Joining element providing a multi-material assembly of three thicknesses

Abstract

The present invention relates to a joining element (2) for irreversibly binding a first part (3) and a second part (5) to a third part (7) by electric resistance welding, comprising: - a head (4) intended to bear on the first part; and - an axial portion extending from the head and intended to pass respectively through the first and second parts in order to be electric-resistance welded to the third part; characterized in that the axial portion has a stepped cross section comprising a first step (6.1) having a first diameter and intended to be crimped into a first opening (3.1) of the first part, and a second step (6.2) having a second diameter, smaller than the first diameter, and intended to be crimped into a second opening (5.1) of the second part.

Description

[0001] DESCRIPTION

[0002] TITLE: JOINING ELEMENT PROVIDING A MULTI-MATERIAL ASSEMBLY OF THREE THICKNESSES

[0003] Technical field

[0004] The present invention claims priority from French application 2400382 filed on January 16, 2024, the content of which (text, drawings and claims) is incorporated herein by reference.

[0005] The present invention relates to the field of motor vehicles, more particularly the field of assemblies of multi-material parts of motor vehicles.

[0006] Prior art

[0007] In the context of a multi-material assembly, i.e. aluminum / steel, steel / composite, steel / plastic, etc. assembly, the use of joining elements to ensure a rigid connection by gluing and / or welding of the different parts is conventionally widespread, in particular to ensure friction welding, in which the joining element is brought into contact and pressed in rotation against the two parts to be assembled, in order to force the connection between said two parts by plastic deformation.

[0008] There is also another type of joining elements allowing multi-material assembly by electric welding. Indeed, these joining elements are conventionally directly welded to a part which generally corresponds to a sheet thickness, while being linked to another part, thus obtaining an assembly of several superimposed parts, for example two or three thicknesses, by means of one or more electrically welded junction(s).

[0009] The published patent document US 2018 / 0354231 A1 discloses an assembly of three sheets together by a rivet having a distal end welded to one of the three sheets, the other two remaining sheets being previously welded together before assembly by said rivet.

[0010] However, the solution proposed by the document requires that all the sheet metal parts be weldable and conductive in order to allow electric welding both between at least two of said sheets, and welding of the distal end of the rivet to the third of said sheets. Thus, said solution does not allow three parts to be assembled, two of which are not weldable or conductive, for example, obtained from insulating material, or from composite, or from any other materials that do not allow their welding by electrical junction.

[0011] To this end, there is a need to assemble three different materials, without necessarily having two weldable sheets, so as to obtain, for example, a multi-material assembly of three parts having at most a single steel part suitable for welding.

[0012] Statement of the invention

[0013] The present invention aims to overcome at least one of the drawbacks of the aforementioned state of the art. More particularly, the invention aims to propose a simple and effective solution allowing an assembly of three parts of different materials by electric welding, two of said parts being non-weldable and / or non-conductive.

[0014] To this end, the invention relates to a joining element, intended to irreversibly connect a first part and a second part to a third part by electrical resistance welding, comprising:

[0015] - a head intended to rest on the first part; and

[0016] - an axial portion extending from the head (4) and intended to pass through, respectively, a first orifice in the first part and a second orifice in the second part, said axial portion comprising, at a distal end, a connecting face intended to be welded by electrical resistance to the third part; remarkable in that the axial portion has a stepped section comprising a first stage having a first diameter and intended to be crimped into the first orifice of the first part, and a second stage having a second diameter smaller than said first diameter and intended to be crimped into the second orifice of the second part.

[0017] Advantageously, the joining element as well as the third part are obtained from a metallic material, and are preferably formed from steel.

[0018] Preferably, the head is continuously circular, and comprises an external upper face which is smooth and devoid of radial notches or grooves. According to one embodiment, the second diameter corresponds to at most 90% of the first diameter.

[0019] According to one embodiment, the first stage comprises a first circular rib forming a circular shoulder with the head.

[0020] According to one embodiment, the second stage comprises a second circular rib coaxial with the first circular rib.

[0021] According to one embodiment, each of the first and second circular ribs is continuous over 360° around a main axis of the axial portion.

[0022] Preferably, the main axis extends substantially perpendicular to the head.

[0023] According to one embodiment, each of the first and second circular ribs has an inclination of at most 45° relative to a main axis of the axial portion.

[0024] According to one embodiment, the distal end of the axial portion has a third diameter smaller than each of the first and second diameters.

[0025] According to one embodiment, the third diameter corresponds to at most 90% of the second diameter.

[0026] The invention also relates to a method of assembling a first part and a second part to a third part by means of a joining element, comprising the steps:

[0027] - making a first hole in the first part;

[0028] - creation of a second orifice in the second part;

[0029] - superposition of the first piece, the second piece and the third piece;

[0030] - inserting a joining element through the first and second orifices;

[0031] - applying an electric current through the joining element and the third part so as to weld the joining element with said third part; remarkable in that the joining element is according to the invention.

[0032] Advantageously, the axial portion is crimped into each of the two respective orifices of the first part and the second part, by means of the stepped section and circular ribs. The invention also relates to a motor vehicle comprising an assembly of at least three parts by means of a joining element, remarkable in that said joining element is according to the invention.

[0033] The measures of the invention are advantageous in that the stepped section of the axial portion makes it possible to ensure effective retention of the first and second parts prior to welding the joining element to the third part. The circular ribs make it possible to further promote the retention by crimping of the joining element in the corresponding orifice, in order to secure a multi-material assembly with two non-weldable parts, without requiring a second weld.

[0034] The joining element is specifically designed for electric welding, ensuring a connection without air confinement to preserve the quality of multi-material assemblies, with robustness in accordance with the quality standards and requirements of electric welding. In addition, its manufacture is simple.

[0035] Brief description of the drawings

[0036] [Fig 1] represents a perspective view of a joining element according to the invention, comprising an axial portion having a stepped section comprising circular ribs intended to be crimped into corresponding orifices of parts to be assembled.

[0037] [Fig 2] schematically represents a sectional view of three parts assembled by electric resistance welding using the joining element of Figure 1.

[0038] Detailed description

[0039] Figure 1 represents a perspective view of a joining element 2 according to the invention, which is intended to irreversibly connect three parts 3, 5 and 7 having different materials, by electrical resistance welding.

[0040] The joining element 2 preferably comprises a substantially cylindrical shape and in revolution around a main axis 2.1, thus forming a joining pin 2, and will be designated as such in the remainder of this description. The pin 2 comprises a head 4 intended to bear on a first part of the three parts to be assembled. This will be detailed according to figure 2, in this description.

[0041] Preferably, the pin 2 comprises an axial portion 6 extending along the main axis 2.1 from the head 4, and ending at a distal end 8 of said pin 2, by a connecting face 10 intended to be welded by electrical resistance to a third part of the three parts to be assembled.

[0042] The connecting face 10 may comprise a generally flat profile as illustrated in FIG. 1, or a curved profile. Said face 10 may alternatively comprise at least one groove acting as a vent allowing the evacuation of any gases which may be produced during electrical welding with the third part.

[0043] Advantageously, the axial portion 6 has a stepped section comprising a first stage 6.1 having a first diameter D1, and a second stage 6.2 having a second diameter D2 smaller than said first diameter D1. Each of the first and second stages 6.1 and 6.2 being intended to engage, preferably by crimping, in an orifice of the corresponding part to be assembled.

[0044] Preferably, the second diameter D2 corresponds to at most 90% of the first diameter D1. More preferably, D1 is greater than D2 by approximately 20% (±10%). The difference in diameters D1 and D2 advantageously makes it possible to create a clearance that further facilitates the engagement of the pin 2 in the corresponding orifices of the parts to be assembled.

[0045] Preferably, the first stage 6.1 comprises a first circular rib 6.1 forming a circular shoulder 12 with the head 4. The second stage 6.2 in turn comprises a second circular rib 6.2 which is coaxial with the first circular rib 6.1, along the main axis 2.1.

[0046] It can be seen that the ribs 6.1, 6.2 are slightly inclined laterally outwards relative to the main axis 2.1. Preferably, each of the first and second circular ribs 6.1, 6.2 has an inclination of at most 45° relative to the main axis 2.1. Advantageously, such an inclination makes it possible to guarantee a tight hold of the rib in the corresponding orifice, thus ensuring an effective fixing (by crimping) allowing the parts to be assembled more securely.

[0047] The distal end 8 of the axial portion 6 has a third diameter D3 which is less than each of the first and second diameters D1 and D2.

[0048] Preferably, the third diameter D3 corresponds to at most 90% of the second diameter D2. More preferably, D2 is greater than D3 by approximately 20% (±10%).

[0049] Figure 2 schematically represents a sectional view of an assembly 9 of three parts 3, 5, 7 assembled by electric resistance welding using the joining pin 2 of figure 1.

[0050] The assembly 9 may, for example, correspond to a body part of a motor vehicle 1.

[0051] The joining pin 2 according to the invention comprises an upper face 4.1 of the head 4 which is completely smooth and devoid of radial notches or grooves. Indeed, the pin 2 allowing electric welding, does not require such irregularities at the level of the head to transmit a rotational movement, to ensure friction welding for example.

[0052] The invention proposes a method for assembling the first part 3 and a second part 5 to the third part 7, comprising a first step of producing a first orifice 3.1 in the first part 3, this being less wide than a diameter of the head 4 of the pin 2. Then, a second orifice 5.1 is produced at the level of the second part 5, and which is less wide than the first orifice 3.1.

[0053] In this configuration, the three parts 3, 5 and 7 can be superimposed, and the pin 2 can be inserted into the holes 3.1 and 5.1 in a single pass, until the connecting face comes into contact with the third part 7. This advantageously allows for a considerable saving of time.

[0054] Thus, electric welding can be carried out by applying an electric current through the joining pin 2 and the third part 7, so as to produce a weld allowing the assembly of the three parts to be fixed.

[0055] Advantageously, the circular shoulder 12 makes it possible to effectively hold the first part 3 to the second part 5 after the electric welding operation. The head 4 thus makes it possible to securely hold the first part 3 with the third part 7 by passing through the second part 5, the assembly 9 is therefore rigid, and this in particular thanks to the stepped section of the axial portion 6 and the circular ribs 6.1 and 6.2 which firstly make it possible to rigidly connect the first part 3 and the second part 5 together, without requiring welding or special secondary fixing between said two parts 3 and 5, before being definitively connected to the third part 7.

[0056] Advantageously, the first part 3 and the second part 5 are made of non-weldable materials, while the third part 7 is the only one that can be welded with the joining pin 2.

[0057] The circular ribs 6.1 and 6.2 advantageously act as two stop stops (terminal contact point) following material consumption during welding of the connecting face with the third part 7, indicating the end of welding.

[0058] The junction 14 visible in figure 2 is advantageously sound and devoid of any recess which could compromise its rigidity, and allowing, in combination with the crimping of the circular ribs 6.1, 6.2 in the corresponding orifices 3.1, 5.1 to ensure the robustness of the assembly 9.

[0059] Alternatively, the invention can also make it possible to ensure the assembly of more than three parts of different materials, for example, with a stepped section carrying a plurality of stages, in particular with as many stages (of circular ribs) as there are parts to be assembled.

Claims

CLAIMS [Claim 1.] Joining element (2), intended to irreversibly connect a first part (3) and a second part (5) to a third part (7) by electrical resistance welding, comprising: - a head (4) intended to rest on the first part (3); and - an axial portion (6) extending from the head (4) and intended to pass through, respectively, a first orifice (3.1) in the first part (3) and a second orifice (5.1) in the second part, said axial portion (6) comprising, at a distal end (8), a connecting face (10) intended to be welded by electrical resistance to the third part (7); characterized in that the axial portion (6) has a stepped section comprising a first stage (6.1) having a first diameter (D1) and intended to be crimped in the first orifice (3.1) of the first part (3), and a second stage (6.2) having a second diameter (D2) smaller than said first diameter (D1) and intended to be crimped in the second orifice (5.1) of the second part (5). [Claim 2.] Junction element (2) according to claim 1, in which the second diameter (D2) corresponds to at most 90% of the first diameter (D1). [Claim 3.] Joining element (2) according to one of claims 1 and 2, in which the first stage (6.1) comprises a first circular rib (6.1) forming a circular shoulder (12) with the head (4). [Claim 4.] Junction element (2) according to claim 3, in which the second stage (6.2) comprises a second circular rib (6.2) coaxial with the first circular rib (6.1). [Claim 5.] Joining element (2) according to one of claims 3 and 4, in which each of the first and second circular ribs (6.1, 6.2) is continuous over 360° around a main axis (2.1) of the axial portion (6). [Claim 6.] Joining element (2) according to one of claims 3 to 5, in which each of the first and second circular ribs (6.1, 6.2) has an inclination of at most 45° relative to a main axis (2.1) of the axial portion (6). [Claim 7.] Joining element (2) according to one of claims 1 to 6, in which the distal end (8) of the axial portion (6) has a third diameter (D3) smaller than each of the first and second diameters (D1, D2). [Claim 8.] Joint element (2) according to claim 7, in which the third diameter (D3) corresponds to at most 90% of the second diameter (D2). [Claim 9.] Method of assembling a first part (3) and a second part (5) to a third part (7) by means of a joining element (2), comprising the steps: - making a first orifice (3.1) in the first part (3); - making a second orifice (5.1) in the second part (5); - superposition of the first part (3), the second part (5) and the third part (7); - inserting a joining element (2) through the first and second orifices (3.1, 5.1); - applying an electric current through the joining element (2) and the third part (7) so as to weld the joining element (2) with said third part (7); characterized in that the joining element (2) is according to one of claims 1 to 8. [Claim 10.] Motor vehicle (1) comprising an assembly (9) of at least three parts (3, 5, 7) by means of a joining element (2), characterized in that said joining element (2) is according to one of claims 1 to 9.

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