FR2832788A1 - Profile for tubes in heat exchangers used in motor vehicles, uses folded metal sheet to form tube and bends one edge over so that it rests on other wall of tube, providing strength to the tube during manufacture - Google Patents

Abstract

The heat exchanger has tubes formed by folding sheet metal to form a flat-sided tube, with the join along the middle of one side. One edge of the sheet is bent to form a wall (18,19) that divides the tube longitudinally, with the bottom of the wall resting (15) flat (28) on the opposite side of the tube. The other edge of the sheet is folded (10,12) to fit into a curve in the top of the wall.

Description

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 The technical sector of the present invention is that of heat exchangers and more particularly of the flat tubes which equip them. These exchangers are used in particular as an evaporator, condenser or heating radiator in an air conditioning system of a motor vehicle or as a radiator in the cooling circuit of such a vehicle.

 Heat exchangers called flat tube exchangers, offering an I, U or methodical circulation, are generally constituted by the assembly of several flat tubes juxtaposed with each other and connected together by an interlayer whose purpose is to promote heat exchange. Each of these tubes is formed by bending from a metal strip to define a circulation conduit through which the fluid passes. This fluid can be a coolant in the case of an evaporator or condenser or a coolant in the case of a radiator. This juxtaposition of tubes is capped at each end by a manifold generally connected by conduits to the rest of the circuit. For a flat tube with methodical circulation, the round-trip circulation of a flat U-shaped tube is generally done by longitudinally separating the interior volume of the tube by means of a partition.

 The various flat tube profiles and the methods for obtaining a flat tube are the subject of numerous publications. Patent DE 32 16 140 describes a flat tube obtained from a metal strip comprising a first part and a second part folded towards the inside of the tube to form a partition wall and thus define two circulation conduits.

Patent DE 195 48 495 also describes a tube of substantially similar design. However, these tube profiles suffer from major drawbacks.

 One of the main drawbacks is poor mechanical strength during assembly with the other components. Indeed, the assembly of tubes and other components forms a heat exchanger maintained by clamping and brazed in the oven to secure the assembly. However, the clamping effort

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 in the longitudinal direction of the tubes causes them to twist. This twist leads to a misalignment of the strip junction and creates a significant risk of leakage with the major consequence of the complete scrap of the heat exchanger.

 Another drawback of the state of the art cited above is that the geometry of the tube profiles as well as the machine capacities depend very largely on the dimensional tolerances of the strip, in particular its width.

 Another drawback of this type of profile is that each of the two faces of the strip must be coated with a material having a lower melting point than the material constituting the strip. Indeed, this coating material, hereinafter called Clad, makes it possible to weld (by brazing) the tube to make it waterproof.

 The object of the present invention is therefore to solve the drawbacks described above mainly by adding a leg or longitudinal beads to, on the one hand, strengthening the mechanical strength of the tube, on the other hand, overcoming the constraints of dimensional tolerance in strip width, no longer being obliged to coat the internal face of the tube with Clad, and, finally, to create a longitudinal weld between the two parts of the tube which cooperates perfectly with the manifolds.

 The subject of the invention is therefore a tube for a heat exchanger designed from a strip comprising a central part separating a first lateral part and a second lateral part both folded on either side of said central part towards a longitudinal axis of said strip thus defining an internal volume, an internal wall and an external wall, said first and second lateral parts each having a respective end edge, the first lateral part having a first fold and the second lateral part having a second fold both oriented towards the interior volume of the tube, said second fold defining a leg up to the end edge, characterized in that

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 the leg cooperates with a docking means made on the first lateral part so that the external wall of the first ply comes into contact on the internal face of the tube opposite to said docking means to define a partition.

 According to a first characteristic of the invention, the docking means has a third fold and a fifth fold oriented towards the interior volume of the tube and a fourth fold oriented towards the external wall, said fourth fold being interposed between the third and the fifth fold.

 According to a second characteristic of the invention, the second lateral part comprises a secondary fold forming, with the second fold, a first bead capable of cooperating with the docking means.

 According to another characteristic of the invention, the first lateral part comprises a sixth fold thus forming, with the first fold, a second bead.

 According to another characteristic of the invention, the second bead has a seventh ply oriented towards the external wall so as to bring into contact on the internal wall of the strip a welding plate defined between the first ply and the end edge.

 According to yet another characteristic of the invention, the third fold and the seventh fold are combined, and in that the fifth fold and the first fold are combined.

 The distance between the third fold and the fourth fold is substantially equal to the leg or the thickness of the first bead.

 Advantageously, at least one of the first, second, third, fourth, fifth, sixth, seventh folds and the secondary fold are oriented at an obtuse angle.

 Advantageously also, the internal wall of the strip defined between the end edge and the sixth fold is in contact with the internal wall of the strip defined between the first fold and the seventh fold.

 The internal wall of the strip defined between the end edge and the secondary fold is in contact with the internal wall of the strip defined by the second part

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 lateral.

 According to a characteristic of the invention, the tube has an internal height of between 0.6 mm and 3 mm, or greater than or equal to between twice the strip thickness.

 According to another characteristic of the invention, the strip comprises at least two superimposed layers of material, one being a substrate constituted by an aluminum alloy and the other a first layer constituted by a material having a lower melting point to the material constituting the substrate.

 According to yet another characteristic of the invention, the strip comprises a second layer consisting of an anti-corrosion material deposited on the substrate.

 Advantageously, the first layer is on the outer wall and the second layer is on the inner wall.

 The material constituting the substrate is of the family of Aluminum 3XXX series, the material of the first layer is of the family of Aluminum 4XXX series and the material of the second layer is of the family of Aluminum 7XXX series.

 A tube / spacer type heat exchanger is characterized in that it comprises at least one tube defined according to any one of the preceding characteristics.

 This exchanger is a radiator or a condenser for a motor vehicle.

 This exchanger is an evaporator for a ventilation, heating and air conditioning installation of a motor vehicle.

 A very first advantage of the heat exchanger tube according to the invention lies in the increase in its mechanical strength with the direct consequence of a reduction in the risk of leakage and as an indirect consequence a significant reduction in the reject rate of the heat exchangers after welding.

 Another advantage lies in the possibility of making folded beads whose width does not pollute the manufacturing processes. Consequently, the strip width tolerances can therefore be much more

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 wide.

 Another non-negligible advantage lies in the fact that this type of profile no longer has a Clad on the internal face of the tube and therefore advantageously makes it possible to separate the alloy layer intended for welding and the alloy layer intended to protect the tube. against corrosion or erosion.

 Another advantage of the invention resides in the fact of designing folds at an obtuse angle so as to offer a certain flexibility to the tube profile at the time of its marriage with the other components of the exchanger.

 Another advantage stems from this structural characteristic. Indeed, the obtuse angle defining the folds allows a perfect distribution of the fluxing product. The latter is a cleaning liquid before soldering, it is therefore essential that it can spread over all contact areas where soldering must be carried out.

- la figure 4 est une vue partielle d'une variante de l'invention, - la figure 5 est une vue partielle en coupe transversale illustrant plus particulièrement une autre variante de l'invention, - la figure 6 est une vue partielle en coupe transversale illustrant plus particulièrement une troisième variante de l'invention. Other characteristics, details and advantages of the invention will emerge more clearly on reading the description given below by way of indication in relation to the drawings in which: - Figure 1 is a perspective view of a tube according to the invention, - Figure 2 is a cross-sectional view detailing more particularly the structure of the docking means of a tube according to the invention, - Figure 3 is a cross-sectional view of a variant of a tube according to the invention,

- Figure 4 is a partial view of a variant of the invention, - Figure 5 is a partial view in cross section illustrating more particularly another variant of the invention, - Figure 6 is a partial view in cross section illustrating more particularly a third variant of the invention.

 Figure 1 illustrates a tube 1 for heat exchanger. The use which can be made of this tube 1 is variable. Indeed, the latter can be a

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 evaporator, radiator or condenser. This type of heat exchanger generally consists of a multitude of tubes 1 juxtaposed with each other and separated by spacers. This type of exchanger is commonly called: tube / spacer exchanger. The number of tubes 1 forming the exchanger is a function of a required heat exchange characteristic.

 The tube 1 shown in this figure is generally formed by folding starting from a strip 2. The latter is defined in width but not in length since it comes continuously from a strip dispensing roller. The tube 1 is cut to a length which is determined by the required thermal performance of the heat exchanger. As this figure shows, the tube 1 has a first lateral part 3 and a second lateral part 4 which are folded on either side of a central part 30, for example at 1800, towards a longitudinal axis 5 of the tube. This folding can be carried out in two stages of an intermediate folding at 900 or can be operated gradually so as to give a rounded shape to the sides of the tube 1 as shown in FIG. 1. This folding of the two lateral parts 3 and 4 allows to define an overall internal volume 6 of the tube 1 which will serve as a fluid circulation conduit as well as an internal wall 7 licked by the fluid circulating in the exchanger and an external wall 8 in contact with the external medium, for example the air. The second lateral part 4 has a first end edge 9 defined by the edge of the strip 2 which connects the internal wall 7 to the external wall 8 and which is equal to the thickness of the strip 2.

 We now refer to FIG. 2 which illustrates the main idea of the invention. The second lateral part 4 has a second fold 10 oriented towards the interior volume 6 of the tube 1 which forms a leg 32. This second fold 10 is folded again towards the interior of the tube 1 at an angle substantially equal, for example to 900 to form a secondary ply 12 and thus define a first bead 11. This secondary ply 12 can be made

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 in the continuity of the second fold 10 so as to form a first bead 11 in which an internal face part 7 of the strip is in contact with an opposite part of the internal face 7 of the second lateral part 4. Thus, the thickness of the first bead 11 is then substantially equal to twice the thickness of the strip 2.

The thickness of the first bead 11 can also be less than twice the thickness of the strip 2 by using a rolling process of the first bead 11.

It should be noted that the positioning of this first bead 11 facilitates this rolling operation (not shown). The thickness of the bead 11 can be less than twice the thickness by not folding the secondary fold 12. In fact, only the leg 32 of a length at least equal to once the thickness of the strip (this length is defined between the external wall 8 of the second part 4 and the end edge 9 may suffice for the object of the invention, on the other hand, the secondary ply 12 can be produced at a distance from the second ply 10 so that the thickness of the first bead 11 is greater than twice the thickness of the strip 2 (not shown).

 The second lateral part 3 of the strip 2 has a docking means 13 intended to cooperate with the first bead 11, a first fold 14 substantially at right angles oriented towards the interior volume 6 of the tube 1 and an end edge 15.

 This docking means 13 is of substantially complementary shape to the leg 32 or to the first bead 11 in order to ensure contact over the entire length of the tube 1 and thus a perfect seal. The cooperation of the leg 32 or of the first bead 11 with the docking means 13 is carried out so that the first ply 14 is in contact against the internal wall 7 of the tube 1 substantially in line with the docking means 13. Thus , a flat 28 defined by the distance separating the first ply 14 from the end edge 15 defines, with the length of the tube, a bearing surface promoting welding. Of course, this first fold 14 can take a slightly obtuse angle so as to allow the fluxing product to penetrate.

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 and best impregnate the dish 28.

on entend par orienté vers la paroi externe du feuillard 2 tout pliage qui rapproche les deux faces externes 8 du feuillard disposé de part et d'autre du pli. Le quatrième pli 17 peut être à angle droit, comprenant avantageusement un rayon de courbure externe arrondi pour coopérer de manière harmonieuse avec le premier bourrelet 11. Dans le cas d'une coopération avec la jambe 32, le pli 17 présente un angle droit qui est pratiquement parfaitement complémentaire avec l'angle droit formé par la jonction entre la jambe 32 et l'arête d'extrémité 9 (représenté à la figure 6). Le quatrième pli 17 est suivi d'un cinquième pli 18 sensiblement à angle droit de manière à ramener le premier pli 14 en appui sur la paroi interne 7 du feuillard 2 opposé au moyen d'accostage 13. La partie de feuillard séparant le cinquième pli 18 du deuxième pli 14 définit alors une cloison de séparation 19 à l'intérieur du tube 1. The docking means 13 is broken down as follows. It has a third fold 16, for example, at a right angle oriented towards the internal volume 6 of the tube 1 followed by a fourth fold 17 oriented towards the external wall of the strip 2. By oriented towards the internal volume is meant a fold which brings the two internal faces 7 of the strip disposed on either side of the fold. Likewise,

the term “oriented towards the external wall of the strip 2” means any folding which brings the two external faces 8 closer to the strip disposed on either side of the fold. The fourth fold 17 may be at a right angle, advantageously comprising a rounded external radius of curvature to cooperate harmoniously with the first bead 11. In the case of cooperation with the leg 32, the fold 17 has a right angle which is practically perfectly complementary with the right angle formed by the junction between the leg 32 and the end edge 9 (shown in Figure 6). The fourth fold 17 is followed by a fifth fold 18 substantially at right angles so as to bring the first fold 14 resting on the internal wall 7 of the strip 2 opposite the docking means 13. The strip part separating the fifth fold 18 of the second fold 14 then defines a partition 19 inside the tube 1.

The internal volume 6 is then divided into two sub-volumes 6a and 6b which can be independent from one another or, in a variant of the invention, be put in communication by at least one adjournment. This adjournment is achieved by holes made in the partition wall 19 or by removing a part of said partition.

The tube thus defined has an internal height 31 of between 0.6 mm and 3 mm. This internal height 31 can also advantageously be between three times the thickness of the strip 2 and at least five times the thickness of the strip 2.

 FIG. 3 illustrates a variant of the invention. The references identical to the description in FIGS. 1 and 2 are retained. This transverse representation of the tube 1 differs in the junction of the partition wall 19

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 on the internal wall 7 of the strip 2. In fact, the first lateral part 3 has a sixth fold 20 oriented towards the internal volume 6 of the tube 1 at an angle substantially equal to 900 to form a second bead 21. The sixth fold 20 can be made in the continuity of the first fold 14 as shown in this figure so as to form this second bead 21 in which an internal face part 7 of the strip is in contact with an opposite part of the internal face 7 of the first lateral part 3 Thus the thickness of the second bead 21 is then substantially equal to twice the thickness of the strip 2.

In a variant of the invention not shown, the thickness of the first bead 11 can also be less than twice the thickness of the strip 2 by using a method of rolling this bead 21. It should be noted that this operation is made possible during the process of producing the tube because this bead 21 is particularly accessible. On the other hand, the sixth fold 20 can be produced at a distance from the first fold 14 so that the thickness of the second bead 21 is greater than twice the thickness of the strip 2 (not shown). The tube profile illustrated in this figure is particularly interesting because it has on the one hand, a first bead 11 or a leg 32 substantially parallel to the longitudinal axis 5 of the tube which offers an improvement in the mechanical strength of the tube 1 according to this axis and, on the other hand, a second bead 21 which participates in the mechanical strength on a plane perpendicular to the axis 5.

 Figure 4 is an illustration of a variant of the invention. The difference with the previous figure is based on the orientation of the second bead 21. Indeed, that includes a seventh fold 27 oriented towards the outer wall 8 of the strip. Thus, the welding plate 28 defined between the first ply 14 and the end edge 15 is brought into contact by a large surface on the internal wall 7 of the strip opposite the docking means 13.

 Figure 5 is a representation of a variant of the invention. As previously described, the first

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 and the second bead 11 and 21 can be of thickness equal to twice the thickness of the strip 2. Thus, the sub-volumes 6a and 6b are directly conditioned by the thicknesses of the beads 11 and 21 and therefore by the thickness of the strip 2. The internal height 31 is, in the case shown in this figure, equal to three times the thickness of strip 2.

 This variant differs from the previous figure for the structures defined below. We note here that the seventh fold 27 and fourth fold 17 are combined. The docking means 13 comprises in this variant the third fold 16 at right angles which cooperates with the first bead 11. In fact, this bead has a first plate 22 which comes into contact on a second plate 23 defined after folding at 900 of the third ply 16. The contact surface between these two plates therefore promotes the brazing of the tube 1. In the same way, a third plate 24 defined by the external wall 8 of the strip 2 comprised between the secondary ply 12 and the edge of end 9 comes into contact on a fourth plate 25 defined on the external wall 8 between the fourth fold 17 and the fifth fold 18.

Again, brazing is greatly improved. In addition, this double brazing described above offers a safety redundancy to fight against leakage of fluid contained in the tube 1. It is also noted in this figure that the curvature profile of the fourth fold 17 is substantially identical on the external wall 8 as on the internal wall 7 strip. On the other hand, the radius of curvature of this fourth ply 17 is less than the radius of curvature of the secondary ply 12 in order to allow perfect positioning of the first bead 11 relative to the docking means 13. The two flats 22 and 23 make it possible to define with the outer wall 8 respectively of the first part 3 and the second part 4 two right angles with substantially zero radius so as to have the smallest possible brazing area and thus optimize the junction between the tube 1 and the manifolds.

 Figure 6 is a variant of the invention described in the previous figure which illustrates the advantage provided by

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 the invention with regard to the width tolerances of the strip 2. It can be seen here that the leg 32 cooperates perfectly with the fold 17. The tightness is nevertheless nevertheless ensured because the end edge 9 of the leg 32 is in contact on the fourth plate 25. Another difference illustrated in this figure consists in the shape of the fourth fold 17. In fact, the internal wall 7 of this fourth fold has any shape 26, advantageously rounded, while the external wall 8 of this same fold has a radius 29 greater than zero degrees.

 In the whole of the above description, it is noted that only the external wall 8 must necessarily be coated with Clad. In fact, all the contact zones (first, second, third, fourth, fifth, sixth folds, flats 22, 23, 24, 25, etc.) where the welding takes place have at least one surface of the external wall 8. Thus, the internal wall 7 can be coated with a corrosion protection material without pollution with the Clad. In other words, the strip 2 comprises at least two superimposed layers of material which are respectively a substrate constituted by an aluminum of the family 3XXX series and a first layer of Clad made of a material having a melting point lower than that of the substrate. This first layer is from the 4XXX series aluminum family. In the case of a 3-layer strip, the second layer consists of an anti-corrosion material from the family of aluminum series 7XXX. The case of a strip with only two layers (substrate and anti-corrosion layer on the external wall) applies to an evaporator or a condenser because the Clad necessary for brazing can be provided by the other components of the exchanger, in particular the spacers. In the case mentioned above, the thermodynamic conditions of the automobile air conditioning system cause condensation which has a corrosive action on the evaporator. This second layer makes it possible to combat this risk of external corrosion. Similarly, the heating radiator of the air conditioning system can be formed from

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 tubes from a strip 2 having only two layers because the corrosive risks are low in this case. These two layers are: the substrate and the first layer of Clad.

 It will be understood from the description above that at least one of the first, second, third, fourth, fifth, sixth, seventh folds respectively referenced 14, 10, 16, 17, 18, 20, 27 and the secondary fold 12 are oriented at an obtuse angle. Thus, the fluxing product can penetrate and clean the dishes and the contacts where brazing takes place. In addition, these obtuse angles participate in the flexibility of the tube thus facilitating its marriage with the other components of the heat exchanger.

 The tube 1 described above is of course applicable to a heat exchanger tube having a U-shaped fluid circulation, but it is easy to apply this tube to exchangers having an I-shaped circulation or to any other form traffic flow, for example in methodical. Of course, the fluid return phase in the case of a U-shaped circulation is ensured by a manifold. In the case of a methodical circulation, this is ensured by holes or postponements provided at one end of the partition wall 19. The tube defined above is particularly suitable for radiators dedicated to engine cooling as well as radiators and evaporators of a motor vehicle air conditioning system.

 It should be noted that a tube as characterized in the present application may include disturbers promoting the heat exchange between the internal wall 7 and the fluid flowing in the heat exchanger. These disturbers are arranged at the level of the first lateral part 3, on the second lateral part 4 and on the central part 30. These disturbers are formed from a deformation of the internal wall 7 or of the external wall 8 of the strip 2 on the corresponding parts mentioned above.

Claims (20)

1. Tube (1) for heat exchanger designed from a strip comprising a central part (30) separating a first lateral part (3) and a second lateral part (4) both folded on either side of said central part towards a longitudinal axis (5) of said strip thus defining an internal volume (6), an internal wall (7) and an external wall (8), said first and second lateral parts (3) and (4) each having a end edge respectively (15) and (9), the first lateral part (3) having a first fold (14) and the second lateral part (4) having a second fold (10) both oriented towards the interior volume ( 6) of the tube, said second fold (10) defining a leg (32) up to the end edge (9), characterized in that the leg (32) cooperates with a docking means (13) formed on the first side part (3) so that the external wall (8) of the first ply (14) comes in contact on the internal face (7) of the tube opposite to said docking means (13) to define a partition (19).  2. Tube (1) for heat exchanger according to claim 1, characterized in that the docking means (13) has a third ply (16) and a fifth ply (18) oriented towards the interior volume (6) of the tube and a fourth fold (17) oriented towards the outer wall (8), said fourth fold being interposed between the third and the fifth fold.  3. Tube (1) for heat exchanger according to one of claims 1 or 2, characterized in that the second lateral part (4) comprises a secondary ply (12) forming, with the second ply (10), a first bead (11) able to cooperate with the docking means (13).  4. Tube (1) for heat exchanger according to any one of claims 1 to 3, characterized in that the first lateral part (3) comprises a sixth ply (20) thus forming, with the first ply (14), a second bead (21).  5. Tube (1) for heat exchanger according to <Desc / Clms Page number 14>  claim 4, characterized in that the second bead (21) has a seventh pleat (27) oriented towards the external wall (8) so as to bring into contact on the internal wall (7) of the strip a welding plate (28) defined between the first fold (14) and the end edge (15).  6. Tube (1) for heat exchanger according to any one of claims 2 to 5, characterized in that the third fold (17) and the seventh fold (27) are combined, and in that the fifth fold (18) and the first fold (14) are combined.  7. Tube (1) for heat exchanger according to any one of claims 1 to 6, characterized in that the distance separating the third ply (16) and the fourth ply (17) is substantially equal to the leg (32) or to the thickness of the first bead (11).  8. Tube (1) for a heat exchanger according to any one of the preceding claims, characterized in that at least one of the first, second, third, fourth, fifth, sixth, seventh folds respectively (14), (10), (16), (17), (18), (20), (27) and the secondary fold (12) are oriented at an obtuse angle.  9. Tube (1) for heat exchanger according to any one of claims 5 to 8, characterized in that the internal wall (7) of the strip (2) defined between the end edge (15) and the sixth fold (20) is in contact with the internal wall (7) of the strip (2) defined between the first ply (14) and the seventh ply (27).  10. Tube (1) for heat exchanger according to any one of the preceding claims, characterized in that the internal wall (7) of the strip (2) defined between the end edge (9) and the secondary ply (12 ) is in contact with the internal wall (7) of the strip (2) defined by the second lateral part (4).  11. Tube (1) for heat exchanger according to any one of the preceding claims, characterized in that it comprises an internal height (31) of between 0.6 mm and 3 mm.  12. Tube (1) for heat exchanger according to one <Desc / Clms Page number 15>  any one of claims 1 to 10, characterized in that it has an internal height (31) greater than or equal to twice the thickness of the strip (2).  13. Tube (1) for a heat exchanger according to any one of the preceding claims, characterized in that the strip (2) comprises at least two layers of material superposed, one being a substrate constituted by an aluminum alloy and the other a first layer consisting of a material having a melting point lower than the material constituting the substrate.  14. Tube (1) for heat exchanger according to claim 12 or 13, characterized in that the strip (2) comprises a second layer consisting of an anti-corrosion material deposited on the substrate.  15. Tube (1) for heat exchanger according to one of claims 13 to 14, characterized in that the first layer is on the outer wall (8).  16. Tube (1) for heat exchanger according to one of claims 1 to 15, characterized in that the second layer is on the internal wall (7).  17. Tube (1) for heat exchanger according to claim 11, characterized in that the material constituting the substrate is of the family of Aluminum 3XXX series, the material of the first layer is of the family of Aluminum Series 4XXX and the material of the second layer is from the 7XXX series Aluminum family.  18. Heat exchanger of the tube / insert type, characterized in that it comprises at least one tube (1) defined according to any one of the preceding claims.  19. Tube / spacer type heat exchanger according to claim 18, characterized in that it is a radiator or a condenser for a motor vehicle.  20. Heat exchanger type tubes / spacers according to claim 18, characterized in that it is an evaporator for a ventilation, heating and air conditioning installation of a motor vehicle.