WO2023041568A1

WO2023041568A1 - Heat exchanger for a motor vehicle and method for manufacturing such a heat exchanger

Info

Publication number: WO2023041568A1
Application number: PCT/EP2022/075504
Authority: WO
Inventors: Laurent Pasquet; Etienne Chardin
Original assignee: Valeo Systemes Thermiques
Priority date: 2021-09-15
Filing date: 2022-09-14
Publication date: 2023-03-23
Also published as: FR3127038A1

Abstract

The invention provides a heat exchanger for a motor vehicle, comprising a plurality of pipes each defining a transverse duct in which a fluid is capable of flowing, the pipes being arranged along a stack with a vertical axis (Z) such that a space is formed between two successive pipes, the space allowing an air flow promoting heat exchange with the fluid to pass through, each pipe being provided with an internal fin, and each space being provided with an external fin, said internal and external fins being folded and having fold peaks in contact with the adjacent pipes, each pipe having a pipe closure region. Said exchanger is characterised in that, for each external fin, each fold peak is provided with a clearance centred on the proximal closure region of the pipe upon which it rests.

Description

DESCRIPTION

Motor vehicle heat exchanger and method of manufacturing such a heat exchanger

Technical field of the invention

The field of the present invention is that of heat exchangers, in particular for motor vehicles, and it relates more particularly to heat exchangers comprising a bundle of tubes and arranged in particular on the front face of the motor vehicle.

The invention also relates to a method of manufacturing such a heat exchanger.

Such heat exchangers are in particular arranged on a loop of a cooling circuit, making it possible to dissipate calories, coming from an internal combustion engine, or from a peripheral, such as an air conditioning module, of the vehicle automobile.

In known manner, a heat exchanger for a motor vehicle comprises a plurality of tubes extending parallel to each other and in which the cooling fluid present in the previously mentioned cooling circuit loop, or the refrigerant fluid (refrigerant) present can circulate. in the previously mentioned air conditioning loop. The heat exchanger is configured to allow an exchange of calories between a flow of air passing through it and the fluid circulating inside the tubes, knowing that the heat exchanger can also comprise heat dissipation devices comprising a plurality external fins, also called "spacers", extending between the tubes, on the passage of the air flow, thus promoting the dissipation of calories at the level of the heat exchanger.

A tube heat exchanger can in particular be located at a front face of the motor vehicle. Thus, when the motor vehicle is moving forward, the outer fins of the heat exchanger are exposed to an air flow from outside the motor vehicle, thus making it possible to improve the dissipation of calories at the level of the heat exchanger.

The heat exchanger may also comprise a plurality of internal fins extending inside the tubes, over the passage of the fluid, thus making it possible to improve the cooling of the tubes.

Technical background

The tubes generally have a flattened and elongated shape.

Each tube is formed from a plate which is curved and whose two lateral edges meet at the level of a closure zone.

The external fins and the internal fins generally have an accordion shape, with successive folds.

When the outer fins are moved into position between the tubes, their fold apices come to rest on the flattened outer face of the tubes.

In the same way, when the internal fins are placed in position within the tubes, their fold apices come into contact with the inner flattened face of the tubes.

The contact between the pleat tops and the tubes is essential to ensure the transfer of calories from one part to another, and therefore to ensure optimal heat exchange.

However, when performing the brazing of the tubes, at the level of the closure zone, it is sometimes possible that the filler metal intended for the closure zone is partly spread on the external fins resting on the tubes, by capillarity . Thus, to successfully braze the tube correctly, it is necessary to add more metal than necessary, which is not desirable from the point of view of the consumption of the filler metal since this can compromise the realization of the other joints of brazing, especially those between tubes and manifolds. Another drawback lies in the fact that the brazing between the tube and the internal fins depends on the geometry of the tube. If the ply tips of the inner fins do not contact the inner wall of the tube, then the solder joints do not form properly, which reduces heat dissipation performance and mechanical strength.

Summary of the invention The object of the present invention is to overcome the various drawbacks stated above, by means of a heat exchanger in which the filler metal arriving at the level of the closure zone of the tube is correctly directed only between the two lateral edges to be brazed of the tube, and does not tend to be attracted towards the external fins by capillarity, and this with practical and ecological means of implementation.

The heat exchanger according to the invention comprises, in a conventional manner, a plurality of tubes each defining a transverse duct in which a fluid is able to circulate, the tubes being arranged according to a stack with a vertical axis (Z) such as a space is provided between two successive tubes, the space allowing the passage of an air flow promoting heat exchange with the fluid, each tube being provided with an internal fin, and each space being provided with a fin external, these internal and external fins being bent and having fold apexes in contact with the adjacent tubes, each tube having a zone of closure of the tube.

This exchanger is mainly characterized in that, for each external fin, each fold apex has a clearance centered on the proximal closure zone of the tube on which it rests.

The main idea of this invention consists in providing a clearance at the replacement level where the brazing of the tube will be carried out, that is to say at the location where the filler metal arrives to join two side edges of the tube, called "ends". By “removal” is meant a withdrawal of the external fin relative to the tube, that is to say a distance from a zone of the external fin relative to the tube.

Thanks to this clearance, there is no longer any risk that the filler metal which arrives at the level of the closure zone does not come into contact with the external fin and therefore be sucked up by the external fin by capillarity. Thus, the quantity of filler metal can be dosed in a reasonable manner, there is no risk of having excess filler metal at the closure zone. In addition, the brazing joint remains correctly sized according to the quantity of filler metal. Also, thanks to this optimal dimensioning, the internal fin located inside the tube can remain correctly in contact with the internal walls of the tube, and this whatever the geometry of the ends, in particular the height of the legs of the tube, in order to ensure the transfer of calories and to promote heat exchange. In the same way, the external fin located outside the tube can remain in contact with the external wall of the tube, except at the level of the release zone of course, in order to ensure the transfer of calories and to promote the heat exchanges.

These supports are important to allow optimal brazing of the external and internal fins on the tubes.

These supports can be linear, when the fin is folded with undulations or with a V shape. These supports can be surface, when the fin is folded with a U-shaped crenellation presenting flat zones. It should be noted that each fold apex of the external fin has this clearance, whether it is an upwards oriented fold or a downwards oriented fold depending on the direction of the stacking of the tubes. and external fins. Thus, the external fin has a symmetry, and can be turned over if necessary during the process of stacking the fins and the tubes, without there being any impact.

According to the different embodiments of the invention, which may be taken together or separately:

- the clearance has a width at least equal to the width of the closure zone: in fact, to be sure that the filler metal does not come into contact with the external fin, the clearance must necessarily be at least as wide as the closure area. Preferably the undercut is slightly wider than the closure area.

- Said closure zone corresponds to a junction of two tube ends, a brazing forming said junction.

- the ends of the tube are curved at the level of the closure zone according to a radius of curvature, and, on either side of the junction, the clearance begins at least at the level of the start of the radius of curvature of the two ends of the tube : thus, the undercut encompasses the entire closure area.

- the clearance extends over a width of between 0.5mm and 5mm: the clearance is more or less wide, depending on whether the closure zone is more or less wide, depending on the type of tube used, several methods of folding the ends of the tube that can be envisaged within the scope of the present invention. - the clearance extends over a depth of between 0.2mm and 2mm: the clearance is more or less deep depending on the configuration of the exchanger.

- the release is carried out without removing material, for example by deformation or by cutting and folding: from an ecological perspective as well as a perspective of process efficiency, it is important that there is no removal of material when making the clearance. Indeed, the absence of material removal makes it possible to avoid waste management on a production line, which represents a saving of time as well as a financial gain. In addition, in the prior art, the removal of material is a step which is generally carried out before the step of forming the fins, so that the material can be removed, which multiplies the steps and complicates the process, as will be explained later in the description.

- the heat exchanger comprises, for each internal fin, a braze between each ply apex and an internal wall of the tube against which it rests.

- the heat exchanger comprises, for each external fin, a braze between each ply apex and an external wall of the tube against which it rests.

- the clearance does not extend outside the top of the fold: the clearance is limited to the top of the fold, and therefore does not extend over the sections connecting the folds. The release is therefore very localized and is different from a discontinuous band which would extend from one fold vertex to the other.

The invention also relates to a method for manufacturing a heat exchanger as described previously, comprising at least one step of shaping the external fins via forming rollers simultaneously creating the folds and clearances, a step of shaping position of the tubes and the outer fins stacked alternately one above the other, and a step of brazing the closing zones of the tubes. The fact that the undercuts are without material removal makes it possible to carry out these undercuts in the same step as that of the creation of the folds. Thus, it is possible to simultaneously create the folds and clearances in a single and unique shaping step of the outer fins. The process is thus facilitated, there is no waste management of materials.

Brief description of figures

Other characteristics and advantages of the invention will appear during the reading of the detailed description which will follow for the understanding of which reference will be made to the appended drawings in which:

[Fig.1] Figure 1 is a perspective view of an embodiment of a heat exchanger according to the prior art;

[Fig.2] Figure 2 is a sectional view of part of the heat exchanger according to the invention;

[Fig .3] Figure 3 is an enlarged view of the closure area according to Figure 2;

[Fig .4] Figure 4 shows embodiments of tubes with internal fins;

[Fig.5] Figure 5 illustrates part of an outer fin according to a first embodiment of the invention;

[Fig.6] Figure 6 illustrates a portion of an outer fin according to a second embodiment of the invention;

[Fig .7] Figure 7 shows specific tools for performing the step of shaping the outer fin.

Detailed description of the invention

In the remainder of the description, elements having an identical structure or analogous functions will be designated by the same references.

Figure 1 illustrates a perspective view of an example of a heat exchanger according to the prior art.

The heat exchanger comprises a plurality of tubes 1 each extending mainly along a first longitudinal axis X and a 2 ^nd transverse axis Y perpendicular to the first axis X, thus defining a first plane D. The tubes 1 are stacked in series one above the other along a ^3rd vertical axis Z perpendicular to the first plane D. The heat exchanger comprises a front face AV, and a rear face AR located opposite the heat exchanger with respect to the front face. The front face and the rear face extend substantially in parallel planes and defined by the transverse axis Y and the vertical axis Z. The heat exchanger is arranged in a motor vehicle.

For example, if it is located at the front of the vehicle, the front front face faces the front of the vehicle and the rear rear face faces the rear of the vehicle. The orientation may be different if the exchanger is located, for example, in the dashboard of the vehicle.

All possible orientations of the exchanger fall within the scope of the present invention.

The heat exchanger is configured so that an air flow, generated by the movement of the motor vehicle in which the heat exchanger is installed, or even by a fan installed near the heat exchanger, circulates along the first longitudinal axis X through the heat exchanger from the front face to the rear face.

The heat exchanger comprises spaces inserted between the tubes 1 along the third axis Z, the spaces allowing the passage of the air flow between the tubes 1 in order to promote the exchange of calories between the fluid circulating inside the tubes 1 and the flow of air licking the walls of these tubes 1 . The heat exchanger is connected to a loop of a circuit by a first collector and a second collector respectively arranged at a transverse end of the bundle of tubes 1 arranged one above the other.

Each collector is fluidically connected to a collector chamber into which the transverse ends of the tubes 1 are introduced, so that each collector chamber is configured to distribute or collect fluid in the set of tubes 1 of the heat exchanger. In this way, the fluid can circulate in the plurality of tubes 1 of the heat exchanger.

Each tube 1 comprises a wall delimiting two ducts 3 separated by a partition situated in the center of the tube 1 (along the first longitudinal axis X) and extending through the tube 1 along the axis Y, the partition making it possible to increase the tube stiffness 1 .

The wall forms a tube 1 of substantially rectangular section with the short sides having a curved shape, curved towards the outside of the tube 1.

These tubes 1 have a shape thus flattened, with the long sides which are flat. The heat exchanger comprises a plurality of external fins 2 placed between the tubes 1 . In other words, between two adjacent tubes 1 there is an outer fin 2, resting against these two adjacent tubes 1. The external fins 2 make it possible to increase the exchange surface between the air flow and the heat exchanger, thus improving the heat dissipation capacity of the heat exchanger.

The heat exchanger according to the invention comprises all the elements mentioned and visible in FIG. It also comprises, as illustrated in Figures 2 and 3, a plurality of internal fins 7 arranged in the tubes 1, which bear against the inner surfaces 13 of the tubes 1. These internal fins 7 make it possible to increase the exchange surface between the fluid and the heat exchanger, thus improving the heat dissipation capacity of the heat exchanger.

These external 2 and internal 7 fins are accordion-shaped, and are thus bent and have fold tops 5, 8 which are brought into contact with the adjacent tubes 1.

In particular, the fold peaks 8 of the internal fin 7 are in contact with the internal wall 13 of the tube 1 in which it is inserted.

And the fold tops 5 of the outer fin 2 are in contact with the outer wall 12 of the tubes 1 between which it is inserted.

It is important that this pressure on the tubes 1 is effective so that there can be a transfer of calories.

As is clearly visible in Figure 2, it is necessary that all the tops of the folds 8 of the internal fin 7, whether it is a high fold or a low fold with respect to the direction of extension Z, is correctly in contact with the long sides of the tube 1 .

In the case of Figure 2, there is a single internal fin 7 per tube 1, which is distributed in the two channels 3. However, there could very well be several internal fins 7 per tube 1, for example an internal fin 7 in each channel 3.

The tubes 1 are generally made from a curved plate to form the short sides of the tube 1, and the side ends 9 of the plate then come into contact at a central closure zone 10. These ends 9, that is to say the side edges, are curved and form same time said partition which separates the two channels 3 within the same tube 1 .

There are many ways to fold the lateral ends 9 of the tube 1, as shown in Figure 4. There are also many ways to fold the internal fin 7, with rather wavy or rather crenellated shapes.

In the case of a corrugated shape, the contact between the internal fin 7 and the internal wall 13 of the tube 1 is rather linear, and in the case of a crenellated shape, the contact between the internal fin 7 and the wall interior 13 of tube 1 is rather surface.

The internal fin 7 can penetrate into the closure zone.

There can be two, three, or n channels, where n is an integer.

All the embodiments of the tube 1 and the internal fins 7 fall within the scope of the present invention, from the moment when there is a closure zone 10 between two ends 9 of the tube 1, and where the fold peaks 8 of the internal fin 7 are in contact with the tube 1.

In this case, at this closure zone 10, a brazing joint 14 is made so as to close the tube 1 in a sealed manner.

It is customary to press the external fins 2 against the tubes 1 so that they exert pressure on the tubes 1 to press the tubes 1 against the internal fins 7 as well as possible. the fold tops 5 of the outer fins 2 bear against the adjacent tubes 1.

However, for each tube 1, in this closure zone 10, the filler metal to make the brazing joint may tend to come into contact with the top of the fold 8 of the external fin 2 in support and thus come to spread the along the top of the fold 8 of the outer fin 2 by a capillarity effect instead of being placed between the two ends 9 of the tube 1 .

The invention thus provides for the production of a clearance 11 on the outer fin 2 facing the closure zone 10. Thus, this clearance 11 is centered with respect to the closure zone 10 and is located strictly at the level of this closure zone 10, so as not to weaken the outer fin 2.

This release 1 1 consists of a recess, so as to distance the outer fin 2 from the two ends 9 of the tube 1 which meet. Thus, the filler metal which arrives in the junction zone between the two ends 9 of the tube 1 can no longer come into contact with the external fin 2, and there is no no more risk of dispersion by capillarity effect. Thus, the quantity of filler metal can be managed in a homogeneous manner on each braze to be made, without it being necessary to bring excess product to successfully fill the junction zone in which there would be a lack of metal following the capillary effect.

This clearance 11 begins at the start of the radii of curvature of the ends 9 of the tube 1.

This clearance 11 can even begin a little before the start of the radii of curvature.

This release has a width at least equal to the width of the closure zone 10.

From a dimensional point of view, clearance 11 preferably extends over a width L of between 0.5 mm and 5 mm.

This clearance 11 extends over a depth H of between 0.2 mm and 2 mm.

As can be clearly seen in FIG. 2, this clearance 11 is made both at the level of the top of the bottom fold 5 and the top of the top fold 5 in the direction of extension Z. In practice, the clearance 11 is made on each fold top 5 of the outer fin 2. There is therefore a symmetry in the clearances 11 of the outer fin 2.

Thus, the outer fin 2 can be used just as well in one direction as in another. Its orientation does not matter, which makes it even easier to place it in the heat exchanger, especially when handling it during the manufacturing process of the heat exchanger.

According to the invention, clearance 11 is made without removing material.

As illustrated in Figure 5 for example, clearances 1 1 can be made by material deformation. We see in this figure that a boss is made so as to form recesses. On the left, the external fin 2 is folded in a V shape, and on the right the external fin 2 is folded in a U shape.

As illustrated in Figure 6 for example, clearances 1 1 can be made by cutting and folding. In this case, the material can be pushed back thanks to deformation lines between the cutting lines.

It is important to provide clearances 1 1 without removing material, so as not to have to manage waste during the manufacturing process of the external fins 2. On the left, the external fin 2 is folded in a V shape, and on the right, the external fin 2 is folded in a U shape.

In these two examples of Figures 5 and 6, it is clearly visible that its recesses 11 are located only at the level of the fold tops 5, and do not extend over the sections between the fold tops 5. It does not it is therefore not a question of long and interrupted cuts, but it is indeed a clearance 11 targeted in a precise zone, in this case centered with respect to the closure zone 10 of the tube 1 on which the fin is placed external 2.

Figure 7 shows an example of tooling making it possible to carry out the step of shaping the external fins 2.

This tool consists in particular of forming rolls 15, 16 between which passes the outer fin 2 in order to be folded. The advantage of these rollers is that they create the clearance 1 1 at the same time as they create the folds. In particular, the rollers 15, 16 correspond to toothed wheels of corresponding shapes.

When the fin passes between a tooth of roller 15 and a hollow area between two teeth of roller 16, this creates a fold. As the rollers rotate, a fold is created with each tooth pass, creating the concertina shape of the outer fin 2.

In the case shown in Figure 7, the folding shape of the outer fin is V-shaped. A U-shape could very well be envisaged. In addition, these forming rollers 15, 16 have at each tooth, and between each tooth, a die system 18 / punch 19 for forming clearance 1 1 by deformation for example.

Thus, it is possible in the same shaping step, to create both the folds and the clearances 1 1 of the outer fin 2.

After this shaping step, it is possible to carry out the step of positioning the tubes 1 and the external fins 2 stacked alternately one above the other. Next, there is a step of brazing the closing zones of the tubes 1 .

The configurations shown in the figures cited are only possible examples, in no way limiting, of the invention which, on the contrary, encompasses the variants of shapes and designs within the reach of those skilled in the art.

Claims

CLAIMS Heat exchanger for a motor vehicle, comprising a plurality of tubes (1) each defining a transverse duct (3) in which a fluid is able to circulate, the tubes (1) being arranged according to a stack with a vertical axis (Z) such that a space is provided between two successive tubes (1), the space allowing the passage of an air flow promoting heat exchange with the fluid, each tube

(1) being provided with an internal fin (7), and each space being provided with an external fin (2), these internal (7) and external (2) fins being folded and having fold apexes (8, 5) in contact with the adjacent tubes (1), each tube (1) having a closure zone (10) of the tube (1), characterized in that, for each external fin

(2), each fold top (5) has a clearance (1 1) centered on the closure zone (10) proximal to the tube (1) on which it rests. Heat exchanger according to the preceding claim, characterized in that the recess (1 1 ) has a width at least equal to the width of the closure zone (1 0). Heat exchanger according to the preceding claim, characterized in that the said closure zone (10) corresponds to a junction of two ends (9) of the tube (1), a brazing producing the said junction. Heat exchanger according to the preceding claim, characterized in that the ends (9) of the tube (1) are curved at the level of the closure zone (10) according to a radius of curvature, and in that, on both sides other of the junction, the clearance (1 1) begins at least at the start of the radius of curvature of the two ends (9) of the tube (1). Heat exchanger according to one of the preceding claims, characterized in that the recess (1 1 ) extends over a width L of between 0.5mm and 5mm.

6. Heat exchanger according to one of the preceding claims, characterized in that the clearance (1 1) extends over a depth H of between 0.2mm and 2mm.

7. Heat exchanger according to one of the preceding claims, characterized in that the release (1 1) is made without removing material, for example by deformation or by cutting and bending.

8. Heat exchanger according to one of the preceding claims, characterized in that it comprises, for each internal fin (7), a brazing between each fold apex (8) and an inner wall (13) of the tube (1 ) against which it leans.

9. Heat exchanger according to one of the preceding claims, characterized in that it comprises, for each outer fin (2), a braze between each fold apex (5) and an outer wall (14) of the tube (1 ) against which it leans.

10. A method of manufacturing a heat exchanger according to any one of the preceding claims, comprising at least one step of shaping the external fins (2) via forming rollers (15, 16) simultaneously creating the folds and clearances (1 1), a step of positioning the tubes (1) and the outer fins (2) stacked alternately one above the other, and a step of brazing the closure zones (10) of the tubes ( 1 ).