Manufacturing process for a double-skinned plate incorporating circulation channels and the resulting plate
The described manufacturing process for double-skinned plates addresses energy consumption and thermal distortions by laser welding and flattening, ensuring precise alignment and reduced deformations for effective temperature regulation.
Patent Information
- Application Number
- FR2022014209
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2022-12-22
- Publication Date
- 2026-02-20
- Estimated Expiration
- 2042-12-22
AI Technical Summary
Existing manufacturing processes for double-skinned temperature control plates in battery cases, such as brazing and laser welding, suffer from energy consumption, mechanical property degradation, residual stresses, and thermal distortions, which affect the plate's geometry and temperature behavior.
A manufacturing process that includes laser welding of aluminum sheets, followed by a flattening step to eliminate thermal distortions, and a forming step using hydraulic pressure to create fluid circulation channels, ensuring precise alignment and reduced deformations.
The process maintains the mechanical properties of the aluminum sheets, reduces energy consumption, and minimizes thermal distortions, resulting in a flat and uniformly deformed plate with improved temperature regulation capabilities.
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Abstract
Description
Title of the invention: Method for manufacturing a double-skinned plate incorporating circulation channels and the resulting plate
[0001] The present invention relates to the field of temperature control equipment, in particular by direct contact, and especially in the form of a plate, with a preferred application in the context of battery boxes for electric or hybrid vehicles.
[0002] The present invention relates more specifically to an improved manufacturing process for such a plate, an installation for its implementation, the plate obtained and a housing containing it.
[0003] Batteries currently used in electric and hybrid vehicles require temperature regulation, particularly during charging and discharging. This is especially true for Li-ion batteries, whose operating temperature must be maintained between 10°C and 30°C.
[0004] To achieve this temperature regulation, the most common solution is the use of a regulating or cooling plate in contact with the battery cells, and generally located at the bottom of the battery casing. This plate, with a double-skinned aluminum structure, has passages in the form of channels, arranged in a network, allowing the circulation of a heat transfer fluid, for example, water with added glycol.
[0005] Three different manufacturing technologies are currently used to produce these plates, namely, i) brazing of two preformed aluminum sheets, ii) laminating of two aluminum sheets having an interlayer of ink whose pattern corresponds to the flow channels and which allows local separation of the sheets during a subsequent hydroforming operation and iii) direct extrusion of the plate with the flow channels (so-called "micro-port extrusion" technique, limited applications and complex and delicate implementation).
[0006] Implementing a brazing or rolling assembly process has the disadvantage of generating significant heat, which can reduce the mechanical properties of the aluminum, consuming a lot of energy, and requiring a filler metal or a coating with a specific alloy for the sheets to be joined (for brazing). Furthermore, the precise assembly of preformed sheets is difficult to achieve, and the residual stresses and strains induced by the preforming process in these sheets negatively impact the final double-skin plate, particularly in terms of contact between the plates during the brazing process. In addition, this process requires complex clamping tooling to ensure sufficient quality of the seal.
[0007] A method for manufacturing a double-skinned plate incorporating channels constituting at least one fluid circulation network or circuit (F) is known from document DE 102017005325. This plate constitutes a temperature control plate for a battery case.
[0008] The process as disclosed in this DE document essentially comprises a first step of supplying two flat sheets of aluminum, or of an aluminum-based alloy, followed by a second step of mutually joining said two sheets into a double-skinned plate by laser welding, according to a linear pattern defining the flow channel pattern, and finally, a third step of forming said flow channels by injecting a pressurized fluid between the two sheets so as to deform areas of one of the sheets, these deformed areas corresponding to said channels and extending between the weld lines of the linear pattern. This last operation is carried out in a forming mold in order to control the final shape of the channels obtained and limit unwanted deformations.
[0009] By implementing a pre-assembly of the aluminium sheets by laser welding, the process known in this DE document makes it possible to overcome the main limitations of the aforementioned manufacturing technologies, laser welding not significantly altering the mechanical properties of the sheets, consuming less energy and not requiring filler material.
[0010] Nevertheless, even if the stresses and strains are significantly reduced by this process, it remains that laser welding still causes certain distortions due to the phenomena of thermal expansion and asymmetric heating of the two sheets (one directly exposed to the laser beam, the other not), which are found in the final plate and affect its geometry and its temperature behavior.
[0011] The main purpose of the present invention is to overcome these remaining drawbacks.
[0012] To this end, it relates to a process such as that mentioned above, characterized in that it also includes a flattening or planing step of the plate made up of the two sheets joined by laser welding, before the forming step, by deformation under pressure, of the flow channels.
[0013] The invention will be better understood from the following description, which relates to preferred embodiments, given by way of non-limiting examples, and explained with reference to the accompanying schematic drawings, in which:
[0014] [Fig.1] is a schematic representation of the three stages of the manufacturing process according to the prior art corresponding to the aforementioned DE document;
[0015] [Fig.2A],
[0016] [Fig.2B] and
[0017] [Fig.2C] represent respectively a top view of a laser welding station in the form of a gantry with two movable laser heads in a plane in accordance with an embodiment of the invention (2A), a partial lateral elevation view at the level of a movable laser head of the station of [Fig.2A] (the latter being equipped with a first variant of movable local clamping means) (2B), and a detailed and partially cross-sectional view illustrating the formation of a weld line with the movable laser head of [Fig.2B] (2C);
[0018] [Fig.3] represents a cross-sectional view similar to that of [Fig.2B], but illustrating the implementation of another variant of clamping means usable in relation to the station of [Fig.2A];
[0019] [Fig.4] schematically illustrates an intermediate planing station in accordance with the invention, treating the plate blank before its forming;
[0020] [Fig. 5A] is a partial, cross-sectional view of a forming mold enclosing a plate during its forming operation, by injection of liquid or gas under pressure, and,
[0021] [Fig.5B] is a detail view of part of the plate of [Fig.5A], illustrating the pressure forces present during the forming operation.
[0022] The invention therefore relates to a method of manufacturing a double-skinned plate (1) incorporating channels (2) constituting at least one fluid circulation network or circuit (F), in particular a temperature control plate for a battery case.
[0023] This process essentially comprises a first step of supplying two flat sheets or plates (3 and 3') of aluminum, or of an aluminum-based alloy, then a step of mutually assembling by laser welding, according to a linear pattern (4) drawing the pattern of the circulation channels (2), of said two sheets (3 and 3') into a double-skinned plate (1), and, finally, a step of forming said circulation channels (2), by injecting a liquid or gaseous fluid under pressure (LP) between the two sheets (3 and 3') so as to deform areas (4') of at least one of the sheets (3, 3'), which correspond to said channels (2) and extend between the weld lines (4”) of the linear pattern (4).
[0024] According to the invention, this process also includes a flattening or planing step of the plate (1) made up of the two sheets (3 and 3') assembled by laser welding, before the forming step (by deformation under pressure) of the circulation channels (2).
[0025] Thanks to the invention, the deformations and stresses induced in the plate (1) by thermal expansion during the laser welding operation, in particular due to the differentiated expansion of the two plates (only one being directly impacted by the laser), are eliminated and said plate regains a flatness similar to the original flatness of the two sheets or plates constituting it.
[0026] In accordance with an advantageous embodiment of the invention, and as shown in [Fig. 4], the flattening or planing step of the plate (1) formed by the two sheets (3 and 3') joined by welding is carried out by planing (for example, using a planer, of the servo-hydraulic or electromechanical type, with two sets or arrays of rollers, upper and lower, as shown in [Fig. 4]). This operation thus makes it possible to eliminate creases, irregularities, flatness defects, and stresses in the double-skinned plate (1), and therefore in and between the two sheets (3 and 3') constituting it.
[0027] Preferably, and in order to guarantee a priori the elimination of any deformation and any flatness defect, the flattening or planing step of a plate (1) comprises at least two successive passes along different directions (D) of passage or movement (for the plate in the planing station). Preferably, this planing step comprises two passes with different directions of passage. Advantageously, the directions (D) of passage or movement of the different passes (two or more) are oriented between 30° and 90° with respect to each other.
[0028] The welding of the two aluminum sheets or plates (3 and 3'), advantageously made of 3xxx or 5xxx series aluminum (easier to weld without the appearance of hot cracks), is carried out, for example, using a fiber laser with a remote welding technique employing a galvanometric scanner to achieve a high welding speed. Alternatively, a laser head mounted on a robotic arm can be used.
[0029] The energy density and focusing of the laser beam, as well as the other parameters of the welding process, are adjusted so that the weld line width at the interface between the two sheets is between 0.7 and 1.0 mm. Since the weld lines can be several tens of meters long (coiled channels with two lines per channel), it is necessary to be able to weld at high speed and high power for industrial and economic reasons. Typically, minimum power levels on the order of 1 kW and speeds on the order of 6 m / min, preferably 10 to 20 m / min, are required.
[0030] In accordance with a first embodiment of the invention, and as shown in [Fig. 2B], it can be provided that during the laser welding step the two sheets (3 and 3') are held pressed against each other locally on either side of the moving laser welding point(s) (5), for example by means of a pair of support or clamping means (6) moved in synchronism with the associated welding beam (7). As shown, the two means move in concert with the laser beam and on either side of it, leaving between them a passage window for the scanning and welding beams, for example from the order of 60 to 100mm.
[0031] In accordance with a second embodiment of the invention, and as shown in [Fig. 3], it can be provided that during the laser welding step the two sheets (3 and 3') are held pressed against each other substantially on all their respective facing surfaces, for example by vacuum clamping. This second method does not require any moving parts with synchronized movement.
[0032] Finally, in accordance with a third embodiment, not specifically represented but combining the solutions of the first two embodiments above, it may be provided that during the course of the laser welding step the two sheets (3 and 3') are kept pressed or clamped against each other, on the one hand, globally and substantially on all their respective mutually facing surfaces, and, on the other hand, locally on either side of the or each point (5) of mobile laser welding.
[0033] It can be noted that each of these clamping methods allows thermal expansion of the sheets during welding, which makes it possible to significantly reduce the formation of gaps resulting from the differentiated thermal expansion caused by the application of energy in a significant and asymmetrical way, and leading to weld defects.
[0034] In relation to each of the three aforementioned embodiments, the welding assembly is carried out progressively from a central interior region of the plate (1) towards the peripheral areas of the latter, by means of a single or at least two laser beam(s) (7) moved in a controlled manner.
[0035] Taking into account the applied energy density and to limit the expansion phenomena, it may also be provided that, during the course of the laser welding step of the two sheets (3 and 3'), at least one of them is subjected to a cooling action, for example by resting on a cooled welding table (10).
[0036] In accordance with another aspect of the invention, and as illustrated by [Fig.5A] by way of example, the step of forming the circulation channels (2), under hydraulic pressure, is carried out by placing the flat plate (1) in a mold (8, 8') allowing deformation under internal pressure of the zones (4') of one (3) of the sheets (3, 3'), zones (4') which correspond to said channels (2) and which extend between the weld lines (4”) of the linear pattern (4), with respect to the other (3') of said sheets (3,3').
[0037] As shown more precisely in [Fig. 5B], it is advantageously provided that, during the course of the channel forming step (2) by injection of a liquid or gaseous fluid under pressure (LP) between the two sheets (3 and 3'), a pressure (PC) is exerted on the sheet (3) containing the areas to be deformed (4'), so as to keep it in close contact with the other sheet (3') at the level of all surface regions of this sheet (3') other than the areas to be deformed (4'), in particular at the level of the strip surface areas extending on either side of the weld lines (4”).
[0038] Hydroforming pressures suitable for the present process are between 6 and 30 MPa, depending on the thickness of the aluminium sheets, the grade and the minimum bending radii to be produced.
[0039] Applying pressure (PC) outside the areas (4') to be deformed limits the stretching of the sheet material in these areas and also helps prevent any warping of the final plate. This pressure must, however, not exceed the elastic limit of the aluminum.
[0040] The regions of the mold part (8) which bear in particular in the surface areas in strips extending on either side of the weld lines, may where appropriate be textured on the surface to increase grip in the contact interfaces.
[0041] The invention also relates to an installation for implementing the process of manufacturing a double-skinned plate (1) incorporating fluid circulation channels (2) (F), as described above.
[0042] Such an installation comprises at least: a welding station (9) with at least one, preferably at least two, laser beam(s) (7) moved in a controlled manner and with one or more means (6) for mutually clamping the two plates (3 and 3'), globally and / or locally, as well as advantageously a cooled welding table (10), a flattening or planing station, advantageously a planing station (11) with at least one roller planer and a forming mold device (8, 8') associated with a device for injecting liquid or gas under pressure (LP). To reduce welding time, the station (9) may include two movable laser heads, mounted on a gantry and guided by a scanner.
[0043] The invention also relates to a double-skinned plate (1), in particular a temperature regulation plate for a battery case, formed by welding two aluminum sheets (3, 3') together and incorporating channels (2) constituting at least one fluid circulation network or circuit (F), of the heat transfer fluid type, said plate (1) being obtained by means of the aforementioned manufacturing process, preferably using the installation mentioned above.
[0044] Finally, the invention further relates to a battery case, particularly for a motor vehicle, comprising a cover and a base, and optionally an intermediate partition wall, in contact with the cells of this battery, a case characterized in that at least one element among said cover, said base and, in the case If applicable, said wall is formed by a double-skinned plate (1) with integrated circulation channels as described above. A plate (1) according to the invention, optionally covered on its outer face with an overmolded layer of plastic material, can thus constitute by itself the lid and / or the bottom of such a housing.
[0045] Of course, the invention is not limited to the embodiments described and shown in the accompanying drawings. Modifications remain possible, particularly with regard to the composition of the various elements or by substitution of technical equivalents, without departing from the scope of protection of the invention.
Claims
Demands
1. A method for manufacturing a double-skinned plate (1) incorporating channels (2) constituting at least one fluid circulation network or circuit (F), in particular a temperature control plate for a battery case, this method essentially comprising a first step of supplying two flat sheets or plates (3 and 3') of aluminum, or of an aluminum-based alloy, then a step of mutually joining by laser welding, according to a linear pattern (4) drawing the pattern of the circulation channels (2), said two sheets (3 and 3') into a double-skinned plate (1), and, finally, a step of forming said circulation channels (2), by injecting a liquid or gaseous fluid under pressure (LP) between the two sheets (3 and 3') so as to deform areas (4') of at least one of the sheets (3, 3'), which correspond to said channels (2) and extend between the weld lines (4”) of the linear pattern (4),a method characterized in that it also includes a flattening or planing step of the plate (1) made up of the two sheets (3 and 3') joined by laser welding, before the forming step, by deformation under pressure, of the flow channels (2) and in that the flattening or planing step of the plate (1) made up of the two sheets (3 and 3') joined by welding, is carried out by planing in a corresponding station (11) and includes at least two passes along different directions (D) of passage or scrolling.
2. A method according to claim 1, characterized in that the flattening or planing step of the plate (1) comprises two passes, with directions (D) of passage or scrolling oriented between 30° and 90° relative to each other.
3. A method according to any one of claims 1 and 2, characterized in that during the laser welding step the two sheets (3 and 3') are held pressed against each other locally on either side of the movable laser welding point(s) (5), for example by means of a pair of support or clamping means (6) moved synchronously with the associated welding beam (7), and in that the weld assembly is carried out progressively from a central inner region of the plate (1) towards the peripheral areas thereof, by means of a single or of at least two laser beam(s) (7) moved in a controlled manner.
4. A method according to any one of claims 1 and 2, characterized in that during the laser welding step the two sheets (3 and 3') are held pressed against each other substantially on all their respective mutually facing surfaces, for example by vacuum suction clamping, and in that the welding assembly is carried out progressively from a central interior region of the plate (1) towards the peripheral areas of the latter, by means of a single or at least two laser beam(s) (7) moved in a controlled manner.
5. A method according to claims 3 and 4, characterized in that during the course of the laser welding step the two sheets (3 and 3') are held pressed or clamped against each other, on the one hand, globally and substantially over all their respective mutually facing surfaces, and, on the other hand, locally on either side of the or each point (5) of moving laser welding.
6. A method according to any one of claims 1 to 5, characterized in that the step of forming the circulation channels (2), under hydraulic pressure, is carried out by placing the flat plate (1) in a mold (8, 8') allowing deformation under internal pressure of the zones (4') of one (3) of the sheets (3, 3'), zones (4') which correspond to said channels (2) and which extend between the weld lines (4”) of the linear pattern (4), relative to the other (3') of said sheets (3,3').
7. A method according to any one of claims 1 to 6, characterized in that, during the laser welding step of the two sheets (3 and 3'), at least one of them is subjected to a cooling action, for example by resting on a cooled welding table (10).
8. A method according to any one of claims 1 to 7, characterized in that, during the course of the channel forming step (2) by injection of a liquid or gaseous fluid under pressure (LP) between the two sheets (3 and 3'), a pressure (PC) is exerted on the sheet (3) having the areas to be deformed (4'), so as to keep it in intimate contact with the other sheet (3') at the level of all surface regions of this sheet (3') other than the areas to be deformed (4'), in particular at the level of the strip surface areas extending on either side of the weld lines (4”).
9. Installation for implementing the manufacturing process of a double-skinned plate (1) incorporating fluid circulation channels (2) (F), according to any one of claims 1 to 8, said installation comprising at least: a welding station (9) with at least one, preferably at least two, laser beam(s) (7) moved in a controlled manner and with one or more means (6) for mutually clamping the two plates (3 and 3'), globally and / or locally, and advantageously a cooled welding table (10), a planing station or flattening station of the planing station type (11) with at least one roller planer enabling at least two planing or flattening passes to be made in different directions (D) of passage or scrolling, and a forming mold device (8, 8') associated with a device for injecting liquid or gas under pressure (LP).
10. Double-skinned temperature-regulating plate (1) for battery housing, formed by welding two aluminum sheets (3, 3') together and incorporating channels (2) constituting at least one fluid circulation network or circuit (F), of the heat transfer fluid type, said plate (1) being obtained by means of the manufacturing process according to any one of claims 1 to 8, preferably using the installation according to claim 9.
11. Battery case, in particular for motor vehicle, comprising a cover and a base, and optionally an intermediate separating wall, in contact with cells of this battery, case characterized in that at least one element among said cover, said base and, where applicable, said wall, is formed by a double-skinned plate (1) with integrated circulation channels, according to claim 10.