed in such a way that one roller is bounded by lateral ends of the other roller in order to prevent a broadening of the material strip to be processed in the course of the deformation process.

In a further preferred embodiment, the rollers have a substantially cylindrical profile.

However, it would also be possible to provide two opposing pads instead of rollers, between which the material is pressed or drawn through.

The change of the profile in at least one procedural step preferably consists in its height and / or width being reduced. Preferably, both the height and the width of the projection are reduced during this method step. In this way it can be achieved that the outer side of the flat tube is leveled in the region of the projection, that is, a recess is reduced in this area.

Preferably, in at least one further method step, the profile of the projection is further changed. In turn, the height is preferred and / or reduces the width of the profile. Preferably, a plurality of method steps are provided in succession, in which the profile of the projection is changed continuously, wherein this change in each case at least in the reduction of the width or the height of the profile. Each of these method steps serves - as stated above - to achieve as much as possible an outer surface of the flat tube profile in the region of the projection.

Preferably, the profile of the projection is changed in at least four, more preferably in at least six process steps. When carrying out fewer process steps, there would be the risk that the material to be processed would not have grown up to the massive transformations that would then be necessary and thus cracks and the like could occur. Upwards, the number of process steps is limited by the efficiency offered both in terms of manufacturing costs, as well as in terms of time.

In a further preferred method, pre-centering of the projection is carried out in a further procedural step. This is preferred over a preference.

The rotatable rollers, through which the material is carried out, preferably have a substantially constant distance from each other. In this way it is achieved that the material to be processed has a substantially constant wall thickness or thickness. The material of the roller is preferably matched to the material to be processed such that a diffusion of material particles is prevented.

In at least one method step, the width of the material strip is preferably reduced. The material is fed to the rolls in the form of strips of predetermined dimensions. Below the width of the material stripe Fens is understood to mean the expansion in the direction of the roller axis. By this procedure, the formation of the respective projection can be achieved in a particularly advantageous manner. In a further preferred embodiment, the width of the material strip remains constant in at least one method step. In these process steps, a change in shape of the projection is achieved substantially without the use of further material from the vicinity of the projection.

Preferably, a plurality of projections are formed from the strip of material. For this purpose, the required amount of additional material can preferably be obtained in a first method step by reducing the length of the strip.

In this case, the projections are preferably formed at predetermined intervals relative to one another. Preferably, the projections are chosen such that the flat tube produced in this way substantially has a plurality of channels with substantially the same cross-section.

In at least one method step, different projections are preferably subjected to different shaping stages. This means that a certain projection is already adapted in its shape, while another projection is first formed or a projection is already given its final shape, while another projection is still adapted in an intermediate step in its shape.

In this way, under certain circumstances, it can be achieved that a plurality of projections are produced with a few forming steps in such a way that protrusions which are already pre-formed or fully formed are no longer changed in their shape. In a further method step, a curved section is preferably produced. Preferably, a curvature of 180 degrees is created so as to arrange the longitudinal walls substantially parallel to each other.

Further advantages and embodiments will become apparent from the accompanying drawings.

Showing:

1 shows an illustration of the method according to the invention for producing a projection;

Figure 2a is an illustration of the shaping units according to the invention for producing a projection.

Fig. 2b is an illustration of the shaping units for changing the profile of the projection;

FIG. 2c a representation of the shaping units for further modification of the profile of the projection; FIG.

Fig. 3 is an illustration for illustrating the manufacturing process for producing an even number of protrusions;

FIG. 4 shows a flat tube finished by the method illustrated in FIG. 3; FIG.

Fig. 5 is a figure for illustrating the production of a flat tube having an odd number of protrusions; FIG. 6 shows a flat tube produced by a method according to FIG. 5; FIG.

7 shows a flat tube according to the invention in a first embodiment;

8 shows a flat tube according to the invention in a second embodiment;

9 shows a flat tube according to the invention in a third embodiment;

10 is an enlarged view of a projection for illustrating the geometric relationships; and

11 shows a flat tube according to the invention for illustrating the geometric conditions.

FIG. 1 shows the individual method steps of a method according to the invention for producing a projection. The individual process steps are marked with the Arabic numbers 1 to 6. The respective lower case letters a) to f) denote the width of the material, that is the material strip, during the manufacturing process. The capital letters A to F mark the end points of the material strip.

It should be noted that the method illustrated in FIG. 1 merely represents a possible variant of the method according to the invention. According to the invention, further method steps can also be provided or individual method steps can be omitted.

The reference symbol L denotes the center line, preferably the axis of symmetry of the protrusion 9a to 9f produced. In the optional Verfahrens¬ step 1a, a pre-centering of the projection 9a is made by a preference. This is particularly advantageous if the projections or webs with large heights HA to HF to be generated. In method step 2, the strip of material or the strip 7 is reshaped in the area Z shown. For this purpose, the respective shaping units, that is to say preferably the rollers, have a bead-like shape. The generation of the protrusion 9b in procedural step 2 produces the total width b of the strip 7, the total width b being less than the total width a, or the total width a 'in the method steps 1 and 1a.

The height HB generated in method step 2 represents the maximum height H _{ma of} the projection 9b, which is at least partially reduced in the course of further method steps.

In stages 2 to 6, the unwinding of the neutral fiber in zone Z remains almost constant. This means that in the region Z, essentially the same amount of material is always supplied to the shaping units or the rollers. This is achieved by appropriate design of the respective shaping stages in steps 2 to 6 by maintaining the respective total strip widths.

The widths of the strip b to f thus remain substantially constant in the process steps 2 to 6. In order to keep the total strip widths b to f constant, the material strip 7 is preferably held with suitable tools at the respective end points B to F.

During the process stages 2 to 6 thus essentially only a transformation of the projection 9 takes place. In detail, both the height H and the width of the projection 9 decrease, and the respective flanks 25 are steeper. Also, the radius of curvature at the tip of the respective projection 9a to 9f decreases in the course of the process. This means that the material which, by reducing the height and width, te is saved, is essentially added by the fact that the surface of the recess 11 is continuously reduced below the projection.

In other words, the width of the strip between the starting point 33 and the end point 34 preferably remains substantially constant during the method steps 2 to 6. During method steps 5 and 6, a closure of the projection or the recess 11 below the projection 11 must be achieved, that is, the respective flanks 29 of the projection are pressed against each other. For this purpose, the material 7 in the region of the projection is substantially completely covered by the corresponding regions of the shaping units.

In method step 5, alternatively, the projection which is still open in method step 4 can also be folded, gathered or squeezed by folding. In such an approach, however, not the height H ₀ or H _{E is} substantially reduced, but the Gesamtstreifen¬ width. In this case, the risk of burr formation between the squeezing tools would have to be counteracted, and in addition, no ideally reduced ridge outer cavity 11 is achieved.

Furthermore, it is also possible to allow a change in the strip width in the region Z in at least one of the method steps 3 to 6, that is, in the method steps 3 to 6, the strip width b to f does not remain constant, at least in part , If this procedure is followed, material or band material can flow back into the band width, that is to say, out of the region of the projection when the projection is compressed. A possible consequence is that too little material is available for closing the outer hollow space 11 in further method steps, or more material has to be drawn in the first stages. In this case, even stronger thinning of the material strip 7 and a higher risk of cracking occur. Furthermore, under certain circumstances, the required web height can not be achieved, and the process becomes more sensitive to fluctuations in the strip material properties.

In the method step 6 shown here, a final height H _{F is} achieved which is less than the height H U in method step 5. Simultaneously, the region 11 which is still present in method step 5 is essentially closed, and therefore the smooth outer profile according to the invention achieved.

The bandwidth or overall width of the strip e is likewise not reduced further, that is, the bandwidth f and the bandwidth e are essentially the same.

FIG. 2 a shows the shaping units for carrying out the method according to the invention, in which it is an upper roller 21 and a lower roller 22. Between these rollers, the Flachrohrmate¬ rial or the material strip 7 is arranged, which is pulled in this way from the rollers through the rollers. The lower roller 22 has a machining projection 25 and the upper roller 21 a with respect to their shape to the machining projection 25 adapted recess. It would also be possible, conversely, to provide the upper roller with a projection and the lower roller with a recess.

The recess 26 and the machining projection 25 are adapted to each other so that between them the material with a predetermined thickness or thickness S can be passed. FIG. 2a shows the roller pair 21, 22 in the processing step 2 of FIG. 1, which means that the machining projection 25 and the recess 26 are adapted so that the resulting projection has the height H _B.

Between the upper roller 21 and the lower roller 22, gaps 13a and 13b are provided. During the first process step material of the strip is still drawn into the area of the upper roll.

2b shows the roller pair for method step 4. In this case, the recess 26 is designed such that the projection reaches the illustrated height HD. The lower roller 22 has here no longer Bearbeitungsvor¬ jump on. The gaps 13a and 13b between the upper roller 21 and the lower roller 22 are meanwhile reduced in width relative to the device shown in FIG. 2a. The lower roller 22 is designed, for example, according to the strip width b of the processing step 4 of FIG.

When compressing the strip of material or the tape runs against the lower roll. In this case, as soon as the height HB shown in FIG. 2a has been reached, the widths of the strip must be substantially constant, so that no area of the strip flows from the area of the projection into the flat area 7b of the strip ,

In Fig. 2c, the apparatus for the process step 6 shown in Fig. 1 is shown. In this case, the lower roller 22 likewise no longer has a machining projection, and only the upper roller 21 has a recess 26. This recess is adapted so that the final height H _{F of} the projection 9 results.

In addition to the method step shown in FIG. 2c, the gap widths 13a and 13b are selected to be minimal, that is to say the material or the band must be completely covered by the two rollers 21 and 22, so that the projection 9 can be reshaped such that the region 11 below the projection 9 can be substantially completely closed and in this way also in the region of the projection 9 a smooth Outside (here underside) of the material 7 results.

Fig. 3 shows the method in the case where a plurality of projections - more precisely, an even number of projections - to be generated. The individual method steps were identified here by the reference symbols I to VIII.

In a first optional step I, a clip 31 is produced by suitably adapted upper and lower rollers, that is, rollers which have a machining projection and a recess, as shown in FIG. The generation of this depression is advantageous in particular when the projections to be produced are to have a comparatively large initial height HB.

In method step II, two projections 9a and 9b are produced. For this purpose, an upper roller with a corresponding recess and a lower roller with a correspondingly adapted machining projection are preferably used. However, it is also possible to provide an under roll without machining projection in this process step.

The bandwidth is reduced from method step I with a stripe width a to method step II to a stripe width b and in step III to a stripe width c. However, it is also possible, in procedural step III, to carry out merely a deformation of the projections 9, that is, in this case, to keep the strip width c substantially constant with respect to the strip width b. In method step IV, two further projections 9c and 9d are produced by suitably adapted upper and lower rollers. For this purpose, the strip width c in method step III is reduced to strip width d in method step IV. For this purpose, the lower roller preferably has machining projections in the region of the projections to be newly produced.

Preferably, in the production of the projections, first the further inside and then the further outward protrusions are generated. This is advantageous, since in this way it is possible to use material from the respective outer regions of the material strip to produce the new projections and to prevent material from being drawn in from the regions of other already produced projections. However, it is also possible, instead of the projection shown here, to provide or to produce a plurality of projections. The method steps shown in FIG. 3 are also only examples. It would also be possible to provide significantly more process steps, as well as several forming processes.

In the process steps VI to VIII, in turn, the deformation of the individual projections already shown in FIG. 1 takes place, with the flanks becoming steeper and the radii of curvature at the tip of the projection becoming smaller and the heights, as shown in FIG and widths of the protrusions are reduced. The entire strip widths, such as f, g and h, are kept substantially constant, as already explained with reference to FIG.

The method step IV can also be supplemented by further method steps in order to produce additional projections or webs.

FIG. 4 shows a flat tube which can be produced by the method outlined in FIG. The flat tube 1 results in a cross section through a deformation of the strip shown in Fig. 3 at VIII. there the strip is bent 180 degrees in an area between the projections 9a and 9b, and further at the respective end portions so as to achieve the curved portions 18 and 19; The reference numerals 14 and 15 refer to the resulting longitudinal walls, which are arranged substantially parallel to each other.

By further molding processes, such as roll forming, the projections 9a to 9d can be arranged to contact the respective opposite wall (in the case of the projections 9b and 9d the wall 15, and in the case of the projections 9a and 9c the wall 14).

Preferably, the projections 9a to 9d or their Endbe¬ rich soldered to the respective opposite longitudinal wall. Likewise, the two bent end regions 18 and 19 are soldered together. By producing the four projections 9a to 9d shown here, a flat tube with a total of five channels is realized.

In Fig. 5, the process steps I to VIII for the production of a flat tube with an odd number of protrusions, more precisely, in this case, three protrusions, are shown. Reference numeral 41 also refers here to a substantially flat or smooth strip of material, that is a smooth belt, which has the width a.

In method step II, similar to method step II in FIG. 3, a projection 9a is produced. This projection is um¬ shaped in step III, wherein in this process step, the strip width a first to the width b, and this in turn to the width c, is reduced, that is, the width c is less than the width b and the width b less than the width a. In method step IV, two further projections 9b and 9c are produced. In this method, the generations of the individual projections 9a and 9b and 9c are offset, that is to say, whereas in the case of the projection 9a the first deformation has already taken place, the sections 9b and 9c have only been produced. The strip width d is further reduced with respect to the strip width c. In this variant as well, the inner and then the outer projections are preferably formed first.

In method step V, the three projections 9a, 9b and 9c are further formed. The strip width remains essentially constant, that is, the bandwidth e substantially corresponds to the bandwidth d.

In method step VI, a further deformation process of the type described above takes place, that is, the height of the individual projections 9a, 9b and 9c is reduced, as well as their width; instead, the flanks are made steeper and thus the radii of curvature at the tip of the projection are lower.

In a further method step VII, the projections are narrowed even further in order finally to be closed in method step VIII. The individual strip widths e, f, g and h remain substantially constant. In the last method step following the method step VIII, corner folds 42a and 42b are bent. These two corner folds lead to the production of a further projection, wherein corner folds can also be produced in a plurality of method steps.

In Fig. 6, a flat tube is shown, which results from the lowest strip shown in Fig. 5. In contrast to the embodiment shown in FIG. 4, the end sections are not in the area of the bends 17 or 16

18 arranged, but in the central area. That's exactly what it's about the respective bent-up folds 42a and 42b. These are welded or soldered together and thus provide another advantage.

In this embodiment too, the individual projections 9a to 9c as well as the projection resulting from the end folds 42a and 42b contact the respectively opposite longitudinal wall of the flat tube. Also in this embodiment, a flat tube with five channels. The method shown in Fig. 5 (step I-VIII) can be generally used for flat tubes with an odd number of protrusions, while the method shown in Fig. 3 is preferably used for flat tubes with an even number of protrusions. The formation of the end folds 42a, 42b according to FIG. 6 or the end folds 18, 19 according to FIG. 4, on the other hand, is largely possible independently of the number of protrusions, in particular in a known manner.

FIG. 7 shows a flat tube according to the invention, the individual dimensions serving for illustration. For a better understanding, the illustration of the smooth or planar outer surface of the flat tube according to the invention, that is, the representation of the miniaturized surface 11 under the projection 9, has been dispensed with. Also, the flanges of the projection were not shown compressed.

The reference a refers to the distance of the webs along a longitudinal wall. The reference symbol K denotes the distance between two adjacent bars, which under certain circumstances form a chamber. Reference T denotes the thickness of the flat tube.

In the embodiment shown here, the thickness T is preferably between 1 mm and 3 mm. The chamber or channel size is chosen here in about half as large as the web distance (distance of the projections) a. Of the In this embodiment, the minimum web spacing is at least twice as large as the width T. Therefore, the minimum chamber size or channel size is at least as great or larger than the thickness T.

In the embodiment shown in Fig. 8 projections 9 are attached only to the longitudinal wall 14, which contact the longitudinal wall 15. In this case, the web distance a is substantially identical to the chamber or channel size K. Also in this embodiment, the minimum web distance a is greater than the thickness T, which is also due here by the manufacturing process. Since the web distance a coincides with the channel size K, the channel size is at least twice as large as the thickness T of the flat tube.

In the embodiment shown in FIG. 9, the individual protrusions 9 do not contact the respectively opposite longitudinal wall 14 or 15, but contact projections 9 attached to the opposite longitudinal wall. This means that the ends of the protrusions are approximately in Contact the center of the flat tube. Also in this case, as in the embodiment of FIG. 8, the channel size K is substantially equal to the land distance a. However, in this case the minimum web spacing is greater than or equal to the thickness T of the flat tube. This also applies to the chamber size or channel size K.

In another embodiment (not shown), it is also conceivable to design the individual projections in such a way that, in contrast to the embodiment shown in FIG. 9, they are laterally slightly offset from each other so that they do not abut each other but on their side surfaces, whereby an increased connection surface can be achieved. 10 shows an enlarged view of a projection 9 according to the invention, in which the dimensions thereof are shown in detail. In order to achieve the final shape shown in Fig. 10, there are provided between four and ten process steps in which the projections are respectively reshaped. The number of process steps to be used depends on the height HF to be achieved, the wall thickness or strip thickness t and the material properties. If a plurality of projections, or webs to be generated, but far more process steps may be necessary.

In Fig. 10, rf denotes the upper radius of curvature, X the width of the projection at its tip, Y the width of the projection 9 at its base, RF the radius of curvature at the base of the projection, and R _D the radius of curvature of the recess 11. The individual Sizes are partly correlated with each other.

The limits shown in the following result from extensive soldering and forming try. In these experiments, the parameters were matched to one another according to a fixed system and the results were used for the limits shown here.

The upper radius of curvature rf in this embodiment lies between 0 and the wall thickness t, ie is smaller than the wall thickness t. The lower radius of curvature RF is less than twice the wall thickness t. The upper width X of the projection is between one and a half times and twice the wall thickness t. The lower width Y of the projection is between two and two and a half times the wall thickness t, that is, the upper width X is smaller than the lower width Y, which results from the Ausformungsprozes. The height of the projection H _F is between the wall thickness t and ten times this wall thickness t. Also, the lower radius of the recess r _D is smaller than the wall thickness t. The wall thickness t is between 0.05 mm, 0.8 mm, preferably between 0.1 mm and 0.7 mm and, more preferably, between 0.1 mm and 0.5 mm. This means that a substantially smooth outer profile is understood as meaning a profile which is caused by radii of curvature fo which are smaller than the wall thickness t. Fig. 11 shows a plan view of the flat tube according to the invention. This has only a single projection or web 9, and is therefore divided into two channels.

The ratio of the tube width b to the tube height H is between 10 and 30, preferably between 10 and 24.

The chamber or the channel size is between one third of the pipe width and half the pipe width.

The height of the projection hp is preferably between three times the wall thickness and eight times the wall thickness. The lower radius of curvature rd is such that it is less than 0.75 times, preferably less than or equal to 0.5 times the wall thickness t. In this embodiment, the wall thickness is between 0.05 mm and 0.6 mm, preferably between 0.1 mm and 0.4 mm and, more preferably, between 0.15 mm and 0.3 mm. This leaves a recess 11 on the outside of the flat tube, which has an area of less than 0.01 mm ² , preferably less than 0.006 mm ² . This represents a significant improvement over the prior art.

The recess 11 shown in FIG. 10 has an area of less than 0.1 mm ² , preferably less than 0.07 mm ² , which also represents a considerable improvement over the prior art. As a result of this considerable reduction in the area of the recess 11, the flat tube, as stated at the outset, can be soldered much more easily to the tube bottom and a leak-free connection can be achieved with considerably less effort.

Claims

Patent claims

1. Multichannel flat tube (1) for a heat exchanger, in particular for a motor vehicle, having a first longitudinal wall (14), a second longitudinal wall (15) which is substantially parallel to the first longitudinal wall (14), at least one bent end section (17) , wherein on at least one longitudinal wall (14,15) on the inner side facing the fluid flow inside a flat tube of the material of the longitudinal wall, a projection (9) is formed, characterized in that on the side facing away from the fluid, the longitudinal wall in Be ¬ rich the projection substantially flat.

2. Flat tube according to claim 1, characterized in that on ei¬ ner longitudinal wall (14,15) formed projection (9) is in contact with the other longitudinal wall (15,14).

3. Flat tube according to at least one of the preceding claims, characterized in that it has two curved end portions (17,18).

4. Flat tube according to at least one of the preceding claims, characterized in that on a longitudinal wall of the material of the longitudinal wall a plurality of projections (9a, 9b, 9c, 9d) are formed.

5. Flat tube according to at least one of the preceding claims, characterized in that on both longitudinal walls (14,15) of the material of the longitudinal walls (14,15) projections (9) are formed.

6. Flat tube according to at least one of the preceding claims, characterized in that a plurality of projections (9a, 9b, 9c, 9d), preferably all the projections contact the respective opposite longitudinal wall (15,14).

7. Flat tube according to at least one of the preceding claims, characterized in that at least one projection (9) on a longitudinal wall (14,15) contacts a projection on the opposite longitudinal wall (15, 14).

8. Flat tube according to at least one of the preceding claims, characterized in that at least one projection (9) has a substantially symmetrical profile.

9. Flat tube according to at least one of the preceding claims, characterized in that the flat tube has a depth between 0.5 mm and 5 mm, preferably between 0.8 mm and 4 mm and particularly preferably between 1 mm and 3 mm.

10. Flat tube according to at least one of the preceding claims, characterized in that at least one projection has a height

HF between three and eight times a wall thickness of Flach¬ tube, in particular between four and six times a Wand¬ strength of the flat tube has.

11. Flat tube according to at least one of the preceding claims, characterized in that at least one wall and preferably the entire flat tube has a wall thickness between 0.05 mm and 0.8 mm, preferably between 0.07 mm and 0.6 mm and more preferably between 0.1 mm and 0.5 mm.

12. Flat tube according to at least one of the preceding claims, characterized in that at least one projection has a recess with a radius of curvature r _D which is less than or equal to a wall thickness of the flat tube, preferably smaller or equal

75% of a wall thickness of the flat tube is.

13. A device for exchanging heat with at least one flat tube according to one of the preceding claims.

14. Method for producing a multi-channel flat tube for a heat exchanger with the method steps:

Producing a projection (9) with a predetermined profile from a strip of material by means of a first shaping unit (21) and a second shaping unit (22) cooperating with the first shaping unit;

Changing the profile of the projection by means of a third shaping unit and a fourth shaping unit cooperating with the third shaping unit.

15. The method according to claim 12, characterized in that the shaping units are mutually rotatable rollers.

16. The method according to at least one of the preceding claims, characterized in that when changing the profile of the projection (9) whose height and / or width is reduced.

17. The method according to at least one of the preceding claims, characterized in that in at least one further procedural step, the profile of the projection (9) is further changed.

18. The method according to at least one of the preceding claims, characterized in that the profile of the projection (9) in at least four, preferably in at least six process steps verän¬ is changed.

19. The method according to at least one of the preceding claims, characterized in that in a process step, a Vor¬ centering of the projection (9) is made.

20. The method according to at least one of the preceding claims, characterized in that the rotatable rollers have mutually parallel axes of rotation.

21. The method according to at least one of the preceding claims, characterized in that at least one method step, the width of the strip of material (7) is reduced.

22. The method according to at least one of the preceding claims, characterized in that in at least one method step, the width of the material strip (7) remains substantially constant, in particular constant.

23. The method according to at least one of the preceding claims, characterized in that a plurality of projections (9a, 9b, 9c, 9d) are formed from the material strip (11).

24. The method according to at least one of the preceding claims, characterized in that the projections (9a, 9b, 9c, 9d) are formed in vor¬ given distances from each other.

25. The method according to at least one of the preceding claims, characterized in that in at least one method step, the projections (9a, 9b, 9c, 9d) are subjected to different shaping stages.

26. The method according to at least one of the preceding claims, characterized in that in a further process step, a curved portion is generated.