EP1805469B1 - Flat tube for a heat exchanger - Google Patents

Description

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 in motor vehicle air conditioners, in the prior art, in addition to collecting devices for a refrigerant flat tubes, which are provided for forwarding 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 known from the prior art flat tubes have webs or projections in their interior, which cause the flat tube is performed a total of multi-channel.

These known from the prior art webs consist of both sides molded beads or one-sided molded webs. However, the flat tubes on their outer side in the region of the webs on no closed or smooth profile. This non-smooth outer profile of the flat tubes means that when inserting the flat tubes in the soil a higher process cost must be operated to a fluid-tight Reach 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.

The EP 0 854 343 shows such flat tubes, which have on their outer side considerable external cavities, which are reduced by a complex process.

Also the EP 1 106 949 and EP 0 829 316 disclose multi-channel flat tubes with protrusions.

The present invention is therefore an object of the invention to provide a flat tube, which has projections in its interior and at the same time largely avoids recesses or recesses 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 13. Preferred developments of the flat tube and the method are the subject of the dependent claims.

• 0<r_F<t,
• R_F<2t,
• 1,5t<X<2t,
• 2t<Y<2,5t,
• r_D<t,
• t<H_F<10t.

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 a side facing the fluid flow in the interior of the flat tube inside of the material of the longitudinal wall is a projection educated. According to the invention, the longitudinal wall is essentially flat on its outer side facing away from the fluid in the area of the projection and has a recess, wherein the wall thickness is t, r _{F is} an upper radius of curvature of the projection at its tip, R _{F is} a lower radius of curvature at its base, X the width of the projection at its tip, Y the width of the projection at its base and r _D the radius of curvature of the recess, and with H _F as the height of the projection, where

• 0 <r _F <t,
• R _F <2t,
• 1.5t <X <2t,
• 2t <Y <2.5t,
• r _D <t,
• t <H _F <10t.

Under a multi-channel tube is understood that a plurality of substantially 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 of the material of the longitudinal wall projection is understood such a projection that 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. Under essentially flat is understood that the outer profile in the region of the projections has 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 on. Preferably, at least one end portion is bent through substantially 180 degrees to cause the two Longitudinal walls are arranged substantially parallel with respect to each other. The second end portion can also be bent to close the flat tube in another way, for example, in the course of the manufacturing process, the respective end portions of the base material can be partially bent by a predetermined angle, and then 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 the 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 mutually substantially separated chambers.

In this case, the distances between the projections can be selected 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 of, more preferably all projections, a substantially symmetrical profile. This means that the projection has an axis of symmetry substantially perpendicular to the plane of the longitudinal wall has, 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 projections are preferably adapted, wherein in particular also procedural framework conditions are to be considered.

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. Preferably, the rollers are designed so that a role is limited by lateral conclusions of the other role, to prevent in this way 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 pulled through.

The change of the profile in at least one method step preferably consists in reducing its height and / or width. Preferably, both the height and the width of the projection during this process step is reduced. 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. These method steps are each used - as stated above - to achieve the most level possible 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 be able to cope with 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, a pre-centering of the projection is carried out in a further method step. This is preferred over a preference.

Preferably, the rotatable rollers, through which the material is passed, have a substantially constant distance from one another. 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 strip 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 by reducing the length of the strip in a first method step.

In this case, the projections are preferably formed at predetermined distances from each other. 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.

Preferably, in at least one process step, different protrusions are subjected to different shaping steps. This means that a certain projection is already adapted in its shape, while another projection is formed or a projection already receives its final form, while another projection is still adapted in an intermediate step in its form.

In this way, it can be achieved under certain circumstances that a plurality of projections are produced with a few forming steps so that already pre-formed or finished molded projections in shape are no longer changed.

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.

• Fig. 1 eine Darstellung des erfindungsgemäßen Verfahrens zur Erzeugung eines Vorsprungs;
• Fig. 2a eine Darstellung der erfindungsgemäßen Formgebungseinheiten zur Herstellung eines Vorsprungs;
• Fig. 2b eine Darstellung der Formgebungseinheiten zur Veränderung des Profils des Vorsprungs;
• Fig. 2c eine Darstellung der Formgebungseinheiten zur weiteren Veränderung des Profils des Vorsprungs;
• Fig. 3 eine Darstellung zur Veranschaulichung des Herstellungsverfahrens für die Erzeugung einer geraden Anzahl von Vorsprüngen;
• Fig. 4 ein durch das in Fig. 3 dargestellte Verfahren fertiggestelltes Flachrohr;
• Fig. 5 eine Figur zur Veranschaulichung der Herstellung eines Flachrohrs mit einer ungeraden Anzahl von Vorsprüngen;
• Fig. 6 ein durch ein Verfahren nach Fig. 5 hergestelltes Flachrohr;
• Fig. 7 ein erfindungsgemäßes Flachrohr in einer ersten Ausführungsform;
• Fig. 8 ein erfindungsgemäßes Flachrohr in einer zweiten Ausführungsform;
• Fig. 9 ein erfindungsgemäßes Flachrohr in einer dritten Ausführungsform;
• Fig. 10 eine vergrößerte Darstellung eines Vorsprungs zur Veranschaulichung der geometrischen Verhältnisse; und
• Fig. 11 ein erfindungsgemäßes Flachrohr zur Veranschaulichung der geometrischen Verhältnisse.

Showing:

• Fig. 1 an illustration of the method according to the invention for producing a projection;
• Fig. 2a a representation of the shaping units according to the invention for the production of a projection;
• Fig. 2b a representation of the shaping units for changing the profile of the projection;
• Fig. 2c a representation of the shaping units for further changing the profile of the projection;
• Fig. 3 a representation for illustrating the manufacturing process for the production of an even number of protrusions;
• Fig. 4 a through the in Fig. 3 illustrated method finished flat tube;
• Fig. 5 a figure illustrating the production of a flat tube with an odd number of protrusions;
• Fig. 6 a by a method according to Fig. 5 manufactured flat tube;
• Fig. 7 a flat tube according to the invention in a first embodiment;
• Fig. 8 a flat tube according to the invention in a second embodiment;
• Fig. 9 a flat tube according to the invention in a third embodiment;
• Fig. 10 an enlarged view of a projection to illustrate the geometric relationships; and
• Fig. 11 an inventive flat tube to illustrate the geometric relationships.

In Fig. 1 the individual process steps of a method according to the invention for producing a projection are shown. 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 in Fig. 1 illustrated method represents only one 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 character L denotes the center line, preferably the axis of symmetry of the protrusion 9a to 9f produced. In the optional method step 1a, pre-centering of the projection 9a is performed by a preference. This is particularly advantageous if the projections or webs with high heights H _A to H _{F 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. By generating the projection 9b in method step 2, the total width b of the strip 7 is generated, wherein the total width b is less than the total width a, or the total width a 'in the method steps 1 and 1a.

The height H _B generated in method step 2 represents the maximum height H _{max of} the projection 9 _b , 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 always substantially the same amount of material is supplied to the shaping units or the rollers. This is achieved by a corresponding 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 decreases, 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 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 during the method steps 2 to 6 preferably remains substantially constant. During the process 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 be closed by folding, gathering or squeezing. In such an approach, however, not the height H _D or H _{E is} substantially reduced, but the total strip 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 partially. If this procedure is followed, when compressing the projection, material or strip material can flow back into the band width, that is, out of the region of the projection. One possible consequence is that too little material is available for closing the outer cavity 11 in further method steps, or more material has to be brought forward in the first stages. In this case, even stronger thinning of the material strip 7 and a higher risk of cracking occur. Furthermore, the required ridge height may not be achieved and the process will be more sensitive to variations in strip material properties.

In the method step 6 shown here, a final height H _{F is} achieved, which is less than the height H _E in step 5. At the same time the area 11, which is still present in step 5, substantially closed and therefore the smooth outer profile according to the invention reached.

The bandwidth or total width of the strip e is also not further reduced, that is, the bandwidth f and the bandwidth e are substantially the same.

Fig. 2a shows the shaping units for carrying out the method according to the invention, which is an upper roller 21 and a lower roller 22. Between these rollers, the flat tube material 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 pair of rollers 21, 22 in the processing step 2 from Fig. 1 that is, 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.

Fig. 2b shows the pair of rollers for the process step 4. In this case, the recess 26 is designed such that the projection reaches the illustrated height H _D. The lower roller 22 has here no more machining projection. The gaps 13a and 13b between the upper roller 21 and the lower roller 22 are now in width with respect to in Fig. 2a reduced device shown. The lower roller 22 is, for example, according to the strip width b of processing step 4 from Fig. 1 designed.

When compressing the strip of material or the tape runs against the lower roll. The widths of the strip, once the in Fig. 2a As a result, the height H _B achieved has to be maintained substantially constant as possible so that no portion of the strip flows from the region of the projection into the flat region 7b of the strip.

In Fig. 2c is the device for the in Fig. 1 shown method step 6 shown. In this case, the lower roller 22 also has no 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 in Fig. 2c shown method step, the gap widths 13a and 13b are chosen to be minimal, that is, 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 event that multiple projections - more precisely, an even number of projections - to be generated. The individual method steps have been identified here by the reference symbols I to VIII.

In a first optional step I, by correspondingly adapted upper and lower rollers, that is, rollers, which have a machining projection and a recess, as in Fig. 2 shown, a trough 31 generated. The generation of this trough is particularly advantageous if the projections to be produced are to have a comparatively large initial height H _B.

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 strip width a to method step II to a strip width b and in method step III to a strip width c. However, it is also possible to perform only a deformation of the projections 9 in step III, that is, in this case, the strip width c relative to the strip width b to keep substantially constant.

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 the 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 because it allows material from the respective outer regions of the material strip to be used to produce the new protrusions and prevents material from being drawn in from the regions of other already produced protrusions. However, it is also possible to provide or produce several projections instead of the projection shown here. Also, the in Fig. 3 shown process steps only as an example. It would also be possible to provide significantly more process steps, as well as several forming processes.

In the process steps VI to VIII again the already in Fig. 1 shown deformation of the individual projections instead, in each case again - as in Fig. 1 the flanks become steeper and the radii of curvature at the tip of the projection become smaller and the heights and widths of the projections are reduced. The entire strip widths, such as f, g and h, are kept essentially constant, as already described with reference to FIG Fig. 1 explained.

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

In Fig. 4 a flat tube is shown, which by the in Fig. 3 sketched method can be produced. The flat tube 1 results in cross section through a deformation of the in Fig. 3 strip shown under 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 end portions are soldered to the respective opposite longitudinal wall. Likewise, the two bent end portions 18 and 19 are sealed 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 For example, the process steps I to VIII are shown to produce a flat tube having an odd number of protrusions, more specifically, three protrusions in this case. 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 process step II is - similarly as in process step II at Fig. 3 - Produces a projection 9a. This projection is transformed into method step III, wherein in this method step the strip width a is first reduced to the width b, and this again to the width c, 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, 9b and 9c are staggered, that is, while in the case of the projection 9a, the first deformation has already taken place, the portions 9b and 9c have been produced first. The strip width d is further reduced with respect to the strip width c. Also in this variant, preferably the inner and then the outer projections are preferably formed first.

In 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 forming 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 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 subsequent to method step VIII, corner folds 42a and 42b are bent. These two Eckfalze lead to the generation of a further projection, which Eckfalze can be produced in several steps.

In Fig. 6 a flat tube is shown, which consists of the in Fig. 5 shown lowest strip results. Unlike the in Fig. 4 shown embodiment, the end portions are not arranged in the region of the curvatures 17 or 18, but in the central region. 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 and 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. This in Fig. 5 illustrated method (step I-VIII) can be used in general for flat tubes with an odd number of protrusions, while the in Fig. 3 shown method is preferably used for flat tubes with an even number of projections use. The formation of the Endfalze 42a, 42b according to Fig. 6 or the Endfalze 18, 19 according to Fig. 4 is, however, largely possible regardless of the number of projections in particular in a known manner.

In Fig. 7 a flat tube according to the invention is shown, wherein the individual dimensions serve to illustrate. For a better understanding, the illustration of the smooth or even outer surface of the flat tube according to the invention, that is, the representation of the minimized surface 11 under the projection 9, has been dispensed with. Also, the flanks of the projection were not shown compressed.

The reference a refers to the distance of the webs along a longitudinal wall. The reference character K denotes the distance between two adjacent webs, which may 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. The minimum pitch is in this embodiment at least twice as large as the width T. Therefore, the minimum chamber size or channel size is at least as large or larger than the thickness T.

At the in Fig. 8 shown embodiment projections 9 are attached only to the longitudinal wall 14, which contact the longitudinal wall 15. In this case, the land distance a substantially coincides with 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.

At the in Fig. 9 In the embodiment shown, the individual projections 9 do not contact the respective opposite longitudinal wall 14 or 15, but on the opposite longitudinal wall in turn attached projections 9. This means that contact the ends of the projections approximately in the middle of the flat tube. Also in this case, as in the embodiment according to 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 a further embodiment (not shown), it is also conceivable to design the individual projections in such a way that, in contrast to those in FIG Fig. 9 shown embodiment - are laterally slightly offset from each other so that they do not contact each other at their respective ends, but at their side surfaces, whereby an increased connection surface can be achieved.

Fig. 10 shows an enlarged view of a projection 9 according to the invention, in which the dimensions are shown in detail. To the in Fig. 10 To reach the final shape shown are provided between four and ten steps in which each of the projections are formed. The number of process steps to be used depends on the height H _{F 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 _{R is} the upper radius of curvature, X is the width of the projection at its tip, Y is the width of the projection 9 at its base, R _{F is} the radius of curvature at the base of the projection, and R _{D is} the radius of curvature of the recess 11. The individual sizes are partially integral correlated.

The limits shown below result from extensive soldering and forming trials. In these experiments, the parameters were matched according to a defined system and the results were used for the limits shown here.

The upper radius of curvature r _F is in the invention between 0 and the wall thickness t, that is smaller than the wall thickness t. The lower radius of curvature R _F 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 twice 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 molding process.

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 r _D 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 H _F 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.

In the Fig. 10 shown recess 11 has an area of less than 0.1 mm ² , preferably less than 0.07 mm ² , which also represents a significant 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 tubesheet and a dense connection can be achieved with considerably less effort.

Claims (25)

1. A multi-channel 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 lies substantially parallel to the first longitudinal wall (14), at least one curved end section (17), wherein a projecting part (9) is configured on at least one longitudinal wall (14, 15) from the material of the longitudinal wall on the inside facing a fluid flow in the interior of the flat tube, wherein the longitudinal wall is essentially level on its outside facing away from the fluid in the area of the projecting part (9) and has a depression (11), wherein the wall thickness is t, R_F is a lower radius of curvature of the projecting part on the base thereof, X is the width of the projecting part on the tip thereof, Y is the width of the projecting part on the base thereof and r_D is the radius of curvature of the depression (11), and with H_F as the height of the projecting part, characterised in that the following applies:

   0 < r_F < t,

   R_F < 2t,

   1.5t < X < 2t,

   2t < Y < 2,5t,

   r_D < t, and

   t < H_F < 10t,

   wherein r_F is an upper radius of curvature of the projecting part at the tip thereof.
2. The flat tube as claimed in claim 1, characterised in that the projecting part (9) configured on a longitudinal wall (14, 15) is in contact with the other longitudinal wall (15, 14).
3. The flat tube as claimed in at least one of the foregoing claims, characterised in that it exhibits two curved end sections (17, 18).
4. The flat tube as claimed in at least one of the foregoing claims, characterised in that a plurality of projecting parts (9a, 9b, 9c, 9d) is configured on a longitudinal wall from the material of the longitudinal wall.
5. The flat tube as claimed in at least one of the foregoing claims, characterised in that projecting parts (9) are configured on both longitudinal walls (14, 15) from the material of the longitudinal walls (14, 15).
6. The flat tube as claimed in at least one of the foregoing claims, characterised in that a plurality of projecting parts (9a, 9b, 9c, 9d), preferably all the projecting parts, make contact with the opposing longitudinal wall (15, 14) in each case.
7. The flat tube as claimed in at least one of the foregoing claims, characterised in that at least one projecting part (9) on one longitudinal wall (14, 15) makes contact with a projecting part on the opposing longitudinal wall (15, 14).
8. The flat tube as claimed in at least one of the foregoing claims, characterised in that at least one projecting part (9) exhibits an essentially symmetrical profile.
9. The flat tube as claimed in at least one of the foregoing claims, characterised in that the flat tube exhibits a depth between 0.5 mm and 5 mm, preferably between 0.8 mm and 4 mm, and especially preferred between 1 mm and 3 mm.
10. The flat tube as claimed in at least one of the foregoing claims, characterised in that at least one projecting part exhibits a height H_F between three times and eight times a wall thickness of the flat tube, in particular between four times and six times a wall thickness of the flat tube.
11. The flat tube as claimed in at least one of the foregoing claims, characterised in that at least one wall and preferably the whole of the flat tube exhibits a wall thickness between 0.05 mm and 0.8 mm, preferably between 0.07 mm and 0.6 mm, and especially preferred between 0.1 mm and 0.5 mm.
12. A device for the exchange of heat having at least one flat tube as claimed in one of the foregoing claims.
13. A process for the manufacture of a multi-channel flat tube as claimed in one of the foregoing claims 1 to 11 for a heat exchanger with the following process stages:

    production of a projecting part (9) with a predetermined profile from a material strip by means of a first forming unit (21) and a second forming unit (22) acting together with the first forming unit;

    modification of the profile of the projecting part by means of a third forming unit and a fourth forming unit acting together with the third forming unit.
14. The process as claimed in claim 13, characterised in that the forming units are rollers that are capable of rotating in relation to one another.
15. The process as claimed in at least one of the foregoing claims 13 or 14, characterised in that, in conjunction with the modification of the profile of the projecting part (9), its height and/or width is reduced.
16. The process as claimed in at least one of the foregoing claims 13 to 15, characterised in that the profile of the projecting part (9) is further modified in at least one further process stage.
17. The process as claimed in at least one of the foregoing claims 13 to 16, characterised in that the profile of the projecting part (9) is modified in at least four, preferably in at least six process stages.
18. The process as claimed in at least one of the foregoing claims 13 to 17, characterised in that pre-centering of the projecting part (9) is undertaken in a process stage.
19. The process as claimed in at least one of the foregoing claims 13 to 18, characterised in that the rotating rollers exhibit axes of rotation that are parallel to one another.
20. The process as claimed in at least one of the foregoing claims 13 to 19, characterised in that the width of the material strip (7) is reduced in at least one process stage.
21. The process as claimed in at least one of the foregoing claims 13 to 20, characterised in that the width of the material strip (7) remains essentially constant, in particular remains constant, in at least one process stage.
22. The process as claimed in at least one of the foregoing claims 13 to 21, characterised in that a plurality of projecting parts (9a, 9b, 9c, 9d) is configured from the material strip (11).
23. The process as claimed in at least one of the foregoing claims 13 to 22, characterised in that the projecting parts (9a, 9b, 9c, 9d) are configured at predetermined distances in relation to one another.
24. The process as claimed in at least one of the foregoing claims 13 to 23, characterised in that the projecting parts (9a, 9b, 9c, 9d) are subjected to different forming steps in at least one process stage.
25. The process as claimed in at least one of the foregoing claims 13 to 24, characterised in that a curved section is produced in a further process stage.

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