FR3140566A1 - Process for assembling two parts, one of which is metallic. - Google Patents

Abstract

Method of assembling a first part (1) to a second part (2), the second part (1, 2) being made of metal sheet, comprising a step of depositing a bead of glue on one of the parts (1, 2), a step 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), remarkable in that it comprises a step of partial polymerization only of a limited part (30) of the bead of glue (3), so that the bead of glue (3) outside said segment or segments (30) remains unpolymerized. Figure for abstract: Figure 2

Description

Process for assembling two parts, one of which is metallic.

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

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 glue bead, it is known to hold said sheets using spot welds. For example, document FR3025847 describes a method of assembling two sheet metal elements comprising depositing a bead of glue on one element, assembling the second sheet metal element on the first and fixing by making points resistance welding to keep the two metal sheet elements stationary 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 weld points at the glue-free sections of the discontinuous gluing line. Then, the glue is polymerized during a heating step, for example during a so-called cataphoresis treatment.

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, that is to say comprising zones without glue following a precise position, and making the welding points on these zones without glue, therefore also at specific positions. Another disadvantage is that if the welding point is made on an area containing glue, the quality of the welding will be degraded, providing less good support, and the glue risks being burned and emitting gases or dust harmful to the environment.

The objective of the invention is to remedy these drawbacks. In particular, one of the aims of the invention is to propose a method allowing two parts to be held together, of which at least only one of the parts is made of metallic material. Another objective is to simplify the process of fixing two parts intended to be fixed by a bead of glue.

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 metal sheet, the method comprising a step of depositing a bead of glue on the one of the parts, a step of assembling the first part onto the second part, so that the bead of glue is in contact with the two parts, remarkable in that the process comprises a stage of partial polymerization of only one or more limited parts of the glue bead, so that the glue bead outside said part or parts are not polymerized during the partial polymerization step.

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

In a particular embodiment of the invention, the step of partial polymerization of the bead of glue is on only one or more segments separated from the bead of glue, so that the bead of glue outside said segment or segments remains unpolymerized.

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

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

Thus advantageously, the length of the segment of polymerized glue bead is short enough to allow rapid partial polymerization of the segment(s), to retain a large part of the unpolymerized glue bead while having effective retention of the parts together. .

In another embodiment of the invention, the partial polymerization step is carried out by localized heating of the second part facing the part or parts of the glue bead to be polymerized.

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.

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 passing through one face of the second part, called the back of the second part, arranged at 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 facing the part or parts of the bead of glue to be polymerized.

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

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.

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

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 the level of one of the parts to be polymerize, and in a second step carrying out the partial polymerization step by heating the area of the back of the second part located opposite the part of the glue bead to be polymerized by emitting a laser beam passing through said area .

Thus advantageously, it is not necessary to use different tools for the two stages, the laser clamp making it possible to carry out both the clamping stage and the partial polymerization stage.

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

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

In another embodiment of the invention, the method comprises a step of complete polymerization of the glue bead after the partial polymerization step.

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 metal sheet, plastic or composite material, the second part being made of metal sheet, a cord of glue being placed between and in contact with said two parts, remarkable in that the glue bead is polymerized only on parts of the glue bead, the rest of the glue bead remaining in a non-polymerized state.

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

schematically represents the process according to the invention.

represents a sectional view of two parts assembled together by a process according to the invention.

is a front view of two parts assembled together by a process according to the invention.

is a view of a laser tweezer used during the process of the invention.

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

There 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 metal sheet. 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 only of a limited part 30 of the glue bead 3, so that the glue bead 3 outside said part 30 remains unpolymerized. In other words, partial polymerization step 103 consists of polymerizing only a limited part of the glue bead, and not its entirety. That is to say, after the partial polymerization step 103, there remain areas of the glue bead 3 which are not polymerized. For example, if the bead of glue 3 is a continuous bead, the polymerized parts 30 are surrounded partly or completely by glue from the unpolymerized bead 3. In a variant not shown, the bead of glue 3 is discontinuous, that is to say formed by segments of bead of glue spaced from one another, and the partial polymerization step 103 is carried out only on certain said segments; in other words, once the partial polymerization step has been carried out, certain segments are polymerized and others are not. The glue of the glue bead 3 is for example an expoxy or polyurethane type glue.

Figures 2 and 3 represent 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 was 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, has segments 30 in this line which are polymerized, the rest of the bead 3 between these segments 30 not being polymerized. There shows the first part 1 with the bead of glue 3 transparently through the second part 2, and of which the continuous bead of glue 3 comprises segments 30 polymerized after the partial polymerization step 103, 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.

Partial polymerization step 103 is carried out by localized heating of the second part 2 facing the part or parts 30 of glue bead 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 through a specific area of one 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 glue bead 3, facing each other -vis the part or parts 30 of the bead 3 to be polymerized. That is to say that 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 transports, as illustrated in . 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 of 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 glue bead 3, at the level of the segment 30 to be polymerized, by conduction through the thickness of the second part 2.

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 greater than 100°C and less than 150°C is necessary to polymerize the glue; the area of the second part 2 will therefore be heated until it reaches a temperature greater than 100°C and less than 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 level of 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.

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

In the embodiment of the , a laser clamp 10 is used to carry out the tightening step 104 and the partial polymerization step 103: said clamp 10 initially clamps the two parts 1 and 2 together at one of the cord segments 30 of glue 3 to be polymerized, then carries out step 103 of 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 emitting a beam laser 5 traveling through said area. Such a clamp 10 is for example a clamp 10 as described in patent EP2149421, which has two jaws, one of which includes a laser capable of being projected onto the gripped parts. In , the clamp 10 is in the clamping position, that is to say applying pressure tightening 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 piece 2.

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 tweezer 10, the dimension of the polymerized part 30 or the area 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 to be able to easily modify the dimension of the heated zone by controlling the laser beam 5 in order to make it cover a given surface, without modifying the tool. Thus, with the same tool, such as for example the laser tweezer 10, it is possible to modify the surface of the heated zone, and therefore the dimension of the part 30 polymerized during the partial polymerization step 103.

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 of 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 attachment with the first part 1 made of plastic or composite material by the polymerized parts 30 of the glue bead 3. The first part 1 can also alternatively be in a metal sheet.

The method further comprises a step 105 of complete polymerization of the glue bead 3 after 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 cooking layers of paint deposited on at least one of the two pieces.

The tightening during the tightening step 104 and the partial polymerization step 103 is calibrated so that the glue bead 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 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 step 103 of partial polymerization. In addition, if this clearance exceeds 2 mm, there is a risk of glue washing, that is to say an evacuation of the glue, by the liquid used during the cataphoresis treatment and in which the glue is immersed. assembly formed by the two parts 1 and 2 in the event of such treatment.

Before carrying out step 105 of complete polymerization, the first part 1, the second part 2, and the bead of glue 3 placed between and in contact with said two parts 1 and 2, form a set of which the bead of glue 3 is polymerized only on segments 30 of the glue bead 3, the rest of the glue bead 3 remaining in a non-polymerized state. The polymerized parts 30 of the glue bead 3 hold the two parts 1 and 2 fixed to each other while the assembly is moved and the complete polymerization step 105 is carried out. The first part 1 is for example a structural part of a vehicle such as a stretcher, a spar or even a side pillar, and the second part 2 is a reinforcement made of plastic or composite material fixed on the first part 1 for the strengthen locally. Complete polymerization step 105 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 (10)

Method of assembling a first part (1) to a second part (2), the second part (1, 2) being made of metal sheet, comprising a step (101) of depositing a bead of glue on the 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 only of one or more limited parts (30) of the glue bead (3), so that the glue bead (3) outside of said part or parts (30) are not polymerized during the partial polymerization step (103). Assembly method according to the preceding claim, in which the step (103) of partial polymerization of the bead of glue (3) is on only one or more segments (30) of the bead of glue (3) separated, so that the bead glue (3) outside said segment(s) (30) remains unpolymerized. Method according to the preceding claim, the partial polymerization step (103) of which polymerizes one or more segments (30) of the glue bead (3) of length less than 70 millimeters, preferably greater than 10 millimeters. Method according to one of the preceding claims, in which the partial polymerization step (103) is carried out by localized heating of the second part (2) facing the part or parts (30) of glue bead ( 3) to polymerize. Method according to the preceding claim, in which the heating of the second part during the partial polymerization step (103) is carried out by a laser beam (5) passing through one face of the second part (2), called the back of the second piece (2), arranged opposite the face of the second piece (2) in contact with the bead of glue (3), facing the part or parts (30) of the bead (3) to polymerize. Method according to the preceding claim, comprising a (104) step of clamping the first part (1) against the second part (2) at the level of the part or parts (30) of the bead of glue (3) to be polymerized, at least during step (103) of partial polymerization. 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) between them at one of the parts (30) to be polymerized, and in a second step carrying out the step (103) of partial polymerization by heating the area of the back of the second part (2) located opposite opposite the part (30) of the glue bead (3) to be polymerized by emission of the laser beam (5) passing through said area. Method according to the preceding claim, the first part (1) of which 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 metal sheet, plastic or composite material, the second part being made of metal sheet, a cord of glue (3) being placed between and in contact with said two parts (1, 2), characterized in that the glue bead (3) is polymerized only on parts (30) of the glue bead (3), the rest of the glue (3) bead of glue (3) remaining in an unpolymerized state.