FR3121204A1 - Process for manufacturing a heat exchanger, heat exchanger obtained by such a process, floor element and floor comprising such a heat exchanger - Google Patents

Abstract

Method of manufacturing a heat exchanger (100) comprising: - a step of forming a main body (1) comprising at least one circuit for a heat transfer fluid, the circuit having two open ends, - a step of closing the at least one of the two ends, wherein the step of closing at least one of the two ends comprises a friction stir welding operation by transparency. Figure for abstract: Figure 1

Description

Process for manufacturing a heat exchanger, heat exchanger obtained by such a process, floor element and floor comprising such a heat exchanger

FIELD OF THE INVENTION

The present invention relates to the field of coolant heat exchangers, more particularly to improvements of such heat exchangers, their manufacturing process and their use.

More specifically, the invention relates to heat exchangers with increased performance thanks in particular to their manufacturing process and their design.

TECHNOLOGICAL BACKGROUND

In known manner, in a heat exchanger, a heat transfer fluid circulates in a circuit between two walls of the heat exchanger, the walls allowing the transfer of heat between the external environment and the heat transfer fluid, in one direction or in the 'other.

The thermal conductivity of the walls providing heat transfer is a key point in the performance of heat exchangers. This is why it is known to use aluminum or an aluminum-based alloy to manufacture the walls of the heat exchanger.

The heat exchanger is for example made by assembling two parts, for example by welding, the circuit being formed between the two parts. However, this embodiment requires ensuring a quality weld to guarantee sealing and good heat transfer, which can be tricky and costly.

Another widespread technique is then extrusion, making it possible to spin the walls of the heat exchanger and the channels of the circuit for the heat transfer fluid in one operation. The body thus obtained is open at both ends. These ends are then closed, so as to form the circuit.

Among the heat exchangers, a particular type is the cold plate, whose flattened shape, of low thickness allows it in particular to be mounted easily, for example on a device to be cooled such as an electronic component, batteries, or a circuit. oil in an engine.

Document US20190288353 describes an example of a cold plate type heat exchanger, obtained by extrusion and welding.

The document US10359239 describes a heat exchanger comprising an extruded body provided with passages for a heat transfer fluid. One end of the extruded body is then closed by a plug welded by friction stir.

Friction stir welding is a welding process by solid way, without addition of material, nor change in the liquid state of the materials, but by mixing the materials of two parts to be welded, carried out using a machine- tool carrying a welding head. The resulting weld has improved characteristics compared to so-called conventional welding techniques, particularly in terms of mechanical strength and sealing.

The principle of friction stir welding consists of penetrating a pin of the welding head by rotation and by exerting an axial pressure at the junction of the two parts. The pin is surmounted by a shoulder, which comes into abutment against the parts to be welded. The weld head is then forcibly moved along the weld joint. The rotation of the pin heats the materials, making them pasty, and ensures their mixing as the head moves.

The shoulder allows both to guide the flow of material that tends to flow outside the weld joint and to exert pressure on the weld joint to guarantee its properties.

For this purpose, it has been determined that the diameter of the shoulder must be at least equal to twice the largest diameter of the pin.

In the case of the manufacture of the heat exchanger, it follows that in order to be able to weld the cap to the end, as in US10359239, the shoulder must be able to rest completely on the end in question. For this purpose, the thickness of the walls of the extruded body must be sufficient, and therefore depends on the thickness of the stopper: the thickness of the walls must be at least equal to half the thickness of the stopper.

However, in order to improve the heat transfer efficiency, the walls must be as thin as possible.

• une étape de formation d’un corps principal comprenant au moins un circuit pour un fluide caloporteur, le circuit présentant deux extrémités ouvertes,
• une étape de fermeture d’au moins une des deux extrémités.

Thus, according to a first aspect, the invention relates to a method of manufacturing a heat exchanger comprising in particular:

• a step of forming a main body comprising at least one circuit for a heat transfer fluid, the circuit having two open ends,
• a step of closing at least one of the two ends.

• la traversée par le pion de soudage d’une première paroi jusqu’à ce que l’épaulement vienne en butée contre une surface extérieure de ladite première paroi, le pion ayant alors également pénétré au moins une deuxième paroi, au moins la première comprenant une paroi du corps principal ;
• le déplacement de la tête de soudage par guidage de l’épaulement sur la surface extérieure le long d’un chemin de soudure déterminé ;
• le retrait du pion (14).

The step of closing at least one of the two ends comprises a welding operation by friction mixing by transparency carried out using at least one welding head having a welding pin surmounted by a shoulder, the operation welding including:

• the crossing by the welding pin of a first wall until the shoulder comes into abutment against an outer surface of the said first wall, the pin having then also penetrated at least one second wall, at least the first comprising a main body wall;
• moving the weld head by guiding the shoulder on the outer surface along a determined weld path;
• the withdrawal of the pawn (14).

The Friction Stir Welding technique ensures a tight seal at the ends of the main body. By applying it transparently, the thickness of its walls can be considerably reduced, this reduction not being limited for example by the thickness of a cork. Performance in terms of thermal conductivity for the heat exchanger is improved.

The process may include any of the following features, considered alone or in combination.

Thus, according to one embodiment, the step of forming the main body may comprise an extrusion operation. The main body comprising channels forming the heat transfer fluid circuit can thus be formed at lower cost and simply, in large quantities, by extrusion and then cutting.

According to one embodiment, the second wall may also comprise a wall of the main body, different from the first wall. The closing step then further comprises a stamping operation in which the first wall and the second wall are brought against each other, away from the circuit of the heat transfer fluid, to close the at least one end. In addition, the welding operation includes the crossing by the welding pin of the first wall until the shoulder comes into abutment against an outer surface, the pin having then also penetrated the second wall. Thus, no cap is necessary, and only one line of welding makes it possible to close the end of the circuit. The welding process is then simplified, and the costs are reduced.

According to one embodiment, the step of closing at least one end may comprise the fitting of at least one plug closing the end. The second wall then comprises the plug, and the welding operation comprises the crossing by the welding pin of the first wall until the shoulder comes into abutment against an external surface of the first wall, the pin then having also penetrated the plug.

Whether with or without a cap, the end closed in this way is perfectly sealed and the mechanical strength of the weld is high. The thickness of the walls of the main body can be particularly thin, without constraint linked to the dimensions of the welding tool.

According to one embodiment, the welding operation may comprise the crossing by a welding pin of another wall of the main body, opposite to the first wall, until a shoulder surmounting the pin comes into abutment against an outer surface of the other wall of the main body, the pin having then also penetrated the plug.

Welding is then carried out in two passes, increasing the quality of the weld. The fact that the second pass can mix materials already mixed during the first pass is irrelevant.

According to one embodiment, the method may further comprise a step of assembling at least one end piece for the heat transfer fluid inlet and/or outlet produced by rotary friction welding. Rotating friction welding makes it easier to fit the end pieces on the thin walls of the heat exchanger body, limiting the risk of damaging and weakening the walls, while providing a high quality seal.

According to one embodiment, the heat transfer fluid circuit may comprise at least two channels extending between the two ends. The main body forming step can then include the machining of at least one junction chamber of the two channels. If necessary, this machining is carried out after the extrusion step, so as to allow a connection between the channels so that the heat transfer fluid circulates therein.

The circuit can in practice comprise a plurality of channels, and junction chambers can easily be machined in order to connect them in series and/or in parallel, the operation of friction stir welding by transparency being perfectly suitable for any configuration channels.

According to one embodiment, at least the main body is made of aluminum or an aluminum alloy. If desired, the cap can also be made of aluminum or aluminum alloy. Aluminum and its alloys are known for their thermal conductivity capabilities particularly suitable for heat exchangers, so the heat exchanger has high performance in terms of heat transfer. In addition, aluminum and its alloys are particularly suitable for an extrusion operation.

According to one embodiment, the heat exchanger is a cold plate. Indeed, the low thickness of the walls makes the heat exchanger particularly suitable for this application.

According to a second aspect, the invention proposes a heat exchanger obtained by the manufacturing process as presented above. The main body is then delimited by at least one wall with a thickness less than or equal to 5mm, or even less than or equal to 2mm.

According to one embodiment, the thickness of at least one wall of the main body is less than half the thickness of the cap.

The low thickness of the walls of the heat exchanger thus increases its technical performance, but the manufacturing costs are not, or very little, increased.

According to one embodiment, the heat exchanger may further comprise at least one insulation channel, forming a heat shield between two main exterior surfaces of the heat exchanger. This heat shield can be made with any fluid. Preferably, the heat shield is made by air, so as not to increase the costs. This screen makes it possible in particular to limit the exchange of heat between the heat transfer fluid of the heat transfer fluid circuit and the external environment on one side of the heat exchanger, for better performance on the other side.

According to one embodiment, the heat exchanger may comprise a coolant fluid inlet fitting and a coolant fluid outlet fitting on the circuit, at least one of the inlet and outlet fittings being assembled on the body by rotary friction.

According to one embodiment, the heat exchanger may comprise an upper wall and a lower wall, at a distance from each other along a first direction, the heat transfer fluid circuit comprising at least two channels extending along a second direction and at a distance from each other in a third direction, the first direction, the second direction and the third direction being mutually perpendicular.

According to a third aspect, the invention proposes a floor element. More specifically, the invention proposes using the heat exchanger to form a floor element for a battery pack. The element comprises a bottom and rims rising on one side from the bottom. The bottom may in particular comprise at least one heat exchanger as presented above.

According to one embodiment, the heat exchanger and the rims are one-piece, that is to say they do not result from an assembly operation. They are formed together, for example by extrusion. As no assembly operation is necessary, the seal is perfect.

According to one embodiment, the floor element may comprise two longitudinal edges extending opposite each other and two transverse edges extending opposite each other. The longitudinal flanges can be welded to the transverse flanges in order to avoid any leakage.

According to a fourth aspect, the invention proposes a floor for a battery pack. More precisely, the invention proposes to use the heat exchanger forming a floor element so as to form part of a floor for a battery pack. The battery pack then comprises at least two elements as presented above, assembled to one another along at least one of their edges. The battery pack floor thus formed makes it possible, with increased sealing and high thermal performance, to support batteries for example for a vehicle while cooling them.

According to one embodiment, at least one floor element comprises may comprise a heat exchanger comprising at least one insulation channel as presented above, the insulation channel being arranged on a side opposite that of the flanges , the latter being arranged on the side of the batteries. Thus, the external environment, for example under the vehicle, which may be at a high temperature, is isolated from the heat transfer fluid circuits formed in the bottom of the battery pack.

According to one embodiment, the floor may comprise two so-called end elements, the two end elements each being provided with a stretcher. The stretchers can in particular be formed during an extrusion step, and are then made in one piece with the rest of the end element concerned. There is then no need for an assembly step, facilitating manufacturing and reducing costs. The battery pack can thus be directly mounted on a vehicle for example.

Embodiments of the invention will be described below with reference to the drawings, briefly described below:

shows an exemplary schematic top view of a cold plate type heat exchanger.

shows a view in longitudinal section of a first example of a body obtained after in particular extrusion, cutting and machining of junction chambers to connect the channels in parallel, for the cold plate of the .

shows a view from one side of an open end of the body of the .

represents a step of closing by welding one end of the body of FIGS. 2 and 3 according to a first embodiment using a plug.

represents a step of closing one end of the body of the according to a variant of the first embodiment of the .

shows a view in longitudinal section of a second example of a body obtained after in particular extrusion, cutting and machining of junction chambers to connect the channels in series, for the cold plate of the .

represents a step of closing the extremities of the body of the according to the first embodiment, in which each end being closed using several caps.

is a view similar to the , for an alternative embodiment of the body of the , in which the channels are connected in series, and in which each end is closed with the aid of a single plug.

is a detail view of the according to circle IX.

represents the closing step for a body similar to that of the , according to a second embodiment.

is a view similar to that of the , for a variant of making the heat exchanger.

shows a longitudinal sectional view of the heat exchanger of the .

shows a three-dimensional view in raised perspective of an embodiment of a floor for a battery pack produced by assembling floor elements comprising a heat exchanger according to the invention.

depicts an elevated perspective three-dimensional view of a floor element of the .

shows a detail view, in perspective from above, of the floor element of the .

shows a detail view, in perspective from below, of the floor element of the .

shows a front view of the floor element of Figures 13 and 14.

shows a cross-sectional view along line XVIII-XVIII of the floor element of the .

In the drawings, identical references designate identical or similar objects.

Claims (20)

Method of manufacturing a heat exchanger (100) comprising:

• a step of forming a main body (1) comprising at least one circuit for a heat transfer fluid, the circuit having two open ends (6),
• a step of closing at least one of the two ends (6),

in which the step of closing at least one of the two ends (6) comprises a friction stir welding operation by transparency carried out using at least one welding head (13) having a pin (14) welding surmounted by a shoulder (15), the welding operation comprising:

• the crossing by the welding pin (14) of a first wall (9, 10, 22) until the shoulder comes into abutment against an outer surface (3, 23) of said first wall (9, 10 , 22), the pin (14) then also having penetrated at least one second wall (9, 10, 22, 12), at least the first wall (9, 10, 22) comprising a wall of the main body (1);
• moving the welding head (13) by guiding the shoulder (15) on the outer surface (3, 22) along a determined welding path;
• the withdrawal of the pawn (14).

Method according to claim 1, wherein the step of forming the main body (1) comprises an extrusion operation. Method according to Claim 1 or Claim 2, in which the second wall (9, 10, 22) also comprises a wall (9, 10, 22) of the main body (1), different from the first wall (9, 10, 22), and wherein the closing step further comprises a stamping operation in which the first wall (9,10,22) and the second wall (9,10,22) are brought together another, at a distance from the circuit of the heat transfer fluid, to close the at least one end (6), and in which the welding operation comprises the crossing by the welding pin (14) of the first wall (9, 10, 22 ) until the shoulder (15) comes into abutment against an outer surface (3, 23), the pin (14) then having also penetrated the second wall (9, 10, 22). Method according to any one of the preceding claims, further comprising a step of assembling at least one end piece for the inlet and/or the outlet of the heat transfer fluid produced by rotary friction welding. Method according to any one of the preceding claims, in which the heat transfer fluid circuit comprises at least two channels (7) extending between the two ends (6), and in which the step of forming the main body (1) includes the machining of at least one chamber (8) for joining the two channels. Method according to any one of the preceding claims, in which at least the main body (1) is made of aluminum or an aluminum alloy. A method according to any preceding claim, wherein the heat exchanger (100) is a cold plate. Method according to any one of the preceding claims, in which the step of closing at least one end (6) comprises placing at least one plug (12) closing the end (6), in which the second wall comprises the cap (12), and in which the welding operation comprises the crossing by the welding pin (14) of the first wall (9, 10, 22) until the shoulder (15 ) abuts against an outer surface (3, 23) of the first wall (9, 10, 22), the pin (14) then having also penetrated the stopper (12). Method according to claim 8, in which the welding operation comprises the crossing by a welding pin (14) of another wall (9, 10) of the main body, opposite to the first wall (9, 10), until a shoulder (15) surmounting the pin (14) comes into abutment against an outer surface (3) of the other wall (9, 10) of the main body, the pin (14) then having also penetrated the cork. Heat exchanger (100) obtained by the manufacturing method according to any one of the preceding claims, in which the main body (1) is delimited by at least one wall (9, 10, 11) of thickness less than or equal to 5mm. Heat exchanger (100) obtained by the manufacturing method according to claim 8 or claim 9, in which the thickness of at least one wall (9, 10, 11) of the main body (1) is less than half the thickness of the cap (12). Heat exchanger (100) according to claim 10 or claim 11, further comprising at least one insulation channel (20), forming a heat shield between two main outer surfaces (3) of the heat exchanger (100). Heat exchanger (100) according to any one of Claims 10 to 12, further comprising a coolant fluid inlet (4) and a coolant fluid outlet (5) on the circuit, at least the one of the inlet and outlet end pieces being assembled on the body by rotary friction. Heat exchanger (100) according to any one of Claims 10 to 13, comprising an upper wall (9) and a lower wall (10), at a distance from each other in a first direction, the fluid circuit coolant comprising at least two channels (7) extending in a second direction and at a distance from each other in a third direction, the first direction, the second direction and the third direction being mutually perpendicular. Floor element (201, 201') for a battery pack, the element (201, 201') comprising a bottom (202) and flanges (203, 204) rising on one side from the bottom (202) , the element (201, 201') being characterized in that the bottom (202) comprises at least one heat exchanger (100) according to any one of claims 10 to 14. Floor element (201, 201') according to the preceding claim, in which the heat exchanger (100) and the flanges (203, 204) are made in one piece. Floor element (201, 201') according to any one of claims 15 or 16, comprising two facing longitudinal flanges (203) and two facing transverse flanges (204), and in wherein the longitudinal flanges (203) are welded to the transverse flanges (204). Floor (200) for a battery pack comprising at least two floor elements (201, 201') according to any one of Claims 15 to 17, assembled together along at least one of their edges (203, 204 ). Floor (200) according to the preceding claim, in which at least one floor element (201, 201') comprises a heat exchanger (100) according to claim 12, the insulation channel (20) being arranged on one side opposite that of the flanges (203, 204). Floor (200) according to claim 18 or claim 19, comprising two so-called end elements (201'), the two end elements (201') each being provided with a stretcher (206).