Welding method for vehicle body

Abstract

The invention relates to a welding method for a vehicle body comprising a welding device. The method comprises the following steps: applying an adhesive element (25) to a first part (22) or to a second part (23); bringing the first part (22) into contact with the second part (23); wherein the first part (22) comprises a cavity; fitting a pin (24) into the cavity, thereby defining an assembly to be welded; placing a first electrode on a portion of the pin (24) and placing a second electrode of the welding device on the assembly; the first electrode and the second electrode being arranged on either side of the assembly to be welded; welding the assembly using the first electrode and the second electrode; and the following substeps: generating a first pulse for a first duration; generating a second pulse, after a rest period, for a second duration.

Description

[0001] Description

[0002] Title of the invention: Welding method for vehicle bodywork

[0003] Technical field of the invention

[0004] The present invention claims priority from French application 2408771 filed on August 8, 2024, the content of which (text, drawings, and claims) is incorporated herein by reference. The present invention relates to a welding method for vehicle bodies. It is applicable in the field of automotive bodywork.

[0005] Previous technique

[0006] Welding is an assembly process that involves melting base materials and adding a filler metal, which forms a permanent bond after cooling and solidification.

[0007] An example of a prior art realization of such a device is shown in Figure 1.

[0008] Figure 1 represents a graph defining a single-pulse welding process.

[0009] In this diagram, an adhesive or bead of glue is applied to the interface of the two metal sheets, including under the pin. Welding cannot be performed correctly because the glue film explodes under the effect of the high-intensity electric current. Indeed, during the welding process, a high-intensity electric current is used to heat and fuse the materials. The adhesive or glue bead, being a non-conductive material, can cause problems when subjected to the intense heat generated by the current.

[0010] Under the influence of the high intensity of the electric current, the adhesive can rapidly reach high temperatures. This rapid heating can cause vaporization or explosive decomposition of the glue, creating gas pockets or bubbles that can disrupt the welding process.

[0011] Presentation of the invention

[0012] The present invention aims to overcome these drawbacks with a completely innovative approach. More specifically, the invention aims to provide a welding process for vehicle bodies.

[0013] One objective of the invention is to provide such a process, which can be easily adapted to existing processes.

[0014] These objectives, as well as others that will appear subsequently, are achieved using a vehicle body welding process comprising a welding apparatus, remarkable in that the process comprises the following successive steps:

[0015] -a) apply an adhesive element to a first piece or to a second piece;

[0016] -b) to connect said first room with said second room; said first room includes a dwelling;

[0017] -c) install a pin in said housing defining a welded assembly; said welded assembly comprises a longitudinal plane;

[0018] -d) placement of a first electrode on a part of said pin and a second electrode on said welding apparatus; said first electrode and said second electrode being arranged on either side of said assembly to be welded along said longitudinal plane;

[0019] -e) weld between the first piece, the second piece and the pin with said first electrode and said second electrode; this step comprises the following sub-steps:

[0020] -1) generate a first pulse for a first duration with the welding device;

[0021] -2) generate a second pulse after a rest period; said second pulse for a second duration with the welding device.

[0022] Thanks to these provisions, this process allows the parts to be welded to assemble multi-material assemblies by adding glue between the two materials without the glue catching fire and exploding; as requested by the design departments to stiffen the structure or to seal it.

[0023] The adhesive element holds the parts in place before welding, reducing the risk of part displacement. The housing in the second part helps align the parts correctly, improving assembly accuracy. Proper alignment minimizes positioning errors and ensures better structural cohesion.

[0024] The first pulse acts as a pre-weld, ensuring the materials begin to melt without overheating. This first pulse prepares the contact surfaces for better adhesion during the second pulse.

[0025] The second pulse, after a rest period, completes the weld by solidifying the assembly.

[0026] The invention is advantageously implemented according to the embodiments and variants set out below, which are to be considered individually or according to any technically feasible combination.

[0027] In one embodiment, the pawn from step b) has a "T" shape.

[0028] In one embodiment, during the substep of generating the first pulse, the first duration is between 20 ms and 300 ms.

[0029] In one embodiment, during the substep of generating the second pulse, the second duration is between 100 ms and 800 ms.

[0030] In one embodiment, during substeps 1) and 2), the first pulse and the second pulse are current pulses.

[0031] In one embodiment, the first pulse is a current pulse between 1 kA and 7 kA.

[0032] In one embodiment, the second pulse carries a current between 4 kA and 15 kA.

[0033] In one embodiment, the process includes a welding force during step c); this force is between 50 daN and 500 daN.

[0034] In one embodiment, the sticky element from step b) is glue and / or adhesive.

[0035] In one embodiment, the first electrode is mobile and the second electrode is stationary.

[0036] Brief description of the figures

[0037] Other advantages, purposes and features of the present invention will become apparent from the following description, given for explanatory purposes and not in any way limiting, with regard to the accompanying drawings, in which: Figure 1 represents (relative to the prior art) a graphic defining a single-pulse welding process;

[0038] Figure 2 represents the welding process for vehicle bodywork.

[0039] Figure 3 represents a graph showing the welding resulting from the process.

[0040] Description of the implementation methods

[0041] Figure 1 shows a graph defining a single-pulse welding process. This figure has been described above.

[0042] Naturally, the invention described above is by way of example. It is understood that a person skilled in the art is capable of carrying out different embodiments of the invention without departing from its scope.

[0043] Figure 2 shows the welding process for vehicle bodywork.

[0044] The process comprises a first piece 22 and a second piece 23 and a pawn 24 in the shape of a "T".

[0045] The first part 22 is an aluminum sheet and the second part 23 is a steel sheet.

[0046] According to one embodiment, the first part 22 or the second part 23 includes a sticky element 25.

[0047] This sticky element 25 is adhesive or glue.

[0048] This adhesive element 22 helps to prevent the spread of corrosion on the sheets.

[0049] The first piece 22 and the second piece 23 are assembled together.

[0050] The second room 23 or the first room 22 contains a dwelling.

[0051] This housing allows the pin 24 to be assembled with the second part 23 and the first part 22, defining a welded assembly. According to one variant shown, only the first part 22 has a housing.

[0052] The process involves a welding apparatus comprising a first electrode and a second electrode.

[0053] The first electrode is mobile and the second electrode is stationary. The assembly to be welded has a longitudinal plane.

[0054] The first electrode and the second electrode being arranged on either side of said assembly to be welded along the longitudinal plane.

[0055] According to one embodiment, the first electrode and the second electrode are on a part of pin 24. According to one embodiment, the first part is made of aluminum or composite, and the second part is made of steel.

[0056] Figure 3 shows a graph representing the welding resulting from the process.

[0057] The graph shows two curves A and B, two ordinate axes x and z, and one abscissa axis y.

[0058] The letter x indicates the current emitted by the welding in kA or kiloamperes.

[0059] The ampere is the base unit of electric current intensity in the International System of Units.

[0060] The letter there indicates the welding time in ms, or milliseconds.

[0061] The second is the base unit of time in the International System of Units.

[0062] The letter z indicates the force represented by the welding device during the process in daN or decanewton.

[0063] Curve A represents the current generated by the welding process. This curve A is supported by the ordinate axis represented by the letter x. According to an example carried out, during welding, curve A has a first pulse 20 and a second pulse 21.

[0064] The first pulse 20 is represented on the graph by a square located in a first duration between 64 ms and 128 ms; preferably between 80 ms and 110 ms.

[0065] This first pulse 20 allows the glue to be burned locally just under the pawn and thus modify its structure locally.

[0066] During the first pulse 20, the current is between 0.1 kA and 3 kA.

[0067] The second pulse 21 is represented on the graph by a rectangle located in a second duration between 192 ms and 512 ms; preferably between 200 ms and 470 ms.

[0068] This second pulse 21 allows the entire welding process to be carried out.

[0069] During the second pulse 21, the current is between 0.1 kA and 10 kA.

[0070] According to an example carried out, the process includes a rest period between the first duration and the second duration.

[0071] This rest period is between 50 ms and 300 ms, preferably between 100 and 200 ms.

[0072] Curve B represents the welding force applied to the first piece, the second piece, and the pin during welding. This welding force is supported by the ordinate axis represented by the letter z.

[0073] The curve is increasing between 0 ms and 64 ms, then straight between 64 ms and 704 ms. This increasing curve indicates the start of welding with the welding machine.

[0074] During the first pulse 20 and the second pulse 21, the welding force has a force between 400 daN and 320 daN.

[0075] It is emphasized that all features, as they are apparent to a person skilled in the art from this description, drawings and attached features, even if in practice they have only been described in relation to other specific features, both individually and in any combinations, may be combined with other features or groups of features disclosed herein, provided that this has not been expressly excluded or that technical circumstances render such combinations impossible or meaningless.

[0076] LIST OF REFERENCE SIGNS

[0077]

[0001] [Table 1]

Claims

Demands Claim 1. A welding process for vehicle bodies comprising a welding apparatus, characterized in that the process comprises the following successive steps: -a) apply a sticky element (25) to a first piece (22) or to a second piece (23); -b) bring said first part (22) into contact with said second part (23); the said first room (22) includes a dwelling; -c) install a pin (24) in said housing defining a weld assembly; said weld assembly comprises a longitudinal plane; -d) placement of a first electrode on a part of said pin (24) and a second electrode on said welding apparatus; said first electrode and said second electrode being arranged on either side of said assembly to be welded along said longitudinal plane; -e) weld between the first piece (22), the second piece (23) and the pin (24) with said first electrode and said second electrode; this step comprises the following substeps: -1) generate a first pulse (20) for a first duration with the welding device; -2) generate a second pulse (21) after a rest period; said second pulse (21) for a second duration with the welding device. Claim 2. A method according to claim 1, wherein the pin (24) from step b) has a "T" shape. Claim 3. A method according to any one of claims 1 to 2, wherein during the substep of generating the first pulse (20), the first duration is between 20 ms and 300 ms. Claim 4. A method according to any one of claims 1 to 3, wherein during the substep of generating the second pulse (21), the second duration is between 100 ms and 800 ms. Claim 5. A method according to any one of claims 1 to 4, wherein in substeps 1) and 2), the first pulse (20) and the second pulse (21) are current pulses. Claim 6. A method according to any one of claims 1 to 5, wherein the first pulse (20) is a current pulse of between 1 kA and 7 kA. Claim 7. A method according to any one of claims 1 to 6, wherein the second pulse (21) has a current between 4 kA and 15 kA. Claim 8. A method according to any one of claims 1 to 7, wherein the method includes a welding force during step c); this force is between 50 daN and 500 daN. Claim 9. A method according to any one of claims 1 to 8, wherein the sticky element (25) from step b) is glue and / or adhesive. Claim 10. A method according to any one of claims 1 to 9, wherein the first electrode is mobile and the second electrode is immobile.

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