A method of assembling two parts, one of which is metallic.

Abstract

A method for assembling a first part (1) to a second part (2), the second part (1, 2) being made of sheet metal, comprising a step of applying a bead of adhesive to one of the parts (1, 2), a step of assembling the first part (1) onto the second part (2), such that the bead of adhesive (3) is in contact with both parts (1, 2), notable in that it includes a step of partially polymerizing only a limited portion (30) of the bead of adhesive (3), such that the bead of adhesive (3) outside of said segment(s) (30) remains unpolymerized. Figure for the abstract: Figure 2

Description

Title of the invention: Method for assembling two parts, one of which is metallic.

[0001] The invention relates to a method for assembling two parts together, as well as a set of parts assembled by such a method.

[0002] It is known to fix two metal sheets together using a bead of glue. In order to hold two sheets together during the polymerization time of the bead of glue, it is known to hold said sheets together using spot welds. For example, document FR3025847 describes a method for assembling two sheet metal elements comprising the depositing of a bead of glue on one element, the assembly of the second sheet metal element on the first and the fixing by making resistance welding points to keep the two sheet metal elements immobile before proceeding with the polymerization of the glue.The bead of glue is deposited discontinuously along a gluing line on the first sheet metal element, then once the second sheet metal element is applied against the first, the two elements are held fixed relative to each other by making welding points at the sections without glue of the discontinuous gluing line. Then, the glue is polymerized during a heating step, for example during a so-called cataphoresis treatment.

[0003] The disadvantage of such a solution is that the two parts must be made of metallic material in order to be able to make the welding points. In addition, the process is complex because it requires creating a discontinuous gluing line, i.e. comprising areas without glue in a precise position, and making the welding points on these areas without glue, therefore also at precise positions. Another disadvantage is that if the welding point is made on an area containing glue, the quality of the weld will be degraded, achieving less good support, and the glue risks being burned and emitting gases or dust harmful to the environment.

[0004] The objective of the invention is to overcome these drawbacks. In particular, one of the aims of the invention is to propose a method for holding two parts together, at least one of which is made of metallic material. Another objective is to simplify the method for fixing two parts intended to be fixed by a bead of glue.

[0005] This aim is achieved according to the invention, thanks to a method of assembling a first part to a second part, the second part being made of sheet metal, the method comprising a step of depositing a bead of glue on one of the parts, a step of assembling the first part on the second part, so that the bead of glue is in contact with the two parts, remarkable in that the method comprises a step of partial polymerization of only one or more limited parts of the bead of glue, so that the bead of glue outside said part or parts is not polymerized during the partial polymerization step.

[0006] Thus, advantageously, it is not necessary to deposit the bead of glue discontinuously to leave spaces in which welding points are made, nor to use a complex process to ensure precise positioning of the welding points relative to these spaces by eliminating the welding step. Indeed, the polymerization of only a part of the bead of glue makes it possible to quickly create sufficient support to keep the glued parts immobile relative to each other during the phase of assembling the elements before the entire bead of glue is hardened by polymerization, in other words by crosslinking, for example during heating in a paint shop at the time of the so-called cataphoresis process.Another advantage of the method is that a fixing between the two parts can be achieved even if one of the two parts is made of a non-metallic material, unlike the prior art which requires two metal parts to perform a spot welding, and this without adding additional fixing elements, for example rivet type. The fact of not creating a welding spot also eliminates any risk of burning the glue bead and therefore eliminates the risks of emission of burnt dust and gases from the glue bead during welding.

[0007] In a particular embodiment of the invention, the step of partial polymerization of the glue bead is on only one or more separate segments of the glue bead, so that the glue bead outside said segment(s) remains unpolymerized.

[0008] That is to say that the segments of the polymerized adhesive bead are separated from each other by segments of unpolymerized adhesive bead. Thus, advantageously, the adhesive bead is polymerized partially but over its entire width.

[0009] In another embodiment of the invention, the partial polymerization step polymerizes one or more segments of the glue bead of length less than 70 millimeters, preferably greater than 10 millimeters.

[0010] Thus advantageously, the length of the polymerized glue bead segment is sufficiently short to allow rapid partial polymerization of the segment(s), to retain a large portion of the unpolymerized glue bead while having effective holding of the parts together.

[0011] In another embodiment of the invention, the partial polymerization step is carried out by localized heating of the second part opposite the part(s) of glue bead to be polymerized.

[0012] Thus advantageously, the polymerization of the parts of the glue bead is carried out simply and quickly because it is carried out not by heating all the parts and the entire glue bead but by localized heating.

[0013] In another preferred embodiment of the invention, the heating of the second part during the partial polymerization step is carried out by a laser beam traveling along a face of the second part, called the back of the second part, arranged opposite the face of the second part in contact with the bead of glue, opposite the part or parts of the bead of glue to be polymerized. Preferably, the laser beam travels along the back of the second part only over the area opposite the part or parts of the bead of glue to be polymerized.

[0014] Thus advantageously, the use of a laser beam allows heating of a precise area, and avoids using a tool comprising a hot element. Another advantage is that heating on localized areas of the back of the second part by laser allows rapid, precise heating which can be easily adapted to various part shapes by modifying the path and the power of the laser.

[0015] In another embodiment of the invention, the method comprises a step of clamping the first part against the second part at the level of the part or parts of the bead of glue to be polymerized, at least during the partial polymerization step, and preferably before and during the partial polymerization step.

[0016] Thus advantageously, the spacing between the two parts at the level of the part of the bead to be polymerized is maintained at a defined value during the partial polymerization step.

[0017] In a preferred embodiment of the invention, the clamping step and the partial polymerization step are carried out by a laser clamp, said clamp initially clamping the two parts together at one of the parts to be polymerized, and secondly carrying out the partial polymerization step by heating the area of ​​the back of the second part located opposite the part of the bead of glue to be polymerized by emitting a laser beam passing through said area.

[0018] Thus advantageously, it is not necessary to use different tools for the two steps, the laser clamp making it possible to carry out both the clamping step and the partial polymerization step.

[0019] In another embodiment of the invention, the first part is made of plastic material or composite material.

[0020] Thus advantageously, the second part can have shapes or mechanical properties other than those of a part made of sheet metal, while allowing its attachment to the second part.

[0021] In another embodiment of the invention, the method comprises a step of complete polymerization of the adhesive bead after the partial polymerization step.

[0022] The invention also relates to a vehicle structure comprising an assembly consisting of a first part and a second part, the first part being made of sheet metal, plastic or composite material, the second part being made of sheet metal, a bead of glue being arranged between and in contact with said two parts, remarkable in that the bead of glue is polymerized only on parts of the bead of glue, the rest of the bead of glue remaining in an unpolymerized state.

[0023] The invention will be better understood on reading the following description, given solely by way of example and with reference to the appended drawings, in which:

[0024] [Fig. 1] schematically represents the method according to the invention.

[0025] [Fig.2] represents a sectional view of two parts assembled together by a method according to the invention.

[0026] [Fig.3] is a front view of two parts assembled together by a method according to the invention.

[0027] [Fig.4] is a view of a laser tweezer used during the method of the invention.

[0028] The drawings are schematic representations to facilitate understanding of the invention. The components are not necessarily shown to scale. The same references correspond to the same components from one figure to another.

[0029] [Fig.l] illustrates the steps of a method of assembling a first part 1 to a second part 2 according to the invention. The second part 2 is made of sheet metal. The method comprises a step 101 of depositing a bead of glue on one of the parts 1 or 2, a step 102 of assembling the first part 1 on the second part 2, so that the bead of glue 3 is in contact with the two parts 1 and 2, and a step 103 of partial polymerization of only a limited part 30 of the bead of glue 3, so that the bead of glue 3 outside said part 30 remains unpolymerized. In other words, the partial polymerization step 103 consists of polymerizing only a limited part of the adhesive bead, and not its entirety. That is to say, after the partial polymerization step 103, there remain areas of the adhesive bead 3 which are not polymerized. For example, if the adhesive bead 3 is a continuous bead, the polymerized parts 30 are surrounded in part or completely by unpolymerized adhesive of the bead 3. In a variant not shown, the adhesive bead 3 is discontinuous, that is to say formed by segments of adhesive bead spaced from one another, and the partial polymerization step 103 is carried out only on some of said segments; in other words, once the partial polymerization step has been carried out, certain segments are polymerized and others are not. The glue in the glue bead 3 is for example an epoxy or polyurethane type glue.

[0030] Figures 2 and 3 show the first part 1 and the second part 2 assembled by the bead of glue 3, in which the step 103 of partial polymerization of the bead of glue 3 has been carried out on several separate segments 30, so that the bead of glue 3 outside said segments 30 is not polymerized. That is to say that the bead of glue 3, deposited so as to form a continuous line, comprises segments 30 in this line which are polymerized, the rest of the bead 3 between these segments 30 not being polymerized. [Fig. 3] shows the first part 1 with the bead of glue 3 in transparency through the second part 2, and whose continuous bead of glue 3 comprises segments 30 polymerized after the step 103 of partial polymerization, the rest of the bead of glue being not polymerized. For example, the length of the segments 30 thus polymerized is less than 70 millimeters and / or greater than 10 millimeters.The width of the glue bead is for example between 2 and 5 millimeters wide before applying the first part 1 to part 2.

[0031] The partial polymerization step 103 is carried out by localized heating of the second part 2 opposite the part or parts 30 of the bead of glue 3 to be polymerized. The heating is carried out for example by contact of a hot tool, for example a soldering iron, against the second part 2. In another variant, the heating of the second part 2 during the partial polymerization step 103 is carried out by a laser beam 5 traveling over a specific area of ​​a face of the second part 2, called the back of the second part 2, arranged opposite the face of the second part 2 in contact with the bead of glue 3, opposite the part or parts 30 of the bead 3 to be polymerized. That is, the laser beam 5 is projected against the specific area of ​​the back of the second part 2, and travels through this area in order to heat the second part 2 thanks to the energy it carries, as illustrated in [Fig.2].The specific zone of the second part 2 thus heated is located at least at the level of a segment 30 of the bead 3 to be polymerized during the partial polymerization step 103, that is to say opposite said segment 30. Several zones are heated at the same time, or alternatively the heating is carried out zone by zone. The heat is transmitted to the bead of glue 3, at the level of the segment 30 to be polymerized, by conduction through the thickness of the second part 2.

[0032] The temperature to which the area of ​​the second part 2, arranged at the level of the part 30 of the bead of glue 3 to be polymerized, is heated depends on the material of the glue. For example, for a single-component epoxy type glue, a temperature above 100°C and below 150°C is necessary to achieve the polymerization of the glue; the area of ​​the second part 2 will therefore be heated until it reaches a temperature above 100°C and below 150°C, this temperature being the temperature to be reached at the surface of the second part 2 receiving the bead of glue 3, at the part 30 to be polymerized, to bring the glue of this part 30 to this temperature level and generate the polymerization of the glue.

[0033] Alternatively, in order to maintain the two parts 1 and 2 with a certain spacing during the partial polymerization step 103, a step 104 of clamping the first part 1 against the second part 2 at the portion or portions 30 of the bead of glue 3 to be polymerized is carried out at least during the partial polymerization step 103. This clamping step 104 is carried out for example before and during the partial polymerization step 103. The spacing is maintained by clamping the two parts 1, 2 towards each other and by the crushing resistance force of the bead of glue 3 which opposes the clamping of the parts 1 and 2. For example, a spacing of 0.5 millimeters is maintained between the two parts 1 and 2 at the segment 30 of the bead of glue 3 to be polymerized, during the partial polymerization step 103.Alternatively, one of the parts 1 or 2 may comprise stops in order to ensure a precise spacing between the parts 1 and 2 during the clamping step 104. These stops are for example close to the segments 30 of the bead of glue 3 to be polymerized. The clamping step 104 is maintained during the partial polymerization step 103 in order to maintain the spacing between the parts 1 and 2, at the segment 30, during the polymerization of the bead of glue 3 at this segment 30. After clamping, the bead of glue 3 has spread, and its width has increased for example to a width greater than or equal to 20 mm, the width depending on the quantity of glue deposited.

[0034] In the embodiment of [Fig. 4], a laser clamp 10 is used to carry out the clamping step 104 and the partial polymerization step 103: said clamp 10 firstly clamps the two parts 1 and 2 together at one of the segments 30 of the bead of glue 3 to be polymerized, then carries out the partial polymerization step 103 by heating the area of ​​the back of the second part 2 located opposite the part 30 of the bead of glue 3 to be polymerized by emitting a laser beam 5 passing through said area. Such a clamp 10 is for example a clamp 10 as described in patent EP2149421, which comprises two jaws, one of which comprises a laser capable of being projected onto the clamped parts. In [Fig.4], the clamp 10 is in the clamping position, i.e. applying pressure clamping the two parts 1 and 2 towards each other and crushing the bead of glue 3, a laser beam 5 being projected against the back of the second part 2.

[0035] The dimension of the polymerized zone during the partial polymerization step 103 depends on the size of the zone heated by the laser beam 5. For example, in the context of the use of the laser tweezers 10, the dimension of the polymerized part 30 or of the zone to be heated can be of substantially rectangular shape. 70 mm long by 20 mm wide. Other dimensions and shapes can be applied. The advantage of using a laser beam 5 is that it is easy to modify the dimension of the heated area by controlling the laser beam 5 so that it travels over a given surface, without modifying the tool. Thus, with the same tool, such as for example the laser clamp 10, it is possible to modify the surface of the heated area, and therefore the dimension of the polymerized part 30 during the partial polymerization step 103.

[0036] The first part 1 is for example made of plastic material or composite material. For example, the first part 1 is made of polyethylene terephthalate known by the abbreviation PET or polyamide 6 known by the abbreviation PA6, possibly loaded with fibers such as glass fibers. The second part 2 is for example made of steel or aluminum sheet. Heating the second part 2 therefore allows fixing with the first part 1 made of plastic or composite material by the polymerized parts 30 of the adhesive bead 3. The first part 1 can also alternatively be in a metal sheet.

[0037] The method further comprises a step 105 of complete polymerization of the bead of glue 3 after the step 103 of partial polymerization. This step is for example a heating of the assembly formed by the first part 1 and the second part 2 held together by the partially polymerized bead of glue 3. This step 105 of complete polymerization is for example carried out during a so-called cataphoresis treatment of the assembly formed by the two parts 1 and 2, or during a passage in an oven of this assembly for example to carry out a baking of the layers of paint deposited on at least one of the two parts.

[0038] The clamping during the clamping step 104 and the partial polymerization step 103 is calibrated so that the bead of glue 3 forms a film of defined thickness between the two parts 1 and 2, for example between 0.2 and 0.3 mm, which corresponds to a spacing between the parts 1 and 2 of between 0.2 and 0.3 mm. A spacing between the two parts 1 and 2 to be assembled that is too large, for example greater than 1 mm, risks causing a loss of rigidity of the bonding following the partial polymerization step 103. In addition, if this clearance exceeds 2 mm, there is a risk of washing out the glue, i.e. evacuation of the glue, by the liquid used during the cataphoresis treatment and in which the assembly formed by the two parts 1 and 2 is immersed in the event of such treatment.

[0039] Before carrying out the complete polymerization step 105, the first part 1, the second part 2, and the bead of glue 3 arranged between and in contact with said two parts 1 and 2, form an assembly in which the bead of glue 3 is polymerized only on segments 30 of the bead of glue 3, the rest of the bead of glue 3 remaining in an unpolymerized state. The polymerized parts 30 of the bead of glue 3 keep the two parts 1 and 2 fixed to each other while moving the assembly and to carry out the complete polymerization step 105. The first part 1 is for example a structural part of a vehicle such as a stretcher, a side member or even a side pillar, and the second part 2 is a reinforcement made of plastic or composite material fixed to the first part 1 to reinforce it locally. Step 105 of complete polymerization is for example carried out during the cataphoresis treatment of a vehicle structure in which the assembly formed by parts 1 and 2 is installed.

Claims

Claims

1. Method for assembling a first part (1) to a second part (2), the second part (1, 2) being made of sheet metal, comprising a step (101) of depositing a bead of glue on one of the parts (1, 2), a step (102) of assembling the first part (1) on the second part (2), so that the bead of glue (3) is in contact with the two parts (1, 2), characterized in that it comprises a step (103) of partial polymerization of only one or more limited parts (30) of the bead of glue (3), so that the bead of glue (3) outside said part or parts (30) are not polymerized during the step (103) of partial polymerization, the step (103) of partial polymerization being carried out by localized heating of the second part (2) opposite the part or parts (30) of bead of glue (3) to be polymerized,the heating of the second part during the partial polymerization step (103) being carried out by a laser beam (5) traveling along a face of the second part (2), called the back of the second part (2), arranged opposite the face of the second part (2) in contact with the bead of glue (3), opposite the part or parts (30) of the bead (3) to be polymerized, characterized in that the method comprises a step (104) of clamping the first part (1) against the second part (2) at the part or parts (30) of the bead of glue (3) to be polymerized, at least during the partial polymerization step (103).,

2. Assembly method according to the preceding claim, in which the step (103) of partial polymerization of the glue bead (3) is on only one or more segments (30) of the glue bead (3) separated, so that the glue bead (3) outside said segment(s) (30) remains unpolymerized.

3. Method according to the preceding claim, in which the step (103) of partial polymerization polymerizes one or more segments (30) of the glue bead (3) of length less than 70 millimeters, preferably greater than 10 millimeters.

4. Method according to the preceding claim, in which the clamping step (104) and the partial polymerization step (103) are carried out by a laser clamp (10), said clamp (10) initially clamping the two parts (1, 2) together at one of the parts (30) to be polymerized, and in a second step carrying out the step (103) of

5.

6.

7. partial polymerization by heating the area of ​​the back of the second part (2) located opposite the part (30) of the bead of glue (3) to be polymerized by emission of the laser beam (5) traveling through said area. Method according to the preceding claim, in which the first part (1) is made of plastic material or composite material. Method according to one of the preceding claims, comprising a step (105) of complete polymerization of the bead of glue (3) after the step (103) of partial polymerization. Vehicle structure comprising an assembly consisting of a first part (1) and a second part (2), the first part being made of sheet metal, plastic or composite material, the second part being made of sheet metal, a bead of glue (3) being arranged between and in contact with said two parts (1, 2), characterized in that the bead of glue (3) is polymerized only on parts (30) of the bead of glue (3), the rest of the bead of glue (3) remaining in an unpolymerized state.

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