A method for creating a pre-support between two parts, and a set of parts thus pre-supported.

Abstract

[Method (100) for creating a pre-support between a first part and a second part, the first part having a contact surface with the second part, said contact surface being made of thermoplastic material, the method (100) comprising in order: - a step (102) of positioning the first part relative to the second part so as to press the contact surface against a receiving surface of the second part; - a step (103) of heating the contact surface so as to melt the thermoplastic material forming the material of said contact surface, the second part being made of metallic material. Figure for the abstract: Fig. 4]

Description

Title of the invention: Method for creating a pre-support between two parts, and assembly of parts thus pre-supported

[0001] The invention relates to a method for pre-holding two parts together, an assembly method, as well as a set of parts assembled by such methods.

[0002] It is known to fasten two parts together, in particular two parts, one of which is made of plastic and the other of metal, by applying a bead of adhesive to the first part, applying the first part against the second part without the adhesive bead contacting the second part by means of a spacer, and then applying additional force to bring the first part closer to the second part by deforming the spacer until the adhesive bead is in contact with the second part. For example, document FR1558840 describes a method for bonding at least two elements of a vehicle structure. At least one of the two supplied elements is a sheet metal part and includes a spacer formed into the sheet metal.The process includes a step of supplying a first element and a second element coated with glue, a step of holding the elements in a waiting position during the bonding of the elements where the spacer comes into contact with the other of the two elements so as to keep the first element away from the glue, and a step of bonding the elements via the glue by joining the first element and the glue, the spacer being then deformed so as to allow the glue and the first element to come closer together.

[0003] The drawback of such a solution is that it does not provide pre-holding of the parts, which is particularly necessary during the handling time before the adhesive polymerizes. To overcome this, it is known to hold two sheets of metal together using spot welds to allow the adhesive to polymerize without the sheets moving relative to each other, as for example in document FR3025847.

[0004] The drawback of such a solution is that it does not allow for pre-holding of parts when at least one of them is not metallic. Furthermore, creating weld points requires sufficient access to the parts to allow the welding gun to pass through, thus limiting freedom in terms of part shape.

[0005] The objective of the invention is to overcome these drawbacks. In particular, one of the aims of the invention is to provide a means of pre-holding two parts together, one of which is made of plastic material, while ensuring a gap between the parts before pre-holding, which is simple to implement and low cost.

[0006] This objective is achieved according to the invention by means of a method for creating a pre-support between a first part and a second part, the first part having a contact surface with the second part, said contact surface being made of a thermoplastic material, the method comprising, in order: - a step of positioning the first part relative to the second part so as to press the contact surface against a receiving surface of the second part; - a step of heating the contact surface so as to melt the thermoplastic material forming the material of said contact surface. The second part is made of a metallic material, preferably a sheet of steel or aluminum.

[0007] Advantageously, by melting the contact surface by heating the thermoplastic material until it melts while in contact with the second part, adhesion between the contact surface and the second part is created without the need for additional parts or specific adhesives. The mass and complexity of the assembly obtained by this pre-fixing of the two parts together are reduced, especially since the first part is made of thermoplastic and not metallic material, and the manufacturing process is simplified. Another advantage is that this process allows for greater freedom in the shape of the parts because it does not require areas of a particular shape and size on the parts to accommodate conventional pre-fixing systems such as rivets or to create weld points. A further advantage is that it does not require significant access for welding or riveting tools.Also, the use of a metallic material allows its thermal conductivity to be used to heat the contact surface of the first part, without having direct access to the first part.

[0008] In one embodiment of the invention, the heating step is carried out by heating the second part.

[0009] Advantageously, the heating of the contact surface is easily achieved solely on that surface thanks to the contact between the first and second parts. Indeed, the metallic material of the second part has a melting point higher than that of the first part, which is made of thermoplastic material. Furthermore, it is not necessary to use tools to heat the first part, but only the second part.

[0010] In another embodiment of the invention, the heating step is carried out by heating the face of the second piece opposite the first piece, opposite the contact surface of the first piece.

[0011] Thus advantageously, there is no need to access the contact zone between the first and second parts locally, at the level of the contact surface, to heat said contact surface, the heating being carried out by the opposite face and the thermal conduction of the material. Another advantage is that the first part can to be placed in hard-to-reach areas because simple access to the face of the second piece located opposite the first piece, for example outside a hollow body in which the first piece is placed, is sufficient, with possibly a simple and space-saving means of holding the first piece during the heating phase.

[0012] In another embodiment of the invention, the heating step is carried out by a laser traversing the face of the second piece opposite the first piece, opposite the contact surface of the first piece.

[0013] In another embodiment of the invention, the contact surface is projecting from a principal face of the first part opposite the second part, or the second part has a projecting face bearing against the contact surface of the first part.

[0014] Thus advantageously, a space between the main face and the second piece can be maintained before heating the contact surface, allowing other material such as a bead of glue to be placed there without it touching the two pieces.

[0015] In another embodiment of the invention, the method includes a step of depositing a bead of glue on one of the parts so as to be outside the contact surface when the two parts are placed against each other after the positioning step, the step of depositing a bead of glue being carried out before the positioning step, the heating step melting the contact surface so as to bring the main face of the second part closer together until the bead of glue is in contact with the two parts.

[0016] Thus advantageously, the two parts can be positioned relative to each other without crushing the glue bead, then the crushing of the glue bead can be achieved at the same time as the pre-holding during the heating of the contact surface by bringing the two parts closer together with the melting of the contact surface.

[0017] The invention also relates to a method of fixing a first part to a second part, comprising a step of creating a pre-holding as described above, and a step of polymerizing the glue bead after the step of creating a pre-holding, preferably carried out by heating the assembly consisting of the two parts pre-held together.

[0018] Thus advantageously, the two parts are properly pre-held during the polymerization stage, avoiding any movement between the parts during their handling, until the polymerization of the glue bead achieves a durable fix.

[0019] The invention also relates to an assembly comprising a first part and a second part fixed together according to a method as described above, the first part being a thermoplastic part and the second part being a part metallic, notable in that the first part comprises a main face having at least one pre-holding stud projecting from the main face, the stud having at its apex the contact surface, and / or the second part comprising a receiving face comprising at least one projecting area whose apex is in contact with the contact surface, a bead of glue being disposed outside the contact surface.

[0020] The invention also relates to a vehicle comprising an assembly as described above.

[0021] Thus advantageously, the parts are pre-held in a simple way and without adding mass, then the final fixing is carried out during heating of the whole vehicle such as in a paint curing oven or during cataphoresis treatment.

[0022] The invention will be better understood upon reading the following description, given solely by way of example and made with reference to the accompanying drawings, on which:

[0023] [Fig-1] represents a front view of an assembly according to the invention.

[0024] [Fig.2] represents a side view of the whole of [Fig.1], in a first configuration.

[0025] [Fig.3] represents a side view of the whole of [Fig.1], in a second configuration.

[0026] [Fig.4] represents the steps of a process according to the invention.

[0027] The drawings are schematic representations to facilitate understanding of the invention. The components are not necessarily shown to scale. The same reference numerals correspond to the same components from one figure to another.

[0028] Fig. 1 illustrates an assembly according to the invention comprising a first part 1 and a second part 2 fixed together in such a way as to achieve a pre-holding. In [Fig. 1], the first part 1 is seen in transparency through part 2. As illustrated in Figures 1 and 2, the first part 1 has a main face 11 and at least one pre-holding stud 12 projecting from the main face 11. The stud 12 has a contact surface 10 at its apex, which bears against a receiving face 20 of the second part 2. In Figures 1 to 3, the first part 1 has several pre-holding studs 12. A bead of adhesive 3 is positioned outside the contact surface 10, against the main face 11. The studs 12 maintain a gap between the main face 11 of the first part 1 and the receiving surface 20 of the second part 2. In other words, there is an air gap between the main face 11 and the receiving surface 20.The first part 1 is made of thermoplastic material and the second part 2 is made of metallic material, such as steel or aluminum. For example, the second part 2 is a part made of sheet steel.

[0029] Figure 2 shows the assembly before a surface heating step 103 contact 10 is not achieved. [Fig. 3] shows this same assembly after step 103 of heating the contact surface 10. During this heating step 103, the contact surface 10 melted and the pads shortened due to the melting of the thermoplastic material composing them, bringing the main face 11 of the first part 1 closer to the receiving surface 20 of the second part 2. To promote this coming together, pressure can, for example, be exerted on one or both parts 1, 2 in a direction bringing them closer together.

[0030] Before heating, the air gap d is, for example, greater than the thickness of the glue bead 3 so that said glue bead 3 does not touch the second part 2. After heating the contact surface 10, as illustrated in [Fig.3], the material composing this contact surface 10 and the studs 12 has melted, reducing the height of said studs 12 relative to the main face 11 and achieving adhesion with the receiving surface 20 of the second part 2. The air gap da decreases until the glue bead 3 is in contact with the receiving surface 20 of the second part 2.

[0031] In one embodiment, to guarantee the size of the air gap d after the heating step 103, i.e., to prevent the air gap d from being too small and the adhesive bead 3 from being too spread out, the first part 1 has spacing stops 4 projecting from the main face 11, the height of which relative to this main face 11 is chosen according to the desired air gap d after the heating step 103 has been applied. Thus, during the melting of the material forming the contact surface 10, and therefore that of the pads 12 located behind this contact surface 10, the first part 1 is brought closer to the second part 2 by crushing the molten material, until the spacing stops 4 come into contact with the second part 2.

[0032] By way of example, the air gap value may be 1 mm before the heating step 103, and 0.5 mm after this step 103, the adhesive bead 3 having a thickness less than 1 mm but greater than 0.5 mm, for example 0.8 mm. Those skilled in the art will adapt these values ​​according to the specific requirements of the particular parts to be joined together. In an alternative not shown, the spacing stops are on the second part 2, for example on the receiving surface 20.

[0033] In Figures 2 and 3, the pre-holding studs 12 are shown in rectangular cross-section. Alternatively, they may have different shapes. For example, the studs 12 may have a rounded cross-section, a hemispherical shape, an elongated cylinder, a rectangular cross-section, or a cone projecting from the main face 11.

[0034] The first part 1 is made of thermoplastic material, for example polyethylene terephthalate known by the abbreviation PET or polyamide 6 known by the abbreviation PA6, optionally filled with fibers such as glass fibers.

[0035] The assembly is, for example, a component of a motor vehicle. For example, the first part 1 is a reinforcement fixed to a part of the vehicle structure forming the second part 2. The second part 2 is, for example, a stretcher, a side member, or a side pillar of the vehicle.

[0036] In an alternative not shown, the second part 2 has a projecting area of ​​the receiving face 20 whose apex is in contact with the contact surface 10. In this alternative, the contact surface 10 also projects beyond the main face 11, or in another alternative is at the same level as the main face 11, the air gap d being maintained by the projecting area from the second part 2. In this last alternative, when the contact surface 10 is heated, the projecting area of ​​the second part 2 enters the first part 1 by melting the material of the contact surface 10.

[0037] Figure 4 illustrates a method 100 for creating a pre-support, according to the invention, of the first part 1 on the second part 2. The method 100 comprises, in order: - a step 102 of positioning the first part 1 relative to the second part 2 so as to press the contact surface 10 against the receiving surface 20 of the second part 2; - a heating step 103 of the contact surface 10 so as to melt the thermoplastic material forming the material of said contact surface 10.

[0038] The heating step 103 is carried out by heating the second part 2. Since the material of the second part 2 is metallic, and the first part 1 is thermoplastic, the melting temperature of the second part 2 is higher than that of the first part 1, so that the material of the first part 1 melts at a lower temperature than that of the second part 2.

[0039] The heating is carried out for example by heating the face of the second part 2 opposite the first part 1, opposite the contact surface 10 of the first part 1; that is to say by heating the face of the second part 2 opposite the receiving face 20.

[0040] The heating step 103 is carried out, for example, using a laser scanning the face of the second part 2 opposite the first part 1. In other words, a laser is pointed at this face, scanning said face, only opposite the contact surface 10, possibly extending beyond it, to ensure localized heating. The material of the second part 2, such as a sheet of steel or aluminum given as an example, will transmit the heat to the receiving face 20, which will in turn heat the contact surface 10 to its melting temperature.

[0041] For example, in the case of a first part 1 made of PET, whose contact surface 10 and pre-holding pads 12 are also made of PET, the second part 2 is heated at a temperature of at least 260°C, corresponding to the melting point of PET, so that the temperature at the receiving face 20, which is in contact with the contact surface 10, is at least 260°C, thus allowing the material to melt at the contact surface 10. In the case of a first part made of PA6, the second part 2 will be heated to a temperature of at least 220°C, corresponding to the melting point of PA6. Since these temperatures are significantly lower than the melting point of the second metallic part 2, this second part 2 will not be, or only very slightly, mechanically affected by this heating.

[0042] The pre-holding creation process includes, as an alternative, a step 101 of applying a bead of adhesive 3 to one of the parts 1, 2 so that it is outside the contact surface 10 when the two parts 1, 2 are placed against each other after the positioning step 102. The step 101 of applying a bead of adhesive 3 is carried out before the positioning step 102. For example, beads of adhesive 3 are placed between the pre-holding pads 12 as illustrated in [Fig. 1]. The heating step 103 melts the contact surface 10 so as to bring the main face 11 of the second part closer together until the bead of adhesive 3 is in contact with both parts 1, 2 as illustrated in [Fig. 3].

[0043] The method 100 for creating a pre-holding is incorporated into a method 110 for attaching the first part 1 to the second part 2, as illustrated in [Fig. 4]. The attachment method comprises a step 100 for creating a pre-holding as described above, and a step 104 for polymerizing the adhesive bead 3 after the pre-holding creation step 100, more precisely after the heating step 103, and optionally after a cooling step 105. The polymerization step 104 is carried out, for example, by heating the assembly consisting of the two pre-held parts. In the context of a vehicle structure comprising the assembly of the two parts 1, 2, this heating is carried out, for example, during the curing of the vehicle structure in an oven, such as a paint curing oven, or during immersion in a cataphoresis bath.The polymerization of the glue bead 3 is for example carried out at a temperature between 100°C and 150°C for a glue bead using a single-component epoxy glue, therefore lower than the melting temperature of the material of the first part 1, avoiding degradation of the hold between the first part 1 and the second part 2 obtained during the implementation of the pre-holding creation process 100.

Claims

Demands

1. Method (100) of creating a pre-holding between a first part (1) and a second part (2), the first part (1) comprising a main face (11) and at least one pre-holding stud (12) projecting from said main face (11), the stud (12) having at its summit a contact surface (10) of thermoplastic material, the second part (2) being of metallic material and comprising a receiving surface (20), the method (100) comprising in order: - a step (101) of depositing a bead of glue (3) on one of the parts (1,2), said bead of glue (3) being disposed outside the contact surface (10);- a step (102) of positioning the first part (1) relative to the second part (2) so as to press the contact surface (10) against a receiving surface (20) of the second part (2), said pre-holding pads (12) maintaining an air gap (d) between the main face (11) and the receiving surface (20), the air gap (d) being greater than the thickness of the glue bead (3) so that, after step (102), the glue bead (3) is not in contact with the second part (2);- a heating step (103) of the second part (2) so that the heat transmitted by conduction melts the thermoplastic material of said contact surface (10), causing a shortening of the pre-holding studs (12) and a bringing of the main face (11) towards the receiving surface (20) until the glue bead (3) is in contact with the two parts (1,2) while creating a local adhesion between the contact surface (10) and the receiving surface (20) constituting said pre-holding.;

2. A method (100) according to the preceding claim, wherein the heating step (103) is carried out by heating the face of the second part (2) opposite the first part (1), opposite the contact surface (10) of the first part (1).

3. A method according to claim 2, wherein the heating step (100) is carried out by a laser traversing the face of the second part (2) opposite the first part (1), opposite the contact surface (10) of the first part (1).

4. A method according to any one of claims 1 to 3, wherein the first part (1) comprises at least one spacing stop (4) projecting from the main face (11), bearing against the second room (2) during the heating stage (103) in order to limit the proximity between the rooms.

5. A method according to any one of claims 1 to 4, wherein the contact surface (10) is projecting from the main face (11) and / or the receiving surface (20) of the second part (2) comprises a projecting area whose apex is in contact with the contact surface (10).

6. Method (110) of fixing a first part (1) to a second part (2), comprising a step (100) of creating a pre-holding according to claim 1, followed by a step (104) of polymerizing the glue bead (3), preferably the polymerization step (104) being carried out by heating the assembly consisting of the two parts (1,2) pre-held together.

7. Assembly comprising a first part (1) and a second part (2) fixed together, the first part (1) being made of thermoplastic material and comprising a main face (11) having at least one protruding pre-holding stud (12), the stud (12) having at its summit a contact surface (10), the second part (2) being made of metallic material and comprising a receiving surface (20), the assembly having been obtained by implementing the process according to any one of claims 1 to 6, a bead of glue (3) being disposed outside the contact surface (10).

8. Vehicle comprising an assembly according to claim?

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