AUTOMOTIVE VEHICLE STRUCTURAL ELEMENT

Abstract

The invention relates to a structural element (1) of a motor vehicle, said structural element being an elongated hollow body comprising two lateral walls (3, 5), one of said lateral walls being an inner lateral wall (3) and the other being an outer lateral wall (5), said structural element (1) being notable in that at least one of its lateral walls exhibits a reinforcement zone (7) over at least a portion of its height, said zone having a mechanical resistance Rm1 of at least 250 MPa as measured according to ISO 6892-1:2016 and in the transverse direction; and in that at least one of said walls comprises, at the level of said reinforcement zone (7), a first stiffening relief (11) extending longitudinally over at least a portion of the length of said structural element (1). Figure to be published with the abstract: Fig. 1

Description

Title of the invention: MOTOR VEHICLE STRUCTURAL ELEMENT

[0001] The present invention relates to a structural element of a motor vehicle, in particular of the hybrid or electric type, the side impact behavior of which has been improved. In particular, the invention relates to structural elements comprising a hollow body of the vehicle chassis side member type.

[0002] In hybrid vehicles, the chassis rail is part of the underbody structure that includes the front floor. The front floor extends from its connection with the bulkhead to an area located under the row of seats of row 1, which is fixed to the floor by means of seat crossmembers. A pair of side members is also fixed to the floor at its lateral edges. The side members are generally elongated hollow bodies formed by the assembly of two stamped profiles, namely an internal side member and an external side member. The ends of the seat crossmembers are placed opposite the internal side members. The external side members are arranged opposite the inner part of the passenger compartment sides.

[0003] In the event of a side impact on the vehicle, part of the forces resulting from the impact pass through the underbody structure. To improve the behavior of the vehicle in such impacts, it is therefore known to use various reinforcements, among which we can cite side member reinforcements (which may be internal side member reinforcements and / or external side member reinforcements), central tunnel reinforcements (which may be partitions), floor reinforcements (which may be cross members), center pillar reinforcements and roof reinforcements. The presence of these different reinforcements makes it possible to limit dynamic intrusions of the doors, tunnel collapses (causing floor tears); and folds or tears in the side members.

[0004] Nevertheless, if the presence of such reinforcements gives satisfactory results for vehicles powered by thermal engines, this is not always the case for rechargeable hybrid vehicles of the PHEV (Plug-in Hybrid Electric Vehicle) type. Indeed, these vehicles integrate batteries and specific equipment which induce an increase in mass of more than 300 kg compared to thermal silhouettes.

[0005] Conventional reinforcements are not sufficient and it would be necessary to add other reinforcements to achieve the desired objectives in terms of side impact behavior. Unfortunately, the addition of additional reinforcements increases the overall mass of the vehicle on the one hand, but also the manufacturing costs of the latter, in particular to the extent that this involves to use a specific production line and no longer a production line common to the different thermal and hybrid silhouettes.

[0006] A first solution was provided by document FR3060511 which proposes a base structure comprising an elongated reinforcement element for absorbing lateral impact, housed in the space between the external side member and the internal part of the passenger compartment side. The reinforcement element is an added part, fixed by welding, on the external face of the external side member. The elongated reinforcement element has a cross-section in the shape of a lying and asymmetrical W. This solution is interesting and efficient, but involves the addition of an additional reinforcement with the disadvantages that this can cause.

[0007] This is why, document FR3063707 has proposed a vehicle structural element such as a side member, comprising two profiles folded and assembled together by means of joining rebates so as to form a hollow body. The second profile is obtained from a sheet blank consisting of several sheets joined end to end. At least one of the sheets comprising an edge forming a joining rebate has a first thickness and at least one other of said sheets, located at a distance from one of the edges forming a joining rebate, has a second thickness greater than the first thickness.

[0008] This solution is interesting because it limits the increase in mass of the vehicle, but also because by keeping the joining rebates thinner than the body of the side member, the underbody structure of the vehicle can be assembled using the same techniques and tools as the profiles of constant thickness forming the thermal silhouettes.

[0009] Nevertheless, it would be interesting to further improve the side impact performance of hybrid vehicles.

[0010] The invention aims to propose a structural element of a motor vehicle showing improved performance in terms of mechanical strength, and which, preferably, can be assembled with existing tools and / or does not increase or only slightly increases the mass of the vehicle.

[0011] To this end, and according to a first aspect, the invention relates to a structural element of a motor vehicle, said structural element being an elongated hollow body comprising two side walls, one of said side walls being an internal side wall and the other being an external side wall, said structural element being remarkable in that at least one of its side walls shows a reinforcement zone over at least part of its height, said zone having a mechanical strength Rml of at least 250 MPa as measured according to the ISO 6892-1:2016 standard and in the transverse direction; and in that at least one of said walls comprises, at its reinforcement zone, at least one first stiffening relief extending longitudinally over at least part of the length of said structural element.

[0012] As will be understood from reading the definition which has just been given, the invention is remarkable in that it combines a local reinforcement of the mechanical properties of at least one of the side walls of the structural element with a first stiffening relief, therefore with a particular geometry of the profile of the structural element, so as to improve the dissipation of the energy of the impact and the behavior of said structural element in a lateral impact kinematics. According to a preferred embodiment, the side wall showing a first stiffening relief also shows at least a second stiffening relief; preferably at least a second stiffening relief is arranged above said first stiffening relief according to the height of said side wall.

[0013] According to a preferred embodiment, the reinforcement zone has a mechanical resistance Rml of at least 300 MPa as measured according to the ISO 6892-1:2016 standard and in the transverse direction; preferably, at least 350 MPa, more preferably at least 400 MPa, even more preferably at least 450 MPa, or at least 500 MPa, or even at least 550 MPa, or at least 600 MPa, or at least 800 MPa, or at least 1000 MPa, or at least 1100 MPa.

[0014] According to a preferred embodiment of the invention, the first stiffening relief is arranged in the lower part of the external side wall, and / or a side wall showing a reinforcement zone is the external side wall. Indeed, in particular when the structural element is a side member, the location of the first stiffening relief in its lower part according to the height of said element and on its external side wall allows loading of the forces downwards which allows better transmission of the forces to the seat cross members. This also makes it possible to avoid rotation of said side member during impact and to limit the risk of tearing of the floor. Advantageously, the structural element is a chassis side member.

[0015] Preferably, the structural element shows at the first stiffening relief a width L1 of at least 1.2 times the minimum width L3 shown by the structural element between its two side walls outside the stiffening relief(s); preferably at least 1.3 times, and more preferably at least 1.4 times. Indeed, it has been found that the energy dissipation was improved by the dimensions shown by said first stiffening relief.

[0016] According to a preferred embodiment, at least one second stiffening relief is arranged above said first stiffening relief according to the height of the external side wall. Preferably, the structural element shows at the level of the second stiffening relief a width L2 less than 1.2 times the minimum width L3 shown by the structural element between its two side walls outside the stiffening reliefs. The invention thus makes it possible to propose a structural element showing an external side wall with a plurality of surfaces arranged in stages along the transverse direction of said structural element so as to be stressed successively during a lateral collision.

[0017] Alternatively or additionally, the first stiffening relief shows a height H1 less than or equal to 50% of the height H3 of said side wall, preferably less than 40% or less than 30%. According to one embodiment, the reinforcement zone extends only over the part of the side wall showing the first stiffening relief, thus the reinforcement zone shows a height H1 less than or equal to 50% of the height H3 of said side wall, preferably less than 40% or less than 30%.

[0018] Alternatively or additionally, the second stiffening relief shows a height H2 less than or equal to 30% of the height H3 of said side wall; preferably less than or equal to 20% of the height H3 of said side wall.

[0019] According to a preferred embodiment, the reinforcement zone of said side wall is formed by at least one strip of sheet metal showing an excess thickness. Preferably; the strip of sheet metal showing an excess thickness has a thickness of at least 1.1 times the thickness shown by the sheet metal outside said excess thickness strip, more preferably at least 1.5 times or at least 2 times; and / or the strip of sheet metal showing an excess thickness has a thickness el of at least 1.1 mm; preferably at least 1.5 mm and more preferably at least 2.0 mm.

[0020] According to an alternative or complementary embodiment, the reinforcement zone of said side wall is formed by at least one strip of sheet metal made of a steel chosen from high elastic limit steels showing an elastic limit ranging from 300 to 700 MPa, very high elastic limit steels showing an elastic limit ranging from 800 to 1000 MPa and ultra high elastic limit steels showing an elastic limit of 1100 to 1500 MPa, the elastic limit being measured according to the ISO 6892-1:2016 standard and in the transverse direction. When the sheet metal used is a stamped sheet metal, the mechanical strength Rml of the reinforcement zone is measured after stamping.

[0021] According to a preferred embodiment, the structural element is formed by assembling at least two profiles so that the internal side wall is formed by a first profile and the external side wall by a second profile, said profiles being assembled by joining rebates, and the joining rebates of the second profile have a thickness e2 less than or equal to 1.2 mm, preferably less than or equal to 1.1 mm or less than or equal to 1.0 mm.

[0022] According to one implementation of the invention, the structural element is formed by assembling at least two profiles so that the internal side wall is formed by a first profile and the external side wall by a second profile, and the second profile is formed by assembling different sheets joined end to end, and at least one of the sheets forming the reinforcement zone is formed from a steel grade showing a mechanical strength greater than at least one other sheet and / or shows a thickness e1 greater than a thickness e2 shown by another sheet.

[0023] According to another implementation of the invention, the structural element is formed by assembling at least two profiles so that the internal side wall is formed by a first profile and the external side wall by a second profile, and the second profile is formed by a single sheet having at least one strip of sheet showing an excess thickness obtained by a method comprising a flexible rolling step; preferably, the flexible rolling step is followed by a step of stamping the sheet.

[0024] According to another implementation of the invention, the structural element, or at least one of the profiles constituting said structural element, is produced by an additive manufacturing process. Preferably, said structural element comprises at least one shock-absorbing means arranged in said hollow body so as to extend over at least part of the length of said structural element, said shock-absorbing element being arranged at the first stiffening relief and being integral with said side wall. Advantageously, the shock-absorbing means is a metal foam.

[0025] According to a second aspect, the invention relates to a motor vehicle which is remarkable in that it comprises at least one structural element as defined according to the first aspect.

[0026] Thus, the subject of the invention is a motor vehicle comprising at least one structural element being an elongated hollow body comprising two side walls, one of said side walls being an internal side wall and the other being an external side wall, said vehicle being remarkable in that at least one of the side walls of said structural element shows a reinforcement zone over at least part of its height, said zone having a mechanical strength Rml of at least 250 MPa as measured according to the ISO 6892-1:2016 standard and in the transverse direction; and in that at least one of said walls comprises, at its reinforcement zone, at least one first stiffening relief extending longitudinally over at least part of the length of said structural element. Preferably, the structural element is a chassis side member.

[0027] The invention will be well understood and other aspects and advantages will appear clearly on reading the following description given with reference to the attached drawings in which:

[0028] [Fig-1] [Fig.l] is a sectional view of a structural element according to the invention.

[0029] [Fig.2] [Fig.2] is a view of the external side wall of a structural element according to the invention.

[0030] In the following description, the term "comprise" is synonymous with "include" and is not limiting in that it allows the presence of other elements or means in the structural element or the vehicle to which it relates, or other steps in the manufacturing process considered. It is understood that the term "comprise" includes the terms "consist of". Similarly, the terms "lower", "upper", "front", "rear", "longitudinal" and "transverse" will be understood in relation to the general orientation of the vehicle as taken in its normal direction of travel, or of the structural element as the case may be. In the different figures, the same references designate identical or similar elements.

[0031] By "profile" is meant an element of elongated shape showing a particular profile according to its cross section. According to the invention, the profiles can be obtained by folding, stamping or profiling a sheet or several sheets previously assembled together. The preliminary assembly of several sheets together end to end before their shaping can be carried out by laser welding. Such blanks are known and commercially available, in particular from the company ArcelorMittal®. It is also possible to produce sheet blanks composed of several sheets by techniques known as roller butt joining. According to the invention, the profiles can also be obtained by additive manufacturing techniques.

[0032] As illustrated in Figures 1 and 2, the invention relates to a structural element 1 of a motor vehicle, said structural element 1 being an elongated hollow body comprising two side walls (3, 5), one of said side walls being an internal side wall 3 and the other being an external side wall 5, said structural element 1 being remarkable in that at least one of its side walls (3, 5) shows a reinforcement zone 7 over at least part of its height, said reinforcement zone 7 having a mechanical strength Rml of at least 250 MPa as measured according to the ISO 6892-1:2016 standard and in the transverse direction; and in that at least one of said walls comprises, at the level of said reinforcement zone 7, at least one first stiffening relief 11 extending longitudinally over at least part of the length of said structural element 1.

[0033] It will be understood that the internal side wall 3 is defined as the one closest to the longitudinal axis of the vehicle. The external side wall 5 is the one which is arranged furthest from the longitudinal axis of the vehicle. In the event of a side collision, the external side wall 5 is therefore stressed before the internal side wall 3.

[0034] Preferably, the structural element according to the invention is a chassis side member located at the level of the underbody of a motor vehicle. Obviously, those skilled in the art will know how to integrate such a reinforcement zone into other constituent elements of a vehicle structure and will not be limited to the side members. According to a preferred embodiment of the invention, at least the external side wall shows a reinforcement zone. Optionally, both the internal and external side walls show a reinforcement zone.

[0035] For ease of explanation, the embodiment in which the structural element is a spar and the wall carrying the reinforcement zone is the external side wall will be described subsequently.

[0036] Such a side member is illustrated in [Fig.l]. The side member 1 comprises an internal side wall 3 intended to be installed near one of the seat cross members of the vehicle and an external side wall 5, the latter being intended to be placed opposite one of the passenger compartment sides of the vehicle. In the embodiment of the invention illustrated in this figure, and according to a preferred embodiment of the invention, the reinforcement zone 7 is located on the external side wall. In the exemplary embodiment, the reinforcement zone 7 extends over the entire height H3 of the external side wall 5 and is represented by a thicker line thickness. The height of the external side wall 5 of the structural element is understood to be without the joining rebates 9.However, a person skilled in the art may envisage that the reinforcement zone extends over only part of the height H3 of the side wall, for example over a height less than 90% of the height H3 of the side wall, preferably less than 80%, more preferably less than 70% or less than 60% or less than 50% or less than 40% or even less than 30% of the height H3 of the side wall.

[0037] At least one reinforcement zone 7 has a specific appearance showing at least one first stiffening relief 11. According to a preferred embodiment, the reinforcement zone 7 showing a first stiffening relief 11 also shows at least one second stiffening relief 13; preferably at least one second stiffening relief 13 is arranged above said first stiffening relief 11 according to the height of the side wall showing said reinforcement zone 7.

[0038] The addition of a reinforcement zone 7 at the level of the side member 1 having improved mechanical resistance makes it possible to ensure the rigidity of the lateral sides of the vehicle so as to better protect the occupants of said vehicle during an impact. In addition, it makes it possible to limit dynamic intrusions of side doors, tunnel collapses causing floor tears as well as folds and tears of the side member 1. Thus, despite the significant difference in mass between vehicles of the type PHEVs and combustion engine vehicles, due to the addition of batteries, side impact performance is similar in both cases. In the absence of such a reinforcement zone, the appearance of an additional intrusion of approximately 30 mm was observed in the case of a PHEV compared to the combustion engine vehicle. This leads to significant degradation of the biomechanical criteria on the passenger compartment side.

[0039] Preferably, the first stiffening relief 11 extends along the entire length of the side member 1 or, at least, at the level of the side openings of the vehicle, thus ensuring the safety of the passengers.

[0040] According to another alternative or complementary definition to the preceding definition, the invention relates to a side member 1 of a motor vehicle, said side member 1 being an elongated hollow body comprising two side walls, one of said side walls (3, 5) being an internal side wall 3 and the other being an external side wall 5, said side member 1 being remarkable in that at least one of its side walls shows a reinforcement zone 7 over at least part of its height, in that said wall comprises, at the level of said reinforcement zone 7, a first stiffening relief 11 extending longitudinally over at least part of the length of said side member 1, and in that said reinforcement zone 7 is formed by at least one strip of sheet metal formed from a steel chosen from high elastic limit steels showing an elastic limit ranging from 300 to 700 MPa,very high yield strength steels showing a yield strength ranging from 800 to 1000 MPa and ultra high yield strength steels showing a yield strength of 1100 to 1500 MPa, the yield strength being measured according to ISO 6892-1:2016 and in the transverse direction.

[0041] The invention is remarkable in that it concentrates the safety benefits on the side member 1 by using steel grades with high mechanical characteristics in the production thereof. In doing so, the invention limits the increase in the manufacturing cost of the vehicle by using other, more rigid steel grades only at the reinforcement zone 7 and not at the level of the entire external side wall 5 of the side member 1.

[0042] According to this embodiment, it is possible to use sheets with thicknesses as thin as in the prior art in the case of thermal engine vehicles, while achieving the mechanical characteristics necessary for a PHEV. The increase in the mass of the vehicle is therefore minimized.

[0043] According to yet another alternative or complementary definition to the preceding definitions, the invention relates to a side member 1 of a motor vehicle, said side member 1 being an elongated hollow body comprising two side walls (3, 5), one of said side walls being an internal side wall 3 and the other being an external side wall 5, said side member 1 being remarkable in that at least one of its side walls shows a reinforcement zone 7 over at least part of its height, said reinforcement zone 7 having a thickness el of at least 1.5 mm, in that said wall comprises, at the level of said reinforcement zone 7, a first stiffening relief 11 extending longitudinally over at least part of the length of said spar 1, so that the spar 1 shows at the level of the first stiffening relief 11 a width L1 of at least 1.2 times the width L3 shown by the spar 1 outside the stiffening relief(s) (11, 13).

[0044] The width L1 is defined by the distance within the hollow body of the spar 1 between the internal side wall 3 and the most distant point belonging to the first stiffening relief 11.

[0045] The width L2 is defined by the distance within the hollow body of the spar 1 between the internal side wall 3 and the most distant point belonging to the second stiffening relief 13.

[0046] Similarly, the width L3 is defined by the distance within the hollow body of the spar 1 between the internal side wall 3 and the point furthest from the external side wall 5 without a stiffening relief.

[0047] The specific shape of the reinforcement zone 7 according to the invention and the presence of a first stiffening relief 11 are intended to better dissipate the energy generated by the lateral impact. The first stiffening relief 11 is designed so as to have a relief complementary to that shown by the side of the passenger compartment. Such a configuration is advantageous in that it makes it possible to use the space existing between the passenger compartment side and the external side wall of the side member, said space having a high potential for energy dissipation.

[0048] The kinematics of the impact follows the following scenario. First, the passenger compartment side deforms and causes the loading of the side member 1 from below, at the level of the first stiffening relief 11. Said first stiffening relief 11 will therefore be crushed towards the inside of the vehicle, dissipating the energy received from the passenger compartment side, then it will be the turn of the second stiffening relief 13 when it is present. Finally, the remaining part of the external side wall 5, whether or not included in the reinforcement zone 7 and devoid of stiffening relief, is also crushed and therefore helps to initiate the impact and dissipate the maximum amount of energy. This crushing kinematics in at least two successive stages ensures good loading of the seat cross member with no rotation of the side member 1 around the x axis defined according to the longitudinal direction of said side member 1.

[0049] The following features may be used in combination with any of the definitions of the invention given above.

[0050] According to a preferred embodiment, the reinforcement zone 7 has a mechanical resistance Rml of at least 250 MPa as measured according to the ISO 6892 standard. 1:2016 and according to the transverse direction of the vehicle in which the side member 1 is mounted; preferably at least 300 MPa or at least 350 MPa, more preferably at least 400 MPa, even more preferably at least 450 MPa, or at least 500 MPa, or at least 550 MPa, or at least 600 MPa, or at least 800 MPa, or at least 1000 MPa, or at least 1100 MPa.

[0051] According to a preferred embodiment of the invention, the first stiffening relief 11 is arranged in the lower part of the external side wall 5.

[0052] Indeed, when the structural element is a spar, the location of the first stiffening relief in its lower part according to the height of said element and on its external side wall allows loading of the forces downwards which allows better transmission of the forces to the seat crosspieces. This also makes it possible to avoid rotation of said spar during impact.

[0053] Ideally, the first stiffening relief 11 shows a height H1 less than or equal to 50% of the height H3 of said side wall, preferably less than 40% or less than 30%. Thus, said first stiffening relief 11 is positioned at the level of the seat crosspiece.

[0054] According to one embodiment, the reinforcement zone extends only over the part of the side wall showing the first stiffening relief 11, thus the reinforcement zone shows a height H1 less than or equal to 50% of the height H3 of said side wall, preferably less than 40% or less than 30%.

[0055] Alternatively or additionally, the second stiffening relief 13 shows a height H2 less than or equal to 30% of the height H3 of said side wall; preferably less than or equal to 20% of the height H3 of said side wall.

[0056] According to one embodiment, the reinforcement zone 7 extends only over the part of the side wall showing the first stiffening relief 11 and the second stiffening relief 13.

[0057] Preferably, the spar 1 shows at the level of the first stiffening relief 11 a width L1 of at least 1.2 times the width L3 shown by the spar 1 outside the zone 7 showing said first stiffening relief 11; preferably at least 1.3 times, and more preferably at least 1.4 times. Indeed, it has been found that the energy dissipation was improved by the dimensions shown by said first stiffening relief 11.

[0058] According to a preferred embodiment, at least one second stiffening relief 13 is arranged above said first stiffening relief 11 according to the height of the external side wall 5. Preferably, the spar 1 shows at the level of the second stiffening relief 13 a width L2 less than 1.2 times the minimum width L3 shown by said spar 1 between its two side walls outside the stiffening relief(s).

[0059] According to a preferred embodiment and illustrated in Figures 1 and 2, the reinforcement zone 7 of said side wall is formed by at least one strip of sheet metal showing an excess thickness. Preferably: the strip of sheet metal showing an excess thickness has a thickness of at least 1.1 times the thickness shown by the sheet metal outside said excess thickness strip, more preferably at least 1.5 times or at least 2 times; and / or the strip of sheet metal showing an excess thickness has a thickness el of at least 1.1 mm; preferably at least 1.5 mm and more preferably at least 2.0 mm.

[0060] This difference in thickness further improves the rigidity of the reinforcement zone 7 only in the region of the spar 1 affected by the impact of a side impact. The part of the external side wall 5 located outside the reinforcement zone 7 is therefore obtained from a thinner sheet metal, which avoids increasing the total mass of the spar.

[0061] According to an alternative or complementary embodiment, the reinforcement zone 7 of said external side wall 5 is formed by at least one strip of sheet metal formed from a steel chosen from high elastic limit steels showing an elastic limit ranging from 300 to 700 MPa, very high elastic limit steels showing an elastic limit ranging from 800 to 1000 MPa and ultra high elastic limit steels showing an elastic limit of 1100 to 1500 MPa, the elastic limit being measured according to the ISO 6892-1:2016 standard and in the transverse direction. When the sheet metal used is a stamped sheet metal, the mechanical resistance Rml of the reinforcement zone is measured after stamping.

[0062] According to a preferred embodiment, the spar 1 is formed by the assembly of at least two profiles so that the internal side wall 3 is formed by a first profile and the external side wall 5 by a second profile, said profiles being assembled by joining rebates 9 and in that the joining rebates 9 of the second profile have a thickness e2 less than or equal to 1.2 mm, preferably less than or equal to 1.1 mm or less than or equal to 1.0 mm.

[0063] The low thickness of the joining grooves 9 is advantageous from a production point of view. Thus, it is possible to maintain the same thickness of the joining grooves between the side members intended to be mounted in thermal engine vehicles and PHEVs. The same assembly line is therefore used in the production of both types of vehicles.

[0064] Obviously, the above embodiments are all complementary. For example, according to an embodiment not illustrated, the second profile carrying the external side wall and having a sheet metal strip showing an excess thickness at the level of the first stiffening relief, shows three different thicknesses: a first thickness corresponding to the junction rebates, a second thickness corresponding to the reinforcement zone without the first stiffening relief and a third thickness corresponding to said sheet metal strip, the thickness values ​​being able to increase from the first to the third. Thus, the profile will have the desired mechanical characteristics while using the minimum of material necessary.

[0065] According to one implementation of the invention, the spar 1 is formed by assembling at least two profiles so that the internal side wall 3 is formed by a first profile and the external side wall 5 by a second profile, and the second profile is formed by assembling different sheets joined end to end, so that at least one of the sheets forming the reinforcement zone 7 is formed from a steel grade showing a mechanical strength greater than at least one other sheet and / or shows a thickness e1 greater than the thickness e2 shown by another sheet. Such a manufacturing method is called butt welding and is well known to those skilled in the art and will not be described further. This is an interesting solution in that the sheet forming the reinforcement zone 7 can be manufactured separately by stamping.

[0066] According to another implementation of the invention, the spar 1 is formed by the assembly of at least two profiles so that the internal side wall 3 is formed by a first profile and the external side wall 5 by a second profile, and the second profile is formed by a single sheet having at least one strip of sheet showing an excess thickness obtained by a method comprising a flexible rolling step; preferably, the flexible rolling step is followed by a step of stamping the sheet.

[0067] It will be noted that the use of sheets showing a variable thickness as well as the methods of manufacturing such a sheet by flexible rolling are known to those skilled in the art. Document KR101825427 describes a method of flexible rolling of the bodywork of a vehicle opening.

[0068] Said extra thickness can therefore correspond to the external side wall 5 in its entirety (except for the joining grooves) or to only a part of said side wall, for example only to the part corresponding to the first stiffening relief 11, or even to the part corresponding to the first and second stiffening relief (11, 13).

[0069] According to another implementation of the invention, the spar, or at least one of the profiles constituting said spar, is produced by an additive manufacturing process. Thanks to this technique, it is possible to manufacture a reinforcement zone 7 showing a thickness with progressive variation according to its height.

[0070] Preferably, said spar 1 further comprises at least one shock absorbing means arranged inside its hollow body so as to extend over at least part of its length. Preferably, said shock absorbing element is arranged at the level of the first stiffening relief and is made of the same material as the external side wall of the spar. Advantageously, the absorption means is a metal foam produced by the additive manufacturing process concomitantly with the production of the rest of the spar.

[0071] Additive manufacturing processes, commonly referred to as "3D printing", offer the possibility of producing complex parts that cannot easily be obtained by other means, such as a sheet of increasing thickness, a spring showing a wire diameter of increasing thickness, or a foam or spring made from a single material with a wall. Additive manufacturing processes make it possible to produce metal elements showing good mechanical properties. To do this, powders, pure or in the form of alloys, based on titanium, nickel, cobalt, aluminum and steel are used.Several techniques can be used, the best known being laser sintering of metal (in English Direct Metal Laser Sintering abbreviated DMLS), selective laser melting (in English Selective Laser Melting abbreviated SLM), laser melting on powder bed (in English Laser Beam Melting abbreviated LBM), or electron beam melting (in English Electron Beam Melting abbreviated EBM).

Claims

Claims

1. Structural element (1) of a motor vehicle, said structural element (1) being an elongated hollow body comprising two side walls (3; 5), one of said side walls being an internal side wall (3) and the other being an external side wall (5), at least one of the side walls of said structural element (1) shows a reinforcement zone (7) over at least part of its height, said zone (7) having a mechanical resistance Rml of at least 250 MPa as measured according to ISO 6892-1:2016 and in the transverse direction;at least one of said walls comprising, at its reinforcement zone (7), at least one first stiffening relief (11) extending longitudinally over at least part of the length of said structural element (1), characterized in that the first stiffening relief (11) shows a height H1 less than or equal to 50% of the height H3 of said side wall and in that the structural element (1) shows at the first stiffening relief (11) a width L1 of at least 1.2 times the minimum width L3 shown by the structural element (1) between its two side walls outside the stiffening relief(s) (11, 13).;

2. Structural element (1) according to claim 1 characterized in that the first stiffening relief (11) is arranged in the lower part of the external side wall (5), and / or in that at least one second stiffening relief (13) is arranged above said first stiffening relief according to the height of the external side wall (5).

3. Structural element (1) according to one of claims 1 or 2, characterized in that the structural element (1) is a chassis side member.

4. Structural element (1) according to one of claims 1 to 3, characterized in that the reinforcement zone (7) has a mechanical resistance Rml of at least 400 MPa as measured according to standard ISO 6892-1:2016 and in the transverse direction.

5. Structural element (1) according to one of claims 1 to 4, characterized in that the reinforcement zone (7) of said side wall is formed by at least one strip of sheet metal showing an excess thickness; preferably: the strip of sheet metal showing an excess thickness has a thickness of at least 1.1 times the thickness shown by the sheet metal in outside of said excess thickness strip; and / or the sheet metal strip showing excess thickness has a thickness el of at least 1.1 mm.

6. Structural element (1) according to one of claims 1 to 5, characterized in that it is formed by the assembly of at least two profiles so that the internal side wall (3) is formed by a first profile and the external side wall (5) by a second profile, said profiles being assembled by joining rebates (9); and in that the joining rebates (9) of the second profile have a thickness e2 less than or equal to 1.1 mm.

7. Structural element (1) according to one of claims 1 to 6, characterized in that the reinforcement zone (7) of said side wall is formed by at least one strip of sheet metal made of a steel chosen from high elastic limit steels showing an elastic limit ranging from 300 to 700 MPa, very high elastic limit steels showing an elastic limit ranging from 800 to 1000 MPa and ultra high elastic limit steels showing an elastic limit of 1100 to 1500 MPa, the elastic limit being measured according to standard ISO 6892-1:2016 and in the transverse direction.

8. Structural element (1) according to one of claims 1 to 7, characterized in that it is formed by the assembly of at least two profiles so that the internal side wall (3) is formed by a first profile and the external side wall (5) by a second profile, and in that the second profile is formed by the assembly of different sheets joined end to end, and that at least one of the sheets forming the reinforcement zone (7) is formed from a steel grade showing a mechanical resistance greater than at least one other sheet and / or shows a thickness el greater than a thickness e2 shown by another sheet.

9. Structural element (1) according to one of claims 1 to 6, characterized in that the structural element (1), or at least one of the profiles constituting said structural element (1), is produced by an additive manufacturing process; or characterized in that it is formed by the assembly of at least two profiles so that the internal side wall (3) is formed by a first profile and the external side wall (5) by a second profile, and in that the second profile is formed by a single sheet having at least one strip of sheet showing an excess thickness obtained by a process comprising a flexible rolling step.

10. Motor vehicle characterized in that it comprises at least one structural element (1) according to one of claims 1 to 9.

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