EP0735337A1 - Heat exchanger, especially for motor vehicles - Google Patents

Abstract

The heat exchanger consists of a water tank (1) with edges (5) which have upper thrust surfaces (6), and a manifold plate (2) with lengthwise edges (11) and U-section sides (18), fitted with seals (19) over the edges of the tank and fixed in place by in-turned locking lugs (20). The manifold plate has at least two auxiliary plates (21) to reinforce its lengthwise edges (11). Each plate, made from aluminium alloy, has a lower section (22) which is at least partially welded or brazed to the outer surface (17) of a lengthwise edge (11), and an upper section (23) which lies perpendicular to the lower one and parallel to the outer surface of the plate's U-shaped side (18). The lengthwise edges of the manifold plate are extended at the top to form locking lugs (20), and the upper section (23) of each auxiliary plate is welded or brazed to the upper portion of a lengthwise edge lying opposite the outer wall of the water tank.

Description

The invention relates to heat exchangers, in particular for a motor vehicle, and more particularly those made of brazed or welded aluminum of the type comprising a fluid box assembled by crimping on a collecting plate with interposition of a seal.

In these heat exchangers, the water box is usually provided with peripheral edges comprising an upper bearing face and intended to be housed at least partially in a peripheral U-shaped groove delimited at least in part by longitudinal edges of the collector plate. , said groove comprising a bottom and vertical front and rear faces. There are also provided crimping means intended to bear on said upper face of the peripheral edges, to immobilize the latter relative to the collector plate.

Generally, the crimping means are fixing lugs which project at the end of the longitudinal edges of the collector plate.

The fluid contained in the water box exerts a very high pressure on the walls of said box, which tends to cause the lateral edges of the box to move apart, although these are held by the fixing lugs .

This effect is all the more marked in current exchangers which include a collector plate and tubes made of aluminum or an alloy of aluminum and manganese (mainly for reasons of ductility, cost and weight), because this type of alloy which does not have good mechanical characteristics bends under the effect of high pressures, and does not allow constant pressure of the fixing lugs on the bearing surface, which can cause local leakage at the seal.

This sometimes results in a separation of the collector plate, by bending of its edges, and therefore a loss of compression of the seal which leads to an even greater leak.

Those skilled in the art have proposed a solution in an attempt to partially solve the problems of the deflection induced by the folding of the fixing lugs and of the poor control of the compression of the seal.

It is thus proposed to add to the exchanger, at each longitudinal edge, a clip ensuring the connection between the water box and the collector plate. The fixing lugs are no longer located at the end of the longitudinal edges, but at the two ends of the staple, the lugs located at the upper end of the staple being folded beforehand, so that there is no more than bending the tabs at the other end. To adjust the compression of the joint it is then necessary to use an additional device which comes to press on the upper fixing lugs, then comes to bend the lower fixing lugs so that they rest on the internal face of the longitudinal edges of the collector plate.

Such an exchanger is taught for example by the publication FR-A-2 550 328.

This type of exchanger has the major drawback of requiring an additional device specially designed to position the clip and immobilize it.

To completely solve the problem posed, one solution would consist in using more resistant materials, based on more complex alloys, to produce the collector plate. However, the soldering method currently used (enclosure under an inert atmosphere and use of a flux based on potassium fluoaluminates) does not allow the production of quality brazing joints between tubes and a collector plate made of such alloys.

There is therefore currently no solution allowing the longitudinal edges of the collector plates to be sufficiently reinforced.

Consequently, an object of the invention is to provide a heat exchanger which does not have the drawbacks of the devices of the prior art.

To this end, the invention provides a heat exchanger of the type described in the introduction, in which at least two auxiliary plates are provided, each forming a reinforcement angle of one of the longitudinal edges of the collector plate and comprising a welded or brazed lower wing. , on a longitudinal edge, at least partially outside the bottom of the peripheral groove, and an upper wing substantially perpendicular to this lower wing and extending parallel to an external face delimiting the peripheral groove.

The use of reinforcement angles at least partially welded or brazed to the collector plate makes it possible, on the one hand, to make the maximum pressure supported by the angle / collector plate edge couple, very significantly greater than the pressure exerted on said edge longitudinal of the collector plate by the fluid contained in the water box, and secondly, to allow the folding of the fixing lugs without bending of the longitudinal edges.

In a first embodiment of the invention, the longitudinal edges of the collector plate delimit the bottom and the external and internal faces of the peripheral groove and are extended by fixing lugs forming the crimping means, and the upper wing of each auxiliary plate is welded or brazed on the part of the longitudinal edges of the collector plate opposite the external face of the peripheral edges of the water box.

The auxiliary plates are, in this embodiment secured to the collector plate during the passage from the heat exchanger to the brazing or welding furnace. The longitudinal edges are thus solidly reinforced, which makes it possible to avoid any bending, including during the step of folding the fixing lugs.

In a second embodiment of the invention, the peripheral groove is delimited by an assembly of the longitudinal edges of the collector plate and the auxiliary plates, said longitudinal edges delimiting the internal face and the bottom of said groove, and the upper wing auxiliary plates delimiting the external face of this groove.

It is also possible to provide at least one other fixing lug forming an extension of the lower wing of an auxiliary plate and intended to rest, after folding along a line substantially parallel to a longitudinal edge, on the part of the longitudinal edges opposite from the inner side of the peripheral throat.

This further increases the resistance of the longitudinal edges to pressure a little more, while facilitating the maintenance of the assembly during passage through the oven.

According to another characteristic of the invention, the auxiliary plates are made of a material at least as resistant as that of the collector plate.

Preferably according to the invention, these auxiliary plates are made of an aluminum alloy of the type with structural hardening.

This type of alloy has much higher mechanical characteristics than the simple aluminum and manganese alloys used to manufacture the collector plates.

This alloy is for example based on aluminum, magnesium and silicon.

• la figure 1 est une coupe transversale d'une partie d'un échangeur de chaleur selon l'invention, dans un premier mode de réalisation, après assemblage;
• la figure 2 est une vue agrandie d'une partie de la figure 1, avant repliement des pattes de fixation;
• la figure 3 est une vue de face, partielle, d'une partie d'une plaque collectrice d'un échangeur de chaleur dans le mode de réalisation illustré à la figure 1;
• la figure 4 est une vue de face, partielle, d'une partie d'une plaque auxiliaire et d'une partie d'une plaque collectrice d'un échangeur de chaleur dans un second mode de réalisation de l'invention;
• la figure 5 est une vue en coupe transversale du second mode de réalisation de l'invention, selon l'axe V-V de la figure 4;
• la figure 6 est une vue en coupe transversale du second mode de réalisation de l'invention, selon l'axe VI-VI de la figure 4; et
• la figure 7 est une vue partielle de l'extrémité d'un bord longitudinal de plaque collectrice selon le second mode de réalisation de l'invention.

In the description which follows, given by way of example, reference is made to the appended drawings, in which:

• Figure 1 is a cross section of part of a heat exchanger according to the invention, in a first embodiment, after assembly;
• Figure 2 is an enlarged view of part of Figure 1, before folding of the fixing lugs;
• Figure 3 is a partial front view of part of a header plate of a heat exchanger in the embodiment illustrated in Figure 1;
• Figure 4 is a partial front view of part of an auxiliary plate and part of a header plate of a heat exchanger in a second embodiment of the invention;
• Figure 5 is a cross-sectional view of the second embodiment of the invention, along the axis VV of Figure 4;
• Figure 6 is a cross-sectional view of the second embodiment of the invention, along the axis VI-VI of Figure 4; and
• Figure 7 is a partial view of the end of a longitudinal edge of the collector plate according to the second embodiment of the invention.

Reference is first made to FIGS. 1 to 3 to describe a first embodiment of the invention.

In FIG. 1 is illustrated, in cross section, the upper part of a heat exchanger comprising a fluid box 1, generally made of rigid plastic, a metal collecting plate 2 and metal tubes 3 forming a bundle of tubes.

In the description which follows, it is considered that the fluid which circulates in the exchanger is water. Therefore, we will call the fluid box: water box. However, it is clear that the invention also applies to exchangers operating for example with oil or with a gas.

The tubes 3 are made of aluminum, or of a fairly ductile alloy comprising aluminum. The collector plate is preferably made of an aluminum and manganese alloy belonging to the so-called "3000" series. The tubes 3 and the collector plate 2 are joined by brazing, or by welding in an oven, under an inert atmosphere, using a stream of potassium fluoaluminates.

The water box 1 comprises a shaped wall 4 intended to receive the water. This wall 4 comprises on its periphery peripheral edges 5 forming beads, comprising an upper support face 6, an internal face 7, an external face 8 and a lower face 9.

Throughout the description, the references to the orientation of the elements are given relative to FIG. 1. It is clear that the inversion of the water box of FIG. 1 would place an element qualified as lower in a position qualified as superior.

The collector plate 2 comprises a central part provided with openings 10 allowing passage of the ends of the tubes 3, and on either side of this central part, longitudinal edges 11 shaped before assembly of the exchanger.

In this first embodiment, the longitudinal edges 11 comprise an internal wall 12 extending substantially perpendicularly to the central part, a lower wall 13 extending the internal wall substantially perpendicularly, so that this lower wall is substantially parallel to the central part, and an external wall 14 extending the bottom wall 13 substantially perpendicularly, so that this wall is substantially parallel and facing the internal wall 12.

The internal, external and lower walls of the longitudinal edges 11 thus respectively delimit the internal faces 15, external 16 and the bottom 17 of a peripheral U-shaped groove 18 which extends over the entire periphery of the collecting plate 2 and intended to receive at least partially the peripheral edges 5 of the water box 1.

To this end, the peripheral groove 18 has a cross section of shape substantially homologous to that of the peripheral edges, but of slightly larger dimensions to allow the interposition in the bottom of the groove of a seal 19.

This seal 19 is made of a deformable and waterproof material, for example of elastomer. It is arranged in the peripheral groove 18 in contact with the lower 13 and inner 12 walls of the longitudinal edges 11.

The outer wall 14 of the longitudinal edges is extended at its end by fixing lugs 20 produced by prior cutting of the collecting plate 2.

These fixing lugs 20 are intended to be folded inwards along an axis XX substantially parallel to a longitudinal edge, so that they bear on the upper support face 6 of the peripheral edges 5, thus immobilizing , under compression, said peripheral edges 5 inside the peripheral groove 18. The intensity of the compression can be adjusted by moving the position of the folding axis XX relative to the line of intersection between the fixing lugs 20 and the external wall 14.

In the example illustrated in FIGS. 2 and 3, the axis X-X coincides with this line of intersection between the fixing lugs 20 and the external wall 14.

In order to avoid a double deflection of the external wall 14 of the longitudinal edges, on the one hand during the folding of the fixing lugs 20, and on the other hand under the effect of the pressure of the water contained in the box. water 1, the invention provides auxiliary reinforcement plates 21, forming angles.

These auxiliary plates 21 comprise a lower wing 22 extended substantially perpendicularly by an upper wing 23. They are made of a material at least as strong as that of the collector plate 2. Preferably, the material used is an aluminum alloy, magnesium and silicon of the so-called "6000" series with structural hardening, which has higher mechanical characteristics than the alloys of the 3000 series.

These 6000 series alloys cannot be used directly to make the collector plates, because they contain too much magnesium which hinders the brazing of the tubes on the collector plates.

The angle iron 21 has a longitudinal extension substantially equal to that of a longitudinal edge 11. Preferably, the lower wing 22 has at least the same extension as the lower wall of a longitudinal edge 11, and the upper wing 23 s 'extends to the fold line XX of the external wall 14 of this same longitudinal edge 11.

The lower wing 22 is brazed on the external face of the lower wall 13 with a longitudinal edge 11, while the upper wing 23 is brazed on the external face of the external wall 14 of this same edge 11.

The brazing of the angles is carried out at the same time as the brazing of the tubes 3 on the collector plates 2. The maintenance of these angles can be carried out, before passage in the furnace, by crimping using fixing tabs, or by welding. by points.

Reference is now made to FIGS. 4 to 7 to describe a second embodiment of the invention.

In this second embodiment, the water box 1, the central part of the collector plate 2, the tubes 3, the seal 19, and the edges 5 of the water box are identical to the elements which respectively carry the same names in the first embodiment described above and illustrated in Figures 1 to 3. Only the embodiment of the peripheral groove differs from the first mode, although the latter retains substantially the same shape.

The central part of the collector plate 2 is extended on either side by longitudinal edges 30. Each edge comprises an internal wall 31 extending substantially perpendicularly the central part 2, and a bottom wall 32 extending the internal wall 31 substantially perpendicular, so that this bottom wall 32 is substantially parallel to the central part 2 of the collector plate.

Each edge thus delimits the internal face 15 and the bottom of a peripheral U-shaped groove 18 which extends over the entire periphery of the collecting plate 2 and intended to at least partially receive the peripheral edges 5 of the water box 1.

To delimit the external face 16 of the peripheral groove 18, an auxiliary plate 33 is provided, comprising an upper wing 34 extended substantially perpendicularly by a lower wing 35. The auxiliary plate 34 thus forms an angle. The upper wing 34 has an extension substantially identical to that of the internal wall 31 of the longitudinal edges 30, and has in its lower part, just above the connection with the lower wing 35, a plurality of rectangular openings 36 intended to receive the ends 37 of the lower wall 32 of the longitudinal edges 30.

These ends 37 extend the lower wall 32, and have a shape substantially homologous to that of the openings made in the upper wing 34 of the angles. They are made by cutting before assembly.

The openings 36, and the ends 37 with which they cooperate, are preferably arranged substantially at the ends of the longitudinal edges 30, and at the center of these same longitudinal edges, in order to allow a homogeneous distribution of the stresses exerted by the peripheral edges 5 on the 'upper wing delimiting the external face of the peripheral groove 18.

It is clear that one can provide more or less than three openings and associated ends.

The auxiliary plates 33 are made of a material at least as strong as that of the collector plate 2. Preferably, this material is an alloy of aluminum, magnesium and silicon of the series called "6000" with structural hardening, which has higher mechanical properties than alloys in the 3000 series.

In this second embodiment, the peripheral groove 18 is therefore produced by assembling the longitudinal edges 30 and the angles 33, by introducing, during said assembly, the ends 37 of the lower walls 32 of the longitudinal edges 30 in the openings 36 of the angles 33.

In order to reinforce the joining of this assembly delimiting the peripheral groove 18, the lower wing 35 of the angles 33 is brazed or welded to the external face of the lower wall 32 of the longitudinal edges 30. This brazing is carried out at the same time as the brazing tubes 3 on the collector plate 2, when passing through the oven.

The upper wing 34 of each angle iron 33 is extended by a plurality of fixing lugs 38 produced by cutting the collecting plate 2 before assembly.

These fixing lugs 20 are intended to be folded inwards along an axis XX substantially parallel to a longitudinal edge, so that they rest on the upper support face 6 of the peripheral edges 5, thus immobilizing, under compression, said peripheral edges 5 inside the peripheral groove 18. The intensity of the compression can be adjusted as a function of the positioning of the folding axis XX relative to the line of intersection between the fixing lugs 20 and the upper wing 34.

The intensity of the compression can be adjusted by moving the position of the folding axis X-X relative to the line of intersection between the fixing lugs 38 and the upper wing 34.

In the example illustrated in FIGS. 4 to 6, the axis X-X coincides with this line of intersection between the fixing lugs 38 and the upper wing 34.

The fixing lugs 38 are shown, in Figures 5 and 6, in their position before folding.

One can also provide other fixing lugs 39 in the extension of the lower wing 35. These lugs fixing 39 are intended to be folded along an axis YY substantially parallel to the longitudinal edges 30, so that these fixing lugs 39 bear on the external face of the internal wall 31 of the longitudinal edges 30.

The fixing lugs 39 are shown in their folded position, in solid lines, in Figures 6 and 7, while they are also shown in their position before folding, in broken lines, in Figure 6 only.

Such fixing lugs have the advantage of immobilizing the assembly of the longitudinal edges 30 and of the angles 33 before passage to the oven, as well as of reinforcing said assembly a little more. During this same passage in the oven, provision may also be made for the fixing lugs 39 to be welded to the internal walls 31.

The invention is not limited to the two embodiments described above, but embraces all the variants which a person skilled in the art may develop within the scope of the claims below.

Thus, it is possible to envisage an embodiment derived from the second mode described above, in which the peripheral groove is produced by assembling the longitudinal edges of the collector plate and the auxiliary plates, the end of the longitudinal edges being extended by fixing lugs. which would come to rest, after folding, on the outside of the upper wing of the auxiliary plates. This would further strengthen the assembly, and / or avoid the use, for the manufacture of auxiliary plates, of material from the 6000 series with structural hardening.

Claims (11)

Heat exchanger, in particular for a motor vehicle, of the type comprising a water box (1) provided with peripheral edges (5) comprising an upper bearing face (6), a collecting plate (2) having longitudinal edges (11; 30) defining at least the internal face (15) and the bottom (17) of a peripheral U-shaped groove (18) intended to receive at least partially the peripheral edges (5) with the interposition of a seal (19 ), and crimping means (20; 38,39) intended to bear on said upper face (6) of the peripheral edges () to immobilize them relative to the collector plate (2),
characterized in that it comprises at least two auxiliary plates (21; 33) each forming a reinforcement angle of one of the longitudinal edges (11; 30) the collector plate (2) and comprising a lower wing (22; 35) welded or brazed at least partially, on a longitudinal edge (11), outside the bottom (17) of the peripheral groove (18), and an upper wing (23; 34) substantially perpendicular to this lower wing (22; 35) and extending parallel to an external face (16) delimiting the peripheral groove (18). Heat exchanger according to claim 1, characterized in that the longitudinal edges (11; 30) of the collecting plate (2) delimit the bottom (17) and the external (16) and internal (15) faces of the peripheral groove ( 18) and are extended by fixing lugs (20) forming the crimping means, and
in that the upper wing (23) of each auxiliary plate (21) is further welded or brazed to the part (13) of the longitudinal edges (11) of the collector plate (2) opposite the external face (8 ) of the peripheral edges (5) of the water box (1). Heat exchanger according to one of claims 1 and 2, characterized in that the upper wing (23) of the auxiliary plates (21) extends substantially up to the line (XX) of folding of the fixing lugs (20 ). Heat exchanger according to claim 1, characterized in that the peripheral groove (18) is delimited by an assembly of the longitudinal edges (30) of the collector plate (2) and the auxiliary plates (33), said longitudinal edges (30) delimiting the internal face (15) and the bottom (17) of said groove, and the upper wing (34) of the auxiliary plates (33) delimiting the external face (16) of this groove. Heat exchanger according to claim 4, characterized in that the ends of the longitudinal edges (30) of the collector plate (2) are provided in at least three predefined locations with extensions (37) of substantially rectangular shape, which are produced by prior cutting of said collector plate. Heat exchanger according to one of claims 1 to 3, characterized in that the upper wing (34) of an auxiliary plate (33) comprises in its lower part, opposite the extensions (37), at least two openings (36) of shape substantially homologous to that of said extensions (37), which allows the assembly of the collector plate (2) and the auxiliary plate (33), by form cooperation. Heat exchanger according to one of claims 4 to 6, characterized in that the crimping means further comprise at least one other fixing lug (39) forming an extension of the lower wing (35) of an auxiliary plate ( 33) and intended to rest, after folding along a line (YY) substantially parallel to a longitudinal edge (30), on the part (31) of the longitudinal edges facing the internal face (15) of the peripheral groove ( 18). Heat exchanger according to one of the preceding claims, characterized in that the auxiliary plates (21; 33) are made of a material at least as strong as that of the collector plate (2). Heat exchanger according to one of claims 1 to 8, characterized in that the auxiliary plates (21; 33) are made of an aluminum alloy of the structural hardening type. Heat exchanger according to claim 9, characterized in that the auxiliary plates (33) are made of an alloy of aluminum, magnesium and silicon. Heat exchanger according to one of the preceding claims, characterized in that the collecting plate (2) is made of an aluminum and manganese alloy.

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