EP0811820B1 - Flat tube with median spacer for heat exchanger - Google Patents

Description

The invention relates to a flat tube for the circulation of a fluid in a heat exchanger, in particular a radiator for cooling the drive motor of a vehicle automobile, formed by folding, in its longitudinal direction, of a sheet metal strip including a first face, defining the outer surface of the tube is coated with a material of brazing, this tube comprising first and second walls main opposites, substantially flat and parallel, connected together by two complementary walls of so as to form a closed profile, the first main wall being formed from a middle region of the width of the strip and the second main wall from two intermediate regions located on either side of the middle region, which come to juxtapose substantially in the same plane, and two marginal regions of the strip, respectively adjacent to said intermediate regions, being folded substantially 180 ° with respect to them towards the interior of the tube and joined by brazing to the inside of the middle region. Such a tube is known from EP-A-302 232.

Such tubes are arranged in one or more rows, the tubes of the same row being mutually aligned in parallel to their thickness, that is to say perpendicular to their main walls. Each tube connects two fluid boxes so as to allow the circulation of the fluid in one or more passes between the fluid boxes, the fluid thus exchanging heat with an air flow crossing the bundle of tubes and sweeping the surface outside of each tube.

In a known tube of this kind, the marginal regions of the strip have a width corresponding to the internal thickness of the tube and are bent at right angles to the regions intermediaries to lean on the inner face of the first main wall. These regions marginal, whose coatings of brazing material are then turned towards each other, are joined by brazing, between them and at the first main wall, forming a tube reinforcement spacer and dividing the interior thereof in two separate parallel conduits.

It is clear that, for a tube having the structure which comes to be described, the shape and dimensions of the section transverse of the tube impose the width of the strip of departure. It is therefore not possible from the same band, unless you cut it, get tubes of sizes different. In addition, the desired width of the strip must be met with precision, which increases its cost by making or causing rejects.

Figure 3 partially shows a tube in which one 114 marginal regions, folded at right angles to to the adjacent region 112 of the strip, normally rests on the inner face of the first main wall 107, while the other shorter marginal region 113 remains away from the wall 107. The region 113 therefore does not participate not to reinforce the tube. In addition, it is difficult to ensure the co-planarity of the adjacent region 111 with the region 112 to form the second main wall of the tube.

In FIG. 4, the region 113 has the desired length, but region 114 is too long and is positioned obliquely relative to the main walls 107 and 111, 112. The regions 113 and 114 are therefore not mutually contiguous and do not provide the desired reinforcement of the tube. Failure sealing may also occur.

The object of the invention is to remedy these drawbacks, and to allow the realization of a tube of determined size at from a strip whose width can vary within a certain measure, and correspondingly to produce tubes of somewhat different sizes from the same width of tape.

The invention relates in particular to a tube of the kind defined in introduction, and anticipates that the first main wall is formed by two zones of the median region located laterally on either side of a fold facing inward of the tube, on which said marginal regions are supported.

• Ledit repli est placé à mi-largeur de la première paroi principale du tube.
• Ledit repli présente une section transversale en U dont les branches sont mutuellement accolées et s'étendent perpendiculairement auxdites parois principales, lesdites régions marginales s'appuyant sur le fond du U.
• Chaque région marginale est repliée en U par rapport à la région intermédiaire adjacente et s'appuie par le fond de son U sur ledit repli.
• Le fond du U de chaque région marginale est en contact avec celui de l'autre région marginale et avec ledit repli, ces trois éléments définissant entre eux une cavité propre à se remplir de matériau de brasage lors de la fusion du revêtement présent sur les régions marginales.
• Chaque région marginale est repliée à plat sur la région intermédiaire adjacente, la région marginale et la région intermédiaire étant en contact mutuel par la seconde face de la bande.
• Les parois complémentaires ont un profil courbe convexe.
• Les parois complémentaires ont un profil sensiblement semi-circulaire.

Optional, complementary or alternative features of the invention are set out below:

• Said fold is placed at half the width of the first main wall of the tube.
• Said fold has a U-shaped cross section whose branches are mutually contiguous and extend perpendicular to said main walls, said marginal regions resting on the bottom of the U.
• Each marginal region is folded in a U with respect to the adjacent intermediate region and is supported by the bottom of its U on said fold.
• The bottom of the U of each marginal region is in contact with that of the other marginal region and with said fold, these three elements defining between them a cavity suitable for filling with brazing material during the melting of the coating present on the regions marginal.
• Each marginal region is folded flat on the adjacent intermediate region, the marginal region and the intermediate region being in mutual contact by the second face of the strip.
• The complementary walls have a convex curved profile.
• The complementary walls have a substantially semi-circular profile.

a) on plie ladite bande longitudinalement pour former ledit repli, le reste de la bande s'étendant sensiblement selon un plan de part et d'autre du repli;

b) on replie les régions marginales de la bande, du côté dudit plan où se trouve le repli, à une distance prédéterminée de celui-ci dans la direction de la largeur de la bande; et

c) on recourbe la bande, à une distance prédéterminée de chaque côté du repli, pour définir les parois complémentaires du tube, lesdites régions intermédiaires pivotant sensiblement de 180° pour amener les régions marginales de la bande en contact avec le repli.

The subject of the invention is also a method for producing a tube as defined above, comprising successive stages during which:

a) folding said strip longitudinally to form said fold, the rest of the strip extending substantially in a plane on either side of the fold;

b) the marginal regions of the strip are folded back, on the side of said plane where the fold is located, at a predetermined distance from the latter in the direction of the width of the strip; and

c) the strip is bent, at a predetermined distance on each side of the fold, to define the complementary walls of the tube, said intermediate regions pivoting substantially 180 ° to bring the marginal regions of the strip into contact with the fold.

• la figure 1 est une vue partielle en coupe transversale d'un tube selon l'invention, avant brasage;
• la figure 2 représente la partie médiane de la coupe transversale d'un tube semblable à celui de la figure 1, réalisé à partir d'une bande un peu plus large;
• les figures 3 et 4 sont des vues analogues à la figure 2, relatives à des tubes selon l'état de la technique; et
• la figure 5 est une vue partielle en coupe transversale de la bande utilisée pour réaliser le tube de la figure 1, en cours de pliage.

The characteristics and advantages of the invention will be explained in more detail in the description below, with reference to the accompanying drawings, in which:

• Figure 1 is a partial cross-sectional view of a tube according to the invention, before brazing;
• 2 shows the middle part of the cross section of a tube similar to that of Figure 1, made from a slightly wider strip;
• Figures 3 and 4 are views similar to Figure 2, relating to tubes according to the prior art; and
• Figure 5 is a partial cross-sectional view of the strip used to make the tube of Figure 1, during folding.

Figure 1 shows in cross section a flat tube 1 produced by folding the strip of metal sheet 2 shown in Figure 5. The side of strip 2 facing down in FIG. 5 is a coating 3 of a brazing material, which covers the entire periphery of the cross section of the tube 1. At the half-width of the strip 2 is formed a fold 4 which penetrates inside the tube. In cross section, this fold has a U shape with branches 5 and 6 are joined together and are bent at right angles by relative to the adjacent regions 7 and 8 of the strip. On the Figure 1, regions 7 and 8 extend in the same plane to form a first main wall of the tube. They connect respectively by regions 9 and 10, curved in half cylinders, to other flat regions 11 and 12 which form the second main wall of the tube, parallel to the wall 7, 8. Thus, the periphery of the tube is formed by the two main faces 7, 8 and 11, 12, flat and parallel, and by two curved complementary walls 9 and 10.

Marginal regions 13 and 14 of the strip, adjacent regions 11 and 12 respectively, are bent 180 ° by relative to these inside the tube, thus forming, with these latter regions, respective U-shaped profiles including the bottoms 15 and 16 are in mutual contact by the coating 3 and each in contact with the bottom 17 of the U formed by the fold 4. There remains between these three funds a cavity 18 of curvilinear triangular cross section, which will fill of brazing material when it is melted. Same time, the melting of the brazing material covering the faces branches 5 and 6 facing one another will ensure the stiffening of the fold 4. This provides excellent holding of the spacer formed by the fold 4 and by the marginal regions 13 and 14, and perfect sealing of the tube at the connection between the three bottoms. The fact that the sealing area is adjacent to the outside of the tube also facilitates brazing preparation operations (degreasing, fluxing, steaming), as well as control appearance before soldering.

The tube of Figure 1 is rigorously symmetrical by relation to plane P passing on the one hand between branches 5 and 6, on the other hand between funds 15 and 16. This symmetry is broken, in the case of the tube of Figure 2, by the fact that marginal region 14 is wider than marginal region 13, the starting strip itself being a little wider than that shown in Figure 5. We see that this increase width does not affect the exterior dimensions of the finished tube, nor the relative shape and position of the three funds of U 15, 16 and 17 and therefore the quality of their bond.

Advantageously, to produce the tube according to the invention, one first forms fold 4 by triple longitudinal folding Of the band. We then fold the marginal regions 13 and 14 to 180 ° relative to the adjacent regions 11 and 12, according to the arrows F1 in FIG. 5. Then, the regions 11 are noted and 12 by rotating them 180 ° relative to the regions 7 and 8 respectively, according to the arrows F2 in FIG. 5, by rolling regions 9 and 10 in half-cylinders. Folding marginal regions 13 and 14 is performed in such a way the bottoms 15 and 16 are formed at a predetermined distance of plane P defined by branches 5 and 6, thanks to which any excess or defect in the width of strip 2 is affects the width of marginal regions 13 and 14 and not on the external dimensions of the tube.

Claims (9)

1. A flat tube (1) for the flow of a fluid within a heat exchanger, especially a cooling radiator for the propulsion engine of a motor vehicle, the tube being formed by bending in its longitudinal direction a sheet metal strip (2), a first face of which, defining the outer surface of the tube, is coated with a braze material (3), the tube having opposed first main walls (7, 8) and second main walls (11, 12), which are substantially flat and parallel to each other and which are joined together through two complementary walls (9, 10) so as to define a closed profile, the first main wall being formed from a middle region (7, 4, 8) of the width of the strip, and the second main wall from two intermediate regions (11, 12) situated on either side of the middle region, which are juxtaposed substantially in a common plane, and two marginal regions (13, 14) of the strip, which are respectively adjacent to the said intermediate regions, being bent back substantially at 180° with respect to the latter towards the inside of the tube, and being secured by brazing to the internal face of the middle region, characterised in that the first main wall is formed from two zones (7, 8) of the middle region which are situated laterally on either side of a pleat facing towards the interior of the tube, with the said marginal regions (13, 14) engaging on the pleat.
2. A tube according to Claim 1, characterised in that the said pleat is located halfway along the width of the first main wall of the tube.
3. A tube according to Claim 1 or Claim 2, characterised in that the said pleat has a U-shaped transverse cross section, the branches (5, 6) of which are in mutual contact and extend at right angles to the said main walls, the said marginal regions engaging on the base of the U.
4. A tube according to one of the preceding Claims, characterised in that each marginal region (13, 14) is bent back in a U-shape with respect to the adjacent intermediate region, and engages, through the base (15, 16) of its U, on the said pleat.
5. A tube according to Claim 4, characterised in that the base (15, 16) of the U in each marginal region is in contact with that of the other marginal region and with the said pleat (4), these three elements together defining a cavity (18) adapted to fill with braze metal during melting of the coating which is present on the marginal regions.
6. A tube according to Claim 4 or Claim 5, characterised in that each marginal region is bent back flat on the adjacent intermediate region, the marginal region and the intermediate region being in mutual contact through the second face of the strip.
7. A tube according to one of the preceding Claims, characterised in that the complementary walls (9, 10) have a convex curved profile.
8. A tube according to Claim 7, characterised in that the complementary walls have a substantially semicircular profile.
9. A method for making a tube according to one of the preceding Claims, comprising successive steps in the course of which:

   (a) the said strip (2) is bent longitudinally so as to form the said pleat (4), with the remainder of the strip extending, substantially in one plane, on either side of the pleat;

   (b) the marginal regions (13, 14) of the strip are bent back on the side of the said plane which contains the pleat, at a predetermined distance from the latter in the direction of the width of the strip; and

   (c) the strip is reformed in a curve at a predetermined distance from each side of the pleat so as to define the complementary walls (9, 10) of the tube, with the said intermediate regions pivoting substantially through 180° so as to bring the marginal regions of the strip into contact with the pleat.

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