FR3127038A1 - Motor vehicle heat exchanger and method of manufacturing such a heat exchanger - Google Patents

Abstract

The invention proposes a heat exchanger for a motor vehicle, comprising a plurality of tubes each defining a transverse duct in which a fluid is able to circulate, the tubes being arranged along a stack with a vertical axis (Z) such as a space is arranged 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 an external fin, these internal and external fins being bent and having fold apices in contact with the adjacent tubes, each tube having a tube closure zone. This exchanger is 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. Figure for abstract: Figure 2

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 moves forward, the external fins of the heat exchanger are exposed to a flow of air coming 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.

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 location where the brazing of the tube is going to be carried out, that is to say at the location where the filler metal arrives to join two lateral edges of the tube, called "ends". “Removal” means a withdrawal of the outer fin relative to the tube, that is to say a distance from a zone of the outer fin relative to the tube.

Thanks to this clearance, there is no longer any risk that the filler metal arriving at the level of the closure zone will come into contact with the external fin and therefore be sucked up by the external fin by capillarity. Thus, the amount of filler metal can be dosed in a reasonable way, there is no risk of having excess filler metal in the closure area. 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 supported against the internal walls of the tube, and this regardless of the geometry of the ends, in particular the height of the legs of the tube, to ensure the transfer of calories and 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 wider than 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 producing said junction.
• the ends of the tube are bent 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 clearance encompasses the entire closure area.
• the clearance extends over a width between 0.5mm and 5mm: the clearance is more or less wide, depending on whether the closure area 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 bending: from an ecological perspective as well as a perspective of process efficiency, it is important that there is no removal of material when performing 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 bears.
• the heat exchanger comprises, for each external fin, a braze between each ply apex and an external wall of the tube against which it bears.
• the clearance does not extend outside the fold vertex: the clearance is limited to the fold vertex, and therefore does not extend on the edges 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 step of shaping the external fins. The process is thus facilitated, there is no management of waste 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:

there is a perspective view of an embodiment of a heat exchanger according to the prior art;

there is a sectional view of part of the heat exchanger according to the invention;

there is an enlarged view of the closure area according to the ;

there shows examples of making tubes with internal fins;

there illustrates part of an outer fin according to a first embodiment of the invention;

there illustrates part of an outer fin according to a second embodiment of the invention;

there represents a specific tool making it possible to carry out the step of shaping the outer fin.

Claims (10)

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 of 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 bent and having pleat apices (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 apex (5) is provided with a clearance (11) centered on the proximal closure zone (10) of the tube (1) on which it rests. Heat exchanger according to the preceding claim, characterized in that the recess (11) has a width at least equal to the width of the closure zone (10). 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 (11) 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 (11) extends over a width L of between 0.5mm and 5mm. Heat exchanger according to one of the preceding claims, characterized in that the recess (11) extends over a depth H of between 0.2mm and 2mm. Heat exchanger according to one of the preceding claims, characterized in that the clearance (11) is produced without removing material, for example by deformation or by cutting and bending. 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 internal wall (13) of the tube (1) against which it supports. Heat exchanger according to one of the preceding claims, characterized in that it comprises, for each external fin (2), a brazing between each fold apex (5) and an external wall (14) of the tube (1) against which it supports. 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 the undercuts (11), 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).